P2Y4/TSP-1/TGF-β1/pSmad2/3 pathway contributes to acute generalized seizures induced by kainic acid

The Contributions of Thrombospondin-1 to Epilepsy Formation

Epilepsy is a neural network disorder caused by uncontrolled neuronal hyperexcitability induced by an imbalance between excitatory and inhibitory networks. Abnormal synaptogenesis plays a vital role in the formation of overexcited networks. Recent evidence has confirmed that thrombospondin-1 (TSP-1), mainly secreted by astrocytes, is a critical cytokine that regulates synaptogenesis during epileptogenesis. Furthermore, numerous studies have reported that TSP-1 is also involved in other processes, such as angiogenesis, neuroinflammation, and regulation of Ca2+ homeostasis, which are closely associated with the occurrence and development of epilepsy. In this review, we summarize the potential contributions of TSP-1 to epilepsy development.

TGF-β signaling in health, disease, and therapeutics

Transforming growth factor (TGF)-β is a multifunctional cytokine expressed by almost every tissue and cell type. The signal transduction of TGF-β can stimulate diverse cellular responses and is particularly critical to embryonic development, wound healing, tissue homeostasis, and immune homeostasis in health. The dysfunction of TGF-β can play key roles in many diseases, and numerous targeted therapies have been developed to rectify its pathogenic activity. In the past decades, a large number of studies on TGF-β signaling have been carried out, covering a broad spectrum of topics in health, disease, and therapeutics. Thus, a comprehensive overview of TGF-β signaling is required for a general picture of the studies in this field. In this review, we retrace the research history of TGF-β and introduce the molecular mechanisms regarding its biosynthesis, activation, and signal transduction. We also provide deep insights into the functions of TGF-β signaling in physiological conditions as well as in pathological processes. TGF-β-targeting therapies which have brought fresh hope to the treatment of relevant diseases are highlighted. Through the summary of previous knowledge and recent updates, this review aims to provide a systematic understanding of TGF-β signaling and to attract more attention and interest to this research area.

Overview Article Astrocytes as Initiators of Epilepsy

Astrocytes play a dual role in the brain. On the one hand, they are active signaling partners of neurons and can for instance control synaptic transmission and its plasticity. On the other hand, they fulfill various homeostatic functions such as clearance of glutamate and K⁺ released from neurons. The latter is for instance important for limiting neuronal excitability. Therefore, an impairment or failure of glutamate and K⁺ clearance will lead to increased neuronal excitability, which could trigger or aggravate brain diseases such as epilepsy, in which neuronal hyperexcitability plays a role. Experimental data indicate that astrocytes could have such a causal role in epilepsy, but the role of astrocytes as initiators of epilepsy and the relevant mechanisms are under debate. In this overview, we will discuss the potential mechanisms with focus on K⁺ clearance, glutamate uptake and homoeostasis and related mechanisms, and the evidence for their causative role in epilepsy.

Serum levels of matrix metalloproteinase 2 and its inhibitor after tonic-clonic seizures

Damage to the blood-brain barrier (BBB) may result from on-going neuroinflammation, which can lead to leakage of blood components, such as leukocytes and serum proteins, into the brain, resulting in disturbed brain homeostasis. The aim of the project was to examine the involvement of modulatory proteins in the processes of BBB integration after epileptic seizures. We investigated serum changes in the levels of MMP-2 and MMP-7 and its inhibitors after seizures in epilepsy patients. Concentrations of these proteins were measured by ELISA in 50 patients at 1-3, 24, and 72 h after generalized tonic-clonic seizures and once in participants of the control group. The level of MMP-2 in serum was slightly higher after seizures (at 1-3 h time point), but the difference was not statistically significant. The levels of trombospondine (TSP) - 1 and - 2 were decreased at 1-3 h after seizures. The expression of TIMP-2 was increased 1 and 24 h after seizures. There were no significant changes in the level of α2-macroglobulin and MMP-7. Changes in the expression of both specific and non-specific inhibitors indicate the initiation of repair processes of the blood-brain barrier and improvement of its integrity. Since we performed serum analysis, further studies are necessary to investigate the correlation with the expression of the investigated markers in the brain. Perhaps this will allow for the identification of new biomarkers associated with epileptic seizures.

Purinergic signaling: A gatekeeper of blood-brain barrier permeation

This review outlined evidence that purinergic signaling is involved in the modulation of blood-brain barrier (BBB) permeability. The functional and structural integrity of the BBB is critical for maintaining the homeostasis of the brain microenvironment. BBB integrity is maintained primarily by endothelial cells and basement membrane but also be regulated by pericytes, neurons, astrocytes, microglia and oligodendrocytes. In this review, we summarized the purinergic receptors and nucleotidases expressed on BBB cells and focused on the regulation of BBB permeability by purinergic signaling. The permeability of BBB is regulated by a series of purinergic receptors classified as P2Y₁, P2Y₄, P2Y₁₂, P2X4, P2X7, A₁, A_2A, A_2B, and A₃, which serve as targets for endogenous ATP, ADP, or adenosine. P2Y₁ and P2Y₄ antagonists could attenuate BBB damage. In contrast, P2Y₁₂-mediated chemotaxis of microglial cell processes is necessary for rapid closure of the BBB after BBB breakdown. Antagonists of P2X4 and P2X7 inhibit the activation of these receptors, reduce the release of interleukin-1 beta (IL-1β), and promote the function of BBB closure. In addition, the CD39/CD73 nucleotidase axis participates in extracellular adenosine metabolism and promotes BBB permeability through A₁ and A_2A on BBB cells. Furthermore, A_2B and A₃ receptor agonists protect BBB integrity. Thus, the regulation of the BBB by purinergic signaling is complex and affects the opening and closing of the BBB through different pathways. Appropriate selective agonists/antagonists of purinergic receptors and corresponding enzyme inhibitors could modulate the permeability of the BBB, effectively delivering therapeutic drugs/cells to the central nervous system (CNS) or limiting the entry of inflammatory immune cells into the brain and re-establishing CNS homeostasis.

Knockdown of P2Y4 ameliorates sepsis-induced acute kidney injury in mice via inhibiting the activation of the NF-κB/MMP8 axis

Sepsis-induced acute kidney injury (S-AKI) has emerged as a frequent and life-threatening complication in critically ill patients, which is characterized by a systematic inflammatory response and a rapid decline in kidney function. P2Y4, a member of G protein–coupled P2Y nucleotide receptor family, has been reported to serve as a crucial player in inflammatory responses during the development of neurocognitive disorder and myocardial infarction. Nonetheless, the biological role of P2Y4 in S-AKI remains largely unclear. This study aimed to decipher the biological role of P2Y4 in S-AKI and illuminate the potential mechanisms. In this study, S-AKI models were successfully established in mice via cecal ligation and puncture. Results showed that the kidney tissues from S-AKI mouse models exhibited a higher P2Y4 expression level than from the sham-operated group. Knockdown of P2Y4 was found to remarkably alleviate kidney damage and reduce inflammatory response in mice of S-AKI models. Moreover, P2Y4 ablation inhibited the activation of the NF-κB/MMP-8 signaling axis. Additionally, mechanistic studies revealed that rescuing MMP-8 reversed the alleviating effects of P2Y4 knockdown against renal cell damage. Collectively, our findings indicate that P2Y4 knockdown ameliorated S-AKI in mice via inhibiting the activation of the NF-κB/MMP-8 axis and that P2Y4 may represent a novel therapeutic target for S-AKI patients.

Inhibition of Aryl Hydrocarbon Receptor Attenuates Hyperglycemia-Induced Hematoma Expansion in an Intracerebral Hemorrhage Mouse Model

Background

Hyperglycemia is associated with greater hematoma expansion (HE) and worse clinical prognosis after intracerebral hemorrhage (ICH). However, the clinical benefits of intensive glucose normalization remain controversial, and there are no approved therapies for reducing HE. The aryl hydrocarbon receptor (AHR) has been shown to participate in hyperglycemia‐induced blood–brain barrier (BBB) dysfunction and brain injury after stroke. Herein, we investigated the role of AHR in hyperglycemia‐induced HE in a male mouse model of ICH.

Methods and Results

CD1 mice (n=387) were used in this study. Mice were subjected to ICH by collagenase injection. Fifty percent dextrose was injected intraperitoneally 3 hours after ICH. AHR knockout clustered regularly interspaced short palindromic repeat was administered intracerebroventricularly to evaluate the role of AHR after ICH. A selective AHR inhibitor, 6,2′,4′‐trimethoxyflavone, was administered intraperitoneally 2 hours or 6 hours after ICH for outcome study. To evaluate the effect of AHR on HE, 3‐methylcholanthrene, an AHR agonist, was injected intraperitoneally 2 hours after ICH. The results showed hyperglycemic ICH upregulated AHR accompanied by greater HE. AHR inhibition provided neurological benefits by restricting HE and preserving BBB function after hyperglycemic ICH. In vivo knockdown of AHR further limited HE and enhanced the BBB integrity. Hyperglycemia directly activated AHR as a physiological stimulus in vivo. The thrombospondin‐1/transforming growth factor‐β/vascular endothelial growth factor axis partly participated in AHR signaling after ICH, which inhibited the expressions of BBB‐related proteins, ZO‐1 and Claudin‐5.

Conclusions

AHR may serve as a potential therapeutic target to attenuate hyperglycemia‐induced hematoma expansion and to preserve the BBB in patients with ICH.

Dynamic resistance exercise increases skeletal muscle-derived FSTL1 inducing cardiac angiogenesis via DIP2A-Smad2/3 in rats following myocardial infarction

PURPOSE

The aim of this study was to investigate the potential of dynamic resistance exercise to generate skeletal muscle-derived follistatin like-1 (FSTL1), which may induce cardioprotection in rats following myocardial infarction (MI) by inducing angiogenesis.

METHODS

Male, adult Sprague-Dawley rats were randomly divided into 5 groups (n = 12 in each group): sham group (S), sedentary MI group (MI), MI + resistance exercise group (MR), MI + adeno-associated virus (AAV)-FSTL1 injection group (MA), and MI + AAV-FSTL1 injection + resistance exercise group (MAR). The AAV-FSTL1 vector was prepared by molecular biology methods and injected into the anterior tibialis muscle. The MI model was established by ligation of the left anterior descending coronary artery. Rats in the MR and MAR groups underwent 4 weeks of dynamic resistance exercise training using a weighted climbing-up ladder. Heart function was evaluated by hemodynamic measures. Collagen volume fraction of myocardium was observed and analyzed by Masson's staining. Human umbilical vein vessel endothelial cells culture and recombinant human FSTL1 protein or transforming growth factor-β receptor 1 (TGFβR1) inhibitor treatment were used to elucidate the molecular signaling mechanism of FSTL1. Angiogenesis, cell proliferation, and disco interacting protein 2 homolog A (DIP2A) location were observed by immunofluorescence staining. The expression of FSTL1, DIP2A, and the activation of signaling pathways were detected by Western blotting. Angiogenesis of endothelial cells was observed by tubule experiment. One-way analysis of variance and Student's t test were used for statistical analysis.

RESULTS

Resistance exercise stimulated the secretion of skeletal muscle FSTL1, which promoted myocardial angiogenesis, inhibited pathological remodeling, and protected cardiac function in MI rats. Exercise facilitated skeletal muscle FSTL1 to play a role in protecting the heart. Exogenous FSTL1 promoted the human umbilical vein vessel endothelial cells proliferation and up-regulated the expression of DIP2A, while TGFβR1 inhibitor intervention down-regulated the phosphorylation level of Smad2/3 and the expression of vascular endothelial growth factor-A, which was not conducive to angiogenesis. FSTL1 bound to the receptor, DIP2A, to regulate angiogenesis mainly through the Smad2/3 signaling pathway. FSTL1-DIP2A directly activated Smad2/3 and was not affected by TGFβR1.

CONCLUSION

Dynamic resistance exercise stimulates the expression of skeletal muscle-derived FSTL1, which could supplement the insufficiency of cardiac FSTL1 and promote cardiac rehabilitation through the DIP2A-Smad2/3 signaling pathway in MI rats.

Succinate accumulation contributes to oxidative stress and iron accumulation in pentylenetetrazol-induced epileptogenesis and kainic acid-induced seizure

This study explored the role of succinate accumulation in the oxidative stress and iron accumulation in both pentylenetetrazol (PTZ)-induced epileptogenesis and kainic acid (KA)-induced status epilepticus (SE). The levels of succinate, oxidative stress, iron content, iron-related protein expression, and the severity of neuronal injury and seizures were measured in both models. We found that increased concentrations of succinate were associated with increased levels of oxidative stress, iron content, iron regulator protein, and iron importer divalent metal transporter 1, as well as decreased levels of iron exporter ferropotin 1. Aggravated neuronal injury was observed in the hippocampi and cortices of both models. The cell-permeable molecule dimethyl malonate (DM), a competitive inhibitor of succinate dehydrogenase (SDH), significantly attenuated succinate accumulation, reduced the oxidative stress and iron levels, and mitigated the severity of the seizures and neuronal injury. Our results thus indicate that the accumulation of succinate due to the reverse catalysis of SDH may exacerbate oxidative stress and thus induce iron accumulation and neuronal injury in both models. Targeting succinate accumulation may achieve neuroprotective and anti-seizure effects.

Xenon Exerts Neuroprotective Effects on Kainic Acid-Induced Acute Generalized Seizures in Rats via Increased Autophagy

Xenon has been shown to have neuroprotective effects and is clinically used as a favorable safe inhalation anesthetic. We previously confirmed the neuroprotective effects of xenon treatment in epileptic animals. However, the mechanism underlying these protective effects remains unclear. We aimed to assess the effects of xenon inhalation on autophagy in neuronal injury induced by acute generalized seizures. Kainic acid (KA) was injected into the lateral ventricle of male Sprague–Dawley rats to induce acute generalized seizures. Next, the rats were treated via inhalation of a 70% xenon/21% oxygen/9% nitrogen mixture for 60 min immediately after KA administration. The control group was treated via inhalation of a 79% nitrogen/21% oxygen mixture. Subsequently, two inhibitors (3-methyladenine or bafilomycin A₁) or an autophagy inducer (rapamycin) were administered, respectively, before KA and xenon administration to determine the role of autophagy in the protective effects of xenon. The levels of apoptosis, neuronal injury, and autophagy were determined in all the rats. Xenon inhalation significantly attenuated the severity of the seizure-induced neuronal injury. Increased autophagy accompanied this inhibitive effect. Autophagy inhibition eliminated these xenon neuroprotective effects. A simulation of autophagy using rapamycin recapitulated xenon’s protective effects on KA-induced acute generalized seizures in the rats. These findings confirmed that xenon exerts strong neuroprotective effects in KA-induced acute generalized seizures. Further, they indicate that increased autophagy may underlie the protective effects of xenon. Therefore, xenon and autophagy inducers may be useful clinical options for their neuroprotective effects in epileptic seizures.

The Progress in Diagnosis and Treatment of Exosomes and MicroRNAs on Epileptic Comorbidity Depression

The occurrence of epilepsy can increase the incidence of depression, and the risk of epilepsy in the patients with depression is also high, both of which have an adverse effect on the life and the psychology of the patient, which is not conducive to the prognosis of the patients with epilepsy. With lucubrating the function of exosomes and microRNAs, some scholars found that the exosomes and its microRNAs have development prospect in the diagnosis and treatment of the disease. MicroRNAs are involved in the regulation of seizures and depression, as biomarkers, that can significantly improve the management of epileptic patients and play a preventive role in the occurrence of epilepsy and epilepsy depressive disorder. Moreover, due to its regulation to genes, appropriate application of microRNAs may have therapeutic effect on epilepsy and depression with the characteristics of long distance transmission and stability of exosomes, to a certain extent. This provides a great convenience for the diagnosis and treatment of epileptic comorbidity depression.

Differential Expression of the Metabotropic P2Y Receptor Family in the Cortex Following Status Epilepticus and Neuroprotection via P2Y1 Antagonism in Mice

Purinergic signaling via P2 receptors is now widely accepted to play a critical role during increased states of hyperexcitability and seizure-induced pathology. In the setting of seizures and epilepsy, most attention has been paid to investigating the fast-acting ATP-gated P2X receptor family. More recent evidence has now also provided compelling evidence of an involvement of the slower-acting P2Y receptor family during seizures. This includes data demonstrating expression changes of P2Y receptors in the hippocampus following acute seizures and during epilepsy and anticonvulsive properties of P2Y-targeting drugs; in particular drugs targeting the P2Y₁ subtype. Seizures, however, also involve damage to extra-hippocampal brain regions such as the cortex, which is thought to contribute to the epileptic phenotype. To analyze expressional changes of the P2Y receptor family in the cortex following status epilepticus and to determine the impact of drugs interfering with P2Y₁ signaling on cortical damage, we used a unilateral mouse model of intraamygdala kainic acid-induced status epilepticus. Analysis of cortical tissue showed that status epilepticus leads to a global up-regulation of the P2Y receptor family in the cortex including P2Y₁, P2Y₂, P2Y₄, and P2Y₆, with the P2Y₁ and P2Y₄ receptor subtypes showing the strongest increase. Supporting a detrimental role of P2Y₁ activation during status epilepticus, treatment with the P2Y₁ agonist MRS2365 exacerbated high frequency high amplitude spiking, synonymous with injury-causing electrographic activity, and treatment with the P2Y₁ antagonists MRS2500 protected against seizure-induced cortical damage. Suggesting P2Y₁-mediated effects are predominantly due to increased microglia activation, treatment with the broad-spectrum anti-inflammatory drug minocycline abolished the observed neuroprotective effects of P2Y₁ antagonism. In conclusion, our results further support a role for P2Y₁-mediated signaling during seizure generation and seizure-induced neurodegeneration, suggesting P2Y₁-targeting therapies as novel treatment for drug-refractory status epilepticus.

Succinate accumulation induces mitochondrial reactive oxygen species generation and promotes status epilepticus in the kainic acid rat model

Though succinate accumulation is associated with reactive oxygen species (ROS) production and neuronal injury, which play critical roles in epilepsy, it is unclear whether succinate accumulation contributes to the onset of epilepsy or seizures. We sought to investigate changes in succinate, oxidative stress, and mito-SOX levels, as well as mitophagy and neuronal change, in different status epilepticus (SE) rat models. Our results demonstrate that KA-induced SE was accompanied by increased levels of succinate, oxidative stress, and mito-SOX, as well as mitophagy and neuronal degeneration. The similarly increased levels of succinate, oxidative stress, and mito-SOX were also found in pilocarpine-induced SE. Moreover, the reduction of succinate accumulation by the inhibition of succinate dehydrogenase (SDH), malate/aspartate shuttle (MAS), or purine nucleotide cycle (PNC) served to reduce succinate, oxidative stress, and mito-SOX levels, thereby preventing oxidative stress-related neuronal damage and lessening seizure severity. Interestingly, simulating succinate accumulation with succinic acid dimethyl ester may induce succinate accumulation and increased oxidative stress and mito-SOX levels, as well as behavior and seizures in electroencephalograms similar to those observed in rats exposed to KA. Our results indicate that succinate accumulation may contribute to the increased oxidative stress/mitochondrial ROS levels, neuronal degeneration, and SE induced by KA administration. Furthermore, we found that succinate accumulation was mainly due to the inverse catalysis of SDH from fumarate, which was supplemented by the MAS and PNC pathways. These results reveal new insights into the mechanisms underlying SE and that reducing succinate accumulation may be a clinically useful therapeutic target in SE.

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KA- or pilocarpine-induced SE was accompanied by succinate accumulation.

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Succinate accumulation caused elevated ROS/mito-ROS levels and neuronal injury.

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Inverse catalysis of SDH from fumarate mainly caused succinate accumulation.

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Inhibiting succinate accumulation relieved oxidative stress level, neuronal injury, and seizure.

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Simulating succinate accumulation induced elevated oxidative stress level and seizure.

Mode-Dependent Effect of Xenon Inhalation on Kainic Acid-Induced Status Epilepticus in Rats

Previous studies have reported the possible neuroprotective effects of xenon treatment. The purpose of this study was to define the range of effective xenon ratio, most effective xenon ratio, and time-window for intervention in the kainic acid (KA) – induced status epilepticus (SE) rat model. Different ratios of xenon (35% xenon, 21% oxygen, 44% nitrogen, 50% xenon, 21% oxygen, 29% nitrogen, 70% xenon, 21% oxygen, and 9% nitrogen) were used to treat the KA-induced SE. Our results confirmed the anti-seizure role of 50 and 70% xenon mixture, with a stronger effect from the latter. Further, 70% xenon mixture was dispensed at three time points (0 min, 15 min delayed, and 30 min delayed) after KA administration, and the results indicated the anti-seizure effect at all treated time points. The results also established that the neuronal injury in the hippocampus and entorhinal cortex (EC), assessed using Fluoro-Jade B (FJB) staining, were reversed by the xenon inhalation, and within 30 min after KA administration. Our study, therefore, indicates the appropriate effective xenon ratio and time-window for intervention that can depress seizures. The prevention of neuronal injury and further reversal of the loss of effective control of depress network in the hippocampus and EC may be the mechanisms underlying the anti-seizure effect of xenon.