Leishmania pifanoiProteoglycolipid Complex P8 Induces Macrophage Cytokine Production through Toll-Like Receptor 4

Abstract

The P8 proteoglycolipid complex (P8 PGLC) is a glyconjugate expressed by Leishmania mexicana complex parasites. We previously have shown that vaccination with P8 PGLC provides protection against cutaneous leishmaniasis in susceptible BALB/c mice. However, the biological importance of this complex remains unknown. Here we show that P8 PGLC localizes to the surface of Leishmania pifanoi amastigotes and that upon exposure to macrophages, P8 PGLC binds and induces inflammatory cytokine and chemokine mRNAs such as tumor necrosis factor alpha and RANTES early after stimulation. Our studies indicate that cytokine and chemokine induction is dependent upon Toll-like receptor 4 (TLR4). Interestingly, key inflammatory cytokines and chemokines (such as interleukin-6 [IL-6], macrophage inflammatory protein 1␤, and beta interferon [IFN-␤]) that can be induced through TLR4 activation were not induced or only slightly upregulated by P8 PGLC. Activation by P8 PGLC does not occur in the presence of TLR4 alone and requires both CD14 and myeloid differentiation protein 2 for signaling; this requirement may be responsible for the limited TLR4 response. This is the first characterization of a TLR4 ligand for Leishmania. In vitro experiments indicate that L. pifanoi amastigotes induce lower levels of cytokines in macrophages in the absence of TLR4; however, notably higher IL-10/IFN-␥ ratios were found for TLR4-deficient mice than for BALB/c mice. Further, increased levels of parasites persist in BALB/c mice deficient in TLR4. Taken together, these results suggest that TLR4 recognition of Leishmania pifanoi amastigotes is important for the control of infection and that this is mediated, in part, through the P8 PGLC.

Toll-Like Receptors Participate in Macrophage Activation and Intracellular Control of Leishmania (Viannia) panamensis

“…Furthermore, L. pifanoi P8 PGLC has been shown to induce TLR4-dependent macrophage cytokine and chemokine production (62). Our data provide evidence that TLR4 is also important during the early L. panamensis-macrophage interaction, since reduced TNF-␣ production and increased parasite survival occurred in TLR4 Ϫ/Ϫ infected mouse macrophages.…”

“…Bone marrow was harvested from mice as previously described (62), in accordance with the guidelines set forth by the University of Massachusetts Medical School and approved by its Institutional Animal Care and Use Committee. BMM precursors from WT (C57BL/6), MD-2…”

Reactive Oxygen Species-Triggered Trophoblast Apoptosis Is Initiated by Endoplasmic Reticulum Stress via Activation of Caspase-12, CHOP, and the JNK Pathway in Toxoplasma gondii Infection in Mice

“…Structures analogous to LPS have been found in T. gondii, such as glycosylphosphatidylinositols (GPI) (9,36). Interestingly, all of these structures can trigger the activation of inflammatory cytokine expression by Toll-like receptor (TLR)-dependent pathways (25), e.g., TLR4 (10,47) and TLR2 (6,38). Some studies have revealed that LPS could induce the production of ROS in some organs, such as lung and liver (8,51), in which ROS are important to the pathogenesis of organ damage (52).…”

A Defective TLR4 Signaling for IFN-β Expression Is Responsible for the Innately Lower Ability of BALB/c Macrophages to Produce NO in Response to LPS as Compared to C57BL/6

“…Also importantly, our findings indicate that macrophages may indeed be the major source of IFN-β in L. major infection in vivo , as previously suggested [53]. The difference between C57BL/6 and BALB/c in the TLR4-IFN-β-STAT-1-iNOS pathway in the absence of adaptive responses is a novel finding that substantiates previous conclusions that early mechanisms involving TLR4, IFN-β and NO [52]–[55], [58] are fundamental to host resistance.…”