pH-dependent Interaction of Rhodopsin with Cyanidin-3-glucoside. 2. Functional Aspects

Nanoencapsulation of Cyanidin 3-O-Glucoside: Purpose, Technique, Bioavailability, and Stability

The current growing attractiveness of natural dyes around the world is a consequence of the increasing rejection of synthetic dyes whose use is increasingly criticized. The great interest in natural pigments from herbal origin such as cyanidin 3-O-glucoside (C3G) is due to their biological properties and their health benefits. However, the chemical instability of C3G during processing and storage and its low bioavailability limits its food application. Nanoencapsulation technology using appropriate nanocarriers is revolutionizing the use of anthocyanin, including C3G. Owing to the chemical stability and functional benefits that this new nanotechnology provides to the latter, its industrial application is now extending to the pharmaceutical and cosmetic fields. This review focuses on the various nanoencapsulation techniques used and the chemical and biological benefits induced to C3G.

Nanoencapsulated anthocyanin as a functional ingredient: Technological application and future perspectives

Anthocyanins are an important group of phenolic compounds responsible for pigmentation in several plants, and regular consumption is associated with a reduced risk of several diseases. However, the application of anthocyanins in foods represents a challenge due to molecular instability. The encapsulation of anthocyanins in nanostructures is a viable way to protect from the factors responsible for degradation and enable the industrial application of these compounds. Nanoencapsulation is a set of techniques in which the bioactive molecules are covered by resistant biomaterials that protect them from chemical and biological factors during processing and storage. This review comprehensively summarizes the existing knowledge about the structure of anthocyanins and molecular stability, with a critical analysis of anthocyanins' nanoencapsulation, the main encapsulating materials (polysaccharides, proteins, and lipids), and techniques used in the formation of nanocarriers to protect anthocyanins. Some studies point to the effectiveness of nanostructures in maintaining anthocyanin stability and antioxidant activity. The main advantages of the application of nanoencapsulated anthocyanins in foods are the increase in the nutritional value of the food, the addition of color, the increase in food storage, and the possible increase in bioavailability after oral ingestion. Nanoencapsulation improves stability for anthocyanin, thus demonstrating the potential to be included in foods or used as dietary supplements, and current limitations, challenges, and future directions of anthocyanins' have also been discussed.

Effects of anthocyanin, astaxanthin, and lutein on eye functions: a randomized, double-blind, placebo-controlled study

We examined the effects of a test food containing anthocyanin, astaxanthin, and lutein on the eye function in healthy Japanese adults with eye fatigue after operating visual display terminals. Forty-four subjects were randomly but equally assigned to the active or placebo group. Two active or placebo capsules were taken once daily for 6 weeks. Accommodative function, tear film break-up time, visual acuity, the value of Schirmer's test, macular pigment optical density level, muscle hardness, and a questionnaire were evaluated before and after a 6-week intervention. Each group included 20 subjects in the efficacy analysis. The active group showed a significant improvement in the percentage of pupillary response of an average of both eyes and dominant eye pre- and post-visual display terminal operation at 6 weeks compared with the placebo group. Moreover, the active group showed a significant improvement in the scores of "A sensation of trouble in focusing the eyes" and "Difficulty in seeing objects in one's hand and nearby, or fine print" compared with the placebo group between before and after ingestion. Therefore, 6-weeks consumption of the test food inhibited a decrease in the accommodative function caused by visual display terminal operation (UMIN000036989).

Cyanidin-3-O-Glucoside Attenuates Lipopolysaccharide-Induced Inflammation in Human Corneal Epithelial Cells by Inducing Let-7b-5p-Mediated HMGA2/PI3K/Akt Pathway

The bacterial keratitis causes viability loss and apoptosis in the corneal epithelial cells (CECs). The cyanidin-3-O-glucoside (C3G) benefits visual system and also possess anti-bacterial and anti-inflammatory potentials. In the current study, the effects of C3G on human CECs (HCECs) against bacterial lipopolysaccharide (LPS)-induced disorders were assessed, and the mechanism driving the protective effect was explored by focusing on let-7b-5p-mediated HMGA2/PI3K/Akt pathway. The HCECs were incubated LPS of P. aeruginosa to induce inflammation and apoptosis, and then treated with C3G. The changes in cell viability, apoptosis, and inflammation were detected. Moreover, the effects of LPS and C3G on let-7b-5p level and HMGA2/PI3K/Akt pathway activity were also assessed. Thereafter, the HCECs were further transfected with let-7b-5p inhibitor to confirm its role in the vision-protective effects of C3G. The interaction between let-7b-5p and HMGA2 was verified with dual luciferase assay. The LPS treatment suppressed viability and induced apoptosis and inflammation in HCECs, which was associated with the down-regulated let-7b-5p level and up-regulated HMGA2/PI3K/Akt pathway activity. The impairments of LPS on HCECs were attenuated by C3G: the compound increased cell viability and inhibited apoptosis and inflammation. The C3G also induced let-7b-5p level and inactivated HMGA2/PI3K/Akt pathway. However, after the inhibition of let-7b-5p, the protective effects of C3G on HCECs against LPS were blocked. The results of dual luciferase assay showed the direct binding let-7b-5p to the promoter of HMGA2 gene. It was inferred that the C3G could ameliorate the LPS-induced disorders in HCECs. The effect depended on the induced level of let-7b-5p, which then inhibited HMGA2/PI3K/Akt pathway.

Recent Research on the Health Benefits of Blueberries and Their Anthocyanins

Awareness of the human health benefits of blueberries is underpinned by a growing body of positive scientific evidence from human observational and clinical research, plus mechanistic research using animal and in vitro models. Blueberries contain a large number of phytochemicals, including abundant anthocyanin pigments. Of their various phytochemicals, anthocyanins probably make the greatest impact on blueberry health functionality. Epidemiological studies associate regular, moderate intake of blueberries and/or anthocyanins with reduced risk of cardiovascular disease, death, and type 2 diabetes, and with improved weight maintenance and neuroprotection. These findings are supported by biomarker-based evidence from human clinical studies. Among the more important healthful aspects of blueberries are their anti-inflammatory and antioxidant actions and their beneficial effects on vascular and glucoregulatory function. Blueberry phytochemicals may affect gastrointestinal microflora and contribute to host health. These aspects have implications in degenerative diseases and conditions as well as the aging process. More evidence, and particularly human clinical evidence, is needed to better understand the potential for anthocyanin-rich blueberries to benefit public health. However, it is widely agreed that the regular consumption of tasty, ripe blueberries can be unconditionally recommended.

The Retinoid and Non-Retinoid Ligands of the Rod Visual G Protein-Coupled Receptor

G protein-coupled receptors (GPCRs) play a predominant role in the drug discovery effort. These cell surface receptors are activated by a variety of specific ligands that bind to the orthosteric binding pocket located in the extracellular part of the receptor. In addition, the potential binding sites located on the surface of the receptor enable their allosteric modulation with critical consequences for their function and pharmacology. For decades, drug discovery focused on targeting the GPCR orthosteric binding sites. However, finding that GPCRs can be modulated allosterically opened a new venue for developing novel pharmacological modulators with higher specificity. Alternatively, focus on discovering of non-retinoid small molecules beneficial in retinopathies associated with mutations in rhodopsin is currently a fast-growing pharmacological field. In this review, we summarize the accumulated knowledge on retinoid ligands and non-retinoid modulators of the light-sensing GPCR, rhodopsin and their potential in combating the specific vision-related pathologies. Also, recent findings reporting the potential of biologically active compounds derived from natural products as potent rod opsin modulators with beneficial effects against degenerative diseases related to this receptor are highlighted here.

Effect of intravitreal and intraperitoneal cyanidin-3-glucoside injection in oxygen-induced retinopathy mouse model

Purpose:

To evaluate the effect of cyanidin-3-glucoside (C3G) in oxygen-induced retinopathy (OIR) mouse model.

Methods:

In this experimental study, 10 C57BL / 6J type mice exposed to room air comprised two control groups (n = 5 each; a negative control and a group receiving intravitreal sterile dimethyl sulfoxide [IVS DMSO]). Thirty C57BL / 6J type mice exposed to 75% ± 2% oxygen from postnatal day 7 to postnatal day 12 comprised the OIR groups. On postnatal day 12, these mice were randomized into six groups (n = 5 each): two OIR control groups (negative control and IVS DMSO), two intravitreal C3G groups (300 and 600 ng/μL), and two intraperitoneal C3G groups (0.05 and 0.1 mg/kg). We quantified neovascularization by counting endothelial cell proliferation on the vitreal side of the inner limiting membrane of the retina and examined histological and ultrastructural changes via light and electron microscopy and apoptosis by terminal deoxynucleotidyl transferase deoxy-UTP-nick end labeling.

Results:

The intravitreal C3G groups yielded lower endothelial cell counts compared with the intravitreal DMSO group. The intraperitoneal high-dose group had lower cell counts compared with the OIR control groups. Electron microscopy revealed significantly less mitochondrial dysmorphology in intravitreal groups and the high-dose intraperitoneal mice. We noted no difference in apoptotic cell count between the controls, low-dose intravitreal, and both intraperitoneal groups. However, apoptotic cell count was significantly higher in the high-dose intravitreal group.

Conclusion:

C3G suppresses endothelial cell proliferation in an OIR mouse model, leads to a reduced hyperoxia-induced mitochondrial dysmorphology, but increases apoptotic cell death in high concentrations.

Flavonoids enhance rod opsin stability, folding, and self-association by directly binding to ligand-free opsin and modulating its conformation

Rhodopsin (Rho) is a visual G protein-coupled receptor expressed in the rod photoreceptors of the eye, where it mediates transmission of a light signal into a cell and converts this signal into a nerve impulse. More than 100 mutations in Rho are linked to various ocular impairments, including retinitis pigmentosa (RP). Accordingly, much effort has been directed toward developing ligands that target Rho and improve its folding and stability. Natural compounds may provide another viable approach to such drug discovery efforts. The dietary polyphenol compounds, ubiquitously present in fruits and vegetables, have beneficial effects in several eye diseases. However, the underlying mechanism of their activity is not fully understood. In this study, we used a combination of computational methods, biochemical and biophysical approaches, including bioluminescence resonance energy transfer, and mammalian cell expression systems to clarify the effects of four common bioactive flavonoids (quercetin, myricetin, and their mono-glycosylated forms quercetin-3-rhamnoside and myricetrin) on rod opsin stability, function, and membrane organization. We observed that by directly interacting with ligand-free opsin, flavonoids modulate its conformation, thereby causing faster entry of the retinal chromophore into its binding pocket. Moreover, flavonoids significantly increased opsin stability, most likely by introducing structural rigidity and promoting receptor self-association within the biological membranes. Of note, the binding of flavonoids to an RP-linked P23H opsin variant partially restored its normal cellular trafficking. Together, our results suggest that flavonoids could be utilized as lead compounds in the development of effective nonretinoid therapeutics for managing RP-related retinopathies.

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.

Cyanidin-3-glucoside Alleviates 4-Hydroxyhexenal-Induced NLRP3 Inflammasome Activation via JNK-c-Jun/AP-1 Pathway in Human Retinal Pigment Epithelial Cells

Recently, the NLRP3 inflammasome activation in the eyes has been known to be associated with the pathogenesis of age-related macular degeneration. The aim of this study was to investigate the protective effects of cyanidin-3-glucoside (C3G), an important anthocyanin with great potential for preventing eye diseases, against 4-hydroxyhexenal- (HHE-) induced inflammatory damages in human retinal pigment epithelial cells, ARPE-19. We noticed that C3G pretreatment to the ARPE-19 cells rescued HHE-induced antiproliferative effects. Cell apoptosis ratio induced by HHE was also decreased by C3G, measured by flow cytometry. The activation of NLRP3 inflammasome induced by HHE was found with increases of caspase-1 activity, proinflammatory cytokine releases (IL-1β and IL-18), and NLRP3 inflammasome-related gene expressions (NLRP3, IL-1β, IL-18, and caspase-1). The C3G showed potent inhibitive effects on these NLRP3 inflammasome activation hallmarks induced by HHE. Moreover, we noticed that the C3G's pretreatment leads to a delayed and a decreased JNK activation in HHE-challenged ARPE-19 cells. Finally, using a luciferase reporter gene assay system, we demonstrated that HHE-induced activation protein- (AP-) 1 transcription activity was abolished by C3G pretreatment in a dose-dependent manner. Taken together, these data showed that HHE leads to inflammatory damages to ARPE-19 cells while C3G has great protective effects, highlighting future potential applications of C3G against AMD-associated inflammation.

A standardized extract of Rhynchosia volubilis Lour. exerts a protective effect on benzalkonium chloride-induced mouse dry eye model

ETHNOPHARMACOLOGICAL RELEVANCE

In contrast to other leguminous plants generally used as food, Rhynchosia volubilis Loureiro, a small soybean with a black seed coat, has been used as a traditional oriental remedy for various human diseases in Eastern Asia. In this study, we demonstrated the protective effect of R. volubilis against dry eye disease.

AIM OF THE STUDY

We aimed to investigate whether a standardized ethanol extract of R. volubilis (EERV) can protect the cornea in a benzalkonium chloride (BAC)-induced mouse dry eye model.

MATERIALS AND METHODS

Experimental dry eye was induced by the instillation of 0.2% BAC on mouse cornea. A standardized ethanol extract of R. volubilis (EERV) was orally administered following BAC treatment. The positive control group was treated with commercial eye drops. Fluorescein staining, tear break-up time (BUT), and hematoxylin and eosin staining were evaluated on the ocular surface. Squamous metaplasia and apoptosis in the corneal epithelial layer were detected by immunostaining. Furthermore, the protein expression of cytochrome c, Bcl-2, and Bax was determined.

RESULTS

EERV treatment significantly improved fluorescein scoring, BUT, and smoothness in the cornea compared to the vehicle group. In addition, EERV inhibited squamous metaplasia and apoptosis in the cornea. The expression of cytochrome c and Bax was upregulated, while that of Bcl-2 was downregulated in the vehicle group compared with that in the control group. However, EERV treatment inhibited the expression of cytochrome c and Bax, while that of Bcl-2 was improved.

CONCLUSION

Standardized EERV could be a beneficial candidate for the treatment of dry eye disease.

The Anthocyanins, Oenin and Callistephin, Protect RPE Cells Against Oxidative Stress

The retinal pigment epithelium (RPE) is a highly metabolic layer of postmitotic cells lining Bruch's membrane in the retina. While these cells contain endogenous photosensitizers that mediate blue light-induced damage, it has also been shown that blue light exposure damages mitochondrial DNA in RPE cells resulting in mitochondrial dysfunction and unregulated generation of reactive oxygen species (ROS). As RPE cells are postmitotic, it is imperative to decrease oxidative stress to these cells and preserve function. Dietary plant-derived antioxidants such as anthocyanins offer a simple and accessible solution for decreasing oxidative stress. The anthocyanins malvidin-3-O-glucoside (oenin) and pelargonidin-3-O-glucoside (callistephin) were tested for their ability and efficacy in decreasing ROS generation and preserving mitochondrial redox activity in blue light-irradiated ARPE-19 cells. A significant decrease in intracellular ROS with concurrent increase in mitochondrial redox activity was observed for tested concentrations of oenin, while callistephin was beneficial to stressed cells at higher concentrations. These findings suggest anthocyanins are effective antioxidants in blue light-stressed RPE cells in vitro. Additionally, oxidation products of these anthocyanins were examined using LC/MS and findings suggest the possibility of multiple oxidation sites for these compounds.

Blueberry effects on dark vision and recovery after photobleaching: placebo-controlled crossover studies

Clinical evidence for anthocyanin benefits in night vision is controversial. This paper presents two human trials investigating blueberry anthocyanin effects on dark adaptation, functional night vision, and vision recovery after retinal photobleaching. One trial, S2 (n = 72), employed a 3 week intervention and a 3 week washout, two anthocyanin doses (271 and 7.11 mg cyanidin 3-glucoside equivalents (C3g eq)), and placebo. The other trial, L1 (n = 59), employed a 12 week intervention and an 8 week washout and tested one dose (346 mg C3g eq) and placebo. In both S2 and L1 neither dark adaptation nor night vision was improved by anthocyanin intake. However, in both trials anthocyanin consumption hastened the recovery of visual acuity after photobleaching. In S2 both anthocyanin doses were effective (P = 0.014), and in L1 recovery was improved at 8 weeks (P = 0.027) and 12 weeks (P = 0.030). Although photobleaching recovery was hastened by anthocyanins, it is not known whether this improvement would have an impact on everyday vision.

Differential effects of black currant anthocyanins on diffuser- or negative lens-induced ocular elongation in chicks

PURPOSE

To compare the inhibitory effects of 4 different types of black currant anthocyanins (BCAs) on ocular elongation in 2 different chick myopia models.

METHODS

In the first model, diffusers were used to induce form vision deprivation. In the second model, negative (-8D) spherical lenses were used to create a defocused retinal image. Either the diffusers or the -8D lenses were placed on the right eyes of 8-day-old chicks for 4 days. Ocular biometric components were measured using an A-scan ultrasound instrument on the third day after application of either the diffusers or -8D lenses. Interocular differences (globe component dimensions of the right diffuser or eyes covered with -8D lenses minus those of the open left eyes) were considered to evaluate the effect of BCAs. The BCAs used were cyanidin-3-glucoside (C3G), cyanidin-3-rutinoside (C3R), delphinidin-3-rutinoside (D3R), and delphinidin-3-glucoside (D3G). Each anthocyanin was administered intravenously at a dose of 0.027 μmol/kg once a day for 3 days.

RESULTS

Compared to the vehicle treatment, C3G and C3R treatments significantly reduced both differential increases (positive values of interocular differences) of the ocular axial length induced by diffusers or -8D lenses (diffusers; C3G, C3R, and control: 0.32±0.051 mm, P<0.05; 0.25±0.034 mm, P<0.01; and 0.52±0.047 mm, -8D lenses; C3G, C3R, and control: 0.25±0.049 mm, P<0.01; 0.17±0.049 mm, P<0.001; and 0.50±0.056 mm). In contrast, compared to vehicle treatment, D3R treatment significantly decreased the differential increases in the ocular axial length only in chicks with myopia induced by -8D lenses (D3R and control: 0.17±0.049 mm and 0.50±0.056 mm, P<0.001). D3G did not inhibit the differential increase in the ocular axial length induced by either diffusers or -8D lenses.

CONCLUSIONS

This study showed that the 4 tested BCAs had different effects on the 2 different experimental models of myopia.

Prophylactic neuroprotection by blueberry-enriched diet in a rat model of light-induced retinopathy

The role of anthocyanins is controversial in vision health. This study investigates the impact of a blueberry-enriched diet as neuroprotectant in a rat model of light-induced retinopathy. Thirty-eight albino Wistar rats and 25 pigmented Brown-Norway rats were fed by gavage with long (7 weeks) and short (2 weeks) intervention with fortified blueberry juice (1 ml; 2.8 mg cyanidin 3-glucoside equivalents) or with a placebo solution (7 weeks) that contained the abundant nonanthocyanin blueberry phenolic, namely, chlorogenic acid, before being submitted to 2 hours of intense light regimen (1.8×10(4) lux). Retinal health was measured by fitting electroretinogram responses with the Naka-Rushton equation. The light-induced retinal damage was severe in the placebo groups, with the maximum amplitude of the electroretinogram being significantly reduced in both Wistar and Brown-Norway rats. The maximum amplitude of the electroretinogram was significantly protected from the light insult in the Wistar rats supplemented with blueberry juice for 7 or 2 weeks, and there was no significant difference between these two groups. The same dietary intervention in the Brown-Norway groups failed to protect the retina. Histological examination of retinal section confirmed the electroretinography results, showing protection of the outer nuclear layer of the retina in the Wistar rats fed with blueberries, while all placebo-fed rats and blueberry-fed Brown-Norway rats showed evidence of retinal damage concentrated in the superior hemiretina. The neuroprotective potential of anthocyanins in this particular model is discussed in terms of interaction with rhodopsin/phototransduction and in terms of antioxidative capacity.

Anthocyanins from the seed coat of black soybean reduce retinal degeneration induced by N-methyl-N-nitrosourea

Anthocyanins are known to have antioxidant effects and thus may play an important role in preventing various degenerative diseases. In this study, we examined the effect of anthocyanins extracted from the seed coat of black soybean on an animal model of retinal degeneration (RD), a leading cause of photoreceptor cell death resulting in blindness. RD was induced in rats by an intraperitoneal injection of N-methyl-N-nitrosourea (MNU) (50mg/kg), a DNA-methylating agent that causes photoreceptor damage. Anthocyanins extracted from black soybean seed coat (50mg/kg) were daily administered, orally, for 1, 2, and 4 weeks after MNU injection. Electroretinographic (ERG) recordings and morphological analyses were performed. In control rats with MNU-induced retinal damage, the ERG recordings showed a gradual significant time-dependent reduction in both a- and b-wave amplitudes compared with those of normal animals. In the MNU-induced RD rats given anthocyanins for 4 weeks, ERG responses were significantly increased compared with untreated RD rats, more apparently in scotopic stimulation than in the photopic condition. However, in the MNU-injected rats given anthocyanins for 1 and 2 weeks, the increase in ERG responses was not significant. Morphologically, the outer nuclear layer, where photoreceptors reside, was well preserved in the anthocyanin-treated rat retinas throughout the experimental period. In addition, retinal injury, evaluated by immunolabeling with an antibody against glial fibrillary acidic protein, was markedly reduced in anthocyanin-treated retinas. These results demonstrate that anthocyanins extracted from black soybean seeds can protect retinal neurons from MNU-induced structural and functional damages, suggesting that anthocyanins from black soybean seed coat may be used as a useful supplement to modulate RD.

The cytoplasmic rhodopsin-protein interface: potential for drug discovery

The mammalian dim-light photoreceptor rhodopsin is a prototypic G protein coupled receptor (GPCR), interacting with the G protein, transducin, rhodopsin kinase, and arrestin. All of these proteins interact with rhodopsin at its cytoplasmic surface. Structural and modeling studies have provided in-depth descriptions of the respective interfaces. Overlap and thus competition for binding surfaces is a major regulatory mechanism for signal processing. Recently, it was found that the same surface is also targeted by small molecules. These ligands can directly interfere with the binding and activation of the proteins of the signal transduction cascade, but they can also allosterically modulate the retinal ligand binding pocket. Because the pocket that is targeted contains residues that are highly conserved across Class A GPCRs, these findings imply that it may be possible to target multiple GPCRs with the same ligand(s). This is desirable for example in complex diseases such as cancer where multiple GPCRs participate in the disease networks.

Dietary anthocyanin-rich plants: biochemical basis and recent progress in health benefits studies

Anthocyanins are one type of flavonoid phytopigment. Although the role of anthocyanins as a functional food factor remains relatively less established than that of other flavonoids, progress in this area has been made at the molecular level in recent years. This review discusses the potential health benefits of plant-derived anthocyanin-rich foods, with a focus on the role of anthocyanins in obesity control, diabetes control, cardiovascular disease prevention, and improvement of visual and brain functions, areas that have attracted much attention. Such health benefits are not necessarily derived from the antioxidant effect of anthocyanins, but in fact are produced by currently unestablished chemical properties beyond the antioxidant capacity of the molecules. However, a better understanding of the physiological functionality of anthocyanins remains to be elucidated. It is desirable, therefore, to clarify the molecular type and composition of the anthocyanins that confer specific health benefits and to conduct further investigation into the underlying molecular mechanisms. The pharmacological actions of anthocyanins could not be fully established without knowledge on the effects of treatment of anthocyanins alone, the effects of non-anthocyanin components, and the possible interactions between anthocyanin and non-anthocyanin species.

Identification of anthocyanin components of wild Chinese blueberries and amelioration of light-induced retinal damage in pigmented rabbit using whole berries

Studies suggest that the consumption of berry fruits rich in anthocyanins may have beneficial effects on improving visual function. This study determined the total polyphenol and total anthocyanin contents in wild Chinese blueberries using the Folin-Ciocalteu reagent method and a pH differential method. Anthocyanin composition and quantity were characterized by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry coupled with mass selective detection. Total polyphenol and anthocyanin contents were 602.9 ± 9.2 and 177.8 ± 8.3 mg/100 g, respectively. Seventeen anthocyanins were discovered, and only 13 were tentatively identified in the wild blueberries. Anthocyanins of malvidin glycosylated with hexose or pentose accounted for >46% of total anthocyanin content. Furthermore, the effect of whole blueberries on retinal damage in pigmented rabbits upon light exposure was investigated, and the retinal functions were evaluated by electroretinogram (ERG). Pigmented rabbits were chosen for this experiment because of their large eyes, which facilitated the operative procedure and observation, and the similarity of their eyes to the human eye structure. Light-induced retinal damage was induced by exposure to white light at 15000 ± 1000 lx for 2 h. Feeding the rabbits with blueberries at a dosage of 1.2 or 4.9 g/kg/day for 4 weeks prior to light exposure effectively reduced photodamage to the retinas. This study adds to the growing body of data supporting the bioactivity of blueberries in improving mammal vision.

Allosteric Modulation of G Protein Coupled Receptors by Cytoplasmic, Transmembrane and Extracellular Ligands

G protein coupled receptors (GPCRs) bind diverse classes of ligands, and depending on the receptor, these may bind in their transmembrane or the extracellular domains, demonstrating the principal ability of GPCRs to bind ligand in either domains. Most recently, it was also observed that small molecule ligands can bind in the cytoplasmic domain, and modulate binding and response to extracellular or transmembrane ligands. Thus, all three domains in GPCRs are potential sites for allosteric ligands, and whether a ligand is allosteric or orthosteric depends on the receptor. Here, we will review the evidence supporting the presence of putative binding pockets in all three domains of GPCRs and discuss possible pathways of communication between these pockets.

Recent research on polyphenolics in vision and eye health

A long-standing yet controversial bioactivity attributed to polyphenols is their beneficial effects in vision. Although anecdotal case reports and in vitro research studies provide evidence for the visual benefits of anthocyanin-rich berries, rigorous clinical evidence of their benefits is still lacking. Recent in vitro studies demonstrate that anthocyanins and other flavonoids interact directly with rhodopsin and modulate visual pigment function. Additional in vitro studies show flavonoids protect a variety of retinal cell types from oxidative stress-induced cell death, a neuroprotective property of significance because the retina has the highest metabolic rate of any tissue and is particularly vulnerable to oxidative injury. However, more information is needed on the bioactivity of in vivo conjugates and the accumulation of flavonoids in ocular tissues. The direct and indirect costs of age-related vision impairment provide a powerful incentive to explore the potential for improved vision health through the intake of dietary polyphenolics.