Mark all fields from a query

I have a column in a database where the I want to search user_id and mark all fields when I get the result. I am not sure how to mark all the fields when I have to data.

my query :

            $user = PrivateMessage::where('recipient_id', '=', $request->authedUser->id)->get();

then I want to set PrivateMessage->read = 1

how would I do this