20-Hydroxyeicosatetraenoic acid (20-HETE) production is increased in ischemic kidney tissue and may contribute to ischemia/reperfusion (I/R) injury by mediating vasoconstriction and inflammation. To test this hypothesis, uninephrectomized male Lewis rats were exposed to warm ischemia following pretreatment with either an inhibitor of 20-HETE synthesis (HET0016), an antagonist (20-hydroxyeicosa-6(Z),15(Z)-dienoic acid), an agonist (20-hydroxyeicosa-5(Z),14(Z)-dienoic acid), or vehicle via the renal artery and the kidneys were examined 2 days after reperfusion. Pretreatment with either the inhibitor or the antagonist attenuated I/R-induced renal dysfunction as shown by improved creatinine clearance and decreased plasma urea levels, compared to controls. The inhibitor and antagonist also markedly reduced tubular lesion scores, inflammatory cell infiltration, and tubular epithelial cell apoptosis. Administering the antagonist accelerated the recovery of medullary perfusion, as well as renal medullary and cortical re-oxygenation, during the early reperfusion phase. In contrast, the agonist did not improve renal injury and reversed the beneficial effect of the inhibitor. Thus, 20-HETE generation and its action mediated kidney injury due to I/R. Whether or not these effects are clinically important will need to be tested in appropriate human studies.

Because of the prominent vascular injury, strategies for endothelial protection should be attempted in grafts with long preservation times in clinical renal transplantation.

Acute kidney injury of various origins shares a common link in the pathophysiological chain of events: imbalance between renal medullary oxygen delivery and oxygen demand. For in vivo assessment of kidney haemodynamics and oxygenation in animals, quantitative but invasive physiological methods are established. A very limited number of studies attempted to link these invasive methods with parametric Magnetic Resonance Imaging (MRI) of the kidney. Moreover, the validity of parametric MRI (pMRI) as a surrogate marker for renal tissue perfusion and renal oxygenation has not been systematically examined yet. For this reason, we set out to combine invasive techniques and non-invasive MRI in an integrated hybrid setup (MR-PHYSIOL) with the ultimate goal to calibrate, monitor and interpret parametric MR and physiological parameters by means of standardized interventions. Here we present a first report on the current status of this multi-modality approach. For this purpose, we first highlight key characteristics of renal perfusion and oxygenation. Second, concepts for in vivo characterization of renal perfusion and oxygenation are surveyed together with the capabilities of MRI for probing blood oxygenation-dependent tissue stages. Practical concerns evoked by the use of strong magnetic fields in MRI and interferences between MRI and invasive physiological probes are discussed. Technical solutions that balance the needs of in vivo physiological measurements together with the constraints dictated by small bore MR scanners are presented. An early implementation of the integrated MR-PHYSIOL approach is demonstrated including brief interventions of hypoxia and hyperoxia.

Ischemia/reperfusion (I/R) injury, a consequence of kidney hypoperfusion or temporary interruption of blood flow is a common cause of acute kidney injury (AKI). There is an unmet need to better understand the mechanisms operative during the initial phase of ischemic AKI. Non-invasive in vivo parametric magnetic resonance imaging (MRI) may elucidate spatio-temporal pathophysiological changes in the kidney by monitoring the MR relaxation parameters T2* and T2, which are known to be sensitive to blood oxygenation. The aim of our study was to establish the technical feasibility of fast continuous T2*/T2 mapping throughout renal I/R. MRI was combined with a remotely controlled I/R model and a segmentation model based semi-automated quantitative analysis. This technique enabled the detailed assessment of in vivo changes in all kidney regions during ischemia and early reperfusion. Significant changes in T2* and T2 were observed shortly after induction of renal ischemia and during the initial reperfusion phase. Our study demonstrated for the first time that continuous and high temporal resolution parametric MRI is feasible for in-vivo monitoring and characterization of I/R induced AKI in rats. This technique may help in the identification of the timeline of key events responsible for development of renal damage in hypoperfusion-induced AKI.

ground. We suggest that initial injury prevention should receive Ischemia-reperfusion injury in renal transplantation is indethe highest priority. pendent of the immunologic background.Background. Adhesion molecule expression is important to early transplant failure. However, whether or not adhesion molecule-facilitated inflammation is antigen-dependent is un-Ischemia-reperfusion injury is an important problem known. We tested this hypothesis. in organ transplantation. Grafts with prolonged cold or Methods. Rat renal grafts were four-hours cold-preserved in University of Wisconsin (UW) solution, transplanted to synwarm ischemia times are more susceptible to short-term geneic or allogeneic recipients, and harvested after 2, 6, 12, 24, or long-term deterioration [1,2]. Clarifying the pathoand 48 hours and after 1 week. The first allogeneic group physiology of ischemia-reperfusion injury and develreceive no immunosuppression; two additional groups received oping new preventive strategies are highly important. either low (1.5 mg/kg) or standard (5 mg/kg) cyclosporine A In native organs, numerous experimental and clinical (CsA). Renal function and morphology were determined; frozen sections were immunostained for P-selectin, L-selectin, studies showed that ischemia reperfusion constitutes an intercellular adhesion molecule-1 (ICAM-1), vascular cell adacute inflammatory process involving cell surface adhehesion molecule-1 (VCAM-1), platelet endothelial cell adhesion molecule expression. These molecules are crucial sion molecule-1 (PECAM-1), leukocyte function associated for the recruitment and infiltration of effector cells into molecule-1 (LFA-1), very late antigen-4 (VLA-4), as well as for neutrophils and monocytes. the postischemic tissue [3]. In transplanted organs, the Results. Selectins increased rapidly at 2 hours and quickly same mechanisms are also involved in subsequently inidecreased by 12 hours. While P-selectin was expressed on vastiating the rejection process [4]. However, to what extent culature, L-selectin was found on inflammatory cells. Neutroalloantigen-dependent mechanisms contribute to the iniphil influx and that of LFA-1-positive cells occurred early, tial injury and whether or not ischemia-reperfusion is an peaked between 12 and 24 hours, and paralleled the maximal impairment in renal function. ICAM-1 and PECAM-1 showed alloantigen-independent phenomenon are unclear. Alsimilar kinetics and a diffuse distribution. VCAM-1 increased though numerous studies have addressed antiadhesion more slowly after 12 hours, peaked at 24 hours, and was localstrategies in rodent models of ischemia reperfusion [5,6], ized predominantly on the endothelium of elastic vessels. Bethe sequence in which different cell subsets arrive and tween 24 hours and 1 week, all grafts progressively developed their time course in relationship to ischemia reperfusion dense VLA-4-positive monocytic infiltrates adjacent to vessels expressing VCAM-1. Functional, morphological, and immunohave not been extensively studied. We tested the h...

Acute kidney injury (AKI) induced by ischaemia and reperfusion (I/R) injury is a common and severe clinical problem. Vascular dysfunction, immune system activation and tubular epithelial cell injury contribute to functional and structural deterioration. The search for novel therapeutic interventions for I/R-induced AKI is a dynamic area of experimental research. Pharmacological targeting of injury mediators and corresponding intracellular signalling in endothelial cells, inflammatory cells and the injured tubular epithelium could provide new opportunities yet may also pose great translational challenge. Here, we focus on signalling mediators, their receptors and intracellular signalling pathways which bear potential to abrogate cellular processes involved in the pathogenesis of I/R-induced AKI. Sphingosine 1 phosphate (S1P) and its respective receptors, cytochrome P450 (CYP450)-dependent vasoactive eicosanoids, NF-κB- and protein kinase-C (PKC)-related pathways are representatives of such 'druggable' pleiotropic targets. For example, pharmacological agents targeting S1P and PKC isoforms are already in clinical use for treatment for autoimmune diseases and were previously subject of clinical trials in kidney transplantation where I/R-induced AKI occurs as a common complication. We summarize recent in vitro and in vivo experimental studies using pharmacological and genomic targeting and highlight some of the challenges to clinical application of these advances.

Abstract-We found earlier that deoxycorticosterone acetate-salt treatment causes blood pressure-independent left ventricular hypertrophy, but only in male mice. To test the hypothesis that the estrogen receptor-␤ (ER␤) protects the females from left ventricular hypertrophy, we treated male and female ER␤-deficient (ER␤ Ϫ/Ϫ ) mice and their male and female littermates (wild-type [WT]) with deoxycorticosterone acetate-salt and made them telemetrically normotensive with hydralazine. WT males had increased (ϩ16%) heart weight/tibia length ratios compared with WT females (ϩ7%) at 6 weeks. In ER␤ Ϫ/Ϫ mice, this situation was reversed. Female WT mice had the greatest heart weight/tibia length ratio increases of all of the groups (ϩ23%), even greater than ER␤ Ϫ/Ϫ males (ϩ10%). Echocardiography revealed concentric left ventricular hypertrophy in male WT mice, whereas ER␤ Ϫ/Ϫ females developed dilative left ventricular hypertrophy. The hypertrophic response in female ER␤ Ϫ/Ϫ mice was accompanied by the highest degree of collagen deposition, indicating maladaptive remodeling. ER␤ ϩ/ϩ females showed robust protective p38 and extracellular signal-regulated kinase 1/2 signaling relationships compared with other groups. Calcineurin A␤ expression and its positive regulator myocyte-enriched calcineurin-interacting protein 1 were increased in deoxycorticosterone acetate-salt female ER␤ Ϫ/Ϫ mice, yet lower than in WT males. Endothelin increased murine cardiomyocyte hypertrophy in vitro, which could be blocked by estradiol and an ER␤ agonist. We conclude that a functional ER␤ is essential for inducing adaptive p38 and extracellular signal-regulated kinase signaling, while reducing maladaptive calcineurin signaling in normotensive deoxycorticosterone acetate female mice. Our findings address the possibility of sex-specific cardiovascular therapies. Key Words: estrogen receptor-␤, heart Ⅲ hypertrophy Ⅲ fibrosis Ⅲ calcineurin Ⅲ p38 MAPK Ⅲ ERK1/2 F emales seem to be relatively protected from cardiovascular disease on the basis of animal and human studies; estrogens could play a role. 1-3 Clinical trials using estrogens for improving cardiovascular health were disappointing, perhaps because of poor estrogen receptor (ER) isoform selectivity and specificity. 4 The 2 functional isoforms, ER␣ and ER␤, are expressed in the myocardium. 5 Receptor-mediated effects of estrogens on cardiomyocyte biology are injury or stimulus dependent, 4,6 which, in turn, implicates activation of distinct, sex-dependent, signaling pathways and gene expression programs. 7 We described recently a sex-specific dimorphism in cardiac adaptation in response to deoxycorticosterone acetate (DOCA)-salt and showed that this response was independent of blood pressure. 8 Male mice developed left ventricular hypertrophy (LVH) that was linked to activation of a calcineurin-dependent pathway, which increased proinflammatory and profibrotic responses. In contrast, female DOCA mice maintained their initial physiological adaptive cardiac phenotype despite mineralocorticoid and...

Aim: Imbalances in cytochrome P450 (CYP)-dependent eicosanoid formation may play a central role in ischemic acute kidney injury (AKI). We reported previously that inhibition of 20-hydroxyeicosatetraenoic acid (20-HETE) action ameliorated ischemia/reperfusion (I/R)-induced AKI in rats. Now we tested the hypothesis that enhancement of epoxyeicosatrienoic acid (EET) actions may counteract the detrimental effects of 20-HETE and prevent the initiation of AKI. Methods: Male Lewis rats underwent right nephrectomy and ischemia was induced by 45 min clamping of the left renal pedicle followed by up to 48 h of reperfusion.Circulating CYP-eicosanoid profiles were compared in patients who underwent cardiac surgery with (n = 21) and without (n = 38) developing postoperative AKI. Results: Ischemia induced an about eightfold increase of renal 20-HETE levels, whereas free EETs were not accumulated. To compensate for this imbalance, a synthetic 14,15-EET analogue was administered by intrarenal infusion before ischemia.The EET analogue improved renal reoxygenation as monitored by in vivo parametric MRI during the initial 2 h reperfusion phase. The EET analogue improved PI3Kas well as mTORC2-dependent rephosphorylation of Akt, induced inactivation of GSK-3β, reduced the development of tubular apoptosis and attenuated inflammatory cell infiltration. The EET analogue also significantly alleviated the I/R-induced drop