Formaldehyde regulates S-adenosylmethionine biosynthesis and one-carbon metabolism

Aldehydes alter TGF-β signaling and induce obesity and cancer

Obesity and fatty liver diseases-metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH)-affect over one-third of the global population and are exacerbated in individuals with reduced functional aldehyde dehydrogenase 2 (ALDH2), observed in approximately 560 million people. Current treatment to prevent disease progression to cancer remains inadequate, requiring innovative approaches. We observe that Aldh2-/- and Aldh2-/-Sptbn1+/- mice develop phenotypes of human metabolic syndrome (MetS) and MASH with accumulation of endogenous aldehydes such as 4-hydroxynonenal (4-HNE). Mechanistic studies demonstrate aberrant transforming growth factor β (TGF-β) signaling through 4-HNE modification of the SMAD3 adaptor SPTBN1 (β2-spectrin) to pro-fibrotic and pro-oncogenic phenotypes, which is restored to normal SMAD3 signaling by targeting SPTBN1 with small interfering RNA (siRNA). Significantly, therapeutic inhibition of SPTBN1 blocks MASH and fibrosis in a human model and, additionally, improves glucose handling in Aldh2-/- and Aldh2-/-Sptbn1+/- mice. This study identifies SPTBN1 as a critical regulator of the functional phenotype of toxic aldehyde-induced MASH and a potential therapeutic target.

Fluorescent probes for formaldehyde based on formaldehyde-promoted C-N cleavage of azanyl carbamates

Formaldehyde (FA) is an endogenous one-carbon metabolite and an environmental pollutant and carcinogen. Elevated FA levels are associated with many diseases. Methods for the convenient and in situ detection of FA levels are of great significance for understanding FA's biofunctions and signalling pathways. Herein, the NAP-FAP2 series of fluorescent probes for FA detection were developed based on FA-promoted C-N cleavage of 3-nitrophenylazanyl N-arylcarbamate via FA-induced intramolecularity, where the aryl group is the fluorophore 1,8-naphthalimide-4-yl. The 3-nitrophenylazanyl containing reactive group also functions as a fluorescence quenching group via a photo-induced electron transfer mechanism to generate turn-on fluorescence response upon reaction with FA. The probes were applied to explore FA level changes in erastin-induced ferroptosis, and it was found that the FA level increases intracellularly, but not in the endoplasmic reticulum, suggesting that the FA level increases in ferroptosis are not derived from lipid peroxidation.

Formaldehyde quantification using gas chromatography-mass spectrometry reveals high background environmental formaldehyde levels

Formaldehyde (HCHO) is a human toxin that is both a pollutant and endogenous metabolite. HCHO concentrations in human biological samples are reported in the micromolar range; however, accurate quantification is compromised by a paucity of sensitive analysis methods. To address this issue, we previously reported a novel SPME-GC-MS-based HCHO detection method using cysteamine as an HCHO scavenger. This method showed cysteamine to be a more efficient scavenger than the widely used O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine, and enabled detection of aqueous HCHO in the nanomolar range and quantification in the micromolar range. However, quantification in this range required immersive extraction of the HCHO-derived thiazolidine, while a high background signal was also observed. Following on from these studies, we now report an optimised head-space extraction SPME-GC-MS method using cysteamine, which provides similarly sensitive HCHO quantification to the immersive method but avoids extensive wash steps and is therefore more amenable to screening applications. However, high background HCHO levels were still observed A Complementary GC-MS analyses using a 2-aza-Cope-based HCHO scavenger also revealed high background HCHO levels; therefore, the combined results suggest that HCHO exists in high (i.e. micromolar) concentration in aqueous samples that precludes accurate quantification below the micromolar range. This observation has important implications for ongoing HCHO quantification studies in water, including in biological samples.

Organelle-resolved imaging of formaldehyde reveals its spatiotemporal dynamics

Understanding the spatiotemporal dynamics of formaldehyde (FA) is crucial for elucidating its pathophysiology. In this study, we designed a series of organelle-resolved probes to investigate FA dynamics. By incorporating various organelle anchors into a coumarin hydrazonate, we developed a series of probes with excellent organelle selectivity and FA specificity, enabling rapid and precise sensing of FA in an organelle-resolved way. Leveraging these probes, we captured the spatiotemporal dynamics of native FA in response to exogenous FA or oxidative stress challenges. In particular, we unveiled the distinct responses of various organelles to identical cellular stressors. Moreover, we observed the dynamic response within individual organelles when cells were exposed to stressors for varying durations. We envision these probes will serve as versatile tools for probing FA pathophysiology.

Regulatory mechanisms of amino acids in ferroptosis

Ferroptosis, an iron-dependent non-apoptotic regulated cell death process, is associated with the pathogenesis of various diseases. Amino acids, which are indispensable substrates of vital activities, significantly regulate ferroptosis. Amino acid metabolism is involved in maintaining iron and lipid homeostasis and redox balance. The regulatory effects of amino acids on ferroptosis are complex. An amino acid may exert contrasting effects on ferroptosis depending on the context. This review systematically and comprehensively summarized the distinct roles of amino acids in regulating ferroptosis and highlighted the emerging opportunities to develop clinical therapeutic strategies targeting amino acid-mediated ferroptosis.

Distinct DNA repair mechanisms prevent formaldehyde toxicity during development, reproduction and aging

Formaldehyde (FA) is a recognized environmental and metabolic toxin implicated in cancer development and aging. Inherited mutations in the FA-detoxifying enzymes ADH5 and ALDH2 genes lead to FA overload in the severe multisystem AMeD syndrome. FA accumulation causes genome damage including DNA-protein-, inter- and intra-strand crosslinks and oxidative lesions. However, the influence of distinct DNA repair systems on organismal FA resistance remains elusive. We have here investigated the consequence of a range of DNA repair mutants in a model of endogenous FA overload generated by downregulating the orthologs of human ADH5 and ALDH2 in C. elegans. We have focused on the distinct components of nucleotide excision repair (NER) during developmental growth, reproduction and aging. Our results reveal three distinct modes of repair of FA-induced DNA damage: Transcription-coupled repair (TCR) operating NER-independently during developmental growth or through NER during adulthood, and, in concert with global-genome (GG-) NER, in the germline and early embryonic development. Additionally, we show that the Cockayne syndrome B (CSB) factor is involved in the resolution of FA-induced DNA-protein crosslinks, and that the antioxidant and FA quencher N-acetyl-l-cysteine (NAC) reverses the sensitivity of detoxification and DNA repair defects during development, suggesting a therapeutic intervention to revert FA-pathogenic consequences.

Flavin-containing monooxygenase (FMO): Beyond xenobiotics

Flavin-containing monooxygenases (FMOs), traditionally known for detoxifying xenobiotics, are now recognized for their involvement in endogenous metabolism. We recently discovered that an isoform of FMO, fmo-2 in Caenorhabditis elegans, alters endogenous metabolism to impact longevity and stress tolerance. Increased expression of fmo-2 in C. elegans modifies the flux through the key pathway known as One Carbon Metabolism (OCM). This modified flux results in a decrease in the ratio of S-adenosyl-methionine (SAM) to S-adenosyl-homocysteine (SAH), consequently diminishing methylation capacity. Here we discuss how FMO-2-mediated formate production during tryptophan metabolism may serve as a trigger for changing the flux in OCM. We suggest formate bridges tryptophan and OCM, altering metabolic flux away from methylation during fmo-2 overexpression. Additionally, we highlight how these metabolic results intersect with the mTOR and AMPK pathways, in addition to mitochondrial metabolism. In conclusion, the goal of this essay is to bring attention to the central role of FMO enzymes but lack of understanding of their mechanisms. We justify a call for a deeper understanding of FMO enzyme's role in metabolic rewiring through tryptophan/formate or other yet unidentified substrates. Additionally, we emphasize the identification of novel drugs and microbes to induce FMO activity and extend lifespan.

A mitochondrial-targeted activity-based sensing probe for ratiometric imaging of formaldehyde reveals key regulators of the mitochondrial one-carbon pool

Formaldehyde (FA) is both a highly reactive environmental genotoxin and an endogenously produced metabolite that functions as a signaling molecule and one-carbon (1C) store to regulate 1C metabolism and epigenetics in the cell. Owing to its signal-stress duality, cells have evolved multiple clearance mechanisms to maintain FA homeostasis, acting to avoid the established genotoxicity of FA while also redirecting FA-derived carbon units into the biosynthesis of essential nucleobases and amino acids. The highly compartmentalized nature of FA exposure, production, and regulation motivates the development of chemical tools that enable monitoring of transient FA fluxes with subcellular resolution. Here we report a mitochondrial-targeted, activity-based sensing probe for ratiometric FA detection, MitoRFAP-2, and apply this reagent to monitor endogenous mitochondrial sources and sinks of this 1C unit. We establish the utility of subcellular localization by showing that MitoRFAP-2 is sensitive enough to detect changes in mitochondrial FA pools with genetic and pharmacological modulation of enzymes involved in 1C and amino acid metabolism, including the pervasive, less active genetic mutant aldehyde dehydrogenase 2*2 (ALDH2*2), where previous, non-targeted versions of FA sensors are not. Finally, we used MitoRFAP-2 to comparatively profile basal levels of FA across a panel of breast cancer cell lines, finding that FA-dependent fluorescence correlates with expression levels of enzymes involved in 1C metabolism. By showcasing the ability of MitoRFAP-2 to identify new information on mitochondrial FA homeostasis, this work provides a starting point for the design of a broader range of chemical probes for detecting physiologically important aldehydes with subcellular resolution and a useful reagent for further studies of 1C biology.

Two-Photon Nanoparticle Probe for Formaldehyde Detection via the AILE Luminescence Mechanism

A two-photon nanoparticle probe was designed and developed based on the principle of intermolecular interaction of the aggregation-induced locally excited emission luminescence mechanism. The probe has the advantages of simple synthesis, convenient use, strong atomic economy, good biocompatibility, and photobleaching resistance. It can produce a specific and sensitive response to formaldehyde, help detect FA in normal cells and cancer cells, and is expected to become a specific detection probe for FA in vitro and in vivo.

Formaldehyde regulates one-carbon metabolism and epigenetics

Recently, Pham et al. used an array of model systems to uncover a role for the enzyme methionine adenosyltransferase (MAT)-1A, which is mainly expressed in liver, in both sensing formaldehyde and regulating transcriptional responses that protect against it. This provides a new lens for understanding the effects of formaldehyde on gene regulation.

The impact of formaldehyde exposure on lung inflammatory disorders: Insights into asthma, bronchitis, and pulmonary fibrosis

Lung inflammatory disorders are a major global health burden, impacting millions of people and raising rates of morbidity and death across many demographic groups. An industrial chemical and common environmental contaminant, formaldehyde (FA) presents serious health concerns to the respiratory system, including the onset and aggravation of lung inflammatory disorders. Epidemiological studies have shown significant associations between FA exposure levels and the incidence and severity of several respiratory diseases. FA causes inflammation in the respiratory tract via immunological activation, oxidative stress, and airway remodelling, aggravating pre-existing pulmonary inflammation and compromising lung function. Additionally, FA functions as a respiratory sensitizer, causing allergic responses and hypersensitivity pneumonitis in sensitive people. Understanding the complicated processes behind formaldehyde-induced lung inflammation is critical for directing targeted strategies aimed at minimizing environmental exposures and alleviating the burden of formaldehyde-related lung illnesses on global respiratory health. This abstract explores the intricate relationship between FA exposure and lung inflammatory diseases, including asthma, bronchitis, allergic inflammation, lung injury and pulmonary fibrosis.

One Carbon to Rule Them All: Formaldehyde is a One-Carbon Signal Connecting One-Carbon Metabolism and Epigenetic Methylation

Formaldehyde is commonly thought of as an environmental toxin or laboratory fixation reagent, but there is a growing appreciation for its broader physiological contributions as a naturally generated one-carbon metabolite across all kingdoms of life. In this In Focus article, we summarize emerging advances in the field that show how formaldehyde plays diverse roles as a one-carbon signal in DNA damage, one-carbon metabolism, and epigenetic regulation.

Aβ-binding with alcohol dehydrogenase drives Alzheimer's disease pathogenesis: A review

Although Alzheimer's disease (AD) characterized with senile plaques and neurofibrillary tangles has been found for over 100 years, its molecular mechanisms are ambiguous. More worsely, the developed medicines targeting amyloid-beta (Aβ) and/or tau hyperphosphorylation did not approach the clinical expectations in patients with moderate or severe AD until now. This review unveils the role of a vicious cycle between Aβ-derived formaldehyde (FA) and FA-induced Aβ aggregation in the onset course of AD. Document evidence has shown that Aβ can bind with alcohol dehydrogenase (ADH) to form the complex of Aβ/ADH (ABAD) and result in the generation of reactive oxygen species (ROS) and aldehydes including malondialdehyde, hydroxynonenal and FA; in turn, ROS-derived H2O2 and FA promotes Aβ self-aggregation; subsequently, this vicious cycle accelerates neuron death and AD occurrence. Especially, FA can directly induce neuron death by stimulating ROS generation and tau hyper hyperphosphorylation, and impair memory by inhibiting NMDA-receptor. Recently, some new therapeutical methods including inhibition of ABAD activity by small molecules/synthetic polypeptides, degradation of FA by phototherapy or FA scavengers, have been developed and achieved positive effects in AD transgenic models. Thus, breaking the vicious loop may be promising interventions for halting AD progression.

Exquisite exposure: Formaldehyde as a metabolic regulator

Throughout life, whether through external consumption or internal production, we are exposed to different reactive metabolites considered toxic to the body. Pham et al.1 uncover metabolic regulation by one such harmful metabolite: formaldehyde.