In vitro evaluation of the anti-leishmanial activity and toxicity of PK11195

BACKGROUND Leishmaniasis, one of the most neglected diseases, is a serious public health problem in many countries, including Brazil. Currently available treatments require long-term use and have serious side effects, necessitating the development of new therapeutic interventions. Because translocator protein (TSPO) levels are reduced in Leishmania amazonensis-infected cells and because this protein participates in apoptosis and immunomodulation, TSPO represents a potential target for Leishmania chemotherapy. The present study evaluated PK11195, a ligand of this protein, as an anti-leishmanial agent. OBJECTIVE To evaluate the leishmanicidal activity of PK11195 against L. amazonensis in infected CBA mouse macrophages in vitro. METHODS The viability of axenic L. amazonensis, Leishmania major, and Leishmania braziliensis promastigotes was assessed after 48 h treatment with PK11195 (0.2-400 µM). Additionally, intracellular parasite viability was evaluated to determine IC50 values and the number of viable parasites in infected macrophages treated with PK11195 (50-100 µM). Infected macrophages were then treated with PK11195 (25-100 µM) to determine the percentage of L. amazonensis-infected cells and the number of parasites per infected cell. Electron microscopy was used to investigate morphological changes caused by PK11195. The production of free oxygen radicals, nitric oxide, and pro-inflammatory cytokines was also evaluated in infected macrophages treated with PK11195 and primed or not primed with IFN-γ. FINDINGS Median IC50 values for PK11195 were 14.2 µM for L. amazonensis, 8.2 µM for L. major, and 3.5 µM for L. braziliensis. The selective index value for L. amazonensis was 13.7, indicating the safety of PK11195 for future testing in mammals. Time- and dose-dependent reductions in the percentage of infected macrophages, the number of parasites per infected macrophage, and the number of viable intracellular parasites were observed. Electron microscopy revealed some morphological alterations suggestive of autophagy. Interestingly, MCP-1 and superoxide levels were reduced in L. amazonensis-infected macrophages treated with PK11195. MAIN CONCLUSIONS PK11195 causes the killing of amastigotes in vitro by mechanisms independent of inflammatory mediators and causes morphological alterations within Leishmania parasites, suggestive of autophagy, at doses that are non-toxic to macrophages. Thus, this molecule has demonstrated potential as an anti-leishmanial agent.

Avaliação do papel do receptor marco na infecção de macrófagos murinos por Leishmania major / Evaluation of the role of the receptor in March infection of murine macrophages with Leishmania major

Camundongos CBA são resistentes à infecção por Leishmania major e permissivos à infecção por L. amazonensis. Adicionalmente, macrófagos de camundongos CBA controlam à infecção por L. major, mas não por L. mazonensis in vitro. Em estudo comparativo realizado por nosso grupo foi demonstrado que o receptor scavenger MARCO teve expressão aumentada em resposta à infecção por L. major, mas não na infecção por L. amazonensis. Ainda, o bloqueio do receptor com o anticorpo específico reduziu a infecção por L. major em 30%, indicando que esta proteína tem participação no reconhecimento de promastigotas de L. major em macrófagos de CBA. Assim, nossa hipótese é que o receptor MARCO participa do reconhecimento e fagocitose de L. major por macrófagos, direcionando o curso da infecção. O objetivo do presente estudo consistiu em evidenciar o papel do receptor MARCO na infecção de macrófagos por L. major. Inicialmente, células J774 foram transfectadas com os vetores pcDNA3.1-MARCO (J774-MARCO) ou pcDNA3.1 (J774-MOCK)...

CBA mice are resistant to Leishmania major yet permissive to L. amazonensis infection. In addition, CBA macrophages control L. major, but not L. amazonensis infection in vitro. In a comparative study performed by our group increase in expression of the scavenger receptor MARCO has been detected in response to L. major, but not to L. amazonensis infection. Moreover, ED31 monoclonal antibody against MARCO reduced by 30% L. major infection in CBA macrophages. These findings indicate that MARCO plays a role in L. major recognition by CBA macrophages. We hypothesized that MARCO receptor participates in the recognition and phagocytosis of L. major by macrophages, directing the outcome of infection. In the present study, we aimed to further disclose the role MARCO plays in L. major infection of murine macrophages. First J774 cells were transfected with pcDNA3.1-MARCO vector (MARCO-J774) or pcDNA3.1 vector (MOCK-J774)...