gms | German Medical Science

122. Kongress der Deutschen Gesellschaft für Chirurgie

Deutsche Gesellschaft für Chirurgie

05. bis 08.04.2005, München

The bile pigment bilirubin: a natural suppressor of arteriosclerosis?

Meeting Abstract

  • corresponding author R. Öllinger - Department of Surgery, Innsbruck Medical University, Innsbruck, Austria
  • M. Bilban - Department of Surgery, BIDMC, Harvard Medical School, Boston, USA
  • A. Erat - Department of Medicine, BIDMC, Harvard Medical School, Boston, USA
  • A. Froio - Department of Surgery, BIDMC, Harvard Medical School, Boston, USA
  • J. McDaid - Department of Surgery, BIDMC, Harvard Medical School, Boston, USA
  • A. Usheva - Department of Medicine, BIDMC, Harvard Medical School, Boston, USA
  • R. Margreiter - Department of Surgery, Innsbruck Medical University, Innsbruck, Austria
  • K. Yamashita - Department of Surgery, Hokkaido University School of Medicine, Sapporo, Japan
  • F.H. Bach - Department of Surgery, BIDMC, Harvard Medical School, Boston, USA

Deutsche Gesellschaft für Chirurgie. 122. Kongress der Deutschen Gesellschaft für Chirurgie. München, 05.-08.04.2005. Düsseldorf, Köln: German Medical Science; 2005. Doc05dgch3238

Die elektronische Version dieses Artikels ist vollständig und ist verfügbar unter: http://www.egms.de/de/meetings/dgch2005/05dgch199.shtml

Veröffentlicht: 15. Juni 2005

© 2005 Öllinger et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielf&aauml;ltigt, verbreitet und &oauml;ffentlich zug&aauml;nglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Introduction

Induction of heme oxygenase 1 (HO-1) ameliorates the development of neointimal hyperplasia, which normally involves oxidative stress and vascular smooth muscle cell (VSMC) proliferation. Bilirubin and biliverdin, generated during heme catabolism by HO-1, are potent antioxidants that play a role in maintenance of homeostasis. Based on the clinical observation that healthy individuals with higher levels of bilirubin develop less arteriosclerosis, we hypothesized that the bile pigments would inhibit VSMC proliferation in vitro and neointima formation in vivo.

Materials

Balloon injury (BI) was performed in the left common carotid artery of congenitally hyperbilirubinemic Gunn rats. The artery was harvested two weeks after BI, and neointima formation was assessed by quantifying intima/media ratio and luminal cross-sectional area narrowing (LCAN). In vitro, proliferation of primary vascular smooth muscle cells (VSMC) was measured by 3H-thymidine incorporation in the presence or absence of bilirubin/ biliverdin. Cell cycle progression was monitored by DNA content analysis; apoptosis by the Annexin V binding assay. Protein levels were detected by western blot. Immunocytochemistry was performed using primary antibodies directed against cdk2 and phospho-p38 in growth stimulated primary VSMCs, in the presence or absence of bilirubin/biliverdin. To further delineate the pathways of bilirubin/biliverdin action on VSMC proliferation, we used VSMCs derived from p53 KO, p21 KO and HO-1 KO mice.

Results

BI mediated neointima formation was significantly reduced in hyperbilirubinemic Gunn rats (serum bilirubin levels: 12.0 ± 2.5 mg/dl) as compared to control Wistar rats (LCAN 0.18 vs. 0.44; p < 0.05). Systemic administration of biliverdin, the precursor of bilirubin, to normal rats also suppressed neointima proliferation (LCAN 0.29 vs. 0.43; p < 0.05). In vitro, bilirubin inhibited VSMC proliferation by arresting VSMC cell cycle progression at the G0/G1 phase, while it did not increase apoptosis (p=0.2816). Inhibition of cell cycle progression was mediated by reduced phosphorylation of p38 MAPK and c-Jun NH2-terminal kinase 1/2 (JNK 1/2), down-regulation of cdk2, cyclins D1, E and A resulting in hypophosphorylation of pRb as demonstrated in nuclear extracts of cultured cells. Further the effect of bilirubin on VSMC proliferation was dependent on p53, but independent of p21 and HO-1.

Discussion

Our studies implicate bilirubin as the molecule to explain the observed associations between higher levels of plasma bilirubin in humans and a lesser incidence of atherosclerosis-related diseases and suggest the future use of bilirubin/biliverdin as a therapeutic to prevent restenosis, chronic rejection and atherosclerosis. [Fig. 1]