Mechanisms of Phototoxic and Photoallergic Reactions

Allergic potential & molecular mechanism of skin sensitization of cinnamaldehyde under environmental UVB exposure

Fragrance, a key ingredient in cosmetics, often triggers skin allergy causes rashes, itching, dryness, and cracked or scaly skin. Cinnamaldehyde (CA), derived from the bark of the cinnamon tree, used as a fragrance and is a moderate skin sensitizer. CA exhibits strong UVB absorption, its allergic potential and the molecular mechanisms underlying skin sensitization under UVB exposure remain largely unexplored. To investigate the allergic potential and molecular mechanisms of CA-induced skin sensitization under ambient UVB radiation, we employed various alternative in-silico, in-chemico and in-vitro tools. CA under ambient UVB isomerizes from trans to cis CA after 1hr of exposure. Furthermore, DPRA assay and docking with simulation studies demonstrated the enhanced allergic potential of cis-CA. Additionally, our study evaluated intracellular ROS levels and the expression of Nrf2, Catalase, and MMP-2, and 9 in KeratinoSens cells, showing significant upregulation under UVB exposure in the presence of CA. Moreover, our findings indicate that CA activates THP-1 cells co-stimulatory surface marker (CD86) via the activation of intracellular ROS, phagocytosis, and genes of the TLR4 pathway. These insights into the mechanisms uncovered by our study are crucial for managing triggers of allergic skin diseases caused by fragrance use and concurrent exposure to environmental UVB/sunlight.

meso-Methyl BODIPY Photocages: Mechanisms, Photochemical Properties, and Applications

meso-methyl BODIPY photocages have recently emerged as an exciting new class of photoremovable protecting groups (PPGs) that release leaving groups upon absorption of visible to near-infrared light. In this Perspective, we summarize the development of these PPGs and highlight their critical photochemical properties and applications. We discuss the absorption properties of the BODIPY PPGs, structure-photoreactivity studies, insights into the photoreaction mechanism, the scope of functional groups that can be caged, the chemical synthesis of these structures, and how substituents can alter the water solubility of the PPG and direct the PPG into specific subcellular compartments. Applications that exploit the unique optical and photochemical properties of BODIPY PPGs are also discussed, from wavelength-selective photoactivation to biological studies to photoresponsive organic materials and photomedicine.

Drug-Induced Photosensitivity-From Light and Chemistry to Biological Reactions and Clinical Symptoms

Photosensitivity is one of the most common cutaneous adverse drug reactions. There are two types of drug-induced photosensitivity: photoallergy and phototoxicity. Currently, the number of photosensitization cases is constantly increasing due to excessive exposure to sunlight, the aesthetic value of a tan, and the increasing number of photosensitizing substances in food, dietary supplements, and pharmaceutical and cosmetic products. The risk of photosensitivity reactions relates to several hundred externally and systemically administered drugs, including nonsteroidal anti-inflammatory, cardiovascular, psychotropic, antimicrobial, antihyperlipidemic, and antineoplastic drugs. Photosensitivity reactions often lead to hospitalization, additional treatment, medical management, decrease in patient's comfort, and the limitations of drug usage. Mechanisms of drug-induced photosensitivity are complex and are observed at a cellular, molecular, and biochemical level. Photoexcitation and photoconversion of drugs trigger multidirectional biological reactions, including oxidative stress, inflammation, and changes in melanin synthesis. These effects contribute to the appearance of the following symptoms: erythema, swelling, blisters, exudation, peeling, burning, itching, and hyperpigmentation of the skin. This article reviews in detail the chemical and biological basis of drug-induced photosensitivity. The following factors are considered: the chemical properties, the influence of individual ranges of sunlight, the presence of melanin biopolymers, and the defense mechanisms of particular types of tested cells.

Systemic drug photosensitivity-Culprits, impact and investigation in 122 patients

BACKGROUND

Systemic drugs are a potentially reversible cause of photosensitivity. We explore prevalence, impact, phototest findings and culprit drugs.

METHODS

Retrospective review of patients was diagnosed with drug-induced photosensitivity in a specialist photoinvestigation centre (2000-2016), using data recorded in standardized pro forma. Patients underwent detailed clinical evaluation. Monochromator phototesting was performed to 300 ± 5 nm, 320 ± 10 nm, 330 ± 10 nm, 350 ± 20 nm, 370 ± 20 nm, 400 ± 20 nm, 500 ± 20nm and 600 ± 20 nm. Broadband UVA and solar-simulated radiation (SSR) testing were performed, and photopatch testing and laboratory tests examined for other causes of photosensitivity. DLQI was evaluated.

RESULTS

Prevalence of drug-induced photosensitivity was 5.4% (122/2243) patients presenting with photosensitivity. Patients with drug-induced photosensitivity were 52.5% female; median 62 years (range 11-86); phototype I (17.2%), II (39.3%), III (26.2%), IV (6.5%), V (4.1%). Fifty-five (45.1%) patients had reduced erythemal thresholds on monochromator phototesting: 83.6%% to UVA alone, 14.5% to both UVA and UVB, 1.8% to UVA and visible light; 61.4% (n = 75) showed abnormal response to broadband UVR. Drugs implicated: quinine (11.5%), diuretics (10.7%; thiazide 9.8%), antifungals (9.8%), proton-pump-inhibitors (9.8%), angiotensin-converting enzyme inhibitors (7.4%), anti-inflammatory drugs (6.6%), statins (5.7%), selective serotonin reuptake inhibitors (4.9%), calcium channel antagonists (3.3%), anti-epileptics (3.3%), tricyclic antidepressants (3.3%), beta-blockers (2.5%), antibiotics (2.5%), others (≤1.6% cases each). Emerging culprits included azathioprine (2.5%) and biologics (TNF-α inhibitors, denosumab; 2.5%). Median DLQI was 11 (range 2-27) for the past year.

CONCLUSION

Classically described photosensitizing drugs such as thiazides and quinine remain common offenders, while emerging culprits include biologics such as TNF-a inhibitors and proton-pump-inhibitors. There is very large impact on life quality; identification facilitates measures including drug cessation and implementation of appropriate photoprotection.

Singlet versus Triplet Excited State Mediated Photoinduced Dehalogenation Reactions of Itraconazole in Acetonitrile and Aqueous Solutions

Photoinduced dehalogenation of the antifungal drug itraconazole (ITR) in acetonitrile (ACN) and ACN/water mixed solutions was investigated using femtosecond and nanosecond time-resolved transient absorption (fs-TA and ns-TA, respectively) and nanosecond time-resolved resonance Raman spectroscopy (ns-TR³) experiments. An excited resonance energy transfer is found to take place from the 4-phenyl-4,5-dihydro-3H-1,2,4-triazol-3-one part of the molecule to the 1,3-dichlorobenzene part of the molecule when ITR is excited by ultraviolet light. This photoexcitation is followed by a fast carbon-halogen bond cleavage that leads to the generation of radical intermediates via either triplet and/or singlet excited states. It is found that the singlet excited state-mediated carbon-halogen cleavage is the predominant dehalogenation process in ACN solvent, whereas a triplet state-mediated carbon-halogen cleavage prefers to occur in the ACN/water mixed solutions. The singlet-to-triplet energy gap is decreased in the ACN/water mixed solvents and this helps facilitate an intersystem crossing process, and thus, the carbon-halogen bond cleavage happens mostly through an excited triplet state in the aqueous solutions examined. The ns-TA and ns-TR³ results also provide some evidence that radical intermediates are generated through a homolytic carbon-halogen bond cleavage via predominantly the singlet excited state pathway in ACN but via mainly the triplet state pathway in the aqueous solutions. In strong acidic solutions, protonation at the oxygen and/or nitrogen atoms of the 1,2,4-triazole-3-one group appears to hinder the dehalogenation reactions. This may offer the possibility that the phototoxicity of ITR due to the generation of aryl or halogen radicals can be reduced by protonation of certain moieties in suitably designed ITR halogen-containing derivatives.