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Trinidad Raices, María Luisa Varela, Casandra Margarita Monzón, María Florencia Correa Torrado, Romina María Pagotto, Marcos Besio Moreno, Carolina Mondillo, Omar Pedro Pignataro and Elba Nora Pereyra

Testicular Leydig cells (LC) are modulated by several pathways, one of them being the histaminergic system. Heme oxygenase-1 (HO-1), whose upregulation comprises the primary response to oxidative noxae, has a central homeostatic role and might dysregulate LC functions when induced. In this report, we aimed to determine how hemin, an HO-1 inducer, affects LC proliferative capacity and whether HO-1 effects on LC functions are reversible. It was also evaluated if HO-1 interacts in any way with histamine, affecting its regulatory action over LC. MA-10 and R2C cell lines and immature rat LC were used as models. Firstly, we show that after a 24-h incubation with 25 µmol/L hemin, LC proliferation is reversibly impaired by cell cycle arrest in G2/M phase, with no evidence of apoptosis induction. Even though steroid production is abrogated after a 48-h exposure to 25 µmol/L hemin, steroidogenesis can be restored to control levels in a time-dependent manner if the inducer is removed from the medium. Regarding HO-1 and histamine interaction, it is shown that hemin abrogates histamine biphasic effect on steroidogenesis and proliferation. Working with histamine receptors agonists, we elucidated that HO-1 induction affects the regulation mediated by receptor types 1, 2 and 4. In summary, HO-1 induction arrests LC functions, inhibiting steroid production and cell cycle progression. Despite their reversibility, HO-1 actions might negatively influence critical phases of LC development and differentiation affecting their function as well as other androgen-dependent organs. What’s more, we have described a hitherto unknown interaction between HO-1 induction and histamine effects.

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Eui Hyun Kim, Geon A Kim, Anukul Taweechaipaisankul, Seok Hee Lee, Muhammad Qasim, Curie Ahn and Byeong Chun Lee

Oxidative stress (OS) is a major problem during in vitro culture of embryos. Numerous studies have shown that melatonin, which is known to have antioxidant properties, prevents the occurrence of OS in embryos. However, the molecular mechanisms by which melatonin prevents OS in embryos are still unclear. The present study suggests a possible involvement of the nuclear factor erythroid 2-related factor 2/antioxidant-responsive element (Nrf2/ARE) signaling pathway, which is one of the prominent signals for OS prevention through Nrf2 activation, connecting melatonin, OS prevention and porcine embryonic development. The aim of this study was to investigate the effects of melatonin (10−7 M) on porcine embryonic development via the Nrf2/ARE signaling pathway; brusatol (50 nM; Nrf2 specific inhibitor) was used to validate the mechanism. Treatment of porcine embryo with melatonin significantly increased formation rates of blastocysts and their total cell numbers and also upregulated the expression of Nrf2/ARE signaling and apoptosis-related genes (MT2, NRF2, UCHL, HO-1, SOD1 and BCL-2). Furthermore, the expression of proteins (NRF2 and MT2) was also upregulated in the melatonin-treated group. Concomitantly, brusatol significantly inhibited these effects, upregulating the expression of KEAP1 and BAX, including the expression level of KEAP1 protein. These results provide evidences that melatonin prevents OS through Nrf2/ARE signaling pathway in porcine in vitro fertilization -derived embryos.

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Ji Chen, Chao Li, Wenjie Liu, Bin Yan, Xiaoling Hu and Fengrui Yang

Neuropathic pain represents one of the most common complications associated with diabetes mellitus (DM) that impacts quality of life. Accumulating studies have highlighted the involvement of miRNAs in DM. Thus, the current study aimed to investigate the roles of miR-155 in diabetic peripheral neuropathy (DPN). In vitro DPN models were established using rat Schwann cells (SCs) by treatment with 5.5 mM glucose. Gain- or loss-of-function studies were conducted to determine the effect of miR-155 on Nrf2, cellular function, reactive oxygen species and inflammation. Rat DNP models were established by streptozotocin injection and damage of sciatic nerve. Next, miR-155 antagomir or agomir was employed to investigate the effects associated with miR-155 on motor and sciatic nerve conduction velocity (MNCV, SNCV), angiogenesis and inflammatory response in vivo. Nrf2 was identified to be a target of miR-155 by dual-luciferase reporter gene assay. Silencing of miR-155 or restoration of Nrf2 promoted cell proliferation, inhibited apoptosis and alleviated inflammation in vitro. miR-155 antagomir-induced inhibition increased MNCV and SNCV, strengthened angiogenesis and alleviated inflammation in DPN rats. Additionally, the effects exerted by miR-155 were reversed when Nrf2 was restored both in vitro and in vivo. Taken together, the key findings of our study provide evidence indicating that miR-155 targeted and suppressed Nrf2 in DPN. miR-155 silencing was found to alleviate sciatic nerve injury in DPN, highlighting its potential as a therapeutic target for DPN.

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Caitlyn Nguyen-Ngo, Nanthini Jayabalan, Carlos Salomon and Martha Lappas

Gestational diabetes mellitus (GDM) imposes serious short- and long-term health problems for mother and baby. An effective therapeutic that can reduce the incidence of GDM and improve long-term maternal and fetal outcomes is a major research priority, crucially important for public health. A lack of knowledge about the underlying pathophysiology of GDM has hampered the development of such therapeutics. What we do know, however, is that maternal insulin resistance, low-grade inflammation and endothelial cell dysfunction are three central features of pregnancies complicated by GDM. Indeed, data generated over the past decade have implicated a number of candidate regulators of insulin resistance, inflammation and endothelial cell dysfunction in placenta, maternal adipose tissue and skeletal muscle. These include nuclear factor-κB (NF-κB), peroxisome proliferator-activated receptors (PPARs), sirtuins (SIRTs), 5′ AMP-activated protein kinase (AMPK), glycogen synthase kinase 3 (GSK3), PI3K/mTOR, inflammasome and endoplasmic reticulum (ER) stress. In this review, the identification of these as key modulators of GDM will be discussed. The biochemical pathways involved in the formation of these may represent potential sites for intervention that may translate to therapeutic interventions to prevent the development of GDM.

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Yefei Pang and Peter Thomas

We have shown progesterone exerts a direct action on vascular smooth muscle cells (VSMCs) to induce relaxation through activation of membrane progesterone receptor alpha (mPRα)-dependent signaling pathways, but information on downstream events is lacking. Progesterone-induced changes in calcium concentrations in human umbilical artery VSMCs through mPRα-dependent signaling pathways and the involvement of Rho/ROCK signaling were investigated. Acute in vitro treatment with progesterone and the selective mPRα agonist 10-ethenyl-19-norprogesterone (Org OD 02-0, 02-0) blocked the rapid prostaglandin F2α-induced calcium increase. This inhibitory progesterone action was prevented by knockdown of mPRα but not by knockdown of the nuclear progesterone receptor, confirming it is mediated through mPRα. The decrease in calcium levels and VSMC relaxation were abolished by treatment with FPL64176 (Ca2+ channel activator), supporting a role for decreased calcium channel activity in this progesterone action. The reduction in calcium was attenuated by pretreatment with pertussis toxin, 8-Bromo-cAMP and forskolin, indicating this progesterone action involves activation of an inhibitory G protein and downregulation of cAMP-dependent signaling. Inhibition of MAPK and Akt signaling with PD98059 and ML-9, respectively, prevented the progesterone-induced calcium concentration decrease and VSMC relaxation. Forskolin decreased progesterone-induced MAPK and Akt phosphorylation which suggests that the cAMP status influences calcium levels indirectly through altering these signaling pathways. Progesterone and 02-0 treatments decreased RhoA activity and ROCK phosphorylation, which suggests that reduced RhoA/ROCK signaling is a component of the mPRα-mediated progesterone actions on VSMCs. The results suggest that progesterone induces VSMC relaxation by reducing cellular calcium levels through mPRα-induced alterations in multiple signaling pathways.

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Guoqing Lei, Linxi Chen, Miao Peng, Bolin Zeng, Qiaoxi Yang, Hening Zhai and Geyang Xu

GLP-1 is a potent glucose-dependent insulinotropic hormone derived from intestinal L cells. Inflammatory Interleukin-27 (IL-27), a pleiotropic two-chain cytokine, is composed of EBI3 and IL-27 p28 subunits. IL-27 has a protective effect on pancreatic β-cell function. The relationship between IL-27 and GLP-1 is still unexplored. Here we showed interleukin-27-stimulated GLP-1 production via the Stat3-mTOR-dependent mechanism. Interleukin 27 receptor subunit alpha (IL-27 Rα) was detected in ileum and STC-1 cells. Co-localization of EBI3 and GLP-1 was observed not only in mouse ileums but also in human ileums and colons. Third-ventricular infusion of IL-27 increased ileal and plasma GLP-1 in both lean C57BL/6J mice and diet-induced obese and diabetic mice. These changes were associated with a significant increase in Stat3-mTOR activity. Treatment of STC-1 cells with IL-27 contributed to the increments of Stat3-mTOR signaling and GLP-1. Interference of mTOR activity by mTOR siRNA or rapamycin abolished the stimulation of GLP-1 production induced by IL-27 in STC-1 cells. Stat3 siRNA also blocked the stimulus effect of IL-27 on GLP-1. IL-27 increased the interaction of mTOR and Stat3 in STC-1 cells. Our results identify Stat3-mTOR as a critical signaling pathway for the stimulation of GLP-1 induced by IL-27.

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Yousheng Xu, Yongshun Wang, Jingjin Liu, Wei Cao, Lili Li, Hongwei Du, Enbo Zhan, Ruoxi Zhang, Huimin Liu, Maoen Xu, Tao Chen, Yilin Qu and Bo Yu

The prevalence of obesity is dramatic increased and strongly associated with cardiovascular disease. Adipokines, secreted from adipose tissues, are critical risk factors for the development of cardiomyopathy. Present study aimed to investigate the pathophysiological role of autotaxin in obesity-related cardiomyopathy. In high-fat diet-fed mice, autotaxin was mainly synthesized and secreted from adipocytes. The increased accumulation of cardiac autotaxin was positively associated with cardiac dysfunction in obese mice. Interestingly, specific blockage of adipose tissue autotaxin effectively protected against high-fat diet-induced cardiac structural disorders, left ventricular hypertrophy and dysfunction. Inhibition of autotaxin further improved high-fat diet-induced cardiac fibrosis and mitochondrial dysfunction, including improvement of mitochondrial structure, mass and activities. Our findings demonstrated intervention of adipose tissue biology could influence cardiac modification in obese mice, and adipocyte-derived autotaxin was a potential diagnostic marker and therapeutic target for obesity-related cardiomyopathy.

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Ulas Ozkurede, Rishabh Kala, Cameron Johnson, Ziqian Shen, Richard A Miller and Gonzalo G Garcia

It has been hypothesized that transcriptional changes associated with lower mTORC1 activity in mice with reduced levels of growth hormone and insulin-like growth factor 1 are responsible for the longer healthy lifespan of these mutant mice. Cell lines and tissues from these mice show alterations in the levels of many proteins that cannot be explained by corresponding changes in mRNAs. Such post-transcriptional modulation may be the result of preferential mRNA translation by the cap-independent translation of mRNA bearing the N6-methyl-adenosine (m6A) modification. The long-lived endocrine mutants – Snell dwarf, growth hormone receptor deletion and pregnancy-associated plasma protein-A knockout – all show increases in the N6-adenosine-methyltransferases (METTL3/14) that catalyze 6-methylation of adenosine (m6A) in the 5′ UTR region of select mRNAs. In addition, these mice have elevated levels of YTH domain-containing protein 1 (YTHDF1), which recognizes m6A and promotes translation by a cap-independent mechanism. Consistently, multiple proteins that can be translated by the cap-independent mechanism are found to increase in these mice, including DNA repair and mitochondrial stress response proteins, without changes in corresponding mRNA levels. Lastly, a drug that augments cap-independent translation by inhibition of cap-dependent pathways (4EGI-1) was found to elevate levels of the same set of proteins and able to render cells resistant to several forms of in vitro stress. Augmented translation by cap-independent pathways facilitated by m6A modifications may contribute to the stress resistance and increased healthy longevity of mice with diminished GH and IGF-1 signals.

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Isabel Moscoso, María Cebro-Márquez, Moisés Rodríguez-Mañero, José Ramón González-Juanatey and Ricardo Lage

Irisin is a newly identified adipokine critical to modulate body metabolism, fatty acid metabolism and oxidative stress; recent evidence suggests a cardioprotective role in ischemic injury. Loss of cardiomyocytes during acute myocardial infarction is strongly associated with energetic changes and lipotoxic-induced apoptosis. Our aim was to study FNDC5/irisin’s potential protective role against hypoxia and lipotoxicity, both related with myocardial infarction environment. H9c2 cells were treated with palmitate and/or irisin in normoxic/hypoxic conditions. Cell viability and apoptosis were assessed by MTT assay and annexin V/PI staining. Immunoblotting was used to confirm apoptotic cascade regulation. Irisin counteracts lipotoxic-induced apoptosis in hypoxic cardiomyoblasts by activating Akt signaling pathway suggesting the potential therapeutic role of irisin in ischemic heart disease.

Open access

Yan Zheng and Kevin D Houston

G protein-coupled estrogen receptor 1 (GPER1) is a seven-transmembrane receptor that mediates rapid cell signaling events stimulated by estrogens. While the role that GPER1 has in the modulation of E2-responsive tissues and cancers is well documented, the molecular mechanisms that regulate GPER1 expression are currently not well defined. The recently identified GPER1-dependent mechanism of tamoxifen action in breast cancer cells underscores the importance of identifying mechanisms that regulate GPER1 expression in this cell type. We hypothesized that GPER1 expression in breast cancer cells is sensitive to [D-glucose] and provide data showing increased GPER1 expression when cells were cultured in low [D-glucose]. To determine if the observed accumulation of GPER1 was AMP-activated protein kinase (AMPK)-dependent, small molecule stimulation or inhibition of AMPK was performed. AMPK inhibition decreased GPER1 accumulation in cells grown in low [D-glucose] while the AMPK-activating compound AICAR increased GPER1 accumulation in cells grown in high [D-glucose] media. Additionally, transfection of cells with a plasmid expressing constitutively active AMPK resulted in increased GPER1 accumulation. To determine if [D-glucose]-dependent GPER1 accumulation altered breast cancer cell response to tamoxifen, cells grown in the presence of decreasing [D-glucose] were co-treated with tamoxifen and IGFBP-1 transcription was measured. The results from these experiments reveal that D-glucose deprivation increased GPER1-mediated and tamoxifen-induced IGFBP-1 transcription suggesting that [D-glucose] may increase breast cancer cell sensitivity to tamoxifen. Taken together, these results identify a previously unknown mechanism that regulates GPER1 expression that modifies one aspect tamoxifen action in breast cancer cells.