Dentsu Inc. said it acquired a 33% stake in Laguna Hills-based Athletes First LLC to help the athlete management agency expand its business in the U.S. and internationally.

Tokyo-based Dentsu, with about $5.7 billion in revenue, is one of the world’s largest advertising companies.

Athletes First represents National Football League players and coaches, ESPN broadcasters, professional baseball players and other athletes in contract negotiations and in commercial endorsements.

It was founded in 2001 and had about $10 million in revenue last year.