CDDO-Me Attenuates Vasogenic Edema and Astroglial Death by Regulating NF-κB p65 Phosphorylations and Nrf2 Expression Following Status Epilepticus

CDDO-Me Attenuates CA1 Neuronal Death by Facilitating RalBP1-Mediated Mitochondrial Fission and 4-HNE Efflux in the Rat Hippocampus Following Status Epilepticus

Ras-related protein Ral-A (RalA)-binding protein 1 (RalBP1, also known as Ral-interacting protein of 76 kDa (RLIP76) or Ral-interacting protein 1 (RLIP1 or RIP1)) is involved in the efflux of 4-hydroxynonenal (4-HNE, an end product of lipid peroxidation), as well as mitochondrial fission. In the present study, we found that 2-cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me) attenuated CA1 neuronal death and aberrant mitochondrial elongations in these neurons coupled with enhanced RalBP1 expression and reduced 4-HNE levels following status epilepticus (SE). RalBP1 knockdown did not affect mitochondrial dynamics and CA1 neuronal death under physiological and post-SE conditions. Following SE, however, cotreatment of RalBP1 siRNA diminished the effect of CDDO-Me on 4-HNE levels, mitochondrial hyperfusion in CA1 neurons, and CA1 neuronal death. These findings indicate that CDDO-Me may ameliorate CA1 neuronal death by facilitating RalBP1-mediated 4-HNE efflux and mitochondrial fission following SE. Therefore, our findings suggest that increased RalBP1 expression/activity may be one of the considerable targets to protect neurons from SE.

Long non-coding RNA Tug1 regulates inflammation in microglia and in status epilepticus rats through the NF-κB signaling pathway

Background

Inflammation plays an important role in the pathogenesis of status epilepticus (SE). The long non-coding RNA (lncRNA) taurine up-regulated gene1 (Tug1) plays a well-defined role in inflammatory diseases. However, the molecular mechanism of Tug1 in SE progression remains unknown. In present study, we investigated whether Tug1 is involved in microglial inflammation in SE rats.

Methods

The SE rat model was established via intraperitoneal injection of lithium chloride-pilocarpine. RNA-binding protein immunoprecipitation (RIP) and RIP sequencing were carried out in rat microglia (RM). Tug1 cloned into the adenovirus was overexpressed in the microglia. Knockdown of Tug1 was performed via siRNA transfection. The level of Tug1 and inflammatory factors IL-1β and TNF-α was examined by real-time polymerase chain reaction (RT-PCR) and western blotting. Protein levels of p65, p-p65, p-ΙκΒα and ΙκΒα were assessed by western blotting.

Results

The RIP-seq result showed 14 lncRNAs that bound to the NF-κB p65 protein in RM. The lncRNA Tug1 directly interacted with p65. The level of declined Tug1 was decreased in the hippocampus of SE rats. Overexpression of Tug1 reduced the LPS-induced inflammation and M1/M2 polarization of microglia, while knockdown of Tug1 aggravated the inflammatory response in microglia. Accordingly, the protein levels of p-p65/p65 and p-ΙκΒα/ΙκΒα were reduced in the Tug1-overexpression microglia and elevated in the Tug1-knockdown microglia.

Conclusions

These findings indicate that Tug1 modulates the inflammation in microglia through the NF-κB signal pathway, and the Tug1/P65 axis are like to play a significant role in the inflammatory processes, providing a valid target for the therapy of SE.

CDDO-Me Attenuates Clasmatodendrosis in CA1 Astrocyte by Inhibiting HSP25-AKT Mediated DRP1-S637 Phosphorylation in Chronic Epilepsy Rats

Clasmatodendrosis is one of the irreversible astroglial degeneration, which is involved in seizure duration and its progression in the epileptic hippocampus. Although sustained heat shock protein 25 (HSP25) induction leads to this autophagic astroglial death, dysregulation of mitochondrial dynamics (aberrant mitochondrial elongation) is also involved in the pathogenesis in clasmatodendrosis. However, the underlying molecular mechanisms of accumulation of elongated mitochondria in clasmatodendritic astrocytes are elusive. In the present study, we found that clasmatodendritic astrocytes showed up-regulations of HSP25 expression, AKT serine (S) 473 and dynamin-related protein 1 (DRP1) S637 phosphorylations in the hippocampus of chronic epilepsy rats. 2-Cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me; bardoxolone methyl or RTA 402) abrogated abnormal mitochondrial elongation by reducing HSP25 upregulation, AKT S473- and DRP1 S637 phosphorylations. Furthermore, HSP25 siRNA and 3-chloroacetyl-indole (3CAI, an AKT inhibitor) abolished AKT-DRP1-mediated mitochondrial elongation and attenuated clasmatodendrosis in CA1 astrocytes. These findings indicate that HSP25-AKT-mediated DRP1 S637 hyper-phosphorylation may lead to aberrant mitochondrial elongation, which may result in autophagic astroglial degeneration. Therefore, our findings suggest that the dysregulation of HSP25-AKT-DRP1-mediated mitochondrial dynamics may play an important role in clasmatodendrosis, which would have implications for the development of novel therapies against various neurological diseases related to astroglial degeneration.

The Function of NF-Kappa B During Epilepsy, a Potential Therapeutic Target

The transcriptional regulator nuclear factor kappa B (NF-κB) modulates cellular biological activity by binding to promoter regions in the nucleus and transcribing various protein-coding genes. The NF-κB pathway plays a major role in the expressing genes related to inflammation, including chemokines, interleukins, and tumor necrosis factor. It also transcribes genes that can promote neuronal survival or apoptosis. Epilepsy is one of the most common brain disorders and it not only causes death worldwide but also affects the day-to-day life of affected individuals. While epilepsy has diverse treatment options, there remain patients who are not sensitive to the existing treatment methods. Recent studies have implicated the critical role of NF-κB in epilepsy. It is upregulated in neurons, glial cells, and endothelial cells, due to neuronal loss, glial cell proliferation, blood-brain barrier dysfunction, and hippocampal sclerosis through the glutamate and γ-aminobutyric acid imbalance, ion concentration changes, and other mechanisms. In this review, we summarize the functional changes caused by the upregulation of NF-κB in the central nervous system during different periods after seizures. This review is the first to deconvolute the complicated functions of NF-κB, and speculate that the regulation of NF-κB can be a safe and effective treatment strategy for epilepsy.

CDDO-Me Attenuates Astroglial Autophagy via Nrf2-, ERK1/2-SP1- and Src-CK2-PTEN-PI3K/AKT-Mediated Signaling Pathways in the Hippocampus of Chronic Epilepsy Rats

Clasmatodendrosis is an autophagic astroglial death showing extensive swollen cell bodies with vacuoles and disintegrated/beaded processes. This astroglial degeneration is closely relevant to the synchronous epileptiform discharges. However, the underlying molecular mechanisms and the roles of clasmatodendrosis in spontaneous seizure activity are still unknown. The 2-cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me; RTA 402) is one of the activators for nuclear factor-erythroid 2-related factor 2 (Nrf2) that is a redox-sensitive transcription factor. In the present study, we explored the effects of CDDO-Me on clasmatodendrosis in chronic epilepsy rats, which could prevent epilepsy-related complications. In the present study, clasmatodendritic astrocytes showed reduced Nrf2 expression and its nuclear accumulation, which were restored by CDDO-Me. CDDO-Me also abrogated heat shock protein 25 (HSP25) upregulation in clasmatodendritic astrocytes by regulating extracellular signal-related kinases 1/2 (ERK1/2)-specificity protein 1 (SP1)- and Src-casein kinase 2 (CK2)-phosphatase and tensin homolog deleted on chromosome 10 (PTEN)-phosphatidylinositol-3-kinase (PI3K)-AKT-glycogen synthase kinase 3β (GSK3β)-bax-interacting factor 1 (Bif-1)-mediated signaling pathways in chronic epilepsy rats. In addition, CDDO-Me ameliorated spontaneous seizure duration, but not seizure frequency and behavioral seizure severity. Therefore, our findings suggest that clasmatodendrosis may affect seizure duration in chronic epilepsy rats, and that CDDO-Me may attenuate autophagic astroglial degeneration by regulating various signaling pathways.

CDDO-Me Distinctly Regulates Regional Specific Astroglial Responses to Status Epilepticus via ERK1/2-Nrf2, PTEN-PI3K-AKT and NFκB Signaling Pathways

2-Cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me) is a triterpenoid analogue of oleanolic acid. CDDO-Me shows anti-inflammatory and neuroprotective effects. Furthermore, CDDO-Me has antioxidant properties, since it activates nuclear factor-erythroid 2-related factor 2 (Nrf2), which is a key player of redox homeostasis. In the present study, we evaluated whether CDDO-Me affects astroglial responses to status epilepticus (SE, a prolonged seizure activity) in the rat hippocampus in order to understand the underlying mechanisms of reactive astrogliosis and astroglial apoptosis. Under physiological conditions, CDDO-Me increased Nrf2 expression in the hippocampus without altering activities (phosphorylations) of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), phosphatidylinositol-3-kinase (PI3K), and AKT. CDDO-Me did not affect seizure activity in response to pilocarpine. However, CDDO-Me ameliorated reduced astroglial Nrf2 expression in the CA1 region and the molecular layer of the dentate gyrus (ML), and attenuated reactive astrogliosis and ML astroglial apoptosis following SE. In CA1 astrocytes, CDDO-Me inhibited the PI3K/AKT pathway by activating PTEN. In contrast, CDDO-ME resulted in extracellular signal-related kinases 1/2 (ERK1/2)-mediated Nrf2 upregulation in ML astrocytes. Furthermore, CDDO-Me decreased nuclear factor-κB (NFκB) phosphorylation in both CA1 and ML astrocytes. Therefore, our findings suggest that CDDO-Me may attenuate SE-induced reactive astrogliosis and astroglial apoptosis via regulation of ERK1/2-Nrf2, PTEN-PI3K-AKT, and NFκB signaling pathways.

Epigallocatechin-3-Gallate and PEDF 335 Peptide, 67LR Activators, Attenuate Vasogenic Edema, and Astroglial Degeneration Following Status Epilepticus

Non-integrin 67-kDa laminin receptor (67LR) is involved in cell adherence to the basement membrane, and it regulates the interactions between laminin and other receptors. The dysfunction of 67LR leads to serum extravasation via blood-brain barrier (BBB) disruption. Polyphenol (–)-epigallocatechin-3-O-gallate (EGCG) and pigment epithelium-derived factor (PEDF) bind to 67LR and inhibit neovascularization. Therefore, in the present study, we investigated the effects of EGCG and NU335, a PEDF-derive peptide, on BBB integrity and their possible underlying mechanisms against vasogenic edema formation induced by status epilepticus (SE, a prolonged seizure activity). Following SE, both EGCG and NU335 attenuated serum extravasation and astroglial degeneration in the rat piriform cortex (PC). Both EGCG and NU335 reversely regulated phosphatidylinositol 3 kinase (PI3K)/AKT–eNOS (endothelial nitric oxide synthase) mediated BBB permeability and aquaporin 4 (AQP4) expression in endothelial cells and astrocytes through the p38 mitogen-activated protein kinase (p38 MAPK) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathways, respectively. Furthermore, EGCG and NU335 decreased p47Phox (a nicotinamide adenine dinucleotide phosphate oxidase subunit) expression in astrocytes under physiological and post-SE conditions. Therefore, we suggest that EGCG and PEDF derivatives may activate 67LR and its downstream effectors, and they may be considerable anti-vasogenic edema agents.

PTEN Is Required for The Anti-Epileptic Effects of AMPA Receptor Antagonists in Chronic Epileptic Rats

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) is one of the ligand-gated ion channels for glutamate, which is an important player in the generation and spread of seizures. The efficacy of AMPAR functionality is regulated by the trafficking, synaptic targeting, and phosphorylation. Paradoxically, AMPAR expression and its phosphorylation level are decreased in the epileptic hippocampus. Therefore, the roles of AMPAR in seizure onset and neuronal hyperexcitability in ictogenesis remain to be elucidated. In the present study, we found that AMPAR antagonists (perampanel and GYKI 52466) decreased glutamate ionotropic receptor AMPA type subunit 1 (GRIA1) surface expression in the epileptic rat hippocampus. They also upregulated phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression and restored to basal levels the upregulated phosphoinositide 3-kinase (PI3K)/AKT1 phosphorylations. Dipotassium bisperoxovanadium(pic) dihydrate (BpV(pic), a PTEN inhibitor) co-treatment abolished the anti-epileptic effects of perampanel and GYKI 52466. Therefore, our findings suggest that PTEN may be required for the anti-epileptic effects of AMPAR antagonists.

Terpenoids from stigma maydis (Zea mays L.) alleviate hydrogen peroxide-induced SH-SY5Y cell injury by activating Nrf2

Five terpenoids (1-5), including three new ent-kaurane diterpenoids (1-3), one new ent-rosane type diterpenoid (4) and one known triterpenoid (5), were isolated from stigma maydis (Zea mays L.). The structures of the compounds were elucidated by comprehensive spectroscopic analyses. The relative configurations of stigmanes A-D (1-4) were determined by NOESY experiments. In addition, the relative configuration of stigmane D (4) was further established by NMR calculations. The absolute configurations of these compounds were identified by a comparison of experimental and calculated specific rotations. The neuroprotective effects of these compounds against H₂O₂-induced injury in human neuroblastoma SH-SY5Y cells were evaluated, and the results showed that among the compounds, 2 exhibited the most significant neuroprotection. Further study demonstrated that 2 could activate nuclear factor E2-related factor (Nrf2), downregulate apoptosis and reactive oxygen species (ROS) generation, and increase antioxidant enzyme activities in SH-SY5Y cells. However, the neuroprotective effect was reversed when Nrf2 was silenced. In conclusion, this study suggested that terpenoids from stigma maydis exerted neuroprotective effects through Nrf2 activation.

CDDO-Me Inhibits Microglial Activation and Monocyte Infiltration by Abrogating NFκB- and p38 MAPK-Mediated Signaling Pathways Following Status Epilepticus

Following status epilepticus (SE, a prolonged seizure activity), microglial activation, and monocyte infiltration result in the inflammatory responses in the brain that is involved in the epileptogenesis. Therefore, the regulation of microglia/monocyte-mediated neuroinflammation is one of the therapeutic strategies for avoidance of secondary brain injury induced by SE. 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid methyl ester (CDDO-Me; RTA 402) is an activator of nuclear factor-erythroid 2-related factor 2 (Nrf2), which regulates intracellular redox homeostasis. In addition, CDDO-Me has anti-inflammatory properties that suppress microglial proliferation and its activation, although the underlying mechanisms have not been clarified. In the present study, CDDO-Me ameliorated monocyte infiltration without vasogenic edema formation in the frontoparietal cortex (FPC) following SE, accompanied by abrogating monocyte chemotactic protein-1 (MCP-1)/tumor necrosis factor-α (TNF-α) expressions and p38 mitogen-activated protein kinase (p38 MAPK) phosphorylation. Furthermore, CDDO-Me inhibited nuclear factor-κB (NFκB)-S276 phosphorylation and microglial transformation, independent of Nrf2 expression. Similar to CDDO-Me, SN50 (an NFκB inhibitor) mitigated monocyte infiltration by reducing MCP-1 and p38 MAPK phosphorylation in the FPC following SE. Therefore, these findings suggest, for the first time, that CDDO-Me may attenuate microglia/monocyte-mediated neuroinflammation via modulating NFκB- and p38 MAPK-MCP-1 signaling pathways following SE.