Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion

BACKGROUND: Nerve growth factor (NGF), glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) all play important roles in the development of the peripheral sensory nervous system. Additionally, these growth factors are proposed to modulate the properties of the sensory system in the adult under pathological conditions brought about by nerve injury or inflammation. We have examined the effects of NGF, GDNF and BDNF on adult rat trigeminal ganglion (TG) neurons in culture to gain a better understanding of how these growth factors alter the cytochemical and functional phenotype of these neurons, with special attention to properties associated with nociception. RESULTS: Compared with no growth factor controls, GDNF, at 1 and 100 ng/ml, significantly increased by nearly 100% the number of neurons in culture at 5 days post-plating. A significant, positive, linear trend of increasing neuron number as a function of BDNF concentration was observed, also peaking at nearly 100%. NGF treatment was without effect. Chronic treatment with NGF and GDNF significantly and concentration-dependently increased 100 nM capsaicin (CAP)-evoked calcitonin gene-related peptide (CGRP) release, reaching approximately 300% at the highest concentration tested (100 ng/ml). Also, NGF and GDNF each augmented anandamide (AEA)- and arachidonyl-2-chloroethylamide (ACEA)-evoked CGRP release, while BDNF was without effect. Utilizing immunohistochemistry to account for the proportions of TRPV1- or CGRP-positive neurons under each growth factor treatment condition and then standardizing evoked CGRP release to these proportions, we observed that NGF was much more effective in enhancing CAP- and 50 mM K(+)-evoked CGRP release than was GDNF. Furthermore, NGF and GDNF each altered the concentration-response function for CAP- and AEA-evoked CGRP release, increasing the E(max )without altering the EC(50 )for either compound. CONCLUSIONS: Taken together, our results illustrate that NGF, GDNF and BDNF differentially alter TG sensory neuron survival, neurochemical properties and TRPV1-mediated neuropeptide release in culture. In particular, our findings suggest that GDNF and NGF differentially modulate TRPV1-mediated neuropeptide secretion sensitivity, with NGF having a much greater effect on a per neuron basis than GDNF. These findings are discussed in relation to possible therapeutic roles for growth factors or their modulators in pathological pain states, especially as these relate to the trigeminal system

Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion-8

<p><b>Copyright information:</b></p><p>Taken from "Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion"</p><p>BMC Neuroscience 2005;6():4-4.</p><p>Published online 24 Jan 2005</p><p>PMCID:PMC548274.</p><p>Copyright © 2005 Price et al; licensee BioMed Central Ltd.</p>tor conditions (n = 6). Panel A illustrates the maximum relative effect of capsaicin under each condition matched to the maximum evoked-CGRP release for that given condition. Panel B depicts the CAP-evoked CGRP release data in terms of CGRP released in fmoles in the presence or absence of NGF or GDNF to illustrate the magnitude of increases in Eand the biphasic nature of the capsaicin-evoked CGRP concentration-response function

Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion-7

<p><b>Copyright information:</b></p><p>Taken from "Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion"</p><p>BMC Neuroscience 2005;6():4-4.</p><p>Published online 24 Jan 2005</p><p>PMCID:PMC548274.</p><p>Copyright © 2005 Price et al; licensee BioMed Central Ltd.</p>er of TRPV1-positive neurons under each growth factor condition (** p < 0.01, *** p < 0.01 for comparisons to no growth factor treated controls; ## p < 0.01, ### p < 0.001 for comparisons to NGF at the equivalent growth factor concentration by two-way ANOVA with Bonferroni post-test; n = 6)

Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion-6

<p><b>Copyright information:</b></p><p>Taken from "Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion"</p><p>BMC Neuroscience 2005;6():4-4.</p><p>Published online 24 Jan 2005</p><p>PMCID:PMC548274.</p><p>Copyright © 2005 Price et al; licensee BioMed Central Ltd.</p> expressing these population markers. Representative 20X photomicrographs of each growth factor at 100 ng/ml for CGRP (left), TRPV1 (middle) and IB(right) are shown as well as control (no growth factor-treated) TG cultures (top panels). All cell bodies containing both NF-H-immunoreactivity and CGRP- or TRPV1-immunoreactivity or IB-binding appear yellow from the overlay of the red with green. In no cases were neurons observed that contained CGRP- or TRPV1-immunoreactivity or IB-binding without the co-presence of NF-H-immunoreactivity

Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion-5

<p><b>Copyright information:</b></p><p>Taken from "Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion"</p><p>BMC Neuroscience 2005;6():4-4.</p><p>Published online 24 Jan 2005</p><p>PMCID:PMC548274.</p><p>Copyright © 2005 Price et al; licensee BioMed Central Ltd.</p>s per condition as a proportion of the no growth factor-treated cultures. Panel C shows total CGRP content by growth factor treatment, and again, panel D shows this data standardized to CGRP-positive neurons, as stated above (*** p < 0.001, n = 6)

Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion-9

<p><b>Copyright information:</b></p><p>Taken from "Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion"</p><p>BMC Neuroscience 2005;6():4-4.</p><p>Published online 24 Jan 2005</p><p>PMCID:PMC548274.</p><p>Copyright © 2005 Price et al; licensee BioMed Central Ltd.</p>�M AEA or 30 μM ACEA for 10 min, and the released CGRP was quantified (n = 12). Panel D, TG neurons were grown in the absence of growth factors or in the presence of 100 ng/ml NGF or GDNF for 5 days and exposed to the indicated concentrations of AEA (molar, log units) to assess CGRP release (### p < 0.001; GDNF and NGF vs. no growth factor; two-way ANOVA, Bonferroni post-test, n = 6)

Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion-0

<p><b>Copyright information:</b></p><p>Taken from "Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion"</p><p>BMC Neuroscience 2005;6():4-4.</p><p>Published online 24 Jan 2005</p><p>PMCID:PMC548274.</p><p>Copyright © 2005 Price et al; licensee BioMed Central Ltd.</p>velength for the corresponding secondary antibody. For the 2 matching wells for each slide (growth factor concentration), the neuron numbers were averaged to give one observation (since the wells were not derived from independent cultures). Each slide contained a no growth factor control (blue), hence n = 9 for this condition. All other growth factors at 1 (i.e. NGF, red), 10 (i.e. GDNF, green) or 100 ng/ml (i.e. BDNF, yellow) are n = 3. The same slides were then utilized to ascertain the proportions of neurons expressing CGRP- or TRPV1-immunoreactivity or IB-binding, as described in Methods. This figure refers to Figures 2 and 3 and Table 1

Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion-4

<p><b>Copyright information:</b></p><p>Taken from "Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion"</p><p>BMC Neuroscience 2005;6():4-4.</p><p>Published online 24 Jan 2005</p><p>PMCID:PMC548274.</p><p>Copyright © 2005 Price et al; licensee BioMed Central Ltd.</p>probed for standardization with β-actin (X = no growth factor; N 100 = NGF 100 ng/ml; G 100 = GDNF 100 ng/ml). Image is of a representative Western blot. Immunoreactivity to a protein corresponding to the size of the glycosyated form of TRPV1 was detected at ~130 kD. Panel B depicts alterations in TRPV1 protein levels standardized to β-actin (* p < 0.05, n = 3

Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion-3

<p><b>Copyright information:</b></p><p>Taken from "Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion"</p><p>BMC Neuroscience 2005;6():4-4.</p><p>Published online 24 Jan 2005</p><p>PMCID:PMC548274.</p><p>Copyright © 2005 Price et al; licensee BioMed Central Ltd.</p>A levels (n = 3)

Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion-2

<p><b>Copyright information:</b></p><p>Taken from "Treatment of trigeminal ganglion neurons in vitro with NGF, GDNF or BDNF: effects on neuronal survival, neurochemical properties and TRPV1-mediated neuropeptide secretion"</p><p>BMC Neuroscience 2005;6():4-4.</p><p>Published online 24 Jan 2005</p><p>PMCID:PMC548274.</p><p>Copyright © 2005 Price et al; licensee BioMed Central Ltd.</p>no growth factor-treated) TG cultures to assess neuronal survival at day 5 post-plating (* p < 0.05, *** p < 0.001)