A role for Akt in the rapid regulation of inflammatory and apoptotic pathways in mouse bladder

Abstract

Akt is linked to both inflammatory and neoplastic pathways. Akt activation is dependent on the phosphatidylinositol-3 kinase (PI3K) signaling pathways. Upon phosphorylation by PI3K, Akt can phosphorylate nuclear factor kappa B (NF-κB) and members of the forkhead family of transcription factors, which includes AFX. Our goal is to examine the effect of Escherichia coli lipopolysaccharide (LPS) on early cellular signaling in inflammatory (NF-κB) and apoptotic pathways (AFX) in a mouse-bladder model and in T-24 urothelial cancer cells. Female C57BL/6 mice were given an intraperitoneal (IP) injection of LPS or LPS free water and sacrificed 0–120 minutes later. Bladders were harvested, and immunohistochemistry (IHC) and/or immunoblotting performed using antibodies to PI3K, inhibitor kappa B-α (IκB-α), and total and phosphorylated Akt, NF-κB and AFX. Levels of IκB-α and total and phosphorylated Akt and NF-κB were determined in T-24 cells treated with LPS for 0–120 minutes. Bladders and T-24 cells were treated with PI3K inhibitors in some experiments. Protein amounts in different samples were normalized to immunoreactive actin. Phosphorylated and non-phosphorylated species of Akt, NF-κB, and AFX were localized to the urothelium. IP LPS injection rapidly (within 30 minutes) increased Akt phosphorylation. IP LPS injection decreased IκB-α levels, and increased NF-κB and AFX phosphorylation. Wortmannin effectively blocked phosphorylation of Akt in LPS-treated mice, and also reduced phosphorylation of AFX and, to a lesser extent, NF-κB. After treatment with LPS, Akt and NF-κB phosphorylation was rapidly increased in T-24 cells. Akt phosphorylation, and to a lesser extent NF-κB phosphorylation, were blocked by LY-294,002. LPS/PI3K/Akt is a cellular signaling pathway which rapidly activates downstream pathways of inflammation and neoplasia in bladder urothelium.