Protective Effect of Peroxiredoxin 6 in Ischemia/Reperfusion-Induced Damage of Small Intestine

Peroxiredoxins and Hypoxia-Inducible Factor-1α in Duodenal Tissue: Emerging Factors in the Pathophysiology of Pediatric Celiac Disease Patients

Celiac disease (CD) is an autoimmune enteropathy. Peroxiredoxins (PRDXs) are powerful antioxidant enzymes having an important role in significant cellular pathways including cell survival, apoptosis, and inflammation. This study aimed at investigating the expression levels of all PRDX isoforms (1-6) and their possible relationships with a transcription factor, HIF-1α, in the small intestinal tissue samples of pediatric CD patients. The study groups consisted of first-diagnosed CD patients (n = 7) and non-CD patients with functional gastrointestinal tract disorders as the controls (n = 7). The PRDXs and HIF-1α expression levels were determined by using real-time PCR and Western blotting in duodenal biopsy samples. It was observed that the mRNA and protein expression levels of PRDX 5 were significantly higher in the CD patients, whereas the PRDX 1, -2, and -4 expressions were decreased in each case compared to the control group. No significant differences were detected in the PRDX 3 and PRDX 6 expressions. The expression of HIF-1α was also significantly elevated in CD patients. These findings indicate, for the first time, that PRDXs, particularly PRDX 5, may play a significant role in the pathogenesis of CD. Furthermore, our results suggest that HIF-1α may upregulate PRDX-5 transcription in the duodenal tissue of CD.

The Intestinal Redox System and Its Significance in Chemotherapy-Induced Intestinal Mucositis

Chemotherapy-induced intestinal mucositis (CIM) is a significant dose-limiting adverse reaction brought on by the cancer treatment. Multiple studies reported that reactive oxygen species (ROS) is rapidly produced during the initial stages of chemotherapy, when the drugs elicit direct damage to intestinal mucosal cells, which, in turn, results in necrosis, mitochondrial dysfunction, and ROS production. However, the mechanism behind the intestinal redox system-based induction of intestinal mucosal injury and necrosis of CIM is still undetermined. In this article, we summarized relevant information regarding the intestinal redox system, including the composition and regulation of redox enzymes, ROS generation, and its regulation in the intestine. We innovatively proposed the intestinal redox “Tai Chi” theory and revealed its significance in the pathogenesis of CIM. We also conducted an extensive review of the English language-based literatures involving oxidative stress (OS) and its involvement in the pathological mechanisms of CIM. From the date of inception till July 31, 2021, 51 related articles were selected. Based on our analysis of these articles, only five chemotherapeutic drugs, namely, MTX, 5-FU, cisplatin, CPT-11, and oxaliplatin were shown to trigger the ROS-based pathological mechanisms of CIM. We also discussed the redox system-mediated modulation of CIM pathogenesis via elaboration of the relationship between chemotherapeutic drugs and the redox system. It is our belief that this overview of the intestinal redox system and its role in CIM pathogenesis will greatly enhance research direction and improve CIM management in the future.

Effects of Peroxiredoxin 6 and Its Mutants on the Isoproterenol Induced Myocardial Injury in H9C2 Cells and Rats

Background

Peroxiredoxin 6 (PRDX6) is an important antioxidant enzyme, with a potential application value in the treatment of diseases caused by oxidative damage.

Methods

PRDX6 and a mutant (mPRDX6) were heterologously expressed by using an E.coli expression system and purified by Ni-affinity chromatography. Isoproterenol (ISO) was used to induce a myocardial cell injury model and an animal myocardial injury model. After the treatment with PRDX6 and mPRDX6, the proliferation activity of H9C2 cells was detected by Cell Counting Kit-8 (CCK8) method; the apoptosis was evaluated by flow cytometry, and the histological changes of myocardial cells were observed by hematoxylin and eosin (H&E) staining, the levels of catalase (CAT), glutathione peroxidase (GPX), malondialdehyde (MDA), and superoxide dismutase (SOD) in ISO-treated H9C2 cells as well as in the heart tissue and serum of rats treated with ISO were detected, and the expression levels of Bax, Bcl-2 and peroxisome proliferators-activated receptors-γ (PPAR-γ) proteins were detected by Western blot.

Results

PRDX6 and mPRDX6 were successfully expressed and purified. The results of efficacy study showed that the mutant mPRDX6, in which the phospholipaseA2 (PLA2) activity of PRDX6 was deleted by site directed mutation, had a better protective effect against the myocardial injury than PRDX6. CCK8 results showed that compared with that in ISO group, the proliferation activity of H9C2 cells was significantly enhanced (P < 0.01), the apoptosis rate was significantly decreased (P < 0.01), and the fluorescence intensity of reactive oxygen species (ROS) was significantly decreased (P < 0.01) in mPRDX6 group. The results of H&E staining showed that the myocardial injury was alleviated to a certain extent in mPRDX6 group. Compared with those in ISO group, the activities of CAT, GPX, and SOD in H9C2 cells and the heart tissue and serum of rats were significantly increased (P < 0.05), while the contents of MDA were significantly decreased (P < 0.05). Western blot analysis showed that the expression level of Bcl-2 in H9C2 cells was significantly decreased (P < 0.01), and that of Bax and PPAR-γ was significantly increased (P < 0.05).

Conclusion

mPRDX6 has a protective effect against the myocardial injury induced by ISO, and the mechanism may be related to its antioxidation. This study may provide a theoretical basis for the research and development of drugs used for the treatment of myocardial injury.

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.

Intestinal ischemic reperfusion injury: Recommended rats model and comprehensive review for protective strategies

Intestinal ischemic reperfusion injury (IIRI) is a life-threatening condition with high morbidity and mortality in the clinic. IIRI was induced by intestinal ischemic diseases such as, small bowel transplantation, aortic aneurysm surgery, and strangulated hernias. Although related mechanisms have not been fully elucidated, during the last decade, researches have demonstrated that many factors are crucial in the pathological process, including oxidative stress (OS), epithelial barrier function disorder, and so on. Rats model, as the most applied animal IIRI model, provides specific targets for researches and therapeutic strategies. Moreover, various treatment strategies such as, anti-oxidative stress, anti-apoptosis, and anti-inflammation, have shown promising effects in alleviating IIRI. However, current researches cannot solve the clinical problems of IIRI, and specific treatment strategies are still needed to be exploited. This review focuses on a recommended experimental IIRI rat model and understanding of the involved mechanisms such as, OS, gut bacteria translocation, apoptosis, and necroptosis, aim at providing novel ideas for therapeutic strategies of IIRI.

Emerging roles of microRNAs in intestinal ischemia/reperfusion-induced injury: a review

Intestinal ischemia/reperfusion (II/R) injury is a serious pathological phenomenon in underlying hemorrhagic shock, trauma, strangulated intestinal obstruction, and acute mesenteric ischemia which associated with high morbidity and mortality. MicroRNAs (miRNAs, miRs) are endogenous non-coding RNAs that regulate post-transcriptionally target mRNA translation via degrading it and/or suppressing protein synthesis. This review discusses on the role of some miRNAs in underlying II/R injury. Some of these miRNAs can have protective action through agomiR or specific antagomiR, and others can have destructive effects in the basal level of II/R insult. Based on these literature reviews, II/R injury affects several miRNAs and their specific target genes. Some miRNAs upregulate under condition of II/R injury, and multiple miRNAs downregulate following II/R damage. Data of this review have been collected from the scientific articles published in databases such as Science Direct, Scopus, PubMed, Web of Science, and Scientific Information Database from 2000 to 2020. It is shown a correlation between changes in the expression of miRNAs and autophagy, inflammation, oxidative stress, apoptosis, and epithelial barrier function. Taken together, agomiR or antagomiR of some miRNAs can be considered as one new target for the research and development of innovative drugs to the prevention or treatment of II/R damage.

Brief topical and intraluminal use of Carolina rinse solution does not attenuate experimental ischemia and reperfusion injury in rabbit jejunum

ABSTRACT Fifteen New Zealand adult rabbits were randomly allocated into three groups: Sham-operated (group A), Ischemia and Reperfusion (group B) and Carolina Rinse Solution (CRS) (group C). Groups B and C were subjected to one hour of ischemia and two hours of reperfusion. In group C, ten minutes before reperfusion, the bowel lumen was filled with CRS, and the segment immersed in CRS. Necrosis and loss of integrity of the villi were visible in groups B and C. Edema of the submucosa and circular muscle was observed in all groups. Hemorrhage was observed in different layers for groups B and C, but group C showed more severe hemorrhage in different layers during reperfusion. All groups showed polymorphonuclear leukocyte infiltration on the base of the mucosa, submucosa, and longitudinal muscle, in addition to polymorphonuclear leukocytes margination in the mucosal and submucosal vessels. Necrosis of enterocytes, muscles, crypts of Lieberkühn and myenteric plexus was observed in groups B and C during reperfusion. Topical and intraluminal Carolina Rinse Solution did not attenuate the effects of ischemia and reperfusion in the small intestine of rabbits.

Comparative Study of Protective Action of Exogenous 2-Cys Peroxiredoxins (Prx1 and Prx2) Under Renal Ischemia-Reperfusion Injury

The pathogenesis of ischemia-reperfusion (I/R) injuries is based on oxidative stress caused by a sharp increase in the concentration of free radicals, reactive oxygen species (ROS) and secondary products of free radical oxidation of biological macromolecules during reperfusion. Application of exogenous antioxidants lowers the level of ROS in the affected tissues, suppresses or adjusts the course of oxidative stress, thereby substantially reducing the severity of I/R injury. We believe that the use of antioxidant enzymes may be the most promising line of effort since they possess higher efficiency than low molecular weight antioxidants. Among antioxidant enzymes, of great interest are peroxiredoxins (Prx1–6) which reduce a wide range of organic and inorganic peroxide substrates. In an animal model of bilateral I/R injury of kidneys (using histological, biochemical, and molecular biological methods) it was shown that intravenous administration of recombinant typical 2-Cys peroxiredoxins (Prx1 and Prx2) effectively reduces the severity of I/R damage, contributing to the normalization of the structural and functional state of the kidneys and an almost 2-fold increase in the survival of experimental animals. The use of recombinant Prx1 or Prx2 can be an efficient approach for the prevention and treatment of renal I/R injury.

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.

In vivo validation of a miniaturized electrochemical oxygen sensor for measuring intestinal oxygen tension

Recent advances in the fields of electronics and microfabrication techniques have led to the development of implantable medical devices for use within the field of precision medicine. Monitoring visceral surface tissue O₂ tension (PTo2) by means of an implantable sensor is potentially useful in many clinical situations, including the perioperative management of patients undergoing intestinal resection and anastomosis. This concept could provide a means by which treatment could be tailored to individual patients. This study describes the in vivo validation of a novel, miniaturized electrochemical O₂ sensor to provide real-time data on intestinal PTo2. A single O₂ sensor was placed onto the serosal surface of the small intestine of anesthetized rats that were exposed to ischemic (superior mesenteric artery occlusion) and hypoxemic (alterations in inspired fractional O₂ concentrations) insults. Control experiments demonstrated that the sensors can function and remain stable in an in vivo environment. Intestinal PTo2 decreased following superior mesenteric artery occlusion and with reductions in inspired O₂ concentrations. These results were reversible after reinstating blood flow or by increasing inspired O₂ concentrations. We have successfully developed an anesthetized rat intestinal ischemic and hypoxic model for validation of a miniaturized O₂ sensor to provide real-time measurement of intestinal PTo2. Our results support further validation of the sensors in physiological conditions using a large animal model to provide evidence of their use in clinical applications where monitoring visceral surface tissue O₂ tension is important.NEW & NOTEWORTHY This is the first report of real-time continuous measurements of intestinal oxygen tension made using a microfabricated O₂ sensor. Using a developed rodent model, we have validated this sensor's ability to accurately measure dynamic and reversible changes in intestinal oxygenation that occur through ischemic and hypoxemic insults. Continuous monitoring of local intestinal oxygenation could have value in the postoperative monitoring of patients having undergone intestinal surgery.

Gardenia Decoction Prevent Intestinal Mucosal Injury by Inhibiting Pro-inflammatory Cytokines and NF-κB Signaling

Gardenia jasminoides Ellis, which belongs to the Rubiaceae family, is a widely used traditional Chinese medicine. Although effect of Gardenia jasminoides Ellis has been widely reported, its anti-inflammatory role in intestinal mucosal injury induced by LPS remains unclear. In the present study, we investigated the effects of decoction extracted from Gardenia jasminoides on the morphology and intestinal antioxidant capacity of duodenum induced by LPS in mice. Further analysis was carried out in the expression of inflammatory and anti-inflammatory cytokines. Nuclear factor-kappa B (NF-κB) was determined by Western blot. Gardenia jasminoides water extract was qualitative analyzed by high-performance liquid chromatography coupled with electro spray ionization quadrupole time-of-flight mass spectrometry. The results showed that Gardenia decoction markedly inhibited the LPS-induced Tumor necrosis factor (TNF)-α, Interleukin (IL)-6, IL-8, and IL-1 production. It was also observed that Gardenia decoction attenuated duodenum histopathology changes in the mouse models. Furthermore, Gardenia decoction inhibited the expression of NF-κB in LPS stimulated mouse duodenum. These results suggest that Gardenia decoction exerts an anti-inflammatory and antioxidant property by up-regulating the activities of the total antioxidant capacity (T-AOC), the total superoxide dismutase (T-SOD), and glutathione peroxidase (GSH-Px). Gardenia decoction is highly effective in inhibiting intestinal mucosal damage and may be a promising potential therapeutic reagent for intestinal mucosal damage treatment.

Peroxiredoxin6 in Endothelial Signaling

Peroxiredoxins (Prdx) are a ubiquitous family of highly conserved antioxidant enzymes with a cysteine residue that participate in the reduction of peroxides. This family comprises members Prdx1–6, of which Peroxiredoxin 6 (Prdx6) is unique in that it is multifunctional with the ability to neutralize peroxides (peroxidase activity) and to produce reactive oxygen species (ROS) via its phospholipase (PLA₂) activity that drives assembly of NADPH oxidase (NOX2). From the crystal structure, a C47 residue is responsible for peroxidase activity while a catalytic triad (S32, H26, and D140) has been identified as the active site for its PLA₂ activity. This paradox of being an antioxidant as well as an oxidant generator implies that Prdx6 is a regulator of cellular redox equilibrium (graphical abstract). It also indicates that a fine-tuned regulation of Prdx6 expression and activity is crucial to cellular homeostasis. This is specifically important in the endothelium, where ROS production and signaling are critical players in inflammation, injury, and repair, that collectively signal the onset of vascular diseases. Here we review the role of Prdx6 as a regulator of redox signaling, specifically in the endothelium and in mediating various pathologies.

Radioprotective Role of Peroxiredoxin 6

Peroxiredoxin 6 (Prdx6) is a member of an evolutionary ancient family of peroxidase enzymes with diverse functions in the cell. Prdx6 is an important enzymatic antioxidant. It reduces a wide range of peroxide substrates in the cell, thus playing a leading role in the maintenance of the redox homeostasis in mammalian cells. Beside peroxidase activity, Prdx6 has been shown to possess an activity of phospholipase A2, an enzyme playing an important role in membrane phospholipid metabolism. Moreover, Prdx6 takes part in intercellular and intracellular signal transduction due to its peroxidase and phospholipase activity, thus facilitating the initiation of regenerative processes in the cell, suppression of apoptosis, and activation of cell proliferation. Being an effective and important antioxidant enzyme, Prdx6 plays an essential role in neutralizing oxidative stress caused by various factors, including action of ionizing radiation. Endogenous Prdx6 has been shown to possess a significant radioprotective potential in cellular and animal models. Moreover, intravenous infusion of recombinant Prdx6 to animals before irradiation at lethal or sublethal doses has shown its high radioprotective effect. Exogenous Prdx6 effectively alleviates the severeness of radiation lesions, providing normalization of the functional state of radiosensitive organs and tissues, and leads to a significant elevation of the survival rate of animals. Prdx6 can be considered as a potent and promising radioprotective agent for reducing the pathological effect of ionizing radiation on mammalian organisms. The radioprotective properties and mechanisms of radioprotective action of Prdx6 are discussed in the current review.

Peroxiredoxins in inflammatory liver diseases and ischemic/reperfusion injury in liver transplantation

Peroxiredoxins (Prxs) belong to the superfamily of thiol-dependent peroxidases, and remove reactive oxygen species (ROS) and other oxidative stress products. The expression and activity of Prxs can be substantially affected by stimuli from the microenvironment, and in turn regulate cytokine secretion in the context of inflammation in both peroxidase-dependent and -independent pathways. Prxs translocate to mitochondria and are hyperoxidized during acute liver damage, and attenuate intracellular ROS accumulation through their peroxidase activity. In particularly, Prx1 modulates the microenvironment in liver injuries by reducing adhesion molecule expression in vascular endothelial cells and inhibiting the inflammatory response and adhesion of macrophages. Prxs have potent prosurvival effects against ROS in ischemic/reperfusion (I/R) injury, but Prxs released from necrotic cells increase secretion of inflammatory cytokines by macrophages through TLR2 and 4 activation, which promotes cell death. Prxs can be used as biomarkers to evaluate I/R injury and predict graft survival in liver transplantation. Prxs are modulated in various types of chronic hepatitis and hepatosteatosis, and mediate disease progression. Alcohol administration increases oxidization and inactivation of Prxs in mice because of oxidative stress. In conclusion, Prxs are essential mediators and biomarkers in inflammatory liver diseases and I/R injury.

Europium-Doped Cerium Oxide Nanoparticles Limit Reactive Oxygen Species Formation and Ameliorate Intestinal Ischemia-Reperfusion Injury

Accumulating evidence suggests that ischemia-reperfusion-induced injury is associated with the formation of reactive oxygen species (ROS). This study demonstrates the therapeutic effectiveness of novel europium-doped cerium oxide nanoparticles (Eu-doped Ceria NPs) as ROS scavengers in a mouse model of intestinal ischemia-reperfusion-induced injury. An increased production of superoxide radicals is detected in the intestine throughout the ischemia stage and again after initiating reperfusion. These changes in superoxide radical formation are associated with the induction of inflammatory cytokines in the intestine. This study further shows that Eu-Ceria NPs exhibit superoxide scavenging activity in vitro. Importantly, administration of Eu-Ceria NPs into the intestinal lumen during the onset of ischemia effectively blocks superoxide accumulation, reduces the expression of IL-1b, and ameliorates the intestinal pathology. These results suggest that early increased production of ROS during the ischemia-reperfusion promotes intestinal pathology and that mucosal delivery of Eu-Ceria NPs may be a potential therapeutic approach to block ROS accumulation and ameliorate the severity of intestinal disease.

Simvastatin nanoparticles attenuated intestinal ischemia/reperfusion injury by downregulating BMP4/COX-2 pathway in rats

The purpose of the research was to explore the therapeutic action of simvastatin-loaded poly(ethylene glycol)-b-poly(gamma-benzyl l-glutamate) (PEG-b-PBLG₅₀) on intestinal ischemia/reperfusion injury (II/RI) through downregulating bone morphogenetic protein 4 (BMP4)/cyclooxygenase-2 (COX-2) pathway as compared to free simvastatin (Sim). Sprague Dawley rats were preconditioned with 20 mg/kg Sim or simvastatin/PEG-b-PBLG₅₀ (Sim/P) compounds, and then subjected to 45 min of ischemia and 1 h of reperfusion. The blood and small intestines were collected, serum levels of interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-α, and nitric oxide (NO) were checked, and the dry/wet intestine ratios, superoxide dismutase activity, myeloperoxidase content, reactive oxygen species, endothelial nitric oxide synthase, protein 47 kDa phagocyte oxidase (p47phox), BMP4, COX-2, and p38 mitogen-activated protein kinase (p38MAPK) expressions were measured in intestinal tissues. Both Sim and Sim/P pretreatment reduced intestinal oxidative damnification, restricted inflammatory harm, and downregulated the BMP4 and COX-2 expressions as compared to II/RI groups, while Sim/P remarkably improved this effect.