Active Colitis Attenuates Ventricular Excitation-Contraction Coupling by T-Tubular Remodeling

In patients, extraintestinal manifestations of inflammatory bowel disease (IBD) are attenuated ventricular contractile function and arrhythmia. To determine the mechanism of IBD-induced changes in ventricular function, we used a mouse model of dextran sodium sulfate (3.5% weight/volume; 7 days)-induced colitis. Changes in cardiac function were quantified in isolated ventricular myocytes (VM) by cell shortening, imaging of [Ca²⁺]_i, reactive oxygen species (ROS), and t-tubular density. During colitis, VMs exhibited attenuated cell-shortening and altered Ca²⁺-handling properties. A prolonged Ca²⁺ transient (CaT) rise time correlated with an increased coefficient of variation in the subcellular Ca²⁺ release and an attenuated t-tubular density. T-tubular loss was accompanied by increased ROS production, calpain-2 (CAPN2) expression, junctophilin-2 (JPH-2) cleavage, and autophagy. Inhibition of Angiotensin-converting enzyme during colitis (Perindopril: 3 mg/kg/day) prevented the increase in CAPN2, ROS production, autophagy, and t-tubular remodeling. It failed, however, to restore full length JPH-2. We conclude that, during IBD, the angiotensin II (AngII)-induced loss of t-tubular integrity and altered cellular Ca²⁺ handling can be prevented by suppression of the AngII-dependent increase in CAPN2 and autophagy and thus suppression of AngII signaling might benefit IBD patients with cardiac manifestations of the disease.