Prediction of metabolic drug clearance in humans: In vitro–in vivo extrapolation vs allometric scaling

Previously in vitro–in vivo extrapolation (IVIVE) with the Simcyp Clearance and Interaction Simulator® has been used to predict the clearance of 15 clinically used drugs in humans. The criteria for the selection of the drugs were that they are used as probes for the activity of specific cytochromes P450 (CYPs) or have a single CYP isoform as the major or sole contributor to their metabolism and that they do not exhibit non-linear kinetics in vivo. Where data were available for the clearance of the drugs in at least three animal species, the predictions from IVIVE have now been compared with those based on allometric scaling (AS). Adequate data were available for estimating oral clearance (CL_p.o.) in 9 cases (alprazolam, sildenafil, caffeine, clozapine, cyclosporine, dextromethorphan, midazolam, omeprazole and tolbutamide) and intravenous clearance in 6 cases (CL_i.v.) (cyclosporine, diclofenac, midazolam, omeprazole, theophylline and tolterodine). AS predictions were based on five different methods: (1) simple allometry (clearance versus body weight); (2) correction for maximum life-span potential (CL?×?MLP); (3) correction for brain weight (CL?×?BrW); (4) the use of body surface area; and (5) the rule of exponents. A prediction accuracy was indicated by mean-fold error and the Pearson product moment correlation coefficient. Predictions were considered successful if the mean-fold error was ≤2. IVIVE predictions were accurate in 14 of 15 cases (mean-fold error range: 1.02–4.00). All five AS methods were accurate in 13, 11, 10, 10 and 14 cases, respectively. However, in some cases the error of AS exceeded fivefold. On the basis of the current results, IVIVE is more reliable than AS in predicting human clearance values for drugs mainly metabolized by CYP450 enzymes. This suggests that the place of AS methods in pre-clinical drug development warrants further scrutiny.     

The Role of Adenosine in Alzheimer��s Disease

Alzheimer’s disease (AD) is a neurodegenerative disorder of the central nervous system manifested by cognitive and memory deterioration, a variety of neuropsychiatric symptoms, behavioral disturbances, and progressive impairment of daily life activities. Current pharmacotherapies are restricted to symptomatic interventions but do not prevent progressive neuronal degeneration. Therefore, new therapeutic strategies are needed to intervene with these progressive pathological processes. In the past several years adenosine, a ubiquitously released purine ribonucleoside, has become important for its neuromodulating capability and its emerging positive experimental effects in neurodegenerative diseases. Recent research suggests that adenosine receptors play important roles in the modulation of cognitive function. The present paper attempts to review published reports and data from different studies showing the evidence of a relationship between adenosinergic function and AD-related cognitive deficits. Epidemiological studies have found an association between coffee (a nonselective adenosine receptor antagonist) consumption and improved cognitive function in AD patients and in the elderly. Long-term administration of caffeine in transgenic animal models showed a reduced amyloid burden in brain with better cognitive performance. Antagonists of adenosine A2A receptors mimic these beneficial effects of caffeine on cognitive function. Neuronal cell cultures with amyloid beta in the presence of an A2A receptor antagonist completely prevented amyloid beta-induced neurotoxicity. These findings suggest that the adenosinergic system constitutes a new therapeutic target for AD, and caffeine and A2A receptor antagonists may have promise to manage cognitive dysfunction in AD.Key Words: Adenosine receptor, Alzheimer’s disease, amyloid beta, caffeine, cognition, neuromodulation.     

Effect of phenytoin sodium on macrophages in rat wounds

本实验旨在研究苯妥英钠（ＰＳ）对伤口巨噬细胞（Ｍ）的影响．从置入大鼠背部伤口的聚乙烯醇海绵中收集巨噬细胞，分别测定其吞噬功能，肿瘤坏死因子α（ＴＮＦα）和白介素１（ＩＬ－１）的释放以及对成纤维细胞增殖调节作用，通过牵拉伤口组织致其断裂时溢出的水的重量而测定伤口牵张强度．结果表明，伤口Ｍ的功能在伤后ｄ５达到高峰，ＰＳ１，１０，５０ｇ·Ｌ－１浓度依赖性地增加伤后ｄ５的伤口Ｍ的数量，吞噬功能，ＴＮＦα和ＩＬ－１的释放，增强Ｍ对成纤维细胞增殖的刺激作用，增强伤口牵张强度．结果说明ＰＳ加速伤口愈合，与其增强Ｍ的功能有关．     

The antihyperglycemic effect of curcumin in high fat diet fed rats. Role of TNF-α and free fatty acids

This study was conducted to investigate the effect of curcumin, obtained from Curcuma longa, in comparison with rosiglitazone on the progression of insulin resistance and type 2 diabetes mellitus (T2DM) and the mechanisms underlying this effect. Insulin resistance and T2DM was induced in male Sprague Dawley rats by high fat diet (HFD) feeding for 60 and for 75 days representing two regimens of the study, protection and treatment. Prophylactic oral administration of curcumin (80 mg/kg), rosiglitazone (1 mg/kg), their combination, or vehicle (in control groups) was started along with HFD feeding in different groups. Treatment is achieved by oral administration of the previously mentioned agents in the last 15 days of HFD feeding after induction of insulin resistance and T2DM in rats.Curcumin showed an anti-hyperglycemic effect and improved insulin sensitivity, and this action may be attributed at least in part to its anti-inflammatory properties as evident by attenuating TNF-α levels in HFD fed rats, and its anti-lipolytic effect as evident by attenuating plasma free fatty acids. The curcumin effects are comparable to those of rosiglitazone, which indicate that they may act similarly. Finally we can say that, curcumin could be a beneficial adjuvant therapy in patients with T2DM.     

The complexity of achieving anticoagulation control in the face of warfarin – phenytoin interaction: an Asian case report

Phenytoin has been reported to have major interactions with warfarin. Phenytoin induces warfarins metabolism. However, there are many case reports which provide conflicting conclusions. Here, we report a case of a 65-year-old man with mechanical heart valve on chronic warfarin therapy who experienced persistent fluctuations of INR and bleeding secondary to probable warfarin–phenytoin interactions. The patients anticoagulation clinic visits prior to hospitalization were thoroughly evaluated and we continued to follow-up the case for 3 months post-hospitalization. The reported interaction could be reasonably explained from the chronology of events and the pattern of INR fluctuations whenever phenytoin was either added or discontinued from his drug regimen.     

The Role of IL-1�� in Nicotine-Induced Immunosuppression and Neuroimmune Communication

Although a number of inflammatory cytokines are increased during sepsis, the clinical trials aimed at down-regulating these mediators have not improved the outcome. These paradoxical results are attributed to loss of the “tolerance” phase that normally follows the proinflammatory response. Chronic nicotine (NT) suppresses both adaptive and innate immune responses, and the effects are partly mediated by the nicotinic acetylcholine receptors in the brain; however, the mechanism of neuroimmune communication is not clear. Here, we present evidence that, in rats and mice, NT initially increases IL-1β in the brain, but the expression is downregulated within 1–2 week of chronic exposure, and the animals become resistant to proinflammatory/pyrogenic stimuli. To examine the relationship between NT, IL-1β, and immunosuppression, we hypothesized that NT induces IL-1β in the brain, and its constant presence produces immunological “tolerance”. Indeed, unlike wild-type C57BL/6 mice, chronic NT failed to induce immunosuppression or downregulation of IL-1β expression in IL-1β-receptor knockout mice. Moreover, while acute intracerebroventricular administration of IL-1β in Lewis (LEW) rats activated Fyn and protein tyrosine kinase activities in the spleen, chronic administration of low levels of IL-1β progressively diminished the pyrogenic and T cell proliferative responses of treated animals. Thus, IL-1β may play a critical role in the perception of inflammation by the CNS and the induction of an immunologic “tolerant” state. Moreover, the immunosuppressive effects of NT might be at least partly mediated through its effects on the brain IL-1β. This represents a novel mechanism for neuroimmune communication.     

What does validation of cases in electronic record databases mean? The potential contribution of free text

Electronic health records are increasingly used for research. The definition of cases or endpoints often relies on the use of coded diagnostic data, using a pre-selected group of codes. Validation of these cases, as 'true' cases of the disease, is crucial. There are, however, ambiguities in what is meant by validation in the context of electronic records. Validation usually implies comparison of a definition against a gold standard of diagnosis and the ability to identify false negatives ('true' cases which were not detected) as well as false positives (detected cases which did not have the condition). We argue that two separate concepts of validation are often conflated in existing studies. Firstly, whether the GP thought the patient was suffering from a particular condition (which we term confirmation or internal validation) and secondly, whether the patient really had the condition (external validation). Few studies have the ability to detect false negatives who have not received a diagnostic code. Natural language processing is likely to open up the use of free text within the electronic record which will facilitate both the validation of the coded diagnosis and searching for false negatives.     

The selectivity of ��-adrenoceptor agonists at human ��1-, ��2- and ��3-adrenoceptors

Background and purpose:

There are two important properties of receptor–ligand interactions: affinity (the ability of the ligand to bind to the receptor) and efficacy (the ability of the receptor–ligand complex to induce a response). Ligands are classified as agonists or antagonists depending on whether or not they have efficacy. In theory, it is possible to develop selective agonists based on selective affinity, selective intrinsic efficacy or both. This study examined the affinity and intrinsic efficacy of 31 β-adrenoceptor agonists at the three human β-adrenoceptors to determine whether the current agonists are subtype selective because of affinity or intrinsic efficacy.

Experimental approach:

Stable clonal CHO-K1 cell lines, transfected with either the human β₁, β₂ or β₃-adrenoceptor, were used, and whole-cell [³H]-CGP 12177 radioligand binding and [³H]-cAMP accumulation were measured.

Key results:

Several agonists were found to be highly subtype selective because of selective affinity (e.g. salmeterol and formoterol, for the β₂-adrenoceptor over the β₁ or β₃), while others (e.g. isoprenaline) had little affinity–selectivity. However, the intrinsic efficacy of salmeterol, formoterol and isoprenaline was similar across all three receptor subtypes. Other ligands (e.g. denopamine for β₁; clenbuterol, AZ 40140d, salbutamol for β₂) were found to have subtype-selective intrinsic efficacy. Several ligands appeared to activate two agonist conformations of the β₁- and β₃-adrenoceptors.

Conclusions and implications:

There are agonists with subtype selectivity based upon both selective affinity and selective intrinsic efficacy. Therefore, there is scope to develop better selective agonists based upon both selective affinity and selective intrinsic efficacy.This article is commented on by Kenakin, pp. 1045–1047 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2010.00764.x     

The use of long-acting propranolol (‘Inderal’ LA) in the management of elderly hypertensive patients

Summary Fifteen elderly patients whose hypertension was controlled by conventional propranolol 80 mg twice a day had their medication changed to one capsule of Inderal LA¹ (160 mg) daily. The blood pressure, heart rate and propranolol concentrations were measured at various time points when the patients were receiving the conventional preparation and these assessments were repeated when the long-acting preparation was administered. Although the heart rate was lower with conventional propranolol than with Inderal LA there was no significant difference in the blood pressure levels. The mean peak blood level of propranolol was, however, significantly lower with Inderal LA compared with conventional propranolol and occurred later. At 12 h the plasma propranolol levels were higher after Inderal LA than following the intake of conventional propranolol (p<0.01); there was no difference in the plasma levels at 24 h. The area under the concentration time curve was significantly higher on conventional propranolol. Compared with published data, the plasma levels were higher than those in younger patients. Inderal LA was well tolerated and side effects were minimal.     

The safe threshold for gluten contamination in gluten‐free products. Can trace amounts be accepted in the treatment of coeliac disease?

BACKGROUND: Gluten contamination in gluten-free products cannot totally be avoided. The safe threshold for gluten remains obscure. AIM: The purpose was to estimate a reasonable limit for residual gluten, based on current literature and measurement of gluten in gluten-free products on the market. METHODS: The gluten content of 59 naturally gluten-free and 24 wheat starch-based gluten-free products were analysed by enzyme-linked immunosorbent assay. The daily intake of flours was calculated in 76 adults on gluten-free diet, and the intake compared with mucosal histology. RESULTS: A number of both naturally gluten-free (13 of 59) and wheat starch-based gluten-free (11 of 24) products contained gluten from 20 to 200 ppm (=mg/kg). The median daily flour consumption was 80 g (range: 10-300). Within these limits, the long-term mucosal recovery was good. CONCLUSIONS: The threshold for gluten-contamination can safely be set at 100 ppm. Provided that the daily flour intake is even 300 g, a level of 100 ppm results in 30 mg of gluten intake. This has been shown to be safe, when correlated to histology, in clinical and challenge studies. The level can be achieved by the industry, and does not make the diet too cumbersome.     

Tuning in to the ��right�� calcium channel regulation in experimental models of diabetes

Elucidation of cellular and molecular mechanisms underlying vascular disease is of fundamental importance to the development of pharmacological agents to target these pathways. Pinho et al. in this issue of the BJP provide highly compelling evidence that the δ isoform of phosphatidyl inositol 3-kinase (PI3K δ) was upregulated and accounted for the increase in L-type, voltage-gated, Ca channel current in aortic vascular smooth muscle (VSM) cells of a mouse model of type 1 diabetes. There are several key issues of broad fundamental significance to this work. Firstly, what is the ‘right’ answer about calcium channel regulation in diabetes? Conflicting reports of increased and decreased Ca channel current may be due to specificity of the vascular bed and species. Then, the time course of diabetic vasculopathy may influence the expression of contractile versus proliferative phenotypes of VSM. Also the metabolic characterization of diabetes may enlighten or confound any study of diabetic vascular disease. These issues need attention to move forward work in this area.

LINKED ARTICLE

This article is a commentary on Pinho et al., pp. 1458–1471 of this issue. To view this paper visit http://dx.doi.org/10.1111/j.1476-5381.2010.00955.x     

The complement system in liposome clearance: Can complement deposition be inhibited?

The activation of complement results in the opsonization of particles for removal by the reticuloendothelial system. Experimental evidence suggests that complement-mediated clearance of liposomal systems may significantly contribute to liposome biodistribution. Because of the multiplicity of complement activation mechanisms and the large number of proteins in the pathway, there are multiple opportunities to reduce or eliminate the opsonic effects of complement activation. This review addresses the state of our understanding of the interaction of liposomes with complement proteins and suggests some approaches to minimize complement activation.     

Section 3 The tolerance and acceptability of ibuprofen (‘Brufen’) in the elderly patient

Summary

Data on the treatment of patients over the age of 65 years were extracted from the computer records of a long-term multi-centre study of ibuprofen. Patients were suffering from rheumatoid disease, osteoarthrosis or an allied condition. Records from 231 patients were available for analysis. Duration of therapy with ibuprofen ranged from 3 months to over 5 years. Assessments of clinical progress, as judged by both patients and physicians, changes in biochemical and haematological parameters, and side-effects showed that ibuprofen is an effective form of therapy and is generally well tolerated in the elderly.     

The Inhibitory Effect of Quercetin-3-O-��-D-Glucuronopyranoside on Gastritis and Reflux Esophagitis in Rats

It was evaluated the inhibitory action of quercetin-3-O-β-D-glucuronopyranoside (QGC) on reflux esophagitis and gastritis in rats. QGC was isolated from the herba of Rumex Aquaticus. Reflux esophagitis or gastritis was induced surgically or by administering indomethacin, respectively. Oral QGC decreased ulcer index, injury area, gastric volume, and acid output and increased gastric pH as compared with quercetin. Furthermore, QGC significantly decreased gastric lesion sizes induced by exposing the gastric mucosa to indomethacin. Malondialdehyde levels were found to increase significantly after inducing reflux esophagitis, and were reduced by QGC, but not by quercetin or omeprazole. These results show that QGC can inhibit reflux esophagitis and gastritis in rats.     

The plant cannabinoid ��9-tetrahydrocannabivarin can decrease signs of inflammation and inflammatory pain in mice

Background and purpose:

The phytocannabinoid, Δ⁹-tetrahydrocannabivarin (THCV), can block cannabinoid CB₁ receptors. This investigation explored its ability to activate CB₂ receptors, there being evidence that combined CB₂ activation/CB₁ blockade would ameliorate certain disorders.

Experimental approach:

We tested the ability of THCV to activate CB₂ receptors by determining whether: (i) it inhibited forskolin-stimulated cyclic AMP production by Chinese hamster ovary (CHO) cells transfected with human CB₂ (hCB₂) receptors; (ii) it stimulated [³⁵S]GTPγS binding to hCB₂ CHO cell and mouse spleen membranes; (iii) it attenuated signs of inflammation/hyperalgesia induced in mouse hind paws by intraplantar injection of carrageenan or formalin; and (iv) any such anti-inflammatory or anti-hyperalgesic effects were blocked by a CB₁ or CB₂ receptor antagonist.

Key results:

THCV inhibited cyclic AMP production by hCB₂ CHO cells (EC₅₀= 38 nM), but not by hCB₁ or untransfected CHO cells or by hCB₂ CHO cells pre-incubated with pertussis toxin (100 ng·mL⁻¹) and stimulated [³⁵S]GTPγS binding to hCB₂ CHO and mouse spleen membranes. THCV (0.3 or 1 mg·kg⁻¹ i.p.) decreased carrageenan-induced oedema in a manner that seemed to be CB₂ receptor-mediated and suppressed carrageenan-induced hyperalgesia. THCV (i.p.) also decreased pain behaviour in phase 2 of the formalin test at 1 mg·kg⁻¹, and in both phases of this test at 5 mg·kg⁻¹; these effects of THCV appeared to be CB₁ and CB₂ receptor mediated.

Conclusions and implications:

THCV can activate CB₂ receptors in vitro and decrease signs of inflammation and inflammatory pain in mice partly via CB₁ and/or CB₂ receptor activation.This article is part of a themed issue on Cannabinoids. To view the editorial for this themed issue visit http://dx.doi.org/10.1111/j.1476-5381.2010.00831.x