Zwitterionic near infrared fluorescent agents for noninvasive real-time transcutaneous assessment of kidney function

Zwitterionic near infrared fluorescent agents were developed for non-invasive real-time transcutaneous assessment of kidney function.

We developed novel zwitterionic near infrared (NIR) fluorescent agents (ABZWCY-HPβCD and AAZWCY-HPβCD), which exhibit favorable hydrophilicity, low plasma protein binding, high stability and non-toxicity. These attractive characteristics ensure that they are excreted rapidly, without any skin accumulation or metabolism in vivo. More importantly, zwitterionic HPβCD based agents can be efficiently filtrated by the glomerulus and completely excreted through the kidneys into urine without reabsorption or secretion in the kidney proximal tubule. Relying on these novel zwitterionic NIR agents and a transcutaneous device, we demonstrate a rapid, robust and biocompatible approach for assessing kidney function in rat models of both healthy rats and those with kidney disease, without the need for time-consuming blood/urine sample preparation. Our work provides a promising tool for in vivo real-time non-invasive kidney function assessment in preclinical applications.

Transcutaneous assessment of glomerular filtration rate

Glomerular filtration rate (GFR) is considered the best parameter for the assessment of renal function, being usually determined on the basis of urine or plasma clearance of exogenous renal markers. The common methodology is invasive, time consuming and cumbersome, with multiple blood and/or urine sampling and following laboratory assays required. The method detailed here allows to transcutaneously determine the renal function in awake animals, in a non-invasive and efficient manner by using an electronic device which detects the fluorescence emitted through the skin from the renal marker FITC-Sinistrin. A crucial target has been to improve the fixation of the device, which is dependent on the skin structure. For validation, the technique has been compared with the classical clearance method, and its robustness has been demonstrated in healthy and diseased murine models. Moreover, the method allows sequential measurements in the same individual. Thus progression and recovery of renal failure can be followed. Therefore, its future application in humans would allow an accurate and appropriate prediction and monitoring of patients with established kidney disease over time. Furthermore, it will be possible to observe those patients under other pathological conditions with associated risk of developing renal problems.

Transcutaneous measurement of renal function in conscious mice

Determination of glomerular filtration rate (GFR) in conscious mice is cumbersome for the experimenter and stressful for the animals. Here we report on a simple new technique allowing the transcutaneous measurement of GFR in conscious mice. This approach extends our previously developed technique for rats to mice. The technique relies on a miniaturized device equipped with an internal memory that permits the transcutaneous measurement of the elimination kinetics of the fluorescent renal marker FITC-sinistrin. This device is described and validated compared with FITC-sinistrin plasma clearance in healthy, unilaterally nephrectomized and pcy mice. In summary, we describe a technique allowing the measurement of renal function in freely moving mice independent of blood or urine sampling as well as of laboratory assays.

Online feedback-controlled renal constant infusion clearances in rats

Constant infusion clearance techniques using exogenous renal markers are considered the gold standard for assessing the glomerular filtration rate. Here we describe a constant infusion clearance method in rats allowing the real-time monitoring of steady-state conditions using an automated closed-loop approach based on the transcutaneous measurement of the renal marker FITC-sinistrin. In order to optimize parameters to reach steady-state conditions as fast as possible, a Matlab-based simulation tool was established. Based on this, a real-time feedback-regulated approach for constant infusion clearance monitoring was developed. This was validated by determining hourly FITC-sinistrin plasma concentrations and the glomerular filtration rate in healthy and unilaterally nephrectomized rats. The transcutaneously assessed FITC-sinistrin fluorescence signal was found to reflect the plasma concentration. Our method allows the precise determination of the onset of steady-state marker concentration. Moreover, the steady state can be monitored and controlled in real time for several hours. This procedure is simple to perform since no urine samples and only one blood sample are required. Thus, we developed a real-time feedback-based system for optimal regulation and monitoring of a constant infusion clearance technique.

Transcutaneous measurement of glomerular filtration rate using FITC-sinistrin in rats

BACKGROUND

Inulin/sinistrin (I/S) clearance is a gold standard for an accurate assessment of glomerular filtration rate (GFR). Here we describe and validate an approach for a transcutaneous determination of GFR by using fluorescein-isothiocyanate-labelled sinistrin (FITC-S) in rats.

METHODS

Using a small animal imager, fluorescence is measured over the depilated ear of a rat after the injection of FITC-S. The decay curve of fluorescence is used for the calculation of half-life and GFR. The thus obtained transcutaneous data were validated by simultaneously performed enzymatic and fluorometric measurements in plasma of both FITC-S and sinistrin.

RESULTS

The results of enzymatic sinistrin determination versus transcutaneous half-life of FITC-S or plasma fluorescence correlated well with each other (R(2) > 0.90). Furthermore, Bland-Altman analyses proved a good degree of agreement of the three methods used. The measurements performed in healthy animals as well as different models of renal failure demonstrate its appropriateness in a wide range of renal function.

CONCLUSIONS

The transcutaneous method described offers a precise assessment of GFR in small animals. As neither blood and/or urine sampling nor time-consuming lab work is required, GFR can be determined immediately after the clearance procedure is finished. This method, therefore, simplifies and fastens GFR determinations in small lab animals compared to conventional bolus clearance techniques based on blood sampling. A low-cost device for the measurement of transcutaneous fluorescence intensity over time is under construction.

Tissue response to subcutaneous implantation of glucose-oxidase-based glucose sensors in rats

Considerable progress in improved control of disturbed glucose metabolism can be expected by continuous glucose monitoring. The aim of the study was to evaluate in male Sprague-Dawley rats tissue response to implantation of a new amperometric glucose-oxidase-based glucose sensor (NTS) compared to a commercially available sensor system CGMS of MiniMed. Both sensors were tested under working conditions over a period of 3 days. Using NTS, glucose in interstitial fluid reflected glucose in arterial blood even in rapidly changing hyper- and hypoglycaemia whereas the CGMS did not detect the experimentally induced glucose changes adequately. Gene expression profiling was performed using Affymetrix chips. Acute phase response to injury by sensor application for a short time is indicated by down regulation of the increase in mRNA of proteases e.g. metallothionein-1alpha and matrix metalloprotease-3 at day 3. Improvement of anabolic situation is suggested by decrease in mRNA of insulin-like growth factor binding protein whereas increase of heme oxygenase and hypoxia-inducible factor may be related to defense mechanisms. Changes of mRNA together with slight fibrous capsule formation suggest good histocompatibility. Comparability of the patterns of changed mRNA in tissue surrounding SCGM with and without operating voltage as shown in dendrogram indicates no contribution of hydrogen peroxide to worsening biocompatibility. Beside established histological investigations of foreign body reaction weeks or months after implantation, gene expression profiling provides additional information to biocompatibility already early after implantation.

Bias and precision of estimated glomerular filtration rate in children

Determining true glomerular filtration rate (GFR) using an exogenous marker is time-consuming and cumbersome. Therefore, creatinine-based estimates of GFR are used. Recent papers using new population-specific/local parameters in their prediction equations, standardizing creatinine determination or adding other endogenous surrogate markers of GFR, like cystatin C, could demonstrate an improvement of bias inherent in the results of the prediction equations. Precision, however, is still poor. Currently, we have to accept a precision (as defined in the so-called Bland-Altman plot) of +/-20% in adults and +/-30-40% in children. This problem of poor precision/uncertainty is especially bothering in the higher, near normal GFR range. Caution should be exercised when applying prediction equations in individuals in need of an accurate GFR determination. In that case, a real clearance procedure has to be performed. In the long run, the true clearance procedure should be simplified using new exogenous GFR markers and developing new devices, allowing GFR measurements to be performed, for example, transcutaneously. Such a procedure would be more acceptable for both patients and physicians.

Plasma creatinine determination in mice and rats: An enzymatic method compares favorably with a high-performance liquid chromatography assay

The use of the colorimetric Jaffé method for the measurement of creatinine in mouse and rat plasma has been criticized as prior studies have shown a dramatic overestimation. We compared a colorimetric picric acid, an enzymatic, and a high-performance liquid chromatography (HPLC) method to assess their appropriateness for routine measurements of creatinine in plasma of healthy and diseased mice (n=61) and rats (n=56). For the colorimetric Jaffé method a pronounced overestimation is confirmed. Additionally the method showed interference with hemoglobin already in a very low, non-visible concentration range in rat plasma. The enzymatic measurement demonstrated a hemoglobin interference in mice, only when hemolysis was visible. The comparison between HPLC and the enzymatic measurement gave a good agreement between both methods in both species. Therefore the enzymatic method fulfills the requirements for a routine screening test for plasma creatinine in healthy as well as diseased mice and rats Kiover a broad concentration range.

Continuous glucose monitoring in interstitial fluid using glucose oxidase-based sensor compared to established blood glucose measurement in rats

Glucose monitoring is of importance for success of complex therapeutic interventions in diabetic patients. Its impact on treatment and glycemic control is demonstrated in large clinical trials. Up to eight blood glucose measurements per day are recommended. Notwithstanding, a substantial number of diabetic patients cannot or will not monitor their blood glucose appropriately. Considerable progress in control of disturbed metabolism in diabetic patients can be expected by continuous glucose monitoring. The aim of the study was to evaluate the performance of a new amperometric glucose oxidase-based glucose sensor in vitro and in vivo after subcutaneous implantation into rats. For in vitro testing current output of sensors was measured by exposure to increasing and decreasing glucose concentrations up to 472 mg dL(-1) over a time period of 7 days. After subcutaneous implantation of sensors into interscapular region of male rats glucose in interstitial fluid was evaluated and compared to glucose in arterial blood up to 7 days. Hyper- and hypoglycaemia were induced by intravenous application of glucose and insulin, respectively. Current of each implanted sensor was converted into glucose concentration using the first blood glucose measurement only. A change of current with glucose of 0.35 nA mg(-1)dL(-1) indicates high sensitivity of the sensor in vitro. The response time (90% of steady state) was calculated by approximately 60s. Test strips for blood glucose measurement as reference for sensor readings was found as an appropriate and rapidly available method in rats by comparison with established hexokinase method in an automated lab analyzer with limits of agreement of +32.8 and -25.7 mg dL(-1) in Bland-Altman analysis. In normo- and hypoglycaemic range sensor readings in interstitial fluid correlated well with blood glucose measurements whereas hyperglycaemia was not reflected by the sensor completely when blood glucose was changing rapidly. The data given characterize a sensor with high sensitivity, long term stability and short response time. A single calibration of the sensor is required only in measurement periods up to 7 days. The findings demonstrate that the sensor is a highly promising candidate for assessment in humans.

Pharmacological profile and toxicity of fluorescein-labelled sinistrin, a novel marker for GFR measurements

There is an evident and growing medical need for an accurate determination of kidney function for a broad spectrum of indications. The glomerular filtration rate (GFR) is the most accepted indicator of renal function. Due to difficulties in performing the test, GFR is currently determined rarely in clinical practice. A procedure for such GFR determination has to be safe, accurate and easy to handle. By using the new compound fluorescein isothiocyanate-sinistrin (FS) these requirements are met. The pharmacological profile and tolerability of FS, selected from among various newly synthesized, labelled compounds intended for use as GFR markers, was characterized in male Sprague-Dawley rats following i.v. application. Using the newly described fluorometric method, FS can be determined much more easily in serum and urine than with the established enzymatic method. After i.v. dosing, FS concentrations in serum declined rapidly in various experimental groups to a comparable extent (t (1/2), mean+/-SD: 22.4+/-8.3 to 26.2+/-5.4 min). Its increase after unilateral nephrectomy reflects the loss of filtration capacity. Comparable concentration-time curves of FS in serum measured fluorometrically and enzymatically suggest no relevant alteration of pharmacokinetic behaviour by the labelling. This notion is supported by the high urinary excretion rate and absence of biliary excretion. The higher sensitivity of the fluorometric method suggests a dose of FS of 100 mg in humans compared with 5 g of sinistrin or inulin. FS was well tolerated after single and multiple applications. On the basis of these results, the kinetics of FS are comparable with the gold standard inulin or sinistrin, but FS is superior in handling. Providing the data can be transferred from rat to human, determination of GFR using the new method should result in an improvement of acceptance by both physicians and patients.

Fluorescein-labeled sinistrin as marker of glomerular filtration rate

There is an obvious and growing medical need for an accurate and easy to handle determination of glomerular filtration rate (GFR) for a broad spectrum of indications. Newly synthesized fluorescein-isothiocyanate (FITC)-sinistrin (FS) with various degrees of labeling was selected by its physicochemical properties and good tolerability out of a number of dye-labeled compounds intended for use as GFR markers for characterization of its pharmacological profile. With respect to solubility FS is more convenient in handling compared to FITC-inulin (FI). Up to 100 mg ml(-1) of FS can be dissolved in aqueous solvents at room temperature, whereas FI can only be solubilized after warming up to 55 degrees C. This reveals a considerable advantage of FS over FI in preparation of galenical formulations for intended i.v. application. A fluorometric method was established to determine FS concentration in blood serum with a comparable accuracy to the established enzymatic method for polyfructosanes. Similar concentration time curves in blood serum of FS measured fluorometrically and enzymatically suggest no relevant change of pharmacokinetic behavior by dye labeling. This notion is supported by the rapid renal and missing of biliary excretion. On the basis of these results, FS is superior in handling to the available GFR markers and makes it highly interesting as a novel diagnostic drug.

Efficacy and immunogenicity of novel erythropoietic agents and conventional rhEPO in rats with renal insufficiency

Recombinant human erythropoietin (rhEPO) is used to treat anemia in chronic renal insufficiency. Erythropoietin (EPO) immunogenicity can lead to EPO-resistant anemia. Conjugating proteins with polyethylene glycol (PEG) can prolong elimination half-life and diminish protein immunogenicity. We investigated the efficacy of new erythropoietic agents, synthesized by single (Ro 50-3821) and multiple (MIX) integrations of PEG and succinimidyl butanoic acid with rhEPO, in rats with chronic renal insufficiency. Sprague-Dawley rats with surgically induced renal insufficiency received Ro 50-3821 or MIX subcutaneously (s.c.) over 4-12 weeks compared to rhEPO and NaCl. Hemoglobin and antibody levels served as primary efficacy and safety variables. Dosing intervals and dose-response characteristics were investigated. Ro 50-3821 (2.5 microg/kg once weekly) increased hemoglobin levels by 7 g/dl after 4 weeks compared to 1 g/dl in NaCl controls (P<0.05). MIX (2.5 microg/kg once weekly) and rhEPO (0.25 microg/kg three times weekly) increased hemoglobin levels by 3 g/dl. Ro 50-3821 administered for 12 weeks (0.75 microg/kg once weekly) increased hemoglobin levels (from 13 to 19 g/dl) more effectively than rhEPO (0.75 microg/kg once weekly, decline from 13 to 11 g/dl, P<0.05). No antibodies against Ro 50-3821 were detected after 12 weeks of treatment. Antibodies against rhEPO were seen in 69% of animals (P<0.00001). Ro 50-3821 increased hemoglobin levels with once weekly s.c. dosing. Multiple pegylated EPO is less effective. In rats, rhEPO failed to increase hemoglobin levels with once weekly long-term dosing. Antibody formation following rhEPO may explain this finding. Therefore, Ro 50-3821 may provide important clinical advantages compared to unpegylated EPO. It can be administered in longer dosing intervals and has a lower risk of unfavorable immunological responses.

Direct fluorometric analysis of a newly synthesised fluorescein-labelled marker for glomerular filtration rate

There is an obvious and growing medical need for an accurate determination of kidney function in the diagnosis and management of renal diseases. The glomerular filtration rate (GFR) is the accepted gold standard measurement of kidney function. Several approaches to estimate the GFR are available, but most of them are inconvenient and, therefore, of limited acceptance. A new method of quantification with fluorescein-isothiocyanate (FITC) sinistrin (FS), a novel GFR marker, has been evaluated. The method is based on the fluorescence label of FS and can be performed with a standard fluorometer. To control the interference of protein with the fluorescence signal, a calibration function was developed. The accuracy of the fluorometric method established is comparable to the so-called "gold standard" of enzymatic determination of polyfructosan. Moreover, FS is easy to handle and requires low-cost instruments. Our results demonstrate the potential of the direct fluorometric analysis of the new FITC-labelled marker of being a precise, simple, rapid and cost-effective method for diagnosing disturbed kidney function and monitoring its treatment efficacy. The dramatic decrease in analytical effort will result in a significantly higher acceptability of GFR determination.

Biocompatibility of an electrochemical sensor for continuous glucose monitoring in subcutaneous tissue

BACKGROUND

The continuous monitoring of glucose allows for tighter control of the glucose concentration and thus may prevent hyper- and hypoglycemia as well as long-term complications of diabetes. While most current systems depend on the transport of fluid to a glucose sensor outside the body, we investigate the possibility of implanting a reagent-based sensor directly into the skin. In this manuscript, the biocompatibility of an electrochemical sensor for continuous glucose monitoring was assessed in vitro and in vivo.

METHODS

Cytotoxicity was investigated in vitro using agar diffusion testing. In vivo biocompatibility was assessed by means of histomorphological examination of the surrounding tissue 10 days after sensor implantation in rats.

RESULTS

The grade of cytotoxicity of the individual sensor components in vitro was between none and mild based on agar diffusion testing. The complete sensor also showed no cytotoxic effects when coated with the co-polymer MPC (2-methacryloyloxyethyl phosphorylcholine, Lipidure CM 5206, NOF Corp., Tokyo, Japan) and when assessed under working conditions, i.e., when a bias voltage was applied to the sensor. Additionally, the hydrogen peroxide-which is inherently generated by the enzymatic glucose detection process using glucose oxidase (GOD)-is likely to have been sufficiently decomposed under these working conditions. Finally, no toxic leachable substances were found during the cytotoxicity testing of sensors and its extracts in vitro. In the in vivo experiments, the strongest foreign body reaction (FBR) was found near the GOD-electrode using a sensor without MPC coating and without a porous membrane. Covering the sensor with MPC, a porous membrane, or both led to a gradual decrease of the FBR down to the level of the negative control.

CONCLUSIONS

The electrochemical, reagent-based sensor with MPC coating and/or a porous membrane is suitable for continuous monitoring of glucose from a biocompatibility standpoint.

Biochemical and morphological effects of K-111, a peroxisome proliferator-activated receptor (PPAR)alpha activator, in non-human primates

K-111 has been characterized as a potent peroxisome proliferator-activated receptor (PPAR)alpha activator. Antidiabetic potency and amelioration of disturbed lipid metabolism were demonstrated in rodents, which were accompanied by elevations of peroxisomal enzymes and liver weight. To examine the possible therapeutic application of K-111 we have now assessed its efficacy in non-human primates with high transferability to humans. For this purpose obese, hypertriglyceridaemic, hyperinsulinaemic prediabetic rhesus monkeys were dosed sequentially with 0, 1, 3 and 10mg/kg per day orally over a period of 4 weeks each. In addition, the effect of K-111 on the peroxisome compartment was analyzed in cynomolgus monkeys using liver samples obtained following a 13-week oral toxicity study. In prediabetic monkeys, the reduction of hyperinsulinaemia and improvement of insulin-stimulated glucose uptake rate indicated amelioration of insulin resistance. These effects were nearly maximal at a dose of 3mg/kg per day, while triglycerides and body weight were lowered significantly in a dose-dependent manner. This reduction of body weight contrasts sharply with the adipogenic response observed with thiazolidinediones, another family of insulin-sensitizing agents. In young cynomolgus monkeys at a dosage of 5mg/kg per day and more, K-111 induced an up to three-fold increase in lipid beta-oxidation enzymes with an 1.5- to 2-fold increase in peroxisome volume density. This moderate increase in peroxisomal activity by K-111 in monkeys is consistent with its role as an PPARalpha activator and corresponds to the observations with fibrates in other low responder mammalian species. The increase in beta-oxidation may explain, at least in part, the lipid modulating effect as well as the antidiabetic potency of K-111. This pharmacological profile makes K-111 a highly promising drug candidate for clinical applications in the treatment of type 2 diabetes, dyslipidaemia, obesity and the metabolic syndrome.

The effects of K-111, a new insulin-sensitizer, on metabolic syndrome in obese prediabetic rhesus monkeys

K-111, formerly BM 17.0744, (2,2-dichloro-12-(4-chlorophenyl)-dodecanoic acid) is a new insulin-sensitizer with peroxisome proliferator-activated receptor (PPAR) alpha activity but without PPAR gamma activity. We determined the efficacy of K-111 in non-human primates in increasing insulin-stimulated glucose uptake and improving metabolic syndrome, assessing the general health-related effects. Six adult male obese normoglycemic prediabetic and insulin-resistant rhesus monkeys were studied on vehicle and following K-111 treatment (four-week chronic dosing each of 3 doses: 1, 3, and 10 mg/kg/d) with assessment of changes in substrate, hormone, and blood pressure measurements and alterations in insulin sensitivity using the euglycemic, hyperinsulinemic clamp technique. K-111 led to significantly decreased body weight and improved hyperinsulinemia, insulin sensitivity, hypertriglyceridemia, and HDL-cholesterol levels without adipogenesis or significant effects on fasting glucose, 24-hour urine glucose excretion, systolic or diastolic blood pressure, plasma fibrinogen, total cholesterol, or chemistry and hematology profile. These benefits are similar to the health-improving effects of calorie restriction, providing preliminary evidence that K-111 has excellent potential as a calorie-restriction mimetic agent. These results indicate the necessity of future study of K-111 for metabolic syndrome in humans, and suggest potential in reducing the risks of diabetes and cardiovascular disease.

Species differences in induction of hepatic enzymes by BM 17.0744, an activator of peroxisome proliferator-activated receptor alpha (PPARalpha)

BM 17.0744, a new anti-diabetic and lipid-lowering agent, leads also to strong hepatomegaly and carnitine acetyl transferase (CAT) increase in the liver of rats, a phenomenon known from fibrates. For information on the relevance of changes in liver of rats to other species, we investigated the effects of BM 17.0744 on lipids and selected marker enzymes related to beta-oxidation in rats, dogs and guinea-pigs, so-called high and low responders to peroxisome proliferators. To examine selectivity other enzymes were also determined, e.g. esterase, urate oxidase (UOX) and cytochrome c oxidase (CYT.C.OX.). Lowering of triglycerides and cholesterol in blood serum and/or liver was observed in pharmacological dose range in the three species tested. In dogs and guinea-pigs, liver and kidney weights were unaffected even in dogs in medium and high dose groups with high systemic exposure and severe toxicity. In male Sprague-Dawley rats treatment with 1.5, 3, 6 and 12.5 mg/kg per day BM 17.0744 selectively elevated the activities of CAT and acyl-CoA oxidase (AOX) by < or =200 and 20-fold, respectively. Administration of BM 17.0744 to Beagle dogs (1.5, 4, 12 mg/kg per day) and guinea-pigs (3 and 12 mg/kg per day) enhanced the activities of CAT and AOX dose-dependently by a factor of two to three only. Immunoblotting revealed a drug-specific enhancement of the amount of beta-oxidation enzymes in rats, which is in accord with the rapid and coordinated transcriptional activation shown in Northern dot blot analysis. Nuclear run-on assays demonstrated a real transcriptional activation. BM 17.0744 activates peroxisome proliferator-activated receptor alpha (PPARalpha), which could be shown by transactivation assays. The stimulation of PPARalpha by BM 17.0744 was stronger than that of the known ligands WY 14.643 and ETYA. Activation of PPARgamma can be excluded. Taken collectively, the data demonstrate an enhancement of the beta-oxidation system by BM 17.0744 paralleled by lipid-lowering in all species investigated. The activation of the nuclear factor PPARalpha may explain the changes in liver and the metabolic effects on the molecular level. The lack of an increase in liver and kidney weights and the relatively moderate enhancement of activities of beta-oxidation-related enzymes in dogs and guinea-pigs indicate that the excessive response observed in rats is not applicable to other, predominantly non-rodent, species. On the basis of these data and the experience with fibrates a specific risk for humans is not expected.

BM 17.0744: a structurally new antidiabetic compound with insulin-sensitizing and lipid-lowering activity

BM 17.0744 (2,2-dichloro-12-(p-chlorophenyl)-dodecanoic acid) is a substance from a group of omega-substituted alkyl carboxylic acids with the general formula, ring-spacer-carboxylic acid. With BM 17.0744-a compound structurally unrelated to thiazolidinediones--antihyperglycemic and antihyperinsulinemic potency has been demonstrated in various animal models of type II diabetes. The antidiabetic effect is independent of the genetic background of the disease, gender, and animal species. The 24-hour blood glucose profile was dose- and time-dependently improved in ob/ob mice after a single and fourth oral administration of 0.3, 1, and 3 mg/kg/d. A dose-dependent reduction of hyperglycemia (10%, 15%, 28%, and 66%) was found in db/db mice after the fifth oral administration of 3, 10, 30, and 100 mg/kg/d. Hyperinsulinemia was reduced dose-dependently in yellow KK mice by 1%, 24%, 34%, and 66% after the fifth oral administration of 0.3, 1, 3, and 10 mg/kg/d. Overall glucose metabolism was predominantly higher in euglycemic-hyperinsulinemic clamp studies in obese fa/fa rats pretreated for 14 days with 10 mg/kg/d BM 17.0744. The data in diabetic and insulin-resistant animals suggest an improvement of insulin action that is supported by enhancement of insulin effects in vitro. There is no evidence of a risk for hypoglycemia in diabetic and metabolically healthy animals. Triglyceride (TG) and cholesterol were reduced in the serum of metabolically healthy rats, as well as serum lipids in db/db mice, which suggests this effect is independent of amelioration of the diabetic status. Lipid-lowering effects in diabetic and healthy animals show an additional property of BM 17.0744. Because of its antidiabetic and lipid-lowering potency, the substance is of great interest in treating the metabolic syndrome. Lipid decreases in rats are associated with a dose-dependent increase in carnitine acetyltransferase activity in the liver to about 100-fold (12.5 mg/kg/d). This together with hepatomegaly in small rodents may indicate peroxisomal proliferation, a phenomenon considered species-specific. Its relevance for humans is well documented for other classes of compounds including fibrates. Specific side effects of insulin sensitizers of the thiazolidinedione type, such as an increase in body weight and heart weight, could not be observed after 4-week oral application of BM 17.0744 in rats. In general, BM 17.0744 was well tolerated in the pharmacological dose range in all species tested.

Apoptosis caused by oxidized LDL is manganese superoxide dismutase and p53 dependent

Oxidized low density lipoprotein (oxLDL) induces apoptosis in human macrophages (Mphi), a significant feature in atherogenesis. We found that induction of apoptosis in Mphi by oxLDL, C2-ceramide, tumor necrosis factor alpha (TNF-alpha), and hydrogen peroxide (H2O2) was associated with enhanced expression of manganese superoxide dismutase (MnSOD) and p53. Treatment of cells with p53 or MnSOD antisense oligonucleotides prior to stimulation with oxLDL, C2-ceramide, TNF-alpha, or H2O2 caused an inhibition of the expression of the respective protein together with a marked reduction of apoptosis. Exposure to N-acetylcysteine before treatment with oxLDL, C2-ceramide, TNF-alpha, or H2O2 reversed a decrease in cellular glutathione concentrations as well as the enhanced production of p53 and MnSOD mRNA and protein. In apoptotic macrophages of human atherosclerotic plaques, colocalization of MnSOD and p53 immunoreactivity was found. These results indicate that in oxLDL-induced apoptosis, a concomitant induction of p53 and MnSOD is critical, and suggest that it is at least in part due to an enhancement of the sphingomyelin/ceramide pathway.

Acute effects of bezafibrate on blood pressure and renal haemodynamics in SHR and WKY rats

BACKGROUND

Bezafibrate, a fibric acid analogue, has well-established lipid- and fibrinogen-lowering properties. Some data exist pointing towards a blood-pressure-lowering effect of bezafibrate. Thus the aim of this study was to examine the acute effect of bezafibrate on blood pressure and renal haemodynamics in hypertensive and normotensive rats.

METHODS

8 Wistar-Kyoto (WKY) and 12 spontaneously hypertensive rats (SHR) were treated with i.v. bolus injections of vehicle and 1-10 mg of bezafibrate in increasing doses every 15 min. Mean arterial pressure (MAP), renal blood flow (RBF), cortical blood flow (CBF), and medullary blood flow (MBF) were monitored continuously, together with plasma renin activity (PRA), urine volume and urinary Na+, K+, and protein concentration (15-min intervals).

RESULTS

Bezafibrate reduced MAP in a dose-dependent manner (mean +/- SEM): in WKY, 1 mg bezafibrate, -1.13 +/- 0.61 mmHg and after 10 mg bezafibrate, -7.25 +/- 1.10 mmHg; in SHR, -0.60 +/- 0.43 and -5.83 +/- 0.90 mmHg respectively. In contrast to vehicle, bezafibrate induced a dose-dependent increase in RBF (WKY, 0.21 +/- 0.10 and 0.83 +/- 0.48 ml/min; SHR, 0.38 +/- 0.10 and 3.09 +/- 0.45 ml/min respectively) and a corresponding decrease in renal vascular resistance which was significantly greater in SHR than in WKY. The increase in RBF was paralleled by an increase in CBF. No effect of bezafibrate on MBF, PRA, urine flow, or urinary Na+, K+ or protein excretion was observed. The observed effects could not be attributed to one of the classic vasodilating mechanisms.

CONCLUSIONS

We conclude that in rats bezafibrate is a potent hypotensive drug exhibiting additional effects on renal haemodynamics.

Induction of mitochondrial manganese superoxide dismutase in macrophages by oxidized LDL: its relevance in atherosclerosis of humans and heritable hyperlipidemic rabbits

The objective of the study was to analyze the intracellular antioxidative response of macrophages (Mphi) exposed to increased levels of low density lipoprotein (LDL). We studied manganese superoxide dismutase (MnSOD) and, in part, GSH in cultured human and rabbit Mphi, and in atheromatous arterial tissue of humans and heritable hyperlipidemic (HHL) rabbits. Incubation of human Mphi with oxidized-LDL (ox-LDL) resulted in an induction of MnSOD mRNA production as shown by RT-PCR. MnSOD immunoreactivity (IR) was found to be located in the mitochondria of Mphi. In HHL rabbits, MnSOD activity and GSH concentration were significantly increased in atherosclerotic intima compared to the media of the aorta, but significantly decreased (P<0.01) in larger plaques compared with smaller ones, resulting in a significant inverse correlation of MnSOD activity (r=-0.67, P<0.001) and GSH concentration (r=-0.57, P<0.01) with plaque size. Immunohistology of the atherosclerotic intima revealed MnSOD-IR in Mac-1 (CD 11b/CD 18)-immunoreactive (ir) Mphi of human arteries and, similarly, in RAM-11-ir Mphi of rabbit ones. The relation of MnSOD-ir Mphi decreased with plaque advancement, which is consistent with biochemical findings. Most MnSOD-ir Mphi in atherosclerotic plaques revealed TUNEL-positive nuclei, indicating DNA strand breaks, and p53-IR. We conclude that mitochondrial antioxidants such as MnSOD are induced in Mphi in vitro and in atherosclerotic arteries as a reply to increased mitochondrial oxidation. As normal consequences of an increased oxidative stress due to the exposure to ox-LDL nuclear DNA strand breaks occur, which are suggested to be a signal to increase p53 protein levels. Reactive oxygen species-mediated mitochondrial-dependent pathways are suggested as major contributing pathomechanisms to nuclear damage, which eventually may result in apoptosis. A common response to increased oxidative stress due to modified LDL is presumed in rabbit and human atherosclerotic plaques.

Effect of alterations of blood cholesterol levels on macrophages in the myocardium of New Zealand White rabbits

We investigated the effect of alterations of blood cholesterol levels on macrophages (mphi) in the myocardium of New Zealand White (NZW) rabbits. Three groups of NZW rabbits were used: controls, rabbits fed a 0.5% cholesterol-enriched diet (CH-D) for 96 days, and rabbits fed a 0.5% CH-D for 96 days followed by normal chow for 4 months. Immunohistochemical analysis by mAbs directed against mphi (RAM-11) and Mn superoxide dismutase (MnSOD) were quantified by computer-assisted morphometry. Using cultured human and rabbit mphi, a cross-reaction of the human MnSOD mAbs was found as well as the predominant localization of MnSOD-immunoreactivity (IR) in mitochondria. In group 1, only a very few RAM-11-immunoreactive (ir) mphi occurred in the interstitial space of the myocardium. In group II blood cholesterol levels significantly increased in parallel with the numbers of mphi, which often contained lipid droplets (foam cells). Although blood cholesterol concentrations regressed about 10-fold in group III, mphi in the myocardium were found to be reduced only about 20%. Most mphi were also MnSOD-ir. In atherosclerotic coronary arteries RAM-11-IR was located in mphi and also extracellularly, whereas MnSOD-IR was found only in mphi. Drastically induced MnSOD in the mitochondria of mphi is suggested as an indicator of increased oxidative stress caused by in vitro conditions or by phagocytosis of low-density lipoprotein in vivo. Elevation of the cholesterol level leads to a long-term increase and its regression results in a delayed reduction of such mphi, which seem to play a key role in the atherogenesis of the coronary arteries as well.

Hypercholesterolemia increases manganese superoxide dismutase immunoreactive macrophages in myocardium

The effect of hypercholesterolemia on manganese superoxide dismutase (MnSOD)-containing macrophages was investigated in male New Zealand white rabbits. Macrophages from control animals, which were marked with the RAM-11 antibody, demonstrated co-localization with MnSOD immunoreactivity, e.g. in the peri- and paravascular space within the myocardium, but not in the bone marrow. In rabbits fed a 0.5% cholesterol-enriched diet for 42 days, a significant increase (P < 0.01) of MnSOD-immunoreactive macrophages within the myocardium was found concomitant to the drastic elevation of serum cholesterol level. In the bone marrow, MnSOD immunoreactivity did not change after cholesterol feeding. Thus in cholesterol-fed rabbits, the increase of MnSOD-containing macrophages seems to parallel that of lipoproteins. MnSOD is considered as being protective against the cytotoxic effects of those superoxide anions, possibly generated in macrophages, which are involved in the metabolism of modified lipoproteins.

The role of elastic recoil after balloon angioplasty of rabbit arteries and its prevention by stent implantation

Elastic recoil, neointima formation and vessel narrowing after balloon angioplasty or stent implantation were compared in 17 non-atherosclerotic New Zealand White rabbits. The implantation of a balloon-expandable Palmaz-Schatz stent was performed in one iliac artery and a balloon angioplasty alone was performed in the contralateral artery (n = 34 arteries). Quantitative histomorphometry was performed by a computer-assisted analysis 1 h and 4, 10 and 24 weeks after the initial procedure. The histological appearance of the neointima was similar to that of human restenosis. The amount of the neointima was increased within stented vessels as compared to balloon angioplasty alone (1.0 +/- 0.1 vs 0.4 +/- 0.1 mm2 at 4 weeks, P < 0.001). However, the neointimal lumen narrowing was smaller in the stented vessels due to persistent increase in vessel perimeter as compared to balloon angioplasty alone (16.5 +/- 0.9 vs 34.7 +/- 16.5% lumen narrowing at 4 weeks, P < 0.05). In conclusion, stent implantation enhances neointima formation as compared to angioplasty in non-atherosclerotic rabbits. The prevention of elastic recoil after stent implantation, however, reduces the neointimal lumen narrowing. This study supports clinical observations demonstrating lower restenosis rates after stent implantation compared to standard balloon angioplasty.

Differences in the response of Sprague-Dawley and Lewis rats to bezafibrate: the hypolipidemic effect and the induction of peroxisomal enzymes

The effects of bezafibrate administered at 10 and 50 mg/kg/day for 7 days to male Sprague-Dawley (SD) and Lewis rats were investigated in order to determine the interrelation between the changes in serum and hepatic lipid contents and activities of selected peroxisomal, microsomal and mitochondrial enzymes in the two rat strains. In both strains, bezafibrate effectively reduced serum and hepatic lipids, increased the liver weight, induced a proliferation of peroxisomes, and selectively elevated the activities of carnitine acetyltransferase and of the enzymes of the peroxisomal beta-oxidation system. Moreover, immunoblotting revealed that the drug specifically enhanced the concentration of only those peroxisomal enzymes involved in fatty acid beta-oxidation. The data obtained demonstrate that although the responses initiated by bezafibrate are qualitatively similar in both strains, they differ in their magnitude in a dose-dependent manner, with the Lewis strain exhibiting a more pronounced response than the SD rats. These results show that dose-dependent strain differences as well as the generally known species differences should be taken into account in pharmacological and toxicological evaluations of fibrates in rodents. Furthermore, generalization and extrapolation from rodent studies should be treated with great caution.

Effects of daltroban, a thromboxane (TX) A2 receptor antagonist, on lipid metabolism and atherosclerosis

In rat hepatocyte cultures daltroban reduced 14C-acetate incorporation stronger into cholesterol (CH) esters than into free CH. Further data suggest that the reduction of cellular sterols by daltroban is independent from its TXA2 receptor antagonistic activity and caused by reduced capacity of ACAT depending CH esterification. In rabbits fed CH-enriched diet treatment with daltroban led to an inhibition of platelet aggregation and to a significant reduction of progression of atherosclerosis. Both reduced CH esterification and TXA2 receptor antagonism may contribute to the diminution of progression of atherosclerosis by daltroban.

The effect of impaired lipid metabolism on the smooth muscle cells of rabbits

Our clinical data enabled us to demonstrate a correlation between impaired lipid metabolism and vasculogenic impotent men. Our aim was to evaluate the effect of an impaired lipid metabolism on the smooth muscle of the corpus cavernosum. A total of 16 rabbits were given a cholesterol-enriched diet for 3 months, and 8 of these received additional thromboxane A2 receptor antagonist; 10 other rabbits (control) were fed a normal diet. Subsequently, cavernous tissue biopsies were taken, and tissue lipid extractions and electron microscopic evaluation were made from 3 rabbits in each group. In the untreated high-cholesterol diet group, cholesterol levels reached approx. 2.1 micrograms/mg body weight compared with 1.07 micrograms/mg b.wt. in the thromboxane A2 receptor antagonist-treated group and elevated levels compared with control group. Similar results were found for the triglyceride and free fatty acid levels. Lecithin tissue levels in treated rabbits were distinctly elevated against those of other 2 groups. Ultramorphological examination of the control group disclosed normal smooth muscle cell (SMC) architecture with numerous sites of intercellular contacts. These findings contrasted with those of the high-cholesterol diet groups which showed significant SMC degeneration with loss of intercellular contacts. Our data imply that impaired lipid metabolism causes cavernous SMC degeneration which plays a major role in the pathogenesis of erectile dysfunction. The thromboxane A2 receptor antagonist seems to produce a protective metabolic effect on the erectile tissue which may have some consequences future treatment strategies.

Atherosclerosis in the aorta of hypercholesterolemic rabbits and the influence of daltroban

These studies have examined aortic atherogenesis in cholesterol-fed rabbits and have correlated the effects of daltroban to the pathomechanism of the vessel wall lesions. After feeding a 0.5% cholesterol-enriched diet for 96 d atherosclerotic alterations were seen, which exhibited a proximo-distal pattern, to which the branching of the aorta contributed considerably. Depending on their localization and size a varying cellular constitution of the plaques was obvious. Large plaques, which were mainly seen in the aortic arch and the proximal descending thoracic aorta, consisted of numerous proliferating cells, masses of fibrillar ground substance, clusters of foam cells, and rarely contained cholesterol crystals and necroses. Emerging plaques mainly found in distal thoracic and abdominal aorta imposed as fatty streaks. Daltroban treatment, used in a clinically relevant doses of 10 mg/kg b. wt. per day, reduced extension and protrusional area of plaques to about 40%, which was evaluated using a newly developed computerized morphormetric method, in association with significant reductions in free cholesterol content within the aorta. The results suggest that daltroban inhibits the progression of atherosclerosis in cholesterol-fed rabbits. This effect may be related to its antagonistic interaction with the thromboxane A2 receptor and also to an inhibition of the cholesterol metabolism.

Effect of a cholesterol synthesis inhibitor (BM 15.766) in the presence and absence of HDL on corticosteroidogenesis of isolated zona glomerulosa and fasciculata cells

The effect of the cholesterol synthesis inhibitor BM 15.766, 4-[2-[1-(4-chlorocinamyl)piperazin-4-yl]ethyl]-benzoic acid on the corticosteroid production was studied in order to reveal the importance of endogenous cholesterol synthesis in the function of zona glomerulosa and zona fasciculata cells of rats. Attempts were made to compensate the effect of BM 15.766 through the application of high-density lipoproteins (HDL). Electron microscopy was used to trace the binding and intracellular accumulation of colloidal gold-labelled HDL (HDL-Au, a cholesterol carrier), in the presence of the cholesterol biosynthesis inhibitor. The stimulation of both types of cells with ACTH was less effective in the presence of 2 x 10(-5) M BM 15.766. The inhibitory effect of BM 15.766 was most marked on the aldosterone production of the zona glomerulosa cells, and could not be reversed by addition of a small amount of HDL-Au. Corticosterone-aldosterone conversion was inhibited by 2 x 10(-5) M BM 15.766. ACTH-stimulated, short-term HDL uptake and internalization was not affected by the cholesterol synthesis inhibitor. The results suggest that certain metabolites of de novo cholesterol biosynthesis may participate in the control of aldosterone production.

Reduction of BM 15.766-induced 7-dehydrocholesterol accumulation by bezafibrate and mevinolin in rats. A non-isotopic in vivo test system for compounds reducing cholesterol synthesis

The effects of mevinolin, a 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitor and bezafibrate, a modulator of lipoprotein metabolism, were measured on BM 15.766-induced 7-dehydrocholesterol (7-DHC) accumulation in liver and serum of rats. BM 15.766, an inhibitor of delta 7 sterol reductase, leads to an accumulation of 7-DHC, which can be used as a measure of cholesterol (CH) synthesis de novo. The investigations were carried out to evaluate the usefulness of this new non-isotopic in vivo method for testing compounds that affect directly and indirectly the CH-biosynthetic pathway. Mevinolin showed a dose-dependent reduction of BM 15.766-induced 7-DHC accumulation after a single oral dose. The dose range for reduction of 7-DHC in the liver of rats was comparable with that for serum CH-lowering in humans. Bezafibrate reduced the BM 15.766-induced 7-DHC accumulation in liver in a dose- and time-dependent manner. These findings agree with the reported reduced activity of HMG-CoA reductase and support the view, that bezafibrate reduces CH biosynthesis by modulation of lipoprotein metabolism. The 7-DHC levels in serum do not reflect those in the liver and cannot be used as a measure of CH biosynthesis. The investigations show that BM 15.766-induced 7-DHC accumulation in liver of rats is an appropriate measure for CH de novo synthesis and can be used for testing compounds that interfere directly and indirectly with the CH-biosynthetic pathway. In contrast to previously described methods, no radiolabelled precursors are necessary.(ABSTRACT TRUNCATED AT 250 WORDS)

Proliferation of peroxisomes without simultaneous induction of the peroxisomal fatty acid beta-oxidation

Marked proliferation of rat hepatic peroxisomes is observed after treatment with a new potent hypolipidemic drug BM 15766, as well as after bezafibrate. Whereas the relative specific activity of the peroxisomal fatty acid beta-oxidation system is not affected by BM 15766 it is significantly increased after bezafibrate. This is also confirmed by immunoblot analysis of individual beta-oxidation enzymes in highly purified peroxisome fractions. These observations suggest that peroxisome proliferation and the induction of the fatty acid beta-oxidation are regulated separately.

Effects of drugs affecting cholesterol biosynthesis pathway on BM 15.766-induced 7-dehydrocholesterol accumulation in rats. An animal model for testing compounds reducing cholesterol synthesis

7-Dehydrocholesterol (7DHC), an intermediate of cholesterol, accumulates in animals after administration of BM 15.766 and can be measured in addition to cholesterol photometrically. The effect of compounds acting at different points in the cholesterol biosynthetic pathway on BM 15.766-induced 7DHC accumulation was investigated in rats to evaluate its usefulness as in vivo test system for cholesterol lowering agents. 7DHC in liver of rats proved to be an appropriate measure for cholesterol de novo synthesis. In contrast to previously described methods no radiolabelled precursors are necessary. The extraction of 7DHC and its photometric determination is, in comparison with separation and measurement of radioactive cholesterol, a simple analytical procedure.

Synthesis and hypolipidemic and antidiabetogenic activities of beta,beta,beta',beta'-tetrasubstituted, long-chain dioic acids

beta,beta,beta',beta'-Tetrasubstituted, long-chain dioic acids of the general formula HOOC-C(XY)-C(R2)-Q-C-(R2)-C(XY)-COOH have been synthesized and evaluated as hypotriglyceridemic-hypocholesterolemic agents in rats and as antidiabetogenic agents in ob/ob diabetic mice. The free carboxyl function of analogues of the series was mandatory for their hypolipidemic-antidiabetogenic effect while nonhydrolyzable diesters were inactive. Other structure-activity relationships were determined as a function of the overall chain length (C12-C22), alpha,alpha'-substitutions (X, Y = H, F, Cl, Br, OH, CN), beta, beta'-substitutions (R = CH3, C6H5), and core substitutions [Q = (CH2)10, (CH2)4CH = CH(CH2)4, 1,4-C6H10[(CH2)3]2, 1,4-C6H4[(CH2)3]2, 1,4-C6H4(CH = CHCH2)2, CH2(OCH2CH2)3OCH2)]. The most effective hypolipidemic-antidiabetogenic members of the series were alpha,alpha'-nonsubstituted, beta,beta'-methyl-substituted analogues of 14-18-carbon chains having either a saturated aliphatic core or a 1,4-bis(propenyl)benzene core in the cis/trans configuration. The hypotriglyceridemic rather than the hypocholesterolemic capacity of members of the series was found to correlate with their respective capacities as liver peroxisomal proliferators in rats.

The induction of liver peroxisomal proliferation by beta,beta'-methyl-substituted hexadecanedioic acid (MEDICA 16)

Treatment of rats by beta,beta'-methyl-substituted hexadecanedioic acid (MEDICA 16) resulted in a dose- and time-dependent increase in liver peroxisomal enoyl-CoA hydratase and cyanide-insensitive palmitoyl-CoA oxidation with a concomitant increase in the volume density of peroxisomes as determined by morphometry. The induced peroxisomal proliferation was sustained as long as treatment was maintained and was accompanied by an increase in liver weight. Incubation of cultured rat hepatocytes in the presence of MEDICA 16 added to the culture medium resulted in a dose-dependent increase in peroxisomal beta-oxidation activities with a concomitant elevation of the volume density of peroxisomes. The induction of peroxisomal proliferation by MEDICA 16 in culture could be prevented in the presence of carnitine palmitoyltransferase inhibitors added to the culture medium, e.g. 2-bromopalmitate, 2-tetradecylglycidic acid or 2-[5-(4-chlorophenyl)-pentyl]oxirane-2-carboxylate. The induction of liver peroxisomes by MEDICA 16 conforms to the previously defined requirement for an amphipathic carboxylate in initiating peroxisomal proliferation. The prevention of peroxisomal proliferation by carnitine acyltransferase inhibitors may implicate the involvement of this acyltransferase in the induction of peroxisomal proliferation by xenobiotic or native amphipathic carboxylates.

Effect of bezafibrate on serum lipids in normo- and spontaneously hyperlipidemic rats

Rats, due to their availability and ease of handling, are a frequently used animal model for studying the effects of drugs on lipid metabolism. Hypolipidemic effects showed great variations in different studies. We investigated the effect of bezafibrate on serum concentrations of cholesterol and triglycerides in different strains of rats from several breeders. Under these conditions Lewis rats seemed to be the most suitable strain to investigate drug effects on cholesterol in serum. A hypercholesterolemic male Lewis rat found in a screening program was mated with normolipidemic female Lewis rats. The hyperlipidemia was found in some of the male and female offspring. Cholesterol and triglycerides were dramatically elevated in older animals. Bezafibrate (75 mg/kg/d) produced a marked reduction of lipids in serum in normo- and hyperlipidemic male rats but only in hyperlipidemic female rats, which is in agreement with former findings. These spontaneously hyperlipidemic rats could be a useful tool for investigation of drug effects on disturbed lipid metabolism and its pathophysiology. Therefore, we tried to establish a hyperlipidemic strain of rats.

The effects of BM 15.766, an inhibitor of 7-dehydrocholesterol delta 7-reductase, on cholesterol biosynthesis in primary rat hepatocytes

The effect of the piperazine derivative BM 15.766 (4-(2-[1-(4-chlorocinnamyl)piperazin-4-yl]ethyl]-benzoic acid) on the biosynthesis of sterols was investigated in adult rat hepatocytes in primary monolayer culture. The substance led to a dose-dependent reduction of cholesterol in the serum of various species of animals such as rat, dog and marmoset. BM 15.766 showed a dose-dependent action on the incorporation of 14C-acetate in neutral, nonsaponifiable lipids. The inhibition of the overall incorporation was 10-12% (10(-5) M). No inhibition was observed in the hepatocytes over the entire dose range of 10(-8) M to 2 X 10(-5) M, while the release of the neutral lipids from the hepatocytes into the culture medium was reduced by up to 40%. The biosynthesis of cholesterol could be reduced by more than 90%. Simultaneously, 7-dehydrocholesterol levels rose in the cells and, to a less marked extent, in the medium. This can be interpreted as an indication that 7-dehydrocholesterol is incorporated into the cell membrane, which results in a lower release of 7-dehydrocholesterol into the medium in comparison with controls. The site of attack is the inhibition of the delta 5.7-sterol delta 7-reductase. The formation of desmosterol and cholestatrienol as well as other 7-dehydrocholesterol precursors could also be demonstrated. After longer incubation, there was an additional accumulation of squalene and lanosterol with simultaneous reduction of 7-dehydrocholesterol by BM 15.766, whereas the total 14C-acetate incorporation in neutral lipids was increased.

Inhibition of cholesterol biosynthesis by BM 15.766

BM 15.766 (4-[2-[1-(4-chlorocinnamyl)piperazin-4-yl]ethyl]benzoic acid) showed a dose dependent action on 14C-acetate incorporation in cholesterol and intermediates including squalene by adult rat hepatocytes in primary monolayer culture. The biosynthesis of cholesterol could be reduced by more than 90%. Simultaneously, the 7-dehydrocholesterol level rose in the cells and, to a less marked extent, in the culture medium.

The pharmacological profile of the thromboxane A2 antagonist BM 13.177. A new anti-platelet and anti-thrombotic drug

BM 13.177 (4-[2-(benzenesulfonamido)-ethyl]-phenoxyacetic acid) is a representative of a new class of sulfonamidophenylcarboxylic acids which possess platelet-inhibitory and anti-thrombotic activity and inhibits the contraction of rabbit aorta stimulated by PG endoperoxides and TXA2. BM 13.177 5 mg/kg body weight p.o. protected rabbits from arachidonate-induced sudden death and greater than or equal to 10 mg/kg dose-dependently reduced the experimental thrombus formation induced in the rabbit aorta by perivascular administration of silver nitrate. In guinea-pigs, the collagen-induced bronchoconstriction was inhibited in a dose- and time-dependent fashion. The formation of TXA2 and the TXA2-induced platelet aggregation and smooth muscle contraction are probably crucial events in these experimental models. The protective effect of BM 13.177 may, therefore, be due to the TXA2-antagonizing effect of BM 13.177, which has been conclusively demonstrated in human platelets (PATSCHEKE and STEGMEIER, Thrombosis Res., 33, 277-288 (1984). The antagonism of TXA2 is supported by the observation that BM 13.177 also specifically inhibits the contraction of isolated arterial strips from rabbits which were stimulated with the thromboxane A2 mimetic U 46619. Schild-plot with a slope close to unity suggests a competitive type of antagonism. BM 13.177 exhibited neither anti-inflammatory nor ulcer-inducing activity of cyclooxygenase inhibitors. Furthermore it did not block the TXB2 formation in spontaneously clotting blood from rabbits and did not inhibit the release of prostacyclin-like activity from rabbit aortas. The lack of toxicological effects in long-term toxicity studies in rat and dog, together with the absence of objective and subjective side effects in the first human studies have encouraged us to initiate clinical trials in order to evaluate the therapeutic benefit of this new approach in humans.