The KATP channel opener, nicorandil, ameliorates brain damage by modulating synaptogenesis after ischemic stroke

Nicorandil restores endothelial cell Kir6.2 expression to alleviate neuropathic pain in mice after chronic constriction injury

The clinical management of neuropathic pain (NP) remains a significant challenge, as current pharmacological treatments do not fully meet clinical needs. Nicorandil, a potassium ATP channel agonist widely used in cardiovascular medicine, has recently been shown to have significant potential for analgesia. This study aimed to investigate the effects and mechanisms of nicorandil in a chronic constriction injury (CCI) mouse model. Nicorandil significantly alleviated pain hypersensitivity and reduced neuronal injury in the sciatic nerve (SN) and dorsal root ganglion (DRG) post-CCI. Nicorandil primarily affected endothelial cells and Schwann cells in the sciatic nerve, restoring the expression of the KATP channel subunit Kir6.2. Furthermore, nicorandil attenuated the hypoxia-induced apoptosis program in sciatic nerve endothelial cells, leading to reduced expression of apoptotic proteins, which provided significant endothelial protection, improved blood-nerve barrier leakage, and decreased the release of DRG inflammatory factors and pain neurotransmitter substance P. In vitro, nicorandil attenuated the apoptosis of human umbilical vein endothelial cells (HUVECs) in a hypoxic environment while maintaining cellular functions. In addition, administering the KATP channel inhibitor glibenclamide in vitro further confirmed the crucial role of Kir6.2 in reducing endothelial hypoxic stress, as confirmed by transmission electron microscopy and behavioural experiments. Overall, these findings indicate that nicorandil significantly ameliorates CCI-induced NP in mice by targeting Kir6.2 in sciatic nerve endothelial cells, thus inhibiting pain sensitization.

ATP-sensitive potassium channel opener, Nicorandil, inhibits NF-κB/AIM2/GSDMD pathway activation to protect against neuroinflammation in ischemic stroke

The absent in melanoma 2 (AIM2) inflammasome contributes to ischemic brain injury by inducing cell pyroptosis and inflammatory responses. Our research group has previously demonstrated that ATP-sensitive potassium channels (KATP channels) openers can modulate neuronal synaptic plasticity post-ischemic stroke for neuroprotection. However, the specific mechanisms of KATP channels in the inflammatory response following ischemic stroke remain unclear. Here, we assessed cellular damage by observing changes in BV-2 morphology and viability. 2,3,5-Triphenyl tetrazolium chloride (TTC) staining, mNSS scoring, Nissl staining, and TdT-mediated dUTP nick end labeling (TUNEL) staining were used to evaluate behavioral deficits, brain injury severity, and neuronal damage in mice subjected to middle cerebral artery occlusion (MCAO). Quantitative real-time polymerase chain reaction (qRT-PCR), Western blotting, immunofluorescence, and enzyme-linked immunosorbent assay (ELISA) were used to measure cell pyroptosis and nuclear factor-kappaB (NF-κB) activation in vivo and in vitro. We observed that AIM2 protein expression was upregulated and localized within the cytoplasm of BV-2 cells. Notably, low-dose Nicorandil treatment reduced inflammatory cytokine secretion and pyroptosis-related protein expression, including AIM2, cleaved cysteinyl aspartate-specific protease-1 (cleaved caspase-1), and Gasdermin D N-terminal (GSDMD-NT). Further investigations revealed that the KATP channel inhibitor 5-HD upregulated p-NF-κB p65, NF-κB p65, and p-IκBα expression, reversing Nicorandil's neuroprotective effect in vivo. In summary, our results suggest that Nicorandil may serve as a potential therapeutic option for ischemic stroke. Targeting AIM2 and NF-κB represents effective strategies for inhibiting neuroinflammation.

Expression and influence of KATP in umbilical artery smooth muscle cells of patients with hypertensive disorders of pregnancy

The objective of this study is to investigate the expression and influence of adenosine triphosphate-sensitive potassium channel (KATP) in human umbilical arterial smooth muscle cells (HUASMCs) of patients with hypertensive disorders of pregnancy (HDP). Western blotting was used to detect the protein expression levels of KATP inwardly rectifying potassium channel (Kir)6.1 and sulphonylurea receptor (SUR)2B subunits in HUASMCs from patients with normal parturients (NP), gestational hypertension (GH), chronic hypertension (CH), preeclampsia (PE) and chronic hypertension with superimposed preeclampsia (CHSP), respectively. There was no significant difference in the protein expression of Kir6.1 subunit in NP group, GH group, CH group, PE group and CHSP group (P > 0.05). The protein expression of SUR2B subunit was gradually decreased in NP group, GH group, CH group, PE group and CHSP group, with statistically significant difference among the groups (P < 0.05). The altered expression level of KATP SUR2B subunit may be involved in the pathogenesis of HDP. The severity of HDP may be related to the degree of decrease of SUR2B subunit.

Nicorandil and carvedilol mitigates motor deficits in experimental autoimmune encephalomyelitis-induced multiple sclerosis: Role of TLR4/TRAF6/MAPK/NF-κB signalling cascade

Multiple sclerosis (MS) is an inflammatory demyelinating neurodegenerative disease that negatively affects neurotransmission. It can be pathologically mimicked by experimental autoimmune encephalomyelitis (EAE) animal model. ATP-sensitive potassium channels (KATP) plays a crucial role in the control of neuronal damage, however their role in MS are still obscure. Additionally, Carvedilol showed a promising neuroprotective activity against several neurological disorders. Therefore, the present study aimed to investigate the potential neuroprotective effect of KATP channel opener (nicorandil) as well as α and β adrenoceptor antagonist (Carvedilol) against EAE induced neurodegeneration in mice. Mice was treated with nicorandil (6 mg/kg/day; p.o.) and carvedilol (10 mg/kg/day; p.o.) for 14 days. Nicorandil and carvedilol showed improvement in clinical scoring, behaviour and motor coordination as established by histopathological investigation and immunohistochemical detection of MBP. Furthermore, both treatments downregulated the protein expression of TLR4/ MYD88/TRAF6 signalling cascade with downstream inhibition of (pT183/Y185)-JNK/p38 (pT180/Y182)-MAPK axis leading to reduction of neuroinflammatory status, as witnessed by reduction of NF-κB, TNF-α, IL-1β and IL-6 contents. Moreover, nicorandil and carvedilol attenuated oxidative damage by increasing Nrf2 content and SOD activity together with reduction of MDA content. In addition, an immunomodulating effect via inhibiting the gene expression of CD4, TGF-β, and IL-17 as well as TGF-β, IL-17, and IL-23 contents along with anti-apoptotic effect by decreasing Bax protein expression and Caspase-3 content and increasing Bcl-2 protein expression was observed with nicorandil and carvedilol treatments. In conclusion, nicorandil and carvedilol exerted a neuroprotective activity against EAE induced neuronal loss via inhibition of TLR4/MYD88/TRAF6/JNK/p38-MAPK axis besides antioxidant and anti-apoptotic effects.

Co-activation of NMDAR and mGluRs controls protein nanoparticle-induced osmotic pressure in neurotoxic edema

BACKGROUND

Glutamate stimuli and hyperactivation of its receptor are predominant determinants of ischemia-induced cytotoxic cerebral edema, which is closely associated with protein nanoparticle (PN)-induced increases in osmotic pressure. Herein, we investigated the electrochemical and mechanical mechanisms underlying the neuron swelling induced by PNs via the co-activation of N-methyl-D-aspartate receptor subunit (NMDAR) and excitatory metabotropic glutamate receptors (mGluRs).

RESULTS

We observed that co-activation of ionic glutamate receptor NMDAR and Group I metabotropic mGluRs promoted alteration of PN-induced membrane potential and increased intracellular osmosis, which was closely associated with calcium and voltage-dependent ion channels. In addition, activation of NMDAR-induced calmodulin (CaM) and mGluR downstream diacylglycerol (DAG)/protein kinase C α (PKCα) were observed to play crucial roles in cytotoxic hyperosmosis. The crosstalk between CaM and PKCα could upregulate the sensitivity and sustained opening of sulfonylurea receptor 1 (SUR1)-transient receptor potential cation channel subfamily M member 4 (TRPM4) and transmembrane protein 16 A (TMEM16A) channels, respectively, maintaining the massive Na+/Cl- influx, and the resultant neuron hyperosmosis and swelling. Intracellular PNs and Na+/Cl- influx were found to be as potential targets for cerebral edema treatment, using the neurocyte osmosis system and a cerebral ischemic rat model.

CONCLUSIONS

This study highlights PNs as a key factor in "electrochemistry-tension" signal transduction controlling Na+/Cl- ion channels and increased osmotic pressure in ischemia-induced cytotoxic edema. Moreover, enhanced sensitivity in both Na+ and Cl- ion channels also has a crucial role in cerebral edema.

The effects of protein-rich extract from Rhizoma Gastrodiae against cerebral ischemia/reperfusion injury via regulating MAPK and PI3K/AKT signaling pathway

BACKGROUND

Rhizoma Gastrodiae is a highly valuable traditional Chinese medicine and functional health food that has been used in China to treat neurological disorders for thousands of years. Rhizoma Gastrodiae contains various of biological activities, such as antioxidative, neuroprotective, learning improvement, anxiolytic, and antidepressant effects. However, no studies have been conducted to explore the effects of the protein components in Rhizoma Gastrodiae (GEPS) and its potential protective effects against ischemic stroke.Our main goal was to investigate the effects of GEPS on ischemia/reperfusion (I/R) injury and its possible mechanisms.

METHODS

A middle cerebral artery occlusion (MCAO) induced focal cerebral ischemia mouse model and an oxygen-glucose deprivation (OGD/R) injury model in HT22 cells were established. A neurobehavioral test was performed 24 h after MCAO, and brain infarction was measured. A Morris water maze experiment was conducted on Day 14 after reperfusion in mice. Hematoxylin and eosin (HE) and TUNEL staining were performed to assess apoptotic neuronal death. Immunohistochemical analysis was used to detect BDNF and GAP43 expression. The content of SOD, MDA, GSH-PX and ROS were detected. The protein expression was analyzed using Western blotting. Cell viability was determined by MTT assay. Cell apoptosis was examined by flow cytometry.

RESULTS

GEPS reduced apoptosis, decreased cerebral infarction, improved neurological defects, and ameliorated oxidative stress in the ischemic penumbra. In addition, GEPS increased the expression of BDNF and GA43 in the penumbra. Mechanistically, GEPS counteracted MCAO-induced PI3K/AKT inhibition and activation of MAPK signaling pathways.

CONCLUSION

GEPS has a clear neuroprotective effect on I/R injury, and its mechanism may be linked to the PI3K/AKT and MAPK signaling pathways.

Microglia as the Critical Regulators of Neuroprotection and Functional Recovery in Cerebral Ischemia

Microglial activation is considered as the critical pathogenic event in diverse central nervous system disorders including cerebral ischemia. Proinflammatory responses of activated microglia have been well reported in the ischemic brain and neuroinflammatory responses of activated microglia have been believed to be the potential therapeutic strategy. However, despite having proinflammatory roles, microglia can have significant anti-inflammatory roles and they are associated with the production of growth factors which are responsible for neuroprotection and recovery after ischemic injury. Microglia can directly promote neuroprotection by preventing ischemic infarct expansion and promoting functional outcomes. Indirectly, microglia are involved in promoting anti-inflammatory responses, neurogenesis, and angiogenesis in the ischemic brain which are crucial pathophysiological events for ischemic recovery. In fact, anti-inflammatory cytokines and growth factors produced by microglia can promote neuroprotection and attenuate neurobehavioral deficits. In addition, microglia regulate phagocytosis, axonal regeneration, blood-brain barrier protection, white matter integrity, and synaptic remodeling, which are essential for ischemic recovery. Microglia can also regulate crosstalk with neurons and other cell types to promote neuroprotection and ischemic recovery. This review mainly focuses on the roles of microglia in neuroprotection and recovery following ischemic injury. Furthermore, this review also sheds the light on the therapeutic potential of microglia in stroke patients.

The modulation of potassium channels by estrogens facilitates neuroprotection

Estrogens, the sex hormones, have the potential to govern multiple cellular functions, such as proliferation, apoptosis, differentiation, and homeostasis, and to exert numerous beneficial influences for the cardiovascular system, nervous system, and bones in genomic and/or non-genomic ways. Converging evidence indicates that estrogens serve a crucial role in counteracting neurodegeneration and ischemic injury; they are thereby being considered as a potent neuroprotectant for preventing neurological diseases such as Alzheimer's disease and stroke. The underlying mechanism of neuroprotective effects conferred by estrogens is thought to be complex and multifactorial, and it remains obscure. It is well established that the K+ channels broadly expressed in a variety of neural subtypes determine the essential physiological features of neuronal excitability, and dysfunction of these channels is closely associated with diverse brain deficits, such as ataxia and epilepsy. A growing body of evidence supports a neuroprotective role of K+ channels in malfunctions of nervous tissues, with the channels even being a therapeutic target in clinical trials. As multitarget steroid hormones, estrogens also regulate the activity of distinct K+ channels to generate varying biological actions, and accumulated data delineate that some aspects of estrogen-mediated neuroprotection may arise from the impact on multiple K+ channels, including Kv, BK, KATP, and K2P channels. The response of these K+ channels after acute or chronic exposure to estrogens may oppose pathological abnormality in nervous cells, which serves to extend our understanding of these phenomena.

Combined Systemic Intake of K-ATP Opener (Nicorandil) and Mesenchymal Stem Cells Preconditioned With Nicorandil Alleviates Pancreatic Insufficiency in a Model of Bilateral Renal Ischemia/Reperfusion Injury

We used nicorandil, a K-ATP channel opener, to study the role of these channels in the amelioration of renal ischemia/reperfusion (I/R)-induced pancreatic injury, and the possible involvement of PI3K/Akt/mTOR signaling pathway. Forty-two male Wistar rats were included in this study, six were sacrificed for extraction of bone marrow mesenchymal stem cells (BM-MSCs) and conducting the in-vitro work, the others were included in vivo study and equally divided into six groups. Group 1 (sham control), but groups 2-6 were subjected to bilateral renal I/R: Group 2 (I/R); Group 3 (I/R-NC), treated with nicorandil; Group 4 (I/R-MSCs), treated with BM-MSCs; Group 5 (I/R-MSCC), treated with nicorandil-preconditioned BM-MSCs; Group 6 (I/R-NC-MSCC), treated with both systemic nicorandil and preconditioned BM-MSCC. Renal injury and subsequent pancreatic damage were detected in the I/R group by a significant increase in serum urea, creatinine, fasting glucose, and pancreatic enzymes. The pancreatic tissues showed a reduction in cellularity and a significant decrease in the expression of the cell survival pathway, PI3K/Akt/mTOR, in the I/R group compared to the control. Preconditioning MSCs with nicorandil significantly enhanced the proliferation assay and decreased their apoptotic markers. Indeed, combined systemic nicorandil and nicorandil-preconditioning maintained survival of MSC in the pancreatic tissue and amelioration of apoptotic markers and pancreatic TNF-α production. Histologically, all treated groups revealed better pancreatic architecture, and increased area % of anti-insulin antibody and CD31, which were all best observed in the NC-MSCC group. Thus, using K-ATP channel opener was efficient to enhance PI3K/Akt/mTOR expression levels (in vivo and in vitro).