Suramin inhibits tumor cell cytotoxicity mediated through natural killer cells, lymphokine-activated killer cells, monocytes, and tumor necrosis factor

Biological inactivation and impaired detection of IL-10 by suramin

Enzyme-linked immunosorbent assay (ELISA) measures the amount of cytokines secreted by cells but "equivalent" ELISAs from different manufacturers may show different results, dependent on the epitopes used to generate the antibodies employed in the ELISAs. This fact was dramatically illustrated in a series of experiments we conducted to analyze the effect of suramin on the lipopolysaccharide-induced interleukin-10 (LPS-induced IL-10) production in human CD14+ monocytes. Use of the human IL-10 DuoSet ELISA from R&D Systems showed no influence of suramin on IL-10 levels, whereas the human IL-10 ELISA from Biosource detected only low amounts of IL-10 in the presence of suramin. The results with the Biosource ELISA reflected not only interference of the recognition of IL-10 in the presence of suramin, but also a block in the biological activity of IL-10. Thus, in the presence of suramin the addition of recombinant biological IL-10 protein could not inhibit the LPS-induced tumor necrosis factor alpha (TNF-alpha) or interleukin-12p40 (IL-12p40) production. Furthermore, suramin very efficiently neutralizes endogenous IL-10, resulting in a pronounced increase in IL-12 and TNF-alpha synthesis. Impaired recognition of biologically inactive conformations of IL-10 was not unique to suramin, in that heat-treated or chemically reduced recombinant IL-10 was also no longer recognized by the Biosource ELISA. This suggests that at least one of the antibodies employed in the Biosource ELISA is conformation sensitive, while the antibodies employed in the R&D Systems ELISA are insensitive to a number of conformation changes. All in all, our results show that suramin neutralizes the biological activity of IL-10 produced by monocytes. Furthermore, the amount of IL-10 detected by the Biosource ELISA correlates with the biological activity of IL-10, whereas the amount detected by the R&D Systems ELISA includes active as well as several inactive forms of IL-10.

Suramin exerts in vivo cytokine modulatory properties on splenocytes from experimental allergic encephalomyelitis-induced SJL mice: implications for autoimmune disease therapy

The present study sought to examine the immunopharmacologic effects of suramin on splenocytes from experimental allergic encephalomyelitis (EAE)-induced mice, taken in line with a previous observed action of suramin in ameliorating EAE. Suramin, a polysulfonated napthylurea, decreased the proliferation of T cells, in the presence of various stimuli, such as guinea pig myelin basic protein (MBP), mouse spinal cord homogenate (MSCH), bovine proteolipid protein (PLP), P1 (synthetic peptide 139-151 of PLP), and Mycobacterium tuberculosis (MTB). Suramin inhibited T cell proliferation in a dose-dependent manner. However, cytokine assays revealed that suramin increased antigen-induced levels of IL-4, whilst IFN-gamma levels were decreased. Using various doses of suramin (25, 15, and 5 micrograms/g), its cytokine modulatory effect displayed a consistent dose-dependent activity in vivo. This cytokine modulation commenced on week 2 after immunization and persisted all throughout the drug administration period, up to the 4th week. These results indicate that the prospects of using suramin in the treatment of multiple sclerosis may be feasible.

In vitro immunopharmacologic effect of suramin on modifying Th-subset cytokine levels in splenocytes and T-cell clones: a therapeutic application for autoimmune disease

The in vitro immunopharmacologic effect of suramin, a polysulfonated napthylurea, was examined on splenocytes and T helper (Th) 1 and 2 clones. Cytokine capture assays revealed that suramin inhibited the production of IFN-gamma, whilst IL-4 is increased in splenocytes. To examine whether suramin preferentially acts on Th cells, clones SP39A1 and SP41D5 were used. The former is a Th1 clone, whereas the latter is Th2. Suramin also inhibited IFN-gamma production by SP39A1, whilst IL-4 production by SP41D5 was enhanced. The action of suramin was of a dose-dependent nature. With regards to T cell proliferation, suramin inhibited the proliferation of both SP39A1 and SP41D5. The ability of suramin to manipulate Th subset cytokine balance can render it a feasible therapeutic agent in autoimmune disorders such as multiple sclerosis.