Cellular defense mechanisms against benzo[a]pyrene in testicular Leydig cells: implications of p53, aryl-hydrocarbon receptor, and cytochrome P450 1A1 status.
Leydig cells of the mammalian testis produce testosterone and support spermatogenesis, and thereby their role in male function is fundamental. Although benzo[a]pyrene (B[a]P) has been known to exhibit carcinogenic, apoptogenic, and endocrine-disrupting activities, its potential signaling system in Leydig cells remains to be discovered. In the present study, using the TM3 Leydig cell line and primary Leydig cells, we showed that Leydig cells do not die by exposure to B[a]P and found that an increased level of X chromosome-linked inhibitor of apoptosis protein may be associated with the antiapoptotic process. The Leydig cells were shown to express p53, but its translational level was extremely low. Although a high level of p53 protein was not necessary for apoptosis induced by B[a]P-7,8-diol-9,10-epoxide (a final B[a]P metabolite) in Leydig cells, the apoptosis of primary Leydig cells appears to be p53 independent. This indicates the lack of p53 function in primary Leydig cells. Furthermore, Leydig cells were found to retain insignificant levels of endogenous aryl-hydrocarbon receptor and AhR nuclear transporter proteins in nature. Exposure to B[a]P did not result in a significant increase in aryl-hydrocarbon receptor proteins that are required for CYP1A1 transcription. CYP1A1 expression was present in Leydig cells but at levels insufficient to exhibit its activity. Finally, we have demonstrated that overexpression of CYP1A1 in Leydig cells sensitizes the cells to exhibit its activity in the presence of B[a]P and, thus, induction of apoptosis. Together, these results indicate that the deficiency of CYP1A1 activity might be a decisive condition rendering Leydig cells secure from exogenous polycyclic aromatic hydrocarbons such as B[a]P.
Chung
Jin-Yong
JY
Department of Anatomy and Cell Biology, College of Medicine, Dong-A University, Dongdaeshin-dong 3-1, Seo-gu, Busan, Korea.
Kim
Ji Young
JY
Kim
Yoon-Jae
YJ
Jung
Sun Ju
SJ
Park
Ji-Eun
JE
Lee
Seung Gee
SG
Kim
Jin Tac
JT
Oh
Seunghoon
S
Lee
Chang Joo
CJ
Yoon
Yong-Dal
YD
Yoo
Young Hyun
YH
Kim
Jong-Min
JM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator / Q000235:genetics / Q000378:metabolism; D001564:Benzo(a)pyrene / Q000633:toxicity*; D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D007985:Leydig Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013737:Testis / Q000166:cytology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
D018336:Receptors, Aryl Hydrocarbon; D016159:Tumor Suppressor Protein p53; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001564:Benzo(a)pyrene; D019363:Cytochrome P-450 CYP1A1