Preferential Induction of TNF-α and IL-1β and Inhibition of IL-10 Secretion by Human Peripheral Blood Monocytes by Synthetic Aza–Alkyl Lysophospholipids

Abstract

Several newly synthesized aza–alkyl lysophospholipids (AALP) have been shown to exert a potent antitumor cytotoxicityin vitro.Their potential usein vivoprompted us to study their effects on the immune system. The present study investigated the effect of AALP on the secretion of cytokines (TNF-α, IL-1β, IL-6, and IL-10) by normal and activated human peripheral blood-derived monocytes (PBM). Five AALP compounds (BN52205, BN52207, BN52211, BN52218, and BN52227) were tested. Human peripheral blood monocytes were cultured for 18 h at 37°C in the presence of AALP and/or LPS (1 μg/ml) or IFN-γ (1000 U/ml) and the supernatants tested for the presence of cytokines by ELISA. All five AALP compounds stimulated TNF-α and IL-1β secretion but not IL-6 secretion from nonstimulated PBM. There were no significant differences among the five AALP compounds tested and BN52207 was selected for further studies. Secretion of TNF-α was significantly potentiated by BN52207 when the PBM were activated by either IFN-γ or LPS. There was also an upregulation of TNF-α mRNA transcription as detected by RT-PCR. The induction of TNF-α secretion by BN52207 was dependent onde novoprotein synthesis as the specific TNF-α inhibitor, pentoxifylline, and the protein synthesis inhibitors, cyclohexamide and emetine, abolished TNF-α secretion. BN52207 also stimulated IL-1β secretion by resting and activated PBM in a concentration-dependent manner. Unlike TNF-α and IL-1β, however, BN52207 had no effect on IL-6 secretion. Noteworthy, unlike the induction of TNF-α and IL-1β secretion, BN52207 inhibited completely the secretion of IL-10 by resting and LPS-activated PBM. Further, BN52207 enhanced the macrophage killing activity of tumor target cells. Overall, this study demonstrates that AALP are endowed with a selective regulation of cytokine synthesis and secretion by resting and activated PBM. This regulation is manifested by upregulating TNF-α and IL-1β secretion and abolishing IL-10 secretion. The selective regulation of cytokine synthesis and secretion by AALP suggest that AALP may have potential therapeutic usesin vivoin clinical disease manifestations that are regulated by cytokines.