Rita M. Turkall

Oral cocaine produces dose-related hepatotoxicity in male mice

Cocaine remains a widely abused substance. While most addicts take cocaine intranasally, a considerable number abuse cocaine by mouth. It has been assumed that after oral exposure cocaine is hydrolyzed in the stomach rendering it ineffective. This study investigated the effect of orally administered cocaine on liver function and integrity as well as its effect on liver and blood antioxidative enzymes. Male CF-1 mice were orally administered either 0, 5, 10 or 20 mg cocaine/kg body weight and sacrificed 24 h after the last treatment. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured as markers of liver injury. Blood and liver glutathione (GSH) levels were determined as well as the activities of glutathione peroxidase (GPx) and catalase (CAT). In addition, the activity of liver glutathione reductase (GRx) was also measured. The results demonstrated that oral cocaine caused hepatotoxicity in a dose dependent manner. Serum ALT and AST were elevated while blood GSH concentration decreased in all cocaine treated animals. In addition, there was a significant dose dependent decrease in the activities of GPx and CAT in blood and liver of cocaine treated animals. However, hepatic GSH content and GRx activity manifested a significant increase, particularly in the group, which received 20 mg/kg cocaine. This study is the first to demonstrate that cocaine-induced hepatotoxicity results following the oral route of administration.

Endotoxin potentiates the hepatotoxicity of cocaine in male mice.

Cocaine produces hepatotoxicity by a mechanism that remains undefined but that has been linked to its oxidative metabolism. Endotoxin (lipopolysaccharide, LPS) is also a well-known cause of hepatic damage, where exposure to non-injurious doses of LPS increases the toxicity of certain hepatotoxins. This study was conducted to investigate the possible potentiation of cocaine-mediated hepatotoxicity (CMH) by LPS. Male CF-1 mice were administered oral cocaine hydrochloride for 5 consecutive days at a dose of 20 mg/kg with and without 12 2 10 6 EU LPS/kg given intraperitoneally 4 h after the last cocaine injection. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured as markers of liver injury. Blood and liver glutathione (GSH) levels were determined, as well as the activities of glutathione peroxidase (GPx) and catalase (CAT). In addition, the activity of liver glutathione reductase (GRx) was measured. The results demonstrate that endotoxin potentiated the hepatotoxicity of cocaine. Serum ALT and AST were significantly elevated with the combined cocaine and LPS treatment versus all other treatments. While cocaine alone resulted in centrilobular necrosis, the cocaine and LPS combination produced submassive necrosis. The increased hepatic GSH content and GRx activity observed with cocaine alone were not observed with the combination treatment, rendering the liver more susceptible to oxidative stress. Moreover, there was a significant decrease in the activities of hepatic GPx and CAT, particularly with the combination treatment. In conclusion, this study demonstrates that LPS potentiates the hepatotoxicity of cocaine as revealed by an array of biochemical and morphological markers.

Effects of soil on the dermal bioavailability of m-Xylene in male rats

Bioavailability of a chemical absorbed through the skin from contaminated soil may differ from that seen following exposure to the pure chemical. The objective of this research was to qualitatively and quantitatively assess the absorption, distribution, excretion, and metabolism of soil-adsorbed m-xylene versus pure m-xylene so that the potential for public health risk following dermal exposure could be evaluated. In this study a shallow glass cap covering a 13-cm2 area was fixed to the shaved skin of each male rat (6-10 rats per group) followed by the addition of 225 microliters of m-xylene containing 20 muCi of m-[14C]xylene alone or with one of two soils. Maximum plasma levels of radioactivity were highest for pure m-xylene while the values for the sandy and clay soil groups were approximately equal. Although clay soil statistically decreased the rate of absorption, the half-lives of elimination and the area under the plasma concentration time curve were not changed by either soil. The major route of excretion in the pure and sandy groups was via expired air followed by urine. However, in the presence of clay soil, the percentage of the initial dose in expired air was similar to that in urine. Forty-eight hours after treatment, skin application sites in both soil treatment groups contained amounts of radioactivity significantly higher than those of m-xylene treatment alone. In the presence of clay soil a statistical increase in m-xylene-derived radioactivity was also observed in fat beneath the treated skin area. Metabolite analysis by HPLC indicated that methylhippuric acid was the main urinary metabolite followed by xylenol and the parent compound in all groups.

Inhibition of cocaine oxidative metabolism attenuates endotoxin potentiation of cocaine mediated hepatotoxicity

The oxidative metabolism of cocaine by the microsomal monooxygenase enzymes has been postulated to be essential for cocaine mediated hepatotoxicity (CMH). Endotoxin (lipopolysaccharide, LPS), a well-known cause of hepatic damage, previously has been demonstrated to dramatically increase CMH. The mechanism of this interaction has not been clearly elucidated, but cocaine oxidative metabolism appears to sensitize hepatocytes so that subsequent exposure to small amounts of LPS can further augment CMH. This study was conducted to investigate if dimethylaminoethyl-2,2-diphenylvalerate (SKF-525A) pretreatment inhibits LPS potentiation of CMH. For 5 consecutive days, male CF-1 mice were administered daily SKF-525A (50 mg/kg) or sterile saline followed an hour later by cocaine (20 mg/kg) or sterile saline. Four hours following the last cocaine or saline treatment, the mice were administered sterile saline 12x10(6) EU LPS/kg, i.p. The mice were sacrificed 18 h later by decapitation. Pretreatment with SKF-525A reversed the hepatic injury caused by cocaine alone or cocaine and LPS treatments, as indicated by both histologic evaluation and serum alanine transaminase (ALT) and aspartate transaminase (AST) activities. In particular, SKF-525A completely reversed the effects of cocaine alone on liver and blood reduced gluthathione (GSH), glutathione peroxidase (GPx) and catalase (CAT) and hepatic glutathione reductase (GRx) activities. However, SKF-525A was ineffective against the effect of LPS alone on liver and blood GPx and CAT or on hepatic GSH and GRx, suggesting that these effects were not mediated by cytochrome P450 oxidative metabolism. The pattern of biochemical changes persisting with SKF-525A pretreatment in the LPS and cocaine group resembled those of the LPS alone group. The results suggest that cytochrome P450 oxidative metabolism of cocaine is largely responsible for CMH with potentiation by LPS achieved through a different mechanism involving oxidative stress.

Immunomodulation by cocaine and ketamine in postnatal rats

The abuse of cocaine (COC) in combination with ketamine (KET) among pregnant women was shown to be high. Transplacental exposure is not the only route by which a newborn may be exposed to these agents, but they can also distribute into breast milk. Chronic COC exposure is associated with immunological modulation in human and animal models. The effect of sub-chronic exposure to COC and KET alone and in combination on the developing immune system was assessed in neonatal male Sprague-Dawley (SD) rats. To simulate the route of exposure during lactation, newborn male rats were treated orally with saline, COC alone (20 mg/kg), KET alone (50 mg/kg), or KET (50 mg/kg) followed 15 min later by COC (20 mg/kg) from days 1 to 21 of life. Pups were sacrificed 30 min following the last treatment. Total circulating leukocyte and lymphocyte counts were decreased with relative neutrophilia, while spleen/body weight ratio and IgM antibody response to sheep red blood cells (SRBCs) were increased in animals treated with COC. Moreover, treatment with COC alone increased serum interleukin 10 (IL-10) concentration; however, it did not affect serum interferon gamma (IFN-gamma) concentration. On the other hand, KET treatment did not produce any significant change of any of these parameters. However, when co-administered with COC, the immunomodulatory effects of COC were prevented. COC caused a significant increase in serum corticosterone concentration that KET effectively prevented. Lack of significant change of plasma and tissue concentrations of norcocaine (NC) suggested no role for COC metabolism in COC-induced immunomodulation. However, the results of this study indicate that COC-induced immunomodulatory reactions and their prevention by KET most likely occurred through neuroendocrinal mechanisms.

Endotoxin Potentiates Cocaine-Mediated Hepatotoxicity by Nitric Oxide and Reactive Oxygen Species

Exposure to small, noninjurious doses of the inflammagen, bacterial endotoxin (lipopolysaccharide, LPS) augments the toxicity of certain hepatotoxicants, including cocaine. The mechanism of this interaction has not been clearly elucidated, but it seems that aspects of the inflammatory response initiated by exposure to LPS may be responsible. In particular, this study examined the role of Kupffer cells and the modulating effects of nitric oxide (NO) and reactive oxygen species (ROS) on the LPS potentiation of cocaine-mediated hepatotoxicity (CMH). Mice were administered oral cocaine hy-drochloride for 5 consecutive days at a dose of 20 mg/kg with and without 12 times 106 EU LPS/kg given intraperitoneally (IP) 4 hours after the last cocaine injection. Pretreatment regimens consisted of administration of 300 mg/kg, IP, of aminoguanidine (AM) or 1,3-dimethylthiourea (DMU) at 1 hour or 15 minutes, respectively, before each cocaine administration. In another group, mice were pretreated with saline using the same cocaine and LPS treatment protocol, but received a single pretreatment of 7 mg gadolinium chloride (Gd Cl3)/kg intravenously (IV), or sterile saline 24 hours prior to the LPS administration. The Gd Cl3 (Kupffer cell inhibitor) pretreatment inhibited the LPS potentiation of CMH, but did not reverse the effects of cocaine alone. On the other hand, AM (NO synthase inhibitor), decreased the synthesis of NO as observed by the decrease in the plasma nitrate/nitrite level and completely reversed the hepatotoxic effects of cocaine and LPS alone and in combination. Moreover, DMU (hydroxyl free radical scavenger) ameliorated the effects of cocaine and significantly reduced the hepatotoxicity observed with the cocaine and LPS administration. These data suggest that cocaine sensitizes the liver and subsequent activation of Kupffer cells by LPS leads to the formation of increased levels of NO, which can promote oxidant stress and thus provide an environment favoring the generation of more reactive species such as the hydroxyl free radical.

Soil Adsorption Alters Bioavailability of Benzene in Dermally Exposed Male Rats

The potential for exposure to chemically contaminated soil is a concern for chemical industry and waste disposal site workers as well as for individuals living near the contamination site. Current assessment of potential health risks from these types of exposures relies almost exclusively on extrapolations from data derived with pure chemicals. Complex interactions with soil, however, may alter greatly the way in which a chemical subsequently interacts with the body. This study was conducted to determine if soil adsorption alters the way in which benzene, a common chemical contaminant, enters and is handled by the body following dermal exposure. A shallow glass cap covering approximately a 13-cm2 area was fixed tightly to the shaved skin of each adult male rat tested; 300 microL of 14C-benzene alone or with 1 g of clay or sandy soil was introduced under the cap through an opening which was sealed immediately. Pure benzene produced the highest peak plasma concentration of radioactivity, followed closely by sandy soil-adsorbed benzene, with the lowest value exhibited by clay soil-adsorbed benzene. The plasma elimination half-lives were as follows:sandy (24.5 hr), pure (23.0 hr), and clay (19.4 hr). The tissue concentrations of radioactivity 48 hr post administration were highest in treated skin (covered by the glass cap), followed by the kidney and liver in both soil-treated groups, and were highest in the kidney followed by the liver and treated skin in the pure group.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of the Dermal Bioavailability of Soil-Aged Benzo(a)pyrene

Exposure to polycyclic aromatic hydrocarbons (PAHs) in soil is a major health concern because of their mutagenic and carcinogenic properties. The aim of this research was to determine the dermal bioavailability of benzo(a)pyrene (BaP) aged in either a sandy or a clay soil in order to assess the health risks and remediation goals for the chemical. In vitro flow-through diffusion cell studies were conducted utilizing dermatomed male pig skin. The amount of radioactive chemical was measured that penetrated skin into receptor fluid and which was bound to skin following soap and water decontamination. BaP bioavailability was decreased by 95 to 98% after 3 months of aging in soil relative to the pure compound. Less than 0.3% of the dose was detected in receptor fluid for all treatments. While most of the dose was bound to skin after administering the pure compound, the majority of the radioactivity was found in the soil and decontaminate after aging. The results indicate that the health risk from exposure to BaP is significantly reduced as the compound ages in soil and that less soil cleanup would be needed at sites contaminated with aged BaP.

Soil adsorption alters kinetics and bioavailability of benzene in orally exposed male rats

A study comparing the bioavailability of pure vs soil-adsorbed benzene was conducted in adult, male rats. Animals were gavaged with an aqueous suspension of benzene alone or adsorbed to either a Keyport series (clay soil) or a Cohansey aquifer solid (sandy soil) from New Jersey. Peak plasma concentration of radioactivity was increased in the presence of either soil vs benzene alone while the sandy soil also decreased the time to reach peak vs benzene alone. Either soil produced an increase in the area under the plasma radioactivity-time curve versus benzene alone, while the clay soil did so in a statistically significant manner. The half-life (t1/2) of absorption into plasma was not statistically different in the presence of either soil, while each soil decreased the t1/2 of elimination vs benzene alone and clay soil did so in a statistically significant manner.Two hr after exposure, stomach tissue contained the highest amount of radioactivity followed by fat in all treatment groups. No differences were detected in the tissue concentration of radioactivity between the treatment groups.Expired air was the primary excretion route following exposure to benzene alone with lesser amounts of radioactivity eliminated in the urine during the 48 hr following exposure. The opposite pattern was detected in the presence of clay soil, while expired air and urine represented approximately equal routes of excretion in the presence of sandy soil. Unmetabolized benzene represented the bulk of total radioactivity in the expired air of all treatment groups with [14C]O2 comprising the remainder. Less than 2% of radioactivity was eliminated by the fecal route for all treatments with significantly higher amounts in the clay soil treatment versus benzene alone.Phenol was the primary benzene metabolite detected in the 0–12 hr urines of all treatment groups. Lesser amounts of hydroquinone, catechol, and benzenetriol were also detected. No differences in the metabolite percentages were detected between the treatment groups.

N -Acetylcysteine Pretreatment Decreases Cocaine and Endotoxin-Induced Hepatotoxicity

Cocaine produces hepatotoxicity by a mechanism that remains undefined but has been linked to its oxidative metabolism. Endotoxin (lipopolysaccharide, LPS) is also a well-known cause of hepatic damage, and exposure to noninjurious doses of LPS increases the toxicity of certain hepatotoxins. Previously it was demonstrated that exposure to noninjurious doses of LPS dramatically increases cocaine-mediated hepatotoxicity (CMH). This study was conducted to investigate whether pretreatment with N-acetylcysteine (NAC), a glutathione (GSH) precursor and an antioxidant agent, inhibits LPS potentiation of CMH. For 5 consecutive days, male CF-1 mice were administered daily oral NAC (200 mg/kg) or sterile saline followed an hour later by cocaine (20 mg/kg) or sterile saline. Four hours following the last cocaine or saline treatment, the mice were administered 12 2 10 6 EU LPS/kg or sterile saline. For the cocaine alone and cocaine and LPS groups, NAC pretreatment significantly decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities with absence of necrotic hepatic lesions, indicating a reduction of liver injury. In addition, in all groups pretreated with NAC, hepatic GSH concentration was significantly increased, as were hepatic and blood glutathione peroxidase (GPx) and catalase (CAT) activities. In conclusion, the results demonstrate that NAC pretreatment exerted a protective effect against LPS potentia-tion of CMH.