Heparin inhibits proinflammatory and promotes anti-inflammatory macrophage polarization under hyperglycemic stress.

Monocytes are rapidly recruited to sites of diabetic complications and differentiate into macrophages. Previously, we showed that rat kidney mesangial cells dividing during hyperglycemic stress abnormally synthesize hyaluronan (HA) in intracellular compartments. This initiates a stress response, resulting in an extracellular HA matrix after division that recruits inflammatory cells. Cell-cell communication among macrophages that are recruited into the glomeruli and the damaged rat mesangial cells leads to diabetic nephropathy, fibrosis, and proteinurea, which are inhibited in heparin-treated diabetic rats. In this study, we found that murine bone marrow-derived macrophages (BMDMs) and a human leukemic cell line, U937 cells, dividing in hyperglycemia also accumulate intracellular HA and that heparin inhibits the HA accumulation. Both cell types expressed increased levels of proinflammatory markers: inducible nitric-oxide synthase and tumor necrosis factor-α, when cultured under hyperglycemic stress, which was inhibited by heparin. Furthermore, the abnormal intracellular HA was also observed in peripheral blood monocytes derived from three different hyperglycemic diabetic mouse models: streptozotocin-treated, high-fat fed, and Ins2Akita. Moreover, peripheral blood monocytes in humans with type 2 diabetes and poorly controlled blood glucose levels (hemoglobin A1c (HbA1c) levels of >7) also had intracellular HA, whereas those with HbA1c of <7, did not. Of note, heparin increased the anti-inflammatory markers arginase 1 and interleukin-10 in murine BMDMs. We conclude that heparin treatment of high glucose-exposed dividing BMDMs promotes an anti-inflammatory tissue-repair phenotype in these cells.