Rag1 immunodeficiency‐induced early aging and senescence in zebrafish are dependent on chronic inflammation and oxidative stress

Abstract

In mammals, recombination activating gene 1 (RAG1) plays a crucial role in adaptive immunity, generating a vast range of immunoglobulins. Rag1−/− zebrafish (Danio rerio) are viable and reach adulthood without obvious signs of infectious disease in standard nonsterile conditions, suggesting that innate immunity could be enhanced to compensate for the lack of adaptive immunity. By using microarray analysis, we confirmed that the expression of immunity‐ and apoptosis‐related genes was increased in the rag1−/− fish. This tool also allows us to notice alterations of the DNA repair and cell cycle mechanisms in rag1−/− zebrafish. Several senescence and aging markers were analyzed. In addition to the lower lifespan of rag1−/− zebrafish compared to their wild‐type (wt) siblings, rag1−/− showed a higher incidence of cell cycle arrest and apoptosis, a greater amount of phosphorylated histone H2AX, oxidative stress and decline of the antioxidant mechanisms, an upregulated expression and activity of senescence‐related genes and senescence‐associated β‐galactosidase, respectively, diminished telomere length, and abnormal self‐renewal and repair capacities in the retina and liver. Metabolomic analysis also demonstrated clear differences between wt and rag1−/− fish, as was the deficiency of the antioxidant metabolite l‐acetylcarnitine (ALCAR) in rag1−/− fish. Therefore, Rag1 activity does not seem to be limited to V(D)J recombination but is also involved in senescence and aging. Furthermore, we confirmed the senolytic effect of ABT‐263, a known senolytic compound and, for the first time, the potential in vivo senolytic activity of the antioxidant agent ALCAR, suggesting that this metabolite is essential to avoid premature aging.

Modulation of the Tissue Expression Pattern of Zebrafish CRP-Like Molecules Suggests a Relevant Antiviral Role in Fish Skin

“…In the case of crp genes, such compensatory effects might be due not only to their recently described antiviral activity [ 23 , 24 , 25 , 40 ] but also their evolutionary-conserved antibody-like activities [ 15 , 67 , 68 , 69 ]. In addition, the upregulation of this type of genes in rag1 −/− mutants has been associated with epigenetic reprogramming [ 70 ], similar to the underlying mechanisms regulating innate trained immunity [ 71 , 72 ], and apparently also occurring in the crp genes in zebrafish [ 73 ].…”

Comparative modulation of lncRNAs in wild-type and rag1-heterozygous mutant zebrafish exposed to immune challenge with spring viraemia of carp virus (SVCV)

“…In contrast to what is observed in homozygous rag1 mutant zebrafish, which are more resistant to infection with SVCV compared to WT fish 31,32 , no significant differences in survival were found between the WT and rag1 -heterozygous fish after SVCV challenge (Supplementary Fig. S1).…”

“…This is the case for the rag1 −/− zebrafish mutant, which is a T and B cell-deficient model, and as a consequence, these animals rely exclusively on their innate immunity 43 . It was previously reported that, under naïve conditions, adult homozygous rag1 −/− fish possess enhanced innate immunity to compensate for the absence of adaptive immunity, and these fish have been shown to be more resistant to SVCV compared to WT fish 31,32,44 . In this study, when we analyzed the survival rates of WT and heterozygous rag1 +/− mutants after challenge with SVCV, we did not observe significant differences in mortality.…”

Zebrafish pten Genes Play Relevant but Distinct Roles in Antiviral Immunity

“…A similar response was previously observed for mutant rag1 −/− zebrafish. These animals do not possess adaptive immunity but show a higher basal innate immunity, including an increased pro-inflammatory status [ 70 , 71 ]; however, after SVCV challenge, the expression of some pivotal pro-inflammatory genes was lower than what was observed in the WT zebrafish [ 70 ].…”