Right click on the file in your library and there should be an option to update the file so your changes become visible outside Lightroom. But, to be honest, I wouldn't do that as then you can not go back to the original file; edits in jpgs can not be saved in a non destructive way like they can with raw (and even there, Lightroom only updates the preview of dng files if you ask it to). Instead I'd export to another file and use that file from within PM.