Pro-interleukin-1 beta and mature interleukin-1 beta in human trophoblast

OBJECTIVE: Inlerleukin-lbeta (IL-lβ) must be cleaved from the inactive intracellular 31kD precursor (pro-IL-lβ) by the protease Interleukin-lβ (Converting Enzyme. (ICF.) to the 17kD mature form (mat-IL-lβ) to have cuokine activity. This investigation evaluates the amounts of pro-IL-lβ and mat-II.-lβ present in human chorioamnion, decidua and villous trophoblast. STUDY DESIGN: Human placentas were obtained from uncomplicated term vaginal deliveries (n = 3), scheduled cesarean sections (n = 2), prctertn baginal delivery (n = 2), and deliveries complicated by chorioamnionitis (n = 2). The chorioamnion, decidua. and villous trophoblast were separated fiom each placenta. The separated tissues were prepared lor Western blot analysis. Protein was assayed by the Lowry method, resoked on a 12% SDS-polvacrylamide gel. and transferred to nitrocellulose paper by electroblotting. The nitrocellulose filter was incubated with polyclonal rabbit anti-human II,-Iβ antibody. Blots were developed with the Enhanced ('hemiluminescence (F.CL) kit. Autoradiography was performed. RESULTS: Signal for pro-IL-1 βwas seen in all tissue types studied. Signal for mat-II.-lβ was seen consistently only in specimens obtained from pregnancies complicated bb preterm deliver)' and chorioamnionitis. Tissues recovered from placental specimens resulting from preterm deliver)' were associated with the most intense signals for pro-11-lβ and mat-IL-lβ in all blots. The chorioamnion showed greater signal for mat-IL-lβ than the villous trophoblast from the corresponding placental specimen. CONCLUSION: The constitutive expression of pro-IL-lβ in human trophoblast indicates thai this protein sei-ves a generalized function in the villous. However, pathological processes in human parturition are accompanied by the greatest amounts ol the active mat-IL-lβ. Modulators of ICF. are critical in the control of these pathologic processes. In addition, the chorioamnion, in closest proximitv to the decidua basalis and myometrium, has an important role in those actions necessitating mat-IL-lβ. These actions include prostaglandin release known to be important in the initiation of labor.