The Effect of mTOR-Inhibition on NF-κB Activity in Kidney Ischemia-Reperfusion Injury in Mice

Kidney ischemia-reperfusion injury (IRI) is associated with a robust inflammatory response, which is regulated by nuclear factor-kappaB (NF-κB), mainly its heterodimeric form p65/p50. Considering immunomodulatory properties of mammalian target of rapamycin (mTOR) inhibitors, the effect of everolimus on NF-κB activation in kidney IRI was determined in this study. IRI was induced in C57/BL6 mice by clamping both renal pedicles for 45 minutes. Application of everolimus (0.25 mg/kg bw subcutaneously daily) was started one day before IRI induction. Both everolimus-treated and nontreated mice were sacrificed at several times starting at 30 minutes and finishing on day 7 after IRI induction. The NF-κB activity, proinflammatory cytokines IL-1β, TNF-α, and anti-inflammatory cytokine IL-10 production were determined in kidneys. Compared with nontreated animals, everolimus-treated animals showed significantly increased TNF-α (2741.6 ± 201.72 pg/mg; 1925 ± 185.81 pg/mg, P < .05) and IL-1β (11.47 ± 1.2 pg/mg; 4.3 ± 0.13 pg/mg, P < .01) production on day 2 after IRI induction accompanied by significantly greater NF-κB/DNA binding activity and p65 nuclear expression (P < .01). Two hours after IRI induction, everolimus-treated animals showed significantly increased IL-1β mRNA expression (P < .05) followed by increased IL-1β protein concentrations when compared with nontreated animals measured 6 hours after IRI induction (11.71 ± 1.5 pg/mg; 7.5 ± 1.11 pg/mg, P < .01). Both experimental groups showed increased NF-κB/DNA binding activity at 7 days after IRI induction. Significantly increased nuclear p65 expression was measured in nontreated animals (P < .01), whereas everolimus-treated hosts showed significantly increased nuclear RelB expression (P < .01). These data suggested that everolimus potentiated innate immunity in the early phase of IRI, stimulating the production of NF-κB–driven proinflammatory cytokines such as TNF-α and IL-1β. The NF-κB activity was potentiated under m-TOR inhibition during kidney IRI, implicating a possible beneficial role of alternative NF-κB activation during the repair phase.