Metallothionein Prevents Age-Associated Cardiomyopathy via Inhibiting NF-κB Pathway Activation and Associated Nitrative Damage to 2-OGD

Aims: Cardiac-specific metallothionein (MT) overexpression extends lifespan, but the mechanism underlying the effect of MT protection against age-associated cardiovascular diseases (CVD) remains elusive. To elucidate this, male wild-type and two lines of MT-transgenic (MT-TG) mice, MM and MT-1 (cardiac-specific overexpressing MT about 10- and 80-fold, respectively) at three representative ages (2-3, 9-10, and 18-20 months), were utilized. A stable human MT2A overexpressing cardiomyocytes (H9c2MT7) was also introduced. Results: Histomorphology and echocardiographic analysis revealed that age-associated cardiac hypertrophy, remodeling, and dysfunction were ameliorated in MT-TG mice. Also, aging-accompanied NF-kappa B activation, characterized by increased nuclear p65 translocation, elevated DNA-binding activity, and upregulation of inflammatory cytokines, was largely attenuated by MT overexpression. Treatment of H9c2 cardiomyocytes with tumor necrosis factor-alpha (TNF-alpha), which mimicked an inflammatory environment, significantly increased NF-kappa B activity, and some age-related phenotypes appeared. The NF-kappa B activation was further proved to be pivotal for both age-associated and TNF-alpha-induced nitrative damage to cardiac 2-oxoglutarate dehydrogenase (2-OGD) by virtue of NF-kappa B p65 gene silencing. MT inhibited NF-kappa B activation and associated nitrative damage to cardiac 2-OGD in both old MT-TG hearts and TNF-alpha-treated H9c2MT7 cardiomyocytes; these protective effects were abolished in H9c2MT7 cardiomyocytes by MT-specific gene silencing. Innovation and Conclusion: Together, these findings indicate that the protective effects of MT against age-associated CVD can be attributed mainly to its role in NF-kappa B inhibition and resultant alleviation of nitrative damage to 2-OGD.