Lidija Begović

Response of Lemna minor L. to short-term cobalt exposure: The effect on photosynthetic electron transport chain and induction of oxidative damage

The effect of two concentrations of cobalt (Co(2+)) on photosynthetic activity and antioxidative response in Lemna minor L. were assessed 24, 48 and 72h after the start of the exposure. Higher concentration of cobalt (1mM) induced growth inhibition while lower concentration (0.01mM) increased photosynthetic pigments content. Analysis of chlorophyll a fluorescence transients revealed high sensitivity of photosystem II primary photochemistry to excess of Co(2+) especially at the higher concentration where decreased electron transport beyond primary quinone acceptor QA(-) and impaired function of oxygen evolving complex (OEC) was observed. Due to impairment of OEC, oxygen production was decreased at higher Co(2+) concentration. Activity of superoxide dismutase was mainly inhibited while lipid peroxidation increased, at both concentrations, indicating that cobalt-induced oxidative damage after short exposure and moreover, susceptibility of the membranes in the cell to cobalt toxicity. Results obtained in this study suggest possible application of used parameters as tools in assessment of early damage caused by metals.

Physiology and biochemistry of leaf bleaching in prematurely aging maple (Acer saccharinum L.) trees. II. Functional and molecular adjustment of PSII

Physiology and biochemistry of leaf bleaching in prematurely aging maple (Acer saccharinum L.) trees. II. Functional and molecular adjustment of PSII In the present study we aimed to investigate physiological and molecular mechanisms of photosynthetic performance decline in prematurely aged bleached leaves of silver maple (Acer saccharinum L.) trees. We used in vivo chlorophyll a fluorescence measurement to analyze changes in PSII photochemistry, relative abundance of photosynthetic proteins (D1, LHCII, Cytf and Rubisco LSU), relations between chlorophylls and their precursor protochlorophyllide as well as elemental composition of the leaves. Decreases in Al, Cr, Cu, Fe, K, Zn and an increase in S concentrations were found in bleached leaves in comparison to healthy green ones. The bleached leaves were visually expressing symptoms characteristic of Fe deficiency. Further, they had considerably decreased chlorophyll contents and protochlorophyllide contents, overall photosynthetic activity and relative abundance of major photosynthetic proteins. All the results indicate that modifications in the molecular organization of photosynthetic electron-transport chain components in bleached leaves led to functional adaptation of the PSII achieved by modifications of some reaction centres (RCs), turning them from active to dissipative. This provided efficient adaptation of bleached leaves to high-light induced oxidative damage during summer.

Modulation of the cell growth by Aloe Vera extract and hydrogen peroxide

Reactive oxygen species (ROS), reactive nitrogen species, and their counterpart antioxidant agents are essential for physiological signaling, while imbalances between oxidants and antioxidants may provoke pathological reactions causing a range of diseases including cancer. In addition, ROS can stimulate signal transduction pathways and lead to activation of key transcription factors such as Nrf2 and NF-κB modulating cell growth and redox balance [1]. The well-known medical plant Aloe vera contains an abundance of antioxidants, which are capable of neutralising ROS [2]. This work evaluates the effects of the genuine Aloe vera extract (AV) on human cells in vitro in respect to the toxic effects of hydrogen peroxide. After propagating Aloe vera for 1 year in 0.5 kg plastic pots, the first fully developed leaf, fourth from the top, was harvested and subjected to biochemical tests for determination of vitamin C, carotenoids and total soluble phenolic content, while total antioxidant capacity of the plant extract was analysed using Brand-Williams method [3]. Afterwards, four different human cell lines, notably HeLa (human cervical cancer), HMEC (human microvascular endothelial cells), HaCat (human keratinocytes) and HOS (human osteosarcoma) were treated with 2 concentrations of AV for 1 hour after one hour pre-treatment with ranging concentrations of H2O2, thus inducing oxidative stress. The viability of the cells was determined by an MTT-based vitality assay, EZ4U (Biomedica, Vienna, Austria). The plant extract expressed strong antioxidant capacities (1.1 mmol of Trolox eq./g FW), mostly likely due to the combined effects of its antioxidants ingredients. However, while H2O2 inhibited in a concentration dependent manner the growth of all cell lines except HOS, the extract of AV did not show any particular effects except a slight stimulation of the HeLa and HMEC cells. We may assume that antioxidants of the plant extract are not involved in the observed growth modifying effects on the different cell lines used. More likely, some components of the plant extract could interfere with the cellular antioxidants and redox signalling and its effects together with hydrogen peroxide. The above actions of AV confirmed that it can potentially act as relatively safe natural source of medical remedies since there were no toxic effects observed, while further studies on the mechanisms of its actions are needed.

Cell-Type-Specific Modulation of Hydrogen Peroxide Cytotoxicity and 4-Hydroxynonenal Binding to Human Cellular Proteins In Vitro by Antioxidant Aloe vera Extract

Although Aloe vera contains numerous bioactive components, the activity principles of widely used A. vera extracts are uncertain. Therefore, we analyzed the effects of genuine A. vera aqueous extract (AV) on human cells with respect to the effects of hydrogen peroxide (H2O2) and 4-hydroxynonenal (HNE). Fully developed A. vera leaves were harvested and analyzed for vitamin C, carotenoids, total soluble phenolic content, and antioxidant capacity. Furthermore, human cervical cancer (HeLa), human microvascular endothelial cells (HMEC), human keratinocytes (HaCat), and human osteosarcoma (HOS) cell cultures were treated with AV extract for one hour after treatment with H2O2 or HNE. The cell number and viability were determined using Trypan Blue, and endogenous reactive oxygen species (ROS) production was determined by fluorescence, while intracellular HNE–protein adducts were measured for the first time ever by genuine cell-based HNE–His ELISA. The AV extract expressed strong antioxidant capacities (1.1 mmol of Trolox eq/g fresh weight) and cell-type-specific influence on the cytotoxicity of H2O2, as well as on endogenous production of ROS and HNE–protein adducts induced by HNE treatment, while AV itself did not induce production of ROS or HNE–protein adducts at all. This study, for the first time, revealed the importance of HNE for the activity principles of AV. Since HMEC cells were the most sensitive to AV, the effects of AV on microvascular endothelia could be of particular importance for the activity principles of Aloe vera extracts.

Cabbage (Brassica oleracea var. capitata) as possible Indicator of Wartime Metal and Metalloid Contamination in Eastern Croatia (ICP-MS Method)

ABSTRACT Biomonitoring of the local population and environmental monitoring in eastern Croatia have revealed abnormalities in metal and metalloid distribution that could be related to war activities during the 1990s. The goal of this study was to determine whether there are differences in the concentrations of metals and metalloids by comparing locations of high and low-intensity combat activity; we also evaluated a possible connection between metal contamination in soil and in humans. We sampled 14 locations and measured the concentrations of 20 war related metals and metalloids (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mg, Ni, Pb, Sb, Si, Sr, U, V and Zn). The results of principal components analysis showed two main clusters: locations Dopsin and Dalj (both characterized by high-intensity combat activity), where the concentrations of most elements (except Hg) were increased. Although the concentrations of metals and metalloids in cabbage samples collected in eastern Croatia did not exceed the maximum allowed values, the results of our study confirmed existance of environmental ‘hotspot’ with higher concentrations of war metals and metalloids. Our findings indicate that there is a possible common source and mechanism of transferring metals from the environment to the population.