CD8 + CD103 + iTregs protect against ischemia-reperfusion-induced acute kidney Injury by inhibiting pyroptosis.

The occurrence of acute kidney injury (AKI) is elevated, one of the main causes is ischemia-reperfusion (I/R). However, no specific therapy is currently available to treat I/R-induced AKI (I/R-AKI). Treg cells have been demonstrated to perform an anti-inflammatory role in a range of autoimmune and inflammatory illnesses. However, there is limited available information about the possible functions of CD8 + CD103 + iTregs in I/R-AKI. We utilized renal tubular epithelial cells (RTECs) subjected to hypoxia-reoxygenation (H/R) and I/R-AKI mouse model to investigate whether CD8 + CD103 + iTregs could attenuate AKI and the underlying mechanism. In vitro, co-cultured with CD8 + CD103 + iTregs alleviated H/R-induced cell injury. After treatment of CD8 + CD103 + iTregs rather than control cells, a significant improvement of I/R-AKI was observed in vivo, including decreased serum creatinine (sCr) and blood urea nitrogen (BUN) levels, reduced renal pathological injury, lowered tubular apoptosis and inhibition of the transition from AKI to chronic kidney disease (CKD). Mechanically, CD8 + CD103 + iTregs alleviated H/R-induced cell injury and I/R-AKI partly by suppressing RTECs pyroptosis via inhibiting the NLRP3/Caspase-1 axis. Our study provides a novel perspective on the possibility of CD8 + CD103 + iTregs for the treatment of I/R-AKI.

Incidence and risk factors of acute kidney injury after transcatheter aortic valve replacement.

PURPOSE: Acute kidney injury (AKI) is a common early complication secondary to transcatheter aortic valve replacement (TAVR). Studies on the incidence and risk factors for AKI after TAVR surgery are limited to date. Here, we retrospectively analyzed the incidence and risk factors for AKI after TAVR surgery in our hospital. MATERIALS AND METHODS: Patients who underwent TAVR surgery at our hospital from November 2017 to February 2023 were selected. AKI was defined using the 2012 KDIGO definition and staging criteria. The relevant data and information between the AKI group and the non-AKI group were compared and analyzed, and a binary logistic regression model was used to analyze the risk factors for AKI. RESULTS: A total of 75 patients who underwent TAVR surgery were included in the retrospective analysis. After TAVR, the incidence of AKI was 17.3% (13/75), of which 8 (61.5%) had stage 1 AKI, 2 (15.4%) had stage 2 AKI, 3 (23.1%) had stage 3 AKI, and 3 needed renal replacement therapy. After multivariate logistic analysis, contrast volume (OR = 1.024 (1.001, 1.047)) was found to be an independent risk factor for AKI, while patients with high estimated glomerular filtration rate (eGFR) (OR = 0.903 (0.826, 0.986)) have a reduced risk of AKI. CONCLUSION: A retrospective study revealed a 17.3% incidence of AKI after TAVR surgery in our hospital, most of which were stage 1 AKI. A low preoperative eGFR and contrast volume were found to be independent risk factors for AKI.

New COL4A5 mutation in IgA nephropathy.

PURPOSE: IgA nephropathy (IgAN) is the most common type of primary glomerulonephritis and a leading cause of chronic kidney disease (CKD) and end-stage kidney disease (ESKD). Recently, some case reports have shown that COL4A5 mutation is associated with IgAN. Here, we identified a new COL4A5 gene mutation in IgAN in a Chinese family. MATERIALS AND METHODS: In the present study, the proband and his 23-year-old younger brother were both diagnosed with IgAN, manifested as haematuria, proteinuria and chronic kidney injury without hearing loss or ocular symptoms. Additionally, the proband's 30-year-old younger brother, also diagnosed with ESKD, had been undergoing dialysis for 2 years with normal hearing and eyesight. To exclude genetic disease, we conducted whole-exome sequencing and Sanger sequencing assays. RESULTS: We found a new mutation in the COL4A5 gene (chrX:107 814 698, c.438+2->AAACCAATTATA-), a novel insertion mutation. Using vector transcription and Minigene transcriptional analyses, we verified, for the first time, the novel mutation pathogenicity of the COL4A5 gene. CONCLUSION: Together with other published data, we suggest that genetic screening should be performed in IgAN, particularly for patients with a familial history. The effects of different mutated splice sites of the COL4A5 gene, as well as the tissue specificity of the splicing machinery contributing to the pathogenesis and prognosis of IgAN, remains unclear and warrants further exploration in the future.

CD4+CD126low/- Foxp3+ Cell Population Represents a Superior Subset of Regulatory T Cells in Treating Autoimmune Diseases.

CD4+Foxp3+ regulatory T (Treg) cells are crucial for maintaining homeostasis and preventing autoimmune diseases. Nonetheless, we and others have previously reported that natural Treg cells are unstable and dysfunctional in the inflamed environment with a high-salt diet, limiting the Treg function in disease control. In this study, we made an innovative observation showing a high degree of heterogeneity within the Treg pool. We identified that CD126, interleukin (IL)-6 receptor alpha chain, contributed to Treg cell instability. Using a series of in vitro and in vivo experimental approaches, we demonstrated that CD126Lo/- Treg cells presented greater function and were more stable than CD126Hi nTreg cells, even in the presence of IL-6 and inflammation. Blockade of programmed death-1 (PD-1) interrupted CD126Lo/- nTreg cell stability. Additionally, CD126Lo/- Treg cells can treat colitis and established collagen-induced arthritis, while the CD126Hi cell population failed to do this. Moreover, we noted that CD126 expression of Treg cells had a positive correlation to rheumatoid arthritis (RA) severity and the stability of Treg cells. Our results strongly suggest that the manipulation of CD126Lo/- nTreg cells could be a novel strategy for the treatment of autoimmune diseases and for other conditions associated with a deficit of Treg cells.

Systematic review and subgroup analysis of the incidence of acute kidney injury (AKI) in patients with COVID-19.

BACKGROUND: Acute kidney injury (AKI) occurs among patients with coronavirus disease-19 (COVID-19) and has also been indicated to be associated with in-hospital mortality. Remdesivir has been authorized for the treatment of COVID-19. We conducted a systematic review to evaluate the incidence of AKI in hospitalized COVID-19 patients. The incidence of AKI in different subgroups was also investigated. METHODS: A thorough search was performed to find relevant studies in PubMed, Web of Science, medRxiv and EMBASE from 1 Jan 2020 until 1 June 2020. The systematic review was performed using the meta package in R (4.0.1). RESULTS: A total of 16,199 COVID-19 patients were included in our systematic review. The pooled estimated incidence of AKI in all hospitalized COVID-19 patients was 10.0% (95% CI: 7.0-12.0%). The pooled estimated proportion of COVID-19 patients who needed continuous renal replacement therapy (CRRT) was 4% (95% CI: 3-6%). According to our subgroup analysis, the incidence of AKI could be associated with age, disease severity and ethnicity. The incidence of AKI in hospitalized COVID-19 patients being treated with remdesivir was 7% (95% CI: 3-13%) in a total of 5 studies. CONCLUSION: We found that AKI was not rare in hospitalized COVID-19 patients. The incidence of AKI could be associated with age, disease severity and ethnicity. Remdesivir probably did not induce AKI in COVID-19 patients. Our systematic review provides evidence that AKI might be closely associated with SARS-CoV-2 infection, which should be investigated in future studies.

Human gingiva-derived mesenchymal stem cells are therapeutic in lupus nephritis through targeting of CD39-CD73 signaling pathway.

Cell specific and cytokine targeted therapeutics have underperformed in systemic lupus erythematosus (SLE). Mesenchymal stem cells (MSCs) have emerged as a novel therapy to address the dysregulation in autoimmune diseases but also have limitations. Human gingiva derived MSCs (GMSCs) are superior in regulating immune responses. Here, we demonstrate that the adoptive transfer of GMSCs homes to and maintains in the kidney and has a robust therapeutic effect in a spontaneous lupus nephritis model. Specifically, GMSCs limits the development of autoantibodies as well as proteinuria, decreases the frequency of plasma cells and lupus nephritis histopathological scores by directly suppressing B cells activation, proliferation and differentiation. The blockage of CD39-CD73 pathway dramatically abrogates the suppressive capacities of GMSCs in vitro and in vivo and highlights the significance of this signaling pathway in SLE. Collectively, manipulation of GMSCs provides a promising strategy for the treatment of patients with SLE and other autoimmune diseases.

CD8+CD103+ iTregs Inhibit Chronic Graft-versus-Host Disease with Lupus Nephritis by the Increased Expression of CD39.

Many patients with systemic lupus erythematosus (SLE) have lupus nephritis, one of the severe complications of SLE. We previously reported that CD8+CD103+ T regulatory cells induced ex vivo with transforming growth factor ß (TGF-ß) (iTregs) inhibited immune cells responses to ameliorate excessive autoimmune inflammation. However, the molecular mechanism(s) underlying the role of these CD8+ iTregs is still unclear. Here we identified that CD39, which is highly expressed on CD8+ iTregs, crucially contributes to the immunosuppressive role of the CD8+CD103+ iTregs. We showed that adoptive transfer of CD8+CD103+ iTregs significantly relieves the chronic graft-versus-host disease with lupus nephritis and CD39 inhibitor mostly abolished the functional activities of these CD8+ iTregs in vitro and in vivo. CD39+ cells sorted from CD8+CD103+ iTregs were more effective in treating lupus nephritis than CD39- partner cells in vivo. Furthermore, human CD8+ iTregs displayed increased CD103 and CD39 expressions, and CD39 was involved in the suppressive function of human CD8+ iTregs. Thus, our data implicated a crucial role of CD39 in CD8+CD103+ iTregs in treating lupus nephritis, and CD39 could be a new phenotypic biomarker for the identification of highly qualified CD8+ Tregs. This subpopulation may have therapeutic potential in patients with SLE nephritis and other autoimmune diseases.

Systemic inflammation modulates the ability of serum ferritin to predict all-cause and cardiovascular mortality in peritoneal dialysis patients.

BACKGROUND: This study aimed to ascertain whether the correlation of high serum ferritin with mortality is affected by systemic inflammation and to investigate the optimal serum ferritin level for predicting death when inflammation is considered in peritoneal dialysis (PD) patients. METHODS: We classified 221 patients into four groups according to serum ferritin concentration (100 µg/L) and high-sensitivity CRP (hs-CRP) level (3 mg/L), and followed them regularly from the date of catheterization to Dec 31, 2016, at Sun Yat-Sen Memorial Hospital, China. Clinical and biochemical data were collected at baseline, and clinical outcomes such as all-cause and cardiovascular mortality were assessed. RESULTS: During a median follow-up of 35 months (3 ~ 109 months), 50 (22.6%) deaths occurred. Cardiovascular disease (46.0%) was the most common cause of death, followed by infection (10.0%). The Kaplan-Meier survival analysis and log-rank test revealed significantly worse survival accumulation among PD patients with higher serum ferritin (≥100 µg/L) under elevated hsCRP levels (> 3 mg/L) (P = 0.022). A multivariate Cox regression analysis revealed that an increased serum ferritin level was independently associated with a higher risk of all-cause and cardiovascular mortality in PD patients (HR = 3.114, P = 0.021; and HR = 9.382, P = 0.032) with hsCRP above 3 mg/L after adjusting for relevant confounding factors. CONCLUSION: Higher serum ferritin levels were associated with an increased risk of all-cause and cardiovascular mortality in patients undergoing PD only in the presence of elevated hsCRP levels. The correlation of serum ferritin with poor outcome should take into consideration systemic inflammation.

Effects of Sacubitril-Valsartan in Heart Failure With Preserved Ejection Fraction in Patients Undergoing Peritoneal Dialysis.

Aims: The effect of the angiotensin receptor-neprilysin inhibitor (ARNI) sacubitril-valsartan in patients with heart failure with preserved ejection fraction (HFpEF) remains unclear, and data on ARNI treatment in peritoneal dialysis (PD) patients are lacking. The present study was designed to assess the efficacy and safety of sacubitril-valsartan in patients with HFpEF undergoing peritoneal dialysis. Methods and Results: End-stage kidney disease (ESKD) patients undergoing PD for 3 months with New York Heart Association (NYHA) class II-IV heart failure, ejection fraction of 50% or higher, and elevated levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP) were assigned to receive sacubitril-valsartan. Patients were followed up regularly after medication treatment. The alterations in clinical and biochemical parameters before and after taking sacubitril-valsartan (generally 50-100 mg b.i.d) were investigated, and safety was also assessed. Twenty-one patients were recruited in this study. Compared with baseline levels, NT-proBNP levels [9769.0 (3093.5-21941.0) vs. 3034.0 (1493.2-6503.0), P = 0.002], and heart rate [80.0 (74.5-90.5) vs. 75.0 (70.3-87.0), P = 0.031] were markedly decreased after treatment with sacubitril-valsartan. Signs and symptoms of heart failure (21/21 vs. 15/21, P = 0.021) were obviously alleviated, NYHA classification and E/e' ratio showed a notable trend of improvement after 3-12 months of follow-up. None of the patients showed adverse drug reactions. Conclusions: The present data suggested that sacubitril-valsartan treatment in patients with HFpEF undergoing PD was effective and safe.

Pleiotropic effects of RecQ in Deinococcus radiodurans.

In Deinococcus radiodurans, there is a unique RecQ homolog (DR1289) with three-tandem HRDC domains. Deletion of drrecQ resulted in a low doubling rate and sensitivity to hydrogen peroxide. Here, we used cDNA microarray and biochemical assays to explore the physiological changes in the drrecQ mutant. The expressions of genes with predicted functions involved in iron homeostasis, antioxidant system, electron transport, and energy metabolism were significantly altered in response to drrecQ disruption. More reactive oxygen species (ROS) was accumulated in drrecQ mutant strain when compared to wild type. In addition, ICP-MS results showed that the intracellular level of iron was relatively higher, whereas the concentration of manganese was lower in drrecQ mutant than in wild type. Furthermore, our microarray data and pulsed-field gel results showed that DNA suffered more damage in drrecQ mutant than in wild type under 20 mM hydrogen peroxide stress. These results suggested that drrecQ is a gene of pleiotropic functions and contributes to the extraordinary resistance of D. radiodurans against stresses.

MicroRNA-140-5p Mediates Renal Fibrosis Through TGF-ß1/Smad Signaling Pathway by Directly Targeting TGFBR1.

Renal tubulointerstitial fibrosis is usually the final outcome of various end-stage renal diseases. Recent studies have reported that microRNAs (miRNAs) play an important role in renal fibrosis. However, the biological function of microRNAs in renal fibrosis is complicated and remains unclear. In this study, our results show that miR-140-5p expression is significantly down-regulated in mice with unilateral ureteral obstruction and human proximal tubule epithelial cells (HK2) treated with TGF-ß1. The knockdown of miR-140-5p upregulates the expression levels of collagen I, collagen IV, and α-SMA, decreases E-cadherin expression, and increases Smad-2/3 phosphorylation. In contrast, the overexpression of miR-140-5p decreases the expression levels of collagen I, collagen IV, and α-SMA, enhances E-cadherin expression, and inhibits the phosphorylation of Smad-2/3 in HK2 cells treated with TGF-ß1. The dual-luciferase reporter assay revealed that TGFBR1 is a direct target gene of miR-140-5p. The enforced expression of miR-140-5p significantly inhibited the expression of TGFBR1 in HK2 cells. Furthermore, the knockdown of TGFBR1 has a similar effect of miR-140-5p overexpression on blocking the TGF-ß1/smad signal pathway activation. In contrast, the overexpression of TGFBR1 reverses the effect of miR-140-5p inhibition on the activation of the TGF-ß1/smad signal pathway. This study demonstrates that miR-140-5p regulates the TGF-ß1/smad signaling pathway by suppressing the expression of TGFBR1. Therefore, miR-140-5p may have a therapeutic potential for preventing fibrotic kidney diseases through inhibiting the TGF-ß1/Smad signaling pathway by directly targeting TGFBR1.

Evaluation of the Thermal and Shrinkage Stresses in Restrained High-Performance Concrete.

The early age volume deformation is the main course for the cracking of high-performance concrete (HPC). Hence, the shrinkage behavior and the restrained stress development of HPC under different restraints and curing conditions were experimentally studied in this paper. The method to separate the stress components in the total restraint stress was proposed. The total restrained stress was separated into autogenous shrinkage stress, drying shrinkage stress and thermal stress. The results showed that the developments of the free shrinkage (autogenous shrinkage and drying shrinkage) and the restrained stress were accelerated when the drying began; but the age when the drying began did not significantly influence the long-term shrinkage and restrained stress of HPC; the autogenous shrinkage stress continuously contributed to the development of the total restrained stress in HPC; the drying shrinkage stress developed very rapidly soon after the drying began; and the thermal stress was generated when the temperature dropped. The thermal stress was predominant at the early age, but the contributions of the three stresses to the total restrained stress were almost the same at the age of 56 d in this study.

Corticosteroids combined with doublet or single-agent immunosuppressive therapy for active proliferative lupus nephritis.

OBJECTIVES: We performed a meta-analysis to assess whether corticosteroids (C) plus (+) doublet immunosuppressive therapy (IT) is superior to the classical combination of C with single-agent IT in active proliferative lupus nephritis (LN). METHOD: Randomized trials evaluating the benefits and risks of C+doublet versus single-agent IT in active proliferative LN were obtained by searching PubMed, EMBASE, and Cochrane Central Register. The primary outcome was overall response rate (ORR). The secondary outcomes were the change from baseline in Systemic Lupus Erythematosus Disease Activity Index (SLE-DAI) score, negative conversion ratio of anti-double-stranded DNA (anti-dsDNA), and adverse events. The PROSPERO registry number is CRD42017068491. RESULTS: Eleven trials with 1855 patients were included. Compared with C+single-agent IT, C+doublet IT had a significantly higher ORR (relative risk [RR], 1.22; 95% confidence interval [CI], 1.09 to 1.35; P < 0.01). In a subgroup analysis, C+doublet IT without biologics had a significantly higher ORR than C+single-agent IT (RR, 1.30; 95% CI, 1.13 to 1.50; P < 0.01), while C+doublet IT including biologics improved ORR only for refractory severe LN (RR, 1.46; 95% CI, 1.09 to 1.96; P = 0.012). A larger change from baseline in SLE-DAI scores (standardized mean difference, - 0.49; 95% CI, - 0.68 to - 0.30; P < 0.01) and a higher negative conversion ratio of anti-dsDNA (RR, 1.34; 95% CI, 1.06 to 1.69; P = 0.014) were observed with C+doublet IT than with C+single-agent IT. The rates of adverse events were similar between the two regimens. CONCLUSIONS: Compared with single-agent IT, the combination of C and doublet IT without biologics improved clinical outcomes in active proliferative LN. Key Points • Compared with corticosteroids + single-agent immunosuppressive therapy, corticosteroids + doublet immunosuppressive therapy without biologics had a significantly higher overall response rate in active proliferative lupus nephritis. • Compared with corticosteroids + single-agent immunosuppressive therapy, corticosteroids + doublet immunosuppressive therapy including biologics improved overall response rate only for refractory severe lupus nephritis. • A larger change from baseline in SLE-DAI scores and a higher negative conversion ratio of anti-dsDNA were observed with corticosteroids + doublet immunosuppressive therapy than with corticosteroids + single-agent immunosuppressive therapy.

Evaluation of the antioxidant effects of carotenoids from Deinococcus radiodurans through targeted mutagenesis, chemiluminescence, and DNA damage analyses.

Deinococcus radiodurans is highly resistant to reactive oxygen species (ROS). The antioxidant effect of carotenoids in D. radiodurans was investigated by using a targeted mutation of the phytoene synthase gene to block the carotenoid synthesis pathway and by evaluating the survival of cells under environmental stresses. The colorless mutant R1DeltacrtB of D. radiodurans failed to synthesize carotenoids, and was more sensitive to ionizing radiation, hydrogen peroxide, and desiccation than the wild type, suggesting that carotenoids in D. radiodurans help in combating environmental stresses. Chemiluminescence analyses showed that deinoxanthin, a major product in the carotenoid synthesis pathway, had significantly stronger scavenging ability on H2O2 and singlet oxygen than two carotenes (lycopene and beta-carotene) and two xanthophylls (zeaxanthin and lutein). Deinoxanthin also exhibited protective effect on DNA. Our findings suggest that the stronger antioxidant effect of deinoxanthin contribute to the resistance of D. radiodurans. The higher antioxidant effect of deinoxanthin may be attributed to its distinct chemical structure which has an extended conjugated double bonds and the presence of a hydroxyl group at C-1' position, compared with other tested carotenoids.

Biochemical characterization of two DNA ligases from Deinococcus radiodurans.

Two genes encoding a NAD(+)-dependent DNA ligase (LigA) and an ATP-dependent DNA ligase (LigB) were identified in the genome of the extremely radioresistant bacterium, Deinococcus radiodurans (DR). The recombinant enzymes expressed in Escherichia coli, were purified to homogeneity and characterized. The optimal temperature and pH value of the two DNA ligases were 60 ( degrees )C and 7.0, respectively. Their optimal concentration of MgCl(2) was 5mM. Their half-lifes of heat inactivation at 100 ( degrees )C were about 3 min and 5 min, respectively. In addition, the results showed that DRLigB displayed higher activity than DRLigA at stick and blunt ended joining of DNA, indicating that DRLigB is a key DNA ligase of D. radiodurans in DNA recombination and double-strand break repair.

Apremilast Ameliorates Experimental Arthritis via Suppression of Th1 and Th17 Cells and Enhancement of CD4+Foxp3+ Regulatory T Cells Differentiation.

Apremilast is a novel phosphodiesterase 4 (PDE4) inhibitor suppressing immune and inflammatory responses. We assessed the anti-inflammatory effects of Apremilast in type II collagen (CII)-induced arthritis (CIA) mouse model. To determine whether Apremilast can ameliorate arthritis onset in this model, Apremilast was given orally at day 14 after CII immunization. Bone erosion was measured by histological and micro-computed tomographic analysis. Anti-mouse CII antibody levels were measured by enzyme-linked immunosorbent assay, and Th17, Th1 cells, and CD4+Foxp3+ regulatory T (Treg) cells were assessed by flow cytometry in the lymph nodes. Human cartilage and rheumatoid arthritis (RA) synovial fibroblasts (RASFs) implantation in the severe combined immunodeficiency mouse model of RA were used to study the role of Apremilast in the suppression of RASF-mediated cartilage destruction in vivo. Compared with untreated and vehicle control groups, we found that Apremilast therapy delayed arthritis onset and reduced arthritis scores in the CIA model. Total serum IgG, IgG1, IgG2a, and IgG2b were all decreased in the Apremilast treatment groups. Moreover, Apremilast markedly prevented the development of bone erosions in CIA mice by CT analysis. Furthermore, in the Apremilast treated group, the frequency of Th17 cells and Th1 cells was significantly decreased while Treg cells' frequency was significantly increased. The high dose of Apremilast (25 mg/kg) was superior to low dose (5 mg/kg) in treating CIA. Apremilast treatment reduced the migratory ability of RASFs and their destructive effect on cartilage. Compared with the model group, Apremilast treatment significantly reduced the RASFs invasion cartilage scores in both primary implant and contralateral implant models. Our data suggest that Apremilast is effective in treating autoimmune arthritis and preventing the bone erosion in the CIA model, implicating its therapeutic potential in patients with RA.

TGF-ß-Induced CD8+CD103+ Regulatory T Cells Show Potent Therapeutic Effect on Chronic Graft-versus-Host Disease Lupus by Suppressing B Cells.

Lupus nephritis is one of most severe complications of systemic erythematosus lupus and current approaches are not curative for lupus nephritis. Although CD4+Foxp3+ regulatory T cells (Treg) are crucial for prevention of autoimmunity, the therapeutic effect of these cells on lupus nephritis is not satisfactory. We previously reported that CD8+CD103+ Treg induced ex vivo with TGF-ß1 and IL-2 (CD8+CD103+ iTreg), regardless of Foxp3 expression, displayed potent immunosuppressive effect on Th cell response and had therapeutic effect on Th cell-mediated colitis. Here, we tested whether CD8+CD103+ iTreg can ameliorate lupus nephritis and determined potential molecular mechanisms. Adoptive transfer of CD8+CD103+ iTreg but not control cells to chronic graft-versus-host disease with a typical lupus syndrome showed decreased levels of autoantibodies and proteinuria, reduced renal pathological lesions, lowered renal deposition of IgG/C3, and improved survival. CD8+CD103+ iTreg cells suppressed not only T helper cells but also B cell responses directly that may involve in both TGF-ß and IL-10 signals. Using RNA-seq, we demonstrated CD8+CD103+ iTreg have its own unique expression profiles of transcription factors. Thus, current study has identified and extended the target cells of CD8+CD103+ iTreg and provided a possible application of this new iTreg subset on lupus nephritis and other autoimmune diseases.

[Construction of a dps mutant and its functional analysis in Deinococcus radiodurans].

Dps (DNA protection during starvation) is a member of the iron-binding protein family in prokaryotes. It has been shown previously that Dps possesses ferroxidase activity and the ability to sequester iron that seems to protect DNA from oxidative damage. Based on the method of Polymerase Chain Reaction and homologous genetic recombination in vivo, the gene (DRB0092) encoding a Dps protein homology in the extremely radioresistant bacterium Deinococcus radiodurans was deleted from the wild type strain R1 genome. The obtained mutant was designated as Kdps and further verified by PCR and sequencing. Survival rates of the mutant and wild type strain were investigated after challenged with different doses of hydrogen peroxide (H2O2). Results showed that the survival rate of dps mutant reduced rapidly under the low concentration of H2O2 (< or = 10mmol/L), while the wild type strain showed no sudden decrease. When the H2O2 concentration was higher than 30mmol/L, the difference of the survival rates between the mutant and wild type was more than 50-folds. The result demonstrated that the loss of dps gene in D. radiodurans made cells become more sensitive to oxidative damage. An iron staining method was used to determinate catalase activity in native polyacrylamide electrophoresis gels. The result displayed that two catalases in dps mutant were enhanced about 2-folds than that of wild type. The soluble Dps protein was obtained after construction of expression plasmid and inducement in E. coli transformant. The Dps protein showed the capacity of DNA binding and protected DNA from hydroxyl free radical cleavage in vitro. This study demonstrates that Dps protein of D. radiodurans plays an important role in its antioxidant system, which may contribute to its extreme resistance of this bacterium.

Dual negative regulatory mechanisms of RecX on RecA functions in radiation resistance, DNA recombination and consequent genome instability in Deinococcus radiodurans.

RecA protein plays a central role in homologous recombination and DNA repair. RecX, a gene directly downstream in Escherichia coli and some other bacterial species, down regulates it. However, the precise mechanism of regulation of RecA by RecX is not known. In order to study the function of RecX in the highly radioresistant bacterium Deinococcus radiodurans, null and overexpression strains were constructed. Our data demonstrates that RecX represses radiation resistance, DNA recombination and consequent genome instability in the stationary phase bacteria. Further biochemical analyses reveal that RecX not only down regulates recA transcription, but also directly inhibits RecA activities in vitro. These data suggests a dual negative regulatory control of RecX on RecA functions in D. radiodurans.

[Construction and functional analysis of the crtl gene disruptant in Deinococcus radiodurans].

With the method of Polymerase Chain Reaction and homologous genetic recombination in vivo, the key gene encoding bacterial-type phytoene desaturase (Crtl) which controls the carotenoids biosynthesis pathway in the non-photosynthetic and extremely radioresistant bacterium Deinococcus radiodurans was deleted from the genome. The colorless mutant obtained was designated as M61. Survival rates of mutant strain and wild type strain were investigated under different doses of gamma-radiation and hydrogen peroxide. The results showed that the radioresistant activity of M61 reduced rapidly under ionization radiation, and it became more sensitive to the treatment of hydrogen peroxide especially to high concentration of hydrogen peroxide compared to that of wild type R1. Reverse Phase High Performance Liquid Chromatography (RP-HPLC) was used to investigate the carotenoid composition of wild type R1 and mutant M61. HPLC results exhibited that the deficient of crtl gene had important effect on pigment biosynthesis pathway, leading to inhibition of the biosynthesis of lycopene and other carotenoids in D. radiodurans. All the results indicated that crtl gene was a key gene controlling the biosynthesis of red carotenoid including lycopene in D. radiodurans. The roles of carotenoids in protecting the bacterial cell from damage by ionization radiation and hydrogen peroxide suggest that the carotenoids contribute to the defense system in D. radiodurans. This study is important for elucidating the radioresistant and antioxidant mechanism in which carotenoids are involved, and it will supply some ideas to the further investigation on the biosynthesis pathway and functions of carotenoids in D. radiodurans.