Melanin regulator

Interferon-gamma, a protein, checks melanin production

By Biplab Das
Published: Saturday 15 March 2014

imageMELANIN is the pigment that gives colour to the skin and protects itÔÇêfrom sunburn. But excess of it causes cell death and could even lead to cancer. So what regulates the productionÔÇêof melanin in the skin? An Indian research team may have found the answer.ÔÇêTheÔÇêresearchersÔÇêanalysed several proteins responsible for immune response to external stimuli, like sunlight, and found that interferon-gamma regulates the enzymes which synthesise melanin.

Melanin is produced by a specialised group of cells called melanocytes. For the study, theÔÇêresearchers probed the cycles of pigment generation and pigment loss in primary human melanocytes and in human skin cancer cells by exposing them to varying concentrations of interferon-gamma. They found that adding a low dose (100 units/ml) of interferon-gamma to both primary human melanocytes and skin cancer cells suppressed pigment generation.

About 40 per cent of the genes associated with interferon-gamma signalling process had lower expressions, indicating that the protein induces pigment loss in skin cancer cells and in primary melanocytes. The treatment also arrested the growth of melanosomes, cellular organelles that synthesise, store and transport melanin. Absence of interferon-gamma reinitiated pigment generation process in the studied cells. “Our study shows that interferon-gamma is a crucial factor secreted by immune cells that maintains these checks and balances of pigment generation in the human skin. Interferon-gamma does not allow more pigment granules to be formed and brings back the activated state to normal,” says lead author of the study Vivek T NatarajanÔÇêfromÔÇêtheÔÇêInstitute of Genomics and Integrative Biology, New Delhi.

To test the link between interferon-gamma and pigment generation,ÔÇêthe researchers also analysed skin samples from leprosy patients. They identified strong interferon-gamma signature in the visibly pigment-depleted lesions compared with unaffected skin. The researchers say the results of this study could be used to design strategies to prevent white patches in leprosy patients and make drugs that alter the skin tone. The study was published on January 28 in PNAS.

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