Hepatic expression of endocannabinoid receptors and their novel  polymorphisms in primary biliary cirrhosis.
BACKGROUND
The endocannabinoid system (EC) has emerged as a crucial mediator in a variety of pathophysiological conditions.


OBJECTIVE
To evaluate: (1) whether the EC system is activated in the livers of patients with primary biliary cirrhosis (PBC); (2) if genetic variations in human EC receptor genes (CB1 and CB2) may be associated with a different phenotypic expression of the disease and response to therapy.


METHODS
The expression of CB1 and CB2 receptors was studied by immunohistochemistry in liver biopsy specimens from 13 patients with PBC, and CB1 and CB2 mRNA expression was studied by real-time polymerase chain reaction testing (RT-PCR) in liver samples. In addition, genetic polymorphisms in the EC receptor gene were sought in 68 patients with PBC from Italy, 84 patients who were residents of the United States (US), and 70 controls matched for sex, age, and for geographical area with the Italian PBC patients. Genomic DNA was extracted from peripheral venous blood leucocytes with standard methods. PCR was used to amplify the coding regions of the CB1 and CB2 genes with specific primers.


RESULTS
CB1 was markedly expressed in hepatocytes and biliary epithelial cells in the livers of patients with PBC; conversely in control liver samples, it was virtually absent. CB2 was expressed in hepatocytes and in cholangiocytes, whereas it was absent from mesenchymal cells. The mRNA of both CB1 and CB2 was detected in the PBC liver samples, as demonstrated by RT-PCR. The CB1 polymorphism (1359 G/A) was present in 26.5% of Italian patients, in 22.9% of healthy controls, and in 27.4% of patients from the US (p = n.s.). The CB2 polymorphism (188-189 AA/GG) was present in 24.4 versus 30.4% of Italian and US patients with PBC, respectively, and in 28.0% of Italian controls samples (p = n.s.). Logistic regression analysis showed that advanced histological stage and the lack of response to ursodeoxycholic acid treatment were significantly correlated with the CB1 polymorphism.


CONCLUSIONS
The EC system is markedly up-regulated in the livers of patients with PBC and it may exert a role regulating adaptive mechanisms in cholestasis.
Floreani
Annarosa
A
Department of Surgical and Gastroenterological Sciences, University of Padua, Via Giustiniani, 2, 35128 Padua, Italy. annarosa.floreani@unipd.it
Lazzari
Roberta
R
Macchi
Veronica
V
Porzionato
Andrea
A
Variola
Angela
A
Colavito
Davide
D
Leon
Alberta
A
Guido
Maria
M
Baldo
Vincenzo
V
De Caro
Raffaele
R
Bergasa
Nora V
NV
D000328:Adult; D000368:Aged; D001706:Biopsy; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007558:Italy; D008099:Liver / Q000166:cytology / Q000473:pathology*; D008105:Liver Cirrhosis, Biliary / Q000235:genetics* / Q000473:pathology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D011446:Prospective Studies; D012333:RNA, Messenger / Q000378:metabolism; D043884:Receptor, Cannabinoid, CB1 / Q000235:genetics*; D043885:Receptor, Cannabinoid, CB2 / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014481:United States; D015854:Up-Regulation
D012333:RNA, Messenger; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2