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Long term exposure to ambient air pollution and incidence of acute coronary events: prospective cohort study and meta-analysis in 11 European cohorts from the ESCAPE Project

BMJ 2014; 348 doi: https://doi.org/10.1136/bmj.f7412 (Published 21 January 2014) Cite this as: BMJ 2014;348:f7412

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Re: Long term exposure to ambient air pollution and incidence of acute coronary events: prospective cohort study and meta-analysis in 11 European cohorts from the ESCAPE Project

Dear editor,

In recent articles published in BMJ [1-4] a problem of cardiovascular diseases (CVD) genesis was discussed. Certainly, environmental factors, lipid excess in nutrition, obesity, renal disease and other traditional risk factors play an important role in development of the CVD. But we believe that molecular genetic defects, particularly mitochondrial genome mutations, might be significant in pathogenesis of cardiovascular diseases [5].

To detect the spectrum of mitochondrial mutations in individuals, we used a high efficiency pyrosequencing of the whole mitochondrial genome.

Whole blood samples were taken from 77 subjects, among them 45 patients had carotid atherosclerosis assessed by ultrasonography [6]; and 32 subjects had no atherosclerotic lesions. DNA was extracted by a phenol chloroform method. Afterwards an enriching of mitochondrial DNA was performed using Qiagen™ REPLI-g Mitochondrial Kit. To carry out a high efficiency pyrosequencing of the whole mitochondrial genome, a system Roche 454 GS Junior Titanium (Roche, USA) was used.

An analysis of mitochondrial DNA sequence was performed using GS Reference Mapper program. The Cambridge standard sequence NC_012920.1 was used for mapping human mitochondrial genome [7]. Statistical data processing was performed by IBM SPSS Statistics v.21.0.

A whole genome pyrosequencing gave an opportunity to detect 58 homoplasmic mitochondrial genome mutations in the investigated samples. The frequency of mutations T152C, G185A, G228A, A263G, 3107delN, T489C, A750G, A1811G, A4769G, C7028T , A8860G, A10398G, A11467G, A11719G, A12308G, G12372A and A15326G turned to be significantly higher in patients with atherosclerosis than in healthy study participants. At the same time mitochondrial mutations T4216C, A4917G, G8697A, T10463C, A11251G, A11812G, A12705T, A13368A, A13617C, G14905A, A15607G, G15928A, T16069T, T16126C, C16223T, C16296T, T16311C and T16519C prevailed in healthy individuals (Figure 1).

In addition, nine heteroplasmic mutations associated with atherosclerosis were found, namely: 576insC, 8516insA, 8516insC, 8528insA, G9477A, 8930insG, 10958insC, 13047insC и 13050insC.

It should be noted that 29% homoplasmic and 33% heteroplasmic proatherogenic mutations of mitochondrial genome belong to genes coding NADH dehydrogenase subunits; 18% homoplasmic atherogenic mutations are localized in genes coding rRNA subunits and 44% heteroplasmic single-nucleotide insertions are localized in genes coding ATP synthetase subunits. It can be assumed that the defects in NADH dehydrogenase, ATP synthetase and mitochondrial ribosomes may participate in realization of the mechanisms of atherogenesis.

Previously, using pyrosequencer PSQTMHS96MA (Biotage, Sweden) we have found 11 heteroplasmic mutations associated with atherosclerosis: 652delG, A1555G, C3256T, T3336C, C5178A, 652insG , G12315A, G14459A, G13513A, G14846A and G15059A [8-10]. In the present study we did not detect the above mutations, possibly due to the fact that an intermediate stage of the whole mitochondrial genome PCR is not necessary for studying separate mutations with a pyrosequenator PSQTMHS96MA. Thus, it can desensitize Roche technology. However, this disadvantage is highly compensated by a high number of mutations associated with atherosclerosis, which can be detected during whole genome pyrosequencing.

This study was supported by the Russian Ministry of Education and Science.

References
1. Long term exposure to ambient air pollution and incidence of acute coronary
events: prospective cohort study and meta-analysis in 11 European cohorts from the ESCAPE Project. Cesaroni G, Forastiere F, Stafoggia M, Andersen ZJ, Badaloni C, Beelen R, Caracciolo B, de Faire U, Erbel R, Eriksen KT, Fratiglioni L, Galassi C, Hampel R, Heier M, Hennig F, Hilding A, Hoffmann B, Houthuijs D, Jöckel KH, Korek M, Lanki T, Leander K, Magnusson PK, Migliore E, Ostenson CG, Overvad K, Pedersen NL, J JP, Penell J, Pershagen G, Pyko A, Raaschou-Nielsen O, Ranzi A, Ricceri F, Sacerdote C, Salomaa V, Swart W, Turunen AW, Vineis P, Weinmayr G, Wolf K, de Hoogh K, Hoek G, Brunekreef B, Peters A.BMJ. 2014 Jan 21;348:f7412. doi: 10.1136/bmj.f7412.
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Perkovic V, Turnbull F, Neal B, Barzi F, Cass A, Baigent C, Chalmers J, Li N, Woodward M, MacMahon S. Blood pressure lowering and major cardiovascular events in people with and without chronic kidney disease: meta-analysis of randomised controlled trials. BMJ. 2013 Oct 3;347:f5680. doi: 10.1136/bmj.f5680»
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Mukhamedova NM, Martirosian DM, Karagodin VP, Orekhov AN. Study of intima-medial thickness (IMT) of the carotid arteries as an indicator of natural atherosclerosis progress in Moscow population. Patol Fiziol Eksp Ter 2012 Jul-Sep;(3):104-8. Russian.
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Competing interests: No competing interests

01 February 2014
Margarita A. Sazonova
Medical molecular geneticist
Zhelankin AV, Barinova VA, Sinyov VV, Khasanova ZB, Postnov A Yu, Sobenin IA, Orekhov AN
Institute of General Pathology and Pathophysiology, Russian Academy of Medical Sciences
8, Baltiyskaya st., Moscow, 125315, Russia