Mechanism of Resistance to an Antitubercular 2-Thiopyridine Derivative That Is Also Active against Burkholderia cenocepacia

The discovery of new compounds that are able to inhibit the growth of Burkholderia cenocepacia is of primary importance for cystic fibrosis patients. Here, the mechanism of resistance to a new pyridine derivative already shown to be effective against Mycobacterium tuberculosis and to have good activity toward B. cenocepacia was investigated. Increased expression of a resistance-nodulation-cell division (RND) efflux system was detected in the resistant mutants, thus confirming their important roles in B. cenocepacia antibiotic resistance.     

<Emphasis Type="Bold">9</Emphasis><Superscript><Emphasis Type="Bold">th</Emphasis></Superscript><Emphasis Type="Bold">International Conference On Homocysteine and One-Carbon Metabolism - HCY2013</Emphasis>

Canavan disease (CD) is a fatal neurological disorder caused by defects in the gene that encodes for a critical metabolic enzyme. The enzyme aspartoacylase catalyzes the deacetylation of N-acetylaspartate to produce acetate required for fatty acid biosynthesis in the brain. The loss of aspartoacylase activity leads to the demyelination and disrupted brain development that is found in CD patients. Sixteen different clinical mutants of aspartoacylase have been cloned, expressed and purified to examine their properties and the relationship between enzyme properties and disease phenotype. In contrast to numerous cell culture studies that reported virtually complete loss of function, each of these purified mutant enzymes was found to have measureable catalytic activity. However, the activities of these mutants are diminished, by as little as three-fold to greater than 100-fold when compared to the native enzyme. Many of these mutated enzyme forms show decreased thermal stability and an increased propensity for denaturation upon exposure to urea, but only four of the 16 mutants examined showed both diminished thermal and diminished conformational stability. Significantly, each of these lower stability mutants are responsible for the more severe phenotypes of CD, while patients with milder forms of CD have aspartoacylase mutants with generally high catalytic activity and with either good thermal or good conformational stability. These results suggest that the loss of catalytic function and the accumulation of N-acetylaspartate in Canavan disease is at least partially a consequence of the decreased protein stability caused by these mutations.     

Panton-Valentine Leucocidin of Staphylococcus aureus Induces Oxidative Stress and Neurotransmitter Imbalance in a Retinal Explant Model

PurposeEndophthalmitis models have reported the virulent role of Panton-Valentine leucocidin (PVL) secreted by Staphylococcus aureus on the retina. PVL targets retinal ganglion cells (RGCs), expressing PVL membrane receptor C5aR. Interactions between PVL and retinal cells lead to glial activation, retinal inflammation, and apoptosis. In this study, we explored oxidative stress and retinal neurotransmitters in a rabbit retinal explant model incubated with PVL.MethodsReactive oxygen species (ROS) production in RGCs has been assessed with fluorescent probes and immunohistochemistry. Nuclear magnetic resonance (NMR) spectroscopy quantified retinal concentrations of antioxidant molecules and neurotransmitters, and concentrations of neurotransmitters released in the culture medium. Quantifying the expression of some pro-inflammatory and anti-inflammatory factors was performed using RT-qPCR.ResultsPVL induced a mitochondrial ROS production in RGCs after four hours’ incubation with the toxin. Enzymatic sources of ROS, involving nicotinamide adenine dinucleotide phosphate–oxidase and xanthine oxidase, were also activated after four hours in PVL-treated retinal explants. Retinal antioxidants defenses, that is, glutathione, ascorbate and taurine, decreased after two hours’ incubation with PVL. Glutamate retinal concentrations and glutamate release in the culture medium remained unaltered in PVL-treated retinas. GABA, glycine, and acetylcholine (Ach) retinal concentrations decreased after PVL treatment. Glycine release in the culture medium decreased, whereas Ach release increased after PVL treatment. Expression of proinflammatory and anti-inflammatory cytokines remained unchanged in PVL-treated explants.ConclusionsPVL activates oxidative pathways and alters neurotransmitter retinal concentrations and release, supporting the hypothesis that PVL could induce a neurogenic inflammation in the retina.     

Outcome in ulcerative colitis after switch from adalimumab/golimumab to infliximab: A multicenter retrospective study

Background

Anti-TNF therapies infliximab (IFX), adalimumab (ADA), and golimumab (GOL) are approved for treating moderate to severe ulcerative colitis (UC). In UC, only the switch from IFX to ADA has been investigated, reaching no more than 10–43% remission rates at 12 months.

Neuronal nitric oxide synthase and renin stimulation by sodium deprivation are dependent on the renal nerves

OBJECTIVE: The aim of the present study was to evaluate the role of the renal nerves in the regulation of neuronal nitric oxide synthase (nNOS) gene expression in normotensive rats on different sodium balance. METHODS: Thirty-six male Sprague-Dawley rats were divided into six experimental groups combining three diets with different NaCl content (normal, 0.4%; low, 0.04%; or high, 4.0%), and bilateral renal denervation or sham denervation. After 7 days of dietary treatment, all rats were sacrificed and plasma renin activity (PRA) measured. The nNOS and renin messenger RNA (mRNA) levels in the renal cortex were determined by semiquantitative polymerase chain reaction. RESULTS: PRA was higher in animals with low sodium diet compared with those with standard diet, while it was lower in animals with high sodium diet. Renal denervation decreased PRA in normal and low sodium groups, while it did not alter the PRA values in the high sodium group. The nNOS gene expression significantly increased in rats fed with the low sodium diet compared with the standard diet group, and it significantly decreased in rats with the high sodium diet. Renal denervation significantly reduced nNOS mRNA levels in rats receiving the low sodium diet, but did not significantly influence nNOS mRNA in normal and high sodium groups. Renin mRNA was influenced by diets and denervation in a parallel way to nNOS mRNA. CONCLUSION: The renal nerves mediate the increase of renin and nNOS mRNA during sodium restriction, while the suppression of nNOS and renin gene expression during a sodium load is independent of the presence of the renal nerves. The parallel changes in renin and nNOS mRNA during different sodium intakes suggest that nNOS can be part of the complex, and still largely unclarified, macula densa mechanism of renin regulation.     

Nitric oxide induction in a rat model of selective pancreatic ischemia and reperfusion

BACKGROUND/AIMS: Ischemia and reperfusion of the pancreas may be important in aggravating the course of acute pancreatitis. In a rat model of selective pancreatic ischemia and reperfusion, we studied plasma levels of nitric oxide and expression of nitric oxide synthase in the pancrease and lung. METHODOLOGY: Pancreatic ischemia was achieved by occlusion of the 4 main pancreatic arteries for 40 min; this was followed by a 7-hour reperfusion period (group A, 10 rats). Outcome measures were compared with those of animals undergoing a sham operation (group B, 10 rats). RESULTS: Pancreatic damage in group A animals was demonstrated by increased serum alpha-amylase and by macroscopic and microscopic evidence. Total nitric oxide synthase activity in pancrease and lung was higher than in shams [median: 0.73 vs. 0.54 pmol/mg protein/min in the pancreas (P = 0.0082); 1.38 vs. 0.68 pmol/mg protein/min in the lung (P = 0.023)]; this was mainly due to activation of the inducible isoform of the enzyme. There was an associated 58.2% increase in plasma levels of nitric oxide metabolites [from mean 55.0 to 131.6 mumol/L (P < 0.001)]. Immunohistochemistry confirmed expression of inducible nitric oxide synthase and nitric oxide-mediated oxidative damage (nitrotyrosine) in both pancreas and lung. CONCLUSIONS: Ischemia and reperfusion of the pancreas induces pancreatic damage, overexpression of inducible nitric oxide synthase and oxidative damage within the pancreas and lung.