Aging gastropathy-novel mechanisms: hypoxia, up-regulation of multifunctional phosphatase PTEN, and proapoptotic factors.
OBJECTIVE
Aging gastric mucosa has impaired mucosal defense and increased susceptibility to injury. Our aims were to determine the mechanisms responsible for above abnormalities.


METHODS
We used Fisher F-344 rats, 3 and 24 months of age. We measured gastric mucosal blood flow; visualized mucosal hypoxia; examined expression of early growth response-1 transcription factor and phosphatase and tensin homologue deleted on chromosome 10 (PTEN); assessed apoptosis; and determined expression of caspase-3, caspase-9, and survivin. We also examined susceptibility of gastric mucosa of young and aging rats to ethanol injury and whether down-regulation of PTEN affects susceptibility of aging gastric mucosa to injury. To determine human relevance, we examined expression of PTEN and survivin in human gastric specimens of young and aging individuals.


RESULTS
Gastric mucosa of aging (vs young) rats has a 60% reduction in mucosal blood flow; prominent hypoxia; and increased early growth response-1 transcription factor and PTEN messenger RNAs, and proteins. It also has increased expression of proapoptotic proteins caspase-3 and capase-9, reduced survivin, and a 6-fold increased apoptosis vs mucosa of young rats. Ethanol-induced gastric mucosal injury in aging (vs young) rats was significantly increased. The down-regulation of PTEN in gastric mucosa of aging rats completely reversed its increased susceptibility to ethanol injury. In aging human gastric mucosa, PTEN expression was significantly increased, whereas survivin was significantly reduced.


CONCLUSIONS
(1) Gastric mucosa of aging rats has significantly reduced blood flow, tissue hypoxia, activation of Egr-1, PTEN; increased caspases; and reduced survivin. (2) These changes increase susceptibility of aging gastric mucosa to injury.
Tarnawski
Andrzej
A
Department of Medicine, VA Long Beach Healthcare System and the University of California, Irvine, California, USA. atarnawski@yahoo.com
Pai
Rama
R
Deng
Xiaoming
X
Ahluwalia
Amrita
A
Khomenko
Tetyana
T
Tanigawa
Tetsuya
T
Akahoshi
Tomohiko
T
Sandor
Zsuzsanna
Z
Szabo
Sandor
S
D000375:Aging / Q000502:physiology*; D000818:Animals; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000378:metabolism; D005753:Gastric Mucosa / Q000098:blood supply / Q000503:physiopathology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D013272:Stomach Diseases / Q000503:physiopathology*; D000077022:Survivin; D015854:Up-Regulation
C516989:Birc5 protein, rat; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D008869:Microtubule-Associated Proteins; D000077022:Survivin; D051059:PTEN Phosphohydrolase; D020169:Caspases