Role of free radicals and poly(ADP-ribose) synthetase in intestinal tight junction permeability

BACKGROUND: Small intestine permeability is frequently altered in inflammatory bowel disease and may be caused by the translocation of intestinal toxins through leaky small intestine tight junctions (TJ) and adherence (1,2). The role of hydrogen peroxide (H2O2), and nitric oxide (NO) and PARS in the permeability and structure of small intestine TJ is not clearly understood. MATERIALS AND METHODS: In vitro study, MDCK (Madin-Darby Canine Kidney) cells were exposed to H2O2 (100 microM for 2h), or zymosan (200 microl of stock solution 1 mg/ml for 4h), in the presence or absence of a treatment with poly(ADP-ribose) synthetase (PARS) inhibitor 3-aminobenzamide (3-AB: 3 mM) or with n-acetylcysteine (NAC 10 mM). In vivo study, wild-type mice (WT) and mice lacking (KO) of the inducible (or type 2) nitric oxide synthase (iNOS) were treated with zymosan (500 mg/kg, suspended in saline solution, i.p.). In addition INOSWT mice were treated with 3-AB (10 mg/kg, i.p.) or with NAC (40 mg/kg, i.p.) 1 hour and 6 h after zymosan administration. RESULTS: Exposure of MDCK cells to hydrogen peroxide caused a significant impairment in mitochondrial respiration that was associated with a reduction of cells adherence as well as derangement of the junctional proteins. A significant increase of nitrate and nitrite levels, stable metabolites of nitric oxide (NO), were found in MDCK supernatant after zymosan incubation. NO production was associated with a significant reduction of cell adherence and impairment of occludin protein. Pre-treatment of the cells with 3-AB or with NAC caused a significant prevention of H2O2-mediated occludin junctional damage as well as reduced the NO-induced occludin damage. In addition, H2O2 and NO are able to induce a significant derangement of beta-catenin and Zonula Ocludence-1 (ZO-1). We found an increase of tight junctional permeability to lanthanum nitrate (molecular weight, 433) in the terminal ileal TJs in zymosan-treated iNOSWT mice compared with permeable TJ in the control animals. Zymosan-treated iNOSKO mice showed a significant increase of tight junctional permselectivity. There were no differences in strand count or strand depth in the ilea from control or treated animals. In addition, a significant disrupted immunofluorescence signal for occludin, ZO-1 and beta-catenin was observed in the terminal ilea of zymosan-treated iNOSWT mice. In ileal fragments from zymosan-treated iNOSKO mice, we found less irregular distribution patterns of occludin, ZO-1 and beta-catenin. Similarly NAC or 3-AB treatments were able to prevent zymosan-induced damage of junctional proteins in iNOSWT mice. CONCLUSION: In conclusion, this study demonstrates that the alteration of permselectivity is most likely induced by ROS and PARS activation.     

Effect of NADPH-oxidase inhibitors in the experimental model of zymosan-induced shock in mice

The aim of this study was to investigate the effects of NADPH-oxidase inhibitors, in a mouse model of zymosan. Zymosan-induced shock was induced in mice by administration of zymosan (500 mg/kg, i.p.). The pharmacological treatment was the administration of apocynin (5 mg/kg 10% DMSO i.p.) and diphenylene iodonium chloride (DPI) (1 mg/kg i.v.) 1 h and 6 h after zymosan administration. MOF and systemic inflammation in mice was assessed 18 h after administration of zymosan. NADPH-oxidase inhibitors caused a significant reduction of the (1) peritoneal exudate formation, (2) neutrophil infiltration, (3) multiple organ dysfunction syndrome, (4) nitrotyrosine, (5) poly (ADP-ribose) (PAR), (6) cytokine formation, (7) adhesion molecule expression, (8) nuclear factor (NF-κB) expression and (9) apoptosis induced by zymosan. Moreover, NADPH-oxidase inhibitors treatment significantly reduced the systemic toxicity, the loss in body weight and the mortality caused by zymosan. This study has shown that NADPH-oxidase inhibitors attenuate the degree of zymosan-induced non-septic shock in mice.     

Effect of NADPH-oxidase inhibitors in the experimental model of zymosan-induced shock in mice

Abstract

The aim of this study was to investigate the effects of NADPH-oxidase inhibitors, in a mouse model of zymosan. Zymosan-induced shock was induced in mice by administration of zymosan (500 mg/kg, i.p.). The pharmacological treatment was the administration of apocynin (5 mg/kg 10% DMSO i.p.) and diphenylene iodonium chloride (DPI) (1 mg/kg i.v.) 1 h and 6 h after zymosan administration. MOF and systemic inflammation in mice was assessed 18 h after administration of zymosan. NADPH-oxidase inhibitors caused a significant reduction of the (1) peritoneal exudate formation, (2) neutrophil infiltration, (3) multiple organ dysfunction syndrome, (4) nitrotyrosine, (5) poly (ADP-ribose) (PAR), (6) cytokine formation, (7) adhesion molecule expression, (8) nuclear factor (NF-κB) expression and (9) apoptosis induced by zymosan. Moreover, NADPH-oxidase inhibitors treatment significantly reduced the systemic toxicity, the loss in body weight and the mortality caused by zymosan. This study has shown that NADPH-oxidase inhibitors attenuate the degree of zymosan-induced non-septic shock in mice.     

Properdin deficiency in murine models of nonseptic shock

Hereditary properdin deficiency is linked to susceptibility to meningococcal disease (Neisseria meningitidis serotypes Y and W-135) with high mortality. Its relative contribution toward the outcome of nonseptic shock has not been investigated. Using properdin-deficient C57BL/6 mice and their littermates, this study examines their survival of zymosan-induced and LPS-induced shock. Properdin-deficient mice were more resistant to zymosan shock compared with wild-type mice, which showed greater impairment of end-organ function 24 h after zymosan injection, higher TNF-alpha production by alveolar and peritoneal macrophages, higher TNF-alpha, and, inversely, lower IL-10 levels in peritoneal lavage and circulation and higher plasma C5a levels. Properdin-deficient mice showed significantly higher mortality in LPS shock, elevated TNF-alpha, and, inversely, reduced IL-10 production by peritoneal macrophages as well as lower plasma C5a levels compared with wild-type littermates. NO production by peritoneal macrophages and plasma alpha1-antitrypsin levels at 24 h after the injection of LPS or zymosan were decreased in properdin-deficient mice in both models, and fewer histopathologic changes in liver were observed in properdin-deficient animals. This study provides evidence that properdin deficiency attenuates zymosan-induced shock and exacerbates LPS-induced shock.     

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.     

Protective effect of Hypericum perforatum in zymosan-induced multiple organ dysfunction syndrome: relationship to its inhibitory effect on nitric oxide production and its peroxynitrite scavenging activity.

Hypericum perforatum is a medicinal plant species containing many polyphenolic compounds, namely flavonoids and phenolic acids. Since polyphenolic compounds have high antioxidant potential, we have investigated the effects of H. perforatum extract on the development of multiple organ dysfunction syndrome caused by zymosan (500 mg/kg, administered i.p. as a suspension in saline) in mice. Organ failure and systemic inflammation in rats was assessed 18 h after administration of zymosan and/or H. perforatum extract and monitored for 12 days (for loss of body weight and mortality). Treatment of mice with H. perforatum extract (30 mg/kg i.p., 1 and 6h after zymosan) attenuated the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan, pulmonary, intestinal and pancreatic injury, and renal dysfunction as well as the increase in myeloperoxidase in the lung and intestine. Immunohistochemical analysis for inducible nitric oxide synthase (iNOS), nitrotyrosine, and poly(ADP-ribose) (PAR) revealed positive staining in lung and intestine tissues obtained from zymosan-injected mice. The degree of staining for nitrotyrosine, iNOS, and PAR was markedly reduced in tissue sections obtained from zymosan-treated mice, which received H. perforatum extract. In conclusion, this study provides evidence, for the first time, that H. perforatum extract attenuates the degree of zymosan-induced multiple organ dysfunction syndrome in mice.     

The role of MIP-1 alpha in the development of systemic inflammatory response and organ injury following trauma hemorrhage

Although MIP-1alpha is an important chemokine in the recruitment of inflammatory cells, it remains unknown whether MIP-1alpha plays any role in the development of systemic inflammatory response following trauma-hemorrhage (T-H). C57BL/6J wild type (WT) and MIP-1alpha-deficient (KO) mice were used either as control, subjected to sham operation (cannulation or laparotomy only or cannulation plus laparotomy) or T-H (midline laparotomy, mean blood pressure 35 +/- 5 mmHg for 90 min, followed by resuscitation) and sacrificed 2 h thereafter. A marked increase in serum alpha-glutathione transferase, TNF-alpha, IL-6, IL-10, MCP-1, and MIP-1alpha and Kupffer cell cytokine production was observed in WT T-H mice compared with shams or control. In addition lung and liver tissue edema and neutrophil infiltration (myeloperoxidase (MPO) content) was also increased following T-H in WT animals. These inflammatory markers were markedly attenuated in the MIP-1alpha KO mice following T-H. Furthermore, compared with 2 h, MPO activities at 24 and 48 h after T-H declined steadily in both WT and KO mice. However, normalization of MPO activities to sham levels within 24 h was seen in KO mice but not in WT mice. Thus, MIP-1alpha plays an important role in mediating the acute inflammatory response following T-H. In the absence of MIP-1alpha, acute inflammatory responses were attenuated; rapidly recovered and less remote organ injury was noted following T-H. Thus, interventions that reduce MIP-1alpha levels following T-H should be useful in decreasing the deleterious inflammatory consequence of trauma.     

Absence of endogenous interleukin-10 enhances the evolution of acute lung injury

Interleukin-10 (IL-10) exerts a wide spectrum of regulatory activities in the immune and inflammatory response. The aim of this study was to investigate the role of endogenous IL-10 on the modulation of the inflammatory response in mice subjected to carrageenan-induced lung injury. When compared to carrageenan-treated IL-10 wild-type (WT) mice, carrageenan-treated IL-10 knock-out mice (IL-10KO) mice experienced a higher rate of pleural exudation, and polymorphonuclear cell migration. Exudate levels of the pro-inflammatory cytokines tumour necrosis factor, interleukin-1beta and interleukin-6 were also greatly enhanced in IL-10KO mice in comparison to wild-type mice. Lung myeloperoxidase (MPO) activity was significantly reduced in IL-10WT mice when compared to IL-10KO mice-treated with carrageenan. The degree of oxidative and nitrosative damage was significantly higher in IL-10KO mice than in wild-type littermates, as indicated by elevated malondialdehyde levels and formation of nitrotyrosine and poly (ADP-ribose) synthetase (PARS). Staining of lung tissue sections obtained from carrageenan-treated IL-10WT with an anti-COX-2 antibody showed a positive staining of the inflamed tissue. Furthermore, expression of inducible nitric oxide synthase (iNOS) was found mainly in the macrophages of the inflamed lungs from carrageenan-treated IL-10WT mice. The intensity and degree of the staining for COX-2 and iNOS were markedly enhanced in tissue sections obtained from carrageenan-treated IL-10KO mice. Most notably, the degree of lung injury caused by carrageenan was also enhanced in IL-10KO mice. Taken together, our results clearly demonstrate that endogenous IL-10 exerts an anti-inflammatory role during acute inflammation and tissue damage associated with carrageenan-induced pleurisy, possibly by regulating neutrophil recruitment, and the subsequent cytokine and oxidant generation.     

Myeloperoxidase deficiency attenuates systemic and dietary iron-induced adverse effects

Iron deficiency is routinely treated with oral or systemic iron supplements, which are highly reactive and could induce oxidative stress via augmenting the activity of proinflammatory enzyme myeloperoxidase (MPO). To investigate the extent to which MPO is involved in iron-induced toxicity, acute (24 h) iron toxicity was induced by intraperitoneal administration of FeSO₄ (25 mg/kg body weight) to MPO-deficient (MpoKO) mice and their wild-type (WT) littermates. Acute iron toxicity was also assessed in WT mice pretreated with an MPO inhibitor, 4-aminobenzoic acid hydrazide. Systemic iron administration up-regulated circulating MPO and neutrophil elastase and elevated systemic inflammatory and organ damage markers in WT mice. However, genetic deletion of MPO or its inhibition significantly reduced iron-induced organ damage and systemic inflammatory responses. In contrast to the acute model, 8 weeks of 2% carbonyl iron diet feeding to WT mice did not change the levels of circulating MPO and neutrophil elastase but promoted their accumulation in the liver. Even though both MpoKO and WT mice displayed similar levels of diet-induced hyperferremia, MpoKO mice showed significantly reduced inflammatory response and oxidative stress than the WT mice. In addition, WT bone-marrow-derived neutrophils (BMDN) generated more reactive oxygen species than MPO-deficient BMDN upon iron stimulation. Altogether, genetic deficiency or pharmacologic inhibition of MPO substantially attenuated acute and chronic iron-induced toxicity. Our results suggest that targeting MPO during iron supplementation is a promising approach to reduce iron-induced toxicity/side effects in vulnerable population.     

IL-10 deficiency augments acute lung but not liver injury in hemorrhagic shock

In hemorrhagic shock and trauma, patients are prone to develop systemic inflammation with remote organ dysfunction, which is thought to be caused by pro-inflammatory mediators. This study investigates the role of the immuno-modulatory cytokine IL-10 in the development of organ dysfunction following hemorrhagic shock. Male C57/BL6 and IL-10 KO mice were subjected to volume controlled hemorrhagic shock for 3 h followed by resuscitation. Animals were either sacrificed 3 or 24 h after resuscitation. To assess systemic inflammation, serum IL-6, IL-10, KC, and MCP-1 concentrations were measured with the Luminex? multiplexing platform; acute lung injury (ALI) was assessed by pulmonary myeloperoxidase (MPO) activity and lung histology and acute liver injury was assessed by hepatic MPO activity, hepatic IL-6 levels, and serum ALT levels. There was a trend towards increased IL-6 and KC serum levels 3 h after resuscitation in IL-10 KO as compared to C57/BL6 mice; however this did not reach statistical significance. Serum MCP-1 levels were significantly increased in IL-10 KO mice 3 and 24 h following resuscitation as compared to C57/BL6 mice. In IL-10 KO mice, pulmonary MPO activity was significantly increased 3 h following resuscitation and after 24 h histological signs of acute lung injury were more apparent than in C57/BL6 mice. In contrast, no significant differences in any liver parameters were detected between IL-10 KO and C57/BL6 mice. Our data indicate that an endogenous IL-10 deficiency augments acute lung but not liver injury following hemorrhagic shock.     

Role of IL-6 in the pleurisy and lung injury caused by carrageenan.

In the present study we used IL-6 knockout mice (IL-6KO) to evaluate the role of IL-6 in the inflammatory response caused by injection of carrageenan into the pleural space. Compared with carrageenan-treated IL-6 wild-type (IL-6WT) mice, carrageenan-treated IL-6KO mice exhibited a reduced degree of pleural exudation and polymorphonuclear cell migration. Lung myeloperoxidase activity and lipid peroxidation were significantly reduced in IL-6KO mice compared with those in IL-6WT mice treated with carrageenan. Immunohistochemical analysis for nitrotyrosine and poly(A)DP-ribose polymerase revealed a positive staining in lungs from carrageenan-treated IL-6WT mice. No positive staining for nitrotyrosine or PARS was found in the lungs of the carrageenan-treated IL-6KO mice. Staining of lung tissue sections obtained from carrageenan-treated IL-6WT mice with an anti-cyclo-oxygenase-2 Ab showed a diffuse staining of the inflamed tissue. Furthermore, expression of inducible nitric oxide synthase was found mainly in the macrophages of the inflamed lungs from carrageenan-treated IL-6WT mice. The intensity and degree of the staining for cyclo-oxygenase-2 and inducible nitric oxide synthase were markedly reduced in tissue sections obtained from carrageenan-treated IL-6KO mice. Most notably, the degree of lung injury caused by carrageenan was also reduced in IL-6KO mice. Treatment of IL-6WT mice with anti-IL-6 (5 microg/day/mouse at 24 and 1 h before carrageenan treatment) also significantly attenuated all the above indicators of lung inflammation. Taken together, our results clearly demonstrate that IL-6KO mice are more resistant to the acute inflammation of the lung caused by carrageenan injection into the pleural space than the corresponding WT mice.     

Role of CD69 in the pathogenesis of elastase-induced pulmonary inflammation and emphysema

Cluster of differentiation 69 (CD69), known as an early activation marker of lymphocytes, has been demonstrated to regulate inflammatory events in various disease models. Although the increased number of CD69-expressed T lymphocytes in the lungs of patients with chronic obstructive pulmonary disease (COPD) has been reported, a functional role of CD69 in the pathogenesis of COPD remains unknown. To address to this question, CD69-deficient (CD69KO) mice and wild-type (WT) mice were subjected to a mouse model of porcine pancreatic elastase (PPE)-induced pulmonary inflammation and emphysema. In the two genotypes, PPE increased counts of macrophages, neutrophils and lymphocytes in bronchoalveolar lavage fluid (BALF) and induced emphysematous changes in the lung, whereas those two pathological signs were significantly enhanced in CD69KO mice compared to WT mice. Moreover, the PPE-induced levels of IL-17 and IL-6 in BALF were significantly higher in CD69KO mice than in WT mice at the acute inflammatory phase. Immunofluorescent studies showed that IL-17 and IL-6 were predominantly expressed in CD4⁺ and γδ T cells and macrophages, respectively. Concomitant administration of IL-17- and IL-6-neutralizing antibodies significantly attenuated the PPE-induced emphysematous changes in the two genotypes. These findings suggest that CD69 negatively regulates the development of PPE-induced emphysema in part at least through modulating function of IL-17-producing T cells.     

Balance of meprin A and B in mice affects the progression of experimental inflammatory bowel disease

MEP1A, which encodes the α subunit of meprin metalloproteinases, is a susceptibility gene for inflammatory bowel disease (IBD), and decreased intestinal meprin-α expression is associated with enhanced IBD in humans. Mice lacking meprin α (α knockout, αKO) have more severe colitis induced by dextran sulfate sodium (DSS) than wild-type (WT) mice, indicating an anti-inflammatory role for meprin A. Previous studies and those herein indicate the meprin B has proinflammatory activities. Therefore, mice lacking both meprin A and B (dKO mice) were generated to determine how their combined absence alters the inflammatory response to DSS. Unchallenged dKO mice grow and reproduce normally and have no obvious abnormal phenotype, except for a slightly elevated plasma albumin in both males and females and a lower urine creatinine level in dKO males. Upon oral administration of 3.5% DSS, the dKO mice have more severe colitis than the WT and βKO mice but significantly less than the αKO mice. The dKO mice lose more weight and have elevated MPO and IL-6 activities in the colon compared with WT mice. Systemic inflammation, monitored by plasma nitric oxide levels, is absent in DSS-treated dKO mice, unlike WT mice. The severity of experimental IBD in dKO mice is intermediate between αKO and WT mice. The data indicate that the absence of meprin A aggravates chronic inflammation and the lack of meprin B affords some protection from injury. Manipulation of the expression of meprin gene products may have therapeutic potential.     

Role of IL-6 in systemic angiogenesis of the lung.

The multifunctional cytokine interleukin (IL)-6 has been shown to modulate inflammation and angiogenesis. In a mouse model of lung angiogenesis induced by chronic left pulmonary artery ligation (LPAL), we previously showed increased expression of IL-6 mRNA in lung homogenates 4 h after the onset of pulmonary ischemia. To determine whether IL-6 influences both new vessel growth and inflammatory cell influx, we studied wild-type (WT) and IL-6-deficient C57Bl/6J (KO) mice after LPAL (4 h and 1, 7, 14 days). We measured IL-6 protein of the lung by ELISA, the lavage cell profile of the left lung, and new systemic vessel growth with radiolabeled microspheres (14 days after LPAL) in WT and KO mice. We confirmed a 2.4-fold increase in IL-6 protein in the left lung of WT mice compared with right lung 4 h after LPAL. A significant increase in lavaged neutrophils (7.5% of total cells) was observed only in WT mice 4 h after LPAL. New vessel growth was significantly attenuated in KO relative to WT (0.7 vs. 1.9% cardiac output). In an additional series, treatment of WT mice with anti-neutrophil antibody demonstrated a reduction in lavaged neutrophils 4 h after LPAL; however, IL-6 protein remained elevated and neovascularization to the left lung (2.3% cardiac output) was not altered. These results demonstrate that IL-6 plays an important modulatory role in lung angiogenesis, but the changes are not dependent on trapped neutrophils.     

Methylguanidine reduces the development of non septic shock induced by zymosan in mice

In the present study we evaluate the effect of methylguanidine (MG), a product of protein catabolism, in a model of acute inflammation (zymosan induced inflammation) in mice where oxyradical and nitric oxide (NO) play a crucial role. Our data show that MG, given intraperitoneally at the dose of 30 mg/Kg, inhibits the inflammatory response reducing significantly (P < 0.05) peritoneal exudates formation, mononuclear cell infiltration and histological injury in mice. Furthermore, our data suggests that there is a significant (P < 0.05) reduction in kidney, liver and pancreas injury as demonstrated by the reduction in amylase, lipase, creatinine, AST, ALT, bilirubine and alkaline phosfatase levels. MG is also able to reduce the appearance of nitrotyrosine and of the nuclear enzyme poly (adenosine diphosphate [ADP]-ribose) synthase (PARS) immunoreactivity in the inflamed intestinal and lung tissues. The histological examination revealed a significant reduction in zymosan-induced intestinal and lung damage in MG-treated mice. Taken together, the present results demonstrate that MG exerts potent anti-inflammatory effects on zymosan-induced shock.     

TGF-beta and Smad3 signaling link inflammation to chronic fibrogenesis

Transient adenovirus-mediated gene transfer of IL-1beta (AdIL-1beta), a proinflammatory cytokine, induces marked inflammation and severe and progressive fibrosis in rat lungs. This is associated with an increase in TGF-beta1 concentration in bronchoalveolar lavage (BAL) fluid. TGF-beta1 is a key cytokine in the process of fibrogenesis, using intracellular signaling pathways involving Smad2 and Smad3. In this study we investigate whether inflammation induced by IL-1beta is able to independently induce lung fibrosis in mice deficient in the Smad3 gene. Seven days after AdIL-1beta administration, similar levels of IL-1beta transgene are seen in BAL in both wild-type (WT) and knockout (KO) mice, and BAL cell profiles demonstrated a similar marked neutrophilic inflammation. Phospho-Smad2 staining was positive in areas of inflammation in both WT and KO mice at day 7. By day 35 after transient IL-1beta expression, WT mice showed marked fibrosis in peribronchial areas, quantified by picrosirius red staining and morphometry. However, there was no evidence of fibrosis or collagen accumulation in IL-1beta-treated KO mice, and peribronchial areas were not different from KO mice treated with the control adenovector. TGF-beta1 and phospho-Smad2 were strongly positive at day 35 in fibrotic areas observed in WT mice, but no such staining was detectable in KO mice. The IL-1beta-induced chronic fibrotic response in mouse lungs is dependent on Smad3. KO and WT animals demonstrated a similar inflammatory response to overexpression of IL-1beta indicating that inflammation must link to the Smad3 pathway, likely through TGF-beta, to induce progressive fibrosis.     

MicroRNA-21 Knockout Improve the Survival Rate in DSS Induced Fatal Colitis through Protecting against Inflammation and Tissue Injury

Background

MicroRNA-21 (miR-21) is overexpressed in most inflammatory diseases, but its physiological role in gut inflammation and tissue injury is poorly understood. The goal of this work is to understand the role of miR-21 in colitis and damage progression of intestine in a genetically modified murine model.

Methods

Experimental colitis was induced in miR-21 KO and wild-type (WT) mice by 3.5% dextran sulphate sodium (DSS) administration for 7 days. Disease activity index(DAI), blood parameters, intestinal permeability, histopathologic injury, cytokine and chemokine production, and epithelial cells apoptosis were examined in colons of miR-21 KO and WT mice.

Results

miR-21 was overexpressed in intestine of inflammatory bowel diseases (IBD) and acute intestinal obstruction (AIO) patients when compared with normal intestinal tissues. Likewise, miR-21 was up-regulated in colon of IL-10 KO mice when compared with control mice. WT mice rapidly lost weight and were moribund 5 days after treatment with 3.5% DSS, while miR-21 KO mice survived for at least 6 days. Elevated leukocytes and more severe histopathology were observed in WT mice when compared with miR-21 KO mice. Elevated levels of TNF-α and macrophage inflammatory protein-2(MIP-2) in colon culture supernatants from WT mice exhibited significant higher than miR-21 KO mice. Furthermore, CD3 and CD68 positive cells, intestinal permeability and apoptosis of epithelial cells were significantly increased in WT mice when compared with miR-21 KO mice. Finally, we found that miR-21 regulated the intestinal barrier function through modulating the expression of RhoB and CDC42.

Conclusion

Our results suggest that miR-21 is overexpressed in intestinal inflammation and tissue injury, while knockout of miR-21 in mice improve the survival rate in DSS-induced fatal colitis through protecting against inflammation and tissue injury. Therefore, attenuated expression of miR-21 in gut may prevent the onset or progression of inflammatory bowel disease in patients.     

Absence of endogenous interleukin-6 enhances the inflammatory response during acute pancreatitis induced by cerulein in mice

Interleukin-6 (IL-6) exerts a wide spectrum of regulatory activities during immune and inflammatory responses. The aim of this study was to investigate the role of endogenous IL-6 in the inflammatory response associated with acute pancreatitis. Acute pancreatitis was induced by hourly (x5) i.p. injections of cerulein (50 microg/kg, suspended in saline solution) in IL-6 deficient mice (IL-6-KO) and wild-type (IL-6WT) littermates. IL-6KO mice exhibited a more severe tissue injury and a higher rate of mortality and when compared to IL-6WT mice. Acute pancreatitis was characterized by edema, neutrophil infiltration, tissue hemorrhage and cell necrosis, upregulation of P-selectin and intercellular adhesion molecule-1 (ICAM-1), as well as increases in the serum levels of amylase and lipase. The degree of oxidative and nitrosative tissue damage was significantly greater in IL-6KO mice than in wild-type littermates, as indicated by higher tissue levels of malondialdehyde and nitrosylated proteins. Plasma levels of the inflammatory cytokines tumour necrosis factor-alpha and interleukin-1beta were also greatly enhanced in IL-6KO mice when compared to wild-type mice. These events were correlated with an increase in the staining (immunoreactivity) for poly (ADP-ribose) polymerase (PARP) in the pancreas of cerulein-treated IL-6WT. The staining for PARP was more pronounced in IL-6KO mice subjected to acute pancreatitis than in the corresponding WT mice. These data demonstrate that endogenous IL-6 exerts an anti-inflammatory role during acute pancreatitis, possibly by regulating the expression of adhesion molecules, the subsequent adhesion and activation of neutrophils and finally the generation of cytokine and reactive oxygen or nitrogen species.     

Contribution of IL-18 to Th1 response and host defense against infection by Mycobacterium tuberculosis: a comparative study with IL-12p40

The present study was conducted to critically determine the protective role of IL-18 in host response to Mycobacterium tuberculosis infection. IL-18-deficient (knockout (KO)) mice were slightly more prone to this infection than wild-type (WT) mice. Sensitivity of IL-12p40KO mice was lower than that of IL-12p40/IL-18 double KO mice. IFN-gamma production caused by the infection was significantly attenuated in IL-18KO mice compared with WT mice, as indicated by reduction in the levels of this cytokine in sera, spleen, lung, and liver, and its synthesis by spleen cells restimulated with purified protein derivatives. Serum IL-12p40 level postinfection and its production by peritoneal exudate cells stimulated with live bacilli were also significantly lower in IL-18KO mice than WT mice, suggesting that attenuated production of IFN-gamma was secondary to reduction of IL-12 synthesis. However, this was not likely the case, because administration of excess IL-12 did not restore the reduced IFN-gamma production in IL-18KO mice. In further studies, IL-18 transgenic mice were more resistant to the infection than control littermate mice, and serum IFN-gamma level and its production by restimulated spleen cells were increased in the former mice. Taken together, our results indicate that IL-18 plays an important role in Th1 response and host defense against M. tuberculosis infection although the contribution was not as profound as that of IL-12p40.     

Hematological and acute-phase responses to diet-induced obesity in IL-6 KO mice

Obesity is associated with chronic inflammation and elevated levels of IL-6. The role of IL-6 in induction of acute-phase proteins and modulation of hematological responses has been demonstrated in models of inflammation and aging, but not in obesity. We hypothesized that IL-6 is necessary to regulate the acute-phase response and hematological changes associated with diet-induced obesity (DIO) in mice. Feeding a 60%kcal/fat diet for 13 weeks to C57BL6 WT male mice induced a significant increase in IL-6 expression in visceral adipose tissue (VAT), but not liver, compared to mice fed chow diet. Significantly elevated IL-6 levels were present in the peritoneal lavage fluid, but not plasma, of DIO compared to lean mice. A comparable degree of obesity, hepatomegaly, hyperleptinemia, VAT inflammation and insulin resistance was observed in DIO WT and IL-6 KO mice compared to WT and KO mice fed chow diet. Significant leukocytosis was observed in DIO WT but not DIO KO mice compared to lean groups. A significant reduction in platelet counts, without alterations in platelet size, percentage of circulating reticulated platelets and number of bone marrow megakaryocytes, was present in DIO KO mice compared to each other group. Hepatic expression of thrombopoietin was comparable in each group, with DIO WT and KO mice having reduced VAT expression compared to lean mice. Lean KO mice had significantly elevated plasma levels of thrombopoietin compared to each other group, whereas liver-associated thrombopoietin levels were comparable in each group. Deficiency of IL-6 resulted in blunted hepatic induction of the acute-phase protein serum amyloid A-1, whereas expression of hepcidin-1 and -2, LPS-binding protein, ceruloplasmin, plasminogen activator inhibitor-1 and thrombospondin-1 was IL-6-independent. In conclusion, in the absence of overt metabolic alterations, IL-6 modulates leukocytosis, thrombopoiesis and induction of SAA-1, but not other acute-phase proteins in obese mice.