Protein S-Nitrosylation in Heart Failure: A Compartment-Resolved Review of Mechanisms, Evidence Boundaries, and...

Heart failure (HF) remains a major cause of morbidity and mortality despite substantial therapeutic progress, and important phenotype-specific treatment gaps persist. Protein S-nitrosylation (SNO) is a reversible cysteine-centered post-translational modification (PTM) whose reported associations with selected HF-relevant contexts, including vascular-endothelial dysfunction, mitochondrial-energetic remodeling, Ca²⁺-handling abnormalities, and selected receptor- or stress-related signaling observations, are supported to varying degrees. In this review, we evaluate reported mechanisms that may regulate cardiac SNO and define the evidentiary boundaries that constrain interpretation across HF-relevant settings. Available studies suggest that altered SNO homeostasis is associated with selected HF-related processes, but the strength of support varies substantially across targets, phenotypes, and disease contexts. Many mechanistic observations derive from animal models, cultured systems, donor-based perturbations, or non-HF settings. These should, therefore, be interpreted as hypothesis-generating rather than as established mechanisms in human HF. We accordingly distinguish findings supported by human HF tissue or HF-relevant in vivo evidence from more preliminary observations and highlight the need for human, site-resolved, and, where feasible, quantitatively grounded datasets. Future studies should prioritize stronger tissue anchoring, better integration of circulating and myocardial readouts, and closer alignment between mechanistic claims and the strength of the supporting evidence.