The effects of phosphanegold(I) thiolates on the biological properties of Acanthamoeba castellanii belonging to the T4 genotype
© The Author(s). 2017
Received: 17 November 2016
Accepted: 9 February 2017
Published: 3 April 2017
Gold compounds have shown promise in the treatment of non-communicable diseases such as rheumatoid arthritis and cancer, and are considered of value as anti-microbial agents against Gram-negative and Gram-positive bacteria, and have anti-parasitic properties against Schistosoma mansoni, Trypanosoma brucei, Plasmodium falciparum, Leishmania infantinum, Giardia lamblia, and Entamoeba histolytica. They are known to affect enzymatic activities that are required for the cellular respiration processes.
Anti-amoebic effects of phosphanegold(I) thiolates were tested against clinical isolate of A. castellanii belonging to the T4 genotype by employing viability assays, growth inhibition assays, encystation assays, excystation assays, and zymographic assays.
The treatment of A. castellanii with the phosphanegold(I) thiolates tested (i) had no effect on the viability of A. castellanii as determined by Trypan blue exclusion test, (ii) did not affect amoebae growth using PYG growth medium, (iii) did not inhibit cellular differentiation, and (iv) had no effect on the extracellular proteolytic activities of A. castellanii.
Being free-living amoeba, A. castellanii is a versatile respirator and possesses respiratory mechanisms that adapt to various aerobic and anaerobic environments to avoid toxic threats and adverse conditions. For the first time, our findings showed that A. castellanii exhibits resistance to the toxic effects of gold compounds and could prove to be an attractive model to study mechanisms of metal resistance in eukaryotic cells.
KeywordsAcanthamoeba Gold compounds Cytotoxicity assays Zymography Encystation Excystation
Acanthamoeba is a free living pathogenic protist that can cause cutaneous lesions, a vision-threatening keratitis, and a rare but fatal infection of the brain, identified as granulomatous amoebic encephalitis [1–4]. Acanthamoeba keratitis infection is of explicit concern given the rise in the number of wearers of contact lenses worldwide, a population susceptible to this infection. Treatment involves hourly topical application of a mixture of drugs comprising of polyhexamethylene biguanide or chlorhexidine digluconate together with propamidine isethionate or hexamidine. Moreover, chloramphenicol or neomycin is also given to prevent mixed bacterial infection . Treatment lasts for several months [5, 6]. Furthermore, the treatment is problematic and cumbersome, in part due to the ability of this facultative parasite to go through phenotypic interchanging into a double-walled cyst form, which is impervious to many anti-microbial drugs and harsh conditions, and an active vegetative trophozoite stage that is more vulnerable to anti-microbials, often leading to recurrence of infection [7–9]. Consequently, there is a crucial need to develop anti-microbials targeting both the cyst stage and the trophozoite stage of Acanthamoeba.
All chemicals were purchased from Sigma Labs (Poole, Dorset, England), unless otherwise stated. The phosphanegold(I) thiolates, AAu1–AAu3, were prepared and characterised using methodology as previously described . The molecular structures and weights of AAu1–AAu3 are given in Fig. 1. A stock solution (10 mM) was prepared and stored at −20 °C until used. Control cultures contained the same volume of respective solvents.
Cultures of A. castellanii
A. castellanii belonging to the T4 genotype (ATCC 50492) is a clinical isolate that was initially isolated from a keratitis patient and grown in 75 cm2 tissue culture flasks in 10 mL at a cell density of 5×105 cells per mL in PYG medium [proteose peptone 0.75% (w/v), yeast extract 0.75% (w/v) and glucose 1.5% (w/v)] without shaking at 30 °C as described previously [22, 23]. At this cell density, parasites reach confluency within 48 h. Active trophozoites are attached to the bottom of the flasks while any dormant cells are non-adherent in the supernatant. To obtain trophozoites, supernatant was aspirated and 10 mL of RPMI-1640 was added. Next, flasks were placed on ice for 20 min to detach bound amoebae followed by gentle tapping and observed under the inverted microscope to ensure amoebae detachment had occurred. Finally, the parasites were collected in 50 mL tubes, followed by centrifugation at 1500×g for 5 min, resuspended in one mL of RPMI-1640 and used in experiments.
To determine amoebicidal activity of AAu1–AAu3, A. castellanii trophozoites (5 × 105 amoebae/0.5 mL/well) were incubated in RPMI-1640 with various concentrations of AAu1–AAu3 in 24-well plates as described previously [20–24]. Plates were incubated at 37 °C for 24 h. Following this incubation, amoebae viability was determined by adding 0.1% Trypan blue and number of live (non-stained) and dead (stained) A. castellanii were enumerated using a haemocytometer. The counts from A. castellanii incubated with RPMI-1640 alone, and the solvent alone (chloroform) were used as controls. Data are represented as the mean ± standard error of at least three independent experiments. To determine whether the effects of AAu1–AAu3 are irreversible, A. castellanii, 5 × 105 trophozoites, were incubated with AAu1–AAu3 for 24 h as described above. After this incubation, amoebae were centrifuged for 10 min at 1,000xg and supernatant was aspirated, followed by the addition of 0.5 mL of RPMI-1640. This process was repeated 3X to remove extracellular AAu1–AAu3. Finally, A. castellanii were re-suspended in PYG as a food source and inoculated in 24-well plates. Plates were incubated at 37 °C for up to 72 h and re-emergence of trophozoites was considered as viable amoebae, and absence of trophozoites was considered as non-viable amoebae. In some experiments, plates were incubated for up to a week to observe the emergence of viable trophozoites.
To determine the effects of AAu1–AAu3 on the growth of A. castellanii, assays were performed by exposing 5 × 105 trophozoites to different concentrations of AAu1–AAu3 in growth medium, i.e., PYG in 24-well plates. Next, the plates were incubated at 30 °C for 48 h. For controls, 5 × 105 trophozoites were inoculated in 100% PYG medium, 100% non-nutritive PBS and respective amounts of solvents plus PYG medium and incubated in the above-mentioned conditions. After this incubation, the number of amoebae was determined by haemocytometer counting. All experiments were performed at least three times in duplicate.
Preparation of A. castellanii cysts and excystation assays
To prepare A. castellanii cysts, encystation was induced by inoculating 5 × 106 A. castellanii trophozoites onto non-nutrient agar plates [prepared using 3% (w/v) bacteriological agar] and incubating at 30 °C for up to 14 days . Food deprivation resulted in trophozoite transformation into the cyst form. Next, 10 mL of PBS was added to each plate. Cysts were then gently scraped off the agar surface using a cell scraper. PBS containing cysts was collected in 15 mL tube and centrifuged at 3000 × g for 10 min to pellet cysts. The supernatant was aspirated and cysts resuspended in RPMI-1640, enumerated using a haemocytometer and used in experiments. To determine the effects of AAu1–AAu3 on excystation, assays were performed by inoculating A. castellanii cysts (5 × 104 cysts per mL PYG per well of 24-well plates) in the presence or absence of different concentrations of AAu1–AAu3. Plates were incubated at 30 °C and observed every 24 h under the inverted microscope for the emergence of viable trophozoites for up to 72 h.
Encystation assays were performed as described previously . Briefly, 2 × 106 amoebae were incubated in 0.5 mL of PBS containing 50 mM MgCl2 and 10% glucose (i.e., encystation trigger) per well of 24-well plates. The plates were incubated at 30 °C for 72 h without shaking. After this incubation, amoebae viability was quantified using a haemocytometer via Trypan blue exclusion assay. Next, SDS (0.5% final conc.) was added for 10 min. At this concentration, SDS solubilizes amoebae trophozoites but not cysts. Finally cysts were enumerated using a haemocytometer and used in experiments. To determine the effects of AAu1–AAu3 on encystation, assays were performed in the presence of different concentrations of drugs. Briefly 2 × 106 amoebae were incubated in PBS with various concentrations of drugs and incubated at room temperature for 20 min. Following this, 50 mM MgCl2 and 10% glucose was added as a trigger for encystation and plates were incubated at 30 °C for 72 h. Finally, parasites counts were determined using a haemocytometer. Amoebae incubated without inhibitors and encystation trigger were used as controls. The respective amounts of solvents were used as solvent controls.
The extracellular proteolytic activities of Acanthamoeba were determined using zymographic assays as previously described . Briefly, A. castellanii were incubated in the presence or absence of various concentrations of AAu1–AAu3 for 24 h. Next day, cell-free supernatants (CM, conditioned medium) were collected by centrifugation. The CM were electrophoresed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) containing gelatin (2 mg/mL) as a protease substrate as previously described . Following electrophoresis, gels were washed in 2.5% Triton X-100 (w/v) for 60 min, then incubated in developing buffer (50 mM Tris–HCl, pH 7.5, containing 10 mM CaCl2) at 37 °C overnight. Next day, gels were stained with Coomassie Brilliant Blue. Areas of gelatin digestion were visualised as non-staining regions in the gel.
Statistical significance for differences was evaluated using 2 sample t-test; two-tailed distribution, comparing the mean of two independent groups in Excel. A critical value of P < 0.05 was used for all analysis. For graphical representation of the data, y-axis error basis indicate the standard error of the data for each point on the figure.
Phosphanegold(I) thiolates, AAu1–AAu3, did not affect A. castellanii trophozoites viability
Phosphanegold(I) thiolates, AAu1–AAu3, did not exhibit amoebistatic effects against A. castellanii trophozoites
Phosphanegold(I) thiolates, AAu1–AAu3, did not affect excystation in A. castellanii
Phosphanegold(I) thiolates, AAu1–AAu3, did not affect encystation in A. castellanii
Phosphanegold(I) thiolates, AAu1–AAu3, did not effect A. castellanii extracellular proteolytic activity
Gold(I) complexes have potential medical applications [10, 11]. Thus, gold(I) derivatives have been explored for anti-tumour activity [16, 17] as well as anti-parasitic  and anti-microbial agents [19–21]. Gold has properties such as high thermal/chemical stability and resistant to oxidation, yet is mechanically soft with high electric conductivity enabling its applications in several disciplines ranging from healthcare to engineering. For example, gold compounds have been successfully used in the treatment of rheumatoid arthritis and are shown to slow down the progression of rheumatic disorder [27, 28]. Many of the biologically active gold(I) compounds contain thiolates and/or phosphane as ligands [10, 11, 16, 17, 21] and inhibit thioredoxin reductase [29, 30]. More recently, it is shown that the gold(I) compounds exhibit anti-parasitic activities such as targeting Schistosoma mansoni , Trypanosoma brucei , Echinococcus granulosus , Plasmodium falciparum , Leishmania infantinum  Giardia lamblia , and Entamoeba histolytica . Furthermore, it was shown that gold(I) compounds target E. histolytica by inhibiting thioredoxin reductase activity . The anti-bacterial activities of gold(I) compounds showed that these compounds affect Clostridium difficile and Treponema denticola by disrupting the selenium metabolism by targeting selenoproteins required for energy [38, 39], while Staphylococcus aureus growth is inhibited by gold(I) compounds . Other studies proposed targets including the inhibition of mitochondrial enzymes and of the proteasome compounds [41, 42] and the inhibition of the zinc finger protein poly (adenosine diphosphate (ADP) ribose) polymerase 1 (PARP-1) [43, 44]. Notably, PARP’s are crucial proteins that are important in drug resistance in cancer as they play an essential role in DNA repair by detecting DNA strand breaks and catalyzing poly (ADP-ribosylation) . Other biological targets of gold(I) compounds with prokaryotic and eukaryotic cells are yet to be discovered.
Based on these findings, it was logical to test the anti-amoebic effects of phosphanegold(I) thiolates, AAu1–AAu3, on the biological properties of A. castellanii belonging to the T4 genotype. The results revealed that AAu1–AAu3 did not show any effects on the biological properties of the parasite. This was determined by performing (i) viability assays using Trypan blue exclusion test, (ii) amoebae growth using PYG growth medium, (iii) cellular differentiation using encystation and excystation assays and (iv) enzymatic activities by determining extracellular proteases profiles. The reported results are highly reproducible and consistently showed that AAu1–AAu3 do not affect the biological properties of A. castellanii. There could be several explanations for the findings observed in this study. For example, the mode of action of gold requires it to enter the cell, via the hydrophobic cell membrane, to produce damage, most likely through transmembrane proteins that may be different in A. castellanii. Notably, gold(I) compounds are well known to affect enzymatic activities that are required for the cellular respiration processes. Being one of the most ubiquitous protists, the natural habitat of Acanthamoeba is the environment with diverse respiratory mechanisms and wide exposure to metals, thus Acanthamoeba is likely to possesses mechanisms to inhibit the toxic effects exerted by metals. A. castellanii is well known as a versatile respirator and possesses several mitochondria per cell and respiratory mechanisms that adapt to various aerobic and anaerobic environments to dodge toxic threat and adverse conditions. It is possible that the toxic effects of metals are compensated by switching the type of respiration or the use of an efflux system to rid toxic metals. Future studies are needed to test higher concentration of phosphanegold(I) thiolates compounds and/or in combining phosphanegold(I) thiolates with current anti-amoeba drugs, such as chlorhexidine to determine their improved efficacy against pathogenic Acanthamoeba. Overall, these findings suggest that Acanthamoeba exhibits resistance to toxic effects of gold(I) compounds and could prove to be an attractive model to study mechanisms of metal resistance in eukaryotic cells.
Although gold compounds have shown promise in the treatment of non-communicable diseases such as rheumatoid arthritis, anti-tumour activities, as well as antibacterial properties, and anti-parasitic properties against protozoan pathogens, T. brucei, P. falciparum, L. infantinum, G. lamblia, and E. histolytica, often by targeting respiration pathways, our studies demonstrated that A. castellanii exhibited resistance against their toxic effects. The gold derivatives tested had no effect on the viability of A. castellanii, did not inhibit amoebae growth, or cellular differentiation processes or extracellular proteolytic activities. As Acanthamoeba is a versatile respirator, it can adapt to various aerobic and anaerobic environments to avoid toxic threats. Our studies suggest that Acanthamoeba could prove to be a useful model to study mechanisms of metal resistance in eukaryotic cells.
This work was supported by the University Research Grant Scheme No. 2015-03, Sunway University, Malaysia.
Availability of data and materials
For data requests, please contact Distinguished Professor Naveed Ahmed Khan (Naveed5438@gmail.com).
RS conceived the study. CIY and ERTT synthesised and characterised AAu1–AAu3. FA and NAK carried out all biological experiments. FA and RS collected relevant literature and wrote the first draft. NAK corrected the original manuscript. All authors approved the final manuscript.
The authors declare that they have no competing interests.
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- Khan NA. Pathogenesis of Acanthamoeba infections. Microb Pathogen. 2003;34:277–85.View ArticleGoogle Scholar
- Khan NA. Acanthamoeba: biology and increasing importance in human health. FEMS Microbiol Rev. 2006;30:564–95.View ArticlePubMedGoogle Scholar
- Visvesvara GS, Moura H, Schuster FL. Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea. FEMS Immunol. Med. Microbiol. 2007;50:1–26.Google Scholar
- Marciano-Cabral F, Cabral G. Acanthamoeba spp. as agents of disease in humans. Clin Microbiol Rev. 2003;16:273–307.View ArticlePubMedPubMed CentralGoogle Scholar
- Perez-Santonja JJ, Kilvington S, Hughes R, Tufail A, Metheson M, Dart JKG. Persistently culture positive Acanthamoeba keratitis: in vivo resistance and in vitro sensitivity. Ophthalmology. 2003;110:1593–600.View ArticlePubMedGoogle Scholar
- Ficker L, Seal D, Warhurst D, Wright P. Acanthamoeba keratitis: resistance to medical therapy. Eye. 1990;4:835–8.View ArticlePubMedGoogle Scholar
- Aksozek A, McClellan K, Howard K, Niederkorn JY, Alizadeh H. Resistance of Acanthamoeba castellanii cysts to physical, chemical, and radiological conditions. J Parasitol. 2002;88(3):621–3.View ArticlePubMedGoogle Scholar
- Lloyd D, Turner NA, Khunkitti W, Hann AC, Furr JR, Russell AD. Encystation in Acanthamoeba castellanii: development of biocide resistance. J Eukaryot Microbiol. 2001;48(1):11–6.View ArticlePubMedGoogle Scholar
- Turner NA, Russel AD, Furr JR, Lloyd D. Emergence of resistance to biocides during differentiation of Acanthamoeba castellanii. J Antimicrob Chem. 2000;46:27–34.View ArticleGoogle Scholar
- Ott I. On the medicinal chemistry of gold complexes as anticancer drugs. Coord Chem Rev. 2009;253:1670–81.View ArticleGoogle Scholar
- Berners-Price SJ, Filipovska A. Gold compounds as therapeutic agents for human diseases. Metallomics. 2011;3:863–73.View ArticlePubMedGoogle Scholar
- Yeo CI, Ooi KK, Akim AM, Ang KP, Fairuz ZA, Halim SNBA, Ng SW, Seng H-L, Tiekink ERT. The influence of R substituents in triphenylphosphinegold(I) carbonimidothioates, Ph3PAu[SC(OR) = NPh] (R = Me, Et and iPr), upon in vitro cytotoxicity against the HT-29 colon cancer cell line and upon apoptotic pathways. J Inorg Biochem. 2013;127:24–38.View ArticlePubMedGoogle Scholar
- Ooi KK, Yeo CI, Ang K-P, Akim AM, Cheah Y-K, Halim SNA, Seng H-L, Tiekink ERT. Phosphanegold(I) thiolates, Ph3PAu[SC(OR) = NC6H4Me-4] for R = Me, Et and iPr, induce apoptosis, cell cycle arrest and inhibit cell invasion of HT-29 colon cancer cells through modulation of the nuclear factor-κB activation pathway and ubiquitination. J Biol Inorg Chem. 2015;20:855–73.View ArticlePubMedGoogle Scholar
- Ooi KK, Yeo CI, Mahandaran T, Ang KP, Akim AM, Cheah Y-K, Seng H-L, Tiekink ERT. G2/M cell cycle arrest on HT-29 cancer cells and toxicity assessment of triphenylphosphanegold(I) carbonimidothioates, Ph3PAu[SC(OR) = NPh], R = Me, Et, and iPr, during zebrafish development. J Inorg Biochem. 2017;166:173-81.
- Yeo CI, Sim JH, Khoo CH, Goh ZJ, Ang KP, Cheah YK, Fairuz ZA, Halim SN, Ng SW, Seng HL, Tiekink ER. Pathogenic Gram-positive bacteria are highly sensitive to triphenylphosphane gold (O-alkylthiocarbamates), Ph3PAu[SC(OR) = N(p-tolyl)] (R = Me, Et and iPr). Gold Bull. 2013;46:145–52.View ArticleGoogle Scholar
- Tiekink ERT. Gold derivatives for the treatment of cancer. Crit Rev Hematol Oncol. 2002;42:225–45.View ArticleGoogle Scholar
- Zou T, Lum CT, Lok C-N, Zhang J-J, Che C-M. Chemical biology of anticancer gold(III) and gold(I) complexes. Chem Soc Rev. 2015;44:8786–801.View ArticlePubMedGoogle Scholar
- Navarro M. Gold complexes as potential anti-parasitic agents. Coord Chem Rev. 2009;253:1619–26.View ArticleGoogle Scholar
- Fillat MF, Gimeno MC, Laguna A, Latorre E, Ortego L, Villacampa MD. Synthesis, structure and bactericide activity of (Aminophosphane) gold(I) Thiolate complexes. Eur J Inorg Chem. 2011;9:1487–95.View ArticleGoogle Scholar
- Ray S, Mohan R, Singh JK, Samantaray MK, Shaikh MM, Panda D, Ghosh P. Anticancer and antimicrobial metallopharmaceutical agents based on palladium, gold, and silver N-heterocyclic carbene complexes. J Am Chem Soc. 2007;129:15042–53.View ArticlePubMedGoogle Scholar
- Glišic BÐ, Djuran MI. Gold complexes as antimicrobial agents: an overview of different biological activities in relation to the oxidation state of the gold ion and the ligand structure. Dalton Trans. 2014;43:5950–69.View ArticlePubMedGoogle Scholar
- Sissons J, Alsam S, Stins M, Ortega-Rivas A, Lorenzo-Morales J, Faull J, Khan NA. Use of In vitro assays to determine effects of human serum in biological characteristics of Acanthamoeba Castellanii. J Clin Microbiol. 2006;44:2595–600.View ArticlePubMedPubMed CentralGoogle Scholar
- Sissons J, Kim KS, Stins M, Jayasekera S, Alsam S, Khan NA. Acanthamoeba castellanii induces host cell death via a phosphatidylinositol 3-kinase-dependent mechanism. Infect Immun. 2005;73:2704–8.View ArticlePubMedPubMed CentralGoogle Scholar
- Siddiqui R, Jarroll EL, Khan NA. Balamuthia mandrillaris: role of galactose in encystment and identification of potential inhibitory targets. Exp Parasitol. 2010;126:22–7.View ArticlePubMedGoogle Scholar
- Dudley R, Jarroll EL, Khan NA. Carbohydrate analysis of Acanthamoeba castellanii. Exp Parasitol. 2009;122:338–43.View ArticlePubMedGoogle Scholar
- Matin A, Stins M, Kim KS, Khan NA. Balamuthia mandrillaris exhibits metalloprotease activities. FEMS Immunol Med Microbiol. 2006;47:83–91.View ArticlePubMedGoogle Scholar
- Shaw III CF. Gold-based therapeutic agents. Chem Rev. 1999;99:2589–600.View ArticleGoogle Scholar
- Kean WF, Kean IRL. linical pharmacology of gold. Inflammopharmacology. 2008;16:112–25.View ArticlePubMedGoogle Scholar
- Bindoli A, Rigobello MP, Scutari G, Gabbiani C, Casini A, Messori L. Thioredoxin reductase: a target for gold compounds acting as potential anticancer drugs. Coord Chem Rev. 2009;253:1692–707.View ArticleGoogle Scholar
- Eisler R. Chrysotherapy: a synoptic review. Inflammation Res. 2003;52:487–501.View ArticleGoogle Scholar
- Kuntz AN, Davioud-Charvet E, Sayed AA, Califf LL, Dessolin J, Amer ESJ, Williams DL. Thioredoxin glutathione reductase from Schistosoma mansoni: an essential parasite enzyme and a key drug target. PLoS Med. 2007;4, e206.View ArticlePubMedPubMed CentralGoogle Scholar
- Lobanov AV, Gromer S, Salinas G, Gladyshev VN. Selenium metabolism in Trypanosoma: characterization of selenoproteomes and identification of a Kinetoplastida-specific selenoprotein. Nucleic Acids Res. 2006;34:4012–24.View ArticlePubMedPubMed CentralGoogle Scholar
- Bonilla M, Denicola A, Novoselov SV, Turanov AA, Protasio A, Izmendi D, Gladyshev VN, Salinas G. Platyhelminth mitochondrial and cytosolic redox homeostasis is controlled by a single thioredoxin glutathione reductase and dependent on selenium and glutathione. J Biol Chem. 2008;283:17898–907.View ArticlePubMedPubMed CentralGoogle Scholar
- Sannella AR, Casini A, Gabbiani C, Messori L, Bilia AR, Vincieri FF, Majori G, Severini C. New uses for old drugs. Auranofin, a clinically established antiarthritic metallodrug, exhibits potent antimalarial effects in vitro: mechanistic and pharmacological implications. FEBS Lett. 2008;582:844–7.View ArticlePubMedGoogle Scholar
- Ilari A, Baiocco P, Messori L, Fiorillo A, Boffi A, Gramiccia M, Di Muccio T, Colotti G. A gold-containing drug against parasitic polyamine metabolism: the X-ray structure of trypanothione reductase from leishmania infantum in complex with auranofin reveals a dual mechanism of enzyme inhibition. Amino Acids. 2012;42:803–11.View ArticlePubMedGoogle Scholar
- Tejman-Yarden N, Miyamoto Y, Leitsch D, Santini J, Debnath A, Gut J, McKerrow JH, Reed SL, Eckman L. A reprofiled drug, auranofin, is effective against metronidazole-resistant Giardia lamblia. Antimicrob Agents Chemother. 2013;57:2029–35.View ArticlePubMedPubMed CentralGoogle Scholar
- Debnath A, Parsonage D, Andrade RM, He C, Cobo ER, Hirata K, Chen S, Garcia-Rivera G, Orozco E, Martinez MB, Gunatilleke SS, Barrios AM, Arkin MR, Poole LB, McKerrow JH, Reed SL. A high-throughput drug screen for Entamoeba histolytica identifies a new lead and target. Nature Med. 2012;18:956–62.View ArticlePubMedPubMed CentralGoogle Scholar
- Jackson-Rosario J, Cowart D, Myers A, Tarrien R, Levine RL, Scott RA, Self WT. Auranofin disrupts selenium metabolism in Clostridium difficile by forming a stable Au-Se adduct. J Biol Inorg Chem. 2009;14:507–19.View ArticlePubMedPubMed CentralGoogle Scholar
- Jackson-Rosario S, Self WT. Inhibition of selenium metabolism in the oral pathogen Treponema denticola. J Bacteriol. 2009;191:4035–40.View ArticlePubMedPubMed CentralGoogle Scholar
- Novelli F, Recine M, Sparatore F, Juliano C. Gold(I) complexes as antimicrobial agents. Farmaco. 1999;54:232–6.View ArticlePubMedGoogle Scholar
- Bertrand B, Casini A. A golden future in medicinal inorganic chemistry: the promise of anticancer gold organometallic compounds. Dalton Trans. 2014;43:4209–19.
- Dalla Via L, Nardon C, Fregona D. Targeting the ubiquitin − proteasome pathway with inorganic compounds to fight cancer: a challenge for the future. Future Med Chem. 2012;4:525–43.View ArticlePubMedGoogle Scholar
- Serratrice M, Edafe F, Mendes F, Scopelliti R, Zakeeruddin SM, Gratzel M, Santos I, Cinellu MA, Casini A. Cytotoxic gold compounds: synthesis, biological characterization and investigation on their inhibition properties of the zinc finger protein PARP-1. Dalton Trans. 2012;41:3287–93.View ArticlePubMedGoogle Scholar
- Mendes F, Groessl M, Nazarov AA, Tsybin YO, Sava G, Santos I, Dyson PJ, Casini A. Metal-based inhibition of poly(ADPribose)polymerase the guardian angel of DNA. J Med Chem. 2011;54:2196–206.View ArticlePubMedGoogle Scholar
- Schreiber V, Dantzer F, Ame JC, De Murcia G. Poly(ADPribose): novel functions for an old molecule. Nat Rev Mol Cell Biol. 2006;7:517–28.View ArticlePubMedGoogle Scholar