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-1β-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-1β-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

TGF-β1 stimulates cyclooxygenase-2 expression and PGE2 production of human dental pulp cells: Role of ALK5/Smad2 and MEK/ERK signal transduction pathways

TGF-β1 is an important growth factor that may influence the odontoblast differentiation and matrix deposition in the reactionary/reparative dentinogenesis to dental caries or other tooth injuries. TGF-β1 exerts its effects through various signaling pathways, such as Smads and MAPKs. Cyclooxygenase-2 (COX-2) is a membrane-associated enzyme that produces prostaglandin E2 (PGE2) at sites of pulpal injury and inflammation, which leads to tissue swelling, redness and pain. The purposes of this study were to investigate the differential signal transduction pathways of TGF-β1 that mediate COX-2 stimulation and PGE2 production in dental pulp cells. Methods: Pulp cells were exposed to TGF-β1 with/without SB431542 (an ALK5/Smad2 inhibitor) and U0126 (a MEK/ERK inhibitor). MTT assay was used to estimate cell viability. Enzyme-linked immunosorbent assay (ELISA) was used for measurement of PGE2 levels. RT-PCR and western blot were used to determined COX-2 mRNA and protein, respectively. Results: Exposure to TGF-β1 (1–10 ng/ml) increased the COX-2 mRNA and protein level of cultured pulp cells. Exposure to TGF-β1 (0.1–10 ng/mL) significantly stimulated PGE2 production of dental pulp cells. Under the pretreatment of SB431542, the stimulatory effect of TGF-β1 on COX-2 level of pulp cells was inhibited. Similarly, U0126 also partly inhibited the TGF-β1-induced COX-2 expression. Conclusion: TGF-β1 increased the COX-2 and PGE2 level of cultured pulp cells. The effect of TGF-β1 on COX-2 protein expression was associated with ALK5/Smad2/3 and MEK/ERK pathways. These events are important in the early inflammation, repair and regeneration of dental pulp in response to injury

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

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

In order to clarify the role of transforming growth factor beta 1 (TGF-β1) in pulp repair/regeneration responses, we investigated the differential signaling pathways responsible for the effects of TGF-β1 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-β1 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-β1 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-β1-induced increase of collagen content and TIMP-1 production of dental pulp cells. Conclusion: These results indicate that TGF-β1 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

Effects of Camphorquinone on Cytotoxicity, Cell Cycle Regulation and Prostaglandin E2 Production of Dental Pulp Cells: Role of ROS, ATM/Chk2, MEK/ERK and Hemeoxygenase-1.

Camphorquinone (CQ) is a popularly-used photosensitizer in composite resin restoration. In this study, the effects of CQ on cytotoxicity and inflammation-related genes and proteins expression of pulp cells were investigated. The role of reactive oxygen species (ROS), ATM/Chk2/p53 and hemeoxygenase-1 (HO-1) and MEK/ERK signaling was also evaluated. We found that ROS and free radicals may play important role in CQ toxicity. CQ (1 and 2 mM) decreased the viability of pulp cells to about 70% and 50% of control, respectively. CQ also induced G2/M cell cycle arrest and apoptosis of pulp cells. The expression of type I collagen, cdc2, cyclin B, and cdc25C was inhibited, while p21, HO-1 and cyclooxygenase-2 (COX-2) were stimulated by CQ. CQ also activated ATM, Chk2, and p53 phosphorylation and GADD45α expression. Besides, exposure to CQ increased cellular ROS level and 8-isoprostane production. CQ also stimulated COX-2 expression and PGE2 production of pulp cells. The reduction of cell viability caused by CQ can be attenuated by N-acetyl-L-cysteine (NAC), catalase and superoxide dismutase (SOD), but can be promoted by Zinc protoporphyin (ZnPP). CQ stimulated ERK1/2 phosphorylation, and U0126 prevented the CQ-induced COX-2 expression and prostaglandin E2 (PGE2) production. These results indicate that CQ may cause cytotoxicity, cell cycle arrest, apoptosis, and PGE2 production of pulp cells. These events could be due to stimulation of ROS and 8-isoprostane production, ATM/Chk2/p53 signaling, HO-1, COX-2 and p21 expression, as well as the inhibition of cdc2, cdc25C and cyclin B1. These results are important for understanding the role of ROS in pathogenesis of pulp necrosis and pulpal inflammation after clinical composite resin filling

Effect of different concentrations of catechol on the (A) COX-1 enzyme activity (n = 6), and (B) COX-2 enzyme activity (n = 6).

<p>Results were expressed as COX-1 and COX-2 enzyme activity as indicated by PGE₂ production (pg/mL). *indicated statistically significant difference when compared with solvent (DMSO) control group (0) (p<0.05).</p

<i>Ex vivo</i> platelet aggregation by AA and its inhibition by administration of catechol.

<p>(A) Intravenous administration of catechol (0.5–5 µmole/mouse) inhibited the AA-induced platelet aggregation <i>ex vivo</i>. One representative picture of platelet aggregation was shown with more similar results. (B) Inhibition of AA-induced platelet aggregation <i>ex vivo</i> by intravenous administration of different amounts of catechol (0.5–5 µmole/mouse) into mice. (n = 7). *denotes significant difference when compared with solvent control group (p<0.05).</p

Inhibition of AA-induced platelet aggregation by different concentrations of catechol.

<p>(A) One representative picture of AA-induced platelet aggregation and its inhibition by catechol was shown. (B) Quantitative analysis of AA (100 µM)-induced platelet aggregation and its inhibition by catechol (0.5–100 µM). Results were expressed as % of platelet aggregation (n = 5–8). (C) Cytotoxicity of catechol to platelets. Results were expressed as % of LDH release (n = 3). ↑indicates the addition of AA, and ⇑ indicates the addition of catechol. *indicates significant difference when compared with AA-treated group (P<0.05).</p

Effect of catechol on AA-induced p38 and ERK phosphrylation in platelets.

<p>One representative western blotting picture was shown. Expression of GAPDH was used as control. Quantitative results of p-ERK/GAPDH and p-p38/GAPDH ratio were measured by Image J analysis and expressed as fold of control (the value in parenthesis).</p

Catechol inhibited the IL-1β-induced PGE₂ production of pulp cells.

<p>Pulp cells were pretreated with catechol with/without further co-incubation by IL-1β for 24-hours. (A) morphology of control fibroblasts, pulp fibroblasts exposed to IL-1β for 24-hours, Pulp fibroblasts incubated with 0.1 mM catechol for 24-hours, and Pulp fibroblasts exposure to 0.1 mM catechol with IL-1β for 24-hours, (B) Viable cells were estimated by MTT assay. MTT reduction was shown as % of control (Mean ± SE) (n = 8). *denotes significant difference (p<0.05) when compared with solvent control group. (C) PGE₂ level in the cultured medium was measured and the PGE₂ concentration was shown as pg/ml (Mean ± SE) (n = 7). *denotes significant difference when compared with solvent control group; #denotes significant difference (p<0.05) when compared with IL-1β solely group. (D) COX-2 expression of pulp cells after exposure to IL-1β with/without pretreatment and co-incubation by catechol. One representative western blotting result was shown.</p