title: Plasma endogenous enkephalin levels in early systemic sclerosis: clinical and laboratory associations.
abstract: OBJECTIVE
  Met- and leu-enkephalins are endogenous opioid neuropeptides with potent analgesic, vasoactive, immunomodulatory and anti-apoptotic properties. We hypothesised that clinical or immunological variables of early systemic sclerosis (SSc) might be correlated to plasma enkephalin levels.
  
  
  METHODS
  Plasma samples were collected at study entry of the Genetics versus Environment in Scleroderma Outcomes Study (GENISOS) cohort (early SSc, n=116). Plasma met-enkephalin and leu-enkephalin levels (microg/ml) were measured by high performance liquid chromatography (HPLC) and correlated to clinical and laboratory parameters in the GENISOS database. Statistical analyses were performed by nonparametric Wilcoxon rank sum tests and Pearson correlation coefficients.
  
  
  RESULTS
  Significantly lower plasma met-enkephalin levels were associated with anti-topoisomerase-I seropositivity (6+8.3 vs. 14.9+22.8 microg/ml, p=0.02). Plasma leu-enkephalin levels were significantly higher in SSc patients with digital pulp loss (95.6+130 vs. 64.9+101 microg/ml, p=0.02). Lower mean plasma met-enkephalin levels and inversely higher leu-enkephalin levels were noted in SSc patients with Raynaud's phenomena (p=NS).
  
  
  CONCLUSIONS
  The associations of plasma enkephalin levels to immunologic or clinical pathologies may underscore their vasogenic or fibrogenic significance and potential as therapeutic targets in early SSc.
authors.affiliation: Division of Rheumatology-UTMB, 301 University Blvd., Galveston, TX 77555-1165, USA. tmcnearn@utmb.edu
authors.forename: Terry A
authors.initials: TA
authors.lastname: McNearney
authors.forename: K A
authors.initials: KA
authors.lastname: Sluka
authors.forename: C
authors.initials: C
authors.lastname: Ahn
authors.forename: J D
authors.initials: JD
authors.lastname: Reveille
authors.forename: Michael
authors.initials: M
authors.lastname: Fischbach
authors.forename: Maureen D
authors.initials: MD
authors.lastname: Mayes
mesh_terms: D001323:Autoantibodies / Q000276:immunology; D002851:Chromatography, High Pressure Liquid; D004264:DNA Topoisomerases, Type I / Q000276:immunology; D004743:Enkephalin, Leucine / Q000097:blood* / Q000502:physiology; D004744:Enkephalin, Methionine / Q000097:blood* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018377:Neurotransmitter Agents / Q000097:blood* / Q000502:physiology; D045743:Scleroderma, Diffuse / Q000097:blood* / Q000276:immunology / Q000503:physiopathology; D045745:Scleroderma, Limited / Q000097:blood* / Q000276:immunology / Q000503:physiopathology
chemical_list: D001323:Autoantibodies; D018377:Neurotransmitter Agents; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D004264:DNA Topoisomerases, Type I