Cobalt Chloride Attenuates Oxidative Stress and Inflammation through NF-kappaB Inhibition in Human Renal Proximal Tubular Epithelial Cells

ABSTRACT

We evaluated the effect of cobalt chloride (CoCl2) on TNF-alpha and IFN-gamma-induced-inflammation and reactive oxygen species (ROS) in renal tubular epithelial cells (HK-2 cells). We treated HK-2 cells with CoCl2 before the administration of TNF-alpha/IFN-gamma. To regulate hemeoxygenase-1 (HO-1) expression, the cells were treated CoCl2 or HO-1 siRNA. CoCl2 reduced the generation of ROS induced by TNF-alpha/IFN-gamma. TNF-alpha/IFN-gamma-treated-cells showed an increase in the nuclear translocation of phosphorylated NF-kappaBp65 protein, the DNA-binding activity of NF-kappaBp50 and NF-kappaB transcriptional activity and a decrease in IkappaBalpha protein expression. These changes were restored by CoCl2. We noted an intense increase in monocyte chemoattractant protein-1 (MCP-1) and regulated on activation normal T cell expressed and secreted (RANTES) production in TNF-alpha/IFN-gamma-treated cells. We demonstrated that this effect was mediated through NF-kappaB signaling because an NF-kappaB inhibitor significantly reduced MCP-1 and RANTES production. CoCl2 effectively reduced MCP-1 and RANTES production. The expression of HO-1 was increased by CoCl2 and decreased by HO-1 siRNA. However, knockdown of HO-1 by RNA interference did not affect MCP-1 or RANTES production. We suggest that CoCl2 has a protective effect on TNF-alpha/IFN-gamma-induced inflammation through the inhibition of NF-kappaB and ROS in HK-2 cells. However, CoCl2 appears to act in an HO-1-independent manner.