cyclic-gmp and Cognitive-Dysfunction

Vascular cognitive impairment (VCI) describes neurodegenerative disorders characterized by a vascular component. Pathologically, it involves decreased cerebral blood flow (CBF), white matter lesions, endothelial dysfunction, and blood-brain barrier (BBB) impairments. Molecularly, oxidative stress and inflammation are two of the major underlying mechanisms. Nitric oxide (NO) physiologically stimulates soluble guanylate cyclase (sGC) to induce cGMP production. However, under pathological conditions, NO seems to be at the basis of oxidative stress and inflammation, leading to a decrease in sGC activity and expression. The native form of sGC needs a ferrous heme group bound in order to be sensitive to NO (Fe(II)sGC). Oxidation of sGC leads to the conversion of ferrous to ferric heme (Fe(III)sGC) and even heme-loss (apo-sGC). Both Fe(III)sGC and apo-sGC are insensitive to NO, and the enzyme is therefore inactive. sGC activity can be enhanced either by targeting the NO-sensitive native sGC (Fe(II)sGC), or the inactive, oxidized sGC (Fe(III)sGC) and the heme-free apo-sGC. For this purpose, sGC stimulators acting on Fe(II)sGC and sGC activators acting on Fe(III)sGC/apo-sGC have been developed. These sGC agonists have shown their efficacy in cardiovascular diseases by restoring the physiological and protective functions of the NO-sGC-cGMP pathway, including the reduction of oxidative stress and inflammation, and improvement of vascular functioning. Yet, only very little research has been performed within the cerebrovascular system and VCI pathology when focusing on sGC modulation and its potential protective mechanisms on vascular and neural function. Therefore, within this review, the potential of sGC as a target for treating VCI is highlighted.

Topics: Cognitive Dysfunction; Cyclic GMP; Heme; Humans; Inflammation; Soluble Guanylyl Cyclase; Vascular Diseases

Phosphodiesterase (PDE) inhibitors improve signaling pathways in brain circuits by increasing intracellular cyclic adenosine monophosphate (cAMP) and/or cyclic guanosine monophosphate (cGMP). In the last decade, the first clinical studies investigating selective PDE inhibitors in Alzheimer's disease (AD) have been initiated, based on their positive effects on cognitive processes and neuroprotection in numerous animal studies. Areas covered: This article reviews the clinical studies investigating the pro-cognitive/neuroprotective effects of PDE inhibitors in patients with AD, as well as in age-associated memory impaired elderly and patients with mild cognitive impairment (MCI), the prodromal stage of AD. PDE inhibitors will also be discussed with respect to adverse effects including safety and tolerability. Expert opinion: The limited available data of clinical studies with PDE inhibitors tested in different populations of AD patients do not allow the drawing of any concrete conclusion yet. Currently, studies with a PDE3 (cilostazol) or PDE9 inhibitor (BI 409,306) are still ongoing in patients with MCI or AD, respectively. Studies with PDE4 inhibitors (HT-0712, roflumilast and BPN14770) in healthy elderly and elderly with age-associated memory impairments indicate that the optimum dose and/or inhibiting the most relevant PDE isoform hold great promise when tested in the appropriate population of patients with MCI or AD eventually.

Topics: Aged; Alzheimer Disease; Animals; Clinical Trials, Phase I as Topic; Clinical Trials, Phase II as Topic; Cognitive Dysfunction; Cyclic AMP; Cyclic GMP; Drug Design; Drugs, Investigational; Humans; Phosphodiesterase Inhibitors; Signal Transduction

Inhibition of phosphodiesterases (PDEs) has been demonstrated to enhance performance of animals in various cognition tasks and accordingly PDE inhibitors have been proposed as new approach for treatment of cognitive dysfunction (Reneerkens et al. Psychopharmacology 202:419-443, 2009; Schmidt Curr Top Med Chem 10(2):222-230, 2010). One of the eleven PDE isoforms, showing expression in cognition relevant brain regions across species, is PDE9, which hydrolyzes cGMP only. Furthermore, it is well established that the nitric oxide (NO)/cGMP pathway and NMDA receptor signaling has a crucial function in synaptic plasticity and cognitive function. In this chapter, we will provide an overview on PDE9, its expression and function in the brain, and hence, its relevance for synaptic plasticity and cognitive performance. Moreover, the recent advances of PDE9 inhibition as potential therapeutic approach for treatment of cognitive dysfunction in CNS disorders will be discussed.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Animals; Brain; Cognition; Cognitive Dysfunction; Cyclic GMP; Humans; Neuronal Plasticity; Nitric Oxide; Phosphodiesterase Inhibitors

The focus of this chapter is on the cyclic nucleotide phosphodiesterase 1 (PDE1) family. PDE1 is one member of the 11 PDE families (PDE 1-11). It is the only phosphodiesterase family that is calcium/calmodulin activated. As a result, whereas other families of PDEs 2-11 play a dominant role controlling basal levels of cyclic nucleotides, PDE1 is involved when intra-cellular calcium levels are elevated and, thus, has an "on demand" or activity-dependent involvement in the control of cyclic nucleotides in excitatory cells including neurons, cardiomyocytes and smooth muscle. As a Class 1 phosphodiesterase, PDE1 hydrolyzes the 3' bond of 3'-5'-cyclic nucleotides, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Here, we review evidence for this family of enzymes as drug targets for development of therapies aimed to address disorders of the central nervous system (CNS) and of degenerative diseases. The chapter includes sections on the potential for cognitive enhancement in mental disorders, as well as a review of PDE1 enzyme structure, enzymology, tissue distribution, genomics, inhibitors, pharmacology, clinical trials, and therapeutic indications. Information is taken from public databases. A number of excellent reviews of the phosphodiesterase family have been written as well as reviews of the PDE1 family. References cited here are not comprehensive, rather pointing to major reviews and key publications.

Topics: Cognitive Dysfunction; Cyclic AMP; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 1; Humans; Mental Disorders; Neurodegenerative Diseases; Phosphodiesterase Inhibitors

Topics: Cognitive Dysfunction; Cyclic GMP; Humans; Memory Disorders; NG-Nitroarginine Methyl Ester; Phosphodiesterase 5 Inhibitors; Scopolamine; Tadalafil

Changes in the cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) signaling are implicated in older people with dementia. Drugs that modulate the cAMP/cGMP levels in the brain might therefore provide new therapeutic options for the treatment of cognitive impairment in aging and elderly with dementia. Phosphodiesterase 2A (PDE2A), which is highly expressed in the forebrain, is one of the key phosphodiesterase enzymes that hydrolyze cAMP and cGMP. In this study, we investigated the effects of PDE2A inhibition on the cognitive functions associated with aging, such as spatial learning, episodic memory, and attention, in rats with a selective, brain penetrant PDE2A inhibitor, N-{(1S)-1-[3-fluoro-4-(trifluoromethoxy)phenyl]-2-methoxyethyl-7-methoxy-2-oxo-2,3-dihydropyrido[2,3-b]pyrazine-4(1H)-carboxamide (TAK-915). Repeated treatment with TAK-915 (3 mg/kg/day, p.o. for 4 days) significantly reduced escape latency in aged rats in the Morris water maze task compared to the vehicle treatment. In the novel object recognition task, TAK-915 (1, 3, and 10 mg/kg, p.o.) dose-dependently attenuated the non-selective muscarinic antagonist scopolamine-induced memory deficits in rats. In addition, oral administration of TAK-915 at 10 mg/kg significantly improved the attentional performance in middle-aged, poorly performing rats in the 5-choice serial reaction time task. These findings suggest that PDE2A inhibition in the brain has the potential to ameliorate the age-related cognitive decline.

Topics: Aging; Animals; Brain; Cognition; Cognition Disorders; Cognitive Dysfunction; Cyclic AMP; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 2; Male; Memory Disorders; Memory, Episodic; Phosphodiesterase Inhibitors; Pyrazines; Pyridines; Rats; Rats, Inbred F344; Rats, Long-Evans; Rats, Sprague-Dawley

Insufficient prefrontal dopamine 1 (D. We hypothesize that PDE1 inhibition improves working memory performance by increasing prefrontal synaptic transmission and/or postsynaptic D

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Brain; Cognition; Cognitive Dysfunction; Cyclic AMP; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 1; Dopamine Agonists; Heterocyclic Compounds, 4 or More Rings; Male; Maze Learning; Memory, Short-Term; Mice; Rats, Sprague-Dawley; Receptors, Dopamine D1; Signal Transduction; Synaptic Transmission

Minimal hepatic encephalopathy (MHE) is associated with cognitive alterations and changes in connectivity. We assessed the relationship of the abnormalities of resting-state functional connectivity (rs-FC) and gray matter (GM) volume with different cognitive alterations and biochemical parameters associated to MHE.. Thirty-nine cirrhotic patients (26 without and 13 with MHE) and 24 controls were widely cognitive assessed with a battery of psychometric tests. Atrophy was determined using Voxel-Based Morphometry and rs-FC was assessed by independent component analysis. Receiver operating characteristic (ROC) curves was performed to assess the diagnostic utility of rs-FC and GM reduction for the discrimination of patients with and without MHE. Blood ammonia, cGMP, and levels of pro-inflammatory interleukins were measured.. MHE patients showed significant decrease of GM volume and lesser degree of rs-FC in different networks related to attention and executive functions as compared to controls and patients without MHE. There is a progressive reduction in rs-FC in the default mode network with the progression of cognitive impairment. MHE patients showed GM reduction in the right frontal lobe, right insula and right cerebellum compared to patients without MHE. Alterations in GM volume and rs-FC correlated with the scores of different cognitive tests.. Decreased cognitive performance is associated by reduced rs-FC and GM atrophy in MHE patients. These changes could have predictive value for detecting MHE.

Topics: Aged; Aged, 80 and over; Ammonia; Area Under Curve; Case-Control Studies; Cognitive Dysfunction; Cyclic GMP; Female; Gray Matter; Humans; Interleukins; Liver Cirrhosis; Magnetic Resonance Imaging; Male; Middle Aged; Psychometrics; ROC Curve

Patients with hepatic encephalopathy (HE) show working memory and visuo-spatial orientation deficits. Hyperammonemia is a main contributor to cognitive impairment in HE. Hyperammonemic rats show impaired spatial learning and learning ability in the Y maze. Intracerebral administration of extracellular cGMP restores learning in the Y-maze. The underlying mechanisms remain unknown. It also remains unknown whether extracellular cGMP improves neuroinflammation or restores spatial learning in hyperammonemic rats and if it affects differently reference and working memory. The aims of this work were: Spatial working and reference memory were assessed using the radial and Morris water mazes and neuroinflammation by immunohistochemistry and Western blot. Membrane expression of NMDA and AMPA receptor subunits was analyzed using the BS3 crosslinker. Extracellular cGMP was administered intracerebrally using osmotic minipumps. Chronic hyperammonemia induces neuroinflammation in hippocampus, with astrocytes activation and increased IL-1β, which are associated with increased NMDA receptors membrane expression and impaired working memory. This process is not affected by extracellular cGMP. Hyperammonemia also activates microglia and increases TNF-α, alters membrane expression of AMPA receptor subunits (increased GluA1 and reduced GluA2) and impairs reference memory. All these changes are reversed by extracellular cGMP. These results show that extracellular cGMP modulates spatial reference memory but not working memory. This would be mediated by modulation of TNF-α levels and of membrane expression of GluA1 and GluA2 subunits of AMPA receptors.

Topics: Animals; Cognitive Dysfunction; Cyclic GMP; Disease Models, Animal; Hippocampus; Hyperammonemia; Inflammation; Interleukin-1beta; Male; Memory, Short-Term; Rats; Rats, Wistar; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Spatial Memory; Tumor Necrosis Factor-alpha

Levels of the cyclic nucleotides guanosine 3', 5'-monophosphate (cGMP) or adenosine 3', 5'-monophosphate (cAMP) that play important roles in memory processes are not characterized in Alzheimer's disease (AD). The aim of this study was to analyse the levels of these nucleotides in cerebrospinal fluid (CSF) samples from patients diagnosed with clinical and prodromal stages of AD and study the expression level of the enzymes that hydrolyzed them [phosphodiesterases (PDEs)] in the brain of AD patients vs.. For cGMP and cAMP CSF analysis, the cohort (n = 79) included cognitively normal participants (subjective cognitive impairment), individuals with stable mild cognitive impairment or AD converters (sMCI and cMCI), and mild AD patients. A high throughput liquid chromatography-tandem mass spectrometry method was used. Interactions between CSF cGMP or cAMP with mini-mental state examination (MMSE) score, CSF Aβ(1-42) and CSF p-tau were analysed. For PDE4, 5, 9 and 10 expression analysis, brains of AD patients vs. controls (n = 7 and n = 8) were used.. cGMP, and not cAMP levels, were significantly lower in the CSF of patients diagnosed with mild AD when compared with nondemented controls. CSF levels of cGMP showed a significant association with MMSE-diagnosed clinical dementia and with CSF biomarker Aβ42 in AD patients. Significant increase in PDE5 expression was detected in temporal cortex of AD patients compared with that of age-matched healthy control subjects. No changes in the expression of others PDEs were detected.. These results support the potential involvement of cGMP in the pathological and clinical development of AD. The cGMP reduction in early stages of AD might participate in the aggravation of amyloid pathology and cognitive decline.

Topics: Aged; Alzheimer Disease; Brain; Cognitive Dysfunction; Cyclic AMP; Cyclic GMP; Female; Humans; Male; Middle Aged; Neuropsychological Tests; Phosphoric Diester Hydrolases