Cyclic nucleotides and phosphodiesterases in monocytic differentiation

Effect of Roflumilast, a Selective PDE4 Inhibitor, on Bone Phenotypes in ADO2 Mice

Autosomal Dominant Osteopetrosis type II (ADO2) is a rare bone disease of impaired osteoclastic bone resorption that usually results from heterozygous missense mutations in the chloride channel 7 (CLCN7) gene. We previously created mouse models of ADO2 (p.G213R) with one of the most common mutations (G215R) as found in humans and demonstrated that this mutation in mice phenocopies the human disease of ADO2. Previous studies have shown that roflumilast (RF), a selective phosphodiesterase 4 (PDE4) inhibitor that regulates the cAMP pathway, can increase osteoclast activity. We also observed that RF increased bone resorption in both wild-type and ADO2 heterozygous osteoclasts in vitro, suggesting it might rescue bone phenotypes in ADO2 mice. To test this hypothesis, we administered RF-treated diets (0, 20 and 100 mg/kg) to 8-week-old ADO2 mice for 6 months. We evaluated bone mineral density and bone micro-architecture using longitudinal in-vivo DXA and micro-CT at baseline, and 6-, 12-, 18-, and 24-week post-baseline time points. Additionally, we analyzed serum bone biomarkers (CTX, TRAP, and P1NP) at baseline, 12-, and 24-week post-baseline. Our findings revealed that RF treatment did not improve aBMD (whole body, femur, and spine) and trabecular BV/TV (distal femur) in ADO2 mice compared to the control group treated with a normal diet. Furthermore, we did not observe any significant changes in serum levels of bone biomarkers due to RF treatment in these mice. Overall, our results indicate that RF does not rescue the osteopetrotic bone phenotypes in ADO2 heterozygous mice.

PDE inhibition in distinct cell types to reclaim the balance of synaptic plasticity

Synapses are the functional units of the brain. They form specific contact points that drive neuronal communication and are highly plastic in their strength, density, and shape. A carefully orchestrated balance between synaptogenesis and synaptic pruning, i.e., the elimination of weak or redundant synapses, ensures adequate synaptic density. An imbalance between these two processes lies at the basis of multiple neuropathologies. Recent evidence has highlighted the importance of glia-neuron interactions in the synaptic unit, emphasized by glial phagocytosis of synapses and local excretion of inflammatory mediators. These findings warrant a closer look into the molecular basis of cell-signaling pathways in the different brain cells that are related to synaptic plasticity. In neurons, intracellular second messengers, such as cyclic guanosine or adenosine monophosphate (cGMP and cAMP, respectively), are known mediators of synaptic homeostasis and plasticity. Increased levels of these second messengers in glial cells slow down inflammation and neurodegenerative processes. These multi-faceted effects provide the opportunity to counteract excessive synapse loss by targeting cGMP and cAMP pathways in multiple cell types. Phosphodiesterases (PDEs) are specialized degraders of these second messengers, rendering them attractive targets to combat the detrimental effects of neurological disorders. Cellular and subcellular compartmentalization of the specific isoforms of PDEs leads to divergent downstream effects for these enzymes in the various central nervous system resident cell types. This review provides a detailed overview on the role of PDEs and their inhibition in the context of glia-neuron interactions in different neuropathologies characterized by synapse loss. In doing so, it provides a framework to support future research towards finding combinational therapy for specific neuropathologies.

A three-gene signature based on tumour microenvironment predicts overall survival of osteosarcoma in adolescents and young adults

Evidences shows that immune and stroma related genes in the tumour microenvironment (TME) play a key regulator in the prognosis of Osteosarcomas (OSs). The purpose of this study was to develop a TME-related risk model for assessing the prognosis of OSs. 82 OSs cases aged ≤25 years from TARGET were divided into two groups according to the immune/stromal scores that were analyzed by the Estimate algorithm. The differentially expressed genes (DEGs) between the two groups were analyzed and 122 DEGs were revealed. Finally, three genes (COCH, MYOM2 and PDE1B) with the minimum AIC value were derived from 122 DEGs by multivariate cox analysis. The three-gene risk model (3-GRM) could distinguish patients with high risk from the training (TARGET) and validation (GSE21257) cohort. Furthermore, a nomogram model included 3-GRM score and clinical features were developed, with the AUC values in predicting 1, 3 and 5-year survival were 0.971, 0.853 and 0.818, respectively. In addition, in the high 3-GRM score group, the enrichment degrees of infiltrating immune cells were significantly lower and immune-related pathways were markedly suppressed. In summary, this model may be used as a marker to predict survival for OSs patients in adolescent and young adults.

The Mucosal Vaccine Adjuvant LT(R192G/L211A) or dmLT

Perhaps the best-studied mucosal adjuvants are the bacterially derived ADP-ribosylating enterotoxins. This adjuvant family includes heat-labile enterotoxin of Escherichia coli (LT), cholera toxin (CT), and mutants or subunits of LT and CT. These proteins promote a multifaceted antigen-specific response, including inflammatory Th1, Th2, Th17, cytotoxic T lymphocytes (CTLs), and antibodies. However, more uniquely among adjuvant classes, they induce antigen-specific IgA antibodies and long-lasting memory to coadministered antigens when delivered mucosally or even parenterally. The purpose of this minireview is to describe the general properties, history and creation, preclinical studies, clinical studies, mechanisms of action, and considerations for use of the most promising enterotoxin-based adjuvant to date, LT(R192G/L211A) or dmLT. This review is timely due to completed, ongoing, and planned clinical investigations of dmLT in multiple vaccine formulations by government, nonprofit, and industry groups in the United States and abroad.

A dominant variant in the PDE1C gene is associated with nonsyndromic hearing loss

Identification of genes with variants causing non-syndromic hearing loss (NSHL) is challenging due to genetic heterogeneity. The difficulty is compounded by technical limitations that in the past prevented comprehensive gene identification. Recent advances in technology, using targeted capture and next-generation sequencing (NGS), is changing the face of gene identification and making it possible to rapidly and cost-effectively sequence the whole human exome. Here, we characterize a five-generation Chinese family with progressive, postlingual autosomal dominant nonsyndromic hearing loss (ADNSHL). By combining population-specific mutation arrays, targeted deafness genes panel, whole exome sequencing (WES), we identified PDE1C (Phosphodiesterase 1C) c.958G>T (p.A320S) as the disease-associated variant. Structural modeling insights into p.A320S strongly suggest that the sequence alteration will likely affect the substrate-binding pocket of PDE1C. By whole-mount immunofluorescence on postnatal day 3 mouse cochlea, we show its expression in outer (OHC) and inner (IHC) hair cells cytosol co-localizing with Lamp-1 in lysosomes. Furthermore, we provide evidence that the variant alters the PDE1C hydrolytic activity for both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Collectively, our findings indicate that the c.958G>T variant in PDE1C may disrupt the cross talk between cGMP-signaling and cAMP pathways in Ca2+ homeostasis.

Interaction between saliva's adenosine and tick parasitism: effects on feeding and reproduction

Background

It has recently been demonstrated that saliva from Rhipicephalus sanguineus ticks contains adenosine (ADO) and prostaglandin E2 (PGE2), two non-protein molecules that have significant immunomodulatory properties. These molecules can inhibit cytokine production by dendritic cells (DCs), while also reducing the expression of CD40 in these cells. However, more studies are needed for a better understanding of their participation in the feeding of ticks in vivo. This work, therefore, evaluated the importance of ADO during tick infestations. Mice were infested with adult ticks (3 couples/mouse), and their skin was collected at the tick-infested site (3rd and 7th day), and mRNA for receptors of ADO was quantified by real-time PCR.

Results

Tick infestation increased by four and two times the expression of the A2b and A3v1 receptors on day 3, respectively, while expression of other ADO receptors was unaltered. In addition, we treated mice (n = 10/group) daily with 8-(p-Sulfophenyl)theophylline, 8-pSPT, 20 mg/kg, i.p.), a non-selective antagonist of ADO receptors, and evaluated the performance of ticks during infestations. Female ticks fed on 8-pSPT-treated mice presented a reduction in their engorgement, weight and hatching rates of egg masses, and survival times of larvae compared to the same parameters presented by ticks in the control group. To investigate if these 8-pSPT-treated mice presented altered immune responses, we performed three tick infestations and collected their lymph node cells to determine the percentages and activation state of DCs and cytokine production by lymphocytes by flow cytometry (Cytometric Bead Array technique, CBA). Our data showed that 8-pSPT-treated mice presented an increase in the percentage of DCs as well as of their stimulatory and co-stimulatory molecules (CD40, CD80 and MHCII). Regarding production of T cell cytokines, we observed a significant increase in the levels of IL-2 and a significant decrease in IL-10, IL-17, TNF-α and IFN-γ cytokines.

Conclusions

These results suggest that ADO produced by ticks helps them feed and reproduce and that this effect may be due to modulation of host DCs and T cells.

Molecular mechanisms underlying β-adrenergic receptor-mediated cross-talk between sympathetic neurons and immune cells

Cross-talk between the sympathetic nervous system (SNS) and immune system is vital for health and well-being. Infection, tissue injury and inflammation raise firing rates of sympathetic nerves, increasing their release of norepinephrine (NE) in lymphoid organs and tissues. NE stimulation of β2-adrenergic receptors (ARs) in immune cells activates the cAMP-protein kinase A (PKA) intracellular signaling pathway, a pathway that interfaces with other signaling pathways that regulate proliferation, differentiation, maturation and effector functions in immune cells. Immune-SNS cross-talk is required to maintain homeostasis under normal conditions, to develop an immune response of appropriate magnitude after injury or immune challenge, and subsequently restore homeostasis. Typically, β2-AR-induced cAMP is immunosuppressive. However, many studies report actions of β2-AR stimulation in immune cells that are inconsistent with typical cAMP-PKA signal transduction. Research during the last decade in non-immune organs, has unveiled novel alternative signaling mechanisms induced by β2-AR activation, such as a signaling switch from cAMP-PKA to mitogen-activated protein kinase (MAPK) pathways. If alternative signaling occurs in immune cells, it may explain inconsistent findings of sympathetic regulation of immune function. Here, we review β2-AR signaling, assess the available evidence for alternative signaling in immune cells, and provide insight into the circumstances necessary for "signal switching" in immune cells.

Cyclic nucleotide phosphodiesterase-1C (PDE1C) drives cell proliferation, migration and invasion in glioblastoma multiforme cells in vitro

Cyclic nucleotides (cAMP & cGMP) are critical intracellular second messengers involved in the transduction of a diverse array of stimuli and their catabolism is mediated by phosphodiesterases (PDEs). We previously detected focal genomic amplification of PDE1C in >90 glioblastoma multiforme (GBM) cells suggesting a potential as a novel therapeutic target in these cells. In this report, we show that genomic gain of PDE1C was associated with increased expression in low passage GBM-derived cell cultures. We demonstrate that PDE1C is essential in driving cell proliferation, migration and invasion in GBM cultures since silencing of this gene significantly mitigates these functions. We also define the mechanistic basis of this functional effect through whole genome expression analysis by identifying down-stream gene effectors of PDE1C which are involved in cell cycle and cell adhesion regulation. In addition, we also demonstrate that Vinpocetine, a general PDE1 inhibitor, can also attenuate proliferation with no effect on invasion/migration. Up-regulation of at least one of this gene set (IL8, CXCL2, FOSB, NFE2L3, SUB1, SORBS2, WNT5A, and MMP1) in TCGA GBM cohorts is associated with worse outcome and PDE1C silencing down-regulated their expression, thus also indicating potential to influence patient survival. Therefore we conclude that proliferation, migration, and invasion of GBM cells could also be regulated downstream of PDE1C.

Human monocytes respond to extracellular cAMP through A2A and A2B adenosine receptors

In this study, we test the hypothesis that cAMP, acting as an extracellular mediator, affects the physiology and function of human myeloid cells. The cAMP is a second messenger recognized as a universal regulator of several cellular functions in different organisms. Many studies have shown that extracellular cAMP exerts regulatory functions, acting as first mediator in multiple tissues. However, the impact of extracellular cAMP on cells of the immune system has not been fully investigated. We found that human monocytes exposed to extracellular cAMP exhibit higher expression of CD14 and lower amount of MHC class I and class II molecules. When cAMP-treated monocytes are exposed to proinflammatory stimuli, they exhibit an increased production of IL-6 and IL-10 and a lower amount of TNF-α and IL-12 compared with control cells, resembling the features of the alternative-activated macrophages or M2 macrophages. In addition, we show that extracellular cAMP affects monocyte differentiation into DCs, promoting the induction of cells displaying an activated, macrophage-like phenotype with reduced capacity of polarized, naive CD4(+) T cells into IFN-γ-producing lymphocytes compared with control cells. The effects of extracellular cAMP on monocytes are mediated by CD73 ecto-5'-nucleotidase and A2A and A2B adenosine receptors, as selective antagonists could reverse its effects. Of note, the expression of CD73 molecules has been found on the membrane of a small population of CD14(+)CD16(+) monocytes. These findings suggest that an extracellular cAMP-adenosine pathway is active in cells of the immune systems.

Gene-expression signatures differ between different clinical forms of familial hemophagocytic lymphohistiocytosis

We performed gene-expression profiling of PBMCs obtained from patients with familial hemophagocytic lymphohistiocytosis (FHL) to screen for biologic correlates with the genetic and/or clinical forms of this disease. Unsupervised hierarchical clustering of 167 differentially expressed probe sets, representing 143 genes, identified 3 groups of patients corresponding to the genetic forms and clinical presentations of the disease. Two clusters of up- and down-regulated genes separated patients with perforin-deficient FHL from those with unidentified genetic cause(s) of the disease. The clusterscomprised genes involved in defense/immune responses, apoptosis, zinc homeostasis, and systemic inflammation. Unsupervised hierarchical clustering partitioned patients with unknown genetic cause(s) of FHL into 2 well-distinguished subgroups. Patterns of up- and down-regulated genes separated patients with “late-onset” and “relapsing” forms of FHL from patients with an “early onset and rapidly evolving” form of the disease. A cluster was identified in patients with “late onset and relapsing” form of FHL related to B- and T-cell differentiation/survival, T-cell activation, and vesicular transport. The resulting data suggest that unique gene-expression signatures can distinguish between genetic and clinical subtypes of FHL. These differentially expressed genes may represent biomarkers that can be used as predictors of disease progression.