Purinergic signaling is required for fluid shear stress-induced NF-[kappa]B 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, P2X7 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 P2X7 -generated lysophosphatidic acid. Our results suggest that fluid shear stress regulates NF-[kappa]B activity through the P2Y6 and P2X7 receptor. [PUBLICATION ABSTRACT]