Adenine-induced Renal Failure Research Articles

Endothelial Dysfunction in Superior Mesenteric Arteries Isolated from Adenine-Induced Renal Failure in Model Rats.

Endothelial dysfunction-a hallmark of chronic kidney disease (CKD)-is one of the major risk factors for cardiovascular diseases (CVD). Imbalances in endothelium-derived relaxing factors (EDRFs) and contracting factors (EDCFs) specific to endothelial dysfunction in CKD are yet to be studied. Therefore, using adenine-treated rats-a CKD rat model-we investigated the responsiveness of superior mesenteric artery (SMA) endothelium to acetylcholine (ACh) stimulation under different experimental conditions. Nine-week-old male Wistar rats were treated daily with adenine (200 and 600 mg/kg body weight) by oral gavage, for 10 d; the two groups were named adenine-200 (200 mg/kg body weight) and adenine-600 (600 mg/kg body weight). The systolic blood pressure (measured 1-, 8-, and 15 d post-treatment) was significantly increased in the adenine-600 group compared with that in the control group; whereas that in the adenine-200 group showed only a slight increase. Moreover, in the adenine-600 group the serum creatinine and blood urea nitrogen (BUN) levels (measured at 18 d post-treatment) were significantly elevated when compared with those in control or adenine-200 groups. The ACh-mediated relaxation was slightly reduced in the adenine-200 group. The ACh- and sodium nitroprusside (SNP)-mediated relaxations were impaired in the adenine-600 group. Although no ACh-mediated contraction was observed in the presence of a nitric oxide (NO) synthase inhibitor, ACh-induced endothelium-derived hyperpolarizing factor-mediated relaxation was largely impaired in the adenine-600 mg/kg group. This study revealed that in the SMA of adenine-induced CKD model rats, EDCF signaling remained unaltered while the NO and EDHF signaling were impaired.

Treatment with imatinib was useful to delay the neointimal hyperplasia of aortocaval fistula in adenine-induced renal failure rats

PurposeThe study was conducted to investigate the effect of the treatment with imatinib, a c-kit specific inhibitor, on the neointimal hyperplasia (NIH) of aortocaval fistula (ACF) in adenine-induced renal failure rats. Materials and methodsAll rats were randomly assigned to 4 groups: rats were fed on a normal diet (normal group); rats were fed on a 0.75% adenine-rich diet (renal failure group). The remaining rats underwent ACF after receiving a 0.75% adenine-rich diet and received daily saline gavage (model group) or imatinib gavage (imatinib group) for 7 days after surgery. Immunohistochemical method was used to detect c-kit expression, and Elastomeric Verhoeff-Van Gieson (EVG) staining was used to observe morphological changes of the ACF. The Pearson correlation analysis was used to evaluate the correlations of c-kit expression with intimal thickness and the percentage of stenosis, respectively. ResultsThe renal failure group showed positive c-kit expression on the intima of the inferior vena cava (IVC), whereas the normal group did not. Compared to the model group, intimal thickness (P = 0.001), the percentage of stenosis (P = 0.006) and c-kit expression (P = 0.04) were decreased in the imatinib group at 8 weeks postoperatively. C-kit expression was positively correlated with both intimal thickness and percentage of stenosis (intimal thickness: R = 0.650, P = 0.003; the percentage of stenosis: R = 0.581, P = 0.011) in both the model and imatinib groups. ConclusionTreatment with imatinib, a c-kit specific inhibitor, was useful to delay the NIH of ACF in adenine-induced renal failure rats.

Upacicalcet, a positive allosteric modulator of the calcium-sensing receptor, prevents vascular calcification and bone disorder in a rat adenine-induced secondary hyperparathyroidism model.

Secondary hyperparathyroidism (SHPT) is a major comorbidity of chronic kidney disease (CKD). Chronic elevation of PTH levels is associated with cortical bone deterioration and increase in the risk of fractures in CKD patients. Here, we evaluated the effect of repeated administration of upacicalcet, a novel positive allosteric modulator of the calcium-sensing receptor, in a rat model of adenine-induced renal failure, by determining serum levels of intact PTH (iPTH), calcium, phosphorus, creatinine, and urea nitrogen. Furthermore, parathyroid hyperplasia (parathyroid gland weight and Ki-67-positive cell density), ectopic calcification (calcium content in the thoracic aorta, kidney and heart and positive von Kossa staining in the thoracic aorta), and bone morphometry parameters (cortical porosity and fibrosis volume) were evaluated. Rats treated with either 0.2mg/kg or 1mg/kg upacicalcet exhibited significantly lower serum iPTH levels than CKD-control rats, as early as 7days after the first dose. Repeated administration of upacicalcet reduced serum iPTH levels and inhibited parathyroid hyperplasia in rats with adenine-induced severe renal failure. Moreover, it suppressed ectopic calcification and cortical pore formation. In contrast, serum calcium and phosphorus levels were not significantly affected, suggesting a low risk of hypocalcemia, which often occurs with SHPT treatment. In conclusion, repeated administration of upacicalcet decreased serum iPTH levels and suppressed parathyroid hyperplasia in the adenine-induced CKD rat model of SHPT. Furthermore, ectopic calcification and cortical pore formation were suppressed without significant changes in blood mineral parameters. Upacicalcet safely inhibited the progression of SHPT in an adenine-induced CKD rat model.

SGLT-1-specific inhibition ameliorates renal failure and alters the gut microbial community in mice with adenine-induced renal failure.

Sodium‐dependent glucose cotransporters (SGLTs) have attracted considerable attention as new targets for type 2 diabetes mellitus. In the kidney, SGLT2 is the major glucose uptake transporter in the proximal tubules, and inhibition of SGLT2 in the proximal tubules shows renoprotective effects. On the other hand, SGLT1 plays a role in glucose absorption from the gastrointestinal tract, and the relationship between SGLT1 inhibition in the gut and renal function remains unclear. Here, we examined the effect of SGL5213, a novel and potent intestinal SGLT1 inhibitor, in a renal failure (RF) model. SGL5213 improved renal function and reduced gut‐derived uremic toxins (phenyl sulfate and trimethylamine‐N‐oxide) in an adenine‐induced RF model. Histological analysis revealed that SGL5213 ameliorated renal fibrosis and inflammation. SGL5213 also reduced gut inflammation and fibrosis in the ileum, which is a primary target of SGL5213. Examination of the gut microbiota community revealed that the Firmicutes/Bacteroidetes ratio, which suggests gut dysbiosis, was increased in RF and SGL5213 rebalanced the ratio by increasing Bacteroidetes and reducing Firmicutes. At the genus level, Allobaculum (a major component of Erysipelotrichaceae) was significantly increased in the RF group, and this increase was canceled by SGL5213. We also measured the effect of SGL5213 on bacterial phenol‐producing enzymes that catalyze tyrosine into phenol, following the reduction of phenyl sulfate, which is a novel marker and a therapeutic target for diabetic kidney disease DKD. We found that the enzyme inhibition was less potent, suggesting that the change in the microbial community and the reduction of uremic toxins may be related to the renoprotective effect of SGL5213. Because SGL5213 is a low‐absorbable SGLT1 inhibitor, these data suggest that the gastrointestinal inhibition of SGLT1 is also a target for chronic kidney diseases.

474-P: Gut Microbiome–Derived Phenyl Sulfate Contributes to Albuminuria in Diabetic Kidney Disease

Diabetic kidney disease is a major cause of renal failure in urgent of breakthrough in disease management. Type 2 diabetes causes significant changes in an array of plasma metabolites, and in the humans, SLCO4C1 is the only transporter contributes to transport them into urine. We generated transgenic (Tg) rats overexpressing SLCO4C1 in the proximal tubule, a typical model for human renal excretion. Using this model, we characterize metabolites that are increased in diabetic wild type rats, but reduced in diabetic Tg rats.PS increase with the progression of diabetes and was decreased in Tg rats with limited proteinuria. In diabetes models, PS administration induced albuminuria and podocyte damage due to the mitochondrial dysfunction. Phenol is synthesized from tyrosine by gut bacterial-specific tyrosine phenol-lyase (TPL) and phenol is metabolized to PS in the liver. Administration of TPL inhibitor reduced not only serum PS level but also albuminuria in diabetic mice. Furthermore, TPL inhibitor significantly ameliorate renal dysfunction in adenine-induced renal failure model. Because TPL inhibitor did not alter the major composition, the non-lethal inhibition of microbial-specific enzymes has a therapeutic advantage with lower selective pressure for the development of drug resistance. We next confirmed whether PS also related with the diabetes and DKD progression in humans. In a diabetic patient cohort (U-CARE study, n=362), serum PS levels related with the basal albuminuria level. In addition, logistic regression analysis showed that among known ACR predictive factors, PS was the only factor which significantly related 2-year progression of albuminuria in patients with microalbuminuria. These data suggested that PS may have a potential as important predictive marker of DKD.PS is a modifiable cause and a target for the treatment of DKD. Chemical reduction of TPL should represent another aspect for developing drugs preventing DKD (Kikuchi et al. Nat. Commun. 10: 1835, 2019). Disclosure K. Kikuchi: None. T. Abe: None.

Effects of the oral adsorbent AST-120 on fecal p-cresol and indole levels and on the gut microbiota composition

In chronic kidney disease, elevated levels of circulating uremic toxins are associated with a variety of symptoms and organ dysfunction. Indoxyl sulfate (IS) and p-cresyl sulfate (pCS) are microbiota-derived metabolites and representative uremic toxins. We have previously shown that the oral adsorbent AST-120 profoundly reduced pCS compared to IS in adenine-induced renal failure in mice. However, the mechanisms of the different attenuation effects of AST-120 between IS and pCS are unclear. To clarify the difference of AST-120 on IS and pCS, we investigated the levels of fecal indole and p-cresol, the respective precursors of IS and pCS, and examined the influence on the gut microbiota. Although fecal indole was detected in all groups analyzed, fecal p-cresol was not detected in AST-120 treatment groups. In genus level, a total of 23 organisms were significantly changed by renal failure or AST-120 treatment. Especially, AST-120 reduced the abundance of Erysipelotrichaceae uncultured and Clostridium sensu stricto 1, which have a gene involved in p-cresol production. Our findings suggest that, in addition to the adsorption of the uremic toxin precursors, AST-120 affects the abundance of some gut microbiota in normal and renal failure conditions, thereby explaining the different attenuation effects on IS and pCS.

Short-chain fatty acid mitigates adenine-induced chronic kidney disease via FFA2 and FFA3 pathways

Short-chain fatty acids (SCFAs), including acetate, butyrate, and propionate, are produced when colonic bacteria in the human gastrointestinal tract ferment undigested fibers. Free fatty acid receptor 2 (FFA2) and FFA3 are G-protein-coupled receptors recently identified as SCFA receptors that may modulate inflammation. We previously showed through in vitro experiments that SCFAs activate FFA2 and FFA3, thereby mitigating inflammation in human renal cortical epithelial cells. This study used a murine model of adenine-induced renal failure to investigate whether or not SCFAs can prevent the progression of renal damage. We also examined whether or not these FFA2 and FFA3 proteins have some roles in this protective mechanism in vivo. Immunohistochemical analyses of mouse kidneys showed that FFA2 and FFA3 proteins were expressed mainly in the distal renal tubules and collecting tubules. First, we observed that the administration of propionate mitigated the renal dysfunction and pathological deterioration caused by adenine. Consistent with this, the expression of inflammatory cytokines and fibrosis-related genes was reduced. Furthermore, the mitigation of adenine-induced renal damage by the administration of propionate was significantly attenuated in FFA2−/− and FFA3−/− mice. Therefore, the administration of propionate significantly protects against adenine-induced renal failure, at least in part, via the FFA2 and FFA3 pathways. Our data suggest that FFA2 and FFA3 are potential new therapeutic targets for preventing or delaying the progression of chronic kidney disease.

The guanylate cyclase C agonist linaclotide ameliorates the gut-cardio-renal axis in an adenine-induced mouse model of chronic kidney disease.

Cardiorenal syndrome is a major cause of mortality in patients with chronic kidney disease (CKD). However, the involvement of detrimental humoral mediators in the pathogenesis of cardiorenal syndrome is still controversial. Trimethylamine-N-oxide (TMAO), a hepatic metabolic product of trimethylamine generated from dietary phosphatidylcholine or carnitine derived by the gut microbiota, has been linked directly with progression of cardiovascular disease and renal dysfunction. Thus, targeting TMAO may be a novel strategy for the prevention of cardiovascular disease and chronic kidney disease. Linaclotide, a guanylate cyclase C agonist, was administered to adenine-induced renal failure (RF) mice and changes in renal function and levels of gut-derived uremic toxins, as well as the gut microbiota community, were analyzed using metabolomic and metagenomic methods to reveal its cardiorenal effect. Linaclotide decreased the plasma levels of TMAO at a clinically used low dose of 10 μg/kg in the adenine-induced RF mouse model. At a high concentration of 100 μg/kg, linaclotide clearly improved renal function and reduced the levels of various uremic toxins. A reduction in TMAO levels following linaclotide treatment was also observed in a choline-fed pro-atherosclerotic model. Linaclotide ameliorated renal inflammation and fibrosis and cardiac fibrosis, as well as decreased the expression of collagen I, transforming growth factor-β, galectin-3 (Gal-3) and ST2 genes. Plasma levels of Gal-3 and ST2 were also reduced. Because exposure of cardiomyocytes to TMAO increased fibronectin expression, these data suggest that linaclotide reduced the levels of TMAO and various uremic toxins and may result in not only renal, but also cardiac, fibrosis. F4/80-positive macrophages were abundant in small intestinal crypts in RF mice, and this increased expression was decreased by linaclotide. Reduced colonic claudin-1 levels were also restored by linaclotide, suggesting that linaclotide ameliorated the 'leaky gut' in RF mice. Metagenomic analysis revealed that the microbial order Clostridiales could be responsible for the change in TMAO levels. Linaclotide reduced TMAO and uremic toxin levels and could be a powerful tool for the prevention and control of the cardiorenal syndrome by modification of the gut-cardio-renal axis.

SUN-004 THE REGULATION OF THE GUT-KIDNEY AXIS IN VIVO BY TOTAL FLAVONE OF ABELMOSCHUS MANIHOT, A NATURAL EXTRACT, CONTRIBUTES TO THE AMELIORATION OF ADENINE-INDUCED RENAL FAILURE

Targeting gut microbiota dysbiosis and uremic toxins accumulation is important for the amelioration of renal dysfunction in chronic renal failure (CRF). Total flavone of abelmoschus manihot (TFA), a natural extract, has been applied extensively for treatment of the CRF patients in China. However, its therapeutic mechanisms remained elusive. Therefore, in this study, using an adenine-induced renal failure (RF) rat model, we examined the effects of TFA on the gut-kidney axis in vivo, compared with lubiprostone (LUB), then to clarify the potential mechanisms. Rats were randomly divided into 4 groups, the Sham-operated group, the Vehicle-given group, the TFA-treated group and the LUB-treated group. TFA, LUB and saline were daily administrated for 4 weeks after induction of RF by adenine gavage with unilateral ureteral obstruction (UUO). Renal injurious and dysfunctional indicators, tubulointerstitial fibrosis (TIF), fecal microbiota, gut-derived uremic toxins, colon histological characteristics and tight junction proteins expressions, as well as the key protein expression levels of TLR4/NF-κB/NLRP3 inflammasome pathways in the colon and the kidneys were examined, respectively. In the RF model rats, in addition to renal lesions and uremic toxins accumulation, the abundance of Lactobacillus in the gut was decreased, while that of C. perfringens in the gut was increased; There appeared the ulcers in the colon, accompanied with the low-expression of ZO-1 and claudin-1; Besides, TLR4/NF-κB/NLRP3 inflammasome pathways in the colon and the kidneys were activated, respectively. After the treatment of TFA or LUB, renal dysfunction and TIF in the RF model rats were significantly improved. Furthermore, the disordered Lactobacillus, Enterococcus, E. coli and C. perfringens in the gut, the damaged intestinal environment and the accumulative indoxyl sulfate and p-cresyl sulfate in serum were all ameliorated. More notably, TFA synchronously inhibited TLR4/NF-κB/NLRP3 inflammasome pathways activity in the colon and the kidneys, whereas, LUB only suppressed TLR4/NF-κB/NLRP3 inflammasome pathway activity in the colon. TFA, as a natural regulator in vivo, regulates the gut-kidney axis and ameliorates renal dysfunction in the RF model rats by modulating gut microbiota, reducing uremic toxins and inhibiting TLR4/NF-κB/NLRP3 inflammasome pathways activity in the colon and the kidneys, which is different from LUB. These findings may provide the first evidence for the gut-kidney axis, as the unusual target of TFA treatment in CRF.

SUN-153 ACCUMULATION OF ACETAMINOPHEN METABOLITES EXERTS KIDNEY PROTECTIVE EFFECT IN RENAL FAILURE RAT MODEL

Acetaminophen (APAP) is recommended preferential use in pain management of chronic kidney disease (CKD) patients owing to fewer side effects in clinical dose. Although it is highly safe drug, usefulness of APAP is not consistent during long-term dosing in renal failure. So far, we have obtained the results that repeated administration of APAP does not worsen renal function in the adenine-induced renal failure model rats, suggesting that APAP might have antioxidant effect. In this study, we focused on the antioxidant effect of APAP and its metabolites, evaluated association between long-term APAP administration and renal function or oxidative stress in vivo and in vitro. first, we carried out daily oral administration of APAP (150 or 750 mg / kg) for 12 weeks against 5/6 nephrectomy (Nx) renal failure model rat, and evaluated the biochemical parameters, oxidative stress markers, as well as the drug concentration of APAP and its metabolites. We also examined the antioxidant capacity of APAP using HUVEC and EPR in vitro. Long-term administration of APAP did not induce further renal dysfunction. Furthermore, the APAP treated group significant inhibited the production of plasma 8-OHdG. Also, results of DHE staining of the renal tissue indicated that an oxidative stress was suppressed by APAP administration. Interestingly, APAP metabolites, normally excreted into urine, accumulated in the plasma and renal tissue. The antioxidant effect of these metabolites was evaluated in vascular endothelial cells (HUVEC), APAP metabolites showed a significant ROS inhibitory effect of ROS induced by uremic toxin indoxyl sulfate. From these results, it is suggested that APAP metabolites accumulated by renal failure might exhibit renal protective effect due to a part its antioxidant capacity. in the Future by monitoring of APAP metabolites by TDM, it is possible to establish a more effective method of APAP administration, the efficacy of a new antioxidant effect of APAP metabolites can be expected.

A Role of Intestinal Alkaline Phosphatase 3 (Akp3) in Inorganic Phosphate Homeostasis

Background/Aims: Hyperphosphatemia is a serious complication of late-stage chronic kidney disease (CKD). Intestinal inorganic phosphate (Pi) handling plays an important role in Pi homeostasis in CKD. We investigated whether intestinal alkaline phosphatase 3 (Akp3), the enzyme that hydrolyzes dietary Pi compounds, is a target for the treatment of hyperphosphatemia in CKD. Methods: We investigated Pi homeostasis in Akp3 knockout mice (Akp3^-/-). We also studied the progression of renal failure in an Akp3^-/- mouse adenine treated renal failure model. Plasma, fecal, and urinary Pi and Ca concentration were measured with commercially available kit, and plasma fibroblast growth factor 23, parathyroid hormone, and 1,25(OH)₂D₃ concentration were measured with ELISA. Brush border membrane vesicles were prepared from mouse intestine using the Ca²⁺ precipitation method and used for Pi transport activity and alkaline phosphatase activity. In vivo intestinal Pi absorption was measured with oral ³²P administration. Results: Akp3^-/- mice exhibited reduced intestinal type II sodium-dependent Pi transporter (Npt2b) protein levels and Na-dependent Pi co-transport activity. In addition, plasma active vitamin D levels were significantly increased in Akp3^-/- mice compared with wild-type animals. In the adenine-induced renal failure model, Akp3 gene deletion suppressed hyperphosphatemia. Conclusion: The present findings indicate that intestinal Akp3 deletion affects Na⁺-dependent Pi transport in the small intestine. In the adenine-induced renal failure model, Akp3 is predicted to be a factor contributing to suppression of the plasma Pi concentration.

Canagliflozin reduces plasma uremic toxins and alters the intestinal microbiota composition in a chronic kidney disease mouse model.

Accumulation of uremic toxins, which exert deleterious effects in chronic kidney disease, is influenced by the intestinal environment; the microbiota contributes to the production of representative uremic toxins, including p-cresyl sulfate and indoxyl sulfate. Canagliflozin is a sodium-glucose cotransporter (SGLT) 2 inhibitor, and it also exerts a modest inhibitory effect on SGLT1. The inhibition of intestinal SGLT1 can influence the gastrointestinal environment. We examined the effect of canagliflozin on the accumulation of uremic toxins in chronic kidney disease using adenine-induced renal failure mice. Two-week canagliflozin (10 mg/kg po) treatment did not influence the impaired renal function; however, it significantly reduced the plasma levels of p-cresyl sulfate and indoxyl sulfate in renal failure mice (a 75% and 26% reduction, respectively, compared with the vehicle group). Additionally, canagliflozin significantly increased cecal short-chain fatty acids in the mice, suggesting the promotion of bacterial carbohydrate fermentation in the intestine. Analysis of the cecal microbiota showed that canagliflozin significantly altered microbiota composition in the renal failure mice. These results indicate that canagliflozin exerts intestinal effects that reduce the accumulation of uremic toxins including p-cresyl sulfate. Reduction of accumulated uremic toxins by canagliflozin could provide a potential therapeutic option in chronic kidney disease.

Evaluation of the impact of gut microbiota on uremic solute accumulation by a CE-TOFMS–based metabolomics approach

Gut microbiota is involved in the metabolism of uremic solutes. However, the precise influence of microbiota to the retention of uremic solutes in CKD is obscure. To clarify this, we compared adenine-induced renal failure and control mice under germ-free or specific pathogen-free (SPF) conditions, examining the metabolite profiles of plasma, feces, and urine using a capillary electrophoresis time-of-flight mass spectrometry-based approach. Mice with renal failure under germ-free conditions demonstrated significant changes in plasma metabolites. Among 183 detected solutes, plasma levels of 11 solutes, including major uremic toxins, were significantly lower in germ-free mice than in SPF mice with renal failure. These 11 solutes were considered microbiota-derived uremic solutes and included indoxyl sulfate, p-cresyl sulfate, phenyl sulfate, cholate, hippurate, dimethylglycine, γ-guanidinobutyrate, glutarate, 2-hydroxypentanoate, trimethylamine N-oxide, and phenaceturate. Metabolome profiling showed that these solutes were classified into three groups depending on their origins: completely derived from microbiota (indoxyl sulfate, p-cresyl sulfate), derived from both host and microbiota (dimethylglycine), and derived from both microbiota and dietary components (trimethylamine N-oxide). Additionally, germ-free renal failure conditions resulted in the disappearance of colonic short-chain fatty acids, decreased utilization of intestinal amino acids, and more severe renal damage compared with SPF mice with renal failure. Microbiota-derived short-chain fatty acids and efficient amino acid utilization may have a renoprotective effect, and loss of these factors may exacerbate renal damage in germ-free mice with renal failure. Thus, microbiota contributes substantially to the production of harmful uremic solutes, but conversely, growth without microbiota has harmful effects on CKD progression.

Renal mitochondria can withstand hypoxic/ischemic injury secondary to renal failure in uremic rats pretreated with sodium thiosulfate.

BACKGROUND:Sodium thiosulfate (STS) is a potent drug used to treat calcific uremic arteriopathy in dialysis patients and its mode of action is envisaged by calcium chelation and antioxidant potential. STS's action on mitochondrial dysfunction, one of the major players in the pathology of vascular calcification is yet to be explored.METHODS:Adenine (0.75%, 28 days)-treated vascular calcified rat kidney was used to isolate mitochondria, where the animal was administered with or without STS for 28 days. Isolated mitochondria were subjected to physiological oxidative stress by nitrogen gas purging (hypoxia/ischemia-reperfusion injury) to assess mitochondrial recovery extent due to STS treatment in vascular calcified rat kidney.RESULTS:The results confirmed an elevated oxidative stress and deteriorated mitochondrial enzyme activities in all groups except the drug-treated group.CONCLUSION:The STS treatment, besides rendering renal protection against adenine-induced renal failure, also helped to maintain mitochondrial functional integrity in a later insult due to hypoxia/ischemia-reperfusion injury.

Alteration of the Intestinal Environment by Lubiprostone Is Associated with Amelioration of Adenine-Induced CKD.

The accumulation of uremic toxins is involved in the progression of CKD. Various uremic toxins are derived from gut microbiota, and an imbalance of gut microbiota or dysbiosis is related to renal failure. However, the pathophysiologic mechanisms underlying the relationship between the gut microbiota and renal failure are still obscure. Using an adenine-induced renal failure mouse model, we evaluated the effects of the ClC-2 chloride channel activator lubiprostone (commonly used for the treatment of constipation) on CKD. Oral administration of lubiprostone (500 µg/kg per day) changed the fecal and intestinal properties in mice with renal failure. Additionally, lubiprostone treatment reduced the elevated BUN and protected against tubulointerstitial damage, renal fibrosis, and inflammation. Gut microbiome analysis of 16S rRNA genes in the renal failure mice showed that lubiprostone treatment altered their microbial composition, especially the recovery of the levels of the Lactobacillaceae family and Prevotella genus, which were significantly reduced in the renal failure mice. Furthermore, capillary electrophoresis-mass spectrometry-based metabolome analysis showed that lubiprostone treatment decreased the plasma level of uremic toxins, such as indoxyl sulfate and hippurate, which are derived from gut microbiota, and a more recently discovered uremic toxin, trans-aconitate. These results suggest that lubiprostone ameliorates the progression of CKD and the accumulation of uremic toxins by improving the gut microbiota and intestinal environment.

Peritoneal Fibrosis Induced by Intraperitoneal Methylglyoxal Injection: The Role of Concurrent Renal Dysfunction

Background: Peritoneal fibrosis (PF) is a serious pathophysiology of peritoneal dialysis (PD). An ongoing focus of research is the potential fibrogenic nature of methylglyoxal (MGO) in conventional PD fluid (PDF). The aim of the current study was to explore the effects of the uremic milieu on the promotion of PF by MGO using rats with adenine-induced renal failure (RF). Methods: Adenine-treated Sprague-Dawley rats were randomly assigned to receive continuous peritoneal injections of PDF with or without MGO for three weeks or were left untreated for the same duration. Rats without RF were also assigned to three groups. The peritoneal histology and expression levels of type I collagen, transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (αSMA), Snail, matrix metalloproteinase-2 (MMP-2), advanced glycation end-products (AGEs) and the receptor for AGE (RAGE) were then analyzed. Results: Peritoneal treatment with 5 m<smlcap>M</smlcap> MGO accelerated the fibrous peritoneal thickening progression promoted by exposure to standard PDF in the rats with RF, but not in the rats with a normal renal function. Treatment with MGO significantly augmented the proliferation of mesenchymal-like mesothelial cells, accumulation of AGE, de novo expression of αSMA and RAGE and gene expression of type I collagen, TGF-β1, Snail and MMP-2, whereas both MGO and RF alone had, at most, marginal effects on the changes in these biological parameters. Conclusions: In the present study, the adverse effects of MGO on the peritoneum became more prominent under conditions of a uremic milieu. These findings imply that MGO and uremia act cooperatively to induce PF.

Cinacalcet attenuates the renal endothelial-to-mesenchymal transition in rats with adenine-induced renal failure

Elevated serum parathyroid hormone (PTH) is an important complicated phenomenon in patients with chronic kidney disease (CKD). Emerging evidence indicates the involvement of PTH in organ fibrosis, and suppression of PTH by cinacalcet (CINA) ameliorates the progression of fibrotic disorders. However, the underlying mechanisms are largely unknown. The endothelial-to-mesenchymal transition (EndMT) has been shown to be an important mechanism involved in renal fibrosis. The present study aimed to investigate whether CINA treatment attenuated renal EndMT in rats with adenine-induced chronic renal failure (CRF). Compared with the control group, serum PTH was significantly higher in the CRF group and was suppressed after CINA treatment. Serum calcium, phosphorus, and calcium × phosphorus product levels were similar in the CRF group and CINA-treated CRF group. Renal collagen accumulation was significantly increased in the CRF group, which was markedly ameliorated by CINA treatment. Expression of the endothelial marker CD31 was significantly downregulated in rats with CRF, whereas expression of the mesenchymal markers fibroblast specific-protein 1 and α-smooth muscle actin was markedly upregulated. These changes were inhibited by CINA treatment. The protein levels of these EndMT-related markers were strongly correlated with serum PTH concentrations. Furthermore, the in vitro study showed that PTH could significantly increase the expression of fibroblast specific-protein 1 and α-smooth muscle actin and decrease CD31 in mRNA and protein levels in a concentration- and time-dependent manner. In conclusion, our study suggests that reducing serum PTH by CINA treatment could attenuate renal fibrosis via suppression of EndMT in the adenine-induced CRF rat model.

Heat-processed ginseng saponin ameliorates the adenine-induced renal failure in rats

To evaluate the effect of the saponin of heat-processed ginseng (Sun ginseng, SG), we investigated the protective effect of SG total saponin fraction against adenine-induced chronic renal failure in rats. SG saponin significantly decreased the levels of urea nitrogen and creatinine in the serum, but increased the urinary excretion of urea nitrogen and creatinine, indicating an improvement of renal function. SG saponin also inhibited adenine-induced kidney hypertrophy and edema. SG saponin reduced serum glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, and lactate dehydrogenase activities increased by adenine. Based on these findings, the ameliorating effect of SG on chronic renal failure may result from its saponin.

Effect of acetaminophen on the progression of renal damage in adenine induced renal failure model rats

AimsAcetaminophen is a safe antipyretic and analgesic drug within the clinically recommended dosage range, but overdose can cause fatal liver and or kidney damage. Most of the nonsteroidal anti-inflammatory drugs (NSAIDs) exert their analgesic effect via inhibition of cyclooxygenase, which also results in a reduction of renal blood flow. Therefore, the use of NSAIDs in pain treatment for chronic kidney disease (CKD) patients is of particular concern. Acetaminophen lacks the anti-inflammatory and anti-coagulatory properties of the NSAIDs. In this study, we investigate whether acetaminophen has an impact on the progression of renal failure. Main methodsAcetaminophen (150mg/kg/day or 750mg/kg/day) or indomethacin (5mg/kg/day) was orally administered to adenine-induced chronic renal failure model rats for 4weeks. The plasma concentrations of acetaminophen and its metabolites were measured during the treatment period; renal function and oxidative stress in the rats were also monitored. Key findingsIndomethacin significantly decreased the survival rate of renal failure model rats. In contrast, both low (150mg/kg) and high (750mg/kg) doses of acetaminophen improved the survival rate. The progression of renal failure was attenuated by acetaminophen (750mg/kg) after administration for 2weeks. The metabolites of acetaminophen were found to accumulate in plasma. Plasma glutathione concentration had significantly recovered after acetaminophen administration. SignificanceAcetaminophen has no effect on the progression of renal damage in adenine-induced renal failure model rats. This result is in part due to acetaminophen's antioxidant activity. These results suggest that acetaminophen is a suitable analgesic agent for treating CKD patients.

Nephrogenic Systemic Fibrosis-Like Effects of Magnetic Resonance Imaging Contrast Agents in Rats with Adenine-Induced Renal Failure

Nephrogenic systemic fibrosis (NSF) is a scleroderma-like disease associated with prior administration of certain gadolinium chelates (GCs). NSF occurs in patients with severe renal failure. The purpose of this study was to set up a rat model of GC-associated NSF to elucidate the mechanism of this devastating disease. Firstly, after characterization of the model, male Wistar rats received a 0.75% adenine-enriched diet for 8, 14, or 16 days to obtain various degrees of renal failure. Rats received five consecutive daily iv injections of saline or gadodiamide (2.5 mmol/kg/day). Secondly, the safety profile and in vivo propensity to dissociate of all categories of marketed GCs (gadoterate, gadobutrol, gadobenate, gadopentetate, and gadodiamide) were compared in rats receiving adenine-enriched diet for 16 days. Serial skin biopsies were performed for blinded histopathological study. Total Gd concentration in tissues was measured by Inductively Coupled Plasma Mass Spectrometry. Relaxometry was used to evaluate the presence of dissociated Gd in skin and bone. Gadodiamide-induced high mortality and skin lesions (dermal fibrosis, calcification, and inflammation) were related to adenine diet duration. No skin lesions were observed with other molecules. Unlike macrocyclic GCs, gadodiamide, gadopentetate, and gadobenate gradually increased the r(1) relaxivity value, consistent with in vivo dissociation and release of soluble Gd (or, in the case of gadobenate, the consequence of protein binding). Gadodiamide-induced cutaneous and systemic toxicity depended on baseline renal function. We demonstrate in vivo dissociation of linear GCs, gadodiamide, and gadopentetate, whereas macrocyclic agents remained stable over the study period.