Perspectives on formaldehyde dysregulation: Mitochondrial DNA damage and repair in mammalian cells

Bimetallic Au and Pd Nanoparticles Modified WO3 Nanosheets for Enhancing the Sensitivity and Selectivity of Formaldehyde Assessment in Aquatic Products

Formaldehyde, a common illegal additive in aquatic products, poses a threat to people's health and lives. In this study, a novel metal oxide semiconductor gas sensor based on AuPd-modified WO3 nanosheets (NSs) had been developed for the highly efficient detection of formaldehyde. WO3 NS modified with 2.0% AuPd nanoparticles showed a higher response (Ra/Rg = 94.2) to 50 ppm of formaldehyde at 210 °C, which was 36 times more than the pristine WO3 NS. In addition, the AuPd/WO3 gas sensor had a relatively short response/recovery time of 10 s/9 s for 50 ppm of formaldehyde at 210 °C, with good immunity to other interfering gases and good stability for formaldehyde. The excellent gas-sensitive performance was attributed to the chemical sensitization of Au, the electronic sensitization of Pd, and the synergistic effect of bimetallic AuPd, which facilitated the recognition and response of formaldehyde molecules. Additionally, the high sensitivity and broad application prospect of the 2.0% AuPd/WO3 NS composite-based sensor in real sample detection were also confirmed by using the above sensor for the detection of formaldehyde in aquatic products such as squid and shrimp.

Atypical K6-ubiquitin chains mobilize p97/VCP and the proteasome to resolve formaldehyde-induced RNA-protein crosslinks

In this issue of Molecular Cell, Rahmanto et al.1 and Zhao et al.2 demonstrate that RNA-protein crosslinks contribute to formaldehyde toxicity by blocking protein synthesis. Furthermore, they identify a ubiquitin-mediated degradation system for RNA-protein crosslink resolution in eukaryotes.

Silencing of peroxiredoxin III inhibits formaldehyde-induced oxidative damage of bone marrow cells in BALB/c mice

BACKGROUND

Formaldehyde (FA) is associated with the occurrence of leukemia, and oxidative stress is considered to be a major reason. As an endogenous biomarker of oxidative stress, few studies focus on the relationship between peroxiredoxin III (PrxIII) and FA toxicity. Our previous research observed high expression of PrxIII occurred in the process of apoptosis of bone marrow cells (BMCs) induced by FA, however the exact mechanism is unclear. Therefore, this paper aimed to explore the possible association between FA toxicity and PrxIII gene.

METHODS

We first, used a Cell Counting Kit-8 (CCK-8) to detect the viability of BMCs after they were exposed to different doses of FA (50, 100, 200 μmol/L) for different exposure time (12, 24, 48 h), then chose 24 h as an exposure time to detect the expression of PrxIII for exposing different doses of FA by Quantitative reverse transcription-PCR (qRT-PCR) and Western blot analysis. Based on our preliminary experimental results, we chose 100 μmol/L FA as an exposure dose to expose for 24 h, and used a small interfering RNA (siRNA) to silenced PrxIII to examine the cell viability by CCK-8, reactive oxygen species (ROS) level by DCFH-DA, apoptosis by Annexin V/PI double staining and cell cycle by flow cytometry (FCM) so as to explore the possible regulatory effect of PrxIII silencing on FA-induced bone marrow toxicity.

RESULTS

High expression of PrxIII occurred in the process of FA-induced oxidative stress. Silencing of PrxIII prevented FA from inducing oxidative stress, thus increasing cell viability, decreasing ROS level, rescuing G0 -G1 and G2 -M arrest, and reducing cell apoptosis.

CONCLUSION

PrxIII silencing might be a potential target for alleviating FA-induced oxidative damage.

Formaldehyde promotes tumor-associated macrophage polarizations and functions through induction of HIF-1α-mediated glycolysis

Formaldehyde (FA) exposure has been positively correlated with many diseases including various types of cancers. However, the mechanisms of FA-related carcinogenesis are still unclear. Tumor-associated macrophages (TAMs) are the most abundant immune cells in tumor microenvironment, which is a heterogeneous population consist of both pro-inflammatory (M1) and immunosuppressive (M2) cells. TAMs are deeply involved in tumor development and progression. Our previous studies demonstrated that FA enhanced M1 polarization of macrophages through induction of HIF-1α-mediated glycolysis. To examine if TAM polarizations are also potentiated by FA, BALB/c nude mice were inoculated with A549 cells to develop subcutaneous tumors and exposed to 2.0 mg/m3 FA for 14 days. Significant increases of both M1 and M2 polarizations of TAMs were observed in tumor tissues of FA-exposed mice. After confirmation of the potentiation effects in RAW264.7 and THP-1-derived in vitro TAM models, FA at 25 and 50 μM was found to enhance TAM immunosuppressive functions and glycolytic metabolism. In addition, FA-induced glycolysis in TAMs was reversed by a specific HIF-1α inhibitor PX-478 at 5 μM, and suppression of glycolytic metabolism with a glucose analog 2-DG at 1 mM also alleviated FA-potentiated TAM functions, which indicated that FA induced TAM polarizations through the upregulation of HIF-1α-mediated glycolysis. These results illustrated a potential carcinogenic mechanism of FA through metabolic disturbance of tumor immunity, which could be utilized to develop preventative or therapeutic agents for FA-induced carcinogenesis and immune disorders.

The Protective Effect of Mangiferin on Formaldehyde-Induced HT22 Cell Damage and Cognitive Impairment

Formaldehyde (FA) has been found to induce major Alzheimer's disease (AD)-like features including cognitive impairment, Aβ deposition, and Tau hyperphosphorylation, suggesting that it may play a significant role in the initiation and progression of AD. Therefore, elucidating the mechanism underlying FA-induced neurotoxicity is crucial for exploring more comprehensive approaches to delay or prevent the development of AD. Mangiferin (MGF) is a natural C-glucosyl-xanthone with promising neuroprotective effects, and is considered to have potential in the treatment of AD. The present study was designed to characterize the effects and mechanisms by which MGF protects against FA-induced neurotoxicity. The results in murine hippocampal cells (HT22) revealed that co-treatment with MGF significantly decreased FA-induced cytotoxicity and inhibited Tau hyperphosphorylation in a dose-dependent manner. It was further found that these protective effects were achieved by attenuating FA-induced endoplasmic reticulum stress (ERS), as indicated by the inhibition of the ERS markers, GRP78 and CHOP, and downstream Tau-associated kinases (GSK-3β and CaMKII) expression. In addition, MGF markedly inhibited FA-induced oxidative damage, including Ca²⁺ overload, ROS generation, and mitochondrial dysfunction, all of which are associated with ERS. Further studies showed that the intragastric administration of 40 mg/kg/day MGF for 6 weeks significantly improved spatial learning ability and long-term memory in C57/BL6 mice with FA-induced cognitive impairment by reducing Tau hyperphosphorylation and the expression of GRP78, GSK-3β, and CaMKII in the brains. Taken together, these findings provide the first evidence that MGF exerts a significant neuroprotective effect against FA-induced damage and ameliorates mice cognitive impairment, the possible underlying mechanisms of which are expected to provide a novel basis for the treatment of AD and diseases caused by FA pollution.

Electrochemical and Optical Sensors for the Detection of Chemical Carcinogens Causing Leukemia

The incidence and mortality due to neoplastic diseases have shown an increasing tendency over the years. Based on GLOBOCAN 2020 published by the International Agency for Research on Cancer (IARC), leukemias are the thirteenth most commonly diagnosed cancer in the world, with 78.6% of leukemia cases diagnosed in countries with a very high or high Human Development Index (HDI). Carcinogenesis is a complex process initiated by a mutation in DNA that may be caused by chemical carcinogens present in polluted environments and human diet. The IARC has identified 122 human carcinogens, e.g., benzene, formaldehyde, pentachlorophenol, and 93 probable human carcinogens, e.g., styrene, diazinone. The aim of the following review is to present the chemical carcinogens involved or likely to be involved in the pathogenesis of leukemia and to summarize the latest reports on the possibility of detecting these compounds in the environment or food with the use of electrochemical sensors.

A NIR fluorescent probe for dual imaging of mitochondrial viscosity and FA in living cells and zebrafish

Formaldehyde (FA) and viscosity play multiple roles in human health and diseases, and viscosity has great regional differences due to the diversity of subcellular organelles. However, it is challenging to achieve dual detection of viscosity and FA in subcellular organelles. Herein, we developed a near infrared (NIR) fluorescent probe FA-Cy, which can simultaneously monitor the viscosity and FA concentration of mitochondria in living cells. The probe could detect mitochondrial viscosity and exogenous and endogenous FA in living cells and zebrafish.

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.

Janus-Faced Fluorescence Imaging Agent for Malondialdehyde and Formaldehyde in Brains

Carbonyl stress caused by reactive carbonyl species (RCS) is closely related to various brain diseases. As the highly reactive, highly toxic, and lipophilic RCS, malondialdehyde (MDA) and formaldehyde (FA) could easily cross the blood-brain barrier (BBB) and induce protein dysfunction or cross-linking in the brain. Do MDA and FA coordinately regulate the physio-pathological processes of the brain? To answer the question, first of all, powerful identification and sensing tools are needed. However, competent probes for simultaneously analyzing MDA and FA in living brains are lacking, which originates from the following three challenges: (1) MDA and FA are difficult to distinguish due to their great similarity in structure and reactivity; (2) to achieve simultaneous and discriminable imaging, same excitation and different emissions are preferable; and (3) the detection of MDA and FA in living brains require the materials to pass through the BBB. Thus, we created a two-photon fluorescent agent, TFCH, for MDA/FA. The hydrazine group in TFCH could successfully differentiate MDA/FA at 440/510 nm under same excitation. Moreover, the lipophilic trifluoromethyl group (-CF₃) in TFCH prompts it to traverse the BBB, thereby realizing the coinstantaneous visualization of MDA and FA in the living brain. Using TFCH, we observed the excessive production of MDA and FA in living PC12 cells under carbonyl stress and oxidative stress. Notably, for the first time, two-photon fluorescence imaging indicated the synchronous increase of MDA and FA in living brains of mice with depression. Altogether, this work provides a promising tool for revealing the carbonyl stress-related molecular mechanism involved in brain diseases.

Systematic Screening of Trigger Moieties for Designing Formaldehyde Fluorescent Probes and Application in Live Cell Imaging

Formaldehyde (FA) is involved in multiple physiological regulatory processes and plays a crucial role in memory storage. Meanwhile, FA has a notorious reputation as a toxic compound, and it will cause a variety of diseases if its level is unbalanced in the human body. To date, there have been numerous fluorescent probes for FA imaging reported. Among them, the probes based on the 2-aza-Cope rearrangement have attracted the most attention, and their applications in cell imaging have been greatly expanded. Herein, we screened the various trigger moieties of FA fluorescent probes based on the mechanism of 2-aza-Cope rearrangement. FA-2, in which a fluorophore is connected to a 4-nitrobenzylamine group and an allyl group, demonstrated the highest sensitivity, selectivity, and reaction kinetics. Furthermore, FA-Lyso, derived from FA-2, has been successfully designed and applied to monitor exogenous and endogenous FA fluctuations in lysosomes of living cells.

Semen Quality Following Long-term Occupational Exposure to Formaldehyde in China

IMPORTANCE

The potential effects of long-term occupational exposure to formaldehyde (FA) on human semen quality is not clear.

OBJECTIVE

To assess whether long-term occupational exposure to FA is associated with semen quality.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study was conducted from June 1 to June 30, 2021, in Xi'an, China. Participants were adults aged 23 to 40 years who had lived in the study area for 24 months or longer. Data analysis was performed from September 1 to October 1, 2021.

EXPOSURES

Long-term occupational exposure to FA was measured using a formaldehyde detector, and the FA exposure index (FEI) was calculated as follows: FEI = final concentration of FA (mg/m3) × work time during a workday (hour) × cumulative workdays (year).

MAIN OUTCOMES AND MEASURES

Semen samples were collected by masturbation after 3 to 7 days of abstinence and were then assessed by the computer-automated semen analysis system, Baso-Papanicolaou staining, and sperm-chromatin structure assay.

RESULTS

A total of 205 men (mean [SD] age, 29.49 [3.64] years), with 124 individuals in the FA exposure group (mean [SD] FEI, 73.72 [54.86]) and 81 age-matched controls, were included in the final analysis. Long-term personal occupational exposure to FA was significantly associated with poor semen quality. Specifically, a 1-unit increase in FEI was associated with a change of -0.99% (95% CI, -1.00% to -0.98%) in total sperm motility, -0.99% (95% CI, -0.99% to -0.97%) in progressive sperm motility, -0.05% (95% CI, -0.08% to -0.02%) in curvilinear velocity, -0.07% (95% CI, -0.10% to -0.04%) in straight line velocity, -0.07% (95% CI, -0.10% to -0.04%) in time-average velocity, -0.98% (95% CI, -0.99% to -0.93%) in normal sperm morphology, -0.24% (95% CI, -0.35% to -0.11%) in seminal neutral glucosidase, -0.61% (95% CI, -0.66% to -0.56%) in seminal plasma zinc, 0.52% (95% CI, 0.15% to 1.02%) in beat cross frequency, and 0.10% (95% CI, 0.06% to 0.14%) in the DNA fragmentation index. These associations remained significant after adjusting for confounding factors. Furthermore, subgroup analysis found that high levels of oxidative stress might promote the associations between FA exposure and semen quality.

CONCLUSIONS AND RELEVANCE

This study found an association between long-term occupational exposure to FA and semen quality. This deterioration was dose and time dependent and might be induced by oxidative stress.

DNA damage and repair in the hematopoietic system

Although hematopoietic stem cells (HSCs) in the bone marrow are in a state of quiescence, they harbor the self-renewal capacity and the pluripotency to differentiate into mature blood cells when needed, which is key to maintain hematopoietic homeostasis. Importantly, HSCs are characterized by their long lifespan ( e. g., up to 60 months for mice), display characteristics of aging, and are vulnerable to various endogenous and exogenous genotoxic stresses. Generally, DNA damage in HSCs is endogenous, which is typically induced by reactive oxygen species (ROS), aldehydes, and replication stress. Mammalian cells have evolved a complex and efficient DNA repair system to cope with various DNA lesions to maintain genomic stability. The repair machinery for DNA damage in HSCs has its own characteristics. For instance, the Fanconi anemia (FA)/BRCA pathway is particularly important for the hematopoietic system, as it can limit the damage caused by DNA inter-strand crosslinks, oxidative stress, and replication stress to HSCs to prevent FA occurrence. In addition, HSCs prefer to utilize the classical non-homologous end-joining pathway, which is essential for the V(D)J rearrangement in developing lymphocytes and is involved in double-strand break repair to maintain genomic stability in the long-term quiescent state. In contrast, the base excision repair pathway is less involved in the hematopoietic system. In this review, we summarize the impact of various types of DNA damage on HSC function and review our knowledge of the corresponding repair mechanisms and related human genetic diseases.