Lipopolysaccharide-induced Systemic Inflammation Research Articles

Reduced ventricular proliferation in the foetal cortex following maternal inflammation in the mouse

It has been well established that maternal inflammation during pregnancy alters neurological function in the offspring, but its impact on cortical development and long-term consequences on the cytoarchitecture is largely unstudied. Here we report that lipopolysaccharide-induced systemic maternal inflammation in C57Bl/6 mice at embryonic Day 13.5 of pregnancy, as early as 8 h after challenge, caused a significant reduction in cell proliferation in the ventricular zone of the developing cerebral cortex, as revealed by quantification of anti-phospho-Histone H3 immunoreactivity and bromodeoxyuridine pulse labelling. The angle of mitotic cleavage, determined from analysis of haematoxylin and eosin staining, cyclin E1 gene expression and the pattern of β-catenin immunoreactivity were also altered by the challenge, which suggests a change from symmetric to asymmetric division in the radial progenitor cells. Modifications of cortical lamination and gene expression patterns were detected at post-natal Day 8 suggesting prolonged consequences of these alterations during embryonic development. Cellular uptake of proteins from the cerebrospinal fluid was observed in brains from lipopolysaccharide-treated animals in radial progenitor cells. However, the foetal blood–brain barrier to plasma proteins remained intact. Together, these results indicate that maternal inflammation can disrupt the ventricular surface and lead to decreased cellular proliferation. Changes in cell density in Layers IV and V at post-natal Day 8 show that these initial changes have prolonged effects on cortical organization. The possible shift in the fate of progeny and the resulting alterations in the relative cell numbers in the cerebral cortex following a maternal inflammatory response shown here will require further investigation to determine the long-term consequences of inflammation on the development of neuronal circuitry and behaviour.

Increased Survival and Reduced Neutrophil Infiltration of the Liver in Rab27a- but Not Munc13-4-Deficient Mice in Lipopolysaccharide-Induced Systemic Inflammation

Genetic defects in the Rab27a or Munc13-4 gene lead to immunodeficiencies in humans, characterized by frequent viral and bacterial infections. However, the role of Rab27a and Munc13-4 in the regulation of systemic inflammation initiated by Gram-negative bacterium-derived pathogenic molecules is currently unknown. Using a model of lipopolysaccharide-induced systemic inflammation, we show that Rab27a-deficient (Rab27a(ash/ash)) mice are resistant to lipopolysaccharide (LPS)-induced death, while Munc13-4-deficient (Munc13-4(jinx/jinx)) mice show only moderate protection. Rab27a(ash/ash) but not Munc13-4(jinx/jinx) mice showed significantly decreased tumor necrosis factor alpha (TNF-α) plasma levels after LPS administration. Neutrophil sequestration in lungs from Rab27a(ash/ash) and Munc13-4(jinx/jinx) LPS-treated mice was similar to that observed for wild-type mice. In contrast, Rab27a- but not Munc13-4-deficient mice showed decreased neutrophil infiltration in liver and failed to undergo LPS-induced neutropenia. Decreased liver infiltration in Rab27a(ash/ash) mice was accompanied by lower CD44 but normal CD11a and CD11b expression in neutrophils. Both Rab27a- and Munc13-4-deficient mice showed decreased azurophilic granule secretion in vivo, suggesting that impaired liver infiltration and improved survival in Rab27a(ash/ash) mice is not fully explained by deficient exocytosis of this granule subset. Altogether, our data indicate that Rab27a but not Munc13-4 plays an important role in neutrophil recruitment to liver and LPS-induced death during endotoxemia, thus highlighting a previously unrecognized role for Rab27a in LPS-mediated systemic inflammation.

Targeted deletion of endothelial lipase increases HDL particles with anti-inflammatory properties both in vitro and in vivo

Previous studies have shown that targeted deletion of endothelial lipase (EL) markedly increases the plasma high density lipoprotein cholesterol (HDL-C) level in mice. However, little is known about the functional quality of HDL particles after EL inhibition. Therefore, the present study assessed the functional quality of HDL isolated from EL(-/-) and wild-type (WT) mice. Anti-inflammatory functions of HDL from EL(-/-) and WT mice were evaluated by in vitro assays. The HDL functions such as PON-1 or PAF-AH activities, inhibition of cytokine-induced vascular cell adhesion molecule-1 expression, inhibition of LDL oxidation, and the ability of cholesterol efflux were similar in HDL isolated from WT and EL(-/-) mice. In contrast, the lipopolysaccharide-neutralizing capacity of HDL was significantly higher in EL(-/-) mice than that in WT mice. To evaluate the anti-inflammatory actions of HDL in vivo, lipopolysaccharide-induced systemic inflammation was generated in these mice. EL(-/-) mice showed higher survival rate and lower expression of inflammatory markers than WT mice. Intravenous administration of HDL isolated from EL(-/-) mice significantly improved the mortality after lipopolysaccharide injection in WT mice. In conclusion, targeted disruption of EL increased HDL particles with preserved anti-inflammatory and anti-atherosclerotic functions. Thus, EL inhibition would be a useful strategy to raise 'good' cholesterol in the plasma.

Filtration Leukocytapheresis Therapy Ameliorates Lipopolysaccharide-Induced Systemic Inflammation in a Rat Model

Systemic inflammation, which is associated with various conditions such as sepsis, pneumonia, and trauma, can lead to multiple organ dysfunction syndrome. Systemic inflammation can be life-threatening and is often associated with conditions seen in the intensive care unit. Leukocytes exert a proinflammatory effect and damage various tissues during systemic inflammation. The purpose of this study was to determine whether leukocytapheresis therapy can prevent lipopolysaccharide (LPS)-induced systemic inflammation in a rat model. Male Wistar rats weighing 250 to 300 g were used for all experiments. Rats received an LPS injection, followed 6 h later by filtration leukocytapheresis or mock treatment for 30 min under sevoflurane anesthesia. Systemic inflammation was induced in rats by intravenous LPS injection (7.5 mg/kg) followed by filtration leukocytapheresis. Following blood filtration, we evaluated lung and liver histology, serum cytokine levels, and survival rate of rats for each treatment group. Histologic examination revealed markedly reduced inflammatory injury in lung and liver tissue harvested from rats 24 h after leukocytapheresis therapy compared with mock treatment. LPS-induced tumor necrosis factor (TNF)-α and interleukin (IL)-6 secretion was also inhibited by leukocytapheresis therapy. Moreover, survival was significantly increased in rats treated with high-efficiency leukocytapheresis compared to mock-treated rats (P<0.05). Taken as a whole, our findings indicate that filtration leukocytapheresis therapy protects against LPS-induced systemic inflammation. Therefore, leukocytapheresis shows potential as a new therapy for various systemic inflammatory diseases.

Detrimental Effect of the Proteasome Inhibitor, Bortezomib in Bacterial Superantigen- and Lipopolysaccharide-induced Systemic Inflammation

Bacterial superantigen (BSAg)-induced toxic shock syndrome (TSS) and bacterial lipopolysaccharide (LPS)-induced shock are characterized by severe systemic inflammation. As nuclear factor kappaB (NF kappaB) plays an important role in inflammation and bortezomib, a proteasome inhibitor widely used in cancer chemotherapy, is a potent inhibitor of NF kappaB activation, we evaluated the therapeutic and prophylactic use of bortezomib in these conditions using murine models. Bortezomib prophylaxis significantly reduced serum levels of many cytokines and chemokines induced by BSAg. However, at 3 hours, serum level of TNF-a, an important cytokine implicated in TSS, was significantly reduced but not abolished. At 6 hours, there was no difference in the serum TNF-a levels between bortezomib treated and untreated mice challenged with staphylococcal enterotoxin B (SEB). Paradoxically, all mice treated with bortezomib either before or after BSAg challenge succumbed to TSS. Neither bortezomib nor BSAg was lethal if given alone. Serum biochemical parameters and histopathological findings suggested acute liver failure as the possible cause of mortality. Liver tissue from SEB-challenged mice treated with bortezomib showed a significant reduction in NF kappaB activation. Because NF kappaB-dependent antiapoptotic pathways protect hepatocytes from TNF-alpha-induced cell death, inhibition of NF kappaB brought forth by bortezomib in the face of elevated TNF-alpha levels caused by BSAg or LPS is detrimental.

Insulin Treatment of Diabetic Rats Reduces Cardiac Function in a Lipopolysaccharide-Induced Systemic Inflammation Model

Diabetes is a common comorbidity in patients with various medical conditions. Tight glucose control is known to improve systemic inflammation; however, whether it is effective in diabetic patients is unknown. The purpose of this study was to examine how strict glucose control affects systemic inflammation in diabetic patients. Male Wistar rats. We determined the effect of insulin therapy on cardiac function in a rat model of systemic inflammation. We administered lipopolysaccharide intravenously, with or without insulin, to streptozotocin-induced diabetic rats. After induction of systemic inflammation, we determined serum cytokine (IL-6 and TNFα) and nitrate/nitrite levels and measured cardiac function. Cytokine levels and cardiac function were significantly reduced in diabetic rats compared to non-diabetic rats. Moreover, insulin treatment was associated with higher cytokine levels and decreased cardiac function. In systemic inflammatory conditions, diabetes increases various proinflammatory mediators and inhibits cardiac function; insulin treatment exacerbates these effects. Thus, strict glucose control may not be desirable in diabetic patients with systemic inflammatory conditions.

Docosahexaenoic acid confers neuroprotection in a rat model of perinatal hypoxia-ischemia potentiated by Escherichia coli lipopolysaccharide-induced systemic inflammation

Lipopolysaccharide pretreatment potentiates hypoxic ischemic injury. We hypothesized that docosahexaenoic acid pretreatment would improve function and reduce brain volume loss in this rat model of perinatal brain injury and inflammation. Seven-day-old rats were divided into 3 groups: intraperitoneal docosahexaenoic acid 1 mg/kg and lipopolysaccharide 0.1 mg/kg, 25% albumin and lipopolysaccharide, and normal saline. Injections were given 2.5 hours before carotid ligation, followed by 90 minutes 8% O2. Rats underwent sensorimotor function testing and brain volume loss assessment on postnatal day 14. Docosahexaenoic acid pretreatment improved vibrissae forepaw placing scores compared with albumin/lipopolysaccharide (mean+/-standard deviation weighted score/20: 17.72+/-0.92 docosahexaenoic acid/lipopolysaccharide vs 13.83+/-0.82 albumin/lipopolysaccharide; P<.007). Albumin/lipopolysaccharide rats scores were worse than those of the normal saline/normal saline rats (13.83+/-0.82 vs 17.21+/-0.71; P=.076). No significant differences in brain volume loss were observed among groups. Lipopolysaccharide inflammatory stimulation in conjunction with hypoxic ischemic resulted in poorer function than hypoxic ischemic alone. Docosahexaenoic acid pretreatment had significantly improved function in neonatal rats exposed to lipopolysaccharide and hypoxic ischemic.

Stimulation of autophagy in the liver by lipopolysaccharide-induced systemic inflammation in a rat model of diabetes mellitus

The dysregulated metabolism associated with diabetes mellitus (DM) impairs membrane trafficking events in the liver, including the process of autophagy, which is an essential ongoing cellular process that is highly regulated by nutrients, endocrine factors, and signaling pathways. High-mobility group box 1 (HMGB1) is a nuclear protein with a known role in systemic inflammation and the related various organ injuries. However, its relationship to autophagy is not well understood. The aim of this study was to investigate the effects of inflammation injury on autophagy in the liver in a rat model of DM. DM was induced in animals with streptozotocin, followed four weeks later by induction of inflammation by LPS injection. At 12 h after LPS administration, autophagy was assessed by immunohistochemistry and Western blot analysis of microtubule-associated protein light chain 3 (LC3)-II, as well as transmission electron microscopy. Expression of HMGB1 was also examined by immunohistochemistry and Western blot analysis. Western blot analysis of liver tissue revealed that levels of LC3-II and HMGB1 protein increased in DM rats subjected to LPS-induced inflammation compared with non-DM rats. Autophagy was particularly enhanced in DM rats. Thus, autophagy might be related to progression to organ injury in patients with DM, and inflammation in these patients might be associated with over-induction of autophagy and increased HMGB1 expression.

Detection of Experimentally Induced Pulmonary Granuloma Inflammation in Monocyte Chemoattractant Protein-1 Reporter Mice

Among different chemokines, monocyte chemoattractant protein-1 (MCP-1) plays an important role in inflammatory disorders of lung. In response to stimuli, MCP-1 increases its transcription as an immediate early gene. In this paper, we describe the MCP-1-enhanced green fluorescent protein(EGFP) transgenic mouse in which EGFP expression is driven by human MCP-1 promoter and mimics the MCP-1 expression in situ. Thus, the MCP-1 reporter mouse model is designed to facilitate a better understanding of its role in various diseases. We employed this mouse model in a pulmonary granulomatous inflammation model using intratracheal instillation of Sephadex (SDX) beads and compared the EGFP reporter expression to endogenous MCP-1 expression through the course of inflammation. We analyzed the temporal pattern of SDX-induced infiltration of inflammatory cells in lung and in bronchoalveolar lavage fluid (BALF). The changes in tissue fluorescence, gene, and protein expressions for both MCP-1 and EGFP were analyzed. SDX instillation caused massive infiltration of inflammatory cells in BALF and lung tissue at the end of day 3. There was an increase of fluorescence in SDX-treated lung and BALF cells. By using lipopolysaccharide-induced systemic inflammation model, increase of fluorescence was found in bone marrow Gr-1(+) cells with high Mac-1 expression. MCP-1 and EGFP gene expression and MCP-1 protein level were increased after day 1, peaked at day 3, and declined toward basal levels at day 5. In contrast, EGFP protein level peaked after day 3 and remained elevated after day 5. Immunohistochemical staining revealed the MCP-1 and EGFP expression primarily at alveolar macrophages, macrophages infiltrating the granulomatous lesions and in bronchiolar epithelial cells. By using a pulmonary granuloma model, we showed that EGFP transgene reporter expression in MCP-1-EGFP mouse was correlated to the endogenous MCP-1 induction. The establishment of this mouse model will provide a valuable tool for monitoring the activation of monocytes/macrophages and facilitate the studies on the roles of MCP-1 gene in various inflammatory diseases.

Hyperglycemia contributes to cardiac dysfunction in a lipopolysaccharide-induced systemic inflammation model*

Hyperglycemia is frequently observed in nondiabetic patients during acute illness. Furthermore, intensive insulin therapy significantly reduces mortality and morbidity due to several critical illnesses, including cardiac or infectious diseases. The purpose of this study was to determine whether cardiac function is affected by hyperglycemia and its treatment with insulin. Lipopolysaccharide (LPS) was administered intravenously to rats, with or without the administration of insulin with glucose. University Medical Center research laboratory. Male Wistar rats. In this study, we determined the effect of hyperglycemia and insulin therapy on cardiac function in an LPS-induced systemic inflammation model. Levels of serum cytokines, nitrate/nitrite, and high-mobility group box 1 protein after LPS treatment were measured in hyperglycemic rats and those treated with insulin. The following parameters were examined to assess cardiac function in Langendorff-perfused hearts: left ventricular developed pressure, left ventricular end-diastolic pressure, and left ventricular pressure development during isovolumetric contraction (+dP/dtmax) and relaxation (-dP/dtmin). We observed that levels of cytokines, nitrate/nitrite, and high-mobility group box 1 significantly increased. However, treatment of hyperglycemic rats with insulin was associated with significantly less severe disease as assessed by cytokine levels. Furthermore, hyperglycemia was associated with decreased +dP/dtmax and -dP/dtmin in Langendorff-perfused hearts of hyperglycemic rats, whereas insulin treatment improved these parameters. Hyperglycemia was associated with the induction of various inflammatory mediators and an inhibition of cardiac function. Treatment of hyperglycemia with insulin protected against inflammation and cardiac dysfunction in a rat model of LPS-induced systemic inflammation. This improvement is likely because of the neutralization of deleterious effects associated with hyperglycemia and the specific actions of insulin on the inflammatory response.

Isolation of rat trachea interstitial fluid and demonstration of local cytokine production in lipopolysaccharide-induced systemic inflammation

Access to interstitial fluid from trachea is important for understanding tracheal microcirculation and pathophysiology. We tested whether a centrifugation method could be applied to isolate this fluid in rats by exposing excised trachea to G forces up to 609 g. The ratio between the concentration of the equilibrated extracellular tracer 51Cr-labeled EDTA in fluid isolated at 239 g and plasma averaged 0.94 +/- 0.03 (n = 14), suggesting that contamination from the intracellular fluid phase was negligible. The protein pattern of the isolated fluid resembled plasma closely and had a protein concentration 83% of that in plasma. The colloid osmotic pressure in the centrifugate in controls (n = 5) was 18.8 +/- 0.6 mmHg with a corresponding pressure in plasma of 22 +/- 1.5 mmHg, whereas after overhydration (n = 5) these pressures fell to 9.8 +/- 0.4 and 11.9 +/- 0.4 mmHg, respectively. We measured inflammatory cytokine concentration in serum, interstitial fluid, and bronchoalveolar lavage fluid in LPS-induced inflammation. In control animals, low levels of IL-1 beta, IL-6, and TNF-alpha in serum, trachea interstitial fluid, and bronchoalveolar lavage fluid were detected. LPS resulted in a significantly higher concentration in IL-1 beta and IL-6 in interstitial fluid than in serum, showing a local production. To conclude, we have shown that interstitial fluid can be isolated from trachea by centrifugation and that trachea interstitial fluid has a high protein concentration and colloid osmotic pressure relative to plasma. Trachea interstitial fluid may also reflect lower airways and thus be of importance for understanding, e.g., inflammatory-induced airway obstruction.

Lactobacillus rhamnosus GG Decreases Lipopolysaccharide‐induced Systemic Inflammation in a Gastrostomy‐fed Infant Rat Model

A gastrostomy-fed rat infant "pup-in-a-cup" model was used to test the hypothesis that enterally administered Lactobacillus rhamnosus GG (LGG) decreases the proinflammatory response induced by Escherichia coli lipopolysaccharide (LPS) in the developing infant rat small intestine, plasma, lung and liver. Two groups of 6- to 7-day-old pups were fed a rat milk substitute with LPS added via the gastrostomy tube for 6 days. One of the rat milk substitute-fed groups received supplemental LGG; another group received LPS without LGG. Age-matched mother-fed rat pups were used as controls. LPS treatment blunted body growth, but LGG supplementation had no effect on weight increments. LGG decreased LPS-induced inflammation in intestinal tissue; CINC-1 (rodent IL-8 equivalent) production in plasma, liver, lung and distal small intestine; and tumor necrosis factor alpha (TNF-alpha) production in plasma and lung. Cytokine multiplex assay showed lung interleukin (IL)-1beta, IL-6, IL-10, IL-18, growth-related oncogene (GRO)/KC (rat CINC-1) and TNF-alpha were significantly higher in gastrostomy-fed, LPS-treated pups than in mother-reared pups, and LGG significantly blunted the LPS-induced elevation of IL-1beta, IL-10, IL-18, GRO/KC and TNF-alpha; liver GRO/KC was significantly higher in gastrostomy-fed, LPS-treated pups than in mother-reared pups, and LGG significantly blunted the LPS-induced elevation of GRO/KC. LGG provided by the enteral route is able to downregulate LPS-induced proinflammatory mediators. This effect is not only present in the splanchnic organs, that is, the intestine and the liver, but extends to the plasma and a distal organ, the lung.

In Vivo Characterization of the Novel Imidazopyridine BYK191023 [2-[2-(4-Methoxy-pyridin-2-yl)-ethyl]-3H-imidazo[4,5-b]pyridine], a Potent and Highly Selective Inhibitor of Inducible Nitric-Oxide Synthase

Excessive release of nitric oxide from inducible nitric-oxide synthase (iNOS) has been postulated to contribute to pathology in a number of inflammatory diseases. We recently identified imidazopyridine derivatives as a novel class of potent nitricoxide synthase inhibitors with high selectivity for the inducible isoform. In the present study, we tested the in vivo potency of BYK191023 [2-[2-(4-methoxy-pyridin-2-yl)-ethyl]-3H-imidazo-[4,5-b]pyridine], a selected member of this inhibitor class, in three different rat models of lipopolysaccharide-induced systemic inflammation. Delayed administration of BYK191023 dose-dependently suppressed the lipopolysaccharide-induced increase in plasma nitrate/nitrite (NO(x)) levels with an ED(50) of 14.9 micromol/kg/h. In a model of systemic hypotension following high-dose lipopolysaccharide challenge, curative administration of BYK191023 at a dose that inhibited 83% of the NO(x) increase completely prevented the gradual decrease in mean arterial blood pressure observed in vehicle-treated control animals. The vasopressor effect was specific for endotoxemic animals since BYK191023 did not affect blood pressure in saline-challenged controls. In addition, in a model of lipopolysaccharide-induced vascular hyporesponsiveness, BYK191023 infusion partially restored normal blood pressure responses to norepinephrine and sodium nitroprusside via an l-arginine competitive mechanism. Taken together, BYK191023 is a member of a novel class of highly isoform-selective iNOS inhibitors with promising in vivo activity suitable for mechanistic studies on the role of selective iNOS inhibition as well as clinical development.

Acute hyperinsulinemia restrains endotoxin-induced systemic inflammatory response: an experimental study in a porcine model.

Intensive insulin therapy in critically ill patients reduces morbidity and mortality. The current study elucidates whether acute hyperinsulinemia per se could attenuate the systemic cytokine response and improve neutrophil function during endotoxin (lipopolysaccharide)-induced systemic inflammation in a porcine model. Pigs were anesthetized, mechanically ventilated, randomized into four groups, and followed for 570 min: group 1 (anesthesia solely, n = 10), group 2 (hyperinsulinemic euglycemic clamp [HEC], n = 9), group 3 (lipopolysaccharide, n = 10), group 4 (lipopolysaccharide-HEC, n = 9). Groups 3 and 4 were given a 180-min infusion of lipopolysaccharide (total, 10 microg/kg). Groups 2 and 4 were clamped (p-glucose: 5 mM/l, insulin 0.6 mU.kg(-1).min(-1)) throughout the study period. Changes in pulmonary and hemodynamic function, circulating cytokines, free fatty acids, glucagon, and neutrophil chemotaxis were monitored. Tumor necrosis factor alpha and interleukin 6 were significantly reduced in the lipopolysaccharide-HEC group compared with the lipopolysaccharide group (both P = 0.04). In the lipopolysaccharide-HEC group, the glucagon response was diminished compared with the lipopolysaccharide group (P < 0.05). Serum free fatty acid concentrations were decreased in animals exposed to HEC. Animals receiving lipopolysaccharide showed an increase in pulmonary pressure (P < 0.001), but otherwise, there were no major changes in pulmonary or hemodynamic function. Neutrophil function was impaired after lipopolysaccharide administration. Hyperinsulinemia concomitant with normoglycemia reduces plasma concentrations of tumor necrosis factor alpha and the catabolic hormone glucagon in lipopolysaccharide-induced systemic inflammation in pigs. The finding strongly supports the role of insulin as an antiinflammatory hormone. Whether the effect to some extent operates via a reduced free fatty acid concentration is unsettled.