6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2h-pyran-2-one and 1-1-1-2-2-pentafluoro-7-phenylheptan-3-one

Na(+)-K(+)-2Cl(-) cotransporter (NKCC2)-mediated NaCl reabsorption in the thick ascending limb (TAL) is stimulated by AVP via V2 receptor/PKA/cAMP signaling. This process is antagonized by locally produced eicosanoids such as 20-HETE or prostaglandin E(2), which are synthesized in a phospholipase A(2)-dependent reaction cascade. Using microarray-based gene expression analysis, we found evidence for an AVP-dependent downregulation of the calcium-independent isoform of PLA(2), iPLA(2)β, in the outer medulla of rats. In the present study, we therefore examined the contribution of iPLA(2)β to NKCC2 regulation. Immunoreactive iPLA(2)β protein was detected in cultured mTAL cells as well as in the entire TAL of rodents and humans with the exception of the macula densa. Administration of the V2 receptor-selective agonist desmopressin (5 ng/h; 3 days) to AVP-deficient diabetes insipidus rats increased outer medullary phosphorylated NKCC2 (pNKCC2) levels more than twofold in association with a marked reduction in iPLA(2)β abundance (-65%; P < 0.05), thus confirming microarray results. Inhibition of iPLA(2)β in Sprague-Dawley rats with FKGK 11 (0.5 μM) or in mTAL cells with FKGK 11 (10 μM) or (S)-bromoenol lactone (5 μM) for 1 h markedly increased pNKCC2 levels without affecting total NKCC2 expression. Collectively, these data indicate that iPLA(2)β acts as an inhibitory modulator of NKCC2 activity and suggest that downregulation of iPLA(2)β may be a relevant step in AVP-mediated urine concentration.

Topics: Animals; Antibodies; Arachidonic Acids; Cells, Cultured; Deamino Arginine Vasopressin; Down-Regulation; Fluorocarbons; Gene Expression; Group VI Phospholipases A2; Guinea Pigs; Humans; Isoenzymes; Ketones; Kidney Medulla; Loop of Henle; Male; Mice; Mice, Inbred C57BL; Naphthalenes; Organophosphonates; Phosphorylation; Pyrones; Rats; Rats, Brattleboro; Rats, Sprague-Dawley; Sodium-Potassium-Chloride Symporters; Solute Carrier Family 12, Member 1; Vasopressins

We and others have shown that calcium-independent phospholipase A(2) (iPLA(2)) is involved in epithelial ovarian cancer (EOC). Hence, we propose that iPLA(2) is a potential effective and novel target for EOC. We tested this concept and found that bromoenol lactone (BEL), a selective inhibitor of iPLA(2), significantly inhibited EOC metastatic tumor growth in mouse xenograft models using human SKOV3 and HEY ovarian cancer cells. Moreover, the combination of BEL with paclitaxel (PTX), one of the most commonly used therapeutic agents in EOC, almost completely blocked tumor development in the xenograft mouse model. BEL showed no detectable cytotoxic effects in mice. Another iPLA(2) inhibitor, FKGK11, also inhibited tumor development in the xenograft mouse model, supporting that the major target of action was iPLA(2). The additional effects of BEL with PTX in vivo likely stem from their distinct cellular effects. BEL and FKGK11 reduced adhesion, migration, and invasion of EOC cells in vitro; the reduced ability to adhere, migrate, and invade seems to increase the vulnerability of tumor cells to PTX. These results provide an important basis for the development of new treatment modalities for EOC.

Topics: Animals; Antineoplastic Agents, Phytogenic; Antineoplastic Combined Chemotherapy Protocols; Cell Adhesion; Cell Line, Tumor; Cell Movement; Cell Proliferation; Female; Fluorocarbons; Group IV Phospholipases A2; Humans; Immunoenzyme Techniques; Ketones; Mice; Mice, Inbred NOD; Mice, SCID; Naphthalenes; Ovarian Neoplasms; Paclitaxel; Phosphodiesterase Inhibitors; Pyrones