Inflammation-dependent changes in α2,3-, α2,6-, and α2,8-sialic acid glycotopes on serum glycoproteins in mice

The expression of acute-phase serum proteins increases in response to inflammatory stimuli. Most of these proteins are glycoproteins that often contain sialic acids (Sia). It is unknown, however, how the expression of Sia in these glycoproteins changes during inflammation. This study demonstrates changes in the alpha 2,3-, alpha 2,6-, and alpha 2,8-Sia glycotopes on serum glycoproteins in response to turpentine oil-induced inflammation, based on lectin- and immunoblot analyses by using sialyl linkage-specific lectins, Maackia amurensis for the alpha 2,3-Sia glycotope and Sambucus sieboldiana for the alpha 2,6-Sia glycotopes, and monoclonal antibody 2413 (mAb.2-413) recognizing the di- and oligomers of the alpha 2,8-Neu5Gc residue. There was an increase in a limited number of sialoglycoproteins containing the alpha 2,3-, alpha 2,6-, or alpha 2,8-Sia glycotopes. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of the expression profiles of mRNAs for the known sialyltransferases in mouse liver during inflammation indicated the up-regulated expression of P-galactoside alpha 2,3-sialyltransferases (ST3Gal I and ST3Gal III) and P-N-acetylgalactosaminide alpha 2,6-sialyltransferase (ST6GalNAc VI) as well as P-galactoside alpha 2,6-sialyltransferase (ST6Gal 1) mRNAs. Notably, ST3Gal I and III and ST6GalNAc VI are involved in the synthesis of the alpha 2,3- and alpha 2,6-Sia glycotopes on O-glycan chains and possibly on gangliosides, whereas ST6Gal I is specific for N-glycan chains. These results provide evidence for the inflammation-induced expression of sialyl glycotopes in serum glycoproteins. We demonstrated that inflammation significantly increased the expression of an unknown 32-kDa glycoprotein containing the alpha 2,8-Sia glycotope. The mechanism for the increase in glycoprotein in inflamed mouse serum remains to be examined, as mRNA expression for all of the alpha 2,8-sialyltransferases (ST8Sia I-VI) was unchanged during inflammation.