Inhibition of gap junctional blockage by palmitoyl carnitine and TMB-8 in a rat liver epithelial cell line

Oh, Saw Yin; Madhukar, Burra V.; Trosko, James E.

doi:10.1093/carcin/9.1.135

Cited by 40 publications

(13 citation statements)

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“…agonists initiate their effects on communication through different receptor systems that are down-regulated by the specific ligand. In the case of PMA, the receptor is likely to be the protein kinase C family of proteins, and preincubation of WB cells with the phorbol ester for 6 h has been shown to cause a marked loss of Ca2+-and phospholipid-dependent kinase activity [21]. Separate experiments established that pretreatment of WB cells with PMA blocked the capacity of the phorbol ester to inhibit dye transfer, but did not decrease the inhibitory effect of LPA (Table 1).…”

Section: Resultsmentioning

confidence: 97%

Lysophosphatidic acid inhibits gap-junctional communication and stimulates phosphorylation of connexin-43 in WB cells: possible involvement of the mitogen-activated protein kinase cascade

Hill

Schmidt

et al. 1994

Biochemical Journal

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Lysophosphatidic acid (LPA) was shown to be a powerful inhibitor of gap-junctional communication between cultured rat liver WB cells, as determined by the transfer of Lucifer Yellow, with 50% inhibition obtained at about 0.3 microM LPA. Inhibition of communication was rapid (5 min) and was maintained for at least 80 min. After incubation for 3 h with LPA, communication competence was partially restored and dye transfer was refractory to further addition of LPA. Communication in LPA-refractory cells retained sensitivity to inhibition by phorbol ester and by epidermal growth factor (EGF). LPA-induced inhibition was associated with phosphorylation of connexin-43 protein, as detected by slower migration of the protein detected on Western blots, which could be eliminated by incubation of samples with alkaline phosphatase. A close correspondence was observed between the time- and dose-dependency of LPA effects on communication and the induction of mitogen-activated protein kinase (MAP kinase). Activation of both the 42 kDa and 44 kDa subspecies were confirmed by mobility shifts on Western blots using an anti-(MAP kinase R1) (erk 1-III) antibody and by fractionation on Mono Q columns. Cells pretreated with phorbol ester for 24 h were insensitive to phorbol ester inhibition of communication or activation of MAP kinase, but retained their sensitivity to LPA. The results indicate that LPA initiates the activation of protein kinase cascades in WB cells that are probably independent of protein kinase C and identifies connexin-43 as one substrate for the activated kinases.

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Section: Resultsmentioning

confidence: 97%

Lysophosphatidic acid inhibits gap-junctional communication and stimulates phosphorylation of connexin-43 in WB cells: possible involvement of the mitogen-activated protein kinase cascade

Hill

Schmidt

et al. 1994

Biochemical Journal

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“…The first concern is that the scraped cells do not uniformly label with Lucifer yellow, regardless of the presence or absence of chemical treatment. Other studies have published photographs illustrating similarly inconsistent labeling patterns (E1-Fouly et al, 1987;Kavanagh et al, 1987;Suter et al, 1987;Oh et al, 1988;Nicholson et al, 1988;Evans et al, 1988aEvans et al, , 1988bMadhukar et al, 1989;Loch-Caruso et al, 1990), and a representative example from our laboratory is shown in Figure 2. Several factors may contribute to this lack of uniform dye labeling.…”

Section: Discussionmentioning

confidence: 57%

“…The SL/DT assay has been used traditionally as a screening tool to evaluate the qualitative effects of chemicals on GJIC. However, more recently, the SL/DT assay has been used to obtain quantitative concentration-dependent responses of chemically induced inhibition (Surer et al, 1987;Evans et al, 1988aEvans et al, , 1988bOh et al, 1988;LochCaruso, 1990). …”

Section: Discussionmentioning

confidence: 99%

“…Several investigators have used the SL/DT assay to determine inhibition of intercellular communication in mammalian cells (E1-Fouly et al, 1987;Kavanagh et al, 1987;Suter et al, 1987;Oh et al, 1988;Evans et al, 1988aEvans et al, , 1988bFlodstrom et al, 1988;Madhukar et al, 1989). The objective of this study was to evaluate and compare various approaches in order to quantify the results generated by the SL/DT technique.…”

Section: Introductionmentioning

confidence: 99%

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Limitations of the scrape-loading/dye transfer technique to quantify inhibition of gap junctional intercellular communication

McKarns

Doolittle

1992

Cell Biol Toxicol

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Gap junctional intercellular communication (GJIC) is recognized as playing an important role in normal cell proliferation and development. Chemically induced alteration of GJIC has been proposed to be associated with abnormal cellular growth and/or tumor promotion. Several in vitro assays are currently used to determine the effects of chemicals on GJIC between cultured mammalian cells. One of these assays, the scrape-loading dye transfer (SL/DT) technique, is based on monitoring the transfer of the fluorescent dye Lucifer yellow from one cell into adjacent cells via functional gap junctions. The objective of our study was to evaluate and compare various approaches for quantifying results obtained with the SL/DT technique. Confluent cultures of either WB rat liver epithelial cells or LC-540 rat leydig cells were exposed to the animal tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), solvent (0.1% ethanol), or culture medium for one hour at 37 degrees C prior to analysis of GJIC. Inhibition of dye transfer was clearly evident following TPA exposure. Quantification of this dye transfer was assessed via four approaches: manually counting the number of labeled cells; measuring the distance of dye travel from the scrape line; quantifying the amount of cellular dye uptake; and determining the distribution of dye away from the scrape line. Our results suggest that while the SL/DT technique can be effectively used as a tool to determine the qualitative presence or absence of GJIC, its use in quantifying changes in GJIC following chemical exposure is limited. Since concentration-dependent responses are critical in chemical testing, application of the SL/DT method should be restricted to a screening assay for qualitatively assessing the presence or absence of GJIC.

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“…Gap junctions provide cells with intracellular conduits for communication and transfer of essential metabolites and ions. Most tumor promoting agents, such as 12-O-tetradecanoylphorbol-13-acetate (TPA), can inhibit intercellular communications in cultured cells [Oh et al, 1988;Gao et al, 1992;Nielson et al, 2000], and reduced or dysfunctional GJIC capacity has been associated with carcinogenesis [Yamasaki, 1996].…”

Section: Introductionmentioning

confidence: 99%

Millimeter wave exposure reverses TPA suppression of gap junction intercellular communication in HaCaT human keratinocytes

Chen

Zeng

et al. 2003

Bioelectromagnetics

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The effect of 30.16 GHz millimeter wave (MMW) exposure at 1.0 and 3.5 mW/cm2 on gap junction intercellular communication (GJIC) was studied in cultured HaCaT keratinocytes, using the fluorescence recovery after photobleaching (FRAP) technique and laser confocal scanning microscopy to follow the intracellular movement of 5,6-carboxyfluorescein diacetate dye. While MMW exposure alone for 1 h at either 1.0 or 3.5 mW/cm2 did not affect GJIC, MMW exposure in combination with 5 ng/ml TPA treatment reversed TPA induced suppression of GJIC. Exposure at 1.0 mW/cm2 resulted in a partial reversal, and exposure at 3.5 mW/cm2 resulted in essentially full reversal of the TPA suppression.

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Inhibition of gap junctional blockage by palmitoyl carnitine and TMB-8 in a rat liver epithelial cell line

Cited by 40 publications

References 0 publications

Lysophosphatidic acid inhibits gap-junctional communication and stimulates phosphorylation of connexin-43 in WB cells: possible involvement of the mitogen-activated protein kinase cascade

Lysophosphatidic acid inhibits gap-junctional communication and stimulates phosphorylation of connexin-43 in WB cells: possible involvement of the mitogen-activated protein kinase cascade

Limitations of the scrape-loading/dye transfer technique to quantify inhibition of gap junctional intercellular communication

Millimeter wave exposure reverses TPA suppression of gap junction intercellular communication in HaCaT human keratinocytes

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