A simplified method for HPLC determination of creatinine in mouse serum

Measured GFR in murine animal models: review on methods, techniques, and procedures

Chronic kidney disease (CKD) is one of the most common chronic diseases worldwide, with increasing rates of morbidity and mortality. Thus, early detection is essential to prevent severe adverse events and the progression of kidney disease to an end stage. Glomerular filtration rate (GFR) is the most appropriate index to evaluate renal function in both clinical practice and basic medical research. Several animal models have been developed to understand renal disease induction and progression. Specifically, murine models are useful to study the pathogenesis of renal damage, so a reliable determination of GFR is essential to evaluate the progression of CKD. However, as in clinical practise, the estimation of GFR in murine by levels of serum/urine creatinine or cystatin-C could not be accurate and needed other more reliable methods. As an alternative, the measurement of GFR by the clearance of exogenous markers like inulin, sinistrin, 51Cr-EDTA, 99mTc-DTPA, 125I-iothalamate, or iohexol could be performed. Nevertheless, both approaches-estimation or measurement of GFR-have their limitations and a standard method for the GFR determination has not been defined. Altogether, in this review, we aim to give an overview of the current methods for GFR assessment in murine models, describing each methodology and focusing on their advantages and limitations.

Targeting RNA oxidation by ISG20-mediated degradation is a potential therapeutic strategy for acute kidney injury

Oxidative stress plays a central role in the pathophysiology of acute kidney injury (AKI). Although RNA is one of the most vulnerable cell components to oxidative damage, it is unclear whether RNA oxidation is involved in the pathogenesis of AKI. In this study, we found that the level of RNA oxidation was significantly enhanced in kidneys of patients with acute tubular necrosis (ATN) and in the renal tubular epithelial cells (TECs) of mice with AKI, and oxidized RNA overload resulted in TEC injury. We further identified interferon-stimulated gene 20 (ISG20) as a novel regulator of RNA oxidation in AKI. Tubule-specific deficiency of ISG20 significantly aggravated renal injury and RNA oxidation in the ischemia/reperfusion-induced AKI mouse model and ISG20 restricted RNA oxidation in an exoribonuclease activity-dependent manner. Importantly, overexpression of ISG20 protected against oxidized RNA overproduction and renal ischemia/reperfusion injury in mice and ameliorated subsequent protein aggresome accumulation, endoplasmic reticulum stress, and unfolded protein response. Thus, our findings provide direct evidence that RNA oxidation contributes to the pathogenesis of AKI and that ISG20 importantly participates in the degradation of oxidized RNA, suggesting that targeting ISG20-handled RNA oxidation may be an innovative therapeutic strategy for AKI.

Ca-EDTA restores the activity of ceftazidime-avibactam or aztreonam against carbapenemase-producing Klebsiellapneumoniae infections

Developing an effective therapy to overcome carbapenemase-positive Klebsiella pneumoniae (CPKp) is an important therapeutic challenge that must be addressed urgently. Here, we explored a Ca-EDTA combination with aztreonam or ceftazidime-avibactam in vitro and in vivo against diverse CPKp clinical isolates. The synergy testing of this study demonstrated that novel aztreonam-Ca-EDTA or ceftazidime-avibactam-Ca-EDTA combination was significantly effective in eliminating planktonic and mature biofilms in vitro, as well as eradicating CPKp infections in vivo. Both combinations revealed significant therapeutic efficacies in reducing bacterial load in internal organs and protecting treated mice from mortality. Conclusively, this is the first in vitro and in vivo study to demonstrate that novel aztreonam-Ca-EDTA or ceftazidime-avibactam-Ca-EDTA combinations provide favorable efficacy and safety for successful eradication of carbapenemase-producing Klebsiella pneumoniae planktonic and biofilm infections.

Direct mapping of kidney function by DCE-MRI urography using a tetrazinanone organic radical contrast agent

Chronic kidney disease (CKD) and acute kidney injury (AKI) are ongoing global health burdens. Glomerular filtration rate (GFR) is the gold standard measure of kidney function, with clinical estimates providing a global assessment of kidney health without spatial information of kidney- or region-specific dysfunction. The addition of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) to the anatomical imaging already performed would yield a 'one-stop-shop' for renal assessment in cases of suspected AKI and CKD. Towards urography by DCE-MRI, we evaluated a class of nitrogen-centered organic radicals known as verdazyls, which are extremely stable even in highly reducing environments. A glucose-modified verdazyl, glucoverdazyl, provided contrast limited to kidney and bladder, affording functional kidney evaluation in mouse models of unilateral ureteral obstruction (UUO) and folic acid-induced nephropathy (FAN). Imaging outcomes correlated with histology and hematology assessing kidney dysfunction, and glucoverdazyl clearance rates were found to be a reliable surrogate measure of GFR.

Perfluorooctanesulfonate Can Cause Negative Bias in Creatinine Measurement in Hemodialysis Patients Using Polysulfone Dialysis Membranes

Serum creatinine is an important clinical marker for renal clearance. However, two conventional methods (Jaffe and enzymatic) are prone to interferences with organic compounds as compared to the standard method (isotope dilution-liquid chromatography-mass spectrometry) and can cause a significant negative bias. Perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) are two common perfluorochemicals (PFCs) that can easily be accumulated in humans. We aimed to verify whether this bias is the result of an accumulation of PFCs. The serum creatinine values of 124 hemodialysis patients were analyzed using the three methods. We also aimed to evaluate which biochemical parameters will influence the difference between the conventional methods and the standard method. We found that a significant underestimation occurred when using the conventional methods. Albumin is an independent factor associated with negative bias, but it loses this correlation after dialysis, likely due to the removal of protein-bound uremic toxins. PFOS can cause negative bias when using the enzymatic method. Furthermore, this linear correlation is more significant in patients who used polysulfone-based dialysis membranes, possibly due to the better clearance of other uremic toxins. The serum creatinine of uremic patients can be significantly underestimated when using conventional methods. PFCs, as well the type of dialysis membrane being used, can be influencing factors.

Tumor Lysis Syndrome and AKI: Beyond Crystal Mechanisms

BACKGROUND

The pathophysiology of AKI during tumor lysis syndrome (TLS) is not well understood due to the paucity of data. We aimed to decipher crystal-dependent and crystal-independent mechanisms of TLS-induced AKI.

METHODS

Crystalluria, plasma cytokine levels, and extracellular histones levels were measured in two cohorts of patients with TLS. We developed a model of TLS in syngeneic mice with acute myeloid leukemia, and analyzed ultrastructural changes in kidneys and endothelial permeability using intravital confocal microscopy. In parallel, we studied the endothelial toxicity of extracellular histones in vitro. RESULTS: The study provides the first evidence that previously described crystal-dependent mechanisms are insufficient to explain TLS-induced AKI. Extracellular histones that are released in huge amounts during TLS caused profound endothelial alterations in the mouse model. The mechanisms of histone-mediated damage implicates endothelial cell activation mediated by Toll-like receptor 4. Heparin inhibits extracellular histones and mitigates endothelial dysfunction during TLS.

CONCLUSION

This study sheds new light on the pathophysiology of TLS-induced AKI and suggests that extracellular histones may constitute a novel target for therapeutic intervention in TLS when endothelial dysfunction occurs.

Combining Neprilysin Inhibitor With AT2R Agonist Is Superior to Combination With AT1R Blocker in Providing Reno-Protection in Obese Rats

Clinical use of the combination therapy of the neprilysin inhibitor sacubitril and angiotensin II type 1 receptor blocker valsartan is known to be associated with albuminuria. Albuminuria is both a risk factor for and an indicator of kidney injury. Earlier work from our laboratory reported that the agonist of angiotensin II type 2 receptor Compound 21 (C21) prevents proteinuria, albuminuria, and is reno-protective in obese Zucker rats fed high salt diet (HSD). Thus, we hypothesized that sacubitril/C21 combination provides superior reno-protection compared to sacubitril/valsartan. Male obese Zucker rats 10–11 weeks old were treated daily with vehicle, sacubitril + C21, or sacubitril + valsartan while fed HSD for 16 days. HSD-feeding caused kidney dysfunction, evident by significant increases in urinary protein, osteopontin, and cystatin C. HSD-feeding lowered plasma cystatin C and creatinine concentrations suggestive of hyperfiltration, which was not affected by either treatment. Unlike sacubitril/valsartan, sacubitril/C21 treatment significantly decreases proteinuria, albuminuria, the expression of nephrin, and kidney weight, independent of hyperfiltration, compared with HSD alone. Moreover, sacubitril/valsartan therapy increased plasma renin and did not prevent HSD-induced increases in renal angiotensin II, while sacubitril/C21 completely prevented these changes. Together, this study suggests that sacubitril/C21 afforded superior reno-protection compared to sacubitril/valsartan therapy in high salt-fed obese Zucker rats.

Novel colistin-EDTA combination for successful eradication of colistin-resistant Klebsiella pneumoniae catheter-related biofilm infections

Development of an effective therapy to overcome colistin resistance in Klebsiella pneumoniae, a common pathogen causing catheter-related biofilm infections in vascular catheters, has become a serious therapeutic challenge that must be addressed urgently. Although colistin and EDTA have successful roles for eradicating biofilms, no in vitro and in vivo studies have investigated their efficacy in catheter-related biofilm infections of colistin-resistant K. pneumoniae. In this study, colistin resistance was significantly reversed in both planktonic and mature biofilms of colistin-resistant K. pneumoniae by a combination of colistin (0.25-1 µg/ml) with EDTA (12 mg/ml). This novel colistin-EDTA combination was also demonstrated to have potent efficacy in eradicating colistin-resistant K. pneumoniae catheter-related biofilm infections, and eliminating the risk of recurrence in vivo. Furthermore, this study revealed significant therapeutic efficacy of colistin-EDTA combination in reducing bacterial load in internal organs, lowering serum creatinine, and protecting treated mice from mortality. Altered in vivo expression of different virulence genes indicate bacterial adaptive responses to survive in hostile environments under different treatments. According to these data discovered in this study, a novel colistin-EDTA combination provides favorable efficacy and safety for successful eradication of colistin-resistant K. pneumonia catheter-related biofilm infections.

The Interplay between Histamine H4 Receptor and the Kidney Function: The Lesson from H4 Receptor Knockout Mice

Previous studies implicated the histamine H₄ receptor in renal pathophysiology. The aim here is to elucidate the role of this receptor on renal function using H₄ receptor knockout mice (H₄R^-/-). Healthy and diabetic H₄R^-/- mice compared to their C57BL/6J wild-type counterpart for renal function and the expression of crucial tubular proteins. H₄R^-/- and wild-type mice, matched for ages, showed comparable weight gain curves reaching similar median weight at the end of the study. However, H₄R^-/- mice displayed a higher basal glycemia. H₄R^-/- mice showed a lower urine 24 h outflow, and albumin-to-creatinine ratio (ACR) compared to wild-type mice. Consistently, H₄R^-/- mice presented a higher expression of megalin and a lower basal expression of the sodium-hydrogen exchanger (NHE)3 and aquaporin (AQP)2. According to these basal differences, diabetic H₄R^-/- mice developed more severe hyperglycemia and a higher 24 h urine volume, but a lower increase in ACR and decrease in urine pH were observed. These events were paralleled by a reduced NHE3 over-expression and megalin loss in diabetic H₄R^-/- mice. The AQP1 and AQP7 patterns were also different between H₄R^-/- and wild-type diabetic mice. The collected results highlight the role of the histamine H₄ receptor in the control of renal reabsorption processes, particularly albumin uptake.

Bioenergetic maladaptation and release of HMGB1 in calcineurin inhibitor-mediated nephrotoxicity

Calcineurin inhibitors (CNIs) are potent immunosuppressive agents, universally used following solid organ transplantation to prevent rejection. Although effective, the long-term use of CNIs is associated with nephrotoxicity. The etiology of this adverse effect is complex, and effective therapeutic interventions remain to be determined. Using a combination of in vitro techniques and a mouse model of CNI-mediated nephrotoxicity, we found that the CNIs, cyclosporine A (CsA), and tacrolimus (TAC) share a similar mechanism of tubular epithelial kidney cell injury, including mitochondrial dysfunction and release of High-Mobility Group Box I (HMGB1). CNIs promote bioenergetic reprogramming due to mitochondrial dysfunction and a shift toward glycolytic metabolism. These events were accompanied by diminished cell-to-cell adhesion, loss of the epithelial cell phenotype, and release of HMGB1. Notably, Erk1/2 inhibitors effectively diminished HMGB1 release, and similar inhibitor was observed on inclusion of pan-caspase inhibitor zVAD-FMK. In vivo, while CNIs activate tissue proremodeling signaling pathways, MAPK/Erk1/2 inhibitor prevented nephrotoxicity, including diminished HMGB1 release from kidney epithelial cells and accumulation in urine. In summary, HMGB1 is an early indicator and marker of progressive nephrotoxicity induced by CNIs. We suggest that proremodeling signaling pathway and loss of mitochondrial redox/bioenergetics homeostasis are crucial therapeutic targets to ameliorate CNI-mediated nephrotoxicity.

Quantitative determination of creatinine from serum of prostate cancer patients by N-doped porous carbon antimony (Sb/NPC) nanoparticles

Creatinine is an indicator of hindrance in urination and renal insufficiency. Creatinine levels are the marker of the late stages of prostate cancer. Early and sensitive detection of creatinine can reduce deaths associated with prostate cancer. In this work, nitrogen-doped porous carbon antimony (Sb/NPC) nanoparticles are fabricated to be employed as a non-enzymatic biosensor. Sb/NPC has promising redox activity and is synthesized by a two-step reaction using low-cost precursors. Electrochemical sensing by Sb/NPC is conducted for standard creatinine solutions on a three-electrodes system. Cyclic voltammetry, amperometry, and electrochemical impedance spectroscopy are used to sense creatinine. LOD and LOQ of the Sb/NPC modified electrode are 0.74 µM and 2.4 µM, respectively. This electrode system analyzes creatinine in the serum of prostate cancer patients who have elevated PSA levels. More than 90% creatinine is recovered from a spiked serum sample of a prostate cancer patient. A direct relation is observed between PSA levels and creatinine levels in prostate cancer. The developed cyclic voltammetric setup detects trace concentrations of creatinine in serum.

Iohexol plasma clearance simplified by Dried Blood Spot (DBS) sampling to measure renal function in conscious mice

There is no simple method to measure glomerular filtration rate (GFR) in mice, which limits the use of mice in models of renal diseases. We aimed at simplifying the plasma clearance of iohexol in mice, using dried blood spot (DBS) sampling in order to reduce the amount of blood taken for analysis. GFR was measured simultaneously by a reference method in total blood—as described before—and tested method using DBS in fifteen male and six female C57BL/6J mice. Total blood extraction was 50 μL for the reference methods and 25μL for the tested methods, distributed in 5 samples. The agreement of GFR values between both methods was analyzed with the concordance correlation coefficient (CCC), total deviation index (TDI) and coverage probability (CP). The agreement between both methods was excellent, showing a TDI = 8.1%, which indicates that 90% of the GFR values obtained with DBS showed an error ranging from − 8 to + 8% of the reference method; a CCC of 0.996 (CI: 0.992), reflecting high precision and accuracy and a CP of 94 (CI: 83), indicating that 6% of the GFR values obtained with DBS had an error greater than 10% of the method in blood. So, both methods are interchangeable. DBS represent a major simplification of GFR measurement in mice. Also, DBS improves animal welfare by reducing the total blood required and refining the procedure.

Targeting mitochondrial oxidative stress with MitoQ reduces NET formation and kidney disease in lupus-prone MRL-lpr mice

OBJECTIVES

Recent investigations in humans and mouse models with lupus have revealed evidence of mitochondrial dysfunction and production of mitochondrial reactive oxygen species (mROS) in T cells and neutrophils. This can provoke numerous cellular changes including oxidation of nucleic acids, proteins, lipids and even induction of cell death. We have previously observed that in T cells from patients with lupus, the increased mROS is capable of provoking oligomerisation of mitochondrial antiviral stimulator (MAVS) and production of type I interferon (IFN-I). mROS in SLE neutrophils also promotes the formation of neutrophil extracellular traps (NETs), which are increased in lupus and implicated in renal damage. As a result, in addition to traditional immunosuppression, more comprehensive treatments for lupus may also include non-immune therapy, such as antioxidants.

METHODS

Lupus-prone MRL-lpr mice were treated from weaning for 11 weeks with the mitochondria-targeted antioxidant, MitoQ (200 µM) in drinking water. Mice were then assessed for ROS production in neutrophils, NET formation, MAVS oligomerisation, serum IFN-I, autoantibody production and renal function.

RESULTS

MitoQ-treated mice manifested reduced neutrophil ROS and NET formation, decreased MAVS oligomerisation and serum IFN-I, and reduced immune complex formation in kidneys, despite no change in serum autoantibody .

CONCLUSIONS

These findings reveal the potential utility of targeting mROS in addition to traditional immunosuppressive therapy for lupus.

Improved Mitochondrial Metabolism and Reduced Inflammation Following Attenuation of Murine Lupus With Coenzyme Q10 Analog Idebenone

OBJECTIVE

A role for mitochondrial dysfunction has been proposed in the immune dysregulation and organ damage characteristic of systemic lupus erythematosus (SLE). Idebenone is a coenzyme Q10 synthetic quinone analog and an antioxidant that has been used in humans to treat diverse diseases in which mitochondrial function is impaired. This study was undertaken to assess whether idebenone ameliorates lupus in murine models.

METHODS

Idebenone was administered orally to MRL/lpr mice at 2 different doses (1 gm/kg or 1.5 gm/kg idebenone-containing diet) for 8 weeks. At peak disease activity, clinical, immunologic, and metabolic parameters were analyzed and compared to those in untreated mice (n = 10 per treatment group). Results were confirmed in the lupus-prone NZM2328 mouse model.

RESULTS

In MRL/lpr mice, idebenone-treated mice showed a significant reduction in mortality incidence (P < 0.01 versus untreated mice), and the treatment attenuated several disease features, including glomerular inflammation and fibrosis (each P < 0.05 versus untreated mice), and improved renal function in association with decreased renal expression of interleukin-17A (IL-17A) and mature IL-18. Levels of splenic proinflammatory cytokines and inflammasome-related genes were significantly decreased (at least P < 0.05 and some with higher significance) in mice treated with idebenone, while no obvious drug toxicity was observed. Idebenone inhibited neutrophil extracellular trap formation in neutrophils from lupus-prone mice (P < 0.05) and human patients with SLE. Idebenone also improved mitochondrial metabolism (30% increase in basal respiration and ATP production), reduced the extent of heart lipid peroxidation (by one-half that of untreated mice), and significantly improved endothelium-dependent vasorelaxation (P < 0.001). NZM2328 mice exposed to idebenone also displayed improvements in renal and systemic inflammation, reducing the kidney pathology score (P < 0.05), IgG/C3 deposition (P < 0.05), and the gene expression of interferon, proinflammatory, and inflammasome-related genes (at least P < 0.05 and some with higher significance).

CONCLUSION

Idebenone ameliorates murine lupus disease activity and the severity of organ damage, supporting the hypothesis that agents that modulate mitochondrial biologic processes may have a therapeutic role in human SLE.

Long-term outcomes in mouse models of ischemia-reperfusion-induced acute kidney injury

Severe acute kidney injury has a high mortality and is a risk factor for progressive chronic kidney disease. None of the potential therapies that have been identified in preclinical studies have successfully improved clinical outcomes. This failure is partly because animal models rarely reflect the complexity of human disease: most preclinical studies are short term and are commonly performed in healthy, young, male mice. Therapies that are effective in preclinical models that share common clinical features seen in patients with acute kidney injury, including genetic diversity, different sexes, and comorbidities, and evaluate long-term outcomes are more likely to predict success in the clinic. Here, we evaluated susceptibility to chronic kidney disease after ischemia-reperfusion injury with delayed nephrectomy by monitoring long-term functional and histological responses to injury. We defined conditions required to induce long-term postinjury renal dysfunction and fibrosis without increased mortality in a reproducible way and evaluate effect of mouse strains, sexes, and preexisting diabetes on these responses.

In vivo evaluation of safety, biodistribution and pharmacokinetics of laser-synthesized gold nanoparticles

Capable of generating plasmonic and other effects, gold nanostructures can offer a variety of diagnostic and therapy functionalities for biomedical applications, but conventional chemically-synthesized Au nanomaterials cannot always match stringent requirements for toxicity levels and surface conditioning. Laser-synthesized Au nanoparticles (AuNP) present a viable alternative to chemical counterparts and can offer exceptional purity (no trace of contaminants) and unusual surface chemistry making possible direct conjugation with biocompatible polymers (dextran, polyethylene glycol). This work presents the first pharmacokinetics, biodistribution and safety study of laser-ablated dextran-coated AuNP (AuNPd) under intravenous administration in small animal model. Our data show that AuNPd are rapidly eliminated from the blood circulation and accumulated preferentially in liver and spleen, without inducing liver or kidney toxicity, as confirmed by the plasmatic ALAT and ASAT activities, and creatininemia values. Despite certain residual accumulation in tissues, we did not detect any sign of histological damage or inflammation in tissues, while IL-6 level confirmed the absence of any chronic inflammation. The safety of AuNPd was confirmed by healthy behavior of animals and the absence of acute and chronic toxicities in liver, spleen and kidneys. Our results demonstrate that laser-synthesized AuNP are safe for biological systems, which promises their successful biomedical applications.

Endothelin receptor-A mediates degradation of the glomerular endothelial surface layer via pathologic crosstalk between activated podocytes and glomerular endothelial cells

Emerging evidence of crosstalk between glomerular cells in pathological settings provides opportunities for novel therapeutic discovery. Here we investigated underlying mechanisms of early events leading to filtration barrier defects of podocyte and glomerular endothelial cell crosstalk in the mouse models of primary podocytopathy (podocyte specific transforming growth factor-β receptor 1 signaling activation) or Adriamycin nephropathy. We found that glomerular endothelial surface layer degradation and albuminuria preceded podocyte foot process effacement. These abnormalities were prevented by endothelin receptor-A antagonism and mitochondrial reactive oxygen species scavenging. Additional studies confirmed increased heparanase and hyaluronoglucosaminidase gene expression in glomerular endothelial cells in response to podocyte-released factors and to endothelin-1. Atomic force microscopy measurements showed a significant reduction in the endothelial surface layer by endothelin-1 and podocyte-released factors, which could be prevented by endothelin receptor-A but not endothelin receptor-B antagonism. Thus, our studies provide evidence of early crosstalk between activated podocytes and glomerular endothelial cells resulting in loss of endothelial surface layer, glomerular endothelial cell injury and albuminuria. Hence, activation of endothelin-1-endothelin receptor-A and mitochondrial reactive oxygen species contribute to the pathogenesis of primary podocytopathies in experimental focal segmental glomerulosclerosis.

A Bioinspired Scaffold with Anti-Inflammatory Magnesium Hydroxide and Decellularized Extracellular Matrix for Renal Tissue Regeneration

Kidney diseases are a worldwide public health issue. Renal tissue regeneration using functional scaffolds with biomaterials has attracted a great deal of attention due to limited donor organ availability. Here, we developed a bioinspired scaffold that can efficiently induce renal tissue regeneration. The bioinspired scaffold was designed with poly(lactide-co-glycolide) (PLGA), magnesium hydroxide (Mg(OH)2), and decellularized renal extracellular matrix (ECM). The Mg(OH)2 inhibited materials-induced inflammatory reactions by neutralizing the acidic microenvironment formed by degradation products of PLGA, and the acellular ECM helped restore the biological function of kidney tissues. When the PLGA/ECM/Mg(OH)2 scaffold was implanted in a partially nephrectomized mouse model, it led to the regeneration of renal glomerular tissue with a low inflammatory response. Finally, the PLGA/ECM/Mg(OH)2 scaffold was able to restore renal function more effectively than the control groups. These results suggest that the bioinspired scaffold can be used as an advanced scaffold platform for renal disease treatment.

Human Peripheral Blood Mononuclear Cells Incubated in Vasculogenic Conditioning Medium Dramatically Improve Ischemia/Reperfusion Acute Kidney Injury in Mice

Acute kidney injury (AKI) is a major clinical problem that still has no established treatment. We investigated the efficacy of cultured human peripheral blood mononuclear cells (PBMNCs) for AKI. Ischemia/reperfusion injury (IRI) was used to induce AKI in male nonobese diabetic (NOD/severe combined immunodeficiency) mice aged 7 to 8 wk. PBMNCs were isolated from healthy volunteers and were subjected to quality and quantity controlled (QQc) culture for 7 d in medium containing stem cell factor, thrombopoietin, Flt-3 ligand, vascular endothelial growth factor, and interleukin 6. IRI-induced mice were divided into 3 groups and administered (1) 1 × 10⁶ PBMNCs after QQc culture (QQc PBMNCs group), (2) 1 × 10⁶ PBMNCs without QQc culture (non-QQc PBMNCs group), or (3) vehicle without PBMNCs (IRI control group). PBMNCs were injected via the tail vein 24 h after induction of IRI, followed by assessment of renal function, histological changes, and homing of injected cells. Blood urea nitrogen and serum creatinine (Cr) 72 h after induction of IRI in the QQc PBMNCs group dramatically improved compared with those in the IRI control and the non-QQc PBMNCs groups, accompanied by the improvement of tubular damages. Interstitial fibrosis 14 d after induction of IRI was also significantly improved in the QQc PBMNCs group compared with the other groups. The renoprotective effect noted in the QQc PBMNCs group was accompanied by reduction of peritubular capillary loss. The change of PBMNCs’ population (increase of CD34+ cells, CD133+ cells, and CD206+ cells) and increased endothelial progenitor cell colony-forming potential by QQc culture might be one of the beneficial mechanisms for restoring AKI. In conclusion, an injection of human QQc PBMNCs 24 h after induction of IRI dramatically improved AKI in mice.

The role of adenosine 1a receptor signaling on GFR early after the induction of sepsis

Sepsis and acute kidney injury (AKI) synergistically increase morbidity and mortality in the ICU. How sepsis reduces glomerular filtration rate (GFR) and causes AKI is poorly understood; one proposed mechanism includes tubuloglomerular feedback (TGF). When sodium reabsorption by the proximal tubules is reduced in normal animals, the macula densa senses increased luminal sodium chloride, and then adenosine-1a receptor (A1aR) signaling triggers tubuloglomerular feedback, reducing GFR through afferent arteriole vasoconstriction. We measured GFR and systemic hemodynamics early during cecal ligation and puncture-induced sepsis in wild-type and A1aR-knockout mice. A miniaturized fluorometer was attached to the back of each mouse and recorded the clearance of FITC-sinistrin via transcutaneous fluorescence to monitor GFR. Clinical organ injury markers and cytokines were measured and hemodynamics monitored using implantable transducer telemetry devices. In wild-type mice, GFR was stable within 1 h after surgery, declined by 43% in the next hour, and then fell to less than 10% of baseline after 2 h and 45 min. In contrast, in A1aR-knockout mice GFR was 37% below baseline immediately after surgery and then gradually declined over 4 h. A1aR-knockout mice had similar organ injury and inflammatory responses, albeit with lower heart rate. We conclude that transcutaneous fluorescence can accurately monitor GFR and detect changes rapidly during sepsis. Tubuloglomerular feedback plays a complex role in sepsis; initially, TGF helps maintain GFR in the 1st hour, and over the subsequent 3 h, TGF causes GFR to plummet. By 18 h, TGF has no cumulative effect on renal or extrarenal organ damage.

Murine Nephrotoxic Nephritis as a Model of Chronic Kidney Disease

Using the nonaccelerated murine nephrotoxic nephritis (NTN) as a model of chronic kidney disease (CKD) could provide an easily inducible model that enables a rapid test of treatments. Originally, the NTN model was developed as an acute model of glomerulonephritis, but in this study we evaluate the model as a CKD model and compare CD1 and C57BL/6 female and male mice. CD1 mice have previously showed an increased susceptibility to CKD in other CKD models. NTN was induced by injecting nephrotoxic serum (NTS) and evaluated by CKD parameters including albuminuria, glomerular filtration rate (GFR), mesangial expansion, and renal fibrosis. Both strains showed significant albuminuria on days 2-3 which remained significant until the last time point on days 36-37 supporting dysfunctional filtration also observed by a significantly declined GFR on days 5-6, 15–17, and 34–37. Both strains showed early progressive mesangial expansion and significant renal fibrosis within three weeks suggesting CKD development. CD1 and C57BL/6 females showed a similar disease progression, but female mice seemed more susceptible to NTS compared to male mice. The presence of albuminuria, GFR decline, mesangial expansion, and fibrosis showed that the NTN model is a relevant CKD model both in C57BL/6 and in CD1 mice.

Histamine H4 receptor antagonism prevents the progression of diabetic nephropathy in male DBA2/J mice

Due to the incidence of diabetes and the related morbidity of diabetic nephropathy, identification of new therapeutic strategies represents a priority. In the last few decades new and growing evidence on the possible role of histamine in diabetes has been provided. In particular, the histamine receptor H₄R is emerging as a new promising pharmacological target for diabetic nephropathy. The aim of this study was to evaluate the efficacy of selective H₄R antagonism by JNJ39758979 on the prevention of diabetic nephropathy progression in a murine model of diabetes induced by streptozotocin injection. JNJ39758979 (25, 50, 100 mg/kg/day p.o.) was administered for 15 weeks starting from the onset of diabetes. Functional parameters were monitored throughout the experimental period. JNJ39758979 did not significantly affect glycaemic status or body weight. The urine analysis indicated a dose-dependent inhibitory effect of JNJ39758979 on Albumin-Creatinine-Ratio, the Creatinine Clearance, the 24 h urine volume, and pH urine acidification (P < 0.05). The beneficial effects of JNJ39758979 on renal function paralleled comparable effects on renal morphological integrity. These effects were sustained by a significant immune infiltration and fibrosis reduction. Notably, megalin and sodium-hydrogen-exchanger 3 expression levels were preserved. Our data suggest that the H₄R participates in diabetic nephropathy progression through both a direct effect on tubular reabsorption and an indirect action on renal tissue architecture via inflammatory cell recruitment. Therefore, H₄R antagonism emerges as a possible new multi-mechanism therapeutic approach to counteract development of diabetic nephropathy development.

Role of α-Dicarbonyl Compounds in the Inhibition Effect of Reducing Sugars on the Formation of 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine

The effect of reducing sugars on formation of PhIP in fried pork was investigated, and the underlying mechanisms were revealed by studying the reaction pathways between α-dicarbonyl compounds (α-DCs) and PhIP. The addition of reducing sugars (such as glucose) greatly reduced the amount of PhIP in fried pork from 15.5 ng/g to less than 1.0 ng/g. The amount of PhIP decreased significantly with an increasing level of added α-DCs in model systems. Similarly, the addition of methylglyoxal (MGO) decreased significantly the levels of phenylalanine (Phe) and creatinine (Crn) but increased significantly the level of phenylacetaldehyde (PEA). 2-Amino-1-methyl-5-(2-oxopropylidene)-imidazol-4-one and N-(1-methyl-4-oxoimidazolidin-2-ylidene) amino propionic acids were identified in MGO/Crn and MGO/Crn/Phe model systems and fried pork with glucose. These results revealed that the degradation products of reducing sugars-α-DCs-play an important role in inhibiting formation of PhIP by reacting with key precursors of PhIP and itself.

CD11b activation suppresses TLR-dependent inflammation and autoimmunity in systemic lupus erythematosus

Genetic variations in the ITGAM gene (encoding CD11b) strongly associate with risk for systemic lupus erythematosus (SLE). Here we have shown that 3 nonsynonymous ITGAM variants that produce defective CD11b associate with elevated levels of type I interferon (IFN-I) in lupus, suggesting a direct link between reduced CD11b activity and the chronically increased inflammatory status in patients. Treatment with the small-molecule CD11b agonist LA1 led to partial integrin activation, reduced IFN-I responses in WT but not CD11b-deficient mice, and protected lupus-prone MRL/Lpr mice from end-organ injury. CD11b activation reduced TLR-dependent proinflammatory signaling in leukocytes and suppressed IFN-I signaling via an AKT/FOXO3/IFN regulatory factor 3/7 pathway. TLR-stimulated macrophages from CD11B SNP carriers showed increased basal expression of IFN regulatory factor 7 (IRF7) and IFN-β, as well as increased nuclear exclusion of FOXO3, which was suppressed by LA1-dependent activation of CD11b. This suggests that pharmacologic activation of CD11b could be a potential mechanism for developing SLE therapeutics.

Antagonism of scavenger receptor CD36 by 5A peptide prevents chronic kidney disease progression in mice independent of blood pressure regulation

Scavenger receptor CD36 participates in lipid metabolism and inflammatory pathways important for cardiovascular disease and chronic kidney disease (CKD). Few pharmacological agents are available to slow the progression of CKD. However, apolipoprotein A-I-mimetic peptide 5A antagonizes CD36 in vitro. To test the efficacy of 5A, and to test the role of CD36 during CKD, we compared wild-type to CD36 knockout mice and wild-type mice treated with 5A, in a progressive CKD model that resembles human disease. Knockout and 5A-treated wild-type mice were protected from CKD progression without changes in blood pressure and had reductions in cardiovascular risk surrogate markers that are associated with CKD. Treatment with 5A did not further protect CD36 knockout mice from CKD progression, implicating CD36 as its main site of action. In a separate model of kidney fibrosis, 5A-treated wild-type mice had less macrophage infiltration and interstitial fibrosis. Peptide 5A exerted anti-inflammatory effects in the kidney and decreased renal expression of inflammasome genes. Thus, CD36 is a new therapeutic target for CKD and its associated cardiovascular risk factors. Peptide 5A may be a promising new agent to slow CKD progression.

Iohexol plasma clearance, a simple and reliable method to measure renal function in conscious mice

In mice, renal function evaluated by serum creatinine has limitations. Gold standard methods using radioactive markers are cumbersome. We aimed to develop the iohexol plasma clearance as a simple assessment of renal function in conscious mice. We used two groups of mice: testing and validation, formed by 16 animals (8 male and 8 female) each. Iohexol was injected intravenously into the tail vein (6.47 mg), and tail tip blood samples were collected at 1, 3, 7, 10, 15, 35, 55, and 75 min. Iohexol plasma clearances were calculated in two ways: (1) two-compartment model (CL2) using all time points and (2) one-compartment model (CL1) using only the last four points. In the testing group, CL1 overestimated the true clearance (CL2). Therefore, CL1 was recalculated applying a correction factor calculated as the ratio between CL2/CL1. The latter was considered as the simplified method. CL2 averaged 223.3 ± 64.3 μl/min and CL1 252.4 ± 76.4 μl/min, which lead to a CF of 0.89. Comparable results for CL2, CL1, and simplified method were observed in the validation group. Additionally, we demonstrated the capacity of the simplified method to quantitatively assess different degrees of renal function in three mouse models: hyperoxaluric-CKD (87.4 ± 28.3 μl/min), heminephrectomized (135-0 ± 50.5 μl/min), and obese (399.6 ± 112.1 μl/min) mice. We have developed a simple and reliable method to evaluate renal function in conscious mice under diverse clinical conditions. Moreover, the test can be repeated in the same animal, which makes the method useful to examine renal function changes over time.

Pulsed focused ultrasound pretreatment improves mesenchymal stromal cell efficacy in preventing and rescuing established acute kidney injury in mice

Animal studies have shown that mesenchymal stromal cell (MSC) infusions improve acute kidney injury (AKI) outcomes when administered early after ischemic/reperfusion injury or within 24 hours after cisplatin administration. These findings have spurred several human clinical trials to prevent AKI. However, no specific therapy effectively treats clinically obvious AKI or rescues renal function once advanced injury is established. We investigated if noninvasive image-guided pulsed focused ultrasound (pFUS) could alter the kidney microenvironment to enhance homing of subsequently infused MSC. To examine the efficacy of pFUS-enhanced cell homing in disease, we targeted pFUS to kidneys to enhance MSC homing after cisplatin-induced AKI. We found that pFUS enhanced MSC homing at 1 day post-cisplatin, prior to renal functional deficits, and that enhanced homing improved outcomes of renal function, tubular cell death, and regeneration at 5 days post-cisplatin compared to MSC alone. We then investigated whether pFUS+MSC therapy could rescue established AKI. MSC alone at 3 days post-cisplatin, after renal functional deficits were obvious, significantly improved 7-day survival of animals. Survival was further improved by pFUS and MSC. pFUS prior to MSC injections increased IL-10 production by MSC that homed to kidneys and generated an anti-inflammatory immune cell profile in treated kidneys. This study shows pFUS is a neoadjuvant approach to improve MSC homing to diseased organs. pFUS with MSC better prevents AKI than MSC alone and allows rescue therapy in established AKI, which currently has no meaningful therapeutic options.

Vitamin D3 pretreatment regulates renal inflammatory responses during lipopolysaccharide-induced acute kidney injury

Vitamin D receptor (VDR) is highly expressed in human and mouse kidneys. Nevertheless, its functions remain obscure. This study investigated the effects of vitamin D3 (VitD3) pretreatment on renal inflammation during lipopolysaccharide (LPS)-induced acute kidney injury. Mice were intraperitoneally injected with LPS. In VitD3 + LPS group, mice were pretreated with VitD3 (25 μg/kg) at 48, 24 and 1 h before LPS injection. As expected, an obvious reduction of renal function and pathological damage was observed in LPS-treated mice. VitD3 pretreatment significantly alleviated LPS-induced reduction of renal function and pathological damage. Moreover, VitD3 pretreatment attenuated LPS-induced renal inflammatory cytokines, chemokines and adhesion molecules. In addition, pretreatment with 1,25(OH)2D3, the active form of VitD3, alleviated LPS-induced up-regulation of inflammatory cytokines and chemokines in human HK-2 cells, a renal tubular epithelial cell line, in a VDR-dependent manner. Further analysis showed that VitD3, which activated renal VDR, specifically repressed LPS-induced nuclear translocation of nuclear factor kappa B (NF-κB) p65 subunit in the renal tubules. LPS, which activated renal NF-κB, reciprocally suppressed renal VDR and its target gene. Moreover, VitD3 reinforced the physical interaction between renal VDR and NF-κB p65 subunit. These results provide a mechanistic explanation for VitD3-mediated anti-inflammatory activity during LPS-induced acute kidney injury.

TLR4 mutant mice are protected from renal fibrosis and chronic kidney disease progression

Chronic kidney disease (CKD) is associated with persistent low-grade inflammation and immunosuppression. In this study we tested the role of Toll-like receptor 4, the main receptor for endotoxin (LPS), in a mouse model of renal fibrosis and in a model of progressive CKD that better resembles the human disease. C3HeJ (TLR4 mutant) mice have a missense point mutation in the TLR4 gene, rendering the receptor nonfunctional. In a model of renal fibrosis after folic acid injection, TLR4 mutant mice developed less interstititial fibrosis in comparison to wild-type (WT) mice. Furthermore, 4 weeks after 5/6 nephrectomy with continuous low-dose angiotensin II infusion, C3HeOuJ (TLR4 WT) mice developed progressive CKD with albuminuria, increased serum levels of BUN and creatinine, glomerulosclerosis, and interstitial fibrosis, whereas TLR4 mutant mice were significantly protected from CKD progression. TLR4 WT mice also developed low-grade systemic inflammation, splenocyte apoptosis and increased expression of the immune inhibitory receptor PD-1 in the spleen, which were not observed in TLR4 mutant mice. In vitro, endotoxin (LPS) directly upregulated NLRP3 inflammasome expression in renal epithelial cells via TLR4. In summary, TLR4 contributes to renal fibrosis and CKD progression, at least in part, via inflammasome activation in renal epithelial cells, and may also participate in the dysregulated immune response that is associated with CKD.

Ficolin B in Diabetic Kidney Disease in a Mouse Model of Type 1 Diabetes

BACKGROUND

The innate immune system may have adverse effects in diabetes and cardiovascular disease. The complement system seems to play a key role through erroneous complement activation via hyperglycaemia-induced neoepitopes. Recently mannan-binding lectin (MBL) was shown to worsen diabetic kidney changes. We hypothesize that mouse ficolin B exerts detrimental effects in the diabetic kidney as seen for MBL.

METHODS

We induced diabetes with streptozotocin in female wild-type mice and ficolin B knockout mice and included two similar nondiabetic groups. Renal hypertrophy and excretion of urinary albumin and creatinine were quantified to assess diabetic kidney damage.

RESULTS

In the wild-type groups, the kidney weighed 24% more in the diabetic mice compared to the controls. The diabetes-induced increase in kidney weight was 29% in the ficolin B knockout mice, that is, equal to wild-type animals (two-way ANOVA, P = 0.60). In the wild-type mice the albumin-to-creatinine ratio (ACR) was 32.5 mg/g higher in the diabetic mice compared to the controls. The difference was 62.5 mg/g in the ficolin B knockout mice, but this was not significantly different from the wild-type animals (two-way ANOVA, P = 0.21).

CONCLUSIONS

In conclusion, the diabetes-induced effects on kidney weight and ACR were not modified by the presence or absence of ficolin B.

BAMBI elimination enhances alternative TGF-β signaling and glomerular dysfunction in diabetic mice

BMP, activin, membrane-bound inhibitor (BAMBI) acts as a pseudo-receptor for the transforming growth factor (TGF)-β type I receptor family and a negative modulator of TGF-β kinase signaling, and BAMBI(-/-) mice show mild endothelial dysfunction. Because diabetic glomerular disease is associated with TGF-β overexpression and microvascular alterations, we examined the effect of diabetes on glomerular BAMBI mRNA levels. In isolated glomeruli from biopsies of patients with diabetic nephropathy and in glomeruli from mice with type 2 diabetes, BAMBI was downregulated. We then examined the effects of BAMBI deletion on streptozotocin-induced diabetic glomerulopathy in mice. BAMBI(-/-) mice developed more albuminuria, with a widening of foot processes, than BAMBI(+/+) mice, along with increased activation of alternative TGF-β pathways such as extracellular signal-related kinase (ERK)1/2 and Smad1/5 in glomeruli and cortices of BAMBI(-/-) mice. Vegfr2 and Angpt1, genes controlling glomerular endothelial stability, were downmodulated in glomeruli from BAMBI(-/-) mice with diabetes. Incubation of glomeruli from nondiabetic BAMBI(+/+) or BAMBI(-/-) mice with TGF-β resulted in the downregulation of Vegfr2 and Angpt1, effects that were more pronounced in BAMBI(-/-) mice and were prevented by a MEK inhibitor. The downregulation of Vegfr2 in diabetes was localized to glomerular endothelial cells using a histone yellow reporter under the Vegfr2 promoter. Thus, BAMBI modulates the effects of diabetes on glomerular permselectivity in association with altered ERK1/2 and Smad1/5 signaling. Future therapeutic interventions with inhibitors of alternative TGF-β signaling may therefore be of interest in diabetic nephropathy.

In vivo RNA interference models of inducible and reversible Sirt1 knockdown in kidney cells

The silent mating type information regulation 2 homolog 1 gene (Sirt1) encodes an NAD-dependent deacetylase that modifies the activity of well-known transcriptional regulators affected in kidney diseases. Sirt1 is expressed in the kidney podocyte, but its function in the podocyte is not clear. Genetically engineered mice with inducible and reversible Sirt1 knockdown in widespread, podocyte-specific, or tubular-specific patterns were generated. We found that mice with 80% knockdown of renal Sirt1 expression have normal glomerular function under the basal condition. When challenged with doxorubicin (Adriamycin), these mice develop marked albuminuria, glomerulosclerosis, mitochondrial injury, and impaired autophagy of damaged mitochondria. Reversal of Sirt1 knockdown during the early phase of Adriamycin-induced nephropathy prevented the progression of glomerular injury and reduced the accumulation of dysmorphic mitochondria in podocytes but did not reverse the progression of albuminuria and glomerulosclerosis. Sirt1 knockdown mice with diabetes mellitus, which is known to cause mitochondrial dysfunction in the kidney, developed more albuminuria and mitochondrial dysfunction compared with diabetic mice without Sirt1 knockdown. In conclusion, these results demonstrate that our RNA interference-mediated Sirt1 knockdown models are valid and versatile tools for characterizing the function of Sirt1 in the kidney; Sirt1 plays a role in homeostatic maintenance of podocytes under the condition of mitochondrial stress/injury.

Detection of urinary creatinine using gold nanoparticles after solid phase extraction

Label-free gold nanoparticles (AuNPs) were utilized in the detection of creatinine in human urine after a sample preparation by extraction of creatinine on sulfonic acid functionalized silica gel. With the proposed sample preparation method, the interfering effects of the urine matrix on creatinine detection by AuNPs were eliminated. Parameters affecting creatinine extraction were investigated. The aggregation of AuNPs induced by creatinine resulted in a change in the surface plasmon resonance signal with a concomitant color change that could be observed by the naked eye and quantified spectrometrically. The effect of AuNP concentration and reaction time on AuNP aggregation was investigated. The method described herein provides a determination of creatinine in a range of 15-40mgL(-1) with a detection limit of 13.7mgL(-1) and it was successfully used in the detection of creatinine in human urine samples.

Regulation of Mitochondrial Dynamics by Dynamin-Related Protein-1 in Acute Cardiorenal Syndrome

Experimental evidence has clarified distant organ dysfunctions induced by AKI. Crosstalk between the kidney and heart, which has been recognized recently as cardiorenal syndrome, appears to have an important role in clinical settings, but the mechanisms by which AKI causes cardiac injury remain poorly understood. Both the kidney and heart are highly energy-demanding organs that are rich in mitochondria. Therefore, we investigated the role of mitochondrial dynamics in kidney-heart organ crosstalk. Renal ischemia reperfusion (IR) injury was induced by bilateral renal artery clamping for 30 min in 8-week-old male C57BL/6 mice. Electron microscopy showed a significant increase of mitochondrial fragmentation in the heart at 24 h. Cardiomyocyte apoptosis and cardiac dysfunction, evaluated by echocardiography, were observed at 72 h. Among the mitochondrial dynamics regulating molecules, dynamin-related protein 1 (Drp1), which regulates fission, and mitofusin 1, mitofusin 2, and optic atrophy 1, which regulate fusion, only Drp1 was increased in the mitochondrial fraction of the heart. A Drp1 inhibitor, mdivi-1, administered before IR decreased mitochondrial fragmentation and cardiomyocyte apoptosis significantly and improved cardiac dysfunction induced by renal IR. This study showed that renal IR injury induced fragmentation of mitochondria in a fission-dominant manner with Drp1 activation and subsequent cardiomyocyte apoptosis in the heart. Furthermore, cardiac dysfunction induced by renal IR was improved by Drp1 inhibition. These data suggest that mitochondrial fragmentation by fission machinery may be a new therapeutic target in cardiac dysfunction induced by AKI.

Nephrin Preserves Podocyte Viability and Glomerular Structure and Function in Adult Kidneys

Nephrin is required during kidney development for the maturation of podocytes and formation of the slit diaphragm junctional complex. Because nephrin expression is downregulated in acquired glomerular diseases, nephrin deficiency is considered a pathologic feature of glomerular injury. However, whether nephrin deficiency exacerbates glomerular injury in glomerular diseases has not been experimentally confirmed. Here, we generated mice with inducible RNA interference-mediated nephrin knockdown. Short-term nephrin knockdown (6 weeks), starting after the completion of kidney development at 5 weeks of age, did not affect glomerular structure or function. In contrast, mice with long-term nephrin knockdown (20 weeks) developed mild proteinuria, foot process effacement, filtration slit narrowing, mesangial hypercellularity and sclerosis, glomerular basement membrane thickening, subendothelial zone widening, and podocyte apoptosis. When subjected to an acquired glomerular insult induced by unilateral nephrectomy or doxorubicin, mice with short-term nephrin knockdown developed more severe glomerular injury compared with mice without nephrin knockdown. Additionally, nephrin-knockdown mice developed more exaggerated glomerular enlargement when subjected to unilateral nephrectomy and more podocyte apoptosis and depletion after doxorubicin challenge. AKT phosphorylation, which is a slit diaphragm-mediated and nephrin-dependent pathway in the podocyte, was markedly reduced in mice with long-term or short-term nephrin knockdown challenged with uninephrectomy or doxorubicin. Taken together, our data establish that under the basal condition and in acquired glomerular diseases, nephrin is required to maintain slit diaphragm integrity and slit diaphragm-mediated signaling to preserve glomerular function and podocyte viability in adult mice.

Blood creatinine level in postmortem cases

Blood chemical analysis for the diagnosis of diseases in forensic cases should be conducted in the same way as for clinical cases. However, it is sometimes difficult to obtain serum samples in forensic cases because of postmortem changes such as hemolysis and putrefaction. This study aimed to evaluate renal function in postmortem cases by blood creatinine analysis. The blood creatinine level was measured by high performance liquid chromatography (HPLC) using whole blood samples taken from 77 postmortem cases, and the relationships between blood creatinine level, postmortem interval, and cause of death were examined. The median blood creatinine level was found to be 1.15 mg/dL, with no significant differences between blood samples taken from different parts of the body. The blood creatinine level was stable for 3 days after death and gradually increased after that period, in line with a previous study using enzymatic analysis that found the serum creatinine level was stable in the early postmortem period. The blood creatinine level was high in the cases of blunt injury, intoxication, and in deaths caused by fire. This was considered to reflect acute renal dysfunction. However, the postmortem blood creatinine level remained higher than the clinical normal value despite omitting cases with renal dysfunction from the analysis. Therefore, we next investigated the change in postmortem creatinine levels in mice and found that the blood creatinine level increased with the emergence of rigor mortis. Our findings indicate that HPLC is useful in the postmortem evaluation of renal function even in the cases where serum cannot be obtained. However, the presence of rigor mortis should be considered in the evaluation of blood creatinine values.

Hypertensive renal injury is associated with gene variation affecting immune signaling

BACKGROUND

The spontaneously hypertensive rat (SHR) strain exists in lines that contrast strongly in susceptibility to renal injury in hypertension. These inbred lines share common ancestry, and only 13% of their genomes arise from different ancestors.

METHODS AND RESULTS

We used next gen sequencing to detect natural allelic variation in 5 genes of the immunoreceptor signaling pathway (IgH, Dok3, Src, Syk, and JunD) that arise from different ancestors in the injury-prone SHR-A3 and the resistant SHR-B2 lines. We created an intercross between these lines, and in the F2 progeny, we observed that the inheritance of haplotype blocks containing the SHR-A3 alleles of these 5 genes correlated with increased albuminuria and histological measures of renal injury. To test whether accumulated genetic variation in this pathway may create a therapeutic target in hypertensive renal injury, rats of both lines were treated with the immunosuppressant mycophenolate mofetil (MMF). MMF reduced proteinuria (albumin to creatinine ratio) from 6.6 to 1.2 mg/mg (P<0.001) in SHR-A3. Glomerular injury scores were reduced in MMF-treated SHR-A3 from 1.6 to 1.4 (P<0.002). Tubulo-interstitial injury was reduced in MMF-treated SHR-A3 from 2.62 to 2.0 (P=0.001). MMF treatment also reduced renal fibrosis in SHR-A3 (3.9 versus 2.0; P<0.001).

CONCLUSIONS

Polygenic susceptibility to renal injury in hypertension arises in association with genetic variation in genes that participate in immune responses and is dramatically improved by reduction of immune system activity.

Pharmacologic targeting of sphingosine-1-phosphate receptor 1 improves the renal microcirculation during sepsis in the mouse

Microvascular failure is hallmark of sepsis in humans and is recognized as a strong predictor of mortality. In the mouse subjected to cecal ligation and puncture (CLP) to induce a clinically relevant sepsis, renal microvascular permeability increases and peritubular capillary perfusion declines rapidly in the kidney leading to acute kidney injury (AKI). Sphingosine-1-phosphate (S1P) is a key regulator of microvascular endothelial function. To investigate the role of S1P in the development of microvascular permeability and peritubular capillary hypoperfusion in the kidney during CLP-induced AKI, we used a pharmacologic approach and a clinically relevant delayed dosing paradigm. Evans blue dye was used to measure renal microvascular permeability and intravital video microscopy was used to quantitate renal cortical capillary perfusion. The S1P receptor 1 (S1P1) agonist SEW2871 [5-[4-phenyl-5-(trifluoromethyl)-2-thienyl]-3-[3-(trifluoromethyl)phenyl]-1,2,4-oxadiazole] and S1P2 antagonist JTE-013 [N-(2,6-dichloro-4-pyridinyl)-2-[1,3-dimethyl-4-(1-methylethyl)-1H-pyrazolo[3,4-b]pyridin-6-yl]-hydrazinecarboxamide] were administered at the time of CLP and produced a dose-dependent but partial reduction in renal microvascular permeability at 6 hours after CLP. However, neither agent improved capillary perfusion at 6 hours. With delayed administration at 6 hours after CLP, only SEW2871 reversed microvascular permeability when measured at 18 hours. Importantly, SEW2871 also restored capillary perfusion and improved renal function. These data suggest that S1P1 and S1P2 do not regulate the early decline in renal capillary perfusion. However, later in the course of sepsis, pharmacologic stimulation of S1P1, even when delaying therapy until after injury has occurred, improves capillary and renal function, suggesting this approach should be evaluated as an adjunct therapy during sepsis.

Establishing standards for studying renal function in mice through measurements of body size-adjusted creatinine and urea levels

Strategies for obtaining reliable results are increasingly implemented in order to reduce errors in the analysis of human and veterinary samples; however, further data are required for murine samples. Here, we determined an average factor from the murine body surface area for the calculation of biochemical renal parameters, assessed the effects of storage and freeze-thawing of C57BL/6 mouse samples on plasmatic and urinary urea, and evaluated the effects of using two different urea-measurement techniques. After obtaining 24 h urine samples, blood was collected, and body weight and length were established. The samples were evaluated after collection or stored at −20°C and −70°C. At different time points (0, 4, and 90 days), these samples were thawed, the creatinine and/or urea concentrations were analyzed, and samples were restored at these temperatures for further measurements. We show that creatinine clearance measurements should be adjusted according to the body surface area, which was calculated based on the weight and length of the animal. Repeated freeze-thawing cycles negatively affected the urea concentration; the urea concentration was more reproducible when using the modified Berthelot reaction rather than the ultraviolet method. Our findings will facilitate standardization and optimization of methodology as well as understanding of renal and other biochemical data obtained from mice.

Effect of imidacloprid on hepatotoxicity and nephrotoxicity in male albino mice

Imidacloprid (IC) is a systemic insecticide related to the tobacco toxin nicotine. IC is a toxic substance frequently used into combat insects, rodents and plants pests and other creatures that can pose problems for agriculture. We, therefore, planned this study to assess risk factors, biochemical and histological alterations associated with hepatotoxicity and nephrotoxicity. Forty-eight adult male albino mice were divided into four groups of 12 animals each. All the animals were given standard synthetic pellet diet. One group served as control, and the other three were served as experimental groups. Decrease in the body weight of the high dose group was observed at 15 mg/kg/day, and no mortality occurred during the treatment period. High dose of imidacloprid caused a significant elevation of serum clinical chemistry parameters, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvate kinase (SGPT), alkaline phosphatase (ALP) and total bilirubin (TBIL). Histology of liver and kidney indicates hepatotoxicity and nephrotoxicity at a high dose of imidacloprid. Based on the morphological, biochemical and histopathological analysis, it is evident that imidacloprid induced toxicological effects at 15 mg/kg/day to mice. The results of the present study demonstrate that IC had significant effects on body weight, liver functions and kidney (p < 0.05) at a dose of 15 mg/kg body weight. IC treatment 5 and 10 mg/kg/day may be considered as no observed adverse effect level (NOAEL) for mice. It was concluded that IC can cause hepatotoxicity and nephrotoxicity at a dose much lower than the LD₅₀ (131 mg/kg body weight) in mice.

Comparison of serum creatinine and serum cystatin C as biomarkers to detect sepsis-induced acute kidney injury and to predict mortality in CD-1 mice

Acute kidney injury (AKI) dramatically increases sepsis mortality, but AKI diagnosis is delayed when based on serum creatinine (SCr) changes, due in part, to decreased creatinine production. During experimental sepsis, we compared serum cystatin C (sCysC), SCr, and blood urea nitrogen (BUN) to inulin glomerular filtration rate (iGFR) before or 3-18 h after cecal ligation and puncture (CLP)-induced sepsis in CD-1 mice. sCysC had a faster increase and reached peak levels more rapidly than SCr in both sepsis and bilateral nephrectomy (BiNx) models. sCysC was a better surrogate of iGFR than SCr during sepsis. Combining sCysC with SCr values into a composite biomarker improved correlation with iGFR better than any biomarker alone or any other combination. We determined the renal contribution to sCysC handling with BiNx. sCysC and SCr were lower post-BiNx/CLP than post-BiNx alone, despite increased inflammatory and nonrenal organ damage biomarkers. Sepsis decreased CysC production in nephrectomized mice without changing body weight or CysC space. Sepsis decreased sCysC production and increased nonrenal clearance, similar to effects of sepsis on SCr. sCysC, SCr, and BUN were measured 6 h postsepsis to link AKI with mortality. Mice with above-median sCysC, BUN, or SCr values 6 h postsepsis died earlier than mice with below-median values, corresponding to a substantial AKI association with sepsis mortality in this model. sCysC performs similarly to SCr in classifying mice at risk for early mortality. We conclude that sCysC detects AKI early and better reflects iGFR in CLP-induced sepsis. This study shows that renal biomarkers need to be evaluated in specific contexts.

Hypertensive renal disease: susceptibility and resistance in inbred hypertensive rat lines

BACKGROUND

Spontaneously hypertensive rat (SHR) lines differ in their susceptibility to hypertensive end-organ disease and may provide an informative model of genetic risk of disease. Lines derived from the original SHR-B and SHR-C clades are highly resistant to hypertensive end-organ disease, whereas lines derived from the SHR-A clade were selected for stroke susceptibility and experience hypertensive renal disease.

METHOD

Here we characterize the temporal development of progressive renal injury in SHR-A3 animals consuming 0.3% sodium in the diet and drinking water. SHR-A3 rats demonstrate albuminuria, glomerular damage, tubulointerstitial injury, and renal fibrosis that emerge at 18 weeks of age and progress.

RESULTS AND CONCLUSION

Mortality of SHR-A3 animals was 50% at 40 weeks of age, and animals surviving to this age had reduced renal function. In contrast SHR-B2, which are 87% genetically identical to SHR-A3, are substantially protected from renal injury and demonstrate only moderate changes in albuminuria and renal histological injury over this time period. At 40 weeks of age, electron microscopy of the renal glomerulus revealed severe podocyte effacement in SHR-A3, but slit diaphragm architecture in SHR-B2 at this age was well preserved. Renal injury traits in the F1 and F2 progeny of an intercross between SHR-A3 and SHR-B2 were measured to determine heritability of renal injury in this model. Heritability of albuminuria, glomerular injury, and tubulointerstitial injury were estimated at 48.9, 66.5 and 58.6%, respectively. We assessed the relationship between blood pressure and renal injury measures in the F2 animals and found some correlation between these variables that explain up to 26% of the trait variation. Quantitative trait locus (QTL) mapping was performed using over 200 single nucleotide polymorphism markers distributed across the 13% of the genome that differs between these two closely related lines. Mapping of albuminuria, tubulointerstitial injury, and renal fibrosis failed to identify loci linked with disease susceptibility, suggesting a complex inheritance of disease risk. We detected a single QTL conferring susceptibility to glomerular injury that was confined to a small haplotype block at chromosome 14:70-76Mb.

Induction of retinol dehydrogenase 9 expression in podocytes attenuates kidney injury

The intracellular concentration of retinoic acid is determined by two sequential oxidation reactions that convert retinol to retinoic acid. We recently demonstrated that retinoic acid synthesis is significantly impaired in glomeruli of HIV-1 transgenic mice (Tg26), a murine model of HIV-associated nephropathy. This impaired retinoic acid synthesis correlates with reduced renal expression of retinol dehydrogenase 9, which catalyzes the rate-limiting step of retinoic acid synthesis by converting retinol to retinal. Because retinoic acid has renal protective effects and can induce podocyte differentiation, we hypothesized that restoration of retinoic acid synthesis could slow the progression of renal disease. Herein, we demonstrate that overexpression of retinol dehydrogenase 9 in cultured podocytes induces the expression of podocyte differentiation markers. Furthermore, we confirm that podocyte-specific overexpression of retinol dehydrogenase 9 in mice with established kidney disease due to either HIV-associated nephropathy or adriamycin-induced nephropathy decreases proteinuria, attenuates kidney injury, and restores podocyte differentiation markers. Our data suggest that restoration of retinoic acid synthesis could be a new approach to treat kidney disease.