Mechanisms of cytokine storm development in COVID-19 and new potential targets of pharmacotherapy

The development of a “cytokine storm”, characteristic of severe COVID-19 forms, can be defined as a state of uncontrolled release of a large number of inflammatory mediators.

The attachment of SARS-CoV-2 S-glycoprotein to angiotensin-converting enzyme 2 is considered a process that triggers complex molecular interactions that lead to hyperinflammation. In its turn, it is realized through several systems: renin-angiotensin-aldosterone, kallikrein-kinin and a complement system. Knowledge of these mechanisms suggests potential therapeutic interventions that can be targeted by existing therapeutic agents to counter the cytokine storm and treat the acute respiratory distress syndrome associated with COVID-19.

The aim of the review article is to summarize the currently known data on the molecular processes underlying the uncontrolled “cytokine storm” in the patients with severe COVID-19, and possible options for their pharmacological correction.

Materials and methods. The data base was represented by such systems as Medline, Cochrane Central Register of Controlled Trials, Scopus, Web of Science Core Collection, Cochrane Library, ClinicalTrials.gov, Elibrary, Google-Academy. A search was carried out for the following keywords and combinations: COVID-19, renin-angiotensin-aldosterone system, bradykinin, complement system, hyaluronic acid, pharmacotherapy.

Results. The development of a “cytokine storm” in COVID-19 is mediated by pathogenetic changes in the body in response to the penetration of SARS-CoV-2 into the cell. In the RAAS, suppression of ACE2 leads to a decrease in its ability to degrade ATII, which, on the one hand, leads to a decrease in the amount of AT1-7, and, on the other hand, to the effect of ATII on AT1R with the subsequent development of vasoconstriction and lung damage. The disturbances in the kallikrein-kinin system are associated, on the one hand, with the increased expression of kallikrein and an increase in the formation of bradykinin and its metabolite des-Arg 9-bradykinin. On the other hand, the disturbances are associated with the suppression of the expression of the C1-esterase inhibitor which prevents the formation of kallikrein, and impaired inactivation of des-Arg 9-bradykinin under the action of ACE 2. The nucleocapsid protein SARS-CoV-2 triggers the activation of the complement system through the lectin pathway. It leads to the production of anaphylatoxins C3a and C5a, which stimulate the synthesis of pro-inflammatory cytokines. Proinflammatory cytokines are potent inducers of the HAS 2 gene in the endothelium, which encodes the membrane enzymes of hyaluronate synthase. The sweating of the fluid into the alveoli caused by the “bradykinin storm” in combination with the overproduction of hyaluronic acid, which accumulates water 1000 times its own mass, can lead to the formation of a dense jelly-like substance that prevents gas exchange.

Conclusion. Promising areas of pharmacotherapy for “cytokine storm” are associated with its impact on the dysfunction of the listed above systems. However, the efficacy and safety of most drugs for the treatment of COVID-19, is to be studied through carefully designed clinical trials.