Signaling Pathways Governing the Caspofungin Paradoxical Effect in Aspergillus fumigatus

ABSTRACT Aspergillus fumigatus is responsible for a wide range of diseases affecting several million people worldwide. Currently, a few families of antifungals are available to fight aspergillosis, and we are facing a worrisome increase in resistance to azoles, the drugs used for both first-line treatment and prophylaxis of invasive aspergillosis. In this context, some of the latest antifungals, i.e., echinocandins, have gained attention. Even though acquired resistance to echinocandins is yet uncommon in A. fumigatus clinical isolates, some strains exhibit another characteristic that relies on their capacity to grow at suprainhibitory echinocandin concentrations in vitro. This intriguing phenomenon, especially observed with caspofungin and now referred to as the caspofungin paradoxical effect (CPE), relies on molecular mechanisms that were hitherto little understood. Here, we discuss the recent key findings of Valero and colleagues published in mBio (C. Valero, A. C. Colabardini, J. Chiaratto, L. Pardeshi, et al., mBio 11:e00816-20, 2020, https://doi.org/10.1128/mBio.00816-20) that will allow a better understanding of the complex regulatory pathway involved in governing the response of A. fumigatus to caspofungin.

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In VitroAntimicrobial Susceptibility Patterns of Blastocystis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04832-14 ◽

2015 ◽

Vol 59 (8) ◽

pp. 4417-4423 ◽

Cited By ~ 4

Author(s):

Tamalee Roberts ◽

Stephen Bush ◽

John Ellis ◽

John Harkness ◽

Damien Stark

Keyword(s):

Current Treatment ◽

Line Treatment ◽

First Line ◽

Content Type ◽

Treatment Regimens ◽

Drug Treatments ◽

Resistant Strains ◽

Susceptibility Patterns ◽

First Line Treatment

ABSTRACTBlastocystisis the most common human enteric protist with controversial clinical significance. Metronidazole is considered a first-line treatment forBlastocystisinfection; however, there has been increasing evidence for the lack of efficacy of this treatment. Treatment failure has been reported in several clinical cases, and recentin vitrostudies have suggested the occurrence of metronidazole-resistant strains. In this study, we tested 12Blastocystisisolates from 4 commonBlastocystissubtypes (ST1, ST3, ST4, and ST8) against 12 commonly used antimicrobials (metronidazole, paromomycin, ornidazole, albendazole, ivermectin, trimethoprim-sulfamethoxazole [TMP-SMX], furazolidone, nitazoxanide, secnidazole, fluconazole, nystatin, and itraconazole) at 10 different concentrationsin vitro. It was found that each subtype showed little sensitivity to the commonly used metronidazole, paromomycin, and triple therapy (furazolidone, nitazoxanide, and secnidazole). This study highlights the efficacy of other potential drug treatments, including trimethoprim-sulfamethoxazole and ivermectin, and suggests that current treatment regimens be revised.

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Echinocandin-Induced Microevolution of Candida parapsilosis Influences Virulence and Abiotic Stress Tolerance

mSphere ◽

10.1128/msphere.00547-18 ◽

2018 ◽

Vol 3 (6) ◽

Cited By ~ 2

Author(s):

Csaba Papp ◽

Katica Kocsis ◽

Renáta Tóth ◽

László Bodai ◽

Jesse R. Willis ◽

...

Keyword(s):

Candida Albicans ◽

Amino Acid ◽

Candida Parapsilosis ◽

Hot Spot ◽

Abiotic Stress Tolerance ◽

Acquired Resistance ◽

Cross Resistance ◽

First Line ◽

Content Type

ABSTRACT Candida species are a major cause of life-threatening bloodstream infections worldwide. Although Candida albicans is responsible for the vast majority of infections, the clinical relevance of other Candida species has also emerged over the last twenty years. This shift might be due in part to changes in clinical guidelines, as echinocandins became the first line of therapeutics for the treatment. Candida parapsilosis is an emerging non-albicans Candida species that exhibits lower susceptibility levels to these drugs. Candida species frequently display resistance to echinocandins, and the mechanism for this is well-known in C. albicans and Candida glabrata, where it is mediated by amino acid substitutions at defined locations of the β-1,3-glucan synthase, Fks1p. In C. parapsilosis isolates, Fks1p harbors an intrinsic amino acid change at position 660 of the hot spot 1 (HS1) region, which is thought to be responsible for the high MIC values. Less is known about acquired substitutions in this species. In this study, we used directed evolution experiments to generate C. parapsilosis strains with acquired resistance to caspofungin, anidulafungin, and micafungin. We showed that cross-resistance was dependent on the type of echinocandin used to generate the evolved strains. During their characterization, all mutant strains showed attenuated virulence in vivo and also displayed alterations in the exposure of inner cell wall components. The evolved strains harbored 251 amino acid changes, including three in the HS1, HS2, and HS3 regions of Fks1p. Altogether, our results demonstrate a direct connection between acquired antifungal resistance and virulence of C. parapsilosis. IMPORTANCE Candida parapsilosis is an opportunistic fungal pathogen with the ability to cause infections in immunocompromised patients. Echinocandins are the currently recommended first line of treatment for all Candida species. Resistance of Candida albicans to this drug type is well characterized. C. parapsilosis strains have the lowest in vitro susceptibility to echinocandins; however, patients with such infections typically respond well to echinocandin therapy. There is little knowledge of acquired resistance in C. parapsilosis and its consequences on other characteristics such as virulence properties. In this study, we aimed to dissect how acquired echinocandin resistance influences the pathogenicity of C. parapsilosis and to develop explanations for why echinocandins are clinically effective in the setting of acquired resistance.

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In VitroSensitivities of Plasmodium falciparum Isolates from the China-Myanmar Border to Piperaquine and Association with Polymorphisms in Candidate Genes

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02306-12 ◽

2013 ◽

Vol 57 (4) ◽

pp. 1723-1729 ◽

Cited By ~ 22

Author(s):

Mingming Hao ◽

Dandan Jia ◽

Qing Li ◽

Yongshu He ◽

Lili Yuan ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Molecular Mechanisms ◽

Inhibitory Concentration ◽

Pearson Correlation ◽

Geometric Mean ◽

Content Type ◽

Artemisinin Derivatives ◽

Wide Range ◽

High Prevalence

ABSTRACTThe recent reports of resistance inPlasmodium falciparumto artemisinin derivatives and their partner drugs demand intensive studies toward understanding the molecular mechanisms of resistance. In this study, we examined thein vitrosusceptibility of 63P. falciparumfield isolates collected from the China-Myanmar border area to chloroquine (CQ) and piperaquine (PPQ). Parasite isolates remained highly resistant to CQ, with the geometric mean 50% inhibitory concentration (IC50) of 252.7 nM and a range of 51.9 to 1,052.0 nM. In comparison, these parasites had a geometric mean IC50of 28.4 nM for PPQ, with a fairly wide range of 5.3 to 132.0 nM, suggesting that certain parasite isolates displayed relatively high levels of resistance to PPQ. Interestingly, within the 4 years of study, the parasites exhibited a continuous decline in susceptibilities to both CQ and PPQ, and there was a significant correlation between responses to CQ and PPQ (Pearson correlation coefficient = 0.79,P< 0.0001). Consistent with the CQ-resistant phenotype, all parasites carried thepfcrtK76T mutation, and most parasites had the CVIET type that is prevalent in Southeast Asia. In contrast,pfmdr1mutations were relatively rare, and no gene amplification was detected. Only thepfmdr1N1042D mutation was associated with resistance to CQ. For thepfmrp1gene, four substitutions reached relatively high prevalence of >22%, and the I876V mutation was associated with reduced sensitivity to CQ. However, we could not establish a link between PPQ responses and the polymorphisms in the three genes associated with quinoline drug resistance.

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Heat-Stable Antifungal Factor (HSAF) Biosynthesis inLysobacter enzymogenesIs Controlled by the Interplay of Two Transcription Factors and a Diffusible Molecule

Applied and Environmental Microbiology ◽

10.1128/aem.01754-17 ◽

2017 ◽

Vol 84 (3) ◽

Cited By ~ 3

Author(s):

Zhenhe Su ◽

Sen Han ◽

Zheng Qing Fu ◽

Guoliang Qian ◽

Fengquan Liu

Keyword(s):

Fungal Pathogens ◽

Bacterial Species ◽

Regulatory Function ◽

Regulatory Pathway ◽

Content Type ◽

Heat Stable ◽

Wide Range ◽

Diffusible Factor ◽

Regulatory Effects

ABSTRACTLysobacter enzymogenesis a Gram-negative, environmentally ubiquitous bacterium that produces a secondary metabolite, called heat-stable antifungal factor (HSAF), as an antifungal factor against plant and animal fungal pathogens. 4-Hydroxybenzoic acid (4-HBA) is a newly identified diffusible factor that regulates HSAF synthesis viaL. enzymogenesLysR (LysRLe), an LysR-type transcription factor (TF). Here, to identify additional TFs within the 4-HBA regulatory pathway that control HSAF production, we reanalyzed the LenB2-based transcriptomic data, in which LenB2 is the enzyme responsible for 4-HBA production. This survey led to identification of three TFs (Le4806, Le4969, and Le3904). Of them, LarR (Le4806), a member of the MarR family proteins, was identified as a new TF that participated in the 4-HBA-dependent regulation of HSAF production. Our data show the following: (i) that LarR is a downstream component of the 4-HBA regulatory pathway controlling the HSAF level, while LysRLeis the receptor of 4-HBA; (ii) that 4-HBA and LysRLehave opposite regulatory effects onlarRtranscription wherebylarRtranscript is negatively modulated by 4-HBA while LysRLe, in contrast, exerts positive transcriptional regulation by directly binding to thelarRpromoter without being affected by 4-HBAin vitro; (iii) that LarR, similar to LysRLe, can bind to the promoter of the HSAF biosynthetic gene operon, leading to positive regulation of HSAF production; and (iv) that LarR and LysRLecannot interact and instead control HSAF biosynthesis independently. These results outline a previously uncharacterized mechanism by which biosynthesis of the antibiotic HSAF inL. enzymogenesis modulated by the interplay of 4-HBA, a diffusible molecule, and two different TFs.IMPORTANCEBacteria use diverse chemical signaling molecules to regulate a wide range of physiological and cellular processes. 4-HBA is an “old” chemical molecule that is produced by diverse bacterial species, but its regulatory function and working mechanism remain largely unknown. We previously found that 4-HBA inL. enzymogenescould serve as a diffusible factor regulating HSAF synthesis via LysRLe. Here, we further identified LarR, an MarR family protein, as a second TF that participates in the 4-HBA-dependent regulation of HSAF biosynthesis. Our results dissected how LarR acts as a protein linker to connect 4-HBA and HSAF synthesis, whereby LarR also has cross talk with LysRLe. Thus, our findings not only provide fundamental insight regarding how a diffusible molecule (4-HBA) adopts two different types of TFs for coordinating HSAF biosynthesis but also show the use of applied microbiology to increase the yield of the antibiotic HSAF by modification of the 4-HBA regulatory pathway inL. enzymogenes.

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The loss of SHMT2 mediates 5-fluorouracil chemoresistance in colorectal cancer by upregulating autophagy

Oncogene ◽

10.1038/s41388-021-01815-4 ◽

2021 ◽

Author(s):

Jian Chen ◽

Risi Na ◽

Chao Xiao ◽

Xiao Wang ◽

Yupeng Wang ◽

...

Keyword(s):

Colorectal Cancer ◽

Patient Survival ◽

Serine Hydroxymethyltransferase ◽

First Line ◽

Xenograft Models ◽

Potential Opportunity ◽

First Line Treatment ◽

Novel Therapeutic

Abstract5-Fluorouracil (5-FU)-based chemotherapy is the first-line treatment for colorectal cancer (CRC) but is hampered by chemoresistance. Despite its impact on patient survival, the mechanism underlying chemoresistance against 5-FU remains poorly understood. Here, we identified serine hydroxymethyltransferase-2 (SHMT2) as a critical regulator of 5-FU chemoresistance in CRC. SHMT2 inhibits autophagy by binding cytosolic p53 instead of metabolism. SHMT2 prevents cytosolic p53 degradation by inhibiting the binding of p53 and HDM2. Under 5-FU treatment, SHMT2 depletion promotes autophagy and inhibits apoptosis. Autophagy inhibitors decrease low SHMT2-induced 5-FU resistance in vitro and in vivo. Finally, the lethality of 5-FU treatment to CRC cells was enhanced by treatment with the autophagy inhibitor chloroquine in patient-derived and CRC cell xenograft models. Taken together, our findings indicate that autophagy induced by low SHMT2 levels mediates 5-FU resistance in CRC. These results reveal the SHMT2–p53 interaction as a novel therapeutic target and provide a potential opportunity to reduce chemoresistance.

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Prostacyclin and cerebral vessel relaxation

Journal of Neurosurgery ◽

10.3171/jns.1982.57.3.0334 ◽

1982 ◽

Vol 57 (3) ◽

pp. 334-340 ◽

Cited By ~ 40

Author(s):

Kamal S. Paul ◽

Eric T. Whalley ◽

Christine Forster ◽

Richard Lye ◽

John Dutton

Keyword(s):

Angiotensin Ii ◽

Arterial Spasm ◽

Cerebral Vessel ◽

Content Type ◽

Wide Range ◽

Potent Vasodilator ◽

Dose Dependent Fashion ◽

Basilar Arteries ◽

High Concentrations

✓ The authors have studied the ability of prostacyclin to reverse contractions of human basilar arteries in vitro that were induced by a wide range of substances implicated in the etiology of cerebral arterial spasm. Prostacyclin (10−10 to 10−6M) caused a dose-related reversal of contractions induced by 5-hydroxytryptamine, noradrenaline, angiotensin II, prostaglandin (PG)F2α, and U-46619 (a thromboxane-A2 mimetic). These agents were tested at concentrations or volumes that produced almost maximum or maximum responses and those that produced approximately 50% of the maximum response. Contractions induced by maximum concentrations of angiotensin II and U-46619 were least affected by prostacyclin. In addition, contractions induced by thromboxane-A2 generated from guinea-pig lung were reversed in a dose-dependent fashion by prostacyclin. This ability of prostacyclin to physiologically antagonize contractions of the human basilar artery in vitro induced by high concentrations of various spasmogenic agents suggests that such a potent vasodilator agent or more stable analogue may be of value in the treatment of such disorders as cerebral arterial spasm following subarachnoid hemorrhage.

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Pharmacodynamics of Itraconazole against Aspergillus fumigatus in anIn VitroModel of the Human Alveolus: Perspectives on the Treatment of Triazole-Resistant Infection and Utility of Airway Administration

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00141-12 ◽

2012 ◽

Vol 56 (8) ◽

pp. 4146-4153 ◽

Cited By ~ 6

Author(s):

Zaid Al-Nakeeb ◽

Ajay Sudan ◽

Adam R. Jeans ◽

Lea Gregson ◽

Joanne Goodwin ◽

...

Keyword(s):

Aspergillus Fumigatus ◽

Therapeutic Strategies ◽

Wild Type ◽

Content Type ◽

Exposure Response ◽

Prevention And Treatment ◽

Resistant Infection ◽

Resistant Strains ◽

Type Strains

ABSTRACTItraconazole is used for the prevention and treatment of infections caused byAspergillus fumigatus. An understanding of the pharmacodynamics of itraconazole against wild-type and triazole-resistant strains provides a basis for innovative therapeutic strategies for treatment of infections. Anin vitromodel of the human alveolus was used to define the pharmacodynamics of itraconazole. Galactomannan was used as a biomarker. The effect of systemic and airway administration of itraconazole was assessed, as was a combination of itraconazole administered to the airway and systemically administered 5FC. Systemically administered itraconazole against the wild type induced a concentration-dependent decline in galactomannan in the alveolar and endothelial compartments. No exposure-response relationships were apparent for the L98H, M220T, or G138C mutant. The administration of itraconazole to the airway resulted in comparable exposure-response relationships to those observed with systemic therapy. This was achieved without detectable concentrations of drug within the endothelial compartment. The airway administration of itraconazole resulted in a definite but submaximal effect in the endothelial compartment against the L98H mutant. The administration of 5FC resulted in a concentration-dependent decline in galactomannan in both the alveolar and endothelial compartments. The combination of airway administration of itraconazole and systemically administered 5FC was additive. Systemic administration of itraconazole is ineffective against Cyp51 mutants. The airway administration of itraconazole is effective for the treatment of wild-type strains and appears to have some activity against the L98H mutants. Combination with other agents, such as 5FC, may enable the attainment of near-maximal antifungal activity.

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DAP12 Inhibits Pulmonary Immune Responses to Cryptococcus neoformans

Infection and Immunity ◽

10.1128/iai.00222-16 ◽

2016 ◽

Vol 84 (6) ◽

pp. 1879-1886 ◽

Cited By ~ 5

Author(s):

Lena J. Heung ◽

Tobias M. Hohl

Keyword(s):

Immune Response ◽

Nk Cells ◽

Cryptococcus Neoformans ◽

Molecular Mechanisms ◽

Content Type ◽

Effector Cells ◽

Opportunistic Fungal Pathogen ◽

Efficient Uptake ◽

Bacteria And Fungi

Cryptococcus neoformansis an opportunistic fungal pathogen that is inhaled into the lungs and can lead to life-threatening meningoencephalitis in immunocompromised patients. Currently, the molecular mechanisms that regulate the mammalian immune response to respiratory cryptococcal challenge remain poorly defined. DAP12, a signaling adapter for multiple pattern recognition receptors in myeloid and natural killer (NK) cells, has been shown to play both activating and inhibitory roles during lung infections by different bacteria and fungi. In this study, we demonstrate that DAP12 plays an important inhibitory role in the immune response toC. neoformans. Infectious outcomes in DAP12−/−mice, including survival and lung fungal burden, are significantly improved compared to those in C57BL/6 wild-type (WT) mice. We find that eosinophils and macrophages are decreased while NK cells are increased in the lungs of infected DAP12−/−mice. In contrast to WT NK cells, DAP12−/−NK cells are able to repressC. neoformansgrowthin vitro. Additionally, DAP12−/−macrophages are more highly activated than WT macrophages, with increased production of tumor necrosis factor (TNF) and CCL5/RANTES and more efficient uptake and killing ofC. neoformans. These findings suggest that DAP12 acts as a brake on the pulmonary immune response toC. neoformansby promoting pulmonary eosinophilia and by inhibiting the activation and antifungal activities of effector cells, including NK cells and macrophages.

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In VivoEfficacy of Anuran Trypsin Inhibitory Peptides against Staphylococcal Skin Infection and the Impact of Peptide Cyclization

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04324-14 ◽

2015 ◽

Vol 59 (4) ◽

pp. 2113-2121 ◽

Cited By ~ 9

Author(s):

U. Malik ◽

O. N. Silva ◽

I. C. M. Fensterseifer ◽

L. Y. Chan ◽

R. J. Clark ◽

...

Keyword(s):

Antimicrobial Agents ◽

Cyclic Peptide ◽

Sequence Similarity ◽

Infection Model ◽

Content Type ◽

Wide Range ◽

Inhibitory Activities ◽

The Impact

ABSTRACTStaphylococcus aureusis a virulent pathogen that is responsible for a wide range of superficial and invasive infections. Its resistance to existing antimicrobial drugs is a global problem, and the development of novel antimicrobial agents is crucial. Antimicrobial peptides from natural resources offer potential as new treatments against staphylococcal infections. In the current study, we have examined the antimicrobial properties of peptides isolated from anuran skin secretions and cyclized synthetic analogues of these peptides. The structures of the peptides were elucidated by nuclear magnetic resonance (NMR) spectroscopy, revealing high structural and sequence similarity with each other and with sunflower trypsin inhibitor 1 (SFTI-1). SFTI-1 is an ultrastable cyclic peptide isolated from sunflower seeds that has subnanomolar trypsin inhibitory activity, and this scaffold offers pharmaceutically relevant characteristics. The five anuran peptides were nonhemolytic and noncytotoxic and had trypsin inhibitory activities similar to that of SFTI-1. They demonstrated weakin vitroinhibitory activities againstS. aureus, but several had strong antibacterial activities againstS. aureusin anin vivomurine wound infection model. pYR, an immunomodulatory peptide fromRana sevosa, was the most potent, with complete bacterial clearance at 3 mg · kg−1. Cyclization of the peptides improved their stability but was associated with a concomitant decrease in antimicrobial activity. In summary, these anuran peptides are promising as novel therapeutic agents for treating infections from a clinically resistant pathogen.

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The Putative APSES Transcription Factor RgdA Governs Growth, Development, Toxigenesis, and Virulence in Aspergillus fumigatus

mSphere ◽

10.1128/msphere.00998-20 ◽

2020 ◽

Vol 5 (6) ◽

Author(s):

Sang-Cheol Jun ◽

Yong-Ho Choi ◽

Min-Woo Lee ◽

Jae-Hyuk Yu ◽

Kwang-Soo Shin

Keyword(s):

Transcription Factor ◽

Aspergillus Fumigatus ◽

Molecular Mechanisms ◽

Pathogenic Fungus ◽

Mrna Levels ◽

Transcript Levels ◽

Content Type ◽

Asexual Sporulation ◽

Human Pathogenic Fungus ◽

Growth Development

ABSTRACT The APSES transcription factor (TF) in Aspergillus species is known to govern diverse cellular processes, including growth, development, and secondary metabolism. Here, we investigated functions of the rgdA gene (Afu3g13920) encoding a putative APSES TF in the opportunistic human-pathogenic fungus Aspergillus fumigatus. The rgdA deletion resulted in significantly decreased hyphal growth and asexual sporulation. Consistently, transcript levels of the key asexual developmental regulators abaA, brlA, and wetA were decreased in the ΔrgdA mutant compared to those in the wild type (WT). Moreover, ΔrgdA resulted in reduced spore germination rates and elevated transcript levels of genes associated with conidium dormancy. The conidial cell wall hydrophobicity and architecture were changed, and levels of the RodA protein were decreased in the ΔrgdA mutant. Comparative transcriptomic analyses revealed that the ΔrgdA mutant showed higher mRNA levels of gliotoxin (GT)-biosynthetic genes and GT production. While the ΔrgdA mutant exhibited elevated production of GT, ΔrgdA strains showed reduced virulence in the mouse model. In addition, mRNA levels of genes associated with the cyclic AMP (cAMP)-protein kinase A (PKA) signaling pathway and the SakA mitogen-activated protein (MAP) kinase pathway were increased in the ΔrgdA mutant. In summary, RgdA plays multiple roles in governing growth, development, GT production, and virulence which may involve attenuation of PKA and SakA signaling. IMPORTANCE Immunocompromised patients are susceptible to infections with the opportunistic human-pathogenic fungus Aspergillus fumigatus. This fungus causes systemic infections such as invasive aspergillosis (IA), which is one of the most life-threatening fungal diseases. To control this serious disease, it is critical to identify new antifungal drug targets. In fungi, the transcriptional regulatory proteins of the APSES family play crucial roles in controlling various biological processes, including mating, asexual sporulation and dimorphic growth, and virulence traits. This study found that a putative APSES transcription factor, RgdA, regulates normal growth, asexual development, conidium germination, spore wall architecture and hydrophobicity, toxin production, and virulence in A. fumigatus. Better understanding the molecular mechanisms of RgdA in human-pathogenic fungi may reveal a novel antifungal target for future drug development.

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