Exposure to ethanol and nicotine induces stress responses in human placental BeWo cells

The invisible enemy: A systematic review and meta-analysis of maternal smokeless tobacco use as a risk factor for low birth weight

INTRODUCTION

Smokeless tobacco use is a growing public health concern, with potential adverse implications for foetal outcomes if consumed during pregnancy. Birth weight is an important predictive measure for health outcomes of a child throughout their lifespan. Despite extensive literature, it is unclear whether smokeless tobacco consumption during pregnancy has an adverse effect on birth weight. Hence, this review was conducted to determine whether an association exists between maternal smokeless tobacco consumption during pregnancy and birth weight of infants.

METHODS

Systematic literature search was performed in Medline (via PubMed), Embase, Scopus, and CINAHL with no restrictions on language or time until May 2024. All observational studies that examined the relationship between maternal smokeless tobacco use and low birth weight of infants were eligible for inclusion. Methodological quality of included studies was assessed using the Newcastle Ottawa Scale.

RESULTS

Thirty-three studies were eligible for the review, including twenty-eight cohort, three case-control and two cross-sectional studies. A statistically significant association between use of smokeless tobacco and low birth weight was reported in thirteen studies. Eleven studies reported a statistically significant reduction in mean birth weight in maternal smokeless tobacco users. Pooled estimates of eighteen studies with 733,061 participants showed that there was a statistically significant association (OR = 2.25 [1.63, 3.11] P<0.001); between maternal smokeless tobacco use during pregnancy and low birth weight. Subgroup analysis found a significant association between mishri consumption during pregnancy and low birth weight (n = 646 participants, OR = 10.98 [2.03, 59.34], P = 0.005), but not betel nut (n = 8007 participants, OR = 1.02 [0.84, 1.25]), betel quid (n = 483 participants, OR = 1.51 [0.47, 4.89]) or khat (n = 475 participants, OR = 1.41 [0.64-3.09]).

CONCLUSIONS

This review presents an association between maternal smokeless tobacco use and low birth weight, and reduction in mean birth weight. It is suggested that cessation and reduction of maternal smokeless tobacco use should receive specific attention within routine prenatal care.

IMPLICATIONS

The results of this study highlight the need for further preventive public health campaigns to create awareness about detrimental effects of smokeless tobacco on foetal outcomes. Patient education in the primary care setting will aid in promoting smokeless tobacco cessation prior to pregnancy.

A stress paradox: the dual role of the unfolded protein response in the placenta

The placenta is a temporary organ that forms during pregnancy and is essential for fetal development and maternal health. As an endocrine organ, proper placental function requires continual production, folding, and transport of proteins and lipids. Central to these processes is the endoplasmic reticulum (ER), a dynamic organelle responsible for maintaining cellular protein and lipid synthesis and processing. ER stress occurs when there is an accumulation of unfolded or misfolded proteins, which triggers the activation of cellular pathways collectively called the unfolded protein response. Unfolded protein response pathways act to alleviate the misfolded protein burden and restore ER homeostasis, or if unresolved, initiate cell death. While prolonged ER stress has been linked to deficient placental function and adverse pregnancy outcomes, basal activation of unfolded protein response pathways is required for placental development and function. This review explores the importance of ER homeostasis in placental development and function, examining how disruptions in ER stress responses may contribute to adverse pregnancy outcomes.

Low levels of nicotine and cotinine but not benzo[a]pyrene induce human trophoblast cell proliferation

E-cigarettes use constitutes a source of thirdhand nicotine exposure. The increasing use of electronic cigarettes in homes and public places increases the risk of exposure of pregnant women to thirdhand nicotine. The effects of exposure of pregnant women to very low levels of nicotine have not been studied in humans but detrimental in experimental animals. The objective of this study is to investigate the effect of nanomolar concentrations of nicotine and its metabolite cotinine on the proliferation of JEG-3, a human trophoblast cell line. We also studied the proliferative effect of nanomolar concentrations of benzo[a]pyrene (B[a]P), a polycyclic hydrocarbon in tobacco smoke, for comparison. We treated JEG-3 cells in culture with nanomolar concentrations of nicotine, cotinine, and B[a]P. Their effect on cell proliferation was determined, relative to untreated cells, by MTT assay. Western blotting was used to assess the mitogenic signaling pathways affected by nicotine and cotinine. In contrast to the inhibitory effects reported with higher concentrations, we showed that nanomolar concentrations of nicotine and cotinine resulted in significant JEG-3 cell proliferation and a rapid but transient increase in levels of phosphorylated ERK and AKT, but not STAT3. Biphasic, non-monotonic effect on cell growth is characteristic of endocrine disruptive chemicals like nicotine. The mitogenic effects of nicotine and cotinine potentially contribute to increased villous epithelial thickness, seen in placentas of some smoking mothers. This increases the diffusion distance for oxygen and nutrients between mother and fetus, contributing to intrauterine growth restriction in infants of smoking mothers.

The effect of ethanol and nicotine on ER stress in human placental villous explants

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Nicotine increased the GRP78/BiP protein in first trimester and term placental villous explants.

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Nicotine can cause endoplasmic reticulum stress in human placenta.

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Placental villous explants can be isolated from first trimester and term placenta to compare responses to toxic compounds.

Pregnant mothers continue smoking and drinking during pregnancy. To clarify the mechanisms of nicotine and ethanol toxicity during development, we have examined their effects on endoplasmic reticulum (ER) stress in human first trimester and term placental explants. First trimester and term human placental explants were treated with ethanol (2 ‰) or nicotine (15 µM), or their combination. The ER stress markers glucose regulated protein 78 (GRP78/BiP) and inositol requiring enzyme 1 α (IRE1α) were analyzed by immunoblotting. A statistically significant increase (p < 0.05) of GRP78/BiP by nicotine was noted in first trimester placental explants at 48 h, and in term placental explants at 24 h. Ethanol did not change protein expression of GRP78/BiP in either first trimester or term placental explants. IRE1α increased, although not statistically significantly, by all treatments in both first trimester and term placental explants. Thus, regardless of the known structural and functional differences in early and late placenta, both responded very similarly to the toxic compounds studied. These data support our earlier results in BeWo cells (Repo et al., 2014) implicating that nicotine induces ER stress in human placenta and may interfere with placental functions potentially disrupting fetal growth and development.

Smoking for two- effects of tobacco consumption on placenta

Tobacco smoking is an important public health issue recognized by the world health organization as one of the most serious, preventable risk factors for developing a series of pregnancy pathologies. Maternal smoking is positively associated with intrauterine growth restriction (IUGR) and gestational diabetes (GDM), but negatively associated with preeclampsia (PE). In this review, we examine epidemiological, clinical and laboratory studies of smoking effects on immunoregulation during pregnancy, trophoblast function, and placental vasculature development and metabolism. We aim to identify effects of tobacco smoke components on specific placental compartments or cells, which may contribute to the understanding of the influences of maternal smoking on placenta function in normal and pathological pregnancies. Data corroborates that in any trimester, smoking is unsafe for pregnancy and that its detrimental effects outweigh questionable benefits. The effects of maternal smoking on the maternal immune regulation throughout pregnancy and the impact of different tobacco products on fetal growth have not yet been fully understood. Smoking cessation rather than treatment with replacement therapies is recommended for future mothers because also single components of tobacco and its smoke may have detrimental effects on placental function.

YAP-Dependent BiP Induction Is Involved in Nicotine-Mediated Oral Cancer Malignancy

Cigarette smoking is a significant risk factor for the development and progression of oral cancer. Previous studies have reported an association between nicotine and malignancy in oral cancer. Recent studies have also demonstrated that nicotine can induce endoplasmic reticulum (ER) stress in tumor cells. Binding immunoglobulin protein (BiP) acts as a master regulator of ER stress and is frequently overexpressed in oral cancer cell lines and tissues. However, the effect of nicotine on BiP in oral cancer is unknown. Therefore, this study aimed to evaluate the role of BiP and its underlying regulatory mechanisms in nicotine-induced oral cancer progression. Our results showed that nicotine significantly induced the expression of BiP in time- and dose-dependent manners in oral squamous cell carcinoma (OSCC) cells. In addition, BiP was involved in nicotine-mediated OSCC malignancy, and depletion of BiP expression remarkably suppressed nicotine-induced malignant behaviors, including epithelial-mesenchymal transition (EMT) change, migration, and invasion. In vivo, BiP silencing abrogated nicotine-induced tumor growth and EMT switch in nude mice. Moreover, nicotine stimulated BiP expression through the activation of the YAP-TEAD transcriptional complex. Mechanistically, we observed that nicotine regulated YAP nuclear translocation and its interaction with TEAD through α7-nAChR-Akt signaling, subsequently resulting in increased TEAD occupancy on the HSPA5 promoter and elevated promoter activity. These observations suggest that BiP is involved in nicotine-induced oral cancer malignancy and may have therapeutic potential in tobacco-related oral cancer.

The role of unfolded protein response in the pathogenesis of endometriosis: contribution of peritoneal fluid

RESEARCH QUESTION

Endoplasmic reticulum stress (ERS) is caused by the accumulation of the misfolded or unfolded proteins in the endoplasmic reticulum and induces the unfolded protein response (UPR). Peritoneal fluid is important in the pathogenesis of endometriosis. In this study, the role of UPR associated with ERS in endometriosis, and peritoneal fluid, were investigated.

DESIGN

Normal, eutopic and ectopic endometrium tissues were divided into menstrual cycle phases, and endometrial stromal cells (ESC) were treated with 10-20% concentration of control peritoneal fluid and peritoneal fluid obtained from women with endometriosis for 10, 30 and 60 min, and 24 and 48 h. The UPR signalling proteins were analysed immunohistochemically and immunocytochemically. Data were compared statistically.

RESULTS

p-IRE1 was increased in ectopic glandular and stromal cells in the early proliferative phase compared with normal and eutopic endometrium. p-PERK increased in ectopic glandular and stromal cells in the late proliferative phase compared with normal endometrium. ATF6 was increased in ectopic glandular epithelium compared with normal endometrium in the proliferative phases, versus eutopic endometrium in the late secretory phase. p-IRE1 and p-PERK were increased in high concentrations of ESC treated with peritoneal fluid obtained from women with endometriosis for 10, 30 and 60 min compared with controls. In ESC treated with peritoneal fluid from women with endometriosis, p-IRE1 decreased at 24-48 h compared with 30 min.

CONCLUSIONS

In endometriosis, UPR pathways are activated as highly dependent on cell type and phase. Also, p-PERK and p-IRE1 increased because of exposure to high-dose peritoneal fluid from women with endometriosis in stromal cells. Our findings provide a basis for further studies searching for a potential biomarker for the diagnosis of endometriosis.

The impact of tobacco chemicals and nicotine on placental development

Despite decades of messages warning about the dangers of tobacco use in pregnancy, 10% to 15% of pregnant women continue to smoke. Furthermore, an increased popularity of electronic nicotine delivery systems (ENDS) over the past decade in women of childbearing age raises parallel concerns regarding the effects of vaporized nicotine use in pregnancy. While research using animal models which mimic tobacco smoke and nicotine exposure in pregnancy have largely replicated findings in humans, few studies focus directly on the effects of these exposures on the placenta. Because the placenta is a fetal derived tissue, and nicotine and other components of tobacco smoke are either processed by or transported directly through the placenta, such studies help us understand the risks of these exposures on the developing fetus. In this review, we summarize research on the placenta and placental-derived cells examining either tobacco smoke or nicotine exposure, including both histologic and subcellular (ie, epigenetic and molecular) modifications. Collectively, these studies reveal that tobacco and nicotine exposure are accompanied by some common and several unique molecular and epigenomic placental modifications. Consideration of the nature and sequelae of these molecular mediators of risk may help to better inform the public and more effectively curtail modifiable behavior.

Δ9-tetrahydrocannabinol exposure during rat pregnancy leads to symmetrical fetal growth restriction and labyrinth-specific vascular defects in the placenta

1 in 5 women report cannabis use during pregnancy, with nausea cited as their primary motivation. Studies show that (-)-△9-tetrahydrocannabinol (Δ9-THC), the major psychoactive ingredient in cannabis, causes fetal growth restriction, though the mechanisms are not well understood. Given the critical role of the placenta to transfer oxygen and nutrients from mother, to the fetus, any compromise in the development of fetal-placental circulation significantly affects maternal-fetal exchange and thereby, fetal growth. The goal of this study was to examine, in rats, the impact of maternal Δ9-THC exposure on fetal development, neonatal outcomes, and placental development. Dams received a daily intraperitoneal injection (i.p.) of vehicle control or Δ9-THC (3 mg/kg) from embryonic (E)6.5 through 22. Dams were allowed to deliver normally to measure pregnancy and neonatal outcomes, with a subset sacrificed at E19.5 for placenta assessment via immunohistochemistry and qPCR. Gestational Δ9-THC exposure resulted in pups born with symmetrical fetal growth restriction, with catch up growth by post-natal day (PND)21. During pregnancy there were no changes to maternal food intake, maternal weight gain, litter size, or gestational length. E19.5 placentas from Δ9-THC-exposed pregnancies exhibited a phenotype characterized by increased labyrinth area, reduced Epcam expression (marker of labyrinth trophoblast progenitors), altered maternal blood space, decreased fetal capillary area and an increased recruitment of pericytes with greater collagen deposition, when compared to vehicle controls. Further, at E19.5 labyrinth trophoblast had reduced glucose transporter 1 (GLUT1) and glucocorticoid receptor (GR) expression in response to Δ9-THC exposure. In conclusion, maternal exposure to Δ9-THC effectively compromised fetal growth, which may be a result of the adversely affected labyrinth zone development. These findings implicate GLUT1 as a Δ9-THC target and provide a potential mechanism for the fetal growth restriction observed in women who use cannabis during pregnancy.

Δ9-Tetrahydrocannabinol leads to endoplasmic reticulum stress and mitochondrial dysfunction in human BeWo trophoblasts

While studies have demonstrated that the main psychoactive component of cannabis, Δ9-tetrahydrocannabinol (Δ9-THC) alone induces placental insufficiency and fetal growth restriction, the underlying mechanisms remain elusive. Given that both (i) endoplasmic reticulum (ER) stress in pregnancy and (ii) gestational exposure to Δ9-THC leads to placental deficiency, we hypothesized that Δ9-THC may directly induce placental ER stress, influencing trophoblast gene expression and mitochondrial function. BeWo human trophoblast cells treated with Δ9-THC (3-30 μM) led to a dose-dependent increase in all ER stress markers and CHOP; these effects could be blocked with CB1R/CB2R antagonists. Moreover, expression of ER stress-sensitive genes ERRγ, VEGFA, and FLT-1 were increased by Δ9-THC, and abrogated with the ER stress inhibitor TUDCA. Δ9-THC also diminished mitochondrial respiration and ATP-coupling due to decreased abundance of mitochondrial chain complex proteins. Collectively, these findings indicate that Δ9-THC can directly augment ER stress resulting in aberrant placental gene expression and impaired mitochondrial function.

Single-Cell RNA Sequencing of Human Embryonic Stem Cell Differentiation Delineates Adverse Effects of Nicotine on Embryonic Development

Nicotine, the main chemical constituent of tobacco, is highly detrimental to the developing fetus by increasing the risk of gestational complications and organ disorders. The effects of nicotine on human embryonic development and related mechanisms, however, remain poorly understood. Here, we performed single-cell RNA sequencing (scRNA-seq) of human embryonic stem cell (hESC)-derived embryoid body (EB) in the presence or absence of nicotine. Nicotine-induced lineage-specific responses and dysregulated cell-to-cell communication in EBs, shedding light on the adverse effects of nicotine on human embryonic development. In addition, nicotine reduced cell viability, increased reactive oxygen species (ROS), and altered cell cycling in EBs. Abnormal Ca2+ signaling was found in muscle cells upon nicotine exposure, as verified in hESC-derived cardiomyocytes. Consequently, our scRNA-seq data suggest direct adverse effects of nicotine on hESC differentiation at the single-cell level and offer a new method for evaluating drug and environmental toxicity on human embryonic development in utero.

The cellular basis of fetal endoplasmic reticulum stress and oxidative stress in drug-induced neurodevelopmental deficits

Prenatal substance exposure is a growing public health concern worldwide. Although the opioid crisis remains one of the most prevalent addiction problems in our society, abuse of cocaine, methamphetamines, and other illicit drugs, particularly amongst pregnant women, are nonetheless significant and widespread. Evidence demonstrates prenatal drug exposure can affect fetal brain development and thus can have long-lasting impact on neurobehavioral and cognitive performance later in life. In this review, we highlight research examining the most prevalent drugs of abuse and their effects on brain development with a focus on endoplasmic reticulum stress and oxidative stress signaling pathways. A thorough exploration of drug-induced cellular stress mechanisms during prenatal brain development may provide insight into therapeutic interventions to combat effects of prenatal drug exposure.

Novel Akt activator SC-79 is a potential treatment for alcohol-induced osteonecrosis of the femoral head

Alcohol is a leading risk factor for osteonecrosis of the femoral head (ONFH). We explored the molecular mechanisms underlying alcohol-induced ONFH and investigated the protective effect of the novel Akt activator SC-79 against this disease. We found that ethanol inhibited expression of the osteogenic genes RUNX2 and OCN, downregulated osteogenic differentiation, impaired the recruitment of Akt to the plasma membrane, and suppressed Akt phosphorylation at Ser473, thereby inhibiting the Akt/GSK3β/β-catenin signaling pathway in bone mesenchymal stem cells. To assess SC-79′s ability to counteract the inhibitory effect of ethanol on Akt-Ser73 phosphorylation, we performed micro-computerized tomography and immunofluorescent staining of osteopontin, osteocalcin and collagen type 1 in a rat model of alcohol-induced ONFH. We found that SC-79 injections inhibited alcohol-induced osteonecrosis. These results show that alcohol-induced ONFH is associated with suppression of p-Akt-Ser473 in the Akt/GSK3β/β-catenin signaling pathway in bone mesenchymal stem cells. We propose that SC-79 treatment to rescue Akt activation could be tested in the clinic as a potential therapeutic approach to preventing the development of alcohol-induced ONFH.

Roles of Grp78 in Female Mammalian Reproduction

The glucose-regulated protein (GRP78) also referred to as immunoglobulin heavy chain binding protein (Bip) is one of the best characterized endoplasmic reticulum (ER) chaperone proteins, which belongs to the heat-shock protein (HSP) family. GRP78 as a central regulator of ER stress (ERS) plays many important roles in cell survival and apoptosis through controlling the activation of transmembrane ERS sensors: PKR-like ER-associated kinase (PERK), inositol requiring kinase 1 (IRE1), and activating transcription factor 6 (ATF6). Many studies have reported that GRP78 is involved in the physiological and pathological process in female reproduction, including follicular development, corpus luteum (CL), oviduct, uterus, embryo, preimplantation development, implantation/decidualization, and the placenta. The present review summarizes the biological or pathological roles and signaling mechanisms of GRP78 during the reproductive processes. Further study on the functions and mechanisms of GRP78 may provide new insight into mammalian reproduction, which not only enhance the understanding of the physiological roles but also support therapy target against infertility.

Nicotine Directly Induces Endoplasmic Reticulum Stress Response in Rat Placental Trophoblast Giant Cells

Nicotine exposure during pregnancy leads to placental insufficiency impairing both fetal and neonatal development. Previous studies from our laboratory have demonstrated that in rats, nicotine augmented endoplasmic reticulum (ER) stress in association with placental insufficiency; however, the underlying mechanisms remain elusive. Therefore, we sought to investigate the possible direct effect of nicotine on ER stress in Rcho-1 rat placental trophoblast giant (TG) cells during differentiation. Protein and/or mRNA expression of markers involved in ER stress (eg, phosphorylated PERK, eIF2α, CHOP, and BiP/GRP78) and TG cell differentiation and function (eg, Pl-1, placental growth factor [Pgf], Hsd11b1, and Hsd11b2) were quantified via Western blot or real-time polymerase chain reaction. Nicotine treatment led to dose-dependent increases in the phosphorylation of PERK[Thr981] and eIF2α[Ser51], whereas pretreatment with a nicotinic acetylcholine receptor (nAChR) antagonist (mecamylamine hydrochloride) blocked the induction of PERK phosphorylation, verifying the direct involvement of nicotine and nAChR binding. We next investigated select target genes known to play essential roles in placental TG cell differentiation and function (Pl-1, Pgf, Hsd11b1, and Hsd11b2), and found that nicotine significantly augmented the mRNA levels of Hsd11b1 in a dose-dependent manner. Furthermore, using tauroursodeoxycholic acid, a safe bile acid known to improve protein chaperoning and folding, we were able to prevent nicotine-induced increases in both PERK phosphorylation and Hsd11b1 mRNA levels, revealing a potential novel therapeutic approach to reverse the deleterious effects of nicotine exposure in pregnancy. Collectively, these results implicate that nicotine, acting through its receptor, can directly augment ER stress and impair placental function.

Adverse effects of perinatal nicotine exposure on reproductive outcomes

Nicotine exposure during pregnancy through cigarette smoking, nicotine replacement therapies or e-cigarette use continues to be a widespread public health problem, impacting both fetal and postnatal health. Yet, at this time, there remains limited data regarding the safety and efficacy in using these nicotine products during pregnancy. Notably, reports assessing the effect of nicotine exposure on postnatal health outcomes in humans, including reproductive health, are severely lacking. Our current understanding regarding the consequences of nicotine exposure during pregnancy is limited to a few animal studies, which do not comprehensively address the underlying cellular mechanisms involved. This paper aims to critically review the current knowledge from human and animal studies regarding the direct and indirect effects (e.g. obesity) of maternal nicotine exposure, regardless of its source, on reproductive outcomes in pregnancy and postnatal life. Furthermore, this review highlights several key cellular mechanisms involved in these adverse reproductive deficits including oxidative stress, inflammation, and endoplasmic reticulum (ER) stress. By understanding the interplay of the cellular mechanisms involved, further strategies could be developed to prevent the reproductive abnormalities resulting from exposure to nicotine in utero and influence informed clinical guidelines for pregnant women.

Maternal nicotine exposure leads to impaired disulfide bond formation and augmented endoplasmic reticulum stress in the rat placenta

Maternal nicotine exposure has been associated with many adverse fetal and placental outcomes. Although underlying mechanisms remain elusive, recent studies have identified that augmented endoplasmic reticulum (ER) stress is linked to placental insufficiency. Moreover, ER function depends on proper disulfide bond formation—a partially oxygen-dependent process mediated by protein disulfide isomerase (PDI) and ER oxidoreductases. Given that nicotine compromised placental development in the rat, and placental insufficiency has been associated with poor disulfide bond formation and ER stress, we hypothesized that maternal nicotine exposure leads to both placental ER stress and impaired disulfide bond formation. To test this hypothesis, female Wistar rats received daily subcutaneous injections of either saline (vehicle) or nicotine bitartrate (1 mg/kg) for 14 days prior to mating and during pregnancy. Placentas were harvested on embryonic day 15 for analysis. Protein and mRNA expression of markers involved in ER stress (e.g., phosphorylated eIF2α, Grp78, Atf4, and CHOP), disulfide bond formation (e.g., PDI, QSOX1, VKORC1), hypoxia (Hif1α), and amino acid deprivation (GCN2) were quantified via Western blot and/or Real-time PCR. Maternal nicotine exposure led to increased expression of Grp78, phosphorylated eIF2α, Atf4, and CHOP (p<0.05) in the rat placenta, demonstrating the presence of augmented ER stress. Decreased expression of PDI and QSOX1 (p<0.05) reveal an impaired disulfide bond formation pathway, which may underlie nicotine-induced ER stress. Finally, elevated expression of Hif1α and GCN2 (p<0.05) indicate hypoxia and amino acid deprivation in nicotine-exposed placentas, respectively, which may also cause impaired disulfide bond formation and augmented ER stress. This study is the first to link maternal nicotine exposure with both placental ER stress and disulfide bond impairment in vivo, providing novel insight into the mechanisms underlying nicotine exposure during pregnancy on placental health.