Genetic Deletion of LRP5 and LRP6 in Macrophages Exacerbates Colitis-Associated Systemic Inflammation and Kidney Injury in Response to Intestinal Commensal Microbiota.

Extraintestinal manifestations are common in inflammatory bowel disease and involve several organs, including the kidney. However, the mechanisms responsible for renal manifestation in inflammatory bowel disease are not known. In this study, we show that the Wnt-lipoprotein receptor-related proteins 5 and 6 (LRP5/6) signaling pathway in macrophages plays a critical role in regulating colitis-associated systemic inflammation and renal injury in a murine dextran sodium sulfate-induced colitis model. Conditional deletion of the Wnt coreceptors LRP5/6 in macrophages in mice results in enhanced susceptibility to dextran sodium sulfate colitis-induced systemic inflammation and acute kidney injury (AKI). Furthermore, our studies show that aggravated colitis-associated systemic inflammation and AKI observed in LRP5/6LysM mice are due to increased bacterial translocation to extraintestinal sites and microbiota-dependent increased proinflammatory cytokine levels in the kidney. Conversely, depletion of the gut microbiota mitigated colitis-associated systemic inflammation and AKI in LRP5/6LysM mice. Mechanistically, LRP5/6-deficient macrophages were hyperresponsive to TLR ligands and produced higher levels of proinflammatory cytokines, which are associated with increased activation of MAPKs. These results reveal how the Wnt-LRP5/6 signaling in macrophages controls colitis-induced systemic inflammation and AKI.

Perinatal intermittent hypoxia increases early susceptibility to ANG II-induced hypertension in adult male but not in female Sprague-Dawley rats.

Prenatal, perinatal, and adulthood exposure to chronic intermittent hypoxia (IH) increases blood pressure in rodents. Males exposed to chronic IH have higher blood pressure versus females. However, it is unknown if this same-sex difference exists with acute perinatal IH. We tested the hypothesis that acute perinatal IH increases baseline blood pressure and enhances sensitivity to angiotensin II (ANG II)-induced hypertension in male Sprague-Dawley rats. Male and female pups were randomized to control (room air) or IH (10 min of ∼10% O2 for 3 times/day) for the first 8 days of life. IH decreased oxygen saturation, as confirmed via a pulse oximeter. Pups were weaned at postnatal day 21. Blood pressure was measured via telemetry beginning at 14 wk of age and analyzed separately into light and dark phases to assess circadian rhythm. Osmotic minipumps to deliver ANG II were implanted at 15 wk of age. Perinatal IH exposure did not alter baseline blood pressure. One week of ANG II treatment increased blood pressure in light and dark periods in males exposed to IH versus control; there was no effect in females. Blood pressure among the groups was comparable following 2 wk of ANG II infusion. Perinatal IH did not change the circadian rhythm. Following ANG II treatment, indexes of renal injury were measured. Perinatal IH did not alter kidney size, structure, nephron number, or creatinine clearance. These data indicate that acute perinatal IH enhances early ANG II-induced hypertension in males, independent of nephron loss or decreases in body weight or kidney function.NEW & NOTEWORTHY The impact of acute intermittent hypoxia (IH) in early life on blood pressure in adulthood is unknown. This study used a new model exposing female and male rat pups to acute IH in the first 8 days of life, without exposing the dam. Although baseline blood pressure was not altered in adulthood, IH increased susceptibility to angiotensin II hypertension only in males, supporting increased susceptibility of males exposed to IH to a second cardiovascular stressor.

Sustained activation of 12/15 lipoxygenase (12/15 LOX) contributes to impaired renal recovery post ischemic injury in male SHR compared to females.

BACKGROUND: Acute kidney injury (AKI) due to ischemia-reperfusion (IR) is a serious and frequent complication in clinical settings, and mortality rates remain high. There are well established sex differences in renal IR, with males exhibiting greater injury following an ischemic insult compared to females. We recently reported that males have impaired renal recovery from ischemic injury vs. females. However, the mechanisms mediating sex differences in renal recovery from IR injury remain poorly understood. Elevated 12/15 lipoxygenase (LOX) activity has been reported to contribute to the progression of numerous kidney diseases. The goal of the current study was to test the hypothesis that enhanced activation of 12/15 LOX contributes to impaired recovery post-IR in males vs. females. METHODS: 13-week-old male and female spontaneously hypertensive rats (SHR) were randomized to sham or 30-minute warm bilateral IR surgery. Additional male and female SHR were randomized to treatment with vehicle or the specific 12/15 LOX inhibitor ML355 1 h prior to sham/IR surgery, and every other day following up to 7-days post-IR. Blood was collected from all rats 1-and 7-days post-IR. Kidneys were harvested 7-days post-IR and processed for biochemical, histological, and Western blot analysis. 12/15 LOX metabolites 12 and 15 HETE were measured in kidney samples by liquid chromatography-mass spectrometry (LC/MS). RESULTS: Male SHR exhibited delayed recovery of renal function post-IR vs. male sham and female IR rats. Delayed recovery in males was associated with activation of renal 12/15 LOX, increased renal 12-HETE, enhanced endoplasmic reticulum (ER) stress, lipid peroxidation, renal cell death and inflammation compared to females 7-days post-IR. Treatment of male SHR with ML355 lowered levels of 12-HETE and resulted in reduced renal lipid peroxidation, ER stress, tubular cell death and inflammation 7-days post-IR with enhanced recovery of renal function compared to vehicle-treated IR male rats. ML355 treatment did not alter IR-induced increases in plasma creatinine in females, however, tubular injury and cell death were attenuated in ML355 treated females compared to vehicle-treated rats 7 days post-IR. CONCLUSION: Our data demonstrate that sustained activation 12/15 LOX contributes to impaired renal recovery post ischemic injury in male and female SHR, although males are more susceptible on this mechanism than females.

Netrin-1 Overexpression Induces Polycystic Kidney Disease: A Novel Mechanism Contributing to Cystogenesis in Autosomal Dominant Polycystic Kidney Disease.

Despite recent advances in understanding the pathogenesis of polycystic kidney disease (PKD), the underlying molecular mechanisms involved in cystogenesis are not fully understood. This study describes a novel pathway involved in cyst formation. Transgenic mice overexpressing netrin-1 in proximal tubular cells showed increased production and urinary excretion of netrin-1. Although no cysts were detectable immediately after birth, numerous small cysts were evident by the age of 4 weeks, and disease was accelerated along with age. Surprisingly, cyst formation in the kidney was restricted to male mice, with 80% penetrance. However, ovariectomy induced kidney cyst growth in netrin-1-overexpressing female mice. Cyst development in males was associated with albuminuria and polyuria and increased cAMP excretion in netrin-1 transgenic mice. Netrin-1 overexpression significantly increased extracellular signal-regulated kinase and focal adhesion kinase phosphorylation and vimentin expression. Interestingly, p53 expression was increased but in an inactive form. Furthermore, netrin-1 expression was increased in cystic epithelia and urine of various rodent models of PKD. siRNA-mediated suppression of netrin-1 significantly reduced cyst growth and improved kidney function in netrin-1 transgenic mice and in two genetic animal models of PKD. Together, these data demonstrate that netrin-1 up-regulation induced cyst formation in autosomal dominant PKD.

Circular RNAs and acute kidney injury: a clinical science commentary on Cao et al.

Acute kidney injury (AKI) remains a significant clinical problem with a high mortality rate. Thus, the need for early recognition and treatment of AKI is an important goal. Clinical Science has a history of publishing high impact work across a breadth of scientific disciplines to improve understanding of disease mechanisms, including nephrology. This commentary spotlights a paper from more recent history that is highly cited. The work focuses on the mechanistic role of circular RNA in the pathobiology of AKI using approaches that include both in vivo experimental models and human cell culture experiments to delineate a potentially novel cellular pathway.

Sex differences in TLR4 expression in SHR do not contribute to sex differences in blood pressure or the renal T cell profile.

Hypertension is a primary risk factor for the development of cardiovascular disease. Mechanisms controlling blood pressure (BP) in men and women are still being investigated; however, there is increasing evidence supporting a role for the innate immune system. Specifically, Toll-like receptors (TLRs), and TLR4 in particular, have been implicated in the development of hypertension in male spontaneously hypertensive rats (SHR). Despite established sex differences in BP control and inflammatory markers in hypertensive males and females, little is known regarding the role of TLR4 in hypertension in females. Our hypotheses were that male SHR have greater TLR4 expression compared with females, and that sex differences in TLR4 contribute to sex differences in BP and the T cell profile. To test these hypotheses, initial studies measured renal TLR4 protein expression in 13-wk-old male and female SHR. Additional SHR were implanted with telemetry devices and randomized to treatment with either IgG or TLR4 neutralizing antibodies. Untreated control male SHR have greater TLR4 protein expression in the kidney compared with females. However, treatment with TLR4 neutralizing antibody for 2 wk did not significantly alter BP in either male or female SHR. Interestingly, neutralization of TLR4 increased renal CD3+ T cells in female SHR, with no alteration in CD4+ T cells or CD8+ T cells in either sex. Taken together, our data indicate that although male SHR have greater renal TLR4 expression than females, TLR4 does not contribute to the higher BP and more proinflammatory renal T cell profile in males versus females.

Persistent vascular congestion in male spontaneously hypertensive rats contributes to delayed recovery of renal function following renal ischemia perfusion compared with females.

Acute kidney injury (AKI) due to ischemia is a serious and frequent clinical complication with mortality rates as high as 80%. Vascular congestion in the renal outer medulla occurs early after ischemia reperfusion (IR) injury, and congestion has been linked to worsened outcomes following IR. There is evidence implicating both male sex and preexisting hypertension as risk factors for poor outcomes following IR. The present study tested the hypothesis that male spontaneously hypertensive rats (SHR) have greater vascular congestion and impaired renal recovery following renal IR vs. female SHR and normotensive male Sprague-Dawley rats (SD). Thirteen-week-old male and female SHR and SD were subjected to sham surgery or 30 min of warm bilateral ischemia followed by reperfusion. Rats were euthanized 24 h or 7 days post-IR. IR increased renal injury in all groups vs. sham controls at 24 h. At 7 days post-IR, injury remained elevated only in male SHR. Histological examination of SD and SHR kidneys 24 h post-IR showed vascular congestion in males and females. Vascular congestion was sustained only in male SHR 7 days post-IR. To assess the role of vascular congestion on impaired recovery following IR, additional male and female SHR were pretreated with heparin (200 U/kg) prior to IR. Heparin pretreatment reduced IR-induced vascular congestion and improved renal function in male SHR 7 days post-IR. Interestingly, preventing increases in blood pressure (BP) in male SHR did not alter sustained vascular congestion. Our data demonstrate that IR-induced vascular congestion is a major driving factor for impaired renal recovery in male SHR.

Splenectomy increases blood pressure and abolishes sex differences in renal T-regulatory cells in spontaneously hypertensive rats.

Over the past decade there has been increasing support for a role of the immune system in the development of hypertension. Our lab has previously reported that female spontaneously hypertensive rats (SHRs) have a blood pressure (BP)-dependent increase in anti-inflammatory renal regulatory T cells (Tregs), corresponding to lower BP compared with males. However, little is known regarding the mechanism for greater renal Tregs in females. The current study was designed to test the hypothesis that the greater relative abundance of renal Tregs in female SHR is due to greater Treg production. To test this hypothesis, T cell profiles were measured in the spleen by flow cytometry in male and female SHR at 5 and 14 weeks of age. Splenic Tregs did not differ between males and females, suggesting sex differences in renal Tregs is not due to differences in production. To assess the role of the spleen in sex differences in renal Tregs and BP control, rats were randomized to receive sham surgery (CON) or splenectomy (SPLNX) at 12 weeks of age and implanted with telemeters to measure BP. After 2 weeks, kidneys were harvested for flow cytometric analysis of T cells. Splenectomy increased BP in both sexes after 2 weeks. Renal Tregs decreased in both sexes after splenectomy, abolishing the sex differences in renal Tregs. In conclusion, splenic Tregs were comparable in male and female SHRs, suggesting that sex differences in renal Tregs is due to differences in renal Treg recruitment, not Treg production.

Implication of N-Methyl-d-Aspartate Receptor in Homocysteine-Induced Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is a leading cause of vision loss. Elevated homocysteine (Hcy) (Hyperhomocysteinemia) (HHcy) has been reported in AMD. We previously reported that HHcy induces AMD-like features. This study suggests that N-Methyl-d-aspartate receptor (NMDAR) activation in the retinal pigment epithelium (RPE) is a mechanism for HHcy-induced AMD. Serum Hcy and cystathionine-ß-synthase (CBS) were assessed by ELISA. The involvement of NMDAR in Hcy-induced AMD features was evaluated (1) in vitro using ARPE-19 cells, primary RPE isolated from HHcy mice (CBS), and mouse choroidal endothelial cells (MCEC); (2) in vivo using wild-type mice and mice deficient in RPE NMDAR (NMDARR-/-) with/without Hcy injection. Isolectin-B4, Ki67, HIF-1α, VEGF, NMDAR1, and albumin were assessed by immunofluorescence (IF), Western blot (WB), Optical coherence tomography (OCT), and fluorescein angiography (FA) to evaluate retinal structure, fluorescein leakage, and choroidal neovascularization (CNV). A neovascular AMD patient's serum showed a significant increase in Hcy and a decrease in CBS. Hcy significantly increased HIF-1α, VEGF, and NMDAR in RPE cells, and Ki67 in MCEC. Hcy-injected WT mice showed disrupted retina and CNV. Knocking down RPE NMDAR improved retinal structure and CNV. Our findings underscore the role of RPE NMDAR in Hcy-induced AMD features; thus, NMDAR inhibition could serve as a promising therapeutic target for AMD.

Hypertensive female Sprague-Dawley rats require an intact nitric oxide synthase system for compensatory increases in renal regulatory T cells.

We have previously shown that hypertensive female rats have more regulatory T cells (Tregs), which contribute more to blood pressure (BP) control in female versus male rats. Based on known protective properties of Tregs, the goal of the present study was to investigate the mechanisms by which female rats maintain Tregs. The present study was designed to 1) compare the impact of three hypertension models on the percentage of renal Tregs and 2) test the hypothesis that nitric oxide synthase (NOS) inhibition prevents increases in renal Tregs and exacerbates renal damage in female Sprague-Dawley rats. Rats (11-14 wk old) were randomized to one of the following four groups: control, norepinephrine (NE) infusion, angiotensin II infusion, or the NOS inhibitor Nω-nitro-l-arginine methyl ester (l-NAME) in drinking water. BP was measured via tail cuff. After 2 wk of treatment, kidneys were isolated and processed to measure Tregs via flow cytometric analysis and renal injury via urinary albumin excretion, plasma creatinine, and histological analyses. Hypertensive treatments increased BP in all experimental animals. Increases in BP in norepinephrine-and angiotensin II-treated rats were associated with increases in renal Tregs versus control. In contrast, l-NAME treatment decreased Tregs compared with all groups. l-NAME treatment modestly increased albumin excretion. However, plasma creatinine was comparable among the groups, and there was no histological evidence of glomerular or tubular injury. This study provides insights into the mechanisms regulating renal Tregs and supports that an intact NOS system is crucial for female rats to have BP-related increases in renal Tregs.

Ultrasound measurement of change in kidney volume is a sensitive indicator of severity of renal parenchymal injury.

Noninvasive determination of the severity of parenchymal injury in acute kidney injury remains challenging. Edema is an early pathological process following injury, which may correlate with changes in kidney volume. The goal of the present study was to test the hypothesis that "increases in kidney volume measured in vivo using ultrasound correlate with the degree of renal parenchymal injury." Ischemia-reperfusion (IR) of varying length was used to produce graded tissue injury. We first determined 1) whether regional kidney volume in rats varied with the severity (0, 15, 30, and 45 min) of warm bilateral IR and 2) whether this correlated with tubular injury score. We then determined whether these changes could be measured in vivo using three-dimensional ultrasound. Finally, we evaluated cumulative changes in kidney volume up to 14 days post-IR in rats to determine whether changes in renal volume were predictive of latent tubular injury following recovery of filtration. Experiments concluded that noninvasive ultrasound measurements of change in kidney volume over 2 wk are predictive of tubular injury following IR even in animals in which plasma creatinine was not elevated. We conclude that ultrasound measurements of volume are a sensitive, noninvasive marker of tissue injury in rats and that the use of three-dimensional ultrasound measurements may provide useful information regarding the timing, severity, and recovery from renal tissue injury in experimental studies.

Greater high-mobility group box 1 in male compared with female spontaneously hypertensive rats worsens renal ischemia-reperfusion injury.

Renal ischemia is the most common cause of acute kidney injury. Damage-associated molecular patterns (DAMPs) initiate an inflammatory response and contribute to ischemia-reperfusion (IR) injury in males, yet the contribution of DAMPs to IR injury in females is unknown. The goal of the current study was to test the hypothesis that males have greater increases in the DAMP high-mobility group box 1 (HMGB1), worsening injury compared with females. Thirteen-week-old male and female spontaneously hypertensive rats (SHR) were subjected to sham or 45-min warm bilateral ischemia followed by 24 h of reperfusion before measurement of HMGB1 and renal function. Additional SHR were pre-treated with control (IgG) or HMGB1 neutralizing antibody (300 µg/rat) 1 h prior to renal ischemia. Blood, urine and kidneys were harvested 24 h post-IR for histological and Western blot analyses. Initial studies confirmed that IR resulted in greater increases in renal HMGB1 in male SHR compared with females. Greater renal HMGB1 in male SHR post-IR resulted in greater increases in serum TNF-α and renal IL-1ß, neutrophil infiltration and tubular cell death. Neutralization of HMGB1 attenuated IR-induced increases in plasma creatinine, blood urea nitrogen (BUN), inflammation, tubular damage and tubular cell death only in male SHR. In conclusion, our data demonstrate that there is a sex difference in the contribution of HMGB1 to IR-induced injury, where males exhibit greater increases in HMGB1-mediated renal injury in response to IR compared with females.

Modulation of the p75 neurotrophin receptor using LM11A-31 prevents diabetes-induced retinal vascular permeability in mice via inhibition of inflammation and the RhoA kinase pathway.

AIMS/HYPOTHESIS: Breakdown of the inner blood-retinal barrier (BRB) is an early event in the pathogenesis of diabetic macular oedema, that eventually leads to vision loss. We have previously shown that diabetes causes an imbalance of nerve growth factor (NGF) isoforms resulting in accumulation of its precursor proNGF and upregulation of the p75 neurotrophin receptor (p75NTR), with consequent increases in the activation of Ras homologue gene family, member A (RhoA). We also showed that genetic deletion of p75NTR in diabetes preserved the BRB and prevented inflammatory mediators in retinas. This study aims to examine the therapeutic potential of LM11A-31, a small-molecule p75NTR modulator and proNGF antagonist, in preventing diabetes-induced BRB breakdown. The study also examined the role of p75NTR/RhoA downstream signalling in mediating cell permeability. METHODS: Male C57BL/6 J mice were rendered diabetic using streptozotocin injection. After 2 weeks of diabetes, mice received oral gavage of LM11A-31 (50 mg kg-1 day-1) or saline (NaCl 154 mmol/l) for an additional 4 weeks. BRB breakdown was assessed by extravasation of BSA-AlexaFluor-488. Direct effects of proNGF were examined in human retinal endothelial (HRE) cells in the presence or absence of LM11A-31 or the Rho kinase inhibitor Y-27632. RESULTS: Diabetes triggered BRB breakdown and caused significant increases in circulatory and retinal TNF-α and IL-1ß levels. These effects coincided with significant decreases in retinal NGF and increases in vascular endothelial growth factor and proNGF expression, as well as activation of RhoA. Interventional modulation of p75NTR activity through treatment of mouse models of diabetes with LM11A-31 significantly mitigated proNGF accumulation and preserved BRB integrity. In HRE cells, treatment with mutant proNGF (10 ng/ml) triggered increased cell permeability with marked reduction of expression of tight junction proteins, zona occludens-1 (ZO-1) and claudin-5, compared with control, independent of inflammatory mediators or cell death. Modulating p75NTR significantly inhibited proNGF-mediated RhoA activation, occludin phosphorylation (at serine 490) and cell permeability. ProNGF induced redistribution of ZO-1 in the cell wall and formation of F-actin stress fibres; these effects were mitigated by LM11A-31. CONCLUSIONS/INTERPRETATION: Targeting p75NTR signalling using LM11A-31, an orally bioavailable receptor modulator, may offer an effective, safe and non-invasive therapeutic strategy for treating macular oedema, a major cause of blindness in diabetes.

Inducible overexpression of endothelial proNGF as a mouse model to study microvascular dysfunction.

Impaired maturation of nerve growth factor precursor (proNGF) and its accumulation has been reported in several neurodegenerative diseases, myocardial infarction and diabetes. To elucidate the direct impact of proNGF accumulation identified the need to create a transgenic model that can express fully mutated cleavage-resistant proNGF. Using Cre-Lox technology, we developed an inducible endothelial-specific proNGF transgenic mouse (proNGFLoxp) that overexpresses GFP-conjugated cleavage-resistant proNGF123 when crossed with VE-cadherin-CreERT2 (Cre). Expression of proNGF, inflammatory mediators, NGF and VEGF was evaluated by PCR, Western blot and immunohistochemistry. EC-proNGF overexpression was confirmed using colocalization of anti-proNGF within retinal vasculature. EC-proNGF did not cause retinal neurotoxicity or marked glial activation at 4-weeks. Microvascular preparation from Cre-proNGF mice showed significant imbalance of proNGF/NGF ratio, enhanced expression of TNF-α and p75NTR, and tendency to impair TrkA phosphorylation compared to controls. EC-proNGF overexpression triggered mRNA expression of p75NTR and inflammatory mediators in both retina and renal cortex compared to controls. EC-proNGF expression induced vascular permeability including breakdown of BRB and albuminuria in the kidney without affecting VEGF level at 4-weeks. Histopathological changes were assessed after 8-weeks and the results showed that EC-proNGF triggered formation of occluded (acellular) capillaries, hall mark of retinal ischemia. EC-proNGF resulted in glomerular enlargement and kidney fibrosis, hall mark of renal dysfunction. We have successfully created an inducible mouse model that can dissect the contribution of autocrine direct action of cleavage-resistant proNGF on systemic microvascular abnormalities in both retina and kidney, major targets for microvascular complication.

Low-Dose IL-17 Therapy Prevents and Reverses Diabetic Nephropathy, Metabolic Syndrome, and Associated Organ Fibrosis.

Diabetes is the leading cause of kidney failure, accounting for >45% of new cases of dialysis. Diabetic nephropathy is characterized by inflammation, fibrosis, and oxidant stress, pathologic features that are shared by many other chronic inflammatory diseases. The cytokine IL-17A was initially implicated as a mediator of chronic inflammatory diseases, but recent studies dispute these findings and suggest that IL-17A can favorably modulate inflammation. Here, we examined the role of IL-17A in diabetic nephropathy. We observed that IL-17A levels in plasma and urine were reduced in patients with advanced diabetic nephropathy. Type 1 diabetic mice that are genetically deficient in IL-17A developed more severe nephropathy, whereas administration of low-dose IL-17A prevented diabetic nephropathy in models of type 1 and type 2 diabetes. Moreover, IL-17A administration effectively treated, prevented, and reversed established nephropathy in genetic models of diabetes. Protective effects were also observed after administration of IL-17F but not IL-17C or IL-17E. Notably, tubular epithelial cell-specific overexpression of IL-17A was sufficient to suppress diabetic nephropathy. Mechanistically, IL-17A administration suppressed phosphorylation of signal transducer and activator of transcription 3, a central mediator of fibrosis, upregulated anti-inflammatory microglia/macrophage WAP domain protein in an AMP-activated protein kinase-dependent manner and favorably modulated renal oxidative stress and AMP-activated protein kinase activation. Administration of recombinant microglia/macrophage WAP domain protein suppressed diabetes-induced albuminuria and enhanced M2 marker expression. These observations suggest that the beneficial effects of IL-17 are isoform-specific and identify low-dose IL-17A administration as a promising therapeutic approach in diabetic kidney disease.

Histone deacetylase­mediated silencing of AMWAP expression contributes to cisplatin nephrotoxicity.

Cisplatin-induced acute kidney injury is a serious problem in cancer patients during treatment of solid tumors. Currently, there are no therapies available to treat or prevent cisplatin nephrotoxicity. Since histone deacetylase (HDAC) inhibition augments cisplatin anti-tumor activity, we tested whether HDAC inhibitors can prevent cisplatin-induced nephrotoxicity and determined the underlying mechanism. Cisplatin upregulated the expression of several HDACs in the kidney. Inhibition of HDAC with clinically used trichostatin A suppressed cisplatin-induced kidney injury, inflammation, and epithelial cell apoptosis. Moreover, trichostatin A upregulated the novel anti-inflammatory protein, activated microglia/macrophage WAP domain protein (AMWAP), in epithelial cells which was enhanced with cisplatin treatment. Interestingly, HDAC1 and -2 specific inhibitors are sufficient to potently upregulate AMWAP in epithelial cells. Administration of recombinant AMWAP or its epithelial cell-specific overexpression reduced cisplatin-induced kidney dysfunction. Moreover, AMWAP treatment suppressed epithelial cell apoptosis, and siRNA-based knockdown of AMWAP expression abolished trichostatin A-mediated suppression of epithelial cell apoptosis in vitro. Thus, HDAC-mediated silencing of AMWAP may contribute to cisplatin nephrotoxicity. Hence, HDAC1 and -2 specific inhibitors or AMWAP could be useful therapeutic agents for the prevention of cisplatin nephrotoxicity.

Deletion of UNC5B in Kidney Epithelium Exacerbates Diabetic Nephropathy in Mice.

BACKGROUND: Guidance cue netrin-1 was shown to have protective effects in diabetic nephropathy. However, the role of its receptor UNC5B in diabetic kidney disease is unknown. Moreover, whether netrin-1 is protective against diabetic kidney disease in a genetic model of nephropathy and in the nephropathy prone DBA background is also unknown. The aim of this study was to determine the significance of UNC5B in tubular epithelial cells in chronic kidney disease due to diabetes and evaluate whether netrin-1 is also protective in the case of a nephropathy-prone mouse. METHODS: Proximal tubular epithelium-specific UNC5B knockout mice as well as heterozygous UNC5B knockout mice were used to determine the roles of UNC5B in nephropathy. Diabetes was induced in these tissue-specific knockout, heterozygous and WT mice, and albuminuria was then monitored. RESULTS: WT and heterozygous diabetic mice developed significant albuminuria at 8 weeks after induction of diabetes as compared to buffer-treated control mice. However, albuminuria was significantly more pronounced in mice with proximal tubule specific deletion of UNC5B. Transgenic overexpression of netrin-1 in proximal tubules in the DBA background and administration of recombinant netrin-1 to Ins2Akita mice also significantly reduced diabetes-induced albuminuria and suppressed glomerular and interstitial lesions. CONCLUSION: Our data suggested that netrin-1 signaling in proximal tubular epithelium may play a critical role in the protection of kidney against diabetic kidney disease.

Honey feeding protects kidney against cisplatin nephrotoxicity through suppression of inflammation.

Cisplatin is a highly effective chemotherapeutic drug used to treat a wide variety of solid tumors. However, its use was limited due its dose-limiting toxicity to the kidney. Currently, there are no therapies available to treat or prevent cisplatin nephrotoxicity. Honey is a naturally occurring complex liquid and widely used in traditional Ayurvedic medicine to treat many illnesses. However, its effect on cisplatin nephrotoxicity is unknown. To determine the role of honey in cisplatin nephrotoxicity, animals were pretreated orally for a week and then cisplatin was administered. Honey feeding was continued for another 3 days. Our results show that animals with cisplatin-induced kidney dysfunction, as determined by increased serum creatinine, which received honey feeding had less kidney dysfunction. Improved kidney function was associated with better preservation of kidney morphology in honey-treated group as compared to the cisplatin alone-treated group. Interestingly, honey feeding significantly reduced cisplatin-induced tubular epithelial cell death, immune infiltration into the kidney as well as cytokine and chemokine expression and excretion as compared to cisplatin treated animals. Western blot analysis shows that cisplatin-induced increase in phosphorylation of NFkB was completely suppressed with honey feeding. In conclusion, honey feeding protects the kidney against cisplatin nephrotoxicity through suppression of inflammation and NFkB activation.

Semaphorin 3A inactivation suppresses ischemia-reperfusion-induced inflammation and acute kidney injury.

Recent studies show that guidance molecules that are known to regulate cell migration during development may also play an important role in adult pathophysiologic states. One such molecule, semaphorin3A (sema3A), is highly expressed after acute kidney injury (AKI) in mice and humans, but its pathophysiological role is unknown. Genetic inactivation of sema3A protected mice from ischemia-reperfusion-induced AKI, improved tissue histology, reduced neutrophil infiltration, prevented epithelial cell apoptosis, and increased cytokine and chemokine excretion in urine. Pharmacological-based inhibition of sema3A receptor binding likewise protected against ischemia-reperfusion-induced AKI. In vitro, sema3A enhanced toll-like receptor 4-mediated inflammation in epithelial cells, macrophages, and dendritic cells. Moreover, administration of sema3A-treated, bone marrow-derived dendritic cells exacerbated kidney injury. Finally, sema3A augmented cisplatin-induced apoptosis in kidney epithelial cells in vitro via expression of DFFA-like effector a (cidea). Our data suggest that the guidance molecule sema3A exacerbates AKI via promoting inflammation and epithelial cell apoptosis.

Guidance cue netrin-1 and the regulation of inflammation in acute and chronic kidney disease.

Acute kidney injury (AKI) is a common problem in the hospital setting and intensive care unit. Despite improved understanding, there are no effective therapies available to treat AKI. A large body of evidence strongly suggests that ischemia reperfusion injury is an inflammatory disease mediated by both adaptive and innate immune systems. Cell migration also plays an important role in embryonic development and inflammation, and this process is highly regulated to ensure tissue homeostasis. One such paradigm exists in the developing nervous system, where neuronal migration is mediated by a balance between chemoattractive and chemorepulsive signals. The ability of the guidance molecule netrin-1 to repulse or abolish attraction of neuronal cells expressing the UNC5B receptor makes it an attractive candidate for the regulation of inflammatory cell migration. Recent identification of netrin-1 as regulators of immune cell migration has led to a large number of studies looking into how netrin-1 controls inflammation and inflammatory cell migration. This review will focus on recent advances in understanding netrin-1 mediated regulation of inflammation during acute and chronic kidney disease and whether netrin-1 and its receptor activation can be used to treat acute and chronic kidney disease.