Lysosomes: How Plasma Membrane Repair Route Can Be Hijacked by Parasites?

Lysosomes are acidic organelles that are not only involved in degradation processes but also participated in other cellular functions, such as specialized secretion and plasma membrane (PM) resealing. When the PM is ruptured, Ca2+ flows from the extracellular milieu toward the cytoplasm potentially triggering cell death. In order to escape from the apoptotic route, cells developed an elegant mechanism in which lysosomes are recruited to the sites of injuries in a Ca2+-dependent fashion. Lysosomes, fuse with the PM releasing their enzymatic content. Acid sphingomyelinase (ASM), one of the secreted enzymes, cleaves sphingomyelin into ceramide, inducing compensatory endocytosis and internalization of the membrane-damaged site. Trypanosoma cruzi, the etiological agent of Chagas disease, relies heavily on lysosomes to successfully invade mammalian cells. By mechanically injuring the host PM, T. cruzi evokes lysosome exocytosis, and subsequently, compensatory endocytosis. The latter drives the parasite into the host cell, where it can replicate. This early association with lysosomes prevents T. cruzi evasion from the host cells allowing colonization of host intracellular milieu. This review chapter will summarize the main contributions in the field exploring the crosstalk between PM repair and T. cruzi invasion and how the understanding of these mechanisms evolved throughout the years

Confirmation of the utility of the International Staging System and identification of a unique pattern of disease in Brazilian patients with multiple myeloma

Santa Casa São Paulo, São Paulo, BrazilUniv Fed Rio de Janeiro, Rio de Janeiro, BrazilUniv São Paulo, São Paulo, BrazilHEMOPE, Recife, PE, BrazilUniversidade Federal de São Paulo, São Paulo, BrazilUniv Fed Bahia, BR-41170290 Salvador, BA, BrazilHosp Brigadeiro São Paulo, São Paulo, BrazilUniv Fed Rio Grande do Sul, BR-90046900 Porto Alegre, RS, BrazilSch Med, Ribeirao Preto, BrazilUniv Fed Minas Gerais, Belo Horizonte, MG, BrazilUniv Fed Parana, BR-80060000 Curitiba, Parana, BrazilUniv Estadual Campinas, BR-13081970 Campinas, SP, BrazilInst Nacl Canc Rio Janeiro, Rio de Janeiro, BrazilCanc Res & Biostat, Seattle, WA USACedars Sinai Outpatient Canc Ctr, Aptium Oncol Inc, Los Angeles, CA USAUniversidade Federal de São Paulo, São Paulo, BrazilWeb of Scienc

The MHC Gene Region of Murine Hosts Influences the Differential Tissue Tropism of Infecting Trypanosoma cruzi Strains

We have previously demonstrated that both parasite genetic variability and host genetic background were important in determining the differential tissue distribution of the Col1.7G2 and JG T. cruzi monoclonal strains after artificial infections in mice. We observed that the JG strain was most prevalent in hearts of mouse lineages with the MHC haplotype H-2d (BALB/c and DBA2), while Col1.7G2 was predominant in hearts from C57BL/6 mice, which have the H-2b haplotype. To assess whether the MHC gene region indeed influenced tissue tropism of T. cruzi, we used the same two parasite strains to infect C57BL/6 (H-2b) and C57BLKS/J (H-2d) mice; the latter strain results from the introgression of DBA2 MHC region into the C57BL/6 background. We also performed ex vivo infections of cardiac explants from four congenic mice lineages with the H-2b and H-2d haplotypes arranged in two different genetic backgrounds: C57BLKS/J (H-2d) versus C57BL/6 (H-2b) and BALB/c (H-2d) versus BALB/B10-H2b (H-2b). In agreement with our former observations, Col1.7G2 was predominant in hearts from C57BL/6 mice (H-2b), but we observed a clear predominance of the JG strain in hearts from C57BLKS/J animals (H-2d). In the ex vivo experiments Col1.7G2 also prevailed in explants from H-2b animals while no predominance of any of the strains was observed in H-2d mice explants, regardless of the genetic background. These observations clearly demonstrate that the MHC region influences the differential tissue distribution pattern of infecting T. cruzi strains, which by its turn may be in a human infection the determinant for the clinical forms of the Chagas disease

Assembléias de Formicidae da serapilheira como bioindicadores da conservação de remanescentes de Mata Atlântica no extremo sul do Estado da Bahia

In the extreme south of Bahia State, the Atlantic rainforest has been strongly affected by anthropogenic actions for a long time. Ants are seen as good biological indicators because of their abundance and sensitivity to changes of environmental conditions, thus allowing the evaluation of environmental impacts. The purpose of this study was to evaluate the environmental quality in four Atlantic Forest remnants through the study of Formicidae assemblages. Four reserves sampled during the experiment were: the school of agriculture EMARC (CEPLAC) in Teixeira de Freitas; Vista Alegre Farm in Alcobaça; FIBRASA Farm in Itamarajú; and Riacho das Pedras Farm in Prado. In each area, 50 units of one square meter of litter were sampled at intervals of 50m and 100m of the border using “Winkler” traps. The most frequent ants in EMARC reserve were: Wasmannia auropunctata (60%) and Solenopsis sp.1 (58%); in FIBRASA farm: W. auropunctata (64%) and Solenopsis sp.1 (46%); in Riacho das Pedras farm: Pyramica eggersi (80%) and Solenopsis sp.1 (64%); in Vista Alegre farm: Pheidole sp.1 (34%), Hypoponera sp.8 (32%) and Pyramica denticulata (24%). The highest value of diversity index (Shannon-Weaver) was observed in FIBRASA farm (3.41), followed by Riacho das Pedras farm (3.31), Vista Alegre farm (3.00), and EMARC reserve (2.33). The largest number of species was observed in FIBRASA and in Riacho das Pedras farms (55 species), followed by Vista Alegre (33) and EMARC (22). The area with the highest estimated diversity is the FIBRASA farm, while the reserve of EMARC had the lowest estimate. There were correlations between the level of human impact, the species found and generic richness, as well as with other ecological variables. All the studied areas had a high occurrence of species typical of degraded lands, showing that urgent conservation measures are needed to the increasingly more rare remnants of forest in the extreme South Bahia State.No extremo sul do Estado da Bahia, a Mata Atlântica tem sido fortemente afetada pelas atividades humanas. As formigas são vistas como indicadores biológicos confiáveis por serem sensíveis às mudanças das condições do ambiente, permitindo uma avaliação do impacto ambiental. O objetivo do presente estudo foi de avaliar a qualidade ambiental em quatro remanescentes de Mata Atlântica através de uma análise da estrutura das assembléias de Formicidae. As quatro reservas estudadas, todas situadas naquela região, foram: reserva da escola agrícola EMARC, Município de Teixeira de Freitas; Fazenda Vista Alegre, Alcobaça; Fazenda FIBRASA, Itamarajú e Fazenda Riacho das Pedras, Prado. Em cada área, foram amostrados 50 pontos de um metro quadrado de serapilheira, com o auxílio de armadilhas de tipo “Winkler”. O maior número de espécies observado foi na Fazenda FIBRASA (55 espécies) e na Fazenda Riacho das Pedras, seguidas pela Fazenda Vista Alegre (33) e a reserva da EMARC (22). A área de maior diversidade de espécies esperada (estimador Chao2) é também a da Fazenda FIBRASA, enquanto a área da EMARC foi também a de menor diversidade esperada. As espécies mais freqüentes na reserva da EMARC foram Wasmannia auropunctata (60% das amostras) e Solenopsis sp1 (58%); na Fazenda FIBRASA, W. auropunctata (64%) e Solenopsis sp.1 (46%); na Fazenda Riacho das Pedras, Pyramica eggersi (80%) e Solenopsis sp.1 (64%); na Fazenda Vista Alegre, Pheidole sp.1 (34%), Hypoponera sp.8 (32%) e Pyramica denticulata (24%). Existem correlações entre o nível de impacto humano e as riquezas específica e genérica, assim como com outras variáveis ecológicas, nas áreas estudadas. Todas essas apresentaram uma ocorrência elevada de espécies típicas de ambientes degradados, como é o caso de W. auropunctata, mostrando a urgência que existe numa política de conservação mais efetiva dos cada vez mais raros remanescentes do extremo sul do Estado da Bahia

Platelet-activating factor receptor (PAF-R)-dependent pathways control tumour growth and tumour response to chemotherapy

<p>Abstract</p> <p>Background</p> <p>Phagocytosis of apoptotic cells by macrophages induces a suppressor phenotype. Previous data from our group suggested that this occurs via Platelet-activating factor receptor (PAF-R)-mediated pathways. In the present study, we investigated the impact of apoptotic cell inoculation or induction by a chemotherapeutic agent (dacarbazine, DTIC) on tumour growth, microenvironmental parameters and survival, and the effect of treatment with a PAF-R antagonist (WEB2170). These studies were performed in murine tumours: Ehrlich Ascitis Tumour (EAT) and B16F10 melanoma.</p> <p>Methods</p> <p>Tumour growth was assessed by direct counting of EAT cells in the ascitis or by measuring the volume of the solid tumour. Parameters of the tumour microenvironment, such as the frequency of cells expressing cyclo-oxygenase-2 (COX-2), caspase-3 and galectin-3, and microvascular density, were determined by immunohistochemistry. Levels of vascular endothelium growth factor (VEGF) and prostaglandin E2 (PGE2) were determined by ELISA, and levels of nitric oxide (NO) by Griess reaction. PAF-R expression was analysed by immunohistochemistry and flow cytometry.</p> <p>Results</p> <p>Inoculation of apoptotic cells before EAT implantation stimulated tumour growth. This effect was reversed by <it>in vivo </it>pre-treatment with WEB2170. This treatment also reduced tumour growth and modified the microenvironment by reducing PGE2, VEGF and NO production. In B16F10 melanoma, WEB2170 alone or in association with DTIC significantly reduced tumour volume. Survival of the tumour-bearing mice was not affected by WEB2170 treatment but was significantly improved by the combination of DTIC with WEB2170. Tumour microenvironment elements were among the targets of the combination therapy since the relative frequency of COX-2 and galectin-3 positive cells and the microvascular density within the tumour mass were significantly reduced by treatment with WEB2170 or DTIC alone or in combination. Antibodies to PAF-R stained the cells from inside the tumour, but not the tumour cells grown <it>in vitro</it>. At the tissue level, a few cells (probably macrophages) stained positively with antibodies to PAF-R.</p> <p>Conclusions</p> <p>We suggest that PAF-R-dependent pathways are activated during experimental tumour growth, modifying the microenvironment and the phenotype of the tumour macrophages in such a way as to favour tumour growth. Combination therapy with a PAF-R antagonist and a chemotherapeutic drug may represent a new and promising strategy for the treatment of some tumours.</p

Membrane Cholesterol Regulates Lysosome-Plasma Membrane Fusion Events and Modulates Trypanosoma cruzi Invasion of Host Cells

Trypanosoma cruzi, is the etiological agent of a neglected tropical malady known as Chagas' disease, which affects about 8 million people in Latin America. 30–40% of affected individuals develop a symptomatic chronic infection, with cardiomyopathy being the most prevalent condition. T. cruzi utilizes an interesting strategy for entering cells: T. cruzi enhances intracellular calcium levels, which in turn trigger the exocytosis of lysosomal contents. Lysosomes then donate their membrane for the formation of the parasitophorous vacuole. Membrane rafts, cholesterol-enriched microdomains in the host cell plasma membrane, have also been implicated in T. cruzi invasion process. Since both plasma membrane and lysosomes collaborate in parasite invasion, we decided to study the importance of these membrane domains for lysosomal recruitment and fusion during T. cruzi invasion into host cells. Our results show that drug dependent depletion of plasma membrane cholesterol changes raft organization and induces excessive lysosome exocytosis in the earlier stages of treatment, leading to a depletion of lysosomes near the cell cortex, which in turn compromises T. cruzi invasion. Based on these results, we propose that cholesterol depletion leads to unregulated exocytic events of pre-docked lysosomes, reducing lysosome availability at the cell cortex and consequently compromising T. cruzi infection

Canine distemper virus induces apoptosis in cervical tumor derived cell lines

Apoptosis can be induced or inhibited by viral proteins, it can form part of the host defense against virus infection, or it can be a mechanism for viral spread to neighboring cells. Canine distemper virus (CDV) induces apoptotic cells in lymphoid tissues and in the cerebellum of dogs naturally infected. CDV also produces a cytopathologic effect, leading to apoptosis in Vero cells in tissue culture. We tested canine distemper virus, a member of the Paramyxoviridae family, for the ability to trigger apoptosis in HeLa cells, derived from cervical cancer cells resistant to apoptosis. To study the effect of CDV infection in HeLa cells, we examined apoptotic markers 24 h post infection (pi), by flow cytometry assay for DNA fragmentation, real-time PCR assay for caspase-3 and caspase-8 mRNA expression, and by caspase-3 and -8 immunocytochemistry. Flow cytometry showed that DNA fragmentation was induced in HeLa cells infected by CDV, and immunocytochemistry revealed a significant increase in the levels of the cleaved active form of caspase-3 protein, but did not show any difference in expression of caspase-8, indicating an intrinsic apoptotic pathway. Confirming this observation, expression of caspase-3 mRNA was higher in CDV infected HeLa cells than control cells; however, there was no statistically significant change in caspase-8 mRNA expression profile. Our data suggest that canine distemper virus induced apoptosis in HeLa cells, triggering apoptosis by the intrinsic pathway, with no participation of the initiator caspase -8 from the extrinsic pathway. In conclusion, the cellular stress caused by CDV infection of HeLa cells, leading to apoptosis, can be used as a tool in future research for cervical cancer treatment and control