CT-1501R selectively inhibits induced inflammatory monokines in human whole blood ex vivo

The effect of (R)-1-(5-hydroxyhexyl)-3,7-dimethylxanthine (CT-1501R; the nonproprietary name for CT-1501R approved by the United States Name Council is lisofylline), an inhibitor of second messenger signaling through phosphatidic acid, on release of endogenous mediators important in the systemic inflammatory response syndrome (SIRS) was studied using the human whole blood ex vivo assay system. Human blood was stimulated with various endotoxin preparations, zymosan, or protein A, and the levels of secreted monokines were measured by enzyme-linked immunosorbent assay. CT-1501R inhibited tumor necrosis factor alpha (TNF-alpha), interleukin 1 beta (IL-1 beta), and IL-6 release in a dose-dependent manner and was active with all stimuli tested including Salmonella and Escherichia coli-derived endotoxin, endotoxin from both rough and smooth E. coli strains, as well as zymosan and protein A. CT-1501R inhibited monokine release by approximately 50% at 200 microM and 30% at 50 microM and was independent of the relative potency of stimulus. CT-1501R also inhibited IL-1 alpha or IL-1 beta induction of either TNF-alpha or IL-1 beta and inhibited the synergistic effects of stimulation with both human IL-1 beta and murine TNF-alpha on release of human TNF-alpha. Inhibition of monokine release following stimulation with monokine(s) was, in general, greater than that achieved with lipopolysaccharide (LPS) stimulation. Northern blot analysis showed decreased mRNA accumulation of TNF-alpha and IL-1 beta in CT-1501R-treated samples following LPS stimulation suggesting that CT-1501R acts at least in part, at the pretranslational level. In contrast, CT-1501R does not inhibit LPS-stimulated IL-8 or IL-1 receptor antagonist (IL-1ra) release in human whole blood or IL-1 alpha-induced release of PGE2 in human foreskin fibroblast cells. These data suggest that CT-1501R may be of use for clinical intervention in SIRS.