cytochrome-c-t and benzophenone

Sunscreen users have been increased, since excessive sun exposure increased the risk of skin diseases. Benzophenone (BP) and its derivatives are commonly used in sunscreens as UV blocker. Its photosafety is concern for human health. Our study showed the role of type-I and type-II radicals in activation of caspase 3 and phototoxicity of BP under sunlight/UV radiation. BP photodegraded and formed two photoproducts. BP generates reactive oxygen species (ROS) singlet oxygen ((1)O2), superoxide anion (O2˙(-)) and hydroxyl radical (˙OH) through type-I and type-II photodynamic mechanisms. Photocytotoxicity significantly reduced cell viability under sunlight, UVB and UVA. DCF fluorescence confirmed intracellular ROS generation. BP showed single strand DNA breakage, further proved by cyclobutane pyrimidine dimmers (CPDs) formation. Lipid peroxidation and LDH leakage were enhanced by BP. P21 dependent cell cycle study showed sub G1 population which advocates apoptotic cell death, confirmed through AO/EB and annexin V/PI staining. BP decreased mitochondrial membrane potential, death protein released and activated caspase. We proposed cytochrome c regulated caspase 3 dependent apoptosis in HaCaT cell line through down regulation of Bcl2/Bax ratio. Phototoxicity potential of its photoproducts is essential to understand its total environmental fate. Hence, we conclude that BP may replace from cosmetics preparation of topical application.

Topics: Apoptosis; bcl-2-Associated X Protein; Benzophenones; Caspase 3; Cell Line; Cell Survival; Cytochromes c; DNA Breaks, Single-Stranded; Dose-Response Relationship, Drug; Enzyme Activation; Humans; Hydroxyl Radical; Keratinocytes; L-Lactate Dehydrogenase; Lipid Peroxidation; Membrane Potential, Mitochondrial; Mitochondria; Oxidative Stress; Photolysis; Proto-Oncogene Proteins c-bcl-2; Risk Assessment; Signal Transduction; Sunscreening Agents; Superoxides; Ultraviolet Rays

Solar UV radiation is main factor of photocarcinogenesis, photoageing, and phototoxicity; thus, protection from UV radiation is major concern. Sunscreens containing UV filters are suggested as sun safe practices, but safety of UV filters remains in controversies. Benzophenone-1 (BP1) is commonly used in sunscreens as UV blocker. We assessed the photogenotoxicity and apoptotic parameters in human keratinocytes (HaCaT cells) by western blot, immunocytochemistry, flowcytometry, comet assay and TEM imaging. Our results exposed that BP1 photosensitized and generated intracellular ROS (2.02 folds) under sunlight/UVR. Decrease in cell viability was recorded as 80.06%, 60.98% and 56.24% under sunlight, UVA and UVB, respectively. Genotoxic potential of BP1 was confirmed through photomicronuclei and CPDs formation. BP1 enhanced lipid peroxidation and leakage of LDH enzyme (61.7%). Apoptotic cells were detected by AnnexinV/PI staining and sub G1 population of cell cycle. BP1 induced up regulation of apoptotic proteins Bax/Bcl2 ratio, Apaf-1, cytochrome c, Smac/DIABLO and cleaved caspase 3 was noticed. Down regulation of pro caspase 3 was inhibited by Z-VAD-fmk (inhibitor of caspase). Thus, study established the involvement of BP1 in photogenotoxicity and apoptosis via release of cytochrome c and Smac/DIABLO. These findings suggest sunscreen user to avoid BP1 in cosmetics preparation for its topical application.

Topics: Amino Acid Chloromethyl Ketones; Annexin A5; Apoptosis; Apoptosis Regulatory Proteins; Apoptotic Protease-Activating Factor 1; bcl-2-Associated X Protein; Benzophenones; Caspase 3; Cell Line; Comet Assay; Cytochromes c; DNA Damage; Down-Regulation; Electrophoresis, Polyacrylamide Gel; Humans; Intracellular Signaling Peptides and Proteins; Keratinocytes; Lipid Peroxidation; Membrane Potential, Mitochondrial; Microscopy, Electron, Transmission; Mitochondrial Proteins; Reactive Oxygen Species; Sunscreening Agents; Ultraviolet Rays

We have shown that diphenlacetaldehyde (DPAA) is able to promote mitochondrial DeltaPsi disruption accompanied by damage in mitochondrial DNA, lipids, and proteins [Almeida, A. M.; Bechara, E. J. H.; Vercesi, A. E.; Nantes, I. L. Free Radic. Biol. Med. 27:744-747; 1999]. In this work, DPAA was used as a model of carbonyl reagent for cytochrome c. The results suggest that DPAA is a redox cytochrome c modifier. Conversion of Fe(III) to Fe(II) cytochrome c promoted by DPAA is pH dependent. The second-order rate determined for heme iron reduction (k2) is 698 M(-1) s(-1) and this process occurs with an activation energy of 8.5 +/- 0.8 kcal/mol. Analysis of the pH profile suggests the presence of two ionizable cytochrome c groups (pKa1 = 8.9 and pKa2 = 11.4) related to the electron transfer from DPAA to heme iron. The heats of ionization of the two prototropic groups, pKa1 (DeltaH(ion) = 6.5 kcal/mol, DeltaS(ion) = -29.0 cal/mol.K), and pKa2 (DeltaH(ion) = 5.0 kcal/mol, DeltaS(ion) = -24.0 cal/mol.K), suggest involvement of two tyrosine residues, probably Y67 and Y74, related to DPAA-promoted heme iron reduction. The cytochrome c chemical modification by iodination of tyrosine groups significantly decreased the reduction rate promoted by DPAA, and shifted the pH(opt) value from 10.0 to 9.25. The cytochrome c-promoted DPAA electron abstraction quickly produces the expected enol-derived radical, as indicated by 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS) spin trapping EPR measurements. This radical reacts with molecular oxygen, producing a peroxyl intermediate radical that, via a putative dioxetane intermediate, promotes formation of benzophenone as the main final product of this reaction, detected by high-performance liquid chromatography coupled with tandem mass spectrometry.

Topics: Aldehydes; Benzophenones; Biphenyl Compounds; Chromatography, High Pressure Liquid; Circular Dichroism; Cytochromes c; Electron Spin Resonance Spectroscopy; Free Radicals; Heme; Hydrogen-Ion Concentration; Iodine; Iron; Mass Spectrometry; Oxidation-Reduction; Oxygen Consumption; Protons; Reducing Agents; Tyrosine