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Published on: February 11, 2017
Decreased expression of peroxisome proliferator activated receptor gamma in cftr-/- mice
Mario Ollero1, Omer Junaidi, Munir M Zaman
1Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
Abstract:
Some of the pathological manifestations of cystic fibrosis are in accordance with an impaired expression and/or activity of PPARgamma. We hypothesized that PPARgamma expression is altered in tissues lacking the normal cystic fibrosis transmembrane regulator protein (CFTR). PPARgamma mRNA levels were measured in colonic mucosa, ileal mucosa, adipose tissue, lung, and liver from wild-type and cftr-/- mice by quantitative RT-PCR. PPARgamma expression was decreased twofold in CFTR-regulated tissues (colon, ileum, and lung) from cftr-/- mice compared to wild-type littermates. In contrast, no differences were found in fat and liver. Immunohistochemical analysis of PPARgamma in ileum and colon revealed a predominantly nuclear localization in wild-type mucosal epithelial cells while tissues from cftr-/- mice showed a more diffuse, lower intensity labeling. A significant decrease in PPARgamma expression was confirmed in nuclear extracts of colon mucosa by Western blot analysis. In addition, binding of the PPARgamma/RXR heterodimer to an oligonucletotide containing a peroxisome proliferator responsive element (PPRE) was also decreased in colonic mucosa extracts from cftr-/- mice. Treatment of cftr-/- mice with the PPARgamma ligand rosiglitazone restored both the nuclear localization and binding to DNA, but did not increase RNA levels. We conclude that PPARgamma expression in cftr-/- mice is downregulated at the RNA and protein levels and its function diminished. These changes may be related to the loss of function of CFTR and may be relevant to the pathogenesis of metabolic abnormalities associated with cystic fibrosis in humans.
Insights
Cystic fibrosis (CFTR) protein deficiency impairs PPARgamma expression and function in mice. This downregulation in CFTR-deficient tissues may contribute to metabolic issues seen in cystic fibrosis patients.
Area of Science:
- Molecular Biology
- Genetics
- Physiology
Background:
- Cystic fibrosis (CFTR) dysfunction is linked to pathological changes.
- Peroxisome proliferator-activated receptor gamma (PPARgamma) plays a role in cellular processes potentially affected by CFTR deficiency.
Purpose of the Study:
- To investigate if PPARgamma expression is altered in tissues lacking the cystic fibrosis transmembrane regulator protein (CFTR).
Main Methods:
- Quantitative RT-PCR to measure PPARgamma mRNA.
- Immunohistochemistry and Western blot analysis for PPARgamma protein expression and localization.
- Electrophoretic mobility shift assay to assess PPARgamma/RXR heterodimer DNA binding.
Main Results:
- PPARgamma mRNA and protein levels were significantly decreased in CFTR-deficient (cftr-/-) mouse colon, ileum, and lung.
- Nuclear localization and DNA binding activity of PPARgamma were reduced in cftr-/- mice.
- Treatment with a PPARgamma ligand (rosiglitazone) improved localization and binding but not RNA levels.
Conclusions:
- PPARgamma expression and function are diminished in CFTR-deficient mice.
- These alterations may be associated with CFTR loss-of-function and contribute to metabolic abnormalities in cystic fibrosis.
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