Fluorescent, genetically encoded sensors of hydrogen peroxide have enabled visualization of perturbations to the intracellular level of this signaling molecule with subcellular and temporal resolution. Ratiometric sensors hold the additional promise of meaningful quantification of intracellular hydrogen peroxide levels as a function of time, a longstanding goal in the field of redox signaling. To date, studies that have connected the magnitudes of observed ratios with peroxide concentrations have either examined suspensions of cells or small numbers of adherent cells (∼10). In this work, we examined the response of all cells in several microscopic fields of view to an identical perturbation and observed a striking degree of heterogeneity of fluorescence ratios from individual cells. The expression level of the probe and phase within the cell cycle were each examined as potential contributors to the observed heterogeneity. Higher ratiometric responses correlated with greater expression levels of the probe and phase in the cell cycle were also shown to influence the magnitude of response. To aid in the interpretation of experimental observations, we incorporated the reaction of the reduced probe with peroxide and the reactions of the oxidized probe with glutathione and glutaredoxin into a larger kinetic model of peroxide metabolism. The predictions of the kinetic model suggest possible explanations for the experimental observations. This work highlights the importance of a systems-level approach to understanding the output of genetically encoded sensors that function via redox reactions involving thiol and disulfide groups.

Background: There is a paucity of data on predictors of mortality in all-cause coronary artery dissection patients. The purpose was to study the baseline characteristics, associated co-morbidities, and in-hospital mortality in coronary artery dissection patients using the Healthcare Cost and Utilization Project National Inpatient Sample database. Methods: The Healthcare Cost and Utilization Project administrative longitudinal database contains encounter-level information on inpatient stays, emergency department visits, and ambulatory surgery in all U.S. hospitals. We performed a cross-sectional analysis on 25005 patients diagnosed with coronary artery dissection during hospitalization from January 2016 to December 2018. The primary outcome was in-hospital mortality. Results: Of the total patient population, 25005 patients were found to have coronary artery dissection. All patients with ages ≥ 18 were included in the study (24980). The observed overall in-hospital mortality was 6.0% (1498 patients out of 24980). The higher mortality was observed in age group >80 years when compared to the age group <40 years (adjusted odds ratio: 8.5; 95% confidence interval: 5.7 to 12.4; p-value < 0.01). Patients with peripheral vascular disease (adjusted odds ratio: 2.0; 95% confidence interval: 1.7 to 2.3; p-value < 0.01) and cardiogenic shock (adjusted odds ratio: 10.8; 95% confidence interval: 9.5 to 12.2; p-value < 0.01) showed higher mortality (Table 1,2). Conclusion: To the best of our knowledge, this is the largest population-based study investigating the predictors of in-hospital mortality in all-cause coronary artery dissection patients. Our analysis showed higher mortality with increasing age and in patients who developed cardiogenic shock and those with peripheral vascular disease.