RAPID CONVERSION TO HIGH XANTHINE-OXIDASE ACTIVITY IN VIABLE KUPFFER CELLS DURING HYPOXIA

Citation
Js. Wiezorek et al., RAPID CONVERSION TO HIGH XANTHINE-OXIDASE ACTIVITY IN VIABLE KUPFFER CELLS DURING HYPOXIA, The Journal of clinical investigation, 94(6), 1994, pp. 2224-2230
Citations number
64
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Medicine, Research & Experimental
ISSN journal
0021-9738
Volume
94
Issue
6
Year of publication
1994
Pages
2224 - 2230
Database
ISI
SICI code
0021-9738(1994)94:6<2224:RCTHXA>2.0.ZU;2-Q
Abstract
It has been widely postulated that the central mechanism of hepatic re perfusion injury involves the conversion, during ischemia, of the enzy me xanthine dehydrogenase (XDH) to its free radical-producing form, xa nthine oxidase (XOD). However, this theory has been questioned because (a) XDH to XOD conversion in whole liver occurs very slowly; (b) the cellular distribution of XDH/XOD is unclear; and (c) the direct demons tration of XDH to XOD conversion in viable cells is lacking. In this p aper, we address all three issues by measuring XDH to XOD conversion a nd cell viability in purified populations of hepatic endothelial cells (EC), Kupffer cells (KC), and hepatocytes (HEP). Although XDH/XOD act ivity on a cellular basis was greater in hepatocytes (0.92+/-0.12 mU/1 0(6) cells) than ECs (0.03+/-0.01) or KCs (0.12+/-0.04),XDH + XOD spec ific activity was similar in all three cell types (HEP 1.85+/-0.10 U/g protein; EC 1.69+/-0.54; KC 2.30+/-0.22). Over 150 min of warm (37 de grees C) or 24 h of cold (4 degrees C) hypoxia, percent XOD activity i ncreased slowly in ECs, from 21+/-2% (basal) to 39+/-3% (warm) and 49/-5% (cold) and in HEPs (29+/-2% to 38+/-3% and 49+/-2%), but converte d significantly faster in KCs (28+/-3% to 91+/-7% and 94+/-4%). The dr amatic changes in Kupffer cell XOD during cold hypoxia occurred despit e only minor changes in cell viability. When hypoxic KCs were reoxygen ated after 16 h of cold hypoxia, there was a marked increase in cell d eath that was significantly blocked by allopurinol. These data suggest that significant conversion to the free radical-producing state occur s within viable KCs, and that Kupffer cell XOD may play an important r ole in mediating reperfusion injury in the liver.