Roles of CD14 in LPS-induced liver injury and lethality in mice pretreated with Propionibacterium acnes

Abstract

The mechanism of the liver damage and lethaliy in Propionibacterium acnes ( P. acnes)-LPS system remains obscure. To examine the role of CD14 in the system, M14M mice, in which CD14 was expressed heterotopically under the control of the metallothionein promoter were used. The production of soluble CD14 (sCD14) was increased by both P. acnes – priming and LPS challenge (1 μg per mouse) in both nontransgenic and M14M mice, although the plasma level was much higher in M14M nontransgenic than mice. The size of granulomas induced by an intraperitoneal administration of P. acnes in M14M mice 7 days after priming was smaller than that in nontransgenic mice. An LPS challenge induced apoptotic and necrotic changes in hepatocytes in nontransgenic mice but not in M14M mice. The challenge dose resulted in almost 90% lethality in nontransgenic mice but not in M14M mice 24 h after challenge. TNF-α, IFN-γ, IL-12, IL-18 and inducible nitric oxide synthase (iNOS) mRNA expressions produced by LPS challenge in M14M mice were low compared with those in nontransgenic mice. IL-18 mRNA expression was upregulated in P. acnes-primed nontransgenic mice but not in M14M mice. These results suggest that the high sCD14 concentration may account for less marked liver damage in M14M mice. Increase in the challenge dose of LPS (2 μg per mouse) resulted in increased lethality of M14M mice without liver damage. The levels of endothelial cell leukocyte adhesion molecule (ELAM)-1 mRNA expression in several organs in M14M mice 1–3 h after LPS challenge were, however, lower than those in nontransgenic mice. The high sCD14 concentration may stimulate endothelial cell activation, which may account for lethality without liver damage in M14M mice. Thus, CD14 is involved in both the priming and induction phases as well as lethality in P. acnes-LPS system.