Laravel 获取多列字段

When i use pluck with multiple columns i get this:

{"Kreis 1 \/ Altstadt":"City","Kreis 2":"Enge","Kreis 3":"Sihifeld","Kreis 4":"Hard","Kreis 5 \/ Industriequartier":"Escher Wyss","Kreis 6":"Oberstrass","Kreis 7":"Witikon","Kreis 8 \/ Reisbach":"Weinegg","Kreis 9":"Altstetten","Kreis 10":"Wipkingen","Kreis 11":"Seebach","Kreis 12 \/ Schwamendingen":"Hirzenbach"

But i need this?

["Rathaus","Hochschulen","Lindenhof","City","Wollishofen","Leimbach","Enge","Alt-Wiedikon","Friesenberg","Sihifeld","Werd","Langstrasse","Hard","Gewerbechule","Escher Wyss","Unterstrass","Oberstrass","Fluntern","Hottingen","Hirslanden","Witikon","Seefeld","M\u00fchlebach","Weinegg","Albisrieden","Altstetten","H\u00f6ngg","Wipkingen","Affoltern","Oerlikon","Seebach","Saatlen","Schwamendingen-Mitte","Hirzenbach"]

Any suggestion how can i do that? This is my method:

    public function autocomplete_districts(Request $request)
   {
      $district = $request->input('query');
      // $ass = /DB::table('districts')->select(array('district', 'region'))->get();
      // dd($ass);
      $data = Districts::whereRaw('LOWER(district) like ?', [strtolower('%'.$district . '%')])->orWhereRaw('LOWER(region) like ?', [strtolower('%'.$district . '%')])->pluck('region','district');

      return response()->json($data);
   }