Ulcerative colitis and
Crohn's disease are classified as chronic
inflammatory bowel diseases (IBD) with known extraintestinal manifestations. The interplay between heart and gut in IBD has previously been noted, but the mechanisms remain elusive. Our objective was to identify
microRNAs mediating molecular remodeling and resulting cardiac impairment in a rat model of
colitis. To induce chronic
colitis,
dextran sodium sulfate (DSS) was given to adult rats for 5 days followed by 9 days with normal
drinking water for 4 cycles over 8 weeks. Echocardiography was performed to evaluate heart function. DSS-induced
colitis led to a significant decrease in ejection fraction, increased left ventricular mass and size, and elevated B-type natriuretic
protein.
MicroRNA profiling showed a total of 56
miRNAs significantly increased in the heart by
colitis, 8 of which are predicted to target
brain-derived neurotrophic factor (
BDNF). RT-qPCR validated the increases of miR-1b, Let-7d, and miR-155. Transient transfection revealed that miR-155 significantly suppresses
BDNF in H9c2 cells. Importantly, DSS
colitis markedly decreased
BDNF in both myocardium and serum. Levels of various
proteins critical to cardiac homeostasis were also altered. Functional studies showed that
BDNF increases cell viability and mitigates H2O2-induced oxidative damage in H9c2 cells, demonstrating its protective role in the adult heart. Mechanistically, cellular experiments identified IL-1β as the inflammatory mediator upregulating cardiac miR-155; this effect was confirmed in adult rats. Furthermore, IL-1β
neutralizing antibody ameliorated the DSS-induced increase in miR-155 and concurrent decrease in
BDNF in the adult heart, showing therapeutic potential. Our findings indicate that chronic
colitis impairs heart function through an IL-1β→miR-155→BDNF signaling axis.