Small interfering RNA knocks down heat shock factor-1 (HSF-1) and exacerbates pro-inflammatory activation of NF-κB and AP-1 in vascular smooth muscle cells

Objectives: Heat shock and elevated expression of heat shock proteins suppress activation of the pro-inflammatory transcription factor NF-kappa B. We hypothesized that knocking down the expression of heat shock factor-1 (HSF-1) with RNAi technology would exacerbate angiotensin (Ang) II-induced inflammatory injury in vascular smooth muscle cells (VSMC). Methods: Rat aorta A 10 cells and human intestinal smooth muscle cells were grown without transfection or with transfection with HSF-1 small interfering RNA (siRNA), or negative control siRNA. Cells were stimulated with Ang II (100 nM) to activate the NF-kappa B signaling pathway. Results: HSF-1 siRNA significantly knocked down HSF-1 expression, and one of the downstream heat shock proteins (Hsp), Hsp27, in both cells lines. HSF-1 siRNA also affected cells stressed with heat shock or Ang II treatment. Ang II induced activation of NF-kappa B and AP-1 in untransfected VSMCs, however, Ang II induced significantly higher activities of these pro-inflammatory transcription factors in HSF-1 siRNA transfected cells. Control siRNA had no apparent effect on HSF-1 and Hsp27 expression and Ang II-induced NF-kappa B and AP-1 activation. Conclusions: These data indicate that the knock down of HSF-1 exacerbates Ang II-induced inflammation in VSMCs, and suggests that heat shock proteins protect against inflammatory injury by suppression of pro-inflammatory transcription factors such as NF-kappa B and AP-1. (c) 2005 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.