Short-term oral gavage administration of adenine induces a model of fibrotic kidney disease in rats

Transcutaneous measurement of renal function in two rodent models of obstructive nephropathy

OBJECTIVE

Glomerular filtration rate (GFR) is a key indicator of renal function. In both clinical practice and pre-clinical research, serum levels of endogenous filtration markers, such as creatinine, are often used to estimate GFR. However, these markers often do not reflect minor changes in renal function. In this study, we therefore set out to evaluate the applicability of transcutaneous GFR (tGFR) measurements to monitor the changes in renal function, as compared to plasma creatinine (pCreatinine), in two models of obstructive nephropathy, namely unilateral ureteral obstruction (UUO) or bilateral ureteral obstruction followed by release (BUO-R) in male Wistar rats.

RESULTS

UUO animals showed a significant reduction in tGFR compared to baseline; whereas pCreatinine levels were not significantly changed. In BUO animals, tGFR drops 24 h post BUO and remains lower upon release of the obstruction until day 11. Concomitantly, pCreatinine levels were also increased 24 h after obstruction and 24 h post release, however after 4 days, pCreatinine returned to baseline levels. In conclusion, this study revealed that the tGFR method is superior at detecting minor changes in renal function as compared to pCreatinine measurements.

Shen Qi Wan attenuates renal interstitial fibrosis through upregulating AQP1

Renal interstitial fibrosis (RIF) is the crucial pathway in chronic kidney disease (CKD) leading to the end-stage renal failure. However, the underlying mechanism of Shen Qi Wan (SQW) on RIF is not fully understood. In the current study, we investigated the role of Aquaporin 1 (AQP1) in SQW on tubular epithelial-to-mesenchymal transition (EMT). A RIF mouse model induced by adenine and a TGF-β1-stimulated HK-2 cell model were etablished to explore the involvement of AQP 1 in the protective effect of SQW on EMT in vitro and in vivo. Subsequently, the molecular mechanism of SQW on EMT was explored in HK-2 cells with AQP1 knockdown. The results indicated that SQW alleviated kidney injury and renal collagen deposition in the kidneys of mice induced by adenine, increased the protein expression of E-cadherin and AQP1 expression, and decreased the expression of vimentin and α-smooth muscle actin (α-SMA). Similarly, treatmement with SQW-containing serum significantly halted EMT process in TGF-β1 stimulated HK-2 cells. The expression of snail and slug was significantly upregulated in HK-2 cells after knockdown of AQP1. AQP1 knockdown also increased the mRNA expression of vimentin and α-SMA, and decreased the expression of E-cadherin. The protein expression of vimentin increased, while the expression of E-cadherin and CK-18 significantly decreased after AQP1 knockdown in HK-2 cells. These results revealed that AQP1 knockdown promoted EMT. Furthermore, AQP1 knockdown abolished the protective effect of SQW-containing serum on EMT in HK-2 cells. In sum, SQW attentuates EMT process in RIF through upregulation of the expression of AQP1.

Soluble guanylate cyclase agonist, isoliquiritigenin attenuates renal damage and aortic calcification in a rat model of chronic kidney failure

AIMS

Chronic kidney disease (CKD) is a growing fatal health problem worldwide associated with vascular calcification. Therapeutic approaches are limited with higher costs and poor outcomes. Adenine supplementation is one of the most relevant CKD models to human. Insufficient Nitric Oxide (NO)/ cyclic Guanosine Monophosphate (cGMP) signaling plays a key role in rapid development of renal fibrosis. Natural products display proven protection against CKD. Current study therefore explored isoliquiritigenin, a bioflavonoid extracted from licorice roots, potential as a natural activator for soluble Guanylate Cyclase (sGC) in a CKD rat model.

MATERIALS AND METHODS

60 male Wistar rats were grouped into Control group (n = 10) and the remaining rats received adenine (200 mg/kg, p.o) for 2 wk to induce CKD. They were equally sub-grouped into: Adenine untreated group and 4 groups orally treated by isoliquiritigenin low or high dose (20 or 40 mg/kg) with/without a selective sGC inhibitor, ODQ (1-H(1,2,4)oxadiazolo(4,3-a)-quinoxalin-1-one, 2 mg/kg, i.p) for 8 wk.

KEY FINDINGS

Long-term treatment with isoliquiritigenin dose-dependently and effectively amended adenine-induced chronic renal and endothelial dysfunction. It not only alleviated renal fibrosis and apoptosis markers but also aortic calcification. Additionally, this chalcone neutralized renal inflammatory response and oxidative stress. Isoliquiritigenin beneficial effects were associated with up-regulation of serum NO, renal and aortic sGC, cGMP and its dependent protein kinase (PKG). However, co-treatment with ODQ antagonized isoliquiritigenin therapeutic impact.

SIGNIFICANCE

Isoliquiritigenin seems to exert protective effects against CKD and vascular calcification by activating sGC, increasing cGMP and its downstream PKG.

Effect of flaxseed on systemic inflammation and oxidative stress in diabetic rats with or without chronic kidney disease

Background

Diabetes mellitus (DM) and chronic kidney disease (CKD) are common causes of morbidity and mortality. Flaxseed contains several bioactive compounds that have been shown to possess anti-inflammatory and antioxidative properties. The aim of the present study was to investigate the possible effect of flaxseed in diabetic rats with adenine–induced CKD.

Methods

Male Wister rats (n = 48) were randomly divided into seven equal groups and treated for 33 consecutive days as follows: G1: control. G2 adenine, G3: streptozotocin (STZ), G4: flaxseed, G5: adenine+flaxseed, G6: STZ+flaxseed, G7: adenine+STZ+flaxseed). DM or CKD were experimentally induced by a single intraperitoneal injection of streptozotocin (STZ) or by adenine via oral gavage, respectively.

Results

Rats fed adenine alone exhibited several changes including decreased body weight, increased food and water intake and urine output, increased urinary albumin/creatinine ratio. They also showed an increase in plasma urea and, creatinine, indoxyl sulfate, neutrophil gelatinase-associated lipocalin and cystatin C, and a decrease in renalase activity. These were associated with significant changes in inflammatory and oxidative biomarkers, e.g., increase in 8-isoprostane, 8 -hydroxy -2-deoxy guanosine and decrease in antioxidant enzymes, as well as increase in interleukins 1β and 6, and NF-κB, and a decrease in interlukin-10. Histopathologically, there was increased tubular necrosis and fibrosis. Concomitant administration of adenine and STZ further worsened the renal damage induced by adenine alone. Flaxseed significantly ameliorated the changes caused by adenine and STZ, given either singly or in combination.

Conclusion

These findings suggest that flaxseed is a potential therapeutic agent in attenuating the progression of CKD in diabetes.

The synergic renoprotective effect of Rehmanniae Radix Preparata and Corni Fructus on adenine-induced chronic kidney disease rats based on integrated plasma metabolomics and network pharmacology approach

AIMS

Rehmanniae Radix Preparata (RR) and Corni Fructus (CF) are commonly used together for the treatment of chronic kidney disease (CKD) in the clinical practices for thousands of years. However, little information on their synergy mechanism is available.

MAIN METHODS

In this study, an integrated approach combining ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS)-based metabonomics and network pharmacology was adopted to elucidate the cooperation mechanism of RR and CF on the amelioration of CKD. Furthermore, the targets from network pharmacology and metabolism pathways were jointly analyzed. Finally, the activities of key metabolic enzymes were experimentally validated by ELISA.

KEY FINDINGS

Metabolic profiling indicated that the metabolic disturbance in plasma was markedly alleviated after treatment. Nine putative biomarkers mainly involving in phenylalanine, tyrosine and tryptophan biosynthesis and tyrosine metabolism were identified. Moreover, the compound-target-pathway network of RR and CF for CKD treatment was constructed by network pharmacology, which was related to tyrosine metabolism and arginine and proline metabolism. The results were partly consistent with the findings of plasma metabolomics.

SIGNIFICANCE

In conclusion, this study solidly supported and enhanced current understanding of the synergy effects of RR and CF on CKD. Meanwhile, it also confirmed the feasibility of combining metabolomics and network pharmacology to identify active components and elucidate the pharmacological effects of traditional Chinese medicines (TCMs).

The Protective Effect of Shen Qi Wan on Adenine-Induced Podocyte Injury

Podocytes are a special type of differentiated epithelial cells that maintain the glomerular filtration barrier in the kidney. Injury or damages in podocytes can cause kidney-related disorders, like CKD. The injury or dysfunction of podocytes can occur by different metabolic disorders. Due to the severity and complexity of podocyte injuries, this state is considered as a serious health issue worldwide. Here, we examined and addressed the efficacy of an alternative Chinese medicine, Shen Qi Wan (SQW), on podocyte-related kidney injury. We evaluated the role and mechanism of action of SQW in podocyte injury. We observed that SQW significantly reduced 24-hour urinary protein and blood urea nitrogen levels and alleviated the pathological damage caused by adenine. Moreover, SQW significantly decreased the expression of nephrin and increased the expression of WT1 and AQP1 in the kidney of mice treated with adenine. We observed that SQW did not effectively reduce the high level of proteinuria in AQP1^−/− mice indicating the prominent role of AQP1 in the SQW-ameliorating pathway. Transmission electron microscopy (TEM) images indicated the food processes effacement in AQP1^−/− mice were not lessened by SQW. In conclusion, podocyte injury could alter the pathological nature of the kidney, and SQW administration relieves the nature of pathogenesis by activating AQP1.

Supramolecular Assembly of Acriflavine on Graphene Oxide for the Sensing of Adenosine Phosphates

An acriflavine-graphene oxide (GAF) supramolecular assembly has been prepared from water-soluble graphene oxide (GO) and a fluorescent dye, acriflavine (AF). Upon binding this non-covalently to the GO, the fluorescence of acriflavine has been "turned off" effectively, competitive binding potential of the sensor substrates such as ATP, ADP, AMP and the pyrophosphate weakens the supramolecular assembly of GAF, which allows the release of acriflavine quantitatively, which also "turns-on" the fluorescence of the dye under UV irradiation. Interestingly, GAF displayed the highest sensitivity towards ATP within the family of adenosine phosphates. We have developed a naked eye detection method for the adenosine phosphates biomolecules. For the first time, acriflavine has been utilized for the sensing of adenosine phosphates in combination with GO, which can be useful for the detection of other biomolecules.

Soluble guanylate cyclase stimulator praliciguat attenuates inflammation, fibrosis, and end-organ damage in the Dahl model of cardiorenal failure

Reduced nitric oxide (NO) and a decrease in cGMP signaling mediated by soluble guanylate cyclase (sGC) has been linked to the development of several cardiorenal diseases. Stimulation of sGC is a potential means for enhancing cGMP production in conditions of reduced NO bioavailability. The purpose of our studies was to determine the effects of praliciguat, a clinical-stage sGC stimulator, in a model of cardiorenal failure. Dahl salt-sensitive rats fed a high-salt diet to induce hypertension and organ damage were treated with the sGC stimulator praliciguat to determine its effects on hemodynamics, biomarkers of inflammation, fibrosis, tissue function, and organ damage. Praliciguat treatment reduced blood pressure, improved cardiorenal damage, and attenuated the increase in circulating markers of inflammation and fibrosis. Notably, praliciguat affected markers of renal damage at a dose that had minimal effect on blood pressure. In addition, liver fibrosis and circulating markers of tissue damage were attenuated in praliciguat-treated rats. Stimulation of the NO-sGC-cGMP pathway by praliciguat attenuated or normalized indicators of chronic inflammation, fibrosis, and tissue dysfunction in the Dahl salt-sensitive rat model. Stimulation of sGC by praliciguat may present an effective mechanism for treating diseases linked to NO deficiency, particularly those associated with cardiac and renal failure. Praliciguat is currently being evaluated in patients with diabetic nephropathy and heart failure with preserved ejection fraction.