Protective Effect of Peroxiredoxin 6 Against Toxic Effects of Glucose and Cytokines in Pancreatic RIN-m5F β-Cells

Protective effect of exogenous peroxiredoxin 6 and thymic peptide thymulin on BBB conditions in an experimental model of multiple sclerosis

This study aimed to assess the effects of the immunomodulator thymulin, a thymic peptide with anti-inflammatory effects, and peroxiredoxin 6 (Prdx6), an antioxidant enzyme with dual peroxidase and phospholipase A2 activities, on the blood‒brain barrier (BBB) condition and general health status of animals with relapsing-remitting experimental autoimmune encephalomyelitis (EAE), which is a model of multiple sclerosis in humans. Both thymulin and Prdx6 significantly improved the condition of the BBB, which was impaired by EAE induction, as measured by Evans blue dye accumulation, tight-junction protein loss in brain tissue, and lymphocyte infiltration through the BBB. The effect was associated with significant amelioration of EAE symptoms. Thymulin treatment was accompanied by a decrease in immune cell activation as judged by interleukin-6, -17, and interferon-gamma cytokine levels in serum and NF-kappaB cascade activation in splenocytes of mice with EAE. Prdx6 did not induce significant immunomodulatory effects but abruptly decreased EAE-induced NOX1 and NOX4 gene expression in brain tissue, which may be one of the possible mechanisms of its beneficial effects on BBB conditions and health status. The simultaneous administration of thymulin and Prdx6 resulted in complete symptomatic restoration of mice with EAE. The results demonstrate prospective strategies for multiple sclerosis treatment.

Protective Effects of Peroxiredoxin 6 in Pro-Inflammatory Response Model Using Raw 264.7 Macrophages

The aim of the work was to study effects of peroxiredoxin 6 (PRDX6), a recombinant antioxidant protein, on the level of pro-inflammatory responses of RAW 264.7 macrophages to endotoxin exposure. Addition of LPS to the RAW 264.7 cell culture medium expectedly increased production of TNF-α, and addition of PRDX6 led to a significant (15-20%) decrease in its production. The level of production of another pro-inflammatory cytokine, IL-1β, which was significantly activated by endotoxin, was completely normalized under the PRDX6 action. Moreover, addition of PRDX6 reduced production of reactive oxygen species (ROS) induced by endotoxin and also prevented overexpression of the iNos gene in the RAW 264.7 cells. The results showed that PRDX6 had a suppressive effect on the expression of Nrf-2 gene and production of the transcription factor NRF-2 during the first 6 h of cell cultivation. Addition of endotoxin caused activation of the NF-κB and SAPK/JNK signaling cascades, while in the presence of PRDX6, activity of these signaling cascades decreases. It is known that the pro-inflammatory response of cells caused by exposure to bacterial LPS leads to activation of apoptosis and elimination of the damaged cells. Our studies confirm this, since exposure to LPS led to activation of the expression of P53 gene, a marker of apoptosis. Peroxiredoxin 6 added within the first hours of the development of acute pro-inflammatory response suppressed the P53 gene expression, indicating protective effect of PRDX6 that reduced apoptosis in the RAW 264.7 macrophages.

The effects of hydroxytyrosol on Prdx6 and insulin expression in diabetic rat pancreases

Diabetes mellitus is a widespread endocrine disease worldwide, accompanying chronic hyperglycemia. In this study, we investigated the effect of hydroxytyrosol, which exerts an antioxidant effect, on the expressions of insulin and peroxiredoxin-6 (Prdx6), which protect cells against oxidative injury in diabetic rat pancreas. This experimental study had four groups with ten animals in each group: control (nondiabetic) group, hydroxytyrosol group [10 mg/kg/day intraperitoneal injection (ip) hydroxytyrosol for 30 days], streptozotocin group (single ip injection of 55 mg/kg streptozotocin), and streptozotocin + hydroxytyrosol group (single ip injection of streptozotocin and ip injection of 10 mg/kg/day hydroxytyrosol for 30 days). During the experiment, blood glucose levels were measured at regular intervals. Insulin expression was determined by immunohistochemistry and Prdx6 expression was determined by immunohistochemistry and western blot. Immunohistochemistry and western blot results were analyzed by one-way ANOVA with applied Holm-Sidak multiple comparison test, and blood glucose results were analyzed by two-way repeated measures ANOVA with applied Tukey's multiple comparison test. Blood glucose levels on days 21 and 28 were significantly lower in the streptozotocin + hydroxytyrosol group compared with the streptozotocin group (day 21, p = 0.049 and day 28, p = 0.003). Expression of both insulin and Prdx6 were lower in the streptozotocin and the streptozotocin + hydroxytyrosol groups compared with the control and hydroxytyrosol groups (p < 0.001). Insulin and Prdx6 expression in the streptozotocin + hydroxytyrosol group were higher compared with the streptozotocin group (p < 0.001). The immunohistochemical findings of Prdx6 and western blot were the same. In conclusion, hydroxytyrosol, which is an antioxidant compound, increased Prdx6 and insulin expression in diabetic rats. Insulin increased by hydroxytyrosol may have been effective in reducing blood glucose levels. Furthermore, hydroxytyrosol may exert its effect on insulin by increasing Prdx6 expression. Thus, hydroxytyrosol may decrease or prevent several hyperglycemia-dependent complications by increasing the expression of these proteins.

Functional thermosensitive hydrogels based on chitin as RIN-m5F cell carrier for the treatment of diabetes

Herein, the thermosensitive hydroxypropyl chitin (HPCT) hydrogel was prepared and the chemical structures, microstructures, rheological properties and degradation in vitro were investigated. The HPCT hydrogel possessed satisfactory biocompatibility in mouse fibroblast cells and Sprague Dawley rats. On the other hand, N-acetylglucosamine (NAG) and carboxymethyl chitosan (CMCS) provided favorable capacity for promoting cell proliferation, delaying cell apoptosis, and facilitating the insulin secretion of rat pancreatic beta cells (RIN-m5F) in three-dimensional culture. Most importantly, the effects of HPCT/NAG and HPCT/CMCS thermosensitive hydrogels as RIN-m5F cells carriers were evaluated via injection into different areas of diabetic rats. Our results demonstrated that HPCT/NAG and HPCT/CMCS hydrogels loaded RIN-m5F cells could keep cells survival, maintain insulin secretion and reduce blood glucose for one week. Overall, the functional thermosensitive hydrogels based on HPCT were effective cell carriers for RIN-m5F cells and might provide novel strategy for the treatment of diabetes via cell engineering.

Peroxiredoxin 6 Applied after Exposure Attenuates Damaging Effects of X-ray Radiation in 3T3 Mouse Fibroblasts

Although many different classes of antioxidants have been evaluated as radioprotectors, none of them are in widespread clinical use because of their low efficiency. The goal of our study was to evaluate the potential of the antioxidant protein peroxiredoxin 6 (Prdx6) to increase the radioresistance of 3T3 fibroblasts when Prdx6 was applied after exposure to 6 Gy X-ray. In the present study, we analyzed the mRNA expression profiles of genes associated with proliferation, apoptosis, cellular stress, senescence, and the production of corresponding proteins from biological samples after exposure of 3T3 cells to X-ray radiation and application of Prdx6. Our results suggested that Prdx6 treatment normalized p53 and NF-κB/p65 expression, p21 levels, DNA repair-associated genes (XRCC4, XRCC5, H2AX, Apex1), TLR expression, cytokine production (TNF-α and IL-6), and apoptosis, as evidenced by decreased caspase 3 level in irradiated 3T3 cells. In addition, Prdx6 treatment reduced senescence, as evidenced by the decreased percentage of SA-β-Gal positive cells in cultured 3T3 fibroblasts. Importantly, the activity of the NRF2 gene, an important regulator of the antioxidant cellular machinery, was completely suppressed by irradiation but was restored by post-irradiation Prdx6 treatment. These data support the radioprotective therapeutic efficacy of Prdx6.

Role of Innate Immunity and Oxidative Stress in the Development of Type 1 Diabetes Mellitus. Peroxiredoxin 6 as a New Anti-Diabetic Agent

The review discusses information on the development of type 1 diabetes mellitus (T1D) as a systemic autoimmune and inflammatory disease. Focus of the review is on the role of innate immune system, including activation of some signaling cascades, cytokine response, and activity of the Toll-like receptors in the development of T1D. Dysfunction of innate immunity is the cause of the attack of pancreatic beta cells by the host T-lymphocytes, which leads to the death of pancreatic beta cells that produce insulin. Lack of insulin causes hyperglycemia and the need for lifelong injections of insulin in patients with T1D, which, nevertheless, does not exclude damage to many organs and tissues, given particular vulnerability of the blood vessels under conditions of hyperglycemia. The review discusses the role of oxidative stress as a factor that plays a major role in damage of vascular system and pancreatic tissue during the development of T1D. Considering high sensitivity of pancreatic beta cells to the action of reactive oxygen species (ROS), the possibility of using antioxidants for reducing the level of pathological consequences in the course of T1D development is discussed. New information on anti-diabetic activity of the exogenous antioxidant enzyme peroxiredoxin 6, which is capable of penetrating cells, activating insulin production in beta cells, reducing ROS levels, as well as decreasing activation of some signaling cascades, production of pro-inflammatory cytokines, and expression of Toll-like receptors in beta cells and in immune cells during T1D development is discussed.

Role of Glutathione Peroxidases and Peroxiredoxins in Free Radical-Induced Pathologies

In this review, we discuss the pathogenesis of some socially significant diseases associated with the development of oxidative stress, such as atherosclerosis, diabetes, and radiation sickness, as well as the possibilities of the therapeutic application of low-molecular-weight natural and synthetic antioxidants for the correction of free radical-induced pathologies. The main focus of this review is the role of two phylogenetically close families of hydroperoxide-reducing antioxidant enzymes peroxiredoxins and glutathione peroxidases - in counteracting oxidative stress. We also present examples of the application of exogenous recombinant antioxidant enzymes as therapeutic agents in the treatment of pathologies associated with free-radical processes and discuss the prospects of the therapeutic use of exogenous antioxidant enzymes, as well as the ways to improve their therapeutic properties.

Thymulin and peroxiredoxin 6 have protective effects against streptozotocin-induced type 1 diabetes in mice

Protective effects of peroxiredoxin 6 (PRDX6) in RIN-m5F β-cells and of thymulin in mice with alloxan-induced diabetes were recently reported. The present work was aimed at studying the efficiency of thymulin and PRDX6 in a type 1 diabetes mellitus model induced by streptozotocin in mice. Effects of prolonged treatment with PRDX6 or thymic peptide thymulin on diabetes development were evaluated. We assessed the effects of the drugs on the physiological status of diabetic mice by measuring blood glucose, body weight, and cell counts in several organs, as well as effects of thymulin and PRDX6 on the immune status of diabetic mice measuring concentrations of pro-inflammatory cytokines in blood plasma (TNF-α, interleukin-5 and 17, and interferon-γ), activity of NF-κB and JNK pathways, and Hsp90α expression in immune cells. Both thymulin and PRDX6 reduced the physiological impairments in diabetic mice at various levels. Thymulin and PRDX6 provide beneficial effects in the model of diabetes via very different mechanisms. Taken together, the results of our study indicated that the thymic peptide and the antioxidant enzyme have anti-inflammatory functions. As increasing evidences show diabetes mellitus as a distinct comorbidity leading to acute respiratory distress syndrome and increased mortality in patients with COVID-19 having cytokine storm, thymulin, and PRDX6 might serve as a supporting anti-inflammatory treatment in the therapy of COVID 19 in diabetic patients.

Participation of Hsp70 and Hsp90α Heat Shock Proteins in Stress Response in the Course of Type 1 Diabetes Mellitus

The role of two heat shock proteins, Hsp70 and Hsp90α, on stress response in mice with severe diabetes mellitus induced by a high dose of alloxan (500 mg/kg body weight), as well as in RIN-m5F β cells cultured in the presence of cytokines (IL-1 and TNF-α) was studied. Our results showed that severe type 1 diabetes mellitus (T1D) caused a higher expression of Hsp90α, but not Hsp70. Moreover, injections of the peroxiredoxin 6 antioxidant enzyme (PRDX6) did not affect the expression of these chaperones. Conversely, pro-inflammatory cytokines added to β-cells caused a significant increase in the expression of Hsp90α and, substantially, Hsp70. Moreover, cells cultivated in the presence of PRDX6 were more susceptible to the cytokine effect. Thus, in the course of severe alloxan-induced T1D, no protective role of the heat shock proteins, was revealed, and their expression level was not increased by PRDX6. At the same time the protective potential of these proteins was shown in vitro with the use of RIN-m5F β cells. Thus, the system of heat shock proteins was unable to prevent the devastating effects of severe T1D accompanied by high animal mortality.

Peroxiredoxin 6 Attenuates Alloxan-Induced Type 1 Diabetes Mellitus in Mice and Cytokine-Induced Cytotoxicity in RIN-m5F Beta Cells

Type 1 diabetes is associated with the destruction of pancreatic beta cells, which is mediated via an autoimmune mechanism and consequent inflammatory processes. In this article, we describe a beneficial effect of peroxiredoxin 6 (PRDX6) in a type 1 diabetes mouse model. The main idea of this study was based on the well-known data that oxidative stress plays an important role in pathogenesis of diabetes and its associated complications. We hypothesised that PRDX6, which is well known for its various biological functions, including antioxidant activity, may provide an antidiabetic effect. It was shown that PRDX6 prevented hyperglycemia, lowered the mortality rate, restored the plasma cytokine profile, reversed the splenic cell apoptosis, and reduced the β cell destruction in Langerhans islets in mice with a severe form of alloxan-induced diabetes. In addition, PRDX6 protected rat insulinoma RIN-m5F β cells, cultured with TNF-α and IL-1β, against the cytokine-induced cytotoxicity and reduced the apoptotic cell death and production of ROS. Signal transduction studies showed that PRDX6 prevented the activation of NF-κB and c-Jun N-terminal kinase signaling cascades in RIN-m5F β cells cultured with cytokines. In conclusion, there is a prospect for therapeutic application of PRDX6 to delay or even prevent β cell apoptosis in type 1 diabetes.