PubMed Health⌕ Search

Biomedical subjects

D R Germolec

Publications and source records attributed to D R Germolec.

70 records · Page 4Linked to original sources
PubMed1989

Selective inhibition of polymorphonuclear neutrophil activity by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Although the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), via its interaction with the Ah receptor, is an extremely potent carcinogen and immunosuppressive agent in experimental animals, its possible actions on polymorphonuclear (PMN) function have not been determined. In addition to their importance against infectious organisms, PMNs have been implicated in antitumor resistance. The present studies examined the effects of in vivo exposure to TCDD on PMN function in B6C3F1 (TCDD sensitive, presence of high affinity Ah receptor) and DBA/2N (TCDD resistant at low doses, defective Ah receptor) mice. Animals received a single oral exposure of 5 or 10 micrograms/kg of TCDD and PMNs were obtained 5 days later from the peritoneal cavity following elicitation with sodium caseinate. TCDD reduced the cytolytic and cytostatic activity of PMA-activated PMNs in B6C3F1, but not in DBA/2N mice, suggesting that this response segregates with the Ah locus. Furthermore, TCDD was found to bind specifically to PMNs from Ah-responsive mice. Neither the production of superoxide and hydrogen peroxide nor degranulation, the latter measured by beta-glucuronidase release, was impaired. Supernatants recovered from PMN cell cultures of TCDD-sensitive mice, but not from resistant DBA/2N mice, showed reduced killing capacity for actinomycin D-treated L929 tumor cells, while their ability to bind to tumor cells was not altered. These data suggest that TCDD interferes with PMN-mediated tumor cell killing by altering the production or secretion of a cytolytic factor. Examination of bone marrow stem cells revealed that granulocytic but not monocytic colonies were reduced after TCDD exposure in vivo and in vitro. Although mature PMNs had detectable levels of Ah receptor, exposure in vitro of these cells to TCDD had no effect on antitumor activity. Thus, it is possible that TCDD may affect PMNs at the level of hematopoiesis, via a direct interaction with granulocyte precursor cells, or modulate PMNs at different stages of maturation.

Animals↗
PubMed1989

A comparison of three nucleoside analogs with anti-retroviral activity on immune and hematopoietic functions in mice: in vitro toxicity to precursor cells and microstromal environment.

A number of 2'3'-dideoxynucleosides have been reported to markedly inhibit the in vitro growth of HIV, the causative agent of acquired immunodeficiency syndrome (AIDS). Clinical trials have shown that the continued therapeutic use of these nucleoside derivatives can be associated with adverse side effects. Since these side effects include myelotoxicity, as occurs in many patients treated with zidovudine (AZT; 3'-azido'3-deoxythymidine), and AIDS patients already represent an immunologically compromised population, we examined the immunological effects of three nucleoside inhibitors, including zidovudine, 2'3'-dideoxycytidine, and 2'3'-dideoxyadenosine (DDA) in a mouse model. Additional studies were conducted to further determine and characterize the potential toxic effects associated with these drugs on the hematopoietic system. Of the three dideoxynucleosides examined, only DDA altered immune functions following a 30-day subchronic exposure in mice. This was evidenced by a marked suppression of the antibody plaque-forming cell response and a slight alteration in macrophage function. None of the nucleoside derivatives affected bone marrow function following in vivo exposure, although AZT produced a mild macrocytic anemia in vivo and was myelotoxic when added in vitro to bone marrow cell cultures. In vitro studies indicated that AZT was capable of affecting both proliferating stem cells as well as the stromal cell microenvironment, both of which play a role in hematopoiesis. These data indicate that, although the mice may not develop the identical toxicities associated with nucleoside therapy in humans, certain adverse immunological and hematological effects were readily discerned which could have relevance to humans.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Toxicology studies of a chemical mixture of 25 groundwater contaminants. II. Immunosuppression in B6C3F1 mice.

Concern over the potential adverse health effects of chemically contaminated groundwater has existed for many years. In general, these studies have focused on retrospective epidemiological studies for cancer risk. In the present studies, immune function was monitored in female B6C3F1 mice exposed to a chemical mixture in drinking water for either 14 or 90 days. The mixture consisted of 25 common groundwater contaminants frequently found near toxic waste dumps, as determined by EPA surveys. None of the animals developed overt signs of toxicity such as body or liver weight changes. Mice exposed to the highest dose of this mixture for 14 or 90 days showed immune function changes which could be related to rapidly proliferating cells, including suppression of hematopoietic stem cells and of antigen-induced antibody-forming cells. Some of these responses, e.g., granulocyte-macrophage colony formation, were also suppressed at lower concentrations of the chemical mixture. There were no effects on T cell function or T and B cell numbers in any of the treatment groups. Altered resistance to challenge with an infectious agent also occurred in mice given the highest concentration, which correlated with the immune function changes. Paired-water studies indicated that the immune effects were related to chemical exposure and not to decreased water intake. These results suggest that long-term exposure to contaminated groundwater may represent a risk to the immune system in humans.

Animals↗
PubMed1989

Perturbations of the immune system by xenobiotics.

Classically, immunotoxicology has been defined as the study of adverse effect on the immune system associated with exposure to environmental chemicals, pharmacologic agents, and biologicals. Although a multitude of immune system defects may occur, these can be generally categorized as immunomodulation (immune suppression or potentiation), hypersensitivity (i.e., allergy), and autoimmunity. We present here a brief synopsis of the ontogeny of immunotoxicology as a discipline including methodology currently used in our laboratory, as well as in others, for investigating the immunomodulatory potential of chemicals at the cellular and biochemical level. Additionally, we summarize some studies related to the immunosuppressive effects of one particular compound, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Last we discuss potential future directions and challenges in the field of immunotoxicology.

Animals↗
PubMed1988

Suppression of B cell function by methotrexate and trimetrexate. Evidence for inhibition of purine biosynthesis as a major mechanism of action.

Methotrexate (MTX) is a widely used drug in the treatment of a variety of human neoplasms. Trimetrexate (TMQ) is a lipid-soluble quinazoline derivate of MTX that, unlike MTX, is not dependent upon membrane folate transport for cellular entry. A number of studies have demonstrated that MTX and, more recently, TMQ possess potent immunosuppressive properties. To examine the cellular events associated with the immunomodulatory effects of anti-folates on humoral immunity, a murine B cell maturation model was used. In vitro, MTX and TMQ reduced the number of antibody-forming cells to SRBC, as well as IgM production. B cells stimulated with anti-Ig demonstrated a dose-related suppression in [3H]UdR incorporation after addition of either drug, suggestive of a decrease in de novo DNA synthesis. B cell activation events preceding S phase were also suppressed by both anti-folates, as evidenced by inhibition of RNA synthesis. However, neither drug affected surface expression of Ia Ag nor inositol phosphate accumulation. Addition of TdR caused a slight non-significant increase in the antibody-forming cell response in the presence of 10(-7) M MTX. However, addition of hypoxanthine or adenine, but not guanine, resulted in complete restoration. Timed addition revealed that the ability of MTX to suppress antibody responses was diminished if added after 48 h of culture, similar to the reversal of this suppression mediated by hypoxanthine. Cell cycle analysis of LPS-stimulated B lymphocytes demonstrated that both drugs modulated events preceding, as well as during, the S phase. The present studies suggest that although drug-induced impairments in dTMP biosynthesis may be responsible for deficient lymphoid proliferation, anti-folate-induced impairment in purine biosynthesis is a major mechanism in anti-folate-induced suppression of humoral immunity.

Animals↗
PubMed1988

Selective effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and corticosteroid on in vitro lymphocyte maturation.

The environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the corticosteroid dexamethasone have potent effects on lymphocyte function, although the effects of the former have not been well characterized. In the present studies murine B cell maturation was used as a model system to examine and compare the effects of TCDD and dexamethasone on cell function. Immunosuppression by TCDD and dexamethasone is mediated by binding to specific intracellular R referred to as the Ah and glucocorticoid R, respectively. Although both compounds were comparable in their ability to inhibit antibody responses to the T-independent antigen TNP-LPS, the events responsible for suppression were found to be distinct. Dexamethasone, although affecting multiple stages of B cell maturation, had its primary effect very early, manifested by inhibition of the phosphoinositide signal transduction pathway. This was evidenced by a decrease in accumulation of inositol phosphate and surface Ia antigen expression as well as an inability to enter the cell cycle after stimulation with anti-Ig. In contrast, neither early signaling events nor proliferation were affected in B cells treated with TCDD. However, TCDD inhibited Ig secretion after stimulation of B cells with T cell-replacing factor, suggesting that TCDD modulates the differentiation of B cells into plasma cells. These differential results were confirmed by monitoring the expression of surface antigens that occur on B cells, including Ia, 7D4, and PC.2, during this maturational process. Whereas dexamethasone inhibited the expression of surface antigens that occur early in maturation (Ia and 7D4), TCDD blocked only the expression of the plasma cell marker PC.2. Although TCDD altered later stages of the B cell cycle, the presence of TCDD was required at the time of initial activation to be effective, suggesting that TCDD may interfere with early cell programming.

Animals↗
PubMed1988

Lack of a relationship between immune function and chemically induced hepatocarcinogenesis in B6C3F1 mice.

The relationship between immune function and chemically induced hepatocarcinogenesis was studied employing an in vivo murine model. Neonatal B6C3F1 mice were given a single carcinogenic dose of diethylnitrosamine (DEN) and the time-response kinetics for the early (foci of alteration) and late (adenomas/carcinomas) phases of hepatocellular carcinogenesis were compared to changes in hematopoiesis and immune functions associated with immune surveillance and natural resistance. Increases in hematopoiesis occurred just prior to or concurrent with the appearance of hepatocellular carcinomas, while increased macrophage and natural killer cell cytotoxicity and suppression of cell-mediated immunity occurred following tumor appearance and progressed with increasing tumor burden. Neither immunological nor hematopoietic changes were associated with early phases of hepatocarcinogenesis, as monitored by the appearance of altered hepatocellular foci. Although changes in hematopoiesis may represent an early indicator for hepatocarcinogenesis in the mouse tumor model, the data suggest that altered immune surveillance and natural resistance are not factors in the development of chemically induced hepatocellular tumors, and the changes in immune function are probably secondary to tumor development.

Animals↗
PubMed1988

Biochemical events associated with inhibition of B-cell proliferation by phorbol diesters.

Phorbol myristate acelate (PMA), a potent tumor promoter, has a variety of effects on cells of the immune system resulting in altered patterns of cell proliferation and differentiation. Although PMA is mitogenic or co-mitogenic for human lymphocytes and murine T-cells, it inhibits proliferation of murine B-cells stimulated by LPS or anti-Ig. PMA, however, does not inhibit the ability of LPS or anti-Ig to activate B-cells, as evidenced by increased Ia antigen expression and RNA synthesis. In the present studies it was shown that inhibition of DNA synthesis by PMA coincided with qualitative and quantitative changes in phosphorylated proteins. In particular, PMA treatment resulted in a unique profile of phosphoproteins independent of LPS or anti-Ig treatment. Inhibition of DNA synthesis occurred over a wide range of PMA concentrations. At concentrations up to 10(-9) M, inhibition of proliferation correlated with decreased phosphatidylinositol turnover and decreased intracellular Ca2+ levels, suggesting that PMA affects the phosphoinositide signal transduction pathway. However, at PMA concentrations less than 10(-10) M, inhibition of anti-Ig- and LPS-mediated proliferation occurred without inhibition of the phosphoinositide transduction signal. At these concentrations, PMA-induced inhibition of DNA synthesis was highly sensitive to recombinant IL-2. These data suggest that the antiproliferative effects of PMA on B-cells stimulated by LPS or anti-Ig may be mediated by two mechanisms. At high concentrations, PMA causes a feedback regulation of the phosphoinositide-dependent messenger system, while at lower concentrations, PMA alters the response to specific growth factors. Since PMA induces unique phosphoproteins and both of these events can be regulated by protein phosphorylation, it is possible that these unique phosphoproteins are responsible for the antiproliferative effects of PMA.

Animals↗
PubMed1987

Selective immunosuppression in mice of natural killer cell activity by ochratoxin A.

Ochratoxin A, a naturally occurring mycotoxin, has recently been shown to cause renal and hepatic carcinomas in mice. In the present studies, the effects of ochratoxin A on immune mechanisms associated with tumor resistance were examined in mice using dose levels similar to those that cause neoplasia. Ochratoxin A was shown to specifically inhibit natural killer (NK) cell activity and increase the growth of transplantable tumor cells without altering T-cell- or macrophage-mediated antitumor activity. In contrast, ochratoxin B, a much less toxic ochratoxin, did not influence immune function. Polyinosinic:polycytidylic induced interferon was markedly reduced in mice following exposure to ochratoxin A although total serum protein levels were slightly increased. Injection of polyinosinic:polycytidylic enhanced NK activity in the presence of ochratoxin A, although the level of enhancement was slightly lower than that produced by the agent in the absence of ochratoxin A. Thus, ochratoxin appears to suppress NK cell activity by inhibiting production of basal interferon. Additionally, these findings suggest a possible role for altered NK cell function in the development of mycotoxin-induced carcinogenesis.

Animals↗
PubMed1987

Comparative effects on the immune system of methotrexate and trimetrexate.

Methotrexate (MTX) is an antimetabolite commonly used in the treatment of neoplastic disease, while trimetrexate (TMQ) is an investigational antifolate which is currently advocated as a potential alternative to MTX. The cytotoxic properties of antifolates to rapidly proliferating cells suggests that the immune system would be a significant and undesirable target for these drugs. We examined the comparative effects of these two chemotherapeutic agents on the murine immune system using in vivo and in vitro methods. Both drugs were potent suppressors of T-dependent antibody formation in vitro as well as in vivo. While TMQ appeared to be more immunosuppressive than MTX following in vitro addition of the drugs, the converse appeared to be true when dosing was performed in vivo. The drug induced suppression of T-dependent antibody formation was dose dependent for both antifolates. Lymphoproliferative studies demonstrated marked suppressive effects on LPS and PHA induced 3H-uridine and 3H-deoxyuridine incorporation following addition of both drugs in vitro suggesting effects on both RNA and thymidylate biosynthesis. Timed addition studies demonstrated a particularly susceptible time period (hours 24-48 after addition of the mitogen LPS) in stimulated lymphocytes with respect to inhibition of 3H-uridine incorporation. Following in vivo administration of either antifolate, natural killer cell activity was significantly decreased with no substantial differences between the two drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Immunological studies on mice exposed subacutely to methyl isocyanate.

The immunotoxicity of methyl isocyanate (MIC) was evaluated in female B6C3F1 mice exposed via inhalation to 0, 1, or 3 ppm for 6 hr per day on 4 consecutive days. The antibody response to sheep erythrocytes and natural killer cell activity were found to be unaffected by MIC exposure. Although lymphoproliferative responses to mitogens were moderately suppressed by MIC, the differences were not statistically significant. The response of splenic lymphocytes to allogeneic leukocytes in a mixed leukocyte response (MLR) was suppressed in a dose-related fashion and was significantly different from the control response at the 3 ppm level. This effect was thought to be secondary and a result of general toxicity, rather than a direct effect of MIC on the immune system. Furthermore, resistance to the infectious agents Listeria monocytogenes, mouse malaria parasite, and influenza virus, or to transplantable tumor cells was not compromised by MIC exposure. Thus, the immune system does not appear to be a primary target for MIC toxicity.

Animals↗
PubMed1986

Immunotoxicity studies in mice exposed to methyl isocyanate.

The effects of methyl isocyanate (MIC) on systemic immunity were evaluated in female B6C3F1 mice exposed via inhalation to 0, 1, or 3 ppm for 6 hr per day on four consecutive days. Humoral immunity, measured as the antibody response to sheep erythrocytes, and natural killer cell activity were not affected by MIC. Furthermore, resistance to the infectious agents Listeria monocytogenes, mouse malaria parasite, and influenza virus, or to B16F10 transplantable tumor cells, was not compromised by MIC exposure. Although lymphoproliferative responses to mitogens were not significantly suppressed, the response of splenic lymphocytes to allogeneic leukocytes in a mixed leukocyte response (MLR) was suppressed in a dose-related fashion and differed significantly from the control response at the 3-ppm level. These studies indicate that MIC exposure in mice does not severely alter systemic immunity. The moderate changes detected in immune function may be a secondary consequence of respiratory toxicity which occurred in these animals.

Animals↗
PubMedDate not supplied

Differential stimulation of IgE production, STAT activation and cytokine and CD86 expression by 2,4-dinitrochlorobenzene and trimellitic anhydride.

It has been reported that dermal exposure to trimellitic anhydride (TMA, 50%), a respiratory allergen, induced greater production of serum IgE and expression of Th2 cytokines than 2,4-dinitrochlorobenzene (DNCB, 1%), a potent contact sensitizer, in female BALB/C mice. To determine if there is any strain difference, four strains (B6C3F1, C57BL/6, BDF1 and BALB/C) of female mice were employed in this study to compare the differential effects of these chemicals on the hypersensitivity responses. Serum IgE levels were increased in TMA-treated B6C3F1, C57BL/6 and BDF1 mice when compared with the DNCB treatment and vehicle controls; in contrast, no difference was observed between TMA- and DNCB-treated BALB/C mice, although both chemicals induced greater IgE production than vehicle controls. In vitro expression of interleukin 4 (IL-4) and IL-13 mRNA by overnight concanavalin A (ConA)-stimulated draining lymph node cells was enhanced following in vivo treatment with TMA but not with DNCB in the B6C3F1, C57BL/6 and BDF1 mice. In contrast, TMA and DNCB induced similar levels of IL-4 and IL-13 mRNA in the BALB/C mice. The IL-4 protein levels in the supernatants of overnight ConA-treated draining lymph node cells were also increased in TMA-treated B6C3F1 and C57BL/6 mice when compared with the DNCB treatment and vehicle controls. Further mechanistic evaluation in the B6C3F1 mice indicated that the activation of STAT6 but not STAT4 by ConA plus IL-2-treated draining lymph node cells was increased in TMA- but not DNCB-treated mice when compared with the vehicle controls. Furthermore, surface expression of B7.2 (CD86) by B cells was increased in both TMA- and DNCB-treated B6C3F1 mice when compared with the vehicles; however, greater B7.2 expression was observed in TMA-treated compared with DNCB-treated. Overall, these results demonstrate that a similar pattern of IgE and cytokine production was observed in these strains of mice except for BALB/C. Furthermore, differential activation of STAT6 and expression of CD86 following exposure to TMA and DNCB may contribute to the differential production of IgE and cytokines.

Administration, Cutaneous↗
PubMedDate not supplied

Acetaminophen-induced hepatotoxicity is associated with early changes in NF-kB and NF-IL6 DNA binding activity.

Nuclear transcription factors, such as NF-kB and NF-IL6, are believed to play an important role in regulating the expression of genes that encode for products involved in tissue damage and inflammation and, thus, may represent early biomarkers for chemical toxicities. In the present study changes in DNA binding activity of these factors were examined in livers of mice administered hepatotoxic doses of acetaminophen (APAP). NF-kB and NF-IL6 DNA binding occurred constitutively in control mouse liver. However, within 4 hr following administration of hepatotoxic doses of APAP, their binding activities were transiently lost and is in contrast to AP-1 transcription factor where activation occurs under similar conditions. These changes corresponded with increased release of inflammatory mediators (IL-6, serum amyloid A) and increased levels of enzymatic markers of hepatocyte damage. Similarly, treatment of mice with gadolinium chloride, an inhibitor of Kupffer cell activation and known to protect against APAP-induced hepatotoxicity, reduced the observed pathophysiological response in the liver while altering the APAP-associated changes in NF-kB DNA binding activity. NF-kB was found predominantly in parenchymal and endothelial cells and was composed primarily of relatively inactive p50 homodimer subunits in control liver. Taken together, these studies suggest that hepatotoxicity is associated with early and complex changes in DNA binding activities of specific transcription factors. In particular, NF-kB and NF-IL6 may serve as negative regulators of hepatocyte-derived inflammatory mediators and is analogous to that previously observed in certain other cell systems such as B lymphocytes.

Acetaminophen↗