Extracellular DNA and Markers of Neutrophil Extracellular Traps in Saliva from Patients with Periodontitis-A Case-Control Study.

Periodontitis is a chronic inflammatory disease. We have previously shown that salivary DNA is higher in patients with periodontitis. Neutrophil extracellular traps (NETs) are involved in the pathogenesis of chronic inflammatory diseases. The objective of this case-control study was to compare patients with periodontitis and healthy controls regarding the salivary concentrations of extracellular DNA and NET components. Unstimulated saliva samples were collected from 49 patients with periodontitis and 71 controls before an oral examination. Salivary extracellular DNA was isolated and quantified fluorometrically and using PCR. NET-associated markers were assessed using ELISA. We have found significantly higher concentrations of salivary extracellular DNA in samples from periodontitis patients (five-times higher for supernatant and three times for pellet). Our results show that patients also have three-times-higher salivary nucleosomes and NET-associated enzymes-myeloperoxidase and neutrophil elastase (both two-times higher). Neutrophil elastase and salivary DNA in the pellet correlated positively with the pocket depth/clinical attachment level in periodontitis patients (r = 0.31-weak correlation; p = 0.03 and r = 0.41-moderate correlation, p = 0.004). Correlations between salivary extracellular DNA and NET enzymes were positive and significant. Based on our results, the higher salivary extracellular DNA in periodontitis seems to be related to components of NETs, albeit with weak to moderate correlations indicating that NETs are produced in periodontitis and can play a role in its pathogenesis similarly to other inflammatory diseases. Further studies should prove this assumption with potential diagnostic and therapeutic consequences.

Dynamics of Urinary Extracellular DNA in Urosepsis.

Extracellular DNA (ecDNA) is a promising candidate marker for the early diagnosis and monitoring of urinary tract infections (UTIs). The aim of our study is to describe the dynamics of ecDNA in the plasma and urine of patients with urosepsis as well as in a mouse model of UTI. Samples of blood and urine were collected from adult patients with UTIs and obstructive uropathy (n = 36) during the first 3 days at the hospital and during a follow-up. Bacterial burden and urinary ecDNA were evaluated in a mouse UTI model (n = 26) at baseline; 24, 48, and 72 h after UTI induction; and 7 days after UTI induction. The plasma ecDNA did not change during urosepsis, but the plasma DNase activity increased significantly at the follow-up. The urinary ecDNA decreased significantly during hospitalization and remained low until the follow-up (90% lower vs. admission). No change was seen in the urinary DNase activity. C-reactive protein (CRP) and procalcitonin are positively correlated with plasma and urinary ecDNA. A UTI caused sepsis in 23% of mice. The urinary ecDNA decreased by three-fold and remained low until day 7 post-infection. Urinary bacterial burden is correlated with urinary ecDNA. Urinary ecDNA is a potential non-invasive marker for monitoring the effects of treatment during urosepsis and is related to UTI progression in the experimental animal model.

Neutrophil extracellular traps in urinary tract infection.

Background: Urinary tract infections (UTI) are common types of bacterial infection in children. UTI treatment is aimed to prevent complications including hypertension, proteinuria, and progression to chronic kidney disease. Activated neutrophils release chromatin-based structures associated with antimicrobial proteins called neutrophil extracellular traps (NETs). We aimed to describe the role of NET-associated markers in children with UTI as well as the role of NETs formation in a mouse model of UTI. Materials and methods: Markers of NETs including extracellular DNA (ecDNA), myeloperoxidase (MPO) and cathelicidin were analyzed in children with febrile UTI caused by E. coli (n = 98, aged 0.3-1.3 years) and in healthy controls (n = 50, 0.5-5.2 years). Moreover, an acute experimental model of UTI was performed on PAD4 knock-out mice with diminished NETs formation (n = 18), and on wild-type mice (n = 15). Results: Children with UTI had significantly higher urinary NETs markers including total ecDNA, nuclear DNA and mitochondrial DNA, altogether with MPO and cathelicidin. The concentrations of MPO and cathelicidin positively correlated with ecDNA (r = 0.53, p ≤ 0.001; r = 0.56, p ≤ 0.001, respectively) and the number of leukocytes in the urine (r = 0.29, p ≤ 0.05; r = 0.27, p ≤ 0.05, respectively). Moreover, urinary MPO was positively associated with cathelicidin (r = 0.61, p ≤ 0.001). In the experimental model, bacterial load in the bladder (20-fold) and kidneys (300-fold) was significantly higher in PAD4 knock-out mice than in wild-type mice. Conclusion: Higher urinary NETs makers-ecDNA, MPO and cathelicidin and their correlation with leukocyturia in children with UTI confirmed our hypothesis about the association between NETs and UTI in children. Higher bacterial load in mice with diminished NETs formation suggests that NETs are not only a simple consequence of UTI, but might play a direct role in the prevention of pyelonephritis and other UTI complications.

Extracellular DNA concentrations in various aetiologies of acute kidney injury.

Extracellular DNA (ecDNA) in plasma is a non-specific biomarker of tissue damage. Urinary ecDNA, especially of mitochondrial origin, is a potential non-invasive biomarker of kidney damage. Despite prominent tissue damage, ecDNA has not yet been comprehensively analysed in acute kidney injury (AKI). We analysed different fractions of ecDNA, i.e. total, nuclear and mitochondrial, in plasma and urine of children, and different animal models of AKI. We also analysed the activity of the deoxyribonuclease (DNase), which is contributes to the degradation of ecDNA. Patients with AKI had higher total and nuclear ecDNA in both, plasma and urine (sixfold and 12-fold in plasma, and 800-fold in urine, respectively), with no difference in mitochondrial ecDNA. This was mainly found for patients with AKI due to tubulointerstitial nephritis and atypical haemolytic uremic syndrome. Increased plasma ecDNA was also found in animal models of AKI, including adenine nephropathy (fivefold), haemolytic uremic syndrome (fourfold), and ischemia-reperfusion injury (1.5-fold). Total urinary ecDNA was higher in adenine nephropathy and ischemia-reperfusion injury (1300-fold and twofold, respectively). DNase activity in urine was significantly lower in all animal models of AKI in comparison to controls. In conclusion, plasma total and nuclear ecDNA and urinary total ecDNA is increased in patients and animals with particular entities of AKI, suggesting a mechanism-dependent release of ecDNA during AKI. Further studies should focus on the dynamics of ecDNA and its potential role in the pathogenesis of AKI.

Transformation of Amorphous Terbium Metal-Organic Framework on Terbium Oxide TbOx(111) Thin Film on Pt(111) Substrate: Structure of TbxOy Film.

The present study is focused on the synthesis and structural properties of amorphous terbium metal-organic framework thin film (TbMOF-TF) and its transformation to terbium oxide by pyrolysis at 450 °C in the air. The crystalline (cTbMOF) and amorphous (aTbMOF) films were prepared by solvothermal synthesis using different amounts (0.4 and 0.7 mmol) of the modulator (sodium acetate), respectively. The powders were characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier transform infrared (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM). The varied chemical composition of the surface of TbMOFs and TbxOy was investigated by X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that aTbMOF had been fully transformed to a Tb4O7 phase with a cubic crystal structure at 450 °C. The amorphous aTbMOF-TF film was prepared by dropping a colloidal solution of amorphous precursor nanocrystals on the SiO2/Si substrates covered with Pt as an interlayer. XPS confirmed the presence of Tb in two states, Tb3+ and Tb4+. The amorphous film has a rough, porous microstructure and is composed of large clusters of worm-like particles, while terbium oxide film consists of fine crystallites of cubic fluorite cF-TbOx, c-Tb4O7, and c-Tb2O3 phases. The surface topography was investigated by a combination of confocal (CM) and atomic force microscopy (AFM). The amorphous film is porous and rough, which is contrast to the crystalline terbium oxide film.

Interaction of thin polyethyleneimine layer with the iron surface and its effect on the electrochemical behavior.

Polymer-coated metals may act as biodegradable orthopedic implants with adjustable corrosion rates. Metallic surfaces represent a dynamic system with specific interactions occurring after the material is implanted into the human body. An additional layer, in the form of polymeric thin film, changes the nature of this metal-body fluids interface. Moreover, the interaction between polymer and metal itself can differ for various systems. Iron-based material modified with a thin layer of polyethyleneimine (PEI) coating was prepared and studied as potential absorbable implant. Computational methods were employed to study the interaction between the metallic surface and polymer functional monomer units at atomic levels. Various spectroscopical and optical methods (SEM, AFM, Confocal, and Raman spectroscopy) were also used to characterize prepared material. Electrochemical measurements have been chosen to study the polymer adsorption process onto the iron surface and corrosion behavior which is greatly influenced by the PEI presence. The adsorption mechanism of PEI onto iron was proposed alongside the evaluation of Fe and Fe-PEI degradation behavior studied using the impedance method. Bonding via amino -NH2 group of PEI onto Fe and enhanced corrosion rate of coated samples were observed and confirmed.

Dynamics of Plasma and Urinary Extracellular DNA in Acute Kidney Injury.

Early and reliable markers of acute kidney injury (AKI) are essential. One such candidate marker of tissue damage is extracellular DNA (ecDNA). The aim of our present study is to describe the unknown dynamics of ecDNA in an animal model of AKI. Glycerol-induced nephropathy was used to model AKI in adult male Wistar rats (n = 93). Blood and urine samples were collected 1, 3, and 24 h after model induction. Total ecDNA and its sub-cellular origin was assessed. In the plasma, total ecDNA and nuclear ecDNA were significantly increased in the AKI group already after 1 h (160% and 270%, respectively, p = 0.02 and p = 0.04). Both nuclear and mitochondrial ecDNA were higher after 3 h (180% and 170%, respectively, p = 0.002 and p = 0.005). Urinary ecDNA concentrations in the AKI group were significantly increased only 24 h after model induction (130% for total ecDNA, p = 0.009; 210% for nuclear ecDNA, p = 0.02; and 200% for mitochondrial ecDNA, p = 0.0009). Our results indicate that plasma ecDNA has the potential to serve as an early and sensitive, albeit non-specific marker of AKI. Further studies should elucidate the source of ecDNA and the dynamics of ecDNA in other animal models of AKI and patients with AKI.

Bone mineral density and oxidative stress in adolescent girls with anorexia nervosa.

Oxidative stress appears to be involved in the pathogenesis of osteoporosis-a serious complication of anorexia nervosa (AN). We evaluated the oxidative status in adolescent girls with AN and its potential relationship with bone mineral density (BMD). Girls with AN (n = 43) and age-matched healthy controls (n = 20) underwent anthropometric and BMD examination. Markers of bone turnover, oxidative stress, and antioxidant status were measured. Participants with AN and controls did not differ in BMD at the lumbar spine (p = 0.17) and total body less head BMD (p = 0.08). BMD at the total hip was lower (p < 0.001) in the AN group compared with the controls. Levels of antioxidant status markers-ferric reduction antioxidant power, total antioxidant capacity, and reduced and oxidized glutathione ratio (all p < 0.001)-were significantly lower, whereas those of advanced oxidation protein products (AOPP), fructosamines, and advanced glycation end products (AGEs) (all p < 0.001) were higher in AN patients than in healthy controls. BMD and bone turnover markers were positively correlated with antioxidant status markers, while they were negatively correlated with AOPP, fructosamines, and AGEs levels.  Conclusion: This is the first study to assess a potential association between oxidative status and BMD in adolescents with AN. We demonstrated that in young girls, the imbalance of oxidative status and reduced BMD are concurrently manifested at the time of the diagnosis of AN. Disturbance of oxidative status could play a pathogenetic role in AN-associated decreased BMD. What is Known: • Osteoporosis is a serious complication of AN, and in affected adolescents may result in a permanent deficit in bone mass. • Oxidative and carbonyl stress may be involved in the development of bone loss. What is New: • Adolescents girls with AN have impaired antioxidant defense and increased oxidative damage to biomolecules. • Disturbance of oxidative status could affect bone loss and could contribute to decreased BMD in adolescent females with AN.

Oxidative status in plasma, urine and saliva of girls with anorexia nervosa and healthy controls: a cross-sectional study.

BACKGROUND: Anorexia nervosa (AN) is a serious psychosomatic disorder with unclear pathomechanisms. Metabolic dysregulation is associated with disruption of redox homeostasis that might play a pivotal role in the development of AN. The aim of our study was to assess oxidative status and carbonyl stress in plasma, urine and saliva of patients with AN and healthy controls. METHODS: Plasma, spot urine, and saliva were collected from 111 girls with AN (aged from 10 to 18 years) and from 29 age-matched controls. Markers of oxidative stress and antioxidant status were measured using spectrophotometric and fluorometric methods. RESULTS: Plasma advanced oxidation protein products (AOPP) and advanced glycation end products (AGEs) were significantly higher in patients with AN than in healthy controls (by 96, and 82%, respectively). Accordingly, urinary concentrations of AOPP and fructosamines and salivary concentrations of AGEs were higher in girls with AN compared with controls (by 250, and 41% in urine; by 92% in saliva, respectively). Concentrations of thiobarbituric acid reactive substances (TBARS) in saliva were 3-times higher in the patients with AN than in the controls. Overall antioxidants were lower in plasma of girls with AN compared to the controls, as shown by total antioxidant capacity and ratio of reduced and oxidized glutathione (by 43, and 31%, respectively). CONCLUSIONS: This is the first study assessing wide range of markers of oxidative status in plasma, urine and saliva of the patients with AN. We showed that both, higher levels of markers of oxidative stress and lower antioxidants play a role in redox disruption. Restoration of redox homeostasis might be of the clinical relevance.

Dynamics of salivary markers of kidney functions in acute and chronic kidney diseases.

Saliva can be used as an alternative diagnostic fluid enabling easy and non-invasive disease monitoring. Urea and creatinine can be measured in saliva and both were shown to be increased in renal failure. However, the dynamics of these markers during the development of kidney diseases is unknown. We aimed to describe the dynamics of salivary urea and creatinine in various animal models of acute kidney injury (AKI) and chronic kidney disease (CKD) and in patients with different stages AKI or CKD. Ninety Wistar rats underwent bilateral nephrectomy (BNX), ischemia-reperfusion injury (IRI) or glycerol-induced kidney injury to model AKI. CKD was modelled using 5/6 nephrectomy. In the clinical part 57 children aged 12.6 ± 4.9 years with AKI (n = 11) or CKD (n = 46) and 29 healthy controls (aged 10.2 ± 3.7 years) were enrolled. Saliva and blood samples were collected in both, animal experiments and the human study. In animal models of AKI, plasma urea and creatinine were higher than in controls. An increase of salivary urea and creatinine (twofold) was observed in BNX and IRI, but only after 12 h and 24 h, respectively. In glycerol nephropathy and 5/6 nephrectomy, salivary urea increased (by 100% and by 50%), while salivary creatinine did not change during the observation period. Salivary urea and creatinine were significantly higher in all patients compared to controls (threefold) and in both, AKI and CKD they were associated with the severity of renal failure. Plasma and salivary concentrations correlated only in children with renal failure (R = 0.72 for urea; R = 0.93 for creatinine), but not in controls (R = -0.007 for urea; R = 0.02 for creatinine). Our study indicates that during the development of renal impairment saliva could be used for non-invasive monitoring in higher stages of AKI or CKD, rather than for screening of early stages of kidney diseases.

Urea and creatinine levels in saliva of patients with and without periodontitis.

Despite the fact that saliva contains measurable concentrations of urea and creatinine, it is not widely used in clinical nephrology. One of the reasons is the high inter- and intra-individual variability in the salivary markers of kidney function. We hypothesized that gingival bleeding in patients with periodontitis could contribute to this variability by increasing the concentration of salivary urea or creatinine. Samples were collected from 25 patients with periodontitis and 29 healthy controls. In addition, saliva samples from five healthy volunteers were artificially contaminated with blood. The concentration of urea, but not that of creatinine, was more than twice as high in patients with periodontitis than in controls. Artificial contamination of saliva with blood did not affect the salivary concentration of creatinine. Salivary urea increased only with very high levels of contamination (≥2.5% blood in saliva), but that did not occur in patients. In conclusion, periodontitis increases the concentration of salivary urea, but this is not likely to be a result of contamination with blood. Future studies should investigate the composition of the oral microbiome, specifically regarding how it affects the concentration of salivary urea. Salivary creatinine seems to be a more robust non-invasive marker of renal functions than salivary urea.

Oxidative Stress in Animal Models of Acute and Chronic Renal Failure.

INTRODUCTION: Kidney disease is a worldwide health and economic burden, with rising prevalence. The search for biomarkers for earlier and more effective disease screening and monitoring is needed. Oxidative stress has been linked to both, acute kidney injury (AKI) and chronic kidney disease (CKD). The aim of our study was to investigate whether the concentrations of systemic markers of oxidative stress and antioxidant status are affected by AKI and CKD, and to identify potential biomarkers. METHODS: In adult male Wistar rats, AKI was induced by bilateral nephrectomy, and CKD was induced by 5/6 nephrectomy. Blood was collected 48 hours after surgery in AKI and 6 months after surgery in CKD. Advanced oxidation protein products (AOPP), thiobarbituric acid reactive substances (TBARS), advanced glycation end products (AGEs), fructosamine, total antioxidant capacity (TAC), and ferric reducing antioxidant power (FRAP) were measured. RESULTS: Impaired renal function was confirmed by high concentrations of plasma creatinine and urea in AKI and CKD animals. AOPP and fructosamine were higher by 100% and 54% in AKI, respectively, and by 100% and 199% in CKD, respectively, when compared to corresponding control groups. Similarly, there was approximately a twofold increase in AGEs (by 92%) and TAC (by 102%) during AKI. In CKD, concentrations of FRAP, as an antioxidative status marker, were doubled (by 107%) when compared to the control group, but concentration of TAC, another marker of antioxidative status, did not differ between the groups. CONCLUSIONS: AKI and CKD led to increased systemic oxidative stress. AOPP and fructosamine could be considered potential biomarkers for both, acute and chronic kidney damage. On the other hand, AGEs, TAC, and FRAP seem to be disease specific, which could help to differentiate between acute and chronic kidney injuries. However, this needs further validation in clinical studies.

Behavioral Changes During Development of Chronic Kidney Disease in Rats.

Decreased renal function due to chronic kidney disease (CKD) is associated with anxiety and cognitive decline. Although these mental disorders are often obvious in late stage renal disease patients, they might be unnoticeable or are neglected in early stages of the CKD development. Associations between renal and cognitive dysfunction have been indicated by studies performed mainly in patients undergoing dialysis, which itself represents a stress and decreased quality of life. However, experimental and causal studies are scarce. Our aim was to investigate dynamic changes in behavioral traits during the progression of CKD in an animal model. Thirty 12-week old male rats were used in this experiment. CKD was induced by a subtotal (5/6) nephrectomy. Two, 4, and 6 months after surgical induction of CKD, the open field, the light-dark box and the novel object recognition tests were conducted to assess the locomotor activity, anxiety-like behavior and the memory function of rats. Blood urea nitrogen (BUN), plasma concentration of creatinine (CREAT), albumin to creatinine ratio in urine (ACR) along with the renal histology were assessed to monitor the development and severity of CKD. In comparison to control rats, 5/6 nephrectomized rats had by 46-66% higher concentration of BUN during the whole follow-up period, as well as by 52% and by 167% higher CREAT and ACR, respectively, 6 months after surgery. Although the effect of time was observed in some behavioral parameters, nephrectomy did not significantly influence either locomotor activity, or anxiety-like behavior, or memory function of animals. Two and 4 months after surgery, animals moved shorter distance and spent less time in the center zone. However, the open-field ambulation returned back to the baseline level 6 months after CKD induction. Although nephrectomized rats displayed impaired kidney function as early as 2 months after surgery, no significant differences were found between the CKD and the control rats in any of the observed behaviors. Further studies are needed in order to evaluate whether behavioral abnormalities are related to severity of CKD or might be attributed to psychosocial aspect of end-stage renal disease and decreased quality of life in dialysis patients.

The effects of sucrose on urine collection in metabolic cages.

Representative urine collection that respects the standards of animal welfare is still an issue in experimental nephrology. The commonly used metabolic cages induce stress in rodents. In mice, the volume of collected urine is sometimes insufficient for further analysis. The aim of this experiment was to analyse the effects of time of day, temperature and 2%, 5% or 10% sucrose solutions on diuresis, weight change and liquid intake of adult mice placed in metabolic cages for urine collection. Mice were placed in metabolic cages for 12 h during the day or night at standard ambient (22℃) and thermoneutral (28℃) temperatures. To determine the effect of acclimatisation, mice were placed in metabolic cages for five consecutive days. Diuresis increased with concentrations of sucrose. Body weight reduction was most rapid in the group given tap water and decreased with increasing sucrose concentrations. A drastic drop in body weight was observed in mice placed in metabolic cages for four consecutive days with access to tap water and food, indicating that time spent in metabolic cages should be kept to a minimum, as prolonged confinement in metabolic cages can be harmful to mice. The administration of concentrated sucrose solutions can potentially aid in mouse urine collection by reducing the time spent in metabolic cages. Sucrose supplementation increased the albumin/creatinine ratio. However, without showing estimates of glomerular filtration rate, renal haemodynamics, plasma electrolytes and urinary electrolyte excretions, the results of this study do not provide any conclusion about the effect of sucrose on renal function.

Early Dynamics of Plasma Dna in a Mouse Model of Sepsis.

Concentration of extracellular DNA (ecDNA) in plasma of septic patients is higher in comparison to healthy controls and is associated with worse prognosis in intensive care patients. Decrease of ecDNA in plasma by treatment with deoxyribonuclease (DNase) showed to have beneficial effects in animal models of sepsis. A previously published study showed that timing of DNase application is crucial for the effect of DNase. No published study monitored plasma ecDNA dynamics during sepsis in detail yet. The aim of our study was to describe the early dynamics of plasma ecDNA but also plasma DNase activity in a mouse model of sepsis. Sepsis was induced using intraperitoneal injection of E. coli and mice were euthanized every hour to obtain sufficient volume of plasma. Our results show that the concentration of plasma ecDNA is rising continuously during the first 5 h after infection and is 20-fold higher 5 h after induction of sepsis in comparison to control mice. Subcellular origin of plasma ecDNA was analyzed but fundamental differences in dynamics between nuclear and mitochondrial ecDNA were not found. DNase activity in plasma seems to rise slowly until the fourth hour, but the interindividual variability is high. In conclusion, this is the first study that describes the dynamics of plasma ecDNA and DNase activity in early sepsis in detail. Our study is the basis for further studies focused on the timing of exogenous DNase treatment in sepsis. Additional studies will be needed to monitor plasma ecDNA in later time points that are more clinically relevant.

Salivary creatinine and urea are higher in an experimental model of acute but not chronic renal disease.

Plasma creatinine and urea are commonly used markers of kidney function in both acute and chronic renal failure. The needed repeated blood collection is associated with pain, stress and might lead to infections. Saliva has the potential to be a non-invasive alternative diagnostic fluid. The use of saliva in clinical practice is limited, since many factors affect the concentration of salivary biomarkers. The aim of our study was to analyze salivary creatinine and urea in the animal models of acute and chronic renal disease. Bilateral nephrectomy and adenine nephropathy were induced in adult male mice. Both, plasma creatinine and urea were higher in animals with renal failure compared to controls. Salivary creatinine was higher by 81% and salivary urea by 43% in comparison to the control group, but only in animals with bilateral nephrectomy and not in adenine nephropathy. Our results indicate that the increase of salivary creatinine and urea depends on the experimental model of renal failure and its severity. Further studies are needed to monitor the dynamics of salivary markers of renal function and to reveal determinants of their variability.

Oxidative stress in the brain caused by acute kidney injury.

Uremic encephalopathy is a severe complication of renal failure. The underlying pathogenesis is unknown although several mechanisms have been suggested. Renal failure causes oxidative stress leading to cardiovascular complications. It has been suggested as the potential mediator of uremic encephalopathy as well, but it is largely unknown whether brain tissue itself undergoes oxidative damage in uremia. The aim of our experiment was to analyze oxidative stress markers in different brain regions in an animal model of acute kidney injury (AKI). AKI was induced by ischemia-reperfusion injury in male Wistar rats. Urine was collected in metabolic cages after 24 h. Samples of plasma and several brain regions were collected after 48 h. Markers of lipid peroxidation, protein oxidation and total antioxidant capacity were assessed. Renal failure was confirmed by high plasma creatinine, urea and urinary albumin to creatinine ratio. Our data confirmed increased systemic oxidative stress in the AKI group with plasma concentrations of markers of oxidative damage being twice as high compared to the sham-operated control group. No effect was seen in the urine. In the hippocampus, lipid and protein oxidation was higher, while antioxidant capacity was lower in the rats with AKI. Lipid oxidation markers in the frontal cortex were higher by 33%. No differences to controls were found in the cerebellum and hypothalamus. In conclusion, our results indicate that AKI leads to oxidative stress in the brain, especially in the hippocampus and in the frontal cortex. This kidney-brain crosstalk mediated by increased oxidative stress might explain some of the symptoms of uremic encephalopathy. The causes and consequences of oxidative damage observed in the brain during AKI remain to be elucidated.

Association between oxidative status and the composition of intestinal microbiota along the gastrointestinal tract.

Studies have shown that the microbiota along the gastrointestinal tract (GIT) plays an important role when it comes to the maintenance of its proper functions. Many studies exist that have analyzed the composition of the bacterial community in the different regions of the GIT of humans and model animals. Microbial imbalance leads to several systemic disorders, including cardiovascular and renal disease. The imbalance between the production of reactive oxygen species (ROS) and their elimination by antioxidants leads to oxidative stress. Oxidative stress plays an important role in a variety of physiological processes, as well as disease. The continuous formation of ROS in the GIT is the result of the interaction between intestinal mucosa, symbiotic bacteria and dietary factors. It has also been proven that ROS play a role in the pathogenesis of several GI disorders, including IBD. We hypothesized that the levels of advanced glycation end products (AGEs) would be the highest in the ileum, caecum or colon, where the microbiota mostly consist of butyrate producing bacteria, Bacterioides, Clostridium, Ruminococcus or Bifidobacterium, which derive energy through carbohydrate fermentation. We also assumed that advanced oxidation protein products (AOPP) mostly act in the segments, where bacteria reside and which are responsible for the amino acid fermentation, such as caecum or colon. Lipid hydroxyperoxides are generated during digestion in the stomach, which contains absorbed oxygen and has a low pH. According to this we hypothesized that the highest concentration of thiobarbituric acid reacting substances (TBARS) could be in the stomach, which, however, has not been confirmed. Because Lactobacilli are able to produce catalase, an endogenous antioxidant, and are abundant in the small intestine, we hypothesized that antioxidant capacity (measured by ferric reducing ability) would be the highest here. The highest levels of AGEs were found in the caecum. The highest level of TBARS was found in the jejunum of the rats. The assessment of our hypothesis also revealed high levels of AOPP in the caecum. It has been shown that AOPP contributes to the progression of IBD. The ferric reducing ability of tissue was the lowest in the colon of the experimental animals, which is in accordance with previous studies that show that rat colon has a lower total antioxidant capacity than the small bowel. In summary, we offer some insight into the differences between the oxidative status along the GIT of rats and some advice concerning supportive antioxidant therapy of gastrointestinal diseases.