Involvement of both caspase-dependent and -independent pathways in apoptotic induction by hexaminolevulinate-mediated photodynamic therapy in human lymphoma cells

Abstract

Photodynamic therapy (PDT) is a cancer treatment based on the interaction of a photosensitizer, light and oxygen. PDT with the endogenous photosensitizer, protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (ALA) or its derivatives is a modification of this treatment modality with successful application in dermatology. However, the mechanism of cell destruction by ALA-PDT has not been elucidated. In this study a human T-cell lymphoma Jurkat cell line was treated with PDT using hexaminolevulinate (HAL, hexylester of ALA). Four hours following treatment nearly 80% of the cells exhibited typical apoptotic features. Mitochondrial pro-apoptotic proteins were evaluated by Western blots in subcellular fractionated samples. PDT caused cytosolic translocation of cytochrome c and nuclear redistribution of apoptosis-inducing factor (AIF), but the release of mitochondrial Smac/DIABLO, Omi/HtrA2 and EndoG was not observed. The release of cytochrome c was followed by the cleavage of caspase-9 and caspase-3 as well as its downstream substrates, together with oligonucleosomal DNA fragmentation. The pan-caspases inhibitor, z-VAD.fmk, prevented oligonucleosomal DNA fragmentation, but failed to inhibit PDT-mediated apoptosis. The apoptotic induction by AIF-mediated caspase-independent pathway was also found after HAL-PDT with large-scale DNA fragmentation in the presence of z-VAD.fmk. These results demonstrate that cytochrome c-mediated caspase-dependent pathway and AIF-induced caspase-independent pathway are simultaneously involved in the apoptotic induction by PDT. When the cytochrome c-induced caspase-dependent pathway is blocked, the cells go into apoptosis via AIF-mediated pathway, clearly demonstrating that the cytochrome c-mediated caspase-dependent pathway is not required for such apoptotic induction. This finding may have an impact on improved PDT effectiveness.

Neurogenesis in an Adult Avian Song Nucleus Is Reduced by Decreasing Caspase-Mediated Apoptosis

“…This observation is especially noteworthy given that there is some evidence that cells that would normally die via activation of caspases may resort to caspase-independent cell death pathways if caspase activity is persistently inhibited (Furre et al, 2006). Caspase inhibitors did not protect HVC soma area from regression in the current study, although the results from two animals seem to indicate some protection of ipsilateral HVC soma area (Fig.…”

Intermediate Filament Proteins of Lamin A/C and Cytokeratin 18 are involved in Apoptotic Induction by Photodynamic Therapy with Hexaminolevulinate in Human Colon Carcinoma Cells

“…A large number of reports have demonstrated that PDT can kill tumour cells via apoptosis [1,3]. Our previous studies have shown that HAL-mediated PDT induces efficiently apoptotic cell death in several human blood malignant cell lines [15][16][17][18]. The mechanisms of such apoptotic induction by PDT are largely dependent upon the intracellularly initial target sites and biological systems.…”

Apoptotic activity of a new jasmonate analogue is associated with its induction of DNA damage

“…In mammalian cells, apoptosis pathway can be divided into caspase-dependent and -independent pathways (24,25). Caspases involved in apoptosis can be grouped into 'apoptotic initiator', such as caspase-9, and 'apoptotic effector', such as caspase-3 based on the substrate specificities and target proteins of caspases (22).…”