Current understanding of the structure and function of family B GPCRs to design novel drugs.

Family B of G-protein-coupled receptors (GPCRs) and their ligands play a central role in a number of homeostatic mechanisms in the endocrine, gastrointestinal, skeletal, immune, cardiovascular and central nervous systems. Alterations in family B GPCR-regulated homeostatic mechanisms may cause a variety of potentially life-threatening conditions, signifying the necessity to develop novel ligands targeting these receptors. Obtaining structural and functional information on family B GPCRs will accelerate the development of novel drugs to target these receptors. Family B GPCRs are proteins that span the plasma membrane seven times, thus forming seven transmembrane domains (TM1-TM7) which are connected to each other by three extracellular (EL) and three intracellular (IL) loops. In addition, these receptors have a long extracellular N-domain and an intracellular C-tail. The upper parts of the TMs and ELs form the J-domain of receptors. The C-terminal region of peptides first binds to the N-domain of receptors. This 'first-step' interaction orients the N-terminal region of peptides towards the J-domain of receptors, thus resulting in a 'second-step' of ligand-receptor interaction that activates the receptor. Activation-associated structural changes of receptors are transmitted through TMs to their intracellular regions and are responsible for their interaction with the G proteins and activation of the latter, thus resulting in a biological effect. This review summarizes the current information regarding the structure and function of family B GPCRs and their physiological and pathophysiological roles.

Diet, serum homocysteine levels and ischaemic heart disease in a Mediterranean population.

Homocysteine (Hcy) is recognised as a risk factor for IHD. Serum Hcy is negatively correlated with serum folate levels, the main sources of which are fruits, vegetables and legumes. The present case-control study was designed to examine the relationship between serum Hcy levels and IHD and to assess the role of dietary factors in the southern Mediterranean population of Crete, Greece. Serum Hcy, folate, vitamin B12, creatinine and glucose levels and a full lipid profile were measured in 152 patients with established IHD, median age 64 (range 33-77) years, and 152 healthy control subjects, age- and sex-matched. Dietary data were assessed using a 3 d food intake record. Compared with controls, patients with IHD had significantly higher daily intakes of vitamin B12 and MUFA and significantly lower intakes of carbohydrate, fibre, folate, cholesterol, n-3 fatty acids and total trans unsaturated fatty acids. Moreover, patients had significantly higher serum Hcy, vitamin B12 and creatinine levels, but significantly lower folate. Serum folate concentrations in both groups had a significant positive correlation with dietary fibre consumption and a significant inverse correlation with vitamin B12 intake. IHD patients should be encouraged to increase their daily dietary intake of fibre, folate and n-3 fatty acids, which are significant components of the traditional Cretan Mediterranean diet. Where dietary folate intake is inadequate, folate supplements are recommended to reduce elevated Hcy levels.

Corticotropin-releasing hormone (CRH) and immunotolerance of the fetus.

The hypothalamic neuropeptide corticotropin-releasing hormone (CRH) is produced by several tissues of the female reproductive system, including the endometrial glands and decidualized stroma, as well as the trophoblast, syncytiotrophoblast, and placental decidua. CRH is also secreted at inflammatory sites and possesses potent pro-inflammatory properties influencing both innate and acquired immune processes. Recent experimental findings show that uterine CRH participates in local immune phenomena associated with early pregnancy, such as differentiation of endometrial stroma to decidua and protection of the fetus from the maternal immune system. CRH induces the expression of apoptotic Fas ligand (FasL) on invasive extravillous trophoblast and maternal decidual cells at the fetal-maternal interface. Furthermore, CRH increases the apoptosis of activated T lymphocytes through FasL induction, participating in the processes of both implantation and early pregnancy tolerance.

Plasma Levels of Nitrites/Nitrates in Patients with Chronic Atrial Fibrillation are Increased after Electrical Restoration of Sinus Rhythm.

INTRODUCTION: Patients with persistent atrial fibrillation (AF) have hemodynamic changes, which impair endothelial cell function resulting in decreased nitric oxide (NO) production. The aim of this work was to assess endothelial function in AF patients before and at various time points after cardioversion. METHODS: Forty-two patients with AF and 21 normal and age-adjusted healthy controls were studied. Nitrites and nitrates (NO(x)) and von Willebrand factor (vWf) concentrations were measured on blood samples taken just before cardioversion and over a 30 day period after the procedure. RESULTS: Plasma levels of NO(x) in AF were significantly lower compared to healthy controls (p < 0.001), but after cardioversion gradually increased to approach to those of the healthy controls by the end of the first month of sustained sinus rhythm (p = 0.004). Interestingly plasma levels of NO(x) were negatively correlated to left atrial volume measured by ultrasonography (r = -0.34, p < 0.05). Plasma levels of vWf in AF patients were significantly higher compared to the healthy controls (p < 0.01) but with sustained sinus rhythm decreased (p = 0.02). CONCLUSION: The parallel normalization of the NO(x) titers and vWf levels suggests that vascular endothelial function improves after 30 days of normal sinus rhythm.