Inhibition of NOX2 Prevents Impairment of Cardiovascular Response and Inflammatory Tissue Injury Mediated by Nitrosative/ Oxidative Stress in the Lipopolysaccharide-Induced Septic Shock Model in Rats.

INTRODUCTION It is unknown whether inhibition of nicotinamide adenine dinucleotide phosphate oxidase (NOX) 2 has protective effects against the impaired cardiovascular response and inflammatory tissue injury mediated by nitrosative/ oxidative stress in bacterial septic shock. Therefore, using the NOX2 inhibitor NOX2ds-stat, the effects of NOX2 inhibition on cardiovascular response were explored in a rat septic shock model induced by lipopolysaccharide (LPS), in relation to cardiovascular/renal inflammatory tissue injury.

Methods

Mean arterial pressure and heart rate were obtained non-invasively using a tail cuff device in rats before and at 1, 2, 3, and 4 hours after injection of saline or LPS. The rats were treated with NOX2ds-stat (0.1, 0.3, or 1 mg/kg) 1 hour following saline or LPS injection. The diazotization method was used to measure nitrite levels in the sera and cardiovascular/renal tissues. The changes in tissue expression of proteins and/or their phosphorylation status related to nuclear factor (NF)-κB/inducible nitric oxide synthase (iNOS)- and NOX2-mediated nitrosative/oxidative stress, as well as peroxisome proliferator-activated receptor (PPAR) α/β/γ, were assessed by the immunoblotting method. Using hematoxylin and eosin staining, histopathological changes in the tissues were evaluated.

Results

A decrease in blood pressure by 48 mmHg and an increase in heart rate by 112 bpm were observed 4 hours after LPS injection. While the expression/ phosphorylation of gp91phox, p47phox, 3-nitrotyrosine, NF-κB p65, iNOS, Vasodilator- Stimulated Phosphoprotein (VASP), and interleukin (IL)-1β proteins was enhanced in the thoracic aorta, renal artery, heart, and kidney tissues, in addition to the levels of nitrite in the sera and tissues of LPS-injected animals, the expression/phosphorylation of endothelial nitric oxide synthase (eNOS), PPARα, PPARβ, and PPARγ was decreased. The LPS-induced changes were ameliorated by NOX2ds-stat (1 mg/kg). NOX2ds-stat also attenuated the LPS-induced increase in scores reflecting inflammatory tissue injury.

Discussion

These findings indicate that selective inhibition of NOX2 prevents both impairment of cardiovascular response and cardiovascular/renal tissue injury, presumably through suppression of NF-κB/iNOS- and NOX2-mediated nitrosative/ oxidative stress associated with increased expression of anti-inflammatory PPARα/β/γ in the rat septic shock model induced by bacterial LPS. Further studies are required to determine whether NOX2 inhibition benefits patients with septic shock.

Conclusion

This study provides novel insights into the pathophysiological mechanisms of septic shock and highlights the potential therapeutic value of targeting NOX2 to improve cardiovascular response and inflammatory tissue injury.