They are very similar, but not the same
Interest could be due to curiosity or due to other needs. For example a doctor in interested in new research not because of curiosity but because he needs it for his work. But I might read the same research article purely out of curiosity.
Issue versus subject... An issue is a particular thing that is being looked at or considered, usually with importance or strong interest connected to it. But a subject is just a topic, often a general topic.