A Study of Epidermal Apoptosis

Park, Young Lip; Whang, Kyu Uang; Park, Jun Hong

Abstract

BACKGROUND: Apoptosis is a highly selective form of cell suicide with characteristic morphologieal and biochemical features, including chromatin condensation, formation of apoptotic bodies, and DNA fragmentation by the activation of endonucleases. Various cytokines and physical or chemical factors can provoke apoptotic changes in the skin.
OBJECTIVE
We investigated the cytotoxic effects with epidermal cytokines and their combinations, K+ ionophores, protein synthesis inhibitor(emetine), inhibitor of endogenous endonuclease(aurintricarboxylic acid, ATA), sodium azide, and retinoic acid witp human epithelial tumor cell lines(A431 cells) to examine the degree of induction of apoptosis in the epidermal keratinocytes.
METHODS
Induction of apoptosis was measured in cultured human keratinocytes, keratinocyte cell lines(A-431, HaCat, KB cells), cultured human melanocytes and malignant melanoma cell lines(SK-28, SK-30) using a mixture of ethidium bromide and acridine orange, DNA agarose gel electrophoresis and TUNEL staining.
RESULTS
l. In the A-431 cells, (1 to a certain degree, the combination of IFN-gamma and TNF-alpha could only induce apoptosis. Q2 most of K+ ionophores were observed to induce necrosis rather than apoptosis. Q3 emetine, a protein synthesis blocker, was found to induce apoptosis in a dose-dependent pattern. Q4 sodium azide at a concentration of 1% .induced apoptosis rather than necrosis. Q5 retinoic acid inhibit the beuvericin induced apoptosis. 2. In human keratinocytes, Ql more resistant in the induction of apoptosis than any cultured keratinocyte cell lines p aurintricarboxylic acid(ATA)-an endonuclease inhibitor, could inhibit UV induced apoptosis 3. In human keratinocytes and cultured keratinocyte cell lines, c-PAF inhibit the beauvericin induced apoptosis. 4. Human melanocytes is very resistant for the induction of apoptosis by beauvericin. 5. In the melanocytes and melanoma cell lines, sodium azide and beauvericin induced necrosis rather than apoptosis.
CONCLUSIONS
The epidermis is continuously exposed to toxic factors which might induce cell death. With the above results, the induction of appeared to be rather resistant, epidermal cell apoptosis which may reflect the existence of some endogenous protective mechanisms in the epidermis to survive at certain toxic environments; melanocytes showed high expression of bcl-2 protein which could play a role in endogenous defense against toxic environments of the epidermis.