Natural and recombinant human glycodelin activate a proapoptotic gene cascade in monocyte cells

Meng Kian Tee^*^,^,1, Jean-Louis Vigne^,1, Jie Yu and Robert N. Taylor^,^,2

^* Departments of Pediatrics and
Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Sciences, University of California, San Francisco, California, USA; and
Department of Gynecology and Obstetrics, Emory University School of Medicine, Atlanta, Georgia, USA

² Correspondence: Department of Gynecology and Obstetrics, Emory University School of Medicine, 1639 Pierce Drive, Suite 4217-WMB, Atlanta, GA 30322, USA. E-mail: robert.n.taylor{at}emory.edu

Glycodelin-A (GdA) is a member of the superfamily of lipocalinsand the predominant glycoprotein secreted by human and primateendometrium in the secretory and early pregnancy phases. GdAcan inhibit NK cell activity, T cell proliferation, and chemotaxisof monocytes. Its physiological function is thought to mediateimmunotolerance at the fetomaternal interface. In the presentstudies, we engineered recombinant Gd (rGd) in yeast and testedits biological effects on monocyte viability. rGd, like thenatural, purified endometrial GdA, is glycosylated and secreted,and they both induced apototic changes in monocytic U937 cellsand primary human monocytes. Trypan blue exclusion, nucleosomerelease, DNA laddering, and immunocytochemistry to detect free3'-OH DNA ends were used to characterize the effects of GdAand rGd. Using U937 cells as a model, cDNA microarray analysesrevealed several pro- and antiapoptotic genes that were up-and down-regulated, respectively, in accordance with the kineticsof rGd-induced monocyte cell death. Real-time RT-PCR confirmedthat Bad, Bax, and TNF-R1 gene expression were increased, whereasBcl-2A1 and a proliferation-inducing ligand (APRIL) were reducedby rGd. Transfection assays in U937 cells indicated that theimmunomodulatory actions of rGd were associated with NF- ${kappa}$ B inhibition.Western blotting of U937 and primary monocyte lysates demonstratedthat rGd activated caspase-8, -2, and -3 to execute programmedcell death in these cells. We postulate that infiltrating monocytesand potentially other innate immune cells of the decidua mightbe manipulated by this glycoprotein to enhance embryonic implantationrates or conversely, to develop novel contraceptive strategies.

Key Words: apoptosis • embryonic implantation • monocytes • pregnancy • decidua