Role for oxidative stress in the regeneration of islet beta cells?

Neutralization Versus Reinforcement of Proinflammatory Cytokines to Arrest Autoimmunity in Type 1 Diabetes

As physiological pathways of intercellular communication produced by all cells, cytokines are involved in the pathogenesis of inflammatory insulitis as well as pivotal mediators of immune homeostasis. Proinflammatory cytokines including interleukins, interferons, transforming growth factor-β, tumor necrosis factor-α, and nitric oxide promote destructive insulitis in type 1 diabetes through amplification of the autoimmune reaction, direct toxicity to β-cells, and sensitization of islets to apoptosis. The concept that neutralization of cytokines may be of therapeutic benefit has been tested in few clinical studies, which fell short of inducing sustained remission or achieving disease arrest. Therapeutic failure is explained by the redundant activities of individual cytokines and their combinations, which are rather dispensable in the process of destructive insulitis because other cytolytic pathways efficiently compensate their deficiency. Proinflammatory cytokines are less redundant in regulation of the inflammatory reaction, displaying protective effects through restriction of effector cell activity, reinforcement of suppressor cell function, and participation in islet recovery from injury. Our analysis suggests that the role of cytokines in immune homeostasis overrides their contribution to β-cell death and may be used as potent immunomodulatory agents for therapeutic purposes rather than neutralized.

The investigation of alfaalfa effect on the activity of superoxide dismutase in chicken meat in dependence on time storage

This study was conducted in order to monitor the effect of adding lucerne meal to chicken feed mixtures. The experiment was conducted at the Department Food Hygiene and Safety, Faculty of Biotechnology and Food Science, Slovak University of Agriculture in Nitra. Chickens for meat production - final type Cobb 500 were used in the experiment. Chickens were placed in boxes all together for one group at the beginning of the experiment and from 14 days of age chickens were divided individually into floor enriched cages. Feeding of chickens lasted 38 days. The experiment was carried out without sex segregation. For the production of a feed composition was used alfalfa (Medicago sativa) as lucerne meal, which was added to the feed at a rate of 4%, namely: starter (HYD-01), growth (HYD-02) and final (HYD-03). The control group did not include the addition of lucerne meal. Chickens were fed ad libitum. Chickens were slaughtered after completion of feeding and the meat samples were taken for analysis. The collected samples were stored at -18 °C. Collected samples of meat were analyzed after slaughter chickens at time intervals of 6, 12 and 18 months. In the experiment was monitored the content of supeoxid dismutase in the chicken meat depending on the length of storage time. Superoxide dismutase content was increasing by storage time, while there were some statistically significant differences between groups.

(-)-Epicatechin rich cocoa mediated modulation of oxidative stress regulators in skeletal muscle of heart failure and type 2 diabetes patients

BACKGROUND

Type 2 diabetes (T2D) and heart failure (HF) are associated with high levels of skeletal muscle (SkM) oxidative stress (OS). Health benefits attributed to flavonoids have been ascribed to antioxidation. However, for flavonoids with similar antioxidant potential, end-biological effects vary widely suggesting other mechanistic venues for reducing OS. Decreases in OS may follow the modulation of key regulatory pathways including antioxidant levels (e.g. glutathione) and enzymes such as mitochondrial superoxide dismutase (SOD2) and catalase.

METHODS

We examined OS-related alterations in SkM in T2D/HF patients (as compared vs. healthy controls) and evaluated the effects of three-month treatment with (-)-epicatechin (Epi) rich cocoa (ERC). To evidence Epi as the mediator of the improved OS profile we examined the effects of pure Epi (vs. water) on SkM OS regulatory systems in a mouse model of insulin resistance and contrasted results vs. normal mice.

RESULTS

There were severe alterations in OS regulatory systems in T2D/HF SkM as compared with healthy controls. Treatment with ERC induced recovery in glutathione levels and decreases in the nitrotyrosilation and carbonylation of proteins. With treatment, key transcriptional factors translocate into the nucleus leading to increases in SOD2 and catalase protein expression and activity levels. In insulin resistant mice, there were alterations in muscle OS and pure Epi replicated the beneficial effects of ERC found in humans.

CONCLUSIONS

Major perturbations in SkM OS can be reversed with ERC in T2D/HF patients. Epi likely mediates such effects and may provide an effective means to treat conditions associated with tissue OS.

The world pandemic of vitamin D deficiency could possibly be explained by cellular inflammatory response activity induced by the renin-angiotensin system

This review attempts to show that there may be a relationship between inflammatory processes induced by chronic overstimulation of the renin-angiotensin system (RAS) and the worldwide deficiency of vitamin D (VitD) and that both disorders are probably associated with environmental factors. Low VitD levels represent a risk factor for several apparently different diseases, such as infectious, autoimmune, neurodegenerative, and cardiovascular diseases, as well as diabetes, osteoporosis, and cancer. Moreover, VitD insufficiency seems to predispose to hypertension, metabolic syndrome, left ventricular hypertrophy, heart failure, and chronic vascular inflammation. On the other hand, inappropriate stimulation of the RAS has also been associated with the pathogenesis of hypertension, heart attack, stroke, and hypertrophy of the left ventricle and vascular smooth muscle cells. Because VitD receptors (VDRs) and RAS receptors are almost distributed in the same tissues, a possible link between VitD and the RAS is even more plausible. Furthermore, from an evolutionary point of view, both systems were developed simultaneously, actively participating in the regulation of inflammatory and immunological mechanisms. Changes in RAS activity and activation of the VDR seem to be inversely related; thus any changes in one of these systems would have a completely opposite effect on the other, making it possible to speculate that the two systems could have a feedback relationship. In fact, the pandemic of VitD deficiency could be the other face of increased RAS activity, which probably causes lower activity or lower levels of VitD. Finally, from a therapeutic point of view, the combination of RAS blockade and VDR stimulation appears to be more effective than either RAS blockade or VDR stimulation individually.

Modulation of apoptosis pathways by oxidative stress and autophagy in β cells

Human islets isolated for transplantation are exposed to multiple stresses including oxidative stress and hypoxia resulting in significant loss of functional β cell mass. In this study we examined the modulation of apoptosis pathway genes in islets exposed to hydrogen peroxide, peroxynitrite, hypoxia, and cytokines. We observed parallel induction of pro- and antiapoptotic pathways and identified several novel genes including BFAR, CARD8, BNIP3, and CIDE-A. As BNIP3 is an inducer of autophagy, we examined this pathway in MIN6 cells, a mouse beta cell line and in human islets. Culture of MIN6 cells under low serum conditions increased the levels of several proteins in autophagy pathway, including ATG4, Beclin 1, LAMP-2, and UVRAG. Amino acid deprivation led to induction of autophagy in human islets. Preconditioning of islets with inducers of autophagy protected them from hypoxia-induced apoptosis. However, induction of autophagy during hypoxia exacerbated apoptotic cell death. ER stress led to induction of autophagy and apoptosis in β cells. Overexpression of MnSOD, an enzyme that scavenges free radicals, resulted in protection of MIN6 cells from cytokine-induced apoptosis. Ceramide, a mediator of cytokine-induced injury, reduced the active phosphorylated form of Akt and downregulated the promoter activity of the antiapoptotic gene bcl-2. Furthermore, cytokine-stimulated JNK pathway downregulated the bcl-2 promoter activity which was reversed by preincubation with SP600125, a JNK inhibitor. Our findings suggest that β cell apoptosis by multiple stresses in islets isolated for transplantation is the result of orchestrated gene expression in apoptosis pathway.

Cutting edge: genetic characterization of IFN-producing killer dendritic cells

The combined phenotypic expression of CD11c(low)B220(+)CD122(+)DX5(+) has been used to define a novel cell type termed IFN-producing killer dendritic cells (IKDC). IKDC readily produce IFN-gamma and demonstrate spontaneous cytotoxic activity toward tumors, suggesting that a modulation of IKDC number may be beneficial in cancer treatment. We examined various mouse strains and found that IKDC number was highly variable between the different strains. A linkage analysis associated the distal arm of chromosome 7 with variations in IKDC number. The genetic contribution of chromosome 7 to the regulation of IKDC number was confirmed through the use of congenic mice. We further demonstrate that IKDC proportion is regulated by intrinsic hematopoietic factors. We discuss the role of various candidate genes in the regulation of this newly described cell type and its implication in therapy.

Regulation of heme oxygenase-1 expression by demethoxy curcuminoids through Nrf2 by a PI3-kinase/Akt-mediated pathway in mouse beta-cells

Curcumin (diferuloylmethane), a component of turmeric, has been shown to have therapeutic properties. Induction of phase 2 detoxifying enzymes is a potential mechanism through which some of the actions of curcumin could proceed. Heme oxygenase-1 (HO-1), an antioxidant phase 2 enzyme, has been reported to have cytoprotective effects in pancreatic beta-cells. Curcumin on further purification yields demethoxy curcumin (DMC) and bisdemethoxy curcumin (BDMC). The objective of the present study was to determine the mechanism by which these purified curcuminoids induce HO-1 in MIN6 cells, a mouse beta-cell line. Demethoxy curcuminoids induced HO-1 promoter linked to the luciferase reporter gene more effectively than curcumin. The induction was dependent on the presence of antioxidant response element (ARE) sites containing enhancer regions (E1 and E2) in HO-1 promoter and nuclear translocation of nuclear factor-E2-related factor (Nrf2), the transcription factor that binds to ARE. Curcuminoids stimulated multiple signaling pathways that are known to induce HO-1. Inhibition of specific signaling pathways with pharmacological inhibitors and cotransfection experiments suggested the involvement of phosphotidylinositol 3-kinase and Akt. Real-time quantitative RT-PCR analysis showed significant elevation in the mRNA levels of HO-1 and two other phase 2 enzymes, the regulatory subunit of glutamyl cysteine ligase, which is needed for the synthesis of glutathione, and NAD(P)H:quinone oxidoreductase, which detoxifies quinones. DMC and BDMC induced the expression of HO-1 and translocated Nrf2 to nucleus in beta-cells of mouse islets. Our observations suggest that demethoxy curcuminoids could be used to induce a cellular defense mechanism in beta-cells under conditions of stress as seen in diabetes.

Activation of superoxide dismutases: putting the metal to the pedal

Superoxide dismutases (SOD) are important anti-oxidant enzymes that guard against superoxide toxicity. Various SOD enzymes have been characterized that employ either a copper, manganese, iron or nickel co-factor to carry out the disproportionation of superoxide. This review focuses on the copper and manganese forms, with particular emphasis on how the metal is inserted in vivo into the active site of SOD. Copper and manganese SODs diverge greatly in sequence and also in the metal insertion process. The intracellular copper SODs of eukaryotes (SOD1) can obtain copper post-translationally, by way of interactions with the CCS copper chaperone. CCS also oxidizes an intrasubunit disulfide in SOD1. Adventitious oxidation of the disulfide can lead to gross misfolding of immature forms of SOD1, particularly with SOD1 mutants linked to amyotrophic lateral sclerosis. In the case of mitochondrial MnSOD of eukaryotes (SOD2), metal insertion cannot occur post-translationally, but requires new synthesis and mitochondrial import of the SOD2 polypeptide. SOD2 can also bind iron in vivo, but is inactive with iron. Such metal ion mis-incorporation with SOD2 can become prevalent upon disruption of mitochondrial metal homeostasis. Accurate and regulated metallation of copper and manganese SOD molecules is vital to cell survival in an oxygenated environment.

Posttranslational modifications in Cu,Zn-superoxide dismutase and mutations associated with amyotrophic lateral sclerosis

Activation of the enzyme Cu,Zn-superoxide dismutase (SOD1) involves several posttranslational modifications including copper and zinc binding, as well as formation of the intramolecular disulfide bond. The copper chaperone for SOD1, CCS, is responsible for intracellular copper loading in SOD1 under most physiological conditions. Recent in vitro and in vivo assays reveal that CCS not only delivers copper to SOD1 under stringent copper limitation, but it also facilitates the stepwise conversion of the disulfide-reduced immature SOD1 to the active disulfide-containing enzyme. The two new functions attributed to CCS, (i.e., O(2)-dependent sulfhydryl oxidase- and disulfide isomerase-like activities) indicate that this protein has attributes of the larger class of molecular chaperones. The CCS-dependent activation of SOD1 is dependent upon oxygen availability, suggesting that the cell only loads copper and activates this enzyme when O(2)-based oxidative stress is present. Thiol/disulfide status as well as metallation state of SOD1 significantly affects its structure and protein aggregation, which are relevant in pathologies of a neurodegenerative disease, amyotrophic lateral sclerosis (ALS). The authors review here a mechanism for posttranslational activation of SOD1 and discuss models for ALS in which the most immature forms of the SOD1 polypeptide exhibits propensity to form toxic aggregates.

The Unitarian Hypothesis for the aetiology of diabetes mellitus

Over the years, several clinical syndromes have been described in diabetes mellitus. Although world opinion has settled somewhat on the main two types, the debate continues as to how the 'formes frustes' syndromes fit in and what if any implications there are for the accepted aetiology of the disease. Type 1, insulin dependent diabetes mellitus, results from pancreatic inadequacy as a result of a variety of insults such as autoimmune attack, toxic damage, etc. Insulin administration is at the core of the therapeutic approach. Type 2, non insulin dependent diabetes mellitus, results from reduced responsiveness of the target tissues to insulin and as such, an insulin resistance syndrome is described. Lifestyle adjustment and oral hypoglycaemic agents are the mainstay of therapy. Over the years, however, insulin insufficiency will develop in most cases and insulin therapy required in order to achieve normoglycaemia. The aetiology of these main two types has been maintained to be distinct from each other and as such types 1 and 2 are described as two separate developmental conditions. Furthermore, the variant patterns, such as malnutrition related, drug induced, intermittent or phasic insulin requiring, gestational, temporary, stress related, etc., all present a challenge as to how they fit in aetiologically. The Unitarian Hypothesis, by presenting this overall cascade of biochemical and physiological interactions, brings a logic which embraces the points of entry of a variety of insults, all of which can lead to the clinical picture of hyperglycaemia and its attendant adverse outcomes. The hypothesis buttresses the belief that nature - the genetic predisposition which directs potential antibody development; and nurture - the environmental influences such as nutritional status (over- or under-), infective and toxic attack, can aggravate or initiate aspects of the cascade of reactions leading to hyperglycaemia. The causative agents functioning internally within the cascade are imputed to be free radicals, oxidizing molecular species and antibodies and the corollary to this overview concept would be that a situation that minimizes the genesis and accumulation of these three agents would minimize the development of diabetes mellitus. Currently the debate is rife about the use of free radical scavengers and antioxidants in the treatment and prevention of diabetes mellitus. The verdict is still out on this approach. Our research on rootcrops such as yams and cassava, staple foods in tropical countries, indicates the presence of cyanoglycosides such as linamarin, which on digestion yields cyanide radicals. These radicals are pancreatotoxic especially in the undernourished state. Dog models however, have shown that free radical scavengers such as riboflavin, Vitamin B(2), is protective against this toxic damage. Further, scientific investigations have clearly demonstrated the role of antibody attack and have been able to ward off the appearance of type 1 diabetes mellitus in susceptible individuals, by the early use of immunosuppressive therapy such as cyclosporin. Thus the Unitarian Hypothesis demonstrates how all types of clinical syndromes being described in diabetes mellitus are not necessarily variants of a specific illness but rather manifestations of a central process of membrane damage-->antibody response-->insulin inadequacy (quantitatively or qualitatively); and the future intervention in containing this disease may well lie in focusing on preservation of the integrity of the body's cell membranes.

"Agouti NOD": identification of a CBA-derived Idd locus on Chromosome 7 and its use for chimera production with NOD embryonic stem cells

Penetrance of the complex of genes predisposing the nonobese diabetic (NOD) mouse to autoimmune diabetes is affected by the maternal environment. NOD.CBALs-Tyr(+)/Lt is an agouti-pigmented Chromosome 7 congenic stock of NOD/Lt mice produced as a resource for embryo transfer experiments to provide the necessary maternal factors and allow the easy identification of NOD (albino) embryo donor phenotype. CBcNO6/Lt, a recombinant congenic agouti stock already containing approximately 50% NOD genome, was used as the donor source of a wild-type CBA tyrosinase allele. When the incidence of diabetes was assessed after nine generations of backcrossing and one generation of sib-sib mating, significant reduction in diabetes development was observed. No difference in diabetes development was observed in Tyr/Tyr(c) heterozygotes, showing that protection was recessive. Analysis of diabetes progression in another NOD stock congenic for C57BL/6 alleles on Chromosome 7 linked to the glucose phosphate isomerase (Gpi1(b)) locus provided no protection, indicating that the diabetes resistance (Idd) gene was distal to 34 cM (D7Mit346). Approximately 5 cM of the distal congenic region overlaps a region from C57L previously associated with protection when homozygous. The delayed onset and reduced frequency of diabetes in the NOD.CBALs-Tyr(+)/Lt stock is an advantage when females of this stock are used as surrogate mothers in studies involving hysterectomy or embryo transfers. Indeed, a newly developed NOD embryonic stem (ES) cell line injected into NOD.CBALs- Tyr(+)/Lt blastocysts produced approximately 50% live-born mice, of which approximately 11% were chimeric. Presumably because of high genomic instability, no germline transmission was observed.