Effects of bryostatin 1, a novel anticancer agent, on intestinal transport and barrier function: role of protein kinase C.
BACKGROUND
Bryostatin 1 is a novel chemotherapeutic agent that activates specific members of the protein kinase C (PKC) family in a complex pattern overlapping with, but distinct from, that of tumor-promoting phorbol esters. Phorbol esters profoundly altered epithelial phenotype, abolishing both barrier function and Cl secretion (the latter due to loss of a key transport site, the Na-K-Cl cotransporter). The effects of bryostatin 1 on these parameters are unknown.


METHODS
Cl secretion and barrier function of T84 human intestinal epithelia were assessed as cyclic adenosine monophosphate-stimulated short-circuit current and transepithelial resistance, respectively. Na-K-Cl cotransporter function and mRNA expression were assayed by 86Rb uptake and Northern analysis.


RESULTS
Bryostatin 1 reduced Cl secretion, Na-K-Cl cotransport, and cotransporter mRNA expression. Unlike phorbol esters, these effects were largely transient. In contrast to phorbol esters, bryostatin 1 did not decrease barrier function.


CONCLUSIONS
Bryostatin 1 transiently inhibits Na-K-Cl cotransport and Cl secretion, possibly through a PKC isoform also targeted by phorbol esters. Unlike phorbol esters, bryostatin 1 does not impair barrier function. The data imply that bryostatin 1 and phorbol esters differentially affect a PKC isoform involved in junctional regulation, and that epithelial transport and barrier function may be regulated by distinct PKC isoforms.
Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass 02215, USA.
O C
OC
Farokhzad
E C
EC
Mun
J K
JK
Sicklick
J A
JA
Smith
J B
JB
Matthews
D000970:Antineoplastic Agents / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D054713:Bryostatins; D002273:Carcinogens / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D007413:Intestinal Mucosa / Q000737:chemistry / Q000166:cytology / Q000201:enzymology*; D007783:Lactones / Q000494:pharmacology*; D018942:Macrolides; D011188:Potassium / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D012964:Sodium / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000970:Antineoplastic Agents; D054713:Bryostatins; D002273:Carcinogens; D002352:Carrier Proteins; D002712:Chlorides; D007783:Lactones; D018942:Macrolides; D012333:RNA, Messenger; D028021:Sodium-Potassium-Chloride Symporters; C046785:bryostatin 1; D012964:Sodium; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D011188:Potassium