NEDD4-1 protects against ischaemia/reperfusion-induced cardiomyocyte apoptosis via the PI3K/Akt pathway

Tudor-SN exacerbates pathological vascular remodeling by promoting the polyubiquitination of PTEN via NEDD4-1

BACKGROUND

Dysregulation of vascular homeostasis can induce cardiovascular diseases and increase global mortality rates. Although lineage tracing studies have confirmed the pivotal role of modulated vascular smooth muscle cells (VSMCs) in the progression of pathological vascular remodeling, the underlying mechanisms are still unclear.

METHODS

The expression of Tudor-SN was determined in VSMCs of artery stenosis, PDGF-BB-treated VSMCs and atherosclerotic plaque. Loss- and gain-of-function approaches were used to explore the role of Tudor-SN in the modulation of VSMCs phenotype both in vivo and in vitro.

RESULTS

In this study, we demonstrate that Tudor-SN expression is significantly elevated in injury-induced arteries, atherosclerotic plaques, and PDGF-BB-stimulated VSMCs. Tudor-SN deficiency attenuates, but overexpression aggravates the synthetic phenotypic switching of VSMCs and pathological vascular remodeling. Loss of Tudor-SN also reduces atherosclerotic plaque formation and increases plaque stability. Mechanistically, PTEN, the major regulator of the MAPK and PI3K-AKT signaling pathways, plays a vital role in Tudor-SN-mediated regulation on proliferation and migration of VSMCs. Tudor-SN facilitates the polyubiquitination and degradation of PTEN via NEDD4-1, thus exacerbating vascular remodeling under pathological conditions. BpV (HOpic), a specific inhibitor of PTEN, not only counteracts the protective effect of Tudor-SN deficiency on proliferation and migration of VSMCs, but also abrogates the negative effect of carotid artery injury-induced vascular remodeling in mice.

CONCLUSIONS

Our findings reveal that Tudor-SN deficiency significantly ameliorated pathological vascular remodeling by reducing NEDD4-1-dependent PTEN polyubiquitination, suggesting that Tudor-SN may be a novel target for preventing vascular diseases.

MicroRNA-155 and exosomal microRNA-155: Small pieces in the cardiovascular diseases puzzle

MicroRNAs (miRs, miRNAs) are known to have a part in various human illnesses, such as those related to the heart. One particular miRNA, miR-155, has been extensively studied and has been found to be involved in hematopoietic lineage differentiation, immunity, viral infections, inflammation, as well as vascular remodeling. These processes have all been connected to cardiovascular diseases, including heart failure, diabetic heart disease, coronary artery disease, and abdominal aortic aneurysm. The impacts of miR-155 depend on the type of cell it is acting on and the specific target genes involved, resulting in different mechanisms of disease. Although, the exact part of miR-155 in cardiovascular illnesses is yet not fully comprehended, as some studies have shown it to promote the development of atherosclerosis while others have shown it to prevent it. As a result, to comprehend the underlying processes of miR-155 in cardiovascular disorders, further thorough study is required. It has been discovered that exosomes that could be absorbed by adjacent or distant cells, control post-transcriptional regulation of gene expression by focusing on mRNA. Exosomal miRNAs have been found to have a range of functions, including participating in inflammatory reactions, cell movement, growth, death, autophagy, as well as epithelial-mesenchymal transition. An increasing amount of research indicates that exosomal miRNAs are important for cardiovascular health and have a major role in the development of a number of cardiovascular disorders, including pulmonary hypertension, atherosclerosis, acute coronary syndrome, heart failure, and myocardial ischemia-reperfusion injury. Herein the role of miR-155 and its exosomal form in heart diseases are summarized.

DMT1 ubiquitination by Nedd4 protects against ferroptosis after intracerebral hemorrhage

OBJECTIVE

Neuronal precursor cells expressed developmentally down-regulated 4 (Nedd4) are believed to play a critical role in promoting the degradation of substrate proteins and are involved in numerous biological processes. However, the role of Nedd4 in intracerebral hemorrhage (ICH) remains unknown. This study aims to investigate the regulatory role of Nedd4 in the ICH model.

METHODS

Male C57BL/6J mice were induced with ICH. Subsequently, the levels of glutathione peroxidase 4 (GPX4), malondialdehyde (MDA) concentration, iron content, mitochondrial morphology, as well as the expression of divalent metal transporter 1 (DMT1) and Nedd4 were assessed after ICH. Furthermore, the impact of Nedd4 overexpression was evaluated through analyses of hematoma area, ferroptosis, and neurobehavioral function. The mechanism underlying Nedd4-mediated degradation of DMT1 was elecidated using immunoprecipitation (IP) after ICH.

RESULTS

Upon ICH, the level of DMT1 in the brain increased, but decreased when Nedd4 was overexpressed using Lentivirus, suggesting a negative correlation between Nedd4 and DMT1. Additionally, the degradation of DMT1 was inhibited after ICH. Furthermore, it was found that Nedd4 can interact with and ubiquitinate DMT1 at lysine residues 6, 69, and 277, facilitating the degradation of DMT1. Functional analysis indicated that overexpression of Nedd4 can alleviate ferroptosis and promote recovery following ICH.

CONCLUSION

The results demonstrated that ferroptosis occurs via the Nedd4/DMT1 pathway during ICH, suggesting it potential as a valuable target to inhibit ferroptosis for the treatment of ICH.

The E3 ubiquitin ligases regulate inflammation in cardiovascular diseases

Accumulating evidence has illustrated that the E3 ubiquitin ligases critically participate in the development and progression of cardiovascular diseases. Dysregulation of E3 ubiquitin ligases exacerbates cardiovascular diseases. Blockade or activation of E3 ubiquitin ligases mitigates cardiovascular performance. Therefore, in this review, we mainly introduced the critical role and underlying molecular mechanisms of E3 ubiquitin ligase NEDD4 family in governing the initiation and progression of cardiovascular diseases, including ITCH, WWP1, WWP2, Smurf1, Smurf2, Nedd4-1 and Nedd4-2. Moreover, the functions and molecular insights of other E3 ubiquitin ligases, such as F-box proteins, in cardiovascular disease development and malignant progression are described. Furthermore, we illustrate several compounds that alter the expression of E3 ubiquitin ligases to alleviate cardiovascular diseases. Therefore, modulation of E3 ubiquitin ligases could be a novel and promising strategy for improvement of therapeutic efficacy of deteriorative cardiovascular diseases.

MicroRNA-155-5p in serum derived-exosomes promotes ischaemia-reperfusion injury by reducing CypD ubiquitination by NEDD4

AIMS

Recovery of blood flow is a therapeutic approach for myocardial infarction but paradoxically induces injury to the myocardium. Exosomes (exos) are pivotal mediators for intercellular communication that can be released by different cells and are involved in cardiovascular diseases. This study aimed to explore the possible effects and mechanisms of miR-155-5p loaded by serum-derived exos in myocardial infarction reperfusion injury (MIRI).

METHODS AND RESULTS

Exos were isolated from mouse serum after induction of ischaemia reperfusion (I/R) and injected into I/R-treated mice to assess cardiac function, infarction size, and cardiomyocyte apoptosis. Primary cardiomyocytes were transfected with miR-155-5p inhibitor before treatment with oxygen-glucose deprivation and re-oxygenation (OGD/R) and exos derived from the serum of I/R-treated mice (I/R-Exos), in which Bcl-2, Bax, and cleaved-caspase-3 levels were detected. The interactions among miR-155-5p, NEDD4, and CypD were evaluated. miR-155-5p level was evidently increased in I/R-Exos than in exos from the serum of sham-operated mice (P < 0.05). In comparison with the I/R group, the I/R-Exos + I/R group had increased infarct size, elevated miR-155-5p expression, and boosted apoptotic rate in mouse myocardium (P < 0.05). In mice treated with I/R-Exos and I/R, miR-155-5p inhibition reduced cardiac infarct size and apoptosis (P < 0.05). NEDD4 was a target gene of miR-155-5p and promoted CypD ubiquitination. Cardiomyocyte apoptosis was markedly increased in the miR-155-5p inhibitor + shNEDD4 + OGD/R group versus the miR-155-5p inhibitor + OGD/R group (P < 0.05), but decreased in the miR-155-5p inhibitor + shNEDD4 + shCypD + OGD/R group than in the miR-155-5p inhibitor + shNEDD4 + OGD/R group (P < 0.05).

CONCLUSIONS

miR-155-5p in I/R-Exos may facilitate MIRI by inhibiting CypD ubiquitination via targeting NEDD4.

The E3 ubiquitin ligase NEDD4-1 protects against acetaminophen-induced liver injury by targeting VDAC1 for degradation

Acetaminophen (APAP) overdose is a major cause of liver injury. Neural precursor cell expressed developmentally downregulated 4-1 (NEDD4-1) is an E3 ubiquitin ligase that has been implicated in the pathogenesis of numerous liver diseases; however, its role in APAP-induced liver injury (AILI) is unclear. Thus, this study aimed to investigate the role of NEDD4-1 in the pathogenesis of AILI. We found that NEDD4-1 was dramatically downregulated in response to APAP treatment in mouse livers and isolated mouse hepatocytes. Hepatocyte-specific NEDD4-1 knockout exacerbated APAP-induced mitochondrial damage and the resultant hepatocyte necrosis and liver injury, while hepatocyte-specific NEDD4-1 overexpression mitigated these pathological events both in vivo and in vitro. Additionally, hepatocyte NEDD4-1 deficiency led to marked accumulation of voltage-dependent anion channel 1 (VDAC1) and increased VDAC1 oligomerization. Furthermore, VDAC1 knockdown alleviated AILI and weakened the exacerbation of AILI caused by hepatocyte NEDD4-1 deficiency. Mechanistically, NEDD4-1 was found to interact with the PPTY motif of VDAC1 through its WW domain and regulate K48-linked ubiquitination and degradation of VDAC1. Our present study indicates that NEDD4-1 is a suppressor of AILI and functions by regulating the degradation of VDAC1.

Interplay between PI3K/AKT pathway and heart disorders

The PI3K/AKT signaling has crucial role in the regulation of numerous physiological functions through activation of downstream effectors and modulation of cell cycle transition, growth and proliferation. This pathway participates in the pathogenesis of several human disorders such as heart diseases through regulation of size and survival of cardiomyocytes, angiogenic processes as well as inflammatory responses. Moreover, PI3K/AKT pathway participates in the process of myocardial injury induced by a number of substances such as H₂O₂, Mercury, lipopolysaccharides, adriamycin, doxorubicin and epirubicin. In this review, we describe the contribution of this pathway in the pathoetiology of myocardial ischemia/reperfusion injury and myocardial infarction, heart failure, cardiac hypertrophy, cardiomyopathy and toxins-induced cardiac injury.

LncRNA RP11-400K9.4 Aggravates Cardiomyocytes Apoptosis After Hypoxia/Reperfusion Injury by Targeting miR-423

Our study was aimed at exploring the roles of lncRNA RP11-400K9.4 (RP11-400K9.4) on hypoxia/reoxygenation (H/R) -induced cardiomyocytes apoptosis. H/R model was constructed in rat primary cardiomyocytes (PC) and H9c2 cells. In this study, the results showed that H/R significantly induced the apoptosis of PC and H9c2 cells. The expression of RP11-400K9.4 was upregulated in H/R-induced PC and H9c2 cells, but miR-423 expression was downregulated. Silencing RP11-400K9.4 could attenuate H/R-induced apoptosis in PC and H9c2 cells. We also found that miR-423 was a potential target of RP11-400K9.4. The effect of silencing RP11-400K9.4 on H/R-induced apoptosis of PC and H9c2 cells was significantly reversed by miR-423 inhibitor transfection. Furthermore, our data confirmed that silencing RP11-400K9.4 promoted the activation of phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) and mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK) /extracellular signal-regulated kinase (ERK) pathways and these phenomena can be reversed by miR-423 inhibitor transfection. In conclusion, our study demonstrated that silencing RP11-400K9.4 could alleviate H/R-induced cardiomyocytes damages via suppressing apoptosis by targeting miR-423 with the activation of PI3K/AKT and MEK/ERK signaling pathways.

IL-22 ameliorated cardiomyocyte apoptosis in cardiac ischemia/reperfusion injury by blocking mitochondrial membrane potential decrease, inhibiting ROS and cytochrome C

Irreversible cardiomyocyte death is one of the main reasons of heart failure following cardiac injury. Therefore, controlling cardiomyocyte death is an effective method to delay the progression of cardiac disease after injury. IL-22 plays critical roles in tissue homeostasis and repair, and has become an important bridge between the immune system and specific tissues or organs. However, whether IL-22 can prevent of cardiomyocyte apoptosis from cardiac injury remains unclear. Therefore, the present work would address the above question. Our results showed that, in vitro, IL-22 prevented cardiomyocyte apoptosis induced by Angiotensin II via enhancing the activity of SOD, blocking the decrease of mitochondrial membrane potential, inhibiting ROS production and release of cytochrome C. The similar results were also found in vivo and patients. Our results shed a light on the therapy of cardiac injury.

Knockdown of Tripartite Motif 8 Protects H9C2 Cells Against Hypoxia/Reoxygenation-Induced Injury Through the Activation of PI3K/Akt Signaling Pathway

Tripartite motif 8 (TRIM8) is a member of the TRIM protein family that has been found to be implicated in cardiovascular disease. However, the role of TRIM8 in myocardial ischemia/reperfusion (I/R) has not been investigated. We aimed to explore the effect of TRIM8 on cardiomyocyte H9c2 cells exposed to hypoxia/reoxygenation (H/R). We found that TRIM8 expression was markedly upregulated in H9c2 cells after stimulation with H/R. Gain- and loss-of-function assays proved that TRIM8 knockdown improved cell viability of H/R-stimulated H9c2 cells. In addition, TRIM8 knockdown suppressed reactive oxygen species production and elevated the levels of superoxide dismutase and glutathione peroxidase. Knockdown of TRIM8 suppressed the caspase-3 activity, as well as caused significant increase in bcl-2 expression and decrease in bax expression. Furthermore, TRIM8 overexpression exhibited apposite effects with knockdown of TRIM8. Finally, knockdown of TRIM8 enhanced the activation of PI3K/Akt signaling pathway in H/R-stimulated H9c2 cells. Inhibition of PI3K/Akt by LY294002 reversed the effects of TRIM8 knockdown on cell viability, oxidative stress, and apoptosis of H9c2 cells. These present findings defined TRIM8 as a therapeutic target for attenuating and preventing myocardial I/R injury.

The Role of HECT-Type E3 Ligase in the Development of Cardiac Disease

Despite advances in medicine, cardiac disease remains an increasing health problem associated with a high mortality rate. Maladaptive cardiac remodeling, such as cardiac hypertrophy and fibrosis, is a risk factor for heart failure; therefore, it is critical to identify new therapeutic targets. Failing heart is reported to be associated with hyper-ubiquitylation and impairment of the ubiquitin–proteasome system, indicating an importance of ubiquitylation in the development of cardiac disease. Ubiquitylation is a post-translational modification that plays a pivotal role in protein function and degradation. In 1995, homologous to E6AP C-terminus (HECT) type E3 ligases were discovered. E3 ligases are key enzymes in ubiquitylation and are classified into three families: really interesting new genes (RING), HECT, and RING-between-RINGs (RBRs). Moreover, 28 HECT-type E3 ligases have been identified in human beings. It is well conserved in evolution and is characterized by the direct attachment of ubiquitin to substrates. HECT-type E3 ligase is reported to be involved in a wide range of human diseases and health. The role of HECT-type E3 ligases in the development of cardiac diseases has been uncovered in the last decade. There are only a few review articles summarizing recent advancements regarding HECT-type E3 ligase in the field of cardiac disease. This study focused on cardiac remodeling and described the role of HECT-type E3 ligases in the development of cardiac disease. Moreover, this study revealed that the current knowledge could be exploited for the development of new clinical therapies.

Ubiquitin Ligases at the Heart of Skeletal Muscle Atrophy Control

Skeletal muscle loss is a detrimental side-effect of numerous chronic diseases that dramatically increases mortality and morbidity. The alteration of protein homeostasis is generally due to increased protein breakdown while, protein synthesis may also be down-regulated. The ubiquitin proteasome system (UPS) is a master regulator of skeletal muscle that impacts muscle contractile properties and metabolism through multiple levers like signaling pathways, contractile apparatus degradation, etc. Among the different actors of the UPS, the E3 ubiquitin ligases specifically target key proteins for either degradation or activity modulation, thus controlling both pro-anabolic or pro-catabolic factors. The atrogenes MuRF1/TRIM63 and MAFbx/Atrogin-1 encode for key E3 ligases that target contractile proteins and key actors of protein synthesis respectively. However, several other E3 ligases are involved upstream in the atrophy program, from signal transduction control to modulation of energy balance. Controlling E3 ligases activity is thus a tempting approach for preserving muscle mass. While indirect modulation of E3 ligases may prove beneficial in some situations of muscle atrophy, some drugs directly inhibiting their activity have started to appear. This review summarizes the main signaling pathways involved in muscle atrophy and the E3 ligases implicated, but also the molecules potentially usable for future therapies.

The NEDD4-1 E3 ubiquitin ligase: A potential molecular target for bortezomib sensitivity in multiple myeloma

E3 ubiquitin ligases primarily determine the substrate specificity of the ubiquitin-proteasome system and play an essential role in the resistance to bortezomib in multiple myeloma (MM). Neural precursor cell-expressed developmentally downregulated gene 4-1 (NEDD4-1, also known as NEDD4) is a founding member of the NEDD4 family of E3 ligases and is involved in the proliferation, migration, invasion and drug sensitivity of cancer cells. In the present study, we investigated the role of NEDD4-1 in MM cells and explored its underlying mechanism. Clinically, low NEDD4-1 expression has been linked to poor prognosis in patients with MM. Functionally, NEDD4-1 knockdown (KD) resulted in bortezomib resistance in MM cells in vitro and in vivo. The overexpression (OE) of NEDD4-1, but not an enzyme-dead NEDD4-1-C867S mutant, had the opposite effect. Furthermore, the overexpression of NEDD4-1 in NEDD4-1 KD cells resensitized the cells to bortezomib in an add-back rescue experiment. Mechanistically, pAkt-Ser473 levels and Akt signaling were elevated and decreased by NEDD4-1 KD and OE, respectively. NEDD4-1 ubiquitinated Akt and targeted pAkt-Ser473 for proteasomal degradation. More importantly, the NEDD4-1 KD-induced upregulation of Akt expression sensitized MM cells to growth inhibition after treatment with an Akt inhibitor. Collectively, our results suggest that high NEDD4-1 levels may be a potential new therapeutic target in MM.

Edaravone reduces oxidative stress and intestinal cell apoptosis after burn through up-regulating miR-320 expression

BACKGROUND

Intestinal mucosa barrier dysfunction after burn injury is an important factor for causing mortality of burn patients. The current study established a burn model in rats and used a free radical scavenger edaravone (ED) to treat the rats, so as to investigate the effect of edaravone on intestinal mucosa barrier after burn injury.

METHODS

Anesthetized rats were subjected to 40% total body surface area water burn immediately, followed by treatment with ED, scrambled antagomir, or antagomiR-320. Intestinal mucosa damage was observed by hematoxylin-eosin staining and graded by colon mucosal damage index (CMDI) score. The contents of total sulfhydryl (TSH), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were determined by spectrophotometry. Cell apoptosis, protein relative expression,and the in situ expressions of p-Akt and p-Bad were detected by flow cytometry, Western blotting and immunohistochemistry, respectively. The miR-320 expression was determined by quantitative real-time polymerase chain reaction.

RESULTS

ED alleviated intestinal mucosal damage caused by burn injury, down-regulated the levels of MDA, cytochrome C, cleaved caspase-9 and cleaved caspase-3, but up-regulated the levels of TSH, SOD, CAT and Bcl-2. We also found that ED could reduce oxidative stress, inhibit cell apoptosis, increase the expressions of p-Akt, p-Bad and miR-320, and decrease PTEN expression. PTEN was predicted to be the target gene for miR-320, and cell apoptosis could be promoted by inhibiting miR-320 expression.

CONCLUSION

ED regulates Akt/Bad/Caspase signaling cascade to reduce apoptosis and oxidative stress through up-regulating miR-320 expression and down-regulating PTEN expression, thus protecting the intestinal mucosal barrier of rats from burn injury.

Inhibition of microRNA-327 ameliorates ischemia/reperfusion injury-induced cardiomyocytes apoptosis through targeting apoptosis repressor with caspase recruitment domain

Apoptosis is the major cause of cardiomyocyte death in myocardial ischemia/reperfusion injury (MI/RI). Increasing evidence suggests that microRNAs (miRNAs) can contribute to the regulation of cardiomyocytes apoptosis by posttranscriptional modulation of gene expression networks. However, the effects of miR-327 in regulating MI/RI-induced cardiomyocytes apoptosis have not been extensively investigated. This study was performed to test whether miR-327 participate in cardiomyocytes apoptosis both in vitro and in vivo, and reveal the potential molecular mechanism of miR-327 regulated MI/RI through targeting apoptosis repressor with caspase recruitment domain (ARC). Sprague-Dawley (SD) rats were subjected to MI/RI by left anterior descending coronary artery occlusion for 30 min and reperfusion for 3 hr. H9c2 cells were exposed to hypoxia for 4 hr and reoxygenation for 12 hr to mimic I/R injury. miRNA-327 recombinant adenovirus vectors were transfected into H9c2 cells for 48 hr and rats for 72 hr before H/R and MI/RI treatment, respectively. The apoptosis rate, downstream molecules of apoptotic pathway, and the target reaction between miRNA-327 and ARC were evaluated. Our results showed that miR-327 was upregulated and ARC was downregulated in the myocardial tissues of MI/RI rats and in H9c2 cells with H/R treatment. Inhibition of miR-327 decreased the expression levels of proapoptotic proteins Fas, FasL, caspase-8, Bax, cleaved caspase-9, cleaved caspase-3, and the release of cytochrome-C, as well as increasing the expression levels of antiapoptotic protein Bcl-2 via negative regulation of ARC both in vivo or vitro. In contrast, overexpression miR-327 showed the reverse effect. Moreover, the results of luciferase reporter assay indicated miR-327 targets ARC directly at the posttranscriptional level. Taken together, inhibition of miR-327 could attenuate cardiomyocyte apoptosis and alleviate I/R-induced myocardial injury via targeting ARC, which offers a new therapeutic strategy for MI/RI.

NEDD4 protects vascular endothelial cells against Angiotensin II-induced cell death via enhancement of XPO1-mediated nuclear export

NEDD4 is an E3 ubiquitin ligase containing the HECT domain, which regulates various cellular processes, but its role in vascular endothelial cells is unknown. In the present study, we found that NEDD4 bound directly to XPO1 by co-immunoprecipitation screening. In HUVECs (human umbilical vein endothelial cells), overexpression of NEDD4 reduced Ang II-induced ROS level and cell apoptosis. Ang II stimulation led to nuclear accumulation of cargoes, while overexpression of NEDD4 enhanced the XPO1-dependent nuclear export of its cargoes. KPT185, an inhibitor of XPO1, can abolished the protective effect of NEDD4 under Ang II treatment. In addition, NEDD4 could promote the interaction between XPO1 and RanBP3 via K63-linked ubiquitination of XPO1. These results suggested that NEDD4 played a protective role in vascular endothelial cell injury through regulating XPO1-mediated nuclear export.

Astragaloside IV attenuates myocardial ischemia/reperfusion injury in rats via inhibition of calcium-sensing receptor-mediated apoptotic signaling pathways

Astragaloside IV (AsIV) is an active saponin extracted from Astragalus membranaceus, which has shown cardioprotective effects in a number of experimental animals. In this study we investigated the molecular mechanisms by which AsIV attenuated the myocardial ischemia reperfusion (MI/R)-induced injury in vitro and in vivo by focusing on calcium-sensing receptor (CaSR) and extracellular signal-regulated kinase 1/2 (ERK1/2). Rat neonatal cardiac myocytes were subjected to a hypoxia/reoxygenation (H/R) procedure in vitro, which significantly decreased the cell viability, increased lactate dehydrogenase (LDH) release, induced cardiomyocyte apoptosis, and increased [Ca²⁺]_i. H/R also increased the expression of CaSR and decreased ERK1/2 phosphorylation levels in H/R-exposed myocytes. Pretreatment with AsIV (60 μmol/L) significantly improved the cell viability and decreased LDH release, attenuated myocyte apoptosis, decreased [Ca²⁺]_i and CaSR expression, and increased the ERK1/2 phosphorylation levels. The protective effects of AsIV against H/R injury were partially inhibited by co-treatment with a CaSR agonist, gadolinium chloride (GdCl₃) or with a specific ERK1/2 inhibitor U0126. For in vivo studies, a rat MI/R model was established. Pre-administration of AsIV (80 mg/kg every day, ig) significantly decreased the myocardium infarct size, creatine kinase-MB (CK-MB) production, serum cardiac troponin (cTnI) levels, and cardiomyocyte apoptosis in the rats with MI/R injury. The therapeutic effects of AsIV were associated with the downregulation of CaSR expression and upregulation of ERK1/2 phosphorylation in myocardial tissues. In summary, astragaloside IV attenuates myocardial I/R injury via inhibition of CaSR/ERK1/2 and the related apoptotic signaling pathways.

Effect of apigenin on apoptosis induced by renal ischemia/reperfusion injury in vivo and in vitro

Objectives: This study aims to investigate the effects and molecular mechanisms of apigenin (ApI) on renal ischemia/reperfusion (I/R) injury in vivo and in vitro.

Methods:In vivo, the left renal artery was clamped for 45 min and the right kidney was removed to study renal I/R injury on Sprague-Dawley (SD) rats. ApI was injected at 60 min before renal ischemia. In vitro, renal tubular epithelial cells (HK-2) were pretreated with or without ApI (20 uM) for 60 min and then treated with hypoxia/reoxygenation (H/R). Renal function, histology, cells apoptosis, and cell viability were tested. Furthermore, the potential molecular mechanisms were assessed.

Results: ApI pretreatment could significantly alleviated the renal function and the pathological damage as well as cells apoptosis after I/R injury. Meanwhile, ApI treatment protects H/R induced HK-2 cell apoptosis in vitro. The results of Western blot showed that ApI significantly increased the expressions of B-cell lymphoma 2 (Bcl-2) and phosphor-AKt (p-AKt), Phosphoinositide 3-kinase (PI3K), while down-regulated the expressions of Caspase3 and Bax induced by H/R injury.

Conclusions: ApI pretreatment can protect renal function against I/R injury and prevent renal tubular cells from apoptosis in vivo and in vitro which might through PI3K/Akt mediated mitochondria-dependent apoptosis signaling pathway.

Recovery from hypoxia-induced internalization of cardiac Na+ /H + exchanger 1 requires an adequate intracellular store of antioxidants

The heart is highly active metabolically but relatively underperfused and, therefore, vulnerable to ischemia. In addition to acidosis, a key component of ischemia is hypoxia that can modulate gene expression and protein function as part of an adaptive or even maladaptive response. Here, using cardiac-derived HL-1 cells, we investigate the effect of various hypoxic stimuli on the expression and activity of Na⁺ /H ⁺ exchanger 1 (NHE1), a principal regulator of intracellular pH. Acute (10 min) anoxia produced a reversible decrease in the sarcolemmal NHE1 activity attributable to NHE1 internalization. Treatment with either 1% O ₂ or dimethyloxaloylglycine (DMOG; 1 mM) for 48-hr stabilized hypoxia-inducible factor 1 and reduced the sarcolemmal NHE1 activity by internalization, but without a change in total NHE1 immunoreactivity or message levels of the coding gene ( SLC9A1) determined in whole-cell lysates. Unlike the effect of DMOG, which was rapidly reversed on washout, reoxygenation after a prolonged period of hypoxia did not reverse the effects on NHE1, unless media were also supplemented with a membrane-permeant derivative of glutathione (GSH). Without a prior hypoxic episode, GSH supplementation had no effect on the NHE1 activity. Thus, posthypoxic NHE1 reinsertion can only take place if cells have a sufficient reservoir of a reducing agent. We propose that oxidative stress under prolonged hypoxia depletes intracellular GSH to an extent that curtails NHE1 reinsertion once the hypoxic stimulus is withdrawn. This effect may be cardioprotective, as rapid postischaemic restoration of the NHE1 activity is known to trigger reperfusion injury by producing an intracellular Na ⁺ -overload, which is proarrhythmogenic.

6-Gingerol Activates PI3K/Akt and Inhibits Apoptosis to Attenuate Myocardial Ischemia/Reperfusion Injury

6-Gingerol (6-G) is known to alleviate myocardial ischemia/reperfusion injury. However, the underlying molecular mechanisms of 6-G myocardial protection are not known. In this study, the protective effect of 6-G on ischemia/reperfusion (I/R) damage and whether such a mechanism was related to apoptosis inhibition and activation of phosphoinositide 3-kinases (PI3K)/serine/threonine kinase (Akt) signaling pathway were investigated. Rats were subjected to I/R in the presence or absence of 6-G and the changes of cardiac function, infarct size and histopathological changes, and the levels of cardiac troponin T, creatine kinase-MB, and myocardial apoptosis were examined. The expression of caspase-3, PI3K, p-Akt, and Akt was also determined. We found that 6-G (6 mg/kg) pretreatment significantly improved heart function and ameliorated infarct size and histopathological changes and cardiac troponin T and creatine kinase-MB levels induced by I/R. Moreover, pretreatment with 6-G significantly inhibited myocardial apoptosis and caspase-3 activation induced by I/R. 6-G also upregulated expression of PI3K, p-Akt, and Akt in myocardial tissues. Taken together, these findings suggest that 6-G inhibits apoptosis and activates PI3K/Akt signaling in response to myocardial I/R injury as a possible mechanism to attenuate I/R-induced injury in heart. These results might be important for developing novel strategies for preventing myocardial I/R injury.

Schisandrin B protects against myocardial ischemia/reperfusion injury via the PI3K/Akt pathway in rats

The natural medicinal monomer, schisandrin B (Sch B), has been shown to exert cardioprotective effects; however, the underlying mechanisms of these effects remain to be fully elucidated. Therefore, the aim of the present study was to investigate whether Sch B attenuated myocardial ischemia/reperfusion (I/R) injury via the phosphoinositide 3‑kinases (PI3K)/Akt signaling pathway. To confirm this, I/R models were established in rats by ligation of the left anterior descending coronary artery. A group of animals were administered with Sch B (60 mg/kg, lavage) and/or the PI3K inhibitor, LY294002 (0.3 mg/kg, intraperitoneal). Myocardial infarct size, myocardial infarct serum markers, myocardial apoptotic index and the expression of Akt were measured in each group. The results demonstrated that the administration of Sch B reduced the size of the myocardial infarct, and this effect was eliminated following LY294002 treatment. In addition, the administration of Sch B decreased the apoptotic index and the serum markers of myocardial infarction. Sch B administration also increased the expression of phosphorylated Akt, and Sch B treatment decreased the B‑cell lymphoma 2 (Bcl‑2)‑like protein 4/Bcl‑2 ratio and the expression of cleaved caspase‑3. Therefore, Sch B may protect myocardial tissue from I/R injury via the PI3K/Akt signaling pathway in rats.

Urolithin A alleviates myocardial ischemia/reperfusion injury via PI3K/Akt pathway

Ischemia/reperfusion (I/R) induces additional damage to the restoration of blood flow to ischemic myocardium. This study examined the effects of urolithin A (UA) on myocardial injury of ischemia/reperfusion in vivo and vitro and explored its underlying mechanisms. Mice were subjected to myocardial ischemia followed by reperfusion. Cells were subjected to hypoxia followed by reoxygenation. UA alleviated hypoxia/reoxygenation (H/R) injury in myocardial cells, reduced myocardial infarct size and cell death in mice after ischemia/reperfusion. Meanwhile, UA enhanced antioxidant capacity in cardiomyocytes following hypoxia/reoxygenation. UA reduced myocardial apoptosis following ischemia/reperfusion. The protection of UA was abolished by LY294002, a PI3K/Akt-inhibitor. These results demonstrated that UA alleviates myocardial ischemia/reperfusion injury probably through PI3K/Akt pathway.