Regulation of Phospholipase Isozymes by Nuclear Factor-κB in Human Gestational Tissues in Vitro

Phospholipid-derived mediators are implicated in the initiation and progression of human labor and delivery, particularly in relation to infection-induced preterm labor. We previously demonstrated that, in human intrauterine tissues, lipopolysaccharide (LPS)-stimulated nuclear factor-κB (NF-κB) DNA binding activity, and subsequent cytokine release can be suppressed by sulfasalazine (SASP) concentrations greater than 5 mm. The aim of this study was to elucidate the effect the SASP on secretory type II phospholipase A₂ (PLA₂), cytosolic PLA₂ (cPLA₂), cyclooxygenase (COX) isozymes, and subsequent prostaglandin F_2α (PGF_2α) production in human gestational tissues. Human placenta, amnion, and choriodecidua (n = 4–9 separate placentas) were incubated in the presence of SASP (0.1, 1, 5, and/or 10 mm) under either basal or LPS (10 μg/ml) conditions. After 6 h incubation, the tissues were collected and assayed for type II PLA₂ by ELISA and cPLA₂, COX-1, and COX-2 content by Western blotting. The incubation medium was collected and assayed for type II PLA₂ and 13,14-dihydro-15-keto PGF_2α release by ELISA and PGF_2α by RIA. Treatment of placenta, amnion, and choriodecidua with SASP concentrations greater than 5 mm significantly inhibited basal and/or LPS-stimulated type II PLA₂ content and release, 13,14-dihydro-15-keto PGF_2α release, and cPLA₂ protein content (ANOVA, P < 0.05); however, no effect of SASP was observed on basal or LPS-stimulated COX-1 or COX-2 protein. Although no effect of SASP was observed on basal and LPS-stimulated PGF_2α release from placenta and amnion, it significantly increased both basal and LPS-stimulated PGF_2α release from choriodecidua. In addition, SASP concentrations of 5 mm or greater significantly suppressed NF-κB DNA binding activity. These data are consistent with the hypothesis that NF-κB regulates the expression and release of phospholipase isozymes.