Growth hormone down-regulation of Interleukin-1beta and Interleukin-6 induced acute phase protein gene expression is associated with increased gene expression of suppressor of cytokine signal-3.

Abstract

Severe burn induces the hepatic acute phase response. We previously showed that recombinant human growth hormone (GH) treatment after burn down-regulated acute phase protein (APP) production and gene expression in vivo. In this study, we hypothesized that the inhibitory effect of GH on the hepatic acute phase response was due to increased suppressor of cytokine signaling (SOCS) gene expression. HepG2 cells were treated with Interleukin-1beta (IL-1beta; 2 ng/mL) and interleukin 6 (IL-6; 20 ng/mL) alone or combined with GH (2 microg/mL) for 15 and 30 min, and 1, 2, and 4 h. The levels of gene expression for alpha1-acid glycoprotein (AGP), alpha1-antitrypsin (ATT), and SOCS (CIS, SOCS-1, 2, and 3) were measured by reverse transcript-polymerase chain reaction (RT-PCR). APP levels in the supernatant were determined by enzyme-linked immunosorbent sandwich assay (ELISA). The gene expression of AGP and ATT were also measured in HepG2 cells transfected with pEF-Flag-l/mSOCS-3 plasmid after IL-1beta or IL-6 treatment. Data are expressed as means +/- SEM, and statistical analysis was performed by one- or two-way analysis of variance. IL-1beta and IL-6 induced AGP and ATT gene expression and protein production, respectively, which was down-regulated by GH treatment. SOCS-3 but not CIS, SOCS-1, or SOCS-2 gene expression was significantly increased by GH treatment. APP gene expression was significantly decreased in cells transfected with plasmid over expressing SOCS-3 after IL-6 and IL-1beta treatment. GH attenuates IL-1beta or IL-6 induced APP gene expression, which is associated with increased expression of SOCS-3. This study suggests that SOCS-3 plays an important role in the suppression of cytokine signaling by GH in down-regulating the acute phase response after injury.