Objective To investigate the role and mechanism of aberrant expression of CCL7 gene in rat renal ischaemia-reperfusion injury (IRI).

Methods Twelve SD rats were randomly divided into two groups: the IRI group (n=6) and the sham-operated group (Sham group, n=6). In the IRI group, non-traumatic microvascular clamps were employed to induce renal ischemia for 30 minutes. In the Sham group, the kidneys were exposed without clamping. Renal tissues were collected, and serum creatinine and blood urea nitrogen levels were measured to evaluate renal function. PAS staining was performed to assess histopathological changes in kidney tissues. Immunohistochemistry was performed to assess variations in the expression of CCL7 and α-SMA genes. Western boltting was used to gauge the expression levels of CCL7 in renal tissues. HK-2 cell hypoxia-reoxygenation (H/R) model was established and divided into Control group and H/R group. Western blotting was applied to assess the relative expression of CCL7, Caspase-3, and Kim-1 proteins. HK-2 cells were transfected with either si-NC or si-CCL7, and Western blotting was used to detect the relative protein expression levels of Caspase-3, and Kim-1. After intraperitoneal injection of Bindarit, Western blotting was performed to detect the relative protein expression levels of Caspase-3 and Kim-1 in renal tissues from three groups of rats: PBS+Sham, PBS+IRI, and Bindarit+IRI groups.

Results Serum creatinine and blood urea nitrogen levels were significantly elevated in the IRI group compared with the Sham group (P < 0.01), accompanied by severe tubular epithelial cell shedding and necrosis. Compared to the Sham group, the significant increase in the relative expression of CCL7 protein in rat tissues (P < 0.01). Post H/R, expression levels of CCL7, Caspase-3, and Kim-1 proteins were significantly increased than Control group (P < 0.05 to P < 0.01). Reduced CCL7 protein expression was observed in si-CCL7-transfected cells compared to si-NC cells (P < 0.01). The relative expression levels of Caspase-3 and Kim-1 proteins were compared among the si-NC+Control group, si-NC+H/R group, and si-CCL7+H/R group, cells in the si-NC+H/R group demonstrated elevated Caspase-3 and Kim-1 expression level compared to si-NC+Control cells (P < 0.05), while the si-CCL7+H/R group exhibited reduced levels in both parameters compared to the si-NC+H/R group (P < 0.05). After intraperitoneal injection of Bindarit, cells in the PBS+IRI group demonstrated elevated Caspase-3 and Kim-1 expression level compared to PBS+Sham cells (P < 0.05), while the Bindarit+IRI group exhibited reduced levels in both parameters compared to the PBS+IRI group (P < 0.05).

Conclusions CCL7 is markedly upregulated during renal IRI. Silencing of CCL7 expression attenuates apoptosis in renal tubular epithelial cells under H/R conditions. Pharmacological inhibition of CCL7 by Bindarit confers renal protection in the IRI model.