Sensitization of the Trigeminovascular System following Environmental Irritant Exposure

Background Air pollution is linked to increased emergency room visits for headache, and migraine patients frequently cite chemicals or odors as headache triggers, but the association between air pollutants and headache is not well understood. We previously reported that nasal administration of environmental irritants acutely increases meningeal blood flow via a TRPA1-dependent mechanism involving the trigeminovascular system. Here, we examine whether chronic environmental irritant exposure sensitizes the trigeminovascular system. Methods Male rats were exposed to acrolein, a TRPA1 agonist, or room air by inhalation for four days prior to meningeal blood flow measurements. Some animals were injected daily with a TRPA1 antagonist, AP-18, or vehicle prior to inhalation exposure. Trigeminal ganglia were isolated following blood flow measurements for immunocytochemistry and/or qPCR determination of TRPV1, TRPA1 and CGRP levels. Results Acrolein inhalation exposure potentiated blood flow responses both to TRPA1 and TRPV1 agonists compared to room air. Acrolein exposure did not alter TRPV1 or TRPA1 mRNA levels or TRPV1 or CGRP immunoreactive cell counts in the trigeminal ganglion. Acrolein sensitization of trigeminovascular responses to a TRPA1 agonist was attenuated by pre-treatment with AP-18. Interpretation These results suggest trigeminovascular sensitization as a mechanism for enhanced headache susceptibility after chemical exposure

XML Template (2015) [26.2.2015–7:52am] [1–10] //blrnas3.glyph.com/cenpro/ApplicationFiles/Journals/SAGE/3B2/CEPJ/Vol00000/150020/APPFile/SG-CEPJ150020.3d (CEP) [PREPRINTER stage] Original Article

Sensitization of the trigeminovascular system following environmental irritant exposur

Intraganglionic signaling as a novel nasal-meningeal pathway for TRPA1-dependent trigeminovascular activation by inhaled environmental irritants.

Headache is the most common symptom associated with air pollution, but little is understood about the underlying mechanism. Nasal administration of environmental irritants activates the trigeminovascular system by a TRPA1-dependent process. This report addresses questions about the anatomical pathway involved and the function of TRP channels in this pathway. TRPV1 and TRPA1 are frequently co-localized and interact to modulate function in sensory neurons. We demonstrate here that resiniferatoxin ablation of TRPV1 expressing neurons significantly reduces meningeal blood flow responses to nasal administration of both TRPV1 and TRPA1 agonists. Accordingly resiniferatoxin also significantly reduces TRPV1 and CGRP immunostaining and TRPV1 and TRPA1 message levels in trigeminal ganglia. Sensory neurons of the trigeminal ganglia innervate the nasal epithelium and the meninges, but the mechanism and anatomical route by which nasal administration evokes meningeal vasodilatation is unclear. Double retrograde labeling from the nose and meninges reveals no co-localization of fluorescent label, however nasal and meningeal labeled cells are located in close proximity to each other within the trigeminal ganglion. Our data demonstrate that TRPV1 expressing neurons are important for TRPA1 responses in the nasal-meningeal pathway. Our data also suggest that the nasal-meningeal pathway is not primarily by axon reflex, but may instead result from intraganglionic transmission

TRPV1 receptor immunoreactivity in trigeminal ganglia in vehicle- and RTX- treated rats.

<p>(A) TRPV1 receptor immunoreactivity is present throughout the ganglia in vehicle-treated but not in RTX-treated rats. One week following RTX treatment, TRPV1 receptor immunoreactivity is nearly abolished. After two and three-week survivals, TRPV1 receptor immunoreactivity is more evident but remains greatly diminished compared with vehicle-treated rats. Scale bar, 200 µm. (B) TRPV1 immunoreactive cell counts per section in the trigeminal ganglia in vehicle and RTX-treated rats. TRPV1 receptor cellular profiles are significantly decreased following RTX-treatment compared to vehicle treated at all survival times. Cell counts represented as mean ± S.E.M. Number of animals per group is indicated.</p

Retrograde double labeling in the trigeminal ganglion.

<p>Representative images two weeks following retrograde labeling of the nasal epithelium (Fluorogold; blue) and middle cerebral artery (MCA) (DiI; red). Numerous labeled cells were observed throughout the trigeminal ganglion and frequently retrograde labeled cells from the nasal mucosa were observed near to or adjacent to those from the MCA. Scale bar 100 µm.</p

Distance measurements between nasal epithelium sensory afferents (FG) and middle meningeal sensory afferents (DI) in the rat trigeminal ganglion.

<p>Distance measurements between nasal epithelium sensory afferents (FG) and middle meningeal sensory afferents (DI) in the rat trigeminal ganglion.</p

Relative expression levels of TRPV1 and TRPA1 mRNA in trigeminal ganglia following RTX treatment.

<p>RTX treatment induced a significant and similar reduction in both TRPV1 and TRPA1 mRNA expression levels at all survival times compared with vehicle injected controls. N = 4–9 animals per group.</p

Blood flow changes in the middle meningeal artery following nasal administration of acrolein (A, B) or capsaicin (C, D) in RTX and vehicle injected animals.

<p>(A, C) Representative traces of middle meningeal blood flow changes in response to nasally administered acrolein or capsaicin. Laser Doppler flowmetry measurements were collected at 1 Hz and filtered at 0.1 Hz for graphical representation. Nasal application of acrolein or capsaicin in vehicle injected animals induced a rapid and robust increase in meningeal blood which returned toward baseline values within minutes while similar application of acrolein or capsaicin in RTX treated animals induced a reduced blood flow response. Arrows indicate nasal administration of agonist. (B, D) Compared to vehicle treated controls, blood flow response to nasal acrolein or capsaicin was diminished at one week of treatment and significantly decreased at two and three weeks of RTX treated. Similar diminished blood flow responses were observed with capsaicin in RTX treated animals. Values are means ± S.E.M. Number of animals per group is indicated. P<0.05 compared to blood flow changes in saline-injected animals.</p

Comprehensive analysis of chromothripsis in 2,658 human cancers using whole-genome sequencing

Analysis of whole-genome sequencing data across 2,658 tumors spanning 38 cancer types shows that chromothripsis is pervasive, with a frequency of more than 50% in several cancer types, contributing to oncogene amplification, gene inactivation and cancer genome evolution.Chromothripsis is a mutational phenomenon characterized by massive, clustered genomic rearrangements that occurs in cancer and other diseases. Recent studies in selected cancer types have suggested that chromothripsis may be more common than initially inferred from low-resolution copy-number data. Here, as part of the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA), we analyze patterns of chromothripsis across 2,658 tumors from 38 cancer types using whole-genome sequencing data. We find that chromothripsis events are pervasive across cancers, with a frequency of more than 50% in several cancer types. Whereas canonical chromothripsis profiles display oscillations between two copy-number states, a considerable fraction of events involve multiple chromosomes and additional structural alterations. In addition to non-homologous end joining, we detect signatures of replication-associated processes and templated insertions. Chromothripsis contributes to oncogene amplification and to inactivation of genes such as mismatch-repair-related genes. These findings show that chromothripsis is a major process that drives genome evolution in human cancer