Remifentanil preconditioning protects rat cardiomyocytes against hypoxia-reoxygenation injury via δ-opioid receptor mediated activation of PI3K/Akt and ERK pathways

The effect of repetitive magnetic stimulation on neuronal apoptosis and PI3K/Akt protein expression in rats with incomplete spinal cord injury

The pathological and physiological process of spinal cord injury is complex, and there is currently no effective treatment method. Magnetic stimulation is an emerging electromagnetic therapy method in recent years, and studies have shown its potential to reduce cell apoptosis. This study used an improved Allen's method to replicate an incomplete spinal cord injury rat model, and repetitive magnetic stimulation (rMS) intervention was performed on the rats for 21 days. The research plan consists of two parts. The first part aims to observe the effects of rMS on motor function and neuronal cell apoptosis in rats. The Basso-Beattie-Bresnahan (BBB) score results indicate that rMS promotes the recovery of motor function in rats; H&E staining showed that rMS improved spinal cord structural damage and inflammatory infiltration; TUNEL and NeuN staining suggest that rMS can reduce cell apoptosis and promote neuronal cell survival. The second part aims to explore the mechanism of action of rMS. Immunofluorescence staining showed that after rMS intervention, the positive counts of PI3K and Akt increased, whereas the positive counts of caspase-3 decreased. Western blot showed that after rMS intervention, the expression of phospho-phosphatidylinositol-3 kinase (p-PI3K)/PI3K, phospho (p)-Akt/Akt, and Bcl-2 increased, whereas the expression of Bcl-2-associated X protein (Bax) and caspase-3 decreased. In summary, rMS can significantly reduce cell apoptosis in the damaged spinal cord and promote neuronal cell survival. Its mechanism of action may be related to promoting the expression of PI3K/Akt pathway proteins, upregulating the antiapoptotic protein Bcl-2, downregulating the proapoptotic protein Bax, and thereby inhibiting the expression of apoptotic protein caspase-3. NEW & NOTEWORTHY Spinal cord injury is a serious disabling central nervous system disease. Recently, research on magnetic stimulation therapy for spinal cord injury has been increasing, and its potential has gradually attracted the attention of experts. This study found that repetitive magnetic stimulation (rMS) can improve motor function and reduce neuronal apoptosis in spinal cord injury rats. The mechanism may be related to increasing the expression of phosphatidylinositol-3 kinase (PI3K)/Akt protein, thereby inhibiting cell apoptosis and promoting neuronal survival.

Targeting the opioid remifentanil: Protective effects and molecular mechanisms against organ ischemia-reperfusion injury

Opioids are widely used in clinical practice by activating opioid receptors (OPRs), but their clinical application is limited by a series of side effects. Researchers have been making tremendous efforts to promote the development and application of opioids. Fortunately, recent studies have identified the additional effects of opioids in addition to anesthesia and analgesia, particularly in terms of organ protection against ischemia-reperfusion (I/R) injury, with unique advantages. I/R injury in vital organs not only leads to cell dysfunction and structural damage but also induces acute and chronic organ failure, even death. Early prevention and appropriate therapeutic targets for I/R injury are crucial for organ protection. Opioids have shown cardioprotective effects for over 20 years, especially remifentanil, a derivative of fentanyl, which is a new ultra-short-acting opioid analgesic widely used in clinical anesthesia induction and maintenance. In this review, we provide current knowledge about the physiological effects related to OPR-mediated organ protection, focusing on the protective effect and mechanism of remifentanil on I/R injury in the heart and other vital organs. Herein, we also explored the potential application of remifentanil in clinical I/R injury. These findings provide a theoretical basis for the use of remifentanil to inhibit or alleviate organ I/R injury during the perioperative period and provide insights for opioid-induced human organ protection and drug development.

Receptor expression and signaling properties in the brain, and structural ligand motifs that contribute to delta opioid receptor agonist-induced seizures

The δ opioid receptor (δOR) is a therapeutic target for the treatment of various neurological disorders, such as migraines, chronic pain, alcohol use, and mood disorders. Relative to μ opioid receptor agonists, δOR agonists show lower abuse liability and may be potentially safer analgesic alternatives. However, currently no δOR agonists are approved for clinical use. A small number of δOR agonists reached Phase II trials, but ultimately failed to progress due to lack of efficacy. One side effect of δOR agonism that remains poorly understood is the ability of δOR agonists to produce seizures. The lack of a clear mechanism of action is partly driven by the fact that δOR agonists range in their propensity to induce seizure behavior, with multiple δOR agonists reportedly not causing seizures. There is a significant gap in our current understanding of why certain δOR agonists are more likely to induce seizures, and what signal-transduction pathway and/or brain area is engaged to produce these seizures. In this review we provide a comprehensive overview of the current state of knowledge of δOR agonist-mediated seizures. The review was structured to highlight which agonists produce seizures, which brain regions have been implicated and which signaling mediators have been examined in this behavior. Our hope is that this review will spur future studies that are carefully designed and aimed to solve the question why certain δOR agonists are seizurogenic. Obtaining such insight may expedite the development of novel δOR clinical candidates without the risk of inducing seizures. This article is part of the Special Issue on "Opioid-induced changes in addiction and pain circuits".

PI3K polymorphism in patients with sporadic Parkinson's disease

Parkinson's disease (PD) is a common irreversible neurodegenerative disease associated with cognitive impairment. To investigate the serum level of phosphatidylinositol-3-kinase (PI3K) and the distribution of the genotypes and alleles of 3 PI3K single-nucleotide polymorphisms (RS37,30,087, RS37,30,088, and RS37,30,089) in PD patients with different clinical characteristics. A total of 54 PD patients and 50 healthy individuals were recruited. The serum PI3K level was measured using the enzyme-linked immunosorbent assay. The severity of PD was assessed using the modified Hoehn-Yahr scale. The cognitive function of PD patients was evaluated using the Mini-Mental State Examination scale and the Montreal Cognitive Assessment. The distribution of the alleles and genotypes of PI3K single-nucleotide polymorphisms (SNPs) was calculated using the Hardy-Weinberg equilibrium. PD patients showed a significantly higher serum level of PI3K compared to healthy individuals. Increased serum PI3K level was observed in PD patients with more severe disease, longer disease duration, and impaired cognitive function. Additionally, no significant differences were observed in the distributions of the genotypes and alleles of 3 PI3K SNPs between PD patients with normal cognitive function and those with cognitive impairment. PD patients with different levels of disease severity, disease duration, and cognitive function had significantly different serum levels of PI3K. However, the PI3K SNPs in patients with normal cognitive function were not significantly different from those in patients with cognitive impairment. These findings contribute to a better understanding of the roles of PI3K and SNPs of the PI3K gene in PD.

Activation of CNR1/PI3K/AKT Pathway by Tanshinone IIA Protects Hippocampal Neurons and Ameliorates Sleep Deprivation-Induced Cognitive Dysfunction in Rats

Sleep deprivation is commonplace in modern society, Short periods of continuous sleep deprivation (SD) may negatively affect brain and behavioral function and may lead to vehicle accidents and medical errors. Tanshinone IIA (Tan IIA) is an important lipid-soluble component of Salvia miltiorrhiza, which could exert neuroprotective effects. The aim of this study was to investigate the mechanism of neuroprotective effect of Tan IIA on acute sleep deprivation-induced cognitive dysfunction in rats. Tan IIA ameliorated behavioral abnormalities in sleep deprived rats, enhanced behavioral performance in WMW and NOR experiments, increased hippocampal dendritic spine density, and attenuated atrophic loss of hippocampal neurons. Tan IIA enhanced the expression of CB1, PI3K, AKT, STAT3 in rat hippocampus and down-regulated the expression ratio of Bax to Bcl-2. These effects were inhibited by cannabinoid receptor 1 antagonist (AM251). In conclusion, Tan IIA can play a neuroprotective role by activating the CNR1/PI3K/AKT signaling pathway to antagonize apoptosis in the hippocampus and improve sleep deprivation-induced spatial recognition and learning memory dysfunction in rats. Our study suggests that Tan IIA may be a candidate for the prevention of sleep deprivation-induced dysfunction in spatial recognition and learning memory.

MAP Kinase Phosphatase-5 Deficiency Protects Against Pressure Overload-Induced Cardiac Fibrosis

Cardiac fibrosis, a pathological condition due to excessive extracellular matrix (ECM) deposition in the myocardium, is associated with nearly all forms of heart disease. The processes and mechanisms that regulate cardiac fibrosis are not fully understood. In response to cardiac injury, macrophages undergo marked phenotypic and functional changes and act as crucial regulators of myocardial fibrotic remodeling. Here we show that the mitogen-activated protein kinase (MAPK) phosphatase-5 (MKP-5) in macrophages is involved in pressure overload-induced cardiac fibrosis. Cardiac pressure overload resulting from transverse aortic constriction (TAC) leads to the upregulation of Mkp-5 gene expression in the heart. In mice lacking MKP-5, p38 MAPK and JNK were hyperactivated in the heart, and TAC-induced cardiac hypertrophy and myocardial fibrosis were attenuated. MKP-5 deficiency upregulated the expression of the ECM-degrading matrix metalloproteinase-9 (Mmp-9) in the Ly6Clow (M2-type) cardiac macrophage subset. Consistent with in vivo findings, MKP-5 deficiency promoted MMP-9 expression and activity of pro-fibrotic macrophages in response to IL-4 stimulation. Furthermore, using pharmacological inhibitors against p38 MAPK, JNK, and ERK, we demonstrated that MKP-5 suppresses MMP-9 expression through a combined effect of p38 MAPK/JNK/ERK, which subsequently contributes to the inhibition of ECM-degrading activity. Taken together, our study indicates that pressure overload induces MKP-5 expression and facilitates cardiac hypertrophy and fibrosis. MKP-5 deficiency attenuates cardiac fibrosis through MAPK-mediated regulation of MMP-9 expression in Ly6Clow cardiac macrophages.

Delta Opioid Receptor Activation with Delta Opioid Peptide [d-Ala2, d-Leu5] Enkephalin Contributes to Synaptic Improvement in Rat Hippocampus against Global Ischemia

Global cerebral ischemia induced by cardiac arrest usually leads to poor neurological outcomes. Numerous studies have focused on ways to prevent ischemic damage in the brain, however clinical therapies are still limited. Our previous studies revealed that delta opioid receptor (DOR) activation with [d-Ala2, d-Leu5] enkephalin (DADLE), a DOR agonist, not only significantly promotes neuronal survival on day 3, but also improves spatial memory deficits on days 5-9 after ischemia. However, the neurological mechanism underlying DADLE-induced cognitive recovery remains unclear. This study first examined the changes in neuronal survival in the CA1 region at the advanced time point (day 7) after ischemia/reperfusion (I/R) injury and found a significant amelioration of damaged CA1 neurons in the rats treated with DADLE (2.5 nmol) when administered at the onset of reperfusion. The structure and function of CA1 neurons on days 3 and 7 post-ischemia showed significant improvements in both the density of the injured dendritic spines and the basic transmission of the impaired CA3-CA1 synapses following DADLE treatment. The molecular changes involved in DADLE-mediated synaptic modulation on days 3 and 7 post-ischemia implied the time-related differential regulation of PKCα-MARCKS on the dendritic spine structure and of BDNF- ERK1/2-synapsin I on synaptic function, in response to ischemic/reperfusion injury as well as to DADLE treatment. Importantly, all the beneficial effects of DADLE on ischemia-induced cellular, synaptic, and molecular deficits were eliminated by the DOR inhibitor naltrindole (2.5 nmol). Taken together, this study suggested that DOR activation-induced protective signaling pathways of PKCα-MARCKS involved in the synaptic morphology and BDNF-ERK-synapsin I in synaptic transmission may be engaged in the cognitive recovery in rats suffering from advanced cerebral ischemia.

Engineered basic fibroblast growth factor-overexpressing human umbilical cord-derived mesenchymal stem cells improve the proliferation and neuronal differentiation of endogenous neural stem cells and functional recovery of spinal cord injury by activating the PI3K-Akt-GSK-3β signaling pathway

Objectives

To investigate the safety for clinic use and therapeutic effects of basic fibroblast growth factor (bFGF)-overexpressing human umbilical cord-derived mesenchymal stem cells (HUCMSCs) in mice with completely transected spinal cord injury (SCI).

Methods

Stable bFGF-overexpressing HUCMSCs clones were established by electrotransfection and then subjected to systematic safety evaluations. Then, bFGF-overexpressing and control HUCMSCs were used to treat mice with completely transected SCI by tail intravenous injection. Therapeutic outcomes were then investigated, including functional recovery of locomotion, histological structures, nerve regeneration, and recovery mechanisms.

Results

Stable bFGF-overexpressing HUCMSCs met the standards and safety of MSCs for clinic use. In the mouse SCI model, stable bFGF-overexpressing HUCMSCs markedly improved therapeutic outcomes such as reducing glial scar formation, improving nerve regeneration and proliferation of endogenous neural stem cells (NSCs), and increasing locomotion functional recovery of posterior limbs compared with the control HUCMSCs group. Furthermore, bFGF-overexpressing HUCMSCs promoted the proliferation and neuronal differentiation of NSCs in vitro through the PI3K-Akt-GSK-3β pathway.

Conclusion

bFGF-overexpressing HUCMSCs meet the requirements of clinical MSCs and improve evident therapeutic outcomes of mouse SCI treatment, which firmly supports the safety and efficacy of gene-modified MSCs for clinical application.

The μ-opioid receptor induces miR-21 expression and is ERK/PKCμ-dependent

Micro RNA-21 (miR-21) is believed to perform an important role in the transition from inflammation to resolution in the innate immune response. The biochemical basis for the induction of miR-21 remains uncertain. However, the activation of the μ-opioid receptor (MOR) induces the expression of miR-21. Our results show that human monocytes treated with μ-opioid agonists exhibit a significant increase in miR-21 expression. We found that MOR-induction of miR-21 requires the activation of the Ras-Raf-MEK-ERK signaling cascade, and to our surprise, the activation of PKCμ (PKD1). These results are significant given the role of miR-21 in the sensitivity to pain.

Remifentanil protects against myocardial ischemia/reperfusion injury via miR-205-mediated regulation of PINK1

Myocardial ischemia/reperfusion (I/R) injury could lead to severe cardiovascular ischemic disease, including myocardial infarction and contractile dysfunction. Remifentanil demonstrated protective effect on myocardial I/R injury. The underlying pathophysiological mechanism was then investigated in this study. In the current study, primary cardiomyocytes were isolated from rats, and then preconditioned with remifentanil. Rats, tail vein injected with miR-205 antagomir, were subjected to infusion of remifentanil, and then subjected to regional ischemia followed by reperfusion. The results demonstrated that cell viability of hypoxia/reoxygenation-induced cardiomyocytes was increased post remifentanil, while the apoptosis was decreased accompanied with reduced cleaved caspase-3 expression. Hypoxia/reoxygenation treatment increased miR-205 and decreased PINK1 (PTEN induced putative kinase 1) expression. However, preconditioning with remifentanil reduced miR-205 and enhanced PINK1. Moreover, over-expression of miR-205 decreased PINK1 expression and counteracted the effects of remifentanil-induced increase of cell viability and decrease of cell apoptosis in hypoxia/reoxygenation-induced cardiomyocytes. Injection with miR-205 antagomir improved remifentanil-induced decrease of infarct size and LDH (lactic acid dehydrogenase) activity in rat model with I/R injury. In conclusion, miR-205 might participate in the protective effect of remifentanil in rat myocardial I/R injury via regulation of PINK1, providing a potential target for amelioration of cardiovascular ischemic disease.

Remifentanil repairs cartilage damage and reduces the degradation of cartilage matrix in post-traumatic osteoarthritis, and inhibits IL-1β-induced apoptosis of articular chondrocytes via inhibition of PI3K/AKT/NF-κB phosphorylation

Background

Remifentanil (RFT) is an opioid analgesic with a unique pharmacokinetic profile, and plays an important role in the intra- and post-operative periods. Post-traumatic osteoarthritis (PTO) is a particular type of osteoarthritis (OA) that occurs secondary to a traumatic injury. In the present study, we investigated the effects of RFT both in vivo and in vitro.

Methods

In vivo, 50 Sprague Dawley (SD) rats (7 weeks old) were randomly divided into five groups. Four groups of rats received RFT (0.2, 0.5, and 1 µg) or vehicle (PTO group), while the remaining group served as the control. A PTO model in rats was established using the Hulth method. The cartilage damage, articular cartilage formation, and the degradation of cartilage matrix were evaluated. The effects of RFT on cell proliferation, apoptosis, and nuclear factor (NF)-κB phosphorylation were also examined.

Results

The results indicated that RFT improved cartilage damage, enhanced articular cartilage formation, and inhibited the degradation of cartilage matrix in PTO model rats. Compared with the control group, the protein levels of Osterix (OSX), Collagen type I alpha 1 (COL1A1), and osteocalcin (OC) were down-regulated in PTO model rats. RFT also inhibited the interleukin-1β (IL-1β)-induced apoptosis of chondrocytes in vitro. Furthermore, the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/NF-κB pathway was inhibited both in vitro and in vitro.

Conclusions

RFT has significant potential as a therapeutic intervention to ameliorate PTO and provides a foundation for further clinical studies.

BW373U86 upregulates autophagy by inhibiting the PI3K/Akt pathway and regulating the mTOR pathway to protect cardiomyocytes from hypoxia-reoxygenation injury

The purpose of this study was to explore the protective effect of BW373U86 (a δ-opioid receptor (DOR) agonist) on ischemia-reperfusion (I/R) injury in rat cardiomyocytes and its underlying mechanism. Primary rat cardiomyocytes were cultured and pretreated with BW373U86 for intervention. The cardiomyocytes were cultured under the condition of 94% N₂ and 5% CO₂ for 24 h to perform hypoxia culture and conventionally cultured for 12 h to perform reoxygenation culture. The cell viability of cardiomyocytes was detected by an MTT assay (Sigma-Aldrich). The autophagy lysosome levels in cardiomyocytes were evaluated by acidic vesicular organelles with dansylcadaverine (MDC) staining (autophagy test kit, Kaiji Biology, kgatg001). The protein expression levels of LC3, p62, and factors in the PI3K/Akt/mTOR signaling pathway were detected by Western blot. Pretreatment with BW373U86 could improve the cell viability of cardiomyocytes with hypoxia-reoxygenation (H/R) injury (p < 0.05). Interestingly, after coculture of BW373U86 and PI3K inhibitor (3-methyladenine), the protein expression levels of p-Akt in cardiomyocytes were markedly increased in comparison with those in the BW373U86 group (p < 0.05). However, there were no significant differences in the protein expression levels of mTOR between the coculture group and the BW373U86 group (p > 0.05). BW373U86 upregulated autophagy to protect cardiomyocytes from H/R injury, which may be related to the PI3K/Akt/m TOR pathway.

Remifentanil preconditioning protects against hypoxia-induced senescence and necroptosis in human cardiac myocytes in vitro

Remifentanil and other opioids are suggested to be protective against ischemia-reperfusion injury in animal models and coronary artery bypass surgery patients, however the molecular basis of such protection is far from being understood. In the present study, we have used a model of human cardiomyocytes treated with the hypoxia-mimetic agent cobalt chloride to investigate remifentanil preconditioning-based adaptive responses and underlying mechanisms. Hypoxic conditions promoted oxidative and nitrosative stress, p21-mediated cellular senescence and the activation of necroptotic pathway that was accompanied by a 2.2-, 9.6- and 8.2-fold increase in phosphorylation status of mixed lineage kinase domain-like pseudokinase (MLKL) and release of pro-inflammatory cytokine IL-8 and cardiac troponin I, a marker of myocardial damage, respectively. Remifentanil preconditioning was able to lower hypoxia-mediated protein carbonylation and limit MLKL-based signaling and pro-inflammatory response to almost normoxic control levels, and decrease hypoxia-induced pro-senescent activity of about 21% compared to control hypoxic conditions. In summary, we have shown for the first time that remifentanil can protect human cardiomyocytes against hypoxia-induced cellular senescence and necroptosis that may have importance with respect to the use of remifentanil to diminish myocardial ischemia and reperfusion injury in patients undergoing cardiac surgery.

Activation of PKG and Akt Is Required for Cardioprotection by Ramelteon-Induced Preconditioning and Is Located Upstream of mKCa-Channels

Ramelteon is a Melatonin 1 (MT1)—and Melatonin 2 (MT2)—receptor agonist conferring cardioprotection by pharmacologic preconditioning. While activation of mitochondrial calcium-sensitive potassium (mK_Ca)-channels is involved in this protective mechanism, the specific upstream signaling pathway of Ramelteon-induced cardioprotection is unknown. In the present study, we (1) investigated whether Ramelteon-induced cardioprotection involves activation of protein kinase G (PKG) and/or protein kinase B (Akt) and (2) determined the precise sequence of PKG and Akt in the signal transduction pathway of Ramelteon-induced preconditioning. Hearts of male Wistar rats were randomized and placed on a Langendorff system, perfused with Krebs–Henseleit buffer at a constant pressure of 80 mmHg. All hearts were subjected to 33 min of global ischemia and 60 min of reperfusion. Before ischemia, hearts were perfused with Ramelteon (Ram) with or without the PKG or Akt inhibitor KT5823 and MK2206, respectively (KT5823 + Ram, KT5823, MK2206 + Ram, MK2206). To determine the precise signaling sequence, subsequent experiments were conducted with the guanylate cyclase activator BAY60-2770 and the mK_Ca-channel activator NS1619. Infarct size was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Ramelteon-induced infarct size reduction was completely blocked by KT5823 (p = 0.0012) and MK2206 (p = 0.0005). MK2206 with Ramelteon combined with BAY60-2770 reduced infarct size significantly (p = 0.0014) indicating that PKG activation takes place after Akt. Ramelteon and KT5823 (p = 0.0063) or MK2206 (p = 0.006) respectively combined with NS1619 also significantly reduced infarct size, indicating that PKG and Akt are located upstream of mK_Ca-channels. This study shows for the first time that Ramelteon-induced preconditioning (1) involves activation of PKG and Akt; (2) PKG is located downstream of Akt and (3) both enzymes are located upstream of mK_Ca-channels in the signal transduction pathway.

Sennoside A Induces GLP-1 Secretion Through Activation of the ERK1/2 Pathway in L-Cells

PURPOSE

Glucagon-like peptide-1 (GLP-1) is secreted from the intestinal L-cells to stimulate insulin secretion in the blood glucose control. Our previous study indicates that Sennoside A (SA) can increase the plasma GLP-1 level in a mouse model of type 2 diabetes. However, the mechanism of SA activity remains largely unknown. This issue was explored in this study.

MATERIALS AND METHODS

C57BL/6 mice were randomly divided into four groups: a control group without drug treatment, and the other groups with different SA dosages, respectively. Blood glucose was assayed by oral glucose tolerance test (OGTT). Plasma GLP-1 and insulin were investigated. Colon tissues were collected for mRNA or Western blot analysis. Immunofluorescence staining assays were performed to evaluate the number of β-cells and L-cells. In NCI-H716 cells, extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitors were employed to investigate the SA-induced GLP-1 secretion mechanism.

RESULTS

In this work, the SA was found to improve OGTT in mice. Plasma GLP-1 and insulin were markedly elevated by SA at the dosage of 45 mg/kg/day. Meanwhile, the increased phosphorylation status of EKR1/2 and prohormone convertase 1/3 (PC1/3) proteins were observed in the colon of SA-treated mice. The number of L-cells exhibited no change in each group. In the NCI-H716 cells, GLP-1 secretion induced by SA was blocked by the ERK1/2 inhibitor.

CONCLUSION

The present study provides a direct evidence for the interaction between SA and L cells for induction of GLP-1 secretion. These data suggest that GLP-1 secretion induced by SA is dependent on the ERK1/2 signaling pathway. Therefore, the SA is a new drug candidate for the type 2 diabetes treatment by induction of GLP-1 secretion.

MicroRNA-31 regulating apoptosis by mediating the phosphatidylinositol-3 kinase/protein kinase B signaling pathway in treatment of spinal cord injury

Apoptosis is a highly conservative energy demand program for non-inflammatory cell death, which is extremely significant in normal physiology and disease. There are many techniques used for studying apoptosis. MicroRNA (miRNA) is closely related to cell apoptosis, and especially microRNA-31 (miR-31) is involved in apoptosis by regulating a large number of target genes and signaling pathways. In many neurological diseases, cell apoptosis or programmed cell death plays an important role in the reduction of cell number, including the reduction of neurons in spinal cord injuries. In recent years, the phosphoinositol 3-kinase/AKT (PI3K/AKT) signal pathway, as a signal pathway involved in a variety of cell functions, has been studied in spinal cord injury diseases. The PI3K/AKT pathway directly or indirectly affects whether apoptosis occurs in a cell, thereby affecting a significant intracellular event sequence. This paper reviewed the interactions of miR-31 target sites in the PI3K/AKT signaling pathway, and explored new ways to prevent and treat spinal cord injury by regulating the effect of miR-31 on apoptosis.

Role of the Extracellular Signal-Regulated Kinase 1/2 Signaling Pathway in Ischemia-Reperfusion Injury

Extracellular signal-regulated kinase 1/2 (ERK_1/2), an important member of the mitogen-activated protein kinase family, is found in many organisms, and it participates in intracellular signal transduction. Various stimuli induce phosphorylation of ERK_1/2 in vivo and in vitro. Phosphorylated ERK_1/2 moves to the nucleus, activates many transcription factors, regulates gene expression, and controls various physiological processes, finally inducing repair processes or cell death. With the aging of the population around the world, the occurrence of ischemia-reperfusion injury (IRI), especially in the brain, heart, kidney, and other important organs, is becoming increasingly serious. Abnormal activation of the ERK_1/2 signaling pathway is closely related to the development and the metabolic mechanisms of IRI. However, the effects of this signaling pathway and the underlying mechanism differ between various models of IRI. This review summarizes the ERK_1/2 signaling pathway and the molecular mechanism underlying its role in models of IRI in the brain, heart, liver, kidneys, and other organs. This information will help to deepen the understanding of ERK_1/2 signals and deepen the exploration of IRI treatment based on the ERK_1/2 study.

Cathelicidin-related antimicrobial peptide protects against myocardial ischemia/reperfusion injury

BACKGROUND

Cathelicidins are a major group of natural antimicrobial peptides which play essential roles in regulating host defense and immunity. In addition to the antimicrobial and immunomodulatory activities, recent studies have reported the involvement of cathelicidins in cardiovascular diseases by regulating inflammatory response and microvascular dysfunction. However, the role of cathelicidins in myocardial apoptosis upon cardiac ischemia/reperfusion (I/R) injury remains largely unknown.

METHODS

CRAMP (cathelicidin-related antimicrobial peptide) levels were measured in the heart and serum from I/R mice and in neonatal mouse cardiomyocytes treated with oxygen glucose deprivation/reperfusion (OGDR). Human serum cathelicidin antimicrobial peptide (LL-37) levels were measured in myocardial infarction (MI) patients. The role of CRAMP in myocardial apoptosis upon I/R injury was investigated in mice injected with the CRAMP peptide and in CRAMP knockout (KO) mice, as well as in OGDR-treated cardiomyocytes.

RESULTS

We observed reduced CRAMP level in both heart and serum samples from I/R mice and in OGDR-treated cardiomyocytes, as well as reduced LL-37 level in MI patients. Knockdown of CRAMP enhanced cardiomyocyte apoptosis, and CRAMP KO mice displayed increased infarct size and myocardial apoptosis. In contrast, the CRAMP peptide reduced cardiomyocyte apoptosis and I/R injury. The CRAMP peptide inhibited cardiomyocyte apoptosis by activation of Akt and ERK1/2 and phosphorylation and nuclear export of FoxO3a. c-Jun was identified as a negative regulator of the CRAMP gene. Moreover, lower level of serum LL-37/neutrophil ratio was associated with readmission and/or death in MI patients during 1-year follow-up.

CONCLUSIONS

CRAMP protects against cardiomyocyte apoptosis and cardiac I/R injury via activation of Akt and ERK and phosphorylation and nuclear export of FoxO3a. Increasing LL-37 might be a novel therapy for cardiac ischemic injury.

Remifentanil Induces Cardio Protection Against Ischemia/Reperfusion Injury by Inhibiting Endoplasmic Reticulum Stress Through the Maintenance of Zinc Homeostasis

BACKGROUND

Although it is well known that remifentanil (Rem) elicits cardiac protection against ischemia/reperfusion (I/R) injury, the underlying mechanism remains unclear. This study tested if Rem can protect the heart from I/R injury by inhibiting endoplasmic reticulum (ER) stress through the maintenance of zinc (Zn) homeostasis.

METHODS

Isolated rat hearts were subjected to 30 minutes of regional ischemia followed by 2 hours of reperfusion. Rem was given by 3 consecutive 5-minute infusions, and each infusion was followed by a 5-minute drug-free perfusion before ischemia. Total Zn concentrations in cardiac tissue, cardiac function, infarct size, and apoptosis were assessed. H9c2 cells were subjected to 6 hours of hypoxia and 2 hours of reoxygenation (hypoxia/reoxygenation [H/R]), and Rem was given for 30 minutes before hypoxia. Metal-responsive transcription factor 1 (MTF1) overexpression plasmids were transfected into H9c2 cells 48 hours before hypoxia. Intracellular Zn level, cell viability, and mitochondrial injury parameters were evaluated. A Zn chelator N,N,N',N'-tetrakis-(2-pyridylmethyl) ethylenediamine (TPEN) or an ER stress activator thapsigargin was administrated during in vitro and ex vivo studies. The regulatory molecules related to Zn homeostasis and ER stress in cardiac tissue, and cardiomyocytes were analyzed by Western blotting.

RESULTS

Rem caused significant reversion of Zn loss from the heart (Rem + I/R versus I/R, 9.43 ± 0.55 vs 7.53 ± 1.18; P < .05) by suppressing the expression of MTF1 and Zn transporter 1 (ZnT1). The inhibited expression of ER stress markers after Rem preconditioning was abolished by TPEN. Rem preconditioning improved the cardiac function accompanied by the reduction of infarct size (Rem + I/R versus I/R, 21% ± 4% vs 40% ± 6%; P < .05). The protective effects of Rem could be reserved by TPEN and thapsigargin. Similar effects were observed in H9c2 cells exposed to H/R. In addition, MTF1 overexpression blocked the inhibitory effects of Rem on ZnT1 expression and ER stress at reoxygenation. Rem attenuated the collapse of mitochondrial membrane potential (ΔΨm) and the generation of mitochondrial reactive oxygen species by inhibiting ER stress via cardiac Zn restoration (Rem + H/R versus H/R, 79.57% ± 10.62% vs 58.27% ± 4.32%; P < .05).

CONCLUSIONS

Rem maintains Zn homeostasis at reperfusion by inhibiting MTF1 and ZnT1 expression, leading to the attenuation of ER stress and cardiac injury. Our findings provide a promising therapeutic approach for managing acute myocardial I/R injury.

Hypoxic conditioning in blood vessels and smooth muscle tissues: effects on function, mechanisms, and unknowns

Hypoxic preconditioning, the protective effect of brief, intermittent hypoxic or ischemic episodes on subsequent more severe hypoxic episodes, has been known for 30 yr from studies on cardiac muscle. The concept of hypoxic preconditioning has expanded; excitingly, organs beyond the heart, including the brain, liver, and kidney, also benefit. Preconditioning of vascular and visceral smooth muscles has received less attention despite their obvious importance to health. In addition, there has been no attempt to synthesize the literature in this field. Therefore, in addition to overviewing the current understanding of hypoxic conditioning, in the present review, we consider the role of blood vessels in conditioning and explore evidence for conditioning in other smooth muscles. Where possible, we have distinguished effects on myocytes from other cell types in the visceral organs. We found evidence of a pivotal role for blood vessels in conditioning and for conditioning in other smooth muscle, including the bladder, vascular myocytes, and gastrointestinal tract, and a novel response in the uterus of a hypoxic-induced force increase, which helps maintain contractions during labor. To date, however, there are insufficient data to provide a comprehensive or unifying mechanism for smooth muscles or visceral organs and the effects of conditioning on their function. This also means that no firm conclusions can be drawn as to how differences between smooth muscles in metabolic and contractile activity may contribute to conditioning. Therefore, we have suggested what may be general mechanisms of conditioning occurring in all smooth muscles and tabulated tissue-specific mechanistic findings and suggested ideas for further progress.

Mechanisms involved in adenosine pharmacological preconditioning-induced cardioprotection

Adenosine is a naturally occurring breakdown product of adenosine triphosphate and plays an important role in different physiological and pathological conditions. Adenosine also serves as an important trigger in ischemic and remote preconditioning and its release may impart cardioprotection. Exogenous administration of adenosine in the form of adenosine preconditioning may also protect heart from ischemia-reperfusion injury. Endogenous release of adenosine during ischemic/remote preconditioning or exogenous adenosine during pharmacological preconditioning activates adenosine receptors to activate plethora of mechanisms, which either independently or in association with one another may confer cardioprotection during ischemia-reperfusion injury. These mechanisms include activation of K_ATP channels, an increase in the levels of antioxidant enzymes, functional interaction with opioid receptors; increase in nitric oxide production; decrease in inflammation; activation of transient receptor potential vanilloid (TRPV) channels; activation of kinases such as protein kinase B (Akt), protein kinase C, tyrosine kinase, mitogen activated protein (MAP) kinases such as ERK 1/2, p38 MAP kinases and MAP kinase kinase (MEK 1) MMP. The present review discusses the role and mechanisms involved in adenosine preconditioning-induced cardioprotection.

Remifentanil preconditioning confers cardioprotection via c-Jun NH2-terminal kinases and extracellular signal regulated kinases pathways in ex-vivo failing rat heart

Remifentanil preconditioning (RPC) exerts protection in normal hearts, but has not been investigated in heart failure. The aim of the present study was to evaluate the effect of RPC in a chronic failing rat heart model and the mechanisms involving mitogen-activated protein kinases (MAPK) and Bcl-2 protein family. The doxorubicin induced failing rat hearts were subjected to 30 min ischemia / 120 min reperfusion (IR) with or without RPC by using Langendorff apparatus. RPC was induced by three cycles of 5 min remifentanil / 5 min drug-free perfusion before IR, with three different concentrations: 25, 50 and 100 μg/l. An extracellular signal regulated kinases (ERK) inhibitor PD98059, p38MAPK inhibitor SB203580, c-Jun NH₂-terminal kinases (JNK) inhibitor SP600125 were perfused at 10 min before RPC. Infarct size, cardiac function and protein kinase activity were determined. RPC significantly reduced infarct size and the rise in lactate dehydrogenase (LDH) level caused by IR injury in failing heart. The JNK inhibitor SP600125 and ERK inhibitor PD98059 abolished the RPC mediated reduction effect on the infarct size and LDH activity after reperfusion. In addition, RPC increased the phosphorylation of JNK, ERK1/2 and the downstream GSK-3β, as well as the Bcl-2/Bax ratio, while, these changes were completely reversed by SP600125 and PD98059. And of note, SB203580 had no effect. In conclusion, our results suggested that the activation of JNK and ERK pathways, by leading to inhibition of GSK-3β and regulating Bcl-2 protein family, is a major mechanism that RPC confers cardioprotection in failing rat heart.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

The key role of microtubules in hypoxia preconditioning-induced nuclear translocation of HIF-1α in rat cardiomyocytes

Background

Hypoxia-inducible factor (HIF)-1 is involved in the regulation of hypoxic preconditioning in cardiomyocytes. Under hypoxic conditions, HIF-1α accumulates and is translocated to the nucleus, where it forms an active complex with HIF-1β and activates transcription of approximately 60 kinds of hypoxia-adaptive genes. Microtubules are hollow tubular structures in the cell that maintain cellular morphology and that transport substances. This study attempted to clarify the role of microtubule structure in the endonuclear aggregation of HIF-1α following hypoxic preconditioning of cardiomyocytes.

Methods

Primary rat cardiomyocytes were isolated and cultured. The cardiomyocyte culture system was used to establish a hypoxia model and a hypoxic preconditioning model. Interventions were performed on primary cardiomyocytes using a microtubule-depolymerizing agent and different concentrations of a microtubule stabilizer. The microtubule structure and the degree of HIF-1α nuclear aggregation were observed by confocal laser scanning microscopy. The expression of HIF-1α in the cytoplasm and nucleus was detected using Western blotting. Cardiomyocyte energy content, reflected by adenosine triphosphate/adenosine diphosphate (ATP/ADP), and key glycolytic enzymes were monitored by colorimetry and high-performance liquid chromatography (HPLC). Reactive oxygen species (ROS) production was also used to comprehensively assess whether microtubule stabilization can enhance the myocardial protective effect of hypoxic preconditioning.

Results

During prolonged hypoxia, it was found that the destruction of the microtubule network structure of cardiomyocytes was gradually aggravated. After this preconditioning, an abundance of HIF-1α was clustered in the nucleus. When the microtubules were depolymerized and hypoxia pretreatment was performed, HIF-1α clustering occurred around the nucleus, and HIF-1α nuclear expression was low. The levels of key glycolytic enzymes were significantly higher in the microtubule stabilizer group than in the hypoxia group. Additionally, the levels of lactate dehydrogenase and ROS were significantly lower in the microtubule stabilizer group than in the hypoxia group.

Conclusion

The microtubules of cardiomyocytes may be involved in the process of HIF-1α endonuclear aggregation, helping to enhance the anti-hypoxic ability of cardiomyocytes.

14,15-EET Suppresses Neuronal Apoptosis in Ischemia-Reperfusion Through the Mitochondrial Pathway

Neuronal apoptosis mediated by the mitochondrial apoptosis pathway is an important pathological process in cerebral ischemia-reperfusion injury. 14,15-EET, an intermediate metabolite of arachidonic acid, can promote cell survival during ischemia/reperfusion. However, whether the mitochondrial apoptotic pathway is involved this survival mechanism is not fully understood. In this study, we observed that infarct size in ischemia-reperfusion injury was reduced in sEH gene knockout mice. In addition, Caspase 3 activation, cytochrome C release and AIF nuclear translocation were also inhibited. In this study, 14,15-EET pretreatment reduced neuronal apoptosis in the oxygen-glucose deprivation and re-oxygenation group in vitro. The mitochondrial apoptosis pathway was also inhibited, as evidenced by AIF translocation from the mitochondria to nucleus and the reduction in the expressions of cleaved-caspase 3 and cytochrome C in the cytoplasm. 14,15-EET could reduce neuronal apoptosis through upregulation of the ratio of Bcl-2 (anti-apoptotic protein) to Bax (apoptosis protein) and inhibition of Bax aggregation onto mitochondria. PI3K/AKT pathway is also probably involved in the reduction of neuronal apoptosis by EET. Our study suggests that 14,15-EET could suppress neuronal apoptosis and reduce infarct volume through the mitochondrial apoptotic pathway. Furthermore, the PI3K/AKT pathway also appears to be involved in the neuroprotection against ischemia-reperfusion by 14,15-EET.

Ilexsaponin A attenuates ischemia-reperfusion-induced myocardial injury through anti-apoptotic pathway

The protective effects of ilexsaponin A on ischemia-reperfusion-induced myocardial injury were investigated. Myocardial ischemia/reperfusion model was established in male Sprague–Dawley rats. Myocardial injury was evaluated by TTC staining and myocardial marker enzyme leakage. The in vitro protective potential of Ilexsaponin A was assessed on hypoxia/reoxygenation cellular model in neonatal rat cardiomyocytes. Cellular viability and apoptosis were evaluated by MTT and TUNEL assay. Caspase-3, cleaved caspase-3, bax, bcl-2, p-Akt and Akt protein expression levels were detected by western-blot. Ilexsaponin A treatment was able to attenuate the myocardial injury in ischemia/reperfusion model by reducing myocardial infarct size and lower the serum levels of LDH, AST and CK-MB. The in vitro study also showed that ilexsaponin A treatment could increase cellular viability and inhibit apoptosis in hypoxia/reoxygenation cardiomyocytes. Proapoptotic proteins including caspase-3, cleaved caspase-3 and bax were significantly reduced and anti-apoptotic protein bcl-2 was significantly increased by ilexsaponin A treatment in hypoxia/reoxygenation cardiomyocytes. Moreover, Ilexsaponin A treatment was able to increase the expression levels of p-Akt in hypoxia/reoxygenation cellular model and myocardial ischemia/reperfusion animal model. Coupled results from both in vivo and in vitro experiments indicate that Ilexsaponin A attenuates ischemia-reperfusion-induced myocardial injury through anti-apoptotic pathway.