Klotho protein alleviates heart ischemia/reperfusion injury and oxidative stress through regulation of the NOS/MMP pathway.

Heart ischemia/reperfusion injury (IRI) significantly contributes to cardiac damage through oxidative and nitrosative stress, where the dysregulation of nitric oxide synthases (NOS) and the subsequent activation of matrix metalloproteinases (MMPs) are observed. Klotho is a multifunctional protein crucial in ageing, metabolism, and ion homeostasis. It has been confirmed that Klotho serves as a critical protective factor across multiple biological systems, with its roles in neuroprotection, cardiovascular health, and renal function being particularly noteworthy. This study aimed to investigate the protective role of Klotho protein against oxidative and nitrosative stress in heart IRI through regulation of the NOS/MMP pathway. The study utilised in vitro human cardiomyocyte culture and ex vivo isolated rat hearts subjected to IRI. Recombinant Klotho protein was administered to evaluate its effects on heart mechanical function, gene and protein expression of NOS isoforms, oxidative and nitrosative stress markers, MMP activity, and lipid metabolism. Administration of Klotho significantly improved heart mechanical and contractile function following ischemia/reperfusion. Klotho normalised the expression and synthesis of endothelial NOS and inducible NOS, resulting in reduced production of reactive nitrogen species and attenuated nitrosative stress. It also limited oxidative damage, reflected by decreased protein oxidation, and restored fatty acid metabolism. Additionally, Klotho regulated MMP-2 and MMP-9 synthesis and activity, thereby protecting heart contractile proteins from degradation. The Klotho protein exhibits significant cardioprotection in IRI by mitigating oxidative and nitrosative stress through the modulation of the NOS/MMP signalling pathway. These findings highlight the therapeutic potential of Klotho in managing ischemic heart conditions and myocardial injury.