In view of the increasing demand for oxidative stress suppressors, there is a general need for cytoprotective antioxidants that support the side effects of free radicals generated chemically and by exposure to sunlight (55,56). Prolonged exposure to sunlight has been linked to several types of skin damage, including sun injury, skin inflammation, photoimmunosuppression, photoaging, photocarcinogenesys, include irritation, inflammation, erythema, and photocarcinogenesys associated with UVR exposure. These pathologies occur through the formation of reactive oxygen species (ROS) (55,56). Fortunately, the skin has endogenous antioxidants that it uses as defense mechanisms to inhibit or delay the oxidative damage generated by UVR. Undoubtedly, this defense system decreases with chronic exposure to ultraviolet rays, therefore, a strategy to remedy this deficiency would be the use of antioxidant phytochemicals capable of delaying or inhibiting cell damage caused by free radicals, providing photoprotection to human skin (57,58,59). It has been observed that bioactive compounds such as flavonoids and carotenoids are capable of inhibiting cellular photo-oxidation. However, in the same way as endogenous antioxidants, exogenous antioxidants could be degraded by chronic UVR exposure. A probable hypothesis to reduce the development of pathologies associated with the effects of UVR is the application of oral, skin, or ocular antioxidants that eliminate reactive oxidants and modulate the cellular redox state. For this reason, part of our study focused on evaluating the photostability of fucoxanthin, blood susceptibility, and in vitro photoprotection efficacy. This study allows obtaining information on the use of antioxidants as photoprotective agents, inhibiting the effects of UVR on different erythrocyte blood groups as part of the erythroprotective potential (51,58,59).
In Vitro Photoprotection Efficacy
Ultraviolet radiation (UVR) induced a substantial decrease in the integrity of the erythrocyte membrane of the eight blood phenotypes, measured through hemoglobin release (
Figure 11). After preincubation with Fucoxanthin, the levels of photoprotection against UV-A radiation increased significantly on non-A RhD-ve blood groups in the first 60 min of exposure with values around 75-99% inhibition of photohemolysis (
Figure 11A). However, after 120 minutes, photoprotection decreased in most blood groups (22-80%), except in groups A RhD+ve and B RhD+ve (90-95%). Undoubtedly, the groups most affected by UV-A radiation were groups A RhD-ve and B RhD-ve, presenting a greater susceptibility to cellular oxidation. Particularly interesting, those erythrocytes with the absence of antigen D showed an increase in their photooxidation, specifically in antigens A and B, being the phenotypes that provided the least photoprotection from fucoxanthin. Meanwhile, it can be seen from
Figure 11B that the photoprotection of fucoxanthin was different against UV-B radiation. Here photooxidation was more evident after 30 minutes of exposure. Despite this, the inhibition of photohemolysis ranged between 60-97% at 30 and 60 min of exposure. In this exposure period, fucoxanthin provided greater photoprotection on blood groups A and B RhD+ve (94-98%). Unlike the results reported for UV-A radiation, UV-B radiation did not drastically affect group A RhD-ve, but rather group AB RhD+ve. At the end of the exposure period (120 min), photoprotection decreased drastically for group B RhD-ve compared to the previous two periods. In general, all groups decreased in this period, with a greater photoprotection present in the O RhD-ve group by Fucoxanthin (85.34 %).
The photoprotective effect exhibited by β-carotene against hemolysis induced by UV-A radiation (
Figure 12A) presented similar values in the three exposure periods on the eight erythrocyte phenotypes. β-Carotene conferred a greater photoprotective effect on A RhD+ve erythrocytes compared to the remaining 7 phenotypes during the three periods. The values ranged between 95-100% inhibition of photohemolysis. While the AB RhD-ve group was the most affected by UV-A radiation despite the photoprotection provided by β-carotene. This means that erythrocytes with AB antigens with absent RhD probably present an antagonistic effect (17-38%). Presenting a significant decrease (p>0.05) with respect to the values presented for groups A and B RhD+ve, A and B RhD-ve, and AB RhD+ve. This same trend occurred in blood groups exposed to UV-B radiation (
Figure 12B). The most notable difference is found under the 120-minute period where the value of the O RhD-ve group decreased to 18.54%.
Figure 13 also shows a notable variability in the photoprotective effect of gallic acid on the different erythrocyte phenotypes as well as the previous bioactive compounds. This variability can be observed in the affinity of gallic acid by the different phenotypes seen in
Figure 13A. This trend indicates that as the exposure time increases, the photoprotective effect of gallic acid decreases. At a time of 120 minutes, erythrocyte hemolysis due to exposure to UV-A radiation is accentuated. Revealing a decrease in the protective effect in groups A RhD-ve, AB RhD+ve and O RhD-ve, with values ranging between 43-51%. Gallic acid showed greater effectiveness in inhibiting photooxidation induced by UV-B radiation (
Figure 13B) on RhD+ve erythrocytes A and B, with notable photoprotective stability in all exposure periods (80-98%). However, free radicals and oxidative stress induced at 120 minutes caused cellular degradation, lipid peroxidation and proteolysis on the erythrocyte membrane of the AB and O RhD-ve groups (≈20%). This result indicates that gallic acid probably did not have such a strong affinity with these blood groups, since this decrease in the photoprotective effect was observed from the first 30 minutes of exposure.
The photoprotective efficacy of quercetin (
Figure 14) showed a behavior dependent on blood groups. Which means that the inhibitory potential of quercetin on free radicals induced by UV-A and UV-B radiation varied depending on the erythrocyte surface antigen.
Figure 13A shows the variation of the effect of quercetin on erythrocyte phenotypes with a very similar behavior for the three exposure periods. A greater response was obtained in groups A, B, and O, where antigen D is present in all three group types (90-98%). In
Figure 14B, a greater photooxidation can be seen with UV-B radiation as opposed to UV-A radiation. Here, the intensity of ultraviolet radiation significantly decreased the photoprotective efficacy of quercetin in the three established time periods. In the first 60 minutes of exposure, quercetin provide the AB RhD+ve group an efficacy between 90 to 95%, which decreased after 120 minutes (58%). Photoprotective efficacy decreased below 60% for all erythrocyte phenotypes.
The results of the efficacy of ascorbic acid showed that blood groups B RhD-ve, AB RhD+ve, and AB RhD-ve were mostly susceptible to degradation by UV-A radiation (45 and 74%) in the three periods (
Figure 15A). The oxidative stress present in these blood groups was evident, when compared to the remaining blood groups. Once again, groups A RhD+ve and B RhD+ve showed a better response to the protection provided by ascorbic acid. Not only this antioxidant, but also the previous antioxidants exhibited significant photoprotection against photooxidation induced by UV-A radiation on these same blood groups. The evaluation of the sensitivity to UV-B radiation of erythrocytes preincubated with ascorbic acid showed statistically significant differences between each blood group tested (
Figure 15B). Ascorbic acid seemed to suppress the effects of UV-B radiation on the erythrocyte membrane of the AB RhD+ve group in the first and second periods (30 and 60 min) of exposure. However, at 120 min, the effects of radiation suppressed the photoprotection provided by ascorbic acid, reducing its effect on all blood groups.
Figure 16 shows the morphological changes of group A RhD+ve erythrocytes exposed to ultraviolet radiation and the photoprotective effect provided by the carotenoids tested. This phenotype was selected for the photoprotective efficacy of these antioxidants. Micrographs A, B, and C are red blood cells not exposed to UV radiation and are used as a control without hemolysis. These erythrocytes show a typical morphology of healthy human erythrocytes, with characteristics such as a well-defined biconcave central zone, measuring between 5 to 6.5 nm. Micrographs D and G are shown to describe the oxidative stress lethality generated by UV-A and UV-B radiation, respectively. These micrographs show erythrocytes exposed to UVR to generate oxidative stress and evaluate its effects on changes in their cellular structure, a model of photohemolysis control. In this case, radiation altered the membrane of the erythrocytes, inducing hemolysis. This alteration releases hemoglobin, a result that is interpreted as possible cell death or eryptosis in the particular case of erythrocytes. UVR wavelengths directly affect the erythrocyte membrane, causing lipid peroxidation and proteolysis. This action promotes the loss of the physical integrity of the membrane, resulting in a typical hemolytic activity, accompanied by release of hemoglobin. On some occasions the biconcave characteristic of the erythrocyte can be lost. Membrane oxidation is characterized by the presence of an intense purple and red color at the periphery of the biconcave disk of the erythrocyte (67-70). Additionally, two groups of micrographs are observed where the photoprotective effect of the carotenoids studied is expressed. Group of erythrocytes exposed to UV-A radiation with photoprotective antioxidants (Figure E and F). Group of erythrocytes exposed to UV-B radiation with photoprotective antioxidants (Figure H and I).
No significant morphological changes are observed in erythrocytes exposed to UV-A radiation in the presence of Fucoxanthin and β-carotene compared to the control (
Figure 16 E and F). Photooxidation inhibited by erythroprotective carotenoids is evident by the preservation of the physical integrity and morphology typical of a healthy cell. In this case, the antioxidants tested largely counteracted all the alterations induced by UV-A rays described above. These same characteristics were observed in the erythrocyte sample exposed to UV-B radiation with β-Carotene (
Figure 16 I) as a photoprotective agent, which maintains the cellular integrity of a healthy erythrocyte. In this case, it was observed that all the effects of photooxidation induced by UV-B rays are counteracted. However, Fucoxanthin partially prevented the damage to the erythrocyte membrane induced by UV-B rays (
Figure 16 H). Therefore, photostability decreased, compromising the stability of erythrocytes. The morphological changes showed partial damage to the erythrocyte, without apparent damage to the integrity of the membrane as a consequence of a decrease in photoprotection. Further analysis is needed to confirm whether this damage could be significant and later contribute to possible eryptosis.
The evaluation of photoprotection with Fucoxanthin and β-Carotene can be observed in micrographs E, F (UV-A), H and I (UV-B), respectively. No significant morphological changes are observed in erythrocytes exposed to UV-A radiation in the presence of Fucoxanthin and β-Carotene. Photooxidation inhibited by erythroprotective antioxidants is evident by the preservation of the physical integrity and the typical morphology of a healthy cell. In this case, the antioxidants tested counteracted all of the above-described UVA-induced alterations to a significant extent. These same characteristics were observed in micrograph I with β-Carotene. In this case, it was observed that all the effects UV-B ray-induced-photooxidation is counteracted. However, fucoxanthin only partially prevented damage to the erythrocyte membrane induced by UV-B rays. Therefore, photostability decreased, compromising erythrocyte stability. The morphological changes made damage to the erythrocyte evident, causing damage to the integrity of the membrane, disruption and lipid oxidation that occurred as a consequence of a decrease in fucoxanthin photoprotection at 120 min with photoinhibition values of ≈70%. More analysis is needed to confirm that this damage could be significant and mitigate eryptosis. Ultraviolet radiation interacts with DNA and human cells in a very complex way. This interaction and the pathological effects have been the introduction for therapeutic advances in the formulation of treatments against eye and skin diseases induced by ultraviolet radiation. Currently, protective mechanisms against UV damage and bioactive photoprotective compounds are the key to reducing the processes that take place when human skin is exposed to sunlight (64). Through of cellular models, it has been possible to study the intervention of drugs and bioactive compounds that could be directly involved in the intervention of photooxidation and consequently cellular mutagenesis. Additionally, study the photoprotective effect, susceptibility, and the association of different blood phenotypes with photooxidation (30).
Sunlight is the main source of human exposure to ultraviolet radiation, which is classified into three main types: UV-A (315-395 nm), UV-B (280-315 nm) and UV-B (100-280 nm). Studies have revealed that overexposure without adequate sun protection has been associated with epidermal diseases. Ultraviolet radiation has adverse effects on the eyes and skin cells, causing sunburn, photodermatitis, premature aging, cataracts formation, mutagenesis, and skin cancer. The main biomolecules affected by UVR are proteins and DNA; this cellular damage stimulates the proliferation of neoplastic cells. There are two pathways of cellular damage mediated by UV radiation: (a) the direct absorption of radiation by cellular components, altering cellular chemistry and the formation of an excited state; and (b) the absorption of radiation by endogenous or exogenous cells that are excited to their triplet states, a mechanism called photosensitization (30,71,72).
Endogenous photosensitization is responsible for inducing reactive oxygen species by UVR, generating superoxide anion and singlet oxygen. Over time, through different mechanisms, it is possible to induce the synthesis of other reactive oxygen species, such as peroxyl radicals, hydrogen peroxide and hydroxyls. In this context, various studies associate the generation of free radicals induced by UVR with skin pathologies. Fortunately, the skin and the human body have an elaborate defense system of endogenous antioxidants capable of mitigating the effects of oxidative stress induced by chemical agents, cellular metabolism, inflammatory processes, and external agents such as UVR. However, excessive exposure to ultraviolet radiation can reduce the skin's antioxidant capacity, limiting its biological action. These antioxidant systems are limited after chronic exposure, reaching damaging levels of free radicals. In this case, it causes oxidative damage, skin lesions, inflammation in the affected area, immunosuppression, premature aging, and skin cancer. Therefore, the intervention of exogenous antioxidants is an interesting strategy to limit and inhibit photooxidation, providing a photoprotective potential to support the endogenous antioxidant system. This can be achieved through the intervention of exogenous antioxidants, such as carotenoids, phenols, flavonoids, and vitamins, expanding options for photoprotective products that could include supplementation with oral, topical and ocular antioxidants (73,74).
Exogenous antioxidants such as carotenoids are fundamental pieces for systemic photoprotection in humans. An exhaustive search indicates that carotenoids such as Astaxanthin, Fucoxanthin, β-Carotene, and lycopene have acted as sunscreens, reducing the risk of inducing pathologies related to oxidative stress induced by UVR (40,71-74). However, there is not enough scientific information about its properties when applied to the different blood phenotypes, which are not only found in erythrocytes, but also in skin cells and other cell lines. Fucoxanthin and β-Carotene have high antioxidant activity, capable of acting as a photoprotective agent on human cells. Despite presenting photoinstability, this carotenoid is considered a promising blood group-dependent photoprotective agent. Since it managed to effectively protect groups A RhD+ve, A RhD-ve (UV-A and UV-B). These results could contribute to generating targeted drugs, nutraceuticals, or functional foods for a population highly susceptible to developing conditions related to overexposure to UVR. The results are promising, since group A RhD-ve was the most susceptible to phototoxicity induced by UV-A and UV-B radiation. Napoleão-Tavares et al. (2020) demonstrated that Fucoxanthin has a photoprotective effect on skin cells exposed to UVA, UVB and visible radiation. The ability to inhibit the formation of reactive oxygen species induced by UVR on fibroblasts and keratinocytes reduces phototoxicity. When human dermal fibroblasts are exposed to moderate doses of UV-A radiation, an apoptotic process is triggered; where, the levels of reactive oxygen species and thiobarbituric acid compromise the integrity of the cell membrane (74,75). Furthermore, it has been reported that during the digestive process, enzymes metabolize fucoxanthin mainly to Fucoxanthinol. This isomer has antimutagenic, anti-inflammatory, antineoplastic and photoprotective properties. The modulating effect of fucoxanthinol intervenes in the arrest of the cell cycle of cancer cells. This property could prevent skin cancer induced by UVR in oral drugs (74,76,77)
In addition to carotenoids, antioxidants such as phenols, flavonoids and vitamins participate in the prevention of skin cancer associated with ultraviolet radiation. Polyphenols such as gallic acid are ideal chemopreventive agents to counteract skin disorders. Particularly, recent advances suggest that gallic acid can suppress, slow, and reverse the process of skin carcinogenesis (28,42,77). The photoprotective potential of these polyphenols has reduced oxidative stress, DNA damage and suppressed the immune response. Additionally, they can nullify the various biochemical processes mediated by ultraviolet radiation at in vitro and in vivo levels. Polyphenols can act as photoprotective agents since they have the ability to absorb radiation in the length spectrum of UV-A and UV-B radiation. However, this characteristic has only been detected in those polyphenols that are yellow, red, or purple. Since gallic acid is a transparent compound, the photoprotective mechanism is probably different (Nichols and Katiyar, 2010). In our study, the photoprotective effect of gallic acid depended on the blood groups tested; where, the most protected group was A RhD+ve (UV-A); A RhD+ve, B RhD+ve, and AB RhD-ve (UV-B). Therefore, gallic acid can be used as an inhibitor of ultraviolet radiation-induced oxidative damage in people with type B RhD+ve, since they are the blood type most susceptible to UVR according to the results obtained.
In view of the increasing demand for oxidative stress suppressors, there is a general need for cytoprotective antioxidants that support the side effects of free radicals generated chemically and by exposure to sunlight. Prolonged exposure to sunlight has been linked to several types of skin damage, including sun injury, skin inflammation, photoimmunosuppression, photoaging, and photocarcinogenesys. With increasing awareness of these potentially harmful effects, there is a need to search for safe and effective photoprotective antioxidant compounds. The development of skin pathologies associated with ultraviolet radiation (UVR) is due to the formation of reactive oxygen species (ROS) and the deterioration of the skin antioxidant system. A probable hypothesis to reduce the development of pathologies associated with the effects of UVR is the application of oral, skin, or ocular antioxidants that eliminate reactive oxidants and modulate the cellular redox state (30,64).
Unlike carotenoids and polyphenols, ascorbic acid (Vitamin C) is not considered a sunscreen due to its chemical nature, because vitamin C does not absorb light in the UV-A or UV-B spectrum. However, vitamin C has a potential antioxidant that is praised for its anti-aging benefits. For this reason, vitamin C has been shown in studies to protect against oxidative damage induced by UV radiation by acting as a sunscreen. There are proteins that transport vitamin C to the site of inflammation that has come into contact with ultraviolet light in harmful amounts. As a consequence, vitamin C increases in keratinocytes, resulting in the need to absorb a higher concentration of vitamin C for adequate protection. In cultured keratinocytes exposed to UVR, vitamin C addition reduces oxidative damage to DNA and lipid peroxidation, prevents lysosomal degradation, inhibiting the release of pro-inflammatory cytokines and protecting against cell death by apoptosis. While in animal models exposed to UV radiation, the addition of vitamin C to the diet of rodents through oral supplementation has reduced the size of skin tumors and the development of dermal neoplastic diseases. However, studies suggest that the combination of vitamin C, vitamin E, RRR-alpha-tocopherol and β-Carotene effectively reduce the damage induced by UV radiation. The synergistic effect would expand the properties of vitamin C as a photoprotective agent in oral supplementation (79). Our study used erythrocytes as a cellular model for the evaluation of the photoprotective effect of vitamin C on the different blood phenotypes exposed to UV-A and UV-B radiation. The addition of vitamin C inhibited the effects of UV-A in groups A RhD+ve and B RhD+ve, preserving cellular integrity without visible oxidative damage, conferring adequate photoprotection. This effect decreased when erythrocytes were exposed to UV-B light, radiation considered more harmful, in this case the photoprotective effect decreased in all blood phenotypes. The AB RhD-ve blood group stood out among the others, being the group mostly protected by vitamin C. The photoprotective potential of vitamin C depended on the surface antigen on the erythrocytes, more studies would have to be carried out in combination with photoprotective antioxidants to evaluate its effect on the groups most susceptible to degradation in the presence of UVR (Anne-Katrin et al., 2002; Chen et al., 2012).