Clinical efficacy and safety of 4-hexyl-1,3-phenylenediol for improving skin hyperpigmentation.

Hyperpigmentation disorders are of social and cosmetic concerns to many individuals due to their prevalent locations on highly visible parts of the body. Topical formulation containing hydroquinone is the most widely used remedy for the treatment of hyperpigmentation disorders. However, reports of side effects in long-term usage have raised concerns for its use in cosmetic products. Thus, it is highly desirable to develop a safe and effective alternative to treat hyperpigmentation disorders. The objective of the current study is to investigate the de-pigmenting efficacy of 4-hexyl-1,3-phenylenediol in various in vitro models and in a randomized controlled clinical study. We showed that 4-hexyl-1,3-phenylenediol significantly reduced melanogenesis in primary human melanocytes, murine melanoma cells, and pigmented human epidermal equivalents. It was determined that the reduction in melanogenesis is mediated through inhibition of tyrosinase enzyme activity and protein expression. Further investigation revealed that the inhibition of melanogenesis is reversible and is not associated with cellular toxicity in melanocytes. In addition, significant improvements in key clinical parameters such as overall skin lightening, appearance of spots on the cheeks, overall contrast between spots and surrounding skin, and overall pigmentation size were detected in a double-blinded, randomized controlled clinical study. In conclusion, our findings clearly demonstrated the potency of 4-hexyl-1,3-phenylenediol in modulating skin pigmentation, and it is safe and well tolerated after 12-week topical application.

Galvanic zinc-copper microparticles inhibit melanogenesis via multiple pigmentary pathways.

The endogenous electrical field of human skin plays an important role in many skin functions. However, the biological effects and mechanism of action of externally applied electrical stimulation on skin remain unclear. Recent study showed that galvanic zinc-copper microparticles produce electrical stimulation and reduce inflammatory and immune responses in intact skin, suggesting the important role of electrical stimulation in non-wounded skin. The objective of this study is to investigate the biological effect of galvanic zinc-copper microparticles on skin pigmentation. Our findings showed that galvanic zinc-copper microparticles inhibited melanogenesis in a human melanoma cell line (MNT-1), human keratinocytes and melanoma cells co-cultures, and in pigmented epidermal equivalents. Treatment of galvanic zinc-copper microparticles inhibited melanogenesis by reducing the promoter transactivation of tyrosinase and tyrosinase-related protein-1 in human melanoma cells. In a co-culture Transwell system of keratinocytes and melanoma cells, galvanic zinc-copper microparticles reduced melanin production via downregulation of endothelin-1 secretion from keratinocytes and reduced tyrosinase gene expression in melanoma cells. In addition, exposure of pigmented epidermal equivalents to galvanic zinc-copper microparticles resulted in reduced melanin deposition. In conclusion, our data demonstrated for the first time that galvanic zinc-copper microparticles reduced melanogenesis in melanoma cells and melanin deposition in pigmented epidermal equivalents by affecting multiple pigmentary pathways.

Parthenolide sensitizes ultraviolet (UV)-B-induced apoptosis via protein kinase C-dependent pathways.

Parthenolide (PN) is the principal sesquiterpene lactone in feverfew (Tanacetum parthenium) with proven anti-inflammatory properties. We have previously reported that PN possesses strong anticancer activity in ultraviolet B (UVB)-induced skin cancer in SKH-1 hairless mice. In order to further understand the mechanism(s) involved in the anticancer activity of PN, we investigated the role of protein kinase C (PKC) in the sensitization activity of PN on UVB-induced apoptosis. Several subtypes of PKC have been reported to be involved in UVB-induced signaling cascade with both pro- and anti-apoptotic activities. Here we focused on two isoforms of PKC: novel PKCdelta and atypical PKCzeta. In JB6 murine epidermal cells, UVB induces the membrane translocations of both PKCs, and PN pre-treatment enhances the membrane translocation of PKCdelta, but inhibits the translocation of PKCzeta. Similar results were also detected when the activities of these PKCs were tested with the PKC kinase assay. Moreover, pre-treatment with a specific PKCdelta inhibitor, rotterlin, completely diminishes the sensitization effect of PN on UVB-induced apoptosis. When cells were transiently transfected with dominant negative PKCdelta or wild-type PKCzeta, the sensitization effect of PN on UVB-induced apoptosis was also drastically reduced. Further mechanistic study revealed that PKCzeta, but not PKCdelta, is required for UVB-induced p38 MAPK activation and PN is likely to act through PKCzeta to suppress p38 activation in UVB-treated JB6 cells. In conclusion, we demonstrated that PN sensitizes UVB-induced apoptosis via PKC-dependent pathways.

Anti-cancer potential of sesquiterpene lactones: bioactivity and molecular mechanisms.

Sesquiterpene lactones (SLs) are the active constituents of a variety of medicinal plants used in traditional medicine for the treatment of inflammatory diseases. In recent years, the anti-cancer property of various SLs has attracted a great deal of interest and extensive research work has been carried out to characterize the anti-cancer activity, the molecular mechanisms, and the potential chemopreventive and chemotherapeutic application of SLs. In this review, we attempt to summarize the current knowledge of the anti-cancer properties of SLs by focusing on the following important issues. First, we discuss the structure-activity relationship of SLs. All SLs contain a common functional structure, an alpha-methylene-gamma-lactone group, and this important chemical characteristic means that the thiol-reactivity of SLs is an underlying mechanism responsible for their bioactivities. Second, we assess the experimental evidence for the anti-cancer function of SLs obtained from both in vitro cell culture and in vivo animal models. Various SLs have been demonstrated to execute their anti-cancer capability via inhibition of inflammatory responses, prevention of metastasis and induction of apoptosis. Thirdly, we outline the molecular mechanisms involved in the anti-cancer activity of SLs, in particular, the SL-thiols reaction, the effect of SLs on cell signaling pathways such as nuclear transcription factor-kappaB (NF-kappaB) and mitogen-activated protein kinases (MAPK). Finally, we recapitulate some important SLs with regards to their anti-cancer activities and their potential in anti-cancer drug development. Taken together, many SLs are emerging as promising anti-cancer agents with potential applications in both cancer chemotherapy and chemoprevention.

Beta-phenylethyl and 8-methylsulphinyloctyl isothiocyanates, constituents of watercress, suppress LPS induced production of nitric oxide and prostaglandin E2 in RAW 264.7 macrophages.

Beta-phenylethyl (PEITC) and 8-methylsulphinyloctyl isothiocyanates (MSO) represent two phytochemical constituents present in watercress Rorripa nasturtium aquaticum, with known chemopreventative properties. In the present investigation, we examined whether PEITC and MSO could modulate the inflammatory response of Raw 264.7 macrophages to bacterial lipopolysaccharide (LPS) by assessment of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. Overproduction of both nitric oxide (NO) and prostaglandins (PGE) has been associated with numerous pathological conditions including chronic inflammation and cancer. Our results demonstrate that LPS (1 microg/ml approximately 24 h) induced nitrite and prostaglandin E2 (PGE-2) synthesis in Raw 264.7 cells was attenuated by both isothiocyanates (ITCs) in a concentration-dependent manner. Both PEITC and MSO decreased (iNOS) and (COX-2) protein expression levels leading to reduced secretion of both pro-inflammatory mediators. Interestingly, the reduction in both iNOS and COX-2 expression were associated with the inactivation of nuclear factor-kappaB and stabilization of IkappaBalpha. Taken together our data gives further insight into the possible chemopreventative properties of two dietary derived isothiocyanates from watercress.

Chemopreventive activity of parthenolide against UVB-induced skin cancer and its mechanisms.

Parthenolide (PN) is a major sesquiterpene lactone of feverfew (Tanacetum parthanium) with known anti-inflammatory activity. However, the anticancer effects of PN have not been well studied. In the present investigation, we examined the cancer chemopreventive property of PN using a combination of in vivo and in vitro approaches. We first tested the anticancer effect of PN in UVB-induced skin cancer model. Mice fed with PN (1 mg/day) showed a delayed onset of papilloma incidence, a significant reduction in papilloma multiplicity (papilloma/mouse) and sizes when compared with the UVB-only group. To our surprise, neither PN nor the known cyclooxygenase (COX)-2 inhibitor celecoxib inhibit UVB-induced COX-2 expression and epidermal prostaglandin E2 (PGE2) production. We next investigated the molecular mechanism(s) involved in its anticancer effects using cultured JB6 murine epidermal cells. Non-cytotoxic concentrations of PN significantly inhibited UVB-induced activator protein-1 DNA binding and transcriptional activity. In addition, PN pre-treatment also inhibited c-Jun-N-terminal kinase (JNK) and p38 kinase activation. More importantly, we found that impaired AP-1, JNK and p38 signaling led to the sensitization of JB6 cells to UVB-induced apoptosis. Data from our study for the first time confirm the anticancer property of PN in an animal model, and provide evidence that the inhibitory effects on AP-1 and mitogen-activated protein kinases serve as one of the underlying mechanisms for the cancer chemopreventive property of PN.