NovelmiRNA-25 inhibits AMPD2 in peripheral blood mononuclear cells of patients with systemic lupus erythematosus and represents a promising novel biomarker.

BACKGROUND: Systemic lupus erythematosus (SLE) is a multisystemic autoimmune disease with various clinical manifestations. MicroRNAs (miRNAs) and immunometabolism are recognized as key elements in SLE pathogenesis; however, the relationship between miRNAs in peripheral blood mononuclear cells (PBMCs) and metabolism in SLE remains unclear. METHODS: We detected PBMC miRNA and mRNA profiles from 3 pooled SLE patients and 3 healthy controls (HCs) using next-generation sequencing, predicted miRNA targets in dysregulated mRNAs, predicted functions and interactions of differentially expressed genes using bioinformatics analysis, validated candidate miRNAs using qRT-PCR, and investigated the association between the expression of candidate miRNAs and SLE clinical characteristics. Moreover, we validated the direct and transcriptional regulatory effect of NovelmiRNA-25 on adenosine monophosphate deaminase 2 (AMPD2) using a dual-luciferase reporter assay and western blot and confirmed AMPD2 mRNA and protein expression in PBMCs using qRT-PCR and western blot, respectively. RESULTS: Multilayer integrative analysis of microRNA and mRNA regulation showed that 10 miRNAs were down-regulated and 19 miRNAs were up-regulated in SLE patient PBMCs compared with HCs. Bioinformatics analysis of regulatory networks between miRNAs and mRNAs showed that 19 miRNAs were related to metabolic processes. Two candidate miRNAs, NovelmiRNA-25 and miR-1273h-5p, which were significantly increased in the PBMCs of SLE patients (P < 0.05), represented diagnostic biomarkers with sensitivities of 94.74% and 89.47%, respectively (area under the curve = 0.574 and 0.788, respectively). NovelmiRNA-25 expression in PBMCs was associated with disease activity in SLE patients, in both active and stable groups (P < 0.05). NovelmiRNA-25 overexpression downregulated AMPD2 expression in HEK293T cells through direct targeting of the AMPD2 3'UTR (P < 0.01), while inhibition of NovelmiRNA-25 activity led to increased AMPD2 expression (P < 0.01). NovelmiRNA-25 overexpression also downregulated AMPD2 protein expression in HEK293T cells; AMPD2 protein expression in SLE patient PBMCs was decreased. Our results show that differentially expressed miRNAs play an important role in SLE. CONCLUSIONS: Our data demonstrate a novel mechanism in SLE development that involves the targeting of AMPD2 expression by NovelmiRNA-25. miRNAs may serve as novel biomarkers for the diagnosis and evaluation of disease activity of SLE and represent potential therapeutic targets for this disease.

[Features of influence adenosine, AMP and hyperadrenalinemiya on the immune status, metabolic enzymes of purine nucleotides and the antioxidant defense system]. / Osobennosti vozdeistviia adenozina, AMP i giperadrenalinemii na immunnyi status, fermenty metabolizma purinovykh nukleotidov i sistemu antioksidantnoi zashchity.

Administration of a large dose of adrenaline (4 mg/kg 60 min before analysis) increased blood levels of total leukocytes, lymphocytes, decreased T-cell suppressors, leukocyte migration inhibition reaction (LMIR) and NBT test, but increased the level of conjugated dienes (CD). Administration of AMPand adenosine increased levels of total leukocytes, lymphocytes, T- lymphocytes, T-helpers, decreased the level of malondialdehyde (MDA), LMIR, and T-cell suppressors. Sympathetic hyperactivation induced by administration of a large dose of adrenaline (4 mg/kg 60 min before analysis) was accompanied by an increase in heart and liver activities of glutathione peroxidase (GPx), catalase, AMP deaminase (AMPD), and adenosine deaminase (AD). Administration of AMP or adenosine caused a decrease in activities of glutathione reductase (GR), GPx, catalase, a decrease in the MDA level and an increase in activities of AMPD and AD in the heart. In the liver AMP and adenosine also caused a decrease in activities of glutathione reductase (GR), GPx, a decrease in the MDA level and an increase in activities of AMPD and AD. The data obtained suggest that administration of adrenaline, AMP, and adenosine influences activity of enzymes involved in purine nucleotide metabolism. However, in contrast to adrenaline, administration of AMP or adenosine does not provoke stress reaction.

[The effect of acute alcohol intoxication on some parameters of nitrogenous metabolism in rats with alloxan diabetes].

Acute alcohol intoxication in rats with alloxan diabetes is accompanied by the increase of urea and uric acid and by the decrease in free fatty acids in serum. In the liver of experimental animals the increase of activity of glutamate dehydrogenase, AMP deaminase, and tyrosine transaminase was found.

[Clinico-pathogenetic significance of enzymes regulating nucleic metabolism in erythrocyte lysates and sera of patients with osteoarthrosis].

Lysates of erythrocytes and sera of 52 patients with osteoarthrosis (OA) and 30 healthy subjects were used used to determine adenosine deaminidase (ADA, AMP deaminase (AMPDA) and adenine deaminidase (AD). Their activities were unrelated to the age and sex of the patients. At admission, patients with OA showed enhanced activity of ADA in sera and reduced activity of AMPDA and AD in lysates compared with normal values. These changes depended on clinical features of OA and were especially pronounced in patients with poly-OA and synovitis. These data suggest participation of enzymes of the adenyl branch of purine metabolism in pathogenesis of OA. Treatment of hospitalized patients allowed to achieve positive dynamics of the above activities coupled to their improved clinical conditions even though enzymatic activity of erythrocyte lysates remained different from that in healthy subjects. It is concluded that enzymatic assays used in the study may be used as additional diagnostic methods for the assessment of synovitis and optimizatic of control over efficiency of OA therapy.

The contribution of Ca+ calmodulin activation of human erythrocyte AMP deaminase (isoform E) to the erythrocyte metabolic dysregulation of familial phosphofructokinase deficiency.

Erythrocyte membrane leakage of Ca2+ in familial phosphofructokinase deficiency results in a compensatory increase of Ca2+-ATPase activity that depletes ATP and leads to diminished erythrocyte deformability and a higher rate of hemolysis. Lowered ATP levels in circulating erythrocytes are accompanied by increased IMP, indicating that activated AMP deaminase plays a role in this metabolic dysregulation. Exposure to a calmodulin antagonist significantly slows IMP accumulation during experimental energy imbalance in patients' cells to levels that are similar to those in untreated controls, implying that Ca2+-calmodulin is involved in erythrocyte AMP deaminase activation in familial phosphofructokinase deficiency. Therapies directed against activated isoform E may be beneficial in this compensated anemia.

A rare case of complete human erythrocyte AMP deaminase deficiency due to two novel missense mutations in AMPD3.

Human erythrocyte AMP deaminase (AMPD3) deficiency is a clinically asymptomatic condition characterized by a 50% increase in steady-state levels of ATP in affected cells. The deficiency in Japanese is associated 75% of the time with the same mutation of R573C, and 25% of the time with other heterogeneous mutations of the AMPD3 gene. The heterozygote frequency was estimated at about 1/30. We previously reported five Japanese individuals who had a complete deficiency of AMPD3. Four were homozygotes for the major mutation of R573C; however, one female did not have the R573C allele. To clarify the mutations in her AMPD3 gene, we analyzed the AMPD3 gene and detected a minor mutation, W450R, derived from the mother and a novel mutation,Q712P, derived from the father. The expression study using AMPD3 cDNA containing both mutations showed that each mutation completely reduced the enzyme activity of AMPD3. As the frequency of carriers heterozygous for these mutations seems to be very low, identifying them may lead to a better understanding of the genetic background of populations in Japan.

Energy metabolism and lipid peroxidation of human erythrocytes as a function of increased oxidative stress.

To study the influence of oxidative stress on energy metabolism and lipid peroxidation in erythrocytes, cells were incubated with increasing concentrations (0.5-10 mM) of hydrogen peroxide for 1 h at 37 degrees C and the main substances of energy metabolism (ATP, AMP, GTP and IMP) and one index of lipid peroxidation (malondialdehyde) were determined by HPLC on cell extracts. Using the same incubation conditions, the activity of AMP-deaminase was also determined. Under nonhaemolysing conditions (at up to 4 mM H2O2), oxidative stress produced, starting from 1 mM H2O2, progressive ATP depletion and a net decrease in the intracellular sum of adenine nucleotides (ATP + ADP + AMP), which were not paralleled by AMP formation. Concomitantly, the IMP level increased by up to 20-fold with respect to the value determined in control erythrocytes, when cells were challenged with the highest nonhaemolysing H2O2 concentration (4 mM). Efflux of inosine, hypoxanthine, xanthine and uric acid towards the extracellular medium was observed. The metabolic imbalance of erythrocytes following oxidative stress was due to a dramatic and unexpected activation of AMP-deaminase (a twofold increase of activity with respect to controls) that was already evident at the lowest dose of H2O2 used; this enzymatic activity increased with increasing H2O2 in the medium, and reached its maximum at 4 mM H2O2-treated erythrocytes (10-fold higher activity than controls). Generation of malondialdehyde was strictly related to the dose of H2O2, being detectable at the lowest H2O2 concentration and increasing without appreciable haemolysis up to 4 mM H2O2. Besides demonstrating a close relationship between lipid peroxidation and haemolysis, these data suggest that glycolytic enzymes are moderately affected by oxygen radical action and strongly indicate, in the change of AMP-deaminase activity, a highly sensitive enzymatic site responsible for a profound modification of erythrocyte energy metabolism during oxidative stress.

Product activation of human erythrocyte AMP deaminase.

IMP was found to activate AMP deaminase in crude glucose-depleted human erythrocyte lysates. Activation of the enzyme by IMP is due to prevention of the inhibitory effect of inorganic phosphate. At 1 mM AMP and 2-3 mM phosphate the addition of 2-5 mM IMP accelerates the AMP deamination two to three times.

Use of dynamic tests of muscle function and histomorphometry of quadriceps muscle biopsies in the investigation of patients with chronic alcohol misuse and chronic fatigue syndrome.

Ischaemic lactate/ammonia tests, serum carnosinase and creatine kinase assays and percutaneous needle muscle biopsies were performed on 10 patients with chronic fatigue syndrome (CFS), and 10 with chronic alcohol misuse complaining of muscular symptoms. Basal serum lactate levels were significantly elevated in the alcohol misusers compared to the CFS patients, but all were within the reference range. Lactate profiles after ischaemic forearm exercise did not differ significantly for the two patient groups. In one patient previously diagnosed as having CFS, myoadenylate deaminase deficiency was identified on the basis of a flat ammonia response to ischaemia and absent muscle adenosine monophosphate deaminase activity. In addition, two further patients in the CFS group were subsequently shown to have other disorders: one had polymyositis and one had myopathy with mild type II fibre atrophy of unknown cause. Histomorphometric examination of muscle needle biopsy in the alcohol misusers showed features of chronic alcohol-induced skeletal myopathy in six patients and polymyositis in one patient. Type II fibre atrophy factors were significantly elevated in the alcohol group but were within the reference range in CFS patients. Dynamic tests of muscle function and muscle histology are valuable tools in excluding alternative pathology in CFS, whereas muscle histomorphometry is of the greatest value in the diagnosis of chronic alcoholic myopathy.

[Value of oxypurines and uric acid in plasma, renal excretion of oxypurines and uric acid as well as plasma adenosine deaminase and AMP deaminase activity in patients with essential hypertension]. / Stezenie oksypuryn i kwasu moczowego w osoczu krwi, nerkowe wydalanie oksypuryn i kwasu moczowego oraz aktywnosc dezaminazy adenozyny i dezaminazy AMP w surowicy krwi chorych na nadcisnienie tetnicze samoistne.

Serum uric acid and oxypurines (hypoxanthine and xanthine) renal excretion of uric acid and oxypurines as well as plasma adenosine deaminase activity and AMP deaminase activity were studied in 18 patients with essential hypertension and in 17 healthy subjects. The aim of the study was to evaluate uric acid production rate in essential hypertension. Serum uric acid was significantly higher (7.04 +/- 2.03 mg% = 370.5 +/- 106 mumol/l; p < 0.01) in essential hypertension in comparison with control group (5.2 +/- 1.0 mg% = 275.0 +/- 51.9 mumol/l) and plasma oxypurines were increased insignificantly. Impairment of fractional excretion of uric acid (p < 0.05) was found in patients with essential hypertension. Plasma adenosine deaminase activity and plasma AMP deaminase activity did not differ in the studied groups. Increased production of uric acid does not contribute the incidence of hyperuricemia in essential hypertension. The results suggest that tubular defect of oxypurines excretion similar to that of uric acid exists in patients with essential hypertension.

The effect of ammonium, phosphate, potassium, and hypotonicity on stored red cells.

The use of an experimental solution that maintained high ATP levels and produced greater than 70 percent viability of stored red cells (RBCs) for up to 18 weeks has been described by other investigators. This solution differed markedly from conventional storage media in that it lacked sodium; contained high concentrations of potassium, ammonium, and phosphate; and was hypotonic. It was not clear which feature or features were responsible for the observed effects. The effects of ammonium, phosphate, potassium, and hypotonicity on stored RBCs have been examined. It was determined that ammonium and phosphate were the important factors in ATP maintenance. The biochemical mechanism by which ammonium acts was studied. In fresh human blood samples, ammonium was found to relieve phosphofructokinase from inhibition by increased ATP concentrations, to have no significant effect on adenine phosphoribosyl transferase activity, and, unexpectedly, to increase the activity of AMP deaminase. Despite prolonged ATP maintenance by ammonium and phosphate-containing storage media, satisfactory viability of RBCs stored up to 77 days was not demonstrated in the rabbit transfusion model.

AMP deaminase from porcine blood platelets, regulation by adenine nucleotides, phosphate and by Na+ and K+ ions.

Porcine blood platelets contain a relatively high amount of AMP deaminase (14.4 U per 10 11 cells). The enzyme showed sigmoidal behaviour as a function of AMP concentration with a S0.5 value (substrate concentration required for half-maximum velocity) of 3.6 and 4.0 mM in the presence of Na+ and K+ respectively. MgATP and MgADP at micromolar concentration activated the enzyme. Activation by saturating MgATP and MgADP in the presence of Na+ or K+ converted the rate versus substrate plots to hyperbolic with a dramatic decrease of S0.5. Phosphate at milimolar concentrations inhibited the enzyme and this inhibitory effect was totally reversed as the concentrations of MgATP and MgADP rised to physiologically high levels. Na+ and K+ activated the enzyme in the absence of MgATP and MgADP. Both cations largely enhanced the Vmax with Na+ being more potent. A comparison of the kinetic behaviour of the enzyme in vitro with the metabolite concentrations in vivo suggest that a substantial regulation can occur through changes in AMP and Na+ concentrations.

A high performance liquid chromatographic assay for AMP-deaminase activity in the erythrocytes of healthy subjects and patients with inherited purine disorders.

A novel method for measuring AMP-deaminase activity in human erythrocytes is presented, based on the determination of the reaction product, IMP, using high performance liquid chromatography. IMP formation was found to be proportional both to the incubation time and the amount of haemolysate over a wide range. The minimal detectable AMP-deaminase activity was more than 1000 times lower than the mean activity found in healthy controls (1083 nmol/h/mg Hb). No marked difference of activity was found in the patients with the following inherited purine disorders: familial juvenile gouty nephropathy and deficiencies of adenosine deaminase, hypoxanthine-guanine phosphoribosyltransferase or adenine phosphoribosyltransferase. The activity in the erythrocytes of patients with chronic renal failure was also similar to controls. The existence of subjects with low erythrocyte AMP-deaminase activity in the population has been confirmed.

Characterization of senescent red cells from the rabbit.

The above data continue to demonstrate the metabolic well being of the aged red cell as it is isolated from rabbits. The abundance of ATP, the absence of surface-bound IgG and a variety of other observations at this time lead to the tentative conclusion that the senescent red cell is amazingly healthy. Many investigators have predicted that the red cell is removed from the circulation as a metabolically exhausted effete cell. There is currently no evidence to support this other than a decrease in deformability of the cells with time, but it is not clear that this decline in deformability is sufficient to keep the cell from circulating. In either case, many of the previously proposed causes of cellular removal are clearly incorrect for the rabbit, and it is now time to focus on new directions for observing either cellular impairment or perhaps the presence of a cellular clock which is independent of the cell's metabolic state. Another point which should be addressed is the reliability of the biotinylation model in rabbits as it relates to red cells in other species. So far several observations in aged red cells isolated with valid models have been reproduced across species boundaries including the rise in ATP, the fall in AMP deaminase activity, the shift in the 4.1a to 4.1b protein ratio, the stability of a number of glycolytic enzymes, and the instability of pyrimidine 5'-nucleotidase activity. To this point, the rabbit has been a reliable model of red cell aging and one with implications for other species.

Time-dependent loss of adenosine 5'-monophosphate deaminase activity may explain elevated adenosine 5'-triphosphate levels in senescent erythrocytes.

Senescent erythrocytes from rabbits were previously shown to have elevated levels of adenine nucleotides. The present study documents that aged red blood cells have a normal synthetic capacity for adenine nucleotides, as indicated by normal levels of adenosine kinase. However, senescent erythrocytes do have decreased levels of adenosine 5'-monophosphate deaminase, the critical enzyme involved in degrading adenine nucleotides. These circumstances of a normal synthetic capacity in the presence of decreased catabolic ability were observed previously in a human genetic deficiency of adenosine 5'-monophosphate deaminase; the red blood cells in these patients accumulate adenosine 5'-triphosphate as do senescent erythrocytes in rabbits.