Nucleotide excision DNA repair is associated with age-related vascular dysfunction

BACKGROUND

Vascular dysfunction in atherosclerosis and diabetes mellitus, as observed in the aging population of developed societies, is associated with vascular DNA damage and cell senescence. We hypothesized that cumulative DNA damage during aging contributes to vascular dysfunction.

METHODS AND RESULTS

In mice with genomic instability resulting from the defective nucleotide excision repair genes ERCC1 and XPD (Ercc1(d/-) and Xpd(TTD) mice), we explored age-dependent vascular function compared with that in wild-type mice. Ercc1(d/-) mice showed increased vascular cell senescence, accelerated development of vasodilator dysfunction, increased vascular stiffness, and elevated blood pressure at a very young age. The vasodilator dysfunction was due to decreased endothelial nitric oxide synthase levels and impaired smooth muscle cell function, which involved phosphodiesterase activity. Similar to Ercc1(d/-) mice, age-related endothelium-dependent vasodilator dysfunction in Xpd(TTD) animals was increased. To investigate the implications for human vascular disease, we explored associations between single-nucleotide polymorphisms of selected nucleotide excision repair genes and arterial stiffness within the AortaGen Consortium and found a significant association of a single-nucleotide polymorphism (rs2029298) in the putative promoter region of DDB2 gene with carotid-femoral pulse wave velocity.

CONCLUSIONS

Mice with genomic instability recapitulate age-dependent vascular dysfunction as observed in animal models and in humans but with an accelerated progression compared with wild-type mice. In addition, we found associations between variations in human DNA repair genes and markers for vascular stiffness, which is associated with aging. Our study supports the concept that genomic instability contributes importantly to the development of cardiovascular disease.

Variation in semicarbazide-sensitive amine oxidase activity in plasma and tissues of mammals

Semicarbazide-sensitive amine oxidase (SSAO) (E.C. 1.4.3.6) is a group of enzymes with as yet poorly understood function which is widely present in nature. The variation in methodology for determination of activity, differences in substrates used and in nomenclature have made it difficult to compare SSAO in different species and tissues. Since SSAO is implicated in the pathophysiology of diabetes mellitus and congestive heart failure, our aim was to analyse the importance and abundance of SSAO in human plasma and tissues compared to other mammals. In plasma of ten different mammals, Vmax values were found to vary more than 10,000-fold, while KM differed much less; in human plasma SSAO activity is relatively low. In some species more than one SSAO entity was present in plasma. SSAO activity was ubiquitous in tissues of human, rat and pig, but varied considerably, both between species and between tissues. In human tissues, SSAO activity is higher than in tissues from rat and pig. Relative to monoamine oxidase-B there is also wide variation in SSAO, with much higher relative activities in human than in rat and pig tissues. We conclude that in plasma, SSAO activity is highest in ruminants, while in tissues, SSAO activity is more prominently present in human than in rat and pig.

Comparison of N-terminal pro-atrial natriuretic peptide and atrial natriuretic peptide in human plasma as measured with commercially available radioimmunoassay kits

Atrial natriuretic peptide (ANP) has become an important parameter for assessing the condition of patients with cardiac disease. Recently, attention has also focused on N-terminal pro-atrial natriuretic peptide (NtproANP) in this context. NtproANP circulates in plasma in higher concentration, is more stable ex vivo, and may be a better parameter for cardiac function over time. We have evaluated a new commercially available radiommunoassay kit for NtproANP and compared results and method with those of ANP measurements. The NtproANP kit was found to be reliable and easy to use (no plasma extraction step is necessary), with good reproducibility (coefficients of variation 7-15%). Normal values in 15 healthy laboratory workers, 25 healthy elderly subjects and 25 patients with heart failure were 207 +/- 70, 368 +/- 134 and 1206 +/- 860 pmol/l, respectively, 8.3, 11.8 and 13.0 times higher, respectively, than corresponding ANP concentrations. NtproANP correlated well with ANP (r 0.64-0.78). We conclude that plasma NtproANP measurement may be a good alternative to plasma ANP measurement: technically, it is easier to perform, and NtproANP is more stable in plasma. Whether NtproANP is a better diagnostic and prognostic parameter than ANP remains to be further established.

Sensitivity and specificity of a new ELISA method for determination of chromogranin A in the diagnosis of pheochromocytoma and neuroblastoma

We have evaluated a new commercially available ELISA kit for determination of plasma chromogranin A with respect to its usefulness in the diagnosis of neuroendocrine tumors, mainly pheochromocytoma. Serum and differently anticoagulated plasmas gave different chromogranin A concentrations. Control values (n = 21) were 18.9 +/- 5.8 units/l. Chromogranin A values > 30.4 units/l (mean + 2 S.D.) were considered elevated. In 22 patients suspected of (but found not to have) pheochromocytoma and in 24 patients with renovascular hypertension, 18% were found to have elevated chromogranin A concentrations. In renovascular hypertension chromogranin A correlated positively with serum creatinine; chromogranin A was strongly elevated especially in chronic renal failure. In 45 patients with pheochromocytoma, 13 (29%) had chromogranin A concentrations within the normal range, as had 3 out of 11 patients with neuroblastoma (27%). In 13 pheochromocytoma patients with elevated chromogranin A, measurements were repeated after surgical removal of the tumor; values then all fell within the normal range. We conclude that measurement of chromogranin A adds little to already existing methods for the diagnosis of pheochromocytoma.