Modified lipoprotein-induced sFlt1 production in human placental trophoblasts is mediated by protein kinase C.

BACKGROUND

Preeclampsia is prevalent in women with diabetes, but the mechanism is unclear. We previously found that oxidized, glycated lipoproteins robustly upregulated soluble fms-like tyrosine kinase-1 (sFlt1), a key mediator of preeclampsia. Here, we determined the role of protein kinase C (PKC) and its subtypes in sFlt1 regulation in placental trophoblasts, and whether this mechanism might mediate the effect of modified lipoproteins.

METHODS

Cultured human HTR8/SVneo and BeWo trophoblasts were treated with the PKC activator phorbol-12-myristate-13-acetate (PMA) for 24h, ± PKC inhibitors GF109203X (general), Ro31-8220 (PKCα-selective), LY333531 (PKCβ-selective) and rottlerin (PKCδ-selective). The effect of 'heavily oxidized, glycated' low-density lipoproteins (HOG-LDL) vs. native LDL (N-LDL), ± high glucose (30 mM), was evaluated in HTR8/SVneo cells. sFlt1 secretion (ELISA), mRNA expression (RT-qPCR), and cellular PKC activity were measured.

RESULTS

PMA stimulated robust sFlt1 release and mRNA expression in both cell lines; these effects were inhibited by GF109203X, Ro31-8220 and LY333531 in a concentration-dependent manner. Rottlerin inhibited sFlt1 in BeWo, but modestly enhanced it in HTR8/SVneo cells. HOG-LDL enhanced PKC activity vs. N-LDL in HTR8/SVneo cells. Also, HOG-LDL, but not high glucose, significantly increased sFlt1 secretion and mRNA expression; this response was inhibited by GF109203X, Ro31-8220 and LY333531 at concentrations comparable to those that blocked PMA induction of sFlt1.

CONCLUSION

Modified lipoproteins upregulate sFlt1 in trophoblasts via a PKC-mediated mechanism, involving at least α and β isoforms. The data suggest potential therapeutic targets to reduce the risk of preeclampsia in women with diabetes.