microRNA-182 Mediates Sirt1-Induced Diabetic Corneal Nerve Regeneration

NEAT1 Deficiency Promotes Corneal Epithelial Wound Healing by Activating cAMP Signaling Pathway

Purpose

This study aimed to investigate the role of the long non-coding RNA (lncRNA) NEAT1 in corneal epithelial wound healing in mice.

Methods

The central corneal epithelium of wild-type (WT), MALAT1 knockout (M-KO), NEAT1 knockout (N-KO), and NEAT1 knockdown (N-KD) mice was scraped to evaluate corneal epithelial and nerve regeneration rates. RNA sequencing of the corneal epithelium from WT and N-KO mice was performed 24 hours after debridement to determine the role of NEAT1. Quantitative PCR (qPCR) and ELISA were used to confirm the bioinformatic analysis. The effects of the cAMP signaling pathway were evaluated in N-KO and N-KD mice using SQ22536, an adenylate cyclase inhibitor.

Results

Central corneal epithelial debridement in N-KO mice significantly promoted epithelial and nerve regeneration rates while suppressing inflammatory cell infiltration. Furthermore, the expression of Atp1a2, Ppp1r1b, Calm4, and Cngb1, which are key components of the cAMP signaling pathway, was upregulated in N-KO mice, indicative of its activation. Furthermore, the cAMP pathway inhibitor SQ22536 reversed the accelerated corneal epithelial wound healing in both N-KO and N-KD mice.

Conclusions

NEAT1 deficiency contributes to epithelial repair during corneal wound healing by activating the cAMP signaling pathway, thereby highlighting a potential therapeutic strategy for corneal epithelial diseases.

Metabolic memory: mechanisms and diseases

Metabolic diseases and their complications impose health and economic burdens worldwide. Evidence from past experimental studies and clinical trials suggests our body may have the ability to remember the past metabolic environment, such as hyperglycemia or hyperlipidemia, thus leading to chronic inflammatory disorders and other diseases even after the elimination of these metabolic environments. The long-term effects of that aberrant metabolism on the body have been summarized as metabolic memory and are found to assume a crucial role in states of health and disease. Multiple molecular mechanisms collectively participate in metabolic memory management, resulting in different cellular alterations as well as tissue and organ dysfunctions, culminating in disease progression and even affecting offspring. The elucidation and expansion of the concept of metabolic memory provides more comprehensive insight into pathogenic mechanisms underlying metabolic diseases and complications and promises to be a new target in disease detection and management. Here, we retrace the history of relevant research on metabolic memory and summarize its salient characteristics. We provide a detailed discussion of the mechanisms by which metabolic memory may be involved in disease development at molecular, cellular, and organ levels, with emphasis on the impact of epigenetic modulations. Finally, we present some of the pivotal findings arguing in favor of targeting metabolic memory to develop therapeutic strategies for metabolic diseases and provide the latest reflections on the consequences of metabolic memory as well as their implications for human health and diseases.

Diabetic Keratopathy: Redox Signaling Pathways and Therapeutic Prospects

Diabetes mellitus, the most prevalent endocrine disorder, not only impacts the retina but also significantly involves the ocular surface. Diabetes contributes to the development of dry eye disease and induces morphological and functional corneal alterations, particularly affecting nerves and epithelial cells. These changes manifest as epithelial defects, reduced sensitivity, and delayed wound healing, collectively encapsulated in the context of diabetic keratopathy. In advanced stages of this condition, the progression to corneal ulcers and scarring further unfolds, eventually leading to corneal opacities. This critical complication hampers vision and carries the potential for irreversible visual loss. The primary objective of this review article is to offer a comprehensive overview of the pathomechanisms underlying diabetic keratopathy. Emphasis is placed on exploring the redox molecular pathways responsible for the aberrant structural changes observed in the cornea and tear film during diabetes. Additionally, we provide insights into the latest experimental findings concerning potential treatments targeting oxidative stress. This endeavor aims to enhance our understanding of the intricate interplay between diabetes and ocular complications, offering valuable perspectives for future therapeutic interventions.

Inhibition of miR-542-3p augments autophagy to promote diabetic corneal wound healing

BACKGROUND

Autophagy has recently been shown to be critical for protecting peripheral nerve regeneration. This study explored the impact of miR-542-3p on diabetic corneal nerve regeneration and epithelial healing through the regulation of autophagy.

METHODS

A type 1 diabetes model was established in male mice through streptozotocin administration. Immunofluorescence staining of β-Tubulin III and sodium fluorescein staining were performed to observe corneal nerve fiber density and corneal epithelial healing, respectively. Western blotting, immunofluorescence and transmission electron microscopy were used to determine autophagy levels. Subconjunctival injection of RAPA and 3-MA altered autophagy levels; with them, we evaluated the role of autophagy in diabetic keratopathy. miRNA sequencing and bioinformatics analysis were performed to identify miRNA-mRNA networks with potential autophagy-regulating roles, and miR-542-3p was measured by quantitative real-time polymerase chain reaction (qRT-PCR). miR-542-3p antagomir was injected subconjunctivally to assess the role in diabetic corneal neuropathy.

RESULTS

Our data suggest that autophagy is suppressed in the diabetic corneal nerve and that activation of autophagy promotes diabetic corneal wound healing. We identified a potential autophagy-regulating miRNA-mRNA network in the diabetic trigeminal ganglion, in which miR-542-3p expression was significantly upregulated. Inhibition of miR-542-3p significantly enhanced the level of autophagy in trigeminal ganglion by upregulating ATG4D expression, thereby accelerating diabetic corneal nerve regeneration and epithelial healing.

CONCLUSIONS

Dysregulated autophagy is an important contributor to delayed diabetic corneal injury healing. Inhibiting miR-542-3p promotes diabetic corneal nerve regeneration and epithelial healing through autophagy activation by ATG4D.

Expression patterns of lncRNA MALAT-1 in SARS-COV-2 infection and its potential effect on disease severity via miR-200c-3p and SIRT1

Downregulating Angiotensin Converting Enzyme2 (ACE2) expression may be a shared mechanism for RNA viruses.

Aim

Evaluate the expressions of ACE2 effectors: the long non-coding RNA 'MALAT-1', the micro-RNA 'miR-200c-3p' and the histone deacetylase 'SIRT1' in SARS-COV-2 patients and correlate to disease severity. Sera samples from 98 SARS-COV-2 patients and 30 healthy control participants were collected. qRT-PCR was used for MALAT-1 and miR-200c-3p expression. SIRT1 was measured using ELISA.

Results

In sera of COVID-19 patients, gene expression of miR-200c-3p is increased while MALAT-1 is decreased. SIRT1 protein level is decreased (P value < 0.001). Findings are accentuated with increased disease severity. Serum MALAT-1, miR-200c-3p and SIRT1 could be used as diagnostic markers at cut off values of 0.04 (95.9 % sensitivity), 5.59 (94.9 % sensitivity, 99 % specificity), and 7.4 (98 % sensitivity) respectively. A novel MALAT-1-miR-200c-3p-SIRT1 pathway may be involved in the regulation of SARS-COV-2 severity.

Oxidative Stress and Epigenetics: miRNA Involvement in Rare Autoimmune Diseases

Autoimmune diseases (ADs) such as Sjögren’s syndrome, Kawasaki disease, and systemic sclerosis are characterized by chronic inflammation, oxidative stress, and autoantibodies, which cause joint tissue damage, vascular injury, fibrosis, and debilitation. Epigenetics participate in immune cell proliferation and differentiation, which regulates the development and function of the immune system, and ultimately interacts with other tissues. Indeed, overlapping of certain clinical features between ADs indicate that numerous immunologic-related mechanisms may directly participate in the onset and progression of these diseases. Despite the increasing number of studies that have attempted to elucidate the relationship between miRNAs and oxidative stress, autoimmune disorders and oxidative stress, and inflammation and miRNAs, an overall picture of the complex regulation of these three actors in the pathogenesis of ADs has yet to be formed. This review aims to shed light from a critical perspective on the key AD-related mechanisms by explaining the intricate regulatory ROS/miRNA/inflammation axis and the phenotypic features of these rare autoimmune diseases. The inflamma-miRs miR-155 and miR-146, and the redox-sensitive miR miR-223 have relevant roles in the inflammatory response and antioxidant system regulation of these diseases. ADs are characterized by clinical heterogeneity, which impedes early diagnosis and effective personalized treatment. Redox-sensitive miRNAs and inflamma-miRs can help improve personalized medicine in these complex and heterogeneous diseases.

Investigation of the Protective Effect of Extracellular Vesicle miR-124 on Retinal Ganglion Cells Using a Photolabile Paper-Based Chip

Purpose

Photolabile paper-based chips were developed to isolate extracellular vesicles (EVs) from small-volume samples (less than 30 µL), such as vitreous humor. Putative neuroprotective effects of EVs' microRNAs were investigated by using the paper chip and a rodent model with nonarteritic anterior ischemic optic neuropathy (rNAION).

Methods

rNAION was established using laser-induced photoactivation of rose bengal administered intravenously. On days 0, 0.25, 1, 3, and 7 after rNAION induction, CD63-positive EV microRNAs (CD63+-EV miRNAs) in vitreous humor samples were enriched using the paper chip and assessed using microarray and quantitative RT-PCR analyses. The viability and visual function of retinal ganglion cells (RGCs) were further assessed by measuring photopic flash visual evoked potentials (FVEPs).

Results

We identified 38 different variations of CD63+-EV miRNAs with more than twofold altered expressions. Among them, M1-related miRNA, mR-31a-5p, and M2-related miRNA, miR-125a-5p, miR-182, miR-181a-5p, and miR-124-3, were capable of coordinating anti-inflammatory reactions during rNAION because of their capacity to activate macrophages. In particular, miR-124, having the most dramatic alteration of gene expression, was synthesized and injected intravitreally. Compared to controls, rats that received miR-124 had shown increased RGC survivability and improved visual function.

Conclusions

Our research team has developed a paper-based chip capable of capturing EVs that can be released after UV exposure. The quantity and quality of EV-miRNAs extracted are adequate for microarray and quantitative RT-PCR analyses. Animal studies suggest that miR-124 may play a neuroprotective role in the natural recovery of rNAION and holds the potential to be a novel treatment option.

MicroRNAs in the Regulation of NADPH Oxidases in Vascular Diabetic and Ischemic Pathologies: A Case for Alternate Inhibitory Strategies?

Since their discovery in the vasculature, different NADPH oxidase (NOX) isoforms have been associated with numerous complex vascular processes such as endothelial dysfunction, vascular inflammation, arterial remodeling, and dyslipidemia. In turn, these often underlie cardiovascular and metabolic pathologies including diabetes mellitus type II, cardiomyopathy, systemic and pulmonary hypertension and atherosclerosis. Increasing attention has been directed toward miRNA involvement in type II diabetes mellitus and its cardiovascular and metabolic co-morbidities in the search for predictive and stratifying biomarkers and therapeutic targets. Owing to the challenges of generating isoform-selective NOX inhibitors (NOXi), the development of specific NOXis suitable for therapeutic purposes has been hindered. In that vein, differential regulation of specific NOX isoforms by a particular miRNA or combina-tion thereof could at some point become a reasonable approach for therapeutic targeting under some circumstances. Whereas administration of miRNAs chronically, or even acutely, to patients poses its own set of difficulties, miRNA-mediated regulation of NOXs in the vasculature is worth surveying. In this review, a distinct focus on the role of miRNAs in the regulation of NOXs was made in the context of type II diabetes mellitus and ischemic injury models.

Circulating salivary and serum miRNA-182, 320a, 375 and 503 expression levels in type 2 diabetes

Aim

Early-stage diagnosis of diabetes through non-invasive and diagnostic biofluid-like saliva has become a very popular approach to facilitate future preventive interventions and improve patient care. Meanwhile, the alteration of small non-coding RNA in human fluids has been suggested as a probable precedent for the early stages of diabetes.

Methods

In the present study, we checked the expression of miR-320a, 182-5p, 503, and 375 by using quantitative PCR in both stimulated and unstimulated saliva and blood samples of 40 adult patients with type-2 diabetes compared to 40 healthy individuals. In addition, we have sought to understand the possibility that miRNAs could provide new information about the status of type 2 diabetes in salivary samples beyond what can now be identified from blood samples and link their expression to the presence of clinically relevant risk factors. For this purpose, we have used a set of multivariate models.

Results

The results showed that three miRNAs were more highly expressed in patients with type 2 diabetes, while miR-320-a was down-regulated in those patients compared to healthy subjects. Furthermore, the data showed that miR-320a was the most reliable predictor for distinguishing diabetic patients from healthy subjects, with AUCs of 0.997, 0.97, and 0.99 (97.4% sensitivity and 100% specificity, p = 0.001) for serum, unstimulated, and stimulated saliva samples, respectively.

Conclusions

Interestingly, the results of this study indicated that the amount of four miRNAs expressed in stimulated saliva was the same as in serum samples, which could conclude that specific miR-320a and 503 in stimulated saliva may introduce credible, non-invasive, and diagnostic biomarkers that can be used to monitor diabetic patients' status, while there is a need to design more research studies to confirm these findings.

The impact of sensory neuropathy and inflammation on epithelial wound healing in diabetic corneas

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes, with several underlying pathophysiological mechanisms, some of which are still uncertain. The cornea is an avascular tissue and sensitive to hyperglycemia, resulting in several diabetic corneal complications including delayed epithelial wound healing, recurrent erosions, neuropathy, loss of sensitivity, and tear film changes. The manifestation of DPN in the cornea is referred to as diabetic neurotrophic keratopathy (DNK). Recent studies have revealed that disturbed epithelial-neural-immune cell interactions are a major cause of DNK. The epithelium is supplied by a dense network of sensory nerve endings and dendritic cell processes, and it secretes growth/neurotrophic factors and cytokines to nourish these neighboring cells. In turn, sensory nerve endings release neuropeptides to suppress inflammation and promote epithelial wound healing, while resident immune cells provide neurotrophic and growth factors to support neuronal and epithelial cells, respectively. Diabetes greatly perturbs these interdependencies, resulting in suppressed epithelial proliferation, sensory neuropathy, and a decreased density of dendritic cells. Clinically, this results in a markedly delayed wound healing and impaired sensory nerve regeneration in response to insult and injury. Current treatments for DPN and DNK largely focus on managing the severe complications of the disease. Cell-based therapies hold promise for providing more effective treatment for diabetic keratopathy and corneal ulcers.

Role of miRNAs in diabetic neuropathy: mechanisms and possible interventions

Accelerating cases of diabetes worldwide have given rise to higher incidences of diabetic complications. MiRNAs, a much-explored class of non-coding RNAs, play a significant role in the pathogenesis of diabetes mellitus by affecting insulin release, β-cell proliferation, and dysfunction. Besides, disrupted miRNAs contribute to various complications, diabetic retinopathy, nephropathy, and neuropathy as well as severe conditions like diabetic foot. MiRNAs regulate various processes involved in diabetic complications like angiogenesis, vascularization, inflammations, and various signaling pathways like PI3K, MAPK, SMAD, and NF-KB signaling pathways. Diabetic neuropathy is the most common diabetic complication, characterized mainly by pain and numbness, especially in the legs and feet. MiRNAs implicated in diabetic neuropathy include mir-9, mir-106a, mir-146a, mir-182, miR-23a and b, miR-34a, and miR-503. The diabetic foot is the most common diabetic neuropathy, often leading to amputations. Mir-203, miR-23c, miR-145, miR-29b and c, miR-126, miR-23a and b, miR-503, and miR-34a are associated with diabetic foot. This review has been compiled to summarize miRNA involved in initiation, progression, and miRNAs affecting various signaling pathways involved in diabetic neuropathy including the diabetic foot. Besides, potential applications of miRNAs as biomarkers and therapeutic targets in this microvascular complication will also be discussed.

Mechanistic investigations of diabetic ocular surface diseases

With the global prevalence of diabetes mellitus over recent decades, more patients suffered from various diabetic complications, including diabetic ocular surface diseases that may seriously affect the quality of life and even vision sight. The major diabetic ocular surface diseases include diabetic keratopathy and dry eye. Diabetic keratopathy is characterized with the delayed corneal epithelial wound healing, reduced corneal nerve density, decreased corneal sensation and feeling of burning or dryness. Diabetic dry eye is manifested as the reduction of tear secretion accompanied with the ocular discomfort. The early clinical symptoms include dry eye and corneal nerve degeneration, suggesting the early diagnosis should be focused on the examination of confocal microscopy and dry eye symptoms. The pathogenesis of diabetic keratopathy involves the accumulation of advanced glycation end-products, impaired neurotrophic innervations and limbal stem cell function, and dysregulated growth factor signaling, and inflammation alterations. Diabetic dry eye may be associated with the abnormal mitochondrial metabolism of lacrimal gland caused by the overactivation of sympathetic nervous system. Considering the important roles of the dense innervations in the homeostatic maintenance of cornea and lacrimal gland, further studies on the neuroepithelial and neuroimmune interactions will reveal the predominant pathogenic mechanisms and develop the targeting intervention strategies of diabetic ocular surface complications.

Role of the AMPK signalling pathway in the aetiopathogenesis of ocular diseases

BACKGROUND

AMP-activated protein kinase (AMPK) plays a precise role as a master regulator of cellular energy homeostasis. AMPK is activated in response to the signalling cues that exhaust cellular ATP levels such as hypoxia, ischaemia, glucose depletion and heat shock. As a central regulator of both lipid and glucose metabolism, AMPK is considered to be a potential therapeutic target for the treatment of various diseases, including eye disorders.

OBJECTIVE

To review all the shreds of evidence concerning the role of the AMPK signalling pathway in the pathogenesis of ocular diseases.

METHOD

Scientific data search and review of available information evaluating the influence of AMPK signalling on ocular diseases.

RESULTS

Review highlights the significance of AMPK signalling in the aetiopathogenesis of ocular diseases, including cataract, glaucoma, diabetic retinopathy, retinoblastoma, age-related macular degeneration, corneal diseases, etc. The review also provides the information on the AMPK-associated pathways with reference to ocular disease, which includes mitochondrial biogenesis, autophagy and regulation of inflammatory response.

CONCLUSION

The study concludes the role of AMPK in ocular diseases. There is growing interest in the therapeutic utilization of the AMPK pathway for ocular disease treatment. Furthermore, inhibition of AMPK signalling might represent more pertinent strategy than AMPK activation for ocular disease treatment. Such information will guide the development of more effective AMPK modulators for ocular diseases.[Formula: see text].

Ginsenoside Rg1 promoted the wound healing in diabetic foot ulcers via miR-489-3p/Sirt1 axis

PURPOSE

Diabetic foot ulcers (DFUs) are common complications of high severity for diabetes. Ginsenoside Rg1 (Rg1) has the potential for diabetes and cardiovascular diseases therapy. This research aimed at exploring the regulation of Rg1 on DFUs treatment and the underlying mechanism.

METHODS

Human umbilical vein endothelial cells (HUVECs) incubated with high-glucose culture medium were established for induction of diabetes model. The MTT assay, Annexin V/PI assay and oxidative stress detection were carried out on high-glucose-induced HUVECs. Dual-luciferase reporter assay was performed to prove the interaction of miR-489-3p and Sirt1. DFUs model was established to determine the efficiency of Rg1 and miR-489-3p in wound closure of DFUs in vivo.

RESULTS

Rg1 promoted cell proliferation, migration and angiogenesis, and reduced cell apoptosis in high-glucose-induced HUVECs. Knockdown of miR-489-3p alleviated the high-glucose-induced damage to HUVECs, while overexpression of miR-489-3p attenuated the protection effects of Rg1. Overexpression Sirt1 promoted wound healing in DFUs and Sirt1 was a direct target of miR-489-3p. In addition, animal experiments demonstrated that Rg1 promoted wound closure by regulating miR-489-3p/Sirt1 axis.

CONCLUSIONS

Rg1 alleviated the DFUs by increasing Sirt1 expression via miR-489-3p downregulation and promoting activation of PI3K/AKT/eNOS signaling.

Long Noncoding RNA 3632454L22Rik Contributes to Corneal Epithelial Wound Healing by Sponging miR-181a-5p in Diabetic Mice

Purpose

This work explores the abnormal expression of long noncoding RNAs (lncRNAs), microRNAs (miRNAs) and messenger RNAs (mRNAs) in diabetic corneal epithelial cells (CECs) and constructs an associated competitive endogenous RNA (ceRNA) network. Moreover, we revealed that Rik may exert advantageous effects on diabetic corneal epithelial wound closure by sponging miR-181a-5p.

Methods

We obtained the profiles of differentially expressed lncRNAs (DELs) of CECs of type 1 diabetic versus control corneas by microarray and summarized the differentially expressed miRNAs (DEmiRs) and differentially expressed genes (DEGs) data by published literature. Subsequently, the ceRNA network was constructed using bioinformatics analyses. The levels of lncRNA ENSMUST00000153610/3632454L22Rik (Rik) and miR-181a-5p were verified. The localization of Rik was identified with fluorescence in situ hybridization (FISH), and dual-luciferase assays proved the targeted relationship between Rik and miR-181a-5p. Furthermore, we validated the functional impact of Rik in vitro.

Results

Overall, 111 upregulated and 117 downregulated DELs were detected in diabetic versus control CECs. The level of Rik located in both the cytoplasm and the nucleus was clearly downregulated, whereas miR-181a-5p was upregulated in vitro and in vivo in the diabetic group versus the control group. Rik can act as a ceRNA to bind to miR-181a-5p, thus promoting diabetic corneal epithelial wound healing in vitro.

Conclusions

This work investigated the expression profile of DELs and constructed ceRNA networks of diabetic CECs for the first time. Furthermore, we revealed that Rik may positively impact diabetic corneal epithelial wound healing by sponging miR-181a-5p, providing a novel potential therapeutic target of diabetic keratopathy (DK).

Transcriptional Network Analysis Reveals the Role of miR-223-5p During Diabetic Corneal Epithelial Regeneration

Diabetes mellitus (DM) is a complex metabolic disorder. Long-term hyperglycemia may induce diabetic keratopathy (DK), which is mainly characterized by delayed corneal epithelial regeneration. MicroRNAs (miRNAs) have been reported to play regulatory roles during tissue regeneration. However, the molecular mechanism by which miRNAs influence epithelial regeneration in DK is largely unknown. In this study, we performed miRNA and mRNA sequencing of regenerative corneal epithelium tissue from streptozotocin-induced type 1 diabetic (T1DM) and wild-type mice to screen for differentially expressed miRNAs and mRNAs. Based on regulatory network analysis, miR-223-5p was selected for subsequent experiments and Hpgds was then identified as a direct target gene. MiR-223-5p downregulation significantly promoted diabetic corneal epithelial wound healing and nerve regeneration. However, the beneficial effects of miR-223-5p inhibition were abolished by an Hpgds inhibitor. Furthermore, mechanistic studies demonstrated that miR-223-5p suppression ameliorated inflammation and enhanced cell proliferation signaling in DK. Taken together, our findings revealed that the regulatory role of miR-223-5p in diabetic corneal epithelial and nerve regeneration by mediating inflammatory processes and cell proliferation signaling. And silencing miR-223-5p may contribute to the development of potential therapeutic strategies for DK.

Nicotinamide Adenine Dinucleotide Phosphate Oxidases in Glucose Homeostasis and Diabetes-Related Endothelial Cell Dysfunction

Oxidative stress within the vascular endothelium, due to excess generation of reactive oxygen species (ROS), is thought to be fundamental to the initiation and progression of the cardiovascular complications of type 2 diabetes mellitus. The term ROS encompasses a variety of chemical species including superoxide anion (O₂^•-), hydroxyl radical (OH^-) and hydrogen peroxide (H₂O₂). While constitutive generation of low concentrations of ROS are indispensable for normal cellular function, excess O₂^•- can result in irreversible tissue damage. Excess ROS generation is catalysed by xanthine oxidase, uncoupled nitric oxide synthases, the mitochondrial electron transport chain and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases. Amongst enzymatic sources of O₂^•- the Nox2 isoform of NADPH oxidase is thought to be critical to the oxidative stress found in type 2 diabetes mellitus. In contrast, the transcriptionally regulated Nox4 isoform, which generates H₂O₂, may fulfil a protective role and contribute to normal glucose homeostasis. This review describes the key roles of Nox2 and Nox4, as well as Nox1 and Nox5, in glucose homeostasis, endothelial function and oxidative stress, with a key focus on how they are regulated in health, and dysregulated in type 2 diabetes mellitus.

Puerarin Attenuates Complete Freund's Adjuvant-Induced Trigeminal Neuralgia and Inflammation in a Mouse Model via Sirt1-Mediated TGF-β1/Smad3 Inhibition

Background

Puerarin, an active compound of radix puerariae, is a major compound used in Chinese herbal medicines and it has been well known for its pharmacological effects, including antioxidant, anti‑inflammatory, neuroprotective and cardioprotective properties. The aim of the present study was to determine the role of puerarin (Pue) in complete Freund’s adjuvant (CFA)-induced trigeminal neuralgia (TN) and the effects of this compound on Sirt1 activity and on the progression of CFA-induced TN.

Methods

Mice were injected with CFA on the unilateral face to induce TN. A cell model of inflammation-associated TN was established by interleukin-1β (IL-1β; 10 ng/mL) and tumor necrosis factor-α (TNF-α; 50 ng/mL) stimulation of neurons. Reverse transcription-quantitative PCR and Western blot analyses were performed to analyze mRNA and protein expression levels in trigeminal ganglion and nerve cells. Terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL) staining was used to determine nerve cell apoptosis following IL-1β/TNF-α or Pue treatment.

Results

Pue is a conceivable Sirtuin1 (Sirt1) activator used for the prevention of trigeminal nerve injury that attenuates CFA-induced TN and inflammatory cytokine-evoked overactivation of neuronal inflammation and apoptosis. Treatment of mice with inflammatory cytokines induced upregulation of cleaved caspase-3 protein expression, which was neutralized by Pue supplementation. Both in vivo and in vitro experiments led to the conclusion that Pue modulated Sirt1 activation and repressed transforming growth factor-β1 (TGF-β1) protein expression and drosophila mothers against decapentaplegic homolog3 (Smad3) phosphorylation in order to exert neuroprotection.

Conclusion

The findings suggested that Pue functioned as a potential Sirt1 activator to improve neuroinflammation-induced TN and neuronal apoptosis via the suppression of TGF-β1/Smad3 activity. The pharmacological activity of Pue provides a new perspective for the effective prevention and treatment of TN.

Astragalus Polysaccharide Regulates miR-182/Bcl-2 Axis to Relieve Metabolic Memory through Suppressing Mitochondrial Damage-Mediated Apoptosis in Retinal Pigment Epithelial Cells

INTRODUCTION

Metabolic memory is one of the causes of diabetic retinopathy, and astragalus polysaccharide (APS) has great advantages in the treatment of diabetes. However, the effect of APS on metabolic memory remains to be investigated.

METHODS

Retinal pigment epithelial cell line ARPE-19 and primary retinal pigment epithelial cells were used to verify the effect of APS on mitochondria damage and apoptosis induced by high glucose-induced metabolic memory. The relationship between miR-182 and Bcl-2 was confirmed by a luciferase activity assay. Western blotting and quantitative reverse-transcriptase polymerase chain reaction were conducted to investigate the changes in mitochondrial damage- and apoptosis-associated markers. The cell mitochondrial membrane potential was assessed by JC-1 fluorescence. Terminal deoxynucleotidyl transferase dUTP nick end labelling staining and flow cytometry assays were performed to determine the occurrence of apoptosis.

RESULTS

Treatment with high glucose followed by normal glucose significantly upregulated the expression of miR-182 and downregulated the expression of its target Bcl-2, and APS treatment reversed the above effects. Additionally, APS treatment restored mitochondrial function and inhibited apoptosis in cells in a state of metabolic memory. The effects of APS against mitochondrial damage and apoptosis were partially inhibited after miR-182 overexpression.

CONCLUSION

APS alleviated mitochondrial damage and apoptosis induced by metabolic memory by regulating the miR-182/Bcl-2 axis, which might serve as a new strategy for the treatment of diabetic retinopathy.

Activating Sirt1 by resveratrol suppresses Nav1.7 expression in DRG through miR-182 and alleviates neuropathic pain in rats

Neuropathic pain is clinically unsatisfactorily treated because of unclear mechanisms. The present study aims to explore the concrete mechanisms underlying the alleviation of resveratrol-activated silent information regulator 1 (Sirt1) to chronic constriction injury (CCI)-induced neuropathic pain. CCI surgery was conducted to the unilateral sciatic nerve of male Sprague-Dawley rats to induce neuropathic pain experimentally. Resveratrol with or without miR-182 antagomir were administered to CCI rats via intrathecal catheter. Behavioral tests including paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were conducted to explore mechanical allodynia and thermal hyperalgesia. Western blot, qRT-PCR were used to detect the expression levels of Sirt1, miR-182, and Nav1.7 in CCI dorsal root ganglions (DRGs). CCI rats displayed lower PWT and PWL compared with the sham control. Also, the CCI DRGs displayed lower Sirt1 and miR-182 expression as well as higher Nav1.7 expression, which would be almost reversed by resveratrol treatment for 4 successive days. We also found that miR-182 expression inhibition erased the analgesia effect of resveratrol to CCI-induced neuropathic pain possibly through upregulating Nav1.7 expression. In summary, resveratrol alleviated CCI-induced neuropathic pain, possibly through activating Sirt1 to suppress Nav1.7 expression via upregulating miR-182 expression in CCI DRGs.

Diabetic neuropathy and neuropathic pain: a (con)fusion of pathogenic mechanisms?

Neuropathy is a common complication of long-term diabetes that impairs quality of life by producing pain, sensory loss and limb amputation. The presence of neuropathy in both insulin-deficient (type 1) and insulin resistant (type 2) diabetes along with the slowing of progression of neuropathy by improved glycemic control in type 1 diabetes has caused the majority of preclinical and clinical investigations to focus on hyperglycemia as the initiating pathogenic lesion. Studies in animal models of diabetes have identified multiple plausible mechanisms of glucotoxicity to the nervous system including post-translational modification of proteins by glucose and increased glucose metabolism by aldose reductase, glycolysis and other catabolic pathways. However, it is becoming increasingly apparent that factors not necessarily downstream of hyperglycemia can also contribute to the incidence, progression and severity of neuropathy and neuropathic pain. For example, peripheral nerve contains insulin receptors that transduce the neurotrophic and neurosupportive properties of insulin, independent of systemic glucose regulation, while the detection of neuropathy and neuropathic pain in patients with metabolic syndrome and failure of improved glycemic control to protect against neuropathy in cohorts of type 2 diabetic patients has placed a focus on the pathogenic role of dyslipidemia. This review provides an overview of current understanding of potential initiating lesions for diabetic neuropathy and the multiple downstream mechanisms identified in cell and animal models of diabetes that may contribute to the pathogenesis of diabetic neuropathy and neuropathic pain.

AQP5 regulates vimentin expression via miR-124-3p.1 to protect lens transparency

The pathogenesis of congenital cataract (CC), a major disease associated with blindness in infants, is complex and diverse. Aquaporin 5 (AQP5) represents an essential membrane water channel. In the present study, whole exome sequencing revealed a novel heterozygous missense mutation of AQP5 (c.152 T > C, p. L51P) in the four generations of the autosomal dominant CC (adCC) family. By constructing a mouse model of AQP5 knockout (KO) using the CRISPR/Cas9 technology, we observed that the lens of AQP5-KO mice showed mild opacity at approximately six months of age. miR-124-3p.1 expression was identified to be downregulated in the lens of AQP5-KO mice as evidenced by qRT-PCR analysis. A dual luciferase reporter assay confirmed that vimentin was a target gene of miR-124-3p.1. Organ-cultured AQP5-KO mouse lenses were showed increased opacity compared to those of WT mice, and vimentin expression was upregulated as determined by RT-PCR, western blotting, and immunofluorescence staining. After miR-124-3p.1 agomir was added, the lens opacity in WT mice and AQP5-KO mice decreased, accompanied by the downregulation of vimentin. AQP5-L51P increased vimentin expression of in human lens epithelial cells. Therefore, a missense mutation in AQP5 (c.152 T > C, p. L51P) was associated with adCC, and AQP5 could participate in the maintenance of lens transparency by regulating vimentin expression via miR-124-3p.1.

Hyperglycemia-reduced NAD+ biosynthesis impairs corneal epithelial wound healing in diabetic mice

OBJECTIVE

Nicotinamide adenine dinucleotide (NAD) is an essential molecule participating in multiple physiological and pathophysiological processes. In diabetic cornea, the NAD⁺-consuming enzyme SIRT1 was down-regulated and contributed to the delayed wound healing. However, the impact of hyperglycemia on corneal NAD⁺ biosynthesis remained elusive. This study was to investigate the relationship of NAD⁺ biosynthesis and the delayed corneal wound healing in diabetic mice.

METHODS

Type 1 diabetes mellitus (DM) mice were induced by streptozotocin and corneal epithelial wound healing models were constructed by epithelial scraping. The NAD⁺ contents of corneal epithelium were measured using the NAD/NADH quantification kit. Expression of key enzymes involved in the NAD⁺ biosynthesis in type 1 DM mice and type 2 DM patients were analyzed. The nicotinamide phosphoribosyltransferase (NAMPT)-specific siRNA and the selective inhibitor FK866 were used to achieve the blockade of NAMPT, whereas exogenous NAD⁺ and its precursors were replenished to the corneal epithelial cells and DM mice.

RESULTS

Hyperglycemia attenuated NAD⁺ content and NAMPT expression in the corneal epithelium of both type 1 DM mice and type 2 DM patients. Local knockdown of NAMPT by siRNA or FK866 consistently recapitulated the delayed corneal epithelial wound healing in normal mice. Moreover, NAD⁺ replenishment recovered the impaired proliferation and migration capacity by either FK866 or high glucose treatment in cultured corneal epithelial cells. Furthermore, in DM mice, NAD⁺ and its precursors nicotinamide mononucleotide and nicotinamide riboside also facilitated corneal epithelial and nerve regeneration, accompanied with the recovered expression of SIRT1 and phosphorylated EGFR, AKT, and ERK1/2 in epithelium and corneal sensitivity.

CONCLUSION

Hyperglycemia-reduced NAD⁺ biosynthesis and contributed to the impaired epithelial wound healing in DM mice. The replenishment of NAD⁺ and its precursors facilitated diabetic corneal wound healing and nerve regeneration, which may provide a novel therapeutic strategy for the treatment of diabetic corneal complications.

The Importance of Non-Coding RNAs in Neurodegenerative Processes of Diabetes-Related Molecular Pathways

Diabetes mellitus (DM) is a complex condition and serious health problem, with growing occurrence of DM-associated complications occurring globally. Persistent hyperglycemia is confirmed as promoting neurovascular dysfunction leading to irreversible endothelial cell dysfunction, increased neuronal cell apoptosis, oxidative stress and inflammation. These collaboratively and individually result in micro- and macroangiopathy as well as neuropathy demonstrated by progressive neuronal loss. Recently, major efforts have been pursued to select not only useful diagnostic and prognostic biomarkers, but also novel therapeutic approaches. Both microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) belong to a class of non-coding RNAs identified in most of the body fluids i.e., peripheral blood, cerebrospinal fluid, brain tissue and neurons. Numerous miRNAs, lncRNAs and their target genes are able to modulate signaling pathways known to play a role in the pathophysiology of progressive neuronal dysfunction. Therefore, they pose as promising biomarkers and treatment for the vast majority of neurodegenerative disorders. This review provides an overall assessment of both miRNAs’ and lncRNAs’ utility in decelerating progressive nervous system impairment, including neurodegeneration in diabetic pathways.

SIRT1 alleviates hepatic ischemia-reperfusion injury via the miR-182-mediated XBP1/NLRP3 pathway

The hepatoprotection of histone deacetylase sirtuin 1 (SIRT1) has been identified to attenuate ischemia-reperfusion (IR)-triggered inflammation and liver damage. This study was performed to characterize the function of SIRT1 in hepatic IR injury. In in vivo assays on liver-specific knockout mice of SIRT1, we first validated the effect of SIRT1 knockout on liver damage and XBP1/NLRP3 inflammasome activation. Next, we examined whether knockdown of XBP1/NLRP3 or miR-182 agomir could reverse the effect of SIRT1 knockout. In in vitro assays, NCTC1469 cells subjected to hypoxia/reoxygenation (H/R) were transduced with small interfering RNA (siRNA)/activator of SIRT1 or miR-182 agomir to confirm the effect of SIRT1 on NCTC1469 cell behaviors as well as the regulation of miR-182 and the XBP1/NLRP3 signaling pathway. Hepatic IR injury was appreciably aggravated in SIRT1 knockout mice, and SIRT1 knockdown abolished the inhibition of XBP1/NLRP3 inflammasome activation, which was reversed by NLRP3 knockdown, XBP1 knockdown, or miR-182 agomir. Mechanistically, miR-182 expression was positively regulated by SIRT1 in hepatic IR injury in mice, and miR-182 inhibited the expression of XBP1 by binding to the 3' untranslated region (UTR) of XBP1. The histone deacetylase SIRT1 inhibits the downstream XBP1/NLRP3 inflammatory pathway by activating miR-182, thus alleviating hepatic IR injury in mice.

MicroRNA, Diabetes Mellitus and Colorectal Cancer

Diabetes mellitus (DM) is an endocrinological disorder that is due to either the pancreas not producing enough insulin, or the body does not respond appropriately to insulin. There are many complications of DM such as retinopathy, nephropathy, and peripheral neuropathy. In addition to these complications, DM was reported to be associated with different cancers. In this review, we discuss the association between DM and colorectal cancer (CRC). CRC is the third most commonly diagnosed cancer worldwide that mostly affects older people, however, its incidence and mortality are rising among young people. We discuss the relationship between DM and CRC based on their common microRNA (miRNA) biomarkers. miRNAs are non-coding RNAs playing important functions in cell differentiation, development, regulation of cell cycle, and apoptosis. miRNAs can inhibit cell proliferation and induce apoptosis in CRC cells. miRNAs also can improve glucose tolerance and insulin sensitivity. Therefore, investigating the common miRNA biomarkers of both DM and CRC can shed a light on how these two diseases are correlated and more understanding of the link between these two diseases can help the prevention of both DM and CRC.

Sirt1 attenuates diabetic keratopathy by regulating the endoplasmic reticulum stress pathway

AIMS

The objectives of this study were to explore physiological and pathological changes in the corneas of diabetic rats by intervening in the expression of silent information regulator 1 (Sirt1) and to investigate whether Sirt1 can regulate the activation of endoplasmic reticulum stress (ERS) while influencing corneal epithelial cell apoptosis under high glucose conditions.

MATERIALS AND METHODS

Using 8-week old Sprague-Dawley rats, we established a model of type 1 diabetes, with or without Sirt1 intervention. Clinical evaluation was performed once per week. Primary rat corneal epithelial cells (RCECs) were cultured by combining Sirt1 intervention under high glucose conditions. Generation of reactive oxygen species (ROS), apoptosis, and the expression of Sirt1 and ERS-related proteins were evaluated in rat corneal tissues and RCECs.

KEY FINDINGS

During the intervention, clinical evaluation of the ocular surface, ROS generation, apoptosis, and protein expression of ERS-related proteins in corneal tissue and cultured RCECs were altered with Sirt1expression levels.

SIGNIFICANCE

Sirt1 expression influences the pathological progression of diabetic keratopathy, plays an important role in regulating the ERS pathway, and decreases corneal epithelial cell apoptosis.

The Role of microRNAs in Metabolic Syndrome-Related Oxidative Stress

Oxidative stress (OxS) is the cause and the consequence of metabolic syndrome (MetS), the incidence and economic burden of which is increasing each year. OxS triggers the dysregulation of signaling pathways associated with metabolism and epigenetics, including microRNAs, which are biomarkers of metabolic disorders. In this review, we aimed to summarize the current knowledge regarding the interplay between microRNAs and OxS in MetS and its components. We searched PubMed and Google Scholar to summarize the most relevant studies. Collected data suggested that different sources of OxS (e.g., hyperglycemia, insulin resistance (IR), hyperlipidemia, obesity, proinflammatory cytokines) change the expression of numerous microRNAs in organs involved in the regulation of glucose and lipid metabolism and endothelium. Dysregulated microRNAs either directly or indirectly affect the expression and/or activity of molecules of antioxidative signaling pathways (SIRT1, FOXOs, Keap1/Nrf2) along with effector enzymes (e.g., GPx-1, SOD1/2, HO-1), ROS producers (e.g., NOX4/5), as well as genes of numerous signaling pathways connected with inflammation, insulin sensitivity, and lipid metabolism, thus promoting the progression of metabolic imbalance. MicroRNAs appear to be important epigenetic modifiers in managing the delicate redox balance, mediating either pro- or antioxidant biological impacts. Summarizing, microRNAs may be promising therapeutic targets in ameliorating the repercussions of OxS in MetS.

Comprehensive analysis of differentially expressed microRNAs and mRNAs involved in diabetic corneal neuropathy

AIMS

Corneal nerve fibers are derived from the ophthalmic division of the trigeminal ganglion (TG). Here, by sequencing of microRNAs (miRNAs) and messenger RNAs (mRNAs) from diabetic and normal TG tissues, we aimed to uncover potential miRNAs, mRNAs, and the network of their interactions involved in the pathogenesis of diabetic corneal neuropathy.

MAIN METHODS

We performed RNA sequencing to systematically screen out differentially expressed miRNAs and mRNAs in TG tissues from diabetic and normal mice. Functional enrichment analyses were performed to illustrate the biological functions of differentially expressed mRNAs (DEmRNAs). Following this, miRNA-mRNA regulatory networks were built by means of bioinformatics methods to suggest regulatory role for miRNAs in the pathogenesis of diabetic corneal neuropathy. Finally, the credibility of the sequencing-based results was validated using qRT-PCR.

KEY FINDINGS

Sequencing analyses disclosed that 68 miRNAs and 114 mRNAs were differentially expressed in diabetic TG tissues compared with normal TG samples. The functional analyses showed that DEmRNAs participated in diabetes-related biological processes. After applying an optimized approach to predict miRNA-mRNA pairs, a miRNA-mRNA interacting network was inferred. Subsequently, the expression and correlation of miR-350-5p and Mup20, miR-592-5p and Angptl7 as well as miR-351-5p and Elovl6 were preliminarily validated.

SIGNIFICANCE

Our study provides a systematic characterization of miRNA and mRNA expression in the TG during diabetic corneal neuropathy and will contribute to the development of clinical diagnostic and therapeutic strategies for diabetic corneal neuropathy.

Diabetic keratopathy: Insights and challenges

Ocular complications from diabetes mellitus are common. Diabetic keratopathy, the most frequent clinical condition affecting the human cornea, is a potentially sight-threatening condition caused mostly by epithelial disturbances that are of clinical and research attention because of their severity. Diabetic keratopathy exhibits several clinical manifestations, including persistent corneal epithelial erosion, superficial punctate keratopathy, delayed epithelial regeneration, and decreased corneal sensitivity, that may lead to compromised visual acuity or permanent vision loss. The limited amount of clinical studies makes it difficult to fully understand the pathobiology of diabetic keratopathy. Effective therapeutic approaches are elusive. We summarize the clinical manifestations of diabetic keratopathy and discuss available treatments and up-to-date research studies in an attempt to provide a thorough overview of the disorder.

Insulin Promotes Corneal Nerve Repair and Wound Healing in Type 1 Diabetic Mice by Enhancing Wnt/β-Catenin Signaling

The insulin and Wnt signaling pathways are involved in cell proliferation, tissue homeostasis, and tumorigenesis. However, their interrelationship in the pathophysiological process of diabetic corneal injury remains unclear. In this study, the role of insulin in the diabetic cornea was investigated in vitro, using cultured TKE2 cells and trigeminal ganglion neurons, and in vivo, by assessing corneal wound-healing responses in diabetic mice. A selective Wnt antagonist (XAV-939) and activator (BML-284) were used to regulate the interactions between insulin and the Wnt pathway. The results demonstrated that insulin promoted corneal epithelial wound healing and sensation recovery, whereas the expression of molecules involved in the Wnt/β-catenin pathway was also up-regulated in the injured corneal epithelium. However, XAV-939 limited the insulin-induced epithelial and corneal nerve repair. By contrast, BML-284 treatment promoted the healing of the corneal epithelium and corneal nerve repair in diabetic mice. These results indicate that insulin, via Wnt signaling, contributes to diabetic corneal epithelial wound healing and nerve injury recovery and is, therefore, a potential protective factor for diabetic corneal epithelial wounds and nerve injury.

PTEN Inhibition Facilitates Diabetic Corneal Epithelial Regeneration by Reactivating Akt Signaling Pathway

Purpose

To investigate the contribution of phosphatase and tensin homologue (PTEN) on the delayed epithelial regeneration and impaired Akt activation in diabetic mice.

Methods

The expression of PTEN on cornea was compared between normal and diabetic mice. The corneal epithelial and nerve regeneration rate was evaluated in diabetic mice after the treatment with PTEN small interfering RNA (siRNA), PTEN inhibitors, or Akt inhibitor. The reactivation of epithelial regeneration-related signaling, including phosphorylated (p)-Akt, p-Stat3, Sirt1, and Parkin, were assessed with Western blot and immunofluorescence staining. The effects of PTEN inhibition on cellular proliferation and migration were further evaluated in cultured mouse corneal epithelial cells.

Results

PTEN messenger RNA and protein levels exhibited up-regulation in diabetic cornea. Upon central epithelial debridement, the epithelial regeneration rate was significantly promoted in diabetic mice with the treatment of PTEN inhibition than that of vehicle control (P < 0.05), which accompanied with the recovered levels of p-Akt, p-Stat3, Sirt1, and Parkin. However, the promotion of diabetic corneal epithelial regeneration rate and Akt reactivation was completed reversed by Akt inhibitor. In vitro, PTEN inhibition promoted their migration, but not the proliferation capacity. In addition, PTEN inhibitor treatment also improved the recovery of corneal nerve fiber density and sensitivity that was impaired in diabetic mice.

Conclusions

Elevated PTEN expression contributes to the impaired corneal epithelial regeneration and Akt activation in diabetic mice, which can be improved with PTEN inhibition.

Translational Relevance

Our study suggests that PTEN inhibition may serve as a new strategy for restoring the impaired corneal epithelial regeneration ability in patients with diabetes.

Protective effect inhibiting the expression of miR-181a on the diabetic corneal nerve in a mouse model

To investigate the protective effect of inhibiting miR-181a on diabetic corneal nerve in mice, we chose male C57BL/6 mice with streptozotocin (STZ) -induced diabetes as animal models. The expression of miR-181a in trigeminal ganglion tissue (TG) of diabetic mice was detected by real-time PCR. In vitro, we cultured mouse trigeminal ganglion neurons and measured the neuronal axon growth when treated under miR-181a antagomir and negative conditions (NTC). Immunofluorescence showed a significant increase in neuronal axon length in trigeminal ganglion cells treated with miR-181a antagomir. In animal models, we performed epithelial scraping and subconjunctival injection of the miR-181a antagomir and miRNA antagomir NTC to observe the corneal nerve repair by corneal nerve staining. miR-181a antagomir subconjunctival injection significantly increased the corneal epithelium healing of diabetic mice compared with that of the NTC group. Meanwhile, corneal nerve staining showed that the repair of corneal nerve endings was significantly promoted. As the targets of the 181a, ATG5 and BCL-2 were previously identified. The results of Western blot showed that the expression of autophagy associated protein ATG5 and LC3B-II and the expression of anti-apoptotic protein Bcl-2 were decreased in the high-glucose cell culture environment and the diabetic TG tissue. The expression of ATG5, LC3B-II and Bcl-2 were significantly increased after miR-181a antagomir treatment compared with negative control group. This study showed that inhibition of miR-181a expression in diabetic mice could increase ATG5-mediated autophagic activation, BCL-2-mediated inhibition of apoptosis, and promote the growth of trigeminal sensory neurons and the regeneration of corneal nerve fibers. It has a protective effect on diabetic corneal neuropathy.

C-Fiber Assays in the Cornea vs. Skin

C-fibers are unmyelinated nerve fibers that transmit high threshold mechanical, thermal, and chemical signals that are associated with pain sensations. This review examines current literature on measuring altered peripheral nerve morphology and discusses the most relevant aspects of corneal microscopy, especially whether corneal imaging presents significant method advantages over skin biopsy. Given its relative merits, corneal confocal microscopy would seem to be a more practical and patient-centric approach than utilizing skin biopsies.

Improved Motor Nerve Regeneration by SIRT1/Hif1a-Mediated Autophagy

Complete restoring of functional connectivity between neurons or target tissue after traumatic lesions is still an unmet medical need. Using models of nerve axotomy and compression, we investigated the effect of autophagy induction by genetic and pharmacological manipulation on motor nerve regeneration. ATG5 or NAD⁺-dependent deacetylase sirtuin-1 (SIRT1) overexpression on spinal motoneurons stimulates mTOR-independent autophagy and facilitates a growth-competent state improving motor axonal regeneration with better electromyographic records after nerve transection and suture. In agreement with this, using organotypic spinal cord cultures and the human cell line SH-SY5Y, we observed that the activation of SIRT1 and autophagy by NeuroHeal increased neurite outgrowth and length extension and that this was mediated by downstream HIF1a. To conclude, SIRT1/Hifα-dependent autophagy confers a more pro-regenerative phenotype to motoneurons after peripheral nerve injury. Altogether, we provide evidence showing that autophagy induction by SIRT1/Hifα activation or NeuroHeal treatment is a novel therapeutic option for improving motor nerve regeneration and functional recovery after injury.

PEDF Reduces the Severity of Herpetic Simplex Keratitis in Mice

Purpose

The purpose of this study was to explore the effects of pigment epithelium derived factor (PEDF) and PEDF-derived peptides Mer44 and Mer34 on the severity of herpetic simplex keratitis (HSK) in mice.

Methods

Adult C57BL/6 mice were infected ocularly with the herpes simplex virus type 1 (HSV-1, McKrae strain) and injected subconjunctivally with PEDF, Mer44, or Mer34. Corneal nerve degeneration, neovascularization, sensitivity, neutrophils, macrophages and CD4+ T-cell infiltration, virus contents, and expressions of VEGF, PEDF, and proinflammatory factors were evaluated during acute period. The direct inhibitory effect of PEDF on HSV-1 replication was further evaluated in cultured monkey Vero cells.

Results

Following HSV-1 infection, corneal PEDF expression decreased at 3 and 7 days postinfection (dpi) but increased at 15 dpi, and returned to the similar level of normal mice at 45 dpi, which was accompanied with the progress of corneal nerve degeneration and neovascularization. Exogenous PEDF application attenuated corneal nerve degeneration and neovascularization and improved the impaired corneal sensitivity. Moreover, PEDF attenuated the neutrophils, but not macrophage or CD4+ T-cell infiltration, with the reduced expressions of IL-1β, IL-6, TNF-α, and VEGF. In addition, PEDF inhibited the replication of HSV-1 both in vitro and in mice. Mer44 attenuated corneal nerve degeneration more significantly than Mer34, whereas Mer34 inhibited corneal neovascularization.

Conclusions

PEDF and its derived peptides reduce the severity of herpetic simplex keratitis in mice, representing the potential therapeutic approach to control HSK lesions.

Cardiac mesenchymal cells from diabetic mice are ineffective for cell therapy-mediated myocardial repair

Although cell therapy improves cardiac function after myocardial infarction, highly variable results and limited understanding of the underlying mechanisms preclude its clinical translation. Because many heart failure patients are diabetic, we examined how diabetic conditions affect the characteristics of cardiac mesenchymal cells (CMC) and their ability to promote myocardial repair in mice. To examine how diabetes affects CMC function, we isolated CMCs from non-diabetic C57BL/6J (CMCWT) or diabetic B6.BKS(D)-Leprdb/J (CMCdb/db) mice. When CMCs were grown in 17.5 mM glucose, CMCdb/db cells showed > twofold higher glycolytic activity and a threefold higher expression of Pfkfb3 compared with CMCWT cells; however, culture of CMCdb/db cells in 5.5 mM glucose led to metabolic remodeling characterized by normalization of metabolism, a higher NAD+/NADH ratio, and a sixfold upregulation of Sirt1. These changes were associated with altered extracellular vesicle miRNA content as well as proliferation and cytotoxicity parameters comparable to CMCWT cells. To test whether this metabolic improvement of CMCdb/db cells renders them suitable for cell therapy, we cultured CMCWT or CMCdb/db cells in 5.5 mM glucose and then injected them into infarcted hearts of non-diabetic mice (CMCWT, n = 17; CMCdb/db, n = 13; Veh, n = 14). Hemodynamic measurements performed 35 days after transplantation showed that, despite normalization of their properties in vitro, and unlike CMCWT cells, CMCdb/db cells did not improve load-dependent and -independent parameters of left ventricular function. These results suggest that diabetes adversely affects the reparative capacity of CMCs and that modulating CMC characteristics via culture in lower glucose does not render them efficacious for cell therapy.

MicroRNA, Proteins, and Metabolites as Novel Biomarkers for Prediabetes, Diabetes, and Related Complications

Type 2 diabetes mellitus (T2DM) is no more a lifestyle disease of developed countries. It has emerged as a major health problem worldwide including developing countries. However, how diabetes could be detected at an early stage (prediabetes) to prevent the progression of disease is still unclear. Currently used biomarkers like glycated hemoglobin and assessment of blood glucose level have their own limitations. These classical markers can be detected when the disease is already established. Prognosis of disease at early stages and prediction of population at a higher risk require identification of specific markers that are sensitive enough to be detected at early stages of disease. Biomarkers which could predict the risk of disease in people will be useful for developing preventive/proactive therapies to those individuals who are at a higher risk of developing the disease. Recent studies suggested that the expression of biomolecules including microRNAs, proteins, and metabolites specifically change during the progression of T2DM and related complications, suggestive of disease pathology. Owing to their omnipresence in body fluids and their association with onset, progression, and pathogenesis of T2DM, these biomolecules can be potential biomarker for prognosis, diagnosis, and management of disease. In this article, we summarize biomolecules that could be potential biomarkers and their signature changes associated with T2DM and related complications during disease pathogenesis.

Efficacy of Sodium Hyaluronate in Murine Diabetic Ocular Surface Diseases

Supplemental Digital Content is Available in the Text.

Purpose:

To evaluate the efficacy of sodium hyaluronate (HA) eye drops for the treatment of diabetic ocular surface diseases in mice.

Methods:

Male 6- to 8-week-old C57BL/6 mice underwent induction of type 1 diabetes with intraperitoneal injections of streptozotocin, with normal mice as the control. Topical 0.3% HA, 0.1% HA, 0.4% polyethylene glycol eye drops, and normal saline were administered to diabetic mice with an intact or debrided corneal epithelium. Normal saline was applied in the controls. Corneal epithelial wound healing rate, corneal sensation, nerve fiber density, conjunctival goblet cell number, and MUC-5AC content were measured and compared.

Results:

Compared with the controls, topical 0.3% HA use in diabetic mice showed significant improvements in the corneal epithelial wound healing rate (48 hours: 91.5% ± 4.8% vs. 79.8% ± 6.1%; P < 0.05), corneal sensitivity (4.1 ± 0.3 cm vs. 3.5 ± 0.3 cm; P < 0.05), nerve fiber density (12.9% ± 2.3% vs. 6.6% ± 2.4%; P < 0.05), conjunctival goblet cell number (31.0 ± 8.4/100 μm vs. 19.6 ± 7.1/100 μm; P < 0.05), and MUC-5AC content (12.5 ± 1.4 ng/mg vs. 7.8 ± 1.5 ng/mg protein; P < 0.05). The beneficial effects of 0.3% HA were better than those of 0.1% HA and 0.4% polyethylene glycol.

Conclusions:

Topical 0.3% HA treatment promoted corneal epithelial regeneration, improved corneal sensation, and increased density of corneal nerve fibers and conjunctival goblet cells in mice with diabetic ocular surface diseases.

Role of Sirtuin 1 in the pathogenesis of ocular disease (Review)

Sirtuin (SIRT)1, a member of the SIRT family, is a highly conserved NAD+‑dependent histone deacetylase, which has a regulatory role in numerous physiological and pathological processes by removing acetyl groups from various proteins. SIRT1 controls the activity of numerous transcription factors and cofactors, which impacts the downstream gene expression, and eventually alleviates oxidative stress and associated damage. Numerous studies have revealed that dysfunction of SIRT1 is linked with ocular diseases, including cataract, age‑associated macular degeneration, diabetic retinopathy and glaucoma, while ectopic upregulation of SIRT1 protects against various ocular diseases. In the present review, the significant role of SIRT1 and the potential therapeutic value of modulating SIRT1 expression in ocular development and eye diseases is summarized.

Netrin-1 promotes diabetic corneal wound healing through molecular mechanisms mediated via the adenosine 2B receptor

Netrins are secreted chemoattractants with the roles in axon guidance, cell migration and epithelial plasticity. In the present study, we investigated the roles of netrin-1 in the regulation of corneal epithelial wound healing, inflammation response and nerve fiber regeneration in diabetic mice and cultured corneal epithelial cells. In diabetic mice, the expression of netrin-1 was decreased when compared with that of normal mice. Furthermore, high glucose blocked the wounding-induced up-regulation of netrin-1 expression in corneal epithelial cells. Exogenous netrin-1 promoted the corneal epithelial wound healing in diabetic mice, and facilitated the proliferation and migration by reactivating the phosphorylation of ERK and EGFR in high-glucose treated corneal epithelial cells. Moreover, netrin-1 decreased the neutrophil infiltration and promoted M2 macrophage transition, accompanied with the attenuated expression of pro-inflammatory factors in diabetic mouse corneal epithelium. The promotions of netrin-1 on corneal epithelial wound healing and inflammation resolution were mediated at least through the adenosine 2B receptor. In addition, netrin-1 promoted the regeneration of corneal nerve fibers that was impaired in diabetic mice. Taken together, netrin-1 regulates corneal epithelial wound healing, inflammation response and nerve fiber regeneration in diabetic mice, indicating the potential application for the therapy of diabetic keratopathy.

A comparative study of risk factors for corneal infection in diabetic and non-diabetic patients

AIM

To compare the clinical characteristics of infectious keratopathy in type 2 diabetes mellitus (T2DM) and non-diabetes mellitus (NDM) and to investigate risk factors for infectious keratopathy in T2DM patients.

METHODS

Totally 230 patients with T2DM and 168 with NDM diagnosed as infectious keratopathy were hospitalized at Qingdao Eye Hospital from 2001 to 2015. Data including sex, age, occupation, season, smoking and alcohol consumption habits, duration between onset and treatments, duration of hospitalization were collected. Initially identified indicators were analyzed with a multivariate logistic regression. Glycosylated hemoglobin A1c (HbA1c) in patients with T2DM was analyzed. The infectious keratopathies in the two groups were categorized and compared.

RESULTS

The diabetic group consisted of 146 (63.5%) males and 84 (36.5%) females. The NDM group consisted of 111 (66.1%) males and 57 (33.9%) females. There was no signigicantly difference in sex distribution between the two groups (P>0.05). There were significant differences in age, occupation of patients, season of the onset of diseases, duration between onset and treatment, and durations of hospitalization between the two groups (P<0.05). In most of the patients in the diabetic group, the duration between onset and treatment was ≤3mo, and most was ≥3mo in the NDM group. Multivariate logistic regression analysis revealed that age and season were related to the development of corneal infection in the T2DM group (OR=1.709, 1.706). In the T2DM group, HbA1c was 9.09%±2.12%. There were statistically significant differences in the incidences of bacterial keratitis and herpes simplex keratitis in the two groups (P<0.05), but no significant statistical difference was found between fungal keratitis and amoebic keratitis (P>0.05).

CONCLUSION

Advanced age and the summer and winter seasons are identified as risk factors for infectious keratopathy in T2DM patients, and T2DM patients are more prone to bacterial keratitis.

Redox regulation of microRNAs in cancer

Dysregulation of microRNAs (miRNAs) has long been implicated in tumorigenesis, whereas the underlying mechanisms remain largely unknown. Oxidative stress is a hallmark of cancer that involved in multiple pathophysiological processes, including the aberrant regulation of miRNAs. Compelling evidences have implied complicated interplay between reactive oxygen species (ROS) and miRNAs. Indeed, ROS induces carcinogenesis through either reducing or increasing the miRNA level, leading to the activation of oncogenes or silence of tumor suppressors, respectively. In turn, miRNAs target ROS productive genes or antioxidant responsive elements to affect cellular redox balance, which contributes to establishing a microenvironment favoring cancer cell growth and metastasis. Both miRNAs and ROS have been identified as potential biomarkers and therapeutic targets in human malignancies, and comprehensive understanding of the molecular events herein will facilitate the development of novel cancer therapeutic strategies.

SIRT1 promotes tumor-like invasion of fibroblast-like synoviocytes in rheumatoid arthritis via targeting TIMP1

Suppression of tissue inhibitor of matrix metalloproteinase (TIMP) is associated with the tumor-like invasion of fibroblast-like synoviocytes (FLSs) that occurs during rheumatoid arthritis-related cartilage destruction. Silent information regulator 2 homolog1 (SIRT1), a histone deacetylase, is widely involved in transcriptional regulation, genomic stability, metabolism and DNA repair. Recent studies suggest that SIRT1 may also impact inflammatory response and the proliferation of FLSs in rheumatoid arthritis (RA). However, it is unknown whether SIRT1 has a role in the tumor-like invasion of FLSs in rheumatoid arthritis. Herein we report that SIRT1 contributes to FLS invasion and cartilage destruction via a TIMP1-dependent mechanism. Elevated SIRT1 in RA synovia suppresses TIMP1 expression via deacetylation of TIMP1-associated histones, thereby disrupting the binding of the transcription factor specificity protein 1 (Sp1) to the TIMP1 promoter. In rats with collagen-induced arthritis, depletion of SIRT1 remarkably promoted TIMP1 expression in synovial tissues and ameliorated cartilage destruction. These results describe a new role for SIRT1 and demonstrate its potential value as a therapeutic target for rheumatoid arthritis.

MicroRNAs in the pathogenesis of type 2 diabetes: new research progress and future direction

miRNA is a short non-coding RNA that can influence mRNA processing at the post-transcriptional level. A large number of miRNAs have been found in virtually all species so far, and these small molecules play an important role in many different physiological processes and various pathologic conditions, such as cell metabolism, cancer, autoimmune disease, and diabetes mellitus. T2D arises from a dysregulated response to the elevated glucose level in the circulation. The prevalence of T2D has increased dramatically in all age groups, and T2D in older adults is associated with more T2D complications and higher mortality. Despite the existing findings describing the pathological mechanism, T2D pathology is more complex and the pathophysiology of the disease is still not fully elucidated. In this review, we summarize the current understanding of miRNA-mediated modulation of gene expression in T2D pathogenesis, as well as related signaling pathways, and insight into the important role of miRNA in various T2D complications. Furthermore, the potential therapeutic value of miRNA for T2D patients is also discussed in detail.

MiR-30a inhibits BECN1-mediated autophagy in diabetic cataract

Purpose

To investigate the role of microRNAs in the regulation of autophagy and apoptosis in lens epithelial cells (LECs) during diabetic cataract formation.

Methods

A miRNA microarray study and quantitative real-time PCR were performed to identify the expression of miRNAs in LECs of diabetic cataract. Human LECs were cultured in high glucose conditions as a diabetic cataract model. BECN1 and LC3B were detected by Western blotting and quantitative real-time PCR. The extent of apoptosis was measured using FACSCalibur flow cytometry.

Results

Downregulation of miR-30a was identified in LECs attached to diabetic cataract tissues. By the bioinformatic assay and the luciferase activity assay, BECN1 was found to be a direct target of miR-30a. MiR-30a reduced the BECN1-mediated autophagy activity induced by high glucose in LECs in vitro. The ratio of LECs apoptosis was also decreased.

Conclusion

MiR-30a was involved in the inhibition of autophagy by targeting BECN1 in LECs in human diabetic cataract.