Oxidative stress induces inactivation of protein phosphatase 2A, promoting proinflammatory NF-κB in aged rat kidney

The molecular inflammation hypothesis of aging proposes that redox dysregulation causes an age-related activation of NF-kappa B and its signaling to upregulate various proinflammatory genes. In the present study, we focused on the inactive form of the protein phosphastase 2 A (PP2A). More specifically, we aimed to define the correlation between PP2A inactivation and NF-kappa B activation by age-related oxidative stress. Experimentations were designed to determine the effect of oxidative stress-induced PP2A inactivation on NF-kappa B activity, utilizing prooxidants t-BHP and AAPH, the PTV inhibitor Na3VO4, and the PP2A inhibitor Calyculin A and PP2A siRNA, in HEK293T cells. We also assessed the phosphorylation of PP2A catalytic subunit (PP2Ac) and the activities of PP2A and NF-kappa B in aged rat kidney, utilizing aging-retarding 40% calorie restriction (CR) -60% of food intake and inflammation-triggering LPS paradigms. Results revealed that an oxidative stress-induced PTK/PTP imbalance led to phosphorylation of PP2Ac, following exposures to t-BHP, MPH, and Na3VO4 in HEK293T cells. Subsequently, we found that Calyculin A and PP2A siRNA activates NIK/IKK and MAPKs, leading to upregulation of NF-kappa B and its dependent oxidative stress. Also, the contrasting relation between PP2A inactivation and NF-kappa B activation was confirmed by AAPH-induced oxidative status in mice, and non-induced normal status or LPS-induced inflammatory status in aged rats while the antioxidative, anti-inflammatory, anti-aging effects of CR significantly blunted these actions. Thus, we present evidence that PP2A inactivation via PTK/PTP imbalance provoked by oxidative stress causes NF-kappa B activation, which contributes to the accumulation of oxidative stress in aged rat kidney. (C) 2013 Elsevier Inc. All rights reserved.