Mini-Factor H Modulates Complement-Dependent IL-6 and IL-10 Release in an Immune Cell Culture (PBMC) Model: Potential Benefits Against Cytokine Storm

Abstract

Cytokine storm (CS), an excessive release of proinflammatory cytokines upon overactivation of the innate immune system, came recently to the focus of interest because of its role in the life-threatening consequences of certain immune therapies and viral diseases, including CAR-T cell therapy and Covid-19. Because complement activation with subsequent anaphylatoxin release is in the core of innate immune stimulation, studying the relationship between complement activation and cytokine release in an in vitro CS model holds promise to better understand CS and identify new therapies against it. We used peripheral blood mononuclear cells (PBMCs) cultured in the presence of autologous serum to test the impact of complement activation and inhibition on cytokine release, testing the effects of liposomal amphotericin B (AmBisome), zymosan and bacterial lipopolysaccharide (LPS) as immune activators and heat inactivation of serum, EDTA and mini-factor H (mfH) as complement inhibitors. These activators induced significant rises of complement activation markers C3a, C4a, C5a, Ba, Bb, and sC5b-9 at 45 min of incubation, with or without ~5- to ~2,000-fold rises of IL-1α, IL-1β, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13 and TNFα at 6 and 18 h later. Inhibition of complement activation by the mentioned three methods had differential inhibition, or even stimulation of certain cytokines, among which effects a limited suppressive effect of mfH on IL-6 secretion and significant stimulation of IL-10 implies anti-CS and anti-inflammatory impacts. These findings suggest the utility of the model for in vitro studies on CS, and the potential clinical use of mfH against CS.

Complement Factor H Family Proteins Modulate Monocyte and Neutrophil Granulocyte Functions

“…These results showing that the FH family proteins influence the LPS-triggered TNFα and IL-10 responses of monocytes may suggest their potential involvement in the regulation of inflammatory processes during infection. Interestingly, a recent study also found that mini-FH modulates complement-dependent IL-6 and IL-10 secretion by peripheral mononuclear cells in the presence of autologous serum; IL-10 release was increased by mini-FH when the cells were stimulated with LPS ( 62 ). When the effect of the FH family proteins was analyzed in isolated form, FH and FHR-1 treatment induced elevated IL-1β and IL-8 secretion ( 16 , 26 , 44 ) ( Figures 6 and 7 , Supplementary Figure 2 ).…”

Zymosan-induced leukocyte and cytokine changes in pigs: a new model for streamlined drug testing against severe COVID-19

“…88 These redundant activation pathways explain the high inter-animal reproducibility of hemodynamic changes caused by zymosan. That zymosan exerts its vasoactivity and pro-inflammatory cytokine inducing effects via cells exposed to plasma is supported by the finding that the kinetics of liberation of TXB 2 and inflammatory cytokines in an in vitro peripheral blood mononuclear cell model of CSS 38 is very similar to those seen in pigs, namely immediate production of TXB 2 and slower release of cytokines on a time scale of hours. 38 Regarding the lymphopenia and its correlation with IL-6 gene expression (Fig.…”

“…That zymosan exerts its vasoactivity and pro-inflammatory cytokine inducing effects via cells exposed to plasma is supported by the finding that the kinetics of liberation of TXB 2 and inflammatory cytokines in an in vitro peripheral blood mononuclear cell model of CSS 38 is very similar to those seen in pigs, namely immediate production of TXB 2 and slower release of cytokines on a time scale of hours. 38 Regarding the lymphopenia and its correlation with IL-6 gene expression (Fig. S1), IL-6 is known to upregulate the pro-apoptotic Fas, resulting in the loss of mature lymphocytes.…”

“…The model utilizes zymosan, a strong activator of the innate immune system, as a highly reproducible positive control, since zymosan's robust pulmonary hypertensive and systemic hypotensive effects are observed essentially in all pigs. [32][33][34] These effects, taken together with the fact that zymosan is known to induce proinflammatory cytokines in murine models 36,37 and human peripheral blood mononuclear cells (PBMCs) 38 led to the hypothesis that zymosan could be used to induce in pigs the above triad of stigmatic endpoints of severe COVID-19.…”

Thrombotic storm in coronavirus disease 2019: from underlying mechanisms to its management

“…The complement system, the first line of immunological defence, has long been known to play a role in the production of cytokines by activated immune cells in the bloodstream [54]. Activation of the complement cascade by inflammation can also attract and activate leukocytes, resulting in a markedly increased local production of proinflammatory cytokines such as IL-1, IL-6, IL-8, and IFN [55].…”