Regulation of tubular cell MCP-1 production by intracellular ions: a role for sodium and calcium.

Proximal tubule cells (PTC) in chronic renal disease produce chemokines which cause renal interstitial inflammation, and also transport more Na+ than normal. To investigate whether these two events might be related, monocyte chemoattractant protein-1 (MCP-1) production was examined in rat PTC in primary culture. Amiloride reduced, while ouabain increased levels of MCP-1 mRNA and protein. Amiloride reduced MCP-1 in cells stimulated with ouabain, lipopolysaccharide (LPS) or albumin. Intracellular Na+ rose with ouabain, but not LPS or albumin. Effects of amiloride, ouabain, LPS and albumin were abrogated by sodium-free but not chloride-free culture medium, and were not explained by changes in intracellular pH. Intracellular Ca2+ rose with ouabain, LPS or albumin and sodium-free medium. BAPTA-AM reduced intracellular Ca2+ and MCP-1 mRNA levels in unstimulated cells, and cells stimulated with ouabain, LPS or albumin. Thus, amiloride and ouabain may alter tubular cell MCP-1 by changing intracellular Na+, with secondary changes in intracellular Ca2+, whereas stimulation by LPS and albumin may involve Ca2+ directly.