Activation of Endogenous Anti-Inflammatory Mediator Cyclic AMP Attenuates Acute Pyelonephritis in Mice Induced by Uropathogenic Escherichia coli

The pathogenesis of pyelonephritis caused by uropathogenic Escherichia coli (UPEC) is not well understood. Here, we show that besides UPEC virulence, the severity of the host innate immune response and invasion of renal epithelial cells are important pathogenic factors. Activation of endogenous anti-inflammatory mediator cAMP significantly attenuated acute pyelonephritis in mice induced by UPEC. Administration of forskolin (a potent elevator of intracellular cAMP) reduced kidney infection (ie, bacterial load, tissue destruction); this was associated with attenuated local inflammation, as evidenced by the reduction of renal production of proinflammatory mediators, renal infiltration of inflammatory cells, and renal myeloperoxidase activity. In primary cell culture systems, forskolin not only down-regulated UPEC-stimulated production of proinflammatory mediators by renal tubular epithelial cells and inflammatory cells (eg, monocyte/macrophages) but also reduced bacterial internalization by renal tubular epithelial cells. Our findings clearly indicate that activation of endogenous anti-inflammatory mediator cAMP is beneficial for controlling UPEC-mediated acute pyelonephritis in mice. The beneficial effect can be explained at least in part by limiting excessive inflammatory responses through acting on both renal tubular epithelial cells and inflammatory cells and by inhibiting bacteria invasion of renal tubular epithelial cells.Urinary tract infections (UTIs) are among the most common infectious diseases, particularly in women, babies, and the elderly, and are the most common hospital-acquired infections in the developed world, which contribute to high financial burden worldwide. Although antibiotics are available to treat the disease, there remain a number of challenges, including frequent recurrence, persistence of infection, and the increasing risk of resistance to antibiotics.^1,2 For these reasons, it is imperative to improve our understanding of the pathogenesis of UTIs and to develop novel treatment strategies that could be used to improve current treatment.UTI usually starts as a bladder infection (cystitis) but can develop to kidney infection (pyelonephritis) that is an organ- and even life-threatening condition, because it may lead to renal scarring, chronic renal failure, sepsis, and severe systemic infection with multiorgan failure.³ Uropathogenic Escherichia coli (UPEC) is the primary cause of UTI. The pathogenesis of UTIs can be influenced both by properties of the infecting pathogens and host responses to pathogens, in addition to other factors such as anatomical abnormality. Most UPEC strains express a variety of fimbriae (eg, P, type 1, Dr) that enable them to attach to uroepithelial cells (a critical step in colonization). On contact with uroepithelial cells, UPEC liberates toxins (eg, hemolysin and cytotoxic necrotizing factor-1) which mediate direct injury to the cells, disrupting the mucosal barrier, and opening access to the underlying tissue.⁴ UPEC is also able to transiently invade, survive, and multiply within uroepithelial cells, which is thought to enable organisms to evade host defenses and to act as a reservoir for further infection. In addition, most human UPEC strains are resistant to complement-mediated killing^5,6 but exploit complement for entering epithelial cells that contribute to kidney infection.^7,8 UPEC has evolved mechanisms through carrying intracellular Toll/IL-1 receptor domain homologous sequences to impair immune protection while promoting inflammation and tissue damage.⁹Besides the properties of UPEC, the host immune response to pathogens has a big effect on the pathogenesis of UTI. Although innate immune responses play essential roles in the first line of host defense against pathogens, they also cause harm when present in excess or are dysregulated. For example, in the acute condition, uroepithelial cells and inflammatory cells, in response to UPEC stimulation, produce a number of proinflammatory mediators [eg, IL-6, tumor necrosis factor (TNF)-α, and IL-8], which (if present in excess) cause epithelial inflammation/damage, allowing bacteria to enter the underlying tissue.¹⁰ In addition, if the activation of neutrophils is not tightly regulated, the reactive oxygen species (ROS) and cytotoxic enzymes and ingested bacteria could be released into the surrounding area, causing tissue destruction and pathogen survival/dissemination.¹¹ Previous studies in acute pyelonephritis have found that paradoxically Tlr4^−/−, Il-1β^−/−, or C3^−/− mice had less severe acute kidney infection and inflammation, suggesting that innate immune responses driven by TLR-4 signaling, proinflammatory cytokine IL-1β, or complement effector molecules are harmful, instead of beneficial for the host.^7,12More than half a century after its discovery cAMP remains the object of intense scientific interest.¹³ cAMP is an intracellular second messenger induced by extracellular signals such as hormones, inflammatory mediators, and cytokines. It induces intracellular signal transduction conveying the cAMP-dependent pathways to regulate diverse cellular responses.¹⁴ Among the diverse functions, cAMP is known as a potent anti-inflammatory mediator, having inhibitory effects on production of proinflammatory cytokines in immune cells,¹⁵ leukocyte chemotaxisis,¹⁶ and release of bioactive molecules and cytotoxic agents from granulocytes.¹⁷ In addition, cAMP is found to regulate exocytic process in a variety of cells¹⁸ and to induce exocytosis of E. coli from bladder epithelial cells, thus reducing E. coli colonization of bladders.¹⁹Forskolin, a potent activator of cAMP, is used for investigating the role of cAMP in various cellular processes and diseases. Previous human and animal studies have found that administration of forskolin is beneficial in several clinical disorders, including UTI, bronchoconstriction, ischemia reperfusion injury, high blood pressure, and leukemia.^19–23 Although forskolin was studied in experimental UTI and showed that forskolin treatment reduces bladder infection (cystitis),¹⁹ it is unknown whether forskolin treatment would be effective in kidney infection (pyelonephritis). Here, we evaluated the effect of forskolin on protection against murine acute pyelonephritis and explored cellular and molecular mechanisms by which forskolin confers the protection. Our results indicate that forskolin treatment significantly reduced kidney infection and suggest that forskolin mediated the suppression of excessive inflammatory responses and inhibition of E. coli invasion of renal tubular epithelial cells (RTECs) that are responsible for the protection.     

FNR Regulates Expression of Important Virulence Factors Contributing to Pathogenicity of Uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is responsible for the majority of urinary tract infections (UTIs), which are some of the world''s most common bacterial infections of humans. Here, we examined the role of FNR (fumarate and nitrate reduction), a well-known global regulator, in the pathogenesis of UPEC infections. We constructed an fnr deletion mutant of UPEC CFT073 and compared it to the wild type for changes in virulence, adherence, invasion, and expression of key virulence factors. Compared to the wild type, the fnr mutant was highly attenuated in the mouse model of human UTI and showed severe defects in adherence to and invasion of bladder and kidney epithelial cells. Our results showed that FNR regulates motility and multiple virulence factors, including expression of type I and P fimbriae, modulation of hemolysin expression, and expression of a novel pathogenicity island involved in α-ketoglutarate metabolism under anaerobic conditions. Our results demonstrate that FNR is a key global regulator of UPEC virulence and controls expression of important virulence factors that contribute to UPEC pathogenicity.     

Adherence of uropathogenic Escherichia coli to human primary epithelial cells of renal pelvis

Human primary epithelial cells of renal pelvis was established to investigate the adherence of uropathogenic Escherichia coli (UPEC) to this cell line, in which the primary cell culture was performed by using cultivation of the normal epithelium of renal pelvis in keratinocyte serum free medium (K-SFM) with epidermal growth factor (EGF) and bovine pituitary extract (BPE). Both UPEC132 obtained from urine specimen of patients with pyelonephritis and the pilus-free representative strain E. coli K-12p678-54 were used to study the adherence of these strains on human primary epithelial cells of renal pelvis. The UPEC adherence was performed with observation on the morphological changes of the adhered cells, while the adhesion rates and indices were calculated in different times of experiment. In addition, the virulence genes hly and cnf1 of UPEC132 were detected by multiplex PCR assay. In this study, the human primary epithelial cells of renal pelvis was found to exhibit the character of the transitional epithelial cells. Compared with the control group, the adhesion rates and indices began to increase from 15 min of the experiment time and reached its peak in 120 min. The adhesion rate and index of UPEC132 to human primary epithelial cells of renal pelvis were 74.4% and 34.0 respectively. Many microscopic changes in the primary cells adhered with UPEC132 could be detected, such as rounding or irregularity in shape, unevenness in staining and the cytoplasmic and nuclear changes. It suggests that human primary epithelial cells of renal pelvis can be used for the experiment on UPEC adhesion, thus providing a basis for the further study on the pathogenesis of UPEC.     

Escherichia coli biofilm formation and recurrences of urinary tract infections in children

It has been suggested that biofilm formation by uropathogenic Escherichia coli (UPEC) isolates is associated with recurrence and persistence of urinary tract infection (UTI). We compared the in vitro biofilm formation of UPEC isolates from children with acute or recurrent UTI. Employing 206 consecutive clinical UPEC isolates from children with proven UTI, i.e., pyelonephritis (n?=?78), recurrent pyelonephritis (n?=?10), cystitis (n?=?84) or recurrent cystitis (n?=?34), we applied 1 % crystal violet staining to polystyrene microtitre plates at 72 h and measured the optical density (OD) values. The method had been validated to measure biofilm formation against confocal laser scanning microscopy and scanning electron microscopy. The OD values were lower in the recurrent cystitis group than in the other groups (mean OD 0.36, SD 0.21 vs mean 0.47, SD 0.36, P?=?0.04) and higher in the recurrent pyelonephritis group than in the other groups (mean OD 0.69, SD 0.33 vs mean OD 0.44, SD 0.34, P?=?0.006) indicating biofilm formation of strains causing recurrent pyelonephritis. It appears that the properties of UPEC isolates required for effective biofilm growth on an abiotic surface are important for recurrent pyelonephritis, but not for recurrent cystitis. It would be valuable in the future to analyze whether the biofilm properties of E. coli observed in vitro predict a slower clinical response to antimicrobial treatment and increased renal scar formation after UTI.     

Suppression of bladder epithelial cytokine responses by uropathogenic Escherichia coli

Urinary tract infections are most commonly caused by uropathogenic strains of Escherichia coli (UPEC), which invade superficial bladder epithelial cells via a type 1 pilus-dependent mechanism. Inside these epithelial cells, UPEC organisms multiply to high numbers to form intracellular bacterial communities, allowing them to avoid immune detection. Bladder epithelial cells produce interleukin-6 (IL-6) and IL-8 in response to laboratory strains of E. coli in vitro. We investigated the ability of UPEC to alter epithelial cytokine signaling by examining the in vitro responses of bladder epithelial cell lines to the cystitis strains UTI89 and NU14. The cystitis strains induced significantly less IL-6 than did the laboratory E. coli strain MG1655 from 5637 and T24 bladder epithelial cells. The cystitis strains also suppressed epithelial cytokine responses to exogenous lipopolysaccharide (LPS) and to laboratory E. coli. We found that insertional mutations in the rfa and rfb operons and in the surA gene all abolished the ability of UTI89 to suppress cytokine induction. The rfa and rfb operons encode LPS biosynthetic genes, while surA encodes a periplasmic cis-trans prolyl isomerase important in the biogenesis of outer membrane proteins. We conclude that, in this in vitro model system, cystitis strains of UPEC have genes encoding factors that suppress proinflammatory cytokine production by bladder epithelial cells.     

特异性小干扰RNA沉默CHOP对肾小管上皮细胞凋亡的影响

目的:研究C/EBP同源蛋白(CHOP)对肾小管上皮HK2细胞凋亡的影响。方法:采用qPCR法检测急性肾损伤患者及健康对照者血清中CHOP的mRNA水平。体外培养肾小管上皮HK2细胞,随机分为对照组、阴性组和si-CHOP组,si-CHOP组和阴性组分别转染CHOP小干扰RNA(siRNA)和阴性对照siRNA,通过转化生长因子β1(TGF-β1)诱导细胞损伤。MTT法检测细胞的活力,流式细胞术检测细胞的凋亡率, Western blot检测细胞中细胞核抗原Ki-67、增殖细胞核抗原(PCNA)、caspase-3和cleaved caspase-3的蛋白水平。结果:与健康对照者相比,急性肾损伤患者血清中CHOP的表达量显著增加(P0.05);转染CHOP siRNA显著降低肾小管上皮细胞HK2中CHOP的水平,与对照组相比差异具有统计学意义(P0.05)。敲减CHOP的表达显著增加肾小管上皮HK2细胞的活力(P0.05),降低其凋亡率(P0.05),增加Ki-67和PCNA的表达量(P0.05),下调cleaved caspase-3的蛋白水平(P0.05)。结论:在急性肾损伤患者血清中CHOP的水平增加。敲减CHOP表达通过调节增殖和凋亡相关蛋白的表达抑制肾小管上皮HK2细胞的凋亡。     

Immune Modulation by Group B Streptococcus Influences Host Susceptibility to Urinary Tract Infection by Uropathogenic Escherichia coli

Urinary tract infection (UTI) is most often caused by uropathogenic Escherichia coli (UPEC). UPEC inoculation into the female urinary tract (UT) can occur through physical activities that expose the UT to an inherently polymicrobial periurethral, vaginal, or gastrointestinal flora. We report that a common urogenital inhabitant and opportunistic pathogen, group B Streptococcus (GBS), when present at the time of UPEC exposure, undergoes rapid UPEC-dependent exclusion from the murine urinary tract, yet it influences acute UPEC-host interactions and alters host susceptibility to persistent outcomes of bladder and kidney infection. GBS presence results in increased UPEC titers in the bladder lumen during acute infection and reduced inflammatory responses of murine macrophages to live UPEC or purified lipopolysaccharide (LPS), phenotypes that require GBS mimicry of host sialic acid residues. Taken together, these studies suggest that despite low titers, the presence of GBS at the time of polymicrobial UT exposure may be an overlooked risk factor for chronic pyelonephritis and recurrent UTI in susceptible groups, even if it is outcompeted and thus absent by the time of diagnosis.     

Bacterial Lysis Liberates the Neutrophil Migration Suppressor YbcL from the Periplasm of Uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) modulates aspects of the innate immune response during urinary tract infection to facilitate bacterial invasion of the bladder epithelium, a requirement for the propagation of infection. For example, UPEC-encoded YbcL suppresses the traversal of bladder epithelia by neutrophils in both an in vitro model and an in vivo murine cystitis model. The suppressive activity of YbcL requires liberation from the bacterial periplasm, though the mechanism of release is undefined. Here we present findings on the site of action of YbcL and demonstrate a novel mode of secretion for a UPEC exoprotein. Suppression of neutrophil migration by purified YbcL_UTI, encoded by cystitis isolate UTI89, required the presence of a uroepithelial layer; YbcL_UTI did not inhibit neutrophil chemotaxis directly. YbcL_UTI was released to a greater extent during UPEC infection of uroepithelial cells than during that of neutrophils. Release of YbcL_UTI was maximal when UPEC and bladder epithelial cells were in close proximity. Established modes of secretion, including outer membrane vesicles, the type II secretion system, and the type IV pilus, were dispensable for YbcL_UTI release from UPEC. Instead, YbcL_UTI was liberated during bacterial death, which was augmented upon exposure to bladder epithelial cells, as confirmed by detection of bacterial cytoplasmic proteins and DNA in the supernatant and enumeration of bacteria with compromised membranes. As YbcL_UTI acts on the uroepithelium to attenuate neutrophil migration, this mode of release may represent a type of altruistic cooperation within a UPEC population during colonization of the urinary tract.     

Origins and virulence mechanisms of uropathogenic Escherichia coli

Strains of uropathogenic E. coli (UPEC) are the primary cause of urinary tract infections, including both cystitis and pyelonephritis. These bacteria have evolved a multitude of virulence factors and strategies that facilitate bacterial growth and persistence within the adverse settings of the host urinary tract. Expression of adhesive organelles like type 1 and P pili allow UPEC to bind and invade host cells and tissues within the urinary tract while expression of iron-chelating factors (siderophores) enable UPEC to pilfer host iron stores. Deployment of an array of toxins, including hemolysin and cytotoxic necrotizing factor 1, provide UPEC with the means to inflict extensive tissue damage, facilitating bacterial dissemination as well as releasing host nutrients and disabling immune effector cells. These toxins also have the capacity to modulate, in more subtle ways, host signaling pathways affecting myriad processes, including inflammatory responses, host cell survival, and cytoskeletal dynamics. Here, we discuss the mechanisms by which these and other virulence factors promote UPEC survival and growth within the urinary tract. Comparisons are also made between UPEC and other strains of extraintestinal pathogenic E. coli that, although closely related to UPEC, are distinct in their abilities to colonize the host and cause disease.     

Epithelial-mesenchymal transition in renal fibrosis - evidence for and against

Epithelial to mesenchymal transition (EMT) is a well established biological process in metazoan embryological development. Over the past 15 years, investigators have sought to establish whether EMT also occurs in renal epithelial cells, following kidney injury, and to show that the mesenchymal cells formed could give rise to myofibroblasts which populate the renal interstitium, causing fibrosis within it. There is no doubt that proximal tubular epithelial cells (PTECs) can undergo EMT in vitro in response to TGFβ-1 and other inflammatory stimuli. Moreover, the results of experiments with animal models of renal fibrosis and examination of biopsies from patients with chronic kidney disease have lent support to the hypothesis that EMT occurs in vivo. This review discusses some of the key evidence underlying that idea and summarises recent advances in understanding the molecular mechanism underlying the process. Early experiments using mice which were genetically engineered to mark PTECs with the LacZ gene to trace their fate following kidney injury provided evidence supporting the occurrence of EMT. Recently, however, cell lineage tracking experiments using the red fluorescent protein (RFP) as a high-resolution marker for cells of renal epithelial origin did not replicate this result; the interstitial space following kidney injury was devoid of RFP expressing cells, leading the investigators to reject the renal EMT hypothesis.     

Pentraxin 3 Inhibits Acute Renal Injury-Induced Interstitial Fibrosis Through Suppression of IL-6/Stat3 Pathway

Acute kidney injury-induced organ fibrosis is recognized as a major risk factor for the development of chronic kidney disease, which remains one of the leading causes of death in the developed world. However, knowledge on molecules that may suppress the fibrogenic response after injury is lacking. The long pentraxin 3 (PTX3), a novel acute renal injury marker, has been reported to be involved in chronic renal injury, but the mechanism is still unknown. In this experiment, the mice subjected to acute kidney injury showed a slow recovery of kidney function compared with PTX3-treated animals. Collagen expression was absent in sham-operated kidneys; however, their expression was significantly increased after reperfusion. And, these changes were reduced in PTX3-treated mouse kidney. Fibrosis was associated with increased expression of IL-6 and extensive activation of Stat3. Administration of IL-6 increased collagen I expression and Stat3 activation in vitro in renal epithelial cells subjected to hypoxia-reoxygenation, which was suppressed by PTX3. Furthermore, we found that the decreased serum creatinine level and the reduced expression of collagen and smooth muscle actin induced by PTX3 were abolished by additional administration of IL-6. The associated p-Stat3 expression which was reduced by PTX3 administration was also inverted by additional IL-6 treatment. Our data suggest that PTX3 inhibits acute renal injury-induced interstitial fibrosis through suppression of IL-6/Stat3 pathway.     

低氧诱导因子1α基因修饰脂肪干细胞修复小鼠急性肾损伤

背景：干细胞移植为肾损伤的治疗提供了一个新的途径,治疗基因转染干细胞可增强对疾病的治疗效果。 目的：探讨低氧诱导因子1α基因修饰的脂肪源性干细胞移植对急性肾损伤小鼠肾脏结构和功能的影响。 方法：连续2 d向BALB/C裸鼠腹腔注射10 mg/kg顺铂诱导急性肾损伤小鼠模型。造模24 h后经小鼠尾静脉注射含1×10⁵个脂肪源性干细胞或转染低氧诱导因子1α的脂肪源性干细胞的细胞悬液,3 d后留取小鼠血液及肾组织标本进行实验。以注射200 μL生理盐水的急性肾损伤小鼠作为模型对照,以正常小鼠作为正常对照。 结果与结论：脂肪源性干细胞干预后急性肾损伤小鼠血清肌酐、尿素氮水平降低,肾组织病理改变及肾小管上皮细胞的凋亡病变减轻,肾组织炎症因子RANTES、肿瘤坏死因子α表达降低,白细胞介素10表达升高;其中低氧诱导因子1α基因修饰的脂肪源性干细胞对肾组织细胞凋亡及炎症因子表达作用更明显。免疫荧光染色可见移植的脂肪源性干细胞的存活,但未见其向肾小管上皮细胞转化。结果表明脂肪源性干细胞移植可改善急性肾损伤小鼠的肾脏结构和功能,经低氧诱导因子1α基因修饰后的脂肪源性干细胞作用更显著。     

Mechanisms of renal tissue destruction in an experimental acute pyelonephritis

To find out the mechanism of renal tissue destruction in Escherichia coli-induced acute pyelonephritis, the relationship between the infiltration of polymorphonuclear leukocytes into the kidney and the renal tissue damage has been investigated. An acute pyelonephritis was produced by administration of E. coli into the kidneysof the leukocyte-depleted and the leukocyte-nondepleted rats, and the sequence of morphologic events in the kidneys has been studied by light and electron microscopy. There was little infiltration of leukocytes into the E. coli-infected kidneys of the leukocyte-depleted rats despite formation of prominent bacterial colonies. Associated with this suppressed leukocytic infiltration into the kidney was a good structural preservation of those kidneys of leukocyte-depleted rats. On the contrary, a massive infiltration of polymorphonuclear luekocytes into the E. coli-infected kidneys was present in the leukocyte-nondepleted rats. Associated with this massive infiltration of leukocytes was a destruction of tubular basement membrane and tubular epithelia. The data appear to indicate that the polymorphonuclear leukocytes infiltrated into the kidney plays a role in renal tissue destruction in the early phase of E. coli-induced acute pyelonephritis.     

Tissue inhibitor of metalloproteinase 1 activates normal human granulocytes, protects them from apoptosis, and blocks their transmigration during inflammation

Urinary levels of tissue inhibitor of metalloproteinase 1 (TIMP-1) higher than those of matrix metalloproteinase 9 (MMP-9) during acute pyelonephritis have previously been associated with a higher degree of acute inflammation and of postinfective renal scarring. The aim of the present study was to evaluate possible mechanisms by which TIMP-1 could affect the scarring process already during the acute phase of inflammation. The growth of Escherichia coli, bactericidal activity of fresh human blood, and respiratory burst, spontaneous apoptosis, and trans-basement membrane migration of normal human granulocytes were studied in vitro in the presence of different concentrations of recombinant human TIMP-1. To imitate the "normal" environment during inflammation in the kidney, granulocytes were also incubated with a conditioned medium from E. coli-stimulated renal epithelial cells. In order to compare our data with the in vivo situation, blood and urinary leukocyte levels were analyzed for 40 children with acute pyelonephritis, together with urinary MMP-9 and TIMP-1 levels. TIMP-1 at a concentration of 500 ng/ml increased the bactericidal activity of blood, increased the respiratory burst of granulocytes, decreased phosphatidylserine exposure and caspase 3 activity, which are features of spontaneous apoptosis, and inhibited granulocyte transmigration. Moreover, in the patients with pyelonephritis, MMP-9/TIMP-1 ratios in urine correlated with the degree of leukocyte transmigration. Thus, our data suggest that TIMP-1 specifically blocks the transmigration of granulocytes into urine. Entrapped and activated granulocytes, protected from apoptosis, might excessively destroy renal parenchyma and thus contribute to the pathogenesis of renal scarring following acute pyelonephritis.     

Relationship between neutrophil-mediated oxidative injury during acute experimental pyelonephritis and chronic renal scarring.

Previous experiments with rats have suggested that pyelonephritic scarring after acute ascending Escherichia coli pyelonephritis partly results from excessive polymorphonuclear leukocyte (PMN) infiltration and activation in the kidney parenchyma. We have studied the role of PMN oxidative metabolism in generating tissue injury during acute pyelonephritis. Rats with acute pyelonephritis were treated with dapsone (25 mg/kg twice daily for 3 days), a compound known to prevent PMN oxidant damage. In vitro, levels of dapsone easily achieved in vivo inhibited myeloperoxidase (MPO)-mediated reactions involving the oxidation of halides to reactive cytotoxic hypohalites (such as MPO-mediated iodination and luminol-enhanced chemiluminescence). In contrast, dapsone had no effect on superoxide production, lysosomal enzyme release, or bacterial killing by activated PMN. In vivo, dapsone treatment had no significant effect on acute pyelonephritis with respect to (i) bacterial counts, (ii) inflammatory swelling, and (iii) PMN infiltration. However, dapsone-treated animals sacrificed 2 months after acute pyelonephritis had a 65% reduction of renal scars when compared with controls. Since dapsone had no antibacterial effect, this protection is compatible with the hypothesis that dapsone prevented oxidant-generated tissue injury due to the extracellular release of the MPO system by activated PMN during acute suppurative pyelonephritis.     

黄芪甲苷孵育脂肪源性干细胞对顺铂诱导肾小管上皮细胞凋亡的影响

背景：干细胞移植用于治疗急性肾损伤的有效性已经被多个研究证实,但其对肾小管上皮细胞损伤的修复机制尚不明确。 目的：观察黄芪甲苷孵育后的脂肪源性干细胞对顺铂诱导的肾小管上皮细胞凋亡的保护作用及机制。 方法：实验分为4组。2.5 μmol/L顺铂诱导肾小管上皮细胞 24 h,建立肾小管细胞损伤模型(顺铂损伤组);将脂肪源性干细胞与损伤肾小管上皮细胞共培养(脂肪源性干细胞+损伤肾小管上皮细胞组);利用Transwell小室将20 mg/L黄芪甲苷孵育脂肪源性干细胞48 h后与损伤肾小管上皮细胞共培养(黄芪甲苷孵育脂肪源性干细胞+损伤肾小管上皮细胞组);以正常肾小管上皮细胞做对照(正常对照组)。 结果与结论：与肾小管上皮细胞损伤组相比,AV/PI和TUNEL结果均显示脂肪源性干细胞+肾小管上皮细胞组和20 mg/L 黄芪甲苷脂肪源性干细胞+肾小管上皮细胞组肾小管上皮细胞发生凋亡的比例和数量明显减少;ELISA结果表明20 mg/L黄芪甲苷脂肪源性干细胞+肾小管上皮细胞组胰岛素样生长因子1分泌显著提高(P < 0.05);Western blot进一步显示20 mg/L 黄芪甲苷脂肪源性干细胞+肾小管上皮细胞组caspase-3蛋白水平明显下降,而Bcl-2的表达量明显增加(P < 0.05)。表明黄芪甲苷孵育的人脂肪源性干细胞对顺铂诱导的肾小管上皮细胞凋亡具有抑制作用,从而有利于肾小管损伤的早期恢复,其保护机制可能与增加胰岛素样生长因子1分泌,抑制caspase-3表达、上调Bcl-2水平有关。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

Megalocytic Interstitial Nephritis Following Acute Pyelonephritis with Escherichia coli Bacteremia: A Case Report

Megalocytic interstitial nephritis is a rare form of kidney disease caused by chronic inflammation. We report a case of megalocytic interstitial nephritis occurring in a 45-yrold woman who presented with oliguric acute kidney injury and acute pyelonephritis accompanied by Escherichia coli bacteremia. Her renal function was not recovered despite adequate duration of susceptible antibiotic treatment, accompanied by negative conversion of bacteremia and bacteriuria. Kidney biopsy revealed an infiltration of numerous histiocytes without Michaelis-Gutmann bodies. The patient''s renal function was markedly improved after short-term treatment with high-dose steroid.

Graphical Abstract

相似文献   

Pyelonephritogenic Escherichia coli and killing of cultured human renal proximal tubular epithelial cells: role of hemolysin in some strains.

Acute pyelonephritis, a complication of Escherichia coli bacteriuria, must represent a bacterial invasion through the kidney epithelium. To study this process, we overlaid bacterial suspensions onto monolayers of cultured human kidney proximal tubular epithelial cells and measured cytotoxicity by release of lactate dehydrogenase (LDH). Thirty-four isolates cultured from patients with acute pyelonephritis were screened for the ability to cause pyelonephritis in CBA mice by transurethral challenge. The eight most virulent strains (greater than or equal to 70% of mice challenged developed greater than or equal to 10(3) CFU/g of kidney after 48 h) were selected for study. Each strain displayed mannose-resistant hemagglutination of human O erythrocytes; three strains were phenotypically and genotypically hemolytic. Pyelonephritogenic strains were significantly more cytotoxic (30.1 +/- 9.5% LDH release after 18 h) than eight fecal control strains (13.5 +/- 11.5% LDH release; P = 0.0068). We selected the most cytotoxic strain, CFT073, for further study. Sterile filtrate from this hemolytic strain was significantly more cytotoxic than was the filtrate of the fecal control strain, FN414. Transposon mutagenesis of CFT073 with TnphoA abolished hemolytic activity and cytotoxicity by both whole cells and sterile filtrate. Southern blot analysis revealed that the Tnphoa insertion mapped to the E. coli chromosomal hly determinant within a 12-kilobase SalI restriction fragment. Transformation of a nonhemolytic strain, CPZ005 with plasmid pSF4000, which carries a cloned hemolysin determinant, resulted in highly elevated cytotoxicity. Light micrographs of proximal tubular epithelial cell cultures demonstrated cell damage by pyelonephritogenic strains that was not induced by a fecal strain or the hemolysin-deficient mutant. Results indicate that pyelonephritogenic E. coli strains are more frequently cytotoxic for a putative target, that is, human renal tubular epithelium, than are fecal isolates. Hemolysin, in some strains, is apparently responsible for this cytotoxicity.     

Enhanced uropathogenic Escherichia coli-induced infection in uroepithelial cells by sugar through TLR-4 and JAK/STAT1 signaling pathways

BackgroundPatients with diabetes mellitus (DM) have higher incidence and more severe urinary tract infections (UTIs) for longer duration than those of the patients without DM. It causes more complicated etiologies during uropathogenic Escherichia coli (UPEC) infection. However, studies regarding the molecular mechanism are scarce.MethodsThe present study (1) aimed to verify if sugar influences the process of UPEC-induced cystitis and invasion into the uroepithelial cells and (2) illustrated the mechanism of effects for sugar enhanced the UPEC infection into uroepithelial cells is related to TLR-4-mediated and JAK/STAT1-dependent pathway.ResultsThe results of the present study indicated that sugar can enhance UPEC infection in uroepithelial cells by up-regulating the transduced circuit between TLR-4-mediated UPEC interaction and JAK/STAT-1 signal pathways. The results of the inhibitor-co-incubating experiments demonstrated that the mechanism involved in the synergistic amplification of TLR-4-mediated UPEC interaction and JAK/STAT1 signaling pathways is responsible for the increased UPEC infection in uroepithelial cells.ConclusionThe results also proved that STAT-1 plays a critical role in the regulation of UPEC invasion and infection in the uroepithelial cells, especially those pretreated with glucose. The present study suggests a possible therapeutic approach to preferentially suppress UPEC infection during UTIs in the patients with diabetes.