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Kidney Week

Abstract: FR-PO099

Involvement of Acid-Sensing Ion Channels in Ischemia/Reperfusion Induced Kidney Injury

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Author

  • Song, Nana, Zhongshan Hospital, Fudan University, Shanghai, SHANGHAI, China
Background

Acidic microenvironment is commonly observed in ischemic tissue. In the kidney, extracellular pH dropped from 7.4 to 6.5 within 10 min initiation of ischemia. Acid-sensing ion channels (ASICs) represent a family of H+-activated Na+ channels. Among six ASICs subunits, ASIC1a and ASIC3 are high proton sensitive, which can be activated by pH drops from 7.4 to 7.0 or lower. However, ASIC1a is the only one that is permeable to Ca2+ besides Na+. Thus, activation of ASIC1a can mediate the intracellular Ca2+ accumulation and play crucial roles in apoptosis of neuron. The aim of the present study was to test the hypothesis that extracellular acidosis caused by ischemia increases renal epithelia cell apoptosis through ASIC1a-mediated calcium entry.

Methods

Immunofluorescence double staining and confocal analysis were applied to observe the co-localization of ASICs with AQP1 (proximal tubule marker), THP (thick ascending limbs and distal tubule marker) and Synaptopodin (podocyte marker). ASIC1a inhibitor PcTx-1 and ASIC3 inhibitor APETx-2 was injected previously to IR operation. After that, the pathological and functional injury of the kidney was assessed by PAS staining and serum creatinine, and the apoptosis of kidney epithelia cells was measured by TUNEL staining and immunohistochemical reaction of caspase3. To demonstrate the underlying mechanism of ASICs induced renal IRI, HK-2 cells was pretreated with PcTx-1 before hypoxia, the intracellular concentration of Ca2+, mitochondrial transmembrane and apoptosis was measured by Fluo-4/AM, JC-1 and AnnexinV/PI and analyzed by flow cytometry.

Results

ASIC1a was found to be co-localized with AQP1 and Synaptopodin. ASIC3 was detected majorly in podocyte and mesenchyma. IRI up-regulated the expression of ASIC1a, however, had little effect on ASIC3, both in vivo and in vitro. Additionally, blocking ASIC1a by administration of PcTx-1 protects kidney from ischemia/reperfusion injury. Inhibition of ASIC3 by APETx2 had no significant effect on renal ischemia/reperfusion injury. Moreover, Blocking ASIC1a attenuated ischemia/reperfusion induced Ca2+ overflow, loss of mitochondrial transmembrane potential and apoptosis in HK-2 cells.

Conclusion

The results revealed that ASIC1a localized in the kidney proximal tubular and contributed to ischemia/reperfusion induced kidney injury. Consequently, targeting the ASIC1a may prove to be a novel strategy for AKI patients.

Funding

  • Clinical Revenue Support