Lipophosphoglycan From Dermotropic New World Leishmania Upregulates Interleukin-32 and Proinflammatory Cytokines Through TLR4 and NOD2 Receptors

Abstract

Interleukin-32 (IL-32) is produced during Leishmania infection, but the components of the parasite that induce its production are unknown. An important multivirulence factor of Leishmania spp. protozoa is the lipophosphoglycan (LPG), which plays a crucial role in the host-parasite interaction. Here, the ability of LPGs from two dermotropic Leishmania species to induce IL-32 production was evaluated in human peripheral blood mononuclear cells (PBMCs). Additionally, the potential receptors involved in this activation were assessed. PBMCs from healthy individuals were stimulated with LPGs from L. amazonensis (La) or L. braziliensis (Lb), live promastigotes of La or Lb and E. coli lipopolysaccharide (LPS, TLR4 agonist) as control. Blockers of TLR4 (Bartonella quintana LPS or monoclonal antibody) and Ponatinib (RIPK2 inhibitor, NOD2 pathway) were used to evaluate the receptors. ELISA was performed for IL-32 expression and cytokine (IL-1β and IL-6) production in cell lysates and in supernatants, respectively. Expression of TLR4 (2 h, 24 h) was assessed by flow cytometry. IL-32γ mRNA transcript was analyzed by qPCR. It was observed that LPG from Leishmania, like whole parasites, induced the production of IL-32, IL-1β and IL-6. Both LPGs induced the expression of IL32γ mRNA. The production of IL-32 was earlier detected (6 h) and positively associated with the production of IL-1β and IL-6. The induction of cytokines (IL-32, IL-1β and IL-6) was dependent on TLR4 and NOD2. The TLR4 was internalized after interaction with LPG. Therefore, our data suggest that LPGs from La and Lb are components of Leishmania able to upregulate IL-32 and other pro-inflammatory cytokines in a TLR4- and NOD2-dependent manner. In addition, LPG-induced IL-32 seems to be necessary for IL-1β and IL-6 production. To identify the parasite factors and host receptors involved in IL-32 induction is crucial to reveal potential targets for novel strategies to control leishmaniasis.

IL-32 is induced by activation of toll-like receptors in multiple myeloma cells

“…IL-32 plays an important role in the host defense against a range of infectious agents ( 4 ) and IL-32 expression can be induced by toll-like receptor (TLR) activation in monocytes/macrophages, dendritic cells, and epithelial cells ( 9 – 13 ). TLRs recognize pathogen associated molecular patterns (PAMPs) and may also recognize and respond to danger associated molecular patterns (DAMPs) released during cell damage and cell death ( 14 , 15 ).…”

Leishmania amazonensis from distinct clinical forms/hosts has polymorphisms in Lipophosphoglycans, displays variations in immunomodulatory properties and, susceptibility to antileishmanial drugs

“…Regarding dermotropic species, functional studies of L. amazonensis LPGs have shown their role in macrophages and neutrophils. Those include induction of neutrophil extracellular traps (Guimarães‐Costa et al, 2009 ), double‐stranded RNA‐dependent protein kinase (PKR) (de Carvalho Vivarini et al, 2011 ), LTB 4 (Tavares et al, 2014 ), NO/cytokines via TLR4 (Nogueira et al, 2016 ), caspase‐11 via NLRP3 (de Carvalho et al, 2019 ), and IL‐32 via TLR2/NOD2 (Silveira et al, 2022 ). However, an unknown aspect of L. amazonensis glycobiology is to what extent LPG polymorphisms from different strains may functionally affect macrophage responses.…”