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Cancer- Liver / Medical Cannabis
#1


[Image: 1-s2.0-S0163725810000069-gr1.jpg]







Emerging role of cannabinoids in gastrointestinal and liver diseases: basic and clinical aspects

A A Izzo1, M Camilleri2

1 Department of Experimental Pharmacology, University of Naples Federico II and Endocannabinoid Research Group, Naples, Italy

2 Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA





Correspondence to:

Professor A A Izzo, Department of Experimental Pharmacology, University of Naples Federico II, via D Montesano 49, 80131, Naples, Italy; aaizzo@unina.it





ABSTRACT

A multitude of physiological effects and putative pathophysiological roles have been proposed for the endogenous cannabinoid system in the gastrointestinal tract, liver and pancreas. These range from effects on epithelial growth and regeneration, immune function, motor function, appetite control, fibrogenesis and secretion. Cannabinoids have the potential for therapeutic application in gut and liver diseases. Two exciting therapeutic applications in the area of reversing hepatic fibrosis as well as antineoplastic effects may have a significant impact in these diseases. This review critically appraises the experimental and clinical evidence supporting the clinical application of cannabinoid receptor-based drugs in gastrointestinal, liver and pancreatic diseases. Application of modern pharmacological principles will most probably expand the selective modulation of the cannabinoid system peripherally in humans. We anticipate that, in addition to the approval in several countries of the CB1 antagonist, rimonabant, for the treatment of obesity and associated metabolic dysfunctions, other cannabinoid modulators are likely to have an impact on human disease in the future, including hepatic fibrosis and neoplasia.



SOURCE: http://gut.bmj.com/c...tract/57/8/1140












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<strong>Cannabinoid 1 and Ulcerative Colitis and the Phenotype in Crohn's Disease </strong>

The Cannabinoid 1 Receptor (CNR1) 1359 G/A Polymorphism Modulates Susceptibility to Ulcerative Colitis and the Phenotype in Crohn's Disease

Martin Storr,1* Dominik Emmerdinger,2 Julia Diegelmann,2 Simone Pfennig,2 Thomas Ochsenkhn,2 Burkhard Gke,2 Peter Lohse,3 and Stephan Brand2

1Division of Gastroenterology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada

2Department of Medicine II Grosshadern, Ludwig-Maximilians-University Munich, Munich, Germany

3Department of Clinical Chemistry Grosshadern, Ludwig-Maximilians-University Munich, Munich, Germany

Syed A. Aziz, Editor

Health Canada, Canada

* E-mail: mstorr@ucalgary.ca

Conceived and designed the experiments: MS JD TO BG PL SB. Performed the experiments: DE. Analyzed the data: MS DE JD SP PL SB. Contributed reagents/materials/analysis tools: MS TO BG PL. Wrote the paper: MS SB.

Received January 15, 2010; Accepted January 27, 2010.

This article has been cited by other articles in PMC.



Abstract



Background



Recent evidence suggests a crucial role of the endocannabinoid system, including the cannabinoid 1 receptor (CNR1), in intestinal inflammation. We therefore investigated the influence of the CNR1 1359 G/A (p.Thr453Thr; rs1049353) single nucleotide polymorphism (SNP) on disease susceptibility and phenotype in patients with ulcerative colitis (UC) and Crohn's disease (CD).



Methods



Genomic DNA from 579 phenotypically well-characterized individuals was analyzed for the CNR1 1359 G/A SNP. Amongst these were 166 patients with UC, 216 patients with CD, and 197 healthy controls.



Results



Compared to healthy controls, subjects A/A homozygous for the CNR1 1359 G/A SNP had a reduced risk to develop UC (p=0.01, OR 0.30, 95% CI 0.120.78). The polymorphism did not modulate CD susceptibility, but carriers of the minor A allele had a lower body mass index than G/G wildtype carriers (p=0.0005). In addition, homozygous carriers of the G allele were more likely to develop CD before 40 years of age (p=5.9107) than carriers of the A allele.



Conclusion



The CNR1 p.Thr453Thr polymorphism appears to modulate UC susceptibility and the CD phenotype. The endocannabinoid system may influence the manifestation of inflammatory bowel diseases, suggesting endocannabinoids as potential target for future therapies.












Introduction



Anecdotal reports suggest that marijuana- or tetrahydrocannabinol-containing products may be effective in alleviating symptoms in patients with ulcerative colitis (UC) and Crohn's disease (CD). [1], [2] This is supported by recent studies of our group and others suggesting that pharmacological activation of the cannabinoid 1 (CB1) receptor with selective receptor agonists decreases the inflammatory response in various murine models of colonic inflammation including dinitrobenzene sulphonic acid (DNBS)-, trinitrobenzene sulphonic acid (TNBS)- and dextran sodium sulfate (DSS)-induced colitis. [3][7]



Interestingly, pharmacological blockade of CB1 receptors or genetic ablation of CB1 receptors (CNR1/ mice) aggravates intestinal inflammation in these models, [3], [7] emphasizing the physiological relevance of the CB1 receptor in the protection against intestinal inflammation. Increased mucosal levels of the endocannabinoid anandamide during intestinal inflammation in humans further stress the role of the CB1 receptor and the endocannabinoid system in intestinal inflammation. [4] Thus, present knowledge suggests up-regulation of endocannabinoids as an important protective mechanism in intestinal inflammation.



The endocannabinoid system and the CB1 and CB2 receptors seem to be crucially involved in the regulation of multiple physiological functions, e.g. in the heart, where they relax coronary arteries and decrease cardiac work, [8] in organ perfusion, [9] in metabolic homeostasis, [10], [11] and in the regulation of bone mass by osteoclasts, [12] as well as in the protection against stress responses, inflammation, and associated repair mechanisms. [13], [14] Although recent evidence suggests that the endocannabinoid system is involved in many physiological and pathophysiological functions of the gastrointestinal tract such as intestinal motility, secretion, and intestinal inflammation [3], [15][20], the exact mechanisms underlying these findings are not yet known. It was recently suggested that CB1 signaling may be up-regulated during colitis, [3] but it is unknown whether this is a specific feature of the colitis model or a general response to intestinal inflammation.



Moreover, the role of the CB1 receptor in human inflammatory bowel disease (IBD) has not been clarified. Increased anandamide levels were found in mucosal biopsies from UC patients, suggesting a role of the endocannabinoid system in UC. [4] In contrast, the colonic exp<b></b>ression of the endocannabinoid 2-acyl-glycerol (2-AG) is not increased in UC. [4] So far, however, no other studies analyzing the endocannabinoid system or the pharmacological effects of cannabinoids in human IBD have been published.



Gastrointestinal inflammation is likely the result of multiple factors, e.g., increased pro-inflammatory stimuli and reduced protective capability. The overall balance between pro- and anti-inflammatory mechanisms may determine the progression and severity of intestinal inflammation. [21], [22] Given the results of recent genome-wide association studies, [23] genetic susceptibility is an important factor contributing to IBD development. Moreover, knowledge of genetic susceptibility factors could provide important pathophysiologic insights for the generation of novel IBD therapeutics.



Considering our previous work on the endocannabinoid system in murine intestinal inflammation, [3], [6], [7], [24] we hypothesized that genetic variants in the CNR1 gene, which may modulate CB1 receptor function, could be associated with an increased susceptibility to IBD. To test our hypothesis, we genotyped a cohort of more than 550 individuals including 382 IBD patients and analyzed whether the 1359 G/A (p.Thr453Thr; rs1049353) single nucleotide polymorphism (SNP) within the CNR1 gene encoding the CB1 receptor modulates the susceptibility to CD and UC or results in a certain IBD phenotype. The selection of the CNR1 1359 G/A SNP was based on previous studies reporting that this polymorphism is associated with other disorders modulated by the endocannabinoid system such as alcohol dependence and hebephrenic schizophrenia. [25], [26]









Methods













<strong>Cannabinoids ameliorate cerebral dysfunction following liver failure </strong><strong>via</strong><strong> AMP-activated protein kinase </strong>



Abstract

Hepatic encephalopathy (HE) is a neuropsychiatric disorder of complex pathogenesis caused by acute or chronic liver failure. We studied the etiology of cerebral dysfunction in a murine model of HE induced by either bile duct ligation or thioacetamide administration. We report that stimulation of cerebral AMP-activated protein kinase (AMPK), a major intracellular energy sensor, is a compensatory response to liver failure. This function of AMPK is regulated by endocannabinoids. The cannabinoid system controls systemic energy balance via the cannabinoid receptors CB-1 and CB-2. Under normal circumstances, AMPK activity is mediated by CB-1 while CB-2 is barely detected. However, CB-2 is strongly stimulated in response to liver failure. Administration of 9-tetrahydrocannabinol (THC) augmented AMPK activity and restored brain function in WT mice but not in their CB-2 KO littermates. These results suggest that HE is a disease of energy flux. CB-2 signaling is a cerebral stress response mechanism and makes AMPK a promising target for its treatment by modulating the cannabinoid system.Dagon, Y., Avraham, Y., Ilan, Y., Mechoulam, R., Berry, E. M. Cannabinoids ameliorate cerebral dysfunction following liver failure via AMP-activated protein kinase.











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#2


Role of cannabinoids In Chronic Liver Diseases





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#3


LIVER DISEASE - NON HEPATITIS - also see HEPATITIS





Reference links provided Granny Storm Crow






LIVER DISEASE - NON HEPATITIS

-
a

lso see

HEPATITIS







HEMP AS A MEDICAMENT : Importance of hemp seeds in the tuberculosis therapy (full- 1955) (EDEZYME recipe)

http://www.greenpassion.org/showthre...753#post306753







A Novel Synthetic Cannabinoid Derivative Inhibits Inflammatory Liver Damage via Negative Cytokine Regulation (full - 2003)

http://molpharm.aspetjournals.org/co...64/6/1334.full







The endocannabinoid system in chronic liver disease (full - 2005)




http://www.medigraphic.com/pdfs/hepa...005/ah054c.pdf







(Marijuana/Hash) Endocannabinoids and liver disease - review (full - 2005)




http://www.natap.org/2005/HCV/091905_01.htm







Endocannabinoid activation at hepatic CB1 receptors stimulates fatty acid synthesis and contributes to diet-induced obesity (full - 2005)

http://www.ncbi.nlm.nih.gov/pmc/arti...tool=pmcentrez







Cannabinoid-2 receptor agonist HU-308 protects against hepatic ischemia/reperfusion injury by attenuating oxidative stress, inflammatory response, and apoptosis (full - 2007)

http://www.jleukbio.org/cgi/content/full/82/6/1382







Cannabinoids ameliorate cerebral dysfunction following liver failure via AMP- activated protein kinase




(full - 2007)




http://hmg.oxfordjournals.org/cgi/co...ull/14/22/3389







Endocannabinoids acting at CB1 receptors mediate the cardiac contractile dysfunction in vivo in cirrhotic rats (full - 2007)

http://www.ncbi.nlm.nih.gov/pmc/arti...tool=pmcentrez







P

ivotal Advance: Cannabinoid-2 receptor agonist HU-308 protects against hepatic ischemia/reperfusion injury by attenuating oxidative stress, inflammatory




response, and apoptosis (full - 2007)




http://www.ncbi.nlm.nih.gov/pmc/arti...tool=pmcentrez







Endocannabinoids and Liver Disease. I. Endocannabinoids and their receptors in the liver (full - 2007)




http://ajpgi.physiology.org/cgi/content/full/294/1/G9







CB2 receptors as new therapeutic targets for liver diseases (full - 2007)




http://www.ncbi.nlm.nih.gov/pmc/arti...1/?tool=pubmed







Cannabinoid-2 receptor mediates protection against hepatic ischemia/reperfusion injury (full - 2007)

http://www.ncbi.nlm.nih.gov/pmc/arti...tool=pmcentrez







Cannabinoid receptors as new targets of antifibrosing strategies during chronic liver diseases. (abst - 2007)




http://www.ncbi.nlm.nih.gov/pubmed/17952109







Cannabinoid receptors as novel therapeutic targets for the management of non- alcoholic steatohepatitis (full - 2008)




http://www.em-consulte.com/article/200095







Regression of Fibrosis after Chronic Stimulation of Cannabinoid CB2 Receptor in Cirrhotic Rats (full - 2008)

http://jpet.aspetjournals.org/content/324/2/475.full?maxtoshow=&hits=80&RESULTFORMAT=




&fulltext=cannabinoid&searchid=1&FIRSTINDEX=320&re sourcetype=HWCIT#content -block







CB2 receptors as new therapeutic targets for liver diseases. (full - 2008)




http://www.ncbi.nlm.nih.gov/pmc/arti...1/?tool=pubmed







Endocannabinoids and Liver Disease. III. Endocannabinoid effects on immune cells: implications for inflammatory liver diseases (full - 2008)

http://www.ncbi.nlm.nih.gov/pmc/arti...tool=pmcentrez







Endocannabinoids and Liver Disease. IV. Endocannabinoid involvement in obesity and hepatic steatosis (full - 2008)

http://ajpgi.physiology.org/cgi/cont...ll/294/5/G1101







Endocannabinoids and cannabinoid receptors in ischaemiareperfusion injury and preconditioning (full - 2008)

http://www.ncbi.nlm.nih.gov/pmc/arti...tool=pmcentrez







Cannabinoids and capsaicin improve liver function following thioacetamide- induced acute injury in mice. (abst - 2008)

http://www.ncbi.nlm.nih.gov/pubmed/19086956







The endocannabinoid system as a novel target for the treatment of liver fibrosis




(abst - 2008)




http://www.ncbi.nlm.nih.gov/pubmed/17412522







Emerging role of cannabinoids in gastrointestinal and liver diseases: basic and clinical aspects (abst - 2008)




http://gut.bmj.com/content/57/8/1140.abstract







Cannabinoid CB2 Receptor Potentiates Obesity-Associated Inflammation, Insulin Resistance and Hepatic Steatosis (full - 2009)

http://www.ncbi.nlm.nih.gov/pmc/arti...0/?tool=pubmed







S

y

stematic review and meta-analysis on the adverse events of rimonabant treatment: Considerations for its potential use in hepatology (full - 2009)

http://www.biomedcentral.com/1471-230X/9/75







Cannabinoids as novel anti-inflammatory drugs. (full - 2009)




http://www.ncbi.nlm.nih.gov/pmc/arti...4/?tool=pubmed







B

e

neficial effects of a Cannabis sativa extract treatment on diabetes-induced neuropathy and oxidative stress. (abst - 2009)

http://www.unboundmedicine.com/medli...1010/abstract/







Cannabidiol ameliorates cognitive and motor impairments in mice with bile duct ligation. (abst - 2009)

http://www.unboundmedicine.com/medline/ebm/record/19596476/abstract/Cannabidiol_ameliorat


es_cognitive_and_motor_impairments_in_mice_with_bi le_duct_ligation_







S

c

ience: Oral intake of a cannabinoid together with a meal improved bioavailability by avoiding first-pass metabolism (abst. - 2009)

http://www.cannabis-med.org/english/...l.php?id=291#2







Recent advances in the understanding of the role of the endocannabinoid system in liver diseases. (abst - 2010)




http://www.ncbi.nlm.nih.gov/pubmed/20934397


Reply
#4

  • Recent advances in basic science


Emerging role of cannabinoids in gastrointestinal and liver diseases: basic and clinical aspects



<ol style="list-style-type: decimal">
[*]
A A Izzo1,
[*]
M Camilleri2

</ol>
+ Author Affiliations





<ol style="list-style-type: decimal">
[*][/url]<sup>1</sup>Department of Experimental Pharmacology, University of Naples Federico II and Endocannabinoid Research Group, Naples, Italy
[*]
[url=]Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA

</ol>


<ol style="list-style-type: decimal">[*]
[url=]Professor A A Izzo, Department of Experimental Pharmacology, University of Naples Federico II, via D Montesano 49, 80131, Naples, Italy;
[url=mailto:aaizzo@unina.it]aaizzo@unina.it
</ol>



[url=]Abstract


[url=]<sub>1</sub>

[url=]




[url=]




[url=]




[url=]




[url=]


[url=]Cannabinoid Hyperemesis and Compulsive Bathing: A Case Series and Paradoxical Pathophysiological Explanation[/url]



<ol style="list-style-type: decimal">
[*]
[url=]Dale A. Patterson

[*]
[url=]EmmaLeigh Smith

[*]
[url=]Mark Monahan

[*]
[url=]Andrew Medvecz

[*]
[url=]Beth Hagerty

[*]
[url=]Lisa Krijger

[*]
[url=]Aakash Chauhan

[*]
[url=]Mark Walsh

</ol>


[url=]Case Reports




[url=]Patient 1


[url=]Heliobacter pylori

[url=]




[url=]




[url=]Patient 2


[url=]H. pylori

[url=]




[url=]




[url=]




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[url=]Patient 3




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[/url][url=]More



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Reply
#5
<strong>Capsaicin affects brain function in a model of hepatic encephalopathy associated with fulminant hepatic failure in mice</strong>



Background and purpose:

Hepatic encephalopathy is a neuropsychiatric syndrome caused by liver failure. In view of the effects of cannabinoids in a thioacetamide-induced model of hepatic encephalopathy and liver disease and the beneficial effect of capsaicin (a TRPV1 agonist) in liver disease, we assumed that capsaicin may also affect hepatic encephalopathy.





Experimental approach:

Fulminant hepatic failure was induced in mice by thioacetamide and 24 h later, the animals were injected with one of the following compound(s): 2-arachidonoylglycerol (CB<sub>1</sub>, CB<sub>2</sub> and TRPV1 receptor agonist); HU308 (CB<sub>2</sub> receptor agonist), SR141716A (CB<sub>1</sub> receptor antagonist); SR141716A+2-arachidonoylglycerol; SR144528 (CB<sub>2</sub> receptor antagonist); capsaicin; and capsazepine (TRPV1 receptor agonist and antagonist respectively). Their neurological effects were evaluated on the basis of activity in the open field, cognitive function in an eight-arm maze and a neurological severity score. The mice were killed 3 or 14 days after thioacetamide administration. 2-arachidonoylglycerol and 5-hydroxytryptamine (5-HT) levels were determined by gas chromatography-mass spectrometry and high-performance liquid chromatography with electrochemical detection, respectively.





Results:

Capsaicin had a neuroprotective effect in this animal model as shown by the neurological score, activity and cognitive function. The effect of capsaicin was blocked by capsazepine. Thioacetamide induced astrogliosis in the hippocampus and the cerebellum and raised brain 5-hydroxytryptamine levels, which were decreased by capsaicin, SR141716A and HU-308. Thioacetamide lowered brain 2-arachidonoylglycerol levels, an effect reversed by capsaicin.





Conclusions:

Capsaicin improved both liver and brain dysfunction caused by thioacetamide, suggesting that both the endocannabinoid and the vanilloid systems play important roles in hepatic encephalopathy. Modulation of these systems may have therapeutic value.





Induction of hepatic failure

We adapted the rat model of acute liver failure induced by TAA to mice (Zimmerman et al., 1989; Gabbay et al., 2005; Avraham et al., 2006; 2008a; Dagon et al., 2007; Magen et al., 2008). TAA (Sigma-Aldrich, St. Louis, MO, USA) dissolved in sterile normal saline solution was injected by the intraperitoneal (i.p.) route as a single dose of 200 mgkg<sup>1</sup>. Twenty-four hours later all animals were injected (subcutaneously) with 0.5 mL solution of 0.45% NaCl, 5% dextrose and 0.2% KCl in order to prevent hypovolemia, hypokalemia and hypoglycemia. The mice were intermittently exposed to infrared light in order to prevent hypothermia (Avraham et al., 2006).





Administration of cannabinoid agonists, antagonists and capsaicin

Endocannabinoids and their CB receptor antagonists were dissolved in a vehicle solution composed of ethanol, emulphor and saline in a ratio of 1:1:18, respectively. 2-AG, HU-308 and SR141716A were injected in a dose of 5 mgkg<sup>1</sup> once only after TAA treatment, based on previous experiments (Avraham et al., 2006; 2008a;). Capsaicin and capsazepine were administered at a dose of 1.25 gkg<sup>1</sup> as described by Lu et al. (2005). The solutions were injected i.p. 1 day after TAA administration. Control mice were injected with vehicle. The treatment and sampling schedule is shown in Figure 1.





Results



Induction of FHF and encephalopathy

We have shown (Avraham et al., 2008a) that 2 days after injecting mice with TAA (200 mgkg<sup>1</sup>), there are clear signs of hepatic failure with 30- to 40-fold increases in plasma levels of the hepatic enzymes, alanine amino transferase (ALT) and aspartate amino transferase (AST), accompanied by less dramatic but still significant increases in plasma total bilirubin (3.7-fold) and ammonia (2.7-fold). In the present study, we assessed development of encephalopathy, at the same time (2 days) after TAA, by measuring the neurological scores (higher score is equivalent to poorer neurological function). As shown in Figure 2, the score was significantly higher in mice injected with TAA, in relation to control mice (P < 0.001) and this increase was reversed following capsaicin (P < 0.01). Although neither SR141716A nor SR144528 significantly modulated the effect of capsaicin, the scores in these groups were also not different from the score after TAA alone. However, the beneficial effect of capsaicin was clearly reversed by the TRPV1 receptor antagonist, capsazepine (P < 0.05). Note that giving capsazepine alone to TAA-treated animals did not affect the raised neurological scores in this group.



[Image: bph0158-0896-f2.gif]

Figure 2





Much more





Discussion



Capsaicin, a TRPV1 agonist, has a neuroprotective role in HE

Administration of TAA to mice induced acute liver failure, which led to CNS changes related to those seen in HE (Zimmerman et al., 1989; Gabbay et al., 2005; Avraham et al., 2006; 2008a; Dagon et al., 2007; Magen et al., 2008; Izzo and Camilleri, 2008). As agonists of the vanilloid and the CB<sub>2</sub> receptor systems were found to ameliorate liver damage in FHF (Avraham et al., 2008a), we investigated their possible potential in treating HE. The principal finding in the present study is that capsaicin, a TRPV1 agonist, has a neuroprotective role in HE. This was supported by the following observations. First, TAA administration caused impaired neurological score, decreased activity and diminished cognitive function. Low dose capsaicin reversed these effects to almost to control levels, whereas capsazepine, a TRPV1 antagonist, reduced the beneficial effect of capsaicin indicating that the effects observed were vanilloid receptor-mediated. Second, TAA administration induced astrogliosis in both hippocampus and cerebellum. Capsaicin, SR141716A (a CB<sub>1</sub> receptor antagonist) and HU308 (a CB<sub>2</sub> receptor agonist), ameliorated astrogliosis, whereas SR144528 (a CB<sub>2</sub> receptor antagonist) and noladin (a CB<sub>1</sub> agonist) did not have any effect. Third, TAA increased brain 5-HT levels and capsaicin, SR141716A, HU308 and 2-AG reversed this effect of TAA on brain 5-HT. Fourth, brain levels of 2-AG decreased 14 days after TAA administration and capsaicin reversed this effect. Lastly, the effect of capsaicin on the neurological score, activity and 5-HT levels was impaired by SR141716A which probably competes with capsaicin for binding to the vanilloid receptor and by SR144528, which probably blocked the beneficial effect of endogenous 2-AG via the CB<sub>2</sub> receptors. Cognitive function was not impaired either by SR141716A or by SR144528, presumably indicating that a maximal effect was attained by capsaicin. Capsazepine alone did not affect either the neurological score or cognitive function, but it did reduce the activity score (P < 0.05) (not shown).





Antagonism of CB<sub>1</sub> receptors and agonism at CB<sub>2</sub> receptors have a neuroprotective role in HE, and capsaicin administration normalizes brain 2-AG levels

In a previous study of ours, the effects of endocannabinoids on activity, as well as on neurological and cognitive functions in HE, were studied. Encephalopathic mice treated with SR141716A or 2-AG or both, showed improved neurological function, activity and cognitive function compared with untreated controls. SR141716A showed a dose-response improvement of neurological function. HU308 treatment improved neurological score via the CB<sub>2</sub> receptors. CNS levels of endogenous 2-AG measured 2 days after TAA administration were found to be elevated when compared with healthy controls (Avraham et al., 2006). However, in the current study, brain levels of 2-AG were found to be markedly decreased 14 days after TAA (Figure 9). Capsaicin administration normalized brain 2-AG levels mostly through the TRPV1 receptor, apparently in part through the CB<sub>1</sub> and CB<sub>2</sub> receptors (Figure 9).



In a previous report, using a model of brain injury, levels of 2-AG increased significantly, up to tenfold, 4 h after the injury, and declined thereafter. Administration of 2-AG alleviated oxidative stress, inhibited NF-kappa B, protected the blood-brain-barrier, attenuated neuroinflammatory response and ameliorated neurological deficits (Panikashvili et al. 2001; Panikashvili et al., 2006; Mechoulam and Shohami, 2007). Furthermore, our previous studies have shown neuroprotective effects of 2-AG in experimental HE (Avraham et al., 2006). We have shown also that 2-AG probably plays a role in the pathophysiological changes in the liver, heart, lung and kidney that follow BDL, an animal model of chronic liver disease (Avraham et al., 2008b).





Modulation of increased 5-HT levels following TAA administration

Anorexia, one of the most typical symptoms observed in experimental and human cirrhosis, is assumed to be associated with altered brain 5-HT metabolism. Hence, increased brain 5-HT concentration in TAA treated rats, may be relevant to the pathogenesis of anorexia associated with TAA-induced cirrhosis (Haider et al., 2004). We now show that increased brain 5-HT levels were reversed by SR141716A, 2-AG, HU308 and capsaicin. Decreased 5-HT levels may therefore be associated with increased appetite.





The complex therapeutic mechanism involves both the cannabinoid and the vanilloid systems

The amelioration of astrogliosis following treatment with either SR141716A, HU308 or capsaicin, as well as the modulation of brain 5-HT levels by the same agents, as well as 2-AG, clearly indicate the complexity of the mechanism(s) involved. Previous findings have also shown that both endocannabinoids and capsaicin improve liver function and histopathology (Avraham et al., 2008a). These results may be related to those in a recent publication by Fioravanti et al. (2008), who showed that constitutive activity at the CB<sub>1</sub> receptor is required to maintain the TRPV1 receptor in a sensitized state responsive to chemical stimuli.



We have confirmed now that a very low dose of capsaicin improves neurological function, activity and cognitive function, whereas its antagonist capsazepine reverses the capsaicin improvement. It seems that part of the effect of capsaicin is mediated also via the CB<sub>1</sub> and CB<sub>2</sub> receptors and that SR141716A also competes with capsaicin for the vanilloid receptors.



Thus, the simultaneous blockade of CB<sub>1</sub> receptors and stimulation of both the CB<sub>2</sub> and vanilloid receptors has the best therapeutic effect on the liver. The treatment was very effective, as it was given 1 day after TAA administration and showed therapeutic effects on brain histopathology and function, liver enzyme levels as well as on liver pathology, on day 3.



Our studies are in agreement with those of Teixeira-Clerc et al. (2006; 2008;) and Lotersztajn et al. (2008), who identified the CB<sub>1</sub> receptor as a molecular target for the treatment of liver fibrosis. Our data suggest that TRPV1 receptors might also be involved, although in our experiments an anti-fibrotic effect could not be confirmed morphologically, as the animals were killed a short time after TAA administration. Moreover, our findings raise the possibility of using TRPV1 agonists to treat HE.



Lotersztajn's group (2008) showed that cirrhosis was associated with increased number of fibrogenic cells regulated by cannabinoid receptors (Teixeira-Clerc et al., 2006). CB<sub>2</sub> receptor-mediated suppression of fibrosis is in agreement with our findings and the beneficial effect of HU308 on HE (Julien et al., 2005; Lotersztajn et al., 2008). Earlier studies by Kunos' group showed that endocannabinoids acting at CB<sub>1</sub> receptors in the hepatic vasculature may mediate the vasodilated state and hypotension that accompany advanced liver cirrhosis (Batkai et al., 2001). Thus, CB<sub>1</sub> receptor blockade may improve the prognosis of cirrhotic individuals not only by delaying the fibrotic process, but also by improving the associated haemodynamic abnormalities (Varga et al., 1998; Batkai et al., 2001; Kunos et al., 2006).





The therapeutic effect on brain is either independent or due to liver recovery

Decreased inflammatory cell infiltration was noticed following HU308, SR141716A and capsaicin treatment (Figures 35). However, administration of a CB<sub>2</sub> receptor antagonist did not result in an anti-inflammatory effect. These findings may indicate that the anti-inflammatory effect of these reduced compounds may, at least partly, be related to the improved function of the liver and are CB<sub>2</sub> receptor-mediated.



The regenerative capacity of liver was increased following all but capsaicin treatment, a finding that may be correlated with the reduced hepatic cell injury noticed in this group of animals. Histological findings indicate that the CB<sub>2</sub> receptor-mediated anti-inflammatory effect may be related to the improved functional outcome of the remaining intact and regenerating hepatic cells following TAA administration. However, in the case of capsaicin, an additional factor might be the protection of the hepatic cells. Whether this effect is related to the concomitant anti-inflammatory effect of this compound and/or to a direct protective mechanism could not be clarified in the present study. The beneficial effect of capsaicin on reducing ammonia levels in our previous article (Avraham et al., 2008a) might clarify a possible mechanism.



In a previous study of ours (Dagon et al., 2007), a <sup>9</sup>-tetrahydrocannabinol (THC)-related, AMPK-mediated improvement of cerebral function (but not of hepatic function) was reported. However, our current results indicate that low dose of capsaicin affects both liver and brain function shortly after TAA administration, without side effects.





Astrogliosis following TAA administration and the effect of capsaicin, HU308 or SR141716A

Astrogliosis is a phenomenon that develops in various CNS disorders. Reactive astrocytes are involved in neuronal survival and regeneration. Major reactive changes of astrocytes in vivo are the upregulation of the intermediate filaments, GFAP and vimentin, with accompanying cellular hypertrophy and/or hyperplasia (Eng and Ghirnikar, 1994; Rhl et al., 2007). The cellular and molecular mechanisms leading to astrogliosis are still not completely understood. In general, microglia, which are normally in a quiescent status, become activated by different stimuli associated with neuropathological changes of the CNS. This activation precedes or accompanies astrogliosis (Herber et al., 2006). Glutamine is synthesized in astrocytes from ammonia and glutamate and causes brain swelling that correlates with neuropsychological deterioration. As a result, alterations of astrocyticneuronal cross-talk occur, affecting brain function (Shawcross and Jalan, 2005; Ahboucha and Butterworth, 2007).



At the molecular level, cytokines predominantly secreted by microglia seem to play an important role as triggers and modulators of astrogliosis and within the CNS. The effect of single cytokines on the induction of astrogliosis has been examined in several studies. Prominent representatives of proinflammatory cytokines such as IL-1 and TNF have been shown to induce, enhance or accompany astrogliosis in vivo (Balasingam et al., 1994). In the present work activated astrocytes at the areas of hippocampus and cerebellum, in particular, following TAA administration, were detected. However, capsaicin, HU308 or SR141716A treatment resulted in the amelioration of astrogliosis. 2-AG levels increase within 3 days following TAA administration and decrease thereafter below the control levels over 14 days post-HE induction. Likewise, brain 5-HT levels increase significantly following TAA administration, which parallels the observations of lack of appetite and decrease in weight in humans with HE.



In conclusion, the effects of capsaicin, HU308 or SR141716A, were due to both cerebral and hepatic actions. As capsaicin, SR141716A and HU308 have the advantage of access through the bloodbrain barrier; the brain itself may be a direct therapeutic target. However, an indirect benefit for the brain via liver recovery, cannot be excluded.

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Abbreviations:

2-AG

2-arachidonoylglycerol

5-HT

5-hydroxytryptamine

ALT

alanine amino transferase

AMPK

AMP-activated protein kinase



AST

aspartate amino transferase

FHF

fulminant hepatic failure

GFAP

glial fibrillary acidic protein

HE

hepatic encephalopathy

TAA

thioacetamide

THC

<sup>9</sup>-tetrahydrocannabinol







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