Adult Mice Research Articles

Intriguing astrocyte responses in CA1 to reduced and rehabilitated masticatory function: Dorsal and ventral distinct perspectives in adult mice

ObjectiveWe sought to investigate the plasticity of diet-induced changes in astrocyte morphology of stratum lacunosum-moleculare (SLM) in CA1. DesignThree diet regimes were adopted in 15 mice, from the 21st postnatal day to 6 months. The first diet regimen was pellet feed, called Hard Diet (HD). The second, with reduced masticatory, received a pellet-diet followed by a powdered-diet, and it was identified as Hard Diet/Soft Diet (HD/SD). Finally, the group with rehabilitated masticatory was named Hard Diet/Soft Diet/Hard Diet (HD/SD/HD). In the end, euthanasia and brain histological processing were performed, in which astrocytic immunoreactivity to glial-fibrillary-acidic-protein (GFAP) was tested. In reconstructed astrocytes, morphometric analysis was performed. ResultsAstrocyte morphometric revealed that changes in masticatory regimens impact astrocyte morphology. In the dorsal CA1, switching from a hard diet to a soft diet led to reductions in most variables, whereas in the ventral, fewer variables were affected, highlighting regional differences in astrocyte responses. Cluster analysis further showed that diet-induced changes in astrocyte morphology were reversible in the dorsal region, but not in the ventral region, indicating a persistent impact on astrocyte diversity and complexity in the ventral even after rehabilitation. Correlation tests between astrocyte morphology and behavioral performance demonstrated disrupted relationships under masticatory stress, with effects persisting after rehabilitation. ConclusionChanges in the diet result in significant alterations in astrocyte morphology, suggesting a direct link between dietary modulation and cellular structure. Morphometric analyses revealed distinct alterations in astrocyte morphology in response to changes in the masticatory regimen, with both dorsal/ventral regions displaying notable changes. Moreover, the regional differential effects on astrocytes underscore the complexity of mastication on neuroplasticity and cognitive function.

8780 The Role of Nuclear Receptor Corepressors 1 and 2 on Intestinal Carbohydrate Transport in Mice

Abstract Disclosure: M.J. Ritter: None. I. Amano: None. A.H. van der Spek: None. H.E. Daniel: None. A.N. Hollenberg: None. The nuclear receptor corepressors NCoR1 and NCoR2 are two critical regulators of metabolism that are required for maintaining metabolic homeostasis. Both NCoR1 and NCoR2 (also known as the silencing mediator of retinoic acid and thyroid hormone receptors; SMRT) recruit histone deacetylase 3 (HDAC3) to their deacetylase domain (DAD) to repress nuclear receptor (NR) target gene expression. Interruption of the DAD of NCoR1 in mice leads to lower body weight, decreased whole-body fat mass, insulin sensitization with altered oscillatory patterns of key metabolic genes (1). On the other hand, total body knock-out (KO) of SMRT leads to weight gain, insulin resistance, and hepatic steatosis with an increase in hepatic lipogenesis (2). Previously, we showed that the KO of NCoR1 and SMRT in tandem from adult mice led rapidly to weight loss, hypoglycemia, hypothermia and was lethal. Reductions in intestinal carbohydrate transporters were seen, including sodium-glucose linked transporter-1 (SGLT1), glucose transporter 2 (GLUT2), and glucose transporter 5 (GLUT5) (3). Thus, we hypothesized that NCoR1 and SMRT play unique roles in regulating intestinal carbohydrate metabolism, in turn controlling metabolic parameters including body mass and glucose levels. We then generated a novel model to enable KO of NCoR1 and SMRT throughout intestinal epithelial cells (IECs) in adult mice using a tamoxifen inducible cre under control of the villin 1 promoter. Mice were injected with tamoxifen and body weight and glucose were monitored daily. This was followed by both oral and intraperitoneal glucose tolerance testing (GTT) and metabolic phenotyping. Preliminary data showed that NCoR1 and SMRT KO leads to sustained weight loss and hypoglycemia with 50% survivability. Metabolic phenotyping confirmed reduction in body mass without concomitant reduction in food intake. Oral GTT showed a blunted peak in response to glucose gavage compared to intraperitoneal administration. Gene expression analysis showed reduction in SGLT1, GLUT2, and GLUT5 in addition to changes in metabolic pathways associated with fatty acid metabolism. Here, we show that NCoR1 and SMRT are critical regulators of body mass and glucose in part via their actions on carbohydrate transporters in the intestine. With the global burden of metabolic diseases, including obesity and diabetes, ever-rising, NCoR1 and SMRT represent an overlooked but important area of study to better our understanding of disease processes and identify new targets for treatment. We next aim to determine the functional mechanism by which weight loss and hypoglycemia develop in addition to identifying molecular targets and pathways regulated by NCoR1 and SMRT in IECs.

The activity of suprahyoid muscles during sevoflurane-induced gasping in mice

Sevoflurane-induced gasping in mice involves an enormous increase in inspiratory effort, mandibular movement, and a marked decrease in respiratory frequency (fR). We examined differences in breathing patterns and electromyogram activity (EMGSH) of the suprahyoid muscles (SHMs) during eupnea under 3.2 % (1 MAC: minimum alveolar concentration) sevoflurane inhalation and sevoflurane-induced gasping under 6.5 % (2 MAC) sevoflurane inhalation in eight spontaneously breathing, tracheally intubated, adult mice. We found that the phasic EMGSH is obtained only during inspiration in eupnea and gasping and that integrated EMGSH increases more, as a percent of baseline (% baseline) than tidal volume (VT) during gasping (median [interquartile range]; integrated EMGSH: 720 [425–1965] vs. VT: 300 [238–373], P < 0.05). We also found that the onset of EMGSH precedes the start of airflow while maintaining a bell-shaped EMGSH contour, which characterizes the EMG of upper airway dilator (UAD) muscles during eupnea and gasping. Vigorous respiratory-related mandibular movements were never observed during eupnea but were observed in seven of 8 mice during sevoflurane-induced gasping. Our observations indicate that SHMs act as a preferentially activating UAD muscle, contributing to the development of mandibular respiratory movements.

7996 Neuroanatomic Characterization of Mouse Kisspeptin Neurons in the Bed Nucleus of the Stria Terminalis

Abstract Disclosure: S.T. Zdon: None. M.S. Silva: None. V.M. Navarro: None. Kisspeptin (Kiss1) neurons are essential for reproductive function as they are strong regulators of the hypothalamic-pituitary-gonadal axis (HPG). Mammalian Kiss1 neurons are mainly located in the hypothalamus, controlling gonadotropin-releasing hormone (GnRH) secretion, where the anteroventral periventricular nucleus (AVPV) population is morphologically and functionally sexually differentiated. Kiss1 neurons are also found in limbic areas, such as the bed nucleus of the stria terminalis (BNST). This nucleus is involved in the integration of the HPG axis with sex-dependent social behaviors and metabolic functions. However, it remains unclear whether these populations show sexually dimorphic features. The present study focused on the neuroanatomical characterization of Kiss1BNST neurons in mice on both sexes. A Kiss1cre;salsa6f mouse strain carrying the expression of tdTomato specifically in Kiss1 neurons was used to study the distribution of Kiss1BNST neurons. The BNST is divided into the anterior division of the BNST (aBNST), and a more posterior division called the principal component of the BNST (prBNST). Results indicate that male mice have significantly more Kiss1prBNST neurons than females (Male: 139.4 ± 23.32 vs. Female: 43.70 ± 5.33 neurons; **P &amp;lt; 0.01). This sex-biased distribution was absent in Kiss1aBNST neurons. Additionally, stereotaxically injecting a Cre-dependent recombinant adenovirus carrying the expression of mCherry reporter into the aBNST or prBNST in adult mice was performed to observe neuronal projections. We observed fibers from aBNST-injected Kiss1 neurons projecting widely to areas that include the AVPV, medial preoptic area (MPO), lateral preoptic area (LPO), and periventricular hypothalamic nucleus (PVH). Moreover, fibers and cell bodies from male prBNST-injected Kiss1 neurons projected to dorsal lateral BNST (dlBNST), juxta-periventricular lateral hypothalamic area (JPLH), and the posterolateral stria terminalis (STMPL). This study observed a sexual dimorphic Kiss1 neuronal population in the prBNST, with males having more Kiss1prBNST neurons present and prospective postsynaptic areas in the brain where these neurons project to, helping to aid future studies on characterizing the functional role of these neurons. Presentation: 6/1/2024

7381 Overexpression of Makorin Ring Finger Protein 3 in the Arcuate Nucleus of Postpubertal Female Mice Impacts Neurokinin B and Kisspeptin Co-Expressing Neurons

Abstract Disclosure: S.A. Roberts: None. A. Fontes: None. S. Blau: None. M. Magnuson: None. K.M. McKnight: None. M. Sena-Esteves: None. R.S. Carroll: None. U.B. Kaiser: None. Background: Makorin ring finger protein 3 (MKRN3), an upstream inhibitor of GnRH release, is an important regulator of the age of menarche. Loss-of-function mutations in MKRN3 are the most common genetic etiology of central precocious puberty. However, its potential role in delayed puberty or hypogonadism is not well defined. In mice, expression of Mkrn3 in the hypothalamic arcuate nucleus (ARC), where kisspeptin, neurokinin B and dynorphin (KNDy) co-expressing neurons are located, is high early in life and declines before pubertal onset. Neonatal hypothalamic overexpression of Mkrn3 leads to delayed puberty in female mice and decreased neurokinin B (NKB) and kisspeptin protein levels in the ARC peripubertally. Conversely, Mkrn3-deficient peripubertal mice exhibit increased NKB protein levels in the ARC. We hypothesized that Mkrn3 overexpression in the ARC of postpubertal female mice would result in suppression of the HPG axis, manifested as hypogonadotropic hypogonadism. Methods and Results: Twelve week old adult wild type female mice were injected stereotaxically into the ARC with a novel adeno-associated virus overexpressing Mkrn3 (AAV-Mkrn3-IRES-EGFP; denoted AAV-Mkrn3) or a control virus (AAV-EGFP). Mean body weight did not differ between groups post-injection. AAV-Mkrn3 injected mice spent significantly more time (62.7%) in diestrus three to six weeks post-injection compared to controls (41.3%; P&amp;lt;0.01). Eight weeks post-injection, gonad-intact females were injected with an NKB receptor (NK3R) agonist, senktide (5 nmol or 10 nmol ip). AAV-Mkrn3 mice had a decreased peak LH response twenty minutes post-injection, compared to controls (P&amp;lt;0.001) at both doses. Peak LH levels were also reduced in response to senktide (5 nmol ip) in ovariectomized and estradiol capsule replaced (OVX+E2) AAV-Mkrn3 injected females, compared to controls (P&amp;lt; 0.001). In contrast, in both gonad-intact and OVX+E2 female mice, kisspeptin-10 (1 nmol ip) resulted in similar peak serum LH levels in AAV-Mkrn3 injected mice compared to controls. Immunohistochemistry in the ARC of intact and OVX+E2 AAV-Mkrn3 injected females showed significantly decreased NKB protein expression in AAV-Mkrn3 mice compared to controls. In response to OVX, serum LH levels increased similarly between AAV-Mkrn3 and control-injected mice. LH pulsatility in OVX females, assessed over 3 hours, showed that mean basal LH levels, number of pulses, pulse amplitude and area under the curve did not differ significantly between groups. Conclusions: These findings indicate that MKRN3 can exert inhibitory effects on the reproductive axis in female mice beyond the juvenile period, which has implications as a potential therapeutic target. The blunted response to senktide, and decreased NKB protein levels in the setting of Mkrn3 overexpression, further supports the impact of Mkrn3 on the neuropeptides and/or receptors of KNDy neurons. Presentation: 6/2/2024

Astrocytic neuroligin 3 regulates social memory and synaptic plasticity through adenosine signaling in male mice

Social memory impairment is a key symptom of many brain disorders, but its underlying mechanisms remain unclear. Neuroligins (NLGs) are a family of cell adhesion molecules essential for synapse development and function and their dysfunctions are linked to neurodevelopmental and neuropsychiatric disorders, including autism and schizophrenia. Although NLGs are extensively studied in neurons, their role in glial cells is poorly understood. Here we show that astrocytic deletion of NLG3 in the ventral hippocampus of adult male mice impairs social memory, attenuates astrocytic Ca2+ signals, enhances the expression of EAAT2 and prevents long-term potentiation, and these impairments are rescued by increasing astrocyte activity, reducing EAAT2 function or enhancing adenosine/A2a receptor signaling. This study has revealed an important role of NLG3 in astrocyte function, glutamate homeostasis and social memory and identified the glutamate transporter and adenosine signaling pathway as potential therapeutic strategies to treat brain disorders.

8134 Hypothalamic Dlk1 Expression is Not Essential for Preventing Early Maturation of the Reproductive Axis in Female and Male Mice

Abstract Disclosure: D.B. Macedo: None. H. Kim Kyeol: None. A. Abreu: None. A. Latronico: None. R.S. Carroll: None. U.B. Kaiser: None. Background and Objectives: Inactivating mutations in Delta-like homolog 1 (DLK1), a maternally imprinted gene on chromosome 14, have been recognized as a genetic cause of central precocious puberty (CPP) in humans. It is well established that the timing of puberty, especially in females, is highly sensitive to energy stores and metabolic cues, with lower body fat negatively correlated with age at puberty and menarche. Mice lacking Dlk1 have pre- and postnatal growth retardation. Despite their considerably lower body weight (BW), we found that Dlk1 deficient females achieved puberty at the same age as controls (‘relative precocious puberty’). Moreover, Dlk1 deficiency led to activation of the reproductive axis despite lower levels of kisspeptin and leptin, an adipose tissue hormone with a permissive/stimulatory effect on metabolic control of reproduction. Dlk1 is a transmembrane protein that plays an essential role in inhibiting adipocyte differentiation and its biologically active form is soluble. Increased hypothalamic expression postnatally suggests a neuroendocrine function, but the precise mechanism by which DLK1 deficiency leads to CPP is yet to be deciphered. In this study, we aimed to investigate the role of hypothalamic Dlk1 expression on pubertal onset without the interference of diminished BW, using a conditional knockout (cKO) mouse model. Methods and Results: We generated a targeted Dlk1 knockout mouse model by crossing mice expressing Cre recombinase under the control of Nestin gene (Nes Cre), expressed primarily in neuro-epithelial cells, with mice harboring the Dlk1 gene flanked by loxP sites (Dlk1fl). Since Dlk1 is imprinted and expressed only by the paternal allele, we bred heterozygous Dlk1fl/+ male mice with Nes Cre females to obtain Dlk1fl/Cre (Dlk1 cKO), Dlk1+/Cre (Nes Cre) and Dlk1+/+ (wild type - WT). We confirmed by RT-qPCR that Dlk1 mRNA was undetectable in the mediobasal hypothalamus of Dlk1 cKO adult male mice, whereas it was present in Nes Cre and WT mice. We noted a lower BW in Nes Cre compared to WT mice, as previously reported. However, no difference in BW was observed between Dlk1 cKO and Nes Cre mice at the timing of puberty (females: Dlk1 cKO 12.6 ± 0.8 g vs. Nes Cre 13.8 ± 0.2 g, P = 0.18; males: Dlk1 cKO 12.4 ± 0.2 g vs. Nes Cre 13.1 ± 0.5 g, P = 0.26). Puberty onset, assessed by age at vaginal opening (females) and at preputial separation (males), was not affected by hypothalamic Dlk1 deletion (Dlk1 cKO: 35.6 ± 2.7 days vs. Nes Cre 34.6 ± 0.7 days, P = 0.73; Dlk1 cKO 29.0 ± 0.6 vs. Nes Cre: 30.3 ± 0.6 days, P = 0.19). Conclusion: In contrast to global Dlk1 deficiency, targeted deletion of Dlk1 from neuronal and glial cells did not affect body weight or timing of pubertal onset. These findings suggest that Dlk1 originates from peripheral tissues, such as adipocytes, to regulate reproduction and metabolism. Presentation: 6/1/2024

7662 Mass Spectrometry Imaging Reveals Region-, Age-, And Sex-Specific Effects Of Lipopolysaccharide Administration On Glucocorticoids In Mouse Lymphoid Organs

Abstract Disclosure: M. Salehzadeh: None. S. Khan: None. R. Andrew: None. K.K. Soma: None. Glucocorticoids (GCs) are steroids that are critical for immune function. Immune organs, such as the thymus and spleen, locally produce GCs (i.e., immunosteroids). However, GC concentrations in the thymus and spleen at the cellular level, and how these levels are affected by stress, remain largely unknown. We used state-of-the-art mass spectrometry imaging (MSI) to elucidate the spatial distribution of GCs in the neonatal and adult mouse thymus and spleen 1) at baseline and 2) after an acute stressor. We used MSI to measure 11-deoxycorticosterone (DOC), corticosterone, and 11-dehydrocorticosterone (DHC) in different regions of the thymus (medulla/cortex) and spleen (white/red pulp) after an immunological challenge. We administered lipopolysaccharide (LPS; i.p.) at low (50μg/kg) and high (400μg/kg) doses or saline (vehicle) to male and female C57BL/6J mice at post-natal day (PND) 5 (neonatal) and 90 (adult) (n=6/sex/group/age). 4hr after treatment, we collected thymus and spleen on liquid nitrogen. Cryosections (10μm) were subject to MSI following Girard-T reagent derivatization and α-cyano-4-hydroxycinnamic acid matrix application. Matrix assisted laser desorption/ionisation (MALDI) was used for sampling, coupled to Fourier-transform ion cyclotron mass spectrometry (100μm resolution; positive mode; Bruker 12T SolariX). Adjacent sections were taken to determine histological zones by H&amp;E staining. Preliminary results indicate that LPS increased DOC, corticosterone, and DHC levels by 2- to 9-fold in lymphoid organs at both ages. There was a dose-dependent increase in thymus and spleen GC levels at PND5, but not PND90. At PND5, GC levels were similarly distributed across each tissue in both sexes. In contrast, at PND90, thymic corticosterone levels were greater in males than females in the medulla and cortex. Interestingly, in PND90 thymus, the medulla had greater DHC levels than the cortex only after LPS treatments. In PND90 spleen, GC levels significantly increased after LPS, yet there was no significant difference in GC distribution between sexes or red and white pulp. These results suggest that GC production is uniform across neonatal lymphoid organs. However, in adulthood, the thymus exhibits region-specific GC metabolism. Our results expand knowledge of steroid intracrinology in thymus and spleen and potential effects of environmental stressors (e.g., infectious diseases, toxins) on immune GC responses. Further, our novel MSI method for GC detection in murine lymphoid organs can help inform future techniques in pharmacokinetics for localized thymic and splenic targeting of steroids and steroid modulators. Presentation: 6/3/2024

8650 Co-Localization Pattern of Snhg14 Long Noncoding RNA and Nhlh2 mRNA in Hypothalamus Coincides with Obesity and Endocrine Impairment Phenotypes in Prader-Willi Syndrome

Abstract Disclosure: S. Ariyanfar: None. C.K. Thompson: None. S. Tobet: None. D.J. Good: None. Prader–Willi syndrome (PWS) is a multisystemic neurodevelopmental disorder, characterized by biphasic symptoms, including diminished weight gain during development, along with neonatal hypotonia and failure to thrive, with later onset hyperphagia, severe weight gain, and morbid obesity. PWS arises from the deletion or inactivation of paternally inherited genes, with the smallest region encompassing a group of 30 small nucleolar RNAs ‘snoRNAs’ known as the SNORD116@ locus. SNORD116@ snoRNAs are cleaved from a larger long non-coding gene, SNHG14. Whole-body deletion of Nhlh2 in mice results in PWS-like phenotypes, such as later onset weight gain, and delayed puberty. We previously have shown that overexpression of Snord116-3 in a mouse hypothalamic cell line improves the stability of Nhlh2 mRNA, likely through a motif in the 3’ untranslated region of the Nhlh2 mRNA. This motif can be disrupted by the presence of a single nucleotide polymorphism, confirming the mechanism of action. Nevertheless, to date, no published studies are showing the in vivo co-localization between Nhlh2 and Snord116 (or its host gene, Snhg14), and the question of where and when Snord116 snoRNAs interact with target mRNA Nhlh2 remains unanswered. To fill this gap, we mapped simultaneous expression of Snhg14 and Nhlh2 throughout the adult mouse brain, using quantitative RNA multi-plex in situ hybridization “RNAScope”. In our initial analysis, we focused on Pomc neurons of the hypothalamus as targeted deletion of Nhlh2 in these neurons results in obesity levels similar to that of the whole body deletion of Nhlh2, a present phenotype in PWS. Our data for the first time showed the co-expression of Nhlh2 and Snhg14 in Pomc neurons of Arcuate nucleus. In the analysis of 54 Pomc neurons, 72% and 39% were positive for Nhlh2 and Snhg14 expression respectively, with 39% of detected signals co-expressed in the same cell (correlation coefficient 0.78, P &amp;lt; 0.0001). Interestingly, in neurons that only expressed Nhlh2 (33) there were nearly evenly distributed signals in the cytoplasm (9 cells) and nucleus (10 cells). When both Nhlh2 and Snhg14 messages were coexpressed, 17 of the 21 cells expressed Nhlh2 in the nucleus only (P &amp;lt; 0.0003, P&amp;lt; 0.0007 for the Likelihood ratio test and Chi-square test, respectively). Thus, based on the high magnification cell analysis, acquired 3D images, and probe location, we can conclude that the Snhg14 host transcript and Nhlh2 interact spatially. This new in vivo data supports the previously shown regulatory role for Snord 116 snoRNAs towards Nhlh2 mRNA stability and suggests that regulation may involve nuclear sequestration of Nhlh2. We are currently extending our studies to examine expression in the brains from patients with PWS and determine if energy balance signals affect co-localization patterns within the hypothalamus. Presentation: 6/3/2024

Comparative proteomic analysis of regenerative mechanisms in mouse retina to identify markers for neuro-regeneration in glaucoma

The retina is part of the central nervous system (CNS). Neurons in the CNS and retinal ganglion cells lack the ability to regenerate axons spontaneously after injury. The intrinsic axonal growth regulators, their interaction and roles that enable or inhibit axon growth are still largely unknown. This study endeavored to characterize the molecular characteristics under neurodegenerative and regenerative conditions. Data-Independent Acquisition Mass Spectrometry was used to map the comprehensive proteome of the regenerative retina from 14-day-old mice (Reg-P14) and adult mice after lens injury (Reg-LI) both showing regrowing axons in vitro, untreated adult mice, and retina from adult mice subjected to two weeks of elevated intraocular pressure showing degeneration. A total of 5750 proteins were identified (false discovery rate < 1%). Proteins identified in both Reg-P14 and Reg-LI groups were correlated to thyroid hormone, Notch, Wnt, and VEGF signaling pathways. Common interactors comprising E1A binding protein P300 (EP300), CREB binding protein (CBP), calcium/calmodulin dependent protein kinase II alpha (CaMKIIα) and sirtuin 1 (SIRT1) were found in both Reg-P14 and Reg-LI retinas. Proteins identified in both regenerating and degenerative groups were correlated to thyroid hormone, Notch, mRNA surveillance and measles signaling pathways, along with PD-L1 expression and the PD-1 checkpoint pathway. Common interactors across regenerative and degenerative retinas comprising NF-kappa-B p65 subunit (RELA), RNA-binding protein with serine-rich domain 1 (RNPS1), EP300 and SIN3 transcription regulator family member A (SIN3A). The findings from our study provide the first mapping of regenerative mechanisms across postnatal, mature and degenerative mouse retinas, revealing potential biomarkers that could facilitate neuro-regeneration in glaucoma.

Juruaça virus taxonomy, tolerance and resistance to infection, and inflammatory response modulation in murine model

Juruaça virus (JUAV), previously unclassified, was isolated from bats and administered to neonatal and adult BALB/c mice to investigate acute and chronic disease progression. In this study, we conducted genomic sequencing to achieve taxonomic classification and utilized these models to explore the inflammatory response and sickness behavior in both neonatal and adult mice. Neonates received a single intranasal instillation of infected brain homogenate (20 µL), whereas 31-day-old mice were given the same volume intranasally for three consecutive days. Control groups were administered equal volumes of uninfected brain homogenate. Our findings reveal that intranasal JUAV infection-induced acute meningoencephalitis and death in neonates, while adult mice exhibited chronic infection with variable clinical signs, inflammatory mediator production, histopathological changes, and neuropathological features. Interestingly, only some adult mice showed sickness behavior post-infection, and among these, a subset continued to decline and die. The differential tissue damage observed in mice with and without overt disease symptoms suggests mechanisms of resistance or tolerance, where exceeding tolerance capacity resulted in pathological outcomes, including chronic dysfunction or death. This study provides the first evidence of JUAV’s capability to infect mammals, demonstrating its distinct impact on bats and variable effects in neonatal and adult mice. We provisionally classified JUAV as closely related to the clade containing tombus-like virus 6 found in mute swan feces. Our research highlights the importance of understanding viral–host interactions and the inflammatory responses that contribute to disease variability, offering insights into tolerance and resistance mechanisms based on inflammatory response modulation.

Effects of PACAP Deficiency on Immune Dysfunction and Peyer's Patch Integrity in Adult Mice.

PACAP (pituitary adenylate cyclase activating polypeptide) is a widespread neuropeptide with cytoprotective and anti-inflammatory effects. It plays a role in innate and adaptive immunity, but data are limited about gut-associated lymphoid tissue. We aimed to reveal differences in Peyer's patches between wild-type (WT) and PACAP-deficient (KO) mice. Peyer's patch morphology from young (3-months-old) and aging (12-15-months-old) mice was examined, along with flow cytometry to assess immune cell populations, expression of checkpoint molecules (PD-1, PD-L1, TIM-3, Gal-9) and functional markers (CD69, granzyme B, perforin) in CD3+, CD4+, and CD8+ T cells. We found slight differences between aging, but not in young, WT, and KO mice. In WT mice, aging reduced CD8+ T cell numbers frequency and altered checkpoint molecule expression (higher TIM-3, granzyme B; lower Gal-9, CD69). CD4+ T cell frequency was higher with similar checkpoint alterations, indicating a regulatory shift. In PACAP KO mice, aging did not change cell population frequencies but led to higher TIM-3, granzyme B and lower PD-1, PD-L1, Gal-9, and CD69 expression in CD4+ and CD8+ T cells, with reduced overall T cell activity. Thus, PACAP deficiency impacts immune dysfunction by altering checkpoint molecules and T cell functionality, particularly in CD8+ T cells, suggesting complex immune responses by PACAP, highlighting its role in intestinal homeostasis and potential implications for inflammatory bowel diseases.

Protein kinase R induced by type I interferons is a main regulator of reactive microglia in Zika virus infection.

Microglial cells are the phagocytic cells of the brain that under physiological conditions participate in brain homeostasis and surveillance. Under pathogenic states, microglia undergoes strong morphological and transcriptional changes potentially leading to sustained neuroinflammation, brain damage, and cognitive disorders. Postnatal and adult Zika virus (ZIKV) brain infection is characterized by the induction of reactive microglia associated with brain inflammation, synapse loss and neuropathogenesis. Contrary to neurons, microglial cells are not infected by ZIKV thus raising the question of the mechanism governing ZIKV-induced microglia's reactivity. In this work, we have questioned the role of exogenous, neuronal type I interferons (IFNs-I) in regulating ZIKV-induced microglia's reactivity. Primary cultured microglial cells were either treated with conditioned media from ZIKV-infected mature neurons or co-cultured with ZIKV-infected neurons. Using either an antibody directed against the IFNAR receptor that neutralizes the IFNs-I response or Ifnar-/-microglial cells, we demonstrate that IFNs-I produced by ZIKV-infected neurons are the main regulators of the phagocytic capacity and the pro-inflammatory gene expression profile of reactive, non-infected microglial cells. We identify protein kinase R (PKR), whose expression is activated by IFNs-I, as a major regulator of the phagocytic capacity, pro-inflammatory response, and morphological changes of microglia induced by IFNs-I while up-regulating STAT1 phosphorylation and IRF1 expression. Results obtained herein in vitro with primary cultured cells and in vivo in ZIKV-infected adult immunocompetent mice, unravel a role for IFNs-I and PKR in directly regulating microglia's reactivity that could be at work in other infectious and non-infectious brain pathologies.

An atlas of the aging mouse proteome reveals the features of age-related post-transcriptional dysregulation

To what extent and how post-transcriptional dysregulation affects aging proteome remains unclear. Here, we provide proteomic data of whole-tissue lysates (WTL) and low-solubility protein-enriched fractions (LSF) of major tissues collected from mice of 6, 15, 24, and 30 months of age. Low-solubility proteins are preferentially affected by age and the analysis of LSF doubles the number of proteins identified to be differentially expressed with age. Simultaneous analysis of proteome and transcriptome using the same tissue homogenates reveals the features of age-related post-transcriptional dysregulation. Post-transcriptional dysregulation becomes evident especially after 24 months of age and age-related post-transcriptional dysregulation leads to accumulation of core matrisome proteins and reduction of mitochondrial membrane proteins in multiple tissues. Based on our in-depth proteomic data and sample-matched transcriptome data of adult, middle-aged, old, and geriatric mice, we construct the Mouse aging proteomic atlas (https://aging-proteomics.info/), which provides a thorough and integrative view of age-related gene expression changes.

Nitrous oxide induces hypothermia and TrkB activation: Maintenance of body temperature abolishes antidepressant-like effects in mice

Recent studies indicate that nitrous oxide (N2O), a gaseous anesthetic and an NMDA (N-methyl-D-aspartate) receptor antagonist, produces rapid antidepressant effect in patients suffering from treatment-resistant depression. Our recent work implies that hypothermia and reduced energy expenditure are connected with antidepressant-induced activation of TrkB neurotrophin receptors — a key regulator of synaptic plasticity. In this study, we demonstrate that a brief exposure to N2O leads to a drop in body temperature following the treatment, which is linked to decreased locomotor activity; enhanced slow-wave electroencephalographic activity; reduced brain glucose utilization; and increased phosphorylation of TrkB, GSK3β (glycogen synthase kinase 3β), and p70S6K (a kinase downstream of mTor (mammalian target of rapamycin)) in the medial prefrontal cortex of adult male mice. Moreover, preventing the hypothermic response in a chronic corticosterone stress model of depression attenuated the antidepressant-like behavioral effects of N2O in the saccharin preference test. These findings indicate that N2O treatment modulates TrkB signaling and related neurotrophic signaling pathways in a temperature-dependent manner, suggesting that the phenomenon driving TrkB activation — altered thermoregulation and energy expenditure — is linked to antidepressant-like behavioral responses.

The Organism as the Niche: Physiological States Crack the Code of Adult Neural Stem Cell Heterogeneity.

Neural stem cells (NSCs) persist in the adult mammalian brain and are able to give rise to new neurons and glia throughout life. The largest stem cell niche in the adult mouse brain is the ventricular-subventricular zone (V-SVZ) lining the lateral ventricles. Adult NSCs in the V-SVZ coexist in quiescent and actively proliferating states, and they exhibit a regionalized molecular identity. The importance of such spatial diversity is just emerging, as depending on their position within the niche, adult NSCs give rise to distinct subtypes of olfactory bulb interneurons and different types of glia. However, the functional relevance of stem cell heterogeneity in the V-SVZ is still poorly understood. Here, we put into perspective findings highlighting the importance of adult NSC diversity for brain plasticity, and how the body signals to brain stem cells in different physiological states to regulate their behavior.

Age-dependent changes in visceral adiposity are associated with decreased plasma levels of DHEA-S in sigma-1 receptor knockout male mice

The sigma-1 receptor (S1R) is involved in intracellular lipid synthesis and transport. Recent studies have shown that its genetic inactivation impairs adipogenic differentiation in vitro. This study investigated the role of S1R in adipose tissue physiology and metabolic health using adult and old WT and S1R KO mice.Visceral fat mass was increased in adult, but not old S1R-KO male mice compared to that of WT mice, despite having similar body weights, food intake, and energy expenditure. The average adipocyte size was 64 % larger in adult KO mice than in adult WT mice. Adult S1R-KO mice showed reduced plasma dehydroepiandrosterone sulfate (DHEA-S) and elevated fasting plasma leptin concentrations. Lipidomic analysis revealed alterations in plasma metabolite concentrations, particularly reduced levels of sphingomyelins, ceramides, phosphatidylcholines, lysophosphatidylcholines, and cholesteryl esters in adult mice. Decreased expression of Pparγ, Adipoq, and Atgl was detected in visceral white adipose tissue (vWAT) isolated from adult KO mice. Additionally, Fabp4 and Adipoq expression levels were significantly lower in KO adipose-derived stromal cells than in WT adipose-derived stromal cells. A fivefold increase in the mitochondrial fatty acid oxidation rate and a 43 % increase in electron transfer coupling capacity were detected in adult S1R-KO vWAT.In summary, our investigation revealed an age-dependent association between increased visceral adiposity and decreased plasma levels of DHEA-S in S1R-deficient male mice. These findings underscore the potential role of S1R in regulating metabolic processes in adipose tissue and suggest that DHEA-S is a potential mediator of adiposity changes in the absence of S1R.

Fenofibrate induces liver enlargement in aging mice via activating the PPARα-YAP signaling pathway

Fenofibrate is a clinically prescribed drug for treating hypertriglyceridemia, which is also a classic peroxisome proliferator activated receptor α (PPARα) agonist. We previously reported that fenofibrate induced liver enlargement in adult mice partially through yes-associated protein (YAP) signaling pathway. However, the effects of fenofibrate on liver enlargement and the YAP signaling pathway in aging mice remain unclear. In this study, D-galactose-induced aging mice, naturally aging mice and senescence accelerated mice P8 (SAMP8) were used to investigate the effects of aging on fenofibrate-induced liver enlargement and YAP signaling activation. The results showed that fenofibrate-induced liver enlargement in aging mice was consistent with that of adult mice. The effect of fenofibrate on hepatocyte enlargement around the central vein (CV) area and hepatocyte proliferation around the portal vein (PV) area was comparable between adult and aging mice. There was no significant difference in the upregulation of PPARα downstream proteins between the two groups following fenofibrate treatment. Fenofibrate treatment also increased the expression of proliferation-related proteins and activated the YAP signaling pathway to a similar degree in both groups. In summary, these results demonstrated that the fenofibrate-induced liver enlargement and activation of the YAP pathway are consistent between adult and aging mice, indicating that the effect of fenofibrate on promoting liver enlargement and its activation of the PPARα and YAP pathway were independent of aging. These findings provide a new perspective for the clinical use of fenofibrate in elderly patients and provide a new insight for role of PPARα in liver enlargement.

Vocal communication in asocial BTBR mice is more malleable by a ketogenic diet in juveniles than adults

Deficits in social communication and language development are a hallmark of autism spectrum disorder currently with no effective approaches to reduce the negative impact. Interventional studies using animal models have been very limited in demonstrating improved vocal communication. Autism has been proposed to involve metabolic dysregulation. Ketogenic diet (KD) is a metabolism-based therapy for medically intractable epilepsy, and its applications in other neurological conditions have been increasingly tested. However, how KD would affect vocal communication has not been explored. The BTBR mouse strain is widely used to model asocial phenotypes. They display robust and pronounced deficits in vocalization during social interaction, and have metabolic changes implicated in autism.We investigated the effects of KD on ultrasonic vocalizations (USVs) in juvenile and adult BTBR mice during male–female social encounters.After a brief treatment with KD, the number, spectral bandwidth, and much of the temporal structure of USVs were robustly closer to control levels in both juvenile and adult BTBR mice. Composition of call categories and transitioning between individual call subtypes were more effectively altered to more closely align with the control group in juvenile BTBR mice.Together, our data provide further support to the hypothesis that metabolism-based dietary intervention could modify disease expression, including core symptoms, in autism. Future studies should tease apart the molecular mechanisms of KD’s effects on vocalization.

Maternal exposure to 4-tert-octylphenol causes alterations in the morphology and function of microglia in the offspring mouse brain

4-tert-Octylphenol (OP), an endocrine disrupting chemical is widely used in the production of industrial products. Prenatal exposure to endocrine-disrupting chemicals negatively affects the brain. However, the influence of OP exposure during neurodevelopment in adult offspring remains unclear. Thus, in the present study, we investigated the effects of maternal OP exposure on brain development in adult offspring by analyzing primary glial cell cultures and mice. Our findings revealed that OP exposure led to a specific increase in the mRNA expression of the ionized calcium-binding adapter molecule 1 (Iba-1) and the proportion of amoeboid microglia in the primary glial cell culture and adult offspring mice. Exposure to OP increased the transcriptional activation of Iba-1 and estrogen response element, which were counteracted by estrogen receptor antagonists ICI 182,780. Moreover, OP exposure increased the nuclear localization of the estrogen receptor. Remarkably, OP exposure decreased the mRNA expression levels of proinflammatory cytokines and genes associated with immune response in the brains of the offspring. OP exposure upregulated actin filament-related genes and altered cytoskeletal gene expression, as demonstrated by microarray analysis. The morphological changes in microglia did not result in an inflammatory response following lipopolysaccharide treatment. Taken together, the effects of OP exposure during neurodevelopment persist into adulthood, resulting in microglial dysfunction mediated by estrogen receptor signaling pathways in the brains of adult offspring mice.