Abdominal aortic aneurysm (AAA) is an age-associated disease characterized by chronic inflammation, vascular cell apoptosis and metalloproteinase-mediated extracellular matrix degradation. Despite considerable progress in identifying targets involved in these processes, therapeutic approaches aiming to reduce aneurysm growth and rupture are still scarce. Indoleamine 2-3 dioxygenase 1 (IDO) is the first and rate-limiting enzyme involved in the conversion of tryptophan (Trp) into kynurenine (Kyn) pathway. In this study, we investigated the role of IDO in two different models of AAA in mice.

Variations in plasma fatty acid (FA) concentrations are detected by FA sensing neurons in specific brain areas such as the hypothalamus. These neurons play a physiological role in the control of food intake and the regulation of hepatic glucose production. Le Foll et al. previously showed in vitro that at least 50% of the FA sensing in ventromedial hypothalamic (VMH) neurons is attributable to the interaction of long chain FA with FA translocase/CD36 (CD36). The present work assessed whether in vivo effects of hypothalamic FA sensing might be partly mediated by CD36 or intracellular events such as acylCoA synthesis or β-oxidation. To that end, a catheter was implanted in the carotid artery toward the brain in male Wistar rats. After 1 wk recovery, animals were food-deprived for 5 h, then 10 min infusions of triglyceride emulsion, Intralipid +/- heparin (IL, IL(H), respectively) or saline/heparin (SH) were carried out and food intake was assessed over the next 5 h. Experimental groups included: 1) Rats previously injected in ventromedian nucleus (VMN) with shRNA against CD36 or scrambled RNA; 2) Etomoxir (CPT1 inhibitor) or saline co-infused with IL(H)/S(H); and 3) Triacsin C (acylCoA synthase inhibitor) or saline co-infused with IL(H)/S(H). IL(H) significantly lowered food intake during refeeding compared to S(H) (p<0.001). Five hours after refeeding, etomoxir did not affect this inhibitory effect of IL(H) on food intake while VMN CD36 depletion totally prevented it. Triacsin C also prevented IL(H) effects on food intake. In conclusion, the effect of FA to inhibit food intake is dependent on VMN CD36 and acylCoA synthesis but does not required FA oxidation.

Acetyl Coenzyme A-dependent N-, O- and N,O-acetylation of aromatic amines and hydrazines by arylamine N-acetyltransferases is well characterised. Here, we describe experiments demonstrating that human arylamine N-acetyltransferase Type 1 and its murine homologue (Type 2) can also catalyse the direct hydrolysis of acetyl Coenzyme A in the presence of folate. This folate-dependent activity is exclusive to these two isoforms; no acetyl Coenzyme A hydrolysis was found when murine arylamine N-acetyltransferase Type 1 or recombinant bacterial arylamine N-acetyltransferases were incubated with folate. Proton nuclear magnetic resonance spectroscopy allowed chemical modifications occurring during the catalytic reaction to be analysed in real time, revealing that the disappearance of acetyl CH3 from acetyl Coenzyme A occurred concomitantly with the appearance of a CH3 peak corresponding to that of free acetate and suggesting that folate is not acetylated during the reaction. We propose that folate is a cofactor for this reaction and suggest it as an endogenous function of this widespread enzyme. Furthermore, in silico docking of folate within the active site of human arylamine N-acetyltransferase Type 1 suggests that folate may bind at the enzyme's active site, and facilitate acetyl Coenzyme A hydrolysis. The evidence presented in this paper adds to our growing understanding of the endogenous roles of human arylamine N-acetyltransferase Type 1 and its mouse homologue and expands the catalytic repertoire of these enzymes, demonstrating that they are by no means just xenobiotic metabolising enzymes but probably also play an important role in cellular metabolism. These data, together with the characterisation of a naphthoquinone inhibitor of folate-dependent acetyl Coenzyme A hydrolysis by human arylamine N-acetyltransferase Type 1/murine arylamine N-acetyltransferase Type 2, open up a range of future avenues of exploration, both for elucidating the developmental role of these enzymes and for improving chemotherapeutic approaches to pathological conditions including estrogen receptor-positive breast cancer.

Human arylamine N-acetyltransferase 1 (hNAT1) has become an attractive potential biomarker for estrogen-receptor-positive breast cancers. We describe here the mechanism of action of a selective non-covalent colorimetric biosensor for the recognition of hNAT1 and its murine homologue, mNat2, over their respective isoenzymes, leading to new opportunities in diagnosis. On interaction with the enzyme, the naphthoquinone probe undergoes an instantaneous and striking visible color change from red to blue. Spectroscopic, chemical, molecular modelling and biochemical studies reported here show that the color change is mediated by selective recognition between the conjugate base of the sulfonamide group within the probe and the conjugate acid of the arginine residue within the active site of both hNAT1 and mNat2. This represents a new mechanism for selective biomarker sensing and may be exploited as a general approach to the specific detection of biomarkers in disease.