Antagonism of acute cocaine toxicity by buprenorphine.

The effect of buprenorphine pretreatment on the acute cocaine toxicity was assessed in male Swiss Webster mice. Buprenorphine pretreatment (0.15 or 0.30 mg/kg ip, 30 mins before) significantly attenuated the lethal effects of cocaine (60-140 mg/kg ip). The dose of cocaine which resulted in 50% mortality (LD50) in saline pretreated group was 100.61 mg/kg while the LD50 of cocaine in buprenorphine (0.15 and 0.3 mg/kg) pretreated groups were 113.57 and 118.16 mg/kg respectively. There was no significant change in the ratio of brain/plasma levels of cocaine in buprenorphine pretreated group when compared to the ratio from saline treated controls. Furthermore, neither naloxone (10 mg/kg ip, 15 mins before) nor naltrexone (3 mg/kg ip, 15 mins before) pretreatment affected the LD50 of cocaine. When tested 0.5, 1, 2, 4, 8 and 24 hrs after cocaine administration, sublethal dose of cocaine (80 mg/kg ip) injection resulted in significant increase in the plasma lactate dehydrogenase (LDH) levels. Buprenorphine pretreatment significantly attenuated cocaine-induced release of LDH. These results suggest that buprenorphine could be of potential advantage over naloxone in the management of cocaine and heroin ("speed ball") toxicity and in studies on the pharmacotherapy of cocaine-induced toxicity, LDH levels may be used as a biochemical marker to assess the protective effects of drugs.     

Acteoside inhibits apoptosis in D-galactosamine and lipopolysaccharide-induced liver injury.

We assessed the effect of acteoside, a naturally occurring antioxidative phenylethanoid, on hepatic apoptosis and the subsequent liver failure induced by D-Galactosamine (D-GalN) and lipopolysaccharide (LPS). A co-administration of D-GalN (700 mg/kg) and LPS (35 microg/kg) to mice evoked typical hepatic apoptosis characterized by DNA fragmentation and apoptotic body formation, resulting in fulminant hepatitis and lethality of mice. Pre-administration of acteoside at 10 or 50 mg/kg subcutaneously at 12 and 1 h prior to D-GalN/LPS intoxication significantly inhibited hepatic apoptosis, hepatitis and lethality. Tumor necrosis factor-alpha (TNF-alpha) secreted from LPS-stimulated macrophages is an important mediator of apoptosis in this model. Acteoside showed no apparent effect on the marked elevation of serum TNF-alpha, but it partially prevented in vitro TNF-alpha (100 ng/ml)-induced cell death in D-GalN (0.5 mM)-sensitized hepatocytes at the concentrations of 50, 100 and 200 microM. These results indicated that D-GalN/LPS-induced hepatic apoptosis can be blocked by an exogenous antioxidant, suggesting the involvement of reactive oxygen intermediates (ROIs) in TNF-alpha-dependent hepatic apoptosis.     

Roles of endogenous cytokines in liver apoptosis of mice in lethal Listeria monocytogenes infection

Various bacterial pathogens have been identified as mediators of apoptosis. Apoptosis reportedly shows both detrimental and beneficial effects on biological functions. We studied the role of liver apoptosis in lethal Listeria monocytogenes infection and the regulation of apoptosis by endogenous cytokines during infection. Apoptosis was observed in the spleen but not in the liver of infected mice, whereas the induction of liver necrosis was evident by rising levels of serum aminotransferases in these animals. Apoptosis was detected in the liver of L. monocytogenes-infected mice which had been treated with monoclonal antibody (mAb) against tumor necrosis factor-alpha (TNF-alpha) or interleukin-6 (IL-6), or in TNF-alpha(-/-) mice, but not in gamma- interferon (IFN-gamma)(-/-) mice or mice which had been treated with mAb against IL-4 or IL-10. Augmentation of liver apoptosis in mice treated with mAb against TNF-alpha or IL-6 or in TNF-alpha(-/-) mice correlated with the increase in bacterial numbers in the organ, while no augmentation of apoptosis was observed in the liver of IFN-gamma(-/-) mice irrespective of the marked increase in bacterial numbers in the organs, indicating that augmentation of liver apoptosis may not be merely due to the increase in bacterial growth in the organs. These results suggest that TNF-alpha and IL-6 may play an important role in protecting the liver from apoptosis in lethal L. monocytogenes infection.     

Secoisolariciresinol and isotaxiresinol inhibit tumor necrosis factor-alpha-dependent hepatic apoptosis in mice

The effects of secoisolariciresinol (1) and isotaxiresinol (2), two major lignans isolated from the wood of Taxus yunnanensis, on tumor necrosis factor-alpha (TNF-alpha)-dependent hepatic apoptosis induced by D-galactosamine (d-GalN)/lipopolysaccharide (LPS) were investigated in mice. Co-administration of d-GalN (700 mg/kg) and LPS (10 microg/kg) resulted in a typical hepatic apoptosis characterized by DNA fragmentation and the formation of apoptotic bodies. Serum glutamic pyruvic transaminase (sGPT) and glutamic oxaloacetic transaminase (sGOT) levels were also raised at 8 h after d-GalN/LPS intoxication due to a severe necrosis of hepatocytes. Pre-administration of 1 or 2 (50, 10 mg/kg, i.p.) 12 and 1 h before d-GalN/LPS significantly reduced DNA fragmentation and prevented chromatin condensation, apoptotic body formation and hepatitis. Pro-inflammatory cytokines such as TNF-alpha and interferon-gamma (IFN-gamma) secreted from LPS-activated macrophages are important mediators of hepatocyte apoptosis in this model. Pre-treatment with 1 or 2 significantly inhibited the elevation of serum TNF-alpha and IFN-gamma levels. In a separate experiment, both lignans had a significant dose-dependent protective effect on d-GalN/TNF-alpha-induced cell death in primary cultured mouse hepatocytes and TNF-alpha-mediated cell death in murine L929 fibrosarcoma cells. These results indicated that 1 and 2 prevent d-GalN/LPS-induced hepatic injury by inhibiting hepatocyte apoptosis through the blocking of TNF-alpha and IFN-gamma production by activated macrophages and direct inhibition of the apoptosis induced by TNF-alpha.     

Induction of cardiac cytochrome p450 in cocaine-treated mice

Cytochrome P450 (P450) is a ubiquitous family of enzymes responsible for the metabolism of a wide variety of drugs and their metabolites, including cocaine. To investigate the effects of cocaine on myocardial injuries and cardiac P450 expression, BALB/c mice were injected daily intraperitoneally with cocaine (30 mg/kg) or cocaine plus pretreatment of P450 inhibitors for 14 days. Tumor necrosis factor-alpha (TNF-alpha) content and creatine phosphokinase (CPK) activity in mice hearts and serums were significantly increased after long-term treatment with cocaine. Pretreatment with the P450 inhibitor, cimetidine (Cime, 50 mg/kg) or metyrapone (Mety, 40 mg/kg) abolished or significantly attenuated the effects of cocaine on TNF-alpha and CPK activity. Western blot analysis shows that mouse cardiac tissues express the P450 isoforms CYP1A1, CYP1A2, and CYP2J2. The protein levels normalized with cyclophilin A were 1.20 plus minus 0.07, 0.67 plus minus 0.03, and 1.48 plus minus 0.01 for CYP1A1, CYP1A2, and CYP 2J2, respectively. After cocaine administration, CYP2J2 increased by 43.6% and CYP1A1 increased by 108.5%, but CYP1A2 was not significantly altered. However, the cytochrome P450 inhibitors Cime and Mety suppressed the cocaine-induced increase in CYP1A1 and CYP2J2 expression. Moreover, application of Cime or Mety alone did not alter the level of cardiac TNF-alpha or the expression of P450. Our results demonstrate that long-term exposure to cocaine causes an increase in cardiac CYP1A1 and CYP2J2 concentration. We speculate that induction of P450 isoforms may cause cardiac injury due to cocaine metabolites locally catalyzed by P450 or the increase in P450 expression itself.     

Liver I/R injury is improved by the arginase inhibitor, N(omega)-hydroxy-nor-L-arginine (nor-NOHA)

Liver ischemia-reperfusion (I/R) injury is associated with profound arginine depletion due to arginase release from injured hepatocytes. The purpose of this study was to determine whether arginase inhibition with N(omega)-hydroxy-nor-l-arginine (nor-NOHA) would increase circulating arginine levels and decrease hepatic damage during liver I/R injury. The effects of nor-NOHA were initially tested in normal animals to determine in vivo toxicity. In the second series of experiments, orthotopic syngeneic liver transplantation (OLT) was performed after 18 h of cold ischemia time in Lewis rats. Animals were given nor-NOHA (100 mg/kg) or saline before and after graft reperfusion. In normal animals treated with nor-NOHA, there were no histopathological changes to organs, liver enzymes, serum creatinine, or body weight. In the OLT model, animals treated with saline exhibited markedly elevated serum transaminases and circulating arginase protein levels. Nor-NOHA administration blunted the increase in serum arginase activity by 80% and preserved serum arginine levels at 3 h after OLT. Nor-NOHA treatment reduced post-OLT serum liver enzyme release by 50%. Liver histology (degree of necrosis) in nor-NOHA-treated animals was markedly improved compared with the saline-treated group. Furthermore, use of the arginase inhibitor nor-NOHA did not influence polyamine synthesis owing to the decrease in ornithine levels. Arginase blockade represents a potentially novel strategy to combat hepatic I/R injury associated with liver transplantation.     

Co-administration of gamma-vinyl GABA and cocaine: preclinical assessment of safety.

Gamma-vinyl GABA (GVG, Vigabatrin), an irreversible inhibitor of GABA transaminase (GABA-T) that inhibits cocaine-induced place preference and self administration has been proposed as a treatment for cocaine addiction. It was therefore important to assess if there was an enhanced toxicity from the combination of GVG with cocaine. No mortality was observed with administration of GVG (60 mg/kg i.v.) alone (n=8) or in combination (n=6) with cocaine (5 mg/kg i.v.). Cocaine-induced EKG alterations were not affected by GVG pretreatment. Plasma alanine amino transferase activity was reduced by GVG treatment and this was not further modified by cocaine administration. These results suggest that acute co-administration of GVG and cocaine does not result in immediate cardiovascular or hepatic toxicity of sufficient significance, to preclude further clinical trials.     

Splenocyte subsets in normal and protein malnourished mice after long-term exposure to cocaine or morphine

An experimental model which resembles human drug addiction was developed to study the effect of chronic drug (cocaine or morphine) administration on the immune system. As malnutrition has been associated with drug use, a low protein diet has been evaluated for its contribution to the impairment of the immune system during cocaine/morphine addiction. Female C57BL/6 mice that received a 20% or 4% casein diet were studied. Both drugs were administered intraperitoneally daily for 11 weeks and drugs were administered in increasing daily doses, beginning after 3 weeks of diet consumption. Doses of cocaine began with 5 mg/kg body weight and reached the maximum dose of 40 mg/kg/day at the fourth week. Doses of morphine gradually increased from 10 mg/kg to 75 mg/kg body weight with the maximum dose reached after 5 weeks of treatment. Cocaine administration reduced body weight, particularly in the low protein diet group, and spleen weight in protein malnourished mice. Cocaine as well as saline injected mice showed a decrease in the percentage of CD4+ CD8+ and Mac-1+ cells and an increase in B cells in the spleens of well nourished mice. Morphine-treated mice showed similar results to those observed in cocaine or saline treated mice. These results suggest that cocaine, morphine or saline injection can alter the percentage of cells that express a defined phenotype independently of the nutritional status of the subject. Moreover, the effect appears dependent on a stress mediated process.     

Lobeline augments and inhibits cocaine-induced hyperactivity in rats

Lobeline has high affinity for nicotinic receptors and alters presynaptic dopamine storage and release in brain. Moreover, lobeline decreases the reinforcing and locomotor-activating properties of methamphetamine, suggesting that lobeline may be a pharmacotherapy for psychostimulant abuse. This study determined if lobeline alters cocaine-induced hyperactivity and if lobeline alters the induction and/or expression of sensitization to cocaine. On Days 1-12, male rats were administered lobeline (0.3 or 1.0 mg/kg) or saline, placed in an automated activity monitor for 20 min, administered cocaine (10, 20 or 30 mg/kg) or saline and returned to the monitor for 60 min. On Day 13, the effect of lobeline on the induction and expression of sensitization to cocaine was determined. Lobeline did not alter the effect of cocaine after acute injection. However, 1.0 mg/kg lobeline attenuated cocaine (10 and 20 mg/kg)-induced hyperactivity after repeated administration and prevented the development of sensitization to these cocaine doses. Interestingly, 0.3 mg/kg lobeline augmented cocaine (10 mg/kg)-induced hyperactivity after repeated administration. Lobeline did not alter the effect of 30 mg/kg cocaine. The present results indicate a complex interaction of lobeline with cocaine and support other research indicating a role for nicotinic receptors in the development of sensitization to psychostimulants.     

Post-treatment with glycyrrhizin can attenuate hepatic mitochondrial damage induced by acetaminophen in mice

Overdose of acetaminophen (APAP) is responsible for the most cases of acute liver failure worldwide. Hepatic mitochondrial damage mediated by neuronal nitric oxide synthase- (nNOS) induced liver protein tyrosine nitration plays a critical role in the pathophysiology of APAP hepatotoxicity. It has been reported that pre-treatment or co-treatment with glycyrrhizin can protect against hepatotoxicity through prevention of hepatocellular apoptosis. However, the majority of APAP-induced acute liver failure cases are people intentionally taking the drug to commit suicide. Any preventive treatment is of little value in practice. In addition, the hepatocellular damage induced by APAP is considered to be oncotic necrosis rather than apoptosis. In the present study, our aim is to investigate if glycyrrhizin can be used therapeutically and the underlying mechanisms of APAP hepatotoxicity protection. Hepatic damage was induced by 300 mg/kg APAP in balb/c mice, followed with administration of 40, 80, or 160 mg/kg glycyrrhizin 90 min later. Mice were euthanized and harvested at 6 h post-APAP. Compared with model controls, glycyrrhizin post-treatment attenuated hepatic mitochondrial and hepatocellular damages, as indicated by decreased serum glutamate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase activities as well as ameliorated mitochondrial swollen, distortion, and hepatocellular necrosis. Notably, 80 mg/kg glycyrrhizin inhibited hepatic nNOS activity and its mRNA and protein expression levels by 16.9, 14.9, and 28.3%, respectively. These results were consistent with the decreased liver nitric oxide content and liver protein tyrosine nitration indicated by 3-nitrotyrosine staining. Moreover, glycyrrhizin did not affect the APAP metabolic activation, and the survival rate of ALF mice was increased by glycyrrhizin. The present study indicates that post-treatment with glycyrrhizin can dose-dependently attenuate hepatic mitochondrial damage and inhibit the up-regulation of hepatic nNOS induced by APAP. Glycyrrhizin shows promise as drug for the treatment of APAP hepatotoxicity.     

The effect of Z-FA.FMK on D-galactosamine/TNF-alpha-induced liver injury in mice

Cathepsin B is a cysteine proteinase, considered to have an important role in apoptosis, which is activated by D-galactosamine and tumor necrosis factor-alpha (D-GalN/TNF-alpha). Benzyloxycarbonyl-L-phenylalanine fluoromethyl ketone (Z-FA.FMK) is a cathepsin B inhibitor used in research on apoptotic pathways. The aim of this study was to investigate the role of Z-FA.FMK on apoptotic cell death, cell proliferation and liver damage induced by a D-GalN/TNF-alpha combination in mice. In the study, 1 h after administration of 8 mg/kg Z-FA.FMK by intravenous injection, D-GalN (700 mg/kg) and TNF-alpha (15 microg/kg) were administered by a single intraperitoneal injection. In the group given D-GalN/TNF-alpha, the following results were found: Degenerative changes in the liver tissue, significant increase in the number of both TUNEL and activated caspase-3-positive hepatocytes, a decrease in the number of PCNA-positive hepatocytes, an increase in lipid peroxidation (LPO) levels and a decrease in glutathione (GSH) and DNA levels in the liver tissue. In contrast, in the group given D-GalN/TNF-alpha and Z-FA.FMK, a decrease in the damage of the liver tissue, a significant decrease in TUNEL and activated caspase-3-positive hepatocytes, a significant increase in the number of PCNA-positive hepatocytes, a decrease in the LPO levels, an increase in GSH and DNA levels in the liver tissue were found. As a result, microscopic and biochemical evaluations indicate that Z-FA.FMK plays a protective role against liver injury induced by D-GalN/TNF-alpha and it has an inverse effect on hepatocyte apoptosis and proliferation in BALB/c mice.     

Experimental acute poisoning in mice induced by emestrin,a new mycotoxin isolated from Emericella species

The effects of emestrin (EMS), a secondary metabolite of the Emericella species, on male ICR mice were examined. The intraperitoneal LD₅₀ values of EMS were 17.7 and 13.0 mg/kg at 24 and 48 hr, respectively. The target organs of EMS were the heart, liver and thymus. In doses over 30 mg/kg the experimental animals died from cardiac failure shortly after the injections. Several survivors that were given EMS in doses under 20 mg/kg showed severe centrilobular necrosis in the liver at 24 hr. Marked degeneration of mitochondria was seen in electron micrographs of both cardiac muscle cells and hepatocytes. In the degenerated hepatocytes, prominent proliferation of RER, membrane-limited inclusions containing both ribosome-like granules and RER, and fenestrated lamella-like structures were observed. Massive necrosis of lymphocytes was always observed in the cortical layer of the thymus of the survivors within 24 hr, while bilateral adrenalectomized mice showed no discernible pathomorphological changes in the lymphoid tissues. Pretreatment of mice with diethyl maleate increased the incidence and severity of hepatic necrosis, whereas that with either cysteine or CoCl₂ reduced the severity of centrilobular necrosis of the liver. Pretreatment with phenobarbital had no significant effect on EMS-induced hepatic lesions.     

Sepsis-associated cholestasis is critically dependent on P-selectin-dependent leukocyte recruitment in mice

Cholestasis is a major complication in sepsis although the underlying mechanisms remain elusive. The aim of this study was to evaluate the role of P-selectin and leukocyte recruitment in endotoxemia-associated cholestasis. C57BL/6 mice were challenged intraperitoneally with endotoxin (0.4 mg/kg), and 6 h later the common bile duct was cannulated for determination of bile flow and biliary excretion of bromosulfophthalein. Mice were pretreated with an anti-P-selectin antibody or an isotype-matched control antibody. Leukocyte infiltration was determined by measuring hepatic levels of myeloperoxidase. Tumor necrosis factor-alpha and CXC chemokines in the liver was determined by ELISA. Liver damage was monitored by measuring serum levels of alanine aminotransferase and aspartate aminotransferase. Apoptosis was quantified morphologically by nuclear condensation and fragmentation using Hoechst 33342 staining. Endotoxin induced a significant inflammatory response with increased TNF-alpha and CXC chemokine concentrations, leukocyte infiltration, liver enzyme release, and apoptotic cell death. This response was associated with pronounced cholestasis indicated by a >70% decrease of bile flow and biliary excretion of bromosulfophthalein. Immunoneutralization of P-selectin significantly attenuated endotoxin-induced leukocyte infiltration reflected by a >60% reduction of hepatic myeloperoxidase levels. Interference with P-selectin decreased endotoxin-mediated hepatocellular apoptosis and necrosis, but did not affect hepatic levels of tumor necrosis factor-alpha and CXC chemokines. Of interest, inhibition of P-selectin restored bile flow and biliary excretion of bromosulfophthalein to normal levels in endotoxin-challenged animals. Our study demonstrates for the first time that P-selectin-mediated recruitment of leukocytes, but not the local production of proinflammatory mediators, is the primary cause of cholestasis in septic liver injury.     

Estradiol improves cardiac and hepatic function after trauma-hemorrhage: role of enhanced heat shock protein expression

Although studies indicate that 17beta-estradiol administration after trauma-hemorrhage (T-H) improves cardiac and hepatic functions, the underlying mechanisms remain unclear. Because the induction of heat shock proteins (HSPs) can protect cardiac and hepatic functions, we hypothesized that these proteins contribute to the salutary effects of estradiol after T-H. To test this hypothesis, male Sprague-Dawley rats ( approximately 300 g) underwent laparotomy and hemorrhagic shock (35-40 mmHg for approximately 90 min) followed by resuscitation with four times the shed blood volume in the form of Ringer lactate. 17beta-estradiol (1 mg/kg body wt) was administered at the end of the resuscitation. Five hours after T-H and resuscitation there was a significant decrease in cardiac output, positive and negative maximal rate of left ventricular pressure. Liver function as determined by bile production and indocyanine green clearance was also compromised after T-H and resuscitation. This was accompanied by an increase in plasma alanine aminotransferase (ALT) levels and liver perfusate lactic dehydrogenase levels. Furthermore, circulating levels of TNF-alpha, IL-6, and IL-10 were also increased. In addition to decreased cardiac and hepatic function, there was an increase in cardiac HSP32 expression and a reduction in HSP60 expression after T-H. In the liver, HSP32 and HSP70 were increased after T-H. There was no change in heart HSP70 and liver HSP60 after T-H and resuscitation. Estradiol administration at the end of T-H and resuscitation increased heart/liver HSPs expression, ameliorated the impairment of heart/liver functions, and significantly prevented the increase in plasma levels of ALT, TNF-alpha, and IL-6. The ability of estradiol to induce HSPs expression in the heart and the liver suggests that HSPs, in part, mediate the salutary effects of 17beta-estradiol on organ functions after T-H.     

The influence of BPC 157 on nitric oxide agonist and antagonist induced lesions in broiler chicks

We describe the effects of nitric oxide (NO) agonists and antagonists and the influence of a novel organoprotective pentadecapeptide BPC 157, on the development of pulmonary hypertension syndrome and tissue lesions in chicks. Acute toxicity, which includes single dose application of saline (1 mL intraperitoneally (ip)), BPC 157 (10 μg/kg bw), L-NAME (NO antagonist, doses 50, 100, 150 mg/kg bw) and L-arginine (NO agonist/100 mg/kg bw with their combination L-NAME + BPC 157; L-NAME + L-arginine) was investigated. In this experiment pathohistological examination of the spleen, heart, liver and lungs and hematological analysis was conducted. In the chronic toxicity experiment, the animals were treated daily for 5 weeks with L-NAME (10 mg/kg bw), L-arginine (100 mg/kg bw), BPC 157 (10 μg/kg bw) and their combinations (L-NAME + BPC 157; L-NAME + L-arginine) ip. Seven animals from each group, including controls (saline 1 mL ip) were killed every week. Application of L-NAME caused pulmonary hypertension syndrome (PHS) in the treated chicks, which was prevented by the simultaneous application of L-arginine and BPC 157. Pathohistological examination of both acute and chronic toxicity revealed that L-NAME caused severe tissue damage (myocardial and hepatic cell necrosis, necrosis of the lymphoid cells in the spleen) while L-arginine provoked predominantly congestion, edema and hemorrhages in all organs. The effect of L-NAME was successfully inhibited by the application of L-arginine and BPC 157 but the latter substance did not cause any tissue or organ damage. Hematological analysis shows significant hemoglobin and leukocyte number decrease in the L-NAME-treated groups of chicks.     

Interleukin-22 Protects against Acute Alcohol-Induced Hepatotoxicity in Mice

The protective effects of interleukin-22 (IL-22) on acute alcohol-induced liver injury were investigated. Mice were gavaged with 7 doses of alcohol (56% wt/vol, 15.2 mL/kg of body weight for each dose) over the 24 h, and IL-22 (0.5 mg/kg BW) was given to the mice by injection into the tail vein 1 h after alcohol administration. The results indicated that acute alcohol administration caused prominent hepatic microvesicular steatosis and an elevation of serum transaminase activities, induced a significant decrease in hepatic glutathione in conjunction with enhanced lipid peroxidation, and increased hepatocyte apoptosis as well as hepatic TNF-alpha production. IL-22 treatment attenuated these adverse changes induced by acute alcohol administration. The protective effects of IL-22 on alcohol-induced hepatotoxicity were due mainly to its anti-inflammatory, anti-oxidant, and anti-apoptotic features.     

Nitrendipine: an antidote to cardiac and lethal toxicity of cocaine

Nitrendipine, a Ca2+ modulator was tested in the rat as an antagonist to the cardiac toxicity of cocaine and as an antidote to the acute lethal effects of this drug. In a first series of experiments, nitrendipine (1.46 X 10(-3) mg/kg/min) when simultaneously administered intraarterially with cocaine (2 mg/kg/min) suppresses the arrhythmias induced by cocaine and increases survival time from 73 +/- 33 min to 309 +/- 118 min and the lethal dose of cocaine from 146 +/- 66 mg/kg to 618 +/- 236 mg/kg (p less than 0.003). Nitrendipine also protects the heart from the acute morphological lesions induced by cocaine administration and antagonizes some of the central effects of cocaine. In a second series, 5 rats administered 60 mg/kg of cocaine intraperitoneally had a survival time of 8'06 +/- 5'20. Death was attributed to convulsions and respiratory arrest. Animals treated with nitrendipine (129 +/- 23 mg/kg) 4'30" after cocaine administration survived. Nitrendipine appears to have general protective effects against cocaine cardiac toxicity and the acute lethal effects of this alkaloid.     

Inhibition of TNF-alpha produced by Kupffer cells protects against the nonspecific liver toxicity of immunotoxin anti-Tac(Fv)-PE38, LMB-2

LMB-2 (anti-Tac(Fv)-PE38) is a recombinant immunotoxin composed of the Fv fragment of the anti-Tac Ab fused to a 38-kDa form of Pseudomonas: exotoxin A. Recent clinical trials showed that LMB-2 is a promising agent for the treatment of patients with Tac-positive leukemia or lymphoma. One major side effect that needs to be overcome is nonspecific liver toxicity. In the current study, we have analyzed the mechanism of this toxicity using a mouse model. Mice that were injected with a lethal dose of LMB-2 showed severe hepatic necrosis. Immunohistochemistry revealed that LMB-2 accumulated in Kupffer cells in the liver, suggesting that the damage to the hepatocytes was indirect. When we examined the effects of LMB-2 on peritoneal macrophages, cells in the same lineage as Kupffer cells, we found that LMB-2 induced the production of TNF-alpha by these cells. Following LMB-2 administration to mice, the levels of TNF-alpha in the liver increased to very high levels, whereas the rise in serum levels was modest. In addition, the LMB-2-induced liver toxicity was blocked by a specific TNF binding protein (TNFsRp55). Liver toxicity was also blocked by indomethacin, which also blocked the rise of TNF-alpha in the liver. Both TNFsRp55 and indomethacin treatment protected mice against a lethal dose of LMB-2. These data indicate that TNF-alpha produced in the liver by Kupffer cells has an important causal role in the nonspecific liver toxicity of LMB-2. These findings have important clinical implications for the use of immunotoxins in the therapy of patients with cancer.