5-Methoxytryptophan attenuates oxidative stress-induced downregulation of PINK1 and mitigates mitochondrial damage and apoptosis in cardiac myocytes

Mitochondrial dysfunction is a hallmark of the pathogenesis of various cardiovascular diseases. 5-Methoxytryptophan (5-MTP), an intrinsic amino acid metabolite, exerts cardioprotective effects potentially through the preservation of mitochondrial integrity. This study investigates the mechanisms and contexts in which 5-MTP positively impacts mitochondrial function using cultured human cardiac myocyte cells and HL-1 cardiac cells subjected to oxidative stress (OS).

We first demonstrated that 5-MTP up-regulates the expression of PINK1, a key regulator of mitochondrial homeostasis. PINK1 knockdown attenuated the beneficial effects of 5-MTP on cardiomyocyte apoptosis. Furthermore, in cells exposed to OS, 5-MTP pretreatment led to a notable decrease in mitochondrial superoxide generation. Fluorescence imaging and network analysis showed that 5-MTP preserved mitochondrial membrane potential and enhanced mitochondrial network integrity. Reduced phosphorylation of dynamin-related protein 1, which is involved in mitochondrial fission, uncovered the role of 5-MTP in maintaining mitochondrial dynamics.

Notably, 5-MTP attenuated OS-induced mitophagy, as evidenced by reduced mitophagy detection dye fluorescence and lower mitochondrial Parkin levels, suggesting that mechanisms beyond the PINK1/Parkin pathway are involved. Restoration of AKT phosphorylation and reduced mitochondrial Bax localization further revealed an additional pathway contributing to mitochondrial protection. Moreover, 5-MTP attenuated pro-apoptotic Bax levels and enhanced PINK1 expression in a rat model of ischemic cardiomyopathy, corroborating its cardioprotective role.

Collectively, these findings demonstrate that 5-MTP mitigates mitochondrial dysfunction through coordinated regulation of PINK1, AKT, and Bax, offering potential as a therapeutic agent to enhance cellular resilience in OS-driven mitochondrial damage.