Purinergic P2Y2 receptors promote hepatocyte resistance to hypoxia.
OBJECTIVE
ATP stimulation of purinergic P2 receptors (P2YR and P2XR) regulates several hepatic functions. Here we report the involvement of ATP-mediated signals in enhancing hepatocyte tolerance to lethal stress.


METHODS
The protection given by purinergic agonists was investigated in rat hepatocytes exposed to hypoxia.


RESULTS
ATP released after hypotonic stress (200 mOsm/L) as well as P2YR agonists prevented hepatocyte killing by hypoxia with efficiency ranking UTP > ATPgammaS > ADPbetaS, whereas the P2XR agonist, methylene-adenosine-5'-triphosphate, was ineffective. Adenosine-5'-O-3-thiotriphosphate (ATPgammaS; 100 micromol/L) also prevented Na+ -overload in hypoxic cells by inhibiting the Na+/H+ exchanger, without interfering with hypoxic acidosis. ATPgammaS activated Src and promoted a Src-dependent stimulation of both ERK1/2 and p38MAPK. Blocking p38MAPK with SB203580 reverted the protection given by ATPgammaS on both cell viability and Na+ accumulation, whereas ERK1/2 inhibition with PD98058 was ineffective. An increased phosphorylation of ERK1/2 was also evident in untreated hypoxic hepatocytes. PD98058 ameliorated Na+ accumulation and cell death caused by hypoxia. Hepatocyte pre-treatment with ATPgammaS reverted ERK1/2 activation in hypoxic cells. SB203580 blocked the effects of ATPgammaS on both ERK1/2 and Na+/H+ exchanger.


CONCLUSIONS
The activation of p38MAPK by P2Y2R increases hepatocyte resistance to hypoxia by down-modulating ERK1/2-mediated signals that promote Na+ influx through the Na+/H+ exchanger.
Carini
Rita
R
Department of Medical Sciences, University A. Avogadro of East Piedmont, Novara, Italy. carini@med.unipmn.it
Alchera
Elisa
E
De Cesaris
Maria Grazia
MG
Splendore
Roberta
R
Piranda
Daniela
D
Baldanzi
Gianluca
G
Albano
Emanuele
E
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000345:Affinity Labels / Q000494:pharmacology; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D004195:Disease Models, Animal; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology; D000860:Hypoxia / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009930:Organic Chemicals / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000378:metabolism*; D058473:Receptors, Purinergic P2Y2; D015427:Reperfusion Injury / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D015398:Signal Transduction / Q000187:drug effects; D012964:Sodium / Q000378:metabolism
D000345:Affinity Labels; D009930:Organic Chemicals; C546387:P2ry2 protein, rat; C466090:PD 98058; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate; D012964:Sodium