Singlet Oxygen Generation by UVA Light Exposure of Endogenous Photosensitizers
可以清楚地检测到尿刊酸的单线态氧发光，但信号太弱而无法量化量子产率。核黄素（ΦΔ= 0.54±0.07），FMN（ΦΔ= 0.51±0.07）和FAD（ΦΔ= 0.07±0.02）精确测定单线态氧的量子产率。
UVA light (320–400 nm) has been shown to produce deleterious biological effects in tissue due to the generation of singlet oxygen by substances like flavins or urocanic acid. Riboflavin, flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), β-nicotinamide adenine dinucleotide (NAD), and β-nicotinamide adenine dinucleotide phosphate (NADP), urocanic acid, or cholesterol in solution were excited at 355 nm.
Singlet oxygen was directly detected by time-resolved measurement of its luminescence at 1270 nm. NAD, NADP, and cholesterol showed no luminescence signal possibly due to the very low absorption coefficient at 355 nm.
Singlet oxygen luminescence of urocanic acid was clearly detected but the signal was too weak to quantify a quantum yield. The quantum yield of singlet oxygen was precisely determined for riboflavin (ΦΔ = 0.54 ± 0.07), FMN (ΦΔ = 0.51 ± 0.07), and FAD (ΦΔ = 0.07 ± 0.02).
In aerated solution, riboflavin and FMN generate more singlet oxygen than exogenous photosensitizers such as Photofrin, which are applied in photodynamic therapy to kill cancer cells.
With decreasing oxygen concentration, the quantum yield of singlet oxygen generation decreased, which must be considered when assessing the role of singlet oxygen at low oxygen concentrations (inside tissue).
Jürgen Baier,* Tim Maisch,* Max Maier,† Eva Engel,‡ Michael Landthaler,* and Wolfgang Bäumler*
Department of Dermatology, †Department of Physics, and ‡Department of Organic Chemistry, University of Regensburg, Regensburg, Germany
Singlet Oxygen Generation by UVA Light Exposure of Endogenous Photosensitizers https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1518628/
Toxicity Testing of a Novel Riboflavin-Based Technology for Pathogen Reduction and White Blood Cell Inactivation
The Mirasol PRT System (Gambro BCT, Lakewood, CO) for platelets and plasma uses riboflavin and UV light to reduce pathogens and inactivate white blood cells in donated blood products. An extensive toxicology program, developed in accordance with International Organisation for Standardisation (ISO) 10993 guidelines, was performed for the Mirasol PRT system. Test and control articles for most of the reported studies were treated (test) or untreated (control) blood products. For some studies, pure lumichrome (the major photoproduct of riboflavin) or photolyzed riboflavin solution was used. Systemic toxicity was evaluated with in vivo animal studies in the acute and subchronic settings. Developmental toxicity was evaluated with an in vivo animal study. Genotoxicity and neoantigenicity were evaluated with in vitro and in vivo tests. Hemocompatibility and cytotoxicity were assessed with standard, in vitro assays. The pharmacokinteics, excretion, and tissue distribution of 14C-riboflavin and its photoproducts was evaluated with an in vivo animal study. The possible presence of leachable or extractable compounds (from the disposable set) was evaluated with novel assays for measuring these compounds in blood. No treatment-related toxicity was observed in any of the studies.
Transfusion Medicine Reviews
Volume 22, Issue 2, April 2008, Pages 133-153
Author links open overlay panelHeather L.ReddyAnthony D.Dayan1JoyCavagnaroShayneGadJunzhiLiRaymond P.Goodrich
https://doi.org/10.1016/j.tmrv.2007.12.003Get rights and content
Pathogen Reduction technology
The Mirasol Pathogen Reduction Technology (PRT) System renders a broad range of disease-causing viruses, bacteria and parasites less pathogenic, and inactivates residual white blood cells found in blood components.
Built for efficiency and ease of use, the novel Mirasol PRT system helps improve the safety of the blood supply by reducing the infectious levels of disease-causing agents in platelets and plasma while still maintaining quality blood components
The Mirasol Pathogen Reduction Technology (PRT) System uses a combination of riboflavin (vitamin B2), a non-toxic, naturally occurring compound, and a specific spectrum of ultraviolet (UV) light to inactivate viruses, bacteria, parasites and white blood cells that may be present in collected blood products.
The Mirasol PRT system consists of three main components:
• A disposable kit — includes an illumination/storage bag and sterile riboflavin solution
• The Mirasol Illuminator — provides UV light and agitation for the Mirasol PRT process
• Mirasol® Managersoftware — integrates and manages data reporting and storage
During treatment, a blood product is mixed with the riboflavin solution and placed into the Illuminator where it is exposed to UV light for about five to ten minutes. There is no need to remove riboflavin or its photoproducts; after illumination, the treated products are ready for transfusion or placement into storage.
How the Mirasol PRT system inactivates pathogens and white blood cells:
UV light + riboflavin = irreversible inactivation
Riboflavin molecules associate with nucleic acids of pathogens. Exposure to UV light activates riboflavin and when it is associated with pathogen nucleic acid, riboflavin causes a chemical alteration to functional groups of the nucleic acids (primarily guanine bases), making pathogens unable to replicate.
Treating platelets and plasma in three simple steps:
1. The product is transferred to the Mirasol PRT illumination/storage bag
2. Riboflavin solution is added and mixed with the product
3. The mixture is then exposed to UV light for about five to ten minutes
The Mirasol PRT System
You know better than anyone—these are challenging times. The Mirasol PRT system allows you to meet the needs of your business by optimizing the balance of cost, efficacy and safety of your blood products.2,3
The Mirasol PRT system is the only PRT system:
Shown to reduce incidence of a transfusion-transmitted disease in humans1
That uses riboflavin (vitamin B2), a non-toxic, non-mutagenic compound, to inactivate pathogens and white blood cells1,5,6,7
The Mirasol process has fewer steps than other PRT methods and the device can be used to treat platelets, plasma and whole blood. This simplicity helps minimize the impact to operation.8,9,10
The Mirasol PRT system is effective in protecting against a broad spectrum of emerging tested and untested pathogens, including bacteria, parasites, and enveloped and non-enveloped viruses; it also inactivates white blood cells, adding an extra layer of safety for patients. Blood products treated with the Mirasol PRT system maintain efficacy and help save patients’ lives.11,12,13,14,15,16,17,18,19
The Mirasol PRT system treatment can be used as an alternative to some safety procedures without introducing new risks for operators or patients.20,21,22 Treatment with the Mirasol PRT system can help reduce product discard rates for blood centers and reduce the overall cost of transfusion for hospitals.2,3,8,9
The Mirasol PRT system comes from Terumo BCT, a global leader in blood component technologies.
Mirasol – Rontis Medical http://rontismedical.com/mirasol/
Chemical and metabolomic screens identify novel biomarkers and antidotes for cyanide exposure.
Nath AK1, Roberts LD, Liu Y, Mahon SB, Kim S, Ryu JH, Werdich A, Januzzi JL, Boss GR, Rockwood GA, MacRae CA, Brenner M, Gerszten RE, Peterson RT.
Exposure to cyanide causes a spectrum of cardiac, neurological, and metabolic dysfunctions that can be fatal. Improved cyanide antidotes are needed, but the ideal biological pathways to target are not known. To understand better the metabolic effects of cyanide and to discover novel cyanide antidotes, we developed a zebrafish model of cyanide exposure and scaled it for high-throughput chemical screening. In a screen of 3120 small molecules, we discovered 4 novel antidotes that block cyanide toxicity. The most potent antidote was riboflavin. Metabolomic profiling of cyanide-treated zebrafish revealed changes in bile acid and purine metabolism, most notably by an increase in inosine levels. Riboflavin normalizes many of the cyanide-induced neurological and metabolic perturbations in zebrafish. The metabolic effects of cyanide observed in zebrafish were conserved in a rabbit model of cyanide toxicity. Further, humans treated with nitroprusside, a drug that releases nitric oxide and cyanide ions, display increased circulating bile acids and inosine. In summary, riboflavin may be a novel treatment for cyanide toxicity and prophylactic measure during nitroprusside treatment, inosine may serve as a biomarker of cyanide exposure, and metabolites in the bile acid and purine metabolism pathways may shed light on the pathways critical to reversing cyanide toxicity.
PMID: 23345455 PMCID: PMC3633825 DOI: 10.1096/fj.12-225037
[Indexed for MEDLINE] Free PMC Article
FASEB J. 2013 May;27(5):1928-38. doi: 10.1096/fj.12-225037. Epub 2013 Jan 23.
Chemical and metabolomic screens identify novel biomarkers and antidotes for cyanide exposure. - PubMed - NCBI https://www.ncbi.nlm.nih.gov/pubmed/23345455
Riboflavin induces disease resistance in plants by activating a novel signal transduction pathway
Dong H，Beer SV。
证明了核黄素作为系统抗性的激发子和植物中新信号传导过程的激活剂的作用。在用核黄素处理后，拟南芥（Arabidopsis thaliana）对寄生霜霉（Peronospora parasitica）和丁香假单胞菌（Pseudomonas syringae pv。）产生了系统性抗性。番茄和烟草对烟草花叶病毒（TMV）和链格孢菌（Alternaria alternata）产生了系统性抗性。在抗性诱导所需的浓度下，核黄素不会在植物中引起细胞死亡或直接影响可培养病原体的生长。核黄素诱导植物中发病相关（PR）基因的表达，表明其能够触发导致全身抗性的信号转导途径。蛋白激酶抑制剂K252a和控制防御基因转录的NIM1 / NPR1基因突变均损害对核黄素的反应性。相反，核黄素在NahG植物中诱导抗性和PR基因表达，其不能积累水杨酸（SA）。因此，核黄素诱导的抗性需要蛋白激酶信号传导机制和功能性NIM1 / NPR1基因，但不需要SA的积累。核黄素是系统抗性的激发子，它以不同的方式触发抗性信号转导。
Phytopathology. 2000 Aug;90(8):801-11. doi: 10.1094/PHYTO.2000.90.8.801.
Riboflavin induces disease resistance in plants by activating a novel signal transduction pathway.
Dong H, Beer SV.
The role of riboflavin as an elicitor of systemic resistance and an activator of a novel signaling process in plants was demonstrated. Following treatment with riboflavin, Arabidopsis thaliana developed systemic resistance to Peronospora parasitica and Pseudomonas syringae pv. Tomato, and tobacco developed systemic resistance to Tobacco mosaic virus (TMV) and Alternaria alternata. Riboflavin, at concentrations necessary for resistance induction, did not cause cell death in plants or directly affect growth of the culturable pathogens. Riboflavin induced expression of pathogenesis-related (PR) genes in the plants, suggesting its ability to trigger a signal transduction pathway that leads to systemic resistance. Both the protein kinase inhibitor K252a and mutation in the NIM1/NPR1 gene which controls transcription of defense genes, impaired responsiveness to riboflavin. In contrast, riboflavin induced resistance and PR gene expression in NahG plants, which fail to accumulate salicylic acid (SA). Thus, riboflavin-induced resistance requires protein kinase signaling mechanisms and a functional NIM1/NPR1 gene, but not accumulation of SA. Riboflavin is an elicitor of systemic resistance, and it triggers resistance signal transduction in a distinct manner.
PMID: 18944500 DOI: 10.1094/PHYTO.2000.90.8.801
Free full text
Riboflavin induces disease resistance in plants by activating a novel signal transduction pathway. - PubMed - NCBI https://www.ncbi.nlm.nih.gov/pubmed/18944500
The regulatory role of riboflavin in the drought tolerance of tobacco plants depends on ROS production
Riboflavin (vitamin B2) is required for normal plant growth and development. Previous studies have shown that riboflavin application can enhance pathogen resistance in plants. Here, we investigated the role of riboflavin in increasing drought tolerance (10 % PEG6000 treatment) in plants. We treated 4 week-old tobacco plants with five different levels of riboflavin (0, 4, 20, 100 and 500 μM) for 5 days and examined their antioxidant responses and levels of drought tolerance. Compared with the controls, low and moderate levels of riboflavin treatment enhanced drought tolerance in the tobacco plants, whereas higher concentrations of riboflavin (500 μM) impaired drought tolerance. Further analysis revealed that plants treated with 500 μM riboflavin accumulated higher levels of ROS (O2 − and H2O2) and lipid peroxide than the control plants or plants treated with low levels of riboflavin. Consistent with this observation, the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) were higher in plants treated with low or moderate (4, 20 and 100 μM) levels of riboflavin compared with the control. We also found that chlorophyll degraded rapidly in control and 500 μM riboflavin-treated plants under drought stress conditions. In addition, the survival times of the riboflavin-treated plants were significantly modified by treatment with reduced glutathione, a well-known ROS scavenger, under drought stress conditions. Thus, riboflavin-mediated ROS production may determine the effects of riboflavin on drought tolerance in tobacco plants.
The regulatory role of riboflavin in the drought tolerance of tobacco plants depends on ROS production | SpringerLink https://link.springer.com/article/10.1007%2Fs10725-013-9858-8
From Wikipedia, the free encyclopedia
Photodynamic therapy (PDT), is a form of phototherapy involving light and a photosensitizing chemical substance, used in conjunction with molecular oxygen to elicit cell death (phototoxicity). PDT has proven ability to kill microbial cells, including bacteria, fungi and viruses. PDT is popularly used in treating acne. It is used clinically to treat a wide range of medical conditions, including wet age-related macular degeneration, psoriasis, atherosclerosis and has shown some efficacy in anti-viral treatments, including herpes. It also treats malignant cancers including head and neck, lung, bladder and particular skin. The technology has also been tested for treatment of prostate cancer, both in a dog model and in human prostate cancer patients.
It is recognised as a treatment strategy that is both minimally invasive and minimally toxic. Other light-based and laser therapies such as laser wound healing and rejuvenation, or intense pulsed light hair removal do not require a photosensitizer. Photosensitisers have been employed to sterilise blood plasma and water in order to remove blood-borne viruses and microbes and have been considered for agricultural uses, including herbicides and insecticides.
Photodynamic therapy's advantages lessen the need for delicate surgery and lengthy recuperation and minimal formation of scar tissue and disfigurement. A side effect is the associated photosensitisation of skin tissue.
PDT applications involve three components: a photosensitizer, a light source and tissue oxygen. The wavelength of the light source needs to be appropriate for exciting the photosensitizer to produce radicals and/or reactive oxygen species. These are free radicals (Type I) generated through electron abstraction or transfer from a substrate molecule and highly reactive state of oxygen known as singlet oxygen (Type II).
PDT is a multi-stage process. First a photosensitiser with negligible dark toxicity is administered, either systemically or topically, in the absence of light. When a sufficient amount of photosensitiser appears in diseased tissue, the photosensitiser is activated by exposure to light for a specified period. The light dose supplies sufficient energy to stimulate the photosensitiser, but not enough to damage neighbouring healthy tissue. The reactive oxygen kills the target cells.
Reactive oxygen species
In air and tissue, molecular oxygen (O2) occurs in a triplet state, whereas almost all other molecules are in a singlet state. Reactions between triplet and singlet molecules are forbidden by quantum mechanics, making oxygen relatively non-reactive at physiological conditions. A photosensitizer is a chemical compound that can be promoted to an excited state upon absorption of light and undergo intersystem crossing (ISC) with oxygen to produce singlet oxygen. This species is highly cytotoxic, rapidly attacking any organic compounds it encounters. It is rapidly eliminated from cells, in an average of 3 µs.
When a photosensitiser is in its excited state (3Psen*) it can interact with molecular triplet oxygen (3O2) and produce radicals and reactive oxygen species (ROS), crucial to the Type II mechanism. These species include singlet oxygen (1O2), hydroxyl radicals (•OH) and superoxide (O2−) ions. They can interact with cellular components including unsaturated lipids, amino acid residues and nucleic acids. If sufficient oxidative damage ensues, this will result in target-cell death (only within the illuminated area).
----Some photosensitizers；hemin, riboflavin,rose bengal, methylene, chorophyll
Many photosensitizers for PDT exist. They divide into porphyrins, chlorins and dyes. Examples include aminolevulinic acid (ALA), Silicon Phthalocyanine Pc 4, m-tetrahydroxyphenylchlorin (mTHPC) and mono-L-aspartyl chlorin e6 (NPe6).
Photosensitizers commercially available for clinical use include Allumera, Photofrin, Visudyne, Levulan, Foscan, Metvix, Hexvix, Cysview and Laserphyrin, with others in development, e.g. Antrin, Photochlor, Photosens, Photrex, Lumacan, Cevira, Visonac, BF-200 ALA, Amphinex and Azadipyrromethenes.
The major difference between photosensitizers is the parts of the cell that they target. Unlike in radiation therapy, where damage is done by targeting cell DNA, most photosensitizers target other cell structures. For example, mTHPC localizes in the nuclear envelope. In contrast, ALA localizes in the mitochondria and methylene blue in the lysosomes.
Cyclic tetrapyrrolic chromophores
Cyclic tetrapyrrolic molecules are fluorophores and photosensitisers. Cyclic tetrapyrrolic derivatives have an inherent similarity to the naturally occurring porphyrins present in living matter.
Porphyrins are a group of naturally occurring and intensely coloured compounds, whose name is drawn from the Greek word porphura, or purple. These molecules perform biologically important roles, including oxygen transport and photosynthesis and have applications in fields ranging from fluorescent imaging to medicine. Porphyrins are tetrapyrrolic molecules, with the heart of the skeleton a heterocyclic macrocycle, known as a porphine. The fundamental porphine frame consists of four pyrrolic sub-units linked on opposing sides (α-positions, numbered 1, 4, 6, 9, 11, 14, 16 and 19) through four methine (CH) bridges (5, 10, 15 and 20), known as the meso-carbon atoms/positions. The resulting conjugated planar macrocycle may be substituted at the meso- and/or β-positions (2, 3, 7, 8, 12, 13, 17 and 18): if the meso- and β-hydrogens are substituted with non-hydrogen atoms or groups, the resulting compounds are known as porphyrins.
The inner two protons of a free-base porphyrin can be removed by strong bases such as alkoxides, forming a dianionic molecule; conversely, the inner two pyrrolenine nitrogens can be protonated with acids such as trifluoroacetic acid affording a dicationic intermediate. The tetradentate anionic species can readily form complexes with most metals.
Porphyrin's highly conjugated skeleton produces a characteristic ultra-violet visible (UV-VIS) spectrum. The spectrum typically consists of an intense, narrow absorption band (ε > 200000 l mol−1 cm−1) at around 400 nm, known as the Soret band or B band, followed by four longer wavelength (450–700 nm), weaker absorptions (ε > 20000 L⋅mol−1⋅cm−1 (free-base porphyrins)) referred to as the Q bands.
The Soret band arises from a strong electronic transition from the ground state to the second excited singlet state (S0 → S2); whereas the Q band is a result of a weak transition to the first excited singlet state (S0 → S1). The dissipation of energy via internal conversion (IC) is so rapid that fluorescence is only observed from depopulation of the first excited singlet state to the lower-energy ground state (S1 → S0).
The key characteristic of a photosensitiser is the ability to preferentially accumulate in diseased tissue and induce a desired biological effect via the generation of cytotoxic species. Specific criteria:
Strong absorption with a high extinction coefficient in the red/near infrared region of the electromagnetic spectrum (600–850 nm)—allows deeper tissue penetration. (Tissue is much more transparent at longer wavelengths (~700–850 nm). Longer wavelengths allow the light to penetrate deeper and treat larger structures.)
Suitable photophysical characteristics: a high-quantum yield of triplet formation (ΦT ≥ 0.5); a high singlet oxygen quantum yield (ΦΔ ≥ 0.5); a relatively long triplet state lifetime (τT, μs range); and a high triplet-state energy (≥ 94 kJ mol−1). Values of ΦT= 0.83 and ΦΔ = 0.65 (haematoporphyrin); ΦT = 0.83 and ΦΔ = 0.72 (etiopurpurin); and ΦT = 0.96 and ΦΔ = 0.82 (tin etiopurpurin) have been achieved
Low dark toxicity and negligible cytotoxicity in the absence of light. (The photosensitizer should not be harmful to the target tissue until the treatment beam is applied.)
Preferential accumulation in diseased/target tissue over healthy tissue
Rapid clearance from the body post-procedure
High chemical stability: single, well-characterised compounds, with a known and constant composition
Short and high-yielding synthetic route (with easy translation into multi-gram scales/reactions)
Simple and stable formulation
Soluble in biological media, allowing intravenous administration. Otherwise, a hydrophilic delivery system must enable efficient and effective transportation of the photosensitiser to the target site via the bloodstream.
Low photobleaching to prevent degradation of the photosensitizer so it can continue producing singlet oxygen
Natural fluorescence (Many optical dosimetry techniques, such as fluorescence spectroscopy, depend on fluorescence.)
Photoimmunotherapy is an oncological treatment for various cancers that combines photodynamic therapy of tumor with immunotherapy treatment. Combining photodynamic therapy with immunotherapy enhances the immunostimulating response and has synergistic effects for metastatic cancer treatment.
Some photosensitisers naturally accumulate in the endothelial cells of vascular tissue allowing 'vascular targeted' PDT.
Verteporfin was shown to target the neovasculature resulting from macular degeneration in the macula within the first thirty minutes after intravenous administration of the drug.
Compared to normal tissues, most types of cancers are especially active in both the uptake and accumulation of photosensitizers agents, which makes cancers especially vulnerable to PDT. Since photosensitizers can also have a high affinity for vascular endothelial cells.
PDT is currently in clinical trials as a treatment for severe acne. Initial results have shown for it to be effective as a treatment only for severe acne. The treatment causes severe redness and moderate to severe pain and burning sensation. (see also: Levulan) One phase II trial, while it showed improvement, was not superior to blue/violet light alone.
As cited above, verteporfin was widely approved for the treatment of wet AMD beginning in 1999. The drug targets the neovasculature that is caused by the condition.
Photodynamic therapy - Wikipedia https://en.wikipedia.org/wiki/Photodynamic_therapy