Endothelin increases the proliferation of rat olfactory mucosa cells

International audienceThe olfactory mucosa holds olfactory sensory neurons directly in contact with an aggressive environment. In order to maintain its integrity, it is one of the few neural zones which are continuously renewed during the whole animal life. Among several factors regulating this renewal, endothelin acts as an anti-apoptotic factor in the rat olfactory epithelium. In the present study, we explored whether endothelin could also act as a proliferative factor. Using primary culture of the olfactory mucosa, we found that an early treatment with endothelin increased its growth. Consistently, a treatment with a mixture of BQ(123) and BQ(788) (endothelin receptor antagonists) decreased the primary culture growth without affecting the cellular death level. We then used combined approaches of calcium imaging, reverse transcriptase-quantitative polymerase chain reaction and protein level measurements to show that endothelin was locally synthetized by the primary culture until it reached confluency. Furthermore, in vivo intranasal instillation of endothelin receptor antagonists led to a decrease of olfactory mucosa cell expressing proliferating cell nuclear antigen (PCNA), a marker of proliferation. Only short-term treatment reduced the PCNA level in the olfactory mucosa cells. When the treatment was prolonged, the PCNA level was not statistically affected but the expression level of endothelin was increased. Overall, our results show that endothelin plays a proliferative role in the olfactory mucosa and that its level is dynamically regulated

A la recherche des odeurs d’oestrus chez les mammifères : proposition méthodologique.

National audienc

IL-17c is involved in olfactory mucosa responses to Poly(I:C) mimicking virus presence

ARTICLE IN PRESSInternational audienceAt the interface of the environment and the nervous system, the olfactory mucosa (OM) is a privileged pathway for environmental toxicants and pathogens towards the central nervous system. The OM is known to produce antimicrobial and immunological components but the mechanisms of action of the immune system on the OM remain poorly explored. IL-17c is a potent mediator of respiratory epithelial innate immune responses, whose receptors are highly expressed in the OM of mice. We first characterized the presence of the IL-17c and its receptors in the OM. While IL-17c was weakly expressed in the control condition, it was strongly expressed in vivo after intranasal administration of polyinosinic–polycytidylic (Poly I:C), a Toll Like Receptor 3 agonist, mimicking a viral infection. Using calcium imaging and electrophysiological recordings, we found that IL-17c can effectively activate OM cells through the release of ATP. In the longer term, intranasal chronic instillations of IL-17c increased the cellular dynamics of the epithelium and promoted immune cells infiltrations. Finally, IL-17c decreased cell death induced by Poly(I:C) in an OM primary culture. The OM is thus a tissue highly responsive to immune mediators, proving its central role as a barrier against airway pathogens

Sexual response of male rats to a mixture of odorant molecules potentially indicating oestrus in mammals

National audienc

Central processing of behaviorally relevant odors in brain of awake rats revealed by functional Manganese-enhanced MRI

International audienc

In search of stress odours across species: behavioural responses of rats to faeces from chickens and rats subjected to various types of stressful events

International audienceStressed animals have an increased risk of health and welfare problems, thus methods for easy and early stress detection is important for appropriate animal management. Using the ability of rats to distinguish between faeces odours from stressed and non-stressed conspecifics, we investigated whether rats could detect stress status in another species (the chicken), which would suggest a commonality in odorous stress signatures across species. We carried out four experiments to investigate the existence of stress-specific odours. In the first experiment using a T-maze, male Brown Norway (BN) rats (n = 12) were found to sniff the faeces samples from stressed rats and chickens less relative to the samples from non-stressed individuals (P < 0.05). In the second experiment, where odours were presented in an arena one at a time, male BN rats (n = 16) sniffed faeces samples from stressed rats and chickens for longer than those from non-stressed controls (P< 0.05). Within each test, the same responses to stress odours were seen independent of species of origin. This suggests that both in rats and chickens stress gives rise to specific volatile organic compounds (VOCs). In a third experiment, faeces from chickens, which had been stressed or non-stressed at hatching and subsequently exposed or not to acute stress at two weeks of age were tested on male BN rats (n = 18). These rats were also tested with faeces from non-stressed and acutely stressed rats as well as herb odour (1-hexanol) used as control. Number of freezing episodes was higher when rats were exposed to any of the samples originating from stressed individuals compared to that observed with herb odour (P < 0.05). Also, defensive burying was more likely to occur when rats were exposed to faeces from chickens stressed at hatching (P < 0.05). Finally, a fourth trial analysed faecal samples from non-stressed and acutely stressed rats using gas chromatography coupled with mass spectrometry (GC-MS), and identified ten VOCs potentially involved in the distinctive smell detectable in faeces from acutely stressed rats. These findings confirm the existence of stress-specific odours in rats and indicate that, although not necessarily identical, a similar type of odour may be present in stressed poultry. In addition, this odour could be detected by rats in chicken faeces collected almost two weeks after the birds had been exposed to a stressful event. Our results suggest that patterns of VOCs may have the potential to be used as a tool for early, non-invasive screening of stress status in animals

Comparison of c-Fos immunodetection and MEMRI signal.

<p>Red bars: number of c-Fos⁺ neurons within the anterior piriform cortex of rats stimulated by the odors released by a receptacle either empty or containing chocolate flavored cereals or fox feces. Means ± s.e.m. are shown. *: p<0.05 when compared to the corresponding empty container (control) value. y-axis legend is on the left. Blue bars: Mn contrast enhancement within the anterior piriform cortex in ROIs homologous to the regions examined for Fos immunoreactivity (as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048491#pone-0048491-g003" target="_blank">Figure 3</a>). Odorous stimulation was an airflow odorized with either male fox feces or chocolate flavored cereals. Means ± s.e.m. are shown. *: p<0.05 when compared to the corresponding deodorized airflow (control) value. y-axis legend is on the right.</p

Effect of odorous stimulation on Mn enhancement along the olfactory pathways.

<p>(A) 3D views of the t-map shown in the right column of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048491#pone-0048491-g001" target="_blank">Figure 1</a>. The intersection of this t-map and coronal planes at 22 rostro-caudal levels, (3 levels are shown: 1, 9 and 22) defined a region of interest (ROI) in which Mn enhancement was averaged to assess the effect of odorous stimulation. (B) Rostro-caudal distribution of the mean Mn enhancement in the 3 stimulated groups. At each level, the mean (± sem) Mn enhancement was calculated and compared using a one-way ANOVA. As indicated in the text, fox feces induced enhancement was always significantly different from deodorized air enhancement. Chocolate enhancement significantly differed from that of deodorized air only in slices 6 to 15 and in slice 17.</p

MEMRI contrast enhancement and c-Fos immunodetection in the anterior piriform cortex.

<p>A, C & E: photomicrographs of the right (C) and left (A, E) sides of the brain. MEMRI images of the corresponding slices are shown in inserts with the ROI encompassing the piriform cortex in red. B, D & F: enlargements of the regions delimited by the black rectangles in A, C & E, respectively. A, B: anterior region of the anterior piriform cortex; stimulation: chocolate flavored cereals C, D: medial region of the anterior piriform cortex; stimulation: empty container E, F: posterior region of the anterior piriform cortex; stimulation: fox feces Abbreviations (1), (2), (3): layers 1, 2 and 3 of the piriform cortex, (aca) anterior part of the anterior commissure, (lot) lateral olfactory tract, (rf) rhinal fissure, (Tu) olfactory tubercle. Scale bars (only for Fos images): 1 mm.</p

Figure

<p><b>1. Mn accumulation along olfactory pathways in the absence of olfactory stimulation.</b> T1-weighted MEMRI images were obtained from the 9 rats that did not receive any Mn and were not submitted to any odorous stimulation and from the 7 rats that received 0.3 µmol Mn intranasally and were exposed to a continuous flow of deodorized air. The 16 MEMRI images were normalized both spatially and in intensity as described in the text. The mean intensity values of homologous voxels in the 2 groups were then compared using a Student’s two-tailed t-test. Left column: a parasagittal view of the rat brain intersected by vertical red lines indicating the position, along the rostro-caudal axis, of the coronal sections shown in the three other columns. Center columns: coronal sections through the T1-weighted normalized MEMRI images of the 9 Mn-free unstimulated rats (left) and the 7 Mn-injected rats exposed to deodorized air (right). Right column: statistical t-map overlaid on T1-weighted MEMRI image showing Mn enhancement. T-values in red represent voxels whose mean intensity in the Mn group was higher than that of their homologues in the Mn-free group (p<0.001). Abbreviations: ac anterior commissure, Amyg Amygdaloid nuclei, Ent entorhinal cortex, Fr frontal cortex, Hi hippocampus, OB olfactory bulb, Pir piriform cortex, Tu olfactory tubercle, VS ventral striatum.</p