Modulation by retinoic acid of spontaneous and benzo(a)pyrene-induced c-Ha-ras expression

Genetic instability and atherosclerosis: can somatic mutations account for the development of cardiovascular diseases?

Several observations suggest that cancer and atherosclerosis may entail fundamentally common biological mechanisms. The accumulation of lipids and the proliferation of smooth muscle cells (SMCs) are the main histological features of sclerotic plaque formation. The most prominent theory concerning the pathophysiological mechanisms of atherosclerotic plaque formation is the "inflammatory response to injury" hypothesis, which states that SMC proliferation is an inflammation-fibroproliferative reaction to different insults to the artery wall. However, recent evidence suggests that alterations at the DNA level may contribute significantly to the development of the disease. In accordance with these findings, the "monoclonal" hypothesis of atherosclerosis has been suggested. This hypothesis proposes that atherosclerosis begins as a mutation or viral infection, transforming a single, isolated smooth muscle cell into the progenitor of a proliferative clone, as seen in carcinogenesis. Studies of DNA damage in atherosclerotic tissues are lacking. Biological evidence for the hypothesis that cancer and atherosclerosis may share pathological mechanisms is discussed, emphasizing the need to perform studies investigating the involvement of somatic mutations in heart diseases.

Redox regulation of c-Ha-ras and osteopontin signaling in vascular smooth muscle cells: implications in chemical atherogenesis

Reduction/oxidation (redox) reactions play a central role in the regulation of vascular cell functions. Recent studies in this laboratory have identified c-Ha-ras and osteopontin genes as critical molecular targets during oxidant-induced atherogenesis. This review focuses on the deregulation of gene transcription by redox-activated trans-acting factors after benzo(a)pyrene challenge and the modulation of extracellular matrix signaling in vascular smooth muscle cells by allylamine-induced oxidative injury. The induction of atherogenic vascular smooth muscle cell phenotypes by chemical injury exhibits remarkable parallels with those seen in other forms of atherogenesis.

Putative susceptibility markers of coronary artery disease: association between VDR genotype, smoking, and aromatic DNA adduct levels in human right atrial tissue

Cancer and cardiovascular diseases share risk factors such as smoking, and the onset of both diseases have been suggested to have a common mechanistic basis. The binding of carcinogens to DNA (carcinogen-DNA adducts), genetic polymorphisms in carcinogen-detoxifying enzymes glutathione S-transferases (GSTs), and genetic polymorphisms in the vitamin D receptor (VDR) are among the candidates for modifiers of cancer risk. We determined whether these biomarkers could be related to individual characteristics of patients suffering from cardiovascular diseases. For that purpose, DNA from the right atrial appendage of 41 patients who underwent open heart surgery was analyzed for smoking-related DNA adducts and polymorphisms in GSTM1, GSTT1, and VDR genes. Statistical analysis was used to identify any patient's characteristics associated with these molecular markers. Our results showed that heart tissue of cigarette smokers contained a variety of aromatic DNA adducts in significantly elevated levels compared to ex-smokers (P<0.01) or nonsmokers (P<0.001). A linear relationship was observed between DNA adduct levels and daily cigarette smoking (rs=0.73; P=0.0003). Since cardiac myocytes are terminally differentiated cells that have lost their ability to divide and seemingly have limited DNA repair capacities, their levels might accumulate with time and thereby affect heart cell function or viability. Substantial interindividual differences between DNA adduct levels were observed, and persons with severe coronary artery disease (CAD), as assessed by coronary angiography, had higher DNA adduct levels than persons with no or mild CAD (P=0.04). As polymorphisms in GST genes have been shown to modulate DNA adduct levels and risk for lung cancer in smokers, we explored for the first time whether the GST polymorphisms could also explain deviating heart DNA adduct levels and CAD risk. However, no relation could be found between these covariants. In contrast, a VDR genotype, which has been associated with decreased serum levels of the active hormonal form of vitamin D and increased risk for certain cancers, seemed to be related to severity of CAD (P=0.025). Our findings support the hypothesis that smoking-related DNA damage may be involved in the onset of cardiovascular diseases and suggest that VDR genotype may be a useful susceptibility marker of CAD.

Retinoid receptor expression and all-trans retinoic acid-mediated growth inhibition in vascular smooth muscle cells

BACKGROUND

Retinoids have been used in the successful treatment of a variety of human hyperproliferative diseases. Their role in smooth muscle cell (SMC) growth control, however, has not been clearly established. The present study was designed to assess the retinoid receptor mRNA expression profile in SMCs and to determine whether retinoids exert a growth-inhibitory effect in these cells.

METHODS AND RESULTS

Five of the six retinoid receptors were expressed in both cultured SMCs and aorta as determined by Northern blotting or reverse transcriptase-polymerase chain reaction. Receptor activity was demonstrated in SMCs with the use of a reporter assay with a retinoid receptor DNA binding sequence linked to a chloramphenicol acetyltransferase reporter gene. DNA synthesis and cell proliferation assays were performed to show that all-trans retinoic acid (atRA) antagonized platelet-derived growth factor-BB and serum-stimulated SMC growth. Growth inhibition was distal to early growth-signaling events because induction of c-fos, c-jun, and egr-1 mRNA was unaffected by atRA. However, with an activated protein-1-linked chloramphenicol acetyltransferase reporter, atRA was shown to inhibit the activity of activated protein-1-dependent transcription in a transient transfection assay.

CONCLUSIONS

These results establish the presence of functional retinoid receptors in SMCs and document the growth-inhibitory action of atRA on these cells. Retinoid compounds, already in clinical use as antiproliferative agents for nonvascular indications, should be assessed further in in vivo models of intimal disease.