Expression of Aquaporin-1, -2 and -4 in Mice with a Spontaneous Mutation Leading to Hydronephrosis

Ameliorative impacts of astaxanthin against atrazine-induced renal toxicity through the modulation of ionic homeostasis and Nrf2 signaling pathways in mice

Astaxanthin (ASX), a red pigment belonging to carotenoids, has antioxidant activity and anti-oxidative stress effect. Atrazine (ATZ), a frequently used herbicide, whose degradation products are the cause for nephrosis and other oxidative stress associated diseases. This study was aimed to reveal the potential protective mechanism of astaxanthin against atrazine-induced nephrosis. Atrazine was orally given (250 mg/kg bw) to the mice along with astaxanthin (100 mg/kg bw) for 28 days. Serum biochemical indicators, oxidative stress biomarkers, ATPase activities, ion concentration, histomorphology, and various renal genes expression linked with apoptosis, Nrf2 signaling pathway, and aquaporins (AQPs) were assessed. It was found that serum creatinine (SCr), blood urea nitrogen (BUN), and MDA levels were significantly increased after the treatment of atrazine, whereas serum renal oxidative stress indicators like CAT, GSH, T-AOC, SOD decreased. Renal histopathology showed that atrazine significantly damaged renal tissues. The activities of Ca 2+-Mg 2+-ATPase were increased whereas Na +-K +-ATPase decreased significantly (P < 0.05). Moreover, results confirmed that the expression of AQPs, Nrf2, and apoptosis genes were also altered after atrazine administration. Interestingly, astaxanthin supplementation significantly (P < 0.05) improved atrazine-induced nephrotoxicity via decreasing SCr, BUN, oxidative stress, ionic homeostasis and reversing the changes in AQPs, Nrf2, and apoptosis gene expression. These findings collectively suggested that astaxanthin has strong potential ameliorative impact against atrazine induced nephrotoxicity.

Aquaporins alteration revealed kidney damages in cerebral ischemia/reperfusion rats

Background

Restoration of blood supply is a desired goal for the treatment of acute ischemic stroke. However, the restoration often leads to cerebral ischemia-reperfusion injury (CIR/I), which greatly increases the risk of non-neural organ damage. In particular, the acute kidney injury might be one of the most common complications.

Aims

The study aimed to understand the damage occurred and the potential molecular mechanisms.

Methods

The study was explored on the CIR/I rats generated by performing middle cerebral artery occlusion/reperfusion (MCAO/Reperfusion). The rats were evaluated with injury on the brains, followed by the non-neural organs including kidneys, livers, colons and stomachs. They were examined further with histopathological changes, and gene expression alterations by using RT-qPCR of ten aquaporins (Aqps) subtypes including Aqp1～Aqp9 and Aqp11. Furthermore, the Aqps expression profiles were constructed for each organ and analyzed by performing Principle Component Analysis. In addition, immunohistochemistry was explored to look at the protein expression of Aqp1, Aqp2, Aqp3 and Aqp4 in the rat kidneys.

Results

There was a prominent down-regulation profile in the MCAO/Reperfusion rat kidneys. The protein expression of Aqp1, Aqp2, Aqp3 and Aqp4 was decreased in the kidneys of the MCAO/Reperfusion rats. We suggested that the kidney was in the highest risk to be damaged following the CIR/I. Down-regulation of Aqp2, Aqp3 and Aqp4 was involved in the acute kidney injury induced by the CIR/I.

Cognitive Impairment in Chronic Kidney Disease Is Associated with Glymphatic System Dysfunction

Introduction

This study was designed to explore the associations between impaired cognition in chronic kidney disease (CKD) patients and the dysfunction of the glymphatic system.

Method

Data were obtained from 77 CKD patients and 50 age-matched healthy control individuals from the First Affiliated Hospital of Zhengzhou University. CKD patients were stratified into with and without impaired cognitive function. T2-weighted magnetic resonance imaging results were used to assess area ratios for the perivascular space and ventricles in participants, while the Montreal Cognitive Assessment and the Mini-Mental State Examination were employed to measure cognitive function. Correlations between the perivascular space or ventricle area ratios and cognitive impairment were assessed in CKD patients.

Results

Significant increases in the burden of enlarged perivascular spaces in the frontal cortex and basal ganglia were observed in CKD patients with cognitive impairment relative to those without such impairment, with a concomitant increase in analyzed ventricle area ratios. Enlarged perivascular spaces in the frontal cortex, basal ganglia and increased area ratios of lateral ventricles and 4th ventricle exhibited relatively high sensitivity and specificity as means of differing between the CKD patients with and without cognitive impairment.

Conclusion

These results indicate that the burden of enlarged perivascular spaces in the frontal cortex and basal ganglia and increases in ventricle area ratio values may offer utility as biomarkers that can aid in detection of even mild cognitive decline in individuals with CKD. The dysfunction of the glymphatic system may play a key role in the pathogenesis of CKD-related cognitive impairment.

Pilot Study on the Molecular Pathogenesis of Pyeloureteral Junction Obstruction: Underdevelopment or Fibrosis?

Background and Objectives: Congenital ureteral stenosis is one of the leading causes of impaired urinary drainage and subsequent dilatation of the urinary collecting system, known as hydronephrosis or ureterohydronephrosis. The mechanism that leads to obstruction is not clearly known. Multiple studies in rat models have shown increased angiotensin II and TGFβ levels in obstructed ureteral tissue. The aim of the study is to investigate the expression of fibrosis-related genes in obstructive and normal ureteral tissue. Material and Methods: It is a monocentric pilot study in which nineteen patients were selected prospectively. 17 patients underwent Hynes-Anderson pyeloplasty due to the PUJO; two patients underwent ureteroneocystostomy due to ureterovesical junction obstruction (UVJO); and six patients were chosen for the control group: five underwent nephrectomies due to the kidney tumor and one underwent upper pole heminephrectomy due to the duplex kidney with normal pyeloureteric junctions in all. Tissue RNA was chemically extracted after freezing the biopsy samples in liquid nitrogen, with cDNA synthesis performed immediately after nucleic acid isolation. qPCR was performed to evaluate the relative expression of Tgfb1, Mmp1, Timp1, Pai1, Ctgf, and Vegfa. Expression levels of the Gapdh and Gpi genes (geometric average) were used to calculate the relative expression of the investigated genes. Outliers were removed prior to calculating confidence intervals for the experimental groups, and a Wilcoxon rank-sum test was performed to determine the statistical significance of the differences. Results: Significant differences between healthy and stenotic tissue samples in Ctgf gene expression levels were observed, with the samples from afflicted tissue showing lower expression. No statistical difference in expression levels of Tgfb1, Timp1, Vegfa, Mmp1, and Pai1 was found. Conclusions: These findings suggest that tissue fibrosis, similar to other tissues and organs, is not the leading cause of stenosis, at least at the moment of surgery. Decreased CTGF expression is indicative of the developmental origin of obstruction.

Aquaporins in Urinary System

There are at least eight aquaporins (AQPs) expressed in the kidney. Including AQP1 expressed in proximal tubules, thin descending limb of Henle and vasa recta; AQP2, AQP3, AQP4, AQP5, and AQP6 expressed in collecting ducts; AQP7 expressed in proximal tubules; AQP8 expressed in proximal tubules and collecting ducts; and AQP11 expressed in the endoplasmic reticulum of proximal tubular epithelial cells. Over years, researchers have constructed different AQP knockout mice and explored the effect of AQP knockout on kidney function. Thus, the roles of AQPs in renal physiology are revealed, providing very useful information for addressing fundamental questions about transepithelial water transport and the mechanism of near isoosmolar fluid reabsorption. This chapter introduces the localization and function of AQPs in the kidney and their roles in different kidney diseases to reveal the prospects of AQPs in further basic and clinical studies.

Glymphatic system dysfunction in patients with early chronic kidney disease

Introduction

It is a recent finding that glymphatic system dysfunction contributes to various neurological problems. The purpose of this research was to assess the function of the glymphatic system in neurologically asymptomatic early chronic kidney disease (CKD) patients and healthy controls, using diffusion tensor image analysis along perivascular space (DTI-ALPS) index.

Methods

In a prospective study, we included patients with early CKD who were asymptomatic for neurological issues and obtained clinical and laboratory data. In all participants, brain magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) was conducted. We used DSI program for DTI preprocessing and DTI-ALPS index estimation. The DTI-ALPS index was compared between patients with early CKD and healthy controls, and the association between clinical characteristics and the DTI-ALPS index was investigated.

Results

Eighteen patients with early CKD and 18 healthy controls were included in this study. Patients with early CKD had lower DTI-ALPS index than healthy controls (1.259 ± 0.199 vs. 1.477 ± 0.232, p = 0.004). In the correlation analysis, the DTI-ALPS index had no significant relationship with other clinical factors.

Conclusion

We suggest dysfunction of glymphatic system in patients with early chronic kidney disease using the DTI-ALPS index. This may be related to the pathophysiology of neurological problems including impairment of cognition in patients with early CKD.

Effects of a Chinese herbal extract on the intestinal tract and aquaporin in Adriamycin-induced nephropathy

Wuling Decoction is a traditional Chinese medicine that has been used to open knots, benefit water, transform Qi, return fluid, and has a significant effect on strengthening the spleen and removing dampness. To explore the effects of Wuling Decoction on the intestinal tract and aquaporin in Adriamycin-induced nephropathy, 45 specific pathogen free (SPF) Wistar rats were randomly divided into a blank control group (5 rats), Dosing control group (10 rats), Adriamycin nephropathy model group (10 rats), diarrhea group (10 rats), and an Adriamycin nephropathy diarrhea model group (10 rats). The tissue localization of aquaporin (AQP) was determined by immunohistochemistry. The expression of AQP mRNA and protein was measured by RT-PCR and western blot analysis, respectively. The results indicated that Wuling Decoction causes excretion of AQP2 through the urine, regulates AQP2 levels, and exerts diuretic and anti-diarrheal effects. It also regulates the levels of antidiuretic hormone (ADH) and arginine vasopressin (AVP), affects water absorption rate, and reduces the level of cyclic adenosine monophosphate (cAMP) in each tissue, thus reducing the absorption of AQP2 to water. Wuling Decoction promoted AQP2 expression in the nephropathy model group and inhibited AQP2 expression in the diarrhea group. Wuling Decoction increased the expression of aquaporin in the intestinal tract, reduced the water content of stool by promoting the absorption of water in the intestinal tract, inhibited the expression of aquaporin and its regulatory factors in nephridia tissue, and reduced the reabsorption of water to increase urine volume, to decrease the occurrence of diarrhea.

Aquaporins in Renal Diseases

Aquaporins (AQPs) are a family of highly selective transmembrane channels that mainly transport water across the cell and some facilitate low-molecular-weight solutes. Eight AQPs, including AQP1, AQP2, AQP3, AQP4, AQP5, AQP6, AQP7, and AQP11, are expressed in different segments and various cells in the kidney to maintain normal urine concentration function. AQP2 is critical in regulating urine concentrating ability. The expression and function of AQP2 are regulated by a series of transcriptional factors and post-transcriptional phosphorylation, ubiquitination, and glycosylation. Mutation or functional deficiency of AQP2 leads to severe nephrogenic diabetes insipidus. Studies with animal models show AQPs are related to acute kidney injury and various chronic kidney diseases, such as diabetic nephropathy, polycystic kidney disease, and renal cell carcinoma. Experimental data suggest ideal prospects for AQPs as biomarkers and therapeutic targets in clinic. This review article mainly focuses on recent advances in studying AQPs in renal diseases.

Defective bone microstructure in hydronephrotic mice: a histomorphometric study in ICR/Mlac-hydro mice

Chronic renal impairment can lead to bone deterioration and abnormal bone morphology, but whether hydronephrosis is associated with bone loss remains unclear. Herein, we aimed to use computer-assisted bone histomorphometric technique to investigate microstructural bone changes in Imprinting Control Region (ICR) mice with a spontaneous mutation that was associated with bilateral nonobstructive hydronephrosis (ICR/Mlac-hydro). The results showed that 8-week-old ICR/Mlac-hydro mice manifested decreases in trabecular bone number and thickness, and an increased trabecular separation, thereby leading to a reduction in trabecular bone volume compared with the wild-type mice. Furthermore, histomorphometric parameters related to both bone resorption and formation, that is, eroded surface, osteoclast surface, and osteoblast surface, were much lower in ICR/Mlac-hydro mice than in the wild type. A decrease in moment of inertia was found in ICR/Mlac-hydro mice, indicating a decrease in bone strength. In conclusion, ICR/Mlac-hydro mice exhibited trabecular bone loss, presumably caused by marked decreases in both osteoblast and osteoclast activities, which together reflected abnormally low bone turnover. Thus, this mouse strain appeared to be a valuable model for studying the hydronephrosis-associated bone disease.

Pulmonary edema due to oral gavage in a toxicological study related to aquaporin-1, -4 and -5 expression

A one-time oral gavage can be enough to cause of alveologenic edema with higher expression of AQP-1 and -4 than that with repeated-dose oral gavage, which caused both profound perivascular edema and hydrostatic pressure edema, while AQP-5 was similarly expressed. The alteration of AQPs expression was probably related to alveolar fluid clearance across the alveolar and bronchiolar epithelium in different stages of lung injury. The results clarified the type of lung edema in acute and sub-chronic toxicity studies without treatment related effect of tested material. The pathogenesis of pulmonary edema due to oral gavage toxicological study is associated with the cellular immune response to the reflux materials. Mast cell and leukocyte accumulation may contribute to increase vascular permeability leading to permeability edema. The increase in alveolar septum epithelium, perivascular and peribronchial cuffing, accumulation alveolar lipid containing macrophage and medial hyperplasia of the pulmonary artery might have been caused to increase airway resistance, which resulted in hydrostatic pressure edema.