Rosiglitazone Abrogates Bleomycin-Induced Scleroderma …

1 Matrix PathobiologyRosiglitazone Abrogates bleomycin -InducedScleroderma and Blocks profibrotic ResponsesThrough peroxisome proliferator -ActivatedReceptor- Minghua Wu, Denisa S. Melichian, Eric Chang,Matthew Warner-Blankenship, Asish K. Ghosh,and John VargaFrom the Section of Rheumatology, Northwestern UniversityFeinberg School of Medicine, Chicago, IllinoisThe nuclear hormone receptor, peroxisome prolif-erator-activated receptor (PPAR)- , originally iden-tified as a key mediator of adipogenesis, is ex-pressed widely and implicated in diverse natural and synthetic agonists ofPPAR- abrogated the stimulation of collagen synthe-sis and myofibroblast differentiation induced bytransforming growth factor (TGF)- in vitro.

2 To char-acterize the role of PPAR- in the fibrotic processinvivo, the synthetic agonist Rosiglitazone was used in amouse model of Scleroderma . Rosiglitazone attenu-ated Bleomycin-Induced skin inflammation and der-mal fibrosis as well as subcutaneous lipoatrophy andcounteracted the up-regulation of collagen gene ex-pression and myofibroblast accumulation in the le-sioned treatment reduced the in-duction of the early-immediate transcription factorEgr-1in situwithout also blocking the activation ofSmad2/3. Inboth explanted fibroblasts and skin organcultures, Rosiglitazone prevented thestimulation ofcollagen gene transcription and cell migration elic-ited by TGF.

3 Rosiglitazone -driven adipogenic dif-ferentiation of both fibroblasts and preadipocyteswas abrogated in the presence of TGF- ; this effectwas accompanied by the concomitant down-regula-tion of cellular PPAR- mRNA , these results indicate that Rosiglitazone treat-ment attenuates inflammation, dermal fibrosis, andsubcutaneous lipoatrophy via PPAR- in a mousemodel of Scleroderma and suggest that pharmacolog-ical PPAR- ligands, widely used as insulin sensitizersin the treatment of type-2 diabetes mellitus, may bepotential therapies for Scleroderma .

4 (Am J Pathol2009, 174:519 533; DOI: )Excessive collagen accumulation in the skin and lungs,the hallmark of systemic sclerosis (SSc), can lead toorgan dysfunction, failure, and pathogenesisof fibrosis remains incompletely is a prevalent early feature, its precise rolein fibrosis remains controversial, and anti-inflammatorytherapies are generally ineffective in reversing or slowingthe progression of the , there is anurgent need for anti-fibrotic therapies. The fibroblast isthe key effector cell driving the fibrotic process in SSc.

5 Inresponse to extracellular cues such as transforminggrowth factor (TGF)- , fibroblasts become activated withincreased collagen production, expression of cell surfacereceptors for growth factors, secretion of cytokines andchemokines, resistance to apoptosis induction, and myo-fibroblast light of the key role of TGF- in the pathogenesis of fibrosis, therapeutic strategies toblock its production, activity, or intracellular signaling areunder , because the potent anti-inflammatory and immunosuppressive activities of TGF- are physiologically important.

6 Global TGF- blockadecould be complicated by spontaneous autoimmunity. In-deed, mice lacking TGF- die at an early age from , an ideal anti-fibrotic strategytargeting TGF- must selectively abrogate fibrotic re-sponses without disrupting its important immunosuppres-sive is an insulin-sensitizing agent widely intype 2 diabetes mellitus that exerts its biological effects inSupported by the National Institutes of Health (National Institute of Arthritisand Musculoskeletal and Skin Diseases grants AR-42309 and AR-49025)and the Scleroderma Research for publication November 4, reprint requests to John Varga, Section of Rheumatology,Northwestern University Feinberg School of Medicine, 240 E.

7 Huron St.,Chicago IL 60611. E-mail: American Journal of Pathology, Vol. 174, No. 2, February 2009 Copyright American Society for Investigative PathologyDOI: via the peroxisome proliferator activated receptor(PPAR)- .7 Originally identified in adipose tissue, PPAR- is one of a family of closely related nuclear receptors andligand-activated transcription factors with a primary rolein addition to adipocytes, PPAR- isexpressed in macrophages, vascular endothelial andsmooth muscle cells, and fibroblasts. The PPAR- recep-tor acts as a lipid sensor that can be activated by fattyacids, eicosanoids, and related endogenous products majority of experimental studies ofPPAR- have used the natural ligand 15-deoxy- 12,14prostaglandin J2(15d-PGJ2), or synthetic ligands suchas Rosiglitazone .

8 In theabsence of ligand, PPAR- is com-plexed to the retinoid X receptor (RXR) and co-repressors,preventing its binding to DNA. Upon receptor ligation, co-repressors are displaced from the PPAR- /RXR complexand co-activators such as p300 are recruited,allowingsequence-specific binding to conserved PPAR- re-sponse elements (PPREs) in target gene of PPAR- exert a broad range of proliferative,anti-inflammatory, and repair activities in addition to ad-ipogenesis and insulin studieshave shown that PPAR- inhibits basal and stimulatedcollagen synthesisin vitroandin vivo.

9 Suggesting a novelbiological role in connective tissue 14Li-gand inhibition of TGF- -dependent fibrotic responseswas mediated via the PPAR- receptor and involved an-tagonistic cross talk with the intracellular TGF- /Smadsignal transduction fibroblast activation by TGF- is a key patho-genetic event in SSc, blockade of TGF- signaling byPPAR- could be a novel therapeutic approach to patho-logical fibrogenesis. In the present studies, therefore, weinvestigated the effect of Rosiglitazone , the most potentpharmacological PPAR- agonist, in bleomycin -inducedscleroderma.

10 The results indicate that Rosiglitazone ame-liorated the development of fibrosis in this mouse modelof Scleroderma . The anti-fibrotic effect of rosiglitazoneinvolved blockade of TGF- - induced fibroblast activa-tion, as well as attenuation of the inflammatory , Rosiglitazone counteracted the develop-ment of subcutaneous adipose atrophy and loss of localPPAR- expression. Together, these findings indicatethat ligands of PPAR- , already in clinical use for thetreatment of type 2 diabetes mellitus, block fibrotic TGF- responses without triggering aberrant immunity, suggest-ing their potential as novel anti-fibrotic agents in and MethodsAnimals and Experimental ProtocolsSix- to eight-week-old female BALB/c mice (The JacksonLaboratory, Bar Harbor, ME)