Andrea Jednakovits

Bimoclomol (BRLP-42) Ameliorates Peripheral Neuropathy in Streptozotocin-Induced Diabetic Rats

A reduction in nerve conduction velocity and an increase in resistance to ischemic conduction failure are early signs of neural dysfunction in both diabetic patients and animal models of diabetes. The effect of Bimoclomol (BRLP-42), a drug under clinical development for the treatment of diabetic complications, on experimental peripheral neuropathy was examined in rats made diabetic by injection of streptozotocin. Daily oral doses of Bimoclomol (10 or 20 mg/kg) or control dose of gamma-linolenic acid (260 mg/kg), an agent with known neuropathy-improving effects, were administered for 3 months. Treatments began 1 day after diabetes induction to assess the prophylactic efficacy of Bimoclomol. Neuropathy was evaluated electrophysiologically by measuring motor and sensory nerve conduction velocities and resistance to ischemic conduction failure of sciatic nerve in vivo. Bimoclomol significantly reduced nerve conduction slowing and retarded the typical elevated ischaemic resistance due to streptozotocin-induced neuropathy, suggesting that the drug might be a useful treatment for diabetic peripheral neuropathies.

Effect of BRX-220 against peripheral neuropathy and insulin resistance in diabetic rat models.

Abstract: Bimoclomol (BML), a symptomatic antidiabetic agent, has been developed by Biorex R & D Co. to treat diabetic neuropathy and retinopathy. BRX‐220, an orally active member of the BRX family, has been developed to treat diabetic complications and insulin resistance (IR) as a follow‐up compound. The effect of BRX‐220 on peripheral neuropathy was examined in rats with diabetes (type 1) induced by administration of a β‐cell toxin, streptozotocin (STZ, 45 mg/kg iv). Nerve functions were evaluated by electrophysiological measurements of muscle motor and sensory nerve conduction velocities (MNCV and SNCV, respectively). MNCV and SNCV decreased in diabetic rats by 25% (p < 0.001). A 1‐month preventive treatment with BRX‐220 (2.5, 5, 10, and 20 mg/kg po) dose‐dependently improved diabetes‐related deficits in MNCV (51.3%, 71.3%, 86.1%, and 91.3%) and SNCV (48.9%, 68.5%, 86.1%, and 93.2%). Insulin sensitivity was measured using the insulin tolerance test (ITT), both in STZ diabetic and in Zucker diabetic fatty (ZDF) rats (model of type 2 diabetes). Severe IR was detected in STZ diabetic and ZDF rats. This resistance was significantly (p < 0.05) reduced by BRX‐220 treatment.

Nontoxic heat shock protein coinducer BRX-220 protects against acute pancreatitis in rats

BACKGROUND Nontoxic heat shock protein (HSP) inducer compounds open up promising therapeutic possibilities by activating one of the natural and highly conserved defense mechanisms of the organism. AIMS In the present experiments, we examined the effects of a HSP coinducer drug-candidate, BRX-220, on the cholecystokinin-octapeptide (CCK)-induced acute pancreatitis in rats. METHODS Male Wistar rats weighing 240 to 270 g were divided into two groups. In group B, 20 mg/kg BRX-220 was administered orally, followed by 75 microg/kg CCK subcutaneously three times, after 1, 3, and 5 h. This whole procedure was repeated for 5 d. The animals in group slashed circleB received physiological saline orally instead of BRX-220, but otherwise the protocol was the same as in group B. The rats were exsanguinated through the abdominal aorta 12 h after the last administration of CCK. We determined the serum amylase activity, the plasma trypsinogen activation peptide concentration, the pancreatic weight/body weight ratio, the DNA and total protein contents of the pancreas, the levels of pancreatic HSP60 and HSP72, the activities of pancreatic amylase, lipase, trypsinogen, and free radical scavenger enzymes (superoxide dismutase, catalase, and glutathione peroxidase), the degree of lipid peroxidation, protein oxidation, and the reduced glutathione level. Histopathological investigation of the pancreas was also performed in all cases. RESULTS Repeated CCK treatment resulted in the typical laboratory and morphological changes of experimentally induced pancreatitis. The pancreatic levels of HSP60 and HSP72 were significantly increased in the animals treated with BRX-220. In group B, the pancreatic total protein content and the amylase and trypsinogen activities were significantly higher vs. group slashed circleB. The plasma trypsinogen activation peptide concentration, and the pancreatic lipid peroxidation, protein oxidation, and the activity of Cu/Zn-superoxide dismutase were significantly decreased in group B vs. group slashed circleB, whereas the glutathione peroxidase activity was increased. The morphological damage in group B was significantly lower than that in group slashed circleB. CONCLUSION The HSP coinducer BRX-220, administered for 5 d, has a protective effect against CCK-induced acute pancreatitis.

Pharmacologically activated migration of aortic endothelial cells is mediated through p38 SAPK

Impairment in endothelial cell (EC) function plays a central role in vascular diseases (e.g. atherosclerosis, restenosis, diabetic angiopathies, microvascular angina, peripheral arterial disease). BRX‐235 (a novel small molecule synthesized by Biorex, Hungary) has a potent vasculoprotective activity in different in vivo and in vitro studies. Since the importance of the p38 pathway in EC homeostasis and migration in particular is well documented, we have carried out studies to address the role of the p38 stress activated protein kinase (p38 SAPK) in the mode of action of BRX‐235. In this study, Bovine aortic endothelial cells were used in a wounding migration assay (WMA) and for Western‐blot analysis to study the effect and molecular mechanism of BRX‐235‐induced EC migration. The bovine aortic endothelial (BAE) cells were shown to be good models for EC migration. Both endothelial cell growth factor (ECGF)‐ and BRX‐235‐induced BAE cell migration were shown to be inhibited by SB 203580, a specific inhibitor of p38 SAPK. It was also shown that, BRX‐235 induces phosphorylation of p38 SAPK without affecting p38 SAPK protein levels. Thus, BRX‐235 acts upstream of p38 SAPK. In summary, we have shown that p38 SAPK is a potential pharmacological mediator for candidate drugs that target the endothelium.

Effect of subchronic bimoclomol treatment on vascular responsiveness and heat shock protein production in spontaneously hypertensive rats

This study was designed to investigate the effects of subchronic bimoclomol treatment on endothelial function and expression of 72 kD heat shock protein (HSP-72) in spontaneously hypertensive rats. Endothelial function was tested by monitoring vascular responses to acetylcholine in isolated aortic ring preparations. Polymerase chain reaction was applied to determine HSP-72 mRNA content in the tissue samples. Significant age-dependent declines in relaxation to acetylcholine and vascular HSP-72 mRNA levels were observed in the spontaneously hypertensive animals. Both changes were prevented by subchronic application of bimoclomol suggesting that preservation of endothelial function might be related to sustained levels of HSP-72.

Effects of bimoclomol, the novel heat shock protein coinducer, in dog ventricular myocardium.

The effects of the novel HSP-coinducer bimoclomol was studied on action potentials, ionic currents and [Ca2+]i transients in isolated canine ventricular myocytes using conventional microelectrode techniques and whole cell voltage clamp combined with fluorescent [Ca2+]i measurements. Contractility was studied in right ventricular trabeculae. All preparations were paced with a frequency of 0.2 Hz. Bimoclomol (100 microM) shortened action potential duration measured at 50% repolarization, but lengthened action potentials at the 90% repolarization level, decreased action potential amplitude and maximum depolarization velocity in a reversible manner. In voltage clamped myocytes, the drug activated a steady-state outward current at positive membrane potentials leaving the peak inward current unaffected. [Ca2+]i transients, measured under voltage clamp control, were increased in amplitude and had accelerated decay kinetics in the presence of the compound, in addition to reduction of diastolic [Ca2+]i. Bimoclomol significantly decreased the force of contraction in right ventricular trabeculae. Comparison of present data to previous results indicate that the cardiac effects of bimoclomol strongly depend on actual experimental conditions. The reduced contractility in spite of the increased amplitude of [Ca2+]i transients suggests that 100 microM bimoclomol may decrease calcium sensitivity of the contractile apparatus.

In vivo and in vitro acute cardiovascular effects of bimoclomol.

Effects of bimoclomol, the novel heat shock protein (HSP) coinducer, was studied in various mammalian cardiac and rabbit aortic preparations. Bimoclomol decreased the ST-segment elevation induced by coronary occlusion in anesthetized dogs (56% and 80% reduction with 1 and 5 mg/kg, respectively). In isolated working rat hearts, bimoclomol increased coronary flow (CF), decreased the reduction of cardiac output (CO) and left ventricular developed pressure (LVDP) developing after coronary occlusion, and prevented ventricular fibrillation (VF) during reperfusion. In rabbit aortic preparations, precontracted with phenylephrine, bimoclomol induced relaxation (EC(50)=214 microM). Bimoclomol produced partial relaxation against 20 mM KCl, however, bimoclomol failed to relax preparations precontracted with serotonin, PGF(2) or angiotensin II. All these effects were evident within a few minutes after application of bimoclomol. A rapid bimoclomol-induced compartmental translocation of the already preformed HSPs may explain the protective action of the compound.

Biphasic effect of bimoclomol on calcium handling in mammalian ventricular myocardium

Concentration‐dependent effects of bimoclomol, the novel heat shock protein coinducer, on intracellular calcium transients and contractility were studied in Langendorff‐perfused guinea‐pig hearts loaded with the fluorescent calcium indicator dye Fura‐2. Bimoclomol had a biphasic effect on contractility: both peak left ventricular pressure and the rate of force development significantly increased at a concentration of 10 nM or higher. The maximal effect was observed between 0.1 and 1 μM, and the positive inotropic action disappeared by further increasing the concentration of bimoclomol. The drug increased systolic calcium concentration with a similar concentration‐dependence. In contrast, diastolic calcium concentration increased monotonically in the presence of bimoclomol. Thus low concentrations of the drug (10–100 nM) increased, whereas high concentrations (10 μM) decreased the amplitude of intracellular calcium transients. Effects of bimoclomol on action potential configuration was studied in isolated canine ventricular myocytes. Action potential duration was increased at low (10 nM), unaffected at intermediate (0.1–1 μM) and decreased at high (10–100 μM) concentrations of the drug. In single canine sarcoplasmic calcium release channels (ryanodine receptor), incorporated into artificial lipid bilayer, bimoclomol significantly increased the open probability of the channel in the concentration range of 1–10 μM. The increased open probability was associated with increased mean open time. The effect of bimoclomol was again biphasic: the open probability decreased below the control level in the presence of 1 mM bimoclomol. Bimoclomol (10 μM–1 mM) had no significant effect on the rate of calcium uptake into sarcoplasmic reticulum vesicles of the dog, indicating that in vivo calcium reuptake might not substantially be affected by the drug. In conclusion, the positive inotropic action of bimoclomol is likely due to the activation of the sarcoplasmic reticulum calcium release channel in mammalian ventricular myocardium.

Cardiovascular effects of BRX-005 comparison to bimoclomol.

Concentration-dependent effects of BRX-005, the novel heat shock protein coinducer, cardioprotective and vasoprotective agent, on intracellular calcium transients and contractility were studied in Langendorff-perfused guinea pig hearts loaded with the fluorescent calcium indicator dye Fura-2. BRX-005 increased peak left ventricular pressure, the rate of force development and relaxation significantly in a concentration-dependent manner. The amplitude of [Ca2+]i transients was left unaltered by the drug. In contrast to BRX-005, bimoclomol increased both contractility and the amplitude of [Ca2+]i transients. In canine ventricular cardiomyocytes high concentrations of BRX-005 had no effect on depolarization, whereas bimoclomol suppressed action potential upstroke markedly. In guinea pig pulmonary artery preparations precontracted with phenylephrine, BRX-005 induced concentration-dependent relaxation. This effect of BRX-005 was independent of the integrity of endothelium indicating that vasorelaxant effect of the drug develops directly on vascular smooth muscle.