Berberine protects immortalized line of human melanocytes from H2O2-induced oxidative stress via activation of Nrf2 and Mitf signaling pathway.

BACKGROUND: Oxidative stress plays important roles in the pathogenesis of vitiligo. The removal of hydrogen peroxided (H2O2) has been established to be beneficial to vitiligo patients. Berberine (BBR), a natural isoquinoline alkaloid, has antioxidant activity, however, whether BBR can defend human melanocytes against oxidative injury remains to be elucidated. OBJECTIVE: In the present study, we investigated the potential protective effect of BBR against oxidative stress on an immortalized normal human melanocyte cell line PIG1. METHODS: Generally, PIG1 cells were pretreated with various concentrations of BBR for 1 h followed by exposure to 1.0 mM H2O2 for 24 h. Cell apoptosis, intracellular reactive oxygen species (ROS) levels were assessed through flow cytometry. Cell apoptosis, melanogenesis and the activation of Nrf2-ARE and Mitf signaling pathway were assayed. RESULTS: Our results showed that cell viability rose and intracellular ROS generation, cell apoptosis of melanocytes decreased significantly in response to H2O2 through pretreatment with BBR. Furthermore, We found that BBR can dramatically induce Nrf2 nuclear translocation, increase total Nrf2 levels and enhance ARE activity. Besides, Nrf2-siRNA transfection can abrogate the protection of BBR in melanocytes against oxidative injury. At last, we verified that BBR could facilitate melanogenesis function via modulation of Mitf and its target proteins. CONCLUSION: The results above suggest that BBR can protect melanocytes against oxidative stress via its anti-oxidative activity. Also, we found H2O2-induced activation of NFκB was inhibited by BBR. Therefore, it is worthy of investigation BBR as a potential drug for treatment of vitiligo.

Baicalein protects human vitiligo melanocytes from oxidative stress through activation of NF-E2-related factor2 (Nrf2) signaling pathway.

Vitiligo is a complex disorder characterized by patchy loss of skin pigmentation due to abnormal melanocyte function. Overwhelming evidences have suggested that oxidative stress plays a major role in the loss of melanocytes thereby mediating the onset and progression of vitiligo. The nuclear factor erythroid 2-like factor 2 (Nrf2) is a master regulator of cellular redox homeostasis and the activation of Nrf2 signaling pathway is impaired in the vitiligo melanocytes. Baicalein, as flavonoid extracted from the Scutellaria baicalensis, has been proved to possess the ability to activate Nrf2 signaling pathway in other cell types and mouse model. Our previous data found that baicalein exerts a cytoprotective role in H2O2-induced apoptosis in human melanocytes cell line (PIG1). Based on these founding, we hypothesized that baicalein activates Nrf2 signaling pathway, alleviates H2O2-induced mitochondrial dysfunction and cellular damage, thereby protecting human vitiligo melanocytes from oxidative stress. In the present study, we found that baicalein effectively inhibited H2O2-induced cytotoxicity and apoptosis in human vitiligo melanocytes (PIG3V). Further results demonstrated that baicalein promoted Nrf2 nucleus translocation as well as up-regulated the expression of Nrf2 and its target gene, heme oxygenase-1 (HO-1). Moreover, the protective effects of baicalein against H2O2-induced cellular damage and apoptosis as well as mitochondrial dysfunction were abolished by Nrf2 knockdown. Additionally, we observed that Nrf2 knockdown suppressed proliferation and increased the sensitivity of PIG3V cells to H2O2 treatment. Finally, we explored the mechanism of baicalein associated with Nrf2 activation and found that the phosphorylation of Nrf2 as well as ERK1/2and PI3K/AKT signaling were not involved in the baicalein-induced activation of Nrf2. Taken together, these data clearly suggest that baicalein enhances cellular antioxidant defense capacity of human vitiligo melanocytes through the activation of the Nrf2 signaling pathway, providing beneficial evidence for the application of baicalein in the vitiligo treatment.