Long-term growth arrest of PUVA-treated fibroblasts in G2/M in the absence of p16(INK4a) p21(CIP1) or p53.
Premature aging of the skin is a prominent side-effect of psoralen photoactivation, a therapy used for different skin disorders. Recently, we demonstrated that treatment of fibroblasts with 8-methoxypsoralen and ultraviolet A irradiation resulted in growth arrest with morphological and functional changes reminiscent of replicative senescence. To further elucidate the underlying molecular mechanisms, we analysed the cell-cycle phases of the growth-arrested fibroblasts. After PUVA treatment, fibroblasts arrested in G2/M, in contrast to spontaneously senesced fibroblasts arresting in a cell-cycle phase with many features similar to G1. To address the role of the cell-cycle controlling genes p16(INK4a), p21(CIP1) and p53, we analysed the expression of these genes. p16(INK4a), p21(CIP1) and p53 protein levels increased substantially with different time kinetics in growth-arrested fibroblasts. Because p16(INK4a), p21(CIP1) and p53 are involved in replicative senescence, we applied the PUVA regimen to fibroblasts deficient in either of these genes. p16(INK4a), p21(CIP1) and p53 null mutant fibroblast strains underwent growth arrest with a senescent phenotype similar to wild-type human fibroblasts. Based on these results, we propose that redundant or alternate pathways are involved in the response of dermal fibroblasts to PUVA treatment resulting in a phenocopy of replicative senescence in vitro.
Ma
W
W
Department Dermatology and Allergy, University of Ulm, Ulm, Germany.
Hommel
C
C
Brenneisen
P
P
Peters
T
T
Smit
N
N
Sedivy
J
J
Scharffetter-Kochanek
K
K
Wlaschek
M
M
D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects; D002648:Child; D002675:Child, Preschool; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism*; D004171:Diploidy; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D007223:Infant; D008938:Mitosis / Q000187:drug effects; D011701:PUVA Therapy; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
C493956:CDKN1A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016159:Tumor Suppressor Protein p53