Effect of bilateral sympathectomy in a rat model of dilated cardiomyopathy induced by doxorubicin

The Impact of Highly Selective Thoracic Sympathectomy on the Progression of Monocrotaline-induced Pulmonary Arterial Hypertension in Rats

ABSTRACT

Pulmonary arterial hypertension (PAH) is characterized by persistently elevated pulmonary artery pressure and vascular resistance. Sympathetic overactivity in hypertension participates in pulmonary vascular remodeling and heart failure. The present study aims to explore the efficacy of highly selective thoracic sympathectomy (HSTS) on lowering pulmonary artery pressure, reversing pulmonary vascular remodeling, and improving right ventricular function in rats. A total of 24 Sprague-Dawley rats were randomly assigned into the control group (n = 8) and experimental group (n = 16). Rats in the control group were intraperitoneally injected with 0.9% normal saline, and those in the experimental group were similarly administered with received monocrotaline (MCT) injections at 60 mg/kg. Two weeks later, rats in the experimental group were further subdivided randomly into the MCT-HSTS group (n = 8) and MCT-sham group (n = 8), and they were surgically treated with HSTS and sham operation, respectively. Two weeks later, significantly lowered mean pulmonary artery pressure (mPAP), pulmonary artery systolic pressure (sPAP), and the ratio of sPAP to femoral artery systolic pressure (sFAP) were detected in the MCT-HSTS group than those of the MCT-sham group. In addition, rats in the MCT-HSTS group presented a significantly lower ratio of vascular wall area to the total vascular area (WT%), right ventricular hypertrophy index, and degrees of right ventricular fibrosis and lung fibrosis in comparison to those of the MCT-sham group. HSTS significantly downregulated protein levels of inflammasomes in pulmonary artery smooth muscle cells (PASMCs). Collectively, HSTS effectively reduces pulmonary artery pressure, pulmonary arteriolar media hypertrophy, and right ventricular hypertrophy in MCT-induced PAH rats. It also exerts an anti-inflammatory effect on PASMCs in PAH rats by suppressing inflammasomes and the subsequent release of inflammatory cytokines.

The effects of extracellular vesicles derived from Krüppel-Like Factor 2 overexpressing endothelial cells on the regulation of cardiac inflammation in the dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is one of the common causes of heart failure. Myocardial injury triggers an inflammatory response and recruits immune cells into the heart. High expression of Krüppel-like factor 2 (KLF2) in endothelial cells (ECs) potentially exerts an anti-inflammatory effect. However, the role of extracellular vesicles (EVs) from KLF2-overexpressing ECs (KLF2-EVs) in DCM remains unclear.

METHODS AND RESULTS

EVs were separated from the supernatant of KLF2-overexpressing ECs by gradient centrifugation. Mice were repeatedly administered low-dose doxorubicin (DOX) and then received KLF2-EVs through an intravenous injection. Treatment with KLF2-EVs prevented doxorubicin-induced left ventricular dysfunction and reduced the recruitment of Ly6^high Mo/Mø in the myocardium. We used flow cytometry to detect Ly6^high monocytes in bone marrow and spleen tissues and to elucidate the mechanisms underlying this beneficial effect. KLF2-EVs increased the retention of Ly6C^high monocytes in the bone marrow but not in the spleen tissue. KLF2-EVs also significantly downregulated C-C chemokine receptor 2 (CCR2) protein expression in cells from the bone marrow.

CONCLUSIONS

EVs derived from KLF2-overexpressing ECs reduced cardiac inflammation and ameliorated left ventricular dysfunction in DCM mice by targeting the CCR2 protein to inhibit Ly6C^high monocyte mobilization from the bone marrow.

Perspectives of bilateral thoracic sympathectomy for treatment of heart failure

Surgical neuromodulation therapies are still considered a last resort when standard therapies have failed for patients with progressive heart failure (HF). Although a number of experimental studies have provided robust evidence of its effectiveness, the lack of strong clinical evidence discourages practitioners. Thoracic unilateral sympathectomy has been extensively studied and has failed to show significant clinical improvement in HF patients. Most recently, bilateral sympathectomy effect was associated with a high degree of success in HF models, opening the perspective to be investigated in randomized controlled clinical trials. In addition, a series of clinical trials showed that bilateral sympathectomy was associated with a decreased risk of sudden death, which is an important outcome in patients with HF. These aspects indicates that bilateral sympathectomy could be an important alternative in the treatment of HF wherein pharmacological treatment barely reaches the target dose.