Oligodeoxynucleotide targeted to the alpha(v) gene inhibits alpha(v) integrin synthesis, impairs osteoclast function, and activates intracellular signals to apoptosis

The or, integrin subunit is highly expressed in osteoclasts where it dimeri zes with beta(1) and beta(3) subunits to form receptors for vitronectin and bone sialoproteins. Inhibition of osteoclast adhesion and function has pre viously been achieved by alpha(v)beta(3) antibodies or Arg-Gly-Asp-containi ng peptides which have the disadvantages of blocking a single receptor type , or of being rather nonspecific, respectively. Here we show that alpha(v) integrin expression in rabbit osteoclasts can be inhibited by partially pho sphorothioated antisense oligodeoxynucleotide (ODN) spanning the adenine-ur acil-guarine (AUG) translational start site of the human/rabbit alpha(v) ge ne, a procedure which offers the advantage of affecting all the alpha(v) re ceptors with high efficiency, The alpha(v) antisense ODN caused a dose-depe ndent, substrate-specific reduction of osteoclast adhesion and bone resorpt ion, Control ODNs, such as sense, inverted, and mismatch, were without effe ct, providing evidence of specificity of the antisense reagent. It is likel y as a consequence of loss of substrate interaction, the antisense ODN indu ced osteoclast retraction and apoptosis, increase of the cyclin/cyclin-depe ndent kinase complex inhibitor p21(WAF1/CIP1), and inhibition of the cell s urvival gene, bcl-2. Although the expression of the cell death-promoting ge ne, bar, remained unchanged, a reduction of the bcl-2/bax ratio, known to u nderlie the intracellular signal to apoptosis, was observed. This finding l ed us to hypothesize that these changes could provide a link between reduct ion of alpha(v) synthesis and osteoclast programmed death. In conclusion, t his study provides novel insights into the use of alpha(v) antisense ODN as an efficacious mechanism for blocking osteoclast function and underscores for the first time the involvement of integrins in bone cell apoptosis, In vivo studies may verify potential application of this ODN as alternative th erapy for bone diseases.