Insulin suppresses LPS-induced iNOS and COX-2 expression and NF-kappa B activation in alveolar macrophages

The development of septic shock is a common and frequently lethal consequence of gram-negative infection. Mediators released by lung macrophages activated by bacterial products such as lipopolysaccharide (LPS) contribute to shock symptoms. We have shown that insulin downregulates LPS-induced TNF production by alveolar macrophages (AMs). In the present study, we investigated the effect of insulin on the LPS-induced production of nitric oxide (NO) and prostaglandin (PG)-E(2), on the expression of inducible nitric oxide synthase ( iNOS) and cyclooxygenase (COX)-2, and on nuclear factor kappa B (NF-kappa B) activation in AMs. Resident AMs from male Wistar rats were stimulated with LPS (100 ng/mL) for 30 minutes. Insulin (1 mU/mL) was added 10 min before LPS. Enzymes expression, NF-kappa B p65 activation and inhibitor of kappa B (I-kappa B) a phosphorylation were assessed by immunobloting; NO by Griess reaction and PGE(2) by enzyme immunoassay (EIA). LPS induced in AMs the expression of iNOS and COX-2 proteins and production of NO and PGE(2), and, in parallel, NF-kappa B p65 activation and cytoplasmic I-kappa B alpha phosphorylation. Administration of insulin before LPS suppressed the expression of iNOS and COX-2, of NO and PGE(2) production and Nuclear NF-kappa B p65 activation. Insulin also prevented cytoplasmic I-kappa Ba phosphorylation. These results show that in AMs stimulated by LPS, insulin prevents nuclear translocation of NF-kappa B, possibly by blocking I-kappa Ba degradation, and supresses the production of NO and PGE(2), two molecules that contribute to septic shock. Copyright (C) 2008 S. Karger AG, Basel.

Lung inflammation is induced by renal ischemia and reperfusion injury as part of the systemic inflammatory syndrome

Ischemia and reperfusion injury (IRI) are mainly caused by leukocyte activation, endothelial dysfunction and production of reactive oxygen species. Moreover, IRI can lead to a systemic response affecting distant organs, such as the lungs. The objective was to study the pulmonary inflammatory systemic response after renal IRI. Male C57Bl/6 mice were subjected to 45 min of bilateral renal ischemia, followed by 4, 6, 12, 24 and 48 h of reperfusion. Blood was collected to measure serum creatinine and cytokine concentrations. Bronchoalveolar lavage fluid (BALF) was collected to determine the number of cells and PGE(2) concentration. Expressions of iNOS and COX-2 in lung were determined by Western blot. Gene analyses were quantified by real time PCR. Serum creatinine increased in the IRI group compared to sham mainly at 24 h after IRI (2.57 +/- A 0.16 vs. 0.43 +/- A 0.07, p < 0.01). The total number of cells in BAL fluid was higher in the IRI group in comparison with sham, 12 h (100 x 10(4) +/- A 15.63 vs. 18.1x10(4) +/- A 10.5, p < 0.05) 24 h (124 x 10(4) +/- A 8.94 vs. 23.2x10(4) +/- A 3.5, p < 0.05) and 48 h (79 x 10(4) +/- A 15.72 vs. 22.2 x 10(4) +/- A 4.2, p < 0.05), mainly by mononuclear cells and neutrophils. Pulmonary COX-2 and iNOS were up-regulated in the IRI group. TNF-alpha, IL-1 beta, MCP-1, KC and IL-6 mRNA expression were up-regulated in kidney and lungs 24 h after renal IRI. ICAM-1 mRNA was up-regulated in lungs 24 h after renal IRI. Serum TNF-alpha, IL-1 beta and MCP-1 and BALF PGE(2) concentrations were increased 24 h after renal IRI. Renal IRI induces an increase of cellular infiltration, up-regulation of COX-2, iNOS and ICAM-1, enhanced chemokine expression and a Th1 cytokine profile in lung demonstrating that the inflammatory response is indeed systemic, possibly leading to an amplification of renal injury.

Modulation of inflammatory response by selective inhibition of cyclooxygenase-1 and cyclooxygenase-2 in acute kidney injury

This work explored the role of inhibition of cyclooxygenases (COXs) in modulating the inflammatory response triggered by acute kidney injury. C57Bl/6 mice were used. Animals were treated or not with indomethacin (IMT) prior to injury (days -1 and 0). Animals were subjected to 45 min of renal pedicle occlusion and sacrificed at 24 h after reperfusion. Serum creatinine and blood urea nitrogen, reactive oxygen species (ROS), kidney myeloperoxidase (MPO) activity, and prostaglandin E2 (PGE(2)) levels were analyzed. Tumor necrosis factor (TNF)-alpha, t-bet, interleukin (IL)-10, IL-1 beta, heme oxygenase (HO)-1, and prostaglandin E synthase (PGES) messenger RNA (mRNA) were studied. Cytokines were quantified in serum. IMT-treated animals presented better renal function with less acute tubular necrosis and reduced ROS and MPO production. Moreover, the treatment was associated with lower expression of TNF-alpha, PGE(2), PGES, and t-bet and upregulation of HO-1 and IL-10. This profile was mirrored in serum, where inhibition of COXs significantly decreased interferon (IFN)-gamma, TNF-alpha, and IL-12 p70 and upregulated IL-10. COXs seem to play an important role in renal ischemia and reperfusion injury, involving the secretion of pro-inflammatory cytokines, activation of neutrophils, and ROS production. Inhibition of COX pathway is intrinsically involved with cytoprotection.

Leukotrienes Produced in Allergic Lung Inflammation Activate Alveolar Macrophages

It has been well-documented that leukotrienes (LTs) are released in allergic lung inflammation and that they participate in the physiopathology of asthma. A role for LTs in innate immunity has recently emerged: Cys-LTs were shown to enhance Fc gamma R-mediated phagocytosis by alveolar macrophages (AMs). Thus, using a rat model of asthma, we evaluated Fc gamma R-mediated phagocytosis and killing of Klebsiella pneumoniae by AMs. The effect of treatment with a cys-LT antagonist (montelukast) on macrophage function was also investigated. Male Wistar rats were immunized twice with OVA/alumen intraperitoneally and challenged with OVA aerosol. After 24 h, the animals were killed, and the AMs were obtained by bronchoalveolar lavage. Macrophages were cultured with IgG-opsonized red blood cells (50: 1) or IgG-opsonized K. pneumoniae (30: 1), and phagocytosis or killing was evaluated. Leukotriene C(4) and nitric oxide were quantified by the EIA and Griess methods, respectively. The results showed that AMs from sensitized and challenged rats presented a markedly increased phagocytic capacity via Fc gamma R (10X compared to controls) and enhanced killing of K. pneumoniae (4X higher than controls). The increased phagocytosis was inhibited 15X and killing 3X by treatment of the rats with montelukast, as compared to the non-treated group. cys-LT addition increased phagocytosis in control AMs but had no effect on macrophages from allergic lungs. Montelukast reduced nitric oxide (39%) and LTC(4) (73%). These results suggest that LTs produced during allergic lung inflammation potentiate the capacity of AMs to phagocytose and kill K. pneumonia via Fc gamma R. Copyright (C) 2010 S. Karger AG, Basel

Early Phase of Allergic Airway Inflammation in Diabetic Rats: Role of Insulin on the Signaling Pathways and Mediators

Background: Allergic lung inflammation is impaired in diabetic rats and is restored by insulin treatment. In the present study we investigated the effect of insulin on the signaling pathways triggered by allergic inflammation in the lung and the release of selected mediators. Methods: Diabetic male Wistar rats (alloxan, 42 mg/kg, i.v., 10 days) and matching controls were sensitized by s.c. injections of ovalbumin (OA) in aluminium hydroxide, 14 days before OA (1 mg/0.4 ml) or saline intratracheal challenge. A group of diabetic rats were treated with neutral protamine Hagedorn insulin (NPH, 4 IU, s.c.), 2 h before the OA challenge. Six hours after the challenge, bronchoalveolar lavage (BAL) was performed for mediator release and lung tissue was homogenized for Western blotting analysis of signaling pathways. Results: Relative to non-diabetic rats, the diabetic rats exhibited a significant reduction in OA-induced phosphorylation of the extracellular signal-regulated kinase (ERK, 59%), p38 (53%), protein kinase B (Akt, 46%), protein kinase C (PKC)-alpha (63%) and PKC-delta (38%) in lung homogenates following the antigen challenge. Activation of the NF-kappa B p65 subunit and phosphorylation of I kappa B alpha were almost suppressed in diabetic rats. Reduced expression of inducible nitric oxide synthase (iNOS, 32%) and cyclooxygenase-2 (COX-2, 46%) in the lung homogenates was also observed. The BAL concentration of prostaglandin (PG)-E(2), nitric oxide (NO) and interleukin (IL)-6 was reduced in diabetic rats (74%, 44% and 65%, respectively), whereas the cytokine-induced neutrophil chemoattractant (CINC)-2 concentration was not different from the control animals. Treatment of diabetic rats with insulin completely or partially restored all of these parameters. This protocol of insulin treatment only partially reduced the blood glucose levels. Conclusion: The data presented show that insulin regulates MAPK, PI3K, PKC and NF-kappa B pathways, the expression of the inducible enzymes iNOS and COX-2, and the levels of NO, PGE(2) and IL-6 in the early phase of allergic lung inflammation in diabetic rats. It is suggested that insulin is required for optimal transduction of the intracellular signals that follow allergic stimulation. Copyright (C) 2010 S. Karger AG, Basel

Nitric oxide participation in granulomatous response induced by Paracoccidioides brasiliensis infection in mice

The role of nitric oxide (NO) in granulomas of Paracoccidioides brasiliensis-infected inducible NO synthase-deficient C57BL/6 mice (iNOS KO) and their wild-type counterparts and its association with osteopontin (OPN) and matrix metalloproteinases (MMPs) was studied. At 15 days after infection (DAI), iNOS KO mice showed compact and necrotic granulomas with OPN+ macrophages and multinucleated giant cells, whereas wild-type mice developed loose granulomas with many fungi and OPN+ cells distributed throughout the tissue. In addition, high OPN levels and fungal load were observed in iNOS KO mice. Both experimental groups had MMP-9 activity. At 120 DAI, iNOS KO had smaller granulomas with OPN+ cells, lower OPN levels, lower fungal load and decreased MMP-9 activity compared with wild-type mice. These findings suggest that NO has an important role in granuloma modulation, by controlling OPN and MMP production, as well as by inducing loose granulomas formation and fungal dissemination, resulting, at later phases, in progression of paracoccidioidomycosis.

5-Lipoxygenase plays a role in the control of parasite burden and contributes to oxidative damage of erythrocytes in murine Chagas` disease

Chagas` disease is accompanied by severe anemia and oxidative stress, which may contribute to mortality. In this study, we investigated the role of 5-lipoxygenase (5-LO) in the control of parasitism and anemia associated with oxidative damage of erythrocytes in experimental Trypanosoma cruzi infection. Wild-type C57BL/6, 129Sv mice treated or not with nordihydroguaiaretic acid (NDGA, 5-LO inhibitor), mice lacking the 5-LO enzyme gene (5-LO(-/-)) and inducible nitric oxide synthase gene (iNOS(-/-)) were infected with the Y strain of T cruzi. impairment of 5-LO resulted in increased numbers of trypomastigote forms in the blood and amastigote forms in the heart of infected mice. We assessed oxidative stress in erythrocytes by measuring oxygen uptake, induction time and chemiluminescence following treatment with tert-butyl hydroperoxide (TBH). Our results show that 5-LO metabolites increased lipid peroxidation levels in erythrocytes during the early phase of murine T cruzi infection. NDGA treatment reduced oxidative damage of erythrocytes in C57BL/6 T cruzi-infected mice but not in C57BL/6 iNOS-/- infected mice, showing that the action of NDGA is dependent on endogenous nitric oxide (NO). In addition, our results show that 5-LO metabolites do not participate directly in the development of anemia in infected mice. We conclude that 5-LO products may not only play a major role in controlling heart tissue parasitism, i.e., host resistance to acute infection with T cruzi in vivo, but in the event of an infection also play an important part in erythrocyte oxidative stress, an NO-dependent effect. (C) 2009 Elsevier B.V. All rights reserved.

Different mechanisms underlie the effects of acute and long-term inhibition of nitric oxide synthases in antigen-induced pulmonary eosinophil recruitment in BALB/C mice

Nitric oxide synthase (NOS) inhibitors are largely used to evaluate the NO contribution to pulmonary allergy, but contrasting data have been reported. In this study, pharmacological, biochemical and pharmacokinetic assays were performed to compare the effects of acute and long-term treatment of BALB/C mice with the non-selective NOS inhibitor L-NAME in ovalbumin (OVA)-challenged mice. Acute L-NAME treatment (50 mg/kg, gavage) significantly reduced the eosinophil number in bronchoalveolar lavage fluid (BALF). The inducible NOS (iNOS) inhibitor aminoguanidine (20 mg/kg/day in the drinking water) also significantly reduced the eosinophil number in BALF In contrast, 3-week L-NAME treatment (50 and 150 mg/kg/day in the drinking water) significantly increased the pulmonary eosinophil influx. The constitutive NOS (cNOS) activity in brain and lungs was reduced by both acute and 3-week L-NAME treatments. The pulmonary iNOS activity was reduced by acute L-NAME (or aminoguanidine), but unaffected by 3-week L-NAME treatment. Acute L-NAME (or aminoguanidine) treatment was more efficient to reduce the NO(x) levels compared with 3-week L-NAME treatment. The pharmacokinetic study revealed that L-NAME is not bioavailable when given orally. After acute L-NAME intake, serum concentrations of the metabolite N(omega)-nitro-L-arginine decreased from 30 min to 24 h. In the 3-week L-NAME treatment, the N(omega)-nitro-L-arginine concentration was close to the detection limit. In conclusion, 3-week treatment with L-NAME yields low serum N(omega)-nitro-L-arginine concentrations, causing preferential inhibition of cNOS activity. Therefore, eosinophil influx potentiation by 3-week L-NAME treatment may reflect removal of protective cNOS-derived NO, with no interference on the ongoing inflammation due to iNOS-derived NO. (c) 2008 Elsevier Ltd. All rights reserved.

Inhibition of interferon-gamma-induced nitric oxide production in endotoxin-activated macrophages by cytolethal distending toxin

Introduction: Cytolethal distending toxin (CDT) is a DNA-targeting agent produced by certain pathogenic gram-negative bacteria such as the periodontopathogenic organism Aggregatibacter actinomycetemcomitans. CDT targets lymphocytes and other cells causing cell cycle arrest and apoptosis, impairing the host immune response and contributing to the persistence of infections caused by this microorganism. In this study we explored the effects of CDT on the innate immune response, by investigating how it affects production of nitric oxide (NO) by macrophages. Methods: Murine peritoneal macrophages were stimulated with Escherichia coli sonicates and NO production was measured in the presence or not of active CDT. Results: We observed that CDT promptly and significantly inhibited NO production by inducible nitric oxide synthase (iNOS) in a dose-dependent manner. This inhibition is directed towards interferon-gamma-dependent pathways and is not mediated by either interleukin-4 or interleukin-10. Conclusion: This mechanism may constitute an important aspect of the immunosuppression mediated by CDT and may have potential clinical implications in A. actinomycetemcomitans infections.

iNOS-derived Nitric Oxide Modulates Infection-stimulated Bone Loss

Nitric oxide (NO) derived from inducible nitric oxide synthase (iNOS) plays an important role in host defense, as well as in inflammation-induced tissue lesions. Here we evaluated the role of NO in bone loss in bacterial infection-induced apical periodontitis by using iNOS-deficient mice (iNOS(-/-)). The iNOS(-/-) mice developed greater inflammatory cell recruitment and osteolytic lesions than WT mice. Moreover, tartrate-resistant acid-phosphatase-positive (TRAP(+)) osteoclasts were significantly more numerous in iNOS-/- mice. Furthermore, the increased bone resorption in iNOS(-/-) mice also correlated with the increased expression of receptor activator NF-kappaB (RANK), stromal-cell-derived factor-1 alpha (SDF-1 alpha/CXCL12), and reduced expression of osteoprotegerin (OPG). These results show that NO deficiency was associated with an imbalance of bone-resorption-modulating factors, leading to severe infection-stimulated bone loss.

Role of CcpA in Polyhydroxybutyrate Biosynthesis in a Newly Isolated Bacillus sp MA3.3

The ccpA gene was inactivated in the polyhydroxybutyrate (PHB)-producing strain Bacillus sp. MA3.3 in order to reduce glucose catabolite repression over pentoses and develop improved bacterial strains for the production of PHB from lignocellulosic hydrolysates. Mutant Bacillus sp. MSL7 Delta CcpA are unable to grow on glucose and ammonia as sole carbon and nitrogen sources, respectively. Supplementation of glutamate as the nitrogen source or the substitution of the carbon source by xylose allowed the mutant to partially recover its growth performance. RT-PCR showed that CcpA stimulates the expression of the operon (gltAB), responsible for ammonia assimilation via glutamate in Bacillus sp. MA3.3. Moreover, it was demonstrated that the supplementation of xylose or glutamate was capable of stimulating gltAB operon expression independently of CcpA. In PHB production experiments in mineral media, it has been observed that the glucose catabolite repression over the pentoses was partially released in MSL7. Although the carbohydrate consumption is faster in the ccpA mutant, the biomass and PHB biosynthesis are lower, even with supplementation of glutamate. This is attributed to an increase of acetyl-CoA flux towards the tricarboxylic acid cycle observed in the mutant. Copyright (C) 2011 S. Karger AG, Basel

Characterization of Gtf1p, the Connector Subunit of Yeast Mitochondrial tRNA-dependent Amidotransferase

The bacterial GatCAB operon for tRNA-dependent amidotransferase (AdT) catalyzes the transamidation of mischarged glutamyl-tRNA(Gln) to glutaminyl-tRNA(Gln). Here we describe the phenotype of temperature-sensitive (ts) mutants of GTF1, a gene proposed to code for subunit F of mitochondrial AdT in Saccharomyces cerevisiae. The ts gtf1 mutants accumulate an electrophoretic variant of the mitochondrially encoded Cox2p subunit of cytochrome oxidase and an unstable form of the Atp8p subunit of the F(1)-F(0) ATP synthase that is degraded, thereby preventing assembly of the F(0) sector. Allotopic expression of recoded ATP8 and COX2 did not significantly improve growth of gtf1 mutants on respiratory substrates. However, ts gft1 mutants are partially rescued by overexpression of PET112 and HER2 that code for the yeast homologues of the catalytic subunits of bacterial AdT. Additionally, B66, a her2 point mutant has a phenotype similar to that of gtf1 mutants. These results provide genetic support for the essentiality, in vivo, of the GatF subunit of the heterotrimeric AdT that catalyzes formation of glutaminyl-tRNA(Gln) (Frechin, M., Senger, B., Braye, M., Kern, D., Martin, R. P., and Becker, H. D. (2009) Genes Dev. 23, 1119-1130).

Identification and characterization of antigenic proteins potentially expressed during the infectious process of Paracoccidioides brasiliensis

Paracoccidioides brasiliensis causes paracoccidioidomycosis (PCM), a systemic mycosis presenting clinical manifestations ranging from mild to severe forms. A P. brasiliensis cDNA expression library was produced and screened with pooled sera from PCM patients adsorbed against antigens derived from in vitro-grown P. brasiliensis yeast cells. Sequencing DNA inserts from clones reactive with PCM patients sera indicated 35 open reading frames presenting homology to genes involved in metabolic pathways, transport, among other predicted functions. The complete cDNAs encoding aromatic-L-amino-acid decarboxylase (Pbddc), lumazine synthase (Pbls) and a homologue of the high affinity copper transporter (Pbctr3) were obtained. Recombinant proteins PbDDC and PbLS were obtained; a peptide was synthesized for PbCTR3. The proteins and the synthetic peptide were recognized by sera of patients with confirmed PCM and not by sera of healthy patients. Using the in vivo-induced antigen technology (IVIAT), we identified immunogenic proteins expressed at high levels during infection. Quantitative real time RTPCR demonstrated high transcript levels of Pbddc, Pbls and Pbctr3 in yeast cells infecting macrophages. Transcripts in yeast cells derived from spleen and liver of infected mice were also measured by qRT-PCR. Our results suggest a putative role for the immunogenic proteins in the infectious process of P. brasiliensis. (C) 2009 Elsevier Masson SAS. All rights reserved.

Effects of Plasmodium gallinaceum on hemolymph physiology of Aedes aegypti during parasite development

Insect disease vectors show diminished fecundity when infected with Plasmodium. This phenomenon has already been demonstrated in laboratory models such as Aedes aegypti, Anopheles gambiae and Anopheles stephensi. This study demonstrates several changes in physiological processes of A. aegypti occurring upon infection with Plasmodium gallinaceum, such as reduced ecdysteroid levels in hemolymph as well as altered expression patterns for genes involved in vitellogenesis, lipid transport and immune response. Furthermore, we could show that P. gallinaceum infected A. aegypti presented a reduction in reproductive fitness, accompanied by an activated innate immune response and increase in lipophorin expression, with the latter possibly representing a nutritional resource for Plasmodium sporozoites. (C) 2010 Elsevier Ltd. All rights reserved.

Biochemical characterization of serine acetyltransferase and cysteine desulfhydrase from Leishmania major

Cysteine metabolism exhibits atypical features in Leishmania parasites. The nucleotide sequence annotated as LmjF32.2640 encodes a cysteine desulfhydrase, which specifically catalyzes the breakdown of cysteine into pyruvate, NH(3) and H(2)S. Like in other pathogens, this capacity might be associated with regulatory mechanisms to control the intracellular level of cysteine, a highly toxic albeit essential amino acid, in addition to generate pyruvate for energy production. Besides, our results provide the first insight into the biochemical properties of Leishmania major serine acetyltransferase (SAT), which is likely involved in the two routes for de novo synthesis of cysteine in this pathogen. When compared with other members of SAT family, the N-terminal region of L. major homologue is uniquely extended, and seems to be essential for proper protein folding. Furthermore, unlike plant and bacterial enzymes, the carboxy-terminal-C(10) sequence stretch of L major SAT appears not to be implicated in forming a tight bi-enzyme complex with cysteine synthase. (C) 2010 Elsevier B.V. All rights reserved.