Slavik Dushenkov

Bioconcentration of heavy metals by plants

Abstract Certain plants can concentrate essential and non-essential heavy metals in their roots and shoots to levels far exceeding those present in the soil. Metal-accumulating plant species are invariably restricted to metalliferous soils found in different regions around the world. The mechanisms of metal accumulation, which involve extracellular and intracellular metal chelation, precipitation, compartmentalization and translocation in the vascular system, are poorly understood. Interest in these mechanisms has led to the development of phytoremediation—a new technology to use plants to clean up soil and water contaminated with heavy metals.

Modulation of Inflammatory Genes by Natural Dietary Bioactive Compounds

Several epidemiologic studies have shown that chronic inflammation predisposes individuals to various types of cancer. Many cancers arise from sites of infection, chronic irritation, and inflammation. Conversely, an oncogenic change induces an inflammatory microenvironment that promotes the development of tumors. Natural bioactive compounds in dietary plant products including fruits, vegetables, grains, legumes, tea, and wine are claimed to help prevent cancer, degenerative diseases, and chronic and acute inflammation. Modern methods in cell and molecular biology allow us to understand the interactions of different natural bioactive compounds with basic mechanisms of inflammatory response. The molecular pathways of this cancer-related inflammation are now unraveled. Natural bioactive compounds exert anti-inflammatory activity by modulating pro-inflammatory gene expressions have shown promising chemopreventive activity. This review summarizes current knowledge on natural bioactive compounds that act through the signaling pathways and modulate inflammatory gene expressions, thus providing evidence for these substances in cancer chemopreventive action.

Trends in phytoremediation of radionuclides

Phytoremediation, a novel plant-based remediation technology, is applied to a variety of radionuclide-contaminated sites all over the world. Phytoremediation is defined as the use of green plants to remove pollutants from the environment or to render them harmless. Current status of several subsets of phytoremediation of radionuclides is discussed: (a) phytoextraction, in which high biomass radionuclide-accumulating plants and appropriate soil amendments are used to transport and concentrate radionuclides from the soil into the above-ground shoots, which are harvested with conventional agricultural methods, (b) rhizofiltration, in which plant roots are used to precipitate and concentrate radionuclides from polluted effluents, (c) phytovolatilization, in which plants extract volatile radionuclides from soil and volatilize them from the foliage and (d) phytostabilization, in which plants stabilize radionuclides in soils, thus rendering them harmless. It is shown that phytoremediation is a fast developing field and the phytoremediation of radionuclides might soon become an integral part of the environment management and risk reduction process.

The Composition of Hemp Seed Oil and Its Potential as an Important Source of Nutrition

ABSTRACT The fatty acid and natural product content of hemp seed oil was analyzed by GC-MS and LC-MS. The presence of linoleic acid (LA) and a-linolenic acid (LNA) were confirmed in their previously reported ratio of 3:1 LA:LNA. The presence of β-caryophyllene (740 mg/L), myrcene (160 mg/L), β-sitosterol (100-148 g/L) and trace amounts of methyl salicylate was observed in the oil which had not been previously reported. Trace amounts of cannabidiol (CBD) were also detected. Bioassays were performed with the oil to determine its effectiveness as an antimicrobial agent. Some bioactivity was observed during the primary screening.

Antitumor Activity of 3,5,4 '-trimethoxystilbene in COLO 205 cells and xenografts in SCID mice

Resveratrol (R‐3), a trihydroxy trans‐stilbene from grape, inhibits multistage carcinogenesis in animal models. Here we report that 3,5,4′‐trimethoxystilbene (MR‐3), the permethylated derivative of R‐3 was more potent against the growth of human cancer cells (HT‐29, PC‐3, COLO 205) with estimated IC50 values of 81.31,42.71, and 6.25 µM, respectively. We further observed that MR‐3 induced apoptosis in COLO 205 cells through modulation of mitochondrial functions regulated by reactive oxygen species (ROS). ROS generation occurs in the early stages of MR‐3‐induced apoptosis, preceding cytochrome‐c release, caspase activation, and DNA fragmentation. Significant therapeutic effects were demonstrated in vivo by treating severe combined immune deficiency (SCID) mice bearing COLO 205 tumor xenografts with MR‐3 (50 mg/kg ip). Assays on DNA fragmentation and caspase activation were performed and demonstrated that apoptosis occurred in tumor tissues treated with MR‐3. The appearance of apoptotic cells, as shown by Hematoxylin and Eosin (H&E) staining, and an increase in p21 and decrease in proliferating cell nuclear antigen (PCNA) protein by immuno‐histochemistry were observed in tumor tissues under MR‐3 treatment. Our study identifies the novel mechanisms of the antitumor effects of MR‐3 and indicates that these results may have significant applications for cancer chemotherapy.

Phytoremediation: a novel approach to an old problem

Abstract There is a great need for cost effective technology to remediate soils and bodies of water contaminated with heavy metals and radionuclides. Phytoremediation, an emerging technology of using plants for the removal of pollutants could provide an affordable way to restore the economic value of contaminated land. Two main subsets of phytoremediation have been developed: phytoextration, which is based on using high biomass crop plants in combination with a system of soil amendments to extract heavy metals from soil, and rhizofiltration, a technology which employs plants to remove contaminants from aqueous streams.

Optimizing Phytoremediation of Heavy Metal-Contaminated Soil by Exploiting Plants' Stress Adaptation

Soil phytoextraction is based on the ability of plants to extract contaminants from the soil. For less bioavailable metals, such as Pb, a chelator is added to the soil to mobilize the metal. The effect can be significant and in certain species, heavy metal accumulation can rapidly increase 10-fold. Accumulation of high levels of toxic metals may result in irreversible damage to the plant. Monitoring and controlling the phytotoxicity caused by EDTA-induced metal accumulation is crucial to optimize the remedial process, i.e. to achieve maximum uptake. We describe an EDTA-application procedure that minimizes phytotoxicity by increasing plant tolerance and allows phytoextraction of elevated levels of Pb and Cd. Brassica juncea is tested in soil with typical Pb and Cd concentrations of 500 mg kg−1 and 15 mg kg−1, respectively. Instead of a single dose treatment, the chelator is applied in multiple doses, that is, in several small increments, thus providing time for plants to initiate their adaptation mechanisms and raise their damage threshold. In situ monitoring of plant stress conditions by chlorophyll fluorescence recording allows for the identification of the saturating heavy metal accumulation process and of simultaneous plant deterioration.

Bioengineering of a Phytoremediation Plant by Means of Somatic Hybridization

ABSTRACT Phytoremediation is a technology that exploits a plants ability to remove contaminants from the environment or render toxic compounds harmless. An efficient metal phytoremediating plant must combine high biomass production and established cultivation methods with high tolerance to a specific contaminant and ability for root uptake, translocation, and compartmentalization of contaminants in the above-ground biomass. Symmetric and asymmetric somatic hybridizations were used to introduce toxic metal-resistant traits from Thlaspi caerulescens into Brassica juncea. B. juncea hypocotyl protoplasts were fused with T. caerulescens mesophyll protoplasts. The hypocotyl protoplasts of B. juncea were stained with CFDA before fusion and thus fluoresced green under UV, whereas the mesophyll protoplasts of T. caerulescens had red autofluorescense. Heteroplasmic fusion products were identified and selected by flow cytometry and cell sorting. All putative hybrids grown in the greenhouse had morphological characteristics of B. juncea. A Thlaspi -specific repetitive sequence was hybridized to total DNA of plants, including the parental species. All plants from both symmetric and asymmetric fusions showed Thlaspi- specific hybridization patterns while B. juncea did not exhibit any hybridization signal. Hybrid plants, produced by asymmetric somatic hybridization between the two species, demonstrated high metal accumulation potential, tolerance to toxic metals, and good biomass production.

Polymethoxyflavones activate Ca2+-dependent apoptotic targets in adipocytes.

Induction of apoptosis is an emerging strategy for the prevention and treatment of obesity because removal of adipocytes via apoptosis will result in reducing body fat and may help to maintain a long-lasting weight loss. Our previous studies have shown that a sustained increase in intracellular Ca(2+) triggers apoptosis in various cell types via activation of Ca(2+)-dependent proteases and that the apoptosis-inducing effect of polymethoxyflavones (PMFs) in cancer cells is mediated through Ca(2+) signaling. This paper reports that PMFs induce apoptosis in mature mouse 3T3-L1 adipocytes via activation of Ca(2+)-dependent calpain and Ca(2+)/calpain-dependent caspase-12. Treatment of adipocytes with PMFs evoked, in a concentration- and time-dependent fashion, sustained increase in the basal level of intracellular Ca(2+). The increase in Ca(2+) was associated with induction of apoptosis and activation of mu-calpain and caspase-12. Apoptosis-inducing activity of hydroxylated PMFs was significantly higher than that of the corresponding nonhydroxylated compounds. These results demonstrate that the apoptotic molecular targets activated by PMFs in adipocytes are Ca(2+)-dependent calpain and caspase-12. The findings obtained provide rationale for evaluating the role of PMFs in the prevention and treatment of obesity.

Impact on Epigenetics in Cancer Chemoprevention by Natural Dietary Compounds

Epigenetics refers to modification in gene expression that occurs without a change in DNA sequence. Epigenetic modification mechanisms include DNA methylation, histone modification and microRNA influence. Aberrant epigenetic alterations play a significant role in disease development, including cancer. Natural dietary compounds demonstrate cancer prevention activity by regulating expression of oncogenes or tumor suppressor genes through epigenetic mechanisms. Examples of these natural dietary compound-modulated epigenetic events of cancer prevention include retinoic acid from spinach, genistein and daidzein from soybeans, sulforaphane from broccoli, apigenin from celery, quercetin from berries, resveratrol from grapes, EGCG from green tea, vitamin D3 from fish, and curcumin from turmeric. In this review, we focus on the effect of natural dietary compounds on epigenetic modification during the process of cancer development.