RESUMEN
OBJECTIVE: To investigate the role of sub-transform macrophage in ischemia/reperfusion renal injury in rats, as well as under-lying mechanisms. METHODS: Thirty male Sprague-Dawley rats were randomly divided into ischemia/reperfusion (IRI, n=24, renal artery was occluded for 45 min) group and sham-operation (Sham, n=6) group. The kidneys in IRI group were collected at 0, 6, 24 and 72 h after operation (6 rats for each time point). The injury of the kidney was detected with HE staining. Immunohistochemistry staining was performed to evaluate the expression of proliferating cell nuclear antigen (PCNA). Real-time PCR was used to detect the mRNA expression of macrophage migration inhibitory factor (MIF). Moreover, the expression and location of MIF, monocyte chemoattractant protein-1 (MCP-1) and macrophage marker CD68 were examined by immunofluorescence staining. Most importantly, the distribution of macrophage subtypes M1 and M2 was analyzed by flow cytometry. RESULTS: The worst pathologic damage of the renal tissues, as well as infiltration of inflammatory cells, was observed at 24 h after operation in IRI rats, with obvious recovery afterwards. Immunohistochemistry staining showed that the expression of PCNA was significantly increased after the ischemia/reperfusion, peaking at 6 h and reducing at 72 h after operation. Compared with sham group, the levels of MIF at mRNA and protein levels were both significantly increased after the ischemia/reperfusion, while the expression of MCP-1 was peaked at 6 h and decreased afterwards. Moreover, the expression of CD68-positive macrophages were significantly increased in IRI rats, with peaking at 24 h and reducing at 72 h. Furthermore, after 6 h of reperfusion, the percentage of M1 macrophages reached the peak, and thereafter the relative expression of M1 and M2 was reduced and increased, respectively. CONCLUSIONS: In the early phase of ischemia/per-fu sion renal injury, M1 macrophage results in renal damage, and afterwards the M2 macrophage is increased and repairs the renal damage by improving the cell proliferation.
