title: HMG-CoA reductase inhibition aborts functional differentiation and triggers apoptosis in cultured primary human monocytes: a potential mechanism of statin-mediated vasculoprotection.
abstract: BACKGROUND
  Statins effectively lower blood cholesterol and the risk of cardiovascular death. Immunomodulatory actions, independent of their lipid-lowering effect, have also been ascribed to these compounds. Since macrophages participate in several vascular pathologies, we examined the effect of statin treatment on the survival and differentiation of primary human monocytes.
  
  
  METHODS
  Peripheral blood mononuclear cells (PBMCs) from healthy individuals were cultured in the presence or absence of mevastatin. Apoptosis was monitored by annexin V / PI staining and flow cytometry. In parallel experiments, cultures were stimulated with LPS in the presence or absence of mevastatin and the release of IL-1beta and IL-1Ra was measured by ELISA.
  
  
  RESULTS
  Among PBMCs, mevastatin-treated monocytes were particularly susceptible to apoptosis, which occurred at doses >1 microM and was already maximal at 5 microM. However, even at the highest mevastatin dose used (10 microM), apoptosis occurred only after 24 h of culture, possibly reflecting a requirement for cell commitment to differentiation. After 72 h of treatment the vast majority (>50%) of monocytes were undergoing apoptosis. Stimulation with LPS revealed that mevastatin-treated monocytes retained the high IL-1beta output characteristic of undifferentiated cells; conversely, IL-1Ra release was inhibited. Concurrent treatment with mevalonolactone prevented the induction of apoptosis and suppressed both IL-1beta and IL-1Ra release in response to LPS, suggesting a rate-limiting role for HMG-CoA reductase in monocyte differentiation.
  
  
  CONCLUSIONS
  Our findings indicate that statins arrest the functional differentiation of monocytes into macrophages and steer these cells into apoptosis, suggesting a novel mechanism for the vasculoprotective properties of HMG-CoA reductase inhibitors.
authors.affiliation: Department of Surgery, University of Cambridge, Cambridge, UK. joannis@scientist.com
authors.forename: Joannis E
authors.initials: JE
authors.lastname: Vamvakopoulos
authors.forename: Colin
authors.initials: C
authors.lastname: Green
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000494:pharmacology*; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008148:Lovastatin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D008264:Macrophages / Q000502:physiology; D009000:Monocytes / Q000187:drug effects* / Q000502:physiology; D012795:Sialoglycoproteins / Q000378:metabolism*; D013997:Time Factors
chemical_list: C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D008070:Lipopolysaccharides; D012795:Sialoglycoproteins; C012258:mevastatin; D008148:Lovastatin; D006903:Hydroxymethylglutaryl CoA Reductases