cAMP Content Research Articles

Cyclic Adenosine Monophosphate Eliminates Sex Differences in Estradiol-Induced Elastin Production from Engineered Dermal Substitutes.

Lack of adult cells’ ability to produce sufficient amounts of elastin and assemble functional elastic fibers is an issue for creating skin substitutes that closely match native skin properties. The effects of female sex hormones, primarily estrogen, have been studied due to the known effects on elastin post-menopause, thus have primarily included older mostly female populations. In this study, we examined the effects of female sex hormones on the synthesis of elastin by female and male human dermal fibroblasts in engineered dermal substitutes. Differences between the sexes were observed with 17β-estradiol treatment alone stimulating elastin synthesis in female substitutes but not male. TGF-β levels were significantly higher in male dermal substitutes than female dermal substitutes and the levels did not change with 17β-estradiol treatment. The male dermal substitutes had a 1.5-fold increase in cAMP concentration in the presence of 17β-estradiol compared to no hormone controls, while cAMP concentrations remained constant in the female substitutes. When cAMP was added in addition to 17β-estradiol and progesterone in the culture medium, the sex differences were eliminated, and elastin synthesis was upregulated by 2-fold in both male and female dermal substitutes. These conditions alone did not result in functionally significant amounts of elastin or complete elastic fibers. The findings presented provide insights into differences between male and female cells in response to female sex steroid hormones and the involvement of the cAMP pathway in elastin synthesis. Further explorations into the signaling pathways may identify better targets to promote elastic fiber synthesis in skin substitutes.

Enhancement of DPP-IV Inhibitory Activity and GLP-1 Release Through RADA16-assisted Molecular Designed Rapeseed Peptide Nanogels

Abstract Objectives To produce and evaluate the microstructure and rheological behavior of a nanogel of pentapeptide IPQVS (RAP1) and octopeptide ELHQEEPL (RAP2), derived from rapeseed napin, through RADA16-assisted molecular design. In addition, to determine in vitro the dipeptidyl-peptidase IV (DPP-IV) inhibitory properties, glucagon-like peptide-1 (GLP-1) secretion through activation of calcium-sensing receptor (CaSR) and the intracellular calcium ion mobilization and receptor protein cAMP concentration. Methods An innovative nanogel, which loaded the RAP1 and RAP2 into RADA16 scaffold, respectively, was synthesized. The linker of double Gly was used in the connection of RADA16 and the functional oligopeptide region. DPP-IV inhibitory activity was evaluated in the Caco-2 cell monolayer. The microstructure and rheological behavior of RADA16-RAP1 and RADA16-RAP2 were characterized. The GLP-1 secretion through activation of CaSR receptor and the intracellular calcium ion mobilization and cAMP concentration were determined in STC-1 cells. Results DPP-IV inhibitory activity was reduced (more potent) by over 65% in the presence of 250 μM of the two formed nanogels RADA16–GG-IPQVS and RADA16- GG-ELHQEEPL (p < 0.05). The two nanogel peptides had high stability at low temperature or body temperature and high dispersibility in water. Stable β-sheet structures increased by 5.6-fold and 5.2-fold, respectively, than the original oligopeptides, with a self-assembled fibrous morphology. The nanogels RADA16-RAP1 and RADA16-RAP2 might exhibit good rheological properties for potential injectable applications; storage modulus (G’) was 10 times higher than low modulus (G’’). Furthermore, the RAP2 and its RADA16-assisted nanogel peptide at the concentration of 250 μM significantly (p < 0.05) increased the release of GLP-1 by 35.46% through calcium-sensing receptor (CaSR) pathway in the enteroendocrine STC-1 cells. Conclusions The innovated nanogel with the sequence of RADA16-GG-Xn has the possibility of oral and injection to management type 2 diabetes. DPP-IV inhibitory peptides IPQVS and ELHQEEPL can form a nanogel with high water content through the self-assembly gelation of RADA16. They may attach to the brush border of human intestinal epithelial cells to inhibit DPP-IV in the intestinal lumen. Funding Sources USDA-HATCH [grant number 1017440].

Advances in Cyclic Nucleotide Phosphodiesterase-Targeted PET Imaging and Drug Discovery.

Cyclic nucleotide phosphodiesterases (PDEs) control the intracellular concentrations of cAMP and cGMP in virtually all mammalian cells. Accordingly, the PDE family regulates a myriad of physiological functions, including cell proliferation, differentiation and apoptosis, gene expression, central nervous system function, and muscle contraction. Along this line, dysfunction of PDEs has been implicated in neurodegenerative disorders, coronary artery diseases, chronic obstructive pulmonary disease, and cancer development. To date, 11 PDE families have been identified; however, their distinct roles in the various pathologies are largely unexplored and subject to contemporary research efforts. Indeed, there is growing interest for the development of isoform-selective PDE inhibitors as potential therapeutic agents. Similarly, the evolving knowledge on the various PDE isoforms has channeled the identification of new PET probes, allowing isoform-selective imaging. This review highlights recent advances in PDE-targeted PET tracer development, thereby focusing on efforts to assess disease-related PDE pathophysiology and to support isoform-selective drug discovery.

Genetic deficiency or pharmacological inhibition of soluble epoxide hydrolase ameliorates high fat diet-induced pancreatic β-cell dysfunction and loss

Pancreatic β-cells are crucial regulators of systemic glucose homeostasis, and their dysfunction and loss are central features in type 2 diabetes. Interventions that rectify β-cell dysfunction and loss are essential to combat this deadly malady. In the current study, we sought to delineate the role of soluble epoxide hydrolase (sEH) in β-cells under diet-induced metabolic stress. The expression of sEH was upregulated in murine and macaque diabetes models and islets of diabetic human patients. We postulated that hyperglycemia-induced elevation in sEH leads to a reduction in its substrates, epoxyeicosatrienoic acids (EETs), and attenuates the function of β-cells. Genetic deficiency of sEH potentiated glucose-stimulated insulin secretion in mice, likely in a cell-autonomous manner, contributing to better systemic glucose control. Consistent with this observation, genetic and pharmacological inactivation of sEH and the treatment with EETs exhibited insulinotropic effects in isolated murine islets ex vivo. Additionally, sEH deficiency enhanced glucose sensing and metabolism with elevated ATP and cAMP concentrations. This phenotype was associated with attenuated oxidative stress and diminished β-cell death in sEH deficient islets. Moreover, pharmacological inhibition of sEH in vivo mitigated, albeit partly, high fat diet-induced β-cell loss and dedifferentiation. The current observations provide new insights into the role of sEH in β-cells and information that may be leveraged for the development of a mechanism-based intervention to rectify β-cell dysfunction and loss.

Shenrong Wuzi Pill affects the pathway of thyroid hormone synthesis by targeting thyrotropin-releasing hormone receptor and altering cAMP production

Shenrong Wuzi Pill (SWP) is a traditional Chinese medicine used for hypothyroidism treatment. It contains fourteen herbs. However, little is known about the active components and the mechanism of SWP. To reveal the chemical components and drug targets and to systematically dissect the underlying mechanism of SWP as a treatment for hypothyroidism, a network pharmacology approach was used in this study. Four networks were set up, including a hypothyroidism gene network, a pathway of hypothyroidism network, a compound-compound target network, and a compound-compound target-hypothyroidism gene network. Moreover, further analysis focused on overlapping genes between compound targets and hypothyroidism genes. As a result, 14 compounds, 29 overlapping genes and 3 pathways were selected. It was found that SWP and lauric acid from Plantago asiatica L., both upregulated thyrotropin-releasing hormone receptor (TRHR) at mRNA and protein levels in NG108-15 cells. Additionally, lauric acid and atropine from Lycium barbarum L. both upregulated growth hormone secretagogue receptor (GHSR) at the mRNA level; adenine from Poria cocos (Schw.) Wolf. and 17α-estradiol from Cornu Cervi Pantotrichum upregulated adenylyl cyclase 10 (ADCY10) and follicle ¬stimulating hormone receptor (FSHR) at mRNA levels, respectively. However, mRNA levels of GHSR, ADCY10 and FSHR were not affected significantly by SWP treatment. Furthermore, SWP, lauric acid, adenine and atropine all upregulated cellular cyclic adenosine monophosphate (cAMP) concentration, which is important for triiodothyronine (T3) and thyroxine (T4) production. Taken together, it was concluded SWP affects the pathway of thyroid hormone synthesis by targeting TRHR and altering cAMP production.

Cholinergic regulation of cardiac pacemaker activity by L-type Cav1.3 channels

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Fondation Recherche Médicale Introduction The cholinergic regulation of heart rate (HR) is mediated by acetylcholine (ACh)-dependent activation of M2-receptors (M2R). Activated M2R promote release of the βγ-subunit of G-proteins to directly gate GIRK1/4 channels (underlying the cardiac IKACh current), while αi-subunits inhibit adenylate cyclase (AC) activity. AC inhibition reduces the intracellular concentration of cAMP, decreasing the activity of ion channels involved in pacemaking, including "funny" f-(HCN4) and L-type Cav1.3 calcium channels. Purpose To determine the role of L-type Cav1.3 channels in cholinergic regulation of heart rate. Methods We recorded the frequency of activation and position of pacemaker leading site in ex vivo sinus nodes and the HR of isolated Langendorff perfused hearts of mice at baseline or during ACh perfusion. We used control wild type (WT) mice, and five genetically modified mouse models: Cav1.3 knockout (KO, ablated Cav1.3-mediated L-type current), GIRK4KO (ablated IKACh current), HCN4-CNBD (selective deletion of cAMP-dependent regulation of HCN4), GIRK4KO/HCN4-CNBD and GIRK4KO/Cav1.3KO. We performed in vivo telemetric recordings of heart rate (HR) in WT and GIRK4KO/Cav1.3KO animals. Results Data from optical mapping experiments showed that, under basal conditions, perfusion of 3 μM ACh significantly reduced the frequency of action potentials in WT (44%), HCN4-CNBD (38%), Cav1.3KO (65%) and GIRK4KO (8%) isolated mouse sinus node tissues. ACh application did not significantly affect the frequency of action potentials recorded in tissue from GIRK4KO/HCN4-CNBD and GIRK4KO/Cav1.3KO animals. Furthermore, in all sinus nodes tested, regardless of genotype, ACh shifted the pacemaker leading site from its normal position by at least 0.7 mm. Upon stimulation of the β-adrenergic pathway by Isoproterenol, to reproduce conditions of accentuated antagonism, 3µM ACh reduced HR in isolated hearts from WT (43.8%), HCN4-CNBD (38.7%), Cav1.3KO (25,4%), GIRK4KO (16.9%) and GIRK4KO/HCN4-CNBD (16.4%) mice. No significant HR reduction was recorded in hearts from GIRK4KO/Cav1.3KO animals. In vivo data indicate that HR reduction induced by combined injection of Hexamethonium ( a Nicotinic acetylcholine receptor blocker) with Carbamoylcholine (CCH, M2 receptor agonist) or with 2-Chloro-N6-Cyclopentyladenosine (CCPA, A1 receptor agonist) is higher in WT than in GIRK4KO/Cav1.3KO animals (68% vs 48% CCH, and 79% vs 62% CCPA, respectively). Conclusion Our data indicate that L-type Cav1.3 channels are involved in cholinergic regulation of heart rate in mice. In addition, when the intracellular concentration of cAMP is elevated (i.e. under conditions of accentuated antagonism), cholinergic regulation of sinus node pacemaking is reliant on Cav1.3 and KACh channels.

Spotted seabass, Lateolabrax maculatus can utilize the high-starch diet by effectively regulating the energy metabolism

Carbohydrates are the least cost feed source and conserve protein without affecting the growth of fish at a certain level. However, carnivorous fish fed with trophic levels >3.5 have a limited capability to utilize carbohydrates as an energy source. A 56-day feeding trial was conducted to evaluate the growth performance, hepatic histology, and glucose and lipid metabolism of spotted seabass, Lateolabrax maculatus (initial weight = 10.43 ± 0.01 g), a typical carnivorous fish, fed low - (130 g/kg) or high - starch (202 g/kg) diets (named the LS or HS diets) under satiety and starvation conditions (3 h and 24 h postprandial). The results showed that compared with the LS diet, the HS diet did not negatively affect growth but slightly increased the FR and FCR of spotted seabass. A well-regulated glucose metabolism response was observed in the HS group with significant downregulation of gluconeogenesis (G6P) and upregulation of glycolysis (PK) at 3 h postprandial (P3 h) and downregulation of glycolysis (GK, PFK-1) at the transcription level at 24 h postprandial (P24 h). However, hyperglycemic was still observed in the HS group with increased enzyme activities of gluconeogenesis (G6P) and glycolytic (PK) at P24 h, which indicated that the spotted seabass could not effectively regulate glycolytic under starvation conditions. Excessive starch intake significantly increased hepatic cAMP content, which enhanced the rate of basal metabolism to relieve hyperglycemia at P24 h. No hepatic glycogen accumulation was observed for both groups, and hepatic glycogen content was significantly decreased with upregulation glycogenolysis (PYGL) in the HS group under starvation conditions. In addition, and lipogenesis and lipolysis/β-oxidation were not affected under satiety conditions (P3 h) in the HS group, while the mRNA levels of lipogenesis genes (FASN, ACC1) and β-oxidation (CPT1α, PPARα) were downregulated under starvation conditions. These results indicated that spotted seabass could preferentially utilize glycogen and then lipids under starvation conditions. In conclusion, the spotted seabass could accelerate basal energy metabolism to relieve hyperglycemia and avoid glycogen accumulation and fatty liver after fed HS diet, and preferentially catabolized hepatic glycogen to provide energy under starvation conditions, which indicated that it could effectively regulate energy metabolism after feeding the HS diet.

High glucose induces Nox4 expression and podocyte apoptosis through the Smad3/ezrin/PKA pathway.

ABSTRACTPodocytes are the major target in proteinuric kidney diseases such as diabetic nephropathy. The underlying molecular mechanisms by which high glucose (HG) results in podocyte damage remain unclear. This study investigated the regulatory role of Smad3, ezrin, and protein kinase A (PKA) in NADPH oxidase (Nox4) expression, reactive oxidative species (ROS) production, and apoptosis in HG-treated podocytes. A human podocyte cell line was cultured and differentiated, then treated with 30 mM HG. Apoptosis and intracellular ROS levels were assessed using TUNEL and DCF assays, respectively. Expressions of Nox4, phospho-Smad3Ser423/425, phospho-PKAThr197, and phospho-ezrinThr567 were evaluated using western blotting. ELISA was used to quantify intracellular cAMP concentration and PKA activity. Knockdown assay was used to inhibit the expressions of Smad3, Nox4, and ezrin by lentiviral shRNA. In HG-treated podocytes, the level of phospho-Smad3Ser423/425 and phospho-ezrinThr567 was increased significantly, which was accompanied by the reduction of cAMP and phospho-PKAThr197. HG-induced apoptosis was significantly prevented by the Smad3-inhibitor SIS3 or shRNA-Smad3. In podocytes expressing shRNA-ezrin or shRNA-Nox4, apoptosis was remarkably mitigated following HG treatment. HG-induced upregulation of phospho-ezrinThr567 and downregulation of phospho-PKAThr197 was significantly prevented by SIS3, shRNA-ezrin or shRNA-Smad3. Forskolin, a PKA activator, significantly inhibited HG-mediated upregulation of Nox4 expression, ROS generation, and apoptosis. Additionally, an increase in the ROS level was prohibited in HG-treated podocytes with the knockdown of Nox4, Smad3, or ezrin. Taken together, our findings provided evidence that Smad3-mediated ezrin activation upregulates Nox4 expression and ROS production, by suppressing PKA activity, which may at least in part contribute to HG-induced podocyte apoptosis.

Identification of c-di-GMP/FleQ-Regulated New Target Genes, Including cyaA, Encoding Adenylate Cyclase, in Pseudomonas putida.

The bacterial second messenger cyclic diguanylate (c-di-GMP) modulates plankton-to-biofilm lifestyle transition of Pseudomonas species through its transcriptional regulatory effector FleQ. FleQ regulates transcription of biofilm- and flagellum-related genes in response to c-di-GMP. Through transcriptomic analysis and FleQ-DNA binding assay, this study identified five new target genes of c-di-GMP/FleQ in P. putida, including PP_0681, PP_0788, PP_4519 (lapE), PP_5222 (cyaA), and PP_5586 Except lapE encoding an outer membrane pore protein and cyaA encoding an adenylate cyclase, the functions of the other three genes encoding hypothetical proteins remain unknown. FleQ and c-di-GMP coordinately inhibit transcription of PP_0788 and cyaA and promote transcription of PP_0681, lapE, and PP_5586 Both in vitro and in vivo assays show that FleQ binds directly to promoters of the five genes. Further analyses confirm that LapE plays a central role of in the secretion of adhesin LapA and that c-di-GMP/FleQ increases lapE transcription, thereby promoting adhesin secretion and biofilm formation. The adenylate cyclase CyaA is responsible for synthesis of another second messenger, cyclic AMP (cAMP). FleQ and c-di-GMP coordinate to decrease the content of cAMP, suggesting that c-di-GMP and FleQ coregulate cAMP by modulating cyaA expression. Overall, this study adds five new members to the c-di-GMP/FleQ-regulated gene family and reveals the role of c-di-GMP/FleQ in LapA secretion and cAMP synthesis regulation in P. putida IMPORTANCE c-di-GMP/FleQ promotes the plankton-to-biofilm lifestyle transition at the transcriptional level via FleQ in Pseudomonas species. Identification of new target genes directly regulated by c-di-GMP/FleQ helps to broaden the knowledge of c-di-GMP/FleQ-mediated transcriptional regulation. Regulation of lapE by c-di-GMP/FleQ guarantees highly efficient LapA secretion and biofilm formation. The mechanism of negative correlation between c-di-GMP and cAMP in both P. putida and P. aeruginosa remains unknown. Our result concerning transcriptional inhibition of cyaA by c-di-GMP/FleQ reveals the mechanism underlying the decrease of cAMP content by c-di-GMP in P. putida.

Placentas associated with female neonates from pregnancies complicated by urinary tract infections have higher cAMP content and cytokines expression than males.

The cAMP pathway is involved in important biological processes including immune regulation and hormone signaling. At the feto-maternal unit, cAMP participates in placental function/physiology and the establishment of immunoendocrine networks. Low cAMP in male fetuses cord blood has been linked to poorer perinatal outcomes; however, cAMP placental content and its relationship with immune factors and fetal sex in an infectious condition have not been investigated. Sex-dependent changes in cAMP content and its association with cytokines and antimicrobial peptides expression were studied in human placentas collected from normal pregnancies and with urinary tract infections (UTI). Radioimmunoassay was used to quantify cAMP in placental tissue, while immune markers expression was studied by qPCR. Additionally, cAMP effect on antimicrobial peptides expression was studied in cultured trophoblasts challenged with lipopolysaccharide, to mimic an infection. In UTI, placentas from female neonates had higher cAMP tissue content and increased expression of TNFA, IL1B, and IL10 than those from males, where IFNG was more elevated. While cAMP negatively correlated with maternal bacteriuria and IFNG, it positively correlated with the antimicrobial peptide S100A9 expression in a sex-specific fashion. In cultured trophoblasts, cAMP significantly stimulated β-defensin-1 while reduced the lipopolysaccharide-dependent stimulatory effect on β-defensin-2, β-defensins-3, and S100A9. Our results showed higher cAMP content and defense cytokines expression in placentas associated with female neonates from pregnancies complicated by UTI. The associations between cAMP and bacteriuria/immune markers, together with cAMP's ability to differentially regulate placental antimicrobial peptides expression, suggest a dual modulatory role for cAMP in placental immunity.

Regulation of Cyclic Nucleotide Phosphodiesterase 1 by Endoplasmic Reticulum Stress Contributes to Homocysteine‐induced Cardiac Hypertrophy

Objectives Mechanistic understanding of the role of homocysteine in the development of cardiac hypertrophy is inadequate at present. This study aimed to elucidate the association of cyclic nucleotide phosphodiesterase 1 (PDE1) and endoplasmic reticulum (ER) stress with cardiomyocyte hypertrophy induced by homocysteine. Methods H9c2 cardiomyocytes were allocated to control group and homocysteine-treated group in the presence or absence of ER stress inhibitor tauroursodeoxycholic acid (TUDCA) or PDE1 inhibitor Lu AF58027 for 72h. In another set of experiment, H9c2 cells were transfected with specific siRNA targeting PDE1 subtypes prior to homocysteine exposure. The cell surface area was measured by phase contrast microscope and image analysis software and ultrastructural changes of the cells were observed under transmission electron microscopy. Quantitative polymerase chain reaction and western blot were employed to detect the mRNA and protein expression of the hypertrophic markers beta-smooth muscle myosin heavy chain (β-MHC) and atrial natriuretic peptide (ANP), PDE1 subtypes (PDE1A, 1B, and 1C), and ER stress molecules (GRP78, phosphor-PERK, PERK, phosphor-IRE1, IRE1, and ATF6). The intracellular levels of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) were measured by enzyme linked immunosorbent assay. Results Homocysteine exposure resulted in an enlargement in cell size and an increase in β-MHC and ANP expression. Homocysteine induced ER stress in H9c2 cells, shown by increased expression of GRP78 and enhanced phosphorylation of PERK and IRE1, as well as dilatation and degranulation of rough ER. The expression of PDE1A and PDE1C was significantly upregulated by homocysteine. Inhibition of ER stress or PDE1 suppressed homocysteine-induced upregulation of β-MHC and ANP and alleviated cell enlargement. In addition, the protein expression of PDE1A and PDE1C in homocysteine-exposed H9c2 cells was downregulated by the ER stress inhibitor TUDCA. Silencing of PDE1C significantly inhibited homocysteine-induced cell hypertrophy whereas knockdown of PDE1A showed minor effect. Both cAMP and cGMP levels were lowered in H9c2 cells subjected to homocysteine exposure, while only cAMP content could be restored by Lu AF58027 and TUDCA. Conclusions ER stress mediates homocysteine-induced cardiomyocyte hypertrophy via upregulating PDE1 expression. Cyclic nucleotide, in particular cAMP, is the downstream mediator of the ER stress-PDE1 signaling axis in homocysteine-induced hypertrophy.

Preparation of Cadmium Telluride Quantum Dots and Its Effects on Cyclic Adenosine Monophosphate-cAMP Response Element-Binding Proteins-Brain-Derived Neurotrophic Factor Signaling Pathway in Mouse Hippocampus

N-acetyl-L-cysteine-modified CdTe QDs (Cadmium Telluride Quantum Dots) were obtained by hydrothermal method, and DA (amino deoxyglucose), PEG (polyethylene glycol), and 9-p-D (9 polyamine acid) were obtained by ligand substitution, which were used for remodifying CdTe QDs. Successively, a novel CdTe QDs nanoma-terial, CdTe-NALC, was obtained. This composite nanometer material was characterized by ultraviolet, fluorescence spectrum, nuclear magnetic resonance hydrogen-spectrum, and other methods to study further its biocompatibility and toxic effect on the primary cultured mouse hippocampus neurons. PC12 cells were vitro-cultured and dissolved in the CdTe-NALC solution with different concentrations. After 24 h, the expression levels of proteins related to the cAMP (cyclic adenosine monophosphate)-CREB (cAMP response element-binding proteins)-BDNF (brain-derived neurotrophic factor) signaling pathway in the cells were detected by ELISA (enzyme-linked immunosorbent assay) kit. In the experiment, the DA/9-p-D/PEG-modified CdTe QDs composite nanometer material was successfully manufactured by ligand replacement. The nanoparticles had good dis-persibility with an average particle size of about 9.2 nm. DA/9-p-D/PEG modification improved the biocompatibil-ity of the QDs. CdTe composite nanomaterials could significantly reduce the cell activity of mouse hippocampal neurons and promote their apoptosis, with an evident dose-apoptosis relationship. With the increase of CDTE-NALC solution concentration, cAMP, pCREB (phosphorylated CREB), and BDNF protein content decreased (P < 0.05).

AaPKAc Regulates Differentiation of Infection Structures Induced by Physicochemical Signals From Pear Fruit Cuticular Wax, Secondary Metabolism, and Pathogenicity of Alternaria alternata.

Alternaria alternata, the casual agent of black rot of pear fruit, can sense and respond to the physicochemical cues from the host surface and form infection structures during infection. To evaluate the role of cyclic AMP-dependent protein kinase (cAMP-PKA) signaling in surface sensing of A. alternata, we isolated and functionally characterized the cyclic adenosine monophosphate-dependent protein kinase A catalytic subunit gene (AaPKAc). Gene expression results showed that AaPKAc was strongly expressed during the early stages of appressorium formation on hydrophobic surfaces. Knockout mutants ΔAaPKAc were generated by replacing the target genes via homologous recombination events. We found that intracellular cAMP content increased but PKA content decreased in ΔAaPKAc mutant strain. Appressorium formation and infection hyphae were reduced in the ΔAaPKAc mutant strain, and the ability of the ΔAaPKAc mutant strain to recognize and respond to high hydrophobicity surfaces and different surface waxes was lower than in the wild type (WT) strain. In comparison with the WT strain, the appressorium formation rate of the ΔAaPKAc mutant strain on high hydrophobicity and fruit wax extract surface was reduced by 31.6 and 49.3% 4 h after incubation, respectively. In addition, AaPKAc is required for the hypha growth, biomass, pathogenicity, and toxin production of A. alternata. However, AaPKAc negatively regulated conidia formation, melanin production, and osmotic stress resistance. Collectively, AaPKAc is required for pre-penetration, developmental, physiological, and pathological processes in A. alternata.

Evidence for functional G-coupled protein receptors 43 and 120 in subcutaneous and intramuscular adipose tissue of Angus crossbred steers.

We conducted 3 independent experiments to demonstrate functional G-coupled protein receptor 43 (GPR43) and GPR120 in bovine intramuscular (i.m.) and subcutaneous (s.c.) adipose tissues. We hypothesized that media volatile fatty acids and long-chain fatty acids would affect cAMP-activated protein kinase-alpha (AMPKα) protein expression and cAMP concentrations differently in i.m. and s.c. adipose tissue. Experiment 1: oleic acid (18:1n-9) decreased phosphorylated AMPKα protein (p-AMPKα) and the p-AMPKα/AMPKα protein ratio in i.m. preadipocytes, increased the p-AMPKα/AMPKα protein ratio in bovine satellite cells, and had no effect in s.c. preadipocytes. Experment 2: ex vivo explants from the 5th to 8th longissimus thoracic rib muscle section of Angus crossbred steers were cultured 48 hr in media containing 0.25 µM ciglitizone, 5 mM glucose, and 5 mM acetate, in the absence or the presence of 100 µM oleic acid. Oleic acid increased acetate incorporation into fatty acids and GPR43 gene expression in i.m. adipose tissue (P < 0.05), but oleic acid had no effect on fatty acid synthesis or GPR43 expression in s.c. adipose tissue. Experiment 3: fresh s.c. and i.m. adipose tissue from the 5th to 8th longissimus thoracic rib muscle section of Angus crossbred steers was transferred immediately to 6-well culture plates containing 3 mL of KHB/Hepes/5 mM glucose. Samples were preincubated with 0.5 mM theophylline plus 10 μM forskolin for 30 min, after which increasing concentrations of acetate or propionate (0, 10-3, 10-2.3, and 10-3 M) in the absence or the presence of 100 μM oleic acid or 100 µM palmitic acid (16:0) were added to the incubation media. Acetate had no effect on forskolin-stimulated cAMP production in s.c. adipose tissue but decreased cAMP in i.m. adipose tissue (P < 0.05); this indicates a functional GPR43 receptor in i.m. adipose tissue. The combination of 10-2 M acetate and oleic acid decrease cAMP production in s.c. adipose tissue, consistent with GPR120 receptor activity, but oleic acid and palmitic acid attenuated the depression of cAMP production caused by acetate in i.m. adipose tissue. Palmitic acid depressed cAMP production in s.c. adipose tissue, and increased cAMP production in i.m. adipose tissue (P < 0.05). Propionate had no effect on cAMP production in s.c. or i.m. adipose tissue. These results provide evidence for functional GPR43 receptors in i.m. adipose tissue and GPR120 receptors in s.c. adipose tissue, both of which would suppress lipolysis.

Cardiac cAMP-PKA Signaling Compartmentalization in Myocardial Infarction.

Under physiological conditions, cAMP signaling plays a key role in the regulation of cardiac function. Activation of this intracellular signaling pathway mirrors cardiomyocyte adaptation to various extracellular stimuli. Extracellular ligand binding to seven-transmembrane receptors (also known as GPCRs) with G proteins and adenylyl cyclases (ACs) modulate the intracellular cAMP content. Subsequently, this second messenger triggers activation of specific intracellular downstream effectors that ensure a proper cellular response. Therefore, it is essential for the cell to keep the cAMP signaling highly regulated in space and time. The temporal regulation depends on the activity of ACs and phosphodiesterases. By scaffolding key components of the cAMP signaling machinery, A-kinase anchoring proteins (AKAPs) coordinate both the spatial and temporal regulation. Myocardial infarction is one of the major causes of death in industrialized countries and is characterized by a prolonged cardiac ischemia. This leads to irreversible cardiomyocyte death and impairs cardiac function. Regardless of its causes, a chronic activation of cardiac cAMP signaling is established to compensate this loss. While this adaptation is primarily beneficial for contractile function, it turns out, in the long run, to be deleterious. This review compiles current knowledge about cardiac cAMP compartmentalization under physiological conditions and post-myocardial infarction when it appears to be profoundly impaired.

Melatonin Alleviates the Suppressive Effect of Hypoxanthine on Oocyte Nuclear Maturation and Restores Meiosis via the Melatonin Receptor 1 (MT1)-Mediated Pathway.

It is well known that hypoxanthine (HX) inhibits nuclear maturation of oocytes by elevating the intracellular cAMP level, while melatonin (MT) is a molecule that reduces cAMP production, which may physiologically antagonize this inhibition and restore the meiosis process. We conducted in vitro and in vivo studies to examine this hypothesis. The results showed that 10–3 M MT potentiated the inhibitory effect of HX on mouse oocyte meiosis by lowering the rate of germinal vesicle breakdown (GVBD) and the first polar body (PB1). However, 10–5 M and 10–7 M MT significantly alleviated the nuclear suppression induced by HX and restored meiosis in 3- and 6-week-old mouse oocytes, respectively. We identified that the rate-limiting melatonin synthetic enzyme AANAT and melatonin membrane receptor MT1 were both expressed in oocytes and cumulus cells at the GV and MII stages. Luzindole, a non-selective melatonin membrane receptor antagonist, blocked the activity of MT on oocyte meiotic recovery (P < 0.05). This observation indicated that the activity of melatonin was mediated by the MT1 receptor. To understand the molecular mechanism further, MT1 knockout (KO) mice were constructed. In this MT1 KO animal model, the PB1 rate was significantly reduced with the excessive expression of cAPM synthases (Adcy2, Adcy6, Adcy7, and Adcy9) in the ovaries of these animals. The mRNA levels of Nppc and Npr2 were upregulated while the genes related to progesterone synthesis (Cyp11a11), cholesterol biosynthesis (Insig1), and feedback (Lhcgr, Prlr, and Atg7) were downregulated in the granulosa cells of MT1 KO mice (P < 0.05). The altered gene expression may be attributed to the suppression of oocyte maturation. In summary, melatonin protects against nuclear inhibition caused by HX and restores oocyte meiosis via MT1 by reducing the intracellular concentration of cAMP.

TNF-α impairs EP4 signaling through the association of TRAF2-GRK2 in primary fibroblast-like synoviocytes.

Our previous study showed that chronic treatment with tumor necrosis factor-α (TNF-α) decreased cAMP concentration in fibroblast-like synoviocytes (FLSs) of collagen-induced arthritis (CIA) rats. In this study we investigated how TNF-α impairs cAMP homeostasis, particularly clarifying the potential downstream molecules of TNF-α and prostaglandin receptor 4 (EP4) signaling that would interact with each other. Using a cAMP FRET biosensor PM-ICUE3, we demonstrated that TNF-α (20 ng/mL) blocked ONO-4819-triggered EP4 signaling, but not Butaprost-triggered EP2 signaling in normal rat FLSs. We showed that TNF-α (0.02-20 ng/mL) dose-dependently reduced EP4 membrane distribution in normal rat FLS. TNF-α significantly increased TNF receptor 2 (TNFR2) expression and stimulated proliferation in human FLS (hFLS) via ecruiting TNF receptor-associated factor 2 (TRAF2) to cell membrane. More interestingly, we revealed that TRAF2 interacted with G protein-coupled receptor kinase (GRK2) in the cytoplasm of primary hFLS and helped to bring GRK2 to cell membrane in response of TNF-α stimulation, the complex of TRAF2 and GRK2 then separated on the membrane, and translocated GRK2 induced the desensitization and internalization of EP4, leading to reduced production of intracellular cAMP. Silencing of TRAF2 by siRNA substantially diminished TRAF2-GRK2 interaction, blocked the translocation of GRK2, and resulted in upregulated expression of membrane EP4 and intracellular cAMP. In CIA rats, administration of paroxetine to inhibit GRK2 effectively improved the symptoms and clinic parameters with significantly reduced joint synovium inflammation and bone destruction. These results elucidate a novel form of cross-talk between TNFR (a cytokine receptor) and EP4 (a typical G protein-coupled receptor) signaling pathways. The interaction between TRAF2 and GRK2 may become a potential new drug target for the treatment of inflammatory diseases.

RAGE-MEDIATED CELLULAR SIGNALING IS TRIGGERED BY THE ALLOSTERIC ACTIVATION OF THE AT1 RECEPTOR

Objective: We recently identified the physical interaction of a pattern recognition receptor (PRR), lectin-like oxidized LDL receptor with the GPCR, angiotensin II type 1 receptor (AT1) whereby oxLDL allosterically activates AT1. In this study, we investigated if AT1 physically interacts with another PRR, the receptor for AGE (RAGE), and ligands of RAGE could allosterically activate AT1. Design and method: We used normal rat kidney epithelial cells (NRK52E) to investigate the interaction of the endogenous receptors. We also generated five different genetically-engineered CHO cells to individually analyze the G protein and β-arrestin pathways of AT1 activation; CHO cells expressing human RAGE (CHO-RAGE), CHO cells expressing both hRAGE and hAT1 (CHO-RAGE-AT1), CHO cells expressing both hRAGE and mutated hAT1 with impaired ability to activate G protein, and CHO cells expressing both hLOX-1 and mutated hAT1 with impaired ability to activate β-arrestin Results: In NRK52E, AGE-BSA provoked the activation of MAP kinase (ERK) that was inhibited by ARB or siRNA of AT1 or RAGE. Activation of NfκB and Epithelial mesanchmal transition induced by AGE-BSA was inhibited by ARBs as well as RAGE inhibitor. In genetically engineered CHO-cells, in situ PLA assay and immunoprecipitation confirmed the physical interaction of AT1 and RAGE on cellular membrane. HMGB1, a RAGE ligand induced Gαi-dependent inhibition of cAMP production only in the presence of both RAGE and AT1 with intact G protein binding. The effect of HMGB1 on cAMP content was abolished by ARB as well as RAGE inhibitor. HMGB1 did not induce the accumulation of IP1, a downstream of Gαq signaling, in CHO cells expressing both AT1 and RAGE. Real-time imaging of cellular membrane revealed that RAGE induced endocytosis of LOX-1 that depends on the intact β-arrestin pathway of AT1, and the phenomenon was not inhibited by ARB. Conclusions: RAGE ligands mediates cellular signaling via a physical interaction between RAGE and AT1. The activation of AT1 by RAGE ligands is distinct from that by angiotensin II in terms of selective G protein activation and the effect of ARB on G protein pathway but not on β-arrestin pathway.

An Integrative Pharmacology-Based Strategy to Uncover the Mechanism of Xiong-Pi-Fang in Treating Coronary Heart Disease with Depression.

Objectives: This study aimed to explore the mechanism of Xiong-Pi-Fang (XPF) in the treatment of coronary heart disease (CHD) with depression by an integrative strategy combining serum pharmacochemistry, network pharmacology analysis, and experimental validation. Methods: An ultrahigh performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UPLC-Q-TOF/MS) method was constructed to identify compounds in rat serum after oral administration of XPF, and a component-target network was established using Cytoscape, between the targets of XPF ingredients and CHD with depression. Furthermore, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed to deduce the mechanism of XPF in treating CHD with depression. Finally, in a chronic unpredictable mild stress (CUMS)-and isoproterenol (ISO)-induced rat model, TUNEL was used to detect the apoptosis index of the myocardium and hippocampus, ELISA and western blot were used to detect the predicted hub targets, namely AngII, 5-HT, cAMP, PKA, CREB, BDNF, Bcl-2, Bax, Cyt-c, and caspase-3. Results: We identified 51 compounds in rat serum after oral administration of XPF, which mainly included phenolic acids, saponins, and flavonoids. Network pharmacology analysis revealed that XPF may regulate targets, such as ACE2, HTR1A, HTR2A, AKT1, PKIA, CREB1, BDNF, BCL2, BAX, CASP3, cAMP signaling pathway, and cell apoptosis process in the treatment of CHD with depression. ELISA analysis showed that XPF decreased Ang-II content in the circulation and central nervous system, inhibited 5-HT levels in peripheral circulation, and increased 5-HT content in the central nervous system and cAMP content in the myocardia and hippocampus. Meanwhile, western blot analysis indicated that XPF could upregulate the expression levels of PKA, CREB, and BDNF both in the myocardia and hippocampus. TUNEL staining indicated that the apoptosis index of myocardial and hippocampal cells increased in CUMS-and ISO-induced CHD in rats under depression, and XPF could increase the expression of Bcl-2, inhibit the expression of Bax, Cyt-c, and caspase-3, and rectify the injury of the hippocampus and myocardium, which exerted antidepressant and antimyocardial ischemia effects. Conclusion: Our study proposed an integrated strategy, combining serum pharmacochemistry and network pharmacology to investigate the mechanisms of XPF in treating CHD with depression. The mechanism of XPF in treating CHD with depression may be related to the activation of the cAMP signaling pathway and the inhibition of the apoptosis.

GPER mediates estrogen cardioprotection against epinephrine-induced stress.

Currently, there are no conventional treatments for stress-induced cardiomyopathy (SCM, also known as Takotsubo syndrome), and the existing therapies are not effective. The recently discovered G protein-coupled estrogen receptor (GPER) executes the rapid effects of estrogen (E2). In this study, we investigated the effects and mechanism of GPER on epinephrine (Epi)-induced cardiac stress. SCM was developed with a high dose of Epi in adult rats and human-induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs). (1) GPER activation with agonist G1/E2 prevented an increase in left ventricular internal diameter at end-systole, the decrease both in ejection fraction and cardiomyocyte shortening amplitude elicited by Epi. (2) G1/E2 mitigated heart injury induced by Epi, as revealed by reduced plasma brain natriuretic peptide and lactate dehydrogenase release into culture supernatant. (3) G1/E2 prevented the raised phosphorylation and internalization of β2-adrenergic receptors (β2AR). (4) Blocking Gαi abolished the cardiomyocyte contractile inhibition by Epi. G1/E2 downregulated Gαi activity of cardiomyocytes and further upregulated cAMP concentration in culture supernatant treated with Epi. (5) G1/E2 rescued decreased Ca2+ amplitude and Ca2+ channel current (ICa-L) in rat cardiomyocytes. Notably, the above effects of E2 were blocked by the GPER antagonist, G15. In hiPSC-CM (which expressed GPER, β1AR and β2ARs), knockdown of GPER by siRNA abolished E2 effects on increasing ICa-L and action potential duration in the stress state. In conclusion, GPER played a protective role against SCM. Mechanistically, this effect was mediated by balancing the coupling of β2AR to the Gαs and Gαi signaling pathways.