Heat shock modulates UVB-induced cell death in human epidermal keratinocytes: evidence for a hyperthermia-inducible protective response.
The ability of heat shock to induce functional protection against ultraviolet B (UVB) light was examined in keratinocytes cultured from human skin. Cell death, measured with fluorescent vital dyes, increased in a UVB dose-dependent manner (LD50 approximately 20-60 mJ/cm2). However, a 60-min heat shock at 40 degrees C or 42 degrees C, administered several hours before UVB irradiation, reduced cell death by 2.0-2.5 times. Inducible protection took time to develop, with an optimal interval of approximately 6 h between heat and UVB exposures. Heat-inducible protection was completely blocked if either cordycepin (3'-deoxyadenosine), to inhibit mRNA synthesis, or cycloheximide, to inhibit protein synthesis, were present during the heating period. To determine whether apoptosis might be involved in UVB-induced keratinocyte death in this system, evidence for endonuclease activity was sought via in situ enzymatic labeling with terminal deoxynucleotidyl transferase and biotinylated-dUTP. Labeled nuclei were detected in UVB-irradiated cultures, and heat pretreatment at 6 h prior to UVB exposure (< 60 mJ/cm2) resulted in a 50% reduction in labeled nuclei. Overall, the data show that UVB-induced cell death in human keratinocyte cultures is attenuated by a heat-inducible mechanism that requires ongoing synthesis of mRNA and protein.
Maytin
E V
EV
Cutaneous Biology Research Center, Massachusetts General Hospital, Boston 02114.
Wimberly
J M
JM
Kane
K S
KS
D000328:Adult; D016923:Cell Death / Q000187:drug effects* / Q000528:radiation effects*; D003513:Cycloheximide / Q000494:pharmacology; D005260:Female; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000494:pharmacology*; D006358:Hot Temperature; D006801:Humans; D007231:Infant, Newborn; D015603:Keratinocytes / Q000166:cytology*; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays
D006360:Heat-Shock Proteins; D012333:RNA, Messenger; D011837:Radiation-Protective Agents; D003513:Cycloheximide