Guanosine Monophosphate Research Articles

Guanylate-binding protein 1 inhibits inflammatory factors produced by H5N1 virus through Its GTPase activity

The combination of inflammatory factors resulting from an influenza A virus infection is one of the main causes of death in host animals. Studies have shown that guinea pig guanosine monophosphate binding protein 1 (guanylate-binding protein 1, gGBP1) can downregulate cytokine production induced by the influenza virus. Therefore, exploring the innate immune defense mechanism of GBP1 in the process of H5N1 influenza virus infection has important implications for understanding the pathogenic mechanism, disease prevention, and the control of influenza A virus infections. We found that, in addition to inhibiting the early replication of influenza virus, gGBP1 also inhibited the production of CCL2 and CXCL10 cytokines induced by the influenza virus as well as the proliferation of mononuclear macrophages induced by these cytokines. These findings further confirmed that gGBP1 inhibited the production of cytokines through its GTPase activity and cell proliferation through its C-terminal α-helix structure. This study revealed the effect of gGBP1 on the production of cellular inflammatory factors during influenza virus infection and determined the key amino acid residues that assist in the inhibitory processes mediated by gGBP1.

Second Near‐Infrared Phototheranostics with cGAS‐STING‐Activating Capacity for Photothermal Immunotherapy

AbstractPhotothermal immunotherapy represents an effective approach for eliminating both local and metastatic tumors through priming of the tumor‐specific immune response. Cytosolic delivery of double‐stranded DNA via pH‐responsive vehicles is recently verified to activate the cyclic guanosine monophosphate–adenosine monophosphate (GMP‐AMP) synthase‐stimulator of interferon genes (cGAS‐STING) pathway, which is robust in activating both innate and adaptive antitumor immunity. Herein, multifunctional phototheranostics with excellent photothermal conversion capacity, second near‐infrared (NIR‐II) fluorescence, and cGAS‐STING activating capacity are prepared by encapsulating fish testis DNA and conjugated boron dipyrromethene tetramers with poly(lactic‐co‐glycolic acid) and poly(ethylene glycol)‐b‐poly(lactic‐co‐glycolic acid) via a CaCO3‐assisted double emulsion method. The obtained phototheranostics (coined DB4CaP NPs) after intravenous administration gradually accumulate in tumor regions, as shown by NIR‐II fluorescence imaging. Together with local 915 nm laser exposure, primary tumors in mice treated with DB4CaP NPs could be effectively eradicated, with a complete response of 83.3%. Furthermore, such DB4CaP NPs could synergize with anti‐programmed cell death protein 1 immunotherapy to suppress the growth of distant unirradiated and rechallenged tumors through activating the antitumor immune response. This study highlights a promising strategy for eradicating tumors, particularly invisible and unresectable micronodules, through NIR‐II fluorescence imaging‐guided photothermal immunotherapy.

Exposure to DEP Modifies the Human Umbilical Artery Vascular Resistance Contributing to Hypertension in Pregnancy.

Hypertensive disorders in pregnancy (HDP) are the most prevalent diseases during pregnancy. In addition to the already identified risk factors, exposure to environmental contaminants has been also considered a new one. Phthalates, which are classified as priority environmental pollutants due to their ubiquitousness and endocrine disrupting properties, have been implicated in HDP in some epidemiological studies. Nevertheless, phthalates' vascular impacts still need to be clarified. Thus, we aimed to understand the connection between phthalates exposure and the occurrence of gestational hypertension, as well as the pathway involved in the pathological vascular effects. We investigated diethyl phthalate's (DEP) effect on the vascular reactivity of the human umbilical arteries (HUAs) from normotensive and hypertensive pregnant women. Both DEP's nongenomic (within minutes effect) and genomic (24 h exposure to DEP) actions were evaluated, as well as the contribution of cyclic guanosine monophosphate and Ca2+ channel pathways. The results show that short-term exposure to DEP interferes with serotonin and histamine receptors, while after prolonged exposure, DEP seems to share the same vasorelaxant mechanism as estrogens, through the NO/sGC/cGMP/PKG signaling pathway, and to interfere with the L-type Ca2+ channels. Thus, the vascular effect induced by DEP is similar to that observed in HUA from hypertensive pregnancies, demonstrating that the development of HDP may be a consequence of DEP exposure.

Neutrophil Extracellular Traps Regulate Surgical Brain Injury by Activating the cGAS-STING Pathway

Surgical brain injury (SBI), induced by neurosurgical procedures or instruments, has not attracted adequate attention. The pathophysiological process of SBI remains sparse compared to that of other central nervous system diseases thus far. Therefore, novel and effective therapies for SBI are urgently needed. In this study, we found that neutrophil extracellular traps (NETs) were present in the circulation and brain tissues of rats after SBI, which promoted neuroinflammation, cerebral edema, neuronal cell death, and aggravated neurological dysfunction. Inhibition of NETs formation by peptidylarginine deiminase (PAD) inhibitor or disruption of NETs with deoxyribonuclease I (DNase I) attenuated SBI-induced damages and improved the recovery of neurological function. We show that SBI triggered the activation of cyclic guanosine monophosphate–adenosine monophosphate synthase stimulator of interferon genes (cGAS-STING), and that inhibition of the cGAS-STING pathway could be beneficial. It is worth noting that DNase I markedly suppressed the activation of cGAS-STING, which was reversed by the cGAS product cyclic guanosine monophosphate–adenosine monophosphate (cGMP-AMP, cGAMP). Furthermore, the neuroprotective effect of DNase I in SBI was also abolished by cGAMP. NETs may participate in the pathophysiological regulation of SBI by acting through the cGAS-STING pathway. We also found that high-dose vitamin C administration could effectively inhibit the formation of NETs post-SBI. Thus, targeting NETs may provide a novel therapeutic strategy for SBI treatment, and high-dose vitamin C intervention may be a promising translational therapy with an excellent safety profile and low cost.Graphical The schematic diagram shows the formation of NETs activated cGAS-STING pathway after SBI, leading to increased microglia activation, accompanied with elevation of inflammatory factors, which in turn aggravated brain injury.

Nonlinear system dynamics of calcium and nitric oxide due to cell memory and superdiffusion in neurons

The integer-order interdependent calcium ([Ca2+]) and nitric oxide (NO) systems are unable to shed light on the influences of the superdiffusion and memory in triggering Brownian motion (BM) in neurons. Therefore, a mathematical model is constructed for the fractional-order nonlinear spatiotemporal systems of [Ca2+] and NO incorporating reaction-diffusion equations in neurons. The two-way feedback process between [Ca2+] and NO systems through calcium feedback on NO production and NO feedback on calcium through cyclic guanosine monophosphate (cGMP) with plasmalemmal [Ca2+]-ATPase (PMCA) was incorporated in the model. The Crank–Nicholson scheme (CNS) with Grunwald approximation along spatial derivatives and L1 scheme along temporal derivatives with Gauss–Seidel (GS) iterations were employed. The numerical outcomes were analyzed to get insights into superdiffusion, buffer, and memory exhibiting BM of [Ca2+] and NO systems. The conditions, events and mechanisms leading to dysfunctions in calcium and NO systems and causing different diseases like Parkinson’s were explored in neurons.

Targeting phosphodiesterase 4 as a potential therapy for Parkinson's disease: a review.

Phosphodiesterases (PDEs) have become a promising therapeutic target for various disorders. PDEs are a vast and diversified family of enzymes that degrade cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which have several biochemical and physiological functions. Phosphodiesterase 4 (PDE4) is the most abundant PDE in the central nervous system (CNS) and is extensively expressed in the mammalian brain, where it catalyzes the hydrolysis of intracellular cAMP. An alteration in the balance of PDE4 and cAMP results in the dysregulation of different biological mechanisms involved in neurodegenerative diseases. By inhibiting PDE4 with drugs, the levels of cAMP inside the cells could be stabilized, which may improve the symptoms of mental and neurological disorders such as memory loss, depression, and Parkinson's disease (PD). Though numerous studies have shown that phosphodiesterase 4 inhibitors (PDE4Is) are beneficial in PD, there are presently no approved PDE4I drugs for PD. This review presents an overview of PDE4Is and their effects on PD, their possible underlying mechanism in the restoration/protection of dopaminergic cell death, which holds promise for developing PDE4Is as a treatment strategy for PD. Methods on how these drugs could be effectively delivered to develop as a promising treatment for PD have been suggested.

Possible retinotoxicity of long-term vardenafil treatment

Phosphodiesterase (PDE) inhibitors – such as vardenafil – are used primarily for treating erectile dysfunction via increasing cyclic guanosine monophosphate (cGMP) levels. Recent studies have also demonstrated their significant cardioprotective effects in several diseases, including diabetes, upon long-term, continuous application. However, PDE inhibitors are not specific for PDE5 and also inhibit the retinal isoform. A sustained rise in cGMP in photoreceptors is known to be toxic; therefore, we hypothesized that long-term vardenafil treatment might result in retinotoxicity. The hypothesis was tested in a clinically relevant animal model of type 2 diabetes mellitus. Histological experiments were performed on lean and diabetic Zucker Diabetic Fatty rats. Half of the animals were treated with vardenafil for six months, and the retinal effects were evaluated. Vardenafil treatment alleviated rod outer segment degeneration but decreased rod numbers in some positions and induced changes in the interphotoreceptor matrix, even in control animals. Vardenafil treatment decreased total retinal thickness in the control and diabetic groups and reduced the number of nuclei in the outer nuclear layer. Müller cell activation was detectable even in the vardenafil-treated control animals, and vardenafil did not improve gliosis in the diabetic group. Vardenafil-treated animals showed complex retinal alterations with improvements in some parameters while deterioration in others. Our results point towards the retinotoxicity of vardenafil, even without diabetes, which raises doubts about the retinal safety of long-term continuous vardenafil administration. This effect needs to be considered when approving PDE inhibitors for alternative indications.

Cultivation of phosphate-accumulating biofilm: Study of the effects of acyl-homoserine lactones (AHLs) and cyclic dimeric guanosine monophosphate (c-di-GMP) on the formation of biofilm and the enhancement of phosphate metabolism capacity

This study investigated the mechanisms of microbial growth and metabolism during biofilm cultivation in the biofilm sequencing batch reactor (BSBR) process for phosphate (P) enrichment. The results showed that the sludge discharge was key to biofilm growth, as it terminated the competition for carbon (C) source between the nascent biofilm and the activated sludge. For the tested reactor, after the sludge discharge on 18 d, P metabolism and C source utilization improved significantly, and the biofilm grew rapidly. The P concentration of the recovery liquid reached up to 157.08 mg/L, which was sufficient for further P recovery via mineralization. Meta-omics methods were used to analyze metabolic pathways and functional genes in microbial growth during biofilm cultivation. It appeared that the sludge discharge activated the key genes of P metabolism and inhibited the key genes of C metabolism, which strengthened the polyphosphate-accumulating metabolism (PAM) as a result. The sludge discharge not only changed the types of polyphosphate-accumulating organisms (PAOs) but also promoted the growth of dominant PAOs. Before the sludge discharge, the necessary metabolic abilities that were spread among different microorganisms gradually concentrated into a small number of PAOs, and after the sludge discharge, they further concentrated into Candidatus_Contendobacter (P3) and Candidatus_Accumulibacter (P17). The messenger molecule C-di-GMP, produced mostly by P3 and P17, facilitated P enrichment by regulating cellular P and C metabolism. The glycogen-accumulating organism (GAO) Candidatus_Competibacter secreted N-Acyl homoserine lactones (AHLs), which stimulated the secretion of protein in extracellular polymeric substances (EPS), thus promoting the adhesion of microorganisms to biofilm and improving P metabolism via EPS-based P adsorption. Under the combined action of the dominant GAOs and PAOs, AHLs and C-di-GMP mediated QS to promote biofilm development and P enrichment. The research provides theoretical support for the cultivation of biofilm and its wider application.

Local control: a hub-based model for the c-di-GMP network.

The genome of Pseudomonas fluorescens encodes >50 proteins predicted to play a role in bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP)-mediated biofilm formation. We built a network representation of protein-protein interactions and extracted key information via multidimensional scaling (i.e., principal component analysis) of node centrality measures, which measure features of proteins in a network. Proteins of different domain types (diguanylate cyclase, dual domain, phosphodiesterase, PilZ) exhibit unique network behavior and can be accurately classified by their network centrality values (i.e., roles in the network). The predictive power of protein-protein interactions in biofilm formation indicates the possibility of localized pools of c-di-GMP. A regression model showed a statistically significant impact of protein-protein interactions on the extent of biofilm formation in various environments. These results highlight the importance of a localized c-di-GMP signaling, extend our understanding of signaling by this second messenger beyond the current "Bow-tie Model," support a newly proposed "Hub Model," and suggest future avenues of investigation.

Decoding the influence of low temperature on biofilm development: The hidden roles of c-di-GMP

Biofilms are widely used and play important roles in biological processes. Low temperature of wastewater inhibits the development of biofilms derived from wastewater activated sludge. However, the specific mechanism of temperature on biofilm development is still unclear. This study explored the mechanism of temperature on biofilm development and found a feasible method to enhance biofilm development at low temperature. The amount of biofilm development decreased by approximately 66 % and 55 % at 4 °C and 15 °C, respectively, as compared to 28 °C. The cyclic dimeric guanosine monophosphate (c-di-GMP) concentration also decreased at low temperature and was positively correlated with extracellular polymeric substance (EPS) content, formation, and adhesion strength. Microbial community results showed that low temperature inhibited the normal survival of most microorganisms, but promoted the growth of some psychrophile bacteria like Sporosarcina, Caldilineaceae, Gemmataceae, Anaerolineaceae and Acidobacteriota. Further analysis of functional genes demonstrated that the abundance of functional genes related to the synthesis of c-di-GMP (K18968, K18967 and K13590) decreased at low temperature. Subsequently, the addition of exogenous spermidine increased the level of intracellular c-di-GMP and alleviated the inhibition effect of low temperature on biofilm development. Therefore, the possible mechanism of low temperature on biofilm development could be the inhibition of the microorganism activity and reduction of the communication level between cells, which is the closely related to the EPS content, formation, and adhesion strength. The enhancement of c-di-GMP level through the exogenous addition of spermidine provides an alternative strategy to enhance biofilm development at low temperatures. The results of this study enhance the understanding of the influence of temperature on biofilm development and provide possible strategies for enhancing biofilm development at low temperatures.

Nitric oxide regulation of fetal and newborn lung development and function

In the developing lung, nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) signaling are essential in regulating lung formation and vascular tone. Animal studies have linked many anatomical and pathophysiological features of newborn lung disease to abnormalities in the NO/cGMP signaling system. They have demonstrated that driving this system with agonists and antagonists alleviates many of them. This research has spurred the rapid clinical development, testing, and application of several NO/cGMP-targeting therapies with the hope of treating and potentially preventing significant pediatric lung diseases. However, there are instances when the therapeutic effectiveness of these agents is limited. Studies indicate that injury-induced disruption of several critical components within the signaling system may hinder the promise of some of these therapies. Recent research has identified basic mechanisms that suppress NO/cGMP signaling in the injured newborn lung. They have also pinpointed biomarkers that offer insight into the activation of these pathogenic mechanisms and their influence on the NO/cGMP signaling system's integrity in vivo. Together, these will guide the development of new therapies to protect NO/cGMP signaling and safeguard newborn lung development and function. This review summarizes the important role of the NO/cGMP signaling system in regulating pulmonary development and function and our evolving understanding of how it is disrupted by newborn lung injury.

Favorable osteogenic activity of vericiguat doped in β-tricalcium phosphate: In vitro and in vivo studies.

Recently, more and more studies have shown that guanylate cyclase, an enzyme that synthesizes cyclic guanosine monophosphate (cGMP), plays an important role in bone metabolism. Vericiguat (VIT), a novel oral soluble guanylate cyclase stimulator, directly generates cyclic guanosine monophosphate and reduce the death incidence from cardio-vascular causes or hospitalization. Recent studies have shown beneficial effects of VIT in animal models of osteoporosis, but very little is currently known about the effects of VIT on bone defects in the osteoporotic states. Therefore, in this study, β-tricalcium phosphate (β-TCP) was used as a carrier to explore the effect of local VIT administration on the repair of femoral metaphyseal bone defects in ovariectomized (OVX) rats. When MC3T3-E1 was cultured in the presence of H2H2, VIT, similar to Melatonin (MT), therapy could increase the matrix mineralization and ALP, SOD2, SIRT1, and OPG expression, reduce ROS and Mito SOX production, RANKL expression, Promote the recovery of mitochondrial membrane potential. In the OVX rat model, VIT increases the osteogenic effect of β-TCP and better results were obtained at a dose of 5mg. Local use of VIT can inhibit increased OC, BMP2 and RUNX2 expressions in bone tissue, while decreased SOST and TRAP expressions by RT-PCR and immunohistochemistry. Thereby, VIT stimulates bone regeneration and is a promising candidate for promoting bone repair in osteoporosis.

Increased Cyclic Guanosine Monophosphate and Interleukin-1Beta Is Activated by Mitochondrial Dysfunction and Associated With Heart Failure in Atrial Fibrillation Patients.

This study aimed to identify the association of cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase-stimulator interferon genes (cGAS-STING) pathway with heart failure (HF) in atrial fibrillation (AF) patients. We prospectively enrolled 106 AF patients without evidence of HF. The serum levels of 2'3'-cyclic GMP-AMP (2'3'-cGAMP) and interleukin (IL)-1β were measured by enzyme-linked immunoassay (ELISA). To determine the underlying mechanism, we supplemented the complex I inhibitor rotenone and the specific cGAS inhibitor RU.521 in neonatal rat ventricular cardiomyocytes. During 18-month follow-up, serum concentrations of 2'3'-cGAMP (baseline 51.82 ± 11.34 pg/mL vs. follow-up 124.50 ± 75.83 pg/mL, Ppaired t < 0.01) and IL-1β (baseline 436.07 ± 165.82 vs. follow-up 632.48 ± 119.25 ng/mL, Ppaired t < 0.01) were substantially upregulated in AF patients with HF as compared with those without HF. Furthermore, serum 2'3'-cGAMP and IL-1β levels at 18-month follow-up were independently associated with the occurrence of HF in AF patients. Inhibition of cGAS by RU.521 effectively reversed the upregulation of 2'3'-cGAMP and STING phosphorylation induced by mitochondrial dysfunction, accompanied with inhibition of nod-like receptor protein 3 (NLRP3) inflammasome, IL-1β and IL-18 secretion. Induction of mitochondrial dysfunction causes an upregulation of 2'3'-cGAMP and activation of NLRP3 inflammasome through cGAS-STING pathway in cardiomyocytes.

Phosphodiesterase Inhibitors of Natural Origin

Abstract: Phosphodiesterases (PDEs) function to hydrolyze intracellular cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), regulating a variety of intracellular signal transduction and physiological activities. PDEs can be divided into 11 families (PDE1~11) and the diversity and complex expression of PDE family genes suggest that different subtypes may have different mechanisms. PDEs are involved in various disease pathologies such as inflammation, asthma, depression, and erectile dysfunction and are thus targets of interest for several drug discovery campaigns. Natural products have always been an important source of bioactive compounds for drug discovery, over the years several natural compounds have shown potential as inhibitors of PDEs. In this article, phosphodiesterase inhibitors of natural origin have been reviewed with emphasis on their chemistry and biological activities.

(47) - Prolonged Warm Ischemia and Cold Storage Promote Myocardial Edema in Human Hearts Donated After Circulatory Death via Accumulation of Cyclic Guanosine Monophosphate and Aquaporin 1

(47) - Prolonged Warm Ischemia and Cold Storage Promote Myocardial Edema in Human Hearts Donated After Circulatory Death via Accumulation of Cyclic Guanosine Monophosphate and Aquaporin 1

Polygonatum sibiricum (Huang Jing) polysaccharide reduces diabetic cardiomyopathy through increasing cyclic guanosine monophosphate-protein kinase G signaling in diabetic mice.

Diabetic cardiomyopathy (DCM) is a prevalent condition among individuals with diabetes, and is associated with a high mortality rate. The anti-oxidant properties of Jing Huang or Polygonatum sibiricum polysaccharide (PSP) have been extensively used to treat diabetes-related disorders; however, its potential effectiveness against DCM remains unknown. This study aimed to investigate PSP's therapeutic effects on DCM in an experimental diabetic mouse model. To induce insulin resistance, mice were fed a high-fat diet for 3 months, followed by intraperitoneal streptozotocin injection to induce slight hyperglycemia and develop DCM. Both DCM and control mice were given PSP orally for 3 weeks. Western blotting was used to detect the protein expressions of protein kinase G, C/EBP homologous protein, glucose-regulated protein 78, phosphodiesterase type 5, protein kinase R-like endoplasmic reticulum (ER) kinase, and phospho-protein kinase R-like endoplasmic reticulum kinase in heart tissue. The results showed a reduction in bodyweight and blood glucose levels in the PSP therapy group compared with DCM group. PSP also improved cardiac function and had a negligible effect on malondialdehyde activity. Furthermore, the findings showed that PSP alleviated ER and oxidative stress observed in DCM mice hearts, leading to the inhibition of cyclic guanosine monophosphate-specific phosphodiesterase type 5 and cardiac cyclic guanosine monophosphate reactivation. Phosphodiesterase type 5 inhibition reduced high-fat diet-induced cardiac dysfunction and decreased ER stress. PSP could effectively protect diabetic myocardium by inhibiting endoplasmic reticulum stress. These findings provide crucial insights into the potential of PSP to ameliorate DCM conditions in diabetic mice by decreasing ER and oxidative stress, and enhancing cyclic guanosine monophosphate protein kinase G signaling.

The Xanthine Derivative KMUP-1 Inhibits Hypoxia-Induced TRPC1 Expression and Store-Operated Ca2+ Entry in Pulmonary Arterial Smooth Muscle Cells.

Exposure to hypoxia results in the development of pulmonary arterial hypertension (PAH). An increase in the intracellular Ca2+ concentration ([Ca2+]i) in pulmonary artery smooth muscle cells (PASMCs) is a major trigger for pulmonary vasoconstriction and proliferation. This study investigated the mechanism by which KMUP-1, a xanthine derivative with phosphodiesterase inhibitory activity, inhibits hypoxia-induced canonical transient receptor potential channel 1 (TRPC1) protein overexpression and regulates [Ca2+]i through store-operated calcium channels (SOCs). Ex vivo PASMCs were cultured from Sprague-Dawley rats in a modular incubator chamber under 1% O2/5% CO2 for 24 h to elucidate TRPC1 overexpression and observe the Ca2+ release and entry. KMUP-1 (1 μM) inhibited hypoxia-induced TRPC family protein encoded for SOC overexpression, particularly TRPC1. KMUP-1 inhibition of TRPC1 protein was restored by the protein kinase G (PKG) inhibitor KT5823 (1 μM) and the protein kinase A (PKA) inhibitor KT5720 (1 μM). KMUP-1 attenuated protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA, 1 μM)-upregulated TRPC1. We suggest that the effects of KMUP-1 on TRPC1 might involve activating the cyclic guanosine monophosphate (cGMP)/PKG and cyclic adenosine monophosphate (cAMP)/PKA pathways and inhibiting the PKC pathway. We also used Fura 2-acetoxymethyl ester (Fura 2-AM, 5 μM) to measure the stored calcium release from the sarcoplasmic reticulum (SR) and calcium entry through SOCs in hypoxic PASMCs under treatment with thapsigargin (1 μM) and nifedipine (5 μM). In hypoxic conditions, store-operated calcium entry (SOCE) activity was enhanced in PASMCs, and KMUP-1 diminished this activity. In conclusion, KMUP-1 inhibited the expression of TRPC1 protein and the activity of SOC-mediated Ca2+ entry upon SR Ca2+ depletion in hypoxic PASMCs.

PDE10A Mutation as an Emerging Cause of Childhood-Onset Hyperkinetic Movement Disorders: A Review of All Published Cases.

Cyclic nucleotide phosphodiesterase (PDE) enzymes catalyze the breakdown of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which act as intracellular second messengers for signal transduction pathways and modulate various processes in the central nervous system. Recent discoveries that mutations in genes encoding different PDEs, including PDE10A, are responsible for rare forms of chorea in children led to the recognition of an emerging role of PDEs in the field of pediatric movement disorders. A comprehensive literature review of all reported cases of PDE10A mutations in PubMed and Web of Science was performed in English. We included eight studies, describing 31 patients harboring a PDE10A mutation and exhibiting a hyperkinetic movement disorder with onset in infancy or childhood. Mutations in both GAF-A, GAF-B regulatory domains and outside the GAF domains of the PDE10A gene have been reported to cause hyperkinetic movement disorders. In general, patients with homozygous mutations in either GAF-A domain of PDE10A present with a more severe phenotype and at an earlier age but without any extensive abnormalities of the striata compared with patients with dominant variants in GAF-B domain, indicating that dominant and recessive mutations have different pathogenic mechanisms. PDE10A plays a key role in regulating control of striato-cortical movement. Comprehension of the molecular mechanisms within the cAMP and cGMP signaling systems caused by PDE10A mutations may inform novel therapeutic strategies that could alleviate symptoms in young patients affected by these rare movement disorders.

Abstract 7052: p53 underpins a dependence on oxidative phosphorylation in glycolysis-competent colorectal cancer

Abstract The use of mitochondrial inhibitors to target oxidative phosphorylation (OXPHOS) in cancer treatment presents a challenge due to dose-limiting toxicities. Moreover, while glycolysis-deficient cancers are vulnerable to OXPHOS inhibition in preclinical models, the full extent of phenotypical and mechanistic consequences of inhibiting OXPHOS in cancers capable of glycolysis is not yet well understood. Our results presented here offer promising insights into potential therapeutic gains from combining p53 restoration strategies with OXPHOS inhibitors, even when applied to glycolysis-competent CRC cells. Treatment with mitochondrial complex I inhibitors did not cause energy stress in CRC cells capable of glycolysis. It does, however, induce DNA replication stress, apparent through an observed cell cycle arrest at the S phase, enrichment of the G2/M DNA-damage checkpoint regulation pathway, and replication fork slowdown. Intriguingly, CRC cells harboring wildtype p53 exhibited more severe replication stress than those carrying mutant p53. Furthermore, siRNA knockdown of p53 attenuates replication stress and reduces cell cycle arrest, underlining the important role of p53 in CRC cell responses to OXPHOS inhibition. Our targeted metabolomics analysis reveals that OXPHOS inhibition results in reductions in the purine nucleotides, adenine monophosphate (AMP) and guanine monophosphate (GMP), as well as the pyrimidine nucleotide, uridine monophosphate (UMP), in CRC cells, regardless of their p53 mutational status. By supplementing cell culture mediums with the purine nucleobases adenine and guanine, and the pyrimidine nucleoside uridine, we observed a partial reversal of the replication fork slowdown and reductions in cell viability. This suggests nucleotide deficiencies are involved in the induction of DNA replication stress caused by OXPHOS inhibition. The nucleotide deficiencies were associated with a decrease in the nucleobase precursor aspartate. By adding aspartate at a supraphysiological concentration, to overcome the low expression of the excitatory amino acid transporter 1 required for cellular import of aspartate, we were able to restore the levels of nucleotides. Collectively, our findings suggest broader potential cancer treatment paradigms via OXPHOS targeting, extending beyond glycolysis-deficient cancers. Our data uncovers that CRC cells, which commonly exhibit the glycolytic phenotype, are susceptible to OXPHOS inhibition, with those carrying wildtype p53 showing heightened sensitivity. Therefore, p53 status could serve as a biomarker for predicting CRC responses to OXPHOS inhibitors. Moreover, our findings suggest that combined strategies of restoring p53 function, using small molecules such as APR-246, might enable reduced dosage of OXPHOS inhibitors in CRC treatment, thereby mitigating their dose-limiting toxicities. Citation Format: Xiao Hong Zhao, Man Man Han, Qian Qian Yan, Yi Meng Yue, Kai Hong Ye, Yuan Yuan Zhang, Liu Teng, Liang Xu, Xiao Jing Shi, Ting La, Yu Chen Feng, Ran Xu, Vinod K. Narayana, David P. De Souza, Tao Liu, Mark Baker, Rick F. Thorne, Xu Dong Zhang, Song Chen, Lei Jin. p53 underpins a dependence on oxidative phosphorylation in glycolysis-competent colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7052.

Abstract 1789: Machine learning-based method to analyze metabolic fluxes of patient tumors

Abstract Personalized oncology must overcome the complex challenge of distinct cancer phenotypes in each patient, formed in part in response to unique metabolic crosstalk among cells in the tumor microenvironment which can be a determining factor in therapeutic response. Although isotope tracing sheds light on differences of metabolite enrichments in tumor and normal tissues, quantifying the metabolic fluxes in patients remains elusive. The conventional metabolic flux analysis tools are unable to estimate patient metabolic fluxes because we are limited to a single time point enrichment datapoint from each patient’s in-vivo measurement at isotopic non-steady state. We overcame this challenge by generating training data from the limited patient data and implementing a machine learning model to predict fluxes. To generate training data, we first simulated constrained random fluxes and enrichment patterns at different time points using patient circulating metabolites enrichment via an isotopic non-stationary metabolic flux analysis framework. Using this data, we trained a convolutional neural network to predict flux ratios. To validate our model, we compared predicted flux ratios to the experimental data from mouse models for two different treatments. Our recent findings from a glioblastoma (GBM) mouse model study using conventional metabolic flux analysis revealed higher de novo guanosine monophosphate (GMP) synthesis in GBM than normal cortex. These tumors can be sensitive to mycophenolate mofetil (MMF) which inhibits inosine monophosphate dehydrogenase, but only if the major source of GMP production is de novo synthesis and not salvage. Our machine learning model can discriminate between sources of GMP synthesis in patients, thus enabling prediction of potential responders. Furthermore, we previously showed that serine uptake is higher in GBM than normal cortex, and a serine- and glycine-restricted diet slows tumor growth in mice. While both circulating serine and microenvironment-derived serine could account for serine uptake in GBM, we hypothesized that the circulating serine dependence would better predict response to dietary serine depletion. Hence, we combined patient scRNA-seq and metabolomics data to feed our neural network framework to estimate microenvironmental and circulating serine uptake in six patients with brain cancer. Thus, we have shown that our model can identify patients who will benefit from MMF treatment or a serine- and glycine-restricted diet, enabling administration of highly effective personalized treatments for GBM patients. Citation Format: Baharan Meghdadi, Anjali Mittal, Andrew J. Scott, Sravya Palavalasa, Daniel R. Wahl, Deepak Nagrath. Machine learning-based method to analyze metabolic fluxes of patient tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1789.