Hypoxia and oxidative stress impair autophagy and cell death mechanisms in trophoblast cells and reduce placental effciency in rodents
Authors: Gardner Jennifer , Bradshaw Jessica , Oliveira da Silva Renee de Nazare , Hula Nataliia , Mabry Steve , Wilson E. Nicole , Cunningham Rebecca 
Published: May 2024

Introduction: Hypoxia and oxidative stress can activate autophagy, a lysosomal degradation pathway that maintains cellular homeostasis. Impairments in autophagy mechanisms have been observed in placentas from obstetric complications associated with placental hypoxia and oxidative stress, such as preeclampsia and intrauterine growth restriction. The objective of this study was to investigate the effects of hypoxia and oxidative stress on placental cell autophagy. We hypothesized that exposure to oxidative stress and hypoxia would alter the balance between cytotoxic and cytoprotective mechanisms in human trophoblast cells and rat placentas and would adversely affect placental effciency. Methods: We used an in vitro model incorporating human trophoblast cells (BeWo cells) exposed to an oxidative stressor, antimycin A (10, 100, 320 μM) or vehicle for 4 hours. Trophoblast cell death and autophagy mechanisms were assessed via flow cytometry and western blotting. Additionally, we used a rodent model of gestational sleep apnea, a pregnancy complication associated with placental hypoxia. Long Evans timed-pregnant dams were exposed to chronic intermittent hypoxia (CIH; n=6-8) or normoxia (NX; n=8-9) during their sleep cycle from gestational day (GD) 15 to 20 (term=21-23 days). Results: In trophoblast cells (n=5-9 independent experiments), antimycin A increased necrosis and LC3 A/B II/I ratio (autophagy marker) at 100 μM compared to vehicle (p≤0.015). At antimycin A 320 μM, necrosis remained elevated, while BAX (pro-apoptotic marker) and p62 (autophagosomal flux marker) were reduced compared to vehicle (p<0.0001), and LC3 A/B II/I ratio returned to vehicle levels (p>0.05 vs. vehicle). Placental weights from CIH exposed dams were greater (NX: 0.51±0.02 g vs. CIH: 0.60±0.03 g, p=0.015) and fetal to placental weight ratios (marker of placental effciency) were reduced compared to control pregnancies (NX: 5.25±0.13 vs. CIH: 4.43±0.14, p=0.0006) on GD20. Gestational CIH did not affect (p>0.05) fetal weights (NX: 2.76±0.06 g vs. CIH: 2.61±0.06 g), crown to rump length (NX: 3.32±0.03 cm vs. CIH: 3.18±0.12 cm), abdominal girth (NX: 3.22±0.06 cm vs. CIH: 3.32±0.12 cm), or litter size (NX: 11.9±0.90 vs. CIH: 10.5±0.82). Conclusion: Oxidative stress alters the balance between cytotoxic and cytoprotective mechanisms in trophoblast cells, promoting cell necrosis. Although assessment of autophagy machinery and cell death in placentas from hypoxic pregnancies is ongoing, our results indicate that gestational CIH adversely affects placental effciency. NIH R01 HL146562, AHA 22PRE-900431, T32 AG020494, AHA 22POST-903250. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.