Hyperthermia Enhances CD95-Ligand Gene Expression in T Lymphocytes

Abstract

Hyperthermia represents an interesting therapeutic strategy for the treatment of tumors. Moreover, it is able to regulate several aspects of the immune response. Fas (APO-1/CD95) and its ligand (FasL) are cell surface proteins whose interaction activates apoptosis of Fas-expressing targets. In T cells, the Fas-Fas-L system regulates activation-induced cell death, is implicated in diseases in which lymphocyte homeostasis is compromised, and plays an important role during cytotoxic and regulatory actions mediated by these cells. In this study we describe the effect of hyperthermia on activation of the fas-L gene in T lymphocytes. We show that hyperthermic treatment enhances Fas-L-mediated cytotoxicity, fas-L mRNA expression, and fas-L promoter activity in activated T cell lines. Our data indicate that hyperthermia enhances the transcriptional activity of AP-1 and NF-κB in activated T cells, and this correlates with an increased expression/nuclear translocation of these transcription factors. Moreover, we found that heat shock factor-1 is a transactivator of fas-L promoter in activated T cells, and the overexpression of a dominant negative form of heat shock factor-1 may attenuate the effect of hyperthermia on fas-L promoter activity. Furthermore, overexpression of dominant negative mutants of protein kinase Cε (PKCε) and PKCθ partially inhibited the promoter activation and, more importantly, could significantly reduce the enhancement mediated by hyperthermia, indicating that modulation of PKC activity may play an important role in this regulation. These results add novel information on the immunomodulatory action of heat, in particular in the context of its possible use as an adjuvant therapeutic strategy to consider for the treatment of cancer.

Fever-Like Hyperthermia Controls T Lymphocyte Persistence by Inducing Degradation of Cellular FLIPshort

“…Alterations in CD95 receptor and ligand expression could contribute to the hyperthermia-induced sensitization and it has been reported that long-term hyperthermia increases the expression of CD95L (47). CD95 was similarly expressed on the surface of control and hyperthermia-exposed primary T lymphocytes ( Fig.…”

“…The levels of c-FLIP are reduced upon hyperthermia also earlier during T lymphocyte activation (days 1-3), but not to the extent that would allow triggering of the apoptotic signal, because the c-FLIP quantities are much higher at this time point (data not shown). Interestingly, Cippitelli et al (47) recently showed that long-lasting hyperthermia increases CD95L expression during T cell activation. We were not able to detect such changes in the CD95L levels in Jurkat cells during shorter hyperthermia treatments.…”

“…In contrast, the T lymphocytes produced during clonal expansion need to regain their sensitivity toward death receptormediated apoptosis to be eliminated when the Ags have been cleared out (44). Among a multitude of transcription-dependent (45)(46)(47) and -independent (48 -50) measures to control CD95 responses, the amount of c-FLIP is a major determinant (51)(52)(53)(54)(55). The T lymphocytes are resistant to CD95-mediated apoptosis early upon activation, which has been suggested to be mediated by upregulation of c-FLIP S expression.…”

Fas ligand gene expression is directly regulated by stress-inducible heat shock transcription factor-1

“…22 However, whether this reflects a direct transcriptional function for HSF-1 at the level of the FasL promoter remains unknown.…”

“…21 One study also implicated hyperthermic stress in the transcriptional regulation of FasL in activated T cells to mediate enhanced cytotoxicity of Fas-bearing target cells. 22 Elevated temperature can also impact on the Fas/FasL signaling pathway through its suppression of FLIP levels 23 and expression of a dominant active form of HSF-1 has been reported to elevate sensitivity to Fas-mediated killing, 24 but whether this reflects a simultaneous regulation of FasL levels is unclear. Furthermore, gld mice, lacking functional FasL exhibit a decreased sensitivity to heat shock-induced death.…”