Affiliations: Dipartimento di Biochimica, Università di Bologna,
Via Irnerio 48, 40126 Bologna, Italy | Dipartimento di Scienze Farmacologiche, Biologiche e
Chimiche Applicate, Università di Parma, 43100 Parma, Italy | Dipartimento di Medicina Interna, Cardioangiologia ed
Epatologia, Unità Operativa di Genetica Medica, Policlinico S. Orsola,
Malpighi, 40138 Bologna, Italy
Note: [] Address for correspondence: Prof. Giorgio Lenaz, Dipartimento
di Biochimica, Università di Bologna, Via Irnerio 48, 40126 Bologna, Italy.
Tel.: +39 0512091229; Fax: +39 0512091217; E-mail: [email protected]
Abstract: Dichlorophenol indophenol (DCIP) reduction by intracellualr pyridine
nucleotides was investigated in two different lines of cultured cells
characterized by enhanced production of reacive oxygen species (ROS) with
respect to suitable controls. The first line denominated XTC-UC1 was derived
from a metastasis of an oxyphilic thyroid tumor characterized by mitochondrial
hyperplasia and compared with a line (B-CPAP) derived from a papillary thyroid
carcinoma with normal mitochondrial mass. The second line (170 MN) was a cybrid
line derived from ρ^0 cells from an osteosarcoma line
(143B) fused with platelets from a patient with a nucleotide 9957 mutation in
mitochondrial DNA (encoding for cytochrome c oxidase subunit III) in comparison
with the parent 143B line. The experimental lines had no major decreases of
electron transfer activities with respect to the controls; both of them,
however, exhibited an increased peroxide production. The XTC-UC1 cell line exhibited enhanced activity with respect to
control of dicoumarol-sensitive DCIP reduction, identified with membrane bound
DT-diaphorase, whereas dicoumarol insensitive DCIP reduction was not
significantly changed. On the other hand the mtDNA mutated cybrids exhibited a
strong increase of both dicoumarol sensitive and insensitive DCIP reduction.
The results suggest that enhanced oxidative stress and not deficient
respiratory activity per se is the stimulus triggering over-expression of
plasma membrane oxidative enzymes.
