NADPH Oxidase NOX2 Defines a New Antagonistic Role for Reactive Oxygen Species and cAMP/PKA in the Regulation of Insulin Secretion

In insulin-secreting cells, expression of NADPH oxidase (NOX), a potent source of ROS, has been reported, along with controversial findings regarding its function. Here, the role of NOXs was investigated: first by expression and cellular localization in mouse and human pancreatic islets, and then by functional studies in islets isolated from Nox isoform–specific knockout mice. Both human and mouse β-cells express NOX, in particular NOX2. With use of Nox isoform–specific knockout mice, functional analysis revealed Nox2 as the predominant isoform. In human islets, NOX2 colocalized with both insulin granules and endosome/lysosome membranes. Nox2-deficient islets stimulated with 22.8 mmol/L glucose exhibited potentiation of insulin release compared with controls, an effect confirmed with in vitro knockdown of Nox2. The enhanced secretory function in Nox2-deficient islets was associated with both lower superoxide levels and elevated cAMP concentrations. In control islets, GLP-1 and other cAMP inducers suppressed glucose-induced ROS production similarly to Nox2 deficiency. Inhibiting cAMP-dependent protein kinase reduced the secretory response in Nox2-null islets, although not in control islets. This study ascribes a new role for NOX2 in pancreatic β-cells as negative modulator of the secretory response, reducing cAMP/PKA signaling secondary to ROS generation. Results also show reciprocal inhibition between the cAMP/PKA pathway and ROS.NOX enzymes generate superoxide by transferring one electron from NADPH to oxygen (1). The best known NOX isoform is the phagocyte NADPH oxidase (NOX), a multicomponent complex comprising a membrane catalytic heterodimer, the flavocytochrome b_558, formed by gp91^phox (also referred to as NOX2) and p22^phox (where phox is phagocyte oxidase). The cytosolic regulatory subunits are composed of p40^phox, p47^phox, p67^phox, and GTPases Rac1 or Rac2 (1). Assembly of cytosolic elements to membrane catalytic core initiates the activation of NOX. To date, seven isoforms of NOX (NOX1–5 and dual oxidases DUOX1–2) have been identified with different activation mechanisms and heterogeneous tissue distribution (1). In addition to microbial attack by professional phagocytes, physiopathological roles of NOX have recently attracted attention in nonphagocytic cells, including pancreatic β-cells (2–7). Reactive oxygen species (ROS), such as superoxide and hydrogen peroxide, might participate in β-cell dysfunction (8). The redox imbalance favored by high metabolic rate and a relatively low detoxifying system has contributed to the general concept that β-cells are sensitive to ROS, although they can handle rather high concentrations of H₂O₂ (9).NOX family represents one of the potential sources of ROS in insulin-secreting cells (4). Both rat islets and insulinoma express membrane-associated catalytic components Nox1, Nox2, Nox4, and p22^phox, as well as cytosolic regulators p40^phox, p47^phox, and p67^phox and their homologs Noxo1 and Noxa1 (3,5,6). Regarding their putative function in the β-cell, NOXs have been implicated in glucose-induced ROS production in MIN-6 cells (10). Knockdown of p47^phox results in total inhibition of glucose-stimulated insulin secretion and lowers ROS (11). In animal models of type 2 diabetes, islets exhibit increased NOX components Nox2 and p22^phox, correlating with increased oxidative stress (12). Activation of Nox and accompanying ROS generation were demonstrated in Zucker diabetic fatty (ZDF) rat and diabetic human islets (13). However, inhibition of islet NOX using diphenyleneiodonium (DPI) impairs glucose-stimulated insulin secretion (6) along with blunted glucose-induced superoxide production (5,10). These conflicting findings regarding NOX activity and β-cell function might be attributed to poor specificity of old-generation NOX inhibitors, such as apocynin and DPI (14). The former has been shown to function as a general ROS scavenger, and the latter is a nonspecific inhibitor of electron transporters (1,15).In the current study, we first investigated relative expression levels of the different catalytic subunits of NOXs in both human and mouse pancreatic islets. Then, subcellular distribution of the identified predominant NOX isoform NOX2 was assessed in human islet cells. For avoidance of poor specificity of NOX inhibitors, islets isolated from Nox isoform–specific–deficient mice were used to investigate the contribution of NOXs in insulin secretory function.     

Synthesis and molecular modeling studies of cholinesterase inhibitor dispiro[indoline-3,2′-pyrrolidine-3′,3′′-pyrrolidines]

A set of dispiro[indoline-3,2′-pyrrolidine-3′,3′′-pyrrolidines] 8a–l was regioselectively synthesized utilizing multi-component azomethine cycloaddition reaction of 3-(arylmethylidene)pyrrolidine-2,5-diones 5a–e, isatins 6a–c and sarcosine 7. Single crystal X-ray studies of 8c add conclusive support for the structure. Compounds 8e and 8g reveal cholinesterase inhibitory properties with promising efficacy against both AChE and BChE and were found to be more selective towards AChE than BChE as indicted by the selectivity index like Donepezil (a clinically used cholinesterase inhibitory drug). Molecular modeling studies assist in understanding the bio-observations and identifying the responsible parameters behind biological properties.

Dispiro[indoline-3,2′-pyrrolidine-3′,3′′-pyrrolidines] were regioselectively synthesized revealing cholinesterase (AChE, BChE) inhibitory properties.     

A microscopic and macroscopic investigation of the adsorption of N719 dye on ZnO nanopowders (ZNP) and ZnO nanorods (ZNR) for dye sensitized solar cells using statistical physics treatment and DFT simulation

In this paper, three adsorption isotherms of N719 dye on two different adsorbents, ZnO nanopowder and ZnO nanorods, at three different thicknesses have been fitted using a monolayer model with three types of receptor sites treated by statistical physics. The model involved parameters are: three coefficients (n₁, n₂ and n₃) indicating the numbers of adsorbed dye molecules per site, three parameters (N_m1, N_m2 and N_m3) indicating the receptor site densities and three adsorption energies ((−ε₁), (−ε₂) and (−ε₃)). The evolution of these parameters in relation with thickness of ZnO was discussed. The pore size distribution (PSD) of ZnO nanopowder and ZnO nanorods as a function of the thickness has been studied using the chosen adequate model. The molecular electrostatic potential (MEP) has been investigated to optimize the different adsorbed geometries of the complex N719 dye@ZnO. The intermolecular interactions between the N719 dye and the ZnO surface have been studied by using the quantum theory of atoms in molecules (AIM) and reduced density gradient RDG. The results of the MEP, topological AIM and RDG are in agreement with the results of statistical physics

Adsorption isotherms of N719 dye on (a) ZNP and (b) ZNR and the molecular electrostatic potential (MEP) map of (c) N719 dye and (d) ZnO.     

Gastrointestinal manifestations of Sipple syndrome in children

The diagnosis and management of patients with multiple endocrine neoplasia (MEN) type IIA and type IIB are of special challenge to pediatric surgeons. Patients characteristically present early in life with significant intestinal symptoms at a time when the characteristic phenotypic features of MEN IIB are frequently absent. We are reporting 12 patients with MEN type II (9 with type IIA and 3 type IIB or Sipple's syndrome), all of whom presented with gastrointestinal manifestations. All 12 patients had signs and symptoms of bowel obstruction during the neonatal period. An unusual association of Hirschsprung's disease and MEN IIA was noted in our nine patients found among a kindred of 92 individuals. All three patients with Sipple's syndrome (MEN IIB) had severe gastrointestinal symptoms since birth, including recurrent pseudoobstruction. The possibility of MEN type II should be considered in all cases of bowel obstruction in the newborn period. Screening for medullary carcinoma of the thyroid must be carried out from infancy. A detailed family history is very important to avoid unnecessary surgery for bowel obstruction in Sipple's syndrome.     

The potential role of Rattus rattus in enzootic cycle of Rift Valley Fever in Egypt. 1-Detection of RVF antibodies in R. rattus blood samples by both enzyme linked immuno sorbent assay (ELISA) and immuno-diffusion technique (ID)

Three hundreds of Rattus rattus (R. rattus) were trapped from 3 different governorates of Egypt (one hundred each), blood samples were withdrawal and subjected for detection of anti-RVF antibodies by both ELISA and ID techniques. The prevalence rate of antibodies by ELISA were 88 (29.33%) positive out of 300 tested blood samples, the highest rate was in Behira governorate 36 (36%) and the lowest one was in Alexandria governorate 22 (22%) while it was 30 (30%) in Minia governorate. But when ID technique was applied, it gave only 18 (6%) positive samples out of 300 tested blood samples with the highest rate in Behira and Minia governorates (8%) and it was only (2%) in Alexandria governorate. Our study suggests that these R. rattus make possible candidate as intermediate host in the maintenance cycle of RVF in Egypt.