The Effects Of Phosphodiesterase 5 Inhibitor On Pulmonary Artery Endothelium Function And Pulmonary Vascular Remodeling In Pulmonary Hypertension Rats

Objective: To investigate the different expression of preproET-1 mRNA and eNOSmRNA in increased pulmonary blood flow in rat; By studying two processes of pulmonary hypertension, observed the effects of Phosphodiesterase 5 inhibitor sildenafil on pulmonary hypertension animal models and searched the probable mechanism. Methods: 1) Established the pulmonary hypertension animal model of increased pulmonary blood flow and pulmonary artery pressure in rats by left-to-right shunt operation which were obtained by carotid artery and jugular vein anastomosis and then lived for 6 weeks. Established pulmonary hypertension animal model of induced by monocrotaline in rats. 2) Twenty-four SD rats were randomly divided into 3 groups with 8 in each. Control group (Group C): with sham operation; rats in O₆ group were performed left-to-right shunt operation (interpreted as early) and then lived for 6 weeks; rats in O₁₀ group were performed same operation but after that they were raised for 10 weeks. Then, under general anesthesia the mean systemic blood pressure (mSAP), mean pulmonary arterial pressure(mPAP), blood gas of right atrium blood and index of right ventricle hypertrophy(RVH) were measured. After that the tissue of pulmonary were obtained to measure preproET-1 mRNA and eNOSmRNA by RT-PCR. 3) 40 SD rats were randomly divided into two groups. Rats in group C(acted as control group) were performed sham operation. Rats in group O were performed left-to-right shunt operation. After 10 weeks, group C and group O were divided into 4 subsections(group CP,CS,OP and OS). Group CP was acted as blank group. Rats in group CS and OS were given sildenafil iv; Rats in group CP and OP were given placebo. The mean systemic blood pressure(mSAP), mean pulmonary arterial pressure(mPAP), blood gas of right atrium and index of right ventricle hypertrophy(RVH) were measured all groups before and after iv sildenafil or placebo. After the rats were killed, pulmonary artery(PA) rings were isolated. Responses to acetyleholine(Ach) and nitroglycerin were compared among those subsections with or without sildenafil. 4) 40 Sprague-Dawley rats were administered with abdominal cavity injection or equivalent volume of normal saline (NS)(which were treated as Cgroup) to induce pulmonary hypertension model. 14 days later, rats were randomly treated with abdominal cavity injection sildenafil 25mg/kg/d, sildenafil 25mg/kg/d or placebo to group as S₁, S₁ and P group. After they were raised for 6 weeks, mPAP, RV/LV+S of all animals were measured under general anesthesia. The tissues of pulmonary were obtained to observe pathology of Pulmonary artery; the immunofluorescence staining of α-actin in pulmonary artery were performed. Furthermore, the VEGF mRNA by RT-PCR, protein expression of ERK1/ERK2 as well as MKP1 were measured. Results: 1) the pulmonary hypertension animal model of increased pulmonary blood flow was confirmed by increased mPAP and index of RVH. The monocrotaline induced pulmonary hypertension animal model was confirmed by increased mPAP and index of RVH. There also had pathological changes in pulmonary hypertension artery. 2) In increased pulmonary blood flow animal model study, when compared with group C, the expression of preproET-1 mRNA in group O₆ and group O₁₀ were significantly increased(P<0.05 and P<0.01). The expressions of eNOSmRNA were not significant difference among three groups. 3) iv sildenafil had effects on increased mPAP but not normal mPAP and mSAP. Nitroglycerin and Ach induced relaxation in PA rings was impaired in groups OS and OP. But PA rings in OS group (with sildenafil) had greater relaxed responses than PA rings in OP group (without sildenafil). 4) After 6 weeks administered with abdominal cavity injection of monocrotaline, there were significant elevated mPAP and RV/LV+S in P, S₁ and S₂ groups (which were higher in S₁ and S₂ groups then in P group). The ratio of wall thickness to vessel diameter in pulmonary arteries with diameters<200μm were greater in in P group than S₁ and S₂ groups. The small pulmonary arteries also were charactered by more intensive immunofluorescence staining of α-actin in P than in S₁ and S₂ groups. The expressions of VEGFmRNA were elevated in P, S₁ and S₂ groups but highest in P group, there were significant decreaced expression in S₁ and S₂ group when compared to P group. And a same trend in expressions of protein phosphorylation ERK1/ERK2 was seen. The protein expressions of MKP1 were elevated in Group P as well as in S₁ and S₂ groups. Conclusion: 1) the animal model of increased pulmonary blood flow were successful imitated the hemodynamic change and impaired change of pulmonary hypertension; the induced pulmonary hypertension animal model were successful imitated the pathological changes of pulmonary hypertension. 2) In the study of increased pulmonary blood flow, with the increasing of mPAP and RVH, the expressions ofpreproET-1mRNA were increased at the same time. But the expressions of eNOSmRNA had not changed. 3) Phosphodiesterase 5 inhibition sildenafil could decrease mPAP in animal model of pulmonary hypertension, and it also partly restored the impaired Ach relaxation in hypertensive PA. 4) Sildenafil is effective in decreasing mPAP and inhabiting the progress of pulmonary vascular remodeling in pulmonary hypertension rats induced by monocrotaline. The expressions of VEGFmRNA and phosphorylation of ERK₁/ERK₂ were involved in the mechanism.