Participation of the spleen in the neuroinflammation after pilocarpine-induced status epilepticus: implications for epileptogenesis and epilepsy.

Epilepsy, a chronic neurological disorder characterized by recurrent seizures, affects millions of individuals worldwide. Despite extensive research, the underlying mechanisms leading to epileptogenesis, the process by which a normal brain develops epilepsy, remain elusive. We, here, explored the immune system and spleen responses triggered by pilocarpine-induced status epilepticus (SE) focusing on their role in the epileptogenesis that follows SE. Initial examination of spleen histopathology revealed transient disorganization of white pulp, in animals subjected to SE. This disorganization, attributed to immune activation, peaked at 1-day post-SE (1DPSE) but returned to control levels at 3DPSE. Alterations in peripheral blood lymphocyte populations, demonstrated a decrease following SE, accompanied by a reduction in CD3+ T-lymphocytes. Further investigations uncovered an increased abundance of T-lymphocytes in the piriform cortex and choroid plexus at 3DPSE, suggesting a specific mobilization toward the Central Nervous System. Notably, splenectomy mitigated brain reactive astrogliosis, neuroinflammation, and macrophage infiltration post-SE, particularly in the hippocampus and piriform cortex. Additionally, splenectomized animals exhibited reduced lymphatic follicle size in the deep cervical lymph nodes. Most significantly, splenectomy correlated with improved neuronal survival, substantiated by decreased neuronal loss and reduced degenerating neurons in the piriform cortex and hippocampal CA2-3 post-SE. Overall, these findings underscore the pivotal role of the spleen in orchestrating immune responses and neuroinflammation following pilocarpine-induced SE, implicating the peripheral immune system as a potential therapeutic target for mitigating neuronal degeneration in epilepsy.

Degeneration of cholinergic basal forebrain nuclei after focally evoked status epilepticus.

Status epilepticus (SE) of limbic onset might cause degenerative phenomena in different brain structures, and may be associated with chronic cognitive and EEG effects. In the present study SE was evoked focally by microinfusing picomolar doses of cyclothiazide+bicuculline into the anterior extent of the piriform cortex (APC) in rats, the so-called area tempestas, an approach which allows to evaluate selectively the effects of seizure spreading through the natural anatomical circuitries up to secondary generalization. In the brain of rats submitted to SE we analyzed neuronal density, occurrence of degenerative phenomena (by Fluoro-Jade B-FJB- staining) and expression of heat shock protein-70 (HSP-70) in the piriform cortex, the hippocampus and ventromedial thalamus. We further analyzed in detail, the loss of cholinergic neurons, and the presence of FJB- and HSP-70 positive neurons in basal forebrain cholinergic areas, i.e. the medial septal nucleus (MSN, Ch1), the diagonal band of Broca (DBB, Ch2 and Ch3) and the Nucleus basalis of Meynert (NBM, Ch4). In fact, these nuclei are strictly connected with limbic structures, and play a key pivotal role in different cognitive functions and vigilance. Although recent studies begun to investigate these nuclei in experimental epilepsy and in persons with epilepsy, conflicting results were obtained so far. We showed that after severe and long-lasting, focally induced limbic SE there is a significant cell loss within all of the abovementioned cholinergic nuclei ipsi- and contra-laterally to the infusion site. In parallel, these nuclei show also FJB and heat shock protein-70 expression. Those effects vary depending on the single nucleus assessed and on the severity of the SE seizure score. We also showed the occurrence of cell loss and degenerative phenomena in limbic cortex, hippocampus and limbic thalamic areas. These novel findings show direct evidence of SE-induced neuronal damage which is solely due to seizure activity ruling out potential confounding effects produced by systemic pro-convulsant neurotoxins. A damage to basal forebrain cholinergic nuclei, which may underlie cognitive alterations, is documented for the first time in a model of SE triggered focally.

Blood-brain barrier dysfunction in canine epileptic seizures detected by dynamic contrast-enhanced magnetic resonance imaging.

OBJECTIVE: Dogs with spontaneous or acquired epilepsy exhibit resemblance in etiology and disease course to humans, potentially offering a translational model of the human disease. Blood-brain barrier dysfunction (BBBD) has been shown to partake in epileptogenesis in experimental models of epilepsy. To test the hypothesis that BBBD can be detected in dogs with naturally occurring seizures, we developed a linear dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) analysis algorithm that was validated in clinical cases of seizing dogs and experimental epileptic rats. METHODS: Forty-six dogs with naturally occurring seizures of different etiologies and 12 induced epilepsy rats were imaged using DCE-MRI. Six healthy dogs and 12 naive rats served as control. DCE-MRI was analyzed by linear-dynamic method. BBBD scores were calculated in whole brain and in specific brain regions. Immunofluorescence analysis for transforming growth factor beta (TGF-ß) pathway proteins was performed on the piriform cortex of epileptic dogs. RESULTS: We found BBBD in 37% of dogs with seizures. A significantly higher cerebrospinal fluid to serum albumin ratio was found in dogs with BBBD relative to dogs with intact blood-brain barrier (BBB). A significant difference was found between epileptic and control rats when BBBD scores were calculated for the piriform cortex at 48 hours and 1 month after status epilepticus. Mean BBBD score of the piriform lobe in idiopathic epilepsy (IE) dogs was significantly higher compared to control. Immunohistochemistry results suggested active TGF-ß signaling and neuroinflammation in the piriform cortex of dogs with IE, showing increased levels of serum albumin colocalized with glial acidic fibrillary protein and pSMAD2 in an area where BBBD had been detected by linear DCE-MRI. SIGNIFICANCE: Detection of BBBD in dogs with naturally occurring epilepsy provides the ground for future studies for evaluation of novel treatment targeting the disrupted BBB. The involvement of the piriform lobe seen using our linear DCE-MRI protocol and algorithm emphasizes the possibility of using dogs as a translational model for the human disease.

Genetic absence epilepsy: Effective connectivity from piriform cortex to mediodorsal thalamus.

OBJECTIVE: The objective of the study was to quantify effective connectivity from the piriform cortex to mediodorsal thalamus, in Genetic Absence Epilepsy Rats from Strasbourg (GAERS). METHODS: Local field potentials (LFPs) were recorded using microelectrode arrays implanted in the mediodorsal thalamus and piriform cortex, in three urethane anesthetized GAERS and three control rats. Screw electrodes were placed in the primary motor cortex to identify epileptiform discharges. We used transfer entropy to measure effective connectivity from piriform cortex to mediodorsal thalamus prior to and during generalized epileptiform discharges. RESULTS: We observed increased theta band effective connectivity from piriform cortex to mediodorsal thalamus, prior to and during epileptiform discharges in GAERS compared with controls. Increased effective connectivity was also observed in beta and gamma bands from the piriform cortex to mediodorsal thalamus, but only during epileptiform discharges. CONCLUSIONS: This preliminary study suggests that increased effective theta connectivity from the piriform cortex to the mediodorsal thalamus may be a feature of the 'epileptic network' associated with genetic absence epilepsy. Our findings indicate an underlying predisposition of this direct pathway to propagate epileptiform discharges in genetic absence epilepsy.

Low-grade neuroinflammation due to chronic sleep deprivation results in anxiety and learning and memory impairments.

Chronic sleep loss/fragmentation prevalent in the current 24/7 society is associated with irreversible consequences on health and overall wellbeing. Various studies have well documented the ill effects of acute sleep loss on cognitive functions of individuals; however, the underlying mechanism behind the chronic sleep loss is yet to be explored. The present study was aimed to investigate whether chronic sleep deprivation (CSD) triggers anxiety-like behaviour and memory decline in male Wistar rats. Rats were sleep deprived by placing them over slowly rotating drum (2 rpm) for 18 h (between 4 pm and 10 am) followed by 6 h of recovery sleep for 21 consecutive days. Post CSD regimen, rats were subjected to behavioural tests such as elevated plus maze (EPM), Novel Object Recognition (NOR) and Rotarod performance test and then sacrificed to remove brain for further molecular studies. The study demonstrated that CSD rats showed anxiogenic behaviour along with recognition memory decline compared to control rats. CSD rats further showed elevated levels of inflammatory cytokines (TNFα, IL-1ß) along with activation of NFκB and AP1 transcription factors in hippocampus and piriform cortex (PC) regions of brain. These observations were also accompanied by enhanced expression of GFAP and Iba1 in the two brain regions. The data suggest that CSD triggered low-grade neuroinflammation which caused anxiogenic response and recognition memory impairment. The study provides preliminary leads to further explore the role of astrocytes/microglial cells and inflammatory cytokines in mediating these neurobehavioural consequences of chronic sleep loss and to develop effective interventions to combat them.

Enhanced neurogenesis and possible synaptic reorganization in the piriform cortex of adult rat following kainic acid-induced status epilepticus.

Epileptic seizure has been reported to enhance adult neurogenesis and induce aberrant synaptic reorganization in the human dentate gyrus in the hippocampal formation. However, adult neurogenesis in the extrahippocampal regions has not been well studied. To investigate seizure-enhanced neurogenesis in the extrahippocampal regions, we performed histological and immunohistochemical as well as western blot analyses on the cerebrum of Sprague-Dawley rats (n = 51, male, 7 weeks old, body weight 250-300 g) treated with intraperitoneal injection of kainic acid (KA, 10 mg/kg) to induce status epilepticus (SE) (n = 36) or normal saline solution (n = 15) followed by 5'-bromo-2-deoxyuridine (BrdU) injection to label newborn cells. Even though severe neuronal damage was found in the piriform cortex of rats having SE, immunohistochemistry for double cortin (DCX) revealed an increase in the number of immature neurons in the piriform cortex. Double immunofluorescence staining demonstrated that DCX-positive cells in the piriform cortex were positive for both BrdU and neuronal nuclear antigen. Immunohistochemistry and western blotting revealed increased expressions of synaptophysin and postsynaptic density protein 95 in the piriform cortex of rat having SE. These results suggested the enhanced neurogenesis and possible synaptic reorganization in the piriform cortex of the KA-treated rat.

The role of necroptosis in status epilepticus-induced brain injury in juvenile rats.

PURPOSE: To study the role of necroptosis in status epilepticus (SE)-induced injury in the developing brain and the possible associations of necroptosis with epileptogenesis and cognitive dysfunction. METHODS: The lithium-pilocarpine epilepsy model was reproduced in male rats at postnatal day 25. Propidium iodide (PI) staining was used to detect cell death after SE. Transmission electron microscopy (TEM) was performed to observe morphological changes in injured neurons. Western blot and immunofluorescence (IF) staining were used to investigate the expression of receptor interacting protein kinase-3 (RIP3), mixed lineage kinase domain-like (MLKL), and p-MLKL after SE. EEG was monitored during the chronic epileptic period. The Morris water maze test was performed to evaluate spatial learning and memory in juvenile rats after SE. RESULTS: Massive PI-positive (PI+) neurocytes were observed mainly in the amygdala and piriform cortex 24h to 7days after SE, with the most prominent changes observed after 72h. Injured neurons observed via TEM exhibited necroptotic morphological features, including loss of ribosomes, autophagosome formations, deformed nuclei with condensed and marginated chromatin, and disruptive cell membranes. The expression of RIP3 and p-MLKL increased after 24h, peaked at 72h, and decreased 7days after SE. In addition, IF staining revealed that MLKL was expressed in cell plasma membranes present in the amygdala and piriform cortex. This finding was concomitant with the fact that MLKL is involved in executing necroptosis by binding and disrupting the plasma membrane. During the chronic epileptic period, spontaneous recurrent seizures were observed behaviorally and interictal spikes and sharp waves were recorded by EEG in the SE group. The Morris water maze test revealed that in the place navigation test, the escape latency of the SE group was longer than that of the control group (p<0.05). In the spatial probe test, the number of times the rats in the SE group passed through the original platform site was lesser than that of the rats in the control group (p<0.05). CONCLUSION: SE-induced brain injury leads to neuronal necroptosis in juvenile rats. MLKL may play a significant role in the execution of SE-induced necroptosis. Further studies are required to determine whether inhibiting necroptosis can prevent chronic epileptogenesis and improve cognitive ability for juvenile rats.

Microglia are less pro-inflammatory than myeloid infiltrates in the hippocampus of mice exposed to status epilepticus.

Activated microglia, astrogliosis, expression of pro-inflammatory cytokines, blood brain barrier (BBB) leakage and peripheral immune cell infiltration are features of mesial temporal lobe epilepsy. Numerous studies correlated the expression of pro-inflammatory cytokines with the activated morphology of microglia, attributing them a pro-epileptogenic role. However, microglia and myeloid cells such as macrophages have always been difficult to distinguish due to an overlap in expressed cell surface molecules. Thus, the detrimental role in epilepsy that is attributed to microglia might be shared with myeloid infiltrates. Here, we used a FACS-based approach to discriminate between microglia and myeloid infiltrates isolated from the hippocampus 24 h and 96 h after status epilepticus (SE) in pilocarpine-treated CD1 mice. We observed that microglia do not express MHCII whereas myeloid infiltrates express high levels of MHCII and CD40 96 h after SE. This antigen-presenting cell phenotype correlated with the presence of CD4(pos) T cells. Moreover, microglia only expressed TNFα 24 h after SE while myeloid infiltrates expressed high levels of IL-1ß and TNFα. Immunofluorescence showed that astrocytes but not microglia expressed IL-1ß. Myeloid infiltrates also expressed matrix metalloproteinase (MMP)-9 and 12 while microglia only expressed MMP-12, suggesting the involvement of both cell types in the BBB leakage that follows SE. Finally, both cell types expressed the phagocytosis receptor Axl, pointing to phagocytosis of apoptotic cells as one of the main functions of microglia. Our data suggests that, during early epileptogenesis, microglia from the hippocampus remain rather immune supressed whereas myeloid infiltrates display a strong inflammatory profile. GLIA 2016 GLIA 2016;64:1350-1362.

Expansion of the piriform cortex contributes to corticothalamic pathfinding defects in Gli3 conditional mutants.

The corticothalamic and thalamocortical tracts play essential roles in the communication between the cortex and thalamus. During development, axons forming these tracts have to follow a complex path to reach their target areas. While much attention has been paid to the mechanisms regulating their passage through the ventral telencephalon, very little is known about how the developing cortex contributes to corticothalamic/thalamocortical tract formation. Gli3 encodes a zinc finger transcription factor widely expressed in telencephalic progenitors which has important roles in corticothalamic and thalamocortical pathfinding. Here, we conditionally inactivated Gli3 in dorsal telencephalic progenitors to determine its role in corticothalamic tract formation. In Emx1Cre;Gli3(fl/fl) mutants, only a few corticothalamic axons enter the striatum in a restricted dorsal domain. This restricted entry correlates with a medial expansion of the piriform cortex. Transplantation experiments showed that the expanded piriform cortex repels corticofugal axons. Moreover, expression of Sema5B, a chemorepellent for corticofugal axons produced by the piriform cortex, is similarly expanded. Finally, time course analysis revealed an expansion of the ventral pallial progenitor domain which gives rise to the piriform cortex. Hence, control of lateral cortical development by Gli3 at the progenitor level is crucial for corticothalamic pathfinding.

Editorial commentary: The meth brain: methamphetamines alter brain functions via NMDA receptors.

Commentary to: Functional changes in pyramidal neurons in the chronic methamphetamine-treated rat. (Gen. Physiol. Biophys. 2015, pp.5-12).

Functional changes in piriform cortex pyramidal neurons in the chronic methamphetamine-treated rat.

Chronic treatment of rats with methamphetamine (MAP) causes a range of functional changes to the central nervous system (CNS), including a toxicity that is widespread throughout the brain (Frost and Cadet 2000; Fasihpour et al. 2013). In this report, we examined the effect of chronic MAP treatment on pyramidal neurons of the rat piriform cortex, an area involved in sensory processing, associative learning and a model system for studies on synaptic plasticity. MAP treatment significantly depolarized the membrane potential and decreased neuronal input resistance. Furthermore, the voltage-dependence of both AMPA and NMDA responses was disturbed by chronic MAP treatment, and the extent of long-term potentiation (LTP) was decreased. Morphological changes of MAP-treated rat pyramidal neurons were observed as blebbing of the dendrite trees. The changes we observed represent detrimental effects on the function of piriform cortical neurons further illustrating deficits in synaptic plasticity extend beyond the hippocampus. These changes may contribute to behavioural deficits in chronic MAP-treated animals.

Effect of minocycline on pentylenetetrazol-induced chemical kindled seizures in mice.

Inflammation is one of the mechanisms involved in seizure induction. In this study, the effect of minocycline, an anti-inflammatory drug, was investigated on kindling acquisition. Chemical kindling was induced by injection of a subthreshold dose of pentylenetetrazol (PTZ; 37.5 mg/kg) in mice on every other day. Two groups of animals received minocycline (25 mg/kg) at 1 h before or 1 h after PTZ injection. Following the last PTZ injection, the changes in gene expression of TNF-α receptor, γ2 subunit of GABAA receptor and NR2A subunit of NMDA receptor were assessed in the hippocampus and piriform cortex. Injection of minocycline before PTZ increased the latency to stage 4 seizure, and decreased the duration of stages 4 and 5 seizure. It also prevented the increase in the mRNA of NR2A subunit of NMDA receptor in the hippocampus and removed the PTZ-induced increase in mRNA of γ2 subunit of GABAA receptor in piriform cortex of PTZ kindled mice. Minocycline also prevented the increase in TNF-α receptor gene expression in both hippocampus and piriform cortex. Injection of minocycline after PTZ had no significant effect on measured parameters. Therefore, it can be concluded that minocycline may exert an anticonvulsant effect through preventing the increase in GABAA and NMDA receptor subunits. These effects are accompanied by a reduction in an important inflammation index, TNF-α receptor.

TRAK1-Mediated Abnormality of Mitochondrial Fission Increases Seizure Susceptibility in Temporal Lobe Epilepsy.

Mitochondrial dysfunction is closely related to the occurrence of epilepsy. Homeostasis of mitochondrial fusion and division can alleviate mitochondrial dysfunction. The trafficking kinesin protein 1 (TRAK1) is a key regulator of mitochondrial movement and regulates mitochondrial fusion-fission balance. The pathogenic variants in TRAK1 result in the severe neurodevelopmental disorders. However, the role of TRAK1 in epilepsy remains unclear. In the present study, we report that TRAK1 has a crucial function in regulation of epileptogenesis in temporal lobe epilepsy (TLE). TRAK1 expression is decreased in the patient specimens and animal model of TLE. Knockdown of TRAK1 causes an increase in mitochondrial fission factor (MFF) in vitro and the susceptibility to seizures in vivo. Exogenous overexpression of TRAK1 can rescue the dysfunction caused by TRAK1 knockdown. These findings provide new insights into the fundamental mechanisms of TRAK1 in TLE and have important implications for understanding and treating TLE via targeting mitochondrion.

Perturbation of in vivo Neural Activity Following α-Synuclein Seeding in the Olfactory Bulb.

BACKGROUND: Parkinson's disease (PD) neuropathology is characterized by intraneuronal protein aggregates composed of misfolded α-Synuclein (α-Syn), as well as degeneration of substantia nigra dopamine neurons. Deficits in olfactory perception and aggregation of α-Syn in the olfactory bulb (OB) are observed during early stages of PD, and have been associated with the PD prodrome, before onset of the classic motor deficits. α-Syn fibrils injected into the OB of mice cause progressive propagation of α-Syn pathology throughout the olfactory system and are coupled to olfactory perceptual deficits. OBJECTIVE: We hypothesized that accumulation of pathogenic α-Syn in the OB impairs neural activity in the olfactory system. METHODS: To address this, we monitored spontaneous and odor-evoked local field potential dynamics in awake wild type mice simultaneously in the OB and piriform cortex (PCX) one, two, and three months following injection of pathogenic preformed α-Syn fibrils in the OB. RESULTS: We detected α-Syn pathology in both the OB and PCX. We also observed that α-Syn fibril injections influenced odor-evoked activity in the OB. In particular, α-Syn fibril-injected mice displayed aberrantly high odor-evoked power in the beta spectral range. A similar change in activity was not detected in the PCX, despite high levels of α-Syn pathology. CONCLUSION: Together, this work provides evidence that synucleinopathy impacts in vivo neural activity in the olfactory system at the network-level.

Blockade of 67-kDa Laminin Receptor Facilitates AQP4 Down-Regulation and BBB Disruption via ERK1/2-and p38 MAPK-Mediated PI3K/AKT Activations.

Recently, we have reported that dysfunctions of 67-kDa laminin receptor (67LR) induced by status epilepticus (SE, a prolonged seizure activity) and 67LR neutralization are involved in vasogenic edema formation, accompanied by the reduced aquaporin 4 (AQP4, an astroglial specific water channel) expression in the rat piriform cortex (PC). In the present study, we found that the blockade of 67LR activated p38 mitogen-activated protein kinase (p38 MAPK) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathways, which enhanced phosphatidylinositol 3 kinase (PI3K)/AKT phosphorylations in endothelial cells and astrocytes, respectively. 67LR-p38 MAPK-PI3K-AKT activation in endothelial cells increased vascular permeability. In contrast, 67LR-ERK1/2-PI3K-AKT signaling pathways in astrocytes regulated astroglial viability and AQP4 expression. These findings indicate that PI3K/AKT may integrate p38 MAPK and ERK1/2 signaling pathways to regulate AQP4 expression when 67LR functionality is reduced. Thus, we suggest that 67LR-p38 MAPK/ERK1/2-PI3K-AKT-AQP4 signaling cascades may mediate serum extravasation and AQP4 expression in astroglio-vascular systems, which is one of the considerable therapeutic targets for vasogenic edema in various neurological diseases.

Japanese Encephalitis Virus Infects the Thalamus Early Followed by Sensory-Associated Cortex and Other Parts of the Central and Peripheral Nervous Systems.

Japanese encephalitis (JE) is a known CNS viral infection that often involves the thalamus early. To investigate the possible role of sensory peripheral nervous system (PNS) in early neuroinvasion, we developed a left hindlimb footpad-inoculation mouse model to recapitulate human infection by a mosquito bite. A 1-5 days postinfection (dpi) study, demonstrated focal viral antigens/RNA in contralateral thalamic neurons at 3 dpi in 50% of the animals. From 4 to 5 dpi, gradual increase in viral antigens/RNA was observed in bilateral thalami, somatosensory, and piriform cortices, and then the entire CNS. Infection of neuronal bodies and adjacent nerves in dorsal root ganglia (DRGs), trigeminal ganglia, and autonomic ganglia (intestine, etc.) was also observed from 5 dpi. Infection of explant organotypic whole brain slice cultures demonstrated no viral predilection for the thalamus, while DRG and intestinal ganglia organotypic cultures confirmed sensory and autonomic ganglia susceptibility to infection, respectively. Early thalamus and sensory-associated cortex involvement suggest an important role for sensory pathways in neuroinvasion. Our results suggest that JE virus neuronotropism is much more extensive than previously known, and that the sensory PNS and autonomic system are susceptible to infection.

Association of Piriform Cortex Resection With Surgical Outcomes in Patients With Temporal Lobe Epilepsy.

Importance: A functional area associated with the piriform cortex, termed area tempestas, has been implicated in animal studies as having a crucial role in modulating seizures, but similar evidence is limited in humans. Objective: To assess whether removal of the piriform cortex is associated with postoperative seizure freedom in patients with temporal lobe epilepsy (TLE) as a proof-of-concept for the relevance of this area in human TLE. Design, Setting, and Participants: This cohort study used voxel-based morphometry and volumetry to assess differences in structural magnetic resonance imaging (MRI) scans in consecutive patients with TLE who underwent epilepsy surgery in a single center from January 1, 2005, through December 31, 2013. Participants underwent presurgical and postsurgical structural MRI and had at least 2 years of postoperative follow-up (median, 5 years; range, 2-11 years). Patients with MRI of insufficient quality were excluded. Findings were validated in 2 independent cohorts from tertiary epilepsy surgery centers. Study follow-up was completed on September 23, 2016, and data were analyzed from September 24, 2016, through April 24, 2018. Exposures: Standard anterior temporal lobe resection. Main Outcomes and Measures: Long-term postoperative seizure freedom. Results: In total, 107 patients with unilateral TLE (left-sided in 68; 63.6% women; median age, 37 years [interquartile range {IQR}, 30-45 years]) were included in the derivation cohort. Reduced postsurgical gray matter volumes were found in the ipsilateral piriform cortex in the postoperative seizure-free group (n = 46) compared with the non-seizure-free group (n = 61). A larger proportion of the piriform cortex was resected in the seizure-free compared with the non-seizure-free groups (median, 83% [IQR, 64%-91%] vs 52% [IQR, 32%-70%]; P < .001). The results were seen in left- and right-sided TLE and after adjusting for clinical variables, presurgical gray matter alterations, presurgical hippocampal volumes, and the proportion of white matter tract disconnection. Findings were externally validated in 2 independent cohorts (31 patients; left-sided TLE in 14; 54.8% women; median age, 41 years [IQR, 31-46 years]). The resected proportion of the piriform cortex was individually associated with seizure outcome after surgery (derivation cohort area under the curve, 0.80 [P < .001]; external validation cohorts area under the curve, 0.89 [P < .001]). Removal of at least half of the piriform cortex increased the odds of becoming seizure free by a factor of 16 (95% CI, 5-47; P < .001). Other mesiotemporal structures (ie, hippocampus, amygdala, and entorhinal cortex) and the overall resection volume were not associated with outcomes. Conclusions and Relevance: These results support the importance of resecting the piriform cortex in neurosurgical treatment of TLE and suggest that this area has a key role in seizure generation.

Type 2 diabetes impairs odour detection, olfactory memory and olfactory neuroplasticity; effects partly reversed by the DPP-4 inhibitor Linagliptin.

Recent data suggest that olfactory deficits could represent an early marker and a pathogenic mechanism at the basis of cognitive decline in type 2 diabetes (T2D). However, research is needed to further characterize olfactory deficits in diabetes, their relation to cognitive decline and underlying mechanisms.The aim of this study was to determine whether T2D impairs odour detection, olfactory memory as well as neuroplasticity in two major brain areas responsible for olfaction and odour coding: the main olfactory bulb (MOB) and the piriform cortex (PC), respectively. Dipeptidyl peptidase-4 inhibitors (DPP-4i) are clinically used T2D drugs exerting also beneficial effects in the brain. Therefore, we aimed to determine whether DPP-4i could reverse the potentially detrimental effects of T2D on the olfactory system.Non-diabetic Wistar and T2D Goto-Kakizaki rats, untreated or treated for 16 weeks with the DPP-4i linagliptin, were employed. Odour detection and olfactory memory were assessed by using the block, the habituation-dishabituation and the buried pellet tests. We assessed neuroplasticity in the MOB by quantifying adult neurogenesis and GABAergic inhibitory interneurons positive for calbindin, parvalbumin and carletinin. In the PC, neuroplasticity was assessed by quantifying the same populations of interneurons and a newly identified form of olfactory neuroplasticity mediated by post-mitotic doublecortin (DCX) + immature neurons.We show that T2D dramatically reduced odour detection and olfactory memory. Moreover, T2D decreased neurogenesis in the MOB, impaired the differentiation of DCX+ immature neurons in the PC and altered GABAergic interneurons protein expression in both olfactory areas. DPP-4i did not improve odour detection and olfactory memory. However, it normalized T2D-induced effects on neuroplasticity.The results provide new knowledge on the detrimental effects of T2D on the olfactory system. This knowledge could constitute essentials for understanding the interplay between T2D and cognitive decline and for designing effective preventive therapies.

A switch in G protein coupling for type 1 corticotropin-releasing factor receptors promotes excitability in epileptic brains.

Anxiety and stress increase the frequency of epileptic seizures. These behavioral states induce the secretion of corticotropin-releasing factor (CRF), a 40-amino acid neuropeptide neurotransmitter that coordinates many behavioral responses to stress in the central nervous system. In the piriform cortex, which is one of the most seizurogenic regions of the brain, CRF normally dampens excitability. By contrast, CRF increased the excitability of the piriform cortex in rats subjected to kindling, a model of temporal lobe epilepsy. In nonkindled rats, CRF activates its receptor, a G protein (heterotrimeric guanosine triphosphate-binding protein)-coupled receptor, and signals through a Gαq/11-mediated pathway. After seizure induction, CRF signaling occurred through a pathway involving Gαs This change in signaling was associated with reduced abundance of regulator of G protein signaling protein type 2 (RGS2), which has been reported to inhibit Gαs-dependent signaling. RGS2 knockout mice responded to CRF in a similar manner as epileptic rats. These observations indicate that seizures produce changes in neuronal signaling that can increase seizure occurrence by converting a beneficial stress response into an epileptic trigger.

Type 2 diabetes-induced neuronal pathology in the piriform cortex of the rat is reversed by the GLP-1 receptor agonist exendin-4.

Type 2 diabetes (T2D) patients often present olfactory dysfunction. However, the histopathological basis behind this has not been previously shown. Since the piriform cortex plays a crucial role in olfaction, we hypothesize that pathological changes in this brain area can occur in T2D patients along aging. Thus, we determined potential neuropathology in the piriform cortex of T2D rats, along aging. Furthermore, we determined the potential therapeutic role of the glucagon-like peptide-1 receptor (GLP1-R) agonist exendin-4 to counteract the identified T2D-induced neuropathology. Young-adult and middle-aged T2D Goto-Kakizaki rats were compared to age-matched Wistars. Additional Goto-Kakizaki rats were treated for six weeks with exendin-4/vehicle before sacrifice. Potential T2D-induced neuropathology was assessed by quantifying NeuN-positive neurons and Calbindin-D28k-positive interneurons by immunohistochemistry and stereology methods. We also quantitatively measured Calbindin-D28k neuronal morphology and JNK phosphorylation-mediated cellular stress. PI3K/AKT signalling was assessed by immunohistochemistry, and potential apoptosis by TUNEL.We show T2D-induced neuronal pathology in the piriform cortex along aging, characterized by atypical nuclear NeuN staining and increased JNK phosphorylation, without apoptosis. We also demonstrate the specific vulnerability of Calbindin-D28k interneurons. Finally, chronic treatment with exendin-4 substantially reversed the identified neuronal pathology in correlation with decreased JNK and increased AKT phosphorylation.Our results reveal the histopathological basis to explain T2D olfactory dysfunction. We also show that the identified T2D-neuropathology can be counteracted by GLP-1R activation supporting recent research promoting the use of GLP-1R agonists against brain diseases. Whether the identified neuropathology could represent an early hallmark of cognitive decline in T2D remains to be determined.