Plastid retrograde regulation of miRNA expression in response to light stress

BACKGROUND

MicroRNAs (miRNAs) are a class of endogenous noncoding RNAs that play a pivotal role in the regulation of plant development and responses to the surrounding environment. Despite the efforts made to elucidate their function in the adaptation of plants to many abiotic and biotic stresses, their role in high light (HL) stress is still vague. HL stress often arises upon plant exposure to full sunlight. Subsequent changes in nuclear gene expression are triggered by chloroplast-derived retrograde signals.

RESULTS

In this study, we show that HL is involved in miRNA-dependent regulation in Arabidopsis thaliana rosettes. Microtranscriptomic screening revealed a limited number of miRNAs reacting to HL. To explain the miRNA regulation mechanisms at the different biogenesis stages, chemical and genetic approaches were applied. First, we tested the possible role of plastoquinone (PQ) redox changes using photosynthetic electron transport chain inhibitors. The results suggest that increased primary transcript abundance (pri-miRNAs) of HL-regulated miRNAs is dependent on signals upstream of PQ. This indicates that such signals may originate from photosystem II, which is the main singlet oxygen (¹O₂) source. Nevertheless, no changes in pri-miRNA expression upon a dark-light shift in the conditional fluorescent (flu) mutant producing ¹O₂ were observed when compared to wild-type plants. Thus, we explored the ¹O₂ signaling pathway, which is initiated independently in HL and is related to β-carotene oxidation and production of volatile derivatives, such as β-cyclocitral (β-CC). Pri-miRNA induction by β-CC, which is a component of this ¹O₂ pathway, as well as an altered response in the methylene blue sensitivity 1 (mbs1) mutant support the role of ¹O₂ signaling in miRNA regulation.

CONCLUSIONS

We show that light stress triggers changes in miRNA expression. This stress response may be regulated by reactive oxygen species (ROS)-related signaling. In conclusion, our results link ROS action to miRNA biogenesis, suggesting its contribution to inconsistent pri- and mature miRNA dynamics.

Altered L-arginine metabolism in children with controlled asthma

Decreased level of L-arginine may lead to airway hyperresponsiveness, inflammation, and airway remodeling. Changes in L-arginine metabolism were observed earlier in adult asthmatic patients. Studies on L-arginine metabolism in children with bronchial asthma are limited. Because biosynthesis of L-arginine is insufficient in growing children, its potential metabolic alterations may have important clinical implications. This study was designed to evaluate L-arginine metabolism in children with well-controlled asthma. The studies were conducted on blood serum of 30 asthmatic and 20 healthy children (control group). Levels of L-arginine and its metabolic products, L-citrulline and L-ornithine, were measured by HPLC. Arginase activity was determined spectrophotometrically. Disease severity was evaluated by the asthma control test (ACT) and the level of nitric oxide (NO) in exhaled air. In asthmatic children L-arginine concentration was significantly lowered, whereas arginase activity was unchanged when compared with the healthy group. However, L-ornithine and L-citrulline levels were significantly increased. There was no correlation between arginase activity, amino acids levels, ACT scores, and exhaled NO. In children with chronic, well-controlled asthma L-arginine metabolism is altered. Given that L-arginine is absolutely essential for children, our findings may be of particular importance for the management of children with non-exacerbated asthma. They may also help to develop new therapeutic strategies targeted at L-arginine metabolism in the future.

[Evaluation of some selected structural and functional parameters of red blood cells as oxidative stress markers in elderly people]

The ageing process induces age-related involutionary changes and leads to increased occurrence of many diseases. One of the most important theories of ageing and development of many pathologies is the free radical theory, which assumes that ageing process leads to lost of oxidative balance.

THE AIM

of the research was to evaluate the degree of membrane lipid peroxidation, internal microviscosity, activity of membrane ATPase, both total and Na(+)K(+)-dependent, and markers of oxidative damage in erythrocyte membrane protein in elderly people.

MATERIAL

The examination was performed on 35 people. The examined group (15 persons, mean age 71,3) consisted of healthy elderly people. The reference group was formed with younger healthy people (20 persons, mean age 55).

RESULTS

Erythrocyte membrane lipid peroxidation was found stronger in the group of elderly people. Erythrocyte internal microviscosity was significantly higher in the elderly. The activity of ATPase, both total and Na(+)K(+)-dependent, appeared remarkably greater in the group of younger people. Stronger membrane lipid damage was observed in older age group, which may be implied by lower--SH group concentration, and higher W/S parameter value.

CONCLUSION

The obtained results reveal that in elderly people the intensification of oxidative stress in the entire body occurs, which may be confirmed by structural and functional oxidative erythrocyte damage. This conclusion may be significant for pathogenesis of many diseases in this period of life.

The effect of atorvastatin on erythrocyte membranes and serum lipids in patients with type-2 hypercholesterolemia

BACKGROUND

. The beneficial effects of statins on clinical events may involve mechanisms that modify endothelial dysfunction, plaque stability, thrombus formation, and inflammatory responses. To determine the effect of atorvastatin on blood rheology in patients with familial hypercholesterolemia (FH), we prospectively studied serum lipid concentration, red cell cholesterol content, lipid peroxidation and erythrocyte membrane fluidity. The aim of this paper was to evaluate the effects of atorvastatin therapy on the erythrocyte membrane structure and the hypolipemic efficacy in patients with FH. MATERIALS, METHODS AND SUBJECTS STUDIED:. The study involved 31 patients with FH and 20 healthy individuals as a control group. The program lasted 20 weeks. For the first 8 weeks, the patients were on a hypolipemic diet only and for the subsequent 12 weeks, alongside the diet they were given 10 mg atorvastatin per day. Laboratory tests were carried out before and after 4 weeks and 12 weeks of the pharmacological treatment. Erythrocyte membrane fluidity was determined using the spin labeled method. The peroxidation of lipids was measured in whole erythrocytes as well as in erythrocyte plasma membranes by means of the thiobarbituric acid technique.

RESULTS

. Treatment with atorvastatin reduced serum total cholesterol concentration from 310+/-29 mg/dl in a basal situation to 203+/-34 mg/dl ( P<0.001) at the end of the treatment and low-density lipoprotein (LDL) cholesterol concentration from 225+/-30 mg/dl to 126+/-30 mg/dl ( P<0.001), respectively. The changes observed in the plasma lipids correlate with a significant decrease in erythrocyte membrane cholesterol, from 2.24+/-1.69 to 1.17+/-0.75 mg/mg protein ( P<0.001) after 12 weeks of treatment. The lipid peroxidation in membranes of erythrocytes was lowered from the basal value 0.171+/-0.097 to 0.100+/-0.024 mmol/mg protein ( P<0.05) after 4 weeks of treatment and to 0.057+/-0.020 mmol/mg protein ( P<0.001) after 12 weeks of treatment, and in total erythrocytes from 4.78+/-1.49 to 3.99+/-1.39 mmol/g Hb ( P<0.02) and 2.43+/-0.87 mmol/g Hb ( P<0.001), respectively. The membrane fluidity was estimated by means of parameter S at the depth of the fifth carbon atom. Atorvastatin in hypercholesterolemic erythrocytes enhances the fluidity of the superficial layer from 0.758+/-0.009 up to the values observed in the control group 0.744+/-0.009 ( P<0.001). There is no impact on the microviscosity of the hydrophobic core observed.

CONCLUSION

. Our findings suggest that the atorvastatin therapy reverses the alteration of erythrocyte plasma membrane properties. It may improve blood rheology in patients with FH. This improvement in blood properties may contribute to the well-known beneficial effects of atorvastatin on cardiovascular risk in patients with severe hyperlipidemia and atherosclerotic vascular disease.

Interaction of perindoprilat with human red blood cells

The effects of perindoprilat on the morphology and dynamic properties of human erythrocytes were studied by light microscopy, electron spin resonance spectroscopy and spectrophotometric methods. Erythrocytes were exposed to perindoprilat at 37 degrees C for 30 and 120 min. It was shown that the drug at a concentration of 0.75 microg/ml did not cause significant changes in the structure of erythrocyte membranes. Higher doses of the drug (7.5 and 75 microg/ml) induced changes in membrane fluidity in the hydrophobic core of the lipid bilayer, the conformation of membrane proteins, the number of SH groups and the activity of membrane-bound acetylcholinesterase (AChE). These modifications were accompanied by changes in the shape of erythrocytes and did not depend on time of incubation. Therefore, it is proposed that perindoprilat perturbs the lipid bilayer and disturbs the organization of the protein-lipid environment.

The biostimulatory effect of red laser irradiation on pig blood platelet function

The molecular mechanisms of laser-induced changes in the cell structure and function are not well known. The authors examined the effects of low-power laser irradiation on unnucleated pig blood platelets. The obtained results showed that laser irradiation (1-5 J) caused in blood platelets lipid peroxidation (measured as thiobarbituric acid reactive substances) and superoxide anion generation, concomitant with the release of adenine nucleotides and proteins from platelets. The maximum platelet response to laser irradiation was observed when doses of 1.8-2 J were used. Our results indicate that red laser irradiation induces: (1) platelet secretory process and the release of substances stored in the specific granules (adenine nucleotides, proteins); and (2) lipid peroxidation partly due to stimulation of endogenous arachidonate and production of its metabolites reacting with thiobarbituric acid.

Effect of perindopril therapy on fluidity and potential of erythrocyte membrane from individuals with coronary heart disease

Erythrocyte membrane fluidity and membrane potential were measured in patients suffering from coronary heart disease (CHD) and treated with perindopril. Membrane fluidity was determined using electron paramagnetic resonance (EPR) spectroscopy, and membrane potential was evaluated using potential-sensitive fluorescent dyes. CHD does not change membrane fluidity at the depth of the 5 carbon in the fatty acid chain of membrane phospholipids. However the hydrophobic core of the membrane is altered in CHD. For 19 CHD patients, the correlation times tau B and tau C of a spin label 16DS were higher than for controls: tau B = (1.84 +/- 0.04) x 10(-9) s and tau C = (2.54 +/- 0.04) x 10(-9) s vs. tau B = (1.62 +/- 0.06) x 10(-9) s; and tau C = (2.24 +/- 0.07) x 10(-9) s (results given as mean +/- SEM). Such results indicate the increased microviscosity in hydrophobic regions of CHD erythrocyte membranes in comparison with controls. Perindopril therapy partly abolished these changes. The membrane potential of CHD red blood cells -17.89 +/- 1.36 mV was higher than the control value -9.83 +/- 0.59 mV. Perindopril treatment shifted the membrane potential value to -13.45 +/- 0.99 mV when measured after a single dose of the drug, or even depolarized the membrane after 7 days of therapy -4.95 +/- 0.73 mV. It is concluded that the erythrocyte membrane is more rigid and hyperpolarized in CHD, and perindopril therapy partly abolishes these changes as early as 3 h after administration.

Changes in erythrocyte membranes after fractioned hyperthermia

The structural changes in erythrocytes membranes were examined before and after the second heat shock of erythrocytes. Electrophoretic separation of protein erythrocyte membranes for cells incubated at 48.5 degrees C was different from control i.e. from erythrocytes incubated at 37 degrees C. No quantitative or qualitative changes were spotted in comparison with protein membranes isolated from the erythrocytes following single or double heat shock. Fluidity of erythrocytes membranes was determined by using spin labels, 5-doxylstearic acid and 16-doxylstearic acid. The membranes were more rigid in their hydrophobic regions after incubation of cells at 44 degrees C. It can be suggested that erythrocyte membranes play some role in thermotolerance and heat damage of enucleate cells.

Effect of hyperthermia on the internal microviscosity of erythrocytes and lymphocytes: a spin-label study

The internal microviscosity of human erythrocytes and porcine lymphocytes was investigated, from the electron-spin resonance spectral characteristics of the nitroxyl spin probe, 4-amino-2,2,6,6-tetramethylpiperidinyloxy. Heat-induced permanent damage to cells was observed as an increase in the intracellular microviscosity of nucleate and enucleate cells. Induction of heat resistance was found for erythrocytes treated with a double heat shock.

Does thermotolerance occur in human red cells?

Osmotic fragility and autohemolysis were used as endpoints in the measurement of damage to the plasma membrane in human erythrocytes, after single or double heat treatments. Injury recorded above 46 degrees C, and the induction of thermotolerance in the enucleate cells after a primary heat treatment of 44 degrees C for 15 min, indicates that the plasma membrane plays an important role in heat injury and in thermotolerance.

Phase transitions in spherical bilayer membranes prepared of bulk erythrocyte membrane lipids

The phase transitions of spherical lipid bilayers built of bovine red cell lipids have been studied. The electrical and ESR measurements revealed some conformational changes in lipid bilayers taking place at 36-38 degrees C.

Hyperthermic modification of bleomycin--DNA interaction detected by electron spin resonance

Electron spin resonance spectra of DNA labeled with each of four spin-labeling compounds have been studied to detect interaction between the antibiotic bleomycin and DNA. Only one of these labels, compound IV, resulted in a modified spectrum when bound to DNA and the latter was subjected to bleomycin. This property has been used to monitor DNA-bleomycin interactions under physiological and hyperthermic conditions. Bleomycin produced an increase in rotational correlation time of the residue bound to DNA at 37 degrees C and a significantly higher increase at 43 degrees C. Some effect was still detected with bleomycin at 37 degrees C after preheating at 43 degrees C. Parallel studies have revealed enhanced binding of 59Fe-bleomycin to DNA during and after hyperthermic treatment.

The effects of glutaraldehyde and osmium tetroxide on the erythrocyte membrane. A spin label study

A nitroxide spin label probe technique was applied to study the interaction between glutaraldehyde or osmium tetroxide (OsO4) amd the membranes of horse erythrocytes, ghosts and liposomes prepared from erythrocyte lipids. Two major conclusions have been established: (1) Reaction of the fixation reagents with the membrane is selective. OsO4 reacts predominantly with lipids and glutaraldehyde with membrane proteins. (2) The lipid-protein interactions change after pretreatment by OsO4 or glutaraldehyde.

Calcium-induced aggregation and fusion of mixed phosphatidylcholine-phosphatidic acid vesicles as studied by 31P NMR

1. The transbilayer distribution of the phospholipids in sonicated egg phosphatidylcholine-phosphatidic acid vesicles and the interaction of Ca2+ with these vesicles was studied by 31P NMR. 2. Over a wide composition range the bilayer of these vesicles has a symmetrical phospholipid composition. 3. With ratios of Ca2+ to phosphatidic acid in the outer monolayer of the vesicles up to 0.3, Ca2+ induces vesicle aggregation. The extent of aggregation is increased by the Ca2+ concentration in the medium and the outer monolayer concentration of phosphatidic acid. The vesicle aggregation can be fully reversed by chelating Ca2+. 4. When the ratio exceeds 0.5 Ca2+ induces vesicle fusion. The fusion is maximal for vesicles containing both phosphatidylcholine and phosphatidic acid. The data suggest that Ca2+-induced lateral phase separations make the bilayer more susceptible to fusion.

E.s.r. radiation studies of erythrocyte membrane haemoglobin interaction

The dependence of the yield of free radicals in gamma-irradiated, freeze-dried erythrocyte membranes on their haemoglobin content was studied. A non-monotonous relationship was found--different from that observed in mixtures of freeze-dried membranes and haemoglobin, which suggests the existence of radiation-energy transfer between the membranes and bound haemoglobin.