Carboxyfullerenes localize within mitochondria and prevent the UVB‐induced intrinsic apoptotic pathway

Abstract

Carboxyfullerenes (CF) act as free radical scavengers in many cell settings and prevent apoptosis in vitro and in vivo. CF protect normal human keratinocytes from UVB-induced apoptosis, although the mechanisms underlying this effect remain to be clarified. Double-staining confocal laser microscopy revealed that CF penetrate the cell and colocalize with cytokeratin-18 within cytoplasm. This localization was confirmed by transmission electron microscopy that showed CF intermingled with keratin filaments. Moreover, double-staining with the mitochondrial marker anti-F1-ATPase antibody demonstrated that CF are expressed in mitochondria. Transmission electron microscopy confirmed that CF actually localize within mitochondria. Then, normal human keratinocytes were UVB-irradiated in the presence or absence of CF at different doses. CF protected keratinocytes from apoptosis induced by reactive oxygen species. CF scavenging effect is associated with a partial blockade of the UVB-induced intrinsic apoptotic pathway by down-modulating caspase-9 activation and cytochrome c release, and by inhibiting the down-regulation of the inhibitor of apoptosis proteins (IAP) survivin, livin, IAP-1 and IAP-2. Finally, CF prevented the cleavage of Bid, up-regulation of Bad and down-regulation of Mcl-1 induced by UVB. Taken together, these results indicate that CF penetrate human keratinocytes, localize within mitochondria where they act both by scavenging free radicals and by protecting cells from apoptosis.

Application of Fullerenes in Nanomedicine: An Update

“…However, results suggest that blocking ROS using FDs in response to an immune complex (a FcεRIIA-dependent stimuli [50] ) parallels inhibition of mediator release. This is in line with previous work suggesting that FDs interfere with the generation of mitochondrial-derived ROS [51,52] .…”

Biomedical potential of the reactive oxygen species generation and quenching by fullerenes (C60)

“…This type of cell demise is characterized by activation of the caspase enzyme family and fragmentation of DNA, which occurs without plasma membrane breakdown and is followed by recognition and removal of apoptotic cell by phagocytes in the absence of inflammation [107]. This is consistent with the preferential mitochondrial localization of water-soluble C 60 derivatives [67,68], having in mind that ROSinduced mitochondrial dysfunction is a key initial step in the ''mitochondrial'' pathway of apoptosis [107]. Interestingly, polyhydroxylated C 60 was able to suppress proliferation and induce apoptosis of tumor cells in the absence of photosensitization and ROS production [88,108,109].…”

“…An important feature of various C 60 preparations that facilitates their biological reactivity is the ability to penetrate cell membrane and gain access to cell cytoplasm, organelles and nucleus, as predicted by theoretical studies and confirmed in various experimental settings [67][68][69][70][71]. Singlet oxygen, generated by energy transfer from C 60 to molecular oxygen (Type II photochemical mechanism), could directly react with various biological targets, including lipids, proteins, nucleic acids and carbohydrates, resulting in cell damage or functional alterations [8].…”

AF1q enhancement of γ irradiation-induced apoptosis by up-regulation of BAD expression via NF-κB in human squamous carcinoma A431 cells

“…1A). BAD was reported to play a critical role in radiation-induced apoptosis (26)(27)(28) and was also found to be an important mediator involved in AF1q regulation of doxorubicin-induced apoptosis (24). Therefore, we hypothesized that BAD is also involved in the AF1q enhancement of radiation-induced apoptosis.…”