Knockdown of MALAT1 attenuates high-glucose-induced angiogenesis and inflammation via endoplasmic reticulum stress in human retinal vascular endothelial cells

Role of long noncoding RNAs in diabetes-associated peripheral arterial disease

Diabetes mellitus (DM) is a metabolic disease that heightens the risks of many vascular complications, including peripheral arterial disease (PAD). Various types of cells, including but not limited to endothelial cells (ECs), vascular smooth muscle cells (VSMCs), and macrophages (MΦs), play crucial roles in the pathogenesis of DM-PAD. Long non-coding RNAs (lncRNAs) are epigenetic regulators that play important roles in cellular function, and their dysregulation in DM can contribute to PAD. This review focuses on the developing field of lncRNAs and their emerging roles in linking DM and PAD. We review the studies investigating the role of lncRNAs in crucial cellular processes contributing to DM-PAD, including those in ECs, VSMCs, and MΦ. By examining the intricate molecular landscape governed by lncRNAs in these relevant cell types, we hope to shed light on the roles of lncRNAs in EC dysfunction, inflammatory responses, and vascular remodeling contributing to DM-PAD. Additionally, we provide an overview of the research approach and methodologies, from identifying disease-relevant lncRNAs to characterizing their molecular and cellular functions in the context of DM-PAD. We also discuss the potential of leveraging lncRNAs in the diagnosis and therapeutics for DM-PAD. Collectively, this review provides a summary of lncRNA-regulated cell functions contributing to DM-PAD and highlights the translational potential of leveraging lncRNA biology to tackle this increasingly prevalent and complex disease.

Classical and Innovative Evidence for Therapeutic Strategies in Retinal Dysfunctions

The human retina is a complex anatomical structure that has no regenerative capacity. The pathogenesis of most retinopathies can be attributed to inflammation, with the activation of the inflammasome protein platform, and to the impact of oxidative stress on the regulation of apoptosis and autophagy/mitophagy in retinal cells. In recent years, new therapeutic approaches to treat retinopathies have been investigated. Experimental data suggest that the secretome of mesenchymal cells could reduce oxidative stress, autophagy, and the apoptosis of retinal cells, and in turn, the secretome of the latter could induce changes in mesenchymal cells. Other studies have evidenced that noncoding (nc)RNAs might be new targets for retinopathy treatment and novel disease biomarkers since a correlation has been found between ncRNA levels and retinopathies. A new field to explore is the interaction observed between the ocular and intestinal microbiota; indeed, recent findings have shown that the alteration of gut microbiota seems to be linked to ocular diseases, suggesting a gut-eye axis. To explore new therapeutical strategies for retinopathies, it is important to use proper models that can mimic the complexity of the retina. In this context, retinal organoids represent a good model for the study of the pathophysiology of the retina.

Non-coding RNAs and exosomal non-coding RNAs in diabetic retinopathy: A narrative review

Diabetic retinopathy (DR) is a devastating complication of diabetes, having extensive and resilient effects on those who suffer from it. As yet, the underlying cell mechanisms of this microvascular disorder are largely unclear. Recently, growing evidence suggests that epigenetic mechanisms can be responsible for gene deregulation leading to the alteration of key processes in the development and progression of DR, in addition to the widely recognized pathological mechanisms. It is noteworthy that seemingly unending epigenetic modifications, caused by a prolonged period of hyperglycemia, may be a prominent factor that leads to metabolic memory, and brings epigenetic entities such as non-coding RNA into the equation. Consequently, further investigation is necessary to truly understand this mechanism. Exosomes are responsible for carrying signals from cells close to the vasculature that are participating in abnormal signal transduction to faraway organs and cells by sailing through the bloodstream. These signs indicate metabolic disorders. With the aid of their encased structure, they can store diverse signaling molecules, which then can be dispersed into the blood, urine, and tears. Herein, we summarized various non-coding RNAs (ncRNAs) that are related to DR pathogenesis. Moreover, we highlighted the role of exosomal ncRNAs in this disease.

The Role of TRIM Proteins in Vascular Disease

There are more than 80 different tripartite motifs (TRIM) proteins within the E3 ubiquitin ligase subfamily, including proteins that regulate intracellular signaling, apoptosis, autophagy, proliferation, inflammation, and immunity through the ubiquitination of target proteins. Studies conducted in recent years have unraveled the importance of TRIM proteins in the pathophysiology of vascular diseases. In this review, we describe the effects of TRIM proteins on vascular endothelial cells, smooth muscle cells, heart, and lungs. In particular, we discuss the potential mechanisms by which TRIMs regulate diseases and shed light on the potential therapeutic applications of TRIMs.

Kaempferol protects gut-vascular barrier from high glucose-induced disorder via NF-κB pathway

Kaempferol is a natural edible flavonoid reported to treat high-fat diet-induced intestinal inflammation; however, the underlying molecular mechanisms remain unclear. This research aims to investigate the protective effect of kaempferol on the gut-vascular barrier (GVB) induced by high glucose and elucidate the underlying mechanism. Evans blue albumin efflux assay was used to test endothelial cell permeability. The results showed that kaempferol (50 μM) significantly reversed the high glucose-induced monolayer barrier permeability of rat intestinal microvascular endothelial cells (RIMVECs), while kaempferol significantly alleviated the high glucose-induced rarefication of the tight junction protein Claudin-5. Moreover, kaempferol also reduced high glucose-induced angiogenesis and cell migration via inhibiting the VEGFR2/p38 pathway. Kaempferol also protected against high glucose-induced overproduction of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 by inhibiting NF-κB p65 nuclear translocation. In addition, kaempferol had similar effects to the NF-κB inhibitor SN50 in reducing high glucose-induced ICAM-1 expression and endothelial barrier permeabilization. Our findings in part reveal the pathological mechanism of hyperglycemia-related gastrointestinal diseases and underlie the molecular mechanism of kaempferol in inhibiting bowel inflammation from a novel perspective.

MALAT1 regulates network of microRNA-15a/16-VEGFA to promote tumorigenesis and angiogenesis in multiple myeloma

MALAT1 is one of the most hopeful members implicated in angiogenesis in a variety of non-malignant diseases. In multiple myeloma (MM), MALAT1 is recognized as the most highly expressed long non-coding RNA. However, the functional roles of MALAT1 in angiogenesis and the responsible mechanisms have not yet been explored. Herein, we discovered a novel regulatory network dependent on MALAT1 in relation to MM tumorigenesis and angiogenesis. We observed that MALAT1 was upregulated in MM and significantly associated with poor overall survival. MALAT1 knockdown suppressed MM cell proliferation and promoted apoptosis, while restricting endothelial cells angiogenesis. Moreover, MALAT1 directly targeted microRNA-15a/16, and microRNA-15a/16 suppression partly reverted the effects of MALAT1 deletion on MM cells in vitro as well as tumor growth and angiogenesis in vivo. In addition, further study indicated that MALAT1 functioned as a competing endogenous RNA for microRNA-15a/16 to regulate vascular endothelial growth factor A (VEGFA) expression. Our results suggest that MALAT1 plays an important role in the regulatory axis of microRNA-15a/16-VEGFA to promote tumorigenicity and angiogenesis in MM. Consequently, MALAT1 could serve as a novel promising biomarker and a potential antiangiogenic target against MM.

Expression of Long Non-Coding RNAs in Activated Human Retinal Vascular Endothelial Cells

PURPOSE

Retinal endothelial cell activation is a central event in non-infectious posterior uveitis. There is recent interest in long non-coding (lnc)RNA-targeted therapeutics for retinal diseases. We aimed to identify human retinal endothelial cell lncRNAs that might be involved in activation.

METHODS

Eleven candidate lncRNAs were identified: GAS5, KCNQ1OT1, LINC00294, MALAT1, MEG3, MIR155HG, NEAT1, NORAD, OIP5-AS1, SENCR, TUG1. Expression was assessed by RT-PCR in human retinal endothelial cells, at baseline and following activation with interleukin (IL)-1β and tumor necrosis factor (TNF)-α.

RESULTS

IL-1β significantly upregulated MEG3 and SENCR at 4 and 24 hours; LINC00294, NORAD, OIP5-AS1 and TUG1 at 24 hours; and MIR155HG at 4, 24 and 48 hours; but downregulated GAS5 at 24 and 48 hours. TNF-α significantly upregulated KCNQ1OT1, LINC00294, MEG3, NORAD and SENCR at 4 hours; SENCR and TUG1 at 24 hours; and MIR155HG at all time points.

CONCLUSIONS

Future studies involving manipulation of MIR155HG may be warranted to explore potential therapeutic applications for non-infectious posterior uveitis.

Endoplasmic reticulum stress: molecular mechanism and therapeutic targets

The endoplasmic reticulum (ER) functions as a quality-control organelle for protein homeostasis, or "proteostasis". The protein quality control systems involve ER-associated degradation, protein chaperons, and autophagy. ER stress is activated when proteostasis is broken with an accumulation of misfolded and unfolded proteins in the ER. ER stress activates an adaptive unfolded protein response to restore proteostasis by initiating protein kinase R-like ER kinase, activating transcription factor 6, and inositol requiring enzyme 1. ER stress is multifaceted, and acts on aspects at the epigenetic level, including transcription and protein processing. Accumulated data indicates its key role in protein homeostasis and other diverse functions involved in various ocular diseases, such as glaucoma, diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, achromatopsia, cataracts, ocular tumors, ocular surface diseases, and myopia. This review summarizes the molecular mechanisms underlying the aforementioned ocular diseases from an ER stress perspective. Drugs (chemicals, neurotrophic factors, and nanoparticles), gene therapy, and stem cell therapy are used to treat ocular diseases by alleviating ER stress. We delineate the advancement of therapy targeting ER stress to provide new treatment strategies for ocular diseases.

Spotlight on iron and ferroptosis: research progress in diabetic retinopathy

Iron, as the most abundant metallic element within the human organism, is an indispensable ion for sustaining life and assumes a pivotal role in governing glucose and lipid metabolism, along with orchestrating inflammatory responses. The presence of diabetes mellitus (DM) can induce aberrant iron accumulation within the corporeal system. Consequentially, iron overload precipitates a sequence of important adversities, subsequently setting in motion a domino effect wherein ferroptosis emerges as the utmost pernicious outcome. Ferroptosis, an emerging variant of non-apoptotic regulated cell death, operates independently of caspases and GSDMD. It distinguishes itself from alternative forms of controlled cell death through distinctive morphological and biochemical attributes. Its principal hallmark resides in the pathological accrual of intracellular iron and the concomitant generation of iron-driven lipid peroxides. Diabetic retinopathy (DR), established as the predominant cause of adult blindness, wields profound influence over the well-being and psychosocial strain experienced by afflicted individuals. Presently, an abundance of research endeavors has ascertained the pervasive engagement of iron and ferroptosis in the microangiopathy inherent to DR. Evidently, judicious management of iron overload and ferroptosis in the early stages of DR bears the potential to considerably decelerate disease progression. Within this discourse, we undertake a comprehensive exploration of the regulatory mechanisms governing iron homeostasis and ferroptosis. Furthermore, we expound upon the subsequent detriments induced by their dysregulation. Concurrently, we elucidate the intricate interplay linking iron overload, ferroptosis, and DR. Delving deeper, we engage in a comprehensive deliberation regarding strategies to modulate their influence, thereby effecting prospective interventions in the trajectory of DR's advancement or employing them as therapeutic modalities.

Role of Lnc-RNAs in the Pathogenesis and Development of Diabetic Retinopathy

Important advances in diabetic retinopathy (DR) research and management have occurred in the last few years. Neurodegenerative changes before the onset of microvascular alterations have been well established. So, new strategies are required for earlier and more effective treatment of DR, which still is the first cause of blindness in working age. We describe herein gene regulation through Lnc-RNAs as an interesting subject related to DR. Long non-coding RNAs (Lnc-RNAs) are non-protein-coding transcripts larger than 200 nucleotides. Lnc-RNAs regulate gene expression and protein formation at the epigenetic, transcriptional, and translational levels and can impact cell proliferation, apoptosis, immune response, and oxidative stress. These changes are known to take part in the mechanism of DR. Recent investigations pointed out that Lnc-RNAs might play a role in retinopathy development as Metastasis-Associated Lung Adenocarcinoma Transcript (Lnc-MALAT1), Maternally expressed gene 3 (Lnc-MEG3), myocardial-infarction-associated transcript (Lnc-MIAT), Lnc-RNA H19, Lnc-RNA HOTAIR, Lnc-RNA ANRIL B-Raf proto-oncogene (Lnc-RNA BANCR), small nucleolar RNA host gene 16 (Lnc-RNA SNHG16) and others. Several molecular pathways are impacted. Some of them play a role in DR pathophysiology, including the PI3K-Akt signaling axis, NAD-dependent deacetylase sirtuin-1 (Sirti1), p38 mitogen-activated protein kinase (P38/mapk), transforming growth factor beta signaling (TGF-β) and nuclear factor erythroid 2-related factor 2 (Nrf2). The way Lnc-RNAs affect diabetic retinopathy is a question of great relevance. Performing a more in-depth analysis seems to be crucial for researchers if they want to target Lnc-RNAs. New knowledge on gene regulation and biomarkers will enable investigators to develop more specialized therapies for diabetic retinopathy, particularly in the current growing context of precision medicine.

Research progress on the pathogenesis of diabetic retinopathy

Diabetic retinopathy is one of the most common and serious microvascular complications of diabetes mellitus. There are many factors leading to diabetic retinopathy, and its pathogenesis is still unclear. At present, there are still no effective measures for the early treatment of diabetic retinopathy, and the treatment options available when diabetes progresses to advanced stages are very limited, and the treatment results are often unsatisfactory. Detailed studies on the molecular mechanisms of diabetic retinopathy pathogenesis and the development of new therapeutic agents are of great importance. This review describes the potential pathogenesis of diabetic retinopathy for experimental studies and clinical practice.

Roles of non-coding RNAs in eye development and diseases

The prevalence of ocular disorders is dramatically increasing worldwide, especially those that cause visual impairment and permanent loss of vision, including cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy. Extensive evidence has shown that ncRNAs are key regulators in various biogenesis and biological functions, controlling gene expression related to histogenesis and cell differentiation in ocular tissues. Aberrant expression and function of ncRNA can lead to dysfunction of visual system and mediate progression of eye disorders. Here, we mainly offer an overview of the role of precise modulation of ncRNAs in eye development and function in patients with eye diseases. We also highlight the challenges and future perspectives in conducting ncRNA studies, focusing specifically on the role of ncRNAs that may hold expanded promise for their diagnostic and therapeutic applications in various eye diseases. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA in Disease and Development > RNA in Disease RNA in Disease and Development > RNA in Development.

LncRNA MALAT1 knockdown inhibits the development of choroidal neovascularization

In the pathogenesis of age-related macular degeneration, long non-coding RNAs have become important regulators. This study aimed to investigate the role of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in the progression of choroidal neovascularization (CNV) and the underlying mechanisms. The in vivo and in vitro model of CNV was established using laser-induced mouse CNV model and human choroidal vascular endothelial cells (HCVECs) exposed to hypoxia respectively. We explore the role of MALAT1 in the pathogenesis of CNV by using the small interference RNA both in vivo and in vitro. MALAT1 expression was found to be upregulated in the retinal pigment epithelial-choroidal complexes. MALAT1 knockdown inhibited CNV development and leakage in vivo and decreased HCVECs proliferation, migration, and tube formation in vitro. MALAT1 performed the task as a miR-17-5p sponge to regulate the expression of vascular endothelial growth factor A (VEGFA) and E26 transformation specific-1 (ETS1). This study provides a new perspective on the pathogenesis of CNV and suggests that the axis MALAT/miR-17-5p/VEGFA or ETS1 may be an effective therapeutic target for CNV.

Endoplasmic reticulum stress: a novel targeted approach to repair bone defects by regulating osteogenesis and angiogenesis

Bone regeneration therapy is clinically important, and targeted regulation of endoplasmic reticulum (ER) stress is important in regenerative medicine. The processing of proteins in the ER controls cell fate. The accumulation of misfolded and unfolded proteins occurs in pathological states, triggering ER stress. ER stress restores homeostasis through three main mechanisms, including protein kinase-R-like ER kinase (PERK), inositol-requiring enzyme 1ɑ (IRE1ɑ) and activating transcription factor 6 (ATF6), collectively known as the unfolded protein response (UPR). However, the UPR has both adaptive and apoptotic effects. Modulation of ER stress has therapeutic potential for numerous diseases. Repair of bone defects involves both angiogenesis and bone regeneration. Here, we review the effects of ER stress on osteogenesis and angiogenesis, with emphasis on ER stress under high glucose (HG) and inflammatory conditions, and the use of ER stress inducers or inhibitors to regulate osteogenesis and angiogenesis. In addition, we highlight the ability for exosomes to regulate ER stress. Recent advances in the regulation of ER stress mediated osteogenesis and angiogenesis suggest novel therapeutic options for bone defects.

Knockdown of Krüppel-Like Factor 9 Inhibits Aberrant Retinal Angiogenesis and Mitigates Proliferative Diabetic Retinopathy

Advanced proliferative diabetic retinopathy (PDR) characterized by aberrant retinal angiogenesis is a leading cause of retinal detachment and blindness. Krüppel-like factor 9 (KLF9), a member of the zinc-finger family of transcription factors, participates in the development of diabetic nephropathy and the promotion of angiogenesis of human umbilical vein endothelial cells. Therefore, we speculate that KLF9 may exert a crucial role in PDR. The current study revealed that KLF9 was highly expressed in the high glucose (HG)-treated human retinal microvascular endothelial cells (HRMECs) and the retinas of oxygen-induced retinopathy (OIR) rats. Knockdown of KLF9 inhibited the proliferation, migratory capability, invasiveness and tube formation of HG-treated HRMECs. Besides, knockdown of KLF9 decreased the expression of yes-associated protein 1 (YAP1) in HG-treated HRMECs. Dual-luciferase reporter assays confirmed that KLF9 transcriptionally upregulated YAP1 expression. Overexpression of YAP1 reversed the KLF9 silencing-induced repression of HRMEC proliferation and tube formation. Further in vivo evidence demonstrated that knockdown of KLF9 reduced the expression of Ki67, CD31 and vascular endothelial growth factor A (VEGFA) in the retinas of OIR rats. Collectively, KLF9 silencing might mitigate the progression of PDR by inhibiting angiogenesis via blocking YAP1 transcription.

Aberrant lncRNA expression in patients with proliferative diabetic retinopathy: preliminary results from a single-center observational study

BACKGROUND

Diabetic retinopathy (DR) is a leading cause of blindness. Vision threat is particularly severe in patients with retinal neovascularization. However, little is known about the role of long noncoding RNAs (lncRNAs) in proliferative diabetic retinopathy (PDR). The goal of this study was to identify lncRNAs involved in PDR.

METHODS

We compared lncRNA expression profiles in the vitreous between patients with PDR and those with idiopathic macular hole (IMH) and between patients with PDR who had received anti-vascular endothelial growth factor (VEGF) therapy and those who had not. Vitreous samples from patients with PDR and IMH were screened for lncRNAs using microarray-based analysis, and quantitative real-time polymerase chain reaction (qRT-PCR) was used to confirm the microarray results. Bioinformatic analysis was also performed. Moreover, the effect of anti-VEGF therapy was investigated in vitreous samples of patients with PDR treated with anti-VEGF therapy and those who were not.

RESULTS

A total of 1067 differentially expressed noncoding RNA transcripts were found during screening in the vitreous humor of patients with PDR than in those with IMH. Five lncRNAs were subjected to qRT-PCR. RP11-573 J24.1, RP11-787B4.2, RP11-654G14.1, RP11-2A4.3, and RP11-502I4.3 were significantly downregulated; this was validated by the comparison using the microarray data. In addition, 835 differentially expressed noncoding RNA transcripts were found during screening in the vitreous humor of patients with PDR treated with anti-VEGF therapy compared with untreated PDR patients. RP4-631H13.2 was significantly upregulated, which is consistent with the trend of the microarray analysis.

CONCLUSIONS

There were systemic expression differences in the vitreous at the microarray level between patients with PDR and those with IMH and between patients with PDR after anti-VEGF treatment and those that did not receive anti-VEGF treatment. LncRNAs identified in the vitreous humor may be a novel research field for PDR.

Long non-coding RNAs in retinal neovascularization: current research and future directions

PURPOSE

Retinal neovascularization (RNV) is an intractable pathological hallmark of numerous ocular blinding diseases, including diabetic retinopathy, retinal vein occlusion, and retinopathy of prematurity. However, current therapeutic methods have potential side effects and limited efficacy. Thus, further studies on the pathogenesis of RNV-related disorders and novel therapeutic targets are critically required. Long non-coding RNAs (lncRNAs) have various functions and participate in almost all biological processes in living cells, such as translation, transcription, signal transduction, and cell cycle control. In addition, recent research has demonstrated critical modulatory roles of various lncRNAs in RNV. In this review, we summarize current knowledge about the expression and regulatory functions of lncRNAs related to the progression of pathological RNV.

METHODS

We searched databases such as PubMed and Web of Science to gather and review information from the published literature.

CONCLUSIONS

In general, lncRNA MEG3 attenuates RNV, thus protecting the retina from excessive and dysregulated angiogenesis under high glucose stress. In contrast, lncRNAs MALAT1, MIAT, ANRIL, HOTAIR, HOTTIP, and SNHG16, have been identified as causative molecules in the pathological progression of RNV. Comprehensive and in-depth studies of the roles of lncRNAs in RNV indicate that targeting lncRNAs may be an alternative therapeutic approach in the near future, enabling new options for attenuating RNV progression and treating RNV-related retinal diseases.

Salubrinal Ameliorates Inflammation and Neovascularization via the Caspase 3/Enos Signaling in an Alkaline-Induced Rat Corneal Neovascularization Model

Background and Objectives: Ocular alkaline burn is a clinical emergency that can cause permanent vision loss due to limbal stem cell deficiency and corneal neovascularization (CNV). Although the basic pathogenetic mechanisms are considered to be acute oxidative stress and corneal neovascularization triggered by inflammation, the underlying intracellular mechanisms have not been clearly elucidated. The aim of this study was to investigate the role of endoplasmic reticulum (ER) stress on inflammation and neovascularization, and the effect of the ER stress inhibitor salubrinal (SLB), as a novel treatment in a corneal alkaline burn model in rats. Methods: Chemical burns were created by cautery for 4 s using a rod coated with 75% silver nitrate and 25% potassium nitrate in the corneal center for the corneal neovascularization (CNV) model. Twenty-eight Wistar albino rats were divided into four groups: SHAM, CNV, CNV + SLB, and CNV + bevacizumab (BVC). After the CNV model was applied to the right eye, a single subconjunctival dose (0.05 mL) of 1 mg/kg salubrinal was injected into both eyes in the CNV + SLB group. A total of 1.25 mg/mL of subconjunctival BVC was administered to the CNV + BVC group. Fourteen days after experimental modeling and drug administration, half of the globes were placed in liquid nitrogen and stored at -20 °C until biochemical analysis. The remaining tissues were collected and fixed in 10% buffered formalin for histopathological and immunohistochemical analysis. Three qualitative agents from three different pathways were chosen: TNFR for inflammation, endothelial nitric oxide synthase (e-NOS) for vascular endothelial growth factor (VEGF)-mediated vascular permeability, and caspase-3 for cellular apoptosis. Results: Significantly lower caspase-3 and eNOS levels were detected in the CNV + SLB and CNV + BVC groups than in the CNV group. Additionally, histopathological evaluation revealed a significant decrease in neovascularization, inflammatory cell infiltration, and fibroblast activity in the CNV + SLB and CNV + BVC groups. The endoplasmic reticulum stress inhibitor, salubrinal, administered to the treatment group, attenuated apoptosis (caspase-3) and inflammation (e-NOS). In the control group (left eyes of the SLB group), salubrinal did not have a toxic effect on the healthy corneas. Conclusion: The ER stress pathway plays an important role in angiogenesis after alkaline corneal burns, and treatment with SLB modulates this pathway, reducing caspase-3 and eNOS levels. Further studies are needed to understand the molecular mechanisms altered by SLB-mediated therapy. The fact that more than one mechanism plays a role in the pathogenesis of CNV may require the use of more than one molecule in treatment. SLB has the potential to affect multiple steps in CNV pathogenesis, both in terms of reducing ER stress and regulating cellular homeostasis by inhibiting the core event of integrated stress response (ISR). Therefore, it can be used as a new treatment option and as a strengthening agent for existing treatments. Although blockade of intracellular organelle stress pathways has shown promising results in experimental studies, more in-depth research is needed before it can be used in routine practice. To the best of our knowledge, this study is the first to report the role of ER stress in corneal injury.

Ascorbic acid protects retinal pigment epithelial cells from high glucose by inhibiting the NF-κB signal pathway through MALAT1/IGF2BP3 axis

BACKGROUND

Diabetic retinopathy (DR) is a common complication of diabetes with nocuous effects on patients' eye health, typically accompanies by excessive inflammation and oxidative stress. Insulin-like growth factor-2 messenger RNA-binding protein 3 (IGF2BP3) was engaged with inflammation, whereas its precise role in the DR process was unclear. And enhanced lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and decreased ascorbic acid (AA) were also found in DR. This study was to explore the regulatory role and mechanism of IGF2BP3, MALAT1 and AA in the high glucose (HG)-induced retinal pigment epithelial (RPE) cell injury.

METHODS

ARPE-19 cells were treated with HG to establish the in vitro RPE cell injury model. The mRNA and protein levels of the gene were evaluated by qRT-PCR or Western blot. Immunofluorescence detected the translocation condition of the p65 protein. Inflammatory factor levels were detected by ELISA assays. Apoptosis was detected by flow cytometry. The binding interaction of IGF2BP3 and MALAT1 was validated by RIP-qPCR assays.

RESULTS

In HG-induced RPE cell injury, IGF2BP3 expression, inflammatory response and apoptosis were enhanced. Next, the IGF2BP3 activated the NF-κB signalling to promote the RPE cell injury development. MALAT1 could directly bind with IGF2BP3 and up-regulate its expression. In addition, AA ameliorated the HG-induced RPE cell injury through the regulation of MALAT1.

CONCLUSION

Ascorbic acid ameliorated HG-induced RPE cell injury by repressing the NF-κB signalling pathway via modulating the MALAT1/IGF2BP3 axis.

Role of Long Non-Coding RNA in Regulating ER Stress Response to the Progression of Diabetic Complications

Chronic hyperglycemia damages the nerves and blood vessels, culminating in other vascular complications. Such complications enhance cytokine, oxidative and endoplasmic reticulum (ER) stress. ER is the primary organelle where proteins are synthesised and attains confirmatory changes before its site of destination. Perturbation of ER homeostasis activates signaling sensors within its lumen, the unfolded protein response (UPR) that orchestrates ER stress and is extensively studied. Increased ER stress markers are reported in diabetic complications in addition to lncRNA that acts as an upstream marker inducing ER stress response. This review focuses on the mechanisms of lncRNA that regulate ER stress markers, especially during the progression of diabetic complications. Through this systemic review, we showcase the dysfunctional lncRNAs that act as a leading cause of ER stress response to the progression of diabetic complications.

Gastric Cancer Cell-Derived Exosomal GRP78 Enhances Angiogenesis upon Stimulation of Vascular Endothelial Cells

Exosomes containing glucose-regulated protein 78 (GRP78) are involved in cancer malignancy. GRP78 is thought to promote the tumor microenvironment, leading to angiogenesis. No direct evidence for this role has been reported, however, mainly because of difficulties in accurately measuring the GRP78 concentration in the exosomes. Recently, exosomal GRP78 concentrations were successfully measured using an ultrasensitive ELISA. In the present study, GRP78 concentrations in exosomes collected from gastric cancer AGS cells with overexpression of GRP78 (OE), knockdown of GRP78 (KD), or mock GRP78 (mock) were quantified. These three types of exosomes were then incubated with vascular endothelial cells to examine their effects on endothelial cell angiogenesis. Based on the results of a tube formation assay, GRP78-OE exosomes accelerated angiogenesis compared with GRP78-KD or GRP78-mock exosomes. To investigate the mechanisms underlying this effect, we examined the Ser473 phosphorylation state ratio of AKT, which is involved in the angiogenesis process, and found that AKT phosphorylation was increased by GRP78-OE exosome application to the endothelial cells. An MTT assay showed that GRP78-OE exosome treatment increased the proliferation rate of endothelial cells, and a wound healing assay showed that this treatment increased the migration capacity of the endothelial cells. These findings demonstrated that GRP78-containing exosomes promote the tumor microenvironment and induce angiogenesis.

MG53 represses high glucose-induced inflammation and angiogenesis in human retinal endothelial cells by repressing the EGR1/STAT3 axis

BACKGROUND

Diabetic retinopathy (DR) is a vascular complication of diabetes mellitus that leads to visual injury and blindness. Both angiogenesis and inflammation play an important role in the pathogenesis of DR. Here we aimed to explore the mechanisms of mitsugumin 53 (MG53) in ameliorating the dysfunction induced by high glucose (HG) in humans retinal microvascular endothelial cells (HRECs).

METHODS

HRECs were subjected to HG in the presence or absence of MG53 overexpression. The effect of MG53 on cell viability and inflammatory response in HG-treated HRECs was measured using the Cell Counting Kit-8 and ELISAs, respectively. Expression of MG53, EGR1, p-STAT3, FGF2, TGFB1, and Angiopoietin-1 in HG-treated HRECs was quantified by western blot or quantitative real-time polymerase chain reaction.

RESULTS

HG significantly downregulated MG53 in HRECs, which reduced cell viability while inducing angiogenesis and inflammatory response. Upregulation of MG53 reversed these effects of HG. MG53 directly interacted with EGR1 and repressed its expression, which decreased phosphorylation of STAT3 and downregulated FGF2, TGFB1, and Angiopoietin-1. EGR1 up-regulation or STAT3 activation antagonized the protective effects of MG53.

CONCLUSION

MG53 alleviates HG-induced dysfunction in HRECs by repressing EGR1/STAT3 signaling. Thereby MG53 may have therapeutic potential in DR.

Long non-coding RNA CATIP antisense RNA 1 (lncRNA CATIP-AS1) downregulation contributes to the progression and metastasis of thyroid cancer via epithelial-mesenchymal transition (EMT) pathway

Thyroid cancer (THCA) is the most common cancer of the endocrine system across the globe. To date, the mechanism of development of THCA remains scarcely known. In this study, we aim to elucidate the long non-coding RNA CATIP antisense RNA 1 (lncRNA CATIP-AS1/CATIP-AS1) role in the pathogenesis of THCA and its regulatory mechanism. The result shows that the CATIP-AS1 was significantly downregulated in THCA tissues and cells and was associated with a poor prognosis of patients diagnosed with THCA. The overexpression of CATIP-AS1 significantly inhibited THCA cell proliferation, migration, and epithelial–mesenchymal transition (EMT) but increased the THCA cell apoptosis. We found that CATIP-AS1 endogenously sponges miR-515-5p and its overexpression could inhibit miR-515-5p regulatory effect. Moreover, the overexpression of miR-515-5p repressed the Smad4 expression level, consequently reversed the inhibiting effect of overexpressed CATIP-AS1 on the proliferation, and migration of THCA cell. It also reversed the increased THCA cell apoptosis and the downregulated-CATIP-AS1-induced cell EMT inhibition. Summarily, we demonstrated that the CATIP-AS1 promotes the progression and metastasis of THCA via EMT pathway partly through regulating the miR-515-5p and Smad4 expression in THCA cell. The CATIP-AS1 could be a promising biomarker for early THCA detection and prognosis and a possible therapeutic target for its treatment.

The lncRNA Malat1 regulates microvascular function after myocardial infarction in mice via miR-26b-5p/Mfn1 axis-mediated mitochondrial dynamics

RATIONALE

Myocardial infarction (MI) is a leading cause of cardiovascular mortality globally. The improvement of microvascular function is critical for cardiac repair after MI. Evidence now points to long non-coding RNAs (lncRNAs) as key regulators of cardiac remodelling processes. The lncRNA Malat1 is involved in the development and progression of multiple cardiac diseases. Studies have shown that Malat1 is closely related to the regulation of endothelial cell regeneration. However, the potential molecular mechanisms of Malat1 in repairing cardiac microvascular dysfunction after MI remain unreported.

METHODS AND RESULTS

The present study found that Malat1 is upregulated in the border zone of infarction in mouse hearts, as well as in isolated cardiac microvascular endothelial cells (CMECs). Targeted knockdown of Malat1 in endothelial cells exacerbated oxidative stress, attenuated angiogenesis and microvascular perfusion, and as a result decreased cardiac function in MI mice. Further studies showed that silencing Malat1 obviously inhibited CMEC proliferation, migration and tube formation, which was at least in part attributed to disturbed mitochondrial dynamics and activation of the mitochondrial apoptosis pathway. Moreover, bioinformatic analyses, luciferase assays and pull-down assays indicated that Malat1 acted as a competing endogenous RNA (ceRNA) for miR-26b-5p and formed a signalling axis with Mfn1 to regulate mitochondrial dynamics and endothelial functions. Overexpression of Mfn1 markedly reversed the microvascular dysfunction and CMEC injuries that were aggravated by silencing Malat1 via inhibition of excessive mitochondrial fragments and mitochondria-dependent apoptosis.

CONCLUSIONS

The present study elucidated the functions and mechanisms of Malat1 in cardiac microcirculation repair after MI. The underlying mechanisms of the effects of Malat1 could be attributed to its blocking effects on miR-26b-5p/Mfn1 pathway-mediated mitochondrial dynamics and apoptosis.

miRNA, lncRNA and circRNA: Targeted Molecules Full of Therapeutic Prospects in the Development of Diabetic Retinopathy

Diabetic retinopathy (DR) is a common diabetic complication and the main cause of blindness worldwide, which seriously affects the quality of life of patients. Studies have shown that noncoding RNA (ncRNA) has distinct differentiated expression in DR and plays an important role in the occurrence and development of DR. ncRNAs represented by microRNAs (miRNAs), lncRNAs (lncRNAs), and circRNAs (circRNAs) have been shown to be widely involved in the regulation of gene expression and affect multiple biological processes of retinopathy. This article will review three RNAs related to the occurrence and development of DR on the basis of previous studies (especially their effects on retinal microangiopathy, retinal pigment epithelial cells, and retinal nerve cells) and discuss their underlying mechanisms and connections. Overall, this review will help us better understand the role of ncRNAs in the occurrence and development of DR and provide ideas for exploring potential therapeutic directions and targets.

Long Noncoding RNA MALAT1 and Regulation of the Antioxidant Defense System in Diabetic Retinopathy

The retina experiences increased oxidative stress in diabetes, and the transcriptional activity of Nrf2, which is critical in regulating many antioxidant genes, is decreased. The nuclear movement/transcriptional activity of Nrf2 is mediated by its intracellular inhibitor Keap1, and retinal Keap1 levels are increased in diabetes. Gene expression is also regulated by long noncoding RNAs (LncRNAs). Our aim was to investigate the role of LncRNA MALAT1 in the regulation of Keap1-Nrf2-antioxidant defense in diabetic retinopathy. LncRNA MALAT1 expression (quantitative real-time PCR, immunofluorescence, and RNA sequencing), its interactions with Keap1 (FACS), Keap1-Nrf2 interactions, and transcription of the antioxidant response genes (immunofluorescence and nuclear RNA sequencing) were investigated in retinal endothelial cells exposed to high glucose. Glucose increased LncRNA MALAT1 levels by increasing Sp1 transcription factor binding at its promoter. Downregulation of LncRNA MALAT1 by its siRNA prevented glucose-induced increase in Keap1 and facilitated Nrf2 nuclear translocation and antioxidant gene transcription. Retinal microvessels from streptozotocin-induced diabetic mice and human donors with diabetic retinopathy also presented similar increases in LncRNA MALAT1 and its interactions with Keap1 and decreases in Nrf2-mediated antioxidant defense genes. Thus, LncRNA MALAT1, via Keap1-Nrf2, regulates antioxidant defense in diabetic retinopathy. Inhibition of LncRNA MALAT1 has potential to protect the retina from oxidative damage and to prevent or slow down diabetic retinopathy.