Nitric oxide activates PI3-K and MAPK signalling pathways in human and rat vascular smooth muscle cells: Influence of insulin resistance and oxidative stress

Unveiling the significance of inducible nitric oxide synthase: Its impact on cancer progression and clinical implications

The intricate role of inducible nitric oxide synthase (iNOS) in cancer pathophysiology has garnered significant attention, highlighting the complex interplay between tumorigenesis, immune response, and cellular metabolism. As an enzyme responsible for producing nitric oxide (NO) in response to inflammatory stimuli. iNOS is implicated in various aspects of cancer development, including DNA damage, angiogenesis, and evasion of apoptosis. This review synthesizes the current findings from both preclinical and clinical studies on iNOS across different cancer types, reflecting the variability depending on cellular context and tumor microenvironment. We explore the molecular mechanisms by which iNOS modulates cancer cell growth, survival, and metastasis, emphasizing its impact on immune surveillance and response to treatment. Additionally, the potential of targeting iNOS as a therapeutic strategy in cancer treatment is examined. By integrating insights from recent advances, this review aims to elucidate the significant role of iNOS in cancer and pave the way for novel diagnostic and therapeutic approaches.

Regulation of mTOR Signaling: Emerging Role of Cyclic Nucleotide-Dependent Protein Kinases and Implications for Cardiometabolic Disease

The mechanistic target of rapamycin (mTOR) kinase is a central regulator of cell growth and metabolism. It is the catalytic subunit of two distinct large protein complexes, mTOR complex 1 (mTORC1) and mTORC2. mTOR activity is subjected to tight regulation in response to external nutrition and growth factor stimulation. As an important mechanism of signaling transduction, the 'second messenger' cyclic nucleotides including cAMP and cGMP and their associated cyclic nucleotide-dependent kinases, including protein kinase A (PKA) and protein kinase G (PKG), play essential roles in mediating the intracellular action of a variety of hormones and neurotransmitters. They have also emerged as important regulators of mTOR signaling in various physiological and disease conditions. However, the mechanism by which cAMP and cGMP regulate mTOR activity is not completely understood. In this review, we will summarize the earlier work establishing the ability of cAMP to dampen mTORC1 activation in response to insulin and growth factors and then discuss our recent findings demonstrating the regulation of mTOR signaling by the PKA- and PKG-dependent signaling pathways. This signaling framework represents a new non-canonical regulation of mTOR activity that is independent of AKT and could be a novel mechanism underpinning the action of a variety of G protein-coupled receptors that are linked to the mTOR signaling network. We will further review the implications of these signaling events in the context of cardiometabolic disease, such as obesity, non-alcoholic fatty liver disease, and cardiac remodeling. The metabolic and cardiac phenotypes of mouse models with targeted deletion of Raptor and Rictor, the two essential components for mTORC1 and mTORC2, will be summarized and discussed.

Malting barley carbon dots-mediated oxidative stress promotes insulin resistance in mice via NF-κB pathway and MAPK cascade

Background

Food-borne carbon dots (CDs) are widely generated during food processing and are inevitably ingested by humans causing toxicity. However, the toxic effects of food-borne CDs on the blood glucose metabolism are unknown.

Results

In this study, we brewed beer via a representative strategy and extracted the melting-barley CDs (MBCDs) to explore the toxic effects on blood glucose in mice. We found the accumulation of fluorescent labeled MBCDs in various organs and oral administration of MBCDs can cause visceral toxicity, manifested as liver damage. Mice were orally administered MBCDs (5 and 25 mg/kg) for 16 weeks, and increased levels of fasting blood glucose were observed in both MBCDs-treated groups. Transcriptomic analyses revealed that MBCDs activate oxidative stress, inflammatory responses, the MAPK cascade, and PI3K/Akt signaling in mice livers. Mechanistically, MBCDs exposure-induced reactive oxygen species (ROS) overproduction activates the nuclear factor-κB (NF-κB) signaling pathway and MAPK cascade, thereby promoting phosphorylated insulin receptor substrate (IRS)-1 at Ser307 and inducing insulin resistance (IR). Meanwhile, the IR promoted gluconeogenesis, which enhanced MBCDs-induced hyperglycemia of mice. Importantly, inhibition of the ROS significantly attenuated the MBCDs-induced inflammatory response and MAPK cascade, thereby alleviating IR and hyperglycemia in mice.

Conclusion

In summary, this study revealed that MBCDs promote ROS overproduction and thus induced IR, resulting in imbalance of glucose homeostasis in mice. More importantly, this study was further assessed to reveal an imperative emphasis on the reevaluation of dietary and environmental CDs exposure, and has important implications for T2DM prevention research.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01543-1.

Deregulation of Ca2+-Signaling Systems in White Adipocytes, Manifested as the Loss of Rhythmic Activity, Underlies the Development of Multiple Hormonal Resistance at Obesity and Type 2 Diabetes

Various types of cells demonstrate ubiquitous rhythmicity registered as simple and complex Ca²⁺-oscillations, spikes, waves, and triggering phenomena mediated by G-protein and tyrosine kinase coupled receptors. Phospholipase C/IP₃-receptors (PLC/IP₃R) and endothelial NO-synthase/Ryanodine receptors (NOS/RyR)–dependent Ca²⁺ signaling systems, organized as multivariate positive feedback generators (PLC-G and NOS-G), underlie this rhythmicity. Loss of rhythmicity at obesity may indicate deregulation of these signaling systems. To issue the impact of cell size, receptors’ interplay, and obesity on the regulation of PLC-G and NOS-G, we applied fluorescent microscopy, immunochemical staining, and inhibitory analysis using cultured adipocytes of epididumal white adipose tissue of mice. Acetylcholine, norepinephrine, atrial natriuretic peptide, bradykinin, cholecystokinin, angiotensin II, and insulin evoked complex [Ca²⁺]_i responses in adipocytes, implicating NOS-G or PLC-G. At low sub-threshold concentrations, acetylcholine and norepinephrine or acetylcholine and peptide hormones (in paired combinations) recruited NOS-G, based on G proteins subunits interplay and signaling amplification. Rhythmicity was cell size- dependent and disappeared in hypertrophied cells filled with lipids. Contrary to control cells, adipocytes of obese hyperglycemic and hypertensive mice, growing on glucose, did not accumulate lipids and demonstrated hormonal resistance being non responsive to any hormone applied. Preincubation of preadipocytes with palmitoyl-L-carnitine (100 nM) provided accumulation of lipids, increased expression and clustering of IP₃R and RyR proteins, and partially restored hormonal sensitivity and rhythmicity (5–15% vs. 30–80% in control cells), while adipocytes of diabetic mice were not responsive at all. Here, we presented a detailed kinetic model of NOS-G and discussed its control. Collectively, we may suggest that universal mechanisms underlie loss of rhythmicity, Ca²⁺-signaling systems deregulation, and development of general hormonal resistance to obesity.

Insulin's actions on vascular tissues: Physiological effects and pathophysiological contributions to vascular complications of diabetes

Background

Insulin has been demonstrated to exert direct and indirect effects on vascular tissues. Its actions in vascular cells are mediated by two major pathways: the insulin receptor substrate 1/2-phosphoinositide-3 kinase/Akt (IRS1/2/PI3K/Akt) pathway and the Src/mitogen-activated protein kinase (MAPK) pathway, both of which contribute to the expression and distribution of metabolites, hormones, and cytokines.

Scope of review

In this review, we summarize the current understanding of insulin's physiological and pathophysiological actions and associated signaling pathways in vascular cells, mainly in endothelial cells (EC) and vascular smooth muscle cells (VSMC), and how these processes lead to selective insulin resistance. We also describe insulin's potential new signaling and biological effects derived from animal studies and cultured capillary and arterial EC, VSMC, and pericytes. We will not provide a detailed discussion of insulin's effects on the myocardium, insulin's structure, or its signaling pathways' various steps, since other articles in this issue discuss these areas in depth.

Major conclusions

Insulin mediates many important functions on vascular cells via its receptors and signaling cascades. Its direct actions on EC and VSMC are important for transporting and communicating nutrients, cytokines, hormones, and other signaling molecules. These vascular actions are also important for regulating systemic fuel metabolism and energetics. Inhibiting or enhancing these pathways leads to selective insulin resistance, exacerbating the development of endothelial dysfunction, atherosclerosis, restenosis, poor wound healing, and even myocardial dysfunction. Targeted therapies to improve selective insulin resistance in EC and VSMC are thus needed to specifically mitigate these pathological processes.

•

Insulin's actions in vascular cells have a significant influence on systemic metabolism.

•

Insulin exerts its vascular effects through its receptors and signaling cascades.

•

Inhibition or enhancement of different insulin signaling leads to selective insulin resistance.

•

Loss of insulin's actions causes endothelial dysfunction and vascular complications in diabetes.

Cyclic Nucleotides Signaling and Phosphodiesterase Inhibition: Defying Alzheimer's Disease

Defects in brain functions associated with aging and neurodegenerative diseases benefit insignificantly from existing options, suggesting that there is a lack of understanding of pathological mechanisms. Alzheimer's disease (AD) is such a nearly untreatable, allied to age neurological deterioration for which only the symptomatic cure is available and the agents able to mould progression of the disease, is still far away. The altered expression of phosphodiesterases (PDE) and deregulated cyclic nucleotide signaling in AD has provoked a new thought of targeting cyclic nucleotide signaling in AD. Targeting cyclic nucleotides as an intracellular messenger seems to be a viable approach for certain biological processes in the brain and controlling substantial. Whereas, the synthesis, execution, and/or degradation of cyclic nucleotides has been closely linked to cognitive deficits. In relation to cognition, the cyclic nucleotides (cAMP and cGMP) have an imperative execution in different phases of memory, including gene transcription, neurogenesis, neuronal circuitry, synaptic plasticity and neuronal survival, etc. AD is witnessed by impairments of these basic processes underlying cognition, suggesting a crucial role of cAMP/cGMP signaling in AD populations. Phosphodiesterase inhibitors are the exclusive set of enzymes to facilitate hydrolysis and degradation of cAMP and cGMP thereby, maintains their optimum levels initiating it as an interesting target to explore. The present work reviews a neuroprotective and substantial influence of PDE inhibition on physiological status, pathological progression and neurobiological markers of AD in consonance with the intensities of cAMP and cGMP.

Silicon dioxide nanoparticles induce insulin resistance through endoplasmic reticulum stress and generation of reactive oxygen species

Background

Silicon dioxide nanoparticles (SiO₂ NPs) are one of the most widely utilized NPs in various food sectors. However, the potential endocrine toxicity of SiO₂ NPs has not been characterized.

Results

In the present study, mice were orally administered a series of doses of SiO₂ NPs. All doses of SiO₂ NPs were absorbed into the blood, liver, and pancreas of the mice. Administration of 100 mg/kg bw (body weight) of SiO₂ NPs significantly increased blood glucose levels in mice. However, the same dose of SiO₂ fine-particles (FPs) did not result in altered blood glucose. Whole-genome analysis showed that SiO₂ NPs affected the expression of genes associated with reactive oxygen species (ROS) production and endoplasmic reticulum (ER) stress. In addition, we showed that SiO₂ NPs activated xenobiotic metabolism, resulting in ER stress. Endoplasmic reticulum stress resulted in increased ROS production, which activated the NF-κB pathway leading to expression of inflammatory cytokines. Increased inflammatory cytokine expression resulted in serine phosphorylation of IRS1, which induced insulin resistance (IR). Furthermore these inflammatory cytokines activated the MAPK pathway, which further promoted the serine phosphorylation of IRS1. Insulin resistance resulted in elevated blood glucose. The ER stress inhibitor 4-phenylbutyric acid (4-PBA) inhibited SiO₂ NP-induced ROS production. The ROS scavenger N-acetylcysteine (NAC) did not affect SiO₂ NP-induced ER stress, but inhibited SiO₂ NP-induced activation of the NF-κB and MAPK pathways, expression of inflammatory cytokines, SiO₂ NP-induced serine phosphorylation of IRS1, and SiO2 NP-induced elevations of blood glucose.

Conclusion

Silicon dioxide NPs induced IR through ER stress and generation of ROS, but SiO₂ FPs did not. Therefore, lifelong exposure of humans to SiO₂ NPs may result in detrimental effects on blood glucose. The results of this study strongly suggested that non-nanoformed SiO₂ should be used as food additives.

Molecular mechanisms underlying zinc oxide nanoparticle induced insulin resistance in mice

Zinc oxide nanoparticles (ZnO NPs) represent an important class of commercially applied materials. Recently, adverse effects of ZnO NPs were found in humans and animals following ingestion, although the effects on endocrine system disease remain unclear. In this study, ZnO NPs were orally administered to mice, and at doses of 25 mg/kg bw (body weight) ZnO NPs and above, plasma glucose increased significantly. The genome-wide effects of ZnO NPs were then investigated using RNA-sequencing technology. In the cluster analysis, the most significantly enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways concerned membranes and their close association with endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) generation. Biochemical and gene and protein expression analyses revealed that ZnO NPs activated a xenobiotic biodegradation response and increased the expression of cytochrome P450 (CYP) enzymes in mice livers, leading to ER stress. The ER stress increased ROS generation. The high levels of ROS activated the MAPK and NF-κB pathways and induced an inflammation response, resulting in the phosphorylation of insulin receptor substrate 1. Thus, the insulin resistance that developed was the primary mechanism for the increase in the plasma glucose of mice treated orally with ZnO NPs.

Differential radio-adaptive responses in BALB/c and C57BL/6 mice: pivotal role of calcium and nitric oxide signalling

Purpose: Our earlier studies demonstrated that transient radio-adaptive responses (RAR) in BALB/c mice were due to MAPK hyperactivation. The objective of this study was to determine the time duration of this low dose induced MAPK activation in BALB/c mice and to find out if similar adaptive responses are observed in C57BL/6 mice. Materials and methods: Mice were irradiated with 0.1 Gy priming dose (PD), 2 Gy challenge dose (CD) with an interval of 4 h (P + CD) and radiation induced immunosuppression in splenic lymphocytes was monitored as the endpoint for RAR. Results: Time kinetics following 0.1 Gy demonstrated persistence of MAPK hyperactivation till 48 h. Similar experiments in C57BL/6 mice indicated absence of RAR at 24 h following CD, in spite of MAPK activation which was also confirmed by time kinetics. Therefore, upstream activators of MAPK, viz., reactive oxygen and nitrogen species (ROS, RNS) and calcium levels were estimated. There was increased intracellular calcium (Ca²⁺) and nitric oxide (NO) in BALB/c and an increase in intracellular ROS in C57BL/6 mice 24 h after PD. Inhibition of NO and calcium chelation abrogated RAR in BALB/c mice. In vitro treatment of spleen cells with combination of NO donor and Ca²⁺ ionophore mimicked the effect of PD and induced adaptive response after 2 Gy not only in BALB/c but also in C57BL/6 mice confirming their crucial role in RAR. Conclusions: These results suggest that low dose induced differential induction of Ca²⁺ and NO signaling along with MAPK was responsible for contrasting RAR with respect to immune system of BALB/c and C57BL/6 mice. Abbreviations [³H]-TdR: ³H-methyl-thymidine; BAPTA: 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; CD: Challenge Dose; CFSE: Carboxy Fluorescein Succinamidyl Ester; on A: Concanavalin A; DAF-FM: 4-amino-5-methylamino-2',7'-difluorescein; DCF-DA: 2',7'-dichlorofluorescein diacetate; DSB: Double Strand Break; ELISA: Enzyme Linked ImmunoSorbent Assay; ERK: Extracellular signal-Regulated protein Kinase; FBS: Fetal Bovine Serum; HIF-1A: Hypoxia-Inducible Factor 1-alpha; LDR: Low Dose Radiation; MAPK: Mitogen Activated Protein Kinase; MAPKK/MKK: MAPK Kinase; MAPKKK: MAPK Kinase Kinase; NO: Nitric Oxide; NOS: Nitric Oxide Synthase; P + CD: Priming + Challenge dose; PBS: Phosphate Buffered Saline; PBST: Phosphate Buffered Saline-Tween 20; PD: Priming Dose; PI3K: Phosphatidyl Inositol 3-Kinase; PKC: Protein Kinase C; RAR: Radio Adaptive Response; RNS: Reactive Nitrogen Species; ROS: Reactive Oxygen Species; RPMI-1640: Roswell Park Memorial Institute-1640 medium; SAPK/JNK: Stress-Activated Protein Kinase/ c-Jun NH2-terminal Kinase; SEM: Standard Error of Mean; SNAP: S-nitro amino penicillamine; TP53: Tumor Protein 53; γ-H2AX: Gamma- H2A histone family member X; Th1: Type 1 helper T cell responses; Th2: Type 2 helper T cell responses.

Emerging Role of mTOR Signaling-Related miRNAs in Cardiovascular Diseases

Mechanistic/mammalian target of rapamycin (mTOR), an atypical serine/threonine kinase of the phosphoinositide 3-kinase- (PI3K-) related kinase family, elicits a vital role in diverse cellular processes, including cellular growth, proliferation, survival, protein synthesis, autophagy, and metabolism. In the cardiovascular system, the mTOR signaling pathway integrates both intracellular and extracellular signals and serves as a central regulator of both physiological and pathological processes. MicroRNAs (miRs), a class of short noncoding RNA, are an emerging intricate posttranscriptional modulator of critical gene expression for the development and maintenance of homeostasis across a wide array of tissues, including the cardiovascular system. Over the last decade, numerous studies have revealed an interplay between miRNAs and the mTOR signaling circuit in the different cardiovascular pathophysiology, like myocardial infarction, hypertrophy, fibrosis, heart failure, arrhythmia, inflammation, and atherosclerosis. In this review, we provide a comprehensive state of the current knowledge regarding the mechanisms of interactions between the mTOR signaling pathway and miRs. We have also highlighted the latest advances on mTOR-targeted therapy in clinical trials and the new perspective therapeutic strategies with mTOR-targeting miRs in cardiovascular diseases.

Cardiac natriuretic peptides promote adipose 'browning' through mTOR complex-1

OBJECTIVE

Activation of thermogenesis in brown adipose tissue (BAT) and the ability to increase uncoupling protein 1 (UCP1) levels and mitochondrial biogenesis in white fat (termed 'browning'), has great therapeutic potential to treat obesity and its comorbidities because of the net increase in energy expenditure. β-adrenergic-cAMP-PKA signaling has long been known to regulate these processes. Recently PKA-dependent activation of mammalian target of rapamycin complex 1 (mTORC1) was shown to be necessary for adipose 'browning' as well as proper development of the interscapular BAT. In addition to cAMP-PKA signaling pathways, cGMP-PKG signaling also promotes this browning process; however, it is unclear whether or not mTORC1 is also necessary for cGMP-PKG induced browning.

METHOD

Activation of mTORC1 by natriuretic peptides (NP), which bind to and activate the membrane-bound guanylyl cyclase, NP receptor A (NPRA), was assessed in mouse and human adipocytes in vitro and mouse adipose tissue in vivo.

RESULTS

Activation of mTORC1 by NP-cGMP signaling was observed in both mouse and human adipocytes. We show that NP-NPRA-PKG signaling activate mTORC1 by direct PKG phosphorylation of Raptor at Serine 791. Administration of B-type natriuretic peptide (BNP) to mice induced Ucp1 expression in inguinal adipose tissue in vivo, which was completely blocked by the mTORC1 inhibitor rapamycin.

CONCLUSION

Our results demonstrate that NP-cGMP signaling activates mTORC1 via PKG, which is a component in the mechanism of adipose browning.

Pancreatic-β-cell survival and proliferation are promoted by protein kinase G type Iα and downstream regulation of AKT/FOXO1

Early studies showed nitric oxide as a pro-inflammatory-cytokine-induced toxin involved in pancreatic β-cell destruction during pathogenesis of type-1 diabetes. However, nitric oxide has both cytotoxic and cytoprotective effects on mammalian cells, depending on concentration and micro-environmental surroundings. Our studies have shown that low/physiological-level nitric oxide selectively activates protein kinase G type Iα isoform, promoting cytoprotective/pro-cell-survival effects in many cell types. In bone marrow-derived stromal/mesenchymal stem cells, protein kinase G type Iα mediates autocrine effects of nitric oxide and atrial natriuretic peptide, promoting DNA-synthesis/proliferation and cell survival. In this study, endothelial nitric oxide synthase/neuronal nitric oxide synthase inhibitor L-NIO (L-N(5)-(1-iminoethyl)ornithine), soluble guanylyl cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3,-a] quinoxalin-1-one), atrial natriuretic peptide-receptor inhibitor A71915 and protein kinase G type Iα kinase activity inhibitor DT-2 all increased apoptosis and decreased insulin secretion in RINm5F pancreatic β-cells, suggesting autocrine regulatory role for endogenous nitric oxide- and atrial natriuretic peptide-induced activation of protein kinase G type Iα. In four pancreatic β-cell lines, Beta-TC-6, RINm5F, INS-1 and 1.1B4, protein kinase G type Iα small-interfering RNA decreased phospho-serine-239-VASP (indicator of endogenous protein kinase G type Iα kinase activity), increased apoptosis and decreased proliferation. In protein kinase G type Iα-knockdown β-cell lines, expressions of phospho-protein kinase B (PKB/AKT) (AKT), phospho-Forkhead box protein O1 (FOXO1) (transcriptional repressor of pancreas duodenum homobox-1) and pancreas duodenum homobox-1 were decreased, suppressing proliferation and survival in pancreatic β-cells. The data suggest autocrine nitric oxide/atrial natriuretic peptide-induced activation of protein kinase G type Iα/p-AKT/p-FOXO1 promotes survival and proliferation in pancreatic β-cells, providing therapeutic implications for development of new therapeutic agents for diabetes.

Phosphodiesterase Inhibitors as a Therapeutic Approach to Neuroprotection and Repair

A wide diversity of perturbations of the central nervous system (CNS) result in structural damage to the neuroarchitecture and cellular defects, which in turn are accompanied by neurological dysfunction and abortive endogenous neurorepair. Altering intracellular signaling pathways involved in inflammation and immune regulation, neural cell death, axon plasticity and remyelination has shown therapeutic benefit in experimental models of neurological disease and trauma. The second messengers, cyclic adenosine monophosphate (cyclic AMP) and cyclic guanosine monophosphate (cyclic GMP), are two such intracellular signaling targets, the elevation of which has produced beneficial cellular effects within a range of CNS pathologies. The only known negative regulators of cyclic nucleotides are a family of enzymes called phosphodiesterases (PDEs) that hydrolyze cyclic nucleotides into adenosine monophosphate (AMP) or guanylate monophosphate (GMP). Herein, we discuss the structure and physiological function as well as the roles PDEs play in pathological processes of the diseased or injured CNS. Further we review the approaches that have been employed therapeutically in experimental paradigms to block PDE expression or activity and in turn elevate cyclic nucleotide levels to mediate neuroprotection or neurorepair as well as discuss both the translational pathway and current limitations in moving new PDE-targeted therapies to the clinic.

AdipoRon, an adiponectin receptor agonist, attenuates PDGF-induced VSMC proliferation through inhibition of mTOR signaling independent of AMPK: Implications toward suppression of neointimal hyperplasia

Hypoadiponectinemia is associated with an increased risk of coronary artery disease. Although adiponectin replenishment mitigates neointimal hyperplasia and atherosclerosis in mouse models, adiponectin therapy has been hampered in a clinical setting due to its large molecular size. Recent studies demonstrate that AdipoRon (a small-molecule adiponectin receptor agonist) improves glycemic control in type 2 diabetic mice and attenuates postischemic cardiac injury in adiponectin-deficient mice, in part, through activation of AMP-activated protein kinase (AMPK). To date, it remains unknown as to whether AdipoRon regulates vascular smooth muscle cell (VSMC) proliferation, which plays a major role in neointima formation. In the present study, oral administration of AdipoRon (50mg/kg) in C57BL/6J mice significantly diminished arterial injury-induced neointima formation by ∼57%. Under in vitro conditions, AdipoRon treatment led to significant inhibition of platelet-derived growth factor (PDGF)-induced VSMC proliferation, DNA synthesis, and cyclin D1 expression. While AdipoRon induced a rapid and sustained activation of AMPK, it also diminished basal and PDGF-induced phosphorylation of mTOR and its downstream targets, including p70S6K/S6 and 4E-BP1. However, siRNA-mediated AMPK downregulation showed persistent inhibition of p70S6K/S6 and 4E-BP1 phosphorylation, indicating AMPK-independent effects for AdipoRon inhibition of mTOR signaling. In addition, AdipoRon treatment resulted in a sustained and transient decrease in PDGF-induced phosphorylation of Akt and ERK, respectively. Furthermore, PDGF receptor-β tyrosine phosphorylation, which controls the phosphorylation state of Akt and ERK, was diminished upon AdipoRon treatment. Together, the present findings suggest that orally-administered AdipoRon has the potential to limit restenosis after angioplasty by targeting mTOR signaling independent of AMPK activation.

A novel thermoregulatory role for PDE10A in mouse and human adipocytes

Phosphodiesterase type 10A (PDE10A) is highly enriched in striatum and is under evaluation as a drug target for several psychiatric/neurodegenerative diseases. Preclinical studies implicate PDE10A in the regulation of energy homeostasis, but the mechanisms remain unclear. By utilizing small-animal PET/MRI and the novel radioligand [(18)F]-AQ28A, we found marked levels of PDE10A in interscapular brown adipose tissue (BAT) of mice. Pharmacological inactivation of PDE10A with the highly selective inhibitor MP-10 recruited BAT and potentiated thermogenesis in vivo In diet-induced obese mice, chronic administration of MP-10 caused weight loss associated with increased energy expenditure, browning of white adipose tissue, and improved insulin sensitivity. Analysis of human PET data further revealed marked levels of PDE10A in the supraclavicular region where brown/beige adipocytes are clustered in adults. Finally, the inhibition of PDE10A with MP-10 stimulated thermogenic gene expression in human brown adipocytes and induced browning of human white adipocytes. Collectively, our findings highlight a novel thermoregulatory role for PDE10A in mouse and human adipocytes and promote PDE10A inhibitors as promising candidates for the treatment of obesity and diabetes.

Nicorandil, a Nitric Oxide Donor and ATP-Sensitive Potassium Channel Opener, Protects Against Dystrophin-Deficient Cardiomyopathy

BACKGROUND

Dystrophin-deficient cardiomyopathy is a growing clinical problem without targeted treatments. We investigated whether nicorandil promotes cardioprotection in human dystrophin-deficient induced pluripotent stem cell (iPSC)-derived cardiomyocytes and the muscular dystrophy mdx mouse heart.

METHODS AND RESULTS

Dystrophin-deficient iPSC-derived cardiomyocytes had decreased levels of endothelial nitric oxide synthase and neuronal nitric oxide synthase. The dystrophin-deficient cardiomyocytes had increased cell injury and death after 2 hours of stress and recovery. This was associated with increased levels of reactive oxygen species and dissipation of the mitochondrial membrane potential. Nicorandil pretreatment was able to abolish these stress-induced changes through a mechanism that involved the nitric oxide-cyclic guanosine monophosphate pathway and mitochondrial adenosine triphosphate-sensitive potassium channels. The increased reactive oxygen species levels in the dystrophin-deficient cardiomyocytes were associated with diminished expression of select antioxidant genes and increased activity of xanthine oxidase. Furthermore, nicorandil was found to improve the restoration of cardiac function after ischemia and reperfusion in the isolated mdx mouse heart.

CONCLUSION

Nicorandil protects against stress-induced cell death in dystrophin-deficient cardiomyocytes and preserves cardiac function in the mdx mouse heart subjected to ischemia and reperfusion injury. This suggests a potential therapeutic role for nicorandil in dystrophin-deficient cardiomyopathy.

Involvement of nitric oxide in the induction of interleukin-1 beta in microglia

In response to in vitro stimulation with lipopolysaccharide (LPS), microglia induce the production of the inflammatory cytokine interleukin-1 beta (IL-1β) together with nitric oxide (NO) and superoxide anion (O2(-)). Here we investigated the role of NO and O2(-) in the signaling mechanism by which IL-1β is induced in microglia. The LPS-inducible IL-1β was significantly suppressed by pretreatment with the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide, but not by pretreatment with the O2(-) scavenger N-acetyl cysteine, suggesting the close association of NO with IL-1β induction. The pretreatment of microglia with the inducible NO synthase inhibitor 1400W prior to LPS stimulation significantly reduced the production of IL-1β, and the addition of the NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP) into microglia led to the induction of IL-1β. These results suggested that NO induces IL-1β through a specific signaling cascade. LPS-dependent IL-1β induction was significantly suppressed by inhibitors of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and nuclear factor kappaB (NFκB), indicating that ERK/JNK and NFκB serve in the cascade of IL-1β induction. As expected, ERK/JNK and NFκB were all activated in the SNAP-stimulated microglia. Taken together, these results indicate that NO is an important signaling molecule for the ERK/JNK and NFκB activations, which are requisite to the induction of IL-1β in microglia.

Role of the mevalonate pathway in specific CpG site demethylation on AGEs-induced MMP9 expression and activation in keratinocytes

BACKGROUND

Advanced glycation end products (AGEs) played an important role for the development of diabetic foot. In the present study we tried to show the mevalonate pathway and the key demethylation site(s) in the MMP-9 cis-promoter to the component of MMP-9 by AGEs in keratinocyte.

METHOD

Human keratinocyte cell line (HaCaT) cells were exposed to AGE-BSA. The plasmid construction and site-directed mutagenesis, dual-luciferase reporter assays, immunoblot, zymography, pull down, bisulfite sequencing PCR analysis and Western blotting were applied.

RESULTS

The AGE-BSA could increase and more activate the MMP9 in keratinocyte. The RhoA and ROCK1 also could be activated. These affects were blocked by the simvastatin. Meanwhile, the CpG site at -562 site was largely demethylated with AGE-BSA treatment. The cis-promoter sequences with -562 bp site methylated had a lower activity change, which had a highest expression activity and was decreased by simvastatin. Moreover, site-directed mutagenesis of CpG site (-562 bp) in the recombinant plasmid pCpGL-571 brought more reduction in activity, and the activity of methylated mutation pCpGL-571 remains decreased.

CONCLUSION

The cis-promoter regions of MMP9 would be methylated by AGE-BSA in keratinocyte through the mevalonate pathway, especially the -562 bp site.

Bioinformatics approach to evaluate differential gene expression of M1/M2 macrophage phenotypes and antioxidant genes in atherosclerosis

Atherosclerosis is a pro-inflammatory process intrinsically related to systemic redox impairments. Macrophages play a major role on disease development. The specific involvement of classically activated, M1 (pro-inflammatory), or the alternatively activated, M2 (anti-inflammatory), on plaque formation and disease progression are still not established. Thus, based on meta-data analysis of public micro-array datasets, we compared differential gene expression levels of the human antioxidant genes (HAG) and M1/M2 genes between early and advanced human atherosclerotic plaques, and among peripheric macrophages (with or without foam cells induction by oxidized low density lipoprotein, oxLDL) from healthy and atherosclerotic subjects. Two independent datasets, GSE28829 and GSE9874, were selected from gene expression omnibus (http://www.ncbi.nlm.nih.gov/geo/) repository. Functional interactions were obtained with STRING (http://string-db.org/) and Medusa (http://coot.embl.de/medusa/). Statistical analysis was performed with ViaComplex(®) (http://lief.if.ufrgs.br/pub/biosoftwares/viacomplex/) and gene score enrichment analysis (http://www.broadinstitute.org/gsea/index.jsp). Bootstrap analysis demonstrated that the activity (expression) of HAG and M1 gene sets were significantly increased in advance compared to early atherosclerotic plaque. Increased expressions of HAG, M1, and M2 gene sets were found in peripheric macrophages from atherosclerotic subjects compared to peripheric macrophages from healthy subjects, while only M1 gene set was increased in foam cells from atherosclerotic subjects compared to foam cells from healthy subjects. However, M1 gene set was decreased in foam cells from healthy subjects compared to peripheric macrophages from healthy subjects, while no differences were found in foam cells from atherosclerotic subjects compared to peripheric macrophages from atherosclerotic subjects. Our data suggest that, different to cancer, in atherosclerosis there is no M1 or M2 polarization of macrophages. Actually, M1 and M2 phenotype are equally induced, what is an important aspect to better understand the disease progression, and can help to develop new therapeutic approaches.

Inhibition of NOS-NO System Prevents Autoimmune Orchitis Development in Rats: Relevance of NO Released by Testicular Macrophages in Germ Cell Apoptosis and Testosterone Secretion

Background

Although the testis is considered an immunoprivileged organ it can orchestrate immune responses against pathological insults such as infection and trauma. Experimental autoimmune orchitis (EAO) is a model of chronic inflammation whose main histopathological features it shares with human orchitis. In EAO an increased number of macrophages infiltrate the interstitium concomitantly with progressive germ cell degeneration and impaired steroidogenesis. Up-regulation of nitric oxide (NO)-NO synthase (NOS) system occurs, macrophages being the main producers of NO.

Objective

The aim of our study was to evaluate the role of NO-NOS system in orchitis development and determine the involvement of NO released by testicular macrophages on germ cell apoptosis and testosterone secretion.

Method and Results

EAO was induced in rats by immunization with testicular homogenate and adjuvants (E group) and a group of untreated normal rats (N) was also studied. Blockage of NOS by i.p. injection of E rats with a competitive inhibitor of NOS, L-NAME (8mg/kg), significantly reduced the incidence and severity of orchitis and lowered testicular nitrite content. L-NAME reduced germ cell apoptosis and restored intratesticular testosterone levels, without variations in serum LH. Co-culture of N testicular fragments with testicular macrophages obtained from EAO rats significantly increased germ cell apoptosis and testosterone secretion, whereas addition of L-NAME lowered both effects and reduced nitrite content. Incubation of testicular fragments from N rats with a NO donor DETA-NOnoate (DETA-NO) induced germ cell apoptosis through external and internal apoptotic pathways, an effect prevented by N-acetyl-L-cysteine (NAC). DETA-NO inhibited testosterone released from Leydig cells, whereas NAC (from 2.5 to 15 mM) did not prevent this effect.

Conclusions

We demonstrated that NO-NOS system is involved in the impairment of testicular function in orchitis. NO secreted mainly by testicular macrophages could promote oxidative stress inducing ST damage and interfering in Leydig cell function.

Tissue inflammation and nitric oxide-mediated alterations in cardiovascular function are major determinants of endotoxin-induced insulin resistance

BACKGROUND

Endotoxin (i.e. LPS) administration induces a robust inflammatory response with accompanying cardiovascular dysfunction and insulin resistance. Overabundance of nitric oxide (NO) contributes to the vascular dysfunction. However, inflammation itself also induces insulin resistance in skeletal muscle. We sought to investigate whether the cardiovascular dysfunction induced by increased NO availability without inflammatory stress can promote insulin resistance. Additionally, we examined the role of inducible nitric oxide synthase (iNOS or NOS2), the source of the increase in NO availability, in modulating LPS-induced decrease in insulin-stimulated muscle glucose uptake (MGU).

METHODS

The impact of NO donor infusion on insulin-stimulated whole-body and muscle glucose uptake (hyperinsulinemic-euglycemic clamps), and the cardiovascular system was assessed in chronically catheterized, conscious mice wild-type (WT) mice. The impact of LPS on insulin action and the cardiovascular system were assessed in WT and global iNOS knockout (KO) mice. Tissue blood flow and cardiac function were assessed using microspheres and echocardiography, respectively. Insulin signaling activity, and gene expression of pro-inflammatory markers were also measured.

RESULTS

NO donor infusion decreased mean arterial blood pressure, whole-body glucose requirements, and MGU in the absence of changes in skeletal muscle blood flow. LPS lowered mean arterial blood pressure and glucose requirements in WT mice, but not in iNOS KO mice. Lastly, despite an intact inflammatory response, iNOS KO mice were protected from LPS-mediated deficits in cardiac output. LPS impaired MGU in vivo, regardless of the presence of iNOS. However, ex vivo, insulin action in muscle obtained from LPS treated iNOS KO animals was protected.

CONCLUSION

Nitric oxide excess and LPS impairs glycemic control by diminishing MGU. LPS impairs MGU by both the direct effect of inflammation on the myocyte, as well as by the indirect NO-driven cardiovascular dysfunction.

Exercise training reduces insulin resistance in postmyocardial infarction rats

Myocardial infarction (MI) induces cardiac dysfunction and insulin resistance (IR). This study examines the effects of MI-related IR on vasorelaxation and its underlying mechanisms, with a specific focus on the role of exercise in reversing the impaired vasorelaxation. Adult male Sprague-Dawley rats were divided into three groups: Sham, MI, and MI+Exercise. MI+Exercise rats were subjected to 8 weeks of treadmill training. Cardiac contraction, myocardial and arterial structure, vasorelaxation, levels of inflammatory cytokines, expression of eNOS and TNF-α, and activation of PI3K/Akt/eNOS and p38 mitogen-activated protein kinase (p38 MAPK) were determined in aortas. MI significantly impaired endothelial structure and vasodilation (P < 0.05-0.01), as indicated by decreased arterial vasorelaxation to ACh and insulin. MI also attenuated the myocardial contractile response, decreased aortic PI3K/Akt/eNOS expression and phosphorylation by insulin, and increased IL-1β, IL-6, and TNF-α expression and p38 MAPK activity (P < 0.05-0.01). Exercise improved insulin sensitivity in aortas, facilitated myocardial contractile response and arterial vasorelaxation to ACh and insulin, and increased arterial PI3K/Akt/eNOS activity. Moreover, exercise markedly reversed increased p38 MAPK activity and normalized inflammatory cytokines in post-MI arteries. Inhibition of PI3K with LY-294002, and eNOS with L-NAME significantly blocked arterial vasorelaxation and PI3K/Akt/eNOS phosphorylation in response to insulin. In conclusion, these results demonstrate that endothelial dysfunction in response to insulin plays an important role in MI-related IR. The reversal of IR by exercise is most likely associated with normalizing inflammatory cytokines, increasing the activation of PI3K/Akt/eNOS, and reducing the activation of p38 MAPK.

Nicorandil directly and cyclic GMP-dependently opens K+ channels in human bypass grafts

As we previously demonstrated the role of different K(+) channels in the action of nicorandil on human saphenous vein (HSV) and human internal mammary artery (HIMA), this study aimed to analyse the contribution of the cGMP pathway in nicorandil-induced vasorelaxation and to determine the involvement of cGMP in the K(+) channel-activating effect of nicorandil. An inhibitor of soluble guanylate cyclase (GC), ODQ, significantly inhibited nicorandil-induced relaxation, while ODQ plus glibenclamide, a selective ATP-sensitive K(+) (KATP) channel inhibitor, produced a further inhibition of both vessels. In HSV, ODQ in combination with 4-aminopyridine, a blocker of voltage-gated K(+) (KV) channels, did not modify the concentration-response to nicorandil compared with ODQ, whereas in HIMA, ODQ plus iberiotoxin, a selective blocker of large-conductance Ca(2+)-activated K(+) (BKCa) channels, produced greater inhibition than ODQ alone. We showed that the cGMP pathway plays a significant role in the vasorelaxant effect of nicorandil on HSV and HIMA. It seems that nicorandil directly opens KATP channels in both vessels and BKCa channels in HIMA, although it is possible that stimulation of GC contributes to KATP channels activation in HIMA. Contrary, the activation of KV channels in HSV is probably due to GC activation and increased levels of cGMP.

Insulin resistance in chronic kidney disease is ameliorated by spironolactone in rats and humans

In this study, we examined the association between chronic kidney disease (CKD) and insulin resistance. In a patient cohort with nondiabetic stages 2-5 CKD, estimated glomerular filtration rate (eGFR) was negatively correlated and the plasma aldosterone concentration was independently associated with the homeostasis model assessment of insulin resistance. Treatment with the mineralocorticoid receptor blocker spironolactone ameliorated insulin resistance in patients, and impaired glucose tolerance was partially reversed in fifth/sixth nephrectomized rats. In these rats, insulin-induced signal transduction was attenuated, especially in the adipose tissue. In the adipose tissue of nephrectomized rats, nuclear mineralocorticoid receptor expression, expression of the mineralocorticoid receptor target molecule SGK-1, tissue aldosterone content, and expression of the aldosterone-producing enzyme CYP11B2 increased. Mineralocorticoid receptor activation in the adipose tissue was reversed by spironolactone. In the adipose tissue of nephrectomized rats, asymmetric dimethylarginine (ADMA; an uremic substance linking uremia and insulin resistance) increased, the expression of the ADMA-degrading enzymes DDAH1 and DDAH2 decreased, and the oxidative stress increased. All of these changes were reversed by spironolactone. In mature adipocytes, aldosterone downregulated both DDAH1 and DDAH2 expression, and ADMA inhibited the insulin-induced cellular signaling. Thus, activation of mineralocorticoid receptor and resultant ADMA accumulation in adipose tissue has, in part, a relevant role in the development of insulin resistance in CKD.

Inducible nitric oxide synthase drives mTOR pathway activation and proliferation of human melanoma by reversible nitrosylation of TSC2

Melanoma is one of the cancers of fastest-rising incidence in the world. Inducible nitric oxide synthase (iNOS) is overexpressed in melanoma and other cancers, and previous data suggest that iNOS and nitric oxide (NO) drive survival and proliferation of human melanoma cells. However, specific mechanisms through which this occurs are poorly defined. One candidate is the PI3K-AKT-mTOR pathway, which plays a major role in proliferation, angiogenesis, and metastasis of melanoma and other cancers. We used the chick embryo chorioallantoic membrane (CAM) assay to test the hypothesis that melanoma growth is regulated by iNOS-dependent mTOR pathway activation. Both pharmacologic inhibition and siRNA-mediated gene silencing of iNOS suppressed melanoma proliferation and in vivo growth on the CAM in human melanoma models. This was associated with strong downregulation of mTOR pathway activation by Western blot analysis of p-mTOR, p70 ribosomal S6 kinase (p-P70S6K), p-S6RP, and p-4EBP1. iNOS expression and NO were associated with reversible nitrosylation of tuberous sclerosis complex (TSC) 2, and inhibited dimerization of TSC2 with its inhibitory partner TSC1, enhancing GTPase activity of its target Ras homolog enriched in brain (Rheb), a critical activator of mTOR signaling. Immunohistochemical analysis of tumor specimens from stage III melanoma patients showed a significant correlation between iNOS expression levels and expression of the mTOR pathway members. Exogenously supplied NO was also sufficient to reverse the mTOR pathway inhibition by the B-Raf inhibitor vemurafenib. In summary, covalent modification of TSC2 by iNOS-derived NO is associated with impaired TSC2/TSC1 dimerization, mTOR pathway activation, and proliferation of human melanoma. This model is consistent with the known association of iNOS overexpression and poor prognosis in melanoma and other cancers.

Nitric oxide directly promotes vascular endothelial insulin transport

Insulin resistance strongly associates with decreased nitric oxide (NO) bioavailability and endothelial dysfunction. In the vasculature, NO mediates multiple processes that affect insulin delivery, including dilating both resistance and terminal arterioles in skeletal muscle in vivo. However, whether NO directly regulates vascular endothelial cell (EC) insulin uptake and its transendothelial transport (TET) is unknown. We report in this article that L-N(G)-nitro-L-arginine methyl ester (L-NAME) pretreatment blocked, whereas L-arginine and sodium nitroprusside (SNP) each enhanced, EC uptake of fluorescein isothiocyanate (FITC)-labeled insulin. SNP also partly or fully reversed the inhibition of EC insulin uptake caused by L-NAME, wortmannin, the Src inhibitor PP1, and tumor necrosis factor-α. In addition, SNP promoted [(125)I]Tyr(A14)insulin TET by ~40%. Treatment with insulin with and without SNP did not affect EC cyclic guanosine monophosphate (cGMP) levels, and the cGMP analog 8-bromo-cGMP did not affect FITC-insulin uptake. In contrast, treatment with insulin and SNP significantly increased EC protein S-nitrosylation, the colocalization of S-nitrosothiol (S-NO) and protein-tyrosine phosphatase 1B (PTP1B), and Akt phosphorylation at Ser(473) and inhibited PTP1B activity. Moreover, a high-fat diet significantly inhibited EC insulin-stimulated Akt phosphorylation and FITC-insulin uptake that was partially reversed by SNP in rats. Finally, inhibition of S-nitrosylation by knockdown of thioredoxin-interacting protein completely eliminated SNP-enhanced FITC-insulin uptake. We conclude that NO directly promotes EC insulin transport by enhancing protein S-nitrosylation. NO also inhibits PTP1B activity, thereby enhancing insulin signaling.

A dietary supplementation with leucine and antioxidants is capable to accelerate muscle mass recovery after immobilization in adult rats

Prolonged inactivity induces muscle loss due to an activation of proteolysis and decreased protein synthesis; the latter is also involved in the recovery of muscle mass. The aim of the present work was to explore the evolution of muscle mass and protein metabolism during immobilization and recovery and assess the effect of a nutritional strategy for counteracting muscle loss and facilitating recovery. Adult rats (6–8 months) were subjected to unilateral hindlimb casting for 8 days (I0–I8) and then permitted to recover for 10 to 40 days (R10–R40). They were fed a Control or Experimental diet supplemented with antioxidants/polyphenols (AOX) (I0 to I8), AOX and leucine (AOX + LEU) (I8 to R15) and LEU alone (R15 to R40). Muscle mass, absolute protein synthesis rate and proteasome activities were measured in gastrocnemius muscle in casted and non-casted legs in post prandial (PP) and post absorptive (PA) states at each time point. Immobilized gastrocnemius protein content was similarly reduced (-37%) in both diets compared to the non-casted leg. Muscle mass recovery was accelerated by the AOX and LEU supplementation (+6% AOX+LEU vs. Control, P<0.05 at R40) due to a higher protein synthesis both in PA and PP states (+23% and 31% respectively, Experimental vs. Control diets, P<0.05, R40) without difference in trypsin- and chymotrypsin-like activities between diets. Thus, this nutritional supplementation accelerated the recovery of muscle mass via a stimulation of protein synthesis throughout the entire day (in the PP and PA states) and could be a promising strategy to be tested during recovery from bed rest in humans.

Oleic acid increases synthesis and secretion of VEGF in rat vascular smooth muscle cells: role of oxidative stress and impairment in obesity

Obesity is characterized by poor collateral vessel formation, a process involving vascular endothelial growth factor (VEGF) action on vascular smooth muscle cells (VSMC). Free fatty acids are involved in the pathogenesis of obesity vascular complications, and we have aimed to clarify whether oleic acid (OA) enhances VEGF synthesis/secretion in VSMC, and whether this effect is impaired in obesity. In cultured aortic VSMC from lean and obese Zucker rats (LZR and OZR, respectively) we measured the influence of OA on VEGF-A synthesis/secretion, signaling molecules and reactive oxygen species (ROS). In VSMC from LZR we found the following: (a) OA increases VEGF-A synthesis/secretion by a mechanism blunted by inhibitors of Akt, mTOR, ERK-1/2, PKC-beta, NADPH-oxidase and mitochondrial electron transport chain complex; (b) OA activates the above mentioned signaling pathways and increases ROS; (c) OA-induced activation of PKC-beta enhances oxidative stress, which activates signaling pathways responsible for the increased VEGF synthesis/secretion. In VSMC from OZR, which present enhanced baseline oxidative stress, the above mentioned actions of OA on VEGF-A, signaling pathways and ROS are impaired: this impairment is reproduced in VSMC from LZR by incubation with hydrogen peroxide. Thus, in OZR chronically elevated oxidative stress causes a resistance to the action on VEGF that OA exerts in LZR by increasing ROS.

Vascular extracellular signal-regulated kinase mediates migraine-related sensitization of meningeal nociceptors

OBJECTIVE

To examine changes in the response properties of meningeal nociceptors that might lead to migraine pain and examine endogenous processes that could play a role in mediating them using a clinically relevant model of migraine triggering, namely infusion of the nitric oxide (NO) donor nitroglycerin (NTG).

METHODS

Single-unit recordings made in the trigeminal ganglion of rats were used to test changes in the activity and mechanosensitivity of meningeal nociceptors in response to administration of the migraine trigger NTG or another NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP) at doses relevant to the human model of migraine headache. Immunohistochemistry and pharmacological manipulations were used to investigate the possible role of meningeal vascular signaling in mediating the responses of meningeal nociceptors to NO.

RESULTS

Infusion of NTG promoted a delayed and robust increase in the mechanosensitivity of meningeal nociceptors, with a time course resembling the development of the delayed migraine headache. A similar sensitization was elicited by dural application of NTG and SNAP. NTG-evoked delayed meningeal nociceptor sensitization was associated with a robust extracellular signal-regulated kinase (ERK) phosphorylation in meningeal arteries. Pharmacological blockade of meningeal ERK phosphorylation inhibited the development of NTG-evoked delayed meningeal nociceptor sensitization.

INTERPRETATION

The development of delayed mechanical sensitization evoked by the migraine trigger NTG is potentially of great importance as the first finding of a neurophysiological correlate of migraine headache in meningeal nociceptors. The arterial ERK phosphorylation and its involvement in mediating the NTG-evoked delayed sensitization points to an important, yet unappreciated, role of the meningeal vasculature in the genesis of migraine pain.

Acetylcholine promotes Ca2+ and NO-oscillations in adipocytes implicating Ca2+→NO→cGMP→cADP-ribose→Ca2+ positive feedback loop--modulatory effects of norepinephrine and atrial natriuretic peptide

PURPOSE

This study investigated possible mechanisms of autoregulation of Ca(2+) signalling pathways in adipocytes responsible for Ca(2+) and NO oscillations and switching phenomena promoted by acetylcholine (ACh), norepinephrine (NE) and atrial natriuretic peptide (ANP).

METHODS

Fluorescent microscopy was used to detect changes in Ca(2+) and NO in cultures of rodent white adipocytes. Agonists and inhibitors were applied to characterize the involvement of various enzymes and Ca(2+)-channels in Ca(2+) signalling pathways.

RESULTS

ACh activating M3-muscarinic receptors and Gβγ protein dependent phosphatidylinositol 3 kinase induces Ca(2+) and NO oscillations in adipocytes. At low concentrations of ACh which are insufficient to induce oscillations, NE or α1, α2-adrenergic agonists act by amplifying the effect of ACh to promote Ca(2+) oscillations or switching phenomena. SNAP, 8-Br-cAMP, NAD and ANP may also produce similar set of dynamic regimes. These regimes arise from activation of the ryanodine receptor (RyR) with the implication of a long positive feedback loop (PFL): Ca(2+)→NO→cGMP→cADPR→Ca(2+), which determines periodic or steady operation of a short PFL based on Ca(2+)-induced Ca(2+) release via RyR by generating cADPR, a coagonist of Ca(2+) at the RyR. Interplay between these two loops may be responsible for the observed effects. Several other PFLs, based on activation of endothelial nitric oxide synthase or of protein kinase B by Ca(2+)-dependent kinases, may reinforce functioning of main PFL and enhance reliability. All observed regimes are independent of operation of the phospholipase C/Ca(2+)-signalling axis, which may be switched off due to negative feedback arising from phosphorylation of the inositol-3-phosphate receptor by protein kinase G.

CONCLUSIONS

This study presents a kinetic model of Ca(2+)-signalling system operating in adipocytes and integrating signals from various agonists, which describes it as multivariable multi feedback network with a family of nested positive feedback.

S-nitrosoglutathione induces ciliary neurotrophic factor expression in astrocytes, which has implications to protect the central nervous system under pathological conditions

Accumulating evidence suggests that reactive astrogliosis has beneficial and detrimental outcomes in various CNS disorders, but the mechanism behind this dichotomy is unclear. Recent advances in this direction suggested that NO signaling is critical to regulate the outcomes of reactive astrogliosis in vivo. Using biochemical and genetic approaches, we here investigated the effect of S-nitrosoglutathione (GSNO; a physiological NO donor) in astrocytes in vitro settings. GSNO enhanced the expressions of glial fibrillary acidic protein and neurotrophic factors including ciliary neurotrophic factor (CNTF) in astrocytes in a dose-dependent manner. The enhanced CNTF expression in GSNO-treated astrocytes was ascribed to NO-mediated sGC/cGMP/PKG signaling. It was associated with p38 MAPK-dependent increased peroxisome proliferator-activated receptor-γ transactivation. In addition, the chromatin accessibility of peroxisome proliferator-activated receptor-γ accompanied with ATF2 and CREB (cAMP-response element-binding protein) was enhanced across the CNTF gene promoter in GSNO treated astrocytes. Interestingly, secreted CNTF was responsible for increased expression of glial fibrillary acidic protein in GSNO-treated astrocytes in an autocrine manner via a JAK2- and STAT3-dependent mechanism. In addition, CNTF secreted by GSNO-treated astrocytes enhanced the differentiation of immature oligodendrocytes in vitro. These effects of GSNO were consistent with an endogenously produced NO in astrocytes stimulated with proinflammatory cytokines in vitro. We conclude that NO signaling induces CNTF expression in astrocytes that favors the beneficial outcomes of reactive astrogliosis in vivo. Our data suggest that the endogenously produced NO or its exogenous source has potential to modulate the outcomes of reactive astrogliosis to protect CNS under pathological conditions.

Phosphodiesterases in neurodegenerative disorders

Cyclic nucleotide phosphodiesterases (PDEs) are responsible for the breakdown of cyclic nucleotides, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). As such, they are crucial regulators of levels of cyclic nucleotide-mediated signaling. cAMP signaling and cGMP signaling have been associated with neuroplasticity and protection, and influencing their levels in the cell by inhibition of PDEs has become a much studied target for treatment in a wide array of disorders, including neurodegenerative disorders. In this review, we will focus on the involvement of PDEs in neurodegenerative disorders. In comparison with preclinical work, data on human patients are scarce. Alzheimer's disease is associated with changes in PDE4, PDE7, and PDE8 expression in the brain. Altered functioning of PDE4 as well as PDE11 is associated with major depressive disorder. In multiple sclerosis, there are indications of alterations in expression of several PDE subtypes in the central nervous system; however, evidence is indirect. In Huntington's disease and Parkinson's disease, most research has focused on PDE1B and PDE10, because of their abundant presence in striatal neurons. In another rare, neurodegenerative striatal motor disorder, that is, autosomal-dominant striatal degeneration, genetic defects in PDE8B gene are thought to underlie the neurodegenerative processes. Although the latter disorder has showed a causative dysfunction of PDEs, this does not hold for the neurodegenerative disorders discussed above, in which changes in PDE levels seemingly rather represent secondary changes and compensation to prior existing dysfunction. However, normalizing cyclic nucleotide signaling via PDE inhibition remains interesting for the treatment of neurodegenerative disorders.

[Update on diabetic macroangiopathy]

Current findings from the literature on the multifactorial genesis of macroangiopathy of diabetes mellitus (DM) were compiled using the PubMed database. The primary aim was to find an explanation for the morphological, immunohistochemical and molecular characteristics of this form of atherosclerosis. The roles of advanced glycation end products (AGE), defective signal transduction and imbalance of matrix metalloproteinases in the increased progression of atherosclerosis in coronary and cerebral arteries as well as peripheral vascular disease are discussed. The restricted formation of collateral arteries (arteriogenesis) in diabetic patients with postischemic lesions is also a focus of attention. The increased level of prothrombotic factors and the role of diabetic neuropathy in DM are also taken into account. Therapeutic influences of AGE-RAGE (receptor of AGE) interactions on the vascular wall and the effects of endothelial progenitor cells in the repair of diabetic vascular lesions are additionally highlighted.

Involvement of RAGE, MAPK and NF-κB pathways in AGEs-induced MMP-9 activation in HaCaT keratinocytes

Advanced glycation end products (AGEs) exert divergent effects on the pathogenesis of diabetes complications. Excessive expression of matrix metalloproteinases-9 (MMP-9) is deleterious to the cutaneous wound-healing process in the context of diabetes. However, the effect of AGEs on MMP-9 induction in skin cells and the exact molecular mechanisms involved are still poorly understood. In this study, we investigated the effect of AGEs on the production of MMP-9 in HaCaT keratinocytes and characterized the signal transduction pathways activated by AGEs that are involved in MMP-9 regulation. We showed that AGE-BSA increased MMP-9 expression in HaCaT cells at both the protein and mRNA levels. The stimulatory effect of AGE-BSA on MMP-9 was attenuated by inhibitors of extracellular-signal-regulated kinase (ERK1/2, U0126), p38 mitogen-activated protein kinase (MAPK, SB203580) and NF-κB, but not c-Jun N-terminal kinase. Furthermore, receptor for advanced glycation end products (RAGE) was expressed in keratinocytes, and incubation with AGE-BSA resulted in a significant upregulation of RAGE expression in a dose-dependent manner. Silencing of the RAGE gene prevented AGE-BSA-induced MMP-9 activation and the phosphorylation of ERK1/2 and p38 MAPK. We also observed the involvement of NF-κB in AGE-BSA-induced MMP-9 activation, which was not blocked by U0126 and SB203580. These results suggest that AGEs may play an important role in the impairment of diabetic wound healing by upregulating MMP-9 expression in keratinocytes via the RAGE, ERK1/2 and p38 MAPK pathways; activation of NF-κB is also involved in this process. These pathways may represent potential targets for drug interventions to improve diabetic wound healing, a process in which MMP-9 plays a critical role.