Extracellular superoxide dismutase is necessary to maintain renal blood flow during sepsis development

Understanding mechanisms of antioxidant action in health and disease

Several different reactive oxygen species (ROS) are generated in vivo. They have roles in the development of certain human diseases whilst also performing physiological functions. ROS are counterbalanced by an antioxidant defence network, which functions to modulate ROS levels to allow their physiological roles whilst minimizing the oxidative damage they cause that can contribute to disease development. This Review describes the mechanisms of action of antioxidants synthesized in vivo, antioxidants derived from the human diet and synthetic antioxidants developed as therapeutic agents, with a focus on the gaps in our current knowledge and the approaches needed to close them. The Review also explores the reasons behind the successes and failures of antioxidants in treating or preventing human disease. Antioxidants may have special roles in the gastrointestinal tract, and many lifestyle features known to promote health (especially diet, exercise and the control of blood glucose and cholesterol levels) may be acting, at least in part, by antioxidant mechanisms. Certain reactive sulfur species may be important antioxidants but more accurate determinations of their concentrations in vivo are needed to help assess their contributions.

Molecular Mechanisms of Oxidative Stress in Acute Kidney Injury: Targeting the Loci by Resveratrol

Reactive oxygen species are a group of cellular molecules that stand as double-edged swords, their good and bad being discriminated by a precise balance. Several metabolic reactions in the biological system generate these molecules that interact with cellular atoms to regulate functions ranging from cell homeostasis to cell death. A prooxidative state of the cell concomitant with decreased clearance of such molecules leads to oxidative stress, which contributes as a prime pathophysiological mechanism in various diseases including renal disorders, such as acute kidney injury. However, targeting the generation of oxidative stress in renal disorders by an antioxidant, resveratrol, is gaining considerable therapeutic importance and is known to improve the condition in preclinical studies. This review aims to discuss molecular mechanisms of oxidative stress in acute kidney injury and its amelioration by resveratrol. The major sources of data were PubMed and Google Scholar, with studies from the last five years primarily included, with significant earlier data also considered. Mitochondrial dysfunction, various enzymatic reactions, and protein misfolding are the major sources of reactive oxygen species in acute kidney injury, and interrupting these loci of generation or intersection with other cellular components by resveratrol can mitigate the severity of the condition.

Low Antioxidant Enzyme Levels and Oxidative Stress in Laryngopharyngeal Reflux (LPR) Patients

OBJECTIVE

Laryngopharyngeal reflux disease (LPR) is a characterized by symptoms different from gastroesophageal reflux disease (GERD). LPR can causes chronic mucosal inflammation which may lead to an increase in cytokine production, and a systemic decrease in antioxidant enzyme levels. Our aim in this study is to evaluate antioxidant enzyme levels in patients with LPR.

METHODS

Reflux Symptom Index (RSI) questionnaire, extraesophageal symptom questionnaire which is included in RSI and Reflux Finding Score (RFS) evaluation with 70° rigid laryngoscope were performed to patients who applied to the otolaryngology clinic with a typical LPR complaint, and 60 patients who had an RSI score above 13 and an RFS score above 7 were included in the study. Thirty people consisting of healthy volunteers were included in the control group. Antioxidant enzyme SOD, GSH-Px and CAT levels were measured in the blood serum of the patients and compared with the control group. Results obtained from biochemical tests were expressed as mean ± SE. Descriptive statistical methods (mean ± standard error) were used for the independent t test for the control and study group. P < 0.05 was considered statistically significant.

RESULTS

In the LPR group, 28 (46%) were women, 32 (53%) were men, and age range was 21-60, average age was 36.45 ± 1.147.There was no significant difference between LPR and control group in terms of age, gender and Body Mass Index (BMI). In the LPR group, the lowest score for RSI was 14 and the highest score was 39. The average RSI was 23.67. RFS ranges from 8-22. The mean RFS was 13.50. A highly significant statistical correlation was observed between RSI and total RFS (P < 0.001). There was a significant difference between the antioxidant enzyme levels of the control group and the LPR group. Antioxidant enzyme levels of the control group were SOD 274.10 ± 26.836 U / L, GSH-Px 174.20 ± 20.699 µU / mL and CAT 42.2898 ± 20.699 KU / L. Antioxidant enzyme level results of the LPR group were SOD 147 ± 14.022 U / L (P < 0.01), GSH-Px 88.28 ± 9.113 µU / mL (P < 0.01) and CAT 12.67 ± 0.799 KU / L (P < 0.001). The RSI results ranges from 4 to 39 and the RFS from 8 to 22. Antioxidant enzyme levels demonstrated fairly consistent reliability with individual variables from both RFS and RFS. There was also a highly significant statistical correlation between RSI and RFS.

CONCLUSION

We found that the antioxidant enzymes SOD, GPX and catalase enzyme levels were significantly lower in LPR patients. Treatment modalities to reduce oxidative stress (OS) in LPR should be investigated.

Moderate exercise-induced dynamics on key sepsis-associated signaling pathways in the liver

BACKGROUND

There is a clear relationship between quantitative measures of fitness (e.g., VO₂ max) and outcomes after surgical procedures. Whether or not fitness is a modifiable risk factor and what underlying biological processes drive these changes are not known. The purpose of this study was to evaluate the moderate exercise training effect on sepsis outcomes (survival) as well as the hepatic biological response. We chose to study the liver because it plays a central role in the regulation of immune defense during systemic infection and receives blood flow directly from the origin of infection (gut) in the cecal ligation and puncture (CLP) model.

METHODS

We randomized 50 male (♂) and female (♀) Sprague-Dawley rats (10 weeks, 340 g) to 3 weeks of treadmill exercise training, performed CLP to induce polymicrobial "sepsis," and monitored survival for five days (Part I). In parallel (Part II), we randomized 60 rats to control/sedentary (G1), exercise (G2), exercise + sham surgery (G3), CLP/sepsis (G4), exercise + CLP [12 h (G5) and 24 h (G6)], euthanized at 12 or 24 h, and explored molecular pathways related to exercise and sepsis survival in hepatic tissue and serum.

RESULTS

Three weeks of exercise training significantly increased rat survival following CLP (polymicrobial sepsis). CLP increased inflammatory markers (e.g., TNF-a, IL-6), which were attenuated by exercise. Sepsis suppressed the SOD and Nrf2 expression, and exercise before sepsis restored SOD and Nrf2 levels near the baseline. CLP led to increased HIF1a expression and oxidative and nitrosative stress, the latter of which were attenuated by exercise. Haptoglobin expression levels were increased in CLP animals, which was significantly amplified in exercise + CLP (24 h) rats.

CONCLUSIONS

Moderate exercise training (3 weeks) increased the survival in rats exposed to CLP, which was associated with less inflammation, less oxidative and nitrosative stress, and activation of antioxidant defense pathways.

Postbiotics as potential new therapeutic agents for sepsis

Sepsis is the main cause of death in critically ill patients and gut microbiota dysbiosis plays a crucial role in sepsis. On the one hand, sepsis leads to the destruction of gut microbiota and induces and aggravates terminal organ dysfunction. On the other hand, the activation of pathogenic gut flora and the reduction in beneficial microbial products increase the susceptibility of the host to sepsis. Although probiotics or fecal microbiota transplantation preserve gut barrier function on multiple levels, their efficacy in sepsis with intestinal microbiota disruptions remains uncertain. Postbiotics consist of inactivated microbial cells or cell components. They possess antimicrobial, immunomodulatory, antioxidant and antiproliferative activities. Microbiota-targeted therapy strategies, such as postbiotics, may reduce the incidence of sepsis and improve the prognosis of patients with sepsis by regulating gut microbial metabolites, improving intestinal barrier integrity and changing the composition of the gut microbiota. They offer a variety of mechanisms and might even be superior to more conventional 'biotics' such as probiotics and prebiotics. In this review, we present an overview of the concept of postbiotics and summarize what is currently known about postbiotics and their prospective utility in sepsis therapy. Overall, postbiotics show promise as a viable adjunctive therapy option for sepsis.

Bioinspired copper single-atom nanozyme as a superoxide dismutase-like antioxidant for sepsis treatment

Sepsis is a systemic inflammatory response syndrome with high morbidity and mortality mediated by infection-caused oxidative stress. Early antioxidant intervention by removing excessively produced reactive oxygen and nitrogen species (RONS) is beneficial to the prevention and treatment of sepsis. However, traditional antioxidants have failed to improve patient outcomes due to insufficient activity and sustainability. Herein, by mimicking the electronic and structural characteristics of natural Cu-only superoxide dismutase (SOD5), a single-atom nanozyme (SAzyme) featuring coordinately unsaturated and atomically dispersed Cu-N4 site was synthesized for effective sepsis treatment. The de novo-designed Cu-SAzyme exhibits a superior SOD-like activity to efficiently eliminate O2 •-, which is the source of multiple RONS, thus blocking the free radical chain reaction and subsequent inflammatory response in the early stage of sepsis. Moreover, the Cu-SAzyme effectively harnessed systemic inflammation and multi-organ injuries in sepsis animal models. These findings indicate that the developed Cu-SAzyme possesses great potential as therapeutic nanomedicines for the treatment of sepsis.

The role of nitric oxide in sepsis-associated kidney injury

Sepsis is one of the leading causes of acute kidney injury (AKI), and several mechanisms including microcirculatory alterations, oxidative stress, and endothelial cell dysfunction are involved. Nitric oxide (NO) is one of the common elements to all these mechanisms. Although all three nitric oxide synthase (NOS) isoforms are constitutively expressed within the kidneys, they contribute in different ways to nitrergic signaling. While the endothelial (eNOS) and neuronal (nNOS) isoforms are likely to be the main sources of NO under basal conditions and participate in the regulation of renal hemodynamics, the inducible isoform (iNOS) is dramatically increased in conditions such as sepsis. The overexpression of iNOS in the renal cortex causes a shunting of blood to this region, with consequent medullary ischemia in sepsis. Differences in the vascular reactivity among different vascular beds may also help to explain renal failure in this condition. While most of the vessels present vasoplegia and do not respond to vasoconstrictors, renal microcirculation behaves differently from nonrenal vascular beds, displaying similar constrictor responses in control and septic conditions. The selective inhibition of iNOS, without affecting other isoforms, has been described as the ideal scenario. However, iNOS is also constitutively expressed in the kidneys and the NO produced by this isoform is important for immune defense. In this sense, instead of a direct iNOS inhibition, targeting the NO effectors such as guanylate cyclase, potassium channels, peroxynitrite, and S-nitrosothiols, may be a more interesting approach in sepsis-AKI and further investigation is warranted.

The Effect of Superoxide Dismutase on Inhibition of Acute Kidney Injury Induced by Sepsis Based on Kidney Tissue Histology and Murine Sepsis Score

Sepsis is one of the leading causes contributing to the incidence of acute kidney injury (AKI). Oxidative stress can be used as the main approach against sepsis-induced AKI. One of the primary antioxidants that plays a role in warding off oxidative stress is superoxide dismutase (SOD). This research aimed to observe the effect of antioxidant SOD in inhibiting sepsis in AKI based on kidney tissue histopathology. The research method was an experimental laboratory with a post-test-only control group design. Twenty-five adult male rats aged 12–16 weeks, weighing between 200 and 250 g, were randomly divided into five groups: Group I, as a positive control, where rats were injected with lipopolysaccharides (LPS); Group II, as a negative control; Group III, as treatment 1, where rats were injected with LPS and administered orally with SOD (Glisodin®) 250 IU daily; Group IV, as treatment 2, where rats were injected with LPS and administered orally with SOD (Glisodin®) 500 IU daily; and Group V, as treatment 2, where rats were injected with LPS and administered orally with SOD (Glisodin®) 1000 IU daily. Rats were administered with SOD (Glisodin®) by oral gavage with a flexible feeding tube for 16 weeks, given once daily in the morning, and then injected with LPS of 10 mg/kg body weight. Glisodin SOD had a significant effect on murine sepsis score (MSS). MSS influenced the tubular injury score linearly. We conclude that the optimal dose of SOD at 1000 IU for inhibiting sepsis-induced AKI incidence is compared to SOD at a dose of 250 and 500 IU. The antioxidant effect of SOD can prevent sepsis-induced AKI with oxidative stress events.

Extracellular superoxide dismutase, a molecular transducer of health benefits of exercise

Extracellular superoxide dismutase (EcSOD) is the only extracellular scavenger of superoxide anion (O2.-) with unique binding capacity to cell surface and extracellular matrix through its heparin-binding domain. Enhanced EcSOD activity prevents oxidative stress and damage, which are fundamental in a variety of disease pathologies. In this review we will discuss the findings in humans and animal studies supporting the benefits of EcSOD induced by exercise training in reducing oxidative stress in various tissues. In particularly, we will highlight the importance of skeletal muscle EcSOD, which is induced by endurance exercise and redistributed through the circulation to the peripheral tissues, as a molecular transducer of exercise training to confer protection against oxidative stress and damage in various disease conditions.