Intensified oxidative and nitrosative stress following combined ALA-based photodynamic therapy and local hyperthermia in rat tumors.
Oxidative stress-related changes in tumors upon localized hyperthermia (HT), 5-aminolevulinic acid-based photodynamic therapy (ALA-PDT) and their combination (ALA+HT) were examined after the observation that the antitumor effects of ALA-PDT could be significantly enhanced upon simultaneous application of HT. Rats bearing s.c. DS-sarcomas (0.6-1.0 ml) on the hind foot dorsum were anesthetized and underwent one of the following treatments: (i) ALA-PDT (375 mg/kg 5-ALA i.v.); (ii) localized HT, 43 degrees C for 60 min; (iii) combined ALA-PDT and HT [=ALA+HT]. Appropriate control experiments were also performed. After treatment, tumors were excised and rapidly frozen for later analysis of nitrosative stress (protein nitration), apoptotic events (TUNEL, caspase activation, DNA and RNA fragmentation), expression of heat shock proteins (hsp70 and HO-1), glutathione (GSH) levels and glutathione peroxidase (GPx) activity. Protein nitration was found to increase upon treatment, being especially pronounced in the ALA+HT group, and could partially be related to areas surrounding microvessels. The extent of nitrosative stress also correlated well with the appearance of the markers of apoptosis and the inhibition of in vivo tumor growth as seen in a previous study. GSH levels decreased upon treatment, the reduction being most prominent in the ALA-PDT and ALA+HT groups. GPx activity, however, showed a significant decrease only in the ALA-PDT group. Whereas hsp70 expression increased upon HT, ALA-PDT caused a decrease, and these opposing effects were nullified with ALA+HT. The results obtained point to a number of cellular mechanisms-including effects on cellular defense mechanisms and an abrogation of the heat shock defense mechanism-that may interact to achieve the potentiated tumor response rate seen in vivo upon combined treatment.
Institute of Biological Chemistry and Nutrition, University of Hohenheim, Fruwirthstrasse 12, D-70593 Stuttgart, Germany. frank140@uni-hohenheim.de
Juergen
J
Frank
Christine
C
Lambert
Hans Konrad
HK
Biesalski
Oliver
O
Thews
Peter
P
Vaupel
Debra K
DK
Kelleher
D000622:Aminolevulinic Acid / Q000627:therapeutic use*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics; D051547:Heme Oxygenase-1; D008027:Light; D008297:Male; D015538:Nitrosation; D010105:Oxygenases; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012509:Sarcoma / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology
D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid; D005979:Glutathione Peroxidase; D010105:Oxygenases; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C491523:Hmox1 protein, rat; D005978:Glutathione