View Abstract

A3875 - Caveolin Scaffolding Peptide Regulates Glucose Metabolism in Lung Fibrosis
Author Block: V. Gopu, S. Shetty, N. Mavanoor, Y. Bhandary, S. Idell, S. Shetty; BMR-32, UTHCT, Tyler, TX, United States.
Introduction: Increased metabolism is one of the major factors distinguishing fibrotic lung fibroblasts (fLfs). Tumor suppressor protein, p53 and its transcriptional target microRNA-34a have been implicated in the regulation of glucose metabolism and mitochondrial respiration. However, the precise mechanism contributing to dysregulation of glucose metabolism in fLfs has not been fully elucidated. Further, it is unclear whether anti-fibrotic effects of caveolin-1 scaffolding domain peptides (CSP) and its deletion fragment, CSP7 involve regulation of altered glucose metabolism through restoration of baseline p53 and microRNA-34a expression in fLfs.
Methods: Human nLfs and fLfs (IPF) were isolated from control and IPF lung tissues. Mouse nLfs were isolated from the lungs of mice without any lung injury and mouse fLfs were isolated from mice with bleomycin (BLM) induced established PF. For generation of inducible p53cKO or microRNA-34acKO mice lacking their expression in fibroblasts, p53fl/fl or microRNA-34a fl/fl mice were cross-bred with ColCre mice. We analyzed changes in the expression of glycolytic enzymes (hexokinase 2, phosphofructokinase, pyruvate kinase and 6-phosphofructo-2-kinae/fructose-2,6-biphosphatase 3), and hypoxia inducible factor1-α (HIF1-α) in these lung fibroblasts to determine whether loss of p53 and its downstream target microRNA-34a contributes to dysregulated glucose metabolism. We further tested whether restoration of their baseline expression by treatment of fLfs with CSP or CSP7 reverse altered glucose metabolism.
Results: Lactate and succinate levels were increased in fLfs isolated from human and mouse lungs indicating elevated glucose metabolism. These cells also showed increased baseline expression of glycolytic enzymes and hypoxia inducible factor1-α. Further, overexpression of p53-binding 3’untranlated region sequences or microRNA-34a in fLfs reduced the expression of enzymes involved in glycolysis and HIF1-α. On the contrary, inhibition of basal p53 or microRNA-34a expression in nLfs increased glucose metabolism. Further, treatment of fLfs or mice having BLM- or TGF-β1-induced established PF with CSP or CSP7 reduced the expression of the enzymes involved in glycolysis and HIF1-α. Further, tamoxifen inducible p53cKO or microRNA-34acKO mice lacking their expression in fibroblasts failed to respond to CSP or CSP7 treatment.
Conclusion: Our data indicates that dysregulation of glucose metabolism due to glycolytic reprogramming in fLfs is causally linked to loss of basal expression of p53 and its target microRNA-34a. Further, treatment with CSP or CSP7 constrain aberrant glucose metabolism and the process involves restoration of p53-miR-34a feed forward induction.