Gleason has struggled this season with just one assist in 17 games, but his presence is an upgrade to the Toronto blue-line because of his defensive abilities. Offensively, he has 15 goals and 113 assists in 615 NHL games.
The Leafs also sent 2011 sixth-round pick Dennis Robertson to Carolina in the trade. Robertson, a 22-year-old defenceman, is a senior at Brown University.
Liles, 33, spent the majority of the first half of the season with the AHL's Toronto Marlies, appearing in just six Leafs games and going scoreless. The Hurricanes inherit the final two of his contract and the ensuing US$3.875 million cap hit.
Gleason has two more seasons at a cap hit of $US 4 million left on his deal.
The 30-year-old Michigan native was a first-round pick of the Ottawa Senators in 2001. He's a left-handed shot who could fit in as a top-four defenceman for the Leafs.
This is the second major transaction Toronto has made while in Ann Arbor for the Winter Classic. The team announced captain Dion Phaneuf's US$49-million, seven-year contract extension Tuesday before practice.
Liles was a healthy scratch for the Winter Classic, his fourth straight game out of the lineup. Gleason had been held out of games and practices by Carolina in preparation for a move.
Gleason was a member of the silver-medal-winning U.S. team at the 2010 Vancouver Olympics. In the past three seasons, he has just one goal and 27 assists in 141 regular-season games.