Upregulation of miR-216a exerts neuroprotective effects against ischemic injury through negatively regulating JAK2/STAT3-involved apoptosis and inflammatory pathways.

OBJECTIVE: Ischemic stroke remains a significant cause of death and disability in industrialized nations. Janus tyrosine kinase (JAK) and signal transducer and activator of transcription (STAT) of the JAK2/STAT3 pathway play important roles in the downstream signal pathway regulation of ischemic stroke-related inflammatory neuronal damage. Recently, microRNAs (miRNAs) have emerged as major regulators in cerebral ischemic injury; therefore, the authors aimed to investigate the underlying molecular mechanism between miRNAs and ischemic stroke, which may provide potential therapeutic targets for ischemic stroke. METHODS: The JAK2- and JAK3-related miRNA (miR-135, miR-216a, and miR-433) expression levels were detected by real-time quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) and Western blot analysis in both oxygen-glucose deprivation (OGD)-treated primary cultured neuronal cells and mouse brain with middle cerebral artery occlusion (MCAO)-induced ischemic stroke. The miR-135, miR-216a, and miR-433 were determined by bioinformatics analysis that may target JAK2, and miR-216a was further confirmed by 3' untranslated region (3'UTR) dual-luciferase assay. The study further detected cell apoptosis, the level of lactate dehydrogenase, and inflammatory mediators (inducible nitric oxide synthase [iNOS], matrix metalloproteinase-9 [MMP-9], tumor necrosis factor-α [TNF-α], and interleukin-1ß [IL-1ß]) after cells were transfected with miR-NC (miRNA negative control) or miR-216a mimics and subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) damage with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, annexin V-FITC/PI, Western blots, and enzyme-linked immunosorbent assay detection. Furthermore, neurological deficit detection and neurological behavior grading were performed to determine the infarction area and neurological deficits. RESULTS: JAK2 showed its highest level while miR-216a showed its lowest level at day 1 after ischemic reperfusion. However, miR-135 and miR-433 had no obvious change during the process. The luciferase assay data further confirmed that miR-216a can directly target the 3'UTR of JAK2, and overexpression of miR-216a repressed JAK2 protein levels in OGD/R-treated neuronal cells as well as in the MCAO model ischemic region. In addition, overexpression of miR-216a mitigated cell apoptosis both in vitro and in vivo, which was consistent with the effect of knockdown of JAK2. Furthermore, the study found that miR-216a obviously inhibited the inflammatory mediators after OGD/R, including inflammatory enzymes (iNOS and MMP-9) and cytokines (TNF-α and IL-1ß). Upregulating miR-216a levels reduced ischemic infarction and improved neurological deficit. CONCLUSIONS: These findings suggest that upregulation of miR-216a, which targets JAK2, could induce neuroprotection against ischemic injury in vitro and in vivo, which provides a potential therapeutic target for ischemic stroke.

MMP-mediated cleavage of beta-dystroglycan in myelin sheath is involved in autoimmune neuritis.

Alpha-/beta-dystroglycans (DG) located at the outmost layer of myelin sheath play a critical role in its formation and stability in the peripheral nerve system. The demyelination of nerve fibers is present in autoimmune neuritis, however, it is not known about the molecular mechanisms underlying this pathological process. In an animal model of experimental autoimmune neuritis, we observed that beta-DG cleavage was associated with the demyelination of peripheral nerves. The neuritis and beta-DG cleavage were accompanied by matrix metalloproteinase (MMP)-2/-9 over-expressions and attenuated by captopril, a MMP inhibitor. The blockade of MMPs also improves clinical signs. Our results reveal a crucial role of MMP-mediated beta-DG cleavage in autoimmune neuritis, such as Guillain-Barre' syndrome, and bring insights into therapeutic strategies for autoimmune diseases.