Protective effect of sodium 4-phenylbutyrate on rats with acute respiratory distress syndrome related right ventricular dysfunction by alleviating endoplasmic reticulum stress

Abstract

To investigate the role of endoplasmic reticulum stress (ERS) in rats with acute respiratory distress syndrome (ARDS) related right ventricular dysfunction and the protective effect of sodium 4-phenylbutyrate (4-PBA) on right ventricle. Sixty male Spragne-Dawley (SD) rats were randomly divided into control group (CON group), lipopolysaccharide (LPS) model group, 4-PBA prevention group and 4-PBA treatment group, with 15 rats in each group. ARDS rat model was established by intratracheal instillation of LPS 10 mg/kg after tracheotomy; CON group was given the same amount of saline. 4-PBA prevention group and 4-PBA treatment group were given 4-PBA 500 mg/kg intragastric administration 2 hours before and after LPS respectively. Echocardiography was performed 12 hours after treatment to evaluate the right ventricular function. Then, the rats were sacrificed by bloodletting, and the serum and right ventricular tissue were harvested. The histopathological changes of myocardial were observed by hematoxylin-eosin (HE) staining, the levels of tumor necrosis factor-α (TNF-α), interleukins (IL-1β and IL-6) in serum and myocardial were detected by enzyme linked immunosorbent assay (ELISA), and Western Blot was used to detect the expression of the marker proteins of ERS in myocardial, including glucose regulatory protein 78 (GRP78), C/EBP cyclic adenosine phosphate reaction primitive binding transcription factor homologous protein (CHOP), caspase-12 and caspase-3. Compared with the CON group, the echocardiography showed pulmonary artery maximum pressure gradient (PAmaxPG), pulmonary artery acceleration time (PAAT), tricuspid annular plane systolic excursion (TAPSE) in LPS model group were significantly decreased, and right ventricular end-diastolic excursion (RVDd) was significantly increased, and the levels of TNF-α, IL-1β and IL-6 in serum and myocardial, as well as the expressions of GRP78, CHOP, caspase-12 and caspase-3 in myocardial were significantly increased. Compared with LPS model group, TAPSE of 4-PBA preventive and treatment groups were significantly increased (mm: 3.08±0.65, 2.96±0.61 vs. 2.48±0.45), RVDd were significantly decreased (mm: 3.67±0.58, 3.60±0.61 vs. 4.18±0.71), the levels of TNF-α, IL-1β and IL-6 in serum and myocardial were significantly decreased [TNF-α (ng/L): 187.98±18.98, 176.08±17.98 vs. 332.00±19.90 in serum, 135.06±19.00, 132.78±17.00 vs. 155.00±20.00 in myocardial; IL-1β(ng/L): 12.07±2.98, 11.05±2.41 vs. 24.06±4.01 in serum, 19.89±2.80, 21.06±2.80 vs. 26.00±2.60 in myocardial; IL-6 (ng/L): 42.98±7.90, 34.05±6.09 vs. 89.80±10.07 in serum, 129.45±25.00, 127.08±26.06 vs. 145.77±23.00 in myocardial]; the expressions of GRP78, CHOP, caspase-12 and caspase-3 in myocardial were significantly decreased (GRP78/GAPDH: 0.090±0.070, 0.103±0.060 vs. 0.167±0.090, CHOP/GAPDH: 0.109±0.090, 0.090±0.080 vs. 0.186±0.090, caspase-12/GAPDH: 0.769±0.230, 0.799±0.210 vs. 1.040±0.350, caspase-3/GAPDH: 0.391±0.060, 0.401±0.054 vs. 0.603±0.340), with statistically significant differences (all P < 0.05). There were no significant differences in each indexes between 4-PBA prevention group and 4-PBA treatment group (all P > 0.05). ERS is involved in ARDS-related right ventricular dysfunction. 4-PBA can protect the right ventricular function of ARDS rats by inhibiting ERS and alleviating inflammation, and the preventive and therapeutic effects of 4-PBA are similar.