Chemogenetic inhibition of subicular seizure-activated neurons alleviates cognitive deficit in male mouse epilepsy model.

Cognitive deficit is a common comorbidity in temporal lobe epilepsy (TLE) and is not well controlled by current therapeutics. How epileptic seizure affects cognitive performance remains largely unclear. In this study we investigated the role of subicular seizure-activated neurons in cognitive impairment in TLE. A bipolar electrode was implanted into hippocampal CA3 in male mice for kindling stimulation and EEG recording; a special promoter with enhanced synaptic activity-responsive element (E-SARE) was used to label seizure-activated neurons in the subiculum; the activity of subicular seizure-activated neurons was manipulated using chemogenetic approach; cognitive function was assessed in object location memory (OLM) and novel object recognition (NOR) tasks. We showed that chemogenetic inhibition of subicular seizure-activated neurons (mainly CaMKIIα+ glutamatergic neurons) alleviated seizure generalization and improved cognitive performance, but inhibition of seizure-activated GABAergic interneurons had no effect on seizure and cognition. For comparison, inhibition of the whole subicular CaMKIIα+ neuron impaired cognitive function in naïve mice in basal condition. Notably, chemogenetic inhibition of subicular seizure-activated neurons enhanced the recruitment of cognition-responsive c-fos+ neurons via increasing neural excitability during cognition tasks. Our results demonstrate that subicular seizure-activated neurons contribute to cognitive impairment in TLE, suggesting seizure-activated neurons as the potential therapeutic target to alleviate cognitive impairment in TLE.

Glutamatergic and GABAergic neurons in the vLGN mediate the nociceptive effects of green and red light on neuropathic pain.

Phototherapy is an emerging non-pharmacological treatment for depression, circadian rhythm disruptions, and neurodegeneration, as well as pain conditions including migraine and fibromyalgia. However, the mechanism of phototherapy-induced antinociception is not well understood. Here, using fiber photometry recordings of population-level neural activity combined with chemogenetics, we found that phototherapy elicits antinociception via regulation of the ventral lateral geniculate body (vLGN) located in the visual system. Specifically, both green and red lights caused an increase of c-fos in vLGN, with red light increased more. In vLGN, green light causes a large increase in glutamatergic neurons, whereas red light causes a large increase in GABAergic neurons. Green light preconditioning increases the sensitivity of glutamatergic neurons to noxious stimuli in vLGN of PSL mice. Green light produces antinociception by activating glutamatergic neurons in vLGN, and red light promotes nociception by activating GABAergic neurons in vLGN. Together, these results demonstrate that different colors of light exert different pain modulation effects by regulating glutamatergic and GABAergic subpopulations in the vLGN. This may provide potential new therapeutic strategies and new therapeutic targets for the precise clinical treatment of neuropathic pain.

Inflachromene attenuates seizure severity in mouse epilepsy models via inhibiting HMGB1 translocation.

Epilepsy is not well controlled by current anti-seizure drugs (ASDs). High mobility group box 1 (HMGB1) is a DNA-binding protein in the nucleus regulating transcriptional activity and maintaining chromatin structure and DNA repair. In epileptic brains, HMGB1 is released by activated glia and neurons, interacting with various receptors like Toll-like receptor 4 (TLR4) and downstream glutamatergic NMDA receptor, thus enhancing neural excitability. But there is a lack of small-molecule drugs targeting the HMGB1-related pathways. In this study we evaluated the therapeutic potential of inflachromene (ICM), an HMGB-targeting small-molecule inhibitor, in mouse epilepsy models. Pentylenetetrazol-, kainic acid- and kindling-induced epilepsy models were established in mice. The mice were pre-treated with ICM (3, 10 mg/kg, i.p.). We showed that ICM pretreatment significantly reduced the severity of epileptic seizures in all the three epilepsy models. ICM (10 mg/kg) exerted the most apparent anti-seizure effect in kainic acid-induced epileptic status (SE) model. By immunohistochemical analysis of brain sections from kainic acid-induced SE mice, we found that kainic acid greatly enhanced HMGB1 translocation in the hippocampus, which was attenuated by ICM pretreatment in subregion- and cell type-dependent manners. Notably, in CA1 region, the seizure focus, ICM pretreatment mainly inhibited HMGB1 translocation in microglia. Furthermore, the anti-seizure effect of ICM was related to HMGB1 targeting, as pre-injection of anti-HMGB1 monoclonal antibody (5 mg/kg, i.p.) blocked the seizure-suppressing effect of ICM in kainic acid-induced SE model. In addition, ICM pretreatment significantly alleviated pyramidal neuronal loss and granule cell dispersion in kainic acid-induced SE model. These results demonstrate that ICM is an HMGB-targeting small molecule with anti-seizure potential, which may help develop a potential drug for treating epilepsy.

(+)-Borneol enantiomer ameliorates epileptic seizure via decreasing the excitability of glutamatergic transmission.

Epilepsy is one common brain disorder, which is not well controlled by current pharmacotherapy. In this study we characterized the therapeutic potential of borneol, a plant-derived bicyclic monoterpene compound, in the treatment of epilepsy and elucidated the underlying mechanisms. The anti-seizure potency and properties of borneol were assessed in both acute and chronic mouse epilepsy models. Administration of (+)-borneol (10, 30, 100 mg/kg, i.p.) dose-dependently attenuated acute epileptic seizure in maximal-electroshock seizure (MES) and pentylenetetrazol (PTZ)-induced seizure models without obvious side-effect on motor function. Meanwhile, (+)-borneol administration retarded kindling-induced epileptogenesis and relieved fully kindled seizures. Importantly, (+)-borneol administration also showed therapeutic potential in kainic acid-induced chronic spontaneous seizure model, which was considered as a drug-resistant model. We compared the anti-seizure efficacy of 3 borneol enantiomers in the acute seizure models, and found (+)-borneol being the most satisfying one with long-term anti-seizure effect. In electrophysiological study conducted in mouse brain slices containing the subiculum region, we revealed that borneol enantiomers displayed different anti-seizure mechanisms, (+)-borneol (10 µM) markedly suppressed the high frequency burst firing of subicular neurons and decreased glutamatergic synaptic transmission. In vivo calcium fiber photometry analysis further verified that administration of (+)-borneol (100 mg/kg) inhibited the enhanced glutamatergic synaptic transmission in epilepsy mice. We conclude that (+)-borneol displays broad-spectrum anti-seizure potential in different experimental models via decreasing the glutamatergic synaptic transmission without obvious side-effect, suggesting (+)-borneol as a promising anti-seizure compound for pharmacotherapy in epilepsy.

GPR177 in A-fiber sensory neurons drives diabetic neuropathic pain via WNT-mediated TRPV1 activation.

Diabetic neuropathic pain (DNP) is a common and devastating complication in patients with diabetes. The mechanisms mediating DNP are not completely elucidated, and effective treatments are lacking. A-fiber sensory neurons have been shown to mediate the development of mechanical allodynia in neuropathic pain, yet the molecular basis underlying the contribution of A-fiber neurons is still unclear. Here, we report that the orphan G protein-coupled receptor 177 (GPR177) in A-fiber neurons drives DNP via WNT5a-mediated activation of transient receptor potential vanilloid receptor-1 (TRPV1) ion channel. GPR177 is mainly expressed in large-diameter A-fiber dorsal root ganglion (DRG) neurons and required for the development of DNP in mice. Mechanistically, we found that GPR177 mediated the secretion of WNT5a from A-fiber DRG neurons into cerebrospinal fluid (CSF), which was necessary for the maintenance of DNP. Extracellular perfusion of WNT5a induced rapid currents in both TRPV1-expressing heterologous cells and nociceptive DRG neurons. Computer simulations revealed that WNT5a has the potential to bind the residues at the extracellular S5-S6 loop of TRPV1. Using a peptide able to disrupt the predicted WNT5a/TRPV1 interaction suppressed DNP- and WNT5a-induced neuropathic pain symptoms in rodents. We confirmed GPR177/WNT5A coexpression in human DRG neurons and WNT5A secretion in CSF from patients with DNP. Thus, our results reveal a role for WNT5a as an endogenous and potent TRPV1 agonist, and the GPR177-WNT5a-TRPV1 axis as a driver of DNP pathogenesis in rodents. Our findings identified a potential analgesic target that might relieve neuropathic pain in patients with diabetes.

Comparative Proteomic Analysis Reveals the Effects of Exogenous Calcium against Acid Rain Stress in Liquidambar formosana Hance Leaves.

Acid rain (AR) impacts forest health by leaching calcium (Ca) away from soils and plants. Ca is an essential element and participates in various plant physiological responses. In the present study, the protective role of exogenous Ca in alleviating AR stress in Liquidambar formosana Hance at the physiological and proteomic levels was examined. Our results showed that low Ca condition resulted in the chlorophyll content and photosynthesis decreasing significantly in L. formosana leaves; however, these effects could be reversed by high Ca supplementation. Further proteomic analyses successfully identified 81 differentially expressed proteins in AR-treated L. formosana under different Ca levels. In particular, some of the proteins are involved in primary metabolism, photosynthesis, energy production, antioxidant defense, transcription, and translation. Moreover, quantitative real time polymerase chain reaction (qRT-PCR) results indicated that low Ca significantly increased the expression level of the investigated Ca-related genes, which can be reversed by high Ca supplementation under AR stress. Further, Western blotting analysis revealed that exogenous Ca supply reduced AR damage by elevating the expression of proteins involved in the Calvin cycle, reactive oxygen species (ROS) scavenging system. These findings allowed us to better understand how woody plants respond to AR stress at various Ca levels and the protective role of exogenous Ca against AR stress in forest tree species.