Project title
探討C/EBP Homologous Protein (CHOP)剔除減緩腎臟纖維化的分子機轉
Internal ID
NSC101-2314-B002-068
Principal Investigator
Start Date
August 1, 2012
End Date
July 12, 2013
Investigators
Organizations
Partner Organizations
Project Web Site
C/Ebp Homologous Protein (Chop) Knockout Alleviates Renal Fibrosis: Explore the Molecular Mechanisms = 探討C/EBP Homologous Protein (CHOP)剔除減緩腎臟纖維化的分子機轉
Keywords
內質網壓力
腎臟纖維化
結締組織生長因子
CHOP
基因剔除鼠
ER stress
renal fibrosis
CTGF
CHOP
knockout mice
Description
Regardless of etiology, all patients with chronic renal disease show a progressive decline in renal function with time. Fibrosis, so-called scarring, is a key factor of this pathophysiologic changes. Fibrosis involves an excess accumulation of extracellular matrix and usually results in loss of function when normal tissue is replaced with scar tissue. Before the development of chronic fibrosis, renal parenchyma attempts to maintain the integrity of tubules, there is an activation of proliferative pathways within the epithelial cells. If the proliferative forces or homeostatic factors within the kidney dissipate, the apoptotic pathway(s) overwhelms the ability of tubular epithelial cells to survive and tubular atrophy ensues. The endoplasmic reticulum(ER) plays an important role in maintaining protein homeostasis through controlling client protein’s concentration, conformation, folding, and trafficking. Hypoxia, glucose depletion, and oxidative stress may lead to ER dysfunction, which can induce both adaptive unfolded protein responses (UPRs) and ER stress. Initially, UPRs serve as the adaptive response, but will further induce apoptosis in cells under overwhelming ER stress. Oxidative stress and inflammation are also compounded by ER stress via the UPRs, suggesting the potential pathophysiological significance of this response across a wide range of diseases. Evidences suggest that ER stress contributes to glomerular and tubular injury in patients with acute and chronic kidney disease. Our recent publication demonstrated the downregulation of adaptive UPRs and upregulation of overwhelming ER stess, which included a highly upregulated C/EBP Homologous Protein (CHOP) in the unilateral ureteral obstruction (UUO) fibrosis model. In addition to proapoptic signals, CHOP is also interacted with inflammatory networks. In this project, we hypothesized that activation of CHOP may not only contribute to the major roles of tubular damage and renal fibrosis, but also activate the inflammatory signals. Our preliminary results shown that the chop deficiency mice attenuated renal fibrosis as shown by lower fibronectin, alpha-smooth muscle actin and Masson’s Trichrome staining. It is deserved to explore the mechanisms of CHOP-related signals in renal fibrosis and inflammation. In the first year, we will confirm the potential protective effects of chop deficiency in the UUO mice. The profibrotic genes expression and histopathologic severity will be evaluated comprehensively. In the second year, potential mechanisms of chop deficiency will be studied. These included the severity of apoptosis, ATP depletion, ROS levels and profibrotic genes. The differential activation of ER stress signals in both wild type and chop knockout mice will also be studied. Our unpublished data found that connective tissue growth factor (CTGF) has been significantly down regulated in UUO chop knockout mice. In vitro, we will study the relationship between CHOP and CTGF. In the third year, we prepare to use dominant active (DA) and dominant negative (DN) vectors of chop transfection in renal tubular cells. ER stress inducers, including tunicamycin and thapsigargin, will treat the transfected tubular cells. We hope to analyze the DNA binding sequences of chop, and the chop-regulated target genes. Base on the combination of ChIP sequences and cDNA array, we can compare differential expression profiles between DA and DN condition, which would be clearly demonstrated the chop target genes and gene expression profiles. Using these available tools will help us to identify well-known and novel genes in our institute. We hope such novel approaches can actively contribute to the National Research Program for Biopharmaceuticals (NRPB) in Taiwan.