Mass spectrometry techniques in the survey of steroid metabolites as potential disease biomarkers: a review

Abstract

Mass spectrometric approaches have been fundamental to the identification of metabolites associated with steroid hormones, yet this topic has not been reviewed in depth in recent years. To this end, and given the increasing relevance of liquid chromatography-mass spectrometry (LC-MS) studies on steroid hormones and their metabolites, the present review addresses this subject. This review provides a timely summary of the use of various mass spectrometry-based analytical techniques during the evaluation of steroidal biomarkers in a range of human disease settings. The sensitivity and specificity of these technologies are clearly providing valuable new insights into breast cancer and cardiovascular disease. We aim to contribute to an enhanced understanding of steroid metabolism and how it can be profiled by LC-MS techniques.

Keywords: 1,2-Dihydroxybenzene (benzene catechol); 1,2-Dihydroxybenzene-Quinone; APCI–MS; APPI–MS; Atmospheric-pressure chemical ionization mass spectrometry; Atmospheric-pressure photoionization mass spectrometry; CA; CAT; CAT-Q; CID; COMT; Cancer biomarkers; Catechol-O-methyltransferase; Cholesterol metabolites; Cholic acid; Collision-induced dissociation; DCA; Deoxycholic acid; ESI–MS; Electrospray ionization; Estradiol metabolites; FIA; FTMS; Flow injection analysis; Fourier transform mass spectrometry; GC–MS; GP; Gas chromatography–mass spectrometry; Girard P; HPLC–EDC; High performance liquid chromatography–electro-chemical detection; LC–MS; Liquid chromatography–mass spectrometry; MALDI-TOF; Mass spectrometry; Matrix-assisted laser desorption/ionization-time-of-flight; N-AcCys; N-acetylcysteine; N-acetyldopamine; N-acetyldopamine-quinone; NADA; NADA-Q; NQO-2; NRH quinone oxidoreductase 2; Resv; Resveratrol; SLOS; SPE; SRM; Selected reaction monitoring; Smith–Lemli–Opitz syndrome; Solid phase extration; TOF; Time-of-flight; UPLC–MS/MS; Ultra-performance liquid chromatography-tandem mass spectrometry.

Fig. 1

Biosynthesis and metabolic activation of estrogens E₁ and E₂. One of the major pathways of E1 and E2 leads to 2- and 4-catechol derivatives, which are further, oxidized to yield the corresponding reactive quinones; these can react with DNA to form depurinating DNA adducts. In the deactivation pathway, which operates in parallel, the catechol derivatives are methylated to form methoxy catechol estrogens. In addition, the quinones are reduced by quinone reductase, as well as conjugated to GSH and thus rendered harmless. A shift in the apparent balance between activating and deactivating pathways towards formation of depurinating DNA adducts could lead to initiation of breast cancer (adapted from [38].) 2-OHE₁(E₂) – 2-hydroxyestrone(estradiol); 4-OHE₁(E₂) - 4-hydroxyestrone(estradiol); 2-OCH₃E₁(E₂) – 2-methoxyestrone(estradiol); 4-OCH₃E₁(E₂)- 4-methoxyestrone(estradiol); E₁(E₂)-2,3-SQ- Estrone(estradiol)-2,3-semiquinone; E₁(E₂)-2,3-Q – Estrone(estradiol)-2,3-quinone; E₁(E₂)-3,4-SQ - Estrone(estradiol)-3,4-semiquinone; E₁(E₂)-3,4-Q Estrone(estradiol)-3,4-quinones; 2-OHE₂-6-N3Ade- 2-hydroxyestradiol-6-N3Adenine; 4-OHE₁(E₂)-1-N3Ade- 4-hydroxyestrone(estradiol)-1-N3Adenine; 4-OHE₁(E₂)-1-N7Gua- 4-hydroxyestrone(estradiol)-1-N7Guanine.

Fig. 2

Mechanism by which Resv is proposed to prevent estrogen-initiated breast cancer (reproduced from [45]).

Fig. 3

Biosynthetic pathways for key regulatory oxysterols. Hydroxycholesterols are synthesized from cholesterol, whereas 24S,25-epoxycholesterol is derived from a shunt in the cholesterol biosynthetic pathway. CH25H, cholesterol 25-hydroxylase; 4β-OH, 4β-hydroxycholesterol; 7α-OH, 7α-hydroxycholesterol; 22R-OH, 22R-hydroxycholesterol; 24S-OH, 24S-hydroxycholesterol; 25-OH, 25-hydroxycholesterol and 27-OH, 27-hydroxycholesterol (reproduced from (61).)