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Streptococcus pyogenes, commonly known as Group A Streptococcus (GAS), is a significant human pathogen responsible for a wide range of diseases, from mild pharyngitis to severe conditions such as necrotizing fasciitis and toxic shock syndrome. The increasing antibiotic resistance, especially against macrolide antibiotics, poses a challenge to the effective treatment of these infections. This paper reviews the current state and mechanisms of antibiotic resistance in S. pyogenes. Furthermore, molecular targets for developing anti-virulence agents, which aim to attenuate virulence rather than killing it outright, are explored. This review specifically focuses on virulence regulators, proteins that coordinate the expression of multiple virulence factors in response to environmental signals, playing a crucial role in the pathogen's ability to cause disease. Key regulatory systems, such as RopB, Mga, CovRS, and the c-di-AMP signaling system, are discussed for their roles in modulating virulence gene expression. Additionally, potential molecular target sites for the development of anti-virulence agents are suggested. By concentrating on these regulatory pathways, it is proposed that anti-virulence strategies could enhance the effectiveness of existing antibiotics and reduce the selective pressure that drives the development of resistance. [ABSTRACT FROM AUTHOR]

Bioethanol fermentation from lignocellulosic hydrolysates is negatively affected by the presence of acetic acid. The budding yeast S. cerevisiae adapts to acetic acid stress partly by activating the transcription factor, Haa1. Haa1 induces the expression of many genes, which are responsible for increased fitness in the presence of acetic acid. Here, we show that protein kinase A (PKA) is a negative regulator of Haa1-dependent gene expression under both basal and acetic acid stress conditions. Deletions of RAS2, encoding a positive regulator of PKA, and PDE2, encoding a negative regulator of PKA, lead to an increased and decreased expression of Haa1-regulated genes, respectively. Importantly, the deletion of HAA1 largely reverses the effects of ras2∆. Additionally, the expression of a dominant, hyperactive RAS2A18V19 mutant allele also reduces the expression of Haa1-regulated genes. We found that both pde2Δ and RAS2A18V19 reduce cell fitness in response to acetic acid stress, while ras2Δ increases cellular adaptation. There are three PKA catalytic subunits in yeast, encoded by TPK1, TPK2, and TPK3. We show that single mutations in TPK1 and TPK3 lead to the increased expression of Haa1-regulated genes, while tpk2Δ reduces their expression. Among tpk double mutations, tpk1Δ tpk3Δ greatly increases the expression of Haa1-regulated genes. We found that acetic acid stress in a tpk1Δ tpk3Δ double mutant induces a flocculation phenotype, which is reversed by haa1Δ. Our findings reveal PKA to be a negative regulator of the acetic acid stress response and may help engineer yeast strains with increased efficiency of bioethanol fermentation. [ABSTRACT FROM AUTHOR]

Aims Gene therapy with cardiac phosphodiesterases (PDEs), such as phosphodiesterase 4B (PDE4B), has recently been described to effectively prevent heart failure (HF) in mice. However, exact molecular mechanisms of its beneficial effects, apart from general lowering of cardiomyocyte cyclic adenosine monophosphate (cAMP) levels, have not been elucidated. Here, we studied whether gene therapy with two types of PDEs, namely PDE2A and PDE4B, can prevent pressure-overload-induced HF in mice by acting on and restoring altered cAMP compartmentation in distinct subcellular microdomains. Methods and results HF was induced by transverse aortic constriction followed by tail-vein injection of adeno-associated-virus type 9 vectors to overexpress PDE2A3, PDE4B3, or luciferase for 8 weeks. Heart morphology and function was assessed by echocardiography and histology which showed that PDE2A and especially PDE4B gene therapy could attenuate cardiac hypertrophy, fibrosis, and decline of contractile function. Live cell imaging using targeted cAMP biosensors showed that PDE overexpression restored altered cAMP compartmentation in microdomains associated with ryanodine receptor type 2 (RyR2) and caveolin-rich plasma membrane. This was accompanied by ameliorated caveolin-3 decline after PDE2A3 overexpression, reduced RyR2 phosphorylation in PDE4B3 overexpressing hearts, and antiarrhythmic effects of both PDEs measured under isoproterenol stimulation in single cells. Strong association of overexpressed PDE4B but not PDE2A with RyR2 microdomain could prevent calcium leak and arrhythmias in human-induced pluripotent stem-derived cardiomyocytes with the A2254V mutation in RyR2 causing catecholaminergic polymorphic ventricular tachycardia. Conclusion Our data indicate that gene therapy with phosphodiesterases can prevent HF including associated cardiac remodelling and arrhythmias by restoring altered cAMP compartmentation in functionally relevant subcellular microdomains. [ABSTRACT FROM AUTHOR]

Bioethanol fermentation from lignocellulosic hydrolysates is negatively affected by the presence of acetic acid. The budding yeast S. cerevisiae adapts to acetic acid stress partly by activating the transcription factor, Haa1. Haa1 induces the expression of many genes, which are responsible for increased fitness in the presence of acetic acid. Here, we show that protein kinase A (PKA) is a negative regulator of Haa1-dependent gene expression under both basal and acetic acid stress conditions. Deletions of RAS2, encoding a positive regulator of PKA, and PDE2, encoding a negative regulator of PKA, lead to an increased and decreased expression of Haa1-regulated genes, respectively. Importantly, the deletion of HAA1 largely reverses the effects of ras2∆. Additionally, the expression of a dominant, hyperactive RAS2A18V19 mutant allele also reduces the expression of Haa1-regulated genes. We found that both pde2Δ and RAS2A18V19 reduce cell fitness in response to acetic acid stress, while ras2Δ increases cellular adaptation. There are three PKA catalytic subunits in yeast, encoded by TPK1, TPK2, and TPK3. We show that single mutations in TPK1 and TPK3 lead to the increased expression of Haa1-regulated genes, while tpk2Δ reduces their expression. Among tpk double mutations, tpk1Δ tpk3Δ greatly increases the expression of Haa1-regulated genes. We found that acetic acid stress in a tpk1Δ tpk3Δ double mutant induces a flocculation phenotype, which is reversed by haa1Δ. Our findings reveal PKA to be a negative regulator of the acetic acid stress response and may help engineer yeast strains with increased efficiency of bioethanol fermentation.

The second messenger molecule, c-di-AMP, plays a critical role in pathogenesis and virulence in S. pyogenes. We previously reported that deleting the c-di-AMP phosphodiesterase gene pde2 severely suppresses SpeB production at the transcriptional level. We performed transposon mutagenesis to gain insight into the mechanism of how Pde2 is involved in SpeB regulation. We identified one of the genes of the dlt operon, dltX, as a suppressor of the SpeB-null phenotype of the Δpde2 mutant. The dlt operon consists of five genes, dltX, dltA, dltB, dltC, and dltD in many Gram-positive bacteria, and its function is to incorporate D-alanine into lipoteichoic acids. DltX, a small membrane protein, is a newly identified member of the operon. The in-frame deletion of dltX or insertional inactivation of dltA in the Δpde2 mutant restored SpeB production, indicating that D-alanylation is crucial for the suppressor phenotype. These mutations did not affect the growth in lab media but showed increased negative cell surface charge and enhanced sensitivity to polymyxin B. Considering that dlt mutations change cell surface charge and sensitivity to cationic antimicrobial peptides, we examined the LiaFSR system that senses and responds to cell envelope stress. The ΔliaR mutation in the Δpde2 mutant also derepressed SpeB production, like the ΔdltX mutation. LiaFSR controls speB expression by regulating the expression of the transcriptional regulator SpxA2. However, the Dlt system did not regulate spxA2 expression. The SpeB phenotype of the Δpde2ΔdltX mutant in higher salt media differed from that of the Δpde2ΔliaR mutant, suggesting a unique pathway for the Dlt system in SpeB production, possibly related to ion transport or turgor pressure regulation. [ABSTRACT FROM AUTHOR]

The second messenger molecule, c-di-AMP, plays a critical role in pathogenesis and virulence in S. pyogenes. We previously reported that deleting the c-di-AMP phosphodiesterase gene pde2 severely suppresses SpeB production at the transcriptional level. We performed transposon mutagenesis to gain insight into the mechanism of how Pde2 is involved in SpeB regulation. We identified one of the genes of the dlt operon, dltX, as a suppressor of the SpeB-null phenotype of the Δpde2 mutant. The dlt operon consists of five genes, dltX, dltA, dltB, dltC, and dltD in many Gram-positive bacteria, and its function is to incorporate D-alanine into lipoteichoic acids. DltX, a small membrane protein, is a newly identified member of the operon. The in-frame deletion of dltX or insertional inactivation of dltA in the Δpde2 mutant restored SpeB production, indicating that D-alanylation is crucial for the suppressor phenotype. These mutations did not affect the growth in lab media but showed increased negative cell surface charge and enhanced sensitivity to polymyxin B. Considering that dlt mutations change cell surface charge and sensitivity to cationic antimicrobial peptides, we examined the LiaFSR system that senses and responds to cell envelope stress. The ΔliaR mutation in the Δpde2 mutant also derepressed SpeB production, like the ΔdltX mutation. LiaFSR controls speB expression by regulating the expression of the transcriptional regulator SpxA2. However, the Dlt system did not regulate spxA2 expression. The SpeB phenotype of the Δpde2ΔdltX mutant in higher salt media differed from that of the Δpde2ΔliaR mutant, suggesting a unique pathway for the Dlt system in SpeB production, possibly related to ion transport or turgor pressure regulation.

Urolithins are the gut microbiota metabolites of ellagitannins which are found in natural plants such as pomegranate, strawberry, and raspberry, and in nuts. Recently, several reports have clarified the underlying mechanism of urolithins in central nervous system inflammation. Therefore, urolithins have become potential therapeutic drug candidate molecules for central nervous system diseases. Derivatives 1–1d, 1–1f, 3–2a, and 3–2b of urolithin A, urolithin B, and methoxyurolithin A were found to have had significant inhibitory activity against phosphodiesterase II with IC50 values of 35.42, 39.96, 25.58, and 13.84 μM, respectively. Herein, we report the design and synthesis of urolithin derivatives along with a biological evaluation of their activity against phosphodiesterase II. [ABSTRACT FROM AUTHOR]

A major challenge facing scientists using conventional approaches for solving PDEs is the simulation of extreme multi-scale problems. While exascale computing will enable simulations of larger systems, the extreme multiscale nature of many problems requires new techniques. Deep learning techniques have disrupted several domains, such as computer vision, language (e.g., ChatGPT), and computational biology, leading to breakthrough advances. Similarly, the adaptation of these techniques for scientific computing has led to a new and rapidly advancing branch of High-Performance Computing (HPC), which we call neural-HPC (NeuHPC). Proof of concept studies in domains such as computational fluid dynamics and material science have demonstrated advantages in both efficiency and accuracy compared to conventional solvers. However, NeuHPC is yet to be embraced in plasma simulations. This is partly due to general lack of awareness of NeuHPC in the space physics community as well as the fact that most plasma physicists do not have training in artificial intelligence and cannot easily adapt these new techniques to their problems. As we explain below, there is a solution to this. We consider NeuHPC a critical paradigm for knowledge discovery in space sciences and urgently advocate for its adoption by both researchers as well as funding agencies. Here, we provide an overview of NeuHPC and specific ways that it can overcome existing computational challenges and propose a roadmap for future direction.

Abstract Background Farnesol has potential antifungal activity against Candida albicans biofilms, but the molecular mechanism of this activity is still unclear. Farnesol inhibits hyphal growth by regulating the cyclic AMP (cAMP) signalling pathway in C. albicans, and CYR1 and PDE2 regulate a pair of enzymes that are directly responsible for cAMP synthesis and degradation. Here, we hypothesize that farnesol enhances the antifungal susceptibility of C. albicans biofilms by regulating CYR1 and PDE2. Results The resistance of the CYR1- and PDE2-overexpressing strains to caspofungin, itraconazole and terbinafine was increased in planktonic cells, and that to amphotericin B was increased in biofilms. Meanwhile, the biofilms of the CYR1- and PDE2-overexpressing strains were thicker (all p

Background: Phosphodiesterase-2 (PDE2) is a cyclic nucleotide phosphodiesterase and is highly expressed in the amygdala, which suggests its important role in anxiety-like behavior.Aims: The present study examined whether reduced PDE2A expression in the central nucleus of the amygdala (CeA) produces anxiolytic-like effects in mice.Methods: PDE2A knockdown in amygdaloid (AR5) cells or the CeA was established using a lentiviral vector-based siRNA system. The anxiety-like behaviors were detected by the elevated plus maze (EPM) and hole-board tests in mice. The related proteins involved in cAMP/cGMP-dependent signaling, such as specific marker VASPser239, CREBser133 and BDNF were detected by immunoblot analysis.Results: PDE2A inhibition in AR-5 cells resulted in increases in cAMP/cGMP-related pVASPser239 and pCREBser133. Behavioral tests showed that PDE2A knockdown in the CeA induced anxiolytic-like effects as evidenced by the increases in percentages of open-arm entries and time spent in the open arms in the EPM test, and the increases in head dips and time spent in head dipping in the hole-board test. However, these anxiolytic-like effects were antagonized by pre-treatment of soluble guanylyl cyclase inhibitor ODQ or adenylate cyclase inhibitor SQ. Furthermore, PDE2A knockdown significantly increased pVASPSer239, pCREBSer133 and decreased BDNF expression in the amygdala. Pre-intra-CeA of ODQ or SQ reversed or partially prevented the effects of PDE2A knockdown on these proteins.Conclusions: The results suggest that PDE2A plays a crucial role in the regulation of anxiety by the cGMP/cAMP-dependent pVASP-pCREB-BDNF signaling pathway. [ABSTRACT FROM AUTHOR]

Isolates of Cryptococcus neoformans , a fungal pathogen that kills over 112,000 people each year, differ from a 19-Mb reference genome at a few thousand up to almost a million DNA sequence positions. We used bulked segregant analysis and association analysis, genetic methods that require no prior knowledge of sequence function, to address the key question of which naturally occurring sequence variants influence fungal virulence. We identified a region containing such variants, prioritized them, and engineered strains to test our findings in a mouse model of infection. At one locus, we identified a 4-nt variant in the PDE2 gene that occurs in common laboratory strains and severely truncates the encoded phosphodiesterase. The resulting loss of phosphodiesterase activity significantly impacts virulence. Our studies demonstrate a powerful and unbiased strategy for identifying key genomic regions in the absence of prior information and provide significant sequence and strain resources to the community. [Display omitted] • Bulked segregant analysis revealed sequence variants that influence fungal virulence • Targeted variant swaps between strains showed reciprocal shifts in pathogenicity • Common lab strains have a defect in phosphodiesterase activity that reduces virulence Agustinho et al. identified naturally occurring genome sequence variants that influence virulence of the fungal pathogen Cryptococcus neoformans using genetic strategies that require no prior knowledge of sequence function. This offers a powerful approach for the discovery of sequences relevant to virulence or other phenotypes of interest. [ABSTRACT FROM AUTHOR]

Rationale: Alcohol use disorder (AUD) is a chronically relapsing condition, which affects nearly 11% of population worldwide. Currently, there are only three FDA-approved medications for treatment of AUD, and normally, satisfactory effects are hard to be achieved. Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) signaling has been implicated in regulation of ethanol intake. Phosphodiesterase 2 (PDE), a dual substrate PDE that hydrolyzes both cAMP and cGMP, may play a crucial role in regulating ethanol consumption.Methods: The present study determined whether PDE2 was involved in the regulation of ethanol intake and preference. The two-bottle choice procedure was used to examine the effects of the selective PDE2 inhibitor Bay 60-7550 on ethanol intake. The sucrose and quinine intake (taste preference) and locomotor activity (sedative effects) were also measured to exclude the false positive effects of Bay 60-7550.Results: Treatment with Bay 60-7550 (1 and 3 mg/kg, i.p.) decreased ethanol intake and preference, without changing total fluid intake. In addition, Bay 60-7550 at doses that reduced ethanol intake did not affect sucrose and quinine intake and preference, which excluded the potential influence of taste preference and sedative effects on ethanol drinking behavior. Moreover, Bay 60-7550 at 3 mg/kg did not alter locomotor activity or ethanol metabolism, further supporting the specific effect of Bay 60-7550 on ethanol drinking behavior.Conclusions: The results suggest that PDE2 plays a role in the regulation of ethanol consumption and that PDE2 inhibitors may be a novel class of drugs for treatment of alcoholism. [ABSTRACT FROM AUTHOR]

An internal HTS effort identified a novel PDE2 inhibitor series that was subsequently optimized for improved PDE2 activity and off-target selectivity. The optimized lead, compound 4 , improved cognitive performance in a rodent novel object recognition task as well as a non-human primate object retrieval task. In addition, co-crystallization studies of close analog of 4 in the PDE2 active site revealed unique binding interactions influencing the high PDE isoform selectivity. [ABSTRACT FROM AUTHOR]

Platelet activation contributes to normal haemostasis but also to pathologic conditions like stroke and cardiac infarction. Signalling by cGMP and cAMP inhibit platelet activation and are therefore attractive targets for thrombosis prevention. However, extensive cross-talk between the cGMP and cAMP signalling pathways in multiple tissues complicates the selective targeting of their activities. We have used mathematical modelling based on experimental data from the literature to quantify the steady state behaviour of nitric oxide (NO)/cGMP/cAMP signalling in platelets. The analysis provides an assessment of NO-induced cGMP synthesis and PKG activation as well as cGMP-mediated cAMP and PKA activation though modulation of phosphodiesterase (PDE2 and 3) activities. Both one- and two-compartment models of platelet cyclic nucleotide signalling are presented. The models provide new insight for understanding how NO signalling to cGMP and indirectly cAMP, can inhibit platelet shape-change, the initial step of platelet activation. Only the two-compartment models could account for the experimental observation that NO-mediated PKA activation can occur when the bulk platelet cAMP level is unchanged. The models revealed also a potential for hierarchical interplay between the different platelet phosphodiesterases. Specifically, the models predict, unexpectedly, a strong effect of pharmacological inhibitors of cGMP-specific PDE5 on the cGMP/cAMP cross-talk. This may explain the successful use of weak PDE5-inhibitors, such as dipyridamole, in anti-platelet therapy. In conclusion, increased NO signalling or PDE5 inhibition are attractive ways of increasing cGMP-cAMP cross-talk selectively in platelets. [ABSTRACT FROM AUTHOR]

Phosphodiesterase 2 (PDE2) has received much attention for the potential treatment of the central nervous system (CNS) disorders and pulmonary hypertension. Herein, we identified that clofarabine ( 4 ), an FDA-approved drug, displayed potential PDE2 inhibitory activity (IC 50  = 3.12 ± 0.67 μM) by structure-based virtual screening and bioassay. Considering the potential therapeutic benefit of PDE2, a series of purine nucleoside derivatives based on the structure and binding mode of 4 were designed, synthesized and evaluated, which led to the discovery of the best compound 14e with a significant improvement of inhibitory potency (IC 50  = 0.32 ± 0.04 μM). Further molecular docking and molecular dynamic (MD) simulations studies revealed that 5′-benzyl group of 14e could interact with the unique hydrophobic pocket of PDE2 by forming extra van der Waals interactions with hydrophobic residues such as Leu770, Thr768, Thr805 and Leu809, which might contribute to its enhancement of PDE2 inhibition. These potential compounds reported in this article and the valuable structure-activity relationships (SARs) might bring significant instruction for further development of potent PDE2 inhibitors. [ABSTRACT FROM AUTHOR]

We have identified a novel PDE2 inhibitor series using fragment-based screening. Pyrazolopyrimidine fragment 1, while possessing weak potency (K i  = 22.4 μM), exhibited good binding efficiencies (LBE = 0.49, LLE = 4.48) to serve as a start for structure-based drug design. With the assistance of molecular modeling and X-ray crystallography, this fragment was developed into a series of potent PDE2 inhibitors with good physicochemical properties. Compound 16, a PDE2 selective inhibitor, was identified that exhibited favorable rat pharmacokinetic properties. [ABSTRACT FROM AUTHOR]

The cyclic nucleotides cAMP and cGMP are central second messengers in cardiac cells and critical regulators of cardiac physiology as well as pathophysiology. Consequently, subcellular compartmentalization allows for spatiotemporal control of cAMP/cGMP metabolism and subsequent regulation of their respective effector kinases PKA or PKG is most important for cardiac function in health and disease. While acute cAMP-mediated signalling is a mandatory prerequisite for the physiological fight-or-flight response, sustained activation of this pathway may lead to the progression of heart failure. In contrast, acute as well as sustained cGMP-mediated signalling can foster beneficial features, e.g. anti-hypertrophic and vasodilatory effects. These two signalling pathways seem to be intuitively counteracting and there is increasing evidence for a functionally relevant crosstalk between cAMP and cGMP signalling pathways on the level of cyclic nucleotide hydrolysing phosphodiesterases (PDEs). Among this diverse group of enzymes, PDE2 may fulfill a unique integrator role. Equipped with dual substrate specificity for cAMP as well as for cGMP, it is the only cAMP hydrolysing PDE, which is allosterically activated by cGMP. Recent studies have revealed strongly remodelled cAMP/cGMP microdomains and subcellular concentration profiles in different cardiac pathologies, leading to a putatively enhanced involvement of PDE2 in cAMP/cGMP breakdown and crosstalk compared to the other cardiac PDEs. This review sums up the current knowledge about molecular properties and regulation of PDE2 and explains the complex signalling network encompassing PDE2 in order to better understand the functional role of PDE2 in distinct cell types in cardiac health and disease. Moreover, this review gives an outlook in which way PDE2 may serve as a therapeutic target to treat cardiac disease. [ABSTRACT FROM AUTHOR]

Previously reported self-cloning procedures for breeding of industrial yeast strains require DNA from other strains, plasmid DNA, or mutagenesis. Therefore, we aimed to construct a self-cloning baker's yeast strain that exhibits freeze tolerance via an improved self-cloning procedure. We first disrupted the URA3 gene of a prototrophic baker's yeast strain without the use of any marker gene, resulting in a Δura3 homozygous disruptant. Then, the URA3 gene of the parental baker's yeast strain was used as a selection marker to introduce the constitutive TDH3 promoter upstream of the PDE2 gene encoding high-affinity cyclic AMP phosphodiesterase. This self-cloning procedure was performed without using DNA from other Saccharomyces cerevisiae strains, plasmid DNA, or mutagenesis and was therefore designated an intra-strain self-cloning procedure. Using this self-cloning procedure, we succeeded in producing self-cloning baker's yeast strains that harbor the TDH3 p- PDE2 gene heterozygously and homozygously, designated TDH3 p- PDE2 hetero and TDH3 p- PDE2 homo strains, respectively. These self-cloning strains expressed much higher levels of PDE2 mRNA than the parental strain and exhibited higher viability after freeze stress, as well as higher fermentation ability in frozen dough, when compared with the parental strain. The TDH3 p- PDE2 homo strain was genetically more stable than the TDH3 p- PDE2 hetero strain. These results indicate that both heterozygous and homozygous strains of self-cloning PDE2 -overexpressing freeze-tolerant strains of industrial baker's yeast can be prepared using the intra-strain self-cloning procedure, and, from a practical viewpoint, the TDH3 p- PDE2 homo strain constructed in this study is preferable to the TDH3 p- PDE2 hetero strain for frozen dough baking. [ABSTRACT FROM AUTHOR]

The emergence of multidrug-resistant fungal pathogens is a significant concern for global public health. Candida auris poses a considerable threat as a multidrug-resistant fungal pathogen. Our recent study revealed that the adenylyl cyclase Cyr1 and protein kinase A (PKA) pathways play distinct and redundant roles in drug resistance and pathogenicity of C. auris . However, the upstream and negative feedback regulatory mechanisms of C. auris are not yet fully understood. In this study, we discovered that the small GTPase Ras1, along with its nucleotide exchange factor Cdc25 and GTPase-activating protein Ira2, plays a major role in regulating cAMP/PKA-dependent traits, while G-protein-coupled receptor Gpr1 and heterotrimeric G-protein α subunit Gpa2 play a minor role. Pde2 plays a major role in negative feedback regulation of the cAMP/PKA pathway, while Pde1 plays a minor role. Hyperactivation of the Ras/cAMP/PKA pathway by deleting PDE2 or BCY1 renders C. auris cells thermosensitive and susceptible to nutrient deficiency, which leads to attenuated virulence. Our study demonstrates the distinct contributions of hyperactivation of the Ras/cAMP/PKA signaling pathway to C. auris pathogenesis and suggests potential therapeutic targets for C. auris- mediated candidiasis. IMPORTANCE Candida auris is a major concern as a multidrug-resistant fungal pathogen. While our previous studies highlighted the crucial roles of the cAMP/protein kinase A (PKA) pathway in regulating drug resistance, stress responses, morphogenesis, ploidy change, biofilm formation, and pathogenicity in this pathogen, their regulatory mechanism remains unclear. In our study, we provided evidence that the cAMP/PKA signaling pathway in C. auris is primarily governed by the small GTPase RAS rather than a G-protein-coupled receptor. Additionally, we discovered that the negative feedback regulation of cAMP, controlled by phosphodiesterases, is vital for C. auris virulence by promoting resistance to high temperatures and nutrient deficiencies. These findings underscore the diverse pathobiological significance of the Ras/cAMP/PKA signaling pathway in C. auris , shedding light on potential therapeutic targets and strategies for combating this multidrug-resistant fungal pathogen.

In order to observe the changes of PDE2 and PDE3 in gastric smooth muscle of diabetic gastroparesis rats, rat model of diabetes mellitus was induced by injected streptozotocin (STZ). To record gastric smooth muscle contraction of diabetes rat with multichannel physiology signal recording system. Diabetes rats with gastric smooth muscle contraction indiscriminate were identified as diabetic gastroparesis model. Then to observe content of PDE2 and PDE3 in diabetic gastroparesis rats gastric smooth muscle by immunohistochemistry. Compared with control group rats, PDE2 content in gastroparesis rat gastric smooth muscle was not significantly different, but PDE3 content increased significantly (P<0. 05). Thus, Gastroparesis of diabetes rats may be correlated with PDE3 down-regulation in gastric smooth muscle, and cGMP-PDE3 signal system may be involved in the pathogenesis and development of diabetic gastropathy of gastroparesis. [ABSTRACT FROM AUTHOR]

Impaired phosphodiesterase (PDE) function and mitochondrial Ca2+ (i.e., [Ca2+]m) lead to multiple health syndromes by an unknown pathway. Here, we fluorescently monitor robust [Ca2+]m efflux mediated by the mitochondrial Na+/Ca2+ exchanger NCLX in hippocampal neurons sequentially evoked by caffeine and depolarization. Surprisingly, neuronal depolarization-induced Ca2+ transients alone fail to evoke strong [Ca2+]m efflux in wild-type (WT) neurons. However, pre-treatment with the selective PDE2 inhibitor Bay 60-7550 effectively rescues [Ca2+]m efflux similarly to caffeine. Moreover, PDE2 acts by diminishing mitochondrial cAMP, thus promoting NCLX phosphorylation at its PKA site. We find that the protection of neurons against excitotoxic insults, conferred by PDE2 inhibition in WT neurons, is NCLX dependent. Finally, the administration of Bay 60-7550 enhances new object recognition in WT, but not in NCLX knockout (KO), mice. Our results identify a link between PDE and [Ca2+]m signaling that may provide effective therapy for cognitive and ischemic syndromes. [Display omitted] • Caffeine-activated mitochondrial Ca2+ efflux by NCLX in hippocampal neurons • Caffeine is acting by inhibiting PDE2 • Inhibition of PDE2 triggers NCLX phosphorylating, thereby accelerating NCLX activity • PDE2-dependent activation of NCLX protects against excitotoxicity and enhances learning Rozenfeld et al. report that caffeine and the PDE2 blocker Bay-607550 stimulate mitochondrial Ca2+ removal in neurons. Inhibition of PDE2 stimulates PKA, which phosphorylates the regulatory domain of the mitochondrial exchanger NCLX, leading to its activation. Upregulation of NCLX prevents excitotoxic neuronal death and enhances new object learning in mice. [ABSTRACT FROM AUTHOR]

Introduction: Nitric oxide-stimulated cGMP synthesis represents an important signalling pathway in the urinary bladder. Inhibitors of the PDE1 and PDE5 enzyme have been studied to treat storage and voiding disorders in clinical settings. The distribution of PDE2 in the bladder is unknown. This study focuses on the distribution and site of action of PDE2 within the guinea pig urinary bladder wall. Methods: Six male guinea pig bladders were dissected and treated in 2 ml Krebs' solution and 10 µM of the specific PDE2 inhibitor, Bay 60-7550 at 36 °C for 30 min. After stimulating tissues with 100 µM of diethylamine-NONOate for 10 min, the tissues were snap frozen and cut in 10 µm sections which were examined for cGMP immune-reactivity, co-stained with either vimentin, synaptic vesicle protein 2, calcitonin gene-related protein and protein gene product 9.5. Results: PDE2 inhibitor Bay 60-7550 inhibits cGMP breakdown the most in the urothelial and suburothelial layers, as well as on the nerve fibres. After inhibition by Bay 60-7550, cGMP was mainly expressed in the intermuscle interstitial cells and the nerve fibres of the outer muscle layers of lateral wall, indicating the presence of PDE2 activity. Discussion and conclusion: Our study is the first to show the distribution of PDE2 in the bladder which was shown to be present in the urothelium, mainly umbrella cells, the interstitial cells of the suburothelium and the outer muscle, as well as in nerve fibres. [ABSTRACT FROM AUTHOR]

Aims Compartmentalization of cAMPand PKA activity in cardiac muscle cells plays a key role in maintaining basal and enhanced contractility stimulated by sympathetic nerve activity. In cardiomyocytes, activation of adrenergic receptor increases cAMP production, which is countered by the hydrolytic activity of selective phosphodiesterases (PDEs). The intracellular regional dynamics of cAMP production and hydrolysis modulate downstream signals resulting in different biological responses. The interplay between beta receptors (bARs) signalling and phosphodiesterase 5 (PDE5) activity remains to be addressed. Methods and results Using combined strategies with pharmacological inhibitors and genetic deletion of PDEs andbARisoforms, werevealed a specific pool ofcAMPthat is under dual regulation byPDE2and, indirectly, PDE5activity. Inhibition ofPDE5with sildenafil produces a cGMP-dependent activation of PDE2 that attenuates cAMP generation induced by bAR agonists, with concomitant modulation of stimulated contraction rate and calcium transients. PDE2 haploinsufficiency abolished the effects of sildenafil. The negative chronotropic effect of PDE5 inhibition through PDE2 activationwas also observed in sinoatrial node tissue from adult mice. PDE5 inhibition selectively lowered contraction rate stimulated by b2AR, but not b1AR activation, supporting a compartmentalization of the cGMP-modulated pool of cAMP. Conclusion These data identify a new effect of PDE5 inhibitors on the modulation of cardiomyocyte response to adrenergic stimulation via PDE5-PDE2-mediated cross-talk. [ABSTRACT FROM AUTHOR]

Chronic stress and neuronal vulnerability have recently been recognized as factors contributing to cognitive disorders. One way to modify neuronal vulnerability is through mediation of phosphodiesterase 2 (PDE2), an enzyme that exerts its action on cognitive processes via the control of intracellular second messengers, cGMP and, to a lesser extent, cAMP. This study explored the effects of a PDE2 inhibitor, Bay 60-7550, on stress-induced learning and memory dysfunction in terms of its ramification on behavioral, morphologic, and molecular changes. Bay 60-7550 reversed stress-induced cognitive impairment in the Morris water maze, novel object recognition, and location tasks (object recognition test and/or object location test), effects prevented by treatment with 7-NI, a selective inhibitor of neuronal nitric oxide synthase; MK801, a glutamate receptor (NMDAR) inhibitor; myr-AIP, a CaMKII inhibitor; and KT5823, a protein kinase G inhibitor. Bay 60-7550 also ameliorated stress-induced structural remodeling in the CA1 of the hippocampus, leading to increases in dendritic branching, length, and spine density. However, the neuroplasticity initiated by Bay 60-7550 was not seen in the presence of 7-NI, MK801, myr-AIP, or KT5823. PDE2 inhibition reduced stress-induced extracellular-regulated protein kinase activation and attenuated stress-induced decreases in transcription factors (e.g., Elk-1, TORC1, and CREB phosphorylation) and plasticity-related proteins (e.g., Egr-1 and brain-derived neurotrophic factor). Pretreatment with inhibitors of NMDA, CaMKII, neuronal nitric oxide synthase, and protein kinase G (or protein kinase A) blocked the effects of Bay 60-7550 on cGMP or cAMP signaling. These findings indicate that the effect of PDE2 inhibition on stress-induced memory impairment is potentially mediated via modulation of neuroplasticity-related NMDAR-CaMKII-cGMP/cAMP signaling. [ABSTRACT FROM AUTHOR]

Selective inhibition of phosphodiesterase 2 (PDE2) in cells where it is located elevates cyclic guanosine monophosphate (cGMP) and acts as novel analgesic with antinociceptive activity. Three-dimensional quantitative structure–activity relationship (QSAR) studies for pyrazolodiazepinone inhibitors exhibiting PDE2 inhibition were performed using comparative molecular field analysis (CoMFA), comparative molecular similarity indices analysis (CoMSIA) and Topomer CoMFA, and two-dimensional QSAR study was performed using a Hologram QSAR (HQSAR) method. QSAR models were generated using training set of 23 compounds and were validated using test set of nine compounds. The optimum partial least squares (PLS) for CoMFA-Focusing, CoMSIA-SDH, Topomer CoMFA and HQSAR models exhibited good ‘leave-one-out’ cross validated correlation coefficient (q2) of 0.790, 0.769, 0.840 and 0.787, coefficient of determination (r2) of 0.999, 0.964, 0.979 and 0.980, and high predictive power (r2pred) of 0.796, 0.833, 0.820 and 0.803 respectively. Docking studies revealed that those inhibitors able to bind to amino acid Gln859 by cGMP binding orientation called ‘glutamine-switch’, and also bind to the hydrophobic clamp of PDE2 isoform, could possess high selectivity for PDE2. From the results of all the studies, structure–activity relationships and structural requirements for binding to active site of PDE2 were established which provide useful guidance for the design and future synthesis of potent PDE2 inhibitors. [ABSTRACT FROM AUTHOR]

Abstract: Production of high titer of antibodies against nuclear components is a hallmark of systemic lupus erythematosus, an autoimmune disease characterized by the progressive chronic inflammation of multiple joints and organs. Organ damage and dysfunction such as renal failure are typical clinical features in lupus. Cell hypermetabolism and hypertrophy can accelerate organ dysfunction. In this study we focus on a specific murine model of lupus, the MRL/lpr strain, and investigated the role of cyclic guanosine monophosphate (cGMP) catabolism in organ remodeling of main target tissues (kidney, spleen and liver) in comparison with age-matched control mice. In MRL/lpr-prone mice, the cGMP-phosphodiesterase (PDE) activities were significantly increased in the kidney (3-fold, P <0.001), spleen (2-fold, P <0.001) and liver (1.6-fold, P <0.05). These raised activity levels were paralleled by both an increased activity of PDE1 in the kidney (associated with nephromegaly) and in the liver, and PDE2 in the spleen of lupus-prone mice. The up-regulation of PDE1 and PDE2 activities were associated with a decrease in intracellular cGMP levels. This underlines an alteration of cGMP-PDE signaling in the kidney, spleen and liver targeting different PDEs according to organs. In good agreement with these findings, a single intravenous administration to MRL/lpr mice of nimodipine (PDE1 inhibitor) but not of EHNA (PDE2 inhibitor) was able to significantly lower peripheral hypercellularity (P =0.0401), a characteristic feature of this strain of lupus-prone mice. Collectively, our findings are important for generating personalized strategies to prevent certain forms of the lupus disease as well as for understanding the role of PDEs and cGMP in the pathophysiology of lupus. [Copyright &y& Elsevier]

Impaired phosphodiesterase (PDE) function and mitochondrial Ca 2 + (i.e., [Ca 2+ ]m) lead to multiple health syndromes by an unknown pathway. Here, we fluorescently monitor robust [Ca 2+ ]m efflux mediated by the mitochondrial Na + /Ca 2+ exchanger NCLX in hippocampal neurons sequentially evoked by caffeine and depolarization. Surprisingly, neuronal depolarization-induced Ca 2+ ]m efflux in wild-type (WT) neurons. However, pre-treatment with the selective PDE2 inhibitor Bay 60-7550 effectively rescues [Ca 2+ ]m efflux similarly to caffeine. Moreover, PDE2 acts by diminishing mitochondrial cAMP, thus promoting NCLX phosphorylation at its PKA site. We find that the protection of neurons against excitotoxic insults, conferred by PDE2 inhibition in WT neurons, is NCLX dependent. Finally, the administration of Bay 60-7550 enhances new object recognition in WT, but not in NCLX knockout (KO), mice. Our results identify a link between PDE and [Ca 2+ ]m efflux similarly to caffeine. Moreover, PDE2 acts by diminishing mitochondrial cAMP, thus promoting NCLX phosphorylation at its PKA site. We find that the protection of neurons against excitotoxic insults, conferred by PDE2 inhibition in WT neurons, is NCLX dependent. Finally, the administration of Bay 60-7550 enhances new object recognition in WT, but not in NCLX knockout (KO), mice. Our results identify a link between PDE and [Ca 2+ ]m signaling that may provide effective therapy for cognitive and ischemic syndromes., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022. Published by Elsevier Inc.)

Highlights: [•] The PDE2-I BAY 60-7550 affects auditory information processing in the vertex. [•] The PDE10-I PQ-10 affects auditory information processing in the hippocampus. [•] The PDE5-I vardenafil does not affect auditory information processing. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, we investigated the mechanism of C-type natriuretic peptide (CNP)-induced inhibitory effect on spontaneous contraction of gastric antral smooth muscle to clarify CNP-NPR-B/pGC-cGMP downstream signal transduction pathway using organ bath and ELISA methods in rat. CNP significantly reduced the amplitude of the spontaneous contraction and increased the contents of cGMP and cAMP in the gastric antral smooth muscle tissue. In the presence of IBMX, a non-selective phosphodiesterase (PDE) inhibitor, the inhibitory effect of CNP on spontaneous contraction was significantly suppressed; however, the production of cGMP but not cAMP was still increased by CNP. EHNA, a PDE2 inhibitor, did not affect both CNP-induced inhibition of the contraction and CNP-induced increase of cGMP and cAMP generations in gastric smooth muscle tissue, while milrinone, a PDE3 inhibitor, similar to IBMX, attenuated the CNP-induced inhibitory effect on spontaneous contraction and increased the content of cGMP but not cAMP. The results suggest that cGMP–PDE3–cAMP signal pathway is also involved in the CNP-induced inhibition of gastric motility in rat. [Copyright &y& Elsevier]

Cyclic guanosine monophosphate (cGMP) and its primary signaling kinase, protein kinase G, play an important role in counterbalancing stress remodeling in the heart. Growing evidence supports a positive impact on a variety of cardiac disease conditions from the suppression of cGMP hydrolysis. The latter is regulated by members of the phosphodiesterase (PDE) superfamily, of which cGMP-selective PDE5 has been best studied. Inhibitors such as sildenafil and tadalafil ameliorate cardiac pressure and volume overload, ischemic injury, and cardiotoxicity. Clinical trials have begun exploring their potential to benefit dilated cardiomyopathy and heart failure with a preserved ejection fraction. This review discusses recent developments in the field, highlighting basic science and clinical studies. [ABSTRACT FROM AUTHOR]

Understanding the genetic basis of the yeast ability to proliferate and ferment in the presence of restrictive concentrations of ethanol is of importance to both science and technology. In this study, we searched for genes that improve ethanol tolerance in ethanol-sensitive strains. To screen for suppressors of ethanol sensitivity, we introduced a 2µ-based genomic library, prepared from the ethanol-tolerant yeast S288 C, into the ethanol-sensitive strain W303-1 A. Two genomic fragments from this library rescued the ethanol sensitivity of W303-1 A. One contained the PDE2 gene, which when over-expressed, conferred ethanol tolerance. Surprisingly, the effect of PDE2 was not mediated via MSN2/ MSN4 transcription factors, as it was able to improve ethanol tolerance in msn2Δmsn4Δ strain. In the second genomic fragment, it was the N-terminal region of the SSD1 gene that carried the ethanol-tolerant phenotype. The SSD1-V allele of the polymorphic SSD1 gene expressed from a low-copy number plasmid also resulted in the tolerant phenotype. Both SSD1 and PDE2 seemed to improve ethanol tolerance by maintaining robustness of the yeast cell wall. [ABSTRACT FROM AUTHOR]

Abstract: β3-Adrenergic receptors (ARs) have been recently identified in mammalian hearts where, unlike β1- and β2-ARs, induce cardio-suppressive effects. The aim of this study was to describe β3-AR role in the frog (Rana esculenta) heart and to examine its signal transduction pathway. The presence of β3-AR, by using Western blotting analysis, has been also identified. BRL37344 , a selective β3-AR agonist, induced a dose-dependent negative inotropic effect at concentrations from 10−12 to 10−6 M. This effect was not modified by nadolol (β1/β2-AR antagonist) and by phentolamine (α-AR antagonist), but it was suppressed by the β3-AR-specific antagonist SR59230 and by exposure to the Gi/o proteins inhibitor Pertussis Toxin. In addition, the involvement of EE-NOS-cGMP-PKG/PDE2 pathway in the negative inotropism of BRL37344 has been assessed. BRL37344 treatment induced eNOS and Akt phosphorylation as well as an increase of cGMP levels. β3-ARs activation induce a non-competitive antagonism against ISO stimulation which disappeared in presence of PKG and PDE2 inhibition. Taken together our findings provide, for the first time in the frog, a role for β3-ARs in the cardiac performance modulation which involves Gi/o protein and occurs via an EE-NO-cGMP-PKG/PDE2 cascade. [ABSTRACT FROM AUTHOR]

The genome of the yeast Saccharomyces cerevisiae encodes two cyclic AMP (cAMP) phosphodiesterases, a low-affinity one, Pde1, and a high-affinity one, Pde2. Pde1 has been ascribed a function for downregulating agonist-induced cAMP accumulation in a protein kinase A (PKA)-governed negative feedback loop, whereas Pde2 controls the basal cAMP level in the cell. Here we show that PKA regulates the localization and protein concentration of Pde2. Pde2 is accumulated in the nucleus in wild-type cells growing on glucose, or in strains with hyperactive PKA. In contrast, in derepressed wild-type cells or cells with attenuated PKA activity, Pde2 is distributed over the nucleus and cytoplasm. We also show evidence indicating that the Pde2 protein level is positively correlated with PKA activity. The increase in the Pde2 protein level in high-PKA strains and in cells growing on glucose was due to its increased half-life. These results suggest that, like its low-affinity counterpart, the high-affinity phosphodiesterase may also play an important role in the PKA-controlled feedback inhibition of intracellular cAMP. [ABSTRACT FROM AUTHOR]

The mammalian olfactory system recognizes a wide range of chemical stimuli. The majority of cells in the main olfactory epithelium (MOE) use a cAMP-mediated signaling system to transduce odor signals. However, a subset of MOE neurons instead expresses components of a cGMP signaling cascade, including the receptor guanylyl cyclase GC-D and the cyclic nucleotide-gated channel subunit CNGA3. We used a combination of molecular biological, physiological, and imaging approaches to characterize this neuronal population. Neurons expressing GC-D show excitatory responses to the natriuretic peptide hormones uroguanylin and guanylin, as well as to stimuli present in urine, that are dependent on both GC-D and CNGA3. Though all GC-D-expressing neurons are highly sensitive to these stimuli, individual cells are differentially tuned to either one or both of the peptides. Together, these findings suggest that neurons expressing GC-D are part of a specialized olfactory subsystem that is responsive to semiochemicals. [ABSTRACT FROM AUTHOR]

Abstract: Gene transfer of neuronal nitric oxide synthase (nNOS) can decrease cardiac sympathetic outflow and facilitate parasympathetic neurotransmission. The precise pathway responsible for nitric oxide (NO) mediated inhibition of sympathetic neurotransmission is not known, but may be related to NO–cGMP activation of cGMP-stimulated phosphodiesterase (PDE2) that enhances the breakdown of cAMP to deactivate protein kinase A (PKA), resulting in a decrease in Ca2+ influx mediated exocytosis of the neurotransmitter. We investigated depolarization evoked Ca2+ influx in nNOS gene transduced sympathetic neurons from stellate ganglia with a noradrenergic cell specific vector (Ad.PRS-nNOS or empty vector), and examined how nNOS gene transfer affected cAMP and cGMP levels in these neurons. We found that targeting nNOS into these sympathetic neurons reduced amplitudes of voltage activated Ca2+ transients by 44%. nNOS specific inhibition by N-[(4S)-4-Amino-5-[(2-aminoetyl](amino] pentyl]-N′-nitroguanidine (AAAN) reversed this response. nNOS gene transfer also increased intracellular cGMP (47%) and decreased cAMP (29%). A PDE2 specific inhibitor Bay60-7557 reversed the reduction in cAMP caused by Ad.PRS-nNOS. These results suggest that neuronal NO modulates cGMP and PDE2 to regulate voltage gated intracellular Ca2+ transients in sympathetic neurons. Therefore, we propose this as a possible key step involved in NO decreasing cardiac sympathetic neurotransmission. [Copyright &y& Elsevier]

Abstract: NMDA receptor-induced cAMP and cGMP are selectively hydrolyzed by PDE4 and PDE2, respectively, in rat primary cerebral cortical and hippocampal cultures. Because cAMP levels regulate the expression of PDE4 in rat primary cortical cultures, we examined the manner in which NMDA receptor activity regulates the age-dependent increase in the expression of PDE4A observed in vivo and in vitro. Inhibiting the activity of NR2B subunit with ifenprodil blocked NMDA receptor-induced cGMP synthesis and increased NMDA receptor-induced cAMP levels in a manner that reduced PDE4 activity. Therefore, NR1/NR2B receptor-induced cGMP signaling is involved in an acute cross-talk regulation of NR1/NR2A receptor-induced cAMP levels, mediated by PDE4. Chronic inhibition of NMDA receptor activity with MK-801 reduced PDE4A1 and PDE4A5 expression and activity in a time-dependent manner; this effect was reversed by adding the PKA activator dbr-cAMP. Inhibiting GABA receptors with bicuculline increased NMDA receptor-induced cAMP synthesis and PDE4A expression in cultures treated between DIV 16 and DIV 21 but not in cultures treated between DIV 8 and DIV 13. This effect was due to a high tone of NMDA receptor-induced cGMP in younger cultures, which negatively regulated the expression of PDE4A by a PKG-mediated process. The present results are consistent with behavioral data showing that both PDE4 and PDE2 are involved in NMDA receptor-mediated memory processes. [Copyright &y& Elsevier]

The Ste50 adaptor protein is involved in a variety of cellular pathways that yeast cells use to adapt rapidly to environmental changes. A highly activated Ras–cyclic AMP (cAMP) pathway by deletion of the high-affinity cAMP-dependent phosphodiesterase 2 ( PDE2) leads to repression of a stress mediated response and cell survival. Here we show that inactivation of STE50 confers a synthetic genetic interaction with pde2Δ. A hyperosmotic stress growth defect of s te50Δ pde2Δ cells is exacerbated by extracellular cAMP or by galactose as the sole carbon source in the medium. The inactivation of the serine/threonine protein-kinase Akt homologue Sch9 increase stress resistance and extend chronological life span. By pde2Δ-dependent increase of the Ras–cAMP pathway activity, inactivation of STE50 results in an extreme shortening of life span and oxidative stress sensitivity of sch9Δ mutants. Furthermore, sch9Δ can promote transcription of the small heat shock protein HSP26 in a PDE2-dependent manner; however, sch9Δ can promote transcription of the mitochondrial superoxide dismutase SOD2 in a PDE2- and STE50-dependent manner. These data indicate that inactivation of STE50 influences stress tolerance in mutants of the Ras–cAMP pathway, which is a major determinant of intrinsic stress tolerance and cell survival of the Saccharomyces cerevisiae. [ABSTRACT FROM AUTHOR]

Abstract: The present study investigated the time-dependent memory enhancing properties of three selective phosphodiesterase inhibitors (PDE-I) vardenafil (PDE5-I), rolipram (PDE4-I) and BAY 60-7550 (PDE2-I) in the object recognition task. In particular, the time-dependent involvement of cAMP and cGMP in memory consolidation was assessed by altering the time points of drug administration. Vardenafil (1 mg/kg, p.o.), rolipram (0.03 mg/kg, i.p.), and BAY 60-7550 (3 mg/kg, p.o.) were tested in rats with a 24 h delay between the learning and the test trial. The PDE-Is were administered at different time points, i.e. directly after, 1 h, 3 h and 6 h after the first trial. Using a 24 h interval, vardenafil only showed an effect on object memory when injected directly after trial 1, rolipram only showed an improvement when injected 3 h after trial 1 and BAY 60-7550 improved memory when injected either directly after or 3 h after trial 1. No treatment effects were found when the compounds were administered 1 h or 6 h after the first trial. Our results extend our previous data that different types of PDE-Is affect different stages of memory consolidation. Moreover, the present study provides further support that selective PDE-Is can influence memory consolidation in a time-dependent manner, assumingly by elevating central cAMP and cGMP levels. [Copyright &y& Elsevier]

Abstract: Phosphodiesterase 4 (PDE4) inhibitors are effective anti-inflammatory drugs, although some adverse effects are observed in animals and humans. These effects have forced researchers to find new PDE4 inhibitors with less adverse effects. We recently reported the synthesis of novel heterocyclic-fused pyridazinones that inhibit PDE4. As a first step in the study of the anti-inflammatory properties of these compounds, we studied the effects of local administration of these pyridazinone derivatives in a mouse model of acute inflammation. We found that 6-Benzyl-3-methyl-4-phenylpyrazolo[3,4-d]pyridazin-7(6H)-one (CC4), ethyl 6,7-dihydro-6-ethyl-3-methyl-7-oxo-4-phenyl-thieno[2,3-d]pyridazine-2-carboxylate (CC6) and ethyl 6,7-dihydro-6-ethyl-3-methyl-4-phenyl-1H-pyrrolo[2,3-d]pyridazine-2-carboxylate (CC12) reduced the paw edema induced by zymosan in mice as rolipram (the PDE4 inhibitor prototype with anti-inflammatory activity) and indomethacin did. It is well known that rolipram locally administered induces some adverse effects such as hyperalgesia. Thus, we studied this effect after local administration of CC4, CC6 and CC12 in the formalin test. We found that CC6 induced hyperalgesic effects, whereas CC4 and CC12 did not change the nociceptive threshold. Furthermore, we found that rolipram and CC6 reduced locomotor activity, whereas CC4 and CC12 did not change locomotor performance of the mice. Since CC4 and CC12 neither affected the nociceptive threshold nor changed the locomotor performance of mice, they appear more suitable than CC6 for future studies on animals and could be developed as an anti-inflammatory drug for humans. [Copyright &y& Elsevier]

Abstract: Oxindole (2) is a potent and selective PDE2 inhibitor with a favorable ADME, physiochemical and pharmacokinetic profile to allow for use as a chemical tool in elucidating the physiological role of PDE2. [Copyright &y& Elsevier]