Abstract Body (Do not enter title and authors here): Introduction: Pulmonary arterial hypertension (PAH) is a serious condition that impacts the lung vasculature and has diverse underlying factors. Previous research has shown that mitochondrial dysfunction (MD) significantly contributes to PAH; however, the mechanisms remain unclear. Our recent findings indicate that in PAH, anaplerosis enhances the TCA cycle in pulmonary vascular cells, compensating for MD.
Hypothesis: We hypothesize that inhibiting anaplerosis by targeting pyruvate carboxylase (PC) and glutaminolysis (GLUD1) in early PAH can prevent metabolic changes and pulmonary vascular remodeling.
Methods: PAH was induced in female SD rats using Sugen/Hypoxia (Su/Hx). Anaplerosis inhibitors-phenylacetic acid (PAA), a PC inhibitor, at 20 mg/kg every other day (i.p.), and R162, a GLUD1 inhibitor, at 30 mg/kg daily (i.p.) were initiated after the right ventricular systolic pressure (RVSP) reached above 70 mmHg at week-two and continued for three weeks.
Results: Hemodynamics in Su/Hx showed a PAH phenotype with increased RVSP. However, inhibiting anaplerosis reduced RVSP (111.10±3.59 mmHg to 45.87±2.202 mmHg, p<0.001), Fulton Index (0.59±0.017 to 0.45±0.024, p<0.001), and myocardial contractility (Max dP/dt 4511±196.9 mmHg/s to 2403.63±123.7 mmHg/s, p<0.001). Our PAH model showed increased glycolytic flux with the activation of HK1 (p<0.001) and PKM1 (p<0.05). Increased glycolysis was found to shift to the pentose phosphate pathway via myo-inositol oxygenase (p<0.001), generating ROS in the early PAH model. This leads to mitochondrial dysfunction with a reduction in complex-II (p<0.05) expression and activation in the glycerophosphate shuttle with increased GPD2 (p<0.001). These mitochondrial and redox imbalances trigger the endo-mesenchymal transition, leading to vascular remodeling in the late PAH model. Furthermore, the increased proliferative demand shifts the metabolism towards anabolism with NTX1 activation (p<0.05), leading to proliferative signaling such as Akt (p<0.01) and STAT3 (p<0.05). Remarkably, inhibiting anaplerotic pathways with combined PAA and R162 therapy in the Su/Hx PAH model significantly attenuated metabolic dysfunction and prevented proliferative signaling, thus averting lung vascular remodeling.
Conclusion: Our research indicates that inhibiting both pyruvate carboxylase and glutaminolysis-driven anaplerosis is a promising therapeutic approach for addressing vascular remodeling in PAH.