Proteomic analysis of human iPSC-derived sympathetic neurons identifies proteostasis collapse as a molecular signature following subtoxic rotenone exposure.

Rotenone is a toxic isoflavone and an inhibitor of the mitochondrial respiratory chain. Rotenone is commonly used due to its piscicidal and pesticidal properties. The peripheral nervous system (PNS) lacks protective barriers and is exposed to many environmental substances due to its long-reaching structure. A causal association between rotenone and human PNS dysfunction is currently a subject of investigation. Here, we treated human induced pluripotent stem cell (iPSC)-derived peripheral sympathetic neurons with a subtoxic dose of rotenone (10 µg/L) that is considered safe for human health and is permitted for environmental use. Indeed, no overt toxicity was observed in the human peripheral neurons and neurite morphology was intact in the treated neurons. Surprisingly, we detected significant changes in the proteome of rotenone-exposed sympathetic neurons with a signature of protein homeostasis (proteostasis) collapse. Screening the proteostasis modules of protein translation, proteolysis, and chaperones, revealed severe perturbations in clusters of autophagy regulators. Our proteomic profiling reveals compromised proteostasis as a consequence of low-dose non-toxic exposure to rotenone, which can disrupt the ability of the PNS to cope with proteotoxic stress. Exposed individuals may have varying degrees of tolerance to such vulnerabilities but they may eventually progress into peripheral neuropathies.