Oxidative Damage and Mitochondrial Injuries Are Induced by Various Irrigation Pressures in Rabbit Models of Mild and Severe Hydronephrosis

Comparison of intrarenal pressure between convention and vacuum-assisted ureteral access sheath using an ex vivo porcine kidney model

OBJECTIVE

This study aimed to prove the vacuum-assisted ureteral access sheath (vaUAS) is more effective in maintaining a lower IRP than conventional ureteral access sheath (cUAS).

MATERIALS

The model consisted of 12 freshly harvested adult porcine kidneys.

METHODS

Either a 12/14F cUAS or vaUAS was alternately inserted into the ureter to one cm below the renal pelvis. Upper, middle, and lower calyces were punctured, and 6F pressure monitor catheters were introduced. IRP with cUAS was monitored using various irrigation rates. IRP with vaUAS was monitored with the same irrigation rates; various aspiration pressures; and vent fully closed, 50% closed, and fully open.

RESULTS

cUAS with irrigation rate of 50 cc/min resulted in IRP < 30 mmHg. 50 to 100 cc/min should be used with caution. When irrigation rate exceeded 100 cc/min, IRP rose to ≥ 30 mmHg in most instances. With vent closed, vaUAS with vacuum pressure ≥ 150 mmHg and irrigation rate of 50 cc, 100 cc, and 150 cc/min generally resulted in IRPs < 5 mmHg. With vent half closed, vaUAS with vacuum pressure ≥ 300 mmHg and irrigation rate of ≤ 100 cc/min avoided IRP > 30 mmHg. vaUAS with vent open showed limited advantages over cUAS.

CONCLUSION

vaUAS maintains lower IRP than cUAS under same parameters. Both vaUAS and cUAS can be used when irrigation is ≤ 50 cc/min vaUAS showed clear advantages over cUAS in maintaining lower pressure when irrigation rate is ≥ 100 cc/min.

Loss of Pten in Renal Tubular Cells Leads to Water Retention by Upregulating AQP2

Introduction

Phosphatase and tensin (PTEN) is a multifunctional gene associated with the normal development and physiological function of various tissues including the kidney. However, its role in renal tubular reabsorption function has not been well elucidated.

Methods

We generated a renal tubule-specific Pten knockout mouse model by crossing Pten^fl/fl mice with Ksp-Cre transgenic mice, evaluated the effect of Pten loss on renal tubular function, and investigated the underlying mechanisms.

Results

Pten loss resulted in abnormal renal structure and function and water retention in multiple organs. Our results also demonstrated that aquaporin-2 (AQP2), an important water channel protein, was upregulated and concentrated on the apical plasma membrane of collecting duct cells, which could be responsible for the impaired water balance in Pten loss mice. The regulation of Pten loss on AQP2 was mediated by protein kinase B (AKT) activation.

Conclusions

Our results reveal a connection between PTEN gene inactivation and water retention, suggesting the importance of PTEN in normal kidney development and function.

Comparison of intrarenal pressure between convention and vacuum-assisted ureteral access sheath using an ex vivo porcine kidney model

OBJECTIVE

This study aimed to prove the vacuum-assisted ureteral access sheath (vaUAS) is more effective in maintaining a lower IRP than conventional ureteral access sheath (cUAS).

MATERIALS

The model consisted of 12 freshly harvested adult porcine kidneys.

METHODS

Either a 12/14F cUAS or vaUAS was alternately inserted into the ureter to one cm below the renal pelvis. Upper, middle, and lower calyces were punctured, and 6F pressure monitor catheters were introduced. IRP with cUAS was monitored using various irrigation rates. IRP with vaUAS was monitored with the same irrigation rates; various aspiration pressures; and vent fully closed, 50% closed, and fully open.

RESULTS

cUAS with irrigation rate of 50 cc/min resulted in IRP < 30 mmHg. 50 to 100 cc/min should be used with caution. When irrigation rate exceeded 100 cc/min, IRP rose to ≥ 30 mmHg in most instances. With vent closed, vaUAS with vacuum pressure ≥ 150 mmHg and irrigation rate of 50 cc, 100 cc, and 150 cc/min generally resulted in IRPs < 5 mmHg. With vent half closed, vaUAS with vacuum pressure ≥ 300 mmHg and irrigation rate of ≤ 100 cc/min avoided IRP > 30 mmHg. vaUAS with vent open showed limited advantages over cUAS.

CONCLUSION

vaUAS maintains lower IRP than cUAS under same parameters. Both vaUAS and cUAS can be used when irrigation is ≤ 50 cc/min vaUAS showed clear advantages over cUAS in maintaining lower pressure when irrigation rate is ≥ 100 cc/min.

Filtering through the role of NRF2 in kidney disease

Kidney disease affects ~ 10% of the population worldwide, resulting in millions of deaths each year. Mechanistically, oxidative stress is a major driver of various kidney diseases, and promotes the progression from acute to chronic injury, as well as renal cancer development. NRF2, the master regulator of redox balance, has been shown to protect against kidney disease through its negation of reactive oxygen species (ROS). However, many kidney diseases exhibit high levels of ROS as a result of decreased NRF2 protein levels and transcriptional activity. Many studies have tested the strategy of using NRF2 inducing compounds to alleviate ROS to prevent or slow down the progression of kidney diseases. Oppositely, in specific subsets of renal cancer, NRF2 is constitutively activated and contributes to tumor burden and overall poor prognosis; therefore, there has been a recent interest in studies investigating the benefits of NRF2 inhibition. In this review, we summarize recent literature investigating the role of NRF2 and oxidative stress in various kidney diseases, and how pharmacological modification of NRF2 signaling could play a protective role.

[Role of pressure and temperature in ureterorenoscopy and percutaneous nephrolitholapaxy : Pressure and temperature changes during stone treatment]

Ureterorenoscopy and percutaneous nephrolitholapaxy are minimally invasive procedures and are the standard procedures for the treatment of kidney stones and ureteral calculi. To achieve an adequate view, in both methods an optimal and sufficient irrigation flow is necessary. The intrarenal pressure is influenced by the irrigation pressure and irrigation volume and has to be controlled. Pathologically elevated intrarenal pressure can lead to irreversible damage of the kidneys. Lasers are frequently used for stone fragmentation. It has been shown in studies that the laser energy can lead to an increase in the temperature and that thermal effects can also damage the kidneys. This article provides the surgeon with an overview about the effects of temperature and pressure changes during ureterorenoscopy and percutaneous nephrolitholapaxy and how damages can be avoided.

Cathepsin S regulates renal fibrosis in mouse models of mild and severe hydronephrosis

As a member of the cysteine protease family, cathepsin S (CTSS) serves an important role in diseases such as cancer, arthritis and atherosclerosis. Nevertheless, its role in renal fibrosis is unknown. In the present study, the effects of CTSS on renal fibrosis in mild (group M) and severe (group S) hydronephrosis were studied by reverse transcription‑-quantitative PCR (RT‑qPCR), western blot analysis (WB), Masson's trichrome staining and immunohistochemical staining in mouse models. The effects of CTSS on extracellular matrix (ECM) deposition and epithelial‑mesenchymal transition (EMT) and the potential mechanisms were further studied by RT‑qPCR and WB in transforming growth factor (TGF‑β1)‑stimulated TCMK‑1 cells. Compared with group N (no hydronephrosis), the expression levels of CTSS in the M and S groups were significantly higher, and a significant increase in ECM deposition was observed in the S group. In addition, compared with group N, the expression levels of TGF‑β1, α‑smooth muscle actin (α‑SMA), SMAD2, SMAD3, phosphorylated (p)SMAD2 and pSMAD3 in groups M and S were significantly higher, whereas the expression of E‑cadherin was significantly lower. Inhibition of CTSS expression increased the expression levels of TGF‑β1, α‑SMA, fibronectin, collagen‑I, SMAD2, SMAD3, pSMAD2 and pSMAD3, whereas E‑cadherin expression decreased. A significant increase in CTSS was observed in the TGF‑β1‑stimulated TCMK‑1 cell line. ECM deposition and EMT were also intensified. The opposite outcomes occurred after intervention with small interfering RNA targeting CTSS. In conclusion, CTSS affected EMT and the deposition of ECM. CTSS may mediate the regulation of fibrosis by the TGF‑β/SMAD signaling pathway. CTSS may serve an important role in the treatment of renal fibrosis.

Kidney fibrosis induced by various irrigation pressures in mouse models of mild and severe hydronephrosis

OBJECTIVE

We want to study whether the degree of fibrosis in the mild and severe hydronephrosis is different, and whether the irrigation pressure will affect the fibrosis of the hydronephrosis.

METHODS

Animal models of mild and severe hydronephrosis in the left kidney were established: 72 healthy C57BL/6 mice were randomly divided into nine groups (eight in each group). The N group was used as a control group, and 0 mmHg pressure perfusion was given. The M and S groups were used as mild and severe hydronephrosis groups, respectively. The mild and severe hydronephrosis groups were subdivided into eight subgroups, M0-M3 and S0-S3. Among them, groups 0, 1, 2, and 3 were perfused with 0 mmHg, 20 mmHg, 60 mmHg, and 100 mmHg, respectively. We investigated the effects of irrigation pressures on renal fibrosis in mild (group M) and heavy (group S) hydronephrosis by quantitative real-time polymerase chain reaction, Western blot analysis, Masson staining and immunohistochemistry staining in mouse models.

RESULTS

Compared with group N, EMT and ECM deposits were significantly aggravated in both the mild and severe hydronephrosis groups, TGF-β signaling pathway-related molecules significantly changed too. In terms of ECM deposition, S2 and S3 are significantly increased compared to S0.The EMT of M2 and M3 changed significantly compared with M0; the EMT of S1, S2 and S3 changed significantly compared with S0.The molecules related to TGF-β signaling pathway also changed: M0 and S0 changed significantly compared with N; M1, M2 and M3 changed significantly compared with M0; compared with S0, S1, S2 and S3 changed significantly.

CONCLUSION

Compared with mild hydronephrosis, renal fibrosis in severe hydronephrosis is more severe and its tolerance to perfusion pressure is lower. These changes may be related to the TGF-β signalling pathway.

Pressure matters: intrarenal pressures during normal and pathological conditions, and impact of increased values to renal physiology

PURPOSE

To perform a review on the latest evidence related to normal and pathological intrarenal pressures (IRPs), complications of incremented values, and IRP ranges during endourology.

METHODS

A literature search was performed using PubMed, restricted to original English-written articles, including animal, artificial model, and human studies. Different keywords were: percutaneous nephrolithotomy, PCNL, ureteroscopy, URS, RIRS, irrigation flow, irrigation pressure, intrarenal pressure, intrapelvic pressure and renal pelvic pressure.

RESULTS

Normal IRPs range from zero to a few cm H₂O. Pyelovenous backflow may occur at pressure range of 13.6-27.2 cm H₂O. During upper tract endourology, complications such as pyelorenal backflow, sepsis, and renal damage are directly related to increased IRPs. Duration of increased IRPs and concomitant obstruction are independent predictors of complication development.

CONCLUSIONS

IRP increase remains a neglected predictor of upper tract endourology complications and its intraoperative monitoring should be taken into consideration. Further research is necessary, to quantify pressures generated during upper tract endourology, and introduce means of controlling them.

Oxidative damage and mitochondrial injuries differ following pneumoperitoneum pressure in rabbit models of varying degrees of hydronephrosis

The influence of intraabdominal pressure which is necessary to maintain the operating area during the surgery cannot be ignored especially on the kidneys. Many articles have reported the effect of intraabdominal pressure on normal kidneys. However, the influence of intraabdominal pressure on hydronephrosis kidneys is rarely studied. The aim of the present study was to clarify whether intraabdominal pressure tolerance is modified in various degrees of kidney hydronephrosis by evaluating oxidative damage and mitochondrial injuries. A total of 72 rabbits were randomly divided into three groups (groups N, M and S, which represented rabbits with no, mild and severe hydronephrosis, respectively). Rabbits in groups M (n=24) and S (n=24) underwent a surgical procedure inducing mild or severe hydronephrosis, respectively. Subsequently, rabbits in all groups were allocated to 4 subgroups (N0‑N3, M0‑M3 and S0‑S3) consisting of 6 rabbits each. Groups 0 to 3 were, respectively, subjected to intraabdominal pressures of 0, 5, 10 and 15 mmHg. Oxidative damage was assessed by analyzing levels of reactive oxygen species (ROS), superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GSH‑Px), catalase (CAT) and lactate (LD). Mitochondrial injuries were assessed based on mitochondrial membrane potential (MMP) alterations, mitochondrial structure and cytochrome c (cytc) protein expression, as measured by JC‑1 staining, electron microscopy and western blotting, respectively. Oxidative damage and mitochondrial injuries were noticeably exacerbated in group N and M with increased levels of ROS, MDA and LD, decreased levels of SOD, GSH‑Px, CAT and MMP, mitochondrial vacuolization and higher expression of cytc when the intraabdominal pressure reached 15 mmHg. In group S, these alterations occurred at pressures of 10 and 15 mmHg. Therefore, it was concluded that in rabbits exposed to pneumoperitoneal pressure, kidneys with severe hydronephrosis were more likely to suffer from oxidative damage and mitochondrial injuries compared with kidneys with mild hydronephrosis and normal kidneys.

Ectopic Expression of Innate Immune Protein, Lipocalin-2, in Lactococcus lactis Protects Against Gut and Environmental Stressors

BACKGROUND

Lipocalin-2 (Lcn2) is a multifunctional innate immune protein that exhibits antimicrobial activity by the sequestration of bacterial siderophores, regulates iron homeostasis, and augments cellular tolerance to oxidative stress. Studies in the murine model of colitis have demonstrated that Lcn2 deficiency exacerbates colitogenesis; however, the therapeutic potential of Lcn2 supplementation has yet to be elucidated. In light of its potential mucoprotective functions, we, herein, investigated whether expression of Lcn2 in the probiotic bacterium can be exploited to alleviate experimental colitis.

METHODS

Murine Lcn2 was cloned into the pT1NX plasmid and transformed into Lactococcus lactis to generate L. lactis-expressing Lcn2 (Lactis-Lcn2) or the empty plasmid (Lactis-Con). Lactis-Lcn2 was characterized by immunoblot and enzyme-linked immunosorbent assay and tested for its antimicrobial efficacy on Escherichia coli. The capacity of Lactis-Lcn2 and Lactis-Con to withstand adverse conditions was tested using in vitro viability assays. Dextran sodium sulfate colitis model was used to investigate the colonization ability and therapeutic potential of Lactis-Lcn2 and Lactis-Con.

RESULTS

Lcn2 derived from Lactis-Lcn2 inhibited the growth of E. coli and reduced the bioactivity of enterobactin (E. coli-derived siderophore) in vitro. Lactis-Lcn2 displayed enhanced tolerance to adverse pH, high concentration of bile acids, and oxidative stress in vitro and survived better in the inflamed gut than Lactis-Con. Consistent with these features, Lactis-Lcn2 displayed better mucoprotection against intestinal inflammation than Lactis-Con when administered into mice with dextran sulfate sodium-induced acute colitis.

CONCLUSIONS

Our findings suggest that Lcn2 expression can be exploited to enhance the survivability of probiotic bacteria during inflammation, which could further improve its efficacy to treat experimental colitis.