Expression and regulation of interferon-gamma-inducible protein 10 gene in rat Leydig cells.

In the present study, we report the cloning of a gene that is differentially expressed in normal adult rat Leydig cells and whose expression is inhibited by hCG but is induced by interferon-γ (IFNγ). DNA sequence analysis identified this gene as rat IFNγ-inducible protein 10 (IP-10), a member of the -C-X-C- chemokine superfamily of proinflammatory cytokines. High levels of IP-10 messenger RNA (mRNA) were constitutively expressed in freshly isolated and primary cultured Leydig cells. hCG inhibited this expression in a dose-dependent manner. The addition of 1 ng/ml hCG inhibited IP-10 mRNA levels more than 80%. Conversely, IP-10 mRNA levels were markedly increased in response to murine interleukin-1α, murine tumor necrosis factor-α, and murine IFNγ by 3.3-, 10-, and 26-fold, respectively. Concomitant addition of murine interleukin-1α, murine tumor necrosis factor-α, and murine IFNγ synergistically increased IP-10 mRNA levels by 58-fold. Furthermore, in addition to one previously described rat IP-10 mRNA tra...