The aging kidney: increased susceptibility to nephrotoxicity

Youthful systemic milieu alleviates renal ischemia-reperfusion injury in elderly mice

The incidence of acute kidney injury (AKI) is high in elderly people, and is difficult to prevent and treat. One of its major causes is renal ischemia-reperfusion injury (IRI). A young systemic environment may prevent the senescence of old organs. However, it is unknown whether a young milieu may reduce renal IRI in the elderly. To examine this question, bilateral renal IRI was induced in old (24 months) mice three weeks after parabiosis model establishment. At 24 hours after IRI, compared to old wild-type mice, the old mice with IRI had significantly damaged renal histology, decreased renal function, increased oxidative stress, inflammation, and apoptosis. However, there was no increase in autophagy. Compared to old mice with IRI, old-old parabiosis mice with IRI did not show differences in renal histological damage, oxidative stress, inflammation, apoptosis, or autophagy, but did exhibit improved renal function. Compared to the old-old parabiosis mice with IRI, the old mice with IRI in the young (12 week)-old parabiosis showed less renal histological injury and better renal function. Renal oxidative stress, inflammation, and apoptosis were significantly decreased, and autophagy was significantly increased. Thus, a youthful systemic milieu may decrease oxidative stress, inflammation, and apoptosis, and increase autophagy in old mice with IRI. These effects ameliorated IRI injuries in old mice. Our study provides new ideas for effectively preventing and treating AKI in the elderly.

Characteristics of and risk factors for death in elderly patients with acute kidney injury: a multicentre retrospective study in China

Purpose of the study

The incidence of acute kidney injury (AKI) with a poor prognosis in the elderly has been increasing each year. This study aimed to investigate the clinical characteristics of and risk factors for death from AKI in the elderly and help improve prognosis.

Study design

This study was a retrospective cohort study based on data from adult patients (≥18 years old) admitted to 15 hospitals in China between 1 January 2009 and 31 December 2011. The characteristics of AKI in the elderly were compared with those in younger patients.

Results

In elderly patients with AKI, rates of hypertension, cardiovascular disease and multiple organ dysfunction syndrome (MODS) were higher than in younger patients (44.2% vs 31.2%, 16.1% vs 4.6% and 20.9% vs 16.9%, respectively), the length of ICU stay was longer (3.8 days vs 2.7 days, P=0.019) and renal biopsy (1.0% vs 7.13%, P<0.001) and dialysis (9.6% vs 19.2%, P<0.001) were performed less. Hospital-acquired (HA) AKI was more common than community-acquired (CA) AKI (60.3% vs 39.7%), while the most common cause of AKI was pre-renal (53.5%). Multiple logistic regression analysis showed that age (OR 1.041, 95% CI 1.023 to 1.059), cardiovascular disease (OR 1.980, 95% CI 1.402 to 2.797), cancer (OR 2.302, 95% CI 1.654 to 3.203), MODS (OR 3.023, 95% CI 1.627 to 5.620) and mechanical ventilation (OR 2.408, 95% CI 1.187 to 4.887) were significant risk factors for death.

Conclusions

HA-AKI and pre-renal AKI were more common in the elderly. Age, cardiovascular disease, cancer, MODS and mechanical ventilation were independent risk factors for death in the elderly with AKI.

Tick-Tock Chimes the Kidney Clock - from Biology of Renal Ageing to Clinical Applications

Ageing of the kidney is a multi-dimensional process that occurs simultaneously at the molecular, cellular, histological, anatomical and physiological level. Nephron number and renal cortical volume decline, renal tubules become atrophic and glomeruli become sclerotic with age. These structural changes are accompanied by a decline in glomerular filtration rate, decreased sodium reabsorption and potassium excretion, reduced urinary concentrating capacity and alterations in the endocrine activity of the kidney. However, the pace of progression of these changes is not identical in everyone - individuals of the same age and seemingly similar clinical profile often exhibit stark differences in the age-related decline in renal health. Thus, chronological age poorly reflects the time-dependent changes that occur in the kidney. An ideal measure of renal vitality is biological kidney age - a measure of the age-related changes in physiological function. Replacing chronological age with biological age could provide numerous clinical benefits including improved prognostic accuracy in renal transplantation, better stratification of risk and identification of those who are on a fast trajectory to an age-related drop in kidney health.

3D virtual histology of murine kidneys -high resolution visualization of pathological alterations by micro computed tomography

The increasing number of patients with end stage chronic kidney disease not only calls for novel therapeutics but also for pioneering research using convincing preclinical disease models and innovative analytical techniques. The aim of this study was to introduce a virtual histology approach using micro computed tomography (µCT) for the entire murine kidney in order to close the gap between single slice planar histology and a 3D high resolution dataset. An ex vivo staining protocol based on phosphotungstic acid diffusion was adapted to enhance renal soft tissue x-ray attenuation. Subsequent CT scans allowed (i) the detection of the renal cortex, medulla and pelvis in greater detail, (ii) the analysis of morphological alterations, (iii) the quantification of the volume as well as the radio-opacity of these portions and (iv) the quantification of renal fibrotic remodeling based on altered radio-opacity using the unilateral ureteral obstruction model. Thus, virtual histology based on PTA contrast enhanced CT will in future help to refine the outcome of preclinical research on kidney associated murine disease models.

Acute Kidney Injury in Elderly Population: A Prospective Observational Study

BACKGROUND/AIMS

Acute kidney injury (AKI) has been reported as a recognized condition among the elderly population; however, its clinical epidemiology is still poorly evaluated. We propose to evaluate the epidemiological profile of AKI in hospitalized elderly patients and the variables associated with renal replacement therapy (RRT) dependency at discharge after an episode of AKI.

METHODS

This prospective observational study enrolled 286 elderly patients (aged ≥60 years), who had a diagnosis of AKI and were admitted to a tertiary care hospital. Clinical data were analyzed, which included RRT indication, referral time to nephrologist support, standby period in the emergency care units (ECU) before a transfer to an intensive care unit, staff criteria used to indicate palliative care, and the incidence of patients who stayed on chronic dialysis for at least 6 months after discharge.

RESULTS

The overall hospital mortality was 56.3%. Acute Kidney Injury Network (AKIN) 3 at the time of admission was significantly higher in patients who underwent RRT. Intrinsic AKI (p < 0.001), AKIN 3 (p < 0.001), RRT (p < 0.001), and increased length of stay in ECUs (p = 0.01) all had a significantly higher prevalence among non-survivors. On multivariate analysis, however, only renal aetiology (intrinsic AKI) was independently associated with mortality (OR 2.88; 95% CI [1.29-6.13]). Approximately 85% of the discharged patients (n = 125) were dialysis free and 36.4% of them who had a previous diagnosis of chronic kidney disease (CKD) upon admission had a worse renal function. Age, AKIN 3, RRT, prior history of CKD, diabetes mellitus, and the number of hemodialysis sessions showed to have an impact on dialysis dependence. Furthermore, 24 of 161 patients who had a dialysis indication were placed on palliative care.

CONCLUSIONS

The severity of AKI and the need for RRT were risk factors for mortality and dependence on dialysis. Antecedents of CKD seem to be associated with a poor renal outcome following an AKI episode. Starting RRT had an impact on the clinical decision to enroll these patients into palliative care.

Clinical Update on Nursing Home Medicine: 2016

This is the tenth clinical update. It covers chronic kidney disease, dementia, hypotension, polypharmacy, rapid geriatric assessment, and transitional care.

Protein extracted from Porphyra yezoensis prevents cisplatin-induced nephrotoxicity by downregulating the MAPK and NF-κB pathways

Acute renal failure is a serious complication of treatment with the anticancer drug cisplatin. Cisplatin exerts a cytotoxic effect on renal cells by inducing apoptosis through activating the tumor suppressor p53, nuclear factor‑κB (NF‑κB) and mitogen‑activated protein kinase (MAPK)/p38 pathways. Effects of protein extracts of the brown seaweed Porphyra yezoensis (P. yezoensis) on cytotoxicity, inflammation and cell proliferation have been reported; however, the effects of P. yezoensis protein (PYP) extract on cisplatin‑induced renal injury have remained elusive. The present study investigated the effects of PYP on cisplatin‑induced nephrotoxicity in the HK2 human proximal tubular epithelial cell line. PYP treatment reduced cisplatin‑induced apoptosis and death of HK2 cells by restoring the B‑cell lymphoma‑2 (Bcl‑2)‑associated X protein (Bax)/Bcl‑2 imbalance, cytochrome c release and caspase‑3 activation. In addition, PYP activated the redox‑sensitive transcription factor NF‑κB via stimulating the nuclear translocation of p65 in HK2 cells. PYP also restored renal antioxidant levels and increased the total and nuclear accumulation of NF erythroid 2‑related factor 2 in HK2 cells. PYP markedly attenuated cisplatin‑induced p38, MAPK and c‑Jun N‑terminal kinase phosphorylation. Furthermore, treatment with PYP ameliorated cisplatin‑induced renal cell damage by upregulating antioxidant defense mechanisms and downregulating the MAPK and NF‑κB signaling pathways. In addition, mice were divided into three treatment groups (control, cisplatin and PYP + cisplatin) and the effects of PYP were evaluated in a mouse model of cisplatin‑induced acute kidney injury. The concentrations of blood urea nitrogen and serum creatinine in the PYP + cisplatin group were lower than those in the cisplatin group. The mRNA expression levels of inflammatory factors interleukin‑6 (IL‑6), IL‑1β, tumor necrosis factor‑α and monocyte chemoattractant protein‑1 in the kidney tissues of the PYP + cisplatin group were also lower than those in the cisplatin group. These results suggest that PYP treatment had a preventive effect on nephrotoxicity, specifically by downregulating the MAPK and NF‑κB signaling pathways and the mRNA levels of inflammatory genes.

Epidemiology and prognosis of candidaemia in elderly patients

The aim of the study was to analyse the epidemiology and prognosis of candidaemia in elderly patients. We performed a comparison of clinical presentation of candidaemia according to age and a study of hazard factors within a prospective programme performed in 29 hospitals. One hundred and seventy-six episodes occurred in elderly patients (>75 years), 227 episodes in middle-aged patients (61-75 years) and 232 episodes in younger patients (16-60 years). Central venous catheter, parenteral nutrition, neutropenia, immunosuppressive therapy and candidaemia caused by Candida parapsilosis were less frequent in elderly patients. These patients received inadequate antifungal therapy (57.3%) more frequently than middle-aged and younger patients (40.5% P < .001). Mortality during the first week (20%) and 30 days (42%) was higher in elderly patients. The variables independently associated with mortality in elderly patients during the first 7 days were acute renal failure (OR: 2.64), Pitt score (OR: 1.57) and appropriate antifungal therapy (OR: 0.132). Primary candidaemia (OR: 2.93), acute renal failure (OR: 3.68), Pitt score (OR: 1.38), appropriate antifungal therapy (OR: 0.3) and early removal of the central catheter (OR: 0.47) were independently associated with 30-day mortality.In conclussion, inadequate antifungal treatment is frequently prescribed to elderly patients with candidaemia and is related with early and late mortality.

Unique sex- and age-dependent effects in protective pathways in acute kidney injury

Sex and age influence susceptibility to acute kidney injury (AKI), with young females exhibiting lowest incidence. In these studies, we investigated mechanisms which may underlie the sex/age-based dissimilarities. Cisplatin (Cp)-induced AKI resulted in morphological evidence of injury in all groups. A minimal rise in plasma creatinine (PCr) was seen in Young Females, whereas in Aged Females, PCr rose precipitously. Relative to Young Males, Aged Males showed significantly, but temporally, comparably elevated PCr. Notably, Aged Females showed significantly greater mortality, whereas Young Females exhibited none. Tissue KIM-1 and plasma NGAL were significantly lower in Young Females than all others. IGFBP7 levels were modestly increased in both Young groups. IGFBP7 levels in Aged Females were significantly elevated at baseline relative to Aged Males, and increased linearly through day 3, when these levels were comparable in both Aged groups. Plasma cytokine levels similarly showed a pattern of protective effects preferentially in Young Females. Expression of the drug transporter MATE2 did not explain the sex/age distinctions. Heme oxygenase-1 (HO-1) levels (~28-kDa species) showed elevation at day 1 in all groups with highest levels seen in Young Males. Exclusively in Young Females, these levels returned to baseline on day 3, suggestive of a more efficient recovery. In aggregate, we demonstrate, for the first time, a distinctive pattern of response to AKI in Young Females relative to males which appears to be significantly altered in aging. These distinctions may offer novel targets to exploit therapeutically in both females and males in the treatment of AKI.

Intravascular imaging in cardiovascular ageing

Ageing is related to complex molecular, inflammatory and biochemical changes that affect coronary pathology and often lead to coronary artery disease and cardiovascular events. Intravascular imaging is considered as the ideal technique to study coronary plaque morphology and assess its burden. Over the recent years several studies have been performed that investigated the association between pathophysiological mechanisms that promote vascular ageing and plaque morphology. In addition, several reports have compared plaque pathology in different age groups and a few studies included serial intravascular imaging to assess changes in the atheroma burden and compositional characteristics of the plaque. This review article summarizes the evidence derived from intravascular imaging studies about the implications of vascular ageing on coronary artery morphology and discusses the potential of coronary imaging in assessing atherosclerotic evolution.

An intracellular matrix metalloproteinase-2 isoform induces tubular regulated necrosis: implications for acute kidney injury

Acute kidney injury (AKI) causes severe morbidity, mortality, and chronic kidney disease (CKD). Mortality is particularly marked in the elderly and with preexisting CKD. Oxidative stress is a common theme in models of AKI induced by ischemia-reperfusion (I-R) injury. We recently characterized an intracellular isoform of matrix metalloproteinase-2 (MMP-2) induced by oxidative stress-mediated activation of an alternate promoter in the first intron of the MMP-2 gene. This generates an NH₂-terminal truncated MMP-2 (NTT-MMP-2) isoform that is intracellular and associated with mitochondria. The NTT-MMP-2 isoform is expressed in kidneys of 14-mo-old mice and in a mouse model of coronary atherosclerosis and heart failure with CKD. We recently determined that NTT-MMP-2 is induced in human renal transplants with delayed graft function and correlated with tubular cell necrosis. To determine mechanism(s) of action, we generated proximal tubule cell-specific NTT-MMP-2 transgenic mice. Although morphologically normal at the light microscopic level at 4 mo, ultrastructural studies revealed foci of tubular epithelial cell necrosis, the mitochondrial permeability transition, and mitophagy. To determine whether NTT-MMP-2 expression enhances sensitivity to I-R injury, we performed unilateral I-R to induce mild tubular injury in wild-type mice. In contrast, expression of the NTT-MMP-2 isoform resulted in a dramatic increase in tubular cell necrosis, inflammation, and fibrosis. NTT-MMP-2 mice had enhanced expression of innate immunity genes and release of danger-associated molecular pattern molecules. We conclude that NTT-MMP-2 "primes" the kidney to enhanced susceptibility to I-R injury via induction of mitochondrial dysfunction. NTT-MMP-2 may be a novel AKI treatment target.

Sulfated glycosaminoglycans in bladder tissue and urine of rats after acute exposure to paraoxon and cyclophosphamide

Glycosaminoglycans (GAGs) in the urine of Wistar rats, and on the surface of the epithelium and lamina propria of the bladder, were quantitatively assessed before and after acute intoxication with paraoxon or cyclophosphamide. Paraoxon was administered subcutaneously (s.c.) twice with an interval of 1h to a final dose of 275mg/kg; cyclophosphamide was administered intraperitoneally (i.p.) with a single dose of 100mg/kg or to a final dose of 240mg/kg (three times per 80mg/kg every 12h). GAGs on the surface of the epithelium and lamina propria of the urinary bladder of rats were quantitatively determined by Alcian blue dye staining. GAGs in the urine were determined spectrophotometrically with 1-9-dimethyl methylene blue. By 48-96h after intoxication with either paraoxon or cyclophosphamide, statistically significant increases in the concentration of GAGs were obtained both for the tissues of the bladder and the urine of rats. Cyclophosphamide, in contrast to paraoxon, caused the development of hemorrhagic cystitis in the animals. The synthesis of GAGs is considered to be compensatory response to the toxic xenobiotics.

The aging kidney and the nephrotoxic effects of mercury

Owing to advances in modern medicine, life expectancies are lengthening and leading to an increase in the population of older individuals. The aging process leads to significant alterations in many organ systems, with the kidney being particularly susceptible to age-related changes. Within the kidney, aging leads to ultrastructural changes such as glomerular and tubular hypertrophy, glomerulosclerosis, and tubulointerstitial fibrosis, which may compromise renal plasma flow (RPF) and glomerular filtration rate (GFR). These alterations may reduce the functional reserve of the kidneys, making them more susceptible to pathological events when challenged or stressed, such as following exposure to nephrotoxicants. An important and prevalent environmental toxicant that induces nephrotoxic effects is mercury (Hg). Since exposure of normal kidneys to mercuric ions might induce glomerular and tubular injury, aged kidneys, which may not be functioning at full capacity, may be more sensitive to the effects of Hg than normal kidneys. Age-related renal changes and the effects of Hg in the kidney have been characterized separately. However, little is known regarding the influence of nephrotoxicants, such as Hg, on aged kidneys. The purpose of this review was to summarize known findings related to exposure of aged and diseased kidneys to the environmentally relevant nephrotoxicant Hg.

Reducing the risk of stroke in elderly patients with non-valvular atrial fibrillation: a practical guide for clinicians

Non-valvular atrial fibrillation (NVAF) significantly contributes to the burden of stroke, particularly in elderly patients. The challenge of optimizing anticoagulation therapy is balancing efficacy and bleeding risk, especially as the same patients at high risk of stroke also tend to be at high risk of bleeding. Treating the elderly patient with NVAF presents special challenges because of their heightened risk for both stroke and bleeding. Despite clinical trial data and evidence-based guidelines, surveys indicate that physicians underuse anticoagulation in older patients for reasons that include overemphasis of bleeding risk, particularly with the increased risk of falling, at the cost of thromboembolic risk. Clinical trial data are now available, and real-world data are emerging, to illustrate the relative merits of the non-vitamin K antagonist oral anticoagulants compared with conventional anticoagulation in the treatment of elderly patients with this condition, and to suggest some subgroups of older patients who may be more suitable candidates for particular agents. Care of elderly patients with NVAF is often complicated by factors including risk of falling, adherence, health literacy, cognitive function, adverse effects, and involvement of caregivers, as well as other factors including the patient–provider relationship and logistical barriers to obtaining medication. Thus, conversations between clinicians and patients, as well as shared decision making, are important. In addition, elderly patients often suffer from comorbidities including hypertension, coronary heart disease, diabetes mellitus, COPD, and/or heart failure, which necessitate the use of multiple concomitant medications, increasing the risk of drug/drug interactions. This review provides an overview of clinical trial data on the use of non-vitamin K anticoagulant agents in elderly populations, and serves as a practical resource for the management of NVAF in the elderly patient.

Delineating the Role of Various Factors in Renal Disposition of Digoxin through Application of Physiologically Based Kidney Model to Renal Impairment Populations

Development of submodels of organs within physiologically-based pharmacokinetic (PBPK) principles and beyond simple perfusion limitations may be challenging because of underdeveloped in vitro-in vivo extrapolation approaches or lack of suitable clinical data for model refinement. However, advantage of such models in predicting clinical observations in divergent patient groups is now commonly acknowledged. Mechanistic understanding of altered renal secretion in renal impairment is one area that may benefit from such models, despite knowledge gaps in renal pathophysiology. In the current study, a PBPK kidney model was developed for digoxin, accounting for the roles of organic anion transporting peptide 4C1 (OATP4C1) and P-glycoprotein (P-gp) in its tubular secretion, with the aim to investigate the impact of age and renal impairment (moderate to severe) on renal drug disposition. Initial PBPK simulations based on changes in glomerular filtration rate (GFR) underestimated the observed reduction in digoxin renal excretion clearance (CL_R) in subjects with moderately impaired renal function relative to healthy. Reduction in either proximal tubule cell number or the OATP4C1 abundance in the mechanistic kidney model successfully predicted 59% decrease in digoxin CL_R, in particular when these changes were proportional to reduction in GFR. In contrast, predicted proximal tubule concentration of digoxin was only sensitive to changes in the transporter expression/ million proximal tubule cells. Based on the mechanistic modeling, reduced proximal tubule cellularity and OATP4C1 abundance, and inhibition of OATP4C1-mediated transport, are proposed as possible causes of reduced digoxin renal secretion in renally impaired patients.

The mitochondrial-targeted peptide, SS-31, improves glomerular architecture in mice of advanced age

Although age-associated changes in kidney glomerular architecture have been described in mice and man, the mechanisms are unknown. It is unclear if these changes can be prevented or even reversed by systemic therapies administered at advanced age. Using light microscopy and transmission electron microscopy, our results showed glomerulosclerosis with injury to mitochondria in glomerular epithelial cells in mice aged 26 months (equivalent to a 79-year-old human). To test the hypothesis that reducing mitochondrial damage in late age would result in lowered glomerulosclerosis, we administered the mitochondrial targeted peptide, SS-31, to aged mice. Baseline (24-month-old) mice were randomized to receive 8 weeks of SS-31, or saline, and killed at 26 months of age. SS-31 treatment improved age-related mitochondrial morphology and glomerulosclerosis. Assessment of glomeruli revealed that SS-31 reduced senescence (p16, senescence-associated-ß-Gal) and increased the density of parietal epithelial cells. However, SS-31 treatment reduced markers of parietal epithelial cell activation (Collagen IV, pERK1/2, and α-smooth muscle actin). SS-31 did not impact podocyte density, but it reduced markers of podocyte injury (desmin) and improved cytoskeletal integrity (synaptopodin). This was accompanied by higher glomerular endothelial cell density (CD31). Thus, despite initiating therapy in late-age mice, a short course of SS-31 has protective benefits on glomerular mitochondria, accompanied by temporal changes to the glomerular architecture. This systemic pharmacological intervention in old-aged animals limits glomerulosclerosis and senescence, reduces parietal epithelial cell activation, and improves podocyte and endothelial cell integrity.

Fascin2 regulates cisplatin-induced apoptosis in NRK-52E cells

Previous studies have shown that the aging kidney has a marked loss of α(E)-catenin in proximal tubular epithelium. α-Catenin, a key regulator of the actin cytoskeleton, interacts with a variety of actin-binding proteins. Cisplatin-induced loss of fascin2, an actin bundling protein, was observed in cells with a stable knockdown of α(E)-catenin (C2 cells), as well as in aging (24 mon), but not young (4 mon), kidney. Fascin2 co-localized with α-catenin and the actin cytoskeleton in NRK-52E cells. Knockdown of fascin2 increased the susceptibility of tubular epithelial cells to cisplatin-induced injury. Overexpression of fascin2 in C2 cells restored actin stress fibers and attenuated the increased sensitivity of C2 cells to cisplatin-induced apoptosis. Interestingly, fascin2 overexpression attenuated cisplatin-induced mitochondrial dysfunction and oxidative stress in C2 cells. These data demonstrate that fascin2, a putative target of α(E)-catenin, may play important role in preventing cisplatin-induced acute kidney injury.

Nephrotoxic Medication Exposure in U.S. Adults with Predialysis Chronic Kidney Disease: Health Services Utilization and Cost Outcomes

BACKGROUND

Nephrotoxic medication exposure increases risks for acute kidney injury, permanent renal function loss, and costly preventable adverse drug events. Exposure to medications associated with inducing acute tubular nephritis or tubular toxicity versus nonexposure among those with predialysis renal disease-a population vulnerable to increased risk of kidney injury-may affect health services utilization and cost outcomes. Few studies quantify nephrotoxic medication exposure in chronic kidney disease (CKD) and associated costs.

OBJECTIVE

To examine exposure to medications associated with inducing acute tubular nephritis or tubular toxicity versus nonexposure and the effect on health services utilization and cost outcomes in a nationally representative sample of adults with predialysis CKD.

METHODS

This retrospective study used Medical Expenditure Panel Survey (MEPS) household component longitudinal files (years 2006-2012; panels 11-16). Participants included 809 MEPS respondents aged > 18 years with predialysis CKD, after excluding those participants with cancer, kidney stone, renal dialysis, or transplant procedures (approximately 14.7 million U.S. noninstitutionalized individuals). Two groups were created to evaluate the main measures: (1) participants prescribed 1 or more medications associated with risk of acute tubular nephritis and/or tubular toxicity (termed "nephrotoxic exposure") and (2) participants with nonexposure. Medications cited in published literature as associated with tubular kidney damage were used. Multivariable regression models assessed the pattern of nephrotoxic medication exposure and its effect on health services utilization and expenses.

RESULTS

Nephrotoxic medication exposure occurred in 72% of adult MEPS respondents. Of those, 47.2% and 52.8% were prescribed 1 and at least 2 nephrotoxic medications, respectively. Coexistent chronic conditions included hypertension (72.3%), diabetes (49.5%), coronary heart disease (33%), arthritis (23.6%), and chronic obstructive pulmonary disease (17.6%). Eligible MEPS respondents aged ≥ 65 years, from the U.S. South region, and with Charlson Comorbidity Index (CCI) score > 0 were 75% (vs. aged 18-45 years), 83% (vs. Northeast), and 72%-96% (vs. CCI = 0) more likely to be exposed to nephrotoxic medications. Uninsured participants showed 55% less likelihood of nephrotoxic exposure, compared with privately insured participants. Higher utilization was shown in the nephrotoxic medication exposure group (vs. nonexposure): prescription fills (52.8 vs. 26.8, P < 0.001), emergency department visits (56.2 vs. 29.3 per 1,000 patient months, P < 0.001), and hospitalization (51.8 vs. 23.4 per 1,000 patient months, P < 0.001). Unadjusted all-cause expenses were greater for the following categories: medical ($119,935 vs. $11,462, P < 0.001), prescription drug ($4,828 vs. $2,816, P < 0.001), and total health expenses ($24,663 vs. $14,277, P < 0.001). Adjusted all-cause expenses were greater for total (29.7% greater, P = 0.003), prescription medications (56.6% greater, P < 0.001), and medical (23.4% greater, P = 0.036), but there were no differences in predialysis CKD-related utilization and expenses.

CONCLUSIONS

Increased vigilance is needed when prescribing nephrotoxic medications in predialysis CKD, particularly in patients with comorbid conditions and the elderly. Nephrotoxic medication exposure in predialysis CKD has the potential for increased health services utilization and cost outcomes.

DISCLOSURES

There was no grant or intramural funding for this research. The authors have no conflicts of interest, financial or otherwise, to disclose. Study concept and design were primarily contributed by Davis-Ajami, along with Fink and Wu. Davis-Ajami took the lead in data collection, along with Wu, and data interpretation was performed by David-Ajami, Wu, and Fink. All authors participated in manuscript preparation and revision.

Pyridoxamine reduces postinjury fibrosis and improves functional recovery after acute kidney injury

Acute kidney injury (AKI) is a common and independent risk factor for death and chronic kidney disease (CKD). Despite promising preclinical data, there is no evidence that antioxidants reduce the severity of injury, increase recovery, or prevent CKD in patients with AKI. Pyridoxamine (PM) is a structural analog of vitamin B6 that interferes with oxidative macromolecular damage via a number of different mechanisms and is in a phase 3 clinical efficacy trial to delay CKD progression in patients with diabetic kidney disease. Because oxidative stress is implicated as one of the main drivers of renal injury after AKI, the ability of PM to interfere with multiple aspects of oxidative damage may be favorable for AKI treatment. In these studies we therefore evaluated PM treatment in a mouse model of AKI. Pretreatment with PM caused a dose-dependent reduction in acute tubular injury, long-term postinjury fibrosis, as well as improved functional recovery after ischemia-reperfusion AKI (IR-AKI). This was associated with a dose-dependent reduction in the oxidative stress marker isofuran-to-F2-isoprostane ratio, indicating that PM reduces renal oxidative damage post-AKI. PM also reduced postinjury fibrosis when administered 24 h after the initiating injury, but this was not associated with improvement in functional recovery after IR-AKI. This is the first report showing that treatment with PM reduces short- and long-term injury, fibrosis, and renal functional recovery after IR-AKI. These preclinical findings suggest that PM, which has a favorable clinical safety profile, holds therapeutic promise for AKI and, most importantly, for prevention of adverse long-term outcomes after AKI.

Autophagy, Innate Immunity and Tissue Repair in Acute Kidney Injury

Kidney is a vital organ with high energy demands to actively maintain plasma hemodynamics, electrolytes and water homeostasis. Among the nephron segments, the renal tubular epithelium is endowed with high mitochondria density for their function in active transport. Acute kidney injury (AKI) is an important clinical syndrome and a global public health issue with high mortality rate and socioeconomic burden due to lack of effective therapy. AKI results in acute cell death and necrosis of renal tubule epithelial cells accompanied with leakage of tubular fluid and inflammation. The inflammatory immune response triggered by the tubular cell death, mitochondrial damage, associative oxidative stress, and the release of many tissue damage factors have been identified as key elements driving the pathophysiology of AKI. Autophagy, the cellular mechanism that removes damaged organelles via lysosome-mediated degradation, had been proposed to be renoprotective. An in-depth understanding of the intricate interplay between autophagy and innate immune response, and their roles in AKI pathology could lead to novel therapies in AKI. This review addresses the current pathophysiology of AKI in aspects of mitochondrial dysfunction, innate immunity, and molecular mechanisms of autophagy. Recent advances in renal tissue regeneration and potential therapeutic interventions are also discussed.

Renal Function and All-Cause Mortality Risk Among Cancer Patients

Renal dysfunction predicts all-cause mortality in general population. However, the prevalence of renal insufficiency and its relationship with mortality in cancer patients are unclear.We retrospectively studied 9465 patients with newly diagnosed cancer from January 2010 to December 2010. Renal insufficiency was defined as an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m using the Chronic Kidney Disease Epidemiology Collaboration equation. The hazard ratio (HR) of all-cause mortality associated with baseline eGFR was assessed by Cox regression.Three thousand sixty-nine patients (32.4%) exhibited eGFR <90 mL/min/1.73 m and 3% had abnormal serum creatinine levels at the time of diagnosis. Over a median follow-up of 40.5 months, 2705 patients (28.6%) died. Compared with the reference group (eGFR ≥ 60 mL/min/1.73 m), an elevated all-cause mortality was observed among patients with eGFR < 60 mL/min/1.73 m stratified by cancer stage in the entire cohort, the corresponding hazard ratios were 1.87 (95% CI, 1.41-2.47) and 1.28 (95% CI, 1.01-1.62) for stage I to III and stage IV, respectively. However, this relationship was not observed after multivariate adjustment. Subgroup analysis found that eGFR < 60 mL/min/1.73 m independently predicted death among patients with hematologic (adjusted HR 2.93, 95% CI [1.36-6.31]) and gynecological cancer (adjusted HR 2.82, 95% CI [1.19-6.70]), but not in those with other cancer. Five hundred fifty-seven patients (6%) had proteinuria. When controlled for potential confounding factors, proteinuria was a risk factor for all-cause mortality among patients in the entire cohort, regardless of cancer stage and eGFR values. When patients were categorized by specific cancer type, the risk of all-cause death was only significant in patients with digestive system cancer (adjusted HR, 1.85 [1.48-2.32]).The prevalence of renal dysfunction was common in patients with newly diagnosed cancer. Patients with eGFR < 60 mL/min/1.73 m or proteinuria were associated with increased risk for all-cause mortality, this relation depended on cancer site.

Acute Kidney Injury: Definition, Pathophysiology and Clinical Phenotypes

Acute kidney injury (AKI) is a clinical syndrome that complicates the course and worsens the outcome in a significant number of hospitalised patients. Recent advances in clinical and basic research will help with a more accurate definition of this syndrome and in the elucidation of its pathogenesis. With this knowledge we will be able to conduct more accurate epidemiologic studies in an effort to gain a better understanding of the impact of this syndrome. AKI is a syndrome that rarely has a sole and distinct pathophysiology. Recent evidence, in both basic science and clinical research, is beginning to change our view for AKI from a single organ failure syndrome to a syndrome where the kidney plays an active role in the progress of multi-organ dysfunction. Accurate and prompt recognition of AKI and better understanding of the pathophysiologic mechanisms underlying the various clinical phenotypes are of great importance to research for effective therapeutic interventions. In this review we provide the most recent updates in the definition, epidemiology and pathophysiology of AKI.

Renoprotective approaches and strategies in acute kidney injury

Acute kidney injury (AKI) is a major renal disease associated with high mortality rate and increasing prevalence. Decades of research have suggested numerous chemical and biological agents with beneficial effects in AKI. In addition, cell therapy and molecular targeting have been explored for reducing kidney tissue damage and promoting kidney repair or recovery from AKI. Mechanistically, these approaches may mitigate oxidative stress, inflammation, cell death, and mitochondrial and other organellar damage, or activate cytoprotective mechanisms such as autophagy and pro-survival factors. However, none of these findings has been successfully translated into clinical treatment of AKI. In this review, we analyze these findings and propose experimental strategies for the identification of renoprotective agents or methods with clinical potential. Moreover, we propose the consideration of combination therapy by targeting multiple targets in AKI.

The perfect storm: older adults and acute kidney injury

Older adults have a high risk for acute kidney injury (AKI), often necessitating critical care admission. The majority of older adults live with 1 or more chronic conditions requiring multiple medications, and when faced with acute illness increased vulnerability can lead to poor health outcomes. When combined with circumstances that exacerbate chronic conditions, clinicians may witness the perfect storm. Some factors that contribute to AKI risk include the aging kidney, sepsis, polypharmacy, and nephrotoxic medications and contrast media. This paper discusses specific risks and approaches to care for older adults with AKI who are in critical care.

Endostatin and transglutaminase 2 are involved in fibrosis of the aging kidney

Endostatin (EST), an antiangiogenic factor, is enriched in aging kidneys. EST is also an interactive partner of transglutaminase 2 (TG2), an enzyme that cross-links extracellular matrix proteins. Here we tested whether EST and TG2 play a role in the fibrosis of aging. In wild-type mice, aging kidneys exhibited a 2- to 4-fold increase in TG2 paralleled by increased cross-linked extracellular matrix proteins and fibrosis. Mice transgenic to express EST showed renal fibrosis at a young age. One-month delivery of EST via minipumps to young mice showed increased renal fibrosis that became more robust when superimposed on folic acid-induced nephropathy. Upregulated TG2 and impaired renal function were apparent with EST delivery combined with folic acid-induced nephropathy. Subcapsular injection of TG2 and/or EST into kidneys of young mice not only induced interstitial fibrosis, but also increased the proportion of senescent cells. Thus, kidney fibrosis in aging may represent a natural outcome of upregulated EST and TG2, but more likely it appears to be a result of cumulative stresses occurring on the background of synergistically acting geronic (aging) proteins, EST and TG2.

Chronic Kidney Disease in Aged Cats: Clinical Features, Morphology, and Proposed Pathogeneses

Chronic kidney disease (CKD) is the most common metabolic disease of domesticated cats, with most affected cats being geriatric (>12 years of age). The prevalence of CKD in cats exceeds that observed in dogs, and the frequency of the diagnosis of CKD in cats has increased in recent decades. Typical histologic features include interstitial inflammation, tubular atrophy, and fibrosis with secondary glomerulosclerosis. In contrast to people and dogs, primary glomerulopathies with marked proteinuria are remarkably rare findings in cats. Although a variety of primary renal diseases have been implicated, the disease is idiopathic in most cats. Tubulointerstitial changes, including fibrosis, are present in the early stages of feline CKD and become more severe in advanced disease. A variety of factors-including aging, ischemia, comorbid conditions, phosphorus overload, and routine vaccinations-have been implicated as factors that could contribute to the initiation of this disease in affected cats. Factors that are related to progression of established CKD, which occurs in some but not all cats, include dietary phosphorus intake, magnitude of proteinuria, and anemia. Renal fibrosis, a common histologic feature of aged feline kidneys, interferes with the normal relationship between peritubular capillaries and renal tubules. Experimentally, renal ischemia results in morphologic changes similar to those observed in spontaneous CKD. Renal hypoxia, perhaps episodic, may play a role in the initiation and progression of this disease.

Compensatory renal hypertrophy and the handling of an acute nephrotoxicant in a model of aging

Aging often results in progressive losses of functioning nephrons, which can lead to a significant reduction in overall renal function. Because of age-related pathological changes, the remaining functional nephrons within aged kidneys may be unable to fully counteract physiological and/or toxicological challenges. We hypothesized that when the total functional renal mass of aged rats is reduced by 50%, the nephrons within the remnant kidney do not fully undergo the functional and physiological changes that are necessary to maintain normal fluid and solute homeostasis. We also tested the hypothesis that the disposition and handling of a nephrotoxicant are altered significantly in aged kidneys following an acute, 50% reduction in functional renal mass. To test these hypotheses, we examined molecular indices of renal cellular hypertrophy and the disposition of inorganic mercury (Hg(2+)), a model nephrotoxicant, in young control, young uninephrectomized (NPX), aged control and aged NPX Wistar rats. We found that the process of aging reduces the ability of the remnant kidney to undergo compensatory renal growth. In addition, we found that an additional reduction in renal mass in aged animals alters the disposition of Hg(2+) and potentially alters the risk of renal intoxication by this nephrotoxicant. To our knowledge, this study represents the first report of the handling of a nephrotoxicant in an aged animal following a 50% reduction in functional renal mass.

Loss of α(E)-catenin promotes Fas mediated apoptosis in tubular epithelial cells

The aging kidney undergoes structural and functional alterations which make it more susceptible to drug-induced acute kidney injury (AKI). Previous studies in our lab have shown that the expression of α(E)-catenin is decreased in aged kidney and loss of α(E)-catenin potentiates AKI-induced apoptosis, but not necrosis, in renal tubular epithelial cells (NRK-52E cells). However, the specific apoptotic pathway underlying the increased AKI-induced cell death is not yet understood. In this study, cells were challenged with nephrotoxicant cisplatin to induce AKI. A ~5.5-fold increase in Fas expression in C2 (stable α(E)-catenin knockdown) relative to NT3 (non-targeted control) cells was seen. Increased caspase-8 and -9 activation was induced by cisplatin in C2 as compared to NT3 cells. In addition, decreased Bcl-2 expression and increased BID cleavage and cytochrome C release were detected in C2 cells after cisplatin challenge. Treating the cells with cisplatin, in combination with a Bcl-2 inhibitor, decreased the viability of NT3 cells to the same level as C2 cells after cisplatin. Furthermore, caspase-3/-7 activation is blocked by Fas, caspase-8, caspase-9 and pan-caspase inhibitors. These inhibitors also completely abolished the difference in viability between NT3 and C2 cells in response to cisplatin. These results demonstrate a Fas-mediated apoptotic signaling pathway that is enhanced by the age-dependent loss of α(E)-catenin in renal tubule epithelial cells.

Comparative Pathology of Aging Great Apes: Bonobos, Chimpanzees, Gorillas, and Orangutans

The great apes (chimpanzees, bonobos, gorillas, and orangutans) are our closest relatives. Despite the many similarities, there are significant differences in aging among apes, including the human ape. Common to all are dental attrition, periodontitis, tooth loss, osteopenia, and arthritis, although gout is uniquely human and spondyloarthropathy is more prevalent in apes than humans. Humans are more prone to frailty, sarcopenia, osteoporosis, longevity past reproductive senescence, loss of brain volume, and Alzheimer dementia. Cerebral vascular disease occurs in both humans and apes. Cardiovascular disease mortality increases in aging humans and apes, but coronary atherosclerosis is the most significant type in humans. In captive apes, idiopathic myocardial fibrosis and cardiomyopathy predominate, with arteriosclerosis of intramural coronary arteries. Similar cardiac lesions are occasionally seen in wild apes. Vascular changes in heart and kidneys and aortic dissections in gorillas and bonobos suggest that hypertension may be involved in pathogenesis. Chronic kidney disease is common in elderly humans and some aging apes and is linked with cardiovascular disease in orangutans. Neoplasms common to aging humans and apes include uterine leiomyomas in chimpanzees, but other tumors of elderly humans, such as breast, prostate, lung, and colorectal cancers, are uncommon in apes. Among the apes, chimpanzees have been best studied in laboratory settings, and more comparative research is needed into the pathology of geriatric zoo-housed and wild apes. Increasing longevity of humans and apes makes understanding aging processes and diseases imperative for optimizing quality of life in all the ape species.

Oxidative stress response and Nrf2 signaling in aging

Increasing oxidative stress, a major characteristic of aging, has been implicated in a variety of age-related pathologies. In aging, oxidant production from several sources is increased, whereas antioxidant enzymes, the primary lines of defense, are decreased. Repair systems, including the proteasomal degradation of damaged proteins, also decline. Importantly, the adaptive response to oxidative stress declines with aging. Nrf2/EpRE signaling regulates the basal and inducible expression of many antioxidant enzymes and the proteasome. Nrf2/EpRE activity is regulated at several levels, including transcription, posttranslation, and interactions with other proteins. This review summarizes current studies on age-related impairment of Nrf2/EpRE function and discusses the changes in Nrf2 regulatory mechanisms with aging.

Chronic Arachidonic Acid Administration Decreases Docosahexaenoic Acid- and Eicosapentaenoic Acid-Derived Metabolites in Kidneys of Aged Rats

Arachidonic acid (ARA) metabolites produced by cyclo-oxygenase and lipoxygenase are important mediators maintaining physiological renal function. However, the effects of exogenous ARA on kidney function in vivo remain unknown. This study examined the effects of long-term oral ARA administration on normal renal function as well as inflammation and oxidative stress in aged rats. In addition, we measured levels of renal eicosanoids and docosanoids using liquid chromatography–tandem mass spectrometry. Control or ARA oil (240 mg/kg body weight/day) was orally administered to 21-month-old Wistar rats for 13 weeks. Levels of plasma creatinine, blood urea nitrogen, inflammatory and anti-inflammatory cytokines, reactive oxygen species, and lipid peroxidation were not significantly different between the two groups. The ARA concentration in the plasma, kidney, and liver increased in the ARA-administered group. In addition, levels of free-form ARA, prostaglandin E₂, and 12- and 15-hydroxyeicosatetraenoic acid increased in the ARA-administered group, whereas renal concentration of docosahexaenoic acid and eicosapentaenoic acid decreased in the ARA-administered group. Levels of docosahexaenoic acid-derived protectin D1, eicosapentaenoic acid-derived 5-, and 18-hydroxyeicosapentaenoic acids, and resolvin E2 and E3 decreased in the ARA-administered group. Our results indicate that long-term ARA administration led to no serious adverse reactions under normal conditions and to a decrease in anti-inflammatory docosahexaenoic acid- and eicosapentaenoic acid-derived metabolites in the kidneys of aged rats. These results indicate that there is a possibility of ARA administration having a reducing anti-inflammatory effect on the kidney.

Molecular aspects of renal senescence

PURPOSE OF REVIEW

The aging kidney undergoes profound changes that lead to a reduction in stress resistance and impaired repair capacity. In order to improve the outcome of acute and chronic kidney damage, it is instrumental to understand the mechanisms that cause these changes. Cellular senescence has emerged as an important cellular process that contributes to age-associated kidney changes and chronic kidney disease progression.

RECENT FINDINGS

New mechanistic insights into excessive intracellular glucose, advanced glycation end products and endoplasmatic reticulum stress further support the importance of cellular senescence in the development of diabetic nephropathy. As telomere length of leukocytic DNA is increasingly used as a biomarker to estimate senescence in clinical cohort studies, this review also summarizes the literature on telomere length with respect to the kidney and evaluates the strengths and weaknesses of this methodology. Furthermore, novel findings on the relationships among telomeres, senescence and autophagy are discussed.

SUMMARY

Cellular senescence contributes to the decline in renal function during aging and defective regeneration in kidney diseases. Further insight into the underlying molecular mechanisms of senescence will establish a basis for preventive strategies that improve renal stress resistance and regenerative capacity.

Estrogen administered after cardiac arrest and cardiopulmonary resuscitation ameliorates acute kidney injury in a sex- and age-specific manner

Introduction

There is a sex difference in the risk of ischemic acute kidney injury (AKI), and estrogen mediates the protective effect of female sex. We previously demonstrated that preprocedural chronic restoration of physiologic estrogen to ovariectomized female mice ameliorated AKI after cardiac arrest and cardiopulmonary resuscitation (CA/CPR). In the present study, we hypothesized that male mice and aged female mice would benefit from estrogen administration after CA/CPR. We tested the effect of estrogen in a clinically relevant manner by administrating it after CA/CPR.

Methods

CA/CPR was performed in young (10–15 weeks), middle-aged (43–48 weeks), and aged (78–87 weeks) C57BL/6 male and female mice. Mice received intravenous 17β-estradiol or vehicle 15 min after resuscitation. Serum chemistries and unbiased stereological assessment of renal injury were completed 24 h after CA. Regional renal cortical blood flow was measured by a laser Doppler, and renal levels of estrogen receptor alpha (ERα) and G protein-coupled estrogen receptor (GPER) were evaluated with immunoblotting.

Results

Post-arrest estrogen administration reduced injury in young males without significant changes in renal blood flow (percentage reduction compared with vehicle: serum urea nitrogen, 30 %; serum creatinine (sCr), 41 %; volume of necrotic tubules (VNT), 31 %; P < 0.05). In contrast, estrogen did not affect any outcomes in young females. In aged mice, estrogen significantly reduced sCr (80 %) and VNT (73 %) in males and VNT (51 %) in females. Serum estrogen levels in aged female mice after CA/CPR were the same as levels in male mice. With age, renal ERα was upregulated in females.

Conclusions

Estrogen administration after resuscitation from CA ameliorates renal injury in young males and aged mice in both sexes. Because injury was small, young females were not affected. The protective effect of exogenous estrogen may be detectable with loss of endogenous estrogen in aged females and could be mediated by differences in renal ERs. Post-arrest estrogen administration is renoprotective in a sex- and age-dependent manner.

Programmed cell death in aging

Programmed cell death (PCD) pathways, including apoptosis and regulated necrosis, are required for normal cell turnover and tissue homeostasis. Mis-regulation of PCD is increasingly implicated in aging and aging-related disease. During aging the cell turnover rate declines for several highly-mitotic tissues. Aging-associated disruptions in systemic and inter-cell signaling combined with cell-autonomous damage and mitochondrial malfunction result in increased PCD in some cell types, and decreased PCD in other cell types. Increased PCD during aging is implicated in immune system decline, skeletal muscle wasting (sarcopenia), loss of cells in the heart, and neurodegenerative disease. In contrast, cancer cells and senescent cells are resistant to PCD, enabling them to increase in abundance during aging. PCD pathways limit life span in fungi, but whether PCD pathways normally limit adult metazoan life span is not yet clear. PCD is regulated by a balance of negative and positive factors, including the mitochondria, which are particularly subject to aging-associated malfunction.

Interstitial pericytes decrease in aged mouse kidneys

With increasing age, the kidney undergoes characteristic changes in the glomerular and tubulo-interstitial compartments, which are ultimately accompanied by reduced kidney function. Studies have shown age-related loss of peritubular vessels. Normal peritubular vessel tone, function and survival depend on neighboring pericytes. Pericyte detachment leads to vascular damage, which can be accompanied by their differentiation to fibroblasts and myofibroblasts, a state that favors matrix production. To better understand the fate of pericytes in the aged kidney, 27 month-old mice were studied. Compared to 3 month-old young adult mice, aged kidneys showed a substantial decrease in capillaries, identified by CD31 staining, in both cortex and medulla. This was accompanied by a marked decrease in surrounding NG2+ / PDGFRβ+ pericytes. This decrease was more pronounced in the medulla. Capillaries devoid of pericytes were typically dilated in aged mice. Aged kidneys were also characterized by interstitial fibrosis due to increased collagen-I and -III staining. This was accompanied by an increase in the number of pericytes that acquired a pro-fibrotic phenotype, identified by increased PDGFRβ+ / αSMA+ staining. These findings are consistent with the decline in kidney interstitial pericytes as a critical step in the development of changes to the peritubular vasculature with aging, and accompanying fibrosis.