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.
Farokhzad
O C
OC
Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass 02215, USA.
Mun
E C
EC
Sicklick
J K
JK
Smith
J A
JA
Matthews
J B
JB
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