Publications

The association between serum beta-carotene or retinol concentration and level of ventilatory function was investigated in a population of asbestos-exposed men with a high rate of current and former cigarette smoking. The study population consisted of 816 subjects enrolled in the pilot component of the Carotene and Retinol Efficacy Trial (CARET), a placebo-controlled trial of supplemental beta-carotene and retinyl palmitate for the chemoprevention of lung cancer. Data available for analysis included baseline questionnaire, spirometry, chest X-ray, food frequency questionnaire, and serum beta-carotene and retinol concentrations. Serum beta-carotene concentration was associated with FEV1 (p < 0.05) and FVC (p < 0.05), with an approximately 100-ml increase over predicted values associated with raising the serum concentration from the 25th to the 75th percentile of the distribution in the study population (absolute difference = 155 ng/ml), even after adjustment for the confounding effects of asbestos exposure and cigarette smoking. Raising the serum retinol concentration from the 25th to the 75th percentile (absolute difference = 211 ng/ml) was associated with an approximately 70 ml increase in FVC (p < 0.05) over the predicted value. These results provide support for the hypothesis that beta-carotene and retinol have a protective effect on loss of ventilatory function.

OBJECTIVE

To examine the combined influence of workplace demands and changes in blood pressure induced by stress on the progression of carotid atherosclerosis.

DESIGN

Population based follow up study of unestablished as well as traditional risk factors for carotid atherosclerosis, ischaemic heart disease, and other outcomes.

SETTING

Eastern Finland.

SUBJECTS

591 men aged 42-60 who were fully employed at baseline and had complete data on the measures of carotid atherosclerosis, job demands, blood pressure reactivity, and covariates.

MAIN OUTCOME MEASURES

Change in ultrasonographically assessed intima-media thickness of the right and left common carotid arteries from baseline to 4 year follow up.

RESULTS

Significant interactions between workplace demands and stress induced reactivity were observed for all measures of progression (P < 0.04). Men with large changes in systolic blood pressure (20 mm Hg or greater) in anticipation of a maximal exercise test and with high job demands had 10-40% greater progression of mean (0.138 v 0.123 mm) and maximum (0.320 v 0.261 mm) intima-media thickness and plaque height (0.347 v 0.264) than men who were less reactive and had fewer job demands. Similar results were obtained after excluding men with prevalent ischaemic heart disease at baseline. Findings were strongest among men with at least 20% stenosis or non-stenotic plaque at baseline. In this subgroup reactive men with high job demands had more than 46% greater atherosclerotic progression than the others. Adjustment for atherosclerotic risk factors did not alter the results.

CONCLUSIONS

Men who showed stress induced blood pressure reactivity and who reported high job demands experienced the greatest atherosclerotic progression, showing the association between dispositional risk characteristics and contextual determinants of disease and suggesting that behaviourally evoked cardiovascular reactivity may have a role in atherogenesis.

The molecular basis of receptor/G protein coupling selectivity was studied by using the m2 muscarinic receptor, a prototypical G(i/o)-coupled receptor as a model system. We could recently show that the m2 receptor can efficiently interact with mutant G protein alpha(q) subunits in which the last five amino acids were replaced with alpha(i2) or alpha(o) sequence [Liu, J., Conklin, B. R., Blin, N., Yun, J., & Wess, J. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 11642-11646]. Additional mutagenesis studies led to the identification of a four-amino-acid motif on the m2 receptor (Val385, Thr386, Ile389, and Leu390) that is predicted to functionally interact with the C-terminal portion of alpha(i/o) subunits. To further investigate the structural requirements for this interaction to occur, these four m2 receptor residues were replaced, either individually or in combination, with the corresponding residues present in the G(q/11)-coupled muscarinic receptors (m1, m3, and m5). The ability of the resulting mutant m2 receptors to interact with a mutant alpha(q) subunit (qo5) in which the last five amino acids were replaced with alpha(o) sequence was investigated in co-transfected COS-7 cells [studied biochemical response: stimulation of phosphatidyl inositol (PI) hydrolysis]. Our data suggest that the presence of three of the four targeted m2 receptor residues (Val385, Thr386, and Ile389) is essential for efficient recognition of C-terminal alpha(i/o) sequences. To study which specific amino acids within the C-terminal segment of alpha(i/o) subunits are critical for this interaction to occur, the wild type m2 receptor was co-expressed with a series of mutant alpha(q) subunits containing single or multiple alpha(q) --> alpha(i1,2) point mutations at their C-terminus. Remarkably, the wild type m2 receptor, while unable to efficiently stimulate wild type alpha(q), gained the ability to productively interact with three alpha(q) single-point mutants, providing the first example that the receptor coupling selectivity of G protein alpha subunits can be switched by single amino acid substitutions. Given the high degree of structural homology among different G protein-coupled receptors and among different classes of G protein alpha subunits, our results should be of broad general relevance.