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

Abstract.

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 < 0.01). 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 0h: 3.78 ± 0.25 %; LPS/AG 8 h: 5.34 ± 0.3 %; LPS/AG 0 + 8 h: 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/mm², 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/mm²).¶Conclusions: In EIU, administration of AG or L-NAME causes enhanced leukocyte rolling in the early inflammatory response. However, firm adhesion of leukocytes to the vascular endothelium decreases and this effect prevails, ameliorating leukocyte infiltration.