Membrane damage and interleukin-1 production in murine macrophages exposed to listeriolysin O

To obtain some insight into the interaction between listeriolysin O (LLO) and the macrophage membrane, we examined the effect of purified Listeria monocytogenes hemolysin on the viability and functions of mouse peritoneal exudate macrophages. The study showed that purified LLO impaired a variety of functions of the macrophages. First, it suppressed the luminol-dependent chemiluminescence response of macrophages. Second, it suppressed the phagocytic ingestion of opsonized sheep erythrocytes and latex beads. Third, exposure of macrophages to LLO resulted in an increase in dead cells, as determined by the trypan blue dye exclusion method. An interesting observation of this study is that the LLO-induced production of interleukin-1 from macrophages could not be blocked by preincubation with cholesterol, while the membrane-damaging ability could be blocked by cholesterol. The dissociation of the blocking effects of cholesterol suggests that the interleukin-1-inducing ability of LLO may be distinct from its membrane-damaging ability.