ACUTE INFLAMMATORY RESPONSE IN THE MOUSE - EXACERBATION BY IMMUNONEUTRALIZATION OF LIPOCORTIN-1

1 An immuno-neutralization strategy was employed to investigate the ro le of endogenous lipocortin 1 (LC1) in acute inflammation in the mouse . 2 Mice were treated subcutaneously with phosphate-buffered solution (PBS), non-immune sheep serum (NSS) or with one two sheep antisera rai sed against LC1 (LCS3), or its N-terminal peptide (LCPS1), three times over a period of seven days. Twenty four hours after the last injecti on several parameters of acute inflammation were measured including zy mosan-induced inflammation in 6-day-old air-pouches, zymosan-activated serum (ZAS)-induced oedema in the skin, platelet-activating factor (P AF)-induced neutrophilia and interleukin-1 beta (IL-1 beta)-induced co rticosterone (CCS) release. 3 At the 4 h time-point of the zymosan inf lamed air-pouch model, treatment with LCS3 did not modify the number o f polymorphonuclear leucocytes (PMN) recruited: 7.84 +/- 1.01 and 7.00 +/- 0.77 x 10(6) PMN per mouse for NSS- and LCS3 group, n = 7. Howeve r, several other parameters of cell activation including myeloperoxida se (MPO) and elastase activities were increased (2.2 fold, P < 0.05, a nd 6.5 fold, P < 0.05, respectively) in the lavage fluids of these mic e. Similarly, a significant increase in the amount of immunoreactive p rostaglandin E(2) (PGE(2); 1.81 fold, P < 0.05) and IL-1 alpha (2.75 f old, P < 0.05), but not tumour necrosis factor-alpha (TNF-alpha), was also observed in LCS3-treated mice. 4 The recruitment of PMN into the zymosan inflamed air-pouches by 24 h had declined substantially (4.13 +/- 0.61 x 10(6) PMN per mouse, n = 12) in the NSS-treated mice, where as high values were still measured in those treated with LCS3 (9.35 +/ - 1.20 x 10(6) PMN per mouse, n = 12, P < 0.05). A similar effect was also found following sub-chronic treatment of mice with LCPS1: 6.48 +/ - 0.10 x 10(6) PMN per mouse, vs. 2.77 +/- 1.20 and 2.64 +/- 0.49 x 10 (6) PMN per mouse for PBS- and NSS-treated groups (n = 7, P < 0.05). M ost markers of inflammation were also increased in the lavage fluids o f LCS3-treated mice: MPO and elastase showed a 2.47 fold and 17 fold i ncrease respectively (P < 0.05 in both cases); TNF-alpha showed a 11.1 fold increase (P < 0.05) whereas the IL-1 alpha levels were not signi ficantly modified. PGE(2) was still detectable in most (5 out of 7) of the mice treated with LCS3 but only in 2 out of 7 of the NSS-treated mice. 5 Intradermal injection of 50% ZAS caused a significant increase in the 2 hoedema formation in the skin of LCS3-treated mice in compar ison to PBS- and NSS-treated animals: 16.7 +/- 1.5 mu l vs. 10.8 +/- 1 .2 mu l and 10.2 +/- 1.0 mu l, respectively (n = 14 mice per group, P < 0.05). ZAS-induced oedema had subsided by 24 h in control animals bu t a residual significant amount of extravasation was still detectable in LCS3-treated mice: 4.4 +/- 0.8 mu l (P < 0.05). 6 A recently descri bed model driven by endogenous glucocorticoids is the blood neutrophil ia observed following administration of PAF. In our experimental condi tions, a single bolus of PAF (100 ng, i.v.) provoked a marked neutroph ilia at 2 h (2.43 and 2.01 fold) in NSS- and PBS-treated mice (n = 11) , respectively, which was significantly attenuated in the animals trea ted with LCS3: 1.26 fold increase in circulating PMN (n = 11, P < 0.01 vs. NSS- and PBS-groups). 7 Intraperitoneal injection of IL-1 beta (5 mu g kg(-1)) caused a marked increase in circulating plasma CCS by 2 h, to a similar extent in all experimental groups. In contrast, measur ement of CCS levels in the plasma of mice bearing air-pouches inflamed with zymosan revealed significant differences between LCS3 and NSS-tr eated mice at the 4 h time-point: 198 +/- 26 ng ml(-1) vs. 110 +/- 31 ng ml(-1) (n = 8, P < 0.05). 8 In conclusion, we found a remarkable ex acerbation of the inflammatory process with respect to both humoral an d cellular components in mice passively immunised against LC1, suggest ing the existence of a negative modulatory role for this protein in th e normal regulation of the host defence mechanism.