Rationale: Remote ischemic preconditioning (rIPC) with short episodes of ischemia/reperfusion (I/R) of an organ remote from the heart is a powerful approach to protect against myocardial I/R injury. The signal transduction pathways for the cross talk between the remote site and the heart remain unclear in detail.Objective: To elucidate the role of circulating nitrite in cardioprotection by rIPC. Methods and Results: Mice were subjected to 4 cycles of no-flow ischemia with subsequent reactive hyperemia within the femoral region and underwent in vivo myocardial I/R (30 minutes/5 minutes or 24 hours). The mouse experiments were conducted using genetic and pharmacological approaches. Shear stress-dependent stimulation of endothelial nitric oxide synthase within the femoral artery during reactive hyperemia yielded substantial release of nitric oxide, subsequently oxidized to nitrite and transferred humorally to the myocardium. Within the heart, reduction of nitrite to nitric oxide by cardiac myoglobin and subsequent S-nitrosation of mitochondrial membrane proteins reduced mitochondrial respiration, reactive oxygen species formation, and myocardial infarct size. Pharmacological and genetic inhibition of nitric oxide/nitrite generation by endothelial nitric oxide synthase at the remote site or nitrite bioactivation by myoglobin within the target organ abrogated the cardioprotection by rIPC. Transfer experiments of plasma from healthy volunteers subjected to rIPC of the arm identified plasma nitrite as a cardioprotective agent in isolated Langendorff mouse heart preparations exposed to I/R. Conclusions:

Aims Cardiac biomarkers are a mainstay in diagnosis of cardiovascular disease but their role in cardio‐oncology has not yet been systematically evaluated. This meta‐analysis aims to determine whether cardiac troponins and (N‐terminal pro) brain natriuretic peptide (BNP/NT‐proBNP) predict cancer therapy‐related left ventricular (LV) dysfunction. Methods and results Scientific databases were searched for studies that assessed troponins or BNP/NT‐proBNP in adult patients undergoing cancer therapy. Data from 61 trials with 5691 patients were included. Cancer therapy was associated with an increase in troponin levels [odds ratio (OR) 14.3, 95% confidence interval (CI) 6.0–34.1; n = 3049]. Patients with elevated troponins receiving chemotherapy or human epidermal growth factor receptor 2 inhibitor therapy were at higher risk for LV dysfunction (OR 11.9, 95% CI 4.4–32.1; n = 2163). Troponin had a negative predictive value of 93%. Mean BNP/NT‐proBNP levels were increased in patients post‐treatment (standardized mean difference 0.6, 95% CI 0.3–0.9; n = 912), but the available evidence did not consistently indicate prediction of LV dysfunction (OR 1.7, 95% CI 0.7–4.2; n = 197). β‐blocker and angiotensin‐converting enzyme inhibitor therapy to mitigate cardiotoxicity during cancer therapy was associated with a decline in serum troponins (OR 4.1, 95% CI 1.7–9.8; n = 466). Conclusion Elevated troponin levels predict LV dysfunction in patients receiving cancer therapy. Assessment of troponin levels may qualify as a screening test to identify patients who require referral to cardio‐oncology units and benefit from preventive strategies. Further evidence is required for both biomarkers.

Background Hypoxic vasodilation is a physiological response to low oxygen (O2) tension that increases blood supply to match metabolic demands. While this response has been characterized for more than 100 years, the underlying hypoxic sensing and effector signaling mechanisms remain uncertain. We have shown that deoxygenated myoglobin (deoxyMb) in the heart can reduce nitrite to nitric oxide (NO˙) and thereby contribute to cardiomyocyte NO˙ signaling during ischemia. Based on recent observations that Mb is expressed in the vasculature of hypoxia-tolerant fish, we hypothesized that endogenous nitrite may contribute to physiological hypoxic vasodilation via reactions with vascular Mb to form NO˙. Methods and Results We here show that Mb is expressed in vascular smooth muscle and contributes significantly to nitrite-dependent hypoxic vasodilation in vivo and ex vivo. The generation of NO˙ from nitrite reduction by deoxyMb activates canonical soluble guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP) signaling pathways. In vivo and ex vivo vasodilation responses, the reduction of nitrite to NO˙ and the subsequent signal transduction mechanisms were all significantly impaired in mice without myoglobin (Mb−/−). Hypoxic vasodilation studies in Mb, endothelial and inducible NO synthase knockout models (eNOS−/−, iNOS−/−) suggest that only Mb contributes to systemic hypoxic vasodilatory responses in mice. Conclusions Endogenous nitrite is a physiological effector of hypoxic vasodilation. Its reduction to NO˙ via the heme globin Mb enhances blood flow and matches O2 supply to increased metabolic demands under hypoxic conditions.