Activation of guanylate cyclase C signaling pathway protects intestinal epithelial cells from acute radiation-induced apoptosis.
Uroguanylin (UGN) is a peptide hormone that binds to and activates the intestinal epithelial cell (IEC) transmembrane receptor guanylate cyclase C (GC-C), which in turn increases intracellular cGMP. Gene targeting of murine UGN or GC-C results in significantly lower levels of cGMP in IECs. On the basis of effects of cGMP in nonintestinal systems, we hypothesized that loss of GC-C activation would increase intestinal epithelial apoptosis following radiation-induced injury. We first compared apoptosis from the proximal jejunum of C57BL/6 wild-type (WT) and GC-C knockout (KO) mice 3 h after they received 5 Gy of gamma-irradiation. We then investigated whether supplementation via intraperitoneal injection of 1 mM 8BrcGMP would mitigate radiation-induced apoptosis in these experimental animals. Identical experiments were performed in BALB/c UGN WT and KO mice. Apoptosis was assessed by quantitating morphological indications of cell death, terminal dUTP nick-end labeling, and cleaved caspase 3 immunohistochemistry. Both UGN KO and GC-C KO mice were more susceptible than their WT littermates in this in vivo model of apoptotic injury. Furthermore, cGMP supplementation in both GC-C and UGN KO animals ameliorated radiation-induced apoptosis. Neither WT strain demonstrated significant alteration in apoptotic susceptibility as a result of cGMP supplementation before radiation injury. These in vivo findings demonstrate increased radiosensitivity of IECs in UGN and GC-C KO mice and a role for cGMP as a primary downstream mediator of GC-C activation in the protection of these IECs from radiation-induced apoptosis.
Garin-Laflam
M P
MP
Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, and University of Cincinnati, MLC 2010, 3333 Burnet Ave., Cincinnati, OH 45229-3039, USA.
Steinbrecher
K A
KA
Rudolph
J A
JA
Mao
J
J
Cohen
M B
MB
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D006152:Cyclic GMP / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects* / Q000528:radiation effects*; D005260:Female; D005720:Gamma Rays / Q000009:adverse effects; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D045265:Natriuretic Peptides / Q000235:genetics / Q000378:metabolism; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013047:Specific Pathogen-Free Organisms
D045265:Natriuretic Peptides; D018000:Receptors, Peptide; C084362:uroguanylin; D006162:Guanylate Cyclase; C000613655:Gucy2c protein, mouse; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D006152:Cyclic GMP