Microcirculatory dysfunction and reactive nitrogen species generation during sepsis-induced acute kidney injury.

摘要

The mortality rate for septic patients with acute kidney injury (AKI) is extremely high. This poor outcome suggests that current treatments for sepsis-induced AKI are largely ineffective. Understanding the mechanism of sepsis-induced AKI will likely uncover new therapeutic targets and improve therapy.; To characterize the pathogenesis of sepsis-induced AKI, intravital videomicroscopy (IVVM) was utilized in two murine models of sepsis, lipopolysaccharide administration and cecal ligation and puncture. IVVM revealed a dramatic decrease in capillary perfusion as an early event in both models of sepsis. The significant decline in functional capillaries preceded an increase in cellular stress (indicated by NAD(P)H autofluorescence) and reactive nitrogen/oxygen species (RNS/ROS) generation (indicated by rhodamine fluorescence), all occurring prior to the development of renal failure. The generation of RNS was supported by the detection of nitrotyrosine-protein adducts in the kidney using immunohistochemistry. Additionally IVVM revealed relationships between dysfunctional capillaries, redox stress and RNS/ROS generation in the capillary/tubular microenvironment.; The role of inducible nitric oxide synthase (iNOS) in these models was investigated using the iNOS inhibitor L-N6-(1-iminoethyl)-lysine (L-NIL; 3mg/kg, i.p.). L-NIL blocked the increase in rhodamine fluorescence, the increase in NAD(P)H autofluorescence, and the capillary perfusion defects in both models of sepsis. Additionally, L-NIL protected the mice from renal failure. These results suggest that iNOS-derived NO acts as an important source for RNS and contributes to the peritubular capillary perfusion defects and tubular injury during sepsis. The ability of the superoxide/peroxynitrite scavenger, MnTDE-2-ImP5+ (10 mg/kg, i.p.) to reverse the capillary perfusion defects, attenuate cellular stress, prevent RNS generation, and preserve renal function provided additional support for the role of RNS.; In summary, this dissertation uncovered a renal microcirculatory defect following septic challenge that may regulate oxidant generation in the renal microenvironment. Additionally, pharmacological interventions in two animal models of sepsis identified iNOS and RNS/ROS as potentially important targets for developing novel therapeutics for the treatment of sepsis.