Oxidative stress reduction related to the efficacy of n-3 polyunsaturated fatty acids in first episode schizophrenia: Secondary outcome analysis of the OFFER randomized trial.

Intervention studies of n-3 polyunsaturated fatty acids (n-3 PUFA) as add-on therapy in patients with schizophrenia have not examined changes in oxidative stress. A randomized placebo-controlled trial of a 26-week intervention composed of 2.2g/day of n-3 PUFA was found to reduce symptom severity in first-episode schizophrenia patients. The present study is an extension of our previous report, whose secondary aim was to assess the association between the clinical effect of n-3 PUFA and changes in oxidative stress indices. Seventy-one patients aged 16-35 were enrolled in the study and randomly assigned to the study arms. Total plasma antioxidant capacity and 8-epi-isoprostane F2α content were assessed at baseline and at weeks 8 and 26 of the study as secondary outcome measures. Significant changes in oxidative stress indices favouring the intervention group were observed: decreases in 8-isoprostane F2α (p<0.001) and increases in total plasma antioxidant capacity (p<0.001). Significant correlations between changes in clinical scores relevant to symptom severity and changes in oxidative indices were observed. The results of the present study hence suggest that the efficacy of a six-month intervention with n-3 PUFA observed in first-episode schizophrenia may be related to improvement in oxidative stress indices.

The association between polyunsaturated fatty acid consumption and the transition to psychosis in ultra-high risk individuals.

PUFA deficiencies in cellular membranes have been observed in ultra-high risk (HR) individuals and in early schizophrenia. It is uncertain whether dietary PUFA consumption can be associated with the risk of transition to psychosis in HR individuals. The aim of the study was to assess PUFA consumption and confirm whether dietary habits are related to the risk of transition to full-threshold psychosis in HR individuals during a 12-month follow-up. PUFA consumption during the previous year was analyzed in 62 h individuals and 33 healthy controls (HC) at the beginning of the follow-up period using a validated Food-Frequency Questionnaire and the Polish Food Composition Tables. Fifteen HR individuals converted into psychosis (C-HR) during the 12-month follow-up. C-HR individuals reported significantly higher consumption of n-6 fatty acids (linoleic acid, LA and arachidonic acid, AA) in comparison with individuals who did not develop psychosis (NC-HR). The C-HR group reported a significantly higher AA/(EPA+DHA) consumption ratio than the NC-HR group. HC reported significantly higher consumption of most n-3 PUFA and lower consumption of all n-6 PUFA than both groups of HR individuals. The results suggest that dietary patterns of PUFA consumption may play a role in the conversion to psychosis of HR individuals.

Essentiality and toxicity of vanadium supplements in health and pathology.

The biological properties of vanadium complexes have become an object of interest due to their therapeutic potential in several diseases. However, the mechanisms of action of vanadium salts are still poorly understood. Vanadium complexes are cofactors for several enzymes and also exhibit insulin-mimetic properties. Thus, they are involved in the regulation of glucose metabolism, including in patients with diabetes. In addition, vanadium salts may also normalize blood pressure and play a key role in the metabolism of the thyroid and of iron as well as in the regulation of total cholesterol, cholesterol HDL and triglyceride (TG) levels in blood. Moreover, in cases of hypoxia, vanadium compounds may improve cardiomyocytes function. They may also exhibit both carcinogenic and anti-cancer properties. These include dose- and exposure-time-dependent induction and inhibition of the proliferation and survival of cancer cells. On the other hand, the balance between vanadium's therapeutic properties and its side effects has not yet been determined. Therefore, any studies on the potential use of vanadium compounds as supplements to support the treatment of a number of diseases must be strictly monitored for adverse effects.

Id1 Expression Level Determines the Differentiation of Human Dental Pulp Stem Cells.

TWIST1 plays a crucial role in dentinogenesis, and its activity depends on both a dimerization partner selection and phosphorylation. Other factors, like Id proteins, can affect the availability of dimerization partners for TWIST1, subsequently leading to diverse biological outcomes. The purpose of this study was to evaluate an impact of Id1 expression on differentiation of dental pulp stem cells (DPSCs). The altered expression of Id1 was achieved by transfection of human DPSCs with lentiviral vectors either driving an entire sequence of Id1, hence leading to Id1 overexpression, or carrying the Id1 silencing sequence. We observed that both overexpression and silencing of Id1 modulated human DPSC differentiation. Id1 overexpression resulted in a prevailing formation of TWIST1 homodimer and increased expression of genes encoding dentin sialophosphoprotein and dentin matrix protein 1, which confirm an enhanced odontogenic differentiation of DPSCs. Concurrently, Id1 silencing produced an opposite effect, slowing DPSC differentiation. These results highlight Id1 as an important modulator of molecular events during DPSC commitment and differentiation, which should be considered in dental research on tissue engineering. Moreover, we assume that the balance between TWIST1 dimerization forms in DPSCs might function in a cell-type-specific manner.

Impact of adenosine receptors on immunoglobulin production by human peripheral blood B lymphocytes.

Adenosine is an endogenous compound that regulates function of several immune cells including lymphocytes by activating adenosine receptors (ARs). Several reports indicate that stimulation of ARs on lymphocytes affects lymphocyte activation, proliferation and lymphocyte-mediated cytolysis. Unfortunately, most studies focused on T lymphocytes and little information exists on involvement of ARs in B cells regulation. In this study we elucidated the impact of ARs activation on immunoglobulin M (IgM) production by purified human peripheral blood B lymphocytes stimulated in vitro with Staphyloccocus aureus Covan I (SAC) plus IL-2. Performed experiments showed that endogenous adenosine that is released/produced by human B lymphocytes is able to induce cAMP accumulation in the cell through activation of A2A-AR however, this takes place only when other ARs are inhibited by selective antagonists. We observed that accumulated intracellular cAMP suppressed IgM production by B cells stimulated with SAC plus IL-2. Our experiments showed that human B cells cultured at 25 mM glucose produced significantly less IgM in response to stimulation with SAC comparing to cells maintained in media containing 5 mM glucose. However, the high glucose effect on IgM production by B cells stimulated with SAC depended on other factor/s than ARs.

Recent advances in understanding the relationship between adenosine metabolism and the function of T and B lymphocytes in diabetes.

Adenosine plays an important role in physiology of several organs. Its turnover inside and outside of the cell is controlled by several enzymes and transport processes. The action of extracellular adenosine is mediated via at least four receptors named A(1), A(2A), A(2B), and A(3). Recent studies have reported that adenosine is a significant mediator of regulatory lymphocyte function. Numerous data indicates that adenosine affects T lymphocyte activation, proliferation and lymphocyte-mediated cytolysis. Impaired lymphocyte functioning and enhanced susceptibility to infections is a common feature of human diabetes. This review collects data bringing us closer to understanding the disturbances in lymphocytes adenosine homeostasis in diabetes. Adenosine receptors and nucleoside transporters are targets for potential drugs in many pathophysiological situations. Therefore, action of adenosine on lymphocyte function in diabetes may be important target for modulation of immune responses and understanding of mechanisms leading to several pathologies of immune cells observed in diabetes.

Acetyl-CoA metabolism in amprolium-evoked thiamine pyrophosphate deficits in cholinergic SN56 neuroblastoma cells.

Inhibition of pyruvate (PDHC) and ketoglutarate (KDHC) dehydrogenase complexes induced by thiamine pyrophosphate deficits is known cause of disturbances of cholinergic transmission in the brain, yielding clinical symptoms of cognitive, vegetative and motor deficits. However, particular alterations in distribution of key acetylcholine precursor, acetyl-CoA, in the cholinergic neuron compartment of thiamine pyrophosphate-deficient brain remain unknown. Therefore, the aim of our work was to find out how amprolium-induced thiamine pyrophosphate deficits (TD) affect distribution of acetyl-CoA in the compartment of pure cholinergic neuroblastoma SN56 cells originating from murine septum. Amprolium caused similar concentration-dependent decreases in thiamine pyrophosphate levels in nondifferentiated (NC) and differentiated (DC) cells cultured in low thiamine medium. In such conditions DC displayed significantly greater loss of viability than the NC ones, despite of lesser suppressions of PDHC activities and tetrazolium salt reduction rates in the former. On the other hand, intramitochondrial acetyl-CoA levels in DC were 73% lower than in NC, which explains their greater susceptibility to TD. Choline acetyltransferase activity and acetylcholine content in DC were two times higher than in NC. TD caused 50% decrease of cytoplasmic acetyl-CoA levels that correlated with losses of acetylcholine pool in DC but not in NC. These data indicate that particular sensitivity of DC to TD may result from relative shortage of acetyl-CoA due to its higher utilization in acetylcholine synthesis.

Adenosine 5'-triphosphate is the predominant source of peripheral adenosine in human B lymphoblasts.

Adenosine 5'-triphosphate (ATP) and adenosine are the crucial endogenous signaling molecules in immunity and inflammation. In this study we identified the source of extracellular adenosine in human B lymphoblasts, and evaluate the ATP release and metabolism. We observed that the B cells continuously released substantial quantities of ATP (35 pmol/10(6) cells) when subjected to slow motion in the incubation medium. The adenosine level in the B cell incubation medium was very low, and increased (5-fold) upon inhibition of adenosine deaminase activity with 10 muM of 2-deoxycoformycin (DCF). Inclusion of an inhibitor of equilibrate nucleoside transport (nitrobenzylthioinosine) in the incubation medium in the presence of DCF resulted in the elevation of adenosine level by 9-fold. Inhibition of ecto-ATPase activity with 100 muM of ARL67156 was associated with a 2-fold increase of the extracellular ATP level and a 3-fold decrease of adenosine concentration in the cell culture media. Inclusion of alpha,alpha-methyleneadenosine 5'-diphosphate, a selective inhibitor of ecto-5'-nucleotidase in the incubation medium resulted in a significant decrease (7-fold) the adenosine concentration. In conclusion, our results indicate that ATP released from the B cell is the primary source of peripheral adenosine, and that the activities of ecto enzymes and the efficiency of Ado uptake through the nucleoside transporters determine the Ado level on the B cell surface.

Protein kinase C mediated high glucose effect on adenosine receptors expression in rat B lymphocytes.

Hyperglycemia-induced alterations of adenosine receptors (ARs) expression are implicated in the pathomechanism leading to impaired function of the lymphocytes in diabetes. However, the signaling pathways utilized by glucose to regulate ARs expression are unknown. This work was undertaken to investigate the impact of high glucose level on the ARs expression in rat B lymphocytes. The results presented in this report demonstrate that rat B lymphocytes express all four types of ARs at the mRNA and protein level. Exposing B cells to high glucose (25 mM) suppressed the expression of A(1)-AR, A(2B)-AR, and A(3)-AR, but had no effect on the expression of A(2)A-AR. A selective inhibitor of Ca(2+)-dependent protein kinase C (PKC) isoforms suppressed the high glucose effect on A(1)-AR expression. Inhibition of PKC-delta with rottlerin blocked the high glucose effect on A(1)-AR mRNA level. An inhibitor of Raf-1 kinase completely blocked the high glucose effect on A(2B)-AR expression. The suppression of A(1)-AR and A(2B)-AR mRNA expression induced by high glucose was blocked by an inhibitor (PD98059) of MAPK kinase (MEK). In conclusion, high glucose utilizes a signaling pathway involving some elements of the MAPK pathway and different PKC isoforms to suppress the expression of A(1)-AR, A(2B)-AR, and A(3)-AR in rat B lymphocytes.

Phenotype-dependent susceptibility of cholinergic neuroblastoma cells to neurotoxic inputs.

A preferential loss of brain cholinergic neurons in the course of Alzheimer's disease and other encephalopathies is accompanied by a proportional impairment of acetyl-CoA synthesizing capacity in affected brains. Particular susceptibility of cholinergic neurons to neurodegeneration might results from insufficient supply of acetyl-CoA for energy production and acetylcholine synthesis in these conditions. Exposure of SN56 cholinergic neuroblastoma cells to dibutyryl cAMP and retinoic acid for 3 days caused their morphologic differentiation along with the increase in choline acetyltransferase activity, acetylcholine content and release, calcium content, and the expression of p75 neurotrophin receptors. Acetyl-CoA content correlated inversely with choline acetyltransferase activity in different lines of SN56 cells. In differentiated cells, aluminum (1 mM), amyloid beta(25-35) (0.001 mM), and sodium nitroprusside (1 mM), caused much greater decrease of pyruvate dehydrogenase and choline acetyltransferase activities and cell viability than in nondifferentiated ones. Aluminum (1 mM) aggravated suppressory effects of amyloid beta on choline acetyltransferase and pyruvate dehydrogenase activities and viability of differentiated cells. Similar additive inhibitory effects were observed upon combined exposure of differentiated cells to sodium nitroprusside and amyloid beta(25-35). None or much smaller suppressory effects of these neurotoxins were observed in nondifferentiated cells. Increase in the fraction of nonviable differentiated cells positively correlated with losses of choline acetyltransferase, pyruvate dehydrogenase activities, and cytoplasmic cytochrome c content in different neurotoxic conditions. These data indicate that highly differentiated cholinergic neurons may be more susceptible to aluminum and other neurotoxins than the nondifferentiated ones due to relative shortage of acetyl-CoA, increased content of Ca(2+), and expression of p75 receptors, yielding increase in cytoplasmic cytochrome c and subsequently grater rate of death of the former ones.

Prevalence of unidirectional Na+-dependent adenosine transport and altered potential for adenosine generation in diabetic cardiac myocytes.

Adenosine is an important physiological regulator of the cardiovascular system. The goal of our study was to assess the expression level of nucleoside transporters (NT) in diabetic rat cardiomyocytes and to examine the activities of adenosine metabolizing enzymes. Isolated rat cardiomyocytes displayed the presence of detectable amounts of mRNA for ENT1, ENT2, CNT1, and CNT2. Overall adenosine (10 microM) transport in cardiomyocytes isolated from normal rat was 36 pmol/mg/min. The expression level of equilibrative transporters (ENT1, ENT2) decreased and of concentrative transporters (CNT1, CNT2) increased in myocytes isolated from diabetic rat. Consequently, overall adenosine transport decreased by 30%, whereas Na(+)-dependent adenosine uptake increased 2-fold, and equilibrative transport decreased by 60%. The activity ratio of AMP deaminase/5'-nucleotidase in cytosol of normal cardiomyocytes was 11 and increased to 15 in diabetic cells. The activity of ecto-5'-nucleotidase increased 2-fold in diabetic cells resulting in a rise of the activity ratio of ecto-5'-nucleotidase/adenosine deaminase from 28 to 56.These results indicate that in rat cardiomyocytes diabetes alters activities of adenosine metabolizing enzymes in such a way that conversion of AMP to IMP is favored in the cytosolic compartment, whereas the capability to produce adenosine extracellularly is increased. This is accompanied by an increased unidirectional Na(+)-dependent uptake of adenosine and significantly reduced bidirectional adenosine transport.

Altered expression of adenosine receptors in heart of diabetic rat.

Diabetes results in functional, biochemical, and morphological abnormalities in the heart. Some of these changes may be attributed to altered adenosine action. This study aimed to examine the expression level of adenosine receptors (AR) in heart of streptozotocin-induced diabetic rat. Performed analyses revealed detectable levels of A1-AR, A2a-AR, A2b-AR, A3-AR mRNA and protein in whole heart and isolated cardiac myocytes. An increase in A1-AR protein content with no changes in mRNA level was observed in isolated cardiac myocytes. Diabetes resulted in an increase of A3-AR mRNA and protein levels in heart and in cardiac myocytes. The level of A2a-AR mRNA was increased in whole diabetic heart, but it decreased in cardiac myocytes with no detectable changes in protein content. We did not observe any changes in expression level of A2b-AR in diabetic heart and isolated cardiac myocytes. Administration of insulin to diabetic rat for four days resulted in returning of the ARs mRNA and protein to the levels observed in heart of normal rat. These changes in ARs genes expression, and receptors protein content correspond to some abnormalities characteristic of the diabetic heart, suggesting involvement in pathogenesis of diabetic cardiomyopathy.

Responsiveness of renal glomeruli to adenosine in streptozotocin-induced diabetic rats dependent on hyperglycaemia level.

Glomerular filtration rate (GFR) in response to adenosine precursor, NAD, and glomeruli contractility in response to adenosine were evaluated in streptozotocin-induced diabetic rats with severe (blood glucose 27.8 +/- 1.2 mmol/L) and moderate hyperglycaemia (18.2 +/- 0.9 mmol/L) compared with nondiabetic (ND)-rats. In anaesthetised rats, basal GFR was greater in moderately diabetic rats compared with severely diabetic rats (p < 0.05) and ND-rats (p < 0.02). Intravenous infusion of 5 nmol x min(-1) x kg(-1) NAD reduced GFR and renal plasma flow (RPF) in diabetic rats but had no effect on these parameters in ND-rats. Moreover, NAD-induced reduction of GFR and RPF was greater in rats with severe diabetes (41% and 30%, respectively) than in with moderate diabetes (25% and 26%, respectively). Theophylline (0.2 micromol x min(-1) x kg(-1) ) abolished renal response to NAD. Isolated glomeruli contraction in response to adenosine, assessed by glomerular 3H-inulin space reduction, was lowered in moderately diabetic-group and enhanced in severely diabetic-group. compared with ND-group (p < 0.05). Adenosine A1-receptor antagonist DPCPX inhibited adenosine-induced glomeruli contraction. This differential response of diabetic renal glomeruli to adenosine suggests that impaired glomerular contractility in response to adenosine could be responsible for hyperfiltration in moderate diabets, whereas, the increased adenosine-dependent contractility of glomeruli in severe diabetes may increase the risk of acute renal failure in this condition.

Amplification of c-myc gene and overexpression of c-Myc protein in breast cancer and adjacent non-neoplastic tissue.

BACKGROUND: Deregulated c-Myc expression and alterations of c-myc oncogene have been reported to play an important role in breast cancer tumorigenesis. We examined the relationship between c-Myc protein level, amplification of c-myc oncogene and commonly used clinical and pathologic factors. METHODS: The studies were conducted on 94 ductal and lobular cancers. Amplification of c-Myc was assessed by the semiquantitative multiplex PCR assay. The amount of c-Myc protein was estimated by the densitometry analysis of Western blots. RESULTS: Amplification of c-Myc was found in 21% of examined cancers. There was no association of c-myc amplification with established risk factors. Overexpression of c-Myc protein without c-myc amplification was associated with negative status of axillary lymph node. The size of lobular carcinoma displaying overexpression of c-Myc and the normal copy number of c-myc gene was significantly smaller than the size of tumor with elevated c-Myc and amplification of c-myc gene (p < 0.01). Within tumors displaying overexpression of c-Myc protein and c-myc gene amplification the size of ductal carcinoma was smaller than the size of lobular carcinoma (p < 0.007). CONCLUSION: Data presented in this study suggest that alterations of c-myc gene and c-Myc protein level might be related to breast cancer progression. The prognostic utility of elevated level of c-Myc protein associated with normal status of c-myc gene for patients with lobular carcinoma requires further studies.

Distribution of Fhit protein in rat tissues and its intracellular localization.

The FHIT (fragile histidine triad) gene located at chromosome 3p14.2 has been proposed as a candidate tumor suppressor gene in human cancers. Fhit protein with the diadenosine 5',5'''-P1,P3-triphosphate (Ap3A) hydrolase activity is the protein product of FHIT gene. The way in which Fhit exerts its tumor suppressor activity and the relationship of the Ap3A hydrolase activity to tumor suppression are not known. As a step toward understanding of the Fhit function in the cell we have explored its intracellular localization and distribution in the rat tissues. Data obtained from immunoblot analysis showed that Fhit protein was most abundant in spleen and brain. Moderate amount of Fhit was detected in kidney and liver, whereas the level of Fhit protein in heart, skeletal muscle and kidney glomeruli was undetectable. RT-PCR performed on RNA isolated from these tissues showed no product, whereas the level of Fhit mRNA in spleen, brain, kidney, liver and lung correlated with the Fhit protein level. The immunoblot analysis performed on subcellular fractions of various rat tissues obtained by differential and density-gradient centrifugation showed that Fhit protein was localized exclusively in nucleus and at the plasma membrane. Presented data showing nuclear and plasma membrane localization of Fhit may support the hypothesis concerning Fhit as a signaling molecule.

Expression level of adenosine kinase in rat tissues. Lack of phosphate effect on the enzyme activity.

In this report we describe cloning and expression of rat adenosine kinase (AK) in Esccherichaia coli cells as a fusion protein with 6xHis. The recombinant protein was purified and polyclonal antibodies to AK were generated in rabbits. Immunoblot analysis of extracts obtained from various rat tissues revealed two protein bands reactive with anti-AK IgG. The apparent molecular mass of these bands was 48 and 38 kDa in rat kidney, liver, spleen, brain, and lung. In heart and muscle the proteins that react with AK antibodies have the molecular masses of 48 and 40.5 kDa. In order to assess the relative AK mRNA level in rat tissues we used the multiplex PCR technique with beta-actin mRNA as a reference. We found the highest level of AK mRNA in the liver, which decreased in the order kidney > spleen > lung > heart > brain > muscle. Measurement of AK activity in cytosolic fractions of rat tissues showed the highest activity in the liver (0.58 U/g), which decreased in the order kidney > spleen > lung > brain > heart > skeletal muscle. Kinetic studies on recombinant AK as well as on AK in the cytosolic fraction of various rat tissues showed that this enzyme is not affected by phosphate ions. The data presented indicate that in the rat tissues investigated at least two isoforms of adenosine kinase are expressed, and that the expression of the AK gene appears to have some degree of tissue specificity.

Protein kinase C-gamma phorbol-binding domain involved in protein-protein interaction.

Protein kinase C-gamma (PKC-gamma) contains two cysteine-rich regions (Cys1, Cys2) responsible for interaction with phospholipids. However, previous experiments suggested that, only Cys1 represents the high affinity site involved in diacylglycerol-dependent activation of PKC-gamma. This raises the question whether Cys2 might participate in other functions of the PKC-gamma regulatory domain. The purpose of our studies was to examine the ability of Cys2 domain to bind cellular proteins. The Cys2 domain (residues 92-173) was expressed as a fusion protein with glutathione-S-transferase (GST) in Escherichia coli and purified. In order to investigate protein-protein interaction of Cys2 domain we used affinity column and an overlay assay. Our results demonstrate that the Cys2 domain of PKC-gamma binds several proteins from rat brain extracts. In the absence of phospholipids the Cys2 domain binds some proteins in the cytosolic fraction of rat brain, but no binding was detected with the proteins extracted from particulate fraction. Ca2+ at 1 microM concentration potentiated binding of cellular proteins to Cys2 domain. In the absence of Ca2+ the Cys2 domain binds proteins in the cytosolic fraction of rat brain in the presence of phosphatidylserine and to the lesser extend in the presence of phosphatidylinositol but neither phosphatidylcholine nor phosphatidylethanolamine. These results suggest that the Cys2 domain of PKC-gamma has the ability to interact with two classes of proteins. One class binds the Cys2 domain in the phosphatidylserine dependent fashion, and the other proteins bind Cys-2 domain in the Ca2+ dependent and phospholipid independent manner.

Expression in Escherichia coli and simple purification of human Fhit protein.

The fragile histidine triad (Fhit) protein is a homodimeric protein with diadenosine 5',5"'-P(1),P(3)-triphosphate (Ap(3)A) asymmetrical hydrolase activity. We have cloned the human cDNA Fhit in the pPROEX-1 vector and expressed with high yield in Escherichia coli with the sequence Met-Gly-His(6)-Asp-Tyr-Asp-Ile-Pro-Thr-Thr followed by a rTEV protease cleavage site, denoted as "H6TV," fused to the N-terminus of Fhit. Expression of H6TV-Fhit in BL21(DE3) cells for 3 h at 37 degrees C produced 30 mg of H6TV-Fhit from 1 L of cell culture ( approximately 4 g of cells). The H6TV-Fhit protein was purified to homogeneity in a single step, with a yield of 80%, using nickel-nitrilotriacetate resin and imidazole buffer as eluting agent. Incubation of H6TV-Fhit with rTEV protease at 4 degrees C for 24 h resulted in complete cleavage of the H6TV peptide. There were no unspecific cleavage products. The purified Fhit protein could be stored for 3 weeks at 4 degrees C without loss of activity. The pure protein was stable at -20 degrees C for at least 18 months when stored in buffer containing 25% glycerol. Purified Fhit was highly active, with a K(m) value for Ap(3)A of 0.9 microM and a k(cat)(monomer) value of 7.2 +/- 1.6 s(-1) (n = 5). The catalytic properties of unconjugated Fhit protein and the H6TV-Fhit fusion protein were essentially identical. This indicates that the 24-amino-acid peptide containing the six histidines fused to the N-terminus of Fhit does not interfere in forming the active homodimers or in the binding of Ap(3)A.

Decreased expression of adenosine kinase in streptozotocin-induced diabetes mellitus rats.

Adenosine has been implicated as an important endogenous regulator of various tissue functions. In diabetes, the responsiveness of several tissues to adenosine is altered. The aim of this study was to investigate the activities of enzymes metabolizing adenosine in tissues of diabetic rats. The cytosolic activity (V(max)) of adenosine kinase (AK) was decreased by 50% in the kidney and by 40% in the heart and liver of diabetic rats. A decrease in the V(max) of AK in diabetic tissues was not associated with a change in the K(m) for adenosine. Evaluation of AK gene transcript status showed significantly lower levels of AK mRNA in diabetic tissues as compared to normal tissues. In diabetic kidneys, the level of AK gene transcript was lowered by 50% on first day after streptozotocin administration, and these reduced levels were sustained declined during the next 10 days. Smaller changes in AK gene transcript levels were observed in the heart and liver than in the kidney. The cytosolic activities of 5'-nucleotidase, AMP deaminase, and adenosine deaminase were unchanged in kidney, heart, and liver of diabetic rats. These results suggest that the turnover of the AMP-adenosine metabolic cycle might be impaired in diabetic tissues due to the reduced activity of adenosine kinase.

The ultraviolet studies on protein-lipid interaction of a protein kinase C-gamma phorbol-binding domain.

Family of protein kinase C (PKC) isozymes play a key role in transducing a vast number of signals into the cells. The members of classical PKC family are activated by binding of various lipid ligands to one of the several cysteine-rich domains of the enzyme. Second cysteine-rich (Cys2) domain of PKC-gamma was expressed in Escherichia coli as a fusion protein with glutathione-S-transferase (GST) using the cDNA sequence from rat brain. The Cys2 protein after cleavage from GST was purified to homogeneity using glutathione-agarose and Mono-S cation exchanger column. In order to investigate the interaction of lipids and calcium with Cys2 protein we used UW spectroscopy. The UV spectrum of Cys2 protein exhibited a maximum at 205 nm. Exposition of Cys2 protein to phosphatidylserine (PS) vesicles resulted in significant decrease in the absorbance in the 210 nm region. Changes in UW spectrum of Cys2 protein induced by phorbol 12,13-dibutyrate (PDB) were smaller than those induced by PS, and addition of PDB with PS had no effect on the PS induced changes in UV spectrum of Cys2. Neither phosphatidylcholine (PC) nor phosphatidylethanolamine (PE) affected UV spectrum of Cys2 but in the presence of phosphatidylinositol 4,5 bisphosphate (PIP2) or phosphatidyliinositol 4-phosphate (PIP) vesicles some changes were observed. Calcium ions alone or in the presence of PS had no effect on the UV spectrum of Cys2 protein. These data indicate that PS comparing to PDB, interacts with a larger area of Cys2 protein, and that the binding sites for these two molecules are at least overlapping. The site of PIP and PIP2 interaction with PKC-gamma is distinct from that of phorbol ester binding site.