Astaxanthin Inhibits Expression of Retinal Oxidative Stress and Inflammatory Mediators in Streptozotocin-Induced Diabetic Rats

Astaxanthin supplementation ameliorates simulated heat stress by regulating physio-biochemical responses in Sirohi goats

The present study was undertaken to assess the ameliorative effect of dietary supplementation of astaxanthin in Sirohi goats under simulated heat stress conditions. Eighteen healthy female Sirohi goats were divided equally into three groups (n = 6): Heat-Stressed Control (HSC), Treatment 1 (T1), and Treatment 2 (T2). During the experiment, goats in the T1 group were supplemented with astaxanthin at the rate of 25 mg/animal/day, while those in the T2 group received supplementation of 50 mg/animal/day. The experiment was conducted for 42 days: 14 days of acclimatization period, next 21 days animals were exposed to 42ºC for 6 h from 09:00 h to 15:00 h and 7 days of recovery period. On a daily basis, we recorded the physiological responses of goats and collected environmental data at the experimental site. Blood samples were collected 0 and 14th days of acclimatization, on 1st, 6th, 11th, 16th and 21st day of heat exposure and on the 7th day of the recovery period. The rectal temperature and respiration rates of the treatment groups were lower than those of the HSC group during the exposure period. Heat stress in the supplemented groups was associated with reduced levels of hepatic enzymes such as AST and ALT. Serum urea, creatinine and albumin levels were significantly (P < 0.05) different between control and treatment groups. It was thus concluded that dietary inclusion of antioxidant astaxanthin can ameliorate induced thermal load as evident from changes in physio-biochemical parameters in the Sirohi goats, that was more prominent at 50 mg/ animal/day than 25 mg/ animal/day.

Comparative genomic analysis and optimization of astaxanthin production of Rhodotorula paludigena TL35-5 and Rhodotorula sampaioana PL61-2

Astaxanthin is a powerful antioxidant known to enhance skin, cardiovascular, eye, and brain health. In this study, the genome insights and astaxanthin production of two newly isolated astaxanthin-producing yeasts (TL35-5 and PL61-2) were evaluated and compared. Based on their phenotypic and genotypic characteristics, TL35-5 and PL61-2 were identified as basidiomycetous yeasts belonging to Rhodotorula paludigena and Rhodotorula sampaioana, respectively. To optimize astaxanthin production, the effects of cultural medium composition and cultivation conditions were examined. The optimal conditions for astaxanthin production in R. paludigena TL35-5 involved cultivation in AP medium containing 10 g/L glucose as the sole carbon source, supplemented with 1.92 g/L potassium nitrate, pH 6.5, and incubation at 20°C for 3 days with shaking at 200 rpm. For R. sampaioana PL61-2, the optimal medium composition for astaxanthin production consisted of AP medium with 40 g/L glucose, supplemented with 0.67 g/L urea, pH 7.5, and the fermentation was carried out at 20°C for 3 days with agitating at 200 rpm. Under their optimal conditions, R. paludigena TL35-5 and R. sampaioana PL61-2 gave the highest astaxanthin yields of 3.689 ± 0.031 and 4.680 ± 0.019 mg/L, respectively. The genome of TL35-5 was 20,982,417 bp in length, with a GC content of 64.20%. A total of 6,789 protein-encoding genes were predicted. Similarly, the genome of PL61-2 was 21,374,169 bp long, with a GC content of 64.88%. It contained 6,802 predicted protein-encoding genes. Furthermore, all essential genes involved in astaxanthin biosynthesis, including CrtE, CrtYB, CrtI, CrtS, and CrtR, were identified in both R. paludigena TL35-5 and R. sampaioana PL61-2, providing evidence for their ability to produce astaxanthin.

Marine Natural Products Rescuing the Eye: A Narrative Review

Different degrees of visual impairment lead to a decrease in patient wellbeing, which has an adverse effect on many facets of social and professional life. Eye disorders can affect several parts of the eye, most notably the retina and the cornea, and the impacted areas might share a common form of cellular damage or dysfunction (such as inflammation, oxidative stress and neuronal degeneration). Considering that marine organisms inhabit a broad variety of marine habitats, they display a great degree of chemical diversity. As a result, molecules with a marine origin are receiving more and more attention in the hopes of developing novel therapeutic approaches. For instance, fucoxanthin has been demonstrated to be effective in protecting the retina against photo-induced damage, while largazole, astaxanthin and spirulina have all shown antioxidant, anti-inflammatory and antiapoptotic activities that can be useful for the management of several ocular diseases, such as age-related macular degeneration and ocular surface disorders. The aim of this review is to analyze the scientific literature relating to the therapeutic effects on the eye of the main natural marine products, focusing on their mechanism of action and potential clinical uses for the management of ocular diseases.

Pharmacotherapy and Nutritional Supplements for Neovascular Eye Diseases

In this review, we aim to provide an overview of the recent findings about the treatment of neovascular retinal diseases. The use of conventional drugs and nutraceuticals endowed with antioxidant and anti-inflammatory properties that may support conventional therapies will be considered, with the final aim of achieving risk reduction (prevention) and outcome improvement (cooperation between treatments) of such sight-threatening proliferative retinopathies. For this purpose, we consider a medicinal product one that contains well-defined compound(s) with proven pharmacological and therapeutic effects, usually given for the treatment of full-blown diseases. Rarely are prescription drugs given for preventive purposes. A dietary supplement refers to a compound (often an extract or a mixture) used in the prevention or co-adjuvant treatment of a given pathology. However, it must be kept in mind that drug-supplement interactions may exist and might affect the efficacy of certain drug treatments. Moreover, the distinction between medicinal products and dietary supplements is not always straightforward. For instance, melatonin is formulated as a medicinal product for the treatment of sleep and behavioral problems; at low doses (usually below 1 mg), it is considered a nutraceutical, while at higher doses, it is sold as a psychotropic drug. Despite their lower status with respect to drugs, increasing evidence supports the notion of the beneficial effects of dietary supplements on proliferative retinopathies, a major cause of vision loss in the elderly. Therefore, we believe that, on a patient-by-patient basis, the administration of nutraceuticals, either alone or in association, could benefit many patients, delaying the progression of their disease and likely improving the efficacy of pharmaceutical drugs.

Astaxanthin as a King of Ketocarotenoids: Structure, Synthesis, Accumulation, Bioavailability and Antioxidant Properties

Astaxanthin (3,3-dihydroxy-β, β-carotene-4,4-dione) is a ketocarotenoid synthesized by Haematococcus pluvialis/lacustris, Chromochloris zofingiensis, Chlorococcum, Bracteacoccus aggregatus, Coelastrella rubescence, Phaffia rhodozyma, some bacteria (Paracoccus carotinifaciens), yeasts, and lobsters, among others However, it is majorly synthesized by Haematococcus lacustris alone (about 4%). The richness of natural astaxanthin over synthetic astaxanthin has drawn the attention of industrialists to cultivate and extract it via two stage cultivation process. However, the cultivation in photobioreactors is expensive, and converting it in soluble form so that it can be easily assimilated by our digestive system requires downstream processing techniques which are not cost-effective. This has made the cost of astaxanthin expensive, prompting pharmaceutical and nutraceutical companies to switch over to synthetic astaxanthin. This review discusses the chemical character of astaxanthin, more inexpensive cultivating techniques, and its bioavailability. Additionally, the antioxidant character of this microalgal product against many diseases is discussed, which can make this natural compound an excellent drug to minimize inflammation and its consequences.

The protective effects of flavonoids and carotenoids against diabetic complications-A review of in vivo evidence

Diabetes mellitus is a chronic metabolic disorder caused either by inadequate insulin secretion, impaired insulin function, or both. Uncontrolled diabetes is characterized by hyperglycemia which over time leads to fatal damage to both macro-and microvascular systems, causing complications such as cardiovascular diseases, retinopathy and nephropathy. Diabetes management is conventionally delivered through modifications of diet and lifestyle and pharmacological treatment, using antidiabetic drugs, and ultimately insulin injections. However, the side effects and financial cost of medications often reduce patient compliance to treatment, negatively affecting their health outcomes. Natural phytochemicals from edible plants such as fruits and vegetables (F&V) and medicinal herbs have drawn a growing interest as potential therapeutic agents for treating diabetes and preventing the onset and progression of diabetic complications. Flavonoids, the most abundant polyphenols in the human diet, have shown antidiabetic effects in numerous in vitro and preclinical studies. The underlying mechanisms have been linked to their antioxidant, anti-inflammatory and immunomodulatory activities. Carotenoids, another major group of dietary phytochemicals, have also shown antidiabetic potential in recent in vitro and in vivo experimental models, possibly through a mechanism of action similar to that of flavonoids. However, scientific evidence on the efficacy of these phytochemicals in treating diabetes or preventing the onset and progression of its complications in clinical settings is scarce, which delays the translation of animal study evidence to human applications and also limits the knowledge on their modes of actions in diabetes management. This review is aimed to highlight the potential roles of flavonoids and carotenoids in preventing or ameliorating diabetes-related complications based on in vivo study evidence, i.e., an array of preclinical animal studies and human intervention trials. The current general consensus of the underlying mechanisms of action exerted by both groups of phytochemicals is that their anti-inflammatory action is key. However, other potential mechanisms of action are considered. In total, 50 in vivo studies were selected for a review after a comprehensive database search via PubMed and ScienceDirect from January 2002 to August 2022. The key words used for analysis are type-2 diabetes (T2DM), diabetic complications, flavonoids, carotenoids, antioxidant, anti-inflammatory, mechanisms of prevention and amelioration, animal studies and human interventions.

Potential Properties of Natural Nutraceuticals and Antioxidants in Age-Related Eye Disorders

Eye health is crucial, and the onset of diseases can reduce vision and affect the quality of life of patients. The main causes of progressive and irreversible vision loss include various pathologies, such as cataracts, ocular atrophy, corneal opacity, age-related macular degeneration, uncorrected refractive error, posterior capsular opacification, uveitis, glaucoma, diabetic retinopathy, retinal detachment, undetermined disease and other disorders involving oxidative stress and inflammation. The eyes are constantly exposed to the external environment and, for this reason, must be protected from damage from the outside. Many drugs, including cortisonics and antinflammatory drugs have widely been used to counteract eye disorders. However, recent advances have been obtained via supplementation with natural antioxidants and nutraceuticals for patients. In particular, evidence has accumulated that polyphenols (mostly deriving from Citrus Bergamia) represent a reliable source of antioxidants able to counteract oxidative stress accompanying early stages of eye diseases. Luteolin in particular has been found to protect photoreceptors, thereby improving vision in many disease states. Moreover, a consistent anti-inflammatory response was found to occur when curcumin is used alone or in combination with other nutraceuticals. Additionally, Coenzyme Q10 has been demonstrated to produce a consistent effect in reducing ocular pressure, thereby leading to protection in patients undergoing glaucoma. Finally, both grape seed extract, rich in anthocyanosides, and polynsatured fatty acids seem to contribute to the prevention of retinal disorders. Thus, a combination of nutraceuticals and antioxidants may represent the right solution for a multi-action activity in eye protection, in association with current drug therapies, and this will be of potential interest in early stages of eye disorders.

Microalgal Carotenoids: Therapeutic Application and Latest Approaches to Enhance the Production

Microalgae are microscopic photosynthetic organisms frequently found in fresh and marine water ecosystems. Various microalgal species have been considered a reservoir of diverse health-value products, including vitamins, proteins, lipids, and polysaccharides, and are broadly utilized as food and for the treatment of human ailments such as cancer, cardiovascular diseases, allergies, and immunodeficiency. Microalgae-derived carotenoids are the type of accessory pigment that possess light-absorbing potential and play a significant role in metabolic functions. To date, nearly a thousand carotenoids have been reported, but a very less number of microalgae have been used for the commercial production of carotenoids. This review article briefly discussed the carotenoids of microalgal origin and their therapeutic application. In addition, we have briefly compiled the optimization of culture parameters used to enhance microalgal carotenoid production. In addition, the latest biotechnological approaches used to improve the yields of carotenoid has also been discussed.

Modulating antioxidant systems as a therapeutic approach to retinal degeneration

The human retina is facing a big challenge of reactive oxygen species (ROS) from endogenous and exogenous sources. Excessive ROS can cause damage to DNA, lipids, and proteins, triggering abnormal redox signaling, and ultimately lead to cell death. Thus, oxidative stress has been observed in inherited retinal diseases as a common hallmark. To counteract the detrimental effect of ROS, cells are equipped with various antioxidant defenses. In this review, we will focus on the antioxidant systems in the retina and how they can protect retina from oxidative stress. Both small antioxidants and antioxidant enzymes play a role in ROS removal. Particularly, the thioredoxin and glutaredoxin systems, as the major antioxidant systems in mammalian cells, exert functions in redox signaling regulation via modifying cysteines in proteins. In addition, the thioredoxin-like rod-derived cone viability factor (RdCVFL) and thioredoxin interacting protein (TXNIP) can modulate metabolism in photoreceptors and promote their survival. In conclusion, elevating the antioxidant capacity in retina is a promising therapy to curb the progress of inherited retinal degeneration.

Recent advancements in astaxanthin production from microalgae: A review

Microalgae have emerged as the best source of high-value astaxanthin producers. Algal astaxanthin possesses numerous bioactivities hence the rising demand for several health applications and is broadly used in pharmaceuticals, aquaculture, health foods, cosmetics, etc. Among several low-priced synthetic astaxanthin, natural astaxanthin is still irreplaceable for human consumption and food-additive uses. This review highlights the recent development in production enhancement and cost-effective extraction techniques that may apply to large-scale astaxanthin biorefinery. Primarily, the biosynthetic pathway of astaxanthin is elaborated with the key enzymes involved in the metabolic process. Moreover, discussed the latest astaxanthin enhancement strategies mainly including chemicals as product inducers and byproducts inhibitors. Later, various physical, chemical, and biological cell disruption methods are compared for cell disruption efficiency, and astaxanthin extractability. The aim of this review is to provide a comprehensive review of advancements in astaxanthin research covering scalable upstream and downstream astaxanthin bioproduction aspects.

The landscape of potential health benefits of carotenoids as natural supportive therapeutics in protecting against Coronavirus infection

The Coronavirus Disease-2019 (COVID-19) pandemic urges researching possibilities for prevention and management of the effects of the virus. Carotenoids are natural phytochemicals of anti-oxidant, anti-inflammatory and immunomodulatory properties and may exert potential in aiding in combatting the pandemic. This review presents the direct and indirect evidence of the health benefits of carotenoids and derivatives based on in vitro and in vivo studies, human clinical trials and epidemiological studies and proposes possible mechanisms of action via which carotenoids may have the capacity to protect against COVID-19 effects. The current evidence provides a rationale for considering carotenoids as natural supportive nutrients via antioxidant activities, including scavenging lipid-soluble radicals, reducing hypoxia-associated superoxide by activating antioxidant enzymes, or suppressing enzymes that produce reactive oxygen species (ROS). Carotenoids may regulate COVID-19 induced over-production of pro-inflammatory cytokines, chemokines, pro-inflammatory enzymes and adhesion molecules by nuclear factor kappa B (NF-κB), renin-angiotensin-aldosterone system (RAS) and interleukins-6- Janus kinase-signal transducer and activator of transcription (IL-6-JAK/STAT) pathways and suppress the polarization of pro-inflammatory M1 macrophage. Moreover, carotenoids may modulate the peroxisome proliferator-activated receptors γ by acting as agonists to alleviate COVID-19 symptoms. They also may potentially block the cellular receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), human angiotensin-converting enzyme 2 (ACE2). These activities may reduce the severity of COVID-19 and flu-like diseases. Thus, carotenoid supplementation may aid in combatting the pandemic, as well as seasonal flu. However, further in vitro, in vivo and in particular long-term clinical trials in COVID-19 patients are needed to evaluate this hypothesis.

Carotenoids in Drug Discovery and Medicine: Pathways and Molecular Targets Implicated in Human Diseases

Carotenoids are isoprenoid-derived natural products produced in plants, algae, fungi, and photosynthetic bacteria. Most animals cannot synthesize carotenoids because the biosynthetic machinery to create carotenoids de novo is absent in animals, except arthropods. Carotenoids are biosynthesized from two C20 geranylgeranyl pyrophosphate (GGPP) molecules made from isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) via the methylerythritol 4-phosphate (MEP) route. Carotenoids can be extracted by a variety of methods, including maceration, Soxhlet extraction, supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), accelerated solvent extraction (ASE), ultrasound-assisted extraction (UAE), pulsed electric field (PEF)-assisted extraction, and enzyme-assisted extraction (EAE). Carotenoids have been reported to exert various biochemical actions, including the inhibition of the Akt/mTOR, Bcl-2, SAPK/JNK, JAK/STAT, MAPK, Nrf2/Keap1, and NF-κB signaling pathways and the ability to increase cholesterol efflux to HDL. Carotenoids are absorbed in the intestine. A handful of carotenoids and carotenoid-based compounds are in clinical trials, while some are currently used as medicines. The application of metabolic engineering techniques for carotenoid production, whole-genome sequencing, and the use of plants as cell factories to produce specialty carotenoids presents a promising future for carotenoid research. In this review, we discussed the biosynthesis and extraction of carotenoids, the roles of carotenoids in human health, the metabolism of carotenoids, and carotenoids as a source of drugs and supplements.

The Effect of Two Different Doses of Astaxanthin on Alveolar Bone Loss in an Experimental Model of Periodontitis in Diabetic Rats

This study evaluated the effects of astaxanthin (ASX) on alveolar bone loss, receptor activator of nuclear factor-κB ligand (RANKL), and osteoprotegerin (OPG) activity in ligature-induced periodontitis in diabetic rats. Diabetes mellitus (DM) was induced with 50 mg/kg intraperitoneal streptozotocin in 40 male Wistar rats. The Wistar rats were divided into six experimental groups: non-ligated (NL; n = 6); ligature only (L; n = 6); DM only (D; n = 6); DM + ligature (DP; n = 6); DM + ligature + 1 mg/kg/day ASX (ASX 1 group; n = 8); and DM + ligature + astaxanthin 5 mg/kg/day ASX (ASX 5 group; n = 8). Silk ligatures were placed along the gingival margin of the left mandibular first molar tooth. The study duration was 11 days, after which the animals were euthanised. Changes in alveolar bone levels were clinically measured, and RANKL and OPG activities were immunohistochemically examined. Alveolar bone loss was the most significant in the DP group (p < 0.05). Decreased alveolar bone loss was observed in the ASX 5 group (p < 0.05). Although RANKL activity was highest in the DP group, it was observed at lower levels in the groups to which ASX was administered. OPG activity did not differ between groups (p > 0.05). The results of this study suggested that 1 and 5 mg/kg ASX administration reduced RANKL activity and alveolar bone loss in rats with experimentally induced periodontitis.

Astaxanthin Ameliorates Diabetic Retinopathy in Swiss Albino Mice via Inhibitory Processes of Neuron-Specific Enolase Activity

Retinopathy is one of the most common complications of diabetes mellitus. Diabetic retinopathy (DR) occurs due to microvascular damage in retinal tissues provoked by high blood sugar levels. The available drugs for DR are limited. Astaxanthin (AST) has anti-hypertensive, anti-obesity, and anti-diabetic properties. However, the therapeutic effect of AST on DR remains elusive. The present study is designed to investigate the effects of AST on DR via inhibition of neuron-specific enolase (NSE) activity. DR was induced by the administration of streptozotocin (STZ, 35 mg/kg: intraperitoneal; and 20 μL of STZ: intravitreal) in mice. AST (10 and 20 mg/kg) was administered orally (p.o.) for 21 days. The DR associated visual changes were assessed at different time intervals via optokinetic motor response (OMR) and penta-maze (PM) tests. Blood glucose level as well as retinal catalase, lactate dehydrogenase (LDH), & neuron-specific enolase (NSE) were estimated. The reference drug i.e., dexamethasone (DEX, 10 mg/kg; p.o.) was administered for 21 days. The administration of AST showed significant ameliorative potential in DR. Hence, AST can be used as a natural medicine for the management of DR due to its potential antioxidant, anti-diabetic, and NSE inhibitory properties.

Health benefits of astaxanthin against age-related diseases of multiple organs: A comprehensive review

Age-related diseases are associated with increased morbidity in the past few decades and the cost associated with the treatment of these age-related diseases exerts a substantial impact on social and health care expenditure. Anti-aging strategies aim to mitigate, delay and reverse aging-associated diseases, thereby improving quality of life and reducing the burden of age-related pathologies. The natural dietary antioxidant supplementation offers substantial pharmacological and therapeutic effects against various disease conditions. Astaxanthin is one such natural carotenoid with superior antioxidant activity than other carotenoids, as well as well as vitamins C and E, and additionally, it is known to exhibit a plethora of pharmacological effects. The present review summarizes the protective molecular mechanisms of actions of astaxanthin on age-related diseases of multiple organs such as Neurodegenerative diseases [Alzheimer's disease (AD), Parkinson's disease (PD), Stroke, Multiple Sclerosis (MS), Amyotrophic lateral sclerosis (ALS), and Status Epilepticus (SE)], Bone Related Diseases [Osteoarthritis (OA) and Osteoporosis], Cancers [Colon cancer, Prostate cancer, Breast cancer, and Lung Cancer], Cardiovascular disorders [Hypertension, Atherosclerosis and Myocardial infarction (MI)], Diabetes associated complications [Diabetic nephropathy (DN), Diabetic neuropathy, and Diabetic retinopathy (DR)], Eye disorders [Age related macular degeneration (AMD), Dry eye disease (DED), Cataract and Uveitis], Gastric Disorders [Gastritis, Colitis, and Functional dyspepsia], Kidney Disorders [Nephrolithiasis, Renal fibrosis, Renal Ischemia reperfusion (RIR), Acute kidney injury (AKI), and hyperuricemia], Liver Diseases [Nonalcoholic fatty liver disease (NAFLD), Alcoholic Liver Disease (AFLD), Liver fibrosis, and Hepatic Ischemia-Reperfusion (IR) Injury], Pulmonary Disorders [Pulmonary Fibrosis, Acute Lung injury (ALI), and Chronic obstructive pulmonary disease (COPD)], Muscle disorders (skeletal muscle atrophy), Skin diseases [Atopic dermatitis (ATD), Skin Photoaging, and Wound healing]. We have also briefly discussed astaxanthin's protective effects on reproductive health.

Recent Advances and the Mechanism of Astaxanthin in Ophthalmological Diseases

Astaxanthin (AST) is a naturally occurring carotenoid that has strong antioxidant, anti-inflammatory, and antiapoptosis effects and is used for the prevention of cancer. There is growing evidence that AST has multiple protective effects against various eye diseases. This article reviews the function and the potential mechanism of AST in dry eye syndrome, keratitis, cataract, diabetic retinopathy, age-related macular degeneration, high intraocular pressure, and other ocular diseases. It provides a theoretical basis for the clinical application of AST as a potential nutraceutical.

Mechanistic Pathogenesis of Endothelial Dysfunction in Diabetic Nephropathy and Retinopathy

Diabetic nephropathy (DN) and diabetic retinopathy (DR) are microvascular complications of diabetes. Microvascular endothelial cells are thought to be the major targets of hyperglycemic injury. In diabetic microvasculature, the intracellular hyperglycemia causes damages to the vascular endothelium, via multiple pathophysiological process consist of inflammation, endothelial cell crosstalk with podocytes/pericytes and exosomes. In addition, DN and DR diseases development are involved in several critical regulators including the cell adhesion molecules (CAMs), the vascular endothelial growth factor (VEGF) family and the Notch signal. The present review attempts to gain a deeper understanding of the pathogenesis complexities underlying the endothelial dysfunction in diabetes diabetic and retinopathy, contributing to the development of new mechanistic therapeutic strategies against diabetes-induced microvascular endothelial dysfunction.

From the Sea for the Sight: Marine Derived Products for Human Vision

Visual impairment, at different degrees, produce a reduction of patient wellness which negatively impact in many aspects of working and social activities. Eye diseases can have common cellular damages or dysfunctions (e.g., inflammation, oxidative stress, neuronal degeneration), and can target several eye compartments, primarily cornea and retina. Marine organisms exhibit high chemical diversity due to the wide range of marine ecosystems where they live; thus, molecules of marine origin are gaining increasing attention for the development of new mutation-independent therapeutic strategies, to reduce the progression of retina pathologies having a multifactorial nature and characterized by high genetic heterogeneity. This review aims to describe marine natural products reported in the recent literature that showed promising therapeutic potential for the development of new drugs to be used to contrast the progression of eye pathologies. These natural compounds exhibited beneficial and protective properties on different in vitro cell systems and on in vivo models, through different mechanisms of action, including anti-inflammatory, antioxidant, antiangiogenic/vasoprotective or cytoprotective effects. We report compounds produced by several marine source (e.g., sponges, algae, shrimps) that can be administrated as food or with target-specific strategies. In addition, we describe and discuss the uses of opsin family proteins from marine organisms for the optimization of new optogenetic therapeutic strategies.

Therapeutic promise of carotenoids as antioxidants and anti-inflammatory agents in neurodegenerative disorders

Neurodegenerative disorders (NDs) including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis have various disease-specific causal factors and pathological features. A very common characteristic of NDs is oxidative stress (OS), which takes place due to the elevated generation of reactive oxygen species during the progression of NDs. Furthermore, the pathological condition of NDs including an increased level of protein aggregates can further lead to chronic inflammation because of the microglial activation. Carotenoids (CTs) are naturally occurring pigments that play a significant role in averting brain disorders. More than 750 CTs are present in nature, and they are widely available in plants, microorganisms, and animals. CTs are accountable for the red, yellow, and orange pigments in several animals and plants, and these colors usually indicate various types of CTs. CTs exert various bioactive properties because of its characteristic structure, including anti-inflammatory and antioxidant properties. Due to the protective properties of CTs, levels of CTs in the human body have been markedly linked with the prevention and treatment of multiple diseases including NDs. In this review, we have summarized the relationship between OS, neuroinflammation, and NDs. In addition, we have also particularly focused on the antioxidants and anti-inflammatory properties of CTs in the management of NDs.

Benefits and Safety of Astaxanthin in the Treatment of Mild-To-Moderate Dry Eye Disease

Objectives: To evaluate the effect of astaxanthin in the treatment of mild-to-moderate dry eye disease (DED) in middle-aged and elderly patients.

Methods: 120 eyes of 60 middle-aged and elderly patients with mild-to-moderate DED were enrolled in this prospective, one-group, quasi-experimental study. Six milligram Astaxanthin tablets (Weihong Haematococcus Pluvialis Astaxanthin, Hangzhou Xinwei Low Carbon Technology R&D Co., Ltd., China) were administered orally, twice daily for 30 ± 2 days. History of eye diseases, treatment, systemic disease, and medication before the test were recorded. In addition, the ocular surface disease index (OSDI) questionnaire, non-invasive tear break-up time (NIBUT), fluorescein break-up time (FBUT), corneal fluorescein staining (CFS) score, eyelid margin signs, meibomian gland (MG) expressibility, meibum quality, meibomian gland dropout (MGDR), Schirmer I test (SIt), tear meniscus height (TMH), bulbar conjunctiva congestion degree, blink frequency, incomplete blink rate, and thickness of tear film lipid layer were collected before treatment, 2 weeks after the initiation of treatment, and at the end of treatment. Visual acuity (VA), intraocular pressure (IOP), anterior segment, fundus, discomfort symptoms and other adverse reactions were also monitored throughout the study to assess the safety.

Results: OSDI score, NIBUT, BUT, CFS score, eyelid margin signs, MG expressibility, meibum quality, and blink frequency improved significantly to varying degrees after treatment compared with those before the treatment (P < 0.05), while TMH, SIt, conjunctival congestion, the thickness of tear film lipid layer, MGDR, incomplete blink rate, VA and IOP did not differ (P > 0.05).

Conclusions: Oral administration of astaxanthin improves the symptoms and signs of middle-aged and elderly patients with mild-to-moderate DED.

Nanotechnology-Abetted Astaxanthin Formulations in Multimodel Therapeutic and Biomedical Applications

Astaxanthin (AXT) is one of the most important fat-soluble carotenoids that have abundant and diverse therapeutic applications namely in liver disease, cardiovascular disease, cancer treatment, protection of the nervous system, protection of the skin and eyes against UV radiation, and boosting the immune system. However, due to its intrinsic reactivity, it is chemically unstable, and therefore, the design and production processes for this compound need to be precisely formulated. Nanoencapsulation is widely applied to protect AXT against degradation during digestion and storage, thus improving its physicochemical properties and therapeutic effects. Nanocarriers are delivery systems with many advantages─ease of surface modification, biocompatibility, and targeted drug delivery and release. This review discusses the technological advancement in nanocarriers for the delivery of AXT through the brain, eyes, and skin, with emphasis on the benefits, limitations, and efficiency in practice.

Fractalkine-induced microglial vasoregulation occurs within the retina and is altered early in diabetic retinopathy

Local blood flow control within the central nervous system (CNS) is critical to proper function and is dependent on coordination between neurons, glia, and blood vessels. Macroglia, such as astrocytes and Müller cells, contribute to this neurovascular unit within the brain and retina, respectively. This study explored the role of microglia, the innate immune cell of the CNS, in retinal vasoregulation, and highlights changes during early diabetes. Structurally, microglia were found to contact retinal capillaries and neuronal synapses. In the brain and retinal explants, the addition of fractalkine, the sole ligand for monocyte receptor Cx3cr1, resulted in capillary constriction at regions of microglial contact. This vascular regulation was dependent on microglial Cx3cr1 involvement, since genetic and pharmacological inhibition of Cx3cr1 abolished fractalkine-induced constriction. Analysis of the microglial transcriptome identified several vasoactive genes, including angiotensinogen, a constituent of the renin-angiotensin system (RAS). Subsequent functional analysis showed that RAS blockade via candesartan abolished microglial-induced capillary constriction. Microglial regulation was explored in a rat streptozotocin (STZ) model of diabetic retinopathy. Retinal blood flow was reduced after 4 wk due to reduced capillary diameter and this was coincident with increased microglial association. Functional assessment showed loss of microglial-capillary response in STZ-treated animals and transcriptome analysis showed evidence of RAS pathway dysregulation in microglia. While candesartan treatment reversed capillary constriction in STZ-treated animals, blood flow remained decreased likely due to dilation of larger vessels. This work shows microglia actively participate in the neurovascular unit, with aberrant microglial-vascular function possibly contributing to the early vascular compromise during diabetic retinopathy.

Astaxanthin Inhibits Diabetes-Triggered Periodontal Destruction, Ameliorates Oxidative Complications in STZ-Injected Mice, and Recovers Nrf2-Dependent Antioxidant System

Numerous studies highlight that astaxanthin (ASTX) ameliorates hyperglycemic condition and hyperglycemia-associated chronic complications. While periodontitis and periodontic tissue degradation are also triggered under chronic hyperglycemia, the roles of ASTX on diabetes-associated periodontal destruction and the related mechanisms therein are not yet fully understood. Here, we explored the impacts of supplemental ASTX on periodontal destruction and systemic complications in type I diabetic mice. To induce diabetes, C57BL/6 mice received a single intraperitoneal injection of streptozotocin (STZ; 150 mg/kg), and the hyperglycemic mice were orally administered with ASTX (12.5 mg/kg) (STZ+ASTX group) or vehicle only (STZ group) daily for 60 days. Supplemental ASTX did not improve hyperglycemic condition, but ameliorated excessive water and feed consumptions and lethality in STZ-induced diabetic mice. Compared with the non-diabetic and STZ+ASTX groups, the STZ group exhibited severe periodontal destruction. Oral gavage with ASTX inhibited osteoclastic formation and the expression of receptor activator of nuclear factor (NF)-κB ligand, 8-OHdG, γ-H2AX, cyclooxygenase 2, and interleukin-1β in the periodontium of STZ-injected mice. Supplemental ASTX not only increased the levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and osteogenic transcription factors in the periodontium, but also recovered circulating lymphocytes and endogenous antioxidant enzyme activity in the blood of STZ-injected mice. Furthermore, the addition of ASTX blocked advanced glycation end products-induced oxidative stress and growth inhibition in human-derived periodontal ligament cells by upregulating the Nrf2 pathway. Together, our results suggest that ASTX does not directly improve hyperglycemia, but ameliorates hyperglycemia-triggered periodontal destruction and oxidative systemic complications in type I diabetes.

Multi-Mechanistic Antidiabetic Potential of Astaxanthin: An Update on Preclinical and Clinical Evidence

Diabetes mellitus (DM) is a cluster of physiological dysfunctions typified by persistent hyperglycemia. Diet plays a paramount role in human health, and regular consumption of a fruit- and vegetable-rich diet can delay or prevent DM and its associated complications. The promising effect of fruits and vegetables could be partly attributed to their antioxidant constituents, including carotenoids. Carotenoids are natural antioxidants that occur in many vegetables, fruits, microalgae, and other natural sources. Astaxanthin is a xanthophyll carotenoid predominantly present in microalgae and some red-colored marine organisms. It is currently marketed as a health supplement and is well-known for its antioxidant capacity. Accumulating evidence indicates that astaxanthin exerts its beneficial effects against DM by acting on various molecular targets and signaling pathways in multiple organs/tissues. Astaxanthin can lower blood glucose levels by preserving β-cell function, improving insulin resistance (IR), and increasing insulin secretion. This manuscript summarizes the connection between glucose homeostasis, oxidative stress, and DM. This is followed by a review of recent studies on astaxanthin's pharmacological effects against IR, microvascular (diabetic retinopathy, diabetic nephropathy, and neurological damage), and macrovascular DM complications emphasizing the cellular and molecular mechanisms involved. A few lines of clinical evidence supporting its antidiabetic potential are also highlighted.

The neuroprotective potential of carotenoids in vitro and in vivo

BACKGROUND

Despite advances in research on neurodegenerative diseases, the pathogenesis and treatment response of neurodegenerative diseases remain unclear. Recent studies revealed a significant role of carotenoids to treat neurodegenerative diseases. The aim of this study was to systematically review the neuroprotective potential of carotenoids in vivo and in vitro and the molecular mechanisms and pathological factors contributing to major neurodegenerative diseases (Alzheimer's disease, Huntington's disease, Parkinson's disease, amyotrophic lateral sclerosis, and stroke).

HYPOTHESIS

Carotenoids as therapeutic molecules to target neurodegenerative diseases.

RESULTS

Aggregation of toxic proteins, mitochondrial dysfunction, oxidative stress, the excitotoxic pathway, and neuroinflammation were the major pathological factors contributing to the progression of neurodegenerative diseases. Furthermore, in vitro and in vivo studies supported the beneficiary role of carotenoids, namely lycopene, β-carotene, crocin, crocetin, lutein, fucoxanthin and astaxanthin in alleviating disease progression. These carotenoids provide neuroprotection by inhibition of neuro-inflammation, microglial activation, excitotoxic pathway, modulation of autophagy, attenuation of oxidative damage and activation of defensive antioxidant enzymes. Additionally, studies conducted on humans also demonstrated that dietary intake of carotenoids lowers the risk of neurodegenerative diseases.

CONCLUSION

Carotenoids may be used as drugs to prevent and treat neurodegenerative diseases. Although, the in vitro and in vivo results are encouraging, further well conducted clinical studies on humans are required to conclude about the full potential of neurodegenerative diseases.

Anti-Inflammatory and Anticancer Effects of Microalgal Carotenoids

Acute inflammation is a key component of the immune system's response to pathogens, toxic agents, or tissue injury, involving the stimulation of defense mechanisms aimed to removing pathogenic factors and restoring tissue homeostasis. However, uncontrolled acute inflammatory response may lead to chronic inflammation, which is involved in the development of many diseases, including cancer. Nowadays, the need to find new potential therapeutic compounds has raised the worldwide scientific interest to study the marine environment. Specifically, microalgae are considered rich sources of bioactive molecules, such as carotenoids, which are natural isoprenoid pigments with important beneficial effects for health due to their biological activities. Carotenoids are essential nutrients for mammals, but they are unable to synthesize them; instead, a dietary intake of these compounds is required. Carotenoids are classified as carotenes (hydrocarbon carotenoids), such as α- and β-carotene, and xanthophylls (oxygenate derivatives) including zeaxanthin, astaxanthin, fucoxanthin, lutein, α- and β-cryptoxanthin, and canthaxanthin. This review summarizes the present up-to-date knowledge of the anti-inflammatory and anticancer activities of microalgal carotenoids both in vitro and in vivo, as well as the latest status of human studies for their potential use in prevention and treatment of inflammatory diseases and cancer.

Central Nervous System Migration of Astaxanthin and Adonixanthin Following Their Oral Administration in Cynomolgus Monkeys

Astaxanthin, which has been shown to have significant antioxidant activity, is rapidly spreading as a health functioning ingredient in the health food and cosmetics sectors worldwide. It is well known that astaxanthin acts on the brain; however, there is little evidence of brain translocation due to the difficulty in identifying astaxanthin in tissues. Therefore, in this study, we investigated the concentrations of astaxanthin and adonixanthin, the latter being a biosynthetic intermediate from β-carotene to astaxanthin, in the brain after oral administration in primates. Cynomolgus monkeys were orally administered astaxanthin or adonixanthin at a dose of 50 mg/kg for 10 d, through a disposable catheter inserted into the stomach via the nasal passage. Following euthanization, the monkeys' brains and various other organs were collected. The carotenoid content in serum and individual organs was analyzed by high-performance liquid chromatography. Adonixanthin was found to accumulate at a higher concentration than astaxanthin in monkey brain tissues. Also, both astaxanthin and adonixanthin were found to be distributed in the heart, spleen, liver, and kidneys. These findings indicate that astaxanthin and adonixanthin can enter the central nervous system of primates following their oral administration. This provides important evidence for the activity of astaxanthin and adonixanthin on the central nervous system.

Fibroblast Growth Factor Type 1 Ameliorates High-Glucose-Induced Oxidative Stress and Neuroinflammation in Retinal Pigment Epithelial Cells and a Streptozotocin-Induced Diabetic Rat Model

Diabetic retinopathy (DR) is a common complication of diabetes that causes severe visual impairment globally. The pathogenesis of DR is related to oxidative stress and chronic inflammation. The fibroblast growth factor type 1 (FGF-1) mitogen plays crucial roles in cell function, development, and metabolism. FGF-1 is involved in blood sugar regulation and exerts beneficial antioxidative and anti-inflammatory effects on various organ systems. This study investigated the antioxidative and anti-inflammatory neuroprotective effects of FGF-1 on high-glucose-induced retinal damage. The results revealed that FGF-1 treatment significantly reversed the harmful effects of oxidative stress and inflammatory mediators in retinal tissue in a streptozotocin-induced diabetic rat model. These protective effects were also observed in the in vitro model of retinal ARPE-19 cells exposed to a high-glucose condition. We demonstrated that FGF-1 attenuated p38 mitogen-activated protein kinase and nuclear factor-κB pathway activation under the high-glucose condition. Our results indicated that FGF-1 could effectively prevent retinal injury in diabetes. The findings of this study could be used to develop novel treatments for DR that aim to reduce the cascade of oxidative stress and inflammatory signals in neuroretinal tissue.

A Bittersweet Response to Infection in Diabetes; Targeting Neutrophils to Modify Inflammation and Improve Host Immunity

Chronic and recurrent infections occur commonly in both type 1 and type 2 diabetes (T1D, T2D) and increase patient morbidity and mortality. Neutrophils are professional phagocytes of the innate immune system that are critical in pathogen handling. Neutrophil responses to infection are dysregulated in diabetes, predominantly mediated by persistent hyperglycaemia; the chief biochemical abnormality in T1D and T2D. Therapeutically enhancing host immunity in diabetes to improve infection resolution is an expanding area of research. Individuals with diabetes are also at an increased risk of severe coronavirus disease 2019 (COVID-19), highlighting the need for re-invigorated and urgent focus on this field. The aim of this review is to explore the breadth of previous literature investigating neutrophil function in both T1D and T2D, in order to understand the complex neutrophil phenotype present in this disease and also to focus on the development of new therapies to improve aberrant neutrophil function in diabetes. Existing literature illustrates a dual neutrophil dysfunction in diabetes. Key pathogen handling mechanisms of neutrophil recruitment, chemotaxis, phagocytosis and intracellular reactive oxygen species (ROS) production are decreased in diabetes, weakening the immune response to infection. However, pro-inflammatory neutrophil pathways, mainly neutrophil extracellular trap (NET) formation, extracellular ROS generation and pro-inflammatory cytokine generation, are significantly upregulated, causing damage to the host and perpetuating inflammation. Reducing these proinflammatory outputs therapeutically is emerging as a credible strategy to improve infection resolution in diabetes, and also more recently COVID-19. Future research needs to drive forward the exploration of novel treatments to improve infection resolution in T1D and T2D to improve patient morbidity and mortality.

In Vitro Bioactivity of Astaxanthin and Peptides from Hydrolisates of Shrimp (Parapenaeus longirostris) By-Products: From the Extraction Process to Biological Effect Evaluation, as Pilot Actions for the Strategy "From Waste to Profit"

Non-edible parts of crustaceans could be a rich source of valuable bioactive compounds such as the carotenoid astaxanthin and peptides, which have well-recognized beneficial effects. These compounds are widely used in nutraceuticals and pharmaceuticals, and their market is rapidly growing, suggesting the need to find alternative sources. The aim of this work was to set up a pilot-scale protocol for the reutilization of by-products of processed shrimp, in order to address the utilization of this valuable biomass for nutraceutical and pharmaceuticals application, through the extraction of astaxanthin-enriched oil and antioxidant-rich protein hydrolysates. Astaxanthin (AST) was obtained using “green extraction methods,” such as using fish oil and different fatty acid ethyl esters as solvents and through supercritical fluid extraction (SFE), whereas bioactive peptides were obtained by protease hydrolysis. Both astaxanthin and bioactive peptides exhibited bioactive properties in vitro in cellular model systems, such as antioxidant and angiotensin I converting enzyme (ACE) inhibitory activities (IA). The results show higher astaxanthin yields in ethyl esters fatty acids (TFA) extraction and significant enrichment by short-path distillation (SPD) up to 114.80 ± 1.23 µg/mL. Peptide fractions of <3 kDa and 3–5 kDa exhibited greater antioxidant activity while the fraction 5–10 kDa exhibited a better ACE-IA. Lower-molecular-weight bioactive peptides and astaxanthin extracted using supercritical fluids showed protective effects against oxidative damage in 142BR and in 3T3 cell lines. These results suggest that “green” extraction methods allow us to obtain high-quality bioactive compounds from large volumes of shrimp waste for nutraceutical and pharmaceutical applications.

Therapeutic Potential of Astaxanthin in Diabetic Kidney Disease

Astaxanthin is a carotenoid that has potent protective effects on diabetic kidney disease (DKD) in diabetic mice models. DNA microarray study clearly demonstrated the involvement of mitochondrial oxidative phosphorylation pathway in the renal glomerular cells of diabetic mice and also showed that the expression of upregulated genes associated with this pathway was decreased by the treatment with astaxanthin. Proteomic analysis confirmed that the increases of 4-hydroxy-2-nonenal (HNE)- and N^ε-(hexanonyl)lysine (HEL)-modified proteins were inhibited by the treatment with astaxanthin. These results demonstrated that astaxanthin exerts a protective effect against hyperglycemia-induced DKD by attenuating mitochondrial oxidative stress and subsequent cellular dysfunction.

Astaxanthin protects against early acute kidney injury in severely burned rats by inactivating the TLR4/MyD88/NF-κB axis and upregulating heme oxygenase-1

Early acute kidney injury (AKI) contributes to severe morbidity and mortality in critically burned patients. Renal inflammation plays a vital role in the progression of early AKI, acting as a therapeutic target. Astaxanthin (ATX) is a strong antioxidant widely distributed in marine organisms that exerts many biological effects in trauma and disease. ATX is also suggested to have anti-inflammatory activity. Hence, we attempted to explore the role of ATX in protecting against early postburn AKI via its anti-inflammatory effects and the related mechanisms. A severely burned model was established for histological and biochemical assessments based on adult male rats. We found that oxidative stress-induced tissue inflammation participated in the development of early AKI after burn injury and that the MyD88-dependent TLR4/NF-κB pathway was activated to regulate renal inflammation. The TLR4 and NF-κB inhibitors TAK242 and PDTC showed similar effects in attenuating burn-induced renal inflammation and early AKI. Upon ATX treatment, the release of inflammatory mediators in the kidneys was downregulated, while the TLR4/MyD88/NF-κB axis was inhibited in a dose-related manner. TAK242 and PDTC could enhance the anti-inflammatory effect of high-dose ATX, whereas lipopolysaccharide (LPS) reversed its action. Furthermore, the expression of heme oxygenase (HO)-1 was upregulated by ATX in a dose-related manner. Collectively, the above data suggest that ATX protects against renal inflammation in a dose-related manner by regulating the TLR4/MyD88/NF-κB axis and HO-1 and ultimately prevents early AKI following severe burns.

Natural antioxidants in diabetes treatment and management: prospects of astaxanthin

Diabetes remains a major health emergency in our entire world, affecting hundreds of millions of people worldwide. In conjunction with its much-dreaded complications (e.g., nephropathy, neuropathy, retinopathy, cardiovascular diseases, etc.) it substantially reduces the quality of life, increases mortality as well as economic burden among patients. Over the years, oxidative stress and inflammation have been highlighted as key players in the development and progression of diabetes and its associated complications. Much research has been devoted, as such, to the role of antioxidants in diabetes. Astaxanthin is a powerful antioxidant found mostly in marine organisms. Over the past years, several studies have demonstrated that astaxanthin could be useful in the treatment and management of diabetes. It has been shown to protect β-cells, neurons as well as several organs including the eyes, kidney, liver, etc. against oxidative injuries experienced during diabetes. Furthermore, it improves glucose and lipid metabolism along with cardiovascular health. Its beneficial effects are exerted through multiple actions on cellular functions. Considering these and the fact that foods and natural products with biological and pharmacological activities are of much interest in the 21st-century food and drug industry, astaxanthin has a bright prospect in the management of diabetes and its complications.

The Impaired Bioenergetics of Diabetic Cardiac Microvascular Endothelial Cells

Diabetes causes hyperglycemia, which can create a stressful environment for cardiac microvascular endothelial cells (CMECs). To investigate the impact of diabetes on the cellular metabolism of CMECs, we assessed glycolysis by quantifying the extracellular acidification rate (ECAR), and mitochondrial oxidative phosphorylation (OXPHOS) by measuring cellular oxygen consumption rate (OCR), in isolated CMECs from wild-type (WT) hearts and diabetic hearts (db/db) using an extracellular flux analyzer. Diabetic CMECs exhibited a higher level of intracellular reactive oxygen species (ROS), and significantly reduced glycolytic reserve and non-glycolytic acidification, as compared to WT CMECs. In addition, OCR assay showed that diabetic CMECs had increased maximal respiration, and significantly reduced non-mitochondrial oxygen consumption and proton leak. Quantitative PCR (qPCR) showed no difference in copy number of mitochondrial DNA (mtDNA) between diabetic and WT CMECs. In addition, gene expression profiling analysis showed an overall decrease in the expression of essential genes related to β-oxidation (Sirt1, Acox1, Acox3, Hadha, and Hadhb), tricarboxylic acid cycle (TCA) (Idh-3a and Ogdh), and electron transport chain (ETC) (Sdhd and Uqcrq) in diabetic CMECs compared to WT CMECs. Western blot confirmed that the protein expression of Hadha, Acox1, and Uqcrq was decreased in diabetic CMECs. Although lectin staining demonstrated no significant difference in capillary density between the hearts of WT mice and db/db mice, diabetic CMECs showed a lower percentage of cell proliferation by Ki67 staining, and a higher percentage of cellular apoptosis by TUNEL staining, compared with WT CMECs. In conclusion, excessive ROS caused by hyperglycemia is associated with impaired glycolysis and mitochondrial function in diabetic CMECs, which in turn may reduce proliferation and promote CMEC apoptosis.

The protective effect of astaxanthin on the ganglion cell complex in glutamate/aspartate transporter deficient mice, a model of normal tension glaucoma, analyzed by spectral domain-optical coherence tomography

Astaxanthin (AST), a natural marine carotenoid, possess a wide variety of biological functions. In particular, as a strong antioxidant, AST effectively scavenges oxygen free radicals and reduces oxidative stress. In addition, recent in vitro studies have suggested that AST attenuates glutamate-induced apoptosis and cytotoxicity. The glutamate/aspartate transporter (GLAST) deficient (GLAST-/-) mouse is a mouse model of normal tension glaucoma (NTG) caused by both the glutamate neurotoxicity and oxidative stress in the retina. In the present study, we investigated the effects of AST on the ganglion cell complex, indicator of glaucomatous structural damage, using spectral domain-optical coherence tomography. As a result, AST significantly attenuated the thinning of ganglion cell complex in GLAST-/- mice in comparison to an AST-free control group. Our results suggest the possibility that AST has protective effects against glutamate neurotoxicity and oxidative stress in the retina. At present, the only treatment for NTG that is available in the clinical setting is to reduce the IOP as much as possible. Thus, our results suggest that AST supplementation may be effective for some types of NTG in which glutamate neurotoxicity and oxidative stress are involved.

Astaxanthin Protects Retinal Photoreceptor Cells against High Glucose-Induced Oxidative Stress by Induction of Antioxidant Enzymes via the PI3K/Akt/Nrf2 Pathway

Diabetic retinopathy (DR) is a major microvascular complication that can lead to severe visual impairment in patients with diabetes. The elevated oxidative stress and increased reactive oxygen species (ROS) production induced by hyperglycemia have been reported to play an important role in the complex pathogenesis of DR. Astaxanthin (AST), a natural carotenoid derivative, has been recently recognized as a strong free radical scavenger and might, therefore, be beneficial in different diseases, including DR. In this study, we evaluated the potential role of AST as an antioxidative and antiapoptotic agent in protecting retinal cells and also investigated the involvement of the PI3K/Akt/Nrf2 pathway in AST-mediated effects. We treated high glucose-cultured mouse photoreceptor cells (661W) with different concentrations of AST and analyzed ROS production and cell apoptosis in the different regimens. Moreover, we also analyzed the expression of PI3K, Akt, Nrf2, and Phase II enzymes after AST treatment. Our results showed that AST dose-dependently reduced ROS production and attenuated 661W cell apoptosis in a high glucose environment. Importantly, its protective effect was abolished by treatment with PI3K or Nrf2 inhibitors, indicating the involvement of the PI3K/Akt/Nrf2 pathway. These results suggest AST as a nutritional supplement that could benefit patients with DR.

Impact of Astaxanthin on Diabetes Pathogenesis and Chronic Complications

Oxidative stress (OS) plays a pivotal role in diabetes mellitus (DM) onset, progression, and chronic complications. Hyperglycemia-induced reactive oxygen species (ROS) have been shown to reduce insulin secretion from pancreatic β-cells, to impair insulin sensitivity and signaling in insulin-responsive tissues, and to alter endothelial cells function in both type 1 and type 2 DM. As a powerful antioxidant without side effects, astaxanthin (ASX), a xanthophyll carotenoid, has been suggested to contribute to the prevention and treatment of DM-associated pathologies. ASX reduces inflammation, OS, and apoptosis by regulating different OS pathways though the exact mechanism remains elusive. Based on several studies conducted on type 1 and type 2 DM animal models, orally or parenterally administrated ASX improves insulin resistance and insulin secretion; reduces hyperglycemia; and exerts protective effects against retinopathy, nephropathy, and neuropathy. However, more experimental support is needed to define conditions for its use. Moreover, its efficacy in diabetic patients is poorly explored. In the present review, we aimed to identify the up-to-date biological effects and underlying mechanisms of ASX on the ROS-induced DM-associated metabolic disorders and subsequent complications. The development of an in-depth research to better understand the biological mechanisms involved and to identify the most effective ASX dosage and route of administration is deemed necessary.

Anti-inflammatory Activity of Bioactive Compounds from Microalgae and Cyanobacteria by Focusing on the Mechanisms of Action

Microalgae and cyanobacteria are the potentially valuable source of bioactive compounds applied in the various industries and human usage in different fields of pharmaceutical, nutraceutical, and cosmetic disciplines. One of the interesting aspects is their application as the anti-inflammatory agents for treatment of inflammation related mal-conditions. Natural compounds are of great importance in the treatment of inflammations to reduce the reaction of immune system against pathogens, toxic compounds and damaged cells. A wide range of different metabolites with various chemical structures, including small molecules and peptides and proteins, polysaccharides, fatty acids and their derivatives have been found in microalgae and cyanobacteria which have anti-inflammatory activity. In this review, we summarized different metabolites with anti-inflammatory activity that were extracted from these microorganisms and their mechanisms. The bioactive compounds from microalgae and cyanobacteria have exhibited anti-inflammatory activity through different mechanisms acting intra- or extra- cellularly. So, they could be considered as promising anti-inflammatory agents in treatment of related diseases.

Nanophytomedicines for the Prevention of Metabolic Syndrome: A Pharmacological and Biopharmaceutical Review

Metabolic syndrome includes a series of metabolic abnormalities that leads to diabetes mellitus and cardiovascular diseases. Plant extracts, due to their unique advantages like anti-inflammatory, antioxidant, and insulin sensitizing properties, are interesting therapeutic options to manage MetS; however, the poor solubility and low bioavailability of lipophilic bioactive components in the herbal extracts are two critical challenges. Nano-scale delivery systems are suitable to improve delivery of herbal extracts. This review, for the first time, focuses on nanoformulations of herbal extracts in MetS and related complications. Included studies showed that several forms of nano drug delivery systems such as nanoemulsions, solid lipid nanoparticles, nanobiocomposites, and green-synthesized silver, gold, and zinc oxide nanoparticles have been developed using herbal extracts. It was shown that the method of preparation and related parameters such as temperature and type of polymer are important factors affecting physicochemical stability and therapeutic activity of the final product. Many of these formulations could successfully decrease the lipid profile, inflammation, oxidative damage, and insulin resistance in in vitro and in vivo models of MetS-related complications. Further studies are still needed to confirm the safety and efficacy of these novel herbal formulations for clinical application.

Suppression of the Reactive Oxygen Response Alleviates Experimental Autoimmune Uveitis in Mice

Reactive oxygen species (ROS) are produced by host phagocytes and play an important role in antimicrobial actions against various pathogens. Autoimmune uveitis causes blindness and severe visual impairment in humans at all ages worldwide. However, the role of ROS in autoimmune uveitis remains unclear. We used ROS-deficient (Ncf1^−/−) mice to investigate the role of ROS in experimental autoimmune uveitis (EAU). Besides, we also used the antioxidant N-acetylcysteine (NAC) treatment to evaluate the effect of suppression of ROS on EAU in mice. The EAU disease scores of Ncf1^−/− mice were significantly lower than those of wild-type mice. EAU induction increased the levels of cytokines (interleukin (IL)-1α, IL-1β, IL-4, IL-6, IL-12, IL-17, and tumor necrosis factor (TNF)-α) and chemokines (monocyte chemoattractant protein (MCP)-1) in the retinas of wild-type mice but not in those of Ncf1^−/− mice. EAU induction enhanced the level of NF-κB activity in wild-type mice. However, the level of NF-κB activity in Ncf1^−/− mice with EAU induction was low. Treatment with the antioxidant NAC also decreased the severity of EAU in mice with reduced levels of oxidative stress, inflammatory mediators, and NF-κB activation in the retina. We successfully revealed a novel role of ROS in the pathogenesis of EAU and suggest a potential antioxidant role for the treatment of autoimmune uveitis in the future.

Clinical Applications of Astaxanthin in the Treatment of Ocular Diseases: Emerging Insights

Astaxanthin is a naturally occurring red carotenoid pigment belonging to the family of xanthophylls, and is typically found in marine environments, especially in microalgae and seafood such as salmonids, shrimps and lobsters. Due to its unique molecular structure, astaxanthin features some important biologic properties, mostly represented by strong antioxidant, anti-inflammatory and antiapoptotic activities. A growing body of evidence suggests that astaxanthin is efficacious in the prevention and treatment of several ocular diseases, ranging from the anterior to the posterior pole of the eye. Therefore, the present review aimed at providing a comprehensive evaluation of current clinical applications of astaxanthin in the management of ocular diseases. The efficacy of this carotenoid in the setting of retinal diseases, ocular surface disorders, uveitis, cataract and asthenopia is reported in numerous animal and human studies, which highlight its ability of modulating several metabolic pathways, subsequently restoring the cellular homeostatic balance. To maximize its multitarget therapeutic effects, further long-term clinical trials are warranted in order to define appropriate dosage, route of administration and exact composition of the final product.

Optimized nonionic emulsifier for the efficient delivery of astaxanthin nanodispersions to retina: in vivo and ex vivo evaluations

Astaxanthin (AST) is a naturally occurring carotenoid with potent anti-oxidative and anti-inflammatory potency against chronic diseases. In this study, we suspended AST in different nonionic emulsifiers to produce nanodispersions. The basic physicochemical properties of the produced AST nanodispersions were verified to select the optimized nonionic emulsifier. Among the tested emulsifiers, Polysorbate 20 produced the AST nanoemulsions with smaller particle diameters, narrower size distributions, and higher AST contents among these emulsifiers. The N-methyl-N-nitrosourea (MNU) administered mouse is a chemically induced retinal degeneration (RD) model with rapid progress rate. AST suspended in Polysorbate 20 was demonstrated to ameliorate the dramatic consequences of MNU on retina architectures and function in several different tests encompassing from electrophysiology to histology and molecular tests. Furthermore, the multi-electrodes array (MEA) was used to detect the firing activities of retinal ganglion cells within the inner retinal circuits. We found that AST nanodispersions could restrain the spontaneous firing response, enhance the light induced firing response, and preserve the basic configurations of visual signal pathway in degenerative retinas. The MEA assay provided an appropriate example to evaluate the potency of pharmacological compounds on retinal plasticity. In summary, emulsifier type affects the basic physicochemical characteristic of AST nanodispersions. Polysorbate 20 acts as an optimized nonionic emulsifier for the efficient delivery of AST nanodispersions to retina. AST nanodispersions can alleviate the photoreceptor loss and rectify the abnormities in visual signal transmission.

Adjuvant Therapies in Diabetic Retinopathy as an Early Approach to Delay Its Progression: The Importance of Oxidative Stress and Inflammation

Diabetes mellitus (DM) is a progressive disease induced by a sustained state of chronic hyperglycemia that can lead to several complications targeting highly metabolic cells. Diabetic retinopathy (DR) is a multifactorial microvascular complication of DM, with high prevalence, which can ultimately lead to visual impairment. The genesis of DR involves a complex variety of pathways such as oxidative stress, inflammation, apoptosis, neurodegeneration, angiogenesis, lipid peroxidation, and endoplasmic reticulum (ER) stress, each possessing potential therapeutic biomarkers. A specific treatment has yet to be developed for early stages of DR since no management is given other than glycemic control until the proliferative stage develops, offering a poor visual prognosis to the patient. In this narrative review article, we evaluate different dietary regimens, such as the Mediterranean diet, Dietary Pattern to Stop Hypertension (DASH) and their functional foods, and low-calorie diets (LCDs). Nutraceuticals have also been assessed in DR on account of their antioxidant, anti-inflammatory, and antiangiogenic properties, which may have an important impact on the physiopathology of DR. These nutraceuticals have shown to lower reactive oxygen species (ROS), important inflammatory factors, cytokines, and endothelial damage biomarkers either as monotherapies or combined therapies or concomitantly with established diabetes management or nonconventional adjuvant drugs like topical nonsteroidal anti-inflammatory drugs (NSAIDs).

Placoid choroidopathy after bilateral uncomplicated descemet's membrane endothelial keratoplasty

Purpose

To describe a case of bilateral, sequential placoid choroidopathy following uncomplicated Descemet's membrane endothelial keratoplasty (DMEK).

Observations

A 49-year old woman presented with flashing lights and central visual field scotomas after undergoing uncomplicated DMEK combined with cataract surgery for Fuch's endothelial dystrophy in the right eye. She was found to have placoid choroidopathy responsive to systemic steroids and for which a comprehensive work-up was unrevealing. Three and a half months later, she underwent DMEK surgery in the fellow eye and again developed placoid choroidopathy in the operated eye. Work-up was again unrevealing and the lesion followed a similar course to the first eye on systemic steroids. Over the course of seven (right eye) and three and a half months (left eye) of follow-up, the uncorrected visual acuity was 20/20 bilaterally and the retinal lesions had modestly improved.

Conclusions and Importance

We report a case of placoid choroidopathy following uncomplicated DMEK combined with cataract surgery in both eyes of a single patient. This case expands upon the reported complications following DMEK surgery and suggests a need to remain aware of posterior segment complications following endothelial keratoplasty.

Haematococcus pluvialis-Derived Astaxanthin Is a Potential Neuroprotective Agent against Optic Nerve Ischemia

Astaxanthin, a xanthophyll belonging to the family of carotenoids, is a potent antioxidant. However, much less is known about its protective effects on the oxidative stress of ischemic optic nerve. We hypothesized that astaxanthin treatment could protect retinal ganglion cells (RGCs) from death via anti-oxidative and anti-apoptotic responses. Adult male Wistar rats were fed astaxanthin (100 mg/kg/day) by daily gavage for seven consecutive days, either before or after inducing oxidative stress in the retina by photodynamic treatment. The visual function, RGC apoptosis, macrophage infiltration in the optic nerve, expression of p-Akt, p-mTOR, SGK1, pS6K, Nrf2, p62, TNFα, Il1β in retinas were investigated. The visual function and the RGC densities were significantly higher in both pre- and post-treatment groups. The numbers of apoptotic RGCs and extrinsic macrophage infiltration in the optic nerve were significantly decreased in both astaxanthin-treated groups. Furthermore, pre- and post-treatment of astaxanthin showed a higher expression of p-Akt, p-mTOR, Nrf2 and superoxide dismutase activity, and a lower expression of cleaved caspase-3, suggesting anti-apoptotic and anti-oxidative roles. Our findings indicate that astaxanthin can preserve visual function and reduce RGC apoptosis after ischemic insults. Including astaxanthin in daily diet as a supplement may be beneficiary for ischemic optic neuropathy.