Chemokine expression in experimental tubulointerstitial nephritis.

Chemokines may be important in the pathogenesis of leukocyte infiltration in tubulointerstitial nephritis associated with glomerular disease. We studied the renal cortical expression of the C-C (macrophage inflammatory protein-1alpha (MIP-1alpha)), monocyte chemotactic protein-1 (MCP-1), and RANTES) and C-X-C (interferon-inducible protein-10 (IP-10), MIP-2, and cytokine-induced neutrophil chemoattractant (CINC)) chemokines 4, 6, 8, 10, 14, and 21 days after the induction of puromycin aminonucleoside (PAN) nephrosis. There was a 7- to 10-fold increase in the steady state mRNA expression of IP-10 and MCP-1 in the renal cortex of rats 6 to 8 days after the administration of PAN that declines thereafter reaching control values by day 21. The site of IP-10 and MCP-1 mRNA production was localized to intrinsic tubulointerstitial cells and not to infiltrating monocytes or macrophages. By comparison, there was a low basal expression of RANTES mRNA in the renal cortex of nephrotic rats that did not differ from those of control rats. In contrast, CINC, MIP-2, and MIP-1alpha mRNAs were not detected. Translation of MCP-1 mRNA into protein was confirmed with an ELISA. These changes in chemokine gene expression were associated with a tubulointerstitial T lymphocyte and macrophage infiltration beginning on day 6 that peaked on day 10. Administration of a neutralizing Ab to rat MCP-1 (n = 5) beginning on day 4 resulted in a 45% decline in tubulointerstitial macrophage infiltration from 8.4 +/- 1.3% to 4.6 +/- 0.4% (p < 0.001) on day 6. These data provide evidence that MCP-1, and possibly IP-10, are important in the pathogenesis of monocyte/macrophage infiltration in the tubulointerstitial nephritis associated with PAN nephrosis.