A preliminary investigation of phoshodiesterase 7 inhibitor VP3.15 as therapeutic agent for the treatment of experimental autoimmune encephalomyelitis mice

VP3.15 reduces acute cerebellum damage after germinal matrix-intraventricular hemorrhage of the preterm newborn

Germinal matrix-intraventricular hemorrhage (GM-IVH) is one of the most common complications of the preterm newborn. The pathology of the GM-IVH is not completely understood and even regions distant from the lesion area are severely affected. It has been suggested that cerebellar diaschisis may underlie the neurodevelopmental problems that many of these kids show, including cerebral palsy, attention deficit disorders or hyperactivity. Additionally, GM-IVH has no successful treatment. VP3.15 is a dual action phosphodiesterase 7 (PDE7) and glycogen synthase kinase-3β (GSK-3β) inhibitor that limits neuroinflammation and neuronal loss. Therefore, it might also provide a relevant tool to reduce complications associated with GM-IVH. We have used a murine model of GM-IVH to analyze the short and long-term effects of VP3.15 in brain pathology and behavioral complications. In our hands, the induction of unilateral GM-IVH to P7 CD1 mice results in a short-term (P14) compromise of the cerebellar neuronal population and Purkinje cells arborization, an increase of microglia burden in the nuclei and an overall increase of punctuate cerebellar hemorrhages. Whereas brain alterations are no longer observed in the long term (P110), these animals present overt hyperactivity when analyzed in the adulthood, supporting the long-term behavioral impairment. Also, hyperactivity significantly correlates with ipsi and contralateral cerebellar sizes, neuronal densities and myelin basic protein levels. Importantly, treatment with VP3.15 significantly reduces neuronal loss, Purkinje cells simplification, the presence of cerebellar hemorrhages, as well as hyperactivity. Altogether, our data support the neuroprotective effects of VP3.15 in GM-IVH of the PT.

Agriculture and environmental management through nanotechnology: Eco-friendly nanomaterial synthesis for soil-plant systems, food safety, and sustainability

Through the advancement of nanotechnology, agricultural and food systems are undergoing strategic enhancements, offering innovative solutions to complex problems. This scholarly essay thoroughly examines nanotechnological innovations and their implications within these critical industries. Traditional practices are undergoing radical transformation as nanomaterials emerge as novel agents in roles traditionally filled by fertilizers, pesticides, and biosensors. Micronutrient management and preservation techniques are further enhanced, indicating a shift towards more nutrient-dense and longevity-oriented food production. Nanoparticles (NPs), with their unique physicochemical properties, such as an extraordinary surface-to-volume ratio, find applications in healthcare, diagnostics, agriculture, and other fields. However, concerns about their potential overuse and bioaccumulation raise unanswered questions about their health effects. Molecule-to-molecule interactions and physicochemical dynamics create pathways through which nanoparticles cause toxicity. The combination of nanotechnology and environmental sustainability principles leads to the examination of green nanoparticle synthesis. The discourse extends to how nanomaterials penetrate biological systems, their applications, toxicological effects, and dissemination routes. Additionally, this examination delves into the ecological consequences of nanomaterial contamination in natural ecosystems. Employing robust risk assessment methodologies, including the risk allocation framework, is recommended to address potential dangers associated with nanotechnology integration. Establishing standardized, universally accepted guidelines for evaluating nanomaterial toxicity and protocols for nano-waste disposal is urged to ensure responsible stewardship of this transformative technology. In conclusion, the article summarizes global trends, persistent challenges, and emerging regulatory strategies shaping nanotechnology in agriculture and food science. Sustained, in-depth research is crucial to fully benefit from nanotechnology prospects for sustainable agriculture and food systems.

Glycogen Synthase Kinase-3β Inhibitor VP3.15 Ameliorates Neurogenesis, Neuronal Loss and Cognitive Impairment in a Model of Germinal Matrix-intraventricular Hemorrhage of the Preterm Newborn

Advances in neonatology have significantly reduced mortality rates due to prematurity. However, complications of prematurity have barely changed in recent decades. Germinal matrix-intraventricular hemorrhage (GM-IVH) is one of the most severe complications of prematurity, and these children are prone to suffer short- and long-term sequelae, including cerebral palsy, cognitive and motor impairments, or neuropsychiatric disorders. Nevertheless, GM-IVH has no successful treatment. VP3.15 is a small, heterocyclic molecule of the 5-imino-1,2,4-thiadiazole family with a dual action as a phosphodiesterase 7 and glycogen synthase kinase-3β (GSK-3β) inhibitor. VP3.15 reduces neuroinflammation and neuronal loss in other neurodegenerative disorders and might ameliorate complications associated with GM-IVH. We administered VP3.15 to a mouse model of GM-IVH. VP3.15 reduces the presence of hemorrhages and microglia in the short (P14) and long (P110) term. It ameliorates brain atrophy and ventricle enlargement while limiting tau hyperphosphorylation and neuronal and myelin basic protein loss. VP3.15 also improves proliferation and neurogenesis as well as cognition after the insult. Interestingly, plasma gelsolin levels, a feasible biomarker of brain damage, improved after VP3.15 treatment. Altogether, our data support the beneficial effects of VP3.15 in GM-IVH by ameliorating brain neuroinflammatory, vascular and white matter damage, ultimately improving cognitive impairment associated with GM-IVH.

Efficacy of a benzothiazole-based LRRK2 inhibitor in oligodendrocyte precursor cells and in a murine model of multiple sclerosis

AIMS

Multiple sclerosis (MS) is a chronic neurological disease that currently lacks effective curative treatments. There is a need to find effective therapies, especially to reverse the progressive demyelination and neuronal damage. Oligodendrocytes form the myelin sheath around axons in the central nervous system (CNS) and oligodendrocyte precursor cells (OPCs) undergo mechanisms that enable spontaneously the partial repair of damaged lesions. The aim of this study was to discover small molecules with potential effects in demyelinating diseases, including (re)myelinating properties.

METHODS

Recently, it has been shown how LRRK2 inhibition promotes oligodendrogliogenesis and therefore an efficient repair or myelin damaged lesions. Here we explored small molecules inhibiting LRRK2 as potential enhancers of primary OPCs proliferation and differentiation, and their potential impact on the clinical score of experimental autoimmune encephalomyelitys (EAE) mice, a validated model of the most frequent clinical form of MS, relapsing-remitting MS.

RESULTS

One of the LRRK2 inhibitors presented in this study promoted the proliferation and differentiation of OPC primary cultures. When tested in the EAE murine model of MS, it exerted a statistically significant reduction of the clinical burden of the animals, and histological evidence revealed how the treated animals presented a reduced lesion area in the spinal cord.

CONCLUSIONS

For the first time, a small molecule with LRRK2 inhibition properties presented (re)myelinating properties in primary OPCs cultures and potentially in the in vivo murine model. This study provides an in vivo proof of concept for a LRRK2 inhibitor, confirming its potential for the treatment of MS.

Neuronal activity and remyelination: new insights into the molecular mechanisms and therapeutic advancements

This article reviews the role of neuronal activity in myelin regeneration and the related neural signaling pathways. The article points out that neuronal activity can stimulate the formation and regeneration of myelin, significantly improve its conduction speed and neural signal processing ability, maintain axonal integrity, and support axonal nutrition. However, myelin damage is common in various clinical diseases such as multiple sclerosis, stroke, dementia, and schizophrenia. Although myelin regeneration exists in these diseases, it is often incomplete and cannot promote functional recovery. Therefore, seeking other ways to improve myelin regeneration in clinical trials in recent years is of great significance. Research has shown that controlling neuronal excitability may become a new intervention method for the clinical treatment of demyelinating diseases. The article discusses the latest research progress of neuronal activity on myelin regeneration, including direct or indirect stimulation methods, and the related neural signaling pathways, including glutamatergic, GABAergic, cholinergic, histaminergic, purinergic and voltage-gated ion channel signaling pathways, revealing that seeking treatment strategies to promote myelin regeneration through precise regulation of neuronal activity has broad prospects.

Phosphodiesterase 7 as a therapeutic target - Where are we now?

Cyclic nucleotide phosphodiesterases (PDEs) are a superfamily of enzymes that hydrolyse the intracellular second messengers cAMP and cGMP to their inactive forms 5'AMP and 5'GMP. Some members of the PDE family display specificity towards a single cyclic nucleotide messenger, and PDE4, PDE7, and PDE8 specifically hydrolyse cAMP. While the role of PDE4 and its use as a therapeutic target have been well studied, less is known about PDE7 and PDE8. This review aims to collate the present knowledge on human PDE7 and outline its potential use as a therapeutic target. Human PDE7 exists as two isoforms PDE7A and PDE7B that display different expression patterns but are predominantly found in the central nervous system, immune cells, and lymphoid tissue. As a result, PDE7 is thought to play a role in T cell activation and proliferation, inflammation, and regulate several physiological processes in the central nervous system, such as neurogenesis, synaptogenesis, and long-term memory formation. Increased expression and activity of PDE7 has been detected in several disease states, including neurodegenerative diseases such as Parkinson's, Alzheimer's and Huntington's disease, autoimmune diseases such as multiple sclerosis and COPD, and several types of cancer. Early studies have shown that administration of PDE7 inhibitors may ameliorate the clinical state of these diseases. Targeting PDE7 may therefore provide a novel therapeutic strategy for targeting a broad range of disease and possibly provide a complementary alternative to inhibitors of other cAMP-selective PDEs, such as PDE4, which are severely limited by their side-effects.

Peripheral myeloid-derived suppressor cells are good biomarkers of the efficacy of fingolimod in multiple sclerosis

Background

The increasing number of treatments that are now available to manage patients with multiple sclerosis (MS) highlights the need to develop biomarkers that can be used within the framework of individualized medicine. Fingolimod is a disease-modifying treatment that belongs to the sphingosine-1-phosphate receptor modulators. In addition to inhibiting T cell egress from lymph nodes, fingolimod promotes the immunosuppressive activity of myeloid-derived suppressor cells (MDSCs), whose monocytic subset (M-MDSCs) can be used as a biomarker of disease severity, as well as the degree of demyelination and extent of axonal damage in the experimental autoimmune encephalomyelitis (EAE) model of MS. In the present study, we have assessed whether the abundance of circulating M-MDSCs may represent a useful biomarker of fingolimod efficacy in EAE and in the clinical context of MS patients.

Methods

Treatment with vehicle or fingolimod was orally administered to EAE mice for 14 days in an individualized manner, starting the day when each mouse began to develop clinical signs. Peripheral blood from EAE mice was collected previous to treatment and human peripheral blood mononuclear cells (PBMCs) were collected from fingolimod to treat MS patients’ peripheral blood. In both cases, M-MDSCs abundance was analyzed by flow cytometry and its relationship with the future clinical affectation of each individual animal or patient was assessed.

Results

Fingolimod-treated animals presented a milder EAE course with less demyelination and axonal damage, although a few animals did not respond well to treatment and they invariably had fewer M-MDSCs prior to initiating the treatment. Remarkably, M-MDSC abundance was also found to be an important and specific parameter to distinguish EAE mice prone to better fingolimod efficacy. Finally, in a translational effort, M-MDSCs were quantified in MS patients at baseline and correlated with different clinical parameters after 12 months of fingolimod treatment. M-MDSCs at baseline were highly representative of a good therapeutic response to fingolimod, i.e., patients who met at least two of the criteria used to define non-evidence of disease activity-3 (NEDA-3) 12 months after treatment.

Conclusion

Our data indicate that M-MDSCs might be a useful predictive biomarker of the response of MS patients to fingolimod.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02635-3.

Pharmacokinetic/Pharmacodynamic Evaluation of a New Purine-2,6-Dione Derivative in Rodents with Experimental Autoimmune Diseases

Current treatment strategies of autoimmune diseases (ADs) display a limited efficacy and cause numerous adverse effects. Phosphodiesterase (PDE)4 and PDE7 inhibitors have been studied recently as a potential treatment of a variety of ADs. In this study, a PK/PD disease progression modeling approach was employed to evaluate effects of a new theophylline derivative, compound 34, being a strong PDE4 and PDE7 inhibitor. Activity of the studied compound against PDE1 and PDE3 in vitro was investigated. Animal models of multiple sclerosis (MS), rheumatoid arthritis (RA), and autoimmune hepatitis were utilized to assess the efficacy of this compound, and its pharmacokinetics was investigated in mice and rats. A new PK/PD disease progression model of compound 34 was developed that satisfactorily predicted the clinical score-time courses in mice with experimental encephalomyelitis that is an animal model of MS. Compound 34 displayed a high efficacy in all three animal models of ADs. Simultaneous inhibition of PDE types located in immune cells may constitute an alternative treatment strategy of ADs. The PK/PD encephalomyelitis and arthritis progression models presented in this study may be used in future preclinical research, and, upon modifications, may enable translation of the results of preclinical investigations into the clinical settings.

Pharmacokinetic/Pharmacodynamic Assessment of Selective Phosphodiesterase Inhibitors in a Mouse Model of Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a life-threatening disorder currently treated with nonspecific immunosuppressive drugs. It is postulated that phosphodiesterase (PDE) inhibitors, as agents exerting anti-inflammatory and immunomodulatory activities, may constitute a possible treatment of autoimmune disorders. This study develops a pharmacokinetic/pharmacodynamic (PK/PD) model to assess the effects of PDE-selective inhibitors, namely, cilostazol (PDE3), rolipram (PDE4), and BRL-50481 (PDE7), in a mouse model of AIH. The pharmacokinetics of the PDE inhibitors (PDEi) were assessed in male BALB/c mice after intraperitoneal administration. In pharmacodynamic studies, mice received PDEi and AIH was induced in these animals by intravenous injection of concanavalin A (ConA). Serum drug concentrations, tumor necrosis factor α (TNFα), interleukin 17 (IL-17), and aminotransferase activities were quantified. The PK/PD analysis was performed using ADAPT5 software. The PK/PD model assumes inhibition of cAMP hydrolysis in T cells by PDEi, ConA-triggered formation of TNFα and IL-17, suppression of TNFα and IL-17 production by cAMP, and stimulatory effects of TNFα and IL-17 on the hepatic release of aminotransferases. Selective blockage of PDE4 leads to the highest inhibition of cAMP degradation in T cells and amelioration of disease outcomes. However, inhibition of both PDE3 and PDE7 also contribute to this effect. The proposed PK/PD model may be used to assess and predict the activities of novel PDEi and their combinations in ConA-induced hepatitis. A balanced suppression of different types of PDE appears to be a promising treatment option for AIH; however, this hypothesis warrants testing in humans based on translation of the PK/PD model into clinical settings. SIGNIFICANCE STATEMENT: A novel PK/PD model of PDE inhibitor effects in mice with ConA-induced autoimmune hepatitis was developed involving a mechanistic component describing changes in cAMP concentrations in mouse T cells. According to model predictions, inhibition of PDE4 in T cells causes the highest cAMP elevation in T cells, but suppression of PDE3 and PDE7 also contribute to this effect. A balanced inhibition of PDE3, PDE4, and PDE7 appears to be a promising treatment strategy for AIH.

Phosphodiesterase 7(PDE7): A unique drug target for central nervous system diseases

Phosphodiesterase 7 (PDE7), one of the 11 phosphodiesterase (PDE) families, specifically hydrolyzes cyclic 3', 5'-adenosine monophosphate (cAMP). PDE7 is involved in many important functional processes in physiology and pathology by regulating intracellular cAMP signaling. Studies have demonstrated that PDE7 is widely expressed in the central nervous system (CNS) and potentially related to pathogenesis of many CNS diseases. Here, we summarized the classification and distribution of PDE7 in the brain and its functional roles in the mediation of CNS diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS), and schizophrenia. It is expected that the findings collected here will not only lead to a better understanding of the mechanisms by which PDE7 mediates CNS function and diseases, but also aid in the development of novel drugs targeting PDE7 for treatment of CNS diseases.

The Role of PDE8 in T Cell Recruitment and Function in Inflammation

Inhibitors targeting cyclic nucleotide phosphodiesterases (PDEs) expressed in leukocytes have entered clinical practice to treat inflammatory disorders, with three PDE4 inhibitors currently in clinical use as therapeutics for psoriasis, psoriatic arthritis, atopic dermatitis and chronic obstructive pulmonary disease. In contrast, the PDE8 family that is upregulated in pro-inflammatory T cells is a largely unexplored therapeutic target. It was shown that PDE8A plays a major role in controlling T cell and breast cancer cell motility, including adhesion to endothelial cells under physiological shear stress and chemotaxis. This is a unique function of PDE8 not shared by PDE4, another cAMP specific PDE, employed, as noted, as an anti-inflammatory therapeutic. Additionally, a regulatory role was shown for the PDE8A-rapidly accelerated fibrosarcoma (Raf)-1 kinase signaling complex in myelin antigen reactive CD4⁺ effector T cell adhesion and locomotion by a mechanism differing from that of PDE4. The PDE8A-Raf-1 kinase signaling complex affects T cell motility, at least in part, via regulating the LFA-1 integrin mediated adhesion to ICAM-1. The findings that PDE8A and its isoforms are expressed at higher levels in naive and myelin oligodendrocyte glycoprotein (MOG)_35–55 activated effector T (Teff) cells compared to regulatory T (Treg) cells and that PDE8 inhibition specifically affects MOG_35–55 activated Teff cell adhesion, indicates that PDE8A could represent a new beneficial target expressed in pathogenic Teff cells in CNS inflammation. The implications of this work for targeting PDE8 in inflammation will be discussed in this review.

Synthesis and preclinical evaluation of [11C]MTP38 as a novel PET ligand for phosphodiesterase 7 in the brain

Purpose

Phosphodiesterase (PDE) 7 is a potential therapeutic target for neurological and inflammatory diseases, although in vivo visualization of PDE7 has not been successful. In this study, we aimed to develop [¹¹C]MTP38 as a novel positron emission tomography (PET) ligand for PDE7.

Methods

[¹¹C]MTP38 was radiosynthesized by ¹¹C-cyanation of a bromo precursor with [¹¹C]HCN. PET scans of rat and rhesus monkey brains and in vitro autoradiography of brain sections derived from these species were conducted with [¹¹C]MTP38. In monkeys, dynamic PET data were analyzed with an arterial input function to calculate the total distribution volume (V_T). The non-displaceable binding potential (BP_ND) in the striatum was also determined by a reference tissue model with cerebellar reference. Finally, striatal occupancy of PDE7 by an inhibitor was calculated in monkeys according to changes in BP_ND.

Results

[¹¹C]MTP38 was synthesized with radiochemical purity ≥99.4% and molar activity of 38.6 ± 12.6 GBq/μmol. Autoradiography revealed high radioactivity in the striatum and its reduction by non-radiolabeled ligands, in contrast with unaltered autoradiographic signals in other regions. In vivo PET after radioligand injection to rats and monkeys demonstrated that radioactivity was rapidly distributed to the brain and intensely accumulated in the striatum relative to the cerebellum. Correspondingly, estimated V_T values in the monkey striatum and cerebellum were 3.59 and 2.69 mL/cm³, respectively. The cerebellar V_T value was unchanged by pretreatment with unlabeled MTP38. Striatal BP_ND was reduced in a dose-dependent manner after pretreatment with MTP-X, a PDE7 inhibitor. Relationships between PDE7 occupancy by MTP-X and plasma MTP-X concentration could be described by Hill’s sigmoidal function.

Conclusion

We have provided the first successful preclinical demonstration of in vivo PDE7 imaging with a specific PET radioligand. [¹¹C]MTP38 is a feasible radioligand for evaluating PDE7 in the brain and is currently being applied to a first-in-human PET study.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05269-4.

Dynamics of Central Remyelination and Treatment Evolution in a Model of Multiple Sclerosis with Optic Coherence Tomography

The need for remyelinating drugs is essential for healing disabling diseases such as multiple sclerosis (MS). One of the reasons for the lack of this class of therapies is the impossibility to monitor remyelination in vivo, which is of utmost importance to perform effective clinical trials. Here, we show how optical coherence tomography (OCT), a cheap and non-invasive technique commonly used in ophthalmology, may be used to assess remyelination in vivo in MS patients. Our pioneer approach validates OCT as a technique to study remyelination of the optic nerve and reflects what is occurring in non-accessible central nervous system (CNS) structures, like the spinal cord. In this study we used the orally bioavailable small molecule VP3.15, confirming its therapeutical potential as a neuroprotective, anti-inflammatory, and probably remyelinating drug for MS. Altogether, our results confirm the usefulness of OCT to monitor the efficacy of remyelinating therapies in vivo and underscore the relevance of VP3.15 as a potential disease modifying drug for MS therapy.

Pharmacological inhibition of phosphodiesterase 7 enhances consolidation processes of spatial memory

Augmentation of cAMP signaling through inhibition of phosphodiesterases (PDE) is known to enhance plasticity and memory. Inhibition of PDE4 enhances consolidation into memory, but less is known about the role of other cAMP specific PDEs. Here, we tested the effects of oral treatment with a selective inhibitor of PDE7 of nanomolar potency on spatial and contextual memory. In an object location task, doses of 0.3-3 mg/kg administered 3 h after training dose-dependently attenuated time-dependent forgetting in rats. Significant enhancement of memory occurred at a dose of 3 mg/kg with corresponding brain levels consistent with PDE7 inhibition. The same dose given prior to training augmented contextual fear conditioning. In mice, daily dosing before training enhanced spatial memory in two different incremental learning paradigms in the Barnes Maze. Drug treated mice made significantly less errors locating the escape in a probe-test 24 h after the end of training, and they exhibited hippocampal-dependent spatial search strategies more frequently than controls, which tended to show serial sampling of escape locations. Acquisition and short-term memory, in contrast, were unaffected. Our data provide evidence for a role of PDE7 in the consolidation of hippocampal-dependent memory. We suggest that targeting PDE7 for memory enhancement may provide an alternative to PDE4 inhibitors, which tend to have undesirable gastrointestinal side-effects.

Role of Phosphodiesterase 7 (PDE7) in T Cell Activity. Effects of Selective PDE7 Inhibitors and Dual PDE4/7 Inhibitors on T Cell Functions

Phosphodiesterase 7 (PDE7), a cAMP-specific PDE family, insensitive to rolipram, is present in many immune cells, including T lymphocytes. Two genes of PDE7 have been identified: PDE7A and PDE7B with three or four splice variants, respectively. Both PDE7A and PDE7B are expressed in T cells, and the predominant splice variant in these cells is PDE7A1. PDE7 is one of several PDE families that terminates biological functions of cAMP—a major regulating intracellular factor. However, the precise role of PDE7 in T cell activation and function is still ambiguous. Some authors reported its crucial role in T cell activation, while according to other studies PDE7 activity was not pivotal to T cells. Several studies showed that inhibition of PDE7 by its selective or dual PDE4/7 inhibitors suppresses T cell activity, and consequently T-mediated immune response. Taken together, it seems quite likely that simultaneous inhibition of PDE4 and PDE7 by dual PDE4/7 inhibitors or a combination of selective PDE4 and PDE7 remains the most interesting therapeutic target for the treatment of some immune-related disorders, such as autoimmune diseases, or selected respiratory diseases. An interesting direction of future studies could also be using a combination of selective PDE7 and PDE3 inhibitors.

Comparative study of the expression of cholinergic system components in the CNS of experimental autoimmune encephalomyelitis mice: Acute vs remitting phase

Acetylcholine (ACh) is involved in the modulation of the inflammatory response. ACh levels are regulated by its synthesizing enzyme, choline acetyltransferase (ChAT), and by its hydrolyzing enzymes, mainly acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). A more comprehensive understanding of the cholinergic system in experimental autoimmune encephalomyelitis (EAE) disease progression could pave the path for the development of therapies to ameliorate multiple sclerosis (MS). In this work, we analyzed possible alterations of the CNS cholinergic system in the neuroinflammation process by using a MOG-induced EAE mice model. MOG- and vehicle-treated animals were studied at acute and remitting phases. We examined neuropathology and analyzed mRNA expression of ChAT, AChE and the α7 subunit of the nicotinic acetylcholine receptor (α7nAChR), as well as AChE and BuChE enzyme activities, in brain and spinal cord sections during disease progression. The mRNA expression and enzyme activities of these cholinergic markers were up- or down-regulated in many cholinergic areas and other brain areas of EAE mice in the acute and remitting phases of the disease. BuChE was present in a higher proportion of astroglia and microglia/macrophage cells in the EAE remitting group. The observed changes in cholinergic markers expression and cellular localization in the CNS during EAE disease progression suggests their potential involvement in the development of the neuroinflammatory process and may lay the ground to consider cholinergic system components as putative anti-inflammatory therapeutic targets for MS.

Phosphodiesterase 7 Regulation in Cellular and Rodent Models of Parkinson's Disease

Parkinson's disease is characterized by a loss of dopaminergic neurons in the ventral midbrain. This disease is diagnosed when around 50% of these neurons have already died; consequently, therapeutic treatments start too late. Therefore, an urgent need exists to find new targets involved in the onset and progression of the disease. Phosphodiesterase 7 (PDE7) is a key enzyme involved in the degradation of intracellular levels of cyclic adenosine 3', 5'-monophosphate in different cell types; however, little is known regarding its role in neurodegenerative diseases, and specifically in Parkinson's disease. We have previously shown that chemical as well as genetic inhibition of this enzyme results in neuroprotection and anti-inflammatory activity in different models of neurodegenerative disorders, including Parkinson's disease. Here, we have used in vitro and in vivo models of Parkinson's disease to study the regulation of PDE7 protein levels. Our results show that PDE7 is upregulated after an injury both in the human dopaminergic cell line SH-SY5Y and in primary rat mesencephalic cultures and after lipopolysaccharide or 6-hidroxydopamine injection in the Substantia nigra pars compacta of adult mice. PDE7 increase takes place mainly in degenerating dopaminergic neurons and in microglia cells. This enhanced expression appears to be direct since 6-hydroxydopamine and lipopolysaccharide increase the expression of a 962-bp fragment of its promoter. Taking together, these results reveal an essential function for PDE7 in the pathways leading to neurodegeneration and inflammatory-mediated brain damage and suggest novel roles for PDE7 in neurodegenerative diseases, specifically in PD, opening the door for new therapeutic interventions.

Phosphodiesterases as therapeutic targets for respiratory diseases

Chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and asthma, affect millions of people all over the world. Cyclic adenosine monophosphate (cAMP) which is one of the most important second messengers, plays a vital role in relaxing airway smooth muscles and suppressing inflammation. Given its vast role in regulating intracellular responses, cAMP provides an attractive pharmaceutical target in the treatment of chronic respiratory diseases. Phosphodiesterases (PDEs) are enzymes that hydrolyze cyclic nucleotides and help control cyclic nucleotide signals in a compartmentalized manner. Currently, the selective PDE4 inhibitor, roflumilast, is used as an add-on treatment for patients with severe COPD associated with bronchitis and a history of frequent exacerbations. In addition, other novel PDE inhibitors are in different phases of clinical trials. The current review provides an overview of the regulation of various PDEs and the potential application of selective PDE inhibitors in the treatment of COPD and asthma. The possibility to combine various PDE inhibitors as a way to increase their therapeutic effectiveness is also emphasized.

Sildenafil Inhibits Myelin Expression and Myelination of Oligodendroglial Precursor Cells

Phosphodiesterases (PDEs) have previously been implicated in oligodendrocyte maturation and myelination of central nervous system axons. Sildenafil citrate is a phosphodiesterase inhibitor known to block PDE5, which also reduces inflammation in the experimental autoimmune encephalomyelitis demyelinating model. To find out whether this inhibitor might exert beneficial effects on central nervous system myelin repair activities, we investigated to what degree sildenafil modulates differentiation and maturation of cultured primary rat oligodendroglial precursor cells (OPCs). To this end, gene and protein expression of 2',3'-cyclic-nucleotide 3'-phosphodiesterase, myelin basic protein, and myelin oligodendrocyte glycoprotein, as well as of negative regulators of myelin expression (Hes1, Hes5, Id2, Id4, Rock2, and p57Kip2) were measured in OPCs treated with sildenafil. Moreover, the subcellular distribution of the p57kip2 protein was determined after sildenafil treatment, as this revealed to be an early predictor of the oligodendroglial differentiation capacity. In vitro myelination assays were done to measure the myelination capacity of oligodendrocytes treated with sildenafil. We found that sildenafil significantly diminished myelin gene expression and protein expression. Moreover, sildenafil also increased the expression of Id2 and Id4 negative transcriptional regulators, and the degree of OPCs with cytoplasmic p57kip2 protein localization was reduced, providing evidence that the PDE blocker impaired the differentiation capacity. Finally, sildenafil also interfered with the establishment of internodes as revealed by in vitro myelination assays. We therefore conclude that blocking PDE5 activities exerts a negative impact on intrinsic oligodendroglial differentiation processes.