Epigenetic control of proteolytic pathways in the diaphragm during prolonged mechanical ventilation

Abstract

Background & Aims: It is well established that prolonged mechanical ventilation (MV) triggers diaphragm atrophy and that uregulation of the proteasome and autophagy pathways has been implicated in this process. MicroRNAs (miR) are short non-coding RNAs that regulate mRNA and protein expressions of specific genes. In this study, we aimed at evaluating the expression of microRNAs that regulate the expression of autophagy-related genes and ubiquitin E3 ligases (Atrogin-1 and MuRF-1).

Methods: Adult male Wistar rats were divided into two groups. The control group was spontaneously breathing while the second group was submitted to 24h of CMV. The diaphragm and gastrocnemius muscles were excised and frozen. The expression of miRs that regulate LC3B (miR-204), p62 (miR-20a, miR-17, miR-20a, miR93, miR-106b), BECLIN1 (miR-376b, miR-30a), ATG5 (miR-30a), BNIP3 (miR-210, miR-145) and Atrogin-1 and MuRF1 (miR-23a) was quantified using qPCR.

Results: Prolonged CMV induced significant fiber atrophy in the DIA and significantly induced autophagy and upregulation of Atrogin-1 and MuRF1 mRNAs in the diaphragm. Prolonged CMV downregulated miR-30a, mir-145, miR-23a and mir-204 in the diaphragm. No significant alterations in the expression of remaining autophagy-related miRNAs. No significant alterations in the expression of these microRNAs were observed in the gastrocnemius.

Conclusions: We conclude that prolonged MV induces significant atrophy as a result of an increase in autophagy and proteasome activities and that prolonged MV is associated with significant downregulation of specific miRNAs that negatively regulate the expression of autophagy-related genes and muscle-specific E3 ligases.