Effects of apigenin on steroidogenesis and steroidogenic acute regulatory gene expression in mouse Leydig cells.
Previous studies reported that the age-related decline in testosterone biosynthesis is associated with a decrease in the steroidogenic acute regulatory (StAR) protein which regulates the rate-limiting step of testosterone biosynthesis. To explore the possibility of delaying this decline using a dietary approach, we have examined the effect of a natural flavonoid, apigenin, on StAR gene expression in mouse Leydig cells. Incubation of these cells with the flavonoid enhanced cyclic adenosine monophosphate (cAMP)-induced steroidogenesis and StAR protein expression. The results from the analyses of StAR mRNA by reverse transcription-polymerase chain reaction and the luciferase assays of StAR promoter activity indicated that this flavonoid enhanced StAR gene expression at the level of transcription. Further studies showed that apigenin blocked the thromboxane A2 receptor and interrupted the signaling through the cyclooxygenase-2-thromboxane A synthase-thromboxane A2-receptor pathway, resulting in a reduction of DAX-1 (dosage sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene-1) protein, a transcriptional repressor of StAR gene expression. When DAX-1 protein was reduced, the sensitivity of the Leydig cells was dramatically enhanced, with sub-threshold level of cAMP being able to induce maximal levels of StAR protein expression and steroid hormone production. The present study suggests a potential application of apigenin to improve StAR protein expression and steroidogenic sensitivity of aging Leydig cells.
Garrison Institute on Aging, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
Wei
W
Li
Akhilesh K
AK
Pandey
Xiangling
X
Yin
Jau-Jiin
JJ
Chen
Douglas M
DM
Stocco
Paula
P
Grammas
Xingjia
X
Wang
D000818:Animals; D047310:Apigenin / Q000494:pharmacology*; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000378:metabolism; D057137:DAX-1 Orphan Nuclear Receptor / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007985:Leydig Cells / Q000378:metabolism*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D044262:Prostaglandin H2 / Q000378:metabolism; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000378:metabolism; D015398:Signal Transduction; D013256:Steroids / Q000378:metabolism*; D013930:Thromboxane-A Synthase / Q000378:metabolism; D000098682:Steroidogenic Acute Regulatory Protein
D057137:DAX-1 Orphan Nuclear Receptor; D010750:Phosphoproteins; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D013256:Steroids; D000098682:Steroidogenic Acute Regulatory Protein; D044262:Prostaglandin H2; D047310:Apigenin; D000242:Cyclic AMP; D051546:Cyclooxygenase 2; D013930:Thromboxane-A Synthase