Caveolin-1 (cav-1) has been reported to regulate apoptosis, lipid metabolism and endocytosis. In the present study, we demonstrate that cav-1 can act as a potent immunomodulatory molecule in murine macrophages and play an important role in the development of fibrosis.
In murine alveolar and peritoneal macrophages, loss of function experiments using siRNA showed that down-regulating cav-1 expression increased lipopolysaccharide (LPS)-induced proinflammatory cytokine tumor necrosis factor-alpha (TNF-á) and interleukin-6 (IL-6) production but decreased anti-inflammatory cytokine interleukin-10 (IL-10) production. Gain of function experiments demonstrated that overexpression of cav-1 in RAW264.7 decreased LPS-induced TNF-á and IL-6 production and augmented IL-10 production. Cav-1 interacted with TLR4 as revealed by co-immunoprecipitation in peritoneal macrophages. Overexpressing cav-1 in RAW264.7 disrupted Toll like receptor 4 (TLR4) MyD88 and TRIF complex formation; regulated mitogen-activated protein kinase (MAPK) phosphorylation; and inhibited NF-êB activation. Furthermore, the anti-inflammatory modulation by cav-1 involved p38, since the administration of SB203580 significantly abrogated the effects of cav-1, and peritoneal macrophages isolated from MKK3 null mice did not demonstrate any modulation of cav-1. Interestingly, HO-1 translocated into caveolae after LPS stimulation. Carbon monoxide (CO), the gaseous byproduct of HO activity responsible for the anti-inflammatory effects of HO-1, did not regulate cytokines production in cav-1 null macrophages.
We observed marked reduction of cav-1 expression in lung tissues and in primary pulmonary fibroblasts from IPF patients, compared to controls. Transforming growth factor-â1 (TGF-â1), the well-known pro-fibrotic cytokine, decreased cav-1 expression in human pulmonary fibroblasts. Cav-1 was able to suppress TGF-â1-induced extracellular matrix (ECM) production in cultured fibroblasts through the regulation of the c-Jun N-terminal kinase (JNK) pathway. Interestingly, highly activated JNK was detected in IPF and bleomycin (BLM)-instilled lung tissue samples, which was dramatically suppressed by adenovirus cav-1 infection. Moreover, JNK1 null fibroblasts showed reduced Smads cascades signaling, mimicking the effects of cav-1. We also demonstrated that cav-1 markedly ameliorated BLM-induced pulmonary fibrosis as evidenced by histological analysis, hydroxyproline content and immunoblot analysis.
In summary, our data suggest that cav-1 acts as a potent immunomodulatory and anti-fibrotic effector molecule. Cav-1 may mediate the anti-inflammatory effects of HO-1/CO in immune cells involving the MKK3/p38 MAPK pathway. Cav-1 also plays a pivotal role in ECM regulation and the development of fibrosis, possibly through the MAPK and Smads pathway. This study suggests cav-1 as a novel therapeutic target for patients with fibrosis and inflammation.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-12072006-155317 |
| Date | 13 December 2006 |
| Creators | Wang, Xiaomei |
| Contributors | Augustine M.K. Choi, Robert P. Bowser, Xiao-Ming Yin, Bruce R. Pitt, Tim D. Oury |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-12072006-155317/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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