In vitro studies on nobiletin isolated from citrus plants and the bioactive metabolites, inhibitory action against gelatinase enzymatic activity and the molecular mechanisms in human retinal Müller cell line

Antisolvent precipitation for the synergistic preparation of ultrafine particles of nobiletin under ultrasonication-homogenization and evaluation of the inhibitory effects of α-glucosidase and porcine pancreatic lipase in vitro

To further enhance the application of nobiletin (an important active ingredient in Citrus fruits), we used ultrasonic homogenization-assisted antisolvent precipitation to create ultrafine particles of nobiletin (UPN). DMSO was used as the solvent, and deionized water was used as the antisolvent. When ultrasonication (670 W) and homogenization (16000 r/min) were synergistic, the solution concentration was 57 mg/mL, and the minimum particle size of UPN was 521.02 nm. The UPN samples outperformed the RN samples in terms of the inhibition of porcine pancreatic lipase, which was inhibited (by 500 mg/mL) by 68.41 % in the raw sample, 90.34 % in the ultrafine sample, and 83.59 % in the positive control, according to the data. Fourier transform infrared spectroscopy analysis revealed no chemical changes in the samples before or after preparation. However, the crystallinity of the processed ultrafine nobiletin particles decreased. Thus, this work offers significant relevance for applications in the realm of food chemistry and indirectly illustrates the expanded application potential of nobiletin.

Effects of Nobiletin supplementation on the freezing diluent on porcine sperm cryo-survival and subsequent in vitro embryo development

Nobiletin (NOB) is a bioflavonoid compound isolated from citrus fruit peels. The present study aimed to elucidate whether NOB facilitates the porcine sperm cryosurvival and embryo development after in vitro fertilization (IVF). To this end, spermatozoa were diluted and cryopreserved in a freezing extender supplemented with 0 (control), 50, 100, 150, and 200 μM Nobiletin. The kinematic patterns of frozen-thawed (FT) sperm were assessed after 30 and 90 min incubation using a Sperm Class Analyzer (SCA). Viability, acrosome integrity, and mitochondrial membrane potential (MMP) were measured by fluorescence microscopy 30 min after thawing using SYBR-14/PI, PSA/FITC, and R123/PI, respectively. Lipid peroxidation was determined using MDA assay after incubation for 90 min. The addition of 100 μM and 150 μM NOB to the extender significantly improved sperm progressive motility, and acrosome integrity compared to the control group (P < 0.05). The proportion of viable spermatozoa was significantly higher in the 150 μM NOB group. MDA levels were less in 50 μM and 150 μM NOB treated groups compared to the control. In addition, IVF with FT sperm was used to assess the embryo developmental competence. Treatment with 150 μM NOB before cryopreservation increased the cleavage and blastocyst formation rates compared to the control group. Furthermore, the relative expression of POU5F1 and AMPK, genes related to pluripotency and cell differentiation were significantly upregulated in embryos resulting from NOB-treated sperm compared to the control group. These results suggest that Nobiletin is a functionally novel phytochemical to mitigate oxidative stress during the freezing-thawing of porcine spermatozoa as reflected by improved FT sperm quality and IVF outcome.

Omnifarious fruit polyphenols: an omnipotent strategy to prevent and intervene diabetes and related complication?

Diabetes mellitus is a metabolic syndrome which cannot be cured. Recently, considerable interest has been focused on food ingredients to prevent and intervene in complications of diabetes. Polyphenolic compounds are one of the bioactive phytochemical constituents with various biological activities, which have drawn increasing interest in human health. Fruits are part of the polyphenol sources in daily food consumption. Fruit-derived polyphenols possess the anti-diabetic activity that has already been proved either from in vitro studies or in vivo studies. The mechanisms of fruit polyphenols in treating diabetes and related complications are under discussion. This is a comprehensive review on polyphenols from the edible parts of fruits, including those from citrus, berries, apples, cherries, mangoes, mangosteens, pomegranates, and other fruits regarding their potential benefits in preventing and treating diabetes mellitus. The signal pathways of characteristic polyphenols derived from fruits in reducing high blood glucose and intervening hyperglycemia-induced diabetic complications were summarized.

Bone marrow mesenchymal stem cells-induced exosomal microRNA-486-3p protects against diabetic retinopathy through TLR4/NF-κB axis repression

AIM

Diabetic retinopathy (DR) is a chronic disease causing health and economic burdens on individuals and society. Thus, this study is conducted to figure out the mechanisms of bone marrow mesenchymal stem cells (BMSCs)-induced exosomal microRNA-486-3p (miR-486-3p) in DR.

METHODS

The putative miR-486-3p binding sites to 3'untranslated region of Toll-like receptor 4 (TLR4) was verified by luciferase reporter assay. High glucose (HG)-treated Muller cells were transfected with miR-486-3p or TLR4-related oligonucleotides and plasmids to explore theirs functions in DR. Additionally, HG-treated Muller cells were co-cultured with BMSC-derived exosomes, exosomes collected from BMSCs that had been transfected with miR-486-3p or TLR4-related oligonucleotides and plasmids to explore their functions in DR. MiR-486-3p, TLR4 and nuclear factor-kappaB (NF-κB) expression, angiogenesis-related factors, oxidative stress factors, viability and apoptosis in HG-treated Muller cells were detected by RT-qPCR, western blot analysis, ELISA, MTT assay and flow cytometry, respectively.

RESULTS

MiR-486-3p was poorly expressed while TLR4 and NF-κB were highly expressed in HG-treated Muller cells. TLR4 was a target of miR-486-3p. Upregulating miR-486-3p or down-regulating TLR4 inhibited oxidative stress, inflammation and apoptosis, and promoted proliferation of HG-treated Muller cells. Meanwhile, BMSC-derived exosomes inhibited oxidative stress, inflammation and apoptosis, and promoted proliferation of HG-treated Muller cells. Restoring miR-486-3p further enhanced, while up-regulating TLR4 reversed, the improvement of exosomes treatment.

CONCLUSION

Our study highlights that up-regulation of miR-486-3p induced by BMSC-derived exosomes played a protective role in DR mice via TLR4/NF-κB axis repression.

Regulation of Endothelium-Reticulum-Stress-Mediated Apoptotic Cell Death by a Polymethoxylated Flavone, Nobiletin, Through the Inhibition of Nuclear Translocation of Glyceraldehyde 3-Phosphate Dehydrogenase in Retinal Müller Cells

In the early stages of diabetic retinopathy (DR), subtle biochemical and functional alterations occur in Müller cells, which are one of the components of the blood-retinal barrier (BRB). Müller cells are the principal glia of the retina and have shown a strong involvement in the maintenance of homeostasis and the development of retinal tissue. Their functional abnormalities and eventual loss have been correlated with a decrease in the tight junctions between endothelial cells and a consequent breakdown of the BRB, leading to the development of DR. We demonstrated that the endothelium reticulum (ER) triggers Müller cell death and that nuclear accumulation of glyceraldehyde 3-phosphate dehydrogenase is closely associated with ER-induced Müller cell death. In addition, induction of ER stress in Müller cells increased vascular endothelial growth factor expression but decreased pigment-epithelium-derived factor (PEDF) expression in Müller cells. We found that nobiletin, a polymethoxylated flavone from citrus explants, exerts protective action against ER-stress-induced Müller cell death. In addition, nobiletin was found to augment PEDF expression in Müller cells, which may lead to the protection of BRB integrity. These results suggest that nobiletin can be an attractive candidate for the protection of the BRB from breakdown in DR.

[Structure Activity Relationship Study of Polymethoxylated Flavones Targeted Retinal Müller Cells for Prevention of Retinal Diseases]

Diabetic retinopathy (DR) is a retinal disease representing one of the main causes of vision loss in developed countries. In the early stage of DR, disruption of blood retinal barrier (BRB) is observed, and it will lead to vascular permeability and visual impairment. Therefore, protection against the breakdown of BRB may be useful strategy for prevention of DR. Matrix metalloproteinases (MMPs) plays an important role in the degradation of extracellular matrix proteins. In DR, they attribute to increased vascular permeability by degrading the junction proteins, such as occuldin and cadherin that are important to maintain the BRB junction complex. Müller cells constitute the main glial cells of the retina and are involved in many retinal functions. They are reported to be one of the MMP-producing cells in the retina. In this symposium review, I present the molecular mechanism of MMP expression in retinal Müller cells. In addition, I would like to introduce polymethoxylated flavones, nobiletin and the derivatives isolated from natural resource as novel MMP inhibitors, which may be applicable to prevention of DR.

Flavones as a Privileged Scaffold in Drug Discovery: Current Developments

BACKGROUND

Flavones are one of the main subclasses of flavonoids with diverse pharmacological properties. They have been reported to possess antimalarial, antimicrobial, anti-tuberculosis, anti-allergic, antioxidant, anti-inflammatory activities, among others.

OBJECTIVE

The present review summarizes the recent information on the pharmacological properties of naturally occurring and synthetic flavones.

METHODS

Scientific publications referring to natural and synthetic flavones in relation to their biological activities were hand-searched in databases such as SciFinder, PubMed (National Library of Medicine), Science Direct, Wiley, ACS, SciELO, Springer, among others.

RESULTS

As per the literature, seventy-five natural flavones were predicted as active compounds with reference to their IC50 (<20 µg/mL) in in vitro studies. Also, synthetic flavones were found active against several diseases.

CONCLUSION

As per the literature, flavones are important sources for the potential treatment of multifactorial diseases. However, efforts toward the development of flavone-based therapeutic agents are still needed. The appearance of new catalysts and chemical transformations is expected to provide avenues for the synthesis of unexplored flavones, leading to the discovery of flavones with new properties and biological activities.

Potential Therapeutic Agents, Polymethoxylated Flavones Isolated from Kaempferia parviflora for Cataract Prevention through Inhibition of Matrix Metalloproteinase-9 in Lens Epithelial Cells

Natural flavonoids have powerful antioxidant activity and have been reported to show promising protective effects against cataracts. The plant Kaempferia parviflora (K. parviflora) is indigenous to southeast Asia, including Thailand, and typically contains polymethoxylated flavones. The flavones in K. parviflora are reported to have various biological properties. Recently, polymethoxylated flavones of K. parviflora (KPMFs) were shown to have potent Sirtuin 1 enzyme-stimulating and anti-glycation activities that led to the suppression of cataract formation. Matrix metalloproteinases (MMPs) are upregulated in several pathologic ocular diseases, including cataracts, and have been established as an attractive target for the prevention and/or treatment of specific cataract phenotypes, such as anterior subcapsular cataract (ASC) and posterior capsular opacification (PCO). In the present study, we investigated the effect of KPMFs on MMP (gelatinase) activity in the human lens epithelial cell line, SRA01/04. We demonstrated that KPMFs inhibited the phorbol ester-induced MMP-9 activity and the mRNA expression through the suppression of mitogen-activated protein kinases (MAPKs) phosphorylation in human lens epithelial cells; 5,7-dimethoxyflavone was found to exert the most potent inhibition, but 3,5,7,4'-tetramethoxyflavone and 3,5,7,3',4'-pentamethoxyflavone also resulted in considerable inhibition. Our results suggested that the consumption of PMFs isolated from K. parviflora, may be an effective strategy to delay the development of cataracts, such as ASC and PCO.

Müller cells in pathological retinal angiogenesis

Müller cells are the major glial cells spanning the entire layer of the retina and maintaining retinal structure. Under pathological conditions, Müller cells are involved in retinal angiogenesis, a process of growing new blood vessels from pre-existing capillaries. In response to hypoxia, high glucose, and inflammation conditions, multiple signaling pathways are activated in Müller cells, followed by the increased production of proangiogenic factors including vascular endothelial growth factor, basic fibroblast growth factor, matrix metalloproteinases, Netrin-4, and angiopoietin-like 4. Expression of antiangiogenic factors is also downregulated in Müller cells. Besides, proliferation and dedifferentiation of Müller cells facilitates retinal angiogenesis. In this review, we summarized molecular mechanisms of Müller cells-related retinal angiogenesis. The potential of Müller cells as a therapeutic target for retinal angiogenesis was also discussed.

Nobiletin suppresses high-glucose-induced inflammation and ECM accumulation in human mesangial cells through STAT3/NF-κB pathway

Diabetic nephropathy (DN) is a complication of chronic diabetes and the main cause of end-stage renal disease all over the world. Inflammation and extracellular matrix (ECM) accumulation play important roles in the pathogenesis of DN. Evidence suggested that nobiletin acts anti-inflammatory role and plays a critical role in diabetes; however, its role in DN remains unclear. In the current study, we promulgated the nobiletin involved in high-glucose-induced glomerular mesangial cell inflammation and ECM accumulation. Nobiletin treatment significantly abrogated high-glucose-induced glomerular mesangial cell proliferation. Nobiletin treatment markedly suppressed inflammation cytokine secretion, including interleukin (IL)-1β, IL-6, tumor necrosis factor α, and monocyte chemoattractant protein 1 in high-glucose-induced glomerular mesangial cell. Also, exposed nobiletin to high-glucose-induced glomerular mesangial cell considerably reduced ECM accumulation through inhibited ECM-associated protein type 4 collagen and fibronectin expression. Furthermore, nobiletin treatment abolished nuclear factor κB (NF-κB) pathway activation through signal transducer and activator of transcription 3 (STAT3) inhibition. Overexpression STAT3 reversed the effects of nobiletin on high-glucose-induced glomerular mesangial cell proliferation, inflammation, ECM accumulation, and NF-κB pathway activation. Hence, our results suggest that nobiletin play roles in high-glucose-induced glomerular mesangial cells through inhibiting inflammation and ECM accumulation, and the STAT3/NF-κB pathway was involved in the function of nobiletin.

Nobiletin bioactivation in MDA-MB-468 breast cancer cells by cytochrome P450 CYP1 enzymes

Nobiletin is a fully methoxylated flavone that has demonstrated anticancer activity via multiple modes of action. In the present study, the metabolism and further antiproliferative activity of nobiletin was evaluated in the CYP1 expressing human breast cancer cell line MDA-MB-468 and the normal breast cell line MCF10A. Nobiletin was metabolized in MDA-MB-468 cells to a single-demethylated derivative assigned NP1. This metabolite was absent in MCF10A cells that did not express CYP1 enzymes. Nobiletin exhibited submicromolar IC50 (0.1 ± 0.04 μM) in MDA-MB-468 cells, whereas it was considerably less active in MCF10A cells (40 μM). In MDA-MB-468 cells that were coincubated with the CYP1 inhibitor acacetin, an approximately 300-fold increase was noted in the IC50 (30 ± 2.4 μM) of nobiletin. In the presence of the CYP1 inhibitor acacetin, the conversion of nobiletin to NP1 was significantly reduced in MDA-MB-468 cells. Furthermore, a significant increase was noted in the population of the cells at the G1 phase, following treatment with nobiletin (10 μM) for 24 h compared with the control cells treated with DMSO (0.1%) alone (55.9 ± 0.14 vs. 45.6 ± 1.96), whereas the cell cycle of MCF10A cells was not significantly altered under the same treatment conditions. Taken collectively, the results suggest that nobiletin is selectively bioactivated in MDA-MB-468 breast cancer cells via metabolism by the cytochrome P450 CYP1 family of enzymes.