Ibudilast: a non-selective PDE inhibitor with multiple actions on blood cells and the vascular wall

Actn2 defects accelerates H9c2 hypertrophy via ERK phosphorylation under chronic stress

BACKGROUND

In humans, ACTN2 mutations are identified as highly relevant to a range of cardiomyopathies such as DCM and HCM, while their association with sudden cardiac death has been observed in forensic cases. Although ACTN2 has been shown to regulate sarcomere Z-disc organization, a causal relationship between ACTN2 dysregulation and cardiomyopathies under chronic stress has not yet been investigated.

OBJECTIVE

In this work, we explored the relationship between Actn2 dysregulation and cardiomyopathies under dexamethasone treatment.

METHODS

Previous cases of ACTN2 mutations were collected and the conservative analysis was carried out by MEGA 11, the possible impact on the stability and function of ACTN2 affected by these mutations was predicted by Polyphen-2. ACTN2 was suppressed by siRNA in H9c2 cells under dexamethasone treatment to mimic the chronic stress in vitro. Then the cardiac hypertrophic molecular biomarkers were elevated, and the potential pathways were explored by transcriptome analysis.

RESULTS

Actn2 suppression impaired calcium uptake and increased hypertrophy in H9c2 cells under dexamethasone treatment. Concomitantly, hypertrophic molecular biomarkers were also elevated in Actn2-suppressed cells. Further transcriptome analysis and Western blotting data suggested that Actn2 suppression led to the excessive activation of the MAPK pathway and ERK cascade. In vitro pharmaceutical intervention with ERK inhibitors could partially reverse the morphological changes and inhibit the excessive cardiac hypertrophic molecular biomarkers in H9c2 cells.

CONCLUSION

Our study revealed a functional role of ACTN2 under chronic stress, loss of ACTN2 function accelerated H9c2 hypertrophy through ERK signaling. A commercial drug, Ibudilast, was identified to reverse cell hypertrophy in vitro.

Therapeutic perspectives on PDE4B inhibition in adipose tissue dysfunction and chronic liver injury

INTRODUCTION

Chronic liver disease (CLD) is a complex disease associated with profound dysfunction. Despite an incredible burden, the first and only pharmacotherapy for metabolic-associated steatohepatitis was only approved in March of this year, indicating a gap in the translation of preclinical studies. There is a body of preclinical work on the application of phosphodiesterase 4 inhibitors in CLD, none of these molecules have been successfully translated into clinical use.

AREAS COVERED

To design therapies to combat CLD, it is essential to consider the dysregulation of other tissues that contribute to its development and progression. As such, proper therapies must combat this throughout the body rather than focusing only on the liver. To detail this, literature characterizing the pathogenesis of CLD was pulled from PubMed, with a particular focus placed on the role of PDE4 in inflammation and metabolism. Then, the focus is shifted to detailing the available information on existing PDE4 inhibitors.

EXPERT OPINION

This review gives a brief overview of some of the pathologies of organ systems that are distinct from the liver but contribute to disease progression. The demonstrated efficacy of PDE4 inhibitors in other human inflammatory diseases should earn them further examination for the treatment of CLD.

Emerging Potential of the Phosphodiesterase (PDE) Inhibitor Ibudilast for Neurodegenerative Diseases: An Update on Preclinical and Clinical Evidence

Neurodegenerative diseases constitute a broad range of central nervous system disorders, characterized by neuronal degeneration. Alzheimer's disease, Parkinson's disease, amyolotrophic lateral sclerosis (ALS), and progressive forms of multiple sclerosis (MS) are some of the most frequent neurodegenerative diseases. Despite their diversity, these diseases share some common pathophysiological mechanisms: the abnormal aggregation of disease-related misfolded proteins, autophagosome-lysosome pathway dysregulation, impaired ubiquitin-proteasome system, oxidative damage, mitochondrial dysfunction and excessive neuroinflammation. There is still no effective drug that could halt the progression of neurodegenerative diseases, and the current treatments are mainly symptomatic. In this regard, the development of novel multi-target pharmaceutical approaches presents an attractive therapeutic strategy. Ibudilast, an anti-inflammatory drug firstly developed as an asthma treatment, is a cyclic nucleotide phosphodiesterases (PDEs) inhibitor, which mainly acts by increasing the amount of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), while downregulating the pro-inflammatory factors, such as tumor necrosis factor-α (TNF-α), macrophage migration inhibitory factor (MIF) and Toll-like receptor 4 (TLR-4). The preclinical evidence shows that ibudilast may act neuroprotectively in neurodegenerative diseases, by suppressing neuroinflammation, inhibiting apoptosis, regulating the mitochondrial function and by affecting the ubiquitin-proteasome and autophagosome-lysosome pathways, as well as by attenuating oxidative stress. The clinical trials in ALS and progressive MS also show some promising results. Herein, we aim to provide an update on the emerging preclinical and clinical evidence on the therapeutic potential of ibudilast in these disorders, discuss the potential challenges and suggest the future directions.

Ibudilast attenuates cocaine self-administration and prime- and cue-induced reinstatement of cocaine seeking in rats

Ibudilast is a non-selective phosphodiesterase (PDE) inhibitor and glial cell modulator which has shown great promise for the treatment of drug and alcohol use disorders in recent clinical studies. However, it is unknown whether and how ibudilast affects cocaine seeking behavior. Here we show that systemic administration of ibudilast dose-dependently reduced cocaine self-administration under fixed- and progressive-ratio reinforcement schedules in rats and shifted cocaine dose-response curves downward. In addition, ibudilast decreased cocaine prime- and cue-induced reinstatement of cocaine seeking. These results indicate that ibudilast was effective in reducing the reinforcing effects of cocaine and relapse to cocaine seeking. Chronic cocaine exposure induces cAMP-related neuroadaptations in the reward circuitry of the brain. To investigate potential mechanisms for ibudilast-induced attenuation of cocaine self-administration, we recorded from ventral tegmental area (VTA) dopamine neurons in ex vivo midbrain slices prepared from rats that had undergone saline and cocaine self-administration. We found cocaine self-administration led to a decrease in inhibitory postsynaptic currents (IPSCs), an increase in the AMPAR/NMDAR ratio, and an increase in the excitation to inhibition (E/I) ratio. Ibudilast pretreatments enhanced GABAergic inhibition and did not further change cocaine-induced potentiation of excitation, leading to normalization of the E/I ratio. Restoration of the balance between excitation and inhibition in VTA dopamine neurons may contribute to the attenuation of cocaine self-administration by ibudilast.

Ibudilast attenuates peripheral inflammatory effects of methamphetamine in patients with methamphetamine use disorder

BACKGROUND

Preclinical studies suggest that the non-selective phosphodiesterase inhibitor, Ibudilast (IBUD) may contribute to the treatment of methamphetamine (METH) use disorder through the attenuation of METH-induced inflammatory markers such as adhesion molecules, sICAM-1 and sVCAM-1, and cytokines, IL-6 and TNF-α.

OBJECTIVE

The present study aimed to test whether treatment with IBUD can attenuate peripheral markers of inflammation during a METH challenge in an inpatient clinical trial of 11 patients.

METHODS

This trial followed a randomized, within-subjects crossover design where participants received a METH challenge, during which five participants were treated with placebo then with IBUD, while the remaining six participants were treated with IBUD prior to placebo. Mixed effects regression modeled changes in peripheral markers of inflammation-sICAM-1, sVCAM-1, TNF-α, IL-6, MIF, and cathepsin D-by treatment condition, with measurements at baseline, 60 min post-METH infusion, and 360 min post-METH infusion.

RESULTS

While on placebo, sICAM-1, sVCAM-1, and cathepsin D significantly increased by 60 min post-METH infusion, while IL-6 significantly increased 360 min post-METH infusion. Treatment with IBUD significantly reduced METH-induced levels of sICAM-1, sVCAM-1, and cathepsin D at 60 min post-METH infusion.

CONCLUSIONS

Our findings demonstrate that IBUD attenuated acute pro-inflammatory effects of METH administration, which may have implications for treatment of METH use disorder.

Association between preoperative use of antithrombotic medications and intraoperative transfusion in older patients undergoing cancer surgery

BACKGROUND

Management of antiplatelet agents and other chronic anticoagulation medications in patients scheduled for surgery can reduce intraoperative bleeding complications. However, few studies on the association of antithrombotics, relative to their duration of action, with intraoperative transfusion have been conducted. We aimed to determine the association of recent use of antithrombotics, relative to their duration of action, with intraoperative transfusion in elderly people undergoing cancer surgery.

METHODS

The study subjects were patients aged 65 years or older who were scheduled for cancer surgery and presented for comprehensive geriatric assessment. We reviewed the baseline patient characteristics obtained from electronic medical records and the patients' preoperative medication history, including anticoagulants, antiplatelet agents, and streptokinase/streptodornase.

RESULTS

A total of 475 cancer patients were included. Multivariate analysis showed that long-acting anticoagulant therapy before surgery was a significant risk factor for intraoperative transfusion. Long-acting anticoagulants increased the risk of transfusion approximately 15.9-fold (95% CI 1.9-136.2). The attributable risk of long-acting anticoagulants to transfusion was approximately 93.7%. Also, low body mass index (BMI) and hepato-pancreato-biliary (HPB) surgery were significantly associated with intraoperative transfusion. The adjusted odds ratios for low BMI (<18.5 kg/m²) and HPB surgery (reference: lower gastrointestinal surgery) were 5.3 (95% CI 1.8-15.4) and 4.9 (95% CI 1.9-12.5), respectively.

CONCLUSIONS

It was found that the perioperative use of long-acting anticoagulants was associated with an increased risk of intraoperative transfusion, further highlighting the importance of medication optimization for elderly patients with cancer surgery.

Ibudilast attenuates expression of behavioral sensitization to cocaine in male and female rats

There are no FDA-approved pharmacotherapies for cocaine use disorder, indicating a need to identify novel reagents with therapeutic potential. Ibudilast is an anti-inflammatory glial attenuator and non-selective phosphodiesterase inhibitor currently undergoing clinical evaluations for methamphetamine, opiate, and alcohol abuse disorders. We previously showed that twice daily (b.i.d.) ibudilast reduces the development of methamphetamine sensitization in male mice. However, nothing is known about the ability of ibudilast to modulate the expression of sensitization that occurs after drug re-exposure during abstinence, effects on cocaine-mediated behaviors, or potentially sexually dimorphic effects. Male and female rats were administered cocaine for 7 days and expression of sensitization was assessed by cocaine challenge after 21 days abstinence. On test days, 15 mg/kg i. p. cocaine was evaluated, whereas 30 mg/kg was administered on intervening days. Lower test doses avoid competition of non-motor behaviors with locomotion. In all measures where sensitization was expressed, ibudilast (7.5 and 10 mg/kg, i. p., b. i.d. for 3 days and once on test day) reversed this behavior to levels seen after acute exposure, but not below. There were some intriguing sexually dimorphic effects that were not a function of estrous cycle. Specifically, distance travelled in the center of the test arena and rearing only sensitized in male rats, and ibudilast reversed these behaviors to levels seen after acute cocaine exposure. In females, center distance travelled was reduced below acute cocaine levels by 7.5 mg/kg ibudilast. Increased distance travelled in the center versus periphery is thought to model anxiolytic-like behavior due to increased predation risk. Taken together, these data suggest that the clinical evaluation of ibudilast could be extended to cocaine use disorder.

Ibudilast, a nonselective phosphodiesterase inhibitor, regulates Th1/Th2 balance and NKT cell subset in multiple sclerosis

We investigated the immunoregulatory effects of ibudilast, a nonselective phosphodiesterase inhibitor, at a clinically applicable dose (60 mg/day p.o. for four weeks) in multiple sclerosis (MS) patients. Sensitive real-time PCR for quantifying cytokine mRNA in the blood CD4- cells revealed that the ibudilast monotherapy significantly reduced tumour necrosis factor-a and interferon (IFN)-g mRNA and the IFN-g/interleukin-4 mRNA ratio, suggesting a shift in the cytokine profile from Th1 toward Th2 dominancy. In a flow cytometric analysis, natural killer T cells, which have been reported to relate to Th2 responses in MS and its animal model (experimental autoimmune encephalomyelitis), increased significantly after the therapy. None of the significant immunological changes were seen in healthy subjects or untreated MS patients. Ibudilast may be a promising therapy for MS and its clinical effects warrant further study.

Opioid adjuvant strategy: improving opioid effectiveness

Opioid analgesics continue to be the mainstay of pharmacologic treatment of moderate to severe pain. Many patients, particularly those suffering from chronic pain, require chronic high-dose analgesic therapy. Achieving clinical efficacy and tolerability of such treatment regimens is hampered by the appearance of opioid-induced side effects such as tolerance, hyperalgesia and withdrawal syndrome. Among the therapeutic options to improve the opioid effectiveness, this current review focuses on strategies combining opioids to other drugs that can modulate opioid-mediated effects. We will discuss about experimental evidences reported for several potential opioid adjuvants, including N-methyl-d-aspartate receptor antagonists, 5-HT7 agonists, sigma-1 antagonists, I2-R ligands, cholecystokinin antagonists, neuropeptide FF-R antagonists and toll-like receptor 4 antagonists.

New therapeutic approaches for the prevention and treatment of migraine

The management of patients with migraine is often unsatisfactory because available acute and preventive therapies are either ineffective or poorly tolerated. The acute treatment of migraine attacks has been limited to the use of analgesics, combinations of analgesics with caffeine, ergotamines, and the triptans. Successful new approaches for the treatment of acute migraine target calcitonin gene-related peptide (CGRP) and serotonin (5-hydroxytryptamine, 5-HT1F) receptors. Other approaches targeting the transient receptor potential vanilloid (TRPV1) receptor, glutamate, GABAA receptors, or a combination of 5-HT1B/1D receptors and neuronal nitric oxide synthesis have been investigated but have not been successful in clinical trials thus far. In migraine prevention, the most promising new approaches are humanised antibodies against CGRP or the CGRP receptor. Non-invasive and invasive neuromodulation approaches also show promise as both acute and preventive therapies, although further studies are needed to define appropriate candidates for these therapies and optimum protocols for their use.

Drug Repurposing for the Development of Novel Analgesics

Drug development consumes huge amounts of time and money and the search for novel analgesics, which are urgently required, is particularly difficult, having resulted in many setbacks in the past. Drug repurposing - the identification of new uses for existing drugs - is an alternative approach, which bypasses most of the time- and cost-consuming components of drug development. Recent, unexpected findings suggest a role for several existing drugs, such as minocycline, ceftriaxone, sivelestat, and pioglitazone, as novel analgesics in chronic and neuropathic pain states. Here, we discuss these findings as well as their proposed antihyperalgesic mechanisms and outline the merits of pathway-based repurposing screens, in combination with bioinformatics and novel cellular reprogramming techniques, for the identification of novel analgesics.

A Review: Molecular Aberrations within Hippo Signaling in Bone and Soft-Tissue Sarcomas

The Hippo signaling pathway is an evolutionarily conserved developmental network vital for the regulation of organ size, tissue homeostasis, repair and regeneration, and cell fate. The Hippo pathway has also been shown to have tumor suppressor properties. Hippo transduction involves a series of kinases and scaffolding proteins that are intricately connected to proteins in developmental cascades and in the tissue microenvironment. This network governs the downstream Hippo transcriptional co-activators, YAP and TAZ, which bind to and activate the output of TEADs, as well as other transcription factors responsible for cellular proliferation, self-renewal, differentiation, and survival. Surprisingly, there are few oncogenic mutations within the core components of the Hippo pathway. Instead, dysregulated Hippo signaling is a versatile accomplice to commonly mutated cancer pathways. For example, YAP and TAZ can be activated by oncogenic signaling from other pathways, or serve as co-activators for classical oncogenes. Emerging evidence suggests that Hippo signaling couples cell density and cytoskeletal structural changes to morphogenic signals and conveys a mesenchymal phenotype. While much of Hippo biology has been described in epithelial cell systems, it is clear that dysregulated Hippo signaling also contributes to malignancies of mesenchymal origin. This review will summarize the known molecular alterations within the Hippo pathway in sarcomas and highlight how several pharmacologic compounds have shown activity in modulating Hippo components, providing proof-of-principle that Hippo signaling may be harnessed for therapeutic application in sarcomas.

Pretreatment with antiasthmatic drug ibudilast ameliorates Aβ 1-42-induced memory impairment and neurotoxicity in mice

Amyloid-β peptide (Aβ) is thought to be associated with the progressive neuronal death observed in Alzheimer's disease (AD). However, effective neuroprotective approaches against Aβ neurotoxicity are unavailable. Here, we investigated possible preventive effects of ibudilast, as a pharmacologic phosphodiesterase inhibitor, currently used for treatment of inflammatory diseases such as asthma, on Aβ 1-42-induced neuroinflammatory, apoptotic responses and memory impairment. We found that pretreatment with ibudilast (4 or 12 mg/kg, i.p.) significantly ameliorated impaired spatial learning and memory in intracerebroventricularly (ICV) Aβ 1-42-injected mice, as evidenced by decrease in escape latency during acquisition trials and increase in exploratory activities in the probe trial in Morris water maze (MWM) task, and by increase in the number of correct choices and decrease in latency to enter the shock-free compartment in Y-maze test. Further study showed that ibudilast prevented generation of pro-inflammatory cytokines such as NF-κB p65 and TNF-α as well as pro-apoptotic molecule caspase-3 activation and anti-apoptotic protein Bcl-2 downregulation in both hippocampus and cortex of ICV Aβ 1-42-injected mice. Taken together, our findings suggest that ibudilast has preventive effects on Aβ-induced cognitive impairment via inhibiting neuroinflammatory and apoptotic responses.

Clinical and molecular genetics of the phosphodiesterases (PDEs)

Cyclic nucleotide phosphodiesterases (PDEs) are enzymes that have the unique function of terminating cyclic nucleotide signaling by catalyzing the hydrolysis of cAMP and GMP. They are critical regulators of the intracellular concentrations of cAMP and cGMP as well as of their signaling pathways and downstream biological effects. PDEs have been exploited pharmacologically for more than half a century, and some of the most successful drugs worldwide today affect PDE function. Recently, mutations in PDE genes have been identified as causative of certain human genetic diseases; even more recently, functional variants of PDE genes have been suggested to play a potential role in predisposition to tumors and/or cancer, especially in cAMP-sensitive tissues. Mouse models have been developed that point to wide developmental effects of PDEs from heart function to reproduction, to tumors, and beyond. This review brings together knowledge from a variety of disciplines (biochemistry and pharmacology, oncology, endocrinology, and reproductive sciences) with emphasis on recent research on PDEs, how PDEs affect cAMP and cGMP signaling in health and disease, and what pharmacological exploitations of PDEs may be useful in modulating cyclic nucleotide signaling in a way that prevents or treats certain human diseases.

Neuroinflammation and neuroimmune dysregulation after acute hypoxic-ischemic injury of developing brain

Hypoxic-ischemic (HI) injury to developing brain results from birth asphyxia in neonates and from cardiac arrest in infants and children. It is associated with varying degrees of neurologic sequelae, depending upon the severity and length of HI. Global HI triggers a series of cellular and biochemical pathways that lead to neuronal injury. One of the key cellular pathways of neuronal injury is inflammation. The inflammatory cascade comprises activation and migration of microglia - the so-called "brain macrophages," infiltration of peripheral macrophages into the brain, and release of cytotoxic and proinflammatory cytokines. In this article, we review the inflammatory and immune mechanisms of secondary neuronal injury after global HI injury to developing brain. Specifically, we highlight the current literature on microglial activation in relation to neuronal injury, proinflammatory and anti-inflammatory/restorative pathways, the role of peripheral immune cells, and the potential use of immunomodulators as neuroprotective compounds.

Glial modulators as potential treatments of psychostimulant abuse

Glia (including astrocytes, microglia, and oligodendrocytes), which constitute the majority of cells in the brain, have many of the same receptors as neurons, secrete neurotransmitters and neurotrophic and neuroinflammatory factors, control clearance of neurotransmitters from synaptic clefts, and are intimately involved in synaptic plasticity. Despite their prevalence and spectrum of functions, appreciation of their potential general importance has been elusive since their identification in the mid-1800s, and only relatively recently have they been gaining their due respect. This development of appreciation has been nurtured by the growing awareness that drugs of abuse, including the psychostimulants, affect glial activity, and glial activity, in turn, has been found to modulate the effects of the psychostimulants. This developing awareness has begun to illuminate novel pharmacotherapeutic targets for treating psychostimulant abuse, for which targeting more conventional neuronal targets has not yet resulted in a single, approved medication. In this chapter, we discuss the molecular pharmacology, physiology, and functional relationships that the glia have especially in the light in which they present themselves as targets for pharmacotherapeutics intended to treat psychostimulant abuse disorders. We then review a cross section of preclinical studies that have manipulated glial processes whose behavioral effects have been supportive of considering the glia as drug targets for psychostimulant-abuse medications. We then close with comments regarding the current clinical evaluation of relevant compounds for treating psychostimulant abuse, as well as the likelihood of future prospects.

Importance of glial activation in neuropathic pain

Glia plays a crucial role in the maintenance of neuronal homeostasis in the central nervous system. The microglial production of immune factors is believed to play an important role in nociceptive transmission. Pain may now be considered a neuro-immune disorder, since it is known that the activation of immune and immune-like glial cells in the dorsal root ganglia and spinal cord results in the release of both pro- and anti-inflammatory cytokines, as well as algesic and analgesic mediators. In this review we presented an important role of cytokines (IL-1alfa, IL-1beta, IL-2, IL-4, IL-6, IL-10, IL-15, IL-18, TNFalpha, IFNgamma, TGF-beta 1, fractalkine and CCL2); complement components (C1q, C3, C5); metaloproteinases (MMP-2,-9) and many other factors, which become activated on spinal cord and DRG level under neuropathic pain. We discussed the role of the immune system in modulating chronic pain. At present, unsatisfactory treatment of neuropathic pain will seek alternative targets for new drugs and it is possible that anti-inflammatory factors like IL-10, IL-4, IL-1alpha, TGF-beta 1 would fulfill this role. Another novel approach for controlling neuropathic pain can be pharmacological attenuation of glial and immune cell activation. It has been found that propentofylline, pentoxifylline, minocycline and fluorocitrate suppress the development of neuropathic pain. The other way of pain control can be the decrease of pro-nociceptive agents like transcription factor synthesis (NF-kappaB, AP-1); kinase synthesis (MEK, p38MAPK, JNK) and protease activation (cathepsin S, MMP9, MMP2). Additionally, since it is known that the opioid-induced glial activation opposes opioid analgesia, some glial inhibitors, which are safe and clinically well tolerated, are proposed as potential useful ko-analgesic agents for opioid treatment of neuropathic pain. This review pointed to some important mechanisms underlying the development of neuropathic pain, which led to identify some possible new approaches to the treatment of neuropathic pain, based on the more comprehensive knowledge of the interaction between the nervous system and glial and immune cells.

Glial cell modulators attenuate methamphetamine self-administration in the rat

Neuroinflammation induced by activated microglia and astrocytes can be elicited by drugs of abuse. Methamphetamine administration activates glial cells and increases proinflammatory cytokine production, and there is recent evidence of a linkage between glial cell activation and drug abuse-related behavior. We have previously reported that ibudilast (AV411; 3-isobutyryl-2-isopropylpyrazolo-[1,5-a]pyridine), which inhibits phosphodiesterase (PDE) and pro-inflammatory activity, blocks reinstatement of methamphetamine-maintained responding in rats, and that ibudilast and AV1013, an amino analog of ibudilast, which has similar glial-attenuating properties but limited PDE activity, attenuate methamphetamine-induced locomotor activity and sensitization in mice. The present study's objective was to determine whether co-administered ibudilast, AV1013, or minocycline, which is a tetracycline derivative that also suppresses methamphetamine-induced glial activation, would attenuate active methamphetamine i.v. self-administration in Long-Evans hooded rats. Rats were initially trained to press a lever for 0.1mg/kg/inf methamphetamine according to a FR1 schedule during 2-h daily sessions. Once stable responding was obtained, twice daily ibudilast (1, 7.5, 10mg/kg), AV1013 (1, 10, 30mg/kg), or once daily minocycline (10, 30, 60mg/kg), or their corresponding vehicles, were given i.p. for three consecutive days during methamphetamine (0.001, 0.03, 0.1mg/kg/inf) self-administration. Ibudilast, AV1013, and minocycline all significantly (p<0.05) reduced responding maintained by 0.03mg/kg/inf methamphetamine that had maintained the highest level of infusions under vehicle conditions. These results suggest that targeting glial cells may provide a novel approach to pharmacotherapy for treating methamphetamineabuse.

Effect of ibudilast on the reciprocal inhibitory visual-vestibular interaction closely related to dizziness after cerebral ischemia

BACKGROUND

Many patients with chronic cerebrovascular diseases suffer dizziness. Our earlier findings suggested that prolonged terms of dizziness episodes may decrease the regional cerebral blood flow (CBF) in the occipital visual cortex via a remote effect from the vestibular cortex.

METHODS

We studied 9 patients who suffered episodes of dizziness since the onset of chronic cerebral ischemia. Their at-rest CBF was measured at entry into the study and approximately 3 months after the start of ibudilast therapy when all patients reported the resolution of dizziness.

RESULTS

After 3 months of ibudilast their at-rest CBF was significantly increased in the left occipital lobe (P = .02). CBF after acetazolamide (ACZ) loading was significantly increased in the bilateral occipital lobes (right, P = .049; left, P = .02) and in the bilateral parieto-insular vestibular cortex (PIVC; right and left, P = .02). There were no significant CBF changes in any other areas.

CONCLUSIONS

Our findings indicate that the occipital cortex and PIVC were implicated in their dizziness after cerebral ischemia. We discuss the underlying mechanism(s) and the relationship between dizziness and reciprocal inhibitory visual-vestibular interactions.

The glial modulatory drug AV411 attenuates mechanical allodynia in rat models of neuropathic pain

Controlling neuropathic pain is an unmet medical need and we set out to identify new therapeutic candidates. AV411 (ibudilast) is a relatively nonselective phosphodiesterase inhibitor that also suppresses glial-cell activation and can partition into the CNS. Recent data strongly implicate activated glial cells in the spinal cord in the development and maintenance of neuropathic pain. We hypothesized that AV411 might be effective in the treatment of neuropathic pain and, hence, tested whether it attenuates the mechanical allodynia induced in rats by chronic constriction injury (CCI) of the sciatic nerve, spinal nerve ligation (SNL) and the chemotherapeutic paclitaxel (Taxol). Twice-daily systemic administration of AV411 for multiple days resulted in a sustained attenuation of CCI-induced allodynia. Reversal of allodynia was of similar magnitude to that observed with gabapentin and enhanced efficacy was observed in combination. We further show that multi-day AV411 reduces SNL-induced allodynia, and reverses and prevents paclitaxel-induced allodynia. Also, AV411 cotreatment attenuates tolerance to morphine in nerve-injured rats. Safety pharmacology, pharmacokinetic and initial mechanistic analyses were also performed. Overall, the results indicate that AV411 is effective in diverse models of neuropathic pain and support further exploration of its potential as a therapeutic agent for the treatment of neuropathic pain.

The Neuroprotective Effects of BNG-1: A New Formulation of Traditional Chinese Medicines for Stroke

BNG-1, a novel mixture of traditional Chinese medicines with a long history in the treatment of stroke, exhibited acute neuroprotection effect on rats with middle cerebral artery occlusion (MCAO). Anti-ischemic effects were seen in both animals receiving BNG-1 before the ischemic insult as well as in animals receiving the drug formulation after surgical occlusion of the artery. Anti-thrombic activity was seen in vitro to inhibit arachidonic acid-induced platelet aggregation and in vivo to prolong bleeding time in mice. BNG-1 was also found to inhibit several phosphodiesterase (PDE) isoforms with potency order of the following rank: PDE 1>PDE 3>PDE 6>PDE 2>PDE 4>PDE 5. Other pre-clinical results and emerging clinical data coupled with the present findings suggest that BNG-1 may be a safe and effective therapy for both the prevention and treatment of cerebral stroke. Moreover, the fundamental cellular mechanism underlying its therapeutic effects may result from phosphodiesterase inhibition.

The glial cell modulators, ibudilast and its amino analog, AV1013, attenuate methamphetamine locomotor activity and its sensitization in mice

Over 800,000 Americans abuse the psychomotor stimulant, methamphetamine, yet its abuse is without an approved medication. Methamphetamine induces hypermotor activity, and sensitization to this effect is suggested to represent aspects of the addiction process. Methamphetamine's regulation of 3'-5'-cyclic adenosine monophosphate (cAMP) levels may be partially responsible for its behavioral effects, and compounds that inhibit phosphodiesterase (PDE), the enzyme that degrades cAMP, can alter methamphetamine-induced behaviors. Methamphetamine also activates glial cells and causes a subsequent increase in pro-inflammatory cytokine levels. Modulation of glial cell activation is associated with changes in behavioral responses, and substances that oppose inflammatory activity can attenuate drug-induced behaviors. Ibudilast (aka AV411; 3-isobutyryl-2-isopropylpyrazolo-[1,5-a]pyridine), inhibits both PDE and glial pro-inflammatory activity. Ibudilast's amino analog, AV1013, modulates similar glial targets but negligibly inhibits PDE. The present study determined whether ibudilast and AV1013 would attenuate methamphetamine-induced locomotor activity and its sensitization in C57BL/6J mice. Mice were treated b.i.d. with ibudilast (1.8-13 mg/kg), AV1013 (10-56 mg/kg) or their vehicles intraperitoneally for 7 days, beginning 48 h before 5 days of daily 1-h locomotor activity tests. Each test was initiated by either a methamphetamine (3 mg/kg) or a saline injection. Ibudilast significantly (P<0.05) reduced the acute, chronic, and sensitization effects of methamphetamine's locomotor activity without significantly affecting activity by itself. AV1013 had similar anti-methamphetamine effects, suggesting that glial cell activity, by itself, can modulate methamphetamine's effects and perhaps serve as a medication target for its abuse.

The antinociceptive effect of the asthma drug ibudilast in rat models of peripheral and central neuropathic pain

Ibudilast, an asthma drug, has demonstrated antinociceptive effects in several rat models of peripheral neuropathic pain, and a proposed mechanism of action is the inhibition of release of the cytokine tumor necrosis factor-α (TNF-α) from activated spinal microglia. Spinal glial activation has also been demonstrated in rat models of central neuropathic pain following spinal cord injury (SCI). The current study evaluated the effect of a short course of treatment with ibudilast on SCI-induced pain, and for comparison, following a chronic constriction injury (CCI; the Bennett model) of the sciatic nerve in rats. The effects of ibudilast treatment on spinal (SCI and CCI rats), and nerve tissue (CCI only) TNF-α content were also evaluated. Following an acute midthoracic SCI with a microvascular clip (20-g force), hindpaw withdrawal thresholds were significantly decreased, indicating below-level cutaneous tactile hypersensitivity. Likewise, unilateral loose ligation of the sciatic nerve led to a robust ipsilateral tactile hypersensitivity. Rats were treated with either ibudilast (10 mg/kg IP) or vehicle (2 mL/kg) during the period of robust and steady hindpaw hypersensitivity for each model--CCI rats were treated 14-16 days post-surgery, and SCI rats were treated 30-32 days post-surgery--and tested daily. Ibudilast ameliorated hindpaw hypersensitivity in both SCI and CCI rats, whereas vehicle treatment had no effect. Interestingly, repeated treatment led to increased baseline thresholds, beyond the duration of the drug half-life, suggesting persistent changes in neuropathic pain processing. In SCI rats, an increase in TNF-α content in spinal tissue rostral to the SCI was observed. Ibudilast treatment did not significantly alter this increase. In rats with a CCI, TNF-α content was markedly increased in the ipsilateral sciatic nerve and was partially reduced following ibudilast, but not vehicle, treatment. Ibudilast could be useful for the treatment of neuropathic pain of central as well as peripheral origin.

Phosphodiesterase inhibitors. Part 1: Synthesis and structure-activity relationships of pyrazolopyridine-pyridazinone PDE inhibitors developed from ibudilast

Ibudilast [1-(2-isopropylpyrazolo[1,5-a]pyridin-3-yl)-2-methylpropan-1-one] is a nonselective phosphodiesterase inhibitor used clinically to treat asthma. Efforts to selectively develop the PDE3- and PDE4-inhibitory activity of ibudilast led to replacement of the isopropyl ketone by a pyridazinone heterocycle. Structure-activity relationship exploration in the resulting 6-(pyrazolo[1,5-a]pyridin-3-yl)pyridazin-3(2H)-ones revealed that the pyridazinone lactam functionality is a critical determinant for PDE3-inhibitory activity, with the nitrogen preferably unsubstituted. PDE4 inhibition is strongly promoted by introduction of a hydrophobic substituent at the pyridazinone N(2) centre and a methoxy group at C-7' in the pyrazolopyridine. Migration of the pyridazinone ring connection from the pyrazolopyridine 3'-centre to C-4' strongly enhances PDE4 inhibition. These studies establish a basis for development of potent PDE4-selective and dual PDE3/4-selective inhibitors derived from ibudilast.

CD74: an emerging opportunity as a therapeutic target in cancer and autoimmune disease

INTRODUCTION

CD74, also known as the invariant chain, participates in several key processes of the immune system, including antigen presentation, B-cell differentiation and inflammatory signaling. Despite being described more than 3 decades ago, new functions and novel interactions for this evolutionarily conserved molecule are still being unraveled. As a participant in several immunological processes and an indicator of disease in some conditions, it has potential as a therapeutic target.

AREAS COVERED

The relationship between the structure of CD74 variants and their physiological functions is detailed in this review. The function of CD74 in several cell lineages is examined with a focus on the interactions with cathepsins and, in an inflammatory milieu, the pro-inflammatory cytokine macrophage migratory inhibitory factor. The role of CD74 signaling in inflammatory and carcinogenic processes is outlined as is the use of CD74 as a therapeutic target (in cancer) and tool (as a vaccine).

EXPERT OPINION

CD74 has several roles within the cell and throughout the immune system. Most prominent amongst these are the complex relationships with MIF and cathepsins. Modulation of CD74 function shows promise for the effective amelioration of disease.

Glia-induced reversible disruption of blood-brain barrier integrity and neuropathological response of the neurovascular unit

The blood-brain barrier (BBB) is the regulated interface that mediates selective transcellular transport of nutrients and essential components from the blood into the brain parenchyma. Many neurodegenerative diseases including stroke, multiple sclerosis, rheumatoid arthritis, and AIDS dementia exhibit loss of BBB integrity. Despite the increasing body of evidence for the involvement of glia in maintaining the BBB, few studies have addressed glial/endothelial/extracellular matrix interactions. A chemically induced astrocyte lesion provides a noninvasive model to study reversible BBB dysfunction in vivo. Blood-brain barrier integrity was assessed with fluorescent dextran tracers (3-70 kDa) and magnetic resonance imaging, in parallel with confocal and electron microscopy imaging of the neurovascular unit. These studies demonstrated modified tight-junction protein expression with loss of vascular integrity. We propose that adherens junction proteins and extracellular matrix remodeling provide a temporary size-selective barrier, whereas astrocyte and microglia activation direct tight-junction proteins to paracellular domains and restore BBB integrity. Morphological comparisons were made with the area postrema, a circumventricular organ with a naturally porous BBB. Further studies into cellular mechanisms of glial/endothelial/extracellular matrix interactions may identify novel glial-based therapeutic targets and innovate therapies for modulating diseases in which gliosis and raised levels of pro-inflammatory mediators are central components.

Ibudilast, a mixed PDE3/4 inhibitor, causes a selective and nitric oxide/cGMP-independent relaxation of the intracranial vertebrobasilar artery

Ibudilast, a mixed phosphodiesterase (PDE) 3/4 inhibitor, is a cerebral vasodilator widely used in Japan for treating post-stroke dizziness. However, little studies have been conducted on the vasorelaxant effects of PDE inhibitors in the vertebrobasilar artery associated with dizziness onset. The in vitro vasorelaxant properties of ibudilast were, therefore, investigated by comparing with known selective PDE inhibitors, using vertebrobasilar arteries. Vasorelaxant activities of PDE3, PDE4, PDE5 inhibitors, and ibudilast were assessed in 5-hydroxytryptamine precontracted ring preparations from rabbit intracranial and extracranial vertebrobasilar arteries. Ibudilast more selectively relaxed the intracranial than extracranial artery. Similarly, selective PDE3 and PDE4 inhibitors showed higher selectivity for intracranial arteries. Furthermore, like selective PDE4 inhibitor, the vasorelaxation by ibudilast accompanied by increase in cAMP levels was inhibited by the adenylyl cyclase inhibitor SQ22536 in intracranial arteries. Next, it was examined whether nitric oxide (NO)/cGMP signaling is involved in this vasorelaxation in intracranial arteries. The suppression of NO/cGMP signaling by an NO synthase inhibitor or a guanylyl cyclase inhibitor potentiated the vasorelaxion by a PDE3 inhibitor and reduced that by a PDE4 inhibitor, while either suppression of the signaling had little influence on that by ibudilast. These results suggest that ibudilast has the high vasoselectivity for intracranial artery based on a mixed PDE3 and PDE4-inhibition, and effectively relaxes intracranial arteries independently of NO/cGMP signaling because of its vasorelaxation compensated by either PDE3- or PDE4-inhibition depending on the state of NO/cGMP signaling change.

The effect of morphine on glial cells as a potential therapeutic target for pharmacological development of analgesic drugs

Opioids have played a critical role in achieving pain relief in both modern and ancient medicine. Yet, their clinical use can be limited secondary to unwanted side effects such as tolerance, dependence, reward, and behavioral changes. Identification of glial-mediated mechanisms inducing opioid side effects include cytokine receptors, kappa-opioid receptors, N-methyl-D-aspartate receptors, and the recently elucidated Toll-like receptors. Newer agents targeting these receptors such as AV411, MK-801, AV333, and SLC022, and older agents used outside the United States or for other disease conditions, such as minocycline, pentoxifylline, and UV50488H, all show varied but promising profiles for providing significant relief from opioid side effects, while simultaneously potentiating opioid analgesia.

Ibudilast inhibits cerebral aneurysms by down-regulating inflammation-related molecules in the vascular wall of rats

OBJECTIVE

Phosphodiesterase-4 (PDE-4) is a cyclic adenosine monophosphate-specific enzyme involved in various inflammatory diseases. We studied its role in and the effect of ibudilast, which predominantly blocks PDE-4, on rat cerebral aneurysms.

METHODS

Cerebral aneurysms were induced at the anterior cerebral artery-olfactory artery bifurcation of female rats subjected to hypertension, increased hemodynamic stress, and estrogen deficiency. The effect of ibudilast (30 or 60 mg/kg/d for 3 months) on their cerebral aneurysms was studied by morphological and immunohistochemical assessment and quantitative real-time polymerase chain reaction assay. In our in vitro study, we grew endothelial cells stimulated by angiotensin II under estrogen-free conditions and examined the effect of ibudilast on PDE-4 activation and the cyclic adenosine monophosphate level.

RESULTS

Morphological evaluation using vascular corrosion casts showed ibudilast significantly suppressed cerebral aneurysms in a dose-dependent manner. In rats with induced cerebral aneurysms, the gene and protein expression of PDE-4 was high, and endothelial leukocyte adhesion molecules (P-selectin, intracellular adhesion molecule 1, and vascular adhesion molecule 1), matrix metalloproteinase-9, and tumor necrosis alpha were expressed. Macrophage migration was also increased. Treatment with ibudilast down-regulated these molecules, suppressed macrophage migration into the aneurysm wall, and inhibited PDE-4 activation and the elevation of cyclic adenosine monophosphate in endothelial cells.

CONCLUSION

These results suggest that blocking of PDE4 is associated with the reduction of inflammation-related molecules and macrophage migration, thereby reducing the progression of cerebral aneurysms. It may represent a new conservative therapy to treat patients with cerebral aneurysms.

Cross-species comparisons of the pharmacokinetics of ibudilast

To enable clinical development of ibudilast for new indications, its pharmacokinetics were characterized in mice, rats, rabbits, dogs, cynomolgus monkeys, and minipigs. Animal pharmacokinetics were compared with a separate study in healthy volunteers. Following oral dosing, the dose-normalized area under the curve (AUC) (DN-AUC(24h)) in humans is 896 ((ng*h ml(-1))/(mg kg(-1))), and in animals ranges from 0.3 to 87. The variability among species cannot be explained by intrinsic clearance, which in intravenous dosing experiments shows only moderate interspecies variation (13-41 l h(-1) m(-2)). A portal vein rat pharmacokinetics model suggested that differences in first-pass gut clearance may explain some of the interspecies variation in oral bioavailability. Ibudilast shows auto-induction of metabolism in some animals, but not in humans. Plasma protein binding in humans and some animals is greater than or equal to 95%. The primary metabolite 6,7-dihyrdodiol-ibudilast is measurable and has been quantitated in plasma from animals and humans. Finally, biodistribution studies show that ibudilast distributes rapidly, extensively, and reversibly to the central nervous system.

A Cell-based beta-Lactamase Reporter Gene Assay for the CREB Signaling Pathway

The Cyclic-AMP Response Element Binding (CREB) proteins comprise a family of transcription factors that stimulate or repress the expression of a wide variety of genes by binding to nucleotide sequences known as cAMP Response Elements. CREB-mediated transcription has been implicated in a wide variety of important physiological processes, including long-term memory, and enhancement of CREB signaling has been suggested as an attractive therapeutic strategy for human memory disorders. To identify small molecule compounds that enhance CREB pathway signaling, we have optimized and validated a cell-based β-lactamase reporter gene CREB pathway assay in 1536-well plate format. The LOPAC library of 1280 compounds was screened in triplicate in this assay on a quantitative high throughput screening (qHTS) platform. A variety of compounds which affect known members of the CREB pathway were identified as active, including twelve known phosphodiesterase (PDE) inhibitors, and forskolin, a known activator of adenylate cyclase, thus validating the assay’s performance. This qHTS platform assay will facilitate identification of novel small molecule CREB signaling enhancers, which will be useful for chemical genetic dissection of the CREB pathway and as starting points for potentially memory-enhancing therapeutics.

Ibudilast-induced decreases in cytosolic Ca(2+) level and contraction in rat aorta

The mechanism by which ibudilast induces vasodilation was examined in isolated endothelium-denuded rat aorta. Ibudilast inhibited the contractions induced by phenylephrine (PE) and high K(+) with decrease of [Ca(2+)](i) level in a concentration-dependent manner, to the same degree. 3-Isobutyl-1-methylxanthine (IBMX) inhibited PE-induced contraction and [Ca(2+)](i) level in a concentration-dependent manner, but it inhibited high K(+)-induced contraction without decrease of [Ca(2+)](i) level. In comparison with IBMX, the increases of cAMP and cGMP contents in ibudilast were much smaller than that of muscle tension. Ibudilast did not inhibit 12-deoxyphorbol 13-isobutyrate (DPB)-induced contraction in the presence of verapamil. Treatment with 30 microM ibudilast inhibited the extracellularly added Ca(2+)-induced muscle tension and increases in [Ca(2+)](i) level during high K(+) depolarization. These results suggested that ibudilast inhibited PE- and high K(+)-induced muscle contractions mainly by the inhibition of [Ca(2+)](i) level in endothelium-denuded rat aorta.

Ibudilast (AV-411)

The treatment of neuropathic pain is a major unresolved medical challenge. Present pharmacotherapies only have modest efficacy and numerous side effects. The use of opioid analgesics is additionally coupled with dependence and withdrawal syndromes. Ibudilast (AV-411) is a non-selective phosphodiesterase inhibitor that is also known to suppress glial cell activation. It has been used clinically for other indications with a good safety profile. As glial cell activation is considered to crucially contribute to neuropathic pain as well as opioid dependence and withdrawal, the authors conceived that ibudilast may be useful for treating these conditions. Preclinical data indicate that ibudilast crosses the blood-brain barrier, is well tolerated, is active on oral administration, reduces glial activation and attenuates pain symptoms in diverse rat models of neuropathic pain. In addition, it enhances acute morphine analgesia and attenuates morphine tolerance and withdrawal. Thus ibudilast may improve opioid efficacy and is a promising therapeutic candidate for neuropathic pain, with a novel mechanism of action.

Preferential inhibition of human phosphodiesterase 4 by ibudilast

Ibudilast ophthalmic solution exhibited an improved clinical efficacy over cromoglycate in the treatment of allergic conjunctivitis. To further characterize its principal mode of action, the phosphodiesterase (PDE) inhibitory profile of ibudilast has been examined using human recombinant enzymes. Ibudilast, but not the other commonly used anti-allergic ophthalmic solutions including cromoglycate, ketotifen, tranilast and levocabastine, potently inhibits purified human PDE4A, 4B, 4C and 4D with IC50 values at 54, 65, 239 and 166 nM, respectively. Ibudilast effectively blocks lipopolysaccharide (LPS)-induced tumor necrosis factor (TNFalpha, IC50 = 6.2 microM) and N-formyl-Met-Leu-Phe (fMLP)-induced leukotriene (LT) B4 biosynthesis (IC50 = 2.5 microM) in human whole blood, which are 3 and 6-fold more potent than cilomilast, respectively. The attenuated inflammatory and allergic responses from the potent and preferential PDE4 inhibition of ibudilast may have contributed significantly to its beneficial pharmacological responses and distinguishes ibudilast from the other ophthalmic solutions in the treatment of ocular allergy.

Cyclic nucleotide phosphodiesterases and their role in immunomodulatory responses: advances in the development of specific phosphodiesterase inhibitors

The activity of phosphodiesterases (PDEs) is associated with a wide variety of diseases and an intense effort toward the development of specific PDEs inhibitors has been generated for the last years. They are the enzymes responsible for the hydrolysis of intracellular cyclic adenosine and guanosine monophosphate, and their complexity, as well as their different functional role, makes these enzymes a very attractive therapeutic target. This review is focused on the role of PDEs played on immunomodulatory processes and the advance on the development of specific inhibitors, covering PDEs mainly related to the regulation of autoimmune processes, PDE4 and PDE7. The review also highlights the novel structural classes of PDE4 and PDE7 inhibitors, and the therapeutic potential that combined PDE4/PDE7 inhibitors offer as immunomodulatory agents.

Ibudilast, a phosphodiesterase inhibitor, protects against white matter damage under chronic cerebral hypoperfusion in the rat

Cerebrovascular white matter (WM) lesions, which are frequently observed in vascular cognitive impairment and vascular dementia, can be produced in rats by clipping the common carotid arteries bilaterally. Since TNF-alpha is known to cause the degeneration of myelin, we examined whether these lesions can be ameliorated by ibudilast, a cyclic AMP phosphodiesterase (PDE) inhibitor that suppresses tumor necrosis factor (TNF)-alpha production. After the ligation of both common carotid arteries in 29 rats, 21 rats received a daily oral administration of 10, 30 or 60 mg/kg ibudilast and 8 rats received vehicle for 14 days. The pathological changes in the white matter were quantified in terms of white matter lesions and the emergence of activated microglia immunoreactive for major histocompatibility complex (MHC) antigen. In the vehicle-treated animals, white matter lesions and microglial activation occurred in the optic tract, internal capsule and corpus callosum. A low dose (10 mg/kg) of ibudilast failed to suppress the white matter lesions and microglial activation, whereas a dose of either 30 or 60 mg/kg ibudilast ameliorated these lesions (p<0.001). Without an alterations in laboratory blood data, 60 mg/kg ibudilast exhibited percent reduction of the white matter lesions ranging between 50% and 70%, which was more effective than 30 mg/kg ibudilast (p<0.05). The TNF-alpha immunoreactive glia decreased in number in the 60 mg/kg ibudilast-treated group as compared to the vehicle-treated group (p<0.001). These results indicate a dose-dependent protective effect of ibudilast against cerebrovascular white matter lesions and suggest a potential use for ibudilast in the treatment of vascular dementia.

Toward safer methodologies for the synthesis of polyheterocyclic systems: intramolecular arylation of arenes under Mizoroki-Heck reaction conditions

[reaction: see text] A straightforward synthesis of ibudilast-related pyrazolo[1,5-f]phenanthridines is accomplished by a tandem amine-exchange/heterocyclization of arylenaminones followed by an intramolecular biaryl coupling of the so-formed diarylpyrazoles. The direct, environmentally convenient ring-closure of the latter pyrazole intermediates, which show a close resemblance to the antiinflammatory drug celecoxib, is efficiently performed under Mizoroki-Heck reaction conditions.