Activation of PINK1-Parkin-dependent mitophagy in Tri-ortho-cresyl phosphate-treated Neuro2a cells

Elevated intracellular Ca2+ functions downstream of mitodysfunction to induce Wallerian-like degeneration and necroptosis in organophosphorus-induced delayed neuropathy

Neurotoxic organophosphorus compounds can induce a type of delayed neuropathy in humans and sensitive animals, known as organophosphorus-induced delayed neuropathy (OPIDN). OPIDN is characterized by axonal degeneration akin to Wallerian-like degeneration, which is thought to be caused by increased intra-axonal Ca2+ concentrations. This study was designed to investigate that deregulated cytosolic Ca2+ may function downstream of mitodysfunction in activating Wallerian-like degeneration and necroptosis in OPIDN. Adult hens were administrated a single dosage of 750 mg/kg tri-ortho-cresyl phosphate (TOCP), and then sacrificed at 1 day, 5 day, 10 day and 21 day post-exposure, respectively. Sciatic nerves and spinal cords were examined for pathological changes and proteins expression related to Wallerian-like degeneration and necroptosis. In vitro experiments using differentiated neuro-2a (N2a) cells were conducted to investigate the relationship among mitochondrial dysfunction, Ca2+ influx, axonal degeneration, and necroptosis. The cells were co-administered with the Ca2+-chelator BAPTA-AM, the TRPA1 channel inhibitor HC030031, the RIPK1 inhibitor Necrostatin-1, and the mitochondrial-targeted antioxidant MitoQ along with TOCP. Results demonstrated an increase in cytosolic calcium concentration and key proteins associated with Wallerian degeneration and necroptosis in both in vivo and in vitro models after TOCP exposure. Moreover, co-administration with BATPA-AM or HC030031 significantly attenuated the loss of NMNAT2 and STMN2 in N2a cells, as well as the upregulation of SARM1, RIPK1 and p-MLKL. In contrast, Necrostatin-1 treatment only inhibited the TOCP-induced elevation of p-MLKL. Notably, pharmacological protection of mitochondrial function with MitoQ effectively alleviated the increase in intracellular Ca2+ following TOCP and mitigated axonal degeneration and necroptosis in N2a cells, supporting mitochondrial dysfunction as an upstream event of the intracellular Ca2+ imbalance and neuronal damage in OPIDN. These findings suggest that mitochondrial dysfunction post-TOCP intoxication leads to an elevated intracellular Ca2+ concentration, which plays a pivotal role in the initiation and development of OPIDN through inducing SARM1-mediated axonal degeneration and activating the necroptotic signaling pathway.

Ambient ozone exposure induces ROS related-mitophagy and pyroptosis via NLRP3 inflammasome activation in rat lung cells

OBJECTIVE

To study the regulatory relationship between ozone-induced mitophagy and pyroptosis in lung epithelial cells.

RESULTS

First, type I primary alveolar epithelial cells and male Wistar rats were treated with ozone at different dosages. The ATP content and mitochondrial membrane potential significantly decreased in type I primary alveolar epithelial cells. The mitophagy-related markers and PINK1/Parkin pathway-related proteins, and the co-localization of LC3, Parkin, and mitochondria in type I alveolar epithelial cells indicated that ozone exposure triggered mitophagy. On the other hand, the reactive oxygen species (ROS) inhibitor NAC could significantly alleviate mitophagy in epithelial cells. After treatment with the mitophagy inhibitor MDIVI-1, the levels of the NLRP3 inflammasome, cleaved caspase-1, and N-gasdermin D (N-GSDMD) significantly decreased in the cells. Altogether, these results indicated that mitophagy can be triggered by ozone exposure, and subsequently induces cell death mediated by the NLRP3 inflammasome. Finally, the overexpression and knockdown of NLRP3 confirmed this conclusion.

CONCLUSION

Ozone exposure induced oxidative damage, leading to mitochondrial structural and functional damage. Ozone-induced ROS triggered mitophagy through the activation of the PINK1/Parkin signaling pathway, then pyroptosis through activation of the NLRP3 inflammasome.

Quality Control Mechanisms of Mitochondria: Another Important Target for Treatment of Peripheral Neuropathy

Mitochondria provide energy for various cellular activities and are involved in the regulating of several physiological and pathological processes. Mitochondria constitute a dynamic network regulated by numerous quality control mechanisms; for example, division is necessary for mitochondria to develop, and fusion dilutes toxins produced by the mitochondria. Mitophagy removes damaged mitochondria. The etiologies of peripheral neuropathy include congenital and acquired diseases, and the pathogenesis varies; however, oxidative stress caused by mitochondrial damage is the accepted pathogenesis of peripheral neuropathy. Regulation and control of mitochondrial quality might point the way toward potential treatments for peripheral neuropathy. This article will review mitochondrial quality control mechanisms, their involvement in peripheral nerve diseases, and their potential therapeutic role.

Advances in Cardiotoxicity Induced by Altered Mitochondrial Dynamics and Mitophagy

Mitochondria are the most abundant organelles in cardiac cells, and are essential to maintain the normal cardiac function, which requires mitochondrial dynamics and mitophagy to ensure the stability of mitochondrial quantity and quality. When mitochondria are affected by continuous injury factors, the balance between mitochondrial dynamics and mitophagy is broken. Aging and damaged mitochondria cannot be completely removed in cardiac cells, resulting in energy supply disorder and accumulation of toxic substances in cardiac cells, resulting in cardiac damage and cardiotoxicity. This paper summarizes the specific underlying mechanisms by which various adverse factors interfere with mitochondrial dynamics and mitophagy to produce cardiotoxicity and emphasizes the crucial role of oxidative stress in mitophagy. This review aims to provide fresh ideas for the prevention and treatment of cardiotoxicity induced by altered mitochondrial dynamics and mitophagy.

The crosstalk between mitochondrial dysfunction and endoplasmic reticulum stress promoted ATF4-mediated mitophagy induced by hexavalent chromium

Chromium (Cr) compounds are markedly toxic and carcinogenic. Previously, we found that Cr (VI) induced autophagy in A549 cells. Here, the effect of mitochondrial dysfunction and endoplasmic reticulum (ER) stress on inducing mitophagy was investigated in both A549 and H1299 cells. Exposure to Cr (VI) for 6 h significantly enhanced reactive oxygen species (ROS) production and reduced mitochondrial membrane potential (MMP). Transmission electron microscopy showed that Cr (VI) induced mitochondrial morphological changes, such as, mitochondrial swelling and vacuolization. The elevated expression of GRP78 and p-PERK suggested that Cr (VI) resulted in ER stress. Both mitochondrial dysfunction and ER stress played an important role in Cr (VI)-induced mitophagy, as the mitochondrial function inhibitor, carbonyl cyanide 3-chlorophenylhydrazone (CCCP) induced PINK1 and PARK2 and increased the expression of GRP78 and p-PERK while the levels of Cr (VI)-induced PINK1, PARK2, LC3-II were reduced after ER stress inhibitor, phenylbutyric acid (4PBA) pretreatment. When A549 cells were treated with CCCP and 4-PBA simultaneously, CCCP-induced expressions of PINK1, PARK2 and LC3-II decreased significantly compared with that of only CCCP-treated cells, indicating that there was a crosstalk between mitochondria and ER in inducing mitophagy. Additionally, the crosstalk between mitochondrial dysfunction and ER stress modulated the expression of Cr (VI)-induced ATF4, which resulted in mitophagy. Collectively, our data demonstrated that Cr (VI)-induced mitophagy mediated by ATF4 via the crosstalk between ER stress and mitochondrial dysfunction.