Serum modulation of the effects of TCDD on the in vitro antibody response and on enzyme induction in primary hepatocytes.
We have recently reported that the effects of TCDD on the in vitro antibody response can vary considerably depending on the serum conditions used in the culture media. To further investigate this phenomenon, studies were performed to compare the effects of TCDD on both splenocyte antibody responses and P450 enzyme induction (EROD) in primary hepatocytes (HPTC) derived from B6C3F1 and DBA/2 mice when evaluated in the presence of either fetal bovine serum (FBS), newborn calf serum (NBCS) or normal mouse serum (NMS). The latter studies with NMS also included crossovers where splenocytes and HPTC from B6C3F1 mice were cultured in the presence of DBA/2 serum and vice versa. Results with NBCS showed comparable suppression of antibody responses by TCDD in splenocytes from B6C3F1 and DBA/2 mice where we detected IC50 values of 3.0 and 2.8 nM, respectively. In contrast, responses in the presence of NMS showed an Ah-dependency that was characterized by a dose-related suppression of antibody responses by B6C3F1 splenocytes, but a lack of suppression in the responses by DBA/2 splenocytes. Distribution studies with radiolabelled TCDD indicated that the observed profile of activity could not be attributed to a differential uptake of the chemical into splenocytes from B6C3F1 or DBA/2 under the various serum conditions. Serum was also found to modulate the TCDD-induced EROD activity in primary HPTC and the profile of activity was identical to the effects of TCDD on in vitro antibody responses. We observed an enhanced induction of EROD in the presence of NBCS (immunosuppressive conditions) and a lower induction in the presence of FBS (non-immunosuppressive conditions), each giving the same relative magnitude of induction regardless of the mouse strain used as the source of HPTC. In contrast, induction in the presence of NMS showed an Ah-dependency and resulted in a dose-related enhancement in EROD activity in B6C3F1 HPTC but decreased activity in the DBA/2 HPTC. Cross-over studies further showed that the pattern of effects on both splenocytes and HPTC was not altered by changing the strain of mouse used as the source of serum, where each gave equivalent results. These findings demonstrate that the Ah-dependency for the effects of TCDD on both the in vitro antibody response and P450 enzyme induction are modulated by the serum environment in which the cells are exposed. The studies with NMS indicate that it is the genotype of the lymphocyte (i.e., or the HPTC), and not the strain-specific hormone environment, which confers sensitivity to TCDD.(ABSTRACT TRUNCATED AT 400 WORDS)
Morris
D L
DL
Department of Pharmacology and Toxicology, Medical College of Virginia/Virginia Commonwealth University, Richmond 23298.
Jeong
H G
HG
Stevens
W D
WD
Chun
Y J
YJ
Karras
J G
JG
Holsapple
M P
MP
D000818:Animals; D000917:Antibody Formation / Q000187:drug effects; D001769:Blood; D002478:Cells, Cultured; D003470:Culture Media / Q000494:pharmacology*; D019363:Cytochrome P-450 CYP1A1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis; D004790:Enzyme Induction / Q000187:drug effects*; D005260:Female; D005838:Genotype; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D010088:Oxidoreductases / Q000096:biosynthesis; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000502:physiology; D013154:Spleen / Q000276:immunology
D003470:Culture Media; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D019363:Cytochrome P-450 CYP1A1