Age-related learning and memory deficits in rats: role of altered brain neurotransmitters,acetylcholinesterase activity and changes in antioxidant defense system

Oxidative stress from generation of increased reactive oxygen species or free radicals of oxygen has been reported to play an important role in the aging. To investigate the relationship between the oxidative stress and memory decline during aging, we have determined the level of lipid peroxidation, activities of antioxidant enzymes, and activity of acetylcholine esterase (AChE) in brain and plasma as well as biogenic amine levels in brain from Albino–Wistar rats at age of 4 and 24 months. The results showed that the level of lipid peroxidation in the brain and plasma was significantly higher in older than that in the young rats. The activities of antioxidant enzymes displayed an age-dependent decline in both brain and plasma. Glutathione peroxidase and catalase activities were found to be significantly decreased in brain and plasma of aged rats. Superoxide dismutase (SOD) was also significantly decreased in plasma of aged rats; however, a decreased tendency (non-significant) of SOD in brain was also observed. AChE activity in brain and plasma was significantly decreased in aged rats. Learning and memory of rats in the present study was assessed by Morris Water Maze (MWM) and Elevated plus Maze (EPM) test. Short-term memory and long-term memory was impaired significantly in older rats, which was evident by a significant increase in the latency time in MWM and increase in transfer latency in EPM. Moreover, a marked decrease in biogenic amines (NA, DA, and 5-HT) was also found in the brain of aged rats. In conclusion, our data suggest that increased oxidative stress, decline of antioxidant enzyme activities, altered AChE activity, and decreased biogenic amines level in the brain of aged rats may potentially be involved in diminished memory function.     

Enhancing the efficacy of fluocinolone acetonide by encapsulating with PLGA nanoparticles and conjugating with linear PEG polymer

Abstract

Fluocinolone acetonide (FA), a glucocorticoid is used to treat inflammation in the posterior segment of the eye. Due to short half-life and body clearance, it will not be able to give therapeutic effect for long time with a single injection. Formulating FA nanoparticles (NPs) or PEG conjugates can be an effective way to overcome these disadvantages. We prepared two formulations, FA loaded in PLGA nanoparticles (NPs-FA) and FA conjugated to linear PEG (PEG-FA). The NPs-FA were characterised for size and zeta potential using particle size analyser and shape and morphology by using scanning electron microscope (SEM). The amount of drug loaded per mg of NPs and in-vitro release of FA from NPs were calculated using reverse phase high pressure liquid chromatography (RP-HPLC). NPs synthesis was optimized with factorial and Response Surface Methodology (RSM). Chemically synthesized PEG-FA conjugates were characterized using H-NMR and purity of the conjugate was analysed using RP-HPLC. Visualization of cellular uptake of NPs was done by coumarin-6 loaded NPs under fluorescent microscope. RAW 264.7 macrophages were treated with NPs-FA and PEG-FA conjugates to study their effectiveness in inhibiting TNF-α levels compared to free FA treatment. Stability test confirmed that FA is more stable within NPs than in free form. Particle size and zeta potential were found to be 183.6?±?12.47nm and ?25.6?±?4.4mV, respectively. 149.58?±?11.3µg of FA was encapsulated per mg of NPs and 61?µg of FA was present per mg of PEG-FA conjugate. In vitro drug release study showed a sustained release of FA from the NPs for a period of 30?days. Fluorescent microscope images showed uptake of NPs by RAW 264.7 cells. TNF-α assay confirmed that substantial inhibition of TNF-α levels from both formulations compared to free FA. From the results, we conclude that new formulations will greatly reduce drug dosage and frequency of administration for long term treatment of inflammation in posterior part of the eye.     

Dietary cancer risk from conditional cancerogens in produce of livestock fed on species of spurge (Euphorbiaceae)

Special procedures were developed to investigate poisonous milk of lactating goats fed experimentally on aerial parts of the herb Euphorbia peplus L. In extracts of the milk, weakly irritant in the mouse-ear assay, three diterpene ester toxins were detected by techniques of high-performance liquid chromatography. They are of the ingenane structural type: Euphorbia␣factor Pel (ingenol 20-acetate 3-angelate), Euphorbia factor Pe2 (20-deoxyingenol 3-angelate) and Euphorbia factor␣Pe4 (20-deoxyingenol-6α,7α-epoxide 3-angelate). From goats milk collected 15 days after cessation of the experimental feeding period, extracts were completely free of diterpene ester toxins. The toxins polluting the milk are identical to diterpene ester entities occurring in the aerial parts of E. peplus. Of these, Euphorbia factors Pe1 and Pe2 are known as promoters of tumors of mouse skin. Apart from the toxic Euphorbia factors, the non-toxic parent alcohol ingenol was also detected in the milk. It is absent in the plant, and may have been generated metabolically from a certain portion of the toxic diterpene esters picked up by the goats from their fodder. The results presented here provide, for the first time, data for a novel interpretation of the locally high incidence of esophageal cancer observed in certain areas in the Caspian littoral of Iran, associated with a greater consumption of goat's (and sheep's) milk. Received: 4 August 1997 / Accepted: 3 February 1998