[Expression and significance of tight junction proteins in the kidney in a mouse model of renal ischemia-reperfusion injury].

OBJECTIVE: To study the expression and significance of tight junction proteins (claudin-2, claudin-10, and claudin-17) in a mouse model of renal ischemia-reperfusion injury. METHODS: A total of 152 male C57BL/6 mice were randomly assigned to control group (n=8), sham-operation group (n=72), and model group (n=72). The renal pedicles at both sides were clamped for 30 minutes to establish a mouse model of renal ischemia-reperfusion injury. According to the time points of reperfusion (0, 3, 6, 12, 24, 48, and 72 hours and 5 and 7 days), the sham-operation group and the model group were further divided into 9 subgroups, with 8 mice in each subgroup. RT-PCR and immunohistochemistry were used to measure the mRNA and protein expression of claudin-2, claudin-10, and claudin-17 in renal tissue. RESULTS: The control and sham-operation groups had no significant changes in the mRNA and protein expression of claudin-2, claudin-10, and claudin-17 in renal tissue over the time of reperfusion (P>0.05). Compared with the control and sham-operation groups, the model group had decreased mRNA and protein expression of claudin-2 and claudin-10 after reperfusion, and the expression decreased gradually over the time of reperfusion, with the lowest levels at 24 hours of reperfusion (P<0.05). Compared with the control and sham-operation groups, the model group had increased mRNA and protein expression of claudin-17 after reperfusion, and the expression increased gradually over the time of reperfusion, with the highest mRNA level at 12 hours and the highest protein level at 24 hours of reperfusion (P<0.05). CONCLUSIONS: Renal ischemia-reperfusion injury is closely associated with abnormal expression of tight junction proteins claudin-2, claudin-10, and claudin-17.

Remote ischemic preconditioning upregulates microRNA-21 to protect the kidney in children with congenital heart disease undergoing cardiopulmonary bypass.

BACKGROUND: Acute kidney injury (AKI) is one of the most common emergencies and severe diseases in the clinic. We sought to verify whether remote ischemic preconditioning (RIPC) has a protective effect on the kidney of child with congenital heart disease undergoing cardiopulmonary bypass (CPB) surgery. We hypothesized it may be related to the up-regulation of microRNA-21 (miR-21). METHODS: We performed a prospective randomized clinical study among children with congenital heart disease undergoing CPB surgery between January and December 2016. Children were randomized to an RIPC or control group. Patients in each group were divided into an AKI and a non-AKI group according to the occurrence of AKI at 48 h after surgery. Remote ischemic preconditioning (RIPC) conducted by blood-pressure cuff was performed 12 h before surgery. Serum creatinine (SCr), tumor necrosis factor-α (TNF-α), and miR-21 expression in blood and urine were measured at different time points. RESULTS: A total of 449 cases (200 RIPC; 249 controls) were enrolled. The male/female ratio was 1.18, with a mean age of 37.50 ± 25.31 months. The incidence of AKI in the RIPC group was significantly lower than that in the control group (19.0% vs. 46.2%, P<0.01). In further analysis, at 6 h, 24 h, and 48 h after CPB operation, blood TNF-α levels were significantly lower in the RIPC group than in the control group (P<0.01); at 24 h, 48 h, and 72 h, urine TNF-α levels were significantly lower in the RIPC group than in the control group (P<0.05). Urine and blood miR-21 expression in the RIPC group increased significantly, while there was no obvious change in the control group. CONCLUSIONS: Remote ischemic preconditioning has a protective effect on the kidney in children with congenital heart disease, which may be related with the up-regulation of miR-21 and down-regulating the inflammatory mediator, such as TNF-α.

Elevation of miR-21, through targeting MKK3, may be involved in ischemia pretreatment protection from ischemia-reperfusion induced kidney injury.

BACKGROUND: Ischemia-reperfusion (IR) causes acute kidney injury (AKI), and ischemia pretreatment may exert protection. Mitogen-activated protein kinase kinase 3 (MKK3), which is involved in the signal transduction pathway in IR-induced injury, is a potential target of miR-21. We aimed to verify the targeting regulation of miR-21 on MKK3 and to explore the effects of miR-21-mediated MKK3 expression changes in AKI. METHODS: Vectors containing the MKK3 3'UTR and mutated MKK3-3U-M were constructed and co-transfected with nonsense miR, miR-21-5p mimics or inhibitor in HEK293 cells. Gene expressions were detected by dual luciferase reporter assay. The effects of miR-21 on mRNA and protein of MKK3 were investigated in HK-2 cells. Male C57BL/6J mice were treated with ischemic preconditioning (IPC) and IR. Kidney functions were assessed through monitoring serum creatinine (Scr) and blood urea nitrogen (BUN). Pathological changes were observed and scored with histological samples of kidney. Expression levels of miR-21, MKK3, interleukin (IL)-6, tumor necrosis factor (TNF)-α before and after IPC and IR were examined by real-time polymerase chain reaction and/or immunohistochemistry. RESULTS: miR-21 regulated the expression of MKK3 via 3'UTR. Following IR, MKK3, IL-6 and TNF-α levels were increased. Scr, BUN and pathological injuries were aggravated, and miR-21 expression was increased. IPC increased miR-21 levels ahead of IR and inhibited the increases in MKK3, IL-6 and TNF-α levels and the aggravation of Scr, BUN and pathological injuries. CONCLUSIONS: miR-21 targets MKK3 in vivo and in vitro, inhibiting the downstream factors IL-6 and TNF-α. Therefore, miR-21 might be involved in protection of IPC against IR of the kidney.

[Significance of trace deposition of immunoglobulin M in glomerular mesangium in children with minimal change nephrotic syndrome].

OBJECTIVE: To study the significance of trace immunoglobulin M (IgM) deposits in glomerular mesangium in children with minimal change primary nephrotic syndrome (PNS). METHODS: One hundred and six children who were clinically diagnosed with PNS and pathologically diagnosed with minimal change disease (MCD) and trace deposition of IgM in renal tissues were enrolled as subjects. Eighty-one PNS children with MCD but no deposition of immune complexes were used as the control group. The clinical characteristics and efficacies of glucocorticoids and immunosuppressants were retrospectively analyzed in the two groups. All patients were given full-dose prednisone by oral administration, and patients with glucocorticoid resistance or frequent relapses were additionally given immunosuppressants. RESULTS: The incidence of glucocorticoid resistance in the IgM deposit group was significantly higher than that in the control group (27.2% vs 12.3%; P<0.05). The incidence of frequent relapses in the IgM deposit group was also significantly higher than that in the control group (48.1% vs 10.4%; P<0.05). The complete remission rate for glucocorticoid-resistant patients treated with prednisone combined with mycophenolate mofetil (MMF) was 68% and 62% respectively in the IgM deposit and control groups (P>0.05). The relapse frequency in patients with frequent relapses was significantly reduced in both groups after treatment with prednisone and MMF in combination (P<0.05). CONCLUSIONS: Trace deposition of IgM in renal tissues may be an important factor for glucocorticoid resistance and frequent relapses in PNS children with MCD. Prednisone combined with MMF may be a better choice in the treatment of patients with glucocorticoid resistance or frequent relapses.