MON-478 Antinflammatory and Antioxidant Effects of MIA-690 and MR-409 in GHRHKO Mice Colon and Prefrontal Cortex

GH-releasing hormone (GHRH) exerts various effects on multiple peripheral organs, including brain, heart, kidney and retina, in addition to its growth hormone (GH)-stimulatory effect on the pituitary somatotroph cells. Various agonistic and antagonistic analogs of GHRH have been synthesized and studied for their biological activity. In the present study we investigated the potential anti-inflammatory and antioxidant effects of the GHRH agonist, MR-409, and GHRH antagonist, MIA-690, on isolated mouse prefrontal cortex and colon specimens treated with lipopolysaccaride (LPS), a validated ex vivo model of inflammation. Specifically, we studied the effects of these two compounds on LPS-induced production of prostaglandin (PG)E2, a marker of inflammation, and 8-iso-prostaglandin (8-iso-PG)F2α, a marker of oxidative stress, both in GH deficient mice with generalized ablation of the GHRH gene (GHRH knock out, GHRHKO) (-/-) and wild type (WT, controls) (+/+) adult mice. Animals (n=8) were sacrificed and cortex and colon specimens were immediately collected and maintained in a humidified incubator with 5% CO2 at 37°C for 4 h, in RPMI buffer with added bacterial LPS (10 μg/mL) (incubation period). During the incubation period, tissues were treated with vehicle or increasing concentrations of MIA-690 (1-5 μM) and MR-409 (1-5 μM). Tissue perfusates were collected and PGE2 and 8-iso-PGF2α levels (ng/mg wet tissue) were measured by radioimmunoassay (RIA). Differences between groups were analyzed by one-way Anova followed by Newman-Keul’s. P < 0.05 was considered statistically significant. Compared to controls, -/- mice showed increased PGE2 and 8-iso-PGF2α levels after LPS-challenge in both tissues. MIA-690 and MR-409 were found to inhibit LPS-induced cortex and colon production of PGE2 and 8-iso-PGF2α in a dose-dependent manner in both +/+ and -/- mice. MIA-690 and MR-409 were significantly more effective in -/- mice compared to +/+ animals. In addition, MR-409 was more effective than MIA-690 to inhibit LPS-induced cortex and colon production of PGE2 and 8-iso-PGF2α. In conclusion, generalized GHRH ablation is associated with increased prefrontal cortex and colonic sensitivity to inflammatory stimuli, as shown by higher PGE2 and 8-iso-PGF2α production. Surprisingly, both MR-409 and MIA-690 exhibit anti-inflammatory and antioxidant effects.