Histone code of genes induced by co-treatment with a glucocorticoid hormone agonist and a p44/42 MAPK inhibitor in human small intestinal Caco-2 cells

Background

Inactivation of glucocorticoid hormones and p44/42 mitogen-activated protein kinase (MAPK) is thought to be important in small intestinal maturation and expression of genes related to intestinal differentiation and functions.

Methods

We investigated target genes induced by co-treatment for 48 h with a glucocorticoid hormone agonist, dexamethasone (Dex), and a p44/42 MAPK inhibitor, PD98059 (PD), in a small intestine-like cell line (Caco-2) using microarray analysis. We also investigated whether expression changes of the target genes induced by the co-treatment are associated with histone modifications around these genes.

Results

Co-treatment of Caco-2 cells with Dex and PD enhanced several genes related to intestinal differentiation and functions such as SCNN1A, FXYD3, LCT and LOX. Induction of the SCNN1A gene was associated with increased presence of acetylated histone H3 and H4 and di-methylated histone H3 at lysine (K) 4 around the transcribed region of the gene, and induction of the FXYD3 gene was associated with increased presence of acetylated histones H3 and H4 from the promoter/enhancer to the transcribed region of the gene. Induction of LCT and LOX genes was associated with increased presence of acetylated histone H4 on the promoter/enhancer region of the genes.

Conclusions

Histone acetylation and/or histone H3 K4 methylation around the promoter/enhancer or/and transcribed regions of target genes are associated with induction of the genes by co-treatment with Dex and PD in Caco-2 cells.

General significance

The histone code is specific to each gene with respect to induction by glucocorticoid hormone and inhibition of p44/42 MAPK in Caco-2 cells.     

PD98059 enhanced insulin, cytokine, and growth factor activation of xanthine oxidoreductase in epithelial cells involves STAT3 and the glucocorticoid receptor

PD98059 and U0126 are organic compound inhibitors frequently used to block the activity of the MEK-1/2 protein kinase. In the present work, promoter activation analyses of xanthine oxidoreductase (XOR) in epithelial cells uncovered the unexpected opposite effect of these inhibitors on activation of XOR. Activation of an XOR-luciferase fusion gene was studied in stably transfected epithelial cells. The XOR reporter gene was activated by the epidermal growth factors (EGF), prolactin, and dexamethasone and by the acute phase cytokines (APC) IL-1, IL-6, and TNFalpha as previously reported for its native gene, and insulin further stimulated activation induced with acute phase cytokines or growth factors. Activation of the proximal promoter was blocked by inhibitors of the glucocorticoid receptor (GR), p38 MAP kinase, and U0126. Unexpectedly, PD98059 activated the promoter and significantly enhanced expression induced by insulin, APC, or growth factors. Analysis of the XOR upstream DNA and proximal promoter revealed primary roles for the GR and STAT3 in mediating the effects of PD98059 on XOR activation and protein complex formation with the promoter. STAT3 phosphotyrosine-705 was rapidly induced by PD98059, dexamethasone, and insulin. XOR activation by PD98059, dexamethasone, or insulin was superinduced by a constitutively active derivative of STAT3, while a dominant negative derivative of STAT3 blocked the enhancing effect of PD98059 on XOR activation. These data demonstrate a previously unrecognized effect of PD98059 on STAT3 and the GR that could have unanticipated consequences when used to infer the involvement of the MEK-1/2 protein kinase.     

Endothelin-1 increases glucose transporter glut1 mRNA accumulation in 3T3-L1 adipocytes by a mitogen-activated protein kinase-dependent pathway

The mechanism of enhancing glucose transport by prolonged endothelin-1 (ET-1) treatment of 3T3-L1 adipocytes was examined. Western and Northern blot analyses indicated that ET-1 increased the amount of both GLUT1 protein and mRNA. The degradation rate of GLUT1 mRNA as measured in the presence of actinomycin D, nevertheless, was not significantly altered by ET-1. Whereas various inhibitors for distinct signalling pathways were tested, only the mitogen-activated protein kinase (MAPK) kinase inhibitor, PD98059, was found to decrease significantly the enhancing effect of ET-1. Similar extent of inhibition was observed in cells pretreated with pertussis toxin (PT). Immunoblot analysis revealed that ET-1 may stimulate a transient phosphorylation of p42/p44 MAPK and both PT and PD98059 inhibited this stimulation. In addition, the effect of ET-1 on GLUT1 mRNA accumulation was inhibited by PD98059 and cycloheximide, implying that a trans-activation was involved. Taken together, these results suggest that ET-1 may induce GLUT1 gene expression by a MAPK-dependent mechanism.     

Glucocorticoid receptor (GR)-associated SMRT binding to C/EBPbeta TAD and Nrf2 Neh4/5: role of SMRT recruited to GR in GSTA2 gene repression

The expression of the glutathione S-transferase gene (GST), whose induction accounts for cancer chemoprevention, is regulated by activation of CCAAT/enhancer binding protein beta (C/EBPbeta) and NF-E2-related factor 2 (Nrf2). The present study investigated the repressing effects of activating glucocorticoid receptor (GR) on C/EBPbeta- and Nrf2-mediated GSTA2 gene induction and the mechanism. Dexamethasone that activates GR inhibited constitutive and oltipraz- or tert-butylhydroquinone (t-BHQ)-inducible GSTA2 expression in H4IIE cells. Also, dexamethasone repressed GSTA2 promoter-luciferase gene activity. Dexamethasone-GR activation did not inhibit nuclear translocation of C/EBPbeta or Nrf2 nor their DNA binding activities induced by oltipraz or t-BHQ. Deletion of the glucocorticoid response element (GRE) in the GSTA2 promoter abolished dexamethasone inhibition of the gene induction. Immunoprecipitation-immunoblotting, chromatin immunoprecipitation, and GST pull-down assays revealed that silencing mediator for retinoid and thyroid hormone receptors (SMRT), a corepressor recruited to steroid-GR complex for histone deacetylation, bound to TAD domain of C/EBPbeta and Neh4/5 domain of Nrf2. The GSTA2 promoter-luciferase activities were decreased by SMRT but not by truncated SMRTs. The small interference RNA (siRNA) against SMRT abolished SMRT repression of the gene induction by C/EBPbeta or Nrf2. The plasmid transfection and siRNA experiments directly evidenced the functional role of SMRT in GSTA2 repression. In conclusion, dexamethasone antagonizes C/EBPbeta- and Nrf2-mediated GSTA2 gene induction via ligand-GR binding to the GRE, and steroid-mediated GSTA2 repression involves inactivation of C/EBPbeta and Nrf2 by SMRT recruited to steroid-GR complex.     

Role of MAPK in chronic cerebral vasospasm

This study was undertaken to investigate the role of p44/42 MAPK in a dog double hemorrhage model of subarachnoid hemorrhage (SAH), and whether MEK inhibitors can alter the degree of SAH-induced vasoconstriction. The diameter of the basilar artery, which was compared with day 0 angiogram, decreased gradually in a time-dependent manner from day 3 (80%), day 5 (68%) through day 7 (53.5%). The level of MAPK (p44/42) immunoprecipitation peaked on day 3 and remained enhanced through day 7 (P < 0.05). MEK inhibitor PD98059 significantly reduced p44/42 MAPK immunoprecipitation and significantly reversed vasospasm and increased residual diameter to 79.0% on day 7. These results demonstrated that p44/42 MAPK kinase is involved in the pathogenesis of cerebral vasospasm. The MEK inhibitor PD98059 might be useful in the treatment of vasospasm.     

5-HT Induction of c-fos gene expression requires reactive oxygen species and rac1 and ras GTPases

Serotonin (5-HT) stimulates superoxide release, phosphorylation, of p42/p44 mitogen-activated protein kinase (MAPK), and DNA synthesis in bovine pulmonary artery smooth muscle cells. Both p42/p44 MAPK and reactive oxygen species (ROS) generation are required for 5-HT-induced growth in SMC. Agents that block the production of ROS, or ROS scavengers, block MAPK activation by 5-HT. However, specific signal transduction by 5-HT leading to proteins that control entrance into the cell cycle are not well defined in smooth muscle cells. Here, we show by Western blot that 5-HT upregulates c-Fos, an immediate early gene product known to regulate the entrance of quiescent cells into the cell cycle. Northern blots showed that c-fos mRNA is induced by 5-HT in 30 min. This induction is blocked by PD98059, indicating that activation of MAPK is required. 5-HT-induced expression of a 350 bp c-fos promoter in a luciferase reporter is blocked by PD98059 and diphenyliodonium (DPI). The GTPases Rac1 and Ras have been implicated in growth factor-induced generation of ROS. Overexpression of either dominant negative (DN) Rac1 or DN Ras inhibited 5-HT-mediated c-fos promoter activation. 5-HT also induced expression from a truncated c-fos promoter containing an isolated serum response element. This activation was blocked by DPI and PD98059. Overexpression of activated Ras and Rac1 were additive for activation of the serum response element promoter. Regulation of cyclin D1, a protein shown to be regulated by c-fos and required for entry into the cell cycle, is upregulated by 5-HT and is blocked by DPI and PD98059. Nuclear factor-κB, which can also regulate cyclin D1, was not activated. We conclude that 5-HT stimulates c-fos and cyclin D1 expression through a ROS-dependent mechanism that requires Ras, Rac1, and MAPK.     

Tumor necrosis factor alpha produces insulin resistance in skeletal muscle by activation of inhibitor kappaB kinase in a p38 MAPK-dependent manner

Insulin stimulation produced a reliable 3-fold increase in glucose uptake in primary neonatal rat myotubes, which was accompanied by a similar effect on GLUT4 translocation to plasma membrane. Tumor necrosis factor (TNF)-alpha caused insulin resistance on glucose uptake and GLUT4 translocation by impairing insulin stimulation of insulin receptor (IR) and IR substrate (IRS)-1 and IRS-2 tyrosine phosphorylation, IRS-associated phosphatidylinositol 3-kinase activation, and Akt phosphorylation. Because this cytokine produced sustained activation of stress and proinflammatory kinases, we have explored the hypothesis that insulin resistance by TNF-alpha could be mediated by these pathways. In this study we demonstrate that pretreatment with PD169316 or SB203580, inhibitors of p38 MAPK, restored insulin signaling and normalized insulin-induced glucose uptake in the presence of TNF-alpha. However, in the presence of PD98059 or SP600125, inhibitors of p42/p44 MAPK or JNK, respectively, insulin resistance by TNF-alpha was still produced. Moreover, TNF-alpha produced inhibitor kappaB kinase (IKK)-beta activation and inhibitor kappaB-beta and -alpha degradation in a p38 MAPK-dependent manner, and treatment with salicylate (an inhibitor of IKK) completely restored insulin signaling. Furthermore, TNF-alpha produced serine phosphorylation of IR and IRS-1 (total and on Ser(307) residue), and these effects were completely precluded by pretreatment with either PD169316 or salicylate. Consequently, TNF-alpha, through activation of p38 MAPK and IKK, produces serine phosphorylation of IR and IRS-1, impairing its tyrosine phosphorylation by insulin and the corresponding activation of phosphatidylinositol 3-kinase and Akt, leading to insulin resistance on glucose uptake and GLUT4 translocation.     

Sustained phosphorylation of mitogen-activated protein kinase is required for basic fibroblast growth factor-mediated axonal branch formation in cultured rat hippocampal neurons

Basic fibroblast growth factor (bFGF) has been reported to promote the formation of axonal branches in cultured brain neurons. In the present study, we investigated whether the mitogen-activated protein kinase (MAPK) cascade was involved in this action of bFGF in cultured rat hippocampal neurons. Recombinant human bFGF (0.1-10 ng/ml) induced phosphorylation of p44/42 MAPK in a concentration and time-dependent manner. The phosphorylation of p44/42 MAPK occurred rapidly within 5 min after addition of bFGF, and lasted for 48 h. The bFGF-induced phosphorylation of p44/42 MAPK and axonal branch formation were both blocked by simultaneous addition of U0126 and PD98059, specific inhibitors of MAPK kinases. Furthermore, when U0126 and PD98059 were added 24 h after bFGF, phosphorylation of p44/42 m MAPK was decreased, and axonal branch formation was stopped. These results suggest that sustained activation of the MAPK cascade is required for bFGF-mediated axonal branch formation.     

Inhibition of p42 and p44 Mitogen-Activated Protein Kinase Activity by PD98059 Does Not Suppress Nerve Growth Factor-Induced Survival of Sympathetic Neurones

Abstract: Nerve growth factor (NGF) induces persistent p42 and p44 mitogen-activated protein kinase (MAPK) activity in sympathetic neurones in parallel to its survival-promoting activity. To investigate whether these MAPK activities are necessary for NGF-induced survival, we have inhibited NGF-stimulated p42/p44 MAPK activity over extended periods using the compound 2-(2'-amino-3'-methoxyphenyl)-oxanaphthalen-4-one (PD98059). Despite attaining up to 95% inhibition of p42/p44 MAPK activity in cultures treated with NGF and PD98059, neuronal survival is maintained undiminished, although a decrease in the density of the neuritic network is observed. Because p21Ras activity is essential for NGF-induced survival, we conclude that p21Ras-linked activities other than p42 and p44 MAPKs are responsible for mediating NGF-dependent survival of rat sympathetic neurones.     

Evidence that inhibition of p44/42 mitogen-activated protein kinase signaling is a factor in proteasome inhibitor-mediated apoptosis

The proteasome is emerging as a target for cancer therapy because small molecule inhibitors of its catalytic activity induce apoptosis in both in vitro and in vivo models of human malignancies and are proving to have efficacy in early clinical trials. To further elucidate the mechanism of action of these inhibitors, their impact on signaling through the p44/42 mitogen-activated protein kinase (MAPK) pathway was studied. Proteasome inhibition with either carbobenzoxy-leucyl-leucyl-phenylalaninal or lactacystin led to a loss of dually phosphorylated, activated p44/42 MAPK in A1N4-myc human mammary and MDA-MB-231 breast carcinoma cells in a dose- and time-dependent fashion. This correlated with an induction of the dual specificity MAPK phosphatases (MKP)-1 and -2, and blockade of MKP induction using either actinomycin D or Ro-31-8220 significantly decreased loss of activated p44/42 MAPK. Inhibition of p44/42 MAPK signaling by use of the MAPK kinase inhibitors PD 98059 or U0126, or by use of a dominant negative MAPK construct, enhanced proteasome inhibitor-mediated apoptosis. Conversely, activation of MAPK by epidermal growth factor, or use of a mutant MAPK resistant to MKP-mediated dephosphorylation, inhibited apoptosis. These studies support a role for inactivation of signaling through the p44/42 MAPK pathway in proteasome inhibitor-mediated apoptosis.     

Intracellular signalings underlying bradykinin-induced matrix metalloproteinase-9 expression in rat brain astrocyte-1

Bradykinin (BK), an inflammatory mediator, has been shown to increase the expression of proteins such as matrix metalloproteinases (MMPs) on brain cells and contributes to the pathophysiology of inflammatory responses. However, the mechanisms regulating MMP-9 expression by BK in rat brain astrocytes-1 (RBA-1) remain unclear. Here we report that the mitogen-activated protein kinase (MAPK) and NF-kappaB pathways participate in the induction of MMP-9 expression induced by BK in RBA cells. Zymographic, Western blotting, and RT-PCR analyses showed that BK increased expression of MMP-9 mRNA and protein in a time- and concentration-dependent manner. BK-induced MMP-9 mRNA and protein expression was inhibited by MEK1/2 inhibitor PD98059, PI3-K inhibitor LY294002, and NF-kappaB inhibitor helenalin. In accordance with these findings, BK-induced phosphorylation of p42/p44 MAPK and Akt and activation of NF-kappaB was attenuated by prior treatment with PD98059, LY294002, and helenalin, respectively. The effects of BK on MMP-9 expression and p42/p44 MAPK and Akt phosphorylation were inhibited by B(2) receptor antagonist Hoe 140, indicating the involvement of B(2) receptors revealed by [(3)H]-BK binding assay. Furthermore, BK-stimulated translocation of NF-kappaB into the nucleus was revealed by Western blotting and immnofluorescence staining and blocked by Hoe140, PD98059, LY294002, and helenalin. Taken together, these results suggest that in RBA cells, activation of p42/p44 MAPK and Akt cascades mediated through NF-kappaB pathway are essential for BK-induced MMP-9 gene expression. This study may provide insights into the regulation of MMP-9 production in CNS, which may occur in vivo in pathological situations such as CNS inflammation and brain astrocytoma.     

Arachidonic acid modulates the spatiotemporal characteristics of agonist-evoked Ca2+ waves in mouse pancreatic acinar cells

In pancreatic acinar cells analysis of the propagation speed of secretagogue-evoked Ca2+ waves can be used to examine coupling of hormone receptors to intracellular signal cascades that cause activation of protein kinase C or production of arachidonic acid (AA). In the present study we have investigated the role of cytosolic phospholipase A2 (cPLA2) and AA in acetylcholine (ACh)- and bombesin-induced Ca2+ signaling. Inhibition of cPLA2 caused acceleration of ACh-induced Ca2+ waves, whereas bombesin-evoked Ca2+ waves were unaffected. When enzymatic metabolization of AA was prevented with the cyclooxygenase inhibitor indomethacin or the lipoxygenase inhibitor nordihydroguaiaretic acid, ACh-induced Ca2+ waves were slowed down. Agonist-induced activation of cPLA2 involves mitogen-activated protein kinase (MAPK) activation. An increase in phosphorylation of p38(MAPK) and p42/44(MAPK) within 10 s after stimulation could be demonstrated for ACh but was absent for bombesin. Rapid phosphorylation of p38(MAPK) and p42/44(MAPK) could also be observed in the presence of cholecystokinin (CCK), which also causes activation of cPLA2. ACh-and CCK-induced Ca2+ waves were slowed down when p38(MAPK) was inhibited with SB 203580, whereas inhibition of p42/44(MAPK) with PD 98059 caused acceleration of ACh- and CCK-induced Ca2+ waves. The spreading of bombesin-evoked Ca2+ waves was affected neither by PD 98059 nor by SB 203580. Our data indicate that in mouse pancreatic acinar cells both ACh and CCK receptors couple to the cPLA2 pathway. cPLA2 activation occurs within 1-2 s after hormone application and is promoted by p42/44(MAPK) and inhibited by p38(MAPK). Furthermore, the data demonstrate that secondary (Ca2+-induced) Ca2+ release, which supports Ca2+ wave spreading, is inhibited by AA itself and not by a metabolite of AA.