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PubMed1998

Intercellular communication in normal and aberrant crypts of rat colon mucosa.

An original system was developed to detect intercellular communication between epithelial cells of rat colon mucosa. Cell-to-cell communication was tested both in normal and in azoxymethane (AOM)-induced aberrant crypts in an attempt to identify chemically-induced modifications of cell properties. Stripes of unstained live tissue were superfused and oxygenated at room temperature and single cells at the top of the crypt were injected with fluorescent dyes. The bottom cells were filled in isolated crypts. Dyes injected into cells at the surface of the mucosa failed to diffuse to adjacent ones, whereas cells at the base of the crypts were dye-coupled. Surface cells from aberrant crypt foci (ACF) did not transfer the dye, therefore behaving like normal crypts. These results indicate that the pattern of intercellular communication between colon crypt cells changes as these cells differentiate and migrate to the top of the crypts and that the pattern of dye transfer between surface cells is maintained in ACF.

Animals↗
PubMed2005

Nerve growth factor increases connexin43 phosphorylation and gap junctional intercellular communication.

The function of gap junctions is regulated by the phosphorylation state of their connexin subunits. Numerous growth factors are known to regulate connexin phosphorylation; however, the effect of nerve growth factor on gap junction function is not understood. The phosphorylation of connexin subunits is a key event during many aspects of the lifecycle of a connexin, including open/close states, assembly/trafficking, and degradation, and thus affects the functionality of the channel. PC12 cells infected with connexin43 (Cx43) retrovirus were used as a neuronal model to characterize the signal transduction pathways activated by nerve growth factor (NGF) that potentially affect the functional state of Cx43. Immunoblot analysis demonstrated that Cx43 and the mitogen-activated protein kinase (MAPK), ERK-1/2, were phosphorylated in response to TrkA activation via NGF and that phosphorylation could be prevented by treatment with the MEK-1/2 inhibitor U0126. The effects of NGF on gap junction intercellular communication were examined by monitoring fluorescence recovery after photobleaching PC12-Cx43 cells preloaded with calcein. Fluorescence recovery in the photobleached area increased after NGF treatment and decreased when pretreated with the MEK-1/2 inhibitor U0126. These data are the first to show a direct signaling link between neurotrophins and the phosphorylation of connexin proteins through the MAPK pathway resulting in increased gap junctional intercellular communication. Neurotrophic regulation of connexin activity provides a novel mechanism of regulating intercellular communication between neurons during nervous system development and repair.

Animals↗
PubMed1995

In vitro inhibition of gap junctional intercellular communication by chemical carcinogens.

This study was conducted to assess the effects of chemical carcinogens on the gap junction-mediated intercellular communication in cultured mammalian cells. The method of scrape-loading dye transfer of lucifer yellow was adapted as a measure of gap junctional communication. Clone 9 cells derived from rat liver were treated with a model chemical carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and the gap junctional communication was assessed by measuring the transfer of scrape-loaded lucifer yellow dye. When cells were treated with the carcinogen at 0.3 mg/ml, the fluorescent dye transfer was inhibited by 90% in 60 min. Other chemical agents, which include direct or indirect carcinogens and antitumor drugs, were also examined for their effects on the gap junctional communication. Direct carcinogens, such as MNNG, hydroxylamine and ethidium bromide, exhibited strong inhibition of intercellular communication, while indirect carcinogens, such as aflatoxin B1 and ethionine, exerted minor effects. Effects of test chemicals on the cell communication through gap junctions were readily quantitated by counting the number of cells stained with the fluorescent dye.

Animals↗
PubMed2005

Inhibition of gap junction-mediated intercellular communication by TNF-alpha in cultured human corneal fibroblasts.

PURPOSE: Keratocytes are connected to each other by gap junctions, which mediate intercellular communication and contribute to maintenance of corneal homeostasis. The possible effect of tumor necrosis factor (TNF)-alpha, a proinflammatory cytokine, on gap junctional intercellular communication (GJIC) in cultured human corneal fibroblasts was examined. METHODS: GJIC activity was measured by observing the intercellular diffusion of the fluorescent dye Lucifer yellow. The expression of the gap junction protein connexin43 (Cx43) was evaluated by immunofluorescence and immunoblot analyses with a specific monoclonal antibody. The abundance of Cx43 mRNA was determined by quantitative reverse transcription and polymerase chain reaction analysis. RESULTS: TNF-alpha induced a time- and concentration-dependent decrease in GJIC activity in human corneal fibroblasts. Immunofluorescence analysis revealed that TNF-alpha reduced the level of specific staining for Cx43 at sites of contact between adjacent cells. Immunoblot analysis detected four specific Cx43 bands, one corresponding to the nonphosphorylated form of the protein and three corresponding to phosphorylated forms. Exposure of cells to TNF-alpha reduced the relative abundance of the three phosphorylated forms of Cx43. The amount of Cx43 mRNA was not affected by TNF-alpha. CONCLUSIONS: TNF-alpha inhibited GJIC in cultured human corneal fibroblasts, an effect that was possibly mediated by dephosphorylation and consequent degradation of Cx43. The downregulation of GJIC among keratocytes in response to TNF-alpha may contribute to the breakdown of corneal homeostasis during corneal inflammation.

Cell Communication↗
PubMed2006

The antiarrhythmic peptide rotigaptide (ZP123) increases gap junction intercellular communication in cardiac myocytes and HeLa cells expressing connexin 43.

We investigated the effects of rotigaptide (ZP123), a stable hexapeptide with antiarrhythmic properties, on gap junction mediated intercellular communication in contracting rat neonatal cardiac myocytes, HL-1 cells derived from cardiac atrium and in HeLa cells transfected with cDNA encoding Cx43-GFP, Cx32-GFP, Cx26-GFP, wild-type Cx43 or wild-type Cx26. Intercellular communication was monitored before and after treatment with rotigaptide following microinjection of small fluorescent dyes (MW<1 kDa). The communication-modifying effect of rotigaptide was confined to cells expressing Cx43 since the peptide had no effect on dye transfer in HeLa cells expressing Cx32-GFP, Cx26-GFP or wild-type Cx26. In contrast, HeLa cells expressing Cx43-GFP exposed to 50 nM rotigaptide for 5 h showed a 40% increase in gap junction mediated communication. Rotigaptide (50 nM) increased intercellular dye transfer in myocytes and atrial HL-1 cells, where Cx43 is the dominant connexin. However, it caused no change in cell beating rates of cardiac myocytes. Western blot analysis showed that rotigaptide did not modify the overall level of Cx43 expression and changes in the phosphorylation status of the protein were not observed.We conclude that the effects of rotigaptide were confined to cells expressing Cx43.

Animals↗
PubMedDate not supplied

Relationship between intercellular communication and adriamycin resistance in non-small cell lung cancer.

The adriamycin chemosensitivity and extent of gap junctional intercellular communication were assessed in a panel of seven human non-small cell lung cancer (NSCLC) cell lines. Communication was assessed by autoradiographic detection of transfer of 3H uridine nucleotides between coupled cells. The strength of coupling varied widely between the cell lines and they could be separated into 3 groups: those which exhibited strong coupling, L-DAN and A549; those which exhibited weak coupling, SK-MES-1, Calu-3 and NCI-H125; and an intermediate group, WIL and NCI-H23. Adriamycin chemosensitivity was assessed by both clonogenic and MTT assays. The range of IC50 values as measured by either assay was extremely narrow, with no important differences between the lines. Thus, despite the wide spectrum of intercellular communication observed in these lines, this did not correlate with their adriamycin resistance.

Autoradiography↗
PubMed1981

Hormonal regulation of cytodifferentiation and intercellular communication in cultured granulosa cells.

Granulosa cells from immature hypophysectomized diethylstilbestrol-treated rats displayed pronounced intracellular and intercellular changes after 48 hr of exposure to follicle-stimulating hormone (FSH) in vitro. As determined by light and electron microscopy, most of the FSH-treated cells became highly aggregated and grew in multilayered clusters. Numerous gap junctions were seen between cells, indicating the presence of significant intercellular communication. Microvilli densely covered the surface of the hormone-stimulated cells, which contained enlarged mitochondria with convoluted cristae, characteristic of steroidogenic cells. Luteinizing hormone receptors, identified by autoradiography with 125I-labeled human chorionic gonadotropin, were mainly associated with aggregated cells, whereas single cells were usually free of the labeled hormone. Addition of a gonadotropin-releasing hormone agonist prevented the appearance of luteinizing hormone receptors and markedly impaired cyclic AMP and progesterone production, as well as the morphological changes induced by FSH. The majority of the granulosa cells grown in the absence of either hormone assumed a flattened, and smooth shape and grew primarily in monolayers. The maintenance of cellular aggregation and intercellular communication by FSH, and its inhibition by gonadotropin-releasing hormone, may play an important role in the cytodifferentiation of ovarian granulosa cells.

Animals↗
PubMed1998

Ineffectiveness of oxytocin on intercellular communication between term pregnant human myometrial cells before labor.

OBJECTIVE: The effects of the uterotonic agent oxytocin on intercellular communication between term pregnant human myometrial cells before labor were studied to investigate its contribution to the synchronicity of uterine contractions. STUDY DESIGN: The membrane potential and the input resistance of myometrial cells were measured with intracellular micropipettes, and dye-coupling assays were concomitantly performed while the tissues were perfused with three concentrations of oxytocin (10(-8) mol/L, 10(-7) mol/L, and 10(-6) mol/L). The results were compared with those obtained from tissues perfused with gap junctional uncoupling agent octanol and those with Tyrode's solution (control). RESULTS: Octanol increased input resistance and inhibited dye coupling but did not affect membrane potential compared with controls. Oxytocin depolarized membrane potential at all studied concentrations. The mean input resistance values and detectable dye propagation with oxytocin were similar to controls. CONCLUSION: Oxytocin does not contribute to gap junctional intercellular communication in term pregnant human myometrium before labor but may affect contractions by depolarizing membrane potential.

Cell Communication↗
PubMed1993

Intercellular communication in colonies of Syrian hamster embryo cells and the susceptibility for morphological transformation.

The levels of gap junctional intercellular communication (GJIC) were studied in normal, morphologically altered and morphologically transformed colonies formed in the Syrian hamster embryo (SHE) cell transformation assay. The colonies were selected from non-exposed dishes or dishes exposed to 12-O-tetradecanoylphorbol-13-acetate (TPA, 0.16 microM), di(2-ethylhexyl)phthalate (DEHP, 77 microM), Na-orthovanadate (vanadate, 3.4 microM) or dieldrin (25 microM) for 7 days during colony formation. TPA, DEHP and vanadate induced increased frequencies of morphological transformation of colonies. At the same time, TPA and DEHP decreased GJIC in the colonies by approximately 30% under the conditions used. All categories of colonies were equally affected. Vanadate did not change the level of GJIC in any of the categories of colonies compared to unexposed control. Dieldrin strongly suppressed GJIC in all colonies without increasing the frequency of transformation. The compounds affected GJIC after short-term exposures (4 and 24 h) to cell monolayers rather similarly to that found after long-term exposure to the colonies. Transformation assays with coexposure of dieldrin together with the transforming agents vanadate, DEHP or benzo[a]pyrene did not increase transformation frequencies compared to the transforming agents alone. The GJIC level in all coexposure groups was similar to that of dieldrin alone. Furthermore, regardless of whether dieldrin was present or not, removal of vanadate 24 h before fixation of the colonies caused a slight decrease in the transformation frequency. The results suggest that: (i) morphologically transformed colonies have the same ability of intercellular communication as normal colonies; (ii) decreased GJIC is probably not either sufficient or necessary to induce transformation of SHE cell colonies; (iii) a decreased level of GJIC does not necessarily increase the susceptibility of SHE cells for transformation; and (iv) inhibition of GJIC may not have an impact on the maintenance of the transformed phenotype of SHE cell colonies.

Animals↗
PubMedDate not supplied

Role of protein kinase C in the deficient gap junctional intercellular communication of K-ras-transformed murine lung epithelial cells.

BACKGROUND: Protein kinase C (PKC) activity is increased and gap junctional intercellular communication (GJIC) is decreased frequently in Ras-transformed cells. We investigated the roles of Ras and PKC in the deficient gap junctional intercellular communication (GJIC) of K-ras-transformed E9 mouse lung carcinoma cells. METHODS: GJIC was measured by fluorescent dye microinjection. Ras activity was blocked with lovastatin or a K-ras antisense oligonucleotide. PKC activity was inhibited with GF 109203X or apigenin or was downregulated by overnight treatment with 12-O-tetradecanoylphorbol-13-acetate. The content and phosphorylation of the gap junction protein, connexin43 (Cx43), was assessed by Western blot. RESULTS: E9 cell GJIC was increased two-three fold by lovastatin, the K-ras antisense oligonucleotide, and PKC inhibition/downregulation. Cx43 content and phosphorylation were unchanged, however. CONCLUSIONS: Oncogenic Ras blocks GJIC in E9 cells through a PKC-dependent mechanism, but this does not directly involve Cx43 expression or phosphorylation.

Animals↗
PubMed2000

Intercellular communication and cell proliferation in precision-cut rat liver slices: effect of medium composition and DDT.

Gap junctional intercellular communication (GJIC) and cell proliferation were studied in control and 1,1'-bis(p-chlorophenyl)-2, 2,2,-trichloroethane (DDT) treated precision-cut liver slices of rat by evaluating connexin 32 (Cx32) expression and 5-bromo-2'-deoxyuridine (BrdU) incorporation. In addition, the effect of different culture media (RPMI and WME) on control and DDT influenced Cx32 expression and cell proliferation was determined. Cx32 expression in control precision-cut liver slices was maintained during 8 h of culturing, but decreased after prolonged culturing. Control cell proliferation was significantly higher when WME was used as culture medium than when RPMI was used. In slices treated with DDT Cx32 expression was decreased. In slices cultured in RPMI medium, this decrease preceded a dose-dependent increase in cell proliferation. These results show the usefulness of precision-cut liver slices in studying cellular proliferation and intercellular communication.

Animals↗
PubMed1992

Effects of hydrocarbons on transformation and intercellular communication in Syrian hamster embryo cells.

The ability of 18 different hydrocarbons to induce and promote morphological transformation and to inhibit intercellular communication in primary Syrian hamster embryo cells in culture have been studied. The compounds were: the n-alkanes octane, nonane, decane, undecane, dodecane and tridecane; the iso-alkanes 2-methylheptane, 2-methyloctane and 2-methylnonane; the naphthenes 1,2-dimethylcyclohexane, 1,2,4-trimethylcyclohexane and tert-butylcyclohexane; the aromates 1,2-dimethylbenzene, 1,2,4-trimetylbenzene and tert-butylbenzene; and the alkenes 1-octene, 1-nonene and 1-decene. None of the hydrocarbons induced morphological transformation of Syrian hamster embryo cells. When the hydrocarbons were incubated together with benzo(a)pyrene, enhancement of the transformation frequency was observed for the naphthene 1,2-dimethylcyclohexane and the iso-alkanes 2-methylheptane and 2-methyloctane. None of the n-alkanes, alkenes or aromates enhanced the transformation frequency induced by benzo(a)pyrene. The alkane tridecane and the iso-alkanes 2-methyloctane and 2-methylnonane reduced intercellular communication in the primary Syrian hamster embryo cells.

Animals↗
PubMed1983

Is there a relationship between hypoxia, contact resistance, and intercellular communication?

This investigation addresses the shape of radiation survival curves of cells cultured as multicell spheroids. It is shown that spheroids of cells capable of intercellular communication by gap-junctions display survival curves lacking a radioresistant fraction of hypoxic cells. Compared to the corresponding monolayers, these spheroid survival curves exhibit a uniform increase in radioresistance due to the "contact effect". In contrast, biphasic survival curves indicative of hypoxic cells are obtained with non-communicating spheroids, however, without indication of a contact effect. Evidence is presented that this relationship between intercellular communication, hypoxia, and contact effect may possibly also hold for survival curves of solid tumors.

Animals↗
PubMed1979

Junctional intercellular communication pattern of cultured human breast cancer cells.

Junctional intercellular communication between several established human breast cancer cell lines and a variety of mammalian cells has been examined. All the cancer cell lines were found to be either noncommunicators or nonselective communicators. This contrasts with normal human mammary epithelium which shows selectivity in junctional communication. Loss of selectivity in junctional communication appears to be a general feature of cultured human breast cancer cells.

Animals↗
PubMed1991

Intercellular communication in cultured rabbit gastric epithelial cells.

The effects of drugs related to cyclic AMP and a tumor promoter, phorbol ester, on intercellular communications via gap junctions were investigated by the Lucifer Yellow-transfer method in cultured rabbit gastric epithelial cells. Cells were in contact with each drug for 4 hr before the microinjection of the dye into a cell. Dye transfer capacity was significantly increased by dibutyryl cyclic AMP (10(-3) M), theophylline (10(-3) M), 3-isobutyl-1-methylxanthine (10(-4) M), forskolin (10(-6) M) and irsogladine (10(-4) M); and it was inhibited by 12-O-tetradecanoyl-phorbol-13-acetate (100 ng/ml). These results suggest that the intercellular communication between cultured rabbit gastric epithelial cells is upregulated by cyclic AMP.

Animals↗
PubMed2005

ATP-dependent paracrine intercellular communication in cultured bovine corneal endothelial cells.

PURPOSE: Intercellular communication (IC) in nonexcitable cells is mediated through gap junctions and/or through the release of paracrine mediators. This study was conducted to investigate adenosine-5' triphosphate (ATP)-dependent paracrine IC in the propagation of Ca2+ waves in confluent monolayers of cultured bovine corneal endothelial cells (BCECs). METHODS: A Ca2+ wave was induced by point mechanical stimulation (PMS) of a single cell by indentation with a glass micropipette (approximately 1 microm tip) for <1 second. Dynamic changes in [Ca2+]i in the mechanically stimulated (MS) cell and in the neighboring (NB) cells were visualized with a confocal microscope, using a fluorescent dye. Normalized fluorescence (NF), calculated as the ratio of the average fluorescence of a cell to the average under resting conditions, was used as a measure of [Ca2+]i. Expression of P2Y receptors and ecto-adenosine triphosphatases (ATPases) was investigated by RT-PCR. ATP release in response to PMS was measured by luciferin-luciferase (LL) bioluminescence. RESULTS: BCECs subjected to PMS showed a transient [Ca2+]i increase. Under control conditions, the maximum NF in the MS cell occurred within 600 ms, and the fluorescence returned to baseline within 170 seconds. NB cells also presented a [Ca2+]i increase with a transient characterized by decreasing maximum NF and increasing latency as a function of the distance from the MS cell. These transients propagated as an intercellular Ca2+ wave to a distance of five or six NB cells away from the MS cell, covering areas (called active areas, AAs) up to 77,000 +/- 3,200 microm2 (N=21). The percentage of responsive cells (defined as cells showing maximum NF >1.1) decreased with increasing distance from the MS cell. The Ca2+ wave crossed cell-free lanes. Pretreatment of cells with the nonselective purinergic receptor antagonist suramin (200 microM), exogenous apyrases, which break down nucleotides (10 U/mL), or the PLC inhibitor U-73122 (10 microM) reduced the wave propagation, whereas the ecto-ATPase inhibitor ARL-67156 (100 microM) significantly enhanced it. ATP-dependent LL bioluminescence increased after PMS. RT-PCR showed mRNAs for P2Y1 and P2Y2 receptors and ecto-ATPases in BCECs. CONCLUSIONS: PMS of BCECs induces release of ATP and a concomitant intercellular Ca2+ wave, even in the absence of direct cell-cell contacts. The AA of the wave is modulated by agents that affect P2Y receptor activity. Thus, PMS-induced intercellular Ca2+ wave propagation in BCECs involves ATP-dependent paracrine IC.

Adenosine Triphosphatases↗
PubMed1985

Use of a new citrulline incorporation assay to investigate inhibition of intercellular communication by 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane in human fibroblasts.

A citrulline incorporation assay has been developed to measure intercellular communication between argininosuccinate synthetase-deficient and argininosuccinate lyase-deficient human fibroblasts (J. S. Davidson, I. M. Baumgarten, and E. H. Harley, Exp. Cell Res., 150: 367-378, 1984). This method was used to investigate the effects of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) on intercellular junctional communication. DDT at a concentration of 20 micrograms/ml inhibited metabolic cooperation by 90 to 98%. This inhibition was of rapid onset and was rapidly reversed by washing the cells. Inhibition of metabolic cooperation by DDT was not dependent on the presence of extracellular free calcium, indicating that DDT does not act by increasing net calcium influx into cells. This system should prove useful in elucidating the relationship between tumor promotion and intercellular communication.

2,4-Dinitrophenol↗
PubMedDate not supplied

[Colonial organization and intercellular communication of microorganisms].

This review covers the modern concepts and recent data demonstrating the integrity and coherence of microbial populations (colonies, biofilms, etc.) as peculiar "super-organisms." Special attention is given to such relevant phenomena as apoptosis, bacterial altruism, quorum effects, collective differentiation of microbial cells, and the formation of population-level structures such as an extracellular matrix. Emphasis is placed on the channels in colonies and agents of intercellular communication in microbial populations. The involvement of a large number of evolutionarily conserved communicational facilities and patterns of intercellular interactions is underscored. Much attention is also given to the role of colonial organization and intercellular communication in parasite/commensal/symbiont-multicellular host organism systems.

Apoptosis↗