Suramin inhibits antibody binding to cell surface antigens and disrupts complement-mediated mesangial cell lysis

Abstract

Suramin inhibits immune responses and protects cells against inflammatory cell injury. However, little is known about its mechanisms. Using an in vitro model of glomerular mesangial cell (MC) lysis induced by antibodies plus complement, we investigated the potential protective effects and mechanisms of suramin on immunologic cell injury. Exposure of rat MCs to anti-Thy-1 antibody plus complement or anti-MC rabbit serum caused complement-dependent cell lysis, which was blocked by suramin and its structural analogue NF023 and NF049, but not by PPADS, an antagonist of purinergic receptors. Addition of exogenous ATP also failed to affect MC lysis. Further analysis revealed that suramin interfered with antibody binding to cell membrane antigens and suppressed antibody-induced phosphorylation of several proteins, including p38. Inhibition of p38 with chemical inhibitor significantly attenuated cell injury. Collectively, our results indicate that suramin protects cells against antibody-initiated and complement-dependent cell injury through inhibition of antibody binding to cell surface antigens and suppression of p38 activation. Our study thus provides novel mechanistic insights into the actions of suramin and suggests that suramin might be used to treat certain immune diseases.

Glutathione inhibits antibody and complement-mediated immunologic cell injury via multiple mechanisms

“…We have recently reported that incubation of MCs with a rabbit serum from the Japanese White Strain Rabbit caused a complement-dependent MC lysis due to the presence of several antibodies against MCs [18]. In this study, we have used the same cell model.…”

“…Rat glomerular mesangial cells (MCs) were obtained from the outgrowth of the isolated glomeruli, as described previously [18], [19]. Cells were cultured in DMEM (Gibco-BRL, Gaithersburg, MD, USA) supplemented with 5% FBS for passage and expansion.…”

“…Cell viability was determined by the Calcein-AM/PI live/dead staining as described previously [18]. Living cells exhibit positive staining for calcein-AM activity (green fluorescence), whereas dead cells stain positive for PI (red fluorescence).…”

“…Immunoglobulins (Igs) bound to the cell membrane were precipitated using a mixture of protein A and G beads as reported previously [18]. MCs were reacted with rabbit serum or antibodies for the indicated period.…”

“…The supernatant was recovered and determined for protein concentration using the Micro BCA Protein Assay Kit (Thermo Fisher Scientific, Waltham, MA). Western blot was performed by the enhanced chemiluminescence system [18], [19], [20]. Briefly, extracted cellular proteins were separated by polyvinylidene difluoride membranes.…”