Modulation of leukocyte-endothelium interaction by nitric oxide synthase inhibitors: effects on leukocyte adhesion in endotoxin-induced uveitis

Objective and design: To examine the effects of the nitric oxide synthase (NOS) inhibitors aminoguanidine (AG) and L-NAME on leukocyte adhesion in endotoxin-induced uveitis (EIU). Material: Uveitis was induced in Lewis rats (n = 124) by LPS injection (Salmonella typhimurium). Treatment: Rats either (1) did not receive any LPS or other treatments (controls), received (2) only subcutaneous saline injections with LPS administration, (3) a single s.c. dose of AG (100 mg/kg body weight) at the time of LPS administration, (4) a single s. c. injection of AG 8 h after LPS injection, (5) s.c. injections of AG at the time of LPS administration and 8 h after LPS injection or (6) received a single dose of L-NAME (75 mg/kg body weight) at the time of LPS administration. Methods: Intravital microscopy (IVM) of iris vessels was performed at 2, 4, 8, 16, 24 and 48 h after endotoxin injection. Aqueous humor analysis for protein concentration and cell count was performed after IVM. Results: At 2 h after the induction of uveitis, significantly more rolling leukocytes were detected in the AG and L-NAME-treated group than in untreated EIU (4.8 +/- 0.31 and 9.83 +/- 0.64 vs. 2.85 +/- 0.37 %, mean SEM, p < 0.0 1). However, at 16 h the percentage of rolling leukocytes was significantly reduced in all groups which had received AG (LPS: 8.08 +/- 0.37 %; LPS/AG 0 h: 3.78 +/- 0.25 %; LPS/AG 8 h: 5.34 +/- 0.3%; LPS/AG 0+8h: 3.86 +/- 0.31%). L-NAME enhanced leukocyte rolling even at 24 h after LPS (12.38 +/- 0.64%). Early treatment of EIU with AG significantly reduced the number of sticking leukocytes at 4, 8 and 24 h (306 +/- 13 vs. 571 +/- 41, 228 +/- 12 vs. 345 +/- 19 and 240 +/- 14 vs. 469 +/- 23 cells/mm(2), respectively). L-NAME inhibited LPS-induced sticking of leukocytes at all observed time points and this effect was most pronounced at 24 h (147 +/- 10 vs. 469 23 cells/mm(2)). Conclusions: In EIU, administration of AG or L-NAME causes enhanced leukocyte rolling in the early inflammatory leukocyte infiltration response. However, firm adhesion of leukocytes to the vascular endothelium decreases and this effect prevails, ameliorating leukocyte infiltration.