title: Retrograde response of the rat facial motor nucleus to muscle inflammation elicited by phytohaemagglutinin.
abstract: To investigate whether motoneurons react to signals deriving from target inflammation, we studied the facial motor nucleus after injections of phytohaemagglutinin in the snout of adult rats. This plant lectin is a tool widely used to induce proliferation and activation of T lymphocytes, and we observed marked lymphocyte infiltration in the injected facial muscles. Retrograde labelling of motoneurons was not detected after peripheral injections of fluorochrome-conjugated phytohaemagglutinin. Nitric oxide synthase, revealed by NADPH-diaphorase histochemistry, OX-42-immunoreactive microglia, and expression of the cell death repressor gene bcl-2, investigated with nonradioactive in situ hybridization and immunohistochemistry, were evaluated in the facial nucleus. Daily phytohaemagglutinin injections for 4 days, mimicking repeated muscle exposure to inflammatory stimuli, resulted after 2-day survival in NADPH-diaphorase induction in motoneurons and marked activation of the surrounding microglia. Quantitative image analysis of NADPH-diaphorase staining, and OX-42 immunoreactivity and microglial cell counts indicated highly significant increases with respect to saline-injected control cases. The occurrence of a neuroprotective retrograde response was evaluated monitoring bcl-2 expression. Following single phytohaemagglutinin administration, bcl-2 mRNA was significantly upregulated at 6 h in facial motoneurons and returned to basal levels at 24 h. Bcl-2 immunoreactivity was markedly upregulated at 24 h and was still significantly higher than in controls at 7 days, when concomitant NADPH-diaphorase induction in motoneurons and microglia activation was also observed. No degenerative features were observed in motoneurons after phytohaemagglutinin injections at the examined time-points. The data point out that local muscle inflammation retrogradely elicits gene activation in motoneurons and their microenvironment.
authors: Department of Morphological and Biomedical Sciences, Section of Anatomy and Histology, Medical Faculty, Strada Le Grazie 8, 37134 Verona, Italy.
authors: R
authors: R
authors: Mariotti
authors: E
authors: E
authors: Tongiorgi
authors: C
authors: C
authors: Bressan
authors: M
authors: M
authors: Armellin
authors: K
authors: K
authors: Kristensson
authors: M
authors: M
authors: Bentivoglio
mesh_terms: D000818:Animals; D015703:Antigens, CD; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D030161:Avian Proteins; D051926:Basigin; D001798:Blood Proteins; D005154:Facial Nerve / Q000166:cytology / Q000276:immunology*; D015870:Gene Expression / Q000276:immunology; D008214:Lymphocytes / Q000276:immunology; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis; D017628:Microglia / Q000737:chemistry / Q000502:physiology; D009046:Motor Neurons / Q000737:chemistry / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000276:immunology* / Q000294:innervation*; D009220:Myositis / Q000139:chemically induced / Q000276:immunology / Q000503:physiopathology*; D009252:NADPH Dehydrogenase / Q000032:analysis; D019001:Nitric Oxide Synthase / Q000378:metabolism; D010835:Phytohemagglutinins; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015703:Antigens, CD; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D030161:Avian Proteins; D001798:Blood Proteins; C102624:Bsg protein, Gallus gallus; C079432:Bsg protein, rat; D008562:Membrane Glycoproteins; D010835:Phytohemagglutinins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051926:Basigin; D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase