s A.I.S.F. Annual Meeting (Rome, February 25th−26th, 2010) / Digestive and Liver Disease 42 Suppl. 1 (2010) S1–S51 S17 T.N.6 INTRAHEPATIC RENIN-ANGIOTENSIN SYSTEM AND LIVER CIRRHOSIS: AN UPDATED REAPPRAISAL G. Sansoe1, M. Aragno2, C. Tomasinelli2, R. Mastrocola2, M. Parola2. Division of Gastroenterology, Gradenigo Hospital, Torino, Italy.; Department of Experimental Medicine and Oncology, University of Torino, Italy The concentrations of angiotensin II are 100-fold higher in renal, hepatic and myocardial tissue fluids than in the systemic circulation, due to local production of this hormone. 90% of this huge amount of tissue angiotensin II is not produced by ACE. Instead, angiotensin II in the above organs is produced by means of chymase (a membrane-bound enzyme) from circulating angiotensin I [1]. Another newly described enzyme (ACE2) degrades angiotensin II (composed of 8 aminoacids) into angiotensin-(1−7). Angiotensin II is a vasoconstrictor and stimulates fibrogenesis, but angiotensin-(1−7) is a strong vasodilator and inhibits fibrogenesis [2]. Moreover, chymase generates also endothelin-1 from precursors (big-endothelin and endothelin1−31) and activates TGF-beta. Both endothelin-1 and TGFbeta are fibrogenic agents in the cirrhotic liver. This study aims at evaluating the content of chymase, ACE and ACE2 inside the livers of normal rats (n = 5) and rats with CCl4-induced liver cirrhosis (n = 5) by means of quantitative western blotting. Normal and cirrhotic liver slices were also submitted to immuno-histochemistry studies in order to identify the location of these enzymes. Finally, normal and cirrhotic liver samples were studied by means of HPLC in order to determine tissue fluid concentrations of angiotensin II and angiotensin-(1−7). In cirrhotic liver samples we found out a marked over-expression of chymase and ACE (all P< 0.01) and, to a lesser extent, also of ACE2 (P< 0.05). In normal liver, concentrations of angiotensin II and angiotensin-(1−7) were similar (below 50 pg/ml); conversely, cirrhotic liver tissue showed increased concentrations of angiotensin II (1400±380 pg/ml) and of angiotensin-(1−7) (260±110 pg/ml). In other words, in cirrhotic liver the ratio between angiotensin II and angiotensin-(1−7) was five times higher than in control liver, arguably contributing to fibrogenesis. The reason for a preferential production of tissue angiotensin II inside the cirrhotic liver is the concurrently increased content of ACE and chymase, with respect to a smaller over-expression of the sole ACE2. These data indicate modulation of the chymase/ACE2 system seems promising in order to alter the process of fibrogenesis in chronic liver diseases.
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