Abstract
Carotenoids are biologically active pigments that are well-known to enhance the defense and immunity of the vertebrate system. However, in invertebrates, the role of carotenoids in immunity is not clear. Therefore, this study aims to review the scientific evidence for the role of carotenoids in invertebrate immunization. From the analysis of published literatures and recent studies from our laboratory, it is obvious that carotenoids are involved in invertebrate immunity in two ways. On the one hand, carotenoids can act as antioxidant enzymes to remove singlet oxygen, superoxide anion radicals, and hydroxyl radicals, thereby reducing SOD activity and reducing the cost of immunity. In some organisms, carotenoids have been shown to promote SOD activity by up-regulating the expression of the ZnCuSOD gene. Carotenoids, on the other hand, play a role in the expression and regulation of many genes involved in invertebrate immunity, including thioredoxins (TRX), peptidoglycan recognition receptor proteins (PGRPs), ferritins, prophenoloxidase (ProPO), vitellogenin (Vg), toll-like receptor (TLRs), heat shock proteins (HSPs), and CuZnSOD gene. The information in this review is very useful for updating our understanding of the progress of carotenoid research in invertebrate immunology and to help identify topics for future topics.
Highlights
Vertebrates possess both innate and adaptive immune systems, of which the adaptive immune system has many specialized cells and molecules that interact in a particular way [1]
Invertebrates account for 97% of animal diversity and can be found in any environment
The results indicated that the double mutants of Drosophila larvae contain negligible circulating hemocytes, but high levels of antimicrobial peptides (AMPs) did not survive from opportunistic bacterial or fungal infection [60]
Summary
Vertebrates possess both innate and adaptive immune systems, of which the adaptive immune system has many specialized cells and molecules that interact in a particular way [1]. The only line of defense for invertebrates is innate immune system [2]. Being lack of specific immunity, both enzymes and non-enzymatic antioxidants play a crucial role in immunity of invertebrates [7]. The main enzymes in the innate immune system include catalase (CAT), superoxide dismutase (SOD), glutaredoxins, thioredoxins (TRX), peroxiredoxins (PRXs), and GSH-Px [8]. Major non-enzymatic antioxidants, including carotenoids, polyunsaturated fatty acids (PUFA), uric acid, vitamins (vitamins C and E) and GSH, and a tripeptide (L-g-glutamyl-L-cysteinyl-L-glycine), comprise a thiol (sulfhydryl) group [8, 9]
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