Exosomal miR-7 Mediates Bystander Autophagy in Lung after Focal Brain Irradiation in Mice

Abstract

This study investigated whether exosomal microRNA-7 (miR-7) mediates lung bystander autophagy after focal brain irradiation in mice. After 10 Gy or sham irradiation of mice brains, lung tissues were extracted for the detection of autophagy markers by immunohistochemistry, western blotting, and quantitative real-time reverse transcription PCR (qRT-PCR), meanwhile the brains were dissociated, the neuron/astrocyte/microglia/oligodendrocyte were isolated, and the miR-7 expression in each population were detected, respectively. A dual-luciferase reporter assay was developed to identify whether Bcl-2 is a target gene of miR-7. After 10 Gy or sham irradiation of astrocytes, exosomes were extracted, stained with Dil (1,1'-Dioctadecyl-3,3,3',3'-Tetramethylindocarbocyanine Perchlorate), and added into non-irradiated astrocytes. Meanwhile, Dil-stained exosomes released from 10 Gy or sham irradiated astrocytes were injected into LC3B-GFP mice via the tail vein. Lung tissues were then extracted for western blotting and qRT-PCR. Irradiation of mouse brains increased the LC3B-II/I ratio, Beclin-1 and miR-7 levels, while decreased the Bcl-2 level in non-irradiated lung tissue. Interestingly, brain irradiation remarkably increased the miR-7 expression in astrocyte and oligodendrocyte. MiR-7 significantly inhibited the luciferase activity of the wild-type Bcl-2-3′-untranslated regions (UTR) reporter vector, but not that of the Bcl-2-3′-UTR mutant vector, indicating that Bcl-2 is directly targeted by miR-7. In in vitro study, the addition of irradiated astrocyte-secreted exosomes increased the LC3B-II/I ratio, Beclin-1 and miR-7 levels, while decreased the Bcl-2 level in non-irradiated astrocytes. Further, the injection of irradiated astrocyte-secreted exosomes through the tail vein increased the lung LC3B-II/I ratio, Beclin-1 and miR-7 level, but decreased the Bcl-2 level in vivo. We concluded that exosomal miR-7 targets Bcl-2 to mediate distant bystander autophagy in the lungs after brain irradiation.

High Levels of miR-7-5p Potentiate Crizotinib-Induced Cytokilling and Autophagic Flux by Targeting RAF1 in NPM-ALK Positive Lymphoma Cells

“…Finally, LC3B and p62 western-blotting further corroborated our findings ( Figure S1C ). We concluded that miR-7-5p, through the binding and downregulation of potentially several targeted mRNAs, is a potent regulator of cell viability and cell autophagy in Karpas-299 cells, as previously described in other studies [ 55 , 56 , 57 , 58 ].…”

Uric acid and sphingomyelin enhance autophagy in iPS cell-originated cardiomyocytes through lncRNA MEG3/miR-7-5p/EGFR axis

“…These results may be interpreted that MEG3 acted as a sponge of miR-7-5p to regulate the activation of downstream mTOR signalling, and in turn, modulate cardiomyocytes autophagy. MiR-7-5P is an important regulator in cell autophagy in various cell type [55][56][57].…”

Extracellular Vesicles in Prostate Cancer Carcinogenesis, Diagnosis, and Management

“…Exosomes containing miR-7-5p proved to be internalized by non-irradiated BEP2D cells which, therefore, entered in autophagy, by reduced expression of EGFR, a known target of miR-7-5p ( 174 ). A distant bystander effect was also demonstrated in vivo ( 175 ). After focal brain irradiation of mice, exosomes were obtained from irradiated astrocytes and found to express high levels of miR-7.…”

“…After focal brain irradiation of mice, exosomes were obtained from irradiated astrocytes and found to express high levels of miR-7. Injected into the tail vein of non-irradiated mice, they were able to induce autophagy of lung tissues by directly targeting Bcl-2 ( 175 ). Other miRs may have similar effects, such as miR-145, which proved to sensitize PCa cells to radiation ( 176 ).…”