ABSTRACT
OBJECTIVE: Defective expression of Ras guanil releasing protein-1 (RasGRP-1) and increased apoptosis have been reported in lymphocytes from SLE patients. Whether these aberrations are correlated and linked to disease activity has not been elucidated. METHODS: Expression of normal 90 kDa RasGRP-1, its most prevalent 86 kDa isoform and full PARP-1 116 kDa and its cleavage fragment 84 kDa were determined in whole protein lysates of peripheral blood mononuclear cells (PBMC) in correlation with mitogen activated protein kinase (MAPK) activity and SLE clinical status in a large group of SLE patients during 1 year follow-up. RESULTS: Expression of normal 90 kDa RasGRP-1 was comparable in patients and controls. However, SLE patients demonstrated a constitutively increased 86 kDa/90 kDA ratio (p < 0.01) and decreased full poly (ADP-ribose) polymerase protein-1 (PARP-1) expression (p < 0.002) compared with controls who were disease-independent. A remission in disease activity was associated with decreased RasGRP-1 expression. Expression of 84 kDa PARP-1 cleavage fragment was found in 15% of patients but in none of the controls. In addition, expression of PARP-1 correlated positively with normal 90 kDa RasGRP-1 expression and negatively with the RasGRP-1 86 kDa/90 kDA ratio. CONCLUSIONS: These data suggest that constitutive aberrant expression of PARP-1 and RasGRP-1 ratio may act in concert to impair survival of lymphocytes in SLE patients.
Subject(s)
DNA-Binding Proteins/metabolism , Guanine Nucleotide Exchange Factors/metabolism , Leukocytes, Mononuclear/metabolism , Lupus Erythematosus, Systemic/metabolism , Poly(ADP-ribose) Polymerases/metabolism , Adult , Aged , Female , Humans , Male , Middle Aged , Mitogen-Activated Protein Kinases/metabolism , Poly (ADP-Ribose) Polymerase-1 , Prospective Studies , Protein Isoforms/metabolismABSTRACT
BACKGROUND: Aberrant signalling along the p21ras/MAP kinase pathway has been demonstrated in systemic lupus erythematosus (SLE). OBJECTIVE: To determine whether expression and activity of the MAP kinases ERK and JNK reflect disease activity in patients with SLE. METHODS: Blood samples of 42 outpatients with SLE were prospectively collected during four consecutive visits. The control group included 20 healthy subjects. Disease activity was assessed using the SLE Disease Activity Index (SLEDAI). Expression of total ERK and JNK kinases and their active forms (pERK and pJNK) was determined in whole protein lysates of peripheral blood mononuclear cells. RESULTS: The mean levels of the active kinases pERK and pJNK were significantly increased in patients with active disease (SLEDAI 4-20) as compared with patients with inactive disease (SLEDAI 0-3), p = 0.04, as well as with healthy controls, p = 0.03 and p = 0.003 for pERK and pJNK, respectively. The percentage of activated forms of ERK and JNK of the total expression of these MAP kinases was also gradually increased, reaching 50% for pERK and >40% for pJNK in patients with SLE with moderate-to-severe disease (SLEDAI 7-20), p = 0.005, p = 0.005 and p = 0.02, p = 0.05 as compared with controls and inactive patients, respectively. A decrease of more than three SLEDAI points was associated with a significant reduction in the expression of both total and activated forms of ERK and JNK, p = 0.03, p = 0.01, respectively. CONCLUSIONS: The results show that ERK and JNK activity reflects disease activity in patients with SLE. These MAP kinases may serve as additional tools for the evaluation of disease activity and management of these patients.
