Glial-derived neurotrophic factor modulates enteric neuronal survival and proliferation through neuropeptide Y.
OBJECTIVE
Glial-derived neurotrophic factor (GDNF) promotes the survival and proliferation of enteric neurons. Neuropeptide Y (NPY) is an important peptide regulating gastrointestinal motility. The role of NPY on the survival and proliferation of enteric neurons is not known. We examined the effects of GDNF on the expression and release of NPY from enteric neurons and the role of NPY in promoting enteric neuronal proliferation and survival.


METHODS
Studies were performed in primary enteric neuronal cultures and NPY knockout mice (NPY(-/-)). GDNF-induced expression of NPY was assessed by reverse-transcription polymerase chain reaction (RT-PCR), immunocytochemistry, and enzyme-linked immunosorbent assay. Using NPY-siRNA and NPY-Y1 receptor antagonist, we examined the role of NPY in mediating the survival and proliferation effects of GDNF. Gastrointestinal motility was assessed by measuring gastric emptying, intestinal transit, and isometric muscle recording from intestinal muscle strips.


RESULTS
GDNF induced a significant increase in NPY messenger RNA and protein expression in primary enteric neurons and the release of NPY into the culture medium. NPY (1 mumol/L) significantly increased proliferation of neurons and reduced apoptosis. In the presence of NPY-siRNA and NPY-Y1 receptor antagonist or in enteric neurons cultured from NPY(-/-) mice, GDNF-mediated neuronal proliferation and survival was reduced. NPY increased the phosphorylation of Akt, a downstream target of the PI-3-kinase pathway. In NPY(-/-) mice, there were significantly fewer nNOS-containing enteric neurons compared with wild-type (WT) mice. NPY(-/-) mice had accelerated gastric emptying and delayed intestinal transit compared with WT mice.


CONCLUSIONS
We demonstrate that NPY acts as an autocrine neurotrophic factor for enteric neurons.
Anitha
Mallappa
M
Division of Digestive Diseases, Emory University, Whitehead Research Building, 615 Michael Street, Atlanta, GA 30322, USA.
Chandrasekharan
Bindu
B
Salgado
Joana R
JR
Grouzmann
Eric
E
Mwangi
Simon
S
Sitaraman
Shanthi V
SV
Srinivasan
Shanthi
S
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005746:Gastric Emptying / Q000502:physiology; D005769:Gastrointestinal Motility / Q000502:physiology; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000378:metabolism* / Q000494:pharmacology; D007422:Intestines / Q000294:innervation / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009025:Morpholines / Q000494:pharmacology; D009126:Muscle Relaxation / Q000502:physiology; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology; D009197:Myenteric Plexus / Q000166:cytology* / Q000502:physiology*; D009474:Neurons / Q000166:cytology*; D009478:Neuropeptide Y / Q000235:genetics / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017476:Receptors, Neuropeptide Y / Q000037:antagonists & inhibitors / Q000378:metabolism
D002867:Chromones; D004791:Enzyme Inhibitors; D051100:Glial Cell Line-Derived Neurotrophic Factor; D009025:Morpholines; D009478:Neuropeptide Y; D052248:Nitric Oxide Synthase Type I; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D017476:Receptors, Neuropeptide Y; C097212:neuropeptide Y-Y1 receptor; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C496321:Nos1 protein, mouse