Sirtuin 1 activity in peripheral blood mononuclear cells of patients with osteoporosis.

BACKGROUND: Sirtuin 1 (SIRT1) is a class III histone deacetylase that may play a critical role in several biological functions, including lifespan, stress, and inflammation. Our main objective was to evaluate SIRT1 activity in peripheral blood mononuclear cells (PBMCs) in patients with osteoporosis and to analyze the relationship between the SIRT 1 activity and markers of inflammation and bone remodelling. MATERIAL AND METHODS: We performed a prospective monocentric study of patients with osteoporosis and measured the nuclear and cytoplasmic activities of SIRT1 in PBMCs. Levels of proinflammatory cytokines were assessed in culture supernatants of PBMCs isolated from the osteoporosis patients. The level of serum C-terminal cross-linking telopeptide of type I collagen (CTX), a marker of bone resorption, was measured in the serum of osteoporosis patients. RESULTS: Sixteen women with osteoporosis were included. A statistically significant correlation between the cytoplasmic and nuclear SIRT 1 activities was found in PBMCs of patients with osteoporosis. Although non-significant, we observed a negative trend between nuclear SIRT 1 activity and the rate of serum CTX and a positive trend between IL-6 and CTX levels in patients with osteoporosis. CONCLUSIONS: This study shows that the cytoplasmic and nuclear SIRT 1 activities are measurable in circulating PBMCs of patients with osteoporosis and that these 2 activities are correlated. The potential role of inflammation in bone resorption in patients with osteoporosis was also studied.

Imbalance between HAT and HDAC activities in the PBMCs of patients with ankylosing spondylitis or rheumatoid arthritis and influence of HDAC inhibitors on TNF alpha production.

OBJECTIVE: Acetylation or deacetylation of histone proteins may modulate cytokine gene transcription such as TNF alpha (TNF). We evaluated the balance between histone deacetytlase (HDAC) and histone acetyltransferase (HAT) in patients with rheumatoid arthritis (RA) or ankylosing spondylitis (AS) compared to healthy controls (HC) and determined the influence of HDAC inhibitors (trichostatin A -TSA- or Sirtinol -Sirt-) on these enzymatic activities and on the PBMC production of TNF. METHODS: 52 patients with RA, 21 with AS and 38 HC were evaluated. HAT and HDAC activities were measured on nuclear extracts from PBMC using colorimetric assays. Enzymatic activities were determined prior to and after ex vivo treatment of PBMC by TSA or Sirt. TNF levels were evaluated in PBMC culture supernatants in the absence or presence of TSA or Sirt. RESULTS: HAT and HDAC activities were significantly reduced in AS, while these activities reached similar levels in RA and HC. Ex vivo treatment of PBMC by HDACi tended to decrease HDAC expression in HC, but Sirt significantly reduced HAT in RA. TNF production by PBMC was significantly down-regulated by Sirt in HC and AS patients. CONCLUSION: HAT and HDAC were disturbed in AS while no major changes were found in RA. HDACi may modulate HDAC and HAT PBMC expression, especially Sirt in RA. Sirtinol was able to down regulate TNF production by PBMC in HC and AS. An imbalance between HAT and HDAC activities might provide the rationale for the development of HDACi in the therapeutic approach to inflammatory rheumatic diseases.

Resveratrol, a sirtuin 1 activator, increases IL-6 production by peripheral blood mononuclear cells of patients with knee osteoarthritis.

BACKGROUND: Sirtuin 1 (Sirt1) is a nuclear enzyme from the class III histone deacetylases that modulates gene expression and is involved in bone and cartilage remodeling. The goal of our study was to evaluate Sirt1 activity in peripheral blood mononuclear cells in patients with osteoarthritis in comparison with control patients, and to determine the relationship between Sirt1 activity and production of TNFα, IL-6 and IL-8 by peripheral blood mononuclear cells after ex vivo treatment with resveratrol, a Sirt1 activator. RESULTS: A prospective study was performed to compare the activity of Sirt1 in patients with primary osteoarthritis of the knee (American College of Rheumatology criteria) with its activity in controls. Peripheral blood mononuclear cells were isolated from peripheral blood, and Sirt1 activity evaluated from cytoplasmic and nuclear compartments using a fluorometric assay. Culture supernatant levels of TNFα, IL-6, and IL-8 were quantified before and after resveratrol ex vivo treatment. Nineteen patients with symptomatic knee osteoarthritis (age 64 ±9 years) and 18 controls (age 54 ±13 years) were included. No differences were found in cytoplasmic or nuclear Sirt1 activity between patients and controls. After resveratrol treatment, no changes in TNFα or IL-8 levels were found, but a significant dose-dependent increase in IL-6 levels was demonstrated in patients with osteoarthritis, but not controls. Sirt1 activity did not correlate with clinical activity (Lequesne's index) or inflammation (erythrocyte sedimentation rate, C-reactive protein). CONCLUSION: Sirt1 activity (cytoplasmic and nuclear) from peripheral blood mononuclear cells did not differ between patients with osteoarthritis and controls. Ex vivo treatment of peripheral blood mononuclear cells with resveratrol was associated with a dose-dependent increase in IL-6 levels only in patients with osteoarthritis.