To investigate the expression of microRNA in the patients with acute respiratory distress syndrome (ARDS) caused by cardiopulmonary bybass (CPB), and primarily explore the possible mechanism.

Four time points were set up: the beginning of CPB operation (T1), 4 h after the start of operation (T2), 8 h after operation (T3), and 16 h after operation (T4). MicroRNA microarray was used to analyze the expression of microRNAs in 32 patients with ARDS induced by CPB. Quantitative real time polymerase chain reaction (qRT-PCR) was performed to verify the expression of microRNAs. Enzyme linked immunosorbent assay detected tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) levels of patients in T1-T4 time points. Respiratory index and oxygenation index were also calculated. Pearson correlation analysis investigated the correlation between microRNA-320 (miR-320) expression and TNF-α, IL-6, respiratory index, oxygenation index, Murray acute lung injury score and acute physiology and chronic health evaluation (APACHE) Ⅱ score. Furthermore, human lung adenocarcinoma A549 cells were in vitro cultured, and then pcDNA3.1-miR-320 was transfected into cells; CCK-8 kits and flow cytometry were used to determine the survival and apoptosis rates of A549 cell at 48 h after transfection.

In patients with ARDS induced by CPB, expressions of eight microRNAs were changed significantly at T1 and T4 time points(t=28.313, 30.014, 25.313, 20.312, 29.442, 21.443, 18.427, 22.369; all P < 0.001); five increased and three decreased. The decrease level of miR-499 (0.28 + 0.09) and increase level of miR-320 (1.62 + 0.12) both changed significantly (all P < 0.05). qRT-PCR found that only the relative expression levels of miR-320 (1.00, 1.14 + 0.07, 1.34 + 0.06, 1.71 + 0.08) gradually increased from T1 to T4 time points, and the difference was statistically significant (F=20.648, P < 0.05). In these CPB induced ARDS patients, TNF-α level [(110 ± 10) ng/L vs. (254 ± 16) ng/L], IL-6 level [(86 ± 8) ng/L vs. (165 ± 11) ng/L], respiratory index [(0.182 ± 0.021) vs. (0.381 ± 0.032)] all dramatically increased, while oxygenation index [(350 ± 22) vs. (245 ± 18)] declined when comparing T1 and T4 time points (all P < 0.05). Pearson correlation analysis found the expression of miR-320 was positively correlated with Murray acute lung injury score, APACHEⅡscore, and TNF-α level, IL-6 level, respiratory index in T4 time point (r=0.685, 0.744, 0.737, 0.711, 0.846; all P < 0.05), and negatively correlated with oxygenation index (r=-0.745, P < 0.05). Moreover, the survival [(82% ± 8%) vs. 100%] and apoptosis [(20.0% ± 1.1%) vs. (9.4% ± 0.8%)] rates after 48 h transfection between the pcDNA3.1-miR-320 transfected A549 cell group and control group were remarkably different (both P < 0.05).

MiR-320 expression is correlated with the lung injury indicators such as TNF-α and IL-6, and its high expression may mediate ARDS caused by CPB. The mechanism is to induce apoptosis of alveolar epithelial cells. Thus, miR-320 detection has clinical value for diagnosis and assessment of ARDS.