Egr-1 mediates low-dose arecoline induced human oral mucosa fibroblast proliferation via transactivation of Wnt5a expression

Arecoline Induces ROS Accumulation, Transcription of Proinflammatory Factors, and Expression of KRT6 in Oral Epithelial Cells

Areca nut is a major contributor to the high prevalence of oral cancer in Asia. The precise mechanisms by which areca nut stimulates mucosal cells and contributes to the progression of oral cancer urgently require clarification. The current study aimed to assess the effects of arecoline on the normal human gingival epithelium cell line S-G. Cell viability, levels of reactive oxygen species (ROS), protein expression, cellular morphology, and gene expression were evaluated using the MTT test, flow cytometry, Western blot analysis, optical or confocal microscopy, and RT-qPCR. Keratin (KRT6) analysis involved matched normal and cancer tissues from clinical head and neck specimens. The results demonstrated that 12.5 µg/mL of arecoline induced ROS production, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) mRNA expression in S-G cells. This activation of the MAPK/ERK pathway increased KRT6 expression while limiting cell migration. In head and neck cancer tissues, KRT6B gene expression exceeded that of normal tissues. This study confirms that arecoline induces ROS accumulation in normal cells, leading to the secretion of proinflammatory factors and KRT6 expression. This impedes oral mucosal healing, thereby promoting the progression of oral cancer.

Targeting histone deacetylase 9 represses fibrogenic phenotypes in buccal mucosal fibroblasts with arecoline stimulation

Background/purpose

Oral submucosal fibrosis (OSF) is a premalignant disorder positively associated with betel nut chewing. Recent studies supported the promising benefits of histone deacetylase (HDAC) inhibitors for fibrosis treatment. Here we aim to clarify the pro-fibrogenic role of HDAC9 in regulating OSF.

Materials and methods

Healthy and OSF specimens were collected to investigate the clinical significance of HDAC9. Chronic arecoline treatment process was used to induce arecoline-mediated myofibroblasts-related activation of primary buccal mucosa fibroblasts (BMFs). Functional analysis of collagen gel contraction, transwell migration, and wound-healing assays were performed to assess the change in pro-fibrogenic properties of BMFs and fibrotic BMFs (fBMFs). Lentiviral-mediated HDAC9 knockdown was used to verify the role of HDAC9 in the pro-fibrogenic process.

Results

We found that arecoline significantly increased the mRNA and protein expression of HDAC9 of BMFs in a dose-dependent manner. Knockdown of HDAC9 in BMFs reversed the strengthened effects of arecoline on collagen gel contraction, cell migration, and wound-healing ability. We further demonstrated that knockdown of HDAC9 in fBMFs significantly attenuated its inherent pro-fibrogenic properties. Furthermore, we confirmed a significantly increased expression of HDAC9 mRNA in OSF compared to normal tissues, which suggested a positive correlation between the up-regulation of HDAC9 and OSF.

Conclusion

We demonstrated that silencing of HDAC9 inhibited arecoline-induced activation and inherent pro-fibrogenic properties, suggesting potential therapeutics by targeting HDAC9 in the OSF treatment.

A Critical Interpretive Synthesis of the Role of Arecoline in Oral Carcinogenesis: Is the Local Cholinergic Axis a Missing Link in Disease Pathophysiology?

Arecoline is the primary active carcinogen found in areca nut and has been implicated in the pathogenesis of oral squamous cell carcinoma (OSCC) and oral submucous fibrosis (OSF). For this study, we conducted a stepwise review process by combining iterative scoping reviews with a post hoc search, with the aim of identifying the specific mechanisms by which arecoline initiates and promotes oral carcinogenesis. Our initial search allowed us to define the current trends and patterns in the pathophysiology of arecoline-induced OSF and OSCC, which include the induction of cell proliferation, facilitation of invasion, adhesion, and migration, increased collagen deposition and fibrosis, imbalance in immune and inflammatory mechanisms, and genotoxicity. Key molecular pathways comprise the activation of NOTCH1, MYC, PRDX2, WNT, CYR61, EGFR/Pl3K, DDR1 signaling, and cytokine upregulation. Despite providing a comprehensive overview of potential pathogenic mechanisms of OSF, the involvement of molecules functioning as areca alkaloid receptors, namely, the muscarinic and nicotinic acetylcholine receptors (AChRs), was not elucidated with this approach. Accordingly, our search strategy was refined to reflect these evidence gaps. The results of the second round of reviews with the post hoc search highlighted that arecoline binds preferentially to muscarinic AChRs, which have been implicated in cancer. Consistently, AChRs activate the signaling pathways that partially overlap with those described in the context of arecoline-induced carcinogenesis. In summary, we used a theory-driven interpretive review methodology to inform, extend, and supplement the conventional systematic literature assessment workflow. On the one hand, the results of this critical interpretive synthesis highlighted the prevailing trends and enabled the consolidation of data pertaining to the molecular mechanisms involved in arecoline-induced carcinogenesis, and, on the other, brought up knowledge gaps related to the role of the local cholinergic axis in oral carcinogenesis, thus suggesting areas for further investigation.

EGR-1 Contributes to Pulmonary Edema by Regulating the Epithelial Sodium Channel in Lipopolysaccharide-Induced Acute Lung Injury

Acute lung injury (ALI) is a common lung disease with increasing morbidity and mortality rates due to the lack of specific drugs. Impaired alveolar fluid clearance (AFC) is a primary pathological feature of ALI. Epithelial sodium channel (ENaC) is a primary determinant in regulating the transport of Na+ and the clearance of alveolar edema fluid. Therefore, ENaC is an important target for the development of drugs for ALI therapy. However, the role of ENaC in the progression of ALI remains unclear. Inhibition of early growth response factor (EGR-1) expression has been reported to induce a protective effect on ALI; therefore, we evaluated whether EGR-1 participates in the progression of ALI by regulating ENaC-α in alveolar epithelium. We investigated the potential mechanism of EGR-1-mediated regulation of ENaC in ALI. We investigated whether EGR-1 aggravates the pulmonary edema response in ALI by regulating ENaC. ALI mouse models were established by intrabronchial injection of lipopolysaccharides (LPS). Lentiviruses with EGR-1 knockdown were transfected into LPS-stimulated A549 cells. We found that EGR-1 expression was upregulated in the lung tissues of ALI mice and in LPS-induced A549 cells, and was negatively correlated with ENaC-α expression. Knockdown of EGR-1 increased ENaC-α expression and relieved cellular edema in ALI. Moreover, EGR-1 regulated ENaC-α expression at the transcriptional level, and correspondingly promoted pulmonary edema and aggravated ALI symptoms. In conclusion, our study demonstrated that EGR-1 could promote pulmonary edema by downregulating ENaC-α at the transcriptional level in ALI. Our study provides a new potential therapeutic strategy for treatment of ALI.

Low-dose arecoline regulates distinct core signaling pathways in oral submucous fibrosis and oral squamous cell carcinoma

BACKGROUND

Betel nut chewing plays a role in the pathogenesis of oral submucous fibrosis (OSF) and oral squamous cell carcinoma (OSCC). As the major active ingredient of the betel nut, the effect of arecoline and its underlying mechanism to OSF and OSCC pathogenesis remain unclear.

METHODS

Next-generation sequencing-based transcriptome and dRRBS analysis were performed on OSF and OSCC cells under low-dose arecoline exposure. Functional analyses were performed to compare the different roles of arecoline during OSF and OSCC pathogenesis, and key genes were identified.

RESULTS

In this study, we identified that low-dose arecoline promoted cell proliferation of both NFs and OSCC cells via the acceleration of cell cycle progression, while high-dose arecoline was cytotoxic to both NFs and OSCC cells. We performed for the first time the transcriptome and methylome landscapes of NFs and OSCC cells under low-dose arecoline exposure. We found distinct transcriptome and methylome profiles mediated by low-dose arecoline in OSF and OSCC cells, as well as specific genes and signaling pathways associated with metabolic disorders induced by low-dose arecoline exposure. Additionally, low-dose arecoline displayed different functions at different stages, participating in the modulation of the extracellular matrix via Wnt signaling in NFs and epigenetic regulation in OSCC cells. After exposure to low-dose arecoline, the node roles of FMOD in NFs and histone gene clusters in OSCC cells were found. Meanwhile, some key methylated genes induced by arecoline were also identified, like PTPRM and FOXD3 in NFs, SALL3 and IRF8 in OSCC cells, indicating early molecular events mediated by arecoline during OSF and OSCC pathogenesis.

CONCLUSIONS

This study elucidated the contribution of low-dose arecoline to OSF and OSCC pathogenesis and identified key molecular events that could be targeted for further functional studies and their potential as biomarkers.

Fucoidan-Mediated Inhibition of Fibrotic Properties in Oral Submucous Fibrosis via the MEG3/miR-181a/Egr1 Axis

Oral submucous fibrosis (OSF) is a chronic fibrotic remodeling disease that can progress to oral cancer. However, efficient clinical diagnosis and treatment methods for OSF are still lacking. This study investigated the anti-fibrotic effect of fucoidan on oral fibrosis. To evaluate the fibrotic ability (myofibroblast activities), we performed wound-healing, Transwell migration, and collagen contraction assays by using patient-derived normal and fibrotic buccal submucous fibroblasts (BMFs and fBMFs, respectively). RNA-sequencing and dual-luciferase reporter and RNA immunoprecipitation chip assays were performed to identify the clinical significance and molecular mechanism of non-coding RNAs. Fucoidan suppressed the myofibroblast activities and inhibited the MEG3 in fBMFs. MEG3 was overexpressed in the OSF tissue and was positively associated with myofibroblast markers. Knockdown of MEG3 markedly inhibited myofibroblast activities, which were restored by inhibiting miR-181a and overexpressing Egr1. The results from luciferase reporter and RIP assays confirmed that MEG3 functioned as a competing endogenous RNA (ceRNA) and could directly target miR-181a, thereby preventing the miR-181a-mediated translational repression of Egr1. This study demonstrated that MEG3 exerts a profibrotic effect on OSF by targeting miR-181a/Egr1. Therefore, the administration of fucoidan may serve as a potential therapeutic strategy for OSF by targeting the overexpression of MEG3.