Urea Memory: Transient Cell Exposure to Urea Causes Persistent Mitochondrial ROS Production and Endothelial Dysfunction

Oxidised rice bran oil induced oxidative stress and apoptosis in IPEC-J2 cells via the Nrf2 signalling pathway

Rice bran oil is a type of rice oil made by leaching or pressing during rice processing and has a high absorption rate after consumption. When oxidative rancidity occurs, it may cause oxidative stress (OS) and affect intestinal function. Meanwhile, the toxic effects of oxidised rice bran oil have been less well studied in pigs. Therefore, the IPEC-J2 cells model was chosen to explore the regulatory mechanisms of oxidised rice bran oil on OS and apoptosis. Oxidised rice bran oil extract treatment (OR) significantly decreased the viability of IPEC-J2 cells. The results showed that OR significantly elevated apoptosis and reactive oxygen species levels and promoted the expression of pro-apoptotic gene Caspase-3 messenger RNA levels. The activation of Nrf2 signalling pathway by OR decreased the cellular antioxidant capacity. This was further evidenced by the expression of kelch-like ECH-associated protein 1, heme oxygenase 1, NADH: quinone oxidoreductase 1, superoxide dismutase 2 and heat shock 70 kDa protein genes and proteins were all downregulated. In conclusion, our results suggested that oxidised rice bran oil induced damage in IPEC-J2 cells through the Nrf2 signalling pathway.

What is the role of the neutrophil extracellular traps in the cardiovascular disease burden associated with hemodialysis bioincompatibility?

Despite significant progress in dialysis modalities, intermittent renal replacement therapy remains an "unphysiological" treatment that imperfectly corrects uremic disorders and may lead to low-grade chronic inflammation, neutrophil activation, and oxidative stress due to repetitive blood/membrane interactions contributing to the "remaining uremic syndrome" and cardiovascular disease burden of hemodialysis patients. Understanding dialysis bioincompatibility pathways still remains a clinical and biochemical challenge. Indeed, surrogate biomarkers of inflammation including C-reactive protein could not discriminate between all components involved in these complex pathways. A few examples may serve to illustrate the case. Cytokine release during dialysis sessions may be underestimated due to their removal using high-flux dialysis or hemodiafiltration modalities. Complement activation is recognized as a key event of bioincompatibility. However, it appears as an early and transient event with anaphylatoxin level normalization at the end of the dialysis session. Complement activation is generally assumed to trigger leukocyte stimulation leading to proinflammatory mediators' secretion and oxidative burst. In addition to being part of the innate immune response involved in eliminating physically and enzymatically microbes, the formation of Neutrophil Extracellular Traps (NETs), known as NETosis, has been recently identified as a major harmful component in a wide range of pathologies associated with inflammatory processes. NETs result from the neutrophil degranulation induced by reactive oxygen species overproduction via NADPH oxidase and consist of modified chromatin decorated with serine proteases, elastase, bactericidal proteins, and myeloperoxidase (MPO) that produces hypochlorite anion. Currently, NETosis remains poorly investigated as a sensitive and integrated marker of bioincompatibility in dialysis. Only scarce data could be found in the literature. Oxidative burst and NADPH oxidase activation are well-known events in the bioincompatibility phenomenon. NET byproducts such as elastase, MPO, and circulating DNA have been reported to be increased in dialysis patients more specifically during dialysis sessions, and were identified as predictors of poor outcomes. As NETs and MPO could be taken up by endothelium, NETs could be considered as a vascular memory of intermittent bioincompatibility phenomenon. In this working hypothesis article, we summarized the puzzle pieces showing the involvement of NET formation during hemodialysis and postulated that NETosis may act as a disease modifier and may contribute to the comorbid burden associated with dialysis bioincompatibility.

The role of hepatic and renal functions in the development of retinopathy of prematurity: Is proteinuria a new risk factor?

PURPOSE

To investigate the association of hepatic and renal parameters with the development of retinopathy of prematurity (ROP) in premature infants with a gestational age ≤ 32 weeks.

METHODS

Medical records of 240 preterm infants were reviewed retrospectively, 85 of them were grouped as type 1, type 2 ROP, and control group. The 4th week hepatic and renal function test results of the groups, on the day of their first ROP examinations, were compared for the risk of development of ROP and the development of type 1 ROP.

RESULTS

In this study, 12, 35, and 38 infants were enrolled in the type 1, type 2 ROP, and control group, respectively. The average gestational age and birth weight were higher; however, the duration of oxygen treatment was lower in the control group (p < 0.001). The blood glucose level was significantly higher in the type 1 ROP group than in the other groups (p = 0.023). The mean of total serum bilirubin of the type 1 ROP group was significantly lower than those of the type 2 ROP and control group (p = 0.032). Proteinuria was present in 85.7% of preterms with treatment-requiring ROP and proteinuria increased the risk of ROP by 3.9 times (OR with 95% CI 3.9 (1.19-12.75), p = 0.042).

CONCLUSION

We found significantly higher blood glucose and lower total bilirubin level in the type 1 ROP group. Moreover, our findings suggest that proteinuria may not be only a comorbidity factor but also related to a higher frequency of ROP and type 1 ROP in preterm infants.

Effects of Physiological and Pathological Urea Concentrations on Human Microvascular Endothelial Cells

Urea is the uremic toxin accumulating with the highest concentration in the plasma of chronic kidney disease (CKD) patients, not being completely cleared by dialysis. Urea accumulation is reported to exert direct and indirect side effects on the gastrointestinal tract, kidneys, adipocytes, and cardiovascular system (CVS), although its pathogenicity is still questioned since studies evaluating its side effects lack homogeneity. Here, we investigated the effects of physiological and pathological urea concentrations on a human endothelial cell line from the microcirculation (Human Microvascular Endothelial Cells-1, HMEC-1). Urea (5 g/L) caused a reduction in the proliferation rate after 72 h of exposure and appeared to be a potential endothelial-to-mesenchymal transition (EndMT) stimulus. Moreover, urea induced actin filament rearrangement, a significant increase in matrix metalloproteinases 2 (MMP-2) expression in the medium, and a significant up- or down-regulation of other EndMT biomarkers (keratin, fibrillin-2, and collagen IV), as highlighted by differential proteomic analysis. Among proteins whose expression was found to be significantly dysregulated following exposure of HMEC-1 to urea, dimethylarginine dimethylaminohydrolase (DDAH) and vasorin turned out to be down-regulated. Both proteins have been directly linked to cardiovascular diseases (CVD) by in vitro and in vivo studies. Future experiments will be needed to deepen their role and investigate the signaling pathways in which they are involved to clarify the possible link between CKD and CVD.

Mitochondrial dysfunction in vascular endothelial cells and its role in atherosclerosis

The mitochondria are essential organelles that generate large amounts of ATP via the electron transport chain (ECT). Mitochondrial dysfunction causes reactive oxygen species accumulation, energy stress, and cell death. Endothelial mitochondrial dysfunction is an important factor causing abnormal function of the endothelium, which plays a central role during atherosclerosis development. Atherosclerosis-related risk factors, including high glucose levels, hypertension, ischemia, hypoxia, and diabetes, promote mitochondrial dysfunction in endothelial cells. This review summarizes the physiological and pathophysiological roles of endothelial mitochondria in endothelial function and atherosclerosis.

Uremic Toxins and Cardiovascular Risk in Chronic Kidney Disease: What Have We Learned Recently beyond the Past Findings?

Patients with chronic kidney disease (CKD) have an elevated prevalence of atheromatous (ATH) and/or non-atheromatous (non-ATH) cardiovascular disease (CVD) due to an array of CKD-related risk factors, such as uremic toxins (UTs). Indeed, UTs have a major role in the emergence of a spectrum of CVDs, which constitute the leading cause of death in patients with end-stage renal disease. The European Uremic Toxin Work Group has identified over 100 UTs, more than 25 of which are dietary or gut-derived. Even though relationships between UTs and CVDs have been described in the literature, there are few reviews on the involvement of the most toxic compounds and the corresponding physiopathologic mechanisms. Here, we review the scientific literature on the dietary and gut-derived UTs with the greatest toxicity in vitro and in vivo. A better understanding of these toxins' roles in the elevated prevalence of CVDs among CKD patients might facilitate the development of targeted treatments. Hence, we review (i) ATH and non-ATH CVDs and the respective levels of risk in patients with CKD and (ii) the mechanisms that underlie the influence of dietary and gut-derived UTs on CVDs.

Metabolomic Profiling of Brain Protective Effect of Edaravone on Cerebral Ischemia-Reperfusion Injury in Mice

Edaravone (EDA) injection has been extensively applied in clinics for treating stroke. Nevertheless, the metabolite signatures and underlying mechanisms associated with EDA remain unclear, which deserve further elucidation for improving the accurate usage of EDA. Ischemia stroke was simulated by intraluminal occlusion of the right middle cerebral artery for 1 h, followed by reperfusion for 24 h in mice. Brain infarct size, neurological deficits, and lactate dehydrogenase (LDH) levels were improved by EDA. Significantly differential metabolites were screened with untargeted metabolomics by cross-comparisons with pre- and posttreatment of EDA under cerebral ischemia/reperfusion (I/R) injury. The possibly involved pathways, such as valine, leucine, and isoleucine biosynthesis, and phenylalanine, taurine, and hypotaurine metabolisms, were enriched with differential metabolites and relevant regulatory enzymes, respectively. The network of differential metabolites was constructed for the integral exhibition of metabolic characteristics. Targeted analysis of taurine, an important metabolic marker, was performed for further validation. The level of taurine decreased in the MCAO/R group and increased in the EDA group. The inhibition of EDA on cerebral endothelial cell apoptosis was confirmed by TdT-mediated dUTP nick-end labeling (TUNEL) stain. Cysteine sulfinic acid decarboxylase (CSAD), the rate-limiting enzyme of taurine generation, significantly increased along with inhibiting endothelial cell apoptosis after treatment of EDA. Thus, CSAD, as the possible new therapeutic target of EDA, was selected and validated by Western blot and immunofluorescence. Together, this study provided the metabolite signatures and identified CSAD as an unrecognized therapeutic intervention for EDA in the treatment of ischemic stroke via inhibiting brain endothelial cell apoptosis.

Sexual Dimorphism in Alternative Metabolic Pathways of L-Arginine in Circulating Leukocytes in Young People with Type 1 Diabetes Mellitus

Background: Sexual dimorphism in specific biochemical pathways and immune response, underlies the heterogeneity of type 1 diabetes mellitus (T1DM) and affects the outcome of immunotherapy. Arginase and nitric oxide (NO) synthase (NOS) metabolize L-arginine and play opposite roles in the immune response and autoimmune processes.Objective: We hypothesized that the above mentioned enzymes can be involved in sex and age differences in T1DM and its treatment. Based on this, the enzymes have been studied in peripheral blood leukocytes (PBL) and plasma of young people with T1DM.Methods: Patients were recruited from Muratsan University Hospital (Yerevan, Armenia) and were divided into groups: girls and boys by age, from children to adolescents and adolescents/young adults with recent-onset T1DM (RO-T1DM) (0.1-1 years) and long-term T1DM (LT-T1DM) (1.6-9.9 years). Arginase activity was assessed by L-arginine-dependent production of L-ornithine, and the NOS activity was assessed by NO/nitrite production. Glycemic control was assessed using hemoglobin A1c test. Plasma HbA1c concentration below 7.5% (median (range) 6.7 [6.2-7.5]) was taken as good glycemic control (+) and above 7.5% (median (range) 10.5 [7.6-13]) as poor glycemic control (-). Healthy volunteers with corresponding sex and age were used as the control group.Results: All the patients with RO-T1DM, with poor glycemic control, had increased arginase activity in the cytoplasm (cARG) and mitochondria (mARG) in PBL. In girls with RO-T1DM, with good glycemic control, the subcellular arginase activity decreased, and normalized in LT-T1DM, regardless of age. In contrast, boys from both age groups showed high arginase activity, regardless of glycemic control and duration of T1DM along with insulin therapy. At the same time, a significant decrease in the subcellular production of bioavailable NO was observed in children/preadolescents, regardless of glycemic control and duration of diabetes. In adolescents/young adult boys with RO-T1DM, with (-), the subcellular production of NO decreased significantly, and with LT-T1DM, the decrease was attenuated, but even with (+) remained lower than in healthy people. In contrast, in the group of same age girls with RO-T1DM, NO production increased above normal in both cellular compartments, while with LT-T1DM it normalized in the cytoplasm. In adolescents/young adults with LT-T1DM, NO production in PBL mitochondria decreased by almost a half, regardless of glycemic control and gender. Changes in the metabolic pathways of L-arginine in plasma differed and were less substantial than in the PBL cellular compartments in T1DM.Conclusions: Glycemic status and duration of T1DM along with insulin therapy affect the activity of arginase and NOS-dependent production of bioavailable NO in the cytoplasm and mitochondria in PBL of young patients with T1DM, depending on sex and age. Arginase and NOS can directly affect the processes occurring in the pancreas and the outcome of therapy through infiltrated leukocytes. Obtained data can be useful for understanding the heterogeneity of T1DM and using it to develop available criteria for assessing the severity and treatment of autoimmune diabetes.

Uremic Toxins and Vascular Dysfunction

Vascular dysfunction is an essential element found in many cardiovascular pathologies and in pathologies that have a cardiovascular impact such as chronic kidney disease (CKD). Alteration of vasomotricity is due to an imbalance between the production of relaxing and contracting factors. In addition to becoming a determining factor in pathophysiological alterations, vascular dysfunction constitutes the first step in the development of atherosclerosis plaques or vascular calcifications. In patients with CKD, alteration of vasomotricity tends to emerge as being a new, less conventional, risk factor. CKD is characterized by the accumulation of uremic toxins (UTs) such as phosphate, para-cresyl sulfate, indoxyl sulfate, and FGF23 and, consequently, the deleterious role of UTs on vascular dysfunction has been explored. This accumulation of UTs is associated with systemic alterations including inflammation, oxidative stress, and the decrease of nitric oxide production. The present review proposes to summarize our current knowledge of the mechanisms by which UTs induce vascular dysfunction.

Aging Neurovascular Unit and Potential Role of DNA Damage and Repair in Combating Vascular and Neurodegenerative Disorders

Progressive neurological deterioration poses enormous burden on the aging population with ischemic stroke and neurodegenerative disease patients, such as Alzheimers’ disease and Parkinson’s disease. The past two decades have witnessed remarkable advances in the research of neurovascular unit dysfunction, which is emerging as an important pathological feature that underlies these neurological disorders. Dysfunction of the unit allows penetration of blood-derived toxic proteins or leukocytes into the brain and contributes to white matter injury, disturbed neurovascular coupling and neuroinflammation, which all eventually lead to cognitive dysfunction. Recent evidences suggest that aging-related oxidative stress, accumulated DNA damage and impaired DNA repair capacities compromises the genome integrity not only in neurons, but also in other cell types of the neurovascular unit, such as endothelial cells, astrocytes and pericytes. Combating DNA damage or enhancing DNA repair capacities in the neurovascular unit represents a promising therapeutic strategy for vascular and neurodegenerative disorders. In this review, we focus on aging related mechanisms that underlie DNA damage and repair in the neurovascular unit and introduce several novel strategies that target the genome integrity in the neurovascular unit to combat the vascular and neurodegenerative disorders in the aging brain.