Post-nursing early life macronutrient balance promotes persistent and malleable biometric and metabolic traits in mice.

It is known that dietary factors within the gestational and nursing period affect early life and stably affect later life traits in animals. However, there is very little understanding of whether dietary factors within the early life period from post-nursing to adulthood affect traits in adulthood. To address this, we conducted studies on male C57Bl/6J mice fed from 3 weeks (immediately post-nursing) until 12 weeks (full maturity) using nine different diets varying in all three major macronutrients to parse out the effects of individual macronutrients. Early life macronutrient balance affected body composition and glucose homeostasis in early adulthood, with dietary protein and fat showing major effects. Despite this, mice showed rapid reversal of the effects on body composition and glucose homeostasis of early life diet feeding, upon standard diet feeding in adulthood. However, some traits were persistent, with early life low dietary protein levels stably affecting lean and muscle mass, and early life dietary fat levels stably affecting serum and liver triglyceride levels. In summary, macronutrient balance in the post-nursing early life period does not stably affect adiposity or glucose homeostasis but does impact muscle mass and lipid homeostasis in adulthood, with prominent effects of both protein and fat levels. KEY POINTS: Early life dietary low protein and high fat levels lowered and heightened body mass, respectively. These effects did not substantially persist into adulthood with rapid catch-up growth on a normal diet. Early life protein (negative) and fat (positive) levels affected fat mass. Early life low protein levels negatively affected lean mass. Low protein effects on lower lean and muscle mass persisted into adulthood. Early life macronutrient balance effects did not affect later life glucose homeostasis but early life high fat level affected later life dyslipidaemia. Effects of dietary carbohydrate levels in early and later life were minor.

Activin A causes endothelial dysfunction of mouse aorta and human aortic cells.

Preeclampsia is a multisystem hypertensive disorder of pregnancy that remains one of the leading causes of maternal and perinatal morbidity and mortality worldwide. The widespread maternal endothelial dysfunction that underlies preeclampsia is thought to arise from excessive placental production of various factors combined with enhanced oxidative stress. While previous studies have reported elevated activin A in women diagnosed with preeclampsia, whether activin A can cause vascular dysfunction has not yet been thoroughly investigated. Here, we demonstrated that different subtypes of activin A receptors were localised to the endothelial and smooth muscle cells of mouse and human aortae. Then, the aorta of healthy female C57Bl6J mice (n = 8) were incubated for 24 h in various concentrations of recombinant activin A to mimic early pregnancy (5 ng/mL), late pregnancy (20 ng/mL) and preeclampsia (50 ng/mL). Vascular reactivity as assessed by wire myography revealed that only the preeclamptic level of activin A impaired agonist-mediated endothelium-dependent relaxation by reducing the vasodilator prostanoid contribution to relaxation. However, agonist-mediated endothelium-independent mechanisms were unaffected. Further investigations carried out on human aortic endothelial cells suggested that the impairment of aorta relaxation could also be driven by increased endothelial cell permeability, and decreased cell viability, adherence and proliferation. This is the first direct evidence to show that activin A can induce endothelial dysfunction in whole blood vessels, suggesting that at high circulating levels it may contribute to the widespread endothelial dysfunction in women with preeclampsia.

Comparative Microarray Analysis Identifies Commonalities in Neuronal Injury: Evidence for Oxidative Stress, Dysfunction of Calcium Signalling, and Inhibition of Autophagy-Lysosomal Pathway.

Mitochondrial dysfunction, ubiquitin-proteasomal system impairment and excitotoxicity occur during the injury and death of neurons in neurodegenerative conditions. The aim of this work was to elucidate the cellular mechanisms that are universally altered by these conditions. Through overlapping expression profiles of rotenone-, lactacystin- and N-methyl-D-aspartate-treated cortical neurons, we have identified three affected biological processes that are commonly affected; oxidative stress, dysfunction of calcium signalling and inhibition of the autophagic-lysosomal pathway. These data provides many opportunities for therapeutic intervention in neurodegenerative conditions, where mitochondrial dysfunction, proteasomal inhibition and excitotoxicity are evident.

Glutaredoxin1 protects neuronal cells from copper-induced toxicity.

Glutaredoxin1 (GRX1) is a glutathione (GSH)-dependent thiol oxidoreductase. The GRX1/GSH system is important for the protection of proteins from oxidative damage and in the regulation of protein function. Previously we demonstrated that GRX1/GSH regulates the activity of the essential copper-transporting P1B-Type ATPases (ATP7A, ATP7B) in a copper-responsive manner. It has also been established that GRX1 binds copper with high affinity and regulates the redox chemistry of the metallochaperone ATOX1, which delivers copper to the copper-ATPases. In this study, to further define the role of GRX1 in copper homeostasis, we examined the effects of manipulating GRX1 expression on copper homeostasis and cell survival in mouse embryonic fibroblasts and in human neuroblastoma cells (SH-SY5Y). GRX1 knockout led to cellular copper retention (especially when cultured with elevated copper) and reduced copper tolerance, while in GRX1-overexpressing cells challenged with elevated copper, there was a reduction in both intracellular copper levels and copper-induced reactive oxygen species, coupled with enhanced cell proliferation. These effects are consistent with a role for GRX1 in regulating ATP7A-mediated copper export, and further support a new function for GRX1 in neuronal copper homeostasis and in protection from copper-mediated oxidative injury.

Silencing of Nrf genes in the human placenta as measured by SDS-PAGE and Western Blotting techniques.

Nuclear factor erythroid 2-related factor-2 (Nrf2), and the less well characterised proteins Nrf1 and Nrf3, are member of the cap 'n' collar family of transcription factors. Nrf proteins regulate the expression of endogenous antioxidant enzymes and have recently become the targets for various therapeutic treatments. Recently, Nrf proteins have been of particular interest as a target in placental-derived oxidative stress induced pregnancy disorders. Here, we report the presence of Nrf1, Nrf2 and Nrf3 proteins in both human primary trophoblast and human trophoblast choriocarcinoma cell line (BeWo). We also detail the steps taken to successfully silence all Nrf proteins in both human primary trophoblast cells and BeWo via detection of mRNA and protein using quantitative PCR, and SDS-PAGE and Western Blotting respectively.

Liver alanine catabolism promotes skeletal muscle atrophy and hyperglycaemia in type 2 diabetes.

Both obesity and sarcopenia are frequently associated in ageing, and together may promote the progression of related conditions such as diabetes and frailty. However, little is known about the pathophysiological mechanisms underpinning this association. Here we show that systemic alanine metabolism is linked to glycaemic control. We find that expression of alanine aminotransferases is increased in the liver in mice with obesity and diabetes, as well as in humans with type 2 diabetes. Hepatocyte-selective silencing of both alanine aminotransferase enzymes in mice with obesity and diabetes retards hyperglycaemia and reverses skeletal muscle atrophy through restoration of skeletal muscle protein synthesis. Mechanistically, liver alanine catabolism driven by chronic glucocorticoid and glucagon signalling promotes hyperglycaemia and skeletal muscle wasting. We further provide evidence for amino acid-induced metabolic cross-talk between the liver and skeletal muscle in ex vivo experiments. Taken together, we reveal a metabolic inter-tissue cross-talk that links skeletal muscle atrophy and hyperglycaemia in type 2 diabetes.

Restriction of essential amino acids dictates the systemic metabolic response to dietary protein dilution.

Dietary protein dilution (DPD) promotes metabolic-remodelling and -health but the precise nutritional components driving this response remain elusive. Here, by mimicking amino acid (AA) supply from a casein-based diet, we demonstrate that restriction of dietary essential AA (EAA), but not non-EAA, drives the systemic metabolic response to total AA deprivation; independent from dietary carbohydrate supply. Furthermore, systemic deprivation of threonine and tryptophan, independent of total AA supply, are both adequate and necessary to confer the systemic metabolic response to both diet, and genetic AA-transport loss, driven AA restriction. Dietary threonine restriction (DTR) retards the development of obesity-associated metabolic dysfunction. Liver-derived fibroblast growth factor 21 is required for the metabolic remodelling with DTR. Strikingly, hepatocyte-selective establishment of threonine biosynthetic capacity reverses the systemic metabolic response to DTR. Taken together, our studies of mice demonstrate that the restriction of EAA are sufficient and necessary to confer the systemic metabolic effects of DPD.

Ablation of phosphoinositide-3-kinase class II alpha suppresses hepatoma cell proliferation.

Cancer such as hepatocellular carcinoma (HCC) is characterized by complex perturbations in multiple signaling pathways, including the phosphoinositide-3-kinase (PI3K/AKT) pathways. Herein we investigated the role of PI3K catalytic isoforms, particularly class II isoforms in HCC proliferation. Among the siRNAs tested against the eight known catalytic PI3K isoforms, specific ablation of class II PI3K alpha (PIK3C2alpha) was the most effective in impairing cell growth and this was accompanied by concomitant decrease in PIK3C2alpha mRNA and protein levels. Colony formation ability of cells deficient for PIK3C2alpha was markedly reduced and growth arrest was associated with increased caspase 3 levels. A small but significant difference in gene dosage and expression levels was detected between tumor and non-tumor tissues in a cohort of 19 HCC patients. Taken together, these data suggest for the first time that in addition to class I PI3Ks in cancer, class II PIK3C2alpha can modulate HCC cell growth.

Chlorinative stress: an under appreciated mediator of neurodegeneration?

Oxidative stress has been implicated as playing a role in neurodegenerative disorders, such as ischemic stroke, Alzheimer's, Huntington's, and Parkinson's disease. Persuasive evidences have shown that microglial-mediated oxidative stress contributes significantly to cell loss and accompanying cognitive decline characteristic of the diseases. Based on the facts that (i) levels of catalytically active myeloperoxidase are elevated in diseased brains and (ii) myeloperoxidase polymorphism is associated with the risk of developing neurodegenerative disorders, HOCl as a major oxidant produced by activated phagocytes in the presence of myeloperoxidase is therefore suggested to be involved in neurodegeneration. Its association with neurodegeneration is further showed by elevated level of 3-chlorotyrosine (bio-marker of HOCl in vivo) in affected brain regions as well as HOCl scavenging ability of neuroprotectants, desferrioxamine and uric acid. In this review, we will summary the current understanding concerning the association of HOCl and neuronal cell death where production of HOCl will lead to further formation of reactive nitrogen and oxygen species. In addition, HOCl also causes tissue destruction and cellular damage leading cell death.

Early induction of calpains in rotenone-mediated neuronal apoptosis.

Rotenone is an inhibitor of mitochondrial complex I that produces a model of Parkinson's disease (PD), where neurons undergo apoptosis by caspase-dependent and/or caspase-independent pathways. Inhibition of calpains has recently been shown to attenuate neuronal apoptosis. This study aims to establish for the first time, the time-point of calpain activation with respect to the caspase activation and the possibility of cell cycle re-entry in rotenone-mediated cell death. Immunoblot results revealed calpain activation occurred at 5, 10h prior to caspase-3 activation (at 15 h), suggesting calpain activation was an earlier cellular event compared to caspase activation in the rotenone-mediated apoptosis. In addition, an upregulation of phospho-p53 was observed at 21 h. However, no expression or upregulation of cell cycle regulatory proteins including cdc25a, cyclin-D1 and cyclin-D3 were observed, strongly suggesting that cell cycle re-entry did not occur. These findings provide new insights into the differential patterns of calpain and caspase activation that result from rotenone poisoning and which may be relevant to the therapeutic management of PD.

Gene profiling identifies commonalities in neuronal pathways in excitotoxicity: evidence favouring cell cycle re-activation in concert with oxidative stress.

Excitotoxicity, induced by the aberrant rise in cytosolic Ca(2+) level, is a major neuropathological process in numerous neurodegenerative disorders. It is triggered when extracellular glutamate (Glu) concentration reaches neuropathological levels resulting in dysregulation and hyper-activation of ionotropic glutamate receptor subtype (iGluRs). Even though all three members of the iGluRs, namely N-methyl-d-aspartate (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPAR) and kainate (KAR) receptors are implicated in excitotoxicity, their individual contributions to downstream signaling transduction have not been explored. In this study, we report a comprehensive description of the recruitment of cellular processes in neurons upon iGluR activation during excitotoxicity through temporal (5h, 15h, and 24h) global gene profiling of AMPA, KA, NMDA, and Glu excitotoxic models. DNA microarray analyses of mouse primary cortical neurons treated with these four pharmacological agonists are further validated via real-time PCR. Bi-model analyses against Glu model demonstrate that NMDARs and KARs play a more pivotal role in Glu-mediated excitotoxicity, with a higher degree of global gene profiling overlaps, as compared to that of AMPARs. Comparison of global transcriptomic profiles reveals aberrant calcium ion binding and homeostasis, organellar (lysosomal and endoplasmic reticulum) stress, oxidative stress, cell cycle re-entry and activation of cell death processes as the main pathways that are significantly modulated across all excitotoxicity models. Singular profile analyses demonstrate substantial transcriptional regulation of numerous cell cycle proteins. For the first time, we show that iGluR activation forms the basis of cell cycle re-activation, and together with oxidative stress fulfill the "two-hit" hypothesis that accelerates neurodegeneration.

Gene expression profiling of rotenone-mediated cortical neuronal death: evidence for inhibition of ubiquitin-proteasome system and autophagy-lysosomal pathway, and dysfunction of mitochondrial and calcium signaling.

Mitochondrial dysfunction and oxidative stress are currently considered two key mechanisms contributing to pathobiology in neurodegenerative conditions. The current study investigated the temporal molecular events contributing to programmed cell death after treatment with the mitochondrial complex I inhibitor rotenone. Microarray analysis was performed using cultured neocortical neurons treated with 10nM rotenone for 8, 15, and 24h. Genes showing at least ±1.2-fold change in expression at one time point were considered significant. Transcriptomic analysis of the 4178 genes probes revealed major changes to nine biological processes, including those eliciting mitochondrial dysfunction, activation of calcium signaling, increased expression of apoptotic genes, and downplay of chaperones/co-chaperones, ubiquitin-proteasome system and autophagy. These data define targets for intervention where mitochondrial complex I dysfunction plays a substantial role, most notably Parkinson's disease.

Temporal transcriptomic profiling reveals cellular targets that govern survival in HOCl-mediated neuronal apoptosis.

AIMS: With the identification of hypochlorous acid (HOCl) as a biomarker in diseased brains and endogenous detection of its modified proteins, HOCl might be implicated in the development of neurodegenerative disorders. However, its effect on neuronal cell death has not yet been investigated at gene expression level. MAIN METHODS: Therefore, DNA microarray was performed for screening of HOCl-responsive genes in primary mouse cortical neurons. Neurotoxicity caused by physiological relevant HOCl (250µM) exhibited several biochemical markers of apoptosis. KEY FINDINGS: The biological processes affected during HOCl-mediated apoptosis included cell death, response to stress, cellular metabolism, and cell cycle. Among them, mRNAs level of cell death and stress response genes were up-regulated while expression of metabolism and cell cycle genes were down-regulated. SIGNIFICANCE: Our results showed, for the first time, that HOCl induces apoptosis in cortical neurons by upregulating apoptotic genes and gene expression of stress response such as heat shock proteins and antioxidant proteins were enhanced to provide protection. These data form a foundation for the development of screening platforms and define targets for intervention in HOCl neuropathologies where HOCl-mediated injury is causative.

Proteasome inhibition: an early or late event in nitric oxide-induced neuronal death?

Nitric oxide (NO), ubiquitously expressed in the central nervous system, has been perceived to be a potential neuromodulator. Employing cultured murine primary cortical neurons, NO resulted in an inhibition of the ubiquitin-proteasome system (UPS) with a dose- and time-dependent decrease in cell viability. This is consistent with a previous study that reported a dysfunction of UPS with consequential apoptotic death in macrophage cell with NO treatment. However, it cannot be unclear if the drop in UPS efficiency is directly imposed on by NO. Therefore by using microarray analysis, our study revealed an early down-regulation or non-significant differential expression of genes encoding UPS proteins in NOC-18 (NO donor)-treated neurons as compared to an observed elevation of corresponding gene expression genes in lactacystin (classical proteasome inhibitor)-treated neurons (conducted earlier). Furthermore, time-course analysis of proteasome activity in NOC-18-treated neurons demonstrated a late onset of reduction. This is intriguing as it is well established that in an exclusive proteasome dysfunction-induced cell death, a compensatory feedback mechanism will be activated with an initial and concerted up-regulation of genes encoding proteins involved in UPS as seen when neurons were treated with lactacystin. Thus, it is highly suggestive that NO-triggered neuronal death takes on a different signaling cascade from that of a classical proteasome inhibitor, and that the late reduction of proteasome activity is a downstream event following the activation of apoptotic cellular signaling cascade. In intracellular condition, the proteasome is not NO preferred primary target responsible for the trigger of the cell death machinery. In conclusion, we presented novel findings that shed light into NO-induced cell death signaling cascade, which would be important in understanding the pathogenesis of neurodegenerative disorders such as Parkinson's disease.

Hypochlorous acid induces apoptosis of cultured cortical neurons through activation of calpains and rupture of lysosomes.

3-Chlorotyrosine, a bio-marker of hypochlorous acid (HOCl) in vivo, was reported to be substantially elevated in the Alzheimer's disease (AD) brains. Thus, HOCl might be implicated in the development of AD. However, its effect and mechanism on neuronal cell death have not been investigated. Here, we report for the first time that HOCl treatment induces an apoptotic-necrotic continuum of concentration-dependent cell death in cultured cortical neurons. Neurotoxicity caused by an intermediate concentration of HOCl (250 microm) exhibited several biochemical markers of apoptosis in the absence of caspase activation. However, the involvement of calpains was demonstrated by data showing that calpain inhibitors protect cortical neurons from apoptosis and the formation of 145/150 kDa alpha-fodrin fragments. Moreover, an increase in cytosolic Ca2+ concentration was associated with HOCl neurotoxicity and Ca2+ channel antagonists, and Ca2+ chelators prevented cleavage of alpha-fodrin and the induction of apoptosis. Finally, we found that calpain activation ruptured lysosomes. Stabilization of lysosomes by calpain inhibitors or imidazoline drugs, as well as inhibition of cathepsin protease activities, rescued cells from HOCl-induced neurotoxicity. Our results showed for the first time that HOCl induces apoptosis in cortical neurons, and that the cell death process involves calpain activation and rupture of lysosomes.