Abstract

Aims:Increased connexin-43 (Cx43)-hemichannel activity exacerbates inflammation in diabetic retinopathy, effects dampened by the hemichannel blocker Tonabersat. In the kidney, tubulointerstitial inflammation and fibrosis contribute to diabetic nephropathy and develop in response to activation of multiple cell types. A role for tubuleCx43 in mediating this damage remains to be determined.
Methods:Using the Nephroseq database, transcriptomic analysis examined gene expression in kidneys with and without diabetic nephropathy. The unilateral ureteral obstruction (UUO) mouse model of advanced interstitial inflammation and fibrosis was used in the presence of a tubule- specific Cx43 (Pax8- rtTA-cre:cx43 flox Cx43−/−)knockout (n = 6– 12). Human primary proximal tubule epithelial cells (hPTECs) were cultured in 5 mM/25 mM glucose ± interleukin (IL)1β (10 ng) and tumour necrosis factor- alpha (TNFα; 10 ng) ± Tonabersat (50 μM), for 48 h(n = 3– 5). Real- time qPCR examined mRNA expression, whilst immunostaining assessed macrophage and fibroblast accumulation.
Results:Renal Cx43 mRNA expression was upregulated in diabetic nephropathy from 1.65 ± 0.42 to 2.80 ± 0.31; (p < 0.05; n = 12) as compared to control (n = 10). Tubule- specific Cx43 knockout (Cx43−/−) reduced UUO- induced increases in IL1β (25 ± 1.4; p < 0.05), IL6 (59 ± 4.9 p < 0.01) and monocyte chemoattractant protein 1 (MCP1) (52 ± 12.5; p < 0.001) expression. This paralleled reduced fibroblast accumulation (135 ± 11.4; p < 0.001) and macrophage infiltration (2.3 ± 0.1; p < 0.001). Tonabersat reduced upregulation of IL1β (57 ± 5.3%; p < 0.001), IL6 (49 ± 3.7%; p < 0.001) and MCP1 (44 ± 7.8%; p < 0.001) in glucose/cytokine treated hPTECs in vitro.
Conclusion:Renal tubule inflammation is driven by aberrant Cx43- hemichannel activity, which when blocked reduces the release of chemo- attractants, dampening immune cell recruitment and activation. These data highlight the therapeutic potential for targeting Cx43- hemichannels in diabetic nephropathy.