Severe
hemorrhage can lead to global
ischemia and
hemorrhagic shock (HS), resulting in
multiple organ failure (MOF) and death. Restoration of blood flow and re-oxygenation is associated with an exacerbation of tissue injury and inflammatory response. The
neuronal nitric oxide synthase (nNOS) has been implicated in vascular collapse and systemic
inflammation of
septic shock; however, the role of nNOS in HS is poorly understood. The aim of this study was to evaluate the role of nNOS in the MOF associated with HS.Rats were subjected to HS under
anesthesia. Mean arterial pressure was reduced to 30 mmHg for 90 min, followed by
resuscitation with shed blood. Rats were randomly treated with two chemically distinct nNOS inhibitors [
ARL 17477 (1 mg/kg) and 7-nitroindazol (5 mg/kg)] or vehicle upon
resuscitation. Four hours later, parameters of organ injury and dysfunction were assessed.HS was associated with MOF development. Inhibition of nNOS activity at
resuscitation protected rats against the MOF and vascular dysfunction. In addition, treatment of HS rats with nNOS inhibitors attenuated neutrophil infiltration into target organs and decreased the activation of NF-κB, iNOS expression, NO production, and nitrosylation of
proteins. Furthermore, nNOS inhibition also reduced the levels of pro-inflammatory
cytokines TNF-α and
IL-6 in HS rats.In conclusion, two distinct inhibitors of nNOS activity reduced the MOF, vascular dysfunction, and the systemic
inflammation associated with HS. Thus, nNOS inhibitors may be useful as an adjunct
therapy before fluids and blood administration in HS patients to avoid the MOF associated with
reperfusion injury during
resuscitation.