Urinary biomarkers monitoring for experimental fluoride nephrotoxicity

A New Phenothiazine-Based Fluorescent Probe for Rapid and Specific Detection of Fluoride

Fluorescent probes with specific and rapid response to fluoride ions are important mediators for detecting fluoride ions in biological systems. In this study, a phenothiazine-based fluorescent probe, PTC, was designed and synthesized, which undergoes cleavage activation and cyclization induced by fluoride ions targeting Si-O bonds. The probe exhibits strong anti-interference properties and reaches peak fluorescence within 5 min, allowing for quantitative detection of fluoride ions content in the concentration range of 0 to 12.5μM, suitable for live cell fluorescence imaging. The research findings suggest its potential application value in biological systems.

Inflammation- and cancer-related microRNAs in rat renal cortex after subchronic exposure to fluoride

The proximal tubule is a target of subchronic exposure to fluoride (F) in the kidney. Early markers are used to classify kidney damage, stage, and prognosis. MicroRNAs (miRNAs) are small sequences of non-coding single-stranded RNA that regulate gene expression and play an essential role in developing many pathologies, including renal diseases. This study aimed to evaluate the expression of Cytokine-Chemokine molecules (IL-1α/1β/4/6/10, INF-γ, MIP-1α, MCP-1, RANTES, and TGF β1/2/3) and inflammation-related miRNAs to evidence the possible renal mechanisms involved in subchronic exposure to F. Total protein and miRNAs were obtained from the renal cortex of male Wistar rats exposed to 0, 15 and 50 mg NaF/L through drinking water during 40 and 80 days. In addition, cytokines-chemokines were analyzed by multiplexing assay, and a panel of 77 sequences of inflammatory-related miRNAs was analyzed by qPCR. The results show that cytokines-chemokines expression was concentration- and time-dependent with F, where the 50 mg NaF/L were the main altered groups. The miRNAs expression resulted in statistically significant differences in thirty-four miRNAs in the 50 mg NaF/L groups at 40 and 80 days. Furthermore, a molecular interaction network analysis was performed. The relevant pathways modified by subchronic exposure to fluoride were related to extracellular matrix-receptor interaction, Mucin type O-glycan biosynthesis, Gap junction, and miRNAs involved with renal cell carcinoma. Thus, F-induced cytokines-chemokines suggest subchronic inflammation; detecting miRNAs related to cancer and proliferation indicates a transition from renal epithelium to pathologic tissue after fluoride exposure.

Exposure to fluoride induces apoptosis in the liver, kidney, and heart of Xenopus laevis by regulating the Caspase-8/3 signaling pathway

Fluoride compounds are abundant and widely distributed in the environment at various concentrations, which can seriously injure the human body. In this study, we aim to evaluate the effects of excessive fluoride exposure on the liver, kidney, and heart tissues of healthy female Xenopus laevis by administering NaF (0, 100, and 200 mg/L) in drinking water for 90 days. The expression level of procaspase-8, cleaved-caspase-8, and procaspase-3 proteins were determined by Western blot. Compared with the control group, the group exposed to NaF exhibited expression levels of procaspase-8, cleaved-caspase-8, and procaspase-3 proteins that were considerably upregulated at a concentration of 200 mg/L in the liver and kidney. The cleaved-caspase-8 protein expression in the group exposed to a high concentration of NaF was lower than that in the control group in heart. Histopathological results by hematoxylin and eosin staining showed that excessive NaF exposure caused necrosis of hepatocytes and vacuolization degeneration. Granular degeneration and necrosis in renal tubular epithelial cells were also observed. Moreover, hypertrophy of myocardial cells, atrophy of myocardial fibers and disorder of myocardial fibers were detected. These results demonstrated that NaF-induced apoptosis and the mediated death receptor pathway activation ultimately damaged the liver and kidney tissues. This finding offers a fresh perspective on the effects of F-induced apoptosis in X. laevis.

A review of molecular mechanisms linked to potential renal injury agents in tropical rural farming communities

The chronic kidney disease of unknown etiology (CKDu) is a global health concern primarily impacting tropical farming communities. Although the precise etiology is debated, CKDu is associated with environmental exposures including heat stress and chemical contaminants such as fluoride, heavy metals, and herbicide glyphosate. However, a comprehensive synthesis is lacking on molecular networks underpinning renal damage induced by these factors. Addressing this gap, here we present key molecular events associated with heat and chemical exposures. We identified that caspase activation and lipid peroxidation are common endpoints of glyphosate exposure, while vasopressin and polyol pathways are associated with heat stress and dehydration. Heavy metal exposure is shown to induce lipid peroxidation and endoplasmic reticulum stress from ROS activated MAPK, NFĸB, and caspase. Collectively, we identify that environmental exposure induced increased cellular oxidative stress as a common mechanism mediating renal cell inflammation, apoptosis, and necrosis, likely contributing to CKDu initiation and progression.

Renal adaptive response to exposure to low doses of uranyl nitrate and sodium fluoride in mice

BACKGROUND

Despite their differences in physicochemical properties, both uranium (U) and fluoride (F) are nephrotoxicants at high doses but their adverse effects at low doses are still the subject of debate.

METHODS

This study aims to improve the knowledge of the biological mechanisms involved through an adaptive response model of C57BL/6 J mice chronically exposed to low priming doses of U (0, 10, 20 and 40 mg/L) or F (0, 15, 30 and 50 mg/L) and then challenged with acute exposure of 5 mg/kg U or 7.5 mg/kg NaF.

RESULTS

We showed that an adaptive response occurred with priming exposures to 20 mg/L U and 50 mg/L F, with decreased levels of the biomarkers KIM-1 and CLU compared to those in animals that received the challenge dose only (positive control). The adaptive mechanisms involved a decrease in caspase 3/7 activities in animals exposed to 20 mg/L U and a decrease in in situ VCAM expression in mice exposed to 50 mg/L F. However, autophagy and the UPR were induced independently of priming exposure to U or F and could not be identified as adaptive mechanisms to U or F.

CONCLUSION

Taken together, these results allow us to identify renal adaptive responses to U and F at doses of 20 and 50 mg/L, probably through decrease apoptosis and inflammatory cell recruitment.

Selenium Exerts Protective Effects Against Fluoride-Induced Apoptosis and Oxidative Stress and Altered the Expression of Bcl-2/Caspase Family

Fluoride is widely distributed in nature, and at high concentrations, it targets the kidney and especially proximal tubule epithelial cells. Selenium is a typical trace element beneficial to humans, and the role of selenium in the prevention and treatment of fluoride-induced organ damage is an important research topic. The purpose of this study was to investigate the possible protective effects of selenium against fluoride-induced oxidative stress and apoptosis in rat renal tubular epithelial cells. We showed that the activity of antioxidant enzymes (superoxide dismutase and glutathione peroxidase) and total antioxidant capacity were significantly reduced in NaF-treated normal rat kidney cells (NRK-52E), whereas the levels of nitrogen monoxide (NO) and malondialdehyde (MDA) were significantly increased. Moreover, the number of apoptotic cells, mRNA expression of Bax, Bad, caspase-3, caspase-8, and caspase-9, and protein expression of Bax were elevated, while mitochondrial membrane potential and the protein expression of Bcl-2 were reduced. Compared with the NaF group, pretreatment with selenium enhanced the activity of antioxidant enzymes, mitochondrial membrane potential, and protein expression of Bcl-2, while the levels of NO and MDA, number of apoptotic cells, mRNA expression of Bax, Bad, caspase-3, caspase-8, and caspase-9, and protein expression of Bax were decreased. In conclusion, selenium exerted remarkable protective effect against NaF-induced oxidative stress and apoptosis and altered the expression of Bcl-2/caspase family.

The Use of Biomarkers as Alternatives to Current Animal Tests on Food Chemicals

Recent developments in biomarkers relating to the interrelationship of diet, disease and health were surveyed. Most emphasis was placed on biomarkers of deleterious effects, since these are of greatest relevance to the subject of this review. The area of greatest activity was found to be that relating to biomarkers of mutagenic, genotoxic and carcinogenic effects. This is also one of the major areas of concern in considerations of the beneficial and deleterious effects of dietary components, and also the area in which regulatory testing requires studies of the longest duration. A degree of progress has also been made in the identification and development of biomarkers relating to certain classes of target organ toxicity. Biomarkers for other types of toxicity, such as immunotoxicity, neurotoxicity, reproductive toxicity and developmental toxicity, are less developed, and further investigation in these areas is required before a comprehensive biomarker strategy can be established. A criticism that recurs constantly in the biomarker literature is the lack of standardisation in the methods used, and the lack of reference standards for the purposes of validation and quality control. It is encouraging to note the growing acknowledgement of the need for validation of biomarkers and biomarker assays. Some validation studies have already been initiated. This review puts forward proposals for criteria to be used in biomarker validation. More discussion on this subject is required. It is concluded that the use of biomarkers can, in some cases, facilitate the implementation of the Three Rs with respect to the testing of food chemicals and studies on the effects of diet on health. The greatest potential is seen to be in the refinement of animal testing, in which biomarkers could serve as early and sensitive endpoints, in order to reduce the duration of the studies and also reduce the number of animals required. Biomarkers could also contribute to establishing a mechanistic basis for in vitro test systems and to facilitating their validation and acceptance. Finally, the increased information that could result from the incorporation of biomarker determinations into population studies could reduce the need for supplementary animal studies. This review makes a number of recommendations concerning the prioritisation of future activities on dietary biomarkers in relation to the Three Rs. It is emphasised, however, that further discussions will be required among toxicologists, epidemiologists and others researching the relationship between diet and health.

Big toenail and hair samples as biomarkers for fluoride exposure - a pilot study

BACKGROUND

Biomarkers can aid in detecting and preventing clinical disease through the recognition of change in biological samples. The objective of this case-control study was to further the knowledge on the use of big toenail and hair samples as biomarkers for fluoride exposure.

METHODS

A total of 48 participants from an endemic (IC) and a non-endemic (SC) fluorosis region were included. Big toenail and hair samples were collected from each participant and the fluoride concentration was determined. The results of 42 participants were reported: 21 participants (11 males and 10 females, mean age 15.66 + 2.61 years) from IC and 21 participants (11 males and 10 females, mean age 15.06 + 0.79 years) from SC.

RESULTS

The mean fluoride concentration of big toenail (2.34 ± 0.26 mg/kg) and hair (0.24 ± 0.04 mg/kg) in the endemic region was significantly higher than the mean fluoride concentration of big toenail (0.98 ± 0.08 mg/kg) and hair (0.14 ± 0.02 mg/kg) in the non-endemic region (p < 0.001 and p = 0.004, respectively). The Receiver Operating Characteristic (ROC) analysis showed that the Area Under the Curve (AUC) value was 0.889 for big toenail (p < 0.001) and 0.762 for hair (p = 0.004) samples. The fluoride assay for big toenails exhibits greater observed accuracy than does the fluoride assay for hair.

CONCLUSION

Nail and hair samples can serve as biomarkers to detect biological fluoride exposure according to the data of this pilot study. Nevertheless, hair is less sensitive and specific as a biomarker when AUC values of big toenail and hair samples were compared.

In Vivo Comparison of the Phenotypic Aspects and Molecular Mechanisms of Two Nephrotoxic Agents, Sodium Fluoride and Uranyl Nitrate

Because of their nephrotoxicity and presence in the environment, uranium (U) and fluoride (F) represent risks to the global population. There is a general lack of knowledge regarding the mechanisms of U and F nephrotoxicity and the underlying molecular pathways. The present study aims to compare the threshold of the appearance of renal impairment and to study apoptosis and inflammation as mechanisms of nephrotoxicity. C57BL/6J male mice were intraperitoneally treated with a single dose of U (0, 2, 4 and 5 mg/kg) or F (0, 2, 5, 7.5 and 10 mg/kg) and euthanized 72 h after. Renal phenotypic characteristics and biological mechanisms were evaluated by urine biochemistry, gene/protein expression, enzyme activity, and (immuno)histological analyses. U and F exposures induced nephrotoxicity in a dose-dependent manner, and the highest concentrations induced severe histopathological alterations as well as increased gene expression and urinary excretion of nephrotoxicity biomarkers. KIM-1 gene expression was induced starting at 2 mg/kg U and 7.5 mg/kg F, and this increase in expression was confirmed through in situ detection of this biomarker of nephrotoxicity. Both treatments induced inflammation as evidenced by cell adhesion molecule expression and in situ levels, whereas caspase 3/7-dependent apoptosis was increased only after U treatment. Overall, a single dose of F or U induced histopathologic evidence of nephrotoxicity renal impairment and inflammation in mice with thresholds under 7.5 mg/kg and 4 mg/kg, respectively.

Fluoride-associated ultrastructural changes and apoptosis in human renal tubule: a pilot study

The susceptibility of the kidneys to fluoride toxicity can largely be attributed to its anatomy and function. As the filtrate moves along the complex tubular structure of each nephron, it is concentrated in the proximal and distal tubules and collecting duct. It has been frequently observed that the children suffering from renal impairments also have some symptoms of dental and skeletal fluorosis. The findings suggest that fluoride somehow interferes with renal anatomy and physiology, which may lead to renal pathogenesis. The aim of this study was to evaluate the fluoride-associated nephrotoxicity. A total of 156 patients with childhood nephrotic syndrome were screened and it was observed that 32 of them had significantly high levels ( p ≤ 0.05) of fluoride in urine (4.01 ± 1.83 ppm) and serum (0.1 ± 0.013 ppm). On the basis of urinary fluoride concentration, patients were divided into two groups, namely group 1 (G-1) ( n = 32) containing normal urine fluoride (0.61 ± 0.17 ppm) and group 2 (G-2) ( n = 32) having high urine fluoride concentration (4.01 ± 1.83 ppm). Age-matched healthy subjects ( n = 33) having normal levels of urinary fluoride (0.56 ± 0.15 ppm) were included in the study as control (group 0 (G-0)). Kidney biopsies were taken from G-1 and G-2 only, who were subjected to ultrastructural (transmission electron microscopy) and apoptotic (terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling) analysis. Various subcellular ultrastructural changes including nuclear disintegration, chromosome condensation, cytoplasmic ground substance lysis, and endoplasmic reticulum blebbing were observed. Increased levels of apoptosis were observed in high fluoride group (G-2) compared to normal fluoride group (G-1). Various degrees of fluoride-associated damages to the architecture of tubular epithelia, such as cell swelling and lysis, cytoplasmic vacuolation, nuclear condensation, apoptosis, and necrosis, were observed.

Comparison of the Biological Impacts of the Fluoride Compounds by Graphical Risk Visualization Map Technique

Various fluoride compounds are widely used in industry. The present risk assessment study was conducted using a series of inorganic binary fluorides of the type XFn, where X(n) = Na(+), K(+), Li(+), Mg(2+), Ca(2+), Sr(2+), Ba(2+), Al(3+), Nd(3+), La(3+), Ce(3+), Sm(3+), Gd(3+), Y(3+), Yb(2+), and Zn(2+). The aqueous solutions of these salts were orally administrated to 16 experimental groups (one for each of the salts tested). The levels of fluoride, N-acetyl-β-D-glucosaminidase in cumulative 24-h urine samples and creatinine clearance were measured to assess possible acute renal damages. The levels of fluoride, alanine aminotransferase, and aspartate aminotransferase were also determined in serum samples to assess possible acute hepatic damages. The results reveal that sodium fluoride (NaF), potassium fluoride (KF), and zinc fluoride tetrahydrate (ZnF2 (.)4H2O) can carry the fluoride ion into the bloodstream and that it is excreted via urine more readily than the other compounds tested. These fluorides were assigned the highest risk impact factor. Most of the rare earth fluorides are insoluble in water while those groups 2 and 13 of the periodic table are slightly soluble, so that they do not have a significant negative risk. These findings suggest that the biological impact of fluoride depends on the accompanying counter ion and its solubility. The risk map obtained in the present study shows that the graphical visualization map technique employed is a valuable new tool to assess the toxicological risk of chemical compounds.

An Open-label Comparison of a New Generic Sevoflurane Formulation With Original Sevoflurane in Patients Scheduled for Elective Surgery Under General Anesthesia

PURPOSE

To compare the stability, effectiveness, and safety profiles of a new generic sevoflurane with those of the original sevoflurane formulation in patients undergoing elective surgery.

METHODS

An accelerated 3-month storage test was performed to evaluate the compositional changes in generic sevoflurane stored in glass bottles. In addition, 182 patients were randomly allocated to receive generic (n = 89 [54 men and 35 women]; mean [SD] age, 49.9 [11.6] years) or original (n = 93 [61 men and 32 women]; mean [SD] age, 49.6 [11.1] years) sevoflurane at a gas flow of 3 L/min for approximately 3 hours. The mean minimum alveolar concentration (MAC) during sevoflurane anesthesia was evaluated, and gas samples for measuring compound A were collected from the inspiratory limb of the circuit at preset intervals. Blood samples for measuring serum inorganic fluoride were obtained at preset intervals (pharmacokinetic group: generic/original sevoflurane = 45/46). Renal biomarkers, such as N-acetyl-β-glucosaminidase, α- and π-glutathione-S-transferase, albumin, urine protein and osmolality, serum creatinine and osmolality, creatinine clearance, and blood urea nitrogen, were measured at preset intervals (renal biomarker group: generic/original sevoflurane = 44/47). Adverse reactions were monitored for 72 hours after discontinuation of sevoflurane use.

FINDINGS

Generic sevoflurane contained in glass bottles was stable for 3 months. The mean MAC was similar for generic and original sevoflurane (median [range], 0.93 [0.67-1.29] vs 0.94 [0.63-1.5] vol%). Adverse event rates were similar (90.3% vs 84.3%), as were the AUClast of inorganic fluoride (333.7 [112.7-1264.7] vs 311.9 [81.5-1266.5] hours·μmol/L) and compound A (51.8 [6.3-204.5] vs 55.3 [10.8-270.6] hours·ppm). Biomarkers associated with renal injury were not significantly different between the 2 formulations.

IMPLICATIONS

No significant difference was found in the mean MAC between generic and original sevoflurane. ClinicalTrials.gov identifier: NCT01096212.

Variation of nephrotoxicity biomarkers by urinary storage condition in rats

Recently, there has been an increase in the use of several nephrotoxicity biomarkers in preclinical experiments. In addition, it has been indicated that the result may have been influenced by secondary factors, such as sample storage condition or storage period. In this study, we have assessed the variation in urinary nephrotoxicity biomarkers as a result of urine storage conditions and storage period of the urine. Urine was sampled from specific pathogen-free Sprague-Dawley rats (19 weeks old), which were housed individually in hanged stainless steel wire mesh cages. Urine was stored at 20℃, at 4℃, or at −70℃ after sampling. The levels of the biomarkers such as beta-2 microglobulin (B2M), cystatin-C (Cys-C), N-acetyl-β- D-glucosaminidase (NAG), micro albumin (MA), micro protein (MP) were measured at 6, 24, 48 and 144 hr after sampling. The B2M level was significantly decreased at 6, 24, 48, and 144 hr compared to 0 hr at −70℃ (p < 0.05, p < 0.01, p < 0.05, and p < 0.05, respectively) and 24 and 144 hr at 20℃ (p < 0.01, p < 0.01, respectively). The Cys-C level was significantly decreased at 144 hr compared to 0 hr at 4℃ (p < 0.01), at 20℃ (p < 0.05) and at 70℃ (p < 0.01). MP and MA levels were not different for 144 hr in all storage conditions. Taken together, B2M and Cys-C levels were modulated by storage temperature and period. For the enhancement of test accuracy, it is suggested that strict protocols be established for samples to minimize the effects of the storage conditions on the detected levels of biomarkers.

Glutathione S-transferase as a toxicity indicator in general anesthesia: genetics and biochemical function

General anesthesia may lead in patients to unexpected and adverse reactions including toxicity. Glutathione S-transferases (GSTs) are enzymes responsible for the detoxification process of anesthetic agents. Plasma and urine GST measurements are used in multiple studies as a hepatocellular integrity or renal injury indicator. The importance of GST enzyme measurements in monitoring the hepatotoxic and nephrotoxic effect in anesthetized patients is presented. The biochemical function and specific properties of GST render it a prognostic biomarker. This review demonstrates that GST can be valuable and promising toxicity indicator in patients undergoing general anesthesia.

Risk assessment visualization of rubidium compounds: comparison of renal and hepatic toxicities, in vivo

Rubidium has been considered to be nontoxic. Its use includes thin film on glass deposition and as medical contrast medium. Recent technology innovations also involve the use of rubidium, but there is limited information about the biological effects of its various compounds. In the present risk assessment study, a series of rubidium compounds with different counter anions-acetate, bromide, carbonate, chloride, and fluoride-were orally administrated in a single dose to several groups of rats. Cumulative 24-h urine samples were obtained, and the levels of rubidium, fluoride, N-acetyl-β-D-glucosaminidase and creatinine were measured to evaluate possible acute renal effects. Daily samples of serum were also obtained to determine the levels of aspartate and alanine aminotransferases to assess possible acute hepatic effects. Urinary rubidium excretion recovery of 8.0-10.5% shows that urine can be a useful diagnostic tool for rubidium exposure. The present results reveal that rubidium shows different biological effects depending on the counter anion. A pattern of large significant NAG leakage and elevation of ALT observed in rats treated with anhydrous rubidium fluoride indicates renal and hepatic toxicities that can be attributed to fluoride. The techniques reported in this study will be of help to assess the potential risks of toxicity of rubidium compounds with a variety of anions.

Effects of acute sodium fluoride exposure on kidney function, water homeostasis, and renal handling of calcium and inorganic phosphate

Fluoride compounds are abundant and widely distributed in the environment at a variety of concentrations. Further, fluoride induces toxic effects in target organs such as the liver and kidney. In this study, we performed an early analysis of renal function using a clearance technique in Wistar rats acutely exposed to fluoride at a plasma concentration of 0.625 μg/ml. Our results revealed that fluoride, at a concentration close to the concentration present in the serum after environmental exposure, induced a significant tubular dysfunction, resulting in diluted urine, impaired protein reabsorption, and increased calcium and phosphate urinary excretion. Our work demonstrates that even acute exposures to low concentrations of NaF may induce renal damage and confirms that, after exposure, the kidney participates directly in the calcium and phosphate deficiencies observed in fluoride-exposed populations.

Preclinical perspective of urinary biomarkers for the detection of nephrotoxicity: what we know and what we need to know

The assessment of kidney damage is a challenge and must incorporate assessment of the functional capacity of the kidney, as well as a comprehensive understanding of the kidney's role. Multiple parameters have been used for many years to measure renal functionality to assess renal damage. It is astonishing that, beside histopathology, the most common traditional parameters are serum based. However, urine is also used to obtain additional information regarding the health status of the kidneys. Since 2008, several novel urinary protein biomarkers have been qualified by the US FDA and the European Medicines Agency in conjunction with the Predictive Safety Testing Consortium in a specially developed qualification process. Subsequently, the Pharmaceuticals and Medical Devices Agency accepted the qualification of these seven urinary biomarkers. This review will give an overview of the state-of-the-art detection based on urinary biomarkers, which will enhance toxicological research in the future. In addition, the qualification process that leads to acceptance of these biomarkers will be described because of its uniqueness and importance for the field of biomarker research.

Urinary biomarkers for the detection of renal injury

Despite the well-known limitations, currently the most widely used biomarkers for the early detection of chronic kidney disease or acute kidney injury are proteinuria, serum creatinine, and blood urea nitrogen. All of these are less than optimal and tend to focus attention on later stages of injury when therapies may be less effective. Recently, there has been a great surge of interest in identifying novel biomarkers that can be easily detected in the urine that can diagnose renal injury at the earliest stages. A variety of methods have been employed to identify these biomarkers including transcriptomics, proteomics, metabolomics, lipidomics, and gene arrays. Currently, several candidate biomarkers have been identified and studied in different renal injury states. These include kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), interleukin (IL)-18, and fatty-acid binding proteins (FABPs). This review will highlight the current state of knowledge of these biomarkers as well as the limitation of these biomarkers in the early diagnosis of renal injury.

Is albumin administration in hypoalbuminemic elderly cardiac surgery patients of benefit with regard to inflammation, endothelial activation, and long-term kidney function?

BACKGROUND

Because patients with low albumin levels may benefit from human albumin (HA) administration, we studied correction of hypovolemia with HA in hypoalbuminic elderly cardiac surgery patients.

METHODS

In a prospective, randomized study, 50 patients aged >80 yr undergoing cardiac surgery using cardiopulmonary bypass with a preoperative serum albumin concentration of <3.5 mg/dL, received either 5% HA (n = 25) or hydroxyethyl starch (6% HES 130/0.4) (n = 25). Volume was added to the priming (500 mL) and given until the morning of the second postoperative day to keep pulmonary capillary wedge pressure or central venous pressure between 12 and 14 mm Hg.

RESULTS

Inflammatory response (interleukins-6, -10), endothelial activation (intercellular adhesion molecule-1), and kidney function (including glutathione transferase-alpha and neutrophil gelatinase-associated lipocalin) were measured after induction of anesthesia, 5 h after surgery, and the first and second postoperative day. A follow-up, approximately 60 days after discharge from the hospital, was done. Two thousand nine hundred eighty +/- 430 mL of HA and 3060 +/- 680 mL of HES 130/0.4 were given. Serum albumin concentration was significantly increased by HA (to 4.5 +/- 0.3 mg/dL). Serum creatinine, glomerular filtration rate, and urinary levels of alpha-glutathione transferase and neutrophil gelatinase-associated lipocalin were not different in the HA-compared to the HES-treated patients. The inflammatory response was similar in both groups, whereas endothelial activation was less in the HES group. None of the patients developed renal failure requiring renal replacement therapy.

CONCLUSION

Use of HA in hypoalbuminemic cardiac surgery patients aged >80 yr was without benefit with regard to inflammatory response, endothelial activation, and renal function compared to 6% HES 130/0.4.

Effects of sodium fluoride treatment in vitro on cell proliferation, apoptosis and caspase-3 and caspase-9 mRNA expression by neonatal rat osteoblasts

Long-term excessive fluoride intake is linked to skeletal disease. Skeletal health is influenced by the balance between bone formation and resorption of which osteoblast function is critical. The objectives of this study were to determine the effect of fluoride treatment on osteoblast proliferation, apoptosis and caspase-3 and caspase-9 mRNA expression in vitro. Neonatal rat osteoblasts were cultured in the presence of varying concentrations (0.5-30 mg/l) of sodium fluoride and effects of treatments were determined. Treatment with sodium fluoride inhibited osteoblast proliferation in a dose-dependent fashion and effects were maximal after 120 h incubation. A significant increase in osteoblast apoptosis was observed (after 24 and 72-h treatment) in response to the lowest dose of sodium fluoride (0.5 mg/l) and osteoblast apoptosis was further increased in response to higher doses. Increased-osteoblast caspase-3 and caspase-9 mRNA was also observed in response to sodium fluoride treatment (5 mg/l) for 72 h. Results indicate that negative effects of excess fluoride on skeletal health may be mediated in part by inhibition of osteoblast survival.

Urinary biomarkers as a diagnostic tool for acute kidney injury

Acute kidney injury is a common condition in hospitalized patients with significant associated morbidity and mortality. Although impressive progress has been made in the understanding of the molecular and biochemical mechanisms of kidney injury, the ability to effectively treat and thus impact on the outcomes of acute kidney injury has been disappointing. One of the major reasons for this has been the reliance on current measures of renal dysfunction, such as serum creatinine and blood urea nitrogen, which are insensitive to small changes in renal function and subtle signs of kidney injury. This insensitivity of commonly used biomarkers of renal dysfunction not only prevents timely diagnosis and estimation of injury severity, but also delays administration of putative therapeutic agents. A number of serum and urinary proteins have been identified that may herald acute kidney injury prior to a rise in serum creatinine. Further characterization of these candidate biomarkers will clarify their utility and define new diagnostic and prognostic paradigms for acute kidney injury, facilitate clinical trials and lead to novel effective therapies.

Influence of volume therapy with a modern hydroxyethylstarch preparation on kidney function in cardiac surgery patients with compromised renal function: a comparison with human albumin

OBJECTIVE

There is continuing concern about the influence of hydroxyethylstarch on renal function in patients with compromised kidney function.

DESIGN

Prospective, randomized, single-center study.

SETTING

University-affiliated hospital.

PATIENTS

Fifty patients undergoing elective, first-time coronary artery bypass grafting using cardiopulmonary bypass with a preoperative serum creatinine between 1.5 and 2.5 mg/dL.

INTERVENTIONS

According to a prospective, randomized sequence, the patients received either hydroxyethylstarch with a low molecular weight (mean molecular weight 130 kD) and a low molar substitution (0.4) (6% hydroxyethylstarch 130/0.4) (n = 25) or 5% human albumin (n = 25). Volume was added to the priming (500 mL) and given perioperatively until the second postoperative day to keep pulmonary artery occlusion pressure or central venous pressure between 12 and 14 mm Hg.

MEASUREMENTS AND MAIN RESULTS

Serum creatinine and cystatin plasma levels were measured from arterial blood samples. From urine specimens, N-acetyl-beta-D-glucosaminidase, glutathione transferase-alpha, and neutrophil gelatinase-associated lipocalin were measured. Measurements were performed after induction of anesthesia, at the end of surgery, 5 hrs after surgery, and on the first and second postoperative days. A follow-up after discharge from the hospital (60 days) was also done. Similar amounts of hydroxyethylstarch and albumin were infused. Serum creatinine, glomerular filtration rate, and cystatin C plasma levels were without significant differences between the groups. Concentrations of kidney-specific proteins were elevated at baseline and increased significantly after surgery without showing group differences. Urinary levels of neutrophil gelatinase-associated lipocalin increased more in the albumin- than in the hydroxyethylstarch-treated patients. None of the patients developed acute renal failure requiring renal replacement therapy during the hospital stay and thereafter.

CONCLUSIONS

A hydroxyethylstarch preparation with a low molecular weight and a low molar substitution given in cardiac surgery patients with preoperative compromised kidney function did not negatively influence kidney integrity compared with a human albumin-based volume replacement strategy.

Anesthesia and renal disease

PURPOSE OF REVIEW

To present and interpret the relevant research (Jan 2001-Feb 2002) which has the most important implications for clinical anesthesiology as regards the prevention of perioperative renal dysfunction and the anesthetic management of patients with renal disease.

RECENT FINDINGS

Prolonged sevoflurane anesthesia with fresh gas flow less than 1 l min is unlikely to lead to clinically significant renal injury. When used as maintenance agents for patients undergoing coronary artery bypass grafting, sevoflurane anesthesia at a fresh gas flow of 3 l min, isoflurane and propofol are associated with similar rates of postoperative renal dysfunction. Less compound A is produced with smaller soda lime containers. High flow sevoflurane anesthesia (fresh gas flow of 4-6 l min) in combination with perioperative ketorolac is unlikely to lead to renal injury. Chronic treatment with angiotensin-converting enzyme inhibitors is associated with an increased incidence of postoperative renal impairment in patients undergoing elective aortic surgery. Thoracic epidural anesthesia and postoperative analgesia are associated with a decreased incidence of renal failure in patients undergoing coronary artery bypass grafting. Compared with open surgical repair, endovascular repair of aortic aneurysm is associated with less renal injury.

SUMMARY

Sevoflurane anesthesia at low or high fresh gas flow rates is probably no more injurious to the kidneys than other commonly used maintenance agents. Chronic angiotensin-converting enzyme inhibition may increase perioperative renal dysfunction. The use of thoracic epidural anesthesia and analgesia may reduce the incidence of postoperative renal failure.

Urine profiling by SELDI-TOF/MS: monitoring of the critical steps in sample collection, handling and analysis

The topic of this study is the impact of several pre-analytical and analytical variables on proteomic profiling of human urine by surface enhanced laser desorption/ionization time of flight-mass spectrometry (SELDI-TOF-MS) in healthy subjects. Urine storage at room temperature caused a progressive degradation of proteins, which was prevented by the addition of protease inhibitors only up to 2 h from the collection. The timing of collection over the day had only a minor impact on protein profile, although influencing the intensity of peaks. Repeated freeze/thaw cycles (up to five) did not affect either the number or the intensity of the peaks. A comparison of the protein profile from eight different healthy individuals showed fairly consistent inter-subject similarities, along with between-subject differences, which were markedly dependent on the sex and the type of ProteinChip array used. The addition of a variety of denaturing agents improved the quality of the spectra with all the chips tested (CM10, Q10 and H50), but not with the copper-coated IMAC-30 chip. Finally, SPA matrix allowed to achieve a better performance of SELDI-TOF/MS spectrum, as compared with CHCA, regardless of the ProteinChip array used and even in the low m/z range (2500-10,000). In conclusion, we suggest that a careful choice of a number of pre-analytical and analytical conditions is required to accomplish and define a unifying protocol for the analysis of human urine by SELDI-TOF/MS, in physiological and in pathological states.

Quantitative detection of promoter hypermethylation as a biomarker of acute kidney injury during transplantation

Aberrant promoter hypermethylation, also known as epigenetics, is thought to be a promising biomarker approach to diagnose malignancies. Kidney repair after injury is a recapitulation of normal morphogenesis, with similarities to malignant transformation. We hypothesized that changes in urine epigenetics could be a biomarker approach during early kidney transplant injury and repair. We examined urine DNA for aberrant methylation of two gene promoters (DAPK and CALCA) by quantitative methylation-specific polymerase chain reaction from 13 deceased and 10 living donor kidney transplant recipients on postoperative day 2 and 65 healthy controls. Results were compared with clinical outcomes and to results of the kidney biopsy. Transplant recipients were significantly more likely to have aberrant hypermethylation of the CALCA gene promoter in urine than healthy controls (100% vs 31%; P < .0001). There was increased CALCA hypermethylation in the urine of deceased versus living donor transplants (21.60 +/- 12.5 vs 12.19 +/- 4.7; P = .04). Furthermore, there was a trend toward increased aberrant hypermethylation of urine CALCA in patients with biopsy-proven acute tubular necrosis versus acute rejection and slow or prompt graft function (mean: 20.40 +/- 6.9, 13.87 +/- 6.49, 17.17 +/- 13.4; P = .67). However, there was no difference of CALCA hypermethylation in urine of patients with delayed graft function versus those with slow or prompt graft function (16.9 +/- 6.2 vs 18.5 +/- 13.7, respectively; P = .5). There was no aberrant hypermethylation of DAPK in the urine of transplant patients. Urine epigenetics is a promising biomarker approach for acute ischemic injury in transplantation that merits future study.

Oxidative stress induced by fluoride in adult mice and their suckling pups

To assess renal and liver damages in pregnant and lactating mice as well as in their suckling pups, Wistar female mice were given 500 ppm NaF (226 ppm F-) in drinking water from the 15th day of pregnancy until day 14 after delivery. All mice were sacrificed on day 14 after parturition. In the present work, we evaluated the effects of sodium fluoride on histopathological aspects of kidney, antioxidant status, lipid peroxidation levels and on the expression of four stress proteins (namely, the cytosolic heat shock proteins: HSP72, 73, 90 and the reticulum-associated GRP94). Histological studies have shown many abnormalities in mothers and their pups. Biochemical results showed that lipid peroxidation increased in NaF-treated mice, as evidenced by high kidney and liver thiobarbituric acid reactive substance (TBARS) levels. Alteration of the antioxidant system was confirmed by the significant decline of serum total antioxidant status and of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in red blood cells. Besides, fluoride treatment induced a decrease in serum levels of non-enzymatic antioxidants such as uric acid and of some oligoelements: zinc and copper, known to be cofactors of superoxide dismutase (SOD-Cu-Zn). Compared to control group, the 72kDa protein was found to be overexpressed in kidney of 14-day-old mice only. HSP90 expression in liver appeared moderately inhibited in mothers, but decreased significantly in their pups. No significant changes were detected in the expression of 94kDa protein in both liver and kidney. Results showed that fluoride given to dams led to an oxidative stress in mothers as well as in offspring able to induce enhanced lipid peroxidation levels and protein conformational changes, as suggested by stress protein (HSP, GRP) expression changes.

Dose-effect relationship between drinking water fluoride levels and damage to liver and kidney functions in children

Although a dose-effect relationship between water fluoride levels and damage to liver and kidney functions in animals has been reported, it was not demonstrated in humans. To evaluate the effects of drinking water fluoride levels on the liver and kidney functions in children with and without dental fluorosis, we identified 210 children who were divided into seven groups with 30 each based on different drinking water fluoride levels in the same residential area. We found that the fluoride levels in serum and urine of these children increased as the levels of drinking water fluoride increased. There were no significant differences in the levels of total protein (TP), albumin (ALB), aspartate transamine (AST), and alanine transamine (ALT) in serum among these groups. However, the activities of serum lactic dehydrogenase (LDH), urine N-acetyl-beta-glucosaminidase (NAG), and urine gamma-glutamyl transpeptidase (gamma-GT) in children with dental fluorosis and having water fluoride of 2.15-2.96 mg/L and in children having water fluoride of 3.15-5.69 mg/L regardless of dental fluorosis were significantly higher than children exposed to water fluoride of 0.61-0.87 mg/L in a dose-response manner. In contrast to children with dental fluorosis and having water fluoride of 2.15-2.96 and 3.10-5.69 mg/L, serum LDH activity of children without dental fluorosis but exposed to the same levels of water fluoride as those with dental fluorosis were also markedly lower, but the activities of NAG and gamma-GT in their urine were not. Therefore, our results suggest that drinking water fluoride levels over 2.0mg/L can cause damage to liver and kidney functions in children and that the dental fluorosis was independent of damage to the liver but not the kidney. Further studies on the mechanisms and significance underlying damage to the liver without dental fluorosis in the exposed children are warranted.

Mechanistic biomarkers for cytotoxic acute kidney injury

Acute kidney injury is a common condition and is associated with a high mortality rate. It has been recognised that routinely used measures of renal function, such as levels of blood urea nitrogen and serum creatinine, increase significantly only after substantial kidney injury occurs and then with a time delay. Insensitivity of such tests delays the diagnosis in humans, making it particularly challenging to administer putative therapeutic agents in a timely fashion. Furthermore, this insensitivity affects the evaluation of toxicity in preclinical studies by allowing drug candidates, which have low, but nevertheless important, nephrotoxic side effects in animals, to pass the preclinical safety criteria only to be found to be clinically nephrotoxic with great human costs. This review presents the current status of sensitive and specific biomarkers to detect preclinical and clinical renal injury and summarises the techniques used to quantitate these biomarkers in biological fluids.

The value of an albumin-based intravascular volume replacement strategy in elderly patients undergoing major abdominal surgery

The value of human albumin (HA) for treating hypovolemia is controversial. Less expensive alternatives such as hydroxyethyl starch (HES) are sometimes refused because of unwanted side effects. We prospectively randomized 50 patients older than 70 years old undergoing major abdominal surgery to receive either 5% HA (n = 25) or a third generation HES preparation (6% HES 130/0.4; n = 25) when mean arterial blood pressure was <60 mm Hg and central venous pressure was <10 mm Hg. Hemodynamics, inflammation (interleukin-6), endothelial activation-integrity (adhesion molecules), coagulation (thrombelastography), and renal function (including kidney-specific proteins) were monitored after the induction of anesthesia, after surgery, 5 h in the intensive care unit, and on the first postoperative day. HA patients received 3960 +/- 590 mL of HA and 5070 +/- 1030 mL of Ringer's lactate solution, and HES patients received 3500 +/- 530 mL of HES and 4550 +/- 880 mL of Ringer's lactate solution. Total protein remained normal only in the HA-treated patients. No significant differences (P > 0.1) between the groups were seen with regard to hemodynamics, coagulation, and kidney function. Plasma levels of interleukin-6 and soluble adhesion molecules were significantly (P < 0.05) higher in the HA- than in the HES-treated patients. We conclude that HA in elderly patients undergoing major abdominal surgery can easily be replaced by a modern HES preparation. Because of the decreased inflammatory response and endothelial activation-injury, HES 130/0.4 seems to be the more appropriate fluid strategy for these patients.

Assessment of renal injury in vivo

The ICH S7A (Safety Pharmacology for Human Pharmaceuticals) guidelines specify that potential adverse pharmacologic effects of a test substance on renal function should be evaluated in supplemental studies when there is a cause for concern (ICH, 2001). For the most part, this can easily be accomplished by examination of the appropriate analytes in urine and blood collected as part of the routine preclinical safety studies. This review will serve as an overview of the selection, interpretation and limitations of standard clinical pathology methods (serum chemistry and urinalysis) for assessment of renal function in such studies, as well as provide some information on emerging biomarkers of renal function.

Urinary kidney injury molecule-1: a sensitive quantitative biomarker for early detection of kidney tubular injury

Sensitive and specific biomarkers are needed to detect early kidney injury. The objective of the present work was to develop a sensitive quantitative urinary test to identify renal injury in the rodent to facilitate early assessment of pathophysiological influences and drug toxicity. Two mouse monoclonal antibodies were made against the purified ectodomain of kidney injury molecule-1 (Kim-1), and these were used to construct a sandwich Kim-1 ELISA. The assay range of this ELISA was 50 pg/ml to 5 ng/ml, with inter- and intra-assay variability of <10%. Urine samples were collected from rats treated with one of three doses of cisplatin (2.5, 5, or 7.5 mg/kg). At one day after each of the doses, there was an approximately three- to fivefold increase in the urine Kim-1 ectodomain, whereas other routinely used biomarkers measured in this study [plasma creatinine, blood urea nitrogen (BUN), urinary N-acetyl-beta-glucosaminidase (NAG), glycosuria, proteinuria] lacked the sensitivity to show any sign of renal damage at this time point. When rats were subjected to increasing periods (10, 20, 30, or 45 min) of bilateral ischemia, there was an increasing amount of urinary Kim-1 detected. After only 10 min of bilateral ischemia, Kim-1 levels on day 1 were 10-fold higher (5 ng/ml) than control levels, whereas plasma creatinine and BUN were not increased and there was no glycosuria, increased proteinuria, or increased urinary NAG levels. Thus urinary Kim-1 levels serve as a noninvasive, rapid, sensitive, reproducible, and potentially high-throughput method to detect early kidney injury in pathophysiological studies and in preclinical drug development studies for risk-benefit profiling of pharmaceutical agents.

Biologic markers for the early detection of acute kidney injury

PURPOSE OF REVIEW

This review discusses the current status of several biomarkers as potential diagnostic tools in patients with acute kidney disease.

RECENT FINDINGS

Although the term "acute renal failure" has generally been used to describe acute kidney dysfunction that runs the spectrum from mild prerenal azotemia with no renal pathologic changes and no functional failure to severe oliguric renal dysfunction associated with tubular necrosis with failure of function, this spectrum is better described by the term "acute kidney injury." The mortality rate of hospitalized patients with severe acute kidney disease has not decreased significantly over the past 50 years despite advances in supportive care. The absence of sensitive and specific biomarkers for detecting injury early, grading the severity of the injury, and monitoring the response to therapy has impaired progress in the field and has had a very detrimental effect on the design and outcome of clinical trials in acute kidney disease. As a result of reliance on serum creatinine as a marker for injury and diagnosis, the institution of therapy is markedly delayed.

SUMMARY

The search for new biomarkers for acute kidney injury is evolving rapidly with advancement in modern technologies. With better biomarkers we will have the ability to detect injury earlier, identify subclinical injury, provide prognostic information on the course of renal impairment, identify the nephron segments most affected, provide a rationale for segmentation of patients for clinical studies, guide timing of therapy, assess response to therapy, and screen patients at risk for renal injury.

The effect of Pycnogenol on fluoride induced rat kidney lysosomal damage in vitro

Pycnogenol (PYC) is a procyanidin-rich extract of the bark of French maritime pine (Pinus pinaster) with a potent ability to scavenge free radicals. Lysosome-rich fractions from rat renal cortices were incubated with varying amounts of PYC and challenged with noxious doses of fl uoride. Controls were also included. The release of N-acetyl-beta-D-glucosaminidase (NAG) isozymes in the supernatant was estimated by spectrophotometric methods. The protein content of the renal cortex was also determined. Our results show that fluoride in unhealthy doses can cause a concentration dependent release of N-acetyl-beta-D-glucosaminidase (NAG) isozymes from the renal lysosomes. This may be related to its known ability to initiate free radical formation or direct damaging effects on the lysosomal membrane. As a blend of bio flavonoids pycnogenol has a potent ability to scavenge free radicals. In our study PYC was effective in preventing fluoride induced release of NAG isozymes from the renal lysosomes.

Serum fluoride levels in a group of Egyptian infants and children from Cairo city

In this study, the authors investigated fluoride levels in the serum of infants and children (n = 296) and in the breast milk from nursing mothers (n = 60) in Cairo city. Their goal was to evaluate the necessity and safety of implementing a fluoride supplementation program. The authors used an ion-selective electrode to assay fluoride by direct potentiometry. Also, 2- to 12-yr-old participants underwent clinical dental examinations to detect caries and/or fluorosis. The serum fluoride levels of infants were significantly lower than levels found in preschoolers and school-age children. Serum fluoride correlated positively with age; it was significantly lower during the 1st than 2nd yr of infancy (p = 0.005). Breast or formula feeding did not influence serum fluoride status; the fluoride levels in mothers' milk reflected the serum levels of their own infants. Dental examinations revealed that 81% of the children had caries, whereas there was no evidence of fluorosis. Serum fluoride levels did not vary with the presence or absence of dental caries and did not correlate with the number of decayed, missing, or filled teeth. Gender did not influence serum fluoride expression, and the percentile values were unrelated to height, weight, or head circumference. These findings suggest the necessity and safety of improving the fluoride consumption levels of infants and children in Cairo city. Wider-scale studies are needed to obtain better insight into the problem.

Bone as a biomarker of acute fluoride toxicity

The use of bone as a biomarker for chronic and acute exposure to fluoride salts has been suggested, but there are no data published about its use to evaluate lethal intoxication. One hundred and sixty rats were divided into eight groups that received a single oral intubation dose from 0 (control) to 90 mg F/kg as NaF. The animals' time of death was recorded and their femurs were removed for fluoride analysis. Acid-soluble fluoride was determined in the whole bone and on the surface (periosteal), using an ion specific electrode. The data showed a statistically significant relationship between fluoride dose and the number of deaths (P<0.0001). A statistically significant relationship was also found between fluoride dose and fluoride concentration ([F]) in either the whole femur (P<0.0017), on the surface (P<0.0001) or for the ratio periosteal [F]/whole [F] (P<0.0001). However, the [F] on the femur surface was more closely correlated with mortality than that in the whole bone, showing statistically significant differences among the lethal doses and control (P<0.05). The data suggest that the ratio [F] periosteal bone/[F] whole bone, is a biomarker for acute fluoride toxicity.