Inhibition of tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) secretion but not IL-6 from activated human peripheral blood monocytes by a new synthetic demethylpodophyllotoxin derivative

Abstract

A newly synthesized demethylpodophyllotoxin derivative, 4-O-butanoyl-4′-demethylpodophyllotoxin (BDPT) or BN58705, has recently been shown to exert a potent cytotoxic activityin vitro against a variety of drug-resistant human tumor cell lines. The effect of this agent on effector cells of the immune system, however, has not been examined. The present study investigated the effect of BDPT on the response of activated human peripheral blood derived monocytes (PBM) to secrete cytokines. Activation of PBM overnight with LPS, IFN-γ, or PMA resulted in secretion into the supernatant of TNF-α, IL-1β, IL-6, and IL-8 as assessed by ELISA. The addition of BDPT to the stimulated cultures resulted in significant inhibition of TNF-α and IL-1β secretion, whereas the secretion of IL-6 and IL-8 was not affected. The selective inhibition of TNF-α and IL-1β secretion by BDPT-treated PBM was observed with all three stimuli tested. The inhibitory effect mediated by BDPT was concentration dependent and was optimal at 6–20 μM. Time kinetic analysis indicated that the inhibition of secretion was rapid and detected as soon as 2 hr following stimulation of the PBM and lasted for as long as 24 hr. A comparison was made between BDPT and pentoxyfilline, a xanthine-derived phosphodisterase inhibitor that was reported to inhibit TNF-α and IL-1β secretion by PBM. Both BDPT and PTX showed similar time kinetics and patterns of inhibition. However, the concentration used by BDPT to achieve optimal inhibition of secretion was 10- to 20-fold less than that needed by PTX. The selective inhibition of TNF-α secretion by BDPT and PTX was corroborated by inhibition of TNF-α mRNA but not IL-6 mRNA as assessed by RT-PCR analysis. These studies demonstrate that the antitumor cytotoxic compound BDPT is also an immunomodulatory agent that can inhibit selectively TNF-α and IL-1β secretion by PBM. Further, the low toxicity and low concentrations of BDPT needed for optimal inhibition suggest that BDPT may have potential in its therapeutic application in diseases that are mediated by TNF-α and IL-1 like septic shock, inflammatory responses, and infections.