Calcium channel Orai1 promotes lymphocyte IL-17 expression and progressive kidney injury

We hypothesized that the store-operated calcium entry (SOCE) channel, Orai1, participates in the activation of Th17 cells and influences renal injury. In rats, following renal ischemia/reperfusion (I/R), there was a rapid and sustained influx of Orai1+ CD4 T cells and IL-17 expression was restricted to Orai1+ cells. When kidney CD4+ cells of post-acute kidney injury (post-AKI) rats were stimulated with angiotensin II and elevated Na+ (10-7 M/170 mM) in vitro, there was an enhanced response in intracellular Ca2+ and IL-17 expression, which was blocked by SOCE inhibitors 2APB, YM58483/BTP2, or AnCoA4. In vivo, YM58483/BTP2 (1 mg/kg) attenuated IL-17+ cell activation, inflammation, and severity of AKI following either I/R or intramuscular glycerol injection. Rats treated with high-salt diet (5-9 weeks after I/R) manifested progressive disease indicated by enhanced inflammation, fibrosis, and impaired renal function. These responses were significantly attenuated by YM58483/BTP2. In peripheral blood of critically ill patients, Orai1+ cells were significantly elevated by approximately 10-fold and Th17 cells were elevated by approximately 4-fold in AKI versus non-AKI patients. Further, in vitro stimulation of CD4+ cells from AKI patients increased IL-17, which was blocked by SOCE inhibitors. These data suggest that Orai1 SOCE is a potential therapeutic target in AKI and CKD progression

Renal endothelial dysfunction in acute kidney ischemia reperfusion injury

Acute kidney injury is associated with alterations in vascular tone that contribute to an overall reduction in GFR. Studies in animal models indicate that ischemia triggers alterations in endothelial function that contribute significantly to the overall degree and severity of a kidney injury. Putative mediators of vasoconstriction that may contribute to the initial loss of renal blood flow and GFR are highlighted. In addition, there is discussion of how intrinsic damage to the endothelium impairs homeostatic responses in vascular tone as well as promotes leukocyte adhesion and exacerbating the reduction in renal blood flow. The timing of potential therapies in animal models as they relate to the evolution of AKI, as well as the limitations of such approaches in the clinical setting are discussed. Finally, we discuss how acute kidney injury induces permanent alterations in renal vascular structure. We posit that the cause of the sustained impairment in kidney capillary density results from impaired endothelial growth responses and suggest that this limitation is a primary contributing feature underlying progression of chronic kidney disease

A 3/2-approximation algorithm for some minimum-cost graph problems

International audienceWe consider a class of graph problems introduced in a paper of Goemans and Williamson that involve finding forests of minimum edge cost. This class includes a number of location/routing problems; it also includes a problem in which we are given as input a parameter k, and want to find a forest such that each component has at least k vertices. Goemans and Williamson gave a 2-approximation algorithm for this class of problems. We give an improved 3/2-approximation algorithm

Anti-angiogenic activity of kidney derived endothelial cells

poster abstractThe identification of novel endogenous mediators of angiogenic/vasculogenic processes may provide for novel therapeutic targets to modulate blood vessel growth in disease states, such as cardiovascular disease or cancer. Studies in our lab have shown that blood vessels in kidney have little endogenous regenerative capacity. Kidney derived microvascular endothelial cells (KEC) were isolated from rat kidney or from transgenic mice bearing the temperature sensitive SV40 mutant (and subsequently grown at non-permissive temperature, 37oC). Both rat and mouse KECs manifested significantly reduced growth rates when compared with several commonly used EC lines (rat pulmonary EC, HUVEC and human cord blood colony forming ECs). In 2D matrigel assays, all commonly used ECs faithfully formed characteristic branching structures; while all KECs failed to form stabile branching structures. Time-course analysis of branching activity demonstrated that KEC initially formed primitive branching nodes within 3 hours of culture, but these structures regressed such that no branched structures were observed between 6-12 hours. Co-culture of KECs with any branching competent EC impaired branching dose dependently. When co-cultured with ECFC, labeled KECs incorporated into primitive ECFC branches within the first 3 hours of plating. However, when compared with ECFC branches, ECFC-KEC mixed branches showed a more rapid regression of the branched structures between 12-24 hrs. Interestingly, conditioned media from KEC did not affect branching of competent ECFC. Taken together, these data indicate that KEC have anti-angiogenic activity that may destabilize ECs during angiogenesis. The anti-angiogenic activity requires cell-cell contact, suggesting the possible presence of an angio-inhibitory molecule on the cell surface of KECs. Current and future studies seek to generate additional KEC lines, and will determine if KEC cell fractions mediate the anti-angiogenic effect. In addition, we will seek to determine if KECs mitigate progression of angiogenic dependent tumor formation in vivo

Macrophage dynamics in kidney repair: elucidation of a COX-2–dependent MafB pathway to affect macrophage differentiation

Following acute injury to the kidney, macrophages play an important role in recovery of functional and structural integrity, but organ fibrosis and progressive functional decline occur with incomplete recovery. Pro-resolving macrophages are characterized by increased cyclooxygenase 2 (COX-2) expression and this expression was selectively increased in kidney macrophages following injury and myeloid-specific COX-2 deletion inhibited recovery. Deletion of the myeloid prostaglandin E2 (PGE2) receptor, E-type prostanoid receptor 4 (EP4), mimicked effects seen with myeloid COX-2-/- deletion. PGE2-mediated EP4 activation induced expression of the transcription factor MafB in kidney macrophages, which upregulated antiinflammatory genes and suppressed pro-inflammatory genes. Myeloid Mafb deletion recapitulated the effects seen with either myeloid COX-2 or EP4 deletion following acute kidney injury, with delayed recovery, persistent presence of pro-inflammatory kidney macrophages, and increased kidney fibrosis. Thus, our studies identified a previously unknown mechanism by which prostaglandins modulate macrophage phenotype following acute organ injury and provide new insight into mechanisms underlying detrimental kidney effects of non-steroidal antiinflammatory drugs that inhibit cyclooxygenase activity

Endothelial colony-forming cells and pro-angiogenic cells: clarifying definitions and their potential role in mitigating acute kidney injury

Acute kidney injury (AKI) represents a significant clinical concern that is associated with high mortality rates and also represents a significant risk factor for the development of chronic kidney disease (CKD). This article will consider alterations in renal endothelial function in the setting of AKI that may underlie impairment in renal perfusion and how inefficient vascular repair may manifest post-AKI and contribute to the potential transition to CKD. We provide updated terminology for cells previously classified as ‘endothelial progenitor’ that may mediate vascular repair such as pro-angiogenic cells and endothelial colony-forming cells. We consider how endothelial repair may be mediated by these different cell types following vascular injury, particularly in models of AKI. We further summarize the potential ability of these different cells to mitigate the severity of AKI, improve perfusion and maintain vascular structure in pre-clinical studies

Th-17 cell activation in response to high salt following acute kidney injury is associated with progressive fibrosis and attenuated by AT-1R antagonism

Exposure of rats to elevated dietary salt following recovery from acute kidney injury (AKI) accelerates the transition to chronic kidney disease (CKD), and is dependent on lymphocyte activity. Here we tested whether high salt diet triggers lymphocyte activation in postischemic kidneys to worsen renal inflammation and fibrosis. Male Sprague-Dawley rats on a 0.4% salt diet were subjected to left unilateral ischemia-reperfusion and allowed to recover for 5 weeks. This resulted in a mild elevation of CD4(+) T cells relative to sham animals. Contralateral unilateral nephrectomy and elevated dietary salt (4%) for 4 extra weeks hastened CKD and interstitial fibrosis. Activated T cells were increased in the kidney threefold after 4 weeks of elevated dietary salt exposure relative to post-AKI rats before salt feeding. The T cell subset was largely positive for IL-17, indicative of Th-17 cells. Because angiotensin II activity may influence lymphocyte activation, injured rats were given the AT1R antagonist, losartan, along with high salt diet. This significantly reduced the number of renal Th-17 cells to levels of sham rats, and significantly reduced the salt-induced increase in fibrosis to about half. In vitro studies in AKI-primed CD4(+) T cells indicated that angiotensin II and extracellular sodium enhanced, and losartan inhibited, IL-17 expression. Thus, dietary salt modulates immune cell activity in postischemic recovering kidneys because of the activity of local RAS, suggesting the participation of these cells in CKD progression post-AKI

Human adipose stromal cell therapy improves survival and reduces renal inflammation and capillary rarefaction in acute kidney injury

Damage to endothelial cells contributes to acute kidney injury (AKI) by causing impaired perfusion, while the permanent loss of the capillary network following AKI has been suggested to promote chronic kidney disease. Therefore, strategies to protect renal vasculature may impact both short-term recovery and long-term functional preservation post-AKI. Human adipose stromal cells (hASCs) possess pro-angiogenic and anti-inflammatory properties and therefore have been tested as a therapeutic agent to treat ischaemic conditions. This study evaluated hASC potential to facilitate recovery from AKI with specific attention to capillary preservation and inflammation. Male Sprague Dawley rats were subjected to bilateral ischaemia/reperfusion and allowed to recover for either two or seven days. At the time of reperfusion, hASCs or vehicle was injected into the suprarenal abdominal aorta. hASC-treated rats had significantly greater survival compared to vehicle-treated rats (88.7% versus 69.3%). hASC treatment showed hastened recovery as demonstrated by lower creatinine levels at 48 hrs, while tubular damage was significantly reduced at 48 hrs. hASC treatment resulted in a significant decrease in total T cell and Th17 cell infiltration into injured kidneys at 2 days post-AKI, but an increase in accumulation of regulatory T cells. By day 7, hASC-treated rats showed significantly attenuated capillary rarefaction in the cortex (15% versus 5%) and outer medulla (36% versus 18%) compared to vehicle-treated rats as well as reduced accumulation of interstitial alpha-smooth muscle actin-positive myofibroblasts. These results suggest for the first time that hASCs improve recovery from I/R-induced injury by mechanisms that contribute to decrease in inflammation and preservation of peritubular capillaries

Effect of renal shock wave lithotripsy on the development of metabolic syndrome in a juvenile swine model: a pilot study

PURPOSE: We performed a pilot study to assess whether renal shock wave lithotripsy influences metabolic syndrome onset and severity. MATERIALS AND METHODS: Three-month-old juvenile female Ossabaw miniature pigs were treated with shock wave lithotripsy (2,000 shock waves at 24 kV with 120 shock waves per minute in 2) or sham shock wave lithotripsy (no shock waves in 2). Shock waves were targeted to the upper pole of the left kidney to model treatment that would also expose the pancreatic tail to shock waves. Pigs were then instrumented to directly measure arterial blood pressure via an implanted radiotelemetry device. They later received a hypercaloric atherogenic diet for about 7 months. Metabolic syndrome development was assessed by the intravenous glucose tolerance test. RESULTS: Metabolic syndrome progression and severity were similar in the sham treated and lithotripsy groups. The only exception arterial blood pressure, which remained relatively constant in sham treated pigs but began to increase at about 2 months towards hypertensive levels in lithotripsy treated pigs. Metabolic data on the 2 groups were pooled to provide a more complete assessment of metabolic syndrome development and progression in this juvenile pig model. The intravenous glucose tolerance test revealed substantial insulin resistance with impaired glucose tolerance within 2 months on the hypercaloric atherogenic diet with signs of further metabolic impairment at 7 months. CONCLUSIONS: These preliminary results suggest that renal shock wave lithotripsy is not a risk factor for worsening glucose tolerance or diabetes mellitus onset. However, it appears to be a risk factor for early onset hypertension in metabolic syndrome