Main Mitogen-activated Protein Kinases Research Articles

The Antiviral Effects of Jasminin via Endogenous TNF-α and the Underlying TNF-α-Inducing Action.

Previous studies have reported that recombinant tumor necrosis factor (TNF)-α has powerful antiviral activity but severe systematic side effects. Jasminin is a common bioactive component found in Chinese herbal medicine beverage “Jasmine Tea”. Here, we report that jasminin-induced endogenous TNF-α showed antiviral activity in vitro. The underlying TNF-α-inducing action of jasminin was also investigated in RAW264.7 cells. The level of endogenous TNF-α stimulated by jasminin was first analyzed by an enzyme-linked immunosorbent assay (ELISA) from the cell culture supernatant of RAW264.7 cells. The supernatants were then collected to investigate the potential antiviral effect against herpes simplex virus 1 (HSV-1). The antiviral effects of jasminin alone or its supernatants were evaluated by a plaque reduction assay. The potential activation of the PI3K–Akt pathway, three main mitogen-activated protein kinases (MAPKs), and nuclear factor (NF)–κB signaling pathways that induce TNF-α production were also investigated. Jasminin induces TNF-α protein expression in RAW264.7 cells without additional stimuli 10-fold more than the control. No significant up-expression of type I, II, and III interferons; interleukins 2 and 10; nor TNF-β were observed by the jasminin stimuli. The supernatants, containing jasminin-induced-TNF-α, showed antiviral activity against HSV-1. The jasminin-stimulated cells caused the simultaneous activation of the Akt, MAPKs, and NF–κB signal pathways. Furthermore, the pretreatment of the cells with the Akt, MAPKs, and NF–κB inhibitors effectively suppressed jasminin-induced TNF-α production. Our research provides evidence that endogenous TNF-α can be used as a strategy to encounter viral infections. Additionally, the Akt, MAPKs, and NF–κB signaling pathways are involved in the TNF-α synthesis that induced by jasminin.

Effects of fusariotoxin co-exposure on THP-1 human immune cells.

Deoxynivalenol (DON), nivalenol (NIV), T-2 toxin (T2), fumonisin B1 (FB1), zearalenone (ZEA), and moniliformin (MON) mycotoxins are common food and feed contaminants produced by Fusarium spp. However, while they are usually found to co-occur in a large range of commodities, only few data are available on mycotoxin co-exposure effects and cellular response mechanisms. In this study, the individual and combined toxic effects of these fusariotoxins were evaluated on the THP-1 human immune cell line as major fusariotoxins are mostly potent immunomodulators. In particular, four relevant fusariotoxin mixtures, namely DON-MON, DON-FB1, DON-ZEA, and NIV-T2, were studied using several parameters including cell viability as well as the expression of cell surface markers and the main mitogen-activated protein kinases (MAPKs). After 48h exposure, a reduction of cell viability in a dose-dependent manner was observed for T2, the most cytotoxic mycotoxin, followed by NIV, DON, MON, FB1, and ZEA. Regarding mycotoxin mixtures, they mainly showed antagonism on cell viability reduction. Interestingly, at concentrations inhibiting 50% of cell viability, most viable cells exhibited surface marker loss and thus became potentially non-functional. In addition, during the first 18h of exposure, the effects of mycotoxin mixtures on early cell apoptosis and necrosis were found to be different from those induced by the toxins alone. At the molecular level, after 1h exposure of individual and combined mycotoxins, the three main MAPK signaling pathways (p38, SAPK/JNK, and ERK1/2) were activated, highlighting a fast reaction of the exposed cells even at low cytotoxicity levels.

Analysis of the activation routes induced by different metal oxide nanoparticles on human lung epithelial cells.

Nanoparticles (Nps) can induce toxicity in the lung by accidental or intentional exposure. The main objective of the study reported here was to characterize the effect that four metal oxide Nps (CeO2, TiO2, Al2O3 and ZnO) had at the cellular level on a human lung epithelial cell line. This goal was achieved by studying the capacity of the Nps to activate the main mitogen-activated protein kinases (MAPKs) and the nuclear factor NFκB. Only ZnO Nps were able to activate all of the MAPKs and the release of Zn2+ ions was the main cause of activation. ZnO and Al2O3 Nps activated the NFκB pathway and induced the release of inflammatory cytokines. CeO2 and TiO2 Nps were found to have safer profiles. The graphical abstract was obtained using Servier Medical Art.

C11 cyclopentenone from the ascidian Diplosoma sp. prevents epidermal growth factor-induced transformation of JB6 cells

C<sub>11</sub> cyclopentenone, 5-hydroxy-7-prop-2-en- (E)-ylidene-7,7a-dihydro-2H-cyclopenta[b] pyran-6-one, isolated earlier from the sponges and ascidians, is known as a natural product possessing antimicrobial and cytotoxic properties. However, its cancer preventive activity has not been studied. Cancer preventive and proapoptotic properties of the compound as well as its effect on the main Mitogen- Activated Protein-Kinase (MAPK) signaling pathways were examined by the methods of epidermal growth factor- induced (EGFinduced) JB6 Cl41 P+ cell transformation in soft agar, flow cytometry, and MTS test of cell viability. Results: the compound inhibits EGFinduced neoplastic JB6 Cl41 P+ cell transformation in soft agar and induces apoptosis of HL-60 and THP-1 human leukemia cells. Jun N-terminal Kinase and p38 MAPK signaling pathways are involved in the cellular response to the treatment by the compound. Conclusions: 5-hydroxy-7-prop-2-en-(E)-ylidene- 7,7a-dihydro-2H-cyclopenta[b]pyran-6- one and other related marine C11 cyclopentenones have potential for development of a new antitumor agent in cancer prophylactics and should be further investigated.

The response of human ectomesenchymal dental pulp stem cells to cisplatin treatment

To determine the response of dental pulp stem cells (DPSCs) to DNA-damaging cytostatic cisplatin and compare it with the response of normal human dermal fibroblasts (HDFs). Dental pulp stem cells were exposed to 5, 10, 20 or 40 μmol L(-1) of cisplatin. The proliferation of affected cells was assessed by a Z2 Counter and viability was assessed by means of a Vi-Cell XR using Trypan blue exclusion staining. Cell cycle analysis and induction of apoptosis were performed by flow cytometry. Induction of apoptosis was determined by monitoring the activities of caspases. The expression of proteins was detected by electrophoresis and Western blotting. The descriptive statistics of the results was analyzed by Student's t-test. Dental pulp stem cells had a greater genotoxic stress response to cisplatin compared to HDFs. All three main Mitogen-activated protein kinases (MAPK) families - extracellular signal-regulated kinases (ERK), c-Jun-N-terminal kinase (JNK) and p38 were activated after treatment of DPSCs with cisplatin. The activation of MAPK pathways was not observed in HDFs exposed to cisplatin. The exposure of DPSCs and HDFs to cisplatin provoked an increase in p53 and p21 expression and p53 phosphorylation of serine 15. Higher concentrations of cisplatin reduced the viability of DPSCs and HDFs and induced the activation of caspases 3/7 and 9. Dental pulp stem cells had a greater genotoxic stress response to cisplatin compared to HDFs. Cisplatin in higher concentrations triggered activation of MAPK and apoptosis in DPSCs but not in HDFs.

Prevotella intermedialipopolysaccharide stimulates release of tumor necrosis factor-α through mitogen-activated protein kinase signaling pathways in monocyte-derived macrophages

The purpose of this study was to investigate the effects of lipopolysaccharide from Prevotella intermedia, a major cause of inflammatory periodontal disease, on the production of tumor necrosis factor (TNF)-alpha and the expression of TNF-alpha mRNA in differentiated THP-1 cells, a human monocytic cell line. The potential involvement of the three main mitogen-activated protein kinase (MAPK) signaling pathways in the induction of TNF-alpha production was also investigated. Lipopolysaccharide from P. intermedia ATCC 25611 was prepared by the standard hot phenol-water method. THP-1 cells were incubated in the medium supplemented with phorbol myristate acetate to induce differentiation into macrophage-like cells. It was found that P. intermedia lipopolysaccharide can induce TNF-alpha mRNA expression and stimulate the release of TNF-alpha in differentiated THP-1 cells without additional stimuli. Treatment of the cells with P. intermedia lipopolysaccharide resulted in a simultaneous activation of three MAPKs [extracellular signal-related kinase 1/2 (ERK1/2), c-Jun N-terminal kinase 1/2 (JNK1/2) and p38]. Pretreatment of the cells with MAPK inhibitors effectively suppressed P. intermedia lipopolysaccharide-induced TNF-alpha production without affecting the expression of TNF-alpha mRNA. These data thus provided good evidence that the MAPK signaling pathways are required for the regulation of P. intermedia lipopolysaccharide-induced TNF-alpha synthesis at the level of translation more than at the transcriptional level.

Involvement of mitogen-activated protein kinases and protein kinase C in cadmium-induced prostaglandin E2 production in primary mouse osteoblastic cells.

We previously reported that cadmium (Cd) induced prostaglandin E2 (PGE2) biosynthesis through the activation of cytosolic phospholipase A2 (cPLA2) and induction of cyclooxygenase 2 (COX-2) in primary mouse osteoblastic cells. In the present study, we further investigated the mechanism of PGE2 production by Cd focusing on the main mitogen-activated protein kinase (MAPK) subfamilies that mediate prostaglandin synthesis, extracellular signal-regulated kinase (ERK1/2 MAPK), c-jun-amino-terminal kinase (JNK MAPK) and p38 MAPK, and protein kinase C (PKC) which is activated by Cd in several kinds of cells. Cd at 2 microM and above stimulated PGE2 production in osteoblastic cells and its production was inhibited by the kinase-specific inhibitors PD98059, SB203580, curcumin, and calphostin C. Calphostin C also inhibited the production of PGE2 by phorbol 12-myristate 13-acetate (PMA), which is a potent activator of PKC. PD98059 inhibited PGE2 production stimulated by PMA as well as Cd, indicating that activation of PKC by ERK1/2 MAPK was necessary for Cd-stimulated PGE2 production. Moreover, Cd stimulated the phosphorylation of these three MAPKs, and inhibition of the phosphorylation of ERK1/2 MAPK by calphostin C was also observed. On the other hand, Cd was found to phosphorylate cPLA2 and the phosphorylation was inhibited by PD98059, indicating that cPLA2 was activated by Cd through ERK1/2 MAPK and released arachidonic acid (AA), a substrate of COX-2, from membranous phospholipids. From these results, it was suggested that activation of each of the ERK1/2, p38, and JNK MAPK cascades in addition to that of PKC and cPLA2 played an important role in the Cd-stimulated biosynthesis of PGE2 in mouse osteoblastic cells.

Activation of MAPKs by G protein-coupled receptors.

AbstractG protein-coupled receptors (GPCRs) constitute the largest family of cell-surface molecules involved in signal transmission. These receptors play key physiologic roles, with their dysfunction resulting in a number of disease states (1). Recently, we have learned that many of the cellular responses mediated by GPCRs do not involve the sole stimulation of conventional second-messenger-generating systems, but result from the functional integration of an intricate network of intracellular signaling pathways. Among these, the main mitogenactivated protein kinase (MAPK) pathways, those mediated by extracellular signal-regulated kinase (ERK)1-2, c-Jun N-terminal kinase (JNK), p38, and ERK5/big mitogen-activated protein kinase (BMK), are potently activated by GPCRs (2). GPCRs owe their name to their extensively studied interaction with heterotrimeric G proteins (α-, β-, and γ-subunits), which undergo conformational changes that lead to the exchange of guanosine 5′-diphosphate for guanosine 5′-triphosphate (GTP) bound to the α-subunit on receptor activation. Consequently, Gα- and Gβγ-subunits stimulate effector molecules, including adenylyl and guanylyl cyclases, phosphodiesterases, phospholipase A2 (PLA2) and PLC, and phosphatidylinositol-3 kinases, thereby activating or inhibiting the production of a variety of second messengers, such as cyclic adenosine monophosphate, cyclic guanosine monophosphate, diacylglycerol, inositol triphosphate (IP3), and phosphatidyinositol triphosphate (PIP3), arachidonic and phosphatidic acid, and promoting (Ca2+) elevation and the opening or closing of a variety of ion channels (3). KeywordsMyelin Basic ProteinGuanylyl CyclaseInositol TriphosphateSodium VanadateAgonist IsoproterenolThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.