ATPergic signaling disruption in human sepsis as a potential source of biomarkers for clinical use.

Sepsis is a life-threatening organ dysfunction caused by a dysregulated inflammatory response to infection. To date, there is no specific treatment established for sepsis. In the extracellular compartment, purines such as adenosine triphosphate (ATP) and adenosine play essential roles in the immune/inflammatory responses during sepsis and septic shock. The balance of extracellular levels among ATP and adenosine is intimately involved in the signals related to immune stimulation/immunosuppression balance. Specialized enzymes, including CD39, CD73, and adenosine deaminase (ADA), are responsible to metabolize ATP to adenosine which will further sensitize the P2 and P1 purinoceptors, respectively. Disruption of the purinergic pathway had been described in the sepsis pathophysiology. Although purinergic signaling has been suggested as a potential target for sepsis treatment, the majority of data available were obtained using pre-clinical approaches. We hypothesized that, as a reflection of deregulation on purinergic signaling, septic patients exhibit differential measurements of serum, neutrophils and monocytes purinergic pathway markers when compared to two types of controls (healthy and ward). It was observed that ATP and ADP serum levels were increased in septic patients, as well as the A2a mRNA expression in neutrophils and monocytes. Both ATPase/ADPase activities were increased during sepsis. Serum ATP and ADP levels, and both ATPase and ADPase activities were associated with the diagnosis of sepsis, representing potential biomarkers candidates. In conclusion, our results advance the translation of purinergic signaling from pre-clinical models into the clinical setting opening opportunities for so much needed new strategies for sepsis and septic shock diagnostics and treatment.

Induction of murine adenosine A(2A) receptor expression by LPS: analysis of the 5' upstream promoter.

Non-activated macrophages express low levels of A(2A)Rs and lipopolysaccharides (LPS) upregulates A(2A)R expression in an NF-κB-dependent manner. The murine A(2A)R gene is encoded by three exons, m1, m2 and m3. Exons m2 and m3 are conserved, while m1 encodes the 5' untranslated UTR. Three m1 variants have been defined, m1A, m1B and m1C, with m1C being farthest from the transcriptional start site. LPS upregulates A(2A)Rs in primary murine peritoneal and bone-marrow-derived macrophages and RAW264.7 cells by selectively splicing m1C to m2, through a promoter located upstream of m1C. We have cloned ∼1.6 kb upstream of m1C into pGL4.16(luc2CP/Hygro) promoterless vector. This construct in RAW 264.7 cells responds to LPS, and adenosine receptor agonists augmented LPS responsiveness. The NF-κB inhibitors BAY-11 and triptolide inhibited LPS-dependent induction. Deletion of a key proximal NF-κB site (402-417) abrogated LPS responsiveness, while deletion of distal NF-κB and C/EBPß sites did not. Site-directed mutagenesis of CREB (309-320), STAT1 (526-531) and AP2 (566-569) sites had little effect on LPS and adenosine receptor agonist responsiveness; however, mutation of a second STAT1 site (582-588) abrogated this responsiveness. Further analysis of this promoter should provide valuable insights into regulation of A(2A)R expression in macrophages in response to inflammatory stimuli.

Endocannabinoids and cannabinoid receptors in ischaemia-reperfusion injury and preconditioning.

Ischaemia-reperfusion (I/R) is a pivotal mechanism of organ injury during stroke, myocardial infarction, organ transplantation and vascular surgeries. Ischaemic preconditioning (IPC) is a potent endogenous form of tissue protection against I/R injury. On the one hand, endocannabinoids have been implicated in the protective effects of IPC through cannabinoid CB1/CB2 receptor-dependent and -independent mechanisms. However, there is evidence suggesting that endocannabinoids are overproduced during various forms of I/R, such as myocardial infarction or whole body I/R associated with circulatory shock, and may contribute to the cardiovascular depressive state associated with these pathologies. Previous studies using synthetic CB1 receptor agonists or knockout mice demonstrated CB1 receptor-dependent protection against cerebral I/R injury in various animal models. In contrast, several follow-up reports have shown protection afforded by CB1 receptor antagonists, but not agonists. Excitedly, emerging studies using potent CB2 receptor agonists and/or knockout mice have provided compelling evidence that CB2 receptor activation is protective against myocardial, cerebral and hepatic I/R injuries by decreasing the endothelial cell activation/inflammatory response (for example, expression of adhesion molecules, secretion of chemokines, and so on), and by attenuating the leukocyte chemotaxis, rolling, adhesion to endothelium, activation and transendothelial migration, and interrelated oxidative/nitrosative damage. This review is aimed to discuss the role of endocannabinoids and CB receptors in various forms of I/R injury (myocardial, cerebral, hepatic and circulatory shock) and preconditioning, and to delineate the evidence supporting the therapeutic utility of selective CB2 receptor agonists, which are devoid of psychoactive effects, as a promising new approach to limit I/R-induced tissue damage.

CB2 cannabinoid receptor agonists attenuate TNF-alpha-induced human vascular smooth muscle cell proliferation and migration.

BACKGROUND AND PURPOSE: Vascular smooth muscle proliferation and migration triggered by inflammatory stimuli are involved in the development and progression of atherosclerosis and restenosis. Cannabinoids may modulate cell proliferation in various cell types through cannabinoid 2 (CB2) receptors. Here, we investigated the effects of CB2 receptor agonists on TNF-alpha-induced proliferation, migration and signal transduction in human coronary artery smooth muscle cells (HCASMCs). EXPERIMENTAL APPROACH: HCASMCs were stimulated with TNF-alpha. Smooth muscle proliferation was determined by the extent of BrdU incorporation and the migration was assayed by modified Boyden chamber. CB2 and/or CB1 receptor expressions were determined by immunofluorescence staining, western blotting, RT-PCR, real-time PCR and flow cytometry. KEY RESULTS: Low levels of CB2 and CB1 receptors were detectable in HCASMCs compared to the high levels of CB2 receptors expressed in THP-1 monocytes. TNF-alpha triggered up to approximately 80% increase (depending on the method used) in CB2 receptor mRNA and/or protein expression in HCASMCs, and induced Ras, p38 MAPK, ERK 1/2, SAPK/JNK and Akt activation, while increasing proliferation and migration. The CB2 agonists, JWH-133 and HU-308, dose-dependently attenuated these effects of TNF-alpha. CONCLUSIONS AND IMPLICATIONS: Since the above-mentioned TNF-alpha-induced phenotypic changes are critical in the initiation and progression of atherosclerosis and restenosis, our findings suggest that CB2 agonists may offer a novel approach in the treatment of these pathologies by decreasing vascular smooth muscle proliferation and migration.

The adenosine A2A receptor agonist CGS 21680 fails to ameliorate the course of dextran sulphate-induced colitis in mice.

OBJECTIVE: In this study we investigated the effect of CGS 21680 (2-p-(2-Carboxyethyl)phenethylamino-5-N-ethylcarboxamidoadenosine hydrochloride), an adenosine A2A receptor agonist, in a model of dextran sulphate sodium (DSS)-induced colitis. METHODS: NMRI mice were fed 5 % (w/v) DSS, and were treated intraperitoneally with 0.5 mg/kg CGS 21680 or vehicle for 10 days. Changes of bodyweight, colon length, the incidence of rectal bleeding, levels of macrophage inflammatory protein (MIP)-1alpha, MIP-2, interferon gamma, interleukin (IL)-1beta, IL-12 and tumour necrosis factor-alpha from homogenates of colon biopsies, and the release of [3H]acetylcholine (ACh) from longitudinal muscle strip were determined. RESULTS: DSS significantly decreased bodyweight, colon length, and it increased the incidence of rectal bleeding and levels of MIP-1alpha, MIP-2 and IL-1beta compared to DSS-untreated animals. CGS 21680 had no effect on these changes. No change could be observed in release of ACh in DSS-induced colitis with or without CGS 21680. CONCLUSION: In summary, CGS 21680 is ineffective in ameliorating DSS-induced colitis in mice.

Inosine reduces inflammation and improves survival in a murine model of colitis.

Inosine, a naturally occurring purine formed from the breakdown of adenosine, has recently been shown to exert powerful anti-inflammatory effects both in vivo and in vitro. This study evaluated inosine as a potential therapy for colitis. Colitis was induced in mice by the administration of dextran sulfate sodium (DSS). Oral treatment with inosine was begun either before the onset of colitis or as a posttreatment once colitis was established. Evaluation of colon damage and inflammation was determined grossly (body wt, rectal bleeding), histologically, and biochemically (colon levels of MPO, MDA, and cytokines). DSS-induced colitis significantly increased inflammatory cell infiltration into the colon. DSS-induced colitis also increased colon levels of lipid peroxidation, cytokines, and chemokines. Inosine protected the colon from DSS-induced inflammatory cell infiltration and lipid peroxidation. Inosine also partially reduced these parameters in an experimental model of established colitis. Thus inosine treatment may be a potential therapy in colitis.

NFkappaB1 (p50)-deficient mice are not susceptible to multiple low-dose streptozotocin-induced diabetes.

Insulin-dependent diabetes mellitus (IDDM) is a disease characterized by the autoimmune destruction of the pancreatic beta-cells, which requires the expression of a number of immune-related genes including major histocompatibility complex proteins, cytokines, chemokines, and cytotoxic enzymes, many of which are regulated by the transcription factor, NFkappaB. Inhibition of the entire NFkappaB family of transcription factors may be harmful, as these factors are involved in many normal physiological processes. However, identifying and targeting specific NFkappaB subunits critical for the pathogenesis of disease may prove to be valuable in designing new therapeutic strategies. To assess the potential role of the NFkappaB subunit, p50, in the development of IDDM, mice with gene disruption for NFkappaB (p50) were investigated for susceptibility to IDDM. We found that p50-deficient mice were fully resistant against multiple low-dose streptozotocin-induced diabetes, a model of diabetes with a strong autoimmune component. The site of involvement of NFkappaB (p50) lies at an early, critical juncture of immune activation and proinflammatory mediator production, because: (1) isolated islets of Langerhans from NFkappaB (p50)-deficient mice were not protected from the islet dysfunction induced by in vitro application of proinflammatory cytokines; (2) p50-deficient mice were not resistant to diabetes induced by a single high dose of streptozotocin, a model with a large oxidant component and no autoimmune involvement; and (3) diabetes induced up-regulation of nitric oxide and interleukin-12 was blocked in the p50-deficient mice. Our data suggest that NFkappaB (p50) has an essential role in the development of autoimmune diabetes. Selective therapeutic blockade of this subunit may be beneficial in preventing IDDM.

Activation of poly(ADP-ribose) polymerase contributes to development of doxorubicin-induced heart failure.

Activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) by oxidant-mediated DNA damage is an important pathway of cell dysfunction and tissue injury in conditions associated with oxidative stress. Increased oxidative stress is a major factor implicated in the cardiotoxicity of doxorubicin (DOX), a widely used antitumor anthracycline antibiotic. Thus, we hypothesized that the activation of PARP may contribute to the DOX-induced cardiotoxicity. Using a dual approach of PARP-1 suppression, by genetic deletion or pharmacological inhibition with the phenanthridinone PARP inhibitor PJ34, we now demonstrate the role of PARP in the development of cardiac dysfunction induced by DOX. PARP-1+/+ and PARP-1-/- mice received a single injection of DOX (25 mg/kg i.p). Five days after DOX administration, left ventricular performance was significantly depressed in PARP-1+/+ mice, but only to a smaller extent in PARP-1-/- ones. Similar experiments were conducted in BALB/c mice treated with PJ34 or vehicle. Treatment with a PJ34 significantly improved cardiac dysfunction and increased the survival of the animals. In addition PJ34 significantly reduced the DOX-induced increase in the serum lactate dehydrogenase and creatine kinase activities but not metalloproteinase activation in the heart. Thus, PARP activation contributes to the cardiotoxicity of DOX. PARP inhibitors may exert protective effects against the development of severe cardiac complications associated with the DOX treatment.

Platelet-activating factor evokes Ca2+ transients after the blockade of ryanodine receptor by dantrolene in RAW 264.7 macrophages.

In the present study we studied platelet-activating factor (PAF)-, and ATP-induced increases in intracellular Ca2+ concentration ([Ca2+]i) using RAW 264.7 macrophages filled with fura-2/AM and imaged with fluorescence video microscopy. We found that the prevalence of detectable [Ca2+]i responses to PAF application was significantly higher in the presence of dantrolene. Dantrolene itself significantly decreased basal [Ca2+]i of macrophages compared to control cases after a 20-min incubation period. In the dantrolene-treated cells even the peak [Ca2+]i in response to PAF (as an average of all cells) was below the baseline of control suggesting that decreased [Ca2+]i plays a permissive role in the Ca2+ rise induced by PAF in macrophages. In contrast to the effect of PAF, neither the amplitude of response to ATP nor the frequency of responding cells changed significantly during dantrolene treatment in our experiments. These cells were able to respond to a standard immune stimulus as well: lipopolysaccharide (LPS) was able to increase [Ca2+]i. Our data indicate that the effectiveness of PAF to increase [Ca2+]i in RAW 264.7 macrophages depends on the resting [Ca2+]i. It has also been shown in this study that PAF and ATP differently regulate Ca2+ homeostasis in macrophages during inflammatory response and therefore they possibly differently modulate cytokine production by macrophages.

Receptor-mediated interaction between the sympathetic nervous system and immune system in inflammation.

The sympathetic nervous system plays a central role in establishing communication between the central nervous system and the immune system during inflammation. Inflammation activates the sympathetic nervous system, which causes release of the transmitters of the sympathetic nervous system in the periphery. The transmitters of the sympathetic nervous system are the catecholamines noradrenaline and adrenaline and the purines ATP, adenosine, and inosine. Once these transmitters are released, they stimulate both presynaptic receptors on nerve terminals and post-synaptic receptors on immune cells. The receptors that are sensitive to catecholamines are termed adrenoceptors, whereas the receptors that bind purines are called purinoceptors. Stimulation of the presynaptic receptors exerts an autoregulatory effect on the release of transmitters. Ligation of the postsynaptic receptors on inflammatory cells modulates the inflammatory activities of these cells. The present review summarizes some of the most important aspects of the current state of knowledge about the interactions between the sympathetic nervous system and the immune system during inflammation with a special emphasis on the role of adreno and purinoceptors.

Enhanced tumor necrosis factor-alpha-specific and decreased interleukin-10-specific immune responses to LPS during the third trimester of pregnancy in mice.

It is increasingly apparent that there is a bidirectional interaction between the maternal immune system and the reproductive system during pregnancy. Pregnancy is associated with a suppression of maternal specific immune responses, which process underlies the protection of fetal tissues expressing paternally inherited alloantigens. However, recent evidence indicates that the suppression of specific, lymphocyte-mediated immune responses during pregnancy is accompanied by activation of the non-specific arm of the maternal immune response. In the present study, we have investigated the effect of pregnancy on the non-specific immune response induced by bacterial lipopolysaccharide (LPS, endotoxin) in mice. Pregnancy enhanced the LPS-induced production of proinflammatory cytokines, including tumor necrosis factor-alpha, interleukin (IL)-6, and interferon-gamma. On the other hand, LPS-induced levels of the anti-inflammatory cytokine IL-10 were suppressed in pregnant mice. These alterations in cytokine production correlated with an increased susceptibility for endotoxemic mortality in the pregnant mice. Although adrenergic receptors are important regulators of cytokine production in non-pregnant mice, the alpha(2)- and the beta-adrenoceptor-mediated modulation of cytokine production ceases to operate during pregnancy associated with severe endotoxemia. These data may explain how excessive activation of the non-specific immune responses during pregnancy can contribute to the increased severity of some maternal diseases, including septic shock, and can be an important pathophysiological factor in disseminated intravascular coagulation or preeclampsia.

Anti-inflammatory effects of inosine in human monocytes, neutrophils and epithelial cells in vitro.

Inosine is an endogenous purine, which has been recently shown to exert immunomodulatory, anti-inflammatory and anti-shock effects in rodent experimental systems. Some of these actions may be related to partial adenosine receptor agonistic effects. It has not been investigated previously whether inosine exerts similar immunomodulatory or anti-inflammatory effects in human cells or enzymes. Here we investigated the effects of inosine on the activation of human monocytes, neutrophils and epithelial cells in vitro. Furthermore, using a human inosine-5'-monophosphate dehydrogenase (IMPDH) enzyme, we examined the potential effects of inosine on the activity of IMPDH, an enzyme involved in the regulation of certain inflammatory/immune processes. Tumor necrosis factor alpha (TNF-alpha) production of bacterial lipopolysaccharide (LPS) stimulated whole blood was used as an indicator of human monocyte activation. The response was dose-dependently, partially suppressed in the presence of inosine. Inosine exerted a dose-dependent and, at the highest dose (3 mM), complete inhibition of the ability of human neutrophils activated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) to induce cytochrome C reduction in vitro. In the human colon cancer cell line HT-29, inosine dose-dependently attenuated the production of IL-8. Inosine failed to affect the activity of IMPDH. Taken together, we conclude that inosine exerts anti-inflammatory effects in many human cell types. Further studies need to establish whether inosine supplementation exerts anti-inflammatory effects in human beings.

Inosine reduces systemic inflammation and improves survival in septic shock induced by cecal ligation and puncture.

Inosine is a naturally occurring purine formed from the breakdown of adenosine. Here we have evaluated the effects of inosine in a murine model of polymicrobial sepsis induced by cecal ligation and puncture (CLP). Mice subjected to CLP were treated with either inosine (100 mg/kg, intraperitoneally) or vehicle 1 h before and 6 h after CLP. After 12 h tumor necrosis factor alpha, interleukin 6 (IL-6), and IL-10 were measured in plasma. Biochemical markers of organ damage, liver NAD+/NADH (indicator of the mitochondrial redox state), plasma nitrate, tissue myeloperoxidase (MPO, indicator of neutrophil accumulation) and malondialdehyde (MDA, indicator of lipid peroxidation), liver and lung chemokines (macrophage inflammatory protein 1alpha [MIP-1alpha] and MIP-2), and ex vivo vascular reactivity in aortic rings were also measured. Mice treated with inosine had significantly lower levels of circulating cytokines. Organ damage was significantly reduced by inosine treatment, which was associated at the tissue level with an increased hepatic NAD+/NADH ratio, decreased MPO activity in the lung, reduced MDA formation in the gut and liver, and decreased MIP-1alpha and MIP-2 in the lung and liver. Furthermore, inosine significantly improved endothelium-dependent relaxant responses of aortic rings. These effects were associated with significant improvement of the survival of CLP mice treated with inosine, an effect that was still observed when inosine treatment was delayed 1 h after CLP, especially when it was associated with appropriate antibiotic treatment. Thus, inosine reduced systemic inflammation, organ damage, tissue dysoxia, and vascular dysfunction, resulting in improved survival in septic shock.

Sulphasalazine inhibits macrophage activation: inhibitory effects on inducible nitric oxide synthase expression, interleukin-12 production and major histocompatibility complex II expression.

The anti-inflammatory agent sulphasalazine is an important component of several treatment regimens in the therapy of ulcerative colitis, Crohn's disease and rheumatoid arthritis. Sulphasalazine has many immunomodulatory actions, including modulation of the function of a variety of cell types, such as lymphocytes, natural killer cells, epithelial cells and mast cells. However, the effect of this agent on macrophage (M phi) function has not been characterized in detail. In the present study, we investigated the effect of sulphasalazine and two related compounds - sulphapyridine and 5-aminosalicylic acid - on M phi activation induced by bacterial lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma). In J774 M phi stimulated with LPS (10 microg/ml) and IFN-gamma (100 U/ml), sulphasalazine (50-500 microM) suppressed nitric oxide (NO) production in a concentration-dependent manner. The expression of the inducible NO synthase (iNOS) was suppressed by sulphasalazine at 500 microM. Sulphasalazine inhibited the LPS/IFN-gamma-induced production of both interleukin-12 (IL-12) p40 and p70. The suppression of both NO and IL-12 production by sulphasalazine was superior to that by either sulphapyridine or 5-aminosalicylic acid. Although the combination of LPS and IFN-gamma induced a rapid expression of the active forms of p38 and p42/44 mitogen-activated protein kinases and c-Jun terminal kinase, sulphasalazine failed to interfere with the activation of any of these kinases. Finally, sulphasalazine suppressed the IFN-gamma-induced expression of major histocompatibility complex class II. These results demonstrate that the M phi is an important target of the immunosuppressive effect of sulphasalazine.

Injury-enhanced calcium mobilization in circulating rat neutrophils models human PMN responses.

G-protein coupled (GPC) chemoattractants are important neutrophil (PMN) activators in human shock and sepsis, acting in part by increasing cytosolic calcium ([Ca2+]i). Rats are widely used as laboratory models of shock and sepsis, but reports of [Ca2+]i flux in circulating rat PMN are rare. Moreover, the [Ca2+]i values reported often differ markedly from human systems. We developed study methods where basal [Ca2+]i values in circulating rat PMN were comparable to human PMN, but rat PMN still mobilized calcium poorly after stimulation. Trauma (laparotomy) did not change rat PMN basal [Ca2+]i, but induced brisk [Ca2+]i responses to chemokine and lipid mediators that approximated human PMN responses. This was associated with marked loading of microsomal calcium stores. Formyl peptides still mobilized calcium less well in rat than human PMN. Normal rat PMN appear to circulate in a less mature or primed form than human PMN. A very limited injury rapidly converts rat PMN to a more activated phenotype. PMN thus activated act quite similar to human PMN in terms of GPC receptor-mediated calcium mobilization. Trauma enhances rat PMN responses to GPC agonists at least in part by loading cell calcium stores.

Peroxynitrite production, DNA breakage, and poly(ADP-ribose) polymerase activation in a mouse model of oxazolone-induced contact hypersensitivity.

Peroxynitrite-induced poly(ADP-ribose) polymerase activation has been implicated in the pathogenesis of various inflammatory conditions. Here we have investigated whether peroxynitrite and poly(ADP-ribose) polymerase may play a role in the pathophysiology of the elicitation phase of contact hypersensitivity. We have detected nitrotyrosine, DNA breakage, and poly(ADP-ribose) polymerase activation in the epidermis of mice in an oxazolone-induced contact hypersensitivity model. As tyrosine nitration is mostly mediated by peroxynitrite, a nitric-oxide-derived cytotoxic oxidant capable of causing DNA breakage, we have applied peroxynitrite directly on mouse skin and showed poly(ADP-ribose) polymerase activation in keratinocytes and in some scattered dermal cells. We have also investigated the cellular effects of peroxynitrite in HaCaT cells, a human keratinocyte cell line. We found that peroxynitrite inhibited cell proliferation and at higher concentrations also caused cytotoxicity. Peroxynitrite activates poly(ADP-ribose) polymerase in HaCaT cells and poly(ADP-ribose) polymerase activation contributes to peroxynitrite-induced cytotoxicity, as indicated by the cytoprotective effect of the poly(ADP-ribose) polymerase inhibitor 3-aminobenzamide. The cytoprotective effect of 3-aminobenzamide cannot be attributed to inhibition of apoptosis, as apoptotic parameters (caspase activation and DNA fragmentation) were not reduced in the presence of 3-aminobenzamide in peroxynitrite-treated cells. Moreover, poly(ADP-ribose) polymerase inhibition by 3-aminobenzamide dose-dependently reduced interferon-induced intercellular adhesion molecule 1 expression as well as interleukin-1beta-induced interleukin-8 expression. Our results indicate that peroxynitrite and poly(ADP-ribose) polymerase regulate keratinocyte function and death in contact hypersensitivity.

Inhibition of poly (ADP-ribose) synthetase by gene disruption or inhibition with 5-iodo-6-amino-1,2-benzopyrone protects mice from multiple-low-dose-streptozotocin-induced diabetes.

Activation of poly(ADP-ribose) synthetase (PARS, also termed polyADP-ribose polymerase or PARP) has been proposed as a major mechanism contributing to beta-cell destruction in type I diabetes. In the present study, we have investigated the role of PARS in mediating the induction of diabetes and beta-cell death in the multiple-low-dose-streptozotocin (MLDS) model of type I diabetes. Mice genetically deficient in PARS were found to be less sensitive to MLDS than wild type mice, with a lower incidence of diabetes and reduced hyperglycemia. A potent inhibitor of PARS, 5-iodo-6-amino-1,2-benzopyrone (INH(2)BP), was also found to protect mice from MLDS and prevent beta-cell loss, in a dose-dependent manner. Paradoxically, in the PARS deficient mice, the compound increased the onset of diabetes. In vitro the cytokine combination; interleukin-1beta, tumor necrosis factor-alpha and interferon-gamma inhibited glucose-stimulated insulin secretion from isolated rat islets of Langerhans and decreased RIN-5F cell viability. The PARS inhibitor, INH(2)BP, protected both the rat islets and the beta-cell line, RIN-5F, from these cytokine-mediated effects. These protective effects were not mediated by inhibition of cytokine-induced nitric oxide formation. Inhibition of PARS by INH(2)BP was unable to protect rat islet cells from cytokine-mediated apoptosis. Cytokines, peroxynitrite and streptozotocin were all shown to induce PARS activation in RIN-5F cells, an effect suppressed by INH(2)BP. The present study provides evidence for in vivo PARS activation contributing to beta-cell damage and death in the MLDS model of diabetes, and indicates a role for PARS activation in cytokine-mediated depression of insulin secretion and cell viability in vitro.

Inhibition of the Na(+)/H(+) antiporter suppresses IL-12 p40 production by mouse macrophages.

The amiloride-inhibitable Na(+)/H(+) antiporter plays an important role in macrophage activation. The intracellular pathways leading to interleukin (IL)-12 p40 production by activated macrophages are incompletely understood. In the present study, we examined the contribution of the Na(+)/H(+) antiporter to the production of IL-12 p40. Amiloride or its analogs decreased the production of IL-12 p40 in macrophages stimulated with bacterial lipopolysaccharide and interferon-gamma. The order of potency of amiloride analogs was consistent with the proposition that the effect of amiloride is mediated by the inhibition of the Na(+)/H(+) antiporter. The effect of amiloride was post-transcriptional, as IL-12 p40 mRNA levels induced by lipopolysaccharide and interferon-gamma were not affected by this inhibitor. Furthermore, the inhibitory effect of amiloride on IL-12 p40 production was not a result of interference with the activation of the p38 and p42/44 mitogen-activated protein kinases or c-Jun kinase. In summary, the production of IL-12 p40 requires a functional Na(+)/H(+) antiporter.

Evidence for reactive nitrogen species formation in the gingivomucosal tissue.

An increase in nitric oxide production has been demonstrated in periodontitis. Here we investigated the potential role of nitric-oxide-derived nitrating species (such as peroxynitrite) in a rat model of ligature-induced periodontitis. Formation of 3-nitrotyrosine, the stable product formed from tyrosine reacting with nitric-oxide-derived nitrating species, was detected in the gingivomucosal tissue. 3-Nitrotyrosine immunohistochemical analysis revealed a significant elevation in the number of immunopositive leukocytes, and higher immunoreactivity of the gingival ligaments and epithelium in the ligated than in the contralateral (control) side. On both sides, several 3-nitrotyrosine-positive bands and, on the ligated side, a unique 52-kDa 3-nitrotyrosine-positive band were detected by Western blot. However, in the sterile gingivomucosal tissue of rat pups, no 3-nitrotyrosine or inducible nitric oxide synthase immunoreactivity was found. Analysis of these data suggests that resident bacteria of the gingivomucosal tissue induce an increase in reactive nitrogen species, which is greatly enhanced by plaque formation in periodontitis.

Inosine improves gut permeability and vascular reactivity in endotoxic shock.

OBJECTIVE: To investigate the effects of inosine administration on vascular reactivity, gut permeability, neutrophil accumulation and lipid peroxidation in tissues in murine endotoxin shock. DESIGN: Randomized, prospective laboratory study. SETTING: Research laboratory. SUBJECTS: BALB/c mice 6-8 wks age. INTERVENTIONS: BALB/c mice were randomly assigned to one of five groups: a) vehicle controls, which received saline intraperitoneally; b) inosine controls, which received inosine alone (100 mg/kg, ip); c) lipopolysaccharide (LPS)-treated animals, which received LPS (40 and 100 mg/kg, ip, depending on the experimental protocol); d) inosine pretreatment group, which received inosine (100 mg/kg, ip) 30 mins before LPS; and finally, e) inosine posttreatment group, which received inosine (100 mg/kg, ip) 60 mins after LPS. MEASUREMENTS AND MAIN RESULTS: The passage of fluorescein isothiocyanate-conjugated dextran (4 kDa, FD4) was analyzed in everted gut ileal sacs incubated ex vivo as an index of gut permeability. LPS induced a significant intestinal hyperpermeability, and inosine exerted protective effects both in pre- and posttreatment regimens. Myeloperoxidase and malondialdehyde were also measured to study neutrophil accumulation and lipid peroxidation in selected tissues. Inosine, both in pre- and posttreatment regimens ameliorated the increases in myeloperoxidase and malondialdehyde in the lung and gut. LPS-treated animals showed decreased contractile and relaxant responses, and inosine pretreatment (but not posttreatment) partially improved these responses. CONCLUSIONS: Taken together, inosine has organ protective effects during shock. A significant portion of its protective action is maintained even in the posttreatment scenario.