TRPV1 Channels and Neuropathic Pain

Neuromics' TRPV1 Stain Neurons and Microglia for Study

TRPV1 is mainly functional in the microglia. Its activation, beyond controlling microglia reaction per se, modulated microglia-neuron communication, by promoting release of extracellular vesicles (EVs) from microglia. Indeed, EVs are important mediators of intercellular communication between microglia and brain cells: Maria Cristina Marrone, Annunziato Morabito, Michela Giustizieri, Valerio Chiurchiù, Alessandro Leuti, Marzia Mattioli, Sara Marinelli, Loredana Riganti, Marta Lombardi, Emanuele Murana, Antonio Totaro, Daniele Piomelli, Davide Ragozzino, Sergio Oddi, Mauro Maccarrone, Claudia Verderio & Silvia Marinelli. TRPV1 channels are critical brain inflammation detectors and neuropathic pain biomarkers in mice. Nature Communications 8, Article number: 15292 (2017) doi:10.1038/ncomms15292.

(a–f) Sections of cortical tissue from WT and TRPV1−/− mice, fixed after exposure to ACSF (a,d), ACSF plus vehicle (DMSO; b,e) and ACSF plus 1μM capsaicin (c,f) and immune-processed for iba-1 to stain microglia cells (in red). INSETs are zoom images taken from an area delimited by the yellow square for each condition. (g), Bar graph of percentage of cortical microglia cell phenotype (resting, ameboid, bushy and hypertrophied), in control (grey bars), vehicle- (dark grey bars) and capsaicin- treated (red bars) cortical sections from WT mice. Capsaicin treatment causes a significant shift from ramified and bushy to hypertrophied morphology. (h), Same as in ‘g’ but in cortical sections from TRPV1−/− mice. In these tissues capsaicin fails to induce morphological changes of microglia cells. Note that microglia cells in −/− tissues are already hypertrophied in control conditions (d–f,h).

Our Pain and Inflammation Research Antibodies Continue to be widely used and frequently published.

Science Behind Elecroacupuncture for Treating Shingles

Postherpetic neuralgia (PHN) or shingles, caused by caused by herpes zoster, causes nerve damage in the skin and results in abnormal electrical signals to the brain,  and may persist or recur for months, years or for life.

Electroacupuncture (EA) is effective in relieving pain in patients with PHN. Researchers in this study determined the beneficial effect of EA and the potential mechanisms in a rat model of PHN. They use our TRPV1 antibody to track expression in the Dorsal Root Ganglia (DRG) and Dorsal Horn (DH): Cai-hua Wu, Zheng-tao Lv, Yin Zhao, Yan Gao, Jia-qing Li, Fang Gao, Xian-fang Meng, Bo Tian, Jing Shi, Hui-lin Pan and Man Li. Electroacupuncture improves thermal and mechanical sensitivities in a rat model of postherpetic neuralgia. Molecular Pain 2013, 9:18 doi:10.1186/1744-8069-9-18


Conclusions: EA treatment improves thermal perception by recovering TRPV1-positive sensory neurons
and nerve terminals damaged by RTX. EA Also reduces RTX-induced tac tile allodynia by attenuating the damage of myelinated afferent nerves and their abnormal sprouting into the spinal lamina II. Our study provides new information about the mechanisms of the therapeutic actions of EA in the treatment of PHN.

Figure 2:  Effect of EA on RTX-induced deletion of TRPV1-immunoreactive neuron s in the DRG. A, Representative images showing TRPV1-immunoreactive neurons in the lumbar DRG of vehicle ( a ) , RTX ( b ), RTX plus 2 Hz EA ( c ), RTX plus 15 Hz EA ( d ), RTX plus 100 Hz EA ( e ), and RTX plus sham EA ( f ) groups. Scale bar, 50 μ m. B, Summary data show the number of TRPV1 immunoreactive neurons in different groups. Data are expresse d as means ± SEM (n = 6 rats in each group). *P < 0.05, compared with the vehicle group; # P< 0.05, compared with the sham EA group.

Figure 3: Effect of EA on RTX-induced deletion of TRPV1 immunoreactive central terminals in the spinal dorsal horn. A, Representative images showing TRPV1 immunoreactive central terminals of afferent fibers in the spinal dorsal horn of vehicle (a) ,RTX (b), RTX plus 2 Hz EA (c), RTX plus 15 Hz EA (d), RTX plus 100 Hz EA (e), and RTX plus sham EA (f) groups. Scale bar, 50 μm. B, Summary data show the area of TRPV1 immunoreactive central terminals in different groups. Data are expressed as means ± SEM (n= 6 rats in each group). *P < 0.05, compared with the vehicle group; # P < 0.05, compared with the sham EA group. 

I am always interested in how our Pain and Inflammation Research Markers are used to help understand the science behind pain therapies and also discovery of new therapies. There are multiple postings on these subjects with many more to come.

TRPV1s in Action

Our TRPV1s continue to be widely used and published. This recent publication features use out TRPV1-C guinea pig polyclonal for immunohistochemistry and TRPV1-mouse specific for Western Blotting: Sarah E. Canetta, Edlira Luca, Elyse Pertot, Lorna W. Role, David A. Talmage. Type III Nrg1 Back Signaling Enhances Functional TRPV1 along Sensory Axons Contributing to Basal and Inflammatory Thermal Pain Sensation. PLoS ONE 6(9): e25108. doi:10.1371/journal.pone.0025108...IHC: TRPV1 (guinea pig, 1:1000, GP14100 Neuromics); WB: TRPV1 (rabbit, 1:1000, RA14113 Neuromics).

Figure. Sensory axons, but not soma, from Type III Nrg1+/− mice show reduced capsaicin responsiveness compared to axons from WT mice. (A) Representative traces of intracellular calcium along sensory axons in response to 1 µM capsaicin or 56 mM KCl. The change in intracellular calcium from baseline over time ([(F−F0)/F0]*100) is shown for WT (left) and Type III Nrg1+/− (right) axons. Hatched diagonal lines indicate where the time course was non-continuous. (B) Quantification of the maximum change in intracellular calcium in response to application of 1 µM capsaicin or 56 mM KCl by genotype. Averages of 5 animals per genotype were compared using a Student's t-test. Type III Nrg1+/− axons showed a significantly decreased response to capsaicin (p<0.05), but not to KCl, relative to WTs. Graph shows mean±SEM. (C) Type III Nrg1+/− sensory soma show normal response to capsaicin. Quantification of maximal change in fluorescence from baseline ([(F−F0)/F0]*100) in WT or Type III Nrg1+/− sensory neuron soma in response to 1 µM capsaicin or 56 mM KCl. Average responses from 4 WT and 4 Type III Nrg1+/− animals to application of capsaicin or KCl were compared by genotype using a Student's t-test. There was no statistically significant difference between genotypes. Graphs show mean±SEM. (D) Type III Nrg1 (green) and TRPV1 (red) are co-expressed along P21 WT cultured sensory neuron axons identified with a pan-axonal (PA) marker (blue). White arrows indicate examples where Type III Nrg1 and TRPV1 are in close proximity. Scale bar equals 10 µm. (E) P21 WT and Type III Nrg1+/− sensory neuron cultures have equivalent levels of total TRPV1 protein. Total TRPV1 protein measurement by immunoblot. The 95 kD TRPV1 band and the 35 kD GAPDH band are shown from a representative experiment comparing protein from P21 WT and Type III Nrg1+/− cultures. Quantification of fold change in intensity of TRPV1:GAPDH normalized to WT average. There was no statistically significant change in the ratio of TRPV1 to GAPDH between genotypes (WT, Type III Nrg1+/−, n = 3 animals). Genotype comparisons were made using a Student's t-test. Graph shows mean±SEM. doi:10.1371/journal.pone.0025108.g004
All TRPV1 Publications.

TRPV1 Expression and Temporal Lobe Epilepsy

Dr Bret. Smith and his lab at Tulane have demontrated a link between Temporal Lobe Epilepsy (TLE) and VR1 N-Terminus (TRPV1) expression.

In this excellent study they showed an increase in expression in TLE mice vs controls.

Muthu D. Bhaskaran and Bret N. Smith. Effects of TRPV1 activation on synaptic excitation in the dentate gyrus of a mouse model of temporal lobe epilepsy. doi:10.1016/j.expneurol.2010.01.021
...with polyclonal VR1 N-terminus (1:2500) (Neuromics, Edina)..

Abstract: Temporal lobe epilepsy (TLE) is a condition characterized by an imbalance between excitation and inhibition in the temporal lobe. Hallmarks of this change are axon sprouting and accompanying synaptic reorganization in the temporal lobe. Synthetic and endogenous cannabinoids have variable therapeutic potential in treating intractable temporal lobe epilepsy, in part because cannabinoid ligands can bind multiple receptor types. This study utilized in vitro electrophysiological methods to examine the effect of transient receptor potential vanilloid type 1 (TRPV1) activation in dentate gyrus granule cells in a murine model of TLE. Capsaicin, a selective TRPV1 agonist had no measurable effect on overall synaptic input to granule cells in control animals, but significantly enhanced spontaneous and miniature EPSC frequency in mice with TLE. Exogenous application of anandamide, an endogenous cannabinoid that acts at both TRPV1 and cannabinoid type 1 receptors (CB1R), also enhanced glutamate release in the presence of a CB1R antagonist. Anandamide reduced the EPSC frequency when TRPV1 were blocked with capsazepine. Western blot analysis of TRPV1 receptor indicated protein expression was significantly greater in the dentate gyrus of mice with TLE compared with control mice. This study indicates that a prominent cannabinoid agonist can increase excitatory circuit activity in the synaptically reorganized dentate gyrus of mice with TLE by activating TRPV1 receptors, and suggests caution in designing anticonvulsant therapy based on modulating the endocannabinoid system.

Images: Western blot detection of TRPV1 receptor expression in the dentate gyrus. A. Diagram of dentate gyrus showing the microdissected area (box). B. Western blot showing TRPV1 receptor expression in two untreated mice and in two pilocarpine-treated mice that survived SE. Actin was used as the loading control which did not change significantly. C. Graph showing a significant (p less than 0.05; n=4) TRPV1 expression in epileptic mice.

Related Reagents:

TRPV (Vanilloid); TRPM; TRPA and TRPCs

Neurotransmission Research Antibodies-GPCRs, Ligand Gated Ion Channels, Biogenic Amines and more

Primary Neurons and Astrocytes- Primary human, rat and mouse neurons and astrocytes by Category.

TRPV1 and Retinal Ganglion Cell Apoptosis

The publications referencing our TRPV (Vanilloid); TRPM; TRPA and TRPC Antibodies keep on coming.

In this February 2009 publication, Dr. David Calkins and his team at Vanderbilt demontrate that Retinal Ganglian Cells express the TRPV1 channel and that TRPV1 activation contributes to their death with exposure to hydrostatic pressure . We also demonstrated that activation of TRPV1 alone was sufficient to induce apoptosis of RGCs.

Rebecca M. Sappington, Tatiana Sidorova, Daniel J. Long, and David J. Calkins. TRPV1: Contribution to Retinal Ganglion Cell Apoptosis and Increased Intracellular Ca2+ with Exposure to Hydrostatic Pressure. Invest. Ophthalmol. Vis. Sci., Feb 2009; 50: 717 - 728.
...we used rabbit anti-mouse TRPV1 IgG (1:500; catalog number RA14113; Neuromics, Edina, MN) against the absolute C terminus of mouse TRPV1 (EDAEVFKDSMAPGEK)...

TRPV1 localization in RGCs of rat retina. (A) Immunocytochemical labeling for TRPV1 shows strong localization in the outer retina and in RGCs (large cell bodies); there is little or no label in smaller displaced amacrine cells of the GCL. Clear examples of amoeboid-shaped cell bodies of microglia cells are indicated (ovals). Right: Control section preabsorbed using the TRPV1 blocking peptide (+BP). (B) Confocal image stack through GCL and NFL showing labeling for TRPV1 in wholemount preparation counterlabeled with antibodies against heavy-chain neurofilaments that recognize broad-field RGCs (SMI32). Image shows punctate localization to dendrites (arrows) as well as intense label to cell bodies (brackets); smaller cell bodies with TRPV1 label are in the background. (C) Confocal image stack through GCL and NFL of peripheral retina shows TRPV1 in RGC cell bodies (bracket) and in small bundles of RGC axons (arrows). (D) Confocal stack from central retina shows TRPV1 in RGC cell bodies (bracket) and in axon bundles in the NFL as they course toward the optic nerve head. Amoeboid-shaped cell bodies of microglia are apparent (ovals). (E) Confocal image in single plane at GCL/NFL border shows Iba-1–labeled microglia processes colocalizing with TRPV1, as we previously demonstrated.51 TRPV1-label RGC cell bodies (brackets) and axons (arrows) are indicated for reference. (F) Immunocytochemical labeling demonstrates strong perinuclear and dendritic localization of TRPV1 in cultured RGCs counterstained with the nuclear label DAPI. Localization to dendritic processes and neurites (dashed circles) includes node-like clusters; right: these regions are shown at higher magnification. (G, top) Western blot against TRPV1 in brain and whole retina from adult rat shows band at expected molecular weight (arrowheads; 100–113 kDa). Retina demonstrates an additional band with a slightly lower molecular weight that probably corresponds to a different glycosylation state for this antibody.79 Bottom: Control Western blot with preabsorption of TRPV1 antibody using the blocking peptide prevents detection of both bands. ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer; NFL, nerve fiber layer.

Excellent TRPV1-N IHC and WB

Kudos to Dr. Federica MF van Dissel-Emiliani and her team for the excellent Immunohistochemistry and Western Blot results using our TRPV1-N Antibody(Catalog #: RA10110) . The antibody was in their study demonstrating the sensitivity of spermatogenesis to capsaicin.

Here's the related publication:

Sefika C Mizrak, Bart M Gadella, Hatice Erdost, Aytekin Ozer, Ana MM van Pelt, Federica MF van Dissel-Emiliani. Spermatogonial stem cell sensitivity to capsaicin: An in vitro study. Reproductive Biology and Endocrinology 2008, 6:52 doi:10.1186/1477-7827-6-52.

Anti TRPV1 antibody staining: Bouin's fixed, paraffin embedded 5 um-thick rat testis sections were deparaffinized and boiled in a microwave oven (700 Watt) 3x10 min in sodium citrate buffer (0.1 mM, pH=6) for antigen retrieval. All subsequent incubations were performed for 1 hour at room temperature. The slides were then blocked with 5 % goat serum in 1 % BSA/PBS and incubated with the rabbit anti human - VR1 antibody (Neuromics, Edina, MN, USA; 1:500 in 1% BSA/PBS). Biotinilated goat anti-rabbit secondary antibody (BA-1000, Vector Labs; 1:200 in 1% BSA/PBS) was then applied. The ABC kit was finally used according to the manufacturer's instructions. Antibody reactivity was finally detected by diaminobenzidine staining (DAB, Sigma, St. Louis, MO, USA). Sections were counterstained with hematoxylin, dehydrated, mounted with Pertex and studied. Goat serum was applied on control sections.

Image: Photomicrograph of a section through an adult rat testis showing TRPV1 labelling of premeiotic germ cells, at stage II of the seminiferous epithelium. Arrow, undifferentiated spermatogonia; arrow head, early pachytene spermatocytes; asterisk, Sertoli cells.

SDS-PAGE and Western blotting: Protein lysates from the cell lines Gc-5spg and Gc-6spg and the control glioma cell line (A10-85) were prepared in RIPA buffer (PBS, 1% NP40, 0.5% sodium deoxycholate, 0.1% SDS) including 1 mM phenylmethylsulfonylfluoride. Of each sample, 50 μg were separated on a 12% SDS-polyacrylamide gel and blotted onto a polyvinylidene fluoride membrane (Millipore Corp., Bedford, MA, USA). Western blots were blocked using Blotto-A, containing 5% Protifar (Nutricia, Zoetermeer, The Netherlands) in Tris-buffered saline (10 mM Tris; 150 mM NaCl, pH 7.6), including 0.05% Tween-20. Rabbit polyclonal anti-VR1 antibody (Neuromics) was diluted 1:1000 in Blotto-A and incubated for 1 h at room temperature. Blots were washed with Tris-buffered saline with 0.05% Tween-20. After incubation with goat anti-rabbit-HRP (P-0260 Dako Cytomation, 1:5000 inBlotto-A) secondary antibody for 1 h, blots were incubated with the electrochemiluminescence kit (ECL, Amersham Pharmacia Biotech, Little Chalfont, UK)and exposed to an x-ray film (RX-omat, Kodak, Chalone / Saone, France).