Tesofensine, a novel antiobesity drug, silences GABAergic hypothalamic neurons.

Obesity is a major global health epidemic that has adverse effects on both the people affected as well as the cost to society. Several anti-obesity drugs that target GLP-1 receptors have recently come to the market. Here, we describe the effects of tesofensine, a novel anti-obesity drug that acts as a triple monoamine neurotransmitter reuptake inhibitor. Using various techniques, we investigated its effects on weight loss and underlying neuronal mechanisms in mice and rats. These include behavioral tasks, DeepLabCut videotaped analysis, electrophysiological ensemble recordings, optogenetic activation, and chemogenetic silencing of GABAergic neurons in the Lateral Hypothalamus (LH). We found that tesofensine induces a greater weight loss in obese rats than lean rats, while differentially modulating the neuronal ensembles and population activity in LH. In Vgat-ChR2 and Vgat-IRES-cre transgenic mice, we found for the first time that tesofensine inhibited a subset of LH GABAergic neurons, reducing their ability to promote feeding behavior, and chemogenetically silencing them enhanced tesofensine's food-suppressing effects. Unlike phentermine, a dopaminergic appetite suppressant, tesofensine causes few, if any, head-weaving stereotypy at therapeutic doses. Most importantly, we found that tesofensine prolonged the weight loss induced by 5-HTP, a serotonin precursor, and blocked the body weight rebound that often occurs after weight loss. Behavioral studies on rats with the tastant sucrose indicated that tesofensine's appetite suppressant effects are independent of taste aversion and do not directly affect the perception of sweetness or palatability of sucrose. In summary, our data provide new insights into the effects of tesofensine on weight loss and the underlying neuronal mechanisms, suggesting that tesofensine may be an effective treatment for obesity and that it may be a valuable adjunct to other appetite suppressants to prevent body weight rebound.

The Triple Combination Phentermine Plus 5-HTP/Carbidopa Leads to Greater Weight Loss, With Fewer Psychomotor Side Effects Than Each Drug Alone.

Obesity has become a serious public health problem. Although diet, surgery, and exercise are the primary treatments for obesity, these activities are often supplemented using appetite suppressants. A previous study reported that obesity specialists frequently prescribed a new drug combination for its treatment that includes phentermine (Phen; dopaminergic appetite suppressant), a serotonin (5-HT) precursor 5-hydroxytryptophan (5-HTP; an appetite suppressant that increases the 5-HT concentration), and carbidopa (CB; peripheral blocker of conversion of 5-HTP to 5-HT). Despite its widespread use, there is neither a preclinical study confirming the drug efficacy nor studies of its effects on the brain. To fill this gap, in rats for seven consecutive days, we administered Phen intraperitoneally at different doses either alone or in combination with a fixed dose of 5-HTP/CB. In a different group, we infused drugs via an intraperitoneal catheter while extracellular-recordings were performed in the nucleus accumbens shell (NAcSh), a brain region with dopamine-releasing effects that is involved in the action of appetite suppressants. We found that the triple-drug combination leads to greater weight-loss than each drug alone. Moreover, and as the treatment progresses, the triple drug combination partially reversed psychomotor side-effects induced by Phen. Electrophysiological results revealed that Phen alone evoked a net inhibitory imbalance in NAcSh population activity that correlated with the onset of psychomotor effects. In addition, and unlike the greater weight loss, the addition of 5-HTP/CB did not alter the Phen-evoked inhibitory imbalance in NAcSh responses. Subsequent experiments shed light on the underlying mechanism. That is the majority of NAcSh neurons modulated by 5-HTP/CB were suppressed by Phen. Notably, and despite acting via a different mechanism of action (DA for Phen vs. 5-HT for 5-HTP/CB), both drugs recruited largely overlapping NAcSh neuronal ensembles. These data suggest that the neural correlates of the greater weight loss could be located outside the NAcSh, in other brain circuits. Furthermore, we conclude that Phen + 5-HTP/CB is a potential treatment for overweight and obesity.

Encoding of Sucrose's Palatability in the Nucleus Accumbens Shell and Its Modulation by Exteroceptive Auditory Cues.

Although the palatability of sucrose is the primary reason for why it is over consumed, it is not well understood how it is encoded in the nucleus accumbens shell (NAcSh), a brain region involved in reward, feeding, and sensory/motor transformations. Similarly, untouched are issues regarding how an external auditory stimulus affects sucrose palatability and, in the NAcSh, the neuronal correlates of this behavior. To address these questions in behaving rats, we investigated how food-related auditory cues modulate sucrose's palatability. The goals are to determine whether NAcSh neuronal responses would track sucrose's palatability (as measured by the increase in hedonically positive oromotor responses lick rate), sucrose concentration, and how it processes auditory information. Using brief-access tests, we found that sucrose's palatability was enhanced by exteroceptive auditory cues that signal the start and the end of a reward epoch. With only the start cue the rejection of water was accelerated, and the sucrose/water ratio was enhanced, indicating greater palatability. However, the start cue also fragmented licking patterns and decreased caloric intake. In the presence of both start and stop cues, the animals fed continuously and increased their caloric intake. Analysis of the licking microstructure confirmed that auditory cues (either signaling the start alone or start/stop) enhanced sucrose's oromotor-palatability responses. Recordings of extracellular single-unit activity identified several distinct populations of NAcSh responses that tracked either the sucrose palatability responses or the sucrose concentrations by increasing or decreasing their activity. Another neural population fired synchronously with licking and exhibited an enhancement in their coherence with increasing sucrose concentrations. The population of NAcSh's Palatability-related and Lick-Inactive neurons were the most important for decoding sucrose's palatability. Only the Lick-Inactive neurons were phasically activated by both auditory cues and may play a sentinel role monitoring relevant auditory cues to increase caloric intake and sucrose's palatability. In summary, we found that auditory cues that signal the availability of sucrose modulate its palatability and caloric intake in a task dependent-manner and had neural correlates in the NAcSh. These findings show that exteroceptive cues associated with feeding may enhance positive hedonic oromotor-responses elicited by sucrose's palatability.

D1 and D2 antagonists reverse the effects of appetite suppressants on weight loss, food intake, locomotion, and rebalance spiking inhibition in the rat NAc shell.

Obesity is a worldwide health problem that has reached epidemic proportions. To ameliorate this problem, one approach is the use of appetite suppressants. These compounds are frequently amphetamine congeners such as diethylpropion (DEP), phentermine (PHEN), and bupropion (BUP), whose effects are mediated through serotonin, norepinephrine, and dopaminergic pathways. The nucleus accumbens (NAc) shell receives dopaminergic inputs and is involved in feeding and motor activity. However, little is known about how appetite suppressants modulate its activity. Therefore, we characterized behavioral and neuronal NAc shell responses to short-term treatments of DEP, PHEN, and BUP. These compounds caused a transient decrease in weight and food intake while increasing locomotion, stereotypy, and insomnia. They evoked a large inhibitory imbalance in NAc shell spiking activity that correlated with the onset of locomotion and stereotypy. Analysis of the local field potentials (LFPs) showed that all three drugs modulated beta, theta, and delta oscillations. These oscillations do not reflect an aversive-malaise brain state, as ascertained from taste aversion experiments, but tracked both the initial decrease in weight and food intake and the subsequent tolerance to these drugs. Importantly, the appetite suppressant-induced weight loss and locomotion were markedly reduced by intragastric (and intra-NAc shell) infusions of dopamine antagonists SCH-23390 (D1 receptor) or raclopride (D2 receptor). Furthermore, both antagonists attenuated appetite suppressant-induced LFP oscillations and partially restored the imbalance in NAc shell activity. These data reveal that appetite suppressant-induced behavioral and neuronal activity recorded in the NAc shell depend, to various extents, on dopaminergic activation and thus point to an important role for D1/D2-like receptors (in the NAc shell) in the mechanism of action for these anorexic compounds.

Allopurinol reverses liver damage induced by chronic carbon tetrachloride treatment by decreasing oxidative stress, TGF-ß production and NF-κB nuclear translocation.

Allopurinol is an inhibitor of xanthine oxidase. The aim of this work was to evaluate the efficacy of allopurinol to reverse the experimental cirrhosis induced by CCl4. Rats received CCl4 for 8 weeks, and immediately after allopurinol was administered for 4 weeks more. Allopurinol reversed all markers of liver damage and oxidative stress to normal values, restoring the metabolic capacity of the liver. Chronic injury by CCl4 induced significant overexpression of profibrogenic cytokine TGF-ß, while allopurinol decreased this production and consequently decreased the collagen content. Moreover, allopurinol is capable of partially inhibiting NF-κB. These findings suggest that allopurinol is capable of reversing the cirrhosis induced by CCl4, modulating oxidative stress, TGF-ß expression and NF-κB nuclear translocation.

Secondary biliary cirrhosis in the rat is prevented by decreasing NF-κB nuclear translocation and TGF-ß expression using allopurinol, an inhibitor of xanthine oxidase.

Allopurinol is an inhibitor of xanthine oxidase (XO), and XO is an enzyme that generates great amounts of reactive oxygen species. The aim of this work was to evaluate the efficacy of allopurinol to prevent experimental cirrhosis. Fibrosis and cirrhosis were induced by common bile duct ligation (BDL) for 4 weeks in rats. Animals were divided into 4 groups: sham-operated rats (SHAM); BDL group; BDL plus allopurinol (100 mg·kg⁻¹, p.o.), and SHAM plus allopurinol treatment. Alanine aminotransferase, γ-glutamyl transpeptidase, and alkaline phosphatase were increased in BDL rats but were preserved normal by allopurinol. XO activity was prevented by allopurinol; however, lipophilic and hydrophilic oxidative stress was not prevented by the drug. Allopurinol partially suppresses nuclear factor-κB (NF-κB) nuclear translocation and transforming growth factor-ß (TGF-ß) expression, and increased the active form of matrix metalloproteinase-13 (MMP-13). Moreover, collagen production induced by BDL was partially but significantly reduced by allopurinol. These findings suggest that allopurinol possesses a hepatoprotective effect probably by modulating proteins such as NF-κB, TGF-ß, and MMP-13, helping to protect against liver damage induced by chronic cholestasis and a mechanism independent of oxidative stress.

Effects of acetyl salycilic acid and ibuprofen in chronic liver damage induced by CCl4.

Non-steroidal anti-inflammatory drugs (NSAIDs) are drugs used primarily to treat inflammation, pain and fever. Their main mechanism of action is cyclooxygenase (COX) inhibition, and this enzyme has been linked to hepatotoxicity. The association of COX and liver injury has been, in part, due to the presence of COX-2 isoform in damaged liver and the possible induction of this enzyme by profibrotic molecules like Transforming Growth Factor-ß (TGF-ß). The aim of this work was to evaluate the effects of two of the most used NSAIDs, acetyl salicylic acid (ASA) and ibuprofen (IBP), on experimental liver fibrosis. We formed experimental groups of rats including vehicle and drug controls, damage induced by chronic CCl4 (0.4 g kg(-1) , i.p., three times per week, for 8 weeks) administration, and CCl4 plus ASA (100 mg kg(-1) , p.o., daily) or IBP (30 mg kg(-1) , p.o., daily). Both drugs showed important antifibrotic properties. They inhibited COX-2 activity, prevented oxidative stress measured as lipid peroxidation and glutathione content, and ASA inhibited partially and IBP totally increased TGF-ß expression and collagen content. ASA and IBP prevented translocation of NFκB to the nucleus and, interestingly, ASA induced MMP-2 and MMP-13 whereas IBP induced MMP-2, MMP-9 and MMP-13. As a whole, these effects explain the beneficial effects of ASA and IBP on experimental liver fibrosis.

Protective effects of allopurinol against acute liver damage and cirrhosis induced by carbon tetrachloride: modulation of NF-κB, cytokine production and oxidative stress.

BACKGROUND: The aim of this work was to evaluate the hepatoprotective ability of allopurinol to prevent the liver injury induced by carbon tetrachloride (CCl(4)). METHODS: Acute liver damage was induced with CCl(4) (4g/kg, by gavage); allopurinol (50mg/kg, by gavage) was given 1h before and 1h after CCl(4) intoxication and two daily doses for the previous three days. Cirrhosis was established by CCl(4) administration (0.4g/kg, i. p. three times a week, eight weeks); allopurinol was administered (100mg/kg, by gavage, daily) during the long-term of CCl(4) treatment. Alanine aminotransferase (ALT), γ-glutamyl transpeptidase (γ-GTP), xanthine oxidase (XO), lipid peroxidation, reduced and oxidized glutathione (GSH, GSSG, respectively), hydroxyproline and histopathologycal analysis were performed. Nuclear factor-κB (NF-κB), pro-inflammatory and anti-inflammatory cytokines, transforming growth factor-ß (TGF-ß) and metalloproteinase-13 (MMP-13) were analyzed by Western blots. RESULTS: Acute injury increased ALT and γ-GTP activities, additionally enhanced NF-κB nuclear translocation and cytokines production such as tumor necrosis factor-α, interleukine-1ß, and interleukine-6. Allopurinol partially prevented these effects, while increased interleukine-10. Acute and chronic CCl(4) treatments altered the levels of XO activity, lipid peroxidation, and GSH/GSSG ratio, while these remained within normal range with allopurinol administration. Necrosis, fibrosis and TGF-ß production induced in chronic injury were partially prevented by allopurinol, interestingly, this drug induced MMP-13 activity. CONCLUSIONS: Allopurinol possesses antioxidant, anti-inflammatory and antifibrotic properties, probably by its capacity to reduce NF-κB nuclear translocation and TGF-ß expression, as well as to induce MMP-13. General significance Allopurinol might be effective treatment of liver diseases.

Coffee prevents CCl(4)-induced liver cirrhosis in the rat.

PURPOSE: Previous clinical observations suggested that coffee may have beneficial effects on the liver. In fact, an inverse relationship between coffee consumption and liver cirrhosis has been reported in humans. However, the causative role of coffee has not been established; therefore, the aim of this work was to study the effect of coffee in an experimental model of liver damage. METHODS: In this work, cirrhosis was induced by chronic CCl(4) administration and soluble or grain coffee (SC, GC, respectively) were co-administered for 8 weeks. RESULTS: CCl(4) administration elevated serum alkaline phosphatase and alanine aminotranspherase, liver lipid peroxidation, collagen content (fourfold) and TGF-ß mRNA, and protein levels; depleted liver glycogen and reduced glutathione (GSH) content. Coffee prevented most of the changes produced by CCl(4). Histopathological analysis was in agreement with biochemical and molecular data. The best effect was produced by GC. It is worth noting that GC preserved the normal collagen content as well as the normal TGF-ß mRNA and protein levels. CONCLUSIONS: Our results suggest (1) that coffee plays a causative role in preventing cirrhosis (at least experimental cirrhosis); (2) that action mechanisms are probably associated with down regulation of the profibrogenic cytokine TGF-ß and to its antioxidant properties and, (3) that GC is more potent than SC. These findings suggest a beneficial effect of coffee on the liver. However, more clinical and basic studies must be performed before reaching a final recommendation.

Antifibrotic and fibrolytic properties of celecoxib in liver damage induced by carbon tetrachloride in the rat.

BACKGROUND: Transforming growth factor-beta (TGF-beta) plays a pivotal role in liver fibrosis, because it activates hepatic stellate cells, stimulating extracellular matrix deposition. Cyclooxygenase-2 (COX-2) has been associated with TGF-beta because its inhibition decreases TGF-beta expression and collagen production in some cultured cell types. AIM: The aim of this work was to evaluate the ability of celecoxib (a selective COX-2 inhibitor) to prevent and to reverse the liver fibrosis induced by CCl(4). METHODS: We established experimental groups of rats including vehicle and drug controls, damage induced by chronic CCl(4) administration and CCl(4) plus pharmacological treatment in both prevention and reversion models. We determined: alanine aminotransferase, alkaline phosphatase, gamma-glutamyl transpeptidase, COX and metalloproteinase-2 and -9 activities, lipid peroxidation, glutathione levels, glycogen and collagen content and TGF-beta expression. RESULTS: Celecoxib prevented and aided to the recovery of livers with necrotic and cholestatic damage. Celecoxib exhibited anti-oxidant properties by restoring the redox equilibrium (lipid peroxidation and glutathione levels). Glycogen was decreased by CCl(4), while celecoxib partially prevented and reversed this effect. Celecoxib inhibited COX-2 activity, decreased TGF-beta expression, induced metalloproteinase-2 activity and, consequently, prevented and reversed collagen accumulation. CONCLUSION: Our findings indicate that celecoxib exerts strong antifibrogenic and fibrolytic effects in the CCl(4) model of cirrhosis.

N-acetylcysteine prevents carbon tetrachloride-induced liver cirrhosis: role of liver transforming growth factor-beta and oxidative stress.

OBJECTIVES: N-acetylcysteine (NAC) is an antioxidant, a precursor of reduced glutathione, and an inhibitor of the profibrotic cytokine liver transforming growth factor-beta (TGF-beta). Carbon tetrachloride (CCl4) cirrhosis is characterized by oxidative stress and fibrosis. Therefore, the aim of this work was to study the effect of NAC on experimental cirrhosis. METHODS: CCl4 was chronically administered for 8 weeks along with 300 mg/kg of NAC orally once a day. Alkaline phosphatase, alanine aminotransferase, and gamma-glutamyltranspeptidase were measured in plasma. Hydroxyproline, glycogen, lipid peroxidation, glutathione were determined in liver samples by colorimetric methods. TGF-beta was evaluated by western blotting, and a histopathological analysis was performed. RESULTS: Serum markers of liver damage increased by CCl4 intoxication (P<0.05), whereas cotreatment with NAC prevented these increases (P<0.05); glycogen was depleted in the cirrhotic group (P<0.05), but preserved by NAC (P<0.05). Lipid peroxidation increased and glutathione decreased by the administration of CCl4 (P<0.05), again NAC prevented both effects (P<0.05). Importantly, collagen increased by about seven-fold in the CCl4 group (P<0.05); administration of NAC preserved the normal levels of collagen (P<0.05). Biochemical determinations were corroborated by hematoxylin and eosin, and trichromic stains. Western blots revealed a four-fold increase in TGF-beta in the group receiving CCl4, NAC cotreatment abolished TGF-beta signal (P<0.05). CONCLUSION: Our results strongly suggest that NAC prevents experimental cirrhosis by two mechanisms: by preventing oxidative stress and by downregulating the profibrogenic cytokine TGF-beta. As NAC is currently used in humans intoxicated with paracetamol, it can be tested in fibrotic or cirrhotic patients under controlled trials.

Trolox down-regulates transforming growth factor-beta and prevents experimental cirrhosis.

Cirrhosis is a very common disease and its treatment is limited due to lack of effective drugs. Some studies indicate that this disease is associated with oxidative stress. Therefore, we decided to study the effect of trolox, an effective antioxidant, on experimental cirrhosis. Cirrhosis was induced by CCl4 administration (0.4 g/kg, intraperitoneally, three times per week, for 8 weeks) to Wistar male rats. Trolox was administered daily (50 mg/kg, orally). Fibrosis was assessed histologically and by measuring liver hydroxyproline content. Glutathione, lipid peroxidation and glycogen were measured in liver; serum markers of liver damage were also quantified. Transforming growth factor-beta (TGF-beta) was determined by Western blot and quantified densitometrically. Alkaline phosphatase, gamma-glutamyl transpeptidase and alanine aminotransferase increased in the group receiving CCl4; trolox completely or partially prevented these alterations. Glycogen was almost depleted by CCl4 but was partially preserved by trolox. Lipid peroxidation increased while glutathione decreased by CCl4 administration; trolox corrected both effects. Histology showed thick bands of collagen, necrosis and distortion of the hepatic parenchyma in the CCl4 group, such effects were prevented by trolox. Hydroxyproline content increased 5-fold by CCl4, while the group receiving both CCl4 and trolox showed no significant difference compared to the control group. CCl4 increased 3-fold TGF-beta, while trolox completely prevented this increase. We found that trolox effectively prevented cirrhosis induced with CCl4 in the rat. Our results suggest that the beneficial effects of trolox may be associated to its antioxidant properties and to its ability to reduce the profibrogenic cytokine TGF-beta expression.

Curcumin prevents and reverses cirrhosis induced by bile duct obstruction or CCl4 in rats: role of TGF-beta modulation and oxidative stress.

Curcumin is a phytophenolic compound, which is highly efficacious for treating several inflammatory diseases. The aim of this study was to evaluate the efficacy of curcumin in preventing or reversing liver cirrhosis. A 4-week bile duct ligation (BDL) rat model was used to test the ability of curcumin (100 mg/kg, p.o., daily) to prevent cirrhosis. To reverse cirrhosis, CCl(4) was administered chronically for 3 months, and then it was withdrawn and curcumin administered for 2 months. Alanine aminotransferase, gamma-glutamyl transpeptidase, liver histopathology, bilirubin, glycogen, reduced and oxidized glutathione, and TGF-beta (mRNA and protein) levels were assessed. Curcumin preserved normal values of markers of liver damage in BDL rats. Fibrosis, assessed by measuring hydroxyproline levels and histopathology, increased nearly fivefold after BDL and this effect was partially but significantly prevented by curcumin. BDL increased transforming growth factor-beta (TGF-beta) levels (mRNA and proteins), while curcumin partially suppressed this mediator of fibrosis. Curcumin also partially reversed the fibrosis induced by CCl(4). Curcumin was effective in preventing and reversing cirrhosis, probably by its ability of reducing TGF-beta expression. These data suggest that curcumin might be an effective antifibrotic and fibrolitic drug in the treatment of chronic hepatic diseases.

Methyl palmitate prevents CCl(4)-induced liver fibrosis.

Liver fibrosis is characterized by an excess of collagen fiber deposition, and it is known that Kupffer cells play an important role by immunomodulation of the toxic response. Methyl palmitate (MP) is an effective Kupffer cell inhibitor. The aim of this work was to evaluate the effect of MP on experimental liver fibrosis. Four groups were formed: the control group, which received the vehicles only; CCl(4) group (0.4 g kg(-1), i.p., three times a week, for eight weeks); CCl(4) plus MP (300 mg kg(-1), i.p., daily); and MP alone. Alanine aminotransferase was increased by CCl(4), and MP did not prevent this increase. Lipid peroxidation was increased markedly by CCl(4); again, MP was not able to prevent this effect. Fibrosis increased nearly 6-fold (measured as liver hydroxyproline content) in the CCl(4) group; MP preserved the normal content of collagen. These results were corroborated by histopathology. To elucidate the antifibrogenic mechanism of MP, we measured the production of TGF-beta; CCl(4) increased this cytokine several-fold, and MP abolished this increase. Collectively the present results indicate that MP possesses a strong antifibrogenic effect at least in the CCl(4) model of fibrosis. The antifibrotic effect of MP is probably associated with its ability to reduce TGF-beta content, maybe by immunomodulation of Kupffer cells functioning.

Resveratrol prevents fibrosis, NF-kappaB activation and TGF-beta increases induced by chronic CCl4 treatment in rats.

Resveratrol is a nonflavonoid polyphenol with antioxidant, anticancer and antiinflammatory properties. Moreover, it has been reported that this compound inhibits NF-kappaB, which regulates the transcription of several genes including cytokines such as the profibrogenic TGF-beta. The aim of this work was to evaluate the pharmacological effects of resveratrol on CCl(4)-induced cirrhosis in the rat. Four groups were formed: the control group that received the vehicles only; the CCl(4) group that received the toxin (0.4 g kg(-1), i.p., three times a week, for 8 weeks); the CCl(4) plus resveratrol (10 mg kg(-1), daily) group; and the resveratrol alone group. Alanine aminotransferase, alkaline phosphatase and bilirubins were increased by CCl(4), but resveratrol afforded some degree of protection. Glycogen was decreased markedly by CCl(4) and resveratrol prevented almost completely this effect. No antioxidant effect of resveratrol was observed. One of the most prominent effects was on fibrosis which increased near 5-fold (hydroxyproline) in the CCl(4) group; resveratrol preserved the content of collagen. These results were corroborated by histopathology. To elucidate the antifibrogenic mechanism of resveratrol, the activation of NF-kappaB and the production of TGF-beta were measured; in both cases CCl(4) increased them and resveratrol abolished them; however, changes in NF-kappaB were modest and did not reach statistical significance, while the increase in TGF-beta was about three fold and resveratrol decreased it under control values. Together, the present results indicate that resveratrol possesses a strong antifibrogenic effect at least in the CCl(4) model of cirrhosis. Moreover, the action mechanism is probably associated with its ability to reduce NF-kappaB activation and TGF-beta content.

Curcumin protects against acute liver damage in the rat by inhibiting NF-kappaB, proinflammatory cytokines production and oxidative stress.

Curcumin, an anti-inflammatory and antioxidant compound, was evaluated for its ability to suppress acute carbon tetrachloride-induced liver damage. Acute hepatotoxicity was induced by oral administration of CCl4 (4 g/kg, p.o.). Curcumin treatment (200 mg/kg, p.o.) was given before and 2 h after CCl4 administration. Indicators of necrosis (alanine aminotransferase) and cholestasis (gamma-glutamyl transpeptidase and bilirubins) resulted in significant increases after CCl4 intoxication, but these effects were prevented by curcumin treatment. As an indicator of oxidative stress, GSH was oxidized and the GSH/GSSG ratio decreased significantly by CCl4, but was preserved within normal values by curcumin. In addition to its antioxidants properties, curcumin is capable of preventing NF-kappaB activation and therefore to prevent the secretion of proinflammatory cytokines. Therefore, in this study we determined the concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6) mRNA, and NF-kappaB activation. CCl4-administered rats depicted significant increases in TNF-alpha, IL-1beta, and IL-6 production, while curcumin remarkably suppressed these mediators of inflammation in liver damage. These results were confirmed by measuring TNF-alpha, and IL-1beta protein production using Western Blot analysis. Accordingly, these proteins were increased by CCl4 and this effect was abolished by curcumin. Administration of CCl4 induced the translocation of NF-kappaB to the nucleus; CCl4 induced NF-kappaB DNA binding activity was blocked by curcumin treatment. These findings suggest that curcumin prevents acute liver damage by at least two mechanisms: acting as an antioxidant and by inhibiting NF-kappaB activation and thus production of proinflammatory cytokines.

Effect of alpha-asarone and a derivative on lipids, bile flow and Na+/K+-ATPase in ethinyl estradiol-induced cholestasis in the rat.

Administration of ethinyl estradiol (EE), a widely used component of oral contraceptives, has been associated with impairment of bile flow and the capacity to excrete organic anions in man and experimental animals. alpha-Asarone (2,4,5-trimethoxypropenylbenzene) and 2-methoxy-4-(2-propenyl) phenoxyacetic acid (MPPA) have shown hypolipidemic effects. In addition to these effects, we decided to evaluate the properties of these compounds on EE-induced cholestasis. Wistar male rats were injected subcutaneously with 10 mg/kg of EE for 5 days; simultaneously, alpha-asarone or MPPA were also administered and appropriate controls were performed. alpha-asarone and MPPA decreased plasma and bile cholesterol. EE diminished triglycerides total, low-density lipoprotein, high-density lipoprotein and bile cholesterol. MPPA further decreased these lipid parameters. Alkaline phosphatase (an enzyme marker of cholestasis) was increased after administration of EE, but this effect was prevented significantly by alpha-asarone or MPPA administration. Bile flow was importantly decreased by EE and increased by alpha-asarone alone. Furthermore, alpha-asarone or MPPA preserved the normal bile flow in EE-treated rats. EE inhibited the activity of the Na(+)/K(+)-ATPase, while both alpha-asarone and MPPA preserved this enzyme activity. Na(+)/K(+)-ATPase is involved in Na(+)-coupled uptake of bile acids into hepatocytes and, therefore, ultimately is the driving force for the generation of bile flow. Therefore, the anticholestatic effects of alpha-asarone and MPPA, described herein by the first time, may be due to its ability to preserve ATPase activity. This enzyme is negatively regulated by membrane cholesterol, thus the hypolipidemic effects of the compounds tested may be responsible for Na(+)/K(+)-ATPase activity and bile flow maintenance.

Inducible nitric oxide synthase is not essential for the development of fibrosis and liver damage induced by CCl4 in mice.

The aim of the present work was to investigate the role of inducible nitric oxide (NO) synthase (iNOS) in CCl(4)-induced cirrhosis by utilizing iNOS knock out mice (iNOS(-/-)). Cirrhosis was produced by i.p. administration of CCl(4) (1 ml kg(-1) of body weight) dissolved in olive oil three times a week for 3 months to iNOS(-/-) or iNOS(+/+) (wild type) mice; appropriate olive oil controls were performed. Nitrite plus nitrate levels were lower in iNOS(-/-) compared with iNOS(+/+) mice, but CCl(4) did not produce a significant effect in any mice. Reduced (GSH) glutathione was increased in iNOS(-/-) mice receiving vehicle and in both groups receiving CCl(4); lipid peroxidation increased significantly in iNOS(+/+) but not in iNOS(-/-) mice. Bilirubins, alanine aminotransferase and collagen (measured as the hepatic hydroxyproline content) were increased significantly by the chronic intoxication with CCl(4) in both iNOS(-/-) and iNOS(+/+) mice; importantly there was no difference between these groups. This study clearly suggests that NO derived from iNOS does not participate in cholestasis, necrosis or fibrosis induced by CCl(4) in the mice. The present results are in disagreement with several studies indicating a beneficial or detrimental effect of this molecule utilizing different experimental approaches and in agreement with some studies indicating that NO does not affect liver damage in some models. It must be pointed out that this is the first report in iNOS knock out mice utilizing the chronic model of intoxication with CCl(4); thus, comparisons with other models or approaches are difficult to reconcile.

Gadolinium Chloride Inhibits the Spontaneous Resolution of Fibrosis in CCL(4)-Induced Cirrhosis.

Current evidence indicates that liver fibrosis is dynamic and can be bidirectional, involving phases of progression and regression, and that in addition to increased matrix synthesis, this pathological process involves major changes in the regulation of matrix degradation. There is also evidence that Kupffer cells participate in both fibrogenesis and fibrolysis. Therefore, the aim of the present work was to study the participation of Kupffer cells on the spontaneous resolution of hepatic fibrosis. Cirrhosis was produced by 3 months of chronic CCl(4) intoxication in male Wistar rats, and then CCl(4) was discontinued and two groups were formed: One group received gadolinium chloride (10 mg/kg, IP, daily) and the other received the vehicle (water) only for 2 months. Serum enzyme activities of alkaline phosphatase and alanine aminotransferase and liver lipid peroxidation increased by CCl(4) treatment but returned to normal by discontinuation of CCl(4). GSH, GSH/GSSG, and GSH+GSSG decreased significantly by CCl(4), but withdrawal of CCl(4) restored normal glutathione parameters. Fibrosis increased five-fold and glycogen decreased significantly by CCl(4) treatment, while discontinuation of CCl(4) reversed completely glycogen depletion and partially fibrosis. Gadolinium chloride showed effects only in the content of glycogen and collagen; the former was decreased further and the latter remained elevated despite discontinuation of the toxic agent. Persistent fibrosis induced by gadolinium chloride, a selective inhibitor of Kupffer cells, indicates that these cells play a pivotal role in fibrolysis.

Resolution of liver fibrosis in chronic CCl4 administration in the rat after discontinuation of treatment: effect of silymarin, silibinin, colchicine and trimethylcolchicinic acid.

The purpose of this work was to obtain a suitable model of fibrosis, in which spontaneous reversion was minimal, to study the ability of silymarin, silibinin, colchicine and trimethylcolchicinic acid (TMCA) to reverse it. Reversal of liver fibrosis was studied in male Wistar rats after one, two or three months of CCl(4) administration (0.4 g/kg intraperitoneally, three times per week), by discontinuation of the toxin for 2 months. Silymarin (50 mg/kg), silibinin (50 mg/kg), colchicine (10 microg/rat) and trimethylcolchicinic acid (100 microg/rat) were administered daily, by gavage, after 3 months of CCl(4) administration. Collagen content was determined by measuring hydroxyproline in liver samples; glycogen, was determined utilizing the anthrone reagent; Mallory's trichromic stains of liver sections were performed. The best scheme of treatment was obtained when CCl(4) was administered during three months (collagen increased 6 times). Discontinuation of the toxin for two months produced a significant but relative small reduction of fibrosis (collagen was still 4.5 times over control). Colchicine, TMCA, silymarin or silibinin treatment showed no significant fibrolitic effect. This scheme of treatment may be an excellent tool to study the ability of drugs to reverse fibrosis. The hepatoprotective properties of silymarin, silibinin, colchicine and trimethylcolchinic acid may be irrelevant to reverse established cirrhosis.