Selective enhancement of cytochrome p-450 activity in rat hepatocytes by in vitro heat shock.
We investigated the effect of heat shock on cytochrome P-450 activity in rat hepatocytes and report a significant, selective, and time-dependent enhancement of cytochrome P-450 activity in heatshocked hepatocytes. Stable long-term cultures of rat hepatocytes were heat shocked (42.5 degrees C) for 1 to 3 h and allowed to recover at 37 degrees C. Cytochrome P-450-dependent ethoxyresorufin O-dealkylase (EROD) and benzyloxyresorufin O-dealkylase (BROD) activities were measured up to 48 h after heat shock treatment. In general, the optimal heat shock exposure time was between 2 and 3 h. BROD activity (induced by sodium phenobarbital) increased approximately 6-fold in hepatocytes heat shocked for 3 h in comparison with hepatocytes maintained at 37 degrees C. EROD activity (induced by 3-methylcholanthrene) increased 2-fold on exposure to heat shock for 2 h. The expression of inducible heat shock proteins Hsp70 and Hsp32 was verified by Western immunoblot analyses. In the absence of the appropriate inducer, heat shock treatment did not enhance cytochrome P-450 activity. Furthermore, enhanced P-450 enzyme activity was delayed for heat-shocked hepatocytes. It is hypothesized that heat shock treatment attenuates the negative effects triggered by the addition of the toxic inducers and possibly stabilizes the levels of cytochrome P-450 proteins. These results suggest that heat shock treatment may be used to enhance the functionality of hepatocytes, specifically, in bioartificial liver assist devices.
Rajagopalan
Padmavathy
P
Center for Engineering in Medicine, Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, Boston, Massachusetts 02114, USA.
Berthiaume
François
F
Tilles
Arno W
AW
Toner
Mehmet
M
Yarmush
Martin L
ML
D000418:Albumins / Q000096:biosynthesis; D000818:Animals; D015153:Blotting, Western; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000378:metabolism; D004247:DNA / Q000032:analysis; D004790:Enzyme Induction; D005260:Female; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis; D018869:Heat-Shock Response; D006419:Heme Oxygenase (Decyclizing) / Q000032:analysis; D022781:Hepatocytes / Q000166:cytology* / Q000201:enzymology* / Q000378:metabolism*; D009569:Nitric Oxide / Q000032:analysis; D051381:Rats; D011917:Rats, Inbred Lew; D013997:Time Factors; D014508:Urea / Q000378:metabolism
D000418:Albumins; D018840:HSP70 Heat-Shock Proteins; D009569:Nitric Oxide; D014508:Urea; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D006419:Heme Oxygenase (Decyclizing); C491523:Hmox1 protein, rat