Impaired vascular function in sepsis-surviving rats mediated by oxidative stress and Rho-Kinase pathway

We investigated long-lasting changes in endothelial and vascular function in adult rat survivors of severe sepsis induced by cecal ligation and puncture (CLP) model. For this, male Wistar rats (200-350g) had their cecum punctured once (non-transfixing hole) with a 14-gauge needle. Performed in this way, a mortality rate around 30% was achieved in the first 72h. The survivors, together with age-matched control rats (not subjected to CLP), were maintained in our holding room for 60 days (S60 group) and had the descending thoracic aorta processed for functional, histological, biochemical or molecular analyses. Endothelium-intact aortic rings obtained from sepsis-surviving S60 group displayed increased angiotensin II-induced contraction, accompanied by decreased activity of the endogenous superoxide dismutase, augmented reactive oxygen species generation, and increased levels of tyrosine nitration compared with vessels from control group. The superoxide scavengers superoxide dismutase and tempol, and the antioxidant apocynin, were able to avoid this enhanced contractility to angiotensin II in aortic rings from the S60 group. In addition, aortic rings from the S60 group presented reduced sensitivity to Y-27632, a Rho-kinase (ROCK) inhibitor. Immunoblot analyses revealed augmented RhoA and ROCK II, and high levels of phosphorylation of myosin phosphatase target subunit 1 in vessels from S60 rats. In conclusion, aortic rings from sepsis-surviving rats display endothelial dysfunction mediated by the increased production of reactive oxygen species, which in turn reduces the bioavailability of nitric oxide and increases the formation of peroxynitrite, and enhances RhoA-ROCK-mediated calcium sensitization, leading to augmented contractile responses to angiotensin II. Notably, this is the first study demonstrating long-term dysfunction in the vasculature of sepsis-surviving rats, which take place or remain beyond the acute septic insult.