Complications of progression of CKD

The role of PI3K/Akt signaling pathway in chronic kidney disease

Chronic kidney disease (CKD), including chronic glomerulonephritis, IgA nephropathy and diabetic nephropathy, are common chronic diseases characterized by structural damage and functional decline of the kidneys. The current treatment of CKD is symptom relief. Several studies have reported that the phosphatidylinositol 3 kinases (PI3K)/protein kinase B (Akt) signaling pathway is a pathway closely related to the pathological process of CKD. It can ameliorate kidney damage by inhibiting this signal pathway which is involved with inflammation, oxidative stress, cell apoptosis, epithelial mesenchymal transformation (EMT) and autophagy. This review highlights the role of activating or inhibiting the PI3K/Akt signaling pathway in CKD-induced inflammatory response, apoptosis, autophagy and EMT. We also summarize the latest evidence on treating CKD by targeting the PI3K/Akt pathway, discuss the shortcomings and deficiencies of PI3K/Akt research in the field of CKD, and identify potential challenges in developing these clinical therapeutic CKD strategies, and provide appropriate solutions.

Astragaloside IV Blunts Epithelial-Mesenchymal Transition and G2/M Arrest to Alleviate Renal Fibrosis via Regulating ALDH2-Mediated Autophagy

Previous studies show that astragaloside IV (ASIV) has anti-renal fibrosis effects. However, its mechanism remains elusive. In this study, we investigated the anti-fibrosis mechanisms of ASIV on chronic kidney disease (CKD) in vivo and in vitro. A CKD model was induced in rats with adenine (200 mg/kg/d, i.g.), and an in vitro renal fibrosis model was induced in human kidney-2 (HK-2) cells treated with TGF-β1. We revealed that ASIV significantly alleviated renal fibrosis by suppressing the expressions of epithelial-mesenchymal transition (EMT)-related proteins, including fibronectin, vimentin, and alpha-smooth muscle actin (α-SMA), and G2/M arrest-related proteins, including phosphorylated p53 (p-p53), p21, phosphorylated histone H3 (p-H3), and Ki67 in both of the in vivo and in vitro models. Transcriptomic analysis and subsequent validation showed that ASIV rescued ALDH2 expression and inhibited AKT/mTOR-mediated autophagy. Furthermore, in ALDH2-knockdown HK-2 cells, ASIV failed to inhibit AKT/mTOR-mediated autophagy and could not blunt EMT and G2/M arrest. In addition, we further demonstrated that rapamycin, an autophagy inducer, reversed the treatment of ASIV by promoting autophagy in TGF-β1-treated HK-2 cells. A dual-luciferase report assay indicated that ASIV enhanced the transcriptional activity of the ALDH2 promoter. In addition, a further molecular docking analysis showed the potential interaction of ALDH2 and ASIV. Collectively, our data indicate that ALDH2-mediated autophagy may be a novel target in treating renal fibrosis in CKD models, and ASIV may be an effective targeted drug for ALDH2, which illuminate a new insight into the treatment of renal fibrosis and provide new evidence of pharmacology to elucidate the anti-fibrosis mechanism of ASIV in treating renal fibrosis.

Prevalence of anemia and its predictors among patients with chronic kidney disease admitted to a teaching hospital in Ethiopia: A hospital-based cross-sectional study

Anemia is a common complication of chronic kidney disease (CKD) and is associated with adverse patient outcomes. However, data on the prevalence of anemia in CKD patients is sparse, particularly in resource-limited settings. Therefore, this study aimed to assess the prevalence of anemia and its predictors among patients with CKD admitted to the Jimma medical center, southwest Ethiopia. A hospital-based prospective cross-sectional study was conducted from September 1 to November 30, 2020. All adult patients with CKD aged ≥18 years who fulfilled the inclusion criteria were consecutively recruited into the study. Data were entered into the Epi data manager version 4.4.1 and then exported to SPSS version 22 (IBM Corp., Armonk, NY) for analysis. The predictors of anemia were determined using multivariable logistic regression analysis. Statistical significance was set at P < .05. A total of 150 patients were included in this study. Of these, 64.67% were male, 56.67% had stage 5 CKD, 78% had a CKD duration of less than 1 year, and 74% had proteinuria. Hypertension (40.7%) and diabetes (14.7%) were the common causes of CKD. The prevalence of anemia was 85.33%. Of the patients, 28.67%, 40.67%, and 16% had mild, moderate, and severe anemia, respectively. On multivariate logistic regression, stage 4 CKD (adjusted odds ratio [AOR] 3.2, confidence interval [CI]: 1.78-12.91, P = .025), stage 5 CKD (AOR 4.03, CI: 1.17-13.73, P = .016), and CKD duration of less than 1 year (AOR 3, CI: 1.19-9.11, P = .007) were significantly associated with anemia. The prevalence of anemia among stage 3 to 5 CKD patients was very high. Anemia was significantly associated with the severity and duration of CKD. Therefore, serial follow-up of patients with a long duration and advanced stages of CKD may help prevent anemia and its adverse consequences.

Pruritus in Chronic Kidney Disease: An Update

Chronic kidney disease-associated pruritus (CKDaP) is an often under-diagnosed and under-recognized condition, despite its considerable prevalence within the chronic kidney disease (CKD) population. Universally accepted guidelines are also lacking. The true prevalence of CKDaP worldwide therefore remains unknown, although its negative impact on mortality and health-related quality of life outcomes is very clear. The pathophysiological mechanisms leading to the onset of CKDaP are only partly understood. CKDaP is currently believed to be caused by a multifactorial process, from local skin changes, metabolic alterations, the development of neuropathy and dysregulation of opioid pathways, and psychological factors. Much work has been carried out towards a more systematic and structured approach to clinical diagnosis. Various tools are now available to assess the severity of CKDaP. Many of these tools require greater validation before they can be incorporated into the guidelines and into routine clinical practice. Further efforts are also needed in order to increase the awareness of clinicians and patients so that they can identify the CKDaP signs and symptoms in a timely manner. Currently established treatment options for CKDaP focus on the prevention of xerosis via topical emollients, the optimization of dialysis management, early referral to kidney transplantation if appropriate, oral antihistamine, and a variety of neuropathic agents. Other novel treatment options include the following: topical analgesics, topical tacrolimus, cannabinoid-containing compounds, antidepressants, oral leukotrienes, opioids, and non-pharmacological alternative therapies (i.e., phototherapy, dietary supplements, acupuncture/acupressure). We provide an updated review on the evidence relating to the epidemiology, the pathophysiology, the clinical assessment and diagnosis, and the management of CKDaP.

Corni Fructus Alleviates UUO-Induced Renal Fibrosis via TGF-β/Smad Signaling

Renal fibrosis is a type of chronic kidney disease (CKD) induced by infiltration of inflammatory cells, myofibroblast accumulation, and ECM production in the kidney. From a long time ago, Corni Fructus (CF) is known to supplement the liver and kidney with its tepid properties. In this study, we investigated the renal protective mechanism of CF, which is known to supplement the kidney, in rat model of unilateral ureteral obstruction (UUO). After inducing UUO through surgery, the group was separated ( $n=8$ ) and the drug was administered for 2 weeks; normal rats (normal), water-treated UUO rats (control), CF 100 mg/kg-treated UUO rats (CF100), and CF 200 mg/kg-treated UUO rats (CF200). As a result of histopathological examination of kidney tissue with H&E, MT, and PAS staining, it was confirmed that the infiltration of inflammatory cells and the erosion of collagen were relatively decreased in the kidneys treated with CF. Also, CF significantly reduced the levels of MDA and BUN in serum. As a result of confirming the expression of the factors through western blotting, CF treatment significantly reduced the expression of NADPH oxidase and significantly regulated the AMPK/LKB1/NF-κB pathway associated with inflammation. In addition, it downregulated the expression of major fibrotic signaling factors, such as α-SMA, collagen I, MMP-2, and TIMP-1, and significantly regulated the TGF-β1/Smad pathway, which is known as a major regulator of renal fibrosis. Taken together, these findings indicate that CF can alleviate renal fibrosis by regulating the TGF-β1/Smad pathway through inhibition of oxidative stress in UUO.

Association of chronic kidney disease with exposure to polycyclic aromatic hydrocarbons in the US population

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants formed from the incomplete combustion of carbon-containing products. Exposure can occur through ingestion or inhalation and has been linked to depression, stroke, liver disease, asthma, diabetes, heart failure, and cancer. Few studies have investigated the association between exposure to PAHs and chronic kidney disease (CKD) in humans. This study aims to investigate the association between seven urinary PAH concentrations (1-hydroxynaphthalene, 2-hydroxynaphthalene, 3-hydroxyfluorene 2-hydroxyfluorene, 1-hydroxyphenanthrene, 1-hydroxypyrene, and 2 & 3-hydroxyphenanthrene) and CKD in the US adult population. A cross-sectional analysis using the 2015-2016 National Health and Nutrition Examination Survey (NHANES) dataset was conducted. CKD was defined with estimated glomerular filtration rate (eGFR) and albumin to creatinine ratio (ACR). Participants with an eGFR < 60 ml/min/1.73m² or ACR > 30 mg/gm were considered to have CKD. A specialized complex survey design analysis package using R version 4.0.3 was used in the data analysis. Multivariate logistic regression was used to study the correlation between seven forms of urinary PAH concentrations and CKD associated with abnormal eGFR or ACR. The models were adjusted for lifestyle and demographic factors. The study included a total of 4117 adults aged ≥ 20 years, with 49.6% males and 50.4% females. Urinary 2-hydroxynaphthalene (OR: 1.600, 95% CI: 1.141, 2.243) was significantly associated with an increased odds of CKD; the other six forms of urinary PAHs were not associated with CKD. Non-Hispanic Black (OR: 1.569, 95% CI: 1.168, 2.108), age of 60 years and older (OR: 2.546, 95% CI: 1.865, 3.476), and BMIs of underweight (OR: 2.386, 95% CI: 1.259, 4.524) and obese (OR: 1.407, 95% CI: 1.113, 1.778) all had significantly increased odds for CKD. Our study concluded that urinary 2-hydroxynaphthalene, a form of PAH, is significantly associated with CKD.

Risk factors associated with albuminuria in Rwanda: results from a STEPS survey

BACKGROUND

Non-communicable diseases (NCDs) are a growing burden which affects every part of the world, including developing countries. Chronic kidney disease (CKD) has varied etiology which can result from or complicate other NCDs such as diabetes and cardiovascular diseases. The growing prevalence of NCDs coupled with the increasing age in most developing countries, has seen a marked increase of CKD in these settings. CKD has been described as "the most neglected NCD" and greatly affects the quality of life of patients. It also places a huge economic burden on societies. However, few epidemiological data exist, particularly in sub-Saharan Africa. Assessment of the prevalence of albuminuria as a marker of kidney damage and CKD progression and its main risk factors was thus needed in Rwanda.

METHODS

This study analyzed data collected during the first STEPwise approach to NCD risk factor Surveillance (STEPS) survey in Rwanda, conducted from 2012 to 2013, to assess the prevalence of albuminuria. A multistage cluster sampling allowed to select a representative sample of the general population. Furthermore, descriptive, as well as univariable analyses and multiple logistic regression were performed to respond to the research question.

RESULTS

This survey brought a representative sample of 6,998 participants, among which 4,384 (62.65%) were female. Median age was 33 years (interquartile range, IQR 26-44), and over three quarters (78.45%) lived in rural areas. The albuminuria prevalence was 105.9 per 1,000 population. Overall, semi-urban and urban residency were associated with lower odds of CKD (odds ratio, OR 0.36, CI 0.23-0.56, p<0.001 and OR 0.34, CI 0.23-0.50, p<0.001, respectively) than rural status. Being married or living with a partner had higher odds (OR 1.44 (CI 1.03-2.02, p=0.031) and OR 1.62 (CI 1.06-2.48, p=0.026), respectively) of CKD than being single. Odds of positive albuminuria were also greater among participants living with human immunodeficiency virus (HIV) (OR 1.64, CI 1.09- 2.47, p=0.018). Gender, age group, smoking status and vegetable consumption, body mass index (BMI) and hypertension were not associated with albuminuria.

CONCLUSION

The albuminuria prevalence was estimated at 105.9 per 1,000 in Rwanda. Rural residence, partnered status and HIV positivity were identified as main risk factors for albuminuria. Increased early screening of albuminuria to prevent CKD among high-risk groups, especially HIV patients, is therefore recommended.

Additional cost of end-stage kidney disease in diabetic patients according to renal replacement therapy modality: a systematic review

The prevalence of end-stage kidney disease (ESKD) is growing worldwide; the survival of these patients requires renal replacement therapy (RRT, a complex and costly treatment). Over 20% of the patients that start RTT had diabetes. Limited evidence on the effect of comorbidities on the cost of RRT exists. This review summarizes the available evidence on the effect of diabetes mellitus (DM) on the cost of RRT. Electronic databases were searched using key words that combined RRT with DM and cost. References were identified with title, abstract, and full-text screening. The studies included were published in English and presented data on the cost of RRT in ESKD patients with comparison between DM status. Seventeen studies were included in this review. The crude and adjusted cost of care estimates for patients on dialysis was generally higher for DM patients. The cost of care of ESKD patients differed according to various treatment modalities and these differences, mainly driven by inpatient costs. Overall, we found an increased cost of RRT care in patients with DM regardless of the type of treatment. Future analysis of the effects of multiple comorbidities should be considered to better understand the effect of DM on the cost of RRT.

Association between dietary patterns and chronic kidney disease in a middle-aged Chinese population

OBJECTIVE

To explore the relationship between dietary patterns and risk of chronic kidney disease (CKD) in Chinese adults aged 45-59 years.

DESIGN

Dietary data were collected using a semi-quantitative FFQ. Factor analysis was used to identify the major dietary patterns. Logistic regression models were applied to clarify the association between dietary patterns and the risk of CKD.

SETTING

The present study population was a part of the population-based Nutrition and Health Study performed in the city of Hangzhou, Zhejiang Province, eastern China.

PARTICIPANTS

A total of 2437 eligible participants (45-59 years) were enrolled in the present cross-sectional study from June 2015 to December 2016.

RESULTS

Three major dietary patterns were identified: 'traditional southern Chinese', 'Western' and 'grains-vegetables' patterns, collectively accounting for 25·6 % of variance in the diet. After adjustment for potential confounders, participants in the highest quartile of the Western pattern had greater odds for CKD (OR = 1·83, 95 % CI 1·21, 2·81; P < 0·05) than those in the lowest quartile. Compared with the lowest quartile of the grains-vegetables pattern, the highest quartile had lower odds for CKD (OR = 0·84, 95 % CI 0·77, 0·93; P < 0·05). In addition, there was no significant association between the traditional southern Chinese pattern and risk of CKD (P > 0·05).

CONCLUSIONS

Our results suggest that the Western pattern is associated with an increased risk, whereas the grains-vegetables pattern is associated with a reduced risk for CKD. These findings can guide dietary interventions for the prevention of CKD in a middle-aged Chinese population.

The interplay between mineral metabolism, vascular calcification and inflammation in Chronic Kidney Disease (CKD): challenging old concepts with new facts

Chronic kidney disease (CKD) is one of the most powerful predictors of premature cardiovascular disease (CVD), with heightened susceptibility to vascular intimal and medial calcification associated with a high cardiovascular mortality. Abnormal mineral metabolism of calcium (Ca) and phosphate (P) and underlying (dys)regulated hormonal control in CKD-mineral and bone disorder (MBD) is often accompanied by bone loss and increased vascular calcification (VC). While VC is known to be a multifactorial process and a major risk factor for CVD, the view of primary triggers and molecular mechanisms complexity has been shifting with novel scientific knowledge over the last years. In this review we highlight the importance of calcium-phosphate (CaP) mineral crystals in VC with an integrated view over the complexity of CKD, while discuss past and recent literature aiming to highlight novel horizons on this major health burden. Exacerbated VC in CKD patients might result from several interconnected mechanisms involving abnormal mineral metabolism, dysregulation of endogenous calcification inhibitors and inflammatory pathways, which function in a feedback loop driving disease progression and cardiovascular outcomes. We propose that novel approaches targeting simultaneously VC and inflammation might represent valuable new prognostic tools and targets for therapeutics and management of cardiovascular risk in the CKD population.

Food Patterns are Associated with Likelihood of CKD in US Adults

We investigated the association between dietary patterns and prevalent chronic kidney diseases (CKD), in participants of the 2005–2012 US National Health and Nutrition Examination Survey (NHANES) conducted between 2005 and 2012, who had measured data on dietary intake and kidney function. Analyse of covariance (ANCOVA) and logistic regression models were employed to account for the survey design and sample weights. A total of 21,649 eligible participants (634 with and 20,015 without prevalent CKD) were included in the final analysis. Three food patterns together explained 50.8% of the variance of the dietary nutrients consumption. The first food pattern was representative of a diet containing high levels of saturated and mono-unsaturated fatty acids; the second food pattern comprised vitamins and trace elements; and the third food pattern was mainly representative of polyunsaturated fatty acids. The odd of prevalent CKD decreased across increasing quarters of vitamins and trace elements, so that the top quarter was associated with a 53% (95%CI: 42–62%) lower odds of CKD in age, sex and race adjusted logistic regression models. These results suggest that vitamins and trace elements intake are associated with lower risk of prevalent CKD.

Eryptosis - the Neglected Cause of Anemia in End Stage Renal Disease

End stage renal disease (ESRD) invariably leads to anemia which has been mainly attributed to compromised release of erythropoietin from the defective kidneys with subsequent impairment of erythropoiesis. However, erythropoietin replacement only partially reverses anemia pointing to the involvement of additional mechanisms. As shown more recently, anemia of ESRD is indeed in large part a result of accelerated erythrocyte loss due to suicidal erythrocyte death or eryptosis, characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the cell surface. Phosphatidylserine exposing erythrocytes are bound to and engulfed by macrophages and are thus rapidly cleared from circulating blood. If the loss of erythrocytes cannot be fully compensated by enhanced erythropoiesis, stimulation of eryptosis leads to anemia. Eryptotic erythrocytes may further adhere to the vascular wall and thus impair microcirculation. Stimulators of eryptosis include complement, hyperosmotic shock, energy depletion, oxidative stress, and a wide variety of xenobiotics. Signaling involved in the stimulation of eryptosis includes increase of cytosolic Ca2+ activity, ceramide, caspases, calpain, p38 kinase, protein kinase C, Janus-activated kinase 3, casein kinase 1α, and cyclin-dependent kinase 4. Eryptosis is inhibited by AMP-activated kinase, p21-activated kinase 2, cGMP-dependent protein kinase, mitogen- and stress-activated kinase MSK1/2, and some illdefined tyrosine kinases. In ESRD eryptosis is stimulated at least in part by a plasma component, as it is triggered by exposure of erythrocytes from healthy individuals to plasma from ESRD patients. Several eryptosis-stimulating uremic toxins have been identified, such as vanadate, acrolein, methylglyoxal, indoxyl sulfate, indole-3-acetic acid and phosphate. Attempts to fully reverse anemia in ESRD with excessive stimulation of erythropoiesis enhances the number of circulating suicidal erythrocytes and bears the risk of interference with micocirculation, At least in theory, anemia in ESRD could preferably be treated with replacement of erythropoietin and additional inhibition of eryptosis thus avoiding eryptosis-induced impairment of microcirculation. A variety of eryptosis inhibitors have been identified, their efficacy in ESRD remains, however, to be shown.

Potential Use of Autologous Renal Cells from Diseased Kidneys for the Treatment of Renal Failure

Chronic kidney disease (CKD) occurs when certain conditions cause the kidneys to gradually lose function. For patients with CKD, renal transplantation is the only treatment option that restores kidney function. In this study, we evaluated primary renal cells obtained from diseased kidneys to determine whether their normal phenotypic and functional characteristics are retained, and could be used for cell therapy. Primary renal cells isolated from both normal kidneys (NK) and diseased kidneys (CKD) showed similar phenotypic characteristics and growth kinetics. The expression levels of renal tubular cell markers, Aquaporin-1 and E-Cadherin, and podocyte-specific markers, WT-1 and Nephrin, were similar in both NK and CKD kidney derived cells. Using fluorescence- activated cell sorting (FACS), specific renal cell populations were identified and included proximal tubular cells (83.1% from NK and 80.3% from CKD kidneys); distal tubular cells (11.03% from NK and 10.9% from CKD kidneys); and podocytes (1.91% from NK and 1.78% from CKD kidneys). Ultra-structural analysis using scanning electron microscopy (SEM) revealed microvilli on the apical surface of cultured cells from NK and CKD samples. Moreover, transmission electron microscopy (TEM) analysis showed a similar organization of tight junctions, desmosomes, and other intracellular structures. The Na⁺ uptake characteristics of NK and CKD derived renal cells were also similar (24.4 mmol/L and 25 mmol/L, respectively) and no significant differences were observed in the protein uptake and transport characteristics of these two cell isolates. These results show that primary renal cells derived from diseased kidneys such as CKD have similar structural and functional characteristics to their counterparts from a normal healthy kidney (NK) when grown in vitro. This study suggests that cells derived from diseased kidney may be used as an autologous cell source for renal cell therapy, particularly in patients with CKD or end-stage renal disease (ESRD).

Cardiorenal syndrome type 4: From chronic kidney disease to cardiovascular impairment

Cardiorenal syndrome type 4 (CRS type 4), or chronic renocardiac syndrome, has been defined as "chronic abnormalities in renal function leading to cardiac disease" and recognizes the extreme burden of cardiovascular disease (CVD) risk in patients with chronic kidney disease (CKD). CKD is common and increasingly recognized as a risk factor for CVD. Even though the treatment for CVD has dramatically improved over the past decades, it still takes responsibility for up to 50% of deaths in CKD patients. For this reason, patients with CKD should be thoroughly evaluated for cardiovascular risk factors that require careful management, given the significant burden of CRS type 4 on the healthcare system. This review focuses on the most significant conventional and non-conventional CVD risk factors related to CKD.

Micronutrient Intakes and Incidence of Chronic Kidney Disease in Adults: Tehran Lipid and Glucose Study

The aim of this study was to investigate the associations between micronutrient intakes and the 3.6-year incidence of chronic kidney disease (CKD) in adults. This cohort study was conducted, within the framework of the Tehran Lipid and Glucose Study, on 1692 subjects, aged ≥30 years, without CKD at the baseline. Dietary intakes were collected using a valid and reliable food-frequency questionnaire. Anthropometrics and biochemical measurements were taken. Chronic kidney disease was defined as eGFR < 60 mL/min/1.73 m². The mean age of participants was 43.3 ± 11.4 years. In the fully adjusted model, individuals in the top quintile of folate (OR: 0.44, 95% CI: 0.24–0.80), cobalamin (OR: 0.57, 95% CI: 0.34–0.93), vitamin C (OR: 0.38, 95% CI: 0.21–0.69), vitamin E (OR: 0.45, 95% CI: 0.22–0.92), vitamin D (OR: 0.39, 95% CI: 0.21–0.70), potassium (OR: 0.47, 95% CI: 0.23–0.97) and magnesium (OR: 0.41, 95% CI: 0.22–0.76) had decreased risk of CKD, and in the top quintile of sodium (OR: 1.64, 95% CI: 1.03–2.61), subjects had increased risk of CKD, in comparison to the bottom quintile. No significant associations were found between the intakes of other micronutrients. High intake of several micronutrients including vitamins C, E, D, cobalamin, folate, magnesium, and potassium was associated with a decreased risk, while sodium was associated with an increased risk of incident CKD.

Therapeutic potential of manipulating suicidal erythrocyte death

INTRODUCTION

Eryptosis, the suicidal erythrocyte death, is characterized by erythrocyte shrinkage and phosphatidylserine translocation to the erythrocyte surface. Eryptosis is triggered by cell stress such as energy depletion and oxidative stress, by Ca(2+)-entry, ceramide, caspases, calpain and/or altered activity of several kinases. Phosphatidylserine-exposing erythrocytes adhere to the vascular wall and may thus impede microcirculation. Eryptotic cells are further engulfed by phagocytes and thus rapidly cleared from circulation.

AREAS COVERED

Stimulation of eryptosis contributes to anemia of several clinical conditions such as metabolic syndrome, diabetes, malignancy, hepatic failure, heart failure, uremia, hemolytic uremic syndrome, sepsis, fever, dehydration, mycoplasma infection, malaria, iron deficiency, sickle cell anemia, thalassemia, glucose-6-phosphate dehydrogenase deficiency and Wilson's disease. On the other hand, eryptosis with subsequent clearance of infected erythrocytes in malaria may counteract parasitemia.

EXPERT OPINION

In theory, anemia due to excessive eryptosis could be alleviated by treatment with small molecules inhibiting eryptosis. In malaria, stimulators of eryptosis may accelerate death of infected erythrocytes and thus favorably influence the clinical course of the disease. Many small molecules inhibit or stimulate eryptosis. Several stimulators favorably influence murine malaria. Further preclinical and subsequent clinical studies are required to elucidate the therapeutic potential of stimulators or inhibitors of eryptosis.

Triggers, inhibitors, mechanisms, and significance of eryptosis: the suicidal erythrocyte death

Suicidal erythrocyte death or eryptosis is characterized by erythrocyte shrinkage, cell membrane blebbing, and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include Ca(2+) entry, ceramide formation, stimulation of caspases, calpain activation, energy depletion, oxidative stress, and dysregulation of several kinases. Eryptosis is triggered by a wide variety of xenobiotics. It is inhibited by several xenobiotics and endogenous molecules including NO and erythropoietin. The susceptibility of erythrocytes to eryptosis increases with erythrocyte age. Phosphatidylserine exposing erythrocytes adhere to the vascular wall by binding to endothelial CXC-Motiv-Chemokin-16/Scavenger-receptor for phosphatidylserine and oxidized low density lipoprotein (CXCL16). Phosphatidylserine exposing erythrocytes are further engulfed by phagocytosing cells and are thus rapidly cleared from circulating blood. Eryptosis eliminates infected or defective erythrocytes thus counteracting parasitemia in malaria and preventing detrimental hemolysis of defective cells. Excessive eryptosis, however, may lead to anemia and may interfere with microcirculation. Enhanced eryptosis contributes to the pathophysiology of several clinical disorders including metabolic syndrome and diabetes, malignancy, cardiac and renal insufficiency, hemolytic uremic syndrome, sepsis, mycoplasma infection, malaria, iron deficiency, sickle cell anemia, thalassemia, glucose 6-phosphate dehydrogenase deficiency, and Wilson's disease. Facilitating or inhibiting eryptosis may be a therapeutic option in those disorders.

Mechanisms and pathophysiological significance of eryptosis, the suicidal erythrocyte death

Eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and cell membrane scrambling, is stimulated by Ca(2+) entry through Ca(2+)-permeable, PGE2-activated cation channels, by ceramide, caspases, calpain, complement, hyperosmotic shock, energy depletion, oxidative stress, and deranged activity of several kinases (e.g. AMPK, GK, PAK2, CK1α, JAK3, PKC, p38-MAPK). Eryptosis is triggered by intoxication, malignancy, hepatic failure, diabetes, chronic renal insufficiency, hemolytic uremic syndrome, dehydration, phosphate depletion, fever, sepsis, mycoplasma infection, malaria, iron deficiency, sickle cell anemia, thalassemia, glucose 6-phosphate dehydrogenase deficiency, and Wilson's disease. Eryptosis may precede and protect against hemolysis but by the same token result in anemia and deranged microcirculation.

Multicenter epidemiological study to assess the population of CKD patients in Greece: results from the PRESTAR study

BACKGROUND

Chronic Kidney Disease (CKD) is a relatively common condition not only associated with increased morbidity and mortality but also fuelling End Stage Renal Disease (ESRD). Among developed nations, Greece has one of the highest ESRD incidence rates, yet there is limited understanding of the epidemiology of earlier stages of CKD.

METHODS

Cross-sectional survey of pre-dialysis CKD outpatients in nephrology clinics in the National Health Care system between October 2009 and October 2010. Demographics, cause of CKD, blood pressure, level of renal function, duration of CKD and nephrology care, and specialty of referral physician were collected and analyzed. Different methods for estimating renal function (Cockroft-Gault [CG], CKD-Epi and MDRD) and staging CKD were assessed for agreement.

RESULTS

A total of 1,501 patients in 9 centers were enrolled. Diabetic nephropathy was the most common nephrologist assigned cause of CKD (29.7%). In total, 36.5% of patients had self-referred to the nephrologist; patients with diabetes or serum creatinine above 220 µmol/l (eGFR<40 ml/min/1.73 m2) were more likely to have been referred by a physician. Agreement between MDRD and CKD-Epi, but not between CG, the other estimating equations, was excellent. There was substantial heterogeneity with respect to renal diagnoses, referral patterns and blood pressure among participating centers.

CONCLUSIONS

In this first epidemiologic assessment of CKD in Greece, we documented delayed referral and high rates of self-referral among patients with CKD. eGFR reporting, currently offered by a limited number of laboratories, may facilitate detection of CKD at an earlier, more treatable stage.

Oxidative stress and suicidal erythrocyte death

SIGNIFICANCE

Eryptosis, the suicidal erythrocyte death, is characterized by cell shrinkage, membrane blebbing, and phosphatidylserine translocation to the outer membrane leaflet. Phosphatidylserine at the erythrocyte surface binds endothelial CXCL16/SR-PSOX (CXC-Motiv-Chemokin-16/Scavenger-receptor-for-phosphatidylserine-and-oxidized-low-density-lipoprotein) and fosters engulfment of affected erythrocytes by phagocytosing cells. Eryptosis serves to eliminate infected or defective erythrocytes, but excessive eryptosis may lead to anemia and may interfere with microcirculation. Clinical conditions with excessive eryptosis include diabetes, chronic renal failure, hemolytic uremic syndrome, sepsis, malaria, iron deficiency, sickle cell anemia, thalassemia, glucose 6-phosphate dehydrogenase deficiency, glutamate cysteine ligase modulator deficiency, and Wilson's disease.

RECENT ADVANCES

Eryptosis is triggered by a wide variety of xenobiotics and other injuries such as oxidative stress. Signaling of eryptosis includes prostaglandin E₂ formation with subsequent activation of Ca(2+)-permeable cation channels, Ca(2+) entry, activation of Ca(2+)-sensitive K(+) channels, and cell membrane scrambling, as well as phospholipase A2 stimulation with release of platelet-activating factor, sphingomyelinase activation, and ceramide formation. Eryptosis may involve stimulation of caspases and calpain with subsequent degradation of the cytoskeleton. It is regulated by AMP-activated kinase, cGMP-dependent protein kinase, Janus-activated kinase 3, casein kinase 1α, p38 kinase, and p21-activated kinase 2. It is inhibited by erythropoietin, antioxidants, and further small molecules.

CRITICAL ISSUES

It remains uncertain for most disorders whether eryptosis is rather beneficial because it precedes and thus prevents hemolysis or whether it is harmful because of induction of anemia and impairment of microcirculation.

FUTURE DIRECTIONS

This will address the significance of eryptosis, further mechanisms underlying eryptosis, and additional pharmacological tools fostering or inhibiting eryptosis.

Suicidal erythrocyte death in end-stage renal disease

Anemia in end-stage renal disease (ESRD) results mainly from erythropoietin and iron deficiency. Anemia could be confounded, however, by accelerated clearance of circulating erythrocytes because of premature suicidal erythrocyte death or eryptosis characterized by phosphatidylserine exposure at the erythrocyte surface. Triggers of eryptosis include increased cytosolic Ca(2+) concentration ([Ca(2+)]i), oxidative stress, and ceramide. The present study explored whether and how ESRD influences eryptosis. Blood was drawn from healthy volunteers (n = 20) as well as ESRD patients (n = 20) prior to and after hemodialysis. Phosphatidylserine exposure was estimated from annexin V binding, [Ca(2+)]i from Fluo3-fluorescence, reactive oxygen species (ROS) from 2',7'dichlorodihydrofluorescein fluorescence, and ceramide from fluorescein-isothiocyanate-conjugated antibody binding in flow cytometry. Measurements were made in erythrocytes from freshly drawn blood and in erythrocytes from healthy volunteers exposed in vitro for 24 h to plasma from healthy volunteers or ESRD patients prior to and following dialysis. The patients suffered from anemia (hemoglobin 10.1 ± 0.5 g/100 ml) despite 1.96 ± 0.34 % reticulocytes. The percentage of phosphatidylserine-exposing erythrocytes was significantly higher in ESRD patients (0.84 ± 0.09 %) than in healthy volunteers (0.43 ± 0.04 %) and was significantly increased immediately after dialysis (1.35 ± 0.13 %). The increase in phosphatidylserine exposure was paralleled by increase in [Ca(2+)]i, oxidative stress, and ceramide abundance. As compared to addition of plasma from healthy individuals, addition of predialytic but not of postdialytic plasma from ESRD patients increased phosphatidylserine exposure, [Ca(2+)]i, ROS, and ceramide abundance. In conclusion, both, dialyzable components of uremic plasma and dialysis procedure, trigger eryptosis at least in part by increasing erythrocyte [Ca(2+)]i, ROS, and ceramide formation.

KEY MESSAGES

Anemia in uremia results in part from eryptosis, the suicidal erythrocyte death. Eryptosis in uremia is triggered in part by a dialyzable plasma component. Eryptosis in uremia is further triggered by dialysis procedure. Eryptosis in uremia is in part due to increased cytosolic Ca(2+) concentration. Eryptosis in uremia is further due to oxidative stress and ceramide formation.

A retrospective case-control analysis of the outpatient expenditures for western medicine and dental treatment modalities in CKD patients in Taiwan

BACKGROUND

To determine if expenditures for dentistry (DENT) correlate with severity of chronic kidney disease (CKD).

METHODS

A total of 10,457 subjects were enrolled from January 2008 to December 2010, divided into three groups: healthy control (HC) group (n = 1,438), high risk (HR) group (n = 3,392), and CKD group (n = 5,627). Five stages were further categorized for the CKD group. OPD utilization and expenditures for western medicine (WM), DENT, and TCM (traditional Chinese medicine) were analyzed retrospectively (2000-2008) using Taiwan's National Health Insurance Research Database. Three major areas were analyzed among groups CKD, HR and HC in this study: 1) demographic data and medical history; 2) utilization (visits/person/year) and expenditures (9-year cumulative expenditure, expenditure/person/year) for OPD services in WM, DENT, and TCM; and 3) utilization and expenditures for dental OPD services, particularly in dental filling, root canal and periodontal therapy.

RESULTS

OPD utilization and expenditures of WM increased significantly for the CKD group compared with the HR and HC groups, and increased steadily along with the severity of CKD stages. However, overall DENT and TCM utilization and expenditures did not increase for the CKD group. In comparison among different CKD stages, the average expenditures and utilization for DENT including restorative filling and periodontal therapy, but not root canal therapy, showed significant decreases according to severity of CKD stage, indicating less DENT OPD utilization with progression of CKD.

CONCLUSIONS

Patients with advanced CKD used DENT OPD service less frequently. However, the connection between CKD and DENT service utilization requires further study.

Stimulation of suicidal erythrocyte death by increased extracellular phosphate concentrations

BACKGROUND/AIM

Anemia in renal insufficiency results in part from impaired erythrocyte formation due to erythropoietin and iron deficiency. Beyond that, renal insufficiency enhances eryptosis, the suicidal erythrocyte death characterized by phosphatidylserine-exposure at the erythrocyte surface. Eryptosis may be stimulated by increase of cytosolic Ca(2+)-activity ([Ca(2+)]i). Several uremic toxins have previously been shown to stimulate eryptosis. Renal insufficiency is further paralleled by increase of plasma phosphate concentration. The present study thus explored the effect of phosphate on erythrocyte death.

METHODS

Cell volume was estimated from forward scatter, phosphatidylserine-exposure from annexin V binding, and [Ca(2+)]i from Fluo3-fluorescence.

RESULTS

Following a 48 hours incubation, the percentage of phosphatidylserine exposing erythrocytes markedly increased as a function of extracellular phosphate concentration (from 0-5 mM). The exposure to 2 mM or 5 mM phosphate was followed by slight but significant hemolysis. [Ca(2+)]i did not change significantly up to 2 mM phosphate but significantly decreased at 5 mM phosphate. The effect of 2 mM phosphate on phosphatidylserine exposure was significantly augmented by increase of extracellular Ca(2+) to 1.7 mM, and significantly blunted by nominal absence of extracellular Ca(2+), by additional presence of pyrophosphate as well as by presence of p38 inhibitor SB203580.

CONCLUSION

Increasing phosphate concentration stimulates erythrocyte membrane scrambling, an effect depending on extracellular but not intracellular Ca(2+) concentration. It is hypothesized that suicidal erythrocyte death is triggered by complexed CaHPO4.

Triggering of suicidal erythrocyte death by uremic toxin indoxyl sulfate

Background

Anemia in end stage renal disease is attributed to impaired erythrocyte formation due to erythropoietin and iron deficiency. On the other hand, end stage renal disease enhances eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and phosphatidylserine-exposure at the erythrocyte surface. Eryptosis may be triggered by increase of cytosolic Ca²⁺-activity ([Ca²⁺]_i) and by ceramide, which sensitizes erythrocytes to [Ca²⁺]_i. Mechanisms triggering eryptosis in endstage renal disease remained enigmatic. The present study explored the effect of indoxyl sulfate, an uremic toxin accumulated in blood of patients with chronic kidney disease.

Methods

Cell volume was estimated from forward scatter, phosphatidylserine-exposure from annexin V binding, ceramide abundance by specific antibodies, hemolysis from hemoglobin release, and [Ca²⁺]_i from Fluo3-fluorescence.

Results

A 48 hours exposure to indoxyl sulfate significantly increased [Ca²⁺]_i (≥ 300 μM), significantly decreased forward scatter (≥ 300 μM) and significantly increased annexin-V-binding (≥ 50 μM). Indoxyl sulfate (150 μM) induced annexin-V-binding was virtually abolished in the nominal absence of extracellular Ca²⁺. Indoxyl sulfate (150 μM) further enhanced ceramide abundance.

Conclusion

Indoxyl sulfate stimulates suicidal erythrocyte death or eryptosis, an effect in large part due to stimulation of extracellular Ca²⁺entry with subsequent stimulation of cell shrinkage and cell membrane scrambling.

Retrotransposon insertion in the T-cell acute lymphocytic leukemia 1 (Tal1) gene is associated with severe renal disease and patchy alopecia in Hairpatches (Hpt) mice

“Hairpatches” (Hpt) is a naturally occurring, autosomal semi-dominant mouse mutation. Hpt/Hpt homozygotes die in utero, while Hpt/+ heterozygotes exhibit progressive renal failure accompanied by patchy alopecia. This mutation is a model for the rare human disorder “glomerulonephritis with sparse hair and telangiectases" (OMIM 137940). Fine mapping localized the Hpt locus to a 6.7 Mb region of Chromosome 4 containing 62 known genes. Quantitative real time PCR revealed differential expression for only one gene in the interval, T-cell acute lymphocytic leukemia 1 (Tal1), which was highly upregulated in the kidney and skin of Hpt/+ mice. Southern blot analysis of Hpt mutant DNA indicated a new EcoRI site in the Tal1 gene. High throughput sequencing identified an endogenous retroviral class II intracisternal A particle insertion in Tal1 intron 4. Our data suggests that the IAP insertion in Tal1 underlies the histopathological changes in the kidney by three weeks of age, and that glomerulosclerosis is a consequence of an initial developmental defect, progressing in severity over time. The Hairpatches mouse model allows an investigation into the effects of Tal1, a transcription factor characterized by complex regulation patterns, and its effects on renal disease.