Elastase inhibition affects collagen transcription and prostaglandin secretion in mare endometrium during the estrous cycle

Contents We have shown that bacteria induce neutrophil extracellular traps (NETs) in mare endometrium. Besides killing pathogens, NETs may contribute for endometrosis (chronic endometrium fibrosis). Since elastase (ELA) is a NETs component that regulates fibrosis and prostaglandin (PG) output, the aim was to evaluate if inhibition of ELA would affect collagen 1 (COL1) transcription and PGs secretion by endometrium explants, in different estrous cycle phases. Follicular-FP (n=8) and mid luteal-MLP (n=7) phases explants were cultured for 24-48hr with medium alone (Control), ELA (0.5g/ml,1g/ml), sivelestat - ELA inhibitor (INH,10g/ml), or ELA (0.5g/ml,1g/ml)+INH (10g/ml). COL1 gene transcription was done by qRT-PCR and PGE(2) and PGF(2) determination in culture medium by EIA. In FP, at 24hr, ELA0.5 increased COL1 transcription (p<0.001) but its inhibition (ELA0.5+INH10) decreased COL1 transcription (p<0.01) and PGF(2) production (p<0.05). Also, ELA0.5+INH10 or ELA1+INH10 raised PGE(2) production (p<0.01). At 48hr, ELA1 increased COL1 transcription (p<0.01) and PGF(2) production (p<0.001), but its inhibition (ELA1+INH10) decreased these actions (p<0.01; p<0.05, respectively). Besides, ELA1+INH10 incubation increased PGE(2) (p<0.05). PGF(2) also augmented with ELA0.5 (p<0.001), but lowered with ELA0.5+INH10 (p<0.01). In MLP, ELA0.5 up-regulated COL1 transcription (24hr, p<0.01; 48hr, p<0.001), but ELA0.5+INH10 decreased it (24hr, p<0.05; 48hr, p<0.001). At 48hr, incubation with ELA1 also increased COL1 transcription and PGF(2) production (p<0.05), but PGF(2) production decreased with ELA1+INH10 incubation (p<0.05). PGE(2) production was higher in ELA1+INH10 incubation (p<0.05). Therefore, ELA inhibition may reduce the establishment of mare endometrial fibrosis by stimulating the production of anti-fibrotic PGE(2) and inhibiting pro-fibrotic PGF(2).