Comparative proteomics study on meglumine antimoniate sensitive and resistant Leishmania tropica isolated from Iranian anthroponotic cutaneous leishmaniasis patients

The potential role of protein disulfide isomerases (PDIs) during parasitic infections: a focus on Leishmania spp

Leishmaniasis is a group of vector-borne diseases caused by intracellular protozoan parasites belonging to the genus Leishmania. Leishmania parasites can employ different and numerous sophisticated strategies, including modulating host proteins, cell signaling, and cell responses by parasite proteins, to change the infected host conditions to favor the parasite persistence and induce pathogenesis. In this sense, protein disulfide isomerases (PDIs) have been described as crucial proteins that can be modulated during leishmaniasis and affect the pathogenesis process. The effect of modulated PDIs can be investigated in both aspects, parasite PDIs and infected host cell PDIs, during infection. The information concerning PDIs is not sufficient in parasitology; however, this study aimed to provide data regarding the biological functions of such crucial proteins in parasites with a focus on Leishmania spp. and their relevant effects on the pathogenesis process. Although there are no clinical trial vaccines and therapeutic approaches, highlighting this information might be fruitful for the development of novel strategies based on PDIs for the management of parasitic diseases, especially leishmaniasis.

Identification of protein profile in metacyclic and amastigote-like stages of Leishmania tropica: a proteomic approach

Leishmaniasis is a tropical disease that leads to various clinical phenotypes. This study aimed to investigate protein expression changes in metacyclic and amastigote-like stages of L. tropica isolated from Iranian cutaneous leishmaniasis patients. Isolated samples were cultured and species type identified using PCR–RFLP technique. The promastigotes were grown in RPMI1640 media and differentiated to metacyclic and amastigote-like forms, followed by the extracted proteins of both successive stages carried out for proteomics and bioinformatics analysis. Using SWATH-MS quantitative proteomics technique, a total 176 and 155 distinct proteins were identified in metacyclic and axenic amastigote stages, respectively. Of these, 65 proteins were altered significantly (p-value < 0.05 and fold change ≥ 2) between studied stages. Several gene ontology (GO) categories were enriched for biological process during conversion of metacyclic promastigotes into amastigote-like, which “metabolic process” (GO: 0044281, P-Value: 6.52e-5), and “translation” (GO: 0006412, p-value: 5.01e–14) were disclosed as the top category in up and down-regulated proteins, respectively. Also, the KEGG pathway analysis indicated “metabolic pathways” and “ribosome” term as the most important pathways in up and down-regulated proteins, respectively. According to protein interaction network analysis, enolase (ENOL) has been detected as main hub proteins during differentiation, followed by Putative NADH-dependent fumarate reductase (LmjF.35.1180) and 40S ribosomal protein S2 (LmjF.32.0450). Overall, protein changes possibly play important roles in L. tropica biology. Anabolic pathways were down-regulated, whereas catabolic pathways were up-regulated during L. tropica differentiation. These protein expression changes could provide parasite survival in host macrophages, and could use as novel potential drug and vaccine targets for leishmaniasis.

Graphical Abstract

Trypanothione Reductase Gene Mutations in Meglumine Antimoniate Resistant Isolates from Cutaneous Leishmaniasis Patients Using Molecular Dynamics Method

Background:

In this study, mutations in the tripanothion reductase of Leishmania tropica isolated from Iran was investigated using sequencing and simulation of the enzyme by the molecular dynamic method.

Methods:

Fifteen susceptible and 15 clinical resistant L. tropica specimens were collected from skin lesions from different regions of Iran in 2017. After DNA extraction, trypanothione reductase (TRYR or TPR), gene fragment was amplified using PCR and sequencing methods. In the case of structural mutations, the components were simulated by molecular dynamics using the GROMACS software.

Results:

Some structural mutations were observed in 9 amino acids surrounding the active site of the TRYR gene of L. tropica with three-dimensional trypanothione reductase alteration.

Conclusion:

Change in the active site of TRYR of L. tropica, could probably contribute to the development of resistant L. tropica to glucantime. Because of the likely occurrence of mutations in glucantime as well as the ease of development of L. tropica resistant populations, more samples are needed to demonstrate the relationship between mutations in this enzyme and clinical resistance to glucantime. On the other hand, it is recommended that enzymatic studies be performed to confirm the role of mutation in the function and expression of trypanothione reductase in glucantime resistant and susceptible populations.

Experimental Strategies to Explore Drug Action and Resistance in Kinetoplastid Parasites

Kinetoplastids are the causative agents of leishmaniasis, human African trypanosomiasis, and American trypanosomiasis. They are responsible for high mortality and morbidity in (sub)tropical regions. Adequate treatment options are limited and have several drawbacks, such as toxicity, need for parenteral administration, and occurrence of treatment failure and drug resistance. Therefore, there is an urgency for the development of new drugs. Phenotypic screening already allowed the identification of promising new chemical entities with anti-kinetoplastid activity potential, but knowledge on their mode-of-action (MoA) is lacking due to the generally applied whole-cell based approach. However, identification of the drug target is essential to steer further drug discovery and development. Multiple complementary techniques have indeed been used for MoA elucidation. In this review, the different 'omics' approaches employed to define the MoA or mode-of-resistance of current reference drugs and some new anti-kinetoplastid compounds are discussed.

Comparative Two-dimensional Gel Electrophoresis Maps for Amastigote-like Proteomes of Iranian Leishmania Tropica and Leishmania Major Isolates

BACKGROUND

Leishmania major and Leishmania tropica are the main causative agents of cutaneous leishmaniasis. Proteomics as a novel approaches could be used to evaluate protein expression levels in different stages of Leishmania species. We compare the protein contents of amastigote-like forms in L. tropica and L. major using two-dimensional gel electrophoresis (2-DE) and bioinformatics methods.

MATERIALS AND METHODS

Leishmania parasites were isolated from the lesions of Iranian patients and identified using restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR). Five isolates of each two species were cultured in specific media to obtain amastigote-like forms to be prepared for proteomics study. Total protein contents were separated using 2-DE. The gels were stained by silver nitrate and scan was imaged. The protein spots with different expression changes in each gel were analyzed using Progenesis SameSpots software.

RESULTS

A total of 354 protein spots were detected in both amastigote-like forms. Comparative analysis of protein spots with different expressions in the two amastigote-like form species showed 173 highly expressed spots of which 74 L. tropica and 99 L. major proteins were spotted with fold≥2. Also, 16 and 20 new protein spots were uniquely found in L. tropica and L. major, respectively. Clustering of different detected proteins using correlation analysis divided the proteins into two clusters based on their expression level. Furthermore, clustering results were confirmed by principal component analysis.

CONCLUSION

Using proteomics methods specially 2-DE and statistical analysis demonstrated significant changes in protein expression levels in amastigote-like forms of L. tropica and L. major isolates.

Gene expression analysis of antimony resistance in Leishmania tropica using quantitative real-time PCR focused on genes involved in trypanothione metabolism and drug transport

Pentavalent antimonials remain the treatment of choice for all the clinical forms of leishmaniasis. The increasing rates of antimony resistance are becoming a serious health problem in treatment of anthroponotic cutaneous leishmaniasis (ACL). Accordingly, unraveling molecular markers is crucial for improving medication strategies and monitoring of drug-resistant parasites. Different studies have suggested the importance of genes involved in trypanothione metabolism and drug transport. In this regard, present study was designed to investigate the RNA expression level of five genes including γ-GCS, ODC, TRYR (involved in trypanothione metabolism), AQP1 (acts in drug uptake) and MRPA (involved in sequestration of drug) in sensitive and resistant Leishmania tropica isolates. Seven antimony-resistant and seven antimony-sensitive L. tropica clinical isolates were collected from ACL patients. Drug sensitivity test was performed on the samples as well as reference strains; afterwards, gene expression analysis was performed on clinical isolates by quantitative real-time PCR. The results revealed that the average expression level of AQP1 gene was decreased (0.47-fold) in resistant isolates compared to sensitive ones whereas MRPA (2.45), γ-GCS (2.1) and TRYR (1.97) was upregulated in resistant isolates. The average expression of ODC (1.24-fold) gene was not different significantly between sensitive and resistant isolates. Our findings suggest that AQP1, MRPA, GSH1 and TRYR can be considered as potential molecular markers for screening of antimony resistance in some L. tropica clinical isolates.

Expression analysis of activated protein kinase C gene (LACK1) in antimony sensitive and resistant Leishmania tropica clinical isolates using real-time RT-PCR

BACKGROUND

Resistance to pentavalent antimonial drugs has become a serious problem in the treatment of cutaneous leishmaniasis in some endemic areas. Investigations on molecular markers involved in drug resistance are essential for monitoring of the disease. Leishmania-activated C kinase gene (LACK1) is involved in multiple central processes such as signal transduction. According to the probable role of the LACK1 gene in antimony resistance, we used real-time reverse transcription-polymerase chain reaction (PCR) to investigate the expression of this gene in clinical L. tropica strains, which were resistant or sensitive to meglumine antimoniate.

METHODS

We analyzed the expression level of LACK in 18 sensitive and 14 resistant L. tropica isolates collected from patients with anthroponotic cutaneous leishmaniasis. After cDNA synthesis, gene expression analysis was performed by quantitative real-time PCR using SYBR Green. In addition, the full length of the LACK gene from six reference strains was cloned and sequenced then deposited in the NCBI database to confirm our strains.

RESULTS

Real-time reverse transcription-PCR revealed that the average RNA expression level of LACK in isolates from unresponsive and responsive patients were 0.479 and 4.583, respectively, and expression of LACK was significantly downregulated (9.56-fold) in resistant isolates compared to sensitive ones.

CONCLUSION

Results of the present study suggest the probable role of the LACK gene in antimony resistance. Moreover, it can be considered as a potential marker for monitoring antimony resistance in clinical isolates. However, further studies are required to exploit the biological functions of it in antimony resistance.

Overexpression of ubiquitin and amino acid permease genes in association with antimony resistance in Leishmania tropica field isolates

The mainstay therapy against leishmaniasis is still pentavalent antimonial drugs; however, the rate of antimony resistance is increasing in endemic regions such as Iran. Understanding the molecular basis of resistance to antimonials could be helpful to improve treatment strategies. This study aimed to recognize genes involved in antimony resistance of Leishmania tropica field isolates. Sensitive and resistant L. tropica parasites were isolated from anthroponotic cutaneous leishmaniasis patients and drug susceptibility of parasites to meglumine antimoniate (Glucantime®) was confirmed using in vitro assay. Then, complementary DNA-amplified fragment length polymorphism (cDNA-AFLP) and real-time reverse transcriptase-PCR (RT-PCR) approaches were utilized on mRNAs from resistant and sensitive L. tropica isolates. We identified 2 known genes, ubiquitin implicated in protein degradation and amino acid permease (AAP3) involved in arginine uptake. Also, we identified 1 gene encoding hypothetical protein. Real-time RT-PCR revealed a significant upregulation of ubiquitin (2.54-fold), and AAP3 (2.86-fold) (P<0.05) in a resistant isolate compared to a sensitive one. Our results suggest that overexpression of ubiquitin and AAP3 could potentially implicated in natural antimony resistance.

Identification of antimony resistance markers in Leishmania tropica field isolates through a cDNA-AFLP approach

Pentavalent antimonial compounds have been the first line therapy for leishmaniasis; unfortunately the rate of treatment failure of anthroponotic cutaneous leishmaniasis (ACL) is increasing due to emerging of drug resistance. Elucidation of the molecular mechanisms operating in antimony resistance is critical for development of new strategies for treatment. Here, we used a cDNA-AFLP approach to identify gene(s) which are differentially expressed in resistant and sensitive Leishmania tropica field isolates. We identified five genes, aquaglyceroporin (AQP1) acts in drug uptake, ATP-binding cassette (ABC) transporter (MRPA) involved in sequestration of drug, phosphoglycerate kinase (PGK) implicated in glycolysis metabolism, mitogen activated protein kinase (MAPK) and protein tyrosine phosphatase (PTP) responsible for phosphorylation pathway. The results were confirmed using real time RT-PCR which revealed an upregulation of MRPA, PTP and PGK genes and downregulation of AQP1 and MAPK genes in resistant isolate. To our knowledge, this is the first report of identification of PTP and PGK genes potentially implicated in resistance to antimonials. Our findings support the idea that distinct biomolecules might be involved in antimony resistance in L. tropica field isolates.