Inhibitors of nitric oxide synthase attenuate human neutrophil chemotaxis in vitro.

Products released through the L-arginine/nitric oxide biosynthetic pathway regulate soluble guanyl cyclase activity, which in turn modulates polymorphonuclear leukocyte chemotaxis. We hypothesized that inhibitors of nitric oxide synthase attenuate polymorphonuclear leukocyte chemotaxis in vitro. To test this hypothesis, unstimulated polymorphonuclear leukocytes were pretreated with buffer or the nitric oxide synthase inhibitors NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine methyl ester, and L-canavanine before being exposed to three structurally unrelated chemoattractants, N-formyl-methionyl-leucyl-phenylalanine, C5a des arginine, and leukotriene B4. Polymorphonuclear leukocyte chemotaxis was quantified with a modified blind-well chamber technique. We found that L-NMMA and L-canavanine but not NG-nitro-L-arginine significantly attenuated polymorphonuclear leukocyte chemotaxis (p < 0.05). L-Arginine but not D-arginine, the nitric oxide donor sodium nitroprusside, and 8-bromo-cyclic guanosine monophosphate restored polymorphonuclear leukocyte chemotaxis attenuated by L-NMMA. Chemotaxis of polymorphonuclear leukocytes primed with lipopolysaccharide (Escherichia coli 0127:B8) or phorbol-13-butyrate was also significantly attenuated by pretreatment with L-NMMA and L-canavanine. Consistent with these observations, intracellular concentrations of cyclic guanosine monophosphate in polymorphonuclear leukocytes was decreased by L-NMMA during exposure to N-formyl-methionyl-leucyl-phenylalanine. These data indicate that nitric oxide synthase inhibitors attenuate chemotaxis of unstimulated and primed polymorphonuclear leukocytes in vitro. We suggest that the L-arginine/nitric oxide biosynthetic pathway plays an important role in regulating polymorphonuclear leukocyte emigration in vivo.

Nitric oxide synthase inhibitors attenuate human monocyte chemotaxis in vitro.

Nitric oxide synthase (NOS) inhibitors have been shown to modulate neutrophil migration. We hypothesized that the NOS inhibitors NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine methyl ester (L-NAME), and L-canavanine (L-CAN) also modulate human peripheral blood monocyte chemotaxis. To test this hypothesis, monocyte chemotaxis toward formylmethionylleucyl-phenylalanine (fMLP) was assessed using a modified blindwell chemotaxis chamber technique. L-NMMA and L-NAME, but not D-NMMA or L-CAN, significantly attenuated fMLP-induced monocyte chemotaxis (P < .05). L-Arginine and sodium nitroprusside, but not D-arginine, reversed NOS inhibitor-induced responses. Dibutryl cyclic guanyl monophosphate (cGMP) attenuated the inhibitory effects of L-NMMA on monocyte chemotaxis (P < .05). Finally, fMLP increased cGMP generation by monocytes, which was significantly attenuated by L-NMMA (P < .05). These data indicate that the L-arginine/NO biosynthetic pathway regulates human monocyte chemotaxis in vitro.