Neuronal Nitric Oxide Synthase alters inflammatory response after endotoxin challenge (96.16)

Abstract

Abstract We have recently shown that mice deficient in the neuronal isoform of NOS (nNOS−/−, KO) have higher mortality compared to wild type (nNOS +/+, WT) in a polymicrobial sepsis model. We sought to determine what effect the genetic deficiency of nNOS had on LPS-induced expression of cytokines. KO and WT mice were injected with LPS (i.p.) and sacrificed 6 or 24 h later. Peritoneal lavage cells (PLCs) were counted and profiled for cell type. RNA from spleens and PLCs was isolated and the relative expression of cytokines was determined by real-time PCR. After LPS challenge, KO mice had higher mortality (100% vs. 40% at 40 mg/kg), higher number of PLCs at 6 and 24h, higher proportion of macrophages at 6h and higher neutrophils counts at 24h compared to WT. In splenocytes, relative expression of proinflammatory cytokines at 6 hours was lower in KO (TNFα=0.18, IL1β=0.05) compared to WT mice (TNFα= 12.1, IL1β =2.9, p ≤ 0.002). Conversely in PLCs, KO mice had significantly higher IL-1β mRNA levels compared to WT (251 vs. 0.64, p ≤ 0.008). These results suggest that KO mice have altered neutrophil trafficking to peritoneum, do not mount a global inflammatory immune response, and exhibit aberrant local immune response after LPS challenge. These differences may explain increased mortality in knockout mice after LPS challenge and polymicrobial sepsis and indicate that nNOS has an important role in immune response during sepsis.