Nana Song

Renal Protection Mediated by Hypoxia Inducible Factor-1α Depends on Proangiogenesis Function of mir-21 by Targeting Thrombospondin 1

Background Angiogenesis contributes to the repair process after renal ischemia/reperfusion (I/R) injury. In the present study, we tested the role of miR-21 in the angiogenesis induced by hypoxia inducible factor (HIF)-1&agr; through inhibiting a predicted target gene thrombospondin 1 (TSP-1). Methods To stabilize HIF-1&agr;, hypoxia (1% O2 for 24 hours) was performed in human umbilical vein endothelial cells and cobalt chloride (CoCl2) was pretreated intraperitoneally 24 hours before renal I/R in mice. Locked nucleic acid modified anti-miR-21 and scrambled control was transfected with hypoxic cells or delivered into the mice via tail vein 1 hour before CoCl2 injection. The kidneys and blood were collected at 24 hours after reperfusion. Results HIF-1&agr; induced by hypoxia and CoCl2 upregulated vascular endothelial growth factor and miR-21, and increased angiogenesis. It was found that expression of TSP-1 was inversely related with miR-21 in vitro and in vivo. Targeting of TSP-1 by miR-21 was further confirmed in vitro. Furthermore, HIF-1&agr; improved renal function, accompanied with increased angiogenesis after I/R injury in mice. The protective effect of HIF-1&agr; was attenuated by inhibition of miR-21. Conclusions HIF-1&agr; induced angiogenesis by upregulating not only vascular endothelial growth factor but also miR-21 via inhibiting a novel target gene TSP-1. Both of them may contribute to the protective effect of HIF-1&agr; on renal I/R injury.

Augmented O-GlcNAc signaling via glucosamine attenuates oxidative stress and apoptosis following contrast-induced acute kidney injury in rats

ABSTRACT Contrast‐induced acute kidney injury (CI‐AKI) is an iatrogenic renal injury and associated with substantial morbidity and mortality in susceptible individuals. Despite extensive study of a variety of agents for renal protection, limited strategies have been shown to be effective in the reduction of CI‐AKI. O‐linked &bgr;‐N‐acetylglucosamine (O‐GlcNAc) is a post‐translational regulatory modification of intracellular proteins and governs the function of numerous proteins, both cytosolic and nuclear. Increasing evidence suggests that O‐GlcNAc levels are increased in response to stress and that acute augmentation of this reaction is cytoprotective. However, the underlying mechanisms by which augmented OGlcNAc signaling provides renoprotection against contrast media insults is still unknown. Here, we investigated the effect of augmented O‐GlcNAc signaling via glucosamine on CI‐AKI and explored the underlying molecular mechanisms, particularly its relationship with PI3‐kinase (PI3K)/Akt signaling. We used a novel and reliable CI‐AKI model consisting of 5/6 nephrectomized (NE) rats, and a low‐osmolar contrast media (iohexol, 10 mL/kg, 3.5gI) injected via the tail vein after dehydration for 48 h. The results showed that augmented O‐GlcNAc signaling by glucosamine prevented the kidneys against iohexol‐induced injury characterized by the attenuation of renal dysfunction, tubular damage, apoptosis and oxidative stress. Furthermore, this renoprotection was blocked by treatment with alloxan, an O‐GlcNAc transferase inhibitor. Augmented O‐GlcNAc signaling also increased the protein expression levels of phospho‐Akt (Ser473, but not Thr308 and Thr450), phospho‐GSK‐3&bgr;, Nrf2, and Bcl‐2, and decreased the levels of Bax and cleaved caspase‐3. Both alloxan and specific inhibitors of PI3K (Wortmannin and LY294002) blocked the protection of glucosamine via inhibiting Akt signaling pathway. We further identified O‐GlcNAcylated Akt through immunoprecipitation and western blot. We confirmed that Akt was modified by O‐GlcNAcylation, and glucosamine pretreatment increased the O‐GlcNAcylation of Akt. Collectively, the results demonstrate that glucosamine induces renoprotection against CI‐AKI through augmented O‐GlcNAc and activation of PI3K/Akt signaling, making it a promising strategy for preventing CI‐AKI. HighlightsIncreasing evidence suggests that O‐linked &bgr;‐N‐acetylglucosamine (O‐GlcNAc) levels are increased in response to stress and that acute augmentation of this reaction is cytoprotective.We used a novel and reliable contrast‐induced acute kidney injury (CI‐AKI) model and the results showed that augmented O‐GlcNAc signaling by glucosamine prevented the kidneys against iohexol‐induced injury by the attenuation of apoptosis and oxidative stress.Furthermore, both alloxan and specific inhibitors of PI3K (Wortmannin and LY294002) blocked the protection of glucosamine via inhibiting Akt signaling pathway.

Effect of Hypoxia on the Differentiation and the Self-Renewal of Metanephrogenic Mesenchymal Stem Cells

Hypoxia is an important and influential factor in development. The embryonic kidney is exposed to a hypoxic environment throughout its development. The Wnt/β-catenin pathway plays vital roles in the differentiation and self-renewal of metanephrogenic mesenchymal stem cells (MMSCs) from which the kidney is derived. Thus, we hypothesized that hypoxia can regulate the differentiation and pluripotency of MMSCs through the Wnt/β-catenin pathway. To test this hypothesis, MMSCs from rats at embryonic day 18.5 were cultured in normoxic (21% O2) and hypoxic (1% O2) conditions. The effects of hypoxia on differentiation, stemness, proliferation, and apoptosis of cultured MMSCs and on the activity of the Wnt/β-catenin pathway were tested. Our results revealed that the hypoxic condition increased the number of epithelial cells (E-cadherin+ or CK18+) as well the expression of markers of renal tubule epithelia cells (CDH6, Aqp1, and OPN), decreased the number and proliferation of stem cells (SIX-2+ or CITED1+), and induced apoptosis. Additionally, hypoxia reduced the expression of Wnt4 as well as its downstream molecules β-catenin, LEF-1, and Axin2. Activation of the Wnt/β-catenin pathway by LiCl or BIO modified the effects of hypoxia on the differentiation and self-renewal of MMSCs. Thus, we concluded that hypoxia induces the differentiation and inhibits the self-renewal of MMSCs by inhibiting the Wnt/β-catenin pathway. The observations further our understanding of the effects of hypoxia on kidney.

Factors associated with the elevated percentage of CD4CD69 T cells in maintained hemodialysis patients

Abstract Background: CD4 T-cell abnormality, influencing the outcome of the maintained hemodialysis (MHD), is common in patients on dialysis. We try to find out factors associated with the activated CD4 T cells, CD4CD69 T cells, to improve the dialysis quality. Methods: A cross-sectional study was conducted to evaluate the change of CD4CD69 in MHD patients and healthy controls in our hospital from September 2015 to May 2016. A total of 164 MHD patients and 24 healthy controls were included according to the criteria. Univariate and multivariate logistic regression models after correlation analysis were executed to discover the related factors of CD4CD69 T-cell posterior to the division of the CD4CD69 T cell according to its median. Results: The lymphocytes were lower, but the percentage of CD4CD69 T cells was higher in MHD patients compared with healthy controls, even after the propensity score matching based on age and sex. The percentage of CD4 T cells showed no significant difference between the two groups. Further multivariate logistic regression models revealed that CD4CD69 T cell was independently associated with serum total protein (OR 95%CI: 0.830[0.696, 0.990], p = .038), transferrin (OR 95%CI: 3.072[1.131, 8.342], p = .028) and magnesium (OR 95%CI: 16.960[1.030, 279.275], p = .048). Conclusion: The percentage of CD4CD69 T cells, activated CD4 T cells, elevated in hemodialysis patients despite the decrease in lymphocytes. The elevated CD4CD69 T cells were independently associated with serum total protein negatively, but transferrin and magnesium positively. Strengthening nutrition, reducing the concentration of transferrin and magnesium might be beneficial to reduce the activation of CD4 T cells and improve the outcome of MHD patients.

Role of miR‑21 on vascular endothelial cells in the protective effect of renal delayed ischemic preconditioning

Vascular endothelial cells may serve crucial roles in the development of acute kidney injury (AKI). microRNA (miR)-21, which possesses a renal protective function has been found on vascular endothelial cells. The present study aimed to test the hypothesis that miR-21 may protect vascular endothelial cells against injury, which may contribute to the protective effects of renal delayed ischemic preconditioning (IPC). Preconditioned (15 min ischemia) or Sham mice (not clamped) were subjected to 35 min occlusion of bilateral renal pedicles 4 days following preconditioning or Sham treatment. Human umbilical vein endothelial cells (HUVECs) were treated with cobalt(II) chloride (CoCl2) to establish an in vitro hypoxia model. Locked nucleic acid-modified anti-miR-21 or scrambled control oligonucleotides were transfected into cells or delivered into mice via tail vein injection <1 h prior to IPC. Following 24 h of reperfusion or hypoxia, morphological and functional parameters, apoptosis and miR-21 and programmed cell death 4 (PDCD4) expression were assessed in vivo and in vitro. Treatment of HUVECs with CoCl2 led to an upregulation of miR-21 expression, a downregulation of PDCD4 protein expression and attenuation of apoptosis. Inhibition of miR-21 expression led to increased expression levels of PDCD4 protein and apoptosis in HUVECs. IPC attenuated renal IR injury in mice. The protective effect of IPC appeared to be dependent on upregulated miR-21 expression. IPC-induced upregulation of miR-21 expression also occurred in HUVECs, and IPC also led to reduced PDCD4 expression and vascular permeability in mouse kidneys. The effects of IPC were attenuated by the inhibition of miR-21; miR-21 expression attenuated damage in vascular endothelial cells, which may contribute to the protective effects of delayed IPC on renal IR injury. The present study suggested a novel target for the prevention and repair of AKI in the future.

miR-21 Protects Against Ischemia/Reperfusion-Induced Acute Kidney Injury by Preventing Epithelial Cell Apoptosis and Inhibiting Dendritic Cell Maturation

Renal tubular injury and innate immune responses induced by hypoxia contribute to acute kidney injury. Accumulating evidence suggests that miR-21 overexpression protects against kidney ischemia injury. Additionally, miR-21 emerges as a key inhibitor in dendritic cell maturation. Thus, we hypothesized that miR-21 protects the kidney from IR injury by suppressing epithelial cell damage and inflammatory reaction. In this study, we investigated effects of miR-21 and its signaling pathways (PTEN/AKT/mTOR/HIF, PDCD4/NFκ-B) on kidney ischemia/reperfusion (IR) injury in vitro and in vivo. The results revealed that IR increased miR-21, HIF1α, and 2α expression in vivo and in vitro. MiR-21 interacted with HIF1α and 2α through the PTEN/AKT/mTOR pathway. Moreover, inhibition of miR-21 activated PDCD4/NFκ-B pathways, which are critical for dendritic cell maturation. Renal IR triggers local inflammation by inducing the dendritic cell maturation and promoting the secretion of IL-12, IL-6, and TNF-α cytokines. Knockdown of miR-21 intensified the effect of IR on tubular epithelial cell apoptosis and dendritic cell maturation. Our results suggested that IR-inducible miR-21 protects epithelial cells from IR injury via a feedback interaction with HIF (PTEN/AKT/mTOR/HIF/miR-21) and by inhibiting maturation of DCs through the PDCD4/NF-κB pathway. These findings highlight new therapeutic opportunities in AKI.

Delayed Ischemic Preconditioning Attenuated Renal Ischemia-Reperfusion Injury by Inhibiting Dendritic Cell Maturation

Background/Aims: Even though delayed ischemic preconditioning (DIPC) has been reported to produce renal protection, the underlying mechanism remains poorly understood. We reported that a 15-minute renal ischemic preconditioning (IPC) 4 days before subsequent ischemia-reperfusion attenuated renal injury Kidney dendritic cells (DCs) are abundant in the renal tubulointerstitium and, depending on their status, can induce immune activation or tolerance. The aim of the present study was to investigate the role of DCs in IPC of the kidney. Methods: Mouse kidneys were challenged by transient brief episodes of sublethal ischemia followed by subsequent prolonged ischemia. DC abundance and maturation in the spleen and kidney were measured by flow cytometry and immunohistochemical staining. To confirm the function of mature DCs in the renoprotective effect of IPC on renal ischemia-reperfusion injury the A2 adenosine receptor (A2AR) antagonist SCH58261 was administered to stimulate DC maturation prior to assessment of renal functional and histological injury and the inflammatory reaction. Results: Compared with sham-operated animals, preconditioned mice had a reduced injury with less CD11c+ cells, lower levels of the pro-inflammatory cytokine IL-17 and reduced expression of the mature DC marker CCR7. Preconditioned mice also produced more of the anti-inflammatory cytokine IL-10. Both renal cells and splenocytes from these mice had more DCs (CD45+/CD11c+/F4/80-), but fewer of these DCs were mature (CD45+/CD11c+/ F4/80-/MHC-II+/CD80+) compared with those from sham-treated animals, suggesting that the immunomodulatory effect of renal ischemic preconditioning is both local and systemic. Additionally, injection of the A2AR antagonist SCH58261 reversed IPC-induced inhibition of DC maturation and mitigated the protective effect of preconditioning, suggesting that DC maturation contributes to immune cell-mediated ischemic preconditioning. Conclusion: Our results show that DIPC of the kidney provides local and systemic immunosuppression by inhibiting DC maturation and hence mediates a renal protective effect.