Cyclosporine directly causes oxidative stress and promotes Epstein-Barr virus transformation of human B cells.
BACKGROUND
We have previously shown that oxidative stress alone can promote transformation of human B cells infected with Epstein-Barr virus (EBV) in vitro, an accepted model mimicking posttransplant lymphoproliferative disorders (PTLDs). Our laboratory has investigated the direct effects of cyclosporine A (CyA) as an oxidant promoting B-cell transformation and we have proposed that CyA directly promotes B-cell transformation and that this effect can be blocked by antioxidants.


METHODS
Human splenocytes were prepared by centrifugation and plating technique to provide a greater than 80% pure preparation of B cells that was used for the direct oxidative stress experiments. These cells were cocultured with CyA (500 ng/ml) and hydrogen peroxide (H(2)O(2), 0.15 mM) with or without antioxidant vitamin E (40 microM). Oxidative stress was evaluated by using a commercial lipid hydroperoxide (LPO) assay kit. In another set of three separate experiments, human B lymphocytes infected with EBV were cultured with CyA (500 ng/ml), H(2)O(2) (0.15 mM), and vitamin E (40 microM). B-Cell transformation by EBV was evaluated by counting colony number and [(3)H]-thymidine incorporation.


RESULTS
At therapeutic concentrations, CyA (500 ng/mL) had an oxidative effect on human splenocytes in vitro, similar to the effect of H(2)O(2) (90 and 97% increases, respectively in LPO production over control P < 0.005), which was abrogated by the addition of vitamin E. Similarly, both CyA and H(2)O(2) promoted transformation of B cells infected with EBV(75 and 108% increases respectively in colony counts over control, P < 0.005). This effect was also blocked by vitamin E.


CONCLUSIONS
Both CyA and H(2)O(2) have a direct oxidative effect on human B cells and cause promotion of EBV-induced transformation of B cells. These effects are blocked by the antioxidant vitamin E. These findings may have future therapeutic implications for PTLDs.
Chen
C
C
C-453 Transplant Section, Division of General Surgery, University of Kentucky, 800 Rose Street, Lexington, KY 40536, USA.
Johnston
T D
TD
Reddy
K S
KS
Merrick
J C
JC
Mastrangelo
M
M
Ranjan
D
D
D000975:Antioxidants / Q000494:pharmacology; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000821:virology*; D002452:Cell Count; D002472:Cell Transformation, Viral / Q000187:drug effects*; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D020031:Epstein-Barr Virus Infections / Q000188:drug therapy / Q000378:metabolism*; D004854:Herpesvirus 4, Human; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D013154:Spleen / Q000166:cytology; D013936:Thymidine / Q000493:pharmacokinetics; D014316:Tritium; D014810:Vitamin E / Q000494:pharmacology
D000975:Antioxidants; D004791:Enzyme Inhibitors; D016877:Oxidants; D014316:Tritium; D014810:Vitamin E; D016572:Cyclosporine; D006861:Hydrogen Peroxide; D013936:Thymidine