Analysis of the temporal expression of chemokines and chemokine receptors during experimental granulomatous inflammation:: role and expression of MIP-1α and MCP-1

1 Chemokine expression and function was monitored in an experimental model of granulomatous tissue formation after injection of croton oil in complete Freund's adjuvant (CO/CFA) into mouse dorsal air-pouches up to 28 days. 2 In the first week, mast cell degranulation and leukocyte influx (mononuclear cell, MNC, and polymorphonuclear cell, PMN) were associated with CXCR2, KC and macrophage inflammatory protein (MIP)-2 mRNA expression, as determined by TaqMan (R) reverse transcriptase-polymerase chain reaction. KC (similar to 400 pg mg protein(-1), n = 12) and MIP-2 (similar to 800 pg mg protein(-1), n = 12) proteins peaked at day 7, together with myeloperoxidase (MPO) activity. Highest MIP-1 alpha (>1 ng mg protein(-1), n = 12) levels were measured at day 3. 3 After day 7, a gradual increase in CCR2 and CCR5 mRNA, monocyte chemoattractant protein (MCP)-1 mRNA and protein expression was measured. MCP-1 protein peaked at day 21 (similar to 150 pg mg protein (1), n = 12) and was predominantly expressed by mast cells. A gradual increase in N-acetyl-beta -D-glucosaminidase (NAG) activity (maximal at 28 days) was also measured. 4 An antiserum against MIP-1 alpha did not modify the inflammatory response measured at day 7 (except for a 50% reduction in MIP-1 alpha levels), but provoked a significant increase in MPO, NAG and MCP-1 levels as measured at day 21 (n=6, P <0.05). An antiserum to MCP-1 reduced NAG activity at day 21 but increased MPO activity values (n=8, P <0.05). 5 In conclusion, we have shown that CO/CFA initiates a complex inflammatory reaction in which initial expression of MIP-1 alpha serves a protective role whereas delayed expression of MCP-1 seems to have a genuine pro-inflammatory role.