Investigation of GMP signalling systems in lower vertebrates

This research examined aspects of the cyclic GMP signalling system in fish and amphibians. It contributed new knowledge to our understanding of the role of the system in the development of zebrafish, a model fish species, and in control of the vasculature by the regulatory molecule, nitric oxide.

Whey protein ingestion activates mTOR-dependent signalling after resistance exercise in young men : a double-blinded randomized controlled trial

The effect of resistance exercise with the ingestion of supplementary protein on the activation of the mTOR cascade, in human skeletal muscle has not been fully elucidated. In this study, the impact of a single bout of resistance exercise, immediately followed by a single dose of whey protein isolate (WPI) or placebo supplement, on the activation of mTOR signalling was analyzed. Young untrained men completed a maximal single-legged knee extension exercise bout and were randomized to ingest either WPI supplement (n = 7) or the placebo (n = 7). Muscle biopsies were taken from the vastus lateralis before, and 2, 4 and 24 hr post-exercise. WPI or placebo ingestion consumed immediately post-exercise had no impact on the phosphorylation of Akt (Ser⁴⁷³). However, WPI significantly enhanced phosphorylation of mTOR (Ser²⁴⁴⁸), 4E-BP1 (Thr^37/46) and p70S6K (Thr³⁸⁹) at 2 hr post-exercise. This study demonstrates that a single dose of WPI, when consumed in modest quantities, taken immediately after resistance exercise elicits an acute and transient activation of translation initiation within the exercised skeletal muscle.

Akt signalling through GSK-3beta, mTOR and Foxo1 is involved in human skeletal muscle hypertrophy and atrophy

Skeletal muscle size is tightly regulated by the synergy between anabolic and catabolic signalling pathways which, in humans, have not been well characterized. Akt has been suggested to play a pivotal role in the regulation of skeletal muscle hypertrophy and atrophy in rodents and cells. Here we measured the amount of phospho-Akt and several of its downstream anabolic targets (glycogen synthase kinase-3β (GSK-3β), mTOR, p70s6k and 4E-BP1) and catabolic targets (Foxo1, Foxo3, atrogin-1 and MuRF1). All measurements were performed in human quadriceps muscle biopsies taken after 8 weeks of both hypertrophy-stimulating resistance training and atrophy-stimulating de-training. Following resistance training a muscle hypertrophy (∼10%) and an increase in phospho-Akt, phospho-GSK-3β and phospho-mTOR protein content were observed. This was paralleled by a decrease in Foxo1 nuclear protein content. Following the de-training period a muscle atrophy (5%), relative to the post-training muscle size, a decrease in phospho-Akt and GSK-3β and an increase in Foxo1 were observed. Atrogin-1 and MuRF1 increased after the hypertrophy and decreased after the atrophy phases. We demonstrate, for the first time in human skeletal muscle, that the regulation of Akt and its downstream signalling pathways GSK-3β, mTOR and Foxo1 are associated with both the skeletal muscle hypertrophy and atrophy processes.

Multifaceted role of nitric oxide in an in vitro mouse neuronal injury model: transcriptomic profiling defines the temporal recruitment of death signalling cascades

Nitric oxide is implicated in the pathogenesis of various neuropathologies characterized by oxidative stress. Although nitric oxide has been reported to be involved in the exacerbation of oxidative stress observed in several neuropathologies, existent data fail to provide a holistic description of how nitrergic pathobiology elicits neuronal injury. Here we provide a comprehensive description of mechanisms contributing to nitric oxide induced neuronal injury by global transcriptomic profiling. Microarray analyses were undertaken on RNA from murine primary cortical neurons treated with the nitric oxide generator DETA-NONOate (NOC-18, 0.5 mM) for 8–24 hrs. Biological pathway analysis focused upon 3672 gene probes which demonstrated at least a ±1.5-fold expression in a minimum of one out of three time-points and passed statistical analysis (one-way anova, P < 0.05). Numerous enriched processes potentially determining nitric oxide mediated neuronal injury were identified from the transcriptomic profile: cell death, developmental growth and survival, cell cycle, calcium ion homeostasis, endoplasmic reticulum stress, oxidative stress, mitochondrial homeostasis, ubiquitin-mediated proteolysis, and GSH and nitric oxide metabolism. Our detailed time-course study of nitric oxide induced neuronal injury allowed us to provide the first time a holistic description of the temporal sequence of cellular events contributing to nitrergic injury. These data form a foundation for the development of screening platforms and define targets for intervention in nitric oxide neuropathologies where nitric oxide mediated injury is causative.

Early events of HIV-1 infection : can signalling be the next therapeutic target?

Intracellular signaling events are signposts of biological processes, which govern the direction and action of biological activities. Through millions of years of evolution, pathogens, such as viruses, have evolved to hijack host cell machinery to infect their targets and are therefore dependent on host cell signaling for replication. This review will detail our current understanding of the signaling events that are important for the early steps of HIV-1 replication. More specifically, the therapeutic potential of signaling events associated with chemokine coreceptors, virus entry, viral synapses, and post-entry processes will be discussed. We argue that these pathways may represent novel targets for antiviral therapy.

Skeletal muscle nitric oxide signalling and exercise: a focus on glucose metabolism

Nitric oxide (NO) is an important vasodilator and regulator in the cardiovascular system, and this link was the subject of a Nobel prize in 1998. However, NO also plays many other regulatory roles, including thrombosis, immune function, neural activity, and gastrointestinal function. Low concentrations of NO are thought to have important signaling effects. In contrast, high concentrations of NO can interact with reactive oxygen species, causing damage to cells and cellular components.

A less-recognized site of NO production is within skeletal muscle, where small increases are thought to have beneficial effects such as regulating glucose uptake and possibly blood flow, but higher levels of production are thought to lead to deleterious effects such as an association with insulin resistance.

This review will discuss the role of NO in skeletal muscle during and following exercise, including in mitochondrial biogenesis, muscle efficiency, and blood flow with a particular focus on its potential role in regulating skeletal muscle glucose uptake during exercise.

Alterations in Notch signalling in skeletal muscles from mdx and dko dystrophic mice and patients with Duchenne muscular dystrophy.

New Findings What is the central question of this study? The Notch signalling pathway plays an important role in muscle regeneration, and activation of the pathway has been shown to enhance muscle regeneration in aged mice. It is unknown whether Notch activation will have a similarly beneficial effect on muscle regeneration in the context of Duchenne muscular dystrophy (DMD). What is the main finding and its importance? Although expression of Notch signalling components is altered in both mouse models of DMD and in human DMD patients, activation of the Notch signalling pathway does not confer any functional benefit on muscles from dystrophic mice, suggesting that other signalling pathways may be more fruitful targets for manipulation in treating DMD. Abstract In Duchenne muscular dystrophy (DMD), muscle damage and impaired regeneration lead to progressive muscle wasting, weakness and premature death. The Notch signalling pathway represents a central regulator of gene expression and is critical for cellular proliferation, differentiation and apoptotic signalling during all stages of embryonic muscle development. Notch activation improves muscle regeneration in aged mice, but its potential to restore regeneration and function in muscular dystrophy is unknown. We performed a comprehensive examination of several genes involved in Notch signalling in muscles from dystrophin-deficient mdx and dko (utrophin- and dystrophin-null) mice and DMD patients. A reduction of Notch1 and Hes1 mRNA in tibialis anterior muscles of dko mice and quadriceps muscles of DMD patients and a reduction of Hes1 mRNA in the diaphragm of the mdx mice were observed, with other targets being inconsistent across species. Activation and inhibition of Notch signalling, followed by measures of muscle regeneration and function, were performed in the mouse models of DMD. Notch activation had no effect on functional regeneration in C57BL/10, mdx or dko mice. Notch inhibition significantly depressed the frequency-force relationship in regenerating muscles of C57BL/10 and mdx mice after injury, indicating reduced force at each stimulation frequency, but enhanced the frequency-force relationship in muscles from dko mice. We conclude that while Notch inhibition produces slight functional defects in dystrophic muscle, Notch activation does not significantly improve muscle regeneration in murine models of muscular dystrophy. Furthermore, the inconsistent expression of Notch targets between murine models and DMD patients suggests caution when making interspecies comparisons.

Granulocyte colony-stimulating factor receptor signalling via Janus kinase 2/signal transducer and activator of transcription 3 in ovarian cancer

Ovarian cancer remains a major cause of cancer mortality in women, with only limited understanding of disease aetiology at the molecular level. Granulocyte colony-stimulating factor (G-CSF) is a key regulator of both normal and emergency haematopoiesis, and is used clinically to aid haematopoietic recovery following ablative therapies for a variety of solid tumours including ovarian cancer.