Pregnane X Receptor Not Nuclear Factor-kappa B Up-regulates P-glycoprotein Expression in the Brain of Chronic Epileptic Rats Induced by Kainic Acid

Photobiomodulation reduces neuropathic pain after spinal cord injury by downregulating CXCL10 expression

BACKGROUND

Many studies have recently highlighted the role of photobiomodulation (PBM) in neuropathic pain (NP) relief after spinal cord injury (SCI), suggesting that it may be an effective way to relieve NP after SCI. However, the underlying mechanisms remain unclear. This study aimed to determine the potential mechanisms of PBM in NP relief after SCI.

METHODS

We performed systematic observations and investigated the mechanism of PBM intervention in NP in rats after SCI. Using transcriptome sequencing, we screened CXCL10 as a possible target molecule for PBM intervention and validated the results in rat tissues using reverse transcription-polymerase chain reaction and western blotting. Using immunofluorescence co-labeling, astrocytes and microglia were identified as the cells responsible for CXCL10 expression. The involvement of the NF-κB pathway in CXCL10 expression was verified using inhibitor pyrrolidine dithiocarbamate (PDTC) and agonist phorbol-12-myristate-13-acetate (PMA), which were further validated by an in vivo injection experiment.

RESULTS

Here, we demonstrated that PBM therapy led to an improvement in NP relative behaviors post-SCI, inhibited the activation of microglia and astrocytes, and decreased the expression level of CXCL10 in glial cells, which was accompanied by mediation of the NF-κB signaling pathway. Photobiomodulation inhibit the activation of the NF-κB pathway and reduce downstream CXCL10 expression. The NF-κB pathway inhibitor PDTC had the same effect as PBM on improving pain in animals with SCI, and the NF-κB pathway promoter PMA could reverse the beneficial effect of PBM.

CONCLUSIONS

Our results provide new insights into the mechanisms by which PBM alleviates NP after SCI. We demonstrated that PBM significantly inhibited the activation of microglia and astrocytes and decreased the expression level of CXCL10. These effects appear to be related to the NF-κB signaling pathway. Taken together, our study provides evidence that PBM could be a potentially effective therapy for NP after SCI, CXCL10 and NF-kB signaling pathways might be critical factors in pain relief mediated by PBM after SCI.

The Prevention and Reversal of a Phenytoin-Resistant Model by N-acetylcysteine Therapy Involves the Nrf2/P-Glycoprotein Pathway at the Blood-Brain Barrier

The transporter hypothesis is one of the most popular hypotheses of drug-resistant epilepsy (DRE). P-glycoprotein (P-gp), a channel protein at the blood-brain barrier (BBB), plays an important role in the transport of some anti-seizure drugs from brain tissue into vessels, which reduces drug concentrations and diminishes the effects of drug treatment. We performed this study to test whether P-gp is overexpressed in DRE and identify ways to prevent and reverse DRE. In this study, we established a phenytoin (PHT)-resistant mouse model and revealed that P-gp was overexpressed at the BBB in PHT-resistant mice. The P-gp inhibitor nimodipine decreased the resistance of phenytoin. Antioxidative preventive treatment with N-acetylcysteine (NAC) prevented the mice from entering a PHT-resistant state, and NAC therapy tended to reverse PHT resistance into sensitivity. We were also able to induce PHT resistance by activating the Nrf2/P-gp pathway, which indicates that oxidative stress plays an important role in drug resistance. Taken together, these findings suggest that antioxidative therapy may be a promising strategy for overcoming DRE.

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.

Relevance of NR1I2 variants on carbamazepine therapy in Mexican Mestizos with epilepsy at a tertiary-care hospital

Aim: We evaluated the potential influence of genetic (CYP3A5, EPHX1, NR1I2, HNF4A, ABCC2, RALBP1, SCN1A, SCN2A and GABRA1) and nongenetic factors on carbamazepine (CBZ) response, adverse drug reactions and CBZ plasma concentrations in 126 Mexican Mestizos (MM) with epilepsy. Subjects & methods: Patients were genotyped for 27 variants using TaqMan^® assays. Results: CBZ response was associated with NR1I2 variants and lamotrigine cotreatment. CBZ-induced adverse drug reactions were related to antiepileptic polytherapy and SCN1A rs2298771/rs3812718 haplotype. CBZ plasma concentrations were influenced by NR1I2-rs2276707 and -rs3814058, and by phenytoin cotreatment. CBZ daily dose was also influenced by NR1I2-rs3814055 and EPHX1-rs1051740. Conclusion: Interindividual variability in CBZ treatment was partly explained by NR1I2, EPHX1 and SCN1A variants, as well as antiepileptic cotreatment in MM with epilepsy.

How to Find Candidate Drug-targets for Antiepileptogenic Therapy?

Although over 25 antiepileptic drugs (AEDs) have become currently available for clinical use, the incidence of epilepsy worldwide and the proportions of drug-resistant epilepsy among them are not significantly reduced during the past decades. Traditional screens for AEDs have been mainly focused on their anti-ictogenic roles, and their efficacies primarily depend on suppressing neuronal excitability or enhancing inhibitory neuronal activity, almost without the influence on the epileptogenesis or with inconsistent results from different studies. Epileptogenesis refers to the pathological process of a brain from its normal status to the alterations with the continuous prone of unprovoked spontaneous seizures after brain insults, such as stroke, traumatic brain injury, CNS infectious, and autoimmune disorders, and even some specific inherited conditions. Recently growing experimental and clinical studies have discovered the underlying mechanisms for epileptogenesis, which are multi-aspect and multistep. These findings provide us a number of interesting sites for antiepileptogenic drugs (AEGDs). AEGDs have been evidenced as significantly roles of postponing or completely blocking the development of epilepsy in experimental models. The present review will introduce potential novel candidate drug-targets for AEGDs based on the published studies.

An Insight into Molecular Mechanisms and Novel Therapeutic Approaches in Epileptogenesis

Epilepsy is the second most common neurological disease with abnormal neural activity involving the activation of various intracellular signalling transduction mechanisms. The molecular and system biology mechanisms responsible for epileptogenesis are not well defined or understood. Neuroinflammation, neurodegeneration and Epigenetic modification elicit epileptogenesis. The excessive neuronal activities in the brain are associated with neurochemical changes underlying the deleterious consequences of excitotoxicity. The prolonged repetitive excessive neuronal activities extended to brain tissue injury by the activation of microglia regulating abnormal neuroglia remodelling and monocyte infiltration in response to brain lesions inducing axonal sprouting contributing to neurodegeneration. The alteration of various downstream transduction pathways resulted in intracellular stress responses associating endoplasmic reticulum, mitochondrial and lysosomal dysfunction, activation of nucleases, proteases mediated neuronal death. The recently novel pharmacological agents modulate various receptors like mTOR, COX-2, TRK, JAK-STAT, epigenetic modulators and neurosteroids are used for attenuation of epileptogenesis. Whereas the various molecular changes like the mutation of the cell surface, nuclear receptor and ion channels focusing on repetitive episodic seizures have been explored by preclinical and clinical studies. Despite effective pharmacotherapy for epilepsy, the inadequate understanding of precise mechanisms, drug resistance and therapeutic failure are the current fundamental problems in epilepsy. Therefore, the novel pharmacological approaches evaluated for efficacy on experimental models of epilepsy need to be identified and validated. In addition, we need to understand the downstream signalling pathways of new targets for the treatment of epilepsy. This review emphasizes on the current state of novel molecular targets as therapeutic approaches and future directions for the management of epileptogenesis. Novel pharmacological approaches and clinical exploration are essential to make new frontiers in curing epilepsy.

Host-microbiome interactions: the aryl hydrocarbon receptor as a critical node in tryptophan metabolites to brain signaling

Tryptophan (Trp) is not only a nutrient enhancer but also has systemic effects. Trp metabolites signaling through the well-known aryl hydrocarbon receptor (AhR) constitute the interface of microbiome-gut-brain axis. However, the pathway through which Trp metabolites affect central nervous system (CNS) function have not been fully elucidated. AhR participates in a broad variety of physiological and pathological processes that also highly relevant to intestinal homeostasis and CNS diseases. Via the AhR-dependent mechanism, Trp metabolites connect bidirectional signaling between the gut microbiome and the brain, mediated via immune, metabolic, and neural (vagal) signaling mechanisms, with downstream effects on behavior and CNS function. These findings shed light on the complex Trp regulation of microbiome-gut-brain axis and add another facet to our understanding that dietary Trp is expected to be a promising noninvasive approach for alleviating systemic diseases.

Regulation of brain drug metabolizing enzymes and transporters by nuclear receptors

Nuclear receptors (NRs) belong to a family of ligand-dependent transcription factors. The target genes of NRs include many drug metabolizing enzymes and transporters. The central nervous system (CNS) bears the expression of NRs, drug metabolizing enzymes and transporters. NRs that express in the brain can be divided into three groups according to their characteristics of ligand binding: steroid hormone receptors, non-steroid hormone receptors, and orphan receptors. The NR-mediated regulation of drug metabolizing enzymes and transporters plays important roles in the metabolism and disposition of drugs in the CNS and the penetration of endogenous and exogenous substances through the blood-brain barrier (BBB). NR-mediated regulation of drug metabolizing enzymes and transporters can cause the toxicological effects of xenobiotics in the CNS and also lead to drug resistance in the centrum. The regulatory pathways of drug metabolizing enzymes and transporters can provide new strategies for selective regulation of the BBB permeability and drug metabolism in the brain. This review focuses on the importance of NR-mediated regulation of drug metabolizing enzymes and transporters in the CNS and the implications of this regulation in the therapeutic effect of CNS drugs and CNS side effects of drugs and other xenotoxicants.

Effects of carbamazepine on the P-gp and CYP3A expression correlated with PXR or NF-κB activity in the bEnd.3 cells

Drug-resistant epilepsy (DRE) is present in 20-30% of all patients who develop epilepsy. Growing evidences demonstrated that glutamate released during seizures to increase the brain P-glycoprotein (P-gp) expression. Carbamazepine (CBZ) is known to influence the P-gp and cytochrome P450 (CYP) expression. However, the exact molecular mechanism is still unknown. We investigated that the effects of NF-κB and pregnane X receptor (PXR) activity on P-gp and CYP3A expression in mouse brain endothelial (bEnd.3) cells treated with l-glutamate (mimicking the seizure conditions), CBZ (mimicking the AED treating conditions) or both (l-glutamate plus CBZ) through qPCR and Western blotting assay. Mean fluorescence intensity was used to observe P-gp efflux function by analysis of intracellular Rhodamine123 (Rho123) accumulation. P-gp, CYP3A, PXR and NF-κB p65 were elevated in bEnd.3 cells incubated with l-glutamate, CBZ or CBZ pretreated by l-glutamate for 30 min. Both the mRNA and protein levels of P-gp and CYP3A were remarkably reduced by PXR or NF-κB p65 knock-down by siRNA transfections. The decreased intracellular accumulation of Rho123 suggested that the expression of P-gp was enhanced in bEnd.3 cells. These data suggested that overexpression of P-gp and CYP3A during seizures and treated with CBZ may be regulated by PXR or NF-κB p65 activity and expression, which revealed a mechanism underlying the development of DRE.