Early enhanced local neutrophil recruitment in peritonitis-induced sepsis improves bacterial clearance and survival.

Neutrophils are critical for the rapid eradication of bacterial pathogens, but they also contribute to the development of multiple organ failure in sepsis. We hypothesized that increasing early recruitment of neutrophils to the focus of infection will increase bacterial clearance and improve survival. Sepsis was induced in mice, using cecal ligation and puncture (CLP); blood samples were collected at 6 and 24 h; and survival was followed for 28 d. In separate experiments, peritoneal bacteria and inflammatory cells were measured. Septic mice predicted to die based on IL-6 levels (Die-P) had higher concentrations of CXCL1 and CXCL2 in the peritoneum and plasma compared with those predicted to live (Live-P). At 6 h, Live-P and Die-P had equivalent numbers of peritoneal neutrophils and bacteria. In Die-P mice the number of peritoneal bacteria increased between 6 and 24 h post-CLP, whereas in Live-P it decreased. The i.p. injection of CXCL1 and CXCL2 in naive mice resulted in local neutrophil recruitment. When given immediately after CLP, CXC chemokines increased peritoneal neutrophil recruitment at 6 h after CLP. This early increase in neutrophils induced by exogenous chemokines resulted in significantly fewer peritoneal bacteria by 24 h [CFU (log) = 6.04 versus 4.99 for vehicle versus chemokine treatment; p < 0.05]. Chemokine treatment significantly improved survival at both 5 d (40 versus 72%) and 28 d (27 versus 52%; p < 0.02 vehicle versus chemokines). These data demonstrate that early, local treatment with CXC chemokines enhances neutrophil recruitment and clearance of bacteria as well as improves survival in the CLP model of sepsis.

Untreated type 1 diabetes increases sepsis-induced mortality without inducing a prelethal cytokine response.

Diabetes mellitus is the leading comorbidity in patients with sepsis, but its impact upon survival and immunoinflammatory signaling in sepsis is undetermined. We investigated the effect of untreated diabetes mellitus upon survival and immunoinflammatory responses in the acute phase (days 1-5) of murine polymicrobial sepsis using the AKITA model of type 1 diabetes. Diabetic female C57BL/6-Ins2 (AKITA) and C57BL/6 wild-type (WT) mice underwent cecal ligation and puncture (CLP), blood (20 µL) was sampled for 5 days, and survival was monitored for 28 days. By day 5, all 8 AKITA mice died compared with 10 of 28 deaths in WT mice. Blood glucose declined post-CLP in all groups (most dramatically in AKITAs by 75%). To compare the evolution of inflammatory profiles, mice were retrospectively divided based on outcome into AKITA, WT-Died, and WT-Survived (within days 1-5). Hypoglycemia developed in all groups, which resolved in WT-Survived (97 mg/dL at 96 h) but intensified in WT-Died and AKITAs (∼30 mg/dL). Dramatic increases in both proinflammatory and anti-inflammatory cytokines were observed in WT-Died (i.e., interleukin 6, 38.2 ± 17.8 ng/mL at 24 h), which contrasted with a lack of prelethal cytokine response in AKITA mice (interleukin 6, 4.3 ± 3.4 ng/mL at 24 h). A prelethal composite cytokine score was calculated on values obtained 24 h before death. This score was 3-fold lower for proinflammatory cytokines and 6-fold lower for anti-inflammatory mediators in the AKITA mice compared with the WT-Died mice but identical to the composite score in WT-Survived. These data demonstrate that untreated type I diabetes mellitus severely exacerbates sepsis mortality without inducing a prelethal release of systemic proinflammatory or anti-inflammatory cytokines.