I'm working with cyanobacterial extracts that are only showing mutagenicity with TA100 (without S9) and did not show any kind of mutagenicity with TA102 which detects mutations due to oxidative stress however, they were producing high amounts of 8-OHdG lesions in lymphocytes. My question is is it possible? If yes then what could be the underlying cause?
P.S: I forgot to add that the extracts were non-mutagenic against TA102 with and without S9 activation however they were mutagenic against TA100 with and without S9 activation.
Thanx!
Saadia, yes this might be possible, if you consider the possibility of biotransformation of your extracts by the lymphocytes. Metabolites might be the underlying cause of the observed oxidative DNA damage.
@Michel Kranendonk, Thank you very much. Yes! this seems quite plausible however they were not mutagenic against TA102 even in the presence of S9 activation. I forgot to mention this in my question sorry.
Ok.
You might consider the use of a lymphocyte extract, adding cofactors as with S9 and use this with the TA102 strain.......
OK, your drug is a direct acting base pair mutagen. But as Michel points out, all sorts of biotransformations are possible in lymphocytes. In addition, these cells already contain 8-OHG in their DNA (I guess that's what you mean by lesions??) , so what serves for the negative control in your ELISA and by how much are those levels increased after drug?
P.S. I just checked and I read that TA100 is reverted (?) via GC changes and TA102 by AT changes: both indicate point mutations (base pair substitutions). So doesn't that mean that in fact TA100 can indicate oxidative damage?
@ Michel Kranendonk, I could use S9 mix however I used whole blood instead of isolated lymphocytes since whole blood properties are common with the liver microsomal cytochrome P450 system . Am i right? I didn't use extra S9 since extracts were showing cytotoxicity in its presence.
@ Geoff Margison, Thank you. The negative control showed 1.3/10^6 dG; Vehicle control (0.2% DMSO) showed 1.44 /10^6 dG; Positive control doxorubicin showed 41.54/10^6 dG and the extract showed 24.35/10^6 dG.
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