Oxidative stress has been related to the etiopathogenesis of several chronic diseases and plays a paramount role in the aging process. Of the many biological targets of oxidative stress, lipids are the most involved class of biomolecules. Lipid oxidation gives rise to a number of secondary products. These products are mainly aldehydes, with the ability to exacerbate oxidative damage. Longevity and high reactivity allow these molecules to act inside and outside the cells, interacting with biomolecules such as nucleic acids and proteins, often irreversibly damaging the delicate mechanisms involved in cell functionality. Malondialdehyde (MDA) is the principal and most studied product of polyunsaturated fatty acid peroxidation. Malondialdehyde (MDA) is the organic compound with the formula CH2(CHO)2. The structure of this species is more complex than this formula suggests. This reactive species occurs naturally and is a marker for oxidative stress.
Figure 1. Principal steps in the formation of MDA
The main source of MDA in biological samples is the peroxidation of polyunsaturated fatty acids with two or more methylene-interrupted double bonds. Three attractive hypotheses describing the in vivo formation of MDA have been proposed. Pryor and Stanley, basing their hypothesised mechanism on the non-volatile nature of the MDA precursor, described that precursor as a bicyclic endoperoxide similar to the one formed during prostaglandin biosynthesis. MDA is believed to originate from these precursors under stressed conditions. This mechanism has been confirmed by an elegant study carried out by Frankel and Neff, who observed which oxidized lipids were able to produce MDA as a decomposition product. The other two mechanisms are based on successive hydroperoxide formations and b-cleavage of the fatty acid chain to give a hydroperoxyaldehyde; MDA is then generated by b-scission or by reaction of the final acrolein radical with a hydroxyl radical. MDA can be also generated in vivo by enzymatic processes from various prostaglandins as described by Hecker and Ullrich. They showed that the biosynthesis of thromboxane A2 (TXA2) leads to malondialdehyde and 12(S)-hydroxy-8,10(E,E)- heptadecadienoic acid (HHT) with a high yield as secondary products.
MDA is able to impair several physiological mechanisms of the human body through its ability to react with molecules such as DNA and proteins. It is therefore useful to consider this molecule as something more than a lipid peroxidation product. In its physiological state, at neutral pH, MDA is present as an enolate anion and is of low chemical reactivity. Nevertheless, this molecule is able to interact with nucleic acid bases to form several different adducts. The main product of this reaction is known to be M1G. The most recent mutation mechanism proposed for this adduct is reported by VanderVeen et al. This study clearly indicates that M1G is able to induce sequence-dependent frameshift mutations and base-pair substitutions in bacteria and mammalian cells. On the other hand, an alternative mechanism of genotoxicity is proposed by Niedernhofer and colleagues, involving the ability of MDA to create interstrand cross-links in DNA, which have potent biological effects.
Most assays to determine MDA have been developed on the basis of its derivatization with thiobarbituric acid (TBA). The condensation of these two molecules gives rise to a high absorbivity adducts which can be easily assessed with a spectrophotometer. Unfortunately, the specificity of the test based on this reaction is low, as TBA may react with several compounds other than MDA also derived from oxidation. Moreover, the treatment of biological samples to obtain the condensation product is usually carried out at high temperature (around 100 °C) and may generate further oxidation of the matrix with obvious overestimation of the results. Currently, a reliable and reproducible method using highly sensitive HPLC platform for the rapid identification and quantification of MDA in different sample types has been established by the experienced scientists at Creative Proteomics, which can satisfy the needs of academic and industrial study in your lab.
With integrated set of separation, characterization, identification and quantification systems featured with excellent robustness & reproducibility, high and ultra-sensitivity, Creative Proteomics provides reliable, rapid and cost-effective malondialdehyde targeted metabolomics services.
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