Nephrotoxicity and its prevention by vitamin E in ferric nitrilotriacetate-promoted lipid peroxidation

BRCA1 haploinsufficiency promotes chromosomal amplification under fenton reaction-based carcinogenesis through ferroptosis-resistance

Germline-mutation in BRCA1 tumor suppressor gene is an established risk for carcinogenesis not only in females but also in males. Deficiency in the repair of DNA double-strand breaks is hypothesized as a responsible mechanism for carcinogenesis. However, supporting data is insufficient both in the mutation spectra of cancers in the patients with BRCA1 germline-mutation and in murine knockout/knock-in models of Brca1 haploinsufficiency. Furthermore, information on the driving force toward carcinogenesis in BRCA1 mutation carriers is lacking. Here we applied Fenton reaction-based renal carcinogenesis to a rat heterozygously knockout model of BRCA1 haploinsufficiency (mutant [MUT] model; L63X/+). Rat MUT model revealed significant promotion of renal cell carcinoma (RCC) induced by ferric nitrilotriacetate (Fe-NTA). Array-based comparative genome hybridization of the RCCs identified significant increase in chromosomal amplification, syntenic to those in breast cancers of BRCA1 mutation carriers, including c-Myc, in comparison to those in the wild-type. Subacute-phase analysis of the kidney after repeated Fe-NTA treatment in the MUT model revealed dysregulated iron metabolism with mitochondrial malfunction assessed by expression microarray and electron microscopy, leading to renal tubular proliferation with iron overload. In conclusion, we for the first time demonstrate that biallelic wild-type BRCA1 provides more robust protection for mitochondrial metabolism under iron-catalyzed oxidative stress, preventing the emergence of neoplastic cells with chromosomal amplification. Our results suggest that oxidative stress via excess iron is a major driving force for carcinogenesis in BRCA1 haploinsufficiency, which can be a target for cancer prevention and therapeutics.

•

Rat BRCA1 haploinsufficiency promoted Fenton reaction-based renal carcinogenesis.

•

BRCA1 haploinsufficiency allowed chromosomal amplification under excess iron.

•

BRCA1 haploinsufficiency caused more mitochondrial damage with ferroptosis resistance.

The Role of Ferric Nitrilotriacetate in Renal Carcinogenesis and Cell Death: From Animal Models to Clinical Implications

Iron is essential for cellular growth, and various ferroproteins and heme-containing proteins are involved in a myriad of cellular functions, such as DNA synthesis, oxygen transport, and catalytic reactions. As a consequence, iron deficiency causes pleiotropic effects, such as hypochromic microcytic anemia and growth disturbance, while iron overload is also deleterious by oxidative injury. To prevent the generation of iron-mediated reactive oxygen species (ROS), ferritin is synthesized to store excess iron in cells that are consistent with the clinical utility of the serum ferritin concentration to monitor the therapeutic effect of iron-chelation. Among the animal models exploring iron-induced oxidative stress, ferric nitrilotriacetate (Fe-NTA) was shown to initiate hepatic and renal lipid peroxidation and the development of renal cell carcinoma (RCC) after repeated intraperitoneal injections of Fe-NTA. Here, current understanding of Fe-NTA-induced oxidative stress mediated by glutathione-cycle-dependent iron reduction and the molecular mechanisms of renal carcinogenesis are summarized in combination with a summary of the relationship between the pathogenesis of human RCC and iron metabolism. In addition to iron-mediated carcinogenesis, the ferroptosis that is triggered by the iron-dependent accumulation of lipid peroxidation and is implicated in the carcinogenesis is discussed.

Iron as spirit of life to share under monopoly

Any independent life requires iron to survive. Whereas iron deficiency causes oxygen insufficiency, excess iron is a risk for cancer, generating a double-edged sword. Iron metabolism is strictly regulated via specific systems, including iron-responsive element (IRE)/iron regulatory proteins (IRPs) and the corresponding ubiquitin ligase FBXL5. Here we briefly reflect the history of bioiron research and describe major recent advancements. Ferroptosis, a newly coined Fe(II)-dependent regulated necrosis, is providing huge impact on science. Carcinogenesis is a process to acquire ferroptosis-resistance and ferroptosis is preferred in cancer therapy due to immunogenicity. Poly(rC)-binding proteins 1/2 (PCBP1/2) were identified as major cytosolic Fe(II) chaperone proteins. The mechanism how cells retrieve stored iron in ferritin cores was unraveled as ferritinophagy, a form of autophagy. Of note, ferroptosis may exploit ferritinophagy during the progression. Recently, we discovered that cellular ferritin secretion is through extracellular vesicles (EVs) escorted by CD63 under the regulation of IRE/IRP system. Furthermore, this process was abused in asbestos-induced mesothelial carcinogenesis. In summary, cellular iron metabolism is tightly regulated by multi-system organizations as surplus iron is shared through ferritin in EVs among neighbor and distant cells in need. However, various noxious stimuli dramatically promote cellular iron uptake/storage, which may result in ferroptosis.

Has vitamin E any shreds of evidence in cisplatin-induced toxicity

Cisplatin is one of the highly consumed and effective antitumor agents whose clinical application is accompanied by nephrotoxicity adverse reaction. Also, other complications such as ototoxicity and hepatotoxicity are a matter of concern. Today, it is suggested that cisplatin-associated toxicities are mainly induced by free radicals production, which will result in oxidative organ injury. The evidence is growing over the protective effects of antioxidants on cisplatin-induced adverse reactions especially nephrotoxicity. The possible protective effects of vitamin E and its derivative in cisplatin-induced nephrotoxicity and ototoxicity are reviewed here at the light of pertinent results from basic and clinical research. Administration of vitamin E alone or in combination with other antioxidant agents could cause amelioration in oxidative stress biomarkers such as decreasing the level of malondialdehyde, reducing serum urea and creatinine, and also enhancing the activities of renal antioxidant enzymes including renal catalase, glutathione-S-transferase, and superoxide dismutase. Although the data from most of the studies are in favors of protective effects of vitamin E against cisplatin-induced toxicity, more clinical trials are needed to clarify the clinical importance of vitamin E administration as an antioxidant during cisplatin therapy in cancer condition.

Blood pressure and kidney cancer risk: meta-analysis of prospective studies

BACKGROUND

Globally, kidney cancer is the twelfth most common cancer, accounting for 337 860 cases recorded in 2012. By 2020, this number has been estimated to reach 412 929 or increase by 22%. Over the past few decades, a number of prospective studies have investigated the association between blood pressure (BP) and risk of kidney cancer, using either recorded BP levels or reported hypertension as the principal exposure variable. However, the relation of BP to kidney cancer remains incompletely understood, and the data on sex-specific differences in risk estimates have been inconsistent.

METHOD

PubMed and Web of Science databases were searched for studies assessing the association between BP and kidney cancer through July 2016. The summary relative risk with 95% confidence intervals was calculated using a random-effects model.

RESULT

A total of 18 prospective studies with 8097 kidney cancer cases from 3 628 479 participants were included in our meta-analysis. History of hypertension was associated with 67% increased risk of kidney cancer. Significant heterogeneity and evidence of publication bias were observed. However, the results remain unchanged after introducing the trim and fill method to correct the publication bias. Accordingly, each 10-mmHg increase in SBP and DBP was associated with 10 and 22% increased risk of kidney cancer.

CONCLUSION

Collectively, the present meta-analysis of 18 prospective studies provides further support for a positive association between hypertension and kidney cancer risk.

Iron and thiol redox signaling in cancer: An exquisite balance to escape ferroptosis

Epidemiological data indicate a constant worldwide increase in cancer mortality, although the age of onset is increasing. Recent accumulation of genomic data on human cancer via next-generation sequencing confirmed that cancer is a disease of genome alteration. In many cancers, the Nrf2 transcription system is activated via mutations either in Nrf2 or Keap1 ubiquitin ligase, leading to persistent activation of the genes with antioxidative functions. Furthermore, deep sequencing of passenger mutations is clarifying responsible cancer causative agent(s) in each case, including aging, APOBEC activation, smoking and UV. Therefore, it is most likely that oxidative stress is the principal initiating factor in carcinogenesis, with the involvement of two essential molecules for life, iron and oxygen. There is evidence based on epidemiological and animal studies that excess iron is a major risk for carcinogenesis, suggesting the importance of ferroptosis-resistance. Microscopic visualization of catalytic Fe(II) has recently become available. Although catalytic Fe(II) is largely present in lysosomes, proliferating cells harbor catalytic Fe(II) also in the cytosol and mitochondria. Oxidative stress catalyzed by Fe(II) is counteracted by thiol systems at different functional levels. Nitric oxide, carbon monoxide and hydrogen (per)sulfide modulate these reactions. Mitochondria generate not only energy but also heme/iron sulfur cluster cofactors and remain mostly dysfunctional in cancer cells, leading to Warburg effects. Cancer cells are under persistent oxidative stress with a delicate balance between catalytic iron and thiols, thereby escaping ferroptosis. Thus, high-dose L-ascorbate and non-thermal plasma as well as glucose/glutamine deprivation may provide additional benefits as cancer therapies over preexisting therapeutics.

Premenopausal plasma ferritin levels, HFE polymorphisms, and risk of breast cancer in the nurses' health study II

BACKGROUND

Evidence from the Nurses' Health Study II (NHSII) suggests that red meat consumption is associated with increased breast cancer risk in premenopausal women. Iron may be responsible by contributing to oxidative stress or effects on immune function.

METHODS

We conducted a case-control study nested within the NHSII, examining prediagnostic plasma ferritin (n = 795 cases, 795 controls), 15 hemochromatosis gene (HFE) single-nucleotide polymorphisms (SNP; n = 765 cases, 1,368 controls), and breast cancer risk. Cases were diagnosed after providing blood samples between 1996 and 1999. ORs and 95% confidence intervals (CI) were calculated for ferritin levels by conditional logistic regression and for HFE SNPs by unconditional logistic regression.

RESULTS

We did not observe a significant association between ferritin levels and breast cancer (top vs. bottom quartile multivariate OR: 1.05; 95% CI, 0.77-1.45; PTrend = 0.77). Results did not change when restricted to women who were premenopausal at blood draw, and were similar when cases were examined by hormone receptor status, and menopausal status at diagnosis. No HFE SNPs were significantly associated with breast cancer in a log-additive manner. Among controls, ferritin levels were nominally associated with SNPs rs9366637 (PTrend = 0.04), rs6918586 (PTrend = 0.06), and rs13161 (PTrend = 0.07), but results did not remain significant after adjusting for multiple testing.

CONCLUSIONS

Ferritin levels and HFE SNPs were not associated with breast cancer risk in this population.

IMPACT

Components of red meat other than iron are likely responsible for its positive association with breast cancer in premenopausal women.

Dietary intake of heme iron and risk of gastric cancer in the European prospective investigation into cancer and nutrition study

Even though recent studies suggest that a high intake of heme iron is associated with several types of cancer, epidemiological studies in relation to gastric cancer (GC) are lacking. Our previous results show a positive association between red and processed meat and non cardia gastric cancer, especially in Helicobacter pylori infected subjects. The aim of the study is to investigate the association between heme iron intake and GC risk in the European prospective investigation into cancer and nutrition (EURGAST-EPIC). Dietary intake was assessed by validated center-specific questionnaires. Heme iron was calculated as a type-specific percentage of the total iron content in meat intake, derived from the literature. Antibodies of H. pylori infection and vitamin C levels were measured in a sub-sample of cases and matched controls included in a nested case-control study within the cohort. The study included 481,419 individuals and 444 incident cases of GC that occurred during an average of 8.7 years of followup. We observed a statistically significant association between heme iron intake and GC risk (HR 1.13 95% CI: 1.01-1.26 for a doubling of intake) adjusted by sex, age, BMI, education level, tobacco smoking and energy intake. The positive association between heme iron and the risk of GC was statistically significant in subjects with plasma vitamin C <39 mmol/l only (log2 HR 1.54 95% CI (1.01-2.35). We found a positive association between heme iron intake and gastric cancer risk.

Homozygous deletion of CDKN2A/2B is a hallmark of iron-induced high-grade rat mesothelioma

In humans, mesothelioma has been linked to asbestos exposure, especially crocidolite and amosite asbestos, which contain high amounts of iron. Previously, we established a rat model of iron-induced peritoneal mesothelioma with repeated intraperitoneal injections of iron saccharate and an iron chelator, nitrilotriacetate. Here, we analyze these mesotheliomas using array-based comparative genomic hybridization (aCGH) and gene expression profiling by microarray. Mesotheliomas were classified into two distinct types after pathologic evaluation by immunohistochemistry. The major type, epithelioid mesothelioma (EM), originated in the vicinity of tunica vaginalis testis, expanded into the upper peritoneal cavity and exhibited papillary growth and intense podoplanin immunopositivity. The minor type, sarcomatoid mesothelioma (SM), originated from intraperitoneal organs and exhibited prominent invasiveness and lethality. Both mesothelioma types showed male preponderance. SMs revealed massive genomic alterations after aCGH analysis, including homozygous deletion of CDKN2A/2B and amplification of ERBB2 containing region, whereas EMs showed less genomic alterations. Uromodulin was highly expressed in most of the cases. After 4-week treatment, iron deposition in the mesothelia was observed with 8-hydroxy-2'-deoxyguanosine formation. These results not only show two distinct molecular pathways for iron-induced peritoneal mesothelioma, but also support the hypothesis that oxidative stress by iron overload is a major cause of CDKN2A/2B homozygous deletion.

Does excess iron play a role in breast carcinogenesis? An unresolved hypothesis

Free iron is a pro-oxidant and can induce oxidative stress and DNA damage. The carcinogenicity of iron has been demonstrated in animal models, and epidemiologic studies have shown associations with several human cancers. However, a possible role of excess body iron stores or of elevated iron intake in breast carcinogenesis has received little attention epidemiologically. We propose that iron overload and the disruption of iron homeostasis with a resulting increase in free iron may contribute to the development of breast cancer, and we summarize the relevant evidence from mechanistic studies, animal experiments, and studies in humans. Over time a high intake of iron can lead to iron overload. Furthermore, body iron stores increase in women following menopause. Reactive oxygen species produced by normal aerobic cellular metabolism can lead to the release of free iron from ferritin. In the presence of superoxide radical and hydrogen peroxide, stored ferric iron (Fe(3+)) is reduced to ferrous iron (Fe(2+)), which catalyzes the formation of the hydroxyl radical (*OH). *OH in turn can promote lipid peroxidation, mutagenesis, DNA strand breaks, oncogene activation, and tumor suppressor inhibition, increasing the risk of breast cancer. In addition to its independent role as a proxidant, high levels of free iron may potentiate the effects of estradiol, ethanol, and ionizing radiation - three established risk factors for breast cancer. In order to identify the role of iron in breast carcinogenesis, improved biomarkers of body iron stores are needed, as are cohort studies which assess heme iron intake. Ultimately, it is important to determine whether iron levels in the breast and iron-induced pathology are higher in women who go on to develop breast cancer compared to women who do not.

Fermented grain products, production, properties and benefits to health

Fermented foods such as Japanese traditional food "miso (fermented soy bean paste)" have been shown to be rich source of micronutrients with the potential to prevent various human diseases. We have introduced effects of a new dietary supplement of fermented grain foods mixture containing extracts from wheat germ, soybeans, rice bran, tear grass, sesame, wheat, citrus lemon, green tea, green leaf extract and malted rice under the trade name of antioxidant biofactor (AOB). Chemical analysis of AOB shows the presence of various phenolic compounds (catechins, rutin, genistin, daidzin, etc.). AOB has strong antioxidant properties and additional biological effects, which might be of importance in context with the prevention of degenerative diseases. This paper focuses on the effect of supplementing AOB in various animal models and humans.

Relations between clusters of oxidatively damaged nucleotides and active or open nucleosomes in the rat Nth 1 gene

The distribution of oxidative damage to bases such as 8-hydroxyguanine (8-OH-Gua), was determined at the nucleotide level of resolution using the ligation-mediated PCR technique. Administration of a renal carcinogen, ferric nitrilotriacetate (Fe-NTA), is known to induce oxidative stress and subsequent formation of 8-OH-Gua in the kidney. Whole genomic DNA was isolated from the rat kidney with or without Fe-NTA treatment and then digested with formamidopyrimidine-DNA glycosylase (Fpg). As a target, we focused on the gene of a DNA repair enzyme for thymine glycol, Nth 1. Cleaved signals were found in exon 1 and exon 3, but not exon 5. Nucleosomes in these regions, enriched in damaged nucleotides, were highly accessible to micrococcal nuclease, especially in the kidney. Taking into account the function of the protein segment encoded by these regions, we discussed the molecular mechanism of the restricted formation of the damaged nucleotides.

Renal carcinogenesis induced by ferric nitrilotriacetate in mice, and protection from it by Brazilian propolis and artepillin C

The protective effect of Brazilian propolis and its extract Artepillin C against ferric nitrilotriacetate (Fe-NTA)-induced renal lipid peroxidation and carcinogenesis was studied in male ddY mice. Fe-NTA-induced renal lipid peroxidation leads to a high incidence of renal cell carcinoma (RCC) in mice. Administration of propolis by gastric intubation 2 h before or Artepillin C at either the same time, 2 h, or 5 h before the intraperitoneal injection of Fe-NTA (7 mg Fe/kg) effectively inhibited renal lipid peroxidation. This was evaluated from the measurement of renal thiobarbituric acid-reactive substances (TBARS) or histochemical findings of 4-hydroxy-2-nonenal (4-HNE)-modified proteins and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Repeated injection of Fe-NTA (10 mg Fe/kg per day, twice a week for a total of 16 times in 8 weeks) caused subacute nephrotoxicity as revealed by necrosis and pleomorphic large nuclear cells in the renal proximal tubules, and gave rise to RCC 12 months later. A protective effect from carcinogenicity was observed in mice given propolis or Artepillin C. Furthermore, the mice given Fe-NTA only developed multiple cysts composed of precancerous lesions with multilayered and proliferating large atypical cells. Mice treated with propolis and Artepillin C also had cysts, but these were dilated and composed of flat cells. These results suggest that propolis and Artepillin C prevent oxidative renal damage and the carcinogenesis induced by Fe-NTA in mice.

Inhibitory effects of melatonin on ferric nitrilotriacetate-induced lipid peroxidation and oxidative DNA damage in the rat kidney

Ferric nitrilotriacetate (Fe-NTA) is a known complete renal carcinogen which induces lipid peroxidation and oxidative DNA damage in rat kidney. In this study, the in vivo and in vitro effects of melatonin on Fe-NTA-induced lipid and oxidative DNA damage were determined. The levels of malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA) were assayed as an index of lipid peroxidation and the levels of 8-hydroxydeoxyguanosine (8-OH-dG) as an endpoint of oxidative DNA damage. In in vitro studies, the increased levels of MDA and 4-HDA induced by Fe-NTA were observed to be dose-dependent and time-dependent. The increase in lipid peroxidation was inhibited by melatonin in a concentration-dependent manner. When Fe-NTA(15 mg Fe/kg body weight) was intraperitoneally injected into rats, the levels of MDA + 4-HDA and 8-OH-dG in the rat kidney were increased 1 h after its administration as compared to levels of these constituents in the control group. Pretreatment with melatonin (25 mg/kg or 50 mg/kg) 30 min before the Fe-NTA injection resulted in a significant reduction in the levels of lipid peroxidation and 8-OH-dG induced by Fe-NTA in the rat kidney. These results are consistent with the conclusion that the toxicity of Fe-NTA is due to the generation of reactive oxygen species and that melatonin's protective effects relate to its direct radical scavenging ability and due to other antioxidative processes induced by the indole.

2-Hydroxyadenine, a mutagenic form of oxidative DNA damage, is not repaired by a glycosylase type mechanism in rat organs

Oxygen radicals are known to play a role in causing cellular DNA damage, which is involved in carcinogenesis. 8-Hydroxyguanine (8-OH-Gua) is a major form of oxidative DNA damage and is known as a useful marker of DNA oxidation. Recently, we found another type of oxidative DNA damage, 2-hydroxyadenine (2-OH-Ade), which has a mutation frequency comparable to that of 8-OH-Gua. We compared the repair activities for two types of oxidative DNA damage, 8-OH-Gua and 2-OH-Ade, in 7-week-old male Sprague-Dawley (SD) rat organs. The repair activities were measured by an endonuclease nicking assay using 22 mer [32P]-end-labeled double-stranded DNA substrates, which contained either 8-OH-Gua (opposite C) or 2-OH-Ade (opposite T or C). In all of the SD rat organs we studied, the nicking activity for 2-OH-Ade was not detected, while that for 8-OH-Gua was clearly detected with the same conditions. Moreover, the 2-OH-Ade nicking activity was not induced in Wistar rat kidney extracts prepared after ferric nitrilotriacetate (Fe-NTA) treatment, which is known to increase 8-OH-Gua repair activity. These results suggest that 2-OH-Ade might not be repaired by the glycosylase type mechanism in mammalian cells.

The prevention of ferric nitrilotriacetate-induced nephro- and hepatotoxicity by methylenedioxybenzene antioxidants

Previously it was shown that methylenedioxybenzenes (MDBs), particularly isosafrole, were highly effective at preventing CCl4-induced liver necrosis in vivo (Z.S. Zhao, P.J. O'Brien, The prevention of CCl4-induced liver necrosis in mice by naturally occurring methylenedioxybenzenes, Toxicol. Appl. Pharmacol., 140 (1996) 411-421), probably as a result of forming metabolic intermediate complexes with cytochrome P450. In the following it was shown that pretreatment of mice with isosafrole also completely prevented ferric nitrilotriacetate (FeNTA)-induced renal necrosis and lipid peroxidation, even though metabolic activation by cytochrome P450 is not involved. The naturally occurring or synthetic MDBs that prevented CCl4 hepatotoxicity also prevented hepatocyte lipid peroxidation. induced by FeNTA, but other cytochrome P450 inhibitors were ineffective. These compounds, in decreasing order of antioxidant effectiveness, were sesamol, 4-t-butyl-methylenedioxybenzene, isosafrole, piperonyl butoxide and 4-bromo-methylenedioxybenzene and safrole, whereas, benzodioxole, 3,4-(methylenedioxy)-toluene and 1,2-(methylenedioxy)-4-nitrobenzene were ineffective. Pre-incubating the hepatocytes with P450 inhibitors decreased the protective effects of isosafrole, suggesting that the catecholic metabolites of MDBs were responsible for the antioxidant activity. A greater inhibition of FeNTA-induced lipid peroxidation by catecholic metabolites was observed. Since cytochrome P450 did not participate in FeNTA-induced hepatocyte or microsomal lipid peroxidation, it is likely that the antioxidant properties of MDBs or their catecholic metabolites also contribute to their in vivo protection against CCl4 or FeNTA-induced hepato- or nephrotoxicity.

Vitamin E may slow kidney failure owing to oxidative stress

Progression to kidney failure in a number of major renal diseases is now thought to be significantly worsened by oxidative stress at the biochemical level. Evidence is accumulating that the rate of deterioration could, in many cases, be slowed down to a more acceptable level by the simple expedient of dietary supplementation with the antioxidant, vitamin E. Evidence for the potential use of vitamin E as an adjunctive therapy to help prolong kidney function in conditions that are accelerated by oxidative stress is discussed.

Protection by alpha G-rutin, a water-soluble antioxidant flavonoid, against renal damage in mice treated with ferric nitrilotriacetate

The protective effect of alpha G-Rutin against ferric nitrilotriacetate (Fe-NTA)-induced renal damage was studied in male ICR mice. Fe-NTA induces renal lipid peroxidation, leading to a high incidence of renal cell carcinoma in rodents. Administration of alpha G-Rutin (50 mumol as rutin/kg) by gastric intubation 30 min after i.p. injection of Fe-NTA (7 mg Fe/kg) most effectively suppressed renal lipid peroxidation. Repeated i.p. injection of Fe-NTA (2 mg Fe/kg/day for the first 3 days and 3 mg Fe /kg/day for 12 days, 5 days a week) causes subacute nephrotoxicity as revealed by induction of karyomegalic cells in renal proximal tubules. A protective effect was observed in mice given alpha G-Rutin 30 min after each Fe-NTA treatment. To elucidate the mechanism of protection by alpha G-Rutin, the pharmacokinetics and hydroxyl radical-scavenging effect of alpha G-Rutin were investigated by HPLC analysis and by electron spin resonance (ESR) spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), respectively. When mice were given alpha G-Rutin (50 mumol as rutin/kg) by gastric intubation, rapid absorption into the circulation was observed. The plasma concentration of alpha G-Rutin reached the highest level 30 min after oral administration and then decreased to the control level within 60 min, alpha G-Rutin inhibited the formation of DMPO-OH in a concentration-dependent manner. Further, chelating activity of alpha G-Rutin to ferric ions was shown by spectrophotometric analysis. These results suggest that absorbed alpha G-Rutin works as an antioxidant in vivo either by scavenging reactive oxygen species or by chelating ferric ions and this serves to prevent oxidative renal damage in mice treated with Fe-NTA.

Tubular PAH transport capacity in human kidney tissue and in renal cell carcinoma: correlation with various clinical and morphological parameters of the tumor

In vitro accumulation of p-aminohippurate (PAH) was investigated in "intact" human renal cortical slices of normal kidney tissue and in tissue slices of renal cell carcinoma (RCC). The technique used was established in preliminary experiments on rat kidney tissue slices. In principle, the accumulation capacity is comparable in renal tissue slices of both species (slice to medium accumulation ratios between 4 and 8). In man sex differences in accumulation capacity do not exist. But, as shown in detail for rats, accumulation capacity drops with age. Tissue slices of RCC are unable to accumulate PAH actively; slice to medium ratio reaches about 1 and indicates passive PAH uptake only. Surprisingly, in tumors of stage pT1 PAH uptake is lowest. perhaps as a sign of PAH transport out of the cells. There is no difference between peripheral and central parts of RCC. Age and sex are without influence on PAH uptake in RCC tissue slices. Interestingly, the accumulation capacity of "intact" tissue of kidneys infested with RCC also depends on the severity of the tumor (stage, diameter), but not on grading and formation of metastases.

Iron-induced tissue damage and cancer: the role of reactive oxygen species-free radicals

Oxygen is poisonous, but we cannot live without it. The high oxidizing potential of oxygen molecules (dioxygen) is a valuable source of energy for the organism and its reactivity is low; that is, spin forbidden. However, the dioxygen itself is a 'free radical' and, especially in the presence of transition metals, it is a major promoter of radical reactions in the cell. Humans survive only by virtue of their elaborate defense mechanisms against oxygen toxicity. Iron is the most abundant transition metal in the human body. Because iron shows wide variation in redox potential with different co-ordination ligands, it may be used as a redox intermediate in many biological mechanism. However, it is precisely this redox activeness that makes iron a key participant in free radical production. The current research on the relationship between iron and cancer is briefly reviewed. Research results are reported here which indicate that iron, when bound to certain ligands, can cause free-radical mediated tissue damage and become carcinogenic. The present study also suggests that iron may also have a significant role in spontaneous human cancer.

Iron-induced carcinogenesis: the role of redox regulation

Redox cycling is a characteristic of transition metals such as iron. Iron is hypothesized to have been actively involved in the birth of primitive life on earth through the generation of reducing equivalents in the presence of UV light. Iron is an essential metal in mammals for oxygen transport by hemoglobin and for the function of many enzymes including catalase and cytochromes. However, the "free" or "catalytic" form of iron mediates the production of reactive oxygen species via the Fenton reaction and induces oxidative stress. Serum "free" iron is observed in rare situations such as in severe hemochromatosis in which serum transferrin is saturated. However, it is known that superoxide can release "free" iron from ferritin and hemosiderin in the cell. "Free" iron is quite cytotoxic as well as mutagenic and carcinogenic. Iron compounds were first reported to induce sarcomas in rats by Richmond in 1959. Thereafter, several iron-induced carcinogenesis models were established, including the ferric nitrilotriacetate model by Okada and colleagues. Iron may have a role in the carcinogenic process of other transition metals such as copper and nickel, or other kinds of carcinogens such as nitrosamine and even virus-induced carcinogenesis. In humans, genetic hemochromatosis and asbestosis are two major diseases associated with iron-induced carcinogenesis. There is an increasing number of reports of an association between increased body iron stores and increased risk of cancer. Iron-induced oxidative stress results in two possible consequences: (1) redox regulation failure that leads to lipid peroxidation and oxidative DNA and protein damage; (2) redox regulation that activates a variety of reducing and oxystress-protective mechanisms via signal transduction. Both consequences appear to play a role in iron-induced carcinogenesis.

Sex hormone-dependent renal cell carcinogenesis induced by ferric nitrilotriacetate in Wistar rats

Ferric nitrilotriacetate (Fe-NTA), an iron chelate, induces necrosis of renal proximal convoluted tubules as a consequence of lipid peroxidation, and a high incidence of renal cell carcinoma (RCC) is also observed in rats and mice. The incidence of RCC and the extent of lipid peroxidation are greater in males than females. In the present study, the effects of castration or ovariectomy, and sex hormone treatment on Fe-NTA-induced renal carcinogenesis in rats were examined. Male and female Wistar rats were each divided into 5 groups. In group 1, rats were sham-operated and treated intraperitoneally (i.p.) with nitrilotriacetate (NTA). In group 2, sham-operated rats were treated with Fe-NTA (5-10 mg iron/kg/day, i.p.). Castrated or ovariectomized rats treated with Fe-NTA served as group 3. Group 4 or 5 was treated in the same way as group 3, but in addition received either testosterone (group 4) or estradiol (group 5). NTA, Fe-NTA or sex hormone treatments were initiated 4 weeks after the operation. NTA or Fe-NTA treatments were conducted for 12 weeks, and sex hormones were administered for 10 months. After 10 months of treatment, all rats were autopsied and both kidneys were examined histopathologically. In NTA-treated groups, there was no pathological change in the kidneys. In Fe-NTA-treated groups (groups 2-5), testosterone treatment or ovariectomy increased the incidence of RCC, and estradiol treatment or castration decreased the incidence of RCC (male: sham operation, castration and testosterone treatment > castration > castration and estradiol treatment, female: ovariectomy and testosterone treatment > ovariectomy > sham operation, ovariectomy and estradiol treatment). These results indicate that sex differences observed in the incidence of RCC induced by Fe-NTA are dependent upon sex hormones.

Urinary iron speciation in nephrotic syndrome

In nephrotic syndrome, iron is presented to the tubule fluid in a nonreactive form in association with transferrin as a result of the glomerular protein leak. At an alkaline pH, iron remains bound to transferrin throughout the nephron and is excreted as such in the urine. As urine pH decreases below 6, iron is dissociated from transferrin. In the dissociated form, iron exists in the urine in a soluble, ultrafiltrable, and labile state. It is suggested that iron is maintained in this state by chelation to a relatively small organic compound, such as citrate. This non-transferrin-bound iron is capable of catalyzing bleomycin degradation of DNA, suggesting that this labile form of iron is able to catalyze free radical formation and cause tubule cell injury. Urine from proteinuric states represents one of the few, if not only, biologic fluids containing large amounts of reactive iron species. This may explain the mechanism by which proteinuric states cause tubulointerstitial disease and renal failure.

Acute nephrotoxicity of a carcinogenic iron chelate. Selective inhibition of a proteolytic conversion of alpha 2U-globulin to the kidney fatty acid-binding protein

The mechanism of acute nephrotoxicity of an iron chelate in vivo has been investigated. Administration of a renal carcinogen ferric nitrilotriacetate (Fe-NTA) (15 mg Fe/kg body weight, intraperitoneally) led to selective loss of a renal protein with an apparent molecular mass of 17 kDa. Analysis of the 17 kDa protein by NH2-terminal sequence demonstrated its identity over 16 NH2-terminal residues as a kidney fatty acid-binding protein (k-FABP) that is a proteolytically modified form of alpha 2U-globulin, a major urinary protein of adult male rats. An immunochemical study using anti-alpha 2U-globulin polyclonal antibodies confirmed that a single injection of Fe-NTA led to a decrease in k-FABP levels. However, a 19-kDa protein identical to the alpha 2U-globulin progressively appeared in the kidney, suggesting that the proteolytic processing of alpha 2U-globulin in the renal proximal tubules was suppressed by the treatment with Fe-NTA. By monitoring k-FABP and its precursor alpha 2U-globulin, it was determined that repeated exposure to Fe-NTA caused suppression of both proteolytic and endocytotic activity of the kidney. The implications of these data in relation to the nephrotoxicity of Fe-NTA are discussed.

Possible role of oxidative damage in metal-induced carcinogenesis

This review presents and evaluates evidence relevant to the mechanisms of metal carcinogenicity with special emphasis on the emerging hypothesis of the oxidative nature of metals' effect on DNA. The carcinogenic transition metals are capable of in vivo binding with the cell nucleus and causing promutagenic damage that includes DNA base modifications, inter- and intramolecular crosslinking of DNA and proteins, DNA strand breaks, rearrangements, and depurination. The chemistry of that damage and the resulting mutations observed in vitro and in metal-induced tumors are both characteristic for oxidative attack on DNA. The underlying mechanism involves various kinds of active oxygen and other radical species arising from metal-catalyzed redox reactions of O2, H2O2, lipid peroxides, and others, with certain amino acids, peptides, and proteins. Other metal-mediated pathogenic effects, such as enhancement of lipid peroxidation, stimulation of inflammation, inhibition of cellular antioxidant defenses, and inhibition of DNA repair, may also contribute to that mechanism. Thus far, published data revealing the oxidative character of metal-induced promutagenic DNA alterations are particularly strong for two of the most powerful human metal carcinogens, chromium and nickel. However, without excluding contribution of other effects, the promotion of oxidative damage tends to take the leading role in explaining mechanisms of carcinogenicity and acute toxicity of certain other metals as well.

Formation of 4-hydroxy-2-nonenal-modified proteins in the renal proximal tubules of rats treated with a renal carcinogen, ferric nitrilotriacetate

An iron chelate, ferric nitrilotriacetate (Fe-NTA), induces proximal tubular necrosis, a consequence of lipid peroxidation, that finally leads to a high incidence of renal adenocarcinoma in rodents. Lipid peroxidation as monitored by formation of thiobarbituric acid-reactive substances and free 4-hydroxy-2-nonenal (HNE) was observed in the kidney homogenates of rats treated with Fe-NTA. Based on the fact that HNE is capable of reacting with cellular proteins, we attempted to detect the localization of HNE-modified proteins in rat kidney tissues with an immunohistochemical procedure. By means of an immunohistochemical technique using polyclonal antibody against the HNE-modified proteins, it was shown that HNE-modified proteins are formed in the target cells of this carcinogenesis model. HNE-modified proteins were detected in the renal proximal tubules 1 hr after i.p. administration of Fe-NTA (15 mg of iron per kg). Intense positivity was found in the cells with degeneration. After 6 hr, the level of HNE-protein conjugates decreased due to the subsequent necrosis. The intensity of the immunochemical reaction with HNE-modified proteins increased in parallel with an increase in the amounts of thiobartituric acid-reactive substances and free HNE that were found. Furthermore, histochemical detection of aldehydes by cold Schiff's reagent demonstrated that location of aldehydes was identical to that of the HNE-modified proteins determined by immunohistochemical procedures. It would thus appear that the production of HNE, a genotoxic and mutagenic aldehyde, and its reaction with proteins may play a role in Fe-NTA-induced renal carcinogenesis.

Effects of nicotinamide and its isomers on iron-induced renal damage

The effects of three isomers of pyridinecarboxamide (picolinamide (2-pyridinecarboxamide), nicotinamide (3-pyridinecarboxamide) and isonicotinamide (4-pyridinecarboxamide)) on iron-induced renal damage were studied. Pyridinecarboxamide (250 mg/kg body weight, ip) was administered 10 min before injection of ferric nitrilotriacetate (Fe(III)-NTA) (7.5 mgFe/kg body weight, ip). In picolinamide-treated rats, the renal tubular necrosis induced by Fe(III)-NTA was attenuated and serum creatinine did not increase. Picolinamide most efficiently suppressed renal lipid peroxidation in vivo-induced by Fe(III)-NTA. Non-heme iron levels in the kidneys after Fe(III)-NTA injection did not differ in groups to which pyridinecarboxamides were administered. To elucidate the protective effects of picolinamide, we studied the action of pyridinecarboxamides on lipid peroxidation and DNA damage in vitro. These isomers inhibited iron-induced lipid peroxidation of linolenic acid. Picolinamide had no effect on DNA damage, but nicotinamide and isonicotinamide promoted DNA damage by iron, especially when ascorbate was used as a reductant. None of these pyridinecarboxamide isomers changed the chlelate structure of Fe(III)-NTA as shown by electronic absorption spectra. Among the three isomers, picolinamide most effectively protected the kidneys against iron-induced renal damage, since it not only inhibited iron-induced lipid peroxidation, but also had little enhancing action on DNA damage by iron.

Peroxide-dependent and -independent lipid peroxidations catalyzed by chelated iron

Oxidation of linoleic acid (LA) in tetradecyltrimethylammonium bromide micelles was induced by ferrous- and ferric-chelates in the presence of linoleic acid hydroperoxide (LOOH). Ferrous-chelates also induced lipid peroxidation in the presence of H2O2, but ferric-chelates did not, thought they could generate OH-radicals in the presence of H2O2, resulting in deoxyribose degradation. Of the chelators tested, nitrilotriacetic acid (NTA) chelated with iron showed the highest activity for induction of H2O2- and LOOH-dependent lipid peroxidations and H2O2-dependent deoxyribose degradation. NTA with ferrous ion, but not with ferric ion, also initiated oxidation of LA after a short lag period in the absence of peroxides such as H2O2 and LOOH, but other chelators with ferrous ion did not. The peroxide-independent lipid peroxidation and associated oxidation of ferrous-NTA to ferric-NTA progressed in two steps: an induction step in a lag period and then a propagation step. Ferrous ion complexed with NTA was autoxidized pH-dependently and synchronously with oxygen uptake. The rates of both reactions increased with increase of pH, but were not related to the length of the lag period, which was also dependent on pH, and was shortest at pH 4.2. The EPR spectrum of the ferric-NTA complex prepared directly from ferric salt was different from that of the complex prepared from ferrous salt, confirming that some ferric-type active oxygen participated in induction of peroxide-independent lipid peroxidation. From these results, we propose a possible mechanism of lipid peroxidation induced by ferrous-NTA without peroxides. The finding that iron-NTA had the highest activity for induction of the oxidations of LA and deoxyribose is discussed in relation to the carcinogenic and nephrotoxic effects of this chelating agent.

Sex differences in the localization and severity of ferric nitrilotriacetate-induced lipid peroxidation in the mouse kidney

Male mice are much more susceptible than female mice to acute renal proximal tubular necrosis as well as the carcinogenic effect induced by an iron-chelate, ferric nitrilotriacetate (Fe-NTA). In the present study, iron-promoted lipid peroxidation was analyzed histochemically in frozen kidney sections using cold Schiff's reagent and biochemically by measuring thiobarbituric acid-reactive substance in the kidney. When untreated mouse frozen kidney sections were exposed to ascorbic acid-Fe-NTA (0.8 mM, 0.2 mM and 0.4 mM) in vitro for 40 min and washed, diffuse Schiff positivity was obtained along the proximal tubules, and no sex differences were evident. When non-reduced Fe-NTA (0.2 mM and 0.4 mM) was layered on untreated kidney sections from males, about half of the cortical proximal tubules showed a positive reaction with Schiff's reagent, whereas in females the proximal tubules of the outer stripe of the outer medulla were positive. In an ex vivo study, 30 to 40 min after i.p. injection of Fe-NTA (5 mg Fe/kg), Schiff-positive areas corresponded to those observed in the in vitro non-reduced Fe-NTA study in each sex. However, in males, the positive tubular cells gradually became necrotic, whereas in females the positivity disappeared with time and there was no tubular necrosis. Results of the thiobarbituric acid test were correlated with the above findings. In conclusion, the localization and severity of Fe-NTA-induced lipid peroxidation in the tubules differed between the sexes. We suspect that these results reflect functional heterogeneity in the ability of the tubules to reduce iron.

Site-specific mechanisms of initiation by chelated iron and inhibition by alpha-tocopherol of lipid peroxide-dependent lipid peroxidation in charged micelles

To obtain information on the role of iron-catalyzed lipid peroxidation in the presence of the small amount of lipid peroxide in deterioration of biological membranes, we examined factors affecting peroxidation of fatty acids in charged micelles. Peroxidation of linoleic acid (LA) was catalyzed by Fe2+ via reductive cleavage of linoleic acid hydroperoxide (LOOH) in negatively charged sodium dodecyl sulfate micelles, but not in positively charged tetradecyltrimethylammonium bromide (TTAB) micelles. However, this Fe2(+)-induced, LOOH-dependent lipid peroxidation could be induced in TTAB micelles in the presence of a negatively charged iron chelator, nitrilotriacetic acid (NTA). The linoleic acid alkoxy radical (LO.) generated by the LOOH-dependent Fenton reaction was also trapped by N-t-butyl-alpha-phenylnitrone at the surface of TTAB micelles in the presence of NTA, but not in its absence. The degradation rates of two spin probes, N-oxyl-4,4'-dimethyloxazolidine derivatives of stearic acid (5-NS and 16-NS), were investigated to determine the site of production of radicals formed during LOOH-dependent lipid peroxidation. The rate of consumption of 16-NS during the LOOH-dependent Fenton-like reaction was higher in TTAB micelles containing LA than in those containing lauric acid (LauA), although the rates of formation of LO. in the two types of fatty acid micelles were similar. The rates of 5-NS consumption in LA and LauA micelles were almost the same and were as low as that of 16-NS consumption in LauA micelles. 16-NS was more inhibitory than 5-NS of LOOH-dependent lipid peroxidation, and this inhibition was associated with its higher consumption of 16-NS than of 5-NS. alpha-Tocopherol inhibited NTA-Fe2(+)-induced LOOH-dependent lipid peroxidation in TTAB micelles, and was oxidized during this inhibition process. The rate and amount of alpha-tocopherol oxidized by the LOOH-dependent Fenton reaction were higher in LA micelles than in LauA micelles. alpha-Tocopherol inhibited the consumption of 16-NS during NTA-Fe2(+)-induced LOOH-dependent lipid peroxidation more effectively than that of 5-NS. The distribution of the chromanol moiety of alpha-tocopherol was studied by the fluorescence quenching method. There was no difference between Stern-Volmer plots of the quenchings of alpha-tocopherol fluorescence by 5-NS and 16-NS. From these results, we discuss the mechanism of induction of LOOH-dependent peroxidation of LA and the mechanism of the antioxidant effects of alpha-tocopherol on it from the viewpoint of site-specific reaction.

Oxidative DNA damage, lipid peroxidation and nephrotoxicity induced in the rat kidney after ferric nitrilotriacetate administration

8-Hydroxydeoxyguanosine (8-OH-dG) was examined in the kidneys of rats after single i.p. administration of ferric nitrilotriacetate (Fe-NTA) for variable periods of time at various doses along with the measurement of lipid peroxidation and serum biochemical parameters and histopathological examination. Though lipid peroxide level increased rapidly and decreased sharply after reaching a much higher peak 1 h after treatment, significant higher levels of 8-OH-dG were observed at 1, 6 and 24 h after injection. On the other hand, the increase of 8-OH-dG formation was observed in a similar dose-dependent manner to the appearance of nephrotoxic responses in terms of serum biochemical and histopathological changes.

Rapid in vitro transformation system for liver epithelial cells by iron chelate, Fe-NTA

We have previously found toxic effects of iron chelate, Fe-NTA on cultured normal rat liver epithelial cells (RL34). In the present study, when RL34 cells were exposed to 50 micrograms/ml iron of Fe-NTA for 15 days, besides the expected cytolytic effects in most cells, the appearance of resistant cells was observed. The resistant cells showed drastic morphological transformation, grew in soft agar, and induced hepatocellular carcinomas when transplanted into syngeneic newborn rats in a short period of time. Since DNA instability in the transformed cells was ascertained by differential AO staining, it is suggested that DNA damage by Fe-NTA is of a critical importance for extremely rapid neoplastic transformation of normal epithelial cells.

Thiobarbituric acid-reactive substance formation of rat kidney brush border membrane vesicles induced by ferric nitrilotriacetate

An iron chelate, ferric nitrilotriacetate (Fe3+-NTA), is nephrotoxic and also carcinogenic to the kidney in experimental animals. Iron-promoted lipid peroxidation in the proximal tubules is thought to be responsible for the pathologic process. In the present study, iron-promoted lipid peroxidation, with thiobarbituric acid (TBA) formation as an indication, in the tubular surface was simulated in vitro using rat kidney brush border membrane vesicles and the results were compared with those using linoleate micelles and rat liver microsomal lipid liposomes. Addition of ascorbate, cysteine, or dithiothreitol to the Fe3+-NTA solution resulted in consumption of dissolved oxygen and promoted the lipid peroxidation in the micelles and in the liposomes. In contrast, addition of glutathione to the Fe3+-NTA solution caused only sluggish oxygen consumption and far less peroxidation in these lipid systems. When the brush border membrane vesicles were used for the peroxidation substrate, Fe3+-NTA and glutathione could promote TBA formation at a rate comparable to that elicited by Fe3+-NTA with cysteine or dithiothreitol. Acivicin, a gamma-glutamyl transpeptidase inhibitor, suppressed the peroxidation of the brush border membrane vesicles promoted by Fe3+-NTA and glutathione. These results suggest the following mechanism of proximal tubular cell lipid peroxidation promoted by Fe-NTA: Fe3+-NTA filtered through glomeruli is rapidly reduced by cysteine and Fe2+-NTA starts lipid peroxidation at the site, leading to proximal tubular necrosis. Cysteine is amply supplied by the decomposition of glutathione within the lumen by the action of gamma-glutamyl transpeptidase and dipeptidase situated at the proximal tubular brush border membrane.

Effects of acute and sub-chronic administration of iron nitrilotriacetate in the rat

Parenteral administration of iron nitrilotriacetate (FeNTA) to rats resulted in marked loss in body weight, and increases in liver/and kidney/body weight ratios. Fatalities, due to renal failure, depended on dosage and age of the animals, and were greater (70%) after a single large dose (12 mg iron) than after repeated smaller doses (30%). FeNTA administered subchronically gave rise to an increase in ethane exhalation, and to decreased liver glutathione peroxidase activity, and decreased cytochrome P-450 concentration and benzphetamine N-demethylase activity. It also resulted in severe renal tubular necrosis, with deposition of iron in the tubular cells and loss of brush border alkaline phosphatase activity, resulting in a dose-dependent diuresis, with increased urinary excretion of glucose, iron and lipid peroxidation products, and decreased urine creatinine concentration. NTA alone had none of these effects but slightly decreased the hepatic concentration of iron.

Oxygen reduction and lipid peroxidation by iron chelates with special reference to ferric nitrilotriacetate

A certain iron chelate, ferric nitrilotriacetate (Fe3+-NTA) is nephrotoxic and also carcinogenic to the kidney in mice and rats, a distinguishing feature not shared by other iron chelates tested so far. Iron-promoted lipid peroxidation is thought to be responsible for the initial events. We examined its ability to initiate lipid peroxidation in vitro in comparison with that of other ferric chelates. Chelation of Fe2+ by nitrilotriacetate (NTA) enhanced the autoxidation of Fe2+. In the presence of Fe2+-NTA, lipid peroxidation occurred as measured by the formation of conjugated diene in detergent-dispersed linoleate micelles, and by the formation of thiobarbituric acid-reactive substances in the liposomes of rat liver microsomal lipids. Addition of ascorbic acid to Fe3+-NTA solution promoted dose-dependent consumption of dissolved oxygen, which indicates temporary reduction of iron. On reduction, Fe3+-NTA initiated lipid peroxidation both in the linoleate micelles and in the liposomes. Fe3+-NTA also initiated NADPH-dependent lipid peroxidation in rat liver microsomes. Although other chelators used (deferoxamine, EDTA, diethylenetriaminepentaacetic acid, ADP) enhanced autoxidation, reduction by ascorbic acid, or in vitro lipid peroxidation of linoleate micelles or liposomal lipids, NTA was the sole chelator that enhanced all the reactions.

Sex differences in ferric nitrilotriacetate-induced lipid peroxidation and nephrotoxicity in mice

Since male A/J mice are much more susceptible to both acute and subacute nephrotoxicity and the carcinogenic effect of ferric nitrilotriacetate than female mice, sex differences in the lipid peroxidation level after ferric nitrilotriacetate use were examined. The effects of orchiectomy and testosterone were also investigated. Male and female A/J mice were given a single intraperitoneal injection of ferric nitrilotriacetate (3 mg of iron/kg of body weight) and then thiobarbituric acid reactivity was determined in the liver and the kidney. Only male mice showed high thiobarbituric acid reactivity after 30 min, with the kidney showing higher activity than the liver. Castrated male mice showed a reduction in thiobarbituric acid reactivity, whereas testosterone-pretreated castrated male or testosterone-pretreated female mice showed increased thiobarbituric acid reactivity. In addition, daily intraperitoneal injections of ferric nitrilotriacetate resulted in the death of all normal male mice within 6 days, whereas all female and castrated male mice survived 3 months of treatment. Thus, male and female mice showed differences in ferric nitrilotriacetate-induced toxicity as reflected in the degree of lipid peroxidation and mortality.