Gestational chronic intermittent hypoxia induces hypertension, proteinuria, and fetal growth restriction in mice

Melatonin alleviates high temperature exposure induced fetal growth restriction via the gut-placenta-fetus axis in pregnant mice

INTRODUCTION

Global warming augments the risk of adverse pregnancy outcomes in vulnerable expectant mothers. Pioneering investigations into heat stress (HS) have predominantly centered on its direct impact on reproductive functions, while the potential roles of gut microbiota, despite its significant influence on distant tissues, remain largely unexplored. Our understanding of deleterious mechanisms of HS and the development of effective intervention strategies to mitigate the detrimental impacts are still limited.

OBJECTIVES

In this study, we aimed to explore the mechanisms by which melatonin targets gut microbes to alleviate HS-induced reproductive impairment.

METHODS

We firstly evaluated the alleviating effects of melatonin supplementation on HS-induced reproductive disorder in pregnant mice. Microbial elimination and fecal microbiota transplantation (FMT) experiments were then conducted to confirm the efficacy of melatonin through regulating gut microbiota. Finally, a lipopolysaccharide (LPS)-challenged experiment was performed to verify the mechanism by which melatonin alleviates HS-induced reproductive impairment.

RESULTS

Melatonin supplementation reinstated gut microbiota in heat stressed pregnant mice, reducing LPS-producing bacteria (Aliivibrio) and increasing beneficial butyrate-producing microflora (Butyricimonas). This restoration corresponded to decreased LPS along the maternal gut-placenta-fetus axis, accompanied by enhanced intestinal and placental barrier integrity, safeguarding fetuses from oxidative stress and inflammation, and ultimately improving fetal weight. Further pseudo-sterile and fecal microbiota transplantation trials confirmed that the protective effect of melatonin on fetal intrauterine growth under HS was partially dependent on gut microbiota. In LPS-challenged pregnant mice, melatonin administration mitigated placental barrier injury and abnormal angiogenesis via the inactivation of the TLR4/MAPK/VEGF signaling pathway, ultimately leading to enhanced nutrient transportation in the placenta and thereby improving the fetal weight.

CONCLUSION

Melatonin alleviates HS-induced low fetal weight during pregnancy via the gut-placenta-fetus axis, the first time highlighting the gut microbiota as a novel intervention target to mitigate the detrimental impact of global temperature rise on vulnerable populations.

Hydrogen sulfide sustains mitochondria functions via targeting mitochondria fission regulator 1 like protein to restore human cytotrophoblast invasion and migration

Hydrogen sulfide (H2S) is bioactive in mammals. Reduced H2S was observe in pregnancy complications, pre-eclampsia (PE). Our previous data demonstrated that low dose of H2S enhanced cytotrophoblast (CTB) invasion and migration via mitochondria dynamics without knowing the mechanisms. This study was designed to explore the functional regulation of CTB by mitochondrial fission regulator 1 like (MTFR1L) and the mechanisms. By studying human placenta samples and HTR-8/SVneo cell line, MTFR1L was found expressed in CTB. While MTFR1L expression was lower in PE placenta and CTB comparing with Normal pregnancy. Knockdown of MTFR1L decreased CTB invasion and migration, as well as the ATP production, while increased the mitochondria fragmentation, ROS production and mitochondria membrane potential indicating MTFR1L was key regulator of mitochondria. The posttranslational modulation analysis showed enhanced persulfidation of MTFR1L on cystine 222 and 230 by H2S. Mutations of MTFR1LC222/C230 suppressed ATP production, CTB invasion, migration, and increased mitochondria fragmentation, ROS production and mitochondria membrane potential. The present study showed the functional MTFR1L received endogenous CBS/H2S regulation. MTFR1LC222/230 persulfidation by H2S maintained mitochondria morphology and functions thus restored CTB invasion and migration. These findings established a new regulatory pathway for CTB invasion and migration, and provided new targets for PE treatment.

Effects of gestational intermittent hypoxia on the respiratory system: A tale of the placenta, fetus, and developing offspring

Obstructive sleep apnea (OSA) is a common sleep disorder that is associated with a wide variety of health conditions, including cardiovascular, cerebrovascular, metabolic, neoplastic, and neurocognitive manifestations. OSA, as a chronic condition, is mainly characterised by repeated upper airway obstructions during sleep that cause episodes of intermittent hypoxia (IH), resulting in tissue hypoxia-reoxygenation cycles. Decreased arterial oxygen pressure (PaO2) and haemoglobin saturation (SatO2) stimulate reflex responses to overcome the obstruction. The prevalence of OSA is significant worldwide, and an underrated problem when focussing on women during pregnancy. The physiological changes associated with pregnancy, especially during its latest stages, are related to a higher prevalence of OSA events in pregnant mothers, and associated with an increased risk of hypertension, pre-eclampsia and diabetes, among other deleterious consequences. Furthermore, OSA during pregnancy can interfere with normal fetal development and is associated with growth retardation, preterm birth, or low birth weight. Carotid body overstimulation and hypoxia-reoxygenation episodes contribute to cardiovascular disease and oxidative stress, which can harm both mother and fetus and have long-lasting effects that can reach into adulthood. Because IH is the hallmark of OSA, this review examines the literature available about the impact of gestational intermittent hypoxia (GIH) on the respiratory system at maternal, fetal, and offspring levels. Offering the latest scientific data about OSA during pregnancy, we may help to tackle this condition with lifestyle changes and therapeutic approaches, that could influence the mothers, but also impact adult health problems, mostly unknown, inherited from these hypoxic episodes in the uterus.

Sleep apnea-related hypoxic burden as a predictor of pregnancy and neonatal outcome

STUDY OBJECTIVES

To determine the clinical impact of sleep apnea-related hypoxic burden in pregnant women and neonates.

METHODS

This is a secondary analysis of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b) study. Hypoxia burden was calculated from the home sleep apnea test (HSAT) and defined as the total area under respiratory events. Logistic regression analysis assessed the relationship between hypoxia burden and pregnancy/neonatal outcomes.

RESULTS

A total of 3006 subjects in the early term, and 2326 subjects in the middle term of pregnancy, had HSAT. A hypoxic burden greater than 6.8%min was present in 1740 at early term and associated with a higher risk of preeclampsia (odds ratio 1.297, 95 % confidence interval 1.032-1.630, p: 0.026) after adjusted by obstructive sleep apnea (OSA) severity. In the middle term, 1058 subjects had a hypoxia burden more than 11.8%min, which was a predictor for higher incidence of gestational diabetes (OR 1.795, 95 % CI 1.097-2.938, p: 0.020) and an Apgar <7 at 1 min (OR 1.446, 95 % CI 1.079-1.939, p: 0.012) after adjusted by obstructive sleep apnea (OSA) severity. After adjusted by oxygenation disturbance index, HB was not related with Apgar <7 at 1 min (p:0.565).

CONCLUSIONS

The hypoxic burden is an independent predictor for preeclampsia and gestational diabetes and an Apgar <7 at 1 min.

Effect of Obstructive Sleep Apnea during Pregnancy on Fetal Development: Gene Expression Profile of Cord Blood

Obstructive sleep apnea (OSA) is quite prevalent during pregnancy and is associated with adverse perinatal outcomes, but its potential influence on fetal development remains unclear. This study investigated maternal OSA impact on the fetus by analyzing gene expression profiles in whole cord blood (WCB). Ten women in the third trimester of pregnancy were included, five OSA and five non-OSA cases. WCB RNA expression was analyzed by microarray technology to identify differentially expressed genes (DEGs) under OSA conditions. After data normalization, 3238 genes showed significant differential expression under OSA conditions, with 2690 upregulated genes and 548 downregulated genes. Functional enrichment was conducted using gene set enrichment analysis (GSEA) applied to Gene Ontology annotations. Key biological processes involved in OSA were identified, including response to oxidative stress and hypoxia, apoptosis, insulin response and secretion, and placental development. Moreover, DEGs were confirmed through qPCR analyses in additional WCB samples (7 with OSA and 13 without OSA). This highlighted differential expression of several genes in OSA (EGR1, PFN1 and PRKAR1A), with distinct gene expression profiles observed during rapid eye movement (REM)-OSA in pregnancy (PFN1, UBA52, EGR1, STX4, MYC, JUNB, and MAPKAP). These findings suggest that OSA, particularly during REM sleep, may negatively impact various biological processes during fetal development.

Obstructive Sleep Apnea-Associated Intermittent Hypoxia-Induced Immune Responses in Males, Pregnancies, and Offspring

Obstructive sleep apnea (OSA), a respiratory sleep disorder associated with cardiovascular diseases, is more prevalent in men. However, OSA occurrence in pregnant women rises to a level comparable to men during late gestation, creating persistent effects on both maternal and offspring health. The exact mechanisms behind OSA-induced cardiovascular diseases remain unclear, but inflammation and oxidative stress play a key role. Animal models using intermittent hypoxia (IH), a hallmark of OSA, reveal several pro-inflammatory signaling pathways at play in males, such as TLR4/MyD88/NF-κB/MAPK, miRNA/NLRP3, and COX signaling, along with shifts in immune cell populations and function. Limited evidence suggests similarities in pregnancies and offspring. In addition, suppressing these inflammatory molecules ameliorates IH-induced inflammation and tissue injury, providing new potential targets to treat OSA-associated cardiovascular diseases. This review will focus on the inflammatory mechanisms linking IH to cardiovascular dysfunction in males, pregnancies, and their offspring. The goal is to inspire further investigations into the understudied populations of pregnant females and their offspring, which ultimately uncover underlying mechanisms and therapeutic interventions for OSA-associated diseases.

Gestational intermittent hypoxia induces endothelial dysfunction and hypertension in pregnant rats: role of endothelin type B receptor†

Obstructive sleep apnea is a recognized risk factor for gestational hypertension, yet the exact mechanism behind this association remains unclear. Here, we tested the hypothesis that intermittent hypoxia, a hallmark of obstructive sleep apnea, induces gestational hypertension through perturbed endothelin-1 signaling. Pregnant Sprague-Dawley rats were subjected to normoxia (control), mild intermittent hypoxia (10.5% O2), or severe intermittent hypoxia (6.5% O2) from gestational days 10-21. Blood pressure was monitored. Plasma was collected and mesenteric arteries were isolated for myograph and protein analyses. The mild and severe intermittent hypoxia groups demonstrated elevated blood pressure, reduced plasma nitrate/nitrite, and unchanged endothelin-1 levels compared to the control group. Western blot analysis revealed decreased expression of endothelin type B receptor and phosphorylated endothelial nitric oxide synthase, while the levels of endothelin type A receptor and total endothelial nitric oxide synthase remained unchanged following intermittent hypoxia exposure. The contractile responses to potassium chloride, phenylephrine, and endothelin-1 were unaffected in endothelium-denuded arteries from mild and severe intermittent hypoxia rats. However, mild and severe intermittent hypoxia rats exhibited impaired endothelium-dependent vasorelaxation responses to endothelin type B receptor agonist IRL-1620 and acetylcholine compared to controls. Endothelium denudation abolished IRL-1620-induced vasorelaxation, supporting the involvement of endothelium in endothelin type B receptor-mediated relaxation. Treatment with IRL-1620 during intermittent hypoxia exposure significantly attenuated intermittent hypoxia-induced hypertension in pregnant rats. This was associated with elevated circulating nitrate/nitrite levels, enhanced endothelin type B receptor expression, increased endothelial nitric oxide synthase activation, and improved vasodilation responses. Our data suggested that intermittent hypoxia exposure during gestation increases blood pressure in pregnant rats by suppressing endothelin type B receptor-mediated signaling, providing a molecular mechanism linking intermittent hypoxia and gestational hypertension.