Myo-inositol oxygenase expression profile modulates pathogenic ferroptosis in the renal proximal tubule
Fei Deng, … , Ming Yang, Yashpal S. Kanwar
Fei Deng, … , Ming Yang, Yashpal S. Kanwar
Published August 22, 2019
Citation Information: J Clin Invest. 2019;129(11):5033-5049. https://doi.org/10.1172/JCI129903.
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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.