Glutathionylation chemistry promotes interleukin-1 beta-mediated glycolytic reprogramming and pro-inflammatory signaling in lung epithelial cells

Subnormothermic ex vivo lung perfusion possibly protects against ischemia-reperfusion injury via the mTORC-HIF-1α pathway

Background

Ex vivo lung perfusion (EVLP) is a useful technique for evaluating and repairing donor lungs for transplantation. However, studies examining the effects of perfusate temperature on graft function are limited. Thus, this study aimed to examine these effects during EVLP on ischemic-reperfusion injury in the donor lung.

Methods

Twenty-four male Sprague-Dawley rats were randomly divided into three groups, as follows: no treatment (sham group, n=5), normothermic EVLP (37 °C, n=5), and subnormothermic EVLP (30 °C, n=5). Lung function analyses, including oxygen capacity (OC), compliance, and pulmonary vascular resistance (PVR), were performed hourly during EVLP. Further, after 4 h of EVLP, histological evaluation of the right lobe was performed using the lung injury severity (LIS) scale. The expression levels of inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-18 were evaluated. Metabolomic analysis of left lung tissues was conducted using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) after 4 h of EVLP in the EVLP groups and after 1 h of cold preservation in the sham group.

Results

Compared with those in the normothermic group, in the subnormothermic group, functional parameters during EVLP and subsequent histologic results were significantly superior, expression levels of inflammatory cytokines such as TNF-α, IL-1β, IL-6, and IL-18 were significantly lower, and glycolytic activity was significantly decreased. Furthermore, expression levels of mammalian target of rapamycin complex (mTORC), hypoxia-inducible factor (HIF) 1α, and nucleotide-binding domain, leucine-rich-containing family pyrin domain containing 3 (NLRP3) and its effector caspase-1 were significantly lower in the subnormothermic group than in the normothermic group.

Conclusions

EVLP with subnormothermic perfusion improves lung graft function by reducing the expression of pro-inflammatory cytokines and glycolytic activity during EVLP. Additionally, EVLP can be a useful target for the improvement of graft function after transplantation.

Glutaredoxin attenuates glutathione levels via deglutathionylation of Otub1 and subsequent destabilization of system xC. SCIENCE ADVANCES 2023;9:eadi5192. [PMID: 37703360 PMCID: PMC10499329 DOI: 10.1126/sciadv.adi5192]

Glutathione (GSH) is a critical component of the cellular redox system that combats oxidative stress. The glutamate-cystine antiporter, system xC-, is a key player in GSH synthesis that allows for the uptake of cystine, the rate-limiting building block of GSH. It is unclear whether GSH or GSH-dependent protein oxidation [protein S-glutathionylation (PSSG)] regulates the activity of system xC-. We demonstrate that an environment of enhanced PSSG promotes GSH increases via a system xC--dependent mechanism. Absence of the deglutathionylase, glutaredoxin (GLRX), augmented SLC7A11 protein and led to significant increases of GSH content. S-glutathionylation of C23 or C204 of the deubiquitinase OTUB1 promoted interaction with the E2-conjugating enzyme UBCH5A, leading to diminished ubiquitination and proteasomal degradation of SLC7A11 and augmentation of GSH, effects that were reversed by GLRX. These findings demonstrate an intricate link between GLRX and GSH via S-glutathionylation of OTUB1 and system xC- and illuminate a previously unknown feed-forward regulatory mechanism whereby enhanced GSH protein oxidation augments cellular GSH.

Structural and functional fine mapping of cysteines in mammalian glutaredoxin reveal their differential oxidation susceptibility

Protein-S-glutathionylation is a post-translational modification involving the conjugation of glutathione to protein thiols, which can modulate the activity and structure of key cellular proteins. Glutaredoxins (GLRX) are oxidoreductases that regulate this process by performing deglutathionylation. However, GLRX has five cysteines that are potentially vulnerable to oxidative modification, which is associated with GLRX aggregation and loss of activity. To date, GLRX cysteines that are oxidatively modified and their relative susceptibilities remain unknown. We utilized molecular modeling approaches, activity assays using recombinant GLRX, coupled with site-directed mutagenesis of each cysteine both individually and in combination to address the oxidizibility of GLRX cysteines. These approaches reveal that C8 and C83 are targets for S-glutathionylation and oxidation by hydrogen peroxide in vitro. In silico modeling and experimental validation confirm a prominent role of C8 for dimer formation and aggregation. Lastly, combinatorial mutation of C8, C26, and C83 results in increased activity of GLRX and resistance to oxidative inactivation and aggregation. Results from these integrated computational and experimental studies provide insights into the relative oxidizability of GLRX's cysteines and have implications for the use of GLRX as a therapeutic in settings of dysregulated protein glutathionylation.

In vivo evaluation of the effect of sickle cell hemoglobin S, C and therapeutic transfusion on erythrocyte metabolism and cardiorenal dysfunction

Despite a wealth of exploratory plasma metabolomics studies in sickle cell disease (SCD), no study to date has evaluate a large and well phenotyped cohort to compare the primary erythrocyte metabolome of hemoglobin SS, SC and transfused AA red blood cells (RBCs) in vivo. The current study evaluates the RBC metabolome of 587 subjects with sickle cell sickle cell disease (SCD) from the WALK-PHaSST clinical cohort. The set includes hemoglobin SS, hemoglobin SC SCD patients, with variable levels of HbA related to RBC transfusion events. Here we explore the modulating effects of genotype, age, sex, severity of hemolysis, and transfusion therapy on sickle RBC metabolism. Results show that RBCs from patients with Hb SS genotypes-compared to AA RBCs from recent transfusion events or SC RBCs-are characterized by significant alterations of RBC acylcarnitines, pyruvate, sphingosine 1-phosphate, creatinine, kynurenine and urate metabolism. Surprisingly, the RBC metabolism of SC RBCs is dramatically different from SS, with all glycolytic intermediates significantly elevated in SS RBCs, with the exception of pyruvate. This result suggests a metabolic blockade at the ATP-generating phosphoenolpyruvate to pyruvate step of glycolysis, which is catalyzed by redox-sensitive pyruvate kinase. Metabolomics, clinical and hematological data were collated in a novel online portal. In conclusion, we identified metabolic signatures of HbS RBCs that correlate with the degree of steady state hemolytic anemia, cardiovascular and renal dysfunction and mortality.

Red Blood Cell Metabolism In Vivo and In Vitro

Red blood cells (RBC) are the most abundant cell in the human body, with a central role in oxygen transport and its delivery to tissues. However, omics technologies recently revealed the unanticipated complexity of the RBC proteome and metabolome, paving the way for a reinterpretation of the mechanisms by which RBC metabolism regulates systems biology beyond oxygen transport. The new data and analytical tools also informed the dissection of the changes that RBCs undergo during refrigerated storage under blood bank conditions, a logistic necessity that makes >100 million units available for life-saving transfusions every year worldwide. In this narrative review, we summarize the last decade of advances in the field of RBC metabolism in vivo and in the blood bank in vitro, a narrative largely influenced by the authors' own journeys in this field. We hope that this review will stimulate further research in this interesting and medically important area or, at least, serve as a testament to our fascination with this simple, yet complex, cell.

Metabolic reprogramming of pulmonary fibrosis

Pulmonary fibrosis is a progressive and intractable lung disease with fibrotic features that affects alveoli elasticity, which leading to higher rates of hospitalization and mortality worldwide. Pulmonary fibrosis is initiated by repetitive localized micro-damages of the alveolar epithelium, which subsequently triggers aberrant epithelial-fibroblast communication and myofibroblasts production in the extracellular matrix, resulting in massive extracellular matrix accumulation and interstitial remodeling. The major cell types responsible for pulmonary fibrosis are myofibroblasts, alveolar epithelial cells, macrophages, and endothelial cells. Recent studies have demonstrated that metabolic reprogramming or dysregulation of these cells exerts their profibrotic role via affecting pathological mechanisms such as autophagy, apoptosis, aging, and inflammatory responses, which ultimately contributes to the development of pulmonary fibrosis. This review summarizes recent findings on metabolic reprogramming that occur in the aforementioned cells during pulmonary fibrosis, especially those associated with glucose, lipid, and amino acid metabolism, with the aim of identifying novel treatment targets for pulmonary fibrosis.

Ketone body augmentation decreases methacholine hyperresponsiveness in mouse models of allergic asthma

Background

Individuals with allergic asthma exhibit lung inflammation and remodeling accompanied by methacholine hyperresponsiveness manifesting in proximal airway narrowing and distal lung tissue collapsibility, and they can present with a range of mild-to-severe disease amenable or resistant to therapeutic intervention, respectively. There remains a need for alternatives or complements to existing treatments that could control the physiologic manifestations of allergic asthma.

Objectives

Our aim was to examine the hypothesis that because ketone bodies elicit anti-inflammatory activity and are effective in mitigating the methacholine hyperresponsiveness associated with obese asthma, increasing systemic concentrations of ketone bodies would diminish pathologic outcomes in asthma-relevant cell types and in mouse models of allergic asthma.

Methods

We explored the effects of ketone bodies on allergic asthma-relevant cell types (macrophages, airway epithelial cells, CD4 T cells, and bronchial smooth muscle cells) in vitro as well as in vivo by using preclinical models representative of several endotypes of allergic asthma to determine whether promotion of ketosis through feeding a ketogenic diet or providing a ketone precursor or a ketone ester dietary supplement could affect immune and inflammatory parameters as well as methacholine hyperresponsiveness.

Results

In a dose-dependent manner, the ketone bodies acetoacetate and β-hydroxybutyrate (BHB) decreased proinflammatory cytokine secretion from mouse macrophages and airway epithelial cells, decreased house dust mite (HDM) extract-induced IL-8 secretion from human airway epithelial cells, and decreased cytokine production from polyclonally and HDM-activated T cells. Feeding a ketogenic diet, providing a ketone body precursor, or supplementing the diet with a ketone ester increased serum BHB concentrations and decreased methacholine hyperresponsiveness in several acute HDM sensitization and challenge models of allergic asthma. A ketogenic diet or ketone ester supplementation decreased methacholine hyperresponsiveness in an HDM rechallenge model of chronic allergic asthma. Ketone ester supplementation synergized with corticosteroid treatment to decrease methacholine hyperresponsiveness in an HDM-driven model of mixed-granulocytic severe asthma. HDM-induced morphologic changes in bronchial smooth muscle cells were inhibited in a dose-dependent manner by BHB, as was HDM protease activity.

Conclusions

Increasing systemic BHB concentrations through dietary interventions could provide symptom relief for several endotypes of allergic asthmatic individuals through effects on multiple asthma-relevant cells.

S-Glutathionylation-Controlled Apoptosis of Lung Epithelial Cells; Potential Implications for Lung Fibrosis

Glutathione (GSH), a major antioxidant in mammalian cells, regulates several vital cellular processes, such as nutrient metabolism, protein synthesis, and immune responses. In addition to its role in antioxidant defense, GSH controls biological processes through its conjugation to reactive protein cysteines in a post-translational modification known as protein S-glutathionylation (PSSG). PSSG has recently been implicated in the pathogenesis of multiple diseases including idiopathic pulmonary fibrosis (IPF). Hallmarks of IPF include repeated injury to the alveolar epithelium with aberrant tissue repair, epithelial cell apoptosis and fibroblast resistance to apoptosis, and the accumulation of extracellular matrix and distortion of normal lung architecture. Several studies have linked oxidative stress and PSSG to the development and progression of IPF. Additionally, it has been suggested that the loss of epithelial cell homeostasis and increased apoptosis, accompanied by the release of various metabolites, creates a vicious cycle that aggravates disease progression. In this short review, we highlight some recent studies that link PSSG to epithelial cell apoptosis and highlight the potential implication of metabolites secreted by apoptotic cells.

Therapeutic ketosis decreases methacholine hyperresponsiveness in mouse models of inherent obese asthma

Obese asthmatics tend to have severe, poorly controlled disease and exhibit methacholine hyperresponsiveness manifesting in proximal airway narrowing and distal lung tissue collapsibility. Substantial weight loss in obese asthmatics or in mouse models of the condition decreases methacholine hyperresponsiveness. Ketone bodies are rapidly elevated during weight loss, coinciding with or preceding relief from asthma-related comorbidities. As ketone bodies may exert numerous potentially therapeutic effects, augmenting their systemic concentrations is being targeted for the treatment of several conditions. Circulating ketone body levels can be increased by feeding a ketogenic diet or by providing a ketone ester dietary supplement, which we hypothesized would exert protective effects in mouse models of inherent obese asthma. Weight loss induced by feeding a low-fat diet to mice previously fed a high-fat diet was preceded by increased urine and blood levels of the ketone body β-hydroxybutyrate (BHB). Feeding a ketogenic diet for 3 wk to high-fat diet-fed obese mice or genetically obese db/db mice increased BHB concentrations and decreased methacholine hyperresponsiveness without substantially decreasing body weight. Acute ketone ester administration decreased methacholine responsiveness of normal mice, and dietary ketone ester supplementation of high-fat diet-fed mice decreased methacholine hyperresponsiveness. Ketone ester supplementation also transiently induced an "antiobesogenic" gut microbiome with a decreased Fermicutes/Bacteroidetes ratio. Dietary interventions to increase systemic BHB concentrations could provide symptom relief for obese asthmatics without the need for the substantial weight loss required of patients to elicit benefits to their asthma through bariatric surgery or other diet or lifestyle alterations.

Pharmacometabolomics Profiling of Preterm Infants Validates Patterns of Metabolism Associated With Response to Dexamethasone Treatment for Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is one of the most common health complications of premature birth. Corticosteroids are commonly used for treatment of BPD, but their use is challenging due to variability in treatment response. Previous pharmacometabolomics study has established patterns of metabolite levels with response to dexamethasone. We obtained additional patient samples for metabolomics analysis to find associations between the metabolome and dexamethasone response in a validation cohort. A total of 14 infants provided 15 plasma and 12 urine samples. The measure of treatment response was the calculated change in respiratory severity score (deltaRSS) from pre-to-post treatment. Each metabolite was assessed with paired analysis of pre and post-treatment samples using Wilcoxon signed rank test. Correlation analysis was conducted between deltaRSS and pre-to-post change in metabolite level. Paired association analysis identified 20 plasma and 26 urine metabolites with significant level difference comparing pre to post treatment samples (p < 0.05). 4 plasma and 4 urine metabolites were also significant in the original study. Pre-to-post treatment change in metabolite analysis identified 4 plasma and 8 urine metabolites significantly associated with deltaRSS (p < 0.05). Change in urine citrulline levels showed a similar correlation pattern with deltaRSS in the first study, with increasing level associated with improved drug response. These results help validate the first major findings from pharmacometabolomics of BPD including key metabolites within the urea cycle and trans-4-hydroxyproline as a potential marker for lung injury. Ultimately, this study furthers our understanding of the mechanisms of steroid response in BPD patients and helps to design future targeted metabolomics studies in this patient population.