Autocrine effects of neuromedin B stimulate the proliferation of rat primary osteoblasts

Disruption of neuromedin B receptor improves mitochondrial oxidative phosphorylation capacity in gastrocnemius muscle of female mice

Neuromedin B (NB), a bombesin-like peptide, exerts its specific actions by binding to the neuromedin B receptor (NBR), a G protein-coupled receptor. Female NBR-knockout (NBR-KO) mice exhibit resistance to diet-induced obesity, without hyperphagia, suggesting possible increase in energy expenditure. Skeletal muscle (SM) is crucial for whole body energy homeostasis, however, the presence of NB-NBR signaling and its effects in SM are unknown. Here, we show that male and female wild type express Nmbr and Nmb mRNA in SM, with higher levels in females. Female NBR-KO gastrocnemius showed increased Myh7 mRNA level, which characterizes type I fibers (oxidative profile). Their permeabilized gastrocnemius fibers, studied by high-resolution respirometry, exhibited higher consumption of O₂ coupled to ATP synthesis and unaltered uncoupled respiration. NBR-KO gastrocnemius had higher protein levels of ATP-synthase and Nduf9 mRNA, corresponding to mitochondrial complex I subunit. NBR-KO gastrocnemius exhibited slight increase in mitochondria number, increased thickness of Z line at electron microscopy, and unaltered mitochondrial dynamics markers. Therefore, in the females' gastrocnemius, a predominantly glycolytic SM, the NBR absence promotes changes that favor mitochondrial oxidative phosphorylation capacity. In addition, in L6 myocytes, NB treatment (5 μg/mL/16 h) promoted lower O₂ consumption coupled to ATP synthesis, suggesting direct action at SM cells. Altogether, the study reinforces the hypothesis that inhibition of NB-NBR signaling enhances the capacity for oxidative phosphorylation of white SM, encouraging future studies to elucidate their contribution on other types of SM and whole body energy expenditure, which may lead to a new target to drug development for obesity treatment.NEW & NOTEWORTHY This study describes neuromedin B (NB) and NB receptor as new regulators of skeletal muscle mitochondrial function. The white skeletal muscle mitochondrial oxidative phosphorylation capacity was increased by NB receptor genetic disruption in female mice. These findings may contribute to the resistance to diet-induced obesity, previously found in these mice, which requires future studies. Thus, investigations are necessary to clarify if blockade of NB receptor may be an approach to develop drugs to combat obesity.

Nerve growth factor promotes osteogenic differentiation of MC3T3-E1 cells via BMP-2/Smads pathway

BACKGROUND

Exogenous nerve growth factor (NGF) can induce osteogenic precursor cell differentiation and promote fracture healing. However, the molecular mechanism by which NGF induces osteogenesis is not well understood. BMP-2 has good osteogenic efficacy and is one of the most osteogenic-inducing growth factors known. Therefore, this study aimed to determine whether NGF induces osteogenic differentiation of mouse embryonic osteogenic precursor cell line MC3T3-E1 by BMP-2 and search further mechanisms of NGF on BMP-2.

METHODS

MC3T3-E1 cells were treated with NGF at a concentration gradient for indicated times, after which the cell viability was measured by CCK-8 kit. Osteogenic differentiation was detected with quantification of alkaline phosphatase (ALP) activity also visualized with ALP staining. The transcription and expression of relevant genes were detected by qPCR and western blotting, respectively. NGF's effect on BMP2 was studied with qPCR and luciferase reporter assay. The phosphorylation of Smads was probed with specific antibodies by western blotting, and the location of Smads was observed through immunofluorescence.

RESULTS

We found that NGF promoted proliferation and osteogenic differentiation of MC3T3-E1, increased the expression level of BMP-2, as well as the phosphorylation and nuclear translocation of Smad1/5/8. However, neutralization of BMP-2 with si-BMP-2 or BMP-2 signal inhibitors reversed NGF induced phosphorylation and nuclear translocation of Smad1/5/8, as well as the expression of Runx2, type I collagen, osteocalcin and osteopontin. In addition, si-BMP-2 abrogated NGF-induced ALP activity.

CONCLUSION

NGF induced osteogenic differentiation of MC3T3-E1 cells through BMP-2/Smads pathway and induction of Runx2. Our study would provide a theoretical basis for clinical treatment of fractures using NGF.

Neuromedin B regulates steroidogenesis, cell viability and apoptosis in rabbit Leydig cells

Mammalian bombesin-related peptide, neuromedin B (NMB) action is mediated by its receptor (NMBR), and NMB/NMBR system plays a major role in regulating hormone secretions, reproduction and cell growth. Here we report the functions of NMB in regulating steroidogenesis (testosterone synthesis), cell viability and apoptosis. The primary rabbit Leydig cells were employed as the paradigm for this research. We initially confirmed that NMBR is distributed in Leydig cells of rabbit testis, and a certain dose of NMB could increase the secretion of testosterone in primary cultured rabbit Leydig cells. Subsequently, the accumulated NMBR, StAR, CYP11A1, 3β-HSD and PKC protein could be induced by a certain dose of NMB in Leydig cells. Moreover, we found that NMB could decrease the cell viability, and decreased the expression of PCNA protein in Leydig cells; meanwhile, except for 100 nM, other doses of NMB could suppress the cell apoptosis, and regulate Caspase-3 protein expression in Leydig cells, respectively. These results identify that NMB may be a key factor in regulating testosterone synthesis through taking part in NMBR/PKC/steroidogenesis signaling pathway, as well as the cell viability and proliferation in rabbit Leydig cells.

Pituitary Transcriptomic Study Reveals the Differential Regulation of lncRNAs and mRNAs Related to Prolificacy in Different FecB Genotyping Sheep

Long non-coding RNA (LncRNA) have been identified as important regulators in the hypothalamic-pituitary-ovarian axis associated with sheep prolificacy. However, their expression pattern and potential roles in the pituitary are yet unclear. To explore the potential mRNAs and lncRNAs that regulate the expression of the genes involved in sheep prolificacy, we used stranded specific RNA-seq to profile the pituitary transcriptome (lncRNA and mRNA) in high prolificacy (genotype FecB BB, litter size = 3; H) and low prolificacy sheep (genotype FecB B+; litter size = 1; L). Our results showed that 57 differentially expressed (DE) lncRNAs and 298 DE mRNAs were found in the pituitary between the two groups. The qRT-PCR results correlated well with the RNA-seq results. Moreover, functional annotation analysis showed that the target genes of the DE lncRNAs were significantly enriched in pituitary function, hormone-related pathways as well as response to stimulus and some other terms related to reproduction. Furthermore, a co-expression network of lncRNAs and target genes was constructed and reproduction related genes such as SMAD2, NMB and EFNB3 were included. Lastly, the interaction of candidate lncRNA MSTRG.259847.2 and its target gene SMAD2 were validated in vitro of sheep pituitary cells. These differential mRNA and lncRNA expression profiles provide a valuable resource for understanding the molecular mechanisms underlying Hu sheep prolificacy.

Neuropeptide W regulates proliferation and differentiation of ATDC5: Possible involvement of GPR7 activation, PKA and PKC-dependent signalling cascades

Various neuropeptides related to the energy equilibrium affect bone growth in humans and animals. Neuropeptides W (NPW) are identical in the internal ligands of the two G‐protein receptors (GPRs) included in subtypes 7 and 8. Neuropeptides W inhibits proliferation in the cultivated rat calvarial osteoblast‐like (ROB) cells. This study examines the expression of NPW and GPR7 in murine chondrocyte and their function. An immunohistochemical analysis showed that NPW and GPR7 were expressed in the proliferative chondrocytes of the growth plates in the hind limbs of mice. The NPW mRNA quickly elevated in the early differentiation (7‐14 days) of ATDC5 cells, while NPW and GPR7 mRNA were reduced during the late stage (14‐21 days) of differentiation. Neuropeptide W‐23 (NPW‐23) promoted the proliferation of ATDC5 cells, which was attenuated by inhibiting the GPR7, protein kinase A (PKA), protein kinase C (PKC) and ERK1/2 pathways. Neuropeptide W‐23 enhanced the early cell differentiation, as evaluated by collagen type II and the aggrecan gene expression, which was unaffected by inhibiting the ERK1/2 pathway, but significantly decreased by inhibiting the PKA, PKC and p38 MAPK pathways. In contrast, NPW‐23 was not involved in the terminal differentiation of the chondrocytes, as evaluated by the mineralization of the chondrocytes and the activity of the alkaline phosphatase. Neuropeptides W stimulated the PKA, PKC, p38 MAPK and ERK1/2 activities in a dose‐ and time‐dependent manner in the ATDC5 cells. These results show that NPW promotes the proliferation and early differentiation of murine chondrocyte via GPR7 activation, as well as PKA and PKC‐dependent signalling cascades, which may be involved in endochondral bone formation.

Effects of neuromedin B on steroidogenesis, cell proliferation and apoptosis in porcine Leydig cells

Neuromedin B (NMB), a mammalian bombesin-related peptide, has numerous physiological functions, including regulating hormone secretions, cell growth, and reproduction, by binding to its receptor (NMBR). In this study, we investigated the effects of NMB on testosterone secretion, steroidogenesis, cell proliferation, and apoptosis in cultured primary porcine Leydig cells. NMBR was mainly expressed in the Leydig cells of porcine testes, and a specific dose of NMB significantly promoted the secretion of testosterone in the primary Leydig cells; moreover, NMB increased the expression of mRNA and/or proteins of NMBR and steroidogenic mediators (steroidogenic acute regulatory (STAR), CYP11A1, and HSD3B1) in the Leydig cells. In addition, specific doses of NMB promoted the proliferation of Leydig cells and increased the expression of proliferating cell nuclear antigen and Cyclin B1 proteins, while suppressing Leydig cell apoptosis and decreasing BAX and Caspase-3 protein expression. These results suggest that the NMB/NMBR system might play an important role in regulating boar reproductive function by modulating steroidogenesis and/or cell growth in porcine Leydig cells.

Neuromedin B and its receptor silencing suppresses osteoclast generation by modulating precursor proliferation via M-CSF/c-Fms/D-type cyclins

Neuromedin B (NMB), a mammalian bombesin-like peptide, regulates diverse physiological processes, such as energy metabolism, memory and fear behavior, and cellular growth, through its cognate receptor, NMBR. In this study, we report that NMB expression was upregulated during osteoclast development and that silencing NMB or NMBR attenuated osteoclast generation mediated by macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL). We found that knockdown of NMB or NMBR using a small hairpin RNA suppressed M-CSF-induced proliferation of osteoclast precursor cells without altering osteoclast differentiation. Interestingly, NMB or NMBR knockdown reduced the expression of the M-CSF receptor, c-Fms, which is an important modulator of osteoclast development. Consequently, NMB or NMBR silencing inhibited M-CSF/c-Fms-mediated downstream signaling pathways like activation of ERK and Akt and induction of D-type cyclins, cyclin D1 and D2. Moreover, knockdown of NMB or NMBR accelerated apoptosis in osteoclast lineage cells by inducing caspase-3, caspase-9, and Bim expression. In summary, our study demonstrates that the NMB/NMBR axis plays a pivotal role in osteoclast generation by modulating the proliferation and survival of osteoclast lineage cells.

Ranatensin-HL: A Bombesin-Related Tridecapeptide from the Skin Secretion of the Broad-Folded Frog, Hylarana latouchii

Bombesin-related peptides are a family of peptides whose prototype was discovered in amphibian skin and which exhibit a wide range of biological activities. Since the initial isolation of bombesin from Bombina bombina skin, diverse forms of bombesin-related peptides have been found in the skins across Anura. In this study, a novel bombesin-related peptide of the ranatensin subfamily, named ranatensin-HL, was structurally-characterised from the skin secretion of the broad-folded frog, Hylarana latouchii, through combination of molecular cloning and mass spectrometric methodologies. It is composed of 13 amino acid residues, pGlu-RAGNQWAIGHFM-NH₂, and resembles an N-terminally extended form of Xenopus neuromedin B. Ranatensin-HL and its C-terminal decapeptide (ranatensin-HL-10) were chemically synthesised and subjected to in vitro smooth muscle assays in which they were found to display moderate stimulatory effects on rat urinary bladder and uterus smooth muscles with EC₅₀ values in the range of 1–10 nM. The prepro-ranatensin-HL was highly homological to a bombesin-like peptide from Rana catesbeiana at both nucleotide and amino acid levels, which might provide a clue for the taxonomic classification of ranid frogs in the future.

Age dependent neuroprotective effects of medhya rasayana prepared from Clitoria ternatea Linn. in stress induced rat brain

ETHNOPHARMACOLOGICAL RELEVANCE

Indian traditional medicinal system in Ayurveda suggests several preparations, known as medhya rasayanas, of diverse plant origin to enhance the health in general, reduce stress and improve brain function in particular during ageing. These effects in the context of contemporary knowledge and the underlying mechanisms are not clearly understood. Autophagy and DNA damage induced repair are inter-related quintessential pathways and are significantly altered during stress and ageing. Hence, medhya rasayana prepared from Clitoria ternatea (locally known as shankhpushpi) was used to test these effects in Wistar rat model of various age groups upon stereotaxic mediated kainic acid induced brain injury.

MATERIALS AND METHODS

The rodent experiments were carried out in one, twelve and eighteen months old male Wistar rats. The rats were orally fed with medhya rasayana prepared from Clitoria ternatea (3g per kg body weight/day) for 60 days. Stereotaxic mediated kainate stress to the hippocampus was performed on day 61. The rats were sacrificed on 66th day and the brain tissues were analyzed histologically and measured for autophagy, base excision repair and antioxidant enzyme activities. In addition, cognitive functions were analyzed by employing novel object recognition task and Morris water maze tests. The gene expression profile of hippocampus was assessed by microarray hybridization and two genes are validated.

RESULTS

Our study showed significant decrease of autophagy by medhya rasayana in both 12 and 18 months old rats. The hippocampal CA3 cellularity were increased in stereotaxic mediated stressed rats by medhya rasayana. There were no significant differences in constitutive base excision repair and antioxidant enzyme activities. Medhya rasayana treatment also significantly increased episodic memory in rats. Microarray experiments for pathway specific gene expression analysis showed altered expression of genes of long-term potentiation, axon guidance, neuroactive ligand-receptor interaction, regulation of autophagy, lysosome, homologous recombination and nucleotide excision repair pathways in adult rats by medhya rasayana.

CONCLUSIONS

In the present study, we show that reduction in autophagy is crucial for medhya rasayana induced protection of rat hippocampal cells and that artificially enhanced autophagy protects the brain cell damage by maintaining the selective DNA damage repair pathway and removal of reactive oxygen species to inhibit apoptosis. These findings suggest autophagy directed pathways by medhya rasayana prepared from C. ternatea protects the brain cells from stress induced injury.

Blood-brain barrier transport kinetics of the neuromedin peptides NMU, NMN, NMB and NT

The neuromedin peptides are peripherally and centrally produced, but until now, it is generally believed that they only function as locally acting compounds without any quantitative knowledge about their blood-brain barrier (BBB) passage. Here, we characterize the transport kinetics of four neuromedins (NMU, NMN, NMB and NT) across the BBB, as well as their metabolization profile, and evaluate if they can act as endocrine hormones. Using the in vivo mouse model, multiple time regression (MTR), capillary depletion (CD) and brain efflux studies were performed. Data was fitted using linear (NMU, NT and NMB) or biphasic modeling (NMU and NMN). Three of the four investigated peptides, i.e. NMU, NT and NMN, showed a significant influx into the brain with unidirectional influx rate constants of 1.31 and 0.75 μL/(g × min) for NMU and NT respectively and initial influx constants (K1) of 72.14 and 7.55 μL/(g × min) and net influx constants (K) of 1.28 and 1.36 × 10(-16) μL/(g×min) for NMU and NMN respectively. The influx of NMB was negligible. Only NMN and NT showed a significant efflux out of the brain with an efflux constant (kout) of 0.042 min(-1) and 0.053 min(-1) respectively. Our results indicate that locally produced neuromedin peptides and/or fragments can be transported through the whole body, including passing the BBB, and taken up by different organs/tissues, supporting the idea that the neuromedins could have a much bigger role in the regulation of biological processes than currently assumed.

Expression and regulation of neuromedin B in pituitary corticotrophs of male melanocortin 2 receptor-deficient mice

The hypothalamic-pituitary-adrenal (HPA) axis is a major part of the neuroendocrine system that controls responses to stress, and has an important function in the regulation of various body processes. We previously created a mouse line deficient in the melanocortin 2 receptor (MC2R). MC2R-deficient mice (MC2R(-/-) mice) have high adrenocorticotropic hormone (ACTH) levels because of undetectable corticosterone levels. Increased neuromedin B (NMB) expression was recently reported in the pituitary gland of adrenalectomized mice, a model for acute adrenal insufficiency. To investigate gene expression in the pituitary gland under chronic adrenal deficiency, we examined the pituitary gland of MC2R(-/-) mice, a model of chronic adrenal insufficiency. To understand the molecular background of pituitary cells under chronic adrenal deficiency, we first performed DNA microarray analyses using the pituitary glands of the MC2R(-/-) mice. The DNA microarray analysis and real-time polymerase chain reaction showed that NMB expression was higher in the MC2R(-/-) than in the wild-type (WT) mice. We detected NMB expression in the MC2R(-/-) pituitary corticotrophs by immunohistochemistry using the specific antibodies for ACTH and NMB. In addition, the plasma NMB concentration was significantly higher in the MC2R(-/-) mice than in the WT mice. Subcutaneous implantation of a sustained-release corticosterone pellet decreased the expression of NMB mRNA as well as pituitary proopiomelanocortin mRNA. In isolated anterior pituitary cells, NMB mRNA expression was increased by the administration of corticotropin-releasing hormone (CRH) and was suppressed by dexamethasone treatment. In this study, we first demonstrate NMB expression in corticotrophs and its regulation by CRH and glucocorticoids. Furthermore, corticotrophs seemed to secrete NMB into the systemic circulation.

Hypoxia regulates the expression of the neuromedin B receptor through a mechanism dependent on hypoxia-inducible factor-1α

The neuromedin B receptor (NMB-R), a member of the mammalian bombesin receptor family, is frequently overexpressed in various tumors. In the present study, we found that exposure to hypoxic conditions increases the levels of NMBR mRNA and protein in breast cancer cells, which are tightly regulated by hypoxia-inducible factor-1α (HIF-1α). We confirmed the effect of HIF-1α on NMBR transcription by performing an NMBR promoter-driven reporter assay and then identified a functional hypoxia-responsive element (HRE) in the human NMBR promoter region. Further, the binding of HIF-1α to the NMBR promoter was corroborated by electrophoretic mobility shift and chromatin immunoprecipitation assays, which showed that HIF-1α specifically and directly bound to the NMBR promoter in response to hypoxia. Immunohistochemical analysis of a xenograft and a human breast cancer tissue array revealed a significant correlation between NMB-R and HIF-1α expression. Taken together, our findings indicate that hypoxia induces NMB-R expression through a novel mechanism to regulate HIF-1α expression in breast cancer cells.

Stress and eating: a dual role for bombesin-like peptides

The current obesity “epidemic” in the developed world is a major health concern; over half of adult Canadians are now classified as overweight or obese. Although the reasons for high obesity rates remain unknown, an important factor appears to be the role stressors play in overconsumption of food and weight gain. In this context, increased stressor exposure and/or perceived stress may influence eating behavior and food choices. Stress-induced anorexia is often noted in rats exposed to chronic stress (e.g., repeated restraint) and access to standard Chow diet; associated reduced consumption and weight loss. However, if a similar stressor exposure takes place in the presence of palatable, calorie dense food, rats often consume an increase proportion of palatable food relative to Chow, leading to weight gain and obesity. In humans, a similar desire to eat palatable or “comfort” foods has been noted under stressful situations; it is thought that this response may potentially be attributable to stress-buffering properties and/or through activation of reward pathways. The complex interplay between stress-induced anorexia and stress-induced obesity is discussed in terms of the overlapping circuitry and neurochemicals that mediate feeding, stress and reward pathways. In particular, this paper draws attention to the bombesin family of peptides (BBs) initially shown to regulate food intake and subsequently shown to mediate stress response as well. Evidence is presented to support the hypothesis that BBs may be involved in stress-induced anorexia under certain conditions, but that the same peptides could also be involved in stress-induced obesity. This hypothesis is based on the unique distribution of BBs in key cortico-limbic brain regions involved in food regulation, reward, incentive salience and motivationally driven behavior.