Endotoxin-induced cardiovascular dysfunction in mice: effect of simvastatin

Abstract

Lung infections are associated with acute lung injury (ALI), systemic inflammation, and vascular events. Clinical studies suggest that statins improve health outcomes of patients with pneumonia and ALI. The mechanisms by which this occurs are unknown. The aim of this study was to determine whether statins attenuate systemic inflammation and cardiovascular dysfunction related to ALI in mice. Simvastatin (SS; 20 mg/kg) or vehicle solution was instilled intraperitoneally into mice 24 h before and again just prior to intratracheal LPS instillation (1 μg/g). These mice were then anesthetized with 2.0% isoflurane and underwent a short surgical procedure to instill LPS. Four hours later, IL-6 levels in bronchoalveolar lavage fluid and in arterial and venous serum were measured. Cardiac function was evaluated using 2-D echocardiography, and endothelial function was determined using wire myography on aortic sections. LPS induced a significant increase in serum IL-6 levels. SS reduced venous ( P = 0.040) but not arterial concentrations of IL-6 ( P = 0.112). SS improved the maximal vasodilatory response of the aorta to ACh ( P = 0.004) but not to sodium nitroprusside ( P = 1.000). SS also improved cardiac output ( P = 0.023). Vasodilatory response to ACh was impaired when aorta from untreated mice was incubated with ex vivo IL-6 ( P = 0.004), whereas in the aorta from mice pretreated with SS, the vasodilatory response did not change with IL-6 incubation ( P = 0.387). SS significantly improved LPS-induced cardiovascular dysfunction possibly by reducing systemic expression of IL-6 and its downstream signaling pathways. These findings may explain how statins improve health outcomes in patients with ALI.