Excess glucose induce trophoblast inflammation and limit cell migration through HMGB1 activation of Toll-Like receptor 4

Problem: Hyperglycemia increases the risk of preeclampsia. Hyperglycemia induces a placental trophoblast inflammatory (IL-1 beta, IL-6, IL-8), antiangiogenic (sFlt-1, sEndoglin), and anti-migratory profile. The IL-1 beta response is mediated via inflammasome activation by the damage-associated molecular pattern (DAMP), uric acid. The objective of this study was to determine the role of high-mobility group box-1 (HMGB1), a DAMP that activates Toll-like receptor 4 (TLR4), in human first trimester trophoblast responses to hyperglycemia. The trophoblast response to excess glucose under different oxygen tensions was also investigated. Method of study: The human first trimester trophoblast cell line (Sw.71) was exposed to glucose mimicking normoglycemia (5 mmol/L) and hyperglycemia (10 mmol/L), either alone or with the TLR4 antagonist, LPS-RS; or the HMGB1 inhibitor, glycyrrhizin. Cells were also treated with glucose under hyperoxic (21% O-2), normoxic (8% O-2), and hypoxic (2% O-2) conditions. Cell-free supernatants were assayed by ELISA and bioassays for inflammatory: IL-1 beta, IL-6, and IL-8; inflammasome-associated: uric acid and caspase-1; angiogenic: sEndoglin, sFlt-1, and PlGF; and the DAMP, HMGB1. Cell migration was measured using a two-chamber colormetric assay. Results: Excess glucose triggered a trophoblast sterile inflammatory IL-8 and antimigratory response through HMGB1 activation of TLR4. The IL-1 beta and sFlt-1/PlGF response was TLR4-mediated, but HMGB1-independent, suggesting another DAMP may be involved. Hyperoxia rather than normoxia or hypoxia was a major driver of trophoblast dysfunction in response to excess glucose. Conclusion: The findings from this study indicate a novel mechanism by which hyperglycemia may impact trophoblast function, early placentation, and ultimately, pregnancy outcome.