Sang Kyu Lee

Hepatotoxic effect of 1-bromopropane and its conjugation with glutathione in male ICR mice

The hepatotoxic effects of 1-bromopropane (1-BP) and its conjugation with glutathione were investigated in male ICR mice. A single dose (1000 mg/kg, po) of 1-BP in corn oil to mice significantly increased serum activities of alanine aminotransferase and aspartate aminotransferase. Glutathione (GSH) content was dose-dependently reduced in liver homogenates 12 h after 1-BP treatment. In addition, 1-BP treatment dose-dependently increased levels of S-propyl GSH conjugate at 12 h after treatment, as measured by liquid chromatography-electrospray ionization tandem mass spectrometry. The GSH conjugate was maximally increased in liver at 6 h after 1-BP treatment (1000 mg/kg), with a parallel depletion of hepatic GSH content. Finally, 1-BP induced the production of malondialdehyde in liver. The present results suggest that 1-BP might cause hepatotoxicity, including lipid peroxidation via the depletion of GSH, due to the formation of GSH conjugates in male ICR mice.

The Effects of Rutaecarpine on the Pharmacokinetics of Acetaminophen in Rats

Rutaecarpine, an alkaloid originally isolated from the unripe fruit ofEvodia rutaecarpa, has been shown to be anti-inflammatory as it inhibits cyclooxygenase-2. It induces the activities of hepatic CYP 1A2, 2B, and 2E1 in rats. A possible interaction between rutaecarpine and acetaminophen (APAP) was investigated in male Sprague Dawley rats in the present study. When 25 mg/kg APAP was intravenously administered concurrently with 80 mg/kg rutaecarpine, the area under the curve of1H in plasma was significantly decreased when compared to that of APAP alone. When the rats were pre-treated orally with 40 and 80 mg/kg rutaecarpine for 3 days, the % value of Cmax, and area under the curve of acetaminophen-sulfate conjugate were significantly decreased to 56.4% and 61.7% of the vehicle control group, respectively. These results suggest that rutaecarpine might cause changes in the pharmacokinetic parameters of APAP in rats.

Nephrotoxic Potential and Toxicokinetics of Tetrabromobisphenol a in Rat for Risk Assessment

Tetrabromobisphenol A (TBBPA), one of the most widely used global brominated flame retardants, is used to improve fire safety of laminates in electrical and electronic equipment. To investigate the nephrotoxic potential of TBBPA and its toxicokinetic profile in rats, single-dose and daily 14-d repeated-dose toxicity studies at 200, 500, or 1000 mg/kg were performed. Several biochemical parameters were analyzed to evaluate nephrotoxicity of TBBPA. High-dose 1000 mg/kg TBBPA significantly elevated renal thiobarbituric acid-reactive substance (TBARS) levels, and superoxide dismutase (SOD) activity was increased at all 3 doses administered. This was associated with no change in the activity of catalase (CAT). Our results suggest that acute 1-d high-dose administration of TBBPA produced transient renal changes at 5 h. Subsequently, TBBPA in serum, urine, and kidney was determined by liquid chromatography–mass spectroscopy (LC/MS). Toxicokinetic studies indicated that TBBPA shows relatively a short half-life (7–9 h) and was eliminated almost completely in feces by 2 d. Based on the results from the 14-d repeated-dose study, TBBPA did not accumulate in the rat, and was eliminated in feces. The present results suggested that TBBPA may not be toxic to kidney, as the chemical is not bioavailable and is not present in renal tissue.

Role of Metabolism in Parathion-Induced Hepatotoxicity and Immunotoxicity

The objective of this study was to investigate whether metabolic activation of parathion by cytochrome P-450s (CYPs) was responsible for pesticide-induced hepatotoxicity and immunotoxicity. Initially, to investigate parathion metabolism in vitro, the production of paraoxon and p-nitrophenol, major metabolites of parathion, was determined by high-performance liquid chromatography (HPLC). Subsequently, metabolic fate and CYP enzymes involved in the metabolism of parathion were partially monitored in rat liver microsomes in the presence of the NADPH-generating system. Among others, phenobarbital (PB)-induced microsomes produced the metabolites paraoxon and p-nitrophenol to the greatest extent, indicating the involvement of CYP 2B in parathion metabolism. When female BALB/c mice were treated orally with 1, 4, or 16 mg/kg of parathion in corn oil once, parathion suppressed the antibody response to sheep red blood cells. To further investigate a possible role of metabolic activation by CYP enzymes in parathion-induced toxicity, female BALB/c mice were pretreated intraperitoneally with 40 mg/kg PB for 3 d, followed by a single oral treatment with 16 mg/kg parathion. PB pretreatment produced a decrease in hepatic glutathione content and increases in hepatotoxic paramenters in parathion-treated mice with no changes in the antibody response. In addition, greater p-nitrophenol amounts were produced when mice were pretreated with PB, compared to treatment with parathion alone. These results indicate that parathion-induced hepatotoxicity might be differentiated from immunotoxicity in mice.

Effects of rutaecarpine on the metabolism and urinary excretion of caffeine in rats

Although rutaecarpine, an alkaloid originally isolated from the unripe fruit of Evodia rutaecarpa, has been reported to reduce the systemic exposure of caffeine, the mechanism of this phenomenon is unclear. We investigated the microsomal enzyme activity using hepatic S-9 fraction and the plasma concentration-time profiles and urinary excretion of caffeine and its major metabolites after an oral administration of caffeine in the presence and absence of rutaecarpine in rats. Following oral administration of 80 mg/kg rutaecarpine for three consecutive days, caffeine (20 mg/kg) was given orally. Plasma and urine were collected serially for up to 24 h and the plasma and urine concentrations of caffeine and its metabolites were measured, and compared with those in control rats. The areas under the curve of both caffeine and its three major metabolites (paraxanthine, theophylline, and theobromine) were significantly reduced by rutaecarpine, indicating that caffeine was rapidly converted into the desmethylated metabolites, and that those were also quickly transformed into further metabolites via the hydroxyl metabolites due to the remarkable induction of CYP1A2 and 2E1. The significant induction of ethoxyresorufin O-deethylase, pentoxyresorufin O-depentylase, and p-nitrophenol hydroxylase strongly supported the decrease in caffeine and its major metabolites in plasma, as well as in urine. These results clearly suggest that rutaecarpine increases the metabolism of caffeine, theophylline, theobromine, and paraxanthine by inducing CYP1A2 and CYP2E1 in rats.

Characterization of the Phase II metabolites of rutaecarpine in rat by liquid chromatography-electrospray ionization-tandem mass spectrometry

From the authors’ previous studies on the Phase I metabolism of rutaecarpine, nine metabolites formed were identified as products of hydroxylation on the aromatic rings in rat liver microsomes. In order to determine the possible metabolic fate of rutaecarpine, the Phase II metabolites of rutaecarpine were characterized in the present study by using liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS). When male Sprague–Dawley rats were treated intravenously with 4u2009mgu2009kg−1 rutaecarpine, 16 different Phase I and II metabolites were identified in urine including four sulfate and four glucuronide conjugates. Phase I metabolites of rutaecarpine were identified as four mono-hydroxylated metabolites (M2–5) and four isobaric di-hydroxylated metabolites (M6–9). These metabolites were identical to the in vitro metabolites except one, which was hydroxylated in the aliphatic moiety. In addition, Phase II metabolites were identified as conjugated with sulfate (S1–4) and glucuronide (G1–4). In faeces, 11 different metabolites were identified. The metabolites M8 and glucuronide conjugated (G1–4) were not detected. Structures of all metabolites were confirmed with CID fragmentation spectra of MS2, MS3 and retention times by LC/ESI-MS.

Role of Metabolism In 1-Bromopropane-Induced Hepatotoxicity in Mice

A possible role of metabolism in 1-bromopropane (1-BP)-induced hepatotoxicity was investigated in male ICR mice. The depletion of glutathione (GSH) by formation of GSH conjugates was associated with increased hepatotoxicity in 1-BP-treated mice. The formation of S-propyl and 2-hydroxypropyl GSH conjugates were identified in the liver following 1-BP treatment. In addition, the formation of reactive metabolites of 1-BP by certain cytochrome P-450 (CYP) may be involved in 1-BP-induced hepatotoxicity. The decreased content of hepatic GSH produced by 1-BP was associated not only with increased activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) but also with elevated levels of hepatic thiobarbituric acid-reactive substance (TBARS) in mice where metabolic enzymes were induced by pretreatment with phenobarbital. In addition, the hepatotoxicity induced by 1-BP was prevented by pretreatment with SKF-525A. Taken together, the formation of reactive metabolites by CYP and depletion of GSH may play important roles in hepatotoxicity induced by 1-BP.

Hepatotoxic and Immunotoxic Effects produced by 1,3‐Dibromopropane and Its Conjugation with Glutathione in Female BALB/c Mice

To determine a possible role of glutathione (GSH) conjugation in 1,3-dibromopropane (1,3-DBP)-induced hepatotoxicity and immunotoxicity, female BALB/c mice were treated orally with 1,3-DBP. Based on the liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS) analyses, two forms of S‐bromopropyl GSH were observed at m/z 427.9 and 429.9 in the positive ESI spectrum with a retention time of 5.29 and 5.23 min, respectively. Following single treatment of mice with 150, 300 or 600 mg/kg 1,3-DBP for 12 hr, the amount of S-bromopropyl GSH was detected maximally in liver homogenates at 600 mg/kg 1,3‐DBP. Hepatic GSH levels were significantly decreased by treatment with 1,3-DBP. In a time course study, production of S‐bromopropyl GSH rose maximally 6 hr after treatment and decreased gradually thereafter. The liver weights were significantly increased by treatment with 600 mg/kg 1,3-DBP. When mice were treated orally with 600 mg/kg 1,3-DBP for 12 hr, the activities of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were increased by 365- and 83-fold. In addition, oral 1,3-DBP significantly suppressed the antibody response to a T‐dependent antigen at 600 mg/kg 1,3-DBP. 1,3-DBP elevated hepatic levels of malondialdehyde and suppressed the activities of some hepatic enzymes involved in anti-oxidation. Taken together, the formation of GSH conjugate with 1,3-DBP may deplete cellular GSH and, subsequently, produce hepatotoxicity and immunotoxicity via damage to the cellular anti-oxidative system.

Acute effects of 2-bromopropane and 1,2-dibromopropane on hepatotoxic and immunotoxic parameters in female BALB/c mice

In the present studies, the acute toxic effects of 2-bromopropane (2-BP) and its analog, 1,2-dibromopropane (1,2-DBP), were investigated in female BALB/c mice. The mice were treated orally with either 2-BP at 2000 and 4000 mg/kg or 1,2-DBP at 300 and 600 mg/kg. Four days before necropsy, the mice were immunized intraperitoneally with sheep red blood cells (SRBCs). 1,2-DBP reduced the weights of the spleen and thymus weights and decreased the number of splenic cells. In addition, treatment with 1,2-DBP suppressed the antibody response to SRBCs. Meanwhile, only the antibody response was significantly suppressed by treatment with 2-BP. In the subsequent studies, the time course effects of 2-BP and 1,2-DBP on the hepatotoxic parameters were compared in female BALB/c mice. When mice were treated orally with either one of these chemicals for 6, 12, 24 and 48 h, the activities of serum alanine aminotransferase and aspartate aminotransferase elevated significantly only with 1,2-DBP 24 h after the treatment. The hepatic content of glutathione was reduced by 1,2-DBP. Meanwhile, these parameters were increased by 2-BP. The present results suggest that 1,2-DBP in the Solvent 5200 also contributes to the immnunotoxicity, although 2-BP is a major component.

In Vivo and in Vitro Immunosuppressive Effects of Benzo[k]fluoranthene in Female Balb/c Mice

Although polycyclic aromatic hydrocarbons (PAHs) have been known to suppress immune responses, few studies have addressed the immunotoxicity of benzo[k]fluoranthene (B[k]F). In this study, we investigated the immunosuppression by B[k]F, both in vivo and in vitro, in female BALB/c mice. To assess the effects of B[k]F on humoral immunity as splenic antibody response to sheep red blood cells (SRBCs), B[k]F was given a single dose or once daily for 7 consecutive days po with 30, 60, and 120 micromol/kg. B[k]F reduced the number of antibody-forming cells (AFCs) in a dose-dependent manner. Subacute treatment with B[k]F caused weight increases in liver and decreases in spleen and thymus. The number of AFCs was dramatically decreased by B[k]F in a dose-dependent manner. In a subsequent study, mice were subacutely exposed to the same doses of B[k]F without an immunization with SRBCs, followed by splenic and thymic lymphocyte phenotypings using a flow cytometry and ex vivo mitogen-stimulated proliferation. B[k]F-exposed mice exhibited reduced splenic and thymic cellularity, decreased numbers of total T cells, CD4(+) cells, and CD8(+) cells in spleen, and immature CD4(+)CD8(+) cells, CD4(+)CD8(-) cells, and CD8(+)CD4(-) cells in thymus. The number of CD4(+) IL-2(+) cells was reduced by about 11%, 31%, and 53% following exposure of mice to 30, 60, and 120 micromol/kg of B[k]F, respectively. In the ex vivo lymphocyte proliferation assay, B[k]F inhibited splenocyte proliferation by LPS and Con A. In the in vitro mitogen-stimulated proliferation by untreated splenic suspensions, B[k]F only suppressed splenocyte proliferation to LPS. These results suggested that B[k]F-induced immunosuppression might be mediated, at least in part, through the IL-2 production, and caused by mechanisms associated with metabolic processes.Although polycyclic aromatic hydrocarbons (PAHs) have been known to suppress immune responses, few studies have addressed the immunotoxicity of benzo[k]fluoranthene (B[k]F). In this study, we investigated the immunosuppression by B[k]F, both in vivo and in vitro, in female BALB/c mice. To assess the effects of B[k]F on humoral immunity as splenic antibody response to sheep red blood cells (SRBCs), B[k]F was given a single dose or once daily for 7 consecutive days po with 30, 60, and 120 μmol/kg. B[k]F reduced the number of antibody-forming cells (AFCs) in a dose-dependent manner. Subacute treatment with B[k]F caused weight increases in liver and decreases in spleen and thymus. The number of AFCs was dramatically decreased by B[k]F in a dose-dependent manner. In a subsequent study, mice were subacutely exposed to the same doses of B[k]F without an immunization with SRBCs, followed by splenic and thymic lymphocyte phenotypings using a flow cytometry and ex vivo mitogen-stimulated proliferation. B[k]F-exposed mice exhibited reduced splenic and thymic cellularity, decreased numbers of total T cells, CD4+ cells, and CD8+ cells in spleen, and immature CD4+CD8+ cells, CD4+CD8− cells, and CD8+CD4− cells in thymus. The number of CD4+ IL-2+ cells was reduced by about 11%, 31%, and 53% following exposure of mice to 30, 60, and 120 μmol/kg of B[k]F, respectively. In the ex vivo lymphocyte proliferation assay, B[k]F inhibited splenocyte proliferation by LPS and Con A. In the in vitro mitogen-stimulated proliferation by untreated splenic suspensions, B[k]F only suppressed splenocyte proliferation to LPS. These results suggested that B[k]F-induced immunosuppression might be mediated, at least in part, through the IL-2 production, and caused by mechanisms associated with metabolic processes.