Caudal Nerve Conduction Velocity Research Articles

Abstract 4653: Pharmacokinetics and biodistribution of eribulin mesylate, paclitaxel, and ixabepilone in mouse

Abstract Chemotherapy-induced peripheral neurotoxicity is a major clinical problem representing the dose-limiting side effect of many antineoplastic drugs. The degree and type of neuropathy incurred is dependent on the chemotherapeutic drug, dose intensity, and cumulative dose. In an earlier study by our group, we found that paclitaxel and ixabepilone, administered to mice at their respective MTDs, produced dose dependent deficits in caudal nerve conduction velocity, caudal amplitude and digital nerve amplitudes, as well as moderate to severe degenerative pathologic changes in dorsal root ganglia (DRG) and sciatic nerve (SN). In contrast, eribulin mesylate produced no significant deleterious effects on any nerve conduction parameter measured and caused milder, less frequent effects on morphology. Similar trends for eribulin to cause less neuropathy (including later onset and resolution) in the clinic have also been reported (Cigler and Vadhat, 2010; Jain and Cigler 2012, Vadhat et al., 2013). Differences in tubulin binding may, in part, potentially explain the differential effect (Perez et al 2009; Jordan et al 2005). Another potential explanation may reside in different pharmacokinetic (PK) and peripheral nerve distribution of these agents. To elucidate this, mice received a single dose of paclitaxel, ixabepilone or eribulin mesylate (30, 3 and 1.75mg/kg respectively, based on an MTD regimen), administered IV into the caudal vein. Plasma, DRG and SN samples were obtained at 0.25, 1, 3, 6, 8, 24, 48, and 72 h post dose. Tissues were homogenized and after extraction, concentrations of eribulin mesylate, ixabepilone and paclitaxel were determined in each matrix using LC/MS/MS. PK parameters were calculated using noncompartmental analysis in WinNonLin v 5.0.3. We report that all 3 chemotherapies rapidly penetrated both SN and DRG with maximal concentrations seen at, or within 15 mins after administration. Concentrations of all 3 agents in DRG and SN then declined by 30-50% over the first 1-3h and thereafter remained relatively stable in the tissue for up to 72 h, despite clearing rapidly from plasma to reach levels below quantification, (<5 ng/ml), by 24 h. Overall, dose normalized AUC in SN was similar for eribulin mesylate and ixabepilone and higher than for paclitaxel (1927 vs 2451 vs 793 ng/h/per g tissue, respectively). The ranking for the dose normalized AUC in DRG was eribulin mesylate < paclitaxel < ixabepilone (3894 vs 7217 vs 22800 ng/h/per g tissue, respectively). These findings suggest that peripheral nerve exposure is likely not the underlying mechanism for the differential propensity of eribulin mesylate, paclitaxel and ixabepilone to produce neurotoxicity. This work was financially supported by Eisai. Citation Format: Krystyna Wozniak, Ying Wu, Kenichi Nomoto, Bruce A. Littlefield, Christopher DesJardins, Edgar Schuck, Phil Saxton, Nancy Wong, Barbara S. Slusher. Pharmacokinetics and biodistribution of eribulin mesylate, paclitaxel, and ixabepilone in mouse. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4653. doi:10.1158/1538-7445.AM2014-4653

Neuropathy-Inducing Effects of Eribulin Mesylate Versus Paclitaxel in Mice with Preexisting Neuropathy

Eribulin mesylate (E7389, INN:eribulin mesilate Halaven(®)) is a non-taxane microtubule dynamics inhibitor currently in clinical use for advanced breast cancer. Other microtubule-targeting agents for breast cancer, including paclitaxel and ixabepilone, display a common treatment dose-limiting toxicity of peripheral neuropathy (PN). In an earlier study, we found eribulin mesylate had a lower propensity to induce PN in mice than either paclitaxel or ixabepilone. In the current study, we compared additional PN induced by paclitaxel versus eribulin mesylate when administered to mice with preexisting paclitaxel-induced PN. Initially, paclitaxel at 0.75 × its maximum tolerated dose (MTD; 22.5 mg/kg) was given on a Q2Dx3 regimen for 2 weeks. The second chemotherapy was 0.5 MTD eribulin mesylate (0.875 mg/kg) or paclitaxel (15 mg/kg) on a similar regimen, starting 2 weeks after the first. Initial paclitaxel treatment produced significant decreases in caudal nerve conduction velocity (NCV; averaging 19.5 ± 1 and 22.2 ± 1.3 %, p < 0.001) and amplitude (averaging 53.2 ± 2.6 and 72.4 ± 2.1 %, p < 0.001) versus vehicle when measured 24 h or 2 weeks after dosing cessation, respectively. Additional 0.5 MTD paclitaxel further reduced caudal NCV and amplitude relative to immediately before initiation of the second regimen (by 11 ± 2.1 and 59.2 ± 5 %, p < 0.01, respectively). In contrast, 0.5 MTD eribulin mesylate caused no further decrease in caudal NCV. In conclusion, unlike additional paclitaxel treatment, eribulin mesylate administered to mice with preexisting paclitaxel-induced PN had limited additional deleterious effects at 6 weeks. These preclinical data suggest that eribulin mesylate may have reduced tendency to exacerbate preexisting paclitaxel-induced PN in clinical settings.

Influence of aging on peripheral nervous system: a morphological and morphometric study

It is well known that aging influences several functional and structural features of peripheral nerves (Verdu et al., 2000; Ceballos et al., 1999; Jeronimo et al., 2008). However, the role of these changes in the damage/repair mechanisms occurring in acquired peripheral neuropathies is still unclear. To this aim, a multimodal, long-term assessment in a mice model would represent an optimal tool to perform experimental neuropathy studies designed to evaluate the role of aging in relationship with a given nerve injury. In this study we used 40 females one-month-old C57B1/6 mice and we followed-up them for fifteen months. Digital and caudal nerve conduction velocity (NCV) studies were performed monthly to evaluate changes in electrophysiological features; moreover, four animals were sacrificed every two months in order to collect caudal nerve, sciatic nerve, dorsal root ganglia (DRG) and skin for morphological and morphometric analysis. The neurophysiological assessments showed a remarkable increase of caudal NCV until the age of 9 months and then it remained unchanged until the end of the observation period; in the same period, digital NCV increase was also present although less marked. At the pathological level, both caudal and sciatic nerves showed a decrease in fibres density related with age, whereas axon and fibres diameters tended to increase. These preliminary data can be considered a first step aiming at creating a background for future studies on the relationship between aging and peripheral nervous system induced damage.

Muscle NT-3 levels increased by exercise training contribute to the improvement in caudal nerve conduction velocity in diabetic rats

The aim of the present study was to explore the role of exercise in diabetic peripheral neuropathy (DPN) and the mechanisms involved. For this purpose, 31 male Sprague-Dawley rats were used. The rats were assigned to 5 groups: diabetic rats subjected to exercise training (swimming) for 8 weeks (D-Ex1 group), diabetic rats subjected to exercise training for 4 weeks after 4 weeks of being sedentary (D-Ex2 group), diabetic rats which remained sedentary for 8 weeks (D-Sed group), control rats subjected to exercise training for 8 weeks (C-Ex1 group) and control rats which remained sedentary for 8 weeks (C-Sed group). Blood glucose levels and caudal nerve conduction velocity (NCV) were evaluated at 0 (baseline), 28 (4 weeks) and 56 days (8 weeks) after the induction of diabetes. The levels of neurotrophin-3 (NT-3) in skeletal muscle were measured by ELISA at the end of the experiment. Blood glucose levels in the D-Ex1 group rats decreased significantly after 8 weeks of exercise. The caudal NCV markedly decreased in all diabetic rats and significantly increased after 4 or 8 weeks of exercise training. Muscle NT-3 levels were significantly lower in the D-Sed compared to the 4 other groups. Muscle NT-3 levels positively correlated with caudal NCV. In conclusion, swimming training has a beneficial effect on DPN and muscle NT-3 levels, which could help improve caudal NCV in streptozotocin-induced diabetic rats.

Abstract 933: Peripheral neuropathy induced by chronic administration of Cisplatin, taxol and bortezomib in several murine models

Abstract Cisplatin (CDDP), Taxol (TAX) and Bortezomib (BZ) are chemotherapeutic drugs commonly employed in clinical practice for the treatment of solid and haematological tumors. Their clinical use is limited by the development of a peripheral neuropathy characterized by sensory alterations, pain and, in part, by motor and autonomic dysfunctions. Several rat models had been performed to study and describe the mechanisms of the peripheral neurotoxicity induced by these drugs. However, since only few cancer cell lines are able to induce the development of cancer in the rat, we focused our attention on mice models to allow the combined study of the antineoplastic activity and of the neurotoxic effects of the anticancer compounds. Moreover, different mice strains should be useful for different kind of studies. Here we investigated the interactions between the mice genotype and their drug response to determine the susceptibility to the development of chemotherapy-induced peripheral neuropathy. To this aim, we investigated the neurophysiological and neuropathological alterations induced by the chronic treatment with different chemotherapy drugs in female Balb/c, CD1 and c57 mice and in male c57 and FVB mice. Mice were injected with Cisplatin (2, 4 mg/Kg, ip, 2qw), or Taxol (50, 70, 80 mg/Kg, iv, 1qw) or Bortezomib (0.4, 0.8 mg/Kg, iv, 2qw) for a period of 4-6 weeks. At the end of the treatment the nerve conduction velocities (NCVs) were determined in the caudal and in the digital nerves and the dorsal root ganglia (DRG) and sciatic nerves collected for the neuropathological analysis; behavioural tests were performed to study if these drugs are able to induce allodynia or hyperalgesia. In all mice models we observed that TAX and CDDP induced a significant alteration in body weight at the end of the treatment. All the drugs induced a significant reduction in the caudal and digital NCV in Balb/c and CD1 mice. TAX and BZ caused the axonal degeneration of the sciatic nerves while CDDP and BZ morphological alterations in the DRG. In c57 female mice, only BZ induced a significant reduction in caudal NCV while in c57 male mice only CDDP caused neurophysiological impairments. By contrast, male FVB mice showed any neurophysiological alterations. All these models, except FVB mice, have shown the onset of allodynia and hyperalgesia at the end of the treatment. In conclusion we can affirm that, even if at different extent, Balb/c, CD1 and c57 mice were able to develop the different chemotherapy-induced peripheral neuropathies. Moreover, also the gender seemed to be involved in the severity of the neuropathy. By contrast, FVB mice were less susceptible to the neurotoxic damage. This study would give a useful guideline for the choice of mouse strains in the combined studies of the antineoplastic activity and of the neurotoxic effects of chemotherapy drugs. Partially supported by a grant from “Fondazione Banca del Monte di Lombardia”. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 933. doi:1538-7445.AM2012-933

Abstract 934: Electrophysiological, behavioural and molecular characterization of the neuropathic pain in bortezomib-induced peripheral neuropathy

Abstract Bortezomib (BZ) is a potent and selective first-in-class proteasome inhibitor that is mainly used to treat relapsed, refractory multiple myeloma. Painful peripheral neuropathy (PPN) is a significant side effect of BZ-based chemotherapy and, although it is one of the major reasons for a dose reduction and discontinuation of life-saving therapy, its mechanisms remain poorly understood. Recently, BZ has been shown to cause metabolic changes that result from drug accumulation in the dorsal root ganglia (DRG). Moreover, deficits in the major peripheral nerve fibres may contribute to the pathogenesis of the distal sensory axonal PPN. The effects of BZ and the involvement of changes in the spinal dorsal horn have yet to be elucidated. Here we characterized the effects of 4 weeks of intravenous BZ treatment in BALB/c mice. We examined the development of peripheral neuropathy by measuring caudal and digital nerve conduction velocities (NCV) and histology to detect pathological changes in the DRG and sciatic nerve. We also assessed changes in the mechanical/thermal thresholds and the effects of the drug on sensory fiber function by measuring current perception threshold (CPT) with a Neurometer. To investigate relevant spinal cord structures involved in BZ-induced PPN, we conducted electrophysiological recordings of spinal dorsal horn (SDH) neurons to examine their electrical activity, immunofluorescence assays to detect neuronal apoptotic events and a morphological analysis of spinal cord and roots. BZ treatment produced an impairment of the caudal and digital NCV. DRG of BZ-treated mice often had evidence of sensory neuron and satellite cell degeneration. Moreover BZ caused severe axonal degeneration of myelinated and unmyelinated fibres. BZ-induced mechanical allodynia also developed and CPT analysis demonstrated a partial impairment of the Aβ and C fibers function. The electrophysiological recordings in the SDH revealed that, despite the inability of BZ to cross the blood-brain barrier, it induced an increase in wide dynamic range neuron activity, particularly after light stimulations of the hind paw. Lastly, morphological alterations in the dorsal roots and in the dorsal column of the spinal cord were evident. Our results demonstrate that chronic treatment with BZ produces a painful neuropathy in the mouse and that both peripheral and central nervous system structures are affected. Therefore, this model will enable us to conduct further mechanistic studies of BZ-related antineoplastic activity, peripheral neurotoxicity and pain. Further, this model can be used as a reference in the preclinical discovery of new neuroprotective as well as of analgesic compounds. This work was partially funded by “AISAL, Associazione per le Scienze degli Animali da Laboratorio” and by P30 NR011396 to S.G.D. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 934. doi:1538-7445.AM2012-934

Comparison of Neuropathy-Inducing Effects of Eribulin Mesylate, Paclitaxel, and Ixabepilone in Mice

Chemotherapy-induced neurotoxicity is a significant problem associated with successful treatment of many cancers. Tubulin is a well-established target of antineoplastic therapy; however, tubulin-targeting agents, such as paclitaxel and the newer epothilones, induce significant neurotoxicity. Eribulin mesylate, a novel microtubule-targeting analogue of the marine natural product halichondrin B, has recently shown antineoplastic activity, with relatively low incidence and severity of neuropathy, in metastatic breast cancer patients. The mechanism of chemotherapy-induced neuropathy is not well understood. One of the main underlying reasons is incomplete characterization of pathology of peripheral nerves from treated subjects, either from patients or preclinically from animals. The current study was conducted to directly compare, in mice, the neuropathy-inducing propensity of three drugs: paclitaxel, ixabepilone, and eribulin mesylate. Because these drugs have different potencies and pharmacokinetics, we compared them on the basis of a maximum tolerated dose (MTD). Effects of each drug on caudal and digital nerve conduction velocity, nerve amplitude, and sciatic nerve and dorsal root ganglion morphology at 0.25 × MTD, 0.5 × MTD, 0.75 × MTD, and MTD were compared. Paclitaxel and ixabepilone, at their respective MTDs, produced significant deficits in caudal nerve conduction velocity, caudal amplitude and digital nerve amplitudes, as well as moderate to severe degenerative pathologic changes in dorsal root ganglia and sciatic nerve. In contrast, eribulin mesylate produced no significant deleterious effects on any nerve conduction parameter measured and caused milder, less frequent effects on morphology. Overall, our findings indicate that eribulin mesylate induces less neuropathy in mice than paclitaxel or ixabepilone at equivalent MTD-based doses.

Multimodal Assessment of Painful Peripheral Neuropathy Induced by Chronic Oxaliplatin-Based Chemotherapy in Mice

BackgroundA major clinical issue affecting 10-40% of cancer patients treated with oxaliplatin is severe peripheral neuropathy with symptoms including cold sensitivity and neuropathic pain. Rat models have been used to describe the pathological features of oxaliplatin-induced peripheral neuropathy; however, they are inadequate for parallel studies of oxaliplatin's antineoplastic activity and neurotoxicity because most cancer models are developed in mice. Thus, we characterized the effects of chronic, bi-weekly administration of oxaliplatin in BALB/c mice. We first studied oxaliplatin's effects on the peripheral nervous system by measuring caudal and digital nerve conduction velocities (NCV) followed by ultrastructural and morphometric analyses of dorsal root ganglia (DRG) and sciatic nerves. To further characterize the model, we examined nocifensive behavior and central nervous system excitability by in vivo electrophysiological recording of spinal dorsal horn (SDH) wide dynamic range neurons in oxaliplatin-treated miceResultsWe found significantly decreased NCV and action potential amplitude after oxaliplatin treatment along with neuronal atrophy and multinucleolated DRG neurons that have eccentric nucleoli. Oxaliplatin also induced significant mechanical allodynia and cold hyperalgesia, starting from the first week of treatment, and a significant increase in the activity of wide dynamic range neurons in the SDH.ConclusionsOur findings demonstrate that chronic treatment with oxaliplatin produces neurotoxic changes in BALB/c mice, confirming that this model is a suitable tool to conduct further mechanistic studies of oxaliplatin-related antineoplastic activity, peripheral neurotoxicity and pain. Further, this model can be used for the preclinical discovery of new neuroprotective and analgesic compounds.

Neurophysiological and neuropathological characterization of new murine models of chemotherapy-induced chronic peripheral neuropathies

Cisplatin, paclitaxel and bortezomib belong to some of the most effective families of chemotherapy drugs for solid and haematological cancers. Epothilones represent a new family of very promising antitubulin agents. The clinical use of all these drugs is limited by their severe peripheral neurotoxicity. Several in vivo rat models have reproduced the characteristics of the peripheral neurotoxicity of these drugs. However, since only a very limited number of cancer types can be studied in immunocompetent rats, these animal models do not represent an effective way to evaluate, at the same time, the antineoplastic activity and the neurotoxic effects of the anticancer compounds. In this study, we characterized the neurophysiological impairment induced by chronic chemotherapy treatment in BALB/c mice, a strain suitable for assessing the activity of anticancer treatments. At the end of a 4-week period of treatment with cisplatin, paclitaxel, epothilone-B or bortezomib, sensory and sensory/motor nerve conduction velocities (NCV) were determined in the caudal and digital nerves and dorsal root ganglia (DRG) and sciatic nerves were collected for histopathological analysis. The electrophysiological studies revealed that all the compounds caused a statistically significant reduction in the caudal NCV, while impairment of the digital NCV was less severe. This functional damage was confirmed by the histopathological observations evidencing axonal degeneration in the sciatic nerve induced by all the drugs associated with pathological changes in DRG induced only by cisplatin and bortezomib. These results confirm the possibility to use our models to combine the study of the antineoplastic activity of anticancer drugs and of their toxic effects on the peripheral nervous system in the BALB/c mouse strain.

Abstract 4438: Comparison of neuropathy-inducing effects of eribulin versus paclitaxel in mice

Abstract Eribulin (referred to as E7389 in the mesylate salt form) is a structurally simplified analog of the potent anticancer agent halichondrin B. Eribulin inhibits microtubule dynamics via a mechanism that is distinct from that of other tubulin-targeting drugs. Eribulin has recently shown activity in Phase III trials for advanced metastatic breast cancer. Current standard treatment for breast cancer includes paclitaxel, whose major dose-limiting toxicity is peripheral neuropathy. This study was conducted to directly compare the neuropathy-producing effects of paclitaxel versus eribulin in mice. Maximum tolerated dose (MTD) levels using a 3x/week intravenous regimen (Q2D x 3) for 2 weeks, were determined for each compound. Neuropathy studies were then conducted in mice dosed at the respective MTDs or fractions thereof (0.75, 0.5 and 0.25 of the MTD), or with vehicle control. Mice were evaluated for nerve conduction velocity (NCV) and amplitude in caudal and digital nerves 24 hr after their last treatment. Sciatic nerves and dorsal root ganglia (DRG) were subsequently removed for pathological assessment. After 2 weeks dosing with paclitaxel, clear dose-dependent decreases in caudal NCV and amplitude were evident. At MTD (30 mg/kg), paclitaxel caused a significant reduction in caudal NCV compared to control (18 +/− 3.8%; p&amp;lt;0.01), while both MTD and 0.75 MTD doses caused significant reduction in caudal amplitude compared to control (63.5 +/− 4.8% and 48.8 +/− 4.2%, respectively; p&amp;lt;0.001). Both MTD and 0.75 MTD paclitaxel also caused significant reduction in digital nerve amplitude (62.8 +/− 4.1 % and 35.2 +/− 4.3 %, p&amp;lt;0.001 and p&amp;lt;0.05 respectively). In contrast, after 2 weeks dosing with eribulin, there were no decreases in caudal or digital NCV or amplitude at any dose, including the MTD (1.75 mg/kg). Microscopic examination revealed that paclitaxel induced moderate to severe dose-dependent pathological changes in sciatic nerve and DRG at doses of 0.5 MTD or higher. Eribulin produced some mild pathological changes in DRG neurons and sciatic nerve, which although less severe, were clearly evident at the 0.75 MTD and MTD doses. In conclusion, eribulin administered to mice intravenously at doses up to and including the MTD, during an intensive two week regimen induced no significant reduction in nerve conduction velocity or amplitude in caudal and digital nerves, findings that contrast markedly with the significant decreases in nerve conduction velocity and amplitude induced by paclitaxel. In addition, eribulin caused less severe morphological changes in DRG and sciatic nerves at equivalent MTD-based doses. Overall, these preclinical findings suggest that eribulin may be less likely to induce neuropathy than paclitaxel. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4438.

Abstract 1664: Characterization of new murine models of peripheral neuropathy induced by chronic administration of antineoplastic drugs

Abstract In this study we report the neurophysiological and neuropathological characterization of new murine models of chemotherapy-induced peripheral neuropathy (CIPN). Cisplatin, oxaliplatin, paclitaxel, epothilone-B and bortezomib represent some of the most frequently employed chemotherapy treatments in breast cancer, colon cancer, genitourinary cancers and multiple myeloma. Nevertheless, the clinical use of these drugs is often associated to the development of a potentially severe peripheral neuropathy characterized by sensory distal alterations such as pareshesias and dysesthesias, ataxia, burning sensations, diminished reflexes and, at least in part, by motor and autonomic dysfunctions. Several rat models of CIPN had been established in the past to describe the mechanisms of its development and pathogenesis revealing that, as well as in humans, all chronic chemotherapy regimens cause neurophysiological impairments, neuropathological and molecular alterations in peripheral nerves and DRG. However, since only a limited number of cancer cell lines is able to induce the development of cancer in the rat, this animal model does not represent the most effective way to study, at the same time, the antineoplastic activity and the neurotoxic effects of the anticancer compounds. In this work, in order to characterize the neurophysiological impairments induced by chronic chemotherapy treatment in balb-c mice, the drugs were administered for a 4 weeks-period. Cisplatin at the doses of 2 or 4 mg/Kg, paclitaxel 50 or 70 mg/Kg, oxaliplatin 3.5 mg/Kg, epothilone-B 2 or 4 mg/Kg and bortezomib 0.4 or 0.8 mg/Kg. At the end of the treatment, sensory/motor and sensory nerve conduction velocities (NCVs) were determined stimulating respectively the caudal and the digital nerves by using an electromyography apparatus. DRG and sciatic nerves were collected for the neuropathological analysis at the light and electron microscope and the morphometrical analysis of sensory neurons. The electrophysiological study revealed that all compounds determined a statistically significant reduction in caudal NCV, while only some selected doses induced a significant impairment also of the digital NCV. These functional damages were confirmed by morphological observations describing an axonal degeneration in the sciatic nerve induced by paclitaxel, epothilone-B and bortezomib and alterations in DRG induced by platinum compounds and bortezomib. Platinum compounds determined also a somatic and nucleolar quantitative reduction-in-size of DRG sensory neurons. These results suggest that the selected treatment schedules are able to induce both sensory/motor and pure sensory peripheral neuropathies in the mice and allow to combine the study of the antineoplastic activity and of peripheral neurotoxicity, and can be used as a reference for new anticancer drugs as well as for neuroprotection studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1664.

Longitudinal studies of time‐dependent changes in both bladder and erectile function after streptozotocin‐induced diabetes in Fischer 344 male rats

To provide sensitive physiological endpoints for the onset and long-term progression of deficits induced by diabetes mellitus (DM) in bladder and erectile function in male rats, and to evaluate parallel changes in urogenital and nerve function induced by hyperglycaemia over a protracted period as a model for chronic deficits in patients with diabetes. The study comprised in 877 male, 3-month-old, Fischer 344 rats; 666 were injected intraperitoneally with 35 mg/kg streptozotocin (STZ) and divided into insulin-treated and untreated diabetic groups. The rats were studied over 8 months and measurements made of both erectile and bladder function, as well as nerve conduction studies over the duration of the study. There was an early (first month) abnormality of both erectile and bladder function that persisted through the 8 months of the study. The erectile dysfunction was manifest as reduced intracavernous pressure/blood pressure ratio, and the bladder dysfunction as a persistent increase in detrusor overactivity with no detrusor decompensation. Insulin treatment prevented or modified the abnormality in each organ. Hyperglycaemia caused a progressive decrease in caudal nerve conduction velocity. The mean digital sensory and tibial motor nerve conduction velocity did not deteriorate over time. Correlation measurements of nerve and organ function were not consistent. The results of this extensive long-term study show early and profound effects of hyperglycaemia on the smooth muscle of the penis and bladder, that were persistent and stable in surviving rats over the 8 months. The physiological changes did not correlate well with neurological measurements of those organs. Significantly, diverse smooth-muscle cellular and subcellular events antedated the measured neurological manifestations of the hyperglycaemia by several months. Although autonomic diabetic neuropathy is a primary life-threatening complication of long-term diabetes in humans, this rat model of STZ-induced diabetes showed that the rapid onset of physiological manifestations was based on many molecular changes in the smooth muscle cells in this model of type 1 DM.

Neurotoxic Effects of Zoniporide: A Selective Inhibitor of the Na+/H+ Exchanger Isoform 1

Zoniporide, an inhibitor of the Na+-H+ exchanger-1, was administered by continuous intravenous infusion to rats and dogs for up to 1 month. In 1-month studies, histological and functional changes were observed in select portions of the peripheral nervous system; however, these findings were not detected in 2-week studies at similar or higher doses. In the 1-month rat study, there was dose-dependent, minimal, focal, or multifocal nerve fiber (axonal) degeneration in the spinal cord and/or sciatic nerve. In a follow-up rat study, findings included slowing of caudal nerve conduction velocity and axonal degeneration in the spinal cord (dorsal funiculus), dorsal roots, dorsal root ganglia (DRG), radial, sciatic, and tibial nerves. In the 1-month dog study, there was impairment of the patellar reflex and associated postural reaction changes, minimal to marked proximal nerve fiber degeneration in the DRG, and minimal nerve fiber degeneration in the dorsal roots and funiculi of the spinal cord. Minimal nerve fiber degeneration of equivocal significance was noted in various peripheral nerves. Taken together, these findings were consistent with a specific effect on peripheral sensory nerve fibers. These studies demonstrated that zoniporide produces clinical, electrophysiologic, and microscopic evidence of peripheral sensory axonopathy and establishes the importance of careful preclinical evaluation of neurological function.

Effects of fidarestat, an aldose reductase inhibitor, on nerve conduction velocity and bladder function in streptozotocin-treated female rats

The effects of fidarestat, an aldose reductase inhibitor (ARI), were assessed on nerve conduction velocity (NCV) in somatic nerves and on multiple measures of bladder function in rats made hyperglycemic with streptozotocin (STZ) and in age-matched controls. Nerve conduction velocity was recorded at baseline and at 10, 20, 30, and 50 days after confirmation of the STZ-induced hyperglycemia in all rats ( N=47); bladder function was assessed in a representative subset of rats ( N=20) at Day 50. Caudal NCV was markedly slowed by STZ, and this effect was significantly reversed by fidarestat. The initial deficit and treatment-related improvement were especially evident for responses driven by high-frequency repetitive stimulation. Of the 11 parameters of bladder activity assessed, four measures—bladder capacity, micturition volume, micturition frequency, and bladder weight—were significantly different in the control and STZ-treated groups. These deficits were not affected by fidarestat. At Day 50, the induced deficits in bladder function were highly correlated with caudal NCV ( r values ranging from 0.70 to 0.96; P values ranging from .02 to <.0001). These results suggested that fidarestat improved the slowing of somatic nerve NCV in hyperglycemic rats, but it was not effective in reversing associated bladder dysfunction, in spite of the highly significant correlation between these two diabetes-induced deficits. Possible explanations for this dissociation are discussed.

Lack of neurotoxicity of the vascular targeting agent ZD6126 following repeated i.v. dosing in the rat

The vascular targeting agent ZD6126 is a water-soluble prodrug of N-acetylcolchinol that acts by disrupting the cytoskeleton of tumor endothelial cells. It is currently undergoing clinical evaluation in man. As peripheral neuropathy is a major dose-limiting toxicity associated with tubulin binding agents, the neurotoxic potential of ZD6126 was investigated in male and female Wistar rats. ZD6126 was administered i.v. at up to maximum tolerated doses using subacute (0 to 20 mg/kg/d for 5 days) and chronic (0 to 10 mg/kg/d for 5 days, repeated monthly for 6 months) dosing regimens. A separate study examined a combination of ZD6126 (three cycles of ZD6126 given as in the chronic dosing regimen) and paclitaxel (12 mg/kg/wk for 9 weeks) to assess whether coadministration of ZD6126 altered the time course or magnitude of a paclitaxel-induced neuropathy. Neurotoxic potential was examined using a comprehensive series of tests including a functional observation battery, measurements of muscle strength (forelimb and hind limb grip strength), nociception (tail flick test), locomotor activity, neuropathology, and whole nerve electrophysiology. There was no evidence that ZD6126 induced neurotoxicity in the rat following either subacute or chronic i.v. dosing. In a chronic electrophysiology study, ZD6126 produced a slight slowing of the maturational increase of caudal nerve amplitude, with some evidence of reversibility. However, this was not associated with any changes in caudal nerve conduction velocity, motor nerve conduction velocity or amplitude, functional observation battery behavioral and function parameters (including no effects on tail flick latency), and neuropathology. As expected, paclitaxel administration was associated with a significant decrease in caudal nerve conduction velocity (P = 0.0001). Coadministration of ZD6126 did not increase the neurotoxicity of paclitaxel. These studies suggest that ZD6126 should not induce the peripheral neuropathy associated with other antitubulin chemotherapeutic agents and that ZD6126 may not exacerbate the neurotoxicity of other agents with dose-limiting neuropathies.

KP544, a nerve growth factor amplifier: Pharmacokinetics, safety, and efficacy in the rat

AbstractIn cultured cells, KP544 [2‐amino‐5‐(4‐chlorophenylethynyl)‐4‐(4‐trans‐hydroxycyclohexyl amino) pyrimidine] amplifies differentiation initiated by nerve growth factor (NGF) or cAMP. This report describes the pharmacokinetics, safety, and neuroprotective efficacy of KP544 in rats. After an oral dose of 10 mg/kg KP544 was 25% bioavailable with a plasma half‐life of 1.3 h and brain levels 6‐fold higher than plasma levels at 4 and 8 h post‐dose. In a safety study, daily oral dosing for 30 days at 10 and 100 mg/kg was well tolerated. The favorable pharmacokinetic and safety profiles, together with its amplification of NGF in vitro, prompted evaluation of KP544 in two models involving NGF deficiencies. In the first model, brains were lesioned with intrastriatal injections of quinolinic acid. KP544 at oral doses of 0.02 to 1.0 mg/kg/day almost completely prevented the resulting learning deficits as evaluated using a radial‐arm‐water maze. At the lowest dose, there was a slower onset of functional improvement. These effects were accompanied by reductions (16–34%) in the striatal lesion size that were greatest at the highest dose and comparable to those seen with NGF therapy. The second model involved a peripheral neuropathy induced by taxol that is associated with decreases in NGF. KP544 at oral doses of 0.1–10 mg/kg/day decreased the severity of the neuropathy as measured by caudal nerve conduction velocities (30–70% return to control values). In both models, KP544 had a large therapeutic index suggesting its potential as a new approach for treating clinical disorders involving deficiencies in NGF. Drug Dev. Res. 62:60–70, 2004. © 2004 Wiley‐Liss, Inc.

Glutathione and alpha-lipoate in diabetic rats: nerve function, blood flow and oxidative state.

Increased oxidative stress is considered to be a causal factor in the development of diabetic complications, among which peripheral neuropathy. The pathophysiology of nerve dysfunction in diabetes has been explained both by reduced endoneurial microcirculation and alterations in endoneurial metabolism. It is unclear whether antioxidants primarily improve nerve blood flow or normalise systemic or endoneurial oxidative metabolism. Therefore, we evaluated the effects of the antioxidants glutathione and alpha-lipoic acid on both nerve microcirculation and the antioxidative capacity and lipid peroxidation in experimentally diabetic rats. Streptozotocin-diabetic rats were treated with different doses of alpha-lipoic acid, reduced glutathione or placebo, and were compared with nondiabetic controls. We measured systemic and endoneurial antioxidants, malondialdehyde and whole blood hydrogen peroxide. Furthermore, we evaluated sciatic and tibial motor and sensory nerve conduction velocity, caudal nerve conduction velocity, and assessed sciatic nerve blood flow and vascular resistance by Laser-Doppler flowmetry. We observed a rise in erythrocyte glutathione by 27 % (P < 0.05), and a trend towards decreased plasma malondialdehyde in alpha-lipoic acid, but not in glutathione-treated animals in comparison with the placebo group. Simultaneously, sciatic nerve blood flow and vascular resistance were improved by daily alpha-lipoic acid administration by 38% (P < 0.05). Peripheral nerve conduction velocity and endoneurial glutathione were not significantly influenced by antioxidant treatment. Only minor beneficial effects of alpha-lipoic acid on nerve blood flow and oxidative state occur at the given doses; these effects were insufficient to improve nerve conduction deficits.

Insulin-like growth factor-I prevents development of a vincristine neuropathy in mice

Vincristine is a commonly used antitumor agent whose major dose-limiting side-effect is a mixed sensorimotor neuropathy. To assess whether insulin-like growth factor-I (IGF-I), a neurotrophic agent that supports the survival of motoneurons and enhances regeneration of motor and sensory neurons, could prevent the peripheral neuropathy produced by vincristine, mice were treated with both vincristine (1.7 mg/kg, i.p., 2×/week) and/or IGF-I (0.3 or 1 mg/kg, s.c. daily) for 10 weeks. In mice treated with vincristine alone, there was evidence of a mixed sensorimotor neuropathy as indicated by changes in behavior, nerve conduction and histology. Caudal nerve conduction velocity was significantly slower in mice treated with vincristine alone as compared with vehicle-treated mice. Vincristine treatment alone also significantly increased hot-plate latencies and reduced gait support and stride length, but not toe spread distances. The effects of vincristine were accompanied by degeneration of sciatic nerve fibers and demyelination, indicating a peripheral neuropathy. IGF-I (1 mg/kg, s.c.) administered to vincristine-treated mice prevented the neurotoxic effects of vincristine as measured by nerve conduction, gait, response to noxious stimuli and nerve histology. At a lower dose of 0.3 mg/kg administered s.c., IGF-I partially ameliorated the neuropathy induced by vincristine as this dose only prevented the change in nerve conduction and hot-plate latencies. IGF-I administered alone had no effect on any of these parameters. These results suggest that IGF-I prevents both motor and sensory components of vincristine neuropathy and may be useful clinically in preventing the neuropathy induced by vincristine treatment.

Neurotropin prevents neurophysiological abnormalities and ADP-induced hyperaggregability in rats with streptozotocin-induced diabetes

Neurotropin, a non-proteinaceous extract from the inflamed dermis of rabbits inoculated with vaccinia virus, was administered for 8 weeks to rats with streptozotocin-induced diabetes. The physiological and biochemical changes of the nerves were studied as well as ADP-induced platelet aggregation. Neurotropin improved the caudal motor nerve conduction velocity, R-R variability, sciatic nerve blood flow, and platelet hyperaggregability in diabetic rats, despite having no effect on sorbitol and fructose accumulation or myoinositol depletion in the sciatic nerve. The correlation between nerve conduction velocity, R-R variability, nerve blood flow, and platelet aggregation were significant between each two parameters (p < 0.0001). Thus, the mechanism of action of neurotropin differed from that of aldose reductase inhibitors. These findings suggest that vascular factors may play an important role in the development of diabetic neuropathy, and that neurotropin may be useful for the treatment of this condition.

Prevention of abnormalities in motor nerve conduction and nerve blood-flow by a prostacyclin analog, beraprost sodium, in streptozotocin-induced diabetic rats

The effects of the prostacyclin analog beraprost sodium on motor nerve function and nerve blood-flow were examined in streptozotocin-induced diabetic rats. Oral administration of beraprost sodium 0.1 mg/kg/day for 8 wks significantly ( P < 0.001) improved caudal motor nerve conduction velocity and sciatic nerve blood-flow, both of which are impaired in diabetic rats. Beraprost sodium did not affect glucose, sorbitol, or fructose levels in the sciatic nerve. However, a decreased content of cyclic AMP in the sciatic nerve and higher level of thromboxane B 2 in the thoracic aorta of diabetic rats, as compared with those in normal rats, were reversed by the treatment with beraprost sodium ( P < 0.01). Results suggest that beraprost sodium may have value in treating diabetic neuropathy, mainly by improving endoneurial blood-flow.