Epidermal growth factor induces c-fos and c-jun mRNA via Raf-1/MEK1/ERK-dependent and -independent pathways in bovine luteal cells

β-carotene inhibits MAPKs signaling pathways on rat colonic epithelial cells to attenuate TNF-α-induced intestinal inflammation and injury

This experiment successfully isolated the rat colonic epithelial cells and established a TNF-α-induced intestinal inflammation model. Western Blot was used to detect the related protein expression levels of the MAPKs signaling pathway. QPCR technology was used to detect the expression of aquaporins, intestinal mucosal repair factor, and inflammatory factors. The results show that 25 μM β-carotene pretreatment at 24 h can inhibit MAPKs signaling pathway activated by TNF-α, change the relative mRNA expression of inflammatory cytokines, intestinal mucosal repair factors, and aquaporins, and the phosphorylated protein expression of p38, ERK, and NF-κB were attenuated to reduce inflammatory damage. After inhibiting p38 and ERK, the effect of β-carotene was reduced significantly (P < 0.05). In conclusion, β-carotene can alleviate the abnormal expression of aquaporins caused by inflammation through the MAPKs signaling pathway. This is for β-carotene as a functional nutrient that provides new insights.

The Therapeutic Potential of MAPK/ERK Inhibitors in the Treatment of Colorectal Cancer

The MAPK/ERK signaling pathway regulates cancer cell proliferation, apoptosis, inflammation, angiogenesis, metastasis and drug resistance. Mutations and up-regulation of components of the MAPK/ERK signaling pathway, as well as over-activation of this critical signaling pathway, are frequently observed in colorectal carcinomas. Targeting the MAPK/ERK signaling pathway, using specific pharmacological inhibitors, elicits potent anti-tumor effects, supporting the therapeutic potential of these inhibitors in the treatment of CRC. Several drugs have recently been developed for the inhibition of the MEK/ERK pathway in preclinical and clinical settings, such as MEK162 and MK-2206. MEK1/2 inhibitors demonstrate promising efficacy and anticancer activity for the treatment of this malignancy. This review summarizes the current knowledge on the role of the MAPK/ERK signaling pathway in the pathogenesis of CRC and the potential clinical value of synthetic inhibitors of this pathway in preventing CRC progression for a better understanding, and hence, better management of colorectal cancer.

Therapeutic Potential of Berberine in the Treatment of Glioma: Insights into Its Regulatory Mechanisms

Glioma is known as one of the most common primary intracranial tumors accounting for four-fifths of malignant brain tumors. There are several biological pathways that play a synergistic, pathophysiological role in glioma, including apoptosis, autophagy, oxidative stress, and cell cycle arrest. According to previous rese arches, the drugs used in the treatment of glioma have been associated with significant limitations. Therefore, improved and/or new therapeutic platforms are required. In this regard, multiple flavonoids and alkaloids have been extensively studied in the treatment of glioma. Berberine is a protoberberine alkaloid with wide range of pharmacological activities, applicable to various pathological conditions. Few studies have reported beneficial roles of berberine in glioma. Berberine exerts its pharmacological functions in glioma by controlling different molecular and cellular pathways. We reviewed the existing knowledge supporting the use of berberine in the treatment of glioma and its effects on molecular and cellular mechanisms.

Toward Modeling Context-Specific EMT Regulatory Networks Using Temporal Single Cell RNA-Seq Data

Epithelial-mesenchymal transition (EMT) is well established as playing a crucial role in cancer progression and being a potential therapeutic target. To elucidate the gene regulation that drives the decision making of EMT, many previous studies have been conducted to model EMT gene regulatory circuits (GRCs) using interactions from the literature. While this approach can depict the generic regulatory interactions, it falls short of capturing context-specific features. Here, we explore the effectiveness of a combined bioinformatics and mathematical modeling approach to construct context-specific EMT GRCs directly from transcriptomics data. Using time-series single cell RNA-sequencing data from four different cancer cell lines treated with three EMT-inducing signals, we identify context-specific activity dynamics of common EMT transcription factors. In particular, we observe distinct paths during the forward and backward transitions, as is evident from the dynamics of major regulators such as NF-KB (e.g., NFKB2 and RELB) and AP-1 (e.g., FOSL1 and JUNB). For each experimental condition, we systematically sample a large set of network models and identify the optimal GRC capturing context-specific EMT states using a mathematical modeling method named Random Circuit Perturbation (RACIPE). The results demonstrate that the approach can build high quality GRCs in certain cases, but not others and, meanwhile, elucidate the role of common bioinformatics parameters and properties of network structures in determining the quality of GRCs. We expect the integration of top-down bioinformatics and bottom-up systems biology modeling to be a powerful and generally applicable approach to elucidate gene regulatory mechanisms of cellular state transitions.

The Expression of ERK1/2 in Female Yak (Bos grunniens) Reproductive Organs

The main reproductive organs undergo different histological appearances and physiological processes under different reproductive statuses. The variation of these organs depends on a delicate regulation of cell proliferation, differentiation, and apoptosis. Extracellular signal-regulated kinases1/2 (ERK1/2) are members of the mitogen-activated protein kinase (MAPK) super family. They have important roles in regulating various biological processes of different cells, tissues, and organ types. Activated ERK1/2 generally promotes cell survival, but under certain conditions, ERK1/2 also have the function of inducing apoptosis. It is widely believed that ERK1/2 play a significant role in regulating the reproductive processes of mammals. The goal of our research is to investigate the expression and distribution of ERK1/2 in the yak's main reproductive organs during different stages. In the present study, samples of the ovary, oviduct, and uterus of 15 adult female yak were collected and used in the experiment. The ERK1/2 proteins, localization, and quantitative expression of their mRNA were investigated using immunohistochemistry (IHC), western blot (WB) and relative quantitative real-time polymerase chain reaction (RT-PCR). The results indicated that ERK1/2 proteins and their mRNA were highly expressed in the ovary of the luteal phase and gestation period, in the oviduct of the luteal phase, and in the uterus of the luteal phase and gestation period. Immunohistochemical analysis revealed a strong distribution of ERK1/2 proteins in follicular granulosa cells, granular luteal cells, villous epithelial cells of the oviduct, endometrial glandular epithelium, and luminal epithelium. These results demonstrated that the expression of ERK1 and ERK2 proteins and their mRNA in the yak's ovary, oviduct, and uterus varies with the stage of the reproductive cycle. The variation character of ERK1 and ERK 2 expression in the yak's main reproductive organs during different stages implies that they play an important role in regulating the reproductive function under different physiological statuses.

FOS, a Critical Downstream Mediator of PGR and EGF Signaling Necessary for Ovulatory Prostaglandins in the Human Ovary

CONTEXT

Fos null mice failed to ovulate and form a corpus luteum (CL) even when given exogenous gonadotropins, suggesting that ovarian Fos expression is critical for successful ovulation and CL formation. However, little is known about FOS in the human ovary.

OBJECTIVES

To determine the expression, regulation, and function of FOS in human periovulatory follicles.

DESIGN/PARTICIPANTS

Timed periovulatory follicles were obtained from normally cycling women. Granulosa/lutein cells were collected from in vitro fertilization patients.

MAIN OUTCOME MEASURES

The in vivo expression after human chorionic gonadotropin (hCG) administration and in vitro regulation of FOS, JUN, JUNB, and JUND was evaluated at the mRNA and protein level. Binding of progesterone receptor (PGR) and FOS to their target genes was assessed by chromatin immunoprecipitation analyses. Prostaglandin E2 (PGE2) and progesterone were measured.

RESULTS

The expression of FOS, JUNB, and JUND drastically increased in ovulatory follicles after hCG administration. In human granulosa/lutein cell cultures, hCG increased the expression of FOS and JUN proteins. Inhibitors of PGR and epidermal growth factor (EGF) receptors reduced hCG-induced increases in the expression and phosphorylation of FOS. PGR bound to the FOS gene. A selective FOS inhibitor blocked hCG-induced increases in PGE2 and the expression of prostaglandin (PG) synthases and transporters (PTGES, SLCO2A1, and ABCC1). FOS bound to the promoter regions of these genes.

CONCLUSIONS

The increase of FOS/activator protein 1 in human periovulatory follicles after hCG administration is mediated by collaborative actions of PGR and EGF signaling and critical for the upregulated expression of key ovulatory genes required for the rise in ovulatory PG in human granulosa cells.

Lactobacillus acidophilus stimulates intestinal P-glycoprotein expression via a c-Fos/c-Jun-dependent mechanism in intestinal epithelial cells

Our previous studies showed that Lactobacillus acidophilus (LA) culture supernatant (CS) increased P-glycoprotein [Pgp/multidrug resistance 1 (MDR1)] function, expression, and promoter activity in Caco-2 cells. The current studies were designed to elucidate the molecular mechanisms mediating the stimulatory effects of LA CS on Pgp promoter activity. Deletion analysis indicated that the LA CS response element(s) is located in the -172/+428-bp region, and sequence analysis of this region revealed three potential binding sites for c-Fos or c-Jun: proximal activating protein (AP) 1a (-119/-98 bp), distal AP1b (-99/-78 bp), and AP1c (+175/+196 bp). LA CS (24 h) showed an approximately twofold increase in the protein expression of c-Fos and c-Jun in Caco-2 cells. Electrophoretic mobility shift assay showed that LA CS markedly increased the binding of Caco-2 nuclear proteins to AP1a and AP1b, but not AP1c. The DNA-protein complex was completely eliminated by c-Fos antibody, while c-Jun antibody partially eliminated the complex. Chromatin immunoprecipitation analysis also showed that LA CS enhanced the association of c-Fos and c-Jun (by ∼4- and 1.5-fold, respectively) with endogenous Pgp promoter in Caco-2 cells (p-172/+1). Interestingly, overexpression of c-Fos or c-Jun activated Pgp promoter by nearly twofold each. This increase was further enhanced (∼14-fold) when c-Fos and c-Jun were simultaneously overexpressed, suggesting that the presence of one of these transcription factors potentiates the effect of the other. These studies, for the first time, provide evidence for the involvement of c-Fos/c-Jun in stimulation of Pgp gene expression by LA CS in the human intestine.

Neuronal Activity Promotes Glioma Growth through Neuroligin-3 Secretion

Active neurons exert a mitogenic effect on normal neural precursor and oligodendroglial precursor cells, the putative cellular origins of high-grade glioma (HGG). By using optogenetic control of cortical neuronal activity in a patient-derived pediatric glioblastoma xenograft model, we demonstrate that active neurons similarly promote HGG proliferation and growth in vivo. Conditioned medium from optogenetically stimulated cortical slices promoted proliferation of pediatric and adult patient-derived HGG cultures, indicating secretion of activity-regulated mitogen(s). The synaptic protein neuroligin-3 (NLGN3) was identified as the leading candidate mitogen, and soluble NLGN3 was sufficient and necessary to promote robust HGG cell proliferation. NLGN3 induced PI3K-mTOR pathway activity and feedforward expression of NLGN3 in glioma cells. NLGN3 expression levels in human HGG negatively correlated with patient overall survival. These findings indicate the important role of active neurons in the brain tumor microenvironment and identify secreted NLGN3 as an unexpected mechanism promoting neuronal activity-regulated cancer growth.

Cyclin-dependent kinase 12 increases 3' end processing of growth factor-induced c-FOS transcripts

Transcriptional cyclin-dependent kinases (CDKs) regulate RNA polymerase II initiation and elongation as well as cotranscriptional mRNA processing. In this report, we describe an important role for CDK12 in the epidermal growth factor (EGF)-induced c-FOS proto-oncogene expression in mammalian cells. This kinase was found in the exon junction complexes (EJC) together with SR proteins and was thus recruited to RNA polymerase II. In cells depleted of CDK12 or eukaryotic translation initiation factor 4A3 (eIF4A3) from the EJC, EGF induced fewer c-FOS transcripts. In these cells, phosphorylation of serines at position 2 in the C-terminal domain (CTD) of RNA polymerase II, as well as levels of cleavage-stimulating factor 64 (Cstf64) and 73-kDa subunit of cleavage and polyadenylation specificity factor (CPSF73), was reduced at the c-FOS gene. These effects impaired 3' end processing of c-FOS transcripts. Mutant CDK12 proteins lacking their Arg-Ser-rich (RS) domain or just the RS domain alone acted as dominant negative proteins. Thus, CDK12 plays an important role in cotranscriptional processing of c-FOS transcripts.

Crosstalk between PKCα and Notch-4 in endocrine-resistant breast cancer cells

The Notch pathway is functionally important in breast cancer. Notch-1 has been reported to maintain an estrogen-independent phenotype in estrogen receptor α (ERα)+ breast cancer cells. Notch-4 expression correlates with Ki67. Notch-4 also plays a key role in breast cancer stem-like cells. Estrogen-independent breast cancer cell lines have higher Notch activity than estrogen-dependent lines. Protein kinase Cα (PKCα) overexpression is common in endocrine-resistant breast cancers and promotes tamoxifen (TAM)-resistant growth in breast cancer cell lines. We tested whether PKCα overexpression affects Notch activity and whether Notch signaling contributes to endocrine resistance in PKCα-overexpressing breast cancer cells.Analysis of published microarray data from ERα+ breast carcinomas shows that PKCα expression correlates strongly with Notch-4. Real-time reverse transcription PCR and immunohistochemistry on archival specimens confirmed this finding. In a PKCα-overexpressing, TAM-resistant T47D model, PKCα selectively increases Notch-4, but not Notch-1, expression in vitro and in vivo. This effect is mediated by activator protein-1 (AP-1) occupancy of the Notch-4 promoter. Notch-4 knockdown inhibits estrogen-independent growth of PKCα-overexpressing T47D cells, whereas Notch-4IC expression stimulates it. Gene expression profiling shows that multiple genes and pathways associated with endocrine resistance are induced in Notch-4IC- and PKCα-expressing T47D cells. In PKCα-overexpressing T47D xenografts, an orally active γ-secretase inhibitor at clinically relevant doses significantly decreased estrogen-independent tumor growth, alone and in combination with TAM. In conclusion, PKCα overexpression induces Notch-4 through AP-1. Notch-4 promotes estrogen-independent, TAM-resistant growth and activates multiple pathways connected with endocrine resistance and chemoresistance. Notch inhibitors should be clinically evaluated in PKCα- and Notch-4-overexpressing, endocrine-resistant breast cancers.

Resveratrol and apoptosis

Resveratrol is a naturally occurring stilbene with desirable cardioprotective and anti-cancer properties. We have demonstrated the existence of a plasma membrane receptor for resveratrol near the arginine-glycine-aspartate (RGD) recognition site on integrin α(v)β₃ that is involved in stilbene-induced apoptosis of cancer cells. Resveratrol treatment in vitro causes activation and nuclear translocation of mitogen-activated protein kinase (ERK1/2), consequent phosphorylation of Ser-15 of p53, and apoptosis. An RGD peptide blocks these actions of resveratrol. By a PD98059-inhibitable process, resveratrol causes inducible COX-2 to accumulate in the nucleus where it complexes with pERK1/2 and p53. Chromatin immunoprecipitation reveals binding of nuclear COX-2 to promoters of certain p53-responsive genes, including PIG3 and Bax. NS-398, a specific pharmacologic inhibitor of COX-2, prevents resveratrol-induced complexing of nuclear ERK1/2 with COX-2 and with pSer-15-p53 and subsequent apoptosis; cyclooxygenase enzyme activity is not involved. Molecular steps in the pro-apoptotic action of resveratrol in cancer cells include induction of intranuclear COX-2 accumulation relevant to activation of p53. Epidermal growth factor, estrogen, and thyroid hormone act downstream of ERK1/2 to prevent resveratrol-induced apoptosis.

Effect of decreasing intraluteal progesterone on sensitivity of the early porcine corpus luteum to the luteolytic actions of prostaglandin F2alpha

Prostaglandin F2alpha (PGF) causes luteolysis of the pig corpus luteum (CL) only after Day 12 of the estrous cycle. Recent evidence indicates that progesterone (P4) may protect the CL from cell death. The present study tested the hypothesis that acute inhibition of P4 by treatment with epostane (EPO; 3betaHSD inhibitor) in CL lacking luteolytic capacity (Day 9 CL) will allow PGF to induce responses associated with luteolysis. Multiple PGF-induced responses were evaluated, including genes involved in production of PGF and estradiol-17beta, apoptosis (caspase 3), and transcription (FOSB). These responses are associated with PGF-induced luteolysis and do not normally occur in CL lacking luteolytic capacity. Animals on Day 7 after estrus were divided into four groups: 1) control (C), 2) PGF, 3) EPO, and 4) PGF plus EPO (PGF+EPO). Treatment with EPO (10 mg/kg) or vehicle was given every 12 h for 36 h. Treatment with PGF (25 mg) or vehicle was given at 38 h, and CL were collected from all animals at 48 h. Some CL from each animal were frozen in liquid nitrogen for mRNA and protein analysis. Remaining CL were incubated in media for 2 h for determination of P4 and PGF production. EPO dramatically decreased production of P4 by luteal tissue (ng/mg tissue) by 90% and 95% in EPO and PGF+EPO groups, respectively, compared to C (P < 0.01). Low production of PGF by luteal tissue was found in C, PGF, and EPO groups; however, treatment with PGF+EPO dramatically increased (782%) luteal PGF production. Similar to intraluteal PGF production, increased mRNA for cyclooxygenase 2 (PTGS2) and phospholipase A2 (group IB; PLA2G1B) was found in the PGF+EPO, but not in the EPO or PGF, group. Aromatase (CYP19A1) mRNA was not induced by PGF or EPO; however, PGF+EPO caused a more than 40-fold increase in CYP19A1 mRNA (P < 0.01). CASP3 mRNA was increased (P < 0.01) by EPO (3.4-fold) and by PGF (2.7-fold) but was most dramatically increased by PGF+EPO (5.3-fold), whereas caspase activity was only increased by PGF (1.5-fold) or PGF+EPO (2.2-fold). Thus, these data support the hypothesis that elimination of the protective effect of intraluteal P4 does not directly cause luteolysis of the early CL but allows PGF to induce luteolytic responses in CL lacking luteolytic capacity.

The small heat shock protein alphaA-crystallin is expressed in pancreas and acts as a negative regulator of carcinogenesis

The small heat shock protein alphaA-crystallin is a structural protein in the ocular lens. In addition, recent studies have also revealed that it is a molecular chaperone, an autokinase and a strong anti-apoptotic regulator. Besides its lenticular distribution, a previous study demonstrates that a detectable level of alphaA-crystallin is found in other tissues including thymus and spleen. In the present study, we have re-examined the distribution of alphaA-crystallin in various normal human and mouse tissues and found that the normal pancreas expresses a moderate level of alphaA-crystallin. Moreover, alphaA-crystallin is found significantly downregulated in 60 cases of pancreatic carcinoma of different types than it is in 11 normal human pancreas samples. In addition, we demonstrate that alphaA-crystallin can enhance the activity of the activating protein-1 (AP-1) through modulating the function of the MAP kinase, and also upregulates components of TGFbeta pathway. Finally, expression of alphaA-crystallin in a pancreatic cancer cell line, MiaPaCa, results in retarded cell migration. Together, these results suggest that alphaA-crystallin seems to negatively regulate pancreatic carcinogenesis.

Raf-1 kinase regulates smooth muscle contraction in the rat mesenteric arteries

We investigated the potential role of Raf-1 kinase in mesenteric arterial contraction. Inhibitors of Raf-1 kinase, GW5074, L779450 and ZM 336372 reversed phenylephrine (PE)-induced mesenteric vascular contraction. Studies in vivo in rats showed that GW5074 inhibited PE-induced increase in mean arterial pressure in adult female Sprague-Dawley rats. Isometric tension studies in mesenteric arteries of rats showed that GW5074 did not change the KCl-evoked contraction but significantly inhibited the contractions to PE, 5-HT, U46619, endothelin 1, angiotensin II and phorbol 12, 13-dibutyrate (PDBu). In mesenteric vascular smooth muscle cells (VSMCs), PE stimulated increase in Raf-1 phosphorylation which was inhibited by GW5074. Measurement of [Ca(2+)](i) with Fura-2 showed that GW5074-mediated inhibition of PE-induced contraction was not associated with decreases in [Ca(2+)](i). VSMCs treated with PE exhibited higher levels of the contractile proteins, p-MYPT1 and p-MLC(20), which was inhibited by GW5074. Similarly, PDBu induced increases in phosphorylation of Raf-1, MLC(20) and MYPT1 and this was inhibited by GW5074. However, GW5074 did not have any significant effect on PE/PDBu-induced MEK/ERK activation. The results indicate that Raf-1 kinase plays an important role in the regulation of vascular contractility through regulation of calcium sensitization.

Caveolin-1 plays important role in EGF-induced migration and proliferation of mouse embryonic stem cells: involvement of PI3K/Akt and ERK

The involvement of caveolin-1 in the regulation of embryonic stem (ES) cell growth by epidermal growth factor (EGF) is by no means clear cut. Thus we examined the relationship between EGF and caveolin-1 in mouse ES cell migration and proliferation. The results revealed that EGF increased Src, caveolin-1, focal adhesion kinase (FAK), Akt, and extracellular signal-regulated kinase-1/2 (ERK) phosphorylation levels. Especially, phosphorylation of caveolin-1 is attenuated by AG1478, herbimycin A (tyrosine kinase inhibitors), and pyrazolopyrimidine 2 (PP2, Src inhibitor) and EGF-induced ERK activation was blocked by PP2, methyl-β-cyclodextrin (MβCD), caveolin-1 small interfering RNA (siRNA), LY-294002 [phosphoinositol-3 kinase inhibitor (PI3K)], and Akt inhibitor. In addition, EGF promoted the cell migration, which was attenuated by PP2, caveolin-1 siRNA, FAK siRNA, LY-294002, Akt inhibitor, and PD-98059. EGF also increased matrix metalloproteinase (MMP-2) expression levels and EGF-induced MMP2 expression was inhibited by caveolin-1 siRNA, FAK siRNA, LY-294002, Akt inhibitor, and PD-98059. Furthermore, EGF-induced increase of cell cycle proteins expression level and [3H]thymidine incorporation was blocked by MMP inhibitor. EGF also significantly increases [3H]thymidine incorporation and cell number, which were significantly blocked by AG 1478, PP2, MβCD, caveolin-1 siRNA, FAK siRNA, LY-294002, and PD-98059 (ERK inhibitor). EGF-induced increase of protooncogenes (c- fos, c- myc, and c- Jun) and cell cycle regulatory proteins (cyclin D1, CDK4, cyclin E, and CDK2) expression levels were also attenuated by caveolin-1 siRNA and FAK siRNA. In conclusion, these results demonstrated that EGF-induced DNA synthesis and cell migration are mediated by caveolin-1, which is activated by Src, FAK, PI3K/Akt, ERK, and MMP-2 signals in mouse ES cells.

c-Fos mediates angiotensin II-induced aldosterone production and protein synthesis in bovine adrenal glomerulosa cells

Angiotensin II (AngII), potassium ion, and ACTH are the main factors controlling aldosterone biosynthesis in adrenal glomerulosa cells. AP-1 response elements for the immediate early gene products, c-Fos and c-Jun, have been identified, among others, in the promoter of the steroidogenic acute regulatory (StAR) protein gene, whose expression is acutely regulated by activators of aldosterone production. In bovine glomerulosa cells, AngII treatment led to a rapid and transient increase in c-fos mRNA expression, c-Fos protein expression, and c-Fos phosphorylation. Inhibition of the ERK1/2 MAPK pathway abolished the effect of AngII on c-fos mRNA, protein, and phosphorylation. EMSA and chromatin immunoprecipitation experiments demonstrated that c-Fos binds with c-Jun to the proximal StAR promoter and that AngII treatment increases the amount of c-Fos bound to the promoter. Overexpression of a dominant-negative form of c-Fos with adenoviral vectors inhibited StAR mRNA and StAR protein expression as well as aldosterone biosynthesis in response to AngII. The dominant-negative c-Fos also prevented the increase in protein synthesis induced by AngII in glomerulosa cells, as assessed by [(3)H]leucine incorporation. These results indicate that AngII rapidly induces c-Fos expression and posttranslational modifications. Furthermore, a heterodimeric c-Fos/c-Jun complex binds to the proximal StAR promoter in glomerulosa cells, thus activating StAR gene expression and acute aldosterone biosynthesis. Finally, c-Fos also contributes to other functional responses to the hormone, such as protein synthesis.

Requirement of Fut8 for the expression of vascular endothelial growth factor receptor-2: a new mechanism for the emphysema-like changes observed in Fut8-deficient mice

alpha1,6-Fucosylation plays key roles in many biological functions, as evidenced by the study of alpha1,6-fucosyltransferase (Fut8) knockout (Fut8(-/-)) mice. Phenotypically, Fut8(-/-) mice exhibit emphysema-like changes in the lung, and severe growth retardation. Fut8(-/-) cells also show marked dysregulation of the TGF-beta1 receptor, EGF receptor, integrin activation and intracellular signalling, all of which can be rescued by reintroduction of Fut8. The results of the present study demonstrated that vascular endothelial growth factor receptor-2 (VEGFR-2) expression was significantly suppressed in Fut8(-/-) mice, suggesting that Fut8 was required for VEGFR-2 expression. The expression of VEGFR-2 mRNA and protein was consistently down-regulated by knockdown of the Fut8 gene with small interference RNA in A549 cells, as well as in TGP49 cells, suggesting that suppression occurs at the level of transcription. In contrast, the expression level of ceramide, an inducer of cell apoptosis, was increased in the lungs of Fut8(-/-) mice. The terminal transferase dUTP nick end-labelling (TUNEL) assay was used to identify apoptotic cells. The number of TUNEL-positive septal epithelia and endothelia cells was significantly increased in the alveolar septa of lungs from Fut8(-/-) mice when in comparison with lungs from wild-type mice. It is well known that, in emphysema, ceramide expression can be greatly enhanced by blockade of the VEGFR-2. Thus, suppression of VEGFR-2 expression may provide a novel explanation for the emphysema-like changes in Fut8(-/-) mice.

Tumor cell phenotype is sustained by selective MAPK oxidation in mitochondria

Mitochondria are major cellular sources of hydrogen peroxide (H₂O₂), the production of which is modulated by oxygen availability and the mitochondrial energy state. An increase of steady-state cell H₂O₂ concentration is able to control the transition from proliferating to quiescent phenotypes and to signal the end of proliferation; in tumor cells thereby, low H₂O₂ due to defective mitochondrial metabolism can contribute to sustain proliferation. Mitogen-activated protein kinases (MAPKs) orchestrate signal transduction and recent data indicate that are present in mitochondria and regulated by the redox state. On these bases, we investigated the mechanistic connection of tumor mitochondrial dysfunction, H₂O₂ yield, and activation of MAPKs in LP07 murine tumor cells with confocal microscopy, in vivo imaging and directed mutagenesis. Two redox conditions were examined: low 1 µM H₂O₂ increased cell proliferation in ERK1/2-dependent manner whereas high 50 µM H₂O₂ arrested cell cycle by p38 and JNK1/2 activation. Regarding the experimental conditions as a three-compartment model (mitochondria, cytosol, and nuclei), the different responses depended on MAPKs preferential traffic to mitochondria, where a selective activation of either ERK1/2 or p38-JNK1/2 by co-localized upstream kinases (MAPKKs) facilitated their further passage to nuclei. As assessed by mass spectra, MAPKs activation and efficient binding to cognate MAPKKs resulted from oxidation of conserved ERK1/2 or p38-JNK1/2 cysteine domains to sulfinic and sulfonic acids at a definite H₂O₂ level. Like this, high H₂O₂ or directed mutation of redox-sensitive ERK2 Cys²¹⁴ impeded binding to MEK1/2, caused ERK2 retention in mitochondria and restricted shuttle to nuclei. It is surmised that selective cysteine oxidations adjust the electrostatic forces that participate in a particular MAPK-MAPKK interaction. Considering that tumor mitochondria are dysfunctional, their inability to increase H₂O₂ yield should disrupt synchronized MAPK oxidations and the regulation of cell cycle leading cells to remain in a proliferating phenotype.

Transcriptional regulation of endothelial nitric oxide synthase expression in uterine artery endothelial cells by c-Jun/AP-1

Despite extensive studies have shown that increased endothelial nitric oxide synthase (NOS3) expression in the uterine artery endothelial cells (UAEC) plays a key role in uterine vasodilatation, the molecular mechanism controlling NOS3 expression in UAEC is unknown. According to the sheep NOS3 promoter sequence isolated in our laboratory, we hypothesize that the activator protein-1 (AP-1) site in the proximal sheep NOS3 promoter (TGAGTCA, -682 to -676) is important for NOS3 expression. We developed a c-Jun adenoviral expression system to overexpress c-Jun protein into UAEC to investigate the effects of c-Jun/AP-1 on NOS3 expression. Basal levels of c-Jun protein and mRNA were detected in UAEC. c-Jun protein was overexpressed in a concentration and time-dependent fashion in UAEC infected with sense c-Jun (S-c-Jun), but not sham and antisense c-Jun (A-c-Jun) adenoviruses. Infection with S-c-Jun adenovirus (25 MOI, multiplicity of infection) resulted in efficient c-Jun protein overexpression in UAEC up to 3 days. In S-c-Jun, but not sham and A-c-Jun adenovirus infected UAEC, NOS3 mRNA and protein levels were increased (P<0.05) compared to noninfected controls. Increased NOS3 expression was associated with increased total NOS activity. Transient transfections showed that c-Jun overexpression augmented the transactivation of the sheep NOS3 promoter-driven luciferase/reporter constructs with the AP-1 site but not of deletion constructs without the AP-1 site. When the AP-1 site was mutated, c-Jun failed to trans-activate the sheep NOS3 promoter. AP-1 DNA binding activity also increased in c-Jun overexpressed UAEC. Lastly, the pharmacological AP-1 activator phorbol myristate acetate increased AP-1 binding, trans-activated the wild-type but not the AP-1 mutant NOS3 promoter and dose-dependently stimulated UAEC NOS3 and c-Jun protein expression. Hence, our data show that c-Jun/AP-1 regulates NOS3 transcription involving the proximal AP-1 site in the 5'-regulatory region of the sheep NOS3 gene.

Bovine germinal vesicle oocyte and cumulus cell proteomics

Germinal vesicle (GV) breakdown is fundamental for maturation of fully grown, developmentally competent, mammalian oocytes. Bidirectional communication between oocytes and surrounding cumulus cells (CC) is essential for maturation of a competent oocyte. However, neither the factors involved in this communication nor the mechanisms of their actions are well defined. Here, we define the proteomes of GV oocytes and their surrounding CC, including membrane proteins, using proteomics in a bovine model. We found that 4395 proteins were expressed in the CC and 1092 proteins were expressed in oocytes. Further, 858 proteins were common to both the CC and the oocytes. This first comprehensive proteome analysis of bovine oocytes and CC not only provides a foundation for signaling and cell physiology at the GV stage of oocyte development, but are also valuable for comparative studies of other stages of oocyte development at the molecular level. Furthermore, some of these proteins may represent molecular biomarkers for developmental potential of oocytes.

Activation of extracellular regulated kinases (ERK1/2) but not AKT predicts poor prognosis in colorectal carcinoma and is associated with k-ras mutations

Signal transduction and modulation represent central mechanisms in cellular processes such as cell-cycle regulation, oncogenesis, and apoptosis. The aim of this study was to determine the prognostic relevance of two kinases important in the regulation of cell proliferation and apoptosis in 135 colorectal cancer cases: AKT and extracellular regulated kinases (ERK1/2). We investigated the relationship of phospho-ERK1/2 (pERK1/2) and phospho-AKT (pAKT) with associated parameters (EGFR, COX-2, cyclin-D1), proliferative activity (Ki-67), and apoptosis (TUNEL) using immunohistochemistry. Additionally, the k-ras gene was screened for mutations to determine its putative association with ERK1/2 activation. Activation of ERK1/2 but not AKT correlated statistically with the presence of k-ras mutations (P = 0.015). Survival analysis of phospho-ERK1/2 immunoexpression showed a significant correlation with decreased overall survival (OS). The multivariate Cox regression analysis identified pERK1/2 as an independent prognostic parameter (P = 0.005). Activation of ERK1/2 in colorectal cancer may indicate aggressive tumor behavior and may constitute an independent prognostic factor. Furthermore, our data suggest that mutations of the k-ras oncogene may induce activation of ERK1/2. We propose immunohistochemical determination of pERK1/2 status as a promising candidate for the identification of high-risk patients who would benefit from new anticancer drugs targeting the ERK pathway.

Mercury pollution in two typical areas in Guizhou province, China and its neurotoxic effects in the brains of rats fed with local polluted rice

Guizhou province, which located in southwestern of China, is an important mercury (Hg) production center. This study was to investigate the environmental levels and ecological effects of mercury in two typical Hg polluted areas in Guizhou province. In addition, to improve the understanding of the neurotoxic effects of Hg, a rats based laboratory study was also carried out in this study. Samples of water, soil, plants, crops and animals collected from Wanshan mercury mine area, Guzhou province, were analyzed by mercury analyzer. The effects of Hg contaminated rice on the expression of c-jun mRNA in rat's brain and the expression of c-JUN protein in cortex, hippocampus were observed using reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemical methods. The results showed that the mercury contents in most environmental samples of aquatics, soil, atmosphere and the biomass of corn, plant and animals, were higher than the national standard and the corresponding data from unpolluted area. It was found mercury pollutions were significant in soil and air. In the laboratory study, the expression of c-jun mRNA and its protein was significantly induced by Hg polluted rice collected from local area. Selenium could reduce the Hg accumulation in the body and had antagonist effect on Hg in terms of the expression of c-jun mRNA and c-JUN protein. The environmental data and Hg levels in different creatures collected in this study will facilitate the environmental and ecological risk assessment of Hg in the polluted areas. It was urged to be alert of mental health problem in human beings when any kind of Hg-polluted food was taken. More efforts should be performed to protect the local ecosystem and human health in the mercury polluted area of Wanshan, Guizhou province of China.

Down-regulation of trypsinogen expression is associated with growth retardation in alpha1,6-fucosyltransferase-deficient mice: attenuation of proteinase-activated receptor 2 activity

Alpha1,6-fucosyltransferase (Fut8) plays important roles in physiological and pathological conditions. Fut8-deficient (Fut8-/-) mice exhibit growth retardation, earlier postnatal death, and emphysema-like phenotype. To investigate the underlying molecular mechanism by which growth retardation occurs, we examined the mRNA expression levels of Fut8-/- embryos (18.5 days postcoitum [dpc]) using a cDNA microarray. The DNA microarray and real-time polymerase chain reaction (PCR) analysis showed that a group of genes, including trypsinogens 4, 7, 8, 11, 16, and 20, were down-regulated in Fut8-/- embryos. Consistently, the expression of trypsinogen proteins was found to be lower in Fut8-/- mice in the duodenum, small intestine, and pancreas. Trypsin, an active form of trypsinogen, regulates cell growth through a G-protein-coupled receptor, the proteinase-activated receptor 2 (PAR-2). In a cell culture system, a Fut8 knockdown mouse pancreatic acinar cell carcinoma, TGP49-Fut8-KDs, showed decreased growth rate, similar to that seen in Fut8-/- mice, and the decreased growth rate was rescued by the application of the PAR-2-activating peptide (SLIGRL-NH2). Moreover, epidermal growth factor (EGF)-induced receptor phosphorylation was attenuated in TGP49-Fut8-KDs, which was highly associated with a reduction of trypsinogens mRNA levels. The addition of exogenous EGF recovered c-fos, c-jun, and trypsinogen mRNA expression in TGP49-Fut8-KDs. Again, the EGF-induced up-regulation of c-fos and c-jun mRNA expression was significantly blocked by the protein kinase C (PKC) inhibitor. Our findings clearly demonstrate a relationship between Fut8 and the regulation of EGF receptor (EGFR)-trypsin-PAR-2 pathway in controlling cell growth and that the EGFR-trypsin-PAR-2 pathway is suppressed in TGP49-Fut8-KDs as well as in Fut8-/- mice.

Follicle-stimulating hormone-induced aromatase in immature rat Sertoli cells requires an active phosphatidylinositol 3-kinase pathway and is inhibited via the mitogen-activated protein kinase signaling pathway

Postnatal development and function of testicular Sertoli cells are regulated primarily by FSH. During this early period of development, estrogens play a role in proliferation of somatic cells, which contributes significantly to testicular development. Growth factors like epidermal growth factor (EGF) are produced in the testis and play a role in regulation of estradiol production and male fertility. Although these divergent factors modulate gonadal function, little is known about their mechanism of action in Sertoli cells. The present study investigates the intracellular events that take place down-stream of FSH and EGF receptors in Sertoli cells isolated from immature (10-d-old) rats, and examines which intracellular signals may be involved in their effects on aromatase activity and estradiol production in immature rat Sertoli cells. Primary cultures of rat Sertoli cells were treated with FSH in combination with EGF and signaling pathway-specific inhibitors. Levels of estradiol production, aromatase mRNA (Cyp19a1), and aromatase protein (CYP19A1) were determined. Western blot analysis was performed to determine the effects of FSH and EGF on levels of activated (phosphorylated) AKT1 and p42 ERK2 and p44 ERK1, also named MAPK1 and MAPK3, respectively. The stimulatory actions of FSH on aromatase mRNA, aromatase protein, and estradiol production were blocked by inhibition of the phosphatidylinositol 3-kinase/AKT1 signaling pathway. In contrast, inhibition of ERK signaling augmented the stimulatory effects of FSH on estradiol production, aromatase mRNA, and protein levels. Furthermore, EGF inhibited the expression of aromatase mRNA and protein in response to FSH, and these inhibitory effects of EGF were critically dependent on the activation of the ERK signaling pathway. We conclude that an active phosphatidylinositol 3-kinase /AKT signaling pathway is required for the stimulatory actions of FSH, whereas an active ERK/MAPK pathway inhibits estradiol production and aromatase expression in immature Sertoli cells.

Prokineticins (endocrine gland-derived vascular endothelial growth factor and BV8) in the bovine ovary: expression and role as mitogens and survival factors for corpus luteum-derived endothelial cells

A highly vascular endocrine gland, the corpus luteum (CL) is an excellent model for the study of angiogenic factors. Prokineticins (PK-1 and -2), also termed endocrine-gland-derived vascular endothelial growth factor (VEGF) and BV8 are newly identified proteins described as selective angiogenic mitogens. We previously identified PK binding sites, two closely homologous G protein-coupled receptors (PK-R1 and PK-R2) in human and bovine ovarian cells, but their function remained unknown. In this study we examined the presence and effects of PK in CL-derived endothelial and steroidogenic cell types (LEC and LSC, respectively). PK-1 mRNA was identified in CL and follicles by real-time PCR, using primers specific for the bovine PK-1 sequence (retrieved from Bos taurus whole genome shotgun database). PK were potent angiogenic mitogens for LEC; they enhanced cell proliferation, elevated [3H]thymidine incorporation, MAPK activation, and c-jun/fos mRNA expression. The effects of PK proteins on cell survival were examined by nuclear morphology (4',6-diamidino-2-phenylindole dihydrochloride staining), measurement of DNA fragmentation (terminal dUTP nucleotide end labeling assay), and caspase-3 cleavage. Results obtained by these techniques demonstrated that PK protected LEC from serum starvation-induced apoptosis. Stress conditions such as serum withdrawal, TNF-alpha, and hypoxia markedly increased PK-R2 expression, whereas mRNA levels of PK-R1 remained unchanged. These suggest that the antiapoptotic effect of PK-1 on LEC may be mediated via PK-R2. PK-1 increased VEGF mRNA expression by LSC, implying that it could also indirectly, via VEGF, affect luteal angiogenesis. Together, these findings suggest an important role for PK-1 in luteal function by acting as a mitogen and survival factor in LEC.

The MAPK signalling pathways and colorectal cancer

There are three major subfamilies of mitogen-activated protein kinases (MAPK): the extracellular-signal-regulated kinases (ERK MAPK); the c-jun N-terminal kinase or stress-activated protein kinases (JNK or SAPK); and MAPK14. The ERK MAPK pathway is one of the most important for cell proliferation. The MAPK pathways are located downstream of many growth-factor receptors, including that for epidermal growth factor. Overexpression and activation of this receptor are commonly detected in colorectal cancer, and several lines of evidence indicate that overexpression and activation of ERK MAPK play an important part in progression of this cancer. ERK MAPK could be a molecular target for treatment of the disorder. This review focuses on the ERK MAPK signal-transduction pathway, the consequences of its dysregulation in colorectal cancer, and its potential as an approach to cancer treatment. Future challenges for the assessment of these targeted agents in the clinic are also presented.

Phosphorylation of c-Fos by members of the p38 MAPK family. Role in the AP-1 response to UV light

Exposure to sources of UV radiation, such as sunlight, induces a number of cellular alterations that are highly dependent on its ability to affect gene expression. Among them, the rapid activation of genes coding for two subfamilies of proto-oncoproteins, Fos and Jun, which constitute the AP-1 transcription factor, plays a key role in the subsequent regulation of expression of genes involved in DNA repair, cell proliferation, cell cycle arrest, death by apoptosis, and tissue and extracellular matrix remodeling proteases. Besides being regulated at the transcriptional level, Jun and Fos transcriptional activities are also regulated by phosphorylation as a result of the activation of intracellular signaling cascades. In this regard, the phosphorylation of c-Jun by UV-induced JNK has been readily documented, whereas a role for Fos proteins in UV-mediated responses and the identification of Fos-activating kinases has remained elusive. Here we identify p38 MAPKs as proteins that can associate with c-Fos and phosphorylate its transactivation domain both in vitro and in vivo. This phosphorylation is transduced into changes in its transcriptional ability as p38-activated c-Fos enhances AP1-driven gene expression. Our findings indicate that as a consequence of the activation of stress pathways induced by UV light, endogenous c-Fos becomes a substrate of p38 MAPKs and, for the first time, provide evidence that support a critical role for p38 MAPKs in mediating stress-induced c-Fos phosphorylation and gene transcription activation. Using a specific pharmacological inhibitor for p38alpha and -beta, we found that most likely these two isoforms mediate UV-induced c-Fos phosphorylation in vivo. Thus, these newly described pathways act concomitantly with the activation of c-Jun by JNK/MAPKs, thereby contributing to the complexity of AP1-driven gene transcription regulation.

EGF stimulates mesangial cell mitogenesis via PI3-kinase-mediated MAPK-dependent and AKT kinase-independent manner: involvement of c-fos and p27Kip1

Epidermal growth factor (EGF) is a potent mitogen for mesangial cells. The mechanism by which EGF induces DNA synthesis is not precisely understood. We investigated the role of phosphatidylinositol (PI)3-kinase in regulating mitogenesis. EGF increased PI3-kinase activity resulting in stimulation of PDK-1 and Akt kinase activities. Blocking of PI3-kinase activity using LY-294002 or adenoviral expression of PTEN, which dephosphorylates PI3,4,5-tris-phosphate and thus inactivates PI3-kinase signaling, significantly inhibits EGF-induced DNA synthesis. Expression of dominant-negative Akt kinase, however, had no effect on DNA synthesis. But it inhibited EGF-induced phosphorylation of FoxO3a transcription factor, thus demonstrating its functional consequences. These data indicate that EGF increases the DNA synthesis in a PI3-kinase-dependent but Akt-independent manner. In addition to activating PI3-kinase signaling, EGF increased Erk1/2 MAPK activity, leading to transcriptional activation of its nuclear target Elk-1 and resulting in c-fos expression. Inhibition of MAPK activity by MEK inhibitor U-0126 abolished EGF-induced DNA synthesis. Because EGF activates PI3-kinase, which also regulates DNA synthesis, the effect of PI3-kinase on MAPK activity was also examined. Inhibition of PI3-kinase signaling blocked EGF-induced MAPK activity as well as Elk-1-dependent reporter transcription and c-fos gene transcription. To further determine the mechanism of EGF-induced DNA synthesis, we investigated the effect of EGF on the cyclin-dependent kinase inhibitor p27(Kip1). EGF reduced the expression of p27(Kip1). Inhibition of PI3-kinase action or MAPK activity abolished the reduction in p27(Kip1) expression induced by EGF. These data provide the evidence that a linear signal transduction pathway involving PI3-kinase-dependent MAPK regulates EGF-induced DNA synthesis in mesangial cells by regulating c-fos and p27(Kip1) expression.

Inhibitory effect of epidermal growth factor on resveratrol-induced apoptosis in prostate cancer cells is mediated by protein kinase C-α

Resveratrol, a naturally occurring stilbene with antitumor properties, caused mitogen-activated protein kinase [MAPK, extracellular signal-regulated kinase 1/2 (ERK1/2)] activation, nuclear translocation of Ser15-phosphorylated p53, and p53-dependent apoptosis in hormone-insensitive DU145 prostate cancer cells. Exposure of these cells to epidermal growth factor (EGF) for up to 4 hours resulted in brief activation of MAPK followed by inhibition of resveratrol-induced signal transduction, p53 phosphorylation, and apoptosis. Resveratrol stimulated c-fos and c-jun expression in DU145 cells, an effect also suppressed by EGF. An inhibitor of protein kinase C (PKC)-α, -β, and -γ (CGP41251) enhanced Ser15 phosphorylation of p53 by resveratrol in the absence of EGF and blocked EGF inhibition of the resveratrol effect. EGF caused PKC-α/β phosphorylation in DU145 cells, an effect reversed by CGP41251. Activation of PKC by phorbol ester (phorbol 12-myristate 13-acetate) enhanced EGF action on ERK1/2 phosphorylation without significantly altering p53 phosphorylation by resveratrol. DU145 cells transfected with a dominant-negative PKC-α construct showed resveratrol-induced ERK1/2 phosphorylation and Ser15 phosphorylation of p53 but were unresponsive to EGF. Thus, resveratrol and EGF activate MAPK by discrete mechanisms in DU145 cells. The stilbene promoted p53-dependent apoptosis, whereas EGF opposed induction of apoptosis by resveratrol via a PKC-α-mediated mechanism. Resveratrol also induced p53 phosphorylation in LNCaP prostate cancer cells, an effect also inhibited by EGF. Inhibition of PKC activation in LNCaP cells, however, resulted in a reduction, rather than increase, in p53 activation and apoptosis, suggesting that resveratrol-induced apoptosis in these two cell lines occurs through different PKC-mediated and MAPK-dependent pathways.

Tyrosine hydroxylase induction by basic fibroblast growth factor and cyclic AMP analogs in striatal neural stem cells: role of ERK1/ERK2 mitogen-activated protein kinase and protein kinase C

Neural stem cells (NSC) with self-renewal and multilineage potential are considered good candidates for cell replacement of damaged nervous tissue. In vitro experimental conditions can differentiate these cells into specific neuronal phenotypes. In the present study, we describe the combined effect of basic fibroblast growth factor (bFGF) and dibutyryladenosine 3',5'-cyclic monophosphate (dbcAMP) on the differentiation of fetal rat striatal NSC into tyrosine hydroxylase-positive cells. Tyrosine hydroxylase induction was accompanied by the activation of ERK1/ERK2 mitogen-activated protein kinase and was inhibited by the ERK1/ERK2 pathway blocker PD98059, suggesting that ERK activation may be important for this process. In addition, protein kinase C (PKC) was shown to be required for tyrosine hydroxylase protein expression. The inhibition of PKC by staurosporin, as well as its downregulation, decreased the ability of bFGF+dbcAMP to generate tyrosine hydroxylase-positive cells. Moreover, the PKC activator phorbol 12-myristate 13-acetate (PMA) together with bFGF and dbcAMP led to a significant increase in phospho-ERK1/ERK2 levels, and the percentage of beta-tubulin III-positive cells that expressed tyrosine hydroxylase increased by 3.5-fold. PMA also promoted the phosphorylation of the cyclic AMP response element binding protein that might contribute to the increase in tyrosine hydroxylase-positive cells observed in bFGF+dbcAMP+PMA-treated cultures. From these results, we conclude that the manipulation in vitro of NSC from rat fetal striatum with bFGF, cyclic AMP analogs, and PKC activators promotes the generation of tyrosine hydroxylase-positive neurons.

Human Bcl-2 activates ERK signaling pathway to regulate activating protein-1, lens epithelium-derived growth factor and downstream genes

The proto-oncogene, bcl-2, has various functions besides its role in protecting cells from apoptosis. One of the functions is to regulate expression of other genes. Previous studies have demonstrated that Bcl-2 regulates activities of several important transcription factors including NF-kappaB and p53, and also their downstream genes. In our recent studies, we reported that Bcl-2 substantially downregulates expression of the endogenous alphaB-crystallin gene through modulating the transcriptional activity of lens epithelium-derived growth factor (LEDGF). In the present communication, we report that human Bcl-2 can positively regulate expression of the proto-oncogenes c-jun and c-fos. Moreover, it enhances the DNA binding activity and transactivity of the activating protein-1 (AP-1). Furthermore, we present evidence to show that Bcl-2 can also activate both ERK1 and ERK2 MAP kinases. Inhibition of the activities of these kinases or the upstream activating kinases by pharmacological inhibitors or dominant-negative mutants abolishes the Bcl-2-mediated regulation of AP-1, LEDGF and their downstream genes. Together, our results demonstrate that through activation of the ERK kinase signaling pathway, Bcl-2 regulates the transcriptional activities of multiple transcription factors, and hence modulates the expression of their downstream genes. Thus, our results provide a mechanism to explain how Bcl-2 may regulate expression of other genes.

Signal transduction events involved in TPA downregulation of SP-A gene expression

Surfactant protein A (SP-A), the most abundant pulmonary surfactant protein, plays a role in innate host defense and blocks the inhibitory effects of serum proteins on surfactant surface tension-lowering properties. SP-A mRNA and protein are downregulated by phorbol esters (TPA) via inhibition of gene transcription. We evaluated the TPA signaling pathways involved in SP-A inhibition in a lung cell line, H441 cells. TPA caused sustained phosphorylation of p44/42 mitogen-activated protein kinase (MAPK), p38 MAPK, and c-Jun-NH2-terminal kinase. An inhibitor of conventional and novel isoforms of protein kinase C (PKC) and two inhibitors of p44/42 MAPK kinase partially or completely blocked the inhibitory effects of TPA on SP-A mRNA levels. In contrast, inhibitors of conventional PKC-α and -β, stress-activated protein kinases, protein phosphatases, protein kinase A, and the phosphatidylinositol 3-kinase pathway had no effect on the TPA-mediated inhibition of SP-A mRNA. TPA also stimulated the synthesis of c-Jun mRNA and protein in a time-dependent manner. Inhibitors of the p44/42 MAPK signaling pathway and PKC blocked the TPA-mediated phosphorylation of p44/42 MAPK and the increase in c-Jun mRNA. We conclude that TPA inhibits SP-A gene expression via novel isoforms of PKC, the p44/42 MAPK pathway, and the activator protein-1 complex.

Mineralocorticoid receptor antagonists do not block rapid ERK activation by aldosterone

Aldosterone can elicit rapid nongenomic effects both in vivo and in vitro, often mediated by signal transduction cascades. However, it is not understood how these rapid effects are initiated. In this study we show that aldosterone leads to rapid activation of mitogen activated protein kinases ERK1/2 in the cortical collecting duct cell line M-1. Inhibitors of transcription and translation could not block this activation, which suggests an extranuclear (nongenomic) mechanism. Although it is known that M-1 cells do not contain a transcriptionally functional MR, it is not known whether a closely related protein still could mediate the effects, or an unrelated nonclassic receptor. To test this hypothesis, the effects of four classical mineralocorticoid receptor antagonists were studied. None of the compounds could block the response to aldosterone. Altogether, the data suggest that rapid aldosterone effects in M-1 cells are initiated by a receptor different from the classical mineralocorticoid receptor.

Protein Kinase C and Mitogen-Activated Protein Kinase Cascade in Mouse Cumulus Cells: Cross Talk and Effect on Meiotic Resumption of Oocyte1

Protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) in cumulus cells are involved in FSH-induced meiotic resumption of cumulus-enclosed oocytes (CEOs), but their regulation and cross talk are unknown. The present experiments were designed to investigate 1) the possible involvement of MAPK cascade in PKC-induced meiotic resumption; 2) the regulation of PKC on MAPK activity in FSH-induced oocyte maturation; and 3) the pattern of PKC and MAPK function in induced meiotic resumption of mouse oocytes. PKC activators, phorbol 12-myristate 13-acetate (PMA) and 1-oleoyl-2-acetyl-sn-glycerol (OAG), induced the meiotic resumption of CEOs and activation of MAPK in cumulus cells, whereas this effect could be abolished by PKC inhibitors, calphostin C and chelerythrine, or MEK inhibitor U0126. These results suggest that PKC might induce the meiotic reinitiation of CEOs by activating MAPK in cumulus cells. Both PKC inhibitors and U0126 inhibited the FSH-induced germinal vesicle breakdown (GVBD) of oocytes and MAPK activation in cumulus cells, suggesting that PKC and MAPK are involved in FSH-induced GVBD of mouse CEOs. Protein synthesis inhibitor cycloheximide (CHX) inhibited FSH- or PMA-induced oocyte meiotic resumption, but not the MAPK activation in cumulus cells. FSH and PKC activators induced the GVBD in denuded oocytes cocultured with cumulus cells in hypoxanthine (HX)-supplemented medium, and this effect could be reversed by U0126. Thus, when activated by FSH and PKC, MAPK may stimulate the synthesis of specific proteins in cumulus cells followed by secretion of an unknown positive factor that is capable of inducing GVBD in oocytes.

Membrane estrogen receptor-dependent extracellular signal-regulated kinase pathway mediates acute activation of endothelial nitric oxide synthase by estrogen in uterine artery endothelial cells

Rapid uterine vasodilatation after estrogen administration is believed to be mediated by endothelial production of nitric oxide (NO) via endothelial NO synthase (eNOS). However, the mechanism(s) by which estrogen activates eNOS in uterine artery endothelial cells (UAEC) is unknown. In this study, we observed that estradiol-17beta (E2) and E2-BSA rapidly (<2 min) increased total NOx production in UAEC in vitro. This was associated with rapid eNOS phosphorylation and activation but was unaltered by pretreatment with actinomycin-D. Estrogen receptor-alpha protein was detectable in isolated plasma membrane proteins by immunoblotting, and E2-BSA-fluorescein isothiocyanate binding was evident on the plasma membrane of UAEC. E2 did not mobilize intracellular Ca2+, but E2 and ionomycin in combination induced greater eNOS phosphorylation than either E2 or ionomycin alone. E2 did not stimulate rapid Akt phosphorylation. E2 stimulated rapid ERK2/1 activation in a time- and dose-dependent manner, with maximal responses observed at 5-10 min with E2 (10 nm to 1 microm) treatment. Acute activation of eNOS and NOx production by E2 could be inhibited by PD98059 but not by LY294002. When E2-BSA was applied, similar responses in NOx production, eNOS, and ERK2/1 activation to those of E2 were achieved. In addition, E2 and E2-BSA-induced ERK2/1 activation and ICI 182,780 could inhibit NOx production by E2. Thus, acute activation of eNOS to produce NO in UAEC by estrogen is at least partially through an ERK pathway, possibly via estrogen receptor localized on the plasma membrane. This pathway may provide a novel mechanism for NO-mediated rapid uterine vasodilatation by estrogen.