Rajagopalan Padmavathy, Berthiaume François, Tilles Arno W, Toner Mehmet, Yarmush Martin L
Center for Engineering in Medicine, Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, Boston, Massachusetts 02114, USA.
Tissue Eng. 2005 Sep-Oct;11(9-10):1527-34. doi: 10.1089/ten.2005.11.1527.
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.
