How to cast object to Action<T>

I've created a simple message bus that queues and emits/publishes events.

I'm using StructureMap to locate the registered handlers (Action<T>) of the event but am not sure how to cast it from the object that StructureMap returns into an invoke-able action.

Since I can't cast to Action<object> I'm assuming that Action<T> is not covariant? Can this be done another way?

public class Bus
{
    private ConcurrentQueue<object> events = new ConcurrentQueue<object>();
    public void Queue<TEvent>(TEvent e)
    {
        events.Enqueue(e);
    }

    public void Emit()
    {
        object e;
        while (events.TryDequeue(out e))
        {
            var handlerType = typeof(Action<>).MakeGenericType(e.GetType());
            foreach (var handler in ObjectFactory.GetAllInstances(handlerType))
            {
                // how to invoke action?
            }
        }
    }
}