Neuroprotective effect of nicorandil through inhibition of apoptosis by the PI3K/Akt1 pathway in a mouse model of deep hypothermic low flow

Therapeutic potential of nicorandil beyond anti-anginal drug: A review on current and future perspectives

Nicorandil (NIC) is a well-known anti-anginal agent, which has been recommended as one of the second-line treatments for chronic stable angina as justified by the European guidelines. It shows an efficacy equivalent to that of classic anti-anginal agents. NIC has also been used clinically in various cardiovascular diseases such as variant or unstable angina and reperfusion-induced damage following coronary angioplasty or thrombolysis. Different mechanisms have been involved in the protective effects of nicorandil in various diseases, including opening of adenosine triphosphate-sensitive potassium (KATP) channel and donation of nitric oxide (NO). In recent years, NIC has been found to show numerous pharmacological activities such as neuroprotective, nephroprotective, hepatoprotective, cardioprotective, and testicular protective effects, among other beneficial effects on the body. The present review dwells on the pharmacological potentials of NIC beyond its anti-anginal action.

Mechanism of action and neuroprotective role of nicorandil in ischemic stroke

Nicorandil is a dual mechanism anti-anginal agent that acts as a nitric oxide (NO) donor and a potassium (K+) channel opener. Recent studies have evaluated the effect of nicorandil on ischemic stroke. Neurons have a low tolerance to hypoxia and therefore the brain tissue is significantly vulnerable to ischemia. Current approved treatments for ischemic stroke are tissue plasminogen activators and clot retrieval methods. The narrow therapeutic time window and lack of efficacy in restoring the dying neurons urge researchers to develop an alternative approach. In the terminal stages of anoxia, K+ channels induce hyperpolarization in various types of neuronal cells, leading to decreased neuronal activity and the preservation of the brain's energy. Nicorandil can open these K+ channels and sustain the hyperpolarization phase, which may have a neuroprotective effect during hypoxia. Additionally, we review how nicorandil can improve overall stroke outcomes through its anti-inflammatory, anti-oxidative, and edema-reducing effects. One of the major components evaluated in stroke patients is blood pressure. Studies have demonstrated that the effect of nicorandil on blood pressure is related to both its K+ channel opening and NO donating mechanisms. Since both hypertension and hypotension need correction before stroke intervention, it's crucial to consider the role of nicorandil and its impact on blood pressure. Previously published studies indicate that the right dosage of nicorandil can improve cerebral blood flow without significant changes in hemodynamic profiles. In this review, we discuss how nicorandil may contribute to better stroke outcomes based on previously published literature and laboratory findings.

Effects of Injury Severity and Brain Temperature on KAT6A Expression after Traumatic Brain Injury in Rats

Background: Traumatic brain injury (TBI) is associated with a range of neural changes. A comprehensive understanding of the injury-induced lysine acetyltransferase 6A (KAT6A) response, particularly the temporal profile of biochemical alterations, is crucial to design effective therapeutic interventions.Methods: Experiments were performed in male Sprague-Dawley rats. The influence of post-traumatic hypothermia (32°C) or hyperthermia (39°C) on the temporal and regional expression profiles of KAT6A was assessed after moderate or severe TBI. qPCR and western blotting were used to determine the expression of KAT6A in different groups.Results: In the ipsilateral and contralateral hemispheres, significantly lower protein and mRNA expression of KAT6A was found after TBI than sham injury. Moreover, two expression minima of KAT6A were observed in the cortex and hippocampus of the ipsilateral hemisphere. A decrease in injury severity was associated with lower levels of KAT6A mRNA at 12 h and protein at 24 h, but KAT6A mRNA at 48 h and protein at 72 h had alterations. Compared with normothermia and hyperthermia, post-traumatic hypothermia intensified the decrease in KAT6A at both the mRNA and protein levels. In contrast, hyperthermia, as compared with normothermia, did not significantly affect the levels of KAT6A mRNA at 12 h and protein at 24 h, but triggered a significant increase in levels of KAT6A mRNA at 24 h and protein at 72 h. Furthermore, an overall upregulation of KAT6A after TBI was associated with greater injury severity in a time-dependent manner.Conclusions: Post-traumatic hypothermia plays a key role in the regulation of KAT6A expression and thus may at least partially explain the phenotype of post-traumatic temperature in secondary injury after TBI.

Effect of nicorandil on the spatial arrangement of primary motor cortical neurons in the sub-acute phase of stroke in a rat model

INTRODUCTION

Ischemic stroke remains a major cause of disability and death worldwide. The density and the spatial distribution of the primary motor (M1) cortical neurons are important in signal transmission and control the movement-related functions. Recently, the neuroprotective effect of nicorandil in cerebral ischemia was described through its anti-apoptosis, antioxidant and anti-inflammatory properties. This study aimed to determine the effects of nicorandil on the neurobehavioral outcome, infarct size, and density, and spatial distribution of M1 cortical neurons after cerebral ischemia.

METHODS

Thirty Sprague-Dawley rats were randomly divided into three groups. Sham underwent surgery without middle cerebral artery occlusion (MCAO) and drug. The MCAO and treatment groups after MCAO received saline or nicorandil 2, 24, 48, and 72 h after the induction of brain ischemia. Neurobehavioral tests were performed, brains removed, sectioned, and stained by 2,3,5-triphenyltetrazolium chloride (TTC) to estimate the size of the infarction and Nissl staining to evaluate the numerical density, mean area, and the distribution pattern of M1 cortical neurons, using Voronoi spatial tessellation.

RESULTS

Although nicorandil treatment significantly decreased the neurological deficits and density of neuronal neighbors, it could not preserve the normal regular spatial distributions of M1 cortical neurons after MCAO. It also could not significantly improve motor function or reduce ischemic lesion size.

CONCLUSIONS

Treatment using the present dose of nicorandil during sub-acute ischemic stroke could not increase neuronal density or preserve the normal regular spatial distributions after MCAO. However, it had beneficial effects on neurobehavioral and motor function and somewhat reduced ischemic lesion size.

Biphalin, a dimeric opioid peptide, reduces neonatal hypoxia-ischemia brain injury in mice by the activation of PI3K/Akt signaling pathway

Previous studies have demonstrated that the activation of delta opioid receptors is neuroprotective against neonatal hypoxia-ischemia (HI) brain injury. The aim of this study was to investigate the neuroprotective effects of biphalin, a dimeric opioid peptide, in a mouse model of neonatal HI and the underlying mechanisms. On postnatal day 10, mouse pups were subjected to unilateral carotid artery ligation followed by 1 h of hypoxia (10 % O₂ in N₂). For treatment, biphalin (5 mg/kg, 10 mg/kg, 20 mg/kg) was administered intraperitoneally immediately after HI. The opioid antagonist naloxone or phosphatidylinositol-3-kinase inhibitor Ly294002 was administered to determine the underlying mechanisms. Infarct volume, brain edema, phosphorylated Akt and apoptosis-related proteins levels were evaluated by using a combination of 2,3,5-triphenyltetrazolium chloride staining, brain water content and Western blotting at 24 h after HI. The long-term effects of biphalin were evaluated by brain atrophy measurement, Nissl staining and neurobehavioral tests at 3 weeks post-HI. Biphalin (10 mg/kg) significantly reduced the infarct volume and ameliorated brain edema. Biphalin also had long-term protective effects against the loss of ipsilateral brain tissue and resulted in improvements in neurobehavioral outcomes. However, naloxone or Ly294002 abrogated the neuroprotective effects of biphalin. Furthermore, biphalin treatment significantly preserved phosphorylated Akt expression, increased Bcl-2 levels, and decreased Bax and cleaved caspase 3 levels after HI. These effects were also reversed by naloxone and Ly294002 respectively. In conclusion, biphalin protects against HI brain injury in neonatal mice, which might be through activation of the opioid receptor/phosphatidylinositol-3-kinase/Akt signaling pathway.

Targeting PI3K-AKT/mTOR signaling in the prevention of autism

PI3K-AKT/mTOR signaling pathway represents an essential signaling mechanism for mammalian enzyme-related receptors in transducing signals or biological processes such as cell development, differentiation, cell survival, protein synthesis, and metabolism. Upregulation of the PI3K-AKT/mTOR signaling pathway involves many human brain abnormalities, including autism and other neurological dysfunctions. Autism is a neurodevelopmental disorder associated with behavior and psychiatric illness. This research-based review discusses the functional relationship between the neuropathogenic factors associated with PI3K-AKT/mTOR signaling pathway. Ultimately causes autism-like conditions associated with genetic alterations, neuronal apoptosis, mitochondrial dysfunction, and neuroinflammation. Therefore, inhibition of the PI3K-AKT/mTOR signaling pathway may have an effective therapeutic value for autism treatment. The current review also summarizes the involvement of PI3K-AKT/mTOR signaling pathway inhibitors in the treatment of autism and other neurodegenerative disorders.

Effects of Nicorandil on Inflammation, Apoptosis and Atherosclerotic Plaque Progression

Nicorandil, a balanced vasodilator, is used in the second-line therapy of angina pectoris. In this study, we aimed to illuminate the effects of nicorandil on inflammation, apoptosis, and atherosclerotic plaque progression. Twenty-five LDL-R -/- mice were fed a high-fat diet for 14 weeks. After 6 weeks mice were randomly allocated to treatment with nicorandil (10 mg/kg/day) or tap water. Nicorandil treatment led to a more stable plaque phenotype, displaying an increased thickness of the fibrous cap (p = 0.014), a significant reduction in cholesterol clefts (p = 0.045), and enhanced smooth muscle cell content (p = 0.009). In endothelial cells nicorandil did not reduce the induction of adhesion molecules or proinflammatory cytokines. In H₂O₂ challenged endothelial cells, pretreatment with nicorandil significantly reduced the percentage of late apoptotic/necrotic cells (p = 0.016) and the ratio of apoptotic to living cells (p = 0.036). Atherosclerotic lesions of animals treated with nicorandil exhibited a significantly decreased content of cleaved caspase-3 (p = 0.034), lower numbers of apoptotic nuclei (p = 0.040), and reduced 8-oxogunanine staining (p = 0.039), demonstrating a stabilizing effect of nicorandil in established atherosclerotic lesions. We suggest that nicorandil has a positive effect on atherosclerotic plaque stabilization by reducing apoptosis.

Effects of lycopene on vascular remodeling through the LXR-PI3K-AKT signaling pathway in APP/PS1 mice

Alzheimer's disease (AD) is the commonest neurodegenerative disease and, in recent years, studies have increasingly shown that vascular lesions are involved in the pathology of AD onset and progression. Many vascular changes precede the pathological changes and clinical symptoms of AD, and vascular lesions and AD have many common risk factors. Understanding the relationship between vascular factors and the pathological process of AD may help us to identify novel prevention and treatment strategies as well as delay disease progress. Previous studies have shown that lycopene has neuroprotective, antioxidant, and anticancer effects; however, the specific molecular mechanism mediating these effects remains unknown. In the present study, we found: 1) lycopene improved learning and memory in an AD mouse model; 2) lycopene inhibited amyloid plaque aggregation and neuroinflammation; and 3) lycopene induced LXR expression and activated the LXR-PI3K-AKT signaling pathway. Our findings suggest that promotion of neurogenesis and improvement of the functions of the neurovascular unit could be a novel direction for the development of AD therapies.

Nicorandil combats doxorubicin-induced nephrotoxicity via amendment of TLR4/P38 MAPK/NFκ-B signaling pathway

Nicorandil ameliorated doxorubicin-induced nephrotoxicity; this study aimed to show and explain the mechanism of this protection. A precise method was elucidated to study the effect of nicorandil on doxorubicin-induced nephrotoxicity in rats depending on the critical inflammation pathway TLR4/MAPK P38/NFκ-B. Adult male rats were subdivided into four groups. The 1st group was normal control, the 2nd group received nicorandil (3 mg/kg; p.o., for 4 weeks), the 3rd group received doxorubicin (2.6 mg/kg, i.p., twice per week for 4 weeks), and the fourth group was combination of doxorubicin and nicorandil for 4 weeks. Nephrotoxicity was assessed by biochemical tests through measuring Kidney function biomarkers such as [serum levels of urea, creatinine, albumin and total protein] besides renal kidney injury molecule-1 (KIM-1) and cystatin C], oxidative stress parameters such as [renal tissue malondialdehyde (MDA), reduced glutathione (GSH), SOD, catalase and nrf-2], mediators of inflammation such as [Toll like receptor 4 (TLR-4), Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), p38 MAPK, Interleukin 1 beta (IL-1 β), and Tumor necrosis factor alpha (TNF-α)] and markers of apoptosis [BAX and Bcl-2 in renal tissue]. Finally, our data were supported by histopathology examination. Nicorandil pretreatment resulted in a significant decrease in nephrotoxicity biomarkers, oxidative stress markers, inflammatory mediators and prevented apoptosis through decreasing BAX and increasing Bcl-2 in renal tissues. Nicorandil prevented all the histological alterations caused by doxorubicin. Nicorandil is a promising antidote against doxorubicin-induced nephrotoxicity by neutralizing all toxicity mechanisms caused by doxorubicin through normalizing inflammatory cascade of TLR4/MAPK P38/NFκ-B.

Protective effect of nicorandil on collapse‑induced lung injury in rabbits by inhibiting apoptosis

The one‑lung ventilation (OLV) technique is vital in thoracic surgery. However, it can result in severe lung injury, which is difficult to manage. The main solution at present is the use of ventilation strategies, including continuous positive oxygen pressure, low tidal volume and high frequency ventilation, and the administering of drugs, including phenylephrine, dexmedetomidine and morphine. However, the protective effect of these methods on the lungs is not sufficient to improve the prognosis of patients. Therefore, how to develop a novel protective drug remains an open question. Nicorandil, a mitochondrial (mito)KATP‑specific opener, serves an important role in cardioprotection, although its effect on lung injury remains unclear. The present study examined the protective role of nicorandil against collapse‑induced lung injury in rabbits undergoing OLV. Changes in arterial oxygen saturation (SaO2), arterial partial pressure for oxygen (PaO2), wet/dry weight ratio, and the microstructure of tissues and cells were observed. Enzyme‑linked immunosorbent assays were used to determine the concentrations of malondialdehyde (MDA) and tumor necrosis factor (TNF)‑α, and the activity of superoxide dismutase (SOD) in rabbits treated with nicorandil. Terminal deoxynucleotidyl transferase transfer‑mediated dUTP nick end‑labeling was used to detect apoptosis and western blotting was used to analyze the relative proteins involved in apoptosis. Western blotting and reverse transcription‑quantitative polymerase chain reaction analysis were used to examine the expression of hypoxia inducible factor 1α (HIF‑1α), phosphatidylinositol‑3‑kinase (PI3K), protein kinase B (Akt) and nuclear factor (NF)‑κB in the lungs of rabbits treated with nicorandil. The SaO2 and PaO2 in the high‑dose group were significantly higher than those in the control group in the process of OLV. The wet/dry weight ratio, and the concentrations of MDA and TNF‑α in the collapsed lung of the high‑dose group were significantly lower than those in the control group. The activity of SOD in the high‑dose group was significantly higher than that in the control group. The lung had improved microstructure and less apoptosis, which was determined by the Bax/Bcl2 ratio in the high‑dose group. The expression levels of PI3K, phosphorylated Akt and HIF‑1α were upregulated, whereas the expression of NF‑κB was downregulated. In conclusion, nicorandil had a protective effect via inhibiting apoptosis in non‑ventilated lung collapsed and re‑expansion during OLV in the rabbit. It acted on mitoKATP through the PI3K/Akt signaling pathway.

Effect of melatonin on attenuating the isoflurane-induced oxidative damage is related to PKCα/Nrf2 signaling pathway in developing rats

Isoflurane, an inhalational anesthesia, has frequently been used in pediatric anesthesia. However, research indicates that isoflurane can induce oxidative stress and affect neural and cognitive development. Melatonin, an endogenous hormone that exhibits antioxidant functions, can play a neuroprotective role by activating the PKCα/Nrf2 signaling pathway in response to oxidative stress. This study aims to determine whether the effect of melatonin on isoflurane-induced oxidative stress is related to activation of the PKCα/Nrf2 signaling pathway. Rat pups at postnatal day 7 were treated with control or 1.5% isoflurane for 4 h after pretreatment for 15 min with either melatonin (10 mg/kg i.p.) or 1% ethanol. The hematoxylin and eosin staining and transmission electron microscopic examination were used for observation of histopathology. The oxidative stress-related indicators were detected by using assay kits. The western blotting, immunohistochemistry and immunofluorescence were used to detect the activation of PKCα/Nrf2 signaling pathway. Results showed that isoflurane induced nerve damage in the hippocampus, and melatonin could reduce this injury. Oxidative stress-related indicators suggested that isoflurane can significantly increase reactive oxygen species and malondialdehyde levels, and decrease superoxide dismutase and glutathione activity compared with the control group, whereas melatonin ameliorated these indices. Expression of proteins associated with the PKCα/Nrf2 signaling pathway indicated that the neuroprotective effect of melatonin is related to activation of the PKCα/Nrf2 signaling pathway. These results suggest that the attenuating effect of melatonin on isoflurane-induced oxidative stress is related to activation of the PKCα/Nrf2 signaling pathway. These findings promote further research into underlying mechanisms and effective treatments to attenuate anesthesia neurotoxicity.

Identification of novel biomarkers for prediction of neurological prognosis following cardiac arrest

Background

Early prognostication of neurological outcome in comatose patients after cardiac arrest (CA) is important for devising patient treatment strategies. However, there is still a lack of sensitive and specific biomarkers for easy identification of these patients. We evaluated whether molecular signatures from blood of CA patients might help to improve the prediction of neurological outcome.

Methods

We examined 22 comatose patients resuscitated after CA and obtained peripheral blood samples 48 hours after CA. To identify novel blood biomarkers, we aimed to measure neurological outcomes according to the Cerebral Performance Category (CPC) score at 6 months after CA and to determine blood transcriptome-based molecular signature of poor neurological outcome group.

Results

According to the CPC score, 10 patients exhibited a CPC score of one and 12 patients, a CPC score four to five. Blood transcriptomics revealed differently expressed profiles between the good outcome group and poor outcome group. A total of 150 genes were down-regulated and 237 genes were up-regulated in the poor neurological outcome group compared with good outcome group. From the blood transcriptome-based signatures, we identified that MAPK3, BCL2 and AKT1 were more specific and sensitive diagnostic biomarkers in poor neurological outcome with an area under the curve of 0.867 (p<0.0001), 0.800 (p=0.003), and 0.767 (p=0.016) respectively.

Conclusions

We identify three biomarkers as potential predictors of neurological outcome following CA. Further assessment of the prognostic value of transcriptomic analysis in larger cohorts of CA patients is needed.

Brain Development and Akt Signaling: the Crossroads of Signaling Pathway and Neurodevelopmental Diseases

Neurodevelopmental biology, coupled with the application of advanced histological, imaging, molecular, cellular, biochemical, and genetic approaches, has provided new insights into these intricate genetic, cellular, and molecular events. During telencephalic development, specific neural progenitor cells (NPCs) proliferate, differentiate into numerous cell types, migrate to their apposite positions, and form an integrated circuitry. Critical disturbance to this dynamic process via genetic and environmental risk can cause neurological disorders and disability. The phosphatidylinositol-3-OH kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) signaling cascade contributes to mediate various cellular processes, including cell proliferation and growth, and nutrient uptake. In light of its critical function, dysregulation of this node has been regarded as a root cause of several neurodevelopmental diseases, such as megalencephaly ("big brain"), microcephaly ("small brain"), autism spectrum disorders, intellectual disability, schizophrenia, and epilepsy. In this review, particular emphasis will be given to the PI3K-Akt-mTOR signaling pathway and their paramount importance in neurodevelopment of the cerebral neocortex, because of its critical roles in complex cognition, emotional regulation, language, and behaviors.

Improved Anatomical Specificity of Non-invasive Neuro-stimulation by High Frequency (5 MHz) Ultrasound

Low frequency ultrasound (<1 MHz) has been demonstrated to be a promising approach for non-invasive neuro-stimulation. However, the focal width is limited to be half centimeter scale. Minimizing the stimulation region with higher frequency ultrasound will provide a great opportunity to expand its application. This study first time examines the feasibility of using high frequency (5 MHz) ultrasound to achieve neuro-stimulation in brain, and verifies the anatomical specificity of neuro-stimulation in vivo. 1 MHz and 5 MHz ultrasound stimulation were evaluated in the same group of mice. Electromyography (EMG) collected from tail muscles together with the motion response videos were analyzed for evaluating the stimulation effects. Our results indicate that 5 MHz ultrasound can successfully achieve neuro-stimulation. The equivalent diameter (ED) of the stimulation region with 5 MHz ultrasound (0.29 ± 0.08 mm) is significantly smaller than that with 1 MHz (0.83 ± 0.11 mm). The response latency of 5 MHz ultrasound (45 ± 31 ms) is also shorter than that of 1 MHz ultrasound (208 ± 111 ms). Consequently, high frequency (5 MHz) ultrasound can successfully activate the brain circuits in mice. It provides a smaller stimulation region, which offers improved anatomical specificity for neuro-stimulation in a non-invasive manner.