Antithrombin Murcia (K241E) causing antithrombin deficiency: a possible role for altered glycosylation

Background

Identification of mutations in the SERPINC1 gene has revealed different mechanisms responsible for antithrombin deficiency. Deletions and nonsense mutations associate with type I deficiency. Certain missense mutations cause type II deficiency by affecting the heparin binding site or the reactive center loop, while others result in type I deficiency by intracellular retention or RNA instability.

Design and Methods

We studied the molecular, biochemical, proteomic and glycomic characterization of a new natural mutant (K241E) that may be classified as pleiotropic.

Results

The mutation caused a significant decrease in the anticoagulant activity mainly due to a reduced heparin affinity and a modification of the electrostatic potential that might explain the impaired ability of the mutant protein to form complexes with the target protease in the absence of heparin. Mass spectrometry and glycomic analyses confirmed an increased molecular weight of 800 Da in the mutant protein possibly due to core-fucosylation, provoking the loss of heparin affinity. Additionally, carriers of this mutation also have a minor mutant isoform that still followed normal glycosylation, retaining similar heparin affinity to wild-type α-antithrombin, and certain anticoagulant activity, which may explain the milder thrombotic risk of patients carrying this mutation. Similar results were observed using recombinant K241E antithrombin molecules.

Conclusions

Our data suggest a new mechanism involved in antithrombin type II deficiency by indirectly affecting the glycosylation of a natural variant. Additional studies are required to confirm this hypothesis.     

Clinical pharmacology of 5-ASA compounds in inflammatory bowel disease

Mesalamine has been the first-line of therapy in patients with inflammatory bowel disease (IBD) since the 1960s. This article serves as a review of the different 5-aminosalicylic acid compounds, release formulations, use and dosing in the treatment of IBD, in particular ulcerative colitis.     

Prospective evaluation of a clinical guideline recommending early patients discharge in bleeding peptic ulcer

Background and Aim: To validate an early discharge policy in patients admitted with upper gastrointestinal bleeding (UGIB) due to ulcers. Methods: Patients with gastroduodenal ulcer or erosive gastritis/duodenitis were included in a previous study aiming to develop a practice guideline for early discharge of patients with UGIB. Variables associated with unfavorable evolution were analyzed in order to identify patients with low‐risk of re‐bleeding. After that, a one‐year prospective analysis of all UGIB episodes was carried out. Results: A total of 341 patients were identified in the retrospective study. Variables associated with unfavorable evolution were: systolic blood pressure ≤ 100 mmHg, heart rate ≥ 100 bpm, and a Forrest endoscopic classification of severe. 10% of patients were immediately discharged; however, if predictive variables obtained in the multivariate analysis had been used, hospitalization could have been prevented in 34% of patients. A total of 77 patients were included in the prospective analysis. Although only 19.5% of patients were immediately discharged without complications, 29 patients (37.7%) were theoretically suitable for early discharge. Conclusions: Patients with UGIB who have clean‐based ulcers and are stable on admission can be safely discharged immediately after endoscopy. Implementation of the clinical practice guideline safely reduced hospital admission for those patients.     

Genetics in gestational diabetes mellitus: association with incidence, severity, pregnancy outcome and response to treatment

Constant advances in gene mapping technology have allowed research to focus from rare monogenic disorders on common complex diseases involving multiple susceptibility genes-environment interactions. Gestational diabetes mellitus (GDM) is a heterogeneous pathogenic condition affecting 2-5% of all pregnant women during pregnancy. GDM is considered to result when genetic predisposition is triggered by increased insulin resistance during pregnancy leading to what seems to be one of the primary characteristics of GDM, the pancreatic b-cell impairment. Genetic predisposition to GDM has been suggested given the occurrence of the disease within family members. Furthermore, GDM is reported to be often present in women with maturity onset diabetes of the young (MODY) gene mutations. In addition, candidate susceptibility gene variants have been suggested to increase the risk of GDM. These genes include glucokinase (GCK), HLA antigens, insulin receptor (INSR), insulin-like growth factor-2 (IGF2), HNF4A, insulin gene (INS-VNTR), plasminogen activator inhibitor 1 (PAI-1), potassium inwardly rectifying channel subfamily J, member 11 (KCNJ11), hepatocyte nuclear factor-4a (HNF4A). Identification of the possible underlying genetic factors of GDM would eventually enrich our knowledge on the pathophysiologic mechanism of the disease and contribute to the individualization of both prevention and treatment of complications for the mother and fetus. However, so far, little is known about the genetic basis of GDM and its potential clinical significance. This review focuses on possible gestational diabetes mellitus susceptibility genes and their association with the disease incidence and severity as well as the pregnancy outcome and the response to treatment.     

Induction of glutathione synthesis and conjugation by 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-dihydroxymethamphetamine (HHMA) in human and rat liver cells, including the protective role of some antioxidants

MDMA (3,4-methylenedioxymethamphetamine) metabolism is a major cause of MDMA-mediated hepatotoxicity. In this study the effects of MDMA and its metabolites on the glutathione system were evaluated. Glutathione (GSH/GSSG) levels and gene expression of glutamate cysteine ligase catalytic subunit (GCLC), glutathione-S-transferase (GST) and pregnane X receptor (PXR) were compared in the immortalized human liver epithelial cell line THLE-Neo lacking phase I metabolism and primary rat hepatocytes expressing both phase I and II metabolism. Furthermore, we evaluated the potential protective effects of two antioxidants, N-acetyl-cysteine (NAC) and sulforaphane (SFN) in these cell systems. In THLE-Neo cells, the MDMA metabolite 3,4-dihydroxymetamphetamine (HHMA) significantly decreased cell viability and depleted GSH levels, resulting in an increased expression of GCLC and GST up to 3.4- and 2.2-fold, respectively. In primary rat hepatocytes, cell viability or GSH levels were not significantly affected upon MDMA exposure. GCLC expression levels where not significantly altered either, although GST expression was increased 2.3-fold. NAC counteracted MDMA-induced cytotoxicity and restored GSH levels. Phase II enzyme expression was also reverted. Conversely, SFN increased MDMA-induced cytotoxicity and GSH depletion, while GCLC and GST expression were significantly induced. In addition, PXR expression decreased after HHMA and MDMA exposure, while co-exposure to SFN induced it up to 3.6- and 3.9-fold compared to vehicle-control in the THLE-Neo cells and rat hepatocytes, respectively. Taken together, these data indicate that HHMA is a major factor in the MDMA-mediated hepatotoxicity through interaction with the glutathione system. The results of our study show that for MDMA intoxication the treatment with an antioxidant such as NAC may counteract the potentially hepatotoxicity. However, SFN supplementation should be considered with care because of the indications of possible drug-drug interactions.     

Latex-allergic patients sensitized to the major allergen hevein and hevein-like domains of class I chitinases show no increased frequency of latex-associated plant food allergy

Allergies to certain fruits such as banana, avocado, chestnut and kiwi are described in 30-70% of latex-allergic patients. This association is attributed to the cross-reactivity between the major latex allergen hevein and hevein-like domains (HLDs) from fruit class I chitinases. We aimed to assess the extent of cross-reactivity between hevein and HLDs using sera from latex-allergic patients with and without plant food allergy. Hevein and HLDs of latex, banana, and avocado chitinases were expressed in Escherichia coli as fusion proteins with the maltose-binding protein and purified by affinity chromatography. IgE binding to these proteins was studied in sera from 59 latex-allergic patients and 20 banana-allergic patients without latex allergy by ELISA and ELISA inhibition. Additionally, 16,408 allergic patients’ sera were tested for IgE binding to hevein, latex chitinase, and wheat germ agglutinin using an allergen microarray. Hevein-specific IgE was detected in 34/59 (58%) latex-allergic patients’ sera. HLDs of latex, banana, and avocado chitinases were recognized by 21 (36%), 20 (34%), and 9 (15%) sera, respectively. In contrast, only one of 20 banana-allergic patients without latex allergy was sensitized to chitinase HLDs. In most tested latex-allergic patients’ sera, IgE binding to hevein was only partially reduced by preincubation with HLDs. Among hevein-sensitized, latex-allergic patients, the percentage of plant food allergy (15/34 = 44%) was equal to latex-allergic patients without hevein sensitization (11/25 = 44%). In the general allergic population, 230 of 16,408 sera (1.4%) reacted to hevein and/or a hevein-like allergen. Of these, 128 sera showed an isolated sensitization to hevein, whereas only 17 bound to latex chitinase or wheat germ agglutinin without hevein sensitization. In conclusion, the IgE response to HLDs is elicited by hevein as sensitizing allergen in most cases. Despite considerable cross-reactivity between these allergens, no correlation between latex-associated plant food allergy and sensitization to hevein or HLDs was found.