Ahmed Riyadh Hamzah Albuhaydar

Maintaining cellular homeostasis in epidermal keratinocytes — including membrane integrity, mitochondrial bioenergetics, intracellular Ca²⁺ regulation, redox balance, and inflammatory tone is essential for skin function and is highly vulnerable to UVA-driven oxidative disruption. Resveratrol (Res), a natural stilbenoid antioxidant, has shown promising photoprotective effects, although its therapeutic potential is constrained by poor aqueous solubility and rapid photodegradation. In the present work, we examined whether pretreatment with PLGA-encapsulated Res nanoparticles (Res-NPs) is able to preserve a broad set of physiological functions in cultured human keratinocytes (HaCaT) following UVA irradiation (10 J/cm²). Compared with the free compound at equivalent concentration (50 µM), Res-NPs markedly reduced UVA-induced lactate dehydrogenase (LDH) leakage (~38% - ~9% of total) and preserved the mitochondrial membrane potential, with the JC-1 red/green ratio held at about 89% of basal values. Intracellular ATP was maintained at 88% of control, while the typical UVA-driven Ca²⁺ overload was substantially attenuated (held below 1.2-fold of basal vs. 2.8-fold for UVA alone). Redox homeostasis was preserved, with the GSH/GSSG ratio close to physiological values. Pro-inflammatory cytokine secretion (IL-6, IL-8, TNF-α) was suppressed by ~70–80%. Furthermore, qPCR analysis showed that Res-NPs largely restored the expression of late differentiation markers (filaggrin, involucrin, loricrin), and the scratch-wound assay revealed near-normal migratory capacity (≈89% closure at 48h). Taken together, these results support nanoencapsulation as an effective strategy for safeguarding the integrated physiological functions of keratinocytes under UVA stress.

Citrullus colocynthis (L.) Schrad, known as colocynth or bitter apple, is a perennial species of cucurbit native to dry zones of Africa, Asia and the Mediterranean basin. Bitter gourd is rich in cucurbitacins (highly oxygenated tetracyclic triterpenoids) and its fruit pulp, seeds and leaves have been a subject of continuous study interest due to their marked antidiabetic and anticancer activities. However, the clinical translation of colocynth-derived preparations is hampered by the absence of standardised extraction techniques, the variation in phytochemical profiles between regional accessions, and the short therapeutic window due to cucurbitacin-associated toxicity. This review offers a comprehensive evaluation of selective extraction procedures for the enrichment of cucurbitacins (mainly types B, E, I and their glycosides) from C. colocynthis plant material and evaluation of contemporary analytical quality control platforms like HPLC-UV, HPLC-MS/MS, UPLC-MS/MS and HPTLC techniques which are important for batch-to-batch standardisation. The molecular mechanisms of the antidiabetic action of cucurbitacins are discussed, focusing on the modulation of the AMPK/PI3K/Akt cascade, GLUT4 translocation and GLP-1 stimulation, along with the anticancer pathways including the inhibition of JAK2/STAT3 and the induction of apoptosis by regulation of Bax/Bcl-2 and cell cycle arrest. Finally, the toxicological profile of colocynth preparations is critically discussed and practical options for the mitigation of side effects are given, including dose optimisation, nanoformulation, prodrug derivatisation and co-administration with hepatic-protective drugs. This review intends to connect ethnopharmacological knowledge with evidence-based medicinal development of cucurbitacin-rich colocynth extracts.

Paracetamol (acetaminophen, APAP) is one of the most popular analgesic and antipyretic medications in the world, although overdose is still a major cause of acute liver failure in developed countries. The hepatotoxic process involves essentially excessive synthesis of N-acetyl-p-benzoquinone imine (NAPQI), which depletes hepatic glutathione reserves, covalently alters mitochondrial proteins, and initiates a cascade of oxidative damage leading to cell death. The current work studied the hepatoprotective effect of methanolic extract produced from Rosmarinus officinalis L. callus culture against APAP-induced cytotoxicity in human hepatocellular carcinoma (HepG2) cells. Callus cultures were produced on Murashige and Skoog medium with 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BAP). Lyophilised callus was extracted with methanol and phytochemical screening indicated the presence of phenolic acids, flavonoids and diterpene substances such as rosmarinic acid and carnosic acid. The HepG2 cells were pre-incubated with the callus extract at various concentrations (25-200 µg/mL) before the APAP insult (10 mM, 24 h). The extract dramatically improved cell survival (from 41.8% to 84.1%), reduced the production of reactive oxygen species (ROS), restored the mitochondrial membrane potential (ΔΨm) and boosted the intracellular glutathione level in a concentration-dependent manner. Moreover, the extract lowered the level of malondialdehyde (MDA) and increased the activity of superoxide dismutase (SOD) and catalase (CAT). These findings indicate that R. officinalis callus extract offers meaningful cytoprotection against APAP-mediated hepatic injury through mitigation of oxidative stress and preservation of mitochondrial integrity.

Ultraviolet radiation is one of the major environmental hazards for skin homeostasis, causing overproduction of melanin and impairing melanocyte survival through oxidative stress-driven mechanisms. The present study examined the modulatory effects of five structurally diverse polyphenolic compounds, epigallocatechin-3-gallate (EGCG), resveratrol, curcumin, gallic acid, and quercetin, on melanin biosynthesis and cellular survival in B16F10 murine melanoma cells exposed to UVB irradiation (30 mJ/cm2). Cells were pre-treated with polyphenols at doses of 10–200 μM for 24 h before UV exposure. Melanin content, tyrosinase activity, cell viability (MTT assay), reactive oxygen species (ROS) formation, and apoptotic markers (Bcl-2/Bax ratio, caspase-3 activation) were evaluated. Additionally, Western blot analysis was performed to determine the expression of major melanogenic transcription factors such as microphthalmia-associated transcription factor (MITF) and downstream signalling mediators (p38 MAPK, PI3K/Akt, Nrf2). All polyphenols studied strongly inhibited UV-induced melanin formation and tyrosinase activity in a dose-dependent manner. EGCG and resveratrol showed the best inhibitory efficacy. Moreover, pre-treatment with these chemicals increased the survival of melanocytes exposed to UV exposure, decreased intracellular ROS generation and modulated the Bcl-2 /Bax ratio toward an anti-apoptotic phenotype. Interestingly, we observed that Nrf2 nuclear translocation was significantly enhanced in polyphenol-treated cells, which was negatively related to melanin production. Collectively, our findings reveal the potential value of natural polyphenols in photoprotective dermatological formulations with the capacity to simultaneously control melanogenesis and increase melanocyte survival under UV-induced oxidative stress.

Ultraviolet B (UVB) is one of the most persistent environmental stresses to which the skin is exposed and the dermal fibroblast, located immediately below the epidermis, is burdened with a large part of the consequent oxidative stress. Much of that damage ends up in the mitochondrion and shows up as a drop in membrane potential, reduced respiration and depleted ATP. In this work we asked a really simple question: can a small group of plant polyphenols, selected precisely for their photostability, restore mitochondrial function in primary human dermal fibroblasts after a sub-lethal acute UVB dose? Cells were irradiated with 60mJ/cm2 and treated with quercetin, rutin or silibinin. A comparison, trans-Resveratrol, a photolabile polyphenol, was co-processed. We monitored photostability, viability, intracellular reactive oxygen species (ROS), mitochondrial membrane potential (ΔΨm), ATP content, oxygen consumption rate and several biogenesis indicators. The three photostable compounds retained 83–91% of their starting material after a cumulative 150 mJ/cm² of exposure, while resveratrol decreased to approximately one quarter. Rutin and quercetin were the most effective in rescuing the cells, restoring basal and maximum respiration to near control levels, recovering ΔΨm, reducing ROS levels and partially restoring mtDNA copy number and PGC-1α expression. Resveratrol was not very active, similar to its degradation under light. The results show that photostability is not a trivial element but a real predictor of the usefulness of a polyphenol in a photo-oxidative situation.

The effect of plant polyphenolic compounds (PPs) on the viability of human keratinocytes exposed to ultraviolet (UV) radiation of range C (UVС) and the number of single-stranded DNA breaks in the nuclei of these cells was studied. The experimental data obtained indicate that, along with the cytoprotective effect, the addition of silybin and acacetin immediately after the UVC exposure leads to a significant decrease in the number of single-stranded DNA breaks in the nuclei of HaCaT keratinocytes 2 and 5 h after exposure. It was concluded that PPs are able to reduce the destructive effect of UV radiation on skin cells, reducing the number of genetic damage.

The work investigated the responses of cultured human keratinocytes to ultraviolet radiation in the C range (UVC) with and without a number of plant polyphenolic compounds. The experimental data obtained in this work indicate a cytoprotective effect of the PPs added immediately after UVC exposure. The cytoprotective activity of plant polyphenolic compounds was reduced in the series: acacetin, silybin, baikalein, leontopodium acid, quercetin, cyanidine chloride, taxifolin, trans-ferulic acid. The effect of UVC irradiation with and without of acacetin on the process of phosphorylation of histones H2AX, the triggering mechanism for the repair of single-stranded DNA damage, was also investigated in keratinocytes. It has been established that, H2AX phosphorylation is activated in response to UVC radiation and acacetin has a significant effect on the kinetics of this process. It is concluded that the PPs can reduce the destructive effect of UVR on the skin cells, activating the process of repairing genetic damage.

Исследованы ответы культивируемых клеток человека – кератиноцитов – на воздействие ультрафиолетового излучения коротковолнового диапазона без растительных полифенольных соединений и совместно с рядом из них. Полученные экспериментальные данные свидетельствуют о наличии цитопротекторного действия указанных соединений, добавленных сразу после воздействия ультрафиолетом. Цитопротекторная активность снижалась в ряду акацетин – силибин – байкалеин – леонтоподиевая кислота – кверцетин – цианидин хлорид – таксифолин – феруловая кислота. Исследовано влияние ультрафиолетового облучения коротковолнового диапазона без акацетина и в его присутствии на реакцию фосфорилирования гистонов H2AX, запускающую процесс репарации однонитевых повреждений ДНК. Установлено, что в ответ на такое облучение в кератиноцитах активируется фосфорилирование гистонов H2AX, и акацетин оказывает существенное влияние на кинетику этой реакции. Сделан вывод, что растительные полифенольные соединения способны уменьшать деструктивное воздействие ультрафиолетового излучения на клетки кожи, активируя процесс репарации генетических повреждений.‏

Исследованы ответы культивируемых клеток человека – кератиноцитов и фибробластов – на воздействие физиологических доз ультрафиолетового излучения без растительных полифенольных соединений и совместно с такими из них, как рутин, кверцетин, таксифолин, силибин и байкалеин. Полученные экспериментальные данные свидетельствуют о наличии синергизма в действии физиологических доз ультрафиолетового излучения и указанных соединений на воспалительные сигнальные пути в кератиноцитах и фибробластах. Сделан вывод, что выявленный синергизм, способствуя адаптации кожи к последующему воздействию ультрафиолета, может быть одним из механизмов фотозащитного действия растительных полифенольных соединений.‏

Solar broadband UV irradiation is commonly regarded as a major causative reason for cutaneous photoaging. The pro-aging molecular pathways and cellular targets affected by UVA+UVB light in human skin have been extensively investigated. Notwithstanding growing knowledge in mechanisms of photoaging, research and development of clinically efficient, nontoxic, and sustainable topical preparations providing full physical, chemical, and biological photoprotection still remain a great challenge for pharmaceutical and cosmetic industries. In this study, we are proposing a panel of the in vitro methods for preselection of natural photoprotective substances with high photostability and low phototoxicity able of absorbing a broadband UVA+UVB irradiation (physical sunscreen), reducing UV-related overproduction of free radicals and loss of endogenous antioxidants (chemical protection), and attenuating UV-induced cytotoxicity and immune and metabolic responses (biological protection) in primary human epidermal keratinocytes and immortalized human keratinocyte cultures. Our data showed that secondary metabolites biosynthesized in plant cells in response to UV irradiation, such as phenylpropanoids and their glycosylated metabolites, aglycons and glycosylated flavonoids, and leontopodic acids, hold the best promise for complete natural topical prevention of photoaging and rejuvenation of photoaged skin. Meristem plant cell cultures elicited by solar simulating UV could be the most environmentally sustainable biotechnological source of polyphenols with combined photoprotective and antiaging properties.

едставлены экспериментальные данные, свидетельствующие о возможности использования различных растительных полифенольных соединений в качестве химических фильтров ультрафиолетового излучения диапазонов А и В. Для расчета эффективности солнцезащитного действия регистрировали спектры поглощения разбавленных растворов растительных полифенольных соединений и определяли величину оптической плотности в области 290 – 400 нм. Установлено, что у большинства исследованных соединений эффективность солнцезащитного действия сравнима или даже превышает эффективность солнцезащитного действия стандартного химического фильтра – бензофенона-3, широко используемого в солнцезащитной косметике. Среди исследованных растительных полифенольных соединений выявлены устойчивые к воздействию ультрафиолетового излучения, а также соединения, в частности ресвератрол и халкон, которые разрушаются с образованием цитотоксичных продуктов даже при кратковременном воздействии ультрафиолетового излучения. При моделировании повреждающего действия ультрафиолетового излучения на клетки кожи среди устойчивых к нему растительных полифенольных соединений выявлены такие, которые обладают эффективным цитопротекторным действием и представляют интерес как потенциальные компоненты солнцезащитных средств. = The aim of research was to quantify in vitro the effectiveness of plant polyphenols as chemical UV-sunscreens. Sun protection factor (SPF) of plant polyphenols (PPs) was determined on the base of spectrophotometric analysis of dilute solutions. Human keratinocytes (HaCaT) viability and proliferation were estimated using PrestoBlue™ reagent. UV-resistant sunscreens possessed very high SPF were found among PPs studied. These compounds effectively protected keratinocytes against UV-induced injury in vitro. We also found that some PPs e. g. resveratrol and chalcone were easily converted by UV-irradiation into extremely cytotoxic intermediates. Our data strongly suggest that PPs may be important component in cosmetic formulations for skin care and sun protection.‏

Кафедра физиологии человека и животных существует в БГУ с 1922 г. На базе фундаментальных исследований, раскрывающих молекулярные механизмы, лежащие в основе биологической активности природных полифенольных соединений, и закономерности, определяющие зависимость между их структурой и свойствами, разработаны инновационные подходы к созданию новых средств защиты и лечения кожи. Созданы и апробированы клеточные модели, позволяющие выявить и оценить специфическую активность потенциальных средств для химиопрофилактики и терапии среди веществ, обладающих противовоспалительным и фотопротекторным действием. Установлено изменение электрических характеристик мембраны идентифицированных нервных клеток в зависимости от возраста животного и в условиях химического стресса. Получены доказательства и выявлены механизмы трансформации рецепторной функции кишечника после кратковременной гипоксии или длительного приема антибиотиков. = New means of skin protection and treatment of the skin diseases were created on the basis of fundamental research revealing the molecular mechanisms underlying the biological activity of natural polyphenolic compounds in relationship between their structure and properties. Cellular models for screening of potential agents for chemoprophylaxis and therapy, among the substances with anti-inflammatory and photoprotective action, were developed and tested. Electrical properties of identified neurons membrane were modifying during ageing and in chemical stress conditions. Evidence for receptor function transformation in bowel after short-term hypoxia and chronic use of antibiotics and mechanisms their underlined were obtained.

Известно, что клеточные ответы на воздействие ультрафиолетового излучения (УФИ) опосредованы активными формами (АФ) кислорода и азота. Еще несколько лет назад внутриклеточную продукцию АФ кислорода, главным образом синглетного кислорода и супероксид радикала, при воздействии УФИ рассматривали только как результат инициирования быстрых фотохимических процессов возбужденными эндогенными фотосенсибилизаторами (например, рибофлавином) непосредственно во время облучения [1, 2]. Однако в последние годы было показано, что повышенная продукция АФ кислорода, а также монооксида азота и пероксинитрита наблюдается в облученных клетках и после прекращения воздействия УФИ [3, 4]. Такая пролонгированная продукция биорадикалов (30 мин и более) осуществляется в результате активации фермент-контролируемых редокс реакций. Ключевую роль в этом процессе играют кератиноциты–основной клеточный компонент кожи. После воздействия солнечного УФ-излучения они производят воспалительные медиаторы, в том числе простагландины, хемокины, цитокины и молекулы адгезии [4–6], которые в свою очередь активируют иммуннокомпетентные клетки, продуцирующие в области формирующегося воспаления большое количество оксида азота, супероксида, H2O2 и гипохлорита [7]. Мы предположили, что ведущую роль в развитии воспалительной реакции клеток кожи при воздействии УФ-облучения играют АФ кислорода и азота, образующиеся в пострадиационный период. С целью проверки данной гипотезы нами было исследовано действие перехватчиков АФ кислорода и азота на различные этапы в последовательности событий, инициируемых в клетках кожи при воздействии УФ-излучения. В качестве перехватчиков АФ кислорода и азота были использованы природные полифенольные соединения (ППС). Для моделирования воспалительных процессов, протекающих в коже, использовали культивируемые кератиноциты. ‏