Tissue- and cell-specific expression of mouse xanthine oxidoreductase gene <i>in vivo</i>: regulation by bacterial lipopolysaccharide

319

222

Obesity is often accompanied by hyperuricemia. However, purine metabolism in various tissues, especially regarding uric acid production, has not been fully elucidated. Here we report, using mouse models, that adipose tissue could produce and secrete uric acid through xanthine oxidoreductase (XOR) and that the production was enhanced in obesity. Plasma uric acid was elevated in obese mice and attenuated by administration of the XOR inhibitor febuxostat. Adipose tissue was one of major organs that had abundant expression and activities of XOR, and adipose tissues in obese mice had higher XOR activities than those in control mice. 3T3-L1 and mouse primary mature adipocytes produced and secreted uric acid into culture medium. The secretion was inhibited by febuxostat in a dose-dependent manner or by gene knockdown of XOR. Surgical ischemia in adipose tissue increased local uric acid production and secretion via XOR, with a subsequent increase in circulating uric acid levels. Uric acid secretion from whole adipose tissue was increased in obese mice, and uric acid secretion from 3T3-L1 adipocytes was increased under hypoxia. Our results suggest that purine catabolism in adipose tissue could be enhanced in obesity.

Section: Obese Mice Have Hyperuricemia and Xor Inhibitor Treatment Rsupporting

confidence: 83%

Uric Acid Secretion from Adipose Tissue and Its Increase in Obesity

Tsushima

Nishizawa

Tochino

et al. 2013

319

222

“…Surprisingly, the XOR transcript is also slightly down-regulated in DBA/2 and CBA relative to what was observed in CD-1 mice. This suggests that the steady-state levels of the XOR protein are controlled not only by the rate of gene expression but also by translational or post-translational events, as observed in other experimental conditions (18,19). All these results were obtained with probes encompassing the 3Ј-untranslated regions of the AOH1, AOX1, and XOR cDNAs; however, similar data were generated with the use of probes corresponding to the coding regions (data not shown).…”

Section: The Dba/2 Mouse Strain Has a Selective Deficit In The Expresmentioning

confidence: 43%

“…The polyclonal anti-XOR antibody was raised against the synthetic peptide, NH 2 -NTMKTQSFIAKH-COOH, according to an established methodology (12). The anti-AOH1, anti-AOX1, anti-AOH2, and anti-XOR rabbit antisera were used for Western blot analyses, which were carried out with a chemiluminescence-based protocol as described previously (12,13,18,19). SDS-PAGE was performed according to standard techniques (20).…”

Section: Methodsmentioning

confidence: 99%

Regulation and Biochemistry of Mouse Molybdo-flavoenzymes

Vila¹,

Kurosaki²,

Barzago³

et al. 2004

Mouse molybdo-flavoenzymes consist of xanthine oxidoreductase, aldehyde oxidase (AOX1), and two recently identified proteins, AOH1 and AOH2 (aldehyde oxidase homologues 1 and 2). Here we demonstrate that CD-1, C57BL/6, 129/Sv, and other mouse strains synthesize high levels of AOH1 in the liver and AOH2 in the skin. By contrast, the DBA/2 and CBA strains are unique, having a selective deficit in the expression of the AOH1 and AOH2 genes. DBA/2 animals synthesize trace amounts of a catalytically active AOH1 protein. However, relative to CD-1 animals, an over 2 log reduction in the steady-state levels of liver AOH1 mRNA, protein, and enzymatic activity is observed in basal conditions and following administration of testosterone. The DBA/2 mouse represents a unique opportunity to purify AOX1 and compare its enzymatic characteristics to those of the AOH1 protein. The spectroscopy and biochemistry of AOX1 are very similar to those of AOH1 except for a differential sensitivity to the non-competitive inhibitory effect of norharmane. AOX1 and AOH1 oxidize an overlapping set of aldehydes and heterocycles. For most compounds, the substrate efficiency (V max /K m ) of AOX1 is superior to that of AOH1. Alkylic alcohols and acetaldehyde, the toxic metabolite of ethanol, are poor substrates of both enzymes. Consistent with this, the levels of acetaldehyde in the livers of ethanol administered CD-1 and DBA/2 mice are similar, indicating that neither enzyme is involved in the in vivo biotransformation of acetaldehyde.

“…7A, a single AOH1 mRNA species is detectable in the liver, testis, and lung, whereas all the other tissues do not synthesize detectable amounts of the transcript. The tissue distribution of AOH1 is very similar to that of mouse AO (14) but significantly different from that of the corresponding XOR mRNA (24). The AOH2 transcript levels are relatively low, being detectable only upon enrichment of the poly(A ϩ ) fraction of cellular RNA.…”

Section: Molecular Cloning Of the Aoh1 And Aoh2 Cdnas-screening Of Thmentioning

confidence: 67%

“…In addition, the corresponding genes have a common origin, as recently indicated by the high degree of conservation of the exon/intron junctions (20 -22). XOR is the key enzyme in the catabolism of purines oxidizing hypoxanthine to xanthine and xanthine to uric acid, although the physiological function of this protein may be more complex than anticipated (23,24). Because of its ability to produce toxic superoxide anions, the oxidase form of XOR (25) has been implicated as a possible mediator of tissue damage in a number of pathological situations, such as ischemia (26), inflammation (27), and infection (28).…”

mentioning

confidence: 99%

Cloning of the cDNAs Coding for Two Novel Molybdo-flavoproteins Showing High Similarity with Aldehyde Oxidase and Xanthine Oxidoreductase

Terao

Kurosaki

Saltini

et al. 2000

113

The cDNAs coding for two novel mouse molybdo-flavoproteins, AOH1 and AOH2 (aldehyde oxidase homolog 1 and 2), were isolated. The AOH1 and AOH2 cDNAs code for polypeptides of 1336 amino acids. The two proteins have similar primary structure and show striking amino acid identity with aldehyde oxidase and xanthine oxidoreductase, two other molybdo-flavoenzymes. AOH1 and AOH2 contain consensus sequences for a molybdopterin-binding site and two distinct 2Fe-2S redox centers. In its native conformation, AOH1 has a molecular weight consistent with a homotetrameric structure. Transfection of the AOH1 and AOH2 cDNAs results in the production of proteins with phenanthridine but not hypoxanthine oxidizing activity. Furthermore, the AOH1 protein has benzaldehyde oxidizing activity with electrophoretic characteristics identical to those of a previously identified aldehyde oxidase isoenzyme (Holmes, R. S. (1979) Biochem. Genet. 17, 517-528). The AOH1 transcript is expressed in the hepatocytes of the adult and fetal liver and in spermatogonia. In liver, the AOH1 protein is synthesized in a gender-specific fashion. The expression of AOH2 is limited to keratinized epithelia and the basal layer of the epidermis and hair folliculi. The selective cell and tissue distribution of AOH1 and AOH2 mRNAs is consistent with the localization of the respective protein products.