Cyclic Guanosine Research Articles

STING agonist-conjugated metal-organic framework induces artificial leukocytoid structures and immune hotspots for systemic antitumor responses

Abstract Radiotherapy is widely used for cancer treatment, but its clinical utility is limited by radioresistance and its inability to target metastases. Nanoscale metal-organic frameworks (MOFs) have shown promise as high-Z nanoradiosensitizers to enhance radiotherapy and induce immunostimulatory regulation of the tumor microenvironment. We hypothesized that MOFs could deliver small-molecule therapeutics to synergize with radiotherapy for enhanced antitumor efficacy. Herein, we developed a robust nanoradiosensitizer, GA-MOF, by conjugating a STING agonist, 2',3'-cyclic guanosine monophosphate–adenosine monophosphate (GA), on MOF for synergistic radiosensitization and STING activation. GA-MOF demonstrated strong anticancer efficacy by forming immune cell-rich nodules (artificial leukocytoid structures) and transforming them into immunostimulatory hotspots with radiotherapy. Further combination with immune checkpoint blockade suppressed distant tumors through systemic immune activation. Our work not only demonstrates potent radiosensitization of GA-MOF, but also provides the detailed mechanisms regarding MOF distribution, immune regulatory pathways, and long-term immune effects.

Malakoplakia: A rare cause of hematochezia in pediatric patients

AbstractMalakoplakia is a rare inflammatory condition characterized by impaired macrophages unable to completely digest and kill phagocytized bacteria, resulting in partially digested bacterial components accumulating within the phagolysosome. Malakoplakia typically presents in immunocompromised individuals due to underlying disease or to medication effects and is rarely diagnosed in the pediatric population. The urinary tract is the most commonly involved site, followed by the gastrointestinal (GI) tract, mainly affecting the descending colon, sigmoid colon, and rectum. Treatment focuses on the use of antibiotics that concentrate in macrophages such as quinolones and trimethoprim‐sulfamethoxazole as well as cholinergic agents such as bethanechol, which raise intracellular levels of cyclic guanosine monophosphate in macrophages to improve bactericidal activity. We report a rare case of GI tract malakoplakia in a pediatric patient undergoing treatment for leukemia.

Evaluation of renal sodium handling in heart failure with preserved ejection fraction: A pilot study.

The pathophysiology behind sodium retention in heart failure with preserved ejection fraction (HFpEF) remains poorly understood. We hypothesized that patients with HFpEF have impaired natriuresis and diuresis in response to volume expansion and diuretic challenge, which is associated with renal hypo-responsiveness to endogenous natriuretic peptides. Nine HFpEF patients and five controls received saline infusion (0.25 mL/kg/min for 60 min) followed by intravenous furosemide (20 mg or home dose) 2 h after the infusion. Blood and urine samples were collected at baseline, 2 h after saline infusion, and 2 h after furosemide administration; urinary volumes were recorded. The urinary cyclic guanosine monophosphate (ucGMP)/plasma B-type NP (BNP) ratio was calculated as a measure of renal response to endogenous BNP. Wilcoxon rank-sum test was used to compare the groups. Compared to controls, HFpEF patients had reduced urine output (2480 vs.3541 mL; p = 0.028), lower urinary sodium excretion over 2 h after saline infusion (the percentage of infused sodium excreted 12% vs. 47%; p = 0.003), and a lower baseline ucGMP/plasma BNP ratio (0.7 vs. 7.3 (pmol/mL)/(mg/dL)/(pg/mL); p = 0.014). Patients with HFpEF had impaired natriuretic response to intravenous saline and furosemide administration and lower baseline ucGMP/plasma BNP ratios indicating renal hypo-responsiveness to NPs.

Lysosomal endonuclease RNase T2 and PLD exonucleases cooperatively generate RNA ligands for TLR7 activation.

Toll-like receptor 7 (TLR7) is essential for recognition of RNA viruses and initiation of antiviral immunity. TLR7 contains two ligand-binding pockets that recognize different RNA degradation products: pocket 1 recognizes guanosine, while pocket 2 coordinates pyrimidine-rich RNA fragments. We found that the endonuclease RNase T2, along with 5' exonucleases PLD3 and PLD4, collaboratively generate the ligands for TLR7. Specifically, RNase T2 generated guanosine 2',3'-cyclic monophosphate-terminated RNA fragments. PLD exonuclease activity further released the terminal 2',3'-cyclic guanosine monophosphate (2',3'-cGMP) to engage pocket 1 and was also needed to generate RNA fragments for pocket 2. Loss-of-function studies in cell lines and primary cells confirmed the critical requirement for PLD activity. Biochemical and structural studies showed that PLD enzymes form homodimers with two ligand-binding sites important for activity. Previously identified disease-associated PLD mutants failed to form stable dimers. Together, our data provide a mechanistic basis for the detection of RNA fragments by TLR7.

An intranasal nanoparticle vaccine elicits protective immunity against Mycobacterium tuberculosis

Mucosal vaccines have the potential to elicit protective immune responses at the point of entry of respiratory pathogens, thus preventing even the initial seed infection. Unlike licensed injectable vaccines, mucosal vaccines comprising protein subunits are only in development. One of the primary challenges associated with mucosal vaccines has been identifying and characterizing safe yet effective mucosal adjuvants that can effectively prime multi-factorial mucosal immunity. In this study, we tested NanoSTING, a liposomal formulation of the endogenous activator of the stimulator of interferon genes (STING) pathway, cyclic guanosine adenosine monophosphate (cGAMP), as a mucosal adjuvant. We formulated a vaccine based on the H1 antigen (fusion protein of Ag85b and ESAT-6) adjuvanted with NanoSTING. Intranasal immunization of NanoSTING-H1 elicited a strong T-cell response in the lung of vaccinated animals characterized by (a) CXCR3+ KLRG1− lung resident T cells that are known to be essential for controlling bacterial infection, (b) IFNγ-secreting CD4+ T cells which is necessary for intracellular bactericidal activity, and (c) IL17-secreting CD4+ T cells that can confer protective immunity against multiple clinically relevant strains of Mtb. Upon challenge with aerosolized Mycobacterium tuberculosis Erdman strain, intranasal NanoSTING-H1 provides protection comparable to subcutaneous administration of the live attenuated Mycobacterium bovis vaccine strain Bacille–Calmette–Guérin (BCG). Our results indicate that NanoSTING adjuvanted protein vaccines can elicit a multi-factorial immune response that protects from infection by M. tuberculosis.

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.

Synthetic cationic helical polypeptides for the stimulation of antitumour innate immune pathways in antigen-presenting cells.

Intracellular DNA sensors regulate innate immunity and can provide a bridge to adaptive immunogenicity. However, the activation of the sensors in antigen-presenting cells (APCs) by natural agonists such as double-stranded DNAs or cyclic nucleotides is impeded by poor intracellular delivery, serum stability, enzymatic degradation and rapid systemic clearance. Here we show that the hydrophobicity, electrostatic charge and secondary conformation of helical polypeptides can be optimized to stimulate innate immune pathways via endoplasmic reticulum stress in APCs. One of the three polypeptides that we engineered activated two major intracellular DNA-sensing pathways (cGAS-STING (for cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes) and Toll-like receptor 9) preferentially in APCs by promoting the release of mitochondrial DNA, which led to the efficient priming of effector T cells. In syngeneic mouse models of locally advanced and metastatic breast cancers, the polypeptides led to potent DNA-sensor-mediated antitumour responses when intravenously given as monotherapy or with immune checkpoint inhibitors. The activation of multiple innate immune pathways via engineered cationic polypeptides may offer therapeutic advantages in the generation of antitumour immune responses.

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.

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.

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.

A Deep Dive into PDE5 Inhibition: Innovative Discoveries via Virtual Screening

Background: PDE5 inhibitors have had a surge in popularity over the last decade owing to their efficacy in the treatment of erectile dysfunction, coronary vasculopathy, and pulmonary arterial hypertension. These inhibitors exhibit competitive binding with phosphodiesterase type 5 and inhibit the hydrolysis of cyclic guanosine monophosphate, hence elevating the levels of cGMP in smooth muscle cells and prolonging the duration of an erection. However, due to production costs and side effects, further research is needed to discover new PDE5 inhibitors. background: The field of PDE5 inhibitors has risen in popularity in the past decade because of the success of PDE5 inhibitors in treating erectile dysfunction. Due to the structural identity with cGMP; PDE5 inhibitors competitively bind with PDE5 and limit cGMP hydrolysis, which raises the cGMP level in smooth muscle cells and lengthens the duration of an erection. PDE5 inhibitors were also found to be beneficial for coronary vasculopathy, pulmonary arterial hypertension, and benign prostatic hyperplasia. But, due to the expensive cost of production and unwanted side effects, it is necessary to explore the possibility of the discovery of new PDE5 inhibitors. Objective: The study aimed to identify potent PDE5 inhibitors by employing the extensive application of computer-aided drug design. objective: To identify potent PDE5 inhibitors by employing the extensive application of computer-aided drug design. Method: Three different databases, named Million Molecules Database, Natural Product Database, and NCI Database, have been screened, which has been followed by filtering based on various druglikeness rules, docking, ADME, toxicity, consensus molecular docking, and 100 ns molecular dynamics simulation. method: Three different databases named Million Molecules Database, Natural Product Database, and NCI Database has been screened followed by filtering based on various drug-likeness such as Lipinski rule of five, Ghose rule, Veber rule, and Muegge rule, docking, ADME, toxicity, consensus molecular docking, and 100 ns Molecular dynamics simulation Results: Three compounds (ZINC05351336, ZINC12030898, and ZINC17949426) have exhibited stable-binding characteristics at the active site of PDE5, demonstrating a robust binding affinity. These molecules have been found to possess drug-like capabilities, effective ADME features, low toxicity, and high stability. Conclusion: The study has delved into the realm of PDE5 inhibitors, which have been found to be effective in treating erectile dysfunction, but high production costs and side effects necessitate new ones. Through computer-aided drug design and screening, three compounds have been identified with promising binding characteristics, drug-appropriate properties, effective ADME profiles, minimal toxicity, and stability, making them potential candidates for future PDE5 inhibitors

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.

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.

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.

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.

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.