NFAT5 protects astrocytes against oxygen-glucose-serum deprivation/restoration damage via the SIRT1/Nrf2 pathway

Rel Family Transcription Factor NFAT5 Upregulates COX2 via HIF-1α Activity in Ishikawa and HEC1a Cells

Nuclear factor of activated T cells 5 (NFAT5) and cyclooxygenase 2 (COX2; PTGS2) both participate in diverse pathologies including cancer progression. However, the biological role of the NFAT5-COX2 signaling pathway in human endometrial cancer has remained elusive. The present study explored whether NFAT5 is expressed in endometrial tumors and if NFAT5 participates in cancer progression. To gain insights into the underlying mechanisms, NFAT5 protein abundance in endometrial cancer tissue was visualized by immunohistochemistry and endometrial cancer cells (Ishikawa and HEC1a) were transfected with NFAT5 or with an empty plasmid. As a result, NFAT5 expression is more abundant in high-grade than in low-grade endometrial cancer tissue. RNA sequencing analysis of NFAT5 overexpression in Ishikawa cells upregulated 37 genes and downregulated 20 genes. Genes affected included cyclooxygenase 2 and hypoxia inducible factor 1α (HIF1A). NFAT5 transfection and/or treatment with HIF-1α stabilizer exerted a strong stimulating effect on HIF-1α promoter activity as well as COX2 expression level and prostaglandin E2 receptor (PGE2) levels. Our findings suggest that activation of NFAT5-HIF-1α-COX2 axis could promote endometrial cancer progression.

Forensic significance of intracardiac expressions of Nrf2 in acute myocardial ischemia

When exposed to oxidative and electrophilic stress, a protective antioxidant response is initiated by nuclear factor erythroid 2-related factor 2 (Nrf2). However, the extent of its importance in the forensic diagnosis of acute ischemic heart diseases (AIHD), such as myocardial infarction (MI), remains uncertain. On the other hand, immunohistochemical analyses of fibronectin (FN) and the terminal complement complex (C5b-9) prove valuable in identifying myocardial ischemia that precedes necrosis during the postmortem diagnosis of sudden cardiac death (SCD). In this study, we investigated the immunohistochemical levels of Nrf2, FN, and C5b-9 in human cardiac samples to explore their forensic relevance for the identification of acute cardiac ischemia. Heart samples were obtained from 25 AIHD cases and 39 non-AIHD cases as controls. Nrf2 was localized in the nuclei of cardiomyocytes, while FN and C5b-9 were detected in the myocardial cytoplasm. The number of intranuclear Nrf2 positive signals in cardiomyocytes increased in AIHD cases compared to control cases. Additionally, the grading of positive portions of cardiac FN and C5b-9 in the myocardium was also significantly enhanced in AIHD, compared to controls. Collectively, these results indicate that the immunohistochemical investigation of Nrf2 combined with FN, and/or C5b-9 holds the potential for identifying early-stage myocardial ischemic lesions in cases of SCD.

Oxidative stress following spinal cord injury: From molecular mechanisms to therapeutic targets

Spinal cord injury (SCI) is a medical condition that results from severe trauma to the central nervous system; it imposes great psychological and economic burdens on affected patients and their families. The dynamic balance between reactive oxygen species (ROS) and antioxidants is essential for maintaining normal cellular physiological functions. As important intracellular signaling molecules, ROS regulate numerous physiological activities, including vascular reactivity and neuronal function. However, excessive ROS can cause damage to cellular macromolecules, including DNA, lipids, and proteins; this damage eventually leads to cell death. This review discusses the mechanisms of oxidative stress in SCI and describes some signaling pathways that regulate oxidative injury after injury, with the aim of providing guidance for the development of novel SCI treatment strategies.

Inhibition of SIRT1 promotes ultraviolet B induced cataract via downregulation of the KEAP1/NFE2L2 signaling pathway

Due to continuous exposure to ultraviolet B(UVB) radiation, eye lenses are constantly subjected to oxidative stress that induces lens epithelial cell (LEC) apoptosis, which has been associated with the inactivation of Sirtuin1 (SIRT1). It is well-established that NFE2L2 has a major protective effect on UVB-induced oxidative stress and damage. However, whether UVB radiation affects oxidative/antioxidative imbalance and damages LECs by inactivating the protective NFE2L2-mediated antioxidative stress pathway through inhibition of SIRT1 is unknown. In our research, we established in vivo and in vitro UVB exposure models in Sprague Dawley rats and SRA01/04 cells, respectively, to investigate the effect of UVB radiation on the NFE2L2/ KEAP1 pathway and the role of SIRT1 in this process. The in vivo findings revealed that UVB radiation exposure decreased Sirt1 and Nfe2l2 levels, upregulated Keap1 expression, led to an oxidative/antioxidative imbalance and increased LEC apoptosis in the eye lens. Sirt1 downregulated Keap1 expression levels, but activated Nfe2l2 and its downstream target proteins. The in vitro findings showed that UVB inhibited the deacetylation of SIRT1 target proteins and increased the acetylation levels of KEAP1 and NFE2L2. We also found that UVB radiation exposure led to a significant decrease in both co-localization levels and protein interaction between SIRT1 and KEAP1. In addition, the inhibition of SIRT1 increased KEAP1 levels, inhibited the activity of NFE2L2 and decreased co- localization levels and protein interactions between NFE2L2 and KEAP1. These results suggested that UVB radiation decreased SIRT1 levels and inhibited the KEAP1/NFE2L2 pathway, thereby reducing its antioxidant effect, which might be an important mechanism of UVB-induced cataract.

Syringin exerts anti-inflammatory and antioxidant effects by regulating SIRT1 signaling in rat and cell models of acute myocardial infarction

INTRODUCTION

This study aimed to investigate the role of syringin in improving heart function during myocardial ischemia/reperfusion (I/R) and to determine whether the sirtuin 1/peroxisome proliferator-activated receptor gamma coactivator 1 alpha (SIRT1/PGC-1α) pathway contributes to this cardioprotective effect in vivo and in vitro.

METHODS

H9c2 cells were incubated with H₂ O₂ for 12 h. The effect of syringin was assessed by measuring cell viability; the apoptotic rate; Keap1/NRF2/HO-1 activation; and the levels of proinflammatory cytokines, oxidative products, and antioxidative enzymes. In addition, SIRT1 was silenced via short hairpin RNA (shRNA)-SIRT1 transfection to evaluate its involvement in syringin-mediated protection. Syringin rescued cells from H₂ O₂ -induced reductions in viability, antioxidative enzyme levels, and NRF2/HO-1 activation; likewise, syringin inhibited apoptosis, inflammation, and oxidative stress. We also created a rat model of I/R by ligating the left anterior descending coronary artery for 30 min, followed by reperfusion for 12 min. Syringin was then intraperitoneally injected, and the effect on infarct size and cardiac function was examined after 7 days. NRF2/HO-1 activity and the levels of myocardial proinflammatory cytokines, oxidative products, and antioxidative enzymes were measured.

RESULTS

In comparison to the untreated I/R group, the syringin treatment group exhibited improved cardiac function and reduced cardiac lesion and infarct size. Syringin administration also markedly reduced the levels of proinflammatory cytokines and reactive oxygen species and promoted antioxidative enzyme expression and NRF2/HO-1 pathway activation.

CONCLUSIONS

Syringin may serve a protective role in animal and cell models of I/R by improving cardiac function, inhibiting the inflammatory response, and activating the antioxidative response.

LncRNA OIP5-AS1 Mitigates Bupivacaine-Induced Neurotoxicity in Dorsal Root Ganglion Neurons Through Regulating NFAT5 Expression via Sponging miR-34b

Bupivacaine (BUP), which is widely used in anesthesia, can cause neurotoxicity and neurological abnormalities. This work intended to study the function of long non-coding RNA (lncRNA) OIP5 antisense RNA 1 (OIP5-AS1) in BUP-triggered neurotoxicity. OIP5-AS1, microRNA (miR)-34b, and nuclear factor of activated T cells 5 (NFAT5) levels were examined via real-time quantitative PCR (RT-qPCR). Cell proliferation, caspase-3 activity, and apoptosis were assessed via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), caspase-3 activity, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays. The regulatory relationships between miR-34b and OIP5-AS1 or NFAT5 were validated via RNA binding protein immunoprecipitation (RIP) and dual-luciferase reporter assays. Our data demonstrated that OIP5-AS1 and NFAT5 levels were downregulated and miR-34b was upregulated upon exposure to BUP. Functional assays implied that the OIP5-AS1 deficiency impeded cell proliferation and enhanced the apoptosis of DRG neurons, while OIP5-AS1 addition reversed these changes. Moreover, OIP5-AS1 could bind to miR-34b and OIP5-AS1 regulated BUP-induced neurotoxicity via miR-34b. Besides, miR-34b could directly interact with NFAT5. Augmentation of miR-34b impeded cell proliferation and expedited the apoptosis and caspase-3 activity, while NFAT5 addition neutralized these impacts. Finally, it was verified that OIP5-AS1 could upregulate NFAT5 through sponging miR-34b. In sum, our results disclosed that OIP5-AS1 ameliorated BUP-caused neurotoxicity via regulating the miR-34b/NFAT5 axis, suggesting that OIP5-AS1 might be a promising therapeutic target for the treatment of BUP-induced neurotoxicity.

Protection of the enhanced Nrf2 deacetylation and its downstream transcriptional activity by SIRT1 in myocardial ischemia/reperfusion injury

Nrf2, the master gene transcriptor of antioxidant proteins, and SIRT1, the unique Class III histone deacetylase of sirtuins, have been involved in protecting myocardial ischemia/reperfusion (MI/R) injury. However, whether the protective effect of SIRT1 is directly related to the deacetylation of Nrf2 in the pathology of MI/R remains to be investigated. The current study was designed to evaluate the regulation of Nrf2 deacetylation and transcriptional activity by SIRT1 in MI/R. Hypoxia/reoxygenation (H/R) cardiomyocytes and MI/R mice were used to assess the role of SIRT1 in Nrf2 activation. Oxidative stress, cardiac function, LDH release, ROS and infarct size were also evaluated. We found that Nrf2 physically interacted with SIRT1 not only in normal and H/R cardiomyocytes in vitro, but also in Sham or I/R hearts in vivo. Adenovirus induced SIRT1 overexpression resulted in protected H/R induced cell death, accompanied by declined LDH release. Through MI/R in vivo, cardiac overexpression of SIRT1 led to ameliorated cardiac function and infarct size, as well as the decreased cardiac oxidative stress. Notably, such beneficial actions of SIRT1 were blocked by the Nrf2 silence. Mechanically, acetylation of Nrf2 was significantly decreased by SIRT1 overexpression in cardiomyocytes or in whole hearts, which upregulated the downstream signaling pathway of Nrf2. Taken together, we uncovered a clue, for the first time that SIRT1 physically interacts with Nrf2. The cardioprotective effect of SIRT1 overexpression against MI/R is associated with the increased Nrf2 deacetylation and activity. These findings have offered a direct proof and new perspective of post-translational modification in the understanding of oxidative stress and MI/R treatment.

Angiogenic Effects and Crosstalk of Adipose-Derived Mesenchymal Stem/Stromal Cells and Their Extracellular Vesicles with Endothelial Cells

Adipose-derived mesenchymal stem/stromal cells (ASCs) are an adult stem cell population able to self-renew and differentiate into numerous cell lineages. ASCs provide a promising future for therapeutic angiogenesis due to their ability to promote blood vessel formation. Specifically, their ability to differentiate into endothelial cells (ECs) and pericyte-like cells and to secrete angiogenesis-promoting growth factors and extracellular vesicles (EVs) makes them an ideal option in cell therapy and in regenerative medicine in conditions including tissue ischemia. In recent angiogenesis research, ASCs have often been co-cultured with an endothelial cell (EC) type in order to form mature vessel-like networks in specific culture conditions. In this review, we introduce co-culture systems and co-transplantation studies between ASCs and ECs. In co-cultures, the cells communicate via direct cell-cell contact or via paracrine signaling. Most often, ASCs are found in the perivascular niche lining the vessels, where they stabilize the vascular structures and express common pericyte surface proteins. In co-cultures, ASCs modulate endothelial cells and induce angiogenesis by promoting tube formation, partly via secretion of EVs. In vivo co-transplantation of ASCs and ECs showed improved formation of functional vessels over a single cell type transplantation. Adipose tissue as a cell source for both mesenchymal stem cells and ECs for co-transplantation serves as a prominent option for therapeutic angiogenesis and blood perfusion in vivo.

Sirtuins: Potential Therapeutic Targets for Defense against Oxidative Stress in Spinal Cord Injury

Spinal cord injury (SCI) is one of the most incapacitating neurological disorders. It involves complex pathological processes that include a primary injury and a secondary injury phase, or a delayed stage, which follows the primary injury and contributes to the aggravation of the SCI pathology. Oxidative stress, a key pathophysiological event after SCI, contributes to a cascade of inflammation, excitotoxicity, neuronal and glial apoptosis, and other processes during the secondary injury phase. In recent years, increasing evidence has demonstrated that sirtuins are protective toward the pathological process of SCI through a variety of antioxidant mechanisms. Notably, strategies that modulate the expression of sirtuins exert beneficial effects in cellular and animal models of SCI. Given the significance and novelty of sirtuins, we summarize the oxidative stress processes that occur in SCI and discuss the antioxidant effects of sirtuins in SCI. We also highlight the potential of targeting sirtuins for the treatment of SCI.

NFAT5-Mediated Signalling Pathways in Viral Infection and Cardiovascular Dysfunction

The nuclear factor of activated T cells 5 (NFAT5) is well known for its sensitivity to cellular osmolarity changes, such as in the kidney medulla. Accumulated evidence indicates that NFAT5 is also a sensitive factor to stress signals caused by non-hypertonic stimuli such as heat shock, biomechanical stretch stress, ischaemia, infection, etc. These osmolality-related and -unrelated stimuli can induce NFAT5 upregulation, activation and nuclear accumulation, leading to its protective role against various detrimental effects. However, dysregulation of NFAT5 expression may cause pathological conditions in different tissues, leading to a variety of diseases. These protective or pathogenic effects of NFAT5 are dictated by the regulation of its target gene expression and activation of its signalling pathways. Recent studies have found a number of kinases that participate in the phosphorylation/activation of NFAT5 and related signal proteins. Thus, this review will focus on the NFAT5-mediated signal transduction pathways. As for the stimuli that upregulate NFAT5, in addition to the stresses caused by hyperosmotic and non-hyperosmotic environments, other factors such as miRNA, long non-coding RNA, epigenetic modification and viral infection also play an important role in regulating NFAT5 expression; thus, the discussion in this regard is another focus of this review. As the heart, unlike the kidneys, is not normally exposed to hypertonic environments, studies on NFAT5-mediated cardiovascular diseases are just emerging and rapidly progressing. Therefore, we have also added a review on the progress made in this field of research.

Up-Regulation of Nfat5 mRNA and Fzd4 mRNA as a Marker of Poor Outcome in Neonatal Hypoxic-Ischemic Encephalopathy

OBJECTIVE

To evaluate umbilical cord messenger RNA (mRNA) expression as biomarkers for the grade of hypoxic-ischemic encephalopathy (HIE) and long-term neurodevelopment outcome.

STUDY DESIGN

Infants were recruited from the BiHiVE1 study, Ireland (2009-2011), and the BiHiVE2 study, Ireland, and Sweden (2013-2015). Infants with HIE were assigned modified Sarnat scores at 24 hours and followed at 18-36 months. mRNA expression from cord blood was measured using quantitative real-time polymerase chain reaction.

RESULTS

We studied 124 infants (controls, n = 37; perinatal asphyxia, n = 43; and HIE, n = 44). Fzd4 mRNA increased in severe HIE (median relative quantification, 2.98; IQR, 2.23-3.68) vs mild HIE (0.88; IQR, 0.46-1.37; P = .004), and in severe HIE vs moderate HIE (1.06; IQR, 0.81-1.20; P = .003). Fzd4 mRNA also increased in infants eligible for therapeutic hypothermia (1.20; IQR, 0.92-2.37) vs those who were ineligible for therapeutic hypothermia group (0.81; IQR, 0.46-1.53; P = .017). Neurodevelopmental outcome was analyzed for 56 infants. Nfat5 mRNA increased in infants with severely abnormal (1.26; IQR, 1.17-1.39) vs normal outcomes (0.97; IQR, 0.83-1.24; P = .036), and also in infants with severely abnormal vs mildly abnormal outcomes (0.96; IQR, 0.80-1.06; P = .013). Fzd4 mRNA increased in infants with severely abnormal (2.51; IQR, 1.60-3.56) vs normal outcomes (0.74; IQR, 0.48-1.49; P = .004) and in infants with severely abnormal vs mildly abnormal outcomes (0.97; IQR, 0.75-1.34; P = .026).

CONCLUSIONS

Increased Fzd4 mRNA expression was observed in cord blood of infants with severe HIE; Nfat5 mRNA and Fzd4 mRNA expression were increased in infants with severely abnormal long-term outcomes. These mRNA may augment current measures as early objective markers of HIE severity at delivery.

GRP78 effectively protect hypoxia/reperfusion-induced myocardial apoptosis via promotion of the Nrf2/HO-1 signaling pathway

Myocardial infarction is a major cause of death worldwide. Despite our understanding of the pathophysiology of myocardial infarction and the therapeutic options for treatment have improved substantially, acute myocardial infarction remains a leading cause of morbidity and mortality. Recent findings revealed that GRP78 could protect myocardial cells against ischemia reperfusion injury‐induced apoptosis, but the exact function and molecular mechanism remains unclear. In this study, we aimed to explore the effects of GRP78 on hypoxia/reperfusion (H/R)‐induced cardiomyocyte injury. Intriguingly, we first observed that GRP78 overexpression significantly protected myocytes from H/R‐induced apoptosis. On mechanism, our work revealed that GRP78 protected myocardial cells from hypoxia/reperfusion‐induced apoptosis via the activation of the Nrf2/HO‐1 signaling pathway. We observed the enhanced expression of Nrf2/HO‐1 in GRP78 overexpressed H9c2 cell, while GRP78 deficiency dramatically antagonized the expression of Nrf2/HO‐1. Furthermore, we found that blocked the Nrf2/HO‐1 signaling by the HO‐1 inhibitor zinc protoporphyrin IX (Znpp) significantly retrieved H9c2 cells apoptosis that inhibited by GRP78 overexpression. Taken together, our findings revealed a new mechanism by which GRP78 alleviated H/R‐induced cardiomyocyte apoptosis in H9c2 cells via the promotion of the Nrf2/HO‐1 signaling pathway.

Exosomes from SIRT1-Overexpressing ADSCs Restore Cardiac Function by Improving Angiogenic Function of EPCs

Acute myocardial infarction (AMI) is one of the leading causes of mortality in cardiovascular diseases. The aim of this study was to investigate whether exosomes from Sirtuin 1 (SIRT1)-overexpressing adipose-derived stem cells (ADSCs) had a protective effect on AMI. The expression of C-X-C chemokine receptor type 7 (CXCR7) was significantly downregulated in peripheral blood endothelial progenitor cells (EPCs) from AMI patients (AMI-EPCs) compared with that in healthy donors, which coincided with impaired tube formation. The exosomes from SIRT1 overexpression in ADSCs (ADSCs-SIRT1-Exos) increased the expression of C-X-C motif chemokine 12 (CXCL12) and nuclear factor E2 related factor 2 (Nrf2) in AMI-EPCs, which promoted migration and tube formation of AMI-EPCs, and overexpression of CXCR7 helped AMI-EPCs to restore the function of cell migration and tube formation. Moreover, CXCR7 was downregulated in the myocardium of AMI mice, and knockout of CXCR7 exacerbated AMI-induced impairment of cardiovascular function. Injection of ADSCs-SIRT1-Exos increased the survival and promoted the recovery of myocardial function with reduced infarct size and post-AMI left ventricular remodeling, induced vasculogenesis, and decreased AMI-induced myocardial inflammation. These findings showed that ADSCs-SIRT1-Exos may recruit EPCs to the repair area and that this recruitment may be mediated by Nrf2/CXCL12/CXCR7 signaling.

LncRNA CCAT1 Protects Astrocytes Against OGD/R-Induced Damage by Targeting the miR-218/NFAT5-Signaling Axis

Spinal cord injury (SCI) is a grievous neurology-related disorder that causes many devastating symptoms. Emerging roles of long non-coding RNAs (lncRNA) have been shown to play critical roles in multiple neurological diseases. This research planned to dig the function and latent molecular mechanisms of the lncRNA CCAT1 on OGD/R-disposed injury in astrocytes. We observed that CCAT1 expression was diminished and miR-218 expression was elevated in astrocytes during OGD/R. Additionally, an abundance of CCAT1 obviously amplified cell viability and restrained OGD/R-triggered apoptosis in astrocytes, as characterized by reduced levels of pro-apoptotic proteins Bax and C-caspase-3, concomitant with elevated level of anti-apoptotic Bcl-2 protein. Furthermore, administration of CCAT1 remarkably mitigated OGD/R injury-induced neuro-inflammatory responses, reflected in a reduction of inflammatory cytokines including TNF-α, IL-1β, and IL-6. In action, CCAT1 served as an endogenous sponge effectively downregulating miR-218 expression by binding directly to it, and a negative regulatory relationship between miR-218 and NFAT5. Mechanistically, introduction of miR-218 reversed the inhibitory effects of CCAT1 on OGD/R-induced apoptosis and inflammation damage, which directly resulted from the inhibition of miR-218 and its targeting of NFAT5. Collectively, our study illuminated a new CCAT1/miR-218/NFAT5 regulatory axis in which CCAT1 served as a competing endogenous RNA by sponging miR-218, effectively upregulating NFAT5 expression, thereby alleviating apoptosis and inflammation damage under OGD/R condition. CCAT1 is, therefore, a putative therapeutic target for SCI, based on the results of this study and the potential application of CCAT1 as a neuroprotective agent.

NFAT5 and HIF-1α Coordinate to Regulate NKCC1 Expression in Hippocampal Neurons After Hypoxia-Ischemia

Hypoxic-ischemic encephalopathy (HIE) is a serious birth complication with severe long-term sequelae such as cerebral palsy, epilepsy and cognitive disabilities. Na⁺-K⁺-2Cl^– cotransporters 1 (NKCC1) is dramatically upregulated after hypoxia-ischemia (HI), which aggravates brain edema and brain damage. Clinically, an NKCC1-specific inhibitor, bumetanide, is used to treat diseases related to aberrant NKCC1 expression, but the underlying mechanism of aberrant NKCC1 expression has rarely been studied in HIE. In this study, the cooperative effect of hypoxia-inducible factor-1α (HIF-1α) and nuclear factor of activated T cells 5 (NFAT5) on NKCC1 expression was explored in hippocampal neurons under hypoxic conditions. HI increased HIF-1α nuclear localization and transcriptional activity, and pharmacological inhibition of the HIF-1α transcription activity or mutation of hypoxia responsive element (HRE) motifs recovered the hypoxia-induced aberrant expression and promoter activity of NKCC1. In contrast, oxygen–glucose deprivation (OGD)-induced downregulation of NFAT5 expression was reversed by treating with hypertonic saline, which ameliorated aberrant NKCC1 expression. More importantly, knocking down NFAT5 or mutation of the tonicity enhancer element (TonE) stimulated NKCC1 expression and promoter activity under normal physiological conditions. The positive regulation of NKCC1 by HIF-1α and the negative regulation of NKCC1 by NFAT5 may serve to maintain NKCC1 expression levels, which may shed light on the transcription regulation of NKCC1 in hippocampal neurons after hypoxia.

MiR-138-5p exacerbates hypoxia/reperfusion-induced heart injury through the inactivation of SIRT1-PGC-1α

OBJECTIVES

A drastic reduction in myocardial cell apoptosis plays a crucial role in the treatment/management of myocardial infarction, a major cardiovascular health challenge confronting the world, especially the Western world. Accumulating evidence indicates that the cardiotoxicity caused by the apoptotic machinery is partly regulated by miRNAs. The aim of this research is to investigate the role of miR-138-5p on hypoxia/reperfusion-induced heart injury.

METHODS

The expression of miR-138-5p was determined in heart tissue from myocardial infarction patients and rats. Rats were transfection with a miR-138-5p inhibitor to silence miR-138-5p. The cardiac function of rats was detected via echocardiography. SIRT1 and PGC-1α expression in cardiac infarction was detected via quantitative Real-time PCR (qPCR) and Western blot analysis, while the TUNEL assay was used to determine myocardial apoptosis.

RESULTS

Our observations showed that miR-138-5p expression was upregulated after the induction of myocardial infarction. The miR-138-5p inhibitor significantly improved cardiac function, increased the expression of SIRT1 and PGC-1α, and decreased the rate of myocardial apoptosis, whereas siRNA-SIRT1 reversed these protective effects.

CONCLUSIONS

In conclusion, our study demonstrated that miR-138-5p could promote cardiac ischemia injury via inhibition of the silent information regulator 1 and peroxisome proliferator-initiated receptor gamma and coactivator 1 alpha (SIRT1-PGC-1α) axis.

Protective effect of dexmedetomidine against diabetic hyperglycemia-exacerbated cerebral ischemia/reperfusion injury: An in vivo and in vitro study

AIMS

Dexmedetomidine (Dex) has been noted to have neuroprotective effect against cerebral ischemia-reperfusion (I/R) injury. However, the effect of Dex in diabetic hyperglycemia-exacerbated cerebral I/R injury and its underlying mechanism remain unclear.

MAIN METHODS

The infarct volume and brain edema were evaluated by 2,3,5-triphenyltetrazolium chloride staining and standard wet-dry method. Modified neurological severity score was utilized to assess the neurological deficits. The oxidative stress and inflammation were evaluated by detecting reactive oxygen species (ROS), malondialdehyde (MDA), tumor necrosis factor (TNF)-α and interleukin (IL)-1β. Terminal deoxynucleotidyl transferase dUTP nick end labeling assay and cell count kit-8 were applied to measure cell apoptosis and viability.

KEY FINDINGS

Dex treatment reduced infarct volume, decreased brain water content and improved neurological deficit in middle cerebral artery occlusion/reperfusion (MCAO/R) mice. Dex treatment reduced the levels of ROS, MDA, TNF-α and IL-1β in the entire middle cerebral artery territory of diabetic mice subjected to MCAO/R, as well as in primary culture of mouse hippocampal neurons stimulated with 50 mM glucose and oxygen glucose deprivation/reperfusion. Dex treatment inhibited neuronal apoptosis induced by diabetic hyperglycemia-exacerbated cerebral I/R injury. Dex upregulated nuclear factor of activated T-cells 5 (NFAT5) and Sirtuin 1 (SIRT1) expression, induced NF-E2-related factor 2 (Nrf2) translocation from cytoplasm to nucleus and inhibited the acetylation of Nrf2. However, these changes triggered by Dex treatment were abrogated by NFAT5 knockdown.

SIGNIFICANCE

Dex protects against diabetic hyperglycemia-exacerbated cerebral I/R injury through attenuation of oxidative stress, inflammation and apoptosis. The underlying mechanism is at least the NFAT5/SIRT1/Nrf2 signaling pathway dependent.

MicroRNA-128-3p aggravates doxorubicin-induced liver injury by promoting oxidative stress via targeting Sirtuin-1

As one classic anticancer drug, clinical application of Doxorubicin (Dox) is limited due to its side effects. In our previous work, we have investigated the drug targets to treat Dox-induced cardiotoxicity, hepatotoxicity and nephrotoxicity. In this paper, the mechanisms and new drug-target associated with Dox-induced hepatotoxicity were explored. The results showed that Dox markedly inhibited cell viability and cellular respiration, induced cell morphologic change and increased ROS level. Moreover, Dox increased ALT and AST levels, caused pathological damage, increased MDA level and decreased SOD level in mice. Mechanism investigation showed that Dox markedly up-regulated the expression level of miR-128-3p, down-regulated Sirt1 expression level and affected the protein levels of Nrf2, Keap1, Sirt3, NQO1 and HO-1 to cause oxidative stress in liver. Furthermore, double-luciferase reporter assay, and co-transfection test showed that miR-128-3p directly targeted Sirt1. In addition, miR-128-3p mimics in AML-12 cells enhanced Dox-induced oxidative damage via inhibiting cellular respiration, increasing ROS level and mitochondrial superoxide formation. The protein levels of Sirt1, Nrf2, Sirt3, NQO1 and HO-1 in miR-128-3p mimic + Dox group were decreased compared with Dox group. Transfection of miR-128-3p inhibitor weakened Dox-induced oxidative damage via increasing cellular respiration, suppressing cellular ROS level and mitochondrial superoxide formation. The protein levels of Sirt1, Nrf2, Sirt3, NQO1 and HO-1 in miR-128-3p inhibitor + Dox group were increased compared with Dox group. In mice, Dox-induced liver damage was deteriorated by miR-128-3p agomir via increasing the levels of ALT, AST, MDA, and down-regulating the protein levels of Sirt1, Nrf2, Sirt3, NQO1 and HO-1. While, miR-128-3p antagomir alleviated liver injury via decreasing the levels of ALT, AST, MDA, and up-regulating the protein levels of Sirt1, Nrf2, Sirt3, NQO1 and HO-1. Our data showed that miRNA-128-3p aggravated Dox-induced liver injury by promoting oxidative stress via targeting Sirt1, which should be considered as one new drug target to treat Dox-induced liver injury.

SIRT1 and NRF2 Gene Transfer Mediate Distinct Neuroprotective Effects Upon Retinal Ganglion Cell Survival and Function in Experimental Optic Neuritis

Purpose

Optic neuritis is a condition defined by autoimmune-mediated demyelination of the optic nerve and death of retinal ganglion cells. SIRT1 and NRF2 stimulate anti-inflammatory mechanisms and have previously demonstrated therapeutic value in preclinical models of neurodegenerative disease. Here we investigated the neuroprotective potential of SIRT1 or NRF2 gene transfer using adeno-associated virus (AAV) vectors in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis.

Methods

C57Bl/6J mice were administered intravitreal doses of AAV2 vectors and immunized to induce EAE symptoms. Visual function was examined by recording the optokinetic response (OKR) just prior to EAE induction and once every 7 days postinduction for 7 weeks. Retina and optic nerves were harvested to investigate retinal ganglion cell survival (immunolabeling with Brn3a antibodies); inflammation (hematoxylin and eosin staining); and demyelination (luxol fast blue staining).

Results

Animals modeling EAE demonstrate reduced visual acuity compared to sham-induced controls. Intravitreal delivery of AAV2-NRF2 did not preserve visual function. However, AAV2-SIRT1 mediated significant preservation of the OKR compared to AAV2-eGFP controls. Treatment with AAV2-NRF2 promoted RGC survival while AAV2-SIRT1 mediated an upward trend in protection compared to vehicle and AAV2-eGFP controls. Neither NRF2 nor SIRT1 gene augmentation was able to suppress optic nerve inflammation or demyelination.

Conclusions

AAV-mediated overexpression of NRF2 or SIRT1 within RGCs mediates distinct neuroprotective effects upon visual function and RGC survival. This study expands our understanding of SIRT1 and NRF2-mediated neuroprotection in the context of MS pathogenesis and optic neuropathies.

Down-regulated miR-448 relieves spinal cord ischemia/reperfusion injury by up-regulating SIRT1

MicroRNAs play a crucial role in the progression of spinal cord ischemia/reperfusion injury (SCII). The role of miR-448 and SIRT1 in SCII was investigated in this study, to provide further insights into prevention and improvement of this disorder. In this study, expressions of miR-448 and SIRT1 protein were determined by qRT-PCR and western blot, respectively. Flow cytometry was used to analyze cell apoptosis. The endogenous expression of genes was modulated by recombinant plasmids and cell transfection. Dual-luciferase reporter assay was performed to determine the interaction between miR-448 and SIRT1. The Basso, Beattie, and Bresnahan score was used to measure the hind-limb function of rat. The spinal cord ischemia reperfusion injury model of adult rats was developed by abdominal aorta clamping, and the nerve function evaluation was completed by motor deficit index score. In SCII tissues and cells treated with hypoxia, miR-448 was up-regulated while SIRT1 was down-regulated. Hypoxia treatment reduced the expression of SIRT1 through up-regulating miR-448 in nerve cells. Up-regulation of miR-448 induced by hypoxia promoted apoptosis of nerve cells through down-regulating SIRT1. Down-regulated miR-448 improved neurological function and hind-limb motor function of rats with SCII by up-regulating SIRT1. Down-regulated miR-448 inhibited apoptosis of nerve cells and improved neurological function by up-regulating SIRT1, which contributes to relieving SCII.

Intronic miRNA-641 controls its host Gene's pathway PI3K/AKT and this relationship is dysfunctional in glioblastoma multiforme

MicroRNAs have established their role as important regulators of the epigenome. A considerable number of human miRNA genes are found in intronic regions of protein-coding host genes, in many cases adopting their regulatory circuitry. However, emerging evidence foreshadows an unprecedented importance for this relationship: Intronic miRNAs may protect the cell from overactivation of the respective host pathway, a setting that may trigger tumor development. AKT2 is a well-known proto-oncogene central to the PI3K/AKT pathway. This pathway is known to promote tumor growth and survival, especially in glioblastoma. Its intronic miRNA, hsa-miR-641, is scarcely investigated, however. We hypothesized that miR-641 regulates its host AKT2 and that this regulation may become dysfunctional in glioblastoma. We found that indeed miR-641 expression differs significantly between GBM tissue and normal brain samples, and that transfection of glioma cells with miR-641 antagonizes the PI3K/AKT pathway. Combining clinical samples, cell cultures, and biomolecular methods, we could show that miR-641 doesn't affect AKT2's expression levels, but down-regulates kinases that are necessary for AKT2-activation, thereby affecting its functional state. We also identified NFAT5 as a miR-641 regulated central factor to trigger the expression of these kinases and subsequently activate AKT2. In summary, our study is the first that draws a connecting line between the proto-oncogene AKT2 and its intronic miRNA miR-641 with implication for glioblastoma development.

Role of Nuclear Factor Erythroid 2-Related Factor 2 in Diabetic Nephropathy

Diabetic nephropathy (DN) is manifested as increased urinary protein level, decreased glomerular filtration rate, and final renal dysfunction. DN is the leading cause of end-stage renal disease worldwide and causes a huge societal healthcare burden. Since satisfied treatments are still limited, exploring new strategies for the treatment of this disease is urgently needed. Oxidative stress takes part in the initiation and development of DN. In addition, nuclear factor erythroid 2-related factor 2 (Nrf2) plays a key role in the cellular response to oxidative stress. Thus, activation of Nrf2 seems to be a new choice for the treatment of DN. In current review, we discussed and summarized the therapeutic effects of Nrf2 activation on DN from both basic and clinical studies.