Administration with telomeric DNA telomere-like oligonucleotides induces enhancement of telomerase activity and resistance against oxidative stress in telomere reverse transcriptase gene-transfected human fibroblasts

Out of normal human fibroblasts OUMS-36 and three clones (T1, T2 and T3) of telomere reverse transcriptase gene (hTERT)-transfectants, telomere length is in order: T3 >T2 >T1 >>OUMS-36 (young) >>OUMS-36 (old), and telomerase activity is in order: T2 >T3 >T1 >>OUMS-36 (young, old), suggesting that telomere length may be roughly governed by telomerase activity. Telomere-like oligonucleotides [5′- (TTAGGG) 1–3-3′] (ON mono-/di-/trimer) and a mononucleotide (T:A:G=2:1:3, mol/mol) mixture (MN mix), as candidates for telomerase activators, maintained above 80% of cell viability at marginally higher doses of 2 μM for MN-mix or ON monomer, 1 μM for ON dimmer and 0.67 μM for ON trimer, respectively, in OUMS-36 and T2 cells, and administered for 4 weeks, resulting in no elongation of telomere length in both the cell lines. In contrast, telomerase activity was enhanced by administration with ON mono-/di-/trimer, but not MN mix, in a manner dependent on treatment periods, in T2 transfectants, whereas similar effects were not observed in OUMS-36 parents. The 4-week treatment with ON mono-/di-/trimers, but not MN mix, also suppressed cell-viability diminishment induced by the oxidative-stressor tert-butylhydroperoxide in T2 cells, but scarcely in OUMS-36 cells. Thus, the promoting effects of oligonucleotide [5′-(TTAGGG)1-3-3′] on both telomerase enhancement and oxidative-stress resistance can be exerted for telomerase-abundant T2 hTERT-transfectants, but not for telomerase-poor OUMS-36 parents.