Ikuyo Makino

Effects of intestinal bacteria-derived p-cresyl sulfate on Th1-type immune response in vivo and in vitro.

Protein fermentation by intestinal bacteria generates various compounds that are not synthesized by their hosts. An example is p-cresol, which is produced from tyrosine. Patients with chronic kidney disease (CKD) accumulate high concentrations of intestinal bacteria-derived p-cresyl sulfate (pCS), which is the major metabolite of p-cresol, in their blood, and this accumulation contributes to certain CKD-associated disorders. Immune dysfunction is a CKD-associated disorder that frequently contributes to infectious diseases among CKD patients. Although some studies imply pCS as an etiological factor, the relation between pCS and immune systems is poorly understood. In the present study, we investigated the immunological effects of pCS derived from intestinal bacteria in mice. For this purpose, we fed mice a tyrosine-rich diet that causes the accumulation of pCS in their blood. The mice were shown to exhibit decreased Th1-driven 2, 4-dinitrofluorobenzene-induced contact hypersensitivity response. The concentration of pCS in blood was negatively correlated with the degree of the contact hypersensitivity response. In contrast, the T cell-dependent antibody response was not influenced by the accumulated pCS. We also examined the in vitro cytokine responses by T cells in the presence of pCS. The production of IFN-γ was suppressed by pCS. Further, pCS decreased the percentage of IFN-γ-producing Th1 cells. Our results suggest that intestinal bacteria-derived pCS suppressesTh1-type cellular immune responses.

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

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.

p-Cresyl sulfate suppresses lipopolysaccharide-induced anti-bacterial immune responses in murine macrophages in vitro.

p-Cresyl sulfate (pCS) is a known uremic toxin that is metabolized from p-cresol produced by intestinal bacteria. Abnormal accumulation of pCS in the blood is a characteristic of chronic kidney disease (CKD). pCS is suggested to cause immune dysfunction and increase the risk of infectious diseases in CKD patients. In this study, we focused on the effects of pCS on macrophage functions related to host defense. We evaluated the effects of pCS on cytokine production, nitric oxide (NO) production, arginase activity, expression of cell-surface molecules, and phagocytosis in the macrophage-like cell line, RAW264.7. pCS significantly decreased interleukin (IL)-12 p40 production and increased IL-10 production. pCS also decreased NO production, but did not influence arginase activity. pCS suppressed lipopolysaccharide-induced CD40 expression on the cell surface, but did not influence phagocytosis. We further assessed whether the effects of pCS observed in the macrophage-like cell line were consistent in primary macrophages. Similar to RAW264.7 cells, pCS decreased IL-12 p40 and p70 production and increased IL-10 production in primary peritoneal macrophages. These data indicate that pCS suppresses certain macrophage functions that contribute to host defense, and may play a role in CKD-related immune dysfunction.

p-Cresyl sulfate decreases peripheral B cells in mice with adenine-induced renal dysfunction

ABSTRACT Infection is a major cause of mortality in chronic kidney disease (CKD) patients. Although immune dysfunction is a risk factor for infection in CKD patients, its causes are not fully elucidated. In the present study, we evaluated whether p‐cresyl sulfate (pCS), an intestinal bacteria‐derived uremic toxin, was involved in immune dysfunction in CKD. We used osmotic pumps to establish adenine‐induced renal dysfunction mice with a chronically high blood pCS concentration. Analysis of lymphocyte subsets revealed that pCS significantly reduced peripheral B cells in renal dysfunction mice. In vitro, pCS inhibited interleukin (IL)‐7‐induced proliferation of CD43+ B‐cell progenitors and suppressed IL‐7‐induced phosphorylation of signal transducer and activator of transcription 5 (STAT5) in these cells. Cell cycle analysis showed that pCS significantly decreased the percentage of CD43+ B‐cell progenitors in S phase and increased that in G1 phase. These results suggest that pCS suppressed IL‐7‐induced STAT5 signaling and inhibited B‐cell progenitor proliferation, leading to reduction of peripheral B cells in adenine‐induced renal dysfunction mice. Therefore, pCS decreases peripheral B cells by inhibiting proliferation of CD43+ B‐cell progenitors and is a likely cause of immune dysfunction in CKD patients. HighlightsRenal dysfunction mice with high blood p‐cresyl sulfate (pCS) were established.pCS significantly reduced peripheral B and NK cells in renal dysfunction mice.pCS inhibited IL‐7‐induced proliferation of B‐cell progenitors.pCS suppressed IL‐7‐induced phosphorylation of STAT5 in B cell progenitors.pCS decreased the percentage of B‐cell progenitors in S phase.