cyclic-gmp and Metabolism--Inborn-Errors

Intensive laboratory investigation of patients with recurrent infections, and with infections with microbial species not usually considered to be pathogenic, have led to the identification of several defects in granulocyte function. The two functions of granulocytes which have received most attention in the past decade have been locomotion (especially response to chemotactic stimulation) and microbicidal activity. Defective granulocyte chemotaxis has been demonstrated in patients with clinical manifestations suggesting abnormalities related to vasoactive amines, i.e., patients with eczema and extreme IgE hyperimmunoglobulinemia. The depressed granulocyte chemotactic responsiveness found in these patients can be reproduced in vitro when histamine and beta adrenergic agents are incubated with control granulocytes. Since these compounds have been shown to increase levels of intracellular cyclic AMP in other cells, there appears to be an association between cyclic nucleotide metabolism and regulation of granulocyte locomotion. Defective granulocyte microbicidal activity is found in patients with chronic granulomatous disease and it has been shown that there is little increase in oxidative metabolism during phagocytosis by these cells. Methods for quantitating the oxidative metabolism of granulocytes and monocytes include oxygen uptake, reduction of nitroblue tetrazolium, formate oxidation, and chemiluminescence response during phagocytosis. Since products of oxygen metabolism, i.e., hydrogen peroxide, superoxide or singlet oxygen do not accumulate in granulocyte phagocytic vacuoles, intracellular microbes are not killed (except bacterial species that produce hydrogen peroxide). The biochemical basis for defective oxidative metabolism in granulocytes from patients with chronic granulomatous disease appears to be associated with abnormal nucleotide oxidase activity.

Topics: Blood Bactericidal Activity; Carbohydrate Metabolism, Inborn Errors; Cell Movement; Chediak-Higashi Syndrome; Chemotaxis, Leukocyte; Cyclic AMP; Cyclic GMP; Granulocytes; Granulomatous Disease, Chronic; Humans; Hydrogen Peroxide; Hydrogen-Ion Concentration; Hydrolases; Leukocytes; Luminescent Measurements; Mannose; Metabolism, Inborn Errors; NADH, NADPH Oxidoreductases; NADP; NADPH Oxidases; Nucleotides, Cyclic; Oxygen Consumption; Peroxidase; Phagocyte Bactericidal Dysfunction; Phagocytosis; Protein-Energy Malnutrition

Gain-of-function mutations in guanylyl cyclase C (GCC) result in persistent diarrhea with perinatal onset. We investigated a specific GCC inhibitor, SSP2518, for its potential to treat this disorder.. We investigated the effect of SSP2518 on GCC-mediated intracellular cyclic guanosine monophosphate (cGMP) levels and on GCC-mediated chloride secretion in intestinal organoids from 3 patients with distinct activating GCC mutations and from controls, with and without stimulation of GCC with heat-stable enterotoxin.. Patient-derived organoids had significantly higher basal cGMP levels than control organoids, which were lowered by SSP2518 to levels found in control organoids. In addition, SSP2518 significantly reduced cGMP levels and chloride secretion in patient-derived and control organoids (P < 0.05 for all comparisons) after heat-stable enterotoxin stimulation.. We reported in this study that the GCC inhibitor SSP2518 normalizes cGMP levels in intestinal organoids derived from patients with GCC gain-of-function mutations and markedly reduces cystic fibrosis transmembrane conductance regulator-dependent chloride secretion, the driver of persistent diarrhea.

Topics: Abnormalities, Multiple; Cyclic GMP; Diarrhea; Gain of Function Mutation; Heterocyclic Compounds, 4 or More Rings; Humans; Metabolism, Inborn Errors; Receptors, Enterotoxin

Oxidant stress has been implicated in the pathogenesis of atherothrombosis and other vascular disorders accompanied by endothelial dysfunction. Glutathione peroxidases (GPx) play an important role in the cellular defense against oxidant stress by utilizing glutathione (GSH) to reduce lipid hydroperoxides and hydrogen peroxide to their corresponding alcohols. Cellular GPx (GPx-1) is the principal intracellular isoform of GPx. We hypothesized that GPx-1 deficiency per se induces endothelial dysfunction and structural vascular abnormalities through increased oxidant stress.. A murine model of heterozygous deficiency of GPx-1 (GPx(+/-)) was investigated to examine this hypothesis. Mesenteric arterioles in GPx-1(+/-) mice demonstrated vasoconstriction to acetylcholine compared with vasodilation in wild-type mice (maximal change in vessel diameter, -13.0+/-2.8% versus 13.2+/-2.8%, P<0.0001). We also noted an increase in the plasma and aortic levels of the isoprostane iPF(2alpha)-III, a marker of oxidant stress, in GPx-1(+/-) mice compared with wild-type mice (170.4+/-23 pg/mL plasma versus 98.7+/-7.1 pg/mL plasma, P<0.03; 11.7+/-0.87 pg/mg aortic tissue versus 8.2+/-0.55 pg/mg aortic tissue, P<0.01). Histological sections from the coronary vasculature of GPx-1(+/-) mice show increased perivascular matrix deposition, an increase in the number of adventitial fibroblasts, and intimal thickening. These structural abnormalities in the myocardial vasculature were accompanied by diastolic dysfunction after ischemia-reperfusion.. These findings demonstrate that heterozygous deficiency of GPx-1 leads to endothelial dysfunction, possibly associated with increased oxidant stress, and to significant structural vascular and cardiac abnormalities. These data illustrate the importance of this key antioxidant enzyme in functional and structural responses of the mammalian cardiovascular system.

Topics: Animals; Antioxidants; Aorta, Thoracic; Bradykinin; Coronary Vessels; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Gene Targeting; Glutathione Peroxidase; Glutathione Peroxidase GPX1; Heterozygote; In Vitro Techniques; Male; Mesentery; Metabolism, Inborn Errors; Mice; Microcirculation; Muscarinic Agonists; Myocardial Contraction; Myocardium; Nitric Oxide Donors; Oxidative Stress; Vasodilator Agents; Vasomotor System