The E-liquid flavoring vanillin alters energy and autophagic pathways in human proximal tubule (HK-2) epithelial cells

The use of flavored e-liquids in electronic nicotine delivery systems (ENDS) has become very popular in recent years, but effects of these products have not been well characterized outside the lung. In this study, acute exposure to the popular flavoring vanillin (VAN) was performed on human proximal tubule (HK-2) kidney cells. Cells were exposed to 0-1000 μM VAN for 24 or 48 h and cellular stress responses were determined. Mitochondrial viability using MTT assay showed a significant decrease between the control and 1000 μM group by 48 h. Seahorse XFp analysis showed significantly increased basal respiration, ATP production, and proton leak after 24 h exposure. By 48 h exposure, these parameters remained significantly increased in addition to non-mitochondrial respiration and maximal respiration. Glycolytic activity after 24 h exposure showed significant decreases in glycolysis, glycolytic capacity, glycolytic reserve, and non-glycolytic acidification. The autophagy markers microtubule-associated protein 1A/1B light chain 3 (LC3B-I and LC3B-II) were probed via western blotting. The ratio of LC3B-II/LC3B-I was significantly increased after 24 h exposure to VAN, but by 48 h this ratio significantly decreased. The mitophagy marker PINK1 showed an increasing trend at 24 h, and its downstream target Parkin was significantly increased between the control and 750 μM group only. Finally, the oxidative stress marker 4-HNE was significantly decreased after 48 h exposure to VAN. These results indicate that acute exposure to VAN in the kidney HK-2 model can induce energy and autophagic changes within the cell.

The e-liquid flavoring cinnamaldehyde induces cellular stress responses in human proximal tubule (HK-2) kidney cells

Flavored e-liquid use has become popular among e-cigarette users recently, but the effects of such products outside the lung are not well characterized. In this work, acute exposure to the popular flavoring cinnamaldehyde (CIN) was performed on human proximal tubule (HK-2) kidney cells. Cells were exposed to 0-100 µM CIN for 24-48 h and cellular stress responses were assessed. Mitochondrial viability via MTT assay was significantly decreased at 20 µM for 24 and 48 h exposure. Seahorse XFp analysis showed significantly decreased mitochondrial energy output at 20 µM by 24 h exposure, in addition to significantly reduced ATP Synthase expression. Seahorse analysis also revealed significantly decreased glycolytic function at 20 µM by 24 h exposure, suggesting inability of glycolytic processes to compensate for reduced mitochondrial energy output. Cleaved caspase-3 expression, a mediator of apoptosis, was significantly increased at the 24 h mark. C/EBP homologous protein (CHOP) expression, a mediator of ER-induced apoptosis, was induced by 48 h and subsequently lost at the highest concentration of 100 µM. This decrease was accompanied by a simultaneous decrease in its downstream target cleaved caspase-3 at the 48 h mark. The autophagy marker microtubule-associated protein 1 A/1B light chain 3 (LC3B-I and LC3B-II) expression was significantly increased at 100 µM by 24 h. Autophagy-related 7 (ATG7) protein and mitophagy-related proteins PTEN-induced putative kinase 1 (PINK1) and PARKIN expression were significantly reduced at 24 and 48 h exposure. These results indicate acute exposure to CIN in the kidney HK-2 model induces mitochondrial dysfunction and cellular stress responses.

An Improved Protocol for the Matrigel Duplex Assay: A Method to Measure Retinal Angiogenesis

Neovascular diseases of the retina, such as diabetic retinopathy (DR) and age-related macular degeneration (AMD), are proliferative retinopathies involving the growth of new blood vessels on the retina, which in turn causes impairment and potential loss of vision. A drawback of conventional angiogenesis assays is that they are not representative of the angiogenic processes in the retina. In the retina, the new blood vessels grow (from pre-existing blood vessels) and migrate into a non-perfused region of the eye including the inner limiting membrane of the retina and the vitreous, both of which contribute to vision loss. The Matrigel Duplex Assay (MDA) measures the migration of angiogenic capillaries from a primary Matrigel layer to a secondary Matrigel layer, which resembles the pathological angiogenesis in AMD and DR. The methodology of MDA is comprised of two steps. In the first step, the human retinal microvascular endothelial cells (HRMECs) are mixed with phenol red-containing Matrigel (in a 1:1 ratio) and seeded in the center of an 8-well chamber slide. After 24 h, a second layer of phenol red-free Matrigel is overlaid over the first layer. Over the course of the next 24 h, the HRMECs invade from the primary Matrigel layer to the secondary layer. Subsequently, the angiogenic sprouts are visualized by brightfield phase contrast microscopy and quantified by ImageJ software. The present manuscript measures the angiogenesis-inhibitory activity of the Src kinase inhibitor PP2 in primary HRMECs using the MDA. The MDA may be used for multiple applications like screening anti-angiogenic drugs, measuring the pro-angiogenic activity of growth factors, and elucidating signaling pathways underlying retinal angiogenesis in normal and disease states.

mTOR Regulation of N-Myc Downstream Regulated 1 (NDRG1) Phosphorylation in Clear Cell Renal Cell Carcinoma

The mechanistic target of rapamycin (mTOR) kinase is a component of two signaling complexes that are known as mTOR complex 1 (mTORC1) and mTORC2. We sought to identify mTOR-phosphorylated proteins that are differently expressed in clinically resected clear cell renal cell carcinoma (ccRCC) relative to pair-matched normal renal tissue. Using a proteomic array, we found N-Myc Downstream Regulated 1 (NDRG1) showed the greatest increase (3.3-fold) in phosphorylation (on Thr346) in ccRCC. This was associated with an increase in total NDRG1. RICTOR is a required subunit in mTORC2, and its knockdown decreased total and phospho-NDRG1 (Thr346) but not NDRG1 mRNA. The dual mTORC1/2 inhibitor, Torin 2, significantly reduced (by ~100%) phospho-NDRG1 (Thr346). Rapamycin is a selective mTORC1 inhibitor that had no effect on the levels of total NDRG1 or phospho-NDRG1 (Thr346). The reduction in phospho-NDRG1 (Thr346) due to the inhibition of mTORC2 corresponded with a decrease in the percentage of live cells, which was correlated with an increase in apoptosis. Rapamycin had no effect on ccRCC cell viability. Collectively, these data show that mTORC2 mediates the phosphorylation of NDRG1 (Thr346) in ccRCC. We hypothesize that RICTOR and mTORC2-mediated phosphorylation of NDRG1 (Thr346) promotes the viability of ccRCC cells.

Identification and Analysis of Antimicrobial Activities from a Model Moss Ceratodon purpureus

The emergence of bacterial drug resistance is often viewed as the next great health crisis of our time. While more antimicrobial agents are urgently needed, very few new antibiotics are currently in the production pipeline. Here, we aim to identify and characterize novel antimicrobial natural products from a model dioicous moss, Ceratodon purpureus. We collected secreted moss exudate fractions from two C. purpureus strains, male R40 and female GG1. Exudates from the female C. purpureus strain GG1 did not exhibit inhibitory activity against any tested bacteria. However, exudates from the male moss strain R40 exhibited strong inhibitory properties against several species of Gram-positive bacteria, including Staphylococcus aureus and Enterococcus faecium, though they did not inhibit the growth of Gram-negative bacteria. Antibacterial activity levels in C. purpureus R40 exudates significantly increased over four weeks of moss cultivation in liquid culture. Size fractionation experiments indicated that the secreted bioactive compounds have a relatively low molecular weight of less than 1 kDa. Additionally, the R40 exudate compounds are thermostable and not sensitive to proteinase K treatment. Overall, our results suggest that the bioactive compounds present in C. purpureus R40 exudates can potentially add new options for treating infections caused by antibiotic-resistant Gram-positive bacteria.

Anti-cancer activity of sustained release capsaicin formulations

Capsaicin (trans-8-methyl-N-vanillyl-6-noneamide) is a hydrophobic, lipophilic vanilloid phytochemical abundantly found in chili peppers and pepper extracts. Several convergent studies show that capsaicin displays robust cancer activity, suppressing the growth, angiogenesis and metastasis of several human cancers. Despite its potent cancer-suppressing activity, the clinical applications of capsaicin as a viable anti-cancer drug have remained problematic due to its poor bioavailability and aqueous solubility properties. In addition, the administration of capsaicin is associated with adverse side effects like gastrointestinal cramps, stomach pain, nausea and diarrhea and vomiting. All these hurdles may be circumvented by encapsulation of capsaicin in sustained release drug delivery systems. Most of the capsaicin-based the sustained release drugs have been tested for their pain-relieving activity. Only a few of these formulations have been investigated as anti-cancer agents. The present review describes the physicochemical properties, bioavailability, and anti-cancer activity of capsaicin-sustained release agents. The asset of such continuous release capsaicin formulations is that they display better solubility, stability, bioavailability, and growth-suppressive activity than the free drug. The encapsulation of capsaicin in sustained release carriers minimizes the adverse side effects of capsaicin. In summary, these capsaicin-based sustained release drug delivery systems have the potential to function as novel chemotherapies, unique diagnostic imaging probes and innovative chemosensitization agents in human cancers.

Antimicrobial Activities of Secondary Metabolites from Model Mosses

Plants synthetize a large spectrum of secondary metabolites with substantial structural and functional diversity, making them a rich reservoir of new biologically active compounds. Among different plant lineages, the evolutionarily ancient branch of non-vascular plants (Bryophytes) is of particular interest as these organisms produce many unique biologically active compounds with highly promising antibacterial properties. Here, we characterized antibacterial activity of metabolites produced by different ecotypes (strains) of the model mosses Physcomitrium patens and Sphagnum fallax. Ethanol and hexane moss extracts harbor moderate but unstable antibacterial activity, representing polar and non-polar intracellular moss metabolites, respectively. In contrast, high antibacterial activity that was relatively stable was detected in soluble exudate fractions of P. patens moss. Antibacterial activity levels in P. patens exudates significantly increased over four weeks of moss cultivation in liquid culture. Interestingly, secreted moss metabolites are only active against a number of Gram-positive, but not Gram-negative, bacteria. Size fractionation, thermostability and sensitivity to proteinase K assays indicated that the secreted bioactive compounds are relatively small (less than <10 kDa). Further analysis and molecular identification of antibacterial exudate components, combined with bioinformatic analysis of model moss genomes, will be instrumental in the identification of specific genes involved in the bioactive metabolite biosynthesis.

Spherical Invasion Assay: A Novel Method to Measure Invasion of Cancer Cells

The invasion of tumor cells into the neighboring blood vessels and lymph nodes is a vital step for distant metastasis. Traditionally, the invasive activity of growth factors (or the anti-invasive activity of drugs) is measured with the Boyden chamber assay. However, this assay has a few disadvantages like poor physiological relevance of transwell inserts and an inability to control chemokine gradients. The Boyden chamber assay is one of the most prevalent methods to measure the invasion of cancer cells. It would be advantageous to develop another assay that could validate the results of the Boyden chamber assay. With this in mind, our laboratory developed the spherical invasion assay (SIA) to measure the pro-invasive activity of human cancer cells. The SIA also circumvents some of the drawbacks of the Boyden chamber assay. The present manuscript measures the anti-invasive activity of the Src kinase inhibitor PP2 in A549 human non-small cell lung carcinoma (NSCLC) cells using the SIA. The SIA protocol is comprised of two steps. In the first step, A549 human NSCLC cells (treated or not with PP2) were mixed with Matrigel and seeded in the middle of an eight-well chamber slide. After 24 h, a second layer of Matrigel was overlaid over the first layer. Over the course of the next 24 h, the A549 cells invade from the primary to the secondary Matrigel layers. Subsequently, the cells are visualized by phase-contrast microscopy and the images obtained are quantified using ImageJ to calculate the anti-invasive activity of PP2 in A549 cells. The results of the SIA correlate well with Boyden chamber assays. The SIA may be adapted for multiple experimental designs, such as drug screening (to combat invasion and metastasis), measuring the pro-invasive activity of growth factors, and elucidating the signaling pathways underlying the pro-invasive/anti-invasive activity of biological modifiers. Graphic abstract: Diagrammatic illustration of the spherical invasion assay ( Hurley et al., 2017 ) . A. The first layer is comprised of human cancer cells mixed in a 1:1 suspension with Phenol Red containing Matrigel (represented as LAYER 1 in the figure). After 24 h, the cancer cells grow and extend up to the boundary of this first layer. B. A second layer of 1:1 solution Phenol Red-free Matrigel, in Phenol Red-free RPMI (represented as LAYER 2 in the figure) is added on top of the first Matrigel spot. The cells are incubated for 24 h at 37°C. C. Over these 24 h, the cancer cells invade from the primary layer into the secondary Matrigel layer. The chamber slides are observed by phase-contrast microscopy. D. A representative photograph of the images obtained by the SIA is shown. The black arrow indicates the cancer cells invading into the second layer of Matrigel. The dotted line represents the interface between the two layers. The distance to which the cells have traveled (into the secondary Matrigel layer) is measured at ten sites (for each photograph) in a randomized double-blind fashion by three independent observers, using NIH ImageJ Version 1.47. This process is repeated for three separate photographic fields per sample.

Nonpungent N-AVAM Capsaicin Analogues and Cancer Therapy

Capsaicin displays robust growth-inhibitory activity in multiple human cancers. However, the feasibility of capsaicin as a clinically relevant anticancer drug is hampered by its adverse side effects. This concern has led to extensive research focused on the isolation and synthesis of second-generation nonpungent capsaicin analogues with potent antineoplastic activity. A major class of nonpungent capsaicin-like compounds belongs to the N-acyl-vanillylamide (N-AVAM) derivatives of capsaicin (hereafter referred as N-AVAM capsaicin analogues). This perspective discusses the isolation of N-AVAM capsaicin analogues from natural sources as well as their synthesis by chemical and enzymatic methods. The perspective describes the pharmacokinetic properties and anticancer activity of N-AVAM capsaicin analogues. The signaling pathways underlying the growth-inhibitory effects of N-AVAM capsaicin analogues have also been highlighted. It is hoped that the insights obtained in this perspective will facilitate the synthesis of a second generation of N-AVAM capsaicin analogues with improved stability and growth-suppressive activity in human cancer.

Nephrotoxic Potential of Putative 3,5-Dichloroaniline (3,5-DCA) Metabolites and Biotransformation of 3,5-DCA in Isolated Kidney Cells from Fischer 344 Rats

The current study was designed to explore the in vitro nephrotoxic potential of four 3,5-dichloroaniline (3,5-DCA) metabolites (3,5-dichloroacetanilide, 3,5-DCAA; 3,5-dichlorophenylhydroxylamine, 3,5-DCPHA; 2-amino-4,6-dichlorophenol, 2-A-4,6-DCP; 3,5-dichloronitrobenzene, 3,5-DCNB) and to determine the renal metabolism of 3,5-DCA in vitro. In cytotoxicity testing, isolated kidney cells (IKC) from male Fischer 344 rats (~4 million/mL, 3 mL) were exposed to a metabolite (0–1.5 mM; up to 90 min) or vehicle. Of these metabolites, 3,5-DCPHA was the most potent nephrotoxicant, with 3,5-DCNB intermediate in nephrotoxic potential. 2-A-4,6-DCP and 3,5-DCAA were not cytotoxic. In separate experiments, 3,5-DCNB cytotoxicity was reduced by pretreating IKC with antioxidants and cytochrome P450, flavin monooxygenase and peroxidase inhibitors, while 3,5-DCPHA cytotoxicity was attenuated by two nucleophilic antioxidants (glutathione and N-acetyl-L-cysteine). Incubation of IKC with 3,5-DCA (0.5–1.0 mM, 90 min) produced only 3,5-DCAA and 3,5-DCNB as detectable metabolites. These data suggest that 3,5-DCNB and 3,5-DCPHA are potential nephrotoxic metabolites and may contribute to 3,5-DCA induced nephrotoxicity in vivo. In addition, the kidney can bioactivate 3,5-DCNB to toxic metabolites, and 3,5-DCPHA appears to generate reactive metabolites to contribute to 3,5-DCA nephrotoxicity. In vitro, N-oxidation of 3,5-DCA appears to be the primary mechanism of bioactivation of 3,5-DCA to nephrotoxic metabolites.

Radiocontrast Agent Diatrizoic Acid Induces Mitophagy and Oxidative Stress via Calcium Dysregulation

Contrast-induced acute kidney injury (CI-AKI) is the third most common cause of hospital associated kidney damage. Potential mechanisms of CI-AKI may involve diminished renal hemodynamics, inflammatory responses, and direct cytotoxicity. The hypothesis for this study is that diatrizoic acid (DA) induces direct cytotoxicity to human proximal tubule (HK-2) cells via calcium dysregulation, mitochondrial dysfunction, and oxidative stress. HK-2 cells were exposed to 0–30 mg I/mL DA or vehicle for 2–24 h. Conversion of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and trypan blue exclusion indicated a decrease in mitochondrial and cell viability within 2 and 24 h, respectively. Mitochondrial dysfunction was apparent within 8 h post exposure to 15 mg I/mL DA as shown by Seahorse XF cell mito and Glycolysis Stress tests. Mitophagy was increased at 8 h by 15 mg I/mL DA as confirmed by elevated LC3BII/I expression ratio. HK-2 cells pretreated with calcium level modulators BAPTA-AM, EGTA, or 2-aminophenyl borinate abrogated DA-induced mitochondrial damage. DA increased oxidative stress biomarkers of protein carbonylation and 4-hydroxynonenol (4HNE) adduct formation. Caspase 3 and 12 activation was induced by DA compared to vehicle at 24 h. These studies indicate that clinically relevant concentrations of DA impair HK-2 cells by dysregulating calcium, inducing mitochondrial turnover and oxidative stress, and activating apoptosis.

Capsaicinoids: Multiple effects on angiogenesis, invasion and metastasis in human cancers

Cancer progression is a complex multistep process comprising of angiogenesis of the primary tumor, its invasion into the surrounding stroma and its migration to distant organs to produce metastases. Nutritional compounds of the "capsaicinoid" family regulate angiogenesis, invasion and metastasis of tumors. Capsaicinoids display robust anti-angiogenic activity in both cell culture and mice models. However, conflicting reports exist about the effect of capsaicinoids on invasion of metastasis of cancers. While some published reports have described an anti-invasive and anti-metastatic role for capsaicinoids, others have argued that capsaicinoids stimulate invasion and metastasis of cancers. The present review article summarizes these findings involving the bioactivity of capsaicin in angiogenesis, invasion and metastasis of cancer. A survey of literature indicate that they are several articles summarizing the growth-inhibitory activity of capsaicinoids but few describe its effects on angiogenesis, invasion and metastasis in detail. Our review article fills this gap of knowledge. The discovery of a second generation of natural and synthetic capsaicin analogs (with anti-tumor activity) will pave the way to improved strategies for the treatment of several human cancers.

Capsaicinoids enhance chemosensitivity to chemotherapeutic drugs

Cytotoxic chemotherapy is the mainstay of cancer treatment. Conventional chemotherapeutic agents do not distinguish between normal and neoplastic cells. This leads to severe toxic side effects, which may necessitate the discontinuation of treatment in some patients. Recent research has identified key molecular events in the initiation and progression of cancer, promoting the design of targeted therapies to selectively kill tumor cells while sparing normal cells. Although, the side effects of such drugs are typically milder than conventional chemotherapies, some off-target effects still occur. Another serious challenge with all chemotherapies is the acquisition of chemoresistance upon prolonged exposure to the drug. Therefore, identifying supplementary agents that sensitize tumor cells to chemotherapy-induced apoptosis and help minimize drug resistance would be valuable for improving patient tolerance and response to chemotherapy. The use of effective supplementary agents provides a twofold advantage in combination with standard chemotherapy. First, by augmenting the activity of the chemotherapeutic drug it can lower the dose needed to kill tumor cells and decrease the incidence and severity of treatment-limiting side effects. Second, adjuvant therapies that lower the effective dose of chemotherapy may delay/prevent the development of chemoresistance in tumors. Capsaicinoids, a major class of phytochemical compounds isolated from chili peppers, have been shown to improve the efficacy of several anti-cancer drugs in cell culture and animal models. The present chapter summarizes the current knowledge about the chemosensitizing activity of capsaicinoids with conventional and targeted chemotherapeutic drugs, highlighting the potential use of capsaicinoids in novel combination therapies to improve the therapeutic indices of conventional and targeted chemotherapeutic drugs in human cancers.

Contrast Induced Acute Kidney Injury and Direct Cytotoxicity of Iodinated Radiocontrast Media on Renal Proximal Tubule Cells

The administration of intravenous iodinated radiocontrast media (RCM) to visualize internal structures during diagnostic procedures has increased exponentially since their first use in 1928. A serious side effect of RCM exposure is contrast-induced acute kidney injury (CI-AKI), which is defined as an abrupt and prolonged decline in renal function occurring 48-72 hours after injection. Multiple attempts have been made to decrease the toxicity of RCM by altering ionic strength and osmolarity, yet there is little evidence to substantiate that a specific RCM is superior in avoiding CI-AKI. RCM-associated kidney dysfunction is largely attributed to alterations in renal hemodynamics, specifically renal vasoconstriction; however, numerous studies indicate direct cytotoxicity as a source of epithelial damage. Exposure of in vitro renal proximal tubule cells to RCM has been shown to affect proximal tubule epithelium in the following manner: 1) changes to cellular morphology in the form of vacuolization; 2) increased production of reactive oxygen species, resulting in oxidative stress; 3) mitochondrial dysfunction, resulting in decreased efficiency of the electron transport chain and ATP production; 4) perturbation of the protein folding capacity of the endoplasmic reticulum (ER) (activating the unfolded protein response and inducing ER stress); and 5) decreased activity of cell survival kinases. The present review focuses on the direct cytotoxicity of RCM on proximal tubule cells in the absence of in vivo complications, such as alterations in renal hemodynamics or cytokine influence.

Rural and urban differences in prenatal exposure to essential and toxic elements

Excess or inadequate levels of inorganic ions may induce significant acute and long-term irreversible dysfunction in humans. The fetus and placenta are particularly vulnerable to toxins due to the immaturity of the blood-brain barrier and diminished biotransformation enzymatic activity. A comparative cross-sectional study was conducted on 172 pregnant women, 79 rural, and 93 urban. Umbilical cord blood was collected at the time of delivery and analyzed for 20 inorganic elements. Significant differences were found between urban and rural samples for two elements where copper (Cu) and molybdenum (Mo) were higher in urban samples. No marked differences between groups occurred for: arsenic, barium, cadmium, calcium, cobalt, lead, lithium, magnesium, manganese, mercury, selenium, strontium, or zinc. All samples were devoid of platinum, silver, thallium or uranium. Data demonstrated significant differences in urban and rural prenatal exposure to Cu and Mo. Further study is needed to determine if there is a causal link between neonatal outcomes and prenatal exposure to these elements.

Anticancer Activity of Natural and Synthetic Capsaicin Analogs

The nutritional compound capsaicin is the major spicy ingredient of chili peppers. Although traditionally associated with analgesic activity, recent studies have shown that capsaicin has profound antineoplastic effects in several types of human cancers. However, the applications of capsaicin as a clinically viable drug are limited by its unpleasant side effects, such as gastric irritation, stomach cramps, and burning sensation. This has led to extensive research focused on the identification and rational design of second-generation capsaicin analogs, which possess greater bioactivity than capsaicin. A majority of these natural capsaicinoids and synthetic capsaicin analogs have been studied for their pain-relieving activity. Only a few of these capsaicin analogs have been investigated for their anticancer activity in cell culture and animal models. The present review summarizes the current knowledge of the growth-inhibitory activity of natural capsaicinoids and synthetic capsaicin analogs. Future studies that examine the anticancer activity of a greater number of capsaicin analogs represent novel strategies in the treatment of human cancers.

Effects of cytochrome P450 single nucleotide polymorphisms on methadone metabolism and pharmacodynamics

Methadone is a synthetic, long-acting opioid with a single chiral center forming two enantiomers, (R)-methadone and (S)-methadone, each having specific pharmacological actions. Concentrations of (R)- and (S)-methadone above therapeutic levels have the ability to cause serious, life-threatening, and fatal side effects. This toxicity can be due in part to the pharmacogenetics of an individual, which influences the pharmacokinetic and pharmacodynamic properties of the drug. Methadone is primarily metabolized in the liver by cytochrome P450 (CYP) enzymes, predominately by CYP2B6, followed by CYP3A4, 2C19, 2D6, and to a lesser extent, CYP2C18, 3A7, 2C8, 2C9, 3A5, and 1A2. Single nucleotide polymorphisms (SNPs) located within CYPs have the potential to play an important role in altering methadone metabolism and pharmacodynamics. Several SNPs in the CYP2B6, 3A4, 2C19, 2D6, and 3A5 genes result in increases in methadone plasma concentrations, decreased N-demethylation, and decreased methadone clearance. In particular, carriers of CYP2B6*6/*6 may have a greater risk for detrimental adverse effects, as methadone metabolism and clearance are diminished in these individuals. CYP2B6*4, on the other hand, has been observed to decrease plasma concentrations of methadone due to increased methadone clearance. The involvement, contribution, and understanding the role of SNPs in CYP2B6, and other CYP genes, in methadone metabolism can improve the therapeutic uses of methadone in patient outcome and the development of personalized medicine.

Role of Free Radicals and Biotransformation in Trichloronitrobenzene-Induced Nephrotoxicity In Vitro

This study determined the comparative nephrotoxic potential of four trichloronitrobenzenes (TCNBs) (2,3,4-; 2,4,5-; 2,4,6-; and 3,4,5-TCNB) and explored the effects of antioxidants and biotransformation inhibitors on TCNB-induced cytotoxicity in isolated renal cortical cells (IRCC) from male Fischer 344 rats. IRCC were incubated with a TCNB up to 1.0 mM for 15–120 min. Pretreatment with an antioxidant or cytochrome P450 (CYP), flavin monooxygenase (FMO), or peroxidase inhibitor was used in some experiments. Among the four TCNBs, the order of decreasing nephrotoxic potential was approximately 3,4,5- > 2,4,6- > 2,3,4- > 2,4,5-TCNB. The four TCNBs exhibited a similar profile of attenuation of cytotoxicity in response to antioxidant pretreatments. 2,3,4- and 3,4,5-TCNB cytotoxicity was attenuated by most of the biotransformation inhibitors tested, 2,4,5-TCNB cytotoxicity was only inhibited by isoniazid (CYP 2E1 inhibitor), and 2,4,6-TCNB-induced cytotoxicity was inhibited by one CYP inhibitor, one FMO inhibitor, and one peroxidase inhibitor. All of the CYP specific inhibitors tested offered some attenuation of 3,4,5-TCNB cytotoxicity. These results indicate that 3,4,5-TCNB is the most potent nephrotoxicant, free radicals play a role in the TCNB cytotoxicity, and the role of biotransformation in TCNB nephrotoxicity in vitro is variable and dependent on the position of the chloro groups.

Capsaicin induces apoptosis in human small cell lung cancer via the TRPV6 receptor and the calpain pathway

Capsaicin, the pungent ingredient of chili peppers, displays potent anti-neoplastic activity in a wide array of human cancer cells. The present manuscript examines the signaling pathways underlying the apoptotic activity of capsaicin in human small cell lung cancer (SCLC) in vitro and in vivo. Studies in neuronal cells show that capsaicin exerts its biological activity via the transient receptor potential vanilloid (TRPV) superfamily of cation-channel receptors. The TRPV family is comprised of six members (TRPV1-6). Capsaicin is a known agonist of the TRPV1 receptor. We observed that capsaicin-induced apoptosis in human SCLC cells was mediated via the TRPV receptor family; however it was independent of TRPV1. Surprisingly, the apoptotic activity of capsaicin required the TRPV6 receptor. Depletion of TRPV6 receptor by siRNA methodology abolished the apoptotic activity of capsaicin in SCLC cells. Immunostaining and ELISA showed that TRPV6 receptor was robustly expressed on human SCLC tissues (from patients) and SCLC cell lines but almost absent in normal lung tissues. This correlates with our results that capsaicin induced very little apoptosis in normal lung epithelial cells. The pro-apoptotic activity of capsaicin was mediated by the intracellular calcium and calpain pathway. The treatment of human SCLC cells with capsaicin increased the activity of calpain 1 and 2 by threefold relative to untreated SCLC cells. Such calpain activation, in response to capsaicin, was downstream of the TRPV6 receptor. Taken together, our data provide insights into the mechanism underlying the apoptotic activity of capsaicin in human SCLCs.

Bioavailability of capsaicin and its implications for drug delivery

The dietary compound capsaicin is responsible for the "hot and spicy" taste of chili peppers and pepper extracts. It is a valuable pharmacological agent with several therapeutic applications in controlling pain and inflammation. Emerging studies show that it displays potent anti-tumor activity in several human cancers. On a more basic research level, capsaicin has been used as a ligand to activate several types of ion-channel receptors. The pharmacological activity of capsaicin-like compounds is dependent on several factors like the dose, the route of administration and most importantly on its concentration at target tissues. The present review describes the current knowledge involving the metabolism and bioavailability of capsaicinoids in rodents and humans. Novel drug delivery strategies used to improve the bioavailability and therapeutic index of capsaicin are discussed in detail. The generation of novel capsaicin-mimetics and improved drug delivery methods will foster the hope of innovative applications of capsaicin in human disease.

Resveratrol attenuates cisplatin renal cortical cytotoxicity by modifying oxidative stress

Cisplatin, a cancer chemotherapy drug, is nephrotoxic. The aim of this study was to investigate whether resveratrol (RES) reduced cisplatin cytotoxicity and oxidative stress. Rat renal cortical slices were pre-incubated 30min with 0 (VEH, ethanol) or 30μg/ml RES followed by 60, 90 or 120min co-incubation with 0, 75, or 150μg/ml cisplatin. Lactate dehydrogenase (LDH) leakage was unchanged at 60 and 90min by cisplatin. Cisplatin increased (p<0.05) LDH leakage at 120min which was protected by RES. Cisplatin induced oxidative stress prior to LDH leakage as cisplatin depressed glutathione peroxidase and superoxide dismutase (SOD) activity, increased lipid peroxidation, protein carbonyls and 4-hydroxynonenal (4-HNE) adducted proteins within 60min. RES failed to reverse glutathione (GSH) depression by cisplatin. In order to eliminated an extracellular interaction between RES and cisplatin, additional studies (RINSE studies) allowed a 30min RES uptake into slices, transfer of slices to buffer lacking RES, followed by 120min cisplatin incubation. RES in the RINSE studies prevented LDH leakage by cisplatin indicating that RES protection was not via a physical interaction with cisplatin in the media. These findings indicate that RES diminished cisplatin in vitro renal toxicity and prevented the development of oxidative stress.

Novel protective mechanisms for S-adenosyl-L-methionine against acetaminophen hepatotoxicity: improvement of key antioxidant enzymatic function

Acetaminophen (APAP) overdose leads to severe hepatotoxicity, increased oxidative stress and mitochondrial dysfunction. S-adenosyl-L-methionine (SAMe) protects against APAP toxicity at a mmol/kg equivalent dose to N-acetylcysteine (NAC). SAMe acts as a principle biological methyl donor and participates in polyamine synthesis which increase cell growth and has a role in mitochondrial protection. The purpose of the current study tested the hypothesis that SAMe protects against APAP toxicity by maintaining critical antioxidant enzymes and markers of oxidative stress. Male C57Bl/6 mice were treated with vehicle (Veh; water 15 ml/kg, ip), SAMe (1.25 mmol/kg, ip), APAP (250 mg/kg, ip), and SAMe+APAP (SAMe given 1 h following APAP). Liver was collected 2 and 4 h following APAP administration; mitochondrial swelling as well as hepatic catalase, glutathione peroxidase (GPx), glutathione reductase, and both Mn- and Cu/Zn-superoxide dismutase (SOD) enzyme activity were evaluated. Mitochondrial protein carbonyl, 3-nitrotyrosine cytochrome c leakage were analyzed by Western blot. SAMe significantly increased SOD, GPx, and glutathione reductase activity at 4 h following APAP overdose. SAMe greatly reduced markers of oxidative stress and cytochrome C leakage following APAP overdose. Our studies also demonstrate that a 1.25 mmol/kg dose of SAMe does not inhibit CYP 2E1 enzyme activity. The current study identifies a plausible mechanism for the decreased oxidative stress observed when SAMe is given following APAP.

Characterization of a novel model for investigation of radiocontrast nephrotoxicity

OBJECTIVES

Radiocontrast agents are one of the most common causes of acute renal failure in the world. These agents are required for both diagnostic and therapeutic modalities of medical intervention, including computed tomography (CT), angiography and cardiac catheterization. Publications over the past 40 years support three potential mechanisms of toxicity: oxidative stress, haemodynamics and hyperosmolar effects. An in vitro model provides a rapid evaluation of cellular toxicity without the complications of haemodynamics. This study evaluated the renal toxicity of radiocontrast agents at clinically relevant concentrations.

METHODS

This study investigated the toxicity of two radiocontrast agents, diatrizoic acid (DA) and iothalamic acid (IA), using an in vitro model. Renal cortical slices isolated from F344 rats were incubated with 0-111 mg I/ml DA or IA.

RESULTS

Renal slices exposed to DA and IA showed toxicity as measured by increased lactate dehydrogenase (LDH) leakage at concentrations lower than previously published using isolated cell models. These data indicate that DA and IA are toxic to renal cortical slices, and this is a more sensitive model than previously used cell culture systems. DA and IA treatment failed to cause a significant decrease in total cellular glutathione or increase in percent glutathione disulphide (GSSG), implying that oxidative stress may not be an initial mechanism of toxicity. Finally, the addition of exogenous glutathione did provide complete protection from DA- and IA-induced LDH leakage.

CONCLUSION

These data validate the renal cortical slice in vitro model for investigation of radiocontrast nephrotoxicity. These studies further showed that glutathione was cytoprotective. Future research using this model is aimed at further characterization of radiocontrast nephrotoxicity, which may allow for improved prevention and treatment of radiocontrast-induced acute renal failure.

Mechanistic aspects of 4-amino-2,6-dichlorophenol-induced in vitro nephrotoxicity

4-Amino-2,6-dichlorophenol (ADCP) is a potent acute nephrotoxicant in vivo inducing prominent renal corticomedullary necrosis. In vitro, ADCP exposure increases lactate dehydrogenase (LDH) release from rat renal cortical slices at 0.05 mM or greater. The purpose of this study was to examine the ability of antioxidants, cytochrome P450 (CYP) and flavin adenine dinucleotide monooxygenase (FMO) activity modulators, indomethacin, glutathione and inhibitors of glutathione conjugate metabolism to attenuate ADCP cytotoxicity in vitro. Renal cortical slices prepared from untreated male Fischer 344 rats (N=4/group) were preincubated at 37 degrees C under a 100% oxygen atmosphere with an inhibitor or vehicle for 5-30 min. ADCP (0.05-0.5mM) or vehicle was added and incubations continued for 120 min. At the end of the incubation period, LDH release was measured as an index of nephrotoxicity. ADCP cytotoxicity was partially attenuated by ascorbate (1.0 or 2.0mM), but not by N,N'-diphenyl-p-phenylenediamine (DPPD), alpha-tocopherol or deferoxamine. Inhibitors of CYP (metyrapone, piperonyl butoxide and isoniazid) and FMO activity modulators (methimazole, N-octylamine) had no effect on ADCP cytotoxicity. Indomethacin or glutathione 1.0mM completely and partially blocked ADCP 0.1 and 0.5mM cytotoxicity, respectively. N-acetylcysteine, AOAA (an inhibitor of cysteine conjugate beta-lyase) and probenecid (an organic anion transport inhibitor), but not AT-125 (an inhibitor of gamma-glutamyl transferase), partially attenuated ADCP 0.1mM cytotoxicity. Overall, these results suggest that reactive metabolites may be produced from ADCP primarily via a co-oxidation-mediated mechanism. The difference in the ability of ascorbate and glutathione to attenuate ADCP-induced cytotoxicity in vitro in kidney cells could indicate that alkylation via the reactive benzoquinoneimine metabolite might be responsible for cytotoxicity rather than a free radical-mediated mechanism.

Nephrotoxicity induced by the R- and S-enantiomers of N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and their sulfate conjugates in male Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity characterized as polyuric renal failure and mediated via metabolites arising from oxidation of the succinimide ring. Recent findings have suggested that the stereochemical nature of NDPS metabolites may be an important factor in NDPS metabolite-induced nephrotoxicity. The purpose of the present study was to determine the role of stereochemistry in the in vivo nephrotoxicity induced by R-(+)- and S-(-)-N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (R- and S-NDHS) and the in vitro nephrotoxicity induced by their enantiomeric sulfate conjugates, R-(-)- and S-(+)-N-(3,5-dichlorophenyl)-2-hydroxysuccinimide-O-sulfate (R- and S-NSC). Male Fischer 344 rats (four rats/group) were administered intraperitoneally (i.p.) an enantiomer of NDHS (0.05, 0.1 or 0.2 mmol/kg) or vehicle, and renal function monitored for 48 h. R-NDHS (0.1 or 0.2 mmol/kg) had little effect on renal function. In contrast, S-NDHS (0.1 mmol/kg) induced marked nephrotoxicity. The nephrotoxic potential of R- and S-NSC (0.5, 0.75 or 1.0mM) was determined using freshly isolated rat renal cortical cells (IRCC, 3-4 x 10(6)cells/ml). Cytotoxicity was determined by measuring the release of lactate dehydrogenase (LDH) at the end of a 1h incubation period. The LDH release observed in these studies was similar between R- and S-NSC. These results indicate that stereochemistry is an important factor for NDPS metabolite nephrotoxicity and that the role of stereochemistry, at least for NSC, occurs at extra-renal sites.

Comparison of S-Adenosyl-l-methionine and N-Acetylcysteine Protective Effects on Acetaminophen Hepatic Toxicity

Nutraceuticals are widely used by the general public, but very little information is available regarding the effects of nutritional agents on drug toxicity. Excessive doses of acetaminophen (APAP, 4-hydroxyacetanilide) induce hepatic centrilobular necrosis. The naturally occurring substance S-adenosyl-l-methionine (SAMe) has been reported to reduce the hepatic toxicity of APAP. The present study was designed to investigate the hepatoprotective effects of SAMe in comparison to the clinically used antidote N-acetylcysteine (NAC). Male C57BL/6 mice were injected intraperitoneally (i.p.) with an equimolar dose (1.25 mmol/kg) of either SAMe or NAC just before APAP, and the groups were denoted SAMe+APAP and NAC+APAP, respectively. Mice were immediately injected i.p. with 300 mg/kg APAP, and hepatotoxicity was evaluated after 4 h. SAMe was more hepatoprotective than NAC at a dose of 1.25 mmol/kg as liver weight was unchanged by APAP injection in the SAMe+APAP group, whereas liver weight was increased in the NAC+APAP group. SAMe was more hepatoprotective for APAP toxicity than NAC, because alanine aminotransferase levels were lower in the SAMe+APAP. Pretreatment with SAMe maintained total hepatic glutathione (GSH) levels higher than NAC pretreatment before APAP, although total hepatic GSH levels were lower in the SAMe+APAP and NAC+APAP groups than the vehicle control values. Oxidative stress was less extensive in the SAMe+APAP group compared with the APAP-treated mice as indicated by Western blots for protein carbonyls and 4-hydroxynonenal-adducted proteins. In summary, SAMe reduced APAP toxicity and was more potent than NAC in reducing APAP hepatotoxicity.

Streptozotocin (STZ) diabetes enhances benzo(alpha)pyrene induced renal injury in Sprague Dawley rats

Information is lacking regarding the biological response to environmental chemicals in the context of pre-existing disease. Benzo(alpha)pyrene (BaP), a polycyclic aromatic hydrocarbon, is a byproduct of combustion that causes renal injury and elicits a nephropathic response. This study evaluated the nephrotoxicity of BaP in normoglycemic and diabetic rats. Female Sprague Dawley rats were divided into four groups: normoglycemic-vehicle (NV), normoglycemic-BaP (N-BaP), diabetic-vehicle (DV) and diabetic-BaP (D-BaP). Diabetes was induced by intraperitoneal (ip) injection of streptozotocin (60 mg/kg, 1 ml/kg). Rats were injected (ip) with vehicle or 10 mg/kg BaP (1 ml/kg) once per week for 5 weeks. Urinary protein and albumin, plasma creatinine and light microscopy were performed to assess the effects of BaP on kidney function. Diabetes was confirmed by plasma glucose levels >400 mg/dl in the DV and D-BaP groups. BaP increased kidney weight and blood urea nitrogen (BUN) levels in the D-BaP relative to the DV group. No change in BUN was observed following 5 weeks of BaP treatment in the normoglycemic animals, however, kidney weight was increased (p=0.013) in the N-BaP relative to the NV animals. STZ diabetes increased susceptibility to BaP mediated renal damage following repeated treatment for 5 weeks when compared to age matched normoglycemic rats.

Pyruvate reduces 4-aminophenol in vitro toxicity

Pyruvate has been observed to reduce the nephrotoxicity of some agents by maintaining glutathione status and preventing lipid peroxidation. This study examined the mechanism for pyruvate protection of p-aminophenol (PAP) nephrotoxicity. Renal cortical slices from male Fischer 344 rats were incubated for 30-120 min with 0, 0.1, 0.25 or 0.5 mM PAP in oxygenated Krebs buffer containing 0 or 10 mM pyruvate or glucose (1.28 or 5.5 mM). LDH leakage was increased above control by 0.25 and 0.5 mM PAP beginning at 60 min and by 0.1 mM PAP at 120 min. Pyruvate prevented an increase in LDH leakage at 60- and 120-min exposure to 0.1 and 0.25 mM PAP. Pyruvate also prevented a decline in ATP levels. Glucose (1.28 and 5.5 mM) provided less protection than pyruvate from PAP toxicity. Total glutathione levels were diminished by 0.1 and 0.25 mM PAP within 60 and 30 min, respectively. Pyruvate prevented the decline in glutathione by 0.1 mM PAP at both time periods and at 30 min for 0.25 mM PAP. Pyruvate reduced the magnitude of glutathione depletion by 0.25 mM PAP following a 60-min incubation. Glutathione disulfide (GSSG) levels in renal slices were increased at 60 min by exposure to 0.25 mM PAP, while pyruvate prevented increased GSSG levels by PAP. Pyruvate also reduced the extent of 4-hydroxynonenal (4-HNE)-adducted proteins present after a 90-min incubation with PAP. These results indicate that pyruvate provided protection for PAP toxicity by providing an energy substrate and reducing oxidative stress.

Pyruvate attenuates myoglobin in vitro toxicity

Myoglobinuria is a complication of crush injury as well as substance abuse. This study examined whether pyruvate modified myoglobin in vitro renal toxicity. Renal slices from Fischer-344 rats were incubated for 120 min with 0-12 mg/ml myoglobin. In an initial study, gluconeogenesis was stimulated by the addition of 10 mM pyruvate during the final 30 min. In all other studies, renal slices were incubated with myoglobin in the presence of 0 or 10 mM pyruvate for 120 min. Myoglobin increased lactate dehydrogenase (LDH) release and this was not modified by the presence of pyruvate for the last 30 min of the incubation. Myoglobin toxicity was reduced by coincubation of myoglobin with pyruvate for 120 min. LDH leakage was increased 1.2-, 1.7-, and 1.8-fold above control by 4, 10, and 12 mg/ml myoglobin, compared to 1.2, 1.3, and 1.3 fold in slices coincubated with 10 mM pyruvate, respectively. Myoglobin diminished adenosine triphosphate (ATP) levels but pyruvate maintained a 5x higher level of ATP within the slices. Glucose (10 mM) provided protection only for the low concentration (4 mg/ml) of myoglobin. Myoglobin induced oxidative stress while pyruvate prevented the rise in lipid peroxidation and glutathione disulfides by myoglobin. Myoglobin diminished total glutathione levels in pyruvate-treated tissue, but glutathione levels remained higher than tissues incubated in the absence of pyruvate. These results indicate that pyruvate reduced toxicity by preventing oxidative stress and via a supply of an energy substrate.

Characterization of myoglobin toxicity in renal cortical slices from Fischer 344 rats

Rhabdomyolysis is associated with acute renal failure. The following study first characterized myoglobin in vitro toxicity using renal cortical slices isolated from male Fischer 344 rats. This model provided interaction between various cells within the nephron and provides myoglobin access predominantly through the basolateral membrane. Second, this study examined the effect of deferoxamine (DFX) and glutathione on myoglobin toxicity to determine the role of radicals and iron. Renal cortical slices were incubated for 30-120 min with 0, 4, 10 or 12 mg/ml myoglobin. Myoglobin was pretreated with 4 mM ascorbic acid prior to addition to the slices to ensure that myoglobin was in its reduced state. In other experiments tissues were pretreated for 15 min with 0.1 mM of the iron chelator DFX or 30 min with 1 mM glutathione prior to co-incubation with myoglobin. Finally, slices were pretreated with 1 mM glutathione for 30 min, rinsed and incubated only with myoglobin. Early event changes occurred within a 60 min exposure and included a decline in pyruvate-stimulated gluconeogenesis, increased lipid peroxidation levels and decreased glutathione levels. Loss of ATP levels and increased lactate dehydrogenase (LDH) release required a 120 min exposure to myoglobin. DFX reduced myoglobin induced effects on LDH leakage but had no effect on gluconeogenesis suggesting that myoglobin toxicity had an iron dependent (LDH) and independent (gluconeogenesis) pathway. Pretreatment with glutathione provided complete protection and was mediated by intracellular events.

Characterization of myoglobin toxicity in renal cortical slices from Fischer 344 rats

Rhabdomyolysis is associated with acute renal failure. The following study first characterized myoglobin in vitro toxicity using renal cortical slices isolated from male Fischer 344 rats. This model provided interaction between various cells within the nephron and provides myoglobin access predominantly through the basolateral membrane. Second, this study examined the effect of deferoxamine (DFX) and glutathione on myoglobin toxicity to determine the role of radicals and iron. Renal cortical slices were incubated for 30-120 min with 0, 4, 10 or 12 mg/ml myoglobin. Myoglobin was pretreated with 4 mM ascorbic acid prior to addition to the slices to ensure that myoglobin was in its reduced state. In other experiments tissues were pretreated for 15 min with 0.1 mM of the iron chelator DFX or 30 min with 1 mM glutathione prior to co-incubation with myoglobin. Finally, slices were pretreated with 1 mM glutathione for 30 min, rinsed and incubated only with myoglobin. Early event changes occurred within a 60 min exposure and included a decline in pyruvate-stimulated gluconeogenesis, increased lipid peroxidation levels and decreased glutathione levels. Loss of ATP levels and increased lactate dehydrogenase (LDH) release required a 120 min exposure to myoglobin. DFX reduced myoglobin induced effects on LDH leakage but had no effect on gluconeogenesis suggesting that myoglobin toxicity had an iron dependent (LDH) and independent (gluconeogenesis) pathway. Pretreatment with glutathione provided complete protection and was mediated by intracellular events.

Increased sensitivity of the obese Zucker rat to deoxycorticosterone-salt-induced hypertension

OBJECTIVE

The objective of this study was to test the hypothesis that obesity increases the sensitivity of rats to experimentally induced hypertension.

DESIGN AND METHODS

To induce hypertension, unilaterally nephrectomized lean and obese Zucker rats were injected with 25 mg/kg of deoxycorticosterone acetate (DOCA) twice weekly for 5 weeks and given water containing 1% NaCl to drink. Unilaterally nephrectomized control rats were injected with vehicle and drank tap water. Systolic blood pressure (SBP) was measured by the tail cuff method. Renal histology and urinary albumin excretion were used to assess the effects of the experimental treatment on the kidney.

RESULTS

Obese rats exhibited a significant rise in SBP at 4 days after the start of DOCA-salt treatment. In contrast, SBP of DOCA-treated lean rats was not significantly elevated from pretreatment measurements until day 22. Moreover, SBP was significantly higher during the plateau phase of blood pressure development in obese DOCA-salt treated rats (196 mmHg) than in correspondingly treated lean rats (150 mmHg). Both obesity and DOCA-salt treatment promoted glomerulosclerosis and mild tubulointerstitial damage in the kidney with DOCA-salt treatment exacerbating the effect of obesity. Urinary albumin excretion was significantly greater in obese control rats compared with lean controls and in DOCA-treated obese rats relative to vehicle-treated obese rats.

CONCLUSION

Results of this study indicate that obese Zucker rats are more sensitive to mineralocorticoid-induced hypertension than lean rats. This study provides experimental evidence supporting the epidemiological findings that obesity is a risk factor for the development of hypertension.

Effect of three n-acetylamino acids on N-(3,5-dichlorophenyl)succinimide (NDPS) and ndps metabolite nephrotoxicity in Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity in mammals characterized as polyuric renal failure and proximal tubular necrosis. Recent studies have suggested that NDPS-induced nephrotoxicity may be mediated by metabolites arising from the nephrotoxic NDPS metabolites N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and/or N-(3,5-dichlorophenyl)-2-succinamic acid (2-NDHSA). The purpose of this study was to examine the effects of N-acetylcysteine (NAC), a nucleophilic agent, and two nonnucleophilic N-acetylamino acids, N-acetylserine (NAS) and N-acetylalanine (NAA), on NDPS and NDPS metabolite-induced nephrotoxicity. Male Fischer 344 rats (4-8/group) were administered intraperitoneally (ip) an N-acetylamino acid (1 mmol/kg) 2 h before an ip injection of NDPS (0.4 mmol/kg), NDHS (0.1 mmol/kg), 2-NDHSA (0.1 mmol/kg), or vehicle. Renal function was then monitored at 24 and 48 h. NAC pretreatment markedly attenuated NDPS-, NDHS-, and 2-NDHSA-mediated nephrotoxicity. The nonnucleophilic N-acetylamino acids (NAS, NAA) only partly reduced NDPS and NDHS nephrotoxicity, and they had little effect on 2-NDHSA nephrotoxicity. These results suggest that reactive NDPS metabolites may be formed from NDHS and 2-NDHSA and that nucleophilic substrates (e.g., NAC) may offer protection from NDPS-induced nephrotoxicity. However, mechanisms other than chemical neutralization of reactive NDPS metabolites may also be contributing to the attenuation of NDPS nephrotoxicity, since nonnucleophilic N-acetylamino acids (e.g., NAA) also provided some protection against NDPS and NDHS nephrotoxicity.

In vitro nephrotoxicity induced by chloronitrobenzenes in renal cortical slices from Fischer 344 rats

Chloronitrobenzenes are important chemical intermediates in the manufacture of industrial, agricultural and pharmaceutical agents. Toxicity induced by the various chloronitrobenzene isomers in vivo includes hematotoxicity, immunotoxicity, hepatotoxicity and nephrotoxicity. The purpose of the study was to determine the direct nephrotoxic effects of nitrobenzene and ten chlorinated nitrobenzene derivatives using renal cortical slices as the in vitro model. Renal cortical slices were prepared from kidneys of untreated, male Fischer 344 rats and incubated with nitrobenzene (1.0-5.0 mM), a chloronitrobenzene (0.5-5.0 mM) or vehicle for 2 h. At the end of the 2 h incubation, tissue gluconeogenesis capacity (pyruvate-stimulated gluconeogenesis) and lactate dehydrogenase (LDH) release were determined as measures of cellular function and cytotoxicity. Based on decreased pyruvate-stimulated gluconeogenesis and increased LDH release, the order of decreasing nephrotoxic potential was trichloronitrobenzenes>dichloronitrobenzenes>monochloronitrobenzenes>nitrobenzene. Among the mono- and dichloronitrobenzenes, 1-chloro-3-nitrobenzene and 3,4-dichloronitrobenzene were the most potent nephrotoxicants, while the two trichloronitrobenzenes tested exhibited similar nephrotoxic potentials. These results demonstrate that chloronitrobenzenes are directly nephrotoxic in vitro and that increasing the number of chloro groups increases the nephrotoxic potential of the resulting chloronitrobenzene derivative.

Characterization of 2-amino-4,5-dichlorophenol (2A45CP) in vitro toxicity in renal cortical slices from male Fischer 344 rats

2-Amino-4,5-dichlorophenol (2A45CP) is a major, aromatic ring hydroxylated metabolite of the renal toxicant, 3,4-dichloroaniline. 3,4-Dichloroaniline is nephrotoxic with primary damage located to the proximal tubules. The purpose of this study was to first characterize the in vitro toxicity of 2A45CP in renal cortical slices. Second, the effect of antioxidants and sulfhydryl containing agents on the severity of 2A45CP toxicity was explored since part of the mechanism of toxicity for aminophenols may involve redox cycling. Renal tissue was isolated from male Fischer 344 rats (190--220 g). Renal slices were rinsed three times for 3 min each in 5-ml Krebs buffer. Tissues were then incubated for 90--120 min with varying concentrations of 2A45CP between 0 and 0.5 mM. In a separate series of experiments, the slices (50--100 mg) were preincubated for 30 min with 1 mM dithiothreitol (DTT), 1 mM glutathione (GSH) or 2 mM ascorbic acid prior to exposure to 0, 0.05, 0.1 or 0.25 mM 2A45CP. 2A45CP produced a concentration and time dependent increase in LDH leakage from renal cortical slices. Total glutathione levels were diminished by 0.5 mM 2A45CP within 30 min. Renal slices incubated for 60 and 120 min with 0.05 and 0.1 mM 2A45CP had lower malondialdehyde levels than control. Pretreatment with DTT did not alter 2A45CP toxicity. Pretreatment of renal cortical slices with GSH or ascorbic acid reduced 2A45CP toxicity. These findings indicate that 2A45CP is directly toxic to renal cortical slices and that cytotoxicity is at least partially mediated by a reactive intermediate.

Role of stereochemistry in N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA) nephrotoxicity

The nephrotoxicity induced by the agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) is mediated through oxidative metabolites of NDPS. Oxidation of the succinimide ring in NDPS yields the nephrotoxic metabolites N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and its hydrolysis product N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA). The oxidation of NDPS on the succinimide ring also introduces an asymmetric carbon atom into these NDPS metabolites, so that R- and S- enantiomers of NDHS and 2-NDHSA are possible. The purpose of this study was to begin to explore the importance of the stereochemical orientation at the asymmetric carbon atom for the nephrotoxicity induced by NDPS metabolites. Male Fischer 344 rats were administered a single intraperitoneal (ip) injection of R-(+)- or S-(-)-2-NDHSA (0.05, 0.1 or 2.0 mmol/kg) or vehicle, and renal function was monitored for 48 h. R-2-NDHSA (0.1 mmol/kg) administration had little effect on renal function. R-2-NDHSA (0.2 mmol/kg) treatment induced mild diuresis on day 1, increased proteinuria, and a small increase in blood urea nitrogen (BUN) concentration, but no change in kidney weight or glucosuria. S-2-NDHSA (0.1 mmol/kg) induced marked nephrotoxicity as evidenced by diuresis on both post-treatment days, increased proteinuria, glucosuria, and increased kidney weight and BUN concentration. No evidence of hepatotoxicity was obtained in any treated group. Thus, the S-isomer of 2-NDHSA is a more potent nephrotoxicant than the R-isomer, and stereochemistry may play a role in NDPS metabolite-induced nephrotoxicity.

Gender differences in the potentiation of N-(3,5-dichlorophenyl)succinimide metabolite nephrotoxicity by phenobarbital

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces acute nephrotoxicity characterized as polyuric renal failure with proximal tubular necrosis. Phenobarbital pretreatment potentiates NDPS and N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS, a nephrotoxic metabolite of NDPS) nephrotoxicity in male rats. The purpose of this study was to determine the ability of phenobarbital pretreatment to potentiate (1) NDHS nephrotoxicity in female rats and (2) N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA, a nephrotoxic metabolite of NDHS) nephrotoxicity in male and female rats. Age-matched male and female Fischer 344 rats (4/group) were pretreated intraperitoneally (ip) with phenobarbital (75 mg/d, 3 d). At 24 h after the last injection of phenobarbital, an ip injection of NDHS (0.025 mmol/kg), 2-NDHSA (0.025 mmol/kg, females; 0.05 mmol/kg, males), or vehicle was given and renal function was monitored at 24 and 48 h post NDPS metabolite or vehicle. Additional groups received the NDPS metabolite or vehicle only and were also monitored for 48 h. In a separate experiment, male Fischer 344 rats were pretreated with piperonyl butoxide (PIBX, 1360 mg/kg) or the PIBX vehicle. 2-NDHSA (0.1 mmol/kg) or vehicle was administered (ip) 30 min after PIBX, and renal function was monitored for 24 h. Phenobarbital markedly potentiated 2-NDHSA nephrotoxicity in male rats as evidenced by increased kidney weight, increased blood urea nitrogen (BUN) concentration, and decreased tetraethylammonium (TEA) accumulation by renal cortical slices. PIBX had no effect on 2-NDHSA nephrotoxicity. Phenobarbital pretreatment did not markedly enhance the nephrotoxic potential of NDHS or 2-NDHSA in female rats. These results indicate that phenobarbital exhibits differential potentiation of NDPS metabolite nephrotoxicity in male and female rats and that the potentiation of 2-NDHSA nephrotoxicity observed in males is not due to cytochrome P-450-mediated oxidative biotransformation.

Sodium sulfate potentiates N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA) nephrotoxicity in the Fischer 344 rat

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity as its major toxicity in rats. Previous studies have shown that NDPS induces nephrotoxicity following oxidation of the succinimide ring to form N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and the hydrolysis product of NDHS, N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA). Our recent work found that sodium sulfate potentiated NDPS nephrotoxicity, suggesting that sulfate conjugation of NDPS metabolites might be a bioactivation step mediating NDPS nephrotoxicity. The purpose of this study was to determine if sodium sulfate also potentiated the nephrotoxicity of the two nephrotoxic metabolites of NDPS and further to see if sodium sulfate potentiated NDHS and 2-NDHSA nephrotoxicity to the same degree. Male Fischer 344 rats (4-16 rats/group) received an intraperitoneal (ip) injection of sodium sulfate (10 mg/kg) 20 min before a non-nephrotoxic dose (0.05 mmol/kg, ip) of NDHS or 2-NDHSA, or vehicle (12.5% dimethyl sulfoxide in sesame oil). Renal function was then monitored over 48 h. Sodium sulfate pretreatment potentiated the renal effects of a non-nephrotoxic dose of NDHS and 2-NDHSA to induce nephrotoxicity. Nephrotoxicity was characterized by diuresis, increased proteinuria, elevated blood urea nitrogen (BUN) concentration, increased kidney weight and proximal tubular necrosis. Differences in the potentiation of NDHS and 2-NDHSA nephrotoxicity by sodium sulfate were also observed as NDHS nephrotoxicity was potentiated to a lesser degree than 2-NDHSA-induced nephrotoxicity. These results support the likelihood that one or more sulfate conjugate(s) of NDPS metabolites contribute to NDPS nephrotoxicity.

Nephrotoxic potential of N-(3,5-dichloro-4-fluorophenyl)succinimide in Fischer 344 rats: comparison with N-(3,4,5-trichlorophenyl)succinimide

Numerous structure-nephrotoxicity relationship studies from our laboratory have demonstrated that N-(3,5-dichlorophenyl)succinimide (NDPS) is one of the most potent nephrotoxicants among the N-arylsuccinimides. The purpose of this study was to extend our previous structure-nephrotoxicity relationship studies by examining the effect of addition of a fluoro verses a chloro group at the 4-phenyl position in NDPS. Male Fischer 344 rats (four rats/group) received a single intraperitoneal (i.p.) injection of N-(3,5-dichloro-4-fluorophenyl)succinimide (NDCFPS) or N-(3,4,5-trichlorophenyl)succinimide (NTCPS)(0.4 or 0.8 mmol/kg) or vehicle, and renal function monitored at 24 and 48 h. NDCFPS did not induce significant nephrotoxicity at either dose tested. In contrast, NTCPS (0.4 or 0.8 mmol/kg) induced marked nephrotoxicity characterized by diuresis, increased proteinuria, glucosuria, elevated kidney weight and increased blood urea nitrogen (BUN) concentration. NTCPS also induced marked proximal tubular necrosis at both doses tested. Neither NDCFPS nor NTCPS induced hepatotoxicity at either dose tested. The results of these experiments indicate that addition of a fluoro group at the 4-position on the phenyl ring of NDPS produces a nonnephrotoxicant NDPS derivative (NDCFPS), while addition of a chloro group at this site produces an NDPS derivative with similar nephrotoxic potential to NDPS. The mechanism for this differential effect between 4-halophenyl substitution is unclear, but may result from increased hydrolysis of the succinimide ring and/or increased clearance of N-arylsuccinimide metabolites when a fluoro group is added to the 4-position of the phenyl ring.