Photodynamic therapy induces caspase-3 activation in HL-60 cells

Abstract

Caspases have been shown to play a crucial role in apoptosis induced by various deleterious and physiologic stimuli. In this study, we show for the first time that photodynamic therapy (PDT), using benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) as the photosensitizer, induces the complete cleavage and subsequent activation of caspase-3 (CPP32/Yama/Apopain) but not caspase-1 (ICE) in human promyelocytic leukemia HL-60 cells. Poly(ADP-ribose) polymerase (PARP) and the catalytic subunit of DNA dependent protein kinase (DNA PK CS ) were cleaved within 60 min of light activation of BPD-MA. The general caspase inhibitor Z-Asp-2,6 dichlorobenzoyloxymethylketone (Z-Asp-DCB) blocked PARP cleavage while the serine protease inhibitors 3,4-dichloroisocoumarin (DCI) and N-tosyl-lysyl chloromethyl ketone (TLCK) blocked the cleavage of caspase-3 suggesting that they act upstream of caspase-3 activation. All three inhibitors were able to block DNA fragmentation that was induced by treatment with BPD-MA followed by light application. These studies demonstrate that protease activity, particularly that of caspase-3, is triggered in HL-60 cells treated with lethal levels of BPD-MA and visible light.

Bcl-2 overexpression blocks caspase activation and downstream apoptotic events instigated by photodynamic therapy

“…At BPD-MA concentrations of less than 50 ng ml -1 , a modest protective effect of Bcl-2 overexpression against PDT-mediated cell death was observed in line with observations for other chemotherapeutic treatments . Although it has been well established by electron microscopy, histological and biochemical analysis that PDT induces apoptosis, we cannot rule out the possibility that PDT inflicts damage to other cell sites promoting passive necrotic cell death at higher drug concentrations (Gomer et al, 1988;Zaidi et al, 1993;Tajiri et al, 1996;Granville et al, 1997). Further understanding towards the mechanisms involved in PDTinduced cell death and how this treatment may be able to overcome the regulatory control of Bcl-2 should provide valuable insights towards the improvement of current cancer treatments.…”

“…We have previously demonstrated that caspase 3, but not caspase 1, is activated leading to PARP and DNA-PK cleavage in HL-60 cells treated with cytotoxic levels of BPD-MA and light (Granville et al, 1997). The present report shows that although Bcl-2 overexpression effectively blocked caspase 3 and caspase 6 activation as well as hypodiploid DNA formation produced by PDT, Bcl-2 had little or no effect on cell death induced by the photoactivation of BPD-MA at high drug doses but did offer a degree of protection against killing at lower levels of the photosensitizer as determined by 3-day culture studies.…”

A photodynamic pathway to apoptosis and necrosis induced by dimethyl tetrahydroxyhelianthrone and hypericin in leukaemic cells: possible relevance to photodynamic therapy

“…The phosphorylation disassembles lamin filaments and manifests nuclear membrane breakdown during apoptosis (Kick et al, 1996) and also mitosis. Lamins also appear to be degraded by caspases during apoptosis (Takahashi et al, 1996) and photosensitization induces the cleavage and activation of caspase 3 (Granville et al, 1997). PKC β II might be a potential target for light-dependent inhibition by HY, with consequent interference with lamin phosphorylation, stabilization of the nucleus and prevention of nuclear fragmentation.…”

Involvement of retinoblastoma (Rb) and E2F transcription factors during photodynamic therapy of human epidermoid carcinoma cells A431

“…Reports have indicated the involvement of phospholipases A 2 and C, and intracellular Ca 2+ in PDTmediated apoptosis (Agarwal et al, 1993). Recent studies have implicated the involvement of ceramide (Separovic et al, 1997) and caspases (Granville et al, 1997;He et al, 1998) during PDT-mediated apoptosis.…”