Prostaglandin-D synthetase induces transcription of the LH beta subunit in the primary culture of chicken anterior pituitary cells via the PPAR signaling pathway

Abstract

Downstream effects of prostaglandin-D synthetase (PGDS) in a primary culture of chicken ( Gallus gallus) anterior pituitary cells were investigated to study how PGDS regulated laying in hens. Either PGDS downstream metabolite, PGD 2 or PGJ 2, elevated LHB mRNA and LHB protein levels in dose- and time-dependent manners, and treatment with arachidonic acid (1 μM) alone upregulated 15-deoxy-Δ 12,14-PGJ 2 (15-d-PGJ 2; derived from PGJ 2)/PGJ 2, LHB mRNA, and LHB protein levels (P < 0.05) in the primary culture of chicken pituitary anterior cells. Transfection of the plasmid Enhanced Green Fluorescent Protein-PGDS plasmid into these cells in medium containing 1 μM arachidonic acid additionally increased 15-d-PGJ 2/PGJ 2, LHB mRNA, and LHB protein levels (P < 0.05). In the hypothalamus/pituitary gland of laying hens, there was a high correlation (r = 0.64; P < 0.05) between PGDS and the peroxisome proliferator-activated receptor A ( PPARA) mRNA level in a high egg production strain, the L2 Taiwan country chickens. In commercial Single-Comb White Leghorn layers, there were high correlation coefficients between PGDS and PPARA (r = 0.65; P < 0.05) and between PGDS and PPARG (r = 0.67; P < 0.01) mRNA levels. A broad-range PPARs agonist, GW9578 (5 to 500 nM), enhanced LHB mRNA and LHB protein levels (P < 0.05). The PPARA-specific (GW6471) and PPARG-specific (T0070907) antagonists suppressed endogenous LHB mRNA and LHB protein levels (P < 0.05); in addition, both antagonists attenuated arachidonic acid–induced LHB mRNA levels (P < 0.05) and PGDS-induced (in the presence of 1 μM arachidonic acid) LHB mRNA and LHB protein (P < 0.05) levels in the primary culture of chicken anterior pituitary cells. Higher LHB mRNA/LHB protein ratios in PGD 2-, PGJ 2-, arachidonic acid-, PGDS-, and GW9578-induced as well as GW6471- and T0070907-suppressed anterior pituitary cells suggested that LHB transcription occurred before translation. In conclusion, PGDS induced LHB transcription and subsequent translation via the PPAR signaling pathway.