Male C57BL/6 mice (6–8 weeks old) were injected with control or REDD-1 siRNA (0.5 mg/kg, intravously) with the in vivo-jetPEI reagent.

Regulated in development and DNA damage responses 1 (REDD-1), an inhibitor of mammalian target of rapamycin (mTOR), is induced by various cell stressors, including LPS, a major player in the pathogenesis of endotoxemic shock. However, the pathologic role of REDD-1 in endotoxemia is largely unknown. We found that LPS increased REDD-1 expression, nuclear transcription factor-kappaB (NF-kappaB) activation, and inflammation and that these responses were suppressed by REDD-1 knockdown and in REDD-1(+/-) macrophages. REDD-1 overexpression stimulated NF-kappaB-dependent inflammation without additional LPS stimulation. REDD-1-induced NF-kappaB activation was independent of 2 classic IKK-dependent NF-kappaB pathways and the mTOR signaling pathway; however, REDD-1, particularly its C-terminal region (178-229), interacted with and sequestered IkappaBalpha, to elicit atypical NF-kappaB activation during the delayed and persistent phases of inflammation after stimulation. Moreover, REDD-1 knockdown mitigated vascular inflammation and permeability in endotoxemic mice, resulting in decreases in immune cell infiltration, systemic inflammation, caspase-3 activation, apoptosis, and consequent mortality. We further confirmed the inflammatory and cytotoxic effects of REDD-1 in endotoxemic REDD-1(+/-) mice. Our data support the likelihood that REDD-1 exacerbates endotoxemic inflammation via atypical NF-kappaB activation by sequestering IkappaBalpha.-Lee, D.-K., Kim, J.-H., Kim, J., Choi, S., Park, M., Park, W., Kim, S., Lee, K.-S., Kim, T., Jung, J., Choi, Y. K., Ha, K.-S., Won, M.-H., Billiar, T. R., Kwon, Y.-G., Kim, Y.-M. REDD-1 aggravates endotoxin-induced inflammation via atypical NF-kappaB activation.