Dysregulation of cardiac CaMKII pathway is increased in aging and chronic inflammation

Abstract

Chronic elevation of inflammatory mediators is common in frail older adults and predicts a host of adverse cardiovascular outcomes, including heart failure and sudden death. To date, few specific molecular mechanisms have been identified that connect chronic inflammation to age-related cardiomyopathies. Dysregulation in Ca2+and calmodulin-dependent protein kinase II (CaMKII) signaling has been implicated in promoting inflammatory responses in cardiomyopathies but is understudied in the context of aging. We compared myocardial CaMKII signaling in young (32 weeks) and old (104 weeks) wild type (WT) and interleukin 10 null mice (IL-10tm/tm), a model of chronic inflammation and frailty. Aged cohorts were treated with 0.6 mg of losartan. Hearts from mouse cohorts were assayed for total and autophosphorylated CaMKII (P-CaMKII) and the phosphorylation status of phospholamban (PLN) (downstream signaling pathway) using western blot techniques. We observed significant increases in total and activated, autophosphorylated, CaMKII (P-CaMKII) (2.4 ± 0.38 vs 1.2 ± 0.12 p< 0.02; 9.0 ± 1.9 vs 0.03 ± 0.01 p< 0.002), but decreases in the phosphorylation of PLN (0.6 ±0.3 vs 1.7 ± 0.3 p<0.03) at a validated CaMKII target site (T17) in old compared to young WT hearts. Similarly, we found increased P-CaMKII (6.9 ± 1.5 vs 0.7 ± 0.4 p< 0.004) and diminished PLN T17 phosphorylation (0.8 ± 0.2 vs 1.5 ± 0.2 p<0.02) in old compared to young IL-10tm/tm mice. Old IL-10tm/tm mouse hearts had less total CaMKII compared to old WT mouse hearts (1.1 ± 0.3 vs 2.9 ±0.2 p< 0.002). Four weeks treatment of old WT mice with Losartan was associated with reversal of observed age-related changes in the CaMKII signaling pathway. We observed decreases in total CaMKII, P-CaMKII (2.9 ± 0.2 vs.1.5 ± 0.2 p<0.001; 2.2 ± 0.9 vs 0.47 ± 0.1 p <0.03), and an increase in PLN T17 phosphorylation (0.55±0.3 vs 2.23 ± 0.4 p< 0.007). The effects of Losartan on the animals aging with chronic inflammation (old IL-10tm/tm) was less clear. We observed a losartan associated increase in total CaMKII (1.41 ± 0.02 vs 1.3 ± 0.02 p<0.02) but no impact on P-CaMKII or PLN T17 phosphorylation. We interpret our findings to suggest that changes in myocardial CaMKII signaling are a feature of aging that is affected by chronic inflammation.