RESUMO
AIM: The aim of this study was to determine whether innate immune signalling influences the vascular repair process in response to mechanical injury of arteries in mice. METHODS AND RESULTS: A non-obstructive collar was introduced around the carotid artery of MyD88-deficient mice, and neointima formation was compared with that observed in MyD88-competent mice. MyD88-deficient mice are characterized by impaired signal transduction from interleukin (IL)-1/IL-18 receptors and most Toll-like receptors (TLRs). The vascular response to injury was severely impaired in MyD88-deficient mice as neointima formation was not different from sham-operated mice, whereas MyD88-competent mice displayed robust neointima formation. Furthermore, infiltration of CD68-positive leucocytes was dependent on MyD88. During the early response to injury, 3 days after collar placement, a transient increase in the expression of TLR4 on vascular smooth muscle cells was observed. To determine the relative importance of IL-1 receptor and TLR4 activation in the vascular response to injury, mice were injected with blocking antibodies to these receptors prior to the collar placement. Neointima formation was reduced by 80% in mice administered IL-1RI blocking antibodies compared with mice given a control antibody, whereas administration of TLR4 blocking antibodies was without effect. CONCLUSION: These results show that inhibition of MyD88- or IL-1 receptor signalling reduces neointima formation in response to vascular injury and could offer therapeutic options for reducing clinical complications of excessive smooth muscle cell proliferation, such as that observed in in-stent restenosis.
Assuntos
Artérias Carótidas/imunologia , Lesões das Artérias Carótidas/imunologia , Proliferação de Células , Imunidade Inata , Fator 88 de Diferenciação Mieloide/metabolismo , Receptores Tipo I de Interleucina-1/metabolismo , Transdução de Sinais , Túnica Íntima/lesões , Análise de Variância , Animais , Anticorpos/farmacologia , Antígenos CD/metabolismo , Antígenos de Diferenciação Mielomonocítica/metabolismo , Artérias Carótidas/efeitos dos fármacos , Artérias Carótidas/metabolismo , Artérias Carótidas/patologia , Lesões das Artérias Carótidas/genética , Lesões das Artérias Carótidas/metabolismo , Lesões das Artérias Carótidas/patologia , Proliferação de Células/efeitos dos fármacos , Modelos Animais de Doenças , Imunidade Inata/efeitos dos fármacos , Leucócitos/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fator 88 de Diferenciação Mieloide/deficiência , Fator 88 de Diferenciação Mieloide/genética , Receptores Tipo I de Interleucina-1/antagonistas & inibidores , Transdução de Sinais/efeitos dos fármacos , Fatores de Tempo , Receptor 4 Toll-Like/antagonistas & inibidores , Receptor 4 Toll-Like/metabolismo , Túnica Íntima/imunologia , Túnica Íntima/metabolismo , Túnica Íntima/patologiaRESUMO
During screening of genes upregulated by lipopolysaccharide (LPS; endotoxin) treatment of bone marrow-derived mouse macrophages, it was unexpectedly found that cholesterol 25-hydroxylase (Ch25h) was strongly upregulated. Treatment of macrophages with 10 ng/ml of LPS for 2 h resulted in a 35-fold increase in the expression of Ch25h. In contrast, LPS treatment did not increase the expression of Cyp27a1 or Cyp7b1. The increased Ch25h expression was found to be independent of Myeloid differentiation protein 88 signaling but dependent on Toll-like receptor 4 signaling. LPS treatment of macrophages caused a 6- to 7-fold increase in cellular 25-hydroxycholesterol concentration. When macrophages were treated with increasing concentrations of 25-hydroxycholesterol, a dose-dependent release of CCL5 into the culture medium was observed. Intravenous injection of LPS in eight healthy volunteers resulted in an increase in plasma 25-hydroxycholesterol concentration. The possibility is discussed that 25-hydroxycholesterol may have a role in the inflammatory response, in addition to its more established role in the regulation of cholesterol homeostasis.