Effect of a BLT receptor antagonist in a model of severe ischemia and reperfusion injury in the rat

FcᵧRIIb protects from reperfusion injury by controlling antibody and type I IFN-mediated tissue injury and death

Intestinal ischemia and reperfusion (I/R) is accompanied by an exacerbated inflammatory response characterized by deposition of IgG, release of inflammatory mediators, and intense neutrophil influx in the small intestine, resulting in severe tissue injury and death. We hypothesized that FcᵧRIIb activation by deposited IgG could inhibit tissue damage during I/R. Our results showed that I/R induction led to the deposition of IgG in intestinal tissue during the reperfusion phase. Death upon I/R occurred earlier and was more frequent in FcᵧRIIb^-/- than WT mice. The higher lethality rate was associated with greater tissue injury and bacterial translocation to other organs. FcᵧRIIb^-/- mice presented changes in the amount and repertoire of circulating IgG, leading to increased IgG deposition in intestinal tissue upon reperfusion in these mice. Depletion of intestinal microbiota prevented antibody deposition and tissue damage in FcᵧRIIb^-/- mice submitted to I/R. We also observed increased production of ROS on neutrophils harvested from the intestines of FcᵧRIIb^-/- mice submitted to I/R. In contrast, FcᵧRIII^-/- mice presented reduced tissue damage and neutrophil influx after reperfusion injury, a phenotype reversed by FcᵧRIIb blockade. In addition, we observed reduced IFN-β expression in the intestines of FcᵧRIII^-/- mice after I/R, a phenotype that was also reverted by blocking FcᵧRIIb. IFNAR^-/- mice submitted to I/R presented reduced lethality and TNF release. Altogether our results demonstrate that antibody deposition triggers FcᵧRIIb to control IFN-β and IFNAR activation and subsequent TNF release, tailoring tissue damage, and death induced by reperfusion injury.

Angioedema and Fatty Acids

Angioedema is a life-threatening emergency event that is associated with bradykinin and histamine-mediated cascades. Although bradykinin-mediated angioedema currently has specific therapeutic options, angioedema is sometimes intractable with current treatments, especially histamine-mediated angioedema, suggesting that some other mediators might contribute to the development of angioedema. Fatty acids are an essential fuel and cell component, and act as a mediator in physiological and pathological human diseases. Recent updates of studies revealed that these fatty acids are involved in vascular permeability and vasodilation, in addition to bradykinin and histamine-mediated reactions. This review summarizes each fatty acid’s function and the specific receptor signaling responses in blood vessels, and focuses on the possible pathogenetic role of fatty acids in angioedema.

The examination of the nephroprotective effect of montelukast sodium and N-acetylcysteine ın renal ıschemia with dimercaptosuccinic acid imaging in a placebo-controlled rat model

Purpose

To determine the nephroprotective effect of NAC and Montelukast Sodium administration against the development of renal damage associated with long warm renal ischemia.

Methods

Twenty-seven rats were randomly divided into 3 study groups, which received NAC, montelukast and placebo, and 3 rats were included in the sham-treated control group. Medications were given 3 days before the procedure. DMSA renal scintigraphy was performed before and after surgery. The right renal pedicle was occluded for 45 min to induce ischemia and then subjected to reperfusion for 6 h (I/R groups).

Results

On pathological examination, the mean pathological scores of the montelukast and NAC groups were significantly lower than those of the placebo group. (p <0.05). In biochemical examination, significant differences were found in all parameter levels between the placebo group and the montelukast and NAC groups. (p <0.05) When postoperative DMSA renal scintigraphy measurements and renal function levels were compared, significant differences were found between the montelukast and NAC groups and the placebo and sham groups.

Conclusion

The administration of NAC and montelukast sodium was seen to have a nephroprotective effect against the development of renal damage associated with warm renal ischemia.

Inhibition of 5-lipoxygenase alleviates graft-versus-host disease

Rezende et al. report that the transplant of 5-lipoxygenase (5-LO)−deficient leukocytes protects mice from GVHD. Treatment with the 5-LO inhibitor zileuton or a LTB₄ antagonist at the initial phase of the transplant achieves similar protective effects. 5-LO is a crucial contributor to tissue damage in GVHD.

Leukotriene B₄ (LTB₄), a proinflammatory mediator produced by the enzyme 5-lipoxygenase (5-LO), is associated with the development of many inflammatory diseases. In this study, we evaluated the participation of the 5-LO/LTB₄ axis in graft-versus-host disease (GVHD) pathogenesis by transplanting 5-LO–deficient leukocytes and investigated the effect of pharmacologic 5-LO inhibition by zileuton and LTB₄ inhibition by CP-105,696. Mice that received allogeneic transplant showed an increase in nuclear 5-LO expression in splenocytes, indicating enzyme activation after GVHD. Mice receiving 5-LO–deficient cell transplant or zileuton treatment had prolonged survival, reduced GVHD clinical scores, reduced intestinal and liver injury, and decreased levels of serum and hepatic LTB₄. These results were associated with inhibition of leukocyte recruitment and decreased production of cytokines and chemokines. Treatment with CP-105,696 achieved similar effects. The chimerism or the beneficial graft-versus-leukemia response remained unaffected. Our data provide evidence that the 5-LO/LTB₄ axis orchestrates GVHD development and suggest it could be a target for the development of novel therapeutic strategies for GVHD treatment.

Microbiota-Induced Antibodies Are Essential for Host Inflammatory Responsiveness to Sterile and Infectious Stimuli

The indigenous intestinal microbiota is frequently considered an additional major organ of the human body and exerts profound immunomodulating activities. Germ-free (GF) mice display a significantly different inflammatory responsiveness pattern compared with conventional (CV) mice, and this was dubbed a "hyporesponsive phenotype." Taking into account that the deposition of immune complexes is a major event in acute inflammation and that GF mice have a distinct Ig repertoire and B cell activity, we aimed to evaluate whether this altered Ig repertoire interferes with the inflammatory responsiveness of GF mice. We found that serum transfer from CV naive mice was capable of reversing the inflammatory hyporesponsiveness of GF mice in sterile inflammatory injury induced by intestinal ischemia and reperfusion, as well as in a model of lung infection by Klebsiella pneumoniae Transferring serum from Ig-deficient mice to GF animals did not alter their response to inflammatory insult; however, injecting purified Abs from CV animals restored inflammatory responsiveness in GF mice, suggesting that natural Abs present in serum were responsible for altering GF responsiveness. Mechanistically, injection of serum and Ig from CV mice into GF animals restored IgG deposition, leukocyte influx, NF-κB activation, and proinflammatory gene expression in inflamed tissues and concomitantly downregulated annexin-1 and IL-10 production. Thus, our data show that microbiota-induced natural Abs are pivotal for host inflammatory responsiveness to sterile and infectious insults.

Secretion of biologically active pancreatitis-associated protein I (PAP) by genetically modified dairy Lactococcus lactis NZ9000 in the prevention of intestinal mucositis

Background

Mucositis is one of the most relevant gastrointestinal inflammatory conditions in humans, generated by the use of chemotherapy drugs, such as 5-fluoracil (5-FU). 5-FU-induced mucositis affects 80% of patients undergoing oncological treatment causing mucosal gut dysfunctions and great discomfort. As current therapy drugs presents limitations in alleviating mucositis symptoms, alternative strategies are being pursued. Recent studies have shown that the antimicrobial pancreatitis-associated protein (PAP) has a protective role in intestinal inflammatory processes. Indeed, it was demonstrated that a recombinant strain of Lactococcus lactis expressing human PAP (LL-PAP) could prevent and improve murine DNBS-induced colitis, an inflammatory bowel disease (IBD) that causes severe inflammation of the colon. Hence, in this study we sought to evaluate the protective effects of LL-PAP on 5-FU-induced experimental mucositis in BALB/c mice as a novel approach to treat the disease.

Results

Our results show that non-recombinant L. lactis NZ9000 have antagonistic activity, in vitro, against the enteroinvasive gastrointestinal pathogen L. monocytogenes and confirmed PAP inhibitory effect against Opportunistic E. faecalis. Moreover, L. lactis was able to prevent histological damage, reduce neutrophil and eosinophil infiltration and secretory Immunoglobulin-A in mice injected with 5-FU. Recombinant lactococci carrying antimicrobial PAP did not improve those markers of inflammation, although its expression was associated with villous architecture preservation and increased secretory granules density inside Paneth cells in response to 5-FU inflammation.

Conclusions

We have demonstrated for the first time that L. lactis NZ9000 by itself, is able to prevent 5-FU-induced intestinal inflammation in BALB/c mice. Moreover, PAP delivered by recombinant L. lactis strain showed additional protective effects in mice epithelium, revealing to be a promising strategy to treat intestinal mucositis.

Leveraging model-based study designs and serial micro-sampling techniques to understand the oral pharmacokinetics of the potent LTB4 inhibitor, CP-105696, for mouse pharmacology studies

1. Leukotriene B4 (LTB4) is a proinflammatory mediator important in the progression of a number of inflammatory diseases. Preclinical models can explore the role of LTB4 in pathophysiology using tool compounds, such as CP-105696, that modulate its activity. To support preclinical pharmacology studies, micro-sampling techniques and mathematical modeling were used to determine the pharmacokinetics of CP-105696 in mice within the context of systemic inflammation induced by a high-fat diet (HFD). 2. Following oral administration of doses > 35 mg/kg, CP-105696 kinetics can be described by a one-compartment model with first order absorption. The compound's half-life is 44-62 h with an apparent volume of distribution of 0.51-0.72 L/kg. Exposures in animals fed an HFD are within 2-fold of those fed a normal chow diet. Daily dosing at 100 mg/kg was not tolerated and resulted in a >20% weight loss in the mice. 3. CP-105696's long half-life has the potential to support a twice weekly dosing schedule. Given that most chronic inflammatory diseases will require long-term therapies, these results are useful in determining the optimal dosing schedules for preclinical studies using CP-105696.

Nanocomposite treatment reduces disease and lethality in a murine model of acute graft-versus-host disease and preserves anti-tumor effects

Graft versus host disease (GVHD) is an immunological disorder triggered by bone marrow transplantation that affects several organs, including the gastrointestinal tract and liver. Fullerenes and their soluble forms, fullerols, are nanocomposites with a closed symmetrical structure with anti-inflammatory and anti-oxidant properties. The present study evaluated the effects of treatment with the fullerol (C60(OH)18-20) in the development and pathogenesis of GVHD in a murine model. Mice with experimental GVHD that were treated with the fullerol showed reduced clinical signs of disease and mortality compared with untreated mice. Treatment with the fullerol decreased the hepatic damage associated with reduced hepatic levels of reactive oxygen species, pro-inflammatory cytokines and chemokines (IFN-γ TNF-α, CCL2, CCL3 and CCL5) and reduced leukocyte accumulation. The amelioration of GVHD after treatment with the fullerol was also associated with reduced intestinal lesions and consequent bacterial translocation to the blood, liver and peritoneal cavity. Moreover, the fullerol treatment alleviated the GVHD while preserving effects of the graft against a leukemia cell line (GFP+P815). In summary, the fullerol was effective in reducing the GVHD inflammatory response in mice and may suggest novel ways to treat this disease.

Cysteinyl leukotriene receptor antagonist montelukast ameliorates acute lung injury following haemorrhagic shock in rats

OBJECTIVES

The aim of this study was to assess the possible protective effect of montelukast against haemorrhagic shock-induced acute lung injury by interfering with inflammatory and oxidative pathways. Acute lung injury following haemorrhagic shock/resuscitation is an important contributor to late morbidity and mortality in trauma patients. Haemorrhagic shock (HS), followed by resuscitation, is considered to be an insult that frequently induces systemic inflammatory response syndrome and oxidative stress, resulting in multiple-organ dysfunction syndrome, including microvascular changes and microscopic damage termed acute lung paraynchymal injury. Montelukast is a cysteinyl leukotriene receptor antagonist that exerts an anti-inflammatory and antioxidant influence.

METHODS

Eighteen adult albino rats were assigned to three groups of six. In Group I, the 'sham' group, rats underwent all the surgical procedures but neither haemorrhagic shock nor resuscitation was carried out. Group II--the 'HS' induced, untreated group--was the control and underwent HS for one hour before being resuscitated with Ringer's lactate for one hour. Group III--the 'montelukast' group--underwent HS and treatment with montelukast (7 mg/kg i.p. injection) 30 min before the induction of HS, with the same dose repeated just before the reperfusion period. At the end of the experiment, two hours after completion of resuscitation, blood samples were collected for measurement of serum tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The trachea was then isolated and bronchoalveolar lavage was carried out for measurement of leukotriene B(4) (LTB(4)), leukotriene C(4) (LTC(4)) and total protein. The lungs were harvested and the left lung was homogenized for measurement of malondialdehyde (MDA) and reduced glutathione (GSH) and the right lung was fixed in 10% formalin for histological examination.

RESULTS

Montelukast treatment (Group III) significantly reduced the total lung injury score, compared with the HS group (Group II) (P < 0.05). Montelukast also significantly decreased serum TNF-α and IL-6; lung MDA; bronchoalveolar lavage fluid (BALF) LTB(4), LTC(4) & total protein compared with the HS group (P < 0.05). Montelukast treatment significantly inhibited decrease in the lung GSH levels, compared with the HS group (P < 0.05).

CONCLUSIONS

The results of the present study reveal that montelukast may ameliorate lung injury in shocked rats by interfering with inflammatory and oxidative pathways, implicating the role of leukotrienes in the pathogenesis of haemorrhagic shock-induced lung inflammation.

Cysteinyl leukotriene receptor antagonism alleviates renal injury induced by ischemia-reperfusion in rats

BACKGROUND

Renal inflammation has an important role in the development of ischemia-reperfusion injury of the kidney. Cysteinyl leukotrienes have been implicated in many inflammatory conditions. The aim of this study was to investigate the ability of the cysteinyl leukotriene receptor blocker, zafirlukast, to alleviate renal dysfunction and injury in a rat model of renal ischemia-reperfusion injury.

METHODS

We induced renal ischemia for 45 min, followed by 24 h reperfusion. We gave zafirlukast at a dose of 20 mg/kg/d for 3 d before ischemia-reperfusion. At the end of the reperfusion (24 h), we collected blood samples to measure blood urea nitrogen, creatinine, tumor necrosis factor-α, intercellular adhesion molecule-1, and nitrite/nitrate. We took kidney samples for histological and immunohistochemical assessment, and to measure malondialdehyde, glutathione content, and myeloperoxidase activity.

RESULTS

Induction of renal ischemia-reperfusion resulted into renal dysfunction, as indicated by elevated levels of blood urea nitrogen and serum creatinine, serum nitrite and nitrate, serum tumor necrosis factor-α, and intercellular adhesion molecule-1. An oxidative stress marker, renal malondialdehyde concentration, was increased, whereas renal reduced glutathione content was decreased. Myeloperoxidase activity, suggestive of neutrophil infiltration, was elevated in renal tissues. Histological changes confirmed these biochemical changes, as did P-selectin overexpression in renal tissues subjected to ischemia-reperfusion. Administration of zafirlukast before ischemia-reperfusion improved renal functions and reduced serum levels of nitrite and nitrate, tumor necrosis factor-α, and intercellular adhesion molecule-1, renal concentration of myeloperoxidase activity, and malondialdehyde concentration, whereas increased renal reduced glutathione concentration. Moreover, zafirlukast reduced histopathological features of tubular injury and P-selectin overexpression in both cortex and medulla.

CONCLUSIONS

These results demonstrate that zafirlukast significantly reduces the severity of ischemic acute renal failure, probably via anti-inflammatory action, reduction of neutrophil infiltration into renal tissues, and oxidative stress subsequent to an attenuation of P-selectin expression.

Transient TLR activation restores inflammatory response and ability to control pulmonary bacterial infection in germfree mice

Mammals are colonized by an astronomical number of commensal microorganisms on their environmental exposed surfaces. These symbiotic species build up a complex community that aids their hosts in several physiological activities. We have shown that lack of intestinal microbiota is accompanied by a state of active IL-10-mediated inflammatory hyporesponsiveness. The present study investigated whether the germfree state and its hyporesponsive phenotype alter host resistance to an infectious bacterial insult. Experiments performed in germfree mice infected with Klebsiella pneumoniae showed that these animals are drastically susceptible to bacterial infection in an IL-10-dependent manner. In germfree mice, IL-10 restrains proinflammatory mediator production and neutrophil recruitment and favors pathogen growth and dissemination. Germfree mice were resistant to LPS treatment. However, priming of these animals with several TLR agonists recovered their inflammatory responsiveness to sterile injury. LPS pretreatment also rendered germfree mice resistant to pulmonary K. pneumoniae infection, abrogated IL-10 production, and restored TNF-α and CXCL1 production and neutrophil mobilization into lungs of infected germfree mice. This effective inflammatory response mounted by LPS-treated germfree mice resulted in bacterial clearance and enhanced survival upon infection. Therefore, host colonization by indigenous microbiota alters the way the host reacts to environmental infectious stimuli, probably through activation of TLR-dependent pathways. Symbiotic gut colonization enables proper inflammatory response to harmful insults to the host, and increases resilience of the entire mammal-microbiota consortium to environmental pressures.

Sensing sterile injury: opportunities for pharmacological control

Sterile injury can trigger an acute inflammatory response, which might be responsible for the pathogenesis of several diseases, including rheumatoid arthritis, lung fibrosis and acute liver failure. A key event for the pathogenesis of these diseases is the recruitment of leukocytes to necrotic areas. Much is known about the mechanisms of recruitment to sites of infection. However, only now is it becoming clear how leukocytes, especially neutrophils, are recruited to areas of tissue damage and necrosis in the absence of infection. Here, we review and discuss mechanisms responsible for sensing and driving the influx of leukocytes, specifically neutrophils, into sites of sterile injury. This knowledge clearly opens new opportunities for therapeutic intervention.

Cooperative role of tumour necrosis factor-α, interleukin-1β and neutrophils in a novel behavioural model that concomitantly demonstrates articular inflammation and hypernociception in mice

BACKGROUND AND PURPOSE; Chronic joint inflammation and pain are the hallmarks of disease in patients with inflammatory arthritis, notably rheumatoid arthritis. The aim of the present study was to investigate the relative contribution of tumour necrosis factor (TNF)-α, interleukin (IL)-1β and neutrophil influx for joint inflammation and nociception in a novel murine model of antigen-induced arthritis (AIA).

EXPERIMENTAL APPROACH

AIA was induced by administration of antigen into knee joint of previously immunized mice. Neutrophil accumulation was determined by counting neutrophils in the joints and assessing myeloperoxidase activity in tissues surrounding the joints. TNF-α, IL-1β and CXCL-1 were measured by elisa. Mechanical hypernociception was assessed in parallel, using an electronic pressure meter.

KEY RESULTS

Hypernociception was dependent on antigen dose and the time after its administration; it was prevented by treatment with morphine and associated with neutrophil infiltration and local production of TNF-α, IL-1β and CXCL-1. Administration of a chimeric monoclonal antibody to TNF-α (infliximab) or IL-1receptor antagonist prevented neutrophil influx and hypernociception, and this was comparable to the effects of dexamethasone. Treatment with fucoidin (a leucocyte adhesion inhibitor) greatly suppressed neutrophil influx and local production of TNF-α and IL-1β, and hypernociception.

CONCLUSIONS AND IMPLICATIONS

In conclusion, the present study describes a new model that allows for the concomitant evaluation of articular hypernociception and inflammation. Using this system, we demonstrated that a positive feedback loop involving neutrophil influx and the pro-inflammatory cytokines TNF-α and IL-1β is necessary for articular hypernociception after antigen challenge of immunized mice.

Protective potential of montelukast against hepatic ischemia/reperfusion injury in rats

Ischemia and reperfusion (I/R) injury is characterized by significant oxidative stress, characteristic changes in the antioxidant system and organ injury leading to significant morbidity and mortality. This study was designed to assess the possible protective effect of montelukast, a selective antagonist of cysteinyl leukotriene receptor 1 (CysLT1), on hepatic I/R injury in rats. Wistar albino rats through clamping hepatic artery, portal vein, and bile duct, were subjected to 45 min of hepatic ischemia followed by 60 min reperfusion period. Montelukast (10 mg/kg; i.p.) was administered 15 min prior to ischemia and immediately before reperfusion period. At the end of the reperfusion period, the rats were killed by decapitation. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) activity, and proinflammatory cytokines (TNF-alpha and IL-1beta) were determined in blood samples. Malondialdehyde (MDA), and glutathione (GSH) levels and myeloperoxidase (MPO) and Na+, K+-ATPase activities were determined in the liver tissue samples while formation of reactive oxygen species was monitored by using chemiluminescence (CL) technique with luminol and lucigenin probes. Tissues were also analyzed histologically. Serum ALT, AST, and LDH activities were elevated in the I/R group, while this increase was significantly decreased by montelukast treatment. Hepatic GSH levels and Na+, K+-ATPase activity, significantly depressed by I/R, were elevated back to control levels in montelukast-treated I/R group. Furthermore, increases in tissue luminol and lucigenin CL, MDA levels, and MPO activity due to I/R injury were reduced back to control levels with montelukast treatment. Since montelukast administration alleviated the I/R-induced liver injury and improved the hepatic structure and function, it seems likely that montelukast with its anti-inflammatory and antioxidant properties may be of potential therapeutic value in protecting the liver against oxidative injury due to ischemia-reperfusion.

Involvement of endogenous leukotriene B4 and platelet-activating factor in polymorphonuclear leucocyte recruitment to dermal inflammatory sites in rats

A critical role for leukotriene B(4) (LTB(4)) and/or platelet-activating factor (PAF) in regulating polymorphonuclear cell (PMN) trafficking to inflammatory sites has been reported in a number of experimental inflammatory models. In vitro, newly synthesized LTB(4) and PAF were shown to act in an autocrine/paracrine or intracrine fashion to enhance intracellular arachidonic acid availability and leukotriene biosynthesis. This suggested potentially cooperative effects of these lipid mediators in regulating PMN extravasation. The present study aimed to elucidate whether endogenous LTB(4) and PAF may both act to regulate plasma extravasation and PMN trafficking to inflammatory sites in experimental inflammation. With this aim, we have used selective and potent PAF and LTB(4) receptor antagonist pretreatments in dermal and pulmonary inflammation models in rats. Our results show additive inhibitory effects of dual LTB(4) and PAF receptor blockade in either PAF- or LTB(4)-elicited cutaneous PMN accumulation compared to single-drug administration. Furthermore, the combined administration of the drugs inhibited the PMN accumulation induced by the chemically unrelated soluble agonists tumour necrosis factor-alpha and C5a. Finally, in a model of pulmonary inflammation induced by the intravenous injection of Sephadex beads, lung neutrophilia was reduced by 63% following the administration of LTB(4) and PAF antagonists, in contrast with the lack of effect of single drug administration. Our results strongly support a role of both endogenous LTB(4) and PAF in regulating PMN trafficking to inflammatory sites in various experimental conditions.

Effects of the treatment with glibenclamide, an ATP-sensitive potassium channel blocker, on intestinal ischemia and reperfusion injury

Intestinal ischemia and reperfusion injury is dependent on the recruitment and activation of neutrophils. Glibenclamide, an ATP-sensitive potassium channel (K(ATP)) blocker, has been shown to suppress neutrophil migration and chemotaxis during acute inflammatory responses by a mechanism dependent on its K(ATP) channel blocking activity. In the present study, we evaluated whether the treatment with glibenclamide prevented local, remote and systemic injury following reperfusion of the ischemic superior mesenteric artery in rats. The artery was made ischemic for a period of 30 or 120 min followed by 30 (mild I/R) or 120 (severe I/R) min of reperfusion, respectively. Glibenclamide (0.8 to 20 mg/kg) or vehicle was administered subcutaneously 40 min prior to the reperfusion. Glibenclamide dose-dependently inhibited the reperfusion-associated increase in vascular permeability and neutrophil accumulation in mild I/R. In the severe injury model, glibenclamide inhibited inflammatory parameters, as assessed by Evans blue extravasation, neutrophil influx and haemoglobin content, and the increase in TNF-alpha (tumor necrose factor-alpha) and IL (interleukin)-6 levels in the intestine and lung. The drug did not affect the increase in IL-1beta and IL-10 levels. TEA, a nonselective potassium channel blocker, also inhibited reperfusion injury in both intestine and lungs of animals submitted to mild and severe I/R. Our experiments suggest a role for K(ATP) channels in mediating neutrophil influx and consequent reperfusion-associated injury in rats. The lack of effect of these drugs on the reperfusion-associated hypotension and lethality may limit their usefulness after severe reperfusion injury.

The balance between the production of tumor necrosis factor-alpha and interleukin-10 determines tissue injury and lethality during intestinal ischemia and reperfusion

A major goal in the treatment of acute ischemia of a vascular territory is to restore blood flow to normal values, i.e. to "reperfuse" the ischemic vascular bed. However, reperfusion of ischemic tissues is associated with local and systemic leukocyte activation and trafficking, endothelial barrier dysfunction in postcapillary venules, enhanced production of inflammatory mediators and great lethality. This phenomenon has been referred to as "reperfusion injury" and several studies demonstrated that injury is dependent on neutrophil recruitment. Furthermore, ischemia and reperfusion injury is associated with the coordinated activation of a series of cytokines and adhesion molecules. Among the mediators of the inflammatory cascade released, TNF-alpha appears to play an essential role for the reperfusion-associated injury. On the other hand, the release of IL-10 modulates pro-inflammatory cytokine production and reperfusion-associated tissue injury. IL-1beta, PAF and bradykinin are mediators involved in ischemia and reperfusion injury by regulating the balance between TNF-alpha and IL-10 production. Strategies that enhance IL-10 and/or prevent TNF-alpha concentration may be useful as therapeutic adjuvants in the treatment of the tissue injury that follows ischemia and reperfusion.

The ATP-sensitive potassium channel blocker glibenclamide prevents renal ischemia/reperfusion injury in rats

BACKGROUND

Renal ischemia/reperfusion (I/R) is a complex neutrophil-mediated syndrome. Adenosine-triphosphate (ATP)-sensitive potassium (K(ATP)) channels are involved in neutrophil migration in vivo. In the present study, we have investigated the effects of glibenclamide, a K(ATP) channel blocker, in renal I/R injury in rats.

METHODS

The left kidney of the rats was excised through a flank incision and ischemia was performed in the contralateral kidney by total interruption of renal artery flow for 45 minutes. Renal perfusion was reestablished, and the kidney and lungs were removed for analysis of vascular permeability, neutrophil accumulation, and content of cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-10] 4 and 24 hours later. Renal function was assessed by measuring creatinine, Na(+), and K(+) levels in the plasma and by determination of creatinine clearance. Drugs were administered subcutaneously after the onset of ischemia.

RESULTS

Reperfusion of the ischemic kidney induced local (kidney) and remote (lung) inflammatory injury and marked renal dysfunction. Glibenclamide (20 mg/kg) significantly inhibited the reperfusion-associated increase in vascular permeability, neutrophil accumulation, increase in TNF-alpha levels and nuclear factor-kappaB (NF-kappaB) translocation. These inhibitory effects were noticed in the kidney and lungs. Moreover, glibenclamide markedly ameliorated the renal dysfunction at 4 and 24 hours.

CONCLUSION

Treatment with glibenclamide is associated with inhibition of neutrophil recruitment and amelioration of renal dysfunction following renal I/R. Glibenclamide may have a therapeutic role in the treatment of renal I/R injury, such as after renal transplantation.

Involvement of the chemokine RANTES (CCL5) in resistance to experimental infection with Leishmania major

The expression and putative role of chemokines during infection with Leishmania major in mice were investigated. CCL5 expression correlates with resistance, and blockade of CCL5 rendered mice more susceptible to infection. CCL5 is part of the cascade of events leading to efficient parasite control in L. major infection.

Repertaxin, a novel inhibitor of rat CXCR2 function, inhibits inflammatory responses that follow intestinal ischaemia and reperfusion injury

1. Neutrophils are thought to play a major role in the mediation of reperfusion injury. CXC chemokines are known inducers of neutrophil recruitment. Here, we assessed the effects of Repertaxin, a novel low molecular weight inhibitor of human CXCL8 receptor activation, on the local, remote and systemic injuries following intestinal ischaemia and reperfusion (I/R) in the rat. 2. Pre-incubation of rat neutrophils with Repertaxin (10(-11)-10(-6) m) inhibited the chemotaxis of neutrophils induced by human CXCL8 or rat CINC-1, but not that induced by fMLP, PAF or LTB(4), in a concentration-dependent manner. Repertaxin also prevented CXCL8-induced calcium influx but not CXCL8 binding to purified rat neutrophils. 2. In a model of mild I/R injury (30 min of ischaemia and 30 min of reperfusion), Repertaxin dose-dependently (3-30 mg kg(-1)) inhibited the increase in vascular permeability and neutrophil influx. Maximal inhibition occurred at 30 mg kg(-1). 4. Following severe I/R injury (120 min of ischaemia and 120 min of reperfusion), Repertaxin (30 mg kg(-1)) markedly prevented neutrophil influx, the increase in vascular permeability both in the intestine and the lungs. Moreover, there was prevention of haemorrhage in the intestine of reperfused animals. 5. Repertaxin effectively suppressed the increase in tissue (intestine and lungs) and serum concentrations of TNF-alpha and the reperfusion-associated lethality. 6. For comparison, we also evaluated the effects of an anti-CINC-1 antibody in the model of severe I/R injury. Overall, the antibody effectively prevented tissue injury, systemic inflammation and lethality. However, the effects of the antibody were in general of lower magnitude than those of Repertaxin. 7. In conclusion, CINC-1 and possibly other CXC chemokines, acting on CXCR2, have an important role during I/R injury. Thus, drugs, such as Repertaxin, developed to block the function of the CXCR2 receptor may be effective at preventing reperfusion injury in relevant clinical situations.

Role of the bradykinin B2 receptor for the local and systemic inflammatory response that follows severe reperfusion injury

1. Bradykinin (BK) appears to play an important role in the development and maintenance of inflammation. Here, we assessed the role of the BK B(2) receptor for the injuries that occur after ischemia and reperfusion (I/R) of the territory irrigated by the superior mesenteric artery. 2. Tissue (lung and duodenum) kallikrein activity increased after ischemia with greater enhancement after reperfusion. A selective inhibitor of tissue kallikrein, Phenylacetyl-Phe-Ser-Arg-N-(2,3-dinitrophenyl)-ethylenediamine (TKI, 0.001-10 mg ml(-1)), inhibited kallikrein activity in a concentration-dependent manner in vitro. In vivo, pretreatment with TKI (30 mg kg(-1)) prevented the extravasation of plasma and the recruitment of neutrophils. 3. Similarly, the bradykinin B(2) receptor antagonists, HOE 140 (0.01-1.0 mg kg(-1)) or FR173657 (10.0 mg kg(-1)), inhibited reperfusion-induced increases in vascular permeability and the recruitment of neutrophils in the intestine and lungs. 4. In a model of more severe I/R injury, HOE 140 (1.0 mg kg(-1)) inhibited the increase in vascular permeability, neutrophil recruitment, haemorrhage and tissue pathology. Furthermore, HOE 140 significantly inhibited the elevations of TNF-alpha in tissue and serum and partially prevented lethality. This was associated with an increase in the concentrations of IL-10 in tissue and serum. 5. Thus, our results demonstrate that, following intestinal I/R injury, there is an increase in tissue kallikrein activity and activation of BK B(2) receptors. B(2) receptor activation is essential for the development of inflammatory tissue injury and lethality. These results contrast with those of others showing that BK mostly exerts a protective role during I/R injury.

IL-1-driven endogenous IL-10 production protects against the systemic and local acute inflammatory response following intestinal reperfusion injury

TNF-alpha release and action are central in the pathogenesis of the local and systemic inflammatory responses that occur after intestinal reperfusion. In this study we examined whether IL-1 participated in the cascade of events leading to TNF-alpha production and TNF-alpha-mediated injury following reperfusion of the ischemic superior mesenteric artery in rats. Blockade of the action of IL-1 by the use of anti-IL-1 antiserum or administration of IL-1R antagonist (IL-1ra), a natural antagonist of IL-1Rs, resulted in marked enhancement of reperfusion-associated tissue injury, TNF-alpha expression, and lethality. In contrast, there was marked decrease in IL-10 production. Facilitation of IL-1 action by administration of anti-IL-1ra, which antagonizes endogenous IL-1ra, or exogenous administration of rIL-1beta suppressed reperfusion-induced tissue pathology, TNF-alpha production, and lethality, but increased IL-10 production. Exogenous administration of IL-10 was effective in preventing the increase in tissue or plasma levels of TNF-alpha, the exacerbated tissue injury, and lethality. An opposite effect was observed after treatment with anti-IL-10, demonstrating a role for endogenous production of IL-10 in modulating exacerbated reperfusion-associated tissue pathology and lethality. Finally, pretreatment with anti-IL-10 reversed the protective effect of IL-1beta on reperfusion-associated lethality. Thus, IL-1 plays a major role in driving endogenous IL-10 production and protects against the TNF-alpha-dependent systemic and local acute inflammatory response following intestinal reperfusion injury.