Pro- and anti-inflammatory mediators change leukotriene B4 and leukotriene C4 synthesis and secretion in an inflamed porcine endometrium

We studied the effect of lipopolysaccharide (LPS), proinflammatory cytokines (tumor necrosis factor α [TNF-α] and interleukin [IL]-1β), and anti-inflammatory cytokines (IL-4 and IL-10) on leukotriene (LT) A4 hydrolase and LTC4 synthase (LTCS) protein expression in, and LTB4 and LTC4 secretion from, an inflamed porcine endometrium. On day 3 of the estrous cycle (day 0 of the study), 50 mL of either saline or Escherichia coli suspension (10(9) CFU/mL) was injected into each uterine horn of gilts (n = 12 per group). Endometrial explants, obtained 8 and 16 days later, were incubated for 24 h with LPS (10 or 100 ng/mL of medium), TNF-α, IL-1β, IL-4, and IL-10 (each cytokine: 1 or 10 ng/mL of medium). Although acute endometritis developed in all bacteria-inoculated gilts, a severe form of acute endometritis was diagnosed more often on day 8 of the study than on day 16. The amount of the LTA4 hydrolase (LTAH) protein in the inflamed endometrium on day 8 was greater after applying the lower dose of TNF-α (P < 0.001) and both doses of IL-1β (P < 0.001) and IL-4 (1 ng, P < 0.01 and 10 ng, P < 0.001) than in the saline-treated uteri. A similar situation was observed in the case of the inflamed tissue on day 16 in response to LPS (100 ng, P < 0.01), TNF-α (10 ng, P < 0.05), and IL-4 (1 ng, P < 0.001). The content of LTC4 synthase in the inflamed endometrium on day 8 was reduced by LPS (100 ng, P < 0.05), IL-1β (10 ng, P < 0.05), IL-4 (1 and 10 ng, P < 0.05), and IL-10 (1 ng, P < 0.01) but increased after the application of LPS (100 ng, P < 0.05) and TNF-α (1 and 10 ng, P < 0.001), IL-1β, and IL-4 (1 ng, P < 0.05 and 10 ng, P < 0.001) on day 16. On day 8, endometrial secretion of LTB4 from the saline-injected and E coli-injected organs was similar in response to all of the used mediators. On the other hand, the contents of LTB4 in the medium decreased after incubating the inflamed tissues from day 16 with TNF-α (1 ng, P < 0.05 and 10 ng, P < 0.01), IL-1β (1 ng, P < 0.01), and IL-10 (10 ng, P < 0.05) compared with the saline-treated ones. Secretion of LTC4 from the inflamed uteri on day 8 was elevated by the lower doses of TNF-α (P < 0.01) and IL-10 (P < 0.05), whereas on day 16, such an effect occurred in response to the higher doses of IL-4 (P < 0.01) and IL-10 (P < 0.05). The obtained results show that pro- and anti-inflammatory mediators participate in the synthesis/secretion of LTs from an inflamed porcine endometrium. Our data suggest that inflammatory mediators may indirectly affect the processes regulated by LTs by influencing LT production.