Estradiol alleviates disease phenotypes caused by m.3635G > a mutations by activating mitochondrial biogenesis and PINK1-Parkin mediated mitophagy in iPSC-derived retinal pigment epithelium cells.

Abstract

Leber's hereditary optic neuropathy (LHON), a mitochondrial disorder marked by central vision loss, exhibits incomplete penetrance and male predominance. Since there are no adequate models for understanding the rapid vision loss associated with LHON, we generated induced pluripotent stem cells (iPSCs) from LHON patients carrying the pathogenic m.3635G > A mutation and differentiated them into retinal pigment epithelium (RPE) cells. The mutation disrupted mitochondrial dynamics, suppressing OPA1-mediated fusion and enhancing DRP1-dependent fission, resulting in decreased expression of ND1, ND5, NDUFB8, SDHB and COX2, impaired mitochondrial bioenergetic function, and cell proliferation. Additionally, the m.3635G > A mutation promoted intrinsic apoptosis, altered autophagic flux, evidenced by elevating levels in apoptotic proteins PARP1, caspase-3, and 9, reduced levels of autophagy protein LC3-II, and increased levels of substrate P62. Moreover, the m.3635G > A mutation inhibited PINK1-Parkin-dependent mitophagy. Based on sex-specific differences in hormone metabolism, we proposed that estrogen plays a protective role in women and showed that estrogen receptor α and β were downregulated in LHON. We demonstrated that estradiol improved cell viability by reducing apoptosis, inducing mitochondrial biogenesis through the PGC1α-NRF1/2-TFAM axis, and vigorously promoting PINK1-Parkin-dependent mitophagy in LHON iPSCs and iPSC-derived RPE cells. Our findings have highlighted the critical role of the m.3635G > A mutation in the pathogenetic process of LHON, and our observations support the hypothesis that estrogen is helpful in the preventive treatment of LHON.