Photoshop allows to jump directly to Bridge via Command+Shift+O (Mac OS)
Is there a similar shortcut to go directly from Photoshop to Lightroom?
There is no such shortcut because Lightroom doesn't open files the way Photoshop does.
To work on a file in Lightroom you have to import it.
If you are working with raw files, they will initially open in Photoshop's Camera Raw plugin, which has the same editing tools as Lightroom.
For none-raw files you can use the Camera Raw filter in Photoshop, which also has these tools.
Thank you very much Per