Phase Of Acute Kidney Injury Research Articles

8165 A Case Of Rhabdomyolysis-Induced Hypocalcemia And Hypercalcemia

Abstract Disclosure: A. Desai: None. A.L. Izzi: None. B. Flores Chang: None. A. Sajan: None. Introduction: Rhabdomyolysis is a syndrome characterized by muscle breakdown and the release of intracellular muscle contents into circulation. It is associated with electrolyte abnormalities and acute renal failure that can lead to prolonged hospitalization. We report a case of persistent hypercalcemia from recovery of acute renal failure and severe rhabdomyolysis. Case Description: A 47-year-old man with past medical history of polysubstance use initially presented with opiate-induced acute encephalopathy and respiratory failure. He developed severe rhabdomyolysis during the hospital course leading to acute renal failure requiring hemodialysis with hypocalcemia. The initial labs showed corrected calcium 6.2 mg/dL [9.2-11.0], ionized calcium 3.48 mg/dL [4.65-5.28], creatinine kinase level was >72,600 U/L [38-174], BUN 110 mg/dL [8-23], creatinine 7.8 mg/dL [0.6-1.2], and GFR 7 ml/min/BSA. His renal function improved over the next several days in the hospital. The serum creatinine improved to 4 mg/dL, BUN 49 mg/dL and GFR 20 ml/min/BSA respectively after couple of intermittent dialysis sessions. Six days after the last hemodialysis session, patient developed severe hypercalcemia with corrected calcium values ranging from 13.5 to 14.7 mg/dL and ionized calcium 7.41 mg/dL. Labs showed PTH 10 pg/mL [15-65], 1,25-dihydroxyvitamin D <10.0 pg/dL [21-65] and 25-OH Vitamin D levels 15.3 ng/ mL [30-96], which is consistent non-PTH medicated hypercalcemia. The 24-hour urine calcium was 696 mg [0-300 mg/24 hrs, 2900 cc]. PTH-related peptide was not collected. He was treated with intermittent doses of calcitonin and a single dose of pamidronate when the calcium levels were >13 mg/dL. Hypercalcemia resolved in eleven days after initially noted to have hypercalcemia. The corrected calcium improved to 10.1 mg/dL on the day of discharge. Discussion:Severe rhabdomyolysis is associated with acute kidney injury. The initial hypocalcemic phase during rhabdomyolysis is due to entry of calcium into damaged myocytes and deposition of calcium salts in damaged muscle. This is seen in the oliguric phase of acute kidney injury. After the recovery of rhabdomyolysis, the polyuric phase persists during renal recovery. During this time, up to one third of patients may have rebound hypercalcemia due to massive muscle calcium release. As per case reports the hypercalcemia phase lasts from 8 days to 3.5 months. In our case, the patient initially developed hypocalcemia in the oliguric phase of acute kidney injury from rhabdomyolysis. He developed hypercalcemia in the polyuric phase of renal recovery. The hypercalcemia resolved with intravenous hydration, calcitonin and pamidronate. Rhabdomyolysis is a rare cause for both hypocalcemia and hypercalcemia. Our case highlights the biphasic calcium response associated with rhabdomyolysis in the setting of renal impairment and recovery. Presentation: 6/1/2024

Regulators of necroinflammation in acute kidney injury

Interleukin (IL)-22 is unique among the ILs as it elicits direct effects on kidney epithelia and regulates cell survival in a context-dependent manner. Studies published in Kidney International and other journals demonstrate opposing roles of IL-22 (e.g., in models of acute kidney injury). In the early necroinflammation phase of acute kidney injury, IL-22 promotes tubular cell death, whereas it enhances the proliferation and regeneration of epithelial barrier function in the healing phase of injured tubules.

Acute phase reactions in Daboia siamensis venom and fraction-induced acute kidney injury: the role of oxidative stress and inflammatory pathways in in vivo rabbit and ex vivo rabbit kidney models.

This study examines the direct nephrotoxic effects of Daboia siamensis venom (RVV) and venom fractions in in vivo and isolated perfused kidneys (IPK) to understand the role of inflammation pathways and susceptibility to oxidative stress in venom or fraction-induced acute renal failure. We administered RVV and its venom fractions (PLA2, MP, LAAO, and PDE) to rabbits in vivo and in the IPK model. We measured oxidative stress biomarkers (SOD, CAT, GSH, and MDA) in kidney tissue, as well as inflammatory cytokines (TNF-α, IL-1β, IFN-γ, IL-4, IL-5, and IL-10), MDA and GSH levels in plasma and urine. We also calculated fractional excretion (FE) for pro-/anti-inflammatory cytokines and oxidative stress biomarkers, including the ratios of pro-/anti-inflammatory cytokines in urine after envenomation. In both kidney models, significant increases in MDA, SOD, CAT, and GSH levels were observed in kidney tissues, along with elevated concentrations of MDA and GSH in plasma and urine after injecting RVV and venom fractions. Moreover, RVV injections led to progressive increases in FEMDA and decreases in FEGSH. The concentrations of IL-4, IL-5, IL-10, IFN-γ, and TNF-α in plasma increased in vivo, as well as in the urine of the IPK model, but not for IL-1β in both plasma and urine after RVV administrations. Urinary fractional excretion of TNF-α, IL-1β, IFN-γ, IL-4, IL-5, and IL-10 tended to decrease in vivo but showed elevated levels in the IPK model. A single RVV injection in vivo disrupted the balance of urinary cytokines, significantly reducing either the TNF-α/IL-10 ratio or the IFN-γ/IL-10 ratio. RVV induces renal tubular toxicity by increasing oxidative stress production and elevating inflammatory cytokines in urine. During the acute phase of acute kidney injury, the balance of urine cytokines shifts toward anti-inflammatory dominance within the first two hours post-RVV and venom fractions.

ZFP24 drives SOX9 upregulation and protects tubular epithelial cells during acute kidney injury

SOX9 is a transcription factor that controls cell-fate determination during embryonic development and adult tissue homeostasis in multiple organs including the kidneys. SOX9 expression is low in the adult kidneys, however, stress conditions can trigger its transcriptional upregulation in tubular epithelial cells. Functionally, SOX9 plays a protective role during the early phase of acute kidney injury (AKI) and facilitates repair during the recovery phase. To identify the upstream transcriptional regulators that drive SOX9 upregulation in tubular epithelial cells, here we have used an unbiased transcription factor screening approach. Our preliminary screening and validation studies show that Zinc finger protein 24 (ZFP24) controls injury induced SOX9 upregulation in tubular epithelial cells. ZFP24, a Cys2-His2 (C2H2) zinc finger protein is essential for oligodendrocyte maturation and myelination, however its role in the kidneys or in SOX9 regulation remains unknown. We find that tubular epithelial ZFP24 gene ablation exacerbates ischemia, rhabdomyolysis, and cisplatin-associated AKI. Importantly, ZFP24 gene deletion results in suppression of SOX9 upregulation in injured tubular epithelial cells. Chromatin immunoprecipitation and promoter luciferase assays confirmed that ZFP24 binds to a specific site in both murine and human SOX9 promoter. Importantly, CRISPR/Cas9 mediated introduction of mutations in the ZFP24 binding site in the SOX9 promoter in vivo led to suppression of SOX9 upregulation during AKI. These findings identify ZFP24 as a critical stress-responsive transcription factor that protects tubular epithelial cells during AKI in part through SOX9 upregulation. The current study was supported by NIDDK 1R01DK132230 grant to N.P. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A case of delayed hypercalcemia during diuretic phase of acute kidney injury due to rhabdomyolysis: evaluation of heterotopic calcification by serial CT

A case of delayed hypercalcemia during diuretic phase of acute kidney injury due to rhabdomyolysis: evaluation of heterotopic calcification by serial CT

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

Cylocloxygenase-2 is an important mediator of arachidonic acid metabolism. Pan etal. recently identified a robust increase in the expression of cylocloxygenase-2 in proresolving macrophages (M2) during the repair phase of acute kidney injury. The investigators determined the prostaglandin E2 was produced in macrophages and demonstrated that signaling through the E-type prostanoid receptor 4 stimulated the expression of the anti-inflammatory transcription factor MafB. MafB was further shown to be essential for macrophage differentiation and mediation of the intrinsic repair response following experimental acute kidney injury.

Selective depletion of a CD64-expressing phagocyte subset mediates protection against toxic kidney injury and failure

Dendritic cells (DC), macrophages, and monocytes, collectively known as mononuclear phagocytes (MPs), critically control tissue homeostasis and immune defense. However, there is a paucity of models allowing to selectively manipulate subsets of these cells in specific tissues. The steady-state adult kidney contains four MP subsets with Clec9a-expression history that include the main conventional DC1 (cDC1) and cDC2 subtypes as well as two subsets marked by CD64 but varying levels of F4/80. How each of these MP subsets contributes to the different phases of acute kidney injury and repair is unknown. We created a mouse model with a Cre-inducible lox-STOP-lox-diphtheria toxin receptor cassette under control of the endogenous CD64 locus that allows for diphtheria toxin-mediated depletion of CD64-expressing MPs without affecting cDC1, cDC2, or other leukocytes in the kidney. Combined with specific depletion of cDC1 and cDC2, we revisited the role of MPs in cisplatin-induced kidney injury. We found that the intrinsic potency reported for CD11c+ cells to limit cisplatin toxicity is specifically attributed to CD64+ MPs, while cDC1 and cDC2 were dispensable. Thus, we report a mouse model allowing for selective depletion of a specific subset of renal MPs. Our findings in cisplatin-induced injury underscore the value of dissecting the functions of individual MP subsets in kidney disease, which may enable therapeutic targeting of specific immune components in the absence of general immunosuppression.

Early-Phase Urine Output and Severe-Stage Progression of Oliguric Acute Kidney Injury in Critical Care.

Background: The relationship between urine output (UO) and severe-stage progression in the early phase of acute kidney injury (AKI) remains unclear. This study aimed to investigate the relationship between early-phase UO6−12h [UO within 6 h after diagnosis of stage 1 AKI by Kidney Disease: Improving Global Outcomes (KDIGO) UO criteria] and severe-stage progression of AKI and to identify a reference value of early-phase UO6−12h for guiding initial therapy in critical care.Methods: Adult patients with UO < 0.5 ml/kg/h for the first 6 h after intensive care unit (ICU) admission (meeting stage 1 AKI by UO) and UO6−12h ≥ 0.5 ml/kg/h were identified from the Medical Information Mart for Intensive Care (MIMIC) III database. The primary outcome was progression to stage 2/3 AKI by UO. After other variables were adjusted through multivariate analysis, generalized additive model (GAM) was used to visualize the relationship between early-phase UO6−12h and progression to stage 2/3 AKI by UO. A two-piecewise linear regression model was employed to identify the inflection point of early-phase UO6−12h above which progression risk significantly leveled off. Sensitivity and subgroup analyses were performed to assess the robustness of our findings.Results: Of 2,984 individuals, 1,870 (62.7%) with KDIGO stage 1 UO criteria progressed to stage 2/3 AKI. In the multivariate analysis, early-phase UO6−12h showed a significant association with progression to stage 2/3 AKI by UO (odds ratio, 0.40; 95% confidence interval, 0.34–0.46; p < 0.001). There was a non-linear relationship between early-phase UO6−12h and progression of AKI. Early-phase UO6−12h of 1.1 ml/kg/h was identified as the inflection point, above which progression risk significantly leveled off (p = 0.780). Patients with early-phase UO6−12h ≥ 1.1 ml/kg/h had significantly shorter length of ICU stay (3.82 vs. 4.17 days, p < 0.001) and hospital stay (9.28 vs. 10.43 days, p < 0.001) and lower 30-day mortality (11.05 vs. 18.42%, p < 0.001). The robustness of our findings was confirmed by sensitivity and subgroup analyses.Conclusions: Among early-stage AKI patients in critical care, there was a non-linear relationship between early-phase UO6−12h and progression of AKI. Early-phase UO6−12h of 1.1 ml/kg/h was the inflection point above which progression risk significantly leveled off.

MO343SERUM RESPONSE FACTOR, A NOVEL EARLY DIAGNOSTIC BIOMARKER OF ACUTE KIDNEY INJURY

Abstract Background and Aims Studies have shown that serum response factor (SRF) is increased in chronic kidney injury, such as diabetic nephropathy, hyperuricemic nephropathy and renal cell carcinoma. The objective is to explore the early diagnostic value of SRF in acute kidney injury (AKI). Method AKI-related microarray data were analyzed, and the expression and location of SRF were investigated in the early phase of AKI. Results Bioinformatics results demonstrated that SRF was dramatically elevated 2-4 h after ischemia/reperfusion (I/R) in mouse renal tissue. In I/R rats, SRF was mostly expressed and located in renal tubular epithelial cells (TECs). SRF started to increase at 1 h, peaked at 3-9 h and started to decrease at 12 h after I/R. The areas under the ROC curve of renal SRF mRNA, renal SRF protein, urinary SRF, serum SRF and serum creatinine (Scr) were 87.9%, 83.0%, 81.3%, 78.8%, 68.8%, respectively. Conclusion SRF is remarkably upregulated in early (before 24 h) AKI and can replace Scr as a potential new early diagnostic biomarker of AKI.

M2 macrophages predict worse long-term outcomes in human acute tubular necrosis

Although macrophages are important players in the injury/repair processes in animal models of acute kidney injury (AKI), their roles in human AKI remains uncertain owing to a paucity of human biopsy studies. We investigated the role of macrophages in 72 cases of biopsy-proven acute tubular necrosis (ATN) and six cases of healthy kidney. Macrophages were identified by CD68 and CD163 immunohistochemistry and analyzed for their effect on renal outcomes. CD163+ M2 macrophages outnumbered CD68+ cells in the healthy kidneys, suggesting that CD163+ macrophages are resident macrophages. The infiltration of both subtypes of macrophages increased significantly in ATN. The density of the CD68+ macrophages was significantly higher in advanced-stage AKI, whereas CD163+ M2 macrophages was not. Eighty percent of patients exhibited renal functional recovery during follow-up. Older age and a higher density of CD163+ macrophages predicted non-recovery, whereas the AKI stage, tubular injury score, and density of CD68+ cells did not. The density of CD163+ M2 macrophages was an independent predictor of low eGFR at 3 months in advanced-stage AKI. This is the first human study demonstrating the possible role of macrophages in the injury and repair phases of AKI.

Double Labeling of PDGFR-β and α-SMA in Swine Models of Acute Kidney Injury to Detect Pericyte-to-Myofibroblast Transdifferentation as Early Marker of Fibrosis.

Growing evidences suggest that peritubular capillaries pericytes are the main source of scar-forming myofibroblasts during chronic kidney disease (CKD), as well as early phases of acute kidney injury (AKI). In a swine model of sepsis and I/R (Ischemia Reperfusion) injury-induced AKI we demonstrated that renal pericytes are able to transdifferentiate toward α-SMA+ myofibroblasts leading to interstitial fibrosis. Even if precise pericytes identification requires transmission electron microscopy and the co-immunostaining of several markers (i.e., Gli, NG2 chondroitin sulphate proteoglycan, CD146, desmin or CD73) and emerging new markers (CD248 or TEM1, endosialin), previous studies suggested that PDGFR-β could be used as marker for renal pericytes characterization. Recently, double immunofluorescence staining of PDGFR-β and α-SMA was performed to identify the damage activated pericytes (PDGFR-β+/α-SMA+ cells) in the early phase of fibrosis development. Our data highlighted the crucial role of renal pericytes in the physiopathology of sepsis and I/R associated AKI. In this protocol, we describe the procedure for double immunofluorescence staining of PDGFR-β and α-SMA in swine Formalin-Fixed Paraffin-Embedded (FFPE) kidney biopsies and the method for image analysis and quantification.

Acute Kidney Injury (AKI) in the Setting of Multi-Organ Dysfunction Syndrome (MODS) Secondary to Yellow Fever Infection (YFI) in a 19-Year-Old Woman

Background: Outbreak of yellow fever infection (YFI), a mosquito-borne disease, occurs sporadically worldwide especially in tropical nations. Acute kidney injury (AKI) commonly results from YFI and could be associated with a poor prognosis for victims even under intensive care unit (ICU). Pathophysiologic mechanisms for AKI include hypovolemic shut down, cytotoxicity, acute tubular necrosis (ATN), hemolysis, or coagulopathy. Early diagnosis, prompt and effective treatment modalities including dialysis improve treatment outcome. Aim: We report the case management of a 19-year-old woman who had yellow fever infection complicated by acute kidney injury in the setting of multi-organ dysfunction syndrome (MODS). Case Presentation: A 19-year-old woman who presented with fever, headache and vomiting for 2 weeks. In the course of the illness, urine volume became reduced and coke colored, followed by body swelling, yellowness of the eyes bleeding from the orifices. Examination revealed an acutely ill looking woman, icteric, and with pedal edema. Her pulse was 100/min and blood pressure was 120/80 mmHg. Liver was enlarged, soft and tender. She had proteinuria 3+ and polymerase chain reaction (PCR) confirmed yellow fever infection. She had markedly deranged serum biochemical parameters for which she had a three-hour session of hemodialysis with Heparin anticoagulation. The urea reduction ratio (URR) was 46.9%. Barrier nursing was commenced. She had 7 units of whole blood and a pint of fresh frozen plasma (FFP) with antibiotics, Rabeprazole, Tranexamic acid, Vitamin K and Frusemide. She had the second dialysis session of HD and entered into the recovering phase of AKI and was subsequently discharged after 18th days on admission. Conclusion: Yellow fever infection occurs sporadically and could lead to MODS involving the kidneys, liver and hematologic system. Prompt initiation of dialysis, correction of coagulopathy, and antibiotics use are measures needed to arrest progression and death. Vaccination, destruction of the natural habitat of the carrier and infective organisms are necessary particularly in endemic regions of the world.

Complement Activation During Ischemia/Reperfusion Injury Induces Pericyte-to-Myofibroblast Transdifferentiation Regulating Peritubular Capillary Lumen Reduction Through pERK Signaling.

Pericytes are one of the principal sources of scar-forming myofibroblasts in chronic kidneys disease. However, the modulation of pericyte-to-myofibroblast transdifferentiation (PMT) in the early phases of acute kidney injury is poorly understood. Here, we investigated the role of complement in inducing PMT after transplantation. Using a swine model of renal ischemia/reperfusion (I/R) injury, we found the occurrence of PMT after 24 h of I/R injury as demonstrated by reduction of PDGFRβ+/NG2+ cells with increase in myofibroblasts marker αSMA. In addition, PMT was associated with significant reduction in peritubular capillary luminal diameter. Treatment by C1-inhibitor (C1-INH) significantly preserved the phenotype of pericytes maintaining microvascular density and capillary lumen area at tubulointerstitial level. In vitro, C5a transdifferentiated human pericytes in myofibroblasts, with increased αSMA expression in stress fibers, collagen I production, and decreased antifibrotic protein Id2. The C5a-induced PMT was driven by extracellular signal-regulated kinases phosphorylation leading to increase in collagen I release that required both non-canonical and canonical TGFβ pathways. These results showed that pericytes are a pivotal target of complement activation leading to a profibrotic maladaptive cellular response. Our studies suggest that C1-INH may be a potential therapeutic strategy to counteract the development of PMT and capillary lumen reduction in I/R injury.

Utility of urinary tubular markers for monitoring chronic tubulointerstitial injury after ischemia-reperfusion.

The aim of this study was to elucidate whether urinary tubular markers during the chronic phase of acute kidney injury (AKI) are associated with chronic tubulointerstitial damage. Male human L-type fatty acid binding protein (L-FABP) chromosomal transgenic (Tg) mice underwent ischaemic reperfusion (I/R) injury via renal pedicle clamping for either 10min or 20min. Contralateral nephrectomy was performed at the time of tissue reperfusion. The kidneys were analyzed 20days after the last I/R. Serum creatinine levels 20days post-I/R were significantly higher in the 20min I/R than in the 10min I/R and control groups and were similar between the 10min I/R and control groups. The degree of tubulointerstitial damage 20days post-I/R was significantly more severe in the 20min I/R than in the 10min I/R and control groups, as well as in the 10min I/R than in the control group. Urinary levels of human L-FABP, albumin, and kidney injury molecule-1 (KIM-1) 20days post-I/R were significantly higher in the 20min I/R than in the control group, whereas urinary L-FABP was significantly higher in the 10min I/R than in the control group. Conversely, urinary neutrophil gelatinase-associated lipocalin levels did not significantly differ between the three groups. Finally, the urinary levels of human L-FABP, albumin, and KIM-1 levels 20days post-I/R were significantly correlated with the degree of renal damage. Urinary levels of human L-FABP, albumin and, KIM-1 may be useful for monitoring AKI-to-CKD transition in clinical practice.

Restored nitric oxide bioavailability reduces the severity of acute-to-chronic transition in a mouse model of aristolochic acid nephropathy.

Aristolochic Acid (AA) nephropathy (AAN) is a progressive tubulointerstitial nephritis characterized by an early phase of acute kidney injury (AKI) leading to chronic kidney disease (CKD). The reduced nitric oxide (NO) bioavailability reported in AAN might contribute to renal function impairment and progression of the disease. We previously demonstrated that L-arginine (L-Arg) supplementation is protective in AA-induced AKI. Since the severity of AKI may be considered a strong predictor of progression to CKD, the present study aims to assess the potential benefit of L-Arg supplementation during the transition from the acute phase to the chronic phase of AAN. C57BL/6J male mice were randomly subjected to daily i.p. injections of vehicle or AA for 4 days. To determine whether renal AA-induced injuries were linked to reduced NO production, L-Arg was added to drinking water from 7 days before starting i.p. injections, until the end of the protocol. Mice were euthanized 5, 10 and 20 days after vehicle or AA administration. AA-treated mice displayed marked renal injury and reduced NO bioavailability, while histopathological features of AAN were reproduced, including interstitial cell infiltration and tubulointerstitial fibrosis. L-Arg treatment restored renal NO bioavailability and reduced the severity of AA-induced injury, inflammation and fibrosis. We concluded that reduced renal NO bioavailability contributes to the processes underlying AAN. Furthermore, L-Arg shows nephroprotective effects by decreasing the severity of acute-to-chronic transition in experimental AAN and might represent a potential therapeutic tool in the future.

Moderate aerobic exercise on the recovery phase of gentamicin-induced acute kidney injury in rats

IntroductionAcute kidney injury is a serious public health problem, especially in intensive care units, where patients may require dialysis support, resulting in 50% mortality. AimTo evaluate the effects of moderate aerobic exercise on the recovery phase of acute kidney injury induced by gentamicin in rats. Main methodsMale adult Wistar rats were allocated into 4 groups: W10+R30, G10+R30, W10+EX30 and G10+EX30; W10 received water (gentamicin vehicle) and G10 received gentamicin for 10days; R30 remained resting and EX30 made exercise for 30days after gentamicin suspension. Training was performed on treadmill. Blood, 24h urine and kidneys were collected for renal function and oxidative stress, antioxidant, TGF-β and histological analysis. Key findingsGentamicin treatment caused decreased renal function significant oxidative stress, reduced urinary nitric oxide and increased TGF-β. G10+R30 presented partial recovery of metabolic data, renal function and lipoperoxidation levels, although they were still altered compared to W10+R30. Besides, we observed the presence of lymphomononuclear infiltrate in the kidneys of G10+R30. G10+EX30 vs G10+R30 showed additional improvement of all the mentioned parameters, showing at histology, regeneration of the tubule epithelium. SignificanceOur data suggest that moderate exercises could help in the recovery of metabolic parameters, renal function and structure on gentamicin-induced AKI, perhaps due to restoration of redox balance. This could protect the kidneys from further insults like challenges with nephrotoxic drugs or the aging per se.

Assessment of oxidative status in patients with acute kidney injury: a pilot study.

Extensive experimental evidence confirms the role of oxidative stress as a major contributor to the pathogenesis of acute kidney injury (AKI). However, less information is available on the evolution of prooxidant-antioxidant parameters from early to end-phase renal function decline in humans. This study aimed to determine the oxidative status in dynamic throughout the evolutionary phases of the disease. The study included patients with cardiovascular pathology and AKI hospitalized in the intensive care unit (n = 69) and age-matched healthy controls (n = 30). They were followed through three phases of AKI; the first [corrected] phase was the phase of diagnosis, which is characterized by oliguria/anuria, the [corrected] second phase was established diuresis, and the [corrected] third phase was the polyuric phase. In these phases of the disease, blood samples were taken from the patients for biochemical analysis. From the collected whole blood, we measured spectrophotometrically prooxidants: index of lipid peroxidation, measured as Thiobarbituric acid reactive substances (TBARS), nitrite (NO₂⁻), superoxide anion radical (O₂⁻) and hydrogen peroxide (H₂O₂), and antioxidants: activity of superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) from erythrocyte lysate. Comparing the results of the three measurements, a significant difference was found in the levels of NO₂⁻ and GSH, both of which increased in the second phase (P < 0.05) and then decreased in the third phase, and a significant increase in TBARS, which was elevated in the second phase (P < 0.05) and did not change significantly until the third phase. Our results showed phase-dependent modification in 3 parameters of the oxidative status (TBARS, NO₂⁻ and GSH). Whether these changes contribute to the deterioration of renal function in AKI remains to be established.

Antithrombin nanoparticles improve kidney reperfusion and protect kidney function after ischemia-reperfusion injury.

In the extension phase of acute kidney injury, microvascular thrombosis, inflammation, vasoconstriction, and vascular endothelial cell dysfunction promote progressive damage to renal parenchyma after reperfusion. In this study, we hypothesized that direct targeting and pharmaceutical knockdown of activated thrombin at the sites of injury with a selective nanoparticle (NP)-based thrombin inhibitor, PPACK (phenylalanine-proline-arginine-chloromethylketone), would improve kidney reperfusion and protect renal function after transient warm ischemia in rodent models. Saline- or plain NP-treated animals were employed as controls. In vivo 19F magnetic resonance imaging revealed that kidney nonreperfusion was evident within 3 h after global kidney reperfusion at 34 ± 13% area in the saline group and 43 ± 12% area in the plain NP group and substantially reduced to 17 ± 4% (∼50% decrease, P < 0.05) in the PPACK NP pretreatment group. PPACK NP pretreatment prevented an increase in serum creatinine concentration within 24 h after ischemia-reperfusion, reflecting preserved renal function. Histologic analysis illustrated substantially reduced intrarenal thrombin accumulation within 24 h after reperfusion for PPACK NP-treated kidneys (0.11% ± 0.06%) compared with saline-treated kidneys (0.58 ± 0.37%). These results suggest a direct role for thrombin in the pathophysiology of AKI and a nanomedicine-based preventative strategy for improving kidney reperfusion after transient warm ischemia.

Diagnosis and early biomarkers of acute kidney injury in children

During recent years,International Nephrology and Emergency Medicine Association preferred a cute kidney injury( AKI)rather than a cute renal failure for the diagnosis and intervention in the early phase of AKI,with the ultimate goal of reducing the mortality rate.It is not sensitive to diagnose AKI in the early phase only according to the change of urine output and serum ereatinine.It is reported that some new biomarkers are sensitive and specific and may play important roles for the early diagnosis of AKI. Key words: Children; Acute kidney injury; Biomarkers

How robust are our methods of detecting impaired glomerular filtration rate in the intensive care unit?

Background: Serum creatinine is not a sensitive marker to assess early loss of renal function in acute kidney injury. Timed creatinine clearance and several formula used to predict glomreular filtration rate have not been validated. Methods: In a prospective observational study in 50 adult patients admitted to the intensive care unit with apparent normal renal function, we assessed the glomerular filtration rate by the formula methods and timed creatinine clearance. Result: The mean serum creatinine was 0.77mg/dl, SD ± 0.15 (range 0.5–1.14 mg/dl). The mean measured creatinine clearance was 87.15 ml/min/1.73m 2, SD ± 20.5 (range 56.9–137 ml/ min/1.73m 2). In 25 (50%) patients, one hour urinary creatinine clearance was <80 ml/min/1.73m 2 and in two (4%) patients, the creatinine clearance was <60 ml/min/1.73m 2. Spearman correlation coefficient and regression analysis revealed a statistically significant correlation for the Cockcroft-Gault and predictive equations when compared with measured creatinine clearance. The differences between the predictive equations and creatinine clearance, as illustrated by the ±95% confidence interval in the Bland-Altman graphs was very significant [Cockcroft-Gault = −40.3 to 17.7 ml/ min/ 1.73m 2, Modification of Diet in Renal Disease equation = −46.2 to 30.6 ml/min/1.73m 2 and the simplified Modification of Diet in Renal Disease equation = -72.8 to 24.8 ml/min/1.73m 2]. Conclusion: Formula methods and creatinine clearance are more sensitive than serum creatinine in detecting early phase of acute kidney injury. However, there is no agreement between these methods of glomerular filtration rate estimation.