The role of peroxiredoxin 4 in inflammatory response and aging

In prior studies, we determined that the moderate overexpression of the Drosophila endoplasmic reticulum (ER)-localized peroxiredoxin (Prx), dPrx4, reduced oxidative damage and conferred beneficial effects on life span, while a high-level expression increased the incidence of tissue-specific apoptosis and dramatically shortened longevity. The detrimental pro-apoptotic and life-shortening effects were attributed to aberrant localization of dPrx4 and the apparent ER stress elicited by dPrx4 overexpression. In addition, the activation of both the NF-κB- and the JAK/STAT-mediated stress responses was detected, although it was not clear whether these served as functional alarm signals. Here we extend these findings to show that the activation of the NF-κB-dependent immunity-related/inflammatory genes, associated with life span shortening effects, is dependent on the activity of a Drosophila NF-κB ortholog, Relish. In the absence of Relish, the pro-inflammatory effects typically elicited by dPrx4 overexpression were not detected. The absence of Relish not only prevented the hyperactivation of the immunity-related genes but also significantly rescued the severe shortening of life span normally observed in dPrx4 overexpressors. The overactivation of the immune/inflammatory responses was also lessened by JAK/STAT signaling. In addition, we found that cellular immune/pro-inflammatory responses provoked by the oxidant paraquat but not bacteria are mediated via dPrx4 activity in the ER, as the upregulation of the immune-related genes was eliminated in flies underexpressing dPrx4, whereas immune responses triggered by bacteria were unaffected. Finally, efforts to reveal critical tissues where dPrx4 modulates longevity showed that broad targeting of dPrx4 to neuronal tissue had strong beneficial effects, while targeting expression to the fat body had deleterious effects.