Cyclic GMP Research Articles

A novel phosphodiesterase 5 inhibitor, RF26, improves memory impairment and ameliorates tau aggregation and neuroinflammation in the P301S tauopathy mouse model of Alzheimer's disease.

Phosphodiesterase-5 (PDE5) inhibitors are primarily used in the treatment of erectile dysfunction and pulmonary hypertension, but have also been reported to have a potential therapeutic effect for the treatment of Alzheimer's disease (AD). This is likely to be through stimulation of nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling by elevating cGMP, a secondary messenger involved in processes of neuroplasticity. In the present study, we evaluated the efficacy of a novel PDE5 inhibitor, RF26, using P301S tauopathy mice model. A body of experimental evidence suggests that the development of tau inclusions leads to the neurodegeneration observed in tauopathies, including AD, Frontotemporal dementia (FTD), Supranuclear palsy and others. RF26 successfully targeted NO/cGMP signaling pathway and showed a significant improvement of spatial memory task performance of P301S mice using Morris Water Maze and T-maze. Furthermore, RF26 -treated mice showed a significant reduction of phosphorylated tau load, gliosis and downregulated pro-inflammatory cytokines. The presented data support the efficacy of RF26 as a potent PDE5 inhibitor and calls for further investigation as a potential therapeutic drug for Alzheimer's and other tauopathy related neurological disorders.

Architecture and activation of single-pass transmembrane receptor guanylyl cyclase.

The heart, in addition to its primary role in blood circulation, functions as an endocrine organ by producing cardiac hormone natriuretic peptides. These hormones regulate blood pressure through the single-pass transmembrane receptor guanylyl cyclase A (GC-A), also known as natriuretic peptide receptor 1. The binding of the peptide hormones to the extracellular domain of the receptor activates the intracellular guanylyl cyclase domain of the receptor to produce the second messenger cyclic guanosine monophosphate. Despite their importance, the detailed architecture and domain interactions within full-length GC-A remain elusive. Here we present cryo-electron microscopy structures, functional analyses and molecular dynamics simulations of full-length human GC-A, in both the absence and the presence of atrial natriuretic peptide. The data reveal the architecture of full-length GC-A, highlighting the spatial arrangement of its various functional domains. This insight is crucial for understanding how different parts of the receptor interact and coordinate during activation. The study elucidates the molecular basis of how extracellular signals are transduced across the membrane to activate the intracellular guanylyl cyclase domain.

The expression of contextual fear conditioning involves the dorsal hippocampus TRPV1 receptor interacting with the NMDA/NO/cGMP signalling pathway.

The dorsal hippocampus (dHIP) is pivotal for learning, memory, and defensive responses. Transient receptor potential vanilloid type 1 (TRPV1) receptors in the dHIP modulate contextual fear conditioning by triggering a cascade involving glutamate release, nitric oxide (NO) formation and cyclic guanosine monophosphate (cGMP) production. The present study investigated the involvement of dHIP TRPV1 receptors and their interaction with the glutamate/NO/cGMP signalling pathway in modulating the expression of contextual fear conditioning (CFC). Male Wistar rats were submitted to an aversive contextual conditioning session and, 48 h later, were re-introduced to the same aversive environment where the freezing response and autonomic activity (evidenced by increased arterial pressure and heart rate and a decrease in tail temperature) were measured. The results demonstrated that the TRPV1 antagonist 6-I-CPS in dHIP reduced the expression of CFC, whereas the agonist capsaicin had the opposite effect. Furthermore, dHIP pre-treatment with an NMDA receptor antagonist (AP7), neuronal NO synthase inhibitor (N-propyl-L-arginine), NO scavenger (c-PTIO) or guanylate cyclase inhibitor (ODQ) attenuated capsaicin-induced increases in CFC. Finally, we observed that re-exposure to the aversive chamber increased dHIP NO levels in conditioned animals compared with a non-conditioned group, which was prevented by the administration of the TRPV1 antagonist, 6-I-CPS. Our study revealed that TRPV1 receptors in the dHIP play a crucial role in modulating contextual fear expression by acting through the NMDA receptor/NO/cGMP signalling pathway, providing important insights into the underlying mechanisms and potential therapeutic avenues associated with these pathways.

Abstract 4134234: Association Between the Natriuretic Peptides-Cyclic Guanosine Monophosphate Cascade and Left Ventricular Reverse Remodeling After Acute Anterior Myocardial Infarction

Background: Natriuretic peptides and their second messenger, cyclic guanosine monophosphate (cGMP), play a critical role in the pathogenesis of cardiovascular diseases by inhibiting the renin-aldosterone system, cardiac hypertrophy, and fibrosis. Recently developed chemiluminescent enzyme immunoassays for proBNP have enabled the estimation of mature BNP (emBNP) by calculating the difference between total BNP and proBNP. Research Questions: The role of cGMP in left ventricular remodeling after acute myocardial infarction (AMI) remains poorly understood. Aims: We aimed to investigate the relationship between the natriuretic peptide-cGMP cascade and left ventricular reverse remodeling (RR) in patients with anterior AMI. Methods: In a prospective 67 patients experiencing their first anterior AMI, plasma BNP fractions and cGMP levels were measured at immediate primary percutaneous coronary intervention (PPCI), 3 days, and 3 months post-AMI. Change in left ventricular end-systolic index (delta-LVESVI) was calculated as the difference between median 10 months and day 10 using cardiac magnetic resonance imaging. Patients were divided into RR and non-RR groups based on regression analysis to compute residuals representing the differences between each individual’s observed delta-LVESVI and delta-LVESVI adjusted by plasma pro-BNP concentration at immediate PPCI because of an inverse correlation between delta-LVESVI and plasma pro-BNP concentration at immediate PPCI (r=0.243, p=0.047). RR group (n=33) demonstrated below-median residual delta-LVESVI, while non-RR group (n=34) had above-median residual. Results: RR group exhibited significantly higher freedom from major adverse cerebral and cardiovascular events (MACCE) during a median of 8.1-year (Interquartile range: 6.7–8.8) follow-up (P=0.024) (Figure A) . Multivariable analysis identified logarithmic plasma pro-BNP, and emBNP at day 3 post-AMI, and plasma cGMP levels at immediate PPCI and day 3 post-AMI, as independent predictors of RR (P<0.05) even after adjusting age, male, hypertension, and infarct size. (Figure B-D) . Conclusion: Early-phase activation of the natriuretic peptides-cGMP cascade may play a protective role in left ventricular remodeling in patients with anterior AMI.

Renal Effects of Combination Phosphodiesterase V Inhibition and Low-Dose B-Type Natriuretic Peptide in Acute Heart Failure: A Randomized Clinical Trial.

Cardiorenal dysfunction with impaired cyclic GMP (cGMP) response is common in patients presenting with acute heart failure (HF). Type V phosphodiesterase (PDEV) is known to be upregulated in HF and may explain the dysfunction of renal response. The aim of this study was to determine whether B-type natriuretic peptide (BNP) alone or in combination with PDEV inhibition improves renal function and increases urinary sodium and cGMP excretion in acute HF. This open-label study included 67 patients hospitalized with acute HF and renal dysfunction. Patients were randomized to standard care, low-dose intravenous BNP (0.005 µg/kg per minute), or combination BNP/PDEV inhibition with sildenafil (25 mg q12 hours) for 48 hours. The coprimary end points were the percent change in estimated glomerular filtration rate and blood urea nitrogen from baseline to 48 hours. Treatment with BNP and BNP/PDEV inhibitor significantly increased plasma cGMP at 24 hours (+25.6% [+9.8%, +84.7%] and +60.8% [+32.3%, +103.8%] for BNP and BNP/PDEV versus -13.5% [-29.1%, +14.2%] with standard care; P=0.001). However, there was no significant change in estimated glomerular filtration rate 0 (-10.8%, +12.7%) for standard care versus 0 (-15.3%, +11.8%) for the BNP group versus -8.8% (-14.3%, +8.3%) for the BNP/PDEV group (P=0.60) or blood urea nitrogen -1.4% (-10.7%, +12.0%) for standard care versus -5.9% (-14.6%, +9.4%) for the BNP group versus +6.9% (-5.3%, +18.8%) for the BNP/PDEV group (P=0.38) between groups. Hypotension was more common in the BNP/PDEV inhibitor group. BNP and combination BNP/PDEV inhibition increased plasma cGMP in patients with acute HF but did not improve renal function or urinary sodium/cGMP excretion. Our study does not support the use of intravenous low-dose BNP with or without PDEV inhibition to enhance renal function in patients admitted with acute HF. URL: https://www.clinicaltrials.gov; Unique identifier: NCT00972569.

Inhibition of Phosphodiesterase 10A Alleviates Pain-like Behavior in Mice.

Emerging evidence indicates that cyclic nucleotide phosphodiesterases exert distinct functions in pain processing and that targeting phosphodiesterases might be a novel strategy for pain relief. This study hypothesized that the phosphodiesterase isoform PDE10A might be a target for analgesic therapy. In situ hybridization, immunostaining, cyclic nucleotide enzyme immunoassays, real-time cyclic guanosine monophosphate imaging, and real-time quantitative reverse transcription polymerase chain reaction were performed to investigate the expression and activity of PDE10A in the dorsal root ganglia and spinal cord. Mice of both sexes were assessed in multiple pain models after the administration of specific PDE10A inhibitors. PDE10A is distinctly expressed in nociceptive neurons in the dorsal root ganglia and spinal cord of mice. Incubation of cultured sensory neurons with the PDE10A inhibitor, TAK-063 (150 nM), increased cyclic guanosine monophosphate levels in enzyme immunoassays and real-time imaging at the single-cell level. Strikingly, treatment with TAK-063 (0.3 mg/kg intraperitoneal) ameliorated the pain-like behavior of female and male mice in models of acute nociceptive pain after intraplantar injection of capsaicin (mean ± SD; 8.87 ± 8.78 s [TAK-063] vs. 51.24 ± 36.36 s [vehicle], P = 0.020) or allyl isothiocyanate (2.46 ± 3.43 s [TAK-063] vs. 10.36 ± 4.87 s [vehicle]; P = 0.018). Furthermore, TAK-063 (0.3 mg/kg intraperitoneal) reduced established pain-like behavior in models of inflammatory pain induced by intraplantar injection of zymosan (Two-way ANOVA, group, F(1, 18) = 48.51, TAK-063 vs. vehicle; P ≤ 0.0001) or complete Freund's adjuvant (F(1, 14) = 46.10, TAK-063 vs. vehicle; P ≤ 0.0001), without the development of antinociceptive tolerance. The antinociceptive effects were recapitulated using the PDE10A inhibitor PF-2545920. Collectively, our data support the idea that PDE10A is a suitable target for the development of efficacious analgesic drugs.

How Does African Swine Fever Virus Evade the cGAS-STING Pathway?

African swine fever (ASF), a highly infectious and devastating disease affecting both domestic pigs and wild boars, is caused by the African swine fever virus (ASFV). ASF has resulted in rapid global spread of the disease, leading to significant economic losses within the swine industry. A significant obstacle to the creation of safe and effective ASF vaccines is the existing knowledge gap regarding the pathogenesis of ASFV and its mechanisms of immune evasion. The cyclic GMP–AMP synthase (cGAS)–stimulator of interferon genes (STING) pathway is a major pathway mediating type I interferon (IFN) antiviral immune response against infections by diverse classes of pathogens that contain DNA or generate DNA in their life cycles. To evade the host’s innate immune response, ASFV encodes many proteins that inhibit the production of type I IFN by antagonizing the cGAS-STING signaling pathway. Multiple proteins of ASFV are involved in promoting viral replication by protein–protein interaction during ASFV infection. The protein QP383R could impair the function of cGAS. The proteins EP364R, C129R and B175L could disturb the function of cyclic guanosine monophosphate-adenosine monophosphate (cGAMP). The proteins E248R, L83L, MGF505-11R, MGF505-7R, H240R, CD2v, E184L, B175L and p17 could interfere with the function of STING. The proteins MGF360-11L, MGF505-7R, I215L, DP96R, A151R and S273R could affect the function of TANK Binding Kinase 1 (TBK1) and IκB kinase ε (IKKε). The proteins MGF360-14L, M1249L, E120R, S273R, D129L, E301R, DP96R, MGF505-7R and I226R could inhibit the function of Interferon Regulatory Factor 3 (IRF3). The proteins MGF360-12L, MGF505-7R/A528R, UBCv1 and A238L could inhibit the function of nuclear factor kappa B (NF-Κb).

Fresh insights into the light‐induced pineal gland circadian rhythm transmission mechanism derived from mRNA and miRNA profiling

AbstractThe circadian clock significantly impacts animal health and productivity, with light playing a crucial role in regulating circadian rhythms. However, the mechanisms behind light‐induced circadian transmission remain unclear, particularly in light‐sensitive avian species. The pineal gland is a key component acting as the photosensitive master oscillator in the avian clock system. Using transcriptome sequencing and small RNA sequencing technologies, we identified circadian genes and miRNAs in the chick pineal gland under light–dark and sudden constant‐light conditions. We observed rhythmic oscillations in up to 1299 genes during the light–dark cycle, with 400 genes maintaining rhythms under constant light. Our findings highlight the light‐sensitive temporal organization in birds as the phase distribution of circadian genes in the pineal gland correlates with light exposure changes. A novel regulatory mechanism involving light, cyclic adenosine monophosphate, cyclic guanosine monophosphate, light‐sensitive miRNAs, such as gga‐miR‐34b‐5p, and light‐sensitive circadian genes, such as CRY2, was discovered to participate in the light input system of the chick pineal clock, through which light regulates the oscillators and outputs of the circadian clock system. Additionally, transcriptomic analysis, liquid chromatography–mass spectrometry, and Oil Red O staining revealed cyclic changes in lipid synthesis and metabolism throughout the circadian day, which may be a key mechanism through which the circadian clock influences pineal physiology. Our results enhance the understanding of light‐induced circadian transmission mechanisms and identify potential targets for optimizing the circadian clock through light.

Multimodal action of phosphodiesterase 5 inhibitors against neurodegenerative disorders: An update review.

Phosphodiesterase type 5 (PDE5) is an enzyme primarily found in the smooth muscle of the corpus cavernosum and also highly expressed in the substantia nigra, cerebellum, caudate, hippocampal regions and cerebellar purkinje cells, responsible for selectively breaking down cyclic guanosine monophosphate (cGMP) into 5'-GMP and regulate intracellular cGMP levels. As a second messenger, cyclic GMP enhances signals at postsynaptic receptors and triggers downstream effector molecules, leading to changes in gene expression and neuronal responses. Additionally, cGMP signaling transduction cascade, present in the brain, is also essential for learning and memory processes. Mechanistically, PDE5 inhibitors share structural similarities with cGMP, competitively binding to PDE5 and inhibiting cGMP hydrolysis. This action enhances the effects of nitric oxide, resulting in anti-inflammatory and neuroprotective effects. Neurodegenerative disorders entail the progressive loss of neuron structure, culminating in neuronal cell death, with currently available drugs providing only limited symptomatic relief, rendering neurodegeneration considered incurable. PDE5 inhibitors have recently emerged as a potential therapeutic approach for neurodegeneration, neuroinflammation, and diseases involving cognitive impairment. This review elucidates the principal roles of 3',5'-cyclic adenosine monophosphate (cAMP) and cGMP signaling pathways in neuronal functions, believed to play pivotal roles in the pathogenesis of various neurodegenerative disorders. It provides an updated assessment of PDE5 inhibitors as disease-modifying agents for conditions such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, cerebral ischemia, Huntington's disease, and neuroinflammation. The paper aims to review the current understanding of PDE5 inhibitors, which concurrently regulate both cAMP and cGMP signaling pathways, positing that they may exert complementary and synergistic effects in modifying neurodegeneration, thus presenting a novel direction in therapeutic discovery. Moreover, the review provides critical about biological functions, therapeutic potentials, limitations, challenges, and emerging applications of selective PDE5 inhibitors. This comprehensive overview aims to guide future academic and industrial endeavors in this field.

Cladophorol-A is an inhibitor of cyclic GMP-AMP synthase

Cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS) is an enzyme sensor of double-stranded DNA (dsDNA) that serves to trigger activation of the cGAS-stimulator of interferon genes (STING) pathway. Excessive activation of this pathway has been demonstrated to contribute to various forms of inflammatory disease. As such, cGAS has arisen as a potential therapeutic target with broad potential applications. Using a pathway-targeted cell-based screening approach, we identified the natural product Cladophorol A as a new class of non-cytotoxic cGAS inhibitor (cell-based IC50 = 370 nM). An x-ray co-crystal structure at 2.75 Å resolution revealed that Cladophorol A inhibits cGAS by binding to its active site within the conserved adenosine nucleobase binding site.

CGMP-dependent pathway and a GPCR kinase are required for photoresponse in the nematode Pristionchus pacificus.

Light sensing is a critical function in most organisms and is mediated by photoreceptor proteins and phototransduction. Although most nematodes lack eyes, some species exhibit phototaxis. In the nematode Caenorhabditis elegans, the unique photoreceptor protein Cel-LITE-1, its downstream G proteins, and cyclic GMP (cGMP)-dependent pathways are required for phototransduction. However, the mechanism of light-sensing in other nematodes remains unknown. To address this question, we used the nematode Pristionchus pacificus, which was established as a satellite model organism for comparison with C. elegans. Similar to C. elegans, illumination with short-wavelength light induces avoidance behavior in P. pacificus. Opsin, cryptochrome/photolyase, and lite-1 were not detected in the P. pacificus genome using orthology and domain prediction-based analyses. To identify the genes related to phototransduction in P. pacificus, we conducted forward genetic screening for light-avoidance behavior and isolated five light-unresponsive mutants. Whole-genome sequencing and genetic mapping revealed that the cGMP-dependent pathway and Ppa-grk-2, which encodes a G protein-coupled receptor kinase (GRK) are required for light avoidance. Although the cGMP-dependent pathway is conserved in C. elegans phototransduction, GRK is not necessary for light avoidance in C. elegans. This suggests similarities and differences in light-sensing mechanisms between the two species. Using a reverse genetic approach, we showed that gamma-aminobutyric acid (GABA) and glutamate were involved in light avoidance. Through reporter analysis and suppression of synapse transmission, we identified candidate photosensory neurons. These findings advance our understanding of the diversity of phototransduction in nematodes even in the absence of eyes.

Mechanism of action of exercise regulating intestinal microflora to improve spontaneous hypertension in rats.

Hypertension is a prevalent cardiovascular disease. Exercise is widely recognized as an effective treatment for hypertension, and it may also influence the composition of the intestinal microflora. However, it remains unclear whether exercise can specifically regulate the intestinal microflora in the context of hypertension treatment. In this study, tail blood pressure in spontaneously hypertensive rats (SHR) was measured using a blood pressure meter after exercise intervention and fecal bacteria transplantation following exercise. Blood lipid levels were assessed using an automatic biochemical analyzer, and 16S rRNA sequencing was employed to analyze the intestinal microflora. Histological examinations of ileal tissue were conducted using HE and Masson staining. Intestinal permeability, inflammatory status, and sympathetic activity were evaluated by measuring the levels of diamine oxidase, D-lactic acid, C-reactive protein, interleukin-6, tumor necrosis factor-α, lipopolysaccharide, norepinephrine, angiotensin II, cyclic adenosine monophosphate, and cyclic guanosine monophosphate. Exercise was found to reduce blood pressure and blood lipid levels in SHR. It also improved the composition of the intestinal microflora, as evidenced by a reduced Firmicutes/Bacteroidetes ratio, an increase in bacteria that produce acetic and butyric acid, and higher Chao 1 and Shannon diversity indices. Furthermore, exercise reduced the thickness of the fibrotic and muscular layers in the ileum, increased the goblet cell/villus ratio and villus length, and decreased intestinal permeability, inflammatory markers, and sympathetic nerve activity. The intestinal microbial flora regulated by exercise demonstrated similar effects on hypertension. In conclusion, exercise appears to regulate the intestinal microflora, and this exercise-induced change in flora may contribute to improvements in hypertension in rats.

Real-time imaging of cGMP signaling shows pronounced differences between glomerular endothelial cells and podocytes.

Recent clinical trials of drugs enhancing cyclic guanosine monophosphate (cGMP) signaling for cardiovascular diseases have renewed interest in cGMP biology within the kidney. However, the role of cGMP signaling in glomerular endothelial cells (GECs) and podocytes remains largely unexplored. Using acute kidney slices from mice expressing the FRET-based cGMP biosensor cGi500 in endothelial cells or podocytes enabled real-time visualization of cGMP. Stimulation with atrial natriuretic peptide (ANP) or SNAP (NO donor) and various phosphodiesterase (PDE) inhibitors elevated intracellular cGMP in both cell types. GECs showed a transient cGMP response upon particulate or soluble guanylyl cyclase activation, while the cGMP response in podocytes reached a plateau following ANP administration. Co-stimulation (ANP + SNAP) led to an additive response in GECs. The administration of PDE inhibitors revealed a broader basal PDE activity in GECs dominated by PDE2a. In podocytes, basal PDE activity was mainly restricted to PDE3 and PDE5 activity. Our data demonstrate the existence of both guanylyl cyclase pathways in GECs and podocytes with cell-specific differences in cGMP synthesis and degradation, potentially suggesting new therapeutic options for kidney diseases.

Latent class analysis reveals a novel phenotype of heart failure that spans the left ventricular ejection fraction range

Abstract Background It is increasingly evident that heart failure (HF) represents a heterogenous syndrome rather than a single clinical entity. The elusiveness of effective therapies for heart failure with preserved ejection fraction (HFpEF) has led to a consensus that our current, unidimensional construct of HF using only left ventricular ejection fraction (LVEF) does not adequately capture the multiplicity of the disease states. The ability to harmonize echocardiographic data from multiple sources has enabled use of unsupervised cluster-based analysis to identify multidimensional cardiac structural phenotypes. Purpose To identify cardiac structural phenotypes of HF across the LVEF spectrum. Methods We harmonized echocardiographic data from eight randomized clinical HF trials (ESCAPE, EXACT-HF, FIGHT, I-PRESERVE, NEAT-HFpEF, RELAX, STICH and TOPCAT), which included both HFrEF and HFpEF populations (total n=4223 echocardiograms). These studies collectively spanned the years 2000 through 2015 and represent a balanced LVEF distribution. Latent class analysis (LCA) was performed iteratively to identify predominant structural phenotypes using LVEF, RV function, LV end diastolic volume, LV mass index, eccentricity, mitral valve deceleration time, and lateral E/e’ ratio. Results LCA identified 4 echocardiographic phenotypes. Three phenotypes skewed toward either high or low EF, but one phenotype demonstrated a relatively even distribution of patients with HFrEF, heart failure with mildly reduced ejection fraction (HFmrEF) and HFpEF (36.0%, 21.4% and 42.7%, respectively). Patients in this phenotype had preserved RV function and left ventricular hypertrophy (97%), of which 56.8% had concentric and 43.2% eccentric LVH. E/e’ was normal in 63% of subjects. A vast majority (91%) of patients had recent-onset HF (diagnosed within the past year). There were no remarkable distinguishing comorbidities. Notable differences in biomarker profile included higher levels of troponin I, cyclic GMP and lower levels of neurohormones (aldosterone, endothelin-1, dopamine, and norepinephrine) than the other phenotypes. Conclusions This is the first cluster-based analysis to identify a quantitative structural HF phenotype of HF that is not distinguished by LVEF. While the underlying pathophysiology is unclear, most patients have recent onset HF and biomarker profiles with relatively low neurohormone activity. These features may reflect a distinct pathophysiology that could indicate a specific, targeted intervention.

Development of a Candidate 11C-Labeled Selective Phosphodiesterase 1 Radioligand for Positron Emission Tomography.

Phosphodiesterases (PDEs) constitute a superfamily of phosphohydrolytic enzymes that regulate intracellular second messenger signaling by hydrolyzing cyclic adenosine monophosphate and cyclic guanosine monophosphate. Among the 11 subfamilies of PDEs, phosphodiesterase 1 (PDE1) stands out due to its broad implications in central and peripheral pathologies. There are three subtypes of PDE1: PDE1A, PDE1B, and PDE1C. While PDE1A and PDE1C are distributed in both the brain and peripheral organs, PDE1B is predominantly expressed in the brain, rendering it an attractive drug target for neurological and psychological disorders. Despite continuous efforts dedicated to the development of novel PDE1 inhibitors, a suitable PDE1 radioligand for human use is currently lacking. In this study, we present the identification and preclinical evaluation of [11C]PF-04822163, a selective radioligand candidate for imaging PDE1 with positron emission tomography. PF-04822163 exhibits excellent potency toward PDE1 and demonstrates great target selectivity over other PDEs. Then, PF-04822163 was labeled with carbon-11 (half-life, 20 min) in favorable radiochemical yields (25 ± 10%, decay-corrected) and high molar activities (106-194 GBq/μmol). Further, in vitro and in vivo evaluations in rodents suggested that [11C]PF-04822163 displayed good brain penetration and a rapid washout. Despite these promising performance characteristics of [11C]PF-04822163, only marginal specific binding was observed in vivo. Further optimization of the scaffold is warranted to obtain favorable pharmacological and ADME properties.

Phase 2 Trial of Vosoritide Use in Patients with Hypochondroplasia: A Pharmacokinetic/Pharmacodynamic Analysis

Introduction: Vosoritide is a C-type natriuretic peptide (CNP) analog that binds its receptor on chondrocytes, promoting growth by inhibiting the ERK1/2-MAPK pathway. We previously reported the results of a phase II study in children with hypochondroplasia. Vosoritide led to an average increase in annualized height velocity (AHV) of 1.81 cm/year and gain of 0.36 in height standard deviation (SD) over 12 months. We present here the pharmacokinetic/pharmacodynamic (PK/PD) data from this study and examine the correlations between these parameters and growth outcomes. Methods: We conducted a phase II trial of daily subcutaneous vosoritide (15 μg/kg/day) in 24 prepubertal subjects with hypochondroplasia (12 females, mean age 5.9 ± 2.3 years, mean height −3.29 + 0.68 SD). Plasma vosoritide levels were assayed using an electrochemiluminescence assay. PD markers including serum collagen X biomarker (CXM) and urine cyclic guanosine monophosphate (cGMP) production were measured at day 1, month 6, and month 12 visits. Pearson correlations and regression analyses were performed between PK and PD parameters and growth outcomes. Results: Vosoritide PK parameters were similar to those previously reported in patients with achondroplasia. CXM levels increased from a baseline mean of 22.5 ± 6.5 to 41.6 ± 15.9 ng/mL after 12 months of treatment (p < 0.0001). Urine cGMP increased within 1 h and peaked at 2 h after injection. The mean AUC for cGMP production was not significantly different at each study visit. The maximum change in cGMP AUC correlated with PK AUC (r = 0.46, p = 0.0001). However, drug exposure, as measured by average PK AUC, did not correlate with any growth outcome. CXM levels correlated with the prior 6-month interval height velocity (partial correlation coefficient = 0.40, p = 0.0048). However, change in CXM did not correlate with change in height velocity or change in height SD during treatment. Conclusions: Vosoritide treatment showed improvement in AHV and height SD in children with hypochondroplasia. PK analysis indicates that drug exposure was correlated to global CNP activity as measured by urine cGMP but did not correlate with growth outcomes. More studies are needed to identify specific patient characteristics that can predict response to therapy and clinical outcomes.

Comparison of sGC activator and sGC stimulator in 5/6 nephrectomized rats on high-salt-diet.

Soluble guanylate cyclase (sGC) stimulators and activators are known to enhance kidney function in various models of chronic kidney disease (CKD) by increasing cyclic guanosine monophosphate (cGMP). Their differential effects on CKD progression, particularly under conditions of oxidative stress, remain unexplored by direct comparative studies. We conducted a side-by-side comparison using 5/6 nephrectomized rats on a high salt diet (5/6Nx+HSD) to evaluate the efficacy of the sGC stimulator BAY 41-8543 and the sGC activator BAY 60-2770 in CKD progression. BAY 41-8543 (1mg/kg; twice daily) and BAY 60-2770 (1mg/kg; once daily) were administered by gavage for 11 weeks. The 5/6Nx+HSD model led to increased plasma creatinine, proteinuria, and blood pressure. Both BAY 41-8543 and BAY 60-2770 significantly reduced systolic and diastolic blood pressure to a similar extent but did not improve renal function parameters. Notably, BAY 60-2770 reduced renal fibrosis, including interstitial fibrosis and glomerulosclerosis, whereas BAY 41-8543 did not. These antifibrotic effects of BAY 60-2770 were independent of blood pressure reduction. Proteomic analysis revealed that BAY 60-2770 corrected the upregulation of 9 proteins associated with apoptosis and fibrosis, including Caspase-3, MKK6 (Mitogen-Activated Protein Kinase Kinase 6), Prdx5 (Peroxiredoxin-5), in the 5/6Nx+HSD group. In contrast, BAY 41-8543 had no significant impact on these proteins. sGC activators were more effective than sGC stimulators in reducing renal fibrosis in 5/6 nephrectomized rats on a high salt diet, and this effect was due to modulation of apoptosis-associated proteins beyond the control of blood pressure.

The Emerging Role of Phosphodiesterase 5 Inhibition in Neurological Disorders: The State of the Art.

Growing evidence suggests that neuroinflammation is not just a consequence of neurodegeneration in pathologies such as Alzheimer's disease, Parkinson's disease, Huntington's disease or Amyotrophic lateral sclerosis, but it is rather a determinant factor, which plays a pivotal role in the onset and progression of these disorders. Neuroinflammation can affect cells and processes in the central nervous system (CNS) as well as immune cells, and might precede protein aggregation, which is a hallmark of the neurodegenerative process. Standard treatment methods are far from being able to counteract inflammation and delay neurodegeneration. Remarkably, phosphodiesterase 5 inhibitors (PDE5is), which represent potent vasoactive drugs used as a first-line treatment for erectile dysfunction (ED), display important anti-inflammatory effects through cyclic guanosine monophosphate (cGMP) level stabilization. Since PDE5 hydrolyzes cGMP, several studies positioned PDE5 as a therapeutic target, and more specifically, PDE5is as potential alternative strategies for the treatment of a variety of neurological disorders. Indeed, PDE5is can limit neuroinflammation and enhance synaptic plasticity, with beneficial effects on cognitive function and memory. The aim of this review is to provide an overview of some of the main processes underlying neuroinflammation and neurodegeneration which may be potential targets for PDE5is, focusing on sildenafil, the most extensively studied. Current strategies using PDEis for the treatment of neurodegenerative diseases will be summarized.

Pharmacologically increasing cGMP improves proteostasis and reduces neuropathy in mouse models of CMT1

Increasing cyclic GMP activates 26S proteasomes via phosphorylation by Protein Kinase G and stimulates the intracellular degradation of misfolded proteins. Therefore, agents that raise cGMP may be useful therapeutics against neurodegenerative diseases and other diseases in which protein degradation is reduced and misfolded proteins accumulate, including Charcot Marie Tooth 1A and 1B peripheral neuropathies, for which there are no treatments. Here we increased cGMP in the S63del mouse model of CMT1B by treating for three weeks with either the phosphodiesterase 5 inhibitor tadalafil, or the brain-penetrant soluble guanylyl cyclase stimulator CYR119. Both molecules activated proteasomes in the affected peripheral nerves, reduced polyubiquitinated proteins, and improved myelin thickness and nerve conduction. CYR119 increased cGMP more than tadalafil in the peripheral nerves of S63del mice and elicited greater biochemical and functional improvements. To determine whether raising cGMP could be beneficial in other neuropathies, we first showed that polyubiquitinated proteins and the disease-causing protein accumulate in the sciatic nerves of the C3 mouse model of CMT1A. Treatment of these mice with CYR119 reduced the levels of polyubiquitinated proteins and the disease-causing protein, presumably by increasing their degradation, and improved myelination, nerve conduction, and motor coordination. Thus, pharmacological agents that increase cGMP are promising treatments for CMT1 neuropathies and may be useful against other proteotoxic and neurodegenerative diseases.

Stimulating Soluble Guanylyl Cyclase with the Clinical Agonist Riociguat Restrains the Development and Progression of Castration-Resistant Prostate Cancer.

Castration-resistant prostate cancer (CRPC) is incurable and fatal, making prostate cancer the second-leading cancer-related cause of death for American men. CRPC results from therapeutic resistance to standard-of-care androgen deprivation (AD) treatments, through incompletely understood molecular mechanisms, and lacks durable therapeutic options. Here, we identified enhanced soluble guanylyl cyclase (sGC) signaling as a mechanism that restrains CRPC initiation and growth. Patients with aggressive, fatal CRPC exhibited significantly lower serum levels of the sGC catalytic product cyclic GMP (cGMP) compared to their castration-sensitive stage. In emergent castration-resistant cells isolated from castration-sensitive prostate cancer (CSPC) populations, the obligate sGC heterodimer was repressed via methylation of its beta subunit. Genetically abrogating sGC complex formation in CSPC cells promoted evasion of AD-induced senescence and concomitant castration-resistant tumor growth. In established castration-resistant cells, the sGC complex was present but in a reversibly oxidized and inactive state. Subjecting CRPC cells to AD regenerated the functional complex, and co-treatment with riociguat, an FDA-approved sGC agonist, evoked redox stress-induced apoptosis. Riociguat decreased castration-resistant tumor growth and increased apoptotic markers, with elevated cGMP levels correlating significantly with lower tumor burden. Riociguat treatment reorganized tumor vasculature and eliminated hypoxic tumor niches, decreasing CD44+ tumor progenitor cells and increasing the radiosensitivity of castration-resistant tumors. Thus, this study showed that enhancing sGC activity can inhibit CRPC emergence and progression through tumor cell-intrinsic and extrinsic effects. Riociguat can be repurposed to overcome CRPC, with noninvasive monitoring of cGMP levels as a marker for on-target efficacy.