20 research outputs found
SCHWANN CELLS MODULATE THE RELEASE OF CALCITONIN GENE-RELATED PEPTIDE FROM SENSORY NEURONS
poster abstractAn alteration in the interaction between Schwann cells and sensory neurons may be involved in inflammatory neuropathies associated with altered sensation and pain. The release of the peptide transmitter, calcitonin gene-related peptide (CGRP), is one method to monitor the sensitivity of a subclass of primary sensory neurons involved in pain signaling. We utilized an in vitro assay to investigate the interaction between Schwann cells and sensory neurons in an inflammatory state. Schwann cells and sensory neurons were isolated from adult mouse sciatic nerve and dorsal root ganglia, respectively, and maintained in culture. Schwann cells were exposed to HEPES buffer containing the inflammatory mediators histamine, prostaglandin E2, bradykinin, and serotonin (all 10-5 M), potassium (7 mM), and at pH 7.0 for 10 minutes. After this activation, the Schwann cells were incubated in HEPES buffer alone for 1 hour. This Schwann cell-conditioned buffer (SCCB) was collected and sensory neurons were exposed to three consecutive 10 minute incubations in HEPES buffer alone or SCCB. The amount of CGRP released during each of these incubations was measured using radioimmunoassay. Incubation with SCCB elicited a seven-fold increase in the release of CGRP compared to neurons exposed to HEPES buffer alone. The release of CGRP elicited by SCCB was abolished when neurons were exposed to SCCB containing no added calcium. After treatment with the inflammatory mediators detailed above for 10 minutes, Schwann cell lysates showed a significant decrease in six cytokines, while SCCB demonstrated an increase in interleukin-6 (IL-6) as measured by a cytokine array panel. These results suggest that during inflammation, Schwann cells release substances, which directly stimulate sensory neurons, as measured by an increase in CGRP release. These findings reinforce the importance of identifying the mechanisms underlying the interaction between Schwann cells and sensory neurons to discover novel therapeutics for treating inflammatory pain
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 1,500Jm-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
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
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 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
Utilizing 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 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 pharmacologic 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
Mechanisims of prostacyclin-induced modulation of neuropeptide release from rat sensory neurons grown in culture
This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department ([email protected])
Ret-dependent and Ret-independent mechanisms of Gfl-induced sensitization
Abstract 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 β-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.</p
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 Ca2+ channels and interacting proteins are essential
in neuronal signaling and synaptic transmission during this period. We
recently identified the presynaptic N-type voltage-gated Ca2+
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 Ca2+ 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
∼70%, whereas siRNA targeting CRMP-2 significantly reduced release of
iCGRP by ∼54% compared with control cultures. These findings support a
novel role for CRMP-2 in the regulation of N-type Ca2+ channels and
in transmitter release