Cytotoxicity In LLC-PK1 Cells Research Articles

Anti-Apoptotic and Antioxidant Effects of 3-Epi-Iso-Seco-Tanapartholide Isolated from Artemisia Argyi Against Iodixanol-Induced Kidney Epithelial Cell Death.

Iodixanol is a non-ionic iso-osmolar contrast agent, but it is a risk factor for kidney damage and increases morbidity and mortality. In this study, we investigated the effect of 9 sesquiterpenes isolated from mugwort (Artemisia argyi) in contrast agent-induced cytotoxicity in LLC-PK1 cells. Cells were exposed to nine sesquiterpene compounds for 2 h, followed by incubation with iodixanol for 3 h. Cell viability was assessed using the Ez-Cytox assay. The level of reactive oxygen species was measured using 2′,7′-dichlorodihydrofluorescein diacetate staining. Apoptotic cell death was detected using annexin V/PI staining. In addition, immunofluorescence staining and western blotting were performed using antibodies against proteins related to apoptosis, oxidative stress, and MAPK pathways. The most effective 3-epi-iso-seco-tanapartholide (compound 8) among the 9 sesquiterpene compounds protected LLC-PK1 cells from iodixanol-induced cytotoxicity, oxidative stress, and apoptotic cell death. Pretreatment with compound 8 reversed iodixanol-induced increases in the expression of JNK, ERK, p38, Bax, caspase-3, and caspase-9. It also reversed the iodixanol-induced decrease in Bcl-2 expression. Furthermore, pretreatment with compound 8 caused nuclear translocation of Nrf2 and upregulated HO-1 via the Nrf2 pathway in iodixanol-treated LLC-PK1 cells. Thus, we demonstrated here that compound 8 isolated from A. argyi has the potential to effectively prevent iodixanol-induced kidney epithelial cell death via the caspase-3/MAPK pathways and HO-1 via the Nrf2 pathway.

Protective Effect of Phenolic Compounds Isolated from Mugwort (Artemisia argyi) against Contrast-Induced Apoptosis in Kidney Epithelium Cell Line LLC-PK1.

We investigated whether 14 phenolic compounds isolated from Artemisia argyi could prevent the apoptotic damage caused by iodixanol, an iodinated contrast agent, on LLC-PK1 cells. Iodixanol was used to induce cytotoxicity in LLC-PK1 cells. Apoptotic cell death was observed as the fluorescence intensity emitted by annexin V and Hoechst 33342 stains. Western blotting was used to detect specific proteins. Seven phenolic compounds protected against iodixanol-induced LLC-PK1 cell death in a concentration-dependent manner. Among them, methyl caffeate exerted the strongest protective effect, and co-treatment with 50 and 100 μM methyl caffeate decreased intracellular reactive oxygen species elevated by 25 mg/mL iodixanol. In addition, the treatment of LLC-PK1 cells with iodixanol resulted in an increase in apoptotic cell death, which decreased by co-treatment with methyl caffeate. Iodixanol caused a cytotoxicity-related increase in the phosphorylation of extracellular-signal-regulated kinase, c-Jun N-terminal kinase, and P38; and a similar increase in the expression levels of kidney injury molecule-1 and cleaved caspase-3. However, the up-regulation of these proteins was reversed by co-treatment with methyl caffeate. These findings suggest that phenolic compounds isolated from A. argyi play an important role in protecting kidney epithelium cells against apoptotic damage caused by iodixanol.

Renoprotective Effects of Hypoxylonol C and F Isolated from Hypoxylon truncatum against Cisplatin-Induced Cytotoxicity in LLC-PK1 Cells.

Although cisplatin is the standard platinum-based anticancer drug used to treat various solid tumors, it can cause damage in normal kidney cells. Protective strategies against cisplatin-induced nephrotoxicity are, therefore, clinically important and urgently required. To address this challenge, we investigated the renoprotective effects of Hypoxylon truncatum, a ball-shaped wood-rotting fungus. Chemical investigation of the active fraction from the methanol extract of H. truncatum resulted in the isolation and identification of the renoprotective compounds, hypoxylonol C and F, which ameliorated cisplatin-induced nephrotoxicity to approximately 80% of the control value at 5 μM. The mechanism of this effect was further investigated using hypoxylonol F, which showed a protective effect at the lowest concentration. Upregulated phosphorylation of p38, extracellular signal-regulated kinases, and c-Jun N-terminal kinases following cisplatin treatment were markedly decreased after pre-treatment with hypoxylonol F. In addition, the protein expression level of cleaved caspase-3 was significantly reduced after co-treatment with hypoxylonol F. These results show that blocking the mitogen-activated protein kinase signaling cascade plays a critical role in mediating the renoprotective effect of hypoxylonol F isolated from H. truncatum fruiting bodies.

Effectiveness of Novel Imidazole-Dioxolane Heme Oxygenase Inhibitors in Renal Proximal Tubule Epithelial Cells

To enhance our understanding of the physiological roles of heme oxygenase (HO) isozymes, HO-1 (inducible) and HO-2 (constitutive), we developed novel imidazole-based HO inhibitors. Unlike the metalloporphyrins, these imidazole-dioxolane compounds are selective for the in vitro inhibition of HO with minimal effects on other heme-dependent enzymes such as nitric oxide synthase and soluble guanylyl cyclase. In the current study, we tested the hypothesis that these novel HO inhibitors are effective in intact cells by extending their application to cultured, renal proximal tubule epithelial cells (LLC-PK1). HO-1 and HO-2 protein expression was enhanced by pretreatment of cells with hemin, transduction with adenovirus encoding human HO-1, and transfection with cDNA for HO-2, respectively. Total HO activity was measured by determining the formation of carbon monoxide (CO), whereas cell viability and apoptosis were measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the expression of activated caspase-3. Gliotoxin/tumor necrosis factor-alpha (TNF-alpha) produced cytotoxicity in wild-type LLC-PK1 cells (P < 0.05) but not in HO-1 and HO-2 overexpressing or wild type cells pretreated with hemin (10 microM). The presence of imidazole-dioxolane HO inhibitors (2-25 microM) decreased cell viability (P < 0.05). A CO-releasing molecule reversed, in a dose-dependent manner, the cytotoxic effects and caspase-3 activation induced by the combination of gliotoxin/TNF-alpha and the HO inhibitors, suggesting an important role for CO in protection against renal toxicity. These data demonstrate a protective role of both HO-1 and HO-2 against gliotoxin/TNF-alpha-induced cytotoxicity in LLC-PK1 cells. The novel imidazole-dioxolane compounds can be used as effective inhibitors of HO activity in cell culture.

S-allylcysteine scavenges singlet oxygen and hypochlorous acid and protects LLC-PK 1 cells of potassium dichromate-induced toxicity

It has been found that S-allylcysteine (SAC), a garlic-derived compound, has in vivo and in vitro antioxidant properties. In addition, it is known that SAC is able to scavenge different reactive oxygen or nitrogen species including superoxide anion ( O 2 - ), hydrogen peroxide (H 2O 2), hydroxyl radical (OH ), and peroxynitrite anion (ONOO −) although the IC 5O values for each reactive species has not been calculated and the potential ability of SAC to scavenge singlet oxygen ( 1O 2) and hypochlorous acid (HOCl) has not been explored. The purposes of this work was (a) to explore the potential ability of SAC to scavenge 1O 2 and HOCl, (b) to further characterize the O 2 - , H 2O 2, OH , and ONOO − scavenging ability of SAC by measuring the IC 50 values using in vitro assays, and (c) to explore the potential ability of SAC to ameliorate the potassium dichromate (K 2Cr 2O 7)-induced cytotoxicity in LLC-PK1 cells in which oxidative stress is involved. The scavenging activity was compared against the following reference compounds: N-acetylcysteine for O 2 - , sodium pyruvate for H 2O 2, dimethylthiourea for OH , lipoic acid and glutathione for 1O 2, lipoic acid for HOCl, and penicillamine for ONOO −. It was found that SAC was able to scavenge concentration-dependently all the species assayed with the following IC 5O (mean ± SEM, mM): O 2 - (14.49 ± 1.67), H 2O 2 (68 ± 1.92), OH (0.68 ± 0.06), 1O 2 (1.93 ± 0.27), HOCl (2.86 ± 0.15), and ONOO − (0.80 ± 0.05). When the ability of SAC to scavenge these species was compared to those of the reference compounds it was found that the efficacy of SAC (a) to scavenge O 2 - , H 2O 2, OH , and ONOO − was lower, (b) to scavenge HOCl was similar, and (c) to scavenge 1O 2 was higher. In addition, it was found that SAC was able to prevent K 2Cr 2O 7-induced toxicity in LLC-PK1 cells in culture. It was showed for the first time that SAC is able to scavenge 1O 2 and HOCl and to ameliorate the K 2Cr 2O 7-induced toxicity.

An in-vitro model of the effects of pH on cisplatin-induced nephrotoxicity

2077 Background: There is evidence that acidic conditions potentiate the cytotoxicity of Cisplatin (Cp) (F. Tanaka et al, Hearing Research: 177, 2003, 21–31). However, little is known about the effects of pH on Cp nephrotoxicity in humans. It was indicated that the proximal renal tubules in humans are more affected by Cp cytotoxicity than the distal renal tubules (G. Daugaard et al, Clin Pharmacol Ther.: 44(2), 1988,164–172). We hypothesize that pH variations in renal tubules are important modulators of Cp nephrotoxicity. Methods: LLC-PK1 (porcine proximal) and MDCK (canine distal) renal tubular epithelium cells were used as in-vitro models to investigate the effect of pH variations on Cp-induced nephrotoxicity. The IC50 of Cp at different pHs after one-hour exposure was determined for these two cell lines using the MTT assay. For LLC-PK1 cells, C-14 thymidine assay was used to examine the effect of Cp on DNA synthesis, and Platinum (Pt) uptake was measured by atomic absorption spectroscopy. Similar experiments are ongoing for MDCK cells. Results: The IC50 of Cp for LLC-PK1 cells at pH 6.0, was 33 μM Cp. The IC50s for MDCK cells was 75 μM (n=3, P< 0.005, r2=0.98). The table below shows the results of LLC-PK1 cells as a function of extracellular pH (pHe) (n=3, P<0.005). Standard errors are not listed, to save space. The highest inhibition in DNA synthesis (12%±3 SD, P<0.0001), and the highest uptake of platinum (Pt) (180ng/106 cells) were detected at pH 6.0 compared to the other pH values tested. Conclusions: These cells developed maximal Cp-induced cytotoxicity at pHe=6.0. This cytotoxicity in LLC-PK1 cells is correlated with intracellular Cp uptake, and with inhibition of DNA synthesis. If impairment of DNA synthesis is ultimately found to be the mechanism of clinical Cp-induced nephrotoxicity, then strategies can be developed to overcome this process, and improve the therapeutic index of Cp. No significant financial relationships to disclose.

GLUTATHIONE, ALBUMIN, CYSTEINE, AND CYS-GLY EFFECTS ON TOXICITY AND ACCUMULATION OF MERCURIC CHLORIDE IN LLC-PK1 CELLS

Speciation plays a profound if not dominant role in both transport and toxicity of Hg(II). Hg(II) has a high affinity for sulfhydryl groups. The formation constant for Hg2+ and the anionic form of a sulfhydryl group R-S- is 1010 higher than that for the carboxyl or amino groups. The kidneys are the target organ for Hg(II) toxicity and the primary site of Hg(II) accumulation. Sulfhydryl groups have been implicated in both transport and nephrotoxicity; however, the role endogenous thiol compounds play in these parameters is not clear. The roles that albumin, glutathione, and the glutathione-derived complexes cysteinylglycine and L-cysteine play in toxicity and accumulation of HgCl2 were studied in LLC-PK1 cells incubated with different Hg(II):thiol ratios. In cysteine-containing medium, almost all 1:2 Hg(II):thiol complexes protected against Hg(II) toxicity up to 120 muM Hg, increased membrane-bound Hg(II), and decreased intracellular Hg(II) accumulation. In cysteine-free medium, all 1:1 Hg(II):thiol complexes were as toxic as uncomplexed Hg(II), and almost all 1:2 Hg(II):thiol complexes protected at 20 muM Hg, except albumin, which protected at 20 muM Hg. In cysteine-free but cystine-containing medium, two 1:1 Hg(II):thiol complexes were toxic at 80 muM Hg and two provided complete protection. All 1:2 complexes provided protection at 80-160 muM Hg. This investigation used defined media to demonstrate that mercury cytotoxicity in LLC-PK1 cells was dependent on Hg(II) concentration, the ligand, and the presence of a cysteine source for the cells. These effects were only partially explained by intracellular Hg(II) levels.

Role of cytochrome P-450 as a source of catalytic iron in cisplatin-induced nephrotoxicity

Iron plays a role in free radical-mediated tissue injury, including cisplatin-induced nephrotoxicity. However, the source of iron (catalyzing free radical reactions) is not known. We examined the role of cytochrome P-450 as a source of catalytic iron in cisplatin-induced nephrotoxicity both in vivo and in vitro. Cisplatin-induced acute renal failure was produced in rats by intraperitoneal injection of cisplatin (10 mg/kg body wt). Piperonyl butoxide, a cytochrome P-450 inhibitor, was administered intraperitoneally (400 mg/kg body wt twice at 48-hr intervals) prior to cisplatin injection. The effects of cisplatin in the absence or presence of piperonyl butoxide on the belomycin-detectable iron, cytochrome P-450 content in the kidney, and renal functional and histological changes were evaluated. In an in vitro study, the effect of cytochrome P-450 inhibitors, cimetidine or piperonyl butoxide, on cisplatin-induced cytotoxicity and catalytic iron release from LLC-PK1 cells was examined. In cisplatin-treated rats, there was a marked decrease in the cytochrome P-450 content specifically in the kidney, accompanied by increased bleomycin-detectable iron content in the kidney. Piperonyl butoxide prevented cisplatin-induced loss of cytochrome P-450 as well as the increase of bleomycin-detectable iron in the kidney, along with both functional and histological protection. Both cimetidine and piperonyl butoxide prevented cisplatin-induced increase in bleomycin-detectable iron and cytotoxicity in LLC-PK1 cells. Treatment of cimetidine did not affect cellular uptake of cisplatin. Cytochrome P-450, a group of heme proteins, may serve as a significant source of catalytic iron in cisplatin-induced nephrotoxicity.

In vitro and in vivo evidence suggesting a role for iron in cisplatin-induced nephrotoxicity

Cisplatin is a widely used antineoplastic agent that has nephrotoxicity as a major side effect. The underlying mechanism of this nephrotoxicity is still not well known. Iron has been implicated to play an important role in several models of tissue injury, presumably through the generation of hydroxyl radicals via the Haber-Weiss reaction or other highly toxic free radicals. In the present study we examined the catalytic iron content and the effect of iron chelators in an in vitro model of cisplatin-induced cytotoxicity in LLC-PK1 cells (renal tubular epithelial cells) and in an in vivo model of cisplatin-induced acute renal failure in rats. Exposure of LLC-PK1 cells to cisplatin resulted in a significant increase in bleomycin-detectable iron (iron capable of catalyzing free radical reactions) released into the medium. Concurrent incubation of LLC-PK1 cells with iron chelators including deferoxamine and 1,10-phenanthroline significantly attenuated cisplatin-induced cytotoxicity as measured by lactate dehydrogenase (LDH) release. Bleomycin-detectable iron content was also markedly increased in the kidney of rats treated with cisplatin. Similarly, administration of deferoxamine in rats provided marked functional (as measured by blood urea nitrogen and creatinine) and histological protection against cisplatin-induced acute renal failure. In a separate study, we examined the role of hydroxyl radical in cisplatin-induced nephrotoxicity. Incubation of LLC-PK1 cells with cisplatin caused an increase in hydroxyl radical formation. Hydroxyl radical scavengers, dimethyl sulfoxide, mannitol and benzoic acid, significantly reduced cisplatin-induced cytotoxicity and, treatment with dimethyl sulfoxide or dimethylthiourea provided significant protection against cisplatin-induced acute renal failure. Taken together, our data strongly support a critical role for iron in mediating tissue injury via hydroxyl radical (or a similar oxidant) in this model of nephrotoxicity.

Disassociation of oxidant-induced ATP depletion and DNA damage from early cytotoxicity in LLC-PK1 cells.

To determine the mechanism(s) of oxidant-mediated cell lysis in renal tubular epithelial cells, we determined ATP depletion, DNA damage, lipid peroxidation, and cytotoxicity in LLC-PK1 cells exposed to 500 microM hydrogen peroxide for 1 h with and without inhibitors of lipid peroxidation including a lazaroid compound, 2-methylaminochroman (2-MAC), and Trolox, a vitamin E analog. ATP levels were determined by luciferin-luciferase, DNA damage by the alkaline unwinding technique, lipid peroxidation by the generation of malondialdehyde, and early cytotoxicity (5 h) by the release of 51Cr, whereas late cytotoxicity (24 h) was determined by release of [3H]leucine from prelabeled cells. Cells exposed to 500 microM hydrogen peroxide demonstrated significant (P < 0.01) ATP depletion, DNA damage, and lipid peroxidation, followed by cell death at 5 h. Concentrations of 0.1-25 microM 2-MAC or 25-500 microM Trolox each markedly and significantly (P < 0.01) inhibited lipid peroxidation and early cytotoxicity but had little to no effect on ATP depletion or DNA damage. Thus oxidant-stressed cells remained intact for several hours despite significant ATP depletion and DNA damage when lipid peroxidation was inhibited with the antioxidant compounds. At 24 h, 2-MAG and Trolox had lost their protective effect, suggesting that mechanisms other than lipid peroxidation play a role in later cytotoxicity. We conclude that ATP depletion and DNA damage are not the primary mediators of early cytotoxicity following oxidant stress, whereas lipid peroxidation plays an central role in mediating early cytotoxicity following oxidant injury.

Structure-mutagenicity and structure-cytotoxicity studies on bromine-containing cysteine S-conjugates and related compounds.

Glutathione and cysteine S-conjugates of several haloalkenes are nephrotoxic and cytotoxic. Chloroalkene-derived S-(1-chloroalkenyl)-L-cysteine conjugates, but not fluoroalkene-derived S-(2,2-dihalo-1,1-difluorethyl)-L-cysteine conjugates, are mutagenic in the Ames test, although both types of S-conjugates are cytotoxic and nephrotoxic. Recent studies showed that bromine-containing S-(2,2-dihalo-1,1-difluoroethyl)-L-cysteine conjugates are mutagenic in the Ames test, thus challenging the generalization that S-(2,2-dihalo-1,1-difluoroethyl)-L-cysteine conjugates are not mutagenic. Hence a series of bromine-containing and bromine-lacking S-(2,2-dihalo-1,1-difluoroethyl)-L-cysteine conjugates was prepared, and their mutagenicity was assessed in the Ames test with Salmonella typhimurium TA2638 as the test strain. In addition, several indices of cytotoxicity, including cytotoxicity in LLC-PK1 cells, induction of Ca2+ release from pig kidney mitochondria, and DNA double-strand breaks in LLC-PK1 cells, were measured. The bromine-containing S-conjugates S-(2-bromo-2-chloro-1,1-difluoroethyl)-L- cysteine (BCD-FC), S-(2-bromo-1,1,2-trifluoroethyl)-L-cysteine (BTFC), and S-(2,2-dibromo-1,1-difluoroethyl)-L-cysteine (DBDFC) were mutagenic in the Ames test, whereas S-(2-chloro-1,1,2-trifluorethyl)-L-cysteine (CTFC), S-(2,2-dichloro-1,1-difluoroethyl)-L-cysteine (DCDFC), and S-(1,1,2,2-tetrafluoroethyl)-L-cysteine (TFC), which lack bromine, were not. BCDFC, BTFC, CTFC, DBDFC, and TFC were cytotoxic in LLC-PK1 cells, and their cytotoxicity was blocked by the cysteine conjugate beta-lyase inhibitor (aminooxy)acetic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrogen peroxide cytotoxicity in LLC-PK1 cells: a role for iron.

Reactive oxygen metabolites have been postulated to play an important role in both toxic and ischemic forms of acute renal tubular epithelial injury. In the present study, we examined the effect of enzymatically generated hydrogen peroxide on LLC-PK1 cells, a renal proximal tubule cell line. Exposure of LLC-PK1 cells to glucose and glucose oxidase (GO; which generates hydrogen peroxide) resulted in cytotoxicity (as measured by trypan blue exclusion) which was dose dependent and increased linearly over time to 81 +/- 5% at 180 minutes (8 +/- 1% at time 0; mean +/- SEM, N = 3 to 7). Catalase (which decomposes hydrogen peroxide) completely prevented the cytotoxicity, confirming that the toxicity was due to hydrogen peroxide production. To assess whether the hydrogen peroxide toxicity was a direct effect or mediated by other toxic oxygen metabolites, several scavengers of reactive oxygen metabolites and iron chelators were used. Superoxide dismutase (a scavenger of superoxide) had no effect. Deferoxamine (DFO), an iron chelator, provided marked protection (GO alone 45.9 +/- 4.4%; GO + DFO 13.0 +/- 2.0%; control 7.1 +/- 1.2%; N = 15 to 17, P less than 0.001). Pretreatment with DFO (1 hr, then 2 washes to remove DFO before GO addition) also markedly inhibited the cytotoxicity, suggesting that DFO's effect was due to iron chelation. Two other metal chelators (dihydroxybenzoic acid and 1,10-phenanthroline) also significantly decreased the GO-induced cytotoxicity. However, three of four hydroxyl radical scavengers used (mannitol, dimethyl sulfoxide, sodium benzoate) did not significantly decrease cell death. Only dimethylthiourea provided protection.(ABSTRACT TRUNCATED AT 250 WORDS)