Idiopathic pulmonary fibrosis (IPF) is a progressive chronic disorder characterized by the activation of fibroblasts and the overproduction of extracellular matrix. Fibroblast resistance to apoptosis leads to increased
fibrosis. Targeting fibroblasts with apoptotic agents represents a major therapeutic intervention for debilitating IPF.
Gallic acid (3,4,5-trihydroxybenzoic acid), a naturally occurring plant
phenol, has been reported to induce apoptosis in tumor cell lines and renal fibroblasts. However, the effects of
gallic acid on lung fibroblasts have not been investigated. The aim of the present study is to determine the effects of
gallic acid on primary cultured mouse fibroblasts. Our results showed that
gallic acid induces the apoptotic death of fibroblasts via both intrinsic and extrinsic apoptotic pathways by the elevation of PUMA, Fas, and
FasL protein levels. Moreover, intracellular
reactive oxygen species (ROS) generation and
8-hydroxy-2'-deoxyguanosine production were observed in
gallic acid-stimulated fibroblasts. Mechanistic studies showed that
gallic acid induces early phosphorylation of p53(Ser18) and
histone 2AX(Ser139) (H2AX) via
ataxia telangiectasia mutated (ATM) activation in response to ROS-provoked DNA damage. When mouse lung fibroblasts were treated with
caffeine, an ATM
kinase inhibitor, the levels of p53, phosphorylated p53(Ser18), and cell death induced by
gallic acid were significantly attenuated. Additionally, pretreatment with
antioxidants drastically inhibited the
gallic acid-induced
8-hydroxy-2'-deoxyguanosine (8-OH-dG) formation and phosphorylation of p53(Ser18) and ATM(Ser1981), as well as apoptosis. Our results provide the first evidence of the activation of ROS-dependent ATM/p53 signaling as a critical mechanism of
gallic acid-induced cell death in primary cultured mouse lung fibroblasts.