Endogenous galectin-1 and acute inflammation: emerging notion of a galectin-9 pro-resolving effect

The role of endogenous galectin-1 (Gal-1) in acute inflammation has been poorly investigated. We therefore performed the carrageenan-induced paw edema model in wild-type and Gal-1(-/-) mice. On subplantar injection of carrageenan, Gal-1(-/-) mice displayed a similar first phase of edema (≤24 hours) to wild-type mice; however, a much less pronounced second phase (48 to 96 hours) was evident in this genotype. This reduced inflammation was associated with lower paw expression of inflammatory genes and cell infiltrates. Analysis of galectin protein and mRNA expression revealed high expression of Gal-1 in wild-type paws during resolution (≥48 hours), with some expression of galectin-9 (Gal-9). Administration of stable Gal-1 to wild-type mice completely ablated the first phase of edema but was ineffective when administered therapeutically at the 24-hour time point. Conversely, Gal-9 administration did not alter the first phase of edema but significantly reduced the second phase when administered therapeutically. This suggests anti-inflammatory actions for both proteins in this model albeit at different phases of the inflammatory response. Collectively, these data indicate that the absence of endogenous Gal-1 results in an abrogated response during the second phase of the edema reaction.