Feedback inhibition of CREB signaling by p38 MAPK contributes to the negative regulation of steroidogenesis

Thromboxane A2 Modulates de novo Synthesis of Adrenal Corticosterone in Mice via p38/14-3-3γ/StAR Signaling

Prostanoids are endogenous lipid bioactive mediators that play essential roles in physiological processes such as glucocorticoid secretion. Here, it is found that the thromboxane (Tx)A2 receptor (TP) is highly expressed in the adrenal cortex of mice. Both global and adrenocortical-specific deletion of the TP receptor lead to increased adiposity in mice by elevating corticosterone synthesis. Mechanistically, the TP receptor deletion increases the phosphorylation of steroidogenic acute regulatory protein (StAR) and corticosterone synthesis in adrenal cortical cells by suppressing p-p38-mediated phosphorylation of 14-3-3γ adapter protein at S71. The activation of the p38 in the adrenal cortical cells by forced expression of the MKK6EE gene attenuates hypercortisolism in TP-deficient mice. These observations suggest that the TxA2/TP signaling regulates adrenal corticosterone homeostasis independent of the hypothalamic-pituitary-adrenal axis and the TP receptor may serve as a promising therapeutic target for hypercortisolism.

Metallothionein-2A Protects Cardiomyocytes from Hypoxia/reper-Fusion through Inhibiting p38

The reperfusion of coronary artery blood supply is often accompanied by myocardial hypoxia/reperfusion (H/R) injury, and induced cardiomyocytes apoptosis. The activation of p38 can induce apoptosis, thereby aggravating the myocardial H/R injury. Metallothionein-2A (MT2A) has the functions of anti-apoptosis and protective effect through p38. However, it is not clear that MT2A may protect cardiomyocytes from H/R injury through p38 signaling pathway. Here, we constructed an H/R model for H9c2 cardiomyocytes to explore the protective effect of MT2A on cardiomyocytes apoptosis during the process of H/R through p38 signal pathway. The results revealed that both endogenously overexpressed MT2A and exogenously added MT2A can inhibit the active expression of p-p38 and cleaved caspase-3 under H/R. Based on our results, H/R induced cardiomyocytes apoptosis and activation of p38. And, MT2A can inhibit the active expression of caspase-3 and p38. We found that MT2A can protect cardiomyocytes apoptosis from H/R injury through p38 signaling pathway.

Chlorpyrifos induces apoptosis and necroptosis via the activation of CYP450s pathway mediated by nuclear receptors in LMH cells

Chlorpyrifos (CPF), an organophosphorus pesticide, is detected commonly in environments, where it is thought to be highly toxic to non-target organisms. However, the mechanism of CYP450s pathway mediated by nuclear receptors on CPF-induced apoptosis and necroptosis at the cellular level and the effect of CPF on the cytotoxicity of the chicken hepatocarcinoma cell line (LMH) has also not been reported in detail. Therefore, this experiment aims to explore whether CPF can improve apoptosis and necroptosis in LMH cells by activating the nuclear receptors/CYP450s axis. LMH cells, the subject of this study, were exposed to 5 μg/mL, 10 μg/mL, and 15 μg/mL doses of CPF. With the increase of CPF concentration, the increase of nuclear receptor level led to the up-regulation of CYP450s activity. With the massive production of ROS, the expression of apoptotic pathway genes (Bax, Caspase9, and Caspase3) enhanced, while Bcl-2 expression dropped sharply. The expression of programmed necroptosis genes (RIPK1, RIPK3, and MLKL) heightened, and Caspase8 reduced considerably. In short, our data suggests that excessive activation of nuclear receptors and CYP450s induced by CPF promotes ROS production, which directs apoptosis and programmed necroptosis in LMH cells.

Role of p38 MAPK Signalling in Testis Development and Male Fertility

The testis is an important male reproductive organ, which ensures reproductive function via the secretion of testosterone and the generation of spermatozoa. Testis development begins in the embryonic period, continues after birth, and generally reaches functional maturation at puberty. The stress-activated kinase, p38 mitogen-activated protein kinase (MAPK), regulates multiple cell processes including proliferation, differentiation, apoptosis, and cellular stress responses. p38 MAPK signalling plays a crucial role in testis development by regulating spermatogenesis, the fate determination of pre-Sertoli, and primordial germ cells during embryogenesis, the proliferation of testicular cells in the postnatal period, and the functions of mature Sertoli and Leydig cells. In addition, p38 MAPK signalling is involved in decreased male fertility when exposed to various harmful stimuli. This review will describe in detail the biological functions of p38 MAPK signalling in testis development and male reproduction, together with its pathological role in male infertility.

Characterization of carbohydrate metabolism in in vivo and in vitro grown and matured mouse antral follicles

Establishing an ideal human follicle culture system for oncofertility patients relies mainly on animal models since donor tissue is scarce and often of suboptimal quality. The in vitro system developed in our laboratory supports the growth of prepubertal mouse secondary follicles up to mature oocytes. Given the importance of glucose in preparing the oocyte for proper maturation, a baseline characterization of follicle metabolism both in the culture system and in vivo was carried out. Markers of glucose-related pathways (glycolysis, tricarboxylic acid (TCA) cycle, pentose phosphate pathway (PPP), polyol pathway, hexosamine biosynthesis pathway (HBP)) as well as for the antioxidant capacity were measured in the different follicle cell types by both enzymatic activities (spectrophotometric detection) and gene expression (qPCR). This study confirmed that in vivo the somatic cells, mainly granulosa, exhibit intense glycolytic activity, while oocytes perform PPP. Throughout the final maturation step, oocytes in vivo and in vitro showed steady levels for all the key enzymes and metabolites. On the other hand, ovulation triggers a boost of pyruvate and lactate uptake in cumulus cells in vivo, consumes reduced nicotinamide adenine dinucleotide phosphate (NADPH) and increases TCA cycle and small molecules antioxidant capacity (SMAC) activities, while in vitro, the metabolic upregulation in all the studied pathways is limited. This altered metabolic pattern might be a consequence of cell exhaustion because of culture conditions, impeding cumulus cells to fulfil their role in providing proper support for acquiring oocyte competence. SUMMARY SENTENCE: In vitro cultured mouse follicles exhibit altered glycolytic activity and redox metabolism in the somatic compartment during meiotic maturation.

BMI1 Drives Steroidogenesis Through Epigenetically Repressing the p38 MAPK Pathway

Testosterone biosynthesis progressively decreases in aging males primarily as a result of functional changes to Leydig cells. Despite this, the mechanisms underlying steroidogenesis remain largely unclear. Using gene knock-out approaches, we and others have recently identified Bmi1 as an anti-aging gene. Herein, we investigate the role of BMI1 in steroidogenesis using mouse MLTC-1 and primary Leydig cells. We show that BMI1 can positively regulate testosterone production. Mechanistically, in addition to its known role in antioxidant activity, we also report that p38 mitogen-activated protein kinase (MAPK) signaling is activated, and testosterone levels reduced, in BMI1-deficient cells; however, the silencing of the p38 MAPK pathway restores testosterone production. Furthermore, we reveal that BMI1 directly binds to the promoter region of Map3k3, an upstream activator of p38, thereby modulating its chromatin status and repressing its expression. Consequently, this results in the inhibition of the p38 MAPK pathway and the promotion of steroidogenesis. Our study uncovered a novel epigenetic mechanism in steroidogenesis involving BMI1-mediated gene silencing and provides potential therapeutic targets for the treatment of hypogonadism.

Glucose metabolism characterization during mouse in vitro maturation identifies alterations in cumulus cells†

In vitro maturation (IVM) is an assisted reproduction technique with reduced hormone-related side-effects. Several attempts to implement IVM in routine practice have failed, primarily due to its relatively low efficiency compared with conventional in vitro fertilization (IVF). Recently, capacitation (CAPA)-IVM-a novel two-step IVM method-has improved the embryology outcomes through synchronizing the oocyte nuclear and cytoplasmic maturation. However, the efficiency gap between CAPA-IVM and conventional IVF is still noticeable especially in the numerical production of good quality embryos. Considering the importance of glucose for oocyte competence, its metabolization is studied within both in vivo and CAPA-IVM matured mouse cumulus-oocyte-complexes (COCs) through direct measurements in both cellular compartments, from transcriptional and translational perspectives, to reveal metabolic shortcomings within the CAPA-IVM COCs. These results confirmed that within in vivo COC, cumulus cells (CCs) are highly glycolytic, whereas oocytes, with low glycolytic activity, are deviating their glucose towards pentose phosphate pathway. No significant differences were observed in the CAPA-IVM oocytes compared with their in vivo counterparts. However, their CCs exhibited a precocious increase of glycolytic activity during the pre-maturation culture step and activity was decreased during the IVM step. Here, specific alterations in mouse COC glucose metabolism due to CAPA-IVM culture were characterized using direct measurements for the first time. Present data show that, while CAPA-IVM CCs are able to utilize glucose, their ability to support oocytes during final maturation is impaired. Future CAPA-IVM optimization strategies could focus on adjusting culture media energy substrate concentrations and/or implementing co-culture strategies.

L-Dopa-Decarboxylase (DDC) Is a Positive Prognosticator for Breast Cancer Patients and Epinephrine Regulates Breast Cancer Cell (MCF7 and T47D) Growth In Vitro According to Their Different Expression of Gi- Protein- Coupled Receptors

A coherence between thyroid dysfunction and breast cancer incidence exists. Thyroid hormone metabolites bind to TAAR1 (trace amine-associated receptor 1) and through that modulate the serotonergic and dopaminergic system. Catecholamines themselves are synthesized by the L-dopa decarboxylase (DDC). The aim of our study was to analyze the influence of catecholamines on the DDC expression in primary breast cancer patients and the role of DDC concerning overall survival (OS). DDC expression was analyzed by immunohistochemistry. The effect of epinephrine on the expression of DDC and the Gi- protein was analyzed on the protein level via Western blot. A viability assay was performed to test the metabolic cell viability. The overexpression of DDC in the primary tumor was associated with longer OS (p = 0.03). Stimulation with epinephrine induced the downregulation of DDC (p = 0.038) and significantly increased viability in T47D cells (p = 0.028). In contrast, epinephrine induced an upregulation of DDC and decreased the proliferation of MCF7 cells (p = 0.028). Epinephrine led to an upregulation of Gi protein expression in MCF7 cells (p = 0.008). DDC is a positive prognostic factor for OS in breast cancer patients, and it is regulated through epinephrine differently in MCF7 and T47D. DDC may represent a novel target for the treatment of breast cancer, especially concerning its interaction with epinephrine.

Redox metabolism modulation as a mechanism in SSRI toxicity and pharmacological effects

Depressive disorders are amongst the greatest mental health challenges, with an increasing number of patients being diagnosed each year. Though it has not yet been fully elucidated, redox metabolism imbalances and oxidative stress seem to play a major role in the pathogenesis of depressive disorders. Selective serotonin reuptake inhibitors (SSRIs) are the most prescribed antidepressants, considered to have a better tolerability. However, several adverse effects have been reported and the mechanisms involved in their pharmacological activity are not entirely understood. SSRIs have been shown to influence the redox metabolism, which could be involved in their toxicity and pharmacological effects. A comparative analysis of published in vivo and in vitro data regarding the activity of SSRIs on the redox metabolism pathways has been performed in this paper, with an emphasis on mechanistical aspects. Furthermore, a comparison between oxidative stress biomarker levels reported by different studies was attempted. The reviewed data point towards both pro- and antioxidant effects of SSRIs, dependent on tissue/cell type and dose/concentration, suggest a redox modulating potential of these compounds. In hepatic and testicular tissue, the majority of reviewed studies reported pro-oxidant effects, with possible implications towards the hepatotoxicity and sexual dysfunction that were reported following SSRI treatment; while in brain, the most common findings were antioxidant effects that could partially explain their antidepressant activity. However, given the heterogeneity of the reviewed data, further research is needed to fully understand the impact of SSRIs on redox metabolism and its implications.

Pregnenolone Inhibits Osteoclast Differentiation and Protects Against Lipopolysaccharide-Induced Inflammatory Bone Destruction and Ovariectomy-Induced Bone Loss

Osteolytic bone disease is characterized by excessive osteoclast bone resorption leading to increased skeletal fragility and fracture risk. Multinucleated osteoclasts formed through the fusion of mononuclear precursors are the principle cell capable of bone resorption. Pregnenolone (Preg) is the grand precursor of most if not all steroid hormones and have been suggested to be a novel anti-osteoporotic agent. However, the effects of Preg on osteoclast biology and function has yet to be shown. Here we examined the effect of Preg on receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclast formation and bone resorption in vitro, and potential therapeutic application in inflammatory bone destruction and bone loss in vivo. Our in vitro cellular assays demonstrated that Preg can inhibit the formation of TRAP^+ve osteoclast formation as well as mature osteoclast bone resorption in a dose-dependent manner. The expression of osteoclast marker genes CTSK, TRAP, DC-STAMP, ATP6V0d2, and NFATc1 were markedly attenuated. Biochemical analyses of RANKL-induced signaling pathways showed that Preg inhibited the early activation of extracellular regulated protein kinases (ERK) mitogen-activated protein kinase (MAPK) and nuclear factor-κB, which consequently impaired the downstream induction of c-Fos and NFATc1. Using reactive oxygen species (ROS) detection assays, we found that Preg exhibits anti-oxidant properties inhibiting the generation of intracellular ROS following RANKL stimulation. Consistent with these in vitro results, we confirmed that Preg protected mice against local Lipopolysaccharide (LPS)-induced inflammatory bone destruction in vivo by suppressing osteoclast formation. Furthermore, we did not find any observable effect of Preg on osteoblastogenesis and mineralization in vitro. Finally Preg was administered to ovariectomy (OVX)-induced bone loss and demonstrated that Preg prevented systemic OVX-induced osteoporosis. Collectively, our observations provide strong evidence for the use of Preg as anti-osteoclastogenic and anti-resorptive agent for the potential treatment of osteolytic bone conditions.

An in vitro attempt at precision toxicology reveals the involvement of DNA methylation alteration in ochratoxin A-induced G0/G1 phase arrest

Precision toxicology evaluates the toxicity of certain substances by isolating a small group of cells with a typical phenotype of interest followed by a single cell sequencing-based analysis. In this in vitro attempt, ochratoxin A (OTA), a typical mycotoxin and food contaminant, is found to induce G0/G1 phase cell cycle arrest in human renal proximal tubular HKC cells at a concentration of 20 μM after a 24h-treatment. A small number of G0/G1 phase HKC cells are evaluated in both the presence and absence of OTA. These cells are sorted with a flow cytometer and subjected to mRNA and DNA methylation sequencing using Smart-Seq2 and single-cell reduced-representation bisulfite sequencing (scRRBS) technology, respectively. Integrated analysis of the transcriptome and methylome profiles reveals that OTA causes abnormal expression of the essential genes that regulate G1/S phase transition, act as signal transductors in G1 DNA damage checkpoints, and associate with the anaphase-promoting complex/cyclosome. The alteration of their DNA methylation status is a significant underlying epigenetic mechanism. Furthermore, Notch signaling and Ras/MAPK/CREB pathways are found to be suppressed by OTA. This attempt at precision toxicology paves the way for a deeper understanding of OTA toxicity and provides an innovative strategy to researchers in the toxicology and pharmacology field.

Ovatodiolide suppresses inflammatory response in BEAS-2B cells by regulating the CREB/AQP5 pathway, and sensitizes nasopharyngeal carcinoma cells to radiation therapy

Due to the radiosensitivity of the airway epithelium, radiation-induced sinusitis or bronchitis is not uncommon, and makes mitigation of resulting inflammatory airway diseases a principal goal of many investigations. This study examined whether Ovatodiolide (Ova) sensitizes the human metastatic nasopharyngeal cancer (NPC) cell line, NPC-BM2, to irradiation using viability, clonogenicity and Western blot assays. Concurrently, we used varying concentrations of histamine and/or Ova to determine the anti-inflammatory potential of Ovatodiolide on normal bronchus epithelial BEAS-2B cells, as well as on the subcellular distribution of Aquaporin 5 (AQP5) and expression levels of p-CREB, AQP5, p38 MAPK, NF-κB, PI3K, Akt and ERK proteins. We demonstrated that Ova in synergism with irradiation inhibited NPC-BM2 cell viability and suppressed their clonogenicity. Immunofluorescence analysis revealed low-dose (≤ 2.5 μM) Ova reversed histamine-induced suppression of AQP5 expression, and abrogated histamine-enhanced NF-κB nuclear translocation, indicating Ova modulates the p38 MAPK/NF-κB signaling pathway and elicits p-CREB/AQP5-mediated antihistamine effects. Similarly, Ova deregulates the PI3K/Akt/ERK signaling in BEAS-2B cells, suggesting its cytoprotective potential. In conclusion, this study highlights the radio-sensitizing anticancer efficacy of Ova in human metastatic NPC cells, as well as its putative cytoprotective role in normal bronchial cells, for airway surface liquid maintenance and homeostasis during or after radiotherapy.

Roles of Cyclic AMP Response Element Binding Activation in the ERK1/2 and p38 MAPK Signalling Pathway in Central Nervous System, Cardiovascular System, Osteoclast Differentiation and Mucin and Cytokine Production

There are many downstream targets of mitogen-activated protein kinase (MAPK) signalling that are involved in neuronal development, cellular differentiation, cell migration, cancer, cardiovascular dysfunction and inflammation via their functions in promoting apoptosis and cell motility and regulating various cytokines. It has been reported that cyclic AMP response element-binding protein (CREB) is phosphorylated and activated by cyclic AMP signalling and calcium/calmodulin kinase. Recent evidence also points to CREB phosphorylation by the MAPK signalling pathway. However, the specific roles of CREB phosphorylation in MAPK signalling have not yet been reviewed in detail. Here, we describe the recent advances in the study of this MAPK-CREB signalling axis in human diseases. Overall, the crosstalk between extracellular signal-related kinase (ERK) 1/2 and p38 MAPK signalling has been shown to regulate various physiological functions, including central nervous system, cardiac fibrosis, alcoholic cardiac fibrosis, osteoclast differentiation, mucin production in the airway, vascular smooth muscle cell migration, steroidogenesis and asthmatic inflammation. In this review, we focus on ERK1/2 and/or p38 MAPK-dependent CREB activation associated with various diseases to provide insights for basic and clinical researchers.

Oocyte Aging: The Role of Cellular and Environmental Factors and Impact on Female Fertility

Female aging is one of the most important factors that impacts human reproduction. With aging, there is a natural decline in female fertility. The decrease in fertility is slow and steady in women aged 30-35 years; however, this decline is accelerated after the age of 35 due to decreases in the ovarian reserve and oocyte quality. Human oocyte aging is affected by different environmental factors, such as dietary habits and lifestyle. The ovarian microenvironment contributes to oocyte aging and longevity. The immediate oocyte microenvironment consists of the surrounding cells. Crosstalk between the oocyte and microenvironment is mediated by direct contact with surrounding cells, the extracellular matrix, and signalling molecules, including hormones, growth factors, and metabolic products. In this review, we highlight the different microenvironmental factors that accelerate human oocyte aging and decrease oocyte function. The ovarian microenvironment and the stress that is induced by environmental pollutants and a poor diet, along with other factors, impact oocyte quality and function and contribute to accelerated oocyte aging and diseases of infertility.

Molecular Mechanisms of Action of FSH

The glycoprotein follicle-stimulating hormone (FSH) acts on gonadal target cells, hence regulating gametogenesis. The transduction of the hormone-induced signal is mediated by the FSH-specific G protein-coupled receptor (FSHR), of which the action relies on the interaction with a number of intracellular effectors. The stimulatory Gαs protein is a long-time known transducer of FSH signaling, mainly leading to intracellular cAMP increase and protein kinase A (PKA) activation, the latter acting as a master regulator of cell metabolism and sex steroid production. While in vivo data clearly demonstrate the relevance of PKA activation in mediating gametogenesis by triggering proliferative signals, some in vitro data suggest that pro-apoptotic pathways may be awakened as a "dark side" of cAMP/PKA-dependent steroidogenesis, in certain conditions. P38 mitogen-activated protein kinases (MAPK) are players of death signals in steroidogenic cells, involving downstream p53 and caspases. Although it could be hypothesized that pro-apoptotic signals, if relevant, may be required for regulating atresia of non-dominant ovarian follicles, they should be transient and counterbalanced by mitogenic signals upon FSHR interaction with opposing transducers, such as Gαi proteins and β-arrestins. These molecules modulate the steroidogenic pathway via extracellular-regulated kinases (ERK1/2), phosphatidylinositol-4,5-bisphosphate 3-kinases (PI3K)/protein kinase B (AKT), calcium signaling and other intracellular signaling effectors, resulting in a complex and dynamic signaling network characterizing sex- and stage-specific gamete maturation. Even if the FSH-mediated signaling network is not yet entirely deciphered, its full comprehension is of high physiological and clinical relevance due to the crucial role covered by the hormone in regulating human development and reproduction.

ROS generation and MAPKs activation contribute to the Ni-induced testosterone synthesis disturbance in rat Leydig cells

Nickel (Ni) can disorder testosterone synthesis in rat Leydig cells, whereas the mechanisms remain unclear. The aim of this study was to investigate the role of reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) in Ni-induced disturbance of testosterone synthesis in rat Leydig cells. The testosterone production and ROS levels were detected in Leydig cells. The mRNA and protein levels of testosterone synthetase, including StAR, CYP11A1, 3β-HSD, CYP17A1 and 17β-HSD, were determined. Effects of Ni on the ERK1/2, p38 and JNK MAPKs were also investigated. The results showed that Ni triggered ROS generation, consequently resulted in the decrease of testosterone synthetase expression and testosterone production in Leydig cells, which were then attenuated by ROS scavengers of N-acetylcysteine (NAC) and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), indicating that ROS are involved in the Ni-induced testosterone biosynthesis disturbance. Meanwhile Ni activated the ERK1/2, p38 and JNK MAPKs. Furthermore, Ni-inhibited testosterone synthetase expression levels and testosterone secretion were all alleviated by co-treatment with MAPK specific inhibitors (U0126 and SB203580, respectively), implying that Ni inhibited testosterone synthesis through activating ERK1/2 and p38 MAPK signal pathways in Leydig cells. In conclusion, these findings suggest that Ni causes testosterone synthesis disorder, partly, via ROS and MAPK signal pathways.