Kathy Chang

CONTEXT: Severe sepsis is typically characterized by initial cytokine-mediated hyper-inflammation. Whether this hyperinflammatory phase is followed by immunosuppression is controversial. Animal studies suggest that multiple immune defects occur in sepsis, but data from humans remain conflicting. OBJECTIVES: To determine the association of sepsis with changes in host innate and adaptive immunity and to examine potential mechanisms for putative immunosuppression. DESIGN, SETTING, AND PARTICIPANTS: Rapid postmortem spleen and lung tissue harvest was performed at the bedsides of 40 patients who died in intensive care units (ICUs) of academic medical centers with active severe sepsis to characterize their immune status at the time of death (2009–2011). Control spleens (n=29) were obtained from patients who were declared brain-dead or had emergent splenectomy due to trauma; control lungs (n=20) were obtained from transplant donors or from lung cancer resections. MAIN OUTCOME MEASURES: Cytokine secretion assays and immunophenotyping of cell surface receptor-ligand expression profiles were performed to identify potential mechanisms of immune dysfunction. Immunohistochemical staining was performed to evaluate the loss of immune effector cells. RESULTS: The mean ages of patients with sepsis and controls were 71.7 (SD, 15.9) and 52.7 (SD, 15.0) years, respectively. The median number of ICU days for patients with sepsis was 8 (range, 1–195 days), while control patients were in ICUs for 4 or fewer days. The median duration of sepsis was 4 days (range, 1–40 days). Compared with controls, anti-CD3/anti-CD28–stimulated splenocytes from sepsis patients had significant reductions in cytokine secretion at 5 hours: tumor necrosis factor, 5361 (95% CI, 3327–7485) pg/mL vs 418 (95% CI, 98–738) pg/mL; interferon γ, 1374 (95% CI, 550–2197) pg/mL vs 37.5 (95% CI, −5 to 80) pg/mL; interleukin 6, 3691 (95% CI, 2313–5070) vs 365 (95% CI, 87–642) pg/mL; and interleukin 10, 633 (95% CI, −269 to 1534) vs 58 (95% CI, −39 to 156) pg/mL; (P<.001 for all). There were similar reductions in 5-hour lipopolysaccharide-stimulated cytokine secretion. Cytokine secretion in sepsis patients was generally less than 10% that in controls, independent of age, duration of sepsis, corticosteroid use, and nutritional status. Although differences existed between spleen and lung, flow cytometric analysis showed increased expression of selected inhibitory receptors and ligands and expansion of suppressor cell populations in both organs. Unique differences in cellular inhibitory molecule expression existed in immune cells isolated from lungs of sepsis patients vs cancer patients and vs transplant donors. Immunohistochemical staining showed extensive depletion of splenic CD4, CD8, and HLA-DR cells and expression of ligands for inhibitory receptors on lung epithelial cells. CONCLUSIONS: Patients who die in the ICU following sepsis compared with patients who die of nonsepsis etiologies have biochemical, flow cytometric, and immunohistochemical findings consistent with immunosuppression. Targeted immune-enhancing therapy may be a valid approach in selected patients with sepsis.

Increased blood flow and vascular leakage of proteins preferentially affect tissues that are sites of diabetic complications in humans and animals. These vascular changes in diabetic rats are largely prevented by aminoguanidine. Glucose-induced vascular changes in nondiabetic rats are also prevented by aminoguanidine and by NG-monomethyl-L-arginine (NMMA), an established inhibitor of nitric oxide (NO.) formation from L-arginine. Aminoguanidine and NMMA are equipotent inhibitors of interleukin-1 beta-induced 1) nitrite formation (an oxidation product of NO.) and cGMP accumulation by the rat beta-cell insulinoma cell line RINm5F, and 2) inhibition of glucose-stimulated insulin secretion and formation of iron-nitrosyl complexes by islets of Langerhans. In contrast, NMMA is approximately 40 times more potent than aminoquanidine in elevating blood pressure in nondiabetic rats. These results demonstrate that aminoguanidine inhibits NO. production and suggest a role for NO. in the pathogenesis of diabetic vascular complications.

Sepsis continues to cause significant morbidity and mortality in critically ill patients. Studies of patients and animal models have revealed that changes in the immune response during sepsis play a decisive role in the outcome. Using a clinically relevant two-hit model of sepsis, i.e., cecal ligation and puncture (CLP) followed by the induction of Pseudomonas aeruginosa pneumonia, we characterized the host immune response. Second, AS101 [ammonium trichloro(dioxoethylene-o,o')tellurate], a compound that blocks interleukin 10 (IL-10), a key mediator of immunosuppression in sepsis, was tested for its ability to reverse immunoparalysis and improve survival. Mice subjected to pneumonia following CLP had different survival rates depending upon the timing of the secondary injury. Animals challenged with P. aeruginosa at 4 days post-CLP had approximately 40% survival, whereas animals challenged at 7 days had 85% survival. This improvement in survival was associated with decreased lymphocyte apoptosis, restoration of innate cell populations, increased proinflammatory cytokines, and restoration of gamma interferon (IFN-gamma) production by stimulated splenocytes. These animals also showed significantly less P. aeruginosa growth from blood and bronchoalveolar lavage fluid. Importantly, AS101 improved survival after secondary injury 4 days following CLP. This increased survival was associated with many of the same findings observed in the 7-day group, i.e., restoration of IFN-gamma production, increased proinflammatory cytokines, and decreased bacterial growth. Collectively, these studies demonstrate that immunosuppression following initial septic insult increases susceptibility to secondary infection. However, by 7 days post-CLP, the host's immune system has recovered sufficiently to mount an effective immune response. Modulation of the immunosuppressive phase of sepsis may aid in the development of new therapeutic strategies.

Boomer, Jonathan S.; To, Kathleen; Chang, Kathy C.; Takasu, Osamu; Osborne, Dale F.; Walton, Andrew H.; Bricker, Traci L.; Jarman, Stephen D. II; Kreisel, Daniel; Krupnick, Alexander S.; Srivastava, Anil; Swanson, Paul E.; Green, Jonathan M.; Hotchkiss, Richard S. Author Information

These experiments were undertaken to assess the role of sorbitol dehydrogenase in mediating sorbitol pathway-linked neural and vascular dysfunction in rats with streptozocin-induced diabetes. 2-methyl-4-[N,N-dimethylsulfamoyl-piperazino]-pyrimidine (S-0773), a putative inhibitor of sorbitol dehydrogenase, was given in the drinking water to control and diabetic rats. After 5 weeks of diabetes, glycosylated hemoglobin levels were increased twofold and were unaffected by S-0773. Sorbitol levels in diabetic rats were increased 11- to 14-fold in ocular tissues and sciatic nerve; S-0773 increased sorbitol levels another 4-fold or more in these same tissues but had much smaller effects in other tissues. Diabetes-associated increases in fructose levels and lactate:pyruvate ratios in retina and in sciatic nerve were markedly attenuated by S-0773. S-0773 also attenuated, but did not completely normalize, impaired caudal nerve conduction and vascular dysfunction in ocular tissues, sciatic nerve, and aorta in diabetic rats. These observations, together with other evidence, suggest that sorbitol pathway-linked vascular dysfunction (in ocular tissues, peripheral nerve, and aorta) and electrophysiological dysfunction (in peripheral nerve) induced by diabetes are more closely linked to increased oxidation of sorbitol to fructose than to putative osmotic effects of elevated sorbitol levels or redox and metabolic imbalances associated with reduction of glucose to sorbitol by aldose reductase.