The RIP1-kinase inhibitor necrostatin-1 prevents osmotic nephrosis and contrast-induced AKI in mice

The pathophysiology of contrast-induced AKI (CIAKI) is incompletely understood due to the lack of an appropriate in vivo model that demonstrates reduced kidney function before administration of radiocontrast media (RCM). Here, we examine the effects of CIAKI in vitro and introduce a murine ischemia/reperfusion injury (IRI)-based approach that allows induction of CIAKI by a single intravenous application of standard RCM after injury for in vivo studies. Whereas murine renal tubular cells and freshly isolated renal tubules rapidly absorbed RCM, plasma membrane integrity and cell viability remained preserved in vitro and ex vivo, indicating that RCM do not induce apoptosis or regulated necrosis of renal tubular cells. In vivo, the IRI-based CIAKI model exhibited typical features of clinical CIAKI, including RCM-induced osmotic nephrosis and increased serum levels of urea and creatinine that were not altered by inhibition of apoptosis. Direct evaluation of renal morphology by intravital microscopy revealed dilation of renal tubules and peritubular capillaries within 20 minutes of RCM application in uninjured mice and similar, but less dramatic, responses after IRI pretreatment. Necrostatin-1 (Nec-1), a specific inhibitor of the receptor-interacting protein 1 (RIP1) kinase domain, prevented osmotic nephrosis and CIAKI, whereas an inactive Nec-1 derivate (Nec-1i) or the pan-caspase inhibitor zVAD did not. In addition, Nec-1 prevented RCM-induced dilation of peritubular capillaries, suggesting a novel role unrelated to cell death for the RIP1 kinase domain in the regulation of microvascular hemodynamics and pathophysiology of CIAKI.

[The cortical collecting duct plays a pivotal role in the kidney's local renin-angiotensin system]

The renin-angiotensin system is one of the most important hormone systems in the body, and the regulations as well as the role in the juxtaglomerular apparatus are well known. The present review focuses on renin secretion in a recently described localization, the cortical collecting duct. The authors display it in parallel of the copying strategy of an adult and a developing kidney. Furthermore, based on different animal studies it highlights the local role of renin released from the collecting duct. In chronic angiotensin II-infused, 2-kidney, 1-clip hypertensive model as well as in diabetic rats the major source of (pro)renin is indeed the collecting duct. In this localization this hormone can reach both the systemic circulation and the interstitial renin-angiotensin system components including the newly described (pro)renin receptor, by which (pro)renin is able to locally activate pro-fibrotic intracellular signal pathways. Consequently, one can postulate that in the future renin may serve either as a new therapeutic target in nephropathy associated with both hypertension and diabetes or as an early diagnostic marker in chronic diseases leading to nephropathy.

Gender differences in serum and glucocorticoid regulated kinase-1 (SGK-1) expression during renal ischemia/reperfusion injury

Several studies reported sexual dimorphism in the signaling mechanisms of renal ischemia/reperfusion (I/R). The anti-apoptotic serum and glucocorticoid-regulated kinase-1 (SGK-1) is up-regulated and has a significant protective role in renal I/R. SGK-1 has several target molecules, and inhibition of the inducible nitric oxide synthase (iNOS) transcription is one of its effector mechanisms. The objective of the present study was to examine if there is a gender-specific expression and activation of SGK-1 during renal I/R injury. In vitro, treatment of HK-2 kidney proximal tubular cells with different concentrations of 17-beta estradiol had no effect, whereas testosterone increased SGK-1 abundance in a dose-dependent manner. In vivo, in a rat model of unilateral renal I/R injury, there was a higher SGK-1 expression and phosphorylation in males 2 and 24 h after ischemia paralleled by reduction in the mRNA expression of iNOS compared to females. Deprivation of testosterone by castration of males resulted in decreased SGK-1 protein level at all time-points and reduced phosphorylation 2 and 24 h after reperfusion. Our results suggest that testosterone up-regulates SGK-1 in the kidney contributing to sexual dimorphisms in the cell signalling machinery. The significance of the testosterone-regulated SGK-1 level and activity in the kidney needs further investigations.

Renoprotective effect of erythropoietin in rats subjected to ischemia/reperfusion injury: gender differences

BACKGROUND

Renal ischemia reperfusion injury induces gender-dependent heat-shock protein 72 expression, which maintains membrane localization of renal Na(+)/K(+)ATPase-α1. The erythropoietin has a protecting effect against ischemia reperfusion injury in various organs. In this study, we investigated whether erythropoietin exerts a beneficial effect against post-ischemic renal injury. Furthermore, we studied the erythropoietin signaling on heat-shock protein 72 and Na(+)/K(+)ATPase-α1 expression and localization.

METHODS

In male and female Wistar rats, rHuEPO (1000 IU/bwkg intraperitoneal) or vehicle was administered 24 hours prior to unilateral left renal ischemia reperfusion (50 minutes). Kidneys were subsequently removed at hours 2 or 24 of the reperfusion; sham-operated rats served as controls (C) (n = 8/group). We measured serum erythropoietin, renal function, evaluated histological injury, and observed heat-shock protein 72 as well as Na(+)/K(+)ATPase-α1 protein level and localization. Additional groups were followed for 7-day survival.

RESULTS

Erythropoietin treatment was associated with better post-ischemic survival and less impaired renal function in males while diminishing the renal structural damage in both sexes. Endogenous erythropoietin was higher in males and increased in both genders after erythropoietin treatment. The erythropoietin treatment elevated protein levels of heat-shock protein 72 and Na(+)/K(+)ATPase-α1 in 24 hours in males, whereas in females, the already higher expression of heat-shock protein 72 and Na(+)/K(+)ATPase-α1 was not increased. Moreover, erythropoietin prevented ischemia reperfusion induced Na(+)/K(+)ATPase-α1 translocation from the basolaterale membrane in males.

CONCLUSION

Erythropoietin diminishes gender difference in the susceptibility to renal post-ischemic injury and reduces post-ischemic structural damage while preserving kidney function, particularly in males. This additional protection may be associated with a heat-shock protein 72-mediated effect on Na(+)/K(+)ATPase-α1 expression and translocation.

Increased expression of hypoxia-inducible factor 1alpha in coeliac disease

Previously, it has been suggested that hypoxia-inducible factor (HIF) 1 signaling may play determinative role in the maintenance of the barrier function of the intestinal epithelium in inflammatory bowel disease. Our aim was to depict the alteration of HIF-1alpha and related genes in celiac disease (CD) where the importance of the barrier function is well known. Duodenal biopsy specimens were collected from 16 children with untreated CD, 9 children with treated CD and 10 controls. HIF-1alpha, trefoil factor 1 (TFF1), ecto-5-prime nucleotidase (CD73), and multi drug resistance gene 1 (MDR1) mRNA and HIF-1alpha protein expression were determined by real-time PCR and Western blot, respectively. Localization of HIF-1alpha was determined by immunofluorescent staining. We found increased HIF-1alpha and TFF1 mRNA and HIF-1alpha protein expression in the duodenal mucosa of children with untreated CD compared with controls or children with treated CD (p < 0.05). In untreated CD children, HIF-1alpha staining was present in cytoplasmic and nuclear region of the villous enterocytes. In treated CD mRNA expression of CD73 and MDR1 were increased compared with controls (p < 0.01 and 0.05, respectively). Our results of increased mucosal HIF-1alpha expression in CD children suggest the contribution of this signaling pathway in the pathomechanism of CD.

Peroxidasin is secreted and incorporated into the extracellular matrix of myofibroblasts and fibrotic kidney

Mammalian peroxidases are heme-containing enzymes that serve diverse biological roles, such as host defense and hormone biosynthesis. A mammalian homolog of Drosophila peroxidasin belongs to the peroxidase family; however, its function is currently unknown. In this study, we show that peroxidasin is present in the endoplasmic reticulum of human primary pulmonary and dermal fibroblasts, and the expression of this protein is increased during transforming growth factor-beta1-induced myofibroblast differentiation. Myofibroblasts secrete peroxidasin into the extracellular space where it becomes organized into a fibril-like network and colocalizes with fibronectin, thus helping to form the extracellular matrix. We also demonstrate that peroxidasin expression is increased in a murine model of kidney fibrosis and that peroxidasin localizes to the peritubular space in fibrotic kidneys. In addition, we show that this novel pathway of extracellular matrix formation is unlikely mediated by the peroxidase activity of the protein. Our data indicate that peroxidasin secretion represents a previously unknown pathway in extracellular matrix formation with a potentially important role in the physiological and pathological fibrogenic response.

Lifestyle, body composition, and physical fitness changes in Hungarian school boys (1975-2005)

General socioeconomic conditions as well as the physical environment have undergone remarkable changes in Hungary during the past 30 years. Unfortunately, these positive processes have resulted in a reduction of habitual physical activity along with unfavorable changes in dietary habits. Therefore, the purpose of the present study was to compare some selected morphological and functional parameters of 7-14-year-old Hungarian schoolboys living in the middle of the 1970s and at the beginning of the new millennium. It was hypothesized that there would be significant differences in morphological and functional characteristics of the Hungarian schoolboy populations, because they were assessed 30 years apart. Means of height, body mass, body mass index (BMI), the sum of five skinfold tests, percentage of body fat, and two running performance times (400 m and 1,200 m) of the boys (N = 3,672) studied in 1975 were compared to those of the boys (N = 3,758) in 2005. Data were analyzed using two-tailed independent samples t tests (p < .05). We observed significant secular changes in body mass and height. In addition, boys in 2005 had significantly more subcutaneous fat compared to 1975. The running times for the two distances were significantly poorer at the time of the second investigation. The remarkable and unfavorable changes in body composition and cardiorespiratory performance were attributed to the continuously decreasing intensity of habitual physical exercise and a lifestyle that had become more sedentary (watching TV playing computer games, etc.). Radical interventions are necessary to reduce these risks associated with the high prevalence of cardiovascular disease in Hungary, and the challenge to resolve the problem requires combined efforts at the educational, societal, corporate, and governmental levels.

Effects of 3 hours a week of physical activity on body fat and cardio-respiratory parameters in obese boys

The prevalence of overweight or fat children and adolescents has markedly increased in Hungary during the past three decades. Among the possible factors insufficient physical activity and a relative or absolute excess of calorie intake associated to it can be regarded as the most important ones. The aim of the study was to analyse the effects of a 20-week aerobic exercise on body composition and on the exercise tested cardio-respiratory functions in 10-year-old obese boys. Obesity was defined by a BMI greater than the cut-off value reported by Cole and co-workers (5) and a relative body fat content above 30% (13). Of the study group 21 volunteer children completed the program; the contrast group contained 28 obese boys. Mean calendar age was 10.03 +/- 0.26 in the study group (S) and 9.88 +/- 0.29 in the control group (C). The members of group S had two curricular physical education (PE) classes a week and three extracurricular aerobic physical activity sessions of 60 min net time in the afternoon, on Mondays (swimming and water games), Wednesdays (folk dance) and Fridays (soccer). Group C had only 2 PE classes a week. Anthropometric and spiroergometric data were collected in the middle of January and June of 2004. Relative body fat content and BMI did not increase during the observation period in contrast to the significant increase of both in the control group. Peak minute ventilation, aerobic power, oxygen pulse, and running distance (performed on a treadmill) increased in group S, and did not change in group C. The program was considered successful despite that the changes in the observed physiological and physical indicators appeared to be slight. However, the 5-month elevated level of physical activity brought about such development in the physical status of the obese subjects that might be an appropriate basis for regular training. Fortunately, the cardio-respiratory functions of the investigated boys were not affected yet by obesity, consequently the really dramatic change in their further lifestyle exclusively depends on their decision.

Overweight and obesity in 7 to 10-year-old Hungarian boys. Short communication

Increasing prevalence of overweight and obesity is a serious social and health problem both in the economically developed and developing countries. Despite this fact the nation-wide growth studies completed in Hungary during the past 30 years had not categorised the children either by body fat content or nutritional status. The aim of the study was to estimate the prevalence of overweight and obese boys in the country at the beginning of the new millennium. Height, body mass and four skinfold thicknesses were measured in 7173 volunteer boys aged between 7 and 10 and living in various urban and rural settlements of Hungary between 2003 and 2005. Nutritional status was qualified by the BMI and relative body fat content. The significantly increasing prevalence with age of overweight and obesity ranged between 10.3 and 23.4%. The results showed the joint effects of a secular trend of growth and of a remarkably changed lifestyle. Of these the consequences of the lifestyle are the more important ones. The high and possibly further increasing prevalence of child-age overweight and obesity reminds one of the observations of Kopp and associates (5), namely that of the increased prevalence of chronic childhood diseases during the past 15 years. More intense habitual physical activity and dramatic changes in dietary habits still promise some solution. No one should reckon, however, with the efficiency of physical education at the schools with its very few classes.