Corticotropin-releasing factor receptors couple to multiple g-proteins to activate diverse intracellular signaling pathways in mouse hippocampus: role in neuronal excitability and associative learning

Corticotropin-releasing factor (CRF) exerts a key neuroregulatory control on stress responses in various regions of the mammalian brain, including the hippocampus. Using hippocampal slices, extracts, and whole animals, we investigated the effects of human/rat CRF (h/rCRF) on hippocampal neuronal excitability and hippocampus-dependent learning in two mouse inbred strains, BALB/c and C57BL/6N. Intracellular recordings from slices revealed that application of h/rCRF increased the neuronal activity in both mouse inbred strains. Inhibition of protein kinase C (PKC) by bisindolylmaleimide I (BIS-I) prevented the h/rCRF effect only in hippocampal slices from BALB/c mice but not in slices from C57BL/6N mice. Inhibition of cAMP-dependent protein kinase (PKA) by H-89 abolished the h/rCRF effect in slices from C57BL/6N mice, with no effect in slices from BALB/c mice. Accordingly, h/rCRF elevated PKA activity in hippocampal slices from C57BL/6N mice but increased only PKC activity in the hippocampus of BALB/c mice. These differences in h/rCRF signal transduction were also observed in hippocampal membrane suspensions from both mouse strains. In BALB/c mice, hippocampal CRF receptors coupled to Gq/11 during stimulation by h/rCRF, whereas they coupled to Gs, Gq/11, and Gi in C57BL/6N mice. As expected on the basis of the slice experiments, h/rCRF improved context-dependent fear conditioning of BALB/c mice in behavioral experiments, and BIS-I prevented this effect. However, although h/rCRF increased neuronal spiking in slices from C57BL/6N mice, it did not enhance conditioned fear. These results indicate that the CRF system activates different intracellular signaling pathways in mouse hippocampus and may have distinct effects on associative learning depending on the mouse strain investigated

Measuring Burden of Diseases in a Rapidly Developing Economy: State of Qatar National Burden of Diseases in Qatar

Abstract Background: The Global Burden of Disease (GBD) study has provided a conceptual and methodological framework to quantify and compare the health of populations. Aim: The objective of the study was to assess the national burden of disease in the population of Qatar using the disability-adjusted life year (DALYs) as a measure of disability. Methods: We adapted the methodology described by the World Health Organization for conducting burden of disease to calculate years of life lost due to premature mortality (YLL), years lived with disability (YLD) and disability adjusted life years (DALYs). The study was conducted during the period from November 2011 to October 2012. Results: The study findings revealed that ischemic heart disease (11.8%) and road traffic accidents (10.3%) were the two leading causes of burden of diseases in Qatar in 2010. The burden of diseases among men (222.04) was found three times more than of women's (71.85). Of the total DALYs, 72.7% was due to non fatal health outcomes and 27.3% was due to premature death. For men, chronic diseases like ischemic heart disease (15.7%) and road traffic accidents (13.7%) accounted great burden and an important source of lost years of healthy life. For women, birth asphyxia and birth trauma (12.6%) and abortion (4.6%) were the two leading causes of disease burden. Conclusion: The results of the study have shown that the national health priority areas should cover cardiovascular diseases, road traffic accidents and mental health. The burden of diseases among men was three times of women's

Association of the 894G>T polymorphism in the endothelial nitric oxide synthase gene with risk of acute myocardial infarction

Background: This study was designed to investigate the association of the 894G>T polymorphism in the eNOS gene with risk of acute myocardial infarction (AMI), extent of coronary artery disease (CAD) on coronary angiography, and in-hospital mortality after AMI. Methods: We studied 1602 consecutive patients who were enrolled in the GEMIG study. The control group was comprised by 727 individuals, who were randomly selected from the general adult population. Results: The prevalence of the Asp298 variant of eNOS was not found to be significantly and independently associated with risk of AMI (RR = 1.08, 95%CI = 0.77–1.51, P = 0.663), extent of CAD on angiography (OR = 1.18, 95%CI = 0.63–2.23, P = 0.605) and in-hospital mortality (RR = 1.08, 95%CI = 0.29–4.04, P = 0.908). Conclusion: In contrast to previous reports, homozygosity for the Asp298 variant of the 894G>T polymorphism in the eNOS gene was not found to be associated with risk of AMI, extent of CAD and in-hospital mortality after AM

Novel insights into the cardio-protective effects of FGF21 in lean and obese rat hearts

Aims: Fibroblast growth factor 21 (FGF21) is a hepatic metabolic regulator with pleotropic actions. Its plasma concentrations are increased in obesity and diabetes; states associated with an increased incidence of cardiovascular disease. We therefore investigated the direct effect of FGF21 on cardio-protection in obese and lean hearts in response to ischemia. Methods and Results: FGF21, FGF21-receptor 1 (FGFR1) and beta-Klotho (βKlotho) were expressed in rodent, human hearts and primary rat cardiomyocytes. Cardiac FGF21 was expressed and secreted (real time RT-PCR/western blot and ELISA) in an autocrine-paracrine manner, in response to obesity and hypoxia, involving FGFR1-βKlotho components. Cardiac-FGF21 expression and secretion were increased in response to global ischemia. In contrast βKlotho was reduced in obese hearts. In isolated adult rat cardiomyocytes, FGF21 activated PI3K/Akt (phosphatidylinositol 3-kinase/Akt), ERK1/2(extracellular signal-regulated kinase) and AMPK (AMP-activated protein kinase) pathways. In Langendorff perfused rat [adult male wild-type wistar] hearts, FGF21 administration induced significant cardio-protection and restoration of function following global ischemia. Inhibition of PI3K/Akt, AMPK, ERK1/2 and ROR-α (retinoic-acid receptor alpha) pathway led to significant decrease of FGF21 induced cardio-protection and restoration of cardiac function in response to global ischemia. More importantly, this cardio-protective response induced by FGF21 was reduced in obesity, although the cardiac expression profiles and circulating FGF21 levels were increased. Conclusion: In an ex vivo Langendorff system, we show that FGF21 induced cardiac protection and restoration of cardiac function involving autocrine-paracrine pathways, with reduced effect in obesity. Collectively, our findings provide novel insights into FGF21-induced cardiac effects in obesity and ischemia

Identification of a novel corticotropin-releasing hormone type 1 beta-Like receptor variant lacking exon 13 in human pregnant myometrium regulated by estradiol-17 beta and progesterone

Two types of CRH receptors mediate the diverse biological functions of CRH and CRH-related peptides. The type 1 CRH-R (CRH-R1) is extensively targeted by pre-mRNA splicing mechanisms that give rise to multiple mRNA splice variants. RT-PCR amplification of CRH-R1 sequences from human myometrium yielded cDNAs that encode a novel CRH-R1 splice variant with structural characteristics identical with CRH-R1 beta except a 14-amino acid deletion in the seventh transmembrane domain characteristic of the CRH-R1d. Transient expression of the hybrid CRH-R1 variant (CRH-R1 beta/d) in human embryonic kidney 293 cells revealed primarily intracellular expression, although some plasma membrane protein expression was also detectable. CRH bound to CRH-R1 beta/d with affinity comparable with the CRH-R1 beta; however, it was unable to stimulate adenylyl cyclase or other second messengers. Using a semiquantitative RT-PCR assay, CRH-R1 beta/d mRNA transcript was detected in human pregnant, but not nonpregnant, myometrium as early as 31 wk of gestation. Furthermore, in human pregnant myometrial cells, the relative expression of CRH-R1 beta and CRH-R1 beta/d mRNA appeared to be regulated by steroids; CRH-R1 beta/d mRNA expression was increased by estradiol-17 beta, whereas CRH-R1 beta mRNA levels were increased by progesterone. Progesterone also substantially increased CRH-R1 alpha mRNA levels and cellular responsiveness to CRH as determined by increased agonist binding and cAMP production as well as resistance to CRH-R heterologous desensitization by phorbol esters. These results provide novel evidence for distinct patterns of CRH-R1 splicing and identify specific steroid-mediated regulation of CRH-R1 variant expression, which might be important for modulating CRH actions during human pregnancy and labour. (Endocrinology 151: 4959-4968, 2010

Structural domains determining signalling characteristics of the CRH-receptor type 1 variant R1 beta and response to PKC phosphorylation

Mammalian adaptive mechanisms to stressful stimuli involve release of corticotropin-releasing hormone (CRH) and downstream activation of specific G-protein-coupled 7 transmembrane domain receptors. These CRH receptors (CRH-R) are expressed as multiple mRNA spliced variants. In contrast to other mammals, the human type 1 CRH-R gene contains an additional exon (exon 6) that needs to be spliced out in order to generate the fully active CRH-R1 alpha. Transcription of all 14 exons results in a CRH-R1 variant (CRH-R1 beta) with an extended 1st intracellular loop (IC1); this sequence modification impairs signalling activity and alters receptor responsiveness to PKC-induced phosphorylation that leads to signalling desensitization and receptor endocytosis. To elucidate structure-function relationships and delineate sequences involved in CRH-R1 beta properties, site directed mutagenesis was used to introduce a number of specific mutations into IC1 of CRH-R1 beta as well as replace specific phospho-acceptor residues within the aminoacid sequence of CRH-R1 alpha and CRH-R1 beta Mutant receptors were transiently expressed in human embryonic kidney (HEK293) cells and tested for their abilities to increase intracellular cAMP and their response to PKC-induced phosphorylation. Results identified a penta-aminoacid cassette within the 29-aminoacid insert of CRH-R1 beta, which contains multiple positive charged aminoacids (F-170-R-174), as an important structural determinant for the impaired cAMP response. Furthermore, serine at position 408 in the carboxy-termimis appears to be important for mediating CRI-R1 alpha resistance, but not CRH-R1 beta susceptibility, to PKC-induced desensitization and internalization. These findings provide new insights about the structural determinants of CRH-R1 coupling to Gs proteins and response to protein kinase phosphorylation. (C) 2007 Elsevier Inc. All rights reserved

Structural domains determining signalling characteristics of the CRH-receptor type 1 variant R1 beta and response to PKC phosphorylation

Mammalian adaptive mechanisms to stressful stimuli involve release of corticotropin-releasing hormone (CRH) and downstream activation of specific G-protein-coupled 7 transmembrane domain receptors. These CRH receptors (CRH-R) are expressed as multiple mRNA spliced variants. In contrast to other mammals, the human type 1 CRH-R gene contains an additional exon (exon 6) that needs to be spliced out in order to generate the fully active CRH-R1 alpha. Transcription of all 14 exons results in a CRH-R1 variant (CRH-R1 beta) with an extended 1st intracellular loop (IC1); this sequence modification impairs signalling activity and alters receptor responsiveness to PKC-induced phosphorylation that leads to signalling desensitization and receptor endocytosis. To elucidate structure-function relationships and delineate sequences involved in CRH-R1 beta properties, site directed mutagenesis was used to introduce a number of specific mutations into IC1 of CRH-R1 beta as well as replace specific phospho-acceptor residues within the aminoacid sequence of CRH-R1 alpha and CRH-R1 beta Mutant receptors were transiently expressed in human embryonic kidney (HEK293) cells and tested for their abilities to increase intracellular cAMP and their response to PKC-induced phosphorylation. Results identified a penta-aminoacid cassette within the 29-aminoacid insert of CRH-R1 beta, which contains multiple positive charged aminoacids (F-170-R-174), as an important structural determinant for the impaired cAMP response. Furthermore, serine at position 408 in the carboxy-termimis appears to be important for mediating CRI-R1 alpha resistance, but not CRH-R1 beta susceptibility, to PKC-induced desensitization and internalization. These findings provide new insights about the structural determinants of CRH-R1 coupling to Gs proteins and response to protein kinase phosphorylation. (C) 2007 Elsevier Inc. All rights reserved