A potential role of caspase recruitment domain family member 9 (Card9) in transverse aortic constriction-induced cardiac dysfunction, fibrosis, and hypertrophy.

Macrophage- and monocyte-derived cytokines are elevated in the myocardium of pressure-overloaded hearts, where they play critical roles in pathological remodeling. Caspase recruitment domain family member 9 (CARD9) regulates macrophage cytokine secretion, but its role in a transverse aortic constriction (TAC) model of pressure overload has not been evaluated. To investigate whether CARD9 may serve as a valuable therapeutic target, wild-type (WT) and CARD9-knockout mice were subjected to 3 months of TAC, and then cardiac function, hypertrophy, and fibrosis were analyzed. The expression of protein markers of myocardial autophagy and nuclear factor kappa B signaling was also investigated. At 1 month after TAC, cardiomyocyte contractile dynamics were measured in a separate cohort to further assess contractility and diastolic function. In WT but not CARD9 ^-/- mice, TAC resulted in severe cardiomyocyte contractile dysfunction at 1 month and functional decrements in fractional shortening at 3 months in vivo. Furthermore, CARD9 ^-/- mice did not develop cardiac fibrosis or hypertrophy. CARD9 ^-/- mice also had decreased protein expression of inhibitor of κB kinase-α/β, decreased phosphorylation of p65, and increased expression of protein markers of autophagy. These findings suggest that CARD9 plays a role in pathological remodeling and cardiac dysfunction in mouse hearts subjected to TAC and should be investigated further.