  We study cosmological application of interacting holographic energy density
in the framework of Brans-Dicke cosmology. We obtain the equation of state and
the deceleration parameter of the holographic dark energy in a non-flat
universe. As system's IR cutoff we choose the radius of the event horizon
measured on the sphere of the horizon, defined as $L=ar(t)$. We find that the
combination of Brans-Dicke field and holographic dark energy can accommodate
$w_D = -1 $ crossing for the equation of state of \textit{noninteracting}
holographic dark energy. When an interaction between dark energy and dark
matter is taken into account, the transition of $w_D$ to phantom regime can be
more easily accounted for than when resort to the Einstein field equations is
made.
