Aldehyde Dehydrogenase Isozymes Research Articles

Evaluation of quercetin as a potential cytoprotector against acetaldehyde using the cultured hepatocyte model with aldehyde dehydrogenase isozyme deficiency.

Protective effect of quercetin against acetaldehyde was evaluated using the cultured hepatocyte models with aldehyde dehydrogenase (ALDH) isozyme deficiency (aldh2-kd and aldh1a1-kd). The quercetin-induced cytoprotection against acetaldehyde in the ALDH1A1-deficient mutant (aldh1a1-kd) was weaker than that in wild type. Furthermore, quercetin did not enhance the ALDH activity in aldh1a1-kd cells, suggesting that ALDH1A1 is involved in the quercetin-induced cytoprotection.

Proteomic profiling reveals an association between ALDH and oxidative phosphorylation and DNA damage repair pathways in human colon adenocarcinoma stem cells

Several members of the aldehyde dehydrogenase (ALDH) family, especially ALDH1 isoenzymes, have been identified as biomarkers of cancer stem cells (CSCs), a small subpopulation of oncogenic cells with self-renewal and multipotency capability. Consistent with this contention, cell populations with high ALDH enzymatic activity exhibit greater carcinogenic potential. It has been reported that ALDH1, especially ALDH1A1, serves as a valuable biomarker for colon CSCs. However, the functional roles of ALDHs in CSCs and solid tumors of the colon tissue is not fully understood. The aim of the present study was to identify molecular signature associated with high ALDH activity in human colorectal adenocarcinoma (COLO320DM) cells by proteomics profiling. Aldefluor™ assay was performed to sort COLO320DM cells exhibiting high (ALDHhigh) and low (ALDHlow) ALDH activity. Label-free quantitative proteomics analyses were conducted on these two cell populations. Proteomics profiling revealed a total of 229 differentially expressed proteins (DEPs) in ALDHhigh relative to ALDHlow cells, of which 182 were down-regulated and 47 were up-regulated. In agreement with previous studies, ALDH1A1 appeared to be the principal ALDH isozyme contributing to the Aldefluor™ assay activity in COLO320DM cells. Ingenuity pathway analysis of the proteomic datasets indicated that DEPs were associated with mitochondrial dysfunction, sirtuin signaling, oxidative phosphorylation and nucleotide excision repair. Our proteomics study predicts that high ALDH1A1 activity may be involved in these cellular pathways to promote a metabolic switch and cellular survival of CSCs.

Expression of aldehyde dehydrogenase 1A1 in oral squamous cell carcinoma and its correlation with clinicopathological parameters.

Background:Aldehyde dehydrogenase 1A1 (ALDH1A1) is a key aldehyde dehydrogenase (ALDH) isozyme, related to the cancer stem cells which are responsible for initiating tumor growth, progression, and recurrence. High expression of ALDH1A1 has been reported in several tumor types in humans and its expression is associated with poor prognosis. The aim of this study was to assess the expression of the ALDH1A1 in oral squamous cell carcinoma (SCC) and its correlation with various clinicopathological parameters.Materials and Methods:ALDH1A1 expression was analyzed by using immunohistochemistry on paraffin blocks of 112 cases of primary oral SCC and their corresponding 68 lymph nodes with metastatic deposits. ALDH1A1 expression was also correlated with various clinicopathological parameters. Statistical analysis was done with statistical analysis software, the Statistical Package for the Social Sciences version 21.0.Results:High ALDH1A1 expression was observed in 31.2% of cases of primary oral SCC as compared to 73.5% in lymph node metastasis. A statistically significant difference (P = 0.04) was observed in high TNM stages (68.6%) of the tumor as compared to low TNM stages (31.4%). However, histopathological grades of tumor showed nonsignificant correlation with ALDH1A1 expression (P = 0.093). 40.2% of patients were expired at the end of the study, and the rate of mortality was significantly higher (P = 0.01) in patients with high ALDH1A1 expression as compared to low expression (60.0% vs. 31.2%).Conclusion:High ALDH1A1 expression was associated with higher TNM tumor stage and high nodal stage. It was also associated with high mortality rate which validates it as a marker of invasiveness and poor prognosis in oral SCC.

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.

Analysis of human aldehyde dehydrogenases (ALDH) gene expression pattern in breast cancer tissue samples: rutin-copper complex inhibit the breast cancer cell proliferation

BackgroundHigher aldehyde dehydrogenases (ALDH) activity is one of the important signatures of breast cancer appearance and has been associated with poor prognosis. ALDH1A3 has been over-expressed in breast cancer patients. This study aims to analyze gene expression patterns of 18 ALDH isozymes in breast cancer tissue samples. It is carried out using a chip-based microarray, next-generation DNA sequencing of ALDH2 gene following in silico study to identify the natural products which act as inhibitors for over-expressed ALDH isoforms. The synthesis of rutin-copper complex and cell viability assay is carried out on MDA-MB-468 cell line.ResultsALDH1A3 and ALDH18A1 have shown the highest positive mean fold of variation; whereas, ALDH2 and ALDH1A2 have shown the highest negative mean fold variation. In silico studies revealed that rutin has the highest binding affinity with both ALDH1A3 and ALDH18A1 and supported with IC50 value of rutin against MDA-MB-468 cells (144.50 μg/ml). Chemically synthesized rutin-copper complex significantly lowered the IC50 value to 119.40 μg/ml. The next-generation sequencing study provides the novel single nucleotide polymorphism (SNP) from T to G in the ALDH2 gene.ConclusionThe present study signifies that, along with ALDH1A3, ALDH18A1 also acts as a marker for breast cancer. Apart from that, inhibitors of ALDH1A3 and ALDH18A1 were attained. Perhaps the single nucleotide polymorphism (SNP) obtained during the mutation analysis may be the probable cause of the highest downregulation of ALDH2 in breast cancer.

Is the mechanism of nitroglycerin tolerance associated with aldehyde dehydrogenase activity? A contribution to the ongoing discussion.

The aim of the study presented here was an attempt to answer the question posed in the title: Is the mechanism of nitroglycerin tolerance associated with aldehyde dehydrogenase (ALDH) activity? Here, we investigated the effect of administration (separately or jointly) of lipoic acid (LA), nitroglycerin (GTN), and disulfiram (DSF; an irreversible in vivo inhibitor of all ALDH isozymes (including ALDH2)), on the development of tolerance to GTN. We also assessed the total activity of ALDH in the rat liver homogenates. Our data revealed that not only DSF and GTN inhibited the total ALDH activity in the rat liver, but LA also proved to be an inhibitor of this enzyme. At the same time, the obtained results demonstrated that the GTN tolerance did not develop in GTN, DSF and LA jointly treated rats, but did develop in GTN and DSF jointly treated rats. This means that the ability of LA to prevent GTN tolerance is not associated with the total ALDH activity in the rat liver. In this context, the fact that animals jointly receiving GTN and DSF developed tolerance to GTN, and in animals that in addition to GTN and DSF also received LA such tolerance did not develop, is - in our opinion - a sufficient premise to conclude that the nitrate tolerance certainly is not caused by a decrease in the activity of any of the ALDH isoenzymes present in the rat liver, including ALDH2. However, many questions still await an answer, including the basic one: What is the mechanism of tolerance to nitroglycerin?

Development of a Retinal-Based Probe for the Profiling of Retinaldehyde Dehydrogenases in Cancer Cells.

Retinaldehyde dehydrogenases belong to a superfamily of enzymes that regulate cell differentiation and are responsible for detoxification of anticancer drugs. Chemical tools and methods are of great utility to visualize and quantify aldehyde dehydrogenase (ALDH) activity in health and disease. Here, we present the discovery of a first-in-class chemical probe based on retinal, the endogenous substrate of retinal ALDHs. We unveil the utility of this probe in quantitating ALDH isozyme activity in a panel of cancer cells via both fluorescence and chemical proteomic approaches. We demonstrate that our probe is superior to the widely used ALDEFLUOR assay to explain the ability of breast cancer (stem) cells to produce all-trans retinoic acid. Furthermore, our probe revealed the cellular selectivity profile of an advanced ALDH1A1 inhibitor, thereby prompting us to investigate the nature of its cytotoxicity. Our results showcase the application of substrate-based probes in interrogating pathologically relevant enzyme activities. They also highlight the general power of chemical proteomics in driving the discovery of new biological insights and its utility to guide drug discovery efforts.

Clinical implications of ALDH1A1 and ALDH1A3 mRNA expression in melanoma subtypes

Aldehyde dehydrogenase (ALDH) activity is not only a valuable marker for cancer cells with stem-like features, but also plays a vital role in drug resistance and disease progression in many tumors including melanoma. However, the precise role of ALDH activity in patient prognosis remains unclear. In this study, using the Cancer Genome Atlas (TCGA) RNA-sequencing expression data, we analyzed gene expression of ALDH isozymes in melanoma tumors to define the expression patterns and the prognostic and predictive values of these enzymes. We found that ALDH1A1 and ALDH1A3 had both higher and broader expression ranges in melanoma patients, and that ALDH1A3 expression correlated with better overall survival in metastatic melanoma. Further, stratification of the TCGA cohorts by the mutational subtypes of melanoma specifically revealed that expression of ALDH1A3 correlated with better prognosis in metastatic BRAF-mutant melanoma while expression of ALDH1A1 correlated with better prognosis in BRAF wild-type melanoma. Gene set enrichment analysis (GSEA) of these cohorts identified upregulation in oxidative phosphorylation, adipogenesis, and fatty acid metabolism signaling in ALDH1Alo patients, suggesting BRAF/MEK inhibitor resistance in that subset of patients. On the other hand, GSEA of ALDH1A3hi cohorts revealed upregulation in glycolysis, hypoxia and angiogenesis, suggesting BRAF/MEK inhibitor sensitivity in that subset of patients. Gene expression analysis using pre-treatment tumor samples supports high ALDH1A3 expression before BRAF/MEK inhibitor treatment as predictive of better treatment response in BRAF-mutant melanoma patients. Our study provides evidence that high ALDH1A3 mRNA expression is not only a prognostic marker but also a predictive marker for BRAF/MEK inhibitor treatment response in BRAF-mutant metastatic melanoma patients.

Differential activation of placental nutrient sensor pathways AMPK, insulin/IGF-1, and mTOR in SGA, AGA and LGA newborns from healthy mothers

Intrauterine growth restriction (IUGR) is a complication of pregnancy that has both short- and long-term sequelae for affected mothers and offspring. The pathophysiology of disease stems from poor nutrient and oxygen provision to the fetus, resulting in increased oxidative stress within the placenta. As the milieu within the local microenvironment alters macrophage differentiation, we hypothesized that macrophage plasticity may be altered in placentas associated with IUGR, and that macrophages would show hallmarks of lipid peroxidation including altered aldehyde metabolism.In human placentas taken from normal pregnancies resulting in appropriate-for-gestational-age (AGA) newborns and placentas associated with IUGR, placental macrophages were evaluated by immunohistochemistry and shown in IUGR to resemble pro-inflammatory activated M1-type macrophages. To link oxidative stress to macrophages, the expression of aldehyde dehydrogenase (ALDHs) isozymes ALDH1, ALDH2, and ALDH3 was assessed.All three isozymes displayed preferential staining for distinct cellular populations within the term human placenta. ALDH1 and ALDH2 were strongly expressed in placental Hofbauer and decidual stromal cells. ALDH3, in contrast, was present in extravillous trophoblasts. Comparing AGA and IUGR-associated placentas, ALDH1 and ALDH2 trended to have greater expression in macrophage populations but lower expression in decidual cell populations in IUGR-associated placentas. ALDH3 had higher expression in IUGR-associated placentas but localized specifically to extravillous trophoblast populations.Therefore, we speculate that specific ALDH isozymes have cell-specific functions related to differentiation, inflammation, or oxidative stress responses that are altered in IUGR-associated term human placentas. This family of isozymes may be a novel method to identify human placentas affected by placental insufficiency/IUGR.

Aldehyde dehydrogenase isoforms and inflammatory cell populations are differentially expressed in term human placentas affected by intrauterine growth restriction

ObjectiveIntrauterine growth restriction (IUGR) is a complication of pregnancy that has both short- and long-term sequelae for affected mothers and offspring. The pathophysiology of disease stems from poor nutrient and oxygen provision to the fetus, resulting in increased oxidative stress within the placenta. As the milieu within the local microenvironment alters macrophage differentiation, we hypothesized that macrophage plasticity may be altered in placentas associated with IUGR, and that macrophages would show hallmarks of lipid peroxidation including altered aldehyde metabolism. MethodsIn human placentas taken from normal pregnancies resulting in appropriate-for-gestational-age (AGA) newborns and placentas associated with IUGR, placental macrophages were evaluated by immunohistochemistry and shown in IUGR to resemble pro-inflammatory activated M1-type macrophages. To link oxidative stress to macrophages, the expression of aldehyde dehydrogenase (ALDHs) isozymes ALDH1, ALDH2, and ALDH3 was assessed. ResultsAll three isozymes displayed preferential staining for distinct cellular populations within the term human placenta. ALDH1 and ALDH2 were strongly expressed in placental Hofbauer and decidual stromal cells. ALDH3, in contrast, was present in extravillous trophoblasts. Comparing AGA and IUGR-associated placentas, ALDH1 and ALDH2 trended to have greater expression in macrophage populations but lower expression in decidual cell populations in IUGR-associated placentas. ALDH3 had higher expression in IUGR-associated placentas but localized specifically to extravillous trophoblast populations. ConclusionTherefore, we speculate that specific ALDH isozymes have cell-specific functions related to differentiation, inflammation, or oxidative stress responses that are altered in IUGR-associated term human placentas. This family of isozymes may be a novel method to identify human placentas affected by placental insufficiency/IUGR.

Abstract P111: A Mendelian Randomization Study of Alcohol Intake and Ischemic Stroke in a Han Chinese Population

Introduction: Observational studies have reported inconsistent relationships between alcohol intake and ischemic stroke risk. The ALDH2 gene encodes an enzyme critical for alcohol metabolism and can serve as an unconfounded proxy for alcohol intake. The current study examined the association between the ALDH2 gene and ischemic stroke among 11,753 Chinese participants. Hypothesis: This study hypothesized that carriers of the ALDH2 variant tend to drink less alcohol and thus have lower risk for ischemic stroke. Methods: The discovery stage included 999 ischemic stroke cases and 1,001 controls with no history of atherosclerotic disease. The ALDH2 gene was sequenced using the SOLiD 4hq platform. Variants with minor allele count (MAC) >10 were each tested for association with stroke using logistic regression models. Interactions between alcohol intake and ALDH2 variants were also tested. Aggregate analysis of rare variants (MAC <20) used the sequence kernel association test. Variants with P<1х10 -4 were replicated among 4,724 ischemic stroke cases and 5,029 controls from the China Stroke Project. Results: An interaction of alcohol drinking with the ALDH2 rs671 variant, which encodes an inactive aldehyde dehydrogenase isozyme that limits tolerability to alcohol, on ischemic stroke risk was identified using the 2 degree of freedom test (P=2.77х10 -5 , 3.66х10 -11 , and 1.01х10 -15 in discovery, replication and joint analyses, respectively). Among drinkers, each copy of the variant allele conferred decreased odds of ischemic stroke, with odds ratios (95% CI) of 0.38 (0.25, 0.60), 0.79 (0.69, 0.91), and 0.74 (0.65, 0.85) in discovery, replication and joint analyses, respectively. While no association between the variant allele and stroke was observed among non-drinkers in the discovery stage [odds ratio (95% CI): 1.00 (0.82, 1.23)], the protective relation persisted among non-drinkers in the replication and joint analyses [odds ratios (95% confidence interval): 0.77 (0.71, 0.84) and 0.80 (0.74, 0.87), respectively]. This inconsistency may have resulted from disparate frequencies of former drinkers included in the non-drinking groups. No additional variants were identified. Conclusions: This large-scale genomic study implicates increased alcohol intake as an etiologically relevant risk factor for ischemic stroke.

Abstract WP251: A Mendelian Randomization Study of Alcohol Intake and Ischemic Stroke in a Han Chinese Population

Introduction: Observational studies have reported inconsistent relationships between alcohol intake and ischemic stroke risk. The ALDH2 gene encodes an enzyme critical for alcohol metabolism and can serve as an unconfounded proxy for alcohol intake. The current study examined the association between the ALDH2 gene and ischemic stroke among 11,753 Chinese participants. Methods: The discovery stage included 999 ischemic stroke cases and 1,001 controls with no history of atherosclerotic disease. The ALDH2 gene was sequenced using the SOLiD 4hq platform. Variants with minor allele count (MAC) >10 were each tested for association with stroke using logistic regression models. Interactions between alcohol intake and ALDH2 variants were also tested. Aggregate analysis of rare variants (MAC <20) used the sequence kernel association test. Variants with P<1х10 -4 were replicated among 4,724 ischemic stroke cases and 5,029 controls from the China Stroke Project. Results: An interaction of alcohol drinking with the ALDH2 rs671 variant, which encodes an inactive aldehyde dehydrogenase isozyme that limits tolerability to alcohol, on ischemic stroke risk was identified using the 2 degree of freedom test (P=2.77х10 -5 , 3.66х10 -11 , and 1.01х10 -15 in discovery, replication and joint analyses, respectively). Among drinkers, each copy of the variant allele conferred decreased odds of ischemic stroke, with odds ratios (95% CI) of 0.38 (0.25, 0.60), 0.79 (0.69, 0.91), and 0.74 (0.65, 0.85) in discovery, replication and joint analyses, respectively. While no association between the variant allele and stroke was observed among non-drinkers in the discovery stage [odds ratio (95% CI): 1.00 (0.82, 1.23)], the protective relation persisted among non-drinkers in the replication and joint analyses [odds ratios (95% confidence interval): 0.77 (0.71, 0.84) and 0.80 (0.74, 0.87), respectively]. This inconsistency may have resulted from disparate frequencies of former drinkers included in the non-drinking groups. No additional variants were identified. Conclusions: This large scale genomic study implicates increased alcohol intake as an etiologically relevant risk factor for ischemic stroke.

Analysis of ALDH1A1 and ALDH1A3 Gene mRNA Expressions in Adipose-Derived Stem Cells (ASCs) and Umbilical Cord Stem Cells (UCSCs)

BACKGROUND: ALDH1A1 and ALDH1A3, the most renowned isozymes of aldehyde dehydrogenase (ALDH)1, are important in regulating the pluripotency of human mesenchymal stem cells (MSCs) and cancer stem cells (CSCs). The study aimed to analyze the mRNA expression of ALDH1A1 and ALDH1A3 genes in adipose stem cells (ASCs) and umbilical cord stem cells (UCSCs) along with their correlations to Oct-4 mRNA expression. Additionally, the interaction between these proteins was also investigated using in silico study to confirm the pluripotency of both MSCs compared to human breast ALDH+ CSCs.METHODS: This research focused on determining mRNA levels of ALDH1A1, ALDH1A3 and Oct-4 in ASCs and UCSCs using one-step qRT-PCR. The data were then normalized to those in human breast CSCs and 18S rRNA. Oct-4 gene expression was also analyzed to determine the pluripotency of ASCs and UCSCs. The protein-protein interactions were in silico analyzed using String 9.1 software.RESULTS: Relatively, ALDH1A3 was expressed at similar level in ASCs and UCSCs, while ALDH1A1 expression level was significantly higher in ASCs compared to UCSCs. In contrast to ALDH1A3, the expressions of ALDH1A1 in both MSCs were significantly lower than breast CSCs similar to Oct-4 expressions, as also revealed by the in silico data showing the interaction between these proteins. This suggests the role of ALDH1A1 on pluripotency.CONCLUSION: ALDH1A1 and ALDH1A3 were distinctly expressed in UCSCs and ASCs, which might be associated with unique properties of ASCs and UCSCs. This study may contribute to further research in terms of implication of ALDH1A1 and ALDH1A3 expressions towards the properties of MSCs and its application in stem cell therapy.KEYWORDS: ALDH1A1, ALDH1A3, UCSC, ASC, breast ALDH+ CSC, Oct-4

A Novel Compound, \u201cFA-1\u201d Isolated from Prunus mume, Protects Human Bronchial Epithelial Cells and Keratinocytes from Cigarette Smoke Extract-Induced Damage

Extract of the Japanese apricot (JAE) has biological properties as an antioxidant and anti-inflammatory agent. We hypothesized that JAE might exert therapeutic effects on cigarette smoke (CS)-induced DNA damage and cytotoxicity. In this study, we found that concentrated JAE protects against cigarette smoke extract (CSE)-induced cytotoxicity and DNA damage accompanied by increased levels of aldehyde dehydrogenase (ALDH)2, 3A1, and Werner’s syndrome protein (WRN) in immortalized human bronchial epithelial cells (HBEC2) and normal human epidermal keratinocytes (NHEK). Using the centrifugal partition chromatography (CPC) method, we identified an undescribed compound, 5-hydroxymethyl-2-furaldehyde bis(5-formylfurfuryl) acetal (which we named FA-1), responsible for the protective effects against CSE. This chemical structure has not been reported from a natural source to date. Protective effects of isolated FA-1 against CSE were observed in both HBEC2 and NHEK cells. The studies described herein suggest that FA-1 isolated from JAE protects against CSE-induced DNA damage and apoptosis by augmenting multiple isozymes of ALDH and DNA repair and reducing oxidative stress.

Targeting USP22 Suppresses Tumorigenicity and Enhances Cisplatin Sensitivity Through ALDH1A3 Downregulation in Cancer-Initiating Cells from Lung Adenocarcinoma.

Loss of monoubiquitination of histone H2B (H2Bub1) was found to be associated with poor-differentiation and enhanced malignancy of lung adenocarcinoma. This study investigated the association and impact of the ubiquitin-specific peptidase 22 (USP22), an H2Bub1 deubiquitinase, on stem cell-like characteristics and cisplatin resistance in cancer-initiating cells (CIC) from primary lung adenocarcinoma. CICs were isolated, enriched, and characterized from patient-derived cancer tissues using both in vitro tumorsphere formation and in vivo xenograft assays. USP22 was determined to be predominantly expressed in CICs, a subpopulation of cells with high expression of the stem cell biomarkers, CD133 and CD44. The expression of USP22 in CICs is markedly reduced upon FBS/retinoic acid-induced differentiation. Moreover, knockdown of USP22 significantly suppressed tumorsphere formation and xenograft growth in NOD-SCID gamma (NSG) mice. Notably, USP22 and aldehyde dehydrogenase (ALDH) activity were elevated in tumorsphere cells that survived cisplatin treatment, whereas knockdown of USP22 significantly sensitizes tumorsphere cells to cisplatin. Interestingly, ALDH1A3, a predominant ALDH isozyme implicated in enhancing cisplatin resistance in lung adenocarcinoma, is significantly downregulated upon knockdown of USP22 in tumorsphere cells. Furthermore, knockdown of ALDH1A3 significantly sensitizes tumorsphere cells to cisplatin. Combined, these data demonstrate that USP22, predominantly expressed in CD133+ CICs, plays a critical role in tumorigenicity and cisplatin resistance in lung adenocarcinoma.Implications: Targeting USP22 represents a potential therapeutic approach to suppress CICs in lung adenocarcinoma partially through downregulation of ALDH1A3 expression. Mol Cancer Res; 16(7); 1161-71. ©2018 AACR.

Role of a membrane-bound aldehyde dehydrogenase complex AldFGH in acetic acid fermentation with Acetobacter pasteurianus SKU1108

Acetic acid fermentation is widely considered a consequence of ethanol oxidation by two membrane-bound enzymes-alcohol dehydrogenase and aldehyde dehydrogenase (ALDH)-of acetic acid bacteria. Here, we used a markerless gene disruption method to construct a mutant of the Acetobacter pasteurianus strain SKU1108 with a deletion in the aldH gene, which encodes the large catalytic subunit of a heterotrimeric ALDH complex (AldFGH), to examine the role of AldFGH in acetic acid fermentation. The ΔaldH strain grew less on ethanol-containing medium, i.e., acetic acid fermentation conditions, than the wild-type strain and significantly accumulated acetaldehyde in the culture medium. Unexpectedly, acetaldehyde oxidase activity levels of the intact ΔaldH cells and the ΔaldH cell membranes were similar to those of the wild-type strain, which might be attributed to an additional ALDH isozyme (AldSLC). The apparent KM values of the wild-type and ΔaldH membranes for acetaldehyde were similar to each other, when the cells were cultured in nonfermentation conditions, where ΔaldH cells grow as well as the wild-type cells. However, the membranes of the wild-type cells grown under fermentation conditions showed a 10-fold lower apparent KM value than those of the cells grown under nonfermentation conditions. Under fermentation conditions, transcriptional levels of a gene for AldSLC were 10-fold lower than those under nonfermentation conditions, whereas aldH transcript levels were not dramatically changed under the two conditions. We suggest that A. pasteurianus SKU1108 has two ALDHs, and the AldFGH complex is indispensable for acetic acid fermentation and is the major enzyme under fermentation conditions.

Importance of an Aldehyde Dehydrogenase 2 Polymorphism in Preventive Medicine

Unlike genetic alterations in other aldehyde dehydrogenase (ALDH) isozymes, a defective ALDH2 polymorphism (rs671), which is carried by almost half of East Asians, does not show a clear phenotype such as a shortened life span. However, impacts of a defective ALDH2 allele, ALDH2*2, on various disease risks have been reported. As ALDH2 is responsible for the detoxification of endogenous aldehydes, a negative effect of this polymorphism is predicted, but bidirectional effects have been actually observed and the mechanisms underlying such influences are often complex. One reason for this complexity may be the existence of compensatory aldehyde detoxification systems and the secondary effects of these systems. There are many issues to be addressed with regard to the ALDH2 polymorphism in the field of preventive medicine, including the following concerns. First, ALDH2 in the fetal stage plays a role in aldehyde detoxification; therefore, prenatal health effects of environmental aldehyde exposure are of concern for ALDH2*2-carrying fetuses. Second, ALDH2*2 carriers are at high risk of drinking-related cancers. However, their drinking habits result in less worsening of physiological findings, such as energy metabolism index and liver functions, compared with non-ALDH2*2 carriers, and therefore opportunities to detect excessive drinking can be lost. Third, personalized medicine such as personalized prescriptions for ALDH2*2 carriers will be required in the clinical setting, and accumulation of evidence is awaited. Lastly, since the ALDH2 polymorphism is not considered in workers' limits of exposure to aldehydes and their precursors, efforts to lower exposure levels beyond legal standards are required.

Aldehyde dehydrogenase 1B1: a novel immunohistological marker for colorectal cancer

Background:Aldehyde dehydrogenase (ALDH) 1A1 is an immunohistological biomarker of various solid tumours, but has not been successfully proved as a colorectal cancer (CRC) marker. We recently reported that ALDH1B1, which has functional roles in tumourigenesis, may be a better CRC marker than ALDH1A1.Methods:Human CRC explants and cell lines were analysed to identify candidate CRC markers from eight ALDH isozymes including ALDH1A1 and ALDH1B1. A tissue microarray, including paired specimens of normal and tumour tissues, was subsequently analysed to determine if candidate ALDHs could distinguish CRC from normal tissue.Results:Based on mRNA analysis, ALDH1B1 and ALDH2 were selected as suitable candidates. These were strongly and regularly expressed in tumour tissue and cell lines, including highly tumourigenic cell populations (ALDH+CD44+ cells), while other ALDHs, including ALDH1A1, showed differential or low expression. No genetic alteration of ALDH1B1 in CRC was suggested by the relationships between mRNA and protein levels/enzymatic activities, and cDNA sequences of CRC cell lines. Tissue microarray findings showed that ALDH1B1, but not ALDH2, could distinguish CRC from normal tissue. Furthermore, ratios of ALDH1B1 to ALDH1A1 or ALDH2 were found to be powerful CRC indicators.Conclusions:These results suggest that ALDH1B1 is a novel human CRC biomarker.

Aldehyde dehydrogenase 2*2 knock-in mice show increased reactive oxygen species production in response to cisplatin treatment

BackgroundThe aldehyde dehydrogenase (ALDH) enzyme family metabolizes and detoxifies both exogenous and endogenous aldehydes. Since chemotherapeutic agents, such as cisplatin, generate cytotoxic aldehydes and oxidative stress, and chemoresistant cancer cells express high levels of ALDH enzymes, we hypothesized that different ALDH expression within cells may show different chemosensitivity. ALDH2 has the lowest Km for acetaldehyde among ALDH isozymes and detoxifies acetaldehydes in addition to other reactive aldehydes, such as 4-hydroxy-nonenal, malondialdehyde and acrolein produced from lipid peroxidation by reactive oxygen species (ROS). Thus, cells with an ALDH2 variant may sensitize them to these ROS-inducing chemotherapy drugs.MethodsHere, we used wild type C57BL/6 mice and ALDH2*2 knock-in mutant mice and compared the basal level of ROS in different tissues. Then, we treated the mice with cisplatin, isolated cells from organs and fractionated them into lysates containing mitochondrial and cytosolic fractions, treated with cisplatin again in vitro, and compared the level of ROS generated.ResultsWe show that overall ROS production increases with cisplatin treatment in cells with ALDH2 mutation. The treatment of cisplatin in the wild type mice did not change the level of ROS compared to PBS treated controls. In contrast, ALDH2*2 knock-in mutant mice showed a significantly increased level of ROS compared to wild type mice in tongue, lung, kidney and brain tissues without any treatment. ALDH2*2 mutant mice showed 20% of the ALDH2 activity in the kidney compared to wild type mice. Treatment of ALDH2*2 mutant mice with cisplatin showed increased ROS levels in the mitochondrial fraction of kidney. In the cytosolic fraction, treatment of mutant mice with cisplatin increased ROS levels in lung and brain compared to PBS treated controls. Furthermore, ALDH2*2 mutant mice treated with cisplatin showed increased cytotoxicity in the kidney cells compared to PBS treated mutant controls.ConclusionsThese data indicate that deficiency in ALDH2 activity may contribute to increased cisplatin sensitivity and cytotoxicity by producing more ROS by the treatment. Based on these data, the amount of cisplatin used in patients may need to be adjusted based on their ALDH2 variant profile.

Aldehyde dehydrogenase activity plays no functional role in stem cell-like properties in anaplastic thyroid cancer cell lines.

Recent studies have revealed that aldehyde dehydrogenase (ALDH) is a candidate marker for thyroid cancer stem cells, although its activity is flexible. The goal of this study is to clarify the functional significance of ALDH enzymatic activity on thyroid cancer stem cells properties in anaplastic thyroid cancer cell lines. In vitro sphere formation assay was used to judge the stemness of 4 anaplastic thyroid cancer cell lines (FRO, ACT1, 8505C, and KTC3). Two well-known ALDH inhibitors, N,N-diethylaminobenzaldehyde (DEAB) and disulfiram (DS), were first used. DEAB (50 μM) almost completely suppressed ALDH activity without affecting cell proliferation or spherogenicity. Lack of effect of ALDH suppression on spherogenicity was confirmed using shRNA for ALDH1A3, an ALDH isozyme predominantly expressed in anaplastic thyroid cancer cell lines. In contrast, an ALDH2 inhibitor DS (1 μM) inhibited spherogenicity but did not inhibit ALDH1A3 activity. Based on the recent article from another group reporting the importance of sonic hedgehog (Shh) signaling in ALDH activity and spherogenicity in thyroid cancer, the effects of the Shh inhibitor cyclopamine were also studied. Like DS, cyclopamine (1 μM) decreased spherogenicity but not ALDH activity. Finally, exogenous expression of ALDH1A3 in otherwise ALDH- TPC1 cells (a papillary thyroid cancer cell line) revealed no effect on spherogenicity. In conclusion, we here show no functional role for ALDH activity in thyroid thyroid cancer stem cells properties. That is, ALDH activity and spherogenicity are clearly dissociable. Further understanding of thyroid cancer stem cells biology in thyroid cancers remains necessary for the future development of thyroid thyroid cancer stem cells-targeted therapies.