5-Methoxytryptophan attenuates postinfarct cardiac injury by controlling oxidative stress and immune activation.

AIMS: Myocardial infarction (MI) remains a major cause of heart failure. 5-Methoxytryptophan (5-MTP), a 5-methoxyindole metabolite of L-tryptophan, exerts anti-inflammatory and antifibrotic effects, but MI impairs the biosynthesis of cardiac 5-MTP. Therefore, we evaluated the effect of exogenous 5-MTP administration on rescuing post-MI cardiac injury. METHODS AND RESULTS: After a detailed pharmacokinetic analysis of 5-MTP, Sprague Dawley rats that had undergone left anterior descending coronary artery ligation received intraperitoneal administration of either 17 mg/kg 5-MTP or saline at 0.5 and 24 h after MI. Cardiac systolic function, infarction size, and fibrosis were evaluated using echocardiography, triphenyltetrazolium chloride staining, and Masson trichrome staining, respectively. Myocardial apoptosis was analyzed by staining for caspase-3 and cardiac troponin I. 5-MTP treatment decreased the infarct area and myocardial apoptosis; attenuated systolic dysfunction and left ventricular dilatation; and reduced cardiomyocyte hypertrophy, myocardial fibrosis, and infarct expansion. Crucially, 5-MTP alleviated oxidative stress by preserving mitochondrial antioxidant enzymes and downregulating reactive oxygen species-generating NADPH oxidase isoforms and endothelin-1. Consequently, 5-MTP-treated MI rat hearts exhibited lower levels of chemokines and cytokines, namely interleukin (IL)-1ß, IL-18, IL-6, C-C motif chemokine ligand (CCL)-2, and CCL5, accompanied by reduced infiltration of CD11b+ cells and CD4+ T cells. Notably, 5-MTP protected against H2O2-induced damage in HL-1 cardiomyocytes and human umbilical vein endothelial cells in vitro. CONCLUSION: 5-MTP prevented post-MI cardiac injury by promoting mitochondrial stabilization and controlling redox imbalance. This cytoprotective effect ameliorated macrophage and T-cell infiltration, thus reducing the infarct size, attenuating fibrosis, and restoring myocardial function.

Human spot 14 protein interacts physically and functionally with the thyroid receptor.

Spot 14 (S14) is a small acidic protein with no sequence similarity to other mammalian gene products. Its biochemical function is elusive. Recent studies have shown that, in some cancers, human S14 (hS14) localizes to the nucleus and is amplified, suggesting that it plays a role in the regulation of lipogenic enzymes during tumorigenesis. In this study, we purified untagged hS14 protein and then demonstrated, using various biochemical methods, including analytic ultracentrifugation, that hS14 might form a homodimer. We also found several lines of evidence to suggest physical and functional interactions between hS14 and the thyroid hormone receptor (TR). The ubiquitous expression of hS14 in various cell lines and its cell-type-dependent functions demonstrated in this study suggest that it acts as a positive or negative cofactor of the TR to regulate malic enzyme gene expression. These findings provide a molecular rationale for the role of hS14 in TR-dependent transcriptional activation of the expression of specific genes.

Structural studies of the pigeon cytosolic NADP(+)-dependent malic enzyme.

Malic enzymes are widely distributed in nature, and have important biological functions. They catalyze the oxidative decarboxylation of malate to produce pyruvate and CO(2) in the presence of divalent cations (Mg(2+), Mn(2+)). Most malic enzymes have a clear selectivity for the dinucleotide cofactor, being able to use either NAD(+) or NADP(+), but not both. Structural studies of the human mitochondrial NAD(+)-dependent malic enzyme established that malic enzymes belong to a new class of oxidative decarboxylases. Here we report the crystal structure of the pigeon cytosolic NADP(+)-dependent malic enzyme, in a closed form, in a quaternary complex with NADP(+), Mn(2+), and oxalate. This represents the first structural information on an NADP(+)-dependent malic enzyme. Despite the sequence conservation, there are large differences in several regions of the pigeon enzyme structure compared to the human enzyme. One region of such differences is at the binding site for the 2'-phosphate group of the NADP(+) cofactor, which helps define the cofactor selectivity of the enzymes. Specifically, the structural information suggests Lys362 may have an important role in the NADP(+) selectivity of the pigeon enzyme, confirming our earlier kinetic observations on the K362A mutant. Our structural studies also revealed differences in the organization of the tetramer between the pigeon and the human enzymes, although the pigeon enzyme still obeys 222 symmetry.