Neuroprotective effect of RO-20-1724-a phosphodiesterase4 inhibitor against intracerebroventricular streptozotocin induced cognitive deficit and oxidative stress in rats.

Cyclic nucleotides viz cGMP and cAMP are known to play an important role in learning and memory processes. Enhancement of cyclic nucleotide signalling through inhibition of phosphodiesterases (PDEs) has been reported to be beneficial in several neurodegenerative disorders associated with cognitive decline. The present study was undertaken to investigate the effect of RO-20-1724-a PDE4 inhibitor on streptozotocin (STZ) induced experimental sporadic dementia of Alzheimer's type. The STZ was injected twice intracerebroventrically (3 mg/kg i.c.v.) on alternate days (day 1 and day 3) in rats. The STZ injected rats were treated with RO-20-1724 (125, 250 and 500 µg/kgi.p.) for 21 days following first i.c.v. STZ administration. Learning and memory in rats were assessed by passive avoidance [PA (days 14 and 15)] and Morris water maze [MWM (days 17, 18, 19, 20 and 21)] following first i.c.v. STZ administration. On day 22 rat cerebral homogenate was used for all the biochemical estimations. The pharmacological inhibition of PDE4 by RO-20-1724 significantly attenuated STZ induced cognitive deficit and oxidative stress. RO-20-1724 was found to not only improve learning and memory in MWM and PA paradigms but also restore STZ induced elevation in cholinesterase activity. Further, RO-20-1724 significantly reduced malondialdehyde and nitrite levels, and restored the glutathione levels indicating attenuation of oxidative stress. Current data complement previous studies by providing evidence for a subset of cognition enhancing effects after PDE4 inhibition. The observed beneficial effects of RO-20-1724 in spatial memory may be due to its ability to restore cholinergic functions and possibly through its antioxidant mechanisms.

SP600125, a competitive inhibitor of JNK attenuates streptozotocin induced neurocognitive deficit and oxidative stress in rats.

Activated JNK has been reported to be located in nucleus in mild cases of Alzheimer's disease (AD), but is exclusively in cytoplasm in more advanced stages of AD and implicated in its pathogenesis, suggesting that activation and re-distribution of JNK correlate with the progress of AD. The present study was designed to investigate the role of JNK in intracerebroventricular streptozotocin (i.c.v. STZ) induced cognitive impairment and oxidative stress. Streptozotocin has been observed to impair learning and memory, increase oxidative-nitritive stress, induce cholinergic hypofunction and neuronal damage in rat brain. Chronic treatment with SP600125 from day 10 to 28 following i.c.v. STZ injections significantly improved spatial memory, attenuate oxidative-nitritive stress. In addition, significant increase in acetylcholinesterase activity and lactate dehydrogenase (LDH) levels was observed in the present model indicating cholinergic hypofunction and increase in neuronal cell damage. Whereas, SP600125 treatment significantly restored acetylcholinesterase activity and reduced LDH levels indicating restorative capacity of SP600125 with respect to cholinergic functions and preventing the neuronal damage. In line with previous report, the current study also supports the potential of JNK inhibition as a possible therapeutic strategy to ameliorate neurodegenerative disorders associated with oxidative stress and cognitive impairment.

Bioenhancers: Revolutionary concept to market.

Treatment cost is a major concern for modern medicine in developing countries like India and systematic innovative means to reduce these costs are needed. This article reviews the concept of bioenhancers to reduce treatment costs by increasing drug bioavailability. This concept, based on the Ayurvedic system of medicine, works for a wide range of ingested substances, and has been applied to modern drugs, particularly single chemicals. It offers a fine example of the benefit of integrating an ancient system with modern medicine in both theory and practice.

Amelioration of intracerebroventricular streptozotocin induced cognitive dysfunction and oxidative stress by vinpocetine -- a PDE1 inhibitor.

Enhancing cyclic nucleotides signaling by inhibition of phosphodiesterases (PDEs) is known to be beneficial in disorders associated with cognitive decline. The present study was designed to investigate the effect of vinpocetine (PDE1 inhibitor) on intracerebroventricular (i.c.v.) streptozotocin induced experimental sporadic dementia of Alzheimer's type. Infusion of streptozotocin impaired learning and memory, increased oxidative-nitritive stress and induced cholinergic hypofunction in rats. Chronic treatment with vinpocetine (5, 10 and 20 mg/kg i.p.) for 21 days following first i.c.v. streptozotocin infusion significantly improved learning and memory in Morris water maze and passive avoidance paradigms. Further, vinpocetine significantly reduced the oxidative-nitritive stress, as evidenced by decrease in malondialdehyde (MDA) and nitrite levels, and restored the reduced glutathione (GSH) levels. Significant increase in acetylcholinesterase activity and lactate dehydrogenase levels was observed in the present model indicating cholinergic hypofunction and increase in neuronal cell damage. Chronic treatment with vinpocetine also reduced significantly the increase in acetylcholinesterase activity and lactate dehydrogenase levels indicating restorative capacity of vinpocetine with respect to cholinergic functions and preventing the neuronal damage. The observed beneficial effects of vinpocetine on spatial memory may be due to its ability to favorably modulate cholinergic functions, prevent neuronal cell damage and possibly through its antioxidant mechanism also.

Immunomodulatory activity of biopolymeric fraction RLJ-NE-205 from Picrorhiza kurroa.

In the last three decades, numerous biopolymeric fractions have been isolated from medicinal plants and used as a source of therapeutic agents. The most promising biopharmacological activities of these biopolymers are their immunomodulatory effects. The biopolymeric fraction RLJ-NE-205 was isolated and purified from the rhizomes of Picrorhiza kurroa. We evaluated the effects of biopolymeric fraction RLJ-NE-205 from P. kurroa on the in vivo immune function of the mouse. Balb/c mice were treated with the biopolymeric fraction RLJ-NE-205 (12.5, 25 and 50 mg/kg body weight) for 14 days with sheep red blood cells (SRBC) as an antigen. Haemagglutination antibody (HA) titre, plaque forming cell (PFC) assay, delayed type hypersensitivity (DTH) reaction, phagocytic index, proliferation of lymphocytes, analysis of cytokines in serum and CD4/CD8 population in spleen (determined by flowcytometry) were studied. At the dose of 50 mg/kg, significant increases in the proliferation of lymphocytes (p<0.001) and cytokine levels (IL-4 and IFN-gamma) in serum (p<0.001) were observed. A dose dependent increase was demonstrated in HA titre (p<0.05), DTH (p<0.01), PFC (p<0.05), phagocytic index (p<0.05) and CD4/CD8 (p<0.01) population. This suggests that the biopolymeric fraction RLJ-NE-205 improves the immune system and might be regarded as a biological response modifier.

Hepatocurative and antioxidant profile of HP-1, a polyherbal phytomedicine.

HP-1 a herbal formulation comprising of Phyllanthus niruri and extracts of Terminalia belerica, Terminalia chebula, Phyllanthus emblica and Tinospora cordifolia has been evaluated for hepatoprotective activity against carbon tetrachloride (CCl4) induced toxicity. Results show that HP-1 reversed the leakage of lactate dehydrogenase (LDH) and glutamate pyruvate transaminase (GPT) and prevented the depletion of glutathione (GSH) levels in a primary monolayer culture of rat hepatocytes (in vitro). HP-1 attenuated the serum toxicity as manifested in elevated levels of transaminases (glutamate oxaloacetate transaminase (GOT), and GPT) The antioxidative enzymes in liver (catalase and superoxide dismutase (SOD)) were restored to normal values after the oral administration of HP-1. HP-1 suppressed the formation of the superoxide anion radical and reduced CCl4 mediated lipid peroxidation (LPO). Silymarin and antioxidants (ascorbic acid, beta-carotene and alpha-tocopherol) were used for comparison. The present study showed that HP-1 is a potential hepatoprotective formulation with an additional attribute of being anti-peroxidative.

Liquid chromatographic method for determination of piperine in rat plasma: application to pharmacokinetics.

Piperine, a major alkaloid of Piper longum and Piper nigrum has been reported to have several pharmacological/toxicological effects. Though a number of methods for analysis of this omnipresent food component in pepper fruits are available, its analysis in body fluids has been largely neglected. A high-performance liquid chromatography method for the analysis of piperine in rat plasma is presented in this communication. Analysis was performed using a Symmetry C(18) column (250x4.6 mm) by isocratic elution with 25 mM KH(2)PO(4) (pH 4.5)-acetonitrile (35:65) and UV detection at 340 nm. The calibration plot was linear over the range studied (2-2000 ng) with correlation coefficient of 0.9984. Limit of detection and limit of quantitation were 1 ng/ml and 3 ng/ml, respectively. Good overall recovery (85.5+/-6%) was obtained with 4 ml ethyl acetate and extraction time of 3 min. Intra- and inter-assay coefficient of variation was found to be less than 7.5%. Plasma concentration-time profile of piperine in a conscious rat implanted with jugular vein cannula was obtained using this method. The method is simple, sensitive and reproducible.

Simple high-performance liquid chromatography method for the simultaneous determination of ketoconazole and piperine in rat plasma and hepatocyte culture.

Piperine, a major alkaloid of black and long peppers has been reported to act as bioavailability enhancer of several drugs by inhibiting drug metabolising enzymes and/or by increasing oral absorption. Ketoconazole is a well established potent inhibitor of CYP 3A4 and P-glycoprotein. A simple and rapid HPLC method has been developed for the simultaneous analysis of ketoconazole and piperine in rat plasma and hepatocyte culture. Analysis was performed using a Symmetry C18 column (150x4.6 mm, 5 microm) and isocratic elution with 25 mM KH2PO4 (pH 4.5)-acetonitrile (50:50) with a flow-rate of 1 ml/min. Photodiode array detection was used to simultaneously monitor piperine at 340 nm and ketoconazole at 231 nm in a single sample. Calibration plots in spiked plasma, hepatocytes and William's medium E were linear over the range studied (10-2000 ng for both drugs). The detection limits for piperine and ketoconazole are 2 and 4 ng, respectively, and the limits of quantitation are 10 and 12 ng, respectively. Intra- and inter-assay variations were less than 8%.

Antidiarrhoeal activity of piperine in mice.

Peppers are common food ingredients used worldwide. They are also added in traditional antidiarrhoeal formulations of different herbs. Piperine (1) is an alkaloidal constituent of black and long peppers recently established as a bioavailability enhancer of drugs and other substances. As a part of efforts to study its effects on the gastrointestinal tract, the experiments were performed to determine the rationale, if any, for its use in traditional antidiarrhoeal formulations. Antidiarrhoeal activity of 1 against castor oil, MgSO4 and arachidonic acid was studied in mice. It significantly inhibited diarrhoea produced by these cathartics at 8 and 32 mg/kg p.o. dose. Inhibition of castor oil induced enteropooling by 1 suggests its inhibitory effect on prostaglandins. The results validate the rationale for its use in traditional antidiarrhoeal formulations.

Piperine inhibits gastric emptying and gastrointestinal transit in rats and mice.

Piperine (1), an alkaloid of black and long peppers, inhibited gastric emptying (GE) of solids/liquids in rats and gastrointestinal transit (GT) in mice in a dose and time dependent manner. Compound 1 significantly inhibited GE of solids and GT at the doses extrapolated from humans (1 mg/kg and 1.3 mg/kg p.o. in rats and mice, respectively). However, at the same dose the effect was insignificant for GE of liquids. One week oral treatment of 1 mg/kg and 1.3 mg/kg in rats and mice, respectively, did not produce a significant change in activity as compared to single dose administration. GE inhibitory activity of 1 is independent of gastric acid and pepsin secretion.

Permeability characteristics of piperine on oral absorption--an active alkaloid from peppers and a bioavailability enhancer.

Piperine, [1-[5-[1,3-benzodioxol-5-yl]-1-oxo-2,4, pentadienyl] piperidine], is a pungent alkaloid present in Piper nigrum Linn, and P. longum Linn. It is shown to enhance the bioavailability of various structurally and therapeutically diverse drugs. A concise mechanism responsible for its bioavailability enhancing action is poorly understood. This study is an effort to understand the absorption dynamics of piperine in intestine on oral absorption. It encompasses intestinal everted sacs as an experimental model. Cycloheximide treatment and exclusion of Na+ salts from incubating medium were the variables used. Absorption half life, absorption rate, absorption clearance and apparent permeability co-efficient were computed from the data. Experiments to denote physico-chemical characteristics of this moiety exhibited that it is a weak base, highly lipophilic in nature with partial solubility in aqueous media. It exhibited passive diffusion constituting non-saturable absorption kinetics. Transport of piperine was not resisted by UWL and was proposed to be absorbed through transcellular pathway. It displayed short absorption clearance and high apparent permeability co-efficient. Data thus obtained suggested that piperine is absorbed very fast across the intestinal barrier. It may act as an apolar molecule and form apolar complex with drugs and solutes. It may modulate membrane dynamics due to its easy partitioning thus helping in efficient permeability across the barriers.

Piperine modulation of carcinogen induced oxidative stress in intestinal mucosa.

Reactive oxygen species (ROS) and reactive metabolic intermediates generated from various chemical carcinogens are known to play an important role in cell damage and in the initiation and progression of carcinogenesis. Many radical scavengers, interestingly naturally occuring antioxidants have been found to be effective in inhibiting the induction of carcinogenesis by a wide variety of chemical carcinogens. Studies have also indicated that various spice principles form an important group as antioxidants. In the present study our goal was to investigate whether piperine an pungent principle of black and long peppers was able to inhibit or reduce the oxidative changes induced by chemical carcinogens in rat intestinal model. Carcinogenesis was initiated in intestinal lumen of male rats with 7,12,dimethyl benzanthracene, dimethyl amino-methyl azobenzene and 3-methyl cholenthrene. Oxidative alterations were assessed by determining thiobarbituric reactive substances, mainly malonaldehyde (as a measure of lipid peroxidation), thiol status and expression of gamma-GT and Na+-K+-ATPase activity in intestinal mucosa. Data indicated that carcinogens treatment induced GSH depletion with substantial increase in thiobarbituric reactive substances and enzyme activities. Piperine treatment with carcinogens resulted in inhibition of thiobarbituric reactive substances. It mediated a significant increase in the GSH levels and restoration in gamma-GT and Na+-K+-ATPase activity. The studies thus indicate a protective role of piperine against the oxidative alterations by carcinogens. It may be suggested that piperine modulates the oxidative changes by inhibiting lipid peroxidation and mediating enhanced synthesis or transport of GSH thereby replenishing thiol redox.

Effect of piperine on bioavailability and pharmacokinetics of propranolol and theophylline in healthy volunteers.

The effect of piperine on the bioavailability and pharmacokinetics of propranolol and theophylline has been examined in a crossover study. Six subjects in each group received a single oral dose of propranolol 40 mg or theophylline (150 mg) alone or in combination with piperine 20 mg daily for 7 days. An earlier tmax and a higher Cmax and AUC were observed in the subjects who received piperine and propranolol. It produced a higher Cmax, longer elimination half-life and a higher AUC with theophylline. In clinical practice, the enhanced systemic availability of oral propranolol and theophylline could be exploited to achieve better therapeutic control and improved patient compliance.