Secondary Dark Reactions Following Photodynamic Treatment are More Damaging Than Previously Thought

Chiemezie, Callistus; Greer, Alexander

doi:10.1111/php.12984

Cited by 4 publications

(2 citation statements)

References 6 publications

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“…We believe that this premise has merits based on preliminary reports of damaging secondary dark reactions following a photodynamic treatment. A previous work 11,12 has shown the existence of oxidation products bearing toxicity competitive to their photogenerated ROS precursors. The process is illustrated in Figure 3.…”

Section: ■ Introductionmentioning

confidence: 97%

A Singlet Oxygen Priming Mechanism: Disentangling of Photooxidative and Downstream Dark Effects

et al. 2020

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Airborne singlet oxygen obtained from photosensitization of triplet dioxygen is shown to react with an alkene surfactant (8-methylnon-7-ene-1 sulfonate) leading to “ene” hydroperoxides that in the dark inactivate planktonic Escherichia coli (E. coli). The “ene” hydroperoxide photoproducts are not toxic on their own, but they become toxic after the bacteria are pretreated with singlet oxygen. The total quenching rate constant (k T) of singlet oxygen of the alkene surfactant was measured to be 1.1 × 106 M–1 s–1 at the air/liquid interface. Through a new mechanism called singlet oxygen priming (SOP), the singlet oxygen leads to hydroperoxides then to peroxyl radicals, tetraoxides, and decomposition products, which also promote disinfection, and therefore offer a “one-two” punch. This offers a strong secondary toxic effect in an otherwise indiscernible dark reaction. The results provide an insight into assisted killing by an exogenous alkene with dark toxicity effects following exposure to singlet oxygen.

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Section: ■ Introductionmentioning

confidence: 97%

A Singlet Oxygen Priming Mechanism: Disentangling of Photooxidative and Downstream Dark Effects

et al. 2020

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“…Additionally, lipid hydroperoxides can react with metal ions, heme proteins, or other oxidants, producing alkoxyl and peroxyl radicals (28). These radicals can further propagate lipid peroxidation by fueling radical chain reactions and by promoting the generation of excited species, such as O2 ( 1 ∆g) (29)(30)(31)(32)(33).…”

Section: Introductionmentioning

confidence: 99%

Plasmalogen oxidation induces the generation of excited molecules and electrophilic lipid species

Faria,

Prado,

Junqueira

et al. 2024

Preprint

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Plasmalogens are glycerophospholipids with a vinyl-ether linkage at the sn-1 position of the glycerol backbone. Despite being suggested as antioxidants due to the high reactivity of their vinyl ether groups with reactive oxygen species (ROS), our study reveals the generation reactive oxygen and electrophilic lipid species from oxidized plasmalogen intermediates. By conducting a comprehensive analysis of the oxidation products by liquid chromatography coupled to high-resolution mass spectrometry (LC-MS) we demonstrate that singlet molecular oxygen [O2(1Δg)] reacts with the vinyl ether bond, producing hydroperoxyl acetal as major primary product (97%) together with minor quantities of dioxetane (3%). Furthermore, we show that these primary oxidized intermediates lead to the formation of excited triplet carbonyls, O2(1Δg), and electrophilic phospholipid and fatty aldehyde species, as secondary reactive products. The generation of excited triplet carbonyls from dioxetane thermal decomposition was confirmed by light emission measurements in the visible region using dibromoantracene as a triplet enhancer. Moreover, O2(1Δg) generation from dioxetane and hydroperoxyacetal was evidenced by detection of near-infrared light emission at 1270 nm and chemical trapping experiments. Additionally, we have thoroughly characterized alpha-beta unsaturated phopspholipid and fatty aldehydes by LC-MS analysis using two probes that specifically reacts with aldehydes and alpha-beta unsaturated carbonyls. Overall, our findings demonstrate the generation of excited molecules and electrophilic lipid species from oxidized plasmalogen species unveiling the potential prooxidant nature of plasmalogen oxidized products.Significance StatementPlasmalogens, the most abundant subclass of ether lipids in mammalian cells, have traditionally been regarded as antioxidants. However, our study reveals a new perspective, shedding light on the generation of chemiexcited and reactive lipid species during plasmalogen photooxidation. We provide direct evidence revealing the production of excited triplet carbonyls and singlet molecular oxygen as secondary reactive products originating from dioxetane and hydroperoxyacetal intermediates. Importantly, we also demonstrate the generation of electrophilic alpha-beta unsaturated phospholipids and fatty aldehydes through plasmalogen oxidation. These findings highlight the production of excited states and reactive lipid species resulting from plasmalogen oxidation, which can potentially induce oxidative modifications in biological systems.

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Electrophilic oxysterols: generation, measurement and protein modification

Miyamoto

Lima

Inague

et al. 2021

Free Radical Research

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Secondary Dark Reactions Following Photodynamic Treatment are More Damaging Than Previously Thought

Cited by 4 publications

References 6 publications

A Singlet Oxygen Priming Mechanism: Disentangling of Photooxidative and Downstream Dark Effects

A Singlet Oxygen Priming Mechanism: Disentangling of Photooxidative and Downstream Dark Effects

Plasmalogen oxidation induces the generation of excited molecules and electrophilic lipid species

Electrophilic oxysterols: generation, measurement and protein modification

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