FUNDC1-dependent mitochondrial-ER membranes mediate mitochondrial dysfunction and melanocyte damage under oxidative stress

Background: Mitochondria play a pivotal role in oxidative stress-induced melanocyte destruction in vitiligo. FUN14 domain containing 1 (FUNDC1), a mitochondrial outer-membrane protein, has an important role in mitochondrial function by regulating Mitophagy and mitochondria-associated endoplasmic reticulum membranes (MAM). However, the role of FUNDC1 in melanocyte damage under oxidative remains unclear.

Objectives: To determine the contribution of FUNDC1 to oxidative stress-triggered melanocyte damage in vitiligo.

Methods: We treated human melanocyte cell line PIG1 with H₂O₂ to establish an oxidative stress model. Cell viability, mitochondrial function and dynamics as well as Mitophagy were detected. The transmission electron microscopy was used to assess MAM structure. FUNDC1 was then knocked down to examine its effects on MAM structure and mitochondrial function under H₂O₂ treatment. Additionally, we compared FUNDC1 expression, MAM structure and mitochondrial function between PIG1 cells and human vitiligo melanocyte cell line PIG3V. Finally, FUNDC1 expression and MAM structure were analyzed in vitiligo lesions and healthy control skin.

Results: H₂O₂ treatment significantly increased intracellular H₂O₂ level, mitochondrial superoxide and lipid peroxide (LPO), while decreased glutathione (GSH) level in PIG1 cells. Impaired cell viability and mitochondrial function as well as excessive mitochondrial fission in PIG1 cells were observed after H₂O₂ incubation. However, H₂O₂ treatment didn't induce Mitophagy but enhanced FUNDC1 expression and altered MAM structure. FUNDC1 knockdown inhibited H₂O₂-induced changes of MAM structure, mitochondrial calcium overloading, mitochondrial dysfunction, and recovered cell viability under oxidative stress. Interestingly, persistent H₂O₂ exposure reduced FUNDC1 expression, leading to MAM formation deficiency, excessive mitochondrial fusion and compromised mitochondrial function in the human vitiligo melanocyte cell line PIG3V. Finally, the decreased FUNDC1 expression and dysregulated MAM formation were confirmed in vitiligo lesions.

Conclusions: FUNDC1-dependent MAM structure mediates oxidative stress-induced mitochondrial dysfunction and melanocytes damage in vitiligo, suggesting that FUNDC1 and its associated MAM structure are potential targets for vitiligo treatment.

FUNDC1; MAM structure; Melanocytes; Mitochondria; Oxidative stress; Vitiligo.