Biomedical subjects

Christos Tsatsanis

Publications and source records attributed to Christos Tsatsanis.

At least 19 recordsLinked to original sources

PubMed2007

Corticotropin releasing factor receptor 1 (CRF1) and CRF2 agonists exert an anti-inflammatory effect during the early phase of inflammation suppressing LPS-induced TNF-alpha release from macrophages via induction of COX-2 and PGE2.

Corticotropin-releasing factor (CRF), the principal regulator of the hypothalamus-pituitary-adrenal (HPA) axis, also modulates the inflammatory response directly, via its effect on mast cells and macrophages. On macrophages, it augments production of lipopolysaccharide (LPS)-induced pro-inflammatory cytokines. CRF and its related peptides may also act as anti-inflammatory agents. Aim of the present work was to examine the role of macrophages on the anti-inflammatory effects of CRF-peptides and the mechanism involved. Thus, we examined if CRF receptor 1 (CRF1) and CRF2 agonists exert any anti-inflammatory effect on primary mouse macrophages. We have found that: (a) CRF, Urocortin (UCN)1 and UCN2 transiently suppressed the release of Tumor Necrosis Factor-alpha (TNF-alpha) in LPS-activated macrophages, an effect peaking at 4 h. This effect did not involve changes on TNF-alpha transcription. (b) CRF peptide-induced suppression of TNF-alpha release depended on induction of COX-2 and PGE2 synthesis. (c) Use of specific CRF1 and CRF2 antagonists suggested that this effect involved both CRF receptor types. (d) The effect of CRF-peptides on COX-2 was mediated via PI3K and p38MAPK. (e) Longer exposure of macrophages to CRF-peptides resulted in induction of TNF-alpha production via enhancement of its transcription. In conclusion, this is the first report suggesting that CRF1 and CRF2 agonists exert a biphasic effect on macrophages. During the early stages of the inflammatory response, they suppress TNF-alpha release via induction of COX-2/PGE2 while later on they induce TNF-alpha transcription. Hence, the reported anti-inflammatory effect of CRF-peptides appears to involve macrophages and is confined at the early stage of inflammation.

Animals↗

PubMed2006

Signalling networks regulating cyclooxygenase-2.

Cyclooxygenease-2 (COX-2) is the key enzyme regulating the production of prostaglandins, central mediators of inflammation. The expression of cyclooxygenease-2 is induced by several extra cellular signals including pro-inflammatory and growth-promoting stimuli. All signals converge to the activation of mitogen-activated protein kinases (MAPK) that regulate cyclooxygenease-2 mRNA levels both at the transcriptional and post-transcriptional level. The machinery appears to be highly specialized involving activation of distinct signalling molecules depending on the type of extracellular stimulus. Expression of cyclooxygenease-2 mRNA is regulated by several transcription factors including the cyclic-AMP response element binding protein (CREB), nuclear factor kappa B (NFkB) and the CCAAT-enhancer binding protein (C/EBP). Cyclooxygenease-2 is also affected post-transcriptionaly, at the level of mRNA stability. Finally, cyclooxygenease-2 can be affected directly at its enzymatic activity by nitric oxide and nitric oxide synthase (iNOS). Each step of cyclooxygenease-2 regulation can be used as potential therapeutic target.

Animals↗

PubMed2006

Corticotropin-releasing factor and the urocortins induce the expression of TLR4 in macrophages via activation of the transcription factors PU.1 and AP-1.

Corticotropin-releasing factor (CRF) augments LPS-induced proinflammatory cytokine production from macrophages. The aim of the present study was to determine the mechanism by which CRF and its related peptides urocortins (UCN) 1 and 2 affect LPS-induced cytokine production. We examined their role on TLR4 expression, the signal-transducing receptor of LPS. For this purpose, the murine macrophage cell line RAW 264.7 and primary murine peritoneal macrophages were used. Exposure of peritoneal macrophages and RAW 264.7 cells to CRF, UCN1, or UCN2 up-regulated TLR4 mRNA and protein levels. To study whether that effect occurred at the transcriptional level, RAW 264.7 cells were transfected with a construct containing the proximal region of the TLR4 promoter linked to the luciferase gene. CRF peptides induced activation of the TLR4 promoter, an effect abolished upon mutation of a proximal PU.1-binding consensus or upon mutation of an AP-1-binding element. Indeed, all three peptides promoted PU.1 binding to the proximal PU.1 site and increased DNA-binding activity to the AP-1 site. The effects of CRF peptides were inhibited by the CRF2 antagonist anti-sauvagine-30, but not by the CRF1 antagonist antalarmin, suggesting that CRF peptides mediated the up-regulation of TLR4 via the CRF2 receptor. Finally, CRF peptides blocked the inhibitory effect of LPS on TLR4 expression. In conclusion, our data suggest that CRF peptides play an important role on macrophage function. They augment the effect of LPS by inducing Tlr4 gene expression, through CRF2, via activation of the transcription factors PU.1 and AP-1.

Animals↗

PubMed2006

G protein-associated, specific membrane binding sites mediate the neuroprotective effect of dehydroepiandrosterone.

The neurosteroid dehydroepiandrosterone (DHEA) at 1 nM protects NMDA-/GABAA-receptor negative neural crest-derived PC12 cells from apoptosis. We now report that membrane-impermeable DHEA-BSA conjugate replaces unconjugated DHEA in protecting serum-deprived PC12 cells from apoptosis (IC50=1.5 nM). Protection involves phosphorylation of the prosurvival factor Src and induction of the anti-apoptotic protein Bcl-2 and is sensitive to pertussis toxin. Binding assays of [3H]DHEA on isolated PC12 cell membranes revealed saturation within 30 min and binding of DHEA with a Kd of 0.9 nM. A similar binding activity was detectable in isolated membranes from rat hippocampus and from normal human adrenal chromaffin cells. The presence of DHEA-specific membrane binding sites was confirmed by flow cytometry and confocal laser microscopy of DHEA-BSA-FITC stained cells. In contrast to estrogens and progestins, glucocorticoids and androgens displaced DHEA from its membrane binding sites but with a 10-fold lower affinity than DHEA (IC50=9.3 and 13.6 nM, respectively). These agents acted as pure antagonists, blocking the antiapoptotic effect of DHEA as well as the induction of Bcl-2 proteins and Src kinase activation. In conclusion, our findings suggest that neural crest-derived cells possess specific DHEA membrane binding sites coupled to G proteins. Binding to these sites confers neuroprotection.

Adrenal Medulla↗

PubMed2006

Expansion of toll-like receptor 9-expressing B cells in active systemic lupus erythematosus: implications for the induction and maintenance of the autoimmune process.

OBJECTIVE: Toll-like receptors (TLRs) are pattern-associated receptors in innate immunity that may be involved in the recognition of self antigens and the production of pathogenic autoantibodies. This study was undertaken to examine the expression and function of various TLRs in subpopulations of peripheral blood mononuclear cells (PBMCs) of patients with systemic lupus erythematosus (SLE). METHODS: The expression of TLRs in PBMCs from 50 SLE patients with active disease (SLE Disease Activity Index [SLEDAI] score >or=8; n = 26) or inactive disease (SLEDAI score <8; n = 24) and 20 healthy controls was studied by flow cytometry. TLR expression was assessed on various subpopulations of PBMCs (TLR-2 and TLR-4 by membrane staining; TLR-3 and TLR-9 by intracellular staining). TLR function was accessed by stimulating PBMCs with specific ligands. RESULTS: The proportion of B cells and monocytes expressing TLR-9 was higher among patients with active SLE (mean +/- SD 49.5 +/- 24.4% and 30.7 +/- 24.1%, respectively) than among patients with inactive disease (22.8 +/- 19.6% and 14.3 +/- 8.4%, respectively; P = 0.02 and P = 0.03). Among B cells, the proportion of plasma cells and memory B cells expressing TLR-9 was increased in patients with active SLE. Increased percentages of TLR-9-expressing B cells correlated with the presence of anti-double-stranded DNA antibodies (P = 0.007). Treatment with serum from patients with active disease increased the percentage of TLR-9-expressing plasma cells in serum from healthy controls. Enhanced induction of HLA-DR after TLR-9 stimulation was documented in B cells from patients with active disease. CONCLUSION: In patients with active SLE, the proportion of peripheral blood memory B cells and plasma cells expressing TLR-9 is increased. Endogenous nucleic acids released during apoptotic cell death may stimulate B cells via TLR-9 and contribute to SLE pathogenesis.

Adult↗

PubMed2006

Neurosteroids as endogenous inhibitors of neuronal cell apoptosis in aging.

The neuroactive steroids dehydroepiandrosterone (DHEA), its sulfate ester DHEAS, and allopregnanolone (Allo) are produced in the adrenals and the brain. Their production rate and levels in serum, brain, and adrenals decrease gradually with advancing age. The decline of their levels was associated with age-related neuronal dysfunction and degeneration, most probably because these steroids protect central nervous system (CNS) neurons against noxious agents. Indeed, DHEA(S) protects rat hippocampal neurons against NMDA-induced excitotoxicity, whereas Allo ameliorates NMDA-induced excitotoxicity in human neurons. These steroids exert also a protective role on the sympathetic nervous system. Indeed, DHEA, DHEAS, and Allo protect chromaffin cells and the sympathoadrenal PC12 cells (an established model for the study of neuronal cell apoptosis and survival) against serum deprivation-induced apoptosis. Their effects are time- and dose-dependent with EC(50) 1.8, 1.1, and 1.5 nM, respectively. The prosurvival effect of DHEA(S) appears to be NMDA-, GABA(A)- sigma1-, or estrogen receptor-independent, and is mediated by G-protein-coupled-specific membrane binding sites. It involves the antiapoptotic Bcl-2 proteins, and the activation of prosurvival transcription factors CREB and NF-kappaB, upstream effectors of the antiapoptotic Bcl-2 protein expression, as well as prosurvival kinase PKCalpha/beta, a posttranslational activator of Bcl-2. Furthermore, they directly stimulate biosynthesis and release of neuroprotective catecholamines, exerting a direct transcriptional effect on tyrosine hydroxylase, and regulating actin depolymerization and submembrane actin filament disassembly, a fast-response cellular system regulating trafficking of catecholamine vesicles. These findings suggest that neurosteroids may act as endogenous neuroprotective factors. The decline of neurosteroid levels during aging may leave the brain unprotected against neurotoxic challenges.

Aging↗

PubMed2006

Peripheral factors in the metabolic syndrome: the pivotal role of adiponectin.

Several recently published reports, including ours, suggest that adiponectin is a strong proinflammatory agent. Indeed, exposure of human placenta and adipose tissue to adiponectin induces the production of interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor alpha (TNF-alpha), and prostaglandin E2 (PGE2). We have previously shown that adiponectin is a powerful inducer of proinflammatory cytokines production by macrophages. The reported anti-inflammatory effect of adiponectin may be due to the induction of macrophage tolerance to further adiponectin exposure or to other proinflammatory stimuli including the Toll-like receptor (TLR) 3 ligand polyI:C and the TLR4 ligand lipopolysaccharide (LPS). We now present additional data supporting the hypothesis that adiponectin is a strong proinflammatory adipokine. More specifically, we demonstrate that adiponectin induces IL-1beta and IL-8 from THP-1 macrophage cell line. The effect of adiponectin is not restricted to differentiated THP-1 macrophages but it is evident at lower levels in undifferentiated THP-1 monocytes promoting TNF-alpha, IL-6, and IL-8 production. Thus, its high levels in the circulation of lean subjects render their macrophages resistant to several proinflammatory stimuli including its own thus acting in effect as an anti-inflammatory agent. Lowering of its high levels, as a consequence of increased body mass index (BMI), renders macrophages sensitive to any proinflammatory insult.

Adiponectin↗

PubMed2005

Adiponectin induces TNF-alpha and IL-6 in macrophages and promotes tolerance to itself and other pro-inflammatory stimuli.

Adiponectin exerts anti-inflammatory effects via macrophages, suppressing the production of pro-inflammatory cytokines in response to bacterial lipopolysaccharide (LPS). Here, we provide experimental evidence that the "anti-inflammatory" effect of adiponectin may be due to an induction of macrophage tolerance: globular adiponectin (gAd) is a powerful inducer of TNF-alpha and IL-6 secretion in primary human peripheral macrophages, in the THP-1 human macrophage cell line, and in primary mouse peritoneal macrophages. Pre-exposure of macrophages to 10 microg/ml gAd rendered them tolerant to further gAd exposure or to other pro-inflammatory stimuli such as TLR3 ligand polyI:C and TLR4 ligand LPS, while pre-exposure to 1 microg/ml of and re-exposure to 10 microg/ml gAd unmasked its pro-inflammatory properties. GAd induced NF-kappaB activation and tolerance to further gAd or LPS exposure. Our data suggest that adiponectin constant presence in the circulation in high levels (in lean subjects) renders macrophages resistant to pro-inflammatory stimuli, including its own.

Adiponectin↗

PubMed2005

Expression of heregulin in human coronary atherosclerotic lesions.

BACKGROUND: Endothelial cells, monocytes/macrophages, and vascular smooth muscle cells contribute to the establishment and progression of atherosclerotic lesions by expressing growth and inflammatory factors. The aim of the present study was to determine whether heregulin (HRG) is associated with human coronary artery disease. METHODS: Twenty-six fresh human coronary artery segments were collected at autopsy. Expression of cysteine-rich 61 (CYR61) and VEGF in response to HRG was studied in the human endothelial cell line EA.hy926, and expression of CYR61 and HRG was evaluated in activated macrophages isolated from peripheral blood of healthy donors. RESULTS: We found that HRG was overexpressed at the protein and mRNA level in all lesions analyzed and gradually increased as the stages of the lesions progressed. Expression of HRG was observed in the intima primarily in macrophages. The same specimens were analyzed for the expression of CYR61, an angiogenetic factor regulated by HRG in breast cancer epithelial cells. CYR61 was expressed in both normal and atheromatic specimens, but its expression was significantly enhanced in macrophages of the intima. Activation of primary human macrophages results in increased expression of both HRG and CYR61. In addition, studies in endothelial cells where no endogenous HRG is present showed that HRG induces expression of CYR61 and secretion of VEGF. CONCLUSIONS: HRG may, therefore, play an important role in the development of coronary artery disease and the expansion of the atherosclerotic plaque and may locally regulate the expression of the angiogenetic factor CYR61.

Adult↗

PubMed2005

Effects of hypoxia and hypercapnia on surfactant protein expression proliferation and apoptosis in A549 alveolar epithelial cells.

UNLABELLED: During lung injury alveolar epithelial cells are directly exposed to changes in PO(2) and PCO(2). Integrity of alveolar epithelial type II cells (AECII) is critical in lung injury but the effect of hypoxia and hypercapnia on AECII function, viability and proliferation has not been clearly investigated. Aim of the present work was to determine the direct effect of hypoxia and hypercapnia on surfactant protein expression, proliferation and apoptosis of lung epithelial cells in vitro. A549 alveolar epithelia cells were subjected to hypoxia (1%O(2)-5% CO(2)) or hypercapnia (21% O(2-) 15% CO(2)) and expression of surfactant protein C was measured and compared to normal conditions (21% O(2)- 5% CO(2)). Cell cycle progression and apoptosis were measured by flow cytometric analysis. RESULTS: A549 alveolar epithelial cells produce surfactant proteins, including surfactant protein C, when cultured under normal conditions, which is reduced under hypoxic conditions. Specifically, pro-SpC expression is moderately decreased after 8 h of culture in hypoxia, and is completely attenuated after 48 h. Hypercapnia decreases pro-SpC expression only after 48 h of exposure. Stimulation with TNF-alpha partly reverses pSPC decrease observed under hypoxic and hypercapnic conditions. Hypoxic culture of A549 cells results in progressive arrest of cells in the G1 phase of the cell cycle and increased apoptosis first observed 4 h following exposure and peaking at 24 h. In contrast hypercapnia has no significant effect on alveolar epithelial cell proliferation or apoptosis. CONCLUSIONS: Taken together we can conclude that hypoxia rapidly and severely affects AECII function and viability while hypercapnia has an inhibitory effect on pro-SpC production only after prolonged exposure.

Apoptosis↗

PubMed2005

Urocortin 1 and Urocortin 2 induce macrophage apoptosis via CRFR2.

Macrophages undergo apoptosis as a mechanism of regulating their activation and the inflammatory reaction. Macrophages express the Corticotropin-Releasing Factor Receptor-2 (CRFR2) the endogenous agonists of which, the urocortins, are also present at the site of inflammation. We have found that urocortins induced macrophage apoptosis in a dose- and time-dependent manner via CRFR2. In contrast to lipopolysaccharide (LPS)-induced apoptosis, the pro-apoptosis pathway activated by urocortins involved the pro-apoptotic Bax and Bad proteins and not nitric oxide, JNK and p38MAPK characteristic of LPS. In conclusion, our data suggest that endogenous CRFR2 ligands exert an anti-inflammatory effect via induction of macrophage apoptosis.

Animals↗

PubMed2005

Corticotropin-releasing hormone activates protein kinase C in an isoenzyme-specific manner.

Protein kinase C (PKC) has recently emerged as mediator of corticotropin-releasing hormone (CRH) effects. Aim of the present study was to study the effects of CRH on each PKC isoenzyme. As a model we have used the PC12 rat pheochromocytoma cell line, expressing the CRH type 1 receptor (CRHR1). Our data were as follows: (a) CRH-induced rapid phosphorylation of conventional PKCalpha and PKCbeta, accompanied by parallel increase of their concentration within nucleus. (b) CRH suppressed the phosphorylation of novel PKCdelta and PKCtheta;, which remained in the cytosol. (c) CRH-induced transient phosphorylation of atypical PKClambda and had no effect on PKCmu. (d) The effect of CRH on each PKC isoenzyme was blocked by a CRHR1 antagonist. (e) Blockade of conventional PKC phosphorylation inhibited CRH-induced calcium ion mobilization from intracellular stores as well as the CRH-induced apoptosis and Fas ligand production. In conclusion, our findings suggest that CRH via its CRHR1 receptor differentially regulates PKC-isoenzyme phosphorylation, an apparently physiologically relevant effect since blockade of conventional PKC phosphorylation abolished the biological effect of CRH.

Animals↗

PubMed2004

Expression of the Tpl2/Cot oncogene in human T-cell neoplasias.

BACKGROUND: Tpl2/Cot oncogene has been identified in murine T-cell lymphomas as a target of MoMuLV insertion. Animal and tissue culture studies have shown that Tpl2/Cot is involved in interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-alpha) production by T-cells contributing to T-cell proliferation. In the present report we examined a series of 12 adult patients with various T-cell malignancies, all with predominant leukemic expression in the periphery, for the expression of Tpl2/Cot oncogene in order to determine a possible involvement of Tpl2/Cot in the pathogenesis of these neoplasms. RESULTS: Our results showed that Tpl2/Cot was overexpressed in all four patients with Large Granular Lymphocyte proliferative disorders (LGL-PDs) but in none of the remaining eight patients with other T-cell neoplasias. Interestingly, three of the LGL-PD patients displayed neutropenia, one in association with sarcoidosis. Serum TNF-alpha levels were increased in all Tpl2/Cot overexpressing patients while serum IL-2 was undetectable in all subjects studied. Genomic DNA analysis revealed no DNA amplification at the Tpl2/Cot locus in any of the samples analyzed. CONCLUSIONS: We conclude that Tpl2/Cot, a gene extensively studied in animal and tissue culture T-cell models may be also involved in the development of human LGL-PD and may have a role in the pathogenesis of immune manifestations associated with these diseases. This is the first report implicating Tpl2/Cot in human T-cell neoplasias and provides a novel molecular event in the development of LGL-PDs.

Adolescent↗

PubMed2004

Dehydroepiandrosterone and allopregnanolone protect sympathoadrenal medulla cells against apoptosis via antiapoptotic Bcl-2 proteins.

The neuroactive steroids dehydroepiandrosterone (DHEA), its sulfate ester DHEA sulfate (DHEAS), and allopregnanolone (Allo), produced by the CNS and the adrenals, appear to exert a protective effect in hippocampal and cortical neuron ischemia- and excitotoxicity-induced injury. We hypothesized that they may also play a protective role on the adrenal medulla, an important part of the sympathetic nervous system, and the tissue adjacent to their primary site of production. DHEA, DHEAS, and Allo protected rat chromaffin cells and the rat pheochromocytoma PC12 cell line, an established model for the study of adrenomedullary cell apoptosis and survival, against serum deprivation-induced apoptosis. Their effects were time- and dose-dependent, with EC50 1.8, 1.1, and 1.5 nM, respectively. The antiapoptotic effect of DHEA DHEAS and Allo was compared to that of a long list of structurally related compounds and was found to be structure-specific, confined mainly to conformation 3beta-OH-Delta5 for androstenes and 3alpha-OH for pregnanes. Indeed, 3-keto, Delta4, or C7 hydroxylated androstenes and 3beta pregnanes were ineffective. The prosurvival effect of DHEA(S) and Allo was N-methyl-D-aspartate-, GABAA-, sigma1-, or estrogen receptor-independent. It involved the antiapoptotic Bcl-2 proteins, their role being sine qua non for their action because Bcl-2 antisense oligonucleotides reversed their effects. Finally, DHEA(S) and Allo activated cAMP response element-binding protein and NF-kappaB, upstream effectors of antiapoptotic Bcl-2 protein expression. They also activated the antiapoptotic kinase PKCalpha/beta, a posttranslational activator of Bcl-2 protein. Our findings suggest that decline of DHEA(S) and Allo during aging or stress may leave the adrenal medulla unprotected against proapoptotic challenges.

Adrenal Medulla↗

PubMed2004

Alendronate reduces serum TNFalpha and IL-1beta, increases neutrophil counts, and improves bone mineral density and bone metabolism indices in patients with chronic idiopathic neutropenia (CIN)-associated osteopenia/osteoporosis.

The current study was undertaken to investigate the effect of alendronate on bone mineral density (BMD), bone metabolism markers, and serum bone-resorbing cytokines in patients with chronic idiopathic neutropenia (CIN)-associated osteopenia/osteoporosis. Sixteen randomly selected women, 7 with CIN-associated osteoporosis and 9 with CIN-associated osteopenia, and 14 age- and menopausal status-matched healthy volunteers, were enrolled in the study. Patients received 10 mg alendronate daily per os for 360 days and studies were done before treatment (day 0) and at varying time points during the study. We found that patients' BMD measurements increased by 5.32% after treatment, and that the elevated serum osteocalcin (OC), a bone formation marker, decreased by day 30, normalized by day 90, and increased again by day 270 of treatment. Elevated values of patients' urine deoxypyridinoline (Dpd) and N-telopeptide of type I of collagen (NTx), two bone resorption markers, returned to the control range by day 30 and decreased thereafter. Increased levels of patients' serum tumor necrosis factor-alpha (TNFalpha) and interleukin-1beta (IL-1beta), two bone resorbing cytokines, returned to the control range by day 30 and decreased thereafter. Peripheral blood neutrophil counts increased by day 30 and continued to rise thereafter, reaching a mean value higher than 2650 neutrophils per microl of blood on day 360. Interestingly, alendronate-induced changes in the levels of both cytokines correlated inversely with the respective changes in neutrophil counts and BMD measurements, and positively with the changes in the respective means of urine NTx and Dpd values. All these findings indicate that alendronate is effective in treating CIN-associated osteopenia/osteoporosis, and that the beneficial effect of the compound may lie, at least in part, in its property to inhibit the production of TNFalpha and IL-1beta by cells of the monocyte/macrophage system, in which osteoclasts are included.

Adult↗

PubMed2004

Oncogenic kinase signaling in human neoplasms.

Oncogenic proteins participate in cellular functions that involve transduction of signals from the extracellular environment, through the membrane, into the cytoplasm towards the nucleus, where transcription is initiated to generate proteins that will eventually contribute to the oncogenic phenotype. The wild-type homologues of cellular oncoproteins (proto-oncoproteins) frequently participate in signal transduction mechanisms that regulate cell and tissue homeostasis. Deregulation of proto-oncoprotein expression or function results in altered cellular signaling, oncogenic transformation, and inhibition of apoptosis. Oncogenic signals initiated from mutant proteins can override endogenous homeostasis control mechanisms such as anoikis and apoptosis and result in anchorage-independent growth, uncontrolled proliferation, and metastasis.

Anoikis↗

PubMed2004

Intercellular communication and human hepatocellular carcinoma.

We have previously reported that gap junction-mediated intercellular communication (GJIC) can be restored in junctionally deficient human prostate epithelial cells, also suggesting that GJIC activity is regulated by estrogen. In the present work, we report studies on sex steroid regulation of GJIC and proliferative activity in both nontumoral (Chang liver, CL) and malignant (HepG2, Huh7) human liver cells. Junctional activity and liver cell growth were measured using the scrape-loading/dye-transfer (SL/DT) and the MTS assay, respectively. Using the SL/DT, only Huh7 cells exhibited a moderate degree of junctional activity in basic conditions, while neither CL nor HepG2 cells showed functional GJIC. Under exactly the same experimental approach used for prostate studies, we observed that, once again, both estrogen (either estradiol or estrone) and FK induce a significant increase of GJIC in Huh7 cells, while exposure of HepG2 cells to FK produces only a limited rise of junctional activity in this cell line. However, estrogen induced a significant increase and reduction of the proliferative activity of CL and Huh7 cells, respectively, while growth of HepG2 cells was not affected. While the above evidence suggests that estrogens are primarily implicated in growth regulation and communication of both prostate and liver epithelial cells, it also implies that compounds able to restore GJIC in junctionally deficient cells or prevent its disruption in junctionally proficient cells may be used for development of new strategies in the prevention and/or treatment of several human malignancies, including hepatocellular carcinoma (HCC).

Carcinoma, Hepatocellular↗

PubMed2002

Corticotropin-releasing hormone induces Fas ligand production and apoptosis in PC12 cells via activation of p38 mitogen-activated protein kinase.

Recent experimental findings involve corticotropin-releasing hormone (CRH) in the cellular response to noxious stimuli and possibly apoptosis. The aim of the present work was to examine the effect of CRH on apoptosis and the Fas/Fas ligand system in an in vitro model, the PC12 rat pheochromocytoma cell line, which is widely used in the study of apoptosis and at the same time expresses the CRH/CRH receptor system. We have found the following. CRH induced Fas ligand production and apoptosis. These effects were mediated by the CRH type 1 receptor because its antagonist antalarmin blocked CRH-induced apoptosis and Fas ligand expression. CRH activated p38 mitogen-activated protein kinase, which was found to be essential for CRH-induced apoptosis and Fas ligand production. CRH also promoted a rapid and transient activation of ERK1/2, which, however, was not necessary for either CRH-induced apoptosis or Fas ligand production. Thus, CRH promotes PC12 apoptosis via the CRH type 1 receptor, which induces Fas ligand production via activation of p38.

Animals↗