Chronopharmacology of angiotensin II-receptor blockers in stroke-prone spontaneously hypertensive rats.

Protective effect of valsartan (Val), an angiotensin II (AII)-receptor blocker (ARB), against organ damage is reported to depend on the dosing time in hypertensive patients. Dosing-time-dependent effect of Val on survival of stroke-prone spontaneously hypertensive rats (SHRSP) under a 12-h lighting cycle was examined. Val (4 mg/kg per day) and olmesartan medoxomil (OM) (1 mg/kg per day), another ARB with a slower dissociation from the AII receptor, were given once daily at 2, 8, 14, or 20 HALO (hours after lights on). Dosing-time-dependent differences in plasma drug concentrations and effect on blood pressure (BP) were also evaluated. Survival of SHRSP showed a dosing-time-dependent change during Val therapy, with a peak at 2 HALO and a trough at 14 HALO. OM equally prolonged survival in all groups. The BP-lowering effect persisted for more than 24 h after dosing of Val at 2 HALO and of OM at 2 and 14 HALO, but disappeared at 5.5-h after Val dosing at 14 HALO. Plasma concentrations of Val and OM were higher after dosing at 2 HALO than at 14 HALO. These results suggest that the chronopharmacological phenomenon of Val was partly due to the dosing-time-dependent difference in plasma concentration and subsequent duration of the antihypertensive effect. Slower dissociation of OM from AII receptors might have blunted a potential dosing-time-dependent event.

Chronopharmacology of Angiotensin II-receptor Blockers in Stroke-Prone Spontaneously Hypertensive Rats.

Protective effect of valsartan (Val), an angiotensin II (AII)-receptor blocker (ARB), against organ damage is reported to depend on the dosing time in hypertensive patients. Dosing-time-dependent effect of Val on survival of stroke-prone spontaneously hypertensive rats (SHRSP) under a 12-h lighting cycle was examined. Val (4 mg/kg per day) and olmesartan medoxomil (OM) (1 mg/kg per day), another ARB with a slower dissociation from the AII receptor, were given once daily at 2, 8, 14, or 20 HALO (hours after lights on). Dosing-time-dependent differences in plasma drug concentrations and effect on blood pressure (BP) were also evaluated. Survival of SHRSP showed a dosing-time-dependent change during Val therapy, with a peak at 2 HALO and a trough at 14 HALO. OM equally prolonged survival in all groups. The BP-lowering effect persisted for more than 24 h after dosing of Val at 2 HALO and of OM at 2 and 14 HALO, but disappeared at 5.5-h after Val dosing at 14 HALO. Plasma concentrations of Val and OM were higher after dosing at 2 HALO than at 14 HALO. These results suggest that the chronopharmacological phenomenon of Val was partly due to the dosing-time-dependent difference in plasma concentration and subsequent duration of the antihypertensive effect. Slower dissociation of OM from AII receptors might have blunted a potential dosing-time-dependent event.

Beta-catenin induces beta-TrCP-mediated PER2 degradation altering circadian clock gene expression in intestinal mucosa of ApcMin/+ mice.

Proliferation of intestinal epithelial cells is rhythmic throughout the day. This temporal organization occurs through the interaction between the endogenous peripheral circadian clock and pathways controlling cell cycle progression. Per2, a core clock gene with tumour suppresser function, is critical to clock function and to the regulation of cellular proliferation. Circadian disruption, which increases colon cancer incidence, may do so by deregulating clock controlled epithelial cell proliferation. Increased expression of beta-catenin is a contributing cause of most familial and spontaneous human colon cancer and the cause of multiple intestinal neoplasia of the Apc(Min/+) mouse. Here we report that increased beta-catenin destabilizes PER2 clock protein by inducing beta-TrCP, an F-box protein of SCF ubiquitin E3 ligase. In the intestinal mucosa of the Apc(Min/)(+) mouse, the decrease in PER2 protein levels is associated with altered circadian rhythms of clock genes, Per1 and Per2, and clock controlled genes, Dbp and Wee1. These findings suggest that disruption of the peripheral intestinal circadian clock may be intimately involved in beta-catenin induced intestinal epithelial neoplastic transformation in both mouse and man.

Successful pediatric living donor liver transplantation from carrier to carrier of hereditary butyrylcholinesterase variant.

Hypocholinesterasemia is often observed clinically, especially in various liver diseases. Not well known, however, is the fact that some patients have a hereditary BChE variant. Little has been reported on liver transplants associated with this hereditary BChE variant. Furthermore, no cases have been reported of a LDLT involving hereditary BChE variant that had been diagnosed preoperatively. A 23-month-old girl who had had a failed Kasai operation for biliary atresia underwent a liver transplant using as a graft her father's lateral segment. Preoperatively, she had been diagnosed with hypocholinesterasemia. As the donor, her father had undergone a preoperative examination, during which he was found to also have hypocholinesterasemia. DNA sequencing revealed that both had the hereditary BChE variant. The unique mutation caused a frame-shift mutation. Variant K was also detected. The patient was discharged 143 days after the operation and has had no problems with immunosuppression since. In conclusion, we report that the hereditary BChE variant is not a contraindication for either transplantation or living liver donation.

Developmental abnormalities in multiple proliferative tissues of Apc(Min/+) mice.

Germ-line mutation of the Apc gene has been linked to familial adenomatous polyposis (FAP) that predisposes to colon cancer. Apc(Min/+) mice, heterozygous for the Apc gene mutation, progressively develop small intestinal tumours in a manner that is analogous to that observed in the colon of patients with FAP (Su et al. 1992; Fodde et al. 1994; Moser et al. 1995). We have studied the effects of Apc gene mutation on murine intestinal and extra-intestinal, proliferatively active tissues. We have contrasted the histology to that of the age- and sex-matched wild-type C57BL/6 mice. Histological assessment of the normal appearing intestinal mucosa demonstrates minimal change in size of crypts. In contrast, villi are longer in the ileum of Apc(Min/+) mice relative to C57BL/6 mice at 12 and 15 weeks of age. Vigorous splenic haematopoiesis in Apc(Min/+) mice was seen at 12 and 15 weeks of age, as reflected by marked splenomegaly, increased splenic haematopoietic cells and megakaryocytes. Peripheral blood counts, however, did not differ between C57BL/6 and Apc(Min/+) mice at 15 weeks of age. Lymphoid depletion in Apc(Min/+) mice was characterized by diminished numbers of splenic lymphoid follicles and small intestinal Peyer's patches. The ovaries of 12- and 15-week-old Apc(Min/+) mice exhibited increased numbers of atretic follicles, and estrous cycling by serial vaginal smears showed tendency of elongation in the mutant mice during these age ranges. The testicles of 10-week-old Apc(Min/+) mice showed increased numbers of underdeveloped seminiferous tubules. Collectively, these data suggest that, in addition to its obvious effects upon intestinal adenoma formation, Apc gene mutation causes impairment of developmental and apparent differentiation blockade in proliferative tissues, including those of the haematopoietic system, lymphoid and reproductive tract.

Interaction between grapefruit juice and hypnotic drugs: comparison of triazolam and quazepam.

OBJECTIVE: Grapefruit juice (GFJ) inhibits cytochrome P450 (CYP) 3A4 in the gut wall and increases blood concentrations of CYP3A4 substrates by the enhancement of oral bioavailability. The effects of GFJ on two benzodiazepine hypnotics, triazolam (metabolized by CYP3A4) and quazepam (metabolized by CYP3A4 and CYP2C9), were determined in this study. METHODS: The study consisted of four separate trials in which nine healthy subjects were administered 0.25 mg triazolam or 15 mg quazepam, with or without GFJ. Each trial was performed using an open, randomized, cross-over design with an interval of more than 2 weeks between trials. Blood samples were obtained during the 24-h period immediately following the administration of each dose. Pharmacodynamic effects were determined by the digit symbol substitution test (DSST) and utilizing a visual analog scale. RESULTS: GFJ increased the plasma concentrations of both triazolam and quazepam and of the active metabolite of quazepam, 2-oxoquazepam. The area under the curve (AUC)(0-24) of triazolam significantly increased by 96% (p<0.05). The AUC(0-24) of quazepam (+38%) and 2-oxoquazepam (+28%) also increased; however, these increases were not significantly different from those of triazolam. GFJ deteriorated the performance of the subjects in the DSST after the triazolam dose (-11 digits at 2 h after the dose, p<0.05), but not after the quazepam dose. Triazolam and quazepam produced similar sedative-like effects, none of which were enhanced by GFJ. CONCLUSION: These results suggest that the effects of GFJ on the pharmacodynamics of triazolam are greater than those on quazepam. These GFJ-related different effects are partly explained by the fact that triazolam is presystemically metabolized by CYP3A4, while quazepam is presystemically metabolized by CYP3A4 and CYP2C9.

Dosing time-dependent effect of temocapril on the mortality of stroke-prone spontaneously hypertensive rats.

This study was undertaken to evaluate a dosing time-dependent effect of temocapril, an angiotensin-converting enzyme (ACE) inhibitor, on the mortality of stroke-prone spontaneously hypertensive rats (SHRSP). Temocapril (1 mg/kg/day) prolonged the survival rate of these animals, with a maximum effect after dosing at the early resting period and a minimum effect after dosing at the early active period. The pharmacokinetics of temocaprilat, an active metabolite of temocapril, did not differ significantly between the two dosing times. However, the inhibition of ACE activity in serum and organs (brain and aorta) and the reduction of blood pressure were significantly greater after dosing at the early resting period than at the early active period. These data suggest that the effect of temocapril on the mortality of SHRSP depends on the time of dosing, with a maximum effect seen after dosing at the early resting period. Dosing time-dependent differences in the pharmacodynamics of temocapril might be involved in explaining this phenomenon.

Exaggerated liver injury induced by ischemia-reperfusion in spontaneously hypertensive rats.

BACKGROUND: The functions of polymorphonuclear leukocytes (PMNs), which play a critical role in organ damage, are primed in patients with essential hypertension and spontaneously hypertensive rats (SHR). Hepatic ischemia-reperfusion (I/R) injury is shown to be caused and aggravated by the PMNs. We examined whether the hepatic I/R injury was exaggerated in SHR. METHODS: The portal vein and artery were partially occluded for 60 min. Blood samples were obtained to determine the degree of liver damage during 48 h after reperfusion. RESULTS: The increase in serum transaminase concentration and hepatic myeloperoxidase content, which reflects the number of PMNs in liver tissue, in SHR were significantly greater than those of their control rats, Wistar-Kyoto rat (WKY). However, the elevations in hepatic transaminases induced by I/R did not differ between other hypertensive animal models (N-nitro-L-arginine methyl ester [L-NAME]-treated and deoxycorticosterone acetate [DOCA]/salt-treated rats) and their controls. CONCLUSIONS: These results suggest that the elevated PMNs, but not high blood pressure per se, contributes to the exaggerated hepatic I/R injury in SHR.

Elevated blood concentrations of calcineurin inhibitors during diarrheal episode in pediatric liver transplant recipients: involvement of the suppression of intestinal cytochrome P450 3A and P-glycoprotein.

We encountered two cases of pediatric living-related liver transplant recipients who showed increases in blood concentration of cyclosporine or tacrolimus, a dual substrate for cytochrome P450 (CYP) 3A and P-glycoprotein (P-gp), during a diarrheal episode. To investigate the effect of intestinal inflammation on the metabolic and efflux pump activities, we conducted the experiments using the lipopolysaccharide (LPS)-induced intestinal damage model. Intestinal epithelial CYP3A activity was assessed by nifedipine oxidation using intestinal epithelial microsomes in rat. Drug efflux by P-gp was tested using digoxin flux with the excised intestine perfusion system in rats. Intraperitoneal injection of LPS (0.3 mg/kg) significantly reduced the intestinal epithelial CYP3A activity by 41% (p < 0.01). In the proximal jejunal segment of the rats treated with LPS, mucosal to serosal flux of digoxin was significantly enhanced compared to that of control (p < 0.05). Efflux of digoxin, which was taken up by intestinal epithelium, to mucosal perfusate was significantly blunted in the jejunum treated with LPS (p < 0.05), which indicates that the LPS treatment reduced the P-gp activity in rat small intestine. These findings suggest that the suppression of CYP3A and P-gp activities may be involved in the mechanism of elevated blood concentrations of cyclosporine and tacrolimus during enteritis-induced diarrhea. To prevent a drug-induced adverse effect, dose of a drug, which is a substrate of CYP3A or P-gp, should be reduced during such an episode.

ACE inhibitors and chronotherapy.

Chronotherapy can improve the effectiveness and reduce the adverse reactions of drugs and actually is used for several conditions including cardiovascular diseases. Although angiotensin converting enzyme (ACE) inhibitors are available for the therapy of patients with hypertension and/or heart failure, these agents have some characteristic adverse effects such as angioedema and dry cough. It has been reported that the dosing of ACE inhibitor at an inactive period has a better protective effect against cardiac hypertrophy in hypertensive rats, and changing dosing time from morning to evening reduces the severity and frequency of the drug-induced dry cough of hypertensive patients treated in the morning. Thus, the dosing of ACE inhibitors in the inactive span is more effective and safe. Dosing in the evening may be an alternative for hypertensives with dry cough with a morning dose of ACE inhibitors, if one ascertains that no circadian hyperamplitude tension is induced by the evening dose of this or any other antihypertensive drug.

Dosing-time-dependent differences in lipopolysaccharide-induced liver injury in rats.

Dosing-time-dependent differences in lipopolysaccharide (LPS)-induced liver injury were examined in rats housed under a 12 h light : dark (LD) cycle. LPS (5 mg/kg) was intravenously injected into different groups of rats at 2, 14, or 20 h after light on (HALO). Elevations in serum liver enzymes after 14 HALO were significantly greater than those after 2 HALO. These parameters were lower in rats given LPS at 20 HALO, compared to 14 HALO. The number of polymorphonuclear cells (PMN) in the liver and the amount of hepatic myeloperoxidase activity, which reflects the number of PMN in liver tissues, was significantly greater in the 14 than in the 2 HALO group. In addition, hepatic interleukin-6 (IL-6) production in the 14 HALO group was enhanced compared to that in the 2 HALO trial. These results suggest that LPS-induced liver injury is greater during the early active than during the early resting period. Dosing-time-dependent variation in the accumulation of PMN in the liver and, potentially, subsequent IL-6 production in liver tissues might be involved in this phenomenon.

Case report of unchanged tacrolimus clearance in a hypoxemic pediatric liver transplant recipient with hepatopulmonary syndrome.

Reductions in hepatic oxygen supply may reduce the oxidative metabolism of drugs, including tacrolimus. We encountered a patient (2.3-year-old girl) with hypoxemia [arterial oxygen tension (PaO2) 40.9 mmHg in room air] due to hepatopulmonary syndrome who had undergone living related liver transplantation. After transplantation, tacrolimus was initially administered by continuous intravenous infusion, and her PaO2 was maintained at more than 50 mmHg [72.8+/-10.4 (SD) mmHg] by oxygen supplementation. Apparent clearance of tacrolimus (calculated as: the infusion rate of tacrolimus/blood concentration) in the patient (0.075 l/h per kg) was comparable to those of non-hypoxemic control pediatric cases (0.092+/-0.014 l/h per kg, n=7, mean age 2.2 years, PaO2 149.2+/-41.5 mmHg), except for the acute decline in the early period after transplantation. These findings suggest that the reduction in tacrolimus clearance is negligible when arterial oxygen tension is maintained at more than 50 mmHg, even in patients with hypoxemia.

Drug interaction between St John's Wort and quazepam.

AIM: St John's Wort (SJW) enhances CYP3A4 activity and decreases blood concentrations of CYP3A4 substrates. In this study, the effects of SJW on a benzodiazepine hypnotic, quazepam, which is metabolized by CYP3A4, were examined. METHODS: Thirteen healthy subjects took a single dose of quazepam 15 mg after treatment with SJW (900 mg day(-1)) or placebo for 14 days. The study was performed in a randomized, placebo-controlled, cross-over design with an interval of 4 weeks between the two treatments. Blood samples were obtained during a 48 h period and urine was collected for 24 h after each dose of quazepam. Pharmacodynamic effects were determined using visual analogue scales (VAS) and the digit symbol substitution test (DSST) on days 13 and 14. RESULTS: SJW decreased the plasma quazepam concentration. The Cmax and AUC(0-48) of quazepam after SJW were significantly lower than those after placebo [Cmax; -8.7 ng ml(-1) (95% confidence interval (CI) -17.1 to -0.2), AUC0-48; -55 ng h ml(-1) (95% CI -96 to -15)]. The urinary ratio of 6beta-hydroxycortisol to cortisol, which reflects CYP3A4 activity, also increased after dosing with SJW (ratio; 2.1 (95%CI 0.85-3.4)). Quazepam, but not SJW, produced sedative-like effects in the VAS test (drowsiness; P < 0.01, mental slowness; P < 0.01, calmness; P < 0.05, discontentment; P < 0.01). On the other hand, SJW, but not quazepam impaired psychomotor performance in the DSST test. SJW did not influence the pharmacodynamic profile of quazepam. CONCLUSIONS: These results suggest that SJW decreases plasma quazepam concentrations, probably by enhancing CYP3A4 activity, but does not influence the pharmacodynamic effects of the drug.

Partial protective effect of Y-27632, a Rho kinase inhibitor, against hepatic ischemia-reperfusion injury in rats.

(+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)-cyclohexanecarboxamide dihydrochloride (Y-27632), a Rho kinase inhibitor, has a suppressive effect on the functions of polymorphonuclear leukocytes. In this study, the influence of Y-27632 on ischemia-reperfusion injury of the liver was examined in rats. Y-27632 (3 mg/kg) or vehicle alone was intravenously injected into rats 60 min before occlusion. Blood samples were obtained for 48 h after reperfusion. At the end of the experiment, the hepatic content of myeloperoxidase, which reflects the number of polymorphonuclear leukocytes in liver tissues, was determined. The increases in serum hepatic aminotransferases and inflammatory cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6] after reperfusion were partially, but significantly, inhibited by Y-27632. The increased hepatic myeloperoxidase content was significantly lowered by Y-27632. These results suggest that Y-27632 has a partial protective effect against hepatic ischemia-reperfusion injury through the suppression of polymorphonuclear leukocytes and inflammatory cytokines.

Pravastatin prevents arrhythmias induced by coronary artery ischemia/reperfusion in anesthetized normocholesterolemic rats.

HMG-CoA reductase inhibitors (statins) have been shown to decrease cardiovascular mortality. Since ventricular tachyarrhythmias are closely related to cardiovascular mortality, we tested effects of the hydrophilic statin pravastatin and the lipophilic statin fluvastatin in a rat arrhythmia model of ischemia/reperfusion and simultaneously measured serum total cholesterol level. Anesthetized rats were subjected to 5-min ischemia and 10-min reperfusion after chronic administration of oral pravastatin (0.02, 0.2, or 2 mg/kg), fluvastatin (0.2, 2, or 4 mg/kg), or vehicle for 22 days, once daily. The acute effect of pravastatin (0.2 or 2 mg/kg, once orally) was also observed. Chronically administrated pravastatin significantly reduced the incidence of ischemia-induced ventricular tachycardia (VT) from 70% (control) to 9% at 2 mg/kg, and it reduced the incidence of reperfusion-induced lethal ventricular fibrillation (VF) from 90% (control) to 20% at 0.2 mg/kg. Acute pravastatin and chronically administrated fluvastatin had no significant effect on these arrhythmias. There were no significant changes in blood pressure, heart rate, QT interval, and serum cholesterol among pravastatin-, fluvastatin-, and vehicle-treated groups. Hydrophilic pravastatin prevented reperfusion-induced lethal VF in anesthetized rats by chronic administration independent of its cholesterol lowering effect. This may be a new beneficial role of pravastatin in decreasing cardiovascular mortality.

Hepatic venous stenosis-related reduction of cyclosporin clearance in a pediatric patient after liver transplantation.

A 20-month-old girl with Alagille syndrome developed stenosis of hepatic venous anastomosis after living related-donor liver transplantation. Cyclosporin (a microemulsion formulation) was given orally at a dose of 50 mg twice daily, and the trough blood concentration was relatively stable. Before balloon angioplasty of the hepatic vein, trough cyclosporin blood concentrations became elevated and consequently, the dosage was reduced to 15 mg twice daily. On the day of angioplasty, the calculated elimination rate constant of cyclosporin was 0.036 hr(-1), while its apparent basal value was 0.078 hr(-1). The cyclosporin trough concentration to dosage (C/D) ratio gradually increased reaching the maximum on the day after angioplasty. Thereafter, the C/D ratio promptly decreased. Thus, it is speculated that the increase in cyclosporine C/D ratio was mainly dependent on reduction of hepatic clearance of cyclosporin due to hepatic congestion caused by the stenosis of the hepatic venous anastomosis.

Stereoselective pharmacokinetics of amlodipine in elderly hypertensive patients.

Amlodipine is a dihydropyridine calcium antagonist and is widely used for the treatment of cardiovascular diseases. Amlodipine has two stereoisomers [R(+), S(-)], and only the S(-) isomer exerts vasodilating action. In this preliminary study, amlodipine (5 mg) was given to three elderly hypertensive patients once daily for 10 days. Blood samples were obtained, and serum concentrations of R(+)- and S(-)-amlodipine were measured by a gas chromatographic method. The R(+)/S(-) ratio of plasma amlodipine in these elderly subjects was greater than that reported in young subjects. These results suggest that the influence of aging on the pharmacokinetic profiles might differ between the R(+)- and S(-)-isomers of amlodipine.

Severe low back pain due to retroperitoneal abscess formation in diabetic patients

We report two cases of diabetic patients with severe low back pain associated with retroperitoneal abscesses. In the first case, multiple retroperitoneal and spinal epidural abscesses were detected. Paraplegia due to the spinal epidural abscess was not relieved by drainage of the abscess and subsequent antibiotic therapy. In the second case, drainage of the retroperitoneal abscess and antibiotics were immediately started, resulting in successful recovery. Thus, we suggest that if a diabetic patient complains of low back pain, potential abscess formations should be considered and given appropriate treatment before administering epidural anesthetic injections for pain relief.

Vasoconstricting effect of angiotensin II in human hand veins: influence of aging, diabetes mellitus and hypertension.

We examined human hand veins to determine whether venoconstricting response to angiotensin II (Ang II) and noradrenaline (NA) was influenced by aging or such diseases as diabetes mellitus (DM) and hypertension (HT). Twenty healthy male subjects (20-73 years), and 8 male patients with non-insulin-dependent DM and 8 male patients with essential HT were included in this study. A constant dose (50 ng/min) of Ang II or increasing dose (2-256 ng/min) of NA was infused into the dorsal hand vein and its diameter was measured using a linear variable differential transformer. The constant infusion of Ang II caused rapid desensitization or tachyphylaxis. The venoconstriction by Ang II in the 8 elderly subjects (58 to 73 years) was significantly (p<0.05) larger than that in the 8 young subjects (20 to 36 years) from 6 to 18 min after the start of the infusion (after 6 min: 63.6+/-11.6 (mean+/-SD)% vs. 39.9+/-20.8%, 12 min: 34.0+/-11.9% vs. 12.0+/-12.0%). However, the venoconstriction by Ang II in the patients with DM or HT was not significantly different from that in the 9 age-matched control subjects. No significant difference in venoconstrictor response to NA was observed between the young and elderly subjects, nor between the control subjects and the patients with DM or HT. These findings indicated that venoconstrictor response to Ang II might be greater in the elderly but might not be influenced by DM nor HT.