Nano Astaxanthin is used in biomedicine and multi-modal treatment
Astaxanthin (AXT) is one of the most important fat-soluble carotenoids, with rich and diverse therapeutic applications such as liver disease, cardiovascular disease, cancer treatment, nervous system protection, and skin protection. and eyes resist UV rays and strengthen the immune system. However, due to its intrinsic reactivity, it is chemically unstable and therefore the design and production process for this compound needs to be precisely formulated. Nanostimulation is widely applied to protect astaxanthin against degradation during digestion and storage, thereby improving its physicochemical properties and therapeutic effects. Nanocarriers are delivery systems with many advantages─easy surface modification, biocompatibility, and targeted drug delivery and release. This review discusses technological advances in nanocarriers for nano astaxanthin delivery through the brain, eye, and skin, with emphasis on benefits, limitations, and practical effectiveness.
Astaxanthin (AXT), a highly active xanthophyll, is a red, lipid-soluble carotenoid.(1,2) Despite its many health benefits, Astaxanthin has limited use in the pharmaceutical industry. and foods due to their poor solubility in water and lack of stability when exposed to oxygen, light, and high temperatures;(3,4)conjugation with fatty acids or proteins promotes its natural stability. (5) Notably, oral administration of astaxanthin is equally limited by its low vascular dispersion rate as well as low cellular absorption. An extensive effort has been made to enhance the bioavailability, stability, and solubility of this powerful antioxidant by nanoization. This method can protect astaxanthin from gastric fluids and allow it to gradually release in intestinal fluids.
Among various nano methods, liposomes, spray drying, solvent evaporation, ionic gelation, coagulation and lyophilization are used in AXT formulation. Particle size control and further product purification due to the use of solvents are limitations of these nanochemical techniques. Recently, supercritical fluid precipitation as an environmentally friendly technology has been used to nanosize astaxanthin.
In a new study, supercritical carbon dioxide (SC-CO 2 ) was used in contact with an emulsion of astaxanthin, ethyl acetate-saturated water, and ethyl cellulose to encapsulate astaxanthin. This method preserves the antioxidant activity of astaxanthin and produces a high production yield with a nanoization efficiency of 84%.(6)In another study, nano astaxanthin was prepared using SC-CO 2 technology with nanoization efficiency of 91.5%; AXT was dissolved in poly( l -lactic acid), dichloromethane and acetone and evaporated into SC-CO 2 mass.(7)The size and structure of the capsule are important factors to be taken into account when nano AXT chemistry. Multilayer structures (liposomes, oil-in-water emulsions) at the nanometer scale provide greater stability and biological activity, and allow for controlled release of astaxanthin.(no. 8)
These micro-/nanocapsules not only protect AXT against gastrointestinal digestion and subsequent release in the intestine, but also smaller astaxanthin-containing carriers (<500 nm) can also be absorbed by endocytosis or through Peyer’s patches, thereby enhancing the bioavailability of AXT.(9)Consequently, physicochemical properties, such as size, charge, surface, and composition of lipid particles, can protect AXT against enzymatic digestion and enhance its stability and bioavailability.(10)
These astaxanthin nanoparticles, due to their lipophilic properties, can adhere to membranes and penetrate cells, thus they are proposed as excellent carriers of AXT across the intestinal barrier. Nanostructured lipid carriers appear to be more stable against degradation than liposomes in the presence of gastric acid and pancreatic lipase secretion. For example, the use of phospholipids, saturated lipids or phytosterols can enhance carrier stability. Additionally, surfactant-based delivery systems such as niosomes are resistant to hydrolysis and acidic environments.(11)Other materials such as alginate/gelatin and whey protein/gum Arabic at stomach acidic pH thick insoluble and prevents degradation but at intestinal pH facilitates dissolution when encapsulated Nano astaxanthin is released.(6) Therefore, the materials selected for nanoization will regulate the release releases AXT in the intestine and causes resistance to its pH, thereby preserving the micro/nanocapsules until decomposition. In addition, the delay in the transit of Nano astaxanthin capsules through the gastrointestinal tract depends on the mucoadhesive properties of the material and the small particle size.
Chitosan-based nanoparticles are beneficial for astaxanthin loading because they are safe, biodegradable, and have high affinity for cell membranes, thereby improving nanoastaxanthin transport across tight junctions tightness of the epithelium. However, these nanoparticles degrade under low pH conditions and cannot protect AXT during gastrointestinal digestion. Studies have demonstrated that chitosan blended with casein and oxidized dextran or other nonionic polymers enhances the physicochemical stability of these nanoparticles.(12)A key criterion for selecting an encapsulation system biopolymer or lipid-based nanoencapsulation is effective and suitable for transporting astaxanthin which is the structure, barrier and cellular composition of the target organ (brain, skin and eye, etc.). The selection of appropriate nanochemical materials enhances the bioaccessibility, solubility, and long-term stability of astaxanthin in target organs. Overall, based on recent studies, chitosan (carbohydrate biopolymer) combined with proteins or other carbohydrates is a valuable carrier for astaxanthin, and among the lipid-based nanocarriers, nanolipids and structural Nanostructures are effective systems compared to other lipid-based systems. Additional parameters in choosing the appropriate encapsulating agent are availability and affordability as well as the appropriate route of administration (oral, ocular, injectable, etc.).(13−16)
The goal of this review is to highlight the properties and applications of Nano astaxanthin. In this regard, the limitations, advantages and practicalities of recent innovations and developments including Nano astaxanthin delivery systems for various diseases (e.g. neurological, eye and skin disorders) has been considered.
SOURCE, STRUCTURE AND EXPLOITATION
AXT is a xanthophyll, with molecular formula C 40 H 52 O 4 and molar mass 596.84 g/mol. It is naturally present in many marine and living organisms, specifically salmon, shrimp, krill, lobsters, microorganisms, and some plants.(17)On the other hand, AXT is synthetically produced by petrochemical products in a multi-step process. Three different methods were used for the chemical synthesis of AXT: hydroxylation of canthaxanthin ( Figure 1 A), oxidation of zeaxanthin ( Figure 1 B), and Wittig reaction (one dialdehyde with two phosphonium) ( Figure 1 C). To date, only natural AXT has been approved for human use. It is used as an expensive material for various therapeutic applications, while the use of the synthetic form mainly falls to aquaculture equipment merely as a feed additive.( 18) Notably, the antioxidant activity of natural AXT is 20–50 times stronger than that of synthetic AXT. It has shown better therapeutic effects and has no toxic effects.(19)Consequently, the consumption of natural Nano astaxanthin and the demand for it have increased significantly compared to the demand for the synthetic . Natural AXT is mainly derived from algae ( Haematococcus Pluvialis ), bacteria ( Paracoccus haeundaensis , Paracoccus carotinifaciens ) and yeast ( Phaffia rhodozyma/Xanthophyllomyces dendrorhous ). Haematococcus pluvialis is a freshwater microalgae and is known as an excellent source of natural astaxanthin.(20,21)Many companies are producing natural AXT from algae due to its growing importance in pharmaceutical industry.(22−24)A significant challenge in producing Nano astaxanthin using biotechnology is the subsequent processes. Because AXT is produced intracellularly and high purity AXT is required for nutritional and pharmaceutical applications, most experience high operating costs; therefore, the cost of the subsequent steps accounts for nearly 80% of the production cost.(25,26) An efficient downstream process can reduce production costs and increase productivity.
Figure 1. Three chemical synthesis strategies of astaxanthin: (A) hydroxylation of canthaxanthin; (B) oxidation of zeaxanthin; and (C) Wittig reaction.
AXT consists of two terminal rings connected by a polyene chain. This molecule contains two asymmetric centers located at the 3 and 3’ positions of the β-ionone ring with a hydroxyl group (-OH) at either end of the molecule ( Figure 2 A). An elongated chain of conjugated double bonds in the center of the molecule is responsible for the antioxidant activity of Nano astaxanthin.(27−30)Due to the presence of oxygen in its rings, AXT has a more polar, making it a powerful antioxidant because it can donate electrons and scavenge free radicals. Notably, the configuration of the stereogenic carbons at positions 3 and 3′ in these rings defines the AXT spatial isomers as symmetric (3S, 3S′) or (3R, 3R′) or average (3R, 3′S), with the configurational enantiomer being the most abundant in nature ( Figure 2 B).
Figure 2. (A) Chemical structure and (B) stereoisomerism of astaxanthin. (C) Structure of the monoester and diester forms of astaxanthin.
The presence of hydroxyl and carbonyl (C═O) in each ionone ring explains characteristics such as its polar nature and ability to undergo esterification. Based on its source, AXT can exist in different forms such as optical R/S isomerism, geometric isomerism, and esterified or free form.
Although the most predominant form of AXT in nature is the esterified form, the non-esterified form can also be found. AXT is found in three different forms based on its two hydroxyl groups: the unesterified form (free form), the monoesterified form (one hydroxyl group is esterified with a fatty acid), and the diesterified form (two hydroxyl groups are esterified with fatty acids) ( Figure 2 C ). Different synthetic sources of AXT contain varying proportions of these three forms. For example, AXT extracted from the yeast Xanthophyllomyces dendrorhous is the (3R, 3′R) isomer in its free form, while Haematococcus pluvialis biosynthesizes the (3S, 3′S) isomer in its monoesterified form. is predominant ( Table 1 ).(31)
The ratio of stereoisomers in synthetic and natural AXT is inherently different. Synthetic AXT contains (1(3R, 3′R):2(3R, 3′S):1(3S, 3′S)) as the free form, while variable ratios of stereoisomers Plants exist in natural AXT mainly in the form of a complex with proteins or lipids, or in esterified form. The remarkable biological activity of AXT originates from the 3S, 3′S isomer, which explains the better bioavailability after dietary supplementation of natural AXT compared to the synthetic form. The study conducted by Yang et al. indicated that AXT diesterified with saturated acids and long chains had higher stability than other forms of AXT.
They showed that AXT stability is directly correlated with the degree of esterification, carbon chain length, and fatty acid saturation state. Furthermore, reducing the degree of esterification, decreasing the carbon chain length, and increasing the fatty acid unsaturation of AXT is beneficial to its bioavailability. During digestion, AXT monomerizes with short-chain and unsaturated fatty acids that are easily hydrolyzed. Therefore, the bioavailability of free AXT is significantly greater than that of monoesterified AXT, and for the monoesterified form is significantly greater than that of diesterified AXT.(33) After addition of (free) AXT or esterified), the only form found in human blood is the free form.
Furthermore, studies in humans have demonstrated that the free form of AXT is the major active form and has greater bioavailability than the esterified form.(36) It is speculated that the amount of AXT esterified at the site of absorption is limited by the need to hydrolyze these esters in the gastrointestinal tract before absorption.(37)During the purification step of the downstream process, impurities such as salts, cell debris, other carotenoids, solvents , proteins, esters and other contaminants are separated and free natural AXT (purity 99% or more) is obtained. After removing the ester groups, free AXT and its isomers can be easily analyzed by chromatographic techniques; Free AXT would constitute useful pharmaceutical antioxidants because they can bind to water-soluble groups.(38)Mimoun-Benarroch et al. demonstrated that the uptake of esterified native AXT from H. pluvialis was slower than that of free AXT from P. carotinifaciens and P. rhodozyma ; Hydrolysis of the esterified form in the intestinal lumen before absorption may contribute to reduced absorption. Additionally, these esterified AXTs cannot be identified by chromatographic analysis unless their fatty acid chains are removed.(39)
However, some studies suggest that esterification makes AXT soluble more soluble and enhances its stability to oxidation; therefore, it may have better pharmacological properties than free AXT.(40)Therefore, some researchers have carried out purification of H. pluvialis AXT and recovered high proportions of free AXT or monoester has been purified.(41,42)Normal phase chromatography combined with reversed phase chromatography can be used to separate free and esterified AXT (mono and diester) in 25 minutes.(43,44)Activity Antioxidant properties of different natural forms of AXT are still debated. It has been claimed that free AXT is more effective than esterified AXT,(45)while others have reported that the esterified form has better antioxidant activity.(46−49)Research by Rao et al . in a mouse skin cancer model showed that esterified AXT had better antioxidant and anticarcinogenic properties than the free form.(50)In addition, comparing these two forms with respect to exercise performance in mice showed that esterified AXT significantly promoted muscular endurance, protected red blood cells from oxidative damage, and increased running time.(51)
Due to the presence of several conjugated double bonds, two types of geometric isomers occur in the AXT molecule: the Z isomer and the total E ( Figure 3 ). The most representative AXT in nature is the all-E stable isomer when the carbon atoms are located at the E position in the double bond. The less stable but more favorable Z isomers (mixture of 9 Z and 13 Z isomers) obtained in AXT extraction are influenced by factors such as metal ions,(52)solvent, temperature or pH of the reaction medium.(53)Viazau et al. examined the isomerization of AXT under thermal and hyperbright conditions and in both in vitro and in vivo systems (H. pluvialis cells). During the first 5 hours of light treatment under in vitro conditions and in the presence of methanol, both Z isomers increased to 5% and then decreased, but during the entire heat treatment period, the amount of copper The cumulative Z fraction has increased. . In H. pluvialis cells, under high light and sodium acetate conditions, the accumulation of the Z isomer initially reached 45% and then gradually decreased; the reduction of isomers may be due to de novo synthesis of all-E-AXT and oxidative degradation of AXT.
To increase total AXT production in H. pluvialis cells, the presence of sodium acetate and long-term light are necessary, and to increase the production of the Z isomer, only short-term light is sufficient.(54)A Several studies have investigated the beneficial properties of the Z isomer over the E isomer of AXT. Yang et al. documented the selective accumulation of 13 Z – AXT in human plasma with the assertion that the Z isomers are more beneficial to human health.(55)Because the Z isomers are more soluble in solution organic solvents, so their extraction process is more effective when a Z-isomer accelerating catalyst is added to the extraction solvent; hence they have better extractability than the all- E isomer.(53)Because some changes take place in the physicochemical properties of AXT in the Z configuration, when they change from the crystalline state to the amorphous (oil), processes such as extraction, emulsification and micronization are facilitated by safe and stable solvents.(56)
Higher dispersion and solubility of the AXT -Z isomer leads to greater bioaccessibility and bioavailability of this molecule; 13 Z – AXT is more bioaccessible than 9 Z – and total E -AXT in an in vitro digestion model.(55)Z isomerization also affects anticancer activities, Antioxidant, anti-inflammatory, anti-aging and anti-atherosclerotic properties of AXT.(56)Yang et al. demonstrated greater inflammation inhibition for the Z isomers, especially 9 Z , by reducing the expression of NK-κ, IL-8, TNF-α, and COX2 in a Caco cell monolayer model -2.(57)Better anti-aging activity of 9Z-AXT was observed as the average lifespan of Caenorhabditis elegans fed with it increased by 59.39% compared to a 30.43% increase when fed with all E isomers.(58)All changes in the function and activity of the AXT- Z isomers are due to altered physicochemical properties of this molecule. Some physicochemical properties that influence E/Z isomerization are solubility, color value, stability, crystallinity, and melting point. Changes in the Gibbs free energy affect the stability of the Z isomer, thereby affecting its antioxidant properties.(59)Liu and Osawa have shown a strong antioxidant effect of Z isomers (especially 9 Z -AXT) in highly effective free radical scavenging activity and also suppress ROS production in neuroblastoma cells as well as inhibit hydroperoxide induction.(60) On the other hand, Yang et al., by different antioxidant activity tests, showed that 13 Z – AXT has stronger antioxidant activity than the whole E and 9 Z. (61)The Z isomer has Higher solubility in organic solvents, vegetable oils and SC-CO 2 enhances their bioaccessibility. Similarly, the uptake of Z isomers into bile acids was improved and their internalization into Caco-2 cells by carotenoid transport proteins was more efficient ( Table 2 ).(55)
Abbreviations: ORAC-L test, oxygen radical absorbance capacity test for lipophilic compounds; PCL test, photochemiluminescence test; CAA assay, cellular antioxidant activity assay; DPPH, 2,2-diphenyl-1-picrylhydrazyl; bioaccessibility, the amount of AXT available for absorption in the intestine after digestion; bioavailability, the amount of AXT that reaches the physiologically active site after administration.(25)
An efficient downstream process will reduce production costs and grow productivity. It is not surprising that natural AXT obtained from Haematococcus pluvialis is very expensive and accounts for only 1% of the total AXT market share while the rest is in the synthetic category.(67)However, there are emerging strategies that have the potential potential to increase the market share of natural AXT in the market.
It is known that AXT can concentrate in Haematococcus pluvialis up to 5% of its dry weight in the aplanospore stage under undesirable conditions, among which can be listed high salinity, high temperature and high light than. On the other hand, if undesirable conditions prevail, it will lead to the accumulation of AXT; the increase in AXT is accompanied by the formation of an acetolysis-resistant wall around the cell with a thickness of up to 2.3 μm, an obstacle to the extraction process.(68,69)Only 5% of AXT in the cell in free form and the remainder bound to fatty acids. Extraction of the free form plus its derivatives requires disruption of the cell wall, but preserving the biological activity of AXT during this process is of vital importance, making it a challenge. notable in this field.(70)A mild one-step strategy has been reported to yield 47 wt% yield through recovery of AXT from mature cysts of Haematococcus pluvialis .
In this method, the cell wall of follicular cells is completely ruptured under mild conditions (200 rpm, room temperature and atmospheric pressure) for a short time (<30 minutes); Subsequent extractions are carried out using various solvents generally recognized as safe (GRAS), e.g. ethanol, acetone, n -hexane, ethyl acetate and isopropyl alcohol). Astaxanthin recovery was highest in ethanol, followed by acetone, ethyl acetate, isopropyl alcohol (IPA) and hexane. Figure 4 shows the optimized one-vessel process along with the conventional dry grinding process and the two-step process for comparison. The one-step strategy avoids pretreatment to disrupt cell walls, making the process more efficient than in previous studies.(71,72)The difference between the dry and wet methods can be clearly seen in Figure 4 B; Dry ball milling, which is widely practiced, causes the formation of cell debris on the balls and chamber walls, which then agglomerates and is therefore less effective. In the case of the two-step process, an initial grinding is performed followed by extraction by Soxhlet, supercritical fluid or other means with low yields, while the one-vessel process allows high yield extraction of AXT. high yield in a short time. at ambient temperature.(67)
Figure 4. (A) Diagram showing the one-vessel strategy for AXT extraction from Haematococcus pluvialis . (B) Comparison between dry and wet techniques using digital camera images: (i) immediately after ball milling, (ii) barrel wall, and (iii) zirconia pellets after the process. (C) AXT performance for the control ( Haematococcus pluvialis lyophilized via Soxhlet extraction with acetone without applying ball milling (12 hours)), the one-pot strategy (up to 20 minutes), and the two-pot technique steps (maximum 60 minutes) ). (D) Digital camera and SEM images showing cell debris (i) before ball milling, (ii) after the two-step method, and (iii) after the one-pot method. Reprinted with modifications from ref (67)with permission of the American Chemical Society.
Although the one-step strategy yielded the highest amount of AXT from Haematococcus pluvialis it is considered an invasive method because it requires complete disruption of the algae. The microalgae biorefinery process involves several steps such as cultivation, harvesting, and subsequent extraction, which is an expensive and time-consuming endeavor. There is a non-invasive strategy that has the potential to reduce both the time and cost of microalgae milking.(73) Like cow milking, the idea behind this process is to reuse biomass to prolong production time; an innovative strategy was applied to extract AXT multiple times from a single Haematococcus pluvialis cell . The process begins with making an incision in the cell wall through a gold nanoscalpel, then extracting AXT and finally healing the wound by providing incubation and nutrients.
It is important that the extraction process is synchronized with the leakage of chlorophyll in addition to AXT. After the extraction process, the addition of nutrients stopped the leakage of pigments and the chlorophyll content increased again, which is important for maintaining cell metabolism. The relationship between chlorophyll and AXT was found to be inverse; A twofold improvement in AXT content compared to the control group was observed after the first extraction process(74)( Figure 5 ). Of course, further research is needed to optimize the milking process and is worth investigating because the process can be reused as many times as desired.
Figure 5. (A) Extraction of regenerated AXT from Haematococcus pluvialis through a gold mill. (B) SEM micrograph of the gold manipulator and etched cell. Reprinted from ref (74)with permission from the American Chemical Society.
Xanthophyll carotenoids, which belong to the AXT group, are dissolved in the small intestine after ingestion. This process is carried out in mixed micelles containing bile acids, phospholipids, cholesterol and fatty acids. These carotenoids then enter epithelial cells by simple and facilitated diffusion across their cytoplasmic membrane. Once they are broken down, carotenoids are stored in the liver. They are next secreted as very low density lipoproteins, low density lipoproteins and high density lipoproteins into the blood and transported to the tissues.
The polar heads of AXT make it more absorbable than other nonpolar carotenoids such as lycopene. It has been shown that esterified AXT is hydrolyzed (fatty acids are removed from either ring) before being transported as low-density lipoprotein.(75,76)AXT is structurally similar to β -carotene, where the former has 13 conjugated double bonds, while the latter has 11; The ability of carotenoids to neutralize free radicals is enhanced by increased conjugated double bonds and the presence of a functional group in its terminal rings.(77)
Polar AXT spans the membrane, with its polar head groups extending toward the leading region of the membrane bilayer. As a result, AXT inhibits free radical chain reactions and scavenges lipid peroxyl radicals and ROS (endogenous ROS) on the membrane surface, while its polyene chain can trap ROS in the membrane interior.(78 )The toxicity and efficacy of oil-based AXT softgels were reported by Satoh et al. According to this analysis, no safety issues were observed while metabolic syndromes improved. The US Food and Drug Administration and the European Food Safety Authority have approved AXT as a dietary supplement, food ingredient and additive. To date, AXT is extracted from H. Pluvialis and P. carotinifaciens have been approved for human use at doses ranging from 12 to 24 mg and 6 mg per day, respectively, for up to 30 days.(79,80)
NANO ASTAXANTHIN FUNCTION IN THE HUMAN BODY: ANTIOXIDANT ACTIVITY AND SIGNAL TRANSDUCTION PATHWAYS
Nano astaxanthin has shown antioxidant properties. It is known that low levels of ROS are beneficial for gene expression, cell signaling, and stimulation of antioxidant defense mechanisms.(81)Several studies have demonstrated that AXT is more potent than beta-carotene in eliminate free radicals caused by internal factors (inflammation, aging, stress and cancer, etc.) or external sources (cigarette smoke, pollutants, UV radiation, etc.)(82 ,83)and preserves unsaturated fatty acid methyl esters by preventing peroxidation. In addition, AXT ester shows high antilipid peroxidation activity.(84,85)The health-promoting effects of AXT on many diseases have been demonstrated in several studies, which highlight its therapeutic effects. promise of AXT.(86,87) Nano astaxanthin enhances and regulates the immune system, and increases antibody production in a T helper-dependent manner. Thus, it increases the number of secretory cells antibodies from spleen cells and immunoglobulin production by blood cells.(88,89)Its very strong antioxidant activity may have a protective effect on the cardiovascular system.(90)Coombes and partner. demonstrated that AXT had no effect on increasing inflammation, oxidative stress, and arterial stiffness in kidney transplant recipients.(91)Other studies showed that AXT has tremendous effects on cardiac function, builds joint strength, exercise performance and post-workout recovery.(92)Also in heart failure patients, consuming AXT for three months has antioxidant effects and improves exercise tolerance. exercise and cardiac contractility.(93)The anticancer effects of AXT include anti-inflammation,(94)anti-proliferation,(95)antioxidation,(96)and increased increased apoptosis 95 has been confirmed in multiple in vivo and in vitro studies. It also improves brain function and may reduce or prevent brain diseases, such as Parkinson’s disease, autism and Alzheimer’s disease.(97,98)AXT reduces skin wrinkling and prevents age spots, improves skin elasticity and reduces UV damage caused by sun rays, thus acting as an internal sunscreen.(99,100)
Nano astaxanthin has an important role in the signaling pathways of inflammation, oxidative stress and reactive oxygen species-dependent apoptosis by disrupting their signaling pathways during neurodegeneration. nerve and related eye and skin damage.(101,102)Although ROS have an important role in nerve signaling and function, unwarranted ROS generation is fatal to cellular function nerves, with permanent oxidation. AXT shows neuroprotective effects by reducing intracellular ROS and preventing the generation of H 2 O 2 in mitochondria .(103)
Nano astaxanthin can prevent inflammation by inhibiting the release of interleukin (IL), tumor necrosis factor (TNF-α), and intercellular adhesion molecule 1 (ICAM1) as shown in Figure 6 .( 101,104)The anti-inflammatory properties of AXT are due to its inhibition of the TLR4 pathway in addition to its ability to regulate the TLR4/MyD88/NF-κB pathway,(105)downregulating TLR4 and MyD88 expression, and inhibiting its activation. TLR4/MyD88/NF-κB pathway, has a significant role in regulating burn-induced kidney tissue inflammation.(106)AXT exerts anti-inflammatory effects in the eye by interfering with the NF-κB signaling pathway through inhibited the induction of TNF-α, NO, and PGE2.(107)Furthermore, AXT suppressed choroidal neovascularization by downregulating ICAM-1, macrophage-derived VEGF, MCP-1 and IL-6 as inflammatory mediators.(108)In addition, it may effectively support additional tissue protection by maintaining the oxidative/antioxidant balance in relation to toxic structures. its originality.(109)
Figure 6. Diagram illustrating the role of Nano astaxanthin on signaling pathways of inflammation, oxidative stress and apoptosis by disrupting their signaling pathways.
To prevent oxidative stress, AXT activates Nrf2/antioxidant response elements (Nrf2/ARE), inhibiting the phosphorylated extracellular regulated protein kinase/protein kinase (p-ERK/ERK) ratio. and increased release of NAD(P)H quinine oxidoreductase-1 (NQO-1) and heme oxygenase-1 (HO-1). It has been shown that Kelch-like ECH-associated protein 1 (Keap1)-Nrf2-ARE has an important function in cellular antioxidant responses.(101)The AXT antioxidant mechanism also includes the regulation of regulates the PI3K/Akt signaling pathway.(110)AXT acts as a shield for photoreceptors from oxidative stress, reducing apoptosis due to stimulation of the PI3K/Akt/Nrf2 signaling pathway under hyperglycemic conditions. AXT reduces retinal ganglion cell and Muller cell damage through enhancing HO-1 production. Different signaling pathways are combined to increase cellular resistance to oxidative stress. In this way, the Nrf2-ARE pathway plays an essential role and maintains cellular function ( Figure 6 ).(101,111)A transcription factor that binds to the ARE is Nrf2, which promotes enzyme expression Phase II. The interaction of Nrf2 with the chaperone Keap1 occurs in the absence of oxidative damage. In contrast, under oxidative conditions, Nrf2, which dissociates from Keap1, is in an activated form and translocated into the nucleus, binding to the ARE and stimulating expression of Phase II enzymes, for example, heme oxygenase-1 (HO-1 ) and NQO1.(81,104)
Nano astaxanthin exhibits antioxidant properties and can generate trace amounts of ROS instead of quenching them, which activates HO-1 expression and regulates GSH-Px expression and activity through the signaling pathway This generated ERK-Nrf-2/HO-1.(81)ROS is harmless to cells because pristine AXT endorses cell proliferation and improves GSH-Px and SOD enzyme activity, also showed a protective effect against H 2 O 2 induced oxidative stress in HUVECs and reduced H 2 induced ROS production Cell 2 .(81)
Additionally, Nrf2 activation may support retinal periphery cell survival. Nano astaxanthin can activate the Nrf2-ARE pathway, thereby enhancing HO-1 and NQO1 expression, while reducing oxidative damage with a protective effect from glucose-induced elevated apoptosis in cells photosensitive ( Figure 6 ).(124)
The role of AXT against apoptosis was ascertained by blocking caspase3,9 as shown in Figure 6 , as well as cytochrome c, p-ERK/ERK and Bax/Bcl2 ratio.(101,111)AXT has a therapeutic effect in spinal cord ischemia-reperfusion injury and induces oxidative stress and neuronal apoptosis by activating the PI3K/Akt/GSK-3β signaling pathway.(112)PI3K signaling pathway/ Akt/GSK-3β shows neuroprotective functions by inhibiting apoptosis and stimulating cell proliferation.(113)
