Purinergic signaling is required for fluid shear stress-induced NF-κB translocation in osteoblasts

Fluid shear stress regulates gene expression in osteoblasts, in part by activation of the transcription factor NF-kappa B. We examined whether this process was under the control of purinoceptor activation. MC3T3-E1 osteoblasts under static conditions expressed the NF-kappa B inhibitory protein I kappa B alpha and exhibited cytosolic localization of NF-kappa B. Under fluid shear stress, I kappa B alpha levels decreased, and concomitant nuclear localization of NF-kappa B was observed. Cells exposed to fluid shear stress in ATP-depleted medium exhibited no significant reduction in I kappa B alpha, and NF-kappa B remained within the cytosol. Similar results were found using oxidized ATP or Brilliant Blue G, P2X(7) receptor antagonists, indicating that the P2X7 receptor is responsible for fluid shear-stress-induced I kappa B alpha degradation and nuclear accumulation of NF-kappa B. Pharmacologic blockage of the P2Y6 receptor also prevented shear-induced I kappa B alpha degradation. These phenomena involved neither ERK1/2 signaling nor autocrine activation by P2X(7)-generated lysophosphatidic acid. Our results suggest that fluid shear stress regulates NF-kappa B activity through the P2Y(6) and P2X(7) receptor. (C) 2011 Elsevier Inc. All rights reserved.