Chronic cocaine exposure is associated with severe cardiac complications, but the mechanisms of cocaine cardiotoxicity remain unclear, and current therapies are unsatisfactory. We investigated the hypothesis of oxidative stress-mediated cardiotoxicity and the role of NADPH oxidase in this process in a mouse model of chronic escalating "binge" cocaine administration (milligrams per kilogram): days 1 to 4 at 3 ϫ 15 mg, days 5 to 8 at 3 ϫ 20 mg, days 9 to 12 at 3 ϫ 25 mg, and days 13 to 14 at 3 ϫ 30 mg. Compared with vehicle controls, chronic binge cocaine administration significantly increased the cardiac NADPH-dependent O 2 . production (1.96-Ϯ 0.4-fold) as detected by tiron (an O 2 . scavenger)-inhibitable lucigenin chemiluminescence and dihydroethidium fluorescence. Cocaine-induced reactive oxygen species (ROS) production was associated with significant increases (ϳ2-fold) in the protein expressions of Nox2 (an isoform of NADPH oxidase) and its regulatory subunits: p22 phox

Cardiac tissues express constitutively an NADPH oxidase, which generates reactive oxygen species (ROS) and is involved in redox signaling. Myocardial metabolism generates abundant adenosine, which binds to its receptors and plays important roles in cardiac function. The adenosine A 2A receptor (A 2A R) has been found to be expressed in cardiac myocytes and coronary endothelial cells. However, the role of the A 2A R in the regulation of cardiac ROS production remains unknown. We found that knockout of A 2A R significantly decreased (39±8%) NADPHdependent O 2•− production in mouse hearts compared to age (10 weeks)-matched wild-type controls. This was accompanied by a significant decrease in Nox2 (a catalytic subunit of NADPH oxidase) protein expression, and down-regulation of ERK1/2, p38MAPK, and JNK phosphorylation (all P<0.05). In wild-type mice, intraperitoneal injection of the selective A 2A R antagonist SCH58261 (3-10 mg/kg body weight for 90 min) inhibited phosphorylation of p47 phox (a regulatory subunit of Nox2), which was accompanied by a down-regulated cardiac ROS production (48±8%), and decreased JNK and ERK1/2 activation by 54±28% (all P<0.05). In conclusion, A 2A R through MAPK signaling regulates p47 phox phosphorylation and cardiac ROS production by NADPH oxidase. Modulation of A 2A R activity may have potential therapeutic applications in controlling ROS production by NADPH oxidase in the heart.

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Background & Aims: Colorectal cancer screening programmes that target detection and excision of adenomatous colonic polyps have been shown to reduce colorectal cancer related mortality. Many screening programmes include an initial faecal occult blood test (FOBt) prior to colonoscopy. To refine the selection of patients for colonoscopy other faecal-based diagnostic tools have been proposed, including tumour M2-pyruvate kinase (tM2-PK). To determine whether tM2-PK quantification may have a role in diverse settings we have assessed the assay in a cohort of patients derived from both the England bowel cancer screening programme (BCSP) and symptomatic individuals presenting to secondary care. Method. Patients undergoing colonoscopy provided faecal samples prior to bowel preparation. Faecal tM2-PK concentrations were measured by ELISA. Sensitivity, specificity, positive predictive value, negative predictive value and ROC analyses were calculated. Results. Ninety-six patients returned faecal samples: 50 of these with adenomas and 7 with cancer. Median age was 68. Median faecal tM2-PK concentration was 3.8 U/mL for individuals without neoplastic findings at colonoscopy, 7.7 U/mL in those with adenomas and 24.4 U/mL in subjects with colorectal cancer (both, p=0.01). ROC analysis demonstrated an AUROC of 0.66 (sensitivity 72.4%, specificity 48.7%, positive predictive value 67.7%, negative predictive value 36.7%). Amongst BCSP patients with a prior positive FOBt faecal tM2-PK was more abundant (median 6.4 U/mL, p=0.03) and its diagnostic accuracy was greater (AUROC 0.82). Conclusion. Our findings confirm that faecal tM2-PK ELISA may have utility as an adjunct to FOBt in a screening context, but do not support its use in symptomatic patients. Abbreviations: BCSP: Bowel cancer screening programme; EMR: Endoscopic mucosal resection; FAP: Familial adenomatous polyposis; FOBt: Faecal occult blood testing; NHS: National Health Service; tM2-PK: tumour M2-pyruvate kinase.