Role of the oxidative stress index, myeloperoxidase, catalase activity for cardiac allograft vasculopathy in heart transplant recipients

Dynamic Thiol-Disulfide Homeostasis in Lung Transplant Recipients

OBJECTIVES

In this study, we investigated dynamic thiol-disulfide homeostasis as a new indicator of oxidative stress in lung transplant recipients. In addition, we compared dynamic thiol-disulfide homeostasis parameters according to transplant indication and time after transplant.

MATERIALS AND METHODS

This study had a single-center, observational, randomized design. In terms of transplant indications, lung transplant recipients were grouped as chronic obstructive pulmonary disease, interstitial lung disease, bronchiectasis, and other indications. To make comparisons based on time after transplant, lung transplant recipients were categorized into the following groups: >6 and ≤24 months, >24 and ≤48 months, >48 and ≤72 months, and >72 months. A fully automated spectrophotometric technique was used to measure dynamic thiol-disulfide homeostasis in fasting blood samples.

RESULTS

Our study included 34 lung transplant recipients and 36 healthy volunteers. Native thiol (P = .005) and total thiol levels (P = .06) were lower in lung transplant recipients. Disulfide levels were similar. Disulfide-to-native thiol (P = .027) and disulfide-to-total thiol ratios (P = .027) were significantly higher in lung transplant recipients. Native thiol-to-total thiol ratios were lower in lung transplant recipients (P = .027). When we examined patients according to transplant indication, no statistically significant differences were found in dynamic thiol-disulfide homeostasis parameters, except for total thiol and disulfide levels. We also found no significant differences when we examined dynamic thiol-disulfide homeostasis parameters according to time after transplant.

CONCLUSIONS

Thiol-related antioxidant activity is significantly reduced after lung transplant, regardless of indication and transplant time. Ensuring oxidative balance in lung transplant recipients with an antioxidant supplement regimen can prevent damage from oxidative stress.

PPAR-γ activation promotes xenogenic bioroot regeneration by attenuating the xenograft induced-oxidative stress

Xenogenic organ transplantation has been considered the most promising strategy in providing possible substitutes with the physiological function of the failing organs as well as solving the problem of insufficient donor sources. However, the xenograft, suffered from immune rejection and ischemia-reperfusion injury (IRI), causes massive reactive oxygen species (ROS) expression and the subsequent cell apoptosis, leading to the xenograft failure. Our previous study found a positive role of PPAR-γ in anti-inflammation through its immunomodulation effects, which inspires us to apply PPAR-γ agonist rosiglitazone (RSG) to address survival issue of xenograft with the potential to eliminate the excessive ROS. In this study, xenogenic bioroot was constructed by wrapping the dental follicle cells (DFC) with porcine extracellular matrix (pECM). The hydrogen peroxide (H₂O₂)-induced DFC was pretreated with RSG to observe its protection on the damaged biological function. Immunoflourescence staining and transmission electron microscope were used to detect the intracellular ROS level. SD rat orthotopic transplantation model and superoxide dismutase 1 (SOD1) knockout mice subcutaneous transplantation model were applied to explore the regenerative outcome of the xenograft. It showed that RSG pretreatment significantly reduced the adverse effects of H₂O₂ on DFC with decreased intracellular ROS expression and alleviated mitochondrial damage. In vivo results confirmed RSG administration substantially enhanced the host's antioxidant capacity with reduced osteoclasts formation and increased periodontal ligament-like tissue regeneration efficiency, maximumly maintaining the xenograft function. We considered that RSG preconditioning could preserve the biological properties of the transplanted stem cells under oxidative stress (OS) microenvironment and promote organ regeneration by attenuating the inflammatory reaction and OS injury.

Investigation of the Role of Oxidative Stress and Factors Associated with Cardiac Allograft Vasculopathy in Patients after Heart Transplantation

Oxidative stress is defined as an imbalance between the production of free radicals and their elimination by the antioxidant defense system. However, the role of oxidative stress in cardiac allograft vasculopathy (CAV) has not been fully understood. Therefore, this study is aimed at determining the role of oxidative-antioxidative balance disturbances in patients after HT. Furthermore, we sought to analyze factors associated with the presence of CAV, with particular emphasis placed on oxidative stress markers. The study analyzed data of 194 consecutive patients after HT who underwent routine visits in the Transplantation Clinic between 2015 and 2016. Total oxidant status (TOS) and total antioxidant capacity (TAC) were measured by the method described by Erel. The oxidative stress index (OSI) was defined as the ratio of the TOS to TAC levels. Patients' mean age was 55.4 ± 15.0 years, and 73.4% were men. The frequency of CAV was 50%. The area under the receiver operating characteristic curves indicated a good discriminatory power of TAC and TOS (0.8940 (0.8515-0.9365); 0.8620 (0.8126-0.9114), respectively) as well as excellent discriminatory power of OSI (0.9530 (0.9279-0.9781)) for CAV detection. Multivariate analysis of the Cox proportional hazard model confirmed that OSI (hazard ratio (HR) = 1.294 (1.204-1.391), p < 0.0001), age (HR = 1.023 (1.006-1.041), p = 0.0091), and high-sensitivity C-reactive protein (HR = 1.049 (1.016-1.083), p = 0.0151) were independently associated with CAV presence. In conclusion, TAC and TOS had a good discriminatory power and OSI had excellent strength for detecting CAV. The independent factors of CAV were higher OSI and CRP levels, as well as older recipient age.

Myeloperoxidase As a Multifaceted Target for Cardiovascular Protection

Significance: Myeloperoxidase (MPO) is a heme peroxidase that is primarily expressed by neutrophils. It has the capacity to generate several reactive species, essential for its inherent antimicrobial activity and innate host defense. Dysregulated MPO release, however, can lead to tissue damage, as seen in several diseases. Increased MPO levels in circulation are therefore widely associated with conditions of increased oxidative stress and inflammation. Recent Advances: Several studies have shown a strong correlation between MPO and cardiovascular disease (CVD), through which elevated levels of circulating MPO are linked to poor prognosis with increased risk of CVD-related mortality. Accordingly, circulating MPO is considered a "high-risk" biomarker for patients with acute coronary syndrome, atherosclerosis, heart failure, hypertension, and stroke, thereby implicating MPO as a multifaceted target for cardiovascular protection. Consistently, recent studies that target MPO in animal models of CVD have demonstrated favorable outcomes with regard to disease progression. Critical Issues: Although most of these studies have established a critical link between circulating MPO and worsening cardiac outcomes, the mechanisms by which MPO exerts its detrimental effects in CVD remain unclear. Future Directions: Elucidating the mechanisms by which elevated MPO leads to poor prognosis and, conversely, investigating the beneficial effects of therapeutic MPO inhibition on alleviating disease phenotype will facilitate future MPO-targeted clinical trials for improving CVD-related outcomes.

In vivo hepatotoxicity of chemically modified nanocellulose in rats

Chemical modification of cellulose is currently attracting attention as researchers attempt to take advantage of the abundance of hydroxyl groups on its surface to introduce extra biological functionality. However, the possible deleterious effect of exposure to functionalized nanocellulose (CSN) remains a concern. Therefore, this study aims to explore the potential mechanisms of hepatotoxicity of CSN modified with oxalate ester (NCD) in rats. A 7-day repeated oral toxicity study of NCD at the doses of 50 and 100 mg kg−1body weight was conducted, and plasma and liver tissue samples were assayed using biochemical analysis, liver histopathology, and protein expression. NCD, at both doses, did not significantly ( p > 0.05) alter the relative weight of liver, alkaline phosphatase activity, and lipid peroxidation levels of the animals. However, NCD at the dose of 100 mg kg−1body weight significantly elevated aspartate aminotransferase, alanine aminotransferase, and myeloperoxidase activities. NCD also enhanced the immunohistochemical expression of inducible nitric oxide synthase and Bcl-2-associated X protein in the liver of rats. Histological observations revealed necrosis and severe cellular infiltration at the high-dose treatment. Our study provides an experimental basis for the safe application of NCDs.

Sodium Sulfite Exacerbates Allograft Vasculopathy and Affects Tryptophan Breakdown in Murine Heterotopic Aortic Transplantation

Graft vasculopathy is the main feature of chronic rejection in organ transplantation, with oxidative stress being a major trigger. Inflammation-associated prooxidant processes may be controlled by antioxidants; however, interference with redox-regulated mechanisms is a complex endeavor. An essential feature of the cellular immune response is the acceleration of tryptophan (Trp) breakdown, leading to the formation of several bioactive catabolites. Long-term activation of this immunobiochemical pathway contributes to the establishment of a tolerogenic environment, thereby supporting allograft survival. Herein, the impact of the antioxidant sodium sulfite on the development of graft vasculopathy was assessed in murine aortic transplantation. Allogeneic (BALB/c to C57BL/6) heterotopic murine aortic transplantations were performed. Animals were left untreated or were treated with 10 μl of 0.1 M, of 0.01 M sodium sulfite, or of 0.1 M sodium sulfate, intraperitoneally once/day, until postoperative day (POD) 100. Grafts were assessed by histology, immunohistochemistry, and adhesion molecule gene expression. Serum concentrations of tryptophan and its catabolite kynurenine (Kyn) were measured. On day 100, graft vasculopathy was significantly increased upon treatment with 0.1 M sodium sulfite, compared to allogeneic untreated controls (p = 0.004), which correlated with a significant increase of α-smooth-muscle-actin, Vcam-1, and P-selectin. Serum Kyn concentrations increased in the allogeneic control group over time (p < 0.05, POD ≥ 50), while low-dose sodium sulfite treatment (0.01 M) treatment resulted in a decrease in Kyn levels over time (p < 0.05, POD ≥ 10), compared to the respective baselines (p < 0.05). Longitudinal analysis of serum metabolite concentrations in the different treatment groups further identified an overall effect of sodium sulfite on Kyn concentrations. Antioxidative treatment may result in ambivalent consequences. Our data reveal that an excess of antioxidants like sodium sulfite can aggravate allograft vasculopathy, which further highlights the challenges associated with interventions that interfere with the complex interplay of redox-regulated inflammatory processes.