Transforming growth factor beta 1 increases collagen content, and stimulates procollagen I and tissue inhibitor of metalloproteinase-1 production of dental pulp cells: Role of MEK/ERK and activin receptor-like kinase-5/Smad signaling.

BACKGROUND/PURPOSE: In order to clarify the role of transforming growth factor beta 1 (TGF-ß1) in pulp repair/regeneration responses, we investigated the differential signaling pathways responsible for the effects of TGF-ß1 on collagen turnover, matrix metalloproteinase-3 (MMP-3), and tissue inhibitor of metalloproteinase-1 (TIMP-1) production in human dental pulp cells. METHODS: Pulp cells were exposed to TGF-ß1 with/without pretreatment and coincubation by 1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenyl mercapto)butadiene (U0126; a mitogen-activated protein kinase kinase [MEK]/extracellular signal-regulated kinase [ERK] inhibitor) and 4-(5-benzol[1,3]dioxol-5-yl-4-pyrldin-2-yl-1H- imidazol-2-yl)-benzamide hydrate (SB431542; an activin receptor-like kinase-5/Smad signaling inhibitor). Sircol collagen assay was used to measure cellular collagen content. Culture medium procollagen I, TIMP-1, and MMP-3 levels were determined by enzyme-linked immunosorbent assay. RESULTS: TGF-ß1 increased the collagen content, procollagen I, and TIMP-1 production, but slightly decreased MMP-3 production of pulp cells. SB431542 and U0126 prevented the TGF-ß1-induced increase of collagen content and TIMP-1 production of dental pulp cells. CONCLUSION: These results indicate that TGF-ß1 may be involved in the healing/regeneration processes of dental pulp in response to injury by stimulation of collagen and TIMP-1 production. These events are associated with activin receptor-like kinase-5/Smad2/3 and MEK/ERK signaling.

Cytotoxicity and transformation of C3H10T1/2 cells induced by areca nut components.

BACKGROUND/PURPOSE: Betel quid (BQ) chewing is popular in Taiwan and many other countries. There are about 200-600 million BQ chewers in the world. BQ chewing is one major risk factor of oral cancer and oral submucous fibrosis (OSF). While areca nut (AN), a main component of BQ, exhibits genotoxicity, its transformation capacity and its role in the initiation and promotion stages of carcinogenesis are not fully clear. METHODS: Mouse C3H10T1/2 cells were exposed to AN extract (ANE) for 24 hours. Cytotoxicity was evaluated by colony forming efficiency. For the transformation assay, C3H10T1/2 cells were exposed to ANE for 24 hours and then incubated in medium with/without 12-O-tetradecanolylphorbol-13-acetate (TPA; a tumor promoter) for 42 days. Cells were stained with Giemsa and type II and type III transformed foci were counted for analysis of the transformation capacity of ANE. RESULTS: ANE exhibited cytotoxicity to C3H10T/12 cells at concentrations higher than 320 µg/mL as shown by a decrease in colony numbers. ANE (80-640 µg/mL) alone mildly stimulated the transformed foci formation (p > 0.05). In the presence of TPA, ANE (80-640 µg/mL) markedly stimulated the transformed foci formation. The percentage of dishes with foci increased from 0% in controls to 20% in ANE (80 µg/mL and 320 µg/mL)-treated groups and further increased to 65-94% in ANE plus TPA groups. CONCLUSION: These results indicate that ANE is a weak complete carcinogen. ANE is an effective tumor initiator and can induce malignant transformation of C3H10T1/2 cells in the presence of a tumor promoter. ANE may be involved in multistep chemical carcinogenesis by its malignant transformation capacity.

Differences in oral habit and lymphocyte subpopulation affect malignant transformation of patients with oral precancer.

BACKGROUND/PURPOSE: In Taiwan, the combination of betel quid chewing, alcohol consumption, and smoking habits increases oral cancer risk by 123-fold compared to persons without these habits. Lymphocyte populations in patients may potentially affect the malignant transformation of oral precancer. METHODS: A total of 28 patients with oral precancer from our previous cohort were enrolled in this study, and their personal information and oral habits were documented. Their lymphocyte populations (CD4+, CD8+, CD19+, and CD56+) and activation markers (CD25 and CD69) were determined by flow cytometry from 1999 to 2004. After follow up till December 2014, data of patients with/without malignant transformation were recorded, and the relation between oral habits and percentage of initial lymphocyte markers was evaluated using the Student t test and Fisher's exact test. RESULTS: Ten precancer patients developed oral squamous cell carcinoma with a mean period of malignant transformation of 6.8 ± 2.1 years. Patients with malignant transformation had a mean age of 48.4 ± 5.0 years (n = 10), relatively more than that of patients without malignant transformation (41.6 ± 6.3 years, n = 18) (p < 0.05). An increase was noted in the population of peripheral blood mononuclear cells expressing CD4+CD69+, CD19+CD69+, and CD56+CD69+ (p < 0.05) in precancer patients with malignant transformation. Alcohol consumption showed an association with the malignant transformation of patients with precancer (p = 0.030), whereas betel quid and smoking showed little effect. CONCLUSION: These results suggest that age, alcohol consumption, and early activation of T cells, B cells, and natural killer cells are crucial in the malignant transformation of oral precancer. Analysis of patient's lymphocyte populations may help predict the malignant transformation of oral precancer.

Stimulation of MMP-9 of oral epithelial cells by areca nut extract is related to TGF-ß/Smad2-dependent and -independent pathways and prevented by betel leaf extract, hydroxychavicol and melatonin.

BACKGROUND: There are 200-600 million betel quid (BQ) chewers in the world. BQ increases oral cancer risk. Matrix metalloproteinase-9 (MMP-9) is responsible for matrix degradation, cancer invasion and metastasis. Whether areca nut extract (ANE), a BQ component, stimulates MMP-9 secretion, and the related signaling pathways awaits investigation. RESULTS: ANE (but not arecoline) stimulated MMP-9 production of gingival keratinocytes and SAS cancer epithelial cells. ANE stimulated TGF-ß1, p-Smad2, and p-TAK1 protein expression. ANE-induced MMP-9 production/expression in SAS cells can be attenuated by SB431542 (ALK5/Smad2 inhibitor), 5Z-7-Oxozeaenol (TAK1 inhibitor), catalase, PD153035 (EGFR tyrosine kinase inhibitor), AG490 (JAK inhibitor), U0126 (MEK/ERK inhibitor), LY294002 (PI3K/Akt inhibitor), betel leaf (PBL) extract, and hydroxychavicol (HC, a PBL component), and melatonin, but not by aspirin. CONCLUSIONS: AN components contribute to oral carcinogenesis by stimulating MMP-9 secretion, thus enhancing tumor invasion/metastasis. These events are related to reactive oxygen species, TGF-ß1, Smad2-dependent and -independent signaling, but not COX. These signaling molecules can be biomarkers of BQ carcinogenesis. PBL, HC and melatonin and other targeting therapy can be used for oral cancer treatment. METHODS: ANE-induced MMP-9 expression/secretion of oral epithelial cells and related TGF-ß1, Smad-dependent and -independent signaling were studied by MTT assay, RT-PCR, western blotting, immunofluorescent staining, and ELISA.

IL-1ß-induced MCP-1 expression and secretion of human dental pulp cells is related to TAK1, MEK/ERK, and PI3K/Akt signaling pathways.

OBJECTIVE: Interleukin-1ß (IL-1ß) is an inflammatory molecule of the dental pulp. IL-1ß stimulates cyclooxygenase-2 (COX-2) and prostaglandins production of pulp cells and affects the pulpal inflammation and repair. However, the effects of IL-1ß on Monocyte Chemotactic Factor-1 (MCP-1) of dental pulp cells and its relation to transforming growth factor ß-activated kinase-1 (TAK1), PI3K/Akt, and MEK/ERK signaling and COX activation are not fully clear. DESIGN: Human dental pulp cells were exposed to IL-1ß with/without pretreatment and co-incubation by aspirin (a COX inhibitor), 5z-7-oxozeaenol (a TAK1 inhibitor), LY294002 (a PI3K/Akt inhibitor) or U0126 (a MEK/ERK inhibitor). Viable cell number was evaluated by MTT assay. MCP-1 mRNA expression was tested by reverse transcriptase-polymerase chain reaction (RT-PCR). MCP-1 and COX-2 protein expression was studied by western blot. MCP-1 in the culture medium was measure by ELISA. RESULTS: IL-1ß showed little cytotoxicity to pulp cells. It stimulated MCP-1 mRNA and protein expression and MCP-1 secretion. Aspirin, U0126, LY294002 and 5z-7-oxozeaenol attenuated the IL-1ß-induced MCP-1 expression. In addition, 5z-7-oxozeaenol, LY294002, U0126 and aspirin prevented the IL-1ß-induced MCP-1 secretion of pulp cells. CONCLUSION: These results indicate that IL-1ß may be involved in the pulpal inflammatory and healing processes by inducing MCP-1 expression and secretion. These events are related to differential activation of TAK1, PI3K/Akt and MEK/ERK 1/2 signaling and COX activation. These results are important for future pharmacologic intervention of pulpal inflammatory diseases.

Role of ALK5/Smad2/3 and MEK1/ERK Signaling in Transforming Growth Factor Beta 1-modulated Growth, Collagen Turnover, and Differentiation of Stem Cells from Apical Papilla of Human Tooth.

INTRODUCTION: Transforming growth factor ß1 (TGF-ß1) plays an important role in cell proliferation, matrix formation, and odontogenesis. This study investigated the effects of TGF-ß1 on stem cells from apical papilla (SCAPs) and its signaling by MEK/ERK and Smad2. METHODS: SCAPs were exposed to TGF-ß1 with/without pretreatment and coincubation by SB431542 (an ALK5/Smad 2/3 inhibitor) or U0126 (a MEK/ERK inhibitor). Cell growth was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide assay or direct counting of viable cells. Collagen content was determined by using the Sircol collagen assay (Biocolor Ltd, Newtownabbey, Northern Ireland). Cell differentiation was evaluated by measuring alkaline phosphatase (ALP) activity. Smad2 and ERK1/2 phosphorylation was analyzed by Western blotting or PathScan phospho-enzyme-linked immunosorbent assay (Cell Signaling Technology Inc, Danvers, MA). RESULTS: TGF-ß1 stimulated the growth and collagen content of cultured SCAPs. TGF-ß1 stimulated ERK1/2 and Smad2 phosphorylation within 60 minutes of exposure. Pretreatment by U0126 and SB431542 effectively prevented the TGF-ß1-induced cell growth and collagen content in SCAPs. TGF-ß1 stimulated ALP activity at lower concentrations (0.1-1 ng/mL) but down-regulated ALP at higher concentrations (>5 ng/mL). U0126 prevented 0.5 ng/mL TGF-ß1-induced ALP activity but showed little effect on 10 ng/mL TGF-ß1-induced decline of ALP in SCAPs. Interestingly, SB431542 attenuated both the stimulatory and inhibitory effects on ALP by TGF-ß1. CONCLUSIONS: TGF-ß1 may affect the proliferation, collagen turnover, and differentiation of SCAPs via differential activation of ALK5/Smad2 and MEK/ERK signaling. These results highlight the future use of TGF-ß1 and SCAP for engineering of pulpal regeneration and apexogenesis.

Antiplatelet effect of catechol is related to inhibition of cyclooxygenase, reactive oxygen species, ERK/p38 signaling and thromboxane A2 production.

Catechol (benzenediol) is present in plant-derived products, such as vegetables, fruits, coffee, tea, wine, areca nut and cigarette smoke. Because platelet dysfunction is a risk factor of cardiovascular diseases, including stroke, atherosclerosis and myocardial infarction, the purpose of this study was to evaluate the anti-platelet and anti-inflammatory effect of catechol and its mechanisms. The effects of catechol on cyclooxygenase (COX) activity, arachidonic acid (AA)-induced aggregation, thromboxane B2 (TXB2) production, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) production and extracellular signal-regulated kinase (ERK)/p38 phosphorylation were determined in rabbit platelets. In addition, its effect on IL-1ß-induced prostaglandin E2 (PGE2) production by fibroblasts was determined. The ex vivo effect of catechol on platelet aggregation was also measured. Catechol (5-25 µM) suppressed AA-induced platelet aggregation and inhibited TXB2 production at concentrations of 0.5-5 µM; however, it showed little cytotoxicity and did not alter U46619-induced platelet aggregation. Catechol (10-50 µM) suppressed COX-1 activity by 29-44% and COX-2 activity by 29-50%. It also inhibited IL-1ß-induced PGE2 production, but not COX-2 expression of fibroblasts. Moreover, catechol (1-10 µM) attenuated AA-induced ROS production in platelets and phorbol myristate acetate (PMA)-induced ROS production in human polymorphonuclear leukocytes. Exposure of platelets to catechol decreased AA-induced ERK and p38 phosphorylation. Finally, intravenous administration of catechol (2.5-5 µmole/mouse) attenuated ex vivo AA-induced platelet aggregation. These results suggest that catechol exhibited anti-platelet and anti-inflammatory effects, which were mediated by inhibition of COX, ROS and TXA2 production as well as ERK/p38 phosphorylation. The anti-platelet effect of catechol was confirmed by ex vivo analysis. Exposure to catechol may affect platelet function and thus cardiovascular health.

Areca nut components affect COX-2, cyclin B1/cdc25C and keratin expression, PGE2 production in keratinocyte is related to reactive oxygen species, CYP1A1, Src, EGFR and Ras signaling.

AIMS: Chewing of betel quid (BQ) increases the risk of oral cancer and oral submucous fibrosis (OSF), possibly by BQ-induced toxicity and induction of inflammatory response in oral mucosa. METHODS: Primary gingival keratinocytes (GK cells) were exposed to areca nut (AN) components with/without inhibitors. Cytotoxicity was measured by 3-(4,5-dimethyl- thiazol- 2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. mRNA and protein expression was evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting. PGE2/PGF2α production was measured by enzyme-linked immunosorbent assays. RESULTS: Areca nut extract (ANE) stimulated PGE2/PGF2α production, and upregulated the expression of cyclooxygenase-2 (COX-2), cytochrome P450 1A1 (CYP1A1) and hemeoxygenase-1 (HO-1), but inhibited expression of keratin 5/14, cyclinB1 and cdc25C in GK cells. ANE also activated epidermal growth factor receptor (EGFR), Src and Ras signaling pathways. ANE-induced COX-2, keratin 5, keratin 14 and cdc25C expression as well as PGE2 production were differentially regulated by α-naphthoflavone (a CYP 1A1/1A2 inhibitor), PD153035 (EGFR inhibitor), pp2 (Src inhibitor), and manumycin A (a Ras inhibitor). ANE-induced PGE2 production was suppressed by piper betle leaf (PBL) extract and hydroxychavicol (two major BQ components), dicoumarol (a NAD(P)H: Quinone Oxidoreductase--NQO1 inhibitor) and curcumin. ANE-induced cytotoxicity was inhibited by catalase and enhanced by dicoumarol, suggesting that AN components may contribute to the pathogenesis of OSF and oral cancer via induction of aberrant differentiation, cytotoxicity, COX-2 expression, and PGE2/PGF2α production. CONCLUSIONS: CYP4501A1, reactive oxygen species (ROS), EGFR, Src and Ras signaling pathways could all play a role in ANE-induced pathogenesis of oral cancer. Addition of PBL into BQ and curcumin consumption could inhibit the ANE-induced inflammatory response.

p-Cresol affects reactive oxygen species generation, cell cycle arrest, cytotoxicity and inflammation/atherosclerosis-related modulators production in endothelial cells and mononuclear cells.

AIMS: Cresols are present in antiseptics, coal tar, some resins, pesticides, and industrial solvents. Cresol intoxication leads to hepatic injury due to coagulopathy as well as disturbance of hepatic circulation in fatal cases. Patients with uremia suffer from cardiovascular complications, such as atherosclerosis, thrombosis, hemolysis, and bleeding, which may be partly due to p-cresol toxicity and its effects on vascular endothelial and mononuclear cells. Given the role of reactive oxygen species (ROS) and inflammation in vascular thrombosis, the objective of this study was to evaluate the effect of p-cresol on endothelial and mononuclear cells. METHODS: EA.hy926 (EAHY) endothelial cells and U937 cells were exposed to different concentrations of p-cresol. Cytotoxicity was evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5 -diphenyltetrazolium bromide (MTT) assay and trypan blue dye exclusion technique, respectively. Cell cycle distribution was analyzed by propidium iodide flow cytometry. Endothelial cell migration was studied by wound closure assay. ROS level was measured by 2',7'-dichlorofluorescein diacetate (DCF) fluorescence flow cytometry. Prostaglandin F2α (PGF2α), plasminogen activator inhibitor-1 (PAI-1), soluble urokinase plasminogen activator receptor (suPAR), and uPA production were determined by Enzyme-linked immunosorbant assay (ELISA). RESULTS: Exposure to 100-500 µM p-cresol decreased EAHY cell number by 30-61%. P-cresol also decreased the viability of U937 mononuclear cells. The inhibition of EAHY and U937 cell growth by p-cresol was related to induction of S-phase cell cycle arrest. Closure of endothelial wounds was inhibited by p-cresol (>100 µM). P-cresol (>50 µM) also stimulated ROS production in U937 cells and EAHY cells but to a lesser extent. Moreover, p-cresol markedly stimulated PAI-1 and suPAR, but not PGF2α, and uPA production in EAHY cells. CONCLUSIONS: p-Cresol may contribute to atherosclerosis and thrombosis in patients with uremia and cresol intoxication possibly due to induction of ROS, endothelial/mononuclear cell damage and production of inflammation/atherosclerosis-related molecules.

Successful treatment of oral verrucous hyperplasia and oral leukoplakia with topical 5-aminolevulinic acid-mediated photodynamic therapy.

BACKGROUND AND OBJECTIVES: Our recent studies showed that a new topical 5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) protocol using a light-emitting diode (LED) light source is an effective and successful treatment modality for five cases of oral verrucous hyperplasia (OVH) and one case of verrucous carcinoma. In this study, we treated eight OVH lesions with the same topical ALA-PDT protocol to further confirm the efficacy of this protocol on OVH lesions. In addition, our recent study demonstrated an unsatisfactory clinical outcome for 24 oral leukoplakia (OL) lesions treated once a week by the same topical ALA-PDT protocol. Therefore, in this study 24 OL lesions were treated twice a week by the same protocol to compare whether the twice-a-week treatment modality could result in a better clinical outcome than the once-a-week treatment modality. STUDY DESIGN/MATERIALS AND METHODS: In this study, 8 OVH and 24 OL lesions were treated by the same topical ALA-PDT once a week and twice a week, respectively. RESULTS: All the former eight OVH lesions treated once a week showed complete response (CR) after 2-5 (mean, 3.8) treatments of ALA-PDT. The latter 24 OL lesions treated twice a week demonstrated CR in 8, partial response (PR) in 16, and no response in none. The present 24 OL lesions treated twice a week had a significantly better clinical outcome than the previous 24 OL lesions treated once a week (P = 0.000, chi-square test). CONCLUSIONS: We conclude that complete regression of OVH lesions can be achieved by less than six treatments of topical ALA-PDT once a week. Although the response of OL lesions to the topical ALA-PDT is not as good as the response of OVH lesions to the same therapy, all OL lesions can have at least PR after eight treatments with the topical ALA-PDT twice a week. In addition, OL lesions treated twice a week have a significantly better clinical outcome than OL lesions treated once a week.