Influence of silicon on maize roots exposed to antimony - growth and antioxidative response.

Pollution of antimony (Sb) raises a serious environmental problem. Although this non-essential element can be taken up by roots and accumulated in plant tissues in relatively high concentrations, there is still lack of knowledge about the effect of Sb on biochemical and metabolic processes in plants. It was shown that application of silicon (Si) can decrease the toxicity of other heavy metals and toxic elements in various plants. The aim of this study was to assess how Si influences the growth and antioxidative response of young Zea mays L. roots exposed to elevated concentrations of Sb. Antimony reduced the root growth and induced oxidative stress and activated antioxidant defense mechanisms in maize. Silicon addition to Sb treated roots decreased oxidative stress symptoms documented by lower lipid peroxidation, proline accumulation, and decreased activity of antioxidative enzymes (ascorbate peroxidase, EC 1.11.1.11; catalase, EC 1.11.1.6; and guaiacol peroxidase, EC 1.11.1.7). Although neither positive nor negative effect of Si has been observed on root length and biomass, changes in the oxidative response of plants exposed to Sb indicate a possible mitigation role of Si on Sb toxicity in plants.

Haloperidol increases expression of the inositol 1,4,5-trisphosphate receptors in rat cardiac atria, but not in ventricles.

Numerous ligands of sigma receptors are known to prolong the QT interval and therefore cause a variety of arrhythmias. High affinity binding sites for the prototypical sigma ligand haloperidol were found in membranes of cardiac myocytes from adult rats. Activation of sigma 1 receptor leads to a release of calcium from the endoplasmic reticulum that follows increased synthesis of inositol 1,4,5-trisphosphate (IP3). We studied the effect of long-term haloperidol treatment on the expression of sigma 1 receptors, IP3 receptors of type 1 and 2 in the individual parts of the rat heart, in isolated rat cardiomyocytes and in PC12 cells. We have found that prolonged treatment with haloperidol significantly increased mRNA levels of sigma 1 receptors in both atria and ventricles. Sigma 1 receptor's mRNA was increased also in isolated cardiomyocytes. Haloperidol treatment affects the expression of IP3 receptors of type 1 and 2 in cardiac atria, but not in cardiac ventricles. We observed increase in IP3 receptors in differentiated PC12 cells, but not in isolated cardiomyocytes. We propose that this increase might participate in triggering cardiac arrhythmias during haloperidol treatment, which has to be further verified.

Effect of 7-nitroindazole on the expression of intracellular calcium channels in the kidney of spontaneously hypertensive rats.

The spontaneously hypertensive rats (SHR) were fed with nitric oxide synthase (NOS) blocker 7-nitroindazole (7-NI, 10 mg/kg/day) for 6 weeks and an expression of intracellular calcium channels, SERCA and proapoptotic agents was evaluated in kidney. Treatment of rats with 7-NI resulted in a significant increase in mRNA and protein levels of the IP3 receptors type 1 and type 2, while mRNA levels of the IP3 receptor type 3 remained unchanged. The mRNA of other intracellular calcium channels, ryanodine receptors type 1 and type 2 was also upregulated by 7-NI treatment. Gene expression of the SERCA2a, calcium pump responsible for loading intracellular stores with calcium, revealed increased gene expression due to 7-NI as well. Interestingly, proapoptotic agents caspase 3 and Bax were also upregulated by the 7-NI treatment. These results may indicate that nNOS blocker 7-NI modifies intracellular calcium transport system, which may have impact on altered calcium handling and regulation of various metabolic pathways.

Type 2 IP(3) receptors are involved in uranyl acetate induced apoptosis in HEK 293 cells.

Calcium released from endoplasmic reticulum through special calcium release channels - inositol 1,4,5-trisphosphate receptors (IP(3)Rs) and ryanodine receptors (RyRs) - serves as a main source of cytosolic calcium signaling in the majority of cell types in physiological state and also in pathological situations. In this work, we studied whether IP(3)Rs can be involved in uranyl acetate induced nephrotoxicity. Using human embryonic kidney cell line (HEK293) as an experimental model we have found that uranyl acetate (5 and 50microM) up-regulates both, mRNA and protein levels of the type 1 and type 2 IP(3) receptors in HEK293 cells. This increase was associated with elevated expression of proapoptotic factors Bax and Caspase 3 and also by higher extent of apoptosis. Vice versa, induction of apoptosis resulted in increased mRNA levels of IP(3)R2 and also elevated levels of apoptotic markers. Therefore we propose that enhanced expression of the type 2 IP(3)Rs can at least partially contribute to increased levels of apoptosis due to uranyl acetate treatment.

Hypoxia differently modulates gene expression of inositol 1,4,5-trisphosphate receptors in mouse kidney and HEK 293 cell line.

Hypoxia is a state of insufficient oxygen supply of the tissue or cell. Kidney tissue is highly sensitive to oxygen deprivation and easily develops renal ischemic injury. Calcium transporters very sensitively react to oxygen deficiency. We investigated whether hypoxia affects the gene expression of intracellular calcium transporters in the intact kidney, and we compared the response to that of HEK 293 cells. Our results showed that, while in mouse kidney tissue hypoxia elevates mRNA for inositol 1,4,5-trisphosphate receptors (IP3R) type 1 (IP3R1) and ryanodine receptors (RyR) type 2 (RyR2), in culture of HEK 293 cells the gene expression of all IP3Rs decreased without affecting viability of the cells. RyR2 mRNA in HEK 293 cells was not significantly changed, but RyR1 gene expression was significantly increased by hypoxia. The different response of kidney tissue and HEK 293 cells to hypoxia could be due to unequal differentiation state of the cells in intact tissue and cultured embryonic cell line. The physiological relevance of this observation remains to be determined.

Lipoprotein lipase HindIII polymorphism influences HDL-cholesterol levels in statin-treated patients with coronary artery disease.

BACKGROUND: HDL-cholesterol (HDL-C) is a recognized athero-protective factor and low levels of HDL-C occur frequently in patients with coronary artery disease. Regulation of HDL-C level most probably results from the interaction of genes involved in lipoprotein metabolism and also from non-genetic factors. We studied associations and interactions among HindIII polymorphisms of the lipoprotein lipase gene LPL and selected non-genetic factors with respect to HDL-C levels in patients with coronary artery disease. PATIENTS AND METHODS: 288 Slovak patients (35% women) with documented coronary artery disease, age (mean +/- SEM) 60 +/- 1 years and BMI 29 +/- 0.3 kg/m(2), were examined and genotyped for LPL HindIII (rs320) using a PCR/RFLP method. HDL-C levels were determined in a direct enzymatic assay. RESULTS: In the sample overall there were no significant differences across the LPL genotypes in adjusted HDL-C levels or in other lipids, although a trend toward higher HDL-C and lower triglycerides in H-H- homozygotes was observed. Multiple linear regression identified a significant interaction between LPL HindIII and statin treatment, which together with sex and diabetes explained 12.1% of HDL-C variance. Accordingly, in statin-treated patients we observed significant stepwise increments of the HDL-C level related to the increasing number of H- alleles (P = 0.04 for linear trend), whereas no such association was observed in patients without hypolipidemic treatment. H-H- homozygotes had a 16% (0.19 mmol/l) higher level of HDL-C than the H+H+ homozygotes (P = 0.06). CONCLUSION: HDL-C may be influenced by an interaction between statin treatment and LPL HindIII genotype. However, the effect of this interaction appears to be small when compared with the effect of non-genetic factors. This finding requires replication in a pharmacogenetic study.

Changes in ultrastructure and endogenous ionic channels activity during culture of HEK 293 cell line.

Human embryonic kidney (HEK) 293 cells were characterised as an expression system for voltage-activated cationic channels. Current density for cationic channels intrinsically expressed in HEK 293 cells as well as cell ultrastructure was described after 7-11, 29-30 and 49-63 days of cell culture. Slowly activating outward potassium current with the current density varying between +10 and +26 pA/pF was observed in 72% to 95% of investigated cells. Rapidly inactivating outward potassium current with the current density varying between +7 and +10 pA/pF was present in 38% to 48% of all cells. 30% of cells exhibited voltage-activated calcium channel with the current density less than -1 pA/pF. Tetrodotoxin-sensitive sodium current with amplitudes between -1.4 and -2.2 pA/pF was initially present in 5% of cells, nevertheless, after 49-63 days of cell culture this proportion increased to 35%. Ultrastructure of HEK 293 cell surface, but not of cell's interior changed during cell culture. The longer the time after thawing the more microvilli and protrusions appear on the cell surface. Irregular cell contours hinder the cells to appose and only small patches of membranes form attachments. Staining of cells with a polycationic dye ruthenium red initially increased and decreased again following prolonged period of time in culture indicating regression of negatively charged layers of the cell surface coat. We suggest that the optimal time window for patch clamp experiment is between days 7 and 63 of cell culture due to alterations of cell surface.