Role of the monocyte chemoattractant protein-1/C-C chemokine receptor 2 signaling pathway in transient receptor potential vanilloid type 1 ablation-induced renal injury in salt-sensitive hypertension

Our recent studies indicate that the transient receptor potential vanilloid type 1 (TRPV1) channel may act as a potential regulator of monocyte/macrophage recruitment to reduce renal injury in salt-sensitive hypertension. This study tests the hypothesis that deletion of TRPV1 exaggerates salt-sensitive hypertension-induced renal injury due to enhanced inflammatory responses via monocyte chemoattractant protein-1 (MCP-1)/C-C chemokine receptor 2 (CCR2)-dependent pathways. Wild type (WT) and TRPV1-null mutant (TRPV1^−/−) mice were subjected to uninephrectomy and deoxycorticosterone acetate (DOCA)-salt treatment for four weeks with or without the selective CCR2 antagonist, RS504393. DOCA-salt treatment increased systolic blood pressure (SBP) to the same degree in both strains, but increased urinary excretion of albumin and 8-isoprostane and decreased creatinine clearance with greater magnitude in TRPV1^−/− mice compared to WT mice. DOCA-salt treatment also caused renal glomerulosclerosis, tubulointerstitial injury, collagen deposition, monocyte/macrophage infiltration, proinflammatory cytokine and chemokine production, and NF-κB activation in greater degree in TRPV1^−/− mice compared to WT mice. Blockade of the CCR2 with RS504393 (4 mg/kg/day) had no effect on SBP in DOCA-salt-treated WT or TRPV1^−/− mice compared to their respective controls. However, treatment with RS504393 ameliorated renal dysfunction and morphological damage, and prevented the increase in monocyte/macrophage infiltration, cytokine/chemokine production, and NF-κB activity in both DOCA-salt hypertensive strains with a greater effect in DOCA-salt-treated TRPV1^−/− mice compared to DOCA-salt-treated WT mice. No differences in CCR2 protein expression in kidney were found between DOCA-salt-treated WT and TRPV1^−/− mice with or without RS504393 treatment. Our studies for the first time indicate that deletion of TRPV1 aggravated renal injury in salt-sensitive hypertension via enhancing MCP-1/CCR2 signaling-dependent inflammatory responses.