Derivation and elimination of uremic toxins from kidney-gut axis.

Uremic toxins are chemicals, organic or inorganic, that accumulate in the body fluids of individuals with acute or chronic kidney disease and impaired renal function. More than 130 uremic solutions are included in the most comprehensive reviews to date by the European Uremic Toxins Work Group, and novel investigations are ongoing to increase this number. Although approaches to remove uremic toxins have emerged, recalcitrant toxins that injure the human body remain a difficult problem. Herein, we review the derivation and elimination of uremic toxins, outline kidney-gut axis function and relative toxin removal methods, and elucidate promising approaches to effectively remove toxins.

Serum metabolic alterations in peritoneal dialysis patients with excessive daytime sleepiness.

Excessive daytime sleepiness (EDS) is associated with quality of life and all-cause mortality in the end-stage renal disease population. This study aims to identify biomarkers and reveal the underlying mechanisms of EDS in peritoneal dialysis (PD) patients. A total of 48 nondiabetic continuous ambulatory peritoneal dialysis patients were assigned to the EDS group and the non-EDS group according to the Epworth Sleepiness Scale (ESS). Ultra-high-performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) was used to identify the differential metabolites. Twenty-seven (male/female, 15/12; age, 60.1 ± 16.2 years) PD patients with ESS ≥ 10 were assigned to the EDS group, while twenty-one (male/female, 13/8; age, 57.9 ± 10.1 years) PD patients with ESS < 10 were defined as the non-EDS group. With UHPLC-Q-TOF/MS, 39 metabolites with significant differences between the two groups were found, 9 of which had good correlations with disease severity and were further classified into amino acid, lipid and organic acid metabolism. A total of 103 overlapping target proteins of the differential metabolites and EDS were found. Then, the EDS-metabolite-target network and the protein-protein interaction network were constructed. The metabolomics approach integrated with network pharmacology provides new insights into the early diagnosis and mechanisms of EDS in PD patients.

Production of monoclonal antibody against grouper (Epinephelus coioides) CD4-1 and the distribution of CD4-1+ cells.

CD4-a transmembrane glycoprotein molecule expressed on the surface of helper T (Th) cells-plays a central role in adaptive immune protection. In the current study, we developed a monoclonal antibody (mAb) against the grouper CD4-1. Western blotting and immunohistochemistry results revealed that the CD4-1 mAb could recognize the recombinant and natural protein of grouper CD4-1 as well as the CD4-1+ cells in the various tissues from grouper. Tissue distribution analyses revealed that the grouper CD4-1+ cells were expressed in all tissues tested in the healthy grouper, with greater localization in the thymus, head kidney, and spleen tissues. In addition, we tested the changes in the proportion of CD4-1+ cells in the thymus, head kidney, and the gills of grouper post the infection by C. irritans. Our data suggest that the CD4-1 mAb produced against grouper in the current study can be used as a tool to characterize CD4-1+ cells and to investigate the functions of the grouper CD4-1+ cells in the host response against pathogens infection.

Transcriptomic analysis reveals innate immune mechanisms of an underlying parasite-resistant grouper hybrid (Epinephelus fuscogutatus × Epinephelus lanceolatus).

Hybridization is an artificial breeding strategy for generating potentially desirable offspring. Recently, a novel Hulong grouper hybrid (Epinephelus fuscogutatus × Epinephelus lanceolatus) yielded significant growth superiority over its parent. Improved innate immunity is considered as another desirable feature during hybridization. However, whether this Hulong grouper achieved disease resistance has not yet been revealed. In this study, we first examine the infection intensity of C. irritans in the Hulong grouper, and found that the Hulong grouper is less susceptible to C. irritans primary infection. A higher immobilization titer was found in the infected Hulong grouper at Day 2 when compared with the control grouper. Furthermore, severe hyperplasia was observed in the orange-spotted grouper, but not in the Hulong grouper's skin epidermis. To further understand the innate immune mechanism against C. irritans, we conducted a comparative transcriptome analysis of the Hulong grouper during the infection. There are 6464 differentially expressed genes (DEGs) identified in the skin between the control and infected Hulong grouper. This indicates that the innate immune components, such as the complement system, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, Interleukin 17 (IL-17) signaling pathway, and Toll-like receptor (TLR) signaling pathway were up-regulated during the infection. These results show that the C. irritans infection can induce a remarkable inflammatory response in the Hulong grouper. Moreover, a total of 75 pairs of orthologs with the ratio of nonsynonymous (Ka) to synonymous (Ks) substitutions ＞1, considered rapidly evolving genes (REGs), was identified between the Hulong and orange-spotted grouper. More critically, most REGs were enriched in the immune system, suggesting that rapid evolution of the immune system might occur in the Hulong grouper. These results provide a more comprehensive understanding of the innate immunity mechanism of the hybrid Hulong grouper.

Recommendations for prevention and management of COVID-19 in peritoneal dialysis patients.

The World Health Organization characterized coronavirus disease (COVID-19) as a pandemic on March 11, 2020. Peritoneal dialysis patients have a weakened immune system that is associated with a high morbidity of infection. Thus, COVID-19 prevention measures and management for patients on peritoneal dialysis are urgent and critical. Based on published research on COVID-19 and previous clinical practices for similar coronavirus outbreaks, we aimed to make recommendations to manage patients undergoing peritoneal dialysis.

Identification and characterization of c-raf from orange-spotted grouper (Epinephelus coioides).

C-Raf proto-oncogene serine/threonine kinase is a mitogen-activated protein kinase (MAP) kinase kinase, which can initiate a mitogen-activated protein kinase (MAPK) cascade by phosphorylating the dual-specific MAP kinase kinases (MEK1/2), and in turn activate the extracellular signal-regulated kinases (ERK1/2). To study the function of c-Raf in teleost fish, a c-Raf cDNA sequence from orange-spotted grouper (Epinephelus coioides) was cloned. Ecc-Raf shared 81%-99% amino acid identity with other vertebrate c-Raf molecules, and shared the highest amino acid identity (99%) with Lates calcarifer c-Raf. Genomic structure analysis revealed that grouper c-Raf shared a conserved exon structure with other vertebrates. Tissue distribution showed that Ecc-Raf was mainly transcribed in systemic immune organs. Ecc-Raf was distributed throughout the cytoplasm of transfected GS cells and the overexpression of Ecc-Raf only slightly enhanced the activation of Activator protein 1. The phosphorylation levels of Ecc-Raf can be induced by PMA and H2O2 treatment, in contrast to DMSO or untreated HKLs. Moreover, the phosphorylation level of the Raf-MEK-ERK axis was downregulated after 24 h of SGIV infection. On the other hand, the total level and phosphorylation level of c-Raf significantly increased post C. irritans infection and showed an enhanced level post immunization. The results of this study suggested that the Raf-MEK-ERK cascade was involved in the response to viral or parasitic infections.

Characterization and functional analysis of grouper (Epinephelus coioides) MEK1 and MEK2.

MEK dual-specificity protein kinases are a group of mitogen-activated protein kinase kinases, which act as an integration point by transferring extracellular signals to the nucleus. To investigate the function of MEK in teleost fish, we cloned MEK1 and MEK2 cDNA sequences from the orange-spotted grouper (Epinephelus coioides). EcMEK1 and EcMEK2 shared 80% amino acid identity with each other. EcMEK1 had 89-99% amino acid identity with teleosts or mammals, whereas EcMEK2 shared 85-97% amino acid identity. The exon structures of the grouper MEK1/2 genes were conserved with zebrafish and human MEK1/2. Tissue distribution analysis showed that EcMEK1 and EcMEK2 had a similar expression pattern in grouper tissues and was mainly transcribe in systemic immune organs. Both EcMEK1 and EcMEK2 were distributed throughout the cytoplasm of transfected GS or HEK293T cells. Overexpression of EcMEK1 or EcMEK2 activated Activator protein 1 dependent luciferase. The phosphorylation levels of EcMEK1/2 and EcERK1/2 were significantly increased in head kidney leukocytes by stimulation with PMA treatment. The grouper MEK1/2-ERK1/2 axis was activated in Cryptocaryon irritans infection and showed an enhanced phosphorylation after immunization.

miR-98 protects endothelial cells against hypoxia/reoxygenation induced-apoptosis by targeting caspase-3.

Endothelial dysfunction is one of the main pathophysiological processes involved in renal ischemia reperfusion injury. Our previous microarray study demonstrated that miR-98 was upregulated in the kidney with ischemia reperfusion injury (IRI). The present study was performed to investigate whether miR-98 was involved in the regulation of endothelial apoptosis under hypoxia and re-oxygenation (H/R) conditions. The dynamic changes of miR-98 in mouse IRI kidney and H/R HUVECs was measured. HUVECs were treated with HIF-1α siRNA to investigate the role of HIF-1α on miR-98 expression. The potential target genes of miR-98 were predicted by bioinformatics analyses. HUVECs were transfected with miR-98 mimics or inhibitor to confirm the role of miR-98 on the expression of target genes and hypoxia-induced apoptosis. The target gene was finally confirmed by dual-luciferase reporter assay. Both of IRI and H/R induced significantly up-regulation of miR-98 in the ischemic kidney and hypoxic HUVECs. HIF-1α siRNA remarkably down-regulated the expression of miR-98 in both normal and hypoxic HUVECs. The putative target genes of miR-98 included IL-6, IL-10 and caspase-3. MiR-98 mimics significantly inhibit caspase-3 expression in HUVECs, while anti-miR-98 significantly up-regulated it. But no change of IL-6 and IL-10 levels was observed after miRNA transfection. miR-98 protected HUVECs against apoptosis induced by hypoxia, while anti-miR-98 had the reverse effect. Furthermore, the dual-luciferase reporter assay confirmed that miR-98 decreased the luciferase activity by targeting the 3' untranslated region of caspase-3. In conclusion, Renal IRI induces up-regulation of miR-98 dependent on HIF-1α, which protects endothelial cells against apoptosis by targeting caspase-3.

Low molecular weight heparin (LMWH) improves peritoneal function and inhibits peritoneal fibrosis possibly through suppression of HIF-1α, VEGF and TGF-ß1.

BACKGROUND: Peritoneal fibrosis is the major cause of ultrafiltration failure, and intraperitoneal administration of Low Molecular Weight Heparin (LMWH) was reported to protect peritoneal function. But the exact mechanism of its influence on peritoneal structure and function is still unknown. METHODS: A fibrosis model of rat was established by intraperitoneal (IP) administration of PD fluid and Erythromycin Lactobionate. Fifty-two rats were randomly divided into 6 groups: (1) normal control group (CON, n = 6); (2) normal saline group (NS, n = 10); (3) high-glucose group (GLU, n = 10); (4) heparin group (HEP, n = 6); (5) low dose LMWH group (LLMWH, n = 10); (6) high dose LMWH group (HLMWH, n = 10). Two hour peritoneal equilibration test was performed after 28 days of intervention. The peritoneum, mesentery and omentum were harvested, and evaluated by Hematoxylin-Eosin and Masson Trichrome staining. The expressions of HIF-1α, VEGF and TGF-ß1 in parietal peritoneum were detected by IHC and RT-PCR (Reverse Transcriptase Polymerase Chain Reaction). RESULTS: Compared with group CON and NS, ultrafiltration volume and D2/D0 glucose in group GLU decreased significantly, D/Purea (Dialysate-Plasma ratio of urea), D/Palb (Dialysate-Plasma ratio of albumin), peritoneal thickness, neoangiogenesis and inflammatory reaction increased significantly (all P<0.05). Administration of heparin and LMWH markedly alleviated these above pathological changes. The protein and mRNA levels of HIF-1α, VEGF and TGF-ß1 increased significantly in group GLU, and decreased significantly after administration of LMWH in a dose-dependent manner. CONCLUSIONS: LMWH ameliorates peritoneal function and inhibits peritoneal fibrosis, possibly through suppression of HIF-1α, VEGF and TGF-ß1.

Screening plasma miRNAs as biomarkers for renal ischemia-reperfusion injury in rats.

BACKGROUND: Acute kidney injury is a common clinical comorbidity and early diagnosis is crucial for improving prognosis, but there is still no ideal biomarker for early diagnosis. MATERIAL AND METHODS: miRNA microarray was used for detecting miRNA in kidney subjected to renal ischemia-reperfusion injury 12 h after reperfusion. Real-time PCR was performed to validate the results of microarray. miRNAs in the ischemia group were twice as high as in the sham group. Kidney-enriched miR-10a, miR-192, and miR-194 were detected in rat plasma to screen potential biomarkers for renal ischemia-reperfusion injury. Aberrant expressed miRNA in plasma at 12 h were further detected at 1 h, 2 h, 6 h, 12 h, and 24 h to observe the changing trend of these miRNAs and were compared to blood urea nitrogen and serum creatinine. RESULTS: Thirty-six miRNAs were aberrantly expressed in kidney of rats with renal ischemia-reperfusion injury, among which 15 miRNAs had a 2-fold greater change. Results of real-time PCR were generally in accordance with microarray results. Levels of the 15 miRNAs differentially expressed in injured kidney were not significantly different from those in sham kidney. However, miR-10a, miR-192, and miR-194 were significantly increased in plasma of rats with renal ischemia-reperfusion injury, among which miR-10a was elevated within 1 h after reperfusion, whereas miR-192 and miR-194 were elevated at 6 h after injury. Blood urea nitrogen was increased at 12 h and serum creatinine was increased at 6 h after injury. CONCLUSIONS: Plasma miR-10a, miR-192, and miR-194 were potential biomarkers for renal ischemia reperfusion injury in rats, and miR-10a might be the most promising plasma biomarker for renal injury because of its elevation within 1 h after renal injury, as well as renal specificity.

Comparative study of scientific publications in urology and nephrology journals originating from USA, China and Japan (2001-2010).

BACKGROUND: In the past decade, scientific research has developed rapidly in China, but the growth seems to vary widely between different disciplines. In this study, we aimed to compare the quantity and quality of publications in urology and nephrology journals from USA, China and Japan. METHODS: Journals listed in the "Urology and Nephrology" category of Science Citation Index Expanded subject categories were included. Scientific papers in these journals written by researchers from USA, Japan and China were retrieved from the "PubMed" and "Web of Knowledge" online databases. RESULTS: The annual number of total scientific articles increased significantly from 2001 to 2010 in China, and has ranked second in the world since 2006. In the field of urology and nephrology, the annual number increased significantly from 2001 to 2010 in USA and China; but not in Japan. The share of articles increased significantly over time in China, decreased significantly in Japan, and remained unchanged in USA. In 2010, USA contributed 32.17% of the total world output in urology and nephrology field and ranked 1(st); Japan contributed 5.19% and ranked 5(th); China contributed 3.83% and ranked 9(th). Publications from USA had the highest accumulated IFs and the highest total citations of articles (USA>Japan>China, p<0.001). No significant difference was found in average IF among the three countries. USA published the most articles in the top 10 urology and nephrology journals (USA(35165)>Japan(6704)>China(2233), p<0.001). Researchers from USA published more clinical trials and randomized controlled trials than Japan and China (USA>Japan>China, p<0.001). CONCLUSION: Although China has undergone significant increase in annual number and percentage of scientific publication in urology and nephrology journals in the past decade, it still lags far behind USA and Japan in the field of urology and nephrology in terms of quantity and quality.