Up-regulation of hexokinase1 in the right ventricle of monocrotaline induced pulmonary hypertension

Abstract

Background: Pulmonary arterial hypertension (PAH) is a proliferative arteriopathy associated with a glycolytic shift during heart metabolism. An increase in glycolytic metabolism can be detected in the right ventricle during PAH. Expression levels of glycolysis genes in the right ventricle during glycolysis that occur in monocrotaline (MCT)-induced pulmonary hypertension (PH) remain unknown.

Methods: PH was induced by a single subcutaneous injection of MCT (50 mg/kg) into rats, eventually causing right heart failure. Concurrently, a control group was injected with normal saline. The MCT-PH rats were randomly divided into three groups according to MCT treatment: MCT-2 week, 3 week, and 4 week groups (MCT-2w, 3w, 4w). At the end of the study, hemodynamics and right ventricular hypertrophy were compared among experimental groups. Expression of key glycolytic candidate genes was screened in the right ventricle.

Results: We observed an increase in mean pulmonary arterial pressure, right ventricular systolic pressure and right ventricular hypertrophy index three weeks following MCT injection. Alterations in the morphology and structure of right ventricular myocardial cells, as well as the pulmonary vasculature were observed. Expression of hexokinase 1 (HK1) mRNA began to increase in the right ventricle of the MCT-3w group and MCT-4w group, while the expression of lactate dehydrogenase A (LDHA) was elevated in the right ventricle of the MCT-4w group. Hexokinase 2(HK2), pyruvate dehydrogenase complex α1 (PDHα1), and LDHA mRNA expression showed no changes in the right ventricle. HK1 mRNA expression was further confirmed by HK1 protein expression and immunohistochemical analyses. All findings underlie the glycolytic phenotype in the right ventricle.

Conclusions: There was an increase in the protein and mRNA expression of hexokinase-1 (HK1) three and four weeks after the injection of monocrotaline in the right ventricle, intervention of HK1 may be amenable to therapeutic intervention.

Figure 1

Monocrotaline (MCT) deteriorateshaemodynamics in rats. A: Mean pulmonary artery pressure (mPAP); B: right ventricular systolic pressure (RVSP); MCT-2w : MCT-2 week group; MCT-3w : MCT-3 week group; MCT-4w : MCT-4 week group; Data shown are means ± SD of 8 –10 rats per group. **P < 0.01 vs. control.

Figure 2

The change of morphology of lung tissue and right ventricle in rats with MCT treatment time. A: lung tissue; B: right ventricle.

Figure 3

The expression of the genes in the glycolytic pathway in right ventricles. HK1: hexokinase 1; HK2: hexokinase 2; LDHA: lactate dehydrogenase A; PDHα1: pyruvate dehydrogenase complex α1. *P < 0.05 vs. controls; #P < 0.05 vs. MCT-3w.

Figure 4

The expression of HK1 protein is evaluated in right ventricular tissue. A: The immunohistochemical expression of HK1 in right ventricle; B: percentage of HK1-positive myocardial cells in right ventricles; C: The expression of HK1 protein in right ventricle. HK1: hexokinase 1; *P < 0.05 vs. controls.