Tonicity inversely modulates lipocalin-2 (Lcn2/24p3/NGAL) receptor (SLC22A17) and Lcn2 expression via Wnt/ß-catenin signaling in renal inner medullary collecting duct cells: implications for cell fate and bacterial infection.

BACKGROUND: We have previously evidenced apical expression of the 24p3/NGAL/lipocalin-2 receptor (Lcn2-R; SLC22A17) in inner medullary collecting duct (IMCD) cells, which are present in vivo in a hyperosmotic/-tonic environment that activates canonical Wnt/ß-catenin signaling. The localization of Lcn2-R in the inner medulla is intriguing considering local bacterial infections trigger toll-like receptor-4 (TLR-4)-mediated secretion of the bacteriostatic Fe3+-free (apo-)Lcn2. AIM: To determine the effects of osmolarity/tonicity changes, Wnt/ß-catenin and TLR-4 activation on Lcn2-R and Lcn2 expression and cell viability in rat primary IMCD and mouse (m)IMCD3 cells. METHODS: Normosmolarity/-tonicity was 300 mosmol/l whereas hyperosmolarity/-tonicity was induced by adding 100 mmol/l NaCl + 100 mmol/l urea (600 mosmol/l, 1-7 days). Lcn2-R and Lcn2 expression were determined by qPCR, immunoblotting, flow cytometry and immunofluorescence microscopy. ß-catenin was silenced by RNAi. Cell viability/death was determined with MTT and LDH release assays. TLR-4 was activated by bacterial lipopolysaccharides (LPS). RESULTS: Hyperosmotic/-tonic media upregulated Lcn2-R by ~4-fold and decreased Lcn2 expression/secretion, along with Wnt/ß-catenin activation, in IMCD cells. These effects of hyperosmotic/-tonic media on Lcn2-R/Lcn2 expression were reverted by normosmolarity/-tonicity, ß-catenin silencing and/or LPS. Exposure of cells with endogenous or stably overexpressing Lcn2-R to apo-Lcn2 or LPS decreased cell viability. CONCLUSIONS: Lcn2-R upregulation and Lcn2 downregulation via Wnt/ß-catenin may promote adaptive osmotolerant survival of IMCD cells in response to hyperosmolarity/-tonicity whereas Lcn2 upregulation and Lcn2-R downregulation via TLR-4 and/or normosmolarity/-tonicity may protect IMCD cells against bacterial infections and prevent autocrine death induction by Lcn2.

Hepcidin as a Major Component of Renal Antibacterial Defenses against Uropathogenic Escherichia coli.

The iron-regulatory peptide hepcidin exhibits antimicrobial activity. Having previously shown hepcidin expression in the kidney, we addressed its role in urinary tract infection (UTI), which remains largely unknown. Experimental UTI was induced in wild-type (WT) and hepcidin-knockout (Hepc-/-) mice using the uropathogenic Escherichia coli CFT073 strain. Compared with infected WT mice, infected Hepc-/- mice showed a dramatic increase in renal bacterial load. Moreover, bacterial invasion was significantly dampened by the pretreatment of WT mice with hepcidin. Infected Hepc-/- mice exhibited decreased iron accumulation in the renal medulla and significant attenuation of the renal inflammatory response. Notably, we demonstrated in vitro bacteriostatic activity of hepcidin against CFT073. Furthermore, CFT073 repressed renal hepcidin, both in vivo and in cultured renal cells, and reduced phosphorylation of SMAD kinase in vivo, suggesting a bacterial strategy to escape the antimicrobial activities of hepcidin. In conclusion, we provide new mechanisms by which hepcidin contributes to renal host defense and suggest that targeting hepcidin offers a strategy to prevent bacterial invasion.

Renal actinomycosis.

Actinomycosis of the kidney is rare and less than 50 cases have been reported in the English literature. Reported presentations are pyelonephritis, renal abscesses or pyonephrosis. To date, one case of actinomycosis associated necrotising papillitis has been reported. We describe the second case of such a rare association of actinomycosis with papillary necrosis.

Early exposure to germs modifies kidney damage and inflammation after experimental ischemia-reperfusion injury.

Kidney ischemia-reperfusion injury (IRI) is, in part, mediated by immune and inflammatory factors. Since microbial stimuli are known to alter immune and inflammatory responses, we hypothesized that differences in perinatal microbial status would modify renal injury following IRI. We performed bilateral renal IRI on 6-wk-old germ-free and control mice and studied the effects on kidney lymphocyte trafficking, cytokines, function, and structure. Compared with control mice, normal kidneys of germ-free mice exhibited more NKT cells and lower IL-4 levels. Postischemia, more CD8 T cells trafficked into postischemic kidneys of germ-free mice compared with control mice. Renal structural injury and functional decline following IRI were more severe in germ-free mice compared with control mice. When germ-free mice were conventionalized with the addition of bacteria to their diet, the extent of renal injury after IRI became equivalent to age-matched control mice, with similar numbers and phenotypes of T cells and NKT cells, as well as cytokine expression in both normal kidneys and postischemic kidneys of conventionalized germ-free mice and age-matched control mice. Thus microbial stimuli influence the phenotype of renal lymphocytes and the expression of cytokines of normal kidneys and also modulate the outcome of IRI.

[Ultrastructural changes in the interstitial cells of the kidney medullary substance in suckling rabbits with experimental cholera]. / Ul'trastrukturnye izmeneniia interstitsial'nykh kletok mozgovogo veshchestva pochek krolikov-sosunkov pri éksperimental'noi kholere.

A culture of virulent selection of cholera vibrios L-top 5879 was introduced through the probe to suckling rabbits-pups 10 to 12 days old. Ultrastructural changes of interstitial cells and capillaries of kidney medulla were studied. During vibrio adhesion (4 hrs after the inaction) interstitial cells acquire dystrophic changes, lipid granules content reduces, while vascular permeability grows higher which suggests the presence of prostaglandin precursors elimination into blood flow. Cholera development (1-2 days later) is accompanied with progressing of signs of prostaglandin synthesis activation and their precursors passage into the vascular bed.

L-651,392, a potent leukotriene inhibitor, controls inflammatory process in Escherichia coli pyelonephritis.

In this study, the relationship between leukotrienes, peritubular cell infiltration with polymorphonuclear cells (PMNs) and renal tubular damage was investigated in a rat model of acute ascending pyelonephritis. Infection was induced by the injection of 10(5) CFU of Escherichia coli into the bladder and occlusion of the left ureter for 24 h. Treatment of infected animals was started 24 h after the induction of pyelonephritis with either hydrocortisone (25 mg/kg of body weight per day), the leukotriene inhibitor L-651,392 (10 mg/kg/day), or the vehicle of L-651,392 and was maintained for 5 days. At the end of treatment, the animals were killed, serum was collected, and both kidneys were removed for colony counts and histopathology. Renal function was evaluated by the measurement of blood urea nitrogen levels and creatinine clearance. The numbers of PMNs and mononuclear cells (MNs) in the cortex and medulla were recorded for all groups on plastic sections done from the left kidney. Infection alone (vehicle of L-651,392) resulted in intensive interstitial infiltration and a severe tubular destruction in the cortex. Treatment with hydrocortisone did not prevent PMN migration and tissue damage. By contrast, treatment with L-651,392 resulted in a significant reduction in PMNs (P < 0.001 in comparisons with all other groups) and greater preservation of the tubular structure despite identical bacterial counts than in the group receiving hydrocortisone. We conclude that L-651,392 prevents inflammatory cells from reaching the site of infection and protects the kidney from tubular damage associated with inflammation during pyelonephritis. Inhibitors of leukotrienes should be further investigated for their potential benefit as adjuvants to antibiotherapy in the treatment of pyelonephritis.

Microbial and host factors that influence adherence of Escherichia coli to kidney epithelium.

The adherence of Escherichia coli 06K13H1 to punch biopsy specimens of rabbit renal pelvic tissue and isolated epithelial cells was examined quantitatively. Organisms with pili adhered readily to kidney tissue, whereas organisms without pili (nonpiliated or grown in glucose-containing media) had significantly less adherence. Adherence was inhibited by antibody to pili antigen but not by mannose (a determinant of adherence to buccal mucosal cells). Studies were done to evaluate adherence under conditions operative in the renal medulla. The combination of hypertonic salt or urea solutions in acid pH interfered with adherence of the mannose-resistant strain. In additional studies of kidneys from humans, a similar effect of antipili serum and mannose was seen. These studies provide further evidence that pili are important in the initiation of upper urinary tract infection and define host factors that may inhibit initiation of infection.

Adenovirus-like particles associated with intranuclear inclusion bodies in the kidney of a common murre (uria aalge).

Adenovirus-like particles were identified by transmission electron microscopy in intranuclear inclusion bodies in the renal collecting tubules of a male common murre. The bird had been trapped in an oil-spill and had been cleaned and held in captivity before euthanasia. The presence of the virus appeared to be causing little or no renal disease. It is thought that this bird suffered activation of a latent viral infection as a result of the stress of oil intoxication, handling, and confinement.

Progressive multifocal leucoencephalopathy: detection of papovavirus JC in kidney tissue.

Cellular DNA of the kidney from a patient with PML was analyzed by reassociation kinetics for the presence of JC virus DNA. Various amounts of viral DNA sequences were detected in different areas of the kidney. The highest concentration (175 genome equivalents/cell) was found in the renal medulla and there were almost none in the renal cortex. Differentiation from the closely related BK virus was carried out by reassociation kinetics and restriction enzyme cleavage with subsequent Southern blot analysis. The enzyme Hind II, which does not cleave within the BK virus genome, generated four restriction enzyme fragments in the cellular DNA from the kidney, thus documenting the presence of JC virus DNA. By examination of the renal DNA with the "no-cut" restriction enzyme XHO I and the "one-cut" enzymes Eco RI and BAM HI it was possible to show that free and not integrated viral DNA was present in these cells. Nonhomogeneous defective DNA bands were not detectable. By in situ hybridization the epithelial cells lining the collecting tubules were found as predominant site of the viral infection in the kidney.

Chronic pyelonephritis. Electron microscopic study. II. Persistence of variant bacterial forms.

Ascending nonobstructive pyelonephritis was produced in nonhuman primates by ureteral catheterization which delivered Escherichia coli (04:H1) to the renal pelvis while creating intrarenal reflux. Female rhesus monkeys (Macaca mulatta) were immunosuppressed by cyclophosphamide before infection and weekly thereafter and compared to those with infection only. Kidney tissue was examined by electron microscopy in an effort to compare the development of the infection in the two groups of monkeys, i.e., immunocompetent and immunosuppressed. Reorganization of bacterial cytoplasm into small dense bodies (averaging 250 A in diameter) was seen in two of the suppressed animals. These particles were within bacteria that were either free in the medullary interstitium or in macrophages. Clusters of electron-dense bodies of the same size and morphology were also seen within subendothelial spaces of glomerular capillaries. Protoplast-like forms were observed within the medullary interstitium. One cell wall-less form contained particles (as previously described) within a large peripheral vesical. Gross pyelonephritic scarring occurred in all immunosuppressed animals. This study has shown morphologically that classical bacterial organisms placed into the intact kidneys of partially immunoincompetent nonhuman primates will cause pyelonephritis and continue to exist for 18 days. These observations of the futile efforts by suppressed populations of leukocytes to clear intrarenal bacteria raise interesting questions about the host-paradise relationship in chronic renal infection.

Significance of anaerobic bacteria isolated from the urinary tract. II. Experimental studies.

An attempt to cause retrograde urinary tract infection with Bacteroides fragilis (a strain subcultured in artificial media) failed to produce any significant renal infection in rats. Intravenous inoculation with Fusobacterium (a strain subcultured in artificial media) also did not cause demonstrable renal infection in rats. Nor could the anaerobic organism be demonstrated in the kidneys of these animals. Animals receiving Bacteroides (a strain subcultured in artificial media) inoculated directly into the renal medulla developed no renal infection. The anaerobic organism however, continued to be demonstrable in the kidneys of 78 per cent of these animals even on the 3rd day after inoculation. Rabbits receiving Bacteroides (a fresh clinical isolate) which was injected into the subcutaneously fixed kidney with ureteral obstruction all developed overt renal infection. There was also evidence of marked proliferation of the injected anaerobic bacteria and pyuria in these cases.

Pathogenicity of stable L-phase variants of Staphylococcus aureus: failure to colonize normal and oxamide-induced hydronephrotic renal medulla of rats.

The direct intramedullary inoculation of stable L-phase variants of Staphylococcus aureus failed to colonize normal and hydronephrotic rat kidneys induced by oral feeding of oxamide.