Molecular Regulation of Ghrelin Expression by Pro-Inflammatory Cytokines TNF-α and IL-6 In Rat Pancreatic AR42J Cell Line

Ghrelin is a 28 amino acid peptide endogenous ligand for growth hormone secretatgogue
receptor (GHS-R) that functions to stimulate growth hormone, regulate inflammation,
appetite and energy balance. However, the regulation of ghrelin expression by
pro-inflammatory cytokines during inflammation process has never been investigated
systematically. This study was carried out to investigate the effects of major
pro-inflammatory cytokines such as TNF-α and IL-6 on ghrelin expression using AR42J rat
pancreatic cell line as model system. The cells were treated with different concentrations of
the cytokines for 24 hours. Real-Time RT-PCR, Western blot and densitometry analysis were
carried out to quantify ghrelin mRNA and protein expression, respectively. Although TNF-α
and IL-6 stimulation resulted in a general down-regulatory pattern in both mRNA and protein
expression of ghrelin, stimulation with 5 ng/ml of TNF-α and IL-6 slightly induced the
expression of ghrelin expression. However, higher doses of the cytokines ranging from
10-50 ng/ml suppressed the ghrelin expression in a dose-dependant manner. These results
indicate that ghrelin in AR42J pancreatic cell line is regulated by the pro-inflammatory
cytokines and that the dosages of the cytokines play an important factor in the regulation of
the expression.