Effects of ibudilast on hippocampal long-term potentiation and passive avoidance responses in rats with transient cerebral ischemia

An experimentally validated approach to automated biological evidence generation in drug discovery using knowledge graphs

Explaining predictions for drug repositioning with biological knowledge graphs is a challenging problem. Graph completion methods using symbolic reasoning predict drug treatments and associated rules to generate evidence representing the therapeutic basis of the drug. Yet the vast amounts of generated paths that are biologically irrelevant or not mechanistically meaningful within the context of disease biology can limit utility. We use a reinforcement learning based knowledge graph completion model combined with an automatic filtering approach that produces the most relevant rules and biological paths explaining the predicted drug's therapeutic connection to the disease. In this work we validate the approach against preclinical experimental data for Fragile X syndrome demonstrating strong correlation between automatically extracted paths and experimentally derived transcriptional changes of selected genes and pathways of drug predictions Sulindac and Ibudilast. Additionally, we show it reduces the number of generated paths in two case studies, 85% for Cystic fibrosis and 95% for Parkinson's disease.

A novel combination treatment for fragile X syndrome predicted using computational methods

Fragile X syndrome is a neurodevelopmental disorder caused by silencing of the fragile X messenger ribonucleotide gene. Patients display a wide spectrum of symptoms ranging from intellectual and learning disabilities to behavioural challenges including autism spectrum disorder. In addition to this, patients also display a diversity of symptoms due to mosaicism. These factors make fragile X syndrome a difficult syndrome to manage and suggest that a single targeted therapeutic approach cannot address all the symptoms. To this end, we utilized Healx's data-driven drug discovery platform to identify a treatment strategy to address the wide range of diverse symptoms among patients. Computational methods identified the combination of ibudilast and gaboxadol as a treatment for several pathophysiological targets that could potentially reverse multiple symptoms associated with fragile X syndrome. Ibudilast is an approved broad-spectrum phosphodiesterase inhibitor, selective against both phosphodiesterase 4 and phosphodiesterase 10, and has demonstrated to have several beneficial effects in the brain. Gaboxadol is a GABAA receptor agonist, selective against the delta subunit, which has previously displayed encouraging results in a fragile X syndrome clinical trial. Alterations in GABA and cyclic adenosine monophosphate metabolism have long since been associated with the pathophysiology of fragile X syndrome; however, targeting both pathways simultaneously has never been investigated. Both drugs have a good safety and tolerability profile in the clinic making them attractive candidates for repurposing. We set out to explore whether the combination of ibudilast and gaboxadol could demonstrate therapeutic efficacy in a fragile X syndrome mouse model. We found that daily treatment with ibudilast significantly enhanced the ability of fragile X syndrome mice to perform a number of different cognitive assays while gaboxadol treatment improved behaviours such as hyperactivity, aggression, stereotypy and anxiety. Importantly, when ibudilast and gaboxadol were co-administered, the cognitive deficits as well as the aforementioned behaviours were rescued. Moreover, this combination treatment showed no evidence of tolerance, and no adverse effects were reported following chronic dosing. This work demonstrates for the first time that by targeting multiple pathways, with a combination treatment, we were able to rescue more phenotypes in a fragile X syndrome mouse model than either ibudilast or gaboxadol could achieve as monotherapies. This combination treatment approach holds promise for addressing the wide spectrum of diverse symptoms in this heterogeneous patient population and may have therapeutic potential for idiopathic autism.

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 may improve attention during early abstinence from methamphetamine

BACKGROUND

Inattention is a deficit related to instilling abstinence from methamphetamine (MA) dependence. This study aimed to determine whether ibudilast (IB; 50mg bid) improves attentional abilities compared to placebo during early abstinence from MA dependence.

METHODS

Attention was assessed in 11 MA-dependent non-treatment seeking participants in a phase IB safety-interaction trial. The Conners' Continuous Performance Test-II (CPT-II), a measure of sustained attention and response inhibition, was administered at baseline and on day 22, 48h post a MA challenge under placebo (P; n=6) or IB 50mg bid (n=5). Group differences were compared using Mann-Whitney U Tests. Groups were similar at baseline in premorbid intellectual functioning, attention deficit hyperactivity symptom scores, impulsivity ratings, and education level, but differed in age. Demographically corrected T-scores for CPT-II performances were utilized.

RESULTS

Although no group differences in sustained attention existed at baseline, at follow-up, the IB group (Mdn=44.4) showed reduced variability in response times compared with the P group (Mdn=69.9), U=0.00, z=-2.74, p=.006, r=.83. The IB group (Mdn=45.8) also gave fewer perseverative responses than the P group (Mdn=67.0), U=2.00, z=-2.50, p=.01, r=.75. No other significant differences were observed.

CONCLUSIONS

Findings suggest that IB may have a protective effect on sustained attention during early abstinence from MA dependence. This may guide thinking about mechanism of action should IB demonstrate efficacy as a treatment for MA dependence.

The phosphodiesterase inhibitor, ibudilast, attenuates neuroinflammation in the MPTP model of Parkinson's disease

Background/Aims

Since the degeneration of the nigrostriatal dopaminergic pathway in Parkinson’s disease (PD) is associated with the inflammation process and decreased levels of cyclic nucleotides, inhibition of up-regulated cyclic nucleotide phosphodiesterases (PDEs) appears to be a promising therapeutic strategy. We used ibudilast (IBD), a non-selective PDE3,4,10,11 inhibitor, due to the abundant PDE 4 and 10 expression in the striatum. The present study for the first time examined the efficacy of IBD in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD.

Methods

IBD [0, 20, 30, 40, or 50 mg/kg] was injected b.i.d. subcutaneously for nine days to three-month-old male C57Bl/10Tar mice, beginning two days prior to MPTP (60 mg/kg) intoxication. High-pressure liquid chromatography, Western blot analysis, and real time RT-PCR methods were applied.

Results

Our study demonstrated that chronic administration of IBD attenuated astroglial reactivity and increased glial cell-derived neurotrophic factor (GDNF) production in the striatum. Moreover, IBD reduced TNF-α, IL-6, and IL-1β expression.

Conclusion

IBD had a well-defined effect on astroglial activation in the mouse model of PD; however, there was no protective effect in the acute phase of injury. Diminished inflammation and an increased level of GDNF may provide a better outcome in the later stages of neurodegeneration.

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.

Ibudilast (AV411), and its AV1013 analog, reduce HIV-1 replication and neuronal death induced by HIV-1 and morphine

OBJECTIVE

We explored the antiviral therapeutic potential of ibudilast (AV411, MN-166) and its amino analog, AV1013.

METHODS

We analyzed whether Ibudilast, a nonselective cyclic AMP phosphodiesterase inhibitor that has been used clinically in Asia for bronchial asthma, poststroke dizziness, and ocular allergies, and AV1013, attenuate HIV-1 replication and the synergistic interactions seen with opiate abuse-HIV-1 comorbidity in neuronal death and inflammation.

RESULTS

AV411 and AV1013 inhibited replication by HIV-1 in microglia and significantly suppressed Tat ± morphine-induced tumor necrosis factor-α and MIF production, the activation of the nuclear factor-kappa B subunit p65, and neuronal death. AV411 and AV1013 prevented HIV-1 replication, and attenuated tumor necrosis factor-α and MIF release at concentrations of 100  nmol/l and 1  μmol/l, which are likely achievable at clinical doses. More importantly, co-exposure with morphine did not negate the inhibitory actions of AV411.

CONCLUSION

Collectively, our data suggest that AV411 and its amino analog, AV1013, may be useful neuroprotective agents counteracting neurotoxicity caused by infected and activated glia, and implicate them as potential therapies for the management of HIV-associated neurocognitive disorders in an opioid-abusing population.

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.

Acute neuroimmune modulation attenuates the development of anxiety-like freezing behavior in an animal model of traumatic brain injury

Chronic anxiety is a common and debilitating result of traumatic brain injury (TBI) in humans. While little is known about the neural mechanisms of this disorder, inflammation resulting from activation of the brain's immune response to insult has been implicated in both human post-traumatic anxiety and in recently developed animal models. In this study, we used a lateral fluid percussion injury (LFPI) model of TBI in the rat and examined freezing behavior as a measure of post-traumatic anxiety. We found that LFPI produced anxiety-like freezing behavior accompanied by increased reactive gliosis (reflecting neuroimmune inflammatory responses) in key brain structures associated with anxiety: the amygdala, insula, and hippocampus. Acute peri-injury administration of ibudilast (MN166), a glial cell activation inhibitor, suppressed both reactive gliosis and freezing behavior, and continued neuroprotective effects were apparent several months post-injury. These results support the conclusion that inflammation produced by neuroimmune responses to TBI play a role in post-traumatic anxiety, and that acute suppression of injury-induced glial cell activation may have promise for the prevention of post-traumatic anxiety in humans.

The sensorimotor and cognitive deficits in rats following 90- and 120-min transient occlusion of the middle cerebral artery

Middle cerebral artery occlusion (MCAO) is the most commonly used method to study the neurological and histological outcomes and the pathological mechanisms of ischaemic stroke. The current work compares sensorimotor and cognitive deficits and the infarct volume in rats following a transient 90- or 120-min MCAO, which allows the appropriate behavioural tests to be chosen based on the goal and design of the experiment. In the beam-walking test, we found significant differences between the 90- and 120-min MCAO groups in the number of foot faults made with the impaired hindlimb on post-stroke days 3, 7 and 14. In the cylinder test, a difference between the 90- and 120-min groups was observed on post-operation day 14. The responses to tactile and proprioceptive stimulation were impaired to a similar extent after 90- and 120-min MCAO in the vibrissae-evoked forelimb-placing and limb-placing tests. Moreover, we found significant memory impairment in the 120-min MCAO group 6 days after the acquisition trial. The brain tissue damage was significantly higher after 120-min occlusion of the MCA compared with 90-min occlusion; the infarct volumes were 13% and 25% of the contralateral hemispheres, respectively. In conclusion, both the 90- and 120-min occlusion models result in a significant impairment of sensorimotor, tactile and proprioceptive function, but memory impairment is only observed in the 120-min MCAO group. The beam-walking and cylinder tests detected neurological dysfunction after the 120-min MCAO, whereas the limb-placing and vibrissae-evoked forelimb-placing tests were able to evaluate the neurological dysfunction in rats after 90- and 120-min MCAO.

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.

Neurosteroid estradiol rescues ischemia-induced deficit in the long-term potentiation of rat hippocampal CA1 neurons

Increasing evidence indicates that neurosteroid 17beta-Estradiol (E2), a type of female sex hormone, has a neuroprotective effect against cerebral injury. However, it remains unknown whether E2 can also protect the hippocampal CA1 neurons from functional deficits in synaptic transmission and plasticity caused by ischemia. To address this issue, adult male Wistar rats were subjected to mild global cerebral ischemia created by four-vessel occlusion (4VO) for 10min, and the effects of E2 administration against the ischemic injury were investigated. The electrophysiological properties of Schaffer collateral-CA1 synapses were examined 7days after ischemia by applying a real-time optical recording technique to the hippocampal slices stained with a voltage-sensitive dye (RH482). The ischemic brain showed a decreased basal synaptic transmission and an impairment of LTP induction, but no alteration in paired-pulse facilitation. The administration of E2 (1mg/kg) 3h before ischemia was able to protect CA1 neurons from these ischemia-induced synaptic dysfunctions. The estrogen receptor-alpha (ERalpha) selective agonist, propyl pyrazole triol (PPT, 2mg/kg), exerted a similar protective effect, but the estrogen receptor-beta (ERbeta) agonist, diarylpropiolnitrile (DPN, 8mg/kg), failed to do so. A histological examination revealed that the transient global cerebral ischemia markedly reduced the density of pyramidal neurons in the CA1 region. The cell loss was significantly attenuated by E2 and PPT but not by DPN, as observed in synaptic functions. These findings suggest that E2 can protect neurons not only from cell death but also from functional damages due to a relatively mild degree of transient cerebral ischemia, and this effect is mediated by ERalpha, but not by ERbeta.

The inhibitory profile of Ibudilast against the human phosphodiesterase enzyme family

Ibudilast is widely used in Japan to treat ischemic stroke and bronchial asthma. Its mode of action is through the inhibition of cyclic nucleotide phosphodiesterases (PDEs). Growing evidence suggests this compound has utility in a range of neurological conditions linked to its ability to elevate cellular cyclic nucleotide concentrations, however limited data exists on Ibudilast's action on individual PDE families. We therefore used an extensive panel of human PDE enzymes to define the PDE inhibitory profile of this compound. Ibudilast preferentially inhibits PDE3A, PDE4, PDE10 and PDE11 with lesser inhibition of a number of other families. The significance of these findings is discussed in relation to Ibudilast's observed effects on certain disease states.

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.