Neuronal nitric oxide synthase (NOS) regulates leukocyte‐endothelial cell interactions in endothelial NOS deficient mice

Abstract

1 The present study was designed to examine the possible role of neuronal nitric oxide synthase (nNOS) in regulation of leukocyte ± endothelial cell interactions in the absence of endothelial nitric oxide synthase (eNOS), using intravital microscopy of the cremasteric microcirculation of eNOS 7/7 mice. 2 Baseline leukocyte rolling and adhesion revealed no di erences between wild-type and eNOS 7/7 mice in either the cremasteric or intestinal microcirculations. 3 Superfusion with L-NAME (100 mM) caused a progressive and signi®cant increase in leukocyte adhesion in both wild-type and eNOS 7/7 mice, without detecting di erences between the two strains of mice. 4 Superfusion with 7-nitroindazole (100 mM), a selective inhibitor of nNOS, had no e ect on leukocyte adhesion in wild-type animals. However, it increased leukocyte adhesion signi®cantly in eNOS 7/7 mice, which was reversed by systemic L-arginine pre-administration. 5 Stimulation of the microvasculature with H 2 O 2 (100 mM) induced a transient elevation in leukocyte rolling in wild-type mice. Conversely, the e ect persisted during the entire 60 min of experimental protocol in eNOS 7/7 mice either with or without 7-nitroindazole. 6 Semi-quantitative analysis by RT ± PCR of the mRNA for nNOS levels in eNOS 7/7 and wildtype animals, showed increased expression of nNOS in both brain and skeletal muscle of eNOS 7/7 mice. 7 In conclusion, we have demonstrated that leukocyte-endothelial cell interactions are predominantly modulated by eNOS isoform in postcapillary venules of normal mice, whereas nNOS appears to assume the same role in eNOS 7/7 mice. Interestingly, unlike eNOS there was insu cient NO produced by nNOS to overcome leukocyte recruitment elicited by oxidative stress, suggesting that nNOS cannot completely compensate for eNOS.

Antiphospholipid antibodies promote leukocyte–endothelial cell adhesion and thrombosis in mice by antagonizing eNOS via β2GPI and apoER2

“…Under the control conditions present with NHIgG treatment, leukocyte adhesion (still images are shown in Figure 6, A and B) and wbc velocity ( Figure 6C) were similar in eNOS +/+ and eNOS -/-mice. Despite the difference in endothelium-derived NO in these mice, similar leukocyte-endothelial cell adhesion has been observed in prior studies at baseline, and this has been attributed to compensatory mechanisms (41). As expected, aPL administration to eNOS +/+ mice caused an increase in leukocyte-endothelial cell interaction ( Figure 6A), and an associated decrease in leukocyte velocity ( Figure 6C).…”

“…The velocity of leukocyte rolling was calculated by measuring the distance leukocytes traveled between frames. It should be noted that velocity was found to be similar in control (NHIgG-treated) eNOS +/+ versus eNOS -/-mice, as has been observed for baseline adhesion to eNOS +/+ versus eNOS -/-endothelium in some but not all prior reports (41,73,74). Thrombus formation was assessed as described previously (47,75).…”

Complementary inhibition of cerebral aneurysm formation by eNOS and nNOS

“…8,26 Recent studies have indicated that nNOS can compensate for the function of eNOS in eNOS À/À mice. For example, the expression of nNOS is upregulated in the brain, 28 the muscles 28 and the smooth muscle cells of coronary arteries 29 of eNOS À/À mice at the protein level. The distribution of nNOS in the retina of eNOS À/À mice is stronger in the vasculature of deep layer, where eNOS is abundantly expressed in wild-type mice than in wild-type mice.…”

Characterization of the non‐adrenergic/non‐cholinergic response to perivascular nerve stimulation in the double‐perfused mesenteric bed of the mouse

“…In support of this concept, Loesch and Burnstock (1998) have immunohistologically identified both nNOS and eNOS in the cytoplasm of endothelial cells. Sanz et al (2001) have subsequently reported that nNOS is importantly involved in leukocyte-endothelial cells interactions in eNOS KO mice.…”