Identifying decidual cell-derived heat resistant factor(s) that limit macrophage tumor necrosis factor-α production in response to lipopolysaccharide challenge
Chorioamnionitis complicates up to 94% of pregnancies delivered at 21-24 weeks of gestation. Bacteria ascending from the vagina can cause chorioamnionitis. Decidual stromal cells (DSCs) in the outer (decidual) portion of gestational membranes are among the initial cells to contact pathogens, as are decidual macrophages. Preliminary data from the Aronoff lab suggested that DSCs regulate macrophage responses to infection. We sought to identify the DSC-derived molecule(s) responsible for limiting macrophage responses to the bacterial cell membrane component, lipopolysaccharide (LPS).
Telomerase-immortalized human endometrial stromal cells (THESCs) were grown in culture, and decidualized to dTHESCs with 8-Bromo-cAMP, estradiol and medroxyprogesterone. dTHESCs and PMA-differentiated THP-1 macrophage-like cells were separately exposed to 1 µg/mL LPS for 24 hr or cocultured (1 THP-1 cell: 10 dTHESC). Conditioned media (CM) harvested from dTHESCs was subjected to protein-denaturing heat (85C x 10 min) or not and then applied to THP-1 cells prior to LPS challenge. THP-1 cells were also treated with PGE2 (1 or 10 µM) for 1 hr prior to LPS treatment. Supernatants from these experiments were collected for TNF-α measurements (ELISA).
dTHESC/THP-1 coculture impaired the normal LPS-stimulated production of TNF-α by THP-1 cells. dTHESC also blunted the THP-1 TNF-α response to LPS, which was exaggerated when the CM was heated. Heat-inactivation did not alter prostaglandin PGE2 levels in dTHESC CM. The addition of exogenous PGE2 to THP-1 cells also suppressed LPS-induced TNF-α response.
PGE2 might be an important mediator derived from dTHESCs that blocks THP-1 production of TNF-α in response to LPS.