PAI‐1 induction during kidney injury promotes fibrotic epithelial dysfunction via deregulation of klotho, p53, and TGF‐β1‐receptor signaling

Abstract

Renal fibrosis leads to chronic kidney disease, which affects over 15% of the U.S. population. PAI‐1 is highly upregulated in the tubulointerstitial compartment in several common nephropathies and PAI‐1 global ablation affords protection from fibrogenesis in mice. The precise contribution of renal tubular PAI‐1 induction to disease progression, however, is unknown and surprisingly, appears to be independent of uPA inhibition. Human renal epithelial (HK‐2) cells engineered to stably overexpress PAI‐1 underwent dedifferentiation (E‐cadherin loss, gain of vimentin), G2/M growth arrest (increased p‐Histone3, p21), and robust induction of fibronectin, collagen‐1, and CCN2. These cells are also susceptible to apoptosis (elevated cleaved caspase‐3, annexin‐V positivity) compared to vector controls, demonstrating a previously unknown role for PAI‐1 in tubular dysfunction. Persistent PAI‐1 expression results in a loss of klotho expression, p53 upregulation, and increases in TGF‐βRI/II levels and SMAD3 phosphorylation. Ectopic restoration of klotho in PAI‐1‐transductants attenuated fibrogenesis and reversed the proliferative defects, implicating PAI‐1 in klotho loss in renal disease. Genetic suppression of p53 reversed the PA1‐1‐driven maladaptive repair, moreover, confirming a pathogenic role for p53 upregulation in this context and uncovering a novel role for PAI‐1 in promoting renal p53 signaling. TGF‐βRI inhibition also attenuated PAI‐1‐initiated epithelial dysfunction, independent of TGF‐β1 ligand synthesis. Thus, PAI‐1 promotes tubular dysfunction via klotho reduction, p53 upregulation, and activation of the TGF‐βRI‐SMAD3 axis. Since klotho is an upstream regulator of both PAI‐1‐mediated p53 induction and SMAD3 signaling, targeting tubular PAI‐1 expression may provide a novel, multi‐level approach to the therapy of CKD.

IL-6 mediated renal tubular cell senescence via GATA2/ SERPINE1 pathway

“…This is in line with the results observed in this study, which showed that the number of cells in G2/M phase increased in HK-2 cells treated with myoglobin and decreased treated with tocilizumab. Similarly, some study has shown that the cell cycle arrest and brosis induced by renal tubular epithelium are related to the PAI-1-Klotho-p53-dependent mechanism, overexpression of PAI-1 increased the total p53 protein level [30]. The above theories further demonstrate our experimental viewpoint.…”

“…In critically ill patients with COVID-19, IL-6 signaling regulates PAI-1 production to form a positive feedback loop, leading to systemic in ammation and systemic circulation deterioration, and alleviates the severe clinical manifestations of patients by blocking IL-6 receptor [25]. Previous studies have shown that sustained PAI-1 (SERPINE1) expression leads to an increase in the percentage of cells in G2 /M phase, accompanied by a decrease in the percentage of cells in G1 phase, an increase in the level of G2 / M arrest marker P-histone H3, upregulation of pro-brotic cytokine, and ECM deposition [30]. This is in line with the results observed in this study, which showed that the number of cells in G2/M phase increased in HK-2 cells treated with myoglobin and decreased treated with tocilizumab.…”

Cancer-Associated Fibroblasts: Mechanisms of Tumor Progression and Novel Therapeutic Targets

“…There are considerable similarities between the development of pathologic fibrosis during injury repair and the emergence of a CAF-enriched tumor stroma, not the least of which involves the engagement of both the canonical (SMAD-dependent) and noncanonical (non-SMAD) arms of the TGF-β signaling network [ 3 , 15 , 20 , 21 , 22 , 23 , 24 , 25 ]. The growing appreciation for the congruities between fibrotic and neoplastic diseases suggests that targeting commonalities may have shared therapeutic utility [ 20 ].…”

TNF-α from the Proximal Nephron Exacerbates Aristolochic Acid Nephropathy

“…14 Activation of p53 protein inhibits CDC2/cyclin B complexes essential for the G2/M transition, yielding cell cycle arrest of TECs at the G2 phase. [42][43][44] Accordingly, pharmacological inhibition or genetic deletion of p53 attenuates tubular injury and apoptosis. [45][46][47][48] We found that restoring the cell cycle with pifithrin-a treatment equalizes levels of kidney injury and renal function between the TNF PTKO and WTs during acute AAN, with similar effects on renal fibrosis in our chronic AAN model.…”