Blockage of Galectin-receptor Interactions by α-lactose Exacerbates Plasmodium berghei-induced Pulmonary Immunopathology

Malaria-associated acute lung injury (ALI) is a frequent complication of severe malaria that is often caused by “excessive” immune responses. To better understand the mechanism of ALI in malaria infection, here we investigated the roles of galectin (Gal)-1, 3, 8, 9 and the receptors of Gal-9 (Tim-3, CD44, CD137, and PDI) in malaria-induced ALI. We injected alpha (α)-lactose into mice-infected with Plasmodium berghei ANKA (PbANKA) to block galectins and found significantly elevated total proteins in bronchoalveolar lavage fluid, higher parasitemia and tissue parasite burden, and increased numbers of CD68(+) alveolar macrophages as well as apoptotic cells in the lungs after blockage. Additionally, mRNA levels of Gal-9, Tim-3, CD44, CD137, and PDI were significantly increased in the lungs at day 5 after infection, and the levels of CD137, IFN-α, IFN-β, IFN-γ, IL-4, and IL-10 in the lungs were also increased after α-lactose treatment. Similarly, the levels of Gal-9, Tim-3, IFN-α, IFN-β, IFN-γ, and IL-10 were all significantly increased in murine peritoneal macrophages co-cultured with PbANKA-infected red blood cells in vitro; but only IFN-α and IFN-β were significantly increased after α-lactose treatment. Our data indicate that Gal-9 interaction with its multiple receptors play an important role in murine malaria-associated ALI.