Skin Fibroblasts derived from Visceral and Post Kala-Azar Dermal Leishmaniasis patients differentially modulate cytokine and chemokine responses in THP-1 cells.

Leishmania donovani infection causes distinct clinical manifestations, including visceral leishmaniasis (VL) and its dermatological sequel, post-kala-azar dermal leishmaniasis (PKDL), but the mechanisms underlying these divergent phenotypes remain poorly understood.This study investigated the role of skin fibroblasts in regulating THP-1 monocyte responses during VL and PKDL. A fibroblast-monocyte co-culture system was established with patient-derived fibroblasts from healthy controls, VL patients and PKDL patients, in combination with THP-1 monocytes in a Transwell system. The cytokine and chemokine were quantified by real-time PCR and ELISA, and nuclear translocation of NF-κB p50/p65 was determined by western blotting and confocal microscopy. VL fibroblasts potently activated THP-1 cells, resulting in high levels of pro- and anti-inflammatory cytokines (IL-1β, IL-6, TNF-α, IFN-γ, IL-10 and TGF-β) and chemokines (CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL8, CXCL10, CXCL11 and CXCL12). Conversely, PKDL fibroblasts produced a more limited cytokine profile consistent with a regulatory immune environment. Presence of L. donovanisignificantly attenuated the expression of cytokines and chemokines induced by VL fibroblasts in THP-1 cells, but increased the levels of IL-10 and IL-12 in THP-1 cells co-cultured with PKDL fibroblasts.VL fibroblast conditioned medium induced nuclear translocation of NF-κB p50/p65 in THP-1 cells and this effect was inhibited by IL-6 neutralization. Conversely, exogenous IL-6 addition restored NF-κB activation in THP-1 cells treated with PKDL fibroblast-conditioned medium. These findings highlight that IL-6 produced by skin fibroblasts differentially modulates NF-κB-dependent activation of THP-1 cells in VL as compared to PKDL, underlining the importance of stromal immune interactions in disease-specific immune responses.