Methylanthranilate, a Food Fragrance Attenuates Skin Pigmentation through Downregulation of Melanogenic Enzymes by cAMP Suppression

Methyl anthranilate (MA) is a botanical fragrance used in food flavoring with unexplored potential in anti-pigment cosmetics. MA dose-dependently reduced melanin content without affecting cell viability, inhibited dendrite elongation and melanosome transfer in the co-culture system of human melanoma cells (MNT-1) and human keratinocyte cell line (HaCaT), and downregulated melanogenic genes, including tyrosinase, tyrosinase-related protein 1 and 2 (TRP-1, TRP-2). Additionally, MA decreased cyclic adenosine monophosphate (cAMP) production and exhibited a significant anti-pigmentary effect in Melanoderm™. These results suggest that MA is a promising anti-pigmentary agent for replacing or complementing existing anti-pigmentary cosmetics.

cAMP regulates the progesterone receptor gene expression through the protein kinase A pathway during decidualization in human immortalized endometrial stromal cells

Decidualization, a crucial process for successful pregnancy establishment and maintenance, involves endometrial stromal cell differentiation. This process is orchestrated by estradiol (E2), progesterone, and other stimuli that increase intracellular cyclic adenosine monophosphate (cAMP) levels. The intracellular progesterone receptor (PR), encoded by the PGR gene, has a key role in decidualization. This study aimed to understand the role of sex steroids and cAMP in regulating PGR expression during the in vitro decidualization of the human immortalized endometrial stromal cell line, T-HESC. We subjected the cells to individual and combined treatments of E2, medroxyprogesterone (MPA), and cAMP. Additionally, we treated cells with PR and estrogen receptor antagonists and a protein kinase A (PKA) inhibitor. We evaluated the expression of PGR isoforms and decidualization-associated genes by RT-qPCR. Our findings revealed that cAMP induced PGR-B and PGR-AB expression by activating the PKA signaling pathway, while MPA downregulated their expression through the PR. Furthermore, downstream genes involved in decidualization, such as those coding for prolactin (PRL), insulin-like growth factor-binding protein-1 (IGFBP1), and Dickkopf-1 (DKK1), exhibited positive regulation via the cAMP-PKA pathway. Remarkably, MPA-activated PR signaling induced the expression of IGFBP1 and DKK1 but inhibited that of PRL. In conclusion, we have demonstrated that the PKA signaling pathway induces PGR gene expression during in vitro decidualization of the T-HESC human endometrial stromal cell line. This study has unraveled some of the intricate regulatory mechanisms governing PGR expression during this fundamental process for implantation and pregnancy maintenance.

The ERβ-cAMP signaling pathway regulates estradiol-induced ovine oocyte meiotic arrest

Although 17β-estradiol (E2) and its receptors (ERs) are reported to play important roles in regulating oocyte maturation, the specific mechanism remains unclear. First, we performed immunohistochemistry analyses to determine the expression of the ERα and ERβ proteins in ovine ovarian tissue. Second, E2 (0.5 ng/mL and 1 μg/mL) were added to pre-IVM medium for 0 h, 1 h and 2 h. The effects of E2 (0.5 ng/mL and 1 μg/mL) on cyclic adenosine monophosphate (cAMP) level in cumulus-oocyte complexes (COCs) and on oocyte meiotic progression were evaluated by ELISA and DAPI staining respectively. Third, the effects of E2 on the gene and protein expression of ERα and ERβ in COCs were investigated by Western blotting and real-time PCR. Afterward, ERβ and cAMP regulators were added to the 2-h pretreatment medium with or without E2 (0.5 ng/mL) to explore the possible interactions among E2, cAMP and ERβ. The results showed that both ERα and ERβ proteins were expressed in ovine cumulus layers and oocytes. E2 significantly increased intra-COC cAMP levels, maintained oocyte meiotic arrest, and promoted ERβ transcript and protein expression. E2 treatment increased the cAMP concentration, which was enhanced by ERβ agonist treatment and remarkably attenuated by ERβ inhibitor treatment. Forskolin plus IBMX treatment increased ERβ protein expression in COCs (P < 0.05), and this was attenuated by Rp-cAMP treatment. In conclusion, E2 (0.5 ng/mL) increased intra-COC cAMP levels by promoting ERβ expression, thereby maintaining oocyte meiotic arrest. cAMP in COCs has a positive feedback effect on ERβ expression, which provides a novel explanation for the positive role of E2 in regulating ovine follicle development and oocyte maturation.

Caveolae-associated cAMP/Ca2+-mediated mechano-chemical signal transduction in mouse atrial myocytes

Caveolae are tiny invaginations in the sarcolemma that buffer extra membrane and contribute to mechanical regulation of cellular function. While the role of caveolae in membrane mechanosensation has been studied predominantly in non-cardiomyocyte cells, caveolae contribution to cardiac mechanotransduction remains elusive. Here, we studied the role of caveolae in the regulation of Ca2+ signaling in atrial cardiomyocytes. In Langendorff-perfused mouse hearts, atrial pressure/volume overload stretched atrial myocytes and decreased caveolae density. In isolated cells, caveolae were disrupted through hypotonic challenge that induced a temporal (<10 min) augmentation of Ca2+ transients and caused a rise in Ca2+ spark activity. Similar changes in Ca2+ signaling were observed after chemical (methyl-β-cyclodextrin) and genetic ablation of caveolae in cardiac-specific conditional caveolin-3 knock-out mice. Acute disruption of caveolae, both mechanical and chemical, led to the elevation of cAMP level in the cell interior, and cAMP-mediated augmentation of protein kinase A (PKA)-phosphorylated ryanodine receptors (at Ser2030 and Ser2808). Caveolae-mediated stimulatory effects on Ca2+ signaling were abolished via inhibition of cAMP production by adenyl cyclase antagonists MDL12330 and SQ22536, or reduction of PKA activity by H-89. A compartmentalized mathematical model of mouse atrial myocytes linked the observed changes to a microdomain-specific decrease in phosphodiesterase activity, which disrupted cAMP signaling and augmented PKA activity. Our findings add a new dimension to cardiac mechanobiology and highlight caveolae-associated cAMP/PKA-mediated phosphorylation of Ca2+ handling proteins as a novel component of mechano-chemical feedback in atrial myocytes.

Increased expression of glucagon-like peptide-1 and cystic fibrosis transmembrane conductance regulator in the ileum and colon in mouse treated with metformin

Metformin, an oral medication, is prescribed to patients with type 2 diabetes mellitus. Although the efficacy, safety, and low economic burden of metformin on patients have long been recognized, approximately 5% of the patients treated with this drug develop severe diarrhea and discontinue the treatment. We previously reported that 1,000 mg·kg^-1·day^-1 of metformin induced diarrhea in diabetic obese (db/db) mice and wood creosote (traditional medication for diarrhea) ameliorated the symptoms. In this study, we attempted to elucidate the molecular mechanisms by which metformin induces diarrhea. Cystic fibrosis transmembrane conductance regulator (CFTR) is a key ion (chloride) channel in cyclic adenosine monophosphate (cAMP)-induced diarrhea. Metformin treatment increased bile flow (bile acids and bilirubin) in the ileum of mice. In addition, the treatment was accompanied by an increase in mRNA and protein levels of CFTR in the mucosa of the ileum and colon in both wild-type (C57BL/6J) and db/db mice. Glucagon-like peptide-1 (GLP-1), as well as cholic acid, induces CFTR mRNA expression in human colon carcinoma Caco-2 cells through cAMP signaling. Although wood creosote (10 mg/kg) ameliorated diarrhea symptoms, it did not alter the mRNA levels of Glp-1 or Cftr. Similar to overeating, metformin upregulated GLP-1 and CFTR expression, which may have contributed to diarrhea symptoms in mice. Although we could not identify db/db mouse-specific factors associated with metformin-induced diarrhea, these factors may modulate colon function. Wood creosote may not interact with these factors but ameliorates diarrhea symptoms.

Fok I and Bsm I gene polymorphism of vitamin D receptor and essential hypertension: a mechanistic link

The vitamin D receptor (VDR) gene serves as a good candidate gene for susceptibility to essential hypertension. The gene regulates the renin angiotensin system by influencing blood pressure regulation. Around 3% of the human genome is regulated by the vitamin D endocrine system. Several studies have reported mixed results with respect to relationship of VDR gene and hypertension. Observational evidence supports the concept that vitamin D plays a role in the pathogenesis of cardiovascular disease and arterial hypertension which is further supported by meta-analysis and case control studies reporting how VDR polymorphism leads to the onset and development of hypertension. In this review, we summarize the existing literature on the link between VDR and hypertension, including mechanistic studies, observational data, and clinical trials showing relationship of vitamin D level and hypertension with a focus on recent findings related to genetic studies that showed the relationship of VDR gene polymorphism with vitamin D level in hypertensive and normotensive groups. As a result, determining the association of VDR polymorphisms with essential hypertension is expected to aid in the risk assessment for the condition.

Cellular Innate Biological Nano Confinements Control Cancer Metastasis Through Materials Seizing and Signaling Regulating

Cancer is a debilitating disease, causing millions of deaths annually throughout the world. Due to their adaptive ability to meet nutritional demands, cancer cells often utilize more energy than normal cells. In order to develop new strategies to treat cancer, it is necessary to understand the underlying mechanisms of energy metabolism, which is yet largely unknown. Recent studies have shown that cellular innate nanodomains are involved in cellular energy metabolism and anabolism and GPCRs signaling regulation, which have a direct effect on cell fate and functions. Therefore, harnessing cellular innate nanodomains may evoke significant therapeutic impact and shift the research focus from exogenous nanomaterials to cellular innate nanodomains, which will have great potential to develop a new treatment modality for cancer. Keeping these points in view, we briefly discuss the impact of cellular innate nanodomains and their potential for advancing cancer therapeutics, and propose the concept of innate biological nano confinements, which include any innate structural and functional nano domains both in extracellular and intracellular with spatial heterogeneity.

Pharmacological modulation of phosphodiesterase-7 as a novel strategy for neurodegenerative disorders

Neurodegenerative illness develops as a result of genetic defects that cause changes at numerous levels, including genomic products and biological processes. It entails the degradation of cyclic nucleotides, cyclic adenosine monophosphate (cAMP), and cyclic guanosine monophosphate (cGMP). PDE7 modulates intracellular cAMP signalling, which is involved in numerous essential physiological and pathological processes. For the therapy of neurodegenerative illnesses, the normalization of cyclic nucleotide signalling through PDE inhibition remains intriguing. In this article, we shall examine the role of PDEs in neurodegenerative diseases. Alzheimer's disease, Multiple sclerosis, Huntington's disease, Parkinson's disease, Stroke, and Epilepsy are related to alterations in PDE7 expression in the brain. Earlier, animal models of neurological illnesses including Alzheimer's disease, Parkinson's disease, and multiple sclerosis have had significant results to PDE7 inhibitors, i.e., VP3.15; VP1.14. In addition, modulation of CAMP/CREB/GSK/PKA signalling pathways involving PDE7 in neurodegenerative diseases has been addressed. To understand the etiology, treatment options of these disorders mediated by PDE7 and its subtypes can be the focus of future research.

Extracellular vesicle-induced cyclic AMP signaling

Second messenger signaling is required for cellular processes. We previously reported that extracellular vesicles (EVs) from stimulated cultured endothelial cells contain the biochemical second messenger, cAMP. In the current study, we sought to determine whether cAMP-enriched EVs induce second messenger signaling pathways in naïve recipient cells. Our results indicate that cAMP-enriched EVs increase cAMP content sufficient to stimulate PKA activity. The implications of our work are that EVs represent a novel intercellular mechanism for second messenger, specifically cAMP, signaling.

Antibacterial Gelidium amansii polysaccharide-based edible films containing cyclic adenosine monophosphate for bioactive packaging

A homogeneous polysaccharide (GAP), with a molecular weight of 51.8 kDa, was isolated from edible red seaweed Gelidium amansii. Composition analysis suggested GAP contained 5.31% sulfate and 17.33% 3,6-anhydro-galactose and was mainly composed of galactose. Furthermore, GAP, as a biopolymer matrix, was used to form the composite films with the small biological molecules cytidine-5'-monophosphate (CMP), adenosine-5'-monophosphate (AMP), and cyclic adenosine monophosphate (cAMP). Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectrum, and X-ray diffraction (XRD) results showed that CMP, AMP, and cAMP interacted with the film substrates and might made films more complex. Notably, the addition of CMP, AMP, and cAMP promoted the light, water vapor, and oxygen barrier ability, surface wettability, mechanical strength, and antimicrobial activity against Gram-negative and -positive bacteria. Finally, GAP-based films composited with cAMP (cAMPF) exhibited the best characteristics were applied to fish packaging and preservation at 4 °C and extended the fish shelf life. All these data suggested the potential value of cAMPF as a functional edible polysaccharide film applied in food industries.

Modification of mesenchymal stem cells by HMGB1 promotes the activity of Cav3.2 T-type calcium channel via PKA/β-catenin/γ-cystathionase pathway

Background

Mesenchymal stem cells (MSC) hold great promise for treating cardiovascular disease. Recently, we genetically modified MSCs with high mobility group box 1 (HMGB1), and these cells demonstrated high mobility by efficient migrating and homing to target neointima. The possible mechanism was investigated in the current study.

Methods

Rat MSCs were transfected with lentivirus containing HMGB1 cDNA to yield MSC-H cell line stably overexpressing HMGB1. The MSC-C cells which were transfected with empty lentivirus served as negative control, and the differentially expressed genes were analyzed by microarray. The cell mobility was determined by transwell migration assay. Intracellular free calcium and the expression of Cav3.2 T-type calcium channel (CACNA1H) were assayed to analyze activity of CACNA1H-mediated calcium influx. H₂S production and γ-cystathionase expression were examined to assess the activity of γ-cystathionase/H₂S signaling. The interaction of HMGB1 with γ-cystathionase in MSC-H cells was analyzed by co-immunoprecipitation. Luciferase reporter assay was performed to determine whether the promoter activity of γ-cystathionase was regulated by interaction of β-catenin and TCF/LEF binding site. Intercellular cAMP, PKA activity, phosphorylation of β-catenin, and GSK3β were investigated to reveal cAMP/PKA mediated β-catenin activation.

Result

Microarray analysis revealed that differentially expressed genes were enriched in cAMP signaling and calcium signaling. CACNA1H was upregulated to increase intracellular free calcium and MSC-H cell migration. Blockage of CACNA1H by ABT-639 significantly reduced intracellular free calcium and cell migration. The γ-cystathionase/H₂S signaling was responsible for CACNA1H activation. H₂S production was increased with high expression of γ-cystathionase in MSC-H cells, which was blocked by γ-cystathionase inhibitor DL-propargylglycine. Upregulation of γ-cystathionase was not attributed to interaction with HMGB1 overexpressed in MSC-H cells although γ-cystathionase was suggested to co-immunoprecipitate with oxidized HMGB1. Bioinformatics analysis identified a conserved TCF/LEF binding site in the promoter of γ-cystathionase gene. Luciferase reporter assay confirmed that the promoter had positive response to β-catenin which was activated in MSC-H cells. Finally, cAMP/PKA was activated to phosphorylate β-catenin at Ser657 and GSK3β, enabling persisting activation of Wnt/β-catenin signaling in MSC-H cells.

Conclusion

Our study revealed that modification of MSCs with HMGB1 promoted CACNA1H-mediated calcium influx via PKA/β-catenin/γ-cystathionase pathway. This was a plausible mechanism for high mobility of MSC-H cell line.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02677-z.

Cis-bifenthrin inhibits cortisol and aldosterone biosynthesis in human adrenocortical H295R cells via cAMP signaling cascade

Cis-bifenthrin (cis-BF) is a common-used pyrethroid insecticide frequently detected in environmental and biological matrices. Mounting evidence highlights the endocrine disrupting effects of cis-BF due to anti-estrogenic or anti-androgenic activity. However, little is known about the exposure effects of cis-BF on adrenal cortex function. In this study, effects of cis-BF on biosynthesis of adrenal steroids, as well as the potential mechanisms were investigated in human adrenocortical carcinoma (H295R) cells. Cis-BF decreased basal production levels of cortisol and aldosterone, as well as cAMP-induced production of cortisol. Both he basal and cAMP-stimulated transcriptional levels of several steroidogenic genes were significantly down-regulated by cis-BF. As an important rate-limiting enzyme in steroidogenesis, the protein level of StAR was prohibited by cis-BF on both basal and cAMP-induced conditions. Intracellular level of cAMP was significantly reduced by cis-BF. Overall, these data suggest that cis-BF may inhibit the biosynthesis of cortisol and aldosterone via disrupting cAMP signaling cascade.

Alarin moderated myocardial hypertrophy via inhibiting cyclic adenosine monophosphate/protein kinase A signaling pathway to attenuate autophagy

Alarin could alleviate myocardial infarction-induced heart failure. The present study was to explore whether alarin could alleviate myocardial hypertrophy via inhibiting cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) signaling pathway to attenuate autophagy. Myocardial hypertrophy was induced by angiotensin (Ang) II infusion in vivo in mice and by Ang II treatment of neonatal rat cardiomyocytes (NRCMs) in vitro. The Ang II-induced hypertrophy and fibrosis of the heart were alleviated after alarin administration in mice. The increased atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and beta-myosin heavy chain (β-MHC), and the decreased alpha-myosin heavy chain (α-MHC) induced by Ang II were reversed by alarin treatment in NRCMs. Alarin inhibited the increases of cAMP and PKA in NRCMs. Treatment with cAMP or overexpression of PKA blocked the attenuating effects of alarin on Ang II-induced hypertrophy in NRCMs. Alarin reduced the Ang II-induced increases of LC3, Beclin 1, autophagy-related gene (Atg)3 and Atg5 in NRCMs. The overexpression of cAMP and PKA reversed the alleviating effects of alarin on the increased autophagy induced by Ang II in NRCMs. These results indicated that alarin could moderate cardiac remodeling. Alarin improved myocardial hypertrophy via inhibiting the cAMP/PKA signaling pathway to attenuate autophagy.

Research progress of phosphodiesterase inhibitors in inflammatory bowel disease treatment

Inflammatory bowel disease is a recurrent chronic intestinal inflammatory disease with unknown etiology and no effective treatment. Phosphodiesterase (PDE) regulates a variety of physiological and pathophysiological processes by mediating the hydrolysis of intracellular second messengers cyclic adenosine monophosphate and cyclic guanosine monophosphate. In recent years, a series of researches suggest that PDE inhibitors such as several PDE4 inhibitors, PDE5 inhibitors (sildenafil, tadalafil and vardenafil), PDE3 inhibitors (cilostazol), PDE9 inhibitor (PF-04447943) and PDE3/PDE4 double inhibitor (pumafentrine) have ameliorating effect on experimental colitis in animals. In clinical trials, PDE4 inhibitor apremilast showed more therapeutic advantage than tetomilast. This article reviews the recent research progress of PDE inhibitors in treatment of inflammatory bowel disease.

Enhanced ATP and antioxidant levels for cAMP biosynthesis by Arthrobacter sp. CCTCC 2013431 with polyphosphate addition

OBJECTIVES

When citrate and pyruvate were utilized to strengthen ATP generation for high cAMP production, oxidative stress became more severe in cells resulting in lower cell viability and cAMP formation at the late fermentation phase. To further improve cAMP biosynthesis, the effects of polyphosphate on cAMP fermentation performance together with intracellular ATP and oxidation levels were investigated under high oxidative stress condition and then high efficient cAMP fermentation process based on polyphosphate and salvage synthesis was developed and studied.

RESULTS

With 2 g/L-broth sodium hexametaphosphate added at 24 h was determined as the optimal condition for cAMP production by Arthrobacter sp. CCTCC 2013431 in shake flasks. Under high oxidative stress condition caused by adding 15 mg/L-broth menadione, cAMP contents and cell viability were improved greatly due to hexametaphosphate addition and also exceeded those of control (without hexametaphosphate and menadione added) when fermentations were conducted in a 7 L bioreactor. Meanwhile, ATP levels and antioxidant capacity were improved obviously by hexametaphosphate as well. Moreover, a fermentation process with hexametaphosphate and hypoxanthine coupling added was developed by which cAMP concentration reached 7.25 g/L with an increment of 87.1% when compared with only hypoxanthine added batch and the high ROS contents generated from salvage synthesis were reduced significantly.

CONCLUSION

Polyphosphate could improve intracellular ATP levels and antioxidant capacity significantly under high oxidative stress condition resulting in enhanced cell viability and cAMP fermentation production no matter by de novo synthesis or salvage synthesis.

Dose dependent effect of cilostazol in induced testicular ischemia reperfusion via modulation of HIF/VEGF and cAMP/SIRT1 pathways

Twisting of the spermatic cord is a common dangerous health problem that may be accompanied with testicular necrosis and infertility. Cilostazol (CLZ) is a selective phosphodiesterase (PDE) 3A inhibitor used for treatment of intermittent claudication. It has a great role in myocardial, spinal cord and hepatic ischaemia/reperfusion. However, till now, there are no researches evaluating its role in testicular ischaemia/reperfusion (TIR). The current work studies its capability to improve TIR induced injury with more concentration on the mechanisms involved in such effect. Four groups of animals were included: sham, TIR induced group, TIR plus CLZ low dose (10 mg/kg), TIR plus CLZ high dose (30 mg/kg). Our results proved that TIR had significant decrease of the serum ELISA of testosterone, marked disturbances in oxidative stress evaluated parameters as malondialdehyde (MDA), reduced glutathione (GSH), total antioxidant capacity (TAC), ELISA measurement of tumor necrosis factor alpha (TNFα) and interleukin 1 beta (IL1β) inflammatory mediators, apoptotic marker (caspase3) using western blotting, immunohistochemistry of hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF). TIR reduced the protective agents as cyclic adenosine monophosphate (cAMP) and sirtuin-1 (SIRT1) by ELISA method with marked germinal cell apoptosis. The biochemical results were confirmed by the histopathological findings that showed marked decrease in both Johnsen's score and Cosentino's score. However, treatment with CLZ significantly reversed the profound TIR damaging effects, on the basis of its anti-inflammatory, anti-oxidant, and anti-apoptotic activities with recuperation of the testicular vascularity. Modulation of HIF/VEGF and cAMP/SIRT1 pathways showed a great role in mediating such effect.

[Effect of electroacupuncture on urodynamics of neurogenic bladder and PACAP/cAMP/PKA signaling pathway in detrusor tissue of rats after suprasacral spinal cord injury]

OBJECTIVE

To observe the effect of electroacupuncture (EA) on urodynamics of neurogenic bladder and pituitary adenylate cyclase activating peptide(PACAP)/cyclic adenosine monophosphate (cAMP)/protein kinase A(PKA) signaling pathway in detrusor tissue of rats after suprasacral spinal cord injury (SCI), so as to explore its possible mechanism in improving detrusor hyperreflexia bladder function after shock stage of suprasacral SCI.

METHODS

Female SD rats were randomly divided into control, sham operation, model and EA groups, with 12 rats in each group. T10 spinal cord transection (SCT) was performed by surgery. Rats in the EA group were given EA (10 Hz/50 Hz, 20 min) at "Ciliao" (BL32), "Zhongji" (CV3) and "Sanyinjiao" (SP6) once daily for 7 days. After the intervention, urodynamics testing was detected in each group. HE staining was used to observe the morphological changes of bladder detrusor. The protein and mRNA expression of PACAP38 in detrusor was detected by immunohistochemistry, Western blot and real-time quantitive PCR, respectively. The contents of cAMP and PKA were determined by ELISA.

RESULTS

Compared with the control and sham operation groups, the maximum bladder capacity and bladder com-pliance, and the protein and mRNA expression of PACAP38, and the contents of cAMP and PKA of the model group were significantly decreased (P<0.01, P<0.05), while the base pressure and leakage point pressure of bladder were significantly increased (P<0.01). After EA intervention, the above indexes were all reversed in the EA group relevant to those of the model group (P<0.01, P<0.05).

CONCLUSION

EA at BL32, CV3 and SP6 can improve the bladder function in rats with bladder detrusor hyperreflexia after SCI, which may be related to its effect in activating the PACAP/cAMP/PKA signaling pathway in detrusor tissue.

Enhanced endogenous amino acids and energy metabolism level for cAMP biosynthesis by Arthrobacter sp. CCTCC 2013431 with citrate as cosubstrate

OBJECTIVES

In our previous study, citrate was used as auxiliary energy substance for improving cAMP fermentation performance, however, the regulation mechanism of citrate on improved cAMP contents was not clear. To elucidate the regulation mechanism, cAMP fermentations with/without citrate addition were conducted in a 7 L fermentor using Arthrobacter sp. CCTCC 2013431 and assays on key enzymes activities, energy metabolism level, amino acids contents and peroxidation level were performed.

RESULTS

With 3 g/L-broth sodium citrate added, cAMP concentration and conversion yield from glucose reached 4.34 g/L and 0.076 g/g which were improved by 30.7% and 29.8%, respectively, when compared with those of control. Citrate changed carbon flux distribution among different routes and more carbon flux was directed into pentose phosphate pathway beneficial to cAMP synthesis. Meanwhile, energy metabolism together with precursor amino acids levels were improved significantly owing to strengthened metabolic intensity of tricarboxylate cycle by exogenous citrate utilization which provided energy and substance basis for cAMP production. Moreover, higher glutamate synthesis and oxidative stress caused by citrate addition consumed excessive NADPH derived from pentose phosphate pathway by which feedback suppression for pentose phosphate pathway was relieved efficiently.

CONCLUSION

Citrate promoted cAMP fermentation production by Arthrobacter sp. CCTCC 2013431 due to enhanced precursor amino acids, energy metabolism level and relieved feedback suppression for pentose phosphate pathway.

Taurochenodeoxycholic acid mediates cAMP-PKA-CREB signaling pathway

Taurochenodeoxycholic acid (TCDCA) is one of the main effective components of bile acid, playing critical roles in apoptosis and immune responses through the TGR5 receptor. In this study, we reveal the interaction between TCDCA and TGR5 receptor in TGR5-knockdown H1299 cells and the regulation of inflammation via the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA)-cAMP response element binding (CREB) signal pathway in NR8383 macrophages. In TGR5-knockdown H1299 cells, TCDCA significantly activated cAMP level via TGR5 receptor, indicating TCDCA can bind to TGR5; in NR8383 macrophages TCDCA increased cAMP content compared to treatment with the adenylate cyclase (AC) inhibitor SQ22536. Moreover, activated cAMP can significantly enhance gene expression and protein levels of its downstream proteins PKA and CREB compared with groups of inhibitors. Additionally, TCDCA decreased tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, IL-8 and IL-12 through nuclear factor kappa light chain enhancer of activated B cells (NF-κB) activity. PKA and CREB are primary regulators of anti-inflammatory and immune response. Our results thus demonstrate TCDCA plays an essential anti-inflammatory role via the signaling pathway of cAMP-PKA-CREB induced by TGR5 receptor.

GIPR antagonist antibodies conjugated to GLP-1 peptide are bispecific molecules that decrease weight in obese mice and monkeys

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) regulate glucose and energy homeostasis. Targeting both pathways with GIP receptor (GIPR) antagonist antibody (GIPR-Ab) and GLP-1 receptor (GLP-1R) agonist, by generating GIPR-Ab/GLP-1 bispecific molecules, is an approach for treating obesity and its comorbidities. In mice and monkeys, these molecules reduce body weight (BW) and improve many metabolic parameters. BW loss is greater with GIPR-Ab/GLP-1 than with GIPR-Ab or a control antibody conjugate, suggesting synergistic effects. GIPR-Ab/GLP-1 also reduces the respiratory exchange ratio in DIO mice. Simultaneous receptor binding and rapid receptor internalization by GIPR-Ab/GLP-1 amplify endosomal cAMP production in recombinant cells expressing both receptors. This may explain the efficacy of the bispecific molecules. Overall, our GIPR-Ab/GLP-1 molecules promote BW loss, and they may be used for treating obesity.

Inhibition of matrix metalloproteinase-9 secretion by dimethyl sulfoxide and cyclic adenosine monophosphate in human monocytes

BACKGROUND

Matrix metalloproteinases (MMPs), including MMP-9, are an integral part of the immune response and are upregulated in response to a variety of stimuli. New details continue to emerge concerning the mechanistic and regulatory pathways that mediate MMP-9 secretion. There is significant evidence for regulation of inflammation by dimethyl sulfoxide (DMSO) and 3',5'-cyclic adenosine monophosphate (cAMP), thus investigation of how these two molecules may regulate both MMP-9 and tumor necrosis factor α (TNFα) secretion by human monocytes was of high interest. The hypothesis tested in this study was that DMSO and cAMP regulate MMP-9 and TNFα secretion by distinct mechanisms.

AIM

To investigate the regulation of lipopolysaccharide (LPS)-stimulated MMP-9 and tumor necrosis factor α secretion in THP-1 human monocytes by dimethyl sulfoxide and cAMP.

METHODS

The paper describes a basic research study using THP-1 human monocyte cells. All experiments were conducted at the University of Missouri-St. Louis in the Department of Chemistry and Biochemistry. Human monocyte cells were grown, cultured, and prepared for experiments in the University of Missouri-St. Louis Cell Culture Facility as per accepted guidelines. Cells were treated with LPS for selected exposure times and the conditioned medium was collected for analysis of MMP-9 and TNFα production. Inhibitors including DMSO, cAMP regulators, and anti-TNFα antibody were added to the cells prior to LPS treatment. MMP-9 secretion was analyzed by gel electrophoresis/western blot and quantitated by ImageJ software. TNFα secretion was analyzed by enzyme-linked immuno sorbent assay. All data is presented as the average and standard error for at least 3 trials. Statistical analysis was done using a two-tailed paired Student t-test. P values less than 0.05 were considered significant and designated as such in the Figures. LPS and cAMP regulators were from Sigma-Aldrich, MMP-9 standard and antibody and TNFα antibodies were from R&D Systems, and amyloid-β peptide was from rPeptide.

RESULTS

In our investigation of MMP-9 secretion from THP-1 human monocytes, we made the following findings. Inclusion of DMSO in the cell treatment inhibited LPS-induced MMP-9, but not TNFα, secretion. Inclusion of DMSO in the cell treatment at different concentrations inhibited LPS-induced MMP-9 secretion in a dose-dependent fashion. A cell-permeable cAMP analog, dibutyryl cAMP, inhibited both LPS-induced MMP-9 and TNFα secretion. Pretreatment of the cells with the adenylyl cyclase activator forskolin inhibited LPS-induced MMP-9 and TNFα secretion. Pretreatment of the cells with the general cAMP phosphodiesterase inhibitor IBMX reduced LPS-induced MMP-9 and TNFα in a dose-dependent fashion. Pre-treatment of monocytes with an anti-TNFα antibody blocked LPS-induced MMP-9 and TNFα secretion. Amyloid-β peptide induced MMP-9 secretion, which occurred much later than TNFα secretion. The latter two findings strongly suggested an upstream role for TNFα in mediating LPS-stimulate MMP-9 secretion.

CONCLUSION

The cumulative data indicated that MMP-9 secretion was a distinct process from TNFα secretion and occurred downstream. First, DMSO inhibited MMP-9, but not TNFα, suggesting that the MMP-9 secretion process was selectively altered. Second, cAMP inhibited both MMP-9 and TNFα with a similar potency, but at different monocyte cell exposure time points. The pattern of cAMP inhibition for these two molecules suggested that MMP-9 secretion lies downstream of TNFα and that TNFα may a key component of the pathway leading to MMP-9 secretion. This temporal relationship fit a model whereby early TNFα secretion directly led to later MMP-9 secretion. Lastly, antibody-blocking of TNFα diminished MMP-9 secretion, suggesting a direct link between TNFα secretion and MMP-9 secretion.

An in vitro bioassay for evaluating the effect of inhaled bronchodilators on airway smooth muscle

PURPOSE

The development of inhaled drug products is expensive and involves time-consuming pharmacokinetic (PK) and pharmacodynamic (PD) studies. There are few in vitro cell-based assays to evaluate the disposition and action of orally inhaled drugs to guide early product development and minimise risk. The aim of the present study was to develop a co-culture bioassay, combining an airway epithelial cell line (Calu-3) with cultured human primary airway smooth muscle cells (ASM), integrated with apparatus to deliver pharmaceutical aerosols.

METHODS

An assay for measuring cyclic adenosine monophosphate (cAMP) in ASM derived from healthy donors was adapted to provide a biochemical surrogate for ASM relaxation. Concentration-response curves for cAMP were established for three drugs that elicit ASM relaxation: isoprenaline (ISO), forskolin (FOR) and salbutamol sulphate. The ASM bioassay was incorporated into a co-culture model in which air-interfaced Calu-3 cell layers, representing the permeability barrier of the airway epithelium, were grown on transwell inserts above ASM cells cultured in the well of the base-plate. The sensitivity of this bioassay to salbutamol delivered using different formulations and aerosol products was evaluated.

RESULTS

ASM responded with concentration dependent increases in cAMP when exposed to 10^-9 to 10^-5 M ISO, FOR or salbutamol sulphate solutions for 15 or 30 min. Salbutamol formulated with different counter ions elicited differential cAMP responses in ASM (xinafoate > base = sulphate) suggesting that this bioassay could discriminate between formulations with different potency. A similar rank order of potency was observed for the different salbutamol salts when applied as aerosols to the co-culture model.

DISCUSSION

We have developed a novel bioassay using human ASM in co-culture with human respiratory epithelial cells to better mimic various elements that contribute to the rate and extent of local drug availability in the lungs following topical administration. The bioassay offers an opportunity to investigate the factors determining the activity of inhaled bronchodilator drugs in a more biologically relevant system than that has previously been described and with further development and validation, this novel bioassay could provide a method to guide the more efficient development of inhaled bronchodilators, reducing the current reliance on in vivo studies.

Commentary: Phosphodiesterase 4 inhibitors as potential adjunct treatment targeting the cytokine storm in COVID-19

The most severe presentation of COVID-19 is characterized by a hyperinflammatory state attributed to the massive pro-inflammatory cytokine release, called "cytokine storm". Several specific anti-inflammatory/immunosuppressive agents are being evaluated by ongoing clinical trials; however, there is currently insufficient evidence for their efficacy and safety in COVID-19 treatment. Given the role of phosphodiesterase 4 (PDE) 4 and cyclic adenosine monophosphate in the inflammatory response, we hypothesize that selective PDE4 inhibition may attenuate the cytokine storm in COVID-19, through the upstream inhibition of pro-inflammatory molecules, particularly TNF-α, and the regulation of the pro-inflammatory/anti-inflammatory balance. Conversely, other anti-cytokine agents lead to the downstream inhibition of specific targets, such as IL-1, IL-6 or TNF-α, and may not be efficient in blocking the cytokine storm, once it has been triggered. Due to their mechanism of action targeting an early stage of the inflammatory response and ameliorating lung inflammation, we believe that selective PDE4 inhibitors may represent a promising treatment option for the early phase of COVID-19 pneumonia before the cytokine storm and severe multiorgan dysfunction take place. Furthermore, PDE4 inhibitors present several advantages including an excellent safety profile; the oral route of administration; the convenient dosing; and beneficial metabolic properties. Interestingly, obesity and diabetes mellitus type 2 have been reported to be risk factors for the severity of COVID-19. Therefore, randomized clinical trials of PDE4 inhibitors are necessary to explore their potential therapeutic effect as an adjunct to supportive measures and other therapeutic regiments.

Chronic morphine induces cyclic adenosine monophosphate formation and hyperpolarization-activated cyclic nucleotide-gated channel expression in the spinal cord of mice

Chronic morphine exposure persistently activates Gαi/o protein-coupled receptors and enhances adenylyl cyclase (AC) activity, which can increase cyclic adenosine monophosphate (cAMP) production. Direct binding of cAMP to the cytoplasmic site on hyperpolarization-activated cyclic nucleotide-gated (HCN) channels increases the probability of channel opening. HCN channels play a prominent role in chronic pain the disease that shares some common mechanisms with opioid tolerance. This compensatory AC activation may be responsible for the induction of morphine-induced analgesic tolerance. We investigated spinal cAMP formation and expression of HCN2 in the spinal cord, and observed the effect of AC inhibition on the induction of morphine analgesic tolerance. We found that chronic morphine-induced antinociceptive tolerance increased spinal cAMP formation and the expression of spinal HCN2. Inhibition of spinal AC partially blocked chronic morphine-induced cAMP formation and prevented the induction of morphine-induced analgesic tolerance. Inhibition of HCN2 also showed a partial preventive effect on morphine-induced tolerance, hypothermia tolerance and also the right-shift of the dose-response curve. We conclude that repeated morphine treatment increases AC activity and cAMP formation, and also spinal HCN2 expression, blockade of AC or HCN2 can prevent the development of morphine-induced analgesic tolerance.

Cyclic AMP represses pathological MEF2 activation by myocyte-specific hypo-phosphorylation of HDAC5

Class IIa histone deacetylases (HDACs) critically regulate cardiac function through the repression of the activity of myocyte enhancer factor 2 (MEF2)-dependent gene programs. Protein kinase D (PKD) and Ca²⁺/Calmodulin-dependent kinase II (CaMKII) activate MEF2 by phosphorylating distinct HDAC isoforms and thereby creating 14-3-3 binding sites for nucleo-cytoplasmic shuttling. Recently, it has been shown that this process is counteracted by cyclic AMP (cAMP)-dependent signaling. Here, we investigated the specific mechanisms of how cAMP-dependent signaling regulates distinct HDAC isoforms and determined their relative contributions to the protection from pathological MEF2 activation. We found that cAMP is sufficient to induce nuclear retention and to blunt phosphorylation of the 14-3-3 binding sites of HDAC5 (Ser259/498) and HDAC9 (Ser218/448) but not HDAC4 (Ser246/467/632). These regulatory events could be observed only in cardiomyocytes and myocyte-like cells but not in non-myocytes, pointing to an indirect myocyte-specific mode of action. Consistent with one previous report, we found that blunted phosphorylation of HDAC5 and HDAC9 was mediated by protein kinase A (PKA)-dependent inhibition of PKD. However, we show by the use of neonatal cardiomyocytes derived from genetic HDAC mouse models that endogenous HDAC5 but not HDAC9 contributes specifically to the repression of endogenous MEF2 activity. HDAC4 contributed significantly to the repression of MEF2 activity but based on the mechanistic findings of this study combined with previous results we attribute this to PKA-dependent proteolysis of HDAC4. Consistently, cAMP-induced repression of agonist-driven cellular hypertrophy was blunted in cardiomyocytes deficient for both HDAC5 and HDAC4. In conclusion, cAMP inhibits MEF2 through both nuclear accumulation of hypo-phosphorylated HDAC5 and through a distinct HDAC4-dependent mechanism.

Cyclic adenosine monophosphate in acute ischemic stroke: some to update, more to explore

The development of effective treatment for ischemic stroke, which is a common cause of morbidity and mortality worldwide, remains an unmet goal because the current first-line treatment management interventional therapy has a strict time window and serious complications. In recent years, a growing body of evidence has shown that the elevation of intracellular and extracellular cyclic adenosine monophosphate (cAMP) alleviates brain damage after ischemic stroke by attenuating neuroinflammation in the central nervous system and peripheral immune system. In the central nervous system, upregulated intracellular cAMP signaling can alleviate immune-mediated damage by restoring neuronal morphology and function, inhibiting microglia migration and activation, stabilizing the membrane potential of astrocytes and improving the cellular functions of endothelial cells and oligodendrocytes. Enhancement of the extracellular cAMP signaling pathway can improve neurological function by activating the cAMP-adenosine pathway to reduce immune-mediated damage. In the peripheral immune system, cAMP can act on various immune cells to suppress peripheral immune function, which can alleviate the inflammatory response in the central nervous system and improve the prognosis of acute cerebral ischemic injury. Therefore, cAMP may play key roles in reducing post-stroke neuroinflammatory damage. The protective roles of the cAMP indicate that the cAMP enhancing drugs such as cAMP supplements, phosphodiesterase inhibitors, adenylate cyclase agonists, which are currently used in the treatment of heart and lung diseases. They are potentially able to be applied as a new therapeutic strategy in ischemic stroke. This review focuses on the immune-regulating roles and the clinical implication of cAMP in acute ischemic stroke.

Effects of cyclic adenosine monophosphate modulators on maturation and quality of vitrified-warmed germinal vesicle stage mouse oocytes

BACKGROUND

It is still one of the unresolved issues if germinal vesicle stage (GV) oocytes can be successfully cryopreserved for fertility preservation and matured in vitro without damage after warming. Several studies have reported that the addition of cyclic adenosine monophosphate (cAMP) modulators to in vitro maturation (IVM) media improved the developmental potency of mature oocytes though vitrification itself provokes cAMP depletion. We evaluated whether the addition of cAMP modulators after GV oocytes retrieval before vitrification enhances maturation and developmental capability after warming of GV oocytes.

METHODS

Retrieved GV oocytes of mice were divided into cumulus-oocyte complexes (COCs) and denuded oocytes (DOs). Then, GV oocytes were cultured with or without dibutyryl-cAMP (dbcAMP, cAMP analog) and 3-isobutyl-l-methylxanthine (phosphodiesterase inhibitor) during the pre-vitrification period for 30 min.

RESULTS

One hour after warming, the ratio of oocytes that stayed in the intact GV stage was significantly higher in groups treated with cAMP modulators. After 18 h of IVM, the percentage of maturation was significantly higher in the COC group treated with dbcAMP. The expression of F-actin, which is involved in meiotic spindle migration and chromosomal translocation, is likewise increased in this group. However, there was no difference in chromosome and spindle organization integrity or developmental competence between the MII oocytes of all groups.

CONCLUSIONS

Increasing the intracellular cAMP level before vitrification of the GV oocytes maintained the cell cycle arrest, and this process may facilitate oocyte maturation after IVM by preventing cryodamage and synchronizing maturation between nuclear and cytoplasmic components. The role of cumulus cells seems to be essential for this mechanism.

The Chronic Adverse Effect of Chloroquine on Kidney in Rats through an Autophagy Dependent and Independent Pathways

BACKGROUND

Chloroquine (CQ), a classic autophagy inhibitor, is used clinically for malaria prophylaxis and pulmonary hypertension treatment. The adverse effects of CQ on morphological and functional changes in the kidney were investigated in the current study due to CQ accumulation in the kidney.

METHODS

Twelve male Sprague-Dawley rats were randomly divided into 2 groups for 4 weeks: group 1, control (n = 6); and group 2, CQ administration group (50 mg-1·kg per day ip; n = 6). Serum aldosterone and vasopressin were measured by radioimmunoassay. Immunofluorescence was used to colocalize Tunel with aquaporin 1, aquaporin 2 (AQP2), and Tamm-Horsfall protein. Expression of AQP2 and mineralocorticoid (MR) was detected by western blot and immunohistochemistry.

RESULTS

In the present study, 4 weeks of CQ administration were shown to induce severe kidney injury, including glomerular sclerosis and tubular cells apoptosis, especially distal tubular cells. Decreased expression of LC3II/I and p-AKT was demonstrated in CQ-treated rats. Glomerular and proximal tubule injury were associated with impaired autophagy flux, and distal tubule injury may be associated with downregulated cyclic adenosine monophosphate (cAMP)/PKA/AKT signaling. Both MR and AQP2, which are mainly located in the distal tubule and collecting duct, were significantly reduced in CQ-treated rats, thus leading to increased exosomal secretion of AQP2 in urine. Additionally, chronic CQ administration increased aldosterone and vasopressin levels in serum, but lowered the blood pressure, glomerular filtration rate, and urine concentration.

CONCLUSIONS

CQ administration damages glomerular, proximal tubule autophagy, and severe distal tubular cells apoptosis by inhibiting cAMP/PKA/AKT signaling.

Flavonoids reduces lipopolysaccharide-induced release of inflammatory mediators in human bronchial epithelial cells: Structure-activity relationship

Flavonoids are polyphenolic compounds that are widely present in food and Chinese medicine. The aim of the present study was to identify the flavonoids with anti-inflammatory effects in the airway; and to determine the role of anti-oxidant and cyclic adenosine monophosphate (cAMP) in the anti-inflammatory effect. Human bronchial epithelial BEAS-2B cells were exposed to bacterial endotoxin lipopolysaccharide (LPS) in the absence or presence of different flavonoids, which are categorized according to their chemical structures in seven subclasses [anthocyanidins, chalcones, flavanes, flavanones, flavones, flavonols, isoflavones]. Among the 17 flavonoids tested, only apigenin (flavones), luteolin (flavones), daidzein (isoflavones) and genistein (isoflavones) reduced LPS-induced release of inflammatory cytokines/chemokines interleukin (IL)-6, IL-8 and monocyte chemoattractant protein-1 in BEAS-2B cells. Quercetin caused further increase in LPS-induced IL-6 and IL-8 levels. It alone significantly increased nuclear factor-kappa B (NF-κB) p65 activity and the cellular oxidative stress marker malondialdehyde (MDA) level in BEAS-2B cells. By contrast, apigenin and genistein reduced LPS-induced increases in nuclear NF-κB activity and MDA level. Apigenin and genistein, but not quercetin, increased the cAMP level in BEAS-2B cells, and the cell-permeable cAMP analogue, 8-Br-cAMP, inhibited LPS-induced increase of IL-8 level. These findings suggest that the presence of C5-OH, C7-OH, C2=C3 and C4=O functional groups in the flavonoids is associated with greater anti-inflammatory effect, while that of C3-OH or glycosylation group at the A-ring greatly decreased the anti-inflammatory effect. The anti-inflammatory effect of these flavonoids may be related to their anti-oxidant properties, and partly to their ability in increasing cAMP level.

Cyclic Adenosine Monophosphate Promotes Odonto/Osteogenic Differentiation of Stem Cells from the Apical Papilla via Suppression of Transforming Growth Factor Beta 1 Signaling

INTRODUCTION

Stem cells from the apical papilla (SCAPs) possess strong odonto/osteogenic differentiation potential. This study investigated the effect of cyclic adenosine monophosphate (cAMP) on odonto/osteogenic differentiation of SCAPs and the underlining interplay between cAMP and transforming growth factor beta 1 (TGF-β1).

METHODS

SCAPs were stimulated with an activator of cAMP (forskolin) in the presence of either TGF-β1 or a TGF-β1 inhibitor. The amounts of calcium mineral deposition and alkaline phosphatase activity were determined. Quantitative real-time polymerase chain reaction was performed to elucidate cAMP on the TGF-β1-mediated odonto/osteogenic differentiation of SCAPs. The effect of cAMP on the phosphorylation of Smad2/Smad3 and extracellular-regulated kinase (ERK)/P38 induced by TGF-β1 was analyzed by Western blotting.

RESULTS

Cotreatment with forskolin and a TGF-β1 inhibitor enhanced alkaline phosphatase activity and deposition of calcium minerals in SCAPs. Moreover, the TGF-β1 inhibitor synergized the effect of forskolin on the expression of type I collagen and runt-related transcription factor 2. The results of Western blotting revealed that forskolin attenuated the unregulated expression of the phosphorylation of Smad3 and ERK induced by TGF-β1, and a cAMP inhibitor (H89) antagonized this effect.

CONCLUSIONS

This study showed that cAMP signaling exerts its up-regulating effects on the odonto/osteogenic differentiation of SCAPs by interfering with TGF-β1 signaling via inhibiting Smad3 and ERK phosphorylation.

Effect of phosphodiesterase (1B, 2A, 9A and 10A) inhibitors on central nervous system cyclic nucleotide levels in rats and mice

Phosphodiesterase (PDE) inhibition has been broadly investigated as a target for a wide variety of indications including central nervous system (CNS) disorders. Cyclic nucleotide (cNT) changes within associated tissues may serve as a biomarker of PDE inhibition. We recently developed robust sample harvesting and bioanalytical methods to quantify cNT levels in rodent brain and cerebrospinal fluid (CSF). Herein, we report on the application of those methods to study rodent species-specific and rodent brain region-specific cNT changes following individual or concomitant PDE inhibitor administration. Male Sprague Dawley (Crl:CD^® [SD]) rats were dosed subcutaneously (sc) with a PDE1B inhibitor (DNS-0056), a PDE2A inhibitor (PF-05180999), a PDE9A inhibitor (PF-4447943), and a PDE10A inhibitor (MP10), each at a single dose of 10 or 30 mg/kg, or concomitantly with all 4 inhibitors at 10 mg/kg each. Male Carworth Farms (Crl:CF1 ^®[CF-1]) mice were dosed intraperitoneally (ip) with the four individual inhibitors at a single dose of 10 mg/kg or concomitantly with all 4 inhibitors at 10 mg/kg each. The doses studied are generally adequate for affecting measurable cNT levels in the tissues of interest and were thereby chosen for this investigation. Measured 3',5'-cyclic adenosine monophosphate (cAMP) changes were generally statistically insignificant in the brain, striatum and CSF after administration of the aforementioned PDE inhibitors. However, the levels of 3',5'-cyclic guanosine monophosphate (cGMP) increased in both rat and mouse striatum (2.2-, 2.1- and 1.7-fold and 6.4-, 2.8- and 1.7-fold, respectively) after PDE2A, 9A, and 10A inhibitor dosing. In all cases, the cNT changes followed the same trend in the brain, striatum and CSF after PDE inhibitor dosing and dose response was observed in rats. Concomitant treatment with PDE1B, PDE2A, PDE9A and PDE10A inhibitors resulted in a 4.4- and 36.7-fold increase of cGMP in rat and mouse striatum. The drug exposures after concomitant treatment were also higher than in the individual inhibitor-treated animals. cGMP enhancement observed could be due to synergistic effects, though an additive effect of the combined inhibitor concentrations may also contribute.

Oil sands process-affected water impairs the olfactory system of rainbow trout (Oncorhynchus mykiss)

Oil sands process-affected water (OSPW), a byproduct of the extraction of bitumen in the surface mining of oil sands, is currently stored in massive on-site tailings ponds. Determining the potential effects of OSPW on aquatic ecosystems is of main concern to oil sands companies and legislators concerned about the reclamation of mining sites. In the present study, the interaction of OSPW with the chemosensory system of rainbow trout was studied. Using an electro-olfactography (EOG) technique, a 24 h inhibition curve was established and concentrations that inhibit the olfactory system by 20% and 80% (IC20 and IC80) were estimated at 3% and 22% OSPW, respectively. To study the interaction of exposure time and concentration along with the mechanism of the toxic effects, rainbow trout were exposed to 3% and 22% OSPW for 2, 24, and 96 h. An EOG investigation of olfactory sensitivity demonstrated a positive interaction between exposure time and concentration of OSPW concentration, because an increase in either or both elevated the inhibitory effect. To investigate whether or not structural damage of the olfactory epithelium could account for the observed inhibitory effects of OSPW on fish olfaction, the ultrastructure of the olfactory epithelium of exposed fish was investigated using scanning electron microscopy (SEM) and light microscopy (LM). The SEM micrographs showed no changes in the structure of the olfactory epithelium. The light micrographs revealed an increase in the number of mucous cells in 22% OSPW. The results of the present study demonstrated that exposure to OSPW impairs the olfactory system of rainbow trout and its effects increase gradually with increasing exposure time. The present study demonstrated that structural epithelial damage did not contribute to the inhibitory effects of OSPW on the olfactory system.

Anti-melanogenic effects of oyster hydrolysate in UVB-irradiated C57BL/6J mice and B16F10 melanoma cells via downregulation of cAMP signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Pacific oyster (Crassostrea gigas) has been used to treat pigmentary disorders such as freckles, melasma, and moles in Korea.

AIM OF THE STUDY

We aimed to investigate the inhibitory effects of oyster hydrolysate (OH) on melanogenesis in B16F10 melanoma cells and UVB-irradiated C57BL/6J mice.

MATERIAL AND METHODS

The molecular weight distribution and peptide sequences of OH were detected using MALDI-TOF and UHPLC. To evaluate the anti-melanogenic effects of OH, cell viability, melanin content, tyrosinase activity, intracellular cyclic adenosine monophosphate (cAMP) and protein expressions levels were measured in B16F10 cells. In addition, OH was orally administered to UVB-irradiated mice for 9 weeks. After sacrificing the mice, the whitening effects of OH were evaluated based on histological observations and protein expression levels.

RESULTS

In B16F10 cells, OH decreased melanin content and tyrosinase activity in a dose-dependent manner. OH exhibited anti-melanogenic activities via downregulation of cAMP signaling pathway, which consequently decreased melanin synthesis. In UVB-irradiated mice groups, OH decreased the number of active melanocytes and melanin granules. The expression of tyrosinase-related proteins and microphthalmia-associated transcription factor (MITF) decreased in the OH-administered groups.

CONCLUSIONS

These results show that OH inhibits melanin synthesis in B16F10 cells via downregulation of cAMP signaling pathway and in UVB-irradiated mice, by decreasing the number of active melanocytes and melanin granules.

Mechanistic role of cAMP and hepatocyte growth factor signaling in thioacetamide-induced nephrotoxicity: Unraveling the role of platelet rich plasma

Chronic kidney diseases occur as result of exposure to wide range of deleterious agents as environmental pollutants, toxins and drug. Currently, there is no effective protective therapy against renal damage, fibrosis and its sequel of end stage renal disease. Platelet-rich plasma (PRP) has a progressively gained consideration in wound healing, repair/regeneration of damaged tissues and conservation of organ function. However, its impact on thioacetamide (TAA) induced chronic renal damage has not been elucidated yet. So, the present study was carried out to evaluate the possible protective and regenerative effect of PRP against TAA induced renal damage and their potential underlying mechanism. PRP treatment improved redox state, renal function disturbed histologicl features; decreased monocyte chemo-attractant protein-1 (MCP-1) level; increased Peroxisome proliferator-activated receptor gamma co-activator-1α (PGC-1α) marker of mitochondrial biogenesis and metabolism; cyclic adenosine monophosphate (cAMP); hepatocyte growth factor (HGF) and autophagy protein beclin-1 level. In addition, PRP treatment decreased apoptosis and fibrosis as evidenced by decreased active caspase3 and α-SMA expression and immunoreactivity, respectively. In conclusion, PRP could potentially protect against TTA-induced chronic kidney damage by alleviating oxidative stress, improving, mitochondrial biogenesis, autophagy, disruption of the inflammatory, apoptotic and fibrotic response induced by TTA.

Role of the hippocampal 5-HT1A receptor-mediated cAMP/PKA signalling pathway in sevoflurane-induced cognitivedysfunction in aged rats

Objective

This study aimed to evaluate the role of the hippocampal 5-hydroxytryptamine-1A (5-HT1A)-mediated cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) signalling pathway in sevoflurane-induced cognitive dysfunction in aged rats.

Methods

Sixty 18-month-old Sprague–Dawley rats were divided into the control (n = 30) and experimental (Sev, n = 30) groups. The experimental group inhaled 50% air/oxygen mixture (2 L/min) and 2% sevoflurane for 4 hours. The control group inhaled 50% air/oxygen mixture (2 L/min) for 4 hours. The Morris water maze test was performed The mRNA expression of 5-HT1A receptor, and cAMP PKA, cAMP response element-binding protein (CREB), and phosphorylated CREB (p-CREB) protein expression were determined.

Results

The escape latency and swimming distance were greater, and the number of crossings of the platform location and time spent in the platform quadrant were less in the Sev group compared with the control group. cAMP, PKA, CREB, and p-CREB protein expression was downregulated in the Sev group 1 day after anaesthesia compared with the control group. Hippocampal 5-HT1A receptor mRNA expression was higher 7 days after anaesthesia compared with the control group.

Conclusion

Sevoflurane-induced cognitive dysfunction in aged rats may be related to inhibited expression of the hippocampal 5-HT1A receptor-mediated cAMP/PKA signalling pathway.

Isolation and Purification of Primary Rodent Schwann Cells

Schwann cells are the main glial cells of the peripheral nervous system (PNS) and play key roles in peripheral nerve development and function, including providing myelin that is essential for normal movement and sensation in the adult. Schwann cells can be readily destabilized by a wide variety of distinct conditions that range from nerve injury to immune assaults, metabolic disturbances, microbial infections, or genetic defects, leading to the breakdown of myelin (demyelination) and a subsequent switch in phenotypic states. This striking feature of Schwann cells forms the cornerstone of several debilitating and even fatal PNS neurological disorders that include the demyelinating neuropathies Guillain Barré syndrome (GBS) and Charcot-Marie-Tooth disease (CMT), and PNS cancers, including Neurofibromatosis.Primary Schwann cell cultures have proved a valuable tool to dissect key mechanisms that regulate proliferation, survival, differentiation, and myelination of these glial cell types. In this chapter, we describe the steps involved in the isolation and purification of Schwann cells from rodent peripheral nerves and the use of these cultures to model myelination in vitro.

A surrogate analyte-based liquid chromatography-tandem mass spectrometry method for the determination of endogenous cyclic nucleotides in rat brain

A robust high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS) assay was developed and qualified for the measurement of cyclic nucleotides (cNTs) in rat brain tissue. Stable isotopically labeled 3',5'-cyclic adenosine-¹³C₅ monophosphate (¹³C₅-cAMP) and 3',5'-cyclic guanosine-¹³C,¹⁵N₂ monophosphate (¹³C¹⁵N₂-cGMP) were used as surrogate analytes to measure endogenous 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP). Pre-weighed frozen rat brain samples were rapidly homogenized in 0.4M perchloric acid at a ratio of 1:4 (w/v). Following internal standard addition and dilution, the resulting extracts were analyzed using negative ion mode electrospray ionization LC-MS/MS. The calibration curves for both analytes ranged from 5 to 2000ng/g and showed excellent linearity (r²>0.996). Relative surrogate analyte-to-analyte LC-MS/MS responses were determined to correct concentrations derived from the surrogate curves. The intra-run precision (CV%) for ¹³C₅-cAMP and ¹³C¹⁵N₂-cGMP was below 6.6% and 7.4%, respectively, while the inter-run precision (CV%) was 8.5% and 5.8%, respectively. The intra-run accuracy (Dev%) for ¹³C₅-cAMP and ¹³C¹⁵N₂-cGMP was <11.9% and 10.3%, respectively, and the inter-run Dev% was <6.8% and 5.5%, respectively. Qualification experiments demonstrated high analyte recoveries, minimal matrix effects and low autosampler carryover. Acceptable frozen storage, freeze/thaw, benchtop, processed sample and autosampler stability were shown in brain sample homogenates as well as post-processed samples. The method was found to be suitable for the analysis of rat brain tissue cAMP and cGMP levels in preclinical biomarker development studies.

Maternal low-protein diet decreases brain-derived neurotrophic factor expression in the brains of the neonatal rat offspring

Prenatal exposure to a maternal low-protein (LP) diet has been known to cause cognitive impairment, learning and memory deficits. However, the underlying mechanisms have not been identified. Herein, we demonstrate that a maternal LP diet causes, in the brains of the neonatal rat offspring, an attenuation in the basal expression of the brain-derived neurotrophic factor (BDNF), a neurotrophin indispensable for learning and memory. Female rats were fed either a 20% normal protein (NP) diet or an 8% LP 3 weeks before breeding and during the gestation period. Maternal LP diet caused a significant reduction in the Bdnf expression in the brains of the neonatal rats. We further found that the maternal LP diet reduced the activation of the cAMP/protein kinase A/cAMP response element binding protein (CREB) signaling pathway. This reduction was associated with a significant decrease in CREB binding to the Bdnf promoters. We also show that prenatal exposure to the maternal LP diet results in an inactive or repressed exon I and exon IV promoter of the Bdnf gene in the brain, as evidenced by fluxes in signatory hallmarks in the enrichment of acetylated and trimethylated histones in the nucleosomes that envelop the exon I and exon IV promoters, causing the Bdnf gene to be refractory to transactivation. Our study is the first to determine the impact of a maternal LP diet on the basal expression of BDNF in the brains of the neonatal rats exposed prenatally to an LP diet.

β-Cell glutamate signaling: Its role in incretin-induced insulin secretion

Insulin secretion from the pancreatic β-cell (referred to as β-cell hereafter) plays a central role in glucose homeostasis. Impaired insulin secretion is a major factor contributing to the development of diabetes and, therefore, is an important target for treatment of the disease. Cyclic adenosine monophosphate is a key second messenger in β-cells that amplifies insulin secretion. Incretins released by the gut potentiate insulin secretion through cyclic adenosine monophosphate signaling in β-cells, which is the basis for the incretin-based diabetes therapies now being used worldwide. Despite its importance, the interaction between glucose metabolism and incretin/cyclic adenosine monophosphate signaling in β-cells has long been unknown. A recent study showed that cytosolic glutamate produced by glucose metabolism in β-cells is a key signal in incretin-induced insulin secretion. Here we review the physiological and pathophysiological roles of β-cell glutamate signaling in incretin-induced insulin secretion.

A capillary zone electrophoresis method for adenine nucleotides analysis in Saccharomyces cerevisiae

Adenosine triphosphate and its metabolites are involved in the cellular metabolism process in Saccharomyces cerevisiae. It is very important to simultaneously determine the relative contents of ATP and its metabolites in yeast. In this study, an effective capillary zone electrophoresis method with high selectivity was established. The calibration curves were linear in the concentration range from 1 to 20mg/L (ATP and cAMP) and 2 to 40mg/L (ADP and AMP) with excellent correlation coefficients (r(2))>0.999. The recovery of ATP, ADP, AMP, and cAMP were 99.4%, 94.7%, 100.3% and 99.6%, respectively. Simple sample preparation and easy detection of ATP and its metabolites make this method suitable for the study of changes in the four adenine nucleotides levels caused by caloric restriction in yeast. It is expected that the current method may contribute to further energy metabolism and related investigations of yeast.

Onion (Allium cepa L.) peel extract has anti-platelet effects in rat platelets

The effects of onion peel extract (OPE) in collagen (5 μg/mL)-stimulated washed rat platelet aggregation were investigated. OPE inhibited platelet aggregation via inhibition of aggregation-inducing molecules, intracellular Ca(2+) and thromboxane A2 (TXA2) by blocking cyclooxygenase-1 (COX-1) and TXA2 synthase (TXAS) activities in a dose-dependent manner. In addition, OPE elevated the formation of cyclic adenosine monophosphate (cAMP), aggregation-inhibiting molecule, but not cyclic guanosine monophosphate (cGMP). High performance liquid chromatography (HPLC) analysis of OPE revealed that OPE contains quercetin, one of the major flavonoids, which has anti-platelet effect. In conclusion, we suggest that OPE is an effective inhibitor of collagen-stimulated platelet aggregation in vitro. Therefore, it can be a promising and safe strategy for anti-cardiovascular diseases.

RNA aptamer based electrochemical biosensor for sensitive and selective detection of cAMP

Cyclic adenosine monophosphate (cAMP) is an important small biological molecule associated with the healthy state of living organism. In order to realize highly sensitive and specific detection of cAMP, here an RNA aptamer and electrochemical impedance spectroscopy (EIS) based biosensor enhanced by gold nanoparticles electrodeposited on the surface of gold electrode is designed. The designed aptasensor has a wide effective measuring range from 50pM to 250pM with a detection limit of 50pM in PBS buffer, and an effective measuring range from 50nM to 1μM with a detection limit of 50nM in serum. The designed biosensor is also able to detect cAMP with high sensitivity, specificity, and stability. Since the biosensor can be easily fabricated with low cost and repeatedly used for at least two times, it owns great potential in wide application fields such as clinical test and food inspection, etc.

Mechanisms of Nattokinase in protection of cerebral ischemia

In vivo, the level of cyclic Adenosine Monophosphate (cAMP) and the pathway of the Janus Kinase1/Signal Transducers and Activators of Transcription1 (JAK1/STAT1) were studied. In vitro, the Ca(2+) mobilization in human platelet stimulated by thrombin was observed. In addition, vasomotion of vascular smooth muscle was measured by adding KCl or norepinephrine(NE) under the Ca(2+) contained bath solutions. The effect induced by NE in the presence of N-nitro-L-arginine methyl ester (L-NAME) or indometacin (Indo) was also detected. At last, the levels of tissue plasminogen activator (t-PA) and Plasminogen activator inhibitor-1 (PAI-1) in cultured supernatans in Human umbilical vein endothelial cells (Huvecs) were measured by means of ELISA kit. Results showed that Nattokinase (NK) significantly increased the cAMP level, activated the signal passage of JAK1/STAT1 in injured part and inhibited remarkably the rise of platelet intracellular Ca(2+) ([Ca(2+)]i) in human platelet. Furthermore, NK relaxed rat thoracic aortic artery in the dose-dependent manner and in the endothelium dependent manner and its effect could be attenuated by L-NAME. Also, the secretion of t-PA and PAI-1 were reduced stimulated by Adr on Huvecs. These data indicated that the neuroprotective effect of NK was associated with its antiplatelet activity by elevating cAMP level and attenuating the calcium release from calcium stores; with its anti-apoptotic effect through the activation of JAK1/STAT1 pathway; with its relaxing vascular smooth muscle by promoting synthesis and release of NO, reducing ROC calcium ion influx and with its protection on endothelial cells through increasing fibrinolytic activity and facilitating spontaneous thrombolysis.

Selective Phosphodiesterase 4B Inhibitors: A Review

Phosphodiesterase 4B (PDE4B) is a member of the phosphodiesterase family of proteins that plays a critical role in regulating intracellular levels of cyclic adenosine monophosphate (cAMP) by controlling its rate of degradation. It has been demonstrated that this isoform is involved in the orchestra of events which includes inflammation, schizophrenia, cancers, chronic obstructive pulmonary disease, contractility of the myocardium, and psoriatic arthritis. Phosphodiesterase 4B has constituted an interesting target for drug development. In recent years, a number of PDE4B inhibitors have been developed for their use as therapeutic agents. In this review, an up-to-date status of the inhibitors investigated for the inhibition of PDE4B has been given so that this rich source of structural information of presently known PDE4B inhibitors could be helpful in generating a selective and potent inhibitor of PDE4B.

Pharmacophore based virtual screening, molecular docking and biological evaluation to identify novel PDE5 inhibitors with vasodilatory activity

Prompted by the role of PDE5 and its closely associated cAMP and cGMP in hypertension, we have attempted to discover novel PDE5 inhibitors through ligand based virtual screening. Rigorously validated model comprising of one HBA, one HY and one RA was used as a query to search the NCI database leading to retrieval of many compounds which were screened on the basis of estimated activity, fit value and Lipinski's violation. Selected compounds were subjected to docking studies which resulted into visualization of potential interaction capabilities of NCI compounds in line to pharmacophoric features. Finally three compounds were subjected to in vitro evaluation using the isolated rat aortic model. The results showed that all three compounds are potent and novel PDE5 inhibitors with vasodilatory activity range from 10(-2) to 10(-5) M.

Effects of peroxisome proliferator-activated receptor γ in simvastatin antiplatelet activity: influences on cAMP and mitogen-activated protein kinases

Statins are widely used as hypolipidemic drugs, and have beneficial effects in reducing cardiovascular events. In addition, recent studies on the pleiotropic effects of statins (i.e., simvastatin) reveal that these drugs have many additional anti-atherogenic effects, including antiplatelet activity. The mechanisms may be partly related to activation of peroxisome proliferator-activated receptors (PPARs), which are present in human platelets, and whose activation inhibits platelet aggregation. However, the details of the signaling pathway by which simvastatin inhibits platelet activation via PPARs have not yet been completely established. The aim of this study was to examine the mechanisms by which the PPAR-mediated pathways contribute to the antiplatelet activity of simvastatin. Simvastatin (3-50 μM) induced PPARα and PPARγ activation in a dose-dependent manner in washed platelets. Additionally, simvastatin inhibited collagen-induced platelet aggregation, expression of CD62 and PAC-1, and Ca(2+) mobilization. These effects of simvastatin on platelet responses were strongly reduced by adding a selective PPARγ antagonist (GW9662), but not PPARα antagonist (GW6471). Moreover, in the presence of GW9662, simvastatin-mediated increase of cyclic adenosine monophosphate (cAMP) production, vasodilator-stimulated phosphoprotein (VASP) Ser(157) phosphorylation and inhibition of Akt phosphorylation were markedly reversed. Furthermore, simvastatin was found to inhibit phosphorylation of mitogen-activated protein kinases (MAPKs, i.e., p38 MAPK, ERK) by increasing the association between PPARγ and the components of MAPKs after platelet activation. Taken together, the present results confirm that simvastatin inhibition of platelet activation is mediated by PPARγ-dependent processes, which involves mediating MAPKs signaling, increase of cAMP formation and VASP Ser(157) phosphorylation, inhibition of Akt phosphorylation and intracellular Ca(2+) mobilization.

The role of transcriptional regulation in maintaining the availability of mycobacterial adenylate cyclases

Mycobacterium species have a complex cAMP regulatory network indicated by the high number of adenylate cyclases annotated in their genomes. However the need for a high level of redundancy in adenylate cyclase genes remains unknown. We have used semiquantitiative RT-PCR to examine the expression of eight Mycobacterium smegmatis cyclases with orthologs in the human pathogen Mycobacterium tuberculosis, where cAMP has recently been shown to be important for virulence. All eight cyclases were transcribed in all environments tested, and only four demonstrated environmental-mediated changes in transcription. M. smegmatis genes MSMEG_0545 and MSMEG_4279 were upregulated during starvation conditions while MSMEG_0545 and MSMEG_4924 were downregulated in H2O2 and MSMEG_3780 was downregulated in low pH and starvation. Promoter fusion constructs containing M. tuberculosis H37Rv promoters showed consistent regulation compared to their M. smegmatis orthologs. Overall our findings indicate that while low levels of transcriptional regulation occur, regulation at the mRNA level does not play a major role in controlling cellular cyclase availability in a given environment.

Decichine enhances hemostasis of activated platelets via AMPA receptors

INTRODUCTION

Dencichine, one of the non-protein amino acids present in the roots of Panax notoginseng, has been found to shorten bleeding time of mice and increase the number of platelets. However, the exact underlying mechanisms have not been elucidated yet. This study was aimed to identify the hemostatic effect of dencichine and uncover its mechanisms.

MATERIALS AND METHODS

Hemostatic effect was assessed by measuring tail bleeding time and coagulation indices of rats. PT, APTT, TT and FIB concentration were measured using a Sysmex CA-1500 plasma coagulation analyzer. Platelet aggregation rate was determined by using a platelet aggregometer. Concentration of cyotosolic calcium was evaluated by Fluo-3 and levels of cyclic adenosine monophosphate (cAMP) and thromboxane A₂ (TXA₂) were measured by ELISA method.

RESULTS AND CONCLUSION

Dencichine administered orally shortened tail bleeding time, reduced APTT and TT but increased the concentration of FIB in plasma in a dose-dependent manner. When induced with trap, dencichine could elevate the cytoplasmic concentration of calcium, and secretion of TXA₂ as well as the ratio of TXA₂ to PGI₂ from platelets. Meanwhile, it decreased the level of intracellular cAMP. However, CNQX could block the enhanced hemostatic effect of dencichine. These results suggested that dencichine exerted hemostatic function via AMPA receptors on platelets, therefore, facilitated coagulation cascade in a paracrine fashion by control of platelet cytosolic calcium influx, cAMP production and TXA₂ release. Current study may contribute to its clinical use in therapy of hemorrhage.

MiR-27 orchestrates the transcriptional regulation of brown adipogenesis

OBJECTIVE

Brown adipose tissue (BAT) produces heat using chemical energy of lipids and glucose, a function induced by cold exposure or diet. The brown adipogenesis is tightly controlled in a coordinated interplay between several transcriptional factors. It is not known what enables and coordinates this robust program of concerted cooperation between the transcriptional factors and co-regulators necessary for the brown adipogenesis.

MATERIALS/METHODS

A. In vivo studies--we investigated the expression levels of miR-27a and b in mice after cold exposure. B. Using gene expression and functional studies together with high throughput imaging in primary preadipocytes, and cell culture models, we investigated the role of miR-27 in beige and brown adipogenesis. C. Using gene silencing and rescue experiments we dissected the molecular mechanisms of the miR-27 action.

RESULTS

After cold exposure, miR-27 is downregulated in BAT and subcutaneous white adipose tissue (SAT). MiR-27 is also downregulated during brown adipogenesis of primary preadipocytes in vitro, and it directly targets and negatively regulates the essential components of the brown transcriptional network: Prdm16, Pparα, Creb, and in part Pgc1β. Together with its direct effect on Pparγ, and indirect on Pgc1α, mir-27 decreases brown differentiation of cultured cells and of primary SAT preadipocytes.

CONCLUSIONS

Our results point to miR-27 as a central upstream regulator of the transcriptional network involved in beige and brown adipogenesis after cold exposure, and suggest miR-27 inhibition as a novel therapeutic approach for metabolic diseases aiming at increasing the beige/brown fat mass.

Characterization of receptor of activated C kinase 1 (RACK1) and functional analysis during larval metamorphosis of the oyster Crassostrea angulata

During a large-scale screen of the larval transcriptome library of the Portuguese oyster, Crassostrea angulata, the oyster gene RACK, which encodes a receptor of activated protein kinase C protein was isolated and characterized. The cDNA is 1,148 bp long and has a predicted open reading frame encoding 317 aa. The predicted protein shows high sequence identity to many RACK proteins of different organisms including molluscs, fish, amphibians and mammals, suggesting that it is conserved during evolution. The structural analysis of the Ca-RACK1 genomic sequence implies that the Ca-RACK1 gene has seven exons and six introns, extending approximately 6.5 kb in length. It is expressed ubiquitously in many oyster tissues as detected by RT-PCR analysis. The Ca-RACK1 mRNA expression pattern was markedly increased at larval metamorphosis; and was further increased along with Ca-RACK1 protein synthesis during epinephrine-induced metamorphosis. These results indicate that the Ca-RACK1 plays an important role in tissue differentiation and/or in cell growth during larval metamorphosis in the oyster, C. angulata.