Hepatic Overexpression of Annexin A1 and A2 in Thioacetamide-Primed Mice Protects Them Against Acetaminophen-Induced Liver Failure and Death.

Compensatory tissue repair (CTR) in thioacetamide (TA)-primed rats protects them against acetaminophen (APAP)-induced lethality. This study was aimed at investigating the mechanisms of CTR-mediated heteroprotection in mice. Male Swiss Webster mice received a priming dose of TA (40 mg/kg body weight [BW] in 10 mL distilled water [DW]/kg BW, intraperitoneally [IP]). Thioacetamide-induced liver injury, CTR, and expression of annexin A1 and A2 (ANX1 and ANX2), the endogenous inhibitors of the death protein secretory phospholipase A2 (sPLA2), were measured over a time course of 84 hours after TA priming. Both centrilobular necrosis and CTR peaked at 36 hours after TA priming as indicated by significantly increased plasma alanine transaminase (ALT) and aspartate transaminase (AST) activities, liver histology, and proliferating cell nuclear antigen immunostaining. Thioacetamide priming resulted in the overexpression of ANX1 and ANX2 at 36 to 84 hours and 12 to 60 hours, respectively. A lethal dose of APAP (600 mg/kg BW in 10 mL 0.45% NaCl/kg BW, IP) was given at 12, 24, or 36 hours after TA-priming. Thioacetamide priming did not affect the rise in plasma ALT, AST, sPLA2, and arachidonic acid levels seen at 2 hours after the APAP overdose. Neither these biochemical parameters nor histology suggested any escalation of hepatic injury at later time points (12 and 24 hours after APAP overdose), consistent with 100% survival of the TA + APAP-treated mice compared to DW + APAP-treated mice, which had 100% mortality. Inhibition of ANX1 and ANX2 biosynthesis using cycloheximide (40 mg/kg BW in 5 mL DW/kg BW, IP) abolished this heteroprotection. Our data indicate that hepatic overexpression of ANX1 and ANX2 inhibits APAP-induced expansion of liver injury.

Strain-dependent dysregulation of one-carbon metabolism in male mice is associated with choline- and folate-deficient diet-induced liver injury.

Dysregulation of one-carbon metabolism-related metabolic processes is a major contributor to the pathogenesis of nonalcoholic fatty liver disease (NAFLD). It is well established that genetic and gender-specific variations in one-carbon metabolism contribute to the vulnerability to NAFLD in humans. To examine the role of one-carbon metabolism dysregulation in the pathogenesis and individual susceptibility to NAFLD, we used a "population-based" mouse model where male mice from 7 inbred were fed a choline- and folate-deficient (CFD) diet for 12 wk. Strain-dependent down-regulation of several key one-carbon metabolism genes, including methionine adenosyltransferase 1α (Mat1a), cystathionine-ß-synthase (Cbs), methylenetetrahydrofolate reductase (Mthfr), adenosyl-homocysteinase (Ahcy), and methylenetetrahydrofolate dehydrogenase 1 (Mthfd1), was observed. These changes were strongly associated with interstrain variability in liver injury (steatosis, necrosis, inflammation, and activation of fibrogenesis) and hyperhomocysteinemia. Mechanistically, the decreased expression of Mat1a, Ahcy, and Mthfd1 was linked to a reduced level and promoter binding of transcription factor CCAAT/enhancer binding protein ß (CEBPß), which directly regulates their transcription. The strain specificity of diet-induced dysregulation of one-carbon metabolism suggests that interstrain variation in the regulation of one-carbon metabolism may contribute to the differential vulnerability to NFLD and that correcting the imbalance may be considered as preventive and treatment strategies for NAFLD.

Interstrain differences in the severity of liver injury induced by a choline- and folate-deficient diet in mice are associated with dysregulation of genes involved in lipid metabolism.

Nonalcoholic fatty liver disease (NAFLD) is a major health problem and a leading cause of chronic liver disease in the United States and developed countries. In humans, genetic factors greatly influence individual susceptibility to NAFLD. The goals of this study were to compare the magnitude of interindividual differences in the severity of liver injury induced by methyl-donor deficiency among individual inbred strains of mice and to investigate the underlying mechanisms associated with the variability. Feeding mice a choline- and folate-deficient diet for 12 wk caused liver injury similar to NAFLD. The magnitude of liver injury varied among the strains, with the order of sensitivity being A/J ≈ C57BL/6J ≈ C3H/HeJ < 129S1/SvImJ ≈ CAST/EiJ < PWK/PhJ < WSB/EiJ. The interstrain variability in severity of NAFLD liver damage was associated with dysregulation of genes involved in lipid metabolism, primarily with a down-regulation of the peroxisome proliferator receptor α (PPARα)-regulated lipid catabolic pathway genes. Markers of oxidative stress and oxidative stress-induced DNA damage were also elevated in the livers but were not correlated with severity of liver damage. These findings suggest that the PPARα-regulated metabolism network is one of the key mechanisms determining interstrain susceptibility and severity of NAFLD in mice.

Plasma microRNAs are sensitive indicators of inter-strain differences in the severity of liver injury induced in mice by a choline- and folate-deficient diet.

MicroRNAs (miRNAs) are a class of small, conserved, tissue-specific regulatory non-coding RNAs that modulate a variety of biological processes and play a fundamental role in the pathogenesis of major human diseases, including nonalcoholic fatty liver disease (NAFLD). However, the association between inter-individual differences in susceptibility to NAFLD and altered miRNA expression is largely unknown. In view of this, the goals of the present study were (i) to determine whether or not individual differences in the extent of NAFLD-induced liver injury are associated with altered miRNA expression, and (ii) assess if circulating blood miRNAs may be used as potential biomarkers for the noninvasive evaluation of the severity of NAFLD. A panel of seven genetically diverse strains of inbred male mice (A/J, C57BL/6J, C3H/HeJ, 129S/SvImJ, CAST/EiJ, PWK/PhJ, and WSB/EiJ) were fed a choline- and folate-deficient (CFD) diet for 12weeks. This diet induced liver injury in all mouse strains; however, the extent of NAFLD-associated pathomorphological changes in the livers was strain-specific, with A/J, C57BL/6J, and C3H/HeJ mice being the least sensitive and WSB/EiJ mice being the most sensitive. The morphological changes in the livers were accompanied by differences in the levels of hepatic and plasma miRNAs. The levels of circulating miR-34a, miR-122, miR-181a, miR-192, and miR-200b miRNAs were significantly correlated with a severity of NAFLD-specific liver pathomorphological features, with the strongest correlation occurring with miR-34a. These observations suggest that the plasma levels of miRNAs may be used as biomarkers for noninvasive monitoring the extent of NAFLD-associated liver injury and susceptibility to NAFLD.

In vivo genotoxicity of furan in F344 rats at cancer bioassay doses.

Furan, a potent rodent liver carcinogen, is found in many cooked food items and thus represents a human cancer risk. Mechanisms for furan carcinogenicity were investigated in male F344 rats using the in vivo Comet and micronucleus assays, combined with analysis of histopathological and gene expression changes. In addition, formamidopyrimidine DNA glycosylase (Fpg) and endonuclease III (EndoIII)-sensitive DNA damage was monitored as a measure of oxidative DNA damage. Rats were treated by gavage on four consecutive days with 2, 4, and 8mg/kg bw furan, doses that were tumorigenic in 2-year cancer bioassays, and with two higher doses, 12 and 16mg/kg. Rats were killed 3h after the last dose, a time established as producing maximum levels of DNA damage in livers of furan-treated rats. Liver Comet assays indicated that both DNA strand breaks and oxidized purines and pyrimidines increased in a near-linear dose-responsive fashion, with statistically significant increases detected at cancer bioassay doses. No DNA damage was detected in bone marrow, a non-target tissue for cancer, and peripheral blood micronucleus assays were negative. Histopathological evaluation of liver from furan-exposed animals produced evidence of inflammation, single-cell necrosis, apoptosis, and cell proliferation. In addition, genes related to apoptosis, cell-cycle checkpoints, and DNA-repair were expressed at a slightly lower level in the furan-treated livers. Although a mixed mode of action involving direct DNA binding cannot be ruled out, the data suggest that furan induces cancer in rat livers mainly through a secondary genotoxic mechanism involving oxidative stress, accompanied by inflammation, cell proliferation, and toxicity.

Secretory phospholipase A2-mediated progression of hepatotoxicity initiated by acetaminophen is exacerbated in the absence of hepatic COX-2.

We have previously reported that among the other death proteins, hepatic secretory phospholipase A2 (sPLA2) is a leading mediator of progression of liver injury initiated by CCl4 in rats. The aim of our present study was to test the hypothesis that increased hepatic sPLA2 released after acetaminophen (APAP) challenge mediates progression of liver injury in wild type (WT) and COX-2 knockout (KO) mice. COX-2 WT and KO mice were administered a normally non lethal dose (400 mg/kg) of acetaminophen. The COX-2 KO mice suffered 60% mortality compared to 100% survival of the WT mice, suggesting higher susceptibility of COX-2 KO mice to sPLA2-mediated progression of acetaminophen hepatotoxicity. Liver injury was significantly higher at later time points in the KO mice compared to the WT mice indicating that the abatement of progression of injury requires the presence of COX-2. This difference in hepatotoxicity was not due to increased bioactivation of acetaminophen as indicated by unchanged cyp2E1 protein and covalently bound ¹4C-APAP in the livers of KO mice. Hepatic sPLA2 activity and plasma TNF-α were significantly higher after APAP administration in the KO mice. This was accompanied by a corresponding fall in hepatic PGE2 and lower compensatory liver regeneration and repair (³H-thymidine incorporation) in the KO mice. These results suggest that hindered compensatory tissue repair and poor resolution of inflammation for want of beneficial prostaglandins render the liver very vulnerable to sPLA2-mediated progression of liver injury. These findings are consistent with the destructive role of sPLA2 in the progression and expansion of tissue injury as a result of continued hydrolytic breakdown of plasma membrane phospholipids of perinecrotic hepatocytes unless mitigated by sufficient co-induction of COX-2.

Mechanisms of epigenetic silencing of the Rassf1a gene during estrogen-induced breast carcinogenesis in ACI rats.

Breast cancer, the most common malignancy in women, emerges through a multistep process, encompassing the progressive sequential evolution of morphologically distinct stages from a normal cell to hyperplasia (with and without atypia), carcinoma in situ, invasive carcinoma and metastasis. The success of treatment of breast cancer could be greatly improved by the detection at early stages of cancer. In the present study, we investigated the underlying molecular mechanisms involved in breast carcinogenesis in Augustus and Copenhagen-Irish female rats, a cross between the ACI strains, induced by continuous exposure to 17beta-estradiol. The results of our study demonstrate that early stages of estrogen-induced breast carcinogenesis are characterized by altered global DNA methylation, aberrant expression of proteins responsible for the proper maintenance of DNA methylation pattern and epigenetic silencing of the critical Rassf1a (Ras-association domain family 1, isoform A) tumor suppressor gene. Interestingly, transcriptional repression of the Rassf1a gene in mammary glands during early stages of breast carcinogenesis was associated with an increase in trimethylation of histones H3 lysine 9 and H3 lysine 27 and de novo CpG island methylation and at the Rassf1a promoter and first exon. In conclusion, we demonstrate that epigenetic alterations precede formation of preneoplastic lesions indicating the significance of epigenetic events in induction of oncogenic pathways in early stages of carcinogenesis.

Effects of intravenous and oral di(2-ethylhexyl) phthalate (DEHP) and 20% Intralipid vehicle on neonatal rat testis, lung, liver, and kidney.

The highest human exposures to the plasticizer di(2-ethylhexyl) phthalate (DEHP) occur through intravenous (iv) exposure from medical procedures. Rodent toxicity studies, mainly using oral exposures, have identified male reproductive toxicity after developmental exposure to DEHP as the primary concern. Other organs are also affected by DEHP and route may influence the degree of target organ involvement. Cammack et al. (2003) reported a critical study focused on testicular toxicity using oral and iv exposures of neonatal Sprague-Dawley rats to 60, 300, or 600 mg/kg body weight/day DEHP in Intralipid vehicle. The present study followed the same dosing paradigm and included assessment of additional organs to evaluate the potential utility of this design for DEHP alternatives. Reduction of testis weight was observed in all DEHP treatment groups and germ cell and Sertoli cell toxicity was observed at the two highest doses with both routes. Lung granulomas occurred in all iv DEHP groups, possibly related to increased fat particle size in DEHP lipid emulsions. Lung alveolar development was inhibited after both oral and iv high dose DEHP. Toxicity of oral Intralipid vehicle was observed in germ and Sertoli cells. The lack of such effects after iv vehicle exposure suggested that this may be a gut-mediated effect.

Hepatic epigenetic phenotype predetermines individual susceptibility to hepatic steatosis in mice fed a lipogenic methyl-deficient diet.

BACKGROUND/AIMS: The importance of epigenetic changes in etiology and pathogenesis of disease has been increasingly recognized. However, the role of epigenetic alterations in the genesis of hepatic steatosis and cause of individual susceptibilities to this pathological state are largely unknown. METHODS: Male inbred C57BL/6J and DBA/2J mice were fed a lipogenic methyl-deficient diet (MDD) that causes liver injury similar to human non-alcoholic steatohepatitis (NASH) for 6, 12, or 18 weeks, and the status of global and repetitive elements cytosine methylation, histone modifications, and expression of proteins responsible for those epigenetic modifications in livers was determined. RESULTS: The development of hepatic steatosis in inbred C57BL/6J and DBA/2J mice was accompanied by prominent epigenetic abnormalities. This was evidenced by pronounced loss of genomic and repetitive sequences cytosine methylation, especially at major and minor satellites, accompanied by increased levels of repeat-associated transcripts, aberrant histone modifications, and alterations in expression of the maintenance DNA methyltransferase 1 (DNMT1) and de novo DNMT3A proteins in the livers of both mouse strains. However, the DBA/2J mice, which were characterized by an initially lower degree of methylation of repetitive elements and lower extent of histone H3 lysine 9 (H3K9) and H3 lysine 27 (H3K27) trimethylation in the normal livers, as compared to those in the C57BL/6J mice, developed more prominent NASH-specific pathomorphological changes. CONCLUSIONS: These results mechanistically link epigenetic alterations to the pathogenesis of hepatic steatosis and strongly suggest that differences in the cellular epigenetic status may be a predetermining factor to individual susceptibilities to hepatic steatosis.

The mRNA expression and histological integrity in rat forebrain motor and sensory regions are minimally affected by acrylamide exposure through drinking water.

A study was undertaken to determine whether alterations in the gene expression or overt histological signs of neurotoxicity in selected regions of the forebrain might occur from acrylamide exposure via drinking water. Gene expression at the mRNA level was evaluated by cDNA array and/or RT-PCR analysis in the striatum, substantia nigra and parietal cortex of rat after a 2-week acrylamide exposure. The highest dose tested (maximally tolerated) of approximately 44 mg/kg/day resulted in a significant decreased body weight, sluggishness, and locomotor activity reduction. These physiological effects were not accompanied by prominent changes in gene expression in the forebrain. All the expression changes seen in the 1200 genes that were evaluated in the three brain regions were < or =1.5-fold, and most not significant. Very few, if any, statistically significant changes were seen in mRNA levels of the more than 50 genes directly related to the cholinergic, noradrenergic, GABAergic or glutamatergic neurotransmitter systems in the striatum, substantia nigra or parietal cortex. All the expression changes observed in genes related to dopaminergic function were less than 1.5-fold and not statistically significant and the 5HT1b receptor was the only serotonin-related gene affected. Therefore, gene expression changes were few and modest in basal ganglia and sensory cortex at a time when the behavioral manifestations of acrylamide toxicity had become prominent. No histological evidence of axonal, dendritic or neuronal cell body damage was found in the forebrain due to the acrylamide exposure. As well, microglial activation was not present. These findings are consistent with the absence of expression changes in genes related to changes in neuroinflammation or neurotoxicity. Over all, these data suggest that oral ingestion of acrylamide in drinking water or food, even at maximally tolerable levels, induced neither marked changes in gene expression nor neurotoxicity in the motor and somatosensory areas of the central nervous system.

Overlapping but distinct effects of genistein and ethinyl estradiol (EE(2)) in female Sprague-Dawley rats in multigenerational reproductive and chronic toxicity studies.

Genistein and ethinyl estradiol (EE(2)) were examined in multigenerational reproductive and chronic toxicity studies that had different treatment intervals among generations. Sprague-Dawley rats received genistein (0, 5, 100, or 500 ppm) or EE(2) (0, 2, 10, or 50 ppb) in a low phytoestrogen diet. Nonneoplastic effects in females are summarized here. Genistein at 500 ppm and EE(2) at 50 ppb produced similar effects in continuously exposed rats, including decreased body weights, accelerated vaginal opening, and altered estrous cycles in young animals. At the high dose, anogenital distance was subtly affected by both compounds, and a reduction in litter size was evident in genistein-treated animals. Genistein at 500 ppm induced an early onset of aberrant cycles relative to controls in the chronic studies. EE(2) significantly increased the incidence of uterine lesions (atypical focal hyperplasia and squamous metaplasia). These compound-specific effects appeared to be enhanced in the offspring of prior exposed generations.

Impact of repeated exposure on toxicity of perchloroethylene in Swiss Webster mice.

The aim was to study the subchronic toxicity of perchloroethylene (Perc) by measuring injury and repair in liver and kidney in relation to disposition of Perc and its major metabolites. Male SW mice (25-29g) were given three dose levels of Perc (150, 500, and 1000 mg/kg day) via aqueous gavage for 30 days. Tissue injury was measured during the dosing regimen (0, 1, 7, 14, and 30 days) and over a time course of 24-96h after the last dose (30 days). Perc produced significant liver injury (ALT) after single day exposure to all three doses. Liver injury was mild to moderate and regressed following repeated exposure for 30 days. Subchronic Perc exposure induced neither kidney injury nor dysfunction during the entire time course as evidenced by normal renal histology and BUN. TCA was the major metabolite detected in blood, liver, and kidney. Traces of DCA were also detected in blood at initial time points after single day exposure. With single day exposure, metabolism of Perc to TCA was saturated with all three doses. AUC/dose ratio for TCA was significantly decreased with a concomitant increase in AUC/dose of Perc levels in liver and kidney after 30 days as compared to 1 day exposures, indicating inhibition of metabolism upon repeated exposure to Perc. Hepatic CYP2E1 expression and activity were unchanged indicating that CYP2E1 is not the critical enzyme inhibited. Hepatic CYP4A expression, measured as a marker of peroxisome proliferation was increased transiently only on day 7 with the high dose, but was unchanged at later time points. Liver tissue repair peaked at 7 days, with all three doses and was sustained after medium and high dose exposure for 14 days. These data indicate that subchronic Perc exposure via aqueous gavage does not induce nephrotoxicity and sustained hepatotoxicity suggesting adaptive hepatic repair mechanisms. Enzymes other than CYP2E1, involved in the metabolism of Perc may play a critical role in the metabolism of Perc upon subchronic exposure in SW mice. Liver injury decreased during repeated exposure due to inhibition of metabolism and possibly due to adaptive tissue repair mechanisms.

Toxicokinetics and toxicity of thioacetamide sulfoxide: a metabolite of thioacetamide.

Thioacetamide (TA) is bioactivated by CYP2E1 to TA sulfoxide (TASO), and to the highly reactive sulfdioxide (TASO(2)), which initiates hepatic necrosis by covalent binding. Previously, we have established that TA exhibits saturation toxicokinetics over a 12-fold dose range, which explains the lack of dose-response for bioactivation-based liver injury. In vivo and in vitro studies indicated that the second step (TASO-->TASO(2)) of TA bioactivation is less efficient than the first one (TA-->TASO). The objective of the present study was to specifically test the saturation of the second step of TA bioactivation by directly administering TASO, which obviates the contribution from first step, i.e. TA-->TASO. Male SD rats were injected with low (50mg/kg, ip), medium (100mg/kg) and high (LD(70), 200mg/kg) doses of TASO. Bioactivation-mediated liver injury that occurs in the initial time points (6 and 12h), estimated by plasma ALT, AST and liver histopathology over a time course, was not dose-proportional. Escalation of liver injury thereafter was dose dependent: low dose injury subsided; medium dose injury escalated upto 36h before declining; high dose injury escalated from 24h leading to 70% mortality. TASO was quantified in plasma by HPLC at various time points after administration of the three doses. With increasing dose (i.e., from 50 to 200mg/kg), area under the curve (AUC) and C(max) increased more than dose proportionately, indicating that TASO bioactivation exhibits saturable kinetics. Toxicokinetics and initiation of liver injury of TASO are similar to that of TA, although TASO-initiated injury occurs at lower doses. These findings indicate that bioactivation of TASO to its reactive metabolite is saturable in the rat as suggested by previous studies with TA.

Dietary modulation of p-nonylphenol-induced polycystic kidneys in male Sprague-Dawley rats.

We had previously found that p-nonylphenol (NP) at 1000-2000 ppm in a soy- and alfalfa-free diet induced severe polycystic kidney disease (PKD) in both male and female pups exposed from gestation day 7 through postnatal day (PND) 50 and hypothesized that differences in dietary components contributed to the severity of lesions relative to those reported in other studies using similar doses of NP. The present study investigated the dietary modulation of NP-induced PKD using the same exposure regimen with 2000 ppm NP in four different diets: the natural ingredient soy- and alfalfa-free diet that had been used in the earlier study, Purina 5K96; two defined diets AIN-93G, designated AIN-CAS, and a modified AIN-93G with soy protein isolate replacing casein as the protein source (AIN-SPI); and the commonly used natural ingredient diet Purina 5001 (P5001). Serum isoflavone levels were negligible in animals fed the soy-free AIN-CAS and 5K96 diets and were 2- to 18-fold higher in animals fed P5001 than in those fed AIN-SPI. Consumption of P5001 was significantly greater than consumption of the other diets, and those animals fed P5001 were generally significantly heavier than animals receiving the other diets. NP significantly reduced body weight gain in male pups regardless of the diet fed. There was no evidence of NP-induced kidney toxicity in male pups at PND 2, 14, or 21 or in the dams. In PND 50 male pups, serum blood urea nitrogen was significantly elevated by NP in all diet groups. Urine volume and urinary N-acetyl beta-glucuronidase were significantly increased by NP in the soy-free 5K96 and AIN-CAS diet groups. Relative kidney weights were increased by NP in all diet groups except P5001, with the greatest increase in AIN-CAS and 5K96 diet groups. Microscopic evaluation of kidneys from the PND 50 males showed that NP induced PKD in all diet groups but with marked variation in the severity depending on the diet. PKD was severe in 100% of the NP-treated animals in the AIN-CAS and 5K96 groups, moderate in 88% of the AIN-SPI diet group, and mild in only 40% of the P5001 diet group. Thus, diet can significantly modulate the development of PKD induced by dietary NP in rats. Soy components, as well as other complex dietary factors, may account for the level of protection afforded by the P5001 diet.

Colchicine antimitosis causes progression of S-(1,2-dichlorovinyl)-L-cysteine-induced injury leading to acute renal failure and death in mice.

Objective of the present study was to test the importance of tissue repair in the final outcome of S-(1,2-dichlorovinyl)-L-cysteine (DCVC)-induced nephrotoxicity using colchicine (CLC) intervention. Male Swiss Webster (SW) mice were administered a normally nonlethal dose of DCVC (30 mg/kg, i.p.) on day 0 and CLC (2 mg/kg, i.p.) at 42 and 66 h after administration of DCVC. The mice were observed for mortality and various renal injury and repair parameters were studied during a time course of 0-14 days. Administration of 30 mg DCVC/kg led to loss of renal architecture by day 1, which sustained until day 5, and regressed thereafter to reach normal architecture by day 10 resulting in 100% survival. Renal dysfunction as assessed by increases in plasma BUN and creatinine levels was concordant during this time course. Urinary volume increased significantly between days 10 and 14 with significant increases in urinary glucose concentrations on days 1-4. Calpain leakage increased from day 1 and remained so until day 5 before declining at later time points. In contrast, CLC intervention led to marked inhibition of S-phase DNA synthesis and 100% mortality by 120 h. H&E sections of kidneys revealed loss of renal architecture on day 1 which progressively worsened from day 2 to 4. Polyuria and glycosuria were evident during the first 2 and 3 days, respectively. Calpain immunohistochemistry revealed progressive leakage of calpain in the extracellular space during 2-4 days which lead to increased renal injury as evident from significant increases in calpain specific breakdown products (CSBPs) of alpha-fodrin during the same period of time. The group of mice receiving 2 mg CLC/kg alone showed a significant increase in urinary creatinine concentration on day 5. Neither the expression nor localization of aquaporin 1 was altered in any of the treatment groups. These results show that antimitotic intervention after DCVC-initiated renal injury leads to expansion and progression of that injury, which appears to be due to proteolytic destruction of neighboring cells mediated by calpain leaking out of necrosed renal tubular epithelial cells.

Prior administration of a low dose of thioacetamide protects type 1 diabetic rats from subsequent administration of lethal dose of thioacetamide.

Previously, we reported that an ordinarily non-lethal dose of thioacetamide (TA, 300 mg/kg) causes 90% mortality in type 1 diabetic rats due to inhibited liver tissue repair, whereas 30 mg TA/kg allows 100% survival due to stimulated although delayed tissue repair. Objective of this investigation was to test whether prior administration of a low dose of TA (30 mg/kg) would lead to sustainable stimulation of liver tissue repair in type 1 diabetic rats sufficient to protect from a subsequently administered lethal dose of TA. Therefore, in the present study, the hypothesis that preplacement of tissue repair by a low dose of TA (30 mg TA/kg, ip) can reverse the hepatotoxicant sensitivity (autoprotection) in type 1 diabetic rats was tested. Preliminary studies revealed that a single intraperitoneal (ip) administration of TA causes 90% mortality in diabetic rats with as low as 75 mg/kg. To establish an autoprotection model in diabetic condition, diabetic rats were treated with 30 mg TA/kg (priming dose). Administration of priming dose stimulated tissue repair that peaked at 72h, at which time these rats were treated with a single ip dose of 75 mg TA/kg. Our results show that tissue repair stimulated by the priming dose enabled diabetic rats to overexpress, calpastatin, endogenous inhibitor of calpain, to inhibit calpain-mediated progression of liver injury induced by the subsequent administration of lethal dose, resulting in 100% survival. Further investigation revealed that protection observed in these rats is not due to decreased bioactivation. These studies underscore the importance of stimulation of tissue repair in the final outcome of liver injury (survival/death) after hepatotoxicant challenge. Furthermore, these results also suggest that it is possible to stimulate tissue repair in diabetics to overcome the enhanced sensitivity of hepatotoxicants.

Database composition can affect the structure-activity relationship prediction.

The percent active (A) and inactive (I) chemicals in a database can directly affect the sensitivity (% active chemicals predicted correctly) and specificity (% inactive chemicals predicted correctly) of structure-activity relationship (SAR) analyses. Subdividing the National Center for Toxicological Research (NCTR) liver cancer database (NCTRlcdb) into various A/I ratios, which varied from 0.2 to 5.5, resulted in sensitivity/specificity ratios that varied from 0.1 to 6.5. As percent active chemicals increased (increasing A/I ratio), the sensitivity rose, the specificity decreased, and the concordance (% total chemicals predicted correctly) remained fairly constant. The numbers of chemicals in the various data sets ranged from 187 to 999 and appeared to have no affect on any of the 3 predictors of sensitivity, specificity, or concordance.

MicroRNA changes, activation of progenitor cells and severity of liver injury in mice induced by choline and folate deficiency.

Dietary deficiency in methyl-group donors and cofactors induces liver injury that resembles many pathophysiological and histopathological features of human nonalcoholic fatty liver disease (NAFLD), including an altered expression of microRNAs (miRNAs). We evaluated the consequences of a choline- and folate-deficient (CFD) diet on the expression of miRNAs in the livers of male A/J and WSB/EiJ mice. The results demonstrate that NAFLD-like liver injury induced by the CFD diet in A/J and WSB/EiJ mice was associated with marked alterations in hepatic miRNAome profiles, with the magnitude of miRNA expression changes being greater in WSB/EiJ mice, the strain characterized by the greatest severity of liver injury. Specifically, WSB/EiJ mice exhibited more prominent changes in the expression of common miRNAs as compared to A/J mice and distinct miRNA alterations, including the overexpression of miR-134, miR-409-3p, miR-410 and miR-495 miRNAs that were accompanied by an activation of hepatic progenitor cells and fibrogenesis. This in vivo finding was further confirmed by in vitro experiments showing an overexpression of these miRNAs in undifferentiated progenitor hepatic HepaRG cells compared to in fully differentiated HepaRG cells. Additionally, a marked elevation of miR-134, miR-409-3p, miR-410 and miR-495 was found in plasma of WSB/EiJ mice fed the CFD diet, while none of the miRNAs was changed in plasma of A/J mice. These findings suggest that miRNAs may be crucial regulators responsible for the progression of NAFLD and may be useful as noninvasive diagnostic indicators of the severity and progression of NAFLD.

Ochratoxin A induces oxidative DNA damage in liver and kidney after oral dosing to rats.

The nephrotoxic/carcinogenic mycotoxin ochratoxin A (OTA) occurs as a contaminant in food and feed and may be linked to human endemic Balkan nephropathy. The mechanism of OTA-derived carcinogenicity is still under debate, since reactive metabolites of OTA and DNA adducts have not been unambiguously identified. Oxidative DNA damage, however, has been observed in vitro after incubation of mammalian cells with OTA. In this study, we investigated whether OTA induces oxidative DNA damage in vivo as well. Male F344 rats were dosed with 0, 0.03, 0.1, 0.3 mg/kg bw per day OTA for 4 wk (gavage, 7 days/wk, five animals per dose group). Subsequently, oxidative DNA damage was determined in liver and kidney by the comet assay (single cell gel electrophoresis) with/without use of the repair enzyme formamido-pyrimidine-DNA-glycosylase (FPG). The administration of OTA had no effect on basic DNA damage (determined without FPG); however, OTA-mediated oxidative damage was detected with FPG treatment in kidney and liver DNA of all dose groups. Since the doses were in a range that had caused kidney tumors in a 2-year carcinogenicity study with rats, the oxidative DNA damage induced by OTA may help to explain its mechanism of carcinogenicity. For the selective induction of tumors in the kidney, increased oxidative stress in connection with severe cytotoxicity and increased cell proliferation might represent driving factors.

Dietary modulation of 7,12-dimethylbenz[a]anthracene (DMBA)-induced adrenal toxicity in female Sprague-Dawley rats.

In this study, dietary modulation of 7,12-dimethylbenz[a]anthracene (DMBA)-induced adrenal toxicity in rats was investigated. Beginning at postnatal day (PND) 21, female Sprague-Dawley rats were fed either soy-containing NIH-31 diet or soy- and alfalfa-free 5K96 diet. On the first day of diestrus when the animals were PND 50 +/- 5, rats received either an oral dose of 80 mg/kg DMBA or sesame oil, the vehicle, and were sacrificed at 24, 36, or 48 h after treatment. Apoptosis was manifested at 24 and 36 h after DMBA treatment in the zona reticularis (ZR) and the zona fasciculata (ZF) of the adrenal cortex; this was followed by severe hemorrhagic necrosis at 48 h. DMBA-induced apoptosis, evaluated by the TUNEL assay, immunohistochemical analysis of activated caspase 3, and the ratio of expression of pro-apoptotic Bax to anti-apoptotic Bcl2, was greater in rats fed NIH-31 diet relative to rats fed 5K96 diet at 24 h after treatment. Four of six DMBA-treated rats fed 5K96 diet had severe adrenal necrosis by 48 h, whereas this lesion was present in only two of six DMBA-treated rats fed NIH-31 diet. DMBA also caused a significant decrease of serum corticosterone relative to controls at 48 h in rats fed 5K96 diet. The present study indicated that diet modulates DMBA-induced adrenal toxicity in female rats, with increased apoptosis early and reduced necrosis later in rats fed a soy-containing diet.