Oligonucleotides suppress PKB/Akt and act as superinductors of apoptosis in human keratinocytes.
DNA oligonucleotides (ODN) applied to an organism are known to modulate the innate and adaptive immune system. Previous studies showed that a CpG-containing ODN (CpG-1-PTO) and interestingly, also a non-CpG-containing ODN (nCpG-5-PTO) suppress inflammatory markers in skin. In the present study it was investigated whether these molecules also influence cell apoptosis. Here we show that CpG-1-PTO, nCpG-5-PTO, and also natural DNA suppress the phosphorylation of PKB/Akt in a cell-type-specific manner. Interestingly, only epithelial cells of the skin (normal human keratinocytes, HaCaT and A-431) show a suppression of PKB/Akt. This suppressive effect depends from ODN lengths, sequence and backbone. Moreover, it was found that TGF alpha-induced levels of PKB/Akt and EGFR were suppressed by the ODN tested. We hypothesize that this suppression might facilitate programmed cell death. By testing this hypothesis we found an increase of apoptosis markers (caspase 3/7, 8, 9, cytosolic cytochrome c, histone associated DNA fragments, apoptotic bodies) when cells were treated with ODN in combination with low doses of staurosporin, a well-known pro-apoptotic stimulus. In summary the present data demonstrate DNA as a modulator of apoptosis which specifically targets skin epithelial cells.
Kippenberger
Stefan
S
Department of Dermatology and Venerology, J.W. Goethe-University, 60590 Frankfurt/Main, Germany. kippenberger@em.uni-frankfurt.de
Müller
Jutta
J
Schultz
Maike
M
Dorn
Annette
A
Bock
Andreas
A
Aygün
Hüseyin
H
Thaçi
Diamant
D
Hofmann
Matthias
M
Kaufmann
Roland
R
Bernd
August
A
D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D004247:DNA / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D009154:Mutation; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism
C518599:CpG-1-phosphorothioate; D053594:Myeloid Differentiation Factor 88; D009838:Oligodeoxyribonucleotides; D051217:Toll-Like Receptor 9; C518598:non-CpG-5-phosphorothioate; D004247:DNA; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt