Integrated NLRP3, AIM2, NLRC4, Pyrin inflammasome activation and assembly drive PANoptosis.

Inflammasomes are important sentinels of innate immune defense; they sense pathogens and induce the cell death of infected cells, playing key roles in inflammation, development, and cancer. Several inflammasome sensors detect and respond to specific pathogen- and damage-associated molecular patterns (PAMPs and DAMPs, respectively) by forming a multiprotein complex with the adapters ASC and caspase-1. During disease, cells are exposed to several PAMPs and DAMPs, leading to the concerted activation of multiple inflammasomes. However, the molecular mechanisms that integrate multiple inflammasome sensors to facilitate optimal host defense remain unknown. Here, we discovered that simultaneous inflammasome activation by multiple ligands triggered multiple types of programmed inflammatory cell death, and these effects could not be mimicked by treatment with a pure ligand of any single inflammasome. Furthermore, NLRP3, AIM2, NLRC4, and Pyrin were determined to be members of a large multiprotein complex, along with ASC, caspase-1, caspase-8, and RIPK3, and this complex drove PANoptosis. Furthermore, this multiprotein complex was released into the extracellular space and retained as multiple inflammasomes. Multiple extracellular inflammasome particles could induce inflammation after their engulfment by neighboring macrophages. Collectively, our findings define a previously unknown regulatory connection and molecular interaction between inflammasome sensors, which drives the assembly of a multiprotein complex that includes multiple inflammasome sensors and cell death regulators. The discovery of critical interactions among NLRP3, AIM2, NLRC4, and Pyrin represents a new paradigm in understanding the functions of these molecules in innate immunity and inflammasome biology as well as identifying new therapeutic targets for NLRP3-, AIM2-, NLRC4- and Pyrin-mediated diseases.

In Vivo Differentiation of Therapeutic Insulin-Producing Cells from Bone Marrow Cells via Extracellular Vesicle-Mimetic Nanovesicles.

The current diabetes mellitus pandemic constitutes an important global health problem. Reductions in the mass and function of ß-cells contribute to most of the pathophysiology underlying diabetes. Thus, physiological control of blood glucose levels can be adequately restored by replacing functioning ß-cell mass. Sources of functional islets for transplantation are limited, resulting in great interest in the development of alternate sources, and recent progress regarding cell fate change via utilization of extracellular vesicles, also known as exosomes and microvesicles, is notable. Thus, this study investigated the therapeutic capacity of extracellular vesicle-mimetic nanovesicles (NVs) derived from a murine pancreatic ß-cell line. To differentiate insulin-producing cells effectively, a three-dimensional in vivo microenvironment was constructed in which extracellular vesicle-mimetic NVs were applied to subcutaneous Matrigel platforms containing bone marrow (BM) cells in diabetic immunocompromised mice. Long-term control of glucose levels was achieved over 60 days, and differentiation of donor BM cells into insulin-producing cells in the subcutaneous Matrigel platforms, which were composed of islet-like cell clusters with extensive capillary networks, was confirmed along with the expression of key pancreatic ß-cell markers. The resectioning of the subcutaneous Matrigel platforms caused a rebound in blood glucose levels and confirmed the source of functioning ß-cells. Thus, efficient differentiation of therapeutic insulin-producing cells was attained in vivo through the use of extracellular vesicle-mimetic NVs, which maintained physiological glucose levels.

Murine Sca1(+)Lin(-) bone marrow contains an endodermal precursor population that differentiates into hepatocytes.

The direct differentiation of hepatocytes from bone marrow cells remains controversial. Several mechanisms, including transdifferentiation and cell fusion, have been proposed for this phenomenon, although direct visualization of the process and the underlying mechanisms have not been reported. In this study, we established an efficient in vitro culture method for differentiation of functioning hepatocytes from murine lineage-negative bone marrow cells. These cells reduced liver damage and incorporated into hepatic parenchyma in two independent hepatic injury models. Our simple and efficient in vitro protocol for endodermal precursor cell survival and expansion enabled us to identify these cells as existing in Sca1(+) subpopulations of lineage-negative bone marrow cells. The endodermal precursor cells followed a sequential developmental pathway that included endodermal cells and hepatocyte precursor cells, which indicates that lineage-negative bone marrow cells contain more diverse multipotent stem cells than considered previously. The presence of equivalent endodermal precursor populations in human bone marrow would facilitate the development of these cells into an effective treatment modality for chronic liver diseases.

Osteo-/odontogenic differentiation of induced mesenchymal stem cells generated through epithelial-mesenchyme transition of cultured human keratinocytes.

INTRODUCTION: Revascularization of necrotic pulp has been successful in the resolution of periradicular inflammation; yet, several case studies suggest the need for cell-based therapies using mesenchymal stem cells (MSCs) as an alternative for de novo pulp regeneration. Because the availability of MSCs may be limited, especially in an aged population, the current study reports an alternative approach in generating MSCs from epidermal keratinocytes through a process called epithelial-mesenchymal transition (EMT). METHODS: We induced EMT in primary normal human epidermal keratinocytes (NHEKs) by transient transfection of small interfering RNA targeting the p63 gene. The resulting cells were assayed for their mesenchymal marker expression, proliferation capacities as a monolayer and in a 3-dimensional collagen scaffold, and differentiation capacities. RESULTS: Transient transfection of p63 small-interfering RNA successfully abolished the expression of endogenous p63 in NHEKs and induced the expression of mesenchymal markers (eg, vimentin and fibronectin), whereas epithelial markers (eg, E-cadherin and involucrin) were lost. The NHEKs exhibiting the EMT phenotype acquired extended replicative potential and an increased telomere length compared with the control cells. Similar to the established MSCs, the NHEKs with p63 knockdown showed attachment onto the 3-dimensional collagen scaffold and underwent progressive proliferation and differentiation. Upon differentiation, these EMT cells expressed alkaline phosphatase activity, osteocalcin, and osteonectin and readily formed mineralized nodules detected by alizarin S red staining, showing osteo-/odontogenic differentiation. CONCLUSIONS: The induction of EMT in primary NHEKs by means of transient p63 knockdown allows the generation of induced MSCs from autologous sources. These cells may be used for tissues engineering purposes, including that of dental pulp.

Extracellular signal-regulated kinase is a direct target of the anti-inflammatory compound amentoflavone derived from Torreya nucifera.

Amentoflavone is a biflavonoid compound with antioxidant, anticancer, antibacterial, antiviral, anti-inflammatory, and UV-blocking activities that can be isolated from Torreya nucifera, Biophytum sensitivum, and Selaginella tamariscina. In this study, the molecular mechanism underlying amentoflavone's anti-inflammatory activity was investigated. Amentoflavone dose dependently suppressed the production of nitric oxide (NO) and prostaglandin E2 (PGE2) in RAW264.7 cells stimulated with the TLR4 ligand lipopolysaccharide (LPS; derived from Gram-negative bacteria). Amentoflavone suppressed the nuclear translocation of c-Fos, a subunit of activator protein (AP)-1, at 60 min after LPS stimulation and inhibited the activity of purified and immunoprecipitated extracellular signal-regulated kinase (ERK), which mediates c-Fos translocation. In agreement with these results, amentoflavone also suppressed the formation of a molecular complex including ERK and c-Fos. Therefore, our data strongly suggest that amentoflavone's immunopharmacological activities are due to its direct effect on ERK.

Efavirenz induces autophagy and aberrant differentiation in normal human keratinocytes.

Although efavirenz (EFV) is efficacious as an antiretroviral therapy when combined with other antiretroviral drugs, it may cause adverse clinical effects, including skin and mucosal eruptions, central nervous system complications, hepatotoxicity, renal failure and pulmonary complications. The present study investigated the phenotypic alterations caused by EFV in normal human keratinocytes (NHKs) and determined the cell death pathways leading to the lack of epithelial proliferation and regeneration. Replication kinetics, cellular morphology, and protein and mRNA levels of cell cycle regulatory genes and cell death markers were compared between the EFV-exposed cells and the untreated control. EFV treatment led to cell proliferation arrest and cell death of the NHKs by inducing autophagy mediated by proteasome-dependent degradation of p53. EFV also reduced the levels of mTOR and active ERK signaling in NHKs. Chemical inhibition of p53 degradation with a proteasome inhibitor led to reduced autophagic response of NHKs to EFV. In addition, EFV triggered terminal differentiation of NHKs by inducing the expression of involucrin, filaggrin, loricrin and genes involved in cornified envelope formation. Inhibition of autophagy in the EFV-treated NHKs with 3-methylalanine reduced the levels of involucrin and the extent of cell death. Our data indicate that EFV elicits cytotoxic effects on NHKs in part through induction of autophagy and aberrant differentiation of cells.

Radical scavenging activity-based and AP-1-targeted anti-inflammatory effects of lutein in macrophage-like and skin keratinocytic cells.

Lutein is a naturally occurring carotenoid with antioxidative, antitumorigenic, antiangiogenic, photoprotective, hepatoprotective, and neuroprotective properties. Although the anti-inflammatory effects of lutein have previously been described, the mechanism of its anti-inflammatory action has not been fully elucidated. Therefore, in the present study, we aimed to investigate the regulatory activity of lutein in the inflammatory responses of skin-derived keratinocytes or macrophages and to elucidate the mechanism of its inhibitory action. Lutein significantly reduced several skin inflammatory responses, including increased expression of interleukin-(IL-) 6 from LPS-treated macrophages, upregulation of cyclooxygenase-(COX-) 2 from interferon- γ /tumor necrosis-factor-(TNF-) α -treated HaCaT cells, and the enhancement of matrix-metallopeptidase-(MMP-) 9 level in UV-irradiated keratinocytes. By evaluating the intracellular signaling pathway and the nuclear transcription factor levels, we determined that lutein inhibited the activation of redox-sensitive AP-1 pathway by suppressing the activation of p38 and c-Jun-N-terminal kinase (JNK). Evaluation of the radical and ROS scavenging activities further revealed that lutein was able to act as a strong anti-oxidant. Taken together, our findings strongly suggest that lutein-mediated AP-1 suppression and anti-inflammatory activity are the result of its strong antioxidative and p38/JNK inhibitory activities. These findings can be applied for the preparation of anti-inflammatory and cosmetic remedies for inflammatory diseases of the skin.

Hydroquinone regulates hemeoxygenase-1 expression via modulation of Src kinase activity through thiolation of cysteine residues.

The hydroxylated benzene metabolite hydroquinone (HQ) is mainly generated from benzene, an important industrial chemical, and is also a common dietary component. Although numerous papers have addressed the potential role of HQ in tumorigenic responses, the immunosuppressive and anti-inflammatory effects of hydroquinone have also been considered. In this study, we characterized the mechanism of the induction of hemeoxygenase (HO)-1 and other phase 2 enzymes by HQ and its derivatives. HQ upregulated the mRNA and protein levels of HO-1 by increasing the antioxidant-response element-dependent transcriptional activation of Nrf-2. Src knockdown or deficiency induced via siRNA treatment and infection with a retrovirus expressing shRNA targeting Src, as well as exposure to PP2, a Src kinase inhibitor, strongly abrogated HO-1 expression. Interestingly, HQ directly targeted and bound to the sulfhydryl group of cysteine-483 (C483) and C400 residues of Src, potentially leading to disruption of intracellular disulfide bonds. Src kinase activity was dramatically enhanced by mutation of these cysteine sites, implying that these sites may play an important role in the regulation of Src kinase activity. Therefore, our data suggest that Src and, particularly, its C483 target site can be considered as prime molecular targets of the HQ-mediated induction of phase 2 enzymes, which is potentially linked to HO-1-mediated cellular responses such as immunosuppressive and anti-inflammatory actions.

Involvement of Src and the actin cytoskeleton in the antitumorigenic action of adenosine dialdehyde.

Transmethylation is an important reaction that transfers a methyl group in S-adenosylmethionine (SAM) to substrates such as DNA, RNA, and proteins. It is known that transmethylation plays critical roles in various cellular responses. In this study, we examined the effects of transmethylation on tumorigenic responses and its regulatory mechanism using an upregulation strategy of adenosylhomocysteine (SAH) acting as a negative feedback inhibitor. Treatment with adenosine dialdehyde (AdOx), an inhibitor of transmethylation-suppressive adenosylhomocysteine (SAH) hydrolase (SAHH), enhanced the level of SAH and effectively blocked the proliferation, migration, and invasion of cancer cells; the treatment also induced the differentiation of C6 glioma cells and suppressed the neovascular genesis of eggs in a dose-dependent manner. Through immunoblotting analysis, it was found that AdOx was capable of indirectly diminishing the phosphorylation of oncogenic Src and its kinase activity. Interestingly, AdOx disrupted actin cytoskeleton structures, leading to morphological changes, and suppressed the formation of a signaling complex composed of Src and p85/PI3K, which is linked to various tumorigenic responses. In agreement with these data, the exogenous treatment of SAH or inhibition of SAHH by specific siRNA or another type of inhibitor, 3-deazaadenosine (DAZA), similarly resulted in antitumorigenic responses, suppressive activity on Src, the alteration of actin cytoskeleton, and a change of the colocalization pattern between actin and Src. Taken together, these results suggest that SAH/SAHH-mediated transmethylation could be linked to the tumorigenic processes through cross-regulation between the actin cytoskeleton and Src kinase activity.

Camphorquinone inhibits odontogenic differentiation of dental pulp cells and triggers release of inflammatory cytokines.

INTRODUCTION: Camphorquinone (CQ) is a photoinitiator that triggers polymerization of light-curing materials such as dental adhesives and composites. CQ does not become a part of the polymer network, suggesting that CQ can be leached out into surrounding environment including dental pulp and exert adversary effects on tissues. In order to understand the mechanisms of CQ-induced side effects, we investigated the effect of CQ on cell viability, cytokine secretion, and odontogenic differentiation of dental pulp stem cells in vitro. METHODS: Cell viability was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay after CQ exposure. Western blotting was performed for p16(INK4A), p21(WAF1), and p53. Secretory cytokines were evaluated using the membrane-enzyme-linked immunosorbent assay as well as conventional and quantitative reverse-transcription polymerase chain reaction. The effects of CQ on odontogenic differentiation were evaluated using alkaline phosphatase and alizarin red S staining methods. RESULTS: CQ treatment suppressed the proliferation of DPSCs and induced the expression of p16(INK4A), p21(WAF1), and p53. Levels of proinflammatory cytokines (eg, interleukin 6, interleukin 8, and matrix metalloproteinase-3 [MMP3]) were increased by CQ treatment. CQ also inhibited odontogenic differentiation and mineralization capacities of DPSC and MC3T3-E1 cells. CONCLUSIONS: Our study showed that CQ may trigger pulpal inflammation by inducing proinflammatory cytokine production from the pulpal cells and may impair odontogenic differentiation of dental pulp cells, resulting in pulpal irritation and inflammation.

Methanol extract of Hopea odorata suppresses inflammatory responses via the direct inhibition of multiple kinases.

ETHNOPHARMACOLOGICAL RELEVANCE: Hopea odorata Roxb. (Dipterocarpaceae) is a representative Thai ethnopharmacological herbal plant used in the treatment of various inflammation-related diseases. In spite of its traditional use, systematic studies of its anti-inflammatory action have not been performed. MATERIALS AND METHODS: The inhibitory activities of a Hopea odorata methanol extract (Ho-ME) on the production of nitric oxide (NO), tumour necrosis factor (TNF)-α, and prostaglandin E(2) (PGE(2)) in RAW264.7 cells and peritoneal macrophages were investigated. The effects of Ho-ME on the gastritis symptoms induced by HCl/EtOH and on ear oedemas induced by arachidonic acid were also examined. Furthermore, to identify the immunopharmacological targets of this extract, nuclear fractionation, a reporter gene assay, immunoprecipitation, immunoblot analysis, and a kinase assay were employed. RESULTS: Ho-ME strongly inhibited the release of NO, PGE(2), and TNF-α in RAW264.7 cells and peritoneal macrophages stimulated by lipopolysaccharide (LPS). Ho-ME also clearly suppressed the gene expression of pro-inflammatory cytokines and chemokines, such as interferon (IFN)-ß, interleukin (IL)-12, and monocyte chemotactic protein-1 (MCP-1). By analysing the inhibited target molecules, Syk and Src were found to be suppressed in the inhibition of nuclear factor (NF)-κB pathway. In addition, the observed downregulation of activator protein (AP)-1 and cAMP response element-binding (CREB) was due to the direct inhibition of interleukin-1 receptor-associated kinase (IRAK)1 and IRAK4, which was also linked to the suppression of c-Jun N-terminal kinase (JNK) and p38. In agreement with the in vitro observations, this extract also ameliorated the inflammatory symptoms in EtOH/HCl-induced gastritis and arachidonic acid-induced ear oedemas in mice. CONCLUSION: Ho-ME has potential as a functional herbal remedy targeting Syk- and Src-mediated anti-inflammatory mechanisms. Future pre-clinical studies will be needed to investigate this possibility.

ERK1- and TBK1-targeted anti-inflammatory activity of an ethanol extract of Dryopteris crassirhizoma.

ETHNOPHARMACOLOGICAL RELEVANCE: Dryopteris crassirhizoma Nakai (Aspiadaceae) has been traditionally used as an herbal medicine for treating various inflammatory and infectious diseases such as tapeworm infestation, colds, and viral diseases. However, no systematic studies on the anti-inflammatory actions of Dryopteris crassirhizoma and its inhibitory mechanisms have been reported. We therefore aimed at exploring the anti-inflammatory effects of 95% ethanol extracts (Dc-EE) of this plant. MATERIALS AND METHODS: The anti-inflammatory effect of Dc-EE on the production of inflammatory mediators in RAW264.7 cells and HCl/EtOH-induced gastritis was examined. Inhibitory mechanisms were also evaluated by exploring activation of transcription factors, their upstream signalling, and target enzyme activities. Finally, the active components from this extract were also identified using HPLC system. RESULTS: Dc-EE diminished the production of nitric oxide (NO) and prostaglandin (PG)E(2) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells in a dose-dependent manner. Dc-EE also downregulated the levels of mRNA expression of pro-inflammatory genes such as inducible NO synthase (iNOS), cyclooxygenase (COX)-2, and TNF-α by inhibiting the activation of activator protein (AP-1) and IRF3. Indeed, the extract strongly blocked the activities of their upstream kinases ERK1 and TBK1. This extract also strongly ameliorated gastritis symptoms stimulated by HCl/EtOH in mice. According to HPLC fingerprinting, resveratrol, quercetin, and kampferol were identified from Dc-EE. CONCLUSION: Dc-EE displays strong anti-inflammatory activity by suppressing ERK/AP-1 and TBK1/IRF3 pathways, which contribute to its major ethno-pharmacological role as an anti-inflammatory and anti-infectious disease remedy.

The role of Src kinase in macrophage-mediated inflammatory responses.

Src kinase (Src) is a tyrosine protein kinase that regulates cellular metabolism, survival, and proliferation. Many studies have shown that Src plays multiple roles in macrophage-mediated innate immunity, such as phagocytosis, the production of inflammatory cytokines/mediators, and the induction of cellular migration, which strongly implies that Src plays a pivotal role in the functional activation of macrophages. Macrophages are involved in a variety of immune responses and in inflammatory diseases including rheumatoid arthritis, atherosclerosis, diabetes, obesity, cancer, and osteoporosis. Previous studies have suggested roles for Src in macrophage-mediated inflammatory responses; however, recently, new functions for Src have been reported, implying that Src functions in macrophage-mediated inflammatory responses that have not been described. In this paper, we discuss recent studies regarding a number of these newly defined functions of Src in macrophage-mediated inflammatory responses. Moreover, we discuss the feasibility of Src as a target for the development of new pharmaceutical drugs to treat macrophage-mediated inflammatory diseases. We provide insights into recent reports regarding new functions for Src that are related to macrophage-related inflammatory responses and the development of novel Src inhibitors with strong immunosuppressive and anti-inflammatory properties, which could be applied to various macrophage-mediated inflammatory diseases.

Syk/Src pathway-targeted inhibition of skin inflammatory responses by carnosic acid.

Carnosic acid (CA) is a diterpene compound exhibiting antioxidative, anticancer, anti-angiogenic, anti-inflammatory, anti-metabolic disorder, and hepatoprotective and neuroprotective activities. In this study, the effect of CA on various skin inflammatory responses and its inhibitory mechanism were examined. CA strongly suppressed the production of IL-6, IL-8, and MCP-1 from keratinocyte HaCaT cells stimulated with sodium lauryl sulfate (SLS) and retinoic acid (RA). In addition, CA blocked the release of nitric oxide (NO), tumor necrosis factor (TNF)-α, and prostaglandin E2 (PGE2) from RAW264.7 cells activated by the toll-like receptor (TLR)-2 ligands, Gram-positive bacterium-derived peptidoglycan (PGN) and pam3CSK, and the TLR4 ligand, Gram-negative bacterium-derived lipopolysaccharide (LPS). CA arrested the growth of dermatitis-inducing Gram-positive and Gram-negative microorganisms such Propionibacterium acnes, Pseudomonas aeruginosa, and Staphylococcus aureus. CA also blocked the nuclear translocation of nuclear factor (NF)-κB and its upstream signaling including Syk/Src, phosphoinositide 3-kinase (PI3K), Akt, inhibitor of κBα (IκBα) kinase (IKK), and IκBα for NF-κB activation. Kinase assays revealed that Syk could be direct enzymatic target of CA in its anti-inflammatory action. Therefore, our data strongly suggest the potential of CA as an anti-inflammatory drug against skin inflammatory responses with Src/NF-κB inhibitory properties.

The pivotal role of TBK1 in inflammatory responses mediated by macrophages.

Inflammation is a complex biological response of tissues to harmful stimuli such as pathogens, cell damage, or irritants. Inflammation is considered to be a major cause of most chronic diseases, especially in more than 100 types of inflammatory diseases which include Alzheimer's disease, rheumatoid arthritis, asthma, atherosclerosis, Crohn's disease, colitis, dermatitis, hepatitis, and Parkinson's disease. Recently, an increasing number of studies have focused on inflammatory diseases. TBK1 is a serine/threonine-protein kinase which regulates antiviral defense, host-virus interaction, and immunity. It is ubiquitously expressed in mouse stomach, colon, thymus, and liver. Interestingly, high levels of active TBK1 have also been found to be associated with inflammatory diseases, indicating that TBK1 is closely related to inflammatory responses. Even though relatively few studies have addressed the functional roles of TBK1 relating to inflammation, this paper discusses some recent findings that support the critical role of TBK1 in inflammatory diseases and underlie the necessity of trials to develop useful remedies or therapeutics that target TBK1 for the treatment of inflammatory diseases.

DeltaNp63α protein triggers epithelial-mesenchymal transition and confers stem cell properties in normal human keratinocytes.

p63 is a p53 family protein required for morphogenesis and postnatal regeneration of epithelial tissues. Here we demonstrate that ΔNp63α, a p63 isoform lacking the N-terminal transactivation domain, induces epithelial-mesenchymal transition (EMT) in primary human keratinocytes in a TGF-ß-dependent manner. Rapidly proliferating normal human epidermal keratinocytes (NHEK) were infected with retroviral vector expressing ΔNp63α or empty vector and serially subcultured until replicative senescence. No phenotypic changes were observed until the culture reached senescence. Then the ΔNp63α-transduced cells underwent morphological changes resembling mesenchymal cells and acquired the EMT phenotype. Treatment with exogenous TGF-ß accelerated EMT in presenescent ΔNp63α-transduced cells, whereas the inhibition of TGF-ß signaling reversed the EMT phenotype. TGF-ß treatment alone led to growth arrest in control NHEK with no evidence of EMT, indicating that ΔNp63α altered the cellular response to TGF-ß treatment. ΔNp63α-transduced cells acquiring EMT gained the ability to be differentiated to osteo-/odontogenic and adipogenic pathways, resembling mesenchymal stem cells. Furthermore, these cells expressed enhanced levels of Nanog and Lin28, which are transcription factors associated with pluripotency. These data indicate that EMT required ΔNp63α transduction and intact TGF-ß signaling in NHEK.

Radioprotective effects of Bmi-1 involve epigenetic silencing of oxidase genes and enhanced DNA repair in normal human keratinocytes.

Normal human keratinocytes (NHKs) undergo premature senescence following exposure to ionizing radiation (IR). This study investigates the effect of Bmi-1, a polycomb group protein, on radiation-induced senescence response. When exposed to IR, NHK transduced with Bmi-1 (NHK/Bmi-1) showed reduced senescent phenotype and enhanced proliferation compared with control cells (NHK/B0). To investigate the underlying mechanism, we determined the production of reactive oxygen species (ROS), expression of ROS-generating enzymes, and DNA repair activities in cells. ROS level was increased upon irradiation but notably reduced by Bmi-1 transduction. Irradiation led to strong induction of oxidase genes, e.g., Lpo (lactoperoxidase), p22-phox, p47-phox, and Gp91, in NHK/B0 but their expression was almost completely silenced in NHK/Bmi-1. Induction of oxidase genes upon irradiation was linked with loss of trimethylated histone 3 at lysine 27 (H3K27Me3), but NHK/Bmi-1 expressed a higher level of H3K27Me3 compared with NHK/B0. Bmi-1 transduction suppressed IR-associated induction of jumanji domain containing 3 while enhancing the expression of EZH2, thereby preventing the loss of H3K27Me3 in the irradiated cells. Furthermore, NHK/Bmi-1 demonstrated increased repair of IR-induced DNA damage compared with NHK/B0. These results indicate that Bmi-1 elicits radioprotective effects on NHK by mitigating the genotoxicity of IR through epigenetic mechanisms.

Bmi-1 extends the life span of normal human oral keratinocytes by inhibiting the TGF-beta signaling.

We previously demonstrated that Bmi-1 extended the in vitro life span of normal human oral keratinocytes (NHOK). We now report that the prolonged life span of NHOK by Bmi-1 is, in part, due to inhibition of the TGF-beta signaling pathway. Serial subculture of NHOK resulted in replicative senescence and terminal differentiation and activation of TGF-beta signaling pathway. This was accompanied with enhanced intracellular and secreted TGF-beta1 levels, phosphorylation of Smad2/3, and increased expression of p15(INK4B) and p57(KIP2). An ectopic expression of Bmi-1 in NHOK (HOK/Bmi-1) decreased the level of intracellular and secreted TGF-beta1 induced dephosphorylation of Smad2/3, and diminished the level of p15(INK4B) and p57(KIP2). Moreover, Bmi-1 expression led to the inhibition of TGF-beta-responsive promoter activity in a dose-specific manner. Knockdown of Bmi-1 in rapidly proliferating HOK/Bmi-1 and cancer cells increased the level of phosphorylated Smad2/3, p15(INK4B), and p57(KIP2). In addition, an exposure of senescent NHOK to TGF-beta receptor I kinase inhibitor or anti-TGF-beta antibody resulted in enhanced replicative potential of cells. Taken together, these data suggest that Bmi-1 suppresses senescence of cells by inhibiting the TGF-beta signaling pathway in NHOK.

Spontaneous tumorigenicity of primary human oral keratinocytes with human papillomavirus negativity and impaired apoptosis.

Although >60% of oral cancer cases are not related to human papillomavirus (HPV) infection, most studies of oral carcinogenesis in human cells in vitro are carried out with human oral keratinocytes immortalized by HPV DNA. To explore whether human oral keratinocytes can spontaneously transform without HPV infection, we attempted to establish spontaneously immortalized and tumorigenic-transformed human oral keratinocytes by serial subculture to the post-mitotic stage. Here we report two spontaneously transformed human oral keratinocyte lines from adult human gingival samples. These lines were obviously immortal (>140 passages) and transformed phenotypes in vitro. One of the lines, Spi-HOK1, remained non-tumorigenic in nude mice, whereas the other line, Spt-HOK80, showed tumorigenicity. These lines showed epithelial origi-nality, but did not contain high-risk types of HPV DNAs. On karyotyping, Spi-HOK1 was aneuploid with a unique stable marker chromosome. Both cell lines revealed a mutation in the p53 gene, loss of p21WAF1/Cip1 and overexpression of p-Rb-Ser807/811. These cell lines were resistant to cisplatin-induced apoptosis by suppressing induction of apoptotic proteins. These results clearly demonstrate that spontaneous immortalization and spontaneous tumorigenic transformation of primary human oral keratinocytes can occur in vitro without HPV infection and are associated with chromosomal alterations, p53 mutation and impaired apoptosis. To our knowledge, this is the first report demonstrating that the Spi-HOK1 and Spt-HOK80 lines are novel cell lines that are spontaneously transformed from primary human oral keratinocytes.

Treponema denticola suppresses expression of human {beta}-defensin-3 in gingival epithelial cells through inhibition of the toll-like receptor 2 axis.

We reported previously that Treponema denticola, one of the periodontal pathogens, suppresses the expression of human beta-defensins (HBDs) in human gingival epithelial cells. To identify the mechanisms involved in this suppression, immortalized and normal human gingival epithelial cells were infected with live or heat-killed T. denticola for 24 h, and then the expression of HBDs was examined by real-time RT-PCR. Live T. denticola suppressed the expression of HBD-3 substantially and also suppressed the expression of HBD-1 and HBD-2. However, heat-killed bacteria did not produce a suppressive effect but instead slightly upregulated the levels of HBD-2 and HBD-3. In contrast to live T. denticola, which reduced the activation of mitogen-activated protein kinase (MAPK) and NF-kappaB within an hour of infection, heat-killed bacteria did not show any inhibitory effect on the MAPK and NF-kappaB signaling pathways. Knockdown of Toll-like receptor 2 (TLR2) via RNA interference abolished the suppressive effect of T. denticola on the expression of HBD-3. Heat-killed T. denticola but not live bacteria could activate TLR2 in CHO/CD14/TLR2 reporter cells, suggesting that T. denticola contains a heat-labile inhibitor(s) of TLR2 in addition to ligands recognized by TLR2. Indeed, live T. denticola was able to inhibit TLR2 activation by Pam(3)CSK. In conclusion, T. denticola suppressed the expression of HBD-3 by inhibiting the TLR2 axis in gingival epithelial cells. These results may provide new insight into the pathogenesis of periodontitis caused by T. denticola.