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Effects of Curcumin on Cyclosporine-Induced Cholestasis and Hypercholesterolemia and on Cyclosporine Metabolism in the Rat
Abstract
Former studies have shown that curcumin, which can be extracted from different Curcuma species, is able to stimulate bile flow and to reduce hypercholesterolemia. We investigated in a subchronic bile fistula model the ability of curcumin to reduce cyclosporine-induced cholestasis and hypercholesterolemia. Male Wistar rats were daily treated with curcumin (100 mg/kg p. o.), cyclosporine (10 mg/kg i. p.), and a combination of curcumin with cyclosporine. After two weeks a bile fistula was installed into the rats to measure bile flow and biliary excretion of bile salts, cholesterol, bilirubin, cyclosporine and its main metabolites. Blood was taken to determine the concentration of these parameters in serum or blood. Cyclosporine reduced bile flow (-14 %) and biliary excretion of bile salts (-10 %) and cholesterol (-61 %). On the other hand, cyclosporine increased serum concentrations of cholesterol and triglycerides by 32 % and 82 %, respectively. Sole administration of curcumin led to a slight decrease of bile flow (-7 %) and biliary bile salt excretion (-12 %), but showed no effect on biliary excretion of cholesterol and serum lipid concentration. When curcumin was given simultaneously with cyclosporine, the cyclosporine-induced cholestasis was enhanced but the cyclosporine-induced hyperlipidemia was not affected. Neither the biliary excretion nor the blood concentration of cyclosporine was influenced by curcumin. The blood concentration of the main cyclosporine metabolites, however, was lowered by half while their biliary excretion was strongly increased by curcumin. From these results we conclude that curcumin is not able to prevent cyclosporine-induced cholestasis and hyperlipidemia after prolonged administration in bile fistula rats.
... Table (1-c) revealed that all groups (G: [13][14][15][16][17][18][19][20][21][22][23][24][25] showed no significant change than their respective hypercholesterolemic control groups (G 12), although they showed slightly higher weights. Also body weight showed a tendency to increase with increasing concentration of the added curcumin, curcumin+piperine and curcum. ...
... Also no significant differences for RLW were found when compared with the untreated hypercholesterolemic control group (G 12), which is quite different for relative heart weight. All groups (G: [13][14][15][16][17][18][19][20][21][22][23][24][25] showed no significant change when compared with normal controls (G1 1 ) and a significant decrease was found on comparing with G 12. Relative heart weight of curcumin-fed (G: 14-17); curcumin+piperine-fed (G 20) and curcum-fed (G:22-25) of hypercholesterolemic rats was significantly lower than initial hypercholesterolemic group (G 26). Table (3-a, b) revealed that serum cholesterol (total, HDL-C, LDL, VLDL) triacylglycerol, and phospholipids levels of 0.1% and 0.25% curcumin-or curcum-fed normal groups (2-3 and 7-8) showed no significant differences when compared with the control, but serum cholesterol (total, LDL, VLDL) of the remaining groups (G: 4-6 and 9-11) of curcumin-or curcum-fed groups was significantly lower than control group. ...
... Data of table (5-b) showed significantly lower levels of hepatic cholesterol, triacylglycerol concentrations; and cardiac cholesterol concentration in curcumin-fed (G: 13-17), curcumin+ piperine-fed (G: [18][19][20], curcum-fed (G: 21-25) groups when compared with control (G 1 1 ), or with untreated hypercholesterolemic control group (G 12) or with control hyperlipidemic group (G 26) except G 18 and 22 when compared with G 12 where no significant change was observed. ...
... In most studies carried out to prove the beneficial effects of curcumin on serum parameters, these levels were diminished or unchanged. The results reported by Deters et al. (2003) [45] suggest that oral administration of curcumin at a 100 mg/kg bw produced no changes in cholesterol or triglyceride levels; nevertheless, a group treated with the same concentration of curcumin and cyclosporine did display an increase in these markers; this suggests the possible antagonistic effect that curcumin may have with some substances. In a report by Qiu et al. (2016) [46], two concentrations of curcumin were tested: 100 and 25 mg; at 100 mg, a decrease in body weight, cholesterol, GLUT 2, and COX 2 was observed; however, an increase in IL 6 and FAS occurred at the 25 mg concentration. ...
... In most studies carried out to prove the beneficial effects of curcumin on serum parameters, these levels were diminished or unchanged. The results reported by Deters et al. (2003) [45] suggest that oral administration of curcumin at a 100 mg/kg bw produced no changes in cholesterol or triglyceride levels; nevertheless, a group treated with the same concentration of curcumin and cyclosporine did display an increase in these markers; this suggests the possible antagonistic effect that curcumin may have with some substances. In a report by Qiu et al. (2016) [46], two concentrations of curcumin were tested: 100 and 25 mg; at 100 mg, a decrease in body weight, cholesterol, GLUT 2, and COX 2 was observed; however, an increase in IL 6 and FAS occurred at the 25 mg concentration. ...
Current changes in diet, characterized by an increase in the intake of sweetened beverages, are heavily related to metabolic disorders such as non-alcoholic fatty liver. This condition can produce simple steatosis and, in worse cases, potentially result in steatohepatitis, fibrosis, and cirrhosis, comparable to the damage caused by the consumption of more or less 20–30 g of alcohol per day. The main objective of this research was to evaluate the effect of curcumin (Curcuma longa) nanoemulsions, using mono- and diacylglycerides medium chain fatty acids as stabilizers in an in vivo hepatic steatosis rat model. Pathology was induced by providing 30% fructose intake in the drinking water. Globule sizes under 200 nm that were stable for 4 weeks were obtained; curcumin encapsulated in the nanoemulsion was >70%. The results revealed an improvement regarding body and liver weight in the animals treated with curcumin nanoemulsions. A decrease in total cholesterol, LDL, AST/ALT, and HDL in serum was observed; however, no apparent improvement regarding serum glucose or triacylglycerides values was noted. Histological analysis showed a significant decrease in the extent of steatosis, inflammation, and brown adipose tissue in the treated animals.
... ANIT+ curcumin and ANIT+ 6ECDCA were treated with curcumin (120 mg/kg) or 6ECDCA (20 mg/kg), respectively, for 5 days while Control and ANIT were given normal saline. (Curcumin at dose of 120 mg/kg or 6ECDCA at dose of 20 mg/kg was selected based on our previous study and published findings [44][45][46] ). Four hours after curcumin or 6ECDCA treatment on day 2, ANIT (dissolved in oil, 60 mg/kg) were administered intragastrically in the ANIT, ANIT+ curcumin, and ANIT+ 6ECDCA groups. ...
Cholestasis is a clinically significant symptom and widely associated with liver diseases, however, there are very few effective therapies for cholestasis. Danning tablet (DNT, a Chinese patent medicine preparation) has been clinically used to treat human liver and gallbladder diseases for more than 20 years in China. However, which ingredients of DNT contributed to this beneficial effect and their mechanistic underpinnings have been largely unknown. In the present study, we discovered that DNT not only demonstrated greater benefits for cholecystitis patients after cholecystectomy surgery in clinic but also showed protective effect against alpha-naphthylisothiocyanate (ANIT)-induced cholestasis model in rodent. Curcumin, one major compound derived from DNT, exerted the protective effect against cholestasis through farnesoid X receptor (FXR), which has been focused as potential therapeutic targets for treating cholestasis. The underlying mechanism of curcumin against cholestasis was restoring bile acid homeostasis and antagonizing inflammatory responses in a FXR-dependent manner and in turn contributed to overall cholestasis attenuation. Collectively, curcumin can be served as a potential treatment option for liver injury with cholestasis.
... This might result from changes in insulin signaling pathways resulting in excess triglyceride production and secretion [81]. Rates of dyslipidemia were lower when sirolimus was combined with TAC compared to CSA [82]. There is similar evidence of a synergistic hyperlipidemic effect between CSA and everolimus [83]. ...
Metabolic syndrome (MS) is an established risk factor for atherosclerosis and cardiovascular disease that affects 20-30% of the adult population in the western world, correlating with increased incidence of cardiovascular disease. Survival following liver transplantation (LT) has been steadily improving over the last 2 decades, with graft loss becoming a relatively rare cause of morbidity and mortality post LT. The improvement in short-term survival following LT has resulted in an increased incidence of metabolic and cardiovascular complications, which affect the mid- and long term survival. Patients following LT typically gain weight and might develop diabetes, hypertension and dyslipidemia as a consequence of their immunosuppressive therapy and their lifestyle. In this paper we review the prevalence of metabolic and cardiovascular complications following LT, their impact on post-transplant morbidity and mortality and their optimal management.
... The net effect of inhibition of calcineurin by CsA is thus a reduced T cell activation response (Baken et al. 2008;Cristillo and Bierer 2002;Ho et al. 1996;Johnson et al. 2003;Mascarell and Truffa-Bachi 2003;Stepkowski and Kirken 2000). Next to its immunosuppressive effects, CsA can also cause hepatotoxicity (cholestasis), neurotoxicity, renal toxicity and carcinogenesis (de Arriba et al. 2013;Deters et al. 2003;Erdem et al. 2011;Klawitter et al. 2010;Kuschal et al. 2012). ...
Transcriptomics in combination with in vitro cell systems is a powerful approach to unravel modes of action of toxicants. An important question is to which extent the modes of action as revealed by transcriptomics depend on cell type, species and study type (in vitro or in vivo). To acquire more insight into this, we assessed the transcriptomic effects of the immunosuppressive drug cyclosporine A (CsA) upon 6 h of exposure of the mouse cytotoxic T cell line CTLL-2, the thymoma EL-4 and primary splenocytes and compared these to the effects in spleens of mice orally treated with CsA for 7 days. EL-4 and CTLL-2 cells showed the highest similarities in response. CsA affected many genes in primary splenocytes that were not affected in EL-4 or CTLL-2. Pathway analysis demonstrated that CsA upregulated the unfolded protein response, endoplasmic reticulum stress and NRF2 activation in EL-4 cells, CTLL-2 cells and primary mouse splenocytes but not in mouse spleen in vivo. As expected, CsA downregulated cell cycle and immune response in splenocytes in vitro, spleens in vivo as well as CTLL-2 in vitro. Genes up- and downregulated in human Jurkat, HepG2 and renal proximal tubular cells were similarly affected in CTLL-2, EL-4 and primary splenocytes in vitro. In conclusion, of the models tested in this study, the known mechanism of immunotoxicity of CsA is best represented in the mouse cytotoxic T cell line CTLL-2. This is likely due to the fact that this cell line is cultured in the presence of a T cell activation stimulant (IL-2) making it more suitable to detect inhibitory effects on T cell activation.
... Moreover lipid Curcuma extract carriers showed a significantly higher and earlier serum peak concentration and a greater AUC 0-∞ compared with Curcuma extract [38]. The phytosomized extract significantly improves its oral bioavailability, and its tissue distribution in spleen, heart, liver, kidney, lung and brain [39]. ...
Curcuma extract exerts a myorelaxant effect on the mouse intestine. In view of a possible use of curcuma extract in motor functional disorders of the gastrointestinal tract, a safety profile study has been carried out in the mouse.
Thirty mice were used to study the in vitro effect of curcuma on gallbladder, bladder, aorta and trachea smooth muscular layers and hearth inotropic and chronotropic activity. The myorelaxant effect on the intestine was also thoroughly investigated. Moreover, curcuma extract (200 mg/Kg/day) was orally administered to twenty mice over 28 days and serum liver and lipids parameters were evaluated. Serum, bile and liver bile acids qualitative and quantitative composition was were also studied.
In the intestine, curcuma extract appeared as a not competitive inhibitor through cholinergic, histaminergic and serotoninergic receptors and showed spasmolytic effect on K(+) induced contraction at the level of L type calcium channels. No side effect was observed on bladder, aorta, trachea and heart when we used a dose that is effective on the intestine. An increase in gallbladder tone and contraction was observed. Serum liver and lipids parameters were normal, while a slight increase in serum and liver bile acids concentration and a decrease in bile were observed.
Although these data are consistent with the safety of curcuma extract as far as its effect on the smooth muscular layers of different organs and on the heart, the mild cholestatic effect observed in absence of alteration of liver function tests must be further evaluated and the effective dose with minimal side effects considered.
... Sirolimus is a potent hyperlipidemic agent [70], possibly by affecting the insulin signaling pathway, increasing adipose tissue lipase activity, and decreasing lipoprotein lipase activity, particularly when used in combination with cyclosporine [71,72]. There is similar evidence of a synergistic hyperlipidemic affect between cyclosporine and everolimus [73]. The basis of the relatively prolipidemic effects of cyclosporine are not known but may involve inhibition of hepatic bile acid 26-hydroxylase, thereby decreasing bile acid synthesis from cholesterol and reducing the subsequent transport of cholesterol into bile and the intestine [74]. ...
Metabolic syndrome is common among liver transplant recipients before and after transplantation. The components of metabolic syndrome are often exacerbated in the post-transplant period by transplant specific factors, such as immunosuppression, and are strong predictors of patient morbidity and mortality. Many aspects of the metabolic syndrome are modifiable. Early recognition, prevention and treatment of post-transplant hypertension, obesity, dyslipidemia and diabetes may impact long-term post-transplant survival. Further study into the prevention and management of these issues in the transplant patient are needed.
... Also dietary curcumin restores progenitor, effector, and circulating Tcells in tumor-bearing hosts [33]. In in-vitro studies, it was demonstrated that CsA aborts PHA and PMA mediated T cell proliferation [34], and curcumin does not influence the action of CsA in-vivo [35]. In this study we show that CsA, aborts curcumin-mediated T cell proliferation capacity invivo. ...
Curcumin specifically exhibits cytostatic and cytotoxic effects against tumors of multiple origin. Previously we have demonstrated apoptotic activity of curcumin against tumor cells with no effect on normal cells in-vitro. Many anti-cancer drugs exhibit deleterious effects on immune cells, which restrict their wide use in-vivo. In the present study, we have evaluated the effect of curcumin on the major functions of T cells, natural killer cells, macrophages and on total splenocytes in-vivo, which insight the role of curcumin on their broad effector functions. This study demonstrates that prolonged curcumin-injections (i.p.) do not impair the cytotoxic function of natural killer cells, the generation of reactive oxygen species and nitric oxide from macrophages and the levels of Th1 regulatory cytokines remained unaltered. Interestingly, curcumin-injections enhanced the mitogen and antigen induced proliferation potential of T cells. We have also evaluated immunomodulatory effects of curcumin in ascites-bearing animals. This study strengthens our belief that curcumin is a safe and useful immunomodulator for the immune system.
Cholestasis is a common manifestation of decreased bile flow in various liver diseases. It results in fibrosis and even cirrhosis without proper treatment. It is believed that a wide range of factors, including transporter dysfunction, oxidative stress, inflammatory damage, and immune disruption, can cause cholestasis. In recent years, natural products have drawn much attention for specific multiple‐target activities in diseases. Many attempts have been made to investigate the anticholestatic effects of natural products with advanced technology. This review summarizes recent studies on the biological activities and mechanisms of recognized compounds for cholestasis treatment. Natural products, including various flavonoids, phenols, acids, quinones, saponins, alkaloids, glycosides, and so on, function as comprehensive regulators via ameliorating oxidative stress, inflammation, and apoptosis, restoring bile acid balance with hepatic transporters, and adjusting immune disruption. Moreover, in this progress, nuclear factor erythroid 2‐related factor 2, reactive oxygen species production, heme oxygenase‐1, NF‐κB, cholesterol 7 alpha‐hydroxylase, and farnesoid X receptors are thought as main targets for the activity of natural products. Therefore, this review presents the detailed mechanisms that include multiple targets and diverse signalling pathways. Natural products are the valuable when seeking novel therapeutic agents to treat cholestatic liver diseases.
Applicability of our computer programs PASS and PharmaExpert for prediction of biological activity spectra of rather complex and structurally diverse phytocomponents of medicinal plants, both separately and in combinations has been evaluated. For this purpose we have created the web-resource containing known information about structural formulas and biological activity of 1906 phytocomponents of 50 Ayurvedic medicinal plants used in Traditional Indian Medicine (TIM) (http://ayurveda.pharmaexpert.ru). The PASS training set was updated by addition of information about structure and biological activity of 946 natural compounds; then the training procedure and validation were performed, to estimate the quality of PASS prediction. It was shown that the differences between the average accuracy of prediction obtained in leave-5%-out cross-validation (94.467%) and in leave-one-out cross-validation (94.605%) are very small thus demonstrating high predictive ability of the program. Results of biological activity spectra prediction for all phytocomponents included in our database coincided in 83.5% of cases with known experimental data. Additional types of biological activity predicted with high probability indicate further promising directions for further studies of certain phytocomponents of some medicinal plants. The analysis of prediction results of sets of phytocomponents in each of 50 medicinal plants was made by the PharmaExpert software. Based on this analysis, we found that the combination of phytocomponents from Passiflora incarnata may exhibit nootropic, anticonvulsant, and antidepressant effects. Experiments carried out in mice models confirmed the predicted effects of P. incarnata extracts.
Curcumin is a polyphenol derived from the most widely used spice turmeric, Curumin as well as turmeric both have been reported to exert beneficial effects in atherosclerosis, hypercholesteremia and ischemic-reperfusion injury of the myocardium. In several experimental studies it has been demonstrated a potent cardioprotective agent. It has been reported to be a potential antioxidant and free radiacal scaverger, which reduces free radicals associated jnjuries and oxidation of low density lipo-protein. A part from potent antioxidant activity, its mechanisms of action include inhibition of several cell-singnaling pathways at multiple levels, effects on cellular enzymes such as cycloxygenase and glutathione S=transferases, immuno-modulation and effects on angiogenesis and cell-cell adhesion. Furthemore, it has also been demonstrated to exhibit artiapoptotic, anti-inflammatory and immunomodulatory properties. These pharmacological effects may explain the perceived benefits derived from treating cardiovascular disease with the herb over the centuries along with potential health promoting properties. The present article mainly focuses on the studies emphasizing its cardioprotective potential and their mechanisms.
Applicability of our computer programs PASS and PharmaExpert to prediction of biological activity spectra of rather complex and structurally diverse phytocomponents of medicinal plants, both separately and in combinations has been evaluated. The web-resource on phytochemicals of 50 medicinal plants used in Ayurveda was created for the study of hidden therapeutic potential of Traditional Indian Medicine (TIM) (http://ayurveda.pharmaexpert.ru). It contains information on 50 medicinal plants, their using in TIM and their pharmacology activities, also as 1906 phytocomponents. PASS training set was updated by addition of information about 946 natural compounds; then the training procedure and validation were performed, to estimate the quality of PASS prediction. It was shown that the difference between the average accuracy of prediction obtained in leave-5%-out cross-validation (94,467%) and in leave-one-out cross-validation (94,605%) is very small. These results showed high predictive ability of the program. Results of biological activity spectra prediction for all phytocomponents included in our database are in good correspondence with the experimental data. Additional kinds of biological activity predicted with high probability provide the information about most promising directions of further studies. The analysis of prediction results of sets of phytocomponents in each of 50 medicinal plants was made by PharmaExpert software. Based on this analysis, we found that the combination of phytocomponents from Passiflora incarnata may exhibit nootropic, anticonvulsant and antidepressant effects. Experiments carried out in mice models confirmed the predicted effects of Passiflora incarnata extracts.
Hyperlipidemia is not unusual in liver transplant recipients, but refractory severe hyperlipidemia is unusual. We treated a 39-year-old man who had severe dyslipidemia after liver transplant. The levels of blood lipids, liver enzymes, and essential indicators of liver pathology were monitored. The first serum sample was collected from the liver recipient 56 days after transplant surgery because samples could not be obtained sooner after the transplant. The levels of liver enzymes and blood lipids were improved with symptomatic treatment but had recurrent fluctuations. Tacrolimus and cyclosporine, even at low doses, may have been the dominant factor affecting the blood lipid levels in the recipient.
Doxorubicin (DOX) emulsified in Lipiodol (LIP) is used as local palliative treatment for unresectable intermediate stage hepatocellular carcinoma. The objective of this study was to examine the poorly understood effects of the main excipient in the drug delivery system, LIP, alone or together with cyclosporin A (CsA), on the in vivo liver disposition of DOX. The advanced, multi-sampling-site, acute pig model was used; samples were collected from three blood vessels (v. portae, v. hepatica and v. femoralis), bile and urine. The four treatment groups (TI-TIV) all received two intravenous 5 min infusions of DOX into an ear vein: at 0 and 200 min. Before the second dose, the pigs received a portal vein infusion of saline (TI), LIP (TII), CsA (TIII) or LIP and CsA (TIV). Concentrations of DOX and its active metabolite doxorubicinol (DOXol) were analyzed using UPLC-MS/MS. A multi-compartment model was developed to describe the distribution of DOX and DOXol in plasma, bile and urine. LIP did not affect the pharmacokinetics of DOX or DOXol. CsA (TIII and TIV) had no effect on the plasma pharmacokinetics of DOX, but a 2-fold increase in exposure to DOXol and a significant decrease in hepatobiliary clearance of DOX and DOXol was observed. Model simulations supported that CsA inhibits 99% of canalicular biliary secretion of both DOX and DOXol, but does not affect the metabolism of DOX to DOXol. In conclusion, LIP did not interact with transporters, enzymes and/or biological membranes important for the hepatobiliary disposition of DOX.
The preventive effect of curcumin, a compound isolated from the rhizome of Curcuma longa, on experimental reflux esophagitis in rats was investigated in order to validate its potential therapeutic use for gastroesophageal reflux disease. Curcumin (20mg/kg, i.d.), the antioxidative agent dimethyl sulfoxide (DMSO) (1ml/kg, i.p.) or the proton pump inhibitor lansoprazole (1mg/kg, i.d.) inhibited the formation of acute acid reflux esophagitis by 52.5, 61.5 and 70.9% respectively. Curcumin alone was not effective in preventing chronic acid reflux esophagitis, but the combination of curcumin and DMSO reduced the mortality rate and the severity of the esophagitis ulcer index to the same extent (56.5%) as did the lansoprazole (53.9%). Intraduodenal administration of curcumin also markedly prevented the formation of acute mixed reflux esophagitis, together with reducing the incidence or the severity of neutrophil infiltration, when compared to a control group. In contrast, lansoprazole tended to increase the severity of all histopathological changes, when compared to either the control or the curcumin-treated group. Aminoguanidine, a specific inducible nitric oxide synthase inhibitor, had no preventive effect against both types of acute reflux esophagitis models, and increased the mortality in the chronic acid reflux esophagitis model. From these results, it is indicated that curcumin can effectively prevent acute reflux esophagitis formation. Although curcumin is less potent than lansoprazole in inhibiting acid reflux esophagitis, it is superior to lansoprazole in inhibiting mixed reflux esophagitis. The antiulcerogenic mechanisms are considered to be closely associated with its antioxidant nature and antiinflammatory property.
To bring further insight into the mechanism of cyclosporine A (CsA)-induced hepatotoxicity, the acute effect of CsA on local hepatic blood flow (LHBF) and its association with systemic hemodynamics, histopathological and biochemical indicators of liver toxicity were studied in guinea pigs in vivo. The association of endothelin (ET) and/or Cremophor-EL (C-EL, vehicle in parenteral CsA preparation) with CsA effects was also investigated.
Animals were assigned into five groups; control, CsA, C-EL, Bosentan (non-selective ET receptor antagonist)+CsA, and BQ-123 (ET(A) receptor antagonist)+CsA. CsA was infused intravenously (i.v.) at 20 and 10mg/kg doses by 15 min interval. Antagonists were administered 15 min before CsA infusion. LHBF and mean arterial blood pressure (MAP) changes were simultaneously recorded. Blood and liver samples were collected for biochemical and histopathological examinations.
CsA, but not C-EL, decreased LHBF by 53.3% at the end of 30 min. Although being non-significant, CsA slightly increased MAP suggesting that, CsA-induced acute decrease in LHBF was likely independent of MAP changes. Bosentan (5mg/kg, i.v.) and BQ-123 (1mg/kg, i.v.) pre-treatments prevented the CsA-induced decrease in LHBF suggesting that CsA decreases LHBF through an ET-related mechanism. Additionally, CsA, but not its vehicle C-EL, caused marked acute pathological changes in the liver morphology.
CsA-induced findings of acute hepatotoxicity were prevented by bosentan and BQ-123 pre-treatments. Thus, CsA seems to exert acute hepatotoxic effect through ET-related mechanisms.
Most of the studies concerning the effects of cyclosporin A (Cs A) on red blood cell (RBC) rheology were carried out in human transplant recipients who may still have residual insufficiency and concomitant administration of other immunosuppressive and antihypertensive drugs. The aim of this study is to evaluate the effects of Cs A on red cell rheology and membrane composition in nontransplant healthy rats. Female Wistar albino rats were divided into two groups of 10 animals each. Rats received 10 mg/kg Cs A, i.p. or saline for 4 weeks. Cs A administration significantly increased the RBC deformability, and plasma and blood viscosity (p < 0.001, p < 0.01 and p < 0.01, respectively). Cs A administration to the rats increased RBC membrane cholesterol (CHO) levels and the CHO/phospholipid (PL) ratio significantly (p < 0.01 and p < 0.05, respectively) but did not change RBC membrane proteins and membrane PL levels. These results suggest that Cs A changes the rheological functions of RBC and lipid content of RBC membrane in healthy rats and thereby it may play an important role in the regulation of microcirculation.
Protections of endothelial integrity by elimination of certain risk have proven to be effective in maintaining hemostasis and in slowing the progress of the cardiovascular disease. Indigenous drugs are the natural source of protection against these disorders, which can be used more effectively by the knowledge of their active ingredients as well as by their mechanism of action. Most prominent among these drugs are garlic, [Alium sativum L., Family: Liliaceae, Bulbs] and turmeric [Curcuma longa L., Family: Zingiberaceae, Rhizomes]; commonly used Indian traditional spices. In the present study, we examined the atheroscleroprotective potential of diet supplementation of garlic and turmeric by measuring serum lipid profile, changes in cardiovascular parameters i.e. arterial blood pressure, electrocardiogram and heart rate. We further tried to elucidate the mechanism of restoration of endothelial function and the role of endothelium-derived factors mainly, nitric oxide (NO) and cycloxygenase derived contracting factors. A notable restoration of arterial blood pressure was seen in animals on garlic and turmeric supplemented diet. Animals on supplemented diet showed a significantly enhanced vasorelaxant response to adenosine, acetylcholine, isoproterenol and contractile effect of 5-hyderoxytryptamine was significantly attenuated. Inhibition of these responses by L-NMMA was smaller in tissues from herbal treated animals. Incubation of tissues with L-arginine (10(-5) M) resulted in a significant reversal of L-NMMA induced inhibition of endothelium-mediated relaxation, which appeared to be pronounced in rings from animals supplemented with herbs as compared to hypercholesterolemic animals. Addition of indomethacin (10(-5) M) augmented the relaxation in all the groups of animals. The present study demonstrated that garlic and turmeric are potent vasorelaxants as well as reduce the atherogenic properties of cholesterol. Whether combination of these vasodilators in cardiovascular disorders with increased peripheral vascular resistance remains to be determined.
Curcumin has long been expected to be a therapeutic or preventive agent for several major human diseases because of its antioxidative, anti-inflammatory, and anticancerous effects. In phase I clinical studies, curcumin with doses up to 3600-8000 mg daily for 4 months did not result in discernible toxicities except mild nausea and diarrhea. The pharmacokinetic studies of curcumin indicated in general a low bioavailability of curcumin following oral application. Nevertheless, the pharmacologically active concentration of curcumin could be achieved in colorectal tissue in patients taking curcumin orally and might also be achievable in tissues such as skin and oral mucosa, which are directly exposed to the drugs applied locally or topically. The effect of curcumin was studied in patients with rheumatoid arthritis, inflammatory eye diseases, inflammatory bowel disease, chronic pancreatitis, psoriasis, hyperlipidemia, and cancers. Although the preliminary results did support the efficacy of curcumin in these diseases, the data to date are all preliminary and not conclusive. It is imperative that well-designed clinical trials, supported by better formulations of curcumin or novel routes of administration, be conducted in the near future.
The immune system has evolved to protect the host from microbial infection; nevertheless, a breakdown in the immune system often results in infection, cancer, and autoimmune diseases. Multiple sclerosis, rheumatoid arthritis, type 1 diabetes, inflammatory bowel disease, myocarditis, thyroiditis, uveitis, systemic lupus erythromatosis, and myasthenia gravis are organ-specific autoimmune diseases that afflict more than 5% of the population worldwide. Although the etiology is not known and a cure is still wanting, the use of herbal and dietary supplements is on the rise in patients with autoimmune diseases, mainly because they are effective, inexpensive, and relatively safe. Curcumin is a polyphenolic compound isolated from the rhizome of the plant Curcuma longa that has traditionally been used for pain and wound-healing. Recent studies have shown that curcumin ameliorates multiple sclerosis, rheumatoid arthritis, psoriasis, and inflammatory bowel disease in human or animal models. Curcumin inhibits these autoimmune diseases by regulating inflammatory cytokines such as IL-1beta, IL-6, IL-12, TNF-alpha and IFN-gamma and associated JAK-STAT, AP-1, and NF-kappaB signaling pathways in immune cells. Although the beneficial effects of nutraceuticals are traditionally achieved through dietary consumption at low levels for long periods of time, the use of purified active compounds such as curcumin at higher doses for therapeutic purposes needs extreme caution. A precise understanding of effective dose, safe regiment, and mechanism of action is required for the use of curcumin in the treatment of human autoimmune diseases.
The aim of this review has been to describe the current state of the therapeutic potential of curcumin in acute and chronic lung injuries. Occupational and environmental exposures to mineral dusts, airborne pollutants, cigarette smoke, chemotherapy, and radiotherapy injure the lungs, resulting in acute and chronic inflammatory lung diseases. Despite major advances in treating lung diseases, until now disease-modifying efficacy has not been demonstrated for any of the existing drugs. Current medical therapy offers only marginal benefit; therefore, there is an essential need to develop new drugs that might be of effective benefit in clinical settings. Over the years, there has been increasing evidence that curcumin, a phytochemical present in turmeric (Curcuma longa), has a wide spectrum of therapeutic properties and a remarkable range of protective effects in various diseases. Several experimental animal models have tested curcumin on lung fibrosis and these studies demonstrate that curcumin attenuates lung injury and fibrosis caused by radiation, chemotherapeutic drugs, and toxicants. The growing amount of data from pharmacological and animal studies also supports the notion that curcumin plays a protective role in chronic obstructive pulmonary disease, acute lung injury, acute respiratory distress syndrome, and allergic asthma, its therapeutic action being on the prevention or modulation of inflammation and oxidative stress. These findings give substance to the possibility of testing curcumin in patients with lung diseases.
Curcumin, a major active component of turmeric, is extracted from the powdered dry rhizome of Curcuma longa Linn (Zingiberaceae) and it has been used for centuries in indigenous medicine. We have shown that curcumin has a protective role against myocardial necrosis in rats. The antioxidant activity of curcumin could be attributed to the phenolic and methoxy groups in conjunction with the 1,3-diketone-conjugated diene system, for scavenging of the oxygen radicals. In addition, curcumin is shown to enhance the activities of detoxifying enzymes such as glutathione-S-transferase in vivo. We have also shown that oxygen free radicals exacerbate cardiac damage and curcumin induces cardioprotective effect and it also inhibits free-radical generation in myocardial ischemia in rats. This chapter on the cardioprotective effects of curcumin covers the following aspects: (1) the history of curcumin and its discovery as a potent drug with relevance to cardiovascular diseases; (2) mechanistic role of curcumin in vitro, emphasizing the antiplatelet and anticoagulant effects; (3) cardiovascular properties of curcumin; (4) application of curcumin in different animal models (viz. myocardial ischemia, myocardial infarction, cardiomyopathy, and arrhythmia in vitro and in vivo); (5) curcumin free-radical scavenging activity, particularly against O2 radical and depletion of the oxidative stress.
In recent years, considerable interest has been focused on curcumin a compound, isolated from turmeric. Curcumin is used as a coloring, flavoring agent and has been traditionally used in medicine and cuisine in India. The varied biological properties of curcumin and lack of toxicity even when administered at higher doses makes it attractive to explore its use in various disorders like tumors of skin, colon, duodenum, pancreas, breast and other skin diseases. This chapter reviews the data on the use of curcumin for the chemoprevention and treatment of various skin diseases like scleroderma, psoriasis and skin cancer. Curcumin protects skin by quenching free radicals and reducing inflammation through nuclear factor-KB inhibition. Curcumin treatment also reduced wound-healing time, improved collagen deposition and increased fibroblast and vascular density in wounds thereby enhancing both normal and impaired wound-healing. Curcumin has also been shown to have beneficial effect as a proangiogenic agent in wound-healing by inducing transforming growth factor-beta, which induces both angiogenesis and accumulation of extracellular matrix, which continues through the remodeling phase of wound repair. These studies suggest the beneficial effects of curcumin and the potential of this compound to be developed as a potent nontoxic agent for treating skin diseases.
Turmeric, the bright yellow spice extracted from the tuberous rhizome of the plant Curcuma longa, has been used in traditional Indian and Chinese systems of medicine for centuries to treat a variety of ailments, including jaundice and hepatic disorders, rheumatism, anorexia, diabetic wounds, and menstrual difficulties. Most of the medicinal effects of turmeric have been attributed to curcumin, the principal curcumanoid found in turmeric. Recent evidence that curcumin exhibits strong anti-inflammatory and antioxidant activities and modulates the expression of transcription factors, cell cycle proteins, and signal transducing kinases has prompted the mechanism-based studies on the potential of curcumin to primarily prevent and treat cancer and inflammatory diseases. Little work has been done to study the effect of curcumin on the development of immune responses. This review discusses current knowledge on the immunomodulatory effects of curcumin on various facets of the immune response, including its effect on lymphoid cell populations, antigen presentation, humoral and cell-mediated immunity, and cytokine production.
This overview presents curcumin as a significant chemosensitizer in cancer chemotherapy. Although the review focuses on curcumin and its analogues on multidrug resistance (MDR) reversal, the relevance of curcumin as a nuclear factor (NF)-KB blocker and sensitizer of many chemoresistant cancer cell lines to chemotherapeutic agents will also be discussed. One of the major mechanisms of MDR is the enhanced ability of tumor cells to actively efflux drugs, leading to a decrease in cellular drug accumulation below toxic levels. Active drug efflux is mediated by several members of the ATP-binding cassette (ABC) superfamily of membrane transporters, which have now been subdivided into seven families designated A through G. Among these ABC families, the classical MDR is attributed to the elevated expression of ABCB1 (Pgp), ABCC1 (MRP1), and ABCG2 (MXR). The clinical importance of Pgp, MRP1, and MXR for MDR and cancer treatment has led to the investigation of the inhibiting properties of several compounds on these transporters. At present, due in part to the disappointing results associated with the many side effects of synthetic modulators that have been used in clinical trials, current research efforts are directed toward the identification of novel compounds, with attention to dietary natural products. The advantage is that they exhibit little or virtually no side effects and do not further increase the patient's medication burden.
Curcumin, the active ingredient of turmeric (Curcuma longa) used in culinary and medical practices in Asia, has immense potential for being used in cancer chemotherapy because of its control over the cell growth regulatory mechanisms. The present chapter throws light on the role of curcumin in modulating the various phases of the cell cycle and its apoptosis-inducing effects. This is followed by a discussion on the implications of these effects of curcumin for its use as a chemotherapeutic agent in cancer. Curcumin affects various cell cycle proteins and checkpoints involving downregulation of some of the cyclins and cyclin-dependent kinases, upregulation of cdk inhibitors, and inhibition of DNA synthesis. In addition, curcumin also exerts indirect control over cell division such as inhibition of telomerase activity. Remarkably, some studies point toward a selective growth-inhibitory effect of curcumin on transformed cell lines compared to nontransformed cell lines. Curcumin has also been demonstrated to have proapoptotic effects in several in vitro studies, mostly through the mitochondria-mediated pathway of apoptosis. Curcumin-mediated regulation of apoptosis involves caspases, Bcl2 family members, inhibitors of apoptosis proteins, and heat shock proteins. The accumulating data on the in vitro and in vivo actions of curcumin together with the ongoing human clinical trials will provide a better understanding of curcumin-mediated cell growth regulation, ultimately catering to the needs of human welfare.
Curcumin possesses anti-inflammatory activity and is a potent inhibitor of reactive-oxygen-generating enzymes such as lipoxygenase/cyclooxygenase, xanthine dehydrogenase/oxidase, and inducible nitric oxide synthase (iNOS); it is an effective inducer of heme oxygenase-1. Curcumin is also a potent inhibitor of protein kinase C (PKC), EGF-receptor tyrosine kinase, and IkappaB kinase. Subsequently, curcumin inhibits the activation of NF-KB and the expressions of oncogenes including c-jun, c-fos, c-myc, NIK, MAPKs, ERK, ELK, PI3K, Akt, CDKs, and iNOS. It is considered that PKC, mTOR, and EGFR tyrosine kinase are the major upstream molecular targest for curcumin intervention, whereas the nuclear oncogenes such as c-jun, c-fos, c-myc, CDKs, FAS, and iNOS might act as downstream molecular targets for curcumin actions. It is proposed that curcumin might suppress tumor promotion through blocking signal transduction pathways in the target cells. The oxidant tumor promoter TPA activates PKC by reacting with zinc thiolates present within the regulatory domain, whereas the oxidized form of cancer chemopreventive agent such as curcumin can inactivate PKC by oxidizing the vicinal thiols present within the catalytic domain. Recent studies indicated that proteasome-mediated degradation of cell proteins play a pivotal role in the regulation of several basic cellular processes, including differentiation, proliferation, cell cycling, and apoptosis. It has been demonstrated that curcumin-induced apoptosis is mediated through the impairment of the ubiquitin-proteasome pathway.
Turmeric (Curcuma longa) is extensively used as a household remedy for various diseases. For the last few decades, work has been done to establish the biological activities and pharmacological actions of curcumin, the principle constituent of turmeric. Curcumin has proven to be beneficial in the prevention and treatment of a number of inflammatory diseases due to its anti-inflammatory activity. Arachidonic acid-derived lipid mediators that are intimately involved in inflammation are biosynthesized by pathways dependent on cyclooxygenase (COX) and lipoxygenase (LOX) enzymes. The role of LOX and COX isoforms, particularly COX-2, in the inflammation has been well established. At cellular and molecular levels, curcumin has been shown to regulate a number of signaling pathways, including the eicosanoid pathway involving COX and LOX. A number of studies have been conducted that support curcumin-mediated regulation of COX and LOX pathways, which is an important mechanism by which curcumin prevents a number of disease processes, including the cancer. The specific regulation of 5-LOX and COX-2 by curcumin is not fully established; however, existing evidence indicates that curcumin regulates LOX and COX-2 predominately at the transcriptional level and, to a certain extent, the posttranslational level. Thus, the curcumin-selective transcriptional regulatory action of COX-2, and dual COX/LOX inhibitory potential of this naturally occurring agent provides distinctive advantages over synthetic COX/LOX inhibitors, such as nonsteroidal anti-inflammatory drugs. In this review, we discuss evidence that supports the regulation of COX and LOX enzymes by curcumin as the key mechanism for its beneficial effects in preventing various inflammatory diseases.
Angiogenesis, the formation of new blood vessels from host vasculature, is critical for tumor growth and metastases. -Curcumin, a novel small-molecular-weight compound, has been shown to inhibit carcinogenesis in different organs and the common link between these actions is its antiangiogenic effect. Curcumin is a direct inhibitor of angiogenesis and also downregulates various proangiogenic proteins like vascular endothelial growth factor and basic fibroblast growth factor. Curcumin's antiangiogenic effect is also in part due to its inhibitory effect on signal transduction pathways, including those involving protein kinase C and the transcription factors NF-kappaB and AP-1. Curcumin has an inhibitory effect on two groups of proteinases involved in angiogenesis that are the members of the matrix metalloproteinase family and the urokinase plasminogen activator family. Cell adhesion molecules are upregulated in active angiogenesis and curcumin can block'this effect, adding further dimensions to curcumin's antiangiogenic effect. Curcumin shows a dose-dependent inhibition on tumor necrosis factor, a versatile cytokine, which has its effect on angiogenesis through the signal transduction pathways, expression of proangiogenic factors, and cell adhesion molecules. Curcumin's effect on the overall process of angiogenesis compounds its enormous potential as an antiangiogenic drug.
Curcumin was found to be cytotoxic in nature to a wide variety of tumor cell lines of different tissue origin. The action of curcumin is dependent on with the cell type, the concentration of curcumin (IC50: 2-40 microg/mL), and the time of the treatment. The major mechanism by which curcumin induces cytotoxicity is the induction of apoptosis. Curcumin decreased the expression of antiapoptotic members of the Bcl-2 family and elevated the expression of p53, Bax, procaspases 3, 8, and 9. Curcumin prevents the entry of nuclear factor KB (NF-KB) into the nucleus there by decreasing the expression of cell cycle regulatory proteins and survival factors such as Bcl-2 and survivin. Curcumin arrested the cell cycle by preventing the expression of cyclin D1, cdk-1 and cdc-25. Curcumin inhibited the growth of transplantable tumors in different animal models and increased the life span of tumor-harboring animals. Curcumin inhibits metastasis of tumor cells as shown in in vitro as well as in vivo models, and the possible mechanism is the inhibition of matrix metalloproteases. Curcumin was found to suppress the expression of cyclooxygenase-2, vascular endothelial growth factor, and intercellular adhesion molecule- and elevated the expression of antimetastatic proteins, the tissue inhibitor of metalloproteases-2, nonmetastatic gene 23, and Ecadherin. These results indicate that curcumin acts at various stages of tumor cell progression.
Chemoprevention, which is referred to as the use of nontoxic natural or synthetic chemicals to intervene in multistage carcinogenesis, has emerged as a promising and pragmatic medical approach to reduce the risk of cancer. Numerous components of edible plants, collectively termed "phytochemicals" have been reported to possess substantial chemopreventive properties. Curcumin, a yellow coloring ingredient derived from Curcuma longa L. (Zingiberaceae), is one of the most extensively investigated and well-defined chemopreventive phytochemicals. Curcumin has been shown to protect against skin, oral, intestinal, and colon carcinogenesis and also to suppress angiogenesis and metastasis in a variety animal tumor models. It also inhibits the proliferation of cancer cells by arresting them in the various phases of the cell cycle and by inducing apoptosis. Moreover, curcumin has a capability to inhibit carcinogen bioactivation via suppression of specific cytochrome P450 isozymes, as well as to induce the activity or expression of phase II carcinogen detoxifying enzymes. Well-designed intervention studies are necessary to assess the chemopreventive efficacy of curcumin in normal individuals as well as high-risk groups. Sufficient data from pharmacodynamic as well as mechanistic studies are necessary to advocate clinical evaluation of curcumin for its chemopreventive potential.
Curcumin is the active ingredient of turmeric that has been consumed as a dietary spice for ages. Turmeric is widely used in traditional Indian medicine to cure biliary disorders, anorexia, cough, diabetic wounds, hepatic disorders, rheumatism, and sinusitis. Extensive investigation over the last five decades has indicated that curcumin reduces blood cholesterol, prevents low-density lipoprotein oxidation, inhibits platelet aggregation, suppresses thrombosis and myocardial infarction, suppresses symptoms associated with type II diabetes, rheumatoid arthritis, multiple sclerosis, and Alzheimer's disease, inhibits HIV replication, enhances wound healing, protects from liver injury, increases bile secretion, protects from cataract formation, and protects from pulmonary toxicity and fibrosis. Evidence indicates that the divergent effects of curcumin are dependent on its pleiotropic molecular effects. These include the regulation of signal transduction pathways and direct modulation of several enzymatic activities. Most of these signaling cascades lead to the activation of transcription factors. Curcumin has been found to modulate the activity of several key transcription factors and, in turn, the cellular expression profiles. Curcumin has been shown to elicit vital cellular responses such as cell cycle arrest, apoptosis, and differentiation by activating a cascade of molecular events. In this chapter, we briefly review the effects of curcumin on transcription factors NF-KB, AP-1, Egr-1, STATs, PPAR-gamma, beta-catenin, nrf2, EpRE, p53, CBP, and androgen receptor (AR) and AR-related cofactors giving major emphasis to the molecular mechanisms of its action.
Curcumin, a yellow pigment from Curcuma longa, is a major component of turmeric and is commonly used as a spice and food-coloring agent. It is also used as a cosmetic and in some medical preparations. The desirable preventive or putative therapeutic properties of curcumin have also been considered to be associated with its antioxidant and anti-inflammatory properties. Because free-radical-mediated peroxidation of membrane lipids and oxidative damage of DNA and proteins are believed to be associated with a variety of chronic pathological complications such as cancer, atherosclerosis, and neurodegenerative diseases, curcumin is thought to play a vital role against these pathological conditions. The anti-inflammatory effect of curcumin is most likely mediated through its ability to inhibit cyclooxygenase-2 (COX-2), lipoxygenase (LOX), and inducible nitric oxide synthase (iNOS). COX-2, LOX, and iNOS are important enzymes that mediate inflammatory processes. Improper upregulation of COX-2 and/or iNOS has been associated with the pathophysiology of certain types of human cancer as well as inflammatory disorders. Because inflammation is closely linked to tumor promotion, curcumin with its potent anti-inflammatory property is anticipated to exert chemopreventive effects on carcinogenesis. Hence, the past few decades have witnessed intense research devoted to the antioxidant and anti-inflammatory properties of curcumin. In this review, we describe both antioxidant and anti-inflammatory properties of curcumin, the mode of action of curcumin, and its therapeutic usage against different pathological conditions.
Curcumin, a compound in the human food supply, represents a near-perfect starting point for drug discovery. Consequently, a number of research groups have taken the natural product as a starting point to prepare and biologically evaluate a wide variety of curcumin analogues. One widely used structural modification truncates the central conjugated beta-diketone in curcumin to the monocarbonyl dienone. A diverse array of the latter compounds exhibit cytotoxicities against an equally diverse set of cancer-related cell lines. Importantly, these compounds still retain toxicity profiles in rodents comparable to the parent natural product, whereas some analogues (e.g., EF-24, 41) exhibit good oral bioavailability and good pharmacokinetics in mice. Thiol conjugates of EF-24 analogues have been prepared that address stability and solubility issues while demonstrating cellular activities similar to the unmodified dienones. In parallel experiments, the factor VIIa-tissue factor complex (fVIIa-TF) has been exploited to develop a targeting strategy for the analogues. In particular, the EF24-FFRck-fVIIa protein conjugate is not only somewhat more effective relative to the drug alone against breast cancer and melanocyte cells. Both simple curcumin analogues and the protein conjugate evidence antiangiogenic activity in cell culture. The implication is that the fVIIa-TF targeting process, like the dienone drugs, permits a double-pronged attack with the potential to destroy a tumor directly by apoptosis.
Turmeric, derived from the plant Curcuma longa, is a gold-colored spice commonly used in the Indian subcontinent, not only for health care but also for the preservation of food and as a yellow dye for textiles. Curcumin, which gives the yellow color to turmeric, was first isolated almost two centuries ago, and its structure as diferuloylmethane was determined in 1910. Since the time of Ayurveda (1900 Bc) numerous therapeutic activities have been assigned to turmeric for a wide variety of diseases and conditions, including those of the skin, pulmonary, and gastrointestinal systems, aches, pains, wounds, sprains, and liver disorders. Extensive research within the last half century has proven that most of these activities, once associated with turmeric, are due to curcumin. Curcumin has been shown to exhibit antioxidant, anti-inflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer's disease, and other chronic illnesses. These effects are mediated through the regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other enzymes. Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal "Spice for Life".
Tacrolimus (FK506) is a potent immunosuppressant widely used for organ transplantation patients while diltiazem (DTZ), a calcium-channel inhibitor, is often used in renal transplantation patients to prevent post-transplant hypertension. However, DTZ has a significant pharmacokinetic interaction with FK506. In this study, a rapid and sensitive ammonium-adduct based liquid chromatography-tandem mass spectrometry (LC/MS/MS) method has been developed and validated for the simultaneous determination of FK506 and DTZ in human whole blood using ascomycin as the internal standard (IS). After extraction of the whole blood samples by ethyl acetate, FK506, DTZ and the IS were subjected to LC/MS/MS analysis using electro-spray positive-ion mode ionization (ESI(+)). Chromatographic separation was performed on a Hypersil BDS C18 column (50 mm x 2.1 mm, i.d., 3 microm). The MS/MS detection was conducted by monitoring the fragmentation of 821.7-->768.9 (m/z) for FK506, 415.5-->310.3 (m/z) for DTZ and 809.8-->757.0 (m/z) for IS. The method had a chromatographic running time of approximately 2 min and linear calibration curves over the concentrations of 0.5-200 ng/mL for FK506 and 2-250 ng/mL for DTZ. The recoveries of liquid-liquid extraction method were 58.3-62.6% for FK506 and 50.4-58.8% for DTZ. The lower limit of quantification (LLOQ) of the analytical method was 0.5 ng/mL for FK506 and 2 ng/mL for DTZ. The intra- and inter-day precision was less than 15% for all quality control samples at concentrations of 2, 10, and 50 ng/mL for FK506 and 5, 25, and 100 ng/mL for DTZ. The validated LC/MS/MS method has been successfully used to analyze the concentrations of FK506 and DTZ in whole blood samples from pharmacokinetic studies in renal transplanted patients.
The canalicular multispecific organic anion transporter (cMOAT), a member of the ATP-binding cassette transporter family, mediates the transport of a broad range of non-bile salt organic anions from liver into bile. cMOAT-deficient Wistar rats (TR-) are mutated in the gene encoding cMOAT, leading to defective hepatobiliary transport of a whole range of substrates, including bilirubin glucuronide. These mutants also have impaired hepatobiliary excretion of GSH and, as a result, the bile flow in these animals is reduced. In the present work we demonstrate a role for cMOAT in the excretion of GSH both in vivo and in vitro. Biliary GSH excretion in rats heterozygous for the cMOAT mutation (TR/tr) was decreased to 63% of controls (TR/TR) (114+/-24 versus 181+/-20 nmol/min per kg body weight). Madin-Darby canine kidney (MDCK) II cells stably expressing the human cMOAT protein displayed >10-fold increase in apical GSH excretion compared with wild-type MDCKII cells (141+/-6.1 pmol/min per mg of protein versus 13.2+/-1.3 pmol/min per mg of protein in wild-type MDCKII cells). Similarly, MDCKII cells expressing the human multidrug resistance protein 1 showed a 4-fold increase in GSH excretion across the basolateral membrane. In several independent cMOAT-transfectants, the level of GSH excretion correlated with the expression level of the protein. Furthermore, we have shown, in cMOAT-transfected cells, that GSH is a low-affinity substrate for the transporter and that its excretion is reduced upon ATP depletion. In membrane vesicles isolated from cMOAT-expressing MDCKII cells, ATP-dependent S-(2,4-dinitrophenyl)glutathione uptake is competitively inhibited by high concentrations of GSH (Ki approximately 20 mM). We concluded that cMOAT mediates low-affinity transport of GSH. However, since hepatocellular GSH concentrations are high (5-10 mM), cMOAT might serve an important physiological function in maintenance of bile flow in addition to hepatic GSH turnover.
The new immunosuppressive agent sirolimus generally is combined in transplant patients with cyclosporine and tacrolimus which both exhibit cholestatic effects. Nothing is known about possible cholestatic effects of these combinations which might be important for biliary excretion of endogenous compounds as well as of immunosuppressants.
Rats were daily treated with sirolimus (1 mg kg−1 p.o.), cyclosporine (10 mg kg−1 i.p.), tacrolimus (1 mg kg−1 i.p.), or a combination of sirolimus with cyclosporine or tacrolimus. After 14 days a bile fistula was installed to investigate the effects of the immunosuppressants and their combinations on bile flow and on biliary excretion of bile salts, cholesterol, and immunosuppressants.
Cyclosporine as well as tacrolimus reduced bile flow (−22%; −18%), biliary excretion of bile salts (−15%;−36%) and cholesterol (−15%; −47%). Sirolimus decreased bile flow by 10%, but had no effect on cholesterol or bile salt excretion.
Combination of sirolimus/cyclosporine decreased bile flow and biliary bile salt excretion to the same extent as cyclosporine alone, but led to a 2 fold increase of biliary cholesterol excretion. Combination of sirolimus/tacrolimus reduced bile flow only by 7.5% and did not change biliary bile salt and cholesterol excretion.
Sirolimus enhanced blood concentrations of cyclosporine (+40%) and tacrolimus (+57%). Sirolimus blood concentration was increased by cyclosporine (+400%), but was not affected by tacrolimus.
We conclude that a combination of sirolimus/tacrolimus could be the better alternative to the cotreatment of sirolimus/cyclosporine in cholestatic patients and in those facing difficulties in reaching therapeutic ranges of sirolimus blood concentration.
British Journal of Pharmacology (2002) 136, 604–612; doi:10.1038/sj.bjp.0704756
Bile flow is rapidly and markedly reduced in hepatic inflammation, correlating with suppression of critical hepatic bile acid transporter gene expression, including the principal hepatic bile acid importer, the Na(+)/taurocholate co-transporting polypeptide (Ntcp, Slc10a1). Endotoxin treatment of rats and interleukin-1 beta (IL-1 beta) treatment of liver-derived HepG2 cells leads to a marked decline in the nuclear binding activity of a main Ntcp gene regulator, the nuclear receptor heterodimer retinoid X receptor:retinoic acid receptor (RXR:RAR). How IL-1 beta signaling leads to reduced RXR:RAR nuclear binding activity is unknown, and we sought to determine whether mitogen-activated protein kinase (MAPK) pathways were involved. IL-1 beta treatment of cultured primary rat hepatocytes markedly reduced Ntcp RNA levels and Ntcp promoter activity in transiently transfected HepG2 cells. Pretreatment with inhibitors of extracellular signal-regulated kinase (ERK, PD98059) or p38 MAPK (SB203580) did not affect IL-1 beta-mediated suppression of Ntcp gene expression, whereas curcumin, a derivative of the spice turmeric and a recently described inhibitor of c-Jun N-terminal kinase (JNK), completely ameliorated the effects of IL-1 beta. Co-transfection of a JNK expression plasmid inhibited RXR:RAR-mediated activation of the Ntcp promoter, while a dominant negative JNK expression plasmid completely blocked IL-1 beta-mediated suppression. Curcumin, but not PD98059 or SB203580, inhibited IL-1 beta-mediated suppression of nuclear RXR:RAR binding activity, which correlated with inhibition of JNK phosphorylation and phospho-JNK-mediated phosphorylation of RXR. Taken together, these data provide evidence supporting a novel player (JNK), as well as its inhibitor (curcumin), in inflammation-mediated regulation of hepatobiliary transporters and correlate JNK-dependent RXR phosphorylation with reduced RXR-dependent hepatic gene expression.
In selectively isolated basolateral (bILPM) and canalicular (cLPM) rat liver plasma membrane vesicles, the in vitro effect of cyclosporine A (CsA) on specific hepatic membrane transport processes was examined. CsA (0.1-200 microM) caused a concentration-dependent inhibition of initial rates of Na(+)-dependent taurocholate uptake in bILPM and cLPM vesicles and Na(+)-independent taurocholate efflux from cLPM vesicles. In contrast, CsA had no effect on Na(+)-dependent L-alanine uptake in bILPM and in cLPM vesicles. In addition, electroneutral pH gradient-driven Na+ uptake in bILPM vesicles was unaffected by CsA treatment. CsA-induced inhibition of taurocholate transport in bILPM and cLPM vesicles was competitive in nature. A hydroxylated (OL-17) and a N-demethylated (OL-21) metabolite of CsA had no effect on taurocholate transport in either membrane vesicle population. These findings suggest that the mechanism of CsA-induced cholestasis is, in part, the result of selective inhibition of bile acid transport by the parent compound at both domains of the hepatocyte plasma membrane.
Using solid-phase extraction columns and "high-performance" liquid-chromatographic (HPLC) analysis, we could determine cyclosporin A and nine of its metabolites in blood, bile, and urine. To facilitate calculations of concentrations of cyclosporin A and its metabolites from the chromatograms, we used cyclosporin D as internal standard. For the HPLC analysis we used two sequential 250-mm analytical columns filled with reversed-phase octyl (C8) sorbent, eluting with a concave gradient of water, adjusted to pH 3.0 with phosphoric acid, and acetonitrile. Peaks were detected at 205 nm. For characterization of the chromatographic peaks, we isolated, by semi-preparative HPLC, 32 fractions representing peaks potentially related to cyclosporin A metabolites and re-injected them into the HPLC system under the same conditions as authentic cyclosporin A metabolites. Analytical recovery was 70-80%. The inter-assay CV for bile was 7.2%, for urine 12.3%. The method was used for routine monitoring of cyclosporin A and its metabolites.
The use of cyclosporin A in transplantation procedures has been reported to cause hepatotoxicity as evidenced by elevated serum bilirubin and bile salt levels. However, these biochemical abnormalities could also result from interference with hepatic transport processes. This possibility was investigated in the present study in which the effect of cyclosporin A on transport processes was examined in isolated rat liver cells. Taurocholate, ouabain, and alpha-aminoisobutyric acid were selected as compounds known to enter liver cells by distinct active transport systems and cadmium was selected as a substance taken up by a combination of simple and facilitated diffusion. Cyclosporin A was found to cause a dose-related inhibition of both taurocholate and ouabain uptake. On the other hand, the uptake of alpha-aminoisobutyric acid and of cadmium were unaffected by cyclosporin A. These findings indicate a substrate-specific effect of cyclosporin A rather than a general effect on cellular transport. Efflux of taurocholate from preloaded hepatocytes was also inhibited by cyclosporin A. Cyclosporin A caused a decrease in maximum velocity for ouabain uptake with no change in Km. Kinetic analysis for both uptake and efflux of taurocholate showed an unchanged maximum velocity and an increased Km. The data indicate that the ability of liver cells to take up and release bile acids is impaired in the presence of cyclosporin A. These findings provide a possible explanation for the finding of increased serum bile acids during cyclosporin A therapy and suggest that hepatic clearance of other compounds could also be impaired.
Two hundred twenty-eight patients from a total of 466 (49%) receiving renal allografts under cyclosporine/prednisone (CsA/Pred) immunosuppression experienced at least one episode of posttransplant hepatotoxicity. All patients were documented to have normal serum bilirubin, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvate transaminase (SGPT), lactic acid dehydrogenase (LDH), and alkaline phosphatase (AP), as well as negative results of biliary ultrasound and upper gastrointestinal contrast examinations prior to transplantation. Hepatotoxic episodes usually were self-limited (82%), and generally occurred during the very early posttransplant period (76%). Liver function abnormalities included hyperbilirubinemia (48% of patients), elevated SGOT (47%), SGPT (73%), LDH (84%), and AP (59%). The CsA serum trough radioimmunoassay (RIA) was relatively high among hepatotoxic patients with a mean value of 225 +/- 17 ng/ml. Pharmacokinetic parameters, including bioavailability and drug clearance, were significantly altered among this group of patients. The management strategy of CsA dose reduction was effective; however, 11 patients (2.4%) developed biliary calculous disease posttransplant while under CsA/Pred immunosuppression. Seven patients had cholelithiasis, and two patients underwent choledochoduodenostomy because of primary choledocholithiasis. The results contrast with 279 renal transplant recipients from an overlapping nonrandomized group treated with azathioprine (Aza)/Pred in whom cholelithiasis was not identified. Pancreatic abnormalities were relatively common, but clinical pancreatic disease occurred in only six patients. There were two episodes of acute pancreatitis, three patients developed pancreatic abscess, and one patient developed a pancreatic pseudocyst. The apparent proclivity of CsA-treated patients to develop biliary calculous disease, and the occurrence of serious pancreatic complications in a small percentage of patients did not affect the majority of CsA-treated patients. They may, however, represent important problems associated with the use of this immunosuppressive agent.
1. The effects of cyclosporine A (CyA) treatment on liver morphology, bile flow and biliary secretion of bile acid, cholesterol and phospholipid and some plasma biochemical indicators of liver function were examined.
2. Wistar rats were treated i.p. with 10 or 20 mg of CyA/kg per day for 1, 2, 3 or 4 weeks.
3. Treatment increased bile acid and bilirubin plasma concentration. Bile flow and biliary secretion of bile acid, cholesterol and phospholipid were reduced in CyA‐treated animals.
4. All these effecs of the drug appeared at 1 week after the start of treatment and were enhanced during prolonged treatment. Cyclosporine A‐induced cholestasis was due to a decrease in both the bile acid‐dependent and ‐independent fractions of bile flow.
5. The reduction in cholesterol and phospholipid biliary output may be secondary to the inhibition of the hepatobiliary flux of bile acid; however, perturbations in the removal of lipids from the canalicular membrane as well as intracanalicular interaction between CyA and lipid vesicles/micelles could also be involved.
The safety of long-term immunosuppression with cyclosporine in renal-transplant recipients is not well understood. This drug may cause a progressive toxic nephropathy, but it also preserves renal function because it prevents rejection. To determine the effect of cyclosporine on renal function and graft rejection, we conducted a retrospective analysis of data on 1663 renal-transplant recipients at six centers.
The rate of graft survival was 78 percent (median follow-up, 36 months). Grafts were was lost in 279 patients (17 percent), mostly because of acute rejection (68 patients) or chronic graft dysfunction that was unresponsive to a reduction in the dose of cyclosporine (125 patients); 92 patients died with functioning grafts. The median change in the serum creatinine concentration in all patients after transplantation was less than 0.001 mg per deciliter per month (< 0.09 mumol per liter per month). Patients who had episodes of rejection had decreased rates of long-term graft function and survival. Eight percent of patients with functioning grafts at one year had first episodes of rejection more than one year after transplantation. These late first rejections were associated with noncompliance with therapy (in 34 percent), blood cyclosporine concentrations that were marginally lower than those of patients who had no episodes of rejection, and a low rate of successful reversal of rejection (77 percent, vs. 97 percent in patients with rejection during the first year; P < 0.001).
The majority of renal-transplant patients tolerate long-term cyclosporine therapy without evidence of progressive toxic nephropathy. Graft failure is most often due to rejection.
The stability of curcumin, as well as the interactions between curcumin and cytochrome P450s (P450s) and glutathione S-transferases (GSTs) in rat liver, were studied. Curcumin is relatively unstable in phosphate buffer at pH 7.4. The stability of curcumin was strongly improved by lowering the pH or by adding glutathione (GSH), N-acetyl L-cysteine (NAC), ascorbic acid, rat liver microsomes, or rat liver cytosol. Curcumin was found to be a potent inhibitor of rat liver P450 1A1/1A2 measured as ethoxyresorufin deethylation (EROD) activity in beta-naphthoflavone (beta NF)-induced microsomes, a less potent inhibitor of P450 2B1/2B2, measured as pentoxyresorufin depentylation (PROD) activity in phenobarbital (PB)-induced microsomes and a weak inhibitor of P450 2E1, measured as p-nitrophenol (PNP) hydroxylation activity in pyrazole-induced microsomes. Ki values were 0.14 and 76.02 microM for the EROD- and PROD-activities, respectively, and 30 microM of curcumin inhibited only 9% of PNP-hydroxylation activity. In ethoxyresorufin deethylation (EROD) and pentoxyresorufin depentylation (PROD) experiments, curcumin showed a competitive type of inhibition. Curcumin was also a potent inhibitor of glutathione S-transferase (GST) activity in cytosol from liver of rats treated with phenobarbital (PB), beta-naphthoflavone (beta NF) and pyrazole (Pyr), when measured towards 1-chloro-2,4-dinitrobenzene (CDNB) as substrate. In liver cytosol from rats treated with phenobarbital (PB), curcumin inhibited GST activity in a mixed-type manner with a Ki of 5.75 microM and Ki of 12.5 microM. In liver cytosol from rats treated with pyrazole (Pyr) or beta-naphthoflavone (beta NF), curcumin demonstrated a competitive type of inhibition with Ki values of 1.79 microM and 2.29 microM, respectively. It is concluded that these strong inhibitory properties of curcumin towards P450s and GSTs, in addition to its well-known antioxidant activity, may help explain the previously observed anticarcinogenic, antimutagenic, and cytoprotective effects of this important natural compound and food constituent.
Unlabelled:
Livers of male rats were perfused for 120 min in a recirculating hemoglobin-free system with different concentrations of cyclosporine (CS 2, 10, 50, 150 and 200 mg/l). CS produced damage to the livers in a dose dependent manner. The first sign of hepatotoxicity was a reduction of bile flow amounting to 50% already at 50 mg/l CS. At concentrations of 150 mg/l and 200 mg/l, CS lead to a nearly complete suppression of bile flow, furthermore to a release of cytosolic (GPT, glutamate-pyruvate transaminase, LDH, lactate dehydrogenase) and mitochondrial (GLDH, glutamate dehydrogenase) enzymes into the perfusate and to a decrease in hepatic oxygen consumption (30% at 200 mg/l CS). As a consequence of the reduced aerobic energy supply, hepatic ATP concentration declined (70% at 200 mg/l CS). The hepatic concentrations of reduced glutathione (GSH) were not changed but those of oxidized glutathione (GSSG) increased up to 5-fold by CS. Malondialdehyde (MDA) concentrations in the liver and in the perfusate were not affected consistently by CS. The toxic actions of CS in the isolated rat liver were not influenced (a) by the feeding status of the rats (fed or fasted before surgery) or (b) by addition of superoxide dismutase (SOD, 20 mg/l) and catalase (20 mg/l) to the perfusate 30 min before CS. On the other hand, CS-induced hepatic injury could be attenuated or inhibited completely by addition to the perfusate of (1) 2 mmol/l GSH; (2) 12 mmol/l serine; (3) 12 mmol/l glycine; (4) 0.09 mmol/l deferoxamine (DFO).
Conclusions:
CS induces cholestasis at lower concentrations, probably by another mechanism(s) than the other signs of hepatotoxicity (enzyme release, ATP depletion). Several lines of evidence indicate a probable participation of reactive oxygen species in CS-induced hepatotoxicity. GSH, DFO, glycine and serine could provide therapeutic opportunities to prevent CS-induced hepatotoxicity in patients treated with high doses of CS.
Curcumin is a natural phenolic compound found in the rhizomes of Curcuma longa and endowed with beneficial biological activities including antioxidant, anticarcinogenic and hepatoprotective effects. In this study curcumin was tested for its potential ability to interact in vitro with hepatic P-glycoprotein (Pgp), in a model system represented by primary cultures of rat hepatocytes, in which spontaneous overexpression of multidrug resistance (mdr) genes occurs. In both freshly-plated hepatocytes, containing low levels of Pgp, and 72 hour-cultured hepatocytes, containing high levels of Pgp, the Rhodamine-123 (R-123) efflux, which represents a specific functional test for Pgp-mediated transport, was inhibited by curcumin in a dose-dependent manner. Western blot analysis showed that 25microM curcumin, when included in the culture medium throughout the experimental observation (72 hours), was able to significantly lower the increase of mAb C219-immunoreactive protein spontaneously occurring in the cells during culture. Curcumin, at doses ranging from 50 to 150microM was cytotoxic for freshly-plated hepatocytes, as shown by the strong decrease in the cell ability to exclude trypan blue 24 hours later, but it was significantly less cytotoxic when added to 24 or 48 hour-cultured cells. The resistance to curcumin, progressively acquired by cells during culture, was significantly reduced by high concentrations of dexamethasone (DEX) or dimethyl-sulfoxide (DMSO), culture conditions known to inhibit the spontaneous overexpression of Pgp. In addition, in a concentration-dependent manner, verapamil reverted curcumin resistance in Pgp overexpressing hepatocytes. In photoaffinity labeling studies, curcumin competed with azidopine for binding to Pgp, suggesting a direct interaction with glycoprotein. These results suggest that curcumin is able to modulate in vitro both expression and function of hepatic Pgp and support the hypothesis that curcumin, a chemopreventive phytochemical, could reveal itself also as a compound endowed with chemosensitizing properties on mdr phenotype.
Biliary glutathione appears to be a major osmotic factor in the generation of bile acid-independent bile flow. This study was designed to investigate its importance in cyclosporine A-induced cholestasis in both acute and short-term-treated rats.
Adult male Wistar rats were treated as follows: (i) with a single i.v. dose of cyclosporine or its vehicle (acute assays); (ii) with cyclosporine, its vehicle or physiological saline, i.p., for 7 days once per day (short-term treatment assays). Bile flow and biliary glutathione levels were determined under anesthesia both before and after intrabiliary hydrolysis of the tripeptide had been inhibited.
Acute cyclosporine administration, at a dose of 20 mg/kg, brought about an abrupt and marked fall in bile flow and bile acid secretion simultaneously with a rapid decrease in the biliary concentration and secretion rates of total, reduced and oxidized glutathione. When the rats were treated with cyclosporine A for 1 week, at a dose of 10 mg/kg per day, similar cholestatic and inhibitory effects on the biliary secretion of glutathione were noted both before and after the intrabiliary catabolism of the tripeptide had been inhibited with acivicin; in addition, the hepatic content of glutathione was also reduced. The cholestatic effect of the drug was associated with reductions in the four bile flow fractions evaluated: bile acid- and glutathione-dependent bile flow and bile acid- and glutathione-independent bile flow.
These findings indicate that cyclosporine-induced cholestasis in the rat is due not only to alterations in the hepatobiliary transport of bile acids but also to an impairment of bile formation dependent on the biliary secretion of glutathione, possibly through inhibition of the canalicular transport of the tripeptide.
Curcumin (Cur) is a phenolic component of common spice, turmeric. We have reported earlier that it possesses antineoplastic and immunosuppressive properties in vitro. It has been reported that cyclosporine A (CyA), a commonly used immunosuppressant does not inhibit CD28 costimulatory pathway of T-cell activation. We hypothesized that Cur, a tyrosine kinase inhibitor, would block CyA-resistant CD28 costimulatory pathway of human T cell proliferation.
Human T-lymphocytes were isolated from healthy donors using gradient centrifugation and rosetting techniques. In four separate experiments T-cells were plated in triplicate in 96-well plates at a density of 2X105 cells/well. These cells were stimulated with 0.5 ng/ml phorbol myristate acetate (PMA) + 0.5 (g/ml anti-CD28 antibody (PMA-CD28 group) or 2.5 microgram/ml PHA (PHA group). Cur or CyA at varying concentrations (0.31, 0.625, 1.25, 2.5, 5, or 10 microgram/ml and 1.25, 2.5, 5, 10, 20, or 250 ng/ml, respectively) was added and cellular proliferation was measured by the uptake of [3H]thymidine and is reported (mean cpm/well(SD). Cells from the PMA-CD28 group that were treated with either curcumin or 0.4% DMSO (vehicle control for curcumin) were studied for evidence of apoptosis by staining with viable dyes MC540 and Hoechst 33342 and subsequently analyzed in the cell sorter.
Cur caused a concentration-dependent inhibition of T-cell proliferation in the PMA-CD28 group (from 32775 +/- 3084 to 66 +/- 42 at 5.0 microgram/ml of cur) and PHA group (from 50956 +/- 5747 to 24 +/- 12 at 5.0 microgram/ml) with a calculated ED50 of 3.5 and 7.7, microM respectively. CyA inhibited T-cell proliferation in the PHA group with a calculated ED50 of 2.7 ng/ml but failed to block PMA + anti-CD28-stimulated T-cell proliferation even at 250 ng/ml. PMA-CD28 group cells treated with 10 microgram/ml curcumin showed a significantly increased apoptosis as compared to control (0.4% DMSO).
Since Cur blocks the CyA-resistant PMA + anti-CD28 pathway of T-cell proliferation, it may have novel adjuvant immunosuppressive properties.
Former studies have shown that curcumin, which can be extracted from different Curcuma species, is able to stimulate bile flow in rats, whereas bisdemethoxycurcumin, which is mainly found in rhizomes of Curcuma longa, is believed to inhibit bile flow. To reevaluate this observation we investigated the influence of both curcuminoids on bile flow, bile acid concentration and excretion over a time period of 180 min in the bile fistula model in rats. Furthermore, we tested the ability of both curcuminoids to reduce cyclosporin-induced cholestasis. 30 min after intravenous injection of 25 mg/kg of curcumin and bisdemethoxycurcumin bile flow was enhanced from 500 microliters/kg/15 min (100%) to 180% and to 220%, respectively. The choleretic effect of bisdemethoxycurcumin lasted longer than that of curcumin. Following intravenous injection of 30 mg/kg of cyclosporin, which reduced bile flow, bile acid concentration (15 mmol/l) and excretion (12.5 mumol/kg/15 min) to 40% of the initial value, administration of curcumin and bisdemethoxycurcumin transiently increased bile flow to 100% and to 125% of the starting value, respectively. However, only bisdemethoxycurcumin statistically significantly attenuated cyclosporin-induced reduction of bile acid excretion. We conclude that the beneficial properties of curcuminoids for the therapy of cyclosporin-induced cholestasis still remain to be proven.
We investigated the ability of curcumin, which can be extracted from different Curcuma species, to prevent cyclosporin-induced reduction of biliary bilirubin and cholesterol excretion, and its influence on biliary excretion of cyclosporin (CS) and its metabolites in the bile fistula model in rats. I.v. injection of curcumin (25 and 50 mg/kg) after 30 min increased dose-dependently basal bile flow (30 microliters/kg/min) up to 200%, biliary bilirubin excretion (3000 pmol/kg/min) up to 150%, and biliary cholesterol excretion (22 nmol/kg/min) up to 113%. CS (30 mg/kg) reduced bile flow to 66% and biliary excretion of bilirubin and of cholesterol to 33% of the basal value 30 min after i.v. injection. I.v. administration of curcumin (25 and 50 mg/kg) 30 min after CS increased bile flow dose dependently again to 130% for 1 hour and biliary excretion of cholesterol and of bilirubin to 100% of the basal value for 30 and 150 min, respectively. Injection of curcumin 15 min before CS prevented the CS-induced drop of bile flow at 50 mg/kg and reduction of biliary bilirubin excretion already at 25 mg/kg until the end of the experiment (180 min). The CS-induced reduction of biliary cholesterol excretion, however, was not prevented by curcumin. Finally, the biliary excretions of CS (1200 ng/kg/min) and its metabolites (1200 ng/kg/min) were slightly reduced by curcumin at a dose of 50 mg/kg (to 83% of the initial values). The clinical importance of these controversial effects remains to be shown.
Bile salts are the major organic solutes in bile and undergo extensive enterohepatic circulation. Hepatocellular bile salt uptake is mediated predominantly by the Na(+)-taurocholate cotransport proteins Ntcp (rodents) and NTCP (humans) and by the Na(+)-independent organic anion-transporting polypeptides Oatp1, Oatp2, and Oatp4 (rodents) and OATP-C (humans). After diffusion (bound by intracellular bile salt-binding proteins) to the canalicular membrane, monoanionic bile salts are secreted into bile canaliculi by the bile salt export pump Bsep (rodents) or BSEP (humans). Both belong to the ATP-binding cassette (ABC) transporter superfamily. Dianionic conjugated bile salts are secreted into bile by the multidrug-resistance-associated proteins Mrp2/MRP2. In bile ductules, a minor portion of protonated bile acids and monomeric bile salts are reabsorbed by non-ionic diffusion and the apical sodium-dependent bile salt transporter Asbt/ASBT, transported back into the periductular capillary plexus by Mrp3/MRP3 [and/or a truncated form of Asbt (tAsbt)], and subjected to cholehepatic shunting. The major portion of biliary bile salts is aggregated into mixed micelles and transported into the intestine, where they are reabsorbed by apical Oatp3, the apical sodium-dependent bile salt transporter (ASBT), cytosolic intestinal bile acid-binding protein (IBABP), and basolateral Mrp3/MRP3 and tAsbt. Transcriptional and posttranscriptional regulation of these enterohepatic bile salt transporters is closely related to the regulation of lipid and cholesterol homeostasis. Furthermore, defective expression and function of bile salt transporters have been recognized as important causes for various cholestatic liver diseases.