INDUCTION OF TUMOR-NECROSIS-FACTOR-ALPHA AND INTERLEUKIN-1-BETA IN SUBCUTANEOUSLY IMPLANTED CHAMBER BY LIPOPOLYSACCHARIDE

Lipopolysaccharide (LPS) is the major component of the outermost membr ane of Gram-negative bacteria and is considered to be one of the major virulence factors of these bacteria. While the effect of systemic inj ection of LPS is well characterized, the characterization of cytokine secretion in response to local injection of LPS is lacking. The presen t study was designed to determine the local production of tumor necros is factor alpha (TNF alpha) and interleukin-1 beta (IL-1 beta) over a 4 day period following injection of LPS into subcutaneous implanted ch ambers in mice. Mice were challenged by a single or repeated injection of Salmonella typhosa LPS into the chambers. Chamber fluids were aspi rated at different time intervals and were used for assessment of leuk ocyte and cytokine levels. A single injection of LPS was found to indu ce cell influx into the chamber which peaked after 4 h. TNF alpha and IL-1 beta levels increased rapidly, reaching their maximum levels with in 4 h. After 24 h, TNF alpha levels declined markedly and were undete ctable at 48 and 96 h. TNF alpha mRNA levels in the sedimented cells f ollowed a similar pattern. In contrast, IL-1 beta showed a more gradua l decrease with levels significantly different from baseline still bei ng present 96 h post-LPS challenge. Four consecutive daily injections of LPS into the chambers resulted in undetectable levels of TNF alpha in the chamber fluid, while significant levels of IL-1 beta were detec ted. These levels were significantly higher than the levels of IL-1 be ta in the chamber fluid 96 h after a single injection and approximatel y 60% of the levels measured 24 h after a single intra-chamber injecti on of LPS. The results emphasize the difference between single and rep eated exposure to LPS in vivo, and suggest a role for TNF alpha in the initial phase of the local inflammatory response and for IL-1 beta in the later phase.