Alternative Splicing of SMAD4 and Its Function in HaCaT Cells in Response to UVB Irradiation

Downregulation of SMAD4 protects HaCaT cells against UVB-induced damage and oxidative stress through the activation of EMT

As a member of the SMAD family, SMAD4 plays a crucial role in several cellular biological processes. However, its function in UVB radiation-induced keratinocyte damage is not yet clarified. Our study aims to provide mechanistic insight for the development of future UVB protective therapies and therapeutics involving SMAD4. HaCaT cells were treated with UVB, and the dose dependence and time dependence of UVB were measured. The cell function of UVB-treated HaCaT cells and the activity of epithelial-mesenchymal transition (EMT) after overexpression or silencing of SMAD4 was observed by flow cytometry, quantitative reverse transcription PCR (qRT-PCR) and Western Blots (WB). We found that a significant decrease in SMAD4 was observed in HaCaT cells induced by UVB. Our data confirm SMAD4 as a direct downstream target of miR-664. The down-regulation of SMAD4 preserved the viability of the UVB-treated HaCaT cells by inhibiting autophagy or apoptosis. Furthermore, the silencing of SMAD4 activated the EMT process in UVB-treated HaCaT cells. Down-regulation of SMAD4 plays a protective role in UVB-treated HaCaT cells via the activation of EMT.

A novel UVA-associated circUBE2I mediates ferroptosis in HaCaT cells

Alternative splicing of precursor messenger RNA (pre-mRNA), including linear splicing and back splicing, produces multiple isoforms that lead to diverse cell fates in response to stimuli including ultraviolet radiation (UVR). Although UVR-induced linear gene splicing has been extensively studied in skin cells, the UVR-induced gene back-splicing events that lead to the production of circular RNAs (circRNAs) have not been thoroughly investigated. The present study used circRNA transcriptome sequencing to screen the differentially expressed circRNAs in human keratinocytes (HaCaT) after UVA irradiation. A total of 312 differentially expressed circRNAs were found in HaCaT cells post-UVR. Among the UVA-induced differentially expressed circRNAs, circUBE2I-a novel circRNA formed by exons 2-6 of the UBE2I gene-was the most significantly upregulated circRNA. RT-qPCR assay further confirmed the increase of circUBE2I level in HaCaT cells after UVA irradiation or H2 O2 treatment. RNase R digestion experiment revealed the stability of circUBE2I. Overexpression of circUBE2I in keratinocytes induced ferroptosis after UVA or H2 O2 , preventable by the ferroptosis inhibitor ferrostatin-1. Our study provides new insights into the role of circular RNAs in UVA-induced skin cell damage and suggests that circUBE2I could be a therapeutic target in UVR-aroused ferroptosis in skin cells.

A Novel multi-fruit acids formula design on molecular basis for skin brightening via a system biology approach

BACKGROUND

Fruit acids have long been recognized as highly effective actives with world-wide popularity, covering skin peeling, anti-acne, anti-wrinkle applications, and skin depigmentation.

AIMS

There are complicated interconnections between the fruit acid formula and skin pigmentation behaviors. However, the lack of systematic researches on multi-ingredient formula restricted our understanding on its mechanism. Therefore, it is of great necessity to study the interactions and cascades among components, potential gene targets, signaling pathways, and biological processes via a system biology approach.

METHODS

We used system biology, molecular fingerprint, and structural biology to calculate and collect target information of the functional formula. Gene Ontology (GO) enrichment analysis was further applied to study the biological processes and pathways of the formula, and a multi-level network model of "component - molecular target - signaling pathway - skin disease" was established. Besides, the zebrafish model was utilized to verify the formula.

RESULTS

We obtained 69 hub targets by constructing a protein-protein interaction (PPI) network based on the intersection between multi-fruit acids formula (mandelic acid, lactobionic acid, niacinamide, and hydroxytyrosol) and skin indications targets (whitening-sebum balance). In vitro zebrafish models, including pigmentation, antioxidant, and radiation protection models, showed that the current formula significantly alleviated pigmentation intensity and intracellular free radical content, thus proving the efficacy of skin brightening and UV irradiation protection.

CONCLUSIONS

This research uncovered the underlying mechanism of multi-fruit acids formula and predicted its function in skin brightening and UV irradiation prevention.

UVB-induced SFRP1 methylation potentiates skin damage by promoting cell apoptosis and DNA damage

In response to the accumulation of genetic mutations and cellular changes, ultraviolet radiation B (UVB) skin lesions undergo dysplasia and transform into a cutaneous squamous cell carcinoma (CSCC). Consistent with our previous findings that secreted frizzled-related protein 1 (SFRP1), a member of the SFRP gene family, was downregulated in human CSCC tissue samples, we found a significant downregulation of SFRP1 in HaCaT, A431, and SCL-1 cells after UVB irradiation. DNA methyltransferase 1 (DNMT1) was significantly increased in CSCC tissues as well as UVB-exposed A431 and SCL-1 cells. Bisulfite genomic sequencing analysis showed that the downregulation of SFRP1 was mainly due to methylation of the SFRP1 promoter, as indicated by increased methylation rate of SFRP1 after UVB irradiation in HaCaT cells. Moreover, demethylation treatment with 5-aza'-deoxycytidine (5-AzaC) increased SFRP1 expression and reduced the methylation rate of SFRP1 in HaCaT cells. Flow cytometry analyses demonstrated that 5-AzaC treatment or overexpression of SFRP1 ameliorated UVB-induced apoptosis, while knockdown of SFRP1 promoted UVB-induced apoptosis in HaCaT cells. In addition, a comet assay confirmed that 5-AzaC treatment reduced DNA damage following UVB irradiation, while knockdown of SFRP1 enhanced DNA damage following UVB irradiation. In conclusion, our study identified DNA methylation of SFRP1 as a key mediator in the UVB-induced apoptosis of keratinocytes. These findings indicate that reinforcing SFRP1 defenses by 5-AzaC may help prevent UVB-induced skin damage.

Novel Alternatively Spliced Variants of Smad4 Expressed in TGF-β-Induced EMT Regulating Proliferation and Migration of A549 Cells

Introduction

Non-small cell lung cancer (NSCLC) is a worldwide malignance threatening human life. TGF-β/Smad signaling is known to regulate cell proliferation, differentiation, migration and growth. As the only co-Smad playing crucial roles in TGF-β signaling, Smad4 is reported to be frequently mutated or to occur as alternatively spliced in tumor cells. Smad4 was reported to be involved in the TGF-β-induced EMT process. However, whether the alternative splicing occurs in the TGF-β-induced EMT process in NSCLC was not clear.

Methods

In our current study, we explored the alternative splicing of Smad4 during the process of TGF-β-induced EMT in A549 cells. 10 ng/mL TGF-β was used to induce EMT. Then, nest-PCR and agarose electrophoresis were performed to detect the expression of Smad4 variants and sequencing to get the variant DNA sequences. For recombinant expression of variants of Smad4 in A549 cells, we used lentiviral variants to infect cells. In order to explore the effects of variants on the proliferation and migration of A549 cells, the MTT assay, colony formation assay and wound-healing assay were done. The effects of variants on E-cad and VIM protein expression were explored through Western blot.

Results

There were several novel gene fragments expressed in TGF-β-induced A549 cells, and the sequencing results showed that they were indeed the Smad4 variants that were not reported. For recombinant expression of Smad4 variants in A549 cells, we found that they have significant effects on the proliferation and migration of cells, and also regulated the E-cad and VIM protein expression.

Conclusion

Our results indicated that novel Smad4 variants were expressed in TGF-β-induced EMT process. The functional study showed that these novel variants regulate cell proliferation and migration and affect E-cad and VIM protein expression, showing the potential as targets for cancer therapy.

The role and mechanism of microRNA‑18a‑5p in oral squamous cell carcinoma

The purpose of this study was mainly to explore the role and mechanism of microRNA-18a-5p (miR-18a-5p) in oral squamous cell carcinoma (OSCC). The expression of miR-18a-5p in OSCC cells and normal cells was firstly detected using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The cell viability, apoptosis, migration and invasion abilities of OSCC cells were determined by MTT, cell apoptosis, wound healing and Transwell assays respectively. Additionally, bioinformatics software analysis and luciferase reporter assays were performed to predict and confirm the candidate target of miR-18a-5p. Western blot analysis was used to assess protein expression. It was revealed that the expression of miR-18a-5p in OSCC cells was higher than that in normal cells. In vitro studies revealed that the cell viability, migration and invasion abilities of OSCC cells were promoted and cell apoptosis was inhibited by miR-18a-5p overexpression. In addition, Smad2 was identified as a target of miR-18a-5p. It was also revealed that miR-18a-5p overexpression significantly inhibited the expression of Smad2, Smad4 and E-cadherin, and the levels of Smad7, collagen I, transforming growth factor-β (TGF-β), α-smooth muscle actin (α-SMA), vimentin were enhanced. While miR-18a-5p downregulation presented the opposite effects. In conclusion, the results indicated that miR-18a-5p can regulate the biological process of OSCC by targeting Smad2 and miR-18a-5p/Smad2 may be potential therapeutic targets for OSCC.