We recently showed that Mycobacterium leprae (ML) is able to induce lipid droplet formation in infected macrophages. We herein confirm that cholesterol (Cho) is one of the host lipid molecules that accumulate in ML-infected macrophages and investigate the effects of ML on cellular Cho metabolism responsible for its accumulation. The expression levels of LDL receptors (LDL-R, CD36, SRA-1, SR-B1, and LRP-1) and enzymes involved in Cho biosynthesis were investigated by qRT-PCR and/or Western blot and shown to be higher in lepromatous leprosy (LL) tissues when compared to borderline tuberculoid (BT) lesions. Moreover, higher levels of the active form of the sterol regulatory element-binding protein (SREBP) transcriptional factors, key regulators of the biosynthesis and uptake of cellular Cho, were found in LL skin biopsies. Functional in vitro assays confirmed the higher capacity of ML-infected macrophages to synthesize Cho and sequester exogenous LDL-Cho. Notably, Cho colocalized to ML-containing phagosomes, and Cho metabolism impairment, through either de novo synthesis inhibition by statins or depletion of exogenous Cho, decreased intracellular bacterial survival. These findings highlight the importance of metabolic integration between the host and bacteria to leprosy pathophysiology, opening new avenues for novel therapeutic strategies to leprosy.

Lepromatous macrophages possess a regulatory phenotype that contributes to the immunosuppression observed in leprosy. CD163, a scavenger receptor that recognizes hemoglobin-haptoglobin complexes, is expressed at higher levels in lepromatous cells, although its functional role in leprosy is not yet established. We herein demonstrate that human lepromatous lesions are microenvironments rich in IDO + CD163 + . Cells isolated from these lesions were CD68 + IDO + CD163 + while higher levels of sCD163 in lepromatous sera positively correlated with IL-10 levels and IDO activity. Different Mycobacterium leprae (ML) concentrations in healthy monocytes likewise revealed a positive correlation between increased concentrations of the mycobacteria and IDO, CD209, and CD163 expression. The regulatory phenotype in ML-stimulated monocytes was accompanied by increased TNF, IL-10, and TGF-β levels whereas IL-10 blockade reduced ML-induced CD163 expression. The CD163 blockade reduced ML uptake in human monocytes. ML uptake was higher in HEK293 cells transfected with the cDNA for CD163 than in untransfected cells. Simultaneously, increased CD163 expression in lepromatous cells seemed to be dependent on ML uptake, and contributed to augmented iron storage in lepromatous macrophages. Altogether, these results suggest that ML-induced CD163 expression modulates the host cell phenotype to create a favorable environment for mycobacterial entry and survival.Keywords: CD163 r IL-10 r Leprosy r Macrophages IntroductionLeprosy is an infectious disease caused by Mycobacterium leprae (ML) in which susceptibility to the mycobacteria and its clinicalmanifestations are attributed to the host immune response. The clinical and immunological patterns of this unique chronic infectious disease clearly demonstrate a continuous scale of changes in histological lesions. Disease classification is defined Correspondence: Dr. Euzenir N. Sarno e-mail: euzenir@fiocruz.br within two poles (tuberculoid to lepromatous) with transitions between these clinical forms. While typical epithelioid macrophages predominate at the paucibacillary tuberculoid pole of the disease, inactivated foamy macrophages predominate at the lepromatous end [1]. In lepromatous leprosy (LL), the lack of systemic inflammatory signals and corresponding local ones strongly indicates that a complex anti-inflammatory network is at work. In this * These authors contributed equally to this work as first authors. * * These authors contributed equally to this work as senior authors. Eur. J. Immunol. 2012. 42: 2925-2936 regard, neuroendocrine system involvement, in conjunction with the existence of multiple suppressive pathways under the control of the innate and adaptive immune response, has been reported [2][3][4][5][6][7].We have suggested that IDO may play a role in a hitherto unknown suppressive mechanism in leprosy [6]. It has also been reported that accumulated oxidized host phospholipids in lepromatous macrophages downregulate the innate immune response [8]. Foamy macrophages seem to sust...

Mycobacterium leprae (ML), the etiologic agent of leprosy, can subvert macrophage antimicrobial activity by mechanisms that remain only partially understood. In the present study, the participation of hormone insulin-like growth factor I (IGF-I) in this phenomenum was investigated. Macrophages from the dermal lesions of the disseminated multibacillary lepromatous form (LL) of leprosy expressed higher levels of IGF-I than those from the self-limited paucibacillary tuberculoid form (BT). Higher levels of IGF-I secretion by ML-infected macrophages were confirmed in ex vivo and in vitro studies. Of note, the dampening of IGF-I signaling reverted the capacity of ML-infected human and murine macrophages to produce antimicrobial molecules and promoted bacterial killing. Moreover, IGF-I was shown to inhibit the JAK/STAT1-dependent signaling pathways triggered by both mycobacteria and IFN-γ most probably through its capacity to induce the suppressor of cytokine signaling-3 (SOCS3). Finally, these in vitro findings were corroborated by in vivo observations in which higher SOCS3 expression and lower phosphorylation of STAT1 levels were found in LL versus BT dermal lesions. Altogether, our data strongly suggest that IGF-I contributes to the maintenance of a functional program in infected macrophages that suits ML persistence in the host, reinforcing a key role for IGF-I in leprosy pathogenesis.

Matrix metalloproteinases (MMPs) compose a family of zinc-and calcium-dependent proteolytic enzymes responsible for extracellular matrix (ECM) remodeling and the regulation of the trans-ECM migration of leukocytes, an important step in inflammatory processes as well as infectious diseases. MMPs are functionally classified according to their relative substrate specificities but have been shown to overlap. Collagenases (MMP-1, -8, and -13) degrade type I collagen, whereas gelatinases A and B (MMP-2 and -9, respectively) degrade denatured type I (gelatin) and type IV collagens, a major component of the basement membrane. Collagenases are produced by many cell types including lymphocytes, granulocytes, astrocytes, and activated macrophages (10, 18).MMP secretion takes place under tight regulatory mechanisms including transcriptional controls in addition to their release as proenzymes, requiring activation by specific proteases and cytokines present in the milieu (2,3,16). Also, the postactivation of MMPs is controlled by metalloproteinase tissue inhibitors (tissue inhibitor of MMP [TIMP]), a family of specific inhibitors, that bind to MMPs in a stoichiometric ratio.