Polycations and polyanions in SARS-CoV-2 infection

We hypothesize that polycations, such as nuclear histones, released by neutrophils COVID-19 aggravate COVID-19 by multiple mechanisms: (A) Neutralization of the electrostatic repulsion between the virus particles and the cell membrane, thereby enhancing receptor-mediated entry. (B) Binding to the virus particles, thereby inducing opsonin-mediated endocytosis. (C) Adding to the cytotoxicity, in conjunction with oxidants, cytokines and other pro-inflammatory substances secreted by cells of the innate immunity system. These effects may be alleviated by the administration of negatively charged polyanions such as heparins and heparinoids.

Inhalable DNase I microparticles engineered with biologically active excipients

Highly viscous mucus poses a big challenge for the delivery of particulates carrying therapeutics to patients with cystic fibrosis. In this study, surface modifying DNase I loaded particles using different excipients to achieve better lung deposition, higher enzyme stability or better biological activity had been exploited. For the purpose, controlled release microparticles (MP) were prepared by co-spray drying DNase I with the polymer poly-lactic-co-glycolic acid (PLGA) and the biocompatible lipid surfactant 1,2-dipalmitoyl-Sn-phosphatidyl choline (DPPC) using various hydrophilic excipients. The effect of the included modifiers on the particle morphology, size, zeta potential as well as enzyme encapsulation efficiency, biological activity and release had been evaluated. Powder aerosolisation performance and particle phagocytosis by murine macrophages were also investigated. The results showed that more than 80% of enzyme activity was recovered after MP preparation and that selected surface modifiers greatly increased the enzyme encapsulation efficiency. The particle morphology was greatly modified altering in turn the powders inhalation indices where dextran, ovalbumin and chitosan hydrochloride increased considerably the respirable fraction compared to the normal hydrophilic carriers lactose and PVP. Despite of the improved aerosolisation caused by chitosan hydrochloride, yet retardation of chitosan coated particles in artificial mucus samples discouraged its application. On the other hand, dextran and polyanions enhanced DNase I effect in reducing cystic fibrosis mucus viscosity. DPPC proved good ability to reduce particles phagocytic uptake even in the presence of the selected adjuvants. The prepared MP systems were biocompatible with lung epithelial cells. To conclude, controlled release DNase I loaded PLGA-MP with high inhalation indices and enhanced mucolytic activity on CF sputum could be obtained by surface modifying the particles with PGA or dextran.

Effect of poly(phosphate) anions on glyceraldehyde-3-phosphate dehydrogenase structure and thermal aggregation: comparison with influence of poly(sulfoanions)

BACKGROUND

It is well documented that poly(sulfate) and poly(sulfonate) anions suppress protein thermal aggregation much more efficiently than poly(carboxylic) anions, but as a rule, they denature protein molecules. In this work, a polymer of different nature, i.e. poly(phosphate) anion (PP) was used to elucidate the influence of phosphate groups on stability and thermal aggregation of the model enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

METHODS

Isothermal titration calorimetry and differential scanning calorimetry were used for studying the protein-polyanion interactions and the influence of bound polyanions on the protein structure. The enzymatic activity of GAPDH and size of the complexes were measured. The aggregation level was determined from the turbidity.

RESULTS

Highly polymerized PP chains were able to suppress the aggregation completely, but at significantly higher concentrations as compared with poly(styrenesulfonate) (PSS) or dextran sulfate chains of the same degree of polymerization. The effect of PP on the enzyme structure and activity was much gentler as opposed to the binding of dextran sulfate or, especially, PSS that denatured GAPDH molecules with the highest efficacy caused by short PSS chains. These findings agreed well with the enhanced affinity of polysulfoanions to GAPDH.

CONCLUSIONS

The revealed trends might help to illuminate the mechanism of control of proteins functionalities by insertion of charged groups of different nature through posttranslational modifications.

GENERAL SIGNIFICANCE

Practical implementation of the results could be the use of PP chains as promising tools to suppress the proteins aggregation without noticeable loss in the enzymatic activity.