Shimin Zhang

Traditional Chinese Medicines Wu Wei Zi (Schisandra chinensis Baill) and Gan Cao (Glycyrrhiza uralensis Fisch) Activate Pregnane X Receptor and Increase Warfarin Clearance in Rats

The traditional Chinese medicines (TCMs) are essential components of alternative medicines. Many TCMs are known to alter the expression of hepatic drug-metabolizing enzymes and transporters. The molecular mechanism by which TCMs and/or their constituents regulate enzyme and transporter expression, however, has remained largely unknown. In this report, we show that two TCMs, Wu Wei Zi (Schisandra chinensis Baill) and Gan Cao (Glycyrrhiza uralensis Fisch), and their selected constituents activate the xenobiotic orphan nuclear receptor pregnane X receptor (PXR). Treatment with TCM extracts and the Schisandrol and Schisandrin constituents of Wu Wei Zi induced the expression of drug-metabolizing enzymes and transporters in reporter gene assays and in primary hepatocyte cultures. The affected enzymes and transporters include CYP3A and 2C isozymes and the multidrug resistance-associated protein 2. In transient transfection and reporter gene assays, the Schisandrin constituents of Wu Wei Zi had an estimated EC50 of 2 and 1.25 μM on hPXR and mPXR, respectively. Interestingly, mutations that were intended to alter the pore of the ligand-binding cavity of PXR had species-specific effects on the activities of the individual Schisandrols and Schisandrins. In rats, the administration of Wu Wei Zi and Gan Cao increased the metabolism of the coadministered warfarin, reinforcing concerns involving the safe use of herbal medicines and other nutraceuticals to avoid PXR-mediated drug-drug interactions. Meanwhile, the activation of PXR and induction of detoxifying enzymes provide a molecular mechanism for the hepatoprotective effects of certain TCMs.

Pharmacokinetics of Mycophenolic Acid after Mycophenolate Mofetil Administration in Liver Transplant Patients Treated with Tacrolimus

The pharmacokinetics of mycophenolic acid (MPA) was studied after oral administration of mycophenolate mofetil (MMF) in 8 liver transplant patients. The mean (± SD) maximum MPA plasma concentration of 10.6 (± 7.5) mg/ml was achieved within 0.5 to 5 hours. The mean (± SD) steady‐state area under the plasma concentration versus time curve (AUC012) was 40 (± 30.9) mg/ml/h. The mean (± SD) half‐life was 5.8 (± 3.8) hours. There was poor correlation between trough blood concentrations of tacrolimus (r = −0.004) or serum creatinine (r = 0.689) with MPA AUC, while the serum bilirubin concentrations correlated (r = 0.743) well with MPA AUC, suggesting impairment in MPA conjugation in patients with liver dysfunction. The mean (± SD) ratio of the AUC of mycophenolic acid glucuronide (MPAG) to MPA was 64 (± 84), which correlated significantly with serum creatinine (r = 0.72) but not with serum bilirubin concentrations (r = 0.309), indicating accumulation of MPAG in patients with renal dysfunction. In 7 primary liver transplant patients on the same dose of MMF, the trough plasma concentrations of MPA during the first week of therapy ranged from < 0.3 to 1.5 pg/ml. The MPA concentrations increased by several folds during the next few weeks, which correlates well with increases in serum albumin concentrations. Changes in albumin appear to partially contribute to the variations in the pharmacokinetics of MPA in liver transplant patients.

Protective role of nitric oxide in ischemia and reperfusion injury of the liver

Abstract Background: The suppressed production of nitric oxide (NO), associated with endothelial dysfunction, is thought to be a cause of ischemia and reperfusion injury of the liver. But findings of the salutary effects of NO enhancement on such injury have been conflicting. In this study, we tested our hypothesis that NO enhancement would attenuate ischemic liver injury. For this purpose, an NO precursor, L-arginine, and a novel NO donor, FK409, were applied to a 2-hour total hepatic vascular exclusion model in dogs. Study Design: L-arginine was administered IV at a dose of 100 mg/kg twice (n = 5), while 300 mg/kg twice of FK409 was infused continuously into the portal vein (n = 5). The drugs were given to the animals for 30 and 60 minutes before and after ischemia, respectively. Nontreated animals were used as the control (n = 10). Two-week survival, systemic and hepatic hemodynamics indices, liver function tests, energy metabolism, and histopathology were analyzed. Results: Both treatments comparably augmented hepatic tissue blood flow, decreased liver enzyme release, and increased high-energy phosphate restoration during the reperfusion period, all of which contributed to rescuing all of the treated animals from the 2-hour total hepatic ischemia. In contrast, ischemia caused 70% mortality in the control group. Histologically, structural abnormality and neutrophil infiltration were markedly attenuated by the treatments. Systemic hypotension was observed in the animals treated with FK409, however. Conclusions: Our data demonstrate that NO enhancement alleviates the liver injury caused by ischemia and reperfusion. The supplementation of L-arginine, rather than FK409, is considered more applicable to clinical use because of the absence of systemic adverse effects.

Intrapulmonary Penetration of Voriconazole in Patients Receiving an Oral Prophylactic Regimen

ABSTRACT Voriconazole penetrated well into the pulmonary epithelial lining fluid (ELF) in lung transplant patients receiving oral prophylaxis. The ELF concentrations exceeded those of the plasma, with an average ELF-to-plasma ratio of 11 (±8). A strong association between plasma and ELF concentrations (r2 = 0.95) was noted.

Attenuation of ischemic liver injury by augmentation of endogenous adenosine

Hepatic grafts from non-heartbeating donors may alleviate the organ shortage, but they inherently suffer from warm ischemia. In the present study, we tested our hypothesis that augmentation of endogenous adenosine by inhibition of nucleoside transport with R75231 attenuates ischemic liver injury. Adult female beagle dogs underwent 2-hr hepatic vascular exclusion with venovenous bypass. R75231 was given to the animals by continuous intravenous infusion for 30 min before ischemia at a dose of 0.1 mg/kg (Group 2, n=6), 0.05 mg/kg (Group 3, n=6), or 0.025 mg/kg (Group 4, n=6). Nontreated animals were used as the control (Group 1, n= 10). Animal survival, hepatic tissue blood flow, liver function, and histopathology were analyzed. Two-week animal survival was 30% in Group 1, 83% in Group 2, 100% in Group 3, and 100% in Group 4. Postreperfusion hepatic tissue blood flow was markedly improved by the treatment. Treatment significantly attenuated liver enzyme release, lipid peroxidation, and changes in adenine nucleotides and purine catabolites. Structural abnormality of the liver after reperfusion was markedly improved by R75231 treatment, showing better architecture and less neutrophil infiltration. Preischemic administration of a nucleoside transport inhibitor ameliorated ischemic liver injury due to the positive effects of augmented endogenous adenosine, and is applicable clinically when the liver is procured from a controlled non-heartbeating donor.

Mucosal damage and recovery of the intestine after prolonged preservation and transplantation in dogs

Background. Although much is known about the mucosal damage that occurs after intestinal warm ischemia and reperfusion and its recovery, little is known about the effect of cold preservation and transplantation on the mucosa. We studied the electrophysiological, biochemical, and histological changes of the intestinal mucosa after preservation for 24 hr and subsequent transplantation. Methods. The small intestines from adult mongrel dogs were harvested. The intestines were orthotopically autotransplanted immediately (control group) or after preservation for 24 hr (preservation group). Jejunal and ileal tissues were taken before harvesting, at the end of preservation, 1 hr after reperfusion, and on postoperative days 3, 7, 14, and 28. The Ussing chamber method was used to study the electrophysiologic changes. Tissue maltase, diamine oxidase, and ornithine decarboxylase were measured. A histological analysis was also performed. Results. Control group grafts showed no evident deterioration in electrophysiology, biochemistry, or morphology. In contrast, preservation group grafts exhibited electrophysiological and biochemical degradation, complete denudation of the villi, and crypt injury (especially in the ileum) after reperfusion. Electrophysiologic function and the mucosa biochemical marker recovered within 3 days in the jejunum and within 7–14 days in the ileum; however, histological recovery of mucosal injury required 28 days in the jejunum and more than 28 days in the ileum. Conclusions. Our study showed that despite severe destruction of mucosal integrity by prolonged preservation and transplantation, the intestinal mucosa has an enormous regenerative capacity. Our study also showed that regeneration was more pronounced in the jejunum than in the ileum.

Lazaroid U-74389G for 48-hour canine liver preservation.

Lazaroids have been reported to attenuate preservation and reperfusion injury. In this study, we examined whether lazaroids can improve the outcome after 48-hr canine liver preservation and transplantation. Adult female beagle dogs were randomized into 4 dosage groups (5 animals each). Lazaroid U-74389G was intravenously administered at a dose of 0 mg/kg, 6 mg/kg, 10 mg/kg, or 15 mg/kg to donors 30 min before harvesting and also to recipients 30 min before revascularization. Control animals (0 mg/kg) were given the lazaroid vehicle. The liver grafts were orthotopically transplanted after 48 hr of hypothermic preservation in UW solution. Lazaroid treatment significantly improved outcome after transplantation. Five-day animal survival increased from 0% in the control to 60% in the 6 mg/kg group, 100% in the 10 mg/kg group, and 80% in the 15 mg/kg group. Lazaroid protected the hepatocytes from damage during preservation, and enhanced energy charge and hepatic blood flow after reperfusion. Histological alterations were significantly less severe in the lazaroid-treated groups. The area of necrotic hepatocytes decreased from 43.7 +/- 17.7 in the control to 13.5 +/- 3.0 in the lazaroid 10 mg/kg group. These results indicate that lazaroid U-74389G has potential for improvement of clinical liver preservation.

Intrapulmonary disposition of amphotericin B after aerosolized delivery of amphotericin B lipid complex (Abelcet; ABLC) in lung transplant recipients

Background. Inhaled amphotericin preparations have been used for prophylaxis against invasive aspergillosis in lung transplant recipients. However, no published data exist regarding the pharmacokinetic profile of amphotericin B lipid complex in lung transplant recipients. Methods. We prospectively determined the concentrations of amphotericin B in the epithelial lining fluid (ELF) and plasma after aerosolized nebulization (AeroEclipse), of amphotericin B lipid complex at 1 mg/kg every 24 hr for 4 days in 35 lung transplant recipients. One brochoalveolar lavage sample and a simultaneous blood sample were collected at various time points after the fourth dose from each subject. High-performance liquid chromatography and high-performance liquid chromatography-MS-MS were used to measure amphotericin B. Results. Concentrations of amphotericin B in ELF (median, 25–75 IQR) were at 4 hr (n=5) 7.20 &mgr;g/mL (1.3–17.6), 24 hr (n=6) 8.26 &mgr;g/mL (3.9–82.7), 48 hr (n=5) 2.15 &mgr;g/mL (1.4–5.5), 72 hr (n=4) 1.25 &mgr;g/mL (0.75–5.5), 96 hr (n=6) 0.86 &mgr;g/mL (0.55–1.4), 120 hr (n=4) 1.04 &mgr;g/mL (0.44–1.6), 144 hr (n=1), 4.25 &mgr;g/mL, 168 hr (n=3) 1.14 &mgr;g/mL, and 192 hr (n=1) 1 &mgr;g/mL. The plasma concentration of the drug remained below 0.08 &mgr;g/mL at all time points. During the study, the side effects noted included wheezing, coughing, and 12% decline in forced expiratory volume in 1 sec. Conclusions. We conclude that administration through aerosolized nebulization of amphotericin B lipid complex every 24 hr for 4 days in lung transplant recipients achieved amphotericin B concentrations in ELF above minimum inhibitory concentration of the Aspergillus nearly at 168 hr after the last inhaled dose and is well tolerated.

Effect of voriconazole and other azole antifungal agents on CYP3A activity and metabolism of tacrolimus in human liver microsomes

Azole antifungal agents are known to inhibit cytochrome P450 3A (CYP3A) enzymes. Limited information is available regarding the effect of voriconazole on CYP3A activity. We examined the effect of voriconazole on CYP3A activity in human liver microsomes as measured by the formation of 6β-hydroxytestosterone from testosterone. We also evaluated the interaction between voriconazole and tacrolimus, an immunosuppressive drug, using human liver microsomes. The effect of voriconazole on CYP3A activity and tacrolimus metabolism was compared to that of other azole antifungal agents. CYP3A4 activity and the metabolism of tacrolimus were measured in the absence and in the presence of various concentrations of voriconazole (0–1.43 mM), fluconazole (0–1.63 mM), itraconazole (0–14 µM) and ketoconazole (0–0.19 µM). At a concentration of 21.2 ± 15.4 µM and 29.8 ± 12.3 µM, voriconazole inhibited the formation of 6β-hydroxytestosterone from testosterone and the metabolism of tacrolimus by 50%, respectively. The rank order of inhibition of 6β-hydroxytestosterone formation from testosterone and the metabolism of tacrolimus, is ketoconazole > itraconazole > voriconazole > fluconazole. Our observations suggest that voriconazole at clinically relevant concentrations will inhibit the hepatic metabolism of tacrolimus and increase the concentration of tacrolimus more than two-fold. Close monitoring of the blood concentrations and adjustment in the dose of tacrolimus are warranted when transplant patients receiving tacrolimus are treated with voriconazole.

Attenuation of ischemic liver injury by monoclonal anti-endothelin antibody, AwETN40 ☆

BACKGROUND Enhanced production of endothelin-1 (ET-1), vasoconstrictive 21 amino acids produced by endothelial cells during ischemia and after reperfusion of the liver, is known to cause sinusoidal constriction and microcirculatory disturbances, which lead to severe tissue damage. Using a 2-hour hepatic vascular exclusion model in dogs, we tested our hypothesis that neutralization of ET-1 by monoclonal anti-ET-1 and anti-ET-2 antibody (AwETN40) abates vascular dysfunction and ameliorates ischemia/reperfusion injury of the liver. STUDY DESIGN After skeletonization, the liver was made totally ischemic by cross-clamping the portal vein, the hepatic artery, and the vena cava (above and below the liver). Veno-venous bypass was used to decompress splanchnic and inferior systemic congestion. AwETN40, 5 mg/kg, was administered intravenously 10 minutes before ischemia (treatment group, n = 5). Nontreated animals were used as controls (control group, n = 10). Animal survival, hepatic tissue blood flow, liver function tests, total bile acid, high-energy phosphate, ET-1 levels, and liver histopathology were studied. RESULTS Treatment with AwETN40 improved 2-week animal survival from 30% to 100%. Hepatic tissue blood flow after reperfusion was significantly higher in the treatment group. The treatment significantly attenuated liver enzyme release, total bile acid, and changes in adenine nucleotides. Immunoreactive ET-1 levels in the hepatic venous blood of the control group showed a significant increase and remained high for up to 24 hours after reperfusion. Histopathologic alterations were significantly lessened in the treatment group. CONCLUSIONS These results indicate that ET-1 is involved in ischemia/reperfusion injury of the liver, which can be ameliorated by the monoclonal anti-ET-1 and anti-ET-2 antibody AwETN40.