title: Examination of the cellular mechanisms by which marinobufagenin inhibits cytotrophoblast function.
abstract: Marinobufagenin (MBG) is an endogenous mammalian cardiotonic steroid involved in the inhibition of Na(+)/K(+)-ATPase. Increased plasma levels have been reported in patients with volume expansion-related hypertension. We have recently demonstrated that MBG impairs first trimester cytotrophoblast (CTB) cell proliferation, migration, and invasion, which may play a role in the development of preeclampsia. However, whether apoptosis contributes to altered CTB cell function by MBG remains unknown. Using the human extravillous CTB cell line SGHPL-4, we examined the effect of MBG and a similar Na(+)/K(+)-ATPase inhibitor, ouabain, on the phosphorylation status of Jnk, p38, and Src. Additionally, we measured apoptosis by caspase 9 and 3/7 activity and by annexin-V staining. We also investigated interleukin-6 (IL-6) secretion with or without p38 and Jnk inhibition. MBG significantly increased the phosphorylation of Jnk, p38, and Src and increased the expression of caspase 9 and 3/7 indicating the activation of apoptosis. MBG treatment also stimulated the expression of the early apoptosis marker, annexin-V, which was prevented by Jnk and p38 inhibition. MBG also stimulated the secretion of IL-6, which was attenuated by p38 inhibition. Ouabain had similar effects to those of MBG, suggesting that the apoptotic effects on CTB cells may be mediated by inhibition of Na(+)/K(+)-ATPase. In conclusion, the MBG-induced impairment of CTB function occurs via activation of Jnk, p38, and Src leading to increased apoptosis and IL-6 secretion. These observations may have clinical applicability with respect to the therapy of preeclampsia.
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Texas A&M Health Science Center, Scott and White Clinic, Temple, TX 76508, USA.
authors.forename: Mohammad N
authors.initials: MN
authors.lastname: Uddin
authors.forename: Darijana
authors.initials: D
authors.lastname: Horvat
authors.forename: Shannon S
authors.initials: SS
authors.lastname: Glaser
authors.forename: Brett M
authors.initials: BM
authors.lastname: Mitchell
authors.forename: Jules B
authors.initials: JB
authors.lastname: Puschett
mesh_terms: D017209:Apoptosis; D002018:Bufanolides / Q000494:pharmacology*; D020169:Caspases / Q000378:metabolism; D002465:Cell Movement; D049109:Cell Proliferation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D008954:Models, Biological; D010042:Ouabain / Q000494:pharmacology; D010766:Phosphorylation; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014327:Trophoblasts / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D002018:Bufanolides; D004791:Enzyme Inhibitors; D015850:Interleukin-6; C093896:marinobufagenin; D010042:Ouabain; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases; D000254:Sodium-Potassium-Exchanging ATPase