Abstract 109

Aims. To investigate the role of MMPs induced through a PG-E2 dependent pathway, involving COX-2, and balanced by natural inhibitors(TIMPs), in neonatal lung tissue damage. Materials. BAL samples obtained from 20 mechanically ventilated newborns (GA 24-41 w, BW 550-4040 g, PNA 0-31 d, with RDS, CDH, BPD). Methods. Separation of cell pellets (CP) from fluid phase (FP). CP resuspension in RPMI medium and incubation c and s LPS (10µg/ml), Ibuprofen (Ibu, 50 mM) and Dexamethasone (Dex, 1mM) to generate conditioned medium (CM). Gelatinolytic activity zymograms for MMPs, reverse zymograms for TIMPs, and RIA for PG-E2 performed on FP and CM. Western Blots for COX-1 and-2 expression performed on CP lysates. Results. Basal MMPs activity (mainly MMP-9 type IV collagenase) was high and TIMPs activity low. A marked induction of MMP-9 and a consistent reduction of TIMPs activities, associated with a 10-100 fold increase in PG-E2 production, were observed after 24 hours of LPS stimulation. A marked decrease in MMPs and an increase in TIMPs activities were observed with Ibu but not with Dex. COX-1 and -2 were well expressed(COX-2 with a lower MW than expected: 18-20 kDa vs 30 kDa); they increased with worsening of clinical conditions and decreased during treatment with Ibu or Dex. Conclusions. The imbalance between MMPs and their inhibitors, the striking increase of PG-E2 under stimulation and the consistent presence of COX-1 and -2 in BALs of ventilated newborns could be important factors in the production of lung damage. MMP-9 specifically degrades type IV collagen, a major constituent of the sub-epithelial basal membrane, with a possible increase in pulmonary permeability. The modulation of this process with drugs acting on the COX-2-mediated PG-E2-inducible synthesis warrants further studies.

(Supported by grant code 95/02/P/411 of the Italian Ministry of Health)