Pathophysiology of Long Non-coding RNAs in Ischemic Stroke

Long non-coding RNA MEG3 promotes cerebral ischemia-reperfusion injury through increasing pyroptosis by targeting miR-485/AIM2 axis

OBJECTIVE

Inflammasome contributes to ischemic brain injury by inducing pyroptosis and inflammation. The aim of this study is to unravel the mechanism of long non-coding RNA (lncRNA) maternally expressed gene 3 (MEG3)-mediated regulation of absent in melanoma 2 (AIM2) inflammasome during cerebral ischemia/reperfusion (I/R).

METHODS

In vivo middle cerebral artery occlusion (MCAO) rat model and in vitro oxygen-glucose deprivation/reperfusion (OGD/R)-treated neurocytes model were generated. TTC, H&E staining and TUNEL were performed to assess the cerebral ischemic injury. LDH and MTT assays were used to detect cell viability and cytotoxicity. qRT-PCR was used to detect the expression levels of MEG3, miR-485 and AIM2. Immunohistochemistry (IHC) and immunofluorescence were conducted to detect the AIM2 expression. ELISA and Western blotting were performed to determine the secretion and protein levels of inflammasome signaling proteins. Dual luciferase reporter assay and Ago2-RIP were used to validate the direct interaction among MEG3, miR-485 and AIM2.

RESULTS

In both MCAO rats and OGD/R-treated neurocytes, MEG3 and AIM2 were significantly up-regulated, whereas miR-485 was down-regulated. MCAO induces pyroptosis and release of IL-1β and IL-18 in ischemia brain. MEG3 acted as a molecular sponge to suppress miR-485, and AIM2 was identified as a direct target of miR-485. Knockdown of MEG3 inhibited OGD/R-induced pyroptosis and inflammation, and lack of MEG3 inhibited caspase1 signaling and decreased the expression of AIM2, ASC, cleaved-caspase1 and GSDMD-N. While overexpression of MEG3 exerted opposite effects.

CONCLUSION

MEG3/miR-485/AIM2 axis contributes to pyroptosis via activating caspase1 signaling during cerebral I/R, suggesting that this axis may be a potent therapeutic target in ischemic stroke.

Overexpression of the long non-coding RNA Oprm1 alleviates apoptosis from cerebral ischemia-reperfusion injury through the Oprm1/miR-155/GATA3 axis

Numerous differentially expressed long non-coding RNAs (lncRNAs) have been identified in cerebral ischemia-reperfusion (I/R) injury using RNA-Seq analysis. However, little is known about whether and how lncRNAs are involved in cerebral I/R injury. In this study, we investigated the function of the lncRNA Oprm1 in cerebral I/R injury and explored the underlying mechanism. An oxygen-glucose deprivation model in N2a cells was utilized to mimic cerebral I/R injury in vitro. Trypan blue staining, terminal deoxytransferase-mediated dUTP-biotin nick end labelling and caspase-3 were measured to evaluate apoptosis. Middle cerebral artery occlusion was performed in mice to evaluate the function of lncRNA Oprm1 in vivo. Real-time PCR and western blotting were used to measure the expression levels of lncRNA Opmr1, caspase-3, miR-155, GATA binding protein 3 (GATA3) and nuclear factor (NF)-κB. lncRNA Oprm1 was mainly located in the cytoplasm. Overexpression of lncRNA Oprm1 alleviated the apoptosis induced by oxygen-glucose deprivation and significantly reduced cleaved caspase-3 levels. Infarct size was distinctly decreased in the lncRNA Oprm1-overexpression group. The neurological score was also improved. Our findings showed that the lncRNA Oprm1/miR-155/GATA3 axis plays an important role in cerebral I/R injury. lncRNA Oprm1 may attenuate cerebral injury through the NF-κB pathway. lncRNA Oprm1 may serve as a potential target for new therapeutic interventions in patients with ischemic stroke.

Long noncoding MIAT acting as a ceRNA to sponge microRNA-204-5p to participate in cerebral microvascular endothelial cell injury after cerebral ischemia through regulating HMGB1

This study is applied to the investigation of the long noncoding RNA myocardial infarction associated transcript's (MIAT's) role in regulating the expression of high-mobility group box 1 (HMGB1) in cerebral microvascular endothelial cell (CMEC) injury after cerebral ischemia by serving as a competitive endogenous RNA (ceRNA) to sponge microRNA-204-5p (miR-204-5p). The cerebral ischemia model of middle cerebral artery occlusion (MCAO) in rats was established by the suture method, in which rats were injected with empty plasmids and MIAT siRNA plasmids. The cerebral ischemia injury model in vitro was established through oxygen glucose deprivation (OGD) in primary cultured CMECs in rats. The cells were transfected with empty plasmids and MIAT siRNA plasmids. The MIAT/miR-204-5p/HMGB1 axis' function in damage and angiogenesis of CMECs were explored. The binding site between MIAT and miR-204-5p along with that between miR-204-5p and HMGB1 was determined. MIAT was overexpressed in MCAO rats' brain tissue and inhibited MIAT attenuated the injury of brain tissue in MCAO rats. Inhibition of MIAT promoted angiogenesis, promoted miR-204-5p expression and inhibited HMGB1 expression in brain tissue of MCAO rats. Inhibition of MIAT reduced CMEC damage, induced angiogenesis of CMECs, increased the number of surviving neurons, promoted miR-204-5p expression and inhibited HMGB1 expression in CMECs treated with OGD. MIAT promoted HMGB1 expression by competitive binding to miR-204-5p to regulate the injury of CMECs after cerebral ischemia. Our study showed that MIAT promoted HMGB1 expression by competitively binding to miR-204-5p to regulate the injury of CMECs after cerebral ischemia.

Silencing of SNHG12 Enhanced the Effectiveness of MSCs in Alleviating Ischemia/Reperfusion Injuries via the PI3K/AKT/mTOR Signaling Pathway

Previous studies have reported that the long non-coding RNA SNHG12 (lncRNA SNHG12) plays a critical role in regulating the function of mesenchymal stem cells (MSCs); however, the effect of lncRNA SNHG12 on MSCs in injured brain tissue has rarely been reported. We studied the effect and mechanism of lncRNA SNHG12-modified mesenchymal stem cells (MSCs) in treating brain injuries caused by ischemia/reperfusion (I/R). I/R treated rat brain microvascular endothelial cells (BMECs) were co-cultured with MSCs or I/R pretreated MSCs. Next, BMEC proliferation was detected by using CCK-8 and EdU assays, and cell apoptosis was determined by using flow cytometry and the Hoechst staining method. Autophagy of BMECs was determined using immunofluorescence and expression of associated pathway proteins were measured by western blotting. Moreover, BMEC proliferation, apoptosis, and autophagy were also determined after the BMECs had been co-cultured with shSNHG12-MSCs. In addition, a rat model of middle cerebral artery occlusion (MCAO) was used to further confirm the findings obtained with cells. I/R treatment significantly decreased the proliferation of BMECs, but increased their levels of SNHG12 expression, apoptosis, and autophagy. However, co-culturing of BMECs with MSCs markedly alleviated the reduction in BMEC proliferation and the increases in BMEC apoptosis and autophagy, as well as the phosphorylation of PI3K, AKT, and mTOR proteins in BMECs that had been induced by I/R. Furthermore, shSNHG12 remarkably enhanced the effects of MSCs. In addition, an injection MSCs reduced the infarct areas and rates of cell apoptosis in MACO rats, and reduced the phosphorylation of PI3K, AKT, and mTOR proteins. Moreover, shSNHG12 enhanced the ameliorative effect of MSCs in treating brain injuries in the MACO rats. In conclusion, silencing of SNHG12 enhanced the effects of MSCs in reducing apoptosis and autophagy of BMECs by activating the PI3K/AKT/mTOR signaling pathway.

Long noncoding RNAs: a missing link in osteoporosis

Osteoporosis is a systemic disease that results in loss of bone density and increased fracture risk, particularly in the vertebrae and the hip. This condition and associated morbidity and mortality increase with population ageing. Long noncoding (lnc) RNAs are transcripts longer than 200 nucleotides that are not translated into proteins, but play important regulatory roles in transcriptional and post-transcriptional regulation. Their contribution to disease onset and development is increasingly recognized. Herein, we present an integrative revision on the studies that implicate lncRNAs in osteoporosis and that support their potential use as therapeutic tools. Firstly, current evidence on lncRNAs involvement in cellular and molecular mechanisms linked to osteoporosis and its major complication, fragility fractures, is reviewed. We analyze evidence of their roles in osteogenesis, osteoclastogenesis, and bone fracture healing events from human and animal model studies. Secondly, the potential of lncRNAs alterations at genetic and transcriptomic level are discussed as osteoporosis risk factors and as new circulating biomarkers for diagnosis. Finally, we conclude debating the possibilities, persisting difficulties, and future prospects of using lncRNAs in the treatment of osteoporosis.

LncRNA ANRIL Expression and ANRIL Gene Polymorphisms Contribute to the Risk of Ischemic Stroke in the Chinese Han Population

The aim of the present study was to explore the role of lncRNA ANRIL in the pathogenesis of ischemic stroke (IS) and coronary artery disease (CAD) and to determine the association between ANRIL variants and the genetic susceptibility of IS and CAD in the Chinese Han population. A genetic association study including 550 IS patients, 550 CAD patients, and 550 healthy controls was conducted. The expression levels of lncRNA ANRIL, CDKN2A, and CDKN2B were detected using qRT-PCR. Genotyping was performed by Sequenom MassARRAY on an Agena platform. Our study showed that IS patients had an increased lncRNA ANRIL expression (P = 0.002) and a decreased CDKN2A expression (P < 0.001) compared with normal controls. A significant difference with regard to the genotype distribution of rs2383207 was found between male IS patients and controls (P = 0.011). The minor allele of rs2383207 significantly increased the IS risk under a recessive model (OR = 1.52, 95% CI = 1.05-2.21, P = 0.027). The minor allele of rs1333049 was significantly associated with the risk of IS among the male patients under a recessive model (OR = 1.56, 95% CI = 1.04-2.35, P = 0.031). However, no significant association was found between the ANRIL variants and the risk of CAD (all P > 0.050). In addition, we found a decreased lncRNA ANRIL expression in IS patients who carried the GG genotype of rs1333049 compared with IS patients who carried the CC or CG genotype (P = 0.041). In summary, we found that IS patients had an increased lncRNA ANRIL expression and a decreased CDKN2A expression compared with the controls, which might play an impellent role in pathological processes of IS. The ANRIL variants rs2383207 and rs1333049 were significantly associated with the risk of IS among males but not females in the Chinese Han population.

Angio-LncRs: LncRNAs that regulate angiogenesis and vascular disease

Long noncoding RNAs (lncRNAs) represent a large subgroup of RNAs that are longer than 200 nucleotides and have no apparent protein coding potential. They have diverse functions in different biological processes by regulating chromatin remodeling or protein translation. This review summarizes the recent progress of lncRNAs in angiogenesis and vascular diseases. A general overview of lncRNA functional mechanisms will be introduced. A list of lncRNAs, which are termed "Angio-LncRs", including MALAT1, MANTIS, PUNISHER, MEG3, MIAT, SENCR and GATA6-AS, will be discussed regarding their expression, regulation, function and mechanism of action in angiogenesis. Implications of lncRNAs in vascular diseases, such as atherosclerosis, hypertension, vascular retinopathies and tumor angiogenesis will also be discussed.