Pretreatment of macrophages with low-dose endotoxin (LPSp) profoundly alters cytokine release in response to subsequent LPSa activation. These qualitative and quantitative alterations in cytokine release have been termed macrophage reprogramming. Macrophage activation by LPS is thought to occur via a mechanism involving an early protein tyrosine kinase (PTK) phosphorylation step. PTK inhibition with genistein or herbimycin A blocks LPSa-stimulated secretion of tumor necrosis factor (TNF) and interleukin-1 (IL-1). In this study we investigated whether a PTK pathway participates in LPSp pretreatment reprogramming. We show that LPSp pretreatment inhibited TNF and augmented IL-1 release in response to subsequent LPSa stimulation. Blockade of PTK activation pathways during the interval when macrophages were exposed to LPSp prevented mitogen-activated protein kinase phosphorylation, as well as LPSp-stimulated release of TNF and IL-1, but did not block LPSp reprogramming effects. We conclude that LPSp pretreatment reprogramming of macrophage cytokine production does not require PTK activation.
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