Natural mutations of human XDH promote the nitrite (NO2-)-reductase capacity of xanthine oxidoreductase: A novel mechanism to promote redox health?

Several rare genetic variations of human XDH have been shown to alter xanthine oxidoreductase (XOR) activity leading to impaired purine catabolism. However, XOR is a multi-functional enzyme that depending upon the environmental conditions also expresses oxidase activity leading to both O2·- and H2O2 and nitrite (NO2-) reductase activity leading to nitric oxide (·NO). Since these products express important, and often diametrically opposite, biological activity, consideration of the impact of XOR mutations in the context of each aspect of the biochemical activity of the enzyme is needed to determine the potential full impact of these variants. Herein, we show that known naturally occurring hXDH mutations do not have a uniform impact upon the biochemical activity of the enzyme in terms of uric acid (UA), reactive oxygen species (ROS) and nitric oxide ·NO formation. We show that the His1221Arg mutant, in the presence of xanthine, increases UA, O2·- and NO generation compared to the WT, whilst the Ile703Val increases UA and ·NO formation, but not O2·-. We speculate that this change in the balance of activity of the enzyme is likely to endow those carrying these mutations with a harmful or protective influence over health that may explain the current equipoise underlying the perceived importance of XDH mutations. We also show that, in presence of inorganic NO2-, XOR-driven O2·- production is substantially reduced. We suggest that targeting enzyme activity to enhance the NO2--reductase profile in those carrying such mutations may provide novel therapeutic options, particularly in cardiovascular disease.

Use of enhanced stent visualisation compared to angiography alone to guide percutaneous coronary intervention.

OBJECTIVE: We aimed to assess the use of enhanced stent visualisation (ESV) on outcomes, after PCI with overlapping stents, specifically using CLEARstent technology. BACKGROUND: Stent underexpansion and overlap are both significant risk factors for restenosis and stent thrombosis. Enhanced stent visualisation (e.g. CLEARstent) systems could provide important data to reduce under-expansion and stent overlap. METHODS: This was a cohort study based on this institution's percutaneous coronary intervention (PCI) registry. A total of 2614 patients who had PCI for stable angina or acute coronary syndromes (ACS, excluding cardiogenic shock) with overlapping 2nd generation drug eluting stents (DES) in the same vessel between May 2015 and January 2018 were included in the analysis. Patients were divided into ESV (n = 1354) and no ESV guided intervention (n = 1260). The primary end-point was major adverse cardiovascular events (MACE: target vessel revascularisation, target vessel myocardial infarction and all-cause mortality) recorded at a median follow up of 2.4 years. RESULTS: Groups were comparable for patient characteristics (age, diabetes mellitus, ACS presentation). A significant difference in MACE was observed between patients who underwent ESV-guided PCI (9.5%) compared with patients who underwent Standard PCI (14.4%, p = .018). This difference was mainly driven by reduced rates of target vessel revascularisation and recurrent myocardial infarction. Overall this difference persisted after multivariate Cox analysis (HR 0.86, 95% CI: 0.73-0.98) and propensity matching (HR = 0.88, 95% CI: 0.69-0.99). CONCLUSION: We suggest that routine clinical use of ESV technology during PCI can be useful, and is associated with better medium-term angiographic and clinical outcomes. Further study is required to build on this promising signal.

Eptifibatide is associated with significant cost savings and similar clinical outcomes to abciximab when used during primary percutaneous coronary intervention for ST-elevation myocardial infarction: An observational cohort study of 3863 patients.

INTRODUCTION: Glycoprotein IIb/IIIa inhibitors are recommended by guidelines in patients with ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention. There are few studies directly comparing these agents. The aim of this study was to assess whether eptifibatide is a safe and cost-effective alternative to abciximab in the treatment of primary percutaneous coronary intervention for ST-segment elevation myocardial infarction. METHODS: This was an observational cohort study of 3863 patients who received a GPIIb/IIIa inhibitor whilst undergoing primary percutaneous coronary intervention from 2007 to 2014. Patients who did not receive a GPIIb/IIIa inhibitor were excluded. Time to first major adverse cardiac event defined as death, non-fatal myocardial infarction, stroke or target vessel revascularization, and total hospital costs were compared between the groups. RESULTS: In all, 1741 patients received abciximab with 2122 receiving eptifibatide. Patients who received eptifibatide had higher rates of previous MI/percutaneous coronary intervention and were more likely to undergo a procedure from the radial route. Unadjusted Kaplan-Meier analysis revealed no significant difference in the 1-year event rates between patients given eptifibatide versus abciximab (p = 0.201). Age-adjusted Cox analysis demonstrated no difference in 1-year outcome between abciximab and eptifibatide (hazard ratio: 0.83; 95% confidence interval: 0.73-1.39), which persisted after multivariate adjustment (hazard ratio: 0.92; 95% confidence interval: 0.79-1.56) including the incorporation of a propensity score (hazard ratio: 0.88; 95% confidence interval: 0.71-1.44). Eptifbatide was associated with significant cost savings being 87% cheaper overall compared to abciximab (on average £650 cheaper per patient and saving approximately £950,000). CONCLUSION: This observational data suggest that eptifibatide is associated with similar outcomes and significant cost savings compared to abciximab when used in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention.

Case fatality rates for South Asian and Caucasian patients show no difference 2.5 years after percutaneous coronary intervention.

OBJECTIVE: To compare short and medium-term prognosis in South Asian and Caucasian patients undergoing percutaneous coronary intervention (PCI) to determine if there are ethnic differences in case death rates. DESIGN: Retrospective cohort study. SETTING: A cardiology referral centre in east London. PATIENTS: 9771 patients who underwent PCI from October 2003 to December 2007 of whom 7966 (81.5%) were Caucasian and 1805 (18.5%) were South Asian. MAIN OUTCOME MEASURES: In-hospital major adverse cardiac events (MACE; death, myocardial infarction, stroke and target vessel revascularisation), subsequent revascularisation rates (PCI and coronary artery bypass grafting; CABG) and all-cause mortality during a median follow-up of 2.5 years (range 1.5-3.6 years). RESULTS: South Asian patients were younger than Caucasian patients (59.69±0.27 vs 64.69±0.13 years, p<0.0001), and more burdened by cardiovascular risk factors, particularly type II diabetes mellitus (45.9%±1.2% vs 15.7%±0.4%, p<0.0001). The in-hospital rates of MACE were similar for South Asians and Caucasians (3.5% vs 2.8%, p=0.40). South Asians had higher rates of clinically driven PCI for restenosis and subsequent CABG, although Kaplan-Meier estimates of all-cause mortality showed no significant differences; this was regardless of whether PCI was performed post-acute coronary syndrome or as an elective procedure. The adjusted hazard of death for South Asians compared with Caucasians was 1.00 (95% CI 0.81 to 1.23). CONCLUSION: In this large PCI cohort, the in-hospital and longer-term mortality of South Asians appeared no worse than that of Caucasians. South Asians had higher rates of restenosis and CABG during follow-up. Data suggest that the excess coronary mortality for South Asians compared with Caucasians is not explained by differences in case-fatality rates.