p38-dependent enhancement of cytokine-induced nitric-oxide synthase gene expression by heat shock protein 70

The neuron-astrocyte-microglia triad involvement in neuroinflammaging mechanisms in the CA3 hippocampus of memory-impaired aged rats

We examined the effects of inflammaging on memory encoding, and qualitative and quantitative modifications on proinflammatory proteins, apoptosis, neurodegeneration and morphological changes of neuron-astrocyte-microglia triads in CA3 Stratum Pyramidale (SP), Stratum Lucidum (SL) and Stratum Radiatum (SR) of young (3months) and aged rats (20months). Aged rats showed short-term memory impairments in the inhibitory avoidance task, increased expression of iNOS and activation of p38MAPK in SP, increase of apoptotic neurons in SP and of ectopic neurons in SL, and decrease of CA3 pyramidal neurons. The number of astrocytes and their branches length decreased in the three CA3 subregions of aged rats, with morphological signs of clasmatodendrosis. Total and activated microglia increased in the three CA3 subregions of aged rats. In aged rats CA3, astrocytes surrounded ectopic degenerating neurons forming "micro scars" around them. Astrocyte branches infiltrated the neuronal cell body, and, together with activated microglia formed "triads". In the triads, significantly more numerous in CA3 SL and SR of aged rats, astrocytes and microglia cooperated in fragmentation and phagocytosis of ectopic neurons. Inflammaging-induced modifications of astrocytes and microglia in CA3 of aged rats may help clearing neuronal debris derived from low-grade inflammation and apoptosis. These events might be common mechanisms underlying many neurodegenerative processes. The frequency to which they appear might depend upon, or might be the cause of, the burden and severity of neurodegeneration. Targeting the triads may represent a therapeutic strategy which may control inflammatory processes and spread of further cellular damage to neighboring cells.

Differential hypoxic tolerance is mediated by activation of heat shock response and nitric oxide pathway

The fall in ambient oxygen pressure in high-altitude milieu elicits a wide range of physiological responses in the myocardium, which may differ from individual to individual. This condition, known as hypobaric hypoxia, invokes the cardioprotective heat shock response. The present study focuses on the role played by this ubiquitous response in mediating a differential tolerance to acute hypoxic stress. Sprague Dawley rats were exposed to simulated hypoxia equivalent to 223 mmHg pressure, screened on the basis of time taken for onset of a characteristic hyperventilatory response, and categorized as susceptible (<10 min), normal (10-25 min), or tolerant (>25 min). The tolerant animals displayed a significant upregulation of heat shock protein (Hsp)70/HSPA, evident through immunohistochemical staining of the cardiac tissue. The increased expression of transcription factor heat shock factor-1 led to the downstream activation of other chaperones, including Hsp90/HSPC, Hsp60/HSPD1, and Hsp27/HSPB1. The higher induction of HSPs in tolerant animals contributed to higher nitric oxide synthesis mediated by both endothelial nitric oxide synthase and inducible nitric oxide synthase activation. Conversely, susceptible animals showed significantly higher expression of the proinflammatory markers tumor necrosis factor alpha and nuclear factor kappa-light-chain enhancer of activated B cells in the myocardium. Evaluation of circulatory stress markers identified increased levels of reactive oxygen species, corticosterone and endothelin-1 in the susceptible animals highlighting their vulnerability to hypoxic stress. The heat shock response, through the action of chaperones and enhanced NO generation thus contributes substantially to the ability to sustain survival under acute sub lethal hypoxia.

Effects of metformin on oxidative stress, adenine nucleotides balance, and glucose-induced insulin release impaired by chronic free fatty acids exposure in rat pancreatic islets

BACKGROUND

In rat pancreatic islets, chronic exposure to high free fatty acid (FFA) levels impairs insulin secretion and β cell mass. The mechanisms underlying this defect are not completely understood. Since islets have intrinsically low anti-oxidant enzyme defense, oxidative stress might be responsible for β cell damage.

AIM

In this study, we investigated if FFA could induce oxidative stress in rat pancreatic islets and if metformin might reverse adverse effects.

MATERIAL AND METHODS

We cultured rat pancreatic islets in the presence or absence of FFA (oleate/palmitate 2:1, 2 mM) for 72 h. In some experiments, we used metformin (2.5 μg/ml) during the last 24 h.

RESULTS

In our model, glucosestimu lated insulin release was markedly reduced (p<0.005) after chronic FFA exposure, and the ATP/ADP ratio was altered (p<0.05). We observed a significant increase of reactive oxygen species (ROS) (p<0.001), malondialdehyde a lipid peroxidation product (p<0.01) and nitric oxide (NO) levels in the culture media (p<0.001). Inducible NO synthase (iNOS) and heat shock protein-70 (HSP-70) protein expression were also increased (p<0.001 and p<0.01, respectively). When metformin was present during the last 24 h of culture, insulin secretion was restored, and the ATP/ADP ratio was normalized. ROS production, NO production, lipid peroxidation, iNOS and HSP-70 protein expression levels had decreased.

CONCLUSIONS

These data indicate that, in rat pancreatic islets, chronic exposure to high FFA induces oxidative stress and that metformin, by reducing this effect, may have a direct beneficial effect on insulin secretion impaired by lipotoxicity.

Dual specificity phosphatase 1 regulates human inducible nitric oxide synthase expression by p38 MAP kinase

The role of dual specificity phosphatase 1 (DUSP1) in inducible nitric oxide synthase (iNOS) expression in A549 human pulmonary epithelial cells, J774 mouse macrophages and primary mouse bone marrow-derived macrophages (BMMs) was investigated. iNOS expression was induced by a cytokine mixture (TNF, IFNγ and IL-1β) in A549 cells and by LPS in J774 cells, and it was inhibited by p38 MAPK inhibitors SB202190 and BIRB 796. Stimulation with cytokine mixture or LPS enhanced also DUSP1 expression. Down-regulation of DUSP1 by siRNA increased p38 MAPK phosphorylation and iNOS expression in A549 and J774 cells. In addition, LPS-induced iNOS expression was enhanced in BMMs from DUSP1^(−/−) mice as compared to that in BMMs from wild-type mice. The results indicate that DUSP1 suppresses iNOS expression by limiting p38 MAPK activity in human and mouse cells. Compounds that enhance DUSP1 expression or modulate its function may be beneficial in diseases complicated with increased iNOS-mediated NO production.

Evaluation of p38 MAPK pathway as a molecular signature in ulcerative colitis

Early diagnosis and treatment of ulcerative colitis (UC) is clinically challenging. To overcome this problem, we explored the interrelated multiplex signaling pathway to identify molecular signatures in UC by using integrated strategy in proteomics. Intestinal mucosa of 12 UC cases and 12 normal controls underwent comparative proteomic analysis. A total of 26 unique differential proteins were identified, including 12 up-regulated and 14 down-regulated in UC group. A differential protein cluster, consisting of 11 proteins involved in p38 mitogen-activated protein kinase (MAPK) pathway, was deduced and validated by Western blot. Furthermore, three proteins elicited from the protein cluster, phosphorylated p38, MAWBP and galectin-3, as a molecular signature, were analyzed by immunohistochemistry on 118 UC and normal samples. Increased expression of P-p38 and down-regulated MAWBP and/or galectin-3 were detected in UC compared to normal samples (p < 0.001). This signature correlated with disease progression of UC (p < 0.01), and classified UC risk with high sensitivity (94.83 ± 2.91%) and specificity (98.33 ± 1.65%). In addition, P38 MAPK pathway modulated the expression of the protein clusters in macrophage cell line as evidenced by the alteration with specific inhibitor SB203580. These results indicate that molecular signature of P38 MAPK pathway might be a potential biomarker for evaluating UC risk.

The level of Hsp27 in lymphocytes is negatively associated with a higher risk of lung cancer

Heat shock proteins (Hsps) can protect cells, organs, and whole organisms against damage caused by abnormal environmental hazards. Some studies have reported that lymphocyte Hsps may serve as biomarkers for evaluating disease status and exposure to environmental stresses; however, few epidemiologic studies have examined the associations between lymphocyte Hsps levels and lung cancer risk. We examined lymphocyte levels of Hsp27 and Hsp70 in 263 lung cancer cases and age- and gender-matched cancer-free controls by flow cytometry. Multivariate logistic regression models were used to estimate the association between lymphocyte Hsps levels and lung cancer risk. Our results showed that Hsp27 levels were significantly lower in lung cancer cases than in controls (16.5 vs 17.8 mean fluorescence intensity, P < 0.001). This was not observed for Hsp70 levels. Further stratification analysis revealed that lymphocyte Hsp27 levels were negatively associated with lung cancer risk especially in males and heavy smokers. There was a statistical trend of low odd ratios (95% confidence intervals) and upper tertile levels of Hsp27 [1.000, 0.904 (0.566-1.444) and 0.382 (0.221-0.658, P (trend) = 0.001) in males and 1.000, 0.9207 (0.465-1.822) and 0.419 (0.195-0.897, P (trend) = 0.036) in heavy smokers] after adjustment for confounding factors. These results suggest that lower lymphocyte Hsp27 levels might be associated with an increased risk of lung cancer. Our findings need to be validated in a large prospective study.

Differential activation of mitogen-activated protein kinases following high and low LET radiation in murine macrophage cell line

Mitogen-activated protein kinases have been shown to respond to various stimuli including cytokines, mitogens and gamma irradiation, leading to cell proliferation, differentiation, or death. The duration of their activation determines the specificity of response to each stimulus in various cells. In this study, the crucial intracellular kinases, ERK, JNK, and p38 kinase involved in cell survival, death, or damage and repair were examined for their activity in RAW 264.7 cells at various time points after irradiation with 2 Gy doses of proton ions or X-rays. This is the first report that shows that the MAPK signaling induced after heavy ion or X-ray exposure is not the same. Unlike gamma irradiation, there was prolonged but marginal activation of prosurvival ERK pathway and significant activation of proapoptotic p38 pathway in response to high LET radiation.

Effect of nitric oxide donor and gamma irradiation on MAPK signaling in murine peritoneal macrophages

Irradiation (IR) of cells is known to activate enzymes of mitogen activated protein kinase (MAPK) family. These are known to be involved in cellular response to stress and are determinants of cell death or survival. When radiotherapy is delivered to malignant cells, macrophages, being radioresistant, survive, get activated, and produce large amounts of nitric oxide. As a result of activation they recognize and phagocytose tumor and normal cell apoptotic bodies leading to tumor regression. In this study, the MAPK signaling in peritoneal macrophages was investigated which plays an important role in its various functions, in an environment which is predominantly nitric oxide, as is after IR. The behavior of macrophages in such an environment was also looked at. The three MAPK (ERK1/2, p38, and JNK) respond differently to Sodium nitroprusside (SNP) alone or IR alone. All the three were activated following IR but only JNK was activated following SNP treatment. Surprisingly, when both the stresses were given simultaneously or one after the other, this differential response was lost and there was a complete inhibition of phosphorylation of all the three MAPKs, irrespective of the order of the two insults (IR and SNP). The noteworthy observation was that despite the complete inhibition of MAPK signaling there was no effect on either the viability or the phagocytic efficiency of peritoneal macrophages.

Cross-Regulation of iNOS and COX-2 by its Products in Murine Macrophages Under Stress Conditions

Exposure of macrophages to heat shock induces rapid synthesis of heat shock proteins (HSPs) which are important for cell homeostasis. Prostaglandins (PGs) and nitric oxide (NO) are important cell regulatory molecules. We have therefore investigated the interactions between these molecules in the LPS-induced expression of iNOS and COX-2 and in the mitochondrial activity of macrophages. Cultures of the murine macrophage cell line, J774, were exposed to heat shock (43 degrees C, 30 min) and stimulated with LPS (1 microg/ml), concomitantly or after 8h of cell recovery. NO production was measured by Griess reaction; PGE(2) by ELISA; HSP70, iNOS and COX-2 by immunobloting; mitochondrial activity by MTT assay. Heat shock induced HSP70, but not iNOS or COX-2 whereas LPS induced iNOS and COX-2 but not HSP70. When heat shock and LPS were given concomitantly, iNOS but not COX-2 expression was reduced. When a period of 8h was given between heat shock and LPS stimulation, iNOS, COX-2, PGE(2) and NO levels were significantly increased. Under these conditions, the expression of COX-2 was reduced by L-NAME (NO-synthesis inhibitor) and of iNOS by nimesulide (PGs-synthesis inhibitor). Such cross-regulation was not observed in cells at 37 degrees C. These treatments significantly reduced MTT levels in cells at 37 degrees C but not in cells submitted to heat shock. These results suggest that HSPs and cross-regulation of iNOS and COX-2 by their products might be of relevance in the control of cell homeostasis during stress conditions.

HEAT SHOCK STRESS AMELIORATES CYTOKINE MIXTURE-INDUCED PERMEABILITY BY DOWNREGULATING THE NITRIC OXIDE AND SIGNAL TRANSDUCER AND ACTIVATOR OF TRANSCRIPTION PATHWAYS IN CACO-2 CELLS

Proinflammatory cytokines are known to impair intestinal barrier function and to activate signaling pathways, whereas heat shock responses prevent cytokine-induced mucosal damage. We hypothesized that heat shock response blocks the effects of proinflammatory cytokines by regulating nitric oxide (NO) production and the activities of the Janus kinase/signal transducer and activator of transcription (STAT) pathway. A monolayer of Caco-2 cells were pretreated with sodium arsenite (SA, 500 micromol/L) for 1 h, followed by a 1-h recovery, and then stimulated with a cytokine mixture (cytomix: tumor necrosis factor alpha [10 ng/mL], interferon beta [1000 U/mL], and interleukin [IL] 1beta [1 ng/mL]) for 24 h. The permeability of horseradish peroxidase and fluorescein isothiocyanate-conjugated Dextran and transepithelial resistance and potential difference were measured in Ussing chambers. Interleukin-6, IL-8, NO, inducible NO synthase mRNA, STAT activity, and suppressor of cytokine signaling (SOCS) expression were measured in medium or cell lysates. Cytomix resulted in increased epithelial permeability of both fluorescein isothiocyanate-conjugated Dextran and horseradish peroxidase; whereas treatment of Caco-2 cells with SA 500 micromol/L blocked the cytomix-induced permeability changes. In addition, SA treatment decreased cytomix-induced NO production and inducible NO synthase mRNA expression and decreased the levels of STAT1, STAT3, SOCS1, and SOCS3. The SA treatment also decreased cytomix-induced IL-6 and IL-8 production in a dose-dependent manner. In conclusion, cytomix increased epithelial permeability, which is associated with increased NO and STAT activities. The SA treatment ameliorated cytomix-induced permeability, possibly through the downregulation of the NO and Janus kinase/STAT pathways.

Arsenite increases vasoconstrictor reactivity in rat blood vessels: role of endothelial nitric oxide function

Arsenite has been shown to inhibit endothelium-dependent, nitric oxide-mediated vasodilation in vitro. This study investigated the effects of arsenite on vascular reactivity in vivo. Saline or sodium arsenite (6 mg kg-1) was administered intravenously in Wistar-Kyoto rats for 4 h. As compared to saline, arsenite significantly increased vasoconstrictor responses to phenylephrine in both rat isolated aorta and renal arteries examined in tissue bath. This change was diminished after preincubation of the tissues with the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester, which increased phenylephrine-induced vasoconstriction to a similar extent as arsenite. In contrast, acetylcholine-induced vasodilation, mediated by nitric oxide in the aorta and by an endothelium-derived hyperpolarizing factor in renal arteries, was not affected by arsenite. Arsenite induced expression of heat shock proteins Hsp72, Hsp32, and Hsp90, but endothelial nitric oxide synthase expression was not changed. The effects of arsenite on vasoreactivity were unlikely to be mediated by heat shock protein induction, because blockade of heat shock protein induction had little effect on the increased vasoconstriction in vessels from arsenite-treated animals. Our study suggests that in vivo arsenic treatment increases vasoconstrictor reactivity by compromising basal endothelial nitric oxide function, which is not caused by altered endothelial nitric oxide synthase expression.

Preventive and therapeutic potential of p38 alpha-selective mitogen-activated protein kinase inhibitor in nonobese diabetic mice with type 1 diabetes

Mitogen-activated protein kinases (MAPKs) and heat shock proteins (HSPs) are ubiquitous proteins that function within T cells in both normal and stress-related pathophysiological states, including type 1 diabetes. The nonobese diabetic (NOD) mouse spontaneously develops T cell-mediated autoimmune pancreatic beta cell destruction that is similar to type 1 diabetes in humans. Because p38 MAPKs have been shown to modulate T cell function, we studied the effects of a p38alpha MAPK-selective inhibitor, indole-5-carboxamide (SD-169), on the development and progression of type 1 diabetes in the NOD mouse. In preventive treatment studies, SD-169 significantly reduced p38 and HSP60 expression in T cells of the pancreatic beta islets. Following treatment, the incidence of diabetes as determined by blood glucose levels was significantly lower, and immuno-histochemistry of pancreatic beta islet tissue demonstrated significant reduction in CD5+ T cell infiltration in the SD-169 treatment group as compared with untreated NOD mice. In therapeutic studies using mildly and moderately hyperglycemic NOD mice, SD-169 treatment lowered blood glucose and improved glucose homeostasis. Furthermore, following cessation of SD-169 treatment, NOD mice showed significant arrest of diabetes. In conclusion, we report that this p38alpha-selective inhibitor prevents the development and progression of diabetes in NOD mice by inhibiting T cell infiltration and activation, thereby preserving beta cell mass via inhibition of the p38 MAPK signaling pathway. These results have bearing on current prophylactic and therapeutic protocols using p38alpha-selective inhibitors in the prediabetic period for children at high risk of type 1 diabetes, in the honeymoon period, and for adults with latent autoimmune diabetes.

Enhanced LPS-induced TNFα production in heat-shocked human promonocytic cells: regulation at the translational/post-translational level

Heat shock proteins (hsps) play an important role in maintaining cellular homeostasis and protecting cells from various insults. Recent evidence also implicates hsps in the regulation of the immune response, particularly the inflammatory process. In the present study, we showed that human promonocytic cells (THP-1) produced elevated levels of tumor necrosis factor alpha (TNF alpha) after incubation with bacterial lipopolysaccharide (LPS) when cells were pre-stressed by a mild heat shock (HS) of 42 degrees C (1.5 h) followed by recovery at 37 degrees C (3 h) in comparison with non-stressed cells also stimulated with LPS. This enhanced TNF alpha production was not due to changes in nuclear factor-kappaB (NF-kappa B) activation, TNF alpha transcription rates, or mRNA stability. Thus, an effect at the translational or posttranslational level is likely responsible. Elevated production of TNF alpha was not observed when cells were stimulated with LPS immediately after stress or when HS temperature was increased to 43 degrees C. This negative effect of HS is likely due to a harmful effect of temperature. Moreover, enhanced LPS-induced TNF alpha production was not observed after differentiation of promonocytes into macrophage-like cells. Thus, our results show that the stress temperature, recovery period, and differentiation stage of the cell modulate the effect of HS on the inflammatory process.

Effects of hypoxia on stress proteins in the piglet heart at birth

Hypoxia at birth represents a very stressful event that can result in severe lifelong consequences in different tissues, including those of the heart. Heat shock and other associated stress proteins are involved in cellular protection, but their roles are not clearly defined at the time of birth. Newborn piglets were subjected to 5% oxygen and 95% nitrogen for either 1 or 4 hours. They were allowed to recover over periods of 1 to 68 hours. The relative levels of alphaB-crystallin, HspB8, Hsp20, Hsp27, Hsp60, and Hsp70 as well as nitric oxide synthases (NOS) (endothelial NOS, inducible NOS, neuronal NOS) were examined by Western blot analysis. Surprisingly, alphaB-crystallin expression was drastically increased in animals submitted to hypoxia. The hypoxia-associated factor HIFlalpha was also strongly and rapidly overexpressed. Heme oxygenase 1 was also increased. To a lesser extent, neuronal NOS was also increased in the left ventricle of animals submitted to hypoxia. This work clearly shows that the Hsp chaperone alphaB-crystallin is strongly overexpressed in the left ventricle of animals submitted to hypoxia. This observation dissociates the response to low oxygenation of alphaB-crystallin and other stress-associated proteins including Hsp27, and it indicates that heme oxygenase is not alone among HSPs in its oxygen-related gene expression.

Effects of hypoxia on stress proteins in the piglet brain at birth

Newborn piglets were submitted to normobaric hypoxia (5% O2, 95% N2) for either 1 or 4 h. The effects of hypoxia on the neonatal brain were characterized through a time-course analysis of levels of various proteins such as heat shock proteins (HSP27, 70, and 90), hypoxia inducible factor-1alpha (HIF-1alpha), neuronal nitric oxide synthase (nNOS), hemeoxygenase-2 (HO-2), and caspase-3. The expression of these proteins was determined at different stages of recovery up to 72 h in cerebellum, cortex, and hippocampus by Western blot analysis in hypoxic maintained animals that were made hypoxic at either 20 or 37 degrees C. In all regions of the brain, HIF-1alpha and HSP27 expression were strongly increased until 22 h of recovery. No significant changes were observed for HSP70, HSP90, and HO-2. A small elevation of expression of nNOS was observed at early stages in the cerebellum and the cortex with no change in the hippocampus. Expression of caspase 3 was strongly increased in the cortex 24 and 48 h after hypoxia but unchanged in the hippocampus. These results are presented in terms of the porcine model of nonischemic hypoxia and its delayed neuronal effects on the cerebral outcome. Because of their recently established biochemical and functional interactions, the expression of the main HSPs, HIF-1alpha, nNOS, and caspase-3 after hypoxia are delineated.

Vitamin E down-modulates iNOS and NADPH oxidase in c-Myc/TGF-alpha transgenic mouse model of liver cancer

BACKGROUND/AIMS

Co-expression of c-Myc and TGF-alpha in the mouse liver accelerates hepatocarcinogenesis and enhances DNA damage due to chronic oxidative stress. Dietary supplementation with vitamin E (VE) inhibits hepatocarcinogenesis and reduces chromosomal alterations in the same mice. Here we investigated the sources of reactive oxygen species (ROS) production in c-Myc/TGF-alpha transgenic mice.

METHODS

Inducible nitric oxide synthase (iNOS) and NADPH oxidase levels were determined in c-Myc, TGF-alpha and c-Myc/TGF-alpha mice by RT-PCR, western blot analysis and immunohistochemistry.

RESULTS

iNOS and nitrotyrosines levels were higher in the three transgenic lines when compared with wild-type mice. Preneoplastic and neoplastic lesions from c-Myc, TGF-alpha and c-Myc/TGF-alpha transgenic mice displayed upregulation of NADPH oxidase subunits p47-, 67-phox, Rac1, HSP 70, and HO-1. Importantly, dietary supplementation with vitamin E abolished iNOS expression, lowered nitrotyrosines, p47-, p67-phox, and Rac1 levels, and suppressed HSP 70 and HO-1 proteins in c-Myc/TGF-alpha livers.

CONCLUSIONS

The results suggest that iNOS and NADPH oxidase are involved in ROS generation during c-Myc/TGF-alpha hepatocarcinogenesis and are inhibited by VE treatment. The data provide additional evidence for the potential use of VE in treatment of chronic liver diseases and HCC prevention.

Switching off HSP70 and i-NOS to study their role in normal and H2O2-stressed human fibroblasts

i-NOS and HSP70 antisense oligonucleotides were used to study the role of the two well known stress-regulated molecules on cell survival of both untreated control, and H2O2-stressed human fibroblasts. Cell survival was assessed either by LDH release or by MTT assay. The levels of cytosolic i-NOS and HSP70 were tested by using immunoblotting analysis, and reactive oxygen species (ROS) production was quantified. Compared to the values observed in untreated control cells, anti HSP70-transfected human fibroblasts showed an increase in ROS production, i-NOS level and LDH release. The addition of 0.12 mM H2O2 for 20 min. to the HSP70-deprived fibroblasts did not modify the percentage of LDH release observed in H2O2 stressed cells, but reduced cell viability increasing both ROS production and i-NOS level. Anti i-NOS-transfected fibroblasts, compared to the control untreated cells, showed no modification in ROS production, while cell survival was improved. When treated with H2O2 the i-NOS depleted cells counteracted ROS formation as well as LDH release but negatively affected cell viability and HSP70 levels, compared to the results obtained with H2O2 alone-treated fibroblasts. The data indicates that the induced decrease in HSP70 level in oxidative stress conditions makes fibroblasts more prone to oxidative injury and also increases i-NOS level. Whereas in one way the forced decrease in i-NOS expression seems to counteract ROS production stimulated by the oxidative insult in the cells, in another way, since it causes a decrease in HSP70 expression as well as in cell viability, it seems to activate some unidentified pathways affecting cell demise.

Synergistic effect of shear stress and streptavidin-biotin on the expression of endothelial vasodilator and cytoskeleton genes

Dual ligand treatment of streptavidin(SA)-biotin and fibronectin (Fn) enhances the adhesion of endothelial cells (EC) onto synthetic surfaces and promotes the quiescent phenotype of adherent EC. The current study investigates the effect of the dual ligand on the expression of endothelial genes in static culture and under shear stress (4 h at 10 dynes/cm2). Expression of 23 genes in the classes of signaling, cytoskeleton/ECM, vasoregulation, and shear-responsive were examined. Eight genes (argininosuccinate synthetase, K+ channel, TGFbeta, Mn-SOD, alpha-tubulin, t-PA, COX2, and eNOS) were significantly upregulated by shear stress. Two genes (caveolin-1 and ET-1) were downregulated by shear stress. Three genes (RhoA, elastin, alpha-actinin) were upregulated by the dual ligand treatment in static culture, and four genes (FAK, elastin, COX2, and eNOS) were upregulated when the dual ligand and shear stress were applied simultaneously. Northern blot analyses on FAK, RhoA, elastin, and alpha-actinin revealed similar results. The results suggest (1) the use of SA-biotin to supplement EC adhesion enhances the integrity of the EC cytoskeleton by upregulating the expression of cytoskeleton/ECM genes, and (2) a likely relationship between the expression of cytoskeleton/ECM genes and the downstream events, such as the shear-induced expression of eNOS and COX2 genes. Analyses presented in this study provide insights into the mechanism by which SA-biotin-supplemented EC mediate gene expression.

Differential induction of TNF-α and NOS2 by mitogen-activated protein kinase signaling pathways during Mycobacterium bovis infection

The role of mitogen-activated protein kinase (MAPK) signaling pathways in the regulation of TNF-alpha and NOS2 production by human monocytes infected with Mycobacterium bovis BCG was examined. Inhibition studies showed that ERK1/2 and p38 MAPK activation were necessary for the monocyte response to M. bovis infection. Analysis of MAPK activation showed rapid phosphorylation of ERK1/2 and p38 in response to M. bovis BCG. Phosphorylation was not due to an autocrine effect of TNF-alpha secretion, since an anti-TNF-alpha antibody had no significant effect on the levels of p38 phosphorylation. The inhibitor PD98059 significantly reduced M. bovis BCG-induced TNF-alpha production and almost completely abrogated phosphorylation of ERK1/2; in addition the potent MEK inhibitor U0126 also abrogated phosphorylation. In contrast, studies using inhibitors selective for ERK1/2 and p38 showed that p38 plays an essential role in the induction of NOS2, whereas the role of ERK1/2 was minor. These results suggest that ERK1/2 and p38 kinases differentially regulate the M. bovis BCG-mediated induction of TNF-alpha and NOS2 in human monocytes.

Cellular redistribution of inducible Hsp70 protein in the human and rabbit heart in response to the stress of chronic hypoxia: role of protein kinases,

Many infants who undergo cardiac surgery have a congenital cyanotic defect where the heart is chronically perfused with hypoxemic blood. Infant hearts adapt to chronic hypoxemia by activation of intracellular protein kinase signal transduction pathways. However, the involvement of heat shock protein 70 in adaptation to chronic hypoxemia and its role in protein kinase signaling pathways is unknown. We determined expression of message and subcellular protein distribution for inducible (Hsp70i) and constitutive heat shock protein 70 (Hsc70) in chronically hypoxic and normoxic infant human and rabbit hearts and their relationship to protein kinases. In chronically hypoxic human and rabbit hearts message levels for Hsp70i were elevated 4- to 5-fold compared with normoxic hearts, Hsp70i protein was redistributed from the particulate to the cytosolic fraction. In normoxic infants Hsp70i protein was distributed almost equally between the cytosolic and particulate fractions. Hsc70 message and subcellular distribution of Hsc70 protein were unaffected by chronic hypoxia. We then determined if protein kinases influence Hsp70i protein subcellular distribution. In rabbit hearts SB203580 and chelerythrine reduced Hsp70i message levels, whereas SB203580, chelerythrine, and curcumin reversed the subcellular redistribution of Hsp70i protein caused by chronic hypoxia, with no effect in normoxic hearts, indicating regulation of Hsp70i message and subcellular distribution of Hsp70i protein in chronically hypoxic rabbit hearts is influenced by protein kinase C and mitogen-activated protein kinases, specifically p38 MAPK and JNK. We conclude the Hsp70 signal transduction pathway plays an important role in adaptation of infant human and rabbit hearts to chronic hypoxemia.

Age, cell signalling and cardioprotection

For many years investigators have been researching methods of preconditioning the myocardium against ischaemia-induced damage; however, a majority of this research has been carried out in young animals and cells. Normal ageing is accompanied by changes in the human myocardium that decrease its capacity to tolerate and respond to various forms of stress. Also, the likelihood of experiencing an ischaemic stress and other cardiovascular complications increases as an individual ages; therefore, an aged population would benefit most from cardioprotective treatments. Methods currently known to provide cardioprotection (or preconditioning) include exercise, heat stress, oxidative stress, brief ischaemia, stretch and certain pharmacological interventions. It is unclear whether the aged myocardium can adapt to a preconditioning stimulus; however, many researchers have observed age-related alterations in the expression and activation of proteins key to the cardioprotective process. These proteins include heat shock protein 70 (HSP70), nitric oxide synthase (NOS), the sodium-hydrogen exchanger (NHE), and the mitogen-activated protein (MAP) kinases c-Jun N-terminal Kinase (JNK), extracellular signal-regulated kinase (ERK), and p38. Therefore, the purpose of the current review will be to outline the current knowledge of these cardioprotective agents in an aged myocardium. Interactions among the cardioprotective agents outlined herein suggest that age-related changes in the myocardium will need to be better understood before cardioprotective interventions that have been proved effective in young animals can be applied to an aged human population.

Strain dependent rat iNOS promoter activity--correlation to identified WT1 transcription factor binding site

The free radical nitric oxide (NO) has been implicated in cytokine mediated destruction of rat beta-cells in islets of Langerhans. Cytokine mediated NO production is associated with increased expression of the inducible nitric oxide synthase (iNOS). We have previously shown a strain dependent difference between Wistar Kyoto (WKY) and Brown Norway (BN) rats of IL-1beta mediated destruction of islets of Langerhans to be related to expression levels of iNOS and NO production. The aim of the present study was to clone and screen the iNOS gene promoter region from WKY and BN rats for polymorphisms and to functionally test such nucleotide differences. Within the total 2077 bp sequenced from both rat strains we identified three polymorphisms in two separate areas: (i) a GT-repeat polymorphism linked to (ii) a C/T polymorphisms, leading to a WT1 binding site approximately 1650bp upstream the BN iNOS promoter and (iii) a G/A SNP in exon 1. Apart from these polymorphisms the homology between all published rat iNOS sequences including the presently described are about 96%. Promoter activity was detected for both genes in a luciferase assay followed cloning of 2012 bp fragments and transient transfection into RIN cells. For both strains IL-1beta induced dose-dependent activity and strain dependent iNOS promoter activity was demonstrated when WT1 was co-expressed. To our knowledge, this is the first demonstration of functional WT1/iNOS promoter interaction. We conclude that the iNOS promoter is strain-dependently regulated which may relate to quantitatively as well as qualitatively strain dependent differences in transcription factor expression, in this study exemplified by WT1.

Macrophage signalling upon mycobacterial infection: the MAP kinases lead the way

Mycobacteria activate a series of macrophage signalling pathways upon engaging host cell receptors and during the invasion process. These signals initiate a cascade of events leading to the production of immune effector molecules including cytokines, chemokines and reactive nitrogen intermediates. This response by the macrophage is critical for the control of the mycobacterial infection and, not surprisingly, pathogenic mycobacteria have evolved mechanisms to limit this macrophage activation. Recent data has suggested that macrophages infected with pathogenic compared to non-pathogenic mycobacteria are restricted in their activation of the mitogen activated protein kinase (MAPK) pathways. Mitogen activated protein kinase activation in macrophages appears to play an important role in promoting antimycobacterial activity and in the production of various effector molecules following a mycobacterial infection. Therefore, the ability of pathogenic mycobacteria to limit MAPK activity is likely an important virulence mechanism and may be a potential therapeutic target.

Regulation of the Expression of Inducible Nitric Oxide Synthase

Nitric oxide (NO), generated by the inducible isoform of nitric oxide synthase (iNOS), has been described to have beneficial microbicidal, antiviral, antiparasital, immunomodulatory, and antitumoral effects. However, aberrant iNOS induction at the wrong place or at the wrong time has detrimental consequences and seems to be involved in the pathophysiology of several human diseases. iNOS is primarily regulated at the expression level by transcriptional and post-transcriptional mechanisms. iNOS expression can be induced in many cell types with suitable agents such as bacterial lipopolysaccharides (LPS), cytokines, and other compounds. Pathways resulting in the induction of iNOS expression may vary in different cells or different species. Activation of the transcription factors NF-kappaB and STAT-1alpha, and thereby activation of the iNOS promoter, seems to be an essential step for iNOS induction in most cells. However, at least in the human system, also post-transcriptional mechanism are critically involved in the regulation of iNOS expression. The induction of iNOS can be inhibited by a wide variety of immunomodulatory compounds acting at the transcriptional levels and/or post-transcriptionally.

Beta-amyloid-induced inflammation and cholinergic hypofunction in the rat brain in vivo: involvement of the p38MAPK pathway

Injection into the nucleus basalis of the rat of preaggregated Abeta(1-42) produced a congophylic deposit and microglial and astrocyte activation and infiltration and caused a strong inflammatory reaction characterized by IL-1beta production, increased inducible cyclooxygenase (COX-2), and inducible nitric oxide synthase (iNOS) expression. Many phospho-p38MAPK-positive cells were observed around the deposit at 7 days after Abeta injection. Phospho-p38MAPK colocalized with activated microglial cells, but not astrocytes. The inflammatory reaction was accompanied by cholinergic hypofunction. We investigated the protective effect of the selective COX-2 inhibitor rofecoxib in attenuating the inflammatory response and neurodegeneration evoked by Abeta(1-42). Rofecoxib (3 mg/kg/day, 7 days) reduced microglia and astrocyte activation, iNOS induction, and p38MAPK activation to control levels. Cholinergic hypofunction was also significantly attenuated by treatment with rofecoxib. We show here for the first time in vivo the pivotal role played by the p38MAPK microglial signal transduction pathway in the inflammatory response to the Abeta(1-42) deposit.

Differential regulation of the mitogen-activated protein kinases by pathogenic and nonpathogenic mycobacteria

Mycobacteria are the etiologic agents of numerous diseases which account for significant morbidity and mortality in humans and other animal species. Many mycobacteria are intramacrophage pathogens and therefore the macrophage response to infection, which includes synthesis of cytokines such as tumor necrosis factor alpha (TNF-alpha) and production of nitric oxide, has important consequences for host immunity. However, very little is known about the macrophage cell signaling pathways initiated upon infection or how pathogenic mycobacteria may modulate the macrophage responses. Using primary murine bone marrow macrophages, we established that p38 and extracellular signal-regulated kinases 1 and 2 of the mitogen-activated protein kinase (MAPK) pathways are activated upon infection with different species of mycobacteria. However, we observed decreased MAPK activity over time in macrophages infected with pathogenic Mycobacterium avium strains relative to infections with nonpathogenic mycobacteria. Furthermore, macrophages infected with M. avium produced lower levels of TNF-alpha, interleukin 1beta, and inducible nitric oxide synthase 2 than macrophages infected with nonpathogenic species. Inhibitor studies indicate that the MAPKs are required for the Mycobacterium-mediated induction of these effector proteins. Our data indicate that MAPKs are activated in macrophages upon invasion by mycobacteria and that this activation is diminished in macrophages infected with pathogenic strains of M. avium, resulting in decreased production of important immune effector proteins. The decreased MAPK activation associated with M. avium infections suggests a novel point of immune intervention by this mycobacterial species.

Heat stress protection against mesenteric I/R-induced alterations in intestinal mucosa in rats

Prior induction of heat shock protein 70 (HSP70) protects against ischemia-reperfusion (I/R) mucosal injury, but the ability of HSP70 to affect I/R-induced alterations in epithelial cell function is unknown. Rats subjected to whole body hyperthermia (41.5-42 degrees C for 6 min) increased HSP70 and heat shock factor 1 mRNA expression, reaching a maximum 2 h after heat stress and declining thereafter. HSP70 production was maximally elevated at 4 h after heat stress and remained elevated until after 12 h. Heat stress alone had no effect on mucosal function except to enhance secretion in response to ACh. Heat stress provided complete morphological protection against I/R-induced mucosal injury but did not confer a similar protection against I/R-induced decreases in mucosal resistance, sodium-linked glucose absorption, or tachykinin-mediated chloride secretion. Heat stress, however, attenuated the I/R-induced suppression of ACh response, and this effect was dependent on enteric nerves. Thus induction of heat shock protein 70 is associated with the preservation of mucosal architecture and attenuation of some specific functional alterations induced by I/R.

The interaction between Hsp70 and TNF-alpha expression: a novel mechanism for protection of the myocardium against post-injury depression

Tumor necrosis factor-alpha (TNF-alpha) depresses myocardial contractility, and overexpression of TNF-alpha in the myocardium contributes to cardiac dysfunction caused by both systemic and local insults. Sepsis, endotoxemia, hemorrhagic shock, and myocardial ischemia-reperfusion all promote cardiac dysfunction in part by a TNF-alpha-mediated mechanism. Thus, TNF-alpha represents an appealing therapeutic target for myocardial protection against multiple clinically relevant insults. The inducible 70-kD heat shock protein (Hsp70) is expressed in the myocardium in response to stress and has been linked to enhanced myocardial resistance to depression associated with ischemia-reperfusion or sepsis. The mechanism by which Hsp70 protects cardiac function against a subsequent insult remains obscure. In vitro induction of Hsp70 in monocytes or macrophages inhibits TNF-alpha production following bacterial lipopolysaccharide stimulation, and in vivo induction of Hsp70 down-regulates tissue TNF-alpha production following an injurious insult. Understanding of the regulatory role of Hsp70 in the myocardial inflammatory response will provide insights into the mechanism by which Hsp70 preserves cardiac function and may yield therapies for protection of the myocardium against depression associated injurious insults.

Inhibition of the ubiquitin-proteasome pathway induces differential heat-shock protein response in cardiomyocytes and renders early cardiac protection

The effects of proteasome inhibition (PI) on heat-shock protein (HSP) expression in cardiomyocytes were investigated. Neonatal rat cardiomyocytes were incubated with MG132 (0.1-10 microM) for 1 h. Induction of various HSPs was determined by real-time PCR and Western blotting. PI induced a 2- to 3-fold increase in HSP27, HSP60, and HSP90, and a 18-fold increase in HSP70 mRNA expression, whereas HSP40 levels were unaffected. Western blotting revealed increased protein expression for HSP70 after PI. Similar results were obtained with MG262. HSP induction correlated with enhanced survival of neonatal cardiomyocytes after sublethal heat stress in XTT testing. In papillary muscles, pretreatment with MG132 (10 microM, 90 min) was associated with enhanced recovery of the contractile parameters after a 40-min hypoxia. In these proof-of-principle experiments, we show that PI induces differential heat-shock response in cardiomyocytes, accompanied by enhanced cell survival and functional recovery after various forms of stress.

HSP90, HSP70, and GAPDH directly interact with the cytoplasmic domain of macrophage scavenger receptors

The macrophage scavenger receptor (MSR) is a trimeric membrane protein which binds to modified low-density lipoprotein (LDL) and has been indicated in the development of atherosclerosis. It has recently been demonstrated that the N-terminal cytoplasmic domain of MSR has an important role in the efficient internalization and cell-surface expression of the receptor. This study shows that the N-terminal cytoplasmic domain in bovine was constructed using a peptide architecture technique in which the peptide chain was bundled at their C-terminus to yield a trimeric form and that this did not form an ordered structure. Furthermore, the binding proteins to the cytoplasmic domain of MSR were determined for the first time using a peptide affinity column. Sequence analyses of the specific binding proteins in bovine revealed that heat shock protein 90 (HSP90), heat shock protein 70 (HSP70), leucine aminopeptidase (LAP), adenocylhomocysteinase, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) were included. GST-pull-down assay and immunoprecipitation analyses on HSP90, HSP70, and GAPDH showed that all these proteins could bind to the cytoplasmic domain of MSR in vitro and in vivo. These proteins interact with the cytoplasmic domain directly and may have an effect on the functions of MSR such as internalization, cell-surface expression, and signal transduction.

Phosphorylation is involved in the activation of metal-regulatory transcription factor 1 in response to metal ions

We have studied the role of phosphorylation in the activation of metal-regulatory transcription factor-1 (MTF-1) and metallothionein (MT) gene expression. We showed that MTF-1 is phosphorylated in vivo and that zinc stimulates MTF-1 phosphorylation 2-4-fold. Several kinase inhibitors were used to examine the possible involvement of kinase cascades in the activation of MTF-1. Metal-induced MT gene expression was abrogated by protein kinase C (PKC), c-Jun N-terminal kinase (JNK), phosphoinositide 3-kinase, and tyrosine-specific protein kinases inhibitors, as assayed by Northern analysis and by cotransfection experiments using a metal regulatory element-luciferase reporter plasmid. The extracellular signal-activated protein kinase and the p38 kinase cascades did not appear to be essential for the activation of MT gene transcription by metals. By using dominant-negative mutants of PKC, JNK, mitogen-activated kinase kinase 4 (MKK4), and MKK7, we provide further evidence supporting a role for PKC and JNK in the activation of MTF-1 in response to metals. Notably, increased MTF-1 DNA binding in response to zinc and MTF-1 nuclear localization was not inhibited in cells preincubated with the different kinase inhibitors despite strong inhibition of MTF-1-mediated gene expression. This suggests that phosphorylation is essential for MTF-1 transactivation function. We hypothesize that metal-induced phosphorylation of MTF-1 is one of the primary events leading to increased MTF-1 activity. Thus, metal ions such as cadmium could activate MTF-1 and induce MT gene expression by stimulating one or several kinases in the MTF-1 signal transduction pathway.

Cardioprotective effect afforded by transient exposure to phosphodiesterase III inhibitors: the role of protein kinase A and p38 mitogen-activated protein kinase

BACKGROUND

Phosphodiesterase III inhibitors (PDEIII-Is) improve the hemodynamic status of heart failure via inotropic/vasodilatory effects attributable to the increase in intracellular cAMP level. Direct cardioprotection by PDEIII-Is and its underlying mechanisms, however, have not been identified. We tested the infarct size-limiting effect of PDEIII-Is and the roles of cAMP, protein kinase (PK) A, PKC, and mitogen-activated protein kinase (MAPK) families in open-chest dogs. Methods and Results-- Milrinone, olprinone (PDEIII-Is), or dibutyryl-cAMP (db-cAMP) was injected intravenously 30 minutes before 90-minute ischemia, followed by 6 hours of reperfusion. Olprinone was also examined with an intracoronary cotreatment with a PKA inhibitor (H89), a PKC inhibitor (GF109203X), an extracellular signal-regulated kinase kinase (MEK) inhibitor (PD98059), or a p38 MAPK inhibitor (SB203580) throughout the preischemic period. Either PDEIII-Is or db-cAMP caused substantial hemodynamic changes, which returned to control levels in 30 minutes. Collateral flow and percent risk area were identical for all groups. Both PDEIII-Is and db-cAMP increased myocardial p38 MAPK activity during the preischemic period, which was blocked by H89, but not by GF109203X. Both PDEIII-Is and db-cAMP reduced infarct size (19.1+/-4.1%, 17.5+/-3.3%, and 20.3+/-4.8%, respectively, versus 36.1+/-6.2% control, P<0.05 each). Furthermore, the effect of olprinone was blunted by either H89 (35.5+/-6.4%) or SB203580 (32.6+/-5.9%), but not by GF109203X or PD98059. H89, GF109203X, PD98059, or SB203580 alone did not influence infarct size.

CONCLUSIONS

Pretreatment with PDEIII-Is has cardioprotective effects via cAMP-, PKA-, and p38 MAPK-dependent but PKC-independent mechanisms in canine hearts.

Nitric oxide metabolites in gnotobiotic piglets orally infected with Salmonella enterica serovar typhimurium

Reactive NO metabolites play a distinct role in the control of Salmonella enterica serovar Typhimurium (ST; a facultative intracellular pathogen) in susceptible host. A significant increase of nitrite and/or nitrate plasma levels, 3-nitro-tyrosine expression and pathological changes in mesenteric lymph nodes have been observed in gnotobiotic piglets orally infected for 1 d with a virulent strain of ST but not in piglets infected with a rough mutant of ST.

LPS stimulation of TNF-receptor deficient macrophages: a differential role for TNF-alpha autocrine signaling in the induction of cytokine and nitric oxide production

To evaluate the role of autocrine TNF-alpha signaling in macrophage activation, immortalized macrophages from normal mice (B6/J2) and from mice containing gene targeted disruptions of the type 1 and type 2 TNF-receptor genes (TRN) were stimulated under CD14-dependent or serum-free conditions. Although the B6/J2 and TRN clones mounted similar nitric oxide responses to LPS in the presence of serum, the TRN macrophages responded poorly when stimulated with LPS under serum free conditions. LPS stimulation of TRN and B6/J2 under serum-free conditions resulted in equivalent levels of IL-1beta, TNF-alpha, and iNOS gene expression. However, Western blot analysis revealed that iNOS protein production by TRN was 2-fold lower than that produced by B6/J2. These results indicate that autocrine TNF-alpha stimulation contributes to the signaling pathways initiated by ligation of LPS receptors in the absence of LBP and is involved in iNOS post-transcriptional regulation.