ACYCLIC ANALOG OF LIPID-A STIMULATES TNF-ALPHA AND ARACHIDONATE RELEASE VIA A UNIQUE LPS-SIGNALING PATHWAY

LPS has been implicated in the pathogenesis of Gram-negative bacterial sepsis. Despite intensive efforts to define the LPS-signal transducti on pathway, CD14 is the sole molecule clearly demonstrated to possess signaling capabilities. However, it remains unclear whether CD14 is th e only LPS-signaling molecule expressed in phagocytes and how CD14-med iated signaling occurs. Compound SDZ 280.961 is a synthetic triacylate d amino acid that structurally resembles the reducing sugar moiety of lipid A. SDZ 280.961 effectively stimulated TNF-alpha release from hum an PBMC. Co-incubation of PBMC with the specific LPS inhibitor Rhodoba cter sphaeroides lipid A inhibited SDZ 280.961-mediated stimulation of TNF-alpha release, indicating that this analogue signals mononuclear cells via a LPS-activated signaling pathway. Induction of TNF-alpha re lease from mononuclear cells by SDZ 280.961 was strongly dependent on the presence of serum and was enabled by the presence of purified LPS- binding protein, characteristics of CD14-mediated signaling. In contra st, SDZ 280.961-mediated signaling was not inhibited by blocking anti- CD14 mAbs. A Chinese hamster ovary fibroblast line transfected with hu man CD14, which responds to LPS in a manner qualitatively similar to t hat of macrophage cell lines, failed to respond to SDZ 280.961. Taken together, these data suggest that the lipid A analogue SDZ 280.961 act ivates monocytes via a unique LPS-signal transduction pathway that app ears to be independent of CD14.