Peritoneal lavage reduces lipopolysaccharide-induced elevation of serum TNF-alpha and IL-6 mortality in mice

Central glucagon-like peptide 1 receptor activation inhibits Toll-like receptor agonist-induced inflammation

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) exert anti-inflammatory effects relevant to the chronic complications of type 2 diabetes. Although GLP-1RAs attenuate T cell-mediated gut and systemic inflammation directly through the gut intraepithelial lymphocyte GLP-1R, how GLP-1RAs inhibit systemic inflammation in the absence of widespread immune expression of the GLP-1R remains uncertain. Here, we show that GLP-1R activation attenuates the induction of plasma tumor necrosis factor alpha (TNF-α) by multiple Toll-like receptor agonists. These actions are not mediated by hematopoietic or endothelial GLP-1Rs but require central neuronal GLP-1Rs. In a cecal slurry model of polymicrobial sepsis, GLP-1RAs similarly require neuronal GLP-1Rs to attenuate detrimental responses associated with sepsis, including sickness, hypothermia, systemic inflammation, and lung injury. Mechanistically, GLP-1R activation leads to reduced TNF-α via α1-adrenergic, δ-opioid, and κ-opioid receptor signaling. These data extend emerging concepts of brain-immune networks and posit a new gut-brain GLP-1R axis for suppression of peripheral inflammation.

Macrophages from Mice Administered Rhus verniciflua Stokes Extract Show Selective Anti-Inflammatory Activity

The bark of Rhus verniciflua Stokes (RVS) is used as a food additive and herbal medicine for various inflammatory disorders and cancer in Eastern Asia. RVS has been shown to exert anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated macrophages in vitro, but whether oral administration of RVS affects the inflammatory response of macrophage needs to be verified. RVS was given orally to mice for ten days. For isolation of macrophages, intraperitoneal injection of thioglycollate was performed. For determination of serum inflammatory response, intraperitoneal injection of LPS was applied. RVS stimulated monocyte differentiation in thioglycollate-induced peritonitis by increasing the population of cells expressing CD11b and class A scavenger receptors. These monocyte-derived macrophages showed an increased uptake of acetylated low-density lipoprotein. When peritoneal macrophages from the RVS group were stimulated with LPS, the levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6 in the supernatant decreased, but the level of IL-12 increased. The surface expression of CD86 was reduced, but surface expression of class II major histocompatibility complex molecules was increased. RVS suppressed the serum levels of LPS-induced TNF-α and IL-6. Collectively, RVS promoted monocyte differentiation upon inflammatory insults and conferred selective anti-inflammatory activity without causing overall inhibitory effects on immune cells.

VIP deficient mice exhibit resistance to lipopolysaccharide induced endotoxemia with an intrinsic defect in proinflammatory cellular responses

Vasoactive intestinal peptide (VIP) is a pleiotropic neuropeptide with immunomodulatory properties. The administration of this peptide has been shown to have beneficial effects in murine models of inflammatory diseases including septic shock, rheumatoid arthritis, multiple sclerosis (MS) and Crohn's disease. However, the role of the endogenous peptide in inflammatory disease remains obscure because VIP-deficient mice were recently found to exhibit profound resistance in a model of MS. In the present study, we analyzed the response of female VIP deficient (KO) mice to intraperitoneal lipopolysaccharide (LPS) administration. We observed significant resistance to LPS in VIP KO mice, as evidenced by lower mortality and reduced tissue damage. The increased survival was associated with decreased levels of proinflammatory cytokines (TNFα, IL-6 and IL-12) in sera and peritoneal suspensions of these mice. Moreover, the expression of TNFα and IL-6 mRNA was reduced in peritoneal cells, spleens and lungs from LPS-treated VIP KO vs. WT mice, suggesting that the resistance might be mediated by an intrinsic defect in the responsiveness of immune cells to endotoxin. In agreement with this hypothesis, peritoneal cells isolated from VIP KO naive mice produced lower levels of proinflammatory cytokines in response to LPS in vitro. Finally, decreased NF-κB pathway activity in peritoneal cells was observed both in vivo and in vitro, as determined by assay of phosphorylated I-κB. The results demonstrate that female VIP KO mice exhibit resistance to LPS-induced shock, explainable in part by the presence of an intrinsic defect in the responsiveness of inflammatory cells to endotoxin.

Trans-Serosal Leakage of Proinflammatory Mediators during Abdominal Aortic Aneurysm Repair: Role of Phospholipase A2 in Activating Leukocytes

Gut barrier failure and the resultant translocation of luminal bacteria and bacterial products into the systemic circulation have been proposed as pathogenic mechanisms of multiorgan dysfunction syndrome (MODS) in open repair of abdominal aortic aneurysm (AAA). Our study aimed to demonstrate the direct release of gut-derived inflammatory mediators via the trans-serosal route in humans. Fifteen patients who underwent elective infrarenal open repair of AAA were randomized into two groups. In Group I patients (n = 10), the small intestine was exteriorized into a bowel bag. In Group II patients (n = 5), the small intestine was packed within the peritoneal cavity using large gauzes. We collected the bowel bag fluid in Group I and the ascites fluid, squeezed out from the gauzes at the end of surgery, in Group II. Leukocytes were collected from patients' blood samples. Incubation with the bowel bag fluid and ascites fluid caused a significant increase in both granulocyte pseudopod formation and CD11b expression compared to that with control fluid (p < 0.01). The addition of phospholipase A2 (PLA2) inhibitor quinacrine abolished leukocyte activation by the bowel bag fluid. Based on these results, we consider that trasns-serosal leakage of gut-derived mediators occurred during the open repair of AAA; further, sPLA2 may be the most potent mediator in the activation of leukocytes among such gut-derived mediators in AAA surgery.

Lipopolysaccharide-stimulated whole blood cytokine production does not predict the inflammatory response in human endotoxemia

A widely applied method to study the activation of the innate immune system is in vitro stimulation of whole blood using lipopolysaccharide (LPS). However, it is unclear if in vitro cytokine production relates to in vivo cytokine levels elicited during experimental endotoxemia or sepsis. To determine the correlation between in vitro cytokine production and the in vivo inflammatory response, blood was obtained from 15 healthy volunteers for in vitro incubation with Escherichia coli LPS, immediately followed by experimental E. coli endotoxemia. Correlations of in vitro and peak in vivo cytokine concentrations were determined using Pearson correlation coefficient. In stimulated whole blood, tumor necrosis factor (TNF)-α, Interleukin (IL)-1β, IL-6, IL-10 and interferon (IFN)-γ were induced to 279 ± 53, 392 ± 64, 5312 ± 624, 83 ± 20 and 343 ± 85 pg/ml, respectively, whereas in vivo cytokine induction led to cytokine levels of 603 ± 123, 11 ± 1, 4999 ± 1228, 167 ± 25 and 194 ± 40 pg/ml, respectively. Correlation coefficients between the in vitro and in vivo cytokine concentrations were for TNF-α, IL-1β, IL-6, IL-10 and IFN-γ -0.10 (P = 0.7), 0.09 (P = 0.8), 0.36 (P = 0.2), 0.19 (P = 0.5) and 0.40 (P = 0.1), respectively. Comparison between in vitro and in vivo stimulation with LPS shows no correlation between the amount of cytokines produced. In vitro cytokine production, therefore, does not predict the in vivo inflammatory response.

PERITONEAL LAVAGE WITH OXYGENATED PERFLUOROCHEMICAL IMPROVES HEMODYNAMICS, INTESTINAL INJURY, AND SURVIVAL IN A RAT MODEL OF SEVERE HEMORRHAGIC SHOCK AND RESUSCITATION

Perfluorochemicals (PFC) are chemical substances that have a high solubility for oxygen. This study investigated the effect of peritoneal lavage with oxygenated PFC (O2-PFC) against hemorrhagic shock and resuscitation (HS/R). Male Sprague-Dawley rats were anesthetized and bled to a mean arterial pressure (MAP) of 30 to 35 mmHg for 120 min. The animals then were resuscitated over 20 min with an infusion of shed blood. Peritoneal lavage was performed by inflow and outflow of the PFC solution at 80 mL/h during the shock-resuscitation period. Rats were divided into four groups. Group I, HS without peritoneal lavage; Group II, HS with nitrogenated PFC (N2-PFC) lavage; Group III, HS with O2-PFC lavage; and Group IV, sham-operated rats. Seven of seven (100%) rats in Group IV and six of seven (85.7%) rats in Group III survived for 48 h, and one of seven (14.3%) rats in Group I and zero of seven rats in Group II survived (P < 0.01). In Group III rats, metabolic acidosis (assessed by blood gas analysis) and depression of intestinal blood flow (assessed by laser Doppler flowmetry) during HS were markedly ameliorated in comparison with those in Group I or Group II rats. The elevation of plasma TNF-alpha and IL-6 after HS/R were also attenuated in Group III. Histological study showed that O2-PFC lavage significantly decreased the degree of intestinal mucosal damage. We conclude that treatment with O2-PFC lavage ameliorated HS/R-induced metabolic acidosis and intestinal damage, which was associated with better mortality, possibly by preserving microvascular perfusion and maintaining oxygen metabolism.

Hyperbaric oxygen protects against lipopolysaccharide-stimulated oxidative stress and mortality in rats

Free radicals and proinflammatory mediators have been implicated in the pathogenesis of endotoxic shock, a disease with high mortality caused by Gram-negative bacterial endotoxin. Hyperbaric oxygen is used as an adjuvant therapy for various inflammatory diseases and shows beneficial effects in lipopolysaccharide-induced shock syndrome. However, the underlying mechanisms for these effects are still to be defined. In this study, we investigated the effect of hyperbaric oxygen on inflammatory mediators, free radicals, and mortality in endotoxic rats. Wistar-Kyoto rats were injected with lipopolysaccharide (10 mg/kg) and then exposed to aminoguanidine, an inhibitor of inducible nitric oxide (NO) synthase (bolus injection 2 h after lipopolysaccharide), or hyperbaric oxygen (2 ATA for 60 min 1, 4, 9, and 24 h after lipopolysaccharide). Plasma tumor necrosis factor alpha (TNF-alpha), NO, and superoxide anion were detected and the vasorelaxation response and survival rate were assessed. The results demonstrated that increases in plasma TNF-alpha and NO, and the vasohyporeactivity induced by lipopolysaccharide treatment were significantly inhibited by hyperbaric oxygen and aminoguanidine. Mortality and vascular superoxide anion production of lipopolysaccharide treatment were also markedly reduced by hyperbaric oxygen treatment, but were not restored by aminoguanidine. None of the parameters was changed by hyperbaric oxygen treatment alone. Thus, repeated hyperbaric oxygen exposure significantly attenuated the inflammatory mediators, free radicals, and mortality in endotoxic rats.

Activation of the STAT pathway in acute lung injury

Acute lung injury (ALI) is a devastating clinical problem with a mortality as high as 60%. It is now appreciated that ALI represents a cytokine excess state that involves the microvasculature of multiple organs. The signal transducers and activators of transcription (STAT) family of transcription factors activate critical mediators of cytokine responses, but there is limited knowledge about their role in mediating ALI. In the present study, we demonstrate that the STAT transcription factors are activated rapidly in the lungs after intraperitoneal and intranasal LPS administration in mice. We also demonstrated that LPS activates both the STAT kinases, Src and JAK, in the lung with kinetics that are consistent with STAT activation. LPS treatment resulted in STAT3 activation throughout the resident lung cells, as well as in the recruited inflammatory cells. Whereas direct LPS treatment did not lead to STAT activation in cultured epithelial or endothelial cells, IL-6 activated STAT3 in both of these cell types. Furthermore, IL-6 was induced by LPS in serum and in the lung with kinetics consistent with STAT3 activation, suggesting that IL-6 may be one mechanism of STAT activation by LPS. In addition, STAT activation required reactive oxygen species, as the overexpression of catalase in mice prevented LPS-mediated STAT activation in the lung. STATs may be a common pathway for mediating ALI, regardless of the inciting factor, as STAT activation also occurred in both a gastric acid aspiration and acute pancreatitis model of ALI. Finally, STATs are activated in the lung long before signs of ALI are present, suggesting that the STAT transcription factors may play a role in initiating the inflammatory response seen in the lung.

Protease inhibition in the intestinal lumen: attenuation of systemic inflammation and early indicators of multiple organ failure in shock

Our recent evidence suggests that pancreatic digestive enzymes in the lumen of the intestine may play a major role in the production of cardiovascular stimulatory factors during splachnic artery occlusion and reperfusion. These stimulators are detected in plasma, but their origin and mechanism of production has remained uncertain. We examine here in the rat the role of pancreatic enzymes with and without administration of a serine protease inhibitor (FOY) into the lumen of the small intestine during splanchnic artery occlusion (90 min) and reperfusion (120 min). In the presence of pancreatic enzyme inhibition in the lumen of the intestine, there is significantly enhanced survival rate, lower levels of inflammatory mediator production, the femoral artery blood pressure is maintained close to control levels, and there are significantly lower levels of cell activators in plasma. These results support the hypothesis that pancreatic enzymes may escape across the brush border barrier during intestinal ischemia and thereby initiate the production of a powerful set of cytotoxic mediators. Blockade of pancreatic enzymes in the lumen of the intestine may be a tool to interfere with inflammation and early indicators of multiorgan failure.

Peritoneal lavage with oxygenated perfluorochemical preserves intestinal mucosal barrier function after ischemia-reperfusion and ameliorates lung injury

OBJECTIVE

To evaluate the effect of peritoneal lavage with an oxygenated perfluorochemical (PFC) on intestinal ischemia-reperfusion injury (IIR), we assessed intestinal barrier function in terms of bacterial translocation and endotoxemia, morphologic changes, and changes of intestinal luminal pH in rats subjected to IIR. We also examined lung injury after IIR to test the effect of oxygenated PFC lavage on remote organ failure.

DESIGN

Prospective, randomized, and controlled animal study.

SETTING

Laboratory of a university hospital.

SUBJECT

Male Sprague-Dawley rats.

INTERVENTIONS

Rats were subjected to ischemia by clipping the superior mesenteric artery. Reperfusion was achieved by release of the clip. Lavage of the abdominal cavity was performed by inflow and outflow of oxygenated PFC solution during ischemia.

RESULTS

Rats undergoing peritoneal lavage with oxygenated PFC (PFC group) showed significantly better survival after IIR. The frequency of bacterial translocation and the endotoxin concentration in superior mesenteric venous blood were significantly lower in the PFC group. Luminal acidosis also was alleviated in the PFC group. Furthermore, PFC lavage preserved the intestinal mucosal architecture and inhibited interstitial edema and infiltration of inflammatory cells in the lungs.

CONCLUSION

We conclude that peritoneal lavage with oxygenated PFC protects the intestinal mucosa and maintains mucosal barrier function after IIR. Preservation of the intestinal mucosa ameliorates lung injury after IIR.

Distinct tumor necrosis factor-alpha responses in alveolar and peritoneal macrophages are associated with local levels of endotoxin

Tumor necrosis factor alpha (TNF-alpha) responses of alveolar macrophages (AMs) and peritoneal macrophages (PMs) were studied in rats after intravenous injection of lipopolysaccharide (LPS). High levels of plasma TNF-alpha, increased pulmonary myeloperoxidase activity, and leukopenia occurred within 2 h after LPS injection. Alveolar spaces exhibited a strict compartment property, as manifested by only slightly increased LPS and TNF-alpha levels in alveolar lavage fluid and an unchanged capacity of AMs to produce TNF-alpha. By contrast, the peritoneal cavity had greatly increased local LPS and TNF-alpha levels and a diminished PMs TNF-alpha response to LPS. The amount of LPS in the alveolar spaces was less than 0.2% of the level in peritoneal fluid. These results indicate that activation of resident macrophages is dependent on the amounts of local LPS and, in addition, suggest that resident AMs neither participate in the plasma TNF-alpha response nor contribute to neutrophil sequestration in the lung during the early stages of endotoxemia.