Expression of Cell-Cycle-Regulating Genes in the Development of Atherosclerosis in Japanese Quail (Coturnix japonica)

Rosiglitazone modulates pigeon atherosclerotic lipid accumulation and gene expression in vitro

Atherosclerosis is a major contributor to the overall United States mortality rate, primarily in the form of heart attacks and stroke. Unlike the human disease, which is believed to be multifactorial, pigeon atherosclerosis is due to a single gene autosomal recessive trait. The White Carneau (WC-As) strain develops atherosclerotic plaques without the presence of known environmental risk factors such as diet and classic predictors such as blood pressure or blood cholesterol levels. With similar parameters, the Show Racer (SR-Ar) is resistant to plaque development. Thiazolidinediones, including rosiglitazone, activate the peroxisome proliferator-activated receptor gamma (PPARγ) raising cellular sensitivity to insulin. The effect of rosiglitazone was evaluated in aortic smooth muscle cells (SMC) from these 2 pigeon breeds. Primary SMC cultures were prepared from WC-As and SR-Ar squabs. Cell monolayers, which achieved confluence in 7 d, were treated with 0 or 4 µM rosiglitazone for 24 h. Cellular lipid accumulation was evaluated by oil red O staining. Control WC-As cells had significantly higher vacuole scores and lipid content than did the SR-Ar control cells. Rosiglitazone treatment decreased WC-As lipid vacuoles significantly compared with the control cells. On the other hand, lipid vacuoles in the treated and untreated SR-Ar cells did not differ significantly. The effect of rosiglitazone on WC-As SMC gene expression was compared with control SMC using representational difference analysis. Significant transcript increases were found for caveolin and RNA binding motif in the control cells compared with the rosiglitazone-treated cells as well as cytochrome p450 family 17 subfamily A polypeptide 1 (CYP171A) in the rosiglitazone-treated cells compared with the control cells. Although rosiglitazone was selected for these experiments because of its role as a PPARγ agonist, it appears that the drug also tempers c-myc expression, as genes related to this second transcription factor were differentially expressed. Both PPARγ and c-myc appear to affect WC-As SMC gene expression, which may relate to disease development, progression, or both.

Regulation of fibrillar collagen-mediated smooth muscle cell proliferation in response to chemical stimuli by telomere reverse transcriptase through c-Myc

Human telomerase reverse transcriptase (hTERT) and oncogene c-Myc have been shown to regulate cell proliferation. Our previous studies demonstrated that fibrillar collagen mediates vascular smooth muscle cell (SMC) cycle progression and proliferation in response to platelet-derived growth factor (PDGF)-BB and interleukin (IL)-1β. However, whether hTERT and c-Myc are involved in these fibrillar collagen-mediated SMC responses remain unclear. The present study elucidated the regulatory role of hTERT and c-Myc in PDGF-BB/IL-1β-induced cell cycle progression in SMCs on fibrillar collagen and its underlying mechanisms. Our results showed that PDGF-BB and IL-1β exert synergistic effects to induce hTERT expression, but not its activity, in human arterial SMCs on fibrillar collagen. This PDGF-BB/IL-1β-induced up-regulation of hTERT contributes to cell cycle progression in SMCs through the up-regulation of cyclin-dependent kinase-6 and down-regulations of p27(KIP1) and p21(CIP1). In addition, PDGF-BB/IL-1β induces up-regulation of c-Myc in SMCs on fibrillar collagen; this response is mediated by the increased binding of hTERT, which can form complexes with TPP1 and hnRNPK, to the guanine-rich region of the c-Myc promoter and consequently contributes to cell cycle progression in SMCs on fibrillar collagen. Moreover, the PDGF-BB/IL-1β-induced hTERT and c-Myc expressions are regulated by phosphatidylinositol 3-kinase/Akt in SMCs on fibrillar collagen. Our findings provide insights into the mechanisms by which hTERT and c-Myc regulates SMC cell cycle progression and proliferation on fibrillar collagen in response to chemical stimuli.

Antiatherosclerotic function of Kokuto, Okinawan noncentrifugal cane sugar

In the present study, we investigated the effect of phenolic compounds (PCs) and policosanol of Kokuto, Okinawan noncentrifugal cane sugar, on the development of atherosclerosis. A total of 67 male Japanese quail were divided into eight dietary groups in trial 1. The dietary groups were fed the atherosclerotic diet (AD) containing 5% corn oil, 2% cholesterol, and 30% sucrose or seven different types of Kokuto. Dietary intakes of Kokuto notably prevented the development of atherosclerosis. Furthermore, there was a significant negative correlation between the serum radical scavenging activity and the degree of atherosclerosis in the dietary groups. In trial 2, a total of 63 Japanese quail were fed AD with sucrose, Kokuto, PC extracts from Kokuto, wax extracts from sugar cane, octacosanol, vitamin C, and vitamin E. As a result, the supplementation of the diet with Kokuto and PCs significantly reduced the development of atherosclerosis as compared with the ingestion of AD with sucrose. In conclusion, these findings suggest that, among various components of Kokuto, PCs play a central role for the prevention of experimental atherosclerosis in Japanese quail.