Role of human aldehyde dehydrogenases in endobiotic and xenobiotic metabolism

A genetically encoded tool to increase cellular NADH/NAD+ ratio in living cells

Impaired redox metabolism is a key contributor to the etiology of many diseases, including primary mitochondrial disorders, cancer, neurodegeneration and aging. However, mechanistic studies of redox imbalance remain challenging due to limited strategies that can perturb redox metabolism in various cellular or organismal backgrounds. Most studies involving impaired redox metabolism have focused on oxidative stress; consequently, less is known about the settings where there is an overabundance of NADH reducing equivalents, termed reductive stress. Here we introduce a soluble transhydrogenase from Escherichia coli (EcSTH) as a novel genetically encoded tool to promote reductive stress in living cells. When expressed in mammalian cells, EcSTH, and a mitochondrially targeted version (mitoEcSTH), robustly elevated the NADH/NAD+ ratio in a compartment-specific manner. Using this tool, we determined that metabolic and transcriptomic signatures of the NADH reductive stress are cellular background specific. Collectively, our novel genetically encoded tool represents an orthogonal strategy to promote reductive stress.

IRF4 Knockdown Inhibits the Chronic Rhinosinusitis Without Nasal Polyps Development by Regulating NLRP3/Caspase-1/GSDMD-Mediated Pyroptosis

Chronic rhinosinusitis without nasal polyps (CRSsNP) is a CRS phenotype. However, the mechanisms of CRSsNP remains unclear. Differentially expressed genes (DEGs) were obtained from the GSE36830 and GSE198950 datasets through the GEO2R tool. The six hub genes were screened by the protein-protein interaction (PPI) network analysis and Cytoscape software. Then we constructed the mouse models of CRS and verified the expression levels of hub genes by reverse transcription quantitative PCR (RT-qPCR). Hematoxylin-eosin (HE) staining was employed to observe pathological alterations in mouse tissues. Casepase-3 expression was detected by immunohistochemistry (IHC). The levels of TNF-α, IL-12, IL-6, IL-1β, LDH, and IL-18 were evaluated using enzyme-linked immunosorbent assay (ELISA). Pyroptosis-related protein expressions were measured by western blotting. Cell counting kit-8 (CCK-8) and flow cytometry were performed to assess the proliferation and apoptosis of lipopolysaccharide (LPS)-induced NP69 cells. Six hub DEGs were identified. The expression levels of IRF4, IKZF1, and CD79A were obviously increased in CRSsNP, while those of ADH6, ADH1A, and LDHC were significantly decreased. IRF4 knockdown attenuated the pathologic features of CRSsNP. IRF4 knockdown reduced levels of the TNF-α, IL-12, IL-6 IL-1β, LDH, and IL-18 as well as the proteins expression of Casepase-1, GSDMD, and NLRP3 both in vivo and in vitro, implying that inflammation and pyroptosis were inhibited. IRF4 knockdown hinders the development of CRSsNP by inhibiting the inflammatory response and NLRP3/Caspase-1/GSDMD-mediated pyroptosis, which offers novel promising treatment strategies for clinical intervention.

A model of alcoholic liver disease based on different hepatotoxics leading to liver cancer

The worst-case scenario related to alcoholic liver disease (ALD) arises after a long period of exposure to the harmful effect of alcohol consumption along with other hepatotoxics. ALD encompasses a broad spectrum of liver-associated disorders, such as steatosis, steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Based on the chronic administration of different hepatotoxics, including ethanol, sucrose, lipopolysaccharide, and low doses of diethylnitrosamine over a short period, here we aimed to develop a multiple hepatotoxic (MHT)-ALD model in the mouse that recapitulates the human ALD-associated disorders. We demonstrated that the MHT-ALD model induces ADH1A and NXN, an ethanol metabolizer and a redox-sensor enzyme, respectively; promotes steatosis associated with the induction of the lipid droplet forming FSP27, inflammation identified by the infiltration of hepatic neutrophils-positive to LY-6G marker, and the increase of MYD88 level, a protein involved in inflammatory response; and stimulates the early appearance of cellular senescence identified by the senescence markers SA-β-gal activity and p-H2A.XSer139. It also induces fibrosis associated with increased desmin, a marker of hepatic stellate cells whose activation leads to the deposition of collagen fibers, accompanied by cell death and compensatory proliferation revealed by increased CASP3-mediated apoptosis, and KI67- and PCNA-proliferation markers, respectively. It also induces histopathological traits of malignancy and the level of the HCC marker, GSTP1. In conclusion, we provide a useful model for exploring the chronological ALD-associated alterations and stages, and addressing therapeutic approaches.

Biological evaluation of levofloxacin and its thionated derivatives: antioxidant activity, aldehyde dehydrogenase enzyme inhibition, and cytotoxicity on A549 cell line

Levofloxacin (LVX) is among the fluoroquinolones antibiotics that has also been studied in vitro and in vivo for its anticancer effects. In this study, we used LVX and novel LVX thionated derivatives; compounds 2 and 3, to evaluate their antioxidant activity, aldehyde dehydrogenase (ALDH) enzymes activity inhibition, and anticancer activity. Combination treatments with doxorubicin (DOX) were investigated as well. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to determine the antioxidant activity. The NADH fluorescence spectrophotometric activity assay was used to determine the ALDH inhibitory effects. Resazurin dye method was applied for cell viability assays. Molecular Operating Environment software was used for the molecular docking experiments. Compared to ascorbic acid, DPPH assay showed that compound 3 had the highest antioxidant activity among the tested compounds with approximately 35% scavenging activity. On ALDH enzymes, compound 3 showed a significant ALDH activity inhibition compared to compound 2 at 200 µM. The IC50 values for the tested compounds were approximately 100 µM on A549 cell line, a non-small cell lung cancer (NSCLC) cell line. However, significant enhancement of cytotoxicity and reduction of IC50 values were observed by combining DOX and synergism was achieved with LVX with a combination index value of 0.4. The molecular docking test showed a minimum binding energy with a good affinity for compound 3 towards ALDH enzymes. Thionated LVX derivatives, may be repurposed for NSCLC therapy in combination with DOX, taking into account the antioxidant activity, ALDH activity inhibition, and the molecular docking results of compound 3.

Informed by Cancer Stem Cells of Solid Tumors: Advances in Treatments Targeting Tumor-Promoting Factors and Pathways

Cancer stem cells (CSCs) represent a subpopulation within tumors that promote cancer progression, metastasis, and recurrence due to their self-renewal capacity and resistance to conventional therapies. CSC-specific markers and signaling pathways highly active in CSCs have emerged as a promising strategy for improving patient outcomes. This review provides a comprehensive overview of the therapeutic targets associated with CSCs of solid tumors across various cancer types, including key molecular markers aldehyde dehydrogenases, CD44, epithelial cellular adhesion molecule, and CD133 and signaling pathways such as Wnt/β-catenin, Notch, and Sonic Hedgehog. We discuss a wide array of therapeutic modalities ranging from targeted antibodies, small molecule inhibitors, and near-infrared photoimmunotherapy to advanced genetic approaches like RNA interference, CRISPR/Cas9 technology, aptamers, antisense oligonucleotides, chimeric antigen receptor (CAR) T cells, CAR natural killer cells, bispecific T cell engagers, immunotoxins, drug-antibody conjugates, therapeutic peptides, and dendritic cell vaccines. This review spans developments from preclinical investigations to ongoing clinical trials, highlighting the innovative targeting strategies that have been informed by CSC-associated pathways and molecules to overcome therapeutic resistance. We aim to provide insights into the potential of these therapies to revolutionize cancer treatment, underscoring the critical need for a multi-faceted approach in the battle against cancer. This comprehensive analysis demonstrates how advances made in the CSC field have informed significant developments in novel targeted therapeutic approaches, with the ultimate goal of achieving more effective and durable responses in cancer patients.

Development of substituted benzimidazoles as inhibitors of human aldehyde dehydrogenase 1A isoenzymes

Aldehyde dehydrogenase 1A (ALDH1A) isoforms may be a useful target for overcoming chemotherapy resistance in high-grade serous ovarian cancer (HGSOC) and other solid tumor cancers. However, as different cancers express different ALDH1A isoforms, isoform selective inhibitors may have a limited therapeutic scope. Furthermore, resistance to an ALDH1A isoform selective inhibitor could arise via induction of expression of other ALDH1A isoforms. As such, we have focused on the development of pan-ALDH1A inhibitors, rather than on ALDH1A isoform selective compounds. Herein, we report the development of a new group of pan-ALDH1A inhibitors to assess whether broad spectrum ALDH1A inhibition is an effective adjunct to chemotherapy in HGSOC. Optimization of the CM10 scaffold, aided by ALDH1A1 crystal structures, led to improved biochemical potencies, improved cellular efficacy as demonstrated by reduction in ALDEFLUOR signal in HGSOC cells, and substantial improvements in liver microsomal stability. Based on this work we identified two compounds 17 and 25 suitable for future in vivo proof of concept experiments.

Potential clinical significance of ALDH3B1 in auxiliary diagnosis of gastric cancer

Objective: This research aimed to explore a diagnostic method based on serum ALDH3B1 and to evaluate the clinical diagnostic efficacy in gastric cancer (GC) by comparing it with the traditional GC diagnostic method, the carcinoembryonic protein (CEA) assay. Methods: Serum samples were collected from 70 healthy volunteers and various patients (GC: 76, benign gastric lesions: 20, postoperative: 37, recurrence: 56). The diagnostic efficacy of serum ALDH3B1, CEA and the co-diagnosis were evaluated by receiver operating characteristic curve. ALDH3B1 protein levels were evaluated by western blot. Results: The co-diagnosis of ALDH3B1 and CEA had the highest diagnostic efficacy (area under the curve = 0.841). Conclusion: Serum ALDH3B1 may be used as an auxiliary diagnostic biomarker for GC, and its co-diagnosis with CEA can improve diagnostic efficacy.

Insights from metabolomics and transcriptomics studies on Perfluorohexanesulfonic acid (PFHxS) exposed zebrafish embryos

Perfluorohexanesulfonic acid (PFHxS) is a short-chain perfluoroalkyl substance widely used to replace the banned perfluorooctanesulfonic acid (PFOS) in various industrial and household products. It can be found in the environment and human bodies; however, its potential toxicities are not well studied. Zebrafish have been extensively used as a model for studying toxicants, and currently, two studies have reported on the toxicity of PFHxS in zebrafish from different approaches. Ulhaq and Tse (J Hazard Mater. 2023; 457: 131722) conducted general biological experiments and applied transcriptomics to demonstrate that PFHxS at a concentration of 5 μM could affect glucose and fatty acid metabolism, leading to oxidative stress, developmental defects, and cell cycle arrest. Xu et al. (Sci Total Environ. 2023; 887: 163770) employed metabolomics and showed that concentrations of various metabolites changed after exposure to 3 and 10 μM PFHxS. As we observed a match between the metabolomics data and our biochemistry experimental findings, we integrated the two studies, which enabled us to unfold the possible mechanism of the deregulated metabolites. We identified 22 differential expressed genes (DEGs) in the tricarboxylic acid (TCA) cycle, 17 DEGs in glcyolytic process, including the critical glucokinase under the carbon metabolism. Besides, genes likes aldehyde dehydrogenases, and histone-lysine N-methyltransferases that participate in lipid peroxidation and amino metabolism respectively were spotted. Lastly, we further strengthen our discoveries by undergoing the gene set enrichment analysis. This article could provide insights into the toxicity of PFHxS, as well as prospects for environmental studies.

ALDEFLUOR activity, ALDH isoforms, and their clinical significance in cancers

High aldehyde dehydrogenase (ALDH) activity is a metabolic feature of adult stem cells and various cancer stem cells (CSCs). The ALDEFLUOR system is currently the most commonly used method for evaluating ALDH enzyme activity in viable cells. This system is applied extensively in the isolation of normal stem cells and CSCs from heterogeneous cell populations. For many years, ALDH1A1 has been considered the most important subtype among the 19 ALDH family members in determining ALDEFLUOR activity. However, in recent years, studies of many types of normal and tumour tissues have demonstrated that other ALDH subtypes can also significantly influence ALDEFLUOR activity. In this article, we briefly review the relationships between various members of the ALDH family and ALDEFLUOR activity. The clinical significance of these ALDH isoforms in different cancers and possible directions for future studies are also summarised.

Patients with Non-Alcoholic Fatty Liver Disease and Alcohol Dehydrogenase 1B/Aldehyde Dehydrogenase 2 Mutant Gene Have Higher Values of Serum Alanine Transaminase

Patients with non-alcoholic fatty liver disease (NAFLD) share similar pathophysiologies to those of patients with alcohol liver disease. Alcoholic metabolic enzyme-related genes (alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2)) may be associated with pathophysiology in NAFLD patients. In this study, the association between ADH1B/ALDH2 gene polymorphism and serum metabolic factors, body statures, and hepatic steatosis/fibrosis status was evaluated in patients with NAFLD. Using biochemistry data, abdominal ultrasonography, fibrosis evaluation (Kpa), and steatosis evaluation (CAP), ADH1B gene SNP rs1229984 and ALDH2 gene SNP rs671 polymorphism were analyzed in sixty-six patients from 1 January 2022 to 31 December 2022. The percentage of the mutant type (GA + AA) was 87.9% (58/66) in the ADH1B allele and 45.5% (30/66) in the ALDH2 allele. Patients with the mutant-type ADH1B/ALDH2 allele had higher values of alanine aminotransferase (ALT) than the wild type (β = 0.273, p = 0.04). No association was observed between body mass index, serum metabolic factors (sugar and lipid profile), CAP, kPa, and ADH1B/ALDH2. A high proportion of the mutant-type ADH1B allele (87.9%) and ALDH2 allele (45.5%) was observed in patients with NAFLD. No association was observed between ADH1B/ALDH2 allele, BMI, and hepatic steatosis/fibrosis. Patients with the mutant-type ADH1B/ALDH2 allele had higher values of ALT than those with the wild type.

An insight into the associations between microRNA expression and mitochondrial functions in cancer cell and cancer stem cell

The self-renew ability of cancer stem cells (CSCs) continues to challenge our determination for accomplishing cancer therapy breakthrough. Ineffectiveness of current cancer therapies to eradicate CSCs has contributed to chemoresistance and tumor recurrence. Yet, the discoveries of highly effective therapies have not been thoroughly developed. Further insights into cancer metabolomics and gene-regulated mechanisms of mitochondria in CSCs can expedite the development of novel anticancer drugs. In cancer cells, the metabolism is reprogrammed from oxidative phosphorylation (OXPHOS) to glycolysis. This alteration allows the cancer cell to receive continuous energy supplies and avoid apoptosis. The pyruvate obtained from glycolysis produces acetyl-coenzyme A (Acetyl-CoA) via oxidative decarboxylation and enters the tricarboxylic acid cycle for adenosine triphosphate generation. Mitochondrial calcium ion (Ca²⁺) uptake is responsible for mitochondrial physiology regulation, and reduced uptake of Ca²⁺  inhibits apoptosis and enhances cell survival in cancer. There have been many discoveries of mitochondria-associated microRNAs (miRNAs) stimulating the metabolic alterations in mitochondria via gene regulation which promote cancer cell survival. These miRNAs are also found in CSCs where they regulate genes and activate different mechanisms to destroy the mitochondria and enhance CSCs survival. By targeting the miRNAs that induced mitochondrial destruction, the mitochondrial functions can be restored; thus, it triggers CSCs apoptosis and completely eliminates the CSCs. In general, this review article aims to address the associations between miRNAs with mitochondrial activities in cancer cells and cancer stem cells that support cancer cell survival and self-renewal.

A Selective ALDH1A3 Inhibitor Impairs Mesothelioma 3-D Multicellular Spheroid Growth and Neutrophil Recruitment

Aldehyde dehydrogenase 1A3 (ALDH1A3), one of the three members of the aldehyde dehydrogenase 1A subfamily, has been associated with increased progression and drug resistance in various types of solid tumours. Recently, it has been reported that high ALDH1A3 expression is prognostic of poor survival in patients with malignant pleural mesothelioma (MPM), an asbestos-associated chemoresistant cancer. We treated MPM cells, cultured as multicellular spheroids, with NR6, a potent and highly selective ALDH1A3 inhibitor. Here we report that NR6 treatment caused the accumulation of toxic aldehydes, induced DNA damage, CDKN2A expression and cell growth arrest. We observed that, in CDKN2A proficient cells, NR6 treatment induced IL6 expression, but abolished CXCL8 expression and IL-8 release, preventing both neutrophil recruitment and generation of neutrophil extracellular traps (NETs). Furthermore, we demonstrate that in response to ALDH1A3 inhibition, CDKN2A loss skewed cell fate from senescence to apoptosis. Dissecting the role of ALDH1A3 isoform in MPM cells and tumour microenvironment can open new fronts in the treatment of this cancer.

In Vitro Evaluation of ALDH1A3-Affinic Compounds on Breast and Prostate Cancer Cell Lines as Single Treatments and in Combination with Doxorubicin

Aldehyde dehydrogenase (ALDH) enzymes are involved in the growth and development of several tissues, including cancer cells. It has been reported that targeting the ALDH family, including the ALDH1A subfamily, enhances cancer treatment outcomes. Therefore, we aimed to investigate the cytotoxicity of ALDH1A3-affinic compounds that have been recently discovered by our group, on breast (MCF7 and MDA-MB-231) and prostate (PC-3) cancer cell lines. These compounds were investigated on the selected cell lines as single treatments and in combination with doxorubicin (DOX). Results showed that the combination treatment experiments of the selective ALDH1A3 inhibitors (compounds 15 and 16) at variable concentrations with DOX resulted in significant increases in the cytotoxic effect on the MCF7 cell line for compound 15, and to a lesser extent for compound 16 on the PC-3 cell line, compared to DOX alone. The activity of compounds 15 and 16 as single treatments on all cell lines was found to be non-cytotoxic. Therefore, our findings showed that the investigated compounds have a promising potential to target cancer cells, possibly via an ALDH-related pathway, and sensitize them to DOX treatment.

The role of acetaldehyde dehydrogenase 2 in the pathogenesis of liver diseases

Common liver tissue damage is mainly due to the accumulation of toxic aldehydes in lipid peroxidation under oxidative stress. Cumulative toxic aldehydes in the liver can be effectively metabolized by acetaldehyde dehydrogenase 2 (ALDH2), thereby alleviating various liver diseases. Notably, gene mutation of ALDH2 leads to impaired ALDH2 enzyme activity, thus aggravating the progress of liver diseases. However, the relationship and specific mechanism between ALDH2 and liver diseases are not clear. Consequently, the review explains the relationship between ALDH2 and liver diseases such as alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), liver fibrosis and hepatocellular carcinoma (HCC). In addition, this review also discusses ALDH2 as a potential therapeutic target for various liver diseases,and focuses on summarizing the regulatory mechanism of ALDH2 in these liver diseases.

Aldehyde dehydrogenase in solid tumors and other diseases: Potential biomarkers and therapeutic targets

The family of aldehyde dehydrogenases (ALDHs) contains 19 isozymes and is involved in the oxidation of endogenous and exogenous aldehydes to carboxylic acids, which contributes to cellular and tissue homeostasis. ALDHs play essential parts in detoxification, biosynthesis, and antioxidants, which are of important value for cell proliferation, differentiation, and survival in normal body tissues. However, ALDHs are frequently dysregulated and associated with various diseases like Alzheimer's disease, Parkinson's disease, and especially solid tumors. Notably, the involvement of the ALDHs in tumor progression is responsible for the maintenance of the stem-cell-like phenotype, triggering rapid and aggressive clinical progressions. ALDHs have captured increasing attention as biomarkers for disease diagnosis and prognosis. Nevertheless, these require further longitudinal clinical studies in large populations for broad application. This review summarizes our current knowledge regarding ALDHs as potential biomarkers in tumors and several non-tumor diseases, as well as recent advances in our understanding of the functions and underlying molecular mechanisms of ALDHs in disease development. Finally, we discuss the therapeutic potential of ALDHs in diseases, especially in tumor therapy with an emphasis on their clinical implications.

"Pulsed Hypoxia" Gradually Reprograms Breast Cancer Fibroblasts into Pro-Tumorigenic Cells via Mesenchymal-Epithelial Transition

Hypoxia arises in most growing solid tumors and can lead to pleotropic effects that potentially increase tumor aggressiveness and resistance to therapy through regulation of the expression of genes associated with the epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET). The main goal of the current work was to obtain and investigate the intermediate phenotype of tumor cells undergoing the hypoxia-dependent transition from fibroblast to epithelial morphology. Primary breast cancer fibroblasts BrC4f, being cancer-associated fibroblasts, were subjected to one or two rounds of "pulsed hypoxia" (PH). PH induced transformation of fibroblast-shaped cells to semi-epithelial cells. Western blot analysis, fluorescent microscopy and flow cytometry of transformed cells demonstrated the decrease in the mesenchymal markers vimentin and N-cad and an increase in the epithelial marker E-cad. These cells kept mesenchymal markers αSMA and S100A4 and high ALDH activity. Real-time PCR data of the cells after one (BrC4f_Hyp1) and two (BrC4f_Hyp2) rounds of PH showed consistent up-regulation of TWIST1 gene as an early response and ZEB1/2 and SLUG transcriptional activity as a subsequent response. Reversion of BrC4f_Hyp2 cells to normoxia conditions converted them to epithelial-like cells (BrC4e) with decreased expression of EMT genes and up-regulation of MET-related OVOL2 and c-MYC genes. Transplantation of BrC4f and BrC4f_Hyp2 cells into SCID mice showed the acceleration of tumor growth up to 61.6% for BrC4f_Hyp2 cells. To summarize, rounds of PH imitate the MET process of tumorigenesis in which cancer-associated fibroblasts pass through intermediate stages and become more aggressive epithelial-like tumor cells.

Krüppel-like factor 15 in liver diseases: Insights into metabolic reprogramming

Liver diseases, characterized by metabolic disorder, have become a global public health problem with high morbidity and mortality. Krüppel-like factor 15 (KLF15) is a zinc-finger transcription factor mainly enriched in liver. Increasing evidence suggests that hepatic KLF15 is activated rapidly during fasting, and contributes to the regulation of gluconeogenesis, lipid, amino acid catabolism, bile acids, endobiotic and xenobiotic metabolism. This review summarizes the latest advances of KLF15 in metabolic reprogramming, and explore the function of KLF15 in acute liver injury, hepatitis B virus, and autoimmune hepatitis. which aims to evaluate the potential of KLF15 as a therapeutic target and prognostic biomarker for liver diseases.

Virtual Screening of FDA-Approved Drugs for Enhanced Binding with Mitochondrial Aldehyde Dehydrogenase

Mitochondrial aldehyde dehydrogenase (ALDH2) is a potential target for the treatment of substance use disorders such as alcohol addiction. Here, we adopted computational methods of molecular dynamics (MD) simulation, docking, and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) analysis to perform a virtual screening of FDA-approved drugs, hitting potent inhibitors against ALDH2. Using MD-derived conformations as receptors, butenafine (net charge q = +1 e) and olaparib (q = 0) were selected as promising compounds with a low toxicity and a binding strength equal to or stronger than previously reported potent inhibitors of daidzin and CVT-10216. A few negatively charged compounds were also hit from the docking with the Autodock Vina software, while the MM-PBSA analysis yielded positive binding energies (unfavorable binding) for these compounds, mainly owing to electrostatic repulsion in association with a negatively charged receptor (q = -6 e for ALDH2 plus the cofactor NAD⁺). This revealed a deficiency of the Vina scoring in dealing with strong charge-charge interactions between binding partners, due to its built-in protocol of not using atomic charges for electrostatic interactions. These observations indicated a requirement of further verification using MD and/or MM-PBSA after docking prediction. The identification of key residues for the binding implied that the receptor residues at the bottom and entrance of the substrate-binding hydrophobic tunnel were able to offer additional interactions with different inhibitors such as π-π, π-alkyl, van der Waals contacts, and polar interactions, and that the rational use of these interactions is beneficial to the design of potent inhibitors against ALDH2.

Electrophilic Aldehyde 4-Hydroxy-2-Nonenal Mediated Signaling and Mitochondrial Dysfunction

Reactive oxygen species (ROS), a by-product of aerobic life, are highly reactive molecules with unpaired electrons. The excess of ROS leads to oxidative stress, instigating the peroxidation of polyunsaturated fatty acids (PUFA) in the lipid membrane through a free radical chain reaction and the formation of the most bioactive aldehyde, known as 4-hydroxynonenal (4-HNE). 4-HNE functions as a signaling molecule and toxic product and acts mainly by forming covalent adducts with nucleophilic functional groups in proteins, nucleic acids, and lipids. The mitochondria have been implicated as a site for 4-HNE generation and adduction. Several studies clarified how 4-HNE affects the mitochondria's functions, including bioenergetics, calcium homeostasis, and mitochondrial dynamics. Our research group has shown that 4-HNE activates mitochondria apoptosis-inducing factor (AIFM2) translocation and facilitates apoptosis in mice and human heart tissue during anti-cancer treatment. Recently, we demonstrated that a deficiency of SOD2 in the conditional-specific cardiac knockout mouse increases ROS, and subsequent production of 4-HNE inside mitochondria leads to the adduction of several mitochondrial respiratory chain complex proteins. Moreover, we highlighted the physiological functions of HNE and discussed their relevance in human pathophysiology and current discoveries concerning 4-HNE effects on mitochondria.

A noncanonical function of EIF4E limits ALDH1B1 activity and increases susceptibility to ferroptosis

Ferroptosis is a type of lipid peroxidation-dependent cell death that is emerging as a therapeutic target for cancer. However, the mechanisms of ferroptosis during the generation and detoxification of lipid peroxidation products remain rather poorly defined. Here, we report an unexpected role for the eukaryotic translation initiation factor EIF4E as a determinant of ferroptotic sensitivity by controlling lipid peroxidation. A drug screening identified 4EGI-1 and 4E1RCat (previously known as EIF4E-EIF4G1 interaction inhibitors) as powerful inhibitors of ferroptosis. Genetic and functional studies showed that EIF4E (but not EIF4G1) promotes ferroptosis in a translation-independent manner. Using mass spectrometry and subsequent protein-protein interaction analysis, we identified EIF4E as an endogenous repressor of ALDH1B1 in mitochondria. ALDH1B1 belongs to the family of aldehyde dehydrogenases and may metabolize the aldehyde substrate 4-hydroxynonenal (4HNE) at high concentrations. Supraphysiological levels of 4HNE triggered ferroptosis, while low concentrations of 4HNE increased the cell susceptibility to classical ferroptosis inducers by activating the NOX1 pathway. Accordingly, EIF4E-dependent ALDH1B1 inhibition enhanced the anticancer activity of ferroptosis inducers in vitro and in vivo. Our results support a key function of EIF4E in orchestrating lipid peroxidation to ignite ferroptosis.

Drug resistance in multiple myeloma: Soldiers and weapons in the bone marrow niche

Multiple myeloma (MM) is still an incurable disease, despite considerable improvements in treatment strategies, as resistance to most currently available agents is not uncommon. In this study, data on drug resistance in MM were analyzed and led to the following conclusions: resistance occurs via intrinsic and extrinsic mechanisms, including intraclonal heterogeneity, drug efflux pumps, alterations of drug targets, the inhibition of apoptosis, increased DNA repair and interactions with the bone marrow (BM) microenvironment, cell adhesion, and the release of soluble factors. Since MM involves the BM, interactions in the MM-BM microenvironment were examined as well, with a focus on the cross-talk between BM stromal cells (BMSCs), adipocytes, osteoclasts, osteoblasts, endothelial cells, and immune cells. Given the complex mechanisms that drive MM, next-generation treatment strategies that avoid drug resistance must target both the neoplastic clone and its non-malignant environment. Possible approaches based on recent evidence include: (i) proteasome and histone deacetylases inhibitors that not only target MM but also act on BMSCs and osteoclasts; (ii) novel peptide drug conjugates that target both the MM malignant clone and angiogenesis to unleash an effective anti-MM immune response. Finally, the role of cancer stem cells in MM is unknown but given their roles in the development of solid and hematological malignancies, cancer relapse, and drug resistance, their identification and description are of paramount importance for MM management.

Development of a Clinical Prognostic Model for Metabolism-Related Genes in Squamous Lung Cancer and Correlation Analysis of Immune Microenvironment

Background

The incidence of squamous lung cancer (LUSC) has substantially increased. Systematic studies of metabolic genomic patterns are fundamental for the treatment and prediction of LUSC. Because cancer metabolism and immune cell metabolism have been studied in depth, metabolism and the state and function of immune cells have become key factors in tumor development. This also indicates that metabolic genes and the tumor immune microenvironment (TME) are crucial in tumor treatment. This study is aimed at dissecting the connection between TME and LUSC digestion-related qualities.

Methods

The information used in this study was obtained from The Cancer Genome Atlas dataset. Metabolism-related genes in patients with LUSC were screened, and relevant clinical data were collated. Next, genes associated with prognosis were screened using univariate COX regression and LASSO regression analyses. Finally, a timer database study was conducted to analyze the molecular mechanisms of immune cell infiltration of LUSC prognosis-related metabolic genes at the immune cell level.

Results

Nine metabolism-related genes were identified: ADCY7, ALDH3B1, CHIA, CYP2C18, ENTPD6, GGCT, HPRT1, PLA2G1B, and PTGIS. A clinical prediction model for LUSC based on metabolism-related genes was constructed. In addition, 22 subpopulations of tumor-infiltrating immune cells (TIIC) in the TME were analyzed using the CIBERSORT algorithm. Finally, we used the TIMER database to analyze the immune infiltration of LUSC and the relationship between metabolism-related genes and immune cells.

Conclusion

Our study identified metabolic genes associated with the prognosis of LUSC, which are important markers for its diagnosis, clinically relevant assessments, and prognosis. The relationship between metabolic genes with prognostic impact and immune infiltration was also analyzed, and a metabolic gene-based clinical prediction model was identified, providing a new perspective for LUSC treatment.

Genome-wide meta-analysis of alcohol use disorder in East Asians

Alcohol use disorder (AUD) is a leading cause of death and disability worldwide. Genome-wide association studies (GWAS) have identified ~30 AUD risk genes in European populations, but many fewer in East Asians. We conducted GWAS and genome-wide meta-analysis of AUD in 13,551 subjects with East Asian ancestry, using published summary data and newly genotyped data from five cohorts: (1) electronic health record (EHR)-diagnosed AUD in the Million Veteran Program (MVP) sample; (2) DSM-IV diagnosed alcohol dependence (AD) in a Han Chinese-GSA (array) cohort; (3) AD in a Han Chinese-Cyto (array) cohort; and (4) two AD Thai cohorts. The MVP and Thai samples included newly genotyped subjects from ongoing recruitment. In total, 2254 cases and 11,297 controls were analyzed. An AUD polygenic risk score was analyzed in an independent sample with 4464 East Asians (Genetic Epidemiology Research in Adult Health and Aging (GERA)). Phenotypes from survey data and ICD-9-CM diagnoses were tested for association with the AUD PRS. Two risk loci were detected: the well-known functional variant rs1229984 in ADH1B and rs3782886 in BRAP (near the ALDH2 gene locus) are the lead variants. AUD PRS was significantly associated with days per week of alcohol consumption (beta = 0.43, SE = 0.067, p = 2.47 × 10-10) and nominally associated with pack years of smoking (beta = 0.09, SE = 0.05, p = 4.52 × 10-2) and ever vs. never smoking (beta = 0.06, SE = 0.02, p = 1.14 × 10-2). This is the largest GWAS of AUD in East Asians to date. Building on previous findings, we were able to analyze pleiotropy, but did not identify any new risk regions, underscoring the importance of recruiting additional East Asian subjects for alcohol GWAS.

Biochemical mechanism underlying the pathogenesis of diabetic retinopathy and other diabetic complications in humans: the methanol-formaldehyde-formic acid hypothesis

Hyperglycemia in diabetic patients is associated with abnormally-elevated cellular glucose levels. It is hypothesized that increased cellular glucose will lead to increased formation of endogenous methanol and/or formaldehyde, both of which are then metabolically converted to formic acid. These one-carbon metabolites are known to be present naturally in humans, and their levels are increased under diabetic conditions. Mechanistically, while formaldehyde is a cross-linking agent capable of causing extensive cytotoxicity, formic acid is an inhibitor of mitochondrial cytochrome oxidase, capable of inducing histotoxic hypoxia, ATP deficiency and cytotoxicity. Chronic increase in the production and accumulation of these toxic one-carbon metabolites in diabetic patients can drive the pathogenesis of ocular as well as other diabetic complications. This hypothesis is supported by a large body of experimental and clinical observations scattered in the literature. For instance, methanol is known to have organ- and species-selective toxicities, including the characteristic ocular lesions commonly seen in humans and non-human primates, but not in rodents. Similarly, some of the diabetic complications (such as ocular lesions) also have a characteristic species-selective pattern, closely resembling methanol intoxication. Moreover, while alcohol consumption or combined use of folic acid plus vitamin B is beneficial for mitigating acute methanol toxicity in humans, their use also improves the outcomes of diabetic complications. In addition, there is also a large body of evidence from biochemical and cellular studies. Together, there is considerable experimental support for the proposed hypothesis that increased metabolic formation of toxic one-carbon metabolites in diabetic patients contributes importantly to the development of various clinical complications.

Effect of different types of muscle activity on the gene and protein expression of ALDH family members in C57BL/6J mouse skeletal muscle

Aldehyde dehydrogenase (ALDH) is an enzyme that detoxifies aldehydes and is primarily involved in alcohol metabolism. Recently, we have shown that ALDH also plays an important role in skeletal muscle homeostasis. To better understand the role of ALDH in skeletal muscle, it is necessary to clarify the adaptability of ALDH. In this study, we examined the effects of endurance training, compensatory hypertrophy by synergist ablation (SA), and denervation-induced atrophy on gene expression and protein levels of selected ALDH isoforms in skeletal muscle. Ten-week-old C57BL/6J mice were subjected to each intervention, and the plantaris muscle was collected. Gene expression levels of Aldh1a1 were decreased by SA and denervation, but ALDH1A1 protein levels were not affected. Protein levels of ALDH1B1 increased after chronic endurance training, SA, and denervation interventions. However, the increase in Aldh1b1 gene expression was observed only after SA. The gene expression of Aldh2 was decreased after SA, but ALDH2 protein levels remained unchanged. Denervation increased both the Aldh2 gene and ALDH2 protein levels. Taken together, each isoform of ALDH undergoes unique quantitative adaptations in skeletal muscle under different conditions.

Retinoids in the Pathogenesis and Treatment of Liver Diseases

Vitamin A (VA), all-trans-retinol (ROL), and its analogs are collectively called retinoids. Acting through the retinoic acid receptors RARα, RARβ, and RARγ, all-trans-retinoic acid, an active metabolite of VA, is a potent regulator of numerous biological pathways, including embryonic and somatic cellular differentiation, immune functions, and energy metabolism. The liver is the primary organ for retinoid storage and metabolism in humans. For reasons that remain incompletely understood, a body of evidence shows that reductions in liver retinoids, aberrant retinoid metabolism, and reductions in RAR signaling are implicated in numerous diseases of the liver, including hepatocellular carcinoma, non-alcohol-associated fatty liver diseases, and alcohol-associated liver diseases. Conversely, restoration of retinoid signaling, pharmacological treatments with natural and synthetic retinoids, and newer agonists for specific RARs show promising benefits for treatment of a number of these liver diseases. Here we provide a comprehensive review of the literature demonstrating a role for retinoids in limiting the pathogenesis of these diseases and in the treatment of liver diseases.

An aldehyde dehydrogenase 1A3 inhibitor attenuates the metastasis of human colorectal cancer

Metastasis is the leading cause of death for patients with colorectal cancer (CRC). The development of therapeutic regimens that selectively inhibit the biological processes involved in CRC cell dissemination is important. We used multiple Affymetrix DNA microarray hybridization datasets to identify genes related to metastasis and have significant prognostic value for patients with CRC. Quantitative real-time PCR, immunofluorescent and immunohistochemical staining were used to evaluate mRNA and protein expression. The function of aldehyde dehydrogenase 1A3 (ALDH1A3) in invasion was assessed by performing transwell assays and animal experiments. Real-time PCR, luciferase reporter assays, and western blotting were used to identify the genes regulated by ALDH1A3. Molecular docking, MTS assays, cellular thermal shift assays, isothermal titration calorimetry, microscale thermophoresis, and enzymatic activity assays were used to screen and verify the efficacy of the ALDH1A3-specific inhibitor YD1701 (dibenzo-30-crown10-ether). Finally, subcutaneous or orthotopic xenograft models were established to investigate the therapeutic potential of YD1701. Human ALDH1A3 was identified to correlate with a metastatic phenotype in CRC cells and a poor patient prognosis. Moreover, ALDH1A3 upregulated the expression of ZEB1 and SNAI2 by inhibiting miR-200 family members. The ALDH1A3-specific inhibitor YD1701 was screened, attenuated the invasion of CRC cells in vitro, and prolonged the survival of mice bearing subcutaneous or orthotopic xenografts. Our results show that ALDH1A3 promotes invasion and metastasis via the miR-200-ZEB1/SANI2 axis and is thus a plausible marker for predicting CRC progression. Inhibiting ALDH1A3 with the identified compound YD1701 might represent an effective therapeutic approach to prevent the metastasis of CRC.

Computational Investigation of Structural Basis for Enhanced Binding of Isoflavone Analogues with Mitochondrial Aldehyde Dehydrogenase

Isoflavone compounds are potent inhibitors against mitochondrial aldehyde dehydrogenase (ALDH2) for the treatment of alcoholism and drug addiction, and an in-depth understanding of the underlying structural basis helps design new inhibitors for enhanced binding. Here, we investigated the binding poses and strengths of eight isoflavone analogues (including CVT-10216 and daidzin) with ALDH2 via computational methods of molecular docking, molecular dynamics (MD) simulation, molecular mechanics Poisson-Boltzmann surface area (MM-PBSA), steered MD, and umbrella sampling. Neither the Vina scoring of docked and MD-sampled complexes nor the nonbonded protein-inhibitor interaction energy from MD simulations is able to reproduce the relative binding strength of the inhibitors compared to experimental IC₅₀ values. Considering the solvation contribution, MM-PBSA and relatively expensive umbrella sampling yield good performance for the relative binding (free) energies. The isoflavone skeleton prefers to form π-π stacking, π-sulfur, and π-alkyl interactions with planar (Phe and Trp) or sulfur-containing (Cys and Met) residues. The enhanced inhibition of CVT-10216 originates from both end groups of the isoflavone skeleton offering strong van der Waals contacts and from the methylsulfonamide group at the 4' position by hydrogen bonding (HB) with neighboring receptor residues. These results indicate that the hydrophobic binding tunnel of ALDH2 is larger than the isoflavone skeleton in length and thus an extended hydrophobic core is likely a premise for potent inhibitors.

A retinoic acid receptor β2 agonist protects against alcohol liver disease and modulates hepatic expression of canonical retinoid metabolism genes

Alcohol abuse reduces hepatic vitamin A (retinoids), reductions that are associated with progression of alcohol liver disease (ALD). Restoring hepatic retinoids through diet is contraindicated in ALD due to the negative effects of alcohol on retinoid metabolism. There are currently no drugs that can both mitigate alcohol-driven hepatic retinoid losses and progression of ALD. Using a mouse model of alcohol intake, we examined if an agonist for the retinoic acid (RA) receptor β2 (RARβ2), AC261066 (AC261) could prevent alcohol-driven hepatic retinoid losses and protect against ALD. Our results show that mice co-treated with AC261 and alcohol displayed mitigation of ALD, including reduced macro, and microvesicular steatosis, and liver damage. Alcohol intake led to increases in hepatic centrilobular levels of ALDH1A1, a rate-limiting enzyme in RA synthesis, and co-localization of ALDH1A1 with the alcohol-metabolizing enzyme CYP2E1, and 4-HNE, a marker of oxidative stress; expression of these targets was abrogated in mice co-treated with AC261 and alcohol. By RNA sequencing technology, we found that AC261 treatments opposed alcohol modulation of 68 transcripts involved in canonical retinoid metabolism. Alcohol modulation of these transcripts, including CES1D, CES1G, RBP1, RDH10, and CYP26A1, collectively favor hepatic retinoid hydrolysis and catabolism. However, despite this, co-administration of AC261 with alcohol did not mitigate alcohol-mediated depletions of hepatic retinoids, but did reduce alcohol-driven increases in serum retinol. Our data show that AC261 protected mice against ALD, even though AC261 did not prevent alcohol-mediated reductions in hepatic retinoids. These data warrant further studies of the anti-ALD properties of AC261.

Novel Disulfiram Derivatives as ALDH1a1-Selective Inhibitors

Aldehyde dehydrogenase-1a1 (ALDH1a1), the enzyme responsible for the oxidation of retinal into retinoic acid, represents a key therapeutic target for the treatment of debilitating disorders such as cancer, obesity, and inflammation. Drugs that can inhibit ALDH1a1 include disulfiram, an FDA-approved drug to treat chronic alcoholism. Disulfiram, by carbamylation of the catalytic cysteines, irreversibly inhibits ALDH1a1 and ALDH2. The latter is the isozyme responsible for important physiological processes such as the second stage of alcohol metabolism. Given the fact that ALDH1a1 has a larger substrate tunnel than that in ALDH2, replacing disulfiram ethyl groups with larger motifs will yield selective ALDH1a1 inhibitors. We report herein the synthesis of new inhibitors of ALDH1a1 where (hetero)aromatic rings were introduced into the structure of disulfiram. Most of the developed compounds retained the anti-ALDH1a1 activity of disulfiram; however, they were completely devoid of inhibitory activity against ALDH2.

Proteomic analysis suggests that monoterpenes in lemongrass disrupt Ca2+ homeostasis in Haemaphysalis longicornis leading to mitochondrial depolarization and cytotoxicity

Complex mixtures of bioactive ingredients in plant essential oils present complex chemistries which involve different modes of action. An increasing body of scientific reports has recently focused on the acaricidal activities of plant essential oils attributed to their monoterpene components, but information about their underlying molecular mechanism of action is scarce. Here, after the chemical analysis of lemongrass oil, a proteomic analysis of the ovary, salivary gland, and midgut of Haemaphysalis longicornis exposed to Cymbopogon citratus (lemongrass) essential oil was performed via data-independent acquisition mass spectrometry (DIA-MS) technology to further elucidate the molecular mechanisms involved. Pathway analysis reveals the activation of metabolic pathways mediated by oxidoreductases and transferases. Furthermore, the upregulation of various calcium-associated proteins and the upregulation of cytochrome c1, cytochrome c oxidase polypeptide IV, and programmed cell death protein 6-like isoform X1 suggest a cytotoxic mode of action via the formation of reactive oxygen species (ROS), mitochondrial Ca²⁺ overload, mitochondrial uncoupling, and depolarization, and ATP depletion leading to either apoptotic or necrotic death. Morphological alterations observed after the RNAi of a major detoxification enzyme (glutathione S-transferase) merit further investigation. Hence, the cytotoxic mode of action exhibited by C. citratus oil could be vital for the development of eco-friendly acaricide.

Profound changes in cerebrospinal fluid proteome and metabolic profile are associated with congenital hydrocephalus

The aetiology of congenital hydrocephalus (cHC) has yet to be resolved. cHC manifests late in rodent gestation, and by 18-22 weeks in human fetuses, coinciding with the start of the major phase of cerebral cortex development. Previously we found that cerebrospinal fluid (CSF) accumulation is associated with compositional changes, folate metabolic impairment and consequential arrest in cortical development. Here, we report a proteomics study on hydrocephalic and normal rat CSF using LC-MSMS and a metabolic pathway analysis to determine the major changes in metabolic and signalling pathways. Non-targeted analysis revealed a proteome transformation across embryonic days 17-20, with the largest changes between day 19 and 20. This provides evidence for a physiological shift in CSF composition and identifies some of the molecular mechanisms unleashed during the onset of cHC. Top molecular regulators that may control the shift in the CSF metabolic signature are also predicted, with potential key biomarkers proposed for early detection of these changes that might be used to develop targeted early therapies for this condition. This study confirms previous findings of a folate metabolic imbalance as well as providing more in depth metabolic analysis and understanding of cHC CSF.

The tetrameric assembly of 2-aminomuconic 6-semialdehyde dehydrogenase is a functional requirement of cofactor NAD+ binding

The bacterium Pseudomonas sp. AP-3 is able to use the environmental pollutant 2-aminophenol as its sole source of carbon, nitrogen, and energy. Eight genes (amnA, B, C, D, E, F, G, and H) encoding 2-aminophenol metabolizing enzymes are clustered into a single operon. 2-Aminomuconic 6-semialdehyde dehydrogenase (AmnC), a member of the aldehyde dehydrogenase (ALDH) superfamily, is responsible for oxidizing 2-aminomuconic 6-semialdehyde to 2-aminomuconate. In contrast to many other members of the ALDH superfamily, the structural basis of the catalytic activity of AmnC remains elusive. Here, we present the crystal structure of AmnC, which displays a homotetrameric quaternary assembly that is directly involved in its enzymatic activity. The tetrameric state of AmnC in solution was also presented using small-angle X-ray scattering. The tetramerization of AmnC is mediated by the assembly of a protruding hydrophobic beta-strand motif and residues V121 and S123 located in the NAD⁺ -binding domain of each subunit. Dimeric mutants of AmnC dramatically lose NAD⁺ binding affinity and failed to oxidize the substrate analogue 2-hydroxymuconate-6-semialdehyde to α-hydroxymuconic acid, indicating that tetrameric assembly of AmnC is functional requirement.

Outcomes of Japanese patients with non-alcoholic fatty liver disease according to genetic background and lifestyle-related diseases

INTRODUCTION AND OBJECTIVES

Genetic background may be involved in the mechanisms of liver injury and the development of non-alcoholic fatty liver disease (NAFLD). However, its contributions to the long-term outcome of NAFLD have been unclear.

METHODS

We enrolled 314 Japanese patients with biopsy-confirmed NAFLD from 2000 to 2018 (161 men [51.3%]; median age, 53 [14-84] years; 114 with advanced fibrosis [37.5%]) in the patients without hepatocellular carcinoma at diagnosis. Genomic DNA was extracted from peripheral blood and single nucleotide polymorphisms (SNPs) were analyzed. Associations of mortality with patatin-like phospholipase 3 (PNPLA3) and aldehyde dehydrogenase 2 (ALDH2) were analyzed. Finally, a subgroup analysis according to lifestyle-related disease was performed.

RESULTS

During the median 7 years of follow-up, 20 patients (6.4%) died (13 liver-related [4.1%] and 7 non-liver-related deaths [2.2%]). Patients with ALDH2 (non-GG genotype) who had reduced alcohol metabolism tended to have a poor prognosis (p = 0.06). Patients carrying both risk SNPs of PNPLA3 (GG) and ALDH2 (non-GG) had a significantly poor prognosis (p = 0.01). In the subgroup analysis, patients with PNPLA3 (GG) who were non-diabetics (p = 0.06) or non-dyslipidemic (p = 0.03), with ALDH2 (non-GG) who were non-dyslipidemic (p = 0.01) or hypertensive (p = 0.03), also had a poor prognosis. The Cox analysis revealed that ALDH2 (non-GG) was associated with a poor prognosis (Hazard ratio: 4.568, 95% Confidence Interval: 1.294-16.131, p = 0.02) similar to the liver function tests.

CONCLUSIONS

Genetic background may affect NAFLD prognosis and ALDH2 SNP could predict the outcome.

Annotation of 1350 Common Genetic Variants of the 19 ALDH Multigene Family from Global Human Genome Aggregation Database (gnomAD)

Human aldehyde dehydrogenase (ALDH) is a multigene family with 19 functional members encoding a class of diverse but important enzymes for detoxification or biotransformation of different endogenous and exogenous aldehyde substrates. Genetic mutations in the ALDH genes can cause the accumulation of toxic aldehydes and abnormal carbonyl metabolism and serious human pathologies. However, the physiological functions and substrate specificity of many ALDH genes are still unknown. Although many genetic variants of the ALDH gene family exist in human populations, their phenotype or clinical consequences have not been determined. Using the most comprehensive global human Genome Aggregation Database, gnomAD, we annotated here 1350 common variants in the 19 ALDH genes. These 1350 common variants represent all known genetic polymorphisms with a variant allele frequency of ≥0.1% (or an expected occurrence of ≥1 carrier per 500 individuals) in any of the seven major ethnic groups recorded by gnomAD. We detailed 13 types of DNA sequence variants, their genomic positions, SNP ID numbers, and allele frequencies among the seven major ethnic groups worldwide for each of the 19 ALDH genes. For the 313 missense variants identified in the gnomAD, we used two software algorithms, Polymorphism Phenotyping (PolyPhen) and Sorting Intolerant From Tolerant (SIFT), to predict the consequences of the variants on the structure and function of the enzyme. Finally, gene constraint analysis was used to predict how well genetic mutations were tolerated by selection forces for each of the ALDH genes in humans. Based on the ratio of observed and expected variant numbers in gnomAD, the three ALDH1A gene members, ALDH1A1, ALDH1A2, and ALDH1A3, appeared to have the lowest tolerance for loss-of-function mutations as compared to the other ALDH genes (# observed/# expected ratio 0.15–0.26). These analyses suggest that the ALDH1A1, ALDH1A2, and ALDH1A3 enzymes may serve a more essential function as compared with the other ALDH enzymes; functional loss mutations are much less common in healthy human populations than expected. This informatic analysis may assist the research community in determining the physiological function of ALDH isozymes and associate common variants with clinical phenotypes.

Aldehyde dehydrogenase 1A1 and 1A3 isoforms - mechanism of activation and regulation in cancer

In some types of human cancer, aldehyde dehydrogenases represent stemness markers and their expression is associated with advanced disease stages and poor prognosis. Although several biological functions are mediated by their product Retinoid acid, the molecular mechanism is tissue-dependent and only partially understood.

In this review, we summarize the current knowledge about the role of ALDH in solid tumours, especially ALDH1A1 and ALDH1A3 isoforms, regarding the molecular mechanism of their transcription and regulation, and their crosstalk with main molecular pathways resulting in the excessive proliferation, chemoresistance, stem cells properties and invasiveness. The recent knowledge of the regulatory effect of lnRNA on ALDH1A1 and ALDH1A3 is discussed too.

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Aldehyde dehydrogenases are important stem cell markers in many human cancer types.

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ALDH1A1 or ALDH1A3 activation participates in tumour progression, chemoresistance, stem-cell properties and invasiveness.

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ALDH1A1 interacts with oncogenic pathways Notch, NRF, CXCR4, Polycomb, MDR, and HOX.

Discovery of benzimidazole derivatives as potent and selective aldehyde dehydrogenase 1A1 (ALDH1A1) inhibitors with glucose consumption improving activity

Aldehyde dehydrogenase 1A1 (ALDH1A1) plays vital physiological and toxicological functions in many areas, such as CNS, inflammation, metabolic disorders, and cancers. Overexpression of ALDH1A1 has been disclosed to play an important role in obesity, diabetes and other diseases, indicating the potential need for the identification and development of small molecule ALDH1A1 inhibitors. Herein, a series of benzimidazole derivatives was designed, synthesized and evaluated. Among them, compounds 21, 27, 29, 61 and 65 exhibited excellent inhibitory activity against ALDH1A1 with IC₅₀ values in the low micromolar range and high selectivity over ALDH1A2, ALDH1A3, ALDH2 and ALDH3A1. Moreover, an in vitro study demonstrated that all five compounds effectively improved glucose consumption in HepG2 cells, of which, 61 and 65 at 10 µM produced nearly equal glucose consumption with positive control Metformin (Met) at 1 mM. Furthermore, 61 and 65 showed desirable metabolic stability in human liver microsomes. All these results suggest that 61 and 65 are suitable for further studies.

Administration of a recombinant ALDH7A1 (rA7) indicates potential regulation of the metabolite and immunology pathways in Atlantic salmon infected with Aeromonas salmonicida

The bacterium Aeromonas salmonicida is the pathogen responsible for furunculosis, which is a serious disease of salmonids. This disease has a significant economic impact on the economic benefits of the global salmon farming industry. However, the pathogenesis of this disease in fish is still unknown. Members of the aldehyde dehydrogenase gene (ALDH) superfamily play a key role in the enzyme detoxification of endogenous and exogenous aldehydes. In this study, we obtained a recombinant aldehyde dehydrogenase 7A1 (ALDH7A1) protein to find its functions on Atlantic salmon infected by A. salmonicida. The transcriptional response in the liver of Atlantic salmon (Salmo salar) with differing levels of A. salmonicida infection was analysed and compared in order to reveal mechanisms by which ALDH7A1 may confer infection resistance. With the addition of ALDH7A1 protein, it was found that a total of 13,369 genes were annotated with one or more KEGG and localized to 360 KEGG pathways in the high concentration infection group. The differential expression genes were more enriched in immune signalling pathways such as the Toll-like receptor signalling pathway, NF-kappa B signalling pathway and TNF signalling pathway. On the other hand, at low concentrations of infection, KEGG enriched a smaller number of differential expression genes. However, these differential genes were more concentrated in immune signalling pathways such as the PI3K-Akt signalling pathway, JAK-STAT signalling pathway and complement and coagulation cascades. In addition, several known immune-related genes including HSP90α, HSP70, DNA damage-inducible transcript 4, integrin alpha 5 and microtubule-associated protein 2 were among the differentially expressed transcripts. These data provide the first insights into the host-ALDH7A1 vaccine interactome. The results of this study contribute to identifying the potential resistance mechanisms of Atlantic salmon to A. salmonicida infection and determining future treatment strategies.

Activation of ALDH1A1 by omeprazole reduces cell oxidative stress damage

Under physiological conditions, cells produce low basal levels of reactive oxygen species (ROS); however, in pathologic conditions ROS production increases dramatically, generating high concentrations of toxic unsaturated aldehydes. Aldehyde dehydrogenases (ALDHs) are responsible for detoxification of these aldehydes protecting the cell. Due to the physiological relevance of these enzymes, it is important to design strategies to modulate their activity. It was previously reported that omeprazole activation of ALDH1A1 protected Escherichia coli cells overexpressing this enzyme, from oxidative stress generated by H2 O2 . In this work, omeprazole cell protection potential was evaluated in eukaryotic cells. AS-30D cell or hepatocyte suspensions were subjected to a treatment with omeprazole and exposure to light (that is required to activate omeprazole in the active site of ALDH) and then exposed to H2 O2 . Cells showed viability similar to control cells, total activity of ALDH was preserved, while cell levels of lipid aldehydes and oxidative stress markers were maintained low. Cell protection by omeprazole was avoided by inhibition of ALDHs with disulfiram, revealing the key role of these enzymes in the protection. Additionally, omeprazole also preserved ALDH2 (mitochondrial isoform) activity, diminishing lipid aldehyde levels and oxidative stress in this organelle, protecting mitochondrial respiration and transmembrane potential formation capacity, from the stress generated by H2 O2 . These results highlight the important role of ALDHs as part of the antioxidant system of the cell, since if the activity of these enzymes decreases under stress conditions, the viability of the cell is compromised.

TP73-AS1 is induced by YY1 during TMZ treatment and highly expressed in the aging brain

Aging is a factor associated with poor prognosis in glioblastoma (GBM). It is therefore important to understand the molecular features of aging contributing to GBM morbidity. TP73-AS1 is a long noncoding RNA (lncRNA) over expressed in GBM tumors shown to promote resistance to the chemotherapeutic temozolomide (TMZ), and tumor aggressiveness. How the expression of TP73-AS1 is regulated is not known, nor is it known if its expression is associated with aging. By analyzing transcriptional data obtained from natural and pathological aging brain, we found that the expression of TP73-AS1 is high in pathological and naturally aging brains. YY1 physically associates with the promoter of TP73-AS1 and we found that along with TP73-AS1, YY1 is induced by TMZ. We found that the TP73-AS1 promoter is activated by TMZ, and by YY1 over expression. Using CRISPRi to deplete YY1, we found that YY1 promotes up regulation of TP73-AS1 and the activation of its promoter during TMZ treatment. In addition, we identified two putative YY1 binding sites within the TP73-AS1 promoter, and used mutagenesis to find that they are essential for TMZ mediated promoter activation. Together, our data positions YY1 as an important TP73-AS1 regulator, demonstrating that TP73-AS1 is expressed in the natural and pathological aging brain, including during neurodegeneration and cancer. Our findings advance our understanding of TP73-AS1 expression, bringing forth a new link between TMZ resistance and aging, both of which contribute to GBM morbidity.

Oncorequisite role of an aldehyde dehydrogenase in the pathogenesis of T-cell acute lymphoblastic leukemia

Aldehyde dehydrogenases (ALDH) are overexpressed in various types of cancers. One of the ALDH family genes, ALDH1A2, is aberrantly expressed in more than 50% of cases of T-cell acute lymphoblastic leukemia (T-ALL). However, its molecular function and role in the pathogenesis of T-ALL are largely unknown. Chromatin immunoprecipitation-sequencing and RNA-sequencing analyses showed that the oncogenic transcription factor TAL1 and its regulatory partners bind to the intronic regulatory element of the ALDH1A2 gene, directly inducing a T-ALL-specific isoform with enzymatic activity. ALDH1A2 was preferentially expressed in the TAL1-positive T-ALL subgroup. In TALL cell lines, depletion of ALDH1A2 inhibited cell viability and induced apoptosis. Interestingly, gene expression and metabolomic profiling revealed that ALDH1A2 supported glycolysis and the tricarboxylic acid cycle, accompanied by NADH production, by affecting multiple metabolic enzymes to promote ATP production. Depletion of ALDH1A2 increased the levels of reactive oxygen species, while the levels were reduced by ALDH1A2 overexpression both in vitro and in vivo. Overexpression of ALDH1A2 accelerated tumor onset and increased tumor penetrance in a zebrafish model of T-ALL. Taken together, our results indicate that ALDH1A2 protects against intracellular stress and promotes T-ALL cell metabolism and survival. ALDH1A2 overexpression enables leukemic clones to sustain a hyper-proliferative state driven by oncogenes.

NADP+-Dependent Dehydrogenase SCO3486 and Cycloisomerase SCO3480: Key Enzymes for 3,6-Anhydro-L-Galactose Catabolism in Streptomyces coelicolor A3(2)

Agarose is a linear polysaccharide composed of D-galactose and 3,6-anhydro-L-galactose (AHG). It is a major component of the red algal cell wall and is gaining attention as an abundant marine biomass. However, the inability to ferment AHG is considered an obstacle in the large-scale use of agarose and could be addressed by understanding AHG catabolism in agarolytic microorganisms. Since AHG catabolism was uniquely confirmed in Vibrio sp. EJY3, a gram-negative marine bacterial species, we investigated AHG metabolism in Streptomyces coelicolor A3(2), an agarolytic gram-positive soil bacterium. Based on genomic data, the SCO3486 protein (492 amino acids) and the SCO3480 protein (361 amino acids) of S. coelicolor A3(2) showed identity with H2IFE7.1 (40% identity) encoding AHG dehydrogenase and H2IFX0.1 (42% identity) encoding 3,6-anhydro-L-galactonate cycloisomerase, respectively, which are involved in the initial catabolism of AHG in Vibrio sp. EJY3. Thin layer chromatography and mass spectrometry of the bioconversion products catalyzed by recombinant SCO3486 and SCO3480 proteins, revealed that SCO3486 is an AHG dehydrogenase that oxidizes AHG to 3,6-anhydro-L-galactonate, and SCO3480 is a 3,6-anhydro-L-galactonate cycloisomerase that converts 3,6-anhydro-L-galactonate to 2-keto-3-deoxygalactonate. SCO3486 showed maximum activity at pH 6.0 at 50°C, increased activity in the presence of iron ions, and activity against various aldehyde substrates, which is quite distinct from AHG-specific H2IFE7.1 in Vibrio sp. EJY3. Therefore, the catabolic pathway of AHG seems to be similar in most agar-degrading microorganisms, but the enzymes involved appear to be very diverse.

Investigating the reaction and substrate preference of indole-3-acetaldehyde dehydrogenase from the plant pathogen Pseudomonas syringae PtoDC3000

Aldehyde dehydrogenases (ALDHs) catalyze the conversion of various aliphatic and aromatic aldehydes into corresponding carboxylic acids. Traditionally considered as housekeeping enzymes, new biochemical roles are being identified for members of ALDH family. Recent work showed that AldA from the plant pathogen Pseudomonas syringae strain PtoDC3000 (PtoDC3000) functions as an indole-3-acetaldehyde dehydrogenase for the synthesis of indole-3-acetic acid (IAA). IAA produced by AldA allows the pathogen to suppress salicylic acid-mediated defenses in the model plant Arabidopsis thaliana. Here we present a biochemical and structural analysis of the AldA indole-3-acetaldehyde dehydrogenase from PtoDC3000. Site-directed mutants targeting the catalytic residues Cys302 and Glu267 resulted in a loss of enzymatic activity. The X-ray crystal structure of the catalytically inactive AldA C302A mutant in complex with IAA and NAD+ showed the cofactor adopting a conformation that differs from the previously reported structure of AldA. These structures suggest that NAD+ undergoes a conformational change during the AldA reaction mechanism similar to that reported for human ALDH. Site-directed mutagenesis of the IAA binding site indicates that changes in the active site surface reduces AldA activity; however, substitution of Phe169 with a tryptophan altered the substrate selectivity of the mutant to prefer octanal. The present study highlights the inherent biochemical versatility of members of the ALDH enzyme superfamily in P. syringae.

Cancer stem cells in colorectal cancer and the association with chemotherapy resistance

The incidence and mortality of colorectal cancer (CRC) have always been among the highest in the world, although the diagnosis and treatment are becoming more and more advanced. At present, the main reason is that patients have acquired drug resistance after long-term conventional drug treatment. An increasing number of evidences confirm the existence of cancer stem cells (CSCs), which are a group of special cells in cancer, only a small part of cancer cells. These special cell populations are not eliminated by chemotherapeutic drugs and result in tumor recurrence and metastasis after drug treatment. CSCs have the ability of self-renewal and multidirectional differentiation, which is associated with the occurrence and development of cancer. CSCs can be screened and identified by related surface markers. In this paper, the characteristic surface markers of CSCs in CRC and the related mechanism of drug resistance will be discussed in detail. A better understanding of the mechanism of CSCs resistance to chemotherapy may lead to better targeted therapy.

PRMT3 interacts with ALDH1A1 and regulates gene-expression by inhibiting retinoic acid signaling

Protein arginine methyltransferase 3 (PRMT3) regulates protein functions by introducing asymmetric dimethylation marks at the arginine residues in proteins. However, very little is known about the interaction partners of PRMT3 and their functional outcomes. Using yeast-two hybrid screening, we identified Retinal dehydrogenase 1 (ALDH1A1) as a potential interaction partner of PRMT3 and confirmed this interaction using different methods. ALDH1A1 regulates variety of cellular processes by catalyzing the conversion of retinaldehyde to retinoic acid. By molecular docking and site-directed mutagenesis, we identified the specific residues in the catalytic domain of PRMT3 that facilitate interaction with the C-terminal region of ALDH1A1. PRMT3 inhibits the enzymatic activity of ALDH1A1 and negatively regulates the expression of retinoic acid responsive genes in a methyltransferase activity independent manner. Our findings show that in addition to regulating protein functions by introducing methylation modifications, PRMT3 could also regulate global gene expression through protein-protein interactions.

Here, the authors demonstrate that protein arginine methyltransferase 3 (PRMT3) interacts with and inhibits the retinal dehydrogenase ALDH1A1, negatively regulating the expression of retinoic acid responsive genes. This study shows that PRMT3 affects diverse biological processes not only by globally regulating protein function through methylation but also by regulating gene expression.

Aldehyde dehydrogenase inhibitors promote DNA damage in ovarian cancer and synergize with ATM/ATR inhibitors

Rationale: Aldehyde dehydrogenase (ALDH) enzymes are often upregulated in cancer cells and associated with therapeutic resistance. ALDH enzymes protect cells by metabolizing toxic aldehydes which can induce DNA double stand breaks (DSB). We recently identified a novel ALDH1A family inhibitor (ALDHi), 673A. We hypothesized that 673A, via inhibition of ALDH1A family members, could induce intracellular accumulation of genotoxic aldehydes to cause DSB and that ALDHi could synergize with inhibitors of the ATM and ATR, proteins which direct DSB repair.

Methods: We used immunofluorescence to directly assess levels of the aldehyde 4-hydroxynonenal and comet assays to evaluate DSB. Western blot was used to evaluate activation of the DNA damage response pathways. Cell counts were performed in the presence of 673A and additional aldehydes or aldehyde scavengers. ALDH inhibition results were confirmed using ALDH1A3 CRISPR knockout. Synergy between 673A and ATM or ATR inhibitors was evaluated using the Chou-Talalay method and confirmed in vivo using cell line xenograft tumor studies.

Results: The ALDHi 673A cellular accumulation of toxic aldehydes which induce DNA double strand breaks. This is exacerbated by addition of exogenous aldehydes such as vitamin-A (retinaldehyde) and ameliorated by aldehyde scavengers such as metformin and hydralazine. Importantly, ALDH1A3 knockout cells demonstrated increased sensitivity to ATM/ATR inhibitors. And, ALDHi synergized with inhibitors of ATM and ATR, master regulators of the DSB DNA damage response, both in vitro and in vivo. This synergy was evident in homologous recombination (HR) proficient cell lines.

Conclusions: ALDHi can be used to induce DNA DSB in cancer cells and synergize with inhibitors the ATM/ATR pathway. Our data suggest a novel therapeutic approach to target HR proficient ovarian cancer cells.

ADP-Ribosylation Factor Like GTPase 4C (ARL4C) augments stem-like traits of glioblastoma cells by upregulating ALDH1A3

Glioma cells with stem cell-like properties are crucial for tumor initiation, progression and therapeutic resistance. Therefore, identifying specific factors in regulating stem-like traits is critical for the design of novel glioma therapeutics.

Herein, we reported that ADP-Ribosylation Factor Like GTPase 4C (ARL4C) was highly expressed in glioma stem-like cells (GSLCs). GSLCs, determined by the efficiency of sphere formation in vitro and tumor growth in vivo, was increased by overexpression of ARL4C. ARL4C induced the tumorigenesis through ALDH1A3. Analyses of 325 patient specimens showed that ARL4C was highly expressed in glioblastoma (GBM) as compared with lower grade gliomas. In addition, higher level ARL4C expression in glioma was correlated with poorer progression-free survival and overall survival of patients. Therefore, ARL4C may act as a novel prognostic marker and a therapeutic target for GBM.

A Comprehensive Review on Source, Types, Effects, Nanotechnology, Detection, and Therapeutic Management of Reactive Carbonyl Species Associated with Various Chronic Diseases

Continuous oxidation of carbohydrates, lipids, and amino acids generate extremely reactive carbonyl species (RCS). Human body comprises some important RCS namely hexanal, acrolein, 4-hydroxy-2-nonenal, methylglyoxal, malondialdehyde, isolevuglandins, and 4-oxo-2- nonenal etc. These RCS damage important cellular components including proteins, nucleic acids, and lipids, which manifests cytotoxicity, mutagenicity, multitude of adducts and crosslinks that are connected to ageing and various chronic diseases like inflammatory disease, atherosclerosis, cerebral ischemia, diabetes, cancer, neurodegenerative diseases and cardiovascular disease. The constant prevalence of RCS in living cells suggests their importance in signal transduction and gene expression. Extensive knowledge of RCS properties, metabolism and relation with metabolic diseases would assist in development of effective approach to prevent numerous chronic diseases. Treatment approaches for RCS associated diseases involve endogenous RCS metabolizers, carbonyl metabolizing enzyme inducers, and RCS scavengers. Limited bioavailability and bio efficacy of RCS sequesters suggest importance of nanoparticles and nanocarriers. Identification of RCS and screening of compounds ability to sequester RCS employ several bioassays and analytical techniques. Present review describes in-depth study of RCS sources, types, properties, identification techniques, therapeutic approaches, nanocarriers, and their role in various diseases. This study will give an idea for therapeutic development to combat the RCS associated chronic diseases.

Transformations of Monoterpenes with the p-Menthane Skeleton in the Enzymatic System of Bacteria, Fungi and Insects

The main objective of this article was to present the possibilities of using the enzymatic system of microorganisms and insects to transform small molecules, such as monoterpenes. The most important advantage of this type of reaction is the possibility of obtaining derivatives that are not possible to obtain with standard methods of organic synthesis or are very expensive to obtain. The interest of industrial centers focuses mainly on obtaining particles of high optical purity, which have the desired biological properties. The cost of obtaining such a compound and the elimination of toxic or undesirable chemical waste is important. Enzymatic reactions based on enzymes alone or whole microorganisms enable obtaining products with a specific structure and purity in accordance with the rules of Green Chemistry.