Faculty Bibliography

Formaldehyde, a reactive aldehyde widely present in the environment and associated with occupational exposure, has been linked to cognitive impairment and Alzheimer's disease (AD) in multiple epidemiological and animal studies. However, its contribution to AD-like pathology in human neural models remains poorly understood. We utilized a 3D culture system of human neural progenitor cells (ReNcell VM) differentiated into neurons and glial cells to model chronic formaldehyde exposure. Additionally, we established a 3D human AD model by transducing ReN cells with APP and PSEN1 mutations to assess the effects of formaldehyde in an AD genetic background. Long-term formaldehyde exposure (up to 12 weeks) induced a dose-dependent increase in Aβ40, Aβ42, APP, and phosphorylated tau levels in both wild-type and AD-mutant 3D cultures. These changes mimic hallmark features of AD neuropathology, suggesting that formaldehyde acts as a pathological driver in both sporadic and familial contexts. Our study provides direct evidence that chronic formaldehyde exposure may initiate and accelerate amyloid and tau pathologies in 3D human neural cell models. These findings support growing concerns about formaldehyde as a modifiable risk factor in neurodegeneration.

Formaldehyde (FA) is a pervasive environmental organic pollutant and a Group 1 human carcinogen. While FA has been implicated in various cancers, its genotoxic effects, including DNA damage and DNA-protein cross-linking, have proven insufficient to fully explain its role in carcinogenesis, suggesting the involvement of epigenetic mechanisms. Histone post-translational modifications (PTMs) on H3 and H4, which are critical for regulating gene expression, may contribute to FA-induced pathogenesis, as lysine and arginine residues serve as targets for FA-protein adduct formation. This study aimed to elucidate the epigenetic consequences of FA on histone methylation and acetylation patterns through a comprehensive peptide analysis. Human bronchial epithelial cells (BEAS-2B) were exposed to low-dose (0.1 mM) and high-dose (0.5 mM) FA for 1 h, and their histone extracts were analyzed using high-resolution liquid chromatography-tandem mass spectrometry-based proteomics followed by PTM-combined peptide analysis and single PTM site/type comparisons. We identified 40 peptides on histone H3 and 16 on histone H4 bearing epigenetic marks. Our findings revealed that FA exposure induced systemic alterations in H3 and H4 methylation and acetylation, including hypomethylation of H3K4 and H3K79; changes in H3K9, H3K14, H3K18, H3K23, H3K27, H3K36, H3K37, and H3R40; as well as modifications in H4K5, H4K8, H4K12, and H4K16. These FA-induced histone modifications exhibited strong parallels with epigenetic alterations observed in cancers, leukemia, and Alzheimer's disease. This study provides novel evidence of FA-induced epigenetic toxicity, offering new insights into the potential mechanisms underlying FA-driven pathogenesis.

Alzheimer's disease (AD) arises from complex multilevel interactions between genetic, epigenetic, and environmental factors. Recent studies suggest that exposure to the environmental and occupational toxicant formaldehyde (FA) may play a significant role in AD development. However, the effects of FA exposure on Aβ and tau pathologies in human neural cell 3D culture systems remain unexplored. To investigate FA's role in AD initiation, we differentiated 3D-cultured immortalized human neural progenitor ReN cells (ReNcell VM) into neurons and glial cells, followed by FA treatment. FA exposure for 12 weeks resulted in a dose-dependent increase in Aβ40, Aβ42, and phosphorylated tau levels. To further examine FA's role in AD progression, we established a 3D human neural cell culture AD model by transfecting ReN cells with AD-related mutant genes, including mutant APP and PSEN1, which recapitulate key AD pathological events. Our findings demonstrate that FA exposure significantly elevated Aβ40, Aβ42, and phosphorylated tau levels in this 3D-cultured AD model. These results suggest that FA exposure contributes to the initiation and progression of AD pathology in 3D-cultured human neural cells.

Nicotine, a naturally occurring tobacco alkaloid responsible for tobacco addiction, has long been considered non-carcinogenic. However, emerging evidence suggests that nicotine may possess carcinogenic properties in mice and could be a potential carcinogen in humans. This review aims to summarize the potential molecular mechanisms underlying nicotine-induced carcinogenesis, with a specific focus on epigenetic regulation and the activation of nicotinic acetylcholine receptors (nAChRs) in addition to genotoxicity and excess reactive oxygen species (ROS). Additionally, we explore a novel hypothesis regarding nicotine's carcinogenicity involving the downregulation of stem-loop binding protein (SLBP), a critical regulator of canonical histone mRNA, and the polyadenylation of canonical histone mRNA. By shedding light on these mechanisms, this review underscores the need for further research to elucidate the carcinogenic potential of nicotine and its implications for human health.

AIM/UNASSIGNED:This study aims to elucidate the involvement of triple-negative breast cancer (TNBC)-derived extracellular vesicles in metastasis. The loss of components in the type 1 interferon (IFN1) signaling pathway has been linked to the promotion of metastasis. However, IFN1 signaling induces immunological dormancy and promotes tumorigenesis. Our hypothesis was that TNBC cells release tumor-derived extracellular vesicles (TEVs) that promote metastasis in an IFN1-independent manner. METHODS/UNASSIGNED:Two murine TNBC models and transgenic mice were used to examine the role of IFN1 in TNBC progression to metastasis. Reserpine was employed to determine the effect of TEV education on TNBC progression and overall survival. EVs from cancer cells treated with vehicle and reserpine and from the serum of tumor-bearing mice receiving reserpine were examined to determine changes in EV release and EV content. RESULTS/UNASSIGNED:. Western blot analysis demonstrated reserpine decreased NUPR1 protein levels in EVs. RNAseq analysis demonstrated that endothelial cells lacking CH25H treated with TEVs exhibited increased NUPR1 expression that was decreased by adding reserpine with the TEVs. NUPR1 overexpression upregulated genes that mediate TEV biogenesis and incorporation. Knockdown of NUPR1 with shRNA decreased the release of TEVs. CONCLUSION/UNASSIGNED:In conclusion, our study suggests that TNBC is driven by aberrant packaging of NUPR1 into TEVs which were transferred into recipient cells to activate pro-metastatic transcription driven by NUPR1.

Arsenic exposure is associated with an increased risk of many cancers, and epigenetic mechanisms play a crucial role in arsenic-mediated carcinogenesis. Our previous studies have shown that arsenic exposure induces polyadenylation of H3.1 mRNA and inhibits the deposition of H3.3 at critical gene regulatory elements. However, the precise underling mechanisms are not yet understood. To characterize the factors governing arsenic-induced inhibition of H3.3 assembly through H3.1 mRNA polyadenylation, we utilized mass spectrometry to identify the proteins, especially histone chaperones, with reduced binding affinity to H3.3 under conditions of arsenic exposure and polyadenylated H3.1 mRNA overexpression. Our findings reveal that the interaction between H3.3 and the histone chaperon protein MCM2 is diminished by both polyadenylated H3.1 mRNA overexpression and arsenic treatment in human lung epithelial BEAS-2B cells. The increased binding of MCM2 to H3.1, resulting from elevated H3.1 protein levels, appears to contribute to the reduced availability of MCM2 for H3.3. To further investigate the role of MCM2 in H3.3 deposition during arsenic exposure and H3.1 mRNA polyadenylation, we overexpressed MCM2 in BEAS-2B cells overexpressing polyadenylated H3.1 or exposed to arsenic. Our results demonstrate that MCM2 overexpression attenuates H3.3 depletion at several genomic loci, suggesting its involvement in the arsenic-induced displacement of H3.3 mediated by H3.1 mRNA polyadenylation. These findings suggest that changes in the association between histone chaperone MCM2 and H3.3 due to polyadenylation of H3.1 mRNA may play a pivotal role in arsenic-induced carcinogenesis.

The use of electronic-cigarettes (e-cigs) has increased substantially in recent years, particularly among the younger generations. Liquid nicotine is the main component of e-cigs. Previous studies have shown that mice exposed to e-cig aerosols developed lung adenocarcinoma and bladder hyperplasia. These findings implicated a potential role for e-cig aerosols and nicotine in cancer development, although the underlying mechanisms are not fully understood. Here we report that exposure to liquid nicotine or nicotine aerosol generated from e-cig induces downregulation of Stem-loop binding protein (SLBP) and polyadenylation of canonical histone mRNAs in human bronchial epithelial cells and in mice lungs. Canonical histone mRNAs typically do not end in a poly(A) tail and the acquisition of such a tail via depletion of SLBP has been shown to causes chromosome instability. We show that nicotine-induced SLBP depletion is reversed by an inhibitor of α7-nicotinic acetylcholine receptors (α7-nAChR) or siRNA specific for α7-nAChR, indicating a nAChR-dependent reduction of SLBP by nicotine. Moreover, PI3K/AKT pathway is activated by nicotine exposure and CK2 and probably CDK1, two kinases well known for their function for SLBP phosphorylation and degradation, are shown to be involved, α7-nAChR-dependently, in nicotine-induced SLBP depletion. Importantly, nicotine-induced anchorage-independent cell growth is attenuated by inhibition of α7-nAChR and is rescued by overexpression of SLBP. We propose that the SLBP depletion and polyadenylation of canonical histone mRNAs via activation of α7-nAChR and a series of downstream signal transduction pathways, are critical for nicotine-induced cell transformation and potential carcinogenesis.

Pre-mRNA processing of the replication-dependent canonical histone mRNAs requires an endonucleolytic cleavage immediately after a conserved stem loop structure which occurs before RNA Pol II encounters any poly(A) signal. Thus, in contrast to all other eukaryotic mRNAs, the canonical histone mRNAs are not polyadenylated in their 3' ends. The binding of stem-loop binding protein (SLBP) to the stem loop structure of the histone mRNAs is required for this process. SLBP is also involved in regulation of histone mRNA nuclear export, degradation, and translation. Depletion of SLBP has been shown to induce polyadenylation of histone mRNAs and alteration of histone protein levels, which are considered to contribute to the observed aberrant cell cycle progress and genomic instability resulting from the loss of SLBP function. Recent studies have demonstrated that some heavy metal carcinogens, including arsenic and nickel, can induce the loss of SLBP and the gain of polyadenylation of canonical histone mRNAs. Polyadenylated canonical histone H3 can result in abnormal transcription, cell cycle arrest, genomic instability, and cell transformation, which links SLBP depletion and subsequent histone mRNA misprocessing to cancer. This review seeks to briefly summarize what is known about regulation of SLBP expression, consequences of SLBP depletion, its roles in cancer-related end points, with particular focus on metal-induced SLBP depletion and the potential of SLBP depletion as a new mechanism for metal-induced carcinogenesis.

Arsenic pollution impacts health of millions of people in the world. Inorganic arsenic is a carcinogenic agent in skin and lung cancers. The stem-loop binding protein (SLBP) binds to the stem-loop of the canonical histone mRNA and regulates its metabolism during cell cycle. Our previous work has shown arsenic induces ubiquitin-proteasome dependent degradation of SLBP and contributes to lung cancer. In this study, we established the first comprehensive SLBP interaction network by affinity purification-mass spectrometry (AP-MS) analysis, and further demonstrated arsenic enhanced the association between SLBP and a crucial chaperone complex containing heat shock proteins (HSPs) and ERp44. Strikingly, knockdown of these proteins markedly rescued the protein level of SLBP under arsenic exposure conditions, and abolished the increasing migration capacity of BEAS-2B cells induced by arsenic. Taken together, our study provides a potential new mechanism that a chaperone complex containing HSPs and ERp44 attenuates the stability of SLBP under both normal and arsenic exposure conditions, which could be essential for arsenic-induced high cell migration.