4. Given $\odot O: x^{2}+y^{2}=5$ and the parabola $C$: $y^{2}=2 p x(p>0)$ intersect at point $A\left(x_{0}, 2\right), A B$ is the diameter of $\odot O$, and a line passing through point $B$ intersects the parabola $C$ at points $D$ and $E$. Then the product of the slopes of $A D$ and $A E$ is $\qquad$