Daily therapy with a slow-releasing H2S donor GYY4137 enables early functional recovery and ameliorates renal injury associated with urinary obstruction.

OBJECTIVES: To assess the effects of slow-releasing H2S donor GYY4137 on post-obstructive renal function and injury following unilateral ureteral obstruction (UUO) by using the UUO and reimplantation (UUO-R) model in rats and to elucidate potential mechanisms by using an in vitro model of epithelial-mesenchymal transition (EMT). METHODS: Male Lewis rats underwent UUO at the left ureterovesical junction. From post-operative day (POD) 1-13, rats received daily intraperitoneal (IP) injection of phosphate buffered saline (PBS, 1 mL) or GYY4137 (200 µmol/kg/day in 1 mL PBS, IP). On POD 14, the ureter was reimplanted back into the bladder, followed by a right nephrectomy. Urine and serum samples were collected to monitor renal function. On POD 30, the left kidney was removed and tissue sections were stained with H&E, TUNEL, CD68, CD206, myeloperoxidase, and Masson's trichrome to determine cortical thickness, apoptosis, inflammation, and fibrosis. In our in vitro model of EMT, NRK52E cells were treated with 10 ng/mL TGF-ß1, 10 µM GYY4137 and/or 50 µM GYY4137. Western blot analysis was performed to determine the expression of E-cadherin, vimentin, Smad7 and TGF-ß1 receptor II (TßRII). RESULTS: GYY4137 led to a moderate decrease in post-obstructive serum creatinine, cystatin C and FENa. We also observed a trend towards a decrease in post-obstructive proteinuria following GYY4137 treatment. Histologically, we observed a significant decrease in apoptosis, inflammation, and fibrosis. Furthermore, our in vitro studies demonstrate that in the presence of TGF-ß1, GYY4137 significantly decreases vimentin and TßRII and significantly increases E-cadherin and Smad7. CONCLUSIONS: H2S may help to accelerate the recovery of renal function post-obstruction and attenuates renal injury associated with UUO. It is possible that H2S mitigates fibrosis by regulating the TGF-ß1-mediated EMT pathway. Taken together, our data suggest that H2S may be a potential novel therapy for improving renal function and limiting renal injury associated with obstructive uropathy.

Is hydrogen sulfide a potential novel therapy to prevent renal damage during ureteral obstruction?

In prolonged complete unilateral ureteral obstruction, reduced renal blood flow places the kidney in a state of ischemia, which can cause tubular injury and inflammation. Infiltrating inflammatory cells release transforming growth factor beta 1, which is a cytokine that initiates fibrosis through the epithelial-mesenchymal-transition pathway. Persistent fibrosis can lead to irreversible renal injury and loss of function. While surgical intervention can remove the obstruction, relief of obstruction may not fully reverse renal injury. Additionally, patients often encounter long wait-times between initial consultation and medical intervention, resulting in the accumulation of renal injury that may cause permanent dysfunction. Currently, accepted pharmacological therapies to mitigate the symptoms of ureteral obstruction include acetaminophen, cyclooxygenase-inhibitors, non-steroidal anti-inflammatory medications, opioids and alpha-receptor blockers. However, there is no evidence that they mitigate renal injury. Therefore, identifying potential therapies that could be administered during obstruction may help to improve renal function following decompression. Evidence suggests that endogenously produced gasotransmitters can exhibit anti-inflammatory and antioxidant effects. Nitric oxide, carbon monoxide, and hydrogen sulfide have been identified as gasotransmitters and have been shown to have cytoprotective effects in various models of tissue injury. Studies have shown that treatment with sodium hydrogen sulfide (a hydrogen sulfide donor salt) mitigated transforming growth factor beta 1 expression, oxidative stress, fibrosis, and inflammation associated with urinary obstruction. More recently, the use of more directed hydrogen sulfide donor molecules, such as GYY4137, has led to significant decreases in inflammation, fibrosis, and expression of epithelial mesenchymal transition markers following urinary obstruction. Taken together, these findings suggest that hydrogen sulfide may be a novel potential therapy against renal injury caused by urinary obstruction. This review will highlight the existing literature about the pathogenesis and treatment of renal damage caused by chronic urinary obstruction and propose novel upcoming strategies that could improve patient outcomes.

A novel approach to off-clamp partial nephrectomy demonstrates significant improvements in renal injury in an experimental porcine model.

INTRODUCTION: We sought to design a partial nephrectomy (PN) with contralateral total nephrectomy porcine model and assess the underlying mechanisms of ischemia reperfusion injury (IRI) after PN using a novel, clinically approved resection device. METHODS: Domestic male pigs (n=9) underwent left lower pole PN, allocated to either standard (Group 1) or no ischemia PN (Group 2), followed by contralateral nephrectomy. Biochemical studies were performed at baseline, Day 2, and Day 7; after sacrifice, kidneys were processed for histological analysis. Apoptotic markers were measured by Western blot analyses. Urinary biomarkers were measured to assess acute kidney injury. RESULTS: At Day 2 following PN, there was a significant rise in serum creatinine in Group 1 compared to Group 2 (355 vs. 136 mmol/L; p=0.008). Intra-renal tissue oxygen saturation after PN was inversely correlated with postoperative creatinine (rs -0.75; p=0.012) and the grade of acute tubular necrosis (rs -0.70; p=0.036). We observed a rise in expression of pro-apoptotic markers and pro-inflammatory markers in Group 1 following PN compared to Group 2. Histological analysis revealed higher grade of apoptosis in Group 1. CONCLUSIONS: IRI associated with standard PN has a deleterious impact on acute renal function, markers of tissue injury, and histological parameters, compared to off-clamp PN using the ALTRUS device. We identified several intraoperative and postoperative markers that may be used as predictors for functional and histological injury following PN.

GYY4137, a Slow-Releasing Hydrogen Sulfide Donor, Ameliorates Renal Damage Associated with Chronic Obstructive Uropathy.

PURPOSE: Chronic obstructive uropathy can cause irreversible kidney injury, atrophy and inflammation, which can ultimately lead to fibrosis. Epithelial-mesenchymal transition is a key trigger of fibrosis that is caused by up-regulation of TGF-ß1 (transforming growth factor-ß1) and ANGII (angiotensin II). H2S is an endogenously produced gasotransmitter with cytoprotective properties. We sought to elucidate the effects of the slow-releasing H2S donor GYY4137 on chronic ureteral obstruction and evaluate the potential mechanisms. MATERIALS AND METHODS: Following unilateral ureteral obstruction male Lewis rats were given daily intraperitoneal administration of phosphate buffered saline vehicle (obstruction group) or phosphate buffered saline plus 200 µmol/kg GYY4137 (obstruction plus GYY4137 group) for 30 days. Urine and serum samples were collected to determine physiological parameters of renal function and injury. Kidneys were removed on postoperative day 30 to evaluate histopathology and protein expression. Epithelial-mesenchymal transition in LLC-PK1 pig kidney epithelial cells was induced with TGF-ß1 and treated with GYY4137 to evaluate potential mechanisms via in vitro scratch wound assays. RESULTS: H2S treatment decreased serum creatinine and the urine protein-to-creatinine excretion ratio after unilateral ureteral obstruction. In addition, H2S mitigated cortical loss, inflammatory damage and tubulointerstitial fibrosis. Tissues showed decreased expression of epithelial-mesenchymal transition markers upon H2S treatment. Epithelial-mesenchymal transition progression in LLC-PK1 was alleviated upon in vitro administration of GYY4137. CONCLUSIONS: To our knowledge our findings demonstrate for the first time the protective effects of H2S in chronic obstructive uropathy. This may represent a potential therapeutic solution to ameliorate renal damage and improve the clinical outcomes of urinary obstruction.

PDLIM7 is a novel target of the ubiquitin ligase Nedd4-1 in skeletal muscle.

Skeletal muscle atrophy remains a complication occurring both as a natural response to muscle disuse and as a pathophysiological response to illness such as diabetes mellitus and nerve injury, such as traumatic muscle denervation. The ubiquitin-proteasome system (UPS) is the predominant proteolytic machinery responsible for atrophy of skeletal muscle, and Nedd4-1 (neural precursor cell-expressed developmentally down-regulated 4-1) is one of a series of E3 ubiquitin ligases identified to mediate inactivity-induced muscle wasting. Targets of Nedd4-1 mediated ubiquitination in skeletal muscle remain poorly understood. In the present study, we identified PDLIM7 (PDZ and LIM domain 7, Enigma), a member of the PDZ-LIM family of proteins, as a novel target of Nedd4-1 in skeletal muscle. The PDZ-LIM family of proteins is known to regulate muscle development and function. We show that Nedd4-1 expression in muscle atrophied by denervation is co-incident with a decrease in PDLIM7 and that PDLIM7 protein levels are stabilized in denervated muscle of Nedd4-1 skeletal muscle-specific knockout mice (SMS-KO). Exogenous PDLIM7 and Nedd4-1 transfected into human embryonic kidney (HEK)293 cells co-immunoprecipitate through binding between the PY motif of PDLIM7 and the second and third WW domains of Nedd4-1 and endogenous PDLIM7 and Nedd4-1 interact in the cytoplasm of differentiated C2C12 myotubes, leading to PDLIM7 ubiquitination. These results identify PDLIM7 as a bona fide skeletal muscle substrate of Nedd4-1 and suggest that this interaction may underlie the progression of skeletal muscle atrophy. This offers a novel therapeutic target that could be potentially used to attenuate muscle atrophy.