Cytokines stimulate expression of inducible nitric oxide synthase in DLD-1 human adenocarcinoma cells by activating poly(A) polymerase.

OBJECTIVE: The stimulation of epithelial cells by cytokines or lipopolysaccharide results in a marked increase in cellular mRNA and protein levels of inducible nitric oxide synthase (iNOS) disproportionate to the small upregulation in transcriptional activity. The molecular mechanisms by which cytokines increase iNOS expression are not well characterized. METHODS: DLD-1 cells were treated with cytokines and we studied the expression patterns of various genes by using western blot analysis and RT-PCR assay method. RESULTS: Expression levels of iNOS protein were detected after 4 h of incubation with cytokines and reached a peak at 10 h. After cytokine treatment, iNOS mRNA molecules received longer poly(A) tails (200-500 adenosine residues) and total iNOS mRNA levels also increased significantly. Western blot analysis revealed that poly(A) polymerase (PAP) undergoes a significant dephosphorylation process. At the same time, cytokines have no significant effect on the expression pattern of other factors involved in polyadenylation. CONCLUSION: Cytokines appear to induce elongation of iNOS mRNA poly(A) tail length by activating PAP. These results indicate a novel link between mRNA 3' end formation and iNOS gene expression.

Topical administration of a novel nitric oxide donor, linear polyethylenimine-nitric oxide/nucleophile adduct (DS1), selectively increases vaginal blood flow in anesthetized rats.

The aim of the present study was to test the effects of a topical administration of a novel nitric oxide donor, linear polyethylenimine-nitric oxide/nucleophile adduct (DS1), on vaginal blood flow and hemodynamics in rats. Laser Doppler flowmetry was used to measure blood flow changes following topical application of DS1 (0.3 or 1.5 mg in 0.15 ml saline) into the vagina of anesthetized Wistar rats. In vivo hemodynamic parameters were measured with Millar-tip-catheter placed in the left ventricle. DS1 (1.5 mg) increased vaginal blood flow by 191+/-24, 226+/-22 and 166+/-23% of the baseline value (at 5, 15 and 30 min, respectively, after application) without affecting systemic blood pressure, heart rate and cardiac function. The increased vaginal blood flow following DS1 application returned to baseline between 45 and 60 min. Thus, topical application of nitric oxide donors such as DS1 may be useful for the treatment of female sexual dysfunction that develops due to an impairment of local blood flow supply to the vaginal tissue.

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.

Nicotine reduces the incidence of type I diabetes in mice.

Nicotine has been previously shown to have immunosuppressive actions. Type I diabetes is an autoimmune disease resulting from the specific destruction of the insulin-producing pancreatic beta-cells. Thus, we hypothesized that nicotine may exert protective effects against type I diabetes. The multiple low-dose streptozotocin (MLDS)-induced model and spontaneous nonobese diabetic (NOD) mouse model of type I diabetes were used to assess whether nicotine could prevent this autoimmune disease. Blood glucose levels, diabetes incidence, pancreas insulin content, and cytokine levels were measured in both models of diabetes, both to asses the level of protection exerted by nicotine and to further investigate its mechanism of action. Nicotine treatment reduced the hyperglycemia and incidence of disease in both the MLDS and NOD mouse models of diabetes. Nicotine also protected against the diabetes-induced decrease in pancreatic insulin content observed in both animal models. The pancreatic levels of the Th1 cytokines interleukin (IL)-12, IL-1, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma were increased in both MLDS-induced and spontaneous NOD diabetes, an effect prevented by nicotine treatment. Nicotine treatment increased the pancreatic levels of the Th2 cytokines IL-4 and IL-10. Nicotine treatment reduces the incidence of type I diabetes in two animal models by changing the profile of pancreatic cytokine expression from Th1 to Th2.

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.

Diabetic endothelial dysfunction: the role of poly(ADP-ribose) polymerase activation.

Diabetic patients frequently suffer from retinopathy, nephropathy, neuropathy and accelerated atherosclerosis. The loss of endothelial function precedes these vascular alterations. Here we report that activation of poly(ADP-ribose) polymerase (PARP) is an important factor in the pathogenesis of endothelial dysfunction in diabetes. Destruction of islet cells with streptozotocin in mice induced hyperglycemia, intravascular oxidant production, DNA strand breakage, PARP activation and a selective loss of endothelium-dependent vasodilation. Treatment with a novel potent PARP inhibitor, starting after the time of islet destruction, maintained normal vascular responsiveness, despite the persistence of severe hyperglycemia. Endothelial cells incubated in high glucose exhibited production of reactive nitrogen and oxygen species, consequent single-strand DNA breakage, PARP activation and associated metabolic and functional impairment. Basal and high-glucose-induced nuclear factor-kappaB activation were suppressed in the PARP-deficient cells. Our results indicate that PARP may be a novel drug target for the therapy of diabetic endothelial dysfunction.

Flagellin, a novel mediator of Salmonella-induced epithelial activation and systemic inflammation: I kappa B alpha degradation, induction of nitric oxide synthase, induction of proinflammatory mediators, and cardiovascular dysfunction.

Gram-negative sepsis is mediated by the actions of proinflammatory genes induced in response to microbes and their products. We report that flagellin, the monomeric subunit of flagella, is a potent proinflammatory species released by Salmonella. Flagellin (1 microgram/ml) induces IkappaBalpha degradation, NF-kappaB nuclear translocation, and inducible NO synthase expression in cultured intestinal epithelial cells (IEC). Aflagellic Salmonella mutants do not induce NF-kappaB activation or NO production by cultured IEC. Antiserum to flagellin blocks NO production in IEC induced by medium conditioned by a variety of motile Gram-negative enteric pathogens (Escherichia coli, Salmonella muenchen, Serratia marcescens, Proteus mirabilis, and Proteus vulgaris). Flagellin, when injected systemically (approximately 10 microgram/mouse), induces systemic inflammation characterized by the systemic expression of a range of proinflammatory cytokines and chemokines and of inducible NO synthase. At higher doses (approximately 300 microgram/mouse), flagellin induces shock, characterized by hypotension, reduced vascular contractility in mice, and death. The effects of flagellin do not diminish in C3H/HeJ LPS-resistant mice, indicating that the Toll-like receptor-4 receptor is not involved in flagellin's actions. In LPS-resistant mice, i.p. injection of S. dublin flagellin or medium conditioned by wild-type S. dublin induces serum IFN-gamma and TNF-alpha, whereas medium conditioned by aflagellic mutants has no effect. Flagellin can be detected in the blood of rats with septic shock induced by live bacteria at approximately 1 microg/ml. We propose that flagellin released by Gram-negative pathogens may contribute to the inflammatory response by an LPS- and Toll-like receptor-4-independent pathway.

Anti-inflammatory effects of a novel, potent inhibitor of poly (ADP-ribose) polymerase.

OBJECTIVE AND DESIGN: Oxygen- and nitrogen-derived free radicals and oxidants play an important role in the pathogenesis of various forms of inflammation. Recent work emphasizes the importance of oxidant-induced DNA strand breakage and activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) in the pathogenesis of various inflammatory diseases. We have recently demonstrated the efficacy of PJ34, a novel, potent phenanthridinone derivative PARP inhibitor, in rodent models of diabetic vascular dysfunction and stroke. Here we tested the efficacy of PARP inhibition in various models of local inflammation in rodents. MATERIALS AND METHODS: PJ34 (at doses of 0.03-30 mg/kg) was tested in rats and mice subjected to standard models of inflammation, with relevant parameters of inflammation measured using standard methods. RESULTS: PJ34 treatment (s.c, i.p. and i.v.) dose-dependently suppressed neutrophil infiltration and nitric oxide (but not KC and IL-1beta) production in peritonitis. In a model of systemic endotoxemia, PJ34 pretreatment significantly reduced plasma levels of TNF-alpha, IL-1beta and nitrite/nitrate (breakdown products of nitric oxide) production. PJ34 treatment (oral gavage) induced a significant suppression of the inflammatory response in dextran sulfate colitis, multiple low dose streptozotocin diabetes and cyclophosphamide-accelerated autoimmune diabetes in the non-obese diabetic mice, and reduced the degree of mononuclear cell infiltration into the iris in an endotoxin-induced uveitis model. Delaying the start of PJ34 administration in the colitis model conferred significant protective effects, while in the arthritis model the post-treatment paradigm lacked protective effects. CONCLUSIONS: PJ34 provides significant, dose-dependent, anti-inflammatory effects in a variety of local inflammation models. Some of its actions are maintained in the post-treatment regimen and/or after discontinuation of treatment. We conclude that PARP inhibition offers a powerful means for reducing the severity of various forms of local inflammatory responses.

Maturation-dependent sequential expression of interferon regulatory factor-1 and inducible nitric oxide synthase in cultured human enterocytes.

We tested the hypothesis that inducible nitric oxide (NO) synthase (iNOS) and interferon regulatory factor 1 (IRF-1), a trans-acting factor in iNOS transcriptional activation, are maturation-dependently expressed in cytokine-stimulated human enterocytes. Caco-2BBe cells, at varying stages of maturation, were stimulated with IL-1beta and IFN-gamma. Cytokine stimulation of 3-day-old undifferentiated Caco-2BBe cells induced low levels of NO production, iNOS and IRF-1 immunoreactivity, iNOS and IRF-1 mRNA expression, and iNOS activity, whereas 24-day-old mature cells responded with a large and prolonged activation of iNOS and IRF-1 expression. The basis for this difference was accounted in part by the relatively greater iNOS transcription rate in 24- vs. 3-day-old cells. Sequential expression of IRF-1 followed by iNOS mRNA occurred in both 3- and 24-day-old cells. We conclude that enterocyte maturation profoundly alters the magnitude and duration of human iNOS and IRF-1 expression in response to cytokine stimulation. The differences in iNOS mRNA levels between the immature and mature cells are only partially explained by difference in transcriptional rates, implying that post-transcriptional regulation may also be influenced by the state of enterocyte maturation. Induction of IRF-1 expression precedes and parallels the level of iNOS expression at all stages of maturation. We propose that IRF-1 may modulate the expression of cytokine-induced iNOS activity in differentiating enterocytes.