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Hydrogen sulfide (H2S) has traditionally been considered as an environmental toxin for animal lineages; yet, it plays a signaling role in various processes at low concentrations. Mechanisms controlling H2S in animals, especially in sulfide-rich environments, are not fully understood. The main detoxification pathway involves the conversion of H2S into less harmful forms, through a mitochondrial oxidation pathway. The first step of this pathway oxidizes sulfide and reduces ubiquinone (UQ) through sulfide-quinone oxidoreductase (SQRD/SQOR). Because H2S inhibits cytochrome oxidase and hence UQ regeneration, this pathway becomes compromised at high H2S concentrations. The free-living nematode C. elegans feeds on bacteria and can face high sulfide concentrations in its natural environment. This organism has an alternative ETC that uses rhodoquinone (RQ) as the lipidic electron transporter and fumarate as the final electron acceptor. In this study, we demonstrate that RQ is essential for survival in sulfide. RQ-less animals (kynu-1 and coq-2e KO) cannot survive high H2S concentrations, while UQ-less animals (clk-1 and coq-2a KO) exhibit recovery, even when provided with a UQ-deficient diet. Our findings highlight that sqrd-1 uses both benzoquinones and that RQ-dependent ETC confers a key advantage (RQ regeneration) over UQ in sulfide-rich conditions. C. elegans also faces cyanide, another cytochrome oxidase inhibitor, whose detoxification leads to H2S production, via cysl-2. Our study reveals that RQ delays killing by the HCN-producing bacteria Pseudomonas aeruginosa PAO1. These results underscore the fundamental role that RQ-dependent ETC serves as a biochemical adaptation to H2S environments, and to pathogenic bacteria producing cyanide and H2S toxins.
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Nematode infections affect a fifth of the human population, livestock, and crops worldwide, imposing a burden to global public health and economies, particularly in developing nations. Resistance to commercial anthelmintics has increased over the years in livestock infections and driven the pursuit for new drugs. We herein present a rapid, cost-effective, and automated assay for nematicide discovery using the free-living nematode Caenorhabditis elegans to screen a highly diverse natural product library enriched in bioactive molecules. Screening of 10,240 fractions obtained from extracts of various biological sources allowed the identification of 7 promising hit fractions, all from marine sponges. These fractions were further assayed for nematicidal activity against the sheep nematode parasite Haemonchus contortus and for innocuity in zebrafish. The most active extracts against parasites and innocuous toward vertebrates belong to two chemotypes. High-performance liquid chromatography (HPLC) coupled with nuclear magnetic resonance (NMR) revealed that the most abundant compound in one chemotype is halaminol A, an aminoalcohol previously identified in a small screen against H. contortus. Terpene-nucleotide hybrids known as agelasines predominate in the other chemotype. This study reinforces the power of C. elegans for nematicide discovery from large collections and the potential of the chemical diversity derived from marine invertebrate biota.
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Antinematódeos , Caenorhabditis elegans , Poríferos , Animais , Poríferos/química , Antinematódeos/farmacologia , Antinematódeos/química , Caenorhabditis elegans/efeitos dos fármacos , Estrutura Molecular , Peixe-Zebra , Haemonchus/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão/métodosRESUMO
The search for new anti-infectives based on metal complexes is gaining momentum. Among the different options taken by researchers, the one involving the use of organometallic complexes is probably the most successful one with a compound, namely, ferroquine, already in clinical trials against malaria. In this study, we describe the preparation and in-depth characterization of 10 new (organometallic) derivatives of the approved antifungal drug fluconazole. Our rationale is that the sterol 14α-demethylase is an enzyme part of the ergosterol biosynthesis route in Trypanosoma and is similar to the one in pathogenic fungi. To demonstrate our postulate, docking experiments to assess the binding of our compounds with the enzyme were also performed. Our compounds were then tested on a range of fungal strains and parasitic organisms, including the protozoan parasite Trypanosoma cruzi (T. cruzi) responsible for Chagas disease, an endemic disease in Latin America that ranks among some of the most prevalent parasitic diseases worldwide. Of high interest, the two most potent compounds of the study on T. cruzi that contain a ferrocene or cobaltocenium were found to be harmless for an invertebrate animal model, namely, Caenorhabditis elegans (C. elegans), without affecting motility, viability, or development.
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Fluconazol , Trypanosoma cruzi , Animais , Antifúngicos/farmacologia , Antifúngicos/uso terapêutico , Metalocenos , Antiparasitários/farmacologia , Caenorhabditis elegans , Inibidores de 14-alfa Desmetilase/química , Trypanosoma cruzi/químicaRESUMO
Aims: To determine the role of the kynurenine (KYN) pathway in rhodoquinone (RQ) and de novo NAD+ biosynthesis and whether NAD+ rescue pathways are essential in parasitic worms (helminths). Results: We demonstrate that RQ, the key electron transporter used by helminths under hypoxia, derives from the tryptophan (Trp) catabolism even in the presence of a minimal KYN pathway. We show that of the KYN pathway genes only the kynureninase and tryptophan/indoleamine dioxygenases are essential for RQ biosynthesis. Metabolic labeling with Trp revealed that the lack of the formamidase and kynurenine monooxygenase genes did not preclude RQ biosynthesis in the flatworm Mesocestoides corti. In contrast, a minimal KYN pathway prevented de novo NAD+ biosynthesis, as revealed by metabolic labeling in M. corti, which also lacks the 3-hydroxyanthranilate 3,4-dioxygenase gene. Our results indicate that most helminths depend solely on NAD+ rescue pathways, and some lineages rely exclusively on the nicotinamide salvage pathway. Importantly, the inhibition of the NAD+ recycling enzyme nicotinamide phosphoribosyltransferase with FK866 led cultured M. corti to death. Innovation: We use comparative genomics of more than 100 hundred helminth genomes, metabolic labeling, HPLC-mass spectrometry targeted metabolomics, and enzyme inhibitors to define pathways that lead to RQ and NAD+ biosynthesis in helminths. We identified the essential enzymes of these pathways in helminth lineages, revealing new potential pharmacological targets for helminthiasis. Conclusion: Our results demonstrate that a minimal KYN pathway was evolutionary maintained for RQ and not for de novo NAD+ biosynthesis in helminths and shed light on the essentiality of NAD+ rescue pathways in helminths.
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INTRODUCTION: Metabolic associated steatohepatitis (MASH) is one of the most frequent causes of chronic liver disease. Liver transaminases are important biomarkers to measure liver injury, however, a proportion of patients with MASH may present with normal levels of transaminases. The levels of serum transaminases may not correlate with the severity of histopathological changes. OBJECTIVE: We aimed to identify the frequency of normal transaminases in obese patients with MASH, as well as to describe the clinical, biochemical and histological characteristics in this specific group of patients. MATERIALS AND METHODS: A retrospective cross-sectional study was conducted in the bariatric surgery service of a private clinic. Obese patients older than 18 years with a body mass index (BMI) >30Kg/m2 and 2 co-morbidities undergoing a gastric sleeve surgery were included. Measurement of biochemical routine laboratory exams was performed. Insulin resistance was calculated using the homeostasis evaluation model (HOMA-IR). All patients underwent liver biopsies prior to surgery and the diagnosis of MASH was based on the Brunt criteria. RESULTS: 159 obese patients with MASH were included, of which 47.2% had normal transaminases and 52.8% elevated transaminases. Factors associated with alteration in transaminases were: being male OR=4.02 (95% CI: 2.03- 7.96; p<0.01), diagnosis of type 2 diabetes mellitus OR=4.86 (95% CI: 1.97- 11.95; p<0.01) and levels of GGT >50 IU/L OR=7.50 (95% CI: 3.40-16.56; p<0.01). The values of HOMA-IR and GGT were significantly higher in the group of high transaminases (p<0.01). Differences in the degree of fibrosis were not associated with transaminases levels. CONCLUSION: In conclusion we found that the frequency of normal transaminases was 47.2% in obese patients with MASH. Factors associated with elevation in liver enzymes were being male, diagnosis of diabetes mellitus and elevation in GGT levels. The degree of fibrosis was not associated with elevations in liver transaminases. These findings suggest that transaminases levels alone are not accurate markers to assess liver injury, as they do not necessarily correlate with histological liver damage.
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Diabetes Mellitus Tipo 2 , Fígado Gorduroso , Hepatopatias , Hepatopatia Gordurosa não Alcoólica , Obesidade Mórbida , Humanos , Masculino , Feminino , Transaminases , Estudos Retrospectivos , Estudos Transversais , Diabetes Mellitus Tipo 2/complicações , Peru , Fígado Gorduroso/diagnóstico , Obesidade/complicações , Hepatopatia Gordurosa não Alcoólica/complicações , Hepatopatia Gordurosa não Alcoólica/diagnóstico , Obesidade Mórbida/complicações , Obesidade Mórbida/cirurgiaRESUMO
Caenorhabditis elegans is a free-living nematode that has been validated for anthelmintic drug screening. However, this model has not been used to address anthelmintic dose-response-time and drug-drug interactions through matrix array methodology. Eprinomectin (EPM) and Ivermectin (IVM) are macrocyclic lactones widely used as anthelmintics. Despite being very similar, EPM and IVM are combined in commercial formulations or mixed by farmers, under the assumption that the combination would increase their efficacy. However, there is no data reported on the pharmacological evaluation of the combination of both drugs. In this study, we assessed the pharmacodynamics and drug-drug interactions of these two anthelmintic drugs. Since the action of these drugs causes worm paralysis, we used an infrared motility assay to measure EPM and IVM effects on worm movement over time. The results showed that EPM was slightly more potent than IVM, that drug potency increased with drug time exposure, and that once paralyzed, worms did not recover. Different EPM/IVM concentration ratios were used and synergy and combination sensitivity scores were determined at different exposure times, applying Highest Single Agent (HSA), Loewe additivity, Bliss and Zero Interaction Potency (ZIP) models. The results clearly indicate that there is neither synergy nor antagonism between both macrocyclic lactones. This study shows that it is more relevant to prioritize the exposure time of each individual drug than to combine them to improve their effects. The results highlight the utility of C. elegans to address pharmacodynamics studies, particularly for drug-drug interactions. Models in vitro can be integrated to facilitate preclinical and clinical translational studies and help researchers to understand drug-drug interactions and achieve rational therapeutic regimes.
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A recent screen of 67,012 compounds identified a new family of compounds with excellent nematicidal activity: the ortho-substituted benzamide families Wact-11 and Wact-12. These compounds are active against Caenorhabditis elegans and parasitic nematodes by selectively inhibiting nematode complex II, and they display low toxicity in mammalian cells and vertebrate organisms. Although a big number of benzamides were tested against C. elegans in high-throughput screens, bioisosteres of the amide moiety were not represented in the chemical space examined. We thus identified an opportunity for the design, synthesis and evaluation of novel compounds, using bioisosteric replacements of the amide group present in benzamides. The compound Wact-11 was used as the reference scaffold to prepare a set of bioisosteres to be evaluated against C. elegans. Eight types of amide replacement were selected, including ester, thioamide, selenoamide, sulfonamide, alkyl thio- and oxo-amides, urea and triazole. The results allowed us to perform a structure-activity relationship, highlighting the relevance of the amide group for nematicide activity. Experimental evidence was complemented with in silico structural studies over a C. elegans complex II model as a molecular target of benzamides. Importantly, compound Wact-11 was active against the flatworm Echinococcus granulosus, suggesting a previously unreported pan-anthelmintic potential for benzamides.
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Anti-Helmínticos , Caenorhabditis elegans , Amidas , Animais , Anti-Helmínticos/química , Anti-Helmínticos/farmacologia , Antinematódeos/farmacologia , Benzamidas/farmacologia , MamíferosRESUMO
Introduction: Metabolic associated steatohepatitis (MASH) is one of the most frequent causes of chronic liver disease. Liver transaminases are important biomarkers to measure liver injury, however, a proportion of patients with MASH may present with normal levels of transaminases. The levels of serum transaminases may not correlate with the severity of histopathological changes. Objective: We aimed to identify the frequency of normal transaminases in obese patients with MASH, as well as to describe the clinical, biochemical and histological characteristics in this specific group of patients. Materials and methods: A retrospective cross-sectional study was conducted in the bariatric surgery service of a private clinic. Obese patients older than 18 years with a body mass index (BMI) >30Kg/m2 and 2 co-morbidities undergoing a gastric sleeve surgery were included. Measurement of biochemical routine laboratory exams was performed. Insulin resistance was calculated using the homeostasis evaluation model (HOMA-IR). All patients underwent liver biopsies prior to surgery and the diagnosis of MASH was based on the Brunt criteria. Results: 159 obese patients with MASH were included, of which 47.2% had normal transaminases and 52.8% elevated transaminases. Factors associated with alteration in transaminases were: being male OR=4.02 (95% CI: 2.037.96; p50 IU/L OR=7.50 (95% CI: 3.40-16.56; p<0.01). The values of HOMA-IR and GGT were significantly higher in the group of high transaminases (p<0.01). Differences in the degree of fibrosis were not associated with transaminases levels. Conclusion: In conclusion we found that the frequency of normal transaminases was 47.2% in obese patients with MASH. Factors associated with elevation in liver enzymes were being male, diagnosis of diabetes mellitus and elevation in GGT levels. The degree of fibrosis was not associated with elevations in liver transaminases. These findings suggest that transaminases levels alone are not accurate markers to assess liver injury, as they do not necessarily correlate with histological liver damage.
Introducción: La esteatohepatitis asociada metabólica (MASH) es una de las causas más frecuentes de enfermedad hepática crónica. Las transaminasas hepáticas son biomarcadores importantes para medir el daño hepático; sin embargo, una proporción de pacientes con MASH pueden presentar niveles normales de transaminasas. Los niveles de transaminasas séricas pueden no estar correlacionados con la gravedad de los cambios histopatológicos. Objetivo: Nuestro objetivo fue identificar la frecuencia de transaminasas normales en pacientes obesos con MASH, así como describir las características clínicas, bioquímicas e histológicas en este grupo específico de pacientes. Materiales y métodos: Se realizó un estudio transversal retrospectivo en el servicio de cirugía bariátrica de una clínica privada. Se incluyeron pacientes obesos mayores de 18 años con índice de masa corporal (IMC) >30Kg/m2 y 2 comorbilidades sometidos a cirugía de manga gástrica. Se realizó la medición de los exámenes bioquímicos de laboratorio de rutina. La resistencia a la insulina se calculó mediante el modelo de evaluación de la homeostasis (HOMA-IR). Todos los pacientes se sometieron a biopsias hepáticas antes de la cirugía y el diagnóstico de MASH se basó en los criterios de Brunt. Resultados: Se incluyeron 159 pacientes obesos con MASH, de los cuales el 47,2% tenían transaminasas normales y el 52,8% transaminasas elevadas. Los factores asociados a la alteración de las transaminasas fueron: ser hombre OR=4,02 (IC 95%: 2,03-7,96; p50 UI/L OR=7,50 (IC 95%: 3,40-16,56; p<0,01). Los valores de HOMA-IR y GGT fueron significativamente mayores en el grupo de transaminasas altas (p<0,01). Las diferencias en el grado de fibrosis no se asociaron con los niveles de transaminasas. Conclusión: Encontramos que la frecuencia de transaminasas normales fue del 47,2% en pacientes obesos con MASH. Los factores asociados con la elevación de las enzimas hepáticas fueron el sexo masculino, el diagnóstico de diabetes mellitus y la elevación de los niveles de GGT. El grado de fibrosis no se asoció con elevaciones de las transaminasas hepáticas. Estos hallazgos sugieren que los niveles de transaminasas por sí solos no son marcadores precisos para evaluar el daño hepático, ya que no necesariamente se correlacionan con el daño hepático histológico.
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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the current coronavirus disease 2019 (COVID-19) pandemic, affecting more than 219 countries and causing the death of more than 5 million people worldwide. The genetic background represents a factor that predisposes the way the host responds to SARS-CoV-2 infection. In this sense, genetic variants of ACE and ACE2 could explain the observed interindividual variability to COVID-19 outcomes. In order to improve the understanding of how genetic variants of ACE and ACE2 are involved in the severity of COVID-19, we included a total of 481 individuals who showed clinical manifestations of COVID-19 and were diagnosed by reverse transcription PCR (RT-PCR). Genomic DNA was extracted from peripheral blood and saliva samples. ACE insertion/deletion polymorphism was evaluated by the high-resolution melting method; ACE single-nucleotide polymorphism (SNP) (rs4344) and ACE2 SNPs (rs2285666 and rs2074192) were genotyped using TaqMan probes. We assessed the association of ACE and ACE2 polymorphisms with disease severity using logistic regression analysis adjusted by age, sex, hypertension, type 2 diabetes, and obesity. The severity of the illness in our study population was divided as 31% mild, 26% severe, and 43% critical illness; additionally, 18% of individuals died, of whom 54% were male. Our results showed in the codominant model a contribution of ACE2 gene rs2285666 T/T genotype to critical outcome [odds ratio (OR) = 1.83; 95%CI = 1.01-3.29; p = 0.04] and to require oxygen supplementation (OR = 1.76; 95%CI = 1.01-3.04; p = 0.04), in addition to a strong association of the T allele of this variant to develop critical illness in male individuals (OR = 1.81; 95%CI = 1.10-2.98; p = 0.02). We suggest that the T allele of rs2285666 represents a risk factor for severe and critical outcomes of COVID-19, especially for men, regardless of age, hypertension, obesity, and type 2 diabetes.
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Enzima de Conversão de Angiotensina 2/genética , COVID-19/genética , Peptidil Dipeptidase A/genética , Polimorfismo de Nucleotídeo Único/genética , Alelos , COVID-19/virologia , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/virologia , Genótipo , Humanos , Masculino , SARS-CoV-2/patogenicidadeRESUMO
We revisit the possibility that dark matter is composed of stable scalar glueballs of a confining dark SU(3) gauge theory coupled only to gravity. The relic abundance of dark glueballs is studied for the first time in a thermal effective theory accounting for strong-coupling dynamics. An important ingredient of our analysis is the use of an effective potential for glueballs that is fitted by lattice simulations. We predict the relic abundance to be in the range 0.12ζ_{T}^{-3}Λ/(137.9 eV)â²Ωh^{2}â²0.12ζ_{T}^{-3}Λ/(82.7 eV), with Λ being the confinement scale, ζ_{T} the visible-to-dark sector temperature ratio, and the uncertainty is coming from the fit to lattice data. This prediction is an order of magnitude smaller than the existing glueball abundance results in the literature. Our framework can be easily generalized to different gauge groups and modified cosmological histories paving the way toward consistent exploration of strongly coupled dark sectors and their cosmological implications.
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Parasitic nematodes constitute a health problem for humans, livestock and crops, and cause huge economic losses to developing-country economies. Due to the spread of nematicide resistance, there is an urgent need for new drugs. C. elegans is now recognized as a cost-effective alternative for the screening of compound libraries with potential nematicidal activity, as parasitic organisms are hard to maintain under laboratory conditions. Here we describe an adaptation of a previously reported high throughput (HTP) infrared-based motility assay that leads to increased sensitivity. The modified assay uses L1 instead of L4 stage worms and matches the sensitivity reported by Burns et al. (2015) for the anthelmintic benzamides Wact11 and Wact11p. In addition, this method presents practical advantages over Burns et al. (2015) and other image-based protocols and provides a robust assay with a fast and simple readout ideal for HTP drug discovery.
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Five heteroleptic compounds, [VVO(IN-2H)(L-H)], where L are 8-hydroxyquinoline derivatives and IN is a Schiff base ligand, were synthesized and characterized in both the solid and solution state. The compounds were evaluated on epimastigotes and trypomastigotes of Trypanosoma cruzi as well as on VERO cells, as a mammalian cell model. Compounds showed activity against trypomastigotes with IC50 values of 0.29-3.02 µM. IN ligand and the new [VVO2(IN-H)] complex showed negligible activity. The most active compound [VVO(IN-2H)(L2-H)], with L2 = 5-chloro-7-iodo-8-hydroxyquinoline, showed good selectivity towards the parasite and was selected to carry out further biological studies. Stability studies suggested a partial decomposition in solution. [VVO(IN-2H)(L2-H)] affects the infection potential of cell-derived trypomastigotes. Low total vanadium uptake by parasites and preferential accumulation in the soluble proteins fraction were determined. A trypanocide effect was observed when incubating epimastigotes with 10 × IC50 values of [VVO(IN-2H)(L2-H)] and the generation of ROS after treatments was suggested. Fluorescence competition measurements with DNA:ethidium bromide adduct showed a moderate DNA interaction of the complexes. In vivo toxicity study on C. elegans model showed no toxicity up to a 100 µM concentration of [VVO(IN-2H)(L2-H)]. This compound could be considered a prospective anti-T. cruzi agent that deserves further research.
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Caenorhabditis elegans/efeitos dos fármacos , Complexos de Coordenação/farmacologia , Oxiquinolina/farmacologia , Tripanossomicidas/farmacologia , Trypanosoma cruzi/efeitos dos fármacos , Vanádio/farmacologia , Animais , Complexos de Coordenação/síntese química , Complexos de Coordenação/química , Estrutura Molecular , Oxiquinolina/química , Testes de Sensibilidade Parasitária , Tripanossomicidas/síntese química , Tripanossomicidas/química , Vanádio/químicaRESUMO
The terpenoid benzoquinone, rhodoquinone (RQ), is essential to the bioenergetics of many organisms that survive in low oxygen environments. RQ biosynthesis and its regulation has potential as a novel target for anti-microbial and anti-parasitic drug development. Recent work has uncovered two distinct pathways for RQ biosynthesis which have evolved independently. The first pathway is used by bacteria, such as Rhodospirillum rubrum, and some protists that possess the rquA gene. These species derive their RQ directly from ubiquinone (UQ), the essential electron transporter used in the aerobic respiratory chain. The second pathway is used in animals, such as Caenorhabditis elegans and parasitic helminths, and requires 3-hydroxyanthranilic acid (3-HAA) as a precursor, which is derived from tryptophan through the kynurenine pathway. A COQ-2 isoform, which is unique to these species, facilitates prenylation of the 3-HAA precursor. After prenylation, the arylamine ring is further modified to form RQ using several enzymes common to the UQ biosynthetic pathway. In addition to current knowledge of RQ biosynthesis, we review the phylogenetic distribution of RQ and its function in anaerobic electron transport chains in bacteria and animals. Finally, we discuss key steps in RQ biosynthesis that offer potential as drug targets to treat microbial and parasitic infections, which are rising global health concerns.
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Bactérias/metabolismo , Vias Biossintéticas , Elétrons , Metabolismo Energético , Ubiquinona/análogos & derivados , Anaerobiose , Animais , Transporte de Elétrons , Ubiquinona/metabolismoRESUMO
Parasitic helminths use two benzoquinones as electron carriers in the electron transport chain. In normoxia, they use ubiquinone (UQ), but in anaerobic conditions inside the host, they require rhodoquinone (RQ) and greatly increase RQ levels. We previously showed the switch from UQ to RQ synthesis is driven by a change of substrates by the polyprenyltransferase COQ-2 (Del Borrello et al., 2019; Roberts Buceta et al., 2019); however, the mechanism of substrate selection is not known. Here, we show helminths synthesize two coq-2 splice forms, coq-2a and coq-2e, and the coq-2e-specific exon is only found in species that synthesize RQ. We show that in Caenorhabditis elegans COQ-2e is required for efficient RQ synthesis and survival in cyanide. Importantly, parasites switch from COQ-2a to COQ-2e as they transit into anaerobic environments. We conclude helminths switch from UQ to RQ synthesis principally via changes in the alternative splicing of coq-2.
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Alquil e Aril Transferases/genética , Processamento Alternativo , Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/genética , Ubiquinona/análogos & derivados , Alquil e Aril Transferases/metabolismo , Animais , Caenorhabditis elegans/enzimologia , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Nematoides/enzimologia , Nematoides/genética , Nematoides/metabolismo , Oxirredução , Platelmintos/enzimologia , Platelmintos/genética , Platelmintos/metabolismo , Ubiquinona/metabolismoRESUMO
Selenium is a trace element for most organisms; its deficiency and excess are detrimental. Selenium beneficial effects are mainly due to the role of the 21st genetically encoded amino acid selenocysteine (Sec). Selenium also exerts Sec-independent beneficial effects. Its harmful effects are thought to be mainly due to non-specific incorporation in protein synthesis. Yet the selenium response in animals is poorly understood. In Caenorhabditis elegans, Sec is genetically incorporated into a single selenoprotein. Similar to mammals, a 20-fold excess of the optimal selenium requirement is harmful. Sodium selenite (Na2SeO3) excess causes development retardation, impaired growth, and neurodegeneration of motor neurons. To study the organismal response to selenium we performed a genetic screen for C. elegans mutants that are resistant to selenite. We isolated non-sense and missense egl-9/EGLN mutants that confer robust resistance to selenium. In contrast, hif-1/HIF null mutant was highly sensitive to selenium, establishing a role for this transcription factor in the selenium response. We showed that EGL-9 regulates HIF-1 activity through VHL-1, and identified CYSL-1 as a key sensor that transduces the selenium signal. Finally, we showed that the key enzymes involved in sulfide and sulfite stress (sulfide quinone oxidoreductase and sulfite oxidase) are not required for selenium resistance. In contrast, knockout strains in the persulfide dioxygenase ETHE-1 and the sulfurtransferase MPST-7 affect the organismal response to selenium. In sum, our results identified a transcriptional pathway as well as enzymes possibly involved in the organismal selenium response.
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Helminths use an alternative mitochondrial electron transport chain (ETC) under hypoxic conditions, such as those found in the gastrointestinal tract. In this alternative ETC, fumarate is the final electron acceptor and rhodoquinone (RQ) serves as an electron carrier. RQ receives electrons from reduced nicotinamide adenine dinucleotide through complex I and donates electrons to fumarate through complex II. In this latter reaction, complex II functions in the opposite direction to the conventional ETC (i.e., as fumarate reductase instead of succinate dehydrogenase). Studies in Ascaris suum indicate that this is possible due to changes in complex II, involving alternative succinate dehydrogenase (SDH) subunits SDHA and SDHD, derived from duplicated genes. We analyzed helminth genomes and found that distinct lineages have different gene duplications of complex II subunits (SDHA, SDHB, SDHC, and SDHD). Similarly, we found lineage-specific duplications in genes encoding complex I subunits that interact with quinones (NDUF2 and NDUF7). The phylogenetic analysis of ETC subunits revealed a complex history with independent evolutionary events involving gene duplications and losses. Our results indicated that there is not a common evolutionary event related to ETC subunit genes linked to RQ. The free-living nematode Caenorhabditis elegans uses RQ and has two genes encoding SDHA (sdha-1 and sdha-2) and two genes encoding NDUF2 (nduf2-1 and nduf2-2). sdha-1 and nduf2-1 are essential genes and have a similar expression pattern during C. elegans lifecycle. Using knockout strains, we found that sdha-2 and nduf2-2 are not essential, even in hypoxia. Yet, sdha-2 and nduf2-2 expression is increased in the early embryo and in dauer larvae, stages where there is low oxygen tension. Strikingly, sdha-1 and sdha-2 as well as nduf2-1 and nduf2-2 showed inverted expression profiles during the C. elegans life cycle. Finally, we found that sdha-2 and nduf2-2 knockout mutant strain progeny is affected. Our results indicate that different complex I and II subunit gene duplications provide increased fitness to worms.
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1,4-Thiazepines derivatives are pharmacologically important heterocycles with different applications in medicinal chemistry. In the present work, we describe the preparation of new bicyclic thiazolidinyl-1,4-thiazepines 3 by reaction between azadithiane compounds and Michael acceptors. The reaction scope was explored and the yields were optimized. The activity of the new compounds was evaluated against Nippostrongylus brasiliensis and Caenorhabditis elegans as anthelmintic models and Trypanosoma brucei brucei. The most active compound was 3l, showing an EC50 = 2.8 ± 0.7 µM against T. b. brucei and a selectivity index >71.
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A key metabolic adaptation of some species that face hypoxia as part of their life cycle involves an alternative electron transport chain in which rhodoquinone (RQ) is required for fumarate reduction and ATP production. RQ biosynthesis in bacteria and protists requires ubiquinone (Q) as a precursor. In contrast, Q is not a precursor for RQ biosynthesis in animals such as parasitic helminths, and most details of this pathway have remained elusive. Here, we used Caenorhabditis elegans as a model animal to elucidate key steps in RQ biosynthesis. Using RNAi and a series of C. elegans mutants, we found that arylamine metabolites from the kynurenine pathway are essential precursors for RQ biosynthesis de novo Deletion of kynu-1, encoding a kynureninase that converts l-kynurenine (KYN) to anthranilic acid (AA) and 3-hydroxykynurenine (3HKYN) to 3-hydroxyanthranilic acid (3HAA), completely abolished RQ biosynthesis but did not affect Q levels. Deletion of kmo-1, which encodes a kynurenine 3-monooxygenase that converts KYN to 3HKYN, drastically reduced RQ but not Q levels. Knockdown of the Q biosynthetic genes coq-5 and coq-6 affected both Q and RQ levels, indicating that both biosynthetic pathways share common enzymes. Our study reveals that two pathways for RQ biosynthesis have independently evolved. Unlike in bacteria, where amination is the last step in RQ biosynthesis, in worms the pathway begins with the arylamine precursor AA or 3HAA. Because RQ is absent in mammalian hosts of helminths, inhibition of RQ biosynthesis may have potential utility for targeting parasitic infections that cause important neglected tropical diseases.