Operational Impact of Neurology Rural Access Model: Reflections on the Importance of Demand-Shaping.

Background and Objectives: Demand for specialty neurologic care has been steadily increasing over the past several decades, and health systems are needing to meet the demands of their patients while managing a dwindling workforce. This retrospective study investigates the operational impact of a regional neurology clinic staffed by advanced practice providers with remote physician oversight in a "hub and spoke" delivery model to serve lower complexity patients. Methods: A retrospective, cross-sectional study was conducted to evaluate outcomes. Descriptive analysis of referral volumes, cancellation/no-show rates, and patient complexity as determined by the reason for referral were used to evaluate patients who received referrals from rural counties north of the primary neurology practice before and after the opening of the regional clinic. These metrics were evaluated longitudinally from counties of interest and for differences in patients seen at the regional clinic vs primary neurology practice. Results: Referral volumes from the northern counties increased at significantly higher rates after the opening of the regional clinic than other counties in the serviced area. This resulted in an increase in patients seen in the hub clinics and spoke clinic. The regional clinic did see patients who were less complex than the primary practice; however, the total volume of low-complexity patients scheduled at the primary practice did not decrease. Cancellation and no-show rates did not seem to be affected in either clinic. Discussion: The opening of a regional "spoke" clinic resulted in the generation of greater referral volumes that exceeded the capacity created by the clinic. Owing to this, there was an increase in the number of patients seen from the regional counties in the hub clinics, negating the potential benefit of improving access for high-complexity patients. Importance of demand-shaping and appropriate utilization as part of the value equation are discussed, followed by discussion of mitigation strategies.

Recommendations for assessing appearance concerns related to plexiform and cutaneous neurofibromas in neurofibromatosis 1 clinical trials.

BACKGROUND/AIMS: Individuals with neurofibromatosis 1 may experience changes in their appearance due to physical manifestations of the disorders and/or treatment sequelae. Appearance concerns related to these physical changes can lead to psychological distress and poorer quality of life. While many neurofibromatosis 1 clinical trials focus on assessing changes in tumor volume, evaluating patients' perspectives on corresponding changes in symptoms such as physical appearance can be key secondary outcomes. We aimed to determine whether any existing patient-reported outcome measures are appropriate for evaluating changes in appearance concerns within neurofibromatosis 1 clinical trials. METHODS: After updating our previously published systematic review process, we used it to identify and rate existing patient-reported outcome measures related to disfigurement and appearance. Using a systematic literature search and initial triage process, we focused on identifying patient-reported outcome measures that could be used to evaluate changes in appearance concerns in plexiform or cutaneous neurofibroma clinical trials in neurofibromatosis 1. Our revised Patient-Reported Outcome Rating and Acceptance Tool for Endpoints then was used to evaluate each published patient-reported outcome measures in five domains, including (1) respondent characteristics, (2) content validity, (3) scoring format and interpretability, (4) psychometric data, and (5) feasibility. The highest-rated patient-reported outcome measures were then re-reviewed in a side-by-side comparison to generate a final consensus recommendation. RESULTS: Eleven measures assessing appearance concerns were reviewed and rated; no measures were explicitly designed to assess appearance concerns related to neurofibromatosis 1. The FACE-Q Craniofacial Module-Appearance Distress scale was the top-rated measure for potential use in neurofibromatosis 1 clinical trials. Strengths of the measure included that it was rigorously developed, included individuals with neurofibromatosis 1 in the validation sample, was applicable to children and adults, covered item topics deemed important by neurofibromatosis 1 patient representatives, exhibited good psychometric properties, and was feasible for use in neurofibromatosis 1 trials. Limitations included a lack of validation in older adults, no published information regarding sensitivity to change in clinical trials, and limited availability in languages other than English. CONCLUSION: The Response Evaluation in Neurofibromatosis and Schwannomatosis patient-reported outcome working group currently recommends the FACE-Q Craniofacial Module Appearance Distress scale to evaluate patient-reported changes in appearance concerns in clinical trials for neurofibromatosis 1-related plexiform or cutaneous neurofibromas. Additional research is needed to validate this measure in people with neurofibromatosis 1, including older adults and those with tumors in various body locations, and explore the effects of nontumor manifestations on appearance concerns in people with neurofibromatosis 1 and schwannomatosis.

Current Recommendations for Patient-Reported Outcome Measures Assessing Domains of Quality of Life in Neurofibromatosis Clinical Trials.

OBJECTIVE: To review and recommend patient-reported outcome (PRO) measures assessing multidimensional domains of quality of life (QoL) to use as clinical endpoints in medical and psychosocial trials for children and adults with neurofibromatosis (NF) type 1, NF2, and schwannomatosis. METHODS: The PRO working group of the Response Evaluation in Neurofibromatosis and Schwannomatosis (REiNS) International Collaboration used systematic methods to review, rate, and recommend existing self-report and parent-report PRO measures of generic and disease-specific QoL for NF clinical trials. Recommendations were based on 4 main criteria: patient characteristics, item content, psychometric properties, and feasibility. RESULTS: The highest-rated generic measures were (1) the Pediatric Quality of Life Inventory (PedsQL) Generic Core Scales for NF clinical trials for children or for children through adults, (2) the Functional Assessment of Cancer Therapy-General for adult medical trials, and (3) the World Health Organization Quality of Life-BREF for adult psychosocial trials. The highest-rated disease-specific measures were (1) the PedsQL NF1 Module for NF1 trials, (2) the NF2 Impact on Quality of Life Scale for NF2 trials, and (3) the Penn Acoustic Neuroma Quality of Life Scale for NF2 trials targeting vestibular schwannomas. To date, there are no disease-specific tools assessing multidimensional domains of QoL for schwannomatosis. CONCLUSIONS: The REiNS Collaboration currently recommends these generic and disease-specific PRO measures to assess multidimensional domains of QoL for NF clinical trials. Additional research is needed to further evaluate the use of these measures in both medical and psychosocial trials.

Patient-reported outcomes of pain and physical functioning in neurofibromatosis clinical trials.

OBJECTIVE: Tumors and other disease complications of neurofibromatosis (NF) can cause pain and negatively affect physical functioning. To document the clinical benefit of treatment in NF trials targeting these manifestations, patient-reported outcomes (PROs) assessing pain and physical functioning should be included as study endpoints. Currently, there is no consensus on the selection and use of such measures in the NF population. This article presents the recommendations of the PRO group of the Response Evaluation in Neurofibromatosis and Schwannomatosis (REiNS) International Collaboration for assessing the domains of pain and physical functioning for NF clinical trials. METHODS: The REiNS PRO group reviewed and rated existing PRO measures assessing pain intensity, pain interference, and physical functioning using their systematic method. Final recommendations are based primarily on 4 main criteria: patient characteristics, item content, psychometric properties, and feasibility for clinical trials. RESULTS: The REiNS PRO group chose the Numeric Rating Scale-11 (≥8 years) to assess pain intensity, the Pain Interference Index (6-24 years) and the Patient-Reported Outcome Measurement Information System (PROMIS) Pain Interference Scale (≥18 years) to evaluate pain interference, and the PROMIS Physical Functioning Scale to measure upper extremity function and mobility (≥5 years) for NF clinical trials. CONCLUSIONS: The REiNS Collaboration currently recommends these PRO measures to assess the domains of pain and physical functioning for NF clinical trials; however, further research is needed to evaluate their use in individuals with NF. A final consensus recommendation for the pain interference measure will be disseminated in a future publication based on findings from additional published research.

Neurofibromin-deficient myeloid cells are critical mediators of aneurysm formation in vivo.

BACKGROUND: Neurofibromatosis type 1 (NF1) is a genetic disorder resulting from mutations in the NF1 tumor suppressor gene. Neurofibromin, the protein product of NF1, functions as a negative regulator of Ras activity in circulating hematopoietic and vascular wall cells, which are critical for maintaining vessel wall homeostasis. NF1 patients have evidence of chronic inflammation resulting in the development of premature cardiovascular disease, including arterial aneurysms, which may manifest as sudden death. However, the molecular pathogenesis of NF1 aneurysm formation is unknown. METHOD AND RESULTS: With the use of an angiotensin II-induced aneurysm model, we demonstrate that heterozygous inactivation of Nf1 (Nf1(+/-)) enhanced aneurysm formation with myeloid cell infiltration and increased oxidative stress in the vessel wall. Using lineage-restricted transgenic mice, we show that loss of a single Nf1 allele in myeloid cells is sufficient to recapitulate the Nf1(+/-) aneurysm phenotype in vivo. Finally, oral administration of simvastatin or the antioxidant apocynin reduced aneurysm formation in Nf1(+/-) mice. CONCLUSION: These data provide genetic and pharmacological evidence that Nf1(+/-) myeloid cells are the cellular triggers for aneurysm formation in a novel model of NF1 vasculopathy and provide a potential therapeutic target.

Patient-reported outcomes in neurofibromatosis and schwannomatosis clinical trials.

OBJECTIVES: Neurofibromatosis (NF) is a genetic disease with multiple clinical manifestations that can significantly impact quality of life (QOL). Clinical trials should include patient-reported outcomes (PROs) as endpoints to assess treatment effects on various aspects of QOL, but there is no consensus on the selection and use of such measures in NF. This article describes the PRO Working Group of the Response Evaluation in Neurofibromatosis and Schwannomatosis (REiNS) Collaboration, its main goals, methods for identifying appropriate PRO measures for NF clinical trials, and recommendations for assessing pain intensity. METHODS: The REiNS PRO group selected core endpoint domains important to assess in NF. The members developed criteria to rate PRO measures, including patient characteristics, psychometric properties, and feasibility, and utilized a systematic process to evaluate PROs for NF clinical trials. Within the subdomain of pain intensity, the group reviewed the Numerical Rating Scale-11 (NRS-11), the Visual Analogue Scale, and the Faces Pain Scale-Revised using this process. RESULTS: Based on the review criteria, each of these pain intensity scales is brief, reliable, valid, and widely used. However, the NRS-11 was given the highest rating for use in NF clinical trials due to recommendations from pain experts and other consensus groups, its extensive use in research, strong psychometric data including sensitivity to change, and excellent feasibility in ages ≥ 8 years. CONCLUSIONS: The systematic review criteria and process are effective for identifying appropriate PRO measures and provide information utilized by the REiNS Collaboration to achieve consensus regarding PROs in NF clinical trials.

Schwannomatosis: the overlooked neurofibromatosis?

OBJECTIVE: Schwannomas are typically benign tumors that occur sporadically, in neurofibromatosis type 2 (NF2), or in an entity called "schwannomatosis." Schwannomatosis patients develop multiple schwannomas without involvement of the vestibular apparatus. Geneticists, neurologists, and pathologists have recognized that schwannomatosis is distinct from NF2, but schwannomatosis remains unfamiliar to many radiologists. This article reviews the current medical literature, highlighting the similarities and differences between the schwannomatosis and NF2 phenotypes, genotypes, clinical manifestations, management considerations, and imaging findings. CONCLUSION: Imaging plays a critical role in diagnosing schwannomatosis, and a basic understanding of this syndrome is of interest to diagnostic radiologists. Moreover, it is imperative that radiologists be able to differentiate schwannomatosis from NF2 on imaging because there are significant differences in the management of these two diseases and clinical outcomes for affected patients.

Development of the adult PedsQL™ neurofibromatosis type 1 module: initial feasibility, reliability and validity.

BACKGROUND: Neurofibromatosis type 1 (NF1) is a common autosomal dominant genetic disorder with significant impact on health-related quality of life (HRQOL). Research in understanding the pathogenetic mechanisms of neurofibroma development has led to the use of new clinical trials for the treatment of NF1. One of the most important outcomes of a trial is improvement in quality of life, however, no condition specific HRQOL instrument for NF1 exists. The objective of this study was to develop an NF1 HRQOL instrument as a module of PedsQL™ and to test for its initial feasibility, internal consistency reliability and validity in adults with NF1. METHODS: The NF1 specific HRQOL instrument was developed using a standard method of PedsQL™ module development - literature review, focus group/semi-structured interviews, cognitive interviews and experts' review of initial draft, pilot testing and field testing. Field testing involved 134 adults with NF1. Feasibility was measured by the percentage of missing responses, internal consistency reliability was measured with Cronbach's alpha and validity was measured by the known-groups method. RESULTS: Feasibility, measured by the percentage of missing responses was 4.8% for all subscales on the adult version of the NF1-specific instrument. Internal consistency reliability for the Total Score (alpha =0.97) and subscale reliabilities ranging from 0.72 to 0.96 were acceptable for group comparisons. The PedsQL™ NF1 module distinguished between NF1 adults with excellent to very good, good, and fair to poor health status. CONCLUSIONS: The results demonstrate the initial feasibility, reliability and validity of the PedsQL™ NF1 module in adult patients. The PedsQL™ NF1 Module can be used to understand the multidimensional nature of NF1 on the HRQOL patients with this disorder.

Imatinib mesylate for plexiform neurofibromas in patients with neurofibromatosis type 1: a phase 2 trial.

BACKGROUND: Plexiform neurofibromas are slow-growing chemoradiotherapy-resistant tumours arising in patients with neurofibromatosis type 1 (NF1). Currently, there are no viable therapeutic options for patients with plexiform neurofibromas that cannot be surgically removed because of their proximity to vital body structures. We undertook an open-label phase 2 trial to test whether treatment with imatinib mesylate can decrease the volume burden of clinically significant plexiform neurofibromas in patients with NF1. METHODS: Eligible patients had to be aged 3-65 years, and to have NF1 and a clinically significant plexiform neurofibroma. Patients were treated with daily oral imatinib mesylate at 220 mg/m(2) twice a day for children and 400 mg twice a day for adults for 6 months. The primary endpoint was a 20% or more reduction in plexiform size by sequential volumetric MRI imaging. Clinical data were analysed on an intention-to-treat basis; a secondary analysis was also done for those patients able to take imatinib mesylate for 6 months. This trial is registered with ClinicalTrials.gov, number NCT01673009. FINDINGS: Six of 36 patients (17%, 95% CI 6-33), enrolled on an intention-to-treat basis, had an objective response to imatinib mesylate, with a 20% or more decrease in tumour volume. Of the 23 patients who received imatinib mesylate for at least 6 months, six (26%, 95% CI 10-48) had a 20% or more decrease in volume of one or more plexiform tumours. The most common adverse events were skin rash (five patients) and oedema with weight gain (six). More serious adverse events included reversible grade 3 neutropenia (two), grade 4 hyperglycaemia (one), and grade 4 increases in aminotransferase concentrations (one). INTERPRETATION: Imatinib mesylate could be used to treat plexiform neurofibromas in patients with NF1. A multi-institutional clinical trial is warranted to confirm these results. FUNDING: Novartis Pharmaceuticals, the Indiana University Simon Cancer Centre, and the Indiana University Herman B Wells Center for Pediatric Research.

Inhibition of transmitter release and attenuation of anti-retroviral-associated and tibial nerve injury-related painful peripheral neuropathy by novel synthetic Ca2+ channel peptides.

N-type Ca(2+) channels (CaV2.2) are a nidus for neurotransmitter release and nociceptive transmission. However, the use of CaV2.2 blockers in pain therapeutics is limited by side effects resulting from inhibition of the physiological functions of CaV2.2 within the CNS. We identified an anti-nociceptive peptide (Brittain, J. M., Duarte, D. B., Wilson, S. M., Zhu, W., Ballard, C., Johnson, P. L., Liu, N., Xiong, W., Ripsch, M. S., Wang, Y., Fehrenbacher, J. C., Fitz, S. D., Khanna, M., Park, C. K., Schmutzler, B. S., Cheon, B. M., Due, M. R., Brustovetsky, T., Ashpole, N. M., Hudmon, A., Meroueh, S. O., Hingtgen, C. M., Brustovetsky, N., Ji, R. R., Hurley, J. H., Jin, X., Shekhar, A., Xu, X. M., Oxford, G. S., Vasko, M. R., White, F. A., and Khanna, R. (2011) Suppression of inflammatory and neuropathic pain by uncoupling CRMP2 from the presynaptic Ca(2+) channel complex. Nat. Med. 17, 822-829) derived from the axonal collapsin response mediator protein 2 (CRMP2), a protein known to bind and enhance CaV2.2 activity. Using a peptide tiling array, we identified novel peptides within the first intracellular loop (CaV2.2(388-402), "L1") and the distal C terminus (CaV1.2(2014-2028) "Ct-dis") that bound CRMP2. Microscale thermophoresis demonstrated micromolar and nanomolar binding affinities between recombinant CRMP2 and synthetic L1 and Ct-dis peptides, respectively. Co-immunoprecipitation experiments showed that CRMP2 association with CaV2.2 was inhibited by L1 and Ct-dis peptides. L1 and Ct-dis, rendered cell-penetrant by fusion with the protein transduction domain of the human immunodeficiency virus TAT protein, were tested in in vitro and in vivo experiments. Depolarization-induced calcium influx in dorsal root ganglion (DRG) neurons was inhibited by both peptides. Ct-dis, but not L1, peptide inhibited depolarization-stimulated release of the neuropeptide transmitter calcitonin gene-related peptide in mouse DRG neurons. Similar results were obtained in DRGs from mice with a heterozygous mutation of Nf1 linked to neurofibromatosis type 1. Ct-dis peptide, administered intraperitoneally, exhibited antinociception in a zalcitabine (2'-3'-dideoxycytidine) model of AIDS therapy-induced and tibial nerve injury-related peripheral neuropathy. This study suggests that CaV peptides, by perturbing interactions with the neuromodulator CRMP2, contribute to suppression of neuronal hypersensitivity and nociception.

Suppression of inflammatory and neuropathic pain by uncoupling CRMP-2 from the presynaptic Ca²âº channel complex.

The use of N-type voltage-gated calcium channel (CaV2.2) blockers to treat pain is limited by many physiological side effects. Here we report that inflammatory and neuropathic hypersensitivity can be suppressed by inhibiting the binding of collapsin response mediator protein 2 (CRMP-2) to CaV2.2 and thereby reducing channel function. A peptide of CRMP-2 fused to the HIV transactivator of transcription (TAT) protein (TAT-CBD3) decreased neuropeptide release from sensory neurons and excitatory synaptic transmission in dorsal horn neurons, reduced meningeal blood flow, reduced nocifensive behavior induced by formalin injection or corneal capsaicin application and reversed neuropathic hypersensitivity produced by an antiretroviral drug. TAT-CBD3 was mildly anxiolytic without affecting memory retrieval, sensorimotor function or depression. At doses tenfold higher than that required to reduce hypersensitivity in vivo, TAT-CBD3 caused a transient episode of tail kinking and body contortion. By preventing CRMP-2-mediated enhancement of CaV2.2 function, TAT-CBD3 alleviated inflammatory and neuropathic hypersensitivity, an approach that may prove useful in managing chronic pain.

Reduced expression of SynGAP, a neuronal GTPase-activating protein, enhances capsaicin-induced peripheral sensitization.

Synaptic GTPase-activating protein (SynGAP) is a neuronal-specific Ras/Rap-GAP that increases the hydrolysis rate of GTP to GDP, converting Ras/Rap from the active into the inactive form. The Ras protein family modulates a wide range of cellular pathways including those involved in sensitization of sensory neurons. Since GAPs regulate Ras activity, SynGAP might be an important regulator of peripheral sensitization and pain. Therefore, we evaluated excitability, stimulus-evoked release of the neuropeptide calcitonin gene-related peptide (CGRP), and nociception from wild-type (WT) mice and those with a heterozygous mutation of the SynGAP gene (SynGAP(+/-)). Our results demonstrate that SynGAP is expressed in primary afferent sensory neurons and that the capsaicin-stimulated CGRP release from spinal cord slices was two-fold higher from SynGAP(+/-) mice than that observed from WT mouse tissue, consistent with an increase in expression of the capsaicin receptor, transient receptor potential cation channel subfamily V member 1 (TRPV1), in SynGAP(+/-) dorsal root ganglia. However, there was no difference between the two genotypes in potassium-stimulated release of CGRP, the number of action potentials generated by a ramp of depolarizing current, or mechanical hypernociception elicited by intraplantar injection of capsaicin. In contrast, capsaicin-induced thermal hypernociception occurred at lower doses of capsaicin and had a longer duration in SynGAP(+/-) mice than WT mice. These results provide the first evidence that SynGAP is an important regulator of neuropeptide release from primary sensory neurons and can modulate capsaicin-induced hypernociception, demonstrating the importance of GAP regulation in signaling pathways that play a role in peripheral sensitization.

Ret-dependent and Ret-independent mechanisms of Gfl-induced sensitization.

BACKGROUND: The GDNF family ligands (GFLs) are regulators of neurogenic inflammation and pain. We have previously shown that GFLs increase the release of the sensory neuron neuropeptide, calcitonin gene-related peptide (CGRP) from isolated mouse DRG. RESULTS: Inhibitors of the mitogen-activated protein kinase (MAPK) pathway abolished the enhancement of CGRP release by GDNF. Neurturin-induced enhancement in the stimulated release of CGRP, used as an indication of sensory neuronal sensitization, was abolished by inhibition of the phosphatidylinositol-3 kinase (PI-3K) pathway. Reduction in Ret expression abolished the GDNF-induced sensitization, but did not fully inhibit the increase in stimulus-evoked release of CGRP caused by neurturin or artemin, indicating the presence of Ret-independent GFL-induced signaling in sensory neurons. Integrin ß-1 and NCAM are involved in a component of Ret-independent GFL signaling in sensory neurons. CONCLUSIONS: These data demonstrate the distinct and variable Ret-dependent and Ret-independent signaling mechanisms by which GFLs induce sensitization of sensory neurons. Additionally, there is a clear disconnect between intracellular signaling pathway activation and changes in sensory neuronal function.

Genetic and cellular evidence of vascular inflammation in neurofibromin-deficient mice and humans.

Neurofibromatosis type 1 (NF1) results from mutations in the NF1 tumor suppressor gene, which encodes the protein neurofibromin. NF1 patients display diverse clinical manifestations, including vascular disease, which results from neointima formation and vessel occlusion. However, the pathogenesis of NF1 vascular disease remains unclear. Vessel wall homeostasis is maintained by complex interactions between vascular and bone marrow-derived cells (BMDCs), and neurofibromin regulates the function of each cell type. Therefore, utilizing cre/lox techniques and hematopoietic stem cell transplantation to delete 1 allele of Nf1 in endothelial cells, vascular smooth muscle cells, and BMDCs alone, we determined which cell lineage is critical for neointima formation in vivo in mice. Here we demonstrate that heterozygous inactivation of Nf1 in BMDCs alone was necessary and sufficient for neointima formation after vascular injury and provide evidence of vascular inflammation in Nf1+/- mice. Further, analysis of peripheral blood from NF1 patients without overt vascular disease revealed increased concentrations of inflammatory cells and cytokines previously linked to vascular inflammation and vasoocclusive disease. These data provide genetic and cellular evidence of vascular inflammation in NF1 patients and Nf1+/- mice and provide a framework for understanding the pathogenesis of NF1 vasculopathy and potential therapeutic and diagnostic interventions.

ALTERED CALCIUM CURRENTS AND AXONAL GROWTH IN Nf1 HAPLOINSUFFICIENT MICE.

Mutations of the neurofibromin gene (NF1) cause neurofibromatosis type 1 (NF1), a disease in which learning disabilities are common. Learning deficits also are observed in mice with a heterozygous mutation of Nf1 (Nf1(+/-)). Dysregulation of regulated neurotransmitter release has been observed in Nf1(+/-) mice. However, the role of presynaptic voltage-gated Ca(2+) channels mediating this release has not been investigated. We investigated whether Ca(2+) currents and transmitter release were affected by reduced neurofibromin in Nf1(+/-) mice. Hippocampal Ca(2+) current density was greater in neurons from Nf1(+/-) mice and a greater fraction of Ca(2+) currents was activated at less depolarized potentials. In addition, release of the excitatory neurotransmitter, glutamate, was increased in neuronal cortical cultures from Nf1(+/-) mice. Dendritic complexity and axonal length were also increased in neurons Nf1(+/-) mice compared to wild-type neurons, linking loss of neurofibromin to developmental changes in hippocampal axonal/cytoskeletal dynamics. Collectively, these results show that altered Ca(2+) channel density and transmitter release, along with increased axonal growth may account for the abnormal nervous system functioning in NF1.

Regulation of N-type voltage-gated calcium channels (Cav2.2) and transmitter release by collapsin response mediator protein-2 (CRMP-2) in sensory neurons.

Collapsin response mediator proteins (CRMPs) mediate signal transduction of neurite outgrowth and axonal guidance during neuronal development. Voltage-gated Ca(2+) channels and interacting proteins are essential in neuronal signaling and synaptic transmission during this period. We recently identified the presynaptic N-type voltage-gated Ca(2+) channel (Cav2.2) as a CRMP-2-interacting partner. Here, we investigated the effects of a functional association of CRMP-2 with Cav2.2 in sensory neurons. Cav2.2 colocalized with CRMP-2 at immature synapses and growth cones, in mature synapses and in cell bodies of dorsal root ganglion (DRG) neurons. Co-immunoprecipitation experiments showed that CRMP-2 associates with Cav2.2 from DRG lysates. Overexpression of CRMP-2 fused to enhanced green fluorescent protein (EGFP) in DRG neurons, via nucleofection, resulted in a significant increase in Cav2.2 current density compared with cells expressing EGFP. CRMP-2 manipulation changed the surface levels of Cav2.2. Because CRMP-2 is localized to synaptophysin-positive puncta in dense DRG cultures, we tested whether this CRMP-2-mediated alteration of Ca(2+) currents culminated in changes in synaptic transmission. Following a brief high-K(+)-induced stimulation, these puncta became loaded with FM4-64 dye. In EGFP and neurons expressing CRMP-2-EGFP, similar densities of FM-loaded puncta were observed. Finally, CRMP-2 overexpression in DRG increased release of the immunoreactive neurotransmitter calcitonin gene-related peptide (iCGRP) by approximately 70%, whereas siRNA targeting CRMP-2 significantly reduced release of iCGRP by approximately 54% compared with control cultures. These findings support a novel role for CRMP-2 in the regulation of N-type Ca(2+) channels and in transmitter release.

Involvement of platelet-activating factor in ultraviolet B-induced hyperalgesia.

Ultraviolet B (UVB) radiation causes cutaneous inflammation. One important clinical consequence of UVB-induced inflammation is increased pain or hyperalgesia, which is likely mediated by enhanced sensitivity of cutaneous sensory neurons. Previous studies have demonstrated that UVB radiation generates the lipid mediator, platelet-activating factor (PAF), as well as oxidized phospholipids that act as PAF-mimetics. These substances exert effects through the PAF receptor (PAF-R). This study was designed to assess whether PAF-R is involved in UVB-induced hyperalgesia. Intradermal injection of carbamoyl PAF (CPAF; 1-hexadecyl-2-N-methylcarbamoyl glycerophosphocholine) resulted in an enhanced response to mechanical stimuli in wild-type mice but not in PAF-R knockout (KO) mice. There was no significant change in paw withdrawal to noxious thermal stimuli in either genotype after intradermal injection of CPAF. Exposure of the hind paw to 1,500 J m(-2) UVB radiation caused an increased sensitivity to both mechanical and thermal stimulation in wild-type mice but not in PAF-R KO mice. The thermal hyperalgesia caused by UVB irradiation was inhibited in mice that lacked PAF-R in bone marrow-derived cells. These data demonstrate that the PAF-R is important for UVB-induced hyperalgesia. Further investigation of the role of PAF-R signaling in UVB-induced hyperalgesia could provide better understanding of the pathological processes initiated by UVB-induced skin damage.

Neurofibromatosis: the role of guanosine triphosphatase activating proteins in sensory neuron function.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disease characterized by formation of multiple benign and malignant tumors. People with this disorder also experience chronic pain, which can be disabling. Neurofibromin, the protein product of the Nf1 gene, is a guanosine triphosphatase activating protein (GAP) for p21Ras (Ras). Loss of Nf1 results in an increase in activity of the Ras transduction cascade. Because of the growing evidence suggesting involvement of downstream components of the Ras transduction cascade in the sensitization of nociceptive sensory neurons, we examined the stimulus-evoked release of the neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP), from primary sensory neurons of mice with a mutation of the Nf1 gene (Nf1+/-). Measuring the levels of SP and CGRP by radioimmunoassay, we demonstrated that capsaicin-stimulated release of neuropeptides is 3-5 folds higher in spinal cord slices from Nf1+/- mice than that from wildtype mouse tissue. In addition, the potassium- and capsaicin-stimulated release of CGRP from the culture of sensory neurons isolated from Nf1+/- mice was more than double that from the culture of wildtype neurons. Using patch-clamp electrophysiological techniques, we also examined the excitability of capsaicin-sensitive sensory neurons. It was found that the number of action potentials generated by the neurons from Nf1+/- mice, responding to a ramp of depolarizing current, was more than three times of that generated by wildtype neurons. Consistent with that observation, neurons from Nf1+/- mice had lower firing thresholds, lower rheobase currents and shorter firing latencies compared with wildtype neurons. These data clearly demonstrate that GAPs, such as neurofibromin, can alter the excitability of nociceptive sensory neurons. The augmented response of sensory neurons with altered Ras signaling may explain the abnormal pain sensations experienced by people with NF1 and suggests an important role of GAPs in the mechanism of sensory neuron sensitization.

Injection of autologous muscle stem cells (myoblasts) for the treatment of vocal fold paralysis: a pilot study.

OBJECTIVE: Autologous muscle stem cell (myoblast) therapy may be an ideal treatment for vocal fold paralysis because of its technical ease (administered by injection), its potential to restore muscular defects and dynamic function, and its autologous origin. The goal of this project was to determine whether autologous myoblast injection into the thyroarytenoid (TA) muscle after recurrent laryngeal nerve (RLN) injury could attenuate TA muscle atrophy and enhance spontaneous reinnervation. STUDY DESIGN: This was an animal experiment. METHODS: Unilateral RLN transection and sternocleidomastoid muscle (approximately 1 g) biopsies were performed in 16 male Wistar rats. Biopsies were used to create myoblast cultures for each animal. One month later, 10(6) autologous myoblasts labeled with fluorescent cell membrane marker (PKH26) were injected into the denervated TA of each study animal, with saline injected into controls. Animals were euthanized at 2 weeks and 2 months after myoblast injection. Outcomes included myoblast survival, TA fiber diameter and volume, and reinnervation status (motor endplate to nerve contact staining). RESULTS: All denervated TA study specimens demonstrated viable myoblasts under fluorescent microscopy, with the myoblasts demonstrating fusion with the TA myofibers at 2 months. The myoblast-treated group had greater mean TA fiber diameter than denervated TA controls at 2 months (25.1 vs. 21.1 microm; P = .04) but not at 2 weeks (25.7 microm vs. 23.5 microm; P = .06). Mean TA volumes were greater in the myoblast-treated groups at both time points. Two of the animals in the myoblast-treated group demonstrated adductor motion at 2 months, whereas none of the 2 week study animals or controls recovered adduction. Reinnervation was not significantly different between the myoblast-treated groups and the denervated controls. CONCLUSIONS: Autologous myoblast therapy may be a future treatment for vocal fold paralysis, with current findings demonstrating myoblast survival with attenuation of TA muscle atrophy.

Neurofibromin-deficient Schwann cells have increased lysophosphatidic acid dependent survival and migration-implications for increased neurofibroma formation during pregnancy.

Neurofibromas are the clinical hallmark of neurofibromatosis Type 1 (NF1), a genetic disorder caused by mutations of the NF1 tumor suppressor gene, which encodes neurofibromin that functions as a GTPase activating protein (GAP) for Ras. During pregnancy, up to 50% of existing neurofibromas enlarge and as many as 60% of new neurofibromas appear for the first time. Lysophosphatidic acid (LPA) is a prototypic lysophospholipid that modulates cell migration and survival of Schwann cells (SCs) and is made in increasing concentrations throughout pregnancy. We addressed the influence of LPA on the biochemical and cellular functions of SCs with a homozygous mutation of the murine homologue of the NF1 gene (Nf1-/-). LPA promoted F-actin polymerization and increased migration and survival of Nf1-/- SCs as compared to wild type (WT) SCs. Furthermore, LPA induced a higher level of Ras-GTP and Akt phosphorylation in Nf1-/- SCs as compared to WT cells. Pharmacologic inhibition or siRNA for the p85beta regulatory subunit of Class I A PI3-K significantly reduced LPA-induced Schwann cell survival and migration. Introduction of NF1-GRD reconstitution was sufficient to normalize the LPA-mediated motility of Nf1-/- SCs. As LPA modulates excessive cell survival and motility of Nf1-/- SCs, which are the tumorigenic cells in NF1, targeting PI3-K may be a potential therapeutic approach in diminishing the development and progression of neurofibromas in pregnant women with NF1.