Scombrotoxic Fish Poisoning Secondary to Tuna Ingestion

Scombrotoxic poisoning results from the improper handling and refrigeration of fish containing naturally occurring histidine. Scombroid fish species such as tuna, mackerel and swordfish contain histidine, which is converted to histamine when inadequately chilled. European legislation states that scombroid fish species should be tested for the presence of histamine and mean values should be <100mg/kg1. The authors report an outbreak of scombrotoxic fish poisoning in 12 individuals following ingestion of tuna. Symptoms occurred rapidly and included flushing, headache, palpitations and diarrhoea. Fortunately, symptoms were short lived and self-limiting except in one individual, who required anti-histamine medication. Adequate refrigeration practices are crucial in preventing scombrotoxic food poisoning.

A Cluster of Hepatitis A Viral Infection in HSE South.

Hepatitis A is an acute viral infection of the liver that produces clinical features ranging from asymptomatic infection to fulminant hepatitis1. The authors report a cluster of 5 serologically-confirmed cases of acute Hepatitis A Virus (HAV), all serum IgM positive for HAV Genotype 1A. This is on a background of only 2 other cases notified to HSE-South in 2016 to date, both travel related. There was a considerable delay in notification in two out of 5 cases. This case report highlights the importance of prompt notification of Hepatitis A, as timely notification would have facilitated prompt contact vaccination and might well have prevented illness in two subsequent household contacts.

Cholecystokinin activates PYK2/CAKbeta by a phospholipase C-dependent mechanism and its association with the mitogen-activated protein kinase signaling pathway in pancreatic acinar cells.

PYK2/CAKbeta is a recently described cytoplasmic tyrosine kinase related to p125 focal adhesion kinase (p125(FAK)) that can be activated by a number of stimuli including growth factors, lipids, and some G protein-coupled receptors. Studies suggest PYK2/CAKbeta may be important for coupling various G protein-coupled receptors to the mitogen-activated protein kinase (MAPK) cascade. The hormone neurotransmitter cholecystokinin (CCK) is known to activate both phospholipase C-dependent cascades and MAPK signaling pathways; however, the relationship between these remain unclear. In rat pancreatic acini, CCK-8 (10 nM) rapidly stimulated tyrosine phosphorylation and activation of PYK2/CAKbeta by both activation of high affinity and low affinity CCK(A) receptor states. Blockage of CCK-stimulated increases in protein kinase C activity or CCK-stimulated increases in [Ca(2+)](i), inhibited by 40-50% PYK2/CAKbeta but not p125(FAK) tyrosine phosphorylation. Simultaneous blockage of both phospholipase C cascades inhibited PYK2/CAKbeta tyrosine phosphorylation completely and p125(FAK) tyrosine phosphorylation by 50%. CCK-8 stimulated a rapid increase in PYK2/CAKbeta kinase activity assessed by both an in vitro kinase assay and autophosphorylation. Total PYK2/CAKbeta under basal conditions was largely localized (77 +/- 7%) in the membrane fraction, whereas total p125(FAK) was largely localized (86 +/- 3%) in the cytosolic fraction. With CCK stimulation, both p125(FAK) and PYK2/CAKbeta translocated to the plasma membrane. Moreover CCK stimulation causes a rapid formation of both PYK2/CAKbeta-Grb2 and PYK2/CAKbeta-Crk complexes. These results demonstrate that PYK2/CAKbeta and p125(FAK) are regulated differently by CCK(A) receptor stimulation and that PYK2/CAKbeta is probably an important mediator of downstream signals by CCK-8, especially in its ability to activate the MAPK signaling pathway, which possibly mediates CCK growth effects in normal and neoplastic tissues.

CCKA receptor activation stimulates p130(Cas) tyrosine phosphorylation, translocation, and association with Crk in rat pancreatic acinar cells.

p130(Cas) (Crk-associated substrate), because of its structure as an adapter protein, can interact when tyrosine-phosphorylated with a large number of cellular proteins and therefore be an important modulator of downstream signals. A number of growth factors, lipids, and a few G protein-coupled receptors can stimulate p130(Cas) tyrosine phosphorylation. Recent studies show that tyrosine phosohorylation of intracellular proteins by the hormone/neurotransmitter cholecystokinin (CCK) in rat pancreatic acinar cells may be an important signaling cascade. In this study, we show in rat dispersed pancreatic acini CCK-8 rapidly stimulates tyrosine phosphorylation of p130(Cas), reaching a maximum (6.6 +/- 1. 4)-fold increase with a half-maximal effect at 0.3 nM. Activation of protein kinase C by TPA or increases in [Ca2+]i by the calcium ionophore A23187 stimulated p130(Cas) phosphorylation. Blockade of CCK increases in [Ca2+]i or PKC activity did not alter CCK-8-stimulated p130(Cas) phosphorylation; however, simultaneous blockage of both cascades caused a 50% inhibition. Partial inactivation by C. botulinum toxin of the small GTP-binding protein Rho caused a 41 +/- 12% decrease in the CCK-stimulated p130(Cas) phosphorylation. Disruption of the actin cytoskeleton with cytochalasin D, but not the microtubule network with colchicine, completely inhibited CCK-8-stimulated p130(Cas) phosphorylation. Total p130(Cas) under basal conditions was largely localized (70 +/- 2%) in the membrane fraction, and stimulation with CCK-8 induced total p130(Cas) translocation from the cytosolic fraction. CCK stimulation also caused a (5 +/- 1)-fold increase in p130(Cas) tyrosine phosphorylated in the plasma membrane. Treatment with tyrphostin B44 inhibited CCK-8-stimulated p130(Cas) phosphorylation, but it had no effect on p130(Cas) translocation. CCK-8 caused rapid formation of a p130(Cas)-Crk complex. In conclusion, our results demonstrate CCKA receptor activation causes rapid tyrosine phosphorylation of p130(Cas) through PLC-dependent and -independent mechanisms that require the participation of the small GTP-binding protein Rho and the integrity of the actin cytoskeleton, but not the microtubule network. Moreover, CCKA receptor activation causes translocation of p130(Cas) to the membrane and an increase in membrane tyrosine-phosphorylated p130(Cas). The translocation to the membrane does not require antecedent tyrosine phosphorylation. CCKA activation promotes the rapid formation of a p130(Cas)-Crk complex. These results suggest that p130(Cas) is likely an important modulator of downstream signals activated by CCK-8, possibly involved in regulating numerous cellular effects, such as effects on cell growth or cell shape.

Constitutive activation of the gastrin-releasing peptide receptor expressed by the nonmalignant human colon epithelial cell line NCM460.

Gastrin-releasing peptide (GRP) causes multiple effects in humans by activating a specific heptaspanning receptor. Within the gastrointestinal tract, GRP receptors (GRP-R) are not normally expressed by mucosal epithelial cells except for those lining the gastric antrum. In contrast, recent studies have shown that up to 40% of resected colon cancers aberrantly express this receptor. This is important because the GRP-R can cause the proliferation of many, but not all, tissues in which it is expressed. Since GRP and other agonists are not known to exist in the colonic lumen, it has not been clear how or even if GRP-R expression in colon cancer contributes to cell proliferation. To evaluate the functional consequence of GRP-R expression on colonic epithelium, we transfected the recently isolated nonmalignant human colon epithelial cell line NCM460 with the cDNA for this receptor. All NCM460 cell lines expressing varying numbers of GRP-R bound selected agonists and antagonists indistinguishably from receptors expressed by other human tissues. Furthermore GRP-R-expressing transfected cell lines, but not wild-type NCM460 cells, proliferated independently of serum or other growth factors. Further evaluation revealed that GRP-R in these cells tonically stimulated G alpha q/11, resulting in increased phospholipase C activation. Since transfected cells do not secrete GRP, nor is their growth influenced by exposure to receptor-specific antagonists, these data indicate that GRP-R ectopically expressed by NCM460 cells are constitutively active. This report provides the first evidence of mutation-independent heptaspanning receptor constitutive activation resulting in cell proliferation, and identifies a potential mechanism whereby the GRP-R may act as an oncogene in human colon cancer.

Location and characterization of the human GRP receptor expressed by gastrointestinal epithelial cells.

The exact location of normal gastrin-releasing peptide (GRP) receptor expression by epithelial cells lining the human gastrointestinal (GI) tract is not known; yet this receptor is found on upwards of 50% of GI cancers. Furthermore, the pharmacology reported for GRP receptors expressed by GI cancers varies considerably. Therefore, the purpose of this study was to determine the normal distribution of GRP receptor expression by cells lining the human GI tract, and then determine the normal pharmacology of the human receptor when ectopically expressed by the nonmalignant human colon epithelial cell line NCM460. We obtained endoscopic pinch biopsies of, and extracted the RNA from, epithelial cells lining the esophagus, stomach, jejunum, ileum, and proximal and descending colon, RT-PCR demonstrated that GRP-R expression is limited to cells lining the gastric antrum, indicating that this receptor is aberrantly expressed by GI cancers. To determine the normal pharmacology of this receptor when expressed by nonmalignant human tissues for the first time, we transfected NCM460 cells with the cDNA for the human GRP receptor. By studying three stable NCM460 cell lines expressing varying numbers of receptors, we demonstrate that agonist and antagonist binding affinity, binding kinetics, and G-protein coupling are all independent of receptor number. Finally, by comparing GRP receptors expressed by GI cancers with those on NCM460-transfected cells, we show that the pharmacology of the aberrantly expressed receptors is significantly altered. Thus, these data demonstrate that GI cancers aberrantly express GRP receptors that then behave abnormally.