Role of Aldehyde Dehydrogenases in Physiopathological Processes

Identification of ALDH7A1 as a DNA-methylation-driven gene in lung squamous cell carcinoma

BACKGROUND

Deoxyribose nucleic acid (DNA) methylation is an important epigenetic modification that plays an important role in the occurrence and development of tumors. Identifying key methylation-driven genes that affect the prognosis of lung squamous cell carcinoma (LUSC) can provide direction for targeted therapy research.

METHODS AND RESULTS

Methylation and RNA-seq data were downloaded from The Cancer Genome Atlas (TCGA). The MethylMix package was used to integrate and analyze the methylation and gene expression data from TCGA, and the LUSC dataset (GSE37745) was downloaded from GEO for validation. Forty-five DNA-methylation-driven genes (MDGs) were obtained, and 3 genes (TRIM61, SMIM22, and ALDH7A1) were significantly associated with survival by using univariate and multivariate Cox regression. A risk model was constructed. KM analysis showed that patients with high-risk scores had poor survival. A nomination plot for prognosis prediction of LUSC patients was constructed, which showed a good predictive efficiency for tumor prognosis. The high expression of ALDH7A1 was an independent risk factor for poor prognosis in LUSC. The expression of ALDH7A1 in LUSC was negatively correlated with its methylation status (COR = -0.655). GSEA analysis showed that high expression of ALDH7A1 could activate multiple signaling pathways (JAK-STAT signaling pathway and mTOR signaling pathway). In vitro cell experiments confirmed that in LUSC, silencing ALDH7A1 could inhibit tumor progression, while overexpression of ALDH7A1 could promote tumor progression.

CONCLUSION

Our results indicated that ALDH7A1, a newly discovered MDG in LUSC, could act as an independent prognostic factor for OS in LUSC, with the potential to become a potential target for LUSC diagnosis and treatment. High expression of ALDH7A1 in LUSC could promote the occurrence and development of tumors. Signaling pathways, such as JAK-STAT and mTOR signaling pathways, might regulate the high expression of ALDH7A1.

19F-labeled molecular probes for fingerprint identification and quantitative analysis of malondialdehyde in urine

Aldehydes are crucial cellular intermediates and early diagnostic biomarkers for numerous diseases and injuries. Despite significant advancements in aldehyde detection, accurately distinguishing and quantifying these biomarkers remains challenging due to their similar chemical reactivities. 19F nuclear magnetic resonance (19F NMR) spectroscopy, characterized by a broad spectral range and unique chemical shifts, provides a powerful approach for the simultaneous and quantitative analysis of multiple targets. Here, we rationally designed a class of 19F-labeled molecular probes featuring a hydrazine moiety as the aldehyde recognition site, enabling specific identification and differentiation of aldehydes via easily interpretable changes in 19F chemical shifts. The chemical shift of the probe 19F-AP-1 at δ19F -120.8 ppm shifted to -112.3 ppm after its reaction with malondialdehyde (MDA). This approach allows for the selective "fingerprint" recognition of malondialdehyde (MDA) within complex aldehyde mixtures under the specified 19F NMR conditions (256 scans, 376 MHz transmitter frequency) with the acquisition time of 7 min 39 s, overcoming interferences from background matrices. This work provides a robust method that allows for qualitative and quantitative analyses of MDA directly in human urine samples without requiring pretreatment, highlighting its potential applicability for MDA detection across a range of biological fluids.

ALDH2 delays ventricular pressure overload-induced heart failure by promoting cardiomyocyte proliferation in mice

The adult mammalian heart is a terminally differentiated organ in which the majority of cardiomyocytes are in a state of cell cycle arrest, rendering them incapable of effectively proliferating to replace damaged cells. ALDH2, an enzyme known for alleviating oxidative stress, has been demonstrated to play a critical role in cardiac protection. However, whether ALDH2 regulates cardiomyocyte proliferation has not been conclusively established. We found that activation of ALDH2 activity significantly promotes cardiomyocyte proliferation and extends the proliferation window during early postnatal development in neonatal mice. Furthermore, administration of Alda-1 to activate ALDH2 in adult mice subjected to transverse aortic constriction markedly enhanced cardiomyocyte proliferation and delayed the onset of pressure overload-induced heart failure. In summary, our findings identify ALDH2 as a potential target for regulating cardiomyocyte proliferation and offer a novel therapeutic approach for treating heart failure.

Hypoxia-inducible factor 1α modulates acrolein-induced cellular damage in bronchial epithelial cells

Acrolein, a highly reactive α,β-unsaturated aldehyde, is a widespread environmental pollutant. It is generated during the incomplete combustion of materials such as tobacco smoke, petrol, coal, forest fires, and plastics, as well as from the overheating of frying oils. Acrolein is known to induce cellular damage and oxidative stress. This study investigates the critical role of hypoxia-inducible factor 1α (HIF-1α), which is a transcription factor required to regulate cell survival and angiogenesis, in protecting bronchial epithelial cells from acrolein-induced cytotoxicity and DNA damage under normoxic and hypoxic conditions. To our knowledge, no prior study has comprehensively evaluated the effects of HIF-1α on cellular responses to acrolein under normoxic and hypoxic conditions in vitro. Therefore, the goal of this study was to explore how silencing HIF-1α influences cellular responses to acrolein, and our study focused on changes in cytotoxicity, metabolic activity, DNA damage, and oxidative stress using the BEAS-2B cell line. We observed enhanced cell damage and reduced viability in cells exposed to acrolein when silenced with HIF-1α, particularly in hypoxic environments. While results indicate that silencing HIF-1α significantly increases cytotoxicity and DNA damage under hypoxia compared to normoxic conditions, oxidative stress indicator levels did not rise noticeably under hypoxia following HIF-1α silencing. This research warrants further investigation to indicate the importance of HIF-1α in adapting to environmental and hypoxic stressors, which are commonly found in chronic lung diseases and ischemic conditions.

ALDH7A1 protects against ferroptosis by generating membrane NADH and regulating FSP1

Ferroptosis is a form of cell death due to iron-induced lipid peroxidation. Ferroptosis suppressor protein 1 (FSP1) protects against this death by generating antioxidants, which requires nicotinamide adenine dinucleotide, reduced form (NADH) as a cofactor. We initially uncover that NADH exists at significant levels on cellular membranes and then find that this form of NADH is generated by aldehyde dehydrogenase 7A1 (ALDH7A1) to support FSP1 activity. ALDH7A1 activity also acts directly to decrease lipid peroxidation by consuming reactive aldehydes. Furthermore, ALDH7A1 promotes the membrane recruitment of FSP1, which is instigated by ferroptotic stress activating AMP-activated protein kinase (AMPK) to promote the membrane localization of ALDH7A1 that stabilizes FSP1 on membranes. These findings advance a fundamental understanding of NADH by revealing a previously unappreciated pool on cellular membranes, with the elucidation of its function providing a major understanding of how FSP1 acts and how an aldehyde dehydrogenase protects against ferroptosis.

ZBiotics ameliorates T2DM-induced histopathological damage in liver, kidney and adipose tissues by modulating the NOD-like receptor signaling in Wistar rats

Probiotics serve as promising candidates in type 2 diabetes mellitus (T2DM) therapy. Not only they presumably reduce the T2DM prevalence, but also keep down its complications. In the present study, we explored the beneficial impact of ZBiotics, an engineered probiotic, on T2DM Wistar rats. In silico analysis was performed to construct a genetic-epigenetic network linked to STING-NOD pathway and autophagy signaling. Then, 30 Wistar rats were divided into 5 groups (each n = 6); normal group, diabetic model, B. subtilis, and ZBiotics treated rats at high and low doses. Experimental procedures were carried out including biochemical and histopathologic analyses. Samples were extracted from rats' blood, liver, kidney and adipose tissues. At the molecular aspect, the molecular players, chosen by the in silico analysis, were assessed using 2-ΔΔCt to estimate their relative quantification. With immunohistochemistry, TNF-alpha and LC3B were assessed as reflectors for inflammation and autophagy respectively. ZBiotics was reported to ameliorate the T2DM-induced histological damage. Besides, it downregulated TNF-alpha and upregulated LC3B expression levels. At the biochemical aspect, ZBiotics corrected LDL-c and improved serum creatinine and CK-MB levels. Inflammation relevant genes have been downregulated regarding CHUK, NFKB1 and miR-611. Therefore, ZBiotics is speculated to operate by modulating the genetic-epigenetic network linked to inflammatory cGAS-STING and autophagy signaling. ZBiotics is recommended for clinical trials as a separate candidate or as an adjuvant to the conventional T2DM therapy.

The role of ALDHs in lipid peroxidation-related diseases

Lipid peroxidation presents the oxidative degradation of polyunsaturated fatty acids lincited by reactive species. Excessive accumulation of lipid peroxidation byproducts, including 4-hydroxy-2-nonenal (4-HNE) and malondialdehyde (MDA), causes protein dysfunction and various illnesses. Aldehyde dehydrogenases (ALDHs) catalyze the metabolism of both endogenous and exogenous aldehydes. These enzymes participate in detoxification and intermediary metabolism. Contemporary research has affirmed the involvement of both enzymatic and non-enzymatic pathways of ALDHs in modulating the evolution of diseases associated with lipid peroxidation. This review provides an overview of the biological functions and clinical implications concerning the enzymatic and non-enzymatic pathways of ALDHs in diseases related to lipid peroxidation, such as, non-alcoholic fatty liver disease (NAFLD), atherosclerosis, and type 2 diabetes (T2DM). Furthermore, the activators or inhibitors of ALDHs represent a promising therapeutic strategy for lipid peroxidation-related diseases.

Genetic Polymorphism of Zinc Transporter-8 Gene (SLC30A8), Serum Zinc Concentrations, and Proteome Profiles Related to Type 2 Diabetes in Elderly

Background and Aims: Older adults are particularly susceptible to type 2 diabetes mellitus (T2DM) due to factors such as age-related insulin resistance, decreased physical activity, and deficiency of micronutrients, especially zinc. Studies have suggested that the risk allele of the zinc transporter 8 gene (SLC30A8) single-nucleotide poly-morphism (SNP) rs13266634 may contribute to T2DM susceptibility in addition to the complex protein interactions and alterations in the protein expressions and modifications associated with T2DM. This study was implemented to study the associations between SLC30A8 polymorphism, serum zinc levels, and the profiles of proteins differentially expressed in nondiabetic (n = 116) and prediabetic/diabetic (n = 149) subjects. Methods: SNP genotyping using TaqMan® assay and proteomic analysis by LC-MS/MS were performed in each group. Results: The results showed a higher risk of diabetes in individuals with the risk genotype CC accompanied by a low serum zinc level than in those with other genotypes. Profiles of proteins differentially expressed between the groups were identified and shown to be particularly associated with zinc-related functions, zinc transporter 8, and glucose metabolism. Proteins exclusively expressed in prediabetes/diabetes were assigned to a Reactome pathway related to zinc transporter and insulin processing. Conclusions: Our findings suggest that individuals carrying at least one copy of SLC30A8 rs13266634 accompanied by a low serum zinc level might be susceptible to T2DM, which could be due to alterations in insulin signaling and zinc metabolism. Understanding this relationship deepens our understanding of the genetic and molecular mechanisms underlying T2DM risk, offering potential targets for therapeutic intervention and prevention strategies.

Reversing Signs of Parkinsonism in a Cell Model Using Mitochondria-Targeted Organoiridium Catalysis

We report the application of organoiridium complexes as catalytic agents for the detoxification of biogenic reactive aldehyde species (RASP), which are implicated in the pathogenesis of neurodegenerative disorders. We show that Ir complexes functionalized with phosphonium cations localize selectively in the mitochondria and have better cellular retention compared to that of their parent Ir species. In a cell model for Parkinsonism, the mitochondria-targeted iridium catalysts exhibited superior cell protecting abilities and longer-lasting effects (up to 6 d) than conventional RASP scavengers, which failed to be effective beyond 24 h. Our biological assays indicate that treatment with the Ir compounds led to reduction in reactive oxygen species and aldehyde levels while partially preserving the native mitochondrial membrane potential and NAD+/NADH ratio in 1-methyl-4-phenylpyridinium-inhibited cells. Our work is the first to demonstrate catalytic nonenzymatic detoxification of RASP in living systems.

Aldehyde dehydrogenases as drug targets for cancer: SAR and structural biology aspects for inhibitor design

Aldehydes are organic compounds containing a carbonyl group found exogenously or produced by normal metabolic processes and their accumulation can lead to toxicity if not cleared. Aldehyde dehydrogenases (ALDHs) are NAD(P)+-dependent enzymes that catalyze the oxidation of such aldehydes and prevent their accumulation. Along with this primary detoxification function, the known 19 human isoforms of ALDHs, which act on different substrates, are also involved in various physiological and developmental processes. Functional alterations of ALDHs via mutations or expression levels cause various disease conditions, including many different cancer types like lung, ovarian, etc. These properties make this family of enzymes an ideal therapeutic and prognostic target for drug development. However, sequence similarities between the ALDH isoforms force the need to design inhibitors for a specific isoform using the differences in the substrate-binding sites of each protein. This has resulted in developing isoform-specific inhibitors, especially for ALDH1A1, ALDH2, and ALDH3A1, which are implicated in various cancers. In this review, we briefly outline the functional roles of the different isoforms of the ALDH family members, their role in cancer and discuss the various selective inhibitors that have been developed for the ALDH1A1 and ALDH3A1 enzymes, along with a detailed examination of the respective structure-activity relationship (SAR) studies available. From the available SAR and structural biology data, insights into the functional groups and interactions necessary to develop selective inhibitors for ALDH1A1 and ALDH3A1 are highlighted, which can act as a guide for developing more potent and selective inhibitors of ALDH isoforms.

The Significance of Aldehyde Dehydrogenase 1 in Cancers

The goal of this paper is to discuss the role of ALDH isozymes in different cancers, review advances in ALDH1-targeting cancer therapies, and explore a mechanism that explains how ALDH expression becomes elevated during cancer development. ALDH is often overexpressed in cancer, and each isoform has a unique expression pattern and a distinct role in different cancers. The abnormal expression of ALDHs in different cancer types (breast, colorectal, lung, gastric, cervical, melanoma, prostate, and renal) is presented and correlated with patient prognosis. ALDH plays a significant role in various cellular functions, such as metabolism, oxidative stress response, detoxification, and cellular differentiation. Among the ALDH families, ALDH1 has gained considerable attention as a cancer stem cell (CSC) marker due to its significant role in the maintenance of stemness and the differentiation of stem cells (SCs), along with its involvement in tumorigenesis. A description of the cellular mechanisms and physiology of ALDH1 that underlies cancer development is provided. Moreover, current advances in ALDH1-targeting cancer therapies are discussed.

ALDH and cancer stem cells: Pathways, challenges, and future directions in targeted therapy

Human ALDH comprise 19 subfamilies in which ALDH1A1, ALDH1A3, ALDH3A1, ALDH5A1, ALDH7A1, and ALDH18A1 are implicated in CSC. Studies have shown that ALDH can also be involved in drug resistance and standard chemotherapy regimens are ineffective in treating patients at the stage of disease recurrence. Existing chemotherapeutic drugs eliminate the bulk of tumors but are usually not effective against CSC which express ALDH+ population. Henceforth, targeting ALDH is convincing to treat the patient's post-relapse. Combination therapies that interlink signaling mechanisms seem promising to increase the overall disease-free survival rate. Therefore, targeting ALDH through ALDH inhibitors along with immunotherapies may create a novel platform for translational research. This review aims to fill in the gap between ALDH1 family members in relation to its cell signaling mechanisms, highlighting their potential as molecular targets to sensitize recurrent tumors and bring forward the future development concerning the current progress and draw backs. This review summarizes the role of cancer stem cells and their upregulation by maintaining the tumor microenvironment in which ALDH is specifically highlighted. It discusses the regulation of ALDH family proteins and the crosstalk between ALDH and CSC in relation to cancer metabolism. Furthermore, it establishes the correlation between ALDH involved signaling mechanisms and their specific targeted inhibitors, as well as their functional modularity, bioavailability, and mechanistic role in various cancers.

Integrated Transcriptomic Analyses of Liver and Mammary Gland Tissues Reveals the Regulatory Mechanism Underlying Dairy Goats at Late Lactation When Feeding Rumen-Protected Lysine

Although low-protein diets can improve the nitrogen utilization efficiency and alleviate economic pressures in ruminants, they may also negatively impact dairy performance. Rumen-protected lysine (RPL) supplementation can improve the health status and growth performance of ruminants without compromising nitrogen utilization efficiency and feed intake. In this study, a total of thirty-three multiparous dairy goats in the late-lactation period were randomly divided into three groups that were separately fed the control diet (namely the protein-adequacy group), the low-protein diet (namely the protein-deficient group), and the RPL-supplemented protein-deficient diet (namely RPL-supplementation group) for five weeks. Here, we investigated the molecular mechanisms regarding how low-protein diets with RPL supplementation compromise lactation phenotypes in dairy goats through cross-tissue transcriptomic analyses. Dietary protein deficiency caused an imbalance in amino acid (AA) intake, disrupted hepatic function, and impaired milk synthesis. Transcriptomic analyses further showed that RPL supplementation exhibited some beneficial effects, like mitigating abnormal lipid and energy metabolism in the liver, elevating hepatic resistance to oxidative stress, improving the mammary absorption of AAs, as well as activating mammary lipid and protein anabolism primarily through peroxisome proliferator-activated receptor (PPAR) and janus kinase-signal transducer (JAK)-signal transducer and activator of transcription (STAT) signaling, respectively. RPL supplementation of a low-protein diet contributes to maintaining late lactation in dairy goats primarily through mitigating hepatic energy disturbances and activating both lipid and protein metabolism in the mammary glands. Since RPL supplementation initiated a series of comprised events on mammary protein and lipid metabolism as well as the hepatic function and energy generation in dairy goats under protein deficiency during late lactation, these findings thus provide some insights into how RPL supplementation helps maintain milk production and health in dairy mammals especially at late lactation.

From Organotypic Mouse Brain Slices to Human Alzheimer's Plasma Biomarkers: A Focus on Nerve Fiber Outgrowth

Alzheimer's disease (AD) is a neurodegenerative disease characterized by memory loss and progressive deterioration of cognitive functions. Being able to identify reliable biomarkers in easily available body fluids such as blood plasma is vital for the disease. To achieve this, we used a technique that applied human plasma to organotypic brain slice culture via microcontact printing. After a 2-week culture period, we performed immunolabeling for neurofilament and myelin oligodendrocyte glycoprotein (MOG) to visualize newly formed nerve fibers and oligodendrocytes. There was no significant change in the number of new nerve fibers in the AD plasma group compared to the healthy control group, while the length of the produced fibers significantly decreased. A significant increase in the number of MOG+ dots around these new fibers was detected in the patient group. According to our hypothesis, there are factors in the plasma of AD patients that affect the growth of new nerve fibers, which also affect the oligodendrocytes. Based on these findings, we selected the most promising plasma samples and conducted mass spectrometry using a differential approach and we identified three putative biomarkers: aldehyde-dehydrogenase 1A1, alpha-synuclein and protein S100-A4. Our method represents a novel and innovative approach for translating research findings from mouse models to human applications.

Computational investigations of flavonoids as ALDH isoform inhibitors for treatment of cancer

Human aldehyde dehydrogenases (ALDHs) are a group of 19 isoforms often overexpressed in cancer stem cells (CSCs). These enzymes play critical roles in CSC protection, maintenance, cancer progression, therapeutic resistance, and poor prognosis. Thus, targeting ALDH isoforms offers potential for innovative cancer treatments. Flavonoids, known for their ability to affect multiple cancer-related pathways, have shown anticancer activity by downregulating specific ALDH isoforms. This study aimed to evaluate 830 flavonoids from the PubChem database against five ALDH isoforms (ALDH1A1, ALDH1A2, ALDH1A3, ALDH2, ALDH3A1) using computational methods to identify potent inhibitors. Extra precision (XP) Glide docking and MM-GBSA free binding energy calculations identified several flavonoids with high binding affinities. MD simulation highlighted flavonoids 1, 2, 18, 27, and 42 as potential specific inhibitors for each isoform, respectively. Flavonoid 10 showed high binding affinities for ALDH1A2, ALDH1A3, and ALDH3A1, emerging as a potential multi-ALDH inhibitor. ADMET property evaluation indicated that the promising hits have acceptable drug-like profiles, but further optimization is needed to enhance their therapeutic efficacy and reduce toxicity, making them more effective ALDH inhibitors for future cancer treatment.

A Systematic Review of Proteomics in Obesity: Unpacking the Molecular Puzzle

PURPOSE OF REVIEW

The present study aims to review the existing literature to identify pathophysiological proteins in obesity by conducting a systematic review of proteomics studies. Proteomics may reveal the mechanisms of obesity development and clarify the links between obesity and related diseases, improving our comprehension of obesity and its clinical implications.

RECENT FINDINGS

Most of the molecular events implicated in obesity development remain incomplete. Proteomics stands as a powerful tool for elucidating the intricate interactions among proteins in the context of obesity. This methodology has the potential to identify proteins involved in pathological processes and to evaluate changes in protein abundance during obesity development, contributing to the identification of early disease predisposition, monitoring the effectiveness of interventions and improving disease management overall. Despite many non-targeted proteomic studies exploring obesity, a comprehensive and up-to-date systematic review of the molecular events implicated in obesity development is lacking. The lack of such a review presents a significant challenge for researchers trying to interpret the existing literature. This systematic review was conducted following the PRISMA guidelines and included sixteen human proteomic studies, each of which delineated proteins exhibiting significant alterations in obesity. A total of 41 proteins were reported to be altered in obesity by at least two or more studies. These proteins were involved in metabolic pathways, oxidative stress responses, inflammatory processes, protein folding, coagulation, as well as structure/cytoskeleton. Many of the identified proteomic biomarkers of obesity have also been reported to be dysregulated in obesity-related disease. Among them, seven proteins, which belong to metabolic pathways (aldehyde dehydrogenase and apolipoprotein A1), the chaperone family (albumin, heat shock protein beta 1, protein disulfide-isomerase A3) and oxidative stress and inflammation proteins (catalase and complement C3), could potentially serve as biomarkers for the progression of obesity and the development of comorbidities, contributing to personalized medicine in the field of obesity. Our systematic review in proteomics represents a substantial step forward in unravelling the complexities of protein alterations associated with obesity. It provides valuable insights into the pathophysiological mechanisms underlying obesity, thereby opening avenues for the discovery of potential biomarkers and the development of personalized medicine in obesity.

Identification of Novel Isatin Derivative Bearing a Nitrofuran Moiety as Potent Multi-Isoform Aldehyde Dehydrogenase Inhibitor

Aldehyde dehydrogenases (ALDHs) are a family of enzymes that aid in detoxification and are overexpressed in several different malignancies. There is a correlation between increased expression of ALDH and a poor prognosis, stemness, and resistance to several drugs. Several ALDH inhibitors have been generated due to the crucial role that ALDH plays in cancer stem cells. All of these inhibitors, however, are either ineffective, very toxic, or have yet to be subjected to rigorous testing on their effectiveness. Although various drug-like compounds targeting ALDH have been reported in the literature, none have made it to routine use in the oncology clinic. As a result, new potent, non-toxic, bioavailable, and therapeutically effective ALDH inhibitors are still needed. In this study, we designed and synthesized potent multi-ALDH isoform inhibitors based on the isatin and indazole pharmacophore. Molecular docking studies and enzymatic tests revealed that among all of the synthesized analogs, compound 3 is the most potent inhibitor of ALDH1A1, ALDH3A1, and ALDH1A3, exhibiting 51.32%, 51.87%, and 36.65% inhibition, respectively. The ALDEFLUOR assay further revealed that compound 3 acts as an ALDH broad spectrum inhibitor at 500 nM. Compound 3 was also the most cytotoxic to cancer cells, with an IC50 in the range of 2.1 to 3.8 µM for ovarian, colon, and pancreatic cancer cells, compared to normal and embryonic kidney cells (IC50 7.1 to 8.7 µM). Mechanistically, compound 3 increased ROS activity due to potent multi-ALDH isoform inhibition, which increased apoptosis. Taken together, this study identified a potent multi-isoform ALDH inhibitor that could be further developed as a cancer therapeutic.

β-escin activates ALDH and prevents cigarette smoke-induced cell death

BACKGROUND

The tobacco use is one of the biggest public health threats worldwide. Cigarette smoke contains over 7000 chemicals among other aldehydes, regarded as priority toxicants. β-escin (a mixture of triterpenoid saponins extracted from the Aesculus hippocastanum. L) is a potent activator of aldehyde dehydrogenase (ALDH) - an enzyme catalyzing oxidation of aldehydes to non-toxic carboxylic acids.

PURPOSE

The aim of this study was to evaluate the effect of β-escin on ALDH activity, ALDH isoforms mRNA expression and cytotoxicity in nasal epithelial cells exposed to cigarette smoke extract (CSE).

METHODS

Nasal epithelial cells from healthy non-smokers were treated with β-escin (1 µM) and exposed to 5% CSE. After 6- or 24-hours of stimulation cell viability, DNA damage, ALDH activity and mRNA expression of ALDH isoforms were examined.

RESULTS

24 h β-escin stimulation revised CSE induced cytotoxicity and DNA damage. Cells cultured with β-escin or exposed to CSE responded with strong increase in ALDH activity. This effect was more pronounced in cultures treated with combination of β-escin and CSE. The strongest stimulatory effect on ALDH isoform mRNA expression was observed in cells cultured simultaneously with β-escin and CSE: at 6 h for ALDH1A1 and ALDH3A1, and at 24 h for ALDH1A3, ALDH3A2, ALDH3B1, and ALDH18A1. Combined β-escin and CSE treatment prevented the CSE-induced inhibition of ALDH2 expression at 24 h.

CONCLUSIONS

β-escin is an effective ALDH stimulatory and cytoprotective agent and might be useful in the prevention or supportive treatment of tobacco smoke-related diseases.

A patent review on aldehyde dehydrogenase inhibitors: an overview of small molecule inhibitors from the last decade

INTRODUCTION

Physiological and pathophysiological effects arising from detoxification of aldehydes in humans implicate the enzyme aldehyde dehydrogenase (ALDH) gene family comprising of 19 isoforms. The main function of this enzyme family is to metabolize reactive aldehydes to carboxylic acids. Dysregulation of ALDH activity has been associated with various diseases. Extensive research has since gone into studying ALHD isozymes, their structural biology and developing small-molecule inhibitors. Novel chemical strategies to enhance the selectivity of ALDH inhibitors have now appeared.

AREAS COVERED

A comprehensive review of patent literature related to aldehyde dehydrogenase inhibitors in the last decade and half (2007-2022) is provided.

EXPERT OPINION

Aldehyde dehydrogenase (ALDH) is an important enzyme that metabolizes reactive exogenous and endogenous aldehydes in the body through NAD(P)±dependent oxidation. Hence this family of enzymes possess important physiological as well as toxicological roles in human body. Significant efforts in the field have led to potent inhibitors with approved clinical agents for alcohol use disorder therapy. Further clinical translation of novel compounds targeting ALDH inhibition will validate the promised therapeutic potential in treating many human diseases.The scientific/patent literature has been searched on SciFinder-n, Reaxys, PubMed, Espacenet and Google Patents. The search terms used were 'ALDH inhibitors', 'Aldehyde Dehydrogenase Inhibitors'.

Investigating Carvedilol's Repurposing for the Treatment of Non-Small Cell Lung Cancer via Aldehyde Dehydrogenase Activity Modulation in the Presence of β-Adrenergic Agonists

Repurposing existing drugs appears to be a potential solution for addressing the challenges in the treatment of non-small cell lung cancer (NSCLC). β-adrenoceptor antagonist drugs (β-blockers) have tumor-inhibiting effects, making them promising candidates for potential NSCLC treatment. This study investigates the anticancer potential of a subset of β-blockers in NSCLC cell lines; A549 and H1299. Additionally, it investigates the underlying mechanism behind β-blockers' anticancer effect by influencing a potential novel target named aldehyde dehydrogenase (ALDH). The MTT assay assessed β-blockers' cytotoxicity on both cell lines, while Western blot and NADH fluorescence assays evaluated their influence on ALDH protein expression and activity. Carvedilol (CAR) was the most effective blocker in reducing cell survival of A549 and H1299 with IC50 of 18 µM and 13.7 µM, respectively. Significantly, CAR led to a 50% reduction in ALDH expression and 80% decrease in ALDH activity in A549 cells, especially when combined with β-agonists, in comparison to the control. This effect might be attributed to β-agonist blockade or an alternative pathway. This novel finding adds to our understanding of CAR's multifaceted anticancer properties, implying that combining CAR with β-agonists could be a useful strategy for lung cancer treatment.

Human Aldehyde Dehydrogenases: A Superfamily of Similar Yet Different Proteins Highly Related to Cancer

The superfamily of human aldehyde dehydrogenases (hALDHs) consists of 19 isoenzymes which are critical for several physiological and biosynthetic processes and play a major role in the organism's detoxification via the NAD(P) dependent oxidation of numerous endogenous and exogenous aldehyde substrates to their corresponding carboxylic acids. Over the last decades, ALDHs have been the subject of several studies as it was revealed that their differential expression patterns in various cancer types are associated either with carcinogenesis or promotion of cell survival. Here, we attempt to provide a thorough review of hALDHs' diverse functions and 3D structures with particular emphasis on their role in cancer pathology and resistance to chemotherapy. We are especially interested in findings regarding the association of structural features and their changes with effects on enzymes' functionalities. Moreover, we provide an updated outline of the hALDHs inhibitors utilized in experimental or clinical settings for cancer therapy. Overall, this review aims to provide a better understanding of the impact of ALDHs in cancer pathology and therapy from a structural perspective.

Hypusination Maintains Intestinal Homeostasis and Prevents Colitis and Carcinogenesis by Enhancing Aldehyde Detoxification

BACKGROUND & AIMS

The amino acid hypusine, synthesized from the polyamine spermidine by the enzyme deoxyhypusine synthase (DHPS), is essential for the activity of eukaryotic translation initiation factor 5A (EIF5A). The role of hypusinated EIF5A (EIF5AHyp) remains unknown in intestinal homeostasis. Our aim was to investigate EIF5AHyp in the gut epithelium in inflammation and carcinogenesis.

METHODS

We used human colon tissue messenger RNA samples and publicly available transcriptomic datasets, tissue microarrays, and patient-derived colon organoids. Mice with intestinal epithelial-specific deletion of Dhps were investigated at baseline and in models of colitis and colon carcinogenesis.

RESULTS

We found that patients with ulcerative colitis and Crohn's disease exhibit reduced colon levels of DHPS messenger RNA and DHPS protein and reduced levels of EIF5AHyp. Similarly, colonic organoids from colitis patients also show down-regulated DHPS expression. Mice with intestinal epithelial-specific deletion of Dhps develop spontaneous colon hyperplasia, epithelial proliferation, crypt distortion, and inflammation. Furthermore, these mice are highly susceptible to experimental colitis and show exacerbated colon tumorigenesis when treated with a carcinogen. Transcriptomic and proteomic analysis on colonic epithelial cells demonstrated that loss of hypusination induces multiple pathways related to cancer and immune response. Moreover, we found that hypusination enhances translation of numerous enzymes involved in aldehyde detoxification, including glutathione S-transferases and aldehyde dehydrogenases. Accordingly, hypusination-deficient mice exhibit increased levels of aldehyde adducts in the colon, and their treatment with a scavenger of electrophiles reduces colitis.

CONCLUSIONS

Hypusination in intestinal epithelial cells has a key role in the prevention of colitis and colorectal cancer, and enhancement of this pathway via supplementation of spermidine could have a therapeutic impact.

Impact of common ALDH2 inactivating mutation and alcohol consumption on Alzheimer's disease

Aldehyde dehydrogenase 2 (ALDH2) is an enzyme found in the mitochondrial matrix that plays a central role in alcohol and aldehyde metabolism. A common ALDH2 polymorphism in East Asians descent (called ALDH2*2 or E504K missense variant, SNP ID: rs671), present in approximately 8% of the world's population, has been associated with a variety of diseases. Recent meta-analyses support the relationship between this ALDH2 polymorphism and Alzheimer's disease (AD). And AD-like pathology observed in ALDH2-/- null mice and ALDH2*2 overexpressing transgenic mice indicate that ALDH2 deficiency plays an important role in the pathogenesis of AD. Recently, the worldwide increase in alcohol consumption has drawn attention to the relationship between heavy alcohol consumption and AD. Of potential clinical significance, chronic administration of alcohol in ALDH2*2/*2 knock-in mice exacerbates the pathogenesis of AD-like symptoms. Therefore, ALDH2 polymorphism and alcohol consumption likely play an important role in the onset and progression of AD. Here, we review the data on the relationship between ALDH2 polymorphism, alcohol, and AD, and summarize what is currently known about the role of the common ALDH2 inactivating mutation, ALDH2*2, and alcohol in the onset and progression of AD.

ALDH2 rs671 and MTHFR rs1801133 polymorphisms are risk factors for arteriosclerosis in multiple arteries

BACKGROUND

Arteriosclerosis in multiple arteries has long been associated with heightened cardiovascular risk. Acetaldehyde dehydrogenase 2 (ALDH2) and methylenetetrahydrofolate reductase (MTHFR) play an important role in the pathogenesis of arteriosclerosis by participating in the oxidation and reduction reactions in vascular endothelial cells. The purpose was to investigate the relationship of ALDH2 and MTHFR gene polymorphisms with arteriosclerosis in multiple arteries.

METHODS

410 patients with arteriosclerosis in single artery and 472 patients with arteriosclerosis in multiple arteries were included. The relationship between ALDH2 rs671 and MTHFR rs1801133 polymorphisms and arteriosclerosis in single artery and arteriosclerosis in multiple arteries was analyzed.

RESULTS

The proportion of ALDH2 rs671 A allele (35.6% vs. 30.9%, P = 0.038) and MTHFR rs1801133 T allele (32.6% vs. 27.1%, P = 0.012) in patients with arteriosclerosis in multiple arteries was significantly higher than that in arteriosclerosis in single artery, respectively. The proportion of history of alcohol consumption in patients with ALDH2 rs671 G/G genotype was higher than those in ALDH2 rs671 G/A genotype and A/A genotype (P < 0.001). The results of logistic regression analysis indicated that ALDH2 rs671 A/A genotype (A/A vs. G/G: OR 1.996, 95% CI: 1.258-3.166, P = 0.003) and MTHFR rs1801133 T/T genotype (T/T vs. C/C: OR 1.943, 95% CI: 1.179-3.203, P = 0.009) may be independent risk factors for arteriosclerosis in multiple arteries (adjusted for age, sex, smoking, drinking, hypertension, and diabetes).

CONCLUSIONS

ALDH2 rs671 A/A and MTHFR rs1801133 T/T genotypes may be independent risk factors for arteriosclerosis in multiple arteries.

Ethanol Metabolism and Melanoma

Malignant melanoma is the deadliest form of skin cancer. Despite significant efforts in sun protection education, melanoma incidence is still rising globally, drawing attention to other socioenvironmental risk factors for melanoma. Ethanol and acetaldehyde (AcAH) are ubiquitous in our diets, medicines, alcoholic beverages, and the environment. In the liver, ethanol is primarily oxidized to AcAH, a toxic intermediate capable of inducing tumors by forming adducts with proteins and DNA. Once in the blood, ethanol and AcAH can reach the skin. Although, like the liver, the skin has metabolic mechanisms to detoxify ethanol and AcAH, the risk of ethanol/AcAH-associated skin diseases increases when the metabolic enzymes become dysfunctional in the skin. This review highlights the evidence linking cutaneous ethanol metabolism and melanoma. We summarize various sources of skin ethanol and AcAH and describe how the reduced activity of each alcohol metabolizing enzyme affects the sensitivity threshold to ethanol/AcAH toxicity. Data from the Gene Expression Omnibus database also show that three ethanol metabolizing enzymes (alcohol dehydrogenase 1B, P450 2E1, and catalase) and an AcAH metabolizing enzyme (aldehyde dehydrogenase 2) are significantly reduced in melanoma tissues.

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.

Nonalcoholic steatohepatitis and mechanisms by which it is ameliorated by activation of the CNC-bZIP transcription factor Nrf2

Non-alcoholic steatohepatitis (NASH) represents a global health concern. It is characterised by fatty liver, hepatocyte cell death and inflammation, which are associated with lipotoxicity, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, iron overload and oxidative stress. NF-E2 p45-related factor 2 (Nrf2) is a transcription factor that combats oxidative stress. Remarkably, Nrf2 is downregulated during the development of NASH, which probably accelerates disease, whereas in pre-clinical studies the upregulation of Nrf2 inhibits NASH. We now review the scientific literature that proposes Nrf2 downregulation during NASH involves its increased ubiquitylation and proteasomal degradation, mediated by Kelch-like ECH-associated protein 1 (Keap1) and/or β-transducin repeat-containing protein (β-TrCP) and/or HMG-CoA reductase degradation protein 1 (Hrd1, also called synoviolin (SYVN1)). Additionally, downregulation of Nrf2-mediated transcription during NASH may involve diminished recruitment of coactivators by Nrf2, due to increased levels of activating transcription factor 3 (ATF3) and nuclear factor-kappaB (NF-κB) p65, or competition for promoter binding due to upregulation of BTB and CNC homology 1 (Bach1). Many processes that downregulate Nrf2 are triggered by transforming growth factor-beta (TGF-β), with oxidative stress amplifying its signalling. Oxidative stress may also increase suppression of Nrf2 by β-TrCP through facilitating formation of the DSGIS-containing phosphodegron in Nrf2 by glycogen synthase kinase-3. In animal models, knockout of Nrf2 increases susceptibility to NASH, while pharmacological activation of Nrf2 by inducing agents that target Keap1 inhibits development of NASH. These inducing agents probably counter Nrf2 downregulation affected by β-TrCP, Hrd1/SYVN1, ATF3, NF-κB p65 and Bach1, by suppressing oxidative stress. Activation of Nrf2 is also likely to inhibit NASH by ameliorating lipotoxicity, inflammation, ER stress and iron overload. Crucially, pharmacological activation of Nrf2 in mice in which NASH has already been established supresses liver steatosis and inflammation. There is therefore compelling evidence that pharmacological activation of Nrf2 provides a comprehensive multipronged strategy to treat NASH.

Recent trends in the application of nanoparticles in cancer therapy: The involvement of oxidative stress

In the biomedical area, the interdisciplinary field of nanotechnology has the potential to bring numerous unique applications, including better tactics for cancer detection, diagnosis, and therapy. Nanoparticles (NPs) have been the topic of many research and material applications throughout the last decade. Unlike small-molecule medications, NPs are defined by distinct physicochemical characteristics, such as a large surface-to-volume ratio, which allows them to permeate live cells with relative ease. The versatility of NPs as both therapeutics and diagnostics makes them ideal for a broad spectrum of illnesses, from infectious diseases to cancer. A significant amount of data has been participated in the current scientific publications, emphasizing the concept that NPs often produce reactive oxygen species (ROS) to a larger degree than micro-sized particles. It is important to note that oxidative stress governs a wide range of cell signaling cascades, many of which are responsible for cancer cell cytotoxicity. Here, we aimed to provide insight into the signaling pathways triggered by oxidative stress in cancer cells in response to several types of nanomaterials, such as metallic and polymeric NPs and quantum dots. We discuss recent advances in developing integrated anticancer medicines based on NPs targeted to destroy malignant cells by increasing their ROS setpoint.

Antioxidant Systems, lncRNAs, and Tunneling Nanotubes in Cell Death Rescue from Cigarette Smoke Exposure

Cigarette smoke is a rich source of carcinogens and reactive oxygen species (ROS) that can damage macromolecules including DNA. Repair systems can restore DNA integrity. Depending on the duration or intensity of stress signals, cells may utilize various survival and adaptive mechanisms. ROS levels are kept in check through redundant detoxification processes controlled largely by antioxidant systems. This review covers and expands on the mechanisms available to cigarette smoke-exposed cancer cells for restoring the redox balance. These include multiple layers of transcriptional control, each of which is posited to be activated upon reaching a particular stress threshold, among them the NRF2 pathway, the AP-1 and NF-kB pathways, and, finally, TP53, which triggers apoptosis if extreme toxicity is reached. The review also discusses long noncoding RNAs, which have been implicated recently in regulating oxidative stress-with roles in ROS detoxification, the inflammatory response, oxidative stress-induced apoptosis, and mitochondrial oxidative phosphorylation. Lastly, the emerging roles of tunneling nanotubes in providing additional mechanisms for metabolic rescue and the regulation of redox imbalance are considered, further highlighting the expanded redox reset arsenal available to cells.

Noninvasive Diagnosis of Gastric Cancer Based on Breath Analysis with a Tubular Surface-Enhanced Raman Scattering Sensor

SERS-based breath analysis as an emerging technique has attracted increasing attention in cancer screening. Here, eight aldehydes and ketones in the human breath are reported as the VOC biomarkers identified by gas chromatography-mass spectrometry (GC-MS) and applied further for the noninvasive diagnosis of gastric cancer (GC) with a tubular SERS sensor. The tubular SERS sensor is prepared with a glass capillary loaded with ZIF-67-coated silver particles (Ag@ZIF-67), which offers Raman enhancement from the plasmonic nanoparticles and gas enrichment from the metal-organic framework (MOF) shells. The composite materials are modified with 4-aminothiophenol (4-ATP) to capture different aldehyde and ketone compounds. The tubular sensor is served simultaneously as a gas flow channel and a detection chamber, bringing a higher gas capture efficiency than the planar SERS sensor. As a proof-of-concept, the tubular SERS sensor is successfully employed to screen gastric cancer patients with an accuracy of 89.83%, based on the noninvasive, rapid, and easily operated breath analysis. The results demonstrate that the established breath analysis method provides an excellent alternative for the screening of GC and other diseases.

Positive selection acts on regulatory genetic variants in populations of European ancestry that affect ALDH2 gene expression

ALDH2 is a key enzyme in alcohol metabolism that protects cells from acetaldehyde toxicity. Using iHS, iSAFE and FST statistics, we identified regulatory acting variants affecting ALDH2 gene expression under positive selection in populations of European ancestry. Several SNPs (rs3184504, rs4766578, rs10774625, rs597808, rs653178, rs847892, rs2013002) that function as eQTLs for ALDH2 in various tissues showed evidence of strong positive selection. Very large pairwise FST values indicated high genetic differentiation at these loci between populations of European ancestry and populations of other global ancestries. Estimating the timing of positive selection on the beneficial alleles suggests that these variants were recently adapted approximately 3000-3700 years ago. The derived beneficial alleles are in complete linkage disequilibrium with the derived ALDH2 promoter variant rs886205, which is associated with higher transcriptional activity. The SNPs rs4766578 and rs847892 are located in binding sequences for the transcription factor HNF4A, which is an important regulatory element of ALDH2 gene expression. In contrast to the missense variant ALDH2 rs671 (ALDH2*2), which is common only in East Asian populations and is associated with greatly reduced enzyme activity and alcohol intolerance, the beneficial alleles of the regulatory variants identified in this study are associated with increased expression of ALDH2. This suggests adaptation of Europeans to higher alcohol consumption.

Emerging Roles of Aldehyde Dehydrogenase Isoforms in Anti-cancer Therapy Resistance

Aldehyde dehydrogenases (ALDHs) are a family of detoxifying enzymes often upregulated in cancer cells and associated with therapeutic resistance. In humans, the ALDH family comprises 19 isoenzymes active in the majority of mammalian tissues. Each ALDH isoform has a specific differential expression pattern and most of them have individual functional roles in cancer. ALDHs are overexpressed in subpopulations of cancer cells with stem-like features, where they are involved in several processes including cellular proliferation, differentiation, detoxification and survival, participating in lipids and amino acid metabolism and retinoic acid synthesis. In particular, ALDH enzymes protect cancer cells by metabolizing toxic aldehydes in less reactive and more soluble carboxylic acids. High metabolic activity as well as conventional anticancer therapies contribute to aldehyde accumulation, leading to DNA double strand breaks (DSB) through the generation of reactive oxygen species (ROS) and lipid peroxidation. ALDH overexpression is crucial not only for the survival of cancer stem cells but can also affect immune cells of the tumour microenvironment (TME). The reduction of ROS amount and the increase in retinoic acid signaling impairs immunogenic cell death (ICD) inducing the activation and stability of immunosuppressive regulatory T cells (Tregs). Dissecting the role of ALDH specific isoforms in the TME can open new scenarios in the cancer treatment. In this review, we summarize the current knowledge about the role of ALDH isoforms in solid tumors, in particular in association with therapy-resistance.

The ALDH Family Contributes to Immunocyte Infiltration, Proliferation and Epithelial-Mesenchymal Transformation in Glioma

Gliomas are malignant tumors that originate from the central nervous system. The aldehyde dehydrogenase family has been documented to affect cancer progression; however, its role in gliomas remains largely unexplored. Bulk RNA-seq analysis and single-cell RNA-Seq analysis were performed to explore the role of the aldehyde dehydrogenases family in gliomas. Training cohort contained The Cancer Genome Atlas data, while data from Chinese Glioma Genome Atlas and Gene Expression Omnibus were set as validation cohorts. Our scoring system based on the aldehyde dehydrogenases family suggested that high-scoring samples were associated with worse survival outcomes. The enrichment score of pathways were calculated by AUCell to substantiate the biofunction prediction results that the aldehyde dehydrogenases family affected glioma progression by modulating tumor cell proliferation, migration, and immune landscape. Tumor immune landscape was mapped from high-scoring samples. Moreover, ALDH3B1 and ALDH16A1, two main contributors of the scoring system, could affect glioblastoma cell proliferation and migration by inducing cell-cycle arrest and the epithelial-mesenchymal transition. Taken together, the aldehyde dehydrogenases family could play a significant role in the tumor immune landscape and could be used to predict patient prognosis. ALDH3B1 and ALDH16A1 could influence tumor cell proliferation and migration.

The essential role of transcription factor Pitx3 in preventing mesodiencephalic dopaminergic neurodegeneration and maintaining neuronal subtype identities during aging

Pituitary homeobox 3 (Pitx3) is required for the terminal differentiation of nigrostriatal dopaminergic neurons during neuronal development. However, whether Pitx3 contributes to the normal physiological function and cell-type identity of adult neurons remains unknown. To explore the role of Pitx3 in maintaining mature neurons, we selectively deleted Pitx3 in the mesodiencephalic dopaminergic (mdDA) neurons of Pitx3fl/fl/DATCreERT2 bigenic mice using a tamoxifen inducible CreERT2/loxp gene-targeting system. Pitx3fl/fl/DATCreERT2 mice developed age-dependent progressive motor deficits, concomitant with a rapid reduction of striatal dopamine (DA) content and a profound loss of mdDA neurons in the substantia nigra pars compacta (SNc) but not in the adjacent ventral tegmental area (VTA), recapitulating the canonical neuropathological features of Parkinson's disease (PD). Mechanistic studies showed that Pitx3-deficiency significantly increased the number of cleaved caspase-3+ cells in SNc, which likely underwent neurodegeneration. Meanwhile, the vulnerability of SNc mdDA neurons was increased in Pitx3fl/fl/DATCreERT2 mice, as indicated by an early decline in glial cell line-derived neurotrophic factor (GDNF) and aldehyde dehydrogenase 1a1 (Aldh1a1) levels. Noticeably, somatic accumulation of α-synuclein (α-syn) was also significantly increased in the Pitx3-deficient neurons. Together, our data demonstrate that the loss of Pitx3 in fully differentiated mdDA neurons results in progressive neurodegeneration, indicating the importance of the Pitx3 gene in adult neuronal survival. Our findings also suggest that distinct Pitx3-dependent pathways exist in SNc and VTA mdDA neurons, correlating with the differential vulnerability of SNc and VTA mdDA neurons in the absence of Pitx3.

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.

Targeting NAD-dependent dehydrogenases in drug discovery against infectious diseases and cancer

Dehydrogenases are oxidoreductase enzymes that play a variety of fundamental functions in the living organisms and have primary roles in pathogen survival and infection processes as well as in cancer development. We review here a sub-set of NAD-dependent dehydrogenases involved in human diseases and the recent advancements in drug development targeting pathogen-associated NAD-dependent dehydrogenases. We focus also on the molecular aspects of the inhibition process listing the structures of the most relevant molecules targeting this enzyme family. Our aim is to review the most impacting findings regarding the discovery of novel inhibitory compounds targeting the selected NAD-dependent dehydrogenases involved in cancer and infectious diseases.

Thermal Proteome Profiling in Zebrafish Reveals Effects of Napabucasin on Retinoic Acid Metabolism

Thermal proteome profiling (TPP) allows for the unbiased detection of drug-target protein engagements in vivo. Traditionally, 1 cell type is used for TPP studies, with the risk of missing important differentially expressed target proteins. The use of whole organisms would circumvent this problem. Zebrafish embryos are amenable to such an approach. Here, we used TPP on whole zebrafish embryo lysate to identify protein targets of napabucasin, a compound that may affect signal transducer and activator of transcription 3 (Stat3) signaling through an ill-understood mechanism. In zebrafish embryos, napabucasin induced developmental defects consistent with inhibition of Stat3 signaling. TPP profiling showed no distinct shift in Stat3 upon napabucasin treatment, but effects were detected on the oxidoreductase, Pora, which might explain effects on Stat3 signaling. Interestingly, thermal stability of several aldehyde dehydrogenases was affected. Moreover, napabucasin activated aldehyde dehydrogenase enzymatic activity in vitro. Aldehyde dehydrogenases have crucial roles in retinoic acid metabolism, and functionally, we validated napabucasin-mediated activation of the retinoic acid pathway in zebrafish in vivo. We conclude that TPP profiling in whole zebrafish embryo lysate is feasible and facilitates direct correlation of in vivo effects of small molecule drugs with their protein targets.

Piperlonguminine a new mitochondrial aldehyde dehydrogenase activator protects the heart from ischemia/reperfusion injury

BACKGROUND

Detoxification of aldehydes by aldehyde dehydrogenases (ALDHs) is crucial to maintain cell function. In cardiovascular diseases, reactive oxygen species generated during ischemia/reperfusion events trigger lipoperoxidation, promoting cell accumulation of highly toxic lipid aldehydes compromising cardiac function. In this context, activation of ALDH2, may contribute to preservation of cell integrity by diminishing aldehydes content more efficiently.

METHODS

The theoretic interaction of piperlonguminine (PPLG) with ALDH2 was evaluated by docking analysis. Recombinant human ALDH2 was used to evaluate the effects of PPLG on the kinetics of the enzyme. The effects of PPLG were further investigated in a myocardial infarction model in rats, evaluating ALDHs activity, antioxidant enzymes, oxidative stress markers and mitochondrial function.

RESULTS

PPLG increased the activity of recombinant human ALDH2 and protected the enzyme from inactivation by lipid aldehydes. Additionally, administration of this drug prevented the damage induced by ischemia/reperfusion in rats, restoring heart rate and blood pressure, which correlated with protection of ALDHs activity in the tissue, a lower content of lipid aldehydes, and the preservation of mitochondrial function.

CONCLUSION

Activation of ALDH2 by piperlonguminine ameliorates cell damage generated in heart ischemia/reperfusion events, by decreasing lipid aldehydes concentration promoting cardioprotection.

Oxidative Stress in Cancer

Contingent upon concentration, reactive oxygen species (ROS) influence cancer evolution in apparently contradictory ways, either initiating/stimulating tumorigenesis and supporting transformation/proliferation of cancer cells or causing cell death. To accommodate high ROS levels, tumor cells modify sulfur-based metabolism, NADPH generation, and the activity of antioxidant transcription factors. During initiation, genetic changes enable cell survival under high ROS levels by activating antioxidant transcription factors or increasing NADPH via the pentose phosphate pathway (PPP). During progression and metastasis, tumor cells adapt to oxidative stress by increasing NADPH in various ways, including activation of AMPK, the PPP, and reductive glutamine and folate metabolism.

Harmful chemicals emitted from electronic cigarettes and potential deleterious effects in the oral cavity

Use of electronic nicotine delivery systems (ENDS), such as electronic cigarettes (e-cigs), is increasing across the US population and is particularly troubling due to their adoption by adolescents, teens, and young adults. The industry’s marketing approach for these instruments of addiction has been to promote them as a safer alternative to tobacco, a behavioral choice supporting smoking cessation, and as the ‘cool’ appearance of vaping with flavored products (e.g. tutti frutti, bubble gum, and buttered popcorn etc.). Thus, there is a clear need to better document the health outcomes of e-cig use in the oral cavity of the addicted chronic user. There appears to be an array of environmental toxins in the vapors, including reactive aldehydes and carbonyls resulting from the heating elements action on fluid components, as well as from the composition of chemical flavoring agents. The chemistry of these systems shows that the released vapors from the e-cigs frequently contain levels of environmental toxins that considerably exceed federal occupational exposure limits. Additionally, the toxicants in the vapors appear to be retained in the host fluids/tissues at levels often approximating 90% of the levels in the e-cig vapors. These water-soluble reactive toxins can challenge the oral cavity constituents, potentially contributing to alterations in the autochthonous microbiome and host cells critical for maintaining oral homeostasis. This review updates the existing chemistry/environmental aspects of e-cigs, as well as providing an overview of the somewhat limited data on potential oral health effects that could occur across the lifetime of daily e-cig users.

Acetylresveratrol as a Potential Substitute for Resveratrol Dragged the Toxic Aldehyde to Inhibit the Mutation of Mitochondrial DNA

The aim of this study was to explore whether or not acetylresveratrol as a potential substitute for resveratrol dragged the toxic aldehyde to inhibit the mutation of mitochondrial DNA. The results revealed that the acetylresveratrol shifted ultraviolet peak of trans-crotonaldehyde from 316 to 311 nm. In mitochondria, the acetylresveratrol split the ultraviolet peak at 311 nm of trans-crotonaldehyde into 311 nm and 309 nm; the aldehyde Raman band of trans-crotonaldehyde was red shifted by the acetylresveratrol from 1689 to 1686 cm^-1 with obvious band decline; Raman bands at 1149 cm^-1, 1168 cm^-1, and 1325 cm^-1 of acetylresveratrol disappeared. In aldehyde dehydrogenase, the aldehyde Raman band of trans-crotonaldehyde was red shifted by the acetylresveratrol from 1689 to 1684 cm^-1 with band decline; Raman bands at 1150 cm^-1, 1168 cm^-1, and 1324 cm^-1 of acetylresveratrol declined. The weak acidic microenvironment was the best, for the acetylresveratrol dragged the toxic aldehyde of trans-crotonaldehyde. Compared with the resveratrol, the effect of the acetylresveratrol on the toxic aldehyde of trans-crotonaldehyde was very similar to that of the resveratrol. The acetylresveratrol is very suitable as a potential substitute for resveratrol dragged the toxic aldehyde to inhibit the mutation of mitochondrial DNA. Graphical Abstract In mitochondria, the Raman band of the toxic -CH=O of trans-crotonaldehyde (TCA) dragged by the Acetyl-Res from 1689 to 1686 cm^-1 with obvious band decline, while the Raman bands at 1149 cm^-1, 1168 cm^-1, and 1325 cm^-1 of the Acetyl-Res disappeared, respectively. The Acetyl-Res is very suitable as a potential substitute, for the Res dragged the toxic -CH=O of TCA to inhibit the mutation of mitochondrial DNA for anticancer.

Development of a Novel Multi-Isoform ALDH Inhibitor Effective as an Antimelanoma Agent

The aldehyde dehydrogenases (ALDH) are a major family of detoxifying enzymes that contribute to cancer progression and therapy resistance. ALDH overexpression is associated with a poor prognosis in many cancer types. The use of multi-ALDH isoform or isoform-specific ALDH inhibitors as anticancer agents is currently hindered by the lack of viable candidates. Most multi-ALDH isoform inhibitors lack bioavailability and are nonspecific or toxic, whereas most isoform-specific inhibitors are not effective as monotherapy due to the overlapping functions of ALDH family members. The present study details the development of a novel, potent, multi-isoform ALDH inhibitor, called KS100. The rationale for drug development was that inhibition of multiple ALDH isoforms might be more efficacious for cancer compared with isoform-specific inhibition. Enzymatic IC50s of KS100 were 207, 1,410, and 240 nmol/L toward ALDH1A1, 2, and 3A1, respectively. Toxicity of KS100 was mitigated by development of a nanoliposomal formulation, called NanoKS100. NanoKS100 had a loading efficiency of approximately 69% and was stable long-term. NanoKS100 was 5-fold more selective for killing melanoma cells compared with normal human fibroblasts. NanoKS100 administered intravenously at a submaximal dose (3-fold lower) was effective at inhibiting xenografted melanoma tumor growth by approximately 65% without organ-related toxicity. Mechanistically, inhibition by KS100 significantly reduced total cellular ALDH activity to increase reactive oxygen species generation, lipid peroxidation, and accumulation of toxic aldehydes leading to apoptosis and autophagy. Collectively, these data suggest the successful preclinical development of a nontoxic, bioavailable, nanoliposomal formulation containing a novel multi-ALDH isoform inhibitor effective in the treatment of cancer.

Endothelial Aldehyde Dehydrogenase 2 as a Target to Maintain Vascular Wellness and Function in Ageing

Endothelial cells are the main determinants of vascular function, since their dysfunction in response to a series of cardiovascular risk factors is responsible for disease progression and further consequences. Endothelial dysfunction, if not resolved, further aggravates the oxidative status and vessel wall inflammation, thus igniting a vicious cycle. We have furthermore to consider the physiological manifestation of vascular dysfunction and chronic low-grade inflammation during ageing, also known as inflammageing. Based on these considerations, knowledge of the molecular mechanism(s) responsible for endothelial loss-of-function can be pivotal to identify novel targets of intervention with the aim of maintaining endothelial wellness and vessel trophism and function. In this review we have examined the role of the detoxifying enzyme aldehyde dehydrogenase 2 (ALDH2) in the maintenance of endothelial function. Its impairment indeed is associated with oxidative stress and ageing, and in the development of atherosclerosis and neurodegenerative diseases. Strategies to improve its expression and activity may be beneficial in these largely diffused disorders.

Design, synthesis characterization and biological evaluation of novel multi-isoform ALDH inhibitors as potential anticancer agents

The aldehyde dehydrogenases (ALDHs) are a family of detoxifying enzymes that are overexpressed in various cancers. Increased expression of ALDH is associated with poor prognosis, stemness, and drug resistance. Because of the critical role of ALDH in cancer stem cells, several ALDH inhibitors have been developed. Nonetheless, all these inhibitors either lack efficacy or are too toxic or have not been tested extensively. Thus, the continued development of ALDH inhibitors is warranted. In this study, we designed and synthesized potent multi-ALDH isoform inhibitors based on the isatin backbone. The early molecular docking studies and enzymatic tests revealed that 3(a-l) and 4(a-l) are the potent ALDH1A1, ALDHA2, and ALDH3A1 inhibitors. ALDH inhibitory IC₅₀s of 3(a-l) and 4(a-l) were 230 nM to >10,000 nM for ALDH1A1, 939 nM to >10,000 nM for ALDH2 and 193 nM to >10,000 nM for ALDH3A1. The most potent compounds 3(h-l) had IC₅₀s for killing melanoma cells ranged from 2.1 to 5.7 μM, while for colon cancer cells, it ranged from 2.5 to 5.8 μM and for multiple myeloma cells ranging from 0.3 to 4.7 μM. Toxicity studies of 3(h-l) revealed that 3h to be the least toxic multi-ALDH isoform inhibitor. Mechanistically, 3(h-l) caused increased ROS activity, lipid peroxidation, and toxic aldehyde accumulation, secondary to potent multi-ALDH isoform inhibition leading to increased apoptosis and G2/M cell cycle arrest. Together, the study details the design, synthesis, and evaluation of potent, multi-isoform ALDH inhibitors to treat cancers.

ALDH3A1 Overexpression in Melanoma and Lung Tumors Drives Cancer Stem Cell Expansion, Impairing Immune Surveillance through Enhanced PD-L1 Output

Melanoma and non-small-cell lung carcinoma (NSCLC) cell lines are characterized by an intrinsic population of cancer stem-like cells (CSC), and high expression of detoxifying isozymes, the aldehyde dehydrogenases (ALDHs), regulating the redox state. In this study, using melanoma and NSCLC cells, we demonstrate that ALDH3A1 isozyme overexpression and activity is closely associated with a highly aggressive mesenchymal and immunosuppressive profile. The contribution of ALDH3A1 to the stemness and immunogenic status of melanoma and NSCLC cells was evaluated by their ability to grow in 3D forming tumorspheres, and by the expression of markers for stemness, epithelial to mesenchymal transition (EMT), and inflammation. Furthermore, in specimens from melanoma and NSCLC patients, we investigated the expression of ALDH3A1, PD-L1, and cyclooxygenase-2 (COX-2) by immunohistochemistry. We show that cells engineered to overexpress the ALDH3A1 enzyme enriched the CSCs population in melanoma and NSCLC cultures, changing their transcriptome. In fact, we found increased expression of EMT markers, such as vimentin, fibronectin, and Zeb1, and of pro-inflammatory and immunosuppressive mediators, such as NFkB, prostaglandin E2, and interleukin-6 and -13. ALDH3A1 overexpression enhanced PD-L1 output in tumor cells and resulted in reduced proliferation of peripheral blood mononuclear cells when co-cultured with tumor cells. Furthermore, in tumor specimens from melanoma and NSCLC patients, ALDH3A1 expression was invariably correlated with PD-L1 and the pro-inflammatory marker COX-2. These findings link ALDH3A1 expression to tumor stemness, EMT and PD-L1 expression, and suggest that aldehyde detoxification is a redox metabolic pathway that tunes the immunological output of tumors.

Omeprazole as a potent activator of human cytosolic aldehyde dehydrogenase ALDH1A1

BACKGROUND

Accumulation of lipid aldehydes plays a key role in the etiology of human diseases where high levels of oxidative stress are generated. In this regard, activation of aldehyde dehydrogenases (ALDHs) prevents oxidative tissue damage during ischemia-reperfusion processes. Although omeprazole is used to reduce stomach gastric acid production, in the present work this drug is described as the most potent activator of human ALDH1A1 reported yet.

METHODS

Docking analysis was performed to predict the interactions of omeprazole with the enzyme. Recombinant human ALDH1A1 was used to assess the effect of omeprazole on the kinetic properties. Temperature treatment and mass spectrometry were conducted to address the nature of binding of the activator to the enzyme. Finally, the effect of omeprazole was evaluated in an in vivo model of oxidative stress, using E. coli cells expressing the human ALDH1A1.

RESULTS

Omeprazole interacted with the aldehyde binding site, increasing 4-6 fold the activity of human ALDH1A1, modified the kinetic properties, altering the order of binding of substrates and release of products, and protected the enzyme from inactivation by lipid aldehydes. Furthermore, omeprazole protected E. coli cells over-expressing ALDH1A1 from the effects of oxidative stress generated by H₂O₂ exposure, reducing the levels of lipid aldehydes and preserving ALDH activity.

CONCLUSION

Omeprazole can be repositioned as a potent activator of human ALDH1A1 and may be proposed for its use in therapeutic strategies, to attenuate the damage generated during oxidative stress events occurring in different human pathologies.