In mice, an overdose of acetaminophen hurts the liver and triggers the body to release more growth hormone (GH) and IGF‑1. Blocking the hormone that normally tells the pituitary to release GH (GHRH) makes the liver damage even worse, while giving a strong GHRH‑like drug helps protect the liver. This shows that GHRH activity plays a protective role in liver stress, likely through the GH/IGF‑I and JAK/STAT pathways.

The aim of the current study is to investigate the effects of growth hormone releasing hormone (GHRH) antagonist on acetaminophen (APAP)-induced acute liver injury in mice. Healthy C57/B6L mice were orally treated with 200 mg/kg APAP with or without a 30-min pre-treatment with 300 µg/kg GHRH antagonist MZ-5-156. After 12 hours, serum, plasma, and liver samples from each mouse were collected for analyses. Our results showed that twelve-hour treatment with APAP caused obvious liver injury, elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, increased oxidative stress, reduced expressions of antioxidant enzymes, accumulated expression of pro-inflammatory cytokines, and increased circulating levels of growth hormone (GH) and insulin-like growth factor-I (IGF-I). Pre-treatment with MZ-5-156 aggravated liver injury, further increased serum ALT and AST levels, exacerbated oxidative stress and inflammation induced by APAP. Treatment of MZ-5-156 also blocked the phosphorylation form and total form of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 5 (STAT5). Treatment of GHRH super-agonist JI-38 immediately after MZ-5-156 treatment partly reversed the liver injury caused by APAP and MZ-5-156. In conclusion, GHRH plays essential protective role in APAP-induced acute liver injury in vivo. The protective properties of GHRH are partially through GH/IGF-I axis and JAK/STAT pathway.