Congenital obstructive nephropathy is the primary cause of chronic renal failure in children. Rapid diagnosis and initiation of the treatment are vital to preserve function and/or to slow down renal injury. The aim of our study was to determine whether urinary (u) kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) may be useful non-invasive biomarkers in children with congenital hydronephrosis (HN) caused by ureteropelvic junction obstruction. The study cohort consisted of 20 children with severe HN who required surgery (median age 2.16 years) and two control groups (control group 1: 20 patients with mild, non-obstructive HN; control group 2: 25 healthy children). All of the children had normal renal function. Immunoenzymatic ELISA commercial kits were used to measure uKIM-1 and uNGAL concentrations. The preoperative median uKIM-1/creatinine (cr.) and uNGAL levels were significantly greater in the children with severe HN than in both control groups. Three months after surgery, uNGAL had decreased significantly (p < 0.05) in the children with severe HN, but was still higher than that in control group 2 children (p < 0.05). Receiver operator characteristic analyses revealed a good diagnostic profile for uKIM-1 and uNGAL in terms of identifying a differential renal function of <40% in HN patients (area under the curve (AUC) 0.8 and 0.814, respectively) and <45% in all examined children (AUC 0.779 and 0.868, respectively). Based on these results, we suggest that increasing uNGAL and uKIM-1 levels are associated with worsening obstruction. Further studies are required to confirm a potential application of uKIM-1 and uNGAL as useful biomarkers for the diagnosis and progression of chronic kidney disease.

There are still missing non-invasive biomarkers of chronic kidney disease (CKD) in children. Therefore, the aim of the study was to evaluate oxidative stress indicators in the non-stimulated (NWS) and stimulated saliva (SWS) of CKD children (n = 25) and healthy controls (n = 25). Salivary antioxidants (catalase (CAT), peroxidase (Px), superoxide dismutase (SOD), uric acid (UA), reduced glutathione (GSH), albumin), redox status (total antioxidant capacity (TAC), total oxidant status (TOS), oxidative stress index (OSI)), and oxidative damage products (advanced glycation end products (AGE), advanced oxidation protein products (AOPP), malondialdehyde (MDA)) were evaluated. We have demonstrated the significantly higher activity of SWS GPx and SOD, as well as elevated concentrations of UA and albumin in NWS and SWS of CKD children vs. the control group. TAC, TOS and OSI were significantly higher only in SWS, while oxidative damage products (AGE, AOPP and MDA) were significantly higher in both NWS and SWS of CKD children. ROC analysis showed a considerably high diagnostic value of AOPP in both NWS and SWS of CKD children compared to controls (AUC = 0.92; 0.98). CKD is responsible for disturbances in salivary antioxidant systems and oxidative damage to proteins and lipids. Salivary AOPP can be a potential biomarker of CKD in children.

The aim of work was to investigate whether serum and urinary neutrophil gelatinase-associated lipocalin(sNGAL and uNGAL, respectively) are potential biomarkers of early cyclosporine A (CsA) nephrotoxicity in steroid-dependent nephrotic children (SDNS). The study group (I) consisted of 19 children with SDNS aged 9.46+/-5.52 years treated with CsA. The children were examined four times: at proteinuria relapse, prior to CsA treatment,then after 3, 6, and 12 months of CsA treatment. The control group (II) consisted of 18 healthy children aged 3-15 years. A commercial enzyme-linked immunosorbent assay method was used to measure NGAL concentration.The sNGAL level in SDNS children prior to the administration of CsA was similar to that in the healthy controls (p>0.05), but it increased significantly during the course of treatment (p<0.01). The uNGAL/creatinine (cr) ratio in SDNS patients was higher before the withdrawal of CsA therapy (p<0.05), and was also increased at the consecutive examinations (p<0.01). There was a positive correlation between both sNGAL and uNGAL levels and CsA serum level. However, based on the serum and urinary NGAL/cr receiver operating characteristic curve and area under the curve (AUC) analysis, it remains uncertain whether uNGAL is a good predictor of cyclosporine nephropathy. Both sNGAL and uNGAL concentrations increased during the course of CsA treatment. Further studies in larger groups of patients are therefore necessary to confirm our experimental data that increased NGAL levels may be a non-invasive marker for the early detection of tubulointerstitial damage in CsA nephrotoxicity.

Oxidative stress plays a critical role in the pathogenesis of hypertension; however, there are no data on salivary redox homeostasis and salivary gland function in children with hypertension. A total of 53 children with hypertension and age-and sex-matched controls were classified for the study. The antioxidant barrier and oxidative/nitrosative stress were evaluated in non-stimulated (NWS) and stimulated (SWS) whole saliva, plasma, and erythrocytes, with Student's t-test and Mann-Whitney U-test used for statistical analysis. We demonstrated that the activities of superoxide dismutase, catalase, and peroxidase were significantly higher in NWS, SWS, and erythrocytes of children with hypertension, similar to oxidative damage in proteins (advanced glycation end products) and lipids (malondialdehyde) as well as nitrosative stress markers (peroxynitrite and nitrotyrosine). The level of uric acid (UA) was significantly higher in NWS, SWS, and plasma of children with hypertension. UA concentration in SWS correlated positively with systolic and diastolic blood pressure and UA content in plasma. This parameter differentiates children with hypertension from healthy controls (AUC = 0.98) with a high degree of sensitivity (94%) and specificity (94%). Stimulated salivary flow was significantly lower in the hypertension group, similar to total protein content and salivary amylase activity. In summary, childhood hypertension is associated with hyposalivation as well as disturbances in antioxidant defense and enhanced oxidative/nitrosative damage both in the plasma/erythrocytes as well as saliva. Salivary UA may be a potential biomarker of hypertension in children.

Obesity is inseparably connected with oxidative stress. This process may disturb the functioning of the oral cavity, although the effect of oxidative stress on salivary gland function and changes in the qualitative composition of saliva are still unknown. Our study is the first to evaluate salivary redox homeostasis in 40 overweight and obese adolescents and in the age- and gender-matched control group. We demonstrated strengthening of the antioxidant barrier (superoxide dismutase, catalase, peroxidase, uric acid, total antioxidant capacity (TAC)) with a simultaneous decrease in reduced glutathione concentration in saliva (non-stimulated/stimulated) in overweight and obese teenagers compared to the controls. The concentration of the products of oxidative damage to proteins (advanced glycation end products), lipids (malondialdehyde, 4-hydroxynonenal) and DNA (8-hydroxydeoxyguanosine) as well as total oxidative status were significantly higher in both non-stimulated and stimulated saliva as well as plasma of overweight and obese adolescents. Importantly, we observed more severe salivary and plasma redox alterations in obese adolescents compared to overweight individuals. In the study group, we also noted a drop in stimulated salivary secretion and a decrease in total protein content. Interestingly, dysfunction of parotid glands in overweight and obese teenagers intensified with the increase of BMI. We also showed that the measurement of salivary catalase and TAC could be used to assess the central antioxidant status of overweight and obese adolescents.

Congenital lower urinary-tract obstruction (LUTO) is caused by anatomical blockage of the bladder outflow tract or by functional impairment of urinary voiding. About three out of 10,000 pregnancies are affected. Although several monogenic causes of functional obstruction have been defined, it is unknown whether congenital LUTO caused by anatomical blockage has a monogenic cause. Exome sequencing in a family with four affected individuals with anatomical blockage of the urethra identified a rare nonsense variant (c.2557C>T [p.Arg853∗]) in BNC2, encoding basonuclin 2, tracking with LUTO over three generations. Re-sequencing BNC2 in 697 individuals with LUTO revealed three further independent missense variants in three unrelated families. In human and mouse embryogenesis, basonuclin 2 was detected in lower urinary-tract rudiments. In zebrafish embryos, bnc2 was expressed in the pronephric duct and cloaca, analogs of the mammalian lower urinary tract. Experimental knockdown of Bnc2 in zebrafish caused pronephric-outlet obstruction and cloacal dilatation, phenocopying human congenital LUTO. Collectively, these results support the conclusion that variants in BNC2 are strongly implicated in LUTO etiology as a result of anatomical blockage.

Chronic kidney disease (CKD) is one of the most common modern-age diseases in children. Kidney failure does not reveal any symptoms for a long time; therefore, new biomarkers are sought, preferably those reflecting an early stage of CKD. The aim of our study was to evaluate total antioxidant potential as a biomarker differentiating the degree of CKD advancement. The study included 30 children with CKD and a control group matched by age and gender. Non-stimulated saliva (NWS), stimulated saliva (SWS), plasma and urine were used as study material. Total antioxidant potential was determined spectrophotometrically using the FRAP method (ferric ion reducing antioxidant parameter) by measuring total FRAP and uric acid (UA)-independent FRAP (FRAP-UA). We demonstrated that total FRAP, FRAP-UA and UA were significantly higher in stimulated saliva, as well as urine of CKD patients compared to the controls. These biomarkers increase with the progression of chronic kidney disease and their concentration in SWS reflects their content in urine. Interestingly, salivary FRAP and uric acid clearly differentiate between various stages of CKD as well as between healthy and ill children. Special attention should be paid to total FRAP which—measured in SWS—distinguishes patients with mildly to moderately decreased kidney function from those with severe renal impairment (AUC = 1, sensitivity = 100%, specificity = 100%). Although salivary FRAP may be a potential CKD biomarker in children, further studies are needed in a larger group of patients.

This study is the first to evaluate protein glycooxidation products, lipid oxidative damage and nitrosative stress in non-stimulated (NWS) and stimulated whole saliva (SWS) of children with chronic kidney disease (CKD) divided into two subgroups: normal salivary secretion (n = 18) and hyposalivation (NWS flow < 0.2 mL min−1; n = 12). Hyposalivation was observed in all patients with severe renal failure (4–5 stage CKD), while saliva secretion > 0.2 mL/min in children with mild-moderate CKD (1–3 stage) and controls. Salivary amylase activity and total protein content were significantly lower in CKD children with hyposalivation compared to CKD patients with normal saliva secretion and control group. The fluorescence of protein glycooxidation products (kynurenine, N-formylkynurenine, advanced glycation end products), the content of oxidative damage to lipids (4-hydroxynonneal, 8-isoprostanes) and nitrosative stress (peroxynitrite, nitrotyrosine) were significantly higher in NWS, SWS, and plasma of CKD children with hyposalivation compared to patients with normal salivary secretion and healthy controls. In CKD group, salivary oxidation products correlated negatively with salivary flow rate, α-amylase activity and total protein content; however, salivary oxidation products do not reflect their plasma level. In conclusion, children with CKD suffer from salivary gland dysfunction. Oxidation of salivary proteins and lipids increases with CKD progression and deterioration of salivary gland function.