Chemical reduction of carboxyl groups in heparin abolishes its vasodilatory activity

Protective Effect of Nebulized Heparin in the Animal Models of Smoke Inhalation Injury: A Meta-analysis and Systematic Review of Experimental Studies

The pathophysiological mechanism of abnormal coagulation can result from smoke inhalation injury (SII). Heparin nebulization is a common treatment for lung disorders. This study aimed to use meta-analysis in animal models to examine the effectiveness of atomized heparin on SII. For our online searches, we used the Cochrane Central Register of Controlled Trials, PubMed, Web of Science, Chinese National Knowledge Infrastructure, Chinese BioMedical Literature Database, and Wanfang Database up to January 2022. Data for SII were retrieved and compared to control animals. The studies' findings were determined by combining standardized mean difference (SMD) analysis with 95% confidence intervals (CIs). The findings showed that as compared to the control group, the heparin-treated group had a lower death rate (relative risk 0.42; 95% CI 0.22, 0.80; p < .05). The meta-analysis demonstrated favorable changes in lung physiology, including PaO2/FiO2 (SMD 1.04; 95% CI 0.65, 1.44; p < .001), lung wet-to-dry weight ratio (SMD -1.83; 95% CI -2.47, -1.18; p < .001), and pulmonary shunt Qs/Qt (SMD -0.69; 95% CI -1.29, -0.08; p < .05) after heparin nebulization for lung injury. The present data indicated that pulmonary artery mean pressure in the heparin therapy group was significantly lowered after 24 and 48 hours of therapy, suggesting that the cardiovascular system could recover following heparin treatment. As a result, heparin nebulization appeared to be more effective against SII and improved cardiopulmonary function compared to the control group. Graphical Abstract.

Haemostatic agent etamsylate in vitro and in vivo antagonizes anti-coagulant activity of heparin

Etamsylate is indicated for several anti-hemorrhagic indications in human and veterinary medicine. However, etamsylate has been shown to be effective only in specific hemorrhagic situations. Furthermore, mechanism of action of etamsylate is not known but recent research has shown its ability to inhibit heparin binding to several growth factors. We have evaluated the ability of etamsylate to interfere with the activities of heparin. Effects of etamsylate on vasodilatory activity of heparin were evaluated in rat aortic segments. Influence of etamsylate on anticoagulant activity of heparin was evaluated in vitro by determining prothrombin (PT) time and activated partial thromboplastin time (aPTT) in dog blood and in vivo by determining the interference of systemic and topical etamsylate on heparin-induced extension in bleeding time (BT) in rats. Despite failing to inhibit heparin-induced vasodilation of rat aorta, etamsylate significantly reduced the increase in aPTT caused by heparin (+30.4 ± 6.7% vs. +15.0 ± 2.8% for etamsylate at 100 µM, P < 0.05). Etamsylate also antagonized the anticoagulant effects driven by heparin in vivo since prevented the heparin-induced increase in BT when systemically (i.p.) administered (+94.6 ± 7.5% vs. +57.9 ± 9.2% at 10 mg/kg, P < 0.05, vs. +22.2 ± 16.8% at 30 mg/kg, P < 0.01). Additionally, topically applied etamsylate (125 mg/ml) significantly reduced heparin-induced BT increase (+102.5 ± 3.2% vs. +54.0 ± 5.8%, P < 0.01). These evidences show a pharmacological interference by etamsylate on heparin activities antagonizing pro-hemorrhagic effects of heparin in vitro and in vivo without inhibiting its vasodilatory properties. This ability could help to explain pharmacological effects of etamsylate and proposes its role for reversing pro-hemorrhagic states.

Heparan sulfate and heparin interactions with proteins

Heparan sulfate (HS) polysaccharides are ubiquitous components of the cell surface and extracellular matrix of all multicellular animals, whereas heparin is present within mast cells and can be viewed as a more sulfated, tissue-specific, HS variant. HS and heparin regulate biological processes through interactions with a large repertoire of proteins. Owing to these interactions and diverse effects observed during in vitro, ex vivo and in vivo experiments, manifold biological/pharmacological activities have been attributed to them. The properties that have been thought to bestow protein binding and biological activity upon HS and heparin vary from high levels of sequence specificity to a dependence on charge. In contrast to these opposing opinions, we will argue that the evidence supports both a level of redundancy and a degree of selectivity in the structure-activity relationship. The relationship between this apparent redundancy, the multi-dentate nature of heparin and HS polysaccharide chains, their involvement in protein networks and the multiple binding sites on proteins, each possessing different properties, will also be considered. Finally, the role of cations in modulating HS/heparin activity will be reviewed and some of the implications for structure-activity relationships and regulation will be discussed.

Microparticles from Patients with the Acute Coronary Syndrome Impair Vasodilatation by Inhibiting the Akt/eNOS-Hsp90 Signaling Pathway

Objectives: Endothelial dysfunction is involved in the development of the acute coronary syndrome (ACS). Plasma microparticles (MPs) from other diseases have been demonstrated to initiate coagulation and endothelial dysfunction. However, whether MPs from ACS patients impair vasodilatation and endothelial function remains unclear. Methods: Patients (n = 62) with ACS and healthy controls (n = 30) were recruited for MP isolation. Rat thoracic aortas were incubated with MPs from ACS patients or healthy controls to determine the effects of MPs on endothelial-dependent vasodilatation, the phosphorylation of Akt and endothelial nitric oxide synthase (eNOS), the interaction of eNOS with heat shock protein 90 (Hsp90), and nitric oxide (NO) and superoxide anion (O2-) production. The origin of MPs was assessed by flow cytometry. Results: MP concentrations were increased in patients with ACS compared with healthy controls. They were positively correlated with the degree of coronary artery stenosis. MPs from ACS patients impair endothelial-dependent vasodilatation, decrease both Akt and eNOS phosphorylation, decrease the interaction between eNOS and Hsp90, and decrease NO production but increase O2- generation in rat thoracic aortas. Endothelial-derived MPs and platelet-derived MPs made up nearly 75% of MPs. Conclusions: Our data indicate that MPs from ACS patients negatively affect endothelial-dependent vasodilatation via Akt/eNOS-Hsp90 pathways.

On the catalytic mechanism of polysaccharide lyases: evidence of His and Tyr involvement in heparin lysis by heparinase I and the role of Ca2+

The structurally diverse polysaccharide lyase enzymes are distributed from plants to animals but share common catalytic mechanisms. One, heparinase I (F. heparinum), is employed in the production of the major anticoagulant drug, low molecular weight heparin, and is a mainstay of cell surface proteoglycan analysis. We demonstrate that heparinase I specificity and efficiency depend on the cationic form of the substrate. Ca(2+)-heparin, in which α-L-iduronate-2-O-sulfate residues adopt (1)C4 conformation preferentially, is a substrate, while Na(+)-heparin is an inhibitor. His and Tyr residues are identified in the catalytic step and a model based on molecular dynamics and docking is proposed, in which deprotonated His203 initiates β-elimination by abstracting the C5 proton of the α-L-iduonate-2-O-sulfate residue in the substrate, and protonated Tyr357 provides the donor to the hexosamine leaving group.