Although right ventricular failure (RVF) is the hallmark of pulmonary arterial hypertension (PAH) the mechanism of RVF is unclear. with folic acid (FA) alleviates ROS generation maintains MMP/TIMP balance and regresses interstitial fibrosis we used a mouse model of pulmonary artery constriction (PAC). After surgery mice were given FA in their drinking water (0.03 g/l) LGD1069 for 4 wk. Production of ROS in the right ventricle (RV) was measured using oxidative fluorescent dye. The level of MMP-2 -9 and -13 and TIMP-4 autophagy marker (p62) mitophagy marker (LC3A/B) collagen interstitial fibrosis and ROS in the RV wall was measured. RV function was measured by Millar catheter. Treatment LGD1069 with FA decreased the pressure to 35 mmHg from 50 mmHg in PAC mice. Similarly RV volume in PAC LGD1069 mice was increased compared with the Sham group. A robust increase of ROS was observed in RV of PAC mice which was decreased by treatment with FA. The protein level of MMP-2 -9 and -13 was increased in RV of PAC mice in comparison with that in the sham-operated mice whereas supplementation with FA abolished this effect and mitigated MMPs levels. The protein level of TIMP-4 was decreased in RV of PAC mice compared with the Sham group. Treatment with FA helped PAC mice to improve the level of TIMP-4. To further support the claim of mitophagy occurrence during RVF the levels of LC3A/B and p62 were measured by Western blot and immunohistochemistry. LC3A/B was increased in RV of PAC mice. Similarly increased p62 protein level was observed in RV of PAC mice. Treatment with FA abolished this effect in PAC mice. These results suggest that FA treatment improves MMP/TIMP balance and ameliorates mitochondrial dysfunction that results in protection of RV failure during pulmonary hypertension. < 0.05) Tukey's multiple comparison test was used to compare CCR5 group means and were considered significant if < 0.05. RESULTS Level of fibrosis. Histological analysis of collagen was performed in the slices of RV. The intensity of trichrome blue stain demonstrated development of significant collagen accumulation in the RV samples from PAC mice hearts compared with those from the Sham-operated mice (Fig. 1). Treatment with folic acid mitigated the formation of fibrosis in the LGD1069 RVs from PAC + folic acid group (Fig. 1). RV wall thickness in PAC mice was thinner compared with that in PAC mice treated with folic acid (Fig. 1). RV was dilated in PAC mice compared with that in sham-operated mice (Fig. 1). Treatment with folic acid decreased RV dilatation in PAC mice (Fig. 1). Fig. 1. Pulmonary artery constriction (PAC)-induced collagen deposition in the right ventricle (RV). and Table 1). Treatment with folic acid improved myocyte properties in PAC mice (Fig. 2and Table 1). PAC significantly impaired contractility of isolated cardiomyocytes (Fig. 2 and and C). Fig. 2. PAC-induced myocyte contractility changes. A: examples of myocytes isolated from Sham Sham + FA PAC and PAC + FA mice. B: examples of cell shortening traces in myocytes from the above mentioned groups. C: changes in percent peak shortening presented … RVF-induced LGD1069 increased ROS production. Production of ROS in the RV was measured using oxidative fluorescent dye DHE. The extent of DHE fluorescence indicated ROS production (Fig. 3). A robust increase of DHE fluorescence was observed in PAC mice (Fig. 3). Treatment with folic acid ameliorated DHE fluorescence intensity in PAC + folic acid mice it was lower compared with that in PAC mice but it was still higher than in age-matched sham-operated mice (Fig. 3). Fig. 3. PAC-induced superoxide production in mice RV. Superoxide production was detected in situ by staining heart tissue with the superoxide sensitive dye DHE (red fluorescence). A: examples of RV images in samples from wild-type (WT) WT + FA PAC and PAC … Role of MMPs during RVF. Representative Immunoblots for MMPs are shown in Fig. 4A. The protein levels of MMP-2 -9 and -13 were robustly increased in RVs of PAC mice compared with those in RV of the sham-operated mice (Fig. 4A). Supplementation with folic acid reversed this effect in RVs of PAC mice (Fig. 4A). Fig. 4. Effect of FA on matrix metalloproteinase (MMP)/tissue inhibitor of metalloproteinases (TIMP) ration mice. A: examples of.