Chemotherapy-evoked painful peripheral neuropathy

Chemotherapy-induced neuropathic pain and its relation to cluster symptoms in breast cancer patients treated with paclitaxel

The majority of patients with breast cancer receiving chemotherapy report multiple symptoms. Compelling evidence has shown that subgroups of patients can be clustered by the severity of symptoms. Recent studies demonstrate that chemotherapy with such substances as paclitaxel can cause neuropathic pain (CINP) and consequently neural damage.

OBJECTIVES

the present study examined the relationship between symptom clusters and CINP among 40 patients with breast cancer. The study was based on 2 sessions conducted before and during paclitaxel treatment. In each session, neuropathic pain was assessed by the DN4 Questionnaire. In the second session, the Lee Fatigue Scale, the General Sleep Disturbance Scale, and the Center for Epidemiological Studies-Depression Scale were also administered, and the worst pain intensity was assessed. Using cluster analysis, 2 symptom clusters were identified on the basis of the severity of the 4 symptoms scores. Patients in the High Cluster (37%) experienced a high level of all symptoms, whereas patients in the Low Cluster (63%) experienced a low level of all symptoms. Twenty patients (50%) were diagnosed with CINP. A subgroup of patients (23%) from the High Cluster was identified as having CINP; 35% were in the Low Cluster and free of CINP. In conclusion, there appears to be a specific subgroup of patients with hypersensitive cancer who need greater attention to symptom management. Early detection of symptoms, together with careful dose selection and assessment of early stages in the development of neuropathic pain, are essential for preventing the simultaneous occurrence of severe multiple symptoms and CINP.

Anti-nociceptive effect of kinin B₁ and B₂ receptor antagonists on peripheral neuropathy induced by paclitaxel in mice

BACKGROUND AND PURPOSE

In the current study, we investigated the role of both kinin B₁ and B₂ receptors in peripheral neuropathy induced by the chronic treatment of mice with paclitaxel a widely used chemotherapeutic agent.

EXPERIMENTAL APPROACH

Chemotherapy-evoked hyperalgesia was induced by i.p. injections of paclitaxel (2 mg·kg⁻¹) over 5 consecutive days. Mechanical and thermal hyperalgesia were evaluated between 7 and 21 days after the first paclitaxel treatment.

KEY RESULTS

Treatment with paclitaxel increased both mechanical and thermal hyperalgesia in mice (C57BL/6 and CD1 strains). Kinin receptor deficient mice (B₁, or B₂ receptor knock-out and B₁B₂ receptor, double knock-out) presented a significant reduction in paclitaxel-induced hypernociceptive responses in comparison to wild-type animals. Treatment of CD1 mice with kinin receptor antagonists (DALBK for B₁ or Hoe 140 for B₂ receptors) significantly inhibited both mechanical and thermal hyperalgesia when tested at 7 and 14 days after the first paclitaxel injection. DALBK and Hoe 140 were also effective against paclitaxel-induced peripheral neuropathy when given intrathecally or i.c.v. A marked increase in B₁ receptor mRNA was observed in the mouse thalamus, parietal and pre-frontal cortex from 7 days after the first paclitaxel treatment.

CONCLUSIONS AND IMPLICATIONS

Kinins acting on both B₁ and B₂ receptors, expressed in spinal and supra-spinal sites, played a crucial role in controlling the hypernociceptive state caused by chronic treatment with paclitaxel.

Comparison of the efficacy of carbamazepine, gabapentin and lamotrigine for neuropathic pain in rats

Background:

Neuropathic pain in cancer patients remain a treatment challenge. Many of the anticancer drugs have to be abandoned because patients develop neuropathic pain. Several antiepileptic drugs like carbamazepine, phenytoin, lamotrigine, felbamate are effective in neuropathic pain and trigeminal neuralgia. However, their efficacy varies.

Aim:

The aim of this study is to compare the efficacy of antiepileptic drugs in neuropathic pain induced by anticancer drugs.

Materials and Methods:

Neuropathic pain was induced in rats by injecting 4 doses of paclitaxel. The rats were divided into four groups of six animals each. Group I was treated with oral carbamazepine (cbz) 100 mg/kg, group II received oral gabapentin (gbp) 60 mg/kg, and group III was treated with oral lamotrigine (lam) 40 mg/kg and group IV was the control group. Behavioural testing for thermal hyperalgesia and mechanical hyperalgesia was assessed from 26^th day of paclitaxel administration to next five days by hot plate method and Randall Siletto test, respectively, in all the four groups. One way analysis of variance followed by Scheffe's post hoc test was used for statistical analysis.

Results:

In thermal hyperalgesia lam treated group was found to be significantly (P < 0.001) superior to cbz and gbp treated group. In mechanical hyperalgesia, lam group showed significant response (P < 0.05) as compared to gbp group. However, the gbp treated group showed a significant (P < 0.01) improvement after three days of treatment.

Conclusions:

In paclitaxel induced neuropathic pain, lamotrigine appears to be a promising drug. The difference in responses shown by different antiepileptics’ depends on the etiology of the underlying mechanisms in neuropathic pain.

Role of Drp1, a key mitochondrial fission protein, in neuropathic pain

While oxidative stress has been implicated in small-fiber painful peripheral neuropathies, antioxidants are only partially effective to treat patients. We have tested the hypothesis that Drp1 (dynamin-related protein 1), a GTPase that catalyzes the process of mitochondrial fission, which is a mechanism central for the effect and production of reactive oxygen species (ROS), plays a central role in these neuropathic pain syndromes. Intrathecal administration of oligodeoxynucleotide antisense against Drp1 produced a decrease in its expression in peripheral nerve and markedly attenuated neuropathic mechanical hyperalgesia caused by HIV/AIDS antiretroviral [ddC (2',3'-dideoxycytidine)] and anticancer (oxaliplatin) chemotherapy in male Sprague Dawley rats. To confirm the role of Drp1 in these models of neuropathic pain, as well as to demonstrate its contribution at the site of sensory transduction, we injected a highly selective Drp1 inhibitor, mdivi-1, at the site of nociceptive testing on the dorsum of the rat's hindpaw. mdivi-1 attenuated both forms of neuropathic pain. To evaluate the role of Drp1 in hyperalgesia induced by ROS, we demonstrated that intradermal hydrogen peroxide produced dose-dependent hyperalgesia that was inhibited by mdivi-1. Finally, mechanical hyperalgesia induced by diverse pronociceptive mediators involved in inflammatory and neuropathic pain-tumor necrosis factor α, glial-derived neurotrophic factor, and nitric oxide-was also inhibited by mdivi-1. These studies provide support for a substantial role of mitochondrial fission in preclinical models of inflammatory and neuropathic pain.

A double-blind, placebo-controlled trial of a topical treatment for chemotherapy-induced peripheral neuropathy: NCCTG trial N06CA

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a troublesome chronic symptom that has no proven pharmacologic treatment. The purpose of this double-blind randomized placebo-controlled trial was to evaluate a novel compounded topical gel for this problem.

METHODS

Patients with CIPN were randomized to baclofen 10 mg, amitriptyline HCL 40 mg, and ketamine 20 mg in a pluronic lecithin organogel (BAK-PLO) versus placebo (PLO) to determine its effect on numbness, tingling, pain, and function. The primary endpoint was the baseline-adjusted sensory subscale of the EORTC QLQ-CIPN20, at 4 weeks.

RESULTS

Data in 208 patients reveal a trend for improvement that is greater in the BAK-PLO arm over placebo in both the sensory (p = 0.053) and motor subscales (p = 0.021). The greatest improvements were related to the symptoms of tingling, cramping, and shooting/burning pain in the hands as well as difficulty in holding a pen. There were no undesirable toxicities associated with the BAK-PLO and no evidence of systemic toxicity.

CONCLUSION

Topical treatment with BAK-PLO appears to somewhat improve symptoms of CIPN. This topical gel was well tolerated, without evident systemic toxicity. Further research is needed with increased doses to better clarify the clinical role of this treatment in CIPN.

The use of vitamin E for the prevention of chemotherapy-induced peripheral neuropathy: results of a randomized phase III clinical trial

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) continues to be a substantial problem for many cancer patients. Pursuant to promising appearing pilot data, the current study evaluated the use of vitamin E for the prevention of CIPN.

METHODS

A phase III, randomized, double-blind, placebo-controlled study was conducted in patients undergoing therapy with neurotoxic chemotherapy, utilizing twice daily dosing of vitamin E (400 mg)/placebo. The primary endpoint was the incidence of grade 2+ sensory neuropathy (SN) toxicity (CTCAE v 3.0) in each treatment arm, analyzed by chi-square testing. Planned sample size was 100 patients per arm to provide 80% power to detect a difference in incidence of grade 2+ SN toxicity from 25% in the placebo group to 10% in the vitamin E group.

RESULTS

Two-hundred seven patients were enrolled between December 1, 2006 and December 14, 2007, producing 189 evaluable cases for analysis. Cytotoxic agents included taxanes (109), cisplatin (8), carboplatin (2), oxaliplatin (50), or combination (20). There was no difference in the incidence of grade 2+ SN between the two arms (34%-vitamin E, 29%-placebo; P = 0.43). There were no significant differences between treatment arms for time to onset of neuropathy (P = 0.58), for chemotherapy dose reductions due to neuropathy (P = 0.21), or for secondary endpoints derived from patient-reported neuropathy symptom assessments. The treatment was well tolerated overall.

CONCLUSIONS

Vitamin E did not appear to reduce the incidence of sensory neuropathy in the studied group of patients receiving neurotoxic chemotherapy.

Cellular and functional evidence for a protective action of neurosteroids against vincristine chemotherapy-induced painful neuropathy

Painful neuropathy is a major side-effect limiting cancer chemotherapy. Therefore, novel strategies are required to suppress the neuropathic effects of anticancer drugs without altering their chemotherapeutic effectiveness. By combining biochemical, neuroanatomical/neurochemical, electrophysiological and behavioral methods, we demonstrated that progesterone-derived neurosteroids including 5alpha-dihydroprogesterone and 3alpha,5alpha-tetrahydroprogesterone suppressed neuropathic symptoms evoked in naive rats by vincristine. Neurosteroids counteracted vincristine-induced alterations in peripheral nerves including 2',3'-cyclic nucleotide 3'-phosphodiesterase, neurofilament-200 kDa and intraepidermal nerve fiber repression, nerve conduction velocity, and pain transmission abnormalities (allodynia/hyperalgesia). In skin-tumor rats generated with carcinosarcoma-cells, vincristine, which suppressed the skin tumor and restored normal blood concentration of vascular endothelial growth factor (VEGF), reproduced neuropathic side-effects. Administered alone, neurosteroids did not affect the tumor and VEGF level. Combined with vincristine, neurosteroids preserved vincristine anti-tumor action but counteracted vincristine-induced neural side-effects. Together, these results provide valuable insight into the cellular and functional mechanisms underlying anticancer drug-induced neuropathy and suggest a neurosteroid-based strategy to eradicate painful neuropathy.

Antinociceptive Effect of Memantine and Morphine on Vincristine-induced Peripheral Neuropathy in Rats

Background

Vincristine-induced peripheral neuropathy is a major dose limiting side effect and thus effective therapeutic strategy is required. In this study, we investigated the antinociceptive effect of memantine and morphine on a vincristine-induced peripheral neuropathy model in rats.

Methods

Male Sprague-Dawley rats weighing 220-240 g were used in all experiments. Rats subsequently received daily intraperitoneal injections of either vincristine sulfate (0.1 ml/kg/day) or saline (0.1 ml/kg/day) over 12 days, immediately following behavioral testing. For assessment of mechanical allodynia, mechanical stimuli using von Frey filament was applied to the paw to measure withdrawal threshold. The effects of N-methyl-D-aspartate receptors antagonist (memantine; 2.5, 5, 10 mg/kg intraperitoneal), opioid agonist (morphine; 2.5, 5, 10 mg/kg intraperitoneal) and vehicle (saline) on vicristine-induced neuropathy were evaluated.

Results

Mechanical allodynia developed over the course of ten daily injections of vincristine relative to groups receiving saline at the same time. Morphine abolished the reduction in paw withdrawal threshold compared to vehicle and produced dose-responsiveness. Only the highest dose of memantine (10 mg/kg) was able to increase paw withdrawal threshold compared to vehicle.

Conclusions

Systemic morphine and memantine have an antinociceptive effect on the vincristine-induced peripheral neuropathy model in rats. These results suggest morphine and memantine may be an alternative approach for the treatment of vincristine-induced peripheral neuropathic pain.

Painful peripheral neuropathies

Peripheral neuropathies are a heterogeneous group of diseases affecting peripheral nerves. The causes are multiple: hereditary, metabolic, infectious, inflammatory, toxic, traumatic. The temporal profile includes acute, subacute and chronic conditions. The majority of peripheral neuropathies cause mainly muscle weakness and sensory loss, positive sensory symptoms and sometimes pain. When pain is present, however, it is usually extremely intense and among the most disabling symptoms for the patients. In addition, the neurological origin of the pain is often missed and patients receive inadequate or delayed specific treatment. Independently of the disease causing the peripheral nerve injury, pain originating from axonal pathology or ganglionopathy privileges neuropathies affecting smaller fibres, a clinical observation that points towards abnormal activity within nociceptive afferents as a main generator of pain. Natural activation of blood vessels or perineurial nociceptive network by pathology also causes intense pain. Pain of this kind, i.e. nerve trunk pain, is among the heralding symptoms of inflammatory or ischemic mononeuropathy and for its intensity represents itself a medical emergency. Neuropathic pain quality rekindles the psychophysical experience of peripheral nerves intraneural microstimulation i.e. a combination of large and small fibres sensation temporally distorted compared to physiological perception evoked by natural stimuli. Pins and needles, burning, cramping mixed with numbness, and tingling are the wording most used by patients. Nociceptive pain instead is most often described as aching, deep and dull. Good command of peripheral nerve anatomy and pathophysiology allows timely recognition of the different pain components and targeted treatment, selected according to intensity, type and temporal profile of the pain.

Matrix metalloprotease regulation of neuropathic pain

Neuropathic pain affects millions of people globally and could be a disease on its own right. Current treatments focus on blocking neurotransmission and have resulted in limited success. Recent progress points to an important role of neuroinflammation in the pathogenesis of neuropathic pain. Matrix metalloproteases (MMPs) comprise a large family of zinc endopeptidases that have been implicated in the generation of neuroinflammation via cleavage of extracellular matrix proteins and activation of proinflammatory cytokines and chemokines. However, little is known about the role of MMPs in chronic pain regulation. Our recent study has shown that neuropathic pain development in the early and late phase requires MMP-9 and MMP-2, respectively. Inhibition of MMP-9 or MMP-2 might provide a new strategy for the prevention and treatment of neuropathic pain.

Anti-inflammatory cytokine gene therapy decreases sensory and motor dysfunction in experimental Multiple Sclerosis: MOG-EAE behavioral and anatomical symptom treatment with cytokine gene therapy

Multiple Sclerosis (MS) is an autoimmune inflammatory disease that presents clinically with a range of symptoms including motor, sensory, and cognitive dysfunction as well as demyelination and lesion formation in brain and spinal cord. A variety of animal models of MS have been developed that share many of the pathological hallmarks of MS including motor deficits (ascending paralysis), demyelination and axonal damage of central nervous system (CNS) tissue. In recent years, neuropathic pain has been recognized as a prevalent symptom of MS in a majority of patients. To date, there have been very few investigations into sensory disturbances in animal models of MS. The current work contains the first assessment of hind paw mechanical allodynia (von Frey test) over the course of a relapsing-remitting myelin oligodendrocyte glycoprotein induced experimental autoimmune encephalomyelitis (MOG-EAE) rat model of MS and establishes the utility of this model in examining autoimmune induced sensory dysfunction. We demonstrate periods of both decreased responsiveness to touch that precedes the onset of hind limb paralysis, and increased responsiveness (allodynia) that occurs during the period of motor deficit amelioration traditionally referred to as symptom remission. Furthermore, we tested the ability of our recently characterized anti-inflammatory IL-10 gene therapy to treat the autoimmune inflammation induced behavioral symptoms and tissue histopathological changes. This therapy is shown here to reverse inflammation induced paralysis, to reduce disease associated reduction in sensitivity to touch, to prevent the onset of allodynia, to reverse disease associated loss of body weight, and to suppress CNS glial activation associated with disease progression in this model.

Experimental studies of potential analgesics for the treatment of chemotherapy-evoked painful peripheral neuropathies

OBJECTIVE

We investigated potential analgesics for chemotherapy-evoked neuropathic pain using rats treated with paclitaxel.

DESIGN

Drugs were tested in a repeated dosing paradigm (four daily injections). Topiramate was tested with a long-term treatment paradigm (12 days). A literature search was performed to summarize prior data.

MEASURES

Mechanical stimulation of the hind paw was used to assay antiallodynic and antihyperalgesic effects acutely and 24 hours after injection.

RESULTS

Amitriptyline produced significant analgesia, but this was not apparent until after the second injection. Baclofen produced significant effects, but the response varied erratically. Mexiletine and NMED-126 (a mixed N- and T-type calcium channel blocker) produced consistent, significant analgesia when tested acutely, but the pain relief did not persist at 24 hours postinjection. Oxcarbazepine had no effect at any time. Tramadol produced consistent, near-complete analgesia when tested acutely, but the analgesia did not persist to 24 hours postinjection. Topiramate produced significant effects that were first evident after 6-8 days of dosing.

CONCLUSIONS

The present data and data from the literature review suggest that there are several potential treatments for chemotherapy-evoked neuropathic pain. Nonsteroidal anti-inflammatory drugs have little or no efficacy. Opioids have an effect, but probably only with high doses. At least some antidepressants are analgesic in these conditions. Some, but clearly not all, anticonvulsants and sodium channel blockers have efficacy. Tramadol is a particularly promising candidate. Topiramate, acetyl-L-carnitine, carbamazepine, and venlafaxine may have protective or restorative effects. Clinical trials of these candidates are needed to advance the treatment of chemotherapy-evoked pain.

Submembraneous microtubule cytoskeleton: biochemical and functional interplay of TRP channels with the cytoskeleton

Much work has focused on the electrophysiological properties of transient receptor potential channels. Recently, a novel aspect of importance emerged: the interplay of transient receptor potential channels with the cytoskeleton. Recent data suggest a direct interaction and functional repercussion for both binding partners. The bi-directionality of physical and functional interaction renders therefore, the cytoskeleton a potent integration point of complex biological signalling events, from both the cytoplasm and the extracellular space. In this minireview, we focus mostly on the interaction of the cytoskeleton with transient receptor potential vanilloid channels. Thereby, we point out the functional importance of cytoskeleton components both as modulator and as modulated downstream effector. The resulting implications for patho-biological situations are discussed.

Selective activation of cannabinoid CB2 receptors suppresses neuropathic nociception induced by treatment with the chemotherapeutic agent paclitaxel in rats

Activation of cannabinoid CB(2) receptors suppresses neuropathic pain induced by traumatic nerve injury. The present studies were conducted to evaluate the efficacy of cannabinoid CB(2) receptor activation in suppressing painful peripheral neuropathy evoked by chemotherapeutic treatment with the antitumor agent paclitaxel. Rats received paclitaxel (2 mg/kg i.p./day) on 4 alternate days to induce mechanical hypersensitivity (mechanical allodynia). Mechanical allodynia was defined as a lowering of the threshold for paw withdrawal to stimulation of the plantar hind paw surface with an electronic von Frey stimulator. Mechanical allodynia developed in paclitaxel-treated animals relative to groups receiving the Cremophor EL/ethanol/saline vehicle at the same times. Two structurally distinct cannabinoid CB(2) agonists, the aminoalkylindole (R,S)-AM1241 [(R,S)-(2-iodo-5-nitrophenyl)-[1-((1-methyl-piperidin-2-yl)methyl)-1H-indol-3-yl]-methanone] and the cannabilactone AM1714 (1,9-dihydroxy-3-(1',1'-dimethylheptyl)-6H-benzo[c]chromene-6-one), produced a dose-related suppression of established paclitaxel-evoked mechanical allodynia after systemic administration. Pretreatment with the CB(2) antagonist SR144528 [5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-N-(1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl)-1H-pyrazole-3-carboxamide], but not the CB(1) antagonist SR141716 [5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide], blocked the antiallodynic effects of both (R,S)-AM1241 and AM1714. Moreover, (R)-AM1241, but not (S)-AM1241, suppressed paclitaxel-evoked mechanical allodynia relative to either vehicle treatment or preinjection thresholds, consistent with mediation by CB(2). Administration of either the CB(1) or CB(2) antagonist alone failed to alter paclitaxel-evoked mechanical allodynia. Moreover, (R,S)-AM1241 did not alter paw withdrawal thresholds in rats that received the Cremophor EL vehicle in lieu of paclitaxel, whereas AM1714 induced a modest antinociceptive effect. Our data suggest that cannabinoid CB(2) receptors may be important therapeutic targets for the treatment of chemotherapy-evoked neuropathy.

Prevention of paclitaxel-evoked painful peripheral neuropathy by acetyl-L-carnitine: effects on axonal mitochondria, sensory nerve fiber terminal arbors, and cutaneous Langerhans cells

Prophylactic treatment with acetyl-L-carnitine (ALCAR) prevents the neuropathic pain syndrome that is evoked by the chemotherapeutic agent, paclitaxel. The paclitaxel-evoked pain syndrome is associated with degeneration of the intraepidermal terminal arbors of primary afferent neurons, with the activation of cutaneous Langerhans cells, and with an increased incidence of swollen and vacuolated axonal mitochondria in A-fibers and C-fibers. Previous work suggests that ALCAR is neuroprotective in other nerve injury models and that it improves mitochondrial dysfunction. Thus, we examined whether the prophylactic efficacy of ALCAR was associated with the prevention of intraepidermal terminal arbor degeneration, the inhibition of Langerhans cell activation, or the inhibition of swelling and vacuolation of axonal mitochondria. In animals with a confirmed ALCAR effect, we found no evidence of a neuroprotective effect on the paclitaxel-evoked degeneration of sensory terminal arbors or an inhibition of the paclitaxel-evoked activation of Langerhans cells. However, ALCAR treatment completely prevented the paclitaxel-evoked increase in the incidence of swollen and vacuolated C-fiber mitochondria, while having no effect on the paclitaxel-evoked changes in A-fiber mitochondria. Our results suggest that the efficacy of prophylactic ALCAR treatment against the paclitaxel-evoked pain may be related to a protective effect on C-fiber mitochondria.

Cannabinoid CB2 receptors: a therapeutic target for the treatment of inflammatory and neuropathic pain

Cannabinoids suppress behavioural responses to noxious stimulation and suppress nociceptive transmission through activation of CB1 and CB2 receptor subtypes. CB1 receptors are expressed at high levels in the central nervous system (CNS), whereas CB2 receptors are found predominantly, but not exclusively, outside the CNS. CB2 receptors are also upregulated in the CNS and dorsal root ganglia by pathological pain states. Here, we review behavioural, neurochemical and electrophysiological data, which identify cannabinoid CB2 receptors as a therapeutic target for treating pathological pain states with limited centrally, mediated side effects. The development of CB2-selective agonists (with minimal affinity for CB1) as well as mutant mice lacking CB2 receptors has provided pharmacological and genetic tools required to evaluate the effectiveness of CB2 agonists in suppressing persistent pain states. This review will examine the efficacy of cannabinoid CB2-selective agonists in suppressing acute, inflammatory and neuropathic nociception following systemic and local routes of administration. Data derived from behavioural, neurochemical and neurophysiological approaches are discussed to better understand the relationship between antinociceptive effects induced by CB2-selective agonists in behavioural studies and neural mechanisms of pain suppression. Finally, the therapeutic potential and possible limitations of CB2-based pharmacotherapies for pathological pain states induced by tissue and nerve injury are discussed.

Chemotherapy-induced peripheral neuropathy: a review and implications for oncology nursing practice

Advances in supportive care have increased the likelihood that previously less common adverse effects of chemotherapy will be more evident. The incidence of chemotherapy-induced peripheral neuropathy (CIPN) is increasing because more neurotoxic drugs have been developed and because patients are living longer and receiving multiple chemotherapy regimens. This article reviews the anatomy of the peripheral nervous system, the proposed mechanisms of CIPN, and manifestations of CIPN from vinca alkaloids, taxanes, and platinum analogs. Major topics of this article are evidence-based data regarding symptom management, a review of medical management, and a synthesis of nursing care for patients at risk for or experiencing CIPN.

Peripheral neuropathy due to paclitaxel: study of the temporal relationships between the therapeutic schedule and the clinical quantitative score (QST) and comparison with neurophysiological findings

Peripheral neuropathy (PN) is one of the most common and dose-limiting side effects of paclitaxel, a chemiotherapeutic drug of proven efficacy in various tumours. We investigated the pathophysiological features of the PN and the temporal relationships between the development of the symptoms and signs associated with paclitaxel administration in two groups of patients with breast cancer: group A received paclitaxel alone (total cumulative dose range: 950-2,475 mg/m2), and group B paclitaxel and adriamycin (total cumulative dose range: 700-2,800 mg/m2). A codified assessment scoring clinical sensory and motor functions according to the Common Toxicity Scale and neurophysiological measurements were made before treatment, after the third and sixth cycles, and at the end of therapy. A total neuropathy score (TNS) included selected clinical and neurophysiological parameters. Both positive and negative sensory and motor symptoms and signs of PN developed during therapy, the most common being painful paresthesias, global areflexia and distal weakness. The neurophysiological study showed an early onset, length-independent and progressive sensory defect, and delayed, distal and length-dependent motor deficits. The neuropathy progressed faster in group A than in group B but, after therapy, most of the patients were TNS grade 2 regardless of their group. The temporal relationships between the PN and paclitaxel were robustly characterised, and thus provide reference data and a model for testing the efficacy of drugs designed to provide neuroprotection.

Activation of cannabinoid CB1 and CB2 receptors suppresses neuropathic nociception evoked by the chemotherapeutic agent vincristine in rats

BACKGROUND AND PURPOSE

The ability of cannabinoids to suppress mechanical hypersensitivity (mechanical allodynia) induced by treatment with the chemotherapeutic agent vincristine was evaluated in rats. Sites of action were subsequently identified.

EXPERIMENTAL APPROACH

Mechanical hypersensitivity developed over the course of ten daily injections of vincristine relative to groups receiving saline at the same times. Effects of the CB1/CB2 receptor agonist WIN55,212-2, the receptor-inactive enantiomer WIN55,212-3, the CB2-selective agonist (R,S)-AM1241, the opiate agonist morphine and vehicle on chemotherapy-induced neuropathy were evaluated. WIN55,212-2 was administered intrathecally (i.t.) or locally in the hindpaw to identify sites of action. Pharmacological specificity was established using competitive antagonists for CB1 (SR141716) or CB2 receptors (SR144528).

KEY RESULTS

Systemic administration of WIN55,212-2, but not WIN55,212-3, suppressed vincristine-evoked mechanical allodynia. A leftward shift in the dose-response curve was observed following WIN55,212-2 relative to morphine treatment. The CB1 (SR141716) and CB2 (SR144528) antagonists blocked the anti-allodynic effects of WIN55,212-2. (R,S)-AM1241 suppressed vincristine-induced mechanical hypersensitivity through a CB2 mechanism. Both cannabinoid agonists suppressed vincristine-induced mechanical hypersensitivity without inducing catalepsy. Spinal sites of action are implicated in cannabinoid modulation of chemotherapy-induced neuropathy. WIN55,212-2, but not WIN55,212-3, administered i.t. suppressed vincristine-evoked mechanical hypersensitivity at doses that were inactive following local hindpaw administration. Spinal coadministration of both the CB1 and CB2 antagonists blocked the anti-allodynic effects of WIN55,212-2.

CONCLUSIONS AND IMPLICATIONS

Cannabinoids suppress the maintenance of vincristine-induced mechanical allodynia through activation of CB1 and CB2 receptors. These anti-allodynic effects are mediated, at least in part, at the level of the spinal cord.

Rapid disassembly of dynamic microtubules upon activation of the capsaicin receptor TRPV1

The transmission of pain signalling involves the cytoskeleton, but mechanistically this is poorly understood. We recently demonstrated that the capsaicin receptor TRPV1, a non-selective cation channel expressed by nociceptors that is capable of detecting multiple pain-producing stimuli, directly interacts with the tubulin cytoskeleton. We hypothesized that the tubulin cytoskeleton is a downstream effector of TRPV1 activation. Here we show that activation of TRPV1 results in the rapid disassembly of microtubules, but not of the actin or neurofilament cytoskeletons. TRPV1 activation mainly affects dynamic microtubules that contain tyrosinated tubulins, whereas stable microtubules are apparently unaffected. The C-terminal fragment of TRPV1 exerts a stabilizing effect on microtubules when over-expressed in F11 cells. These findings suggest that TRPV1 activation may contribute to cytoskeleton remodelling and so influence nociception.

Pain management for the hospitalized pediatric patient

Pediatric hospitalists should make pain assessment and treatment a high priority and a central part of their daily practice. Efforts at improving pain treatment in pediatric hospitals should be multidisciplinary and should involve combined use of pharmacologic and nonpharmacologic approaches. Although available information can permit effective treatment of pain for most children in hospitals, there is a need for more research on pediatric analgesic pharmacology, various nonpharmacologic treatments, and different models of delivery of care.

Molecular mechanisms of cancer pain

Pain is the most disruptive influence on the quality of life of cancer patients. Although significant advances are being made in cancer treatment and diagnosis, the basic neurobiology of cancer pain is poorly understood. New insights into these mechanisms are now arising from animal models, and have the potential to fundamentally change the way that cancer pain is controlled.