Molecular changes induced in rat liver by hemorrhage and effects of melanocortin treatment

Background: Melanocortin peptides improve hemodynamic parameters and prevent death during severe hemorrhagic shock. In the present research we determined influences of a synthetic melanocortin 1/4 receptor agonist on the molecular changes that occur in rat liver during hemorrhage. Methods: Controlled-volume hemorrhage was performed in adult rats under general anesthesia by a stepwise blood withdrawal until mean arterial pressure fell to 40 mmHg. Then rats received either saline or the synthetic melanocortin 1/4 receptor agonist Butir-His-D-Phe-Arg-Trp-Sar- NH 2 (Ro27-3225; n = 6-8 per group). Hemogasanalysis was performed throughout a 60-min period. Gene expression in liver samples was determined at 1 or 3 h using quantitative real-time polymerase chain reaction. Results: At 1 h, in saline-treated shocked rats, there were significant increases in activating transcription factor 3 (Atf3), early growth response 1 (Egr1), heme oxygenase (decycling) 1 (Hmox1), FBJ murine osteosarcoma viral oncogene homolog (Fos), and jun oncogene (Jun). These changes were prevented by Ro27-3225 (mean \ub1 SEM: Atf3 152.83 \ub1 58.62 vs. 579.00 \ub1 124.13, P = 0.002; Egr1 13.21 \ub1 1.28 vs. 26.63 \ub1 1.02, P = 0.001; Hmox1 3.28 \ub1 0.31 vs. 166.54 \ub1 35.03, P = 0.002; Fos 4.36 \ub1 1.03 vs. 14.90\ub13.44, P<0.001; Jun 6.62\ub11.93 vs. 15.07\ub12.09, P = 0.005; respectively). Increases in alpha-2-macroglobulin (A2m), heat shock 70kD protein 1A (Hspa1a), erythropoietin (Epo), and interleukin-6 (Il6) occurred at 3 h in shocked rats and were prevented by Ro27-3225 treatment (A2m 6.90 \ub1 0.82 vs. 36.73 \ub1 4.00, P < 0.001; Hspa1a 10.34 \ub13.28 vs. 25.72 \ub1 3.64, P = 0.001; Epo 0.49 \ub1 0.13 vs. 2.37 \ub1 0.73, P = 0.002; Il6 1.05 \ub1 0.15 vs. 1.88 \ub1 0.23, P < 0.001; respectively). Further, at 3 h in shocked rats treated with Ro27-3225 there were significant increases in tight junction protein 1 (Tjp1; 27.30 \ub1 2.43 vs. 5.03 \ub11.68, P < 0.001) and nuclear receptor subfamily 4, group A, member 1 (Nr4a1; 91.03 \ub1 16.20 vs. 30.43 \ub1 11.0, P = 0.01) relative to sham animals. Treatment with Ro27-3225 rapidly restored blood pressure, hemogasanalysis parameters, and lactate blood levels. Conclusions: Melanocortin treatment significantly prevents most of the systemic and hepatic detrimental changes induced by hemorrhage. Copyrigh