PH regulation of amphotericin B channels activity in the bilayer lipid membrane

Background: Amphotericin B (AmB) is a polyene antibiotic frequently applied in the treatment of systemic fungal infections in spite of its secondary effects. The pH plays a crucial role in modulating biophysical features of ion channels in the bilayer lipid membranes. Aim: In this study, the role of pH in the regulation of AmB channel was assessed by single channel recording of ion channel incorporated in the artificial membrane. Materials and Methods: Bilayer lipid membrane was formed by phosphatidylcholine in a 350 m diameter aperture between two chambers, cis and trans contained 200/50 mMKCl solutions, respectively; then AmB was incorporated into the bilayer lipid membrane. Single channel recordings were used to indicate the effects of pH changes on AmB channels activity. The records were analyzed by Clamp fit 10 software. Results: A kinetic analysis of single channel currents indicated a cation ion channel with 500 pS conductance and voltage-dependence of the open probability of the AmB channel (Po ). A reduction of cis pH to 6 decreased Po and conductance. This effect was also voltage-dependent, being greater at a more positive above -40. The pH changes in the range of 6-8 had no effect on the reversal potential and ion selectivity. Conclusion: Our data indicated that extracellular acidity can reduce AmB activity. © 2016 Journal of Natural Science, Biology and Medicine | Published by Wolters Kluwer - Medknow

Electrophysiological characteristics of cationic single-channel formed by incorporation of amphotericin b in bilayer lipid membrane

BACKGROUND AND OBJECTIVE: Amphotericin B (AmB) is the main antibiotic of polyene type, which is widely used in the treatment of systemic fungal infections. One of the key mechanisms of this drug is the formation of ion channels and increasing permeability of the host cell membranes. This study was conducted to evaluate some of the electrophysiological characteristics of cationic single-channel formed by the incorporation of AmB in bilayer lipid membrane (BLM). METHODS: In this experimental study, phosphatidyl choline was extracted from fresh egg yolk. After the formation of BLM and the incorporation of AmB in the membrane, the channel activity was recorded through +40 to -40 millivolt (mV) voltages. Data analysis was conducted using PClamp10 software to determine the electrophysiological characteristics of the channel. FINDINGS: Reverse potential of Amphotericin B ion Channel was-36 mV. The Channel activity was more in such positive voltages. This means that in voltage -40 mV the current amplitude was 2 Pico Ampère but in voltage +40 mV reach to 30 Pico Ampère. In addition, the channel open probability at voltage -30 mV voltage was low (less than 0.15) but increased to 0.75 in voltage +40 mV. The channel conductance was also 157±4.9 Picoseimence. CONCLUSION: AmB forms cationic channels in BLMs with phosphatidylcholine and without cholesterol. This channel has voltage-dependent electrophysiological characteristics and behaviors. © 2016, Babol University of Medical Sciences. All rights reserved

Quercetin improved spatial memory dysfunctions in rat model of intracerebroventricular streptozotocin-induced sporadic Alzheimer’sdisease

Background: Alzheimer’s disease (AD) is one of the most common neurodegenerative syndromes characterized by a progressive decline in the spatial memory. There are convincing evidences on the neuroprotective effects of flavonoids against AD. Aims and Objective: To determine the effect of quercetin on the acquisition and retention of spatial memory in a rat model of AD. Materials and Methods: Twenty-four male Wistar rats were divided into four groups (six in each): group I: control rats receiving intracerebroventricular (ICV) injection of normal saline, group II: rats induced AD by ICV injection of streptozotocin (STZ; 3 mg/kg bilaterally; twice, on days 1 and 3), and groups III and IV: ICV-STZ AD rats treated intraperitoneally (IP) with 40 and 80 mg/kg/day quercetin, respectively, over a period of 12 days. Then, the rats were trained with four trials per day for five consecutive days in the Morris water maze (MWM). On the sixth day, the memory retention was evaluated. Result: The ICV-STZ AD groups showed a significant impairment in the acquisition and retrieval of spatial memory when compared with the control group (P < 0.001). In the AD groups, the escape latency during the training trials showed a significant decrease (P < 0.001). Meanwhile, during the MWM task, theseratsspentmoretimeinthetargetquadrant in probe trials when compared with the controls. Conclusion: Quercetin acted as a spatial memory enhancer in ICV-STZ–induced AD rats. Hence, this flavonoid can be considered potentially as a promising agent for developing prophylactic and therapeutic neuroprotection. This neuroprotective effect of quercetin may be attributed to its antioxidant and scavenging properties. © 2015 Hamid Sepehri

Modulation of the hepatocyte rough endoplasmic reticulum single chloride channel by nucleotide-Mg 2+ interaction

The effect of nucleotides on single chloride channels derived from rat hepatocyte rough endoplasmic reticulum vesicles incorporated into bilayer lipid membrane was investigated. The single chloride channel currents were measured in 200/50 mmol/l KCl cis/trans solutions. Adding 2.5 mM adenosine triphosphate (ATP) and adenosine diphosphate (ADP) did not influence channel activity. However, MgATP addition inhibited the chloride channels by decreasing the channel open probability (Po) and current amplitude, whereas mixture of Mg 2+ and ADP activated the chloride channel by increasing the Po and unitary current amplitude. According to the results, there is a novel regulation mechanism for rough endoplasmic reticulum (RER) Cl - channel activity by intracellular MgATP and mixture of Mg 2+ and ADP that would result in significant inhibition by MgATP and activation by mixture of Mg 2+ and ADP. These modulatory effects of nucleotide-Mg 2+ complexes on chloride channels may be dependent on their chemical structure configuration. It seems that Mg-nucleotide-ion channel interactions are involved to produce a regulatory response for RER chloride channels. © Springer-Verlag 2012

The Comparison of Antifungal Effects of Methylene Chloride and Methanol Extracts of Green and Black Tea on Candida Albicans

BACKGROUND AND OBJECTIVE: Background: Candidiasis is the most common fungal infection. Nystatin is often used to treating of candidiasis that creates the problem of drug resistance and side effects. Study was performed to determine the antifungal properties of black and green tea extracts against Candida albicans. METHODS: To do this basic study, at first methylene chloride and methanolic extracts of green and black tea were prepared. Disk diffusion method and measuring the diameter of inhibition zone was used to determine anti-fungal extracts against Candida albicans. The methanolic extract at doses of 2, 4, 6, 8 and 10 mg and methylene chloride extracts with concentrations of 0.2, 0.4, 0.6, 0.8 and 1 mg per disk were used and the results compared in 24 and 48 hours. FINDINGS: Methylene chloride extracts of both type of tea create antifungal activity more than methanol extracts. The maximum antifungal activity 24 hours by a concentration of 1 mg hard methylene chloride extract was obtained and in this concentration with formation of zone inhibition 30.57±4.4 and 34.25±2.7 mm, respectively, for the methylene chloride extract of green tea and black more antifungal effect compared to Nystatin (20±1.06 mm) was established (p<0.01). CONCLUSION: The results have shown that green and black tea leaf extract can create antifungal activity effects against Candida albicans as dose -dependent manner and is more effective in the first 24 hours than the 48 hours <xm </x

Characteristics of hepatocyte rough endoplasmic reticulum single cationic channel in Streptozocin- induced diabetic Rats

Background and Objective: The role of ion channels and particularly cationic channels in the pathogenesis of various diseases are being considered carefully. The diabetes mellitus is a common disease which is initiated by ion channel disturbances. This study was done to determine the characteristics of hepatocyte rough endoplasmic reticulum single cationic channel in Streptozocin- induced diabetic rats. Materials and Methods: This experimental study was done on 10 male adult Wistar rats and animals were randomly allocaied into diabetic and control groups. Diabetes induced by STZ (65 mg/kg/bw) intraperitounally. Rough endoplasmic reticulum vesicles were extracted following rat liver excision, homogenization and ultracentrifuging. The bilayer membrane formation was prepared by painting phosphatidylcholine on 250µM aperture in between Cis and Trans sides. The RER vesicles incorporation was performed through gentle and delicate touch of membrane using a dentistry needle. The Pclamp9 software was used for ion channel activity characteristic analysis. Results: The cationic channel current amplitude did not change significantly in voltages more than +3o mV but their open probability (Po) decreased in diabetic group (P<0.05). More severe changes in channel activity were seen in potentials less than the reverse potential. In addition to significant increase of channel Po (P<0.05), also, the channel unitary currents were significantly decreased (P<0.05). The mean current amplitude and channel open probability in voltage +40 mV were 17±2.14 pA and 0.68±0.01 in control group respectively, whereas, the values of these parameters reached to 18.5±2.5 and 0.26±0.03, respectively. In voltage -10 mV, the values of mean current amplitude and Po were -22.3±2.14 pA and <0.1 in control group, respectively but the values changed to -13.1±0.08 and 0.62±0.03 in diabetic group. Conclusion: It seems that RER cationic channel is involved in metabolic changes which cause by diabetes mellitus and this disease can cause probably a channel gating kinetic and behavior change by inducing metabolic stresses

Radiation-induced craniofacial bone growth inhibition: in vitro cytoprotection in the rabbit orbitozygomatic complex periosteum-derived cell culture

BACKGROUND: Radiotherapy for the management of head and neck cancer in pediatric patients results in severe inhibition of craniofacial bone growth. Previously, the infant rabbit orbitozygomatic complex was established as an experimental model. Amifostine, a cytoprotective agent, was found effective in preventing radiation-induced bone growth inhibition. This study was designed to investigate the effects radiation on osteogenic cells from infant rabbit orbitozygomatic complex periostea and to assess the effects of cytoprotection in vitro. METHODS: Infant New Zealand White rabbits (n = 18) were randomized into three groups and received radiation (0, 10, or 15 Gy) to both orbitozygomatic complexes. Cell cultures were developed from orbitozygomatic complex periostea, and cell numbers, proliferation, alkaline phosphatase, and collagen type I expression and mineralization were assessed. Subsequently, rabbits (n = 18) were randomized into three groups to receive either radiation at the effective dose, pretreatment with amifostine (300 mg/kg, intravenously, 20 minutes before irradiation) with the effective radiation dose, or no treatment. Cell cultures were developed and tested for proliferation and alkaline phosphatase expression. RESULTS: Irradiation resulted in a significant inhibition of cell numbers (p < 0.001) and proliferation (p < 0.01) at the 15-Gy dose and no statistically significant changes in alkaline phosphatase activity. Collagen type I expression and mineralization were also significantly reduced at the 15-Gy dose. Pretreatment with amifostine significantly (p < 0.05) enhanced the number of surviving cells. CONCLUSIONS: Amifostine is capable of protecting orbitozygomatic complex periosteum-derived osteogenic cells from the deleterious effects of radiation. This study provides the basis for understanding the cellular mechanisms of radiation-induced craniofacial bone growth inhibition and cytoprotection by amifostine