From methodological limitations to the function of metallothioneins - A guide to approaches for determining weak, moderate, and tight affinity zinc sites

Mammalian metallothioneins (MTs) are small cysteine-rich proteins whose primary role is participation in zinc and copper homeostasis. Ever since their discovery, MTs have been investigated in terms of metal-binding affinity. The initial concept of seven Zn(II) ions (Zn7MT) bound with the same, undifferentiated low picomolar affinity in the α and β domains prevailed for many years and derived from spectroscopic studies. The application of fluorescent zinc probes has changed the perception of MTs, showing that they function in nano- to subnanomolar free zinc concentrations due to the presence of tight, moderate, and weak binding sites. The discovery of Zn(II)-depleted MTs in many tissues and determination of cellular free Zn(II) concentrations with differentiated zinc affinity sites revealed the critical importance of partially saturated Zn4-6MTs species in cellular zinc buffering in a wide pico- to nanomolar range of free Zn(II) concentrations. Until today, there is no clear agreement on the presence of differentiated or only tight zinc sites. Here, we present a series of spectroscopic, mass spectrometry-based, and enzymatic competition experiments which reveal how weak, moderate, or high affinity ligands interact with human MT2, with special attention to the determination of Zn(II) affinities. The results show that the simplification of the stability model is the major reason for determining significantly different stability data that obscured the actual MTs function. Therefore, we emphasize that different metal affinities are the single most reason for their presumed function, which changed over the years from tight binding and, thus, storage to one that is highly dynamic.

Lipoxin (LTX A4 5S, 6R, 15R) levels drastically decrease after 5 years of hemodialysis treatment

The increased risk of atherosclerosis in patients with chronic kidney disease (CKD) is associated with the increased concentration of fatty acids from the omega-6 family. Products of arachidonic acid oxidation, including prostaglandins, thromboxanes, hydroxyleicosa-tetraenoic acids (HETES) and hydroxyoctadecadienoic acids (HODES) are involved in the pathogenesis of cancer and cardiovascular diseases due to increased oxidative stress. The aim of our study was to determine the relations resulting from the duration of CKD treatment. One of our main concerns is, whether and when the cascade of synthesis of inflammatory mediators may be insufficient in patients with CKD during many years of treatment. The study involved 121 patients with CKD and 87 healthy volunteers. Eicosanoid profiles 9(S)-HODE, 13(S)-HODE, 5(S)-HETE, 12(S)-HETE, 15(S)-HETE, 5(S)-oxoETE, 16(RS)-HETE, and 5(S),6(R)-lipoxinA4, 5(S),6(R),15(R)-lipoxinA4 were extracted in plasma. The HPLC separations were performed by means of 1260 liquid chromatography. Patients with CKD have a significantly higher concentration of the following inflammatory mediators: 13(S)-HODE, 5(S)-HETE, 12(S)-HETE, 15(S)-HETE, 5(S)-oxoETE, 16(RS)-HETE, and 5(S),6(R), 15(R)-lipoxinA4 relative to the control group. However, the concentrations of 9(S)-HODE were lower in the CKD group. The comparison of sexes did not show significant differences in terms of CKD. A tendency for lower concentrations of HETE and HODE were observed in the group of men. 15LOX, 12LOX and 5LOX pathways in chronic kidney disease are increased, while COX are suppressed (9-HODE). The analysis of the treatment time of patients with CKD shows that incorrect levels of 5(S), 6(R) and 15(R)-lipoxinA4 are developed. We present a new evidence of possible concepts and future clinical interventions in patients suffering from chronic kidney disease for many years. These data for the first time demonstrate that lipoxin levels drastically decrease in the course of CKD. Therefore, synthetic LXA4 analogues may be used as an antioxidant therapy in CKD, which requires further research.

Enhanced Cellular Uptake and Photodynamic Effect with Amphiphilic Fluorinated Porphyrins: The Role of Sulfoester Groups and the Nature of Reactive Oxygen Species

A class of amphiphilic photosensitizers for photodynamic therapy (PDT) was developed. Sulfonate esters of modified porphyrins bearing-F substituents in the ortho positions of the phenyl rings have adequate properties for PDT, including absorption in the red, increased cellular uptake, favorable intracellular localization, low cytotoxicity, and high phototoxicity against A549 (human lung adenocarcinoma) and CT26 (murine colon carcinoma) cells. Moreover, the role of type I and type II photochemical processes was assessed by fluorescent probes specific for various reactive oxygen species (ROS). The photodynamic effect is improved not only by enhanced cellular uptake but also by the high generation of both singlet oxygen and oxygen-centered radicals. All of the presented results support the idea that the rational design of photosensitizers for PDT can be further improved by better understanding the determinants affecting its therapeutic efficiency and explain how smart structural modifications can make them suitable photosensitizers for application in PDT.

Crosstalk of the structural and zinc buffering properties of mammalian metallothionein-2

Structural insights into partially Zn(ii)-depleted MT2 species and their zinc buffering properties are presented and discussed.

Effect of IGF-I and TNF-α on intensification of steroid pathways in women with PCOS phenotypes are not identical. Enhancement of progesterone pathway in women with PCOS increases the concentration of TNF-α

OBJECTIVE

The aim of this study was to determine the correlations between the concentration of tumor necrosis factor (TNF-α) and insulin-like growth factor I (IGF-I) in each woman with polycystic ovary syndrome (PCOS) phenotypes based on the levels of androgen.

METHODS

Two groups of women with PCOS differing in their levels of androgens. The test group composed of 39 women with PCOS according to the Rotterdam criteria in their reproductive age. The hormonal levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid stimulating hormone (TSH), prolactin (PRL), androstenedione, testosterone (T), estradiol (E₂) and sex hormone binding globulin (SHBG) were measured. Correlations analysis were performed calculating Spearman's rank correlation coefficient of hormones with relation to TNF-α and IGF-I.

RESULTS

There was a medium positive correlation of IGF-1 with LH levels (p < 0.05) and negative medium correlation of TNF-α with of dehydroepiandrosterone (DHEA)-SO₄ levels (p < 0.05) only in group of PCOS women with elevated androgens.

CONCLUSION

Analysis of TNF-α showed that women with high testosterone negative correlation between level of TNF-α and the concentration of DHEA-SO4. Inflammatory state involving TNF-α in women with PCOS and high concentration of androgens is caused by intensified Δ4 (progesterone) pathway and omitted or limited Δ5 (dehydroepiandrosterone) pathway of testosterone biosynthesis.

BICD1 and Chromosome 18 Polymorphisms Associated With Recipients' Telomere Length Affect Kidney Allograft Function After Transplantation

BACKGROUND

Reports regarding recipient's nonmodifiable genetic factors affecting telomerase activity and thus allograft function are lacking. Therefore the aim of this study was to analyze the associations between recipients' rs2735940 hTERT, rs2630578 BICD1, and rs7235755 chromosome 18 polymorphisms and kidney function after transplantation.

METHODS

The study enrolled 119 white Polish kidney allograft recipients (64 men, 55 women; overall mean age, 47.3 ± 14.0 y). To identify genotypes of the studied polymorphisms, real-time polymerase chain reaction was performed.

RESULTS

There were statistically significant differences in distribution of rs7235755 chromosome 18 polymorphism genotypes and alleles between recipients with delayed graft function (DGF) and without DGF (P = .03). The presence of A allele was significantly associated with higher risk of DGF occurrence (AA + GA vs GG: OR, 3.25 [95% CI, 1.16-9.14]; P = .02; GA vs GG: OR, 4.00 [1.35-11.82]; P = .01). Analysis of the rs2630578 BICD1 gene polymorphism genotypes revealed statistically significant differences in long-term creatinine concentrations. The presence of C allele of this polymorphism was significantly associated with higher creatinine concentrations 24, 36, and 18-48 months after transplantation (GC + CC vs GG: P = .008, P = .008, and P = .01, respectively).

CONCLUSIONS

Recipients' polymorphisms of genes associated with telomere length, BICD1 and chromosome 18, but not hTERT, affect kidney allograft early and long-term function after transplantation. There is an urgent need for explanation of these observations in genome-wide association studies.

Resistance of Cu(Aβ4-16) to Copper Capture by Metallothionein-3 Supports a Function for the Aβ4-42 Peptide as a Synaptic Cu(II) Scavenger

Aβ4-42 is a major species of Aβ peptide in the brains of both healthy individuals and those affected by Alzheimer's disease. It has recently been demonstrated to bind Cu(II) with an affinity approximately 3000 times higher than the commonly studied Aβ1-42 and Aβ1-40 peptides, which are implicated in the pathogenesis of Alzheimer's disease. Metallothionein-3, a protein considered to orchestrate copper and zinc metabolism in the brain and provide antioxidant protection, was shown to extract Cu(II) from Aβ1-40 when acting in its native Zn7 MT-3 form. This reaction is assumed to underlie the neuroprotective effect of Zn7 MT-3 against Aβ toxicity. In this work, we used the truncated model peptides Aβ1-16 and Aβ4-16 to demonstrate that the high-affinity Cu(II) complex of Aβ4-16 is resistant to Zn7 MT-3 reactivity. This indicates that the analogous complex of the full-length peptide Cu(Aβ4-42) will not yield copper to MT-3 in the brain, thus supporting the concept of a physiological role for Aβ4-42 as a Cu(II) scavenger in the synaptic cleft.

Propylparaben-induced disruption of energy metabolism in human HepG2 cell line leads to increased synthesis of superoxide anions and apoptosis

The effect of propylparaben (in final concentrations 0.4 ng/ml, 2.3 ng/ml and 4.6 ng/ml) on the energy metabolism of HepG2 hepatocytes, superoxide anion synthesis, apoptosis and necrosis is described. Propylparaben can be toxic to liver cells due to the increased production of superoxide anions, which can contribute to a reduced concentration of superoxide dismutase in vivo and impairment of the body's antioxidant mechanisms. Finally, a further reduction in the mitochondrial membrane potential and uncoupling of the respiratory chain resulting in a reduction in ATP concentration as a result of mitochondrial damage may lead to cell death by apoptosis.

Epithelial Cell Apoptosis in Recurrent Aphthous Ulcers

A recurrent aphthous ulcer (RAU) is a common inflammatory ulcerative lesion affecting oral mucosa. We studied the eventual apoptosis of epithelial cells from the point of view of ulcer and inflammation. RAU lesions and healthy mucosa samples were immunostained for caspase-3 and high-mobility group box 1 (HMGB1). DNA nicks were identified using TUNEL staining. We studied the effects of tumor necrosis factor α (TNFα) and interferon γ (IFNγ) on the toll-like receptor 2 and 4 (TLR2 and TLR4) expression of human oral SCC-25 keratinocytes. We also studied the effects of self-DNA, all-thiol-HMGB1, and disulfide-HMGB1 on epithelial cells, with or without IFNγ. At the edge of RAU lesions, all epithelial cell layers were caspase-3+, TUNEL+, and HMGB-1+ and had widened intercellular spaces. In contrast, healthy epithelial cells were negative for caspase-3 and TUNEL staining. HMGB1 was seen in only the basal cell layers, and the cells retained close cell-to-cell contacts. Self-DNA increased TNF-α mRNA ( P = 0.02) in SCC-25 cells. Both TNFα and IFNγ ( P = 0.01) increased TLR2. Upon TNFα stimulation, SCC-25 cells lost their nuclear HMGB1 staining. HMGB1 did not increase IL-8, IL-6, or TNF-α mRNA in SCC-25 cells, which was unaffected by the presence of IFNγ. We conclude that in healthy epithelium, the most superficial cells at the end of their life cycle are simply desquamated. In contrast, RAU is characterized by top-to-bottom apoptosis such that dead cells may slough off, leading to an ulcer. Because of a lack of scavenging anti-inflammatory macrophages, apoptotic cells probably undergo secondary necrosis releasing proinflammatory danger signals, which may contribute to the peripheral inflammatory halo. This is supported by self-DNA-induced TNFα synthesis. In contrast to TLR4- and TLR2-binding lipopolysaccharide used as a positive control, disulfide-HMGB1 did not stimulate proinflammatory cytokines.

Relationship between the architecture of zinc coordination and zinc binding affinity in proteins – insights into zinc regulation

Relationship between the architecture and stability of zinc proteins.

Apolipoprotein E4 allele is associated with substantial changes in the plasma lipids and hyaluronic acid content in patients with nonalcoholic fatty liver disease

Fat may affect progression of liver damage in patients with non-alcoholic fatty liver disease (NAFLD). In this study we characterize the state of lipid metabolism in 22 patients with NAFLD and different Apo-E variants. Total concentration of plasma total fatty acids was quantified by gas chromatography, while their derivatives by liquid chromatography/tandem mass spectrometry (LC ESI MS/MS). The ratio of plasma saturated fatty acid to monounsaturated fatty acid increased, whereas the ratio of polyunsaturated fatty acids to saturated fatty acids was reduced in Apo-E4 carriers. Simultaneously, the levels of individual plasma linoleic, arachidonic, and alpha linolenic acids significantly increased in subjects with the Apo-E4 allele. The 15-lipoxygenase metabolite, 13-hydroxyoctadecadienoic acid, was significantly higher in Apo-E3 carriers (p<0.006). 5-oxo-6,8,11,14-eicosatetraenoic acid was significantly elevated in Apo-E4 carriers (p<0.009). A significant difference in hyaluronic acid concentration (p<0.0016) as well as predicted advanced fibrosis (using the BARD scoring system) was found in Apo-E4 carriers (p<0.01). We suggest that a distinct mechanism of fibrosis between Apo E alleles. In Apo-E4 carriers, an elevation in 5-oxo-6,8,11,14-eicosatetraenoic acid synthesis and fatty acid dysfunction may induce fibrosis, while an inflammatory process may be the main cause of fibrosis in Apo-E3 carriers.

Local and systemic regulation of sulfur homeostasis in roots of Arabidopsis thaliana

Nutrients are limiting for plant growth and vigour. Hence, nutrient uptake and homeostasis must be adjusted to the needs of the plant according to developmental stages and environmental conditions. A split-root system was applied to analyse the systemic and local response of Arabidopsis thaliana to sulfur starvation. Arabidopsis thaliana plants in which only one root half was starved while the other root half was supplied with sulfate were analysed at the metabolic and transcriptional level. No systemic induction of sulfate uptake or expression of sulfate starvation marker genes was observed in split-roots sufficiently supplied with sulfate. Our data suggest that no activation of sulfur uptake takes part in sulfur-supplied root patches when the general sulfur status declines. When comparing roots of fully sulfate-starved plants with sulfate-starved split-root roots, expression of several potentially OAS responsive genes was attenuated in split-roots depending on the shoot sulfate status and the local root O-acetylserine concentration. In contrast, high-affinity sulfate transporters displayed similar expression in sulphate-starved split-roots and the corresponding controls. Feeding of (35) SO(4) (2-) to the shoot or to either part of a split-root system revealed that sulfate is the most prominent mobile sulfur-containing compound within the plant. Hence, we postulate a model whereby the soil sulfate availability regulates the sulfate uptake system of roots while the shoot sulfur status modulates the local O-acetylserine response in the root by passive 'plant sulfur status-dependent' transport of sulfate.

[Are we controlling the sedation in ICU? A multicenter study results]

The aim of this study is to evaluate the issues of sedation and analgesia in all-purpose ICUs in Russia. To obtain that, a single-day observational survey was performed in 55 ICUs of Ural and Siberia regions. This work enabled to describe the targets, instruments of control and patterns of sedative and analgetics and sedatives prescription, as well as to make conclusions about issues in this area and possibilities of creation and necessity of analgesia and sedation standards. The study has shown a decent percentage of use of standardized scales evaluating pain in ICU and predominance of effectivae drugs and analgesia patterns, which leads to "formalization" of analgesia and decrease of it's effectiveness. Sedation indications do not satisfy the modern concept, sedation level evaluation scores are used only in 13%, schemes and drugs are traditional. The results of this study may serve as a reason for discussion of necessity of introducing of sedative and analgetic therapy in ICU standarts.

Phase II study of recombinant human interferon-gamma in metastatic renal cell carcinoma

The efficacy of a low-dose regimen of human recombinant interferon-gamma was studied in 40 patients with metastatic or locally advanced renal cell carcinoma. Patients received 100 micrograms/m2/day as an infusion over 4 h. The intention was to find an active but tolerable regimen as a basis for future combination treatments with other cytokines or cytotoxic drugs. Activity of this low-dose schedule had been reported. In the absence of rapid progression, treatment was given for at least 3 months, and in case of stable disease it was continued for prolonged periods in order not to miss late remissions. Toxicity was generally mild, with fever and constitutional symptoms predominating. Therapeutic efficacy was low with only one partial remission. Three patients had stable disease over 6, 9, and 15 months. This low-dose schedule cannot be recommended for the treatment of renal cell cancer.