The nuclear transcription factor NF-κB mediates interleukin-1β–induced expression of cyclooxygenase-2 in human myometrial cells

Abstract

Objective: Up-regulation of prostaglandin production by gestational tissues in the setting of intrauterine infection has been implicated as an important contributor to preterm labor and parturition. In this study we investigated the possible role of the nuclear transcription factor NF-κB in interleukin-1 signaling, leading to the expression of cyclooxygenase 2 and prostaglandin production in human myometrial cell cultures. Study Design: Human myometrial smooth muscle cells from an immortalized line were used as a model system between passages 20 and 35. Growth-arrested cell cultures were stimulated with human recombinant interleukin 1, and the activation of NF-κB was assessed by the degradation of the inhibitory protein IκB-α (Western analysis), as well as by nuclear binding of NF-κB by using an electrophoretic mobility shift assay. The abundance of cyclooxygenase-2 messenger ribonucleic acid and protein was measured by Northern and Western analyses, whereas prostaglandin (prostaglandin I 2 and prostaglandin E 2 ) production was determined by specific radioimmunoassays. Results: Within 15 minutes of stimulation with interleukin 1, 90% of IκB-α was degraded. This was temporally associated with nuclear translocation and binding of NF-κB. Within 30 minutes, cyclooxygenase 2 messenger ribonucleic acid appeared, with steady-state levels increasing up to 4 hours. This was followed by an up to 80-fold increase in cyclooxygenase 2 protein and a corresponding time-dependent increase in prostaglandin production. When IκB-α degradation was blocked with calpain I inhibitor, NF-κB translocation, cyclooxygenase 2 messenger ribonucleic acid and protein expression, and prostaglandin synthesis were also inhibited. Conclusion: Stimulation of human myometrial cells with interleukin 1 leads to rapid activation of the transcription factor NF-κB, which is functionally linked to the expression of cyclooxygenase 2 messenger ribonucleic acid, protein, and prostaglandin synthesis. (Am J Obstet Gynecol 1999;181:359-66.)