Cortical spreading depression induces the expression of iNOS, HIF-1α, and LDH-A

Unraveling the interplay of neuroinflammatory signaling between parenchymal and meningeal cells in migraine headache

BACKGROUND

The initiation of migraine headaches and the involvement of neuroinflammatory signaling between parenchymal and meningeal cells remain unclear. Experimental evidence suggests that a cascade of inflammatory signaling originating from neurons may extend to the meninges, thereby inducing neurogenic inflammation and headache. This review explores the role of parenchymal inflammatory signaling in migraine headaches, drawing upon recent advancements. BODY: Studies in rodents have demonstrated that sterile meningeal inflammation can stimulate and sensitize meningeal nociceptors, culminating in headaches. The efficacy of relatively blood-brain barrier-impermeable anti-calcitonin gene-related peptide antibodies and triptans in treating migraine attacks, both with and without aura, supports the concept of migraine pain originating in meninges. Additionally, PET studies utilizing inflammation markers have revealed meningeal inflammatory activity in patients experiencing migraine with aura, particularly over the occipital cortex generating visual auras. The parenchymal neuroinflammatory signaling involving neurons, astrocytes, and microglia, which eventually extends to the meninges, can link non-homeostatic perturbations in the insensate brain to pain-sensitive meninges. Recent experimental research has brought deeper insight into parenchymal signaling mechanisms: Neuronal pannexin-1 channels act as stress sensors, initiating the inflammatory signaling by inflammasome formation and high-mobility group box-1 release in response to transient perturbations such as cortical spreading depolarization (CSD) or synaptic metabolic insufficiency caused by transcriptional changes induced by migraine triggers like sleep deprivation and stress. After a single CSD, astrocytes respond by upregulating the transcription of proinflammatory enzymes and mediators, while microglia are involved in restoring neuronal structural integrity; however, repeated CSDs may prompt microglia to adopt a pro-inflammatory state. Transcriptional changes from pro- to anti-inflammatory within 24 h may serve to dampen the inflammatory signaling. The extensive coverage of brain surface and perivascular areas by astrocyte endfeet suggests their role as an interface for transporting inflammatory mediators to the cerebrospinal fluid to contribute to meningeal nociception.

CONCLUSION

We propose that neuronal stress induced by CSD or synaptic activity-energy mismatch may initiate a parenchymal inflammatory signaling cascade, transmitted to the meninges, thereby triggering lasting headaches characteristic of migraine, with or without aura. This neuroinflammatory interplay between parenchymal and meningeal cells points to the potential for novel targets for migraine treatment and prophylaxis.

Differences and correlations of biochemical index levels in patients with bipolar disorder and major depressive disorder during a stable period

The differences and correlation of biochemical indexes between bipolar disorder (BPD) and major depressive disorder (MDD) in stable stage were analyzed and discussed. Patients diagnosed with BPD and MDD in the Third People's Hospital of Foshan from January 2019 to December 2021 were selected as the research subjects, with 200 cases in each. Fasting serum was collected from patients and then detected regarding TC, TG, high-density lipoprotein, low-density lipoprotein (LDL), aspartate aminotransferase, lactic dehydrogenase, creatine kinase, creatine kinase-MB, urea, creatinine, uric acid, alanine aminotransferase, glucose (GLU), hemoglobin A1c, prolactin, high-sensitivity C-reactive protein, homocysteine. The results showed that the mean age and serum LDL, GLU, and HbAc1 levels of the MDD group were significantly higher than those of the BPD group (P < .05), while there was no significant difference in other indexes (P > .05). The prevalence of BPD was significantly negatively correlated with patient age (r = -0.164, P = .020), LDL (r = -0.150, P = .034), GLU (r = -0.140, P = .048), and HbAc1 (r = -0.215, P = .002) (P < .05). There were no significant differences in serum Hcy and high-sensitivity C-reactive protein levels between the BPD and MDD groups. The age, fasting blood glucose, glycosylated hemoglobin, and LDL of BPD patients were negatively correlated with their incidence.

Genome-wide DNA methylation analysis in an antimigraine-treated preclinical model of cortical spreading depolarization

BACKGROUND

Cortical spreading depolarization, the cause of migraine aura, is a short-lasting depolarization wave that moves across the brain cortex, transiently suppressing neuronal activity. Prophylactic treatments for migraine, such as topiramate or valproate, reduce the number of cortical spreading depression events in rodents.

OBJECTIVE

To investigate whether cortical spreading depolarization with and without chronic treatment with topiramate or valproate affect the DNA methylation of the cortex.

METHODS

Sprague-Dawley rats were intraperitoneally injected with saline, topiramate or valproate for four weeks when cortical spreading depolarization were induced and genome-wide DNA methylation was performed in the cortex of six rats per group.

RESULTS

The DNA methylation profile of the cortex was significantly modified after cortical spreading depolarization, with and without topiramate or valproate. Interestingly, topiramate reduced by almost 50% the number of differentially methylated regions, whereas valproate increased them by 17%, when comparing to the non-treated group after cortical spreading depolarization induction. The majority of the differentially methylated regions lay within intragenic regions, and the analyses of functional group over-representation retrieved several enriched functions, including functions related to protein processing in the cortical spreading depolarization without treatment group; functions related to metabolic processes in the cortical spreading depolarization with topiramate group; and functions related to synapse and ErbB, MAPK or retrograde endocannabinoid signaling in the cortical spreading depolarization with valproate group.

CONCLUSIONS

Our results may provide insights into the underlying physiological mechanisms of migraine with aura and emphasize the role of epigenetics in migraine susceptibility.

Epigenetics and cortical spreading depression: changes of DNA methylation level at retrotransposon sequences

Cortical spreading depression (CSD) is an evolutionarily conserved phenomenon that involves a slow and self-propagating depolarization wave associated with spontaneous depression of electrical neuronal activity. CSD plays a central role in the pathophysiology of several brain diseases and is considered to be able to promote "Preconditioning". This phenomenon consists of the brain protecting itself against future injury by adaptation. Understanding of the molecular mechanisms underlying Preconditioning has significant clinical implications. We have already proposed that the long-lasting effects of CSD could be related to silencing of retrotransposon sequences by histone methylation. We analyzed DNA methylation of two retrotransposon sequences, LINE1 and L1, and their corresponding expression pattern after CSD induction. Based on immunoprecipitation assay of the methylated DNA (meDIP), we demonstrated hypermethylation of both sequences in preconditioned rat brain cortex compared with a control 24 h after CSD induction. Using quantitative PCR, we also showed that CSD induction caused a decrease of the transcript level of both retrotransposon sequences. Our data are consistent with the hypothesis of epigenetic modifications in Preconditioning-dependent neuroprotection by increasing genome stability via the silencing of retrotransposon sequences.

Cortical spreading depression produces a neuroprotective effect activating mitochondrial uncoupling protein-5

Depression of electrocorticogram propagating over the cortex surface results in cortical spreading depression (CSD), which is probably related to the pathophysiology of stroke, epilepsy, and migraine. However, preconditioning with CSD produces neuroprotection to subsequent ischemic episodes. Such effects require the expression or activation of several genes, including neuroprotective ones. Recently, it has been demonstrated that the expression of the uncoupling proteins (UCPs) 2 and 5 is amplified during brain ischemia and their expression exerts a long-term effect upon neuron protection. To evaluate the neuroprotective consequence of CSD, the expression of UCP-5 in the brain cortex was measured following CSD induction. CSD was evoked in four samples of rats, which were sacrificed after 2 hours, 4 hours, 6 hours, and 24 hours. Western blot analyses were carried out to measure UCP-5 concentrations in the prefrontal cortices of both hemispheres, and immunohistochemistry was performed to determine the localization of UCP-5 in the brain cortex. The results showed a significant elevation in UCP-5 expression at 24 hours in all cortical strata. Moreover, UCP-5 was triggered by CSD, indicating that UCP-5 production can have a neuroprotective effect.

Hypoxic Adaptation in the Nervous System: Promise for Novel Therapeutics for Acute and Chronic Neurodegeneration

Homeostasis is the process by which cells adapt to stress and prevent or repair injury. Unique programs have evolved to sense and activate these homeostatic mechanisms and as such, homeostatic sensors may be potent therapeutic targets. The hypoxic response mediated by hypoxia inducible factor (HIF) downstream of oxygen sensing by HIF prolyl 4-hydroxylases (PHDs) has been well-studied, revealing cell-type specific regulation of HIF stability, activity, and transcriptional targets. HIF's paradoxical roles in nervous system development, physiology, and pathology arise from its complex roles in hypoxic adaptation and normoxic biology. Understanding how to engage the hypoxic response so as to recapitulate the protective mechanism of ischemic preconditioning is a high priority. Indeed, small molecules that activate the hypoxic response provide broad neuroprotection in several clinically relevant injury models. Screens for PHD inhibitors have identified novel therapeutics for neuroprotection that are ready to proceed to clinical trials for ischemic stroke. Better understanding the mechanisms of how to engage hypoxic adaption without altering development or physiology may identify additional novel therapeutic targets for diverse acute and chronic neuropathologies.

Cortical spreading depression-induced preconditioning in the brain

Cortical spreading depression is a technique used to depolarize neurons. During focal or global ischemia, cortical spreading depression-induced preconditioning can enhance tolerance of further injury. However, the underlying mechanism for this phenomenon remains relatively unclear. To date, numerous issues exist regarding the experimental model used to precondition the brain with cortical spreading depression, such as the administration route, concentration of potassium chloride, induction time, duration of the protection provided by the treatment, the regional distribution of the protective effect, and the types of neurons responsible for the greater tolerance. In this review, we focus on the mechanisms underlying cortical spreading depression-induced tolerance in the brain, considering excitatory neurotransmission and metabolism, nitric oxide, genomic reprogramming, inflammation, neurotropic factors, and cellular stress response. Specifically, we clarify the procedures and detailed information regarding cortical spreading depression-induced preconditioning and build a foundation for more comprehensive investigations in the field of neural regeneration and clinical application in the future.

Spreading Depression, Spreading Depolarizations, and the Cerebral Vasculature

Spreading depression (SD) is a transient wave of near-complete neuronal and glial depolarization associated with massive transmembrane ionic and water shifts. It is evolutionarily conserved in the central nervous systems of a wide variety of species from locust to human. The depolarization spreads slowly at a rate of only millimeters per minute by way of grey matter contiguity, irrespective of functional or vascular divisions, and lasts up to a minute in otherwise normal tissue. As such, SD is a radically different breed of electrophysiological activity compared with everyday neural activity, such as action potentials and synaptic transmission. Seventy years after its discovery by Leão, the mechanisms of SD and its profound metabolic and hemodynamic effects are still debated. What we did learn of consequence, however, is that SD plays a central role in the pathophysiology of a number of diseases including migraine, ischemic stroke, intracranial hemorrhage, and traumatic brain injury. An intriguing overlap among them is that they are all neurovascular disorders. Therefore, the interplay between neurons and vascular elements is critical for our understanding of the impact of this homeostatic breakdown in patients. The challenges of translating experimental data into human pathophysiology notwithstanding, this review provides a detailed account of bidirectional interactions between brain parenchyma and the cerebral vasculature during SD and puts this in the context of neurovascular diseases.

The loss of NDRG2 expression improves depressive behavior through increased phosphorylation of GSK3β

N-myc downstream-regulated gene 2 (NDRG2) is one of the important stress-inducible genes and plays a critical role in negatively regulating PI3K/AKT signaling during hypoxia and inflammation. Through recruitment of PP2A phosphatase, NDRG2 maintains the dephosphorylated status of PTEN to suppress excessive PI3K/AKT signaling, and loss of NDRG2 expression is frequently seen in various types of cancer with enhanced activation of PI3K/AKT signaling. Because NDRG2 is highly expressed in the nervous system, we investigated whether NDRG2 plays a functional role in the nervous system using Ndrg2-deficient mice. Ndrg2-deficient mice do not display any gross abnormalities in the nervous system, but they have a diminished behavioral response associated with anxiety. Ndrg2-deficient mice exhibited decreased immobility and increased head-dipping and rearing behavior in two behavioral models, indicating an improvement of emotional anxiety-like behavior. Moreover, treatment of wild-type mice with the antidepressant drug imipramine reduced the expression of Ndrg2 in the frontal cortex, which was due to the degradation of HIF-1α through reduced expression of HSP90 protein. Furthermore, we found that the down-regulation of Ndrg2 in Ndrg2-deficient mice and imipramine treatment improved mood behavior with enhanced phosphorylation of GSK3β through activation of PI3K/AKT signaling, suggesting that the expression level of NDRG2 has a causal influence on mood-related phenotypes. Collectively, these results suggest that NDRG2 may be a potential target for mood disorders such as depression and anxiety.

The effect of sumatriptan on nitric oxide synthase enzyme production after iatrogenic inflammation in the brain stem of adolescent rats: A randomized, controlled, experimental study

BACKGROUND

Migraine is a common disabling disorder of childhood and adolescence. Despite advances in the understanding of migraine pathophysiology, treatment remains a challenge.

OBJECTIVES

The aims of this study were to investigate the production of nitric oxide synthase (NOS) enzymes in the brain stem of adolescent rats, using an experimental model of migraine, and the effect of sumatriptan pretreatment on the production of the NOS enzymes.

METHODS

Male adolescent (aged ~2 months) Wistar rats were used in the study. The animals were anesthetized using pentobarbital. The trigeminovascular system was stimulated by injecting a proinflammatory molecule, carrageenan, into the cis-terna magna of the anesthetized rats. The animals were divided into 3 groups of equal size: (1) the study group, in which the rats were treated with sumatriptan succinate 2 hours before intracisternal carrageenan injection; (2) the sham group, in which the rats were not administered intracisternal carrageenan injection or sumatriptan pretreatment; and (3) the control group, in which the rats were administered intracisternal carrageenan injection but were not pretreated with sumatriptan. In the control and study groups, the rats were euthanized using ether anesthesia 1 hour after intracisternal carrageenan injection. Rats in the sham group were euthanized 1 hour after intracisternal catheterization. Brain tissue was removed and endothelial NOS (eNOS), neuronal NOS (nNOS), and inducible NOS (iNOS) immunohistochemistry was performed.

RESULTS

Twenty-one rats were randomized into 3 groups of 7. The mean values of the immunolabeling intensities for eNOS, nNOS, and iNOS enzymes in the brain stem were significantly lower in the sham group compared with the control group (P = 0.001, P = 0.002, and P = 0.001, respectively). The mean values of the immunolabeling intensities of eNOS, nNOS, and iNOS in the brain stem were significantly lower in the study group compared with the control group (P = 0.001, P = 0.025, and P = 0.005, respectively).

CONCLUSIONS

In this experimental model of migraine in adolescent rats, intracisternal injection of carrageenan was associated with a significant increase in the production of NOS enzymes in the brain stem. Pretreatment with sumatriptan was associated with a decrease in NOS production.

[Cortical spreading depolarization phenomena in patients with traumatic and ischemic brain injuries. Results of a pilot study]

OBJECTIVES

To determine the frequency and duration of cortical spreading depolarization (CSD) and CSD-like episodes in patients with traumatic brain injury (TBI) and malignant middle cerebral artery infarction (MMCAI) requiring craniotomy.

DESIGN

A descriptive observational study was carried out during 19 months.

SETTING

Neurocritical patients.

PATIENTS

Sixteen patients were included: 9 with MMCAI and 7 with moderate or severe TBI, requiring surgical treatment.

INTERVENTIONS

A 6-electrode subdural electrocorticographic (ECoG) strip was placed onto the perilesional cortex.

MAIN VARIABLES OF INTEREST

An analysis was made of the time profile and the number and duration of CSD and CSD-like episodes recorded from the ECoGs.

RESULTS

Of the 16 patients enrolled, 9 presented episodes of CSD or CSD-like phenomena, of highly variable frequency and duration.

CONCLUSIONS

Episodes of CSD and CSD-like phenomena are frequently detected in the ischemic penumbra and/or traumatic cortical regions of patients with MMCAI who require decompressive craniectomy or of patients with contusional TBI.

Cortical spreading depression and calcitonin gene-related peptide: a brief review of current progress

Although detailed disease mechanisms of migraine remain poorly understood, migraine is known to have a complex pathophysiology with both vascular and neuronal mechanisms. The neuronal mechanisms of migraine may be attributed to cortical spreading depression (CSD); consequently, CSD has been widely studied for understanding the pathophysiology of migraine. Well validated CSD models have been developed for evaluating anti-migraine drugs. Neuropeptides, mainly, calcitonin gene-related peptide (CGRP), have been proposed as an emerging class of effective drugs against migraine headache. The central role of this neuropeptide has led to research into CSD for understanding disease mechanisms of migraine. This review briefly summarizes our current understanding of CSD and CGRP involvement in CSD. Although CSD can also worsen strokes, this brief paper has excluded the possible connection between the neuropeptide and CSD associated with them. Instead it has focused solely on CGRP in CSD associated with migraine.

Cortical spreading depression differentially affects lysine methylation of H3 histone at neuroprotective genes and retrotransposon sequences

Recently cortical spreading depression (CSD) has been hypothesized to involve epigenetic control of gene expression, by inducing an overall decrease of H3K4 and increase of H3K9 di-methylation. Here we evaluated the H3K4 and H3K9 di-methylation level at specific loci in rat brains 24 h after CSD induction. Analysis of two selected neuroprotective genes, iNOS and HIF-1α, showed marked increase in lysine 4 di-methylation and decrease in lysine 9 di-methylation of H3 histone. In addition, di-methylation of H3K4 increased moving toward 5' end of the genes in CSD-induced rat hemispheres. Such behavior may reflect an epigenetic molecular memory of actively transcribed genes. We extended our analysis on the H3K4 and H3K9 di-methylation levels of two long interspersed sequences (LINEs). We showed that CSD induction led to di-methylation decrease in lysine 4 and increase in lysine 9 of H3 histone, a trend which reflected the overall chromatin changes previously demonstrated. In conclusion, our data corroborate the hypothesis that epigenetic regulation of gene expression can be affected by CSD and that might be a pivotal molecular mechanism of CSD-induced preconditioning phenomenon which induces tolerance to a subsequent episode of ischemia. In such control, we evidenced two effects: i) a molecular memory of transcribed neuroprotective genes, ii) an epigenetic silencing of retrotransposable sequences.

Cortical spreading depression affects reactive oxygen species production

Cortical spreading depression (CSD) is a reversible electrophysiological phenomenon that is not associated with tissue damage under normal blood supply. The induction of CSD during ischemia causes an increase in tissue damage, while pre-conditioning with CSD decreases the damage induced by a subsequent episode of ischemia. The mechanisms underlying these effects are not clear. Because the production of reactive oxygen species (ROS) is involved in tissue damage during ischemia-reperfusion, the aim of the present study was to evaluate the effects of CSD on superoxide production (O(2)(-)), on hydrogen peroxide (H(2)O(2)) production and on superoxide dismutase (SOD) activity in the cerebral cortex. CSD was induced by KCl application on the cortical surface in rats. O(2)(-) production was evaluated using dihydroethidium (DHE) that is oxidized to the fluorescent dye ethidium (HEt) by O(2)(-). The extracellular level of H(2)O(2) was evaluated by microdialysis sampling and HPLC analysis. SOD activity was evaluated with a histochemical assay. The results showed an increase in H(2)O(2) production, an increase in SOD activity and a decrease in O(2)(-) concentration 1h after CSD induction.

Epigenetic chromatin modifications in the cortical spreading depression

Preconditioning with Cortical Spreading Depression induces a sort of tolerance to a subsequent episode of ischemia. The mechanism of this tolerance is not clear. We studied if such treatment induces epigenetic chromatin modifications on the hemispheres of rats preconditioned by Cortical Spreading Depression. The contralateral hemispheres were used as control. We determined the level of H3K4 and H3K9 methylation and the mRNA amounts for the two well known H3K4 methyltransferases (MLL and SET7) in rats 24 degrees h after the Cortical Spreading Depression induction. Western blotting experiments have been performed using three different types of primary antibodies against mono-, di- and tri-methyl H3K4 and primary antibody anti-dimethyl H3K9. In the same samples we checked if the H3 histones were replaced by the H3.3 histone variants that could be an additional marker of chromatin modifications. The level of mono- and di-methyl H3K4 was significantly lower in samples of the treated hemispheres than those of the contralateral hemispheres (40% and about 60%, respectively) while the level of tri-methylation remained unchanged. The level of di-methyl H3K9 was almost 60% higher in the treated hemispheres than the contralateral hemispheres. The treatment for Cortical Spreading Depression affected also the level of expression of H3K4 histone methyltransferase MLL and SET7 that decreased in the treated hemispheres in comparison to the control hemispheres (80% and 40%, respectively). The treatment for Cortical Spreading Depression instead had no effects on the overall amounts of mRNA for H3 and H3.3 histones. In conclusion epigenetic chromatin modifications are evident in rats 24 degrees h after the Cortical Spreading Depression induction.

Investigation of the immunoreactivities of NOS enzymes and the effect of sumatriptan in adolescent rats using an experimental model of migraine

The aim was to investigate the immunoreactivities for NOS enzymes in frontal cortex and meningeal vessels after chemical stimulation of the subarachnoid space of adolescent rats and the effect of sumatriptan pre-treatment on the immunoreactivities of the NOS enzymes. Male adolescent Wistar rats were used. Rats in group 1 did not taken intracisternal injection. Rats in group 2 were taken intracisternal autologous blood injection, but no sumatriptan pre-treatment. Rats in group 3 were taken intracisternal autologous blood injection, but they were taken sumatriptan pre-treatment. Tissue samples were investigated for the presence of NOS immunoreactivity. The mean values of immunolabeling intensities for NOS enzymes in frontal cortex and meningeal vessels were significantly increased in group 2 compared to group 1. The mean values of immunolabeling intensities for NOS enzymes in frontal cortex and meningeal vessels were significantly reduced in group 3 compared to group 2. These results suggest that, chemical stimulation of the subarachnoid space increased the immunoreactivities of NOS enzymes in the brain of adolescent rats. The increased NOS immunoreactivities could be antagonized by pre-treatment with sumatriptan.