Mitochondrial Membrane Potential Drives Early Change in Mitochondrial Morphology After Acetaminophen Exposure

Mitochondrial morphology plays a critical role in regulating mitochondrial and cellular function. It is well established that oxidative stress and mitochondrial injury are central to acetaminophen (APAP) hepatotoxicity. However, the role of mitochondrial dynamics, namely the remodeling of mitochondrial morphology through fusion and fission, has largely gone unexplored. To investigate this, we used primary mouse hepatocytes treated with APAP which allowed for real-time visualization of mitochondrial morphology using mitotracker green. We found that alterations in mitochondrial morphology were dose dependent, with a biphasic response in mitochondrial shape at higher APAP doses. Importantly, these two distinct mitochondrial morphologies corresponded with differences in mitochondrial respiratory function and polarization. The early change in mitochondrial morphology can be reversible and appears to be an adaptive response caused by alterations in membrane potential, which ultimately help preserve mitochondrial function. The later delayed change in mitochondrial morphology is irreversible and is driven by loss of mitochondrial membrane potential, decreased canonical fusion proteins, and alterations in mitochondrial lipid composition. Collectively, these later changes tilt the scales toward mitochondrial fission resulting in fragmented mitochondria with reduced functionality. This work provides evidence of adaptive early changes in mitochondrial morphology, which results in functional consequences that are dictated by the severity of APAP overdose.