Gut microbiota and metabolic profiles in chronic intermittent hypoxia-induced rats: disease-associated dysbiosis and metabolic disturbances

Aim

Chronic intermittent hypoxia (CIH) is a key characteristic of obstructive sleep apnea (OSA) syndrome, a chronic respiratory disorder. The mechanisms of CIH-induced metabolic disturbance and histopathological damage remain unclear.

Methods

CIH-induced rats underwent daily 8-h CIH, characterized by oxygen levels decreasing from 21% to 8.5% over 4 min, remaining for 2 min, and quickly returning to 21% for 1 min. The control rats received a continuous 21% oxygen supply. The levels of hypersensitive C reactive protein (h-CRP), tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), interleukin 8 (IL-8), and nuclear factor kappa-B (NF-κB) were measured by ELISA. Histological analysis of the soft palates was conducted using HE staining. The microbial profiling of fecal samples was carried out by Accu16STM assay. Untargeted metabolomics of serum and soft palate tissue samples were analyzed by UPLC-MS. The protein expression of cAMP-related pathways in the soft palate was determined by Western blot.

Results

After 28 h of CIH induction, a significant increase in pro-inflammatory cytokines was observed in the serum, along with mucosal layer thickening and soft palate tissue hypertrophy. CIH induction altered the diversity and composition of fecal microbiota, specifically reducing beneficial bacteria while increasing harmful bacteria/opportunistic pathogens. Notably, CIH induction led to a significant enrichment of genera such as Dorea, Oscillibacter, Enteractinococcus, Paenibacillus, Globicatella, and Flaviflexus genera. Meanwhile, Additionally, CIH induction had a notable impact on 108 serum marker metabolites. These marker metabolites, primarily involving amino acids, organic acids, and a limited number of flavonoids or sterols, were associated with protein transport, digestion and absorption, amino acid synthesis and metabolism, as well as cancer development. Furthermore, these differential serum metabolites significantly affected 175 differential metabolites in soft palate tissue, mainly related to cancer development, signaling pathways, amino acid metabolism, nucleotide precursor or intermediate metabolism, respiratory processes, and disease. Importantly, CIH induction could significantly affect the expression of the cAMP pathway in soft palate tissue.

Conclusions

Our findings suggest that targeting differential metabolites in serum and soft palate tissue may represent a new approach to clinical intervention and treatment of OSA simulated by the CIH.

Integrating network pharmacology and transcriptomic omics reveals that akebia saponin D attenuates neutrophil extracellular traps-induced neuroinflammation via NTSR1/PKAc/PAD4 pathway after intracerebral hemorrhage

Neutrophils and their production of neutrophil extracellular traps (NETs) significantly contribute to neuroinflammation and brain damage after intracerebral hemorrhage (ICH). Although Akebia saponin D (ASD) demonstrates strong anti-inflammatory activities and blood-brain barrier permeability, its role in regulating NETs formation and neuroinflammation following ICH is uncharted. Our research focused on unraveling the influence of ASD on neuroinflammation mediated by NETs and the mechanisms involved. We found that increased levels of peripheral blood neutrophils post-ICH are correlated with worse prognostic outcomes. Through network pharmacology, we identified ASD as a promising therapeutic target for ICH. ASD administration significantly improved neurobehavioral performance and decreased NETs production in neutrophils. Furthermore, ASD was shown to upregulate the membrane protein NTSR1 and activate the cAMP signaling pathway, confirmed through transcriptome sequencing, western blot, and immunofluorescence. Interestingly, the NTSR1 inhibitor SR48692 significantly nullified ASD's anti-NETs effects and dampened cAMP pathway activation. Mechanistically, suppression of PKAc via H89 negated ASD's anti-NETs effects but did not affect NTSR1. Our study suggests that ASD may reduce NETs formation and neuroinflammation, potentially involving the NTSR1/PKAc/PAD4 pathway post-ICH, underlining the potential of ASD in mitigating neuroinflammation through its anti-NETs properties.

Influence of formaldehyde exposure on the molecules of the NO/cGMP-cAMP signaling pathway in different brain regions of Balb/c mice

This toxicology study was conducted to assess the impact of formaldehyde, a common air pollutant found in Chinese gymnasiums, on the brain function of athletes. In this research, a total of 24 Balb/c male mice of SPF-grade were divided into four groups, each consisting of six mice. The mice were exposed to formaldehyde at different concentrations, including 0 mg/m3, 0.5 mg/m3, 3.0 mg/m3, and 3.0 mg/m3 in combination with an injection of L-NMMA (NG-monomethyl-L-arginine), which is a nitric oxide synthase antagonist. Following a one-week test period (8 h per day, over 7 days), measurements of biomarkers related to the nitric oxide (NO)/cGMP-cAMP signaling pathway were carried out on the experimental animals post-treatment. The study found that: (1) Exposure to formaldehyde can lead to brain cell apoptosis and neurotoxicity; (2) Additionally, formaldehyde exposure was found to alter the biomarkers of the NO/cGMP-cAMP signaling pathway, with some changes being statistically significant (p < 0.05 or p < 0.01); (3) The use of L-NMMA, an antagonist of the NO/cGMP-cAMP signaling pathway, was found to prevent these biomarker changes and had a protective effect on brain cells. The study suggests that the negative impact of formaldehyde on the brain function of mice is linked to the regulation of the NO/cGMP-cAMP signaling pathway.

Temporal and Spatial Gene Expression Profile of Stroke Recovery Genes in Mice

Stroke patients show some degree of spontaneous functional recovery, but this is not sufficient to prevent long-term disability. One promising approach is to characterize the dynamics of stroke recovery genes in the lesion and distant areas. We induced sensorimotor cortex lesions in adult C57BL/6J mice using photothrombosis and performed qPCR on selected brain areas at 14, 28, and 56 days post-stroke (P14-56). Based on the grid walk and rotating beam test, the mice were classified into two groups. The expression of cAMP pathway genes Adora2a, Pde10a, and Drd2, was higher in poor- compared to well-recovered mice in contralesional primary motor cortex (cl-MOp) at P14&56 and cl-thalamus (cl-TH), but lower in cl-striatum (cl-Str) at P14 and cl-primary somatosensory cortex (cl-SSp) at P28. Plasticity and axonal sprouting genes, Lingo1 and BDNF, were decreased in cl-MOp at P14 and cl-Str at P28 and increased in cl-SSp at P28 and cl-Str at P14, respectively. In the cl-TH, Lingo1 was increased, and BDNF decreased at P14. Atrx, also involved in axonal sprouting, was only increased in poor-recovered mice in cl-MOp at P28. The results underline the gene expression dynamics and spatial variability and challenge existing theories of restricted neural plasticity.

(20R)-panaxadiol improves obesity by promoting white fat beigeing

Introduction: Obesity is an important cause of a range of metabolic diseases. However, the complex mechanisms of obesity and its related diseases make some weight loss methods ineffective or have safety issues. Ginseng, a specialty of Jilin Province in China with both edible and medicinal value, contains mainly ginsenosides and other components. In order to study the anti-obesity effect of ginseng, network pharmacology was used to predict and screen the active ingredients, action targets and signaling pathways of ginseng. We found (20R)-panaxadiol (PD) is a more desirable active ingredient due to its high drug-like properties and high bioavailability. Moreover, it is closely related to cAMP pathway which is more important in metabolism regulation. The corresponding pharmacodynamic targets of PD include ADRB2 (the gene encoding the β₂-adrenoceptor receptor). Our study aimed to investigate whether Panaxadiol can promote white adipocyte beigeing and increase thermogenesis through modulating the β₂/cAMP pathway to exert anti-obesity effects. Methods: In vivo, we established high-fat feeding obesity model, genotypically obese mice (ob/ob) model, and administered PD (10 mg/kg). PD treatment in ob/ob mice along with β₂ receptor inhibitor ICI118551. In vitro, differentiated mature 3T3-L1 cells were given palmitate (PA) to induce hypertrophy model along with PD (20 μM). Results: The results of this study demonstrated that PD significantly reduced body weight, improved glucose tolerance and lipid levels in high-fat-induced obese mice and ob/ob mice, and also reduced lipid droplet size in PA-treated hypertrophic adipocytes in vitro. Molecular biology assays confirmed that cAMP response element binding protein (CREB) phosphorylation was increased after PD administration, and the expression of thermogenesis-related proteins UCP1, PRDM16 and mitochondrial biosynthesis-related proteins PGC-1α, TFAM and NRF1 were increased. Molecular docking results showed a low binding energy between β₂ receptors and PD, indicating an affinity between the β₂ receptor and PD. In addition, the β₂ receptor inhibition, reversed the anti-obesity effect of PD on the body weight, lipid droplets, the expression of thermogenesis-related proteins and CREB phosphorylation in ob/ob mice. Discussion: These results suggest that PD may promote the expression of thermogenic proteins through phosphorylation of CREB via β2 receptor activation, and thus exert anti-obesity effects.

The impact of different feeds on DNA methylation, glycolysis/gluconeogenesis signaling pathway, and gene expression of sheep muscle

DNA methylation is an important epigenetic regulatory form that regulates gene expression and tissue development. This study compared the effects of high fiber, low protein (HFLP) and low fiber, high protein (LFHP) diets on the DNA methylation profile of twin lambs' muscles, their effect on glycolysis/gluconeogenesis and related pathways by transcriptome and deep whole-genome bisulfite sequencing (WGBS). Results identified 1,945 differentially methylated regions (DMRs) and 1,471 differentially methylated genes (DMGs). Also, 487 differentially expressed transcripts belonging to 368 differentially expressed genes (DEGs) were discovered between the twin lambs under different diets. Eleven overlapped genes were detected between the DEGs and the DMGs. FKBP5 and FOXO1 were detected to be significantly different. The FOXO1 regulated cAMP and the glycolysis/gluconeogenesis pathways. The glycolysis/gluconeogenesis, and the FOXO pathways were significantly enriched. The expressions of HOMER1 and FOXO1 in the HFLP group were significantly higher than those in the LFHP group. There is a significant correlation between the upregulated gene expression and hypomethylation of HOMER1 and FOXO1 gene in HFLP group. The results showed that FOXO1 induces PDK4 expression in muscle while regulating FKBP5 activity, which stimulates glucose production by activating specific gluconeogenesis target genes. The FOXO1 was able to regulate the glucose metabolism, the cAMP and the occurrence of glycolysis/gluconeogenesis pathways. This study showed that feed type can affect the methylation levels of the glycolysis related gluconeogenesis genes and interaction pathways, providing new ideas for a better understanding of the regulation of muscle energy metabolism and feed development.

Endocytic protein Pal1 regulates appressorium formation and is required for full virulence of Magnaporthe oryzae

Endocytosis plays key roles during infection of plant-pathogenic fungi, but its regulatory mechanisms are still largely unknown. Here, we identified a putative endocytosis-related gene, PAL1, which was highly expressed in appressorium of Magnaporthe oryzae, and was found to be important for appressorium formation and maturation. Deletion of PAL1 significantly reduced the virulence of M. oryzae due to defects in appressorial penetration and invasive growth in host cells. The Pal1 protein interacted and colocalized with the endocytosis protein Sla1, suggesting it is involved in endocytosis. The Δpal1 mutant was significantly reduced in appressorium formation, which was recovered by adding exogenous cAMP and 3-isobutyl-1-methylxanthine (IBMX). Moreover, the phosphorylation level of Pmk1 in Δpal1 was also reduced, suggesting Pal1 functions upstream of both the cAMP and Pmk1 signalling pathways. As a consequence, the utilization of glycogen and lipid, appressorial autophagy, actin ring formation, localization of septin proteins, as well as turgor accumulation were all affected in the Δpal1 mutant. Taken together, Pal1 regulates cAMP and the Pmk1 signalling pathway for appressorium formation and maturation to facilitate infection of M. oryzae.

microRNA-454-mediated NEDD4-2/TrkA/cAMP axis in heart failure: Mechanisms and cardioprotective implications

The current study aimed to investigate the mechanism by which miR-454 influences the progression of heart failure (HF) in relation to the neural precursor cell expressed, developmentally downregulated 4-2 (NEDD4-2)/tropomyosin receptor kinase A (TrkA)/cyclic adenosine 3',5'-monophosphate (cAMP) axis. Sprague-Dawley rats were used to establish a HF animal model via ligation of the left anterior descending branch of the coronary artery. The cardiomyocyte H9c2 cells were treated with H₂ O₂ to stimulate oxidative stress injury in vitro. RT-qPCR and Western blot assay were subsequently performed to determine the expression patterns of miR-454, NEDD4-2, TrkA, apoptosis-related proteins and cAMP pathway markers. Dual-luciferase reporter gene assay coupled with co-immunoprecipitation was performed to elucidate the relationship between miR-454, NEDD4-2 and TrkA. Gain- or loss-of-function experiments as well as rescue experiments were conducted via transient transfection (in vitro) and adenovirus infection (in vivo) to examine their respective functions on H9c2 cell apoptosis and myocardial damage. Our results suggested that miR-454 was aberrantly downregulated in the context of HF, while evidence was obtained suggesting that it targeted NEDD4-2 to downregulate NEDD4-2 in cardiomyocytes. miR-454 exerted anti-apoptotic and protective effects on cardiomyocytes through inhibition of NEDD4-2, while NEDD4-2 stimulated ubiquitination and degradation of TrkA protein. Furthermore, miR-454 activated the cAMP pathway via the NEDD4-2/TrkA axis, which ultimately suppressed cardiomyocyte apoptosis and attenuated myocardial damage. Taken together, the key findings of the current study highlight the cardioprotective role of miR-454, which is achieved through activation of the cAMP pathway by impairing NEDD4-2-induced TrkA ubiquitination.

Rosiglitazone ameliorates palmitic acid-induced endoplasmic reticulum stress and steroidogenic capacity in granulosa cells

Granulosa cells play essential roles in follicular development, oocyte maturation and sex hormone secretion. The exposure of granulosa cells to palmitic acid (PA), the main component of dietary saturated fat, inhibits cell viability. However, the mechanism underlying PA-induced cytotoxicity in granulosa cells has not been deeply investigated. Rosiglitazone (RSG) is a member of the thiazolidinedione family and is reported to protect cells from cytotoxicity and endoplasmic reticulum (ER) stress in other cell types, but whether RSG protects granulosa cells remain unknown. In this study, KGN cell line and primary granulosa cells were used as models of granulosa cells to explore the effects of PA and RSG and the underlying mechanisms. The results showed that PA inhibits cell viability and estradiol secretion through inducing ER stress and cAMP/PKA/CREB pathway. CCAAT/enhancer-binding protein homologous protein (CHOP), an ER stress marker, was demonstrated to participate in PA-induced cytotoxicity. RSG treatment rescued granulosa cells from PA-induced cell death and ER stress. Moreover, RSG was identified to ameliorate ER stress induced by tunicamycin in granulosa cells. In addition, RSG treatment rescued granulosa cells from PA-induced decrease of estrogen secretion by cAMP/PKA/CREB pathway. In conclusion, RSG can protect granulosa cells against PA-induced cytotoxicity by inhibiting ER stress, and can recover steroidogenic capacity, indicating a potential use of RSG in the treatment of granulosa cell dysfunction.

Silencing of RGS2 enhances hippocampal neuron regeneration and rescues depression-like behavioral impairments through activation of cAMP pathway

Depression is one of the most common mental disorders with an increasing incidence. However, factors involved in depression are so complex, thus it is difficult to find effective strategies to reverse the impairments. This study aims to verify the role of regulator of G protein signaling 2 (RGS2) in the mouse mode of unpredictable mild stress-induced depression-like behaviors. Knockdown of RGS2 was achieved by transfection of siRNA-RGS2 in mouse hippocampal (HT-22) cells in vitro and injection of recombinant adenovirus expressing siRNA-RGS2 in mice in vivo. An aberrant high expression of RGS2 was found in mice with depression-like behaviors through immunohistochemical analysis. Silencing of RGS2 or Forskolin (activator of cAMP pathway) developed sweet water consumption, reduced inflammation and oxidative stress injury, and attenuated cognitive impairment and neuronal damage in mice with depression-like behaviors. Furthermore, regeneration was enhanced and apoptosis was repressed in mouse hippocampal neurons in the presence of RGS2 knockdown and Forskolin. Mechanistic studies indicated that silencing of RGS2 promoted the activation of cAMP pathway, thus rescuing depression-like behaviors of mice. Collectively, our study uncovered the role of RGS2-dependent cAMP pathway in regulation of cognitive impairment and hippocampal neuron regeneration in depression-like behaviors of mice, which may be a potential therapeutic target for impairments and symptoms associated with depression.

GPx6 is involved in the in vitro induced capacitation and acrosome reaction in porcine sperm

Glutathione peroxidases (GPxs) are regarded as important protectors against oxidative stress. Some members of this protein family were reported to play key roles in protecting sperm against oxidative stress. Whether GPx6 a member of the GPx family also plays a role in protection against oxidative stress is not known to date. The objective of the present study was to evaluate the localization and function of glutathione peroxidase 6 (GPx6) in boar accessory sex glands, seminal plasma, and sperm, as well as the effect of GPx6 on vitality and capacitation in boar sperm. qPCR and Western blot analysis demonstrated the presence of GPx6 in testis, epididymis, bulbourethral glands, prostate, seminal vesicle, sperm and seminal plasma. Incubation of sperm with an GPx6 antibody had no significant effect on the viability of boar sperm prior to capacitation. Surprisingly, when capacitated sperm was incubated with the GPx6 antibody for 240 min, sperm vitality was significantly improved. Western blotting showed that in capacitated sperm without prior pretreatment, GPx6 protein content was reduced compared to sperm before capacitation. To further confirm a role for GPx6 in sperm capacitation, we tested sperm acrosome reaction by ACR.2 and FITC-PSA. The results showed that treatment of sperm with the GPx6 antibody significantly increased sperm capacitation and acrosome reaction. Furthermore, we examined the concentration of cAMP in sperm after capacitation. ELISA demonstrated that the cAMP concentration in the sperm exposed to the GPx6 antibody was significantly higher than that of the control group. In addition, the exposure of sperm to the GPx6 antibody significantly increased the concentration of H₂O₂, while the expression of SOD3 and CAT were decreased. Based on these observations we would like to postulate that in the boar reproductive tract the GPx6 protein becomes attached to the sperm head preventing the sperm to undergo premature capacitation by affecting components of the antioxidant pathway. How GPx6 expression following ejaculation becomes suppressed to allow sperm capacitation to take place needs further investigation.

GPR64 promotes cAMP pathway in tumor aggressiveness in sparsely granulated growth hormone cell adenomas

PURPOSE

There is an increasing agreement that acromegaly caused by growth hormone (GH) cell adenoma has two distinct subtypes: densely granulated (DG) and sparsely granulated (SG). We hypothesized that differential molecular signatures may explain their behavior.

METHODS

Total transcriptome sequencing was performed on ten DG and seven SG adenomas. The differentially expressed RNAs were identified by bioinformatic analyses, and a candidate RNA was verified by quantitative real-time PCR. Immunohistochemical staining was also performed to detect the protein expression of the candidate. Clinical parameters were correlated with protein expression. Subsequently, cell proliferation, colony formation, and cell cycle progression were analyzed after knockdown of the candidate in pituitary GH3 cells. Activation of the cAMP pathway was assessed by ELISA and Western blot.

RESULTS

We confirmed that there were obvious differentially expressed genes between the subtypes. Through gene profiling, we discovered that an orphan adhesion G protein-coupled receptor, GPR64, was overexpressed in more aggressive SG adenomas. Noticeably, GPR64 knockdown significantly inhibited the proliferation of GH3 tumor cells and decreased colony formation. The knockdown also induced cell cycle arrest in GH3 tumor cells. Further studies revealed that GPR64 knockdown decreased cAMP levels and the ratios of p-CREB/CREB, indicating that it suppressed the cAMP/CREB pathway.

CONCLUSIONS

Our results indicated that GPR64 may promote aggressiveness in SG-type GH cell adenomas and that it is a key factor regulating the cAMP pathway to promote aggressiveness of GH cell adenomas.

Germline Variants in Phosphodiesterase Genes and Genetic Predisposition to Pediatric Adrenocortical Tumors

Phosphodiesterases (PDEs) form a superfamily of enzymes that catalyze the hydrolysis of cyclic nucleotides adenosine 3′5′-cyclic monophosphate (cAMP) and guanosine 3′5′-cyclic monophosphate (cGMP) to their inactive 5′ monophosphates. cAMP plays a critical role as a second messenger in endocrine tissues, and activation of cAMP signaling has been reported in endocrine tumors. Germline variants in PDEs have been associated with benign cortisol-secreting adrenocortical adenomas and testicular germ cell cancer but not adrenocortical carcinoma. We performed whole genome sequencing (WGS) and whole exome sequencing (WES) of paired blood and tumor samples from 37 pediatric adrenocortical tumors (ACTs). Germline inactivating variants in PDEs were observed in 9 of 37 (24%) patients. Tumor DNA analysis revealed loss of heterozygosity, with maintenance of the mutated allele in all cases. Our results suggest that germline variants in PDEs and other regulators of the cAMP-signaling pathway may contribute to pediatric adrenocortical tumorigenesis, perhaps by cooperating with germline hypomorphic mutant TP53 alleles and uniparental disomy of chromosome 11p15 (Beckwith–Wiedemann syndrome).

The role of PKAc1 in gene regulation and trichodimerol production in Trichoderma reesei

Background

Trichoderma reesei represents a model system for investigation of plant cell wall degradation and its connection to light response. The cyclic adenosine monophosphate pathway (cAMP pathway) plays an important role in both physiological outputs, being crucial for regulation of photoreceptor function as well as for cellulase regulation on different carbon sources. Phosphorylation of photoreceptors and of the carbon catabolite repressor CRE1 was shown in ascomycetes, indicating a relevance of protein kinase A in regulation of the target genes of these transcription factors as well as an impact on regulation of induction specific genes. Moreover, the cAMP pathway impacts growth and development.

Results

Here, we investigated gene regulation by the catalytic subunit of protein kinase A (PKAc1) upon growth on cellulose. We found distinct gene sets for regulation upon growth in light and darkness with an overlap of only 13 genes. PKAc1 regulates metabolic genes as well as transport and defense functions. The overlap of gene regulation by PKAc1 with the genes representing the cAMP dependent regulatory output of the photoreceptor ENV1 indicates an involvement of PKA in this pathway, which counteracts its effects by contrasting regulation. Moreover, we found considerable overlap with the gene sets regulated under cellulase inducing conditions and by the carbon catabolite repressor CRE1. Our analysis also showed that PKAc1 regulates the genes of the SOR cluster associated with the biosynthesis of sorbicillinoids. The homologue of gin4, encoding a CAMK type kinase, which is regulated by PKAc1, CRE1 and YPR2 showed a moderate impact on trichodimerol production. We isolated trichodimerol as representative sorbicillin compound and established a method for its quantification in large sample sets using high performance thin layer chromatography (HPTLC), which can be broadly applied for secondary metabolite screening of mutants or different growth conditions. Due to the high expression levels of the SOR cluster under conditions of sexual development we crosschecked the relevance of PKAc1 under these conditions. We could show that PKAc1 impacts biosynthesis of trichodimerol in axenic growth and upon mating.

Conclusions

We conclude that PKAc1 is involved in light dependent regulation of plant cell wall degradation, including carbon catabolite repression as well as secondary metabolism and development in T. reesei.

Phosphodiesterases and cAMP Pathway in Pituitary Diseases

Human phosphodiesterases (PDEs) comprise a complex superfamily of enzymes derived from 24 genes separated into 11 PDE gene families (PDEs 1-11), expressed in different tissues and cells, including heart and brain. The isoforms PDE4, PDE7, and PDE8 are specific for the second messenger cAMP, which is responsible for mediating diverse physiological actions involving different hormones and neurotransmitters. The cAMP pathway plays an important role in the development and function of endocrine tissues while phosphodiesterases are responsible for ensuring the appropriate intensity of the actions of this pathway by hydrolyzing cAMP to its inactive form 5'-AMP. PDE1, PDE2, PDE4, and PDE11A are highly expressed in the pituitary, and overexpression of some PDE4 isoforms have been demonstrated in different pituitary adenoma subtypes. This observed over-expression in pituitary adenomas, although of unknown etiology, has been considered a compensatory response to tumorigenesis. PDE4A4/5 has a unique interaction with the co-chaperone aryl hydrocarbon receptor-interacting protein (AIP), a protein implicated in somatotroph tumorigenesis via germline loss-of-function mutations. Based on the association of low PDE4A4 expression with germline AIP-mutation-positive samples, the available data suggest that lack of AIP hinders the upregulation of PDE4A4 protein seen in sporadic somatotrophinomas. This unique disturbance of the cAMP-PDE pathway observed in the majority of AIP-mutation positive adenomas could contribute to their well-described poor response to somatostatin analogs and may support a role in tumorigenesis.

Effects of sorafenib and an adenylyl cyclase activator on in vitro growth of well-differentiated thyroid cancer cells

Well-differentiated thyroid carcinomas have driver mutations involving growth factor receptor-tyrosine kinases (RTKs) or their intracellular signaling pathway, that is, the mitogen-activated protein kinase (MAPK) pathway. Sorafenib is a multikinase inhibitor of RTKs and the MAPK pathway and has recently been used for the treatment of unresectable well-differentiated thyroid carcinoma. In normal thyroid follicular cells, stimulation of the thyroid-stimulating hormone (TSH) receptor activates the cyclic adenosine monophosphate (cAMP) pathway and promotes cell growth as well as hormonal secretion. However, an adenylyl cyclase (AC) activator, forskolin, has been reported to suppress the growth of thyroid carcinoma cells. To clarify the roles of the MAPK and cAMP pathways in proliferation of well-differentiated thyroid carcinoma cells, we compared the effects of sorafenib and forskolin in in vitro models. Sorafenib inhibited constitutive activation of the MAPK pathway, cyclin-dependent kinase 4 (CDK4), and phosphorylated retinoblastoma protein (RB) in 3 well-differentiated carcinoma cell lines, but it did not show sufficiently effective suppression of cell growth. Forskolin significantly suppressed the growth of all 3 cell lines and also activated the cAMP pathway and inhibited expression of cyclin D1. Our results suggest that activation of the cAMP pathway could be more potent than activation of the MAPK pathway in suppressing proliferation of well-differentiated thyroid cancer cells. We postulate that the AC activator suppresses growth of thyroid carcinoma cells through undetermined mechanisms.

Ethanol potentiates both GABAergic and glutamatergic signaling in the lateral habenula

Ethanol's aversive property may limit it's use, but the underlying mechanisms are no well-understood. Emerging evidence suggests a critical role for the lateral habenula (LHb) in the aversive response to various drugs, including ethanol. We previously showed that ethanol enhances glutamatergic transmission and stimulates LHb neurons. GABAergic transmission, a major target of ethanol in many brain regions, also tightly regulates LHb activity. This study assessed the action of ethanol on LHb GABAergic transmission in rat brain slices. Application of ethanol accelerated spontaneous action potential firing of LHb neurons, and LHb activity was increased by the GABA_A receptor antagonist gabazine, and ethanol-induced acceleration of LHb firing was further increased by gabazine. Additionally, ethanol potentiated GABAergic transmission (inhibitory postsynaptic currents, IPSCs) with an EC₅₀ of 1.5 mM. Ethanol-induced potentiation of IPSCs was increased by a GABA_B receptor antagonist; it was mimicked by dopamine, dopamine receptor agonists, and dopamine reuptake blocker, and was completely prevented by reserpine, which depletes store of catecholamine. Moreover, ethanol-induced potentiation of IPSCs involved cAMP signaling. Finally, ethanol enhanced simultaneously glutamatergic and GABAergic transmissions to the majority of LHb neurons: the potentiation of the former being greater than that of the latter, the net effect was increased firing. Since LHb excitation may contribute to aversion, ethanol-induced potentiation of GABAergic inhibition tends to reduce aversion.

The human CFTR protein expressed in CHO cells activates aquaporin-3 in a cAMP-dependent pathway: study by digital holographic microscopy

The transmembrane water movements during cellular processes and their relationship to ionic channel activity remain largely unknown. As an example, in epithelial cells it was proposed that the movement of water could be directly linked to cystic fibrosis transmembrane conductance regulator (CFTR) protein activity through a cAMP-stimulated aqueous pore, or be dependent on aquaporin. Here, we used digital holographic microscopy (DHM) an interferometric technique to quantify in situ the transmembrane water fluxes during the activity of the epithelial chloride channel, CFTR, measured by patch-clamp and iodide efflux techniques. We showed that the water transport measured by DHM is fully inhibited by the selective CFTR blocker CFTRinh172 and is absent in cells lacking CFTR. Of note, in cells expressing the mutated version of CFTR (F508del-CFTR), which mimics the most common genetic alteration encountered in cystic fibrosis, we also show that the water movement is profoundly altered but restored by pharmacological manipulation of F508del-CFTR-defective trafficking. Importantly, whereas activation of this endogenous water channel required a cAMP-dependent stimulation of CFTR, activation of CFTR or F508del-CFTR by two cAMP-independent CFTR activators, genistein and MPB91, failed to trigger water movements. Finally, using a specific small-interfering RNA against the endogenous aquaporin AQP3, the water transport accompanying CFTR activity decreased. We conclude that water fluxes accompanying CFTR activity are linked to AQP3 but not to a cAMP-stimulated aqueous pore in the CFTR protein.

Plasticity in the Drosophila larval visual system

The remarkable ability of the nervous system to modify its structure and function is mostly experience and activity modulated. The molecular basis of neuronal plasticity has been studied in higher behavioral processes, such as learning and memory formation. However, neuronal plasticity is not restricted to higher brain functions and it may provide a basic feature of adaptation of all neural circuits. The fruit fly Drosophila melanogaster provides a powerful genetic model to gain insight into the molecular basis of nervous system development and function. The nervous system of the larvae is again a magnitude simpler than its adult counter part, allowing the genetic assessment of a number of individual genetically identifiable neurons. We review here recent progress on the genetic basis of neuronal plasticity in developing and functioning neural circuits focusing on the simple visual system of the Drosophila larva.

Decoding high Gonadotropin-releasing hormone pulsatility: a role for GnRH receptor coupling to the cAMP pathway?

The gonadotropin-releasing hormone (GnRH) pulsatile pattern is critical for appropriate regulation of gonadotrope activity but only little is known about the signaling mechanisms by which gonadotrope cells decode such pulsatile pattern. Here, we review recent lines of evidence showing that the GnRH receptor (GnRH-R) activates the cyclic AMP (cAMP) pathway in gonadotrope cells, thus ending a long-lasting controversy. Interestingly, coupling of GnRH-R to the cAMP pathway as well as induction of nitric oxide synthase 1 (NOS1) or follistatin through this signaling pathway take place preferentially under high GnRH pulsatility. The preovulatory surge of GnRH in vivo is indeed associated with an important increase of pituitary cAMP and NOS1 expression levels, both being markedly inhibited by treatment with a GnRH antagonist. Altogether, this suggests that due to its atypical structure and desensitization properties, the GnRH-R may continue to signal through the cAMP pathway under conditions inducing desensitization for most other receptors. Such a mechanism may contribute to decode high GnRH pulsatile pattern and enable gonadotrope cell plasticity during the estrus cycle.

Identification of a specific assembly of the g protein golf as a critical and regulated module of dopamine and adenosine-activated cAMP pathways in the striatum

In the principal neurons of striatum (medium spiny neurons, MSNs), cAMP pathway is primarily activated through the stimulation of dopamine D1 and adenosine A_2A receptors, these receptors being mainly expressed in striatonigral and striatopallidal MSNs, respectively. Since cAMP signaling pathway could be altered in various physiological and pathological circumstances, including drug addiction and Parkinson’s disease, it is of crucial importance to identify the molecular components involved in the activation of this pathway. In MSNs, cAMP pathway activation is not dependent on the classical Gs GTP-binding protein but requires a specific G protein subunit heterotrimer containing Gαolf/β2/γ7 in particular association with adenylyl cyclase type 5. This assembly forms an authentic functional signaling unit since loss of one of its members leads to defects of cAMP pathway activation in response to D1 or A_2A receptor stimulation, inducing dramatic impairments of behavioral responses dependent on these receptors. Interestingly, D1 receptor (D1R)-dependent cAMP signaling is modulated by the neuronal levels of Gαolf, indicating that Gαolf represents the rate-limiting step in this signaling cascade and could constitute a critical element for regulation of D1R responses. In both Parkinsonian patients and several animal models of Parkinson’s disease, the lesion of dopamine neurons produces a prolonged elevation of Gαolf levels. This observation gives an explanation for the cAMP pathway hypersensitivity to D1R stimulation, occurring despite an unaltered D1R density. In conclusion, alterations in the highly specialized assembly of Gαolf/β2/γ7 subunits can happen in pathological conditions, such as Parkinson’s disease, and it could have important functional consequences in relation to changes in D1R signaling in the striatum.