Temporal Expression of Apelin/Apelin Receptor in Ischemic Stroke and its Therapeutic Potential

Ursolic acid inhibits NF-κB signaling and attenuates MMP-9/TIMP-1 in progressive osteoarthritis: a network pharmacology-based analysis

Osteoarthritis (OA) is a degenerative joint disease, characterized by infiltration of monocytes into the synovial joint which promotes inflammation, stiffness, joint swelling, cartilage degradation and further bone destruction. The leaves of Ocimum forskolei have been used for inflammation-related disease management in traditional medicine. Additionally, the downregulation of NF-κB and the MMP/TIMP-1 ratio has been shown to protect against OA. The LC-HR-MS metabolic analysis of Ocimum yielded 19 putative compounds, among which ursolic acid (UA) was detected. Ursolic acid possesses significant anti-inflammatory effects and has been reported to downregulate oxidative stress and inflammatory biomarkers. It was tested on rats in a model of intra-articular carrageenan injection to investigate its efficacy on osteoarthritis progression. The UA emulgel exerted chondroprotective, analgesic and local anaesthetic efficacies confirmed via histopathological investigation and radiographical imaging. A network pharmacology followed by molecular docking highlighted TNF-α, TGF-β and NF-κB as the top filtered genes. Quantitative real-time PCR analysis showed that UA significantly attenuated serum levels of TNF-α, IL-1β, NF-κB, MMP-9/TIMP-1 and elevated levels of TGF-β. Taken together, these results suggest that UA could serve as a functional food-derived phytochemical with a multi-targeted efficacy on progression of OA, regulating the immune and inflammatory responses, particularly, attenuating chondrocytes degeneration via suppression of NF-κB and MMP-9/TIMP-1. Accordingly, UA might be a promising alternative to conventional therapy for safe, easily applicable and effective management of OA.

Immunological characterization of stroke-heart syndrome and identification of inflammatory therapeutic targets

Acute cardiac dysfunction caused by stroke-heart syndrome (SHS) is the second leading cause of stroke-related death. The inflammatory response plays a significant role in the pathophysiological process of cardiac damage. However, the mechanisms underlying the brain-heart interaction are poorly understood. Therefore, we aimed to analysis the immunological characterization and identify inflammation therapeutic targets of SHS. We analyzed gene expression data of heart tissue 24 hours after induction of ischemia stoke by MCAO or sham surgery in a publicly available dataset (GSE102558) from Gene Expression Omnibus (GEO). Bioinformatics analysis revealed 138 differentially expressed genes (DEGs) in myocardium of MCAO-treated compared with sham-treated mice, among which, immune and inflammatory pathways were enriched. Analysis of the immune cells infiltration showed that the natural killer cell populations were significantly different between the two groups. We identified five DIREGs, Aplnr, Ccrl2, Cdkn1a, Irak2, and Serpine1 and found that their expression correlated with specific populations of infiltrating immune cells in the cardiac tissue. RT-qPCR and Western blot methods confirmed significant changes in the expression levels of Aplnr, Cdkn1a, Irak2, and Serpine1 after MCAO, which may serve as therapeutic targets to prevent cardiovascular complications after stroke.

circRNA landscape in dorsal root ganglia from mice with collagen antibody-induced arthritis

Circular RNAs are a novel class of RNA molecules that are covalently closed into a ring structure. They are an epigenetic regulatory mechanism, and their best-studied function is regulation of microRNA activity. As such circular RNAs may be involved in the switch from acute to chronic pain. They have previously been studied in the context of neuropathic pain models, but their importance in inflammation-induced chronic pain models is unexplored. Microarray analysis of dorsal root ganglia collected in the late phase of collagen antibody-induced arthritis (day 59) were used to elucidate the relevance of circular RNAs in the mechanical hypersensitivity caused by this model. 120 circular RNA genes were found to be significantly differentially regulated in female BALB/c mice with collagen antibody-induced arthritis. Six genes were chosen for RT-qPCR analysis in the late (day 54-60) as well as the inflammatory (day 11-12) phase of this model. This validated an increase in circNufip1 expression in the late phase of collagen antibody-induced arthritis. Additionally, it was found that circVps13 and circMicall1 are upregulated in the inflammatory phase. Interestingly, no changes were found in dorsal root ganglia from mice injected with Freund's Complete Adjuvant (day 3) nor mice with spared nerve injury (day 20), despite their similarities to inflammatory and late phase collagen antibody-induced arthritis, respectively. This study provides evidence that mild circular RNA changes occur in dorsal root ganglia of mice with collagen antibody-induced arthritis that are, bioinformatically, predicated to be involved in processes relevant to sensitization.

APJ as Promising Therapeutic Target of Peptide Analogues in Myocardial Infarction- and Hypertension-Induced Heart Failure

The widely expressed G protein-coupled apelin receptor (APJ) is activated by two bioactive endogenous peptides, apelin and ELABELA (ELA). The apelin/ELA-APJ-related pathway has been found involved in the regulation of many physiological and pathological cardiovascular processes. Increasing studies are deepening the role of the APJ pathway in limiting hypertension and myocardial ischaemia, thus reducing cardiac fibrosis and adverse tissue remodelling, outlining APJ regulation as a potential therapeutic target for heart failure prevention. However, the low plasma half-life of native apelin and ELABELA isoforms lowered their potential for pharmacological applications. In recent years, many research groups focused their attention on studying how APJ ligand modifications could affect receptor structure and dynamics as well as its downstream signalling. This review summarises the novel insights regarding the role of APJ-related pathways in myocardial infarction and hypertension. Furthermore, recent progress in designing synthetic compounds or analogues of APJ ligands able to fully activate the apelinergic pathway is reported. Determining how to exogenously regulate the APJ activation could help to outline a promising therapy for cardiac diseases.

The Yin and Yang Effect of the Apelinergic System in Oxidative Stress

Apelin is an endogenous ligand for the G protein-coupled receptor APJ and has multiple biological activities in human tissues and organs, including the heart, blood vessels, adipose tissue, central nervous system, lungs, kidneys, and liver. This article reviews the crucial role of apelin in regulating oxidative stress-related processes by promoting prooxidant or antioxidant mechanisms. Following the binding of APJ to different active apelin isoforms and the interaction with several G proteins according to cell types, the apelin/APJ system is able to modulate different intracellular signaling pathways and biological functions, such as vascular tone, platelet aggregation and leukocytes adhesion, myocardial activity, ischemia/reperfusion injury, insulin resistance, inflammation, and cell proliferation and invasion. As a consequence of these multifaceted properties, the role of the apelinergic axis in the pathogenesis of degenerative and proliferative conditions (e.g., Alzheimer's and Parkinson's diseases, osteoporosis, and cancer) is currently investigated. In this view, the dual effect of the apelin/APJ system in the regulation of oxidative stress needs to be more extensively clarified, in order to identify new potential strategies and tools able to selectively modulate this axis according to the tissue-specific profile.

Elabela-APJ axis attenuates cerebral ischemia/reperfusion injury by inhibiting neuronal ferroptosis

Ferroptosis is a form of non-apoptotic cell death caused by iron-dependent peroxidation of lipids. It contributes to ischemic stroke-induced neuronal damage. Elabela (ELA), a novel endogenous ligand for Apelin receptor (APJ), regulates oxidative stress and exerts a protective role in cardiovascular disease. However, the effect of ELA-APJ axis on cellular ferroptosis in cerebral ischemia/reperfusion (I/R) remains elusive. The present study showed that ELA and APJ were expressed on neurons and increased after cerebral I/R injury. The I/R insult triggered typical molecular and morphological features of neuronal ferroptosis, including iron and MDA accumulation, mitochondrial shrink and membrane rupture, upregulation of positive ferroptosis regulators and downregulation of negative regulators. ELA-32 treatment reduced brain infarction and ameliorated neurobehavioral deficits and cognitive dysfunction. Moreover, ELA-32 administration alleviated neuronal ferroptosis, accompanied by reduced iron deposition, decreased mitochondrial damage, relived lipid peroxidation and glutathione reduction. Such effects of ELA-32 were abolished by AAV-APJ-RNAi or nuclear factor erythroid 2-related factor 2 (NRF2) inhibitor ML385. Mechanistically, ELA was shown to bind to APJ and activate NRF2/ARE anti-oxidative signaling pathway via Gα13. Together, these findings suggested that ELA-APJ axis mitigates neuronal ferroptosis after ischemic stroke and that the ELA-32 peptide may be a putative therapeutic avenue for ischemic stroke.

[Peripheral neuropathy, onycholysis and health-related quality of life in womens with breast cancer treated with taxanes. Prospective longitudinal study.]

OBJECTIVE

Peripheral neuropathy and onycholysis are adverse events produced by taxanes in breast cancer that persist even after the end of treatment and negatively influence quality of life. The objectives of the study were to describe these side effects and the degree of involvement and relating them to the drug doses received.

METHODS

Prospective, cross-sectional study of in 50 womens dignosed of breast cancer, treated with docetaxel and paclitaxel in Hospital Universitario Miguel Servet in Zaragoza (Aragón, Spain). CTCAE v.5.0 scale and Semes Weinsten test were used to evaluate peripheral neuropathy and onycholysis. ECOG scale was performed to measure the health-related quality of life. Study variables were evaluated before-during treatment and 1 and 6 months after finish treatment. Statistical analysis was performed using Jamovi 1.2®. For the relationship of the qualitative variables, the chi-square, Fisher's exact test, Mc's test were used. Nemar and the Odds Ratio test. Effects were considered significant if p<0.05.

RESULTS

43 subjects were included. During treatment the 9.8 presented motor neuropathy and 12.2% sensitive neuropathy, 37.2% onycholisis in upper extremities and 39.5% in lower extremities (χ2=11.3; p<0.001 / χ2=13.0; p<0.001) and 38.1% a health related quality of live limited in excessive activities (χ2=10.3; p=0.001). Post-treatment evaluation the 20.9% presented motor neuropathy and 32.6% sensitive neuropathy (χ2=3.57; p=0.059 / χ2=6.23; p=0.013), the 86% onycholisis in upper extremities and lower extremities (χ2=6.07; p=0.048 / χ2=10.1; p=0.006) and 58.5% a health related quality of live limited in excessive activities (χ2=8.47; p=0.014). 6 month later, the initials parameters were not recuperated.

CONCLUSIONS

Taxanes have a negative impact on the health-related quality of life in patients, even 6 months after finishing treatment due to the peripheral neuropathy and onycholysis that they cause.

Chronic stress-induced apoptosis is mitigated by young mitochondria transplantation in the prefrontal cortex of aged rats

Objectives

Apoptosis is common and often comorbid with aging and stress-related mood disorders. Evidence suggests that fresh mitochondria could reverse age-related dysfunctions in organs, especially in the brain. Therefore, this study investigated the effect of young mitochondria administration on the apoptosis process in the prefrontal cortex (PFC) of aged rats exposed to chronic stress.

Materials and Methods

Aged (22 months old) male rats were randomly assigned into four groups: aged control (AC), aged rats treated with young mitochondria (A+M), aged rats subjected to chronic stress for four weeks (A+St), and aged rats subjected to chronic stress and treated with young mitochondria (A+St+M). A+M and A+St+M groups received a single ICV injection (10 μl) of fresh mitochondria isolated from the brain of young rats for five minutes (2 µl/min). Finally, the levels of Malondialdehyde (MDA), Cytochrome c (Cyt c), Bax, Bcl-2, and Caspase-3 expression were investigated in the PFC.

Results

Young mitochondria administration reduced neuronal apoptosis in the PFC, associated with down-regulation of MDA, Bax, and Caspase-3 and up-regulation of Bcl-2. Moreover, fresh mitochondria partially improved the chronic stress-induced mitochondrial dysfunction in aged rats, as indicated by reduced cytochrome c (Cyt c) release from the mitochondria.

Conclusion

These results suggest mitotherapy could reverse cell viability and mitochondrial dysfunction-induced apoptosis in the PFC tissue of aged rats subjected to stressful stimuli.

Acute and long-term exercise differently modulate plasma levels of oxylipins, endocannabinoids, and their analogues in young sedentary adults: A sub-study and secondary analyses from the ACTIBATE randomized controlled-trial

BACKGROUND

Fatty acid-derived lipid mediators including oxylipins, endocannabinoids (eCBs), and their analogues, have emerged as key metabolites in the inflammatory and immune response to physiological stressors.

METHODS

This report was based on a sub-study and secondary analyses the ACTIBATE single-center unblinded randomized controlled trial (ClinicalTrials.gov ID: NCT02365129). The study was performed in the Sport and Health University Research Institute and the Virgen de las Nieves University Hospital of the University of Granada. Eligible participants were young, sedentary adults with no chronic diseases. Here, we performed both an acute endurance and resistance exercise sub-studies (n.ß=.ß14 and 17 respectively), and a 24-week supervised exercise intervention, combining endurance and resistance exercise training at moderate-intensity (MOD-EX) or vigorous-intensity (VIG-EX) exercise groups, in young sedentary adults. Randomization was performed by unrestricted randomization. Plasma levels of oxylipins, eCBs, and their analogues were measured using liquid chromatography-tandem mass spectrometry.

FINDINGS

Both endurance and resistance exercise increased by.ß+50% the plasma levels of dihomo-..-linolenic acid and arachidonic acid (AA) omega-6 derived oxylipins, as well as eicosapentaenoic acid and docosahexaenoic acid omega-3 derived after 3 and 120.ßmin of the bout of exercise (all ..².ß....ß0.219 and P.ß..±.ß0.039). These exercise modalities also increased the levels of anandamide and eCBs analogues (+25%). 145 young sedentary adults were assigned to a control (CON, n.ß=.ß54), a MOD-EX (n.ß=.ß48) or a VIG-EX (n.ß=.ß43). 102 participants were included in the final long-term analyses (CON, n.ß=.ß36; MOD-EX, n.ß=.ß33; and VIG-EX, n.ß=.ß33) of the trial. After 24-week of supervised exercise, MOD-EX decreased plasma levels of omega-6 oxylipins, concretely linoleic acid (LA) and adrenic acid derived oxylipins, and the eCBs analogues OEA and LEA in comparison to the CON (all P.ß..±.ß0.021). VIG-EX decreased LA-derived oxylipins and LEA compared to CON. No relevant adverse events were recorded.

INTERPRETATION

Endurance and resistance exercises acutely increased plasma levels of oxylipins, eCBs, and their analogues, whereas 24 weeks of exercise training decreased fasting plasma levels of omega-6 oxylipins, and eCBs analogues in young, sedentary adults.

FUNDING

See Acknowledgments section.

Levels of Serum and Urine Catecholaminergic and Apelinergic System Members in Acute Ischemic Stroke Patients

Objective: To compare levels of catecholaminergic system members, renalase, cerebellin, and their substrates, epinephrine, norepinephrine, and dopamine, and apelinergic system members, apelin, elabela, and nitric oxide in the blood and urine of patients with acute ischemic stroke and healthy controls. Materials and Methods: 42 patients with acute ischemic stroke and 42 age and sex-matched healthy controls were included in the study. Blood and urine samples were collected simultaneously and within the first 24 hours after the onset of acute stroke clinical manifestations and were measured using an ELISA method. Results: The levels of serum and urine cerebellin, renalase, epinephrine, norepinephrine, dopamine, apelin, elebela, and nitric oxide were similar in ischemic stroke and in control groups (P>0.05). Strong correlations were found between renalase, cerebellin, and catecholamine levels in serum and urine (p

The Apelin/APLNR system modulates tumor immune response by reshaping the tumor microenvironment

Apelin is an endogenous ligand of the Apelin receptor (APLNR), a seven-transmembrane G protein-coupled receptor, which is widely distributed in human tissue. The Apelin/APLNR system is involved in regulating several physiological and pathological processes. The Apelin expression is increased in a variety of cancer and the Apelin/APLNR system could regulate the development of tumors through mediating autophagy, apoptosis, pyroptosis, and other biological processes to regulate tumor cell proliferation, migration, and invasion. The Apelin/APLNR system also participates in immune response and immune regulation through PI3K-Akt, ERK-MAPK, and other signal pathways. The latest research points out that there is a negative regulatory relationship between APLNR and immune checkpoint PD-L1. In this review, we outline the significance of the Apelin/APLNR signaling pathway in tumorigenesis and its immune regulation. These endeavors provide new insights into the translational application of Apelin/APLNR in cancer and may contribute to the promotion of more effective treatments for cancers.

The Neuroprotective Effect of Shenmai Injection on Oxidative Stress Injury in PC12 Cells Based on Network Pharmacology

Background

Shenmai injection (SMI) has been used in the treatment of cerebrovascular diseases and cardiovascular diseases. However, the underlying mechanism of SMI for neuroprotection after acute ischemic stroke (AIS) remains unclear. This study aimed to explore the potential molecular mechanism of SMI in treating reperfusion injury after AIS and its protective effect on PC12 cells against oxidative stress through in vitro experiments based on network pharmacological predictions.

Methods

The network pharmacology method was used to collect the compounds in SMI and AIS damage targets, construct the "drug-disease" target interaction network diagram, screen the core targets, and predict the potential mechanism of SMI treatment of AIS. In addition, the oxidative stress model of PC12 cells was induced by H₂O₂ to evaluate the neuroprotective effect and predictive mechanism of SMI on PC12 cells.

Results

A component-targeted disease and functional pathway network showed that 24 components from SMI regulated 77 common targets shared by SMI and AIS. In PC12 cells damaged by H₂O₂, SMI increased cell survival, alleviated oxidative stress injury, prevented cell apoptosis, and increased the expression of APJ, AMPK, and p-GSK-3β. After Si-APJ silenced APJ expression, the above protective effect of SMI was significantly weakened.

Conclusion

SMI is characterized by multiple components, multiple targets, and multiple pathways and inhibits oxidative stress and alleviates nerve injury induced by H₂O₂ through regulating the APJ/AMPK/GSK-3β pathway.

Endoplasmic Reticulum Stress and the Unfolded Protein Response in Cerebral Ischemia/Reperfusion Injury

Ischemic stroke is an acute cerebrovascular disease characterized by sudden interruption of blood flow in a certain part of the brain, leading to serious disability and death. At present, treatment methods for ischemic stroke are limited to thrombolysis or thrombus removal, but the treatment window is very narrow. However, recovery of cerebral blood circulation further causes cerebral ischemia/reperfusion injury (CIRI). The endoplasmic reticulum (ER) plays an important role in protein secretion, membrane protein folding, transportation, and maintenance of intracellular calcium homeostasis. Endoplasmic reticulum stress (ERS) plays a crucial role in cerebral ischemia pathophysiology. Mild ERS helps improve cell tolerance and restore cell homeostasis; however, excessive or long-term ERS causes apoptotic pathway activation. Specifically, the protein kinase R-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring enzyme 1 (IRE1) pathways are significantly activated following initiation of the unfolded protein response (UPR). CIRI-induced apoptosis leads to nerve cell death, which ultimately aggravates neurological deficits in patients. Therefore, it is necessary and important to comprehensively explore the mechanism of ERS in CIRI to identify methods for preserving brain cells and neuronal function after ischemia.

Research Progress on Mechanism of Neuroprotective Roles of Apelin-13 in Prevention and Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common type of dementia. Currently, more than 50 million people live with dementia worldwide, and this number is expected to increase. Some of the typical pathological changes of AD include amyloid plaque, hyperphosphorylation of tau protein, secretion of inflammatory mediators, and neuronal apoptosis. Apelin is a neuroprotective peptide that is widely expressed in the body. Among members of apelin family, apelin-13 is the most abundant with a high neuroprotective function. Apelin-13/angiotensin domain type 1 receptor-associated proteins (APJ) system regulates several physiological and pathophysiological cell activities, such as apoptosis, autophagy, synaptic plasticity, and neuroinflammation. It has also been shown to prevent AD development. This article reviews the research progress on the relationship between apelin-13 and AD to provide new ideas for prevention and treatment of AD.

CTRP1 Attenuates Cerebral Ischemia/Reperfusion Injury via the PERK Signaling Pathway

Cerebral ischemic stroke is one of the leading causes of death worldwide. Previous studies have shown that circulating levels of CTRP1 are upregulated in patients with acute ischemic stroke. However, the function of CTRP1 in neurons remains unclear. The purpose of this study was to explore the role of CTRP1 in cerebral ischemia reperfusion injury (CIRI) and to elucidate the underlying mechanism. Middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R) models were used to simulate cerebral ischemic stroke in vivo and in vitro, respectively. CTRP1 overexpression lentivirus and CTRP1 siRNA were used to observe the effect of CTRP1 expression, and the PERK selective activator CCT020312 was used to activate the PERK signaling pathway. We found the decreased expression of CTRP1 in the cortex of MCAO/R-treated rats and OGD/R-treated primary cortical neurons. CTRP1 overexpression attenuated CIRI, accompanied by the reduction of apoptosis and suppression of the PERK signaling pathway. Interference with CTRP1 expression in vitro aggravated apoptotic activity and increased the expression of proteins involved in the PERK signaling pathway. Moreover, activating the PERK signaling pathway abolished the protective effects of CTRP1 on neuron injury induced by CIRI in vivo and in vitro. In conclusion, CTRP1 protects against CIRI by reducing apoptosis and endoplasmic reticulum stress (ERS) through inhibiting the PERK-dependent signaling pathway, suggesting that CTRP1 plays a crucial role in the pathogenesis of CIRI.

Impact of the apelin/APJ axis in the pathogenesis of Parkinson's disease with therapeutic potential

The pathogenesis of Parkinson's disease (PD) remains elusive. There is still no available disease-modifying strategy against PD, whose management is mainly symptomatic. A growing amount of preclinical evidence shows that a complex interplay between autophagy dysregulation, mitochondrial impairment, endoplasmic reticulum stress, oxidative stress, and excessive neuroinflammation underlies PD pathogenesis. Identifying key molecules linking these pathological cellular processes may substantially aid in our deeper understanding of PD pathophysiology and the development of novel effective therapeutic approaches. Emerging preclinical evidence indicates that apelin, an endogenous neuropeptide acting as a ligand of the orphan G protein-coupled receptor APJ, may play a key neuroprotective role in PD pathogenesis, via inhibition of apoptosis and dopaminergic neuronal loss, autophagy enhancement, antioxidant effects, endoplasmic reticulum stress suppression, as well as prevention of synaptic dysregulation in the striatum, excessive neuroinflammation, and glutamate-induced excitotoxicity. Underlying signaling pathways involve phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin, extracellular signal-regulated kinase 1/2, and inositol requiring kinase 1α/XBP1/C/EBP homologous protein. Herein, we discuss the role of apelin/APJ axis and associated molecular mechanisms on the pathogenesis of PD in vitro and in vivo and provide evidence for its challenging therapeutic potential.

Association of serum vaspin, apelin, and visfatin levels and stroke risk in a Chinese case-control study

Adipose tissue acts as an active endocrine organ secreting a number of adipokines and may be involved in biological mechanism of stroke. Vaspin, apelin, and visfatin play important roles in the regulation of vascular disorders.Our aim was to evaluate whether the concentrations of vaspin, apelin, and visfatin were associated with stroke risk.A total of 235 patients with stroke (156 patients with ischemic stroke and 79 patients with hemorrhagic stroke) and 235 age- and gender-matched healthy controls were included in this study. A sandwich ELISA was developed to measure the serum vaspin, apelin, and visfatin levels.There was a statistically significant difference in the median levels of serum vaspin, apelin, and visfatin levels between stroke cases and controls (vaspin: 1.50 vs 1.07 ng/ml; apelin: 1.56 vs 1.32 pg/ml; visfatin: 23.40 vs 19.65 ng/ml; all P values <.001). Multiple logistic regression analysis showed that, serum vaspin and visfatin levels were significantly inversely associated with increased risk of stroke, and the odds ratios (ORs) in the highest tertile were 2.25 [95% confidence interval (CI) 1.38-3.67; P for trend <.001] for vaspin and 2.56 (95% CI 1.46-4.47; P for trend <.001) for visfatin, respectively, compared with the lowest tertile. Higher apelin levels were marginally associated with lower stroke risk (P for trend =.060).Our study indicated that higher vaspin, apelin, and visfatin levels might be associated with increased stroke risk. Necessary prospective cohort studies should be conducted to confirm this association in the future.

Intranasal drug delivery for treatment of Alzheimer's disease

The Alzheimer's disease is a neurodegenerative condition with severe consequences interfering with patient quality of life. It is characterized as a progressive and irreversible brain disorder hampering memory and thinking, affecting the capacity to perform daily tasks leading to physical and cognitive incapacitation. The conventional treatment occurs by the oral route, but it presents relevant drawbacks such as low bioavailability, fast metabolism, limited brain exposure, and undesirable side effects. The intranasal route has been proposed as a promising alternative to deliver drugs and improve the Alzheimer's disease treatment. Still, there is not a clear alternative delivery system available in the market with advantageous bioavailability and safety. The aim of this review is to perform an overview on the strategies for drug intranasal delivery for Alzheimer's disease treatment. The advantages and disadvantages of this delivery route and the delivery systems developed so far are discussed. A special focus is given on the use of permeation enhancers, the types of intranasal drug delivery devices, as well as possible toxicity concerns.

Transcriptome Response and Spatial Pattern of Gene Expression in the Primate Subventricular Zone Neurogenic Niche After Cerebral Ischemia

The main stem cell niche for neurogenesis in the adult mammalian brain is the subventricular zone (SVZ) that extends along the cerebral lateral ventricles. We aimed at characterizing the initial molecular responses of the macaque monkey SVZ to transient, global cerebral ischemia. We microdissected tissue lining the anterior horn of the lateral ventricle (SVZa) from 7 day post-ischemic and sham-operated monkeys. Transcriptomics shows that in ischemic SVZa, 541 genes were upregulated and 488 genes were down-regulated. The transcription data encompassing the upregulated genes revealed a profile typical for quiescent stem cells and astrocytes. In the primate brain the SVZ is morphologically subdivided in distinct and separate ependymal and subependymal regions. The subependymal contains predominantly neural stem cells (NSC) and differentiated progenitors. To determine in which SVZa region ischemia had evoked transcriptional upregulation, sections through control and ischemic SVZa were analyzed by high-throughput in situ hybridization for a total of 150 upregulated genes shown in the www.monkey-niche.org image database. The majority of the differentially expressed genes mapped to the subependymal layers on the striatal or callosal aspect of the SVZa. Moreover, a substantial number of upregulated genes was expressed in the ependymal layer, implicating a contribution of the ependyma to stem cell biology. The transcriptome analysis yielded several novel gene markers for primate SVZa including the apelin receptor that is strongly expressed in the primate SVZa niche upon ischemic insult.

Angiotensin AT1 receptor antagonism by losartan stimulates adipocyte browning via induction of apelin

Adipocyte browning appears to be a potential therapeutic strategy to combat obesity and related metabolic disorders. Recent studies have shown that apelin, an adipokine, stimulates adipocyte browning and has negative cross-talk with angiotensin II receptor type 1 (AT₁ receptor) signaling. Here, we report that losartan, a selective AT₁ receptor antagonist, induces browning, as evidenced by an increase in browning marker expression, mitochondrial biogenesis, and oxygen consumption in murine adipocytes. In parallel, losartan up-regulated apelin expression, concomitant with increased phosphorylation of protein kinase B and AMP-activated protein kinase. However, the siRNA-mediated knockdown of apelin expression attenuated losartan-induced browning. Angiotensin II cotreatment also inhibited losartan-induced browning, suggesting that AT₁ receptor antagonism-induced activation of apelin signaling may be responsible for adipocyte browning induced by losartan. The in vivo browning effects of losartan were confirmed using both C57BL/6J and ob/ob mice. Furthermore, in vivo apelin knockdown by adeno-associated virus carrying-apelin shRNA significantly inhibited losartan-induced adipocyte browning. In summary, these data suggested that AT₁ receptor antagonism by losartan promotes the browning of white adipocytes via the induction of apelin expression. Therefore, apelin modulation may be an effective strategy for the treatment of obesity and its related metabolic disorders.

Using mRNA deep sequencing to analyze differentially expressed genes during Panax notoginseng saponin treatment of ischemic stroke

Treatment with Panax notoginseng saponin (PNS) can prevent neurological damage in middle cerebral artery occlusion model rats to promote recovery after a stroke. However, the exact molecular mechanisms are unknown and require further study. In the present study, mRNA sequencing was employed to investigate differential gene expression between model and sham groups, and between model and PNS-treated groups. Enrichment of gene data was performed using Gene Ontology analysis and the Kyoto Encyclopedia of Genes and Genomes database. Hub genes were identified and networks were constructed using Cytoscape that were further verified by reverse transcription-quantitative PCR. A total of 1,104 genes of interest were found, which included 690 upregulated and 414 downregulated genes that were identified when the model was compared with the sham group. Additionally, 817 genes of interest, which included 390 upregulated and 427 downregulated genes, were identified when the PNS-treated group was compared with the model group. There were 303 overlapping genes of interest between the analysis of model to sham groups, and the analysis of model to PNS-treated groups. The top 10 genes from the 303 aberrantly expressed genes of interest included ubiquitin conjugating enzyme E2 variant 2, small ubiquitin-related modifier 1, small RNA binding exonuclease protection factor La, Finkel-Biskis-Reilly murine sarcoma virus (FBR-MuSV) ubiquitously expressed, centrosomal protein 290 kDa, DNA-directed RNA polymerase II subunit K, cullin-4B, matrin-3 and vascular endothelial growth factor receptor 2. In conclusion, these genes may be important in the underlying mechanism of PNS treatment in ischemic stroke. Additionally, the present data provided novel insight into the pathogenesis of ischemic stroke.

The MT1G Gene in LUHMES Neurons Is a Sensitive Biomarker of Neurotoxicity

Identification of toxicants that underlie neurological diseases is a neglected area awaiting a valid strategy to identify such toxicants. We sought biomarkers that respond to known neurotoxicants in LUHMES immortalized neurons and evaluated these biomarkers for use in screening libraries of environmental toxicants. LUHMES immortalized human dopaminergic neurons were surveyed by RNA sequencing following challenge with parkinsonian toxicants rotenone, 6-hydroxydopamine, MPP+, and ziram (zinc dimethyldithiocarbamate; Zn²⁺DDC₂), as well as additional toxicants paraquat, MS275, and methylmercury. The metallothionein gene MT1G was the most dynamic gene expression response to all seven toxicants. Multiple toxicants also increased transcripts for SLC30A1 and SLC30A2 zinc secretion transporters, the SLC7A11 xCT cystine/glutamate antiporter important for glutathione synthesis, DNA damage inducible transcript 3 (DDIT3), and secreted growth factors FIBIN and CXCL12, whereas several toxicants decreased expression of the apelin growth factor (APLN). These biomarker genes revealed stress responses to many toxicants at sub-cytotoxic concentrations. Since several of these biomarker genes and prior neurological disease studies implicated disruption of metal distribution, we tested metal chelator thiram (dimethyldithiocarbamate, DDC), ziram, and several other metals and metal chelates for cytotoxicity and induction of MT1G expression. Metals and chelators that caused dynamic increases in MT1G expression also caused cytotoxicity, except Ni²⁺DDC₂ induced MT1G at 5 μM, but lacked cytotoxicity up to 100 μM. These results bolster prior work suggesting that neurons are characteristically sensitive to depletion of glutathione or to disruption of cellular metal distribution and provide biomarkers to search for such neurotoxicants in chemical libraries.

(-)-Clausenamide alleviated ER stress and apoptosis induced by OGD/R in primary neuron cultures

OBJECTIVE

The endoplasmic reticulum stress (ERS) and ERS-related neuronal apoptosis contribute to the cerebral ischemia/reperfusion (I/R) injury. (-)-Clausenamide has been reported to be nootropic and improve learning and memory in amnesia animal models. However, whether (-)-Clau could protect neurons from ischemic injury and the possible mechanism needed further study. The present study aimed to explore the effects of (-)-Clau on primary cortical neurons treated with oxygen-glucose deprivation/reoxygenation (OGD/R).

METHODS

Rat primary cortical neurons were used to set up an injury model of OGD/R which imitated the clinical I/R injury. Cell viability and apoptosis were measured by CCK-8 assay, LDH detection and TUNEL staining, respectively. The activation of GRP78/eIF2α-ATF4-CHOP signaling pathway, one of the three branches of ERS, and cleaved caspase-3, the apoptotic marker, were assessed by western blotting.

RESULTS

OGD/R induced activation of GRP78/eIF2α-ATF4-CHOP signaling pathway. (-)-Clau significantly attenuated OGD/R-induced decrease in the cellular viability and the activation of GRP78, eIF2α, ATF4 and CHOP. To further confirm the effect of (-)-Clau on OGD/R-induced ERS activation, the ERS inducer Tunicamycin (TM) was applied. TM significantly abolished (-)-Clau's protective effect against ERS and neuronal apoptosis, indicating that the protective effect of (-)-Clau was dependent on inhibiting ERS.

CONCLUSIONS

The present work demonstrated for the first time that (-)-Clau could reverse the activation of GRP78/eIF2α-ATF4-CHOP branch, thus inhibited ERS and the subsequent apoptosis induced by OGD/R and promoted cell viability in vitro. (-)-Clau could serve as a promising therapeutic agent in the treatment for ischemic stroke in the future.

ABBREVIATIONS

ATF4: activating transcription factor-4; ATF6: activating transcription factor-6; CHOP: transcriptional induction of CCAAT/enhancer binding protein homologous protein; (-)-Clau: 3-hydroxy-4-phenyl-5a-hydroxybenzylN-methyl-g-lactam; eIF2α: eukaryotic initiation factor 2α; ER: endoplasmic reticulum; ERS: endoplasmic reticulum stress; GRP78: 78-kDa glucose regulated protein; I/R: ischemia/reperfusion; IRE1: inositol requiring enzyme-1; JNK: c-Jun N-terminal kinase; OGD/R: oxygen-glucose deprivation/reoxygenation; PERK: double-stranded RNA-dependent protein kinase-like ER kinase; TM: Tunicamycin; UPR: unfolded protein response.

A Novel Compound YS-5-23 Exhibits Neuroprotective Effect by Reducing β-Site Amyloid Precursor Protein Cleaving Enzyme 1's Expression and H2O2-Induced Cytotoxicity in SH-SY5Y Cells

The abnormally accumulated amyloid-β (Aβ) and oxidative stress contribute to the initiation and progression of Alzheimer's disease (AD). β-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the rate-limiting enzyme for the production of Aβ. Furthermore, Aβ was reported to increase oxidative stress; then the overproduced oxidative stress continues to increase the expression and activity of BACE1. Consequently, inhibition of both BACE1 and oxidative stress is a better strategy for AD therapy compared with those one-target treatment methods. In the present study, our novel small molecule YS-5-23 was proved to possess both of the activities. Specifically, we found that YS-5-23 reduces BACE1's expression in both SH-SY5Y and Swedish mutated amyloid precursor protein (APP) overexpressed HEK293 cells, and it can also suppress BACE1's expression induced by H₂O₂. Moreover, YS-5-23 decreases H₂O₂-induced cytotoxicity including alleviating H₂O₂-induced apoptosis and loss of mitochondria membrane potential (MMP) because it attenuates the reactive oxygen species (ROS) level elevated by H₂O₂. Meanwhile, PI3K/Akt signaling pathway is involved in the anti-H₂O₂ and BACE1 inhibition effect of YS-5-23. Our findings indicate that YS-5-23 may develop as a drug candidate in the prevention and treatment of AD.

The Protective Effects and Mechanisms of Apelin/APJ System on Ischemic Stroke: A Promising Therapeutic Target

The orphan receptor APJ and its endogenous ligand apelin, which are expressed in the brain, are the major components of the apelin/APJ system. Growing evidence shows that the apelin/APJ system plays a vital role in the pathophysiology of cerebral ischemic injury. Targeting the apelin/APJ system may have protective effects on cerebral ischemic injury. In this review, we sum up the latest research progress relating to the actions and therapeutic potential of the apelin/APJ system in ischemic stroke. An in-depth knowledge of the pathophysiological effects of the apelin/APJ system and the underlying mechanisms will help to develop novel therapeutic interventions for ischemic stroke.

Cationic Arginine-Rich Peptides (CARPs): A Novel Class of Neuroprotective Agents With a Multimodal Mechanism of Action

There are virtually no clinically available neuroprotective drugs for the treatment of acute and chronic neurological disorders, hence there is an urgent need for the development of new neuroprotective molecules. Cationic arginine-rich peptides (CARPs) are an expanding and relatively novel class of compounds, which possess intrinsic neuroprotective properties. Intriguingly, CARPs possess a combination of biological properties unprecedented for a neuroprotective agent including the ability to traverse cell membranes and enter the CNS, antagonize calcium influx, target mitochondria, stabilize proteins, inhibit proteolytic enzymes, induce pro-survival signaling, scavenge toxic molecules, and reduce oxidative stress as well as, having a range of anti-inflammatory, analgesic, anti-microbial, and anti-cancer actions. CARPs have also been used as carrier molecules for the delivery of other putative neuroprotective agents across the blood-brain barrier and blood-spinal cord barrier. However, there is increasing evidence that the neuroprotective efficacy of many, if not all these other agents delivered using a cationic arginine-rich cell-penetrating peptide (CCPPs) carrier (e.g., TAT) may actually be mediated largely by the properties of the carrier molecule, with overall efficacy further enhanced according to the amino acid composition of the cargo peptide, in particular its arginine content. Therefore, in reviewing the neuroprotective mechanisms of action of CARPs we also consider studies using CCPPs fused to a putative neuroprotective peptide. We review the history of CARPs in neuroprotection and discuss in detail the intrinsic biological properties that may contribute to their cytoprotective effects and their usefulness as a broad-acting class of neuroprotective drugs.

The Association Between Serum Apelin-13 and the Prognosis of Acute Ischemic Stroke

While a number of studies have reported an association between apelin-13 and ischemic stroke, few have verified its clinical effect. We investigated the prognostic value of serum apelin-13 levels in patients with acute ischemic stroke (AIS). We prospectively recruited 244 AIS patients within 24 h after stroke onset, and 167 healthy controls. We assessed the serum apelin-13 levels using ELISA, and the severity of AIS using the National Institutes of Health Stroke Scale (NIHSS). The primary outcomes included death or major disability (modified Rankin Scale score, 3-6) and major disability (modified Rankin Scale score, 3-5). Secondary outcomes included recurrent stroke and combined events (all-cause death, or cardiovascular and cerebrovascular events). We found that the serum apelin-13 levels in the patients (38.63 ng/mL (interquartile range [IQR], 29.86-50.99)) were lower than those in the healthy controls (42.50 ng/mL [IQR, 31.25-59.17]) (P = 0.017). Patients with a NIHSS score ≤ 3 had higher apelin-13 levels than those with a NIHSS score > 3 (P = 0.048). At the 3-month follow-up, multivariate logistic regression analysis indicated an association between apelin-13 and death or major disability (OR 0.31; 95% CI 0.11-0.86; P = 0.024) and major disability (OR 0.32; 95% CI 0.11-0.90; P = 0.030). At the 1-year follow-up, the patients with high apelin-13 levels showed a lower incidence of stroke and combined events (Log-rank test P < 0.05). Our findings indicate that serum apelin-13 may be a potential prognostic biomarker for AIS.

Inhibition of oxidative stress by testosterone improves synaptic plasticity in senescence accelerated mice

It is well known that synaptic plasticity is associated with cognitive performance in Alzheimer's disease (AD). Testosterone (T) is known to exert protective effects on cognitive deficits in AD, but the underlying mechanisms of androgenic action on synaptic plasticity remain unclear. Thus, the aim of this study was to examine the protective mechanism attributed to T on synaptic plasticity in an AD senescence accelerated mouse prone 8 (SAMP8) model. The following parameters were measured: (1) number of intact pyramidal cells in hippocampal CA1 region (2) phosphorylated N-methyl-D-aspartate receptor-1 (p-NMDAR1) and (3) phosphorylated calmodulin-dependent protein kinase II (p-CaMKII). In addition, the content of whole brain malondialdehyde (MDA) as well as activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were determined. Treatment with T significantly elevated the number of intact pyramidal cells in hippocampal CA1 region and markedly increased hippocampal protein and mRNA expression levels of p-NMDAR1 and p-CaMK II. Further, T significantly decreased whole brain MDA levels accompanied by elevated activities of SOD and GSH-Px. Data suggest that the protective effects of T on synaptic plasticity in a mouse AD model may be associated with reduction of oxidant stress.

International Union of Basic and Clinical Pharmacology. CVII. Structure and Pharmacology of the Apelin Receptor with a Recommendation that Elabela/Toddler Is a Second Endogenous Peptide Ligand

The predicted protein encoded by the APJ gene discovered in 1993 was originally classified as a class A G protein-coupled orphan receptor but was subsequently paired with a novel peptide ligand, apelin-36 in 1998. Substantial research identified a family of shorter peptides activating the apelin receptor, including apelin-17, apelin-13, and [Pyr1]apelin-13, with the latter peptide predominating in human plasma and cardiovascular system. A range of pharmacological tools have been developed, including radiolabeled ligands, analogs with improved plasma stability, peptides, and small molecules including biased agonists and antagonists, leading to the recommendation that the APJ gene be renamed APLNR and encode the apelin receptor protein. Recently, a second endogenous ligand has been identified and called Elabela/Toddler, a 54-amino acid peptide originally identified in the genomes of fish and humans but misclassified as noncoding. This precursor is also able to be cleaved to shorter sequences (32, 21, and 11 amino acids), and all are able to activate the apelin receptor and are blocked by apelin receptor antagonists. This review summarizes the pharmacology of these ligands and the apelin receptor, highlights the emerging physiologic and pathophysiological roles in a number of diseases, and recommends that Elabela/Toddler is a second endogenous peptide ligand of the apelin receptor protein.

The Dual Role of Kinin/Kinin Receptors System in Alzheimer's Disease

Alzheimer’s disease (AD) is the most common neurodegenerative disease characterized by progressive spatial disorientation, learning and memory deficits, responsible for 60%–80% of all dementias. However, the pathological mechanism of AD remains unknown. Numerous studies revealed that kinin/kinin receptors system (KKS) may be involved in the pathophysiology of AD. In this review article, we summarized the roles of KKS in neuroinflammation, cerebrovascular impairment, tau phosphorylation, and amyloid β (Aβ) generation in AD. Moreover, we provide new insights into the mechanistic link between KKS and AD, and highlight the KKS as a potential therapeutic target for AD treatment.

TMP21 in Alzheimer's Disease: Molecular Mechanisms and a Potential Target

Alzheimer’s disease (AD) is the most common form of dementia in the elderly, which is characterized by progressive cognitive impairment. Neuritic plaques, neurofibrillary tangles and neuronal loss are the major neuropathological hallmarks in AD brains. TMP21 is a key molecule for protein trafficking in cells. Growing evidence indicates that TMP21 is dysregulated in AD, which plays a pivotal role in neuritic plaque formation. Therefore, we aim to review the dysregulation of TMP21 in AD, the role of TMP21 in neuritic plaque formation and underlying mechanisms. Moreover, the potential role of TMP21 in neurofibrillary tangle formation, synaptic impairment and neuronal loss is discussed. It will provide an outlook into the potential of regulating TMP21 as a therapeutic approach for AD treatment.

Can apelin play a role in the etiology of tinnitus?

Background/aim

Tinnitus is seen in 15% of the general population; in 1%–6% of this number, the quality of life is seriously affected by this chronic condition. Chemical, oxidative, and emotional stressors are important in terms of the clinical course of tinnitus. Apelin is an endogenous peptide which is an oxidative stress mediator. It has been shown that the apelin/APJ (apelin junction receptor) system plays various roles in the physiology and pathophysiology of many organs. However, the role of the apelin/APJ system as an oxidative stress mediator in tinnitus is unknown. We investigated the level of apelin in patients with normal hearing and bilateral tinnitus.

Materials and methods

We enrolled patients diagnosed with bilateral idiopathic tinnitus. Tinnitus severity was determined using the tinnitus handicap inventory (THI). We recorded the levels of plasma apelin-13 and biochemical parameters.

Results

The mean apelin level of the control group was higher than that of the patient group (P = 0.002). A significant negative correlation was evident between the apelin level and the THI (r = –0.460, P = 0.003). The triglyceride (TG) level was significantly higher in the patient group than in the control group (P < 0.001).

Conclusion

In our study, we found a negative correlation between apelin and tinnitus severity. Thus, apelin may play a role in the pathophysiology of idiopathic tinnitus, and may be prescribed during follow-up to reduce oxidative stress in the future. Further clinical studies on the effects of the apelin/APJ (apelin junction receptor) system and the effects of antioxidants in patients with inflammatory diseases are required.

Telomere Length: A Potential Biomarker for the Risk and Prognosis of Stroke

Stroke is one of the leading causes of death and disability worldwide. Age is associated with increased risk of stroke, while telomere length shortening plays a pivotal role in the process of aging. Moreover, telomere length shortening is associated with many risk factors of stroke in addition to age. Accumulated evidence shows that short leukocyte telomere length is not only associated with stroke occurrence but also associated with post-stroke recovery in the elderly population. In this review, we aimed to summarize the association between leukocyte telomere length and stroke, and discuss that telomere length might serve as a potential biomarker to predict the risk and prognosis of stroke.

Homer1a Attenuates Endoplasmic Reticulum Stress-Induced Mitochondrial Stress After Ischemic Reperfusion Injury by Inhibiting the PERK Pathway

Homer1a is the short form of a scaffold protein that plays a protective role in many forms of stress. However, the role of Homer1a in cerebral ischemia/reperfusion (I/R) injury and its potential mechanism is still unknown. In this study, we found that Homer1a was upregulated by oxygen and glucose deprivation (OGD) and that overexpression of Homer1a alleviated OGD-induced lactate dehydrogenase (LDH) release and cell death in cultured cortical neurons. After OGD treatment, the overexpression of Homer1a preserved mitochondrial function, as evidenced by less cytochrome c release, less reactive oxygen species (ROS) production, less ATP and mitochondrial membrane potential (MMP) loss, less caspase-9 activation, and inhibition of endoplasmic reticulum (ER) stress confirmed by the decreased expression of phosphate-PKR-like ER Kinase (p-PERK)/PERK and phosphate- inositol-requiring enzyme 1 (p-IRE1)/IRE1 and immunofluorescence (IF) staining. In addition, mitochondrial protection of Homer1a was blocked by the ER stress activator Tunicamycin (TM) with a re-escalated ROS level, increasing ATP and MMP loss. Furthermore, Homer1a overexpression-induced mitochondrial stress attenuation was significantly reversed by activating the PERK pathway with TM and p-IRE1 inhibitor 3,5-dibromosalicylaldehyde (DBSA), as evidenced by increased cytochrome c release, increased ATP loss and a higher ROS level. However, activating the IRE1 pathway with TM and p-PERK inhibitor GSK2656157 showed little change in cytochrome c release and exhibited a moderate upgrade of ATP loss and ROS production in neurons. In summary, these findings demonstrated that Homer1a protects against OGD-induced injury by preserving mitochondrial function through inhibiting the PERK pathway. Our finding may reveal a promising target of protecting neurons from cerebral I/R injury.

Neuroprotective effect of Apelin 13 on ischemic stroke by activating AMPK/GSK-3β/Nrf2 signaling

Background

Previous studies had showed that Apelin 13 could protect against apoptosis induced by ischemic/reperfusion (I/R). However, the mechanisms whereby Apelin 13 protected brain I/R remained to be elucidated. The present study was designed to determine whether Apelin 13 provided protection through AMPK/GSK-3β/Nrf2 pathway.

Methods

In vivo, the I/R model was induced and Apelin 13 was given intracerebroventricularly 15 min before reperfusion. The neurobehavioral scores, infarction volumes, and some cytokines in the brain were measured. For in vitro study, PC12 cells were used. To clarify the mechanisms, proteases inhibitors or siRNA were used. Protein levels were investigated by western blotting.

Results

The results showed that Apelin 13 treatment significantly reduced infarct size, improved neurological outcomes, decreased brain edema, and inhibited cell apoptosis, oxidative stress, and neuroinflammation after I/R. Apelin 13 significantly increased the expression of Nrf2 and the phosphorylation levels of AMPK and GSK-3β. Furthermore, in cultured PC12 cells, the same protective effects were also observed. Silencing Nrf2 gene with its siRNA abolished the Apelin 13’s prevention of I/R-induced PC12 cell injury, oxidative stress, and inflammation. Inhibition of AMPK by its siRNA decreased the level of Apelin 13-induced Nrf2 expression and diminished the protective effects of Apelin 13. The interplay relationship between GSK-3β and Nrf2 was also verified with relative overexpression. Using selective inhibitors, we further identified the upstream of AMPK/GSK-3β/Nrf2 is AR/Gα/PLC/IP3/CaMKK.

Conclusions

In conclusion, the previous results showed that Apelin 13 protected against I/R-induced ROS-mediated inflammation and oxidative stress through activating the AMPK/GSK-3β pathway by AR/Gα/PLC/IP3/CaMKK signaling, and further upregulated the expression of Nrf2-regulated antioxidant enzymes.

Protective effect of apelin preconditioning in a rat model of hepatic ischemia reperfusion injury; possible interaction between the apelin/APJ system, Ang II/AT1R system and eNOS

Introduction

Hepatic ischemic reperfusion injury occurs in multiple clinical settings. Novel potential protective agents are still needed to attenuate this injury. Apelin preconditioning protects against ischemic reperfusion injury in different organs. However, the protective mechanism of apelin on hepatic ischemic reperfusion injury is not yet clear.

Aim

Evaluate the effect of apelin-13 preconditioning on hepatic ischemic reperfusion injury and clarify possible interactions between apelinergic, renin-angiotensin systems and endothelial nitric oxide synthase.

Methods

In total, 60 rats were assigned to four groups: control sham-operated, ischemic reperfusion, apelin-treated ischemic reperfusion and apelin + N-nitro-L-arginine methyl ester-treated ischemic reperfusion. Apelin 2 µg/kg/day and N-nitro-L-arginine methyl ester 10 mg/kg/day were injected intraperitoneally daily for 3 days and 2 weeks respectively before hepatic ischemic reperfusion. Serum aminotransferase, aspartate aminotransferase, hepatic malondialdehyde, apelin, gene expression of caspase-3, endothelial nitric oxide synthase and angiotensin type 1 receptor and liver histopathology were compared between groups.

Results

Apelin significantly reduced serum aminotransferase, aspartate aminotransferase, hepatic malondialdehyde, caspase-3 and angiotensin type 1 receptor expression, whereas hepatic apelin and endothelial nitric oxide synthase expression were significantly increased with improved hepatic histopathology. N-nitro-L-arginine methyl ester co-administration partially reversed this hepatoprotective effect.

Conclusion

Apelin-13 reduced hepatic ischemic reperfusion injury. This protection could be related to the suppression of hepatic angiotensin type 1 receptor expression and elevation of hepatic apelin level and endothelial nitric oxide synthase expression, which counteracts the pathologic effects of Ang II/angiotensin type 1 receptor. An interaction exists between apelinergic, renin-angiotensin systems and endothelial nitric oxide synthase in hepatic ischemic reperfusion pathophysiology.

The protective mechanism underlying phenylethanoid glycosides (PHG) actions on synaptic plasticity in rat Alzheimer's disease model induced by beta amyloid 1-42

Phenylethanoid glycosides (PHG), derived from Herba cistanche, were found to exert protective effects on cognitive dysfunctions by improving synaptic plasticity in Alzheimer's disease (AD) rat model. However, the mechanisms underlying these effects of PHG on synaptic plasticity remain to be determined. Thus the aim of this study was to examine the influence of PHG on synaptic plasticity in male AD rat model induced by bilateral central nervous system ventricle injections of beta amyloid 1-42 oligomers (Aβ1-42). The following parameters were measured: (1) number of intact pyramidal cells in hippocampal CA1 region by Nissl staining, (2) post synaptic density 95 (PSD-95), phosphorylated N-methyl-D-aspartate receptor-1(p-NMDAR1) and (3) phosphorylated Tau protein (p-Tau) by immunohistochemistry and western blot. In addition, the content of malondialdehyde (MDA) and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were determined. Aβ1-42 lowered the number of intact pyramidal cells in hippocampal CA1 region. In contrast, treatment with PHG significantly elevated this cell number. Aβ1-42 significantly diminished protein expression levels of PSD-95 accompanied by elevated protein expression levels of p-NMDAR1 and p-Tau. PHG markedly increased protein expression levels of PSD-95, but significantly reduced protein expression levels of p-NMDAR1 and p-Tau. Further, Aβ1-42 markedly increased MDA content concomitantly with reduced activities of SOD and GSH-Px. PHG significantly decreased MDA content accompanied by elevated activities of SOD and GSH-Px. Data suggest that the protective effects of PHG on synaptic plasticity may involve inhibition of cytotoxicity-mediated by Aβ-1-42 administration and reduction of oxidant stress.

Apelin-13 reverses memory impairment and depression-like behavior in chronic social defeat stressed rats

The apelin/APJ signaling is composed of the short peptide apelin usually including apelin-13, apelin-17 and apelin-36, and its receptor APJ. This signaling is abundantly expressed in limbic structures such as the hippocampus, suggesting a potential role in stress response and learning and memory. We recently reported that apelin-13 reverses acute stress-induced memory impairment and depression-like behavior in rats. Here, we further investigate whether apelin-13 reverses memory impairment and depression-like behavior in chronic stressed rats. Rats were subjected to chronic social defeat stress (CSDS), and received intracerebroventricular infusion of apelin-13 for one week after stress withdrawal. Behavioral test battery was performed to assess memory performance and depression-like behavior. Results showed that apelin-13 reversed CSDS-induced decrease in the alternation ratio and discrimination index in the Y-maze and novel object recognition tests, respectively. Apelin-13 also reversed CSDS-induced social avoidance in the social interaction test, and behavioral despair in the forced swimming and tail suspension tests. Additionally, apelin-13 did not influence locomotor activity in the open field test. These observations suggest that apelin-13 reverses memory impairment and depression-like behavior in chronic stressed rats.

HDAC4 in ischemic stroke: mechanisms and therapeutic potential

Stroke is one of the leading causes of death and disability worldwide, and the majority of the cases are ischemic stroke. However, it still lacks effective treatment except for thrombolytic therapy in an extremely narrow time window. Increased evidence suggests that histone deacetylase 4 (HDAC4) was dysregulated in ischemic stroke, which plays a key role in the pathogenesis of ischemic stroke and post-stroke recovery by affecting neuronal death, angiogenesis, and neurogenesis. Therefore, we aim to review the dysregulation of HDAC4 in ischemic stroke and the role of dysregulated HDAC4 in the pathogenesis of ischemic stroke. Furthermore, the therapeutic potential of modulating HDAC4 in ischemic stroke is discussed.

Apelin-13 Alleviates Early Brain Injury after Subarachnoid Hemorrhage via Suppression of Endoplasmic Reticulum Stress-mediated Apoptosis and Blood-Brain Barrier Disruption: Possible Involvement of ATF6/CHOP Pathway

Neuronal apoptosis plays important roles in the early brain injury after subarachnoid hemorrhage (SAH). This study first showed that inhibition of activating transcription factor 6 (ATF6) by apelin-13 could reduce endoplasmic reticulum (ER)-stress-mediated apoptosis and blood-brain-barrier (BBB) disruption after SAH. We chose apelin-13, ATF6 and CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) siRNAs to verify the hypothesis. Brain water content, neurological behavior and Evans Blue (EB) were assessed at 24 h after SAH. Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) were applied to evaluate the expression of targets in both protein and mRNA levels. Neuronal apoptosis was assessed with Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) and caspase-3 staining. The results showed that the levels of ATF6, and its downstream protein, CHOP were upregulated and reached the peak at 24 h after SAH. ATF6 was highly expressed in neurons. The administration of apelin-13 could significantly reduce the mRNA and protein levels of ATF6, and its downstream targets, CHOP and caspase-3, but increase the Bcl-2/Bax ratio, Claudin-5, Occludin and ZO-1. What's more, the administration of apelin-13 could reduce brain edema, ameliorate BBB disruption and improve neurological functions. However, the CHOP siRNA could significantly reverse the pro-apoptotic effect induced by the increased ATF6 level after SAH. Apelin-13 could exert its neuroprotective effects via suppression of ATF6/CHOP arm of ER-stress-response pathway in the early brain injury after SAH.

Acute inhalation of ozone induces DNA methylation of apelin in lungs of Long-Evans rats

Apelin has cardiopulmonary protective properties that promote vasodilation and maintenance of the endothelial barrier. While reductions in apelin have been identified as a contributor to various lung diseases, including pulmonary edema, its role in the effect of air pollutants has not been examined. Thus, in the current study, we sought to investigate if apelin is a downstream target of inhaled ozone and if such change in expression is related to altered DNA methylation in the lung. Male, Long-Evans rats were exposed to filtered air or 1.0 ppm ozone for 4 h. Ventilation changes were assessed using whole-body plethysmography immediately following exposure, and markers of pulmonary edema and inflammation were assessed in the bronchoaveolar lavage (BAL) fluid. The enzymatic regulators of DNA methylation were measured in the lung, along with methylation and hydroxymethylation of the apelin promoter. Data showed that ozone exposure was associated with increased enhanced pause and protein leakage in the BAL fluid. Ozone exposure reduced DNA cytosine-5-methyltransferase (DNMT) activity and Dnmt3a/b gene expression. Exposure-induced upregulation of proliferating cell nuclear antigen, indicative of DNA damage, repair, and maintenance methylation. Increased methylation and reduced hydroxymethylation were measured on the apelin promoter. These epigenetic modifications accompanied ozone-induced reduction of apelin expression and development of pulmonary edema. In conclusion, epigenetic regulation, specifically increased methylation of the apelin promoter downstream of DNA damage, may lead to reductions in protective signaling of the apelinergic system, contributing to the pulmonary edema observed following the exposure to oxidant air pollution.

Apelin-13 attenuates ER stress-mediated neuronal apoptosis by activating Gαi/Gαq-CK2 signaling in ischemic stroke

Cerebral ischemia/reperfusion (I/R) injury-induced neuronal apoptosis contributes to the death and disability in patients with ischemic stroke. However, underlying mechanisms remain elusive and it lacks effective treatment. Here we reported that the expression of casein kinase 2 (CK2) was significantly reduced in brains of middle cerebral artery occlusion/reperfusion (MACO/R) model rats and oxygen-glucose deprivation/reperfusion (OGD/R) model neurons, which was associated with the activation of eIF2-ATF4-CHOP signaling pathway, leading to neuronal apoptosis. Moreover, we found that apelin-13 significantly upregulated CK2 expression and inhibited eIF2-ATF4-CHOP activation, attenuating cerebral I/R injury-induced infarct and neuronal apoptosis in MACO/R model rats and OGD/R model neurons. Furthermore, we demonstrated that the rescue effect of apelin-13 on I/R injury-induced neuronal apoptosis was mediated by Gα_i/Gα_q-CK2-dependent inhibition of eIF2-ATF4-CHOP activation. These data indicated cerebral I/R injury reduced CK2 expression and activated eIF2-ATF4-CHOP signaling contributing to neuronal apoptosis, and apelin-13 can activate Gα_i/Gα_q-CK2 signaling attenuating eIF2-ATF4-CHOP-mediated neuronal apoptosis. It provides a novel insight that not only apelin-13 but also CK2 agonists may have therapeutic potential for protecting neurons from I/R injury-induced apoptosis, facilitating post-stroke recovery.

Low Dose of Apelin-36 Attenuates ER Stress-Associated Apoptosis in Rats with Ischemic Stroke

Cerebral ischemia/reperfusion (I/R) injury-induced cellular apoptosis contributes to neuronal death in ischemic stroke, while endoplasmic reticulum stress (ERS) and subsequently triggered unfolded protein response (UPR) are the major mechanisms of cerebral I/R injury-induced apoptosis. A number of studies indicated that apelin-13 protects neurons from I/R injury-induced apoptosis. Apelin-36, the longest isoform of apelin, has stronger affinity to apelin receptor than apelin-13 does. However, the role of apelin-36 in ischemic stroke is less studied. In addition, preventive administration of apelin was applied in most studies, which could not precisely reflect its therapeutic potential in ischemic stroke. Here, we first reported that low dose of apelin-36, other than apelin-13, administrated after ischemic stroke significantly reduced infarct volume in rats. Moreover, apelin-36 attenuated cerebral I/R injury-induced apoptosis and caspase-3 activation. Furthermore, apelin-36 suppressed I/R injury-induced CHOP and GRP78 elevation, indicating that apelin-36 inhibited ERS/UPR activation. Our study first demonstrated that post-stroke administration of low-dose apelin-36 could attenuate cerebral I/R injury-induced infarct and apoptosis, which is associated with the inhibition of cerebral I/R injury-induced ERS/UPR activation. Our data support the therapeutic potential of apelin-36 in ischemic stroke although further investigation is needed.

Prospective evaluation of the diagnostic value of plasma apelin 12 levels for differentiating patients with moyamoya and intracranial atherosclerotic diseases

Patients with moyamoya disease (MMD) or intracranial atherosclerotic disease (ICAD) experience similar cerebral ischaemic events. However, MMD patients show greater angiogenesis and arteriogenesis, which play crucial roles in collateral circulation development to enhance clinical prognosis and outcome. Apelins have been associated with angiogenesis and arteriogenesis. Therefore, the aim of the present study was to determine whether apelin levels were higher in patients with MMD than in patients with ICAD or in healthy controls. We compared plasma apelin levels in 29 patients with MMD, 82 patients with ICAD, and 25 healthy participants. Twelve-hour fasting blood samples were collected and analysed using commercially available kits. Univariate analyses indicated that compared with the ICAD and healthy control groups, the MMD group had higher apelin-12, apelin-13, apelin-36, and nitric oxide levels. Binary logistic regression analyses further showed that the plasma apelin-12 level was substantially higher in MMD patients than in ICAD patients. Patients with MMD were also differentiated from patients with ICAD by their mean ages, with the former being younger. Therefore, the plasma apelin-12 level is a potential diagnostic marker for differentiating MMD and ICAD and may provide a treatment strategy for enhancing collateral circulation development and clinical prognosis and outcome.