[Show abstract][Hide abstract] ABSTRACT: Transient ischemia leads to tolerance to subsequent protracted ischemia. This "ischemia preconditioning" results from the induction of numerous protective genes, involved in cell metabolism, proliferation and survival, in antioxidant capacity, angiogenesis, vascular tone and erythropoiesis. Hypoxia inducible factors (HIF) play a pivotal role in this transcriptional adaptive response. HIF prolyl hydroxylases (PHDs), serving as oxygen sensors control HIFα degradation. HIF-mediated ischemic preconditioning can be achieved with the administration of PHD inhibitors, with the attenuation of organ injury under various hypoxic and toxic insults. Clinical trials are currently under way, evaluating PHD inhibitors as inducers of erythropoietin. Once their safety is established, their potential use might be further tested in clinical trials in various forms of acute ischemic and toxic organ damage. Repeated transient limb ischemia was also found to attenuate ischemic injury in remote organs. This "remote ischemic preconditioning" phenomenon (RIP) has been extensively studied recently in small clinical trials, preceding, or in parallel with an abrupt insult, such as myocardial infarction, cardiac surgery or radiocontrast administration. Initial results are promising, suggesting organ protection. Large scale multi-center studies are currently under way, evaluating the protective potential of RIP in cardiac surgery, in the management of myocardial infarction and in organ transplantation. The mechanisms of organ protection provided by RIP are poorly understood, but HIF seemingly play a role as well. Thus, Inhibition of HIF degradation with PHD inhibitors, as well as RIP (in part through HIF) might develop into novel clinical interventions in organ protection in the near future. This article is protected by copyright. All rights reserved.
Full-text · Article · Oct 2015 · Acta Physiologica
[Show abstract][Hide abstract] ABSTRACT: Renal endothelin-converting enzyme (ECE)-1 is induced in experimental diabetes and following radiocontrast administration, conditions characterized by renal hypoxia, hypoxia-inducible factor (HIF) stabilization, and enhanced endothelin synthesis. Here we tested whether ECE-1 might be a HIF-target gene in vitro and in vivo. ECE-1 transcription and expression increased in cultured vascular endothelial and proximal tubular cell lines, subject to hypoxia, to mimosine or cobalt chloride. These interventions are known to stabilize HIF signaling by inhibition of HIF-prolyl hydroxylases. In rats, HIF-prolyl-hydroxylase inhibition by mimosine or FG-4497 increased HIF-1α immunostaining in renal tubules, principally in distal nephron segments. This was associated with markedly enhanced ECE-1 protein expression, predominantly in the renal medulla. A progressive and dramatic increase in ECE-1 immunostaining over time, in parallel with enhanced HIF expression, was also noted in conditional von Hippel-Lindau knockout mice. Since HIF and STAT3 are cross-stimulated, we triggered HIF expression by STAT3 activation in mice, transfected by or injected with a chimeric IL-6/IL-6-receptor protein, and found a similar pattern of enhanced ECE-1 expression. Chromatin immunoprecipitation sequence (ChIP-seq) and PCR analysis in hypoxic endothelial cells identified HIF binding at the ECE-1 promoter and intron regions. Thus, our findings suggest that ECE-1 may be a novel HIF-target gene.Kidney International advance online publication, 3 December 2014; doi:10.1038/ki.2014.362.
No preview · Article · Dec 2014 · Kidney International
[Show abstract][Hide abstract] ABSTRACT: The most potent intrinsic vasoconstrictor known so far is a 21 aminoacid (aa) peptide discovered in endothelial cells in 1988, and hence, named endothelin (ET). Meanwhile, endothelin has come of age as a factor highly involved in various biological pathways and diseases including inflammation, tissue growth and remodeling (Ahnstedt et al. 2012;Aro et al. 2013), pulmonary and systemic hypertension (Lundgren et al. 2012;Palei et al. 2013), sympathetic nervous activity, salt balance (Zicha et al. 2012), cardiac function (Perjes et al. 2012), arterial hypertension, aging (Nyberg, Mortensen, & Hellsten 2013) etc., while aging in turn modulates the endothelin system (Lind et al. 2013). Several in-depth reviews have covered the field (Dhaun, Webb, & Kluth 2012;Horinouchi et al. 2013;Kohan 2013;Kohan & Pollock 2013;Kuruppu, Rajapakse, & Smith 2013;Moorhouse et al. 2013;Rapoport & Zuccarello 2012;Vignon-Zellweger, Heiden, & Emoto 2011). This article is protected by copyright. All rights reserved.
No preview · Article · Jun 2014 · Acta Physiologica
[Show abstract][Hide abstract] ABSTRACT: Kidney International aims to inform the renal researcher and practicing nephrologists on all aspects of renal research. Clinical and basic renal research, commentaries, The Renal Consult, Nephrology sans Frontieres, minireviews, reviews, Nephrology Images, Journal Club. Published weekly online and twice a month in print.
No preview · Article · Feb 2014 · Kidney International
[Show abstract][Hide abstract] ABSTRACT: Recently, a proteomic study of sera from patients with bladder cancer identified S100A8 and S100A9 as tumor-associated proteins. The present cross-sectional study investigates whether calprotectin, the heterodimer of S100A8/S100A9 may serve as a urinary biomarker for the detection of urothelial bladder cancer.
Urinary calprotectin concentrations were assessed in a population of 181 subjects including 46 cases of bladder cancer. 41 cases of renal cell cancer, 54 cases of prostate cancer, and 40 healthy subjects served as control. Acute kidney injury, urinary tract infection, previous BCG-treatment and secondary transurethral resection of the bladder tumor were defined as exclusion criteria. Assessment was performed by enzyme-linked immunosorbent assay and immunohistochemistry detecting calprotectin.
Median calprotectin concentrations (ng/ml) were significantly higher in patients with bladder cancer than in healthy controls (522.3 vs. 51.0, p < 0.001), renal cell cancer (90.4, p < 0.001), and prostate cancer (71.8, p < 0.001). In urothelial carcinoma prominent immunostaining occurred in a subset of tumor cells and in infiltrating myeloid cells. Receiver operating characteristic analysis provided an area under the curve of 0.88 for the differentiation of bladder cancer and healthy control. A cut-off value of 140 ng/ml (determined by Youden's index) resulted in sensitivity and specificity values of 80.4 and 92.5 %. Low grade tumors were associated with significantly lower calprotectin concentrations than high grade tumors (351.9 vs. 1635.2 ng/ml, p = 0.004).
Urothelial malignancies are associated with highly increased concentrations of calprotecin in the urine. In absence of renal failure and pyuria, calprotectin constitutes a promising biomarker for the detection of bladder cancer.
No preview · Article · Dec 2013 · World Journal of Urology
[Show abstract][Hide abstract] ABSTRACT: Renal neurogenic hypertension (RNH) contributes to cardiovascular morbidity. Renal hypoxia may cause RNH and vice versa, leading to a vicious circle. Hypoxia adaptation is conferred through hypoxia-inducible factors (HIFs). We hypothesized that acute RNH is accompanied by increased renal vascular resistance (RVR) and that hypertension and increased RVR are countered by increasing HIF-1α by cobalt chloride (CoCl2) preconditioning.
First, we studied mean arterial pressure (MAP) and RVR in innervated or denervated contralateral kidneys in anesthetized rats before and after unilateral intrarenal injection of phenol, a manoeuvre known to elicit acute RNH. Then HIFα was induced by CoCl2 in drinking water (2 mM, 10 days) after which we compared intrarenal isotonic saline or phenol injection on MAP and RVR in CoCl2 preconditioned and control rats. HIF-1α was determined by immunohistochemistry.
Unilateral intrarenal phenol induced immediate rise in MAP and contralateral RVR, and comparable HIF-1α upregulation in both kidneys, consistent with bi-renal hypoxia. Removing the phenol-injected kidney immediately normalized MAP. Contralateral renal denervation had no effect on the rise in MAP, but abrogated the contralateral increase in RVR, suggesting mediation by increased efferent nerve activity. Strong renal staining for HIF-1α confirmed efficacy of CoCl2 preconditioning, and time-dependent increase in heme oxygenase-1 gene expression stabilization of HIFα. CoCl2 preconditioning prior to phenol reduced both ΔMAP (+10 ± 2 vs. +20 ± 3%, P = 0.015) and ΔRVR (+21 ± 11 vs. +90 ± 26%, P = 0.003).
Acute RNH leads to renal vasoconstriction and increased renal HIF-1α. Increasing HIF-1α by CoCl2 preconditioning ameliorates intrarenal phenol-induced RNH and renal vasoconstriction.
No preview · Article · Dec 2013 · Journal of Hypertension
[Show abstract][Hide abstract] ABSTRACT: Contrast-induced nephropathy (CIN) remains a leading cause of iatrogenic acute kidney injury, as the usage of contrast media for imaging and intravascular intervention keeps expanding. Diabetes is an important predisposing factor for CIN, particularly in patients with renal functional impairment. Renal hypoxia, combined with the generation of reactive oxygen species, plays a central role in the pathogenesis of CIN, and the diabetic kidney is particularly susceptible to intensified hypoxic and oxidative stress following the administration of contrast media. The pathophysiology of this vulnerability is complex and involves various mechanisms, including a priori enhanced tubular transport activity, oxygen consumption, and the generation of reactive oxygen species. The regulation of vascular tone and peritubular blood flow may also be altered, particularly due to defective nitrovasodilation, enhanced endothelin production, and a particular hyperresponsiveness to adenosine-related vasoconstriction. In addition, micro- and macrovascular diseases and chronic tubulointerstitial changes further compromise regional oxygen delivery, and renal antioxidant capacity might be hampered. A better understanding of these mechanisms and their control in the diabetic patient may initiate novel strategies in the prevention of contrast nephropathy in these susceptible patients.
[Show abstract][Hide abstract] ABSTRACT: Renal hypoxia occurs in AKI of various etiologies, but adaptation to hypoxia, mediated by hypoxia-inducible factor (HIF), is incomplete in these conditions. Preconditional HIF activation protects against renal ischemia-reperfusion injury, yet the mechanisms involved are largely unknown, and HIF-mediated renoprotection has not been examined in other causes of AKI. Here, we show that selective activation of HIF in renal tubules, through Pax8-rtTA-based inducible knockout of von Hippel-Lindau protein (VHL-KO), protects from rhabdomyolysis-induced AKI. In this model, HIF activation correlated inversely with tubular injury. Specifically, VHL deletion attenuated the increased levels of serum creatinine/urea, caspase-3 protein, and tubular necrosis induced by rhabdomyolysis in wild-type mice. Moreover, HIF activation in nephron segments at risk for injury occurred only in VHL-KO animals. At day 1 after rhabdomyolysis, when tubular injury may be reversible, the HIF-mediated renoprotection in VHL-KO mice was associated with activated glycolysis, cellular glucose uptake and utilization, autophagy, vasodilation, and proton removal, as demonstrated by quantitative PCR, pathway enrichment analysis, and immunohistochemistry. In conclusion, a HIF-mediated shift toward improved energy supply may protect against acute tubular injury in various forms of AKI.
No preview · Article · Aug 2013 · Journal of the American Society of Nephrology
[Show abstract][Hide abstract] ABSTRACT: In vitro studies suggest that combined activation of hypoxia-inducible factor (HIF) and signal transducer and activator of transcription 3 (STAT3) promotes the hypoxia response. However, their interrelationship in vivo remains poorly defined. The present study investigated the possible relationship between HIF-1 upregulation and STAT3 activation in the rodent kidney in vivo.Activation of HIF-1 and STAT3 was analysed by immunohistochemical staining and western blot analysis in: (i) models of hypoxia-associated kidney injury induced by radiocontrast media or rhabdomyolysis; (ii) following activation of STAT3 by the interleukin (IL)-6–soluble IL-6 receptor complex; or (iii) following HIF-1α stabilization using hypoxic and non-hypoxic stimuli (mimosine, FG-4497, CO, CoCl2) and in targeted von Hippel-Lindau-knockout mice.Western blot analysis and immunostaining revealed marked induction of both transcription factors under all conditions tested, suggesting that in vivo STAT3 can trigger HIF and vice versa.Colocalization of HIF-1α and phosphorylated STAT3 was detected in some, but not all, renal cell types, suggesting that in some cells a paracrine mechanism may be responsible for the reciprocal activation of the two transcription factors. Nevertheless, in several cell types spatial concordance was observed under the majority of conditions tested, suggesting that HIF-1 and STAT3 may act as cotranscription factors.These in vivo studies suggest that, in response to renal hypoxic-stress, upregulation of HIF-1 and activation of STAT3 may be both reciprocal and cell type dependent.
Full-text · Article · Apr 2013 · Clinical and Experimental Pharmacology and Physiology
[Show abstract][Hide abstract] ABSTRACT: Von Hippel-Lindau protein (VHL) provides the degradation of hypoxia-inducible factor (HIF). Tetracycline-induced, Pax8-rtTA-based knockout of VHL (VHL-KO) affects all renal tubules and periportal hepatocytes and leads to sustained upregulation of HIF. Here, we study the phenotype of VHL-KO in both organs, the time course of changes, and long-term morpho-functional outcome.
Mice with doxycycline-induced VHL-KO and controls (CON) were followed for up to 9 months. Systemic and tissue parameters were evaluated using clinical chemistry, histology, immunohistochemistry, RT-PCR and in situ hybridisation.
At day 3 following VHL-KO, substantial abundance of HIF-1α and -2α was detected in the nuclei of hepatocytes and renal tubular epithelia. Hypoxia, induced by bleeding anaemia, did not further augment HIF signal. Erythropoietin mRNA was detectable in hepatocytes but not in the kidney. Vascular endothelial growth factor mRNA was upregulated in kidney but not in liver. At day 7 following VHL-KO, the renal capillary density was enhanced, reaching its maximum at day 14. Blood haemoglobin increased constantly up to day 28 (23.3 vs. 15.8 g dL(-1) , VHL-KO vs. CON). Thereafter, it was kept within the normal range by weekly blood collections. Pathological changes were absent from kidney and liver 9 months after VHL-KO.
Inducible, Pax8-rtTA-based deletion of VHL leads to organ-specific expression of epithelial HIF and erythropoietin in liver and kidney without causing pathological changes. Uniform, maximal and sustained HIF activation along the renal tubule may serve to study the potential benefits of hypoxia adaptation in experimental renal injury.
No preview · Article · Mar 2013 · Acta Physiologica
[Show abstract][Hide abstract] ABSTRACT: Summary Hypoxia plays a crucial role in the pathophysiology of acute kidney injury (AKI) and presumably also chronic kidney disease (CKD). Hypoxia‐inducible factor (HIF) is the master transcription factor that regulates adaptive responses against hypoxia. Under hypoxic conditions, HIF activates target genes with hypoxia‐responsive elements in their regulatory regions. The HIF isoforms and regulators of HIF (i.e. prolyl hydroxylases) show cell type‐specific distributions. Hypoxia is observed in both ischaemic and so‐called non‐ischaemic forms of AKI. In addition to the acute phase, hypoxia may ensue during the recovery phase of AKI, possibly due to the oxygen‐consuming processes of cell growth and proliferation for repair. Although HIF protects the kidney against AKI, intrinsic HIF activation is submaximal in AKI and further augmentation of HIF ameliorates disease manifestations. The kidney in CKD also suffers from hypoxia caused by multiple mechanisms, including sustained oxygen demands in the remaining nephrons due to maladaptive tubuloglomerular feedback. Whether HIF is chronically upregulated in CKD is contentious. Hypoxia‐inducible factor activation is a promising therapeutic approach to CKD, but excessive activation of HIF may be deleterious. It is likely that there is a therapeutic window of HIF activation in chronic conditions. Under certain circumstances, animals with CKD are protected against AKI and this may be explained by non‐physiological hypoxia of the kidney and subsequent HIF expression. In addition, an acute hypoxic insult may induce long‐lasting changes, possibly including epigenetic modifications induced by HIF. These observations suggest a complex interaction between AKI and CKD via hypoxia and HIF activation.
Preview · Article · Feb 2013 · Clinical and Experimental Pharmacology and Physiology
[Show abstract][Hide abstract] ABSTRACT: Aim:
In the present study, we aimed to elucidate the effects of chronic vasopressin administration on renal medullary oxygen levels.
Adult Sprague Dawley or vasopressin-deficient Brattleboro rats were treated with the vasopressin V2 receptor agonist, desmopressin (5 ng/h; 3d), or its vehicle via osmotic minipumps. Immunostaining for pimonidazole and the transcription factor HIF-1α (hypoxia-inducible factor-1α) were used to identify hypoxic areas. Activation of HIF-target gene expression following desmopressin treatment was studied by microarray analysis.
Pimonidazole staining was detected in the outer and inner medulla of desmopressin-treated rats, whereas staining in control animals was weak or absent. HIF-1α immunostaining demonstrated nuclear accumulation in the papilla of desmopressin-treated animals, whereas no staining was observed in the controls. Gene expression analysis revealed significant enrichment of HIF-target genes in the group of desmopressin-regulated gene products (P = 2.6*10(-21) ). Regulated products included insulin-like growth factor binding proteins 1 and 3, angiopoietin 2, fibronectin, cathepsin D, hexokinase 2 and cyclooxygenase 2.
Our results demonstrate that an activation of the renal urine concentrating mechanism by desmopressin causes renal medullary hypoxia and an upregulation of hypoxia-inducible gene expression.
No preview · Article · Jan 2013 · Acta Physiologica
[Show abstract][Hide abstract] ABSTRACT: Hypoxia plays a role in ischemic, toxic and sepsis-induced acute kidney injury. Evolving hypoxia triggers renal adaptive responses
that may mitigate the insult, leading to sublethal forms of cell injury. The unique capability of the kidney to downregulate
oxygen consumption for tubular transport could represent one such adaptive response which promotes maintenance of renal oxygenation,
thereby preserving cellular integrity. Tran et al. recently explored a novel mechanism that might prevent tubular damage by downregulation of mitochondrial biogenesis and oxygen
consumption. Using expression profiling of kidney RNA in endotoxemic rodents and complementary studies in vitro and in PGC-1α knockout mice, they found a sepsis-related decline in PPARγ coactivator-1α (PGC-1α) expression and of PGC-1α-dependent
genes involved in oxidative phosphorylation. This response may explain their observation of a paradoxical preservation of
kidney oxygenation and structural integrity in sepsis, despite reduced renal blood flow and oxygen delivery. Thus, resetting
of mitochondrial respiration and oxygen consumption during sepsis might be added to the growing list of adaptive responses
that occur during hypoxic stress. This review will focus on these mechanisms that mitigate evolving hypoxic injury, even at
the expense of transient renal dysfunction.
Preview · Article · May 2012 · Nephrology Dialysis Transplantation
[Show abstract][Hide abstract] ABSTRACT: Nephron loss in a diseased kidney invokes adaptations in the remaining nephrons. Whether and how these adaptations condition the response of the kidney to injury is not known. We examined the susceptibility of the kidney after subtotal (5/6th) nephrectomy (STN) to ischemic injury in rats. GFR in STN kidneys did not significantly change after ischemia reperfusion (IR), whereas GFR fell by 70% after IR in unilateral nephrectomy controls. In micropuncture experiments, single-nephron GFR responses mirrored the whole-kidney responses: in STN, single-nephron GFR decreased by 7% after IR compared with 28% in controls. Furthermore, we found that tubuloglomerular feedback, a mechanism that links proximal tubular injury to a fall in GFR, was inoperative in STN but was normal in controls. Restoration of normal feedback in STN attenuated the functional resistance to IR. In addition to the functional resilience, the morphology of the kidney was better preserved in STN. In STN kidneys, the S3 segment of the proximal tubule, normally injured after ischemia, constitutively expressed hypoxia-inducible factor-1α (HIF-1α), which is cytoprotective in ischemia. Inducing HIF before IR improved GFR in control animals, and inhibiting the HIF target heme-oxygenase-1 before IR reduced GFR in STN animals. Taken together, these data suggest that fewer functioning nephrons in a diseased kidney do not increase the susceptibility to injury, but rather, hemodynamic and molecular adaptations in the remnant nephrons precondition them against ischemic injury.
No preview · Article · Mar 2012 · Journal of the American Society of Nephrology
[Show abstract][Hide abstract] ABSTRACT: The Hypoxia-inducible transcription Factor (HIF) represents an important adaptive mechanism under hypoxia, whereas sustained activation may also have deleterious effects. HIF activity is determined by the oxygen regulated α-subunits HIF-1α or HIF-2α. Both are regulated by oxygen dependent degradation, which is controlled by the tumor suppressor "von Hippel-Lindau" (VHL), the gatekeeper of renal tubular growth control. HIF appears to play a particular role for the kidney, where renal EPO production, organ preservation from ischemia-reperfusion injury and renal tumorigenesis are prominent examples. Whereas HIF-1α is inducible in physiological renal mouse, rat and human tubular epithelia, HIF-2α is never detected in these cells, in any species. In contrast, distinct early lesions of biallelic VHL inactivation in kidneys of the hereditary VHL syndrome show strong HIF-2α expression. Furthermore, knockout of VHL in the mouse tubular apparatus enables HIF-2α expression. Continuous transgenic expression of HIF-2α by the Ksp-Cadherin promotor leads to renal fibrosis and insufficiency, next to multiple renal cysts. In conclusion, VHL appears to specifically repress HIF-2α in renal epithelia. Unphysiological expression of HIF-2α in tubular epithelia has deleterious effects. Our data are compatible with dedifferentiation of renal epithelial cells by sustained HIF-2α expression. However, HIF-2α overexpression alone is insufficient to induce tumors. Thus, our data bear implications for renal tumorigenesis, epithelial differentiation and renal repair mechanisms.
[Show abstract][Hide abstract] ABSTRACT: The pathogenesis of sepsis-induced acute kidney injury (AKI) is not fully understood, and may involve altered systemic hemodynamics and renal circulation, renal hypoxia and perhaps direct tubular toxicity. Oxidative stress, induced by systemic and intrarenal generation of reactive oxygen species (ROS) can directly exert renal parenchymal damage and may intensify renal microvascular and functional dysregulation, with a feedforward loop of hypoxia and ROS generation. Herein we review compelling evidence that sepsis is associated with systemic and intrarenal intense oxidative and nitrosative stress with a depletion of antioxidant capacity. Inflammation and tissue hypoxia conceivably play a central role in the generation of ROS in the septic patient. Though oxidative and nitrosative stress are likely to participate in the pathogenesis of sepsis-induced AKI, it is impossible to clearly identify their isolated independent role and renal-specific effect since there are complex interactions involved linking various affected organs, ROS generation with altered systemic hemodynamics, compromised microcirculation, hypoxia and distorted cellular function. Facing this complex disease entity, alleviation of oxidative stress single-handedly is unlikely to be effective in the prevention of sepsis-associated renal dysfunction. However, the addition of antioxidants to a comprehensive treatment strategy seems a reasonable approach.
No preview · Article · Sep 2011 · Contributions to nephrology
[Show abstract][Hide abstract] ABSTRACT: In chronic renal disease, the temporal and spatial relationship between vascular, glomerular and tubular changes is still unclear. Hypertension, an important cause of chronic renal failure, leads to afferent arteriolopathy, segmental glomerulosclerosis and tubular atrophy in the juxtamedullary cortex. We investigated the pathological changes of hypertensive renal disease in aged spontaneously hypertensive rats using a large number of serial sections, where we traced and analyzed afferent arteriole, glomerulus and proximal tubule of single nephrons. Our major finding was that both afferent arteriolopathy and glomerular capillary collapse were linked to tubular atrophy. Only nephrons with glomerular collapse (n = 13) showed tubules with reduced diameter indicating atrophy [21.66 ± 2.56 μm vs. tubules in normotensive Wistar Kyoto rats (WKY) 38.56 ± 0.56 μm, p < 0.05], as well as afferent arteriolar wall hypertrophy (diameter 32.74 ± 4.72 μm vs. afferent arterioles in WKY 19.24 ± 0.98 μm, p < 0.05). Nephrons with segmental sclerosis (n = 10) did not show tubular atrophy and tubular diameters were unchanged (35.60 ± 1.43 μm). Afferent arteriolar diameter negatively correlated with glomerular capillary volume fraction (r = -0.36) and proximal tubular diameter (r = -0.46) implying reduced glomerular and tubular flow. In line with this, chronically damaged tubules showed reduced staining for the ciliary protein inversin indicating changed ciliary signalling due to reduced urinary flow. This is the first morphological study on hypertensive renal disease making correlations between vascular, glomerular and tubular components of individual nephron units. Our data suggest that afferent arteriolopathy leads to glomerular collapse and reduced urinary flow with subsequent tubular atrophy.
Full-text · Article · Jun 2011 · Archiv für Pathologische Anatomie und Physiologie und für Klinische Medicin
[Show abstract][Hide abstract] ABSTRACT: For decades severe tubular necrosis has been the hallmark of experimental models of acute renal failure (ARF), such as prolonged ischemia and reflow. This fits well with the still widely used traditional clinical term 'acute tubular necrosis'. Nevertheless, the rareness of tubular necrosis in human kidney biopsies in the background of hypoxic, toxic and septic AKI led to the adoption of a new term, 'acute kidney injury' (AKI), which refers to such clinical scenarios irrespective of the renal morphology. Indeed, experimental AKI models, which have more limited acute renal parenchymal compromise, underscore the focal and regional tissue injury patterns that range from adaptive stress response, through cellular dysfunction, apoptotic cell death and frank acute tubular necrosis. Such stress and injury patterns, short of necrosis, may go unnoticed morphologically and even functionally, and may even confer resistance to subsequent insults. Herein we describe the spectrum of what we call 'sublethal injury', referring to a condition, which by itself is insufficient to produce cellular death, but may or may not produce organ failure. Such sublethal injury can be detected by overt morphological changes, by the upregulation of cell survival factors, and by recently developed biomarkers and imaging techniques of organ physiology and dysfunction. The use of combined sublethal insults in animal models is an attempt to replicate the clinical situation of comorbidities, a circumstance which underlies most situations of AKI. This review will discuss the definition of such sublethal injury and the modes of its detection.
No preview · Article · Jan 2011 · Contributions to nephrology