p-Cresol inhibits IL-12 production by murine macrophages stimulated with bacterial immunostimulant

Abstract

p-Cresol, an end product of aromatic amino acids, is produced from food proteins by intestinal bacteria, and is detectable in blood and feces. Especially, blood and fecal levels of p-cresol are high in chronic renal failure (CRF) patients. Although it has been suggested that p-cresol is toxic in the body, the effect of p-cresol on immune responses has not yet been clarified. In this study, we investigated the effect of p-cresol on IL-12 production of macrophages stimulated with Lactobacillus casei strain Shirota (LcS) in vitro. Pre-incubation with p-cresol inhibited IL-12 p40 production of LcS-stimulated J774.1 cells, a murine macrophage-like cell line, in a dose-dependent manner. IL-12 p40 and p70 production of LcS-stimulated murine peritoneal macrophages was also inhibited by p-cresol. The inhibitory effect was not dependent on the cytotoxicity of p-cresol. These results indicate that blood and fecal p-cresol may have adverse effects on the host defense system in CRF patients.

Keywords::

• p-Cresol
• renal failure
• IL-12
• macrophage
• mouse

Acknowledgment

We are grateful to Kan Shida for technical advice. We also thank the staff of the animal facility of the Yakult Central Institute for animal care.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.