FOXO and HSF1 rejuvenate immunity via positive feedback regulation of insulin/IGF-1 signaling

A hallmark of aging is immunosenescence, a decline in immune function that appeared to be inevitable. Surprisingly, here we show that genetic inhibition of DAF-2/insulin/IGF-1 receptor drastically delays immunosenescence and even rejuvenates immunity in C. elegans. We find that p38 mitogen activated protein kinase (PMK-1), a key determinant of immunosenescence in wild-type, is dispensable for this rejuvenated immunity. Instead, we demonstrate that longevity-promoting DAF-16/FOXO and heat-shock transcription factor 1 (HSF-1) increase immunocompetence in old daf-2(-) animals. The up-regulation of DAF-16/FOXO and HSF-1 decreases the expression of zip-10/bZip transcription factor, which in turn down-regulates ins-7, an agonistic insulin-like peptide, for further reduction in insulin/IGF-1 signaling (IIS). Thus, reduced IIS bypasses immunosenescence and rejuvenates immunity via up-regulating anti-aging transcription factors that regulate an endocrine insulin-like peptide through a positive feedback mechanism. Because many functions of IIS are conserved across phyla, our study may lead to developing strategies for immune rejuvenation in humans. The investigation of the changes of gene expression in wild-type (WT) and daf-2(-) animals at day 1 (young) and day 9 (old) adulthood