Calcitonin gene-related peptide prevents blood–brain barrier injury and brain edema induced by focal cerebral ischemia reperfusion

Evaluation of the effect of Exercise Trainings and CGRP receptor antagonist (BIBN 4096) on mitochondrial dynamic in the hippocampus of male Wistar rats

BACKGROUND

Exercise training showed beneficial effects on brain. The purpose of the present study is to evaluate the effect of six weeks of high-intensity interval training (HIIT) and Endurance training (ET) with calcitonin gene-related peptide (CGRP) receptor antagonist on the expression of genes involved in mitochondrial dynamics and apoptosis in hippocampal tissue of male Wistar rats.

METHODS

In this study, forty-two healthymale Wistar rats (8-week) were randomly divided into 6 groups (n = 7) as follow; 1) Control; 2) HIIT which performed 6 weeks of HIIT; 3) ET which performed 6 weeks of endurance training; 4) CGRPi received 10 mg/kg CGRP receptor antagonist every day at the last 2 weeks; 5) CGRPi-HIIT performed HIIT and received CGRP receptor antagonist; 6) CGRPi-ET performed ET and received CGRP receptor antagonist. Real-time PCR (2-ΔΔCT) and western blotting were employedto measure the expression of genes and protein, respectively.

RESULTS

HIIT and ET significantly increased Bcl-2, Pgc-1α, Sirt3, and Nrf-1 gene expression in the hippocampal tissue (p < 0.05, p < 0.01, p < 0.01, and p < 0.001, respectively). ET-CGRPi and HIIT-CGRPi significantly increased Sirt3, Pgc-1α, and Nrf-1 gene expression compared to the control group (p < 0.05, p < 0.01, and p < 0.05, respectively).

CONCLUSION

ET and HIIT-induced physiological alterations in the hippocampus. In fact, this modulation showed protective properties in the hippocampusvia up regulation of Bcl-2, Pgc-1α, Nrf-1, and Sirt3 gene expression. CGRPi did not cause gene or protein changes harmful to mitochondrial dynamic balance and apoptosis in the hippocampus of rats.

The exo-microRNA (miRNA) signaling pathways in pathogenesis and treatment of stroke diseases: Emphasize on mesenchymal stem cells (MSCs)

A major factor in long-term impairment is stroke. Patients with persistent stroke and severe functional disabilities have few therapy choices. Long noncoding RNAs (lncRNAs) may contribute to the regulation of the pathophysiologic processes of ischemic stroke as shown by altered expression of lncRNAs and microRNA (miRNAs) in blood samples of acute ischemic stroke patients. On the other hand, multipotent mesenchymal stem cells (MSCs) increase neurogenesis, and angiogenesis, dampen neuroinflammation, and boost brain plasticity to improve functional recovery in experimental stroke models. MSCs can be procured from various sources such as the bone marrow, adipose tissue, and peripheral blood. Under the proper circumstances, MSCs can differentiate into a variety of mature cells, including neurons, astrocytes, and oligodendrocytes. Accordingly, the capability of MSCs to exert neuroprotection and also neurogenesis has recently attracted more attention. Nowadays, lncRNAs and miRNAs derived from MSCs have opened new avenues to alleviate stroke symptoms. Accordingly, in this review article, we examined various studies concerning the lncRNAs and miRNAs' role in stroke pathogenesis and delivered an overview of the therapeutic role of MSC-derived miRNAs and lncRNAs in stroke conditions.

Intrinsic diving reflex induces potent antioxidative response by activation of NRF2 signaling

Aims

This study aims to elucidate the underlying mechanisms of diving reflex, a powerful endogenous mechanism supporting underwater mammalian survival. Antioxidative responses, observed in marine mammals, may be contributing factors. Using a multi-organ approach, this study assesses whether acute and chronic diving reflex activate nuclear factor-erythroid-2-related factor 2 (NRF2) signaling pathways, which regulate cellular antioxidant responses.

Methods

Male Sprague-Dawley rats ( n =38) underwent either a single diving session to elicit acute diving reflex, or daily diving sessions for 4-weeks to produce chronic diving reflex. NRF2 (total, nuclear, phosphorylated), NRF2-downstream genes, and malondialdehyde were assessed via Western blot, immunofluorescence, RT-PCR, and ELISA in brain, lung, kidney, and serum.

Results

Diving reflex increased nuclear NRF2, phosphorylated NRF2, and antioxidative gene expression, in an organ-specific and exposure time-specific manner. Comparing organs, the brain had the highest increase of phosphorylated NRF2 expression, while kidney had the highest degree of nuclear NRF2 expression. Comparing acute and chronic sessions, phosphorylated NRF2 increased the most with chronic diving reflex, but acute diving reflex had the highest antioxidative gene expression. Notably, calcitonin gene-related peptide appears to mediate diving reflex' effects on NRF2 activation.

Conclusions

Acute and chronic diving reflex activate potent NRF2 signaling in the brain and peripheral organs. Interestingly, acute diving reflex induces higher expression of downstream antioxidative genes compared to chronic diving reflex. This result contradicts previous assumptions requiring chronic exposure to diving for induction of antioxidative effects and implies that the diving reflex has a strong translational potential during preconditioning and postconditioning therapies.

Key Points

Diving reflex activates potent NRF2 signaling via multiple mechanisms, including phosphorylation, nuclear translocation, and KEAP1 downregulation with both acute and chronic exposure.Diving reflex activates NRF2 via differential pathways in the brain and other organs; phosphorylated NRF2 increases more in the brain, while nuclear NRF2 increases more in the peripheral organs.Acute diving reflex exposure induces a more pronounced antioxidative effect than chronic diving reflex exposure, indicating that the antioxidative response activated by diving reflex is not dependent upon chronic adaptive responses and supports diving reflex as both a preconditioning and postconditioning treatment.

Calcitonin gene-related peptide: a potential protective agent in cerebral ischemia-reperfusion injury

Ischemic stroke is the most common type of cerebrovascular disease with high disability and mortality rates, which severely burdens patients, their families, and society. At present, thrombolytic therapy is mainly used for the treatment of ischemic strokes. Even though it can achieve a good effect, thrombolytic recanalization can cause reperfusion injury. Calcitonin gene-related peptide (CGRP) is a neuropeptide that plays a neuroprotective role in the process of ischemia-reperfusion injury. By combining with its specific receptors, CGRP can induce vasodilation of local cerebral ischemia by directly activating the cAMP-PKA pathway in vascular smooth muscle cells and by indirectly activating the NO-cGMP pathway in an endothelial cell-dependent manner,thus rapidly increasing ischemic local blood flow together with reperfusion. CGRP, as a key effector molecule of neurogenic inflammation, can reduce the activation of microglia, downregulates Th1 classical inflammation, and reduce the production of TNF-α, IL-2, and IFN-γ and the innate immune response of macrophages, leading to the reduction of inflammatory factors. CGRP can reduce the overexpression of the aquaporin-4 (AQP-4) protein and its mRNA in the cerebral ischemic junction, and play a role in reducing cerebral edema. CGRP can protect endothelial cells from angiotensin II by reducing the production of oxidants and protecting antioxidant defense. Furthermore, CGRP-upregulated eNOS can further induce VEGF expression, which then promotes the survival and angiogenesis of vascular endothelial cells. CGRP can also reduce apoptosis by promoting the expression of Bcl-2 and inhibiting the expression of caspase-3. These effects suggest that CGRP can reduce brain injury and repair damaged nerve function. In this review, we focused on the role of CGRP in cerebral ischemia-reperfusion injury.

Bacteria hijack a meningeal neuroimmune axis to facilitate brain invasion

The meninges are densely innervated by nociceptive sensory neurons that mediate pain and headache1,2. Bacterial meningitis causes life-threatening infections of the meninges and central nervous system, affecting more than 2.5 million people a year3-5. How pain and neuroimmune interactions impact meningeal antibacterial host defences are unclear. Here we show that Nav1.8+ nociceptors signal to immune cells in the meninges through the neuropeptide calcitonin gene-related peptide (CGRP) during infection. This neuroimmune axis inhibits host defences and exacerbates bacterial meningitis. Nociceptor neuron ablation reduced meningeal and brain invasion by two bacterial pathogens: Streptococcus pneumoniae and Streptococcus agalactiae. S. pneumoniae activated nociceptors through its pore-forming toxin pneumolysin to release CGRP from nerve terminals. CGRP acted through receptor activity modifying protein 1 (RAMP1) on meningeal macrophages to polarize their transcriptional responses, suppressing macrophage chemokine expression, neutrophil recruitment and dural antimicrobial defences. Macrophage-specific RAMP1 deficiency or pharmacological blockade of RAMP1 enhanced immune responses and bacterial clearance in the meninges and brain. Therefore, bacteria hijack CGRP-RAMP1 signalling in meningeal macrophages to facilitate brain invasion. Targeting this neuroimmune axis in the meninges can enhance host defences and potentially produce treatments for bacterial meningitis.

Multiple Sclerosis: Inflammatory and Neuroglial Aspects

Multiple sclerosis (MS) represents the most common acquired demyelinating disorder of the central nervous system (CNS). Its pathogenesis, in parallel with the well-established role of mechanisms pertaining to autoimmunity, involves several key functions of immune, glial and nerve cells. The disease's natural history is complex, heterogeneous and may evolve over a relapsing-remitting (RRMS) or progressive (PPMS/SPMS) course. Acute inflammation, driven by infiltration of peripheral cells in the CNS, is thought to be the most relevant process during the earliest phases and in RRMS, while disruption in glial and neural cells of pathways pertaining to energy metabolism, survival cascades, synaptic and ionic homeostasis are thought to be mostly relevant in long-standing disease, such as in progressive forms. In this complex scenario, many mechanisms originally thought to be distinctive of neurodegenerative disorders are being increasingly recognized as crucial from the beginning of the disease. The present review aims at highlighting mechanisms in common between MS, autoimmune diseases and biology of neurodegenerative disorders. In fact, there is an unmet need to explore new targets that might be involved as master regulators of autoimmunity, inflammation and survival of nerve cells.

Advances in Antibody-Based Therapeutics for Cerebral Ischemia

Cerebral ischemia is an acute disorder characterized by an abrupt reduction in blood flow that results in immediate deprivation of both glucose and oxygen. The main types of cerebral ischemia are ischemic and hemorrhagic stroke. When a stroke occurs, several signaling pathways are activated, comprising necrosis, apoptosis, and autophagy as well as glial activation and white matter injury, which leads to neuronal cell death. Current treatments for strokes include challenging mechanical thrombectomy or tissue plasminogen activator, which increase the danger of cerebral bleeding, brain edema, and cerebral damage, limiting their usage in clinical settings. Monoclonal antibody therapy has proven to be effective and safe in the treatment of a variety of neurological disorders. In contrast, the evidence for stroke therapy is minimal. Recently, Clone MTS510 antibody targeting toll-like receptor-4 (TLR4) protein, ASC06-IgG1 antibody targeting acid sensing ion channel-1a (ASIC1a) protein, Anti-GluN1 antibodies targeting N-methyl-D-aspartate (NMDA) receptor associated calcium influx, GSK249320 antibody targeting myelin-associated glycoprotein (MAG), anti-High Mobility Group Box-1 antibody targeting high mobility group box-1 (HMGB1) are currently under clinical trials for cerebral ischemia treatment. In this article, we review the current antibody-based pharmaceuticals for neurological diseases, the use of antibody drugs in stroke, strategies to improve the efficacy of antibody therapeutics in cerebral ischemia, and the recent advancement of antibody drugs in clinical practice. Overall, we highlight the need of enhancing blood-brain barrier (BBB) penetration for the improvement of antibody-based therapeutics in the brain, which could greatly enhance the antibody medications for cerebral ischemia in clinical practice.

Repetitive Transcranial Magnetic Stimulation of the Brain After Ischemic Stroke: Mechanisms from Animal Models

Stroke is a common cerebrovascular disease with high morbidity, mortality, and disability worldwide. Post-stroke dysfunction is related to the death of neurons and impairment of synaptic structure, which results from cerebral ischemic damage. Currently, transcranial magnetic stimulation (TMS) techniques are available to provide clinically effective interventions and quantitative diagnostic and prognostic biomarkers. The development of TMS has been 40 years and a range of repetitive TMS (rTMS) protocols are now available to regulate neuronal plasticity in many neurological disorders, such as stroke, Parkinson disease, psychiatric disorders, Alzheimer disease, and so on. Basic studies in an animal model with ischemic stroke are significant for demonstrating potential mechanisms of neural restoration induced by rTMS. In this review, the mechanisms were summarized, involving synaptic plasticity, neural cell death, neurogenesis, immune response, and blood-brain barrier (BBB) disruption in vitro and vivo experiments with ischemic stroke models. Those findings can contribute to the understanding of how rTMS modulated function recovery and the exploration of novel therapeutic targets. The mechanisms of rTMS in treating ischemic stroke from animal models. rTMS can prompt synaptic plasticity by increasing NMDAR, AMPAR and BDNF expression; rTMS can inhibit pro-inflammatory cytokines TNF and facilitate the expression of anti-inflammatory cytokines IL-10 by shifting astrocytic phenotypes from A1 to A2, and shifting microglial phenotypes from M1 to M2; rTMS facilitated the release of angiogenesis-related factors TGFβ and VEGF in A2 astrocytes, which can contribute to vasculogenesis and angiogenesis; rTMS can suppress apoptosis by increasing Bcl-2 expression and inhibiting Bax, caspase-3 expression; rTMS can also suppress pyroptosis by decreasing caspase-1, IL-1β, ASC, GSDMD and NLRP1 expression. rTMS, repetitive transcranial magnetic stimulation; NMDAR, N-methyl-D-aspartic acid receptors; AMPAR: α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors; BDNF, brain-derived neurotrophic factor; VEGF, vascular endothelial growth factor; GSDMD: cleaved Caspase-1 cleaves Gasdermin D; CBF: cerebral blood flow.

Lipidated Calcitonin Gene-Related Peptide (CGRP) Peptide Antagonists Retain CGRP Receptor Activity and Attenuate CGRP Action In Vivo

Signaling through calcitonin gene-related peptide (CGRP) receptors is associated with pain, migraine, and energy expenditure. Small molecule and monoclonal antibody CGRP receptor antagonists that block endogenous CGRP action are in clinical use as anti-migraine therapies. By comparison, the potential utility of peptide antagonists has received less attention due to suboptimal pharmacokinetic properties. Lipidation is an established strategy to increase peptide half-life in vivo. This study aimed to explore the feasibility of developing lipidated CGRP peptide antagonists that retain receptor antagonist activity in vitro and attenuate endogenous CGRP action in vivo. CGRP peptide analogues based on the archetypal CGRP receptor antagonist, CGRP_8-37, were palmitoylated at the N-terminus, position 24, and near the C-terminus at position 35. The antagonist activities of the lipidated peptide analogues were tested in vitro using transfected Cos-7 cells expressing either the human or mouse CGRP receptor, amylin subtype 1 (AMY₁) receptor, adrenomedullin (AM) receptors, or calcitonin receptor. Antagonist activities were also evaluated in SK-N-MC cells that endogenously express the human CGRP receptor. Lipidated peptides were then tested for their ability to antagonize endogenous CGRP action in vivo using a capsaicin-induced dermal vasodilation (CIDV) model in C57/BL6J mice. All lipidated peptides except for the C-terminally modified analogue retained potent antagonist activity compared to CGRP_8-37 towards the CGRP receptor. The lipidated peptides also retained, and sometimes gained, antagonist activities at AMY₁, AM₁ and AM₂ receptors. Several lipidated peptides produced robust inhibition of CIDV in mice. This study demonstrates that selected lipidated peptide antagonists based on αCGRP_8-37 retain potent antagonist activity at the CGRP receptor and are capable of inhibition of endogenous CGRP action in vivo. These findings suggest that lipidation can be applied to peptide antagonists, such as αCGRP_8-37 and are a potential strategy for antagonizing CGRP action.

Alpha-Calcitonin Gene Related Peptide: New Therapeutic Strategies for the Treatment and Prevention of Cardiovascular Disease and Migraine

Alpha-calcitonin gene-related peptide (α-CGRP) is a vasodilator neuropeptide of the calcitonin gene family. Pharmacological and gene knock-out studies have established a significant role of α-CGRP in normal and pathophysiological states, particularly in cardiovascular disease and migraines. α-CGRP knock-out mice with transverse aortic constriction (TAC)-induced pressure-overload heart failure have higher mortality rates and exhibit higher levels of cardiac fibrosis, inflammation, oxidative stress, and cell death compared to the wild-type TAC-mice. However, administration of α-CGRP, either in its native- or modified-form, improves cardiac function at the pathophysiological level, and significantly protects the heart from the adverse effects of heart failure and hypertension. Similar cardioprotective effects of the peptide were demonstrated in pressure-overload heart failure mice when α-CGRP was delivered using an alginate microcapsules-based drug delivery system. In contrast to cardiovascular disease, an elevated level of α-CGRP causes migraine-related headaches, thus the use of α-CGRP antagonists that block the interaction of the peptide to its receptor are beneficial in reducing chronic and episodic migraine headaches. Currently, several α-CGRP antagonists are being used as migraine treatments or in clinical trials for migraine pain management. Overall, agonists and antagonists of α-CGRP are clinically relevant to treat and prevent cardiovascular disease and migraine pain, respectively. This review focuses on the pharmacological and therapeutic significance of α-CGRP-agonists and -antagonists in various diseases, particularly in cardiac diseases and migraine pain.

Calcitonin gene related peptide in migraine: current therapeutics, future implications and potential off-target effects

Migraine is the second largest cause of years lost to disability globally among all diseases, with a worldwide prevalence over 1 billion. Despite the global burden of migraine, few classes of therapeutics have been specifically developed to combat migraine. After 30 years of translational research, calcitonin gene-related peptide (CGRP) inhibitors have emerged as a promising new tool in the prevention of migraine. Like all new therapeutics; however, we have limited real-world experience and CGRP has several known systemic actions that warrant consideration. This article provides a narrative review of the evidence for CGRP antagonists and summarises the known and potential side effects that should be considered.

Protective mechanism of Erigeron breviscapus injection on blood-brain barrier injury induced by cerebral ischemia in rats

This study investigates the protective effect of Erigeron breviscapus injection, a classic traditional Chinese medicine most typically used by Chinese minority to treat stroke, on cerebral ischemia-reperfusion injury and the related signaling pathways. Use network pharmacology methods to study the relationship between E. breviscapus (Vant.) Hand-Mazz. and ischemic stroke, predict the mechanism and active ingredients of E. breviscapus (Vant.) Hand-Mazz. in improving ischemic stroke disease. We study the protective effect of E. breviscapus injection on blood-brain barrier (BBB) injuries induced by cerebral ischemia in rats by regulating the ROS/RNS-MMPs-TJs signaling pathway. The rat model of focal cerebral ischemia-reperfusion injury has been prepared using the wire-suppository method. Firstly, the efficacy of E. breviscapus injection, Scutellarin and 3,5-dicaffeoylquinic acid in protecting BBB injury caused by cerebral ischemia has been evaluated. Secondly, the following two methods have been used to study the mechanism of E. breviscapus injection in regulating the ROS/RNS-MMPS-TJS signaling pathway: real-time PCR and western blot for the determination of iNOS, MMP-9, claudin-5, occludin, ZO-1 mRNA and protein expression in brain tissue. We find that PI3K-Akt signaling pathway predicted by network pharmaology affects the blood-brain barrier function, so we chose the blood-brain barrier-related MMP-9, claudin-5, iNOS, occludin and ZO-1 proteins are used for research. The results of our research show that 3 drugs can reduce the rate of cerebral infarction in rats, relieve the abnormal neuroethology of rats, reduce the degree of brain tissue lesion, increase the number of the Nissl corpuscle cells and repair the neuron ultrastructure in injured rats. At the same time, it can obviously reduce the ultrastructure damage of the BBB in rats. All three drugs significantly reduced the content of Evans blue in the ischemic brain tissue caused by cerebral ischemia in rats with BBB injury. In addition, E. breviscapus injection, Scutellarin and 3,5-dicaffeoylquinic acid can decrease the protein expression of iNOS and MMP-9 in rat ischemic brain tissue. In addition, 3,5-dicaffeoylquinic acid can increase the protein expression of claudin-5. We conclude that E. breviscapus injection, Scutellarin and 3,5-dicaffeoylquinic acid have obvious therapeutic effects on BBB and neuron injury induced by cerebral ischemia in rats. Our results from studying the mechanism of action show that E. breviscapus injection and Scutellarin inhibited the activation of MMP-9 by inhibiting the synthesis of iNOS, 3,5-dicaffeoylquinic acid inhibits the expression and activation of MMP-9 by inhibiting the activation of iNOS and reducing the generation of free radicals, thus reducing the degradation of important cytoskeleton connexin claudin-5 in the tight junction (TJ) structure by inhibiting the expression and activation of MMP-9. Finally BBB structure integrity was protected.

CGRP outflow into jugular blood and cerebrospinal fluid and permeance for CGRP of rat dura mater

Background

Calcitonin gene-related peptide (CGRP) is released from activated meningeal afferent fibres in the cranial dura mater, which likely accompanies severe headache attacks. Increased CGRP levels have been observed in different extracellular fluid compartments during primary headaches such as migraine but it is not entirely clear how CGRP is drained from the meninges.

Methods

We have used an in vivo preparation of the rat to examine after which time and at which concentration CGRP applied onto the exposed parietal dura mater appears in the jugular venous blood and the cerebrospinal fluid (CSF) collected from the cisterna magna. Recordings of meningeal (dural) and cortical (pial) blood flow were used to monitor the vasodilatory effect of CGRP. In a new ex vivo preparation we examined how much of a defined CGRP concentration applied to the arachnoidal side penetrates the dura. CGRP concentrations were determined with an approved enzyme immunoassay.

Results

CGRP levels in the jugular plasma in vivo were slightly elevated compared to baseline values 5-20 min after dural application of CGRP (10 μM), in the CSF a significant three-fold increase was seen after 35 min. Meningeal but not cortical blood flow showed significant increases. The spontaneous CGRP release from the dura mater ex vivo was above the applied low concentration of 1 pM. CGRP at 1 nM did only partly penetrate the dura.

Conclusions

We conclude that only a small fraction of CGRP applied onto the dura mater reaches the jugular blood and, in a delayed manner, also the CSF. The dura mater may constitute a barrier for CGRP and limits diffusion into the CSF of the subarachnoidal space, where the CGRP concentration is too low to cause vasodilatation.

Neuroprotective Effects of Peptides in the Brain: Transcriptome Approach

The importance of studying the action mechanisms of drugs based on natural regulatory peptides is commonly recognized. Particular attention is paid to the peptide drugs that contribute to the restoration of brain functions after acute cerebrovascular accidents (stroke), which for many years continues to be one of the main problems and threats to human health. However, molecular genetic changes in the brain in response to ischemia, as well as the mechanisms of protective effects of peptides, have not been sufficiently studied. This limits the use of neuroprotective peptides and makes it difficult to develop new, more efficient drugs with targeted action on brain functions. Transcriptome analysis is a promising approach for studying the mechanisms of the damaging effects of cerebral ischemia and neuroprotective action of peptide drugs. Beside investigating the role of mRNAs in protein synthesis, the development of new neuroprotection strategies requires studying the involvement of regulatory RNAs in ischemia. Of greatest interest are microRNAs (miRNAs) and circular RNAs (circRNAs), which are expressed predominantly in the brain. CircRNAs can interact with miRNAs and diminish their activity, thereby inhibiting miRNA-mediated repression of mRNAs. It has become apparent that analysis of the circRNA/miRNA/mRNA system is essential for deciphering the mechanisms of brain damage and repair. Here, we present the results of studies on the ischemia-induced changes in the activity of genes and peptide-mediated alterations in the transcriptome profiles in experimental ischemia and formulate the basic principles of peptide regulation in the ischemia-induced damage.

Anti-migraine Calcitonin Gene-Related Peptide Receptor Antagonists Worsen Cerebral Ischemic Outcome in Mice

Objective

Calcitonin gene–related peptide (CGRP) pathway inhibitors are emerging treatments for migraine. CGRP‐mediated vasodilation is, however, a critical rescue mechanism in ischemia. We, therefore, investigated whether gepants, small molecule CGRP receptor antagonists, worsen cerebral ischemia.

Methods

Middle cerebral artery was occluded for 12 to 60 minutes in mice. We compared infarct risk and volumes, collateral flow, and neurological deficits after pretreatment with olcegepant (single or 10 daily doses of 0.1–1mg/kg) or rimegepant (single doses of 10–100mg/kg) versus vehicle. We also determined their potency on CGRP‐induced relaxations in mouse and human vessels, in vitro.

Results

Olcegepant (1mg/kg, single dose) increased infarct risk after 12‐ to 20‐minute occlusions mimicking transient ischemic attacks (14/19 vs 6/18 with vehicle, relative risk = 2.21, p < 0.022), and doubled infarct volumes (p < 0.001) and worsened neurological deficits (median score = 9 vs 5 with vehicle, p = 0.008) after 60‐minute occlusion. Ten daily doses of 0.1 to 1mg/kg olcegepant yielded similar results. Rimegepant 10mg/kg increased infarct volumes by 60% after 20‐minute ischemia (p = 0.03); 100mg/kg caused 75% mortality after 60‐minute occlusion. In familial hemiplegic migraine type 1 mice, olcegepant 1mg/kg increased infarct size after 30‐minute occlusion (1.6‐fold, p = 0.017). Both gepants consistently diminished collateral flow and reduced reperfusion success. Olcegepant was 10‐fold more potent than rimegepant on CGRP‐induced relaxations in mouse aorta.

Interpretation

Gepants worsened ischemic stroke in mice via collateral dysfunction. CGRP pathway blockers might thus aggravate coincidental cerebral ischemic events. The cerebrovascular safety of these agents must therefore be better delineated, especially in patients at increased risk of ischemic events or on prophylactic CGRP inhibition. ANN NEUROL 2020;88:771–784

Pharmacotranscriptomics of peptide drugs with neuroprotective properties

Here we present a review of studies on the effects of peptides with neuroprotective properties on gene transcription in nerve cells. The few published works in this area clearly demonstrate massive changes in cell transcriptomes induced by peptides under normal conditions and under conditions of experimental brain ischemia. These changes significantly affect signaling and metabolic pathways, affecting various body systems and confirming the multiple target actions of peptides. The importance of noncoding RNAs in the regulation of these processes is shown, and we discuss the prospects of research for determining the main mechanisms of peptide regulation, which is necessary for the further development of drugs with targeted neuroprotective effects.

Endogenous calcitonin gene-related peptide suppresses ischemic brain injuries and progression of cognitive decline

BACKGROUND

Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide and produced by alternative splicing of the transcript of the calcitonin/CGRP gene. Originally identified as a strong vasodilatory and hypotensive peptide, CGRP is now known to be a pleiotropic molecule distributed in various organs, including the brain.

METHOD

In this study, we used CGRP knockout mice (CGRP-/-) to examine the actions of endogenous CGRP during cerebral ischemia. To induce acute and chronic cerebral ischemia, mice were subjected to middle cerebral artery occlusion (MCAO) and bilateral common carotid artery stenosis (BCAS).

RESULTS

In the cerebral cortex of wild-type mice, CGRP expression was upregulated after acute infarction. In CGRP-/- subjected to MCAO or BCAS, recovery of cerebral blood flow was slower and exhibited more extensive neuronal cell death. Expression of the inflammatory cytokines was higher in CGRP-/- than wild type in the acute phase of ischemia. Pathological analysis during the chronic phase revealed more extensive neuronal cell loss and demyelination and higher levels of oxidative stress in CGRP-/- than wild-type. CGRP-/- also showed less compensatory capillary growth. In an eight-arm radial maze test, CGRP-/- exhibited poorer reference memory than wild-type. On the other hand, CGRP administration promoted cerebral blood flow recovery after cerebral ischemia. We also found that CGRP directly inhibited the cell death of primary cortical neurons.

CONCLUSION

These results indicate endogenous CGRP is protective against ischemia-induced neuronal cell injury. CGRP could, thus, be a novel candidate for use in the treatment of both cerebral ischemia and progression of cognitive decline.

Rosmarinus officinalis L. (rosemary) as therapeutic and prophylactic agent

Rosmarinus officinalis L. (rosemary) is a medicinal plant native to the Mediterranean region and cultivated around the world. Besides the therapeutic purpose, it is commonly used as a condiment and food preservative. R. officinalis L. is constituted by bioactive molecules, the phytocompounds, responsible for implement several pharmacological activities, such as anti-inflammatory, antioxidant, antimicrobial, antiproliferative, antitumor and protective, inhibitory and attenuating activities. Thus, in vivo and in vitro studies were presented in this Review, approaching the therapeutic and prophylactic effects of R. officinalis L. on some physiological disorders caused by biochemical, chemical or biological agents. In this way, methodology, mechanisms, results, and conclusions were described. The main objective of this study was showing that plant products could be equivalent to the available medicines.

Understanding CGRP and Cardiovascular Risk

Increasing knowledge about the role of calcitonin gene-related peptide (CGRP) in migraine pathophysiology has led to the development of antibodies against this peptide or its receptor. However, CGRP is widely expressed throughout the body, participating not only in pathophysiological conditions but also in several physiological processes and homeostatic responses during pathophysiological events. Therefore, in this chapter, the risks of long-term blockade of the CGRP pathway will be discussed, with focus on the cardiovascular system, as this peptide has been described to have a protective role during ischemic events, and migraine patients present a higher risk of stroke and myocardial infarction.

The Role of Calcitonin Gene Related Peptide (CGRP) in Neurogenic Vasodilation and Its Cardioprotective Effects

Calcitonin gene-related peptide (CGRP) is a highly potent vasoactive peptide released from sensory nerves, which is now proposed to have protective effects in several cardiovascular diseases. The major α-form is produced from alternate splicing and processing of the calcitonin gene. The CGRP receptor is a complex composed of calcitonin like receptor (CLR) and a single transmembrane protein, RAMP1. CGRP is a potent vasodilator and proposed to have protective effects in several cardiovascular diseases. CGRP has a proven role in migraine and selective antagonists and antibodies are now reaching the clinic for treatment of migraine. These clinical trials with antagonists and antibodies indicate that CGRP does not play an obvious role in the physiological control of human blood pressure. This review discusses the vasodilator and hypotensive effects of CGRP and the role of CGRP in mediating cardioprotective effects in various cardiovascular models and disorders. In models of hypertension, CGRP protects against the onset and progression of hypertensive states by potentially counteracting against the pro-hypertensive systems such as the renin-angiotensin-aldosterone system (RAAS) and the sympathetic system. With regards to its cardioprotective effects in conditions such as heart failure and ischaemia, CGRP-containing nerves innervate throughout cardiac tissue and the vasculature, where evidence shows this peptide alleviates various aspects of their pathophysiology, including cardiac hypertrophy, reperfusion injury, cardiac inflammation, and apoptosis. Hence, CGRP has been suggested as a cardioprotective, endogenous mediator released under stress to help preserve cardiovascular function. With the recent developments of various CGRP-targeted pharmacotherapies, in the form of CGRP antibodies/antagonists as well as a CGRP analog, this review provides a summary and a discussion of the most recent basic science and clinical findings, initiating a discussion on the future of CGRP as a novel target in various cardiovascular diseases.

Regulation of Hypertension for Secondary Prevention of Stroke: The Possible 'Bridging Function' of Acupuncture

Worldwide, stroke is the leading cause of mortality and disability, with hypertension being an independent risk factor for a secondary stroke. Acupuncture for the treatment of hypertension gains more attention in alternative and complementary medicine, but the results are inconsistent. Few studies regarding the secondary prevention of stroke by managing hypertension with acupuncture have been carried out as there are some problems regarding the antihypertensive drug status in the secondary prevention of stroke. Still, the potential of acupuncture in regulating the blood pressure for secondary stroke prevention deserves our focus. This review is based on papers recorded in the PubMed, Embase, and Web of Science databases, from their inception until March 28, 2017, and retrieved with the following search terms: hypertension and acupuncture, limited in spontaneously hypertensive rats (SHRs), stress-induced (or cold-induced) hypertensive or pre-hypertensive models. We find that, in these hypertensive animals, acupuncture could mainly influence factors related to the nervous system, oxidative stress, the endocrine system, cardiovascular function, and hemorheology, which are closely associated with the stroke outcome. This trend may give us a hint that acupuncture might well participate in the secondary prevention of stroke through these pathways when used in the management of hypertension.

Calcitonin gene-related peptide has protective effect on brain injury induced by heat stroke in rats

Heat stroke often leads to multiple organ dysfunction syndrome (MODS) with a neurological morbidity of 30%. Current studies suggested that pathophysiological responses to heat stroke may be due to a systemic inflammatory response syndrome and a series of peptidergic nerve reactions. The mechanisms underlying the high neurological morbidity in heat stroke have remained largely elusive. In recent years, calcitonin gene-related peptide (CGRP) has been considered to have a positive role in central nervous system injury. The present study investigated the influence of CGRP on brain injury induced by heat stroke. A rat model of heat stroke was established in a pre-warmed artificial climate chamber with a temperature of 35.5±0.5°C and a relative humidity of 60±5%. The rectal core temperature (Tc) was monitored. Heat stress was halted at a Tc of no more than 41°C A bolus injection of CGRP was administered to each rat in the HS+CGRP group and a bolus injection of CGRP8-37 was administered to each rat in the HS+CGRP8-37 group after heat stress. After 2 h, electroencephalograms were recorded and the pathological morphology of brain tissue as well as brain cell apoptosis and caspase-3 protein levels in the brain were measured. The EEG of rats in the HS+CGRP group was characterized by a short- to long-term α-wave and low-voltage β-waves as well as a large amount of intermittent δ- and θ-waves. Compared with the HS group, the θ-wave decreased and the α-wave increased significantly (P<0.05). Slight pathological damage of nerve cells appeared in the HS+CGRP group. Greater damage was observed in HS+CGRP8-37 group with neural cell shrinkage, volume reduction, nuclear pyknosis, disappearance of part of the nuclear membrane and cell necrosis. In the HS+CGRP group, apoptotic cells and caspase-3 protein in the brain were significantly decreased when compared with those in the HS group (P<0.05), while they were significantly increased in the HS+CGRP8-37 group (P<0.05 vs. HS group). The results of the present study reflected that CGRP has a protective effect on early-stage brain injury induced by heat stroke in rats.

The Role of Neurogenic Inflammation in Blood-Brain Barrier Disruption and Development of Cerebral Oedema Following Acute Central Nervous System (CNS) Injury

Acute central nervous system (CNS) injury, encompassing traumatic brain injury (TBI) and stroke, accounts for a significant burden of morbidity and mortality worldwide, largely attributable to the development of cerebral oedema and elevated intracranial pressure (ICP). Despite this, clinical treatments are limited and new therapies are urgently required to improve patient outcomes and survival. Originally characterised in peripheral tissues, such as the skin and lungs as a neurally-elicited inflammatory process that contributes to increased microvascular permeability and tissue swelling, neurogenic inflammation has now been described in acute injury to the brain where it may play a key role in the secondary injury cascades that evolve following both TBI and stroke. In particular, release of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) appear to be critically involved. In particular, increased SP expression is observed in perivascular tissue following acute CNS injury, with the magnitude of SP release being related to both the frequency and degree of the insult. SP release is associated with profound blood-brain barrier disruption and the subsequent development of vasogenic oedema, as well as neuronal injury and poor functional outcomes. Inhibition of SP through use of a neurokinin 1 (NK1) antagonist is highly beneficial following both TBI and ischaemic stroke in pre-clinical models. The role of CGRP is more unclear, especially with respect to TBI, with both elevations and reductions in CGRP levels reported following trauma. However, a beneficial role has been delineated in stroke, given its potent vasodilatory effects. Thus, modulating neuropeptides represents a novel therapeutic target in the treatment of cerebral oedema following acute CNS injury.

Protective roles of bioactive peptides during ischemia-reperfusion injury: From bench to bedside

Ischemia-reperfusion (I/R) is a well-known pathological condition which may lead to disability and mortality. I/R injury remains an unresolved and complicated situation in a number of clinical conditions, such as cardiac arrest with successful reanimation, as well as ischemic events in brain and heart. Peptides have many attractive advantages which make them suitable candidate drugs in treating I/R injury, such as low toxicity and immunogenicity, good solubility property, distinct tissue distribution pattern, and favorable pharmacokinetic profile. An increasing number of studies indicate that peptides could protect against I/R injury in many different organs and tissues. Peptides also face several therapeutic challenges that limit their clinical application. In this review, we present the mechanisms of action of peptides in reducing I/R injury, as well as further discuss modification strategies to improve the functional properties of bioactive peptides.

PROTECTIVE EFFECTS OF ETHYL ACETATE EXTRACTION FROM GASTRODIA ELATA BLUME ON BLOOD-BRAIN BARRIER IN FOCAL CEREBRAL ISCHEMIA REPERFUSION

Background:

Damage of the blood brain barrier (BBB) during the process of cerebral ischemic injury is a key factor which influences the therapeutic efficacy to the cerebral ischemic injury. The present study was designed to verify the mechanisms underlying the protective effects of the ethyl acetate (EtOAc) extraction from Gastrodia elata Blume (GEB) on the BBB by developing a model of cerebral ischemia-reperfusion in rats.

Material and methods:

MCAO/R model in rats was developed through a thread embolism method. The neurological scales, the moisture and the evans blue (EB) contents of brains were detected. Meanwhile, the release of nitric oxide (NO) and activities of NO synthase (NOS) in brain tissues were measured. Western blotting analyses were also performed to assess the protein expressions of AQP-4, Occludin and Claudin-5 in brain tissue.

Results:

After rats were pretreated with different concentrations of EtOAc extractions from GEB, the neurologic scores, the EB contents in the brain tissues and the moisture of the brains were significantly decreased. Meanwhile, the release of NO, the activities of nNOS and iNOS were notably inhibited. Furthemore, the protein expression of AQP-4 was markedly decreased, but the protein expressions of -5 and Occludin were significantly increased.

Conclusion:

the EtOAc extracts of GEB may decrease the permeability of BBB when focal cerebral ischemia occurs. The inhibition of the NOS pathways, the attenuation of the protein expression of AQP-4 and the enhancement of the expressions of the tight junction proteins may contribute to the protective effects of the EtOAc extracts from GEB on BBB.

Calcitonin gene-related peptide protects rats from cerebral ischemia/reperfusion injury via a mechanism of action in the MAPK pathway

The aim of the present study was to investigate the protective function and underlying mechanism of calcitonin gene-related peptide (CGRP) on cerebral ischemia/reperfusion damage in rats. Adult male Wistar rats were selected for the establishment of an ischemia/reperfusion injury model through the application of a middle cerebral artery occlusion. Animals were randomly divided into 6 groups of 24 animals. Drugs were administered according to the design of each group; animals were administered CGRP, CGRP8-37, PD98059 and SB20358. The neurobehavioral scores of the rat cerebral ischemia model in each group were calculated. The infarction range of the rat brain tissues was observed by 2,3,5-triphenyltetrazolium chloride staining. The expression levels of three proteins, phosphorylated c-Jun N-terminal kinase (JNK)/JNK, phosphorylated extracellular signal-regulated protein kinase (ERK)/ERK and p-p38/p38, in the mitogen-activated protein kinase (MAPK) pathway in the brain tissues was detected by western blotting. The results showed that CGRP could improve the neurobehavioral function of the ischemic rats and reduce the infarction range. Western blotting results confirmed that the function of the CGRP was mediated mainly through the reduction of the JNK and p38 phosphorylation and the promotion of ERK phosphorylation. Therefore, the present study confirmed that an increase in the exogenous CRGP could effectively improve ischemia/reperfusion injury of the brain tissue. The mechanisms of action were achieved through a reduction in JNK and p38 phosphorylation and an increase in ERL phosphorylation in the MAPK pathway. These mechanisms were interdependent.

Endocannabinoids modulate human blood-brain barrier permeability in vitro

Background and Purpose

Endocannabinoids alter permeability at various epithelial barriers, and cannabinoid receptors and endocannabinoid levels are elevated by stroke, with potential neuroprotective effects. We therefore explored the role of endocannabinoids in modulating blood–brain barrier (BBB) permeability in normal conditions and in an ischaemia/reperfusion model.

Experimental Approach

Human brain microvascular endothelial cell and astrocyte co-cultures modelled the BBB. Ischaemia was modelled by oxygen-glucose deprivation (OGD) and permeability was measured by transepithelial electrical resistance. Endocannabinoids or endocannabinoid-like compounds were assessed for their ability to modulate baseline permeability or OGD-induced hyperpermeability. Target sites of action were investigated using receptor antagonists and subsequently identified with real-time PCR.

Key Results

Anandamide (10 μM) and oleoylethanolamide (OEA, 10 μM) decreased BBB permeability (i.e. increased resistance). This was mediated by cannabinoid CB₂ receptors, transient receptor potential vanilloid 1 (TRPV1) channels, calcitonin gene-regulated peptide (CGRP) receptor (anandamide only) and PPARα (OEA only). Application of OEA, palmitoylethanolamide (both PPARα mediated) or virodhamine (all 10 μM) decreased the OGD-induced increase in permeability during reperfusion. 2-Arachidonoyl glycerol, noladin ether and oleamide did not affect BBB permeability in normal or OGD conditions. N-arachidonoyl-dopamine increased permeability through a cytotoxic mechanism. PPARα and γ, CB₁ receptors, TRPV1 channels and CGRP receptors were expressed in both cell types, but mRNA for CB₂ receptors was only present in astrocytes.

Conclusion and Implication

The endocannabinoids may play an important modulatory role in normal BBB physiology, and also afford protection to the BBB during ischaemic stroke, through a number of target sites.

NK1 tachykinin receptor treatment is superior to capsaicin pre-treatment in improving functional outcome following acute ischemic stroke

Previous results from our laboratory have shown that blockade of the substance P (SP) pathway with an NK1 tachykinin receptor antagonist significantly reduces blood brain barrier breakdown, cerebral edema and functional deficits following ischemic stroke. However, it is unclear whether removal of all neuropeptides is more efficacious than blocking SP alone. As such, the aim of the present study was to determine the effect of neuropeptide depletion with capsaicin pre-treatment on functional outcome following acute ischemic stroke in rats. Animals received 125 mg/kg of capsaicin or equal volume of saline vehicle, administered subcutaneously over a 3-day period. At 14 days following treatment animals were subject to 2h of middle cerebral artery occlusion followed by reperfusion. A subset of animals was treated with an NK1 tachykinin receptor antagonist (NAT) or vehicle at 4h after the onset of stroke only. The functional outcome of animals was assessed for a 7-day period following stroke using a rotarod device, the bilateral asymmetry test, modified neurological severity score, open field and angleboard. Although capsaicin pre-treatment improved outcome, treatment with an NK1 tachykinin receptor antagonist was superior in improving post-stroke functional outcome. This data suggests that some neuropeptides may play a beneficial role following stroke, whilst others such as SP are deleterious.

Catalpol provides protective effects against cerebral ischaemia/reperfusion injury in gerbils

Objectives

To investigate the protective effect of catalpol on cerebral ischaemia/reperfusion (CI/R) injury in gerbils and further explore the underlying mechanism.

Methods

A gerbil model of CI/R was prepared by bilateral common carotid occlusion for 10 min followed by 6 h reperfusion. Catalpol (5, 10 or 20 mg/kg per day) was injected intraperitoneally for 3 days before the carotid occlusion. Stroke index was measured during the reperfusion. The contents of endogenous neuropeptides, endothelin-1 (ET-1) and calcitonin gene-related peptide in plasma were evaluated by radioimmunoassay. Superoxide dismutase (SOD) and malondialdehyde (MDA) in brain tissue homogenate were also examined.

Key findings

The results showed that catalpol significantly improved the stroke index compared with CI/R control group (P &lt; 0.05 or P &lt; 0.01). Catalpol significantly increased the activity of SOD at the doses of 10 and 20 mg/kg (P ≤ 0.05), decreased the brain MDA content and the plasma level of ET-1 at the doses of 10 and 20 mg/kg (P ≤ 0.01).

Conclusions

These data suggested that the efficacy of catalpol pretreatment on CI/R injury may be attributed to reduction of free radicals and inhibition of lipid peroxidation and ET-1 production.

Blocking neurogenic inflammation for the treatment of acute disorders of the central nervous system

Classical inflammation is a well-characterized secondary response to many acute disorders of the central nervous system. However, in recent years, the role of neurogenic inflammation in the pathogenesis of neurological diseases has gained increasing attention, with a particular focus on its effects on modulation of the blood-brain barrier BBB. The neuropeptide substance P has been shown to increase blood-brain barrier permeability following acute injury to the brain and is associated with marked cerebral edema. Its release has also been shown to modulate classical inflammation. Accordingly, blocking substance P NK1 receptors may provide a novel alternative treatment to ameliorate the deleterious effects of neurogenic inflammation in the central nervous system. The purpose of this paper is to provide an overview of the role of substance P and neurogenic inflammation in acute injury to the central nervous system following traumatic brain injury, spinal cord injury, stroke, and meningitis.