Stimulation of TM3 Leydig cell proliferation via GABA(A) receptors: a new role for testicular GABA

Prenatal nicotine exposure leads to epigenetic alterations in peripheral nervous system signaling genes in the testis of the rat

BACKGROUND

Prenatal nicotine exposure (PNE) has been documented to cause numerous deleterious effects on fetal development. However, the epigenetic changes promoted by nicotine exposure on germ cells are still not well understood.

OBJECTIVES

In this study, we focused on elucidating the impact of prenatal nicotine exposure on regulatory epigenetic mechanisms important for germ cell development.

METHODS

Sprague-Dawley rats were exposed to nicotine during pregnancy and male progeny was analyzed at 11 weeks of age. Testis morphology was analyzed using frozen testis sections and expression of germ cell markers was examined by RT-qPCR; histone modifications were assessed by Western Blot (WB). DNA methylation analysis was performed by methylation-specific PCR of bisulfite converted DNA. Genome-wide DNA methylation was analyzed using Methylated DNA immunoprecipitation (MeDIP)-seq. We also carried out transcriptomics analysis of pituitary glands by RNA-seq.

RESULTS

We show that gestational exposure to nicotine reduces germ cell numbers, perturbs meiosis, affects the expression of germ line reprogramming responsive genes, and impacts the DNA methylation of nervous system genes in the testis. PNE also causes perturbation of gene expression in the pituitary gland of the brain.

CONCLUSIONS

Our data demonstrate that PNE leads to perturbation of male spermatogenesis, and the observed effects are associated with changes of peripheral nervous system signaling pathways. Alterations in the expression of genes associated with diverse biological activities such as cell migration, cell adhesion and GABA signaling in the pituitary gland underscore the complexity of the effects of nicotine exposure during pregnancy.

Sub-acute exposure of male guppies (Poecilia reticulata) to environmentally relevant concentrations of PFOA and GenX induces significant changes in the testis transcriptome and reproductive traits

Poly- and perfluoroalkyl substances (PFAS) are frequently detected in the environment and are linked to adverse reproductive health outcomes in humans. Although legacy PFAS have been phased out due to their toxicity, alternative PFAS are increasingly used despite the fact that information on their toxic effects on reproductive traits is particularly scarce. Here, we exposed male guppies (Poecilia reticulata) for a short period (21 days) to an environmentally realistic concentration (1 ppb) of PFOA, a legacy PFAS, and its replacement compound, GenX, to assess their impact on reproductive traits and gene expression. Exposure to PFAS did not impair survival but instead caused sublethal effects. Overall, PFAS exposure caused changes in male sexual behaviour and had detrimental effects on sperm motility. Sublethal variations were also seen at the transcriptional level, with the modulation of genes involved in immune regulation, spermatogenesis, and oxidative stress. We also observed bioaccumulation of PFAS, which was higher for PFOA than for GenX. Our results offer a comprehensive comparison of these two PFAS and shed light on the toxicity of a newly emerging alternative to legacy PFAS. It is therefore evident that even at low concentrations and with short exposure, PFAS can have subtle yet significant effects on behaviour, fertility, and immunity. These findings underscore the potential ramifications of pollution under natural conditions and their impact on fish populations.

Ivermectin prevents stress-induced testicular damage in juvenile rats

Ivermectin is a popular antiparasitic drug used in veterinary and human medicine. Studies by our group have shown that therapeutic doses of ivermectin induce some brain and behavioral impairments, especially in the reproductive sphere. So far, the studies were focused in adulthood. Considering that juveniles are more susceptible to drugs during developmental stages and both farm/domestic animals and humans have been medicated with ivermectin in youth, it is necessary to evaluate the possible harm effects in youth. The stress variable is also important, as it potentially influences the effects produced by ivermectin. Therefore, the objective of this study was to evaluate morphofunctional and hormonal reproductive aspects of juvenile rats exposed to ivermectin and/or stressed. Prepubertal male rats were treated with 0.2 or 1.0 mg/kg of ivermectin (a therapeutic dose and a higher dose, respectively). Rats were also submitted to a restraint stress session. The testis morphology and histology were analyzed and plasma testosterone levels were measured. The two doses of ivermectin did not induce a biologically relevant effect on testis and testosterone levels of rats. However, restraint stress impaired macroscopic and microscopic morphometric and stereological parameters, as well as the histology of the testis: it increased the relative testis weight, the tubular diameter, the tubular luminal diameter, and the tubular cellular index, and injured the interstitial area. Previous treatment of juvenile rats with ivermectin prevented most of the stress-induced testes injuries. In conclusion, in addition to be a remarkable antiparasitic agent, ivermectin prevented stress-induced testes injuries in juvenile rats.

Differentiation of Myoblasts in Culture: Focus on Serum and Gamma-Aminobutyric Acid

There are many facts about the possible role of gamma-aminobutyric acid (GABA) in the development and differentiation of cells not only in nervous but also in muscle tissue. In the present study, a primary culture of rat skeletal muscle myocytes was used to evaluate the correlation between the content of GABA in the cytoplasm and the processes of myocyte division and their fusion into myotubes. The effect of exogenous GABA on the processes of culture development was also estimated. Since the classical protocol for working with myocyte cultures involves the use of fetal bovine serum (FBS) to stimulate cell division (growth medium) and horse serum (HS) to activate the differentiation process (differentiation medium), the studies were carried out both in the medium with FBS and with HS. It was found that cells grown in medium supplemented with FBS contain more GABA compared to cultures growing in medium supplemented with HS. Addition of exogeneous GABA leads to a decrease in the number of myotubes formed in both media, while the addition of an amino acid to the medium supplemented with HS had a more pronounced inhibitory effect. Thus, we have obtained data indicating that GABA is able to participate in the early stages of skeletal muscle myogenesis by modulating the fusion process.

Differential protein expression of GABA A receptor alpha 1 subunit and calbindin in rat spermatozoa associated with proteomic analysis in testis following methamphetamine administration

Methamphetamine (METH) can induce spermatogenesis impairment, testicular apoptosis, and abnormal sperm quality. It also promotes changes in the expression of receptors for sex hormones and neurotransmitters, including GABA receptors in the testis. Proteomic assessment focusing on proteins involved in the calcium signalling pathway in the testis can facilitate diagnostic factors contributing to testicular and sperm functions, especially those related to spermatogenesis and fertilisation. In this study, we proposed to determine the localisation and differential expression of GABA A receptor alpha 1 subunit (GABA A-α1) in the spermatozoa of METH-administered rats. The differential proteomic profile of the testis was also observed by focusing on proteins in the KEGG pathways belonging to the calcium signalling pathway. There were 212 differentially expressed proteins in the rat testis, based on the cut-off value of 1.2-fold change. Most of those proteins, 13 proteins, were classified in the calcium signalling pathway, including 4 down-regulated and 9 up-regulated proteins. An immunolocalisation study of the GABA A-α1 receptor and calbindin revealed their localisation in the equatorial segment of the head in the rat spermatozoa. The expression of calbindin is also found in the middle piece of sperm. An increase in GABA A-α1 receptor in rat spermatozoa was correlated with an increase in abnormal sperm motility and morphology after methamphetamine exposure. Moreover, calbindin expression in sperm decreased in METH-administered rats. All our findings demonstrate that METH influences intracellular calcium homeostasis by acting through the calcium signalling pathway-associated proteins. Moreover, it might disrupt ion homeostasis in sperm through the GABA A-α1 receptor and calbindin, triggering a change in intracellular calcium and chloride ions. These changes may cause abnormalities in spermatogenesis, testicular apoptosis, and sperm quality impairment.

FGF9 promotes cell proliferation and tumorigenesis in TM3 mouse Leydig progenitor cells

Fibroblast growth factor 9 (FGF9) modulates cell proliferation, differentiation and motility for development and tissue repair in normal cells. Growing evidence shows that abnormal activation of FGF9 signaling is associated with tumor malignancy. We have previously reported that FGF9 increases MA-10 mouse Leydig tumor cell proliferation, in vitro, and tumor growth, in vivo. Also, FGF9 promotes the tumor growth and liver metastasis of mouse Lewis lung cancer cells, in vivo. However, the effects of FGF9 in the early stage of tumorigenesis remains elusive. In this study, TM3 mouse Leydig progenitor cells, that are not tumorigenic in immunocompromised mice, were used as a model cell line to investigate the role of FGF9 in tumorigenesis. The results demonstrated that FGF9 significantly induced cell proliferation and activated the MAPK, PI3K and PLCγ signaling pathways in TM3 cells. The percentage of the cell number in G1 phase was reduced and that in S and G2/M phases was increased after FGF9 stimulation in TM3 cells. Cyclin D1, cyclin A1, CDK2, CDK1, and p21 expressions and the phosphorylation level of Rb were all induced in FGF9-treated TM3 cells. In addition, FGF9 increased the expression of FGF receptor 1-4 in TM3 cells, suggesting the positive feedback loop between FGF9 and FGFRs. Furthermore, in the allograft mouse model, FGF9 promoted the tumorigenesis of TM3 cells characterized by higher expression of tumor markers, such as tumor necrosis factor alpha (TNFα) and α-fetoprotein (AFP), in the subcutaneously inoculated TM3 cell tissue. Conclusively, FGF9 induced cell cycle to increase cell proliferation of TM3 cells through FAK, MAPK, PI3K/Akt and PLCγ signaling pathways, in vitro, and promoted the tumorigenesis of TM3 cell allograft tissue, in vivo, which is a potential marker for tumor as well as a target for cancer therapeutic strategies.

Schistosomicidal and hepatoprotective activity of gamma-aminobutyric acid (GABA) alone or combined with praziquantel against Schistosoma mansoni infection in murine model

OBJECTIVE

This study aimed to evaluate the efficacy of gamma-aminobutyric acid (GABA) alone or combined with praziquantel (PZQ) against Schistosoma (S) mansoni infection in a murine model.

METHODS

Five groups, 8 mice each, were studied; GI served as normal controls; GII: S. mansoni-infected control group and the other three S. mansoni-infected groups received drug regimens for 5 consecutive days as follows GIII: Infected-PZQ treated group (200 mg/kg/day); GIV: Infected-GABA treated group (300 mg/kg/day) and GV: Infected-PZQ-GABA treated group (100 mg/kg/day for each drug). All animal groups were sacrificed two weeks later and different parasitological, histopathological and biochemical parameters were assessed.

RESULTS

Combined GABA-PZQ treated group recorded the highest significant reduction in all parasitological, histopathological and biochemical parameters followed by PZQ and finally GABA groups. Combined GABA-PZQ treatment led to the complete disappearance of immature eggs and marked reduction of deposited eggs in liver tissues and improved liver pathology. Significant improvement in hepatic oxidative stress levels, serum albumin and total protein in response to GABA treatment alone or combined with PZQ.

CONCLUSION

GABA had schistosomicidal, hepatoprotective and antioxidant activities against S. mansoni infection, GABA disrupted parasite pairing and activity, reduced the total number of worms recovered and the number of ova in the tissues. GABA may be considered an adjuvant therapy to potentiate PZQ antiparasitic activity and eradicate infection-induced liver damage and oxidative stress.

Long-term stiripentol administration, an anticonvulsant drug, does not impair sperm parameters in rats

In this study, we investigated the influence of long-term administration of stiripentol on sex hormones and semen quality in young Wistar rats. Investigated animals received for 6 months either stiripentol or saline solution. After one month, stiripentol increased temporarily serum level of testosterone (p < 0.05) and FSH (p < 0.01). However, after 6 months levels of testosterone, FSH, LH, prolactin and SHBG were comparable in both groups. After 6 months, semen analysis did not reveal differences in sperm concentration, total sperm count and sperm motility between groups. However, stiripentol increased the rate of head defect (p < 0.001) and midpiece abnormalities (p < 0.05). Flow cytometry revealed higher percentage of live cells without lipid peroxidation (p < 0.00001) and higher percentage of live spermatozoa with intact acrosomes (p < 0.000001) in rats receiving stiripentol. There was no significant difference between groups in sperm mitochondrial activity and DNA fragmentation index. However, percentage of high DNA stainability cells was increased in stiripentol group (p < 0.001). The data showed that stiripentol does not cause obvious disturbances in young rat's semen. Detected changes in semen morphology and chromatin structure need further explanation, and their influence on rat's fertility should be evaluated.

High mRNA expression of GABA receptors in human sperm with oligoasthenoteratozoospermia and teratozoospermia and its association with sperm parameters and intracytoplasmic sperm injection outcomes

Objective

This study investigated the mRNA expression of gamma-aminobutyric acid (GABA) receptors in the sperm of oligoasthenoteratozoospermic (OAT) and teratozoospermic (TER) men compared to normozoospermic (NOR) men, as well as the relationships between GABA receptor expression and sperm parameters, fertilization rate, and embryo quality.

Methods

The mRNA expression of GABA A-α1 and GABA B-R2 receptors in sperm was examined using reverse transcription–polymerase chain reaction in three groups of patients: NOR (n=32), OAT (n=22), and TER (n=45). The fertilization rate and embryo quality were assessed in 35 patients undergoing intracytoplasmic sperm injection (ICSI; 10 NOR, 10 OAT, and 15 TER men).

Results

OAT men had significantly higher mRNA expression of GABA A-α1 and GABA B-R2 receptors in sperm than NOR men; however, the difference between TER and NOR men was not significant. High levels of these receptors were significantly correlated with low sperm concentration, motility, and morphology, as well as the rate of good-quality embryos (GQEs) at the cleavage stage after ICSI. Patients whose female partners had a >50% GQE rate at the cleavage stage had significantly lower levels of GABA A-α1 receptor expression than those whose partners had a ≤50% GQE rate.

Conclusion

Our findings indicate that mRNA levels of GABA receptors in human sperm are correlated with poor sperm quality and associated with embryo development after ICSI treatment. The GABA A-α1 receptor in sperm has a stronger relationship with embryo quality at the cleavage stage than the GABA B-R2 receptor.

Regulation of Human Spermatogenesis

Human spermatogenesis (HS) is an intricate network of sequential processes responsible for the production of the male gamete, the spermatozoon. These processes take place in the seminiferous tubules (ST) of the testis, which are small tubular structures considered the functional units of the testes. Each human testicle contains approximately 600-1200 STs [1], and are capable of producing up to 275 million spermatozoa per day [2].

Propofol induces apoptosis by activating caspases and the MAPK pathways, and inhibiting the Akt pathway in TM3 mouse Leydig stem/progenitor cells

Propofol is an anesthetic agent moderating GABA receptors in the nervous system. A number of studies have demonstrated that propofol exerts a negative effect on neural stem cell development in the neonatal mouse hippocampus. However, to the best of our knowledge, there is no study available to date illustrating whether neonatal exposure to propofol affects Leydig stem/progenitor cell development for normal male reproductive development and functions, and the regulatory mechanism remains elusive. In the present study, TM3 cells, a mouse Leydig stem/progenitor cell line, was treated with propofol. The data illustrated that propofol significantly reduced TM3 cell viability. TM3 subG1 phase cell numbers were significantly increased by propofol assayed by flow cytometric analysis. Annexin V/PI double staining assay of the TM3 Leydig cells also demonstrated that propofol increased TM3 cell apoptosis. In addition, cleaved caspase‑8, ‑9 and ‑3 and/or poly(ADP‑ribose) polymerase (PARP) were significantly activated by propofol in the TM3 cells. Furthermore, the expression levels of phospho‑JNK, phospho‑ERK1/2 and phospho‑p38 were activated by propofol in the TM3 cells, indicating that propofol induced apoptosis through the mitogen‑activated protein kinase (MAPK) pathway. Additionally, propofol diminished the phosphorylation of Akt to increase the apoptosis of TM3 cells. On the whole, the findings of the present study demonstrate that propofol induces TM3 cell apoptosis by activating caspases and MAPK pathways, as well as by inhibiting the Akt pathway in TM3 cells. These findings illustrate that propofol affects the viability of Leydig stem/progenitor cells possibly related to the development of the male reproductive system.

Transcriptome-wide changes in testes reveal molecular differences in photoperiod-induced seasonal reproductive life-history states in migratory songbirds

We investigated the molecular basis of seasonal testicular states in black-headed buntings (Emberiza melanocephala), in which seasonal migrations limit reproduction to a narrow time-window during the year. We examined testicular gene expressions in buntings during short day-induced photosensitive nonreproductive state (SDSE), and during long day-induced early (LDES) and late (LDLS) gonadal maturation and regressed photorefractory (LDRF) seasonal states. Using Kallisto, we pseudoaligned the RNA-Seq transcripts and calculated the transcript abundance. We found 1,799 differentially expressed genes (DEGs) between the four photoperiod-induced seasonal states. Further pairwise comparison with SDSE revealed 1,187, 1,224, and 1,238 DEGs in LDES, LDLS, and LDRF, respectively; 852 genes were common to three comparisons. We then identified genetic pathways putatively involved in seasonal testicular cycle. DEGs that enriched calcium ion binding were highly expressed in testicular maturation states. Similarly, DEGs that enriched glycolytic pathway were highly expressed in LDES and LDRF states. More specifically, quantitative polymerase chain reaction showed significant differences between the photoperiod-induced states in testicular expression of genes (HOOK1, RGS2, PRDX4, BCL6, CYFIP2, PDCD4, P2RX4, and GABRA1) involved in gametogenesis and associated pathways. Overall, these results show significant transcriptional differences, and provide insights into the molecular basis of seasonal changes in the reproductive life-history states in a photoperiodic species.

GABA promotes β-cell proliferation, but does not overcome impaired glucose homeostasis associated with diet-induced obesity

γ-Aminobutyric acid (GABA) administration has been shown to increase β-cell mass, leading to a reversal of type 1 diabetes in mice. Whether GABA has any effect on β cells of healthy and prediabetic/glucose-intolerant obese mice remains unknown. In the present study, we show that oral GABA administration ( ad libitum) to mice indeed increased pancreatic β-cell mass, which led to a modest enhancement in insulin secretion and glucose tolerance. However, GABA treatment did not further increase insulin-positive islet area in high fat diet-fed mice and was unable to prevent or reverse glucose intolerance and insulin resistance. Mechanistically, whether in vivo or in vitro, GABA treatment increased β-cell proliferation. In vitro, the effect was shown to be mediated via the GABA_A receptor. Single-cell RNA sequencing analysis revealed that GABA preferentially up-regulated pathways linked to β-cell proliferation and simultaneously down-regulated those networks required for other processes, including insulin biosynthesis and metabolism. Interestingly, single-cell differential expression analysis revealed GABA treatment gave rise to a distinct subpopulation of β cells with a unique transcriptional signature, including urocortin 3 ( ucn3), wnt4, and hepacam2. Taken together, this study provides new mechanistic insight into the proliferative nature of GABA but suggests that β-cell compensation associated with prediabetes overlaps with, and negates, its proliferative effects.-Untereiner, A., Abdo, S., Bhattacharjee, A., Gohil, H., Pourasgari, F., Ibeh, N., Lai, M., Batchuluun, B., Wong, A., Khuu, N., Liu, Y., Al Rijjal, D., Winegarden, N., Virtanen, C., Orser, B. A., Cabrera, O., Varga, G., Rocheleau, J., Dai, F. F., Wheeler, M. B. GABA promotes β-cell proliferation, but does not overcome impaired glucose homeostasis associated with diet-induced obesity.

Midazolam activates caspase, MAPKs and endoplasmic reticulum stress pathways, and inhibits cell cycle and Akt pathway, to induce apoptosis in TM3 mouse Leydig progenitor cells

Background

Midazolam (MDZ) has powerful hypnosis, amnesia, anti-anxiety and anticonvulsant effects. Studies have shown that prenatally developmental toxicity of diazepam can be observed in many organs/tissues. However, it remains elusive in male reproductive system.

Materials and methods

TM3 mouse Leydig progenitor cell line was used to determine whether MDZ has any unfavorable effects.

Results

Midazolam significantly decreased cell viability in dose- and time-dependent manners in TM3 cells. In flow cytometry analysis, midazolam significantly increased subG1 phase cell numbers, and annexin V/PI double staining assay further confirmed that MDZ induced apoptosis in TM3 cells. Moreover, MDZ significantly induced the expression of caspase-8 and -3 proteins and the phosphorylation of JNK, ERK1/2 and p38. Besides, MDZ didn’t activate Akt pathway in TM3 cells. Furthermore, the expressions of p-EIF2α, ATF4, ATF3 and CHOP were induced by midazolam, suggesting that midazolam could induce apoptosis through endoplasmic reticulum (ER) stress in TM3 cells. Additionally, the expressions of cyclin A, cyclin B and CDK1 were inhibited by midazolam through the regulation of p53 in TM3 cells, indicating that midazolam could regulate cell cycle to induce apoptosis.

Conclusion

Midazolam could activate caspase, MAPKs and ER stress pathways and impede Akt pathway and cell cycle to induce apoptosis in TM3 mouse Leydig progenitor cells.

GABAergic Alterations in the Rat Testis after Methamphetamine Exposure

Gamma-aminobutyric acid (GABA), GABA-A receptors and GABA transporter 1 (GAT1) were reported to be involved in the proliferation of Leydig cells, testosterone production and spermatogenesis. Since methamphetamine (METH) has been reported to have adverse effects on testis and its functions, the aim of this study was therefore to determine the changes of GABAergic activity in testis after METH exposure. Male Sprague-Dawley rats were divided into control, acute binge (AB-METH), escalating dose (ED METH) and escalating dose-binge (ED-binge METH) groups. After sacrifice, rat testes were removed and used to estimate GABA concentration and the expression of GABA-A receptor, GAD1, GAD2 and GAT1 genes by using HPLC and RT-PCR, respectively. The GABA concentration was significantly increased in all METH-administrated groups. In addition, significant increases of GABA-A α1 receptor and GAD1 genes expression were found in the ED-binge METH group. Gene expressions of GAT1 were numerically decreased in all METH-administrated rats and reached significant in the ED METH group. These results indicated a compensatory upregulation of GABA production and its functions in testis after METH exposure. Thus, these changes might represent a homeostatic response of GABAergic to the adverse effects of METH.

Histological and transcriptomic effects of 17α-methyltestosterone on zebrafish gonad development

BACKGROUND

Sex hormones play important roles in teleost ovarian and testicular development. In zebrafish, ovarian differentiation appears to be dictated by an oocyte-derived signal via Cyp19a1a aromatase-mediated estrogen production. Androgens and aromatase inhibitors can induce female-to-male sex reversal, however, the mechanisms underlying gonadal masculinisation are poorly understood. We used histological analyses together with RNA sequencing to characterise zebrafish gonadal transcriptomes and investigate the effects of 17α-methyltestosterone on gonadal differentiation.

RESULTS

At a morphological level, 17α-methyltestosterone (MT) masculinised gonads and accelerated spermatogenesis, and these changes were paralleled in masculinisation and de-feminisation of gonadal transcriptomes. MT treatment upregulated expression of genes involved in male sex determination and differentiation (amh, dmrt1, gsdf and wt1a) and those involved in 11-oxygenated androgen production (cyp11c1 and hsd11b2). It also repressed expression of ovarian development and folliculogenesis genes (bmp15, gdf9, figla, zp2.1 and zp3b). Furthermore, MT treatment altered epigenetic modification of histones in zebrafish gonads. Contrary to expectations, higher levels of cyp19a1a or foxl2 expression in control ovaries compared to MT-treated testes and control testes were not statistically significant during early gonad development (40 dpf).

CONCLUSION

Our study suggests that both androgen production and aromatase inhibition are important for androgen-induced gonadal masculinisation and natural testicular differentiation in zebrafish.

Spermatogenesis in humans and its affecting factors

Spermatogenesis is an extraordinary complex process. The differentiation of spermatogonia into spermatozoa requires the participation of several cell types, hormones, paracrine factors, genes and epigenetic regulators. Recent researches in animals and humans have furthered our understanding of the male gamete differentiation, and led to clinical tools for the better management of male infertility. There is still much to be learned about this intricate process. In this review, the critical steps of human spermatogenesis are discussed together with its main affecting factors.

Gamma aminobutyric acid B and 5-hydroxy tryptamine 2A receptors functional regulation during enhanced liver cell proliferation by GABA and 5-HT chitosan nanoparticles treatment

Liver is one of the major organs in vertebrates and hepatocytes are damaged by many factors. The liver cell maintenance and multiplication after injury and treatment gained immense interest. The present study investigated the role of Gamma aminobutyric acid (GABA) and serotonin or 5-hydroxytryptamine (5-HT) coupled with chitosan nanoparticles in the functional regulation of Gamma aminobutyric acid B and 5-hydroxy tryptamine 2A receptors mediated cell signaling mechanisms, extend of DNA methylation and superoxide dismutase activity during enhanced liver cell proliferation. Liver injury was achieved by partial hepatectomy of male Wistar rats and the GABA and 5-HT chitosan nanoparticles treatments were given intraperitoneally. The experimental groups were sham operated control (C), partially hepatectomised rats with no treatment (PHNT), partially hepatectomised rats with GABA chitosan nanoparticle (GCNP), 5-HT chitosan nanoparticle (SCNP) and a combination of GABA and 5-HT chitosan nanoparticle (GSCNP) treatments. In GABA and 5-HT chitosan nanoparticle treated group there was a significant decrease (P<0.001) in the receptor expression of Gamma aminobutyric acid B and a significant increase (P<0.001) in the receptor expression of 5-hydroxy tryptamine 2A when compared to PHNT. The cyclic adenosine monophosphate content and its regulatory protein, presence of methylated DNA and superoxide dismutase activity were decreased in GCNP, SCNP and GSCNP when compared to PHNT. The Gamma aminobutyric acid B and 5-hydroxy tryptamine 2A receptors coupled signaling elements played an important role in GABA and 5-HT chitosan nanoparticles induced liver cell proliferation which has therapeutic significance in liver disease management.

Role of GABA and serotonin coupled chitosan nanoparticles in enhanced hepatocyte proliferation

The development of nanoparticles containing active molecules having improved stability, sustained release and maximum half life helps in cell proliferation result in enhanced tissue regeneration. Our study focuses on the use of Gamma amino butyric acid (GABA) and serotonin (5-HT) coupled chitosan nanoparticles for the active liver regeneration in male Wistar rats. The nanoparticles were prepared and the morphology was studied using SEM. The FT-IR spectra of the nanoparticles and the maximum encapsulation efficiency of GABA and 5-HT binding to chitosan nanoparticles were observed. The in vitro release studies provided the percentage release of GABA and 5-HT from the nanoparticles at different time intervals. The quantification of DNA and protein syntheses was done using [(3)H] thymidine and [(3)H] leucine uptake studies that determined the enhancement in hepatocyte proliferation. Our results project the role of GABA and 5-HT chitosan nanoparticles in the treatment of liver based diseases.

Role of GABA receptors in fetal lung development in rats

Fluid accumulation is critical for lung distension and normal development. The multi-subunit γ-amino butyric acid type A receptors (GABA_A) mainly act by mediating chloride ion (Cl⁻) fluxes. Since fetal lung actively secretes Cl⁻-rich fluid, we investigated the role of GABA_A receptors in fetal lung development. The physiological ligand, GABA, and its synthesizing enzyme, glutamic acid decarboxylase, were predominantly localized to saccular epithelium. To examine the effect of activating GABA_A receptors in fetal lung development in vivo, timed-pregnant rats of day 18 gestation underwent an in utero surgery for the administration of GABA_A receptor modulators into the fetuses. The fetal lungs were isolated on day 21 of gestation and analyzed for changes in fetal lung development. Fetuses injected with GABA had a significantly higher body weight and lung weight when compared to phosphate-buffered saline (control)-injected fetuses. GABA-injected fetal lungs had a higher number of saccules than the control. GABA increased the number of alveolar epithelial type II cells as indicated by surfactant protein C-positive cells. However, GABA decreased the number of α-smooth muscle actin-positive myofibroblasts, but did not affect the number of Clara cells or alveolar type I cells. GABA-mediated effects were blocked by the GABA_A receptor antagonist, bicuculline. GABA also increased cell proliferation and Cl⁻ efflux in fetal distal lung epithelial cells. In conclusion, our results indicate that GABA_A receptors accelerate fetal lung development, likely through an enhanced cell proliferation and/or fluid secretion.

GABA's control of stem and cancer cell proliferation in adult neural and peripheral niches

Aside from traditional neurotransmission and regulation of secretion, gamma-amino butyric acid (GABA) through GABA(A) receptors negatively regulates proliferation of pluripotent and neural stem cells in embryonic and adult tissue. There has also been evidence that GABAergic signaling and its control over proliferation is not only limited to the nervous system, but is widespread through peripheral organs containing adult stem cells. GABA has emerged as a tumor signaling molecule in the periphery that controls the proliferation of tumor cells and perhaps tumor stem cells. Here, we will discuss GABA's presence as a near-universal signal that may be altered in tumor cells resulting in modified mitotic activity.

Differential expression of gamma-aminobutyric acid receptor A (GABA(A)) and effects of homocysteine

BACKGROUND

gamma-Aminobutyric acid (GABA) is a known inhibitory neurotransmitter in the mammalian central nervous system, and homocysteine (Hcy) behaves as an antagonist for GABA(A) receptor. Although the properties and functions of GABA(A) receptors are well studied in mouse neural tissue, its presence and significance in non-neural tissue remains obscure. The aim of the present study was to examine the expression of GABA(A) receptor and its subunits in non-neural tissue.

METHODS

The mice were analyzed. The presence of GABA(A) receptor and its subunits was evaluated using Western blot and reverse transcription polymerase chain reaction.

RESULTS

We report that GABA(A) receptor protein is abundant in the renal medulla, cortex, heart, left ventricle, aorta and pancreas. Low levels of GABA(A) receptor protein were detected in the atria of the heart, right ventricle, lung and stomach. The mRNA protein expression of GABA(A) receptor subunit shows that alpha1, beta1, beta3 and gamma1 subunits are present only in brain. The mRNA protein expression levels of GABA(A) receptor alpha2, alpha6, beta2 and gamma3 subunits were highly expressed in brain compared to other tested tissue, while GABA(A) receptor gamma2 subunit was expressed only in brain and kidney. Treatment of microvascular endothelial cells with Hcy decreased GABA(A) receptor protein level, which was restored to its baseline level in the presence of GABA(A) receptor agonist, muscimol. The distribution of GABA(A) and GABA(B) receptors in wild type mice was determined and tissue-specific expression patterns were found showing that several receptor subtypes were also expressed in the central nervous system.

CONCLUSIONS

Hcy, a GABA(A) agonist, was found to decrease GABA(A) expression levels. These data enlarge knowledge on distribution of GABA receptors and give novel ideas of the effects of Hcy on different organs.

Heterogeneous population of dopaminergic neurons derived from mouse embryonic stem cells: preliminary phenotyping based on receptor expression and function

The possibility exists that directed differentiation of mouse embryonic stem (mES) cells is capable of yielding enriched populations of dopaminergic neurons, but at present there is little understanding of the pharmacological properties of these cells; or whether such cells represent a pharmacologically, phenotypically similar population. In this study we used a simple culture protocol to generate dopaminergic neurons and offer a preliminary pharmacological investigation of these cells using Ca2+ imaging and [3H]-dopamine release studies. In fluo-4 AM loaded cells, 13-17 days postplating, and after the addition of tetrodotoxin some of the population of mouse embryonic stem cell-derived neurons responded to adenosine triphosphate (ATP), noradrenaline (NA), acetylcholine (ACh) and L-glutamate (L-glut) with elevations of Ca2+ influx. Within the microtubule-associated protein and tyrosine hydroxylase (TH)-positive cell population adenosine triphosphate, noradrenaline, acetylcholine and L-glutamate elicited positive elevations of Ca2+ in 74, 66, 58 and 67% of the population; cells could be further subdivided into three major pharmacologically distinct populations based on the combinations of agonist they responded to. Acetylcholine (30 microM) and noradrenaline (30 microM) were the only agonists to elicit significant tritium overflow from [3H]-dopamine loaded cells. The acetylcholine effect was blocked by atropine (1 microM) and tetrodotoxin (1 microM) and elevated by haloperidol (100 nM). The noradrenaline effects were reduced by cocaine (10 microM), but not by tetrodotoxin (100 nM). These data indicate that the dopaminergic neurons derived from mouse embryonic stem cells represent a heterogeneous population possessing combinations of purinergic, adrenergic, cholinergic and glutamatergic receptors located on the cell soma.

A graphical systems model to facilitate hypothesis-driven ecotoxicogenomics research on the teleost brain-pituitary-gonadal axis

Graphical systems models are powerful tools that can help facilitate hypothesis-driven ecotoxicogenomic research and aid in mechanistic interpretation of results. This paper describes a novel graphical model of the teleost brain-pituitary-gonadal (BPG) axis designed for ecotoxicogenomics research on endocrine-disrupting chemicals using small fish models. The model incorporates six compartments representing the major organs involved in the fish reproductive axis and depicts the interactions of over 105 proteins and 40 simple molecules, transcriptional regulation of 25 genes, and over 300 different reactions/ processes. Application of the model is illustrated in the context of a study examining effects of the competitive aromatase inhibitor, fadrozole, on gene expression in gonad, brain, and liver tissue of fathead minnows. Changes in mRNA transcript abundance were measured using a fathead minnow oligonucleotide microarray and quantitative real-time polymerase chain reaction. Gene expression changes observed in the ovaries of females exposed to 6.3 microg fadrozole/L for7 d were functionally consistent with fadrozole's mechanism of action, and expected compensatory responses of the BPG axis to fadrozole's effects. Furthermore, microarray results helped identify additional elements (genes/ proteins) that could be included in the model to potentially increase its predictive capacity. With proper recognition of

Ablation of the glucagon receptor gene increases fetal lethality and produces alterations in islet development and maturation

Although glucagon (GLU) plays a pivotal role in glucose homeostasis, its role in the regulation of fetal growth and maturation is poorly understood. These issues were examined in a line of mice with a global deletion of the GLU receptor (Gcgr-/-), which are characterized by lower blood glucose levels and by alpha- and delta-cell hyperplasia in adults. Ablation of Gcgr was deleterious to fetal survival; it delayed beta-cell differentiation and perturbed the proportion of beta- to alpha-cells in embryonic islets. In adults, the mutation inhibited the progression of alpha-cells to maturity, affected the expression of several beta-cell-specific genes, and resulted in an augmentation of the alpha-, beta-, and delta-cell mass. This increase was due to an augmentation in both islet number and in the rate of proliferation of cells expressing GLU or insulin. These findings suggest that GLU participates in a feedback loop that regulates the proportion of the different endocrine cell types in islets, the number of islets per pancreas, and development of the mature alpha-cell phenotype.

The aryl hydrocarbon receptor pathway and sexual differentiation of neuroendocrine functions

Historically, much of the research on health effects of environmental pollutants focused on ascertaining whether compounds were carcinogenic. More recent findings show that environmental contaminants also exert insidious effects by disrupting hormone action. Of particular concern are findings that developmental exposure to dioxins, chemicals that act through the aryl hydrocarbon receptor pathway, permanently alters sexually differentiated neural functions in animal models. In this review, we focus on mechanisms through which dioxins disrupt neuroendocrine development as exemplified by effects on a brain region critical for ovulation in rodents. We also provide evidence that dysregulation of GABAergic neural development may be a general mechanism underlying a broad spectrum of effects seen after perinatal dioxin exposure.

The peripheral GABAergic system as a target in endocrine disorders

In addition to its well-recognized function as a cerebral inhibitory transmitter, less well established is the role of GABA in peripheral nervous and endocrine systems. We summarize current evidence that GABA serves as a neurotransmitter or neuromodulator in the autonomic nervous system and as a hormone or trophic factor in non-neuronal peripheral tissue as well. GABA is widely distributed in endocrine tissues including the pituitary, pancreas, adrenal glands, uterus, ovaries, placenta and testis. Moreover, GABA is involved in the pathophysiology of endocrine disorders such as diabetes mellitus, diseases of adrenal glands and reproductive tracts. Current literature indicates that the peripheral GABA system in the autonomic nervous system, endocrine and immune systems is as yet nearly an unexplored target for diagnosis and drug treatment.

Insights into GABA receptor signalling in TM3 Leydig cells

Gamma-aminobutyric acid (GABA) is an emerging signalling molecule in endocrine organs, since it is produced by endocrine cells and acts via GABA(A) receptors in a paracrine/autocrine fashion. Testicular Leydig cells are producers and targets for GABA. These cells express GABA(A) receptor subunits and in the murine Leydig cell line TM3 pharmacological activation leads to increased proliferation. The signalling pathway of GABA in these cells is not known in this study. We therefore attempted to elucidate details of GABA(A) signalling in TM3 and adult mouse Leydig cells using several experimental approaches. TM3 cells not only express GABA(A )receptor subunits, but also bind the GABA agonist [(3)H]muscimol with a binding affinity in the range reported for other endocrine cells (K(d) = 2.740 +/- 0.721 nM). However, they exhibit a low B(max) value of 28.08 fmol/mg protein. Typical GABA(A) receptor-associated events, including Cl(-) currents, changes in resting membrane potential, intracellular Ca(2+) or cAMP, were not measurable with the methods employed in TM3 cells, or, as studied in part, in primary mouse Leydig cells. GABA or GABA(A) agonist isoguvacine treatment resulted in increased or decreased levels of several mRNAs, including transcription factors (c-fos, hsf-1, egr-1) and cell cycle-associated genes (Cdk2, cyclin D1). In an attempt to verify the cDNA array results and because egr-1 was recently implied in Leydig cell development, we further studied this factor. RT-PCR and Western blotting confirmed a time-dependent regulation of egr-1 in TM3. In the postnatal testis egr-1 was seen in cytoplasmic and nuclear locations of developing Leydig cells, which bear GABA(A) receptors and correspond well to TM3 cells. Thus, GABA acts via an atypical novel signalling pathway in TM3 cells. Further details of this pathway remain to be elucidated.