ALDOSTERONE RECEPTOR ANTAGONIST MITIGATES DIASTOLIC HEART FAILURE THROUGH INHIBITION OF INTERLEUKIN-33/ST2 SIGNALING PATHWAY

Ning Ren^{1, #}, Hua Jiang^{1, #}, Shutao Chen^{1, *}, Jibing Du1, Wenyu Li¹, Xingyu Huo¹, Kui Huang¹, Minli Chen¹, Yunjia Lin^{1, 2} 

¹Department of Cardiology, Tianjin Cardiovascular Diseases Institute, Tianjin Chest Hospital, Tianjin 300222, PR. China - ²Department of Ultrasonography, Tianjin Cardiovascular Diseases Institute, Tianjin Chest Hospital, Tianjin 300222, PR. China 

Objective: The study aim to investigate the effects and possible mechanisms of aldosterone receptor antagonist spironolactone in the rat model of diastolic heart failure (DHF). 

Methods: Diastolic heart failure was induced by abdominal aorta coarctation. in rats. A total of 45 male Wistar rats were randomly divided to three groups: sham group (n=15), DHF group (n=15), or spironolactone group (n=15). Spironolactone was intragastrically administrated to the rat at 40 mg/kg/d each day for 8 weeks. Rats in DHF group and sham group were intragastrically administrated the same amount of saline. Hematoxylin-eosin(HE) staining was used to detect the changes of myocardial morphology in different groups. Effects of spironolactone on myocardial fibrosis in DHF rats were described by Sirius red staining. Heart rate (HR), Left ventricular systolic pressure (LVSP), ±dp/dtmax, systolic blood pressure (SBP), diastolic blood pressure (DBP), and left ventricular end-diastolic pressure (LVEDP) were recorded by multi-channel physiological recorder. Ultrasonic diagnostic equipment was used to detect the left ventricular posterior wall thickness in systole (LVPWs), left ventricular posterior wall in diastole (LVPWd), intraventricular septal end systole (IVSs), intraventricular septal end diastole (IVSd), left ventricular ejection fraction (LVEF) at the long axis of the left ventricle (LV), Left ventricular mass (LVM) and Left ventricular mass index (LVMI). Expression levels of il-33 /ST2 protein and mRNA in myocardial tissue were detected by Western blotting and RT-qPCR. In addition, immunohistochemical staining was performed to evaluate the ST2 protein expressions in myocardial tissue. 

Results: H&E staining results showed that spironolactone improved myocardial morphology in DHF rats. Sirius red staining results indicated that spironolactone could significantly suppress cardiac fibrosis. Western blotting results showed that compared with the sham group, the concentrations of IL-33, and sST2 in DHF group were increased significantly. Treatment with spironolactone, inhibited IL-33/ST2 signaling with lower mRNA and protein expression of ST2 and IL-33 in the spironolactone group. Immunohistochemical staining results showed that the protein expression of ST2 in myocardial tissues was down-regulated after spironolactone treatment. HR, LVSP, SBP, DBP and ± dp/dtmax were higher while LVEDP recorded were lower during spironolactone treatment. Compared with the sham group, the LVPWT and IVS in the spironolactone group were significantly thinner, and the LVMI was decreased significantly lower (P<0.05), there was no significant change in LVEF (P>0.05). In conclusion, the results indicated that spironolactone effectively inhibited cardiac fibrosis, improved left ventricular remodeling and diastolic function to mitigate diastolic heart failure through inhibition of the IL-33/ST2 signal pathway. 

Conclusions: Spironolactone indirectly regulates the regulation of myocardial fibrosis and inflammatory response in diastolic heart failure by inhibiting the protein and mRNA expression levels of IL-33 and ST2 to slow down heart failure.