Effects of microRNA-155 on mice with lipopolysaccharide-induced acute lung injury

Abstract

To study the effects of microRNA (miR)-155 on mice with acute lung injury induced by lipopolysaccharide (LPS). According to the random number table, 30 C57 mice were divided into group LPS, group miR-155 inhibitor, group miR control, group miR-155 mimics, normal control group, with 6 mice in each group. Mice in group LPS and the other three treatment groups were given 5 µl LPS (20 µg/µl, in the dose of 4 mg/kg) to reproduce acute lung injury model. Half an hour after injury, group LPS, group miR-155 inhibitor, group miR control, group miR-155 mimics were injected with saline, miR-155 inhibitor, miR control and miR-155 mimics through trachea. Mice in normal control group were received no treatment. All mice were anesthetized after 24 h, while lung tissue samples were harvested for histomorphological observation, detection of mRNA expressions of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) with SYBR Green real-time polymerase chain reaction (PCR), detection of miR-155 in group miR-155 inhibitor, group miR control, group miR-155 mimics by Taqman PCR. The protein expression of cyclooxygenase-2 (COX-2) was determined by western blot. Data were statistically analyzed. The relative mRNA expression values of TNF-α were 24.49 ± 3.64, 38.92 ± 3.40, 36.00 ± 3.86, 12.56 ± 2.06, 1.04 ± 0.41 in group LPS, group miR-155 inhibitor, group miR control, group miR-155 mimics, normal control group. The relative mRNA expression values of IL-1β were 55.96 ± 4.87, 62.90 ± 6.41, 59.99 ± 6.48, 25.33 ± 3.50, 1.11 ± 0.44 in group LPS, group miR-155 inhibitor, group miR control, group miR-155 mimics, normal control group. The differences of TNF-α and IL-1β in group miR-155 mimics were statistically significant by compared with group LPS, group miR-155 inhibitor, group miR control (P < 0.05). The differences were not statistically significant among group LPS, group miR-155 inhibitor, group miR control. Western blot analysis showed the relative expression values of COX-2 were 0.94 ± 0.06, 0.96 ± 0.09, 0.91 ± 0.03, 0.79 ± 0.04, 0.63 ± 0.07 in group LPS, group miR-155 inhibitor, group miR control, miR-155 mimics and normal control group. The value in normal control group was significantly lower than other groups (P < 0.05). Using the miR-155 can effectively alleviate the lung inflammation in mice with acute lung injury induced by LPS.