Involvement of smad2 and Erk/Akt cascade in TGF-β1-induced apoptosis in human gingival epithelial cells

TGF-β signaling in health, disease, and therapeutics

Transforming growth factor (TGF)-β is a multifunctional cytokine expressed by almost every tissue and cell type. The signal transduction of TGF-β can stimulate diverse cellular responses and is particularly critical to embryonic development, wound healing, tissue homeostasis, and immune homeostasis in health. The dysfunction of TGF-β can play key roles in many diseases, and numerous targeted therapies have been developed to rectify its pathogenic activity. In the past decades, a large number of studies on TGF-β signaling have been carried out, covering a broad spectrum of topics in health, disease, and therapeutics. Thus, a comprehensive overview of TGF-β signaling is required for a general picture of the studies in this field. In this review, we retrace the research history of TGF-β and introduce the molecular mechanisms regarding its biosynthesis, activation, and signal transduction. We also provide deep insights into the functions of TGF-β signaling in physiological conditions as well as in pathological processes. TGF-β-targeting therapies which have brought fresh hope to the treatment of relevant diseases are highlighted. Through the summary of previous knowledge and recent updates, this review aims to provide a systematic understanding of TGF-β signaling and to attract more attention and interest to this research area.

Mitochondrial Dysfunction in Periodontitis and Associated Systemic Diseases: Implications for Pathomechanisms and Therapeutic Strategies

Periodontitis is a chronic infectious disorder damaging periodontal tissues, including the gingiva, periodontal ligament, cementum, and alveolar bone. It arises from the complex interplay between pathogenic oral bacteria and host immune response. Contrary to the previous view of "energy factories", mitochondria have recently been recognized as semi-autonomous organelles that fine-tune cell survival, death, metabolism, and other functions. Under physiological conditions, periodontal tissue cells participate in dynamic processes, including differentiation, mineralization, and regeneration. These fundamental activities depend on properly functioning mitochondria, which play a crucial role through bioenergetics, dynamics, mitophagy, and quality control. However, during the initiation and progression of periodontitis, mitochondrial quality control is compromised due to a range of challenges, such as bacterial-host interactions, inflammation, and oxidative stress. Currently, mounting evidence suggests that mitochondria dysfunction serves as a common pathological mechanism linking periodontitis with systemic conditions like type II diabetes, obesity, and cardiovascular diseases. Therefore, targeting mitochondria to intervene in periodontitis and multiple associated systemic diseases holds great therapeutic potential. This review provides advanced insights into the interplay between mitochondria, periodontitis, and associated systemic diseases. Moreover, we emphasize the significance of diverse therapeutic modulators and signaling pathways that regulate mitochondrial function in periodontal and systemic cells.

Mitochondria: An Emerging Unavoidable Link in the Pathogenesis of Periodontitis Caused by Porphyromonas gingivalis

Porphyromonas gingivalis (P. gingivalis) is a key pathogen of periodontitis. Increasing evidence shows that P. gingivalis signals to mitochondria in periodontal cells, including gingival epithelial cells, gingival fibroblast cells, immune cells, etc. Mitochondrial dysfunction affects the cellular state and participates in periodontal inflammatory response through the aberrant release of mitochondrial contents. In the current review, it was summarized that P. gingivalis induced mitochondrial dysfunction by altering the mitochondrial metabolic state, unbalancing mitochondrial quality control, prompting mitochondrial reactive oxygen species (ROS) production, and regulating mitochondria-mediated apoptosis. This review outlines the impacts of P. gingivalis and its virulence factors on the mitochondrial function of periodontal cells and their role in periodontitis.

Interleukin-22 Inhibits Apoptosis of Gingival Epithelial Cells Through TGF-β Signaling Pathway During Periodontitis

Periodontitis is a chronic inflammatory disease characterized by the destruction of tooth-supporting tissues. The gingival epithelium is the first barrier of periodontal tissue against oral pathogens and harmful substances. The structure and function of epithelial lining are essential for maintaining the integrity of the epithelial barrier. Abnormal apoptosis can lead to the decrease of functional keratinocytes and break homeostasis in gingival epithelium. Interleukin-22 is a cytokine that plays an important role in epithelial homeostasis in intestinal epithelium, inducing proliferation and inhibiting apoptosis, but its role in gingival epithelium is poorly understood. In this study, we investigated the effect of interleukin-22 on apoptosis of gingival epithelial cells during periodontitis. Interleukin-22 topical injection and Il22 gene knockout were performed in experimental periodontitis mice. Human gingival epithelial cells were co-cultured with Porphyromonas gingivalis with interleukin-22 treatment. We found that interleukin-22 inhibited apoptosis of gingival epithelial cells during periodontitis in vivo and in vitro, decreasing Bax expression and increasing Bcl-xL expression. As for the underlying mechanisms, we found that interleukin-22 reduced the expression of TGF-β receptor type II and inhibited the phosphorylation of Smad2 in gingival epithelial cells during periodontitis. Blockage of TGF-β receptors attenuated apoptosis induced by Porphyromonas gingivalis and increased Bcl-xL expression stimulated by interleukin-22. These results confirmed the inhibitory effect of interleukin-22 on apoptosis of gingival epithelial cells and revealed the involvement of TGF-β signaling pathway in gingival epithelial cell apoptosis during periodontitis.

TGF-β signaling pathway: Therapeutic targeting and potential for anti-cancer immunity

Transforming growth factor-β (TGFβ) is a pleiotropic secretory cytokine exhibiting both cancer-inhibitory and promoting properties. It transmits its signals via Suppressor of Mother against Decapentaplegic (SMAD) and non-SMAD pathways and regulates cell proliferation, differentiation, invasion, migration, and apoptosis. In non-cancer and early-stage cancer cells, TGFβ signaling suppresses cancer progression via inducing apoptosis, cell cycle arrest, or anti-proliferation, and promoting cell differentiation. On the other hand, TGFβ may also act as an oncogene in advanced stages of tumors, wherein it develops immune-suppressive tumor microenvironments and induces the proliferation of cancer cells, invasion, angiogenesis, tumorigenesis, and metastasis. Higher TGFβ expression leads to the instigation and development of cancer. Therefore, suppressing TGFβ signals may present a potential treatment option for inhibiting tumorigenesis and metastasis. Different inhibitory molecules, including ligand traps, anti-sense oligo-nucleotides, small molecule receptor-kinase inhibitors, small molecule inhibitors, and vaccines, have been developed and clinically trialed for blocking the TGFβ signaling pathway. These molecules are not pro-oncogenic response-specific but block all signaling effects induced by TGFβ. Nonetheless, targeting the activation of TGFβ signaling with maximized specificity and minimized toxicity can enhance the efficacy of therapeutic approaches against this signaling pathway. The molecules that are used to target TGFβ are non-cytotoxic to cancer cells but designed to curtail the over-activation of invasion and metastasis driving TGFβ signaling in stromal and cancer cells. Here, we discussed the critical role of TGFβ in tumorigenesis, and metastasis, as well as the outcome and the promising achievement of TGFβ inhibitory molecules in the treatment of cancer.

Inorganic arsenic promotes apoptosis of human immortal keratinocytes through the TGF-β1/ERK signaling pathway

Chronic exposure to high-dose inorganic arsenic through groundwater, air, or food remains a major environmental public health issue worldwide. Apoptosis, a method of cell death, has recently become a hot topic of research in biology and medicine. Previous studies have demonstrated that extracellular signal-regulated kinase (ERK) is related to arsenic-induced apoptosis. However, the reports are contradictory, and the knowledge of the above-mentioned mechanisms and their mutual regulation remains limited. In this study, the associations between the TGF-β1/ERK signaling pathway and arsenic-induced cell apoptosis were confirmed using the HaCaT cell model. The relative expressions of the indicators of the TGF-β1/ERK signaling pathway, apoptosis-related genes (cytochrome C, caspase-3, caspase-9, cleaved caspase-3, cleaved caspase-9, and Bax), the mitochondrial membrane potential, and the total apoptosis rate were significantly increased (P < .05), while the expression of the antiapoptosis gene Bcl-2 was significantly decreased (P < .05) in cells of the group exposed to arsenic. Moreover, the results demonstrated that the ERK inhibitor (PD98059) and TGF-β1 inhibitor (LY364947) could inhibit the activation of the ERK signaling pathway, thereby reducing the mitochondrial membrane potential, the total apoptosis rate, and the expression of pro-apoptosis-related genes in the cells, while the expression of the antiapoptosis gene Bcl-2 was significantly increased (P < .05). By contrast, the recombinant human TGF-β1 could promote apoptosis of the HaCaT cells by increasing the activation of the ERK signaling pathway (P < .05). These results indicate that inorganic arsenic promotes the apoptosis of human immortal keratinocytes through the TGF-β1/ERK signaling pathway.

Human Endometrial Organoids: Recent Research Progress and Potential Applications

Since traditional two-dimensional (2D) cell culture cannot meet the demand of simulating physiological conditions in vivo, three-dimensional (3D) culture systems have been developed. To date, most of these systems have been applied for the culture of gastrointestinal and neural tissue. As for the female reproductive system, the culture of endometrial and oviductal tissues in Matrigel has also been performed, but there are still some problems that remain unsolved. This review highlights recent progress regarding endometrial organoids, focusing on the signal for organoid derivation and maintenance, the coculture of the epithelium and stroma, the drug screening using organoids from cancer patients, and provides a potential guideline for genome editing in endometrial organoids.

Gremlin aggravates periodontitis via activating the NF-κB signaling pathway

BACKGROUND

Gremlin has been reported to regulate inflammation and osteogenesis. Periodontitis is a destructive disease degenerating periodontal tissues, therefore leads to alveolar bone resorption and tooth loss. Based on the importance of Gremlin's bio-activity, the aim of this study is to, in vivo and in vitro, unveil the function of Gremlin in regulating the development of periodontitis and its consequent effects on alveolar bone loss.

METHODS

Clinical specimens were used to determine the expression of Gremlin in periodontal tissues by immunohistochemical staining and western blot. Then utilizing the rat periodontitis model to investigate the function of gremlin-regulated nuclear factor-kappa B (NF-κB) pathway during the development of periodontal inflammation and the alveolar bone loss. Lastly, the regulation of the osteogenesis of human periodontal ligament stem cells (hPDLSCs) by Gremlin under inflamed condition was analyzed by alkaline phosphatase (ALP) and alizarin red staining (ARS).

RESULTS

We found clinically and experimentally that the expression of Gremlin is markedly increased in periodontitis tissues. Interestingly, we revealed that Gremlin regulated the progress of periodontitis via regulating the activities of NF-κB pathway and interleukin-1β (IL-1β). Notably, we observed that Gremlin influenced the osteogenesis of hPDLSCs. Thus, our present study identified Gremlin as a new key regulator for development of periodontitis.

CONCLUSIONS

Our current study illustrated that Gremlin acts as a crucial mediator and possibly serves as a potential diagnostic marker for periodontitis. Discovery of new factors involved in the pathophysiology of periodontitis could contribute to the development of novel therapeutic treatment for the disease. This article is protected by copyright. All rights reserved.

Ginsenoside Rg3 Alleviates Aluminum Chloride-Induced Bone Impairment in Rats by Activating the TGF-β1/Smad Signaling Pathway

Aluminum (Al)-induced bone formation and metabolism disorder through inhibition of the TGF-β1/Smad signaling pathway is one of the important mechanisms of bone impairment. Ginsenoside Rg3 (Rg3), a specific biological effector molecule, can provide protection to bones. Previously, we demonstrated that Rg3 can reverse aluminum chloride (AlCl₃)-induced oxidative stress and metabolic disorder of bones; however, whether the TGF-β1/Smad signaling pathway is involved in it remains unclear. First, we found that Rg3 attenuated Al-induced bone impairment in vivo and in vitro by relieving structural damage to the femur, increasing MC3T3-E1 cell activity, differentiation, mineralization, inhibition of cell apoptosis, and upregulating the extracellular matrix (ECM) synthesis and the expression of TGF-β1/Smad signaling pathway key factors. Subsequently, in the signal pathway intervention experiment, the protective effect of Rg3 on bone impairment induced by Al was weakened; these results indicate that activating the TGF-β1/Smad signaling pathway is one of the mechanisms of Rg3-attenuated Al-induced bone impairment.

Effects of transforming growth factor-β1 on odontoblastic differentiation in dental papilla cells is determined by IPO7 expression level

Transforming growth factor β1 (TGF-β1) is one of the broad-spectrum growth-promoting factors that participate in tooth development. The influence of TGF-β1 on the odontoblastic differentiation is still controvercy. Mouse primary dental papilla cells (mDPCs) as well as an immortalized mouse dental papilla cell line (mDPC6Ts) were treated with exogenous TGF-β1 during odontoblastic differentiation. RT-qPCR, Western blot, alizarin red staining and ALP staining were carried out to investigate the influence of TGF-β1 on odontoblastic differentiation. IPO7, important for SMAD complex translocation was also detected in mDPCs and mDPC6Ts in response to TGF-β1. After silencing IPO7 by transfection, the translocation process of P-SMAD2 was investigated by nuclear and cytoplasmic extraction as well as co-immunoprecipitation assay. The odontogenic markers, mineralization and IPO7 expression were significantly up-regulated in TGF-β1-treated mDPCs while down-regulated in mDPC6Ts. The total level of P-SMAD2 was not influenced by IPO7 in mDPCs, however, IPO7 could bind to P-SMAD2 and affect the nuclear-cytoplasm-shuttling of P-SMAD2. Our data demonstrated that TGF-β1 plays opposite roles in odontoblast differentiation in mDPCs and immortalized mouse dental papilla cell line (mDPC6Ts), which is determined by IPO7.

NANOG regulates the proliferation of PCSCs via the TGF-β1/SMAD pathway

Purpose

In prostate cancer, castration resistance is a factor that frequently leads to death in individuals with this disease. Recent studies have suggested that prostate cancer stem cells (PCSCs) are pivotal regulators in the establishment of castration resistance. The nanog homeobox (NANOG) and the transforming growth factor (TGF)-β1/drosophila mothers against decapentaplegic protein (SMAD) signaling pathways are involved in several cancer stem cells but are not involved in PCSCs. The purpose of this study is to investigate the effect of NANOG on the proliferation of PCSCs regulated by the TGF-β1/SMAD signaling pathway.

Methods

In this study, we used flow cytometry to isolate CD44+/CD133+/NANOG+ PCSCs from DU145 prostate cancer cells. Then we used short hairpin RNA to silence NANOG and observed the biological behavior and the TGF-β1/SMAD signal of PCSCs.

Results

NANOG decreased PCSC proliferation, increased apoptosis, and blocked cell cycling at G0/G1. Furthermore, reduction in the TGF-β1, p15, and p-SMAD2 expression was observed.

Conclusion

These findings suggest that NANOG positively regulates the growth of PCSCs through the TGF-β1/SMAD signaling pathway.

UVA influenced the SIRT1-miR-27a-5p-SMAD2-MMP1/COL1/BCL2 axis in human skin primary fibroblasts

Both SIRT1 and UVA radiation are involved in cellular damage processes such as apoptosis, senescence and ageing. MicroRNAs (miRNAs) have been reported to be closely related to UV radiation, as well as to SIRT1. In this study, we investigated the connections among SIRT1, UVA and miRNA in human skin primary fibroblasts. Our results showed that UVA altered the protein level of SIRT1 in a time point–dependent manner. Using miRNA microarray, bioinformatics analysis, we found that knocking down SIRT1 could cause up‐regulation of miR‐27a‐5p and the latter could down‐regulate SMAD2, and these results were verified by qRT‐PCR or Western blot. Furthermore, UVA radiation (5 J/cm²), knocking down SIRT1 or overexpression of miR‐27a‐5p led to increased expression of MMP1, and decreased expressions of COL1 and BCL2. We also found additive impacts on MMP1, COL1 and BCL2 under the combination of UVA radiation + Sirtinol (SIRT1 inhibitor), or UVA radiation + miR‐27a‐5p mimic. SIRT1 activator resveratrol could reverse damage changes caused by UVA radiation. Besides, absent of SIRT1 or overexpression of miR‐27a‐5p increased cell apoptosis and induced cell arrest in G2/M phase. Taken together, these results demonstrated that UVA could influence a novel SIRT1‐miR‐27a‐5p‐SMAD2‐MMP1/COL1/BCL2 axis in skin primary fibroblasts, and may provide potential therapeutic targets for UVA‐induced skin damage.

Involvement of activin signal pathway in cyclic apoptosis of the oviductal isthmic epithelium in cows

Activin (ACV) A induces various cellular functions via activin receptor type 2 (ACVR2A/2B)-activin receptor-like kinase (ALK) 4 -Smad 2/3 pathway. Although the production of ACVA is indicated in bovine oviducts, its role on the oviduct is unclear. Oviductal isthmus needs to change its function rapidly at peri-fertilization, however, the mechanism is unknown. This study was aimed to clarify the role of ACVA in the morphological changes of oviductal isthmus in cows. First, mRNA expressions of INHBA (ACVA component) and its receptors (ALK4, ACVR2A and ACVR2B) in the isthmic tissues were examined throughout the estrous cycle. INHBA was the highest, however, ACVR2A was the lowest on the day of ovulation, suggesting reduced ACV signal transduction in the isthmus just after ovulation. Proteins of ACVRs and Smad2/3 were clearly detected in the cultured epithelial cells. It is known that ACVA regulates cellular apoptosis. Our data showed that the number of cleaved caspase-3-positive epithelial cells was largest at 2-3 days after ovulation in the isthmus. Interestingly, our study demonstrated that follistatin (ACV/TGFB/BMP inhibitor) significantly decreased the BCL2/BAX ratio in the cultured isthmic epithelial cells. To clarify which ALK pathway is involved in the regulation of BCL2/BAX ratio, the effects of SB431542 (ACV signaling (ALK4) and TGFB signaling (ALK5) inhibitor), SB525334 (ALK5 inhibitor) and LDN193189 (BMP signaling (ALK2/3) inhibitor) were investigated in the next study. The results showed that only SB431542 significantly decreased BCL2/BAX and the others had no effects. These results suggest that decreased ACVA-ACVR2A-ALK4 signal at the post-ovulation induces cyclic apoptosis of isthmic epithelial cells in bovine oviducts.

MiR-20a-5p suppressed TGF-β1-triggered apoptosis of human bronchial epithelial BEAS-2B cells by targeting STAT3

Apoptosis of bronchial epithelial cells contributes to lung diseases, including asthma. Although miR-20a-5p is reportedly downregulated in the bronchial epithelia of asthmatic patients, its function and mechanism still need to be explored. Here, we explored how miR-20a-5p affects human bronchial epithelial cells stimulated with transforming growth factor (TGF)-β₁. Using qRT-PCR, we observed downregulated miR-20a-5p levels in these cells. After transfecting miR-20a-5p mimics or inhibitors into human bronchial epithelium BEAS-2B cells, a Cell Counting Kit-8 assay and flow cytometry analysis showed that the mimics mitigated suppression of cell viability and acceleration of apoptosis that was triggered by TGF-β₁, whereas the inhibitors exerted the opposite effects. TGF-β₁ induced a decrease in expression of Bcl-2 and an increase in expression of Bax, both of which were inhibited by miR-20a-5p mimics and further enhanced by miR-20a-5p inhibitors. Further study verified that miR-20a-5p targeted the signal transducer and activator of transcription 3 (STAT3) and the STAT3 level was inversely related to the miR-20a-5p level. Furthermore, STAT3 overexpression partly counteracted the miR-20a-5p-induced anti-apoptotic effect in TGF-β1-treated BEAS-2B cells. In summary, this study suggested that miR-20a-5p restrained apoptosis in TGF-β1-stimulated BEAS-2B cells by targeting STAT3. MiR-20a-5p thus may be a novel therapeutic target for asthma treatment.

SMAD2 overexpression rescues the TGF-β3 null mutant mice cleft palate by increased apoptosis

During palatal development, medial edge epithelium (MEE) disappearance is one of the crucial steps in the process of fusion. The fate of these cells is still debated, and controversies remain. During secondary palate fusion, TGF-β3 signaling mediated in the cell through the SMAD2 protein plays an important role and leads to the disappearance of the midline epithelial seam (MES) and the confluence of the palatal mesenchyme. In mice, TGF-β3 knock-out is lethal and mice are born with a cleft in the secondary palate. This phenotype has been rescued by targeted overexpression of SMAD2 in the medial edge epithelium (MEE). The goal of this research was to understand the mechanism of palatal fusion in the rescue mice.

METHODS

The heads of embryos with four different genotypes (wild-type, K14-SMAD2/TGF-β3^(-/-), K14-SMAD2/TGF-β3^(±), and TGF-β3 null) were collected at embryonic day E14.5, genotyped, fixed and embedded in paraffin. Serial sections were studied for detection of apoptosis and epithelial mesenchymal transition using immunofluorescence.

RESULTS

TGF-β3 null mice developed a cleft in the secondary palate while both mice with K14-SMAD2 overexpression had fusion of the secondary palate. The MEE of both the rescue mice and K14-SMAD2 overexpression had a much higher ratio of apoptotic cells than wild-type mice. The increase in apoptosis was correlated with increased phospho-SMAD2 in the MEE.

CONCLUSION

SMAD2 overexpression rescued the cleft in the secondary palate by increasing apoptosis in the medial edge epithelium.

The role of FSH and TGF-β superfamily in follicle atresia

Most of the mammalian follicles undergo a degenerative process called “follicle atresia”. Apoptosis of granulosa cells is the main characteristic of follicle atresia. Follicle stimulating hormone (FSH) and the transforming growth factor β (TGF-β) superfamily have important regulatory functions in this process. FSH activates protein kinase A and cooperating with insulin receptor substrates, it promotes the PI3K/Akt pathway which weakens apoptosis. Both Smad or non-Smad signaling of the transforming growth factor β superfamily seem to be related to follicle atresia, and the effect of several important family members on follicle atresia is concluded in this article. FSH and TGF-β are likely to mutually influence each other and what we have already known about the possible underlying molecular mechanism is also discussed below.

MicroRNA-214 contributes to regulation of necroptosis via targeting ATF4 in diabetes-associated periodontitis

Diabetes and periodontal diseases have a mutual promoting relationship that induces severe tissue damage and cell death. The potential roles of microRNAs (miRNAs) and the type of cell death involved in diabetes-associated periodontitis are obscure. The gingival tissues of patients were obtained and MC3T3-E1 cells were costimulated with high glucose and lipopolysaccharide (LPS). Osseous morphometric analysis was evaluated with micro-CT, and histological characteristics were measured by hematoxylin/eosin and immunohistochemical staining. Cytokine secretion was confirmed by enzyme-linked immunosorbent assay, and reactive oxygen species (ROS) was measured using a DCFH-DA probe kit. Gene expression was measured by real-time quantitative reverse transcription PCR (qRT-PCR), and protein expression was assessed by Western blot and immunofluorescence analysis. The miR-214 level, receptor-interacting serine-threonine protein (RIP) 1, RIP3, and phospho-mixed lineage kinase domain-like (p-MLKL) protein expression were elevated in the inflamed gingival tissues of diabetes-associated periodontitis patients, with activating transcription factor 4 (ATF4) expression showing the opposite effect. The high glucose (22 mM) could not induce significant increase of RIP1, RIP3, and p-MLKL; however, the high glucose and LPS (500-1000 ng/mL) cotreatment resulted in increase in the number of RIP1, RIP3, and p-MLKL in MC3T3-E1 cells. NAC (ROS inhibitor) inhibited RIP1, RIP3, and increased ATF4; however, necrostatin-1 (Nec-1) (RIP1 inhibitor) specifically inhibited the protein expression of RIP1 and RIP3 and had no influence on ATF4. The use of antagomir-214 suppressed the expression of miR-214, RIP1, RIP3, and p-MLKL, but increased ATF4 protein level in glucose and LPS-induced cells. ATF4 knockdown by ATF4 small interfering RNA offset the effect of antagomir-214. RIP1- and RIP3-dependent necroptosis was confirmed in the inflamed gingival tissues of diabetes-associated periodontitis patients and high glucose- and LPS- cotreated cells. It was suggested that miR-214-targeted ATF4 participated in the regulation of necroptosis in vivo and in vitro.

Apoptosis Transcriptional Profile Induced by Porphyromonas gingivalis HmuY

This study aimed at evaluating the transcriptional profile of apoptosis-related genes after in vitro stimulation of peripheral blood mononuclear cells (PBMCs) derived from individuals with periodontitis (P) and healthy nonperiodontitis (NP) control subjects with P. gingivalis HmuY protein. PBMCs from the P and NP groups were stimulated with HmuY P. gingivalis protein, and the expression of genes related to apoptosis was assessed by custom real-time polymerase chain reaction array (Custom RT2 PCR Array). Compared with the NP group, the P group showed low relative levels of apoptosis-related gene expression, downregulated for FAS, FAS ligand, TNFSF10 (TRAIL), BAK1, CASP9, and APAF1 after P. gingivalis HmuY protein stimulation. Furthermore, the P group exhibited low levels of relative gene expression, downregulated for CASP7 when the cells were not stimulated. Our data suggest that P. gingivalis HmuY protein might participate differently in the modulation of the intrinsic and extrinsic apoptosis pathways.

Novel miRNA expression in the delta opioid signaling pathway mediated cell survivability in an in vitro model of ER stress

Micro RNAs (miRNAs) are small non-coding RNAs which bind to the 3'-untranslated region of a mature mRNA to induce degradation; thereby regulating gene expression. It is reported that dysregulated miRNAs involved in neurodegenerative diseases including Parkinson's disease, could play a significant role as prognostic markers and therapeutic targets. Neuroprotective effect of delta opioid receptors (DOR) and its known miRNA regulation against endoplasmic reticulum (ER) stress have been reported previously by our lab. Current study focuses on understanding the regulation of novel miRNAs by DOR under ER stress. Novel miRNAs were identified for three different samples; control, tunicamycin (ER stress inducer), and tunicamycin+DADLE (DOR agonist). Differentially regulated miRNAs between the different samples were identified and pathway/target genes analysis was carried out. The results suggest that following DOR activation novel miRNAs like xxx-m0073-3p, xxx-m0225-3p, xxx-m0088-3p, xxx-m0098-5p etc. could regulate cell survival mechanisms in neuronal cells (SH-SY5Y) under ER stress.

Negative feedback by SNAI2 regulates TGFβ1-induced amelotin gene transcription in epithelial-mesenchymal transition

Junctional epithelium (JE) demonstrates biological responses with the rapid turnover of gingival epithelial cells. The state occurs in inflammation of gingiva and wound healing after periodontal therapy. To understand the underlying mechanisms and to maintain homeostasis of JE, it is important to investigate roles of JE-specific genes. Amelotin (AMTN) is localized at JE and regulated by inflammatory cytokines and apoptotic factors that represent a critical role of AMTN in stabilizing the dentogingival attachment, which is an entrance of oral bacteria. In this study, we demonstrated that the AMTN gene expression was regulated by SNAI2 and transforming growth factor β1 (TGFβ1)-induced epithelial-mesenchymal transition (EMT) that occurs in wound healing and fibrosis during chronic inflammation. SNAI2 downregulated AMTN gene expression via SNAI2 bindings to E-boxes (E2 and E4) in the mouse AMTN gene promoter in EMT of gingival epithelial cells. Meanwhile, TGFβ1-induced AMTN gene expression was attenuated by SNAI2 and TGFβ1-induced SNAI2, without inhibition of the TGFβ1-Smad3 signaling pathway. Moreover, SNAI2 small interfering RNA (siRNA) rescued SNAI2-induced downregulation of AMTN gene expression, and TGFβ1-induced AMTN gene expression was potentiated by SNAI2 siRNA. Taken together, these data demonstrated that AMTN gene expression in the promotion of EMT was downregulated by SNAI2. The inhibitory effect of AMTN gene expression was an independent feedback on the TGFβ1-Smad3 signaling pathway, suggesting that the mechanism can be engaged in maintaining homeostasis of gingival epithelial cells at JE and the wound healing phase.

Transforming Growth Factor β1 (TGF-β1) Appears to Promote Coronary Artery Disease by Upregulating Sphingosine Kinase 1 (SPHK1) and Further Upregulating Its Downstream TIMP-1

BACKGROUND Transforming growth factor (TGF)-β1 is involved in the pathogenesis of coronary artery disease (CAD), but the mechanism of its action remains unclear. Our study aimed to investigate the role of TGF-β1 in CAD and to explore the possible mechanisms. MATERIAL AND METHODS A total of 60 CAD patients and 54 healthy people were included in this study. Blood samples were drawn from each participant to prepare serum. ELISA was utilized to measure serum level of TGF-β1. TGF-β1 expression vector, TGF-β1 siRNA, and TIMP-1 siRNA were transfected into human primary coronary artery endothelial cell (HCAEC) line cells, and expression of TGF-β1 sphingosine kinase 1 (SPHK1) and TIMP metallopeptidase inhibitor 1 (TIMP-1) was detected by Western blot. Cell apoptosis was detected by MTT assay. RESULTS Serum level of TGF-β1 was specifically higher in patients with CAD than in healthy controls. Serum levels of active TGF-β1 can be used to effectively distinguish CAD patients from healthy controls. TGF-β1 overexpression promoted the apoptosis of HCAEC and TGF-β1 siRNA silencing inhibited the apoptosis of HCAEC. TGF-β1 overexpression also promoted the expression of SPHK1 and TIMP-1. SPHK1 overexpression upregulated TIMP-1 but it showed no significant effects on TGF-β1. TIMP-1 overexpression showed no significant effects on TGF-β1 or SPHK1. SPHK1 inhibitor and TIMP-1 silencing reduced the enhancing effects of TGF-β1 overexpression on cell apoptosis. CONCLUSIONS TGF-β1 appears to promote CAD through the induction of cell apoptosis by upregulating SPHK1 expression and further upregulating its downstream TIMP-1.

ZnSO4 rescued vimentin from collapse in DBP-exposed Sertoli cells by attenuating ER stress and apoptosis

Sertoli cells (SCs) provide physical and nutritional support for spermatogenesis. Dibutyl phthalate (DBP) is a plasticizer that has male reproductive toxicity. The collapse of vimentin in DBP-exposed SCs is thought to induce the sloughing of spermatocytes from seminiferous tubules. In this study, we explored methods to rescue vimentin from collapse in DBP-exposed SCs. DBP not only induced the hyperphosphorylation of vimentin but also triggered endoplasmic reticulum (ER) stress and apoptosis in SCs. Treatment with BAPTA-AM, an antagonist of Ca²⁺, significantly decreased the level of phosphorylated vimentin, while LY294002, an inhibitor of Akt1, did not. ER stress and apoptosis remained at high levels, and the distribution of vimentin was not improved. ZnSO₄ treatment did not decrease the level of phosphorylated vimentin. However, after treatment, ER stress and apoptosis were obviously inhibited, and the distribution of vimentin was reconverted. These results indicated that ZnSO₄ could alleviate the collapse of vimentin by attenuating ER stress and apoptosis. This study suggested that an appropriate zinc supply might be a choice to alleviate DBP-induced adverse reproductive effects.

TGFβ1-induced Amelotin gene expression is downregulated by Bax expression in mouse gingival epithelial cells

Amelotin (AMTN) is induced upon initiation of apoptosis by transforming growth factor beta1 (TGFβ1) and is mediated by Smad3 in gingival epithelial cells (GE1 cells). This upregulation of AMTN gene expression is temporary, and the mechanism responsible is still unclear. The present study investigated the transcriptional downregulation of TGFβ1-induced AMTN gene expression in GE1 cells during the progression of apoptosis. To examine time-dependent changes in the levels of AMTN, Smad3 and Bax mRNA induced by TGFβ1, real-time PCR analyses were performed. Immunocytochemistry was carried out to detect the expression of Smad3 and Bax. Transient transfection analyses were performed using mouse AMTN gene promoter constructs of various lengths including Smad response elements (SBEs), in the presence or absence of TGFβ1. Changes in Smad3 binding to SBEs resulting from overexpression of Bax were examined using ChIP assays. Overexpression of Bax dramatically downregulated the levels of TGFβ1-induced AMTN mRNA and transcription of the AMTN gene. Smad3 binding to SBEs in the mouse AMTN gene promoter was induced by overexpression of Smad3 or TGFβ1, and this was inhibited by Bax overexpression. These results show that the levels of AMTN mRNA induced by TGFβ1 and Smad3 are decreased by robust expression of Bax in gingival epithelial cells.

Amelotin gene expression is temporarily being upregulated at the initiation of apoptosis induced by TGFβ1 in mouse gingival epithelial cells

Amelotin (AMTN) is expressed and secreted by ameloblasts in the maturation stage of amelogenesis and persist with low levels in the junctional epithelium (JE) of erupted teeth. The purpose of this study is to investigate the transcriptional regulation of the AMTN gene by transforming growth factor beta1 (TGFβ1) in gingival epithelial (GE1) cells in the apoptosis phase. Apoptosis was evaluated by the fragmentation of chromosomal DNA and TUNEL staining. A real-time PCR was carried out to examine the AMTN mRNA levels induced by TGFβ1 and Smad3 overexpression. Transient transfection analyses were completed using the various lengths of mouse AMTN gene promoter constructs with or without TGFβ1. Chromatin immunoprecipitation (ChIP) assays were performed to investigate the Smad3 bindings to the AMTN gene promoter by TGFβ1. TGFβ1-induced apoptosis in GE1 cells were detected at 24 and 48 h by DNA fragmentation and TUNEL staining. AMTN mRNA levels increased at 6 h and reached maximum at 24 h in GE1 cells. Luciferase activities of the mouse AMTN gene promoter constructs were induced by TGFβ1. The results of the ChIP assays showed that there was an increase in Smad3 binding to Smad-binding element (SBE)#1 and SBE#2 after stimulation by TGFβ1. Immunohistochemical localization of AMTN was detected in the JE, and the AMTN protein levels in Smad3-deficient mice were decreased compared with wild-type mice. AMTN mRNA levels were induced at the initiation of apoptosis by TGFβ1, which mediated through the Smad3 bindings to SBEs in the mouse AMTN gene promoter.

GP73 promotes invasion and metastasis of bladder cancer by regulating the epithelial-mesenchymal transition through the TGF-β1/Smad2 signalling pathway

This study investigated the effects of Golgi membrane protein 73 (GP73) on the epithelial-mesenchymal transition (EMT) and on bladder cancer cell invasion and metastasis through the TGF-β1/Smad2 signalling pathway. Paired bladder cancer and adjacent tissue samples (102) and normal bladder tissue samples (106) were obtained. Bladder cancer cell lines (T24, 5637, RT4, 253J and J82) were selected and assigned to blank, negative control (NC), TGF-β, thrombospondin-1 (TSP-1), TGF-β1+ TSP-1, GP73-siRNA-1, GP73-siRNA-2, GP73-siRNA-1+ TSP-1, GP73-siRNA-1+ pcDNA-GP73, WT1-siRNA and WT1-siRNA + GP73-siRNA-1 groups. Expressions of GP73, TGF-β1, Smad2, p-Smad2, E-cadherin and vimentin were detected using RT-qPCR and Western blotting. Cell proliferation, migration and invasion were determined using MTT assay, scratch testing and Transwell assay, respectively. Compared with the blank and NC groups, levels of GP73, TGF-β1, Smad2, p-Smad2, N-cadherin and vimentin decreased, and levels of WT1 and E-cadherin increased in the GP73-siRNA-1 and GP73-siRNA-2 groups, while the opposite results were observed in the WT1 siRNA, TGF-β, TSP-1 and TGF-β + TSP-1 groups. Cell proliferation, migration and invasion notably decreased in the GP73-siRNA-1 and GP73-siRNA-2 groups in comparison with the blank and NC groups, while in the WT1 siRNA, TGF-β, TSP-1 and TGF-β + TSP-1 groups, cell migration, invasion and proliferation showed the reduction after the EMT. These results suggest that GP73 promotes bladder cancer invasion and metastasis by inducing the EMT through down-regulating WT1 levels and activating the TGF-β1/Smad2 signalling pathway.

Immunolocalization of connective tissue growth factor, transforming growth factor-beta1 and phosphorylated-SMAD2/3 during the postnatal tooth development and formation of junctional epithelium

Connective tissue growth factor (CTGF) is a downstream mediator of transforming growth factor-beta 1 (TGF-β₁) and TGF-β₁-induced CTGF expression is regulated through SMAD pathway. However, there is no literature showing the expression of TGF-β₁-SMAD2/3-CTGF signaling pathway during postnatal tooth development and the formation of junctional epithelium (JE). Hence, we aimed to analyze the localization of TGF-β₁, CTGF and phosphorylated SMAD2/3 (p-SMAD2/3) in the developing postnatal rat molars. Wistar rats were killed at postnatal (PN) 0.5, 3.5, 7, 14 and 21days and the upper jaws were processed for immunohistochemistry. At PN0.5 and PN3.5, weak staining for TGF-β₁ and CTGF was evident in preameloblasts (PA), while moderate to strong staining was seen in odontoblasts (OD), dental papilla (DPL), secretary ameloblasts (SA), preodontoblasts (PO) and polarized odontoblasts (PoO). There was no staining for p-SMAD2/3 in PA, SA, PO and PoO, although strong staining was localized in DPL. OD was initially moderately positive and then negative for p-SMAD2/3. At PN7, intense staining for TGF-β₁ and CTGF was observed in SA, OD, dental pulp (DP) and predentin respectively. p-SMAD2/3 was strongly expressed in DP and moderately expressed in SA and OD. At PN14 and PN21, both reduced enamel epithelium (REE) and JE showed a strong reaction for TGF-β₁ and CTGF. p-SMAD2/3 was intensely and weakly expressed in REE and JE respectively. These data demonstrate that the expression of CTGF, TGF-β₁ and p-SNAD2/3 is tissue-specific and stage-specific, and indicate a regulatory role for a TGF-β₁-SMAD2/3-CTGF signaling pathway in amelogenesis, dentinogenesis and formation of JE.

TGF‑β signaling: A complex role in tumorigenesis (Review)

Tumor progression can be affected by various cellular components of tumor cells and/or by tumor microenvironmental factors. The tumor microenvironment comprises a variety of nonmalignant stromal cells and inflammatory cytokines, which are pivotal in tumor promotion and progression. The transforming growth factor‑β (TGF‑β) ligands (TGF‑β1, 2 and 3) are secreted inflammatory cytokines, which are known to be involved in various aspects of tumor development through two transmembrane serine‑threonine kinase receptors, TGFβR1 and TGFβR2. TGF‑β promotes or inhibits tumorigenesis depending on the concurrent gene mutations and tissue microenvironment present through the small mothers against decapentaplegic (Smad) and non‑Smad pathways. This review aims to provide a comprehensive overview of the role of the TGF‑β pathway in tumor initiation and progression.

Differential expression of transforming growth factor-beta1, connective tissue growth factor, phosphorylated-SMAD2/3 and phosphorylated-ERK1/2 during mouse tooth development

Connective tissue growth factor (CTGF) is a downstream mediator of transforming growth factor-beta 1 (TGF-β₁) and TGF-β₁-induced CTGF expression is regulated through SMAD and mitogen-activated protein kinase (MAPK) signaling pathways. The fine modulation of TGF-β₁ signaling is very important to the process of tooth development. However, little is known about the localization of CTGF, MAPK and SMAD in the context of TGF-β₁ signaling during odontogenesis. Hence, we aimed to investigate the expression of TGF-β₁, CTGF, phosphorylated-SMAD2/3 (p-SMAD2/3) and phosphorylated-ERK1/2 (p-ERK1/2). ICR mice heads of embryonic (E) day 13.5, E14.5, E16.5, postnatal (PN) day 0.5 and PN3.5 were processed for immunohistochemistry. Results revealed that at E13.5, TGF-β₁ and CTGF were strongly expressed in dental epithelium (DE) and dental mesenchyme (DM), while p-SMAD2/3 was intensely expressed in the internal side of DE. p-ERK1/2 was not present in DE or DM. At E14.5 and E16.5, strong staining for TGF-β₁ and CTGF was detected in enamel knot (EK) and dental papilla (DPL). DPL was intensely stained for p-ERK1/2 but negatively stained for p-SMAD2/3. There was no staining for p-SMAD2/3 and p-ERK1/2 in EK. At PN0.5 and PN3.5, moderate to intense staining for TGF-β₁ and CTGF was evident in preameloblasts (PA), secretary ameloblasts (SA) and dental pulp (DP). p-SMAD2/3 was strongly expressed in SA and DP but sparsely localized in PA. p-ERK1/2 was intensely expressed in DP, although negative staining was observed in PA and SA. These data demonstrate that TGF-β₁ and CTGF show an identical expression pattern, while p-SMAD2/3 and p-ERK1/2 exhibit differential expression, and indicate that p-SMAD2/3 and p-ERK1/2 might play a regulatory role in TGF-β₁ induced CTGF expression during tooth development.

Azithromycin ameliorates airway remodeling via inhibiting airway epithelium apoptosis

AIMS

Azithromycin can benefit treating allergic airway inflammation and remodeling. In the present study, we hypothesized that azithromycin alleviated airway epithelium injury through inhibiting airway epithelium apoptosis via down regulation of caspase-3 and Bax/Bcl2 ratio in vivo and in vitro.

MAIN METHODS

Ovalbumin induced rat asthma model and TGF-β1-induced BEAS-2B cell apoptosis model were established, respectively. In vivo experiments, airway epithelium was stained with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) to histologically evaluate the airway inflammation and remodeling. Airway epithelium apoptotic index (AI) was further analyzed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), while expression of apoptosis related gene (Bax, Bcl2, Caspase-3) in lungs were measured by qRT-PCR and western blotting, respectively. In vitro experiments, apoptosis were evaluated by Flow cytometry (FCM) and TUNEL. Above apoptosis related gene were also measured by qRT-PCR and western blotting.

KEY FINDINGS

Compared with the OVA group, azithromycin significantly reduced the inflammation score, peribronchial smooth muscle layer thickness, epithelial thickening and goblet cell metaplasia (P<0.05), and effectively suppressed AI of airway epithelium (P<0.05). Moreover, the increasing mRNA and protein expressions of Caspase-3 and Bax/Bcl-2 ratio in lung tissue were all significantly decreased in azithromycin-treated rats (P<0.05). In vitro, azithromycin significantly suppressed TGF-β1-induced BEAS-2B cells apoptosis (P<0.05) and reversed TGF-β1 elevated Caspase-3 mRNA level and Bax/Bcl-2 ratio (P<0.05).

SIGNIFICANCE

Azithromycin is an attractive treatment option for reducing airway epithelial cell apoptosis by improving the imbalance of Bax/Bcl-2 ratio and inhibiting Caspase-3 level in airway epithelium.

Programmed cell death in periodontitis: recent advances and future perspectives

Periodontitis is a highly prevalent infectious disease, characterized by destruction of the periodontium, and is the main cause of tooth loss. Periodontitis is initiated by periodontal pathogens, while other risk factors including smoking, stress, and systemic diseases aggravate its progression. Periodontitis affects many people worldwide, but the molecular mechanisms by which pathogens and risk factors destroy the periodontium are unclear. Programmed cell death (PCD), different from necrosis, is an active cell death mediated by a cascade of gene expression events and can be mainly classified into apoptosis, autophagy, necroptosis, and pyroptosis. Although PCD is involved in many inflammatory diseases, its correlation with periodontitis is unclear. After reviewing the relevant published articles, we found that apoptosis has indeed been reported to play a role in periodontitis. However, the role of autophagy in periodontitis needs further verification. Additionally, implication of necroptosis or pyroptosis in periodontitis remains unknown. Therefore, we recommend future studies, which will unravel the pivotal role of PCD in periodontitis, allowing us to prevent, diagnose, and treat the disease, as well as predict its outcomes.

Aggregatibacter actinomycetemcomitans outer membrane protein 29 (Omp29) induces TGF-β-regulated apoptosis signal in human gingival epithelial cells via fibronectin/integrinβ1/FAK cascade

Gingival junctional epithelial cell apoptosis caused by periodontopathic bacteria exacerbates periodontitis. This pathological apoptosis is involved in the activation of transforming growth factor β (TGF-β). However, the molecular mechanisms by which microbes induce the activation of TGF-β remain unclear. We previously reported that Aggregatibacter actinomycetemcomitans (Aa) activated TGF-β receptor (TGF-βR)/smad2 signalling to induce epithelial cell apoptosis, even though Aa cannot bind to TGF-βR. Additionally, outer membrane protein 29 kDa (Omp29), a member of the Aa Omps family, can induce actin rearrangements via focal adhesion kinase (FAK) signalling, which also plays a role in the activation of TGF-β by cooperating with integrin. Accordingly, we hypothesized that Omp29-induced actin rearrangements via FAK activity would enhance the activation of TGF-β, leading to gingival epithelial cell apoptosis in vitro. By using human gingival epithelial cell line OBA9, we found that Omp29 activated TGF-βR/smad2 signalling and decreased active TGF-β protein levels in the extracellular matrix (ECM) of cell culture, suggesting the transactivation of TGF-βR. Inhibition of actin rearrangements by cytochalasin D or blebbistatin and knockdown of FAK or integrinβ1 expression by siRNA transfection attenuated TGF-βR/smad2 signalling activity and reduction of TGF-β levels in the ECM caused by Omp29. Furthermore, Omp29 bound to fibronectin (Fn) to induce its aggregation on integrinβ1, which is associated with TGF-β signalling activity. All the chemical inhibitors and siRNAs tested blocked Omp29-induced OBA9 cells apoptosis. These results suggest that Omp29 binds to Fn in order to facilitate Fn/integrinβ1/FAK signalling-dependent TGF-β release from the ECM, thereby inducing gingival epithelial cell apoptosis via TGF-βR/smad2 pathway.