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

Effects of ibudilast on central and peripheral markers of inflammation in alcohol use disorder: A randomized clinical trial

Ibudilast, a neuroimmune modulator, shows promise as a pharmacotherapy for alcohol use disorder (AUD). In vivo administration of ibudilast reduces the expression of pro-inflammatory cytokines in animal models, but its effects on markers of inflammation in humans are unknown. This preliminary study examined the effect of ibudilast on peripheral and potential central markers of inflammation in individuals with AUD. This study also explored the predictive relationship of neurometabolite markers with subsequent drinking in the trial. Non-treatment-seeking individuals with an AUD (n = 52) were randomized to receive oral ibudilast (n = 24) or placebo (n = 28) for 2 weeks. Plasma levels of peripheral inflammatory markers were measured at baseline and after 1 and 2 weeks of medication. At study mid-point, proton magnetic resonance spectroscopy was performed to measure potential neurometabolite markers of inflammation: choline-compounds (Cho), myo-inositol (MI) and creatine + phosphocreatine (Cr) in frontal and cingulate cortices from 43 participants (ibudilast: n = 20; placebo: n = 23). The treatment groups were compared on peripheral and central markers. Ibudilast-treated participants had lower Cho in superior frontal white matter and nominally lower MI in pregenual anterior cingulate cortex. Ibudilast-treated participants had nominally lower C-reactive protein levels at visit 2 and nominally lower TNF-α/IL-10 ratios, relative to placebo. C-reactive protein and Cho levels were correlated, controlling for medication. Superior frontal white matter Cho predicted drinking in the following week. Micro-longitudinal ibudilast treatment may induce peripheral and putative central anti-inflammatory responses in patients with AUD. The neurometabolite responses may be associated with reduction in drinking, suggesting an anti-inflammatory component to the therapeutic action of ibudilast.

Ibudilast Attenuates Folic Acid-Induced Acute Kidney Injury by Blocking Pyroptosis Through TLR4-Mediated NF-κB and MAPK Signaling Pathways

Folic acid (FA)-induced renal tubule damage, which is characterized by extensive inflammation, is a common model of acute kidney injury (AKI). Pyroptosis, a pro-inflammatory form of cell death due to the activation of inflammatory caspases, is involved in AKI progression. Ibudilast, a TLR4 antagonist, has been used in the clinic to exert an anti-inflammatory effect on asthma. However, researchers have not explored whether ibudilast exerts a protective effect on AKI by inhibiting inflammation. In the present study, ibudilast reversed FA-induced AKI in mice, as indicated by the reduced serum creatinine and urea nitrogen levels, and improved renal pathology, as well as the downregulation of kidney injury marker-1. In addition, ibudilast significantly increased the production of the anti-inflammatory factor IL-10 while suppressing the secretion of the pro-inflammatory cytokine TNF-α and macrophage infiltration. Moreover, in the injured kidney, ibudilast reduced the levels of both inflammasome markers (NLRP3) and pyroptosis-related proteins (caspase-1, IL1-β, IL-18, and GSDMD cleavage), and decreased the number of TUNEL-positive cells. Further mechanistic studies showed that ibudilast administration inhibited the FA-induced upregulation of TLR4, blocked NF-κB nuclear translocation, and reduced the phosphorylation of NF-κB and IκBα, p38, ERK, and JNK. Thus, this study substantiates the protective effect of ibudilast on FA-induced AKI in mice and suggests that protection might be achieved by reducing pyroptosis and inflammation, likely through the inhibition of TLR4-mediated NF-κB and MAPK signaling pathways.

Calpain inhibitor and ibudilast rescue β cell functions in a cellular model of Wolfram syndrome

Wolfram syndrome is a rare multisystem disease characterized by childhood-onset diabetes mellitus and progressive neurodegeneration. Most cases are attributed to pathogenic variants in a single gene, Wolfram syndrome 1 (WFS1). There currently is no disease-modifying treatment for Wolfram syndrome, as the molecular consequences of the loss of WFS1 remain elusive. Because diabetes mellitus is the first diagnosed symptom of Wolfram syndrome, we aimed to further examine the functions of WFS1 in pancreatic β cells in the context of hyperglycemia. Knockout (KO) of WFS1 in rat insulinoma (INS1) cells impaired calcium homeostasis and protein kinase B/Akt signaling and, subsequently, decreased cell viability and glucose-stimulated insulin secretion. Targeting calcium homeostasis with reexpression of WFS1, overexpression of WFS1's interacting partner neuronal calcium sensor-1 (NCS1), or treatment with calpain inhibitor and ibudilast reversed deficits observed in WFS1-KO cells. Collectively, our findings provide insight into the disease mechanism of Wolfram syndrome and highlight new targets and drug candidates to facilitate the development of a treatment for this disorder and similar diseases.

Ibudilast, a Phosphodiesterase Inhibitor and Toll-Like Receptor-4 Antagonist, Improves Hemorrhagic Shock and Reperfusion-Induced Left Ventricular Dysfunction by Reducing Myocardial Tumor Necrosis Factor α

OBJECTIVES

Rapid loss of blood volume causes ischemic injury to myocardial cells and impairs cardiac function. Subsequent reperfusion, although necessary to revitalize stunned tissues, can induce production of reactive oxygen species and inflammation, causing further tissue damages and weakening cardiac function. Ibudilast, a Toll-like receptor-4 (TLR4) antagonist and an inhibitor of phosphodiesterase-4, possesses antioxidative and anti-inflammatory capacities. In this study, we aim to examine the protective efficacy of ibudilast against hemorrhagic shock and reperfusion (HSR)-induced myocardial injury and cardiac dysfunction.

METHODS

Studies were conducted on male Sprague-Dawley rats in 3 groups: sham-operated, HSR with, and HSR without pretreatment of ibudilast. Hemorrhagic shock was induced by withdrawing blood from the femoral artery until the mean aortic pressure dropped to around 40 mm Hg; reperfusion was conducted by replenishing blood after 120 minutes of hemorrhagic shock, and the observation continued for another 240 minutes. The left ventricular (LV) contractility, diastolic suction capacity, and ventricular stiffness were evaluated using simultaneous LV pressure, and volume was recorded during a temporary inferior vena cava constriction at the end of reperfusion. Ibudilast (10 mg/kg) was administered intraperitoneally 3 days and 20 minutes prior to HSR. Serum creatine kinase myocardial band (CK-MB) was examined at the end of both HSR, and serum CK-MB, myocardial TLR4 protein expression, and malondialdehyde (MDA) and tumor necrosis factor (TNF)-α levels at the end of reperfusion.

RESULTS

HSR induced an increase in serum CK-MB. Subsequent reperfusion further increased serum CK-MB, upregulated myocardial TLR4 protein expression, and increased tissue levels MDA and TNF-α vs the sham (P < .05). HSR reduced LV contractility, prolonged LV relaxation time, and increased LV diastolic stiffness. Ibudilast pretreatment attenuated HSR-induced TLR4 protein expression, reduced myocardial MDA and TNF-α levels, and protected against cardiac dysfunction.

CONCLUSIONS

Ibudilast pretreatment reduced myocardial TLR4 expression, decreased MDA and TNF-α levels, and protected against HSR-induced decrease in LV contractility, prolonged LV relaxation time, and increased diastolic stiffness.

Identification of novel analgesics through a drug repurposing strategy

The identification of new indications for approved or failed drugs is a process called drug repositioning or drug repurposing. The motivation includes overcoming the productivity gap that exists in drug development, which is a high-cost–high-risk process. Repositioning also includes rescuing drugs that have safely entered the market but have failed to demonstrate sufficient efficiency for the initial clinical indication. Considering the high prevalence of chronic pain, the lack of sufficient efficacy and the safety issues of current analgesics, repositioning seems to be an attractive approach. This review presents example of drugs that already have been repositioned and highlights new technologies that are available for the identification of additional compounds to stimulate the curiosity of readers for further exploration.

NCS-1 is a regulator of calcium signaling in health and disease

Neuronal Calcium Sensor-1 (NCS-1) is a highly conserved calcium binding protein which contributes to the maintenance of intracellular calcium homeostasis and regulation of calcium-dependent signaling pathways. It is involved in a variety of physiological cell functions, including exocytosis, regulation of calcium permeable channels, neuroplasticity and response to neuronal damage. Over the past 30 years, continuing investigation of cellular functions of NCS-1 and associated disease states have highlighted its function in the pathophysiology of several disorders and as a therapeutic target. Among the diseases that were found to be associated with NCS-1 are neurological disorders such as bipolar disease and non-neurological conditions such as breast cancer. Furthermore, alteration of NCS-1 expression is associated with substance abuse disorders and severe side effects of chemotherapeutic agents. The objective of this article is to summarize the current body of evidence describing NCS-1 and its interactions on a molecular and cellular scale, as well as describing macroscopic implications in physiology and medicine. Particular attention is paid to the role of NCS-1 in development and prevention of chemotherapy induced peripheral neuropathy (CIPN).

Targeting cytokines for treatment of neuropathic pain

BACKGROUND

Neuropathic pain is a challenging condition often refractory to existing therapies. An increasing number of studies have indicated that the immune system plays a crucial role in the mediation of neuropathic pain. Exploration of the various functions of individual cytokines in neuropathic pain will provide greater insight into the mechanisms of neuropathic pain and suggest potential opportunities to expand the repertoire of treatment options.

METHODS

A literature review was performed to assess the role of pro-inflammatory and anti-inflammatory cytokines in the development of neuropathic pain. Both direct and indirect therapeutic approaches that target various cytokines for pain were reviewed. The current understanding based on preclinical and clinical studies is summarized.

RESULTS AND CONCLUSIONS

In both human and animal studies, neuropathic pain has been associated with a pro-inflammatory state. Analgesic therapies involving direct manipulation of various cytokines and indirect methods to alter the balance of the immune system have been explored, although there have been few large-scale clinical trials evaluating the efficacy of immune modulators in the treatment of neuropathic pain. TNF-α is perhaps the widely studied pro-inflammatory cytokine in the context of neuropathic pain, but other pro-inflammatory (IL-1β, IL-6, and IL-17) and anti-inflammatory (IL-4, IL-10, TGF-β) signaling molecules are garnering increased interest. With better appreciation and understanding of the interaction between the immune system and neuropathic pain, novel therapies may be developed to target this condition.

The Effects of the Toll-Like Receptor 4 Antagonist, Ibudilast, on Sevoflurane's Minimum Alveolar Concentration and the Delayed Remifentanil-Induced Increase in the Minimum Alveolar Concentration in Rats

BACKGROUND

Ultralow doses of naloxone, an opioid and toll-like receptor 4 antagonist, blocked remifentanil-induced hyperalgesia and the associated increase in the minimum alveolar concentration (MAC), but not tolerance. The aim was to determine the effects of the toll-like receptor 4 antagonist, ibudilast, on the MAC in the rat and how it might prevent the effects of remifentanil.

METHODS

Male Wistar rats were randomly allocated to 5 treatment groups (n = 7 per group): 10 mg/kg ibudilast intraperitoneally, 240 µg/kg/h remifentanil IV, ibudilast plus remifentanil, remifentanil plus naloxone IV, or saline. The sevoflurane MAC was determined 3 times in every rat and every day (days 0, 2, and 4): baseline (MAC-A) and 2 further determinations were made after treatments, 1.5 hours apart (MAC-B and MAC-C).

RESULTS

A reduction in baseline MAC was produced on day 0 by ibudilast, remifentanil, remifentanil plus ibudilast, remifentanil plus naloxone (P < 0.01), but not saline. Similar effects were found on days 2 and 4. A tolerance to remifentanil was found on days 0, 2, and 4, which neither ibudilast nor naloxone prevented. The MAC increase produced by remifentanil on day 4 (P = 0.001) was prevented by either ibudilast or naloxone.

CONCLUSIONS

Ibudilast, besides reducing the MAC, prevented the delayed increase in baseline MAC produced by remifentanil but not the increase in MAC caused by tolerance to remifentanil.

Targeting Opioid-Induced Hyperalgesia in Clinical Treatment: Neurobiological Considerations

Opioid analgesics have become a cornerstone in the treatment of moderate to severe pain, resulting in a steady rise of opioid prescriptions. Subsequently, there has been a striking increase in the number of opioid-dependent individuals, opioid-related overdoses, and fatalities. Clinical use of opioids is further complicated by an increasingly deleterious profile of side effects beyond addiction, including tolerance and opioid-induced hyperalgesia (OIH), where OIH is defined as an increased sensitivity to already painful stimuli. This paradoxical state of increased nociception results from acute and long-term exposure to opioids, and appears to develop in a substantial subset of patients using opioids. Recently, there has been considerable interest in developing an efficacious treatment regimen for acute and chronic pain. However, there are currently no well-established treatments for OIH. Several substrates have emerged as potential modulators of OIH, including the N-methyl-D-aspartate and γ-aminobutyric acid receptors, and most notably, the innate neuroimmune system. This review summarizes the neurobiology of OIH in the context of clinical treatment; specifically, we review evidence for several pathways that show promise for the treatment of pain going forward, as prospective adjuvants to opioid analgesics. Overall, we suggest that this paradoxical state be considered an additional target of clinical treatment for chronic pain.

Neuroinflammatory contributions to pain after SCI: roles for central glial mechanisms and nociceptor-mediated host defense

Neuropathic pain after spinal cord injury (SCI) is common, often intractable, and can be severely debilitating. A number of mechanisms have been proposed for this pain, which are discussed briefly, along with methods for revealing SCI pain in animal models, such as the recently applied conditioned place preference test. During the last decade, studies of animal models have shown that both central neuroinflammation and behavioral hypersensitivity (indirect reflex measures of pain) persist chronically after SCI. Interventions that reduce neuroinflammation have been found to ameliorate pain-related behavior, such as treatment with agents that inhibit the activation states of microglia and/or astroglia (including IL-10, minocycline, etanercept, propentofylline, ibudilast, licofelone, SP600125, carbenoxolone). Reversal of pain-related behavior has also been shown with disruption by an inhibitor (CR8) and/or genetic deletion of cell cycle-related proteins, deletion of a truncated receptor (trkB.T1) for brain-derived neurotrophic factor (BDNF), or reduction by antisense knockdown or an inhibitor (AMG9810) of the activity of channels (TRPV1 or Nav1.8) important for electrical activity in primary nociceptors. Nociceptor activity is known to drive central neuroinflammation in peripheral injury models, and nociceptors appear to be an integral component of host defense. Thus, emerging results suggest that spinal and systemic effects of SCI can activate nociceptor-mediated host defense responses that interact via neuroinflammatory signaling with complex central consequences of SCI to drive chronic pain. This broader view of SCI-induced neuroinflammation suggests new targets, and additional complications, for efforts to develop effective treatments for neuropathic SCI pain.

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.

Systemic administration of propentofylline, ibudilast, and (+)-naltrexone each reverses mechanical allodynia in a novel rat model of central neuropathic pain

Central neuropathic pain (CNP) is a debilitating consequence of central nervous system damage for which current treatments are ineffective. To explore mechanisms underlying CNP, we developed a rat model involving T13/L1 dorsal root avulsion. The resultant dorsal horn damage creates bilateral below-level (L4-L6) mechanical allodynia. This allodynia, termed spinal neuropathic avulsion pain, occurs in the absence of confounding paralysis. To characterize this model, we undertook a series of studies aimed at defining whether spinal neuropathic avulsion pain could be reversed by any of 3 putative glial activation inhibitors, each with distinct mechanisms of action. Indeed, the phosphodiesterase inhibitor propentofylline, the macrophage migration inhibitory factor inhibitor ibudilast, and the toll-like receptor 4 antagonist (+)-naltrexone each reversed below-level allodynia bilaterally. Strikingly, none of these impacted spinal neuropathic avulsion pain upon first administration but required 1 to 2 weeks of daily administration before pain reversal was obtained. Given reversal of CNP by each of these glial modulatory agents, these results suggest that glia contribute to the maintenance of such pain and enduring release of macrophage migration inhibitory factor and endogenous agonists of toll-like receptor 4 is important for sustaining CNP. The markedly delayed efficacy of all 3 glial modulatory drugs may prove instructive for interpretation of apparent drug failures after shorter dosing regimens.

PERSPECTIVE

CNP that develops after trauma is often described by patients as severe and intolerable. Unfortunately, current treatments are not effective. This work suggests that using pharmacologic treatments that target glial cells could be an effective clinical treatment for CNP.

Drug repositioning: playing dirty to kill pain

The number of approved new molecular entity drugs has been decreasing as the pharmaceutical company investment in research and development is increasing. As we face this painful crisis, called an innovation gap, there is increasing awareness that development of new uses of existing drugs may be a powerful tool to help overcome this obstacle because it takes too long, costs too much and can be risky to release drugs developed de novo. Consequently, drug repositioning is emerging in different therapeutic areas, including the pain research area. Worldwide, pain is the main reason for seeking healthcare, and pain relief represents an unmet global clinical need. Therefore, development of analgesics with better efficacy, safety and cost effectiveness is of paramount importance. Despite the remarkable advancement in research on cellular and molecular mechanisms underlying pain pathophysiology over the past three decades, target-based therapeutic opportunities have not been pursued to the same extent. Phenotypic screening remains a more powerful tool for drug development than target-based screening so far. It sounds somewhat heretical, but some multi-action drugs, rather than very selective ones, have been developed intentionally. In the present review, we first critically discuss the utility of drug repositioning for analgesic drug development and then show examples of 'old' drugs that have been successfully repositioned or that are under investigation for their analgesic actions. We conclude that drug repositioning should be more strongly encouraged to help build a bridge between basic research and pain relief worldwide.

Sigma-1 receptor-mediated increase in spinal p38 MAPK phosphorylation leads to the induction of mechanical allodynia in mice and neuropathic rats

The direct activation of the spinal sigma-1 receptor (Sig-1R) produces mechanical allodynia (MA) and thermal hyperalgesia (TH) in mice. In addition, the blockade of the spinal Sig-1R prevents the induction of MA, but not TH in chronic constriction injury (CCI)-induced neuropathic rats. The present study was designed to investigate whether the increase in spinal p38 MAPK phosphorylation (p-p38 MAPK) mediates Sig-1R-induced MA or TH in mice and the induction of MA in neuropathic rats. MA and TH were evaluated using von Frey filaments and a hot-plate apparatus, respectively. Neuropathic pain was produced by CCI of the right sciatic nerve in rats. Western blot assay and immunohistochemistry were performed to determine the changes of p-p38 MAPK expression in the spinal cord. Intrathecal (i.t.) injection of PRE084, a selective Sig-1R agonist, into naïve mice time-dependently increased the expression of p-p38 MAPK, which was blocked by pretreatment with BD1047, a Sig-1R antagonist. I.t. pretreatment with SB203580, a p38 MAPK inhibitor also dose-dependently inhibited PRE084-induced MA, whereas TH induction was not affected. In CCI rats, i.t. injection of BD1047 during the induction phase (postoperative days 0 to 5) reduced the CCI-induced increase in p-p38 MAPK. In addition, i.t. SB203580 treatment during the induction phase also suppressed the development of CCI-induced MA, but not TH. Conversely, i.t. SB203580 treatment during the maintenance phase (postoperative days 15 to 20) had no effect on CCI-induced MA or TH. These results demonstrate that the increase in spinal p-p38 MAPK is closely associated with the induction of Sig-1R mediated MA, but not TH. Sigma-1 receptor modulation of p-p38 MAPK also plays an important role in the induction, but not the maintenance, of MA in neuropathic pain.

Differential development of tolerance to the functional and behavioral effects of repeated baclofen treatment in rats

Baclofen, a gamma-aminobutyric acid (GABA)B receptor agonist, has been used clinically to treat muscle spasticity, rigidity and pain. More recently, interest in the use of baclofen as an addiction medicine has grown, with promising preclinical cocaine and amphetamine data and demonstrated clinical benefit from alcohol and nicotine studies. Few preclinical investigations, however, have utilized chronic dosing of baclofen, which is important given that tolerance can occur to many of its effects. Thus the question of whether chronic treatment of baclofen maintains the efficacy of acute doses is imperative. The neural substrates that underlie the effects of baclofen, particularly those after chronic treatment, are also not known. In the present study, therefore, rats were treated with either a) vehicle, b) acute baclofen (5 mg/kg) or c) chronic baclofen (5 mg/kg, t.i.d. for 5 days). The effects of acute and chronic baclofen administration, compared to vehicle, were assessed using locomotor activity and changes in brain glucose metabolism (a measure of functional brain activity). Acute baclofen significantly reduced locomotor activity (horizontal and total distance traveled), while chronic baclofen failed to affect locomotor activity. Acute baclofen resulted in significantly lower rates of local cerebral glucose utilization throughout many areas of the brain, including the prefrontal cortex, caudate putamen, septum and hippocampus. The majority of these functional effects, with the exception of the caudate putamen and septum, were absent in animals chronically treated with baclofen. Despite the tolerance to the locomotor and functional effects of baclofen following repeated treatment, these persistent effects on functional activity in the caudate putamen and septum may provide insights into the way in which baclofen alters the reinforcing effects of abused substances such as cocaine, alcohol, and methamphetamine both in humans and animal models.

Medication-overuse headache and opioid-induced hyperalgesia: A review of mechanisms, a neuroimmune hypothesis and a novel approach to treatment

Introduction

Patients with chronic headache who consume large amounts of analgesics are often encountered in clinical practice. Excessive intake of analgesics is now considered to be a cause, rather than simply a consequence, of frequent headaches, and as such the diagnosis “medication-overuse headache” (MOH) has been formulated. Despite the prevalence and clinical impact of MOH, the pathophysiology behind this disorder remains unclear and specific mechanism-based treatment options are lacking.

Discussion

Although most acute headache treatments have been alleged to cause MOH, here we conclude from the literature that opioids are a particularly problematic drug class consistently associated with worsening headache. MOH may not be a single entity, as each class of drug implicated may cause MOH via a different mechanism. Recent evidence indicates that chronic opioid administration may exacerbate pain in the long term by activating toll-like receptor-4 on glial cells, resulting in a pro-inflammatory state that manifests clinically as increased pain. Thus, from the available evidence it seems opioid-overuse headache is a phenomenon similar to opioid-induced hyperalgesia, which derives from a cumulative interaction between central sensitisation, due to repeated activation of nociceptive pathways by recurrent headaches, and pain facilitation due to glial activation.

Conclusion

Treatment strategies directed at inhibiting glial activation may be of benefit alongside medication withdrawal in the management of MOH.

Inhibition of paclitaxel-induced decreases in calcium signaling

Peripheral neuropathy is one of the most severe and irreversible side effects caused by treatment from several chemotherapeutic drugs, including paclitaxel (Taxol®) and vincristine. Strategies are needed that inhibit this unwanted side effect without altering the chemotherapeutic action of these drugs. We previously identified two proteins in the cellular pathway that lead to Taxol-induced peripheral neuropathy, neuronal calcium sensor-1 (NCS-1) and calpain. Prolonged treatment with Taxol induces activation of calpain, degradation of NCS-1, and loss of intracellular calcium signaling. This paper has focused on understanding the molecular basis for prevention of peripheral neuropathy by testing the effects of addition of two candidate compounds to the existing chemotherapeutic drug regime: lithium and ibudilast. We found that the co-administration of either lithium or ibudilast to neuroblastoma cells that were treated with Taxol or vincristine inhibited activation of calpain and the reductions in NCS-1 levels and calcium signaling associated with these chemotherapeutic drugs. The ability of Taxol to alter microtubule formation was unchanged by the addition of either candidate compound. These results allow us to suggest that it is possible to prevent the unnecessary and irreversible damage caused by chemotherapeutic drugs while still maintaining therapeutic efficacy. Specifically, the addition of either lithium or ibudilast to existing chemotherapy treatment protocols has the potential to prevent chemotherapy-induced peripheral neuropathy.

Prevention of paclitaxel-induced peripheral neuropathy by lithium pretreatment

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating side effect that occurs in many patients undergoing chemotherapy. It is often irreversible and frequently leads to early termination of treatment. In this study, we have identified two compounds, lithium and ibudilast, that when administered as a single prophylactic injection prior to paclitaxel treatment, prevent the development of CIPN in mice at the sensory-motor and cellular level. The prevention of neuropathy was not observed in paclitaxel-treated mice that were only prophylactically treated with a vehicle injection. The coadministration of lithium with paclitaxel also allows for administration of higher doses of paclitaxel (survival increases by 60%), protects against paclitaxel-induced cardiac abnormalities, and, notably, does not interfere with the antitumor effects of paclitaxel. Moreover, we have determined a mechanism by which CIPN develops and have discovered that lithium and ibudilast inhibit development of peripheral neuropathy by disrupting the interaction between paclitaxel, neuronal calcium sensor 1 (NCS-1), and the inositol 1,4,5-trisphosphate receptor (InsP3R) to prevent treatment-induced decreases in intracellular calcium signaling. This study shows that lithium and ibudilast are candidate therapeutics for the prevention of paclitaxel-induced neuropathy and could enable patients to tolerate more aggressive treatment regimens.