Arabinosylated Lipoarabinomannan Skews Th2 Phenotype towards Th1 during Leishmania Infection by Chromatin Modification: Involvement of MAPK Signaling Parna Bhattacharya1, Gaurav Gupta1, Saikat Majumder1, Anupam Adhikari1, Sayantan Banerjee1, Kuntal Halder1, Suchandra Bhattacharya Majumdar1, Moumita Ghosh2, Shubho Chaudhuri1, Syamal Roy2, Subrata Majumdar1* 1 Division of Molecular Medicine, Bose Institute, Kolkata, India, 2 Division of Infectious Diseases and Immunology, Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, Kolkata, India Abstract The parasitic protozoan Leishmania donovani is the causative organism for visceral leishmaniasis (VL) which persists in the host macrophages by deactivating its signaling machinery resulting in a critical shift from proinflammatory (Th1) to an anti- inflammatory (Th2) response. The severity of this disease is mainly determined by the production of IL-12 and IL-10 which could be reversed by use of effective immunoprophylactics. In this study we have evaluated the potential of Arabinosylated Lipoarabinomannan (Ara-LAM), a cell wall glycolipid isolated from non pathogenic Mycobacterium smegmatis, in regulating the host effector response via effective regulation of mitogen-activated protein kinases (MAPK) signaling cascades in Leishmania donovani infected macrophages isolated from BALB/C mice. Ara-LAM, a Toll-like receptor 2 (TLR2) specific ligand, was found to activate p38 MAPK signaling along with subsequent abrogation of extracellular signal–regulated kinase (ERKs) signaling. The use of pharmacological inhibitors of p38MAPK and ERK signaling showed the importance of these signaling pathways in the regulation of IL-10 and IL-12 in Ara-LAM pretreated parasitized macrophages. Molecular characterization of this regulation of IL-10 and IL-12 was revealed by chromatin immunoprecipitation assay (CHIP) which showed that in Ara- LAM pretreated parasitized murine macrophages there was a significant induction of IL-12 by selective phosphorylation and acetylation of histone H3 residues at its promoter region. While, IL-10 production was attenuated by Ara-LAM pretreatment via abrogation of histone H3 phosphorylation and acetylation at its promoter region. This Ara-LAM mediated antagonistic regulations in the induction of IL-10 and IL-12 genes were further correlated to changes in the transcriptional regulators Signal transducer and activator of transcription 3 (STAT3) and Suppressor of cytokine signaling 3 (SOCS3). These results demonstrate the crucial role played by Ara-LAM in regulating the MAPK signaling pathway along with subsequent changes in host effector response during VL which might provide crucial clues in understanding the Ara-LAM mediated protection during Leishmania induced pathogenesis. Citation: Bhattacharya P, Gupta G, Majumder S, Adhikari A, Banerjee S, et al. (2011) Arabinosylated Lipoarabinomannan Skews Th2 Phenotype towards Th1 during Leishmania Infection by Chromatin Modification: Involvement of MAPK Signaling. PLoS ONE 6(9): e24141. doi:10.1371/journal.pone.0024141 Editor: Je´roˆ me Nigou, French National Centre for Scientific Research - Universite´ de Toulouse, France Received April 1, 2011; Accepted August 1, 2011; Published September 14, 2011 Copyright: 2011 Bhattacharya et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was funded by Council of Scientifc Industrial Research, India (Grant No 37/1280/07/EMR-II) and Division of Molecular Medicine. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: subrata@bic.boseinst.ernet.in Introduction The parasitic protozoan Leishmania donovani, the causative agent of visceral leishmaniasis (VL), resides and multiplies in host macrophages [1]. Activated macrophages eliminate the intracel- lular parasite [2] by initiating host-protective anti-leishmanial responses. To counteract these anti-leishmanial responses parasites deploys different immune evasion strategies to survive within the macrophages [3]. Leishmania-induced macrophage dysfunctions have been correlated mainly with depletion of microbicidal molecules (nitric oxide (NO) and reactive oxygen species) [4,5], and altered signaling events resulting in skewing the T helper cells (Th) to disease promoting Th2 subset that consequently suppress the host protective Th1 subset [6]. The outcome of infection in leishmaniasis is mainly determined by the Th1 versus Th2 effector response and the generation of IL-12 and IL-10 by the infected macrophages is important for this decision [7]. Several immunoprophylactics have been pursued to combat VL, with varying degrees of success. Recently Arabinosylated-lipoar- abinomannan (Ara-LAM), an immunomodulator has emerged as an effective immunoprophylactic tool against VL. It confers protection during leishmanial pathogenesis via Toll-like receptor 2 (TLR2) signaling mediated nuclear factor-kB (NF-kB) translocation and concomitant induction of the proinflammatory mediators [8]. In addition to NF-kB activation, TLR signaling can also activate mitogen-activated protein kinases (MAPK) signaling cascades which include extracellular signal–regulated kinase (ERKs), p38 MAPKs, and c-Jun NH2-terminal kinases (JNK) [9]. Most of the effector functions in response to extracellular cues are regulated by (MAPK) [10,11]. The parasite-triggered recip- rocal MAPK signaling via p38MAPK and ERK1/2 govern the counteracting immune response of the host cell resulting in differential expression of IL-12 and IL-10 in macrophages during Leishmania infection [12]. p38 MAPK activation results in histone PLoS ONE | www.plosone.org 1 September 2011 | Volume 6 | Issue 9 | e24141