Two dietary polyphenols, fisetin and luteolin, reduce inflammation but augment DNA damage-induced toxicity in human RPE cells

Flavonoids as Potential Therapeutics Against Neurodegenerative Disorders: Unlocking the Prospects

Neurodegeneration, the decline of nerve cells in the brain, is a common feature of neurodegenerative disorders (NDDs). Oxidative stress, a key factor in NDDs such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease can lead to neuronal cell death, mitochondria impairment, excitotoxicity, and Ca2+ stress. Environmental factors compromising stress response lead to cell damage, necessitating novel therapeutics for preventing or treating brain disorders in older individuals and an aging population. Synthetic medications offer symptomatic benefits but can have adverse effects. This research explores the potential of flavonoids derived from plants in treating NDDs. Flavonoids compounds, have been studied for their potential to enter the brain and treat NDDs. These compounds have diverse biological effects and are currently being explored for their potential in the treatment of central nervous system disorders. Flavonoids have various beneficial effects, including antiviral, anti-allergic, antiplatelet, anti-inflammatory, anti-tumor, anti-apoptotic, and antioxidant properties. Their potential to alleviate symptoms of NDDs is significant.

Bioactive compounds from Actinidia arguta fruit as a new strategy to fight glioblastoma

In recent years, there has been a significant demand for natural products as a mean of disease prevention or as an alternative to conventional medications. The driving force for this change is the growing recognition of the abundant presence of valuable bioactive compounds in natural products. On recent years Actinia arguta fruit, also known as kiwiberry, has attracted a lot of attention from scientific community due to its richness in bioactive compounds, including phenolic compounds, organic acids, vitamins, carotenoids and fiber. These bioactive compounds contribute to the fruit's diverse outstanding biological activities such as antioxidant, anti-inflammatory, neuroprotective, immunomodulatory, and anti-cancer properties. Due to these properties, the fruit may have the potential to be used in the treatment/prevention of various types of cancer, including glioblastoma. Glioblastoma is the most aggressive form of brain cancer, displaying 90 % of recurrence rate within a span of 2 years. Despite the employment of an aggressive approach, the prognosis remains unfavorable, emphasizing the urgent requirement for the development of new effective treatments. The preclinical evidence suggests that kiwiberry has potential impact on glioblastoma by reducing the cancer self-renewal, modulating the signaling pathways involved in the regulation of the cell phenotype and metabolism, and influencing the consolidation of the tumor microenvironment. Even though, challenges such as the imprecise composition and concentration of bioactive compounds, and its low bioavailability after oral administration may be drawbacks to the development of kiwiberry-based treatments, being urgent to ensure the safety and efficacy of kiwiberry for the prevention and treatment of glioblastoma. This review aims to highlight the potential impact of A. arguta bioactive compounds on glioblastoma, providing novel insights into their applicability as complementary or alternative therapies.

Luteolin regulates the distribution and function of organelles by controlling SIRT1 activity during postovulatory oocyte aging

The quality of oocytes determines their development competence, which will be rapidly lost if the oocytes are not fertilized at the proper time after ovulation. SIRT1, one of the sirtuin family members, has been proven to protect the quality of oocytes during postovulatory oocyte aging. However, evidence of the effect of SIRT1 on the activity of organelles including the mitochondria, the endoplasmic reticulum (ER), the Golgi apparatus, and the lysosomes in postovulatory aging oocyte is lacking. In this study, we investigated the distribution and function of organelles in postovulatory aged oocytes and discovered abnormalities. Luteolin, which is a natural flavonoid contained in vegetables and fruits, is an activator of SIRT1. When the oocytes were treated with luteolin, the abnormal distribution of mitochondria, ER, and Golgi complex were restored during postovulatory oocyte aging. The ER stress protein GRP78 and the lysosome protein LAMP1 increased, while the mitochondrial membrane potential and the Golgi complex protein GOLPH3 decreased in aged oocytes, and these were restored by luteolin treatment. EX-527, an inhibitor of SIRT1, disrupted the luteolin-mediated normal distribution and function of mitochondria, ER, Golgi apparatus, and lysosomes. In conclusion, we demonstrate that luteolin regulates the distribution and function of mitochondria, ER, Golgi apparatus, and lysosomes during postovulatory oocyte aging by activating SIRT1.

A Comprehensive Review of Natural Flavonoids with Anti-SARS-CoV-2 Activity

The COVID-19 pandemic caused by SARS-CoV-2 has majorly impacted public health and economies worldwide. Although several effective vaccines and drugs are now used to prevent and treat COVID-19, natural products, especially flavonoids, showed great therapeutic potential early in the pandemic and thus attracted particular attention. Quercetin, baicalein, baicalin, EGCG (epigallocatechin gallate), and luteolin are among the most studied flavonoids in this field. Flavonoids can directly or indirectly exert antiviral activities, such as the inhibition of virus invasion and the replication and inhibition of viral proteases. In addition, flavonoids can modulate the levels of interferon and proinflammatory factors. We have reviewed the previously reported relevant literature researching the pharmacological anti-SARS-CoV-2 activity of flavonoids where structures, classifications, synthetic pathways, and pharmacological effects are summarized. There is no doubt that flavonoids have great potential in the treatment of COVID-19. However, most of the current research is still in the theoretical stage. More studies are recommended to evaluate the efficacy and safety of flavonoids against SARS-CoV-2.

Preparation and Evaluation of Amorphous Solid Dispersions for Enhancing Luteolin's Solubility in Simulated Saliva

Luteolin (LUT), a bioactive flavonoid, possesses various pharmacological properties, including antioxidant, antimicrobial, anti-allergic, cardio-protective, and anti-cancer activity. Among them, LUT's administration for the treatment of periodontal disease is very promising. However, its low water solubility magnifies the challenge of formulating LUT into an effective dosage form. In this vein, the aim of the present study examines the preparation of amorphous solid dispersions (ASD) for the solubility improvement of LUT in saliva. At first, the physicochemical properties of the active pharmaceutical ingredient (API) were studied before the selection of the most suitable ASD matrix/carrier. For this reason, six commonly used polymeric ASD matrix/carriers (namely, povidone, PVP; copovidone, coPVP; hydroxypropyl cellulose, HPC-SL; hydroxypropyl methyl cellulose acetate succinate, HPMC-AS; Eudragit^® RS, Eud-RS; and Soluplus^®, SOL) were screened via the film casting method, as to whether they could suspend the drug's recrystallization. The most promising matrix/carriers were then evaluated, based on their ability to inhibit LUT's precipitation after its solubilization, via the solvent shift method. Based on both screening methods, it was determined that PVP was the most promising matrix/carrier for the preparation of LUT's ASDs. Hence, in a further step, after the successful testing of components' miscibility, LUT-PVP ASDs were prepared via the solvent evaporation method. These systems (examined via powder X-ray diffractometry, pXRD) showed full API amorphization immediately after preparation and excellent physical stability (since they were stable after 3 months of storage). The study of LUT-PVP ASD's ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) spectra demonstrated strong H-bonds between the molecules of the drug and the matrix/carrier, while molecular dynamics (MD) simulations were able to shed light on these drug-matrix/carrier interactions, at a molecular level. Finally, in vitro dissolution studies in simulated saliva proved that the prepared ASDs were able to significantly enhance LUT's dissolution profile. Hence, according to findings of the present work, the preparation of LUT-ASDs utilizing PVP as the polymeric matrix/carrier is regarded as a highly promising technique for the improvement of API's solubility in the oral cavity.

Bioinformatical and biochemical analyses on the protective role of traditional Chinese medicine against age-related macular degeneration

PURPOSE

Age-related macular degeneration (AMD) is the commonest cause of permanent vision loss in the elderly. Traditional Chinese medicine (TCM) has long been used to treat AMD, although the underlying functional mechanisms are not understood. This study aims to predict the active ingredients through screening the chemical ingredients of anti-AMD Decoction and to elucidate the underlying mechanisms.

METHODS

We collected the prescriptions for effective AMD treatment with traditional Chinese medicine and screened several Chinese medicines that were used most frequently in order to compose "anti-AMD decoction". The pharmacologically active ingredients and corresponding targets in this anti-AMD decoction were mined using the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database. Subsequently, the AMD-related targets were identified through the GeneCards database. Network pharmacology was performed to construct the visual network of anti-AMD Decoction-AMD protein-protein interaction (PPI). Further, the Autodock software was adopted for molecular docking on the core active ingredients and core targets. The function of core ingredients against oxidative stress and inflammation in retinal pigment epithelial cells was assessed using biochemical assays.

RESULTS

We screened out 268 active ingredients in anti-AMD Decoction corresponding to 258 ingredient targets, combined with 2160 disease targets in AMD, and obtained 129 drug-disease common targets. The key core proteins were predominantly involved in inflammation. Furthermore, molecular docking showed that four potential active ingredients (Quercetin, luteolin, naringenin and hederagenin) had good affinity with the core proteins, IL6, TNF and MAPK3. Quercetin, luteolin and naringenin demonstrated capacities against oxidative stress and inflammation in human retinal pigment epithelial cells.

CONCLUSIONS

The data suggests that anti-AMD Decoction has multiple functional components and targets in treating AMD, possibly mediated by suppression of oxidative stress and inflammation.

Anti-Inflammatory and Active Biological Properties of the Plant-Derived Bioactive Compounds Luteolin and Luteolin 7-Glucoside

Flavonoids are interesting molecules synthetized by plants. They can be found abundantly in seeds and fruits, determining the color, flavor, and other organoleptic characteristics, as well as contributing to important nutritional aspects. Beyond these characteristics, due to their biochemical properties and characteristics, they can be considered bioactive compounds. Several interesting studies have demonstrated their biological activity in different cellular and physiological processes in high-order organisms including humans. The flavonoid molecular structure confers the capability of reacting with and neutralizing reactive oxygen species (ROS), behaving as scavengers in all processes generating this class of molecules, such as UV irradiation, a process widely present in plant physiology. Importantly, the recent scientific literature has demonstrated that flavonoids, in human physiology, are active compounds acting not only as scavengers but also with the important role of counteracting the inflammation process. Among the wide variety of flavonoid molecules, significant results have been shown by investigating the role of the flavones luteolin and luteolin-7-O-glucoside (LUT-7G). For these compounds, experimental results demonstrated an interesting anti-inflammatory action, both in vitro and in vivo, in the interaction with JAK/STAT3, NF-κB, and other pathways described in this review. We also describe the effects in metabolic pathways connected with inflammation, such as cellular glycolysis, diabetes, lipid peroxidation, and effects in cancer cells. Moreover, the inhibition of inflammatory pathway in endothelial tissue, as well as the NLRP3 inflammasome assembly, demonstrates a key role in the progression of such phenomena. Since these micronutrient molecules can be obtained from food, their biochemical properties open new perspectives with respect to the long-term health status of healthy individuals, as well as their use as a coadjutant treatment in specific diseases.

Discovering the Potential of Natural Antioxidants in Age-Related Macular Degeneration: A Review

Age-related macular degeneration (AMD) is a multifactorial disease associated with anatomical changes in the inner retina. Despite tremendous advances in clinical care, there is currently no cure for AMD. This review aims to evaluate the published literature on the therapeutic roles of natural antioxidants in AMD. A literature search of PubMed, Web of Science and Google Scholar for peer-reviewed articles published between 1 January 2011 and 31 October 2021 was undertaken. A total of 82 preclinical and 18 clinical studies were eligible for inclusion in this review. We identified active compounds, carotenoids, extracts and polysaccharides, flavonoids, formulations, vitamins and whole foods with potential therapeutic roles in AMD. We evaluated the integral cellular signaling pathways including the activation of antioxidant pathways and angiogenesis pathways orchestrating their mode of action. In conclusion, we examined the therapeutic roles of natural antioxidants in AMD which warrant further study for application in clinical practice. Our current understanding is that natural antioxidants have the potential to improve or halt the progression of AMD, and tailoring therapeutics to the specific disease stages may be the key to preventing irreversible vision loss.

Non-neglectable therapeutic options for age-related macular degeneration: A promising perspective from traditional Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Age-related macular degeneration (AMD) is a chronic neurodegenerative disease which causes irreversible central vision loss among the elderly population. Traditional Chinese Medicine (TCM), including formulas, acupuncture and herbs, has been used in the treatment of AMD for thousands of years and is currently used by many AMD patients around the world.

AIM OF THE REVIEW

A comprehensive, in-depth literature review examining the use of TCM in the treatment of AMD has yet to be compiled. This review will improve current knowledge relating to the use of TCM and will open new avenues of exploration in developing new drugs for the treatment of AMD.

METHODS

A literature search of the PubMed database, Web of Science, Google Scholar and China National Knowledge Infrastructure (CNKI) was performed using relevant terms and keywords related to TCM in the treatment of AMD. Related books, PhD and master's theses were also researched.

RESULTS

The TCM-based interpretation of AMD has been used to establish a theoretical foundation for understanding the effect of TCM formulas and acupuncture on AMD. The possible mechanism of action of common Chinese herbs has also been discussed in detail.

CONCLUSION

TCM is a promising treatment option of AMD patients. However, lack of rigorous scientific evidence has limited the impact and uptake of TCM therapy. Future research should focus on improving understanding of the mechanism of action and bioactive components of TCM therapies.

Oleuropein Protects Human Retinal Pigment Epithelium Cells from IL-1β-Induced Inflammation by Blocking MAPK/NF-κB Signaling Pathways

Proinflammatory mediators such as interleukin (IL)-1β cause retinal pigment epithelium (RPE) inflammation, which is related to visual deterioration, including age-related macular degeneration and diabetic retinopathy. Oleuropein is a polyphenol compound that shows potent anti-inflammatory, antioxidant, and anti-cancer activities, but its effects on IL-1β-induced inflammation have not been examined in the adult RPE cell line ARPE-19. Here, we assessed the ability of oleuropein to attenuate this inflammation in ARPE-19 cells. IL-1β induced secretion of the inflammatory cytokines IL-6, monocyte chemoattractant protein-1 (MCP)-1, and soluble intercellular adhesion molecule (sICAM)-1. As measured by enzyme-linked immunosorbent assay, oleuropein significantly inhibited levels of all three proteins and led to decreased monocyte adhesiveness to ARPE-19 cells. To clarify the underlying anti-inflammatory mechanisms, we used western blots to evaluate the effect of oleuropein on inactivation of the nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. The results showed that oleuropein significantly decreased levels of the inflammatory mediator cyclooxygenase-2 and increased anti-inflammatory protein HO-1 expression. We next examined if the anti-inflammatory activity of oleuropein arises via inactivated NF-κB. We found that suppressing phosphorylation of the JNK1/2 and p38 MAPK signaling pathways inhibited IL-6, MCP-1, and sICAM-1 secretion, implicating these pathways and NF-κB suppression in the effects of oleuropein. These results indicate that oleuropein shows potential for the prevention and treatment of inflammatory diseases of the retina.

Polyphenols and Visual Health: Potential Effects on Degenerative Retinal Diseases

Dietary polyphenols are a group of natural compounds that have been proposed to have beneficial effects on human health. They were first known for their antioxidant properties, but several studies over the years have shown that these compounds can exert protective effects against chronic diseases. Nonetheless, the mechanisms underlying these potential benefits are still uncertain and contradictory effects have been reported. In this review, we analyze the potential effects of polyphenol compounds on some visual diseases, with a special focus on retinal degenerative diseases. Current effective therapies for the treatment of such retinal diseases are lacking and new strategies need to be developed. For this reason, there is currently a renewed interest in finding novel ligands (or known ligands with previously unexpected features) that could bind to retinal photoreceptors and modulate their molecular properties. Some polyphenols, especially flavonoids (e.g., quercetin and tannic acid), could attenuate light-induced receptor damage and promote visual health benefits. Recent evidence suggests that certain flavonoids could help stabilize the correctly folded conformation of the visual photoreceptor protein rhodopsin and offset the deleterious effect of retinitis pigmentosa mutations. In this regard, certain polyphenols, like the flavonoids mentioned before, have been shown to improve the stability, expression, regeneration and folding of rhodopsin mutants in experimental in vitro studies. Moreover, these compounds appear to improve the integration of the receptor into the cell membrane while acting against oxidative stress at the same time. We anticipate that polyphenol compounds can be used to target visual photoreceptor proteins, such as rhodopsin, in a way that has only been recently proposed and that these can be used in novel approaches for the treatment of retinal degenerative diseases like retinitis pigmentosa; however, studies in this field are limited and further research is needed in order to properly characterize the effects of these compounds on retinal degenerative diseases through the proposed mechanisms.

Network Pharmacology Analysis of Traditional Chinese Medicine Formula Shuang Di Shou Zhen Tablets Treating Nonexudative Age-Related Macular Degeneration

Objective

To analyze the pharmacological mechanism of the treatment of dry age-related macular degeneration (dry AMD) based on a network pharmacological approach of Shuang Di Shou Zhen Tablets (SDSZT) and to provide a new reference for the current lack of effective treatment of dry AMD.

Methods

The main chemical constituents and their targets of Rehmanniae Radix Praeparata, Ligustrum lucidum, Mori Fructus, Paeonia albiflora, Rhizoma Dioscoreae, Alisma orientale, Schisandra chinensis, Radix Polygoni Multiflori Preparata, Ophiopogon japonicus, and Radix Rehmanniae were obtained from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) and Traditional Chinese Medicine Integrated Database (TCMID). The active ingredients of traditional Chinese medicine were screened according to Absorption, Distribution, Metabolism, and Excretion (ADME), the gene names of the targets of each active ingredient were obtained from the Uniprot database, the main targets of dry AMD were obtained from GeneCards and DisGeNET database, and the protein interaction analysis was performed on the String database. The Metascape database was used to analyze the “drug-component-target” and the biological processes and networks involved, and then, Cytoscape 3.8.1 was used to construct the “ SDSZT component-dry AMD target-pathway” network.

Results

The main active ingredients of SDSZT for dry AMD treatment are quercetin, kaempferol, luteolin, β-glutamine, β-carotene, etc. And, the core targets are RAC-alpha serine/threonine-protein kinase (AKT1), prostaglandin G/H synthase 1 (PTGS1), tumor necrosis factor (TNF), transcription factor AP-1 (JUN), apoptosis regulator Bcl-2 (BCL2), caspase-3 (CASP3), phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit gamma isoform (PIK3CG), androgen receptor (AR), apoptosis regulator BAX (BAX), etc. The biological pathways for the treatment of age-related macular degeneration by SDSZT mainly act on pathways in cancer, fluid shear stress and atherosclerosis, and TNF signaling pathway, and the main function of SDSZT is to regulate intracellular cytokine receptor binding.

Conclusion

This study initially reveals the multiconstituent, multitarget, and multipathway mechanism of action of SDSZT in the treatment of dry AMD and provides the basis for the clinical application of SDSZT.

Fermented-Rhus verniciflua extract ameliorate Helicobacter pylori eradication rate and gastritis

An antibacterial effect of fermented-Rhus verniciflua extract (FRVE), an urushiol-free extract fermented by Fomitella fraxinea, on Helicobacter pylori was evaluated in mice. Minimal inhibitory concentration of FRVE against H. pylori eradication was checked with serial dilution method in vitro. H. pylori infection-induced mice were utilized to determine the effect of oral administration of FRVE with/without standard triple therapy (STT: metronidazole, omeprazole, and clarithromycin) on H. pylori colonization and gastric inflammation. H. pylori was clearly eradicated by FRVE at a concentration of ≥2 mg/ml in vitro. In animal study, FRVE at a concentration of ≥6 mg/ml significantly reduced colonized H. pylori grading (0.2 vs. 2.2, p < .01) and improved gastric inflammation (0.4 vs. 1.6, p < .01) compared to control. STT with FRVE (3 mg/ml) exerted synergistic effect on both H. pylori colonization grade (STT, 0.6 ± 0.9; FRVE, 1.4 ± 0.5; STT + FRVE, 0.8 ± 0.4) and gastric inflammation (STT, 0.4 ± 0.5; FRVE, 1.4 ± 0.5; STT + FRVE,1.0 ± 0.1) compared with single therapy (p < .01). H. pylori eradication rate of FRVE (6 mg/ml) was higher than that of STT (60% vs. 20%). FRVE has potential antibacterial activity against H. pylori infection and can be used as an additional therapy on STT.

Mechanisms of mitochondrial dysfunction and their impact on age-related macular degeneration

Oxidative stress-induced damage to the retinal pigment epithelium (RPE) is considered to be a key factor in age-related macular degeneration (AMD) pathology. RPE cells are constantly exposed to oxidative stress that may lead to the accumulation of damaged cellular proteins, lipids, nucleic acids, and cellular organelles, including mitochondria. The ubiquitin-proteasome and the lysosomal/autophagy pathways are the two major proteolytic systems to remove damaged proteins and organelles. There is increasing evidence that proteostasis is disturbed in RPE as evidenced by lysosomal lipofuscin and extracellular drusen accumulation in AMD. Nuclear factor-erythroid 2-related factor-2 (NFE2L2) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) are master transcription factors in the regulation of antioxidant enzymes, clearance systems, and biogenesis of mitochondria. The precise cause of RPE degeneration and the onset and progression of AMD are not fully understood. However, mitochondria dysfunction, increased reactive oxygen species (ROS) production, and mitochondrial DNA (mtDNA) damage are observed together with increased protein aggregation and inflammation in AMD. In contrast, functional mitochondria prevent RPE cells damage and suppress inflammation. Here, we will discuss the role of mitochondria in RPE degeneration and AMD pathology focused on mtDNA damage and repair, autophagy/mitophagy signaling, and regulation of inflammation. Mitochondria are putative therapeutic targets to prevent or treat AMD.

Fisetin inhibits proliferation of pancreatic adenocarcinoma by inducing DNA damage via RFXAP/KDM4A-dependent histone H3K36 demethylation

Pancreatic adenocarcinoma (PDAC) is an extremely malignant tumor that is associated with low survival rates. Fisetin is a natural flavonoid that shows diverse antitumor effects, including DNA damage, in various cancers. Increasing studies have demonstrated that epigenetic modifications play critical roles in DNA-damage response. However, the epigenetic regulation mechanism of fisetin in cancers is hardly studied. RFXAP is a critical transcription factor for MHC II molecules, however, its transcriptional role in PDAC is poorly understood. The anti-PDAC effect of fisetin was measured by CCK-8, flow cytometry, xenograft tumor nude mice model. DNA-damage levels were examined by immunofluorescence. Bioinformatics analysis was used to examine the expression of RFXAP and other genes involved in DNA-damage response. ChIP sequencing was used to explore the transcriptional role of RFXAP. The expression of target gene KDM4A was measured by qRT-PCR and western blots. KDM4A promoter activity was analyzed using dual-luciferase reporter assay. RFXAP overexpressing or silencing of PDAC cells was used to explore the effect of RFXAP in DNA damage induced by fisetin. We found that fisetin inhibited cell proliferation and induced DNA damage and S-phase arrest in PDAC. Expression of RFXAP and other DNA-damage response genes were upregulated by fisetin. We revealed that RFXAP expression was relatively low in PDAC and correlated with tumor stage and poor prognosis. Then we explored the transcriptional role of RFXAP and found that RFXAP targeted KDM4A, a special demethylase specific for tri- and dimethylated histone H3K36. We found that overexpression of RFXAP upregulated KDM4A and attenuated methylation of H3K36, thereby impairing DNA repair and enhancing the DNA damage induced by fisetin, while RFXAP silencing showed the opposite effect. We also found the function of fisetin in enhancing the effect of chemotherapy on pancreatic cancer cells. Our findings revealed that fisetin induced DNA damage via RFXAP/KDM4A-dependent histone H3K36 demethylation, thus causing inhibition of proliferation in PDAC.

Luteolin Attenuates IL-1β-Induced THP-1 Adhesion to ARPE-19 Cells via Suppression of NF-κB and MAPK Pathways

Cytokine-induced endothelial dysfunction leads to inflammation and vascular adhesion molecule production in retinal pigment epithelium (RPE) cells. Inflammation is a critical mediator in retinal degeneration (RD) diseases, including age-related macular degeneration (AMD), and RD progression may be prevented through anti-inflammatory activity in RPE cells. The flavonoid polyphenol luteolin (LU) has anti-inflammatory and antidiabetes activities, but its effects regarding retinal protection remain unknown. Here, we examined the ability of luteolin to alleviate markers of inflammation related to RD in cytokine-primed APPE-19 cells. We found that luteolin decreased the levels of interleukin- (IL-) 6, IL-8, soluble intercellular adhesion molecule-1 (sICAM-1), and monocyte chemoattractant protein-1 (MCP-1) and attenuated adherence of the human monocytic leukemia cell line THP-1 to IL-1β-stimulated ARPE-19 cells. Luteolin also increased anti-inflammatory protein heme oxygenase-1 (HO-1) levels. Interestingly, luteolin induced protein kinase B (AKT) phosphorylation, thus inhibiting nuclear factor- (NF-) κB transfer from cytoplasm into the nucleus and suppressing mitogen-activated protein kinase (MAPK) inflammatory pathways. Furthermore, cotreatment with MAPK inhibitors and luteolin decreased inflammatory cytokine and chemokine levels, and further suppressed THP-1 adhesion. Overall, these results provide evidence that luteolin protects ARPE-19 cells from IL-1β-stimulated increases of IL-6, IL-8, sICAM-1, and MCP-1 production by blocking the activation of MAPK and NF-κB signaling pathways, thus ameliorating the inflammatory response.

Polyphenols and their applications: An approach in food chemistry and innovation potential

Polyphenols are compounds naturally present in fruits and vegetables that are gaining more and more attention due to their therapeutic effects and their potential technological applications. In this review, we intend to demonstrate the importance of some phenolic compounds, addressing their biological effects and potential for applications in various industrial fields. The intake of these compounds in appropriate concentrations can present promising effects in the prevention of diseases such as diabetes, obesity, Parkinson's, Alzheimer's, and others. They can also be used to improve the physicochemical properties of starch, in the preservation of foods, as natural dyes, prebiotic ingredients, hydrogels and nanocomplexes. In addition, these compounds have potential for innovation in the most diverse technological fields, including organic fine chemistry, basic materials chemistry, pharmaceuticals, food chemistry, chemical engineering, etc.

Stability of natural polyphenol fisetin in eye drops Stability of fisetin in eye drops

Fisetin is a polyphenolic compound with anti-inflammatory and antioxidant properties. Inflammation and reactive oxygen species play a major role in the pathophysiology of the dry eye syndrome (DES). Patients with DES undergo symptomatic treatment using eye drops known as artificial tears. Addition of fisetin into the eye drops could result in a better recovery of the eye surface. This experimental study examines the stability of fisetin in selected eye drops (Arufil, Hypromelóza-P, Ocutein, Refresh). Absorption spectra of fisetin were measured in selected eye drops, dimethylsulphoxide (DMSO), deionized water and normal saline solution (NSS) during a period of four weeks. The fisetin absorption maximum was placed at 350 – 390 nm depending on the solvent. Good stability of fisetin solutions were observed in DMSO and deionized water. The highest stability of fisetin in selected eye drops was observed in Hypromelóza-P. Irreversible fisetin structural changes were detected in Arufil, Ocutein, Refresh and NSS. For further clinical evaluation, fisetin solution in Hypromelóza-P could be examined.

RNA-sequencing analysis of the effect of luteolin on methamphetamine-induced hepatotoxicity in rats: a preliminary study

In this study, RNA-sequencing (RNA-seq) was utilized to investigate the effects of luteolin on hepatotoxicity caused by methamphetamine (METH). The rats in METH group were administrated with METH (15 mg/kg, two times per day) via intraperitoneal (i.p.) injections for four consecutive days. The rats in luteolin + METH group were firstly administrated with luteolin (100 mg/kg, once a day) by oral gavage for 3 days before METH treatment. Lueolin attenuated the hepatotoxicity induced by METH via histopathological and biochemical analysis. The results of RNA-seq showed that luteolin could regulate 497 differentially expressed genes (DEGs), and the selected DEGs were mainly enriched in eight pathways, according to KEGG analysis. Furthermore, qRT-PCR was utilized to verify the results of RNA-seq. Six genes were selected as follows: liver enriched antimicrobial peptide 2 (Leap2), fatty acid synthase (Fasn), fatty acid binding protein 5 (Fabp5), patatin like phospholipase domain containing 3 (Pnpla3), myelin basic protein (Mbp) and calmodulin 3 (Calm3). Though because of the design flaws, the luteolin group has not been included, this study demonstrated that luteolin might exert hepato-protective effects from METH via modulation of oxidative phosphorylation, cytochrome P450 and certain signaling pathways.

Dietary Polyphenols in Age-Related Macular Degeneration: Protection against Oxidative Stress and Beyond

Age-related macular degeneration (AMD) is a multifactorial disease of the retina featured by degeneration and loss of photoreceptors and retinal pigment epithelium (RPE) cells with oxidative stress playing a role in its pathology. Although systematic reviews do not support the protective role of diet rich in antioxidants against AMD, dietary polyphenols (DPs) have been reported to have beneficial effects on vision. Some of them, such as quercetin and cyanidin-3-glucoside, can directly scavenge reactive oxygen species (ROS) due to the presence of two hydroxyl groups in their B ring structure. Apart from direct ROS scavenging, DPs can lower oxidative stress in several other pathways. Many DPs induce NRF2 (nuclear factor, erythroid 2-like 2) activation and expression of phase II enzymes that are under transcriptional control of this factor. DPs can inhibit A2E photooxidation in RPE cells, which is a source of oxidative stress. Anti-inflammatory action of DPs in RPE cells is associated with regulation of various interleukins and signaling pathways, including IL-6/JAK2 (Janus kinase 2)/STAT3. Some DPs can improve impaired cellular waste clearance, including AMD-specific deficient phagocytosis of the Aβ42 peptide and autophagy.

Anti-inflammatory effects of luteolin: A review of in vitro, in vivo, and in silico studies

ETHNOPHARMACOLOGICAL RELEVANCE

Luteolin (3', 4', 5,7-tetrahydroxyflavone) has been identified as commonly present in plants. Plants with a high luteolin content have been used ethnopharmacologically to treat inflammation-related symptoms. Both isolated luteolin and extracts from luteolin-rich plants have been studied using various models and exhibited anti-inflammatory activity.

AIM OF THE REVIEW

This paper uses recent research findings with a broad range of study models to describe the anti-inflammatory activity of luteolin, particularly its mechanisms at the molecular level; provide guidance for future research; and evaluate the feasibility of developing luteolin into an anti-inflammatory drug.

MATERIALS AND METHODS

We summarize reports about the anti-inflammatory activity of luteolin published since 2009, which we found in MEDLINE/PubMed, Scopus, Web of Knowledge, and Google Scholar. To acquire broad information, we extended our search to online FDA documents.

RESULTS

Luteolin is a flavonoid commonly found in medicinal plants and has strong anti-inflammatory activity in vitro and in vivo. Some of its derivatives, such as luteolin-7-O-glucoside, have also shown anti-inflammatory activity. The action mechanism of luteolin varies, but Src in the nuclear factor (NF)-κB pathway, MAPK in the activator protein (AP)- 1 pathway, and SOCS3 in the signal transducer and activator of transcription 3 (STAT3) pathway are its major target transcription factors. A clinical trial with a formulation containing luteolin showed excellent therapeutic effect against inflammation-associated diseases.

CONCLUSION

In silico, in vitro, in vivo, and clinical studies strongly suggest that the major pharmacological mechanism of luteolin is its anti-inflammatory activity, which derives from its regulation of transcription factors such as STAT3, NF-κB, and AP-1. Much work remains to ensure the safety, quality, and efficacy of luteolin before it can be used to treat inflammation-related diseases in humans.

Effect of fisetin supplementation on inflammatory factors and matrix metalloproteinase enzymes in colorectal cancer patients

A growing body of evidence indicates that inflammation is associated with tumorigenesis, metastasis and chemotherapeutic resistance in patients with colorectal cancer (CRC). Natural flavonoids are promising agents for inflammation-related tumor progression in patients with CRC. This study aimed to assess the efficacy of flavonoid fisetin supplementation on the inflammatory status and matrix metalloproteinase (MMP) levels in these patients. In this double-blind, randomized placebo-controlled clinical trial, 37 CRC patients undergoing chemotherapy were assigned to receive either 100 mg fisetin (n = 18) or placebo (n = 19) for seven consecutive weeks. The supplementation began one week before chemotherapy and continued until the end of the second chemotherapy cycle. Levels of interleukin (IL)-8, IL-10, high-sensitivity C-reactive protein (hs-CRP), MMP-7, and MMP-9 were measured in plasma using ELISA, before and after the intervention. The trial was registered at http://www.irct.ir (code: IRCT2015110511288N9). The participants were 55.59 ± 15.46 years old with 62.16% being male. After the intervention, the plasma levels of IL-8 and hs-CRP reduced significantly in the fisetin group (p < 0.04 and p < 0.01, respectively). Additionally, fisetin supplementation suppressed the values of MMP-7 levels (p < 0.02). However, significant changes were observed only in IL-8 concentrations in the fisetin group when compared with the placebo group (p < 0.03). The changes in the levels of other metabolic factors were not statistically significant. According to the results, fisetin could improve the inflammatory status in CRC patients, suggesting it as a novel complementary antitumor agent for these patients and warranting further studies.

Chrysin Ameliorates Malfunction of Retinoid Visual Cycle through Blocking Activation of AGE-RAGE-ER Stress in Glucose-Stimulated Retinal Pigment Epithelial Cells and Diabetic Eyes

Diabetes-associated visual cycle impairment has been implicated in diabetic retinopathy, and chronic hyperglycemia causes detrimental effects on visual function. Chrysin, a naturally occurring flavonoid found in various herbs, has anti-inflammatory, antioxidant, and neuroprotective properties. The goal of the current study was to identify the retinoprotective role of chrysin in maintaining robust retinoid visual cycle-related components. The in vitro study employed human retinal pigment epithelial (RPE) cells exposed to 33 mM of glucose or advanced glycation end products (AGEs) in the presence of 1–20 μM chrysin for three days. In the in vivo study, 10 mg/kg of chrysin was orally administrated to db/db mice. Treating chrysin reversed the glucose-induced production of vascular endothelial growth factor, insulin-like growth factor-1, and pigment epithelium-derived factor (PEDF) in RPE cells. The outer nuclear layer thickness of chrysin-exposed retina was enhanced. The oral gavage of chrysin augmented the levels of the visual cycle enzymes of RPE65, lecithin retinol acyltransferase (LRAT), retinol dehydrogenase 5 (RDH5), and rhodopsin diminished in db/db mouse retina. The diabetic tissue levels of the retinoid binding proteins and the receptor of the cellular retinol-binding protein, cellular retinaldehyde-binding protein-1, interphotoreceptor retinoid-binding protein and stimulated by retinoic acid 6 were restored to those of normal mouse retina. The presence of chrysin demoted AGE secretion and AGE receptor (RAGE) induction in glucose-exposed RPE cells and diabetic eyes. Chrysin inhibited the reduction of PEDF, RPE 65, LRAT, and RDH5 in 100 μg/mL of AGE-bovine serum albumin-exposed RPE cells. The treatment of RPE cells with chrysin reduced the activation of endoplasmic reticulum (ER) stress. Chrysin inhibited the impairment of the retinoid visual cycle through blocking ER stress via the AGE-RAGE activation in glucose-stimulated RPE cells and diabetic eyes. This is the first study demonstrating the protective effects of chrysin on the diabetes-associated malfunctioned visual cycle.

Luteolin induces myelodysplastic syndrome‑derived cell apoptosis via the p53‑dependent mitochondrial signaling pathway mediated by reactive oxygen species

Luteolin, a common dietary flavonoid, induces the apoptosis of cells in several types of cancer. However, its role in myelodysplastic syndrome (MDS) and the potential underlying mechanisms remain to be elucidated. To evaluate the potential benefit and underlying mechanisms of luteolin in MDS cells, the viability of SKM‑1 cells and primary bone marrow (PBM) mononuclear cells from patients with intermediate‑ or high‑risk MDS were assessed using a Cell Counting Kit‑8 assay. The apoptotic features of cell morphology were assessed using Wright‑Giemsa staining, DNA fragmentation was analyzed by agarose gel electrophoresis, and the extent of apoptosis was quantified by flow cytometry (FCM). Reactive oxygen species (ROS) were measured by FCM with 2,7‑dichlorodihydrofluorescein diacetate staining and mitochondrial membrane potential (ΔΨm) was determined using 5,5',6,6'‑tetrachloro‑1,1',3,3'‑tetraethylbenzimidazolylcarbocyanine iodide staining. Caspase activity was detected using a fluorometric protease assay. Furthermore, the effects of luteolin on the expression of apoptosis‑related proteins were analyzed using western blot analysis. The resulting data revealed that luteolin significantly inhibited the proliferation of SKM‑1 cells in vitro, and its half maximal inhibitory concentration was 139.41 µM at 24 h and 23.95 µM at 72 h. Luteolin also markedly inhibited the proliferation of mononuclear cells from patients with intermediate‑ or high‑risk MDS. Luteolin suppressed cell proliferation, mainly as a result of the induction of apoptosis, as demonstrated by typical apoptotic morphological features, the ladder pattern of genomic DNA fragmentation, and the results of FCM using Annexin V‑FITC/PI double staining. It was also found that short‑term exposure of SKM‑1 cells to luteolin led to a marked increase in the accumulation of ROS. The increased intracellular level of ROS appeared to induce the activation of p53 and elevate the B‑cell lymphoma 2 (Bcl‑2)‑associated X protein/Bcl‑2 ratio, which modulates ΔΨm and triggers the release of cytochrome c, and may increase the activities of apoptotic protease activating factor 1, caspase‑3, ‑8 and ‑9 to further trigger the destruction of structural and specific proteins and thereby cell apoptosis. Notably, the inhibition of ROS generation by the antioxidant N‑acetyl‑L‑cysteine significantly attenuated the luteolin‑induced loss of ΔΨm and activities of caspase‑3, ‑8 and ‑9. These data suggested that luteolin exerts its pro‑apoptotic action partly through the p53‑dependent mitochondrial signaling pathway mediated by intracellular ROS, which provides a promising therapeutic candidate for patients with MDS.

Nepetin inhibits IL-1β induced inflammation via NF-κB and MAPKs signaling pathways in ARPE-19 cells

BACKGROUNDS

Chronic inflammation in retinal pigment epithelial (RPE) cells is related to the pathogenesis of retinal inflammatory blind causing diseases such as age-related macular degeneration (AMD) and diabetic retinopathy (DR). Nepetin, a natural flavonoid compound, has shown potent anti-inflammatory activities but has not been studied on ocular resident cells yet. Here, we assess the ability of Nepetin to alleviate the inflammatory responses of ARPE-19 cells induced by interleukin (IL)-1β.

METHODS

The secretion and mRNA expression of inflammatory cytokines IL-6, IL-8 and monocyte chemoattractant protein-1 (MCP-1) induced by IL-1β are measured by enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-PCR) respectively. To clarify the underlying action mechanism, we examine the effect of Nepetin on activation of nuclear factor of kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways using Western blot.

RESULTS

Nepetin can significantly decrease the three inflammatory mediators at both protein and mRNA level in a dose-dependent manner. Western blot results show that Nepetin can decrease the nuclear translocation of p65 through suppressing phosphorylation of inhibitor of nuclear factor kappa B (IκB) and IκB kinase (IKK). Also, Nepetin can decrease the phosphorylation of extracellular signal-regulated kinases (ERK) 1/2, c-Jun N-terminal kinase (JNK) and p38 MAPK.

CONCLUSIONS

Taken together, Nepetin abolishes IL-1β-induced IL-6, IL-8 and MCP-1 secretion and mRNA expression by repressing the activation of NF-κB and MAPKs. These results indicate that Nepetin shows potential to be used for prevention and treatment of inflammatory retinal diseases or as a lead compound.

CB2 receptor activation causes an ERK1/2-dependent inflammatory response in human RPE cells

A chronic low-level inflammation contributes to the pathogenesis of age-related macular degeneration (AMD), the most common cause of blindness in the elderly in Western countries. The loss of central vision results from attenuated maintenance of photoreceptors due to the degeneration of retinal pigment epithelium (RPE) cells beneath the photoreceptor layer. It has been proposed that pathologic inflammation initiated in RPE cells could be regulated by the activation of type 2 cannabinoid receptors (CB₂). Here, we have analysed the effect of CB₂ activation on cellular survival and inflammation in human RPE cells. RPE cells were treated with the selective CB₂ agonist JWH-133 in the presence or absence of the oxidative stressor 4-hydroxynonenal. Thereafter, cellular viability as well as the release of pro-inflammatory cytokines and potential underlying signalling pathways were analysed. Our results show that JWH-133 led to increased intracellular Ca²⁺ levels, suggesting that RPE cells are capable of responding to a CB₂ agonist. JWH-133 could not prevent oxidative stress-induced cell death. Instead, 10 µM JWH-133 increased cell death and the release of proinflammatory cytokines in an ERK1/2-dependent manner. In contrast to previous findings, CB₂ activation increased, rather than reduced inflammation in RPE cells.

Fisetin Regulates Nrf2 Expression and the Inflammation-Related Signaling Pathway to Prevent UVB-Induced Skin Damage in Hairless Mice

Chronic ultraviolet (UV) exposure may cause skin damage, disrupt skin barrier function, and promote wrinkle formation. UV induces oxidative stress and inflammation, which results in extracellular matrix degradation in the dermis and epidermal hyperplasia. Our previous study demonstrated that fisetin exerts photoprotective activity by inhibiting mitogen-activated protein kinase/activator protein-1/matrix metalloproteinases (MMPs) activation. In this study, fisetin was applied topically to investigate its antiphotodamage effects in hairless mice. The erythema index (a* values) and transepidermal water loss were evaluated to assess skin damage, and immunohistochemical staining was conducted to elucidate the photoprotective mechanism of fisetin. The results revealed that the topical application of fisetin reduced UVB-induced increase in the a* value and wrinkle formation. In addition, fisetin inhibited epidermal hyperplasia and increased the collagen content in the dermis. Fisetin exerted photoprotective activity by inhibiting the expression of MMP-1, MMP-2, and cyclooxygenase-2 and increasing the expression of nuclear factor erythroid 2-related factor. Furthermore, fisetin increased the expression of filaggrin to prevent UVB-induced barrier function disruption. Altogether, the present results provide evidence of the effects and mechanisms of fisetin's antiphotodamage and antiphotoinflammation activities.

Cigarette smoke induced autophagy-impairment regulates AMD pathogenesis mechanisms in ARPE-19 cells

Age related macular degeneration (AMD) is one of the leading causes of blindness. Genetics, environmental insult, and age-related factors all play a key role in altering proteostasis, the homeostatic process regulating protein synthesis, degradation and processing. These factors also play a role in the pathogenesis of AMD and it has been well established that cigarette smoking (CS) initiates AMD pathogenic mechanisms. The primary goal of this study is to elucidate whether CS can induce proteostasis/autophagy-impairment in retinal pigment epithelial (RPE) cells. In our preliminary analysis, it was found that cigarette smoke extract (CSE) induces accumulation of ubiquitinated proteins in the insoluble protein fraction (p < 0.01), which was subsequently mitigated through cysteamine (p < 0.01) or fisetin (p < 0.05) treatment. Further, it was verified that these CSE induced ubiquitinated proteins accumulated in the peri-nuclear spaces (p<0.05) that were cleared- off with cysteamine (p < 0.05) or fisetin (p < 0.05). Moreover, CSE-induced aggresome-formation (LC3B-GFP and Ub-RFP co-localization) and autophagy-flux impairment was significantly (p<0.01) mitigated by cysteamine (p<0.05) or fisetin (p<0.05) treatment, indicating the restoration of CSE-mediated autophagy-impairment. CSE treatment was also found to induce intracellular reactive oxygen species (ROS, p < 0.001) while impacting cell viability (p < 0.001), which was quantified using CMH2DCFDA-dye (ROS) and MTS (proliferation) or propodium iodide staining (cell viability) assays, respectively. Moreover, cysteamine and fisetin treatment ameliorated CS-mediated ROS production (p < 0.05) and diminished cell viability (p < 0.05). Lastly, CSE was found to induce cellular senescence (p < 0.001), which was significantly ameliorated by cysteamine (p < 0.001) or fisetin (p < 0.001). In conclusion, our study indicates that CS induced proteostasis/autophagy-impairment regulates mechanisms associated with AMD pathogenesis. Moreover, autophagy-inducing drugs such as cysteamine or fisetin can ameliorate AMD pathogenesis mechanisms that warrant further investigation in pre-clinical murine models.

DNA damage response and autophagy in the degeneration of retinal pigment epithelial cells-Implications for age-related macular degeneration (AMD)

In this review we will discuss the links between autophagy, a mechanism involved in the maintenance of cellular homeostasis and controlling cellular waste management, and the DNA damage response (DDR), comprising various mechanisms preserving the integrity and stability of the genome. A reduced autophagy capacity in retinal pigment epithelium has been shown to be connected in the pathogenesis of age-related macular degeneration (AMD), an eye disease. This degenerative disease is a major and increasing cause of vision loss in the elderly in developed countries, primarily due to the profound accumulation of intra- and extracellular waste: lipofuscin and drusen. An abundance of reactive oxygen species is produced in the retina since this tissue has a high oxygen demand and contains mitochondria-rich cells. The retina is exposed to light and it also houses many photoactive molecules. These factors are clearly reflected in both the autophagy and DNA damage rates, and in both nuclear and mitochondrial genomes. It remains to be revealed whether DNA damage and DDR capacity have a more direct role in the development of AMD.