Several newly synthesized aza-alkyl lysophospholipids (AALP) have been shown to exert a potent antitumor cytotoxicity in vitro. Their potential use in vivo prompted us to study their effects on the immune system. The present study investigated the effect of AALP on the secretion of cytokines (TNF-alpha, IL-1beta, 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 degrees C in the presence of AALP and/or LPS (1 microg/ml) or IFN-gamma (1000 U/ml) and the supernatants tested for the presence of cytokines by ELISA. All five AALP compounds stimulated TNF-alpha and IL-1beta 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-alpha was significantly potentiated by BN52207 when the PBM were activated by either IFN-gamma or LPS. There was also an upregulation of TNF-alpha mRNA transcription as detected by RT-PCR. The induction of TNF-alpha secretion by BN52207 was dependent on de novo protein synthesis as the specific TNF-alpha inhibitor, pentoxifylline, and the protein synthesis inhibitors, cyclohexamide and emetine, abolished TNF-alpha secretion. BN52207 also stimulated IL-1beta secretion by resting and activated PBM in a concentration-dependent manner. Unlike TNF-alpha and IL-1beta, however, BN52207 had no effect on IL-6 secretion. Noteworthy, unlike the induction of TNF-alpha and IL-1beta 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-alpha and IL-1beta secretion and abolishing IL-10 secretion. The selective regulation of cytokine synthesis and secretion by AALP suggest that AALP may have potential therapeutic uses in vivo in clinical disease manifestations that are regulated by cytokines.
Copyright 1999 Academic Press.