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At least 343 records · Page 19Linked to original sources
PubMed2001

The paracrine role of stem cell factor/c-kit signaling in the activation of human melanocytes in ultraviolet-B-induced pigmentation.

The interaction of stem cell factor with its receptor, c-kit, is well known to be critical to the survival of melanocytes. Little is known about the role(s) of the stem cell factor/c-kit interaction in epidermal pigmentation, however. To clarify whether the stem cell factor/c-kit signaling has a paracrine role in ultraviolet-B-induced pigmentation, we determined whether the exposure of human keratinocytes, melanocytes, and the epidermis to ultraviolet B light stimulates the expression of stem cell factor or c-kit at the gene and/or protein levels. We further examined whether interrupting the binding of stem cell factor to c-kit by subepidermal injection of a monoclonal antibody to c-kit affects ultraviolet-B-induced pigmentation in brownish guinea pig skin. When human keratinocytes and melanocytes in culture were exposed to ultraviolet B light, transcripts of stem cell factor and c-kit (as assessed by reverse transcription polymerase chain reaction) and expression of those proteins (by enzyme-linked immunosorbent assay and western blotting) increased significantly and peaked at a dose of 20-40 mJ per cm2. In ultraviolet-B-exposed human epidermis, stem cell factor transcripts and protein expression were also markedly enhanced compared with the nonexposed epidermis. Immunohistochemistry with antibodies to stem cell factor revealed an increased staining in the ultraviolet-B-exposed epidermis, which was accompanied by a slight epidermal hyperplasia. In the course of ultraviolet-B-induced pigmentation of brownish guinea pig skin, the subepidermal injection of c-kit inhibitory antibodies completely abolished the induction of pigmentation in the ultraviolet-B-exposed area, and there was no increase in the number of dihydroxyphenylalanine-positive melanocytes. These findings indicate that the stem cell factor/c-kit signaling is critically involved in the biologic mechanism of ultraviolet-B-induced pigmentation.

Animals↗
PubMed2001

Lipoprotein-stimulated mesangial cell proliferation and gene expression are regulated by lipoprotein lipase.

BACKGROUND: Hyperlipidemia accelerates the progression of glomerular disease, and lipoproteins bind glomerular mesangial cells (MC) and induce proliferation and cytokine expression. In the vessel wall, the binding of lipoproteins to endothelial cells is markedly enhanced by lipoprotein lipase (LpL), synthesized by the underlying smooth muscle cells. While it is known that LpL is localized to the glomerulus, it is not known if and how it modulates the lipoprotein-mesangial interaction. METHODS: Very low-density lipoprotein (VLDL) was isolated from rats and was used to treat cultured primary rat MCs. Binding studies were done with and without LpL and with/without pretreatment with heparanase, which degrades cell surface heparan sulfate proteoglycan (HSPG), known to modulate the LpL-lipoprotein interaction in blood vessels. VLDL/LpL was also used to assess MC proliferation and gene expression of the cytokine platelet-derived growth factor (PDGF). RESULTS: LpL enhanced VLDL binding to MCs by as much as 200-fold, and most of this effect was blocked by pretreatment with heparanase. LpL amplified VLDL-driven MC proliferation and increased VLDL-induced PDGF expression. Heparanase pretreatment of cells eliminated both of these amplifications. LpL alone increased MC proliferation and PDGF gene expression. DISCUSSION: As in the vessel wall, LpL enhances VLDL binding to MCs. MCs respond to LpL binding by proliferating and expressing cytokines such as PDGF. LpL may be a crucial paracrine mediator of the glomerular response to circulating lipoproteins, amplifying a response that includes cytokine elaboration, influx of circulating monocytes, and eventual sclerosis.

Animals↗
PubMed2003

Glomerular autacoids stimulated by bradykinin regulate efferent arteriole tone.

BACKGROUND: We have shown that when efferent arterioles are perfused retrograde to avoid the influence of vasoactive autacoids released by the glomerulus, bradykinin causes dilatation via release of cytochrome p450 (cp450) metabolites, probably epoxyeicosatrienoic acids (EETs). Here we tested the hypothesis that the glomerulus releases cyclooxygenase (COX) and cp450 metabolites. These eicosanoids, acting as vasopressor and vasodepressor autacoids, control efferent arteriole resistance downstream from the glomerulus. METHODS: Rabbit efferent arterioles were perfused orthograde through the glomerulus from the end of the afferent arteriole to determine whether bradykinin induces the release of glomerular autacoids that influence efferent arteriole resistance. Efferent arterioles were preconstricted with norepinephrine, and increasing doses of bradykinin were added to the perfusate in the presence or absence of COX and cp450 inhibitors. RESULTS: When efferent arterioles were perfused orthograde through the glomerulus, bradykinin at 10 nmol/L caused significant and reproducible dilatation; diameter increased from 8.0 +/- 0.5 to 12.6 +/- 0.4 microm (P < 0.05). This effect was not modified by a nitric oxide synthase (NOS) inhibitor. In the presence of indomethacin, a COX inhibitor, bradykinin-induced dilatation was almost completely blocked (from 8.0 +/- 0.5 to 9.3 +/- 0.6 microm). This blockade was completely reversed by 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (20-HEDE), a specific antagonist of the vasoconstrictor cp450 metabolite 20-hydroxyeicosatetraenoic acid (20-HETE); diameter increased from 6.6 +/- 0.7 to 13.2 +/- 0.5 microm. To test the hypothesis that this dilatation was due to EETs, a specific inhibitor of EET synthesis, N-methylsulphonyl-6-(2-proparglyloxyphenyl)hexanamide (MS-PPOH), was added to the arteriolar perfusate. In the presence of indomethacin and 20-HEDE, bradykinin caused dilatation and this effect was completely blocked by MS-PPOH (1 microm) (from 7.6 +/- 0.6 to 7.3 +/- 0.5 microm). CONCLUSIONS: We concluded that in response to bradykinin, the glomerulus releases COX metabolites (probably prostaglandins) that have a vasodilator effect. When COXs are inhibited, the vasoconstrictor 20-HETE released by the glomerulus is able to oppose the vasodilator effect of bradykinin. This vasodilator effect is mediated by EETs released by the glomerulus and/or the efferent arteriole and does not involve nitric oxide. The balance between these opposing effects of various eicosanoids controls efferent arteriole resistance downstream from the glomerulus.

Amides↗
PubMed2000

Paracrine regulators of implantation.

Classical and contemporary studies have shown that endocrine regulation exerted by ovarian hormones priming the endometrium is essential for embryo implantation. Increasing evidence indicates that steroid-induced molecules acting as paracrine modulators are necessary for embryo-uterine interactions. That is the case for calcitonin, heparin-binding epidermal growth factor (EGF)-like growth factor, leukaemia inhibitory factor and other molecules. Furthermore, when the blastocyst enters the uterine cavity, it starts the complex signals that will drive embryo adhesion. The paracrinology of this process is based on the local interplay of molecules, such as the secretion of cytokines that may facilitate the acquisition of endometrial receptivity by controlling the expression of adhesion and anti-adhesion proteins. Finally, during the embryonic invasive phase, uterine stromal-trophoblast dialogue may modulate this self-controlled proteolytic and immunological process to avoid damage to both the embryo and maternal environment.

Calcitonin↗
PubMed2002

Identification of plasminogen activator inhibitor-2 as a gastrin-regulated gene: Role of Rho GTPase and menin.

BACKGROUND & AIMS: The gastric hormone gastrin regulates acid secretion, gene expression, and the functional development and cellular composition of the gastric mucosa. Using a gene array, we sought to identify major, novel, gastrin-regulated genes. METHODS: A cancer gene array was probed with samples from the gastric cancer cell line AGS, expressing the gastrin-cholecystokinin(B) receptor and stimulated with gastrin. The expression of gastrin-regulated genes was further characterized by Western blots and enzyme-linked immunosorbent assay in tissue and blood of hypergastrinemic patients. Gene expression was studied using promoter-luciferase reporter constructs. RESULTS: Plasminogen activator inhibitor 2 (PAI-2) was identified as a major, previously unknown target of gastrin in the gastric cancer cell line AGS. The relevance was confirmed by showing elevated tissue and plasma PAI-2 in hypergastrinemic patients (pernicious anemia and multiple endocrine neoplasia type 1). PAI-2 promoter-luciferase constructs showed that gastrin stimulated expression via pathways involving Galpha and Gbetagamma subunits, protein kinase C, RhoA, and the transcription factors CREB and AP1. The tumor suppressor menin inhibited transcription. In addition, gastrin stimulated expression in adjacent cells via a paracrine mechanism involving protein kinase C and RhoA but not CREB. CONCLUSIONS: A gene array showed PAI-2 to be a novel gastrin-regulated gene, stimulated in part through CREB and AP-1 and inhibited by the tumor suppressor menin.

Aged↗
PubMed2002

Generation of regulatory gut-homing human T lymphocytes using ex vivo interleukin 10 gene transfer.

BACKGROUND & AIMS: Systemic treatment of Crohn's disease patients using recombinant interleukin (rIL)-10 has not resulted in significant therapeutic benefit presumably because of limited bioavailability and unexpected proinflammatory effects of high-dose rIL-10. Ex vivo gene transfer of the interleukin (IL)-10 gene to gut-homing CD4(+) cells may lead to improved long-term management. METHODS: Peripheral blood mononuclear cells (PBMCs) were transduced with a retroviral vector containing the IL-10 and green fluorescent protein (GFP) gene or a control vector containing GFP only. Transduced CD4(+) cells were sorted and maintained in culture for phenotypic and functional analysis. RESULTS: Stimulated IL-10-GFP CD4(+) cells produced significantly higher levels of IL-10 than control cells for at least 4 months. The IL-10 transgene was biologically active and decreased proliferation of IL-10-GFP CD4(+) cells as well as expression of major histocompatibility class (MHC) class II, proliferation of autologous responder cells, and IL-12 production by dendritic cells (DCs). The majority of transduced CD4(+) cells had a gut-homing potential because they expressed the mucosal integrin alpha4beta7, and displayed efficient binding to MAdCAM-1-expressing cells in vitro. CONCLUSIONS: Transduction of peripheral blood CD4(+) lymphocytes with IL-10 results in a regulatory phenotype. The use of regulatory gut-homing human CD4(+) cells may provide a novel approach to local delivery of immunomodulatory signals to the intestine in Crohn's disease.

Cell Adhesion↗
PubMed1997

Paracrine interaction between hepatocytes and macrophages after extrathyroidal proteolysis of thyroglobulin.

Thyroglobulin (Tg), the precursor of the thyroid hormones triiodothyronine (T3) and thyroxine (T4), is known to derive from thyroid epithelial cells. Part of Tg reaches the circulation as an intact molecule by transcytosis across the epithelial wall of thyroid follicles. Circulating Tg is a potential ligand for the asialoglycoprotein receptor of hepatocytes. In this report we show, however, that clearance of circulating Tg occurred exclusively by endocytosis in liver macrophages, whereas hepatocytes did not participate in this process. The biological significance of this Tg uptake by the macrophages might consist in an increase of thyroid hormones in close proximity to the macrophages, thereby affecting the hepatocyte metabolism. To test this hypothesis, co-cultures of hepatocytes and macrophages were incubated with Tg, which resulted in the release of thyroid hormones and in a significant increase in the activity of lipogenesis and of hepatocellular key enzymes of the hexose monophosphate shunt. This effect of Tg could be mimicked by equivalent amounts of T3 or T4 exclusively in the co-cultures. When hepatocytes were incubated with thyroid hormones in the absence of macrophages, no or only little effect was observed, indicating that the interaction of macrophages and hepatocytes was a prerequisite for the stimulation of the hepatocellular metabolism. We conclude that the paracrine effect on HepG2 cells results from the degradation of Tg in J774 cells. Apparently, this process is not confined to the release of thyroid hormones, but it requires the interaction of both cell types, possibly mediated by an additional, as yet unknown stimulus.

Animals↗
PubMed2003

The normal liver harbors the vitamin D nuclear receptor in nonparenchymal and biliary epithelial cells.

The liver is generally considered negative for the vitamin D nuclear receptor (VDR(n)), even though several studies have shown significant effects of 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) on liver cell physiology. The low abundance of VDR(n) in the liver led us to propose that hepatocytes (the largest hepatic cell population) were most likely negative for the receptor, whereas the small hepatic sinusoidal and ductular cell populations that contain cell types known to express VDR(n) in other tissues should express the receptor. Using freshly isolated cells from normal livers as well as biliary and epithelial hepatic cell lines, our data show that the human, rat, and mouse hepatocytes express very low VDR(n) messenger RNA (mRNA) and protein levels. In contrast, sinusoidal endothelial, Kupffer, and stellate cells of normal rat livers as well as the mouse biliary cell line BDC and rat hepatic neonatal epithelial SD6 cells clearly expressed both VDR(n) mRNA and protein. In addition, specimens of human hepatocarcinoma as well as intrahepatic colon adenocarcinoma metastases were also found to express the VDR(n) gene transcript. Kupffer, stellate, and endothelial cells responded to 1,25(OH)(2)D(3) by a significant increase in the CYP24, indicating that the VDR(n) is fully functional in these cells. In conclusion, selective hepatic cell populations are targets for the vitamin D endocrine/paracrine/intracrine system.

Animals↗
PubMed1999

Paracrine effects of IL-4 transfection on TS/A adenocarcinoma cells mediate reduced in vivo growth.

The in vitro/in vivo growth capacity and phenotype of TS/A and the IL4-transfected TS/A-IL4 cell lines were studied by cell cycle analysis, expression of ICAM-1/CD54, transferrin receptor/CD71 and E-cadherin and by histology of the primary tumors. TS/A-IL4, unlike the TS/A line, shows in vitro a marked increase in the fibroblastoid cell type and a decreased E-cadherin expression. Administration of conditioned medium containing IL4 obtained from the TS/A-IL4 cell line, stimulates CD54 expression in the TS/A cell line. TS/A-IL4 tumors grow more slowly in vivo and are ultimately rejected. These processes are accompanied by a marked increase in collagen and extracellular matrix proteins and increased recruitment and degranulation of mast cells. The paracrine effect of IL4, released by the transfected tumor cells, might be responsible for the reduced in vivo growth of the TS/A cell line in the presence of TS/A-IL4 cells.

Adenocarcinoma↗
PubMed2002

Effects of tanshinone VI on the hypertrophy of cardiac myocytes and fibrosis of cardiac fibroblasts of neonatal rats.

The possible effects of tanshinone VI (tsh), a diterpene from the root of Tan-Shen (Salvia miltiorrhiza, Bunge (Labiatae)) on hypertrophy and fibrosis in cultured neonatal rat cardiac myocytes and fibroblasts were examined. Tsh had no significant effect on protein synthesis, which was evaluated by [3H]-leucine incorporation into the acid insoluble fraction in the cells, in the absence of stimulatory factors in cardiac myocytes. The amount of protein produced in cardiac myocytes was increased by 10(-8) M endothelin-1 (ET-1), 10(-6) M phenylephrine (PE), or 10(-8) M insulin-like growth factor-1 (IGF-1), suggesting that hypertrophy of cardiac myocytes in vitro was induced by these factors. The ET-1-, PE-, or IGF-1-induced increase in protein synthesis was attenuated by treatment with 10(-5) M tsh. Treatment with 10(-5) M tsh significantly decreased the synthesis of collagen by cardiac fibroblasts, which was evaluated by [3H]-proline incorpolation into acid-insoluble fraction of the fiblobrasts, in the absence of stimulatory factors for the production. Fetal bovine serum (FBS) or IGF-1 increased collagen synthesis in a concentration-dependent manner. The increase at 5% FBS or 10(-8) M IGF-1 was inhibited by 10(-5) M tsh. Fibroblast-conditioned medium (FB-CM) increased protein synthesis in cardiac myocytes in a concentration-dependent manner (10; - 100 %). Tsh attenuated the FB-CM-induced increase in protein synthesis by cardiac myocytes. These results show that tsh may attenuate the humoral factor-induced hypertrophy of cardiac myocytes and fibrosis of cardiac fibroblasts. The findings suggest that tsh may improve the development of cardiac remodeling under pathophysiological conditions. Abbreviations. ANP:atrial natriuretic peptide DMEM:Dulbecco-modified Eagle's medium ET-1:endothelin-1 FB-CM:fibroblast-conditioned medium FBS:fetal bovine serum IGF-1:insulin-like growth factor-1 PE:phenylephrine tsh:tanshinone VI

Animals↗
PubMed2002

Paracrine in vivo inhibitory effects of hepatitis B virus X protein (HBx) on liver cell proliferation: an alternative mechanism of HBx-related pathogenesis.

The role of the hepatitis B virus X protein (HBx) in the pathogenesis of hepatitis B virus (HBV) infection remains unclear. HBx exhibits pleiotropic biological effects, whose in vivo relevance is a matter for debate. In the present report, we have used a combination of HBx-expressing transgenic mice and liver cell transplantation to investigate the in vivo impact of HBx expression on liver cell proliferation and viability in a regenerative context. We show that moderate HBx expression inhibits liver regeneration after partial hepatectomy in HBx-expressing transgenic mice. We also demonstrate that the transplantation of HBx-expressing liver cells, isolated from HBx transgenic mice, is sufficient to inhibit overall recipient liver regeneration after partial hepatectomy. Moreover, the injection of serum samples drawn from HBx-expressing transgenic mice mimicked the inhibitory effect of HBx on liver regeneration. Finally, the incubation of primary rat hepatocytes with the supernatant of HBx-expressing liver cells inhibits cellular DNA synthesis. Taken together, our results demonstrate a paracrine inhibitory effect of HBx on liver cell proliferation and lead us to propose HBV as one of the few viruses implicated in human cancer which act, at least in part, through paracrine biological pathways.

Animals↗
PubMed1998

Novel paracrine signaling mechanism in the ocular ciliary epithelium.

The ciliary body contains an epithelial bilayer consisting of an outer pigmented cell layer (PE) and an inner nonpigmented cell layer (NPE) responsible for aqueous humor secretion. Secretion may be mediated in part by cytosolic Ca2+ concentration ([Ca2+]i), but whether or how the two layers could coordinate their Ca2+ signals to regulate secretion is unclear. To investigate interactions between PE and NPE, we examined [Ca2+]i signaling in isolated intact ciliary epithelial bilayers using confocal microscopy. Phenylephrine selectively increased [Ca2+]i in PE and acetylcholine increased [Ca2+]i in NPE, but epinephrine increased [Ca2+]i in both layers. This increase spread from PE to NPE, and [Ca2+]i signaling across the bilayer remained coordinated during [Ca2+]i oscillations. All epinephrine-induced [Ca2+]i signaling was blocked by the alpha1-adrenergic antagonist prazosin, whereas signaling in the NPE but not PE was blocked by the beta-adrenergic antagonist propranolol, the gap junction blockers octanol and 18alpha-glycyrrhetinic acid, or the A kinase inhibitor Rp diastereomer of adenosine 3',5'-cyclic monophosphothioate. The beta-adrenergic agonist isoproterenol failed to increase Ca2+ by itself, but isoproterenol plus phenylephrine-induced [Ca2+]i signals across the bilayer similar to those induced by epinephrine. Finally, isoproterenol increased cell-to-cell spread of lucifer yellow via gap junctions, whereas cell-to-cell spread of [Ca2+]i signals could be induced by photorelease of caged inositol 1,4,5-trisphosphate. Thus, calcium signals are coordinated in the epithelial bilayer so that adrenergic stimulation can increase [Ca2+]i in NPE, but only if NPE are primed by activation of endogenous adenylyl cyclase, whereupon they receive stimulation from adjacent PE via gap junctions. This novel interplay between endocrine and paracrine pathways may coordinate [Ca2+]i signaling across the ciliary epithelial bilayer.

Animals↗
PubMed1998

A paracrine role for the epithelial progesterone receptor in mammary gland development.

Recently generated progesterone receptor (PR)-negative (PR-/-) mice provide an excellent model for dissecting the role of progesterone in the development of the mammary gland during puberty and pregnancy. However, the full extent of the mammary gland defect in these mice caused by the absence of the PR cannot be assessed, because PR-/- mice do not exhibit estrous cycles and fail to become pregnant. To circumvent this difficulty, we have transplanted PR-/- breasts into wild-type mice, and we have demonstrated that the development of the mammary gland in the absence of the PR is arrested at the stage of the simple ductal system found in the young virgin mouse. Mammary transplants lacking the PR in the stromal compartment give rise to normal alveolar growth, whereas transplants containing PR-/- epithelium conserve the abnormal phenotype. Chimeric epithelia in which PR-/- cells are in close vicinity to PR wild-type cells go through complete alveolar development to which the PR-/- cells contribute. Together, these results indicate that progesterone acts by a paracrine mechanism on a subset of mammary epithelial cells to allow for alveolar growth and that expression of the PR is not required in all the cells of the mammary epithelium in order for alveolar development to proceed normally.

Animals↗
PubMed2000

Heparan sulfate proteoglycan isoforms of the CD44 hyaluronan receptor induced in human inflammatory macrophages can function as paracrine regulators of fibroblast growth factor action.

The CD44 glycoprotein is expressed in multiple isoforms on a variety of cell types where it functions as a receptor for hyaluronan-mediated motility. Recently, interest has centered on CD44 heparan sulfate proteoglycan (HSPG) isoforms because of their potential to sequester heparin-binding growth factors and chemokines. Expression of these isoforms on ectodermal cells has recently been shown to regulate limb morphogenesis via presentation of fibroblast growth factor (FGF) 4/FGF 8 while expression on tumor cells was shown to sequester hepatocyte growth factor and promote tumor dissemination. To date, however, CD44 HSPG expression in tissue macrophages and lymphocytes has not been adequately investigated, despite the fact these cells actively synthesize growth factors and chemokines and indirect evidence that monocyte CD44 sequesters macrophage inflammatory protein-1beta. Here we show primary human monocytes rather than lymphocytes express CD44 HSPGs, but only following in vitro differentiation to macrophages or activation with the proinflammatory cytokine interleukin-1alpha or bacterial lipopolysaccharide. Furthermore, we show these isoforms are preferentially modified with heparan rather than chondroitin sulfate, bind the macrophage-derived growth factors FGF-2, vascular endothelial growth factor, and heparin-binding epidermal growth factor with varying affinities (K(d) 25-330 nM) and in the case of FGF-2, can stimulate productive binding to the high affinity tyrosine kinase FGF receptor 1 (FGFR1). In contrast, we find no evidence for significant binding to C-C chemokines. Last, we confirm by immunofluorescent antibody staining that inflamed synovial membrane macrophages express CD44 HSPGs and that expression is greatest in cells containing high FGF-2 levels. These results suggest a paracrine role for macrophage CD44 HSPG isoforms in the regulation of growth factor action during inflammation.

Cell Differentiation↗
PubMed2002

Cytochrome P450 2E1-derived reactive oxygen species mediate paracrine stimulation of collagen I protein synthesis by hepatic stellate cells.

To evaluate possible fibrogenic effects of CYP2E1-dependent generation of reactive oxygen species, a model was developed using co-cultures of HepG2 cells, which do (E47 cells) or do not (C34 cells) express cytochrome P450 2E1 (CYP2E1) with stellate cells. There was an increase in intra- and extracellular H(2)O(2), lipid peroxidation, and collagen type I protein in stellate cells co-cultured with E47 cells compared with stellate cells alone or co-cultured with C34 cells. The increase in collagen was prevented by antioxidants and a CYP2E1 inhibitor. CYP3A4 did not mimic the stimulatory effects found with CYP2E1. Collagen mRNA levels remained unchanged, and pulse-chase analysis indicated similar half-lives of collagen I protein between both co-cultures. However, collagen protein synthesis was increased in E47 co-culture. Hepatocytes from pyrazole-treated rats (with high levels of CYP2E1) induced collagen protein in primary stellate cells, and antioxidants and CYP2E1 inhibitors blocked this effect. These results suggest that increased translation of collagen mRNA by CYP2E1-derived reactive oxygen species is responsible for the increase in collagen protein produced by the E47 co-culture. These co-culture models may be useful for understanding the impact of CYP2E1-derived ROS on stellate cell function and activation.

Animals↗
PubMed2003

Increased Sp1-dependent transactivation of the LAMgamma 1 promoter in hepatic stellate cells co-cultured with HepG2 cells overexpressing cytochrome P450 2E1.

Laminin is a basement-membrane protein that increases in liver fibrosis. To study the role of oxidative stress on laminin expression, hepatic stellate cells (HSC) were co-cultured with HepG2 cells that do or do not express (E47 or C34 cells, respectively) CYP2E1, a potent generator of oxygen radicals. Co-incubation of HSC with E47 cells increased laminin beta1 and gamma1 proteins compared with co-incubation with C34 cells; this increase was prevented by antioxidants and CYP2E1 inhibitors. Similar results were observed in co-culture with primary hepatocytes from saline- or pyrazole-treated (with high levels of CYP2E1) rats. Laminin alpha1 chain was not detectable in the HSC in any of the systems; however, laminin alpha2 chain increased in HSC co-cultured with E47 cells. Synthesis but not turnover of laminin beta1 and gamma1 proteins was increased in HSC in the E47 co-culture. Laminin beta1 and gamma1 mRNAs were up-regulated in HSC in the E47 co-culture because of transcriptional activation of both genes. Transfection experiments in HSC with reporter constructs driven by the laminin gamma1 promoter showed maximal responsiveness with the -230/+106 and the -1400/+106 constructs in the E47 system. Gel-shift assays demonstrated an increase in Sp1 binding to the laminin gamma1 promoter in HSC when co-incubated with E47 cells, which was blocked by an anti-Sp1 antibody. Co-transfection of a Sp1 expression vector further increased the responsiveness of the -330LAMgamma1-CAT reporter vector in HSC in the HSC/E47 system. These results show that diffusable CYP2E1-derived oxidative-stress mediators induce synthesis of laminins by a transcriptional mechanism in HSC. Such interactions between hepatocytes and HSC may be important during liver fibrosis.

Animals↗
PubMed2003

Prostate cancer cell-adipocyte interaction: leptin mediates androgen-independent prostate cancer cell proliferation through c-Jun NH2-terminal kinase.

Prostate cancer is one of the leading causes of death among men in the United States, and acquisition of hormone resistance (androgen independence) by cancer cells is a fatal event during the natural history of prostate cancer. Obesity is another serious health problem and has been shown to be associated with prostate cancer. However, little is known about the molecular basis of this association. Here we show that factor(s) secreted from adipocytes stimulate prostate cancer cell proliferation. Leptin is one of the major adipose cytokines, and it controls body weight homeostasis through food intake and energy expenditure. We identify leptin as a novel growth factor in androgen-independent prostate cancer cell growth. Strikingly, leptin stimulates cell proliferation specifically in androgen-independent DU145 and PC-3 prostate cancer cells but not in androgen-dependent LNCaP-FGC cells, although both cell types express functional leptin receptor isoforms. c-Jun NH2-terminal kinase (JNK) has been shown recently to play a crucial role in obesity and insulin resistance. Intriguingly, leptin induces JNK activation in androgen-independent prostate cancer cells, and the pharmacological inhibition of JNK blocked the leptin stimulation of androgen-independent prostate cancer cell proliferation. This suggests that JNK activation is required for leptin-mediated, androgen-independent prostate cancer cell proliferation. Furthermore, other cytokines produced by adipocytes and critical for body weight homeostasis cooperate with leptin in androgen-independent prostate cancer cell proliferation: interleukin-6 and insulin-like growth factor I demonstrate additive and synergistic effects on the leptin stimulation of androgen-independent prostate cancer cell proliferation, respectively. Therefore, adipose cytokines, as well as JNK, are key mediators between obesity and hormone-resistant prostate cancer and could be therapeutic targets.

Adipocytes↗