Wild-type Rats Research Articles

Abstract 06: Role of the Atrial Natriuretic Peptide in Mitochondria-mediated Proximal Tubule Epithelial Oxidative Stress in Type 1 Diabetic Kidney Disease

Introduction: Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease. Most studies of DKD are glomerulo-centric. The recent progress in the control of renal glucose handling by SGLT2i makes the proximal tubule (PT) a prime candidate. Mitochondrial (mito) dysfunction and mito-induced oxidative stress in DKD is well-studied and is known to accelerate tubular injury. Some studies have suggested the role of the Atrial Natriuretic Peptide (ANP) in DKD. ANP is a hormone that regulates renal salt/water homeostasis and renal hemodynamics. We hypothesize that in DKD, ANP is a beneficial factor that improves proximal tubule mitochondrial function via protection from oxidative stress-induced ferroptosis. Methods: Using male ANP knock-out (SS NPPA-/- ) and wild-type (SS WT ) rats on the Dahl SS background, T1DKD was induced by streptozotocin (STZ; 75mg/kg) at 9-10 weeks of age. Baseline, midpoint, and endpoint blood glucose, urine, and body weights were collected. Western blotting was done on isolated cortical tissue and tissue fibrosis was measured in PicroSirius Red staining. ANOVA through Origin 2019b was used for comparisons. Results: STZ- SS WT and STZ-SS NPPA-/- groups exhibited similar body weight (231.7 ± 14.8 vs. 230.9 ± 8.4 g, respectively), two-kidney weight to body weight ratio (31.8 ± 0.9 vs. 28.4 ± 1.5 mg/g), and endpoint hyperglycemia (with blood glucose levels >650 mg/dL). Both, STZ- SS WT and STZ-SS NPPA-/- groups had high diuresis (59.9 ± 3.1 vs. 52.7 ± 3.2 mL/24hr/100gTBW). Histological analysis revealed elevated cortical fibrosis in the STZ-SS NPPA-/- compared to STZ- SS WT (4.6 ± 0.2 vs. 3.1 ± 0.2 % area, respectively, p<0.05). Moreover, in the kidney cortex, STZ-SS NPPA-/- rats compared to STZ- SS WT rats exhibit a significant increase in OXPHOS complexes IV and V (p<0.05) and a decrease in glutathione peroxidase 4 (GPX4; a core regulator of ferroptosis) abundance (1.5 ± 0.2 vs. 1.9 ± 0.1 a.u., respectively, p<0.05). Conclusion: Data showed that lack of ANP may promote DKD-related tubulointerstitial fibrosis and suggested a relationship with renal cortical mitochondrial function. Future studies will provide mechanistic insight into the role of ANP in mito-related oxidative stress and further assess the role of ANP in PT ferroptosis.

The impact of Kirsten rat sarcoma (KRAS) status on local tumor progression after surgical ablation of colorectal liver metastases

BackgroundKirsten rat sarcoma mutation was reported to adversely affect local tumor control after percutaneous ablation of colorectal liver metastasis. Nevertheless, the effect of Kirsten rat sarcoma mutation on surgical ablation has not been investigated in the literature. The aim of this study is to analyze the impact of Kirsten rat sarcoma mutation on local recurrence after surgical ablation of colorectal liver metastasis. MethodsThis was an institutional review board–approved study of patients who underwent surgical ablation of colorectal liver metastasis between 2005 and 2023 at a single center and underwent Kirsten rat sarcoma testing with ≥1 year follow-up. Local recurrence was analyzed using univariate Kaplan–Meier and multivariate Cox hazard models. ResultsA total of 163 patients with 424 lesions fulfilled inclusion criteria. Fifty (30.7%) patients received radiofrequency ablation and 113 (69.3%) patients received microwave ablation. Fifty-seven patients (32.2%) with 177 lesions were found to have a Kirsten rat sarcoma mutation. Patients with Kirsten rat sarcoma mutation had a larger number of tumors, percentage of posteriorly located tumors, and tumor burden score compared with those with wild-type Kirsten rat sarcoma. Nevertheless, there was no difference between the groups regarding local recurrence per lesion (15% vs 17%, respectively, P = not significant). Independent predictors of local recurrence included tumor size, ablation margin, and blood vessel proximity for radiofrequency ablation compared with tumor size and ablation margin for microwave ablation. ConclusionThere was no effect of Kirsten rat sarcoma mutations on local recurrence after surgical radiofrequency ablation or microwave ablation of colorectal liver metastasis in this study. Tumor size and ablation margin remained as independent predictors.

Insights into epithelial-mesenchymal transition from cystic fibrosis rat models

BackgroundMolecular pathways contributing to Cystic Fibrosis pathogenesis remain poorly understood. Epithelial-mesenchymal transition (EMT) has been recently observed in CF lungs and certain CFTR mutation classes may be more susceptible than others. No investigations of EMT processes in CF animal models have been reported. AimThe aim of this study was to assess the expression of EMT-related markers in Phe508del and knockout (CFTR-KO) rat lung tissue and tracheal-derived basal epithelial stem cells, to determine whether CFTR dysfunction can produce an EMT state. MethodThe expression of EMT-related markers in lung tissue and cultured tracheal basal epithelial stem cells from wildtype (WT), Phe508del, and CFTR-KO rats were assessed using qPCR and Western blots. Cell responses were evaluated in the presence of Rho-associated protein kinase (ROCK) inhibitor Y27632, which blocks EMT-pathways, or after treatment with TGFβ1 to stimulate EMT. ResultsDifferent gene expression profiles were observed between Phe508del and CFTR-KO rat models compared to wild type. There was lower expression of type 1 collagen in KO lungs and primary cell cultures, while Phe508del lungs and cells had higher expression, particularly when treated with TGFβ1. The addition of Y27632 rescued changes in EMT related genes in Phe508del cells but not in KO cells. ConclusionOur findings show the first evidence of upregulated EMT pathways in the lungs and airway cells of any CF animal model. Differences in the regulation of the EMT genes and proteins in the Phe508del and CFTR-KO cells suggest that the signalling pathways underlying EMT are CFTR mutation dependent.

Advancing age and the rs6265 BDNF SNP are permissive to graft-induced dyskinesias in parkinsonian rats

The rs6265 single nucleotide polymorphism (SNP) in the gene for brain-derived neurotrophic factor is a common variant that alters therapeutic outcomes for individuals with Parkinson’s disease (PD). We previously investigated the effects of this SNP on the experimental therapeutic approach of neural grafting, demonstrating that young adult parkinsonian rats carrying the variant Met allele exhibited enhanced graft function compared to wild-type rats and also exclusively developed aberrant graft-induced dyskinesias (GID). Aging is the primary risk factor for PD and reduces graft efficacy. Here we investigated whether aging interacts with this SNP to further alter cell transplantation outcomes. We hypothesized that aging would reduce enhancement of graft function associated with this genetic variant and exacerbate GID in all grafted subjects. Unexpectedly, beneficial graft function was maintained in aged rs6265 subjects. However, aging was permissive to GID induction, regardless of genotype, with the greatest incidence and severity found in rs6265-expressing animals.

SGK3 deficiency in macrophages suppresses angiotensin II–induced cardiac remodeling via regulating Ndufa13–mediated mitochondrial oxidative stress

Infiltration of monocyte-derived macrophages plays a crucial role in cardiac remodeling and dysfunction. The serum and glucocorticoid-inducible protein kinase 3 (SGK3) is a downstream factor of PI3K signaling, regulating various biological processes via an AKT-independent signaling pathway. SGK3 has been implicated in cardiac remodeling. However, the contribution of macrophagic SGK3 to hypertensive cardiac remodeling remains unclear. A cardiac remodeling model was established by angiotensin II (Ang II) infusion in SGK3-Lyz2-CRE (f/f, +) and wild-type mice to assess the function of macrophagic SGK3. Additionally, a co-culture system of SGK3-deficient or wild-type macrophages and neonatal rat cardiomyocytes (CMs) or neonatal rat fibroblasts (CFs) was established to evaluate the effects of SGK3 and the underlying mechanisms. SGK3 levels were significantly elevated in both peripheral blood mononuclear cells and serum from patients with heart failure. Macrophage SGK3 deficiency attenuated Ang II–induced macrophage infiltration, myocardial hypertrophy, myocardial fibrosis, and mitochondrial oxidative stress. RNA sequencing suggested Ndufa13 as the candidate gene in the effect of SGK3 on Ang II–induced cardiac remolding. Downregulation of Ndufa13 in CMs and CFs prevented the suppression of cardiac remodeling caused by SGK3 deficiency in macrophages. Mechanistically, the absence of SGK3 led to a reduction in IL-1β secretion by inhibiting the NLRP3/Caspase-1/IL-1β pathway in macrophages, consequently suppressing upregulated Ndufa13 expression and mitochondrial oxidative stress in CMs and CFs. This study provides new evidence that SGK3 is a potent contributor to the pathogenesis of hypertensive cardiac remodeling, and targeting SGK3 in macrophages may serve as a potential therapy for cardiac remodeling.

The effects of the atrial natriuretic peptide deficiency on renal cortical mitochondrial bioenergetics in the Dahl SS rat.

Atrial Natriuretic Peptide (ANP) plays an important role in blood pressure regulation. Low levels of ANP correlate with the development of salt-sensitive hypertension (SS-HTN). Our previous studies indicated that ANP deficiency exacerbated renal function decline in SS-HTN. In the heart and fat tissue, ANP was reported to affect lipid peroxidation and mitochondrial bioenergetics but the effects of ANP on mitochondrial function in the kidney are unexplored. We hypothesized that ANP deficiency in SS-HTN causes renal bioenergetic shift, leading to disruption of mitochondrial network and oxidative stress. To address the hypothesis, we placed Dahl SS wild-type (SSWT) and ANP knockout (SSNPPA-/-) rats on 4% NaCl high salt (HS) diet to induce HTN or maintained them on 0.4% NaCl normal salt (NS) diet and assessed mitochondrial bioenergetics and dynamics using spectrofluorimetry, Seahorse assay, electron paramagnetic resonance (EPR) spectroscopy, Western blotting, electron microscopy, PCR and cytokine assays. We report that under high salt conditions, associated with hypertension and renal damage, the SSNPPA-/- rats exhibit a decrease in mitochondrial membrane potential and elevation in mitochondrial ROS levels compared to SSWT. The redox shift is also evident by the presence of more pronounced medullar lipid peroxidation in the SSNPPA-/- strain. We also revealed fragmented, more damaged mitochondria in the SSNPPA-/- rats, accompanied by increased turnover and biogenesis. Overall, our data indicate that ANP deficiency causes disruptions in mitochondrial bioenergetics and dynamics which likely contributes to aggravation of the renal damage and hypertension in the Dahl SS rat; the major pathological effects are evident in the groups subjected to a combined salt and ANP deficiency-induced mitochondrial stress.

High-affinity agonism at the P2X7 receptor is mediated by three residues outside the orthosteric pocket

P2X receptors are trimeric ATP-gated ion channels that activate diverse signaling cascades. Due to its role in apoptotic pathways, selective activation of P2X7 is a potential experimental tool and therapeutic approach in cancer biology. However, mechanisms of high-affinity P2X7 activation have not been defined. We report high-resolution cryo-EM structures of wild-type rat P2X7 bound to the high-affinity agonist BzATP as well as significantly improved apo receptor structures in the presence and absence of sodium. Apo structures define molecular details of pore architecture and reveal how a partially hydrated Na+ ion interacts with the conductance pathway in the closed state. Structural, electrophysiological, and direct binding data of BzATP reveal that three residues just outside the orthosteric ATP-binding site are responsible for its high-affinity agonism. This work provides insights into high-affinity agonism for any P2X receptor and lays the groundwork for development of subtype-specific agonists applicable to cancer therapeutics.

Knockout of C6orf120 in Rats Alleviates Concanavalin A-induced Autoimmune Hepatitis by Regulating Macrophage Polarization

ObjectiveThe effect of the functionally unknown gene C6orf120 on autoimmune hepatitis was investigated on C6orf120 knockout rats (C6orf120-/-) and THP-1 cells. MethodSix–eight-week-old C6orf120-/- and wild-type (WT) SD rats were injected with Con A (16 mg/kg), and euthanized after 24 h. The sera, livers, and spleens were collected. THP-1 cells and the recombinant protein (rC6ORF120) were used to explore the mechanism in vitro. The frequency of M1 and M2 macrophages was analyzed using flow cytometry. Western blotting and PCR were used to detect macrophage polarization-associated factors. ResultsC6orf120 knockout attenuated Con A-induced autoimmune hepatitis. Flow cytometry indicated that the proportion of CD68+CD86+M1 macrophages from the liver and spleen in the C6orf120-/- rats decreased. C6orf120 knockout induced downregulation of CD86 protein and the mRNA levels of related inflammatory factors TNF-α, IL-1β, and IL-6 in the liver. C6orf120 knockout did not affect the polarization of THP-1 cells. However, rC6ORF120 promoted the THP-1 cells toward CD68+CD80+M1 macrophages and inhibited the CD68+CD206+M2 phenotype. ConclusionC6orf120 knockout alleviates Con A-induced autoimmune hepatitis by inhibiting macrophage polarization toward M1 macrophages and reducing the expression of related inflammatory factors in C6orf120-/- rats.

Impact of OATP2B1 on Pharmacokinetics of Atorvastatin Investigated in rSlco2b1-Knockout and SLCO2B1-Knockin Rats.

The organic anion transporting polypeptide (OATP) 2B1 is considered an emerging drug transporter that is found expressed in pharmacokinetically relevant organs such as the liver, small intestine, and kidney. Despite its interaction with various substrate drugs, the understanding of its in vivo relevance is still limited. In this study, we first validated the interaction of atorvastatin with rat OATP2B1 using transiently transfected HeLa cells. Moreover, we characterized our rSlco2b1-knockout and SLCO2B1-knockin rats for mRNA, protein expression, and localization of OATP2B1 in the liver, small intestine, and kidney. The transporter showed the highest expression in the liver followed by the small intestine. In humanized rats, human OATP2B1 is localized on the sinusoidal membrane of hepatocytes. In enterocytes of wild-type and humanized rats, the transporter was detected in the luminal membrane with the vast majority being localized subapical. Subsequently, we assessed atorvastatin pharmacokinetics in male wild-type, rSlco2b1-knockout, and SLCO2B1-knockin rats after a single-dose administration (orally and intravenously). Investigating the contribution of rat OATP2B1 or human OATP2B1 to oral atorvastatin pharmacokinetics revealed no differences in concentration-time profiles or pharmacokinetic parameters. However, when comparing the pharmacokinetics of atorvastatin after intravenous administration in SLCO2B1-humanized rats and knockout animals, notable differences were observed. In particular, the systemic exposure (area under the curve) decreased by approximately 40% in humanized animals, whereas the clearance was 57% higher in animals expressing human OATP2B1. These findings indicate that human OATP2B1 influences pharmacokinetics of atorvastatin after intravenous administration, most likely by contributing to the hepatic uptake. SIGNIFICANCE STATEMENT: Wild-type, rSlco2b1-knockout, and SLCO2B1-humanized Wistar rats were characterized for the expression of rat and human SLCO2B1/OATP2B1. Pharmacokinetic studies of atorvastatin over 24 hours were conducted in male wild-type, rSlco2b1-knockout, and SLCO2B1-humanized rats. After a single-dose intravenous administration, a lower systemic exposure and an increase in clearance were observed in SLCO2B1-humanized rats compared with knockout animals indicating a contribution of OATP2B1 to the hepatic clearance.

Pulmonary Hypertension Induced by Right Pulmonary Artery Occlusion: Hemodynamic Consequences of Bmpr2 Mutation.

The primary genetic risk factor for heritable pulmonary arterial hypertension is the presence of monoallelic mutations in the BMPR2 gene. The incomplete penetrance of BMPR2 mutations implies that additional triggers are necessary for pulmonary arterial hypertension occurrence. Pulmonary artery stenosis directly raises pulmonary artery pressure, and the redirection of blood flow to unobstructed arteries leads to endothelial dysfunction and vascular remodeling. We hypothesized that right pulmonary artery occlusion (RPAO) triggers pulmonary hypertension (PH) in rats with Bmpr2 mutations. Male and female rats with a 71 bp monoallelic deletion in exon 1 of Bmpr2 and their wild-type siblings underwent acute and chronic RPAO. They were subjected to full high-fidelity hemodynamic characterization. We also examined how chronic RPAO can mimic the pulmonary gene expression pattern associated with installed PH in unobstructed territories. RPAO induced precapillary PH in male and female rats, both acutely and chronically. Bmpr2 mutant and male rats manifested more severe PH compared with their counterparts. Although wild-type rats adapted to RPAO, Bmpr2 mutant rats experienced heightened mortality. RPAO induced a decline in cardiac contractility index, particularly pronounced in male Bmpr2 rats. Chronic RPAO resulted in elevated pulmonary IL-6 (interleukin-6) expression and decreased Gdf2 expression (corrected P value<0.05 and log2 fold change>1). In this context, male rats expressed higher pulmonary levels of endothelin-1 and IL-6 than females. Our novel 2-hit rat model presents a promising avenue to explore the adaptation of the right ventricle and pulmonary vasculature to PH, shedding light on pertinent sex- and gene-related effects.

Pharmacokinetic Modeling of the Effect of Tariquidar on Ondansetron Disposition into the Central Nervous System

PurposeSerotonin (5-HT3) receptor antagonists are promising agents for treatment of neuropathic pain. However, insufficient drug exposure at the central nervous system (CNS) might result in lack of efficacy. The goal of this study was to evaluate the impact of administration of a Pgp inhibitor (tariquidar) on ondansetron exposure in the brain, spinal cord, and cerebrospinal fluid in a wild-type rat model.MethodsOndansetron (10 mg/kg) and tariquidar (7.5 mg/kg) were administered intravenously, plasma and tissue samples were collected and analyzed by HPLC. A mathematical model with brain, spinal cord, cerebrospinal fluid and two systemic disposition compartments was developed to describe the data.ResultsThe results demonstrate that tariquidar at 7.5 mg/kg resulted in a complete inhibition of Pgp efflux of ondansetron in the brain and spinal cord. The compartmental model successfully captured pharmacokinetics of ondansetron in wild type and Pgp knockout (KO) animals receiving the drug alone or in wild type animals receiving the ondansetron and tariquidar combination.ConclusionsThe study provided important quantitative information on enhancement of CNS exposure to ondansetron using co-administration of Pgp Inhibitor in a rat model, which will be further utilized in conducting a clinical study. Tariquidar co-administration resulted in ondansetron CNS exposure comparable to observed in Pgp KO rats. Results also highlighted the effect of tariquidar on plasma disposition of ondansetron, which may not be dependent on Pgp inhibition, and should be evaluated in future studies.

Exploring microbiota-gut-brain axis biomarkers linked to autism spectrum disorder in prenatally chlorpyrifos-exposed Fmr1 knock-out and wild-type male rats

Fmr1 (fragile X messenger ribonucleoprotein 1)-knockout (KO) rats, modeling the human Fragile X Syndrome (FXS), are of particular interest for exploring the ASD-like phenotype in preclinical studies. Gestational exposure to chlorpyrifos (CPF) has been associated with ASD diagnosis in humans and ASD-like behaviors in rodents and linked to the microbiota-gut-brain axis. In this study, we have used both Fmr1-KO and wild-type male rats (F2 generation) at postnatal days (PND) 7 and 40 obtained after F1 pregnant females were randomly exposed to 1 mg/kg/mL/day of CPF or vehicle. A nuclear magnetic resonance (NMR) metabolomics approach together with gene expression profiles of these F2 generation rats were employed to analyze different brain regions (such as prefrontal cortex, hippocampus, and cerebellum), whole large intestine (at PND7) and gut content (PND40). The statistical comparison of each matrix spectral profile unveiled tissue-specific metabolic fingerprints. Significant variations in some biomarker levels were detected among brain tissues of different genotypes, including taurine, myo-inositol, and 3-hydroxybutyric acid, and exposure to CPF induced distinct metabolic alterations, particularly in serine and myo-inositol. Additionally, this study provides a set of metabolites associated with gastrointestinal dysfunction in ASD, encompassing several amino acids, choline-derived compounds, bile acids, and sterol molecules. In terms of gene expression, genotype and gestational exposure to CPF had only minimal effects on decarboxylase 2 (gad2) and cholinergic receptor muscarinic 2 (chrm2) genes.

In vivo recording of visually evoked potentials with novel full diamond ECoG implants

Implantable neuroprosthetic devices such as electrocorticography (ECoG) and intracortical microelectrodes have the potential to restore neurological functions in disabled individuals. They constitute the direct interface with the body and require long term efficiency. We propose an ultra-thin diamond-based implant to tackle challenges related with long term implantation, and demonstrate its functionality on rodents. Here we take advantage of thin-film diamond to generate not only the electrodes but also the thin passivation foil, leading to a full thin film diamond EcoG. Implants were fabricated based on boron-doped diamond (BDD) electrodes connected through titanium nitride (TiN) conductive tracks, all being encapsulated in intrinsic diamond. A complete electrochemical characterization proved that the TiN tracks were well embedded inside diamond and the efficiency of the BDD electrodes. Functionality of the ECoG device was also provided by the recording of classic visual evoked potentials (VEPs) on wild-type mice and rats. This thin film diamond technology successfully responds to long term issues (linked with electrode material or device packaging) and holds the potential to inspire and pave the way for future generations of various electrode arrays.

Protein-coding mutation in Adcy3 increases adiposity and alters emotional behaviors sex-dependently in rats.

Adenylate cyclase 3 (Adcy3) has been linked to both obesity and major depressive disorder (MDD). Our lab identified a protein-coding variant in the 2nd transmembrane (TM) helix of Adcy3 in rats, and similar obesity variants have been identified in humans. The current study investigates the role of a TM variant in adiposity and behavior. We used CRISPR-SpCas9 to mutate the TM domain of Adcy3 in WKY rats (Adcy3mut/mut). We also created a heterozygous knockout rat in the same strain (Adcy3+/-). Wild-type (WT), Adcy3+/-, and Adcy3mut/mut rats were fed a high-fat diet for 12 weeks. We measured body weight, fat mass, glucose tolerance, food intake, metabolism, emotion-like behaviors, and memory. Adcy3+/- and Adcy3mut/mut rats weighed more than WT rats due to increased fat mass. There were key sex differences: adiposity was driven by increased food intake in males but by decreased energy expenditure in females. Adcy3mut/mut males displayed increased passive coping and decreased memory while Adcy3mut/mut females displayed increased anxiety-like behavior. These studies show that the ADCY3 TM domain plays a role in protein function, that Adcy3 may contribute to the relationship between obesity and MDD, and that sex influences the relationships between Adcy3, metabolism, and behavior.

Loss-of-function G6PD variant moderated high-fat diet-induced obesity, adipocyte hypertrophy, and fatty liver in male rats

Obesity is a major risk factor for liver and cardiovascular diseases. However, obesity-driven mechanisms that contribute to the pathogenesis of multiple organ diseases are still obscure and treatment is inadequate. We hypothesized that increased glucose-6-phosphate dehydrogenase (G6PD), the key rate-limiting enzyme in the pentose shunt, is critical in evoking metabolic reprogramming in multiple organs and is a significant contributor to the pathogenesis of liver and cardiovascular diseases. G6PD is induced by carbohydrate-rich diet and insulin. Long-term (8 months) high-fat diet (HFD) feeding increased body weight and elicited metabolic reprogramming in visceral fat, liver, and aorta, of the wild-type rats. In addition, HFD increased inflammatory chemokines in visceral fat. Interestingly, CRISPR-edited loss-of-function Mediterranean G6PD variant (G6PDS188F) rats, which mimic human polymorphism, moderated HFD-induced weight gain and metabolic reprogramming in visceral fat, liver, and aorta. The G6PDS188F variant prevented HFD-induced CCL7 and adipocyte hypertrophy. Furthermore, the G6PDS188F variant increased Magel2 – a gene encoding circadian clock-related protein that suppresses obesity associated with Prader-Willi syndrome – and reduced HFD-induced non-alcoholic fatty liver. Additionally, the G6PDS188F variant reduced aging-induced aortic stiffening. Our findings suggest G6PD is a regulator of HFD-induced obesity, adipocyte hypertrophy, and fatty liver.

Noradrenergic current responses of neurons in rat oculomotor neural integrators.

The prepositus hypoglossi nucleus (PHN) and the interstitial nucleus of Cajal (INC) are involved in the control of horizontal and vertical gaze, respectively. A previous study showed that PHN neurons exhibit depolarized or hyperpolarized responses to noradrenaline (NA). However, the adrenoceptor types that participate in NA-induced responses and the effects of NA on INC neurons have not yet been investigated. Furthermore, the relationship between NA-induced responses and neuron types defined by neurotransmitter phenotypes has not been determined. In this study, we investigated NA-induced current responses in PHN and INC neurons and the relationships between these responses and neuron types using whole cell recordings in wild-type and transgenic rat brainstem slices. Local application of NA to the cell soma induced slow inward (SI) and slow outward (SO) currents that were mainly mediated by α1 and α2 adrenoceptors, respectively. These current responses were observed in both PHN and INC neurons, although the proportion of INC neurons that responded to NA was low. Analyses of the distributions of the current responses revealed that in the PHN, all fluorescently identified inhibitory neurons exhibited SI currents, whereas glutamatergic and cholinergic neurons exhibited both SI and SO currents. In the INC, glutamatergic and inhibitory neurons preferentially exhibited SI and SO currents, respectively. When the PHN and INC neurons were characterized by their firing pattern, we found that the proportions of the currents depended on their firing pattern. These results suggest that various modes of noradrenergic modulation in horizontal and vertical neural integrators are dependent on neuron type.NEW & NOTEWORTHY Noradrenergic modulation of oculomotor neural integrators involved in gaze control has not been elucidated. Here, we report that noradrenaline (NA)-induced slow inward (SI) and outward (SO) currents are mediated mainly by α1 and α2 adrenoceptors in neurons that participate in horizontal and vertical gaze control. The NA-induced current responses differed depending on the neurotransmitter phenotype and firing pattern. These results suggest various modes of noradrenergic modulation in horizontal and vertical integrator neurons.

Fluoxetine and Ketamine Enhance Extinction Memory and Brain Plasticity by Triggering the p75 Neurotrophin Receptor Proteolytic Pathway

BackgroundDiverse antidepressants were recently described to bind to TrkB (tyrosine kinase B) and drive a positive allosteric modulation of endogenous BDNF (brain-derived neurotrophic factor). Although neurotrophins such as BDNF can bind to p75NTR (p75 neurotrophin receptor), their precursors are the high-affinity p75NTR ligands. While part of an unrelated receptor family capable of inducing completely opposite physiological changes, TrkB and p75NTR feature a crosslike conformation dimer and carry a cholesterol-recognition amino acid consensus in the transmembrane domain. As such qualities were found to be crucial for antidepressants to bind to TrkB and drive behavioral and neuroplasticity effects, we hypothesized that their effects might also depend on p75NTR. MethodsEnzyme-linked immunosorbent assay–based binding and nuclear magnetic resonance spectroscopy were performed to assess whether antidepressants would bind to p75NTR. HEK293T cells and a variety of in vitro assays were used to investigate whether fluoxetine (FLX) or ketamine (KET) would trigger any α- and γ-secretase–dependent p75NTR proteolysis and lead to p75NTR nuclear localization. Ocular dominance shift was performed with male and female p75NTR knockout mice to study the effects of KET and FLX on brain plasticity, in addition to pharmacological interventions to verify how p75NTR signaling is important for the effects of KET and FLX in enhancing extinction memory in male wild-type mice and rats. ResultsAntidepressants were found to bind to p75NTR. FLX and KET triggered the p75NTR proteolytic pathway and induced p75NTR-dependent behavioral/neuroplasticity changes. ConclusionsWe hypothesize that antidepressants co-opt both BDNF/TrkB and proBDNF/p75NTR systems to induce a more efficient activity-dependent synaptic competition, thereby boosting the brain’s ability for remodeling.

Genetic or pharmacological GHSR blockade has sexually dimorphic effects in rodents on a high-fat diet

The stomach-derived hormone ghrelin regulates essential physiological functions. The ghrelin receptor (GHSR) has ligand-independent actions; therefore, GHSR gene deletion may be a reasonable approach to investigate the role of this system in feeding behaviors and diet-induced obesity (DIO). Here, we investigate the effects of a long-term (12-month) high-fat (HFD) versus regular diet on obesity-related measures in global GHSR-KO and wild-type (WT) Wistar male and female rats. Our main findings are that the GHSR gene deletion protects against DIO and decreases food intake during HFD in male but not in female rats. GHSR gene deletion increases thermogenesis and brain glucose uptake in male rats and modifies the effects of HFD on brain glucose metabolism in a sex-specific manner, as assessed with small animal positron emission tomography. We use RNA-sequencing to show that GHSR-KO rats have upregulated expression of genes responsible for fat oxidation in brown adipose tissue. Central administration of a novel GHSR inverse agonist, PF-5190457, attenuates ghrelin-induced food intake, but only in male, not in female mice. HFD-induced binge-like eating is reduced by inverse agonism in both sexes. Our results support GHSR as a promising target for new pharmacotherapies for obesity.

#2607 Generation of a tissue resident macrophage depleted reporter rat to examine cardiovascular homeostasis and kidney disease

Abstract Cardiovascular disease (CVD) and chronic kidney disease (CKD) are currently the 1st and 10th leading cause of global mortality, respectively. By 2050, CKD is predicted to be the 5th leading cause, with most of those individuals dying of CVD. Recent single cell RNA sequencing data has highlighted the plasticity of macrophage populations in both renal and cardiovascular injury and repair. Many of these subpopulations of macrophages remain uncharacterized. We have generated the Red FIRE rat, which is a cross between the Csf1r-mApple reporter rat and the super-enhancer FIRE knockout rat. The Csf1r-mApple reporter rat introduces a fluorescent signal to cells of the monocyte-macrophage lineage and the KO of FIRE (fms-intronic regulatory element), while the FIRE rat has fms-intronic regulatory element (FIRE), which is the superenhancer in the Csf1r locus knocked out, resulting in depletion of tissue resident macrophages. These red FIRE rats will allow us to visualize all Csf1r expressing cells (macrophages) and in the FIRE rats deplete populations of tissue resident macrophages (TRM) (including those in the kidney and heart). This will enable us to visualize and study TRM populations in homeostasis and injury. We hypothesise that the red FIRE rats will show a more severe phenotype in injury and have altered vascular function (local and systemic). Male and female (8–10-week-old) rats underwent a 6- or 12-week 5/6 subtotal nephrectomy (5/6 STNx) in groups of 4-8. Baseline, midpoint and endpoint urine and serum were collected for analysis, as well as blood pressure measurements and echocardiograms to monitor kidney and heart health/decline. At the end of the experiment, kidneys and the heart were collected for flow cytometry, immunofluorescence, RT-qPCR, and histological staining. The thoracic aorta, mesentery, and common renal arteries were collected for functional analysis using isometric (wire)myography. The knockout of the FIRE super enhancer resulted in depletion of kidney TRMs (Fig. 1) as visualised by immunofluorescent staining of both wild type and macrophage-depleted (red FIRE) rat tissue. Figure 1A shows the composite image and individual stains; DAPI, IBa1 (pan macrophage marker), and Csf1r-mApple (tissue resident macrophages) on a naïve heart. Representative composite images also compare STNx hearts (Fig. 1B) and kidneys (Fig. 1C) in both wild type and macrophage-depleted rats. This allowed for comparison of these rats in both injury and homeostasis. Figure 1: Immunofluorescent staining of the uninjured heart of a FIRE wild type (WT), mApple positive rat (A), the injured kidney (B) and heart (C) of mApple positive, FIRE wild type (Control) or mApple positive, FIRE knock out (FIRE) rats post 12-week 5/6 subtotal nephrectomy (5/6 STNx). DAPI: nuclei, IBa1: all macrophages, csf1r (mApple): tissue resident macrophages. Representative imagining, figure made using FIJI. Our preliminary data suggests previously undescribed roles for tissue-resident macrophages in rats i.e. ion handling, vascular homeostasis and roles in CKD and repair. These results could help reveal new specific druggable targets that could be exploited for treatments which could halt progression of disease and thus reduce end stage renal failure patient numbers, healthcare costs and premature CVD-related deaths.

Administration of Atosiban, an oxytocin receptor antagonist, ameliorates autistic-like behaviors in a female rat model of valproic acid-induced autism

Autism spectrum disorder (ASD) is a pervasive developmental disorder with gender differences. Oxytocin (OXT) is currently an important candidate drug for autism, but the lack of data on female autism is a big issue. It has been reported that the effect of OXT is likely to be different between male and female ASD patients. In the study, we specifically explored the role of the OXT signaling pathway in a VPA-induced female rat’s model of autism. The data showed that there was an increase of either oxytocin or its receptor expressions in both the hippocampus and the prefrontal cortex of VPA-induced female offspring. To determine if the excess of OXT signaling contributed to autism symptoms in female rats, exogenous oxytocin and oxytocin receptor antagonists Atosiban were used in the experiment. It was found that exogenous oxytocin triggered autism-like behaviors in wild-type female rats by intranasal administration. More interestingly, several autism-like deficits including social interaction, anxiety, and repeat stereotypical sexual behavior in the VPA female offspring were significantly attenuated by oxytocin receptor antagonists Atosiban. Moreover, Atosiban also effectively improved the synaptic plasticity impairment induced by VPA in female offspring. Our results suggest that oxytocin receptor antagonists significantly improve autistic-like behaviors in a female rat model of valproic acid-induced autism.