[The role of endoplasmic reticulum stress in pulmonary hypertension in rat induced by chronic hypoxia and hypercapnia].

OBJECTIVE

To observe the pulmonary vascular remodeling in rats with pulmonary hypertension induced by hypoxia and hypercapnia, and to explore the role of endoplasmic reticulum stress in pulmonary hypertension.

METHODS

Forty SD rats were random-ly divided into four groups:normoxic control group (N), hypoxia hypercapnia group (HH), ERS inhibitor 4-phenylbutyric acid group (4-PBA), endoplasmic reticulum stress (ERS) pathway agonist tunicamycin group (TM), ten rats in each group.The mean pulmona-ry artery pressure (mPAP), mean carotid artery pressure (mCAP) and right ventricular hypertrophy index of rats in each group were measured.Pulmonary artery smooth muscle cells were identified by immunofluorescence α-smooth muscle actin (α-SMA).Morphologi-cal changes of lung tissue and pulmonary artery were observed by electron microscope.The apoptotic index of pulmonary artery smooth muscle cells in each group was detected by TUNEL.Reverse transcription polymerase chain reaction (RT-PCR) and Western blot were used to detect the expression of glucose-regulated protein (GRP78), C/EBP homologous protein (CHOP), c-Jun N-terminal kinase (JNK) and cysteinyl aspartate specific proteinase-12 (caspase-12) mRNA and protein in each group.

RESULTS

①Compared with the N group, the mPAP, the ratio of right ventricle weight to left ventricle plus ventricular septum weight[RV/(LV+S)]and the ratio of pulmonary artery wall area to total tube area (WA/TA) were increased (<0.01), and the ratio of pulmonary artery luminal area to total tube area (LA/TA) were decreased (<0.01), pulmonary artery smooth muscle cell apoptosis index were decreased (<0.05 or <0.01) in HH group, 4-PBA group and TM group.ERS related protein and mRNA expressions were increased, the differences were statistically significant.②Compared with the HH group, the mPAP, [RV/(LV+S)]and WA/TA of 4-PBA group were decreased ( <0.01), LA/TA and pulmonary artery smooth muscle cell apoptosis index were increased (<0.01, <0.05).The expressions of ERS related protein and mRNA were all decreased (<0.05 or <0.01).③Compared with the HH group, the mPAP, [RV/(LV+S)]and WA/TA of TM group were increased (<0.05 or <0.01), pulmonary artery middle layer thickened, LA/TA and pulmonary artery smooth muscle cell apoptotic index were decreased (<0.01).ERS related protein and mRNA expressions were increased with statistical significance except GRP78 protein.

CONCLUSIONS

Pulmonary vascular remodeling in rats with pulmonary hypertension induced by hypoxia and hypercapnia may be related to the excessive proliferation of pulmonary artery smooth muscle cells and too little apopto-sis;ERS related factors (JNK, caspase-12 and CHOP) are involved in the regulation of pulmonary hypertension induced by hypoxia hypercapnia.