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Background: The Mycobacterium abscessus complex are the rapidly growing mycobacteria (RGM) most commonly causing lung disease, especially in cystic fibrosis (CF) patients. Ireland has the world's highest CF incidence. The molecular epidemiology of M. abscessus complex in Ireland is unreported., Methods: We performed rpoB gene sequencing and multi-locus sequence typing (MLST) on M. abscessus complex strains isolated from thirty-six patients in 2006-2012 (eighteen known CF patients)., Results: Twenty-eight strains (78%) were M. abscessus subsp. abscessus, eight M. abscessus subsp. massiliense, none were M. abscessus subsp. bolletii. Sequence type 1 (ST1) and ST26 (M. abscessus subsp. abscessus) were commonest. Seven M. abscessus subsp. abscessus STs (25%) were novel (two with novel alleles). Seven M. abscessus subsp. massiliense STs were previously reported (88%), including two ST23, the globally successful clone. In 2012, of 552 CF patients screened, eleven were infected with M. abscessus complex strains (2%)., Conclusions: The most prevalent M. abscessus subsp. abscessus and M. abscessus subsp. massiliense strains in Ireland belong to widely-distributed STs, but there is evidence of high M. abscessus subsp. abscessus diversity., (Copyright © 2015 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

In two competing models of toxic cell death, hepatocyte killing by chemical hypoxia (CN/IAA) is attributed to ATP depletion and killing by A23187 is attributed to Ca(2+)-induced damage. The independence of these models can be questioned because CN/IAA elevates Ca2+ before killing 1c1c7 hepatoma cells and because the ATP source fructose prevents hepatocyte killing by Br-A23187. In the present studies, cultured mouse hepatocytes were exposed to CN/IAA, A23187, or treatments in combination. A23187 produced toxicity proportional to Ca(2+)-activated DNA fragmentation. CN/IAA caused comparable toxicity but no fragmentation of DNA. Treatments in combination were more toxic than either treatment alone. Aurintricarboxylic acid, a Ca(2+)-endonuclease inhibitor, decreased DNA fragmentation and the toxicity of A23187 and combination treatment without affecting CN/IAA toxicity. ATP plus oligomycin decreased CN/IAA and combination treatment toxicity but not that of A23187. These findings indicate that cultured mouse hepatocytes are killed through mechanisms that are independent and additive in their toxicities.

Drugs and chemicals that cause irreversible damage to cells may do so by producing specific defects in calcium regulation. The present studies examined glycogen phosphorylase as an index for assessing in vivo changes leading to excessive calcium ion activity, a putative pathogen, during the course of acetaminophen-induced liver injury. Administration of 500 mg/kg acetaminophen per os to mice depleted hepatic glutathione to a nadir by 1 h. Covalent binding to hepatocellular macromolecules commenced at this time and then rose out of the non-injurious background range at 1.5 h, coincident with a sharp rise in phosphorylase a activity. Phosphorylase activation preceded the leakage of alanine aminotransferase into plasma by several hours but appeared only after glutathione was depleted in excess of 80%. During the first 3 h, phosphorylase a activity rose in direct proportion to the amount of acetaminophen covalent binding. Glutathione depletion alone was not responsible for phosphorylase activation because the glutathione biosynthesis inhibitor, D,L-buthionine sulfoximine, produced comparable glutathione depletion but failed to stimulate phosphorylase activity or produce cell injury. Because phosphorylase a activity is thought to mirror changes in Ca2+ activity in vivo, these results support the hypothesis that acetaminophen-induced hepatocellular injury is related to the impairment of Ca2+ regulation.

N-Acetylcysteine stereoisomers were compared for their ability to alter the sulfation and hepatotoxicity of acetaminophen. The clinically used L-isomer increased urinary excretion of inorganic sulfate 2-3 fold and prevented liver injury, but failed to increase acetaminophen sulfation in mice. Conversely, the nonphysiologic D-isomer failed to increase urinary excretion of inorganic sulfate or prevent hepatotoxicity, but increased acetaminophen sulfation appreciably (by 39%). The basis of the incongruence between changes in the availability of inorganic sulfate and the sulfation of acetaminophen is not known. These data indicate that a modest increase in acetaminophen sulfation, occurring alone following N-acetylcysteine treatment, is insufficient to explain the profound efficacy of the antidote in mice, and further suggest that this holds true for other species, such as humans, that are comparatively poor in the sulfoconjugation of acetaminophen.

The obese overfed rat effectively models many of the pharmacological changes in human obesity. Recent data show that the obese rat is unusually susceptible to liver damage by several metabolically activated drugs that may be more toxic in obese humans. Results of the present study suggest a specific molecular locus for this interaction. In obese rats, P450 content of liver and the microsomal concentration of P450 were elevated 88% and 31%, respectively, over nonobese controls. Increases in microsomal ethanol oxidation were of identical magnitude. The ethanol-inducible form of P450 that is responsible for microsomal ethanol oxidation, P450IIE1, bioactivates several drugs that are shown to cause increased injury in obese rats. Collectively, these findings indicate that specific forms of P450 may become up-regulated in obesity, increasing the risk of a biochemically defined spectrum of drug-induced organ injuries.

The status of Na+ regulation was examined during early stages of alkylation insult to rat liver. Na+/K+-ATPase activity in plasma membranes declined by 52% within 3 hr of treatment with 850 mg/kg acetaminophen. This loss preceded the release of alanine aminotransferase (2880 +/- 1550 U/ml) and necrosis (2+) seen at 24 hr. Activities of 5'-nucleotidase and Mg2+-ATPase and recovery of plasma membranes were comparatively unchanged at 3 hr. Because damage to Na+/K+-ATPase appeared early in the pathogenesis of acetaminophen hepatotoxicity, loss of hepatocellular Na+ regulation could represent one of the critical molecular consequences of lethal alkylation by acetaminophen.