Adjuvant epirubicin followed by cyclophosphamide, methotrexate and fluorouracil (CMF) vs CMF in early breast cancer: results with over 7 years median follow-up from the randomised phase III NEAT/BR9601 trials.

BACKGROUND: The National Epirubicin Adjuvant Trial (NEAT) and BR9601 trials tested the benefit of epirubicin when added to cyclophosphamide, methotrexate and 5-fluorouracil (E-CMF) compared with standard CMF in adjuvant chemotherapy for women with early breast cancer. This report details longer follow-up with interesting additional time-dependent analyses. METHODS: National Epirubicin Adjuvant Trial used epirubicin (E) 3-weekly for four cycles followed by classical (c) CMF for four cycles (E-CMF) compared with cCMF for six cycles. BR9601 used E 3-weekly for four cycles followed by CMF 3-weekly for four cycles, compared with CMF 3-weekly for eight cycles. RESULTS: In all, 2391 eligible patients were randomised and with a median 7.4-year follow-up, E-CMF confirmed a significant benefit over CMF in both relapse-free survival (RFS) (78% vs 71% 5 years RFS, respectively, hazard ratio (HR)=0.75 (95% CI: 0.65-0.86), P<0.0001) and overall survival (OS) (84% vs 78% 5 years OS, respectively, HR=0.76 (95% CI: 0.65-0.89), P=0.0007). Interaction of treatment effect and prognostic factors was demonstrated for duplication of chromosome 17 centromeric enumeration (Ch17CEP) as previously reported. Poor prognostic factors at diagnosis (ER and PR negative and HER2 positive) showed time-dependent annual hazard rates for RFS and OS. In univariate analysis, these factors demonstrated more favourable HRs for RFS after 5 years. Treatment effects also suggested a differential benefit for E-CMF within the first 5 years for poor prognosis tumours. CONCLUSION: Longer follow-up has confirmed E-CMF as significantly superior to CMF for all patients. Ch17CEP duplication was the only biomarker that demonstrated significant treatment interaction. Standard poor prognostic factors at diagnosis were time-dependent, and after 5 years disease-free, poor prognosis patients demonstrated favourable HRs for survival.

Survival trends in the United States following exercise-related sudden cardiac arrest in the youth: 2000-2006.

BACKGROUND: Sudden cardiac arrest is the leading cause of death in young athletes. However, limited studies have examined survival rates after exercise-related sudden cardiac arrest in the youth. OBJECTIVE: The Purpose of this study was to monitor exercise-related sudden death in the United States and to assess survival trends following exercise-related sudden cardiac arrest in the youth. METHODS: From January 1, 2000, through December 31, 2006, exercise-related sudden death events in young individuals were identified through a systematic search of public media reports. Media reports were reviewed to clarify case circumstances and relation to exercise, cause of death, outcome, and use of a defibrillator. The study used an observational cohort design with weekly searches and updates to the database. RESULTS: During the 7-year period from 2000-2006, 486 total cases of exercise-related sudden cardiac arrest were identified in elementary school (age 5-11 years), middle school (age 11-14 years), high school (age 14-18 years), and college (age 18-22 years) individuals in the United States, with an average of 69 cases per year (range 48-96 years). Eighty-three percent (405/486) of victims were male and 17% (81/486) were female, with a male-to-female ratio of 5:1. Overall survival during this time period was 11% (55/486), with a range of 4% to 21% survival per year. There was a statistically significant trend toward improved survival in recent years (P = .035). Females were more likely to survive sudden cardiac arrest than were males (21% vs 9%, P = .001). CONCLUSION: Survival following exercise-related sudden cardiac arrest in the youth has been universally poor over the last 7 years in the United States, despite a recent trend toward improved survival. Improved reporting systems are needed to accurately monitor these events, and strategies to improve outcomes from exercise-related sudden cardiac arrest in the youth, such as improved emergency response planning and public access defibrillation programs, should be considered.

Phase II clinical trials of cisplatin-then-paclitaxel and paclitaxel-then-cisplatin in patients with previously untreated advanced epithelial ovarian cancer.

PURPOSE: To examine the activity and safety of two sequentially scheduled chemotherapy regimens comprising four cycles of paclitaxel (pctx) 200 mg/m2/3 hours then four cycles ofcisplatin (cisDDP) 100 mg/m2, and vice versa, in patients with previously untreated advanced ovarian cancer. PATIENTS AND METHODS: Between January 1994 and February 1996, we recruited 30 patients to the pctx-then-cisDDP regimen and 29 to cisDDP-then-pctx, in parallel phase II trials. RESULTS: Both regimens were predictably active with responses seen in 22 of 30 patients (OR 74%; CR 27%, PR 47%) treated with pctx-then-cisDDP, as against 13 of 21 patients (OR 62%; CR 38%, PR 24%) treated with cisDDP-then-pctx. The OR rate to four cycles of pctx (induction) was 43%, with 27% disease progression; the OR to four cycles of cisDDP (induction) was 57%, with 5% progression. However, progression rates across both induction and consolidation phases were 16% (pctx-then-cisDDP) and 29% (cisDDP-then-pctx). Both regimens were unacceptably neurotoxic. II patients suffering grade 3 sensory neurotoxicity (5 on pctx-then-cisDDP, 6 on cisDDP-then-pctx) and 20 having grade 3 deafness (9 on pctx- then-cisDDP, 11 on cisDDP-then-pctx). CONCLUSION: The activity of these sequential regimens justifies their further development using the less neurotoxic platinum analogue carboplatin, perhaps combining paclitaxel with other platinum non-cross resistant drugs.

Characterization of the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in B6C3F1 and DBA/2 mice following single and repeated exposures.

Previous studies have demonstrated that repeated (14 day) administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) enhances the suppression of humoral immunity in DBA/2 (Ah-low responder) mice relative to the effect seen with identical cumulative doses after a single treatment (cumulative doses of 4.2, 14.0, and 42 mg/kg). In the present studies, we have explored this phenomenon further by determining the status of several specific parameters, which might account for the increase in antibody suppression in the DBA/2 strain following repeated TCDD exposures. Included in these studies was the induction of hepatic and splenic microsomal 7-ethoxyresorufin-o-deethylase (EROD; P4501A1) activity and biodistribution of the administered TCDD into various target organs and tissues. Changes in lymphocyte subpopulations within the spleen were also assessed by flow cytometry following both single and repeated dosing. All studies made use of direct comparisons between DBA/2 (Ah-low responder) and B6C3F1 (Ah-high responder) female mice. Results of these studies demonstrate that the enhanced suppression of humoral immunity in DBA/2 mice following repeated exposure to TCDD is not directly associated with increases in liver microsomal EROD activity and does not appear to be correlated with changes in the pattern of biodistribution or amount of TCDD within the liver or spleen of these animals. In contrast, the most significant changes that occurred following repeated dosing in either strain were observed in the levels of microsomal EROD activity and immune cell ratios within the spleen. This effect was characterized as an increase in microsomal EROD activity, and a corresponding reduction in the numbers of a non-B/non-T cell population in the spleen.

Disruption of Th1/Th2 cytokine balance by cocaine is mediated by corticosterone.

Cocaine has been shown to affect immune function through the release of corticosterone. Acute administration of both cocaine and corticosterone produces an enhancement of the T-dependent antibody response to sheep erythrocytes. The T-independent antibody response to DNP-ficoll is not enhanced under identical conditions, suggesting that the T-cell is involved as a cellular target. We examined T-helper cell cytokine production following in vivo cocaine administration and found an increase in IL-4 and IL-10; while IL-2 and IFN-gamma were unaffected. The rise in Th2 cytokines is consistent with an enhanced T-dependent antibody response, a measure of humoral immunity. Because previous results showed that the enhancement by cocaine is mediated via corticosterone, the direct effects of corticosterone on Th1/Th2 in vitro cytokine production were investigated. Th1 cytokines, IL-2 and IFN-gamma, were dose-dependently suppressed by corticosterone at physiologic concentrations. In contrast Th2 cytokines, IL-4 and IL-10, exhibited a biphasic dose response curve, whereby an enhancement was observed at low doses, followed by suppression at higher doses. In order to determine the consequences of this apparent shift towards a Th2 response on a Th1 response, we looked at the delayed-type hypersensitivity response to sheep erythrocytes. This measure of cell-mediated immunity was not significantly affected by acute cocaine, however, corticosterone administration resulted in a significant suppression. These results indicate that corticosterone can produce a shift towards a Th2 predominate response, possibly at the expense of Th1-mediated responses.

Role of corticosterone in the enhancement of the antibody response after acute cocaine administration.

A model has been developed in which acute cocaine administration results in an enhanced T-dependent antibody response to sheep erythrocytes. This enhancement occurs when cocaine (30 mg/kg, twice in 1 day) is administered 1 or 2 days before sensitization with antigen, in mice older than 16 wk. Acute cocaine has been shown to elicit a rise in serum corticosterone, and the administration of exogenous corticosterone, under similar conditions as cocaine, also results in a similar immunoenhancement. Further evidence in support of a role by corticosterone is the lack of an enhancement in adrenalectomized mice and the ability of alpha-helical corticotropin releasing factor to block the enhancement by cocaine. The role of concomitant epinephrine release from the adrenal was addressed by adrenal demedullation. Eliminating epinephrine, but not corticosterone release, had no effect on the cocaine-induced immunoenhancement. The evidence presented provides support for a major role by corticosterone in mediating cocaine's effects on at least one measure of immune function, the T-dependent antibody response.

Evaluation of sex- and strain-dependency of cocaine-induced immunosuppression in B6C3F1 and DBA/2 mice.

The objective of these studies was to determine if the immunotoxic effects of cocaine in mice are sex- and strain-dependent, a profile of activity previously described for cocaine-induced hepatotoxicity. The latter effect has been attributed to differences in the metabolism of cocaine by the cytochrome P-450 system. Subchronic, (14-day) in vivo administration of cocaine to female B6C3F1 mice showed a significant decrease (80%) in the T-dependent primary antibody response only at 80 mg/kg, although exposure to 60 mg/kg produced only a 20% decrease. In contrast, exposure to 60 mg/kg cocaine in female DBA/2 mice produced a significant decrease of 50%. An even greater effect was observed in male mice where exposure to 40 mg/kg cocaine produced > 50% decreases in both B6C3F1 and DBA/2 mice. Similar results were obtained when male mice were only exposed for 7 days. Confirmation that hepatotoxicity occurred with a similar profile of sex- and strain-dependency was obtained in parallel studies when serum chemistries were measured. The immunosuppressive activity of cocaine in female B6C3F1 mice was markedly increased when mice were pretreated with phenobarbital, a cytochrome P-450 inducer. These results extend our previous studies that indicated that cocaine-induced immunosuppression occurs under conditions that are consistent with a mechanism mediated through metabolism by the cytochrome P-450 pathway.

Alternations in splenocyte and thymocyte subpopulations in B6C3F1 mice exposed to cocaine plus diazinon.

Our laboratory has proposed a working model which asserts that cocaine's effects on immunity are mediated by reactive metabolites generated by the cytochrome P-450 system. This metabolic pathway is normally a minor one in humans, but takes on significance when metabolism of cocaine by the P-450 system is increased, as may occur with excessive alcohol consumption (enzyme induction) or after exposure to organophosphate pesticides (esterase inhibition). Results from our laboratory demonstrate that cocaine exerts its most dramatic effects on immunocompetence when administered to mice that have been pretreated with diazinon, an organophosphate esterase inhibitor. Most notably, we observed decreases in both the splenic T-dependent antibody response to sheep erythrocytes and the splenic T-independent antibody response to DNP-ficoll and a dramatic thymic atrophy in mice exposed to cocaine + diazinon, which were not seen in mice exposed to cocaine alone. The primary objective of the present investigation was to determine whether the exposure conditions used to produce the changes noted above are also capable of causing changes in lymphocyte cell types by use of flow cytometric analysis. Administration of cocaine after pretreatment with diazinon only modestly affected splenic lymphocyte subsets, which caused a slight decrease in the number of B cells. No effect was observed in the macrophage, T-helper or T-suppressor subpopulations in the spleen. These results suggest that changes in splenocyte subpopulations induced by cocaine + diazinon cannot account for the suppression of the antibody response. In contrast, all T-cell subsets in the thymus were decreased significantly, with immature double-positive thymocytes suffering the greatest loss in cell number. These results indicate that T cells, especially immature thymocytes located in the thymus, are sensitive to effects associated with the combined treatment of cocaine + diazinon.

Immunosuppression induced by acute exposure to cocaine is dependent on metabolism by cytochrome P-450.

The primary objective of this paper was to characterize the role of metabolism in immunosuppression by acute exposure to cocaine. beta-Ionone has been used to study the role of metabolism in hepatotoxicity associated with acute exposure to cocaine, and was shown to produce a greater effect than other cytochrome P-450 (P-450) inducers. When beta-ionone (600 mg/kg s.c.) was pretreated 72 and 48 hr before the acute administration of cocaine (30 mg/kg i.p.) in B6C3F1 female mice, the antibody response to sheep red blood cells was significantly suppressed. Exposure to cocaine alone produced little or no suppression. The immunosuppression in cocaine + beta-ionone-treated mice was accompanied by a decrease in thymus weight and an increase in liver weight. Administration of metyrapone (40 mg/kg i.p.) 30 min before cocaine administration (40 mg/kg) blocked completely the suppression of the antibody response by cocaine in beta-ionone-pretreated mice. The reversal by metyrapone was additional evidence that a P-450 pathway was the critical metabolic pathway of cocaine to be immunosuppressive, and the inhibitory effect of metyrapone on cocaine N-demethylase was confirmed in liver microsomes. The inductive effects of beta-ionone were also characterized further. Cocaine N-demethylase activity was significantly induced by beta-ionone. The induction of P-450IIB1/2, the only isozyme shown previously to be associated with the hepatotoxicity by cocaine, was demonstrated by Western immunoblotting to be induced by beta-ionone at doses as low as 300 mg/kg; but was less than the induction associated with phenobarbital. Studies confirmed that acute exposure to cocaine also was immunosuppressive in phenobarbital-pretreated mice. Taken together, our present results suggest that the immunosuppression by acute exposure to cocaine is associated with the increased metabolism of cocaine to toxic metabolites by P-450, probably P-450IIB1/2, as demonstrated previously for its hepatotoxicity.

Role of metabolism in cocaine-induced immunosuppression in splenocyte cultures from B6C3F1 female mice.

Cocaine has been reported to directly suppress the in vitro immune responses at very high concentrations. In the present study, the possible role of metabolism in cocaine-induced immunosuppression was investigated in splenocyte cultures isolated from B6C3F1 female mice. Since cocaine can be metabolized by both esterase and P-450 monooxygenase, we studied the direct effects of cocaine, benzoylecgonine and norcocaine on the in vitro T-dependent antibody response to SRBC. Direct exposure to cocaine only produced a modest (30%) but nonsignificant suppression of the antibody response, while benzoylecgonine, a primary product of metabolism by the esterase pathway, was devoid of activity. In contrast, direct exposure to norcocaine, the initial product of N-demethylation by the P-450 pathway, produced significant suppression at concentrations greater than or equal to 10 microM. Similar results were observed in studies measuring LPS and Con A mitogenicity. Furthermore, a significant suppression was observed when splenocytes were preincubated for 1 h with 1 mM cocaine in the presence of liver S-9 fractions isolated from phenobarbital-induced mice. Meanwhile, no suppression was obtained when splenocytes were preincubated in the presence of untreated S-9 fractions. To characterize the mechanism of our results, the capacity of both untreated and phenobarbital-induced microsomes to produce formaldehyde from cocaine was compared. The N-demethylation of cocaine was NADPH-dependent and phenobarbital-induced microsomes produced approx. 6-times higher amounts of formaldehyde, indicating a greater portion of cocaine could be metabolized through the P-450 pathway to its toxic metabolites. Finally, because benzoylecgonine shares with cocaine the presence of a methyl group on the tropane nitrogen, we also compared the ability of N-demethylation from cocaine and benzoylecgonine in mouse liver microsomes. Our results indicated that benzoylecgonine could not be demethylated as determined by a failure to generate any formaldehyde. These results offer further support that the N-demethylation pathway is a critical step to cause its immunotoxicity.

Role of metabolism by esterase and cytochrome P-450 in cocaine-induced suppression of the antibody response.

To investigate the role of metabolism in cocaine-induced immunosuppression, diazinon and beta-ionone were administered as an esterase inhibitor and a cytochrome P-450 (P-450) inducer, respectively, to B6C3F1 female mice. When 10 or 30 mg/kg of diazinon was administered 30 min before cocaine (30 mg/kg) was administered i.p. for 7 consecutive days, the suppression of the T-dependent antibody response to sheep red blood cells was potentiated greatly when compared to the suppression by cocaine alone. Spleen and thymus weights were decreased significantly and serum glutamate-pyruvate transaminase activities were elevated dramatically when cocaine and diazinon were administered together. beta-Ionone was administered s.c. for 7 consecutive days and the P-450 activities were determined 3 days after the last administration. beta-Ionone induced cocaine N-demethylation, which is the first step in the activation of cocaine to the metabolites capable of producing hepatotoxicity, as well as P-450IA1- and P-450IIB1-specific monooxygenases. The inductive effects of beta-ionone on P-450IA1/2 and P-450IIB1/2 proteins were confirmed by using Western immunoblotting with selective monoclonal antibodies. In addition, when beta-ionone (600 mg/kg) was administered with cocaine for 7 days, the suppression of the antibody response was potentiated greatly, thymus weight was decreased significantly and serum glutamate-pyruvate transaminase was elevated. Our present results suggest that inhibition of the esterase pathway of cocaine shunts the metabolism of cocaine into an immunotoxic pathway, and that the metabolism of cocaine by P-450 may be the critical pathway for the generation of the metabolites capable of suppressing the antibody response.

Role of hydrocortisone in dimethylnitrosamine-induced suppression of antibody response in the mixed culture of murine hepatocytes and splenocytes.

We have previously reported that the hormone-supplemented culture condition for primary hepatocytes is required in dimethylnitrosamine (DMN)-induced suppression of antibody response to sheep erythrocytes in the mixed cultures of murine hepatocytes and splenocytes. In the present investigation, the components of the hormone supplement were screened to identify the component(s) responsible for the increased ability of hepatocytes to activate DMN to its immunosuppressive form. The presence of hydrocortisone in the hepatocyte culture media had the primary role in DMN activation in the co-culture system. Other components of the hormone supplement showed slight or no effects. The effects of hydrocortisone were clearly confirmed through the dose-response study of both DMN and hydrocortisone. To characterize whether the effect of hydrocortisone is glucocorticoid-dependent we tested another potent glucocorticoid, dexamethasone (DEX), and determined if the activity by hydrocortisone could be reversed by RU 486. It was found that hepatocytes cultured in DEX-containing media could also activate DMN to its immunosuppressive form. However, the activity by hydrocortisone to increase DMN-induced immunosuppression was not reversed by RU 486. Furthermore, a possible direct interaction between DMN and hydrocortisone was ruled out. Finally, we transferred DMN-pre-treated culture supernatant from hepatocytes to spleen cell cultures, and found that the metabolite of DMN was very unstable, and that DMN-induced suppression of T-dependent antibody response was hepatocyte-dependent. The present results suggest that glucocorticoids, including hydrocortisone and DEX, in hepatocyte culture media can affect DMN-induced immunosuppression in the hepatocyte/splenocyte co-culture system via a pathway which does not appear to be related to the glucocorticoid receptor.

Nursing productivity in rural hospitals.

Monitoring of direct and indirect nursing costs and length of stay is essential for rural hospitals to survive, especially if a high percentage of revenues is from DRG reimbursement. Furthermore, the costs and productivity of other departments that directly affect nursing productivity must be assessed. Nurse administrators should determine accurately the nursing costs and nursing productivity for the high volume DRGs at their hospital. Nurses must be able to demonstrate to hospital administrators, insurance companies and consumers that nursing care is cost-efficient, high-quality and effective.

Immunosuppression in adult female B6C3F1 mice by chronic exposure to ethanol in a liquid diet.

The overall objective of these studies was to characterize the effects of ethanol on the immunocompetence of adult female B6C3F1 mice. To obtain a significant suppression in the antibody response to SRBC, splenocytes from untreated mice had to be directly exposed to concentrations of ethanol from 0.3% to 3.0%, or to acetaldehyde at concentrations greater than 0.03%. We do not believe that these results are consistent with a role by a direct effect by either ethanol or its primary metabolite because these concentrations are higher than what could be obtained as reasonable blood levels. For in vivo exposure, we employed a pair-feeding regimen which was based on a liquid diet containing 5% ethanol (v/v) that provided 36% of the caloric intake as ethanol. Our results indicated that there was a definite temporal relationship to the consequent suppression of the antibody response to SRBC in that no effect was observed after 14 days exposure, and that the magnitude of the suppression increased from 18% after 21 days to 70% after 42 days. We also monitored the liver for histopathology and observed that the ethanol-induced liver damage was restricted to steatosis (fatty liver), which was also manifested with time and which was most pronounced after 42 days exposure. In contrast to our results with the in vivo antibody response, we saw no effect on mitogen-induced proliferation by splenocytes from ethanol-treated mice. These results prompted us to measure in vitro antibody responses by splenocytes from ethanol-treated mice. We saw no suppression of the in vitro antibody responses to SRBC, DNP-Ficoll or LPS after any length of exposure to ethanol, and speculated that the basis for the suppression of the in vivo antibody response was an indirect consequence of exposure. We subsequently determined that when normal splenocytes were cultured in 5% serum from ethanol-exposed mice (42-day group), there was a > 80% suppression relative to the serum from the pair-fed controls. As important controls for these studies, we have demonstrated that there was no difference between the responses of normal lymphocytes cultured in 5% normal mouse serum and in 5% serum taken from the pair-fed restricted controls. A determination of the ethanol content in the serum from ethanol-exposed mice (42-day group) indicated that the amount of ethanol present in these cultures was < 0.003%.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on humoral immunity: I. Similarities to Staphylococcus aureus Cowan Strain I (SAC) in the in vitro T-dependent antibody response.

We have determined that suppression of the in vitro T-dependent humoral immune response by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is dependent on the type and concentration of serum used in the culture media. Only five out of 23 commercial lots of serum (screened at both 5 and 10%) could support a suppression in the presence of 30 nM TCDD, with the remaining lots demonstrating an apparent 'protective-like' effect against the TCDD exposure. When log dose response curves were established with TCDD (0.3, 3.0, and 30 nM) in media containing each of the serum lots supporting a suppression (at both 5 and 10%), we determined that only three lots could support a full dose-responsive suppression. Subsequently, in a comparison study between the effects of TCDD and the polyclonal B-cell activator Staphylococcus aureus Cowan Strain I (SAC) on the in vitro T-dependent humoral immune response, we have found that SAC suppresses the antibody response to SRBC and demonstrates the same serum dependency for this effect as was previously noted for TCDD. Under serum-free culturing conditions, TCDD (30 nM) caused a 15-fold increase in the AFC response to SRBCs over controls, suggesting that direct addition of TCDD to whole splenocyte cultures in the absence of serum-derived growth factors results in an increase in B-cell activation. Likewise, under serum-free conditions, SAC dose-dependently increased the AFC response over media controls, and at doses which achieved the same degree of suppression of the humoral response aa TCDD. Taken together, these studies suggest that TCDD has actions that are similar to a T cell independent polyclonal B cell activator such as SAC, and selectively acts on the B cell to suppress the T-dependent humoral immune response by a mechanism which is unique to this series of compounds. This effect however, is only detectable under appropriate serum-supported (or serum-deficient) culture conditions as described.

The role of metabolism in carbon tetrachloride-mediated immunosuppression: in vivo studies.

The role of metabolic bioactivation for carbon tetrachloride-mediated suppression of humoral responses was investigated in B6C3F1 mice. Subchronic studies with CCl4 demonstrated that this chlorinated hydrocarbon markedly suppressed T-dependent antibody responses following 7 consecutive days of administration at doses between 500 and 5000 mg/kg. No significant difference in the magnitude of suppression was observed between the ip and oral routes of exposure. Thirty-day ip administration of CCl4 at doses as low as 25 mg/kg also resulted in a significant inhibition of T-dependent antibody responses. The results from both the 7-day and the 30-day studies indicate that a greater than 50% suppression of antibody responses could not be achieved even at doses of CCl4 as high as 5000 mg/kg. In vivo studies utilized the cytochrome P450 competitive inhibitor, aminoacetonitrile (AAN), in an effort to block the effects of exposure to CCl4. Both the hepatotoxicity, as measured by serum glutamic pyruvic transaminase levels, and the suppression of the T-dependent antibody response to sRBC were reversed by treatment with AAN. Conversely, induction of cytochrome P450, by pretreatment of mice with ethanol prior to treatment with CCl4, resulted in the potentiation of the immunosuppressive effects of CCl4. AAN and ethanol administered alone had no effect on antibody responses. In order to assess the effect of CCl4 treatment on cytochrome P450 activity at doses which cause immunosuppression, measurements of total microsomal protein and specific substrate activities were determined. Significant decreases were observed in both total hepatic microsomal protein as well as in aminopyrine N-demethylase activity, aniline hydroxylase activity, and aryl hydrocarbon hydroxylase activity following treatment with CCl4 for 7 days at doses ranging from 5 to 1000 mg/kg. All of the cytochrome P450 parameters that were measured, following CCl4 treatment, demonstrated very flat dose-response curves which appeared to parallel the effects of CCl4 on antibody responses.

Suppression of humoral immune responses by dialkylnitrosamines: structure-activity relationships.

Comparisons between chemical structure of N,N-dialkylnitrosamine congeners and their ability to alter the Day 4 IgM antibody response to sRBC, body weights, and organ weights of female B6C3F1 mice were investigated. Short-chain nitrosamine congeners were selected for these studies on the basis of two criteria: (1) congeners with symmetrical aliphatic chain length [N-nitrosodimethylamine (DMN), N-nitrosodiethylamine (DEN), N-nitrosodipropylamine (DPN), N-nitrosodibutylamine (DBN)] and (2) congeners possessing an N-methyl group [N-nitrosomethylethylamine (MEN), N-nitrosomethylpropylamine (MPN), and N-nitrosomethylbutylamine (MBN)]. The immunotoxicity of each congener was evaluated based on the compound's ability to suppress the in vivo sRBC antibody response following 7 consecutive days of treatment. An ED50 dose was calculated, using a linear regression analysis, for each congener and represents the millimoles of congener per kilogram body weight required to cause a 50% suppression of the sRBC response. These studies demonstrated two general trends: (1) those dialkylnitrosamine congeners that possessed an N-methyl group were most immunotoxic and exhibited comparable ED50 concentrations (42-183 mumol/kg); and (2) dialkylnitrosamine congeners possessing symmetrical aliphatic chains demonstrated an inverse relationship between aliphatic chain length and immunotoxic potency--DMN (62 mumol/kg) greater than DEN (276 mumol/kg) greater than DPN (467 mumol/kg) greater than DBN (1557 mumol/kg). Comparisons were also made between the immunotoxic potency of various nitrosamine congeners in the whole animal and their potency in an in vitro hepatocyte-spleen cell coculture system.

Suppression of humoral and cell-mediated immune responses by carbon tetrachloride.

The effects of carbon tetrachloride (CCl4), following 7 consecutive days of exposure ip at 500, 1000, and 1500 mg/kg, were determined on murine humoral and cell-mediated immune responses, body and organ weights, spleen cell blastogenesis following mitogenic stimulation, and clinical serum parameters for liver injury. In vivo sensitization of CCl4-treated B6C3F1 mice resulted in a dose-dependent suppression of the T-dependent antibody response to sheep red blood cells (sRBC) at all doses--36, 48, and 53%, respectively. The T-independent in vivo antibody response to DNP-Ficoll was suppressed only at 1500 mg/kg, and only by approximately 16%. This dosing regimen also resulted in a significant decrease in thymus weights; however, there were no significant effects on liver, kidney, lung, or body weights. The serum chemistry profile indicated a dose-dependent increase in serum glutamic-pyruvic transaminase (SGPT) levels (34-, 47-, and 55-fold) and a non-dose-dependent increase in serum bilirubin and total protein. Serum glucose and albumin levels were unaffected. Splenocytes from mice treated with 1500 mg/kg and sensitized in vitro with antigen demonstrated a comparably suppressed antibody response to the antigens sRBC and DNP-Ficoll as observed in vivo--66 and 28% respectively. This dose of CCl4 had no effect on the in vitro antibody response to the polyclonal antigen lipopolysaccharide. The mixed lymphocyte response was dose dependently suppressed following CCl4 exposure; however, the delayed-type hypersensitivity response was unaffected. Lymphocyte blastogenesis following mitogenic stimulation with lipopolysaccharide or concanavalin A was also inhibited by CCl4 exposure. These studies demonstrate that exposure to CCl4 results in a marked suppression in both humoral and cell-mediated immune responses at concentrations which also affect the liver as evidenced by the marked increase in SGPT levels.