Effects of nitric oxide and tumor necrosis factor-α on production of prostaglandin F_2α and E₂ in bovine endometrial cells

The purpose of this study was to determine whether nitric oxide (NO) mediates tumor necrosis factor (TNF)α influence on the bovine endometrium. TNFα influence on the bovine endometrium is limited to the stromal cells. Therefore, it was interesting to find out whether NO production by the stromal cells, stimulated by TNFα might influence the endometrial epithelium. Moreover, we investigated the intracellular mechanisms of TNFα- and NO-regulated prostaglandin (PG) F_2α and PGE₂ synthesis. Epithelial and stromal cells from the bovine endometrium (Days 2-5 of the oestrous cycle) were separated by means of enzymatic dispersion and cultured for 6-7 days in 48-well plates. The confluent endometrial cells were exposed to a NO donor (S-NAP; 1-1000 μM) for 24 h. S-NAP strongly stimulated PGE₂ production in both bovine endometrial cell types (P<0.001). The effect of SNAP on PGF_2α production was limited only to the stromal cells (P<0.05). To study the intracellular mechanisms of TNFα and NO action, stromal cells were incubated for 24 h with TNFα or S-NAP and with NO synthase (NOS) inhibitor (L-NAME; 10 μM) or an inhibitor of phosphodiesterase (IBMX; 10 μM). When the cells were exposed to TNFα in combination with NOS inhibitor (L-NAME), TNFα-stimulated PGs production was reduced (P<0.05). The inhibition of enzymatic degradation of cGMP by IBMX augmented the actions of S-NAP and TNFα on PGs production (P<0.05). The overall results suggest that TNFα augments PGs production by bovine endometrial stromal cells partially via induction of NOS with subsequent stimulation of NO-cGMP formation. NO also stimulates PGE₂ production in epithelial cells.