Ketamine upregulates eNOS expression in human astroglial A172 cells: Possible role in its antidepressive properties.

Ketamine is a potent anti-depressive agent. Nitric oxide plays an essential role in neuronal transmission and cerebral blood flow and has been implicated in the pathophysiology of major depressive disorder as well as cardiovascular functioning. We investigated the effect of ketamine on eNOS expression in human A172 astroglial cells. Ketamine (50-500µM) increased eNOS expression at 4-24h in a concentration-dependent manner. This effect was mediated by NMDA receptor, Akt inhibition and ERK1/2 activation and was synergistically augmented by rapamycin. The combined effect on the vascular, immune and neuronal systems may be relevant to the rapid antidepressive effect of ketamine.

Immunomodulatory activity of ketamine in human astroglial A172 cells: Possible relevance to its rapid antidepressant activity.

To determine if the immunomodulatory effect of ketamine is relevant to its rapid antidepressant activity, cultured human astroglial cells were incubated with ketamine, cytokine mix, or both. At 24h, ketamine dose-dependently (100-500 µM) decreased IL-6 and TNFα production and gene expression and, at clinically relevant concentration (100 µM), augmented IL-ß release and gene expression in both unstimulated and cytokine-stimulated cells. In unstimulated cells, ketamine also increased IL-8 production and mRNA expression. The reduction in IL-6 mRNA was significant within 1h in unstimulated cells and at 4h after stimulation. Ketamine suppressed the production of the only established depression-relevant proinflammatory cytokines, IL-6 and TNFα.

Apnea induced by respiratory syncytial virus infection is not associated with viral invasion of the central nervous system.

We aimed to study whether direct central nervous system invasion is responsible for the neurologic manifestations seen in hospitalized infants with respiratory syncytial virus (RSV) infection. Cerebrospinal fluid from infants with RSV infection was tested for the detection of the following respiratory RNA viruses: RSV, influenza A and B, pandemic influenza H1N1, Parainfluenza-3, human metapneumovirus, adenovirus, parechovirus and enterovirus. All children tested negative for the presence of viral material in the cerebrospinal fluid. Our results support the notion that the mechanism of RSV-induced neurologic manifestations, including apnea, is not direct central nervous system invasion.

Effect of nitric oxide on microRNA-155 expression in human hepatic epithelial cells.

OBJECTIVE: Nitric oxide (NO) is a signaling molecule and regulator of immunity and inflammation. MicroRNAs (miRNAs) regulate gene transcription and are involved in inflammatory processes and cancer. This study sought to determine if NO activity affects miRNA expression. METHODS: Human liver epithelial (HepG2) cells were treated with the NO-releasing S-nitroso-N-acetylpenicillamine (SNAP) 100 µM for 4 h and subjected to microarray analysis. To examine the underlying mechanisms, cells were exposed to cGMP analog 8-bromo-cGMP, protein kinase inhibitor Rp-*-Br-PET-cGMPS (Rp-PET), or nitric synthase inhibitor L-NAME and evaluated with RT-PCR. RESULTS: MiR-155 was the only miRNA of the 887 arrayed that showed a change in expression after SNAP treatment. Incubation of the cells with 8-bromo-cGMP increased miR-155 expression 4.0 ± 0.7-fold (p < 0.05); Rp-PET before SNAP had a dual, concentration-dependent effect. SNAP treatment induced a 3.1 ± 0.7-fold change in miRNA-155 expression, Rp-PET 25 µM, a 7.3 ± 2.2-fold change, and Rp-PET 100 µM, a 0.79 ± 0.09-fold change (SNAP vs SNAP + Rp-PET, p < 0.05). In unstimulated cells, Rp-PET or L-NAME treatment increased miR-155 expression by 3.5 ± 0.7-fold and 5.6 ± 2.2-fold, respectively (p < 0.05). CONCLUSION: In HepG2 cells, exogenous NO increases miR-155 expression, but endogenous basal NO inhibits it. Both effects are mediated via cGMP/PKG signaling. The upregulation of miR-155 by NO provides a new link between NO, inflammation, and cancer.

Effect of rifampin on production of inflammatory mediators in HepG2 liver epithelial cells.

Rifampin, a potent antibacterial agent, is one of the main drugs used in the treatment of mycobacterial infections. Hepatotoxicity is a well-documented adverse event. The aim of this study was to investigate the effect of rifampin on the production of inflammatory mediators in human epithelial HepG2 liver cells in the absence or presence of proinflammatory cytokines. Incubation of HepG2 cells with a cytokine mix plus rifampin was associated with a significant dose-dependent increase in the production of nitric oxide compared to incubation with the cytokine mix alone (P < 0.05) as well as with an increase in inducible nitric oxide synthase protein and mRNA expression. Rifampin significantly increased the secretion of interleukin 8 (IL-8) in both untreated cells (P < 0.001) and cytokine-treated cells (P < 0.006). An array screening assay revealed that rifampin stimulated the production of IL-1ß and gamma interferon-induced protein-10 (IP-10) in untreated cells and increased the secretion of RANTES in cytokine-treated cells. Together, these results indicate that rifampin may exert proinflammatory effects on liver cells.

Soluble triggering receptor expressed on myeloid cells-1 for diagnosing empyema.

BACKGROUND: Studies have shown that soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) is upregulated by microbial products in the bronchoalveolar lavage fluid, and cerebrospinal fluid of patients with pneumonia and bacterial meningitis, respectively. Our goal was to evaluate whether sTREM-1 in pleural fluid can distinguish pleural empyema from postthoracotomy-related pleural effusion and effusions of other etiologies. METHODS: Patients who presented with pleural effusion were identified through laboratory records. In addition to routine biochemical markers, differential white blood cells, cytology, Gram stain, and pleural fluid culture, pleural fluid sTREM-1 was measured by enzyme-linked immunosorbent assay using a commercial kit (R&D Systems, Minneapolis, MN). RESULTS: Eighty-nine patients were included in the study: 17 with empyema, 7 simple parapneumonic effusion, 18 transudate, 12 postthoracotomy pleural effusion, 22 malignancy, 1 connective tissue disease, and 12 with undetermined effusion. Mean levels of sTREM-1 were significantly higher in empyema than in postthoracotomy pleural effusion (687 +/- 479 pg/mL vs 34 +/- 81 pg/mL, p < 0.0001, respectively) and in effusions of other etiologies (15 +/- 54 pg/mL, p < 0.0001). A cutoff value of 114 pg/mL for pleural sTREM-1 achieved a sensitivity of 94% and a specificity of 93% in differentiating empyema from pleural effusions of other etiologies. The area under the receiver operating characteristic curve for pleural effusion sTREM-1 as a predictor for empyema was 0.966. CONCLUSIONS: Our findings suggest that sTREM-1 in the pleural fluid can potentially assist clinicians in the differentiation of bacterial from nonbacterial pleural effusion, particularly in postthoracotomy pleural effusion.

Roles of NF-kappaB activation and peroxisome proliferator-activated receptor gamma inhibition in the effect of rifampin on inducible nitric oxide synthase transcription in human lung epithelial cells.

Rifampin (rifampicin), an important antibiotic agent and a major drug used for the treatment of tuberculosis, exerts immunomodulatory effects. Previous studies have found that rifampin increases inducible nitric oxide (NO) synthase (iNOS) expression and NO production. The present study investigated the potential mechanism(s) underlying these actions. The incubation of human lung epithelial A549 cells with a cytokine mix (interleukin-1beta, tumor necrosis factor alpha, and gamma interferon) induced the expression of iNOS mRNA. The addition of rifampin increased the iNOS level by 1.9 +/- 0.3-fold at a dose of 10 microg/ml (P < 0.01) and by 4.0 +/- 0.3-fold at a dose of 50 microg/ml (P < 0.001). Rifampin treatment also affected the transcription factors that regulate iNOS mRNA: there was an increased and prolonged degradation of the inhibitory subunit of NF-kappaB, a corresponding increase in the level of cytokine-induced DNA binding of NF-kappaB (2.1 +/- 0.2-fold), and a decrease in the level of expression of peroxisome proliferator-activated receptor gamma (PPARgamma). Specifically, the level of PPARgamma expression dropped by 15% in response to cytokine stimulation and by an additional 40% when rifampin was added (P < 0.001). Rifampin had no effect on the activation of mitogen-activated protein kinases or the signal transducer and transcription activator (STAT-1). In conclusion, rifampin augments NO production by upregulating iNOS mRNA. It also increases the level of NF-kappaB activation and decreases the level of PPARgamma expression. The increases in the levels of NF-kappaB activation and NO production probably contribute to the therapeutic effects of rifampin. However, given the role of NF-kappaB in upregulating many inflammatory genes and the roles of PPARgamma in downregulating inflammatory genes and in lipid and glucose metabolism, these findings have implications for potential adverse effects of rifampin in patients with chronic inflammatory diseases and glucose or lipid disorders.

Rifampin augments cytokine-induced nitric oxide production in human alveolar epithelial cells.

Rifampin increased nitric oxide production and inducible nitric oxide synthase expression in alveolar cells stimulated with cytokines. Nitric oxide concentrations after induction with cytokines, cytokines with 10 microg/ml rifampin, and cytokines with 50 microg/ml rifampin were 3.2, 4.5, and 8.8 microM, respectively (P < 0.02 versus cytokines alone). This indicates that rifampin modulates the immune response.

Heparin added to cardioplegic solution inhibits tumor necrosis factor-alpha production and attenuates myocardial ischemic-reperfusion injury.

OBJECTIVES: Tumor necrosis factor (TNF)-alpha is known to be a proinflammatory cytokine that has a pronounced negative inotropic effect and plays an important role in ischemic-reperfusion injury. METHODS: Twenty isolated rat hearts were randomly divided equally into two groups (heparin and non-heparin) and were perfused with a Krebs-Henseleit solution using a modified Langendorff model. The influence of heparin on the synthesis and release of TNF-alpha by isolated rat hearts after 1 h of global cardioplegic ischemia and on left ventricular (LV) performances during 30 min of postischemic reperfusion was investigated. RESULTS: Significant mean (+/- SEM) amounts of TNF-alpha in myocardial tissue (1,149 +/- 33.7 pg/g) and effluent (951.8 +/- 27.3 pg/mL) from the coronary sinus were detected after global cardioplegic ischemia. The addition of heparin to the cardioplegic solution significantly improved the recovery of LV function in the postischemic heart (p < 0.0001 for all measurements). TNF-alpha protein production in the heparin-treated hearts was below detectable levels despite a postischemic increase of TNF-alpha messenger RNA expression in both heparin-treated hearts and nontreated hearts (0.71 +/- 0.06 and 0.8 +/- 0.12 relative optical density, respectively). CONCLUSION: This study shows, for the first time, that heparin causes the inhibition of TNF-alpha protein synthesis and release from the isolated ischemic rat heart within the posttranscriptional stage, and that it prevents the depression of LV function caused by ischemic-reperfusion injury.

Effect of tumor necrosis factor-alpha on endothelial and inducible nitric oxide synthase messenger ribonucleic acid expression and nitric oxide synthesis in ischemic and nonischemic isolated rat heart.

OBJECTIVES: The present study aimed to investigate the influence of endogenous tumor necrosis factor-alpha (TNF-alpha) that was synthesized during ischemia and exogenous TNF-alpha on endothelial and inducible nitric oxide synthase (eNOS and iNOS) messenger ribonucleic acid (mRNA) expression and nitric oxide (NO) production in the isolated rat heart. BACKGROUND: Tumor necrosis factor-alpha is recognized as being a proinflammatory cytokine with a significant cardiodepressant effect. One of the proposed mechanisms for TNF-alpha-induced cardiac contractile dysfunction is increased NO production via iNOS mRNA upregulation, but the role of NO in TNF-alpha-induced myocardial dysfunction is highly controversial. METHODS: Isolated rat hearts studied by a modified Langendorff model were randomly divided into subgroups to investigate the effect of 1-h global cardioplegic ischemia or the effect of 1-h perfusion with exogenous TNF-alpha on the expression of eNOS mRNA and iNOS mRNA and on NO production. RESULTS: After 1 h of ischemia, there were significant increases in TNF levels in the effluent (from hearts), and eNOS mRNA expression had declined (from 0.91 +/- 0.08 to 0.68 +/- 0.19, p < 0.001); but there were no changes in iNOS mRNA expression, and NO was below detectable levels. Perfusion of isolated hearts with TNF-alpha had a cardiodepressant effect and decreased eNOS mRNA expression to 0.67 +/- 0.04 (p < 0.002). Inducible nitric oxide synthase mRNA was unchanged, and NO was below detectable levels. CONCLUSIONS: We believe this is the first study to directly show that TNF-alpha does not increase NO synthesis and release but does downregulate eNOS mRNA in the ischemic and nonischemic isolated rat heart.

Bidirectional concentration-dependent effects of tumor necrosis factor alpha in Shigella dysenteriae-related seizures.

We have previously demonstrated that pretreatment of mice with Shigella dysenteriae sonicate enhanced their susceptibility to pentylenetetrazole-induced seizures and that tumor necrosis factor alpha (TNF-alpha) was proconvulsive in this respect. The present study shows that TNF-alpha, at high concentrations, may also exert a suppressive effect on Shigella-mediated seizures. This implies that high levels of TNF-alpha may play a protective role in neurologic complications of S. dysenteriae infection.

Enhancement of pentylenetetrazole-induced seizures by Shigella dysenteriae in LPS-resistant C3H/HeJ mice: role of the host response.

Convulsions and encephalopathy are common complications of Shiga toxin (Stx)-producing Shigella and enterohemorrhagic Escherichia coli infections. In previous studies, we demonstrated that Stx and lipopolysaccharide (LPS) act in concert to enhance mice sensitivity to pentylenetetrazole (PTZ)-induced seizures via mechanisms involving tumor necrosis factor alpha (TNFalpha), interleukinl beta and nitric oxide. To further elucidate the role of the host response in Shigella-related seizures, we studied the ability of Shigella dysenteriae and its products to modulate seizures in C3H/HeJ (lps(d/d)) and in C3H/HeN (lps(n/n) mice. Injection of S. dysenteriae 60R sonicate elevated plasma TNFalpha and enhanced the convulsive response to PTZ in both mouse strains. Induced TNFalpha levels were markedly lower in LPS-hyporesponsive C3H/HeJ mice than in LPS- responsive C3H/HeN mice: 7.4 ng/ml vs 44 ng/ml (induced by 4LD50). Accordingly, a higher dose of S. dysenteriae sonicate was needed to sensitize the C3H/HeJ mice to seizures. Stx or LPS alone did not enhance seizures in either strain. Stx together with LPS enhanced seizures in LPS-responsive mice, but not in LPS-hyporesponsive mice in which they induced only a minor elevation in TNFalpha levels (1.5 ng/ml). As compared to LPS-responsive mice, the LPS-hyporesponsive mice were less susceptible to the lethal effects of Shigella sonicate and were resistant to the lethal effect of purified Stx with LPS. These results demonstrate the crucial role of the host response with regard to the sensitivity to to LPS, and specifically TNFalpha production, in Shigella lethality and Shigella-related seizures.