Redox control of p53 in the transcriptional regulation of TGF-β1 target genes through SMAD cooperativity

Abstract

Transforming growth factor-β1 (TGF-β1) regulates the tissue response to injury and is the principal driver of excessive scarring leading to fibrosis and eventual organ failure. The TGF-β1 effectors SMAD3 and p53 are major contributors to disease progression. While SMAD3 is an established pro-fibrotic factor, the role of p53 in the TGF-β1-induced fibrotic program is not clear. p53 gene silencing, genetic ablation/subsequent rescue, and pharmacological inhibition confirmed that p53 was required for expression of plasminogen activator inhibitor-1 (PAI-1), a major TGF-β1 target gene and a key causative element in fibrotic disorders. TGF-β1 regulated p53 activity by stimulating p53Ser15 and 9 phosphorylation and acetylation, promoting interactions with activated SMADs and subsequent binding of p53/SMAD3 to the PAI-1 promoter in HK-2 human renal tubular epithelial cells and HaCaT human keratinocytes. Immunohistochemistry revealed prominent co-induction of SMAD3, p53 and PAI-1 in the tubular epithelium of the obstructed kidney consistent with a potential in vivo role for p53 and SMADs in TGF-β1-driven renal fibrosis. TGF-β1-initiated phosphorylation of p53Ser15 and up-regulation of expression of several pro-fibrotic genes, moreover, was dependent on the rapid generation of reactive oxygen species (ROS). shRNA silencing of the p22Phox subunit of NADP(H) oxidases in HK-2 cells partially attenuated (over 50%) p53Ser15 phosphorylation and PAI-1 induction. These studies highlight the role of free radicals in p53 activation and subsequent pro-fibrotic reprogramming by TGF-β1 via the SMAD3-p53 transcriptional axis. Present findings provide a rationale for therapeutic targeting of SMAD3-p53 in aberrant TGF-β1 signaling associated with renal fibrosis.

AKI on CKD: heightened injury, suppressed repair, and the underlying mechanisms

“…More recent studies have further verified the role of p53 in AKI by testing renal tubule-specific p53 ablation mouse models 51, 52 . Interestingly, CKD may also be associated with the increase or activation of p53 as a consequence of TGF-β up-regulation or PTEN down-regulation 53, 54 . Such “pre-activation” of p53, though at low to moderate levels, may greatly enhance tubular damage upon AKI.…”

Activation of FXR protects against renal fibrosis via suppressing Smad3 expression

“…Lots of evidences have shown that activation of TGF-β signaling (especially TGF-β1 signaling) plays a central role in the pathogenesis of renal fibrosis222232425. TGF-β1 promotes ECM production by activating type I and type II serine/threonine kinase receptors26.…”

Accredited translational medicine centre: Human renal fibrotic disease: Translational research at the Center for Cell Biology and Cancer Research (CCBCR), Albany Medical College, Albany, NY

“…Increased PAI-1 expression, due to increased TGF-β1 in the injured tissue, initiates and perpetuates the fibrotic cycle. The need for novel targeted approaches for the treatment of fibrosis highlights the clinical potential in the current probe of molecular mechanisms underlying TGF-β1-regulated PAI-1 gene control [1–3]. …”

“…The collective research efforts in the CCBCR resulted in the identification of a novel pathway of TGF-β1-initiated fibrotic gene expression in an in vivo model of renal injury that mimics obstructive uropathy in humans [summarized in 1–4]. While TGF-β1-induced SMAD2/3 signaling is a critical event in the progression of chronic kidney disease, the role of non-SMAD mechanisms in the orchestration of fibrotic gene changes remain largely unexplored yet constitute likely targets that could be exploited for clinical gain.…”