Separate roles for H-Ras and Rac in signaling by transforming growth factor (TGF)-beta. H-Ras is essential for activation of MAP kinase, partially required for transcriptional activation by TGF-beta, but not required for signaling of growth suppression by TGF-beta

Mesothelial cells promote early ovarian cancer metastasis through fibronectin secretion

Ovarian cancer (OvCa) metastasizes to organs in the abdominal cavity, such as the omentum, which are covered by a single layer of mesothelial cells. Mesothelial cells are generally thought to be "bystanders" to the metastatic process and simply displaced by OvCa cells to access the submesothelial extracellular matrix. Here, using organotypic 3D cultures, we found that primary human mesothelial cells secrete fibronectin in the presence of OvCa cells. Moreover, we evaluated the tumor stroma of 108 human omental metastases and determined that fibronectin was consistently overexpressed in these patients. Blocking fibronectin production in primary mesothelial cells in vitro or in murine models, either genetically (fibronectin 1 floxed mouse model) or via siRNA, decreased adhesion, invasion, proliferation, and metastasis of OvCa cells. Using a coculture model, we determined that OvCa cells secrete TGF-β1, which in turn activates a TGF-β receptor/RAC1/SMAD-dependent signaling pathway in the mesothelial cells that promotes a mesenchymal phenotype and transcriptional upregulation of fibronectin. Additionally, blocking α5 or β1 integrin function with antibodies reduced metastasis in an orthotopic preclinical model of OvCa metastasis. These findings indicate that cancer-associated mesothelial cells promote colonization during the initial steps of OvCa metastasis and suggest that mesothelial cells actively contribute to metastasis.

Anti-inflammatory cytokine interleukin-19 inhibits smooth muscle cell migration and activation of cytoskeletal regulators of VSMC motility

Vascular smooth muscle cell (VSMC) migration is an important cellular event in multiple vascular diseases, including atherosclerosis, restenosis, and transplant vasculopathy. Little is known regarding the effects of anti-inflammatory interleukins on VSMC migration. This study tested the hypothesis that an anti-inflammatory Th2 interleukin, interleukin-19 (IL-19), could decrease VSMC motility. IL-19 significantly decreased platelet-derived growth factor (PDGF)-stimulated VSMC chemotaxis in Boyden chambers and migration in scratch wound assays. IL-19 significantly decreased VSMC spreading in response to PDGF. To determine the molecular mechanism(s) for these cellular effects, we examined the effect of IL-19 on activation of proteins that regulate VSMC cytoskeletal dynamics and locomotion. IL-19 decreased PDGF-driven activation of several cytoskeletal regulatory proteins that play an important role in smooth muscle cell motility, including heat shock protein-27 (HSP27), myosin light chain (MLC), and cofilin. IL-19 decreased PDGF activation of the Rac1 and RhoA GTPases, important integrators of migratory signals. IL-19 was unable to inhibit VSMC migration nor was able to inhibit activation of cytoskeletal regulatory proteins in VSMC transduced with a constitutively active Rac1 mutant (RacV14), suggesting that IL-19 inhibits events proximal to Rac1 activation. Together, these data are the first to indicate that IL-19 can have important inhibitory effects on VSMC motility and activation of cytoskeletal regulatory proteins. This has important implications for the use of anti-inflammatory cytokines in the treatment of vascular occlusive disease.

Inhibitory effect of glycoprotein isolated from Opuntia ficus-indica var. saboten MAKINO on activities of allergy-mediators in compound 48/80-stimulated mast cells

The present study was performed to investigate the anti-allergy potentials of glycoprotein (90kDa) isolated from Opuntia ficus-indica var. saboten MAKINO (OFI glycoprotein) in vivo (ICR mice) and in vitro (RBL-2H3 cells). At first, to know whether the OFI glycoprotein has an inhibitory ability for allergy in vivo, we evaluated the activities of allergy-related factors such as histamine and beta-hexosaminidase release, lactate dehydrogenase (LDH), and interleukin 4 (IL-4) in compound 48/80 (8 ml/kg BW)-treated ICR mice. After that, we studied to found the effect for anti-allergy in vitro such as nuclear factor kappa B (NF-kappaB) and inducible nitric oxide synthase (iNOS), extracellular signal-regulated kinase (ERK) 1/2, arachidonic acid, and cyclooxygenase-2 (COX-2) in compound 48/80 (5 microg/ml)-treated RBL-2H3 cells. Our results showed that the OFI glycoprotein (5 mg/kg) inhibited histamine and beta-hexosaminidase release, lactate dehydrogenase (LDH), and interleukin 4 (IL-4) in mice serum. Also OFI glycoprotein (25 microg/ml) has suppressive effects on the expression of MAPK (ERK1/2), and on protein expression of anti-allergic proteins (iNOS and COX-2). Thus, we speculate that the OFI glycoprotein is an example of natural compound that blocks anti-allergic signal transduction pathways.

Prevention of radiation-induced pneumonitis by recombinant adenovirus-mediated transferring of soluble TGF-β type II receptor gene

To investigate whether radiation-induced pneumonitis in the mouse-irradiated lung could be prevented by recombinant adenovirus-mediated soluble transforming growth factor-beta (TGF-beta) type II receptor gene therapy. Radiation fibrosis-prone mice (C57BL/6J) were randomly divided into four groups consisting of a (1) control group (sham-irradiated); (2) radiation (RT)-alone group; (3) RT+AdCMVsTbetaR group and (4) RT+AdCMVluc group. The RT-alone and sham-irradiated mice were killed at several time points after thoracic irradiation with a single dose of 9 Gy, and then the TGF-beta1 concentrations in serum and broncho-alveolar lavage fluid (BALF) were quantified by enzyme-linked immunosorbent assay (ELISA). We used an adenoviral vector expressing a soluble TGF-beta type II receptor (AdCMVsTbetaR), which can bind to TGF-beta and then block the TGF-beta receptor-mediated signal transduction. The C57BL/6J mice were intraperitoneally (i.p.) injected with either 5 x 10(8) plaque-forming units of AdCMVsTbetaR or AdCMVluc, a control adenovirus-expressing luciferase, a week preceding and a week following the X-ray thoracic irradiation. Four weeks after irradiation, the mice were killed and the concentration of TGF-beta1 in the serum and BALF were then measured using ELISA and the lung tissue specimens were examined histopathologically. Following thoracic irradiation with a single dose of 9 Gy, radiation-induced TGF-beta1 release in the serum reached the first peak concentration at 12 h and then declined. It reached a maximal value at 2 weeks after irradiation. In the BALF, the TGF-beta1 concentration was appreciable within the first hour and thereafter declined. It reached a maximal value at 3 days after irradiation. A one-time i.p. injection of AdCMVsTbetaR 1 week before irradiation could not completely suppress the two peaks of the radiation-induced TGF-beta1 increase, whereas an injection a week preceding and a week following thoracic irradiation was able to suppress those two peaks thoroughly. The TGF-beta1 was completely suppressed in the AdCMVsTbetaR-treated mouse serum and BALF; however, no statistical difference was observed in the serum and BALF between the AdCMVluc-infected mice and the control mice at 4 weeks after irradiation (P < 0.05). A histopathological examination showed only mild radiation pneumonitis in the irradiated lungs of AdCMVsTbetaR-treated mice in comparison to the AdCMVluc-infected and RT-alone mice. Our results demonstrated that TGF-beta1 plays an important role in radiation pneumonitis, thus suggesting that the adenovirus-mediated overexpression in soluble TGF-beta type II receptor gene therapy may be a potentially feasible and effective strategy for the prevention of radiation pneumonitis.

Angiotensin II-induced activation of p21-activated kinase 1 requires Ca2+ and protein kinase Cδ in vascular smooth muscle cells

ANG II promotes remodeling of vascular smooth muscle cells (VSMCs) in cardiovascular diseases. It has been shown to activate p21-activated kinase (PAK)1, a critical component of signaling pathways implicated in growth and migration. However, the detailed signaling mechanism by which ANG II induces PAK1 activation in VSMCs remains unclear. Therefore, we have examined the mechanism required for activation of PAK1 by ANG II in VSMCs. ANG II, through activation of the ANG II type 1 receptor, rapidly promotes phosphorylation of PAK1 in VSMCs via a pathway independent of transactivation of the epidermal growth factor receptor. Using selective agonists and inhibitors, we demonstrated that mobilization of intracellular Ca2+ and PKCδ activation are required for ANG II-induced PAK1 phosphorylation. Rottlerin, a PKCδ inhibitor, significantly blocked ANG II-induced PAK1 phosphorylation. Further support for this notion was provided through infection of VSMCs with adenovirus encoding a dominant-negative (dn)PKCδ, which also markedly reduced phosphorylation of PAK1 by ANG II. In this pathway, Ca2+ acts upstream of PKCδ because a Ca2+ ionophore rapidly induced PKCδ phosphorylation at Tyr311 and Ca2+-dependent PAK1 phosphorylation was blocked by rottlerin. In addition, dnPYK-2, dnRac, and antioxidants inhibited ANG II-induced PAK1 phosphorylation, suggesting that PYK-2, Rac, and reactive oxygen species are involved in the upstream signaling. Finally, dnPAK1 markedly inhibited ANG II-induced protein synthesis in VSMCs. These data provide a novel signaling pathway by which ANG II may contribute to vascular remodeling.

Effect of inhibition of farnesylation and geranylgeranylation on renal fibrogenesis in vitro

BACKGROUND

The Ras and Rho family of GTPases serve as essential molecular switches in the downstream signalling of many cytokines involved in the regulation of renal fibroblast activity. Prenylation is a post-translational process critical to the membrane localization and function of these GTPases. We studied the effects of a farnesyltransferase inhibitor BMS-191563 and geranylgeranyltransferase inhibitor GGTI-298 on renal fibrogenesis in vitro.

METHODS

Functional studies examined the effects of BMS-191563 and GGTI-298 on rat renal fibroblast kinetics, collagen synthesis and collagen gel contraction. Pro-collagen alpha1(I) mRNA expression was measured by Northern analysis and CTGF expression by Western blotting.

RESULTS

Fibroblast proliferation was significantly reduced by both agents. Exposure of fibroblasts to BMS-191563 resulted in a significant reduction in total collagen production and pro-collagen alpha1(I) mRNA expression, an effect also observed but to a lesser degree with GGTI-298. Both agents significantly reduced CTGF protein expression. Fibroblast-mediated collagen I lattice contraction was decreased at 48 h by GGTI-298, an effect not observed with BMS-191563. Consistent with this finding, marked actin filament disassembly was evident by phalloidin staining of fibroblasts exposed to GGTI-298.

CONCLUSION

BMS-191563 and GGTI-298 exhibit different effects on renal fibroblast function reflecting their predominant roles in inhibiting prenylation of Ras or Rho proteins respectively. Further studies are warranted to establish their potential therapeutic application in the treatment of progressive renal disease.

Expression of granulocyte colony-stimulating factor is induced in injured rat carotid arteries and mediates vascular smooth muscle cell migration

Granulocyte colony-stimulating factor (G-CSF) is a lineage-restricted hematopoietic growth factor that stimulates proliferation and maturation of hematopoietic progenitors and is a known powerful mobilizer of bone marrow-derived stem cells. Very little has been reported on G-CSF expression and modulation of vascular smooth muscle cell (VSMC) activation. The purpose of this study was to characterize the expression and effects of G-CSF on primary human VSMC and balloon angioplasty-injured rat carotid arteries. In cultured human VSMC, G-CSF mRNA and protein expression are induced by several cytokines, with the most potent being fetal calf serum and T-lymphocyte-conditioned media. G-CSF is not expressed in naive rat carotid arteries but is induced in neointimal SMC in carotid arteries subject to balloon angioplasty. G-CSF is chemotactic for human VSMC. There is a significant difference between unstimulated cells and those treated with G-CSF at 100 and 1,000 pg/ml (P < 0.01 and 0.05 for 3 experiments). G-CSF also activates the GTPase Rac1, a regulator of cellular migration in VSMC. Inhibition of Rac1 inhibits G-CSF-driven VSMC migration. Important signal transduction protein kinases, including p44/42 MAPK, Akt, and S6 kinase, are also activated in response to G-CSF. This is the first report describing the expression of G-CSF in injured arteries and the multiple effects of G-CSF on VSMC activation. Together, our data suggest that G-CSF is an important mediator of inflammatory cell-VSMC communication and VSMC autocrine activation and may be an important mediator of the VSMC response to injury.

Involvement of ras activation in toxic hair cell damage of the mammalian cochlea

To identify possible intracellular mediators of hair cell (HC) death due to ototoxins, we treated basal-turn, neonatal, rat HCs in vitro with several intracellular signaling inhibitors, prior to and during gentamicin exposure. The general guanine nucleotide-binding protein (G-protein) inhibitor, GDP-betaS (1 mM), provided potent HC protection, suggesting involvement of G-proteins in the intracellular pathway linking gentamicin exposure to HC death. ADP-betaS had minimal effect, indicating that the protection is specific to guanosine diphosphate (GDP)-binding, rather than a general reaction to nucleotides. Azido-GTP(32) photolabeling and gel electrophoresis indicated activation of an approximately 21 kDa G-protein in HCs after exposure to gentamicin. Spectroscopic analysis of peptide fragments from this band matched its sequence with H-Ras. The Ras inhibitors B581 (50 microM) and FTI-277 (10 microM) provided potent protection against damage and reduced c-Jun activation in HC nuclei, suggesting that activation of Ras is functionally involved in damage to these cells due to gentamicin.

An endogenous inhibitor of focal adhesion kinase blocks Rac1/JNK but not Ras/ERK-dependent signaling in vascular smooth muscle cells

Humoral factors and extracellular matrix are critical co-regulators of smooth muscle cell (SMC) migration and proliferation. We reported previously that focal adhesion kinase (FAK)-related non-kinase (FRNK) is expressed selectively in SMC and can inhibit platelet-derived growth factor BB homodimer (PDGF-BB)-induced proliferation and migration of SMC by attenuating FAK activity. The goal of the current studies was to identify the mechanism by which FAK/FRNK regulates SMC growth and migration in response to diverse mitogenic signals. Transient overexpression of FRNK in SMC attenuated autophosphorylation of FAK at Tyr-397, reduced Src family-dependent tyrosine phosphorylation of FAK at Tyr-576, Tyr-577, and Tyr-881, and reduced phosphorylation of the FAK/Src substrates Cas and paxillin. However, FRNK expression did not alter the magnitude or dynamics of ERK activation induced by PDGF-BB or angiotensin II. Instead, FRNK expression markedly attenuated PDGF-BB-, angiotensin II-, and integrin-stimulated Rac1 activity and attenuates downstream signaling to JNK. Importantly, constitutively active Rac1 rescued the proliferation defects in FRNK expressing cells. Based on these observations, we hypothesize that FAK activation is required to integrate integrin signals with those from receptor tyrosine kinases and G protein-coupled receptors through downstream activation of Rac1 and that in SMC, FRNK may control proliferation and migration by buffering FAK-dependent Rac1 activation.

Upregulation by retinoic acid of transforming growth factor-beta-stimulated heat shock protein 27 induction in osteoblasts: involvement of mitogen-activated protein kinases

We investigated whether transforming growth factor-beta (TGF-beta) stimulates the induction of heat shock protein (HSP) 27 and HSP70 in osteoblast-like MC3T3-E1 cells and the mechanism underlying the induction. TGF-beta increased the level of HSP27 but had no effect on the HSP70 level. TGF-beta stimulated the accumulation of HSP27 dose-dependently, and induced an increase in the level of mRNA for HSP27. TGF-beta induced the phosphorylation of p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase. The HSP27 accumulation induced by TGF-beta was significantly suppressed by PD98059, an inhibitor of the upstream kinase of p44/p42 MAP kinase, or SB203580, an inhibitor of p38 MAP kinase. PD98059 and SB203580 suppressed the TGF-beta-stimulated increase in the level of mRNA for HSP27. Retinoic acid, a vitamin A (retinol) metabolite, which alone had little effect on the HSP27 level, markedly enhanced the HSP27 accumulation stimulated by TGF-beta. Retinoic acid enhanced the TGF-beta-induced increase of mRNA for HSP27. The amplification of TGF-beta-stimulated HSP27 accumulation by retinoic acid was reduced by PD98059 or SB203580. Retinoic acid failed to affect the TGF-beta-induced phosphorylation of p44/p42 MAP kinase or p38 MAP kinase. These results strongly suggest that p44/p42 MAP kinase and p38 MAP kinase take part in the pathways of the TGF-beta-stimulated HSP27 induction in osteoblasts, and that retinoic acid upregulates the TGF-beta-stimulated HSP27 induction at a point downstream from p44/p42 MAP kinase and p38 MAP kinase.

Heterozygous inactivation of TGF-beta1 increases the susceptibility to chemically induced mouse lung tumorigenesis independently of mutational activation of K-ras

Mice heterozygous for deletion of the transforming growth factor beta1 (TGF-beta1) gene show an enhanced rate of lung tumorigenesis following carcinogen treatment. Since the growth inhibitory activity of TGF-beta1 in epithelial cells is associated with K-ras p21, and K-ras mutations commonly occur in chemically-induced mouse lung tumors, we postulated that tumors in heterozygous TGF-beta1 mice might be more likely to have K-ras mutations compared with tumors in wildtype TGF-beta1 mice. Urethane-induced lung tumors in AJBL6 TGF-beta1 +/- and +/+ mice were examined for K-ras mutations by polymerase chain reaction/single strand conformation polymorphism analysis and sequencing. Mutation frequencies were similar in both genotypes: 12/18 +/- tumors (67%) and 10/16 +/+ tumors (62%). Mutations occurred in 80% +/- and 75% +/+ carcinomas, but in only 50% of the adenomas of both TGF-beta1 genotypes. Codon 61 A-->G transition mutations were predominant, occurring in 61% +/- and 44% +/+ tumors. Three +/- (17%) and three +/+ (19%) tumors showed codon 12 mutations, mostly G-->A transitions. Two +/- tumors had both codon 61 and codon 12 mutations. Interestingly, carcinomas with mutations in codon 61 were larger than those with codon 12 changes. It appears that the mechanism of enhanced susceptibility of TGF-beta1+/- mice to urethane-induced lung carcinogenesis does not involve selective development of tumors with K-ras mutations.

Heterogeneity of the signal transduction pathways for VEGF-induced MAPKs activation in human vascular endothelial cells

Vascular endothelial growth factor (VEGF) activates ERK and p38 MAPK in endothelial cells (ECs). The present study was aimed to compare its intracellular signal transduction pathways between three primary cultures of human ECs including human aortic ECs (HAECs), human umbilical vein ECs (HUVECs), and human microvascular ECs (HMVECs). VEGF activated ERK and p38 MAPK in all of three ECs. Isoforms of p38 MAPK that were activated by VEGF in HUVECs were p38-alpha and p38-delta. GF109203X, a specific inhibitor of PKC, markedly inhibited VEGF-induced activation of ERK and p38 MAPK in HAECs and HUVECs, whereas it exhibited little effect in HMVECs. In contrast, dominant negative mutant of Ha-Ras almost completely abrogated VEGF-induced activation of ERK and p38 MAPK in HMVECs. Although dominant negative mutant of Ha-Ras substantially inhibited the basal activities of ERK and p38 MAPK, it exhibited marginal effect on VEGF-induced activation of ERK and p38 MAPK in HUVECs and HAECs. The activation of Ras by VEGF appeared to be most prominent in HMVECs. These results indicate that intracellular signal transduction pathways for VEGF-induced activation of MAPKs are heterogeneous and vary depending on the origin of ECs.

Up-regulation of endothelial nitric-oxide synthase promoter by the phosphatidylinositol 3-kinase gamma /Janus kinase 2/MEK-1-dependent pathway

Our recent study indicates that lysophosphatidylcholine (LPC) enhances Sp1 binding and Sp1-dependent endothelial nitric oxide synthase (eNOS) promoter activity via the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1 (MEK-1) signaling pathway (Cieslik, K., Lee, C.-M., Tang, J.-L., and Wu, K. K. (1999) J. Biol. Chem. 274, 34669-34675). To identify upstream signaling molecules, we transfected human endothelial cells with dominant negative and active mutants of Ras and evaluated their effects on eNOS promoter activity. Neither mutant altered the basal or LPC-induced eNOS promoter function. By contrast, a dominant negative mutant of phosphatidylinositol 3-kinase gamma (PI-3Kgamma) blocked the promoter activity induced by LPC. Wortmannin and LY 294002 had a similar effect. AG-490, a selective inhibitor of Janus kinase 2 (Jak2), also reduced the LPC-induced Sp1 binding and eNOS promoter activity to the basal level. LPC induced Jak2 phosphorylation, which was abolished by LY 294002 and the dominant negative mutant of PI-3Kgamma. LY 294002 and AG-490 abrogated MEK-1 phosphorylation induced by LPC but had no effect on Raf-1. These results indicate that PI-3Kgamma and Jak2 are essential for LPC-induced eNOS promoter activity. This signaling pathway was sensitive to pertussis toxin, suggesting the involvement of a G(i) protein in PI-3Kgamma activation. These results indicate that LPC enhances Sp1-dependent eNOS promoter activity by a pertussis toxin-sensitive, Ras-independent novel pathway, PI-3Kgamma/Jak2/MEK-1/ERK1/2.

Dual role for transforming growth factor beta-dependent signaling in Trypanosoma cruzi infection of mammalian cells

Expression of functional transforming growth factor beta (TGF-beta) receptors (TbetaR) is required for the invasion of mammalian cells by the protozoan parasite Trypanosoma cruzi. However, the precise role of this host cell signaling complex in T. cruzi infection is unknown. To investigate the role of the TGF-beta signaling pathway, infection levels were studied in the mink lung epithelial cell lines JD1, JM2, and JM3. These cells express inducible mutant TbetaR1 proteins that cannot induce growth arrest in response to TGF-beta but still transmit the signal for TGF-beta-dependent gene expression. In the absence of mutant receptor expression, trypomastigotes invaded the cells at a low level. Induction of the mutant receptors caused an increase in infection in all three cell lines, showing that the requirement for TGF-beta signaling at invasion can be divorced from TGF-beta-induced growth arrest. TGF-beta pretreatment of mink lung cells expressing wild-type TbetaR1 caused a marked enhancement of infection, but no enhancement was seen in JD1, JM2, and JM3 cells, showing that the ability of TGF-beta to stimulate infection is associated with growth arrest. Likewise, expression of SMAD7 or SMAD2SA, inhibitors of TGF-beta signaling, did not block infection by T. cruzi but did block the enhancement of infection by TGF-beta. Taken together, these results show that there is a dual role for TGF-beta signaling in T. cruzi infection. The initial invasion of the host cell is independent of both TGF-beta-dependent gene expression and growth arrest, but TGF-beta stimulation of infection requires a fully functional TGF-beta signaling pathway.