Nephron Experimental Nephrology最新文献

Background/aims: Acute kidney injury (AKI) contributes to significant morbidity and mortality in the intensive care unit (ICU). Plasma levels of interleukin (IL)-6 predict the development of AKI and are associated with higher mortality in ICU patients with AKI. Most studies in AKI have focused on the tubulo-interstitium, despite evidence of glomerular involvement. In the following study, our goals were to investigate the expression of IL-6 and its downstream mediators in septic-induced AKI.

Methods: Podocytes were treated in vitro with lipopolysaccharide (LPS) and mice were treated with LPS, and we evaluated IL-6 expression by real-time PCR, ELISA and in situ RNA hybridization.

Results: Following LPS stimulation, IL-6 is rapidly and highly induced in cultured podocytes and in vivo in glomeruli and infiltrating leukocytes. Surprisingly, in direct response to exogenous IL-6, podocytes produce lipocalin-2/neutrophil gelatinase-associated lipocalin (Lcn2/Ngal). LPS also potently induces Lcn2/Ngal expression in podocytes in culture and in glomeruli in vivo. Intense Lcn2/Ngal expression is also observed in IL-6 knockout mice, suggesting that while IL-6 may be sufficient to induce glomerular Lcn2/Ngal expression, it is not essential.

Conclusions: The glomerulus is involved in septic AKI, and we demonstrate that podocytes secrete key mediators of AKI including IL-6 and Lcn2/Ngal.

Epithelial sodium channels (ENaC) are ion transporters in the aldosterone-sensitive distal nephron that play an important role in sodium reabsorption in the terminal nephron. Our study of inbred C57Bl6/J mice given a high-sodium diet showed increased ENaC expression accompanied by tubular renin activation on qRT-PCR of laser-captured tubule specimens and Western blotting of membrane proteins, despite inhibition of aldosterone. Treatment with an angiotensin-converting-enzyme inhibitor (ACEI) or an angiotensin receptor blocker (ARB) effectively lowered blood pressure. In addition to lowering blood pressure, ACEI and ARB inhibition downregulated ENaC and renin expression in renal tubules. These effects would act to suppress sodium reabsorption via ENaC and normalize molecular mechanisms that elevate blood pressure in response to increased salt intake.

Background: The incidence and cost of chronic kidney disease (CKD) are increasing. Renal tubular epithelial cell dysfunction and attrition, involving increased apoptosis and cell senescence, are central to the pathogenesis of CKD. The aim here was to use an in vitro model to investigate the separate and cumulative effects of oxidative stress, mitochondrial dysfunction and cell senescence in promoting loss of renal mass.

Methods: Human kidney tubular epithelial cells (HK2) were treated with moderate hydrogen peroxide (H2O2) for oxidative stress, with or without cell cycle inhibition (apigenin, API) for cell senescence. Adenosine triphosphate (ATP) and oxidative stress were measured by ATP assay, lipid peroxidation, total antioxidant capacity, mitochondrial function with confocal microscopy, MitoTracker Red CMXRos and live cell imaging with JC-1. In parallel, cell death and injury (i.e. apoptosis and Bax/Bcl-XL expression, lactate dehydrogenase), cell senescence (SA-β-galactosidase) and renal regenerative ability (cell proliferation), and their modulation with the anti-oxidant N-acetyl-cysteine (NAC) were investigated.

Results: H2O2 and API, separately, increased oxidative stress and mitochondrial dysfunction, apoptosis and cell senescence. Although API caused cell senescence, it also induced oxidative stress at levels similar to H2O2 treatment alone, indicating that senescence and oxidative stress may be intrinsically linked. When H2O2 and API were delivered concurrently, their detrimental effects on renal cell loss were compounded. The antioxidant NAC attenuated apoptosis and senescence, and restored regenerative potential to the kidney.

Conclusion: Oxidative stress and cell senescence both cause mitochondrial destabilization and cell loss and contribute to the development of the cellular characteristics of CKD.

Experimental peritonitis is a frequently used inflammatory model to evaluate leukocyte recruitment. By the intrinsic characteristics of the peritoneal cavity, the various resident cell populations have a role to play in the initiation, the modulation and the resolution of peritoneal inflammation. Through various manipulations of these cell populations, we gained important knowledge on their respective roles in peritoneal inflammation. In this brief review, we will focus on the cellular regulation of leukocyte recruitment in experimental peritonitis.

Background/aims: The relative contribution of genetic factors and dietary patterns to glomerular damage in healthy individuals and prediabetic conditions is currently unclear. All Rab3A knockout (KO) mice spontaneously develop macroalbuminuria, but only male mice exhibit a glucose-intolerant phenotype, thus making the model suitable to examine the impact of a diet on preexisting podocyte damage.

Methods: Male and female Rab3A KO and wild-type (WT) mice were chronically fed a high-glucose diet (HGD). Biochemical tests, histology and immunohistochemistry were periodically performed whilst primary podocytes served for in vitro analyses.

Results: Chronic administration of an HGD did not induce de novo alterations in WT kidneys but caused progressive worsening of podocyte and glomerular damage in both male and female Rab3A KO. Though glomerular lesions, reminiscent of human diabetic nephropathy, were more severe in male mice, overt proteinuria and renal damage were also evident in female mice. The in vitro analysis of Rab3A WT and KO podocytes revealed diminished actin plasticity in the cell processes of KO podocytes. Furthermore, a modest increase in glucose concentration induced profound cytoskeletal changes only in Rab3A KO cells.

Conclusions: Our data show that chronic administration of an HGD to Rab3A KO mice that have a genetic defect that impairs podocyte actin plasticity results in increased podocyte damage and leads to overt proteinuria. If the same diet is given to male Rab3A KO animals, with additionally altered glucose homeostasis, this results in renal lesions similar to those of human diabetic nephropathy.

The role of toll-like receptors (TLRs) has been described in the pathogenesis of renal ischemia/reperfusion injury, but data on the expression and function of TLR4 during renal allograft damage are still scarce. We analyzed the expression of TLR4 in an experimental rat model 6 and 28 days after allogeneic kidney transplantation in comparison to control rats and rats after syngeneic transplantation. On day 6, a significant induction in TLR4 expression--restricted to the glomerular compartment--was found in acute rejecting allografts only. TLR4 expression strongly correlated with renal function, and TLR4 induction was accompanied by a significant increase in CC chemokine expression within the graft as well as in urinary CC chemokine excretion. TLR4 induction may be caused by an influx of macrophages as well as TLR4-expressing intrinsic renal cells. Fibrinogen deposition in renal allografts correlated with renal TLR4 expression and may act as a potent stimulator of chemokine release via TLR4 activation. This study provides, for the first time, data about the precise intrarenal localization and TLR4 induction after experimental kidney transplantation. It supports the hypothesis that local TLR4 activation by endogenous ligands may be one pathological link from unspecific primary allograft damage to subsequent chemokine release, infiltration and activation of immune cells leading to deterioration of renal function and induction of renal fibrosis.

Background/aims: To examine the role of the angiotensin II (ATII) type 1a receptor (AT1-R) pathway in renal tissue damage and repair, we investigated reversible glomerular injury in a mouse model of habu snake venom (HSV)-induced glomerulonephritis using AT1-R-deficient (AT1a-/-) mice and AT1-R antagonist-treated mice.

Methods: Experimental glomerulonephritis was induced by single administration of HSV to AT1a(+/+) mice (HSV group) and AT1a(-/-) mice (KO-HSV group) and AT1-R antagonist-treated BL6 mice (HSV-ARB group). Morphological change and expression levels of type IV collagen, CD31, and vascular endothelial growth factor (VEGF) were analyzed.

Results: The HSV group showed increased mesangial matrix expansion on day 7, which returned to preinjection levels by day 56, while mes-angial matrix expansion and increased type IV collagen expression were seen throughout days 7 to 56 in the KO-HSV group. The KO-HSV group showed fewer CD31-positive capillary loops and a marked decrease in the number of VEGF-positive cells in the glomeruli than the HSV group. VEGF administration to the KO-HSV group facilitated glomerular capillary repair and reconstruction. The HSV-ARB group showed the same delay in glomerular repair as that seen in the KO-HSV group.

Conclusion: Our results indicate that blocking of the ATII-AT1R pathway delays glomerular repair via angiogenesis inhibition, followed by reduced induction of VEGF.