ABSTRACT
Keratinocyte growth factor (KGF) drives phosphorylated (activated) AKT (pAKT) in bladder urothelium, which correlates with cytoprotection from cyclophosphamide. The current study determined whether: i) KGF modifies AKT targets [B-cell lymphoma protein 2-associated agonist of cell death (BAD) and mammalian target of rapamycin complex (mTORC)-1] that could block apoptosis; ii) AKT signaling is required for KGF cytoprotection; iii) direct AKT activation drives cytoprotection; iv) co-administration of KGF and an AKT inhibitor blocks urothelial cytoprotection and AKT and AKT-target activation; and v) an AKT agonist prevents cyclophosphamide-induced urothelial apoptosis. Mice were given KGF and cyclophosphamide (or sham injury), and pBAD (readout of BAD inhibition) or p-p70S6k (pS6, readout of mTORC1 signaling) was assessed. KGF induced pBAD urothelial staining and prevented cyclophosphamide-induced loss of urothelial pS6 staining (likely stabilizing mTORC1 activity). Co-administration of KGF and AKT inhibitor blocked KGF-driven urothelial cytoprotection from cyclophosphamide and prevented pAKT, pBAD, and pS6 urothelial expression. Conversely, systemic AKT agonist blocked cyclophosphamide-induced urothelial apoptosis and induced pAKT, pBAD, and pS6, similar to KGF. Thus, the KGF-AKT signaling axis appeared to phosphorylate (suppress) BAD and prevent cyclophosphamide-induced loss of mTORC1 signaling, both of which likely suppress apoptosis. Additionally, AKT signaling was required for KGF-driven cytoprotection, and direct AKT activation was sufficient for blocking apoptosis. Thus, AKT may be a therapeutic target for blocking urothelial apoptosis from cyclophosphamide.
