The Role of Heparan Sulfate in CCL26-Induced Eosinophil Chemotaxis.

Proinflammatory chemokine ligand 26 (CCL26, eotaxin-3) mediates transendothelial cell migration of eosinophils by binding and activating the G-protein-coupled (GPC) chemokine receptor 3 on the surface of eosinophilic cells. Here we have investigated the role of glycosaminoglycans (GAGs) as potential co-receptors in the process of CCL26-induced eosinophil chemotaxis. For this purpose, we have first identified the GAG-binding site of CCL26 by a site-directed mutagenesis approach in the form of an alanine screening. A panel of GAG-binding-deficient mutants has been designed, generated, and analyzed with respect to their binding affinities to heparan sulphate (HS) by isothermal fluorescence titration studies. This showed that basic amino acids in the α-helical part of CCL26 are strongly involved in GAG-binding. In chemotaxis experiments, we found that decreased GAG-binding affinity correlated with decreased chemotactic activity, which indicates an involvement of GAGs in eosinophil migration. This was further proven by the negative impact of heparinase III treatment and, independently, by the incubation of eosinophils with an anti heparan sulfate antibody. We finally investigated eosinophils' proteoglycan (PG) expression patterns by real-time PCR, which revealed the highest expression level for serglycin. Including an anti-serglycin antibody in CCL26-induced eosinophil migration experiments reduced the chemotaxis of these immune cells, thereby proving the dependence of eosinophil mobilization on the proteoglycan serglycin.

Disease-specific glycosaminoglycan patterns in the extracellular matrix of human lung and brain.

A wide variety of diseases throughout the mammalian organism is characterized by abnormal deposition of various components of the extracellular matrix (ECM), including the heterogeneous family of glycosaminoglycans (GAGs), which contribute considerably to the ECM architecture as part of the so-called proteoglycans. The GAG's unique sulfation pattern, derived from highly dynamic and specific modification processes, has a massive impact on critical mediators such as cytokines and growth factors. Due to the strong connection between the specific sulfation pattern and GAG function, slight alterations of this pattern are often associated with enormous changes at the cell as well as at the organ level. This review aims to investigate the connection between modifications of GAG sulfation patterns and the wide range of pathological conditions, mainly focusing on a range of chronic diseases of the central nervous system (CNS) as well as the respiratory tract.

Cytokines and Chemokines in SARS-CoV-2 Infections-Therapeutic Strategies Targeting Cytokine Storm.

The recently identified severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, the cause of coronavirus disease (COVID-19) and the associated ongoing pandemic, frequently leads to severe respiratory distress syndrome and pneumonia with fatal consequences. Although several factors of this infection and its consequences are not completely clear, the presence and involvement of specific chemokines is undoubtedly crucial for the development and progression of COVID-19. Cytokine storm and the often-resulting cytokine release syndrome (CRS) are pathophysiological hallmarks in COVID-19 infections related to its most severe and fatal cases. In this hyperinflammatory event, chemokines and other cytokines are highly upregulated and are therefore not fulfilling their beneficial function in the host response anymore but causing harmful effects. Here, we present the recent views on the involvement of chemokines and selected cytokines in COVID-19 and the therapeutics currently in clinical development targeting or interfering with them, discussing their potentials in the treatment of COVID-19 infections.

Enoxaparin and Pentosan Polysulfate Bind to the SARS-CoV-2 Spike Protein and Human ACE2 Receptor, Inhibiting Vero Cell Infection.

As with many other pathogens, SARS-CoV-2 cell infection is strongly dependent on the interaction of the virus-surface Spike protein with the glycosaminoglycans of target cells. The SARS-CoV-2 Spike glycoprotein was previously shown to interact with cell-surface-exposed heparan sulfate and heparin in vitro. With the aim of using Enoxaparin as a treatment for COVID-19 patients and as prophylaxis to prevent interpersonal viral transmission, we investigated GAG binding to the Spike full-length protein, as well as to its receptor binding domain (RBD) in solution by isothermal fluorescence titration. We found that Enoxaparin bound to both protein variants with similar affinities, compared to the natural GAG ligand heparan sulfate (with Kd-values in the range of 600-680 nM). Using size-defined Enoxaparin fragments, we discovered the optimum binding for dp6 or dp8 for the full-length Spike protein, whereas the RBD did not exhibit a significant chain-length-dependent affinity for heparin oligosaccharides. The soluble ACE2 receptor was found to interact with unfractionated GAGs in the low µM Kd range, but with size-defined heparins with clearly sub-µM Kd-values. Interestingly, the structural heparin analogue, pentosan polysulfate (PPS), exhibited high binding affinities to both Spike variants as well as to the ACE2 receptor. In viral infection experiments, Enoxaparin and PPS both showed a strong inhibition of infection in a concentration range of 50-500 µg/mL. Both compounds were found to retain their inhibitory effects at 500 µg/mL in a natural biomatrix-like human sputum. Our data suggest the early topical treatment of SARS-CoV-2 infections with inhaled Enoxaparin; some clinical studies in this direction are already ongoing, and they further imply an oral or nasal prophylactic inactivation of the virus by Enoxaparin or PPS for the prevention of inter-personal viral transmission.