title: Lipoic acid plays a role in scleroderma: insights  obtained from scleroderma dermal fibroblasts.
abstract: BACKGROUND
  Systemic sclerosis (SSc) is a connective tissue disease characterized by fibrosis of the skin and organs. Increase in oxidative stress and platelet-derived growth factor receptor (PDGFR) activation promote collagen I (Col I) production, leading to fibrosis in SSc. Lipoic acid (LA) and its active metabolite dihydrolipoic acid (DHLA) are naturally occurring thiols that act as cofactors and antioxidants, and are produced by lipoic acid synthetase (LIAS). The goal of this study was to examine whether LA and LIAS was deficient in SSc patients and determine the effect of DHLA on the phenotype of SSc dermal fibroblasts. N-acetylcysteine (NAC), a commonly used thiol antioxidant, was included as a comparison.
  
  
  METHODS
  Dermal fibroblasts were isolated from healthy subjects and patients with diffuse cutaneous SSc. Matrix metalloproteinase (MMPs), tissue inhibitors of MMPs (TIMP), plasminogen activator inhibitor-1 (PAI-1) and LIAS were measured by ELISA. The expression of Col I was measured by immunofluorescence, hydroxyproline assay, and quantitative PCR. PDGFR phosphorylation and α-smooth muscle actin (α-SMA) was measured by Western blotting. Student's t-tests were performed for statistical analysis and p-values of less than 0.05 with two-tailed analysis were considered statistically significant.
  
  
  RESULTS
  The expression of LA and LIAS in SSc dermal fibroblasts was lower than normal fibroblasts, however LIAS was significantly higher in SSc plasma and appeared to be released from monocytes. DHLA lowered cellular oxidative stress, and decreased PDGFR phosphorylation, Col I, PAI-1, and α-SMA expression in SSc dermal fibroblasts. It also restored the activities of phosphatases that inactivated the PDGFR. SSc fibroblasts produced lower levels of MMP-1 and 3, and DHLA increased them. In contrast, TIMP-1 levels were higher in SSc but DHLA had minimal effect. Both DHLA and NAC increased MMP-1 activity when SSc cells were stimulated with PDGF. In general, DHLA showed better efficacy than NAC in most cases.
  
  
  CONCLUSIONS
  DHLA not only acts as an antioxidant but also an antifibrotic since it has the ability to reverse the profibrotic phenotype of SSc dermal fibroblasts. Our study suggests that thiol antioxidants, including NAC and LA/DHLA, could be beneficial for patients with SSc.
authors.affiliation: Department of Internal Medicine, Division of Rheumatology, University of Michigan Medical School, 109 Zina Pitcher Dr., 4388 BSRB, Ann Arbor, MI 48109-2200, USA. ptsou@umich.edu
authors.forename: Pei-Suen
authors.initials: PS
authors.lastname: Tsou
authors.forename: Beatrix
authors.initials: B
authors.lastname: Balogh
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Pinney
authors.forename: George
authors.initials: G
authors.lastname: Zakhem
authors.forename: Ann
authors.initials: A
authors.lastname: Lozier
authors.forename: M Asif
authors.initials: MA
authors.lastname: Amin
authors.forename: William A
authors.initials: WA
authors.lastname: Stinson
authors.forename: Elena
authors.initials: E
authors.lastname: Schiopu
authors.forename: Dinesh
authors.initials: D
authors.lastname: Khanna
authors.forename: David A
authors.initials: DA
authors.lastname: Fox
authors.forename: Alisa E
authors.initials: AE
authors.lastname: Koch
mesh_terms: D000328:Adult; D015153:Blotting, Western; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D020405:Dermis / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D008297:Male; D020782:Matrix Metalloproteinases / Q000378:metabolism; D008875:Middle Aged; D018384:Oxidative Stress; D010766:Phosphorylation; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000235:genetics / Q000378:metabolism; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3 / Q000235:genetics / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D045743:Scleroderma, Diffuse / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D013466:Sulfurtransferases / Q000097:blood / Q000378:metabolism; D008063:Thioctic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D019714:Tissue Inhibitor of Metalloproteinases / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D017395:Plasminogen Activator Inhibitor 1; D019714:Tissue Inhibitor of Metalloproteinases; D008063:Thioctic Acid; C015144:dihydrolipoic acid; D017479:Receptors, Platelet-Derived Growth Factor; D013466:Sulfurtransferases; C116435:lipoic acid synthase; C516724:PTPN11 protein, human; C486288:PTPRJ protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3; D020782:Matrix Metalloproteinases