<i>Entamoeba histolytica</i>electrondense granules secretion in vitro and in vivo: Ultrastructural study

Parasitic protozoa are among the most important pathogens worldwide. Diseases such as malaria, leishmaniasis, amoebiasis, giardiasis, trichomoniasis, and trypanosomiasis affect millions of people. Humans are constantly threatened by infections caused by these pathogens. Parasites engage a plethora of surface and secreted molecules to attach to and enter mammalian cells. The secretion of lytic enzymes by parasites into host organs mediates critical interactions because of the invasion and destruction of interstitial tissues, enabling parasite migration to other sites within the hosts. Extracellular matrix is a complex, cross-linked structure that holds cells together in an organized assembly and that forms the basement membrane lining (basal lamina). The extracellular matrix represents a major barrier to parasites. Therefore, the evolution of mechanisms for connective-tissue degradation may be of great importance for parasite survival. Recent advances have been achieved in our understanding of the biochemistry and molecular biology of proteases from parasitic protozoa. The focus of this paper is to discuss the role of protozoan parasitic proteases in the degradation of host ECM proteins and the participation of these molecules as virulence factors. We divide the paper into two sections, extracellular and intracellular protozoa.

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“…In a recent study, Chávez Munguia et al [35] demonstrated that electron-dense granules contain multiple cysteine protease activities.…”

Section: Extracellular Protozoamentioning

confidence: 99%

Host-Parasite Interaction: Parasite-Derived and -Induced Proteases That Degrade Human Extracellular Matrix

Piña-Vázquez

Reyes-López

Ortiz-Estrada

et al. 2012

Journal of Parasitology Research

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“…Contact‐dependent release of EDGs has been reported in E. histolytica and N. fowleri following incubation with cultured epithelial cells or collagen substrates (Chávez‐Munguía et al. , ). Release of these granules has also been observed during excystation in A. castellanii, N. fowleri, and E. invadens (Chávez‐Munguía et al.…”

Section: Discussionmentioning

confidence: 99%

“…In vitro studies have reported that release of EDGs may be induced through contact with collagen or epithelial cells (Chávez‐Munguía et al. ; Martínez‐Palomo et al. ).…”

mentioning

confidence: 99%

“…A common observation both in E. histolytica and in N. fowleri trophozoites recovered from experimental lesions has been the increased number of EDGs compared to EDGs in long‐term cultured parasites (Chávez‐Munguía et al. , ). In Acanthamoeba spp., up‐regulation of genes related with proteolytic activity and virulence has been reported after mouse brain passage of cultured trophozoites (Han et al.…”

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confidence: 99%

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Acanthamoeba culbertsoni: Electron‐Dense Granules in a Highly Virulent Clinical Isolate

Chávez‐Munguía¹,

Salazar‐Villatoro²,

Omaña‐Molina

et al. 2016

J Eukaryotic Microbiology

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The virulence of various amoebic parasites has been correlated with the presence of electron-dense granules (EDGs) in the cytoplasm of trophozoites. Here, we report the finding by transmission electron microscopy of a large number of EDGs in a recent culture of Acanthamoeba culbertsoni, isolated from a severe case of human keratitis. When this isolate was maintained in culture for 6 mo, the granules almost disappeared. However, after induction of mice brain lesions with the long-term cultured isolate, recovered amoebas had abundant EDGs. Trophozoites of the original isolate, or those recovered from experimental lesions, secreted EDGs into the medium when incubated with MDCK cells. To analyze a possible cytotoxic effect the conditioned medium was incubated with MDCK monolayers. After 5 h, the media containing EDGs produced opening of the tight junctions; at 24 h, cell viability was compromised, and at 48 h most of the cells were detached from the monolayer. In contrast, trophozoites in long-term cultures did not release EDGs to the medium during incubation with MDCK cells, and the corresponding conditioned medium did not have any effect on MDCK monolayers. Our observations further support the hypothesis that EDGs play a role in the cytopathogenic mechanisms of A. culbertsoni.

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“…In addition, a correlation between collagenolytic activity and virulence was observed when the levels of activity of different strains (virulent HM-1:IMSS and the less virulent 200-NIH and HK-9) [139–141] or of other virulence factors [142] were compared, suggesting that collagenase may play a role in the pathogenesis of amoebiasis. In a recent study, Chavez-Munguia et al [143] demonstrated that electron-dense granules contain multiple CP activities. …”

Section: Entamoeba Histolyticamentioning

confidence: 99%

Proteases fromEntamoebaspp. and Pathogenic Free-Living Amoebae as Virulence Factors

Serrano-Luna

Piña-Vázquez

Reyes-López

et al. 2013

Journal of Tropical Medicine

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The standard reference for pathogenic and nonpathogenic amoebae is the human parasite Entamoeba histolytica; a direct correlation between virulence and protease expression has been demonstrated for this amoeba. Traditionally, proteases are considered virulence factors, including those that produce cytopathic effects in the host or that have been implicated in manipulating the immune response. Here, we expand the scope to other amoebae, including less-pathogenic Entamoeba species and highly pathogenic free-living amoebae. In this paper, proteases that affect mucin, extracellular matrix, immune system components, and diverse tissues and cells are included, based on studies in amoebic cultures and animal models. We also include proteases used by amoebae to degrade iron-containing proteins because iron scavenger capacity is currently considered a virulence factor for pathogens. In addition, proteases that have a role in adhesion and encystation, which are essential for establishing and transmitting infection, are discussed. The study of proteases and their specific inhibitors is relevant to the search for new therapeutic targets and to increase the power of drugs used to treat the diseases caused by these complex microorganisms.

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Entamoeba histolyticaelectrondense granules secretion in vitro and in vivo: Ultrastructural study

Cited by 10 publications

References 34 publications

Host-Parasite Interaction: Parasite-Derived and -Induced Proteases That Degrade Human Extracellular Matrix

Host-Parasite Interaction: Parasite-Derived and -Induced Proteases That Degrade Human Extracellular Matrix

Acanthamoeba culbertsoni: Electron‐Dense Granules in a Highly Virulent Clinical Isolate

Proteases fromEntamoebaspp. and Pathogenic Free-Living Amoebae as Virulence Factors

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