Intercellular cross-talk induced by dietary nitrate enhances contractile performance in cardiomyocytes after ischemic injury independently of Ca2+ homeostasis alterations
G Pironti, M S Shimari, M C Carlstrom, D C A Andersson, L H L LundAbstract
Background
Reduced nitric oxide (NO) bioavailability is a hallmark of impaired cardiovascular function after ischemic injury and in heart failure. Preeclampsia is associated with a markedly increased long-term risk of cardiovascular disease, with approximately a twofold higher incidence of ischemic heart disease compared to normotensive pregnancies. Strategies restoring NO signaling may therefore be particularly relevant in this high-risk population. Dietary inorganic nitrate is a promising approach to enhance systemic NO availability and improve cardiac performance. Although nitrate supplementation confers cardioprotection, the mechanisms underlying its direct effects on cardiomyocytes and the potential role of circulating cardioprotective factors remain incompletely understood.
Purpose
We investigated whether dietary nitrate induces intercellular cross-talk capable of modulating cardiomyocyte contractility and Ca²⁺ homeostasis after ischemic injury. We hypothesized that inorganic nitrate enhances contractile performance through NO-mediated mechanisms and circulating protective factors.
Methods
Myocardial infarction (MI) was induced in mice to generate HFrEF. Animals received dietary nitrate or control diet for 4–6 weeks. Cardiomyocytes were isolated from post-MI hearts to assess fractional shortening and Ca²⁺ transients. To evaluate circulating mediators, an ex vivo ischemia/reperfusion (I/R) model was used. Cardiomyocytes from naïve mice were subjected to I/R and incubated with plasma from patients randomized to high-nitrate beetroot juice intake or placebo, including women with preeclampsia. Contractility and Ca²⁺ signaling were analyzed. Inflammatory, oxidative stress, and contractile markers were assessed by qPCR and Western blot.
Results
Cardiomyocytes from nitrate-treated HFrEF mice showed significantly enhanced contractility versus controls without changes in Ca²⁺ transient amplitude, while sarcoplasmic reticulum Ca²⁺ reuptake was accelerated. In the ex vivo I/R model, plasma from high-nitrate intake patients improved contractility of injured cardiomyocytes compared with placebo plasma, again without affecting Ca²⁺ transient amplitude. Nitrate induced post-translational modifications of myofilament and Ca²⁺-handling proteins, enhancing cross-bridge efficiency and intracellular Ca²⁺ utilization. Inflammatory and oxidative stress markers were reduced in cardiomyocytes exposed to nitrate-derived plasma.
Conclusions
Dietary nitrate promotes cardioprotection through intercellular cross-talk mechanisms that enhance contractile performance independently of major changes in Ca²⁺ transient amplitude. Improved Ca²⁺ handling kinetics and myofilament efficiency, together with circulating protective factors, contribute to functional recovery after ischemic injury. Targeting NO-mediated communication may represent a therapeutic strategy, particularly in high-risk populations such as women with preeclampsia.