Aging of the retina is accompanied by a sharp increase in the content of lipofuscin granules and bisretinoid A2E in the cells of the retinal pigment epithelium (RPE) of the human eye. It is known that A2E can have a toxic effect on RPE cells. However, the specific mechanisms of the toxic effect of A2E are poorly understood. We investigated the effect of the products of photooxidative destruction of A2E on the modification of bovine serum albumin (BSA) and hemoglobin from bovine erythrocytes. A2E was irradiated with a blue light-emitting diode (LED) source (450 nm) or full visible light (400–700 nm) of a halogen lamp, and the resulting water-soluble products of photooxidative destruction were investigated for the content of carbonyl compounds by mass spectrometry and reaction with thiobarbituric acid. It has been shown that water-soluble products formed during A2E photooxidation and containing carbonyl compounds cause modification of serum albumin and hemoglobin, measured by an increase in fluorescence intensity at 440–455 nm. The antiglycation agent aminoguanidine inhibited the process of modification of proteins. It is assumed that water-soluble carbonyl products formed as a result of A2E photodestruction led to the formation of modified proteins, activation of the inflammation process, and, as a consequence, to the progression of various senile eye pathologies.

Age-related macular degeneration (AMD) is the primary cause of central blindness among the elderly. AMD is associated with progressive accumulation of lipofuscin granules in retinal pigment epithelium (RPE) cells. Lipofuscin contains bisretinoid fluorophores, which are photosensitizers and are phototoxic to RPE and neuroretinal cells. In the presence of oxygen, bisretinoids are also oxidized, forming various products, consisting primarily of aldehydes and ketones, which are also potentially cytotoxic. In a prior study, we identified that in AMD, bisretinoid oxidation products are increased in RPE lipofuscin granules. The purpose of the present study was to determine if these products were toxic to cellular structures. The physicochemical characteristics of bisretinoid oxidation products in lipofuscin, which were obtained from healthy donor eyes, were studied. Raman spectroscopy and time-of-flight secondary ion mass spectrometry (ToF–SIMS) analysis identified the presence of free-state aldehydes and ketones within the lipofuscin granules. Together, fluorescence spectroscopy, high-performance liquid chromatography, and mass spectrometry revealed that bisretinoid oxidation products have both hydrophilic and amphiphilic properties, allowing their diffusion through lipofuscin granule membrane into the RPE cell cytoplasm. These products contain cytotoxic carbonyls, which can modify cellular proteins and lipids. Therefore, bisretinoid oxidation products are a likely aggravating factor in the pathogenesis of AMD.

The objective of this study was screening of ommochromes from the compound eyes of insects and comparison of their antioxidant properties. Ommochromes were isolated in preparative quantities from insects of five different families: Stratiomyidae, Sphingidae, Blaberidae, Acrididae, and Tenebrionidae. The yield of ommochromes (dry pigment weight) was 0.9-5.4% of tissue wet weight depending on the insect species. Isolated pigments were analyzed by high-performance liquid chromatography and represented a mixture of several ommochromes of the ommatin series. The isolated ommochromes displayed a pronounced fluorescence with the emission maxima at 435-450 nm and 520-535 nm; furthermore, the emission intensity increased significantly upon ommochrome oxidation with hydrogen peroxide. The ommochromes produced a stable EPR signal consisting of a singlet line with g = 2.0045-2.0048, width of 1.20-1.27 mT, and high concentration of paramagnetic centers (> 10(17) spin/g dry weight). All the investigated ommochromes demonstrated high antiradical activity measured from the degree of chemiluminescence quenching in a model system containing luminol, hemoglobin, and hydrogen peroxide. The ommochromes strongly inhibited peroxidation of the photoreceptor cell outer segments induced by visible light in the presence of lipofuscin granules from the human retinal pigment epithelium, as well as suppressed iron/ascorbate-mediated lipid peroxidation. The obtained results are important for understanding the biological functions of ommochromes in invertebrates and identifying invertebrate species that could be used as efficient sources of ommochromes for pharmacological preparations to prevent and treat pathologies associated with the oxidative stress development.

A comparative study of melanin and ommochrome-containing samples, isolated from the black soldier fly (BSF) by enzymatic hydrolysis, alkaline and acid alcohol extraction or by acid hydrolysis, was carried out. Melanin was isolated both as a melanin-chitin complex and as a water-soluble melanin. Acid hydrolysis followed by delipidization yielded a more concentrated melanin sample, the electron spin resonance (ESR) signal of which was 2.6 × 1018 spin/g. The ommochromes were extracted from the BSF eyes with acid methanol. The antiradical activity of BSF melanins and ommochromes was determined by the method of quenching of luminol chemiluminescence. It has been shown that delipidization of water-soluble melanin increases its antioxidant properties. A comparison of the antioxidant activity of BSF melanins and ommochromes in relation to photoinduced lipid peroxidation was carried out. The ESR characteristics of native and oxidized melanins and ommochromes were studied. It is assumed that H. illucens adult flies can be a useful source of natural pigments with antioxidant properties.

The antioxidant and antiglycation activity of the water-soluble heterocyclic antioxidant 6‑hydroxy-2-aminobenzothiazole N-acetylcysteinate (HABTI ACC) has been studied. The high antiradical activity of this substance has been found by the chemiluminescence method. HABTI ACC has been found to show the high antioxidant activity in the peroxidation of photoreceptor cells induced by ultraviolet radiation, ferrous ions, and visible light in the presence of age pigment lipofuscin or its A2E fluorophore. HABTI ACC effectively inhibits the fructosylation of serum albumin and proteins of photoreceptor cells. The HABTI ACC inhibitory ability in the process of fructose albumin modification is comparable with the aminoguanidine and pyridoxamine activity, the known antiglycation compounds, and is much higher than that of mexidol. It is suggested that the use of this compound is promising in pharmacological practice for the prevention and treatment of metabolic syndrome.

Актуальность. Недавно нами было показано, что при возрастной макулярной дегенерации сетчатки наблюдается повышенное содержание продуктов фотоокисления и фотодеградации бисретиноидов по сравнению с нормой. Поэтому на сегодняшний день вопрос о фототоксичности этих продуктов становится актуальным для решения проблемы поиска путей лечения и профилактики патологии. Цель. Провести сравнительное исследование фотосенсибилизирующего действия N-ретинилиден-N-ретинилэтаноламина (А2Е) и продуктов его фотоокисления и фотодеградации на индуцированную видимым светом пероксидацию липидов фоторецепторных мембран. Материалы и методы. При помощи метода высокоэффективной жидкостной хроматографии были получены отдельные фракции неокисленных и окисленных бисретиноидов в хлороформном экстракте липофусциновых гранул из ретинального пигментного эпителия кадаверных глаз. Результаты. Проведено сравнительное исследование фототоксических свойств неокисленных и окисленных бисретиноидов липофусциновых гранул из клеток ретинального пигментного эпителия глаза человека на пероксидацию липидов наружных сегментов фоторецепторных клеток. Выводы. Окисленные бисретиноиды липофусциновых гранул менее фототоксичны по сравнению с их неокисленными формами. Background. Recently we have shown that age-related macular degeneration is associated with higher than normal levels of bisretinoid photo-oxidation and photo-degradation products. Therefore, the issue of their phototoxicity currently becomes relevant for finding ways to treat and prevent this pathology. Aim. To conduct a comparative study of the photosensitizing effect of N-retinylidene-N-retinylethanolamine (A2E) and its photooxidation and photodegradation products on light-induced lipid peroxidation in photoreceptor membranes. Materials and methods. Using high-performance liquid chromatography fractions of unoxidized and oxidized bisretinoids were isolated in the chloroform extract of lipofuscin granules from the retinal pigment epithelium of cadaver eyes. Results. The study compared phototoxic effects of unoxidized and oxidized bisretinoids of lipofuscin granules from human retinal pigment epithelial cells on lipid peroxidation in rod outer segments. Conclusions. Oxidized bisretinoids of lipofuscin granules are less phototoxic compared to their unoxidized forms.

Model studies on Coumarin 343–detonation nanodiamond complexes are described. The complexation of coumarin molecules with diamond nanoparticles due to covalent bonding leads to a considerable change in their spectral-luminescence properties, which makes it possible to distinguish between the behaviors of a free dye and a bound luminophore in the studied objects, in particular, in cell cultures. Experiments with an acute monocytic human leukemia culture show that the studied diamond nanocomplexes are easily captured by the cells and visualized in them; therefore, these complexes can be used to transport photocontrolled reagents and, ultimately, new drugs.

Purpose. Comparative study of the melanin content in melanosomes and melanolipofuscin granules from cells of the retinal pigment epithelium of the human eye. Material and methods. The research and comparison of melanosomes and melanolipofuscin granules from cells of human retinal pigment epithelium was carried out by the method of electron paramagnetic resonance (EPR) spectroscopy. Results. It was shown that the EPR spectra in both types of melanin granules, including the main parameters, were similar and corresponded to the EPR spectra characteristic of natural eumelanins and synthetic DOPA-melanin. Conclusion. The results of study indicate that in melanolipofuscin granules as well as in melanosomes, the pigment melanin (eumelanin) is contained, as evidenced by the similarity of their paramagnetic properties. Melanin content in melanosomes is higher than in melanolipofuscin granules on average of one and a half times, which follows from the concentration of their paramagnetic centers per granule.

The treatment with light or light therapy with laser or LED sources at low irradiation intensities is associated with the so-called photobiomodulation process, that is, the beneficial effect of light on certain cellular functions. As a general rule, the treatment with light is carried out in the far red or near infrared spectral ranges, since the shorter wave irradiation can have various toxic effects on the cells.

This work has demonstrated that the life stages of the Hermetia illucens fly are characterized by varying melanin contents with the maximum melanin amount being detected in the pupa. It has been observed that active synthesis of the pigment takes place in the prepupa and coincides with the time when the population migrated for pupation. It has been noted that a high manganese content in the prepupa and pupa indicates the important role that this biogenic element plays in organogenesis and melanogenesis in H. illucens. It has been revealed that in the imago and pupa, the melanin demonstrates broad-range antimicrobial activity and contribute to the insect protection against bacterial and fungal infections.

Melanin with a high antioxidant and sorption activity comparable to that of synthetic dioxyphenylalanine (DOPA)-melanin was isolated from the biomass of the darkling beetle Alphitobius diaperinus. The pigment was extracted with a solution of potassium hydroxide, followed by precipitation with concentrated hydrochloric acid and hydrolysis of the resulting precipitate with the same acid. The electron paramagnetic resonance (EPR) signal of melanin was characteristic of eumelanins with a spin concentration of 4.9 × 1017 spin per 1 g of dry weight. The melanin concentration that induced 50% inhibition of peroxidation was 9.2 μg/mL (the analogous concentration of DOPA-melanin was 8.0 μg/mL). The maximum of methylene-blue binding to the beetle melanin was 700 mg of dye per 1 g of dry weight of the preparation. The lipid-free melanin preparation exhibited antiradical activity.

Из биомассы жука чернотелки Alphitobius diaperinus выделен меланин с высокой антиоксидантной и сорбционной активностями, сопоставимыми с таковыми для синтетического диоксифенилаланина (ДОФА)-меланина. Пигмент экстрагировали раствором гидроксида калия с последующим осаждением концентрированной соляной кислотой и гидролизом полученного осадка этой же кислотой. Сигнал электронного парамагнитного резонанса меланина был характерен для эумеланинов с концентрацией спинов 4.9 1017 спин/г сухой массы. Концентрация меланина, вызывающая 50%-ное ингибирование процесса пероксидации, составляла 9.2 мкг/мл (аналогичная концентрация ДОФА-меланина - 8.0 мкг/мл). Максимальное связывание метиленового голубого меланином жука составляло 700 мг красителя на 1 г сухой массы препарата. Очищенный от жира препарат меланина проявлял антирадикальную активность.

The effect of superoxide radicals on melanin destruction and degradation of melanosomes isolated from cells of retinal pigment epithelium (RPE) of the human eye was studied. We found that potassium superoxide causes destruction of melanin in melanosomes of human and bovine RPE, as well as destruction of melanin from the ink bag of squid, with the formation of fluorescent decay products having an emission maximum at 520-525 nm. The initial kinetics of the accumulation of the fluorescent decay products is linear. Superoxide radicals lead simultaneously to a decrease in the number of melanosomes and to a decrease in concentration of paramagnetic centers in them. Complete degradation of melanosomes leads to the formation of a transparent solution containing dissolved proteins and melanin degradation products that do not exhibit paramagnetic properties. To completely degrade one melanosome of human RPE, 650 ± 100 fmol of superoxide are sufficient. The concentration of paramagnetic centers in a melanolipofuscin granule of human RPE is on average 32.5 ± 10.4% (p < 0.05, 150 eyes) lower than in a melanosome, which indicates melanin undergoing a destruction process in these granules. RPE cells also contain intermediate granules that have an EPR signal with a lower intensity than that of melanolipofuscin granules, but higher than that of lipofuscin granules. This signal is due to the presence of residual melanin in these granules. Irradiation of a mixture of melanosomes with lipofuscin granules with blue light (450 nm), in contrast to irradiation of only melanosomes, results in the appearance of fluorescent melanin degradation products. We suggest that one of the main mechanisms of age-related decrease in melanin concentration in human RPE cells is its destruction in melanolipofuscin granules under the action of superoxide radicals formed during photoinduced oxygen reduction by lipofuscin fluorophores.