Release kinetics of high-sensitivity cardiac troponins I and T and troponin T upstream open reading frame peptide (TnTuORF) in clinically induced acute myocardial infarction.

CONTEXT: Troponin T upstream open reading frame peptide (TnTuORF) may be useful as a novel biomarker in acute cardiac syndromes. OBJECTIVE: The study examined the early release kinetics of TnTuORF. MATERIALS AND METHODS: We analyzed the time course of the release of cardiac troponins I and T and TnTuORF in patients (n = 31) with hypertrophic obstructive cardiomyopathy undergoing transcoronary ablation of septal hypertrophy (TASH). RESULTS: Fifteen minutes after TASH, the levels of both troponins increased significantly (cTnT median: 18 ng/L versus 27 ng/L; cTnI median: 15 ng/L versus 25 ng/L). TnTuORF showed no variation. DISCUSSION: We observed a significantly greater increase in cTnI compared with cTnT. CONCLUSION: Our results demonstrate that troponin assays allow early detection of myocardial injury, whereas TnTuORF levels remain unchanged in this setting.

Lipoxin and resolvin biosynthesis is dependent on 5-lipoxygenase activating protein.

Resolution of acute inflammation is an active process coordinated by proresolving lipid mediators (SPMs) such as lipoxins (LXs) and resolvins (Rvs), which are formed by the concerted action of 2 lipoxygenases (LOs). Because the exact molecular mechanisms of SPM biosynthesis are not completely understood, we aimed to investigate LX and D-type Rv formation in human leukocytes and HEK293T cells overexpressing leukotriene (LT) pathway enzymes. Activity assays in precursor (15-hydroxyeicosatetraenoic acids, 17-HDoHE)-treated granulocytes [polymorphonuclear leukocytes (PMNLs)] showed a strict dependence of LXA4/RvD1 biosynthesis on cell integrity, and incubation with recombinant human 5-LO did not lead to LX or Rv formation. Pharmacologic inhibition of 5-LO activating protein (FLAP) by MK-886 inhibited LXA4/RvD1 biosynthesis in precursor-treated PMNLs (drug concentration causing 50% inhibition ∼ 0.3/0.2 µM), as did knockdown of the enzyme in MM6 cells, and precursor-treated HEK293T overexpressing 5-LO produced high amounts of LXA4 only in the presence of FLAP. In addition, inhibition of cytosolic phospholipase A2α (cPLA2α) interfered with LXA4/RvD1 formation from exogenous precursors in PMNLs. Furthermore, inhibition of the LT synthases LTA4 hydrolase and LTC4 synthase in PMNL/platelet coincubations augmented LXA4 levels. These findings show that several enzymes known to be involved in the biosynthesis of proinflammatory LTs, such as FLAP and cPLA2α, also contribute to LX and Rv formation.

Lipoxin A4: problems with its determination using reversed phase chromatography-tandem mass spectrometry and confirmation with chiral chromatography.

Lipoxins belong to the family of so-called pro-resolving endogenous lipid mediators which are derived from arachidonic acid and play a key role in the counter-regulation of inflammation. Arachidonic acid is also precursor of multiple pro-inflammatory lipid mediators, such as prostaglandins and leukotrienes, which are simultaneously present in biological compartments. The close structural relationship between several of these lipid mediators and the absence of blank matrix samples enormously complicates the unequivocal identification of these compounds. The determination of lipoxin A4 has been accomplished by chromatographic separation using a C18 reversed phase column and tandem mass spectrometry detection. Samples were liquid-liquid extracted with ethyl acetate before injection. Identification of the analyte was done based on three criteria: retention time, ratio of the m/z transitions and MS/MS spectrum. To avoid false positive results due to endogenous interferences, the extracted samples were re-injected into a chiral Lux Amylose-2 chromatographic column. The authors recommend the use of chiral chromatography in the determination of pro-resolving lipid mediators, together with transition area ratio and fragmentation spectra to improve selectivity for identification and quantitation purposes.