Modulatory effects of cAMP and PKC activation on gap junctional intercellular communication among thymic epithelial cells.
BACKGROUND
We investigated the effects of the signaling molecules, cyclic AMP (cAMP) and protein-kinase C (PKC), on gap junctional intercellular communication (GJIC) between thymic epithelial cells (TEC).


RESULTS
Treatment with 8-Br-cAMP, a cAMP analog; or forskolin, which stimulates cAMP production, resulted in an increase in dye transfer between adjacent TEC, inducing a three-fold enhancement in the mean fluorescence of coupled cells, ascertained by flow cytometry after calcein transfer. These treatments also increased Cx43 mRNA expression, and stimulated Cx43 protein accumulation in regions of intercellular contacts. VIP, adenosine, and epinephrine which may also signal through cyclic nucleotides were tested. The first two molecules did not mimic the effects of 8-Br-cAMP, however epinephrine was able to increase GJIC suggesting that this molecule functions as an endogenous inter-TEC GJIC modulators. Stimulation of PKC by phorbol-myristate-acetate inhibited inter-TEC GJIC. Importantly, both the enhancing and the decreasing effects, respectively induced by cAMP and PKC, were observed in both mouse and human TEC preparations. Lastly, experiments using mouse thymocyte/TEC heterocellular co-cultures suggested that the presence of thymocytes does not affect the degree of inter-TEC GJIC.


CONCLUSIONS
Overall, our data indicate that cAMP and PKC intracellular pathways are involved in the homeostatic control of the gap junction-mediated communication in the thymic epithelium, exerting respectively a positive and negative role upon cell coupling. This control is phylogenetically conserved in the thymus, since it was seen in both mouse and human TEC preparations. Lastly, our work provides new clues for a better understanding of how the thymic epithelial network can work as a physiological syncytium.
Nihei
Oscar K
OK
Laboratory of Cellular Communication, Oswaldo Cruz Institute, The Oswaldo Cruz Foundation, Rio de Janeiro, Brazil.
Fonseca
Paula C
PC
Rubim
Nara M
NM
Bonavita
Andre G
AG
Lyra
Jurandy S P O
JS
Neves-dos-Santos
Sandra
S
de Carvalho
Antonio C Campos
AC
Spray
David C
DC
Savino
Wilson
W
Alves
Luiz A
LA
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002450:Cell Communication / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D015536:Down-Regulation; D004847:Epithelial Cells / Q000378:metabolism*; D017629:Gap Junctions / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D051379:Mice; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology*
D018031:Connexin 43; D010703:Phorbol Esters; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP; D011493:Protein Kinase C