Catalytic specificity and crystal structure of cystathionine γ-lyase from Pseudomonas aeruginosa

The escalating drug resistance among microorganisms underscores the urgent need for innovative therapeutic strategies and a comprehensive understanding of bacteria's defense mechanisms against oxidative stress and antibiotics. Among the recently discovered barriers, the endogenous production of hydrogen sulfide (H2S) via the reverse transsulfuration pathway, emerges as a noteworthy factor. In this study, we have explored the catalytic capabilities and crystal structure of cystathionine γ-lyase from Pseudomonas aeruginosa (PaCGL), a multidrug-opportunistic pathogen chiefly responsible for nosocomial infections. In addition to a canonical L-cystathionine hydrolysis, PaCGL efficiently catalyzes the production of H2S using L-cysteine and/or L-homocysteine as alternative substrates. Comparative analysis with the human enzyme and counterparts from other pathogens revealed distinct structural features within the primary enzyme cavities. Specifically, a distinctly folded entrance loop could potentially modulate the access of substrates and/or inhibitors to the catalytic site. Our findings offer significant insights into the structural evolution of CGL enzymes across different pathogens and provide novel opportunities for developing specific inhibitors targeting PaCGL.

Structural basis of the inhibition of cystathionine γ-lyase from Toxoplasma gondii by propargylglycine and cysteine

Cystathionine γ-lyase (CGL) is a PLP-dependent enzyme that catalyzes the last step of the reverse transsulfuration route for endogenous cysteine biosynthesis. The canonical CGL-catalyzed process consists of an α,γ-elimination reaction that breaks down cystathionine into cysteine, α-ketobutyrate, and ammonia. In some species, the enzyme can alternatively use cysteine as a substrate, resulting in the production of hydrogen sulfide (H₂ S). Importantly, inhibition of the enzyme and consequently of its H₂ S production activity, makes multiresistant bacteria considerably more susceptible to antibiotics. Other organisms, such as Toxoplasma gondii, the causative agent of toxoplasmosis, encode a CGL enzyme (TgCGL) that almost exclusively catalyzes the canonical process, with only minor reactivity to cysteine. Interestingly, the substitution of N360 by a serine (the equivalent amino acid residue in the human enzyme) at the active site changes the specificity of TgCGL for the catalysis of cystathionine, resulting in an enzyme that can cleave both the CγS and the CβS bond of cystathionine. Based on these findings and to deepen the molecular basis underlying the enzyme-substrate specificity, we have elucidated the crystal structures of native TgCGL and the variant TgCGL-N360S from crystals grown in the presence of cystathionine, cysteine, and the inhibitor D,L-propargylglycine (PPG). Our structures reveal the binding mode of each molecule within the catalytic cavity and help explain the inhibitory behavior of cysteine and PPG. A specific inhibitory mechanism of TgCGL by PPG is proposed. This article is protected by copyright. All rights reserved.

Restoring cellular magnesium balance through Cyclin M4 protects against acetaminophen-induced liver damage

Acetaminophen overdose is one of the leading causes of acute liver failure and liver transplantation in the Western world. Magnesium is essential in several cellular processess. The Cyclin M family is involved in magnesium transport across cell membranes. Herein, we identify that among all magnesium transporters, only Cyclin M4 expression is upregulated in the liver of patients with acetaminophen overdose, with disturbances in magnesium serum levels. In the liver, acetaminophen interferes with the mitochondrial magnesium reservoir via Cyclin M4, affecting ATP production and reactive oxygen species generation, further boosting endoplasmic reticulum stress. Importantly, Cyclin M4 mutant T495I, which impairs magnesium flux, shows no effect. Finally, an accumulation of Cyclin M4 in endoplasmic reticulum is shown under hepatoxicity. Based on our studies in mice, silencing hepatic Cyclin M4 within the window of 6 to 24 h following acetaminophen overdose ingestion may represent a therapeutic target for acetaminophen overdose induced liver injury.

Cystathionine β-synthase is involved in cysteine biosynthesis and H2S generation in Toxoplasma gondii

Cystathionine β-synthase (CBS) catalyzes the condensation of serine and homocysteine to water and cystathionine, which is then hydrolyzed to cysteine, α-ketobutyrate and ammonia by cystathionine γ-lyase (CGL) in the reverse transsulfuration pathway. The protozoan parasite Toxoplasma gondii, the causative agent of toxoplasmosis, includes both CBS and CGL enzymes. We have recently reported that the putative T. gondii CGL gene encodes a functional enzyme. Herein, we cloned and biochemically characterized cDNA encoding CBS from T. gondii (TgCBS), which represents a first example of protozoan CBS that does not bind heme but possesses two C-terminal CBS domains. We demonstrated that TgCBS can use both serine and O-acetylserine to produce cystathionine, converting these substrates to an aminoacrylate intermediate as part of a PLP-catalyzed β-replacement reaction. Besides a role in cysteine biosynthesis, TgCBS can also efficiently produce hydrogen sulfide, preferentially via condensation of cysteine and homocysteine. Unlike the human counterpart and similar to CBS enzymes from lower organisms, the TgCBS activity is not stimulated by S-adenosylmethionine. This study establishes the presence of an intact functional reverse transsulfuration pathway in T. gondii and demonstrates the crucial role of TgCBS in biogenesis of H₂S.

A western route of prehistoric human migration from Africa into the Iberian Peninsula

Being at the western fringe of Europe, Iberia had a peculiar prehistory and a complex pattern of Neolithization. A few studies, all based on modern populations, reported the presence of DNA of likely African origin in this region, generally concluding it was the result of recent gene flow, probably during the Islamic period. Here, we provide evidence of much older gene flow from Africa to Iberia by sequencing whole genomes from four human remains from northern Portugal and southern Spain dated around 4000 years BP (from the Middle Neolithic to the Bronze Age). We found one of them to carry an unequivocal sub-Saharan mitogenome of most probably West or West-Central African origin, to our knowledge never reported before in prehistoric remains outside Africa. Our analyses of ancient nuclear genomes show small but significant levels of sub-Saharan African affinity in several ancient Iberian samples, which indicates that what we detected was not an occasional individual phenomenon, but an admixture event recognizable at the population level. We interpret this result as evidence of an early migration process from Africa into the Iberian Peninsula through a western route, possibly across the Strait of Gibraltar.

Structural Insights into the Intracellular Region of the Human Magnesium Transport Mediator CNNM4

The four member family of "Cyclin and Cystathionine β-synthase (CBS) domain divalent metal cation transport mediators", CNNMs, are the least-studied mammalian magnesium transport mediators. CNNM4 is abundant in the brain and the intestinal tract, and its abnormal activity causes Jalili Syndrome. Recent findings show that suppression of CNNM4 in mice promotes malignant progression of intestinal polyps and is linked to infertility. The association of CNNM4 with phosphatases of the regenerating liver, PRLs, abrogates its Mg2+-efflux capacity, thus resulting in an increased intracellular Mg2+ concentration that favors tumor growth. Here we present the crystal structures of the two independent intracellular domains of human CNNM4, i.e., the Bateman module and the cyclic nucleotide binding-like domain (cNMP). We also derive a model structure for the full intracellular region in the absence and presence of MgATP and the oncogenic interacting partner, PRL-1. We find that only the Bateman module interacts with ATP and Mg2+, at non-overlapping sites facilitating their positive cooperativity. Furthermore, both domains dimerize autonomously, where the cNMP domain dimer forms a rigid cleft to restrict the Mg2+ induced sliding of the inserting CBS1 motives of the Bateman module, from a twisted to a flat disk shaped dimer.

Main Contributory Factors on Asthma Control and Health-Related Quality of Life in Elderly Asthmatics

OBJECTIVE

To assess the main factors involved in asthma control and health-related quality of life in elderly asthmatic patients.

METHODS

We performed a retrospective case-control study nested in a historical cohort that compared patients who had partly controlled or uncontrolled asthma (Asthma Control Test [ACT] score ≤19) (cases) with patients who had well-controlled asthma (ACT ≥20) (controls). Clinical data were collected from medical records. Outcomes included ACT score and health-related quality of life (Asthma-Specific Quality of Life Questionnaire [AQLQ]). Pulmonary function was determined by spirometry.

RESULTS

We evaluated 209 asthma patients (151 women) aged ≥65 years. Mean age was 73.55 years. Most patients had persistent moderate (47.60%) or severe (47.12%) asthma. A total ACT score ≤19 was obtained in 64 (30.62%) patients. Lack of adherence to treatment and presence of severe exacerbations were risk factors for partly controlled/uncontrolled asthma (OR, 8.33 and 5.29, respectively). In addition, for each additional unit score in the AQLQ, the risk of poor control increased by 1.51. The factors influencing the AQLQ score were asthma control (ACT) and presence of comorbidities such as depression, gastroesophageal reflux disease, and osteoporosis.

CONCLUSIONS

Despite receiving antiasthma therapy, almost one-third of elderly patients had uncontrolled asthma, possibly as a result of poor adherence, exacerbations, and reduced health-related quality of life. Nonrespiratory comorbid conditions in older patients do not seem to be associated with worse control of asthma symptoms, although their effect on health-related quality of life could indirectly affect asthma control.

Transforming Growth Factor Beta 1 and Vascular Risk in Alcoholics

INTRODUCTION

Transforming growth factor beta-1 (TGF-β1) is a pleiotropic cytokine. Its relationship with atherosclerosis is debatable, protective or deleterious effects have been described. Alcoholics are at increased vascular risk. Although TGF-β1 is increased in alcoholics, its role on vascular risk factors has not been analyzed. This is the objective of this study.

PATIENTS AND METHODS

79 heavy alcoholics and 34 controls were included. Calcium deposition in the aortic arch was assessed in the plain thorax X-ray film. Ankle-brachial index was recorded in 48 patients. All the patients underwent complete laboratory evaluation, including serum levels of TGF-β1, tumor necrosis factor (TNF)-α, interleukin (IL)-4, IL-6, and interferon-γ (IFN-γ).We analyzed the relationships between TGF-β1 and vascular risk factors by both univariate (parametric or non parametric tests), or multivariate analysis to discern on which variables TGF-β1 levels depend.

RESULTS

Serum TGF-β1 levels were higher among patients (t = 2.73; P = 0.008), but no differences exist among cirrhotics (17246 ± 11,021 pg/mL) and non-cirrhotics (21,340 ± 12,442 pg/mL). TGF-β1 showed significant correlations with total cholesterol (r = 0.28; P = 0.017) and HDL- cholesterol (r = 0.25; P = 0.042), and inverse correlations with body mass index (BMI; ρ = -0.37; P = 0.004), IL-4 (ρ = -0.31; P = 0.009), INF-γ (ρ = -0.28; P = 0.001), and IL-6 (ρ = -0.38; P = 0.001). By multivariate analysis, only BMI, IL-6 and HDL-cholesterol showed independent relationships with TGF-β1. No relationships were observed with ankle-brachial index or calcium in the aortic arch, hypertension, diabetes, left ventricular hypertrophy or atrial fibrillation.

CONCLUSION

TGF-β1 levels are increased in alcoholics, but are unrelated to vessel wall calcification or arterial stiffness.

Therapy with ombitasvir/paritaprevir/ritonavir plus dasabuvir is effective and safe for the treatment of genotypes 1 and 4 hepatitis C virus (HCV) infection in patients with severe renal impairment: A multicentre experience

Limited data are available on direct-acting antivirals for treating hepatitis C virus (HCV) infection in patients with severe renal impairment. The aim of this study was to evaluate the effectiveness and safety of ombitasvir/paritaprevir/ritonavir (OBV/PTV/r) ± dasabuvir (DSV) ± ribavirin (RBV) in patients with stage 4 or 5 chronic kidney disease (CKD) and HCV genotype 1 or 4 infection in real clinical practice, and to investigate pharmacological interactions. This retrospective study included patients treated with OBV/PTV/r+DSV±RBV or OBV/PTV/r+RBV with CKD stage 4 (eGFR: 15-29 mL/min/1.73m² ) or 5 (eGFR<15 mL/min/1.73m² or requiring dialysis) and HCV infection by genotypes 1 and 4 between April 2015 and October 2015 in nine Spanish centres. Sustained virological response at 12 weeks (SVR12) was assessed, and clinical and laboratory data, fibrosis stage, adverse events and pharmacological interactions were reported. Forty-six patients were included: 10 (21.7%) had CKD stage 4 and 36 (78.2%) CKD stage 5. Seventeen (36.9%) had cirrhosis. SVR12 rate in the intention-to-treat population was 95.7%. Twenty-one (45.6%) received RBV, which was discontinued in two (9.5%) patients. Anaemia (haemoglobin <10 g/dl) occurred in 12 patients (57.1%) with RBV vs 10 (40.0%) without RBV (P=.246). Renal function remained stable during antiviral therapy. Nine patients (19.5%) experienced serious adverse events unrelated to antiviral therapy. Concomitant medication was discontinued or modified in 41.3% of patients. In conclusion, the effectiveness of OBV/PTV/r±DSV±RBV in patients with CKD 4-5 was similar to that observed in those with normal renal function and was not associated with severe adverse events.

Effectiveness and safety of ombitasvir, paritaprevir, ritonavir ± dasabuvir ± ribavirin: An early access programme for Spanish patients with genotype 1/4 chronic hepatitis C virus infection

Over the last 5 years, therapies for hepatitis C virus (HCV) infection have improved significantly, achieving sustained virologic response (SVR) rates of up to 100% in clinical trials in patients with HCV genotype 1. We investigated the effectiveness and safety of ombitasvir/paritaprevir/ritonavir±dasabuvir in an early access programme. This was a retrospective, multicentre, national study that included 291 treatment-naïve and treatment-experienced patients with genotype 1 or 4 HCV infection. Most patients (65.3%) were male, and the mean age was 57.5 years. The mean baseline viral load was 6.1 log, 69.8% had HCV 1b genotype, 72.9% had cirrhosis and 34.7% were treatment-naïve. SVR at 12 weeks posttreatment was 96.2%. Four patients had virological failure (1.4%), one leading to discontinuation. There were no statistical differences in virological response according to genotype or liver fibrosis. Thirty patients experienced serious adverse events (SAEs) (10.3%), leading to discontinuation in six cases. Hepatic decompensation was observed in five patients. Four patients died during treatment or follow-up, three of them directly related to liver failure. Multivariate analyses showed a decreased probability of achieving SVR associated with baseline albumin, bilirubin and Child-Pugh score B, and a greater probability of developing SAEs related to age and albumin. This combined therapy was highly effective in clinical practice with an acceptable safety profile and low rates of treatment discontinuation.

Serum sclerostin in alcoholics: a pilot study

AIMS

Sclerostin is an endogenous inhibitor of the Wnt/β-catenin pathway secreted by osteocytes, which inhibits osteoblast function, differentiation and survival. As a consequence, sclerostin tends to decrease bone mass. Alcoholics frequently present osteoporosis, mainly due to decreased bone synthesis. The behaviour of sclerostin in these patients is unknown. The aim of this work was to analyse the relationship between serum sclerostin levels and bone mineral density (BMD), ethanol consumption, nutritional status, liver function derangement and biomarkers of bone homeostasis in alcoholic patients.

METHODS

We included 31 alcoholic patients, of whom 11 were infected with Hepatitis C virus (HCV) and 7 age and sex-matched controls. All underwent densitometry, and serum sclerostin, osteocalcin, collagen telopeptide, parathyroid hormone (PTH), vitamin D, cortisol and testosterone were determined.

RESULTS

Sclerostin levels were significantly higher in patients (30.95 ± 18.91 pmol/l) than controls (t = 4.4; P < 0.001), especially in non-HCV patients; they showed an inverse correlation with osteocalcin, prothrombin activity and serum albumin, and a direct correlation with bilirubin and telopeptide, but not with BMD, nutritional status or ethanol intake.

CONCLUSIONS

Serum sclerostin was raised in alcoholic patients, and it correlated with decreased markers of bone synthesis and increased markers of bone breakdown. The elevation in sclerostin levels was clearly related with liver function, but not with ethanol intake, nutritional status or concomitant HCV infection.