Neuroexcitatory targets in the female reproductive system of the nonhuman primate (Macaca fascicularis)

A metabotropic glutamate receptor affects the growth and development of Schistosoma japonicum

Schistosomiasis is a zoonotic parasitic disease caused by schistosome infection that severely threatens human health. Therapy relies mainly on single drug treatment with praziquantel. Therefore, there is an urgent need to develop alternative medicines. The glutamate neurotransmitter in helminths is involved in many physiological functions by interacting with various cell-surface receptors. However, the roles and detailed regulatory mechanisms of the metabotropic glutamate receptor (mGluR) in the growth and development of Schistosoma japonicum remain poorly understood. In this study, we identified two putative mGluRs in S. japonicum and named them SjGRM7 (Sjc_001309, similar to GRM7) and SjGRM (Sjc_001163, similar to mGluR). Further validation using a calcium mobilization assay showed that SjGRM7 and SjGRM are glutamate-specific. The results of in situ hybridization showed that SjGRM is mainly located in the nerves of both males and gonads of females, and SjGRM7 is principally found in the nerves and gonads of males and females. In a RNA interference experiment, the results showed that SjGRM7 knockdown by double-stranded RNA (dsRNA) in S. japonicum caused edema, chassis detachment, and separation of paired worms in vitro. Furthermore, dsRNA interference of SjGRM7 could significantly affect the development and egg production of male and female worms in vivo and alleviate the host liver granulomas and fibrosis. Finally, we examined the molecular mechanisms underlying the regulatory function of mGluR using RNA sequencing. The data suggest that SjGRM7 propagates its signals through the G protein-coupled receptor signaling pathway to promote nervous system development in S. japonicum. In conclusion, SjGRM7 is a potential target for anti-schistosomiasis. This study enables future research on the mechanisms of action of Schistosomiasis japonica drugs.

Effect of monosodium glutamate on serum sex hormones and uterine histology in female rats along with its molecular docking and in-silico toxicity

Monosodium glutamate (MSG) is commonly used worldwide as a food flavour enhancer by the food industry. The current study investigated the in vivo toxic effects of MSG on the uterus in adult female Sprague Dawley rats and in vitro using MCF-7 and MDA-MB-231 cells, computational toxicity and molecular docking. The average levels of progesterone and oestrogen in the MSG-treated animals significantly altered. Besides, the average uterine lumen area (μm²) was smaller than the control group. MSG showed high-affinity binding to acetylcholine receptors and disrupted the normal nerve signal with a predicted LD50 of 4500 mg/kg. MSG also demonstrated good binding affinity to human oestrogen receptors beta and some other proteins that have an oxidative stress role in the female reproductive organs. Therefore, a precaution should be taken when utilising this compound, especially for females under the risk factor of hormonal abnormality.

Comparative transcriptome analysis of Indian domestic duck reveals candidate genes associated with egg production

Egg production is an important economic trait and a key indicator of reproductive performance in ducks. Egg production is regulated by several factors including genes. However the genes involved in egg production in duck remain unclear. In this study, we compared the ovarian transcriptome of high egg laying (HEL) and low egg laying (LEL) ducks using RNA-Seq to identify the genes involved in egg production. The HEL ducks laid on average 433 eggs while the LEL ducks laid 221 eggs over 93 weeks. A total of 489 genes were found to be significantly differentially expressed out of which 310 and 179 genes were up and downregulated, respectively, in the HEL group. Thirty-eight differentially expressed genes (DEGs), including LHX9, GRIA1, DBH, SYCP2L, HSD17B2, PAR6, CAPRIN2, STC2, and RAB27B were found to be potentially related to egg production and folliculogenesis. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that DEGs were enriched for functions related to glutamate receptor activity, serine-type endopeptidase activity, immune function, progesterone mediated oocyte maturation and MAPK signaling. Protein-protein interaction network analysis (PPI) showed strong interaction between 32 DEGs in two distinct clusters. Together, these findings suggest a mix of genetic and immunological factors affect egg production, and highlights candidate genes and pathways, that provides an understanding of the molecular mechanisms regulating egg production in ducks and in birds more broadly.

Selected Resources for Pathology Evaluation of Nonhuman Primates in Nonclinical Safety Assessment

Humans and nonhuman primates (NHPs) share numerous anatomical and physiological characteristics, thereby explaining the importance of NHPs as essential animal models for translational medicine and nonclinical toxicity testing. Researchers, toxicologic pathologists, toxicologists, and regulatory reviewers must be familiar with normal and abnormal NHP biological traits when designing, performing, and interpreting data sets from NHP studies. The current compilation presents a list of essential books, journal articles, and websites that provide context to safety assessment and research scientists working with NHP models. The resources used most frequently by the authors have been briefly annotated to permit readers to rapidly ascertain their applicability to particular research endeavors. The references are aimed primarily for toxicologic pathologists working with cynomolgus and rhesus macaques and common marmosets in efficacy and safety assessment studies.

Public health risks associated with chronic, low-level domoic acid exposure: A review of the evidence

Domoic acid (DA), the causative agent for the human syndrome Amnesic Shellfish Poisoning (ASP), is a potent, naturally occurring neurotoxin produced by common marine algae. DA accumulates in seafood, and humans and wildlife alike can subsequently be exposed when consuming DA-contaminated shellfish or finfish. While strong regulatory limits protect people from the acute effects associated with ASP, DA is an increasingly significant public health concern, particularly for coastal dwelling populations, and there is a growing body of evidence suggesting that there are significant health consequences following repeated exposures to levels of the toxin below current safety guidelines. However, gaps in scientific knowledge make it difficult to precisely determine the risks of contemporary low-level exposure scenarios. The present review characterizes the toxicokinetics and neurotoxicology of DA, discussing results from clinical and preclinical studies after both adult and developmental DA exposure. The review also highlights crucial areas for future DA research and makes the case that DA safety limits need to be reassessed to best protect public health from deleterious effects of this widespread marine toxin.

The selective blockade of metabotropic glutamate receptor-5 attenuates fat accumulation in an <em>in vitro</em> model of benign steatosis

It has been previously found that the blockade of metabotropic glutamate receptor type 5 (mGluR5) protects against hepatic ischemia/reperfusion injury and acetaminophen toxicity. The role of mGluR5 in NAFLD has not yet been elucidated. Here, we evaluated the effects of mGluR5 blockade in an in vitro model of steatosis. HepG2 cells were pre-incubated for 12 h with an mGluR5 agonist, a negative allosteric modulator (DHPG and MPEP, respectively) or vehicle, then treated with 1.5 mM oleate/palmitate (O/P) for another 12 h. Cell viability was evaluated with the MTT assay; fat accumulation was measured using the fluorescent dye nile red; SREBP-1, PPAR-α, iNOS and Caspase-3 protein expression were evaluated by Western blot; NFkB activity was evaluated as pNFkB/NFkB ratio. mGluR5 modulation did not alter cell viability in O/P-incubated cells; MPEP prevented intracellular lipid accumulation in O/P treated cells; MPEP administration was also associated with a reversion of O/P-induced changes in SREBP-1 and PPAR-α expression, involved in free fatty acid (FFA) metabolism and uptake. No changes were observed in iNOS and Caspase-3 expression, or in NFkB activity. In conclusion, mGluR5 pharmacological blockade reduced fat accumulation in HepG2 cells incubated with O/P, probably by modulating the expression of SREBP-1 and PPAR-α.

Dysfunction of the blood-cerebrospinal fluid-barrier and N-methyl-D-aspartate glutamate receptor antibodies in dementias

N-Methyl-D-aspartate glutamate receptor (NMDA-R) antibodies (Abs) could play a role in neurodegenerative disorders. Since, in these diseases, NMDA-R Abs were detected in serum, but only sporadic in cerebrospinal fluid (CSF), the origin and impact of the Abs are still unresolved. We examined the presence of NMDA-R Abs in serum and CSF using a cell-based immunofluorescence assay as well as the function of the blood-CSF-barrier (B-CSF-B) by determination of Q albumin (ratio of albumin in CSF and serum) in patients with mild cognitive impairment (MCI; N = 59) and different types of dementia, Alzheimer's disease (AD; N = 156), subcortical ischemic vascular dementia (SIVD; N = 61), and frontotemporal dementia (FTD; N = 34). Serum IgA/IgM NMDA-R Abs and/or a disturbed B-CSF-B were sporadically present in all investigated patients' groups. In AD, these Abs often developed during the disease course. Patients with either no hippocampal atrophy and/or no AD-related characteristic changes in CSF, referred to "non-classical" AD, were characterized by seropositivity at diagnosis and loss of function of the B-CSF-B showed a progressive decline in cognitive functions and a poor prognosis. Our data indicate that NMDA-R Abs are present in different types of dementia and elderly healthy individuals. In combination with disturbed B-CSF-B integrity, they seem to promote their pathological potential on cognitive decline, and thus, a subgroup of dementia patients with these unique characteristics might inform clinicians.

Selective Blockade of the Metabotropic Glutamate Receptor mGluR5 Protects Mouse Livers in In Vitro and Ex Vivo Models of Ischemia Reperfusion Injury

2-Methyl-6-(phenylethynyl)pyridine (MPEP), a negative allosteric modulator of the metabotropic glutamate receptor (mGluR) 5, protects hepatocytes from ischemic injury. In astrocytes and microglia, MPEP depletes ATP. These findings seem to be self-contradictory, since ATP depletion is a fundamental stressor in ischemia. This study attempted to reconstruct the mechanism of MPEP-mediated ATP depletion and the consequences of ATP depletion on protection against ischemic injury. We compared the effects of MPEP and other mGluR5 negative modulators on ATP concentration when measured in rat hepatocytes and acellular solutions. We also evaluated the effects of mGluR5 blockade on viability in rat hepatocytes exposed to hypoxia. Furthermore, we studied the effects of MPEP treatment on mouse livers subjected to cold ischemia and warm ischemia reperfusion. We found that MPEP and 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) deplete ATP in hepatocytes and acellular solutions, unlike fenobam. This finding suggests that mGluR5s may not be involved, contrary to previous reports. MPEP, as well as MTEP and fenobam, improved hypoxic hepatocyte viability, suggesting that protection against ischemic injury is independent of ATP depletion. Significantly, MPEP protected mouse livers in two different ex vivo models of ischemia reperfusion injury, suggesting its possible protective deployment in the treatment of hepatic inflammatory conditions.

Acylated Ghrelin Supports the Ovarian Transcriptome and Follicles in the Mouse: Implications for Fertility

Ghrelin, an orexigenic gut-derived peptide, is gaining increasing attention due to its multifaceted role in a number of physiological functions, including reproduction. Ghrelin exists in circulation primarily as des-acylated and acylated ghrelin. Des-acyl ghrelin, until recently considered to be an inactive form of ghrelin, is now known to have independent physiological functionality. However, the relative contribution of acyl and des-acyl ghrelin to reproductive development and function is currently unknown. Here we used ghrelin-O-acyltransferase (GOAT) knockout (KO) mice that have no measurable levels of endogenous acyl ghrelin and chronically high levels of des-acyl ghrelin, to characterize how the developmental and life-long absence of acyl ghrelin affects ovarian development and reproductive capacity. We combined the assessment of markers of reproductive maturity and the capacity to breed with measures of ovarian morphometry, as well as with ovarian RNA sequencing analysis. Our data show that while GOAT KO mice retain the capacity to breed in young adulthood, there is a diminished number of ovarian follicles (per mm³) in the juvenile and adult ovaries, due to a significant reduction in the number of small follicles, particularly the primordial follicles. We also show pronounced specific changes in the ovarian transcriptome in the juvenile GOAT KO ovary, indicative of a potential for premature ovarian development. Collectively, these findings indicate that an absence of acyl ghrelin does not prevent reproductive success but that appropriate levels of acyl and des-acyl ghrelin may be necessary for optimal ovarian maturation.

Sigma receptors [σRs]: biology in normal and diseased states

This review compares the biological and physiological function of Sigma receptors [σRs] and their potential therapeutic roles. Sigma receptors are widespread in the central nervous system and across multiple peripheral tissues. σRs consist of sigma receptor one (σ₁R) and sigma receptor two (σ₂R) and are expressed in numerous regions of the brain. The sigma receptor was originally proposed as a subtype of opioid receptors and was suggested to contribute to the delusions and psychoses induced by benzomorphans such as SKF-10047 and pentazocine. Later studies confirmed that σRs are non-opioid receptors (not an µ opioid receptor) and play a more diverse role in intracellular signaling, apoptosis and metabolic regulation. σ₁Rs are intracellular receptors acting as chaperone proteins that modulate Ca²⁺ signaling through the IP₃ receptor. They dynamically translocate inside cells, hence are transmembrane proteins. The σ₁R receptor, at the mitochondrial-associated endoplasmic reticulum membrane, is responsible for mitochondrial metabolic regulation and promotes mitochondrial energy depletion and apoptosis. Studies have demonstrated that they play a role as a modulator of ion channels (K⁺ channels; N-methyl-d-aspartate receptors [NMDAR]; inositol 1,3,5 triphosphate receptors) and regulate lipid transport and metabolism, neuritogenesis, cellular differentiation and myelination in the brain. σ₁R modulation of Ca²⁺ release, modulation of cardiac myocyte contractility and may have links to G-proteins. It has been proposed that σ₁Rs are intracellular signal transduction amplifiers. This review of the literature examines the mechanism of action of the σRs, their interaction with neurotransmitters, pharmacology, location and adverse effects mediated through them.

Direct effects of the algal toxin, domoic acid, on ovarian function: Bovine granulosa and theca cells as an in vitro model

Domoic acid (DA) is a potent neurotoxin produced by alga Pseudo-nitzschia spp. and has been associated with reproductive disorders in mammals. The aim of this study was to investigate if DA can affect the reproductive system via direct action on ovarian function. Bovine granulosa and theca cells were used as in vitro models for evaluating DA effects on ovarian cell proliferation and steroid production. In small-follicle granulosa cells (SMGC), cell proliferation and estradiol (E2) production was not affected (P>0.05) while progesterone (P4) production was inhibited (P<0.05) by DA at all doses tested. In large-follicle granulosa cells (LGGC), DA had no effect (P>0.05) on cell proliferation or P4 production while E2 production was stimulated by 1 and 5 µg/ml DA (P<0.05). DA (1 µg/ml) attenuated (P<0.05) insulin-like growth factor 1 (IGF-1)-induced P4 production by large-follicle theca cells (LGTC), but did not affect androstenedione (A4) production or proliferation of LGTC. In glutamate-free medium, DA inhibited (P<0.05) SMGC E2 production and this inhibition was similar to inhibition of E2 by trans-(±)-1-amino-1,3-cyclopentanedicarboxylic acid monohydrate (ACPD; a selective metabotropic glutamate receptor subtype agonist) while kainic acid (KA; an ionotropic glutamate receptor subtype agonist) had no effect (P>0.10) on E2 production. Collectively, these results show for the first time that DA has direct effects on ovarian GC and TC steroidogenesis. Because DA inhibited E2 and P4 production, DA has the potential to be an endocrine disruptor.

Changes in mouse uterine transcriptome in estrus and proestrus

Changes in the CD-1 mouse uterine transcriptome during proestrus and estrus were investigated to help elucidate mechanisms of uterine tissue remodeling during the estrus cycle and their regulation by estrogen and progesterone in preparation of the uterus for pregnancy. Mice were staged beginning at 6 weeks of age, and uterine horns were harvested after monitoring two estrus cycles. Microarray analysis of whole uterine horn RNA identified 2428 genes differentially expressed in estrus compared to proestrus, indicating there is extensive remodeling of mouse uterus during the estrus cycle, affecting ~10% of all protein-encoding genes. Many (~50%) of these genes showed the same differential expression in independent analyses of isolated uterine lumenal epithelial cells. Changes in gene expression associated with structural alterations of the uterus included remodeling of the extracellular matrix, changes in cell keratins and adhesion molecules, activation of mitosis and changes in major histocompatibility complex class II (MHCII) presentation, complement and coagulation cascades, and cytochrome P450 expression. Signaling pathways regulated during the estrus cycle, involving ligand-gated channels, Wnt and hedgehog signaling, and transcription factors with poorly understood roles in reproductive tissues, included several genes and gene networks that have been implicated in pathological states. Many of the molecular pathways and biological functions represented by the genes differentially expressed from proestrus to estrus are also altered during the human menstrual cycle, although not necessarily at the corresponding phases of the cycle. These findings establish a baseline for further studies in the mouse model to dissect mechanisms involved in uterine tissue response to endocrine disruptors and the development of reproductive tract diseases.

Monosodium glutamate versus diet induced obesity in pregnant rats and their offspring

BACKGROUND

We aim at determining the role of monosodium glutamate (MSG) compared with high caloric chow(HCC) in development of obesity in pregnant rats and their offspring.

METHODS

Ninety pregnant rats were divided into 3 groups, control, MSG and HCC fed. We determined energy intake, body weight (BW), abdominal fat, fat to body weight ratio, serum glucose, insulin, leptin, lipid profile, ob and leptin receptor-b gene expressions in pregnant rats and ob and leptin receptor-b gene expressions, serum insulin,glucose, leptin, triacylglycerides (TAG), total lipids (TL) and BW in offspring.

RESULTS

Although daily energy intake and BW of MSG treated rats were lower than those of HCC fed rats, their abdominal fat and fat body weight ratio were higher. MSG or HCC increased Ob gene expression, leptin, insulin,LDL, cholesterol, total lipids (TL), glucose and decreased leptin receptor-b gene expression. In offspring of MSG treated rats, BW, serum glucose, insulin, leptin, TAG, TL and Ob gene expression increased and leptin receptor-b gene expression decreased whereas in offspring of HCC fed rats, serum insulin, leptin, Ob and leptin receptor-b gene expression increased but serum glucose, TAG, TL or BW did not change.

CONCLUSION

We conclude that in pregnant rats, MSG, in spite of mild hypophagia, caused severe increase in fat body weight ratio, via leptin resistance, whereas, HCC increased BW and fat body weight ratio, due to hyperphagia with consequent leptin resistance. Moreover, maternal obesity in pregnancy, caused by MSG, has greater impact on offspring metabolism and BW than that induced by HCC.

Exciting times beyond the brain: metabotropic glutamate receptors in peripheral and non-neural tissues

Metabotropic glutamate (mGlu) receptors are G-protein-coupled receptors expressed primarily on neurons and glial cells, where they are located in the proximity of the synaptic cleft. In the central nervous system (CNS), mGlu receptors modulate the effects of l-glutamate neurotransmission in addition to that of a variety of other neurotransmitters. However, mGlu receptors also have a widespread distribution outside the CNS that has been somewhat neglected to date. Based on this expression, diverse roles of mGlu receptors have been suggested in a variety of processes in health and disease including controlling hormone production in the adrenal gland and pancreas, regulating mineralization in the developing cartilage, modulating lymphocyte cytokine production, directing the state of differentiation in embryonic stem cells, and modulating gastrointestinal secretory function. Understanding the role of mGlu receptors in the periphery will also provide a better insight into potential side effects of drugs currently being developed for neurological and psychiatric conditions. This review summarizes the new potential roles of mGlu receptors and raises the possibility of novel pharmacological targets for various disorders.

Glutamate-mediated signaling in Schistosoma mansoni: a novel glutamate receptor is expressed in neurons and the female reproductive tract

l-Glutamate is a major neurotransmitter of both vertebrates and invertebrates. Earlier studies have shown that glutamate stimulates neuromuscular activity in the bloodfluke, Schistosoma mansoni, but its mode of action is unknown. Here we describe a novel glutamate receptor in S. mansoni (SmGluR), the first of its kind to be identified in a parasitic flatworm. SmGluR belongs to the G protein-coupled receptor (GPCR) superfamily and is distantly related to metabotropic glutamate receptors from other species. The full-length receptor cDNA was cloned, stably expressed in HEK-293 cells and shown to be activated by glutamate, whereas aspartate and the glutamate derivative, gamma-aminobutyric acid (GABA) had no significant effect. Among the classical (mammalian) agonists and antagonists tested, only LY341495 was able to interact with the schistosome receptor, suggesting that the pharmacological profile of SmGluR is substantially different from that of receptors in the host. The presence of SmGluR in the parasite was verified by immunoprecipitation and Western blot analyses, using a specific peptide antibody. Confocal immunolocalization studies revealed that SmGluR is strongly expressed in the nervous system of adult worms and larvae. In the adults, the receptor was detected in the longitudinal nerve cords and cerebral commissures, as well as the peripheral nerve fibers and plexuses innervating the acetabulum and the somatic musculature. Outside the nervous system, SmGluR was detected along the length of the female reproductive system, including the oviduct, ootype and the uterus. A comparative expression analysis at the RNA level revealed that SmGluR is expressed at about the same level in cercaria and adult stages, as determined by quantitative reverse-transcription PCR. The results identify SmGluR as an important neuronal receptor and provide the first molecular evidence for a glutamate signaling system in schistosomes.