Russell L. Delude

Increased iNOS activity is essential for intestinal epithelial tight junction dysfunction in endotoxemic mice

We tested the hypothesis that increased production of nitric oxide (NO·) associated with lipopolysaccharide (LPS)-induced systemic inflammation leads to functionally significant alterations in the expression and/or targeting of key tight junction (TJ) proteins in ileal and colonic epithelium. Wild-type or inducible NO· synthase (iNOS) knockout male C57B1/6J mice were injected intraperitoneally with 2 mg/kg Escherichia coli O111:B4 LPS. iNOS was inhibited using intraperitoneal L-N(6)-(1-iminoethyl)lysine (L-NIL; 5 mg/kg). Immunoblotting of total protein and NP-40 insoluble proteins revealed decreased expression and decreased TJ localization, respectively, of the TJ proteins, zonula occludens (ZO)-1, ZO-2, ZO-3, and/or occludin in ileal mucosa and colonic mucosa (total protein only) after injection of C57B1/6J mice with LPS. Immunohistochemistry showed deranged distribution of ZO-1 and occludin in both tissues from endotoxemic mice. Endotoxemia was associated with evidence of gut epithelial barrier dysfunction evidenced by increased ileal mucosal permeability to fluorescein isothiocyanate-dextran (Mr = 4 kDa) and increased bacterial translocation to mesenteric lymph nodes. Pharmacologic inhibition of iNOS activity using L-NIL or genetic ablation of the iNOS gene ameliorated LPS-induced changes in TJ protein expression and gut mucosal barrier function. These results support the view that at least one mechanism contributing to the pathogenesis of gastrointestinal epithelial dysfunction secondary to systemic inflammation is increased iNOS-dependent NO· production leading to altered expression and localization of key TJ proteins.

Proinflammatory cytokines cause NO*-dependent and -independent changes in expression and localization of tight junction proteins in intestinal epithelial cells.

Intestinal epithelial barrier function is impaired after the exposure of enterocytes to proinflammatory cytokines. The mechanism(s) responsible for this phenomenon remain incompletely understood. We used cultured monolayers of Caco-2 enterocyte-like cells to characterize the effect of cytomix, a mixture of interferon-&ggr;, tumor necrosis factor-&agr;, and interleukin-1&bgr;, on the expression and localization of several tight junctions proteins. Cells were stimulated with cytomix in the presence or absence of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), an NO· scavenger. Some cells were treated with (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl) amino]diazen-1-ium-1,2-diolate] (DETA-NONOate), an NO· donor. Tight junction protein expression was measured in cellular extracts by Western blotting and localized in cells using immunofluorescence. Steady-state mRNA levels were determined using semi-quantitative reverse-transcription polymerase chain reaction. Incubation of cells with DETA-NONOate or cytomix decreased epithelial barrier function, decreased expression of ZO-1 mRNA, decreased expression of ZO-1, ZO-3, and occludin protein, and increased expression of claudin-1 protein. The effects of cytomix on barrier function and tight junction protein expression were modulated by cPTIO. Cytomix caused incorrect subcellular localization of ZO-1, occludin, and claudin-1, and this was modulated by co-incubation with cPTIO. DETA-NONOate caused similar protein mislocalization as observed with cytomix. The effectiveness of cPTIO in maintaining tight junction protein expression and correct subcellular localization was less apparent at early time points (12 h) compared with later points, suggesting an NO·-independent effect of cytokines on barrier function. Thus, cytomix appears to increase the permeability of Caco-2 monolayers through NO·-dependent and -independent mechanisms that are associated with changes in the expression and/or targeting of proteins involved in tight junction function.

Circulating high-mobility group box 1 (HMGB1) concentrations are elevated in both uncomplicated pneumonia and pneumonia with severe sepsis.

Objective:High-mobility group box 1 (HMGB1) has been proposed as a late mediator of sepsis, but human data are sparse and conflicting. We describe plasma HMGB1 concentrations in humans with community-acquired pneumonia (CAP), the most common cause of severe sepsis, and test the hypotheses that HMGB1 levels are higher in CAP than healthy controls, higher in CAP with severe sepsis than CAP without severe sepsis, and higher in severe sepsis nonsurvivors than survivors. Design:Random, outcome-stratified sample from a prospective study of 1,895 subjects hospitalized with CAP. Setting:Twenty-eight U.S. teaching and community hospitals. Patients:There were 122 CAP subjects (43 never developed severe sepsis, 49 developed severe sepsis and survived hospitalization, and 30 developed severe sepsis and died) and 38 healthy controls. Interventions:None. Measurements and Main Results:Median day of onset of severe sepsis was day of admission. HMGB1 was measured daily for the first week and analyzed using repeated-measures models with and without multivariable adjustment for baseline characteristics. HMGB1 concentrations were higher in CAP subjects compared with controls (median concentration on day of admission vs. controls, 190 vs. 0 ng/mL, p = .0001; 93.7% of all CAP measurements were elevated). HMGB1 remained elevated throughout the hospital course with no significant trend (p = .64) and did not differ between those with and without severe sepsis (p = .30). HMGB1 concentrations were higher in severe sepsis nonsurvivors than survivors (p = .001). HMGB1 concentrations remained elevated at discharge (median final HMGB1 measure, 176 ng/mL). Findings persisted in multivariable models and were robust to sensitivity analyses using alternative definitions of severe sepsis. Conclusions:HMGB1 is elevated in almost all CAP subjects, and higher circulating HMGB1 is associated with mortality. But immunodetectable HMGB1 levels were also persistently elevated in those patients who fared well. Thus, additional work is needed to understand the biological activities of serum HMGB1 in sepsis.

RESUSCITATION FROM HEMORRHAGIC SHOCK WITH RINGER'S ETHYL PYRUVATE SOLUTION IMPROVES SURVIVAL AND AMELIORATES INTESTINAL MUCOSAL HYPERPERMEABILITY IN RATS

We previously showed that pretreatment with a solution of ethyl pyruvate in a calcium-containing balanced salt solution, Ringers ethyl pyruvate solution (REPS), ameliorates gut mucosal damage in rats subjected to mesenteric ischemia/reperfusion. Herein, we sought to test the hypothesis that REPS would be beneficial as a post-treatment (i.e., resuscitation fluid) for hemorrhagic shock. Anesthetized Sprague-Dawley rats were bled to a mean arterial pressure (MAP) of 40 mmHg until 40% of shed blood was returned. The animals then were resuscitated over 60 min with the remaining shed blood plus twice the shed blood volume as either Ringers lactate solution (RLS) or REPS. In Experiment 1, RLS or REPS was then infused for 3 h more (or until death) at 3 mL/kg/h. Read-outs were post-resuscitation ileal mucosal permeability to fluorescein-labeled Dextran with an average molecular mass of 4000 Da (FD4) and survival. Permeability, determined just before death (MAP < 40 mmHg) or after 4 h of resuscitation, was assessed using an ex vivo everted gut sac technique and is expressed as a clearance (nL/cm/min). In Experiment 2, the read-outs were ileal FD4 permeability measured at 60 min after starting resuscitation and gut and liver malondialdehyde (MDA) formation. FD4 clearance data were logarithmically transformed prior to performing statistical analyses. In Experiment 1, 4/8 (50%) of RLS-treated rats survived 4 h after resuscitation whereas 7/7 (100%) of REPS-treated rats survived (P < 0.05). Ileal FD4 clearances were 105 ± 30*, 85 ± 34*, and 38 ± 7 for all rats treated with RLS, surviving rats treated with RLS, and rats treated with REPS, respectively (the asterisk indicates P < 0.05 vs. REPS). In Experiment 2, ileal FD4 clearances were 71 ± 13* and 34 ± 8 for rats treated with RLS and REPS (n = 5 each), respectively. Post-resuscitation levels of MDA in the ileum and liver were significantly lower in rats treated with REPS as compared with RLS. Resuscitation with REPS, a stable and nontoxic antioxidant solution, improves survival and ameliorates ileal mucosal permeability in a rat model of severe hemorrhagic shock.

Increased iNOS activity is essential for hepatic epithelial tight junction dysfunction in endotoxemic mice.

We tested the hypothesis that increased production of nitric oxide (NO*) by inducible NO* synthase (iNOS) is a key factor responsible for alterations in the expression, localization, and function of key tight junction (TJ) proteins in mice challenged with lipopolysaccharide (LPS, endotoxin). Endotoxemia was associated with hepatobiliary epithelial barrier dysfunction, as evidenced by increased plasma-to-bile leakage of FITC-labeled dextran (relative molecular mass 40 kDa) and increased circulating levels of bile acids and conjugated bilirubin. Immunoblotting revealed decreased expression of zonula occludens (ZO)-1, ZO-2, ZO-3, and occludin in liver after injection of C57Bl/6J mice with 2 mg/kg Escherichia coli 0111:B4 LPS. Nonidet P-40-insoluble (i.e., TJ-associated) occludin and ZO-1 were virtually undetectable 12 and 18 h after injecting LPS. Immunofluorescence microscopy also revealed deranged subcellular localization of ZO-1 and occludin in endotoxemic mice. Pharmacological inhibition of iNOS activity using l-N6-(1-iminoethyl)lysine (5 mg/kg) or genetic ablation of iNOS ameliorated LPS-induced changes in hepatobiliary barrier function, and these strategies partially preserved TJ protein expression and localization. Steady-state levels of occludin and ZO-3 transcripts decreased transiently after injecting LPS but returned toward normal by 12 and 24 h after induction of endotoxemia, respectively. These results support the view that iNOS-dependent NO* production is an important factor contributing to hepatobiliary epithelial barrier dysfunction resulting from systemic inflammation and suggest that iNOS induction may play a role in the development of cholestatic jaundice in patients with severe sepsis.

Effect of mesenteric ischemia and reperfusion or hemorrhagic shock on intestinal mucosal permeability and ATP content in rats.

In a reductionist in vitro system, intestinal epithelial permeability appears to be dependent on cellular ATP content. In order to extend these prior observations, we used rat models of mesenteric ischemia/reperfusion (I/R) and pressure-controlled hemorrhagic shock to test the hypothesis that intestinal barrier function is directly proportional to tissue ATP content. I/R was induced by clamping the mesenteric vessels for 60 min followed by 60 min of reperfusion. Normal, ischemic, and reperfused ileal segments were prepared from each rat (n = 12). Hemorrhagic shock was induced by bleeding rats (n = 9) to a mean arterial pressure of 30 mmHg and maintaining this pressure for 4 h by infusing Ringers lactate solution as necessary. Ileal segments were harvested before induction of hemorrhage and at 1 h intervals thereafter. Everted gut sacs were prepared to measure the mucosal-to-serosal passage of fluorescein-conjugated dextran (FD4; M.W. = 4 kDa). Tissue ATP levels were determined using a luciferase assay. FD4 clearance rates were plotted as a function of tissue ATP content. Linear regression analyses showed a strong inverse relationship between intestinal permeability and tissue ATP level in rats subjected to I/R (r2 = 0.78; P < 0.001) or hemorrhage (r2 = 0.82; P < 0.001). These data support the idea that ATP content is a determinant of intestinal epithelial barrier function in vivo.

Midregional Proadrenomedullin as a Prognostic Tool in Community-Acquired Pneumonia

BACKGROUND Midregional proadrenomedullin (MR-proADM) is a potential prognostic biomarker in patients with community-acquired pneumonia (CAP). Previous work has been hampered by sample size and illness spectrum limits. We sought to describe the pattern of MR-proADM in a broad CAP cohort, confirm its prognostic role, and compare its performance to procalcitonin, a novel biomarker of infection. METHODS We conducted a multicenter prospective cohort study in 28 community and teaching EDs. Patients with a clinical and radiographic diagnosis of CAP were enrolled. We stratified MR-proADM levels a priori into quartiles and quantified severity of illness using the pneumonia severity index (PSI); and confusion (abbreviated mental test score of <or= 8), urea >or= 7 mmol/L, respiratory rate >or= 30 breaths/min, BP < 90 mm Hg systolic or < 60 mm Hg diastolic, age >or= 65 years (CURB-65). The primary outcome was 30-day mortality. RESULTS A total of 1,653 patients formed the study cohort. MR-proADM levels consistently rose with PSI class and 30-day mortality (p < 0.001). MR-proADM had a higher area under the curve for 30-day mortality than procalcitonin (0.76 vs 0.65, respectively; p < 0.001), but adding MR-proADM to the PSI in all subjects minimally improved performance. Among low-risk subjects (PSI classes I to III), mortality was low and did not differ by MR-proADM quartile. However, among high-risk subjects (PSI class IV/V; n = 546), subjects in the highest MR-proADM quartile (n = 232; 42%) had higher 30-day mortality than those in MR-proADM quartiles 1 to 3 (23% vs 9%, respectively; p < 0.0001). Similar results were seen with CURB-65. MR-proADM and procalcitonin levels were generally concordant; only 6% of PSI class IV/V subjects in the highest MR-proADM quartile had very low procalcitonin levels (< 0.1 ng/mL). CONCLUSIONS In our multicenter CAP cohort, MR-proADM levels correlate with increasing severity of illness and death. High MR-proADM levels offer additional risk stratification in high-risk CAP patients, but otherwise MR-proADM levels do not alter PSI-based risk assessment in most CAP patients.

Understanding the potential role of statins in pneumonia and sepsis

Objective:To examine the association of statin use with clinical outcomes and circulating biomarkers in community-acquired pneumonia and sepsis. Design:Multicenter inception cohort study. Setting:Emergency departments of 28 U.S. hospitals. Patients:A total of 1895 subjects hospitalized with community-acquired pneumonia. Interventions:None. Measurements and Main Results:Our approach consisted of two different comparison cohorts, each reflecting methods used in prior publications in this area. We first compared subjects with prior statin use (prior use cohort), defined as a history of statin use in the week before admission, with those with no prior use. We then compared prior statin users whose statins were continued inhospital (continued use cohort) with those with either no prior use or no inhospital use. We adjusted for patient characteristics, including demographics, comorbid conditions, and illness severity, and accounted for healthy user effect and indication bias using propensity analysis. We determined risk of severe sepsis and 90-day mortality. We measured markers inflammation (tumor necrosis factor, interleukin-6, interleukin-10), coagulation (antithrombin, factor IX, plasminogen activator inhibitor, d-dimer, thrombin antithrombin complex), and lymphocyte cell surface protein expression during the first week of hospitalization. There were no differences in severe sepsis risk between statin users and nonusers for prior (30.8% vs. 30.7%, p = .98) or continued statin use (30.2% vs. 30.8%, p = .85) in univariate analyses and after adjusting for patient characteristics and propensity for statin use. Ninety-day mortality was similar in prior statin users (9.2% vs. 12.0%, p = .11) and lower in continued statin users (7.9% vs. 12.1%, p = .02). After adjusting for patient characteristics and propensity for statin use, there was no mortality benefit for prior (odds ratio, 0.90 [0.63–1.29]; p = .57) or continued statin use (odds ratio, 0.73 [0.47–1.13]; p = .15). Only antithrombin activity over time was higher in statin subjects, yet the magnitude of the difference was modest. There were no differences in other coagulation, inflammatory, or lymphocyte cell surface markers. Conclusions:We found no evidence of a protective effect for statin use on clinical outcomes and only modest differences in circulating biomarkers in community-acquired pneumonia, perhaps as a result of healthy user effects and indication bias.

Ethyl pyruvate ameliorates distant organ injury in a murine model of acute necrotizing pancreatitis.

Objective:Ethyl pyruvate has been shown to be an effective anti-inflammatory agent in a variety of in vitro and in vivo model systems. Herein, we used a murine model of acute pancreatitis to compare the effects of treatment with either Ringer’s lactate solution or ethyl pyruvate solution on several physiologic and biochemical variables related to disease severity. Design:Experimental animal study. Setting:University laboratory. Subjects:C57Bl/6 mice. Interventions:Pancreatitis was induced by feeding the animals a choline-deficient diet supplemented with 0.5% ethionine for 24 hrs and then challenging the animals with seven hourly 50 μg/kg intraperitoneal injections of cerulein and a single intraperitoneal injection of Escherichia coli lipopolysaccharide (4 mg/kg). Measurements and Main Results:When mice were treated with ethyl pyruvate (40 mg/kg intraperitoneally every 6 hrs for 48 hrs) instead of Ringer’s lactate solution starting 2 hrs after the injection of lipopolysaccharide, long-term survival was improved from one of ten to six of ten (p = .057). When mice were treated with a 40 mg/kg dose of ethyl pyruvate just before the first dose of cerulein and then injected with a second 40 mg/kg dose 6 hrs later, serum concentrations of alanine aminotransferase measured 10 hrs after the first cerulein dose were significantly lower than in mice with pancreatitis treated with Ringer’s lactate solution. In this model of acute pancreatitis, the same dosing regimen for ethyl pyruvate also ameliorated bacterial translocation to mesenteric lymph nodes and leakage of fluorescein isothiocyanate-labeled albumin from blood into bronchoalveolar lavage fluid. Treatment with ethyl pyruvate decreased pancreatic expression of tumor necrosis factor and interleukin-6 messenger RNA and nuclear factor-κB DNA binding in nuclear extracts prepared from pancreatic tissue. Conclusion:Treatment with ethyl pyruvate ameliorated the local inflammatory response and decreased local and distant organ injury in a murine model of necrotizing pancreatitis.

Treatment With a Novel Hemigramicidin-TEMPO Conjugate Prolongs Survival in a Rat Model of Lethal Hemorrhagic Shock

Objective:We sought to develop a therapeutic agent that would permit prolongation of survival in rats subjected to lethal hemorrhagic shock (HS), even in the absence of resuscitation with asanguinous fluids or blood. Methods and Results:We synthesized a series of compounds that consist of the electron scavenger and superoxide dismutase mimic, 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl (4-NH2-TEMPO), conjugated to fragments and analogs of the membrane-active cyclopeptide antibiotic, gramicidin S. Using an in vivo assay, wherein isolated intestinal segments were loaded inside the lumen with various test compounds, we studied these compounds for their ability to prevent ileal mucosal barrier dysfunction induced by subjecting rats to profound HS for 2 hours. The most active compound in this assay, XJB-5-131, ameliorated peroxidation of the mitochondrial phospholipid, cardiolipin, in ileal mucosal samples from rats subjected to HS. XJB-5-131 also ameliorated HS-induced activation of the pro-apoptotic enzymes, caspases 3 and 7, in ileal mucosa. Intravenous treatment with XJB-5-131 (2 &mgr;mol/kg) significantly prolonged the survival of rats subjected to profound blood loss (33.5 mL/kg) despite administration of only a minimal volume of crystalloid solution (2.8 mL/kg) and the absence of blood transfusion. Conclusion:These data support the view that mitochondrially targeted electron acceptors and SOD mimics are potentially valuable therapeutics for the treatment of serious acute conditions, such as HS, which are associated with marked tissue ischemia.