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Protective Effect of Tempol on Acute Kidney Injury Through PI3K/Akt/Nrf2 Signaling Pathway
Gensheng Zhang1, Qiaoling Wang, Qin Zhou
1Department of Physiology, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
Background/Aims:
Tempol is a protective antioxidant against ischemic injury in many animal models. The molecular mechanisms are not well understood. Nuclear factor erythroid 2-related factor (Nrf2) is a master transcription factor during oxidative stress, which is enhanced by activation of protein kinase C (PKC) pathway. Another factor, tubular epithelial apoptosis, is mediated by activation of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, Akt) signaling pathway during renal ischemic injury. We tested the hypothesis that tempol activates PKC or PI3K/Akt/Nrf2 pathways to transcribe many genes that coordinate endogenous antioxidant defense.
Methods:
The right renal pedicle was clamped for 45 minutes and the left kidney was removed to study renal ischemia/reperfusion (I/R) injury in C57BL/6 mice. The response was assessed from serum parameters, renal morphology and renal expression of PKC, phosphorylated-PKC (p-PKC), Nrf2, heme oxygenase-1 (HO-1), Akt, phosphorylated-Akt (p-Akt), pro-caspase-3 and cleaved caspase-3 in groups of sham and I/R mice given vehicle, or tempol (50 or 100 mg/kg, intraperitoneal injection).
Results:
The serum malondialdehyde (MDA, marker of reactive oxygen species) doubled and the BUN and creatinine increased 5- to 10-fold after I/R injury. Tempol (50 or 100 mg/kg) prevented the increases in MDA but only tempol (50 mg/kg) lessened the increases in BUN and creatinine and moderated the acute tubular necrosis. I/R did not change expression of PKC or p-PKC but reduced renal expression of Nrf2, p-Akt, HO-1 and pro-caspase-3 and increased cleaved caspase-3. Tempol (50 mg/kg) prevented these changes produced by I/R whereas tempol (100 mg/kg) had lesser or inconsistent effects.
Conclusion:
Tempol (50 mg/kg) prevents lipid peroxidation and attenuates renal damage after I/R injury. The beneficial pathway apparently is not dependent on upregulation or phosphorylation of PKC, at lower tempol doses, does implicate upregulation of Akt with expression of Nrf2 that could account for the increase in the antioxidant gene HO-1 and a reduction in the cleavage of the cellular damage marker pro-caspase-3.
Insights
Tempol (50 mg/kg) protects against kidney damage from ischemia/reperfusion injury by reducing oxidative stress. This antioxidant activates the PI3K/Akt/Nrf2 pathway, increasing antioxidant gene expression and decreasing cellular damage.
Area of Science:
- Nephrology
- Biochemistry
- Molecular Biology
Background:
- Ischemic injury to the kidneys can cause significant damage.
- Tempol is an antioxidant with protective effects in animal models of ischemic injury.
- The precise molecular mechanisms underlying Tempol's protective effects, particularly its interaction with oxidative stress pathways like Nrf2 and PI3K/Akt, require further elucidation.
Purpose of the Study:
- To investigate the molecular mechanisms by which Tempol protects against renal ischemia/reperfusion (I/R) injury.
- To test the hypothesis that Tempol activates protein kinase C (PKC) or phosphoinositide 3-kinase (PI3K)/Akt/Nuclear factor erythroid 2-related factor (Nrf2) pathways.
- To determine if Tempol upregulates endogenous antioxidant defense genes.
Main Methods:
- Renal I/R injury was induced in C57BL/6 mice by clamping the right renal pedicle.
- Mice were treated with vehicle or Tempol (50 or 100 mg/kg).
- Renal function, morphology, and expression of key proteins (PKC, p-PKC, Nrf2, HO-1, Akt, p-Akt, caspase-3) were assessed.
Main Results:
- I/R injury significantly increased serum markers of oxidative stress (MDA) and kidney damage (BUN, creatinine).
- Tempol (50 mg/kg) attenuated these increases and moderated acute tubular necrosis.
- I/R reduced renal Nrf2, p-Akt, and HO-1 expression and increased cleaved caspase-3; Tempol (50 mg/kg) reversed these changes.
Conclusions:
- Tempol at 50 mg/kg effectively prevents lipid peroxidation and mitigates renal damage following I/R injury.
- The protective mechanism involves the PI3K/Akt pathway, leading to Nrf2 activation and increased expression of the antioxidant gene HO-1.
- This pathway also contributes to reduced pro-caspase-3 cleavage, indicating decreased cellular damage.
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