ALDH1A1 Research Articles

Ferroptosis- and stemness inhibition-mediated therapeutic potency of ferrous oxide nanoparticles-diethyldithiocarbamate using a co-spheroid 3D model of pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with a high mortality rate and exhibits a limited response to apoptosis-dependent chemotherapeutic drugs (e.g., gemcitabine, Gem). This is mainly attributed to the antioxidant defense system (glutathione and aldehyde dehydrogenase (ALDH) 1A1), which sustains stemness features of cancer stem cells (CSCs) and activated pancreatic stellate cells (PSCs)-generated excess stromal proteins. This dense stroma retards drug delivery. This study established co-spheroid model consisting of mouse PDAC cell line (KPC) and PSCs (1:5) to accurately investigate the anti-PDAC activity of nanocomplex of ferrous oxide nanoparticles-diethyldithiocarbamate (FeO NPs-DE), compared to Gem, using in vitro and in vivo 3D models. In vitro and in vivo co-spheroid models demonstrated higher therapeutic efficacy of FeO NPs-DE than Gem. FeO NPs-DE induced selective accumulation of iron-dependent ferroptosis (non-apoptosis)-generated a lethal lipid peroxidation that was potentiated by DE-mediated glutathione and ALDH1A1 suppression. This led to collapse of stemness, as evidenced by down-regulating CSC genes and p-AKT protein expression. Subsequently, gene and/or protein levels of PSC activators (transforming growth factor (TGF)-β, plasminogen activator inhibitor-1, ZEB1, and phosphorylated extracellular signal-regulated kinase) and stromal proteins (collagen 1A2, smooth muscle actin, fibronectin, and matrix metalloproteinase-9) were suppressed. Moreover, DE of nanocomplex enhanced caspase 3-dependent apoptosis with diminishing the main oncogene, BCL-2. FeO NPs-DE had a stronger eradicating effect than Gem on primary and metastatic peritoneal PDAC tumors. This nanocomplex-mediated ferroptosis and stemness inhibition provides an effective therapeutic approach for PDAC.

Combined loss of glyoxalase 1 and aldehyde dehydrogenase 3a1 amplifies dicarbonyl stress, impairs proteasome activity resulting in hyperglycemia and activated retinal angiogenesis.

Any energy consumption results in the generation of highly reactive dicarbonyls and the need to prevent excessive dicarbonyls accumulation through the activity of several interdependent detoxification enzymes. Glyoxalase 1 (GLO1) knockout zebrafish showed only moderately elevated methylglyoxal (MG) levels, but increased Aldehyde Dehydrogenases (ALDH) activity and increased aldh3a1 expression. Elevated levels of 4-hydroxynonenal (4-HNE) but no MG increase were observed in ALDH3A1KO. The question of whether ALDH3A1 prevents MG formation as a compensatory mechanism in the absence of GLO1 remained unclear. To investigate whether ALDH3A1 detoxifies MG as a compensatory mechanism in the absence of GLO1, the GLO1/ALDH3A1 double knockout (DKO) zebrafish was first generated. Various metabolites including advanced glycation end products (AGEs), as well as glucose metabolism and hyaloid vasculature were analyzed in GLO1KO, ALDH3A1KO and GLO1/ALDH3A1DKO zebrafish. In the absence of GLO1 and ALDH3A1, MG-H1 levels were increased. MG-H1 accumulation led to a severe deterioration of proteasome function, resulting in impaired glucose homeostasis and consequently amplified angiogenic activation of the hyaloid and retinal vasculature. Rescue of these pathological processes could be observed by using L-carnosine, and proteasome activator betulinic acid. The present data, together with previous studies, suggest that ALDH3A1 and GLO1 are important detoxification enzymes that prevent the deleterious effects of MG-H1 accumulation on proteasome function, glucose homeostasis and vascular function.

MMP2 regulates proliferation and differentiation in chicken primary myoblasts, and RNA-seq screens for key genes.

The growth and development of chicken skeletal muscle directly affects chicken meat production, which is very important for broiler industry. Matrix metallopeptidase 2 (MMP2) exists in skeletal muscle. However, the underlying regulating of MMP2 remain unknown. In this study, MMP2 promoted cell proliferation and inhibited cell differentiation after overexpression in chicken primary myoblasts cells (CPMs). When MMP2 was knocked down, it inhibited CPMs proliferation and promoted cell differentiation. Subsequently, RNA sequencing (RNA-seq) and bioinformatics analysis were performed on overexpressing MMP2. We identified 265 up-regulated genes and 229 down-regulated genes. Based on the fragments per kilobase million (FPKM) ≥ 10, the retained data were analyzed by Pearson correlation analysis. MMP2 was positively correlated with carboxypeptidase M (CPM), MSTRG.14120 and aldehyde dehydrogenase 1 family member A3 (ALDH1A3), and the correlation coefficient was the highest (0.998). MMP2 was negatively correlated with hes family bHLH transcription factor 1 (HES1), and the correlation coefficient was the highest (0.998). Go term was enriched in cellular components or biogenesis, cellular processes, and cell aggregation. KEGG was significantly enriched to the cancer pathway. qRT-PCR analysis validated the transcriptomic results of RNA-seq. In conclusion, these results provided new insights into the molecular mechanisms by which MMP2 affected the proliferation and differentiation of chicken myoblasts.

SIRT2 and ALDH1A1 as critical enzymes for astrocytic GABA production in Alzheimer’s disease

BackgroundAlzheimer’s Disease (AD) is a neurodegenerative disease with drastically altered astrocytic metabolism. Astrocytic GABA and H2O2 are associated with memory impairment in AD and synthesized through the Monoamine Oxidase B (MAOB)-mediated multi-step degradation of putrescine. However, the enzymes downstream to MAOB in this pathway remain unidentified.MethodsUsing transcriptomics analysis, we identified two candidate enzymes, Aldehyde Dehydrogenase 1 family member A1 (ALDH1A1) and Sirtuin 2 (SIRT2) for the steps following MAOB in the astrocytic GABA production pathway. We used immunostaining, metabolite analysis and electrophysiology, both in vitro and in vivo, to confirm the participation of these enzymes in astrocytic GABA production. We checked for the presence of SIRT2 in human AD patients as well as the mouse model APP/PS1 and finally, we selectively ablated SIRT2 in the astrocytes of APP/PS1 mice to observe its effects on pathology.ResultsImmunostaining, metabolite analysis, and electrophysiology recapitulated the participation of ALDH1A1 and SIRT2 in GABA production. Inhibition of SIRT2 reduced the production of astrocytic GABA but not H2O2, a key molecule in neurodegeneration. Elevated expression of these enzymes was found in hippocampal astrocytes of AD patients and APP/PS1 mice. Astrocyte-specific gene-silencing of SIRT2 in APP/PS1 mice restored GABA production and partially improved memory function.ConclusionsOur study is the first to identify the specific role of SIRT2 in reactive astrogliosis and determine the specific pathway and metabolic step catalyzed by the enzyme. We determine the partial, yet significant role of ALDH1A1 in this process, thereby highlighting 2 new players the astrocytic GABA production pathway. Our findings therefore, offer SIRT2 as a new tool to segregate GABA from H2O2 production, aiding future research in neurodegenerative diseases.Graphical

Antisense mediated blockade of Dickkopf 1 attenuates tumor survival, metastases and bone damage in experimental osteosarcoma

Osteosarcoma (OS) is the most common primary bone malignancy. The canonical Wnt inhibitor Dickkopf-1 (Dkk-1) has been implicated in bone destruction, tumor survival and metastases during OS. We examined the role of Dkk-1 in OS disease progression and explored strategies for targeting its activity. Dkk-1 enhances OS survival by amplifying a non-canonical Wnt pathway that upregulates aldehyde dehydrogenase 1A1. Targeting of Dkk-1 transcription with a vivo morpholino (DkkMo) reduced OS survival and enhanced osteogenic activity of OS in vitro. DkkMo as a single agent slowed tumor expansion, increased tumor necrosis, inhibited metastases and preserved bone in a PDX model of OS. DkkMo also reduced the frequency of dividing tumor cells and reinitiated a regenerative osteogenic phenotype in tumors and stroma while reducing infiltration of inflammatory cells. These findings indicate that DkkMo has the potential to safely target osteosarcoma growth, survival, metastases and bone destruction.

Expression of PAX6 and Keratocyte-Characteristic Markers in Human Limbal Stromal Cells of Congenital Aniridia and Healthy Subjects, In Vitro

Purpose Our aim was to examine the expression of PAX6 and keratocyte-specific markers in human limbal stromal cells (LSCs) in congenital aniridia (AN) and in healthy corneas, in vitro. Methods Primary human LSCs were extracted from individuals with aniridia (AN-LSCs) (n = 8) and from healthy corneas (LSCs) (n = 8). The cells were cultured in either normal-glucose serum-containing cell culture medium (NGSC-medium) or low-glucose serum-free cell culture medium (LGSF-medium). Analysis of PAX6 and keratocyte-specific markers was conducted using qPCR and Western blotting. The keratocyte-specific markers included Collagen I (COL1A1), Collagen III (COL3A1), Collagen V (COL5A1), α-smooth muscle actin (ACTA2), Aldehyde Dehydrogenase 3 Family, Member A1 (ALDH3A1), Keratocan (KER), Lumican (LUM), and CD34. Results PAX6 mRNA expression exhibited a significant decrease in AN-LSCs compared to LSCs in both NGSC- and LGSF-medium (p = 0.04; p = 0.014). There was a marked reduction in COL5A1 mRNA expression (p = 0.011), accompanied by notably higher ALDH3A1 and KER mRNA levels (p = 0.007; p = 0.013) in AN-LSCs compared to LSCs when using NGSC-medium. In LGSF-medium, AN-LSCs showed a significant increase in COL1A1 and COL5A1 mRNA expression compared to LSCs (p = 0.048; p = 0.002). Moreover, COL1A1 and α-SMA protein expression were significantly elevated in AN-LSCs compared to LSCs in LGSF-medium (p = 0.048, p = 0.008). Conclusions Our investigation affirms the altered expression of PAX6 and keratocyte-specific markers in AN-LSCs relative to healthy controls. Both NGSC- and LGSF-medium exerted distinct effects on both LSCs and AN-LSCs. The observed variations in PAX6 and keratocyte-specific marker expression in AN-LSCs may play a pivotal role in the development and progression of aniridia-associated keratopathy.

The influence of strain on human keratocyte redox homeostasis and behavior

Aims/Purpose: To study the influence of strain on the expression of specific proteins in human keratocytes and its consequential effects on keratocyte intracellular redox homeostasis and behavior.Methods: Strain was applied to human keratocytes using the Flexcell® Tension Systems. Proteomics and western blot were used to identify proteins regulated in response to strain. Immunofluorescence (IF) staining and live‐cell imaging were employed to monitor reactive oxygen species (ROS) production and mitochondrial membrane potential (ΔΨM). Expression of oxidative stress‐related protein, and its influence on nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) nuclear translocation and keratocyte proliferation and migration, were assessed by western blot, IF staining and bromodeoxyuridine (BrdU) assay. Mouse injury models and keratocytes from keratoconus patients were used to assess how strain (intraocular pressure, IOP) influences downstream protein in vivo.Results: The expression of protein Cytochrome P450 1B1 (CYP1B1) and Aldehyde Dehydrogenase 3 Family Member A1 (ALDH3A1) was significantly upregulated in strained keratocytes. Increased CYP1B1 effectively suppressed H2O2‐induced ROS production and mitigated the dissipation of ΔΨM. ALDH3A1 expression was negatively related to ROS accumulation. When the expression of ALDH3A1 was knocked down, NF‐κB nuclear translocation was promoted, ultimately resulting in increased keratocyte proliferation and migration. Mice and keratoconus patients with increased corneal strain also showed elevated ALDH3A1.Conclusions: Corneal strain significantly upregulates the expression of CYP1B1 and ALDH3A1. Increased CYP1B1 helps maintain keratocyte intracellular redox homeostasis and subsequently regulates keratocyte proliferation and migration via ALDH3A1.

Activity-Based Bioluminescent Logic-Gate Probe Reveals Crosstalk Between the Inflammatory Tumor Microenvironment and ALDH1A1 in Cancer Cells.

Cancer cells with high expression of aldehyde dehydrogenase 1A1 (ALDH1A1) are more resistant to chemotherapy, contribute to tumor progression, and are associated with poor clinical outcomes. ALDH1A1 plays a critical role in protecting cells from reactive aldehydes and, in the case of stem cells, regulates their differentiation through the retinoic acid signaling pathway. Despite the importance of this enzyme, methods to study ALDH1A1 high-expressing cancer cells in vivo remain limited. In this work, we developed AlDeLuc, the first logic-gated bioluminescence probe designed to selectively evaluate ALDH1A1 activity in tumor cells. The probe is sequentially activated by acidic intracellular compartments (i.e., endosomes) and ALDH1A1, ensuring precise detection of ALDH1A1 high-expressing cells and minimizing off-target detection of non-ALDH1A1 cells. Beyond demonstrating efficacy in multiple cancer cell lines and a murine model of breast cancer, we employed AlDeLuc to investigate how the population of ALDH1A1 high-expressing cells is influenced by the inflammatory status of a tumor in the context of a high-fat diet. These findings establish a molecular link between obesity, inflammation, and tumor progression.

Effect of overexpression of aldehyde dehydrogenase family member A2 on hypertrophic growth and proliferation of cardiomyocytes

Retinoic acid signaling pathway plays a role in regulating vertebrate development, cell differentiation, and homeostasis. As a key enzyme that catalyzes the oxidation of retinal to retinoic acid, aldehyde dehydrogenase 1 family member A2 (Aldh1a2) is involved in cardiac development, while whether it functions in heart diseases remains to be studied. In this study, we infected primary cardiomyocytes with adenovirus overexpressing Aldh1a2 (Ad-Aldh1a2) to explore the effects of Aldh1a2 overexpression on the biological function of cardiomyocytes. The results showed that the infection with Ad-Aldh1a2 realized the overexpression of Aldh1a2 in cardiomyocytes. Compared with the control group infected with Ad-GFP, the cardiomyocytes infected with Ad-Aldh1a2 showcased significantly increased size and up-regulated expression levels of the atrial natriuretic factor gene (ANF), brain natriuretic peptide gene (BNP), and β-myosin heavy chain (β-MHC). In addition, 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay demonstrated that Aldh1a2 overexpression increased the proportion of cardiomyocytes with positive EdU signals and upregulated the expression levels of proliferation-related genes cyclin D2 (Ccnd2) and budding uninhibited by benzimidazole 1 (Bub1). The above data indicated that overexpression of Aldh1a2 induced hypertrophic growth and proliferation of cardiomyocytes. This study provides a basis for further understanding the function of Aldh1a2 in heart diseases and developing therapies for heart diseases.

Corneal strain influences keratocyte proliferation and migration through upregulation of ALDH3A1 expression.

Keratocytes are the primary resident cells in the corneal stroma. They play an essential role in maintaining corneal physiological function. Studying the factors that affect the phenotype and behavior of keratocytes offers meaningful perspectives for improving the understanding and treatment of corneal injuries. In this study, 3% strain was applied to human keratocytes using the Flexcell® Tension Systems. Real-time quantitative PCR (RT-qPCR) and western blot were used to investigate the influence of strain on the expression of intracellular aldehyde dehydrogenase 3A1 (ALDH3A1). ALDH3A1 knockdown was achieved using double-stranded RNA-mediated interference (RNAi). Immunofluorescence (IF) staining was employed to observe the impact of changes in ALDH3A1 expression on nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) nuclear translocation. Keratocyte proliferation and migration were assessed by bromodeoxyuridine (BrdU) assay and scratch wound healing assay, respectively. Mouse injury models and single-cell RNA sequencing of keratocytes from keratoconus patients were used to assess how strain influenced ALDH3A1 invivo. Our results demonstrate that 3% strain suppresses keratocyte proliferation and increases ALDH3A1. Increased ALDH3A1 inhibits NF-κB nuclear translocation, a key step in the activation of the NF-κB signaling pathway. Conversely, ALDH3A1 knockdown promotes NF-κB nuclear translocation, ultimately enhancing keratocyte proliferation and migration. Elevated ALDH3A1 levels were also observed in mouse injury models with increased corneal strain and keratoconus patients. These findings provide valuable insights for further research into the role of corneal strain and its connection to corneal injury repair.

Accumulation of ether phospholipids in induced pluripotent stem cells and oligodendrocyte-lineage cells established from patients with Sjögren-Larsson syndrome.

Sjögren-Larsson syndrome (SLS) is an autosomal recessive leukodystrophy characterized by ichthyosis, intellectual disability, and progressive spastic paralysis caused by biallelic pathogenic variants in the ALDH3A2 gene that encodes the fatty aldehyde dehydrogenase, fatty aldehyde dehydrogenase (FALDH); FALDH catalyzes several metabolic reactions involved in fatty aldehyde oxidation. Only a few studies have been performed to determine the lipid profile of patients with SLS. In a previous postmortem study of the brain of a 65-year-old patient with SLS, lipidomic analysis revealed an accumulation of long-chain unsaturated ether lipid species in the white matter and gray matter. In the present study, we established a disease model using patient-derived neuronal and oligodendrocyte lineage cells to analyze the lipid metabolism and gene expression profiles in SLS. To achieve this, we generated induced pluripotent stem cells (iPSCs) from two patients with the SLS phenotype carrying previously known ALDH3A2 pathogenic variants: One was a compound heterozygote (c.1339A>G:p.(Lys447Glu) and c.57_132dup:p.(Ile45Serfs*34)) and the other was a homozygote (c.1339A>G: p.(Lys447Glu)). The FALDH activity was almost zero in the SLS-iPSC lines established from both patients. Phospholipid analysis of neurospheres, and oligospheres (spheres enriched with oligodendrocyte-lineage cells) derived from the iPSCs by liquid chromatography-mass spectrometry showed accumulation of ether phospholipids in the Sjögren-Larsson patient-derived neurospheres and oligospheres. The results are consistent with the previously reported accumulation of ether lipids in the postmortem brain tissue of an SLS patient. Therefore, iPSCs and iPSC-derived neurospheres and oligospheres established from SLS patients can be useful tools for future pathological analysis of the central nervous system pathophysiology in SLS.

Embryoid body-based differentiation of human-induced pluripotent stem cells into cells with a corneal stromal keratocyte phenotype

ObjectiveThe transparency of the cornea is determined by the extracellular matrix, which is secreted by corneal stromal keratocytes (CSKs). Human-induced pluripotent stem cell (hiPSC)-derived keratocytes (hiPSC-CSKs) can be used in...

Relationship between moderate alcohol consumption, genetic polymorphisms and body weight in a population sample of Puerto Madryn, Argentina

Introduction. The relationship between obesity and alcohol consumption is a topic of significant interest to public health. Alcoholic beverages contribute additional calories to the diet, which could be a relevant factor to the overweight risk. However, its association with weight gain is controversial and influenced by multiple factors. Objective. To analyze the relationship between moderate alcohol intake and body mass index, considering the variables that may influence this relationship. Materials and methods. The sample consisted of 155 individuals from Puerto Madryn (Argentina). Each participant completed a questionnaire about health, lifestyle, demographic, and socioeconomic factors. Anthropometric measurements were taken, and polymorphisms of 18 genes related to alcohol metabolism were genotyped. Results. We found that moderate alcohol consumption is associated with a lower body mass index, particularly in females. An increase of 14 grams of alcohol was associated with a risk of 0.68 for obesity and 0.71 for overweight. The T variant of the marker rs4646543 (ALDH1A1), a gene involved in alcohol metabolism and adipogenesis, was associated with a higher frequency of alcohol consumption. Conclusion. The findings of this study suggest that moderate alcohol consumption does not significantly contribute to body weight in the sample studied. Furthermore, the association with genetic variants, such as those of the ALDH1A1 gene, may provide a biological explanation for the inverse relationship observed between weight and alcohol consumption.

Investigating the biology of microRNA links to ALDH1A1 reveals candidates for preclinical testing in acute myeloid leukemia.

Aldehyde dehydrogenase 1 family member A1 (ALDH1A1) is a member of the aldehyde dehydrogenase gene subfamily that encode enzymes with the ability to oxidize retinaldehyde. It was recently shown that high ALDH1A1 RNA abundance correlates with a poor prognosis in acute myeloid leukemia (AML). AML is a hematopoietic malignancy associated with high morbidity and mortality rates. Although there are a number of agents that inhibit ALDH activity, it would be crucial to develop methodologies for adjustable genetic interference, which would permit interventions on several oncogenic pathways in parallel. Intervention in multiple oncogenic pathways is theoretically possible with microRNAs (miRNAs or miRs), a class of small non‑coding RNAs that have emerged as key regulators of gene expression in AML. A number of miRNAs have shown the ability to interfere with ALDH1A1 gene expression directly in solid tumor cells, and these miRNAs can be evaluated in AML model systems. There are indications that a few of these miRNAs actually do have an association with AML disease course, rendering them a promising target for genetic intervention in AML cells.

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.

Construction of a lung cancer 3D culture model based on alginate/gelatin micro-beads for drug evaluation.

Lung cancer is one of the most common malignant tumors worldwide. Despite advances in lung cancer treatment, patients still face challenges related to drug resistance and recurrence. Current methods for evaluating anti-cancer drug activity are insufficient, as they rely on two-dimensional (2D) cell culture and animal models. Therefore, the development of an in vitro drug evaluation model capable of predicting individual sensitivity to anti-cancer drugs would greatly enhance the success rate of drug treatments for lung cancer patients. The purpose of this research is to utilise conditional reprogramming technology to cultivate patient-derived lung cancer cells and to construct an in vitro 3D culture model using sodium alginate (SA) and gelatin. The aim is to study the biological characteristics of cells in the 3D culture model and to further investigate the sensitivity of anti-cancer drugs based on the alginate-gelatin 3D culture model. This approach provides new means and insights for personalized precision anti-cancer therapy and the development of new anti-cancer drugs. Conditional reprogramming technology was used to generate conditionally reprogrammed lung adenocarcinoma cells (CRLCs). Alginate-gelatin hydrogel micro-beads were created to explore their potential use in the assessment of anti-cancer drugs. Cell proliferation was also examined using the MTS assay method. Live/dead staining was performed to estimate cell distribution and viability using calcein acetoxymethyl ester/propidium iodide (calcein-AM/PI) double staining. Protein expression was assessed by Western blot. The cells grown in the three-dimensional (3D) culture were in a state of continuous proliferation, and there was an obvious phenomenon of cell mass growth. The drug sensitivity assay results demonstrated that compared with the 2D-grown cells, the CRLCs grown in the alginate-gelatin hydrogel micro-beads exhibited more resistance to anti-cancer drugs. The results also showed that the 3D-cultured CRLCs showed greater protein expression levels of stem cell hallmarks, such as Nanog Homeobox (NANOG), SRY-Box Transcription Factor 2 (SOX-2), and aldehyde dehydrogenase 1 family member A1 (ALDH1A1), than the 2D-grown cells. These findings suggest that the 3D hydrogel cell culture models more closely mimicked the in vivo biological and clinical behavior of cells, and demonstrated higher innate resistance to anti-cancer drugs than the 2D cell culture models, and thus could serve as valuable tools for diagnosis, drug screening, and personalized medicine.

Targeting ALDH1A1 to enhance the efficacy of KRAS-targeted therapy through ferroptosis

KRAS is among the most commonly mutated oncogenes in human malignancies. Although the advent of sotorasib and adagrasib, has lifted the “undruggable” stigma of KRAS, the resistance to KRAS inhibitors quickly becomes a major issue. Here, we reported that aldehyde dehydrogenase 1 family member A1 (ALDH1A1), an enzyme in retinoic acid biosynthesis and redox balance, increases in response to KRAS inhibitors and confers resistance in a range of cancer types. KRAS inhibitors' efficacy is significantly improved in sensitive or drug-resistant cells, patient-derived organoids (PDO), and xenograft models by ALDH1A1 knockout, loss of enzyme function, or inhibitor. Furthermore, we discovered that ALDH1A1 suppresses the efficacy of KRAS inhibitors by counteracting ferroptosis. ALDH1A1 detoxicates deleterious aldehydes, boosts the synthesis of NADH and retinoic acid (RA), and improves RARA function. ALDH1A1 also activates the CREB1/GPX4 pathway, stimulates the production of lipid droplets in a pH-dependent manner, and subsequently prevents ferroptosis induced by KRAS inhibitors. Meanwhile, we established that GTF2I is dephosphorylated at S784 via ERK by KRAS inhibitors, which hinders its nuclear translocation and mediates ALDH1A1's upregulation in response to KRAS inhibitors. In summary, the results offer valuable insights into targeting ALDH1A1 to enhance the effectiveness of KRAS-targeted therapy through ferroptosis in cancer treatment.

ALDH1A3 is the switch that determines the balance of ALDH+ and CD24−CD44+ cancer stem cells, EMT-MET, and glucose metabolism in breast cancer

Plasticity is an inherent feature of cancer stem cells (CSCs) and regulates the balance of key processes required at different stages of breast cancer progression, including epithelial-to-mesenchymal transition (EMT) versus mesenchymal-to-epithelial transition (MET), and glycolysis versus oxidative phosphorylation. Understanding the key factors that regulate the switch between these processes could lead to novel therapeutic strategies that limit tumor progression. We found that aldehyde dehydrogenase 1A3 (ALDH1A3) regulates these cancer-promoting processes and the abundance of the two distinct breast CSC populations defined by high ALDH activity and CD24−CD44+ cell surface expression. While ALDH1A3 increases ALDH+ breast cancer cells, it inversely suppresses the CD24−CD44+ population by retinoic acid signaling-mediated gene expression changes. This switch in CSC populations induced by ALDH1A3 was paired with decreased migration but increased invasion and an intermediate EMT phenotype. We also demonstrate that ALDH1A3 increases oxidative phosphorylation and decreases glycolysis and reactive oxygen species (ROS). The effects of ALDH1A3 reduction were countered with the glycolysis inhibitor 2-deoxy-D-glucose (2DG). In cell culture and tumor xenograft models, 2DG suppresses the increase in the CD24−CD44+ population and ROS induced by ALDH1A3 knockdown. Combined inhibition of ALDH1A3 and glycolysis best reduces breast tumor growth and tumor-initiating cells, suggesting that the combination of targeting ALDH1A3 and glycolysis has therapeutic potential for limiting CSCs and tumor progression. Together, these findings identify ALDH1A3 as a key regulator of processes required for breast cancer progression and depletion of ALDH1A3 makes breast cancer cells more susceptible to glycolysis inhibition.

Dynamic upregulation of retinoic acid signal in the early postnatal murine heart promotes cardiomyocyte cell cycle exit and maturation

The adult mammalian heart has extremely limited cardiac regenerative capacity. Most cardiomyocytes live in a state of permanent cell-cycle arrest and are unable to re-enter the cycle. Cardiomyocytes switch from cell proliferation to a maturation state during neonatal development. Although several signaling pathways are involved in this transition, the molecular mechanisms by which these inputs coordinately regulate cardiomyocyte maturation are not fully understood. Retinoic acid (RA) plays a pivotal role in development, morphogenesis, and regeneration. Despite the importance of RA signaling in embryo heart development, little is known about its function in the early postnatal period. We found that mRNA expression of aldehyde dehydrogenase 1 family member A2 (Aldh1a2), which encodes the key enzyme for synthesizing all-trans retinoic acid (ATRA) and is an important regulator for RA signaling, was transiently upregulated in neonatal mouse ventricles. Single-cell transcriptome analysis and immunohistochemistry revealed that Aldh1a2 expression was enriched in cardiac fibroblasts during the early postnatal period. Administration of ATRA inhibited cardiomyocyte proliferation in cultured neonatal rat cardiomyocytes and human cardiomyocytes. RNA-seq analysis indicated that cell proliferation-related genes were downregulated in prenatal rat ventricular cardiomyocytes treated with ATRA, while cardiomyocyte maturation-related genes were upregulated. These findings suggest that RA signaling derived from cardiac fibroblasts is one of the key regulators of cardiomyocyte proliferation and maturation during neonatal heart development.

Quercetin Attenuates Acetaldehyde-Induced Cytotoxicity via the Heme Oxygenase-1-Dependent Antioxidant Mechanism in Hepatocytes.

It is still unclear whether or how quercetin influences the toxic events induced by acetaldehyde in hepatocytes, though quercetin has been reported to mitigate alcohol-induced mouse liver injury. In this study, we evaluated the modulating effect of quercetin on the cytotoxicity induced by acetaldehyde in mouse hepatoma Hepa1c1c7 cells, the frequently used cellular hepatocyte model. The pretreatment with quercetin significantly inhibited the cytotoxicity induced by acetaldehyde. The treatment with quercetin itself had an ability to enhance the total ALDH activity, as well as the ALDH1A1 and ALDH3A1 gene expressions. The acetaldehyde treatment significantly enhanced the intracellular reactive oxygen species (ROS) level, whereas the quercetin pretreatment dose-dependently inhibited it. Accordingly, the treatment with quercetin itself significantly up-regulated the representative intracellular antioxidant-related gene expressions, including heme oxygenase-1 (HO-1), glutamate-cysteine ligase, catalytic subunit (GCLC), and cystine/glutamate exchanger (xCT), that coincided with the enhancement of the total intracellular glutathione (GSH) level. Tin protoporphyrin IX (SNPP), a typical HO-1 inhibitor, restored the quercetin-induced reduction in the intracellular ROS level, whereas buthionine sulphoximine, a representative GSH biosynthesis inhibitor, did not. SNPP also cancelled the quercetin-induced cytoprotection against acetaldehyde. These results suggest that the low-molecular-weight antioxidants produced by the HO-1 enzymatic reaction are mainly attributable to quercetin-induced cytoprotection.