Macrophage factor X activator formation: metabolic requirements for synthesis of components

The in vitro production of factor VII-like material and of tissue factor activity by murine thioglycollate exudate macrophages was measured by amidolytic assays. Tissue factor activity was inducible by endotoxin, and its induction was inhibited by 1 microgram/mL of actinomycin D, 10 micrograms/mL of cycloheximide, and 0.2 micrograms/mL of tunicamycin. Soluble factor VII-like material was secreted by macrophages into culture supernatants. The amount produced was not influenced by further activation of the cells by endotoxin, nor was its production inhibited significantly by 1 microgram/mL actinomycin D or 0.2 micrograms/mL tunicamycin. The production of the factor VII-like material was inhibited by 10 micrograms/mL of cycloheximide, and its appearance in culture supernatants was enhanced significantly by the addition of vitamin K1. When lysates of activated macrophages were suspended in ultracentrifuged culture supernatants, a particulate factor X activator was formed. Centrifugation at 100,000 g pelleted the factor X activator and left no factor VII-like material in the supernatant. The data indicate that thioglycollate-induced exudate macrophages make and excrete factor VII-like material, and this production is not modulated by further activation. However, activation of the macrophages induces tissue factor production. The factor X activator appears to result from the interaction and complexing of the soluble factor VII-like material and the membrane-bound tissue factor.     

Hematologic and immunomodulatory effects of an interleukin-1 receptor antagonist coinfusion during low-dose endotoxemia in healthy humans

Endotoxin is a component of gram-negative bacteria that causes hematologic and immunologic changes through its induction of cytokines. Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring inhibitor of IL-1 that competes with IL-1 for occupancy of cell-surface receptors but possesses no agonist activity. We investigated the ability of human recombinant IL-1Ra to block the effects of low-dose endotoxin. Fourteen healthy male volunteers between 18 and 30 years old were injected intravenously with 3 ng/kg Escherichia coli endotoxin. Concurrent with the injections, nine volunteers received a 3-hour continuous intravenous infusion of IL-1Ra. The other five subjects were given a 3-hour infusion of saline. Volunteers injected with endotoxin experienced a threefold increase in circulating neutrophils over baseline. This neutrophilia was significantly reduced by 48% in subjects administered endotoxin plus IL-1Ra (P = .0253). Ex vivo mitogen-induced peripheral blood mononuclear cell proliferation decreased by greater than 60% at 3 and 6 hours after endotoxin injection (P = .0053). This endotoxin-induced reduction in mitogen response was reversed in subjects coinjected with IL-1Ra (P = .0253). Endotoxin-induced symptoms, fever, and tachycardia were unaffected by IL-1Ra. IL-1 appears to be an important mediator in endotoxemia because some of its hematologic and immunomodulatory effects can be blocked by IL-1Ra.     

Rigid membranes of Malayan ovalocytes: a likely genetic barrier against malaria

A high frequency of nonhemolytic hereditary ovalocytosis in Malayan aborigines is thought to result from reduced susceptibility of affected individuals to malaria. Indeed, Kidson et al. recently showed that ovalocytes from Melanesians in Papua New Guinea are resistant to infection in culture by the malarial parasite Plasmodium falciparum. In order to determine if protection against parasitic invasion in these ovalocytes might be the result of some altered membrane material property in these unusual cells, we measured their membrane and cellular deformability characteristics using an ektacytometer . Ovalocytic red cells were found to be much less deformable in comparison to normal discoid red cells. Similar measurements on isolated membrane preparations revealed a marked reduction in ovalocytic membrane deformability. To produce equal deformation of ovalocytic and normal membranes, ovalocytes required an 8-10-fold increase in applied shear stress, indicating that their membrane was capable of deforming under sufficient stress. To test the possibility that this increased membrane rigidity might confer resistance to parasitic invasion, we performed an in vitro invasion assay using Plasmodium falciparum merozoites and Malayan ovalocytes of varying deformability from seven different donors. The level of infection of the ovalocytes ranged from 1% to 35% of that in control cells, and the extent of inhibition appeared to be closely related to the reduction in membrane deformability. Moreover, we were able to induce similar resistance to parasitic invasion in nonovalocytic normal red cells by increasing their membrane rigidity with graded exposure to a protein crosslinking agent. Our findings suggest that resistance to parasite invasion of Malayan ovalocytes is the result of a genetic mutation that causes increased membrane rigidity.     

Is l-Glutathione More Effective Than l-Glutamine in Preventing Enteric Diabetic Neuropathy?

Background

Diabetes and its complications appear to be multifactorial. Substances with antioxidant potential have been used to protect enteric neurons in experimental diabetes.

Aim

This study evaluated the effects of supplementation with l-glutamine and l-glutathione on enteric neurons in the jejunum in diabetic rats.

Methods

Rats at 90 days of age were distributed into six groups: normoglycemic, normoglycemic supplemented with 2 % l-glutamine, normoglycemic supplemented with 1 % l-glutathione, diabetic (D), diabetic supplemented with 2 % l-glutamine (DG), and diabetic supplemented with 1 % l-glutathione (DGT). After 120 days, the jejunums were immunohistochemically stained for HuC/D+ neuronal nitric oxide synthase (nNOS) and vasoactive intestinal polypeptide (VIP). Western blot was performed to evaluate nNOS and VIP. Submucosal and myenteric neurons were quantitatively and morphometrically analyzed.

Results

Diabetic neuropathy was observed in myenteric HuC/D, nNOS, and VIP neurons (p < 0.05). In the submucosal plexus, diabetes did not change nitrergic innervation but increased VIPergic neuronal density and body size (p < 0.05). Supplementation with l-glutathione prevented changes in HuC/D neurons in the enteric plexus (p < 0.05), showing that supplementation with l-glutathione was more effective than with l-glutamine. Myenteric nNOS neurons in the DGT group exhibited a reduced density (34.5 %) and reduced area (p < 0.05). Submucosal neurons did not exhibit changes. The increase in VIP-expressing neurons was prevented in the submucosal plexus in the DG and DGT groups (p < 0.05).

Conclusion

Supplementation with l-glutathione exerted a better neuroprotective effect than l-glutamine and may prevent the development of enteric diabetic neuropathy.     

N-acylhydrazone derivative ameliorates monocrotaline-induced pulmonary hypertension through the modulation of adenosine AA2R activity

Background

Pulmonary arterial hypertension (PAH) is a disease that results in right ventricular (RV) dysfunction. While pulmonary vascular disease is the primary pathological focus, RV hypertrophy and RV dysfunction are the major determinants of prognosis in PAH. The aim of this study was to investigate the effects of (E)-N′-(3,4-dimethoxybenzylidene)-4-methoxybenzohydrazide (LASSBio-1386), an N-acylhydrazone derivative, on the lung vasculature and RV dysfunction induced by experimental PAH.

Methods

Male Wistar rats were injected with a single dose (60 mg/kg, i.p.) of monocrotaline (MCT) and given LASSBio-1386 (50 mg/kg, p.o.) or vehicle for 14 days. The hemodynamic, exercise capacity (EC), endothelial nitric oxide synthase (eNOS), adenosine A_2A receptor (A_2AR), sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA2a), phospholamban (PLB) expression, Ca^2 +-ATPase activity and vascular activity of LASSBio-1386 were evaluated.

Results and conclusions

The RV systolic pressure was elevated in the PAH model and reduced from 49.6 ± 5.0 mm Hg (MCT group) to 27.2 ± 2.1 mm Hg (MCT + LASSBio-1386 group; P < 0.05). MCT administration also impaired the EC, increased the RV and pulmonary arteriole size, and promoted endothelial dysfunction of the pulmonary artery rings. In the PAH group, the eNOS, A_2AR, SERCA2a, and PLB levels were changed compared with the control; in addition, the Ca^2 +-ATPase activity was reduced. These alterations were related with MCT-injected rats, and LASSBio-1386 had favorable effects that prevented the development of PAH. LASSBio-1386 is effective at preventing endothelial and RV dysfunction in PAH, a finding that may have important implications for ongoing clinical evaluation of A_2AR agonists for the treatment of PAH.     

Managing Novel Oral Anticoagulants in Patients With Atrial Fibrillation Undergoing Device Surgery: Canadian Survey

Background

Approximately 10% of patients who undergo surgical procedures require chronic oral anticoagulation. Physicians must balance the thromboembolic and bleeding risks to make informed decisions on whether to continue anticoagulant medication. Evidence is lacking regarding the perioperative management of novel oral anticoagulant (NOAC) agents. This survey aims to describe the management of perioperative NOAC use during device implantation by Canadian centres.

Methods

A Web-based tool was used to survey all Canadian adult pacemaker/defibrillator implant centres. The survey collected data regarding the perioperative management of NOACs in atrial fibrillation patients at high risk for thromboembolism who undergo device implantation.

Results

Twenty-two centres performed approximately 14,971 device implants; 1150 (8%) of these implants were in patients who were prescribed a NOAC. In 82% of centres, the NOAC is discontinued in anticipation of device implantation; 73% of these centres do not bridge with heparin. In patients with normal renal function at high risk of thromboembolic events (Congestive Heart Failure, Hypertension, Age, Diabetes, Stroke/Transient Ischemic Attack; CHADS₂ ≥ 2), 72% of the centres restart the NOAC within 48 hours of the procedure. For patients with abnormal renal function (glomerular filtration rate < 80 mL/min), the timing of NOAC discontinuation is variable. Hematoma rates vary from 0 to 30%.

Conclusions

Most Canadian centres perform device implantation with NOAC interruption without the use of bridging. The timing of stopping and restarting anticoagulation and incidence of bleeding complications is variable. These findings emphasize the need for randomized controlled studies to guide the optimal approach to management of NOACs during device implantation.