23. Nat Prod Res. 2011 Dec 8. [Epub ahead of print]  Silymarin, a molecule of interest for topical photoprotection.  Couteau C, Cheignon C, Paparis E, Coiffard LJ.  a Faculty of Pharmacy , Université de Nantes, Nantes Atlantique Universités , LPiC, MMS, EA2160, 1 rue G. Veil - BP 53508 , Nantes , F-44000 France. 

 Some UV-filters have side effects. For example, oestrogenic effect was demonstrated for 4-methylbenzylidene camphor. Given that secondary metabolites are known for their UVB photoprotective properties in plants that contain them, we chose to study silymarin as an agent which could potentially be used in sun products. This determination is based on the physical determination of the reduction of the energy in the UV range, through a film of product which has previously been spread on an adequate substrate. About 15?�mg of O/W emulsion containing silymarin at various concentrations was applied on roughened PMMA plates and the transmission measurements were carried out using a spectrophotometer equipped with integrating sphere. Incorporated in O/W creams, at a concentration of 10% (w/w), silymarin gives a Sun Protection Factor similar to that of octylmethoxicinnamate, which is why it is predominantly used in Europe. Overall, these results demonstrate that silymarin is a promising new sunscreen agent.  PMID: 22149904  [PubMed - as supplied by publisher] 

22. Strahlenther Onkol. 2011 Aug;187(8):485-91. Epub 2011 Jul 22.  Topical use of a silymarin-based preparation to prevent radiodermatitis : results of a prospective study in breast cancer patients.  Becker-Schiebe M, Mengs U, Schaefer M, Bulitta M, Hoffmann W.  Klinik für Radioonkologie und Strahlentherapie, Klinikum Braunschweig, Braunschweig, Germany. m.schiebe@klinikum-braunschweig.de 

 PURPOSE: More than 80% of patients with breast cancer undergoing postsurgical radiotherapy (RT) will develop radiodermatitis and approximately 10% of these patients show grade 3 lesions. Side effects may reduce the patient's compliance and can be limiting factors to follow RT protocols. Therefore, there is a high need for more effective prophylactic treatments. In this study, a silymarin-based cream (Leviaderm(®)) was tested in comparison to our standard of care (SOC) at the involved site. METHODS: A total of 101 patients were evaluated after breast-conserving surgery followed by RT with 50.4 Gy plus boost 9-16 Gy. Of these, 51 patients were treated with the silymarin-based cream. In addition, 50 patients were documented receiving a panthenol-containing cream interventionally, if local skin lesions occurred. The acute skin reactions were classified according to the RTOG and VAS (Visual Analogue Scale) scores. RESULTS: The median time to toxicity was prolonged significantly with silymarin-based cream (45 vs. 29 days (SOC), p < 0.0001). Only 9.8% of patients using silymarin-based cream showed grade 2 toxicity in week 5 of RT in comparison to 52% with SOC. At the end of RT, 23.5% of patients in the silymarin-based study group developed no skin reactions vs. 2% with SOC, while grade 3 toxicity occurred only in 2% in the silymarin-based arm compared to 28% (SOC). CONCLUSIONS: Silymarin-based cream Leviaderm(®) may be a promising and effective treatment for the prevention of acute skin lesions caused by RT of breast cancer patients. To confirm the results of this nonrandomized, observational trial, this component should be tested in larger multicenter studies in this setting.  PMID: 21786113  [PubMed - indexed for MEDLINE] 

21. PLoS One. 2011;6(6):e21410. Epub 2011 Jun 22.  Silymarin protects epidermal keratinocytes from ultraviolet radiation-induced apoptosis and DNA damage by nucleotide excision repair mechanism.  Katiyar SK, Mantena SK, Meeran SM.  Department of Dermatology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America. skatiyar@uab.edu 

 Solar ultraviolet (UV) radiation is a well recognized epidemiologic risk factor for melanoma and non-melanoma skin cancers. This observation has been linked to the accumulation of UVB radiation-induced DNA lesions in cells, and that finally lead to the development of skin cancers. Earlier, we have shown that topical treatment of skin with silymarin, a plant flavanoid from milk thistle (Silybum marianum), inhibits photocarcinogenesis in mice; however it is less understood whether chemopreventive effect of silymarin is mediated through the repair of DNA lesions in skin cells and that protect the cells from apoptosis. Here, we show that treatment of normal human epidermal keratinocytes (NHEK) with silymarin blocks UVB-induced apoptosis of NHEK in vitro. Silymarin reduces the amount of UVB radiation-induced DNA damage as demonstrated by reduced amounts of cyclobutane pyrimidine dimers (CPDs) and as measured by comet assay, and that ultimately may lead to reduced apoptosis of NHEK. The reduction of UV radiation-induced DNA damage by silymarin appears to be related with induction of nucleotide excision repair (NER) genes, because UV radiation-induced apoptosis was not blocked by silymarin in NER-deficient human fibroblasts. Cytostaining and dot-blot analysis revealed that silymarin repaired UV-induced CPDs in NER-proficient fibroblasts from a healthy individual but did not repair UV-induced CPD-positive cells in NER-deficient fibroblasts from patients suffering from xeroderma pigmentosum complementation-A disease. Similarly, immunohistochemical analysis revealed that silymarin did not reduce the number of UVB-induced sunburn/apoptotic cells in the skin of NER-deficient mice, but reduced the number of sunburn cells in their wild-type counterparts. Together, these results suggest that silymarin exert the capacity to reduce UV radiation-induced DNA damage and, thus, prevent the harmful effects of UV radiation on the genomic stability of epidermal cells.  PMCID: PMC3120878 PMID: 21731736  [PubMed - indexed for MEDLINE] 

20. Int J Oncol. 2010 May;36(5):1053-60.  Molecular mechanisms of inhibition of photocarcinogenesis by silymarin, a phytochemical from milk thistle (Silybum marianum L. Gaertn.) (Review).  Vaid M, Katiyar SK.  Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL 35294, USA. 

 Changes in life style over the past several decades including much of the time spent outdoors and the use of tanning devices for cosmetic purposes by individuals have led to an increase in the incidence of solar ultraviolet (UV) radiation-induced skin diseases including the risk of skin cancers. Solar UV radiations are considered as the most prevalent environmental carcinogens, and chronic exposure of the skin to UV leads to squamous and basal cell carcinoma and melanoma in human population. A wide variety of phytochemicals have been reported to have substantial anti-carcinogenic activity because of their antioxidant and anti-inflammatory properties. Silymarin is one of them and extensively studied for its skin photoprotective capabilities. Silymarin, a flavanolignan, is extracted from the fruits and seeds of milk thistle (Silybum marianum L. Gaertn.), and has been shown to have chemopreventive effects against photocarcinogenesis in mouse tumor models. Topical treatment of silymarin inhibited photocarcinogenesis in mice in terms of tumor incidence, tumor multiplicity and growth of the tumors. Wide range of in vivo mechanistic studies conducted in a variety of mouse models indicated that silymarin has anti-oxidant, anti-inflammatory and immunomodulatory properties which led to the prevention of photocarcinogenesis in mice. This review summarizes and updates the photoprotective potential of silymarin with the particular emphasis on its in vivo mechanism of actions. It is suggested that silymarin may favorably supplement sunscreen protection, and may be useful for skin diseases associated with solar UV radiation-induced inflammation, oxidative stress and immunomodulatory effects.  PMCID: PMC2852174 PMID: 20372777  [PubMed - indexed for MEDLINE]  

19. Int Immunopharmacol. 2008 Oct;8(10):1475-80. Epub 2008 Jun 30.  Inhibition of atopic dermatitis by topical application of silymarin in NC/Nga mice.  Kang JS, Yoon WK, Han MH, Lee H, Lee CW, Lee KH, Han SB, Lee K, Yang KH, Park SK, Kim HM.  Bioevaluation Center, KRIBB, Cheongwon, Chungbuk, Republic of Korea. 

 Silymarin has been known to inhibit chemical-induced irritant contact dermatitis. In the present study, we report that topical application of silymarin suppresses dust mite extract (DPE)-induced atopic dermatitis (AD) in NC/Nga mice. Repeated topical application of ears with DPE caused AD-like skin lesions in NC/Nga mice. However, silymarin reduced AD-like skin lesions in these mice, resulting in decreased ear swelling and leukocyte infiltration into the ear. Moreover, our results showed that mast cell infiltration into the ear was suppressed by silymarin treatment in DPE-treated NC/Nga mice. Silymarin also reduced plasma level of IL-4 and IgE in these mice. Further study demonstrated that the mRNA expression of IL-4 was increased and that of IFN-gamma was decreased by DPE treatment in the ears of NC/Nga mice. However, DPE-induced changes in IL-4 and IFN-gamma mRNA expression were reversed by silymarin. DPE-induced increase in TNF-alpha mRNA expression was also suppressed by silymarin treatment. The results presented in this report suggest that silymarin might be beneficial for the treatment of AD.  PMID: 18593606  [PubMed - indexed for MEDLINE]  

18. J Cosmet Dermatol. 2008 Mar;7(1):8-14.  Combined effects of silymarin and methylsulfonylmethane in the management of rosacea: clinical and instrumental evaluation.  Berardesca E, Cameli N, Cavallotti C, Levy JL, Piérard GE, de Paoli Ambrosi G.  San Gallicano Dermatological Institute, Rome, Italy. berardesca@berardesca.it 

 OBJECTIVE: This study aims to evaluate a topical treatment based on silymarin/methylsulfonilmethane (S-MSM) to improve erythematous-telangiectactic rosacea. METHODS: Forty-six patients affected by stage I-III rosacea entered this double-blind, placebo-controlled study. Subjects were treated for 1 month. Clinical and instrumental evaluations were done at baseline, after 10 and 20 days, and at the end of the study. Itching, stinging, erythema, and papules were investigated clinically as well as hydration and erythema instrumentally with capacitance and color measurements. RESULTS: A statistically significant improvement was observed in many clinical and instrumental parameters investigated (P < 0.001). In particular, improvement of skin redness, papules, itching, hydration, and skin color occurred. CONCLUSIONS: The combination of silymarin and S-MSM can be useful in managing symptoms and condition of rosacea skin, especially in the rosacea subtype 1 erythemato-telangiectatic phase. The action can be considered multicentric and multiphase because of the direct modulating action on cytokines and angiokines normally involved and up-regulated in the case of such skin condition.  PMID: 18254805  [PubMed - indexed for MEDLINE] 

17. Photochem Photobiol. 2008 Mar-Apr;84(2):266-71. Epub 2007 Nov 28.  Silymarin, a flavonoid from milk thistle (Silybum marianum L.), inhibits UV-induced oxidative stress through targeting infiltrating CD11b+ cells in mouse skin.  Katiyar SK, Meleth S, Sharma SD. 

 Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL, USA. skatiyar@uab.edu  Phytochemicals have shown promise in inhibiting UV-induced oxidative stress, and therefore are considered as potent inhibitors of UV-induced oxidative stress-mediated skin diseases. We have shown previously that topical treatment of silymarin, a flavonoid from milk thistle (Silybum marianum), inhibits UV-induced oxidative stress in mouse skin. However, the cellular targets responsible for the inhibition of UV-induced oxidative stress by silymarin are not clearly defined. To address this issue, C3H/HeN mice were UV irradiated (90 mJ cm(-2)) with or without topical treatment with silymarin (1 mg cm(-2) skin area). Mice were killed 48 h later and skin samples collected. Flow cytometric analysis of viable dermal cells revealed that the number of infiltrating CD11b+ cells were the major source of oxidative stress (31.8%) in UV-irradiated skin compared with non-UV-exposed skin (0.4%). Treatment of silymarin inhibited UV-induced oxidative stress through inhibition of infiltrating CD11b+ cells. The analysis of myeloperoxidase also indicated that silymarin significantly (P < 0.001) decreased UV-induced infiltration of leukocytes, and this effect of silymarin was similar to that of intraperitoneal treatment of mice with monoclonal antibodies to CD11b. The inhibitory effect of silymarin, regardless of whether it is topically treated before or after UV irradiation, was of similar magnitude. Intraperitoneal administration of monoclonal antibodies to CD11b (rat IgG2b) to C3H/HeN mice inhibited UVB-induced oxidative stress generated by both epidermal and dermal cells as is evident by relative fluorescence intensity of oxidized rhodamine. Similar to the effect of anti-CD11b, silymarin also inhibited UV-induced oxidative stress in both epidermal and dermal cells. Further, CD11b+ and CD11b- cell subsets from UV-treated or silymarin+UV-treated mice were separated by immunomagnetic cell isolation technique from total epidermal and dermal single cell suspensions and analyzed for reactive oxygen species (ROS)/H2O2 production. Analytic data revealed that CD11b+ cell population from UV-irradiated skin resulted in significantly higher production of ROS in both epidermis and dermis than CD11b- cell population, and that silymarin inhibited UV-induced oxidative stress through targeting infiltrating the CD11b+ cell type in the skin.  PMCID: PMC2394725 PMID: 18221354  [PubMed - indexed for MEDLINE] 

16. Int Immunopharmacol. 2007 Dec 15;7(13):1651-8. Epub 2007 Sep 14.  Topical application of silymarin reduces chemical-induced irritant contact dermatitis in BALB/c mice.  Han MH, Yoon WK, Lee H, Han SB, Lee K, Park SK, Yang KH, Kim HM, Kang JS.  Bioevaluation Center, KRIBB, Cheongwon, Chungbuk, Republic of Korea. 

 Irritant contact dermatitis (ICD) is a non-allergic local inflammatory reaction of a skin and one of the most frequent occupational health problems. Silymarin has been clinically used in Europe for a long time to treat liver diseases and also known to have anti-cancer and anti-inflammatory activities. In the present study, we report that topical application of silymarin reduces chemical-induced ICD. Topical application of 2,4-dinitrochlorobenzene (DNCB) induced an ear swelling in BALB/c mice and silymarin suppressed DNCB-induced increase in ear thickness. Prophylactic and therapeutic application of silymarin showed similar effect on DNCB-induced increase in ear thickness and skin water content. In addition, phobor ester- or croton oil-induced increase in ear thickness was also inhibited by silymarin treatment. Silymarin also blocked neutrophil accumulation into the ear induced by these irritants. Further study demonstrated that DNCB-induced tumor necrosis factor-alpha (TNF-alpha) expression in mouse ear was suppressed by silymarin. DNCB-induced expression of KC, one of the main attractors of neutrophil in mice, and adhesion molecules, including intercellular adhesion molecule-1 (ICAM-1) and E-selectin in mouse ear were also inhibited by silymarin. Moreover, TNF-alpha-induced expression of cytokines, such as TNF-alpha and IL-1beta, and a chemokine, IL-8, were suppressed by silymarin treatment in human keratinocyte cell line, HaCaT. Silymarin also blocked TNF-alpha- and DNCB-induced NF-kappaB activation in HaCaT. Collectively, these results demonstrate that topically applied silymarin inhibits chemical-induced ICD in mice and this might be mediated, at least in part, by blocking NF-kappaB activation and consequently inhibiting the expression of cytokines and adhesion molecules.  PMID: 17996674  [PubMed - indexed for MEDLINE]  

15. J Dermatol Sci. 2007 Dec;48(3):213-24. Epub 2007 Aug 3.  Flavonolignans from Silybum marianum moderate UVA-induced oxidative damage to HaCaT keratinocytes.  Svobodová A, Zdarilová A, Walterová D, Vostálová J.  Department of Medical Chemistry and Biochemistry, Palacký University, Hnevotínská 3, 775 15 Olomouc, Czech Republic. alf.svoboda@seznam.cz  Comment in J Dermatol Sci. 2011 Dec;64(3):243-5. 

 BACKGROUND: UV radiation from sunlight is a very potent environmental risk factor in the pathogenesis of skin cancer. Exposure to UV light, especially the UVA part, provokes the generation of reactive oxygen species (ROS), which induce oxidative stress in exposed cells. Topical application of antioxidants is a successful strategy for protecting the skin against UV-caused oxidative damage. OBJECTIVE: In this study, silybin (SB) and 2,3-dehydrosilybin (DS) (1-50 micromol/l), flavonolignan components of Silybum marianum, were tested for their ability to moderate UVA-induced damage. METHODS: Human keratinocytes HaCaT were used as an appropriate experimental in vitro model, to monitor the effects of SB and DS on cell viability, proliferation, intracellular ATP and GSH level, ROS generation, membrane lipid peroxidation, caspase-3 activation and DNA damage. RESULTS: Application of the flavonolignans (1-50 micromol/l) led to an increase in cell viability of irradiated (20 J/cm(2)) HaCaT keratinocytes. SB and DS also suppressed intracellular ATP and GSH depletion, ROS production and peroxidation of membrane lipids. UVA-induced caspases-3 activity/activation was suppressed by treatment with SB and DS. Lower concentrations of both compounds (10 micromol/l) significantly reduced cellular DNA single strand break formation. CONCLUSION: Taken together, the results suggest that these flavonolignans suppress UVA-caused oxidative stress and may be useful in the treatment of UVA-induced skin damage.  PMID: 17689055  [PubMed - indexed for MEDLINE] 

14. Burns. 2007 Nov;33(7):908-16. Epub 2007 May 22.  Silymarin, the antioxidant component of Silybum marianum, protects against burn-induced oxidative skin injury.  Toklu HZ, Tunali-Akbay T, Erkanli G, Yüksel M, Ercan F, Sener G.  Marmara University, School of Pharmacy, Department of Pharmacology, Tibbiye Cad., 34668 Istanbul, Turkey. 

 BACKGROUND: Despite recent advances, severe burn is one of the most common problems faced in the emergency room. Major thermal injury induces the activation of an inflammatory cascade resulting in local tissue damage, to contribute to the development of subsequent damage of multiple organs distant from the original burn wound. OBJECTIVE: Silymarin, the major component of milk thistle has been shown to have antioxidant properties. In the present study, we investigated the putative antioxidant effect of local or systemic silymarin treatment on burn-induced oxidative tissue injury. METHODS: Wistar albino rats were exposed to 90 degrees C bath for 10 s to induce burn. Silymarin either locally (30 mg/kg) applied on 4 cm(2) area or locally+systemically (50 mg/kg, p.o.) was administered after the burn and repeated twice daily. Rats were decapitated 48 h after injury and blood was collected for tumor necrosis factor-alpha (TNF-alpha) and lactate dehydrogenase (LDH) activity. In skin tissue samples malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity, and luminol-lucigenin chemiluminescense (CL) were measured in addition to the histological evaluation. RESULTS: Burn caused a significant increase in TNF-alpha and LDH levels. MDA levels were increased and GSH levels were decreased in the skin at 48 h after-burn. Both local and systemic silymarin treatments significantly reversed these parameters. The raised MPO activity and luminol-lucigenin CL were also significantly decreased. CONCLUSION: Results indicate that both systemic and local administration of silymarin was effective against burn-induced oxidative damage and morphological alterations in rat skin. Therefore, silymarin merits consideration as a therapeutic agent in the treatment of burns.  PMID: 17521818  [PubMed - indexed for MEDLINE]  

13. J Drugs Dermatol. 2007 Nov;6(11):1084-8.  Botanical ingredients in cosmeceuticals.  Baumann L.  Division of Cosmetic Dermatology, University of Miami Cosmetic Center, Miami, FL 33140, USA. 

 During the last 10 to 15 years, complementary and alternative medicine (CAM) has become increasingly popular in the US. Within this realm of health care, oral and topical herbal supplements have become some of the most frequently used alternative therapies. Most herbal supplements are based on, or include, several botanical ingredients with long histories of traditional or folk medicine usage. Among the numerous botanical ingredients available on the market today, several are believed to confer dermatologic benefits. This article will focus on a select group of botanical compounds, many of which have long traditions in Asian medicine, with potential or exhibited dermatologic applications, including curcumin, Ginkgo biloba, ginseng, silymarin, soy, and tea tree oil. Other botanical agents, such as arnica, bromelain, chamomile, pomegranate, caffeine, green tea, licorice, and resveratrol, are also briefly considered. Some of these ingredients have been incorporated into topical formulations.  PMID: 18038494  [PubMed - indexed for MEDLINE]  

12. Cancer Res. 2007 Apr 1;67(7):3483-91.  Silibinin inhibits inflammatory and angiogenic attributes in photocarcinogenesis in SKH-1 hairless mice.  Gu M, Singh RP, Dhanalakshmi S, Agarwal C, Agarwal R.  Department of Pharmaceutical Sciences, and University of Colorado Cancer Center, University of Colorado Health Sciences Center, Denver, Colorado, USA. 

 Sunscreens partially filter UVB and, therefore, could partially prevent skin cancer; however, efficient approaches are desired to effectively prevent photocarcinogenesis. It is hypothesized that nontoxic pharmacologically active natural compounds can increase photoprotective effects. Our completed studies suggest that silibinin, a bioactive phytochemical, strongly prevents photocarcinogenesis; however, its mechanism is not fully understood. Herein, for the first time, we used a clinically relevant UVB dose (30 mJ/cm(2)/day) to examine the photoprotective effect and associated mechanisms of silibinin in SKH1 hairless mice. Topical or dietary silibinin treatment caused a strong protection against photocarcinogenesis in terms of delay in tumor appearance, multiplicity, and volume. Analyses of normal skin, uninvolved skin from tumor-bearing mice, and skin tumors showed a statistically significant decrease (P < 0.05-0.001) in inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) levels by silibinin. Concomitantly, phospho-signal transducers and activators of transcription 3 (Tyr(705)) and phospho-p65(Ser(536)) were also decreased by silibinin, which are potential up-stream regulators of iNOS and COX-2. Simultaneously, silibinin also decreased UVB-caused increase in cell proliferation and microvessel density. In tumors, hypoxia-inducible factor 1alpha (HIF-1alpha) and vascular endothelial growth factor protein levels were decreased by silibinin. Further analysis showed that silibinin inhibited UVB-caused phosphorylation and nuclear translocation of STAT3 and p65, as well as nuclear factor kappaB (NF-kappaB) DNA binding activity. Together, these results suggest that silibinin causes a strong protective effect against photocarcinogenesis via down-regulation of inflammatory and angiogenic responses, involving HIF-1alpha, STAT3, and NF-kappaB transcription factors, as well as COX2 and iNOS.  PMID: 17409458  [PubMed - indexed for MEDLINE] 

11. Mol Cancer Ther. 2006 Aug;5(8):2121-9.  Differential effect of silibinin on E2F transcription factors and associated biological events in chronically UVB-exposed skin versus tumors in SKH-1 hairless mice.  Gu M, Singh RP, Dhanalakshmi S, Mohan S, Agarwal R.  Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, 4200 East Ninth Avenue, Box C238, Denver, 80262, USA. 

 UVB radiation-induced DNA damage in skin activates cellular pathways involved in DNA repair, cell cycle regulation, and apoptosis, important events that prevent conversion of damaged skin cells into cancer. We reported recently the efficacy of silibinin against photocarcinogenesis along with altered molecular events in tumors (Cancer Research, 64:6349-56, 2004). The molecular and biological events modulated by silibinin in chronically UVB-irradiated skin leading to cancer prevention, however, are not known. Herein, we describe effect of silibinin on skin 15 and 25 weeks after UVB exposure and compared them with molecular alterations in skin tumors. UVB decreased E2F1 but increased E2F2 and E2F3 protein levels in skin, and these were reversed by silibinin treatment. Silibinin-induced E2F1 was accompanied by an inhibition of apoptosis and decreases in p53 and cyclin-dependent kinase inhibitors. Silibinin-caused decrease in E2F2 and E2F3 was accompanied by reduced levels of cyclin-dependent kinases, cyclins, CDC25C, and mitogen-activated protein kinases and Akt signaling and inhibition of cell proliferation. In tumorigenesis protocols, topical or dietary silibinin significantly inhibited tumor appearance and growth. As opposed to UVB-exposed skin, UVB-induced tumors showed elevated levels of E2F1, but these were reduced in silibinin-treated tumors without any effect on E2F2 and E2F3. Contrary to the inhibition of apoptosis and p53 expression in UVB-exposed skin cells, silibinin increased these variables in tumors. These differential effects of silibinin on E2F1 versus E2F2 and E2F3 and their associated molecular alterations and biological effects in chronic UVB-exposed skin suggest their role in silibinin interference with photocarcinogenesis.  PMID: 16928834  [PubMed - indexed for MEDLINE] 

10. Carcinogenesis. 2005 Aug;26(8):1404-13. Epub 2005 Apr 14.  Silibinin inhibits ultraviolet B radiation-induced mitogenic and survival signaling, and associated biological responses in SKH-1 mouse skin.  Gu M, Dhanalakshmi S, Mohan S, Singh RP, Agarwal R.  Department of Pharmaceutical Sciences, School of Pharmacy and University of Colorado Cancer Center, University of Colorado Health Sciences Center, Denver, CO 80262, USA. 

 Ultraviolet B (UVB) radiation is a complete skin carcinogen causing DNA damage as a tumor-initiating event and activating signaling cascades that play a critical role in its tumor-promoting potential. Recently we reported that a naturally occurring flavonoid, silibinin, protects UVB-induced skin damages and prevents photocarcinogenesis. Here we examined silibinin efficacy on acute and chronic UVB-caused mitogen-activated protein kinases (MAPKs) and AKT activation and associated biological responses in SKH-1 hairless mouse skin. A single UVB exposure at 180 mJ/cm2 dose resulted in varying degrees of ERK1/2, JNK1/2, MAPK/p38 and AKT phosphorylation at various time-points in mouse skin; however, topical application of silibinin prior to or immediately after UVB exposure, or its dietary feeding strongly inhibited the activation of these molecules at all the time-points examined. Stronger effects of silibinin towards inhibition of UVB-caused phosphorylation of MAPKs and AKT were also observed in a chronic UVB (180 mJ/cm2/day for 5 days) exposure protocol. Immunohistochemical analysis of chronically exposed skin sections showed that silibinin treatment in all three protocols increases UVB-induced p53-positive cells and decreases UVB-caused cell proliferation, apoptotic and sunburn cells. These findings suggest that silibinin inhibits UVB-induced MAPK and AKT signaling and increases p53 in mouse skin, and that these effects of silibinin possibly lead to a decrease in UVB-caused proliferation and apoptosis, which might, in part, be responsible for its overall efficacy against photocarcinogenesis.  PMID: 15831527  [PubMed - indexed for MEDLINE]  

9. Int J Oncol. 2005 Jan;26(1):169-76.  Silymarin and skin cancer prevention: anti-inflammatory, antioxidant and immunomodulatory effects (Review).  Katiyar SK.  Department of Dermatology, The University of Alabama at Birmingham, Birmingham, AL 35294, USA. skatiyar@uab.edu 

 Several environmental and genetic factors are involved in skin cancer induction, however exposure to chemical carcinogens and solar ultraviolet (UV) radiation are primarily responsible for several skin diseases including skin cancer. Chronic exposure of solar UV radiation to the skin leads to basal cell and squamous cell carcinoma, and melanoma. Chemoprevention of skin cancer by consumption of naturally occurring botanicals appears a practical approach and therefore world-wide interest is considerably increasing to use these botanicals. Sunscreens are useful but their protection is not ideal because of inadequate use, incomplete spectral protection and toxicity. Silymarin, a plant flavonoid isolated from the seeds of milk thistle (Silybum marianum), has been shown to have chemopreventive effects against chemical carcinogenesis as well as photocarcinogenesis in various animal tumor models. Topical treatment of silymarin inhibited 7,12-dimethylbenz(a)anthracene-initiated and several tumor promoters, like 12-O-tetradecanoylphorbol-13-acetate, mezerein, benzoyal peroxide and okadaic acid, induced skin carcinogenesis in mouse models. Similarly, silymarin also prevented UVB-induced skin carcinogenesis. Wide range of in vivo mechanistic studies indicated that silymarin possesses antioxidant, anti-inflammatory and immunomodulatory properties which may lead to the prevention of skin cancer in in vivo animal models. The available experimental information suggests that silymarin is a promising chemopreventive and pharmacologically safe agent which can be exploited or tested against skin cancer in human system. Moreover, silymarin may favorably supplement sunscreen protection and provide additional anti-photocarcinogenic protection.  PMID: 15586237  [PubMed - indexed for MEDLINE]  

8. Cancer Res. 2004 Sep 1;64(17):6349-56.  Silibinin protects against photocarcinogenesis via modulation of cell cycle regulators, mitogen-activated protein kinases, and Akt signaling.  Mallikarjuna G, Dhanalakshmi S, Singh RP, Agarwal C, Agarwal R.  Department of Pharmaceutical Sciences, School of Pharmacy, and University of Colorado Cancer Center, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. 

 Here, we assessed the protective effect of silibinin on UVB-induced skin carcinogenesis in SKH-1 hairless mice. Topical application of silibinin before or immediately after UVB exposure or its dietary feeding resulted in a strong protection against photocarcinogenesis, in terms of tumor multiplicity (60-66%; P < 0.001), tumor volume per mouse (93-97%; P < 0.001) and tumor volume per tumor (80-91%; P < 0.001). Silibinin also moderately inhibited tumor incidence (5-15%; P < 0.01) and delayed tumor latency period (up to 4 weeks; P < 0.01-0.001). To investigate in vivo molecular mechanisms of silibinin efficacy, tumors and uninvolved skin from tumor-bearing mice were examined immunohistochemically for proliferation, p53, apoptosis, and activated caspase-3. Silibinin treatment showed a strong decrease (P < 0.001) in proliferating cell nuclear antigen-positive cells and an increase in p53-positive (P < 0.005-0.001), terminal deoxynucleotidyltransferase-mediated nick end labeling-positive (P < 0.005-0.001), and cleaved caspase-3-positive cells (P < 0.001). Western blot analysis of normal skin and tumor lysates showed that silibinin decreases the levels of cyclin-dependent kinase 2 and cyclin-dependent kinase 4 and associated cyclins A, E, and D1, together with an up-regulation of Cip1/p21, Kip1/p27, and p53. Silibinin also showed a strong phosphorylation of extracellular signal-regulated protein kinase 1/2, stress-activated protein kinase/c-JUN NH2-terminal kinase 1/2, and p38 mitogen-activated protein kinases but inhibited Akt phosphorylation and decreased survivin levels with an increase in cleaved caspase-3. Together, these results show a strong preventive efficacy of silibinin against photocarcinogenesis, which involves the inhibition of DNA synthesis, cell proliferation, and cell cycle progression and an induction of apoptosis. Furthermore, these results also identify in vivo molecular mechanisms of silibinin efficacy against photocarcinogenesis.  PMID: 15342425  [PubMed - indexed for MEDLINE]  

7. Carcinogenesis. 2004 Aug;25(8):1459-65. Epub 2004 Mar 19.  Silibinin prevents ultraviolet radiation-caused skin damages in SKH-1 hairless mice via a decrease in thymine dimer positive cells and an up-regulation of p53-p21/Cip1 in epidermis.  Dhanalakshmi S, Mallikarjuna GU, Singh RP, Agarwal R.  Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver, CO 80262, USA. 

 Non-melanoma skin cancer (NMSC) accounts for >1 million new cases each year in the US alone suggesting that more approaches are needed for its prevention and control. Earlier studies by us have shown that silymarin (a crude form of biologically active silibinin with some other isomers), isolated from milk thistle, affords strong protection against ultraviolet (UV) radiation-induced NMSC in SKH-1 hairless mice; however, the molecular mechanisms of its efficacy are not known. Here, we assessed the effect of silibinin on UV-induced DNA damage and p53-p21/Cip1 accumulation, and their roles in UV-induced cell proliferation and apoptosis in SKH-1 hairless mouse epidermis. Topical application of silibinin prior to, or immediately after, UV irradiation resulted in a very strong protective effect against UV-induced thymine dimer positive cells in epidermis accounting for 76-85% (P < 0.001) inhibition. In other studies, silibinin treatment resulted in a further up-regulation of p53 by approximately 1.6-fold (P < 0.001) together with an increase ( approximately 2-fold, P < 0.001) in p21/Cip1 protein levels. Proliferative cell nuclear antigen staining showed that silibinin pre- or post-topical application significantly inhibits (40-52 and 20-40%, respectively, P < 0.001) UV-induced epidermal cell proliferation. In addition, silibinin strongly decreased UV-caused terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive apoptotic/sunburn cell formation (P < 0.001). These findings suggest that silibinin affords strong protection against UV-induced damage in epidermis by a decrease in thymine dimer positive cells and an up-regulation of p53-p21/Cip1 possibly leading to an inhibition in both cell proliferation and apoptosis. Comparable effects of silibinin following its pre- or post-UV application suggest that mechanisms other than sunscreen effect are operational in silibinin efficacy against UV-caused skin damages.  PMID: 15033902  [PubMed - indexed for MEDLINE] 

6. J Am Acad Dermatol. 2003 Jan;48(1):1-19; quiz 20-2.  Cutaneous photodamage, oxidative stress, and topical antioxidant protection.  Pinnell SR.  Duke University Medical Center, Department of Medicine, Division of Dermatology, Durham, North Carolina 27707, USA. pinne002@mc.duke.edu  Comment in J Am Acad Dermatol. 2003 Dec;49(6):1203-4. 

 New methods to protect skin from photodamage from sun exposure are necessary if we are to conquer skin cancer and photoaging. Sunscreens are useful, but their protection is not ideal because of inadequate use, incomplete spectral protection, and toxicity. Skin naturally uses antioxidants (AOs) to protect itself from photodamage. This scientific review summarizes what is known about how photodamage occurs; why sunscreens--the current gold standard of photoprotection--are inadequate; and how topical AOs help protect against skin cancer and photoaging changes. This review is intended to be a reference source, including pertinent comprehensive reviews whenever available. Although not all AOs are included, an attempt has been made to select those AOs for which sufficient information is available to document their potential topical uses and benefits. Reviewed are the following physiologic and plant AOs: vitamin C, vitamin E, selenium, zinc, silymarin, soy isoflavones, and tea polyphenols. Their topical use may favorably supplement sunscreen protection and provide additional anticarcinogenic protection. (J Am Acad Dermatol 2003;48:1-19.) Learning objective: At the completion of this learning activity, participants should have an understanding of current information about how the sun damages skin to produce skin cancer and photoaging changes, how the skin naturally protects itself from the sun, the shortcomings of sunscreens, and the added advantages of topical AOs for photoprotection.  PMID: 12522365  [PubMed - indexed for MEDLINE]  

5. Int J Oncol. 2002 Dec;21(6):1213-22.  Treatment of silymarin, a plant flavonoid, prevents ultraviolet light-induced immune suppression and oxidative stress in mouse skin.  Katiyar SK.  Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA. skatiyar@uab.edu 

 It is well documented that ultraviolet (UV) light-induced immune suppression and oxidative stress play an important role in the induction of skin cancers. Earlier, we have shown that topical treatment of silymarin, a plant flavonoid from milk thistle (Silybum marianum L. Gaertn.), to mouse skin prevents photocarcinogenesis, but the preventive mechanism of photocarcinogenesis in vivo animal system by silymarin is not well defined and understood. To define the mechanism of prevention, we employed immunostaining, analytical assays and ELISA which revealed that topical treatment of silymarin (1 mg/cm2 skin area) to C3H/HeN mice inhibits UVB (90 mJ/cm2)-induced suppression of contact hypersensitivity (CHS) response to contact sensitizer dinitrofluorobenzene. Prevention of UVB-induced suppression of CHS by silymarin was found to be associated with the inhibition of infiltrating leukocytes, particularly CD11b+ cell type, and myeloperoxidase activity (50-71%). Silymarin treatment also resulted in significant reduction of UVB-induced immunosuppressive cytokine interleukin-10 producing cells and its production (58-72%, p<0.001). Topical treatment of silymarin also resulted in significant reduction of the number of UVB-induced H2O2 producing cells and inducible nitric oxide synthase expressing cells concomitant with decrease in H2O2 (58-65%, p<0.001) and nitric oxide (65-68%, p<0.001) production. Together, these data suggest that prevention of UVB-induced immuno-suppression and oxidative stress by silymarin may be associated with the prevention of photocarcinogenesis in mice. The data obtained from this study also suggest: i) phase-I clinical trial of silymarin in high skin cancer risk human population and ii) development of sunscreen containing silymarin as an antioxidant (chemopreventive agent) or silymarin can be supplemented in skin care products.  PMID: 12429970  [PubMed - indexed for MEDLINE]  

4. Carcinogenesis. 2000 Apr;21(4):811-6.  Inhibitory effect of a flavonoid antioxidant silymarin on benzoyl peroxide-induced tumor promotion, oxidative stress and inflammatory responses in SENCAR mouse skin.  Zhao J, Lahiri-Chatterjee M, Sharma Y, Agarwal R.  Center for Cancer Causation and Prevention, AMC Cancer Research Center, Denver, CO 80214, USA. 

 In this communication, we investigate the preventive effect of a flavonoid antioxidant, silymarin, on free radical-generating skin tumor promoting agent benzoyl peroxide (BPO)-induced tumor promotion, oxidative stress and inflammatory responses in SENCAR mouse skin. Topical application of silymarin at a dose of 6 mg prior to BPO resulted in a highly significant protection against BPO-induced tumor promotion in 7,12-dimethylbenz[a]anthracene-initiated SENCAR mouse skin. The preventive effect of silymarin was evident in terms of a 70% reduction (P < 0.001) in tumor incidence, a 67% reduction (P < 0.001) in tumor multiplicity and a 44% decrease (P < 0.001) in tumor volume/tumor. In oxidative stress studies, topical application of BPO resulted in 75, 87 and 61% depletion in superoxide dismutase (SOD), catalase and glutathione peroxidase (GPX) activities in mouse epidermis, respectively. These decreases in antioxidant enzyme activities were significantly (P < 0.005-0.001) reversed by pre-application of silymarin in a dose-dependent manner. The observed effects of silymarin were 18-66, 32-72 and 20-67% protection against BPO-induced depletion of SOD, catalase and GPX activity in mouse epidermis, respectively. Silymarin pre-treatment also resulted in a dose-dependent inhibition (35-87%, P < 0.05-0. 001) of BPO-induced lipid peroxidation in mouse epidermis. In inflammatory response studies, silymarin showed a strong inhibition of BPO-induced skin edema (62-85% inhibition, P < 0.001), myeloperoxidase activity (42-100% inhibition, P < 0.001) and interleukin-1alpha protein level in epidermis (36-81% inhibition, P < 0.001). These results, together with our other recent studies, suggest that silymarin could be useful in preventing a wide range of carcinogen and tumor promoter-induced cancers.  PMID: 10753220  [PubMed - indexed for MEDLINE] 

3. Mol Carcinog. 1999 Dec;26(4):321-33.  Significant inhibition by the flavonoid antioxidant silymarin against 12-O-tetradecanoylphorbol 13-acetate-caused modulation of antioxidant and inflammatory enzymes, and cyclooxygenase 2 and interleukin-1alpha expression in SENCAR mouse epidermis: implications in the prevention of stage I tumor promotion.  Zhao J, Sharma Y, Agarwal R.  Center for Cancer Causation and Prevention, AMC Cancer Research Center, Denver, Colorado 80214, USA. 

 The flavonoid antioxidant silymarin is used clinically in Europe and Asia for the treatment of liver diseases and is sold in the United States and Europe as a dietary supplement. Recently we showed that silymarin possesses exceptionally high cancer-preventive effects in different mouse skin carcinogenesis models and affords strong anticancer effects in human skin, cervical, prostate, and breast carcinoma cells. More recently, we showed that the anti-tumor-promoting effect of silymarin is primarily targeted against stage I tumor promotion in mouse skin (Cancer Res 1999;59:622-632). Based on this recent study, in this report, further investigations were made to identify and define the biochemical and molecular mechanisms of silymarin's effect during stage I tumor promotion in mouse skin. A single topical application of silymarin at 3-, 6-, and 9-mg doses onto SENCAR mouse skin followed 30 min later with 12-O-tetradecanoylphorbol 13-acetate (TPA) at a 3-microg dose resulted in a 76-95% inhibition (P < 0.001) of TPA-caused skin edema. Similarly, these doses of silymarin also showed 39-90%, 29-85%, and 15-67% protection (P < 0.05 or 0.001), against TPA-caused depletion of epidermal superoxide dismutase, catalase, and glutathione peroxidase activity, respectively. Pretreatment of mice with silymarin also produced highly significant inhibition of TPA-caused induction of epidermal lipid peroxidation (47-66% inhibition, P < 0.001) and myeloperoxidase activity (56-100% inhibition, P < 0.001). In additional studies assessing the effect of silymarin on arachidonic acid metabolism pathways involving lipoxygenase and cyclooxygenase (COX), similar doses of silymarin showed highly significant inhibition of TPA-caused induction of epidermal lipoxygenase (49-77% inhibition, P < 0.001) and COX (35-64% inhibition, P < 0.01 or 0.001) activity. Western immunoblot analysis showed that the observed effect of silymarin on COX activity was due to inhibition of TPA-inducible COX-2 with no change in constitutive COX-1 protein levels. In other studies, silymarin also showed dose-dependent inhibition of TPA-caused induction of epidermal interleukin 1alpha (IL-1alpha) protein (39-72% inhibition, P < 0.005 or 0.001) and mRNA expression. Taken together, the results from these biochemical and molecular studies further substantiate our recent observation of silymarin's anti-tumor-promoting effects primarily at stage I tumor promotion. Furthermore, the observed inhibitory effects of silymarin on COX-2 and IL-1alpha should be further explored to develop preventive strategies against those cancers in which these molecular targets play one of the causative roles, such as non-melanoma skin, colon, and breast cancers in humans.  Copyright 1999 Wiley-Liss, Inc.  PMID: 10569809  [PubMed - indexed for MEDLINE]  

2. Biochem Biophys Res Commun. 1997 Oct 9;239(1):334-9.  Novel cancer chemopreventive effects of a flavonoid antioxidant silymarin: inhibition of mRNA expression of an endogenous tumor promoter TNF alpha.  Zi X, Mukhtar H, Agarwal R.  Department of Dermatology, Case Western Reserve University, Cleveland, Ohio 44106, USA. 

 In this study we describe exceptionally high protective effects of silymarin, a flavonoid antioxidant isolated from milk thistle, against 12-O-tetradecanoylphorbol 13-acetate (TPA)- and okadaic acid (OA)-caused tumor promotion in SENCAR mouse skin. Pre-application of silymarin to that of TPA in 7, 12-dimethylbenz(a)anthracene (DMBA)-initiated mouse skin resulted in almost complete protection in terms of tumor incidence (85%) as well as multiplicity (94%). In OA-caused tumor promotion studies, application of silymarin prior to that of OA in DMBA-initiated mouse skin resulted in a complete protection against tumorigenicity. We next assessed the effect of silymarin on TPA- and OA-caused induction of mRNA expression of tumor necrosis factor alpha (TNF alpha) which is an endogenous tumor promoter and a central mediator of tumor promotion in vivo in the case of both TPA and OA tumor promotion. Topical application of silymarin on mouse skin prior to that of TPA or OA resulted in a highly significant to complete inhibition in a dose-dependent manner against both TPA- and OA-caused induction of TNF alpha mRNA expression in mouse epidermis. These results indicate that silymarin exerts novel chemopreventive effects against tumorigenicity by inhibiting endogenous tumor promoter TNF alpha. Additional studies are warranted in other tumor models to further evaluate the cancer chemopreventive effect of silymarin and to define the involvement of TNF alpha as a molecular target for such an effect.  PMID: 9345320  [PubMed - indexed for MEDLINE] 

1. Carcinogenesis. 1994 Jun;15(6):1099-103.  Inhibitory effect of silymarin, an anti-hepatotoxic flavonoid, on 12-O-tetradecanoylphorbol-13-acetate-induced epidermal ornithine decarboxylase activity and mRNA in SENCAR mice.  Agarwal R, Katiyar SK, Lundgren DW, Mukhtar H.  Department of Dermatology, University Hospitals of Cleveland, Case Western Reserve University, OH 44106. 

 In recent years, considerable emphasis has been placed on identifying new cancer chemopreventive agents which could be useful for human populations. Silymarin, an anti-oxidant flavonoid isolated from artichoke, has been shown to possess significant activity against hepatotoxicity and other pharmacological and physiological disorders. Since many antioxidants inhibit tumor promotion, and because ornithine decarboxylase (ODC) is a well known biochemical marker of tumor promotion, we assessed the effect of skin application of silymarin on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced epidermal ODC activity and ODC mRNA levels in SENCAR mice. Application of silymarin at doses of 0.5-18 mg (1-37 mumol)/mouse prior to that of TPA (2.5 micrograms) treatment resulted in significant inhibition of TPA-induced epidermal ODC activity in a dose- and time-dependent manner. Northern blot analysis revealed that topical application of silymarin at the dose of 2 mg/mouse resulted in almost complete inhibition of TPA-induced epidermal ODC mRNA. In other studies, silymarin also showed significant inhibition of epidermal ODC activity induced by several other tumor promoters, including free radical-generating compounds. Our data suggest that silymarin could be a useful anti-tumor promoting agent capable of ameliorating the tumor promoting effects of a wide range of tumor promoters.  PMID: 8020140  [PubMed - indexed for MEDLINE] 

Advanced skin care research on silymarin, a milk thistle extract, has shown that is effective as an anti-oxidant, an anti-inflammatory, and for UV protection/repair. Silymarin has also been shown to reduce the occurrence of (and spread of) skin cancer in some studies.

Silymarin research