Soluble receptor for advance glycation end-products inhibits ischemia/reperfusion-induced myocardial autophagy via the STAT3 pathway

Soluble RAGE attenuates myocardial I/R injury by suppressing interleukin-6

BACKGROUND

Inflammatory responses play a central role in myocardial ischemia/reperfusion (I/R) injury. Previous studies have demonstrated that the receptor for advanced glycation end-products (RAGE) is involved in the pro-inflammatory process of myocardial I/R injury by binding to diverse ligands. Thus, the inhibitory effects of soluble receptor for advanced glycation end-products (sRAGE), a decoy receptor for RAGE, on myocardial I/R injury may be associated with a reduced inflammatory state.

METHODS

In this study, plasma levels of several inflammatory mediators were measured in patients with acute myocardial infarction (AMI) and I/R-treated cardiomyocyte-specific sRAGE knock-in (sRAGE-CKI) mice. Cardiac function, infarct size, and macrophage phenotypes were examined and documented in mouse hearts.

RESULTS

We enrolled 38 patients diagnosed with myocardial infarction (AMI) [mean age, 58.81 ± 10.40 years] and 26 control with negative coronary arteriographic findings [mean age, 61.84 ± 8.57 years]. The results showed that sRAGE levels were significantly elevated in the AMI patient group compared with the control group (1905.00 [1462.50, 2332.5] vs 1570.00 [1335.00, 1800.00] pg/mL, p < 0.05), which were negatively correlated with interleukin (IL)-1, IL-6, and IL-8 levels. Cardiac-specific overexpression of sRAGE dramatically improved cardiac function and reduced infarct size during myocardial I/R. Furthermore, sRAGE overexpression decreased the plasma IL-6 levels and pro-inflammatory iNOS+ M1-macrophages, and increased CD206+ M2-macrophages in the mouse hearts.

CONCLUSIONS

Our findings suggested that sRAGE protects the heart from myocardial I/R injury by inhibiting the infiltration of pro-inflammatory M1-macrophages, and subsequently decreasing IL-6 secretion.

AGE-RAGE Axis and Cardiovascular Diseases: Pathophysiologic Mechanisms and Prospects for Clinical Applications

Advanced glycation end products (AGE), a diverse array of molecules generated through non-enzymatic glycosylation, in conjunction with the receptor of advanced glycation end products (RAGE), play a crucial role in the pathogenesis of diabetes and its associated complications. Recent studies have revealed that the AGE-RAGE axis potentially accelerated the progression of cardiovascular diseases, including heart failure, atherosclerosis, myocarditis, pulmonary hypertension, hypertension, arrhythmia, and other related conditions. The AGE-RAGE axis is intricately involved in the initiation and progression of cardiovascular diseases, independently of its engagement in diabetes. The mechanisms include oxidative stress, inflammation, alterations in autophagy flux, and mitochondrial dysfunction. Conversely, inhibition of AGE production, disruption of the binding between RAGE and its ligands, or silencing of RAGE expression could effectively impair the function of AGE-RAGE axis, thereby delaying or ameliorating the aforementioned diseases. AGE and the soluble receptor for advanced glycation end products (sRAGE) have the potential to be novel predictors of cardiovascular diseases. In this review, we provide an in-depth overview towards the biosynthetic pathway of AGE and elucidate the pathophysiological implications in various cardiovascular diseases. Furthermore, we delve into the profound role of RAGE in cardiovascular diseases, offering novel insights for further exploration of the AGE-RAGE axis and potential strategies for the prevention and management of cardiovascular disorders.

JAK/STAT3 signaling in cardiac fibrosis: a promising therapeutic target

Cardiac fibrosis is a serious health problem because it is a common pathological change in almost all forms of cardiovascular diseases. Cardiac fibrosis is characterized by the transdifferentiation of cardiac fibroblasts (CFs) into cardiac myofibroblasts and the excessive deposition of extracellular matrix (ECM) components produced by activated myofibroblasts, which leads to fibrotic scar formation and subsequent cardiac dysfunction. However, there are currently few effective therapeutic strategies protecting against fibrogenesis. This lack is largely because the molecular mechanisms of cardiac fibrosis remain unclear despite extensive research. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling cascade is an extensively present intracellular signal transduction pathway and can regulate a wide range of biological processes, including cell proliferation, migration, differentiation, apoptosis, and immune response. Various upstream mediators such as cytokines, growth factors and hormones can initiate signal transmission via this pathway and play corresponding regulatory roles. STAT3 is a crucial player of the JAK/STAT pathway and its activation is related to inflammation, malignant tumors and autoimmune illnesses. Recently, the JAK/STAT3 signaling has been in the spotlight for its role in the occurrence and development of cardiac fibrosis and its activation can promote the proliferation and activation of CFs and the production of ECM proteins, thus leading to cardiac fibrosis. In this manuscript, we discuss the structure, transactivation and regulation of the JAK/STAT3 signaling pathway and review recent progress on the role of this pathway in cardiac fibrosis. Moreover, we summarize the current challenges and opportunities of targeting the JAK/STAT3 signaling for the treatment of fibrosis. In summary, the information presented in this article is critical for comprehending the role of the JAK/STAT3 pathway in cardiac fibrosis, and will also contribute to future research aimed at the development of effective anti-fibrotic therapeutic strategies targeting the JAK/STAT3 signaling.

Melatonin prevents EAAC1 deletion-induced retinal ganglion cell degeneration by inhibiting apoptosis and senescence

Normal tension glaucoma (NTG) is referred to as a progressive degenerative disorder of the retinal ganglion cells (RGCs), resulting in nonreversible visual defects, despite intraocular pressure levels within the statistically normal range. Current therapeutic strategies for NTG yield limited benefits. Excitatory amino acid carrier 1 (EAAC1) knockout (EAAC1-/- ) in mice has been shown to induce RGC degeneration without elevating intraocular pressure, mimicking pathological characteristics of NTG. In this study, we explored whether daily oral administration of melatonin could block RGCs loss and prevent retinal morphology and function defects associated with EAAC1 deletion. We also explored the molecular mechanisms underlying EAAC1 deletion-induced RGC degeneration and the neuroprotective effects of melatonin. Our RNA sequencing and in vivo data indicated EAAC1 deletion caused elevated oxidative stress, activation of apoptosis and cellular senescence pathways, and neuroinflammation in RGCs. However, melatonin administration efficiently prevented these detrimental effects. Furthermore, we investigated the potential role of apoptosis- and senescence-related redox-sensitive factors in EAAC1 deletion-induced RGCs degeneration and the neuroprotective effects of melatonin administration. We observed remarkable upregulation of p53, whereas NRF2 and Sirt1 expression were significantly decreased in EAAC1-/- mice, which were prevented by melatonin treatment, suggesting that melatonin exerted its neuroprotective effects possibly through modulating NRF2/p53/Sirt1 redox-sensitive signaling pathways. Overall, our study provided a solid foundation for the application of melatonin in the management of NTG.

The role of sRAGE in cardiovascular diseases

Advanced glycation end products (AGEs), by-products of glucose metabolism, have been linked to the emergence of cardiovascular disorders (CVD). AGEs can cause tissue damage in four different ways: (1) by altering protein function, (2) by crosslinking proteins, which makes tissue stiffer, (3) by causing the generation of free radicals, and (4) by activating an inflammatory response after binding particular AGE receptors, such as the receptor for advanced glycation end products (RAGE). It is suggested that the soluble form of RAGE (sRAGE) blocks ligand-mediated pro-inflammatory and oxidant activities by serving as a decoy. Therefore, several studies have investigated the possible anti-inflammatory and anti-oxidant characteristics of sRAGE, which may help lower the risk of CVD. According to the results of various studies, the relationship between circulating sRAGE, cRAGE, and esRAGE and CVD is inconsistent. To establish the potential function of sRAGE as a therapeutic target in the treatment of cardiovascular illnesses, additional studies are required to better understand the relationship between sRAGE and CVD. In this review, we explored the potential function of sRAGE in different CVD, highlighting unanswered concerns and outlining the possibilities for further investigation.

Regulation of autophagy of the heart in ischemia and reperfusion

Ischemia/reperfusion (I/R) of the heart leads to increased autophagic flux. Preconditioning stimulates autophagic flux by AMPK and PI3-kinase activation and mTOR inhibition. The cardioprotective effect of postconditioning is associated with activation of autophagy and increased activity of NO-synthase and AMPK. Oxidative stress stimulates autophagy in the heart during I/R. Superoxide radicals generated by NADPH-oxidase acts as a trigger for autophagy, possibly due to AMPK activation. There is reason to believe that AMPK, GSK-3β, PINK1, JNK, hexokinase II, MEK, PKCα, and ERK kinases stimulate autophagy, while mTOR, PKCδ, Akt, and PI3-kinase can inhibit autophagy in the heart during I/R. However, there is evidence that PI3-kinase could stimulate autophagy in ischemic preconditioning of the heart. It was found that transcription factors FoxO1, FoxO3, NF-κB, HIF-1α, TFEB, and Nrf-2 enhance autophagy in the heart in I/R. Transcriptional factors STAT1, STAT3, and p53 inhibit autophagy in I/R. MicroRNAs could stimulate and inhibit autophagy in the heart in I/R. Long noncoding RNAs regulate the viability and autophagy of cardiomyocytes in hypoxia/reoxygenation (H/R). Nitric oxide (NO) donors and endogenous NO could activate autophagy of cardiomyocytes. Activation of heme oxygenase-1 promotes cardiomyocyte tolerance to H/R and enhances autophagy. Hydrogen sulfide increases cardiac tolerance to I/R and inhibits apoptosis and autophagy via mTOR and PI3-kinase activation.

Scavenger Receptors in Myocardial Infarction and Ischemia/Reperfusion Injury: The Potential for Disease Evaluation and Therapy

Scavenger receptors (SRs) are a structurally heterogeneous superfamily of evolutionarily conserved receptors that are divided into classes A to J. SRs can recognize multiple ligands, such as modified lipoproteins, damage-associated molecular patterns, and pathogen-associated molecular patterns, and regulate lipid metabolism, immunity, and homeostasis. According to the literature, SRs may play a critical role in myocardial infarction and ischemia/reperfusion injury, and the soluble types of SRs may be a series of promising biomarkers for the diagnosis and prognosis of patients with acute coronary syndrome or acute myocardial infarction. In this review, we briefly summarize the structure and function of SRs and discuss the association between each SR and ischemic cardiac injury in patients and animal models in detail. A better understanding of the effect of SRs on ischemic cardiac injury will inspire novel ideas for therapeutic drug discovery and disease evaluation in patients with myocardial infarction.

Endothelial Autophagy in Coronary Microvascular Dysfunction and Cardiovascular Disease

Coronary microvascular dysfunction (CMD) refers to a subset of structural and/or functional disorders of coronary microcirculation that lead to impaired coronary blood flow and eventually myocardial ischemia. Amid the growing knowledge of the pathophysiological mechanisms and the development of advanced tools for assessment, CMD has emerged as a prevalent cause of a broad spectrum of cardiovascular diseases (CVDs), including obstructive and nonobstructive coronary artery disease, diabetic cardiomyopathy, and heart failure with preserved ejection fraction. Of note, the endothelium exerts vital functions in regulating coronary microvascular and cardiac function. Importantly, insufficient or uncontrolled activation of endothelial autophagy facilitates the pathogenesis of CMD in diverse CVDs. Here, we review the progress in understanding the pathophysiological mechanisms of autophagy in coronary endothelial cells and discuss their potential role in CMD and CVDs.

Soluble RAGE attenuates myocardial I/R injuries via FoxO3-Bnip3 pathway

Soluble receptor for advanced glycation end-products (sRAGE) was reported to inhibit cardiac apoptosis through the mitochondrial pathway during myocardial ischemia/reperfusion (I/R) injury. Meanwhile, the proapoptotic protein Bcl2 and adenovirus E1B 19-kDa-interacting protein 3 (Bnip3) was reported to mediate mitochondrial depolarization and be activated by the Forkhead box protein O3 (FoxO3a). Therefore, it is supposed that FoxO3a-Bnip3 pathway might be involved in the inhibiting effects of sRAGE on mitochondrial apoptosis during I/R. I/R surgery or glucose deprivation/reoxygenation was adopted to explore mitochondrial depolarization, apoptosis and related signaling pathways in mice hearts and cultured cardiomyocytes. The results showed that overexpression of sRAGE in cardiomyocytes dramatically improved cardiac function and reduced infarct areas in I/R treated mice. sRAGE inhibited mitochondrial depolarization and cardiac apoptosis during I/R, which correlated with reduced expression of Bnip3, Sirt2, phosphorylation of Akt and FoxO3a which translocated into nucleus in cultured cardiomyocytes. Either Sirt2 or FoxO3a silencing enhanced the inhibiting effects of sRAGE on mitochondrial depolarization induced by I/R in cultured cardiomyocytes. Meanwhile, overexpression or silencing of FoxO3a affected the inhibiting effects of sRAGE on Bnip3 and cleaved caspase-3 in cultured cardiomyocytes. Therefore, it is suggested that sRAGE inhibited I/R injuries via reducing mitochondrial apoptosis through the FoxO3a-Bnip3 pathway.

Integrinβ3 mediates the protective effects of soluble receptor for advanced glycation end-products during myocardial ischemia/reperfusion through AKT/STAT3 signaling pathway

Soluble receptor for advanced glycation end-product (sRAGE) was reported to protect myocardial ischemia/reperfusion (I/R) injuries via directly interacting with cardiomyocytes besides competing with RAGE for AGEs. However, the specific molecule for the interaction between sRAGE and cardiomyocytes are not clearly defined. Integrins which were reported to interact with RAGE on leukocytes were also expressed on myocardial cells, therefore it was supposed that sRAGE might interact with integrins on cardiomyocytes to protect hearts from ischemia/reperfusion injuries. The results showed that sRAGE increased the expression of integrinβ3 but not integrinβ1, β2, β4 or β5 in cardiomyocytes during I/R injuries. Meanwhile, the suppressive effects of sRAGE on cardiac function, cardiac infraction size and apoptosis in mice were cancelled by inhibition of integrinβ3 with cilengitide (CLG, 75 mg/kg). The results from cultured cardiomyocytes also proved that sRAGE attenuated myocardial apoptosis and autophagy through interacting with integrinβ3 to activate Akt and STAT3 pathway during oxygen and glucose deprivation/reperfusion (OGD/R) treatment. Furthermore, the phosphorylation of STAT3 was significantly downregulated by the inhibition of Akt (LY294002, 10 μM) in OGD/R and sRAGE treated cardiomyocytes, which suggested that STAT3 pathway was induced by Akt in I/R and sRAGE treated cardiomyocytes. The present study contributes to the understanding of myocardial I/R pathogenesis and provided a novel integrinβ3-dependent therapy strategy for sRAGE ameliorating I/R injuries.

Protective Effects of the Soluble Receptor for Advanced Glycation End-Products on Pyroptosis during Myocardial Ischemia-Reperfusion

Ischemia-reperfusion injury (IRI) is an inevitable process when reperfusion therapy undergoes in acute myocardial infarction patients, which will lead to cardiac cell death. Many factors have been found to protect the myocardium, one of which was the soluble receptor for advanced glycation end-products (sRAGE) that protected the myocardium from apoptosis and autophagy. However, pyroptosis is also an important form of cell death that occurs during ischemia-reperfusion (I/R), whose critical molecule, NLR family pyrin domain containing 3 (NLRP3), was ever reported to be inhibited by sRAGE; therefore, it is hypothesized that sRAGE may decrease the cardiac pyroptosis induced by I/R. The results showed that sRAGE protected cardiomyocytes from I/R-induced pyroptosis by decreasing the expression level of NLRP3, gasdermin D (GSDMD), interleukin-1β (IL-1β), and interleukin-18 (IL-18). Meanwhile, the results from primary cultured cardiomyocytes showed that the NF-κB pathway mediated the effects of sRAGE on pyroptosis. Therefore, it is concluded that sRAGE protects the heart from pyroptosis through inhibiting the NF-κB pathway during myocardial ischemia-reperfusion.

Circ-HIPK2 Accelerates Cell Apoptosis and Autophagy in Myocardial Oxidative Injury by Sponging miR-485-5p and Targeting ATG101

Myocardial injury has been deemed as a major cause of heart diseases including myocarditis and coronary heart disease, which have brought multiple mortalities globally. Long non-coding RNAs (lncRNAs) are widely recognized in diverse diseases. However, the role of circular RNA HIPK2 (circ-HIPK2) remains unclear in myocardial injury induced by H2O2. We attempted to investigate the probable role of circ-HIPK2 in myocardial injury induced by H2O2. This study discovered that the treatment of H2O2 inhibited cell proliferation but boosted cell apoptosis and autophagy. ATG101 was upregulated in primary mouse neonatal cardiomyocytes under H2O2 treatment. ATG101 knockdown promoted proliferation and limited apoptosis by attenuating autophagy in H2O2-injured mouse neonatal cardiomyocytes. Furthermore, miR-485-5p was validated to combine with ATG101 and circ-HIPK2, and circ-HIPK2 positively regulated ATG101 expression by sponging miR-485-5p. At last, silenced circ-HIPK2 mediated the promotion of cell proliferation, and repression of cell apoptosis was restored by ATG101 amplification. In a word, circ-HIPK2 facilitates autophagy to accelerate cell apoptosis and cell death in H2O2-caused myocardial oxidative injury through the miR-485-5p/ATG101 pathway, indicating a novel therapeutic target point for patients with myocardial injury.

Soluble receptor for advanced glycation end-products promotes angiogenesis through activation of STAT3 in myocardial ischemia/reperfusion injury

Soluble receptor for advanced glycation end-products (sRAGE), which exerts cardioprotective effect through inhibiting cardiomyocyte apoptosis and autophagy during ischemia/reperfusion (I/R) injury, is also known to enhance angiogenesis in post-ischemic reperfusion injury-critical limb ischemia (PIRI-CLI) mice. However, whether sRAGE protects the heart from myocardial I/R injury via promoting angiogenesis remains unclear. Myocardial model of I/R injury was conducted by left anterior descending (LAD) ligation for 30 min and reperfusion for 2 weeks in C57BL/6 mice. And I/R injury in cardiac microvascular endothelial cells (CMECs) was duplicated by oxygen and glucose deprivation. The results showed that I/R-induced cardiac dysfunction, inflammation and myocardial fibrosis were all reversed by sRAGE. CD31 immunohistochemistry staining showed that sRAGE increased the density of vessels after I/R injury. The results from cultured CMECs showed that sRAGE inhibited apoptosis and increased proliferation, migration, angiogenesis after exposure to I/R. These effects were dependent on signal transducer and activator of transcription 3 (STAT3) pathway. Together, the present study demonstrated that activation of STAT3 contributed to the protective effects of sRAGE on myocardial I/R injury via promoting angiogenesis.

Targeting RAGE to prevent SARS-CoV-2-mediated multiple organ failure: Hypotheses and perspectives

A novel infectious disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was detected in December 2019 and declared as a global pandemic by the World Health. Approximately 15% of patients with COVID-19 progress to severe pneumonia and eventually develop acute respiratory distress syndrome (ARDS), septic shock and/or multiple organ failure with high morbidity and mortality. Evidence points towards a determinant pathogenic role of members of the renin-angiotensin system (RAS) in mediating the susceptibility, infection, inflammatory response and parenchymal injury in lungs and other organs of COVID-19 patients. The receptor for advanced glycation end-products (RAGE), a member of the immunoglobulin superfamily, has important roles in pulmonary pathological states, including fibrosis, pneumonia and ARDS. RAGE overexpression/hyperactivation is essential to the deleterious effects of RAS in several pathological processes, including hypertension, chronic kidney and cardiovascular diseases, and diabetes, all of which are major comorbidities of SARS-CoV-2 infection. We propose RAGE as an additional molecular target in COVID-19 patients for ameliorating the multi-organ pathology induced by the virus and improving survival, also in the perspective of future infections by other coronaviruses.

Upregulation of Matrix Metalloproteinase-9 Protects against Sepsis-Induced Acute Lung Injury via Promoting the Release of Soluble Receptor for Advanced Glycation End Products

Dysregulation of matrix metalloproteinase- (MMP-) 9 is implicated in the pathogenesis of acute lung injury (ALI). However, it remains controversial whether MMP-9 improves or deteriorates acute lung injury of different etiologies. The receptor for advanced glycation end products (RAGE) plays a critical role in the pathogenesis of acute lung injury. MMPs are known to mediate RAGE shedding and release of soluble RAGE (sRAGE), which can act as a decoy receptor by competitively inhibiting the binding of RAGE ligands to RAGE. Therefore, this study is aimed at clarifying whether and how pulmonary knockdown of MMP-9 affected sepsis-induced acute lung injury as well as the release of sRAGE in a murine cecal ligation and puncture (CLP) model. The analysis of GEO mouse sepsis datasets GSE15379, GSE52474, and GSE60088 revealed that the mRNA expression of MMP-9 was significantly upregulated in septic mouse lung tissues. Elevation of pulmonary MMP-9 mRNA and protein expressions was confirmed in CLP-induced mouse sepsis model. Intratracheal injection of MMP-9 siRNA resulted in an approximately 60% decrease in pulmonary MMP-9 expression. It was found that pulmonary knockdown of MMP-9 significantly increased mortality of sepsis and exacerbated sepsis-associated acute lung injury. Pulmonary MMP-9 knockdown also decreased sRAGE release and enhanced sepsis-induced activation of the RAGE/nuclear factor-κB (NF-κB) signaling pathway, meanwhile aggravating sepsis-induced oxidative stress and inflammation in lung tissues. In addition, administration of recombinant sRAGE protein suppressed the activation of the RAGE/NF-κB signaling pathway and ameliorated pulmonary oxidative stress, inflammation, and lung injury in CLP-induced septic mice. In conclusion, our data indicate that MMP-9-mediated RAGE shedding limits the severity of sepsis-associated pulmonary edema, inflammation, oxidative stress, and lung injury by suppressing the RAGE/NF-κB signaling pathway via the decoy receptor activities of sRAGE. MMP-9-mediated sRAGE production may serve as a self-limiting mechanism to control and resolve excessive inflammation and oxidative stress in the lung during sepsis.

Advanced glycation end products and their adverse effects: The role of autophagy

The critical roles played by advanced glycation endproducts (AGEs) accumulation in diabetes and diabetic complications have gained intense recognition. AGEs interfere with the normal functioning of almost every organ with multiple actions like apoptosis, inflammation, protein dysfunction, mitochondrial dysfunction, and oxidative stress. However, the development of a potential treatment strategy is yet to be established. Autophagy is an evolutionarily conserved cellular process that maintains cellular homeostasis with the degradation and recycling systems. AGEs can activate autophagy signaling, which could be targeted as a therapeutic strategy against AGEs induced problems. In this review, we have provided an overview of the adverse effects of AGEs, and we put forth the notion that autophagy could be a promising targetable strategy against AGEs.

MicroRNA-15a inhibits inflammatory response and apoptosis after spinal cord injury via targeting STAT3

OBJECTIVE

To clarify the function of microRNA-15a in the spinal cord injury (SCI) and its potential mechanism.

PATIENTS AND METHODS

The plasma levels of microRNA-15a and signal transducer and activator of transcription 3 (STAT3) in SCI patients were determined by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The correlation between the expressions of microRNA-15a and STAT3 was analyzed. The in vitro SCI model was established in H2O2-induced C8-D1A and C8B4 cells, and in vivo SCI model was established in mice by hitting T10. The mRNA and protein expressions of tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) were detected in the SCI model. The apoptosis was examined by flow cytometry or TUNEL staining, respectively. The motor function of mouse hindlimb was evaluated using the Basso Beattie Bresnahan (BBB) standard scale. The target gene of microRNA-15a was predicted by bioinformatics and further verified by dual-luciferase reporter gene assay. The expression changes of target genes in C8-D1A and C8B4 cells with microRNA-15a overexpression or knockdown were examined by qRT-PCR and Western blot. Finally, rescue experiments were performed to evaluate the regulatory effects of microRNA-15a and STAT3 on cell apoptosis.

RESULTS

MicroRNA-15a was lowly expressed in plasma of SCI patients, while STAT3 was highly expressed with a negative correlation to microRNA-15a. Identically, microRNA-15a was lowly expressed in H2O2-induced C8-D1A and C8B4 cells, and STAT3 was highly expressed. MicroRNA-15a overexpression downregulated mRNA and protein levels of TNF-α and IL-6 in C8-D1A and C8B4 cells. BBB score was markedly low in SCI mice relative to controls. SCI mice injected with microRNA-15a mimics had higher BBB score than those injected with negative control. Besides, SCI mice with microRNA-15a overexpression had downregulated expressions of STAT3, TNF-α, and IL-6 in the impaired spinal cord tissues, as well as lower apoptotic rate. Through bioinformatics, we found binding sites between STAT3 and microRNA-15a. Their binding conditions were further verified by dual-luciferase reporter gene assay. Moreover, STAT3 expression was negatively regulated by microRNA-15a. Finally, rescue experiments showed that STAT3 overexpression could reverse the regulatory effects of microRNA-15a on expressions of TNF-α and IL-6, as well as apoptosis.

CONCLUSIONS

MicroRNA-15a expression decreases in the SCI model, which participates in the process of SCI by regulating inflammatory response and cell apoptosis via targeting STAT3.

Autophagy Triggered by Oxidative Stress Appears to Be Mediated by the AKT/mTOR Signaling Pathway in the Liver of Sleep-Deprived Rats

Sleep deprivation adversely affects the digestive system. Multiple studies have suggested sleep deprivation and oxidative stress are closely related. Autophagy can be triggered by oxidative stress as a self-defense strategy to promote survival. In this study, we investigated the effects of sleep deprivation on liver functions, oxidative stress, and concomitant hepatocyte autophagy, as well as the associated pathways. Enzymatic and nonenzymatic biochemical markers in the serum were used to assess hepatic function and damage. To evaluate the occurrence of autophagy, expression of autophagy-related proteins was tested and autophagosomes were labeled. Additionally, methane dicarboxylic aldehyde (MDA), antioxidant enzymes, and the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway were analyzed using chemical methods and a Western blot. Serum alanine transaminase, aspartate aminotransferase, and alkaline phosphatase increased in sleep-deprived rats. Total protein and albumin abundance was also abnormal. Sleep deprivation induced histopathological changes in the liver. The superoxide dismutase level decreased significantly in the liver of sleep-deprived rats. In contrast, the MDA content increased in the sleep deprivation group. Moreover, the microtubule-associated protein 1 light chain 3 beta (LC3B) II/I ratio and Beclin I content increased considerably in the sleep-deprived rats, while p62 levels decreased. Sleep deprivation apparently inhibited the AKT/mTOR signaling pathway. We conclude that sleep deprivation can induce oxidative stress and ultimately cause liver injury. Autophagy triggered by oxidative stress appears to be mediated by the AKT/mTOR pathway and plays a role in relieving oxidative stress caused by sleep deprivation.