Yael Yuhas

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

ABSTRACT 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-α) was proconvulsive in this respect. The present study shows that TNF-α, at high concentrations, may also exert a suppressive effect on Shigella-mediated seizures. This implies that high levels of TNF-α may play a protective role in neurologic complications of S. dysenteriae infection.

Rifampin Augments Cytokine-Induced Nitric Oxide Production in Human Alveolar Epithelial Cells

ABSTRACT 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 μg/ml rifampin, and cytokines with 50 μg/ml rifampin were 3.2, 4.5, and 8.8 μM, respectively (P < 0.02 versus cytokines alone). This indicates that rifampin modulates the immune response.

Roles of NF-κB Activation and Peroxisome Proliferator-Activated Receptor Gamma Inhibition in the Effect of Rifampin on Inducible Nitric Oxide Synthase Transcription in Human Lung Epithelial Cells

ABSTRACT 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-1β, 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 μg/ml (P < 0.01) and by 4.0 ± 0.3-fold at a dose of 50 μg/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-κB, a corresponding increase in the level of cytokine-induced DNA binding of NF-κB (2.1 ± 0.2-fold), and a decrease in the level of expression of peroxisome proliferator-activated receptor gamma (PPARγ). Specifically, the level of PPARγ 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-κB activation and decreases the level of PPARγ expression. The increases in the levels of NF-κB activation and NO production probably contribute to the therapeutic effects of rifampin. However, given the role of NF-κB in upregulating many inflammatory genes and the roles of PPARγ 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 Inhibits Prostaglandin E2 Production and Arachidonic Acid Release in Human Alveolar Epithelial Cells

ABSTRACT Rifampin, a potent antimicrobial agent, is a major drug in the treatment of tuberculosis. There is evidence that rifampin also serves as an immunomodulator. Based on findings that arachidonic acid and its metabolites are involved in the pathogeneses of Mycobacterium tuberculosis infections, we investigated whether rifampin affects prostaglandin E2 (PGE2) production in human alveolar epithelial cells stimulated with interleukin-1β. Rifampin caused a dose-dependent inhibition of PGE2 production. At doses of 100, 50, and 25 μg/ml, it inhibited PGE2 production by 75%, 59%, and 45%, respectively (P < 0.001). Regarding the mechanism involved, rifampin caused a time- and dose-dependent inhibition of arachidonic acid release from the alveolar cells. At doses of 100, 50, 25, and 10 μg/ml, it significantly inhibited the release of arachidonic acid by 93%, 64%, 58%, and 35%, respectively (P < 0.001). Rifampin did not affect the phosphorylation of cytosolic phospholipase A2 or the expression of cyclooxygenase-2. The inhibition of PGE2, and presumably other arachidonic acid products, probably contributes to the efficacy of rifampin in the treatment of tuberculosis and may explain some of its adverse effects.

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.

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.