Analysis Of Dorsal Root Ganglia Research Articles

Single-cell analysis of dorsal root ganglia reveals metalloproteinase signaling in satellite glial cells and pain

Satellite glial cells (SGCs) are among the most abundant non-neuronal cells in dorsal root ganglia (DRGs) and closely envelop sensory neurons that detect painful stimuli. However, little is still known about their homeostatic activities and their contribution to pain. Using single-cell RNA sequencing (scRNA-seq), we were able to obtain a unique transcriptional profile for SGCs. We found enriched expression of the tissue inhibitor metalloproteinase 3 (TIMP3) and other metalloproteinases in SGCs. Small interfering RNA and neutralizing antibody experiments revealed that TIMP3 modulates somatosensory stimuli. TIMP3 expression decreased after paclitaxel treatment, and its rescue by delivery of a recombinant TIMP3 protein reversed and prevented paclitaxel-induced pain. We also established that paclitaxel directly impacts metalloproteinase signaling in cultured SGCs, which may be used to identify potential new treatments for pain. Therefore, our results reveal a metalloproteinase signaling pathway in SGCs for proper processing of somatosensory stimuli and potential discovery of novel pain treatments.

CircRNA landscape in dorsal root ganglia from mice with collagen antibody-induced arthritis

Circular RNAs are a novel class of RNA molecules that are covalently closed into a ring structure. They are an epigenetic regulatory mechanism, and their best-studied function is regulation of microRNA activity. As such circular RNAs may be involved in the switch from acute to chronic pain. They have previously been studied in the context of neuropathic pain models, but their importance in inflammation-induced chronic pain models is unexplored. Microarray analysis of dorsal root ganglia collected in the late phase of collagen antibody-induced arthritis (day 59) were used to elucidate the relevance of circular RNAs in the mechanical hypersensitivity caused by this model. 120 circular RNA genes were found to be significantly differentially regulated in female BALB/c mice with collagen antibody-induced arthritis. Six genes were chosen for RT-qPCR analysis in the late (day 54–60) as well as the inflammatory (day 11–12) phase of this model. This validated an increase in circNufip1 expression in the late phase of collagen antibody-induced arthritis. Additionally, it was found that circVps13 and circMicall1 are upregulated in the inflammatory phase. Interestingly, no changes were found in dorsal root ganglia from mice injected with Freund's Complete Adjuvant (day 3) nor mice with spared nerve injury (day 20), despite their similarities to inflammatory and late phase collagen antibody-induced arthritis, respectively. This study provides evidence that mild circular RNA changes occur in dorsal root ganglia of mice with collagen antibody-induced arthritis that are, bioinformatically, predicated to be involved in processes relevant to sensitization.

The Role of Vascular-Immune Interactions in Modulating Chemotherapy Induced Neuropathic Pain.

Chemotherapy causes sensory disturbances in cancer patients that results in neuropathies and pain. As cancer survivorships has dramatically increased over the past 10 years, pain management of these patients is becoming clinically more important. Current analgesic strategies are mainly ineffective and long-term use is associated with severe side effects. The issue being that common analgesic strategies are based on ubiquitous pain mediator pathways, so when applied to clinically diverse neuropathic pain and neurological conditions, are unsuccessful. This is principally due to the lack of understanding of the driving forces that lead to chemotherapy induced neuropathies. It is well documented that chemotherapy causes sensory neurodegeneration through axonal atrophy and intraepidermal fibre degeneration causing alterations in pain perception. Despite the neuropathological alterations associated with chemotherapy-induced neuropathic pain being extensively researched, underlying causes remain elusive. Resent evidence from patient and rodent studies have indicated a prominent inflammatory cell component in the peripheral sensory nervous system in effected areas post chemotherapeutic treatment. This is accompanied by modulation of auxiliary cells of the dorsal root ganglia sensory neurons such as activation of satellite glia and capillary dysfunction. The presence of a neuroinflammatory component was supported by transcriptomic analysis of dorsal root ganglia taken from mice treated with common chemotherapy agents. With key inflammatory mediators identified, having potent immunoregulatory effects that directly influences nociception. We aim to evaluate the current understanding of these immune-neuronal interactions across different cancer therapy drug classes. In the belief this may lead to better pain management approaches for cancer survivors.

Caffeine Consumption Influences Lidocaine Action via Pain-Related Voltage-Gated Sodium Channels: An In Vivo Animal Study.

Several factors might influence the duration and efficiency of local anesthesia. This study investigates the effect of habitual caffeine intake on lidocaine action and explores the potential involvement of voltage-gated sodium channels in the interaction effect. Wistar rats were divided into four groups: (i) control (Ctrl), (ii) lidocaine intraplantar injection (LIDO), (iii) habitual caffeine intake (CAF), and (iv) lidocaine intraplantar injection and habitual caffeine intake (LIDO + CAF). Behavioral assessments, consisting of a paw pressure test for mechanical pressure sensation and a paw withdrawal latency test for thermal pain sensation, were performed at 0, 30, 60, and 90 minutes following lidocaine injection and after 10, 11, and 12 weeks of CAF intake. Pressure sensation was significantly reduced in the LIDO + CAF group compared with the control group. Moreover, the LIDO + CAF group exhibited reduced sensation compared to LIDO alone group. The LIDO + CAF combination exerted a synergistic effect at 30 and 60 minutes compared with the control. This synergistic effect was noted at 60 minutes (11 weeks of CAF intake) and at 30 minutes (12 weeks of CAF intake) compared with LIDO alone. Augmented thermal pain-relieving effects were observed in the LIDO + CAF group at all weeks compared to the control group and at 10 weeks compared to LIDO alone group. The molecular analysis of dorsal root ganglia suggested that CAF upregulated the mRNA expression of the Nav1.3, Nav1.7, and Nav1.8 sodium channel subtypes. Chronic caffeine consumption potentiates the local anesthetic action of lidocaine in an experimental animal model through mechanisms that involve the upregulation of voltage-gated sodium channels in the dorsal root ganglia.

2D vs 3D morphological analysis of dorsal root ganglia in health and painful neuropathy.

Dorsal root ganglia (DRGs) are clusters of sensory neurons that transmit the sensory information from the periphery to the central nervous system, and satellite glial cells (SGCs), their supporting trophic cells. Sensory neurons are pseudounipolar neurons with a heterogeneous neurochemistry reflecting their functional features. DRGs, not protected by the blood brain barrier, are vulnerable to stress and damage of different origin (i.e., toxic, mechanical, metabolic, genetic) that can involve sensory neurons, SGCs or, considering their intimate intercommunication, both cell populations. DRG damage, primary or secondary to nerve damage, produces a sensory peripheral neuropathy, characterized by neurophysiological abnormalities, numbness, paraesthesia and dysesthesia, tingling and burning sensations and neuropathic pain. DRG stress can be morphologically detected by light and electron microscope analysis with alterations in cell size (swelling/atrophy) and in different subcellular compartments (i.e., mitochondria, endoplasmic reticulum, and nucleus) of neurons and/or SGCs. In addition, neurochemical changes can be used to portray abnormalities of neurons and SGC. Conventional immunostaining, i.e., immunohistochemical detection of specific molecules in tissue slices, can be employed to detect, localize and quantify particular markers of damage in neurons (i.e., nuclear expression of ATF3) or SGCs (i.e., increased expression of GFAP), markers of apoptosis (i.e., caspases), markers of mitochondrial suffering and oxidative stress (i.e., 8-OHdG), markers of tissue inflammation (i.e., CD68 for macrophage infiltration) etc. However classical (2D) methods of immunostaining disrupt the overall organization of the DRG, thus resulting in the loss of some crucial information. Whole-mount (3D) methods have been recently developed to investigate DRG morphology and neurochemistry without tissue slicing, giving the opportunity to study the intimate relationship between SGCs and sensory neurons in health and disease. Here, we aim to compare classical (2D) vs whole-mount (3D) approaches to highlight “pros” and “cons” of the two methodologies when analysing neuropathy-induced alterations in DRGs.

Effects of route of administration on neural exposure to platinum-based chemotherapy treatment: a pharmacokinetic study in rat

The persisting need for effective clinical treatment of chemotherapy-induced neurotoxicity (CIN) motivates critical evaluation of preclinical models of CIN for their translational relevance. The present study aimed to provide the first quantitative evaluation of neural tissue exposed in vivo to a platinum-based anticancer compound, oxaliplatin (OX) during and after two commonly used dosing regimens: slow IV infusion used clinically and bolus IP injection used preclinically. Inductively-coupled plasma mass spectrometry analysis of dorsal root ganglia indicated that while differences in the temporal dynamics of platinum distribution exist, key drivers of neurotoxicity, e.g. peak concentrations and exposure, were not different across the two routes of administration. We conclude that the IP route of OX administration achieves clinically relevant pharmacokinetic exposure of neural tissues in a rodent model of CIN.

Inhibition of dual leucine zipper kinase prevents chemotherapy-induced peripheral neuropathy and cognitive impairments.

Chemotherapy-induced peripheral neuropathy (CIPN) and chemotherapy-induced cognitive impairments (CICI) are common, often severe neurotoxic side effects of cancer treatment that greatly reduce quality of life of cancer patients and survivors. Currently, there are no Food and Drug Administration-approved agents for the prevention or curative treatment of CIPN or CICI. The dual leucine zipper kinase (DLK) is a key mediator of axonal degeneration that is localized to axons and coordinates the neuronal response to injury. We developed a novel brain-penetrant DLK inhibitor, IACS'8287, which demonstrates potent and highly selective inhibition of DLK in vitro and in vivo. Coadministration of IACS'8287 with the platinum derivative cisplatin prevents mechanical allodynia, loss of intraepidermal nerve fibers in the hind paws, cognitive deficits, and impairments in brain connectivity in mice, all without interfering with the antitumor activity of cisplatin. The protective effects of IACS'8287 are associated with preservation of mitochondrial function in dorsal root ganglion neurons and in brain synaptosomes. In addition, RNA sequencing analysis of dorsal root ganglia reveals modulation of genes involved in neuronal activity and markers for immune cell infiltration by DLK inhibition. These data indicate that CIPN and CICI require DLK signaling in mice, and DLK inhibitors could become an attractive treatment in the clinic when coadministered with cisplatin, and potentially other chemotherapeutic agents, to prevent neurotoxicities as a result of cancer treatment.

Cell-specific role of histone deacetylase 6 in chemotherapy-induced mechanical allodynia and loss of intraepidermal nerve fibers.

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious adverse side effect of cancer treatment with no Food and Drug Administration-approved medication for its prevention or management. Using RNA sequencing analysis of dorsal root ganglia (DRG), we identify critical contributions of histone deacetylase 6 (HDAC6) and mitochondrial damage to the establishment of CIPN in a mouse model of cisplatin-induced neuropathy. We show that pharmacological inhibition of HDAC6 using ACY-1215 or global deletion of HDAC6 is sufficient to prevent cisplatin-induced mechanical allodynia, loss of intraepidermal nerve fibers (IENFs), and mitochondrial bioenergetic deficits in DRG neurons and peripheral nerves in male and female mice. The bioenergetic deficits in the neuronal cell bodies in the DRG are characterized by reduced oxidative phosphorylation, whereas the mitochondrial deficits in the nerves are due to a reduction in axonal mitochondrial content. Notably, deleting HDAC6 in sensory neurons protects against the cisplatin-induced loss of IENFs and the reduction in mitochondrial bioenergetics and content in the peripheral nerve. By contrast, deletion of HDAC6 in sensory neurons only partially and transiently prevents cisplatin-induced mechanical allodynia and does not protect against impairment of mitochondrial function in DRG neurons. We further reveal a critical role of T cells in the protective effects of HDAC6 inhibition on these signs of CIPN. In summary, we show that cisplatin-induced mechanical allodynia is associated with mitochondrial damage in DRG neurons, whereas the loss of IENFs is related to bioenergetic deficits in peripheral nerves. Moreover, our findings identify cell-specific contributions of HDAC6 to mechanical allodynia and loss of IENFs that characterize cisplatin-induced peripheral neuropathy.

Inflammatory and Neuropathic Gene Expression Signatures of Chemotherapy-Induced Neuropathy Induced by Vincristine, Cisplatin, and Oxaliplatin in C57BL/6J Mice

Vincristine, oxaliplatin, and cisplatin are commonly prescribed chemotherapeutic agents for the treatment of many tumors. However, a main side effect is chemotherapy-induced peripheral neuropathy (CIPN), which may lead to changes in chemotherapeutic treatment. Although symptoms associated with CIPN are recapitulated by mouse models, there is limited knowledge of how these drugs affect the expression of genes in sensory neurons. The present study carried out a transcriptomic analysis of dorsal root ganglia following vincristine, oxaliplatin, and cisplatin treatment with a view to gain insight into the comparative pathophysiological mechanisms of CIPN. RNA-Seq revealed 368, 295, and 256 differential expressed genes induced by treatment with vincristine, oxaliplatin, and cisplatin, respectively, and only 5 shared genes were dysregulated in all 3 groups. Cell type enrichment analysis and gene set enrichment analysis showed predominant effects on genes associated with the immune system after treatment with vincristine, while oxaliplatin treatment affected mainly neuronal genes. Treatment with cisplatin resulted in a mixed gene expression signature. PerspectiveThese results provide insight into the recruitment of immune responses to dorsal root ganglia and indicate enhanced neuroinflammatory processes following administration of vincristine, oxaliplatin, and cisplatin. These gene expression signatures may provide insight into novel drug targets for treatment of CIPN.

Transcriptome analysis of dorsal root ganglia's diabetic neuropathy reveals mechanisms involved in pain and regeneration

Peripheral diabetic neuropathy (DN) manifests in nearly 60% of diabetic patients, being pain its most debilitating symptom. Although electrophysiological and morphological aspects are well described, little is known about its development and progression, undermining effective therapies. Hyperglycemia and insulin signaling impairment are considered the triggering events of oxidative stress observed in the dying nerves, however there are still many gaps in the knowledge of intracellular plastic changes it generates. AimsIn this study we aimed to evaluate the early transcriptome changes in DN when the first symptoms of the disease start to appear. Main methodsNext-Generation Sequencing of messenger RNA (RNA-Seq) of L4 and L5 dorsal root ganglia (DRG) four weeks post-diabetes induction in a rat model for type 1 diabetes. Key findingsRNA sequencing found 66 transcripts differentially expressed between diabetic and control groups, related mainly to the following biological processes: inflammation, hyperalgesia/analgesia, cell growth and cell survival. Given their roles, the differentially expressed genes suggest an attempt to switch to a survival/regenerative program. SignificanceOur results show that changes in the transcriptome profile start to appear early in the course of DN and might be related to secure cell homeostasis. Hence, the present data may indicate how DRG cells are responding to hyperglycemia in its early stages and which mechanisms first fail to respond, further leading to cell damage and cell death. Early screening of cell alterations in DN might lead to more concrete targets for pharmaceutical interventions, which could more efficiently delay cell damage.

Upregulation of P2Y1 in neonatal nociceptors regulates heat and mechanical sensitization during cutaneous inflammation.

The upregulation of various channels and receptors classically linked to sensory transduction from the periphery tightly correspond with changes in the responsiveness of specific subpopulations of primary afferents to mechanical and heat stimulation of the skin at different ages. Previous reports in adults have suggested that the purinergic adenosine diphosphate receptor, P2Y1 can specifically regulate sensory neuron responsiveness to heat stimuli in addition to neurochemical alterations in primary afferents during cutaneous inflammation. To determine if the upregulation of P2Y1 found in the dorsal root ganglia of neonatal mice with cutaneous inflammation initiated at postnatal day 7 (P7) was responsible for the specific alteration in heat sensitivity found in faster conducting (“A”-fiber) nociceptors, we assessed the response properties of cutaneous afferents using an ex vivo hairy hindpaw skin-saphenous nerve-dorsal root ganglion-spinal cord preparation in conjunction with nerve-targeted knockdown of P2Y1. We found that P2Y1 knockdown during neonatal cutaneous inflammation was sufficient to reduce the sensitization of “A”-fiber nociceptors to heat stimuli. Surprisingly, we also found that nerve-specific downregulation of P2Y1 could reduce the observed sensitization of these afferent subtypes to mechanical deformation of the skin. Immunocytochemical analysis of dorsal root ganglia showed that P2Y1 may mediate its effects through modulation of the injury-induced increase of transient receptor potential vanilloid type 1 receptor. This suggests that the upregulation of P2Y1 in cutaneous nociceptors during early life peripheral inflammation can regulate the sensitization of myelinated nociceptors to both mechanical and heat stimuli possibly through modulation of transient receptor potential vanilloid type 1 expression.

An improved method for in vitro morphofunctional analysis of dorsal root ganglia in the normal and diabetic mouse

An improved method for in vitro morphofunctional analysis of dorsal root ganglia in the normal and diabetic mouse

Antineuropathic profile of N-palmitoylethanolamine in a rat model of oxaliplatin-induced neurotoxicity.

Neurotoxicity is a main side effect of the anticancer drug oxaliplatin. The development of a neuropathic syndrome impairs quality of life and potentially results in chemotherapy dose reductions and/or early discontinuation. In the complex pattern of molecular and morphological alterations induced by oxaliplatin in the nervous system, an important activation of glia has been preclinically evidenced. N-Palmitoylethanolamine (PEA) modulates glial cells and exerts antinociceptive effects in several animal models. In order to improve the therapeutic chances for chemotherapy-dependent neuropathy management, the role of PEA was investigated in a rat model of oxaliplatin-induced neuropathy (2.4 mg kg-1 daily, intraperitoneally). On day 21, a single administration of PEA (30 mg kg-1 i.p.) was able to reduce oxaliplatin-dependent pain induced by mechanical and thermal stimuli. The repeated treatment with PEA (30 mg kg-1 daily i.p. for 21 days, from the first oxaliplatin injection) prevented lowering of pain threshold as well as increased pain on suprathreshold stimulation. Ex vivo histological and molecular analysis of dorsal root ganglia, peripheral nerves and spinal cord highlighted neuroprotective effects and glia-activation prevention induced by PEA repeated administration. The protective effect of PEA resulted in the normalization of the electrophysiological activity of the spinal nociceptive neurons. Finally, PEA did not alter the oxaliplatin-induced mortality of the human colon cancer cell line HT-29. The efficacy of PEA in neuropathic pain control and in preventing nervous tissue alteration candidates this endogenous compound as disease modifying agent. These characteristics, joined to the safety profile, suggest the usefulness of PEA in chemotherapy-induced neuropathy.

Promotion of periostin expression contributes to the migration of Schwann cells.

Neuregulin ligands and their ErbB receptors are important for the development of Schwann cells, the glial cells of the peripheral nervous system (PNS). ErbB3 deficiency is characterized by a complete loss of Schwann cells along axons of the peripheral nerves, impaired fasciculation and neuronal cell death. We performed comparative gene expression analysis of dorsal root ganglia (DRG) explant cultures from ErbB3-deficient and wild-type mice in order to identify genes that are involved in Schwann cell development and migration. The extracellular matrix (ECM) gene periostin was found to exhibit the most prominent down regulation in ErbB3-deficient DRG. Expression analysis revealed that the periostin-expressing cell population in the PNS corresponds to Schwann cell precursors and Schwann cells, and is particularly high in migratory Schwann cells. Furthermore, stimulation of Schwann cells with neuregulin-1 (NRG1) or transforming growth factor β (TGFβ-1) resulted in an upregulation of periostin expression. Interestingly, DRG explant cultures of periostin-deficient mice revealed a significant reduction of the number of migrating Schwann cells. These data demonstrate that the expression of periostin is stimulated by ErbB ligand NRG1 and influences the migration of Schwann cell precursors.

Bone marrow-derived TNF-α causes diabetic neuropathy in mice.

Dysregulation of biochemical pathways in response to hyperglycaemia in cells intrinsic to the nervous system (Schwann cells, neurons, vasa nervorum) are thought to underlie diabetic peripheral neuropathy (DPN). TNF-α is a known aetiological factor; Tnf-knockout mice are protected against DPN. We hypothesised that TNF-α produced by a small but specific bone marrow (BM) subpopulation marked by proinsulin production (proinsulin-producing BM-derived cells, PI-BMDCs) is essential for DPN development. We produced mice deficient in TNF-α, globally in BM and selectively in PI-BMDCs only, by gene targeting and BM transplantation, and induced diabetes by streptozotocin. Motor and sensory nerve conduction velocities were used to gauge nerve dysfunction. Immunocytochemistry, fluorescence in situ hybridisation (FISH) and PCR analysis of dorsal root ganglia (DRG) were employed to monitor outcome. We found that loss of TNF-α in BM only protected mice from DPN. We developed a strategy to delete TNF-α specifically in PI-BMDCs, and found that PI-BMDC-specific loss of TNF-α protected against DPN as robustly as loss of total BM TNF-α. Selective loss of PI-BMDC-derived TNF-α downregulated TUNEL-positive DRG neurons. FISH revealed PI-BMDC-neuron fusion cells in the DRG in mice with DPN; fusion cells were undetectable in non-diabetic mice or diabetic mice that had lost TNF-α expression selectively in the PI-BMDC subpopulation. BMDC-specific TNF-α is essential for DPN development; its selective removal from a small PI-BMDC subpopulation protects against DPN. The pathogenicity of PI-BMDC-derived TNF-α may have important therapeutic implications.

Abstract 4388: LipoplatinTM: A less neurotoxic formulation of Cisplatin

Abstract Purpose: Cisplatin is one of the most effective cytotoxic agent in the treatment of solid malignancies, but its use is limited by several side effects. Among them, peripheral neurotoxicity can be dose-limiting. A liposomal formulation of cisplatin, LipoplatinTM, was developed to reduce the systemic toxicity of cisplatin but preventing its efficacy. Aim of this study was to test in an animal model through a multimodal approach if chronic treatment with two different schedules of LipoplatinTM selected in the range of its anticancer effective dose is less neurotoxic than cisplatin administrations. Methods: Female Wistar rats were treated intraperitoneally with cisplatin at the dose of 4mg/kg or with LipoplatinTM 12 and 24mg/kg once weekly for 4 times. General toxicity was assessed by daily observation, body weight change, hematological and blood chemistry analysis and histopathology of liver and kidney. The onset of the peripheral neurotoxicity was assessed using tail nerve conduction velocity (NCV), morphological and morphometrical analysis of dorsal root ganglia (DRG) and by morphological analysis of sciatic nerve. Results: Cisplatin induced a statistically significant reduction in body weight, the development of renal failure and the impairment in NCV with pathological alterations in the DRG and sciatic nerve. By contrast no significant weight gain reduction was observed in animals treated with both doses of LipoplatinTM. Moreover the lowest dose induced a less severe damage to the peripheral nervous system with a moderate decrease of NCV and mild pathological alterations of DRG and sciatic nerve. Conclusions: The results suggest that LipoplatinTM 12mg/kg is less neurotoxic than cisplatin 4mg/kg, thus opening the possibility to use this new formulation in future studies where its anticancer activity and the peripheral neurotoxicity will be assessed in parallel. This study was supported by “Fondazione Banca del Monte di Lombardia” Regulon supported this study exclusively by providing LipoplatinTM Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4388. doi:10.1158/1538-7445.AM2011-4388

Abstract 4384: Characterization of the painful peripheral neuropathy induced by oxaliplatin-based chemotherapy in mice

Abstract Oxaliplatin (OHP) is a platinum-based drug used as first-line chemotherapy for the treatment of metastatic colorectal cancer. It acts by inducing DNA crosslinks that result in apoptotic cell death of dividing cells. A major clinical issue in the use of this drug is severe painful peripheral neuropathy (PN) that affects 10-40% of cancer patients treated with a regimen that includes OHP. Acute OHP-induced PN is characterized by transient paresthesias and dysesthesias enhanced by exposure to cold, while persistent sensory dysfunction is the hallmark of chronic PN. Rat models of OHP-induced PN have been used to describe pathophysiological features, but these models are not sufficient to examine the contribution of drug neurotoxicity and the neuropathic pain of OHP with the effects of antineoplastic activity since most cancer models are developed in mice. We have characterized the effects induced by chronic, bi-weekly intravenous administration of OHP at the four-week timepoint in balb-c mice. We examined sciatic and digital nerve conduction velocities (NCV), the pathological/morphometrical analysis of dorsal root ganglia (DRG) and assessed changes in mechanical/thermal thresholds. Moreover, in order to investigate relevant spinal cord structures involved in neuropathic pain, we conducted electrophysiological recordings of wide dynamic range neurons in the spinal dorsal horn to examine electrical activity. OHP treatment induced a significant impairment of the NCV and of nerve action potential amplitude. At the light and electron microscope analysis, the DRG of OHP-treated mice showed frequent multinucleolated neurons with eccentric nucleoli. Moreover, the morphometrical analysis of DRG demonstrated neuronal atrophy. In addition, OHP induced the development of significant mechanical allodynia and cold hyperalgesia, starting from the first week of treatment. Finally, the electrophysiological assessments performed in the spinal cord revealed that, despite the incapacity of the drug to cross the blood-brain barrier, OHP treatment induced a remarkable increase in the activity of the wide dynamic range neurons in the spinal dorsal horn. Our results demonstrate that the chronic treatment with OHP is able to induce a painful neuropathy in a balb-c mice model. Therefore, this model will enable us to conduct further mechanistic studies of OHP-related antineoplastic activity, peripheral neurotoxicity and pain and can be used as a reference in the preclinical discovery of new neuroprotective as well as of analgesic compounds. Supported by a grant from the AISAL, Associazione Italiana per le Scienze degli Animali da Laboratorio". Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4384. doi:10.1158/1538-7445.AM2011-4384

In vivo comparative study of the cytotoxicity of a liposomal formulation of cisplatin (lipoplatin™)

Cisplatin is one of the most effective cytotoxic agents in the treatment of solid malignancies, but its use is limited by several side effects. Among them, peripheral neurotoxicity can be dose limiting. A liposomal formulation of cisplatin, Lipoplatin™, was developed to reduce the systemic toxicity of cisplatin but without preventing its efficacy. The aim of this study was to use an animal model to establish, through a multimodal approach, whether chronic treatment with two different schedules of Lipoplatin™, selected within the range of its anticancer effective dose, is less neurotoxic than cisplatin administration. Female Wistar rats were treated intraperitoneally with cisplatin at a dose of 4mg/kg or with Lipoplatin™ at doses delivering 12 or 24mg/kg of cisplatin once weekly for 4weeks. General toxicity was assessed by daily observation, body weight change, hematological and blood chemistry analysis, and histopathology of liver and kidney. The onset of peripheral neurotoxicity was assessed by measuring tail nerve conduction velocity (NCV), morphological and morphometric analysis of dorsal root ganglia (DRG), and morphological analysis of the sciatic nerve. Cisplatin induced a statistically significant reduction in body weight, the development of renal failure, and impairment in NCV with pathological alterations in the DRG and sciatic nerve. By contrast, Lipoplatin™ was markedly less nephrotoxic, and no significant weight gain reduction was observed in animals treated with both doses of the drug. Moreover, the lowest dose induced less severe damage to the peripheral nervous system with a moderate decrease in NCV and mild pathological alterations in DRG and the sciatic nerve. The results suggest that Lipoplatin™ 12mg/kg is less neurotoxic than cisplatin 4mg/kg, thus opening up the possibility of using this new formulation in future studies where its anticancer activity and the peripheral neurotoxicity will be assessed in parallel.

Glutamate carboxypeptidase II inhibition IN rat models of chemotherapy-induced peripheral neurotoxicity (CIPN)

9558 Background: Excessive glutamate release is associated with neuronal damage. Inhibition of Glutamate Carboxypeptidase II (GCPII) decreases excitatory glutamate levels and it is neuroprotective in several disorders of the central and peripheral nervous system. Methods: This study had the following aims: to investigate the neuroprotective effect of GCPII inhibitor GPI 16072 at doses ranging from 0.1 to 10 mg/kg/day in cisplatin, oxaliplatin, docetaxel, paclitaxel+cisplatin and bortezomib-induced peripheral neuropathies in rodents through electrophysiological evaluations (NCV), morphologic and morphometric analysis of Dorsal Root Ganglia (DRG) and sciatic nerve; to determine the expression and the distribution of GCPII in DRG and sciatic nerve in order to identify molecular mechanisms of neuroprotection. Results: Electrophysiological analysis demonstrated that drug-induced NCV reduction is significantly counteracted by the co- administration of GPI 16072 in all the animal models. DRG morphometric analysis showed that GPI 16072 10 mg/Kg induced a significant protection against Cisplatin and Paclitaxel+Cisplatin-induced neuronal atrophy. In addition, GPI 16072 did not interfere with the antineoplastic efficacy of oxaliplatin at doses which were neuroprotective. To interpret these results, molecular studies showed that GCPII is expressed both in DRG and in sciatic nerve and it is localized in the cytoplasm of satellite cells in the DRG and in the outer cytoplasm of Schwann cells in sciatic nerve. Conclusions: This study provides evidence for a neuroprotective role of GCPII inhibition in several chronic chemotherapy- induced periheral neuropathies models and provides support for GPI 16072 being an attractive candidate for clinical treatment of these pathologies. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration MGI Pharma, Baltimore MGI Pharma, Baltimore

Receptor for Advanced Glycation End Products (RAGEs) and Experimental Diabetic Neuropathy

Heightened expression of the receptor for advanced glycation end products (RAGE) contributes to development of systemic diabetic complications, but its contribution to diabetic neuropathy is uncertain. We studied experimental diabetic neuropathy and its relationship with RAGE expression using streptozotocin-induced diabetic mice including a RAGE(-/-) cohort exposed to long-term diabetes compared with littermates without diabetes. Structural indexes of neuropathy were addressed with serial (1, 3, 5, and 9 months of experimental diabetes) electrophysiological and quantitative morphometric analysis of dorsal root ganglia (DRG), peripheral nerve, and epidermal innervation. RAGE protein and mRNA levels in DRG, peripheral nerve, and epidermal terminals were assessed in WT and RAGE(-/-) mice, with and without diabetes. The correlation of RAGE activation with nuclear factor (NF)-kappaB and protein kinase C beta II (PKC beta II) protein and mRNA expression was also determined. Diabetic peripheral epidermal axons, sural axons, Schwann cells, and sensory neurons within ganglia developed dramatic and cumulative rises in RAGE mRNA and protein along with progressive electrophysiological and structural abnormalities. RAGE(-/-) mice had attenuated structural features of neuropathy after 5 months of diabetes. RAGE-mediated signaling pathway activation for NF-kappaB and PKC beta II pathways was most evident among Schwann cells in the DRG and peripheral nerve. In a long-term model of experimental diabetes resembling human diabetic peripheral neuropathy, RAGE expression in the peripheral nervous system rises cumulatively and relates to progressive pathological changes. Mice lacking RAGE have attenuated features of neuropathy and limited activation of potentially detrimental signaling pathways.