Prostaglandin synthesis by the porcine corpus luteum: effect of tumor necrosis factor-α

The porcine corpus luteum (CL) displays delayed sensitivity to PGF-2 alpha (luteolytic sensitivity, [LS]) until days 12 to 13 of cycle. The control of LS is unknown, but it is temporally associated with macrophage (which secrete tumor necrosis factor-alpha; TNF-alpha) infiltration into the CL. Other studies showed that TNF-alpha induces LS in vitro and that prostaglandins (PGs) may be involved in this mechanism. In experiment 1, PGF-2 alpha and PGE secretion by luteal cells (LCs) was measured on days 4 to 14 of the estrous cycle, and the expression of PTGES/AKR1B1 and PTGES/mPGES-1, determined by Western blot, before (day 7) vs after (day 13) the onset of LS. Results showed that the PGF-2 alpha:PGE ratio increased significantly (P < 0.05) from day 4 to 13-14, and PTGFS/AKR1B1 and PTGES/mPGES-1 were significantly increased (P < 0.05) on day 13 (vs day 7). In experiment 2, LCs were collected from porcine CL at early (similar to days 4-6) or mid (similar to days 7-12) stages of the estrous cycle and cultured with 0, 0.1, 1, or 10 ng/mL TNF-alpha. Results showed that TNF-alpha significantly increased (P < 0.05) messenger RNA (mRNA) expression of cyclooxygenase (COX)-2 and mPGES-1 but not AKR1B1. TNF-alpha had no significant effects on AKR1B1 or mPGES protein abundance. TNF-alpha significantly increased (P < 0.05) PGE-2 but had no effect on PGF-2 alpha secretion or on the PGF-2 alpha:PGE2 ratio. In conclusion, although TNF-a increased COX2 and mPGES-1 mRNA, and PGE-2 secretion in vitro, it did not increase the PGF-2 alpha:PGE2 ratio. Studies are currently directed toward exploring other pathways (eg, FP receptor signaling) by which TNF-a induces LS in the porcine CL. (C) 2016 Elsevier Inc. All rights reserved.