(829.1) HMGB1 is necessary for the Receptors for Advanced Glycation End-products (RAGE) inhibition of DNA Double Strand Breaks in trophoblast cells

Poster Board Number: D51

Joe Kiehl (Brigham Young University), Katrina Curtis (Brigham Young University), Derek Clarke (Brigham Young University), Paul Reynolds (Brigham Young University), Juan Arroyo (Brigham Young University)

Trophoblasts are critical for a successful pregnancy and they mediate important steps such as implantation and delivery. Increased trophoblast DNA double strand breaks (DNA-DSBs) is implicated in complicated pregnancies. Our laboratory showed a role for increased nuclear placental receptor for advanced glycation end-products (nRAGE) in DNA-DSB repair in trophoblasts. HMGB1 protein (nHMGB1) is a nuclear protein that acts as a chromatin-binding factor involved the regulation of gene transcription that when released extracellularly, is involved in RAGE mediated inflammatory responses. We tested the hypothesis that nHMGB1 correlated with nRAGE availability during DNA-DSB in trophoblasts. DSBs were induced in human trophoblasts with cigarette smoke extract (CSE). Assessment of HMBG1, Beclin1 (involved in phagocytosis) and Caspase 3 (pro-apoptotic) were done by immunoblotting. Immunoprecipitation was used to quantify a RAGE and MNR11 complex. Invasion was measured in trophoblast cells in the presence or absence of an HMGB1 inhibitor (Glycyrrhizin; GLY). Decreased trophoblast nHMGB1 (1.8-fold; plt;0.02) was present during DNA-DSB and this reduction was reversed (4.5-fold; plt;0.02) with GLY treatment. DNA-DSBs induced a MRN11-nRAGE complex (1.4-fold; plt;0.03) in trophoblasts and the complex was decreased (2.5-fold; plt;0.05) by GLY co-treatment. CSE increased Beclin1 (1.9-fold; plt;0.02) and decreased Caspase 3 (2.2-fold; plt;0.02); however, GLY co-treatment significantly decreased Beclin1 (9.0-fold plt;0.02) while increasing Caspase 3 (1.2-fold; plt;0.04). Compromised trophoblast invasion was improved (7.0-fold; plt;0.02) with GLY treatment. We conclude that CSE causes DNA-DSBs in trophoblasts and HMGB1 plausibly regulates nRAGE availability at DNA-DSBs. We further conclude that Beclin1 and Caspase 3 are regulated by HMGB1 inhibition and that HMGB1 targeting could be a factor in regulating trophoblast invasion during DNA-DSBs. These studies provide a critical initial step in dissecting tobacco-mediated placental deficiency.

Support or Funding Information

This work was supported by funding from the Flight Attendant’s Medical Research Institute (FAMRI, PRR and JAA) and by a BYU Mentoring Environment Grant (JAA and PRR).

lt;pgt;This work was supported by funding from the Flight Attendantamp;rsquo;s Medical Research Institute (FAMRI, PRR and JAA) and by a BYU Mentoring Environment Grant (JAA and PRR).lt;/pgt;