Robert De Niro filed for divorce Monday from his second wife, former flight attendant Grace Hightower, 44, a publicist for the Oscar-winning film star said. Stan Rosenfield said De Niro, 55, filed papers in a New York court to dissolve his two-year marriage to Hightower, with whom he has a son. It was the second marriage for De Niro, who divorced Diahnne Abbott in 1988 after a 12-year marriage.