Neutrophils release decondensed chromatin or extracellular traps (NETs) in response to various physiological and pharmacological stimuli. Apart from host defensive functions, NETs play an essential role in the pathogenesis of various autoimmune, inflammatory, and malignant diseases. In recent years, studies have been performed on photo-induced NET formation, mainly activated by UV radiation. Understanding the mechanisms of NET release under the influence of UV and visible light is important to control the consequences of the damaging effects of electromagnetic radiation. Raman spectroscopy was applied to record characteristic Raman frequencies of various reactive oxygen species (ROS) and low-frequency lattice vibrational modes for citrulline. NETosis was induced by irradiation with wavelength-switchable LED sources. Fluorescence microscopy was used to visualize and quantify NET release. The ability of five wavelengths of radiation, from UV-A to red light, to induce NETosis was investigated at three different energy doses. We demonstrated, for the first time, that NET formation is activated not only by UV-A but also by three spectra of visible light: blue, green, and orange, in a dose-dependent manner. Using inhibitory analysis, we established that light-induced NETosis proceeds through NADPH oxidase and PAD4. The development of new drugs designed to suppress NETosis, especially when induced by exposure to intense UV and visible light, can help to mitigate light-induced photoaging and other damaging effects of electromagnetic radiation.

We present a Raman spectroscopy and quantum chemical computational study for model phospholipid membrane molecule dipalmitoylphosphatidylcholine (DPPC) mixed with cholesterol or melatonin at various concentrations. Utilizing a confocal Raman microspectroscopy setup, we capture a DPPC conformation state by evaluating the number of trans/gauche bonds using I 1064 /I 1090 and I 1128 /I 1090 vibrational mode intensity ratios. We show that the cholesterol increases the number of trans bonds in DPPC hydrocarbon chains, that is, causing membrane ordering, while melatonin addition introduces gauche conformers, generating disorder. It is noticed that the I 1128 /I 1090 intensity ratio is a more suitable parameter for the characterization of DPPC hydrocarbon chain structural properties compared with I 1064 /I 1090 . We thus clarify our experimental observations by performing careful density functional theory (DFT) calculations of Raman spectra for DPPC tails, containing up to three gauche bonds at different chain positions. The obtained results demonstrate the strong interconnection between 1064 and 1090 cm À1 vibrational modes originating from their complex splitting and shifting along with continuous Raman activity redistribution upon various gauche bonds introduction, while it is not the case for 1128 and 1090 cm À1 modes pair.