Organ culture of the trigeminal ganglion induces enhanced expression of calcitonin gene-related peptide via activation of extracellular signal-regulated protein kinase 1/2.

Abstract

BACKGROUND AND OBJECTIVE:

Clinical and experimental studies have revealed a central role of calcitonin gene-related peptide (CGRP) in primary headaches. The role of extracellular signal-regulated kinase 1 and 2 (ERK1/2) in neuronal and glial cell expression of CGRP- immunoreactivity (-ir) in rat trigeminal ganglia was studied with an organ culture method.

EXPERIMENTAL PROCEDURES:

Sections of adult rat trigeminal ganglia were cultured for up to 48 hours, examined with immunohistochemistry and quantitative real-time polymerase chain reaction (PCR) assay. Specific antibodies against CGRP, phosphorylated ERK1/2 (pERK1/2), total ERK1/2 (tERK1/2), phosphorylated p38 (pp38), phosphorylated C-Jun-N-terminal protein kinase (pJNK), pro-calcitonin (pro-CT), CGRP receptor activity modifying protein 1 (RAMP1), glutamine synthetase (GS) and pro-CT were used. To explore molecular mechanisms involved in the organ culture-induced CGRP-ir in neurons and glial cells, the effects of the MEK/ERK1/2 inhibitor U0126, its inactive analogue U0124, the p38 inhibitor SB203580 and the JNK inhibitor SP600125 were studied.

RESULTS:

In fresh ganglia, small- and medium-sized neurons were CGRP-ir while some larger neurons displayed RAMP1-ir. Glial cells were negative to both. After organ culture, neurons showed enhanced CGRP- and RAMP1-ir. In addition, some glial cells were RAMP1- and CGRP-ir. Isolated glial cells and neurons were found to contain CGRP mRNA, and showed pro-CT-ir, suggestive of local formation of CGRP. Neurons and glial cells showed enhanced pERK1/2-ir already after two hours of organ culture and this remained elevated for 48 hours. There was transient pJNK-ir in neurons at two hours, while pp38-ir was not altered. U0126 reduced the enhanced pERK1/2-ir, while U0124 had no such effect; the CGRP-ir in neurons and glial cells was reduced at 48 hours and in parallel the CGRP mRNA expression was lower at 24 hours.

CONCLUSION:

We suggest that in conditions of elevated CGRP expression, inhibition of ERK1/2 might be an option for novel treatment.

• Authors: János Tajti, Anikó Kuris, László Vécsei, Cang-Bao Xu, Lars Edvinsson
• Journal: Cephalalgia : an international journal of headache (Cephalalgia) Vol. 31 Issue 1 Pg. 95-105 (Jan 2011) ISSN: 1468-2982 [Electronic] England
• PMID: 20851839 (Publication Type: Journal Article)

Chemical References

• Enzyme Inhibitors
• Mitogen-Activated Protein Kinase 1
• Mitogen-Activated Protein Kinase 3
• Calcitonin Gene-Related Peptide

Topics

• Animals
• Calcitonin Gene-Related Peptide (biosynthesis)
• Enzyme Activation (physiology)
• Enzyme Inhibitors (pharmacology)
• Image Processing, Computer-Assisted
• Immunohistochemistry
• Male
• Mitogen-Activated Protein Kinase 1 (biosynthesis)
• Mitogen-Activated Protein Kinase 3 (biosynthesis)
• Neuroglia (metabolism)
• Neurons (metabolism)
• Organ Culture Techniques
• Rats
• Rats, Sprague-Dawley
• Reverse Transcriptase Polymerase Chain Reaction
• Signal Transduction (drug effects, physiology)
• Trigeminal Ganglion (cytology, metabolism)