Lysophosphatidic acid protects and rescues intestinal epithelial cells from radiation- and chemotherapy-induced apoptosis.
OBJECTIVE
We have investigated whether the phospholipid growth factor lysophosphatidic acid (LPA) could prevent intestinal epithelial cells-6 (IEC-6) from apoptosis elicited by 4 different mechanisms. The antiapoptotic effect of LPA was also tested in a mouse model of radiation-induced apoptosis.


METHODS
Apoptosis was elicited by serum withdrawal, exposure to camptothecin, gamma-irradiation, or rat tumor necrosis factor alpha and evaluated by DNA fragmentation enzyme-linked immunosorbent assay (ELISA) and annexin V staining. Caspase-3/CPP32 activity and activation was measured by ELISA and Western blotting, respectively. Reverse-transcription polymerase chain reaction (RT-PCR) was applied to examine the expression of LPA-receptor transcripts. Mice were treated with 250 microL of 1 mmol/L LPA and exposed to whole-body gamma-irradiation with a dose of 12 or 15 Gy and the number and localization of apoptotic bodies along the crypt were recorded.


RESULTS
LPA pretreatment reduced DNA fragmentation induced in all models of apoptosis. LPA rescued cells from apoptosis when applied up to 1 hour after camptothecin treatment or 2 hours after irradiation. LPA inhibited the activation of caspase-3/CPP32 and attenuated its activity. Blocking LPA1 receptors by pertussis toxin and the inhibition of epithelial growth factor receptor tyrosine kinase significantly attenuated the protective effect. In irradiated mice, oral LPA significantly reduced the number of apoptotic bodies in the crypt.


CONCLUSIONS
(1) LPA prevents and rescues IEC-6 from apoptosis elicited by 4 different mechanisms. (2) This antiapoptotic activity is mediated through LPA1 and LPA2 receptors through the inhibition of caspase-3/CPP32 activation. (3) LPA protects enterocytes against radiation-induced apoptosis. This study suggests that in patients undergoing cancer therapy, dietary LPA might have therapeutically useful antiapoptotic capacity in the intestinal epithelium.
Deng
Wenlin
W
Department of Physiology, University of Tennessee Health Sciences Center, Memphis, Tennessee 38163, USA.
Balazs
Louisa
L
Wang
De-An
DA
Van Middlesworth
Lester
L
Tigyi
Gabor
G
Johnson
Leonard R
LR
D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002166:Camptothecin / Q000494:pharmacology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D066246:ErbB Receptors / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology; D005720:Gamma Rays; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects*; D008246:Lysophospholipids / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D011956:Receptors, Cell Surface / Q000502:physiology; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000502:physiology
D000972:Antineoplastic Agents, Phytogenic; D061945:Caspase Inhibitors; D008246:Lysophospholipids; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D014409:Tumor Necrosis Factor-alpha; D014443:Tyrosine; D066246:ErbB Receptors; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D019204:GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; D002166:Camptothecin