Microglial Acid Sensing Regulates Carbon Dioxide-Evoked Fear

BACKGROUND

Carbon dioxide (CO2) inhalation, a biological challenge and pathologic marker in panic disorder, evokes intense fear and panic attacks in susceptible individuals. The molecular identity and anatomic location of CO2-sensing systems that translate CO2-evoked fear remain unclear. We investigated contributions of microglial acid sensor T cell death-associated gene-8 (TDAG8) and microglial proinflammatory responses in CO2-evoked behavioral and physiological responses.

METHODS

CO2-evoked freezing, autonomic, and respiratory responses were assessed in TDAG8-deficient ((-/-)) and wild-type ((+/+)) mice. Involvement of TDAG8-dependent microglial activation and proinflammatory cytokine interleukin (IL)-1β with CO2-evoked responses was investigated using microglial blocker, minocycline, and IL-1β antagonist IL-1RA. CO2-chemosensitive firing responses using single-cell patch clamping were measured in TDAG8(-/-) and TDAG8(+/+) mice to gain functional insights.

RESULTS

TDAG8 expression was localized in microglia enriched within the sensory circumventricular organs. TDAG8(-/-) mice displayed attenuated CO2-evoked freezing and sympathetic responses. TDAG8 deficiency was associated with reduced microglial activation and proinflammatory cytokine IL-1β within the subfornical organ. Central infusion of microglial activation blocker minocycline and IL-1β antagonist IL-1RA attenuated CO2-evoked freezing. Finally, CO2-evoked neuronal firing in patch-clamped subfornical organ neurons was dependent on acid sensor TDAG8 and IL-1β.

CONCLUSIONS

Our data identify TDAG8-dependent microglial acid sensing as a unique chemosensor for detecting and translating hypercapnia to fear-associated behavioral and physiological responses, providing a novel mechanism for homeostatic threat detection of relevance to psychiatric conditions such as panic disorder.

Central Agonism of GPR120 Acutely Inhibits Food Intake and Food Reward and Chronically Suppresses Anxiety-Like Behavior in Mice

BACKGROUND

GPR120 (FFAR4) is a G-protein coupled receptor implicated in the development of obesity and the antiinflammatory and insulin-sensitizing effects of omega-3 (ω-3) polyunsaturated fatty acids. Increasing central ω-3 polyunsaturated fatty acid levels has been shown to have both anorectic and anxiolytic actions. Despite the strong clinical interest in GPR120, its role in the brain is largely unknown, and thus we sought to determine the impact of central GPR120 pharmacological activation on energy balance, food reward, and anxiety-like behavior.

METHODS

Male C57Bl/6 mice with intracerebroventricular cannulae received a single injection (0.1 or 1 µM) or continuous 2-week infusion (1 µM/d; mini-pump) of a GPR120 agonist or vehicle. Free-feeding intake, operant lever-pressing for palatable food, energy expenditure (indirect calorimetry), and body weight were measured. GPR120 mRNA expression was measured in pertinent brain areas. Anxiety-like behavior was assessed in the elevated-plus maze and open field test.

RESULTS

GPR120 agonist injections substantially reduced chow intake during 4 hours postinjection, suppressed the rewarding effects of high-fat/-sugar food, and blunted approach-avoidance behavior in the open field. Conversely, prolonged central GPR120 agonist infusions reduced anxiety-like behavior in the elevated-plus maze and open field, yet failed to affect free-feeding intake, energy expenditure, and body weight on a high-fat diet.

CONCLUSION

Acute reductions in food intake and food reward suggest that GPR120 could mediate the effects of central ω-3 polyunsaturated fatty acids to inhibit appetite. The anxiolytic effect elicited by GPR120 agonist infusions favors the testing of compounds that can enter the brain to activate GPR120 for the mitigation of anxiety.

Alpha-ketoglutarate promotes skeletal muscle hypertrophy and protein synthesis through Akt/mTOR signaling pathways

Skeletal muscle weight loss is accompanied by small fiber size and low protein content. Alpha-ketoglutarate (AKG) participates in protein and nitrogen metabolism. The effect of AKG on skeletal muscle hypertrophy has not yet been tested, and its underlying mechanism is yet to be determined. In this study, we demonstrated that AKG (2%) increased the gastrocnemius muscle weight and fiber diameter in mice. Our in vitro study also confirmed that AKG dose increased protein synthesis in C2C12 myotubes, which could be effectively blocked by the antagonists of Akt and mTOR. The effects of AKG on skeletal muscle protein synthesis were independent of glutamate, its metabolite. We tested the expression of GPR91 and GPR99. The result demonstrated that C2C12 cells expressed GPR91, which could be upregulated by AKG. GPR91 knockdown abolished the effect of AKG on protein synthesis but failed to inhibit protein degradation. These findings demonstrated that AKG promoted skeletal muscle hypertrophy via Akt/mTOR signaling pathway. In addition, GPR91 might be partially attributed to AKG-induced skeletal muscle protein synthesis.

Retinal lipid and glucose metabolism dictates angiogenesis through the lipid sensor Ffar1

Tissues with high metabolic rates often use lipids, as well as glucose, for energy, conferring a survival advantage during feast and famine. Current dogma suggests that high-energy-consuming photoreceptors depend on glucose. Here we show that the retina also uses fatty acid β-oxidation for energy. Moreover, we identify a lipid sensor, free fatty acid receptor 1 (Ffar1), that curbs glucose uptake when fatty acids are available. Very-low-density lipoprotein receptor (Vldlr), which is present in photoreceptors and is expressed in other tissues with a high metabolic rate, facilitates the uptake of triglyceride-derived fatty acid. In the retinas of Vldlr(-/-) mice with low fatty acid uptake but high circulating lipid levels, we found that Ffar1 suppresses expression of the glucose transporter Glut1. Impaired glucose entry into photoreceptors results in a dual (lipid and glucose) fuel shortage and a reduction in the levels of the Krebs cycle intermediate α-ketoglutarate (α-KG). Low α-KG levels promotes stabilization of hypoxia-induced factor 1a (Hif1a) and secretion of vascular endothelial growth factor A (Vegfa) by starved Vldlr(-/-) photoreceptors, leading to neovascularization. The aberrant vessels in the Vldlr(-/-) retinas, which invade normally avascular photoreceptors, are reminiscent of the vascular defects in retinal angiomatous proliferation, a subset of neovascular age-related macular degeneration (AMD), which is associated with high vitreous VEGFA levels in humans. Dysregulated lipid and glucose photoreceptor energy metabolism may therefore be a driving force in macular telangiectasia, neovascular AMD and other retinal diseases.

Chronic Nicotine Exposure Abolishes Maternal Systemic and Renal Adaptations to Pregnancy in Rats

Pregnancy is characterized by maternal systemic and intrarenal vasodilation, leading to increases in the renal plasma flow (RPF) and glomerular filtration rate (GFR). These responses are mainly mediated by nitric oxide (NO) and relaxin. The impact of cigarette smoking on the maternal adaptations to pregnancy is unclear. Here we evaluated the effects of chronic exposure to nicotine on systemic and intrarenal parameters in virgin (V) and 14-day pregnant (P) Wistar rats. V and P groups received saline or nicotine (6 mg·kg^-1·day^-1) respectively, via osmotic minipumps for 28 days, starting 14 days before pregnancy induction. Nicotine induced a 10% increase in blood pressure in the V group and minimized the characteristic pregnancy-induced hypotension. Renal sympathetic nerve activity (rSNA) and baroreflex sensitivity were impaired by nicotine mainly in the P group, indicating that the effect of nicotine on blood pressure was not mediated by nervous system stimulation. Nicotine had no effect on GFR in the V rats but reduced GFR of the P group by 30%. Renal expression of sodium and water transporters was downregulated by nicotine, resulting in increased fractional sodium excretion mainly in the P group, suggesting that nicotine compromised the sodium and water retention required for normal gestation. There was a reduction in the expression of inducible NO synthase (iNOS) in both the kidney tissue and renal artery, as well as in the expression of the relaxin receptor (LGR7). These results clearly show that nicotine induced deleterious effects in both virgin and pregnant animals, and abolished the maternal capacity to adapt to pregnancy.

Expression of the Bitter Taste Receptor, T2R38, in Enteroendocrine Cells of the Colonic Mucosa of Overweight/Obese vs. Lean Subjects

Bitter taste receptors (T2Rs) are expressed in the mammalian gastrointestinal mucosa. In the mouse colon, T2R138 is localized to enteroendocrine cells and is upregulated by long-term high fat diet that induces obesity. The aims of this study were to test whether T2R38 expression is altered in overweight/obese (OW/OB) compared to normal weight (NW) subjects and characterize the cell types expressing T2R38, the human counterpart of mouse T2R138, in human colon. Colonic mucosal biopsies were obtained during colonoscopy from 35 healthy subjects (20 OW/OB and 15 NW) and processed for quantitative RT-PCR and immunohistochemistry using antibodies to T2R38, chromogranin A (CgA), glucagon like peptide-1 (GLP-1), cholecystokinin (CCK), or peptide YY (PYY). T2R38 mRNA levels in the colonic mucosa of OW/OB were increased (> 2 fold) compared to NW subjects but did not reach statistical significance (P = 0.06). However, the number of T2R38 immunoreactive (IR) cells was significantly increased in OW/OB vs. NW subjects (P = 0.01) and was significantly correlated with BMI values (r = 0.7557; P = 0.001). In both OW/OB and NW individuals, all T2R38-IR cells contained CgA-IR supporting they are enteroendocrine. In both groups, T2R38-IR colocalized with CCK-, GLP1- or PYY-IR. The overall CgA-IR cell population was comparable in OW/OB and NW individuals. This study shows that T2R38 is expressed in distinct populations of enteroendocrine cells in the human colonic mucosa and supports T2R38 upregulation in OW/OB subjects. T2R38 might mediate host functional responses to increased energy balance and intraluminal changes occurring in obesity, which could involve peptide release from enteroendocrine cells.

Diethylstilbestrol Regulates the Expression of LGR8 in Mouse Gubernaculum Testis Cells

BACKGROUND Hormonal effects on the gubernaculum can affect testicular descent. Diethylstilbestrol (DES) is a nonsteroidal synthetic estrogen that disrupts the outgrowth of gubernaculums, leading to testis maldescent. However, the underlying mechanisms remain elusive. MATERIAL AND METHODS The gubernaculum were removed from 3-day-old mice and cultured. The subcultured cells were randomly divided into a normal control group and experimental groups. The DES groups were administered 10 μg/ml, 1 μg/ml, 0.1 μg/ml, 0.01 μg/ml of diethylstilbestrol dissolved in dimethyl sulfoxide (DMSO) respectively. The cell morphology was observed under an inverted microscope, and leucine-rich repeat-containing G protein-coupled receptor 8 (LGR8) was localized by immunofluorescence. The expressions of LGR8 gene and protein in gubernaculum cells were quantified by RT-PCR and Flow Cytometer respectively. RESULTS DES treatment converted cells from a normal fibroblast-like morphology into a more refractile, spindle-shaped morphology or irregular elliptical shapes along with cytoplasmic shrinkage. LGR8 was expressed in the cytoplasmic membrane, DES dose-dependently downregulated LGR8 expression at low doses (≤1.0 μg/ml), but upregulated LGR8 at high doses (10 μg/ml) at both the mRNA and protein levels. CONCLUSIONS These results suggest that DES causes testicular maldescent by altering the LGR8 pathway in mouse gubernaculum testis cells.

Somatic and Neuroendocrine Changes in Response to Chronic Corticosterone Exposure During Adolescence in Male and Female Rats

Prolonged stress and repeated activation of the hypothalamic-pituitary-adrenal axis can result in many sex-dependent behavioural and metabolic changes in rats, including alterations in feeding behaviour and reduced body weight. In adults, these effects of stress can be mimicked by corticosterone, a major output of the hypothalamic-pituitary-adrenal axis, and recapitulate the stress-induced sex difference, such that corticosterone-treated males show greater weight loss than females. Similar to adults, chronic stress during adolescence leads to reduced weight gain, particularly in males. However, it is currently unknown whether corticosterone mediates this somatic change and whether additional measures of neuroendocrine function are affected by chronic corticosterone exposure during adolescence in a sex-dependent manner. Therefore, we examined the effects of non-invasively administered corticosterone (150 or 300 μg/ml) in the drinking water of male and female rats throughout adolescent development (30-58 days of age). We found that adolescent animals exposed to chronic corticosterone gain significantly less weight than controls, which may be partly mediated by the effects of corticosterone on food consumption, fluid intake and gonadal hormone function. Our data further show that, despite similar circulating corticosterone levels, males demonstrate a greater sensitivity to these changes than females. We also found that Npy1 and Npy5 receptor mRNA expression, genes implicated in appetite regulation, was significantly reduced in the ventral medial hypothalamus of corticosterone-treated males and females compared to controls. Finally, parameters of gonadal function, such as plasma sex steroid concentrations and weight of reproductive tissues, were reduced by adolescent corticosterone treatment, although only in males. The data obtained in the present study indicate that chronic corticosterone exposure throughout adolescent development results in significant and sex-dependent somatic and neuroendocrine changes, and the results also provide an experimental framework for further investigating the impact of corticosterone on metabolic and neuroendocrine function during adolescence.

QRFP-26 enhances insulin's effects on glucose uptake in rat skeletal muscle cells

QRFP is expressed in central and peripheral regions important for nutrient intake and metabolism. Central administration of QRFP-26 and QRFP-43 induces a macronutrient specific increase in the intake of high fat diet in male and female rats. Recently, cell culture models have indicated that QRFP-26 and QRFP-43 are involved in glucose and fatty acid uptake in pancreatic islets and adipocytes. Since skeletal muscle is a major consumer of circulating glucose and a primary contributor to whole body metabolism, the current study examined the effects of QRFP-26 and QRFP-43 on insulin-stimulated uptake of glucose in skeletal muscle using L6 myotubes. The current experiments were designed to test the hypothesis that QRFP and its receptors, GPR103a and GPR103b are expressed in L6 myotubes and that QRFP-26 and QRFP-43 affect insulin-stimulated uptake of glucose in L6 myotubes. The results indicate that prepro-QRFP mRNA and GPR103a mRNA are expressed in L6 cells, though GPR103b mRNA was not detected. Using complementary assays, co-incubation with QRFP-26, increased insulin's ability to induce glycogen synthesis and 2-deoxyglucose uptake in L6 cells. These data suggest that QRFP-26, but not QRFP-43, is involved in the metabolic effects of skeletal muscle and may enhance insulin's effects on glucose uptake in skeletal muscle. These data support a role for QRFP as a modulator of nutrient intake in skeletal muscle.

MiR-218 inhibits multidrug resistance (MDR) of gastric cancer cells by targeting Hedgehog/smoothened

Multidrug resistance (MDR) is the main obstacle to successful chemotherapy for patients with gastric cancer. The microRNA miR-218 influences various pathobiological processes in gastric cancer, and its down-regulation in this disease raises the question of whether it normally inhibits MDR. In this study we observed that two MDR gastric cancer cell lines showed lower expression of miR-218 compared with their chemosensitive parental cell line. Overexpressing miR-218 chemosensitizes gastric cancer cells, slowed efflux of adriamycin, and accelerated drug-induced apoptosis. We identified the smoothened (SMO) gene as a functional target of miR-218, and found that SMO overexpression counteracts the chemosensitizing effects of miR-218. These findings suggest that miR-218 inhibits MDR of gastric cancer cells by down-regulating SMO expression.

β-Hydroxybutyric acid inhibits growth hormone-releasing hormone synthesis and secretion through the GPR109A/extracellular signal-regulated 1/2 signalling pathway in the hypothalamus

β-Hydroxybutyric acid (BHBA) has recently been shown to regulate hormone synthesis and secretion in the hypothalamus. However, little is known about the effects of BHBA-mediated hormone regulation or the detailed mechanisms by which BHBA regulates growth hormone-releasing hormone (GHRH) synthesis and secretion. In the present study, we examined the expression of the BHBA receptor GPR109A in primary hypothalamic cell cultures. We hypothesised that BHBA regulates GHRH via GPR109A and its downstream signals. Initial in vivo studies conducted in rats demonstrated that GHRH mRNA expression in the hypothalamus was strongly inversely correlated with BHBA levels in the cerebrospinal fluid during postnatal development (r = -0.89, P < 0.01). Furthermore, i.c.v. administration of BHBA acutely decreased GHRH mRNA expression in rats. Further in vitro studies revealed a decrease in GHRH synthesis and secretion in primary hypothalamic cells after treatment with BHBA; this effect was inhibited when hypothalamic cells were pretreated with pertussis toxin (PTX). BHBA had no effect on GHRH synthesis and secretion in GT1-7 cells, which do not exhibit cell surface expression of GPR109A. Furthermore, BHBA acutely decreased the transcription of the homeobox gene for Gsh-1 in the hypothalamus in both in vivo and in vitro, and this effect was also inhibited by PTX in vitro. In primary hypothalamic cells, BHBA activated the extracellular signal-regulated kinase (ERK)1/2, p38 and c-Jun N-terminal kinase mitogen-activated protein kinase (MAPK) kinases, as shown by western blot analysis. Moreover, inhibition of ERK1/2 with U0126 attenuated the BHBA-mediated reduction in Gsh-1 expression and GHRH synthesis and secretion. These results strongly suggest that BHBA directly regulates GHRH synthesis and secretion via the GPR109A/ERK1/2 MAPK pathway, and also that Gsh-1 is essential for this function.

The expression and regulation of chemerin in the epidermis

Chemerin is a protein ligand for the G protein-coupled receptor CMKLR1 and also binds to two atypical heptahelical receptors, CCRL2 and GPR1. Chemerin is a leukocyte attractant, adipokine, and antimicrobial protein. Although chemerin was initially identified as a highly expressed gene in healthy skin keratinocytes that was downregulated during psoriasis, the regulation of chemerin and its receptors in the skin by specific cytokines and microbial factors remains unexplored. Here we show that chemerin, CMKLR1, CCRL2 and GPR1 are expressed in human and mouse epidermis, suggesting that this tissue may be both a source and target for chemerin mediated effects. In human skin cultures, chemerin is significantly downregulated by IL-17 and IL-22, key cytokines implicated in psoriasis, whereas it is upregulated by acute phase cytokines oncostatin M and IL-1β. Moreover, we show that human keratinocytes in vitro and mouse skin in vivo respond to specific microbial signals to regulate expression levels of chemerin and its receptors. Furthermore, in a cutaneous infection model, chemerin is required for maximal bactericidal effects in vivo. Together, our findings reveal previously uncharacterized regulators of chemerin expression in skin and identify a physiologic role for chemerin in skin barrier defense against microbial pathogens.

Effect of diet on preference and intake of sucrose in obese prone and resistant rats

Increased orosensory stimulation from palatable diets and decreased feedback from gut signals have been proposed as contributing factors to obesity development. Whether altered taste functions associated with obesity are common traits or acquired deficits to environmental factors, such as a high-energy (HE)-diet, however, is not clear. To address this, we examined preference and sensitivity of increasing concentrations of sucrose solutions in rats prone (OP) and resistant (OR) to obesity during chow and HE feeding and measured lingual gene expression of the sweet taste receptor T1R3. When chow-fed, OP rats exhibited reduced preference and acceptance of dilute sucrose solutions, sham-fed less sucrose compared to OR rats, and had reduced lingual T1R3 gene expression. HE-feeding abrogated differences in sucrose preference and intake and lingual T1R3 expression between phenotypes. Despite similar sucrose intakes however, OP rats consumed significantly more total calories during 48-h two-bottle testing compared to OR rats. The results demonstrate that OP rats have an innate deficit for sweet taste detection, as illustrated by a reduction in sensitivity to sweets and reduced T1R3 gene expression; however their hyperphagia and subsequent obesity during HE-feeding is most likely not due to altered consumption of sweets.

LGR5 promotes the proliferation and tumor formation of cervical cancer cells through the Wnt/β-catenin signaling pathway

Leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5), a seven transmembrane receptor known as a potential stem cell marker for intestinal crypts and hair follicles, has recently been found to be overexpressed in some types of human cancers. However, the role of LGR5 in cervical cancer remains unclear. In this study, the expression of LGR5 gradually increases from normal cervix to cervical cancer in situ and to cervical cancers as revealed by immunohistochemistry and western blot analyses. Through knocking down or overexpressing LGR5 in SiHa and HeLa cells, the expression level of LGR5 was found to be positively related to cell proliferation in vitro and to tumor formation in vivo. Further investigation indicated that LGR5 protein could significantly promote the acceleration of cell cycle. Moreover, the TOP-Flash reporter assay and western blot for β-catenin, cyclinD1, and c-myc proteins, target genes of the Wnt/β-catenin pathway, indicated that LGR5 significantly activated Wnt/β-catenin signaling. Additionally, the blockage of Wnt/β-catenin pathway resulted in a significant inhibition of cell proliferation induced by LGR5. Taken together, these results demonstrate that LGR5 can promote proliferation and tumor formation in cervical cancer cells by activating the Wnt/β-catenin pathway.

Cross-species comparison of genes related to nutrient sensing mechanisms expressed along the intestine

INTRODUCTION

Intestinal chemosensory receptors and transporters are able to detect food-derived molecules and are involved in the modulation of gut hormone release. Gut hormones play an important role in the regulation of food intake and the control of gastrointestinal functioning. This mechanism is often referred to as "nutrient sensing". Knowledge of the distribution of chemosensors along the intestinal tract is important to gain insight in nutrient detection and sensing, both pivotal processes for the regulation of food intake. However, most knowledge is derived from rodents, whereas studies in man and pig are limited, and cross-species comparisons are lacking.

AIM

To characterize and compare intestinal expression patterns of genes related to nutrient sensing in mice, pigs and humans.

METHODS

Mucosal biopsy samples taken at six locations in human intestine (n = 40) were analyzed by qPCR. Intestinal scrapings from 14 locations in pigs (n = 6) and from 10 locations in mice (n = 4) were analyzed by qPCR and microarray, respectively. The gene expression of glucagon, cholecystokinin, peptide YY, glucagon-like peptide-1 receptor, taste receptor T1R3, sodium/glucose cotransporter, peptide transporter-1, GPR120, taste receptor T1R1, GPR119 and GPR93 was investigated. Partial least squares (PLS) modeling was used to compare the intestinal expression pattern between the three species.

RESULTS AND CONCLUSION

The studied genes were found to display specific expression patterns along the intestinal tract. PLS analysis showed a high similarity between human, pig and mouse in the expression of genes related to nutrient sensing in the distal ileum, and between human and pig in the colon. The gene expression pattern was most deviating between the species in the proximal intestine. Our results give new insights in interspecies similarities and provide new leads for translational research and models aiming to modulate food intake processes in man.

Biological effects of leukotriene E4 on eosinophils

Studies demonstrate the existence of novel receptors for cysteinyl leukotrienes (CysLTs) that are responsive to leukotriene (LT) E4 and might be pathogenic in asthma. Given the eosinophilic infiltration in this disorder, we investigated eosinophil expression of P2Y12 and gpr99 and their capacity to respond to LTE4. Receptor transcript expression was investigated via quantitative PCR and surface protein expression via flow cytometry. We investigated LTE4 influences on eosinophils including Ca(+2) flux, cAMP induction, modulation of adhesion molecule expression, apoptosis and degranulation. Eosinophils displayed both transcript and surface protein expression of P2Y12 and gpr99. We could not find evidence of LTE4 activation of eosinophils, however, LTE4 induced cAMP expression, and preincubation of eosinophils with LTE4 inhibited degranulation. Even though eosinophils are an important source of CysLTs in AERD, eosinophils are not themselves the pro-inflammatory biological target and, in contrast, LTE4 via cAMP primarily elicits anti-inflammatory responses.

Angiotensin II and 1-7 during aging in Metabolic Syndrome rats. Expression of AT1, AT2 and Mas receptors in abdominal white adipose tissue

Renin-Angiotensin System (RAS) plays an important role in the development of Metabolic Syndrome (MS) and in aging. Angiotensin 1-7 (Ang 1-7) has opposite effects to Ang II. All of the components of RAS are expressed locally in adipose tissue and there is over-activation of adipose RAS in obesity and hypertension. We determined serum and abdominal adipose tissue Ang II and Ang 1-7 in control and MS rats during aging and the expression of AT1, AT2 and Mas in white adipose tissue. MS was induced by sucrose ingestion during 6, 12 and 18 months. During aging, an increase in body weight, abdominal fat and dyslipidemia were found but increases in aging MS rats were higher. Control and MS concentrations of serum Ang II from 6-month old rats were similar. Aging did not modify Ang II seric concentration in control rats but decreased it in MS rats. Ang II levels increased in WAT from both groups of rats. Serum and adipose tissue Ang 1-7 increased during aging in MS rats. Western blot analysis revealed that AT1 expression increased in the control group during aging while AT2 and Mas remained unchanged. In MS rats, AT1 and AT2 expression decreased significantly in aged rats. The high concentration of Ang 1-7 and adiponectin in old MS rats might be associated to an increased expression of PPAR-γ. PPAR-γ was increased in adipose tissue from MS rats. It decreased with aging in control rats and showed no changes during aging in MS rats. Ang 1-7/Mas axis was the predominant pathway in WAT from old MS animals and could represent a potential target for therapeutical strategies in the treatment of MS during aging.

High expression of GPER1, EGFR and CXCR1 is associated with lymph node metastasis in papillary thyroid carcinoma

Clinical and epidemiological studies have shown that estrogen may be involved in the development and progression of papillary thyroid carcinoma (PTC). G protein-coupled estrogen receptor 1 (GPER1) is a novel seven-transmembrane estrogen receptor that functions alongside traditional nuclear estrogen receptors (ERs) to regulate the cellular responses to estrogen. The purpose of this study was to examine GPER1, EGFR and CXCR1 expression in PTC and to assess the association of their expression with clinicopathological indicators. GPER1, EGFR and CXCR1 protein expression in 129 PTCs, 61 nodular hyperplasia and 118 normal thyroid tissue specimens were analyzed using immunohistochemistry. The protein expression levels of these three molecules were up-regulated in PTCs. High protein expression of GPER1, EGFR and CXCR1 was significantly correlated with lymph node metastasis (LNM) (P ≤ 0.001). Furthermore, GPER1, EGFR and CXCR1 protein expression were correlated with one another. Concomitant high expression of these molecules had stronger correlation with LNM than did each alone (P = 0.002 for GPER1/EGFR, P = 0.013 for GPER1/CXCR1, P = 0.018 for EGFR/CXCR1 and P < 0.001 for GPER1/EGFR/CXCR1). Additionally, GPER1, EGFR and CXCR1 mRNA expression was assessed in 30 PTCs, 10 nodular hyperplasia and 10 normal thyroid tissue specimens using real-time RT-PCR. GPER1, EGFR and CXCR1 mRNA expression levels were up-regulated in PTCs, and high mRNA expression of GPER1, EGFR and CXCR1 was significantly correlated with LNM (P < 0.001 for all these three molecules). These results demonstrated that the evaluation of GPER1, EGFR and CXCR1 expression in PTC may be useful in predicting the risk of LNM.

Insulin-like growth factor-I regulates LH release by modulation of kisspeptin and NMDA-mediated neurotransmission in young and middle-aged female rats

This study investigated potential mechanisms by which age and IGF-I receptor (IGF-Ir) signaling in the neuroendocrine hypothalamus affect estradiol-positive feedback effects on GnRH neuronal activation and on kisspeptin and N-methyl-D-aspartate (NMDA)-induced LH release and on the abundance of NMDA receptor subunits Nr1 and Nr2b and Kiss1r transcript and protein in the hypothalamus of young and middle-aged female rats. We infused vehicle, IGF-I, or JB-1, a selective antagonist of IGF-Ir, into the third ventricle of ovariectomized female rats primed with estradiol or vehicle and injected with vehicle, kisspeptin (3 or 30 nmol/kg), or NMDA (15 or 30 mg/kg). Regardless of dose, NMDA and kisspeptin resulted in significantly more LH release, GnRH/c-Fos colabeling, and c-Fos immunoreative cells in young than in middle-aged females. Estradiol priming significantly increased Kiss1r, Nr1, and Nr2b receptor transcript and protein abundance in young but not middle-aged female hypothalamus. JB-1 attenuated kisspeptin and NMDA-induced LH release, numbers of GnRH/c-Fos and c-Fos cells, and Kiss1r, Nr1, and Nr2b transcript and protein abundance in young females to levels observed in middle-aged females. IGF-I significantly enhanced NMDA and kisspeptin-induced LH release in middle-aged females without increasing numbers of GnRH/c-Fos or c-Fos immunoreactive cells. IGF-I infusion in middle-aged females also increased Kiss1r, Nr1, and Nr2b protein and transcript to levels that were equivalent to young estradiol-primed females. These findings indicate that age-related changes in estradiol-regulated responsiveness to excitatory input from glutamate and kisspeptin reflect reduced IGF-Ir signaling.

Lack of G protein-coupled estrogen receptor (GPER) in the plasma membrane is associated with excellent long-term prognosis in breast cancer

G protein-coupled estrogen receptor (GPER), or GPR30, is a membrane receptor reported to mediate non-genomic estrogen responses. Tamoxifen is a partial agonist at GPER in vitro. Here, we investigated if GPER expression is prognostic in primary breast cancer, if the receptor is treatment-predictive for adjuvant tamoxifen, and if receptor subcellular localization has any impact on the prognostic value. Total and plasma membrane (PM) GPER expression was analyzed by immunohistochemistry in breast tumors from 742 postmenopausal lymph node-negative patients subsequently randomized for tamoxifen treatment for 2-5 years versus no systemic treatment, regardless of estrogen receptor (ER) status, and with a median follow-up of 17 years for patients free of event. PM GPER expression was a strong independent prognostic factor for poor prognosis in breast cancer without treatment-predictive information for tamoxifen. In the tamoxifen-treated ER-positive and progesterone receptor (PgR)-positive patient subgroup, the absence of PM GPER (53 % of all ER-positive tumors) predicted 91 % 20-year distant disease-free survival, compared to 73 % in the presence of GPER (p = 0.001). Total GPER expression showed positive correlations with ER and PgR and negative correlation with histological grade, but the correlations were biphasic. On the other hand, PM GPER expression showed strong negative correlations with ER and PgR, and strong positive correlation with HER2 overexpression and high histological grade. GPER overexpression and PM localization are critical events in breast cancer progression, and lack of GPER in the PM is associated with excellent long-term prognosis in ER-positive and PgR-positive tamoxifen-treated primary breast cancer.

Heterodimerization of human apelin and bradykinin 1 receptors: novel signal transduction characteristics

Apelin receptor (APJ) and bradykinin 1 receptor (B1R) are involved in a variety of important physiological processes, which share many similar characteristics in distribution and functions in the cardiovascular system. This study explored the possibility of heterodimerization between APJ and B1R, and investigated the impact of heterodimer on the signal transduction characteristics and the physiological functions in human endothelial cells after stimulation with their agonists. We first identified the endogenous expression of APJ and B1R in HUVECs and their co-localization on HEK293 membrane. The constitutive heterodimerization between the APJ and B1R was then demonstrated by BRET and FRET assays. Stimulation with Apelin-13 and des -Arg(9)-BK enhanced the phosphorylation of eNOS in HUVECs, which could be dampened by the knockdown of APJ or B1R, indicating the co-existence of APJ and B1R is critical for eNOS phosphorylation in HUVECs. Furthermore, APJ/B1R heterodimers were found to enhance the activity of PKC signaling pathway and increase intracellular Ca(2+) concentration in HEK293 cells, which might be the mechanism of APJ/B1R heterodimers promoting the phosphorylation of eNOS and leads to increased Gαq, PKC signal pathway activities and a significant increase in cell proliferation. The results provide a new theoretical and experimental base for revealed intracellular molecular mechanisms of physiological function involved in the APJ and B1R and provide potential new targets for the development of drugs and treating cardiovascular disease.

Expression of the mammalian Xenotropic Polytropic Virus Receptor 1 (XPR1) in tobacco leaves leads to phosphate export

Phosphate homeostasis in multicellular eukaryotes depends on both phosphate influx and efflux. The mammalian Xenotropic Polytropic Virus Receptor 1 (XPR1) shares homology to the Arabidopsis PHO1, a phosphate exporter expressed in roots. However, phosphate export activity of XPR1 has not yet been demonstrated in a heterologous system. Here, wedemonstrate that transient expression in tobacco leaves of XPR1-GFP leads to specific phosphate export. Like PHO1-GFP, XPR1-GFP is localized predominantly to the endomembrane system in tobacco cells. These results show that tobacco leaves are a good heterologous system to study the transport activity of members of the PHO1/XPR1 family.

Sex-steroid regulation of relaxin receptor isoforms (RXFP1 & RXFP2) expression in the patellar tendon and lateral collateral ligament of female WKY rats

The incidence of non-contact knee injury was found higher in female than in male and is related to the phases of the menstrual cycle. This raised the possibility that female sex-steroids are involved in the mechanism underlying this injury via affecting the expression of the receptors for relaxin, a peptide hormone known to modulate ligament laxity. Therefore, this study aims to investigate the effect of sex-steroids on relaxin receptor isoforms (RXFP1 & RXFP2) expression in the ligaments and tendons of the knee.

METHODS

Ovariectomized adult female WKY rats were treated with different doses of estrogen (0.2, 2, 20 μg/kg), progesterone (4mg) and testosterone (125 & 250μg/kg) for three consecutive days. At the end of the treatment, the animals were sacrificed and the patellar tendon and lateral collateral ligament were harvested for mRNA and protein expression analyses by Real Time PCR and Western blotting respectively.

RESULTS

RXFP1, the main isoform expressed in these knee structures and RXFP2 showed a dose-dependent increase in expression with estrogen. Progesterone treatment resulted in an increase while testosterone caused a dose-dependent decrease in the mRNA and protein expression of both relaxin receptor isoforms.

DISCUSSION

Progesterone and high dose estrogen up-regulate while testosterone down-regulates RXFP1 and RXFP2 expression in the patellar tendon and lateral collateral ligament of rat's knee.

CONCLUSION

Relaxin receptor isoforms up-regulation by progesterone and high dose estrogen could provide the basis for the reported increase in knee laxity while down-regulation of these receptor isoforms by testosterone could explain low incidence of non-contact knee injury in male.

Systems pharmacology identifies drug targets for Stargardt disease-associated retinal degeneration

A systems pharmacological approach that capitalizes on the characterization of intracellular signaling networks can transform our understanding of human diseases and lead to therapy development. Here, we applied this strategy to identify pharmacological targets for the treatment of Stargardt disease, a severe juvenile form of macular degeneration. Diverse GPCRs have previously been implicated in neuronal cell survival, and crosstalk between GPCR signaling pathways represents an unexplored avenue for pharmacological intervention. We focused on this receptor family for potential therapeutic interventions in macular disease. Complete transcriptomes of mouse and human samples were analyzed to assess the expression of GPCRs in the retina. Focusing on adrenergic (AR) and serotonin (5-HT) receptors, we found that adrenoceptor α 2C (Adra2c) and serotonin receptor 2a (Htr2a) were the most highly expressed. Using a mouse model of Stargardt disease, we found that pharmacological interventions that targeted both GPCR signaling pathways and adenylate cyclases (ACs) improved photoreceptor cell survival, preserved photoreceptor function, and attenuated the accumulation of pathological fluorescent deposits in the retina. These findings demonstrate a strategy for the identification of new drug candidates and FDA-approved drugs for the treatment of monogenic and complex diseases.