Regulation of the Leishmania-induced innate inflammatory response by the protein tyrosine phosphatase SHP-1

Modulation of the phagocyte protein tyrosine phosphatase (PTP) SHP-1 by the parasite Leishmania favors its survival and propagation within its mammalian host. In vivo, the absence of SHP-1 leads to virtually absent footpad swelling, accompanied by enhanced inducible nitric oxide synthase expression. In this study, using an air pouch model, we show that viable motheaten SHP-1-deficient mice harbored a stronger inflammatory response against Leishmania infection than wild-type mice. This response was portrayed by higher pro-inflammatory cytokine (TNF-alpha,, IL-1 beta and IL-6) expression and secretion and by greater chemokine and chemokine receptor expression. These inflammatory molecules were probably responsible for the stronger cellular recruitment, mainly of neutrophils, seen at the site of infection in viable motheaten mice within 6 h post inoculation. We also provide strong evidence that protein tyrosine phosphatases in general, and SHP-1 in particular, are important regulators of chemokine gene expression. Overall, this study suggests that the ability of Leishmania to induce SHP-1 activity in its host allows the taming of an otherwise strong innate inflammatory response that would be detrimental for its survival and progression.