Agmatine Attenuates Brain Edema and Apoptotic Cell Death after Traumatic Brain Injury

Overexpression of aquaporin-1 plays a vital role in proliferation, apoptosis, and pyroptosis of Wilms' tumor cells

BACKGROUND

Nephroblastoma, also known as Wilms' tumor (WT), is an embryonic malignant tumor and one of the most common malignant tumors in the abdominal region of children. The exact role and underlying mechanisms of aquaporin-1 (AQP1) in the occurrence and development of nephroblastoma remain unclear.

METHODS

After overexpression of AQP1, cell proliferation was assessed using the CCK-8 proliferation assay and EdU staining. Flow cytometry was employed to assess cell apoptosis, and Western blotting (WB) analysis was conducted to validate the expression of relevant protein markers. mRNA sequencing (mRNA-Seq) was performed on WT cells overexpressing AQP1 to predict and characterize the associated mechanisms. Transmission electron microscopy was utilized to observe changes in the ultrastructure of WT cells undergoing apoptosis and pyroptosis following AQP1 overexpression. Functional in vivo validation was conducted through animal experiments.

RESULTS

We validated that overexpression of AQP1 inhibited cell proliferation and promoted cell apoptosis and pyroptosis both in vitro and in vivo. mRNA-Seq analysis of WT cells with AQP1 overexpression suggested that these effects might be mediated through the inhibition of the JAK-STAT signaling pathway. Additionally, we discovered that overexpression of AQP1 activated the classical pyroptosis signaling pathway dependent on caspase-1, thereby promoting pyroptosis in WT.

CONCLUSION

These findings highlight the important functional role of AQP1 in the pathobiology of nephroblastoma, providing novel insights into the development of this disease. Moreover, these results offer new perspectives on the potential therapeutic targeting of AQP1 as a treatment strategy for nephroblastoma.

Neuroprotection by agmatine: Possible involvement of the gut microbiome?

Agmatine, an endogenous polyamine derived from L-arginine, elicits tremendous multimodal neuromodulant properties. Alterations in agmatinergic signalling are closely linked to the pathogeneses of several brain disorders. Importantly, exogenous agmatine has been shown to act as a potent neuroprotectant in varied pathologies, including brain ageing and associated comorbidities. The antioxidant, anxiolytic, analgesic, antidepressant and memory-enhancing activities of agmatine may derive from its ability to regulate several cellular pathways; including cell metabolism, survival and differentiation, nitric oxide signalling, protein translation, oxidative homeostasis and neurotransmitter signalling. This review briefly discusses mammalian metabolism of agmatine and then proceeds to summarize our current understanding of neuromodulation and neuroprotection mediated by agmatine. Further, the emerging exciting bidirectional links between agmatine and the resident gut microbiome and their implications for brain pathophysiology and ageing are also discussed.

Possible involvement of female sex steroid hormones in intracellular signal transduction mediated by cytokines following traumatic brain injury

INTRODUCTION

The aim of this study was to determine the anti-inflammatory effect of female sex hormones on the level of intracellular molecules of cytokine signaling pathway after diffuse traumatic brain injury (TBI) in ovariectomized rats.

METHODS

Female rats were divided into 10 groups: control, sham, TBI, Vehicle (oil), Vehicle E1 (33.3 µg/kg), E2 (1 mg / kg), P1 (1.7 mg/kg), P2 (8 mg / kg), E2 + P1. All drugs were injected 0.5 h after TBI. Brain edema and the brain levels of P-STAT-3, NFκB-P52, NFκB-P65, P-IκB, and SOCS-3 by immunohistochemistry measured at 24 h after TBI.

RESULTS

Increased brain edema after TBI was inhibited by different doses of estrogen, progesterone (P < 0.001), and E2 + P1 (P < 0.05). The brain levels of P-STAT-3, NFκB-P52, NFκB-P65, and p-IκBα that increased after TBI was decreased only by E2 (P < 0.05). E2 and E2 + P1 have increased the SOCS-3 level after TBI (P < 0.05). Also, there was a difference between the E2 with E1 and two progesterone doses (P < 0.05). So that in all cases, the effects of E2 were more significant than the other groups. The target cells for these effects of E2 were microglia and astrocytes.

CONCLUSION

The results indicate that one of the probable mechanism(s) of estrogen anti-inflammatory effect after TBI is either reduction of p-STAT-3, NFκB-P52, p-NFκB-P65, and p-IκBα or increase in SOCS-3 molecules involved in the signaling pathway of inflammatory cytokines.

Agmatine Alleviates Epileptic Seizures and Hippocampal Neuronal Damage by Inhibiting Gasdermin D-Mediated Pyroptosis

Background: Epilepsy is a common neurological disease, and neuroinflammation is one of the main contributors to epileptogenesis. Pyroptosis is a type of pro-inflammatory cell death that is related to epilepsy. Agmatine, has anti-inflammatory properties and exerts neuroprotective effects against seizures. Our study investigated the effect of agmatine on the core pyroptosis protein GSDMD in the context of epilepsy.

Methods: A chronic epilepsy model and BV2 microglial cellular inflammation model were established by pentylenetetrazole (PTZ)-induced kindling or lipopolysaccharide (LPS) stimulation. H&E and Nissl staining were used to evaluate hippocampal neuronal damage. The expression of pyroptosis and inflammasome factors was examined by western blotting, quantitative real-time PCR, immunofluorescence and enzyme-linked immunosorbent assay (ELISA).

Results: Agmatine disrupted the kindling acquisition process, which decreased seizure scores and the incidence of full kindling and blocked hippocampal neuronal damage. In addition, agmatine increased BV2 microglial cell survival in vitro and alleviated seizures in vivo by suppressing the levels of PTZ-induced pyroptosis. Finally, the expression of TLR4, MYD88, phospho-IκBα, phospho-NF-κB and the NLRP3 inflammasome was significantly upregulated in LPS-induced BV2 microglial cells, while agmatine suppressed the expression of these proteins.

Conclusions: Our results indicate that agmatine affects epileptogenesis and exerts neuroprotective effects by inhibiting neuroinflammation, GSDMD activation, and pyroptosis. The inhibitory effect of agmatine on pyroptosis was mediated by the suppression of the TLR4/MYD88/NF-κB/NLRP3 inflammasome pathway. Therefore, agmatine may be a potential treatment option for epilepsy.

Maintenance of the Neuroprotective Function of the Amino Group Blocked Fluorescence-Agmatine

Agmatine, an endogenous derivative of arginine, has been found to be effective in treating idiopathic pain, convulsion, stress-mediated behavior, and attenuate the withdrawal symptoms of drugs like morphine. In the early stages of ischemic brain injury in animals, exogenous agmatine treatment was found to be neuroprotective. Agmatine is also considered as a putative neurotransmitter and is still an experimental drug. Chemically, agmatine is called agmatine 1-(4-aminobutyl guanidine). Crystallographic study data show that positively-charged guanidine can bind to the protein containing Gly and Asp residues, and the amino group can interact with the complimentary sites of Glu and Ser. In this study, we blocked the amino end of the agmatine by conjugating it with FITC, but the guanidine end was unchanged. We compared the neuroprotective function of the agmatine and agmatine-FITC by treating them in neurons after excitotoxic stimulation. We found that even the amino end blocked neuronal viability in the excitotoxic condition, by NMDA treatment for 1 h, was increased by agmatine-FITC, which was similar to that of agmatine. We also found that the agmatine-FITC treatment reduced the expression of nitric oxide production in NMDA-treated cells. This study suggests that even if the amino end of agmatine is blocked, it can perform its neuroprotective function.

Role of agmatine in the application of neural progenitor cell in central nervous system diseases: therapeutic potentials and effects

Agmatine, the primary decarboxylation product of L-arginine, generated from arginine decarboxylase. Since the discovery of agmatine in the mammalian brain in the 1990s, an increasing number of agmatine-mediated effects have been discovered, demonstrating the benefits of agmatine on ischemic strokes, traumatic brain injury and numerous psychological disorders such as depression, anxiety, and stress. Agmatine also has cellular protective effects and contributes to cell proliferation and differentiation in the central nervous system (CNS). Neural progenitor cells are an important component in the recovery and repair of many neurological disorders due to their ability to differentiate into functional adult neurons. Recent data has revealed that agmatine can regulate and increase proliferation and the fate of progenitor cells in the adult hippocampus. This review aims to summarise and discuss the role of agmatine in the CNS; specifically, the effects and relationship between agmatine and neural progenitor cells and how these ideas can be applied to potential therapeutic application.

Pathogenic Functions of Tumor Necrosis Factor Receptor- Factor 6 Signaling Traumatic Brain Injury

Neuroinflammation contributes to delayed (secondary) neurodegeneration following traumatic brain injury (TBI). Tumor necrosis factor receptor-associated factor 6 (TRAF6) signaling may promote post-TBI neuroinflammation, thereby exacerbating secondary injury. This study investigated the pathogenic functions of TRAF6 signaling following TBI in vivo and in vitro. A rat TBI model was established by air pressure contusion while lipopolysaccharide (LPS) exposure was used to induce inflammatory-like responses in cultured astrocytes. Model rats were examined for cell-specific expression of TRAF6, NF-κB, phosphorylated (p)-NF-κB, MAPKs (ERK, JNK, and p38), p-MAPKs, chemokines (CCL2 and CXCL1), and chemokine receptors (CCR2 and CXCR2) by immunofluorescence, RT-qPCR, western blotting, and ELISA, for apoptosis by TUNEL staining, and spatial cognition by Morris water maze testing. These measurements were compared between TBI model rats receiving intracerebral injections of TRAF6-targeted RNAi vector (AAV9-TRAF6-RNAi), empty vector, MAPK/NF-κB inhibitors, or vehicle. Primary astrocytes were stimulated with LPS following TRAF6 siRNA or control transfection, and NF-κB, MAPKs, chemokine, and chemokine receptor expression levels evaluated by western blotting and ELISA. TRAF6 was expressed mainly in astrocytes and neurons of injured cortex, peaking 3 days post-TBI. Knockdown by AAV9-TRAF6-RNAi improved spatial learning and memory, decreased TUNEL-positive cell number in injured cortex, and downregulated expression levels of p-NF-κB, p-ERK, p-JNK, p-p38, CCL2, CCR2, CXCL1, and CXCR2 post-TBI. Inhibitors of NF-κB, ERK, JNK, and p38 significantly suppressed CCL2, CCR2, CXCL1, and CXCR2 expression following TBI. Furthermore, TRAF6-siRNA inhibited LPS-induced NF-κB, ERK, JNK, p38, CCL2, and CXCL1 upregulation in cultured astrocytes. Targeting TRAF6-MAPKs/NF-κB-chemokine signaling pathways may provide a novel therapeutic approach for reducing post-TBI neuroinflammation and concomitant secondary injury.

Targeted Delivery of Iron Oxide Nanoparticle-Loaded Human Embryonic Stem Cell-Derived Spherical Neural Masses for Treating Intracerebral Hemorrhage

This study evaluated the potential of iron oxide nanoparticle-loaded human embryonic stem cell (ESC)-derived spherical neural masses (SNMs) to improve the transportation of stem cells to the brain, ameliorate brain damage from intracerebral hemorrhage (ICH), and recover the functional status after ICH under an external magnetic field of a magnet attached to a helmet. At 24 h after induction of ICH, rats were randomly separated into three experimental groups: ICH with injection of phosphate-buffered saline (PBS group), ICH with intravenous injection of magnetosome-like ferrimagnetic iron oxide nanocubes (FION)-labeled SNMs (SNMs* group), and ICH with intravenous injection of FION-labeled SNMs followed by three days of external magnetic field exposure for targeted delivery by a magnet-embedded helmet (SNMs*+Helmet group). On day 3 after ICH induction, an increased Prussian blue-stained area and decreased swelling volume were observed in the SNMs*+Helmet group compared with that of the other groups. A significantly decreased recruitment of macrophages and neutrophils and a downregulation of pro-inflammatory cytokines followed by improved neurological function three days after ICH were observed in the SNMs*+Helmet group. Hemispheric atrophy at six weeks after ICH was significantly decreased in the SNMs*+Helmet group compared with that of the PBS group. In conclusion, we have developed a targeted delivery system using FION tagged to stem cells and a magnet-embedded helmet. The targeted delivery of SNMs might have the potential for developing novel therapeutic strategies for ICH.

Therapeutic Effect of Agmatine on Neurological Disease: Focus on Ion Channels and Receptors

The central nervous system (CNS) is the most injury-prone part of the mammalian body. Any acute or chronic, central or peripheral neurological disorder is related to abnormal biochemical and electrical signals in the brain cells. As a result, ion channels and receptors that are abundant in the nervous system and control the electrical and biochemical environment of the CNS play a vital role in neurological disease. The N-methyl-D-aspartate receptor, 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl) propanoic acid receptor, kainate receptor, acetylcholine receptor, serotonin receptor, α2-adrenoreceptor, and acid-sensing ion channels are among the major channels and receptors known to be key components of pathophysiological events in the CNS. The primary amine agmatine, a neuromodulator synthesized in the brain by decarboxylation of L-arginine, can regulate ion channel cascades and receptors that are related to the major CNS disorders. In our previous studies, we established that agmatine was related to the regulation of cell differentiation, nitric oxide synthesis, and murine brain endothelial cell migration, relief of chronic pain, cerebral edema, and apoptotic cell death in experimental CNS disorders. In this review, we will focus on the pathophysiological aspects of the neurological disorders regulated by these ion channels and receptors, and their interaction with agmatine in CNS injury.

Neuroprotective Role of Agmatine in Neurological Diseases

Background:

Neurological diseases have always been one of the leading cause of mobility and mortality world-widely. However, it is still lacking efficient agents. Agmatine, an endogenous polyamine, exerts its diverse biological characteristics and therapeutic potential in varied aspects.

Methods:

This review would focus on the neuroprotective actions of agmatine and its potential mechanisms in the setting of neurological diseases.

Results:

Numerous studies had demonstrated the neuroprotective effect of agmatine in varied types of neurological diseases, including acute attack (stroke and trauma brain injury) and chronic neurodegenerative diseases (Parkinson's disease, Alz-heimer’s disease). The potential mechanism of agmatine induced neuroprotection includes anti-oxidation, anti-apoptosis, anti-inflammation, brain blood barrier (BBB) protection and brain edema prevention.

Conclusions:

The safety and low incidence of adverse effects indicate the vast potential therapeutic value of agmatine in the treatment of neurological diseases. However, most of the available studies relate to the agmatine are conducted in experi-mental models, more clinical trials are needed before the agmatine could be extensively clinically used

Endogenous Agmatine Induced by Ischemic Preconditioning Regulates Ischemic Tolerance Following Cerebral Ischemia

Ischemic preconditioning (IP) is one of the most important endogenous mechanisms that protect the cells against ischemia-reperfusion (I/R) injury. However, the exact molecular mechanisms remain unclear. In this study, we showed that changes in the level of agmatine were correlated with ischemic tolerance. Changes in brain edema, infarct volume, level of agmatine, and expression of arginine decarboxylase (ADC) and nitric oxide synthases (NOS; inducible NOS [iNOS] and neural NOS [nNOS]) were analyzed during I/R injury with or without IP in the rat brain. After cerebral ischemia, brain edema and infarct volume were significantly reduced in the IP group. The level of agmatine was increased before and during ischemic injury and remained elevated in the early reperfusion phase in the IP group compared to the experimental control (EC) group. During IP, the level of plasma agmatine was increased in the early phase of IP, but that of liver agmatine was abruptly decreased. However, the level of agmatine was definitely increased in the ipsilateral and contralateral hemisphere of brain during the IP. IP also increased the expression of ADC—the enzyme responsible for the synthesis of endogenous agmatine—before, during, and after ischemic injury. In addition, ischemic injury increased endogenous ADC expression in the EC group. The expression of nNOS was reduced in the I/R injured brain in the IP group. These results suggest that endogenous increased agmatine may be a component of the ischemic tolerance response that is induced by IP. Agmatine may have a pivotal role in endogenous ischemic tolerance.

Agmatine: multifunctional arginine metabolite and magic bullet in clinical neuroscience?

Agmatine, the decarboxylation product of arginine, was largely neglected as an important player in mammalian metabolism until the mid-1990s, when it was re-discovered as an endogenous ligand of imidazoline and α2-adrenergic receptors. Since then, a wide variety of agmatine-mediated effects have been observed, and consequently agmatine has moved from a wallflower existence into the limelight of clinical neuroscience research. Despite this quantum jump in scientific interest, the understanding of the anabolism and catabolism of this amine is still vague. The purification and biochemical characterization of natural mammalian arginine decarboxylase and agmatinase still are open issues. Nevertheless, the agmatinergic system is currently one of the most promising candidates in order to pharmacologically interfere with some major diseases of the central nervous system, which are summarized in the present review. Particularly with respect to major depression, agmatine, its derivatives, and metabolizing enzymes show great promise for the development of an improved treatment of this common disease.

Simulating vasogenic brain edema using chronic VEGF infusion

OBJECTIVE To study peritumoral brain edema (PTBE), it is necessary to create a model that accurately simulates vasogenic brain edema (VBE) without introducing a complicated tumor environment. PTBE associated with brain tumors is predominantly a result of vascular endothelial growth factor (VEGF) secreted by brain tumors, and VEGF infusion alone can lead to histological blood-brain barrier (BBB) breakdown in the absence of tumor. VBE is intimately linked to BBB breakdown. The authors sought to establish a model for VBE with chronic infusion of VEGF that can be validated by serial in-vivo MRI and histological findings. METHODS Male Fischer rats (n = 182) underwent stereotactic striatal implantation of MRI-safe brain cannulas for chronic infusion of VEGF (2-20 µg/ml). Following a preinfusion phase (4-6 days), the rats were exposed to VEGF or control rat serum albumin (1.5 µl/hr) for as long as 144 hours. Serial MRI was performed during infusion on a high-field (9.4-T) machine at 12-24, 24-36, 48-72, and 120-144 hours. Rat brains were then collected and histological analysis was performed. RESULTS Control animals and animals infused with 2 µg/ml of VEGF experienced no neurological deficits, seizure activity, or abnormal behavior. Animals treated with VEGF demonstrated a significantly larger volume (42.90 ± 3.842 mm³) of T2 hyper-attenuation at 144 hours when compared with the volume (8.585 ± 1.664 mm³) in control animals (mean difference 34.31 ± 4.187 mm³, p < 0.0001, 95% CI 25.74-42.89 mm³). Postcontrast T1 enhancement in the juxtacanalicular region indicating BBB breakdown was observed in rats undergoing infusion with VEGF. At the later time periods (120-144 hrs) the volume of T1 enhancement (34.97 ± 8.99 mm³) was significantly less compared with the region of edema (p < 0.0001). Histologically, no evidence of necrosis or inflammation was observed with VEGF or control infusion. Immunohistochemical analysis demonstrated astrocyte activation, vascular remodeling, and increased claudin-5 expression in juxtacanalicular regions. Aquaporin-4 expression was increased in both control and VEGF animals in the juxtacanalicular regions. CONCLUSIONS The results of this study show that chronic brain infusion of VEGF creates a reliable model of VBE. This model lacks necrosis and inflammation that are characteristic of previous models of VBE. The model allows for a precise investigation into the mechanism of VBE formation. The authors also anticipate that this model will allow for investigation into the mechanism of glucocorticoid action in abrogating VBE, and to test novel therapeutic strategies targeting PTBE.

Agmatine ameliorates type 2 diabetes induced-Alzheimer's disease-like alterations in high-fat diet-fed mice via reactivation of blunted insulin signalling

The risk of Alzheimer's disease (AD) is higher in patients with type 2 diabetes mellitus (T2DM). Previous studies in high-fat diet-induced AD animal models have shown that brain insulin resistance in these animals leads to the accumulation of amyloid beta (Aβ) and the reduction in GSK-3β phosphorylation, which promotes tau phosphorylation to cause AD. No therapeutic treatments that target AD in T2DM patients have yet been discovered. Agmatine, a primary amine derived from l-arginine, has exhibited anti-diabetic effects in diabetic animals. The aim of this study was to investigate the ability of agmatine to treat AD induced by brain insulin resistance. ICR mice were fed a 60% high-fat diet for 12 weeks and received one injection of streptozotocin (100 mg/kg/ip) 4 weeks into the diet. After the 12-week diet, the mice were treated with agmatine (100 mg/kg/ip) for 2 weeks. Behaviour tests were conducted prior to sacrifice. Brain expression levels of the insulin signal molecules p-IRS-1, p-Akt, and p-GSK-3β and the accumulation of Aβ and p-tau were evaluated. Agmatine administration rescued the reduction in insulin signalling, which in turn reduced the accumulation of Aβ and p-tau in the brain. Furthermore, agmatine treatment also reduced cognitive decline. Agmatine attenuated the occurrence of AD in T2DM mice via the activation of the blunted insulin signal.

Expression of aquaporin-4 and pathological characteristics of brain injury in a rat model of traumatic brain injury

Aquaporin 4 (AQP4) is a widely distributed membrane protein, which is found in glial cells, ependymocytes and capillary endothelial cells in the brain, and particularly in the choroid plexus. AQP4 is a key regulator of water metabolism, and changes in its expression following brain injury are associated with pathological changes in the damaged side of the brain; however, the effects of brain injury on AQP4 and injury‑induced pathological changes in the contralateral non‑damaged side of the brain remain to be fully elucidated. In the present study, male Sprague‑Dawley rats were subjected to traumatic brain injury (TBI) and changes in brain water content, the expression of AQP4 expression and pathological characteristics in the damaged and contralateral non‑damaged sides of the brain were examined. In the damaged side of the brain, vasogenic edema appeared first, followed by cellular edema. The aggravated cellular edema in the damaged side of the brain resulted in two periods of peak edema severity. Pathological changes in the contralateral non‑damaged side of the brain occurred later than those in the damaged side; cellular edema appeared first, followed by vasogenic edema, which was alleviated earlier than the cellular edema. AQP4 was downregulated during vasogenic edema, and upregulated during cellular edema. Taken together, these results suggested that the downregulation of AQP4 was a result of vasogenic edema and that the upregulation of AQP4 may have induced cellular edema.