Liver fibrosis occurs as a result of exposure to chronic stimuli (i.e., aforementioned etiologies) that cause insult to its architecture . Chronic stimuli cause progressive accumulation and decreased remodeling of the extracellular matrix which can result in fibrosis and progression to cirrhosis . The extracellular matrix transitions from a normal low-density basement-membrane type matrix to an interstitial type, which influences hepatocytes, hepatic stellate cells (HSCs), and endothelial cells . Activation of HSCs is a primary event in hepatic fibrosis . HSCs, found in the space of Disse storing vitamin A and retinoids, are activated by inflammatory cytokines such as platelet-derived growth factor, transforming growth factor-beta (TGF-β), tumor necrosis factor-α, and interleukin-1 . Their activation results in collagen and extracellular matrix deposition as well as their transformation into myofibroblasts . Additionally, defenestration of liver sinusoidal endothelial cells and their subsequent capillarization contribute to hepatocyte dysfunction . Kupffer cells, which are activated by injurious stimuli, also mediate inflammation, further stimulating injury and fibrosis . Apoptosis of the parenchymal cells of the liver (hepatocytes) promotes inflammation, fibrogenesis, and development of cirrhosis due to the release of reactive oxygen species and fibrogenic mediators, activation of HSCs, and stimulation of myofibroblasts . Hypoxic hepatocytes secrete TGF-β, which exacerbates fibrogenesis . Additionally, the extracellular matrix can amplify fibrosis  via changes in membrane receptors that oppose focal adhesion, activation of matrix matalloproteases to release fibrogenic and proliferative growth factors, and stiffening of the matrix .
3. Definition, Etiologies and Clinical Presentation
Cirrhosis can be subcategorized into compensated and decompensated cirrhosis based on prognostic stage . Patients can further be risk stratified by their Child-Turcotte-Pugh classification . This scoring system is based upon serum bilirubin, serum albumin, prothrombin time, ascites, and grade of encephalopathy . Compensated cirrhosis is generally asymptomatic but can be further categorized into those with mild portal hypertension versus those with clinically significant portal hypertension, in whom the hepatic venous pressure gradient is greater than 10 . Those with clinically significant disease are at risk of complications including ascites, encephalopathy, varices, variceal hemorrhage, postsurgical decompensation and hepatocellular carcinoma . Serum albumin, presence of gastroesophageal varices, and Model for End-Stage Liver Disease [MELD] are predictors of decompensation in these patients . Decompensated cirrhosis refers to those who possess one of these complications in the setting of cirrhosis . This classification is specifically relevant to treatment guidelines posed by the AASLD in terms of portal hypertensive bleeding . The MELD score is also used in determining prognosis in cirrhosis patients as well as in the allocation of donor organs for liver transplantation .
For those patients with spontaneous bacterial peritonitis (SBP), treatment includes the use of antibiotics as recommended by EASL and AASLD with chemoprevention thereafter to prevent recurrence [15,16]. Recommendations regarding management of hyponatremia include fluid restriction and use of vaptans in certain scenarios [15,16]. If a patient develops hepatorenal syndrome, EASL suggests specific monitoring parameters and potentially, drug therapy and renal replacement therapy; ultimately, EASL recommends liver transplantation . AASLD also recommends evaluation for liver transplantation for those with hepatorenal syndrome . For those who develop hepatic encephalopathy, lactulose is the recommended first-line agent as suggested by AASLD and EASL . Rifaximin is suggested to be added on to lactulose to prevent recurrence . Guidelines also exist in the management of portal hypertensive bleeding secondary to cirrhosis based on very specific classifications and parameters .
Brain 5-HT levels, measured 12 days after induction of hepatic failure, were increased in the brains of thioacetamide (TAA) mice and were restored by cannabidiol (CBD).
Female Sabra mice (34–36 g), 8 to 10 weeks old, were assigned at random to different groups of 10 mice per cage and were used in all experiments. All cages contained wood-chip bedding and were placed in a temperature-controlled room at 22°C, on a 12 h light/dark cycle (lights on at 07h00min). The mice had free access to water 24 h a day. The food provided was Purina chow and the animals were maintained in the animal facility (Specific Pathogen Free Organism unit) of the Hebrew University Hadassah Medical School, Jerusalem. Mice were killed after each treatment by decapitation between 10h00min and 12h00min. Animals were kept at the animal facility in accordance with NIH guidelines and all experiments were approved by the institutional animal use and care committee, No. MD-89.52-4.
Two days after the induction of hepatic failure, mice were killed by decapitation and brains were excised and fixed in 4% neutral-buffered paraformaldehyde.
All data are expressed as mean ± SEM. Statistical analysis was performed using one-way anova followed by Bonferroni’s post hoc test.
The levels of ammonia ( Figure 6A ), bilirubin ( Figure 6B ) and the liver enzymes AST ( Figure 6C ) and ALT ( Figure 6D ) were increased after TAA administration (ammonia: anova : F3,26= 156.93, P < 0.0001; Bonferroni: P < 0.01 vs. control; bilirubin: anova : F3,27= 34.99, P < 0.0001; Bonferroni: P < 0.01 vs. control; AST: anova : F3,27= 590.84, P < 0.0001; Bonferroni: P < 0.01 vs. control; ALT: anova : F3,27= 314.95, P < 0.0001; Bonferroni: P < 0.01 vs. control). CBD partially restored all of these indices in TAA-treated animals (P < 0.01 vs. TAA only for all parameters). CBD did not affect the levels of any of these substances in control animals.
Hepatic encephalopathy is a neuropsychiatric disorder of complex pathogenesis caused by acute or chronic liver failure. We investigated the effects of cannabidiol, a non-psychoactive constituent of Cannabis sativa with anti-inflammatory properties that activates the 5-hydroxytryptamine receptor 5-HT1A, on brain and liver functions in a model of hepatic encephalopathy associated with fulminant hepatic failure induced in mice by thioacetamide.
Liver histopathological analysis and scoring of necrosis (coagulative, centrilobular) were performed as described previously (Avraham et al., 2008a).
Figure 4 shows images of slices from brains of animals from the control group (A), control + CBD group (B), TAA group (C) and TAA + CBD group (D), immunostained for the detection of astrogliosis. Astrogliosis was observed in visual fields studied in TAA animals, as evident both by the increase in the number of GFAP-positive cells·mm −2 ( Figure 4E ; anova : F3,298= 26.8, P < 0.001; Bonferroni: P < 0.001) and by the increased % of GFAP-positive surface ( Figure 4F ; anova : F3,298= 19.21, P < 0.001; Bonferroni: P < 0.001). Both parameters were unaffected in CBD-treated controls ( Figure 4E and F ). However, the number of GFAP-positive cells·mm −2 in TAA + 5 mg·kg −1 CBD-treated animals was reduced compared to TAA-treated animals ( Figure 4E ; Bonferroni: P= 0.002). In contrast, CBD had no effect on the % of GFAP-positive surface in TAA animals ( Figure 4F ). Overall, it seems that TAA administration increased the number of activated astrocytes and CBD significantly reduced this effect. However, astrocytes in both CBD- and vehicle-treated TAA animals did not differ as regards their cellular size or extension of processes.
TAA significantly increased the neurological score of mice compared to the control group ( Figure 1 ; one-way anova : F3,29= 43.19, P < 0.0001; Bonferroni: P < 0.01). Administration of 5 mg·kg −1 CBD to TAA-treated mice improved the neurological score compared to TAA alone (1 ± 0.15; P < 0.01). CBD did not affect the score of the control animals.