SELECT *
 
  FROM `pl_comprofiler_plugin_messages_read`
 
  WHERE `to_user` = 1155 
  AND `message` = 1428




SELECT COUNT(*)
 
  FROM `pl_comprofiler_plugin_messages` AS m
 
  LEFT JOIN `pl_comprofiler_plugin_messages_read` AS r 
  ON r.`to_user` = 1155 
  AND r.`message` = m.`id`
 
  WHERE ( ( m.`from_user` != 1155 
  AND m.`to_user` = 0 ) OR ( m.`to_user` = 1155 
  AND m.`to_user_delete` = 0 ) )
 
  AND r.`id` IS NULL




1 × SELECT COUNT(*)  
  FROM `pl_comprofiler_plugin_messages` AS m  
  LEFT JOIN `pl_comprofiler_plugin_messages_read` AS r 
  ON r.`to_user` = 1155 
  AND r.`message` = m.`id`




1 × SELECT *  
  FROM `pl_comprofiler_plugin_messages_read`





And also this line, under "Explain":
1	SIMPLE	pl_comprofiler_plugin_messages_read	const	read,message	read	8	const,const	1