Hyperuricaemia Does Not Interfere with Aortopathy in a Murine Model of Marfan Syndrome.

Redox stress is involved in the aortic aneurysm pathogenesis in Marfan syndrome (MFS). We recently reported that allopurinol, a xanthine oxidoreductase inhibitor, blocked aortopathy in a MFS mouse model acting as an antioxidant without altering uric acid (UA) plasma levels. Hyperuricaemia is ambiguously associated with cardiovascular injuries as UA, having antioxidant or pro-oxidant properties depending on the concentration and accumulation site. We aimed to evaluate whether hyperuricaemia causes harm or relief in MFS aortopathy pathogenesis. Two-month-old male wild-type (WT) and MFS mice (Fbn1C1041G/+) were injected intraperitoneally for several weeks with potassium oxonate (PO), an inhibitor of uricase (an enzyme that catabolises UA to allantoin). Plasma UA and allantoin levels were measured via several techniques, aortic root diameter and cardiac parameters by ultrasonography, aortic wall structure by histopathology, and pNRF2 and 3-NT levels by immunofluorescence. PO induced a significant increase in UA in blood plasma both in WT and MFS mice, reaching a peak at three and four months of age but decaying at six months. Hyperuricaemic MFS mice showed no change in the characteristic aortic aneurysm progression or aortic wall disarray evidenced by large elastic laminae ruptures. There were no changes in cardiac parameters or the redox stress-induced nuclear translocation of pNRF2 in the aortic tunica media. Altogether, the results suggest that hyperuricaemia interferes neither with aortopathy nor cardiopathy in MFS mice.

Pharmacokinetics of initial full and subsequent reduced doses of S-1 in patients with locally advanced head and neck cancer-effect of renal insufficiency.

BACKGROUND: S-1 is a combination of tegafur [metabolized to 5-fluorouracil (5-FU)] with the modulators gimeracil (5-chloro-2,4-dihydroxypyridine) and oteracil potassium. 5-Chloro-2,4-dihydroxypyridine maintains plasma 5-FU concentrations by inhibiting dihydropyrimidine dehydrogenase, a pyrimidine catabolism enzyme that degrades 5-FU. As 50% of 5-chloro-2,4-dihydroxypyridine is excreted in urine, renal insufficiency may increase its blood level, increasing 5-FU concentrations. We investigated whether special dose modification is needed in the presence of renal insufficiency. OBJECTIVE: We compared steady state pharmacokinetics of 5-FU for the initial S-1 dose and reduced doses in patients with head and neck cancer requiring dose reduction due to renal and non-renal toxicities. METHODS: Chemoradiotherapy with S-1 and cisplatin was administered every 5 weeks for two courses with a radiation dose totaling 70 Gy over 33-35 fractions. Two additional courses of adjuvant chemotherapy were administered in the case of an objective response. The S-1 and/or cisplatin dose was reduced in response to renal, hematologic or other toxicities. The primary endpoint was the change in area under the plasma concentration-versus-time curve from time 0-10 hours (5-FU AUCss 0-10) between the initial and reduced S-1 doses. RESULTS: Although the mean 5-FU levels in patients with non-renal toxicities significantly decreased between the full and reduced dose, the full-dose and reduced-dose mean maximum 5-FU plasma concentrations at steady state (Css max) and AUCss 0-10 in patients with renal insufficiency were similar. CONCLUSIONS: Standard S-1 dose reduction for renal toxicity did not result in a significant decrease in 5-FU levels at steady state. A greater reduction to lower plasma 5-chloro-2,4-dihydroxypyridine may be necessary in patients with renal insufficiency.

Miracle Fruit (Synsepalum dulcificum) Exhibits as a Novel Anti-Hyperuricaemia Agent.

Miracle fruit (Synsepalum dulcificum) belongs to the Sapotaceae family. It can change flavors on taste buds, transforming acidic tastes to sweet. We evaluated various miracle fruit extracts, including water, butanol, ethyl acetate (EA), and hexane fractions, to determine its antioxidant effects. These extracts isolated from miracle fruit exerted potential for reduction of uric acid and inhibited xanthine oxidase activity in vitro and in monosodiumurate (MSU)-treated RAW264.7 macrophages. Moreover, we also found that the butanol extracts of miracle fruit attenuated oxonic acid potassium salt-induced hyperuricaemia in ICR mice by lowering serum uric acid levels and activating hepatic xanthine oxidase. These effects were equal to those of allopurinol, suggesting that the butanol extract of miracle fruit could be developed as a novel anti-hyperuricaemia agent or health food.

Hyperuricemia influences tryptophan metabolism via inhibition of multidrug resistance protein 4 (MRP4) and breast cancer resistance protein (BCRP).

Hyperuricemia is related to a variety of pathologies, including chronic kidney disease (CKD). However, the pathophysiological mechanisms underlying disease development are not yet fully elucidated. Here, we studied the effect of hyperuricemia on tryptophan metabolism and the potential role herein of two important uric acid efflux transporters, multidrug resistance protein 4 (MRP4) and breast cancer resistance protein (BCRP). Hyperuricemia was induced in mice by treatment with the uricase inhibitor oxonic acid, confirmed by the presence of urate crystals in the urine of treated animals. A transport assay, using membrane vesicles of cells overexpressing the transporters, revealed that uric acid inhibited substrate-specific transport by BCRP at clinically relevant concentrations (calculated IC50 value: 365±13µM), as was previously reported for MRP4. Moreover, we identified kynurenic acid as a novel substrate for MRP4 and BCRP. This finding was corroborated by increased plasma levels of kynurenic acid observed in Mrp4(-/-) (107±19nM; P=0.145) and Bcrp(-/-) mice (133±10nM; P=0.0007) compared to wild type animals (71±11nM). Hyperuricemia was associated with >1.5 fold increase in plasma kynurenine levels in all strains. Moreover, hyperuricemia led to elevated plasma kynurenic acid levels (128±13nM, P=0.005) in wild type mice but did not further increase kynurenic acid levels in knockout mice. Based on our results, we postulate that elevated uric acid levels hamper MRP4 and BCRP functioning, thereby promoting the retention of other potentially toxic substrates, including kynurenic acid, which could contribute to the development of CKD.

Moderate hyperuricaemia ameliorated kidney damage in a low-renin model of experimental renal insufficiency.

Uric acid has promoted renal fibrosis and inflammation in experimental studies, but some studies have shown nephroprotective effects due to alleviated oxidative stress. We studied the influence of experimental hyperuricaemia in surgically 5/6 nephrectomized rats. Three weeks after subtotal nephrectomy or sham operation, the rats were allocated to control diet or 2.0% oxonic acid (uricase inhibitor) diet for 9 weeks. Then blood, urine and tissue samples were taken, and renal morphology and oxidative stress were examined. Inflammation and fibrosis were evaluated using immunohistochemistry and real-time PCR (RT-PCR). Remnant kidney rats ingesting normal or oxonic acid diet presented with ~60% reduction of creatinine clearance and suppressed plasma renin activity. Oxonic acid diet increased plasma uric acid levels by >80 µmol/L. In remnant kidney rats, moderate hyperuricaemia decreased glomerulosclerosis, tubulointerstitial damage and kidney mast cell count, without influencing the fibrosis marker collagen I messenger RNA (mRNA) content. In both sham-operated and 5/6 nephrectomized rats, the mast cell product 11-epi-prostaglandin-F2α excretion to the urine and kidney tissue cyclooxygenase-2 (COX-2) levels were decreased. To conclude, hyperuricaemic remnant kidney rats displayed improved kidney morphology and reduced markers of oxidative stress and inflammation. Thus, moderately elevated plasma uric acid had beneficial effects on the kidney in this low-renin model of experimental renal insufficiency.

[The optimization and assessment of the method for inducing hyperuricemia in rats].

Objective: To explore an effective method for inducing a rat model with hyperuricemia in a short period and assess the effects of the model. Methods: Sprague-Dawley rats were adopted as donors and randomly divided into control group (CT group, n=6) and 5 model groups (M1-M5 groups, n=8 in each group). M1 group (gavage with 10 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, in the 7th day of model inducing), M2 group (gavage with 10 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, in the 1st, 3rd and 7th day of model inducing),M3 group (gavage with 10 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, once per day during the model inducing), M4 group (gavage with 20 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, once per day during the model inducing), M5 group (gavage with 30 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, once per day during the model inducing), and group CT (gavaged with equal volume sterilized water and intraperitoneal injected with normal saline according to the weight and at the same frequency as the model groups). The model inducing lasted for 7 days. After the inducing was finished, blood and 24-hour urine were sampled for uric acid and creatinine determination. Then rats were maintained for 2 weeks and blood and 24-hour urine samples were collected, the concentration of uric acid and creatinine were detected. The kidney and stomach were weighed,morphological changes in kidney were observed. Results: After model inducing, the body weight of rats in all model groups was lower than that of the control group (P＜0.01). Deaths occurred in all the rats with model treatments except M2. M4 and M5 groups were failed to be analyzed because of the high mortality, model 1 and 3 groups had 4 and 2 deaths, respectively. The uric acid levels in blood and urine of the model groups were significantly elevated (P＜ 0.01) at the end of model inducing. The model 2 group's blood uric acid was highest among the model groups (P＜0.05). It sustained a higher concentration than CT group in the three model groups after 2 weeks feeding (P＜0.05). The kidneys in model groups obviously swelling and were heavier than CT group (P＜0.01). The inflammation and structural damages were observed in kidneys of all model groups.Conclusion: The yeast extract (10 g/kg), adenine (100 mg/kg) gavage combined with intraperitoneal injections(the 1st, 3rd, 7th day during inducing) of potassium oxonate can be an rapid and effective method for inducing the rat model with hyperuricemia, which can be suggested to the related research.

Thymoquinone attenuates oxidative stress of kidney mitochondria and exerts nephroprotective effects in oxonic acid-induced hyperuricemia rats.

BACKGROUND: Recent studies indicate hyperuricemia as an aggravating factor for kidney diseases progression. Basic research for novel agents to reduce hyperuricemia and kidney abnormalities will be highly rewarding. Herein, we report Thymoquinone (Tq) as an active constituent of Nigella sativa to have renal protective effective against oxonic acid (OA)-induced hyperuricemia, hypertension, and renal oxidative stress in rat models. METHODS: OA 750 mg/kg BW for 12 weeks was used to induce uricemia in Sprague dawley rats. Tq at 10 and 20 mg/kg BW were administered along with OA for treatment groups. Plasma uric acid concentration and systolic blood pressure were measured. Oxidative stress markers, total ATP content, and membrane bound ATPases were measured in renal mitochondria. Anti-oxidant enzymes were analyzed in the renal tissues. Apoptosis in renal tissue was detected. Key signaling proteins for apoptosis, oxidative stress, and lipid oxidation pathways were determined. RESULTS: OA induced both circulating uric acid levels and hypertension in the control group which was brought down on Tq treatments. Tq effectively prevented accumulation of uric acid and oxidative stress in the renal tissues. Tq also proved to increase the total ATP content of the renal mitochondria and prevented the apoptosis induced by OA. Tq increased the expressions of phosphorylated Akt, Nrf2, and HO-1 proteins while decreasing the levels of cleaved caspase-3 in renal cells. CONCLUSION: In summary, Tq exhibited protective effects on hyperuricemia-mediated renal oxidative stress and mitochondrial abnormalities which could be mediated by Nrf2/HO-1, Akt signaling pathways.

Uric acid metabolism of kidney and intestine in a rat model of chronic kidney disease.

Uric acid (UA) is a potential risk factor of the progression of chronic kidney disease (CKD). Recently, we reported that intestinal UA excretion might be enhanced via upregulation of the ATP-binding cassette transporter G2 (Abcg2) in a 5/6 nephrectomy (Nx) rat model. In the present study, we examined the mRNA and protein expressions of UA transporters, URAT1, GLUT9/URATv1, ABCG2 and NPT4 in the kidney and ileum in the same rat model. Additionally, we investigated the Abcg2 mRNA expression of ileum in hyperuricemic rat model by orally administering oxonic acid. Male Wistar rats were randomly assigned to three groups consisting of Nx group, oxonic acid-treated (Ox) group and sham-operated control group, and sacrificed at 8 weeks. Creatinine and UA were measured and the mRNA expressions of UA transporters in the kidney and intestine were evaluated by a real time PCR. UA transporters in the kidney sections were also examined by immunohistochemistry. Serum creatinine elevated in the Nx group whereas serum UA increased in the Ox group. Both the mRNA expression and the immunohistochemistry of the UA transporters were decreased in the Nx group, suggesting a marginal role in UA elevation in decreased kidney function. In contrast, the mRNA expression of Abcg2 in the ileum significantly increased in the Ox group. These results suggest that the upregulation of Abcg2 mRNA in the ileum triggered by an elevation of serum UA may play a compensatory role in increasing intestinal UA excretion.

The optimization and assessment of the method for inducing hyperuricemia in rats / 中国应用生理学杂志

To explore an effective method for inducing a rat model with hyperuricemia in a short period and assess the effects of the model. Methods: Sprague-Dawley rats were adopted as donors and randomly divided into control group (CT group, n=6) and 5 model groups (M1-M5 groups, n=8 in each group). M1 group (gavage with 10 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, in the 7 day of model inducing), M2 group (gavage with 10 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, in the 1, 3 and 7 day of model inducing),M3 group (gavage with 10 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, once per day during the model inducing), M4 group (gavage with 20 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, once per day during the model inducing), M5 group (gavage with 30 g/kg yeast extracts and 100 mg/kg adenine, twice per day, 300 mg/kg oxonic acid potassium by intraperitoneal injection, once per day during the model inducing), and group CT (gavaged with equal volume sterilized water and intraperitoneal injected with normal saline according to the weight and at the same frequency as the model groups). The model inducing lasted for 7 days. After the inducing was finished, blood and 24-hour urine were sampled for uric acid and creatinine determination. Then rats were maintained for 2 weeks and blood and 24-hour urine samples were collected, the concentration of uric acid and creatinine were detected. The kidney and stomach were weighed,morphological changes in kidney were observed. After model inducing, the body weight of rats in all model groups was lower than that of the control group (P＜0.01). Deaths occurred in all the rats with model treatments except M2. M4 and M5 groups were failed to be analyzed because of the high mortality, model 1 and 3 groups had 4 and 2 deaths, respectively. The uric acid levels in blood and urine of the model groups were significantly elevated (P＜ 0.01) at the end of model inducing. The model 2 group's blood uric acid was highest among the model groups (P＜0.05). It sustained a higher concentration than CT group in the three model groups after 2 weeks feeding (P＜0.05). The kidneys in model groups obviously swelling and were heavier than CT group (P＜0.01). The inflammation and structural damages were observed in kidneys of all model groups. The yeast extract (10 g/kg), adenine (100 mg/kg) gavage combined with intraperitoneal injections(the 1, 3, 7 day during inducing) of potassium oxonate can be an rapid and effective method for inducing the rat model with hyperuricemia, which can be suggested to the related research.

Research progress for animal hyperuricemia model / 中国药理学通报

Hyperuricemia is induced by the mechanism of the elevated production of uric acid or the decreased renal excretion of uric acid. At present, there are three major methods to establish models for hyperuricemia: first, it will elicit pronounced hyperuricemia when feeding or injecting the animal with hypoxanthine 600～1000 mg?kg -1 , xanthine 600 mg?kg -1 , adenine 150～300 mg?kg -1 , yeast 15～30 g?kg -1 , uric acid 250 mg?kg -1 or 350～700 mg?kg -1 because of the elevated serum uric acid. Such effect will be also observed as administrating the animal with the inhibitors of uric acid excretion such as ethambutol 250 mg?kg -1 , nicotinic acid 100 mg?kg -1 at the same time of the above steps. Second, being an uricase inhibitor, when fed the rats 0 4 g?d -1 and uric acid 0 6 g?d -1 for 3～4 weeks, oxonic acid is able to cause the continuously elevated serum uric acid. Similarly, when potassium oxonate 300 mg?kg -1 ip only once, the serum uric acid in mice will be also elevated. Third, to destruct the urate oxidase gene (EC 1.7.3.3) in the mouse by homologous recombination in embryonic stem cells, and then the oxidase deficient mutant mouse as the hyperuricemia model, is generated by gene recombination.The rats and the mice have urate oxidase, which can decompose the uric acid to allantoin, while the avian (such as chicken, coturnix and so on) have not.