Regulation of sterol 27-hydroxylase in human monocyte-derived macrophages: up-regulation by transforming growth factor β1

Chlorpyrifos alters expression of enzymes involved in vitamin D3 synthesis in skin cells

Skin acts as a mechanical barrier between human body and environment. Epidermal cells are regularly exposed to many physiological and environmental stressors, such as pesticides, like chlorpyrifos (CPS). It is recognised that CPS may affect metabolism of other exo- and endogenous substances by affecting enzyme activity and expression. This study aims to investigate the effect of CPS on expression of CYP27A1, CYP27B1 and CYP24A1, the enzymes involved in synthesis and metabolism of vitamin D_3, in human keratinocytes HaCaT and human fibroblasts BJ. Synthesis of vitamin D₃ in cells was initiated by irradiating with UVB. Expression of CYP27A1, CYP27B1 and CYP24A1 was evaluated by RT-qPCR and Western blot. Our experiments revealed that expression of all tested cytochrome P450 isoforms in cells exposed to CPS changed significantly. Exposure of HaCaT keratinocytes to CPS decreased CYP27A1 mRNA levels, but increased CYP27B1 and CYP24A1 mRNA levels. This was confirmed at the protein level, except for the CYP27A1 expression. Outcome for the BJ cells was however less conclusive. Though exposure to CPS decreased CYP27A1 and CYP27B1 mRNA levels, at protein level increasing concentration of CPS and UVB intensity induced expression of CYP27A1 and CYP24A1. The expression of CYP27B1 isoform decreased in line with mRNA level. Nevertheless, it can be concluded that CPS may therefore interrupt vitamin D₃ metabolism in skin cells, but further studies are required to better understand such mechanisms.

Breast cancer and (25R)-26-hydroxycholesterol

(25R)-26-Hydroxycholesterol (27-hydroxycholesterol) has been found to accumulate in breast tissue and to stimulate tumor growth via the estrogen receptor. Although most tissues express CYP27A1, the highest levels are in macrophages and most attention had been given to the production of 27-hydroxycholesterol in sub-endothelial macrophages as part of reverse cholesterol transport. In view of the newly identified biologic activity, it is important to consider the determinants of the levels of 27-hydroxycholesterol in macrophages that infiltrate breast tissue. Among these determinants are the oxysterol binding proteins expressed in macrophages, the level of expression of CYP7B1, the oxysterol 7 alpha hydroxylase that generates an inactive triol, and further oxidation of 27-hydroxycholestrol to the C27 acid by multifunctional CYP27A1. Transport of 27-hydroxycholesterol from macrophages to plasma is HDL-associated. In many tissues the ratio of 27-hydroxycholesterol to cholesterol (ng/μg) is higher than that in plasma. Tamoxifen, an effective estrogen receptor antagonist that prevents breast cancer, also has the biologic property of blocking several steps in the lanosterol to cholesterol metabolic pathway. In genetically disposed women, tamoxifen may increase the amount of 27-hydroxycholesterol in breast tissue.

Activity of 25-hydroxylase in human gingival fibroblasts and periodontal ligament cells

Background

We previously demonstrated that 25-hydroxyvitamin D₃ concentrations in gingival crevicular fluid are 300 times higher than those in the plasma of patients with aggressive periodontitis. Here we explored whether 25-hydroxyvitamin D₃ can be synthesized by periodontal soft tissue cells. We also investigated which of the two main kinds of hydroxylases, CYP27A1 and CYP2R1, is the key 25-hydroxylase in periodontal soft tissue cells.

Methodology/Principal Findings

Primary cultures of human gingival fibroblasts and periodontal ligament cells from 5 individual donors were established. CYP27A1 mRNA, CYP2R1 mRNA and CYP27A1 protein were detected in human gingival fibroblasts and periodontal ligament cells, whereas CYP2R1 protein was not. After incubation with the 25-hydroxylase substrate vitamin D₃, human gingival fibroblasts and periodontal ligament cells generated detectable 25-hydroxyvitamin D₃ that resulted in the production of 1α,25-dihydroxyvitamin D₃. Specific knockdown of CYP27A1 in human gingival fibroblasts and periodontal ligament cells using siRNA resulted in a significant reduction in both 25-hydroxyvitamin D₃ and 1α,25-dihydroxyvitamin D₃ production. Knockdown of CYP2R1 did not significantly influence 25-hydroxyvitamin D₃ synthesis. Sodium butyrate did not influence significantly CYP27A1 mRNA expression; however, interleukin-1β and Porphyromonas gingivalis lipopolysaccharide strongly induced CYP27A1 mRNA expression in human gingival fibroblasts and periodontal ligament cells.

Conclusions

The activity of 25-hydroxylase was verified in human gingival fibroblasts and periodontal ligament cells, and CYP27A1 was identified as the key 25-hydroxylase in these cells.

Increase of 27-hydroxycholesterol in the airways of patients with COPD: possible role of 27-hydroxycholesterol in tissue fibrosis

BACKGROUND

27-Hydroxycholesterol (27-OHC) is produced from cholesterol by sterol 27-hydroxylase as an intermediate in the biosynthesis pathway of bile acid. Recently, 27-OHC was reported to cause inflammation and apoptosis in various types of cells. The aim of this study was to assess the production of 27-OHC in the airways of patients with COPD and to elucidate the possible role of 27-OHC in the tissue fibrosis of COPD.

METHODS

Lung tissues were obtained from six control subjects and six patients with COPD, and sputum samples were obtained from 11 healthy subjects and 15 patients with COPD. The expression of sterol 27-hydroxylase in the lung was investigated by immunohistochemistry. The amounts of 27-OHC in the sputum were quantified by the liquid chromatography-tandem mass spectrometry method. Because peribronchial fibrosis in peripheral airways is involved in the airflow limitation of COPD, we investigated the profibrotic effects of 27-OHC in vitro.

RESULTS

The expression of sterol 27-hydroxylase was significantly enhanced in the lung tissues of patients with COPD compared with control subjects. The amounts of 27-OHC in the sputum were significantly increased in the patients with COPD (P < .01), and the degree of 27-OHC production was negatively correlated with lung function (P < .01). 27-OHC augmented the differentiation of lung fibroblasts into myofibroblasts and the production of extracellular matrix protein through activation of nuclear factor-κB and subsequent transforming growth factor-β(1) upregulation.

CONCLUSIONS

27-OHC production is enhanced in the airways of patients with COPD and might be involved in the pathogenesis of COPD.

Atherosclerosis: immune and inflammatory aspects

This review article discusses the historical origin of our continuously evolving model of the etiology of atherosclerotic cardiovascular disease. The basic molecular biologic concepts underlying the development of coronary artery disease and the dynamic connection between the immune system and arterial integrity are explored. Emphasis is placed on the role of inflammation as a driving force in the process of atherosclerosis and vascular endothelium as a modulating factor in the pathogenesis of coronary artery disease.