Effects of decreased vitamin D and accumulated uremic toxin on human CYP3A4 activity in patients with end-stage renal disease.

In patients with end-stage renal disease, not only renal clearance but also hepatic clearance is known to be impaired. For instance, the concentration of erythromycin, a substrate of cytochrome P450 3A4 (CYP3A4), has been reported to be elevated in patients with end-stage renal disease. The purpose of this study is to elucidate the reason for the decrease in hepatic clearance in patients with end-stage renal disease. Deproteinized pooled sera were used to assess the effects of low-molecular-weight uremic toxins on CYP3A4 activity in human liver microsomes and human LS180 cells. Four uremic toxins (3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, hippuric acid, indole-3-acetic acid, and 3-indoxyl sulfate) present at high concentrations in uremic serum were also studied. Simultaneous treatment of uremic serum (less than 10%) or uremic toxins did not affect testosterone 6ß-hydroxylation in human liver microsomes. On the other hand, pretreatment of each serum activates CYP3A4 in LS180 cells, and the increased CYP3A4 activity in uremic serum-treated cells was smaller than normal serum-treated cells. In addition, CYP3A4 and CYP24A1 mRNA levels also increased in LS180 cells exposed to normal serum, and this effect was reduced in uremic serum-treated cells and in cells exposed to uremic serum added to normal serum. Furthermore, addition of 1,25-dihydroxyvitamin D to uremic serum partially restored the serum effect on CYP3A4 expression. The present study suggests that the decrease of 1,25-dihydroxyvitamin D and the accumulation of uremic toxins contributed to the decreased hepatic clearance of CYP3A4 substrates in patients with end-stage renal disease.

Possible involvement of SDF-1/CXCL12 in the pathogenesis of Degos disease.

BACKGROUND: Degos disease or malignant atrophic papulosis is a rare occlusive vasculopathic disease characterized by pathognomonic cutaneous lesions and frequently fatal systemic involvement. The etiology of malignant atrophic papulosis remains unclear, and there is currently no effective treatment for malignant atrophic papulosis. Several chemokines can potentiate and expand the platelet response to increase thrombus formation. Among these chemokines, this study examined the expression of stromal cell-derived factor (SDF)-1/CXCL12, which is secreted by bone-marrow stromal and endothelial cells, activates megakaryocyte precursors, and costimulates platelet activation. OBJECTIVE: We sought to investigate and compare the expression of SDF-1/CXCL12 in tissue sections taken from 2 patients with Degos disease, 2 patients with other vaso-occlusive diseases, and 2 healthy control subjects. METHODS: Immunohistochemical staining involving antibodies to SDF-1/CXCL12 was performed on 3 skin biopsy specimens taken from 2 patients with Degos disease, 1 from a patient with antiphospholipid syndrome, 1 from a patient with cryoglobulinemia, and 2 from healthy control subjects. RESULTS: Strong SDF-1/CXCL12 staining was observed in the infiltrating inflammatory cells in the perivascular, intravascular, and perineural areas in tissue samples from patients with Degos disease. No staining was observed in samples from patients with antiphospholipid syndrome or cryoglobulinemia or from healthy control subjects. LIMITATIONS: The number of cases available for evaluation was small. The findings were based primarily on the immunohistochemical results and were not confirmed using other techniques. CONCLUSIONS: The intense staining of SDF-1/CXCL12 in lesions attributed to Degos disease, demonstrated for the first time to our knowledge in this study, suggests SDF-1/CXCL12 involvement in the pathogenesis of the disease.