Bcl-2 and Bcl-XL serve an anti-inflammatory function in endothelial cells through inhibition of NF-κB
A.Z. Badrichani, … , F.H. Bach, C. Ferran
A.Z. Badrichani, … , F.H. Bach, C. Ferran
Published February 15, 1999
Citation Information: J Clin Invest. 1999;103(4):543-553. https://doi.org/10.1172/JCI2517.
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Article

Bcl-2 and Bcl-XL serve an anti-inflammatory function in endothelial cells through inhibition of NF-κB

Abstract

To maintain the integrity of the vascular barrier, endothelial cells (EC) are resistant to cell death. The molecular basis of this resistance may be explained by the function of antiapoptotic genes such as bcl family members. Overexpression of Bcl-2 or Bcl-XL protects EC from tumor necrosis factor (TNF)–mediated apoptosis. In addition, Bcl-2 or Bcl-XL inhibits activation of NF-κB and thus upregulation of proinflammatory genes. Bcl-2–mediated inhibition of NF-κB in EC occurs upstream of IκBα degradation without affecting p65-mediated transactivation. Overexpression of bcl genes in EC does not affect other transcription factors. Using deletion mutants of Bcl-2, the NF-κB inhibitory function of Bcl-2 was mapped to bcl homology domains BH2 and BH4, whereas all BH domains were required for the antiapoptotic function. These data suggest that Bcl-2 and Bcl-XL belong to a cytoprotective response that counteracts proapoptotic and proinflammatory insults and restores the physiological anti-inflammatory phenotype to the EC. By inhibiting NF-κB without sensitizing the cells (as with IκBα) to TNF-mediated apoptosis, Bcl-2 and Bcl-XL are prime candidates for genetic engineering of EC in pathological conditions where EC loss and unfettered activation are undesirable.

Authors

A.Z. Badrichani, D.M. Stroka, G. Bilbao, D.T. Curiel, F.H. Bach, C. Ferran

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(a) Adenoviral-mediated gene transfer of Bcl-2 to HUVEC achieves high le...
(a) Adenoviral-mediated gene transfer of Bcl-2 to HUVEC achieves high levels of expression of the transgene. (b) Bcl-2 expression inhibits E-selectin, and (c) VCAM-1 inhibits upregulation by inhibiting NF-κB activation at (d) a level upstream of IκBα degradation. (a) 90%-confluent HUVEC monolayers were either noninfected or infected with the control rAd.β-gal or the rAd.hBcl-2 at a MOI of 100. Forty-eight hours after infection, cell extracts were recovered, and 1.5 μg of protein was run on a SDS-PAGE and checked by Western blot analysis for the expression of the transgene using a rabbit polyclonal anti–human Bcl-2 antiserum. Results show high levels of expression of Bcl-2 in HUVEC infected with the rAd.hBcl-2 (arrow). (b and c) Expression of Bcl-2 in HUVEC significantly decreases TNF-mediated upregulation of E-selectin and VCAM-1 as assessed by flow cytometry. In all cases, E-selectin and VCAM-1 expression levels on nonstimulated HUVEC is represented by a light line, expression after TNF treatment is shown by a dark line, and labeling of an isotype-matched control monoclonal antibody is illustrated by a broken line. (d) Western blot analysis of IκBα expression after TNF treatment. Extracts from noninfected (lanes 1–3), rAd.hBcl-2 (lanes 4–6), and rAd.β-gal (lanes 7–9) were recovered before and 15 min and 2 h after TNF treatment, and assayed for IκBα expression. Results show that Bcl-2 expression in HUVEC inhibits the usual IκBα degradation that occurs 15 min after TNF stimulation (lane 4 vs. lanes 2 and 8). A second, slower migrating form of IκBα is strongly stabilized in the Bcl-2–expressing EC. HUVEC, human umbilical vein cells; MOI, moiety of infection; VCAM-1, vascular cell adhesion molecule-1.