Long-term high altitude hypoxia during gestation suppresses large conductance Ca2+ -activated K+ channel function in uterine arteries: a causal role for microRNA-210

Ca2+-Activated K+ Channels and the Regulation of the Uteroplacental Circulation

Adequate uteroplacental blood supply is essential for the development and growth of the placenta and fetus during pregnancy. Aberrant uteroplacental perfusion is associated with pregnancy complications such as preeclampsia, fetal growth restriction (FGR), and gestational diabetes. The regulation of uteroplacental blood flow is thus vital to the well-being of the mother and fetus. Ca²⁺-activated K⁺ (K_Ca) channels of small, intermediate, and large conductance participate in setting and regulating the resting membrane potential of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) and play a critical role in controlling vascular tone and blood pressure. K_Ca channels are important mediators of estrogen/pregnancy-induced adaptive changes in the uteroplacental circulation. Activation of the channels hyperpolarizes uteroplacental VSMCs/ECs, leading to attenuated vascular tone, blunted vasopressor responses, and increased uteroplacental blood flow. However, the regulation of uteroplacental vascular function by K_Ca channels is compromised in pregnancy complications. This review intends to provide a comprehensive overview of roles of K_Ca channels in the regulation of the uteroplacental circulation under physiological and pathophysiological conditions.

Physiological and Pathophysiological Role of Large-Conductance Calcium-Activated Potassium Channels (BKCa) in HUVECs and Placenta

BKCa channels (large-conductance Ca2+-activated K+ channels) play a critical role in regulating vascular tone and blood pressure. These channels are present in the smooth muscle cells of blood vessels and are activated by voltage and increased intracellular Ca2+ concentration. More recently, the expression and activity of BKCa have been proposed to be relevant in endothelial cells, too, specifically in human umbilical vein endothelial cells (HUVECs), the more studied cell type in the fetoplacental circulation. The role of BKCa in endothelial cells is not well understood, but in HUVECs or placental endothelium, these channels could be crucial for vascular tone regulation during pregnancy as part of endothelium-derived hyperpolarization (EDH), a key mechanism for an organ that lacks nervous system innervation like the placenta.In this review, we will discuss the evidence about the role of BKCa (and other Ca2+-activated K+ channels) in HUVECs and the placenta to propose a physiological mechanism for fetoplacental vascular regulation and a pathophysiological role of BKCa, mainly associated with pregnancy pathologies that present maternal hypertension and/or placental hypoxia, like preeclampsia.

Comparison of relaxant effects of nifedipine and NS11021 on isolated umbilical arteries of healthy and preeclamptic pregnant women

OBJECTIVES

Potassium (K⁺) channel openers and calcium (Ca²⁺) channel blockers are currently used to treat acute severe hypertension in pregnancy. We aimed to investigate the vasorelaxant effect of NS11021, a potent and specific big-conductance Ca²⁺-activated K⁺ (BKCa) channel activator, and to compare it with the vasorelaxant effect of nifedipine on human umbilical arteries (HUAs) isolated from healthy and preeclamptic pregnants.

STUDY DESIGN

A total of 29 HUAs were isolated immediately after delivery from 14 healthy and 15 preeclamptic pregnant with severe features. The concentration-dependent relaxation responses were obtained to nifedipine and NS11021 on HUAs precontracted with endothelin-1 (ET-1) (10^-8 M) in an isolated tissue bath.

RESULTS

Both nifedipine and NS11021 caused concentration-dependent relaxation responses in HUAs from healthy and preeclamptic pregnants. While the maximum responses (Emax) and pD₂ values of nifedipine did not change significantly in both groups, the Emax and pD₂ values of NS11021 were significantly decreased in the preeclampsia group (Emax ± SEM; %75.57 ± 4.53 and %43.75 ± 14.00 and pD₂ ± SEM; 6.92 ± 0.26 and 5.24 ± 0.53 respectively, p < 0.05). In addition, the pD₂ value of NS11021 was not significantly different from that of nifedipine in the control group, but decreased significantly in the preeclampsia group (pD₂ ± SEM 7.1 ± 0.41 and 5.2 ± 0.53, p < 0.05, respectively).

CONCLUSIONS

Efficacy and potency of NS11021 decreased in HUAs from preeclamptic pregnants. Also, NS11021 is less potent than nifedipine in the preeclampsia group. BKCa channels may have a role in the pathogenesis of preeclampsia, however, further experimental studies are needed to elucidate that.

TET1 involved in bisphenol A induced TM3 Leydig cell toxicity by regulating Cav3.3 hydroxymethylation

Bisphenol A (BPA), an important environmental pollutant, is known to damage reproductive development. However, the underlying epigenetic mechanism in Leydig cells during BPA exposure has not been explored in detail. In this study, TM3 Leydig cells were treated with BPA (0, 20, 40 and 80 μM) for 72 h. The differentially expressed TET1 cell model was constructed to explore the mechanism of BPA-induced cytotoxicity. Results showed that BPA exposure significantly inhibited cell viability and increased apoptosis of TM3 Leydig cells. Meanwhile, the mRNA of TET1, Cav3.2 and Cav3.3 decreased significantly with the increase of BPA exposure. Importantly, TET1 significantly promoted proliferation of TM3 Leydig cells and inhibited apoptosis. Differentially expressed TET1 significantly affected BPA-induced toxicity in TM3 Leydig cells. Notably, TET1 elevated the mRNA levels of Cav3.2 and Cav3.3. MeDIP and hMeDIP confirmed that TET1 regulated the expression of Cav3.3 through DNA hydroxymethylation. Our study firstly presented that TET1 participated in BPA-induced toxicity in TM3 Leydig cells through regulating Cav3.3 hydroxymethylation modification. These findings suggest that TET1 acts as a potential epigenetic marker for reproductive toxicity induced by BPA exposure and may provide a new direction for the research on male reproductive damage.

High altitude differentially modulates potassium channel-evoked vasodilatation in pregnant human myometrial arteries

High-altitude (>2500 m or 8200 ft) residence reduces uterine artery blood flow during pregnancy, contributing to an increased incidence of preeclampsia and intrauterine growth restriction. However, not all pregnancies are affected by the chronic hypoxic conditions of high-altitude residence. K+ channels play important roles in the uterine vascular adaptation to pregnancy, promoting a reduction in myogenic tone and an increase in blood flow. We hypothesized that, in pregnancies with normal fetal growth at high altitude, K+ channel-dependent vasodilatation of myometrial arteries is increased compared to those from healthy pregnant women at a lower altitude (∼1700 m). Using pharmacological modulation of two K+ channels, ATP-sensitive (KATP ) and large-conductance Ca2+ -activated (BKCa ) K+ channels, we assessed the vasodilatation of myometrial arteries from appropriate for gestational age (AGA) pregnancies in women living at high or low altitudes. In addition, we evaluated the localization of these channels in the myometrial arteries using immunofluorescence. Our results showed an endothelium-dependent increase in KATP -dependent vasodilatation in myometrial arteries from high versus low altitude, whereas vasodilatation induced by BKCa activation was reduced in these vessels. Additionally, KATP channel co-localization with endothelial markers was reduced in the high-altitude myometrial arteries, which suggested that the functional increase in KATP activity may be by mechanisms other than regulation of channel localization. These observations highlight an important contribution of K+ channels to the human uterine vascular adaptation to pregnancy at high altitude serving to maintain normal fetal growth under conditions of chronic hypoxia. KEY POINTS: High-altitude (>2500 m or 8200 ft) residence reduces uterine blood flow during pregnancy and fetal growth. Animal models of high altitude/chronic hypoxia suggest that these reductions are partially due to reduced vascular K+. channel responses, such as those elicited by large conductance Ca2+ -activated (BKCa ) and ATP-sensitive (KATP ) K+ channel activation. We found that women residing at high versus low altitude during pregnancy showed diminished myometrial artery vasodilatory responses to endothelium-independent BKCa channel activation but greater responses to endothelium-dependent KATP channel activation. Our observations indicate that KATP channels play an adaptive role in maintaining myometrial artery vasodilator sensitivity under chronic hypoxic conditions during pregnancy. Thus, KATP channels represent potential therapeutic targets for augmenting uteroplacental blood flow and, in turn, preserving fetal growth in cases of uteroplacental hypoperfusion.

Potassium Channels in the Uterine Vasculature: Role in Healthy and Complicated Pregnancies

A progressive increase in maternal uterine and placental blood flow must occur during pregnancy to sustain the development of the fetus. Changes in maternal vasculature enable an increased uterine blood flow, placental nutrient and oxygen exchange, and subsequent fetal development. K⁺ channels are important modulators of vascular function, promoting vasodilation, inducing cell proliferation, and regulating cell signaling. Different types of K⁺ channels, such as Ca²⁺-activated, ATP-sensitive, and voltage-gated, have been implicated in the adaptation of maternal vasculature during pregnancy. Conversely, K⁺ channel dysfunction has been associated with vascular-related complications of pregnancy, including intrauterine growth restriction and pre-eclampsia. In this article, we provide an updated and comprehensive literature review that highlights the relevance of K⁺ channels as regulators of uterine vascular reactivity and their potential as therapeutic targets.

Uteroplacental Circulation in Normal Pregnancy and Preeclampsia: Functional Adaptation and Maladaptation

Uteroplacental blood flow increases as pregnancy advances. Adequate supply of nutrients and oxygen carried by uteroplacental blood flow is essential for the well-being of the mother and growth/development of the fetus. The uteroplacental hemodynamic change is accomplished primarily through uterine vascular adaptation, involving hormonal regulation of myogenic tone, vasoreactivity, release of vasoactive factors and others, in addition to the remodeling of spiral arteries. In preeclampsia, hormonal and angiogenic imbalance, proinflammatory cytokines and autoantibodies cause dysfunction of both endothelium and vascular smooth muscle cells of the uteroplacental vasculature. Consequently, the vascular dysfunction leads to increased vascular resistance and reduced blood flow in the uteroplacental circulation. In this article, the (mal)adaptation of uteroplacental vascular function in normal pregnancy and preeclampsia and underlying mechanisms are reviewed.

Hypoxia and the integrated stress response promote pulmonary hypertension and preeclampsia: Implications in drug development

Chronic hypoxia is a common cause of pulmonary hypertension, preeclampsia, and intrauterine growth restriction (IUGR). The molecular mechanisms underlying these diseases are not completely understood. Chronic hypoxia may induce the generation of reactive oxygen species (ROS) in mitochondria, promote endoplasmic reticulum (ER) stress, and result in the integrated stress response (ISR) in the pulmonary artery and uteroplacental tissues. Numerous studies have implicated hypoxia-inducible factors (HIFs), oxidative stress, and ER stress/unfolded protein response (UPR) in the development of pulmonary hypertension, preeclampsia and IUGR. This review highlights the roles of HIFs, mitochondria-derived ROS and UPR, as well as their interplay, in the pathogenesis of pulmonary hypertension and preeclampsia, and their implications in drug development.

The newborn sheep translational model for pulmonary arterial hypertension of the neonate at high altitude

Chronic hypoxia during gestation induces greater occurrence of perinatal complications such as intrauterine growth restriction, fetal hypoxia, newborn asphyxia, and respiratory distress, among others. This condition may also cause a failure in the transition of the fetal to neonatal circulation, inducing pulmonary arterial hypertension of the neonate (PAHN), a syndrome that involves pulmonary vascular dysfunction, increased vasoconstrictor tone and pathological remodeling. As this syndrome has a relatively low prevalence in lowlands (~7 per 1000 live births) and very little is known about its prevalence and clinical evolution in highlands (above 2500 meters), our understanding is very limited. Therefore, studies on appropriate animal models have been crucial to comprehend the mechanisms underlying this pathology. Considering the strengths and weaknesses of any animal model of human disease is fundamental to achieve an effective and meaningful translation to clinical practice. The sheep model has been used to study the normal and abnormal cardiovascular development of the fetus and the neonate for almost a century. The aim of this review is to highlight the advances in our knowledge on the programming of cardiopulmonary function with the use of high-altitude newborn sheep as a translational model of PAHN.

Pregnancy-related acute kidney injury at high altitude: a retrospective observational study in a single center

Background

Pregnancy-related acute kidney injury (Pr-AKI) is associated with maternal and fetal morbidity and mortality. There are few studies focusing on Pr-AKI at high altitude in the literature.

Objectives

to investigate the incidence, etiology, clinical features and maternal-fetal outcomes of Pr-AKI in women living at high altitude.

Methods

6,512 pregnant women attending the Department of Obstetrics & Gynecology at local hospital from January 2015 to December 2018 were screened for Pr-AKI. Patients with serum creatinine above normal range(> 70umol/L) then underwent assessment to confirm the diagnosis of Pr-AKI. AKI was diagnosed and staged based on Kidney Disease Improving Global Outcomes(KDIGO) guideline. Individuals meeting the Pr-AKI criteria were recruited. Their clinical data were recorded and retrospectively analyzed.

Results

Pr-AKI was identified in 136/6512(2.09 %) patients. Hypertensive disorders of pregnancy(HDP) was the leading cause of Pr-AKI(35.3 %). 4(2.9 %) women died and the majority(86.1 %) had recovered renal function before discharge. Fetal outcomes were confirmed in 109 deliveries with gestational age ≥ 20 weeks. Pre-term delivery occurred in 30(27.3 %) cases and perinatal deaths in 17(15.5 %). The rate of low birth weight infant(LBWI) and intrauterine growth restriction(IUGR) was 22.0 and 10.9 % respectively. 16(14.5 %) infants were admitted to NICU after birth. Patients with HDP had a higher cesarean rate(56.3 %). More IUGR(25.0 %) and LBWI(37.8 %) were observed in their infants with a higher risk of admission to NICU(22.0 %). High altitude might have an adverse impact on HDP-related Pr-AKI patients with earlier terminated pregnancy and more stillbirth/neonatal death. Logistic regression models indicated that uncontrolled blood pressure, high altitude and advanced AKI were associated with adverse fetal outcomes in HDP-related Pr-AKI patients.

Conclusions

Pr-AKI was not rare in high-altitude regions and caused severe fetal morbidities and mortalities. Uncontrolled blood pressure, high altitude and advanced AKI were all risk factors for adverse fetal outcomes in Pr-AKI patients, especially for those with hypertensive disorders of pregnancy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02418-7.

Hypoxia and Mitochondrial Dysfunction in Pregnancy Complications

Hypoxia is a common and severe stress to an organism's homeostatic mechanisms, and hypoxia during gestation is associated with significantly increased incidence of maternal complications of preeclampsia, adversely impacting on the fetal development and subsequent risk for cardiovascular and metabolic disease. Human and animal studies have revealed a causative role of increased uterine vascular resistance and placental hypoxia in preeclampsia and fetal/intrauterine growth restriction (FGR/IUGR) associated with gestational hypoxia. Gestational hypoxia has a major effect on mitochondria of uteroplacental cells to overproduce reactive oxygen species (ROS), leading to oxidative stress. Excess mitochondrial ROS in turn cause uteroplacental dysfunction by damaging cellular macromolecules, which underlies the pathogenesis of preeclampsia and FGR. In this article, we review the current understanding of hypoxia-induced mitochondrial ROS and their role in placental dysfunction and the pathogenesis of pregnancy complications. In addition, therapeutic approaches selectively targeting mitochondrial ROS in the placental cells are discussed.

MicroRNA-210 Mediates Hypoxia-Induced Repression of Spontaneous Transient Outward Currents in Sheep Uterine Arteries During Gestation

[Figure: see text].

TET1 may contribute to hypoxia-induced epithelial to mesenchymal transition of endometrial epithelial cells in endometriosis

Background

Endometriosis (EMs) is a non-malignant gynecological disease, whose pathogenesis remains to be clarified. Recent studies have found that hypoxia induces epithelial-mesenchymal transition (EMT) as well as epigenetic modification in EMs. However, the relationship between EMT and demethylation modification under hypoxia status in EMs remains unknown.

Methods

The expression of N-cadherin, E-cadherin and TET1 in normal endometria, eutopic endometria and ovarian endometriomas was assessed by immunohistochemistry and immunofluorescence double staining. 5-hmC was detected by fluorescence-based ELISA kit using a specific 5-hmC antibody. Overexpression and inhibition of TET1 or hypoxia-inducible factor 2α (HIF-2α) were performed by plasmid and siRNA transfection. The expression of HIF-2α, TET1 and EMT markers in Ishikawa (ISK) cells (widely used as endometrial epithelial cells) was evaluated by western blotting. The interaction of HIF-2α and TET1 was analyzed by chromatin immunoprecipitation.

Results

Demethylation enzyme TET1 (ten-eleven translocation1) was elevated in glandular epithelium of ovarian endometrioma, along with the activation of EMT (increased expression of N-cadherin, and decreased expression of E-cadherin) and global increase of epigenetic modification marker 5-hmC(5-hydroxymethylcytosine). Besides, endometriosis lesions had more TET1 and N-cadherin co-localized cells. Further study showed that ISK cells exhibited enhanced EMT, and increased expression of TET1 and HIF-2α under hypoxic condition. Hypoxia-induced EMT was partly regulated by TET1 and HIF-2α. HIF-2α inhibition mitigated TET1 expression changes provoked by hypoxia.

Conclusions

Hypoxia induces the expression of TET1 regulated by HIF-2α, thus may promote EMT in endometriosis.

Gestational Hypoxia Inhibits Pregnancy-Induced Upregulation of Ca2+ Sparks and Spontaneous Transient Outward Currents in Uterine Arteries Via Heightened Endoplasmic Reticulum/Oxidative Stress

Hypoxia during pregnancy profoundly affects uterine vascular adaptation and increases the risk of pregnancy complications, including preeclampsia and fetal intrauterine growth restriction. We recently demonstrated that increases in Ca2+ sparks and spontaneous transient outward currents (STOCs) played an essential role in pregnancy-induced uterine vascular adaptation. In the present study, we hypothesize that gestational hypoxia suppresses Ca2+ sparks/STOCs coupling leading to increased uterine vascular tone via enhanced endoplasmic reticulum (ER)/oxidative stress. Uterine arteries were obtained from nonpregnant and near-term pregnant sheep residing in low altitude or acclimatizing to high-altitude (3801 m) hypoxia for ≈110 days. High-altitude hypoxia suppressed pregnancy-induced upregulation of RyR1 and RyR2 (ryanodine receptor 1 and 2) protein abundance, Ca2+ sparks, and STOCs in uterine arteries. Inhibition of Ca2+ sparks/STOCs with the RyR inhibitor ryanodine significantly increased pressure-dependent myogenic tone in uterine arteries from low-altitude normoxic pregnant animals but not those from high-altitude hypoxic pregnant animals. Gestational hypoxia significantly increased ER/oxidative stress in uterine arteries. Of importance, the hypoxia-mediated suppression of Ca2+ sparks/STOCs and increase in myogenic tone in uterine arteries of pregnant animals were reversed by inhibiting ER/oxidative stress. Of great interest, the impaired sex hormonal regulation of STOCs in high-altitude animals was annulled by scavenging reactive oxygen species but not by inhibiting ER stress. Together, the findings reveal the differential mechanisms of ER and oxidative stresses in suppressing Ca2+ sparks/STOCs and increasing myogenic tone of uterine arteries in hypoxia during gestation, providing new insights into the understanding of pregnancy complications associated with hypoxia.

Exploring the beneficial effects and possible mechanisms of repeated episodes of whole-body hypoxic perconditioning in rat model of preeclampsia

AIM

The study explored the beneficial effects of repeated episodes of whole body hypoxic perconditioning (WHPC) on preeclampsia (PE)-like symptoms in rats.

MATERIAL AND METHODS

PE was induced by administration of L-NAME (75 mg/kg) and WHPC was performed by exposing rats to low O₂ (8%) and normal O₂ of 10 min each in four alternate cycles.

RESULTS

L-NAME induced PE like symptoms in rats along with a decrease in the cystathionine-β-synthase (CBS) activity in the placental tissue, plasma levels of H₂S and NO metabolites in pregnant rats. Two (GD9, GD14) and three episodes (GD9, GD14 and GD18) of WHPC improved PE-like symptoms with an increase in CBS activity and H₂S levels. CBS inhibitor, amino-oxyacetic acid abolished the beneficial effects of three episodes of WHPC; while H₂S donor, 4-methylbenzenecarbothioamide, 4-MBC attenuated PE-like symptoms.

CONCLUSION

WHPC attenuates L-NAME-induced PE-like symptoms due to increase in CBS activity and H₂S-production.

MicroRNAs in Uteroplacental Vascular Dysfunction

Pregnancy complications of preeclampsia and intrauterine growth restriction (IUGR) are major causes of maternal and perinatal/neonatal morbidity and mortality. Although their etiologies remain elusive, it is generally accepted that they are secondary to placental insufficiency conferred by both failure in spiral artery remodeling and uteroplacental vascular malfunction. MicroRNAs (miRNAs) are small no-coding RNA molecules that regulate gene expression at the post-transcriptional level. Increasing evidence suggests that miRNAs participate in virtually all biological processes and are involved in numerous human diseases. Differentially expressed miRNAs in the placenta are typical features of both preeclampsia and IUGR. Dysregulated miRNAs target genes of various signaling pathways in uteroplacental tissues, contributing to the development of both complications. In this review, we provide an overview of how aberrant miRNA expression in preeclampsia and IUGR impacts the expression of genes involved in trophoblast invasion and uteroplacental vascular adaptation.

Effect of Oxidative Stress on the Estrogen-NOS-NO-KCa Channel Pathway in Uteroplacental Dysfunction: Its Implication in Pregnancy Complications

During pregnancy, the adaptive changes in uterine circulation and the formation of the placenta are essential for the growth of the fetus and the well-being of the mother. The steroid hormone estrogen plays a pivotal role in this adaptive process. An insufficient blood supply to the placenta due to uteroplacental dysfunction has been associated with pregnancy complications including preeclampsia and intrauterine fetal growth restriction (IUGR). Oxidative stress is caused by an imbalance between free radical formation and antioxidant defense. Pregnancy itself presents a mild oxidative stress, which is exaggerated in pregnancy complications. Increasing evidence indicates that oxidative stress plays an important role in the maladaptation of uteroplacental circulation partly by impairing estrogen signaling pathways. This review is aimed at providing both an overview of our current understanding of regulation of the estrogen-NOS-NO-K_Ca pathway by reactive oxygen species (ROS) in uteroplacental tissues and a link between oxidative stress and uteroplacental dysfunction in pregnancy complications. A better understanding of the mechanisms will facilitate the development of novel and effective therapeutic interventions.

Epigenetic down-regulation of BKCa channel by miR-181a contributes to the fetal and neonatal nicotine-mediated exaggerated coronary vascular tone in adult life

BACKGROUND

Fetal origin of adult cardiovascular disease is one of the most pressing public concerns and economic problem in modern life. Maternal cigarette smoking/nicotine abuse increases the risk of cardiovascular disease in offspring. However, the underlying mechanisms and theranostics remain unclear. We hypothesized that fetal and neonatal nicotine exposure enhances microRNA-181a (miR-181a) which targets large-conductance Ca²⁺-activated K⁺ (BK_Ca) channels, resulting in increased coronary vascular tone in adult offspring.

METHODS

Nicotine or saline was administered to pregnant rats via subcutaneous osmotic minipumps from gestational day 4 until postnatal day 10. Experiments were conducted in adult (~6 month old) male offspring.

RESULTS

Nicotine enhanced pressure-induced coronary vascular tone, which was abrogated by BK_Ca channel blocker. Nicotine selectively attenuated coronary BK_Ca β1 but not α subunit expression. Functionally, nicotine suppressed BK_Ca current density and inhibited BK_Ca activator NS1619-induced coronary relaxations. Furthermore, activation of BK_Ca increased coronary flow and improved heart ischemia/reperfusion-induced infarction. Nicotine selectively enhanced miR-181a expression. MiR-181a mimic inhibited BK_Ca β1 expression/channel current and decreased NS1619-induced coronary relaxation. Antioxidant eliminated the difference of BK_Ca current density between the saline and nicotine-treated groups and partially restored NS1619-induced relaxation in nicotine group. MiR-181a antisense decreased vascular tone and eliminated the differences between nicotine exposed and control groups.

CONCLUSION

Fetal and neonatal nicotine exposure-mediated miR-181a overexpression plays an important role in nicotine-enhanced coronary vascular tone via epigenetic down-regulation of BK_ca channel mechanism, which provides a potentially novel therapeutic molecular target of miR-181a/BK_ca channels for the treatment of coronary heart ischemic disease.

Potential role for microRNA in facilitating physiological adaptation to hypoxia in the Pacific whiteleg shrimp Litopenaeus vannamei

Hypoxia is one of the most common physiological stressors in shrimp farming. Post-transcriptional regulation by microRNAs has been recognized as a ubiquitous strategy to enable transient phenotypic plasticity and adaptation to stressful environment, but involvement of microRNAs in hypoxia stress response of penaeid shrimp remains elusive. In this study, small RNA sequencing and comparative transcriptomic analysis was conducted to construct a comprehensive microRNA dataset for the whiteleg shrimp Litopenaeus vannamei exposed to hypoxia challenge. A total of 3324 known miRNAs and 8 putative novel miRNAs were identified, providing a valuable resource for future investigation on the functional mechanism of miRNAs in shrimp. Upon hypoxia, 1213 miRNAs showed significant differential expression, and many well-known miRNAs involved in hypoxia tolerance such as miR-210, let-7, miR-143 and miR-101 were identified. Remarkably, the vast majority of these miRNAs were up-regulated, suggesting that up-regulation of miRNAs may represent an effective strategy to inhibit protein translation under stressful hypoxic condition. The differentially expressed miRNAs were potentially targeting a wide variety of genes, including those with essential roles in hypoxia tolerance such as HIF1a and p53. GO and KEGG enrichment analysis further revealed that a broad range of biological processes and metabolic pathways were over-represented. Several GO terms associated with gene transcription and translation and KEGG pathways related to cytoskeleton remodeling, immune defense and signaling transduction were enriched, highlighting the crucial roles of these cellular events in the adaptation to hypoxia. Taken together, our study revealed that the differentially expressed miRNAs may regulate host response to hypoxia by modulating the expression of stress response genes such as HIF1a and p53 and affecting key cellular events involved in hypoxia adaptation. The findings would expand our knowledge of the biochemical and molecular underpinnings of hypoxia response strategies used by penaeid shrimp, and contribute to a better understanding of the molecular mechanisms of hypoxia tolerance in decapod crustaceans.