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Enhanced MCP-1 expression during ischemia/reperfusion injury is mediated by oxidative stress and NF-kappaB
Fion L Sung1, Tong Y Zhu, Kathy K W Au-Yeung
1Department of Pharmacology, Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong, PR China.
Background:
Renal ischemia/reperfusion injury is a major cause of acute renal failure in both native kidneys and renal allografts. One important feature of such injury is monocyte/macrophage infiltration into the renal tissue. The infiltration of monocytes/macrophages can be induced by chemotactic factors produced by renal cells. Monocyte chemoattractant protein-1 (MCP-1) is a potent chemoattractant protein for monocyte recruitment. The objective of the present study was to investigate mechanisms of elevated MCP-1 expression in rat kidney during ischemia/reperfusion injury.
Methods:
The left kidney was subjected to one hour of ischemia followed by reperfusion for various time periods. The expression of MCP-1 mRNA was determined by nuclease protection assay and MCP-1 protein was identified by immunohistochemistry. Activation of a nuclear factor-kappa B (NF-kappaB) was determined by electrophoretic mobility shift assay and the level of lipid peroxides in the kidney was measured.
Results:
There was a significant increase in MCP-1 expression in the ischemia/reperfusion kidney 2 hours after reperfusion (210% of the control). This increase was accompanied by activation of NF-kappaB, suggesting that this transcription factor might be involved in the event. The number of monocytes was significantly elevated in the kidney 3 days after ischemia/reperfusion. Pretreatment of rats with NF-kappaB inhibitors not only prevented NF-kappaB activation induced by ischemia/reperfusion, but also inhibited MCP-1 mRNA expression. Further analysis revealed that oxidative stress and increased IkappaB-alpha phosphorylation might be an underlying mechanism for NF-kappaB activation and subsequent MCP-1 mRNA expression in the ischemia/reperfusion kidney.
Conclusion:
The present study clearly demonstrates that enhanced MCP-1 expression in rat kidney during ischemia/reperfusion injury is mediated by NF-kappaB activation and oxidative stress. Elevated MCP-1 expression might be responsible for increased monocyte infiltration in the injured kidney.