Apoptosis and cytokine release induced by ionizing or ultraviolet B radiation in primary and immortalized human keratinocytes

Abstract

We have compared the induction of apoptosis and cytokine release by UVB and gamma-radiation in primary (untransformed) and in two immortalized human epithelial/keratinocyte cell lines, HaCaT and KB (KB is now known to be a subline of the ubiquitous keratin-forming tumour cell line HeLa and we therefore designate it HeLa-KB). In both the primary and the immortalized cell lines apoptosis and release of the inflammatory cytokine interleukin-6 are induced rapidly following UVB irradiation. In contrast, only the immortalized cells undergo apoptosis and release interleukin-6 after gamma-irradiation and here the onset of apoptosis and cytokine release are delayed. The same distinction between primary and immortalized cells was observed when double-strand breaks were induced with the anticancer drug mitoxantrone, which stabilizes topoisomerase II-cleavable complexes. We suggest that immortalization may sensitize keratinocytes to the apoptogenic effect of ionizing radiation or mitoxantrone by deregulating normal cell cycle checkpoints. In both human keratinocytes and fibroblasts, cell killing, as assayed by loss of colony-forming ability, is not coupled to apoptosis. Immortalization increases resistance to gamma-radiation killing but sensitizes to apoptosis. In contrast, although immortalization also sensitizes to UVB-induced apoptosis, it does not affect UVB-induced cell killing. Apoptosis unambiguously indicates death at the single cell level but clonal cell survival integrates all the cellular and genetic processes which prevent or permit a scorable clone to develop.

Role of Reduced Glutathione Efflux in Apoptosis of Immortalized Human Keratinocytes Induced by UVA

“…6D) 2 ) in the presence of 10 mM glucose and then incubated for 15 h. DNA was extracted and separated on 1.5% agarose gel. B, cells were irradiated with 25 J/cm 2 UVA and incubated for different times (3,6,12,15,18, and 24 h). Extracted DNA was subjected to 1.5% agarose gel electrophoresis.…”

Essential Metalloelement Chelates Facilitate Repair of RadiationInjury

“…Additional evidence for this comes from the correlation between survival of irradiated keratinocytes and the synthesis of IL-6 [55]. It is also known that changes in ceruloplasmin (Cp), a Cu-dependent multifunctional plasma enzyme, the plasma Zn containing a2-macroglobulin, and transferrin, the plasma Fe transporter, mediated responses to injury are regulated by IL-1 and other cytokines m facilitating tissue repair processes.…”

“…Feeding an "antioxidant" diet containing 55 trnol Zn(II)(gluconate)2 kg -day l to C57BL male mice for 45 days before irradiation(6 Gy, 1.8 Gy min") caused an inhibition of TRPM-2, a marker gene for apoptosis expression both before and after irradiation [112]. The bcl-2 mRNA, which is involved in the prevention of apoptosis, and splenocyte number increased steadily after irradiation.…”

Differential Expression of TGF-β Isoforms in Human Kerationocytes by Narrow Band UVB

“…The mechanism by which UVB treats clinical dermatoses is thought to be through the induction of apoptosis. Studies of broad-band UVB (BBUVB)-treated keratinocytes have demonstrated that apoptosis is a direct consequence of dose and exposure time [2][3][4] . NBUVB is also capable of inducing apoptosis in keratinocytes, though at significantly higher doses of energy than BBUVB 5 .…”