Effect of urea-extracted sericin on melanogenesis: potential applications in post-inflammatory hyperpigmentation

BACKGROUND: Hyperpigmentation disorders such as post-inflammatory hyperpigmentation are major concerns not only in light-skinned people but also in Asian populations with darker skin. The anti-tyrosinase and immunomodulatory effects of sericin have been known for decades. However, the therapeutic effects of sericin on hyperpigmentation disorders have not been well documented. METHODS: In this study, we used an in vitro model to study the anti-tyrosinase, tolerogenic, and anti-melanogenic effects of sericin on Staphylococcus aureus peptidoglycan (PEG)-stimulated melanocytes, dendritic cells (DCs), and artificial skin (MelanoDerm™). Enzyme-linked immunosorbent assay, conventional and immunolabeled electron microscopy, and histopathological studies were performed. RESULTS: The results revealed that urea-extracted sericin has strong anti-tyrosinase properties as shown by a reduction of tyrosinase activity in melanin pigments both 48 h and 10 days after allergic induction with PEG. Anti-inflammatory cytokines including interleukin (IL)-4, IL-10, and transforming growth factor-p were upregulated upon sericin treatment (10, 20, and 50 µg/mL), whereas production of allergic chemokines, CCL8 and CCL18, by DCs was diminished 48 h after allergic induction with PEG. Moreover, sericin lowered the expression of micropthalmia-associated transcription factor (MITF), a marker of melanogenesis regulation, in melanocytes and keratinocytes, which contributed to the reduction of melanin size and the magnitude of melanin deposition. However, sericin had no effect on melanin transport between melanocytes and keratinocytes, as demonstrated by a high retention of cytoskeletal components. CONCLUSION: In summary, sericin suppresses melanogenesis by inhibition of tyrosinase activity, reduction of inflammation and allergy, and modulation of MITF function.

Improved antimelanogenesis and antioxidant effects of polysaccharide from Cuscuta chinensis Lam seeds after enzymatic hydrolysis

Cuscuta chinensis polysaccharide (CPS) was extracted using hot water and enzymatically hydrolyzed C. chinensis polysaccharide (ECPS) was produced by the mannase enzymatic hydrolysis process. The purpose of this research was to investigate the antimelanogenic activity of ECPS and CPS in B16F10 melanoma cells. The in vitro antioxidant activity was assessed by their ferric iron reducing power and DPPH free radical scavenging activities. The molecular mass distribution of polysaccharides was determined using SEC-MALLS-RI. CPS was successfully enzymatically degraded using mannase and the weighted average molecular weights of CPS and ECPS were 434.6 kDa and 211.7 kDa. The results of biological activity assays suggested that the enzymatically hydrolyzed polysaccharide had superior antimelanogenic activity and antioxidant effect than the original polysaccharide. ECPS exhibited antimelanogenic activity by down-regulating the expression of tyrosinase, MITF, and TRP-1 without cytotoxic effects in B16F10 melanoma cells. In conclusion, ECPS have the potential to become a skin whitening product.

Chemical leukoderma induced by dimethyl sulfate

Abstract Chemical leukoderma occurs due to the toxic effect of a variety of chemical agents. Mechanisms include either destruction or inhibition of melanocytes. We report two male patients (36 and 51 years old) who presented with multiple hypopigmented macules and patches on the neck, wrist, and legs after exposure to dimethyl sulfate in a chemical industry. Physical examination revealed irregular depigmentation macules with sharp edges and clear hyperpigmentation around the lesions. History of repeated exposure to a chemical agent can help the clinical diagnosis of chemical leukoderma. This diagnosis is very important for prognosis and therapeutic management of the disease.

Lotus (Nelumbo nuficera) flower essential oil increased melanogenesis in normal human melanocytes

In this study, the essential oil from lotus flower extract, including petals and stamens, was assessed with regard to its effects on melanogenesis in human melanocytes. The lotus flower essential oil was shown to stimulate melanin synthesis and tyrosinase activity in a dose-dependent manner. The lotus flower essential oil induced the expression of tyrosinase, microphthalmia-associated transcription factor M (MITF-M), and tyrosinase-related proten-2 (TRP-2) proteins, but not tyrosinase mRNA. Moreover, it increased the phosphorylation of ERK and cAMP response element binding protein (CREB). In order to verify the effective components of the lotus flower oil, its lipid composition was assessed. It was found to be comprised of palmitic acid methyl ester (22.66%), linoleic acid methyl ester (11.16%), palmitoleic acid methyl ester (7.55%) and linolenic acid methyl ester (5.16%). Among these components, palmitic acid methyl ester clearly induced melanogenesis as the result of increased tyrosinase expression, thereby indicating that it may play a role in the regulation of melanin content. Thus, our results indicate that lotus flower oil may prove useful in the development of gray hair prevention agents or tanning reagents.

Effect of xanthohumol on melanogenesis in B16 melanoma cells

Xanthohumol (XH), the principal prenylflavonoid of the hop plant (Humulus lupulus L.), dose-dependently inhibited isobutylmethylxanthine (IBMX)-induced melanogenesis in B16 melanoma cells, with little cytotoxicity at the effective concentrations. Decreased melanin content was accompanied by reduced tyrosinase enzyme activity, protein and mRNA expression. The levels of tyrosinase-related protein 1 and 2 mRNAs were decreased by XH. XH also inhibited alpha-melanocyte stimulating hormone- or forskolin-induced increases in melanogenesis, suggesting an action on the cAMP-dependent melanogenic pathway. XH downregulated the protein and mRNA expression of microphthalmia-associated transcription factor (MITF), a master transcriptional regulator of key melanogenic enzymes. These results suggest that XH might act as a hypo-pigmenting agent through the downregulation of MITF in the cAMP-dependent melanogenic pathway.

effect of acetylsalicylic acid on the release rates of leukotrienes B4 and C4 from cultured skin melanocytes of active vitiligo

The aim of this study is to investigate the effect of the non-steroidal anti-inflammatory agent, acetylsalicylic acid [ASA], otherwise known as aspirin, at different concentrations on the release rates of the pro-inflammatory mediators, leukotriene B4 [LTB4] and leukotriene C4 [LTC4] from in vitro cultured melanocytes obtained from normal pigmented skin of patients with active vitiligo. This study was carried out between April, 2000 and September, 2001, at The Vitiligo Unit, King Abdul-Aziz University Medical Center, Jeddah, Kingdom of Saudi Arabia. Skin biopsies were obtained from patients with active vitiligo [n=7] of different extent and duration, and normal healthy age-matched individuals [n=7] serving as control were recruited to the study. The release rates of LTB4 and LTC4 were determined before and after the addition of the ASA at 3 different concentrations [15, 75, 150 ug/ml] in the primary skin melanocytes culture medium using a commercially available kit based on radioimmunoassay method. Following the ASA treatment at 3 different concentrations [15, 75 and 150 ug/ml], the release rates of LTB4 and LTC4 were increased from melanocytes of the normal individuals [13%, 7.5% and 30%; 7.2%, 51.4% and 60.7%, p<0.001]. However, in patients with active vitiligo, the release rate of LTB4 from melanocytes was decreased [2.9%, 14.4% and 7.4%, p<0.05], whereas that of LTC4 was increased [3.9%, 93.8% and 101.4%, p<0.001]. Acetylsalicylic acid at therapeutic concentrations can regulate the release rates of LTB4 and LTC4 from cultured skin melanocytes of normal and active vitiligo subjects

Topical application of a melanotropin analogue to vulgar vitiligo dermo-epidermal minigrafts

Human subjects with active vulgar vitiligo do not respond well to autologous dermo-epidermal minigrafting. Eighteen subjects were treated with the a-melanocyte-stimulating hormone (a-MSH) synthetic analogue [Nle4, D-Phe7]-a-MSH. The hormone (50 µl, 0.4 mM) was applied topically to 30-cm2 lesions in which 29-48 minigrafts had been made. The hormone did not improve the success of the minigrafting and no differences were observed in local or distant repigmentation in treated subjects as compared to the placebo group. Aliquots of 24-h urine concentrated by lyophilization irreversibly darkened toad skins, demonstrating the presence of the analogue. This is the first report of the transdermal delivery of a topically applied melanotropin in living human subjects

ACTH acts directly on melanocytes to stimulate melanogenesis--an in vitro study.

A total of 108 whole skin organ cultures taken from vitiliginous skin were incubated in MEM containing ACTH. It was observed that 53.7% that is 58 showed a positive response with an increase in pigment production and enzyme activity, as observed on frozen sections stained for dopaoxidase activity. On immunohistochemical staining for locating ACTH binding, it is observed that 27.3% control skin and 72.7% ACTH treated skin show positivity. The ACTH is seen to bind with the melanocyte membrane as well as the cytoplasm. This indicates that ACTH can bind to the MSH-receptors expressed by the melanocyte. Thus, ACTH acts directly on the melanocyte to enhance melanogenesis and does not require to act via the adrenal-pituitary axis. This also indicates that the response is not associated with immune suppression by ACTH.

Evidence for melanin concentrating hormone (MCH) receptors mediating melanosome aggregation in Labeo melanophores.

Melanin concentrating hormone (MCH: 5 x 10(-12)-5 x 10(-8) M) induced a concentration related, rapid and reversible pigment aggregation in innervated melanophores of Labeo rohita. In inducing melanosome aggregation MCH was found to be 10(4) times more potent than norepinephrine. Experiments employing phentolamine and propranolol suggest that MCH acts through its own specific receptors on the melanophores unrelated to adrenoceptors. MCH was able to aggregate the melanosomes even in the absence of extracellular Ca2+.