Differential expression and immunolocalization of antioxidant enzymes in Entamoeba histolytica isolates during metronidazole stress. Biomed Res Int. 2014;2014:704937. [PMID: 25013795 PMCID: PMC4074981 DOI: 10.1155/2014/704937]

An atypical EhGEF regulates phagocytosis in Entamoeba histolytica through EhRho1

The parasite Entamoeba histolytica is the etiological agent of amoebiasis, a major cause of morbidity and mortality due to parasitic diseases in developing countries. Phagocytosis is an essential mode of obtaining nutrition and has been associated with the virulence behaviour of E. histolytica. Signalling pathways involved in activation of cytoskeletal dynamics required for phagocytosis remains to be elucidated in this parasite. Our group has been studying initiation of phagocytosis and formation of phagosomes in E. histolytica and have described some of the molecules that play key roles in the process. Here we showed the involvement of non-Dbl Rho Guanine Nucleotide Exchange Factor, EhGEF in regulation of amoebic phagocytosis by regulating activation of EhRho1. EhGEF was found in the phagocytic cups during the progression of cups, until closure of phagosomes, but not in the phagosomes themselves. Our observation from imaging, pull down experiments and down regulating expression of different molecules suggest that EhGEF interacts with EhRho1 and it is required during initiation of phagocytosis and phagosome formation. Also, biophysical, and computational analysis reveals that EhGEF mediates GTP exchange on EhRho1 via an unconventional pathway. In conclusion, we describe a non-Dbl EhGEF of EhRho1 which is involved in endocytic processes of E. histolytica.

Entamoeba histolytica-Gut Microbiota Interaction: More Than Meets the Eye

Amebiasis is a disease caused by the unicellular parasite Entamoeba histolytica. In most cases, the infection is asymptomatic but when symptomatic, the infection can cause dysentery and invasive extraintestinal complications. In the gut, E. histolytica feeds on bacteria. Increasing evidences support the role of the gut microbiota in the development of the disease. In this review we will discuss the consequences of E. histolytica infection on the gut microbiota. We will also discuss new evidences about the role of gut microbiota in regulating the resistance of the parasite to oxidative stress and its virulence.

Revisiting Drug Development Against the Neglected Tropical Disease, Amebiasis

Amebiasis is a neglected tropical disease which is caused by the protozoan parasite Entamoeba histolytica. This disease is one of the leading causes of diarrhea globally, affecting largely impoverished residents in developing countries. Amebiasis also remains one of the top causes of gastrointestinal diseases in returning international travellers. Despite having many side effects, metronidazole remains the drug of choice as an amebicidal tissue-active agent. However, emergence of metronidazole resistance in pathogens having similar anaerobic metabolism and also in laboratory strains of E. histolytica has necessitated the identification and development of new drug targets and therapeutic strategies against the parasite. Recent research in the field of amebiasis has led to a better understanding of the parasite’s metabolic and cellular pathways and hence has been useful in identifying new drug targets. On the other hand, new molecules effective against amebiasis have been mined by modifying available compounds, thereby increasing their potency and efficacy and also by repurposing existing approved drugs. This review aims at compiling and examining up to date information on promising drug targets and drug molecules for the treatment of amebiasis.

Differential Pathogenic Gene Expression of E. histolytica in Patients with Different Clinical Forms of Amoebiasis

The etiological agent of human amoebiasis is the protozoan parasite E. histolytica; the disease is still an endemic infection in some countries and the outcome of infection in the host infection can range from asymptomatic intestinal infection to intestinal or liver invasive forms of the disease. The invasive character of this parasite is multifactorial and mainly due to the differential expression of multiple pathogenic genes. The aim of the present work was to measure the differential expression of some genes in different specimens of patients with amoebic liver abscess (ALA) and specimens of genital amoebiasis (AG) by RT-qPCR. Results show that the expression of genes is different in both types of samples. Almost all studied genes were over expressed in both sets of patients; however, superoxide dismutase (Ehsod), serine threonine isoleucine rich protein (Ehstirp), peroxiredoxin (Ehprd) and heat shock protein 70 and 90 (Ehhsp-70, EHhsp-90) were higher in AG biopsies tissue. Furthermore, cysteine proteinases 5 and 2 (Ehcp5, Ehcp2), lectin (Ehgal/galnaclectin) and calreticulin (Ehcrt) genes directly associate with pathogenic mechanisms of E. histolytica had similar over expression in both AG and ALA samples. In summary the results obtained show that trophozoites can regulate the expression of their genes depending on stimuli or environmental conditions, in order to regulate their pathogenicity and ensure their survival in the host.

The MPO system participates actively in the formation of an oxidative environment produced by neutrophils and activates the antioxidant mechanism of Naegleria fowleri

Naegleria fowleri produces a fatal disease called primary amebic meningoencephalitis (PAM), which is characterized by an extensive inflammatory reaction in the CNS. It is known that the immune response is orchestrated mainly by neutrophils, which activate several defense mechanisms in the host, including phagocytosis, the release of different enzymes such as myeloperoxidase (MPO), and the production of neutrophil extracellular traps. However, the mechanisms by which amoebas evade the neutrophil response are still unknown. In this study, we analyzed the ability of N. fowleri to respond to the stress exerted by MPO. Interestingly, after the interaction of trophozoites with neutrophils, the amoeba viability was not altered; however, ultrastructural changes were observed. To analyze the influence of MPO against N. fowleri and its participation in free radical production, we evaluated its enzymatic activity, expression, and localization with and without the specific 4-aminobenzoic acid hydrazide inhibitor. The production of oxidizing molecules is the principal mechanism used by neutrophils to eliminate pathogens. In this context, we demonstrated an increase in the production of NO, superoxide anion, and reactive oxygen species; in addition, the overexpression of several antioxidant enzymes present in the trophozoites was quantified. The findings strongly suggest that N. fowleri possesses antioxidant machinery that is activated in response to an oxidative environment, allowing it to evade the neutrophil-mediated immune response, which may contribute to the establishment of PAM.

Iron-modulated virulence factors of Entamoeba histolytica

Entamoeba histolytica is a human parasite that causes amoebiasis, a disease that affects the colon and liver and is prevalent worldwide. This protozoan requires a high concentration of iron to survive and reproduce. Iron modulates the expression of parasite virulence factors, including hemoglobinases, hemoglobin-binding proteins and cysteine proteases, as well as proteins related to the amoebic cytoskeleton. This review summarizes the virulence factors that are affected by iron, resulting in upregulation or downregulation of E. histolytica genes. This review also discusses the functionality of iron in the mechanisms of pathogenesis.

The Role of Iron Status in the Early Progression of Metronidazole Resistance in Trichomonas vaginalis Under Microaerophilic Conditions

Trichomonas vaginalis is the etiological agent of human trichomoniasis. Metronidazole has high treatment success rate among trichomoniasis patients. However, metronidazole-resistant T. vaginalis has been reported, contributing in an increasing number of refractory cases. The mechanism of metronidazole resistance in this parasite is still unclear. In the vaginal environment, where the microaerophilic conditions prevail but the iron concentration is constantly fluctuating, the metronidazole resistance profile of T. vaginalis could be altered. In this study, we developed metronidazole-resistant strains of T. vaginalis and evaluate if iron availability is important to the action of the drug. The modulation of iron levels and iron chelation affected the actions of metronidazole both in susceptible and resistant strains. Interestingly, the early resistant strains exhibited minor iron content. The results of transcription analysis in the early resistant strains showed dysregulation in the expression of genes that codified proteins involved in iron transporter, iron-sulfur cluster assemblage, and oxidative stress response, which could not be observed in the late resistant and susceptible strains. Our results indicate that iron content plays an important role in the metronidazole action in T. vaginalis and likely to be related to iron-sulfur proteins involved in metronidazole activation and oxidative stress via Fenton reaction.

Antioxidant enzyme profile of two clinical isolates of Entamoeba histolytica varying in sensitivity to antiamoebic drugs

AIM

To study the sensitivity and antioxidant enzyme response in two clinical isolates of Entamoeba histolytica (E. histolytica) during treatment with antiamoebic drugs, auranofin and metronidazole.

METHODS

E. histolytica were isolated from stool samples and maintained in Robinson’s biphasic culture medium. Clinial isolates were maintained in xenic culture medium, and harvested for determination of minimum inhibitory concentrations to the two antiamoebic drugs, Metronidazole and Auranofin using microtiter plate tests. The percent survival of the two isolates were determined using the trypan blue cell count. Isolate 980 was treated with 70 μmol/L and 2 μmol/L while isolate 989 was treated with 20 μmol/L and 0.5 μmol/L of metronidazole and auranofin respectively for 24 h. Fifty thousand cells of each isolate were harvested after 24 h of treatment for analysis of the mRNA expressions of the antioxidant enzymes, thioredoxin reductase, peroxiredoxin and FeSOD using the specific primers. Cell lysate was used for determination of enzyme activity of thioredoxin reductase by measuring DTNB reduction spectrophotometrically at 412 nm.

RESULTS

Minimum inhibitory concentration of the clinical isolates 980 and 989 for auranofin was 3 μmol/L and 1 μmol/L respectively while that for metronidazole was 80 μmol/L and 30 μmol/L respectively. Thioredoxin reductase, peroxiredoxin and FeSOD expression levels were significantly reduced in the isolate 980 when treated with Auranofin. Metronidazole treatment showed a down regulation of thioredoxin reductase. Though not significant both at the mRNA and the enzyme activity levels. Peroxiredoxin and FeSOD however remained unchanged. Auranofin treatment of isolate 989, showed an upregulation in expression of thioredoxin reductase while Peroxiredoxin and FeSOD did not show any change in expression. Upon treatment with metronidazole, isolate 989 showed an increase in thioredoxin reductase expression. Peroxiredoxin and FeSOD expressions however remain unchanged both at mRNA and enzyme activity level.

CONCLUSION

Clinical isolates from New Delhi NCR region show different sensitivities to antiamoebic drugs. Auranofin is effective against isolate showing higher tolerance to metronidazole as shown by its inhibition in thioredoxin reductase activity.