Induction of resistance to azole drugs in Trypanosoma cruzi.
ABSTRACT: Trypanosoma cruzi is the protozoan parasite that causes Chagas' disease, a frequently fatal illness affecting the heart and gastrointestinal systems. An estimated 16 million to 18 million people in Latin America and 50,000 to 100,000 people in the United States are infected with this pathogen. Treatment options for T. cruzi infections are suboptimal due to the toxicities and limited effectiveness of the available drugs. Azole antimicrobial agents have been discovered to have antitrypanosomal activity by inhibition of ergosterol synthesis. The triazole itraconazole was recently shown to produce a parasitologic cure rate of 53% in chronically infected patients (W. Apt et al., Am. J. Trop. Med. Hyg. 59:133-138, 1998), a result which may lead to more use of this family of drugs for the treatment of T. cruzi infections. In the experiments reported on here, resistance to azoles was induced in vitro by serial passage of mammalian-stage parasites in the presence of fluconazole for 4 months. These parasites were cross resistant to the other azoles, ketoconazole, miconazole, and itraconazole. They remained susceptible to benznidazole and amphotericin B. The azole-resistant phenotype was stable for more than 2 months of in vitro serial passage without fluconazole. In addition, the parasites resisted treatment in mice receiving ketoconazole. The rapid development of azole resistance in T. cruzi in vitro suggests that resistance to azole drugs has the potential to occur in patients and may pose an impediment to the progress being made in the treatment of T. cruzi infection.
Project description:Azoles are commonly used as antifungal drugs or pesticides to control fungal infections in medicine and agriculture. Fungi adapt to azole stress by rapidly activating the transcription of a number of genes, and transcriptional increases in some azole-responsive genes can elevate azole resistance. The regulatory mechanisms that control transcriptional responses to azole stress in filamentous fungi are not well understood. This study identified a bZIP transcription factor, ADS-4 (antifungal drug sensitive-4), as a new regulator of adaptive responses and resistance to antifungal azoles. Transcription of ads-4 in Neurospora crassa cells increased when they were subjected to ketoconazole treatment, whereas the deletion of ads-4 resulted in hypersensitivity to ketoconazole and fluconazole. In contrast, the overexpression of ads-4 increased resistance to fluconazole and ketoconazole in N. crassa. Transcriptome sequencing (RNA-seq) analysis, followed by quantitative reverse transcription (qRT)-PCR confirmation, showed that ADS-4 positively regulated the transcriptional responses of at least six genes to ketoconazole stress in N. crassa. The gene products of four ADS-4-regulated genes are known contributors to azole resistance, including the major efflux pump CDR4 (Pdr5p ortholog), an ABC multidrug transporter (NcAbcB), sterol C-22 desaturase (ERG5), and a lipid transporter (NcRTA2) that is involved in calcineurin-mediated azole resistance. Deletion of the ads-4-homologous gene Afads-4 in Aspergillus fumigatus caused hypersensitivity to itraconazole and ketoconazole, which suggested that ADS-4 is a functionally conserved regulator of adaptive responses to azoles. This study provides important information on a new azole resistance factor that could be targeted by a new range of antifungal pesticides and drugs.
Project description:Several controlled and uncontrolled studies addressing azole antifungal drugs for cutaneous and mucosal leishmaniasis have been published with inconclusive results. We conducted a systematic literature review of studies evaluating the efficacy and toxicity associated with azole therapy for tegumentary leishmaniasis.PRISMA guidelines for systematic reviews and the Cochrane manual were followed, and the review methodology was registered (PROSPERO; CRD42016048668). Sources included the EMBASE, Web of Science, MEDLINE, LILACS, and IBECS databases along with a manual search of references from evaluated studies. Additional resources such as Google Scholar and clinicaltrials.gov were also searched. We included all studies reporting cure rate after cutaneous or mucosal leishmaniasis treatment with systemic azole drugs, regardless of their design. R software was used to estimate global rates of success and adverse events with each drug. The main outcome of interest was clinical cure, defined as complete re-epithelialization of all lesions.A total of 37 studies involving 1259 patients that reported outcomes after fluconazole (9), ketoconazole (14) and itraconazole (15) treatments were included. Only 14 (38%) were randomized controlled trials (RCT). The pooled azole final efficacy rate was 64% (CI95%: 57-70%) for all studies and 60% (CI95%: 50-70%) (p = 0.41) if only RCTs studies were considered. Twenty-four studies were conducted in the Old World and 13 studies in the Americas. The final efficacy rate according to New and Old World were 62% (CI95%: 43-77%) and 66% (CI95%: 58-73%), respectively. The final efficacy rate of azoles according to species were 89% (CI95%: 50-98%) for L. mexicana; 88% for L. infantum (CI95%: 27-99%); 80% for L. donovani; 53% (CI95%: 29-76%) for L. major; 49% for L. braziliensis (CI95%: 21-78%); and 15% (CI95%: 1-84%) for L. tropica. The cure rates were similar among the fluconazole, ketoconazole and itraconazole group arms (p = 0.89), specifically 61% (CI95%: 48-72%), 64% (CI95%: 44-80%) 65% (CI95%: 56-72%), respectively. Adverse events during fluconazole, itraconazole and ketoconazole therapy were reported in 7% (CI95%: 3-14%), 12% (CI95% 8-19%) and 13% (CI95%: 6-29%) of treated patients, respectively, without difference among them (p = 0.35). This systematic review included studies with small samples and both non-comparative and non-randomized studies and the main limitation was the low quality of the available studies.Available evidence suggests that fluconazole, ketoconazole and itraconazole have similar and modest efficacy rates for tegumentary leishmaniasis treatment. There is insufficient evidence to support the exclusive use of azole therapy as a single agent for leishmaniasis treatment.
Project description:The resistance of Candida albicans to azole drugs represents a great global challenge. This study investigates the potential fungicidal effects of atorvastatin (ATO) combinations with fluconazole (FLU), itraconazole (ITR), ketoconazole (KET) and voriconazole (VOR) against thirty-four multidrug-resistant (MDR) C. albicans using checkerboard and time-kill methods. Results showed that 94.12% of these isolates were MDR to ≥ two azole drugs, whereas 5.88% of them were susceptible to azole drugs. The tested isolates exhibited high resistance rates to FLU (58.82%), ITR (52.94%), VOR (47.06%) and KET (35.29%), whereas only three representative (8.82%) isolates were resistant to all tested azoles. Remarkably, the inhibition zones of these isolates were increased at least twofold with the presence of ATO, which interacted in a synergistic (FIC index ≤ 0.5) manner with tested azoles. In silico docking study of ATO and the four azole drugs were performed against the Lanosterol 14-alpha demethylase enzyme (ERG11) of C. albicans. Results showed that the mechanism of action of ATO against C. albicans is similar to that of azole compounds, with a docking score (-4.901) lower than azole drugs (≥5.0) due to the formation a single H-bond with Asp 225 and a pi-pi interaction with Thr 229. Importantly, ATO combinations with ITR, VOR and KET achieved fungicidal effects (≥ 3 Log<sub>10</sub> cfu/ml reduction) against the representative isolates, whereas a fungistatic effect (≤ 3 Log<sub>10</sub> cfu/ml reduction) was observed with FLU combination. Thus, the combination of ATO with azole drugs could be promising options for treating C. albicans infection.
Project description:Reports on associations between azole antifungal medications and acute liver injury are inconsistent and have not been based on liver-related laboratory tests. We evaluated incidence rates of acute liver injury associated with oral azole antifungals.We conducted a cohort study among Kaiser Permanente Northern California members who initiated an oral azole antifungal in an outpatient setting during 2004-2010. We determined development of: (1) liver aminotransferases >200 U/L, (2) severe acute liver injury (coagulopathy with hyperbilirubinemia), and (3) acute liver failure. We calculated incidence rates of endpoints. Cox regression was used to determine whether chronic liver disease was a risk factor for outcomes.Among 195,334 azole initiators (178,879 fluconazole; 14,296 ketoconazole; 1653 itraconazole; 478 voriconazole; 28 posaconazole), incidence rates (events/1000 person-years [95% confidence intervals (CIs)]) of liver aminotransferases >200 U/L were similarly low with fluconazole (13.0 [11.4-14.6]), ketoconazole (19.3 [13.8-26.3]), and itraconazole (24.5 [10.6-48.2]). Rates were higher with voriconazole (181.9 [112.6-278.0]) and posaconazole (191.1 [23.1-690.4]), but comparable. Severe acute liver injury was uncommon with fluconazole (2.0 [1.4-2.7]), ketoconazole (2.9 [1.1-6.3]), and itraconazole (0.0 [0.0-11.2]), but more frequent with voriconazole (16.7 [2.0-60.2]) and posaconazole (93.4 [2.4-520.6]). One patient developed acute liver failure due to ketoconazole. Pre-existing chronic liver disease increased risks of aminotransferases >200 U/L (hazard ratio 4.68 [95% CI, 3.68-5.94]) and severe acute liver injury (hazard ratio 5.62 [95% CI, 2.56-12.35]).Rates of acute liver injury were similarly low for fluconazole, ketoconazole, and itraconazole. Events were more common among voriconazole and posaconazole users but were comparable. Pre-existing chronic liver disease increased risk of azole-induced liver injury.
Project description:Azole antifungal agents, and especially fluconazole, have been used widely to treat oropharyngeal candidiasis in patients with AIDS. An increasing number of cases of clinical resistance against fluconazole, often correlating with in vitro resistance, have been reported. To investigate the mechanisms of resistance toward azole antifungal agents at the molecular level in clinical C. albicans isolates, we focused on resistance mechanisms related to the cellular target of azoles, i.e., cytochrome P450(14DM) (14DM) and those regulating the transport or accumulation of fluconazole. The analysis of sequential isogenic C. albicans isolates with increasing levels of resistance to fluconazole from five AIDS patients showed that overexpression of the gene encoding 14DM either by gene amplification or by gene deregulation was not the major cause of resistance among these clinical isolates. We found, however, that fluconazole-resistant C. albicans isolates failed to accumulate 3H-labelled fluconazole. This phenomenon was reversed in resistant cells by inhibiting the cellular energy supply with azide, suggesting that resistance could be mediated by energy-requiring efflux pumps such as those described as ATP-binding cassette (ABC) multidrug transporters. In fact, some but not all fluconazole-resistant clinical C. albicans isolates exhibited up to a 10-fold relative increase in mRNA levels for a recently cloned ABC transporter gene called CDR1. In an azole-resistant C. albicans isolate not overexpressing CDR1, the gene for another efflux pump named BENr was massively overexpressed. This gene was cloned from C. albicans for conferring benomyl resistance in Saccharomyces cerevisiae. Therefore, at least the overexpression or the deregulation of these two genes potentially mediates resistance to azoles in C. albicans clinical isolates from AIDS patients with oropharyngeal candidiasis. Involvement of ABC transporters in azole resistance was further evidenced with S. cerevisiae mutants lacking specific multidrug transporters which were rendered hypersusceptible to azole derivatives including fluconazole, itraconazole, and ketoconazole.
Project description:Infections due to Candida albicans are usually treated with azole antifungals such as fluconazole, but treatment failure is not uncommon especially in immunocompromised individuals. Relatedly, in vitro studies demonstrate that azoles are nonfungicidal, with continued growth at strain-dependent rates even at high azole concentrations. We hypothesized that upregulation of ERG11, which encodes the azole target enzyme lanosterol demethylase, contributes to this azole tolerance in Candida species. RNA analysis revealed that ERG11 expression in C. albicans is maximal during logarithmic-phase growth and decreases as the cells approach stationary phase. Incubation with fluconazole, however, resulted in a two- to fivefold increase in ERG11 RNA levels within 2 to 3 h, and this increase was followed by resumption of culture growth. ERG11 upregulation also occurred following treatment with other azoles (itraconazole, ketoconazole, clotrimazole, and miconazole) and was not dependent on the specific medium or pH. Within 1 h of drug removal ERG11 upregulation was reversed. Azole-dependent upregulation was not limited to ERG11: five of five ERG genes tested whose products function upstream and downstream of lanosterol demethylase in the sterol biosynthetic pathway were also upregulated. Similarly, ERG11 upregulation occurred following treatment of C. albicans cultures with terbinafine and fenpropimorph, which target other enzymes in the pathway. These data suggest a common mechanism for global ERG upregulation, e.g., in response to ergosterol depletion. Finally, azole-dependent ERG11 upregulation was demonstrated in three additional Candida species (C. tropicalis, C. glabrata, and C. krusei), indicating a conserved response to sterol biosynthesis inhibitors in opportunistic yeasts.
Project description:Isavuconazole is a novel, broad-spectrum, antifungal azole. In order to evaluate its interactions with known azole resistance mechanisms, isavuconazole susceptibility among different yeast models and clinical isolates expressing characterized azole resistance mechanisms was tested and compared to those of fluconazole, itraconazole, posaconazole, and voriconazole. Saccharomyces cerevisiae expressing the Candida albicans and C. glabrata ATP binding cassette (ABC) transporters (CDR1, CDR2, and CgCDR1), major facilitator (MDR1), and lanosterol 14-?-sterol-demethylase (ERG11) alleles with mutations were used. In addition, pairs of C. albicans and C. glabrata strains from matched clinical isolates with known azole resistance mechanisms were investigated. The expression of ABC transporters increased all azole MICs, suggesting that all azoles tested were substrates of ABC transporters. The expression of MDR1 did not increase posaconazole, itraconazole, and isavuconazole MICs. Relative increases of azole MICs (from 4- to 32-fold) were observed for fluconazole, voriconazole, and isavuconazole when at least two mutations were present in the same ERG11 allele. Upon MIC testing of azoles with clinical C. albicans and C. glabrata isolates with known resistance mechanisms, the MIC90s of C. albicans for fluconazole, voriconazole, itraconazole, posaconazole, and isavuconazole were 128, 2, 1, 0.5, and 2 ?g/ml, respectively, while in C. glabrata they were 128, 2, 4, 4, and 16 ?g/ml, respectively. In conclusion, the effects of azole resistance mechanisms on isavuconazole did not differ significantly from those of other azoles. Resistance mechanisms in yeasts involving ABC transporters and ERG11 decreased the activity of isavuconazole, while MDR1 had limited effect.
Project description:Malassezia globosa cytochromes P450 CYP51 and CYP5218 are sterol 14?-demethylase (the target of azole antifungals) and a putative fatty acid metabolism protein (and a potential azole drug target), respectively. Lanosterol, eburicol and obtusifoliol bound to CYP51 with Kd values of 32, 23 and 28??M, respectively, catalyzing sterol 14?-demethylation with respective turnover numbers of 1.7?min(-1), 5.6?min(-1) and 3.4?min(-1). CYP5218 bound a range of fatty acids with linoleic acid binding strongest (Kd 36??M), although no metabolism could be detected in reconstitution assays or role in growth on lipids. Clotrimazole, fluconazole, itraconazole, ketoconazole, voriconazole and ketaminazole bound tightly to CYP51 (Kd???2 to 11?nM). In contrast, fluconazole did not bind to CYP5218, voriconazole and ketaminazole bound weakly (Kd ~107 and ~12??M), whereas ketoconazole, clotrimazole and itraconazole bound strongest to CYP5218 (Kd ~1.6, 0.5 and 0.4??M) indicating CYP5218 to be only a secondary target of azole antifungals. IC50 determinations confirmed M. globosa CYP51 was strongly inhibited by azole antifungals (0.15 to 0.35??M). MIC100 studies showed itraconazole should be considered as an alternative to ketoconazole given the potency and safety profiles and the CYP51 assay system can be used in structure-activity studies in drug development.
Project description:Aspergillus fumigatus sterol 14-? demethylase (CYP51) isoenzymes A (AF51A) and B (AF51B) were expressed in Escherichia coli and purified. The dithionite-reduced CO-P450 complex for AF51A was unstable, rapidly denaturing to inactive P420, in marked contrast to AF51B, where the CO-P450 complex was stable. Type I substrate binding spectra were obtained with purified AF51B using lanosterol (K(s), 8.6 ?M) and eburicol (K(s), 22.6 ?M). Membrane suspensions of AF51A bound to both lanosterol (K(s), 3.1 ?M) and eburicol (K(s), 4.1 ?M). The binding of azoles, with the exception of fluconazole, to AF51B was tight, with the K(d) (dissociation constant) values for clotrimazole, itraconazole, posaconazole, and voriconazole being 0.21, 0.06, 0.12, and 0.42 ?M, respectively, in comparison with a K(d) value of 4 ?M for fluconazole. Characteristic type II azole binding spectra were obtained with AF51B, whereas an additional trough and a blue-shifted spectral peak were present in AF51A binding spectra for all azoles except clotrimazole. This suggests two distinct azole binding conformations within the heme prosthetic group of AF51A. All five azoles bound relatively weakly to AF51A, with K(d) values ranging from 1 ?M for itraconazole to 11.9 ?M for fluconazole. The azole binding properties of purified AF51A and AF51B suggest an explanation for the intrinsic azole (fluconazole) resistance observed in Aspergillus fumigatus.
Project description:Purified Candida albicans sterol 14-? demethylase (CaCYP51) bound the CYP51 substrates lanosterol and eburicol, producing type I binding spectra with K(s) values of 11 and 25 ?M, respectively, and a K(m) value of 6 ?M for lanosterol. Azole binding to CaCYP51 was "tight" with both the type II spectral intensity (?A(max)) and the azole concentration required to obtain a half-?A(max) being proportional to the CaCYP51 concentration. Tight binding of fluconazole and itraconazole was confirmed by 50% inhibitory concentration determinations from CYP51 reconstitution assays. CaCYP51 had similar affinities for clotrimazole, econazole, itraconazole, ketoconazole, miconazole, and voriconazole, with K(d) values of 10 to 26 ?M under oxidative conditions, compared with 47 ?M for fluconazole. The affinities of CaCYP51 for fluconazole and itraconazole appeared to be 4- and 2-fold lower based on CO displacement studies than those when using direct ligand binding under oxidative conditions. Econazole and miconazole were most readily displaced by carbon monoxide, followed by clotrimazole, ketoconazole, and fluconazole, and then voriconazole (7.8 pmol min(-1)), but itraconzole could not be displaced by carbon monoxide. This work reports in depth the characterization of the azole binding properties of wild-type C. albicans CYP51, including that of voriconazole, and will contribute to effective screening of new therapeutic azole antifungal agents. Preliminary comparative studies with the I471T CaCYP51 protein suggested that fluconazole resistance conferred by this mutation was through a combination of increased turnover, increased affinity for substrate, and a reduced affinity for fluconazole in the presence of substrate, allowing the enzyme to remain functionally active, albeit at reduced velocity, at higher fluconazole concentrations.