Anti-Hyperuricemic Effects of Astaxanthin by Regulating Xanthine Oxidase, Adenosine Deaminase and Urate Transporters in Rats

A metabolomics perspective reveals the mechanism of the uric acid-lowering effect of Prunus salicina Lindl. cv. "furong" polyphenols in hypoxanthine and potassium oxybate-induced hyperuricemic mice

The incidence of hyperuricemia (HUA) shows a gradually increasing trend towards affecting younger individuals, and it can significantly harm the overall health status of the body. Based on a metabolomics perspective, this study reveals the mechanism of the uric acid-lowering action of Prunus salicina Lindl. cv. "furong" polyphenols (PSLP) on a hyperuricemia mouse model induced by hypoxanthine and potassium oxybutyrate. The results demonstrate that PSLP comprise an effective treatment strategy for reducing the levels of serum uric acid (SUA), serum creatinine (SCr) and blood urea nitrogen (BUN) in HUA mice (p < 0.05), wherein the maximum decrease rates are up to 44.50%, 29.46%, and 32.95%, respectively. PSLP are observed to exert a pronounced inhibitory effect on the activities of xanthine oxidase (XOD) and adenosine deaminase (ADA) in the livers of HUA mice, with reductions of up to 16.36% and 20.13%, respectively. These findings illustrate that PSLP exert a significant uric acid-lowering effect. Subsequent metabolomic analysis of mouse serum identified 28 potential biomarkers for hyperuricemia, whose levels were markedly diminished by PSLP. This process involved alterations in purine, glycine, the pentose phosphate pathway, and galactose metabolism. Twenty-eight potential biomarkers were identified for hyperuricemia by subsequent metabolomic analysis of mouse serum, whose levels were markedly reversed by PSLP intervention. The regulation of HUA by PSLP involved alterations in purine metabolism, glycerolipid metabolism, the pentose phosphate pathway, and galactose metabolism. The mechanism of PSLP ameliorated hyperuricemia might be attributed to reduction of the level of the uric acid precursor ribose-5-phosphate in the pentose phosphate pathway, the inhibition of the activities of uric acid synthase XOD and ADA in purine metabolism, and reduction of the synthesis of the end product uric acid. This study provides a theoretical basis for the development of functional foods based on PSLP, which can potentially reduce uric acid levels.

Intermittent high altitude hypoxia induced liver and kidney injury leading to hyperuricemia

About 140 million people worldwide live at an altitude above 2500 m. Studies have showed an increase of the incidence of hyperuricemia among plateau populations, but little is known about the possible mechanisms. This study aims to assess the effects of high altitude on hyperuricemia and explore the corresponding mechanisms at the histological, inflammatory and molecular levels. This study finds that intermittent hypobaric hypoxia (IHH) exposure results in an increase of serum uric acid level and a decrease of uric acid clearance rate. Compared with the control group, the IHH group shows significant increases in hemoglobin concentration (HGB) and red blood cell counts (RBC), indicating that high altitude hyperuricemia is associated with polycythemia. This study also shows that IHH exposure induces oxidative stress, which causes the injury of liver and renal structures and functions. Additionally, altered expressions of organic anion transporter 1 (OAT1) and organic cation transporter 1 (OCT1) of kidney have been detected in the IHH exposed rats. The adenosine deaminase (ADA) expression levels and the xanthione oxidase (XOD) and ADA activity of liver of the IHH exposure group have significantly increased compared with those of the control group. Furthermore, the spleen coefficients, IL-2, IL-1β and IL-8, have seen significant increases among the IHH exposure group. TLR/MyD88/NF-κB pathway is activated in the process of IHH induced inflammatory response in joints. Importantly, these results jointly show that IHH exposure causes hyperuricemia. IHH induced oxidative stress along with liver and kidney injury, unusual expression of the uric acid synthesis/excretion regulator and inflammatory response, thus suggesting a potential mechanism underlying IHH-induced hyperuricemia.

Research Progress on New Functions of Animal and Plant Proteins

Protein is composed of peptides, essential nutrients for human survival and health, and the easy absorption of peptides further promotes human health. According to the source of the protein, it can be divided into plants, animals, and micro-organisms, which have important physiological effects on the health of the body, especially in enhancing immunity. The most widely used raw materials are animal protein and plant protein, and the protein composition formed by the two in a certain proportion is called "double protein". In recent years, China's State Administration for Market Regulation has issued an announcement on the "Implementation Rules for the Technical Evaluation of New Functions and Products of Health Foods (Trial)", which provides application conditions and listing protection for the research and development of new functions of health foods. At present, some researchers and enterprises have begun to pay attention to the potential of animal and plant proteins to be used in new functions. In this article, the research progress of animal and plant proteins in the new functions of Chinese health food is reviewed in detail, and suggestions for future research on animal and plant proteins are put forward.

In vivo anti-hyperuricemia and anti-gouty arthritis effects of the ethanol extract from Amomumvillosum Lour

The incidence of hyperuricemia and gout has been increasing year by year, and it is showing a younger trend. However, the first-line drugs currently used for hyperuricemia and gouty arthritis have serious side effects that limit their clinical application. Amomum villosum Lour. has been widely used in China for thousands of years as a traditional medical and edible plant, and previous screening showed that the ethanol extract of Amomum villosum Lour. could effectively inhibit the activity of xanthine oxidase. Based on this discovery, this paper had achieved in-depth mechanism research. The results showed that the ethanol extract of Amomum villosum Lour. could treat hyperuricemia by reducing the production of uric acid via inhibition of xanthine oxidase and increasing the excretion of uric acid via regulation of urate transporters. Meanwhile, the extract also showed a certain protective effect on hepatic and renal damage caused by hyperuricemia. With the formation of extensive uric acid, gouty arthritis will be induced by the deposition of monosodium urate in the joint. The extract could also relieve the inflammation by reducing the expression of inflammatory cytokines. In conclusion, the extract deserves focused research and development as a potential medicine, health care product or supplemented food for the prevention and treatment of hyperuricemia and gouty arthritis.

Ameliorative Effect of Mannuronate Oligosaccharides on Hyperuricemic Mice via Promoting Uric Acid Excretion and Modulating Gut Microbiota

Mannuronate oligosaccharide (MOS) is α-D-mannuronic acid polymer with 1,4-glycosidic linkages that possesses beneficial biological properties. The aim of this study was to investigate the hypouricemic effect of MOS in hyperuricemic mice and demonstrate the possible protective mechanisms involved. In this research, 200 mg/kg/day of MOS was orally administered to hyperuricemic mice for four weeks. The results showed that the MOS treatment significantly reduced the serum uric acid (SUA) level from 176.4 ± 7.9 μmol/L to 135.7 ± 10.9 μmol/L (p < 0.05). MOS alleviated the inflammatory response in the kidney. Moreover, MOS promoted uric acid excretion by regulating the protein levels of renal GLUT9, URAT1 and intestinal GLUT9, ABCG2. MOS modulated the gut microbiota in hyperuricemic mice and decreased the levels of Tyzzerella. In addition, research using antibiotic-induced pseudo-sterile mice demonstrated that the gut microbiota played a crucial role in reducing elevated serum uric acid of MOS in mice. In conclusion, MOS may be a potential candidate for alleviating HUA symptoms and regulating gut microbiota.

Effects of a Macroporous Resin Extract of Dendrobium officinale Leaves in Rats with Hyperuricemia Induced by Anthropomorphic Unhealthy Lifestyle

Aim

Hyperuricemia (HUA) has received increased attention in the last few decades due to its global prevalence. Our previous study found that administration of a macroporous resin extract of Dendrobium officinale leaves (DoMRE) to rats with HUA that was induced by exposure to potassium oxazine combined with fructose and a high-purine diet led to a significant reduction in serum uric acid (SUA) levels. The aim of this study was to explore the effects of DoMRE on hyperuricemia induced by anthropomorphic unhealthy lifestyle and to elucidate its possible mechanisms of action.

Methods

Dosages (5.0 and 10.0 g/kg/day) of DoMRE were administered to rats daily after induction of HUA by anthropomorphic unhealthy lifestyle for 12 weeks. The levels of UA in the serum, urine, and feces; the levels of creatinine (Cr) in the serum and urine; and the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum were all measured using an automatic biochemical analyzer. The activities of xanthine oxidase (XOD) and adenosine deaminase (ADA) in the serum, liver, and intestine tissue supernatant were measured using appropriate kits for each biological target. The expressions levels of UA transporters (ABCG2 and GLUT9), tight junction (TJ) proteins (ZO-1 and occludin), and inflammatory factors (IL-6, IL-8, and TNF-α) in the intestine were assayed by immunohistochemical (IHC) staining. Hematoxylin and eosin (H&E) staining was used to assess histological changes in the renal and intestinal tissues.

Results

DoMRE treatment significantly reduced SUA levels and concomitantly increased fecal UA (FUA) levels and the fractional excretion of UA (FEUA) in HUA rats. Furthermore, DoMRE significantly reduced both the XOD activity in the serum, liver, and intestine and the ADA activity in the liver and intestine. DoMRE also effectively regulated the expression of GLUT9 and ABCG2 in the intestine, and it significantly upregulated the expression of the intestinal TJ proteins ZO-1 and occludin. Therefore, DoMRE reduced the damage to the intestinal barrier function caused by the increased production of inflammatory factors due to HUA to ensure normal intestinal UA excretion.

Conclusion

DoMRE demonstrated anti-HUA effects in the HUA rat model induced by an anthropomorphic unhealthy lifestyle, and the molecular mechanism appeared to involve the regulation of urate transport-related transporters (ABCG2 and GLUT9) in the intestine, protection of the intestinal barrier function to promote UA excretion, and inhibition of XOD and ADA activity in the liver and intestine to inhibit UA production in the HUA-induced rats.

Ganoderma lucidum polysaccharide peptide alleviates hyperuricemia by regulating adenosine deaminase and urate transporters

Hyperuricemia (HUA) affects human health and is involved in the pathogenesis of common chronic diseases. Previous studies showed that Ganoderma lucidum extract lowered HUA in animals. However, the active ingredient and pharmacological mechanism of Ganoderma lucidum extract in the improvement of HUA are unknown. The purpose of this study was to determine the anti-HUA efficacy and related mechanism of Ganoderma lucidum polysaccharide peptide (GLPP) using a potassium oxonate (PO)-induced mouse model and an adenosine-induced cell model. The experimental results showed that blood uric acid (UA) was decreased up to 40.6% by GLPP in HUA mice in a dose-dependent manner. Additionally, GLPP significantly reduced UA production by inhibiting the hepatic and blood adenosine deaminase (ADA) activity and increased UA excretion by decreasing the expression of glucose transporter 9 (GLUT9) and increasing the expression of organic anion transporter 1 (OAT1) in kidney. The adenosine-induced cell model showed that the inhibitory effect of GLPP on ADA activity may be the main reason for the alleviation of HUA by GLPP. Furthermore, PO-induced renal histopathological damage was also alleviated by GLPP in a dose-dependent manner. The experimental results in this study indicated that GLPP exerted anti-HUA effects via regulating the UA production and excretion, suggesting that GLPP could be developed into a therapeutic agent for HUA.

Optimization of the extraction process and metabonomics analysis of uric acid-reducing active substances from Gymnadenia R.Br. and its protective effect on hyperuricemia zebrafish

Background

As Gymnadenia R.Br. (Gym) has an obvious uric acid-lowering effect, but its specific bioactive substances and mechanism are still unclear. The key metabolites and pathways used by Gym to reduce uric acid (UA) were identify.

Methods

An optimized extraction process for urate-lowering active substances from Gym was firstly been carried out based on the xanthine oxidase (XOD) inhibition model in vitro; then, the Ultra-high-performance liquid chromatography and Q-Exactive mass spectrometry (UHPLC-QE-MS) based on non-targeted metabolomics analysis of Traditional Chinese Medicine were performed for comparison of Gym with ethanol concentration of 95% (low extraction rate but high XOD inhibition rate) and 75% (high extraction rate but low XOD inhibition rate), respectively; finally, the protective effect of ethanolic extract of Gym on zebrafish with Hyperuricemia (referred to as HUA zebrafish) was explored.

Results

We found that the inhibition rate of Gym extract with 95% ethanol concentration on XOD was 84.02%, and the extraction rate was 4.32%. Interestingly, when the other conditions were the same, the XOD inhibition rate of the Gym extract with 75% ethanol concentration was 76.84%, and the extraction rate was 14.68%. A total of 539 metabolites were identified, among them, 162 different metabolites were screened, of which 123 were up-regulated and 39 were down-regulated. Besides significantly reducing the contents of UA, BUN, CRE, ROS, MDA, and XOD activity in HUA zebrafish by Gym and acutely reduce the activity of SOD.

Conclusion

Along with the flavonoids, polyphenols, alkaloids, terpenoids, and phenylpropanoids, the ethanolic extract of Gym may be related to reduce the UA level of Gym.

NRBP1 modulates uric acid transporter ABCG2 expression by activating the Wnt/β-catenin pathway in HK-2 cells

BACKGROUND

Nuclear receptor binding protein 1 (NRBP1) and ATP-binding cassette subfamily G member 2 (ABCG2) was the gout risk gene and high-capacity urate exporter respectively. However, the relationship between NRBP1 and ABCG2 and the underlying molecular mechanism contributing to these associations are unknown.

METHODS

Firstly, the efficiency of the overexpression and knockdown of NRBP1 was confirmed by western blot. Next, the effect of NRBP1 overexpression and knockdown on the expression of ABCG2, organic anion transporter 1 (OAT1), glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1) was detected by qRT-PCR and western blot. At the same time, the cellular location of ABCG2 and its expression after NRBP1 overexpression and knockdown was tested by immunofluorescence (IF) staining. Then, the mechanism of NRBP1 modulates ABCG2 expression was evaluated by western blot with or without the β-catenin inhibitor (21H7).

RESULTS

The lentivirus system was used to generate stable NRBP1 overexpression, while the plasmids carrying a NRBP1 siRNA was generated to knockdown NRBP1 expression in HK-2 cells. Meanwhile, the overexpression of NRBP1 significantly decreased the mRNAs and proteins expression of GLUT9 and URAT1, while the knockdown of NRBP1 increased the mRNAs and proteins expression of ABCG2 significantly. In addition, the NRBP1 modulates the expression of ABCG2 was by ctivating the Wnt/β-catenin pathway in HK-2 cells according to the IF and western blot results.

CONCLUSION

Taken together, our study demonstrated that NRBP1 inhibition played an essential role in attenuating hyperuricemia and gout by upregulation of ABCG2 via Wnt/β-catenin signaling pathway in HK-2 cells.

Fufang Zhenzhu Tiaozhi capsule ameliorates hyperuricemic nephropathy by inhibition of PI3K/AKT/NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Excessive serum uric acid (SUA) causes hyperuricemic nephropathy (HN), characterized by inflammatory infiltration and tubulointerstitial fibrosis. Most recently, we demonstrated that Fufang Zhenzhu Tiaozhi (FTZ) capsule attenuated diabetic nephropathy through inhibition of renal inflammation and fibrosis. However, whether FTZ ameliorates HN is still unclear.

AIM OF THE STUDY

To determine the protective roles and mechanism of FTZ in mouse renal injury and fibrosis under hyperuricemic condition.

MATERIALS AND METHODS

HN mice, induced by potassium oxonate and hypoxanthine, were administrated with 600 and 1200 mg/kg FTZ (intragastrically) daily for three weeks. SUA levels, renal functions and histological changes were analyzed. Western blotting, quantitative real-time PCR (q-PCR) and RNA sequencing were used to identify the roles and underlying mechanism of FTZ in HN mice.

RESULTS

We demonstrated that FTZ treatment mitigated renal injury in mice, as evidenced by the decrease in SUA, serum creatinine (SCr) and cystatin C (Cys C) levels, as well as improved renal histology. FTZ markedly attenuates inflammasome activation, collagen deposition and the imbalance of uric acid transporters. RNA-sequencing revealed a key mechanism involved in the protective effects on HN mice was related to PI3K/AKT/NF-κB pathway. Western blot also confirmed that FTZ diminished the phosphorylation of AKT and p65 in HN mice.

CONCLUSIONS

FTZ prevents renal injury, inflammation and fibrosis in HN mice via promoting uric acid excretion and inhibiting PI3K/AKT/NF-κB signaling pathway.

Metabolomic and transcriptomic exploration of the uric acid-reducing flavonoids biosynthetic pathways in the fruit of Actinidia arguta Sieb. Zucc

Flavonoids from Actinidia arguta Sieb. Zucc. can reduce uric acid in mice. However, the molecular basis of its biosynthesis is still unclear. In this paper, we used a combination of extensively targeted metabolomics and transcriptomics analysis to determine the types and differences of flavonoids in the fruit ripening period (August to September) of two main cultivated varieties in northern China. The ethanol extract was prepared, and the potential flavonoids of Chrysin (Flavone1), Rutin (Flavone2), and Daidzein (Flavone3) in Actinidia arguta Sieb. Zucc. were separated and purified by HPD600 macroporous adsorption resin and preparative liquid chromatography. The structure was identified by MS-HPLC, and the serum uric acid index of male Kunming mice was determined by an animal model test.125 flavonoids and 50 differentially regulated genes were identified. The contents of UA (uric acid), BUN (urea nitrogen), Cr (creatinine), and GAPDH in mouse serum and mouse liver glycogen decreased or increased in varying degrees. This paper reveals the biosynthetic pathway of uric acid-reducing flavonoids in the fruit of Actinidia arguta Sieb. Zucc., a major cultivar in northern China, provides valuable information for the development of food and drug homologous functional foods.

Probiotic effects of Lacticaseibacillus rhamnosus 1155 and Limosilactobacillus fermentum 2644 on hyperuricemic rats

Hyperuricemia is the main cause of gout and involved in the occurrence of multiple diseases, such as hypertension, metabolic disorders and chronic kidney disease. Emerging evidence suggests that lactic acid bacteria (LAB) have shown the beneficial effects on the prevention or treatment of hyperuricemia. In this study, the urate-lowering effect of two LAB strains, Lacticaseibacillus rhamnosus 1155 (LR1155) and Limosilactobacillus fermentum 2644 (LF2644) on hyperuricemic rats were investigated. A hyperuricemic rat model was induced by the intragastric treatment of potassium oxonate, combined with a high purine diet. The oral administration of LR1155, LF2644, or a combination of LR1155 and LF2644 for 4 weeks significantly prevented the rise of the serum uric acid (UA) induced by hyperuricemia. LR1155 and LF2644 significantly elevated the fecal UA levels, increased the UA content and up-regulated gene expression of UA transporter, ATP-binding cassette subfamily G-2 (ABCG2), in colon and jejunum tissues, suggesting the accelerated UA excretion from the intestine. Besides, LR1155 significantly inhibited the activity of xanthine oxidase (XOD) in liver and serum, benefited the reduce of UA production. In addition, LF2644 strengthened the gut barrier functions through an up-regulation of the gene expressions for occluding and mucin2, accompanied with the reduced inflammatory indicators of lipopolysaccharide (LPS) and interleukin-1β (IL-1β) in hyperuricemic rat. Moreover, using 16s rDNA high-throughput sequencing of feces, LR1155 was shown to improve the hyperuricemia induced gut microbial dysbiosis. The genera Roseburia, Butyricicoccus, Prevotella, Oscillibacter, and Bifidobacterium may associate with the effect of LR1155 on microbiota in hyperuricemic rats. Collectively, the results indicated that LR1155 and LF2644 exhibit urate-lowering effects and could be used alone or in combination as a new adjuvant treatment for hyperuricemia.

Novel xanthine oxidase inhibitory peptides derived from whey protein: identification, in vitro inhibition mechanism and in vivo activity validation

As the development of hyperuricemia (HUA) and gout continues to accelerate worldwide, there is increasing interest in the use of xanthine oxidase (XO) inhibitors as therapeutic agents for the management of HUA and gout. In the present study, XO inhibitory peptides were identified from whey protein isolate (WPI) hydrolysates, and the underlying inhibitory mechanism and in vivo activities was investigated. WPI hydrolysates were isolated and purified, and two peptides (ALPM and LWM) with lower binding energy were screened by molecular docking. The result showed that these two peptides interacted with residues around the active site of XO through hydrogen bond and hydrophobic interaction. The IC₅₀ values of ALPM and LWM were 7.23 ± 0.22 and 5.01 ± 0.31 mM, respectively. According to the Lineweaver-Burk curve, the inhibition types of ALPM and LWM were non-competitive inhibition. Circular dichroism (CD) spectra indicated ALPM and LWM could change the secondary structure of XO. Molecular dynamics simulations revealed that XO-peptide complexes were more stable and compact than XO. Moreover, animal studies have shown that ALPM and LWM have anti-hyperuricemia effects in vivo. This study suggested that ALPM and LWM can be considered as natural XO inhibitors for the treatment of HUA.

Dietary Ferulic Acid Ameliorates Metabolism Syndrome-Associated Hyperuricemia in Rats via Regulating Uric Acid Synthesis, Glycolipid Metabolism, and Hepatic Injury

Ferulic acid is a well-known phenolic acid compound and possesses multiple health-promoting and pharmacological effects. Metabolic syndrome (MetS) and hyperuricemia (HUA) have become health problems worldwide and are closely connected. The aim of this study was to explore the influence of ferulic acid on MetS-related HUA and its underlying mechanisms. Rats were administered high-fructose and high-fat diet (HFFD) with or without ferulic acid (0.05 and 0.1%) for 20 weeks. Intake of HFFD resulted in obesity, hyperglycemia, insulin resistance, and dyslipidemia, which were alleviated by ferulic acid consumption. Treatment of rats with ferulic acid diminished the levels of lipids and inflammatory cytokines and enhanced the activities of antioxidant enzymes in the liver caused by HFFD. Additionally, administration of ferulic acid blocked a HFFD-induced elevation in activities and mRNA expression of enzymes involving in uric acid (UA) synthesis. Molecular docking analysis denoted that ferulic acid bound to the active center of these enzymes, indicative of the potential interaction with each other. These two aspects might partially be responsible for the decrement in serum UA content after ferulic acid ingestion. In conclusion, ferulic acid supplementation ameliorated lipid and glucose metabolic abnormalities, hepatic damage, and UA formation in MetS rats. There was a dose correlation between lipid deposition and UA synthesis-related indicators. These findings implied that ferulic acid could be applied as a promising dietary remedy for the management of MetS-associated HUA.

Health benefits of astaxanthin against age-related diseases of multiple organs: A comprehensive review

Age-related diseases are associated with increased morbidity in the past few decades and the cost associated with the treatment of these age-related diseases exerts a substantial impact on social and health care expenditure. Anti-aging strategies aim to mitigate, delay and reverse aging-associated diseases, thereby improving quality of life and reducing the burden of age-related pathologies. The natural dietary antioxidant supplementation offers substantial pharmacological and therapeutic effects against various disease conditions. Astaxanthin is one such natural carotenoid with superior antioxidant activity than other carotenoids, as well as well as vitamins C and E, and additionally, it is known to exhibit a plethora of pharmacological effects. The present review summarizes the protective molecular mechanisms of actions of astaxanthin on age-related diseases of multiple organs such as Neurodegenerative diseases [Alzheimer's disease (AD), Parkinson's disease (PD), Stroke, Multiple Sclerosis (MS), Amyotrophic lateral sclerosis (ALS), and Status Epilepticus (SE)], Bone Related Diseases [Osteoarthritis (OA) and Osteoporosis], Cancers [Colon cancer, Prostate cancer, Breast cancer, and Lung Cancer], Cardiovascular disorders [Hypertension, Atherosclerosis and Myocardial infarction (MI)], Diabetes associated complications [Diabetic nephropathy (DN), Diabetic neuropathy, and Diabetic retinopathy (DR)], Eye disorders [Age related macular degeneration (AMD), Dry eye disease (DED), Cataract and Uveitis], Gastric Disorders [Gastritis, Colitis, and Functional dyspepsia], Kidney Disorders [Nephrolithiasis, Renal fibrosis, Renal Ischemia reperfusion (RIR), Acute kidney injury (AKI), and hyperuricemia], Liver Diseases [Nonalcoholic fatty liver disease (NAFLD), Alcoholic Liver Disease (AFLD), Liver fibrosis, and Hepatic Ischemia-Reperfusion (IR) Injury], Pulmonary Disorders [Pulmonary Fibrosis, Acute Lung injury (ALI), and Chronic obstructive pulmonary disease (COPD)], Muscle disorders (skeletal muscle atrophy), Skin diseases [Atopic dermatitis (ATD), Skin Photoaging, and Wound healing]. We have also briefly discussed astaxanthin's protective effects on reproductive health.

Drug Transporters in the Kidney: Perspectives on Species Differences, Disease Status, and Molecular Docking

The kidneys are a pair of important organs that excretes endogenous waste and exogenous biological agents from the body. Numerous transporters are involved in the excretion process. The levels of these transporters could affect the pharmacokinetics of many drugs, such as organic anion drugs, organic cationic drugs, and peptide drugs. Eleven drug transporters in the kidney (OAT1, OAT3, OATP4C1, OCT2, MDR1, BCRP, MATE1, MATE2-K, OAT4, MRP2, and MRP4) have become necessary research items in the development of innovative drugs. However, the levels of these transporters vary between different species, sex-genders, ages, and disease statuses, which may lead to different pharmacokinetics of drugs. Here, we review the differences of the important transports in the mentioned conditions, in order to help clinicians to improve clinical prescriptions for patients. To predict drug-drug interactions (DDIs) caused by renal drug transporters, the molecular docking method is used for rapid screening of substrates or inhibitors of the drug transporters. Here, we review a large number of natural products that represent potential substrates and/or inhibitors of transporters by the molecular docking method.

Astaxanthin alleviates inflammatory pain by regulating the p38 mitogen-activated protein kinase and nuclear factor-erythroid factor 2-related factor/heme oxygenase-1 pathways in mice

Inflammatory pain is a complex process that has a substantial negative impact on post-injury quality of life. Astaxanthin (AST), which is a lipid-soluble red-orange carotenoid that is found in lobsters, inhibits the development and maintenance of inflammation in mice via its antioxidant and anti-inflammatory activities. However, the specific mechanisms underlying these effects remain unclear. In this study, we aimed to elucidate the mechanism by which astaxanthin alleviated inflammation using a mouse model with Complete Freund's adjuvant (CFA)-induced inflammatory pain. Mechanical allodynia and thermal hyperalgesia were observed on days 1-14 post CFA injection. Expression of p38 mitogen-activated protein kinase (MAPK) in the left paw and L4-6 dorsal root ganglia (DRG) were upregulated in the CFA-induced mice. Expression of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathways were also increased. Astaxanthin relieved mechanical allodynia and thermal hyperalgesia induced by CFA and inhibited the inflammatory response (e.g., infiltration of inflammatory cells and production of inflammatory factors) in the ipsilateral paw and DRG. Additionally, AST  inhibited p38 MAPK and enhanced Nrf2/HO-1 contents in the left paw and DRG, and reversed the pain induced by p38 MAPK agonist and Nrf2 inhibitors. These findings suggest that AST exerts anti-inflammatory effects and regulates p38 MAPK and Nrf2/HO-1 to alleviate inflammatory pain. AST may be a potential therapeutic agent for relieving inflammation.

Ellagic Acid Exerts Beneficial Effects on Hyperuricemia by Inhibiting Xanthine Oxidase and NLRP3 Inflammasome Activation

Hyperuricemia is a metabolic disease caused by impaired uric acid (UA) metabolism. Ellagic acid (EA) is a natural small-molecule polyphenolic compound with known antioxidative and anti-inflammatory properties. Here, we evaluated the regulatory effects of EA on hyperuricemia and explored the underlying mechanisms. We found that EA is an effective xanthine oxidase (XOD) inhibitor (IC₅₀ = 165.6 μmol/L) and superoxide anion scavenger (IC₅₀ = 27.66 μmol/L). EA (5 and 10 μmol/L) treatment significantly and dose-dependently reduced UA levels in L-O2 cells; meanwhile, intraperitoneal EA administration (50 and 100 mg/kg) also significantly reduced serum XOD activity and UA levels in hyperuricemic mice and markedly improved their liver and kidney histopathology. EA treatment significantly reduced the degree of foot edema and inhibited the expression of NLPR3 pathway-related proteins in foot tissue of monosodium urate (MSU)-treated mice. The anti-inflammatory effect was also observed in lipopolysaccharide-stimulated RAW-264.7 cells. Furthermore, EA significantly inhibited the expressions of XOD and NLRP3 pathway-related proteins (TLR4, p-p65, caspase-1, TNF-α, and IL-18) in vitro and in vivo. Our results indicated that EA exerts ameliorative effects in experimental hyperuricemia and foot edema via regulating the NLRP3 signaling pathway and represents a promising therapeutic option for the management of hyperuricemia.

Analysis of Risk Factors for Changes in the Renal Two-Dimensional Image in Gout Patients

OBJECTIVE

To explore the effects of different blood uric acid levels in gout patients on the two-dimensional image of the kidney and the risk factors for gout-related kidney damage for providing clinical evidence to enable early prevention and treatment of gout-related kidney damage.

METHODS

We obtained information of 227 patients with primary gout and estimated the association between two-dimensional kidney images and clinical indicators using binary logistic regression.

RESULTS

Our study showed that different uric acid levels, age, disease course, cystatin C (CysC) level, and γ-glutamyl transpeptidase level were correlated with echo of the renal medulla (P < 0.05). CysC level was correlated with the renal cortex thickness and kidney stones in different uric acid-level groups (P < 0.05). Disease course, aspartate transaminase (AST) level, creatinine (CREA) level, and tophi were risk factors for renal cortex thinning in gout patients (P = 0.045, 0.026, 0.004, 0.006, respectively). The disease course, platelet (PLT) count, and high-density lipoprotein (HDL-C) level were risk factors for kidney stone formation in gout patients (P = 0.037, 0.022, 0.023, respectively), while CysC level and C-reactive protein (CRP) level were risk factors for increased renal medulla echo in these patients (P = 0.022, 0.028, respectively).

CONCLUSION

Our study revealed disease course, AST level, CREA level, tophi, PLT count, HDL-C level, CysC level and CRP level may be important predictors of renal image changes.

Effects of Macroporous Resin Extract of Dendrobium officinale Leaves in Rats with Hyperuricemia Induced by Fructose and Potassium Oxonate

AIM AND OBJECTIVE

Fructose, as a ubiquitous monosaccharide, can promote ATP consumption and elevate circulating uric acid (UA) levels. Our previous studies confirmed that the macroporous resin extract of Dendrobium officinale leaves (DoMRE) could reduce the UA level of rats with hyperuricemia induced by a high-purine diet. This study aimed to investigate whether DoMRE had a UA-lowering effect on rats with hyperuricemia caused by fructose combined with potassium oxonate, so as to further clarify the UA-lowering effect of DoMRE, and to explore the UA-lowering effect of DoMRE on both UA production and excretion.

MATERIALS AND METHODS

Rats with hyperuricemia induced by fructose and potassium oxonate were administered with DoMRE and vehicle control, respectively, to compare the effects of the drugs. At the end of the experiment, the serum uric acid (SUA) and creatinine (Cr) levels were measured using an automatic biochemical analyzer, the activities of xanthine oxidase (XOD) were measured using an assay kit, and the protein expression of urate transporter 1 (URAT1), glucose transporter 9 (GLUT9), and ATP-binding cassette superfamily G member 2 (ABCG2) were assessed using immunohistochemical and western blot analyses. Hematoxylin and eosin staining was used to assess the histological changes in the kidney, liver, and intestine.

RESULTS

Rats with hyperuricemia were induced by fructose and potassiumFructose and potassium induced hyperuricemia in rats. Meanwhile, the activities of XOD were markedly augmented, the expression of URAT1 and GLUT9 was promoted, and the expression of ABCG2 was reduced, which were conducive to the elevation of UA. However, exposure to DoMRE reversed these fructose- and potassium oxonate-induced negative alternations in rats. The activities of XOD were recovered to the normal level, reducing UA formation; the expression of URAT1, ABCG2, and GLUT9 returned to the normal level, resulting in an increase in renal urate excretion.

CONCLUSION

DoMRE reduces UA levels in rats with hyperuricemia induced by fructose combined with potassium oxonate by inhibiting XOD activity and regulating the expression of ABCG2, URAT1, and GLUT9. DoMRE is a potential therapeutic agent for treating hyperuricemia through inhibiting UA formation and promoting UA excretion.

Anti-Inflammatory and Anti-Hyperuricemic Effects of Chrysin on a High Fructose Corn Syrup-Induced Hyperuricemia Rat Model via the Amelioration of Urate Transporters and Inhibition of NLRP3 Inflammasome Signaling Pathway

Hyperuricemia is the main cause of gout and involved in the occurrence of many other diseases such as hyperlipidemia and hypertension correlated with metabolic disorders. Chrysin is a flavonoid compound found naturally in honey, propolis, and mushrooms and has anti-inflammatory and antioxidant effects. However, its mechanism of action is not clear yet. This study investigated the mechanism of chrysin’s anti-hyperuricemic effect in hyperuricemia-induced rats fed with high-fructose corn syrup. Orally administrated chrysin for 28 consecutive days effectively decreased uric acid by inhibiting the activity of xanthine oxidase (XO) in the liver. Moreover, chrysin markedly downregulated the protein expression of uric acid transporter 1 (URAT1) and glucose transporter type 9 (GLUT9) and upregulated the protein expression of organic anion transporter 1 (OAT1) and human ATP-binding cassette subfamily G-2 (ABCG2). In addition, chrysin showed prominent anti-oxidative and inflammatory effects as the malondialdehyde (MDA) and interleukin 1 beta (IL-1β) concentration was reduced in both rat kidney and serum, which aligned with the inhibition of NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signaling pathway activation. Collectively, our results strongly suggest that chrysin exhibits potent anti-hyperuricemic and anti-inflammatory effects that may yield new adjuvant treatments for gout.

MAPK signaling pathway-targeted marine compounds in cancer therapy

PURPOSE

This paper reviews marine compounds that target the mitogen-activated protein kinase (MAPK) signaling pathway and their main sources, chemical structures, major targeted cancers and possible mechanisms to provide comprehensive and basic information for the development of marine compound-based antitumor drugs in clinical cancer therapy research.

METHODS

This paper searched the PubMed database using the keywords "cancer", "marine*" and "MAPK signaling pathway"; this search was supplemented by the literature-tracing method. The marine compounds screened for review in this paper are pure compounds with a chemical structure and have antitumor effects on more than one tumor cell line by targeting the MAPK signaling pathway. The PubChem database was used to search for the PubMed CID and draw the chemical structures of the marine compounds.

RESULTS

A total of 128 studies were searched, and 32 marine compounds with unique structures from extensive sources were collected for this review. These compounds are cytotoxic to cancer cell lines, although their targets are still unclear. This paper describes their anticancer effect mechanisms and the protein expression changes in the MAPK pathway induced by these marine compound treatments. This review is the first to highlight MAPK signaling pathway-targeted marine compounds and their use in cancer therapy.

CONCLUSION

The MAPK signaling pathway is a promising potential target for cancer therapy. Searching for marine compounds that exert anticancer effects by targeting the MAPK signaling pathway and developing them into new marine anticancer drugs will be beneficial for cancer treatment.