Background Leprosy is a chronic infectious disease caused by Mycobacterium leprae , which can lead to a disabling neurodegenerative condition. M. leprae preferentially infects skin macrophages and ...Schwann cells–glial cells of the peripheral nervous system. The infection modifies the host cell lipid metabolism, subverting it in favor of the formation of cholesterol-rich lipid droplets (LD) that are essential for bacterial survival. Although researchers have made progress in understanding leprosy pathogenesis, many aspects of the molecular and cellular mechanisms of host–pathogen interaction still require clarification. The purinergic system utilizes extracellular ATP and adenosine as critical signaling molecules and plays several roles in pathophysiological processes. Furthermore, nucleoside surface receptors such as the adenosine receptor A 2A R involved in neuroimmune response, lipid metabolism, and neuron–glia interaction are targets for the treatment of different diseases. Despite the importance of this system, nothing has been described about its role in leprosy, particularly adenosinergic signaling (AdoS) during M. leprae –Schwann cell interaction. Methods M. leprae was purified from the hind footpad of athymic nu/nu mice. ST88-14 human cells were infected with M. leprae in the presence or absence of specific agonists or antagonists of AdoS. Enzymatic activity assays, fluorescence microscopy, Western blotting, and RT-qPCR analysis were performed. M. leprae viability was investigated by RT-qPCR, and cytokines were evaluated by enzyme-linked immunosorbent assay. Results We demonstrated that M. leprae -infected Schwann cells upregulated CD73 and ADA and downregulated A 2A R expression and the phosphorylation of the transcription factor CREB (p-CREB). On the other hand, activation of A 2A R with its selective agonist, CGS21680, resulted in: 1) reduced lipid droplets accumulation and pro-lipogenic gene expression; 2) reduced production of IL-6 and IL-8; 3) reduced intracellular M. leprae viability; 4) increased levels of p-CREB. Conclusion These findings suggest the involvement of the AdoS in leprosy neuropathogenesis and support the idea that M. leprae , by downmodulating the expression and activity of A 2A R in Schwann cells, decreases A 2A R downstream signaling, contributing to the maintenance of LD accumulation and intracellular viability of the bacillus.
Introdução: a hanseníase é uma doença in fecciosa crônica causada pelo Mycobacterium leprae (M. leprae), um parasita intracelular obrigatório. Assim, a resistência do hospedeiro a esse patógeno ...depende da imunidade celular. O uso de modelos experimentais tem permitido o estudo da hanseníase do ponto de vista imunológico, microbiológico e terapêutico, entretanto, as diferenças na progressão da infecção entre os modelos mais empregados (camundongos imunocompetentes, BALB/c, e camundongos congenitamente atímicos, nude) são pouco estudadas. Objetivo: comparar a evolução da infecção pelo M. leprae em camundongos BALB/c e nude quanto à multiplicação bacilar e avaliação do perfil inflamatório sistêmico pela quantificação sérica de citocinas e óxido nítrico (NO). Métodos: os camundongos foram inoculados com M. leprae nos coxins plantares e avaliados aos 3, 5 e 8 meses após a infecção. Resultados: camundongos nude apresentaram multiplicação bacilar progressiva nos coxins plantares. Em camundongos BALB/c, o número de bacilos foi maior aos 5 meses. Em relação à quantificação de citocinas, nos camundongos BALB/c houve aumento de IL-2 e IL-17A e diminuição de IL-6 e NO aos 8 meses de inoculação. Nos camundongos nude, verificou-se o aumento do TNF aos 8 meses de inoculação e manutenção dos níveis de NO. Conclusão: os resultados encontrados sugerem que em camundongos BALB/c ocorre a ativação de uma resposta imune capaz de controlar a multiplicação do M. leprae, em contrapartida em camundongos nude a infecção é progressiva a despeito de altos níveis de TNF.
Leprosy is a chronic infectious disease caused by Mycobacterium leprae infection in Schwann cells. Axonopathy is considered a hallmark of leprosy neuropathy and is associated with the irreversible ...motor and sensory loss seen in infected patients. Although M. leprae is recognized to provoke Schwann cell dedifferentiation, the mechanisms involved in the contribution of this phenomenon to neural damage remain unclear. In the present work, we used live M. leprae to infect the immortalized human Schwann cell line ST8814. The neurotoxicity of infected Schwann cell‐conditioned medium (SCCM) was then evaluated in a human neuroblastoma cell lineage and mouse neurons. ST8814 Schwann cells exposed to M. leprae affected neuronal viability by deviating glial 14C‐labeled lactate, important fuel of neuronal central metabolism, to de novo lipid synthesis. The phenolic glycolipid‐1 (PGL‐1) is a specific M. leprae cell wall antigen proposed to mediate bacterial–Schwann cell interaction. Therefore, we assessed the role of the PGL‐1 on Schwann cell phenotype by using transgenic M. bovis (BCG)‐expressing the M. leprae PGL‐1. We observed that BCG‐PGL‐1 was able to induce a phenotype similar to M. leprae, unlike the wild‐type BCG strain. We next demonstrated that this Schwann cell neurotoxic phenotype, induced by M. leprae PGL‐1, occurs through the protein kinase B (Akt) pathway. Interestingly, the pharmacological inhibition of Akt by triciribine significantly reduced free fatty acid content in the SCCM from M. leprae‐ and BCG‐PGL‐1‐infected Schwann cells and, hence, preventing neuronal death. Overall, these findings provide novel evidence that both M. leprae and PGL‐1, induce a toxic Schwann cell phenotype, by modifying the host lipid metabolism, resulting in profound implications for neuronal loss. We consider this metabolic rewiring a new molecular mechanism to be the basis of leprosy neuropathy.
Leprosy is a chronic infectious disease caused by the intracellular pathogen M. leprae, known for its predilection to Schwann cells, the principal glial cells of the peripheral nerve. Here, we observed that M. leprae, via PGL‐1, triggers AKT phosphorylation in Schwann cells and contributes to de novo lipid synthesis and mitochondrial dysfunction. Collectively, our data indicate that the decreased production of lactate and the increased lipid release by M. leprae‐infected Schwann cells are able to promote neuronal death and disturbance of neuronal branching/outgrowth.
Brazil has a high leprosy burden and poor treatment outcomes (TOs), manifesting in high relapse rates. Pernambuco, an impoverished Brazilian state suffering notable geographical health inequalities, ...has 'hyperendemic' leprosy. Although current literature identifies barriers and facilitators influencing leprosy treatment compliance, inadequate investigation exists on other factors influencing TOs, including carers' roles and psycho-dermatological impact. This qualitative study explores experiences and perceptions of leprosy patients and their carers in Pernambuco, Brazil; to identify location-specific factors influencing TOs, and consequently inform future management.
27, semi-structured, in-depth interviews were conducted with 14 patients and 13 carers. Participants were recruited using maximum variation and snowball sampling from three clinics in Petrolina, Pernambuco. Transcripts and field notes from both participant groups were separately analysed using conventional thematic and deviant case analysis. The University of Birmingham Internal Research Ethics Committee and Instituto Lauro de Souza Lima provided ethical approval.
Two homologous sets of four, primary, interdependent themes influencing leprosy TOs emerged: 'personal factors'; 'external factors'; 'clinical factors'; and 'the healthcare professional (HCP)-patient-carer relationship'. Poor participant knowledge and lack of symptomatic relief caused patients to distrust treatment. However, because participants thought HCP-led interventions were vital for optimal TOs, patients were effectively persuaded to adhere to pharmaceutical treatments. High standard patient and population education facilitated treatment engagement by encouraging evidence-based medicine belief, and dispelling health myths and stigma. Healthcare, on occasions, was perceived as disorganised, particularly in resource-scarce rural areas, and for those with mental health needs. Participants additionally experienced incorrect/delayed diagnoses and poor contact tracing. Leprosy's negative socio-economic impact on employment - together with stigma, dependency and changing relationships - caused altered senses of identity, negatively impacting TOs. Better dialogue between patients, HCPs and carers facilitated individualised patient support.
This study highlights the importance of: effective evidence-based leprosy education; communication between HCPs, patients and carers; state-funded support; and healthcare resource distribution. These findings, if prioritised on governmental scales, provide the valuable insight needed to inform location-specific management strategies, and consequently improve TOs. Future research should evaluate the effectiveness of these implementations. Failure to address these findings will hinder regional elimination efforts.
The multidrug therapy (MDT) for leprosy treatment adopted by Brazil in the 1990s was important for reducing leprosy in the country; however, recurrent cases remained problematic. Mechanisms involved ...in leprosy recurrence are heterogeneous and can be sorted into three groups: insufficient therapy, bacillary persistence and new infections. This study aimed to analyse the time interval of leprosy recurrence in relation to the therapeutic scheme in the state of Acre. The hypotheses were as follows: 1) treatments (a) rifampicin, ofloxacin and minocycline (ROM) and (b) dapsone (DDS) have a short leprosy recurrence time, 2) treatments based on MDT have a long leprosy recurrence time, 3) there is a dose-response relationship between MDT and the time interval between leprosy episodes.
This retrospective cohort study included 201 patients with a second episode of clinical leprosy at the reference centers for leprosy control in the state of Acre. Exposure was the type of therapeutic scheme as follows: 1) ROM, 2) DDS, 3) MDT
, 4) MDT
, 5) MDT
, and 6) MDT
. Outcome was the time interval between release from treatment and a diagnosis of a recurrent leprosy case. Incidence rate ratios and relative risk Poisson regressions adjusted by age and sex were calculated with 95% confidence intervals.
The 201 patients studied during this retrospective follow-up resulted in a total of 224 cases of recurrent leprosy. Incidence rate ratios within this therapeutic scheme were as follows: 3.3 (2.39, 4.2; ROM/MDT
), 1.12 (0.33, 1.92; DDS/MDT
), 2.17 (1.39, 2.94; MDT
/MDT
), 1.94 (1.13, 2.75; MDT
/MDT
) and 1.26 (0.47, 2.05; MDT
/MDT
). Relative risk Poisson regressions showed a protective effect of MDT
in comparison with ROM (0.22; 0.07, 0.72), MDT
(0.42; 0.21, 0.85), and MDT
(0.44; 0.21, 0.92). No differences among MDT
and DDS (0.71; 0.36, 1.41) and MDT
(0.76; 0.38, 1.49) were observed.
New infection is an important-yet neglected-mechanism in leprosy recurrence in the state of Acre and can challenge the leprosy elimination plan in Brazil. MDT with few doses might be associated with leprosy recurrence due to insufficient therapy or bacillary persistence.
Mycobacterium leprae, an obligate intracellular bacillus, infects Schwann cells (SCs), leading to peripheral nerve damage, the most severe leprosy symptom. In the present study, we revisited the ...involvement of phenolic glycolipid I (PGL I), an abundant, private, surface M. leprae molecule, in M. leprae-SC interaction by using a recombinant strain of M. bovis BCG engineered to express this glycolipid. We demonstrate that PGL I is essential for bacterial adhesion and SC internalization. We also show that live mycobacterium-producing PGL I induces the expression of the endocytic mannose receptor (MR/CD206) in infected cells in a peroxisome proliferator-activated receptor gamma (PPARγ)-dependent manner. Of note, blocking mannose recognition decreased bacterial entry and survival, pointing to a role for this alternative recognition pathway in bacterial pathogenesis in the nerve. Moreover, an active crosstalk between CD206 and the nuclear receptor PPARγ was detected that led to the induction of lipid droplets (LDs) formation and prostaglandin E2 (PGE2), previously described as fundamental players in bacterial pathogenesis. Finally, this pathway was shown to induce IL-8 secretion. Altogether, our study provides evidence that the entry of live M. leprae through PGL I recognition modulates the SC phenotype, favoring intracellular bacterial persistence with the concomitant secretion of inflammatory mediators that may ultimately be involved in neuroinflammation.
Herein, we performed microarray experiments in Schwann cells infected with live M. leprae and identified novel differentially expressed genes (DEG) in M. leprae infected cells. Also, we selected ...candidate genes associated or implicated with leprosy in genetic studies and biological experiments. Forty-seven genes were selected for validation in two independent types of samples by multiplex qPCR. First, an in vitro model using THP-1 cells was infected with live Mycobacterium leprae and M. bovis bacillus Calmette-Guérin (BCG). In a second situation, mRNA obtained from nerve biopsies from patients with leprosy or other peripheral neuropathies was tested. We detected DEGs that discriminate M. bovis BCG from M. leprae infection. Specific signatures of susceptible responses after M. leprae infection when compared to BCG lead to repression of genes, including CCL2, CCL3, IL8 and SOD2. The same 47-gene set was screened in nerve biopsies, which corroborated the down-regulation of CCL2 and CCL3 in leprosy, but also evidenced the down-regulation of genes involved in mitochondrial metabolism, and the up-regulation of genes involved in lipid metabolism and ubiquitination. Finally, a gene expression signature from DEG was identified in patients confirmed of having leprosy. A classification tree was able to ascertain 80% of the cases as leprosy or non-leprous peripheral neuropathy based on the expression of only LDLR and CCL4. A general immune and mitochondrial hypo-responsive state occurs in response to M. leprae infection. Also, the most important genes and pathways have been highlighted providing new tools for early diagnosis and treatment of leprosy.
PDF
