Cholinergic transmission from the basal forebrain modulates social memory in male mice

Target inhibition of NAT10-mediated ac4C modification prevents seizure behavior in mice

N4-acetylation of Cytidine (ac4C), catalyzed by its only known enzyme N-acetyltransferase 10 (NAT10), facilitates cellular mRNA translation and stability, but its function in brain disorders especially epilepsy is poorly understood. By using pentylenetetrazole (PTZ) induced mouse model of epilepsy, we first displayed spatiotemporally expression of ac4C and NAT10 in the mouse brain. To corroborate the alteration of ac4C and NAT10 in epilepsy, we used acute PTZ, chronic PTZ and intrahippocampal kainic acid (IHKA) mouse model. We then utilized a combination of viral tool and pharmacological approaches to implicate NAT10 mediated ac4C modification in seizure behaviors. We found that the expression of ac4C was increased in epileptic brain tissues in mouse models of epilepsy, which might be due to the up-regulated NAT10. Block of NAT10 led to both reduced brain ac4C level and resistance to PTZ or KA-induced seizure behavior, while hippocampal over-expression of NAT10 causes exacerbated seizure behavior. In support of such a role, our data demonstrated that the loss or gains of ac4C modification could normalize or exacerbate neuronal over-activation in epileptic brain tissues, respectively. Mechanically, we observed that block the NAT10 or over-expression NAT10 lead to reduced or enhanced BDNF, respectively. While the BDNF pathway inhibitor rescued the hippocampal NAT10 over-expression induced aggravated seizure behavior in the chronic PTZ treated mice. Therefore, our work provides the first demonstration of the ac4C levels in an epilepsy mice model, targeted to prevent ac4C by NAT10 inhibition seems to be effective in preventing and treating epilepsy.

Targeted suppression of BRD7 with BI-9564 prevents seizure behaviors in pentylenetetrazol and pilocarpine-induced mouse model of epilepsy

Epilepsy is a serious neurological disorder, but its underlying cellular and molecular mechanisms remains incomplete. As a member of the bromodomain-containing protein (BCP) family, BRD7 has been implicated in a variety of cellular processes, including chromatin remodeling, transcriptional regulation, and cell cycle progression. However, the role of BRD7 in epilepsy in vivo is still poorly understood. In the present study, we found that pentylenetetrazole (PTZ)-induced epilepsy increased hippocampal BRD7, which was mainly localized in neurons. In addition, the enhanced expression of hippocampal BRD7 was normalized by using the anti-epilepsy drug valproic acid (VPA). Furthermore, we identified that the BRD7 inhibitor BI-9564 could dose dependently alleviated the seizure behavior in PTZ treated mice, which was also validated in pilocarpine mouse model. Mechanistically, the anti-seizure effect of BI- 9564 might be due to its negative-regulation of hippocampal TRPV4 that downregulated neuronal over-excitability. Importantly, BRD7 blockade retained its antiepileptic activity over chronic dosing that was not related to psychomotor or cognitive effects. To our knowledge, these results are the first evidence to demonstrate that BRD7 inhibitor can down-regulate neuronal over-excitation caused by epilepsy possible by regulating TRPV4. Targeting BRD7 through the development of selective inhibitors may lead to disease-modifying therapies that reduce seizure behavior.

Rapid changes in plasma corticosterone and medial amygdala transcriptome profiles during social status change reveal molecular pathways associated with a major life history transition in mouse dominance hierarchies

Social hierarchies are a common form of social organization across species. Although hierarchies are largely stable across time, animals may socially ascend or descend within hierarchies depending on environmental and social challenges. Here, we develop a novel paradigm to study social ascent and descent within male CD-1 mouse social hierarchies. We show that mice of all social ranks rapidly establish new stable social hierarchies when placed in novel social groups with animals of equivalent social status. Seventy minutes following social hierarchy formation, males that were socially dominant prior to being placed into new social hierarchies exhibit higher increases in plasma corticosterone and vastly greater transcriptional changes in the medial amygdala (MeA), which is central to the regulation of social behavior, compared to males who were socially subordinate prior to being placed into a new hierarchy. Specifically, the loss of social status in a new hierarchy (social descent) is associated with reductions in MeA expression of myelination and oligodendrocyte differentiation genes. Maintaining high social status is associated with high expression of genes related to cholinergic signaling in the MeA. Conversely, gaining social status in a new hierarchy (social ascent) is related to relatively few unique rapid changes in the MeA. We also identify novel genes associated with social transition that show common changes in expression when animals undergo either social descent or social ascent compared to maintaining their status. Two genes, Myosin binding protein C1 (Mybpc1) and μ-Crystallin (Crym), associated with vasoactive intestinal polypeptide (VIP) and thyroid hormone pathways respectively, are highly upregulated in socially transitioning individuals. Further, increases in genes associated with synaptic plasticity, excitatory glutamatergic signaling and learning and memory pathways were observed in transitioning animals suggesting that these processes may support rapid social status changes.

Amygdalar neurotransmission alterations in the BTBR mice model of idiopathic autism

Autism Spectrum Disorders (ASD) are principally diagnosed by three core behavioural symptoms, such as stereotyped repertoire, communication impairments and social dysfunctions. This complex pathology has been linked to abnormalities of corticostriatal and limbic circuits. Despite experimental efforts in elucidating the molecular mechanisms behind these abnormalities, a clear etiopathogenic hypothesis is still lacking. To this aim, preclinical studies can be really helpful to longitudinally study behavioural alterations resembling human symptoms and to investigate the underlying neurobiological correlates. In this regard, the BTBR T+ Itpr3tf/J (BTBR) mice are an inbred mouse strain that exhibits a pattern of behaviours well resembling human ASD-like behavioural features. In this study, the BTBR mice model was used to investigate neurochemical and biomolecular alterations, regarding Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF), together with GABAergic, glutamatergic, cholinergic, dopaminergic and noradrenergic neurotransmissions and their metabolites in four different brain areas, i.e. prefrontal cortex, hippocampus, amygdala and hypothalamus. In our results, BTBR strain reported decreased noradrenaline, acetylcholine and GABA levels in prefrontal cortex, while hippocampal measurements showed reduced NGF and BDNF expression levels, together with GABA levels. Concerning hypothalamus, no differences were retrieved. As regarding amygdala, we found reduced dopamine levels, accompanied by increased dopamine metabolites in BTBR mice, together with decreased acetylcholine, NGF and GABA levels and enhanced glutamate content. Taken together, our data showed that the BTBR ASD model, beyond its face validity, is a useful tool to untangle neurotransmission alterations that could be underpinned to the heterogeneous ASD-like behaviours, highlighting the crucial role played by amygdala.

Blocking salt-inducible kinases with YKL-06-061 prevents PTZ-induced seizures in mice

INTRODUCTION

Epilepsy is one of the most common neurological diseases, while over one third of adults with epilepsy still have inadequate seizure control. Although mutations in salt-inducible kinases (SIKs) have been identified in epileptic encephalopathy, it is not known whether blocking SIKs can prevent pentylenetetrazole (PTZ)-induced seizures.

METHODS

We first determined the time course of SIKs (including SIK 1, 2, and 3) in the hippocampus of PTZ treated mice. And then, we evaluated the effects of anti-epilepsy drug valproate acid (VPA) on the expression of SIK 1, 2, and 3 in the hippocampus of PTZ treated mice. Next, we investigated the effect of different dose of SIKs inhibitor YKL-06-061 on the epileptic seizures and neuronal activation by determining the expression of immediate early genes (IEGs) in the PTZ treated mice.

RESULTS

We found that PTZ selectively induced enhanced expression of SIK1 in the hippocampus, which was blocked by VPA treatment. Notably, YKL-06-061 decreased seizure activity and prevented neuronal overactivity, as indicated by the reduced expression of IEGs in the hippocampus and prefrontal cortex.

CONCLUSION

Our findings provide the first evidence that SIK1 affects gene regulation in neuronal hyperactivity, which is involved in seizure behavior. Targeting SIK1 through the development of selective inhibitors may lead to disease-modifying therapies that reduce epilepsy progression.

Betaine prevents cognitive dysfunction by suppressing hippocampal microglial activation in chronic social isolated male mice

Chronic social isolation (SI) stress, which became more prevalent during the COVID-19 pandemic, contributes to abnormal behavior, including mood changes and cognitive impairment. Known as a functional nutrient, betaine has potent antioxidant and anti-inflammatory properties in vivo. However, whether betaine can alleviate the abnormal behavior induced by chronic SI in mice remains unknown. In this study, we investigated the efficacy of betaine in the treatment of behavioral changes and its underlying mechanism. Three-week-old male mice were randomly housed for 8 weeks in either group housing (GH) or SI. The animals were divided into normal saline-treated GH, normal saline-treated SI, and betaine-treated SI groups in the sixth week. The cognitive and depression-like behavior was determined in the eighth week. We found that long-term betaine administration improved cognitive behavior in SI mice but failed to prevent depression-like behavior. Moreover, long-term betaine administration inhibited hippocampal microglia over-activation and polarized microglia toward the M2 phenotype, which effectively inhibited the expression of inflammatory factors in SI mice. Finally, the protective effect of betaine treatment in SI mice might not be due to altered activity of the hypothalamic-pituitary-adrenal axis. Collectively, our findings reveal that betaine can improve SI-induced cognitive impairment, thus providing an alternative natural source for the prevention of memory loss caused by SI or loneliness.

The anterior olfactory nucleus revisited - an emerging role for neuropathological conditions?

Olfaction is an important sensory modality for many species and greatly influences animal and human behavior. Still, much about olfactory perception remains unknown. The anterior olfactory nucleus is one of the brain's central early olfactory processing areas. Located directly posterior to the olfactory bulb in the olfactory peduncle with extensive in- and output connections and unique cellular composition, it connects olfactory processing centers of the left and right hemispheres. Almost 20 years have passed since the last comprehensive review on the anterior olfactory nucleus has been published and significant advances regarding its anatomy, function, and pathophysiology have been made in the meantime. Here we briefly summarize previous knowledge on the anterior olfactory nucleus, give detailed insights into the progress that has been made in recent years, and map out its emerging importance in translational research of neurological diseases.

ChAT::Cre transgenic rats show sex-dependent altered fear behaviors, ultrasonic vocalizations and cholinergic marker expression

The cholinergic system is a critical regulator of Pavlovian fear learning and extinction. As such, we have begun investigating the cholinergic system's involvement in individual differences in cued fear extinction using a transgenic ChAT::Cre rat model. The current study extends behavioral phenotyping of a transgenic ChAT::Cre rat line by examining both freezing behavior and ultrasonic vocalizations (USVs) during a Pavlovian cued fear learning and extinction paradigm. Freezing, 22 kHz USVs, and 50 kHz USVs were compared between male and female transgenic ChAT::Cre+ rats and their wildtype (Cre-) littermates during fear learning, contextual and cue-conditioned fear recall, cued fear extinction, and generalization to a novel tone. During contextual and cued fear recall ChAT::Cre+ rats froze slightly more than their Cre- littermates, and displayed significant sex differences in contextual and cue-conditioned freezing, 22 kHz USVs, and 50 kHz USVs. Females showed more freezing than males in fear recall trials, but fewer 22 kHz distress calls during fear learning and recall. Females also produced more 50 kHz USVs during exposure to the testing chambers prior to tone (or shock) presentation compared with males, but this effect was blunted in ChAT::Cre+ females. Corroborating previous studies, ChAT::Cre+ transgenic rats overexpressed vesicular acetylcholine transporter immunolabeling in basal forebrain, striatum, basolateral amygdala, and hippocampus, but had similar levels of acetylcholinesterase and numbers of ChAT+ neurons as Cre- rats. This study suggests that variance in behavior between ChAT::Cre+ and wildtype rats is sex dependent and advances theories that distinct neural circuits and processes regulate sexually divergent fear responses.

Spinal cord from body donors is suitable for multicolor immunofluorescence

Immunohistochemistry is a powerful tool for studying neuronal tissue from humans at the molecular level. Obtaining fresh neuronal tissue from human organ donors is difficult and sometimes impossible. In anatomical body donations, neuronal tissue is dedicated to research purposes and because of its easier availability, it may be an alternative source for research. In this study, we harvested spinal cord from a single organ donor 2 h (h) postmortem and spinal cord from body donors 24, 48, and 72 h postmortem and tested how long after death, valid multi-color immunofluorescence or horseradish peroxidase (HRP) immunohistochemistry is possible. We used general and specific neuronal markers and glial markers for immunolabeling experiments. Here we showed that it is possible to visualize molecularly different neuronal elements with high precision in the body donor spinal cord 24 h postmortem and the quality of the image data was comparable to those from the fresh organ donor spinal cord. High-contrast multicolor images of the 24-h spinal cords allowed accurate automated quantification of different neuronal elements in the same sample. Although there was antibody-specific signal reduction over postmortem intervals, the signal quality for most antibodies was acceptable at 48 h but no longer at 72 h postmortem. In conclusion, our study has defined a postmortem time window of more than 24 h during which valid immunohistochemical information can be obtained from the body donor spinal cord. Due to the easier availability, neuronal tissue from body donors is an alternative source for basic and clinical research.

Targeting PERK mediated endoplasmic reticulum stress attenuates neuroinflammation and alleviates lipopolysaccharide-induced depressive-like behavior in male mice

Neuroinflammation plays a key role in the development of depression-like behaviors.Endoplasmic reticulum (ER) stress,defined as accumulation of unfolded proteins in the ER,is suggested tocollaboratewithinflammation process to drive sustained neuroinflammation. Protein kinase R-like endoplasmic reticulum kinase (PERK) is ofparticularly attractive target because it plays key rolein the regulation of ER stress-induced neuroinflammation, however, little isknown whether PERKmediatedER stress is implicated in LPS-induced depression-like behaviors.Thus, we aimed to evaluate the induction of PERK pathwayin mice with depression-like behaviors induced by LPS, as well as the alterations in depression-like behaviorsfollowing the blocking of PERK pathway.We found that LPS challenges resulted in enhanced PERK in the hippocampus, with no alteration in the prefrontal cortex. Importantly, we found that PERKinhibitorISRIB reducedthe proinflammatory responsesof microglia in the context of acute LPS-induced brain inflammation, and subsequent the preserved hippocampal neurogenesis, and improvement in depression-like behavioroutcomes following LPS challenges.It was also worth mentioning thatISRIB treatmentreduced the peripheral pro-inflammatory cytokines includingIL-1β, IL-6 and IL-18. Thus, targetingPERK mediated Endoplasmic reticulum stress may be a promising antidepressant and anti-inflammatory candidate drug for the alleviation of neuroinflammationmediated depression, and PERKinhibitorISRIBmay havebenefits for combating major depressive disorder.

TRPV4 inhibitor HC067047 produces antidepressant-like effect in LPS-induced depression mouse model

Inflammation is a crucial component that contributes to the pathogenesis of major depressive disorder. It has been revealed that the nonselective cation channel transient receptor potential vanilloid 4 (TRPV4) profoundly affects a variety of physiological processes, including inflammation. However, its roles and mechanisms in LPS-induced depression are still unclear. Here, for the first time, we found that there was a significant increase in TRPV4 in the hippocampus in a depression mouse model induced by LPS. TRPV4 inhibitor HC067047 or knockdown the hippocampal TRPV4 with TRPV4 shRNA could effectively rescue the aberrant behaviors. Furthermore, TRPV4 inhibitor HC067047 reduced the activation of astrocyte and microglia, decreased expression of CaMKII-NLRP3 inflammasome and increased the expression of neurogenesis marker DCX in the hippocampus. In addition, enhanced neuroinflammation in the serum was also reversed by TRPV4 inhibitor HC067047. Thus, we consider that TRPV4 has an important role in contributing to the depression-like behavior following LPS-induced systemic inflammation.