Myo-inositol oxygenase expression profile modulates pathogenic ferroptosis in the renal proximal tubule
Fei Deng, Isha Sharma, Yingbo Dai, Ming Yang, Yashpal S. Kanwar
Fei Deng, Isha Sharma, Yingbo Dai, Ming Yang, Yashpal S. Kanwar
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Research Article Nephrology

Myo-inositol oxygenase expression profile modulates pathogenic ferroptosis in the renal proximal tubule

Abstract

Overexpression of myo-inositol oxygenase (MIOX), a proximal tubular enzyme, exacerbates cellular redox injury in acute kidney injury (AKI). Ferroptosis, a newly coined term associated with lipid hydroperoxidation, plays a critical role in the pathogenesis of AKI. Whether or not MIOX exacerbates tubular damage by accelerating ferroptosis in cisplatin-induced AKI remains elusive. Cisplatin-treated HK-2 cells exhibited notable cell death, which was reduced by ferroptosis inhibitors. Also, alterations in various ferroptosis metabolic sensors, including lipid hydroperoxidation, glutathione peroxidase 4 (GPX4) activity, NADPH and reduced glutathione (GSH) levels, and ferritinophagy, were observed. These perturbations were accentuated by MIOX overexpression, while ameliorated by MIOX knockdown. Likewise, cisplatin-treated CD1 mice exhibited tubular damage and derangement of renal physiological parameters, which were alleviated by ferrostatin-1, a ferroptosis inhibitor. To investigate the relevance of MIOX to ferroptosis, WT mice, MIOX-overexpressing transgenic (MIOX-Tg) mice, and MIOX-KO mice were subjected to cisplatin treatment. In comparison with cisplatin-treated WT mice, cisplatin-treated MIOX-Tg mice had more severe renal pathological changes and perturbations in ferroptosis metabolic sensors, which were minimal in cisplatin-treated MIOX-KO mice. In conclusion, these findings indicate that ferroptosis, an integral process in the pathogenesis of cisplatin-induced AKI, is modulated by the expression profile of MIOX.

Authors

Fei Deng, Isha Sharma, Yingbo Dai, Ming Yang, Yashpal S. Kanwar

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Figure 8

MIOX overexpression promotes lysosomal permeability and decreases GSH concentration, GPX4 activity, and NADPH levels in cisplatin-treated HK-2 cells.

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MIOX overexpression promotes lysosomal permeability and decreases GSH co...
Lysosomal permeability was investigated by AO staining. AO-associated green fluorescence in the cytoplasm increased, while red fluorescence in the lysosome decreased, suggesting increased lysosomal permeability of HK-2 cells following cisplatin treatment (B vs. A). The changes in fluorescence were accentuated in cisplatin-treated MIOX-overexpressing cells but attenuated in cisplatin-treated cells transfected with MIOX siRNA (C–F). The expression of GPX4, a key enzyme for ferroptosis inhibition, decreased after cisplatin treatment (M). A substantial decline in GPX4 activity was also observed in both HK-2 cells and MIOX-overexpressing cells, and this decrease was negated by the concomitant transfection with MIOX siRNA (N) (n = 6; *P < 0.05 compared with the control group, #P < 0.05 compared with the CP group, 1-way ANOVA with Dunn’s multiple comparisons). The status of intracellular GSH levels was assessed by monobromobimane (MBB) staining. Blue fluorescence was decreased after cisplatin treatment, and further decreased in cisplatin-treated MIOX-overexpressing cells, while partially restored by MIOX siRNA transfection (G–L and O) (n = 6; *P < 0.05 compared with the control group, #P < 0.05 compared with the CP group, 1-way ANOVA with Dunn’s multiple comparisons). The NADPH levels were also found to be low in MIOX-overexpressing cells and cisplatin-treated cells (P). There was further depletion of NADPH in cisplatin-treated MIOX-overexpressing cells, which was blocked by MIOX gene disruption (P) (n = 6; *P < 0.05 compared with the control group, #P < 0.05 compared with the CP group, 1-way ANOVA with Dunn’s multiple comparisons). Scale bars: 30 μm.