Influence of miRNA-30a-5p on Pulmonary Fibrosis in Mice with Streptococcus pneumoniae Infection through Regulation of Autophagy by Beclin-1

Abstract

The study is aimed at observing the influence of microribonucleic acid- (miRNA-) 30a-50p on the pulmonary fibrosis in mice with Streptococcus pneumoniae infection through the regulation of autophagy by Beclin-1. Specific pathogen-free mice were instilled with Streptococcus pneumoniae through the trachea to establish the pulmonary fibrosis model. Then, they were divided into the miRNA-30a-50p mimics group (mimics group, n = 10 ) and miRNA-30a-5p inhibitors group (inhibitors group, n = 10 ), with the control group ( n = 10 ) also set. Pulmonary tissue wet weight/dry weight (W/D) was detected. The content of tumor necrosis factor-α (TNF-α), interleukin- (IL-) 6, and myeloperoxidase (MPO) was determined using enzyme-linked immunosorbent assay (ELISA). Besides, the changes in the pulmonary function index dynamic lung compliance (Cdyn), plateau pressure (Pplat), and peak airway pressure (Ppeak) were monitored, and the gene and protein expression levels were measured via quantitative PCR (qPCR) and Western blotting. The expression level of miRNA-30a-5p was substantially raised in the mimics group ( p < 0.05 ), but extremely low in the inhibitors group ( p < 0.05 ). The mimics group had obviously raised levels of serum aminotransferase (AST), glutamic-pyruvic transaminase (GPT), alkaline phosphatase (ALP), and pulmonary tissue W/D ( p < 0.05 ). Additionally, the expression levels of TNF-α, IL-6, and MPO were notably elevated in the mimics group, while their expression levels showed the opposite conditions in the inhibitors group ( p < 0.05 ). According to the HE staining results, the inhibitors group had arranged orderly cells, while the mimics group exhibited lung injury, pulmonary edema, severe inflammatory response, and alveolar congestion. In the inhibitors group, Cdyn was remarkably elevated, but Pplat and Ppeak declined considerably ( p < 0.05 ). Besides, the inhibitors group exhibited elevated messenger RNA (mRNA) levels of Beclin-1 and LC3, lowered mRNA levels of α-SMA and p62, a raised protein level of Beclin-1, and a markedly decreased protein level of p62 ( p < 0.05 ). Silencing miRNA-30a-5p expression can promote the expression of Beclin-1 to accelerate the occurrence of autophagy, thereby treating pulmonary fibrosis in mice with Streptococcus pneumoniae infection.

TOM5 regulates the mitochondrial membrane potential of alveolar epithelial cells in organizing pneumonia

“…Likewise, it has been proven that serum LDH levels in fibrotic interstitial lung disease patients were significantly higher than those in nonfibrotic interstitial lung disease patients [ 30 ]. Serum ALP is an important indicator to measure the degree of lung fibrosis [ 31 ]. These results were in agreement with our findings.…”

Animal models of acute exacerbation of pulmonary fibrosis

“…The transgenic mouse model was established for modeling pulmonary fibrosis by intratracheal delivered with adenovirus vector, followed by overexpressing of TGFα [90], TNF-α [90], TGF-β [91], IL-13 [92] or IL-1β [93]. The induction of pulmonary fibrosis was observed following targeted damage to AEC2 through the administration of diphtheria toxin in transgenic mice expressing the human diphtheria toxin receptor under the control of the AEC2 promoter region [94].…”

“…In addition, primary fibroblasts isolated from patients with IPF were injected into immunodeficient mice and a humanized mouse model of pulmonary fibrosis was successfully established [95]. Two weeks after injection of Spn intratracheally, the pulmonary fibrosis in the lung tissue were observed in miRNA-30a-5p overexpression mice, and the contents of hydroxyproline in lung tissue, the expression levels of α-SMA were significantly increased in Spn mouse model [90].…”

The role and mechanism of microRNAs in infections with Streptococcus pneumoniae

“…Autophagy regulation through Beclin-1 activation avoids additional inflammation growth and eventually influences pulmonary fibrosis growth, which offers fresh theoretical prevention and curing foundation forS. pneumoniae infected mice as well [38]. In mice infected with S. pneumoniae , bacteria led to effective harm to AEC(alveolar epithelial cells), subsequently with a slow regeneration procedure.…”