Saxitoxin Exposure Confirmed by Human Urine and Food Analysis

A case of an elderly female with suspected paralytic shellfish poisoning (PSP) is presented. The patient shared a meal of recreationally-harvested shellfish with her family and soon began to experience nausea and weakness. She was taken to the local emergency department and then transported to a larger hospital in Anchorage where she was admitted to the intensive care unit with respiratory depression and shock. Her condition improved, and she was discharged from the hospital 6 days later. No others who shared the meal reported symptoms of PSP. A clam remaining from the meal was collected and analyzed for paralytic shellfish toxins (PST) by the Alaska Department of Environmental Conservation Environmental Health Laboratory; the clam tested positive for saxitoxin (STX; 277 μg/100 g), neosaxitoxin (NEO; 309 μg/100 g), multiple gonyautoxins (GTX; 576-2490 μg/100 g), decarbamoyl congeners (7.52-11.3 μg/100 g) and C-toxins (10.8-221 μg/100 g) using high-pressure liquid chromatography with post-column oxidation (AOAC Method 2011.02). Urine from the patient was submitted to Centers for Disease Control for analysis of selected PSTs and creatinine. STX (64.0 μg/g-creatinine), NEO (60.0 μg/g-creatinine) and GTX1-4 (492-4780 μg/g-creatinine) were identified in the urine using online solid phase extraction with HPLC and tandem mass spectrometry. This was the first time GTX were identified in urine of a PSP case from Alaska, highlighting the need to include all STX congeners in testing to protect the public's health through a better understand of PST toxicity, monitoring and prevention of exposures.

Peroxiredoxin-4 interacts with and regulates the thromboxane A(2) receptor

We identified peroxiredoxin-4 (Prx-4) as a protein interacting with the beta isoform of the thromboxane A(2) receptor (TPbeta) by yeast two-hybrid analysis. Prx-4 co-immunoprecipitated constitutively with TPbeta in HEK293 cells. The second and third intracellular loops as well as the C-terminus of TPbeta interacted directly with Prx-4. Co-expression of Prx-4 caused a 60% decrease in cell surface expression of TPbeta. Prx-4 and TPbeta predominantly co-localized in the endoplasmic reticulum. Co-expression of Prx-4 in cells treated with H(2)O(2) targeted TPbeta for degradation. We show for the first time an interaction between a receptor involved in oxidative stress and Prx-4, an anti-oxidative enzyme.

Differential regulation of the signaling and trafficking of the two prostaglandin D2 receptors, prostanoid DP receptor and CRTH2

Prostaglandin D2 (PGD2) exerts its actions on two G protein-coupled receptors, the prostanoid DP receptor and CRTH2 (chemoattractant homologous receptor expressed on TH2 cells). Here, we characterize the regulation of the signaling and trafficking of the prostanoid DP receptor and CRTH2. Time-course and dose-response curves showed that both receptors expressed in HEK293 cells internalized maximally after 2 h of stimulation with 1 microM PGD2. Co-expression of the G protein-coupled receptor kinases GRK2, GRK5 or GRK6 increased agonist-induced internalization of CRTH2, while only GRK2 had an effect on the internalization of the prostanoid DP receptor. Protein kinase C (PKC) activation stimulated the internalization of both receptors. Interestingly, only PGD2-induced internalization of CRTH2, and not of prostanoid DP receptor, was decreased by inhibition of PKC or protein kinase A (PKA). Our data also indicate that CRTH2 is subjected to basal phosphorylation by PKA, which appears to be involved in CRTH2 internalization. Prostanoid DP receptor internalization was promoted by co-expression of arrestin-2 and -3, while the internalization of CRTH2 was increased by co-expression of arrestin-3 only. The detection of prostanoid DP receptor and CRTH2 internalization was reduced by the co-expression of Rab4 and Rab11, respectively, suggesting differential regulation of receptor recycling. Moreover, immunofluorescence microscopy experiments showed that the prostanoid DP receptor specifically co-localized with Rab4, and CRTH2 with Rab11. The signaling of the prostanoid DP receptor was regulated by GRK2 overexpression, while that of CRTH2 was modulated by overexpression of GRK2, -5 and -6. Our results show a differential regulation of the prostanoid DP receptor and CRTH2, two receptors for PGD2.

The Intracellular Trafficking of the G Protein-coupled Receptor TPβ Depends on a Direct Interaction with Rab11

Intracellular trafficking pathways of cell surface receptors following their internalization are the subject of intense research efforts. However, the mechanisms by which they recycle back to the cell surface are still poorly defined. We have recently demonstrated that the small Rab11 GTPase protein is a determinant factor in controlling the recycling to the cell surface of the beta-isoform of the thromboxane A2 receptor (TPbeta) following its internalization. Here, we demonstrate with co-immunoprecipitation studies in HEK293 cells that there is a Rab11-TPbeta association occurring in the absence of agonist, which is not modulated by stimulation of TPbeta. We show with purified TPbeta intracellular domains fused to GST and HIS-Rab11 proteins that Rab11 interacts directly with the first intracellular loop and the C-tail of TPbeta. Amino acids 335-344 of the TPbeta C-tail were determined to be essential for the interaction of Rab11 with this receptor domain. This identified sequence appears to be important in directing the intracellular trafficking of the receptor from the Rab5-positive intracellular compartment to the perinuclear recycling endosome. Interestingly, our data indicate that TPbeta interacts with the GDP-bound form, and not the GTP-bound form, of Rab11 which is necessary for recycling of the receptor back to the cell surface. To our knowledge, this is the first demonstration of a direct interaction between Rab11 and a transmembrane receptor.

Nm23-H2 Interacts with a G Protein-coupled Receptor to Regulate Its Endocytosis through an Rac1-dependent Mechanism

G protein-coupled receptors (GPCRs) represent a vast family of transmembrane proteins involved in the regulation of several physiological responses. The thromboxane A2 receptor (present as two isoforms: TP alpha and TP beta) is a GPCR displaying diverse pharmacological effects. As seen for many other GPCRs, TP beta is regulated by agonist-induced internalization. In the present study, we report the identification by yeast two-hybrid screening of Nm23-H2, a nucleoside diphosphate kinase, as a new interacting molecular partner with the C-terminal tail of TP beta. This interaction was confirmed in a cellular context when Nm23-H2 was co-immunoprecipitated with TP beta in HEK293 cells, a process dependent on agonist stimulation of the receptor. We observed that agonist-induced internalization of TP beta was regulated by Nm23-H2 through modulation of Rac1 signaling. Immunofluorescence microscopy in HEK293 cells revealed that Nm23-H2 had a cytoplasmic and nuclear localization but was induced to translocate to the plasma membrane upon stimulation of TP beta to show extensive co-localization with the receptor. Our findings represent the first demonstration of an interaction of an Nm23 protein with a membrane receptor and constitute a novel molecular regulatory mechanism of GPCR endocytosis.

[Reoperations of rectal resection for recurrence after previous resection for rectosigmoid cancer]

From June 1986 to December 1992, 16 patients (12 men and 4 women, 63 years-old [36 to 79]) who underwent a prior sphincter-saving resection for colorectal adenocarcinoma were operated on for locoregional recurrence with a surgical resection. Eight patients had a second anterior resection (5 colorectal, 2 coloanal and 1 ileoanal anastomosis), one a resection without anastomosis, and 7 an abdomino-perineal resection. Nine patients received an intraoperative irradiation (10 to 25 Gy). Excisions of surrounding organs were often necessary. Post-operative complications occurred in most of the patients. Excluding 3 post-operative deaths, 9 patients died of disease in a median of 12.9 months after surgery (range: 3 to 32 months). Four patients are still living 5 to 14 months after the second resection. There is little in the surgical literature dealing with these difficult surgical problem of which results are always uncertain. An earlier diagnosis of the recurrence would result in a more satisfactory procedure, but is difficult because of the limited possibilities of detection after surgical treatment and often external irradiation.

[Fatal hydatid pulmonary embolism during hepatectomy for hydatid cyst. Apropos of a case]

Liver Hydatid cysts located close to the inferior vena cava and the sus-hepatic veins are known for their risk of rupture inside these veins. The authors report the case of a patient who died from massive pulmonary embolism during the surgical treatment (hepatectomy) of liver hydatid cysts. Diagnosis and treatment of these fistula are reviewed.