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 24-48 hr with medium alone (Control), ELA (0.5 μg/ml,1 μg/ml), sivelestat - ELA inhibitor (INH,10 μg/ml), or ELA (0.5 μg/ml,1 μg/ml) + INH (10 μg/ml). COL1 gene transcription was done by qRT-PCR and PGE₂ and PGF₂ α determination in culture medium by EIA. In FP, at 24 hr, ELA0.5 increased COL1 transcription (p < 0.001) but its inhibition (ELA0.5 + INH10) decreased COL1 transcription (p < 0.01) and PGF₂ α production (p < 0.05). Also, ELA0.5 + INH10 or ELA1 + INH10 raised PGE₂ production (p < 0.01). At 48 hr, ELA1 increased COL1 transcription (p < 0.01) and PGF₂ α production (p < 0.001), but its inhibition (ELA1 + INH10) decreased these actions (p < 0.01; p < 0.05, respectively). Besides, ELA1 + INH10 incubation increased PGE₂ (p < 0.05). PGF₂ α 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 (24 hr, p < 0.01; 48 hr, p < 0.001), but ELA0.5 + INH10 decreased it (24 hr, p < 0.05; 48 hr, p < 0.001). At 48 hr, incubation with ELA1 also increased COL1 transcription and PGF₂ α production (p < 0.05), but PGF₂ α production decreased with ELA1 + INH10 incubation (p < 0.05). PGE₂ 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 PGE₂ and inhibiting pro-fibrotic PGF₂ α.

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