The Potential for Plant Derivatives against Acrylamide Neurotoxicity.

Certain industrial chemicals and food contaminants have been demonstrated to possess neurotoxic activity and have been suspected to cause brain-related disorders in humans. Acrylamide (ACR), a confirmed neurotoxicant, can be found in trace amount in commonly consumed human aliments as a result of food processing or cooking. This discovery aroused a great concern in the public, and increasing efforts are continuously geared towards the resolution of this serious threat. The broad chemical diversity of plants may offer the resources for novel antidotes against neurotoxicants. With the goal of attenuating neurotoxicity of ACR, several plants extracts or derivatives have been employed. This review presents the plants and their derivatives that have been shown most active against ACR-induced neurotoxicity, with a focus on their origin, pharmacological activity, and antidote effects.

In vitro evaluation of the antioxidant potential, phenolic and flavonoid contents of the stem bark ethanol extract of Anogeissus leiocarpus.

Plant-derived antioxidants with free radical scavenging activities can be relevant as chemopreventive agents against the numerous diseases associated with free radicals and reactive oxygen species. Some phytoconstituents possess antioxidant activities in biological systems. On this basis, we evaluated the antioxidant potential, and determined the total phenolic and flavonoid contents of the ethanol extract of the stem bark of Anogeissus leiocarpus [EESAL]. Antioxidant assays carried out include: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, phosphomolybdate, ß-carotene bleaching, ferric reducing, and hydroxyl radical scavenging activities. Results of DPPH assay showed no significant difference (p < 0.001) between EESAL and butylated hydroxyanisole [BHA], while EESAL exhibited a significantly (p < 0.001) higher activity than BHT [butylated hydroxytoluene]. Phosphomolybdate method recorded a total antioxidant capacity of 190.00 ± 70.53 µg butylated hydroxytoluene equivalents [BHTE]/mg dry extract, while ß-carotene bleaching assay gave percent antioxidant activities of both EESAL and BHT as 81.46±1.62 and 80.90±1.39 respectively. Ferric reducing abilities of both EESAL and ascorbic acid increased in a concentration-dependent manner with EESAL displaying a significantly (p < 0.001) higher reductive activity than vitamin C. EESAL displayed a significantly higher hydroxyl radical scavenging activity as compared with BHT at the lowest concentration with no significant difference at the highest concentration. Total phenolic and flavonoid contents of EESAL were obtained as 608.10 ± 2.12 µg GAE/mg and 78.96 ± 3.37 µg QE/mg respectively. Taken together, the free radical scavenging and antioxidant activity of EESAL is likely due to its high phenolic content with complementary effects of the flavonoid components.

Hepatoprotective and anticlastogenic effects of ethanol extract of Irvingia gabonensis (IG) leaves in sodium arsenite-induced toxicity in male Wistar rats.

Consumption of arsenic contaminated water has been associated with diverse health defects such as cancer and skin lesions. Some plants of medicinal value have been reported to show protective effects against toxins. In this study, the effects of ethanol extract of the leaves of Irvingia gabonensis (IG) against sodium arsenite (SA) induced hepatotoxicity and clastogenicity in male Wistar rats was investigated. Eight groups of five rats each were used for the study. They were administered with 250 or 500 mg/kg body weight of IG with or without SA at 2.5 mg/kg body weight. IG extract has a significant (p<0.05) reducing effect on serum liver function enzymes, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma glutamyltransferase (γGT) activities. This was corroborated with the histopathological analysis findings. Also the groups treated with both the extract and SA recorded significantly (p<0.05) reduced number of micronuclei when compared with the group treated with SA only. IG extract also reduced the oxidative stress induced by SA as measured by the reduced generation of hydrogen peroxide (H2O2) and significant (p<0.05) difference in the CAT and SOD activities between the groups treated with both SA and extract, and the positive control group administered SA alone. This study therefore shows that the ethanol leaf extract of Irvingia gabonensis have hepatoprotective and anticlastogenic effects against sodium arsenite-induced toxicity possibly by enhancing the antioxidant status in the Wistar rats.

Transposable elements in the genomes: parasites, junks or drivers of evolution?

In many organisms with large and complex genomes, transposable elements (TEs) constitute up to 50% of the genomic DNA. TEs have been widely studied and they showed high similarities across kingdoms. Several reasons have been adduced for the diverse TEs among plants and animal species. Activities of TEs could give rise to altered gene or genome at very high frequencies in both germinal and somatic tissues. TE-induced genetic variability can range widely; from changes in the arrangement of the whole genome to changes in single nucleotides. This may produce major effects on the phenotypic traits or small silent changes detectable only at the DNA sequence level. TE-induced mutation in the regulatory sequences may be of evolutionary significance and insertions in promoter sequences can alter tissue-specific patterns of gene expression. In addition, transposons can be involved in amplification and dispersal of genes by taking up portions of other sequences within the TEs themselves, moving them to new locations, thereby increasing their copy number. Therefore, mobilization of TEs might benefit the host through enhancement of genetic diversity. However, TE movement have been linked with undesirable traits in plants, hybrid dysgenesis in Drosophila and genome instability and diseases in mammals. This review summarises the diversity of TEs across plant and animal kingdoms and their impact and possible role in genomic evolution. It also describes some adverse effects of TEs as agents of genomic instability and diseases such as cancers, and the genetic regulations of their activities.

Isolation and partial characterization of a root-specific promoter for stacking multiple traits into cassava (Manihot esculenta CRANTZ).

Cassava can be cultivated on impoverished soils with minimum inputs, and its storage roots are a staple food for millions in Africa. However, these roots are low in bioavailable nutrients and in protein content, contain cyanogenic glycosides, and suffer from a very short post-harvest shelf-life, and the plant is susceptible to viral and bacterial diseases prevalent in Africa. The demand for improvement of cassava with respect to these traits comes from both farmers and national agricultural institutions. Genetic improvement of cassava cultivars by molecular biology techniques requires the availability of appropriate genes, a system to introduce these genes into cassava, and the use of suitable gene promoters. Cassava root-specific promoter for auxin-repressed protein was isolated using the gene walking approach, starting with a cDNA sequence. In silico analysis of promoter sequences revealed putative cis-acting regulatory elements, including root-specific elements, which may be required for gene expression in vascular tissues. Research on the activities of this promoter is continuing, with the development of plant expression cassettes for transformation into major African elite lines and farmers' preferred cassava cultivars to enable testing of tissue-specific expression patterns in the field.

Enhancer/Suppressor mutator (En/Spm)-like transposable elements of cassava (Manihot esculenta) are transcriptionally inactive.

Transposable elements contribute to the size, structure, variation, and diversity of the genome and have major effects on gene function. Sequencing projects have revealed the diversity of transposable elements in many organisms and have shown that they constitute a high percentage of the genome. PCR-based techniques using degenerate primers designed from conserved enzyme domains of transposable elements can provide quick and extensive surveys, making study of diversity and abundance and their applications possible in species where full genome sequence data are not yet available. We studied cassava (Manihot esculenta) En/Spm-like transposons (Meens) with regard to genomic distribution, sequence diversity and methylation status. Cassava transposase fragments characteristic of En/Spm-like transposons were isolated, cloned and characterized. Sequence analysis showed that cassava En/Spm-like elements are highly conserved, with overall identity in the range of 68-98%. Southern hybridization supports the presence of multiple copies of En/Spm-like transposons integrated in the genome of all cassava cultivars that we tested. Hybridization patterns of HpaII- and MspI-digested cassava genomic DNA revealed highly methylated sequences. There were no clear differences in hybridization pattern between the cultivars. We did not detect RNA transcripts of Meens by Northern procedures. We examined the possibility of recent transposition activities of the cassava En/Spm-like elements.

Aqueous and ethanolic leaf extracts of Ocimum basilicum (sweet basil) protect against sodium arsenite-induced hepatotoxicity in Wistar rats.

We evaluated the effects of aqueous and ethanolic leaf extracts of Ocimum basilicum (sweet basil) on sodium arsenite-induced hepatotoxicity in Wistar rats. We observed that treatment of the animals with the extracts before or just after sodium arsenite administration significantly (p < 0.05) reduced mean liver and serum γ-Glutamyl transferase (γGT), and serum alkaline phosphatase (ALP) activities when compared with the group administered the toxin alone. In addition, treatments of the animals with aqueous or ethanolic extract of O. basilicum before the administration of sodium arsenite resulted in the attenuation of the sodium arsenite-induced aspartate and alanine aminotransferase activities: ALT (from 282.6% to 167.7% and 157.8%), AST (from 325.1% to 173.5% and 164.2%) for the group administered sodium arsenite alone, the aqueous extracts plus sodium arsenite, and ethanolic extracts plus sodium arsenite respectively, expressed as percentage of the negative control. These findings support the presence of hepatoprotective activity in the O.basilicum extracts.

Nitroxyl anion regulation of the NMDA receptor.

Nitric oxide (NO) is an important regulator of NMDA channel function in the CNS. Recent findings suggest that nitroxyl anion (NO(-)) may also be generated by nitric oxide synthase, which catalyzes production of NO. Using recombinant NMDA receptors (NMDA-r) transfected into human embryonic kidney cells, our data demonstrate that the nitroxyl anion donor, Angeli's salt (AS; Na(2)N(2)O(3)) dramatically blocked glycine-independent desensitization in NMDA-r containing NR1-NR2A subunits. AS did not affect glycine-dependent desensitization, calcium dependent inactivation or glutamate affinity for the NMDA-r. This effect could be mimicked by treatment with DPTA, a metal chelator and was not evident under hypoxic conditions. In contrast, receptors containing the NR1-NR2B subunits demonstrated an approximate 25% reduction in whole cell currents in the presence of AS with no apparent change in desensitization. Our data suggest that the regulation of NMDA-r function by nitroxyl anion is distinctly different from NO and may result in different cellular outcomes compared with NO.

Hypoxia modulates nitric oxide-induced regulation of NMDA receptor currents and neuronal cell death.

Nitric oxide (NO) released from a new chemical class of donors enhances N-methyl-D-aspartate (NMDA) channel activity. Using whole cell and single-channel patch-clamp techniques, we have shown that (Z)-1-[N-(3-ammoniopropyl)-N-(n-propyl)amino]-NO (PAPA-NO) and diethylamine NO, commonly termed NONOates, potentiate the glutamate-mediated response of recombinant rat NMDA receptors (NR1/NR2A) expressed in HEK-293 cells. The overall effect is an increase in both peak and steady-state whole cell currents induced by glutamate. Single-channel studies demonstrate a significant increase in open probability but no change in the mean single-channel open time or mean channel conductance. Reduction in oxygen levels increased and prolonged the PAPA-NO-induced change in both peak and steady-state glutamate currents in transfected HEK cells. PAPA-NO also enhanced cell death in primary cultures of rodent cortical neurons deprived of oxygen and glucose. This potentiation of neuronal injury was blocked by MK-801, indicating a critical involvement of NMDA receptor activation. The NO-induced increase in NMDA channel activity as well as NMDA receptor-mediated cell death provide firm evidence that NO modulates the NMDA channel in a manner consistent with both a physiological role under normoxic conditions and a pathophysiological role under hypoxic conditions.

Regional and ontogenic expression of the NMDA receptor subunit NR2D protein in rat brain using a subunit-specific antibody.

A polyclonal antibody for the NMDA receptor subunit NR2D has been developed that identifies an approximately 160-kDa band on immunoblots from NR2D transfected cells and CNS tissues. No cross-reactivity is seen with other NMDA receptor subunits. The NR2D receptor subunit is N-glycosylated in both brain and transfected cells. Transfected cells expressing NR2D are immunofluorescently labeled, whereas untransfected cells or cells transfected with other NMDA receptor subunit cDNAs are not. Similarly, the NR2D subunit is selectively and quantitatively immunoprecipitated, whereas the NR1, NR2A, or NR2B subunit is not. The relative densities of the NR2D subunit in nine areas of postnatal day 7 and adult rat brains have been determined by quantitative immunoblotting. NR2D was expressed at highest levels in the thalamus, midbrain, medulla, and spinal cord, whereas intermediate levels of this subunit were found in the cortex and hippocampus. Low or undetectable levels were seen in the olfactory bulb, striatum, and cerebellum. Following a peak after the first week of birth, NR2D protein levels decreased by about twofold in adulthood in all rat brain regions examined. More complete ontogenic profiles were determined for the diencephalon, telencephalon, and spinal cord where similar ontogenic patterns were seen. NR2D protein is present at high levels at embryonic stages of development, rises to a peak at postnatal day 7, and decreases but remains measurable during late postnatal life. This study demonstrates the generation and characterization of an antibody selective for the NR2D NMDA receptor subunit as well as a determination of the distribution and ontogenic profile of this subunit in rat brain. The results suggest that native NMDA receptors containing the NR2D subunit may have functional roles not only in the young brain but also in adult brain.

Kinetics of the reaction of baker's yeast glucose-6-phosphate dehydrogenase with 5,5'-dithiobis(2-nitrobenzoic acid).

The kinetics of the reaction of baker's yeast glucose-6-phosphate dehydrogenase with excess 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) were studied at pH 8.5 and 30 degrees C and at constant ionic strength of 0.01 and in the absence and in the presence of NADP+ or glucose 6-phosphate. The reaction follows pseudo-first-order kinetics irrespective of whether these substrates are absent or present. The observed pseudo-first-order rate constant is reduced in the presence of NADP+ or glucose 6-phosphate but on a molar basis, glucose 6-phosphate is more effective than NADP+ in protecting the sulfhydryl groups of the enzyme against the reaction with DTNB. In the presence of NADP+, the observed pseudo-first-order rate constant decreases to a constant, but finite, value at a saturating coenzyme concentration. The effect of NADP+ on the rate constant is consistent with the presence of noninteracting coenzyme binding sites in baker's yeast glucose-6-phosphate dehydrogenase.