Conditional deletion of menin results in antral G cell hyperplasia and hypergastrinemia

Antral gastrin is the hormone known to stimulate acid secretion and proliferation of the gastric corpus epithelium. Patients with mutations in the multiple endocrine neoplasia type 1 (MEN1) locus, which encodes the protein menin, develop pituitary hyperplasia, insulinomas, and gastrinomas in the duodenum. We previously hypothesized that loss of menin leads to derepression of the gastrin gene and hypergastrinemia. Indeed, we show that menin represses JunD induction of gastrin in vitro. Therefore, we examined whether conditional deletion of Men1 (Villin-Cre and Lgr5-EGFP-IRES-CreERT2), with subsequent loss of menin from the gastrointestinal epithelium, increases gastrin expression. We found that epithelium-specific deletion of Men1 using Villin-Cre increased plasma gastrin, antral G cell numbers, and gastrin expression in the antrum, but not the duodenum. Moreover, the mice were hypochlorhydric by 12 mo of age, and gastric somatostatin mRNA levels were reduced. However, duodenal mRNA levels of the cyclin-dependent kinase inhibitor p27(Kip1) were decreased, and cell proliferation determined by Ki67 staining was increased. About 11% of the menin-deficient mice developed antral tumors that were negative for gastrin; however, gastrinomas were not observed, even at 12 mo of age. No gastrinomas were observed with conditional deletion of Men1 in the Lgr5 stem cells 5 mo after Cre induction. In summary, epithelium-specific deletion of the Men1 locus resulted in hypergastrinemia due to antral G cell hyperplasia and a hyperproliferative epithelium, but no gastrinomas. This result suggests that additional mutations in gene targets other than the Men1 locus are required to produce gastrin-secreting tumors.     

Production of superoxide ions by leukocytes of the American alligator (Alligator mississippiensis)

This study was conducted to characterize the production of superoxide ions by leukocytes in whole blood of the American alligator (Alligator mississippiensis). We used WST-1, a tetrazolium salt which can be reduced to a water-soluble formazan compound with high molar absorptivity at 438 nm, to probe the production of superoxide by alligator leukocytes. Incubation of alligator whole blood with WST-1 resulted in a time- and concentration-dependent increase in absorbance of the plasma at 438 nm. The reduction of WST-1 was inhibited in a concentration-dependent manner by superoxide dismutase, an enzyme that catalyzes the reduction of superoxide to peroxide, confirming that the reduction of WST-1 was due to the presence of superoxide. Treatment of whole blood with nitrotetrazolium blue (NBT) resulted in the staining of heterophils and monocytes, enforcing the idea that that the production of superoxide is due to the presence of leukocytes, and not other blood cell components. It is interesting to note that the production of superoxide by the alligator leukocytes required no external stimulation while human leukocytes must be stimulated with an immunological challenge before producing superoxide. This is the first report of the production of superoxide as an innate immune mechanism in crocodilians.     

Identifying the neural circuitry of alcohol craving and relapse vulnerability

With no further intervention, relapse rates in detoxified alcoholics are high and usually exceed 80% of all detoxified patients. It has been suggested that stress and exposure to priming doses of alcohol and to alcohol-associated stimuli (cues) contribute to the relapse risk after detoxification. This article focuses on neuronal correlates of cue responses in detoxified alcoholics. Current brain imaging studies indicate that dysfunction of dopaminergic, glutamatergic and opioidergic neurotransmission in the brain reward system (ventral striatum including the nucleus accumbens) can be associated with alcohol craving and functional brain activation in neuronal systems that process attentional relevant stimuli, reward expectancy and experience. Increased functional brain activation elicited by such alcohol-associated cues predicted an increased relapse risk, whereas high brain activity elicited by affectively positive stimuli may represent a protective factor and was correlated with a decreased prospective relapse risk. These findings are discussed with respect to psychotherapeutic and pharmacological treatment options.     

Self-renewal of acute lymphocytic leukemia cells is limited by the Hedgehog pathway inhibitors cyclopamine and IPI-926

Conserved embryonic signaling pathways such as Hedgehog (Hh), Wingless and Notch have been implicated in the pathogenesis of several malignancies. Recent data suggests that Hh signaling plays a role in normal B-cell development, and we hypothesized that Hh signaling may be important in precursor B-cell acute lymphocytic leukemia (B-ALL). We found that the expression of Hh pathway components was common in human B-ALL cell lines and clinical samples. Moreover, pathway activity could be modulated by Hh ligand or several pathway inhibitors including cyclopamine and the novel SMOOTHENED (SMO) inhibitor IPI-926. The inhibition of pathway activity primarily impacted highly clonogenic B-ALL cells expressing aldehyde dehydrogenase (ALDH) by limiting their self-renewal potential both in vitro and in vivo. These data demonstrate that Hh pathway activation is common in B-ALL and represents a novel therapeutic target regulating self-renewal and persistence of the malignant clone.     

Precious metal economy

The zebrafish is emerging as a system of choice for modeling human disease. In this issue of Cell Metabolism, Mendelsohn et al. (2006) describe a model for Menkes disease, a genetic disorder in copper utilization. Using genetic and chemical screens, the authors highlight the impact of maternal nutrition on embryo development. The work reveals a hierarchy of temporal and dosage-dependent phenotypes for copper nutrition.     

Geographical variation in temporal and spatial vocalization patterns of male harbour seals in the mating season

In the aquatically mating harbour seal, Phoca vitulina, oestrous females show marked differences in spatial and temporal distribution between geographical areas. This suggests that the males' display behaviour may also vary between areas. We recorded male vocalizations in two areas, the Moray Firth and Orkney, U.K. In the Moray Firth, females haul out on a few intertidal sandbars and travel along predictable routes to forage at sea. In Orkney, female haul out sites are much less influenced by tidal availability and females are much more dispersed. In the Moray Firth, males vocalized only during a short mating season, from 1 July to 12 August. Vocalizations varied significantly with the tide, the peak at high tide clearly coinciding with the period when most females were in the water. In contrast, vocalizations in Orkney were significantly related to both tidal and diel patterns. We suggest that the timing of male vocalizations reflects differences in female availability between sites. In the inner Moray Firth, vocalizations were heard throughout the females' range, whereas vocalizations in Orkney were heard only in two discrete areas. However, at both sites the density of vocalizing males was highest in narrow channels and/or along predictable female travel routes. Therefore, males clearly adapt their temporal and spatial behaviour patterns to variations in female distribution and density. These results suggest that male mating strategies in aquatically mating pinnipeds are more variable than was previously envisaged. Copyright 1999 The Association for the Study of Animal Behaviour.     

Amelioration of ischemia-reperfusion injury with cyclic peptide blockade of ICAM-1

Neutrophils are pivotal in the pathogenesis of ischemia-reperfusion (I/R) injury leading to muscle damage. Firm adhesion of neutrophils to the endothelium is initiated by an interaction between intercellular adhesion molecular-1 (ICAM-1) on the endothelium and beta(2)-integrins on neutrophils. Inhibition of ICAM-1-dependent binding using monoclonal antibodies has been shown to be efficacious in ameliorating I/R injury by preventing the influx of neutrophils into the ischemic tissue. We recently described a cyclic peptide that is a potent and selective inhibitor of ICAM-1 (IP25) in vitro. In this study, we tested the hypothesis that IP25-mediated blockade of ICAM-1 would inhibit neutrophil influx during reperfusion of ischemic tissue and consequently attenuate muscle injury in a tourniquet hindlimb murine model of I/R injury. Varying amounts of peptide drug were injected at the beginning of the reperfusion period. The neutrophil influx and size of infarction at the end of 2 h of reperfusion were compared with those in untreated control mice and contralateral nonischemic limbs. Mice receiving IP25 immediately before reperfusion showed a 56% reduction in neutrophil infiltration in the ischemic muscle, accompanied by a 40% reduction in the infarct size. No effect on I/R injury was seen if IP25 administration was delayed for 60 min after reperfusion. We conclude that IP25 effectively inhibits ICAM-1-mediated adhesion of neutrophils to the endothelium in mice leading to a protective effect and suggests that synthetic peptide antagonists have a potential role as therapeutic tools.