Telomeres are structures at the ends of chromosomes that shorten during cell division and eventually signal an irreversible state of growth arrest known as cellular senescence. To delay this cellular aging, human T cells, which are critical in the immune control over infections and cancer, activate the enzyme telomerase, which binds and extends the telomeres. Several different extracts from the Astragalus membranaceus root have been documented to activate telomerase activity in human T cells. The objective of this research was to compare two extracts from Astragalus membranaceus, TA-65 and HTA, for their effects on both telomerase and proliferative activity of human CD4 and CD8 T cells. Our results demonstrate that, TA-65 increased telomerase activity significantly (1.3 to 3.3-fold relative to controls) in T cell cultures from six donors tested, whereas HTA only increased telomerase levels in two out of six donors. We also demonstrate that TA-65 activates telomerase by a MAPK- specific pathway. Finally, we determine that during a three-day culture period, only the T cells treated with the TA-65 extract showed a statistically significant increase in proliferative activity. Our results underscore the importance of comparing multiple telomerase activators within the same experiment, and of including functional assays in addition to measuring telomerase activity.
References
[1]
de Lange, T. Shelterin: The protein complex that shapes and safeguards human telomeres. Gene Dev. 2005, 19, 2100–2110, doi:10.1101/gad.1346005.
[2]
Artandi, S.E.; DePinho, R.A. Telomeres and telomerase in cancer. Carcinogenesis 2010, 31, 9–18, doi:10.1093/carcin/bgp268.
[3]
Counter, C.M.; Avilion, A.A.; LeFeuvre, C.E.; Stewart, N.G.; Greider, C.W.; Harley, C.B.; Bacchetti, S. Telomere shortening associated with chromosome instability is arrested in inmortal cells which express telomerase activity. EMBO J. 1992, 11, 1921–1929.
[4]
Price, C. M. Centromeres and telomeres. Curr Opin Cell Biol 1992, 4, 379–84, doi:10.1016/0955-0674(92)90002-T.
[5]
Monteiro, J.; Batliwalla, F.; Ostrer, H.; Gregersen, P.K. Shortened telomeres in clonally expanded CD28-CD8+ T cells imply a replicative history that is distinct from their CD28+CD8+ counterparts. J. Immunol. 1996, 156, 3587–3590.
[6]
Roth, A.; Yssel, H.; Pene, J.; Chavez, E.A.; Schertzer, M.; Lansdorp, P.M.; Spits, H.; Luiten, R.M. Telomerase levels control the lifespan of human T lymphocytes. Blood 2003, 102, 849–857, doi:10.1182/blood-2002-07-2015.
[7]
Weng, N.P.; Levine, B.L.; June, C.H.; Hodes, R.J. Human naive and memory T lymphocytes differ in telomeric length and replicative potential. Proc. Natl. Acad. Sci. USA 1995, 92, 11091–11094, doi:10.1073/pnas.92.24.11091.
[8]
Valenzuela, H.F.; Effros, R.B. Divergent telomerase and CD28 expression patterns in human CD4 and CD8 T cells following repeated encounters with the same antigenic stimulus. Clin. Immunol. 2002, 105, 117–125, doi:10.1006/clim.2002.5271.
[9]
Hiyama, K.; Hirai, Y.; Kyoizumi, S.; Akiyama, M.; Hiyama, E.; Piatyszek, M.A.; Shay, J.W.; Ishioka, S.; Yamakido, M. Activation of telomerase in human lymphocytes and hematopoietic progenitor cells. J. Immunol. 1995, 155, 3711–3715.
[10]
Jaskelioff, M.; Muller, F.L.; Paik, J.H.; Thomas, E.; Jiang, S.; Adams, A.C.; Sahin, E.; Kost-Alimova, M.; Protopopov, A.; Cadinanos, J.; et al. Telomerase reactivation reverses tissue degeneration in aged telomerase-deficient mice. Nature 2011, 469, 102–106.
[11]
de Jesus, B.B.; Schneeberger, K.; Vera, E.; Tejera, A.; Harley, C.B.; Blasco, M.A. The telomerase activator TA-65 elongates short telomeres and increases health span of adult/old mice without increasing cancer incidence. Aging Cell 2011, 10, 604–621, doi:10.1111/j.1474-9726.2011.00700.x.
[12]
Dagarag, M.; Evazyan, T.; Rao, N.; Effros, R.B. Genetic manipulation of telomerase in HIV-specific CD8+ T cells: enhanced antiviral functions accompany the increased proliferative potential and telomere length stabilization. J. Immunol. 2004, 173, 6303–6311.
[13]
Fauce, S.R.; Jamieson, B.D.; Chin, A.C.; Mitsuyasu, R.T.; Parish, S.T.; Ng, H.L.; Kitchen, C.M.; Yang, O.O.; Harley, C.B.; Effros, R.B. Telomerase-based pharmacologic enhancement of antiviral function of human CD8+ T lymphocytes. J. Immunol. 2008, 181, 7400–7406.
[14]
Harley, C.B.; Liu, W.; Blasco, M.; Vera, E.; Andrews, W.H.; Briggs, L.A.; Raffaele, J.M. A natural product telomerase activator as part of a health maintenance program. Rejuvenation Res. 2011, 14, 45–56.
[15]
Harley, C.B.; Futcher, A.B.; Greider, C.W. Telomeres shorten during ageing of human fibroblasts. Nature 1990, 345, 458–460, doi:10.1038/345458a0.
[16]
Allsopp, R.C.; Vaziri, H.; Patterson, C.; Goldstein, S.; Younglai, E.V.; Futcher, A.B.; Greider, C.W.; Harley, C.B. Telomere length predicts replicative capacity of human fibroblasts. Proc. Natl. Acad. Sci. USA 1992, 89, 10114–10118.
[17]
Bodnar, A.G.; Ouellette, M.; Frolkis, M.; Holt, S.E.; Chiu, C.P.; Morin, G.B.; Harley, C.B.; Shay, J.W.; Lichtsteiner, S.; Wright, W.E. Extension of life-span by introduction of telomerase into normal human cells. Science 1998, 279, 349–352, doi:10.1126/science.279.5349.349.
[18]
Parish, S.T.; Wu, J.E.; Effros, R.B. Sustained CD28 expression delays multiple features of replicative senescence in human CD8 T lymphocytes. J. Clin. Immunol. 2010, 30, 798–805, doi:10.1007/s10875-010-9449-7.
[19]
Hooijberg, E.; Ruizendaal, J.J.; Snijders, P.J.; Kueter, E.W.; Walboomers, J.M.; Spits, H. Immortalization of human CD8+ T cell clones by ectopic expression of telomerase reverse transcriptase. J. Immunol. 2000, 165, 4239–4245.
[20]
Migliaccio, M.; Amacker, M.; Just, T.; Reichenbach, P.; Valmori, D.; Cerottini, J.C.; Romero, P.; Nabholz, M. Ectopic human telomerase catalytic subunit expression maintains telomere length but is not sufficient for CD8+ T lymphocyte immortalization. J. Immunol. 2000, 165, 4978–84.
[21]
Denzler, K.L.; Waters, R.; Jacobs, B.L.; Rochon, Y.; Langland, J.O. Regulation of inflammatory gene expression in PBMCs by immunostimulatory botanicals. PLoS One 2010, 5, e12561.
[22]
Auyeung, K.K.; Mok, N.L.; Wong, C.M.; Cho, C.H.; Ko, J.K. Astragalus saponins modulate mTOR and ERK signaling to promote apoptosis through the extrinsic pathway in HT-29 colon cancer cells. Int. J. Mol. Med. 2010, 26, 341–9.
[23]
Collins, R.A. A ten-year audit of traditional Chinese medicine and other natural product research published in the Chinese Medical Journal (2000–2009). Chin. Med. J. (Engl) 2011, 124, 1401–1408.
