Molecular Mechanism of the Anti-Inflammatory Action of Heparin.

Leandar Litov,Elena Krachmarova,Miroslav Rangelov,Genoveva Nacheva,Kristina Malinova,Rossitsa Hristova,Anastas Gospodinov,Nadezhda Todorova,Elena Lilkova,Peicho Petkov,Nevena Ilieva,Ivan Ivanov

doi:10.3390/ijms221910730

Abstract

Our objective is to reveal the molecular mechanism of the anti-inflammatory action of low-molecular-weight heparin (LMWH) based on its influence on the activity of two key cytokines, IFNγ and IL-6. The mechanism of heparin binding to IFNγ and IL-6 and the resulting inhibition of their activity were studied by means of extensive molecular-dynamics simulations. The effect of LMWH on IFNγ signalling inside stimulated WISH cells was investigated by measuring its antiproliferative activity and the translocation of phosphorylated STAT1 in the nucleus. We found that LMWH binds with high affinity to IFNγ and is able to fully inhibit the interaction with its cellular receptor. It also influences the biological activity of IL-6 by binding to either IL-6 or IL-6/IL-6Rα, thus preventing the formation of the IL-6/IL-6Rα/gp130 signalling complex. These findings shed light on the molecular mechanism of the anti-inflammatory action of LMWH and underpin its ability to influence favourably conditions characterised by overexpression of these two cytokines. Such conditions are not only associated with autoimmune diseases, but also with inflammatory processes, in particular with COVID-19. Our results put forward heparin as a promising means for the prevention and suppression of severe CRS and encourage further investigations on its applicability as an anti-inflammatory agent.

Highlights

There is a considerable volume of observational data regarding the use of lowmolecular-weight heparin in the treatment of COVID-19 because of its anti-coagulatory effect
Our investigations reveal another facet of heparin: a potent anti-inflammatory agent due to its ability to engage with two of the key cytokines in the development of the cytokine storm, IFNγ and IL-6, downregulating their biological activity
Such conditions are associated with autoimmune diseases, and with uncontrolled inflammatory processes, in particular with COVID-19, where they often lead to a lethal exit

Summary

Introduction

Heparin is a member of the glycosaminoglycan (GAG) family, a linear highly sulfated polysaccharide chain of variable length, composed of repeating disaccharide units. This structure defines one of the most prominent characteristics of the molecule—its highdensity negative electric charge. This is the main reason for the high biological activity of heparin. It binds to more than 700 proteins. Heparin is widely used in medical practice as an anticoagulant, with generally mild side effects. The molecular weight of natural heparin ( known as unfractionated heparin, UFH) varies between 5 kDa and more than

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