Chrysin, a natural flavonoid enhances steroidogenesis and steroidogenic acute regulatory protein gene expression in mouse Leydig cells

Abstract

During the aging process of males, testosterone biosynthesis declines in testicular Leydig cells resulting in decreases in various physiological functions. To explore the possibility of delaying the decline using food supplements, we have studied steroidogenic effects of a natural flavonoid, chrysin, in mouse Leydig cells. Chrysin dramatically increased cyclic AMP (cAMP)-induced steroidogenesis in MA-10 mouse Leydig tumor cells. This result was confirmed using Leydig cells isolated from mouse testes. The steroidogenic effect of chrysin is not associated with an increase in expression of the P450 side-chain cleavage enzyme, required for the conversion of cholesterol to pregnenolone. In addition, when 22(R)hydroxylcholesterol was used as a substrate, chrysin induced a non-significant increase in steroid hormone, suggesting that the majority of the observed increase in steroidogenesis was due to the increased supply of substrate cholesterol. These observations were corroborated by showing that chrysin induced a marked increase in the expression of steroidogenic acute regulatory (StAR) protein, the factor that controls mitochondrial cholesterol transfer. Also, chrysin significantly increased StAR promoter activity and StAR mRNA level. Further studies indicated that this compound depressed expression of DAX-1, a repressor in StAR gene transcription. In the absence of cAMP, chrysin did not increase steroidogenesis. However, when a sub-threshold level of cAMP was used, StAR protein and steroid hormone were increased by chrysin to the levels seen with maximal stimulation of cAMP. These results suggest that while chrysin itself is unable to induce StAR gene expression and steroidogenesis, it appears to function by increasing the sensitivity of Leydig cells to cAMP stimulation.

Natural Flavonoids in StAR Gene Expression and Testosterone Biosynthesis in Leydig Cell Aging

“…Chrysin has been described as a testosterone-increasing agent that blocks further testosterone metabolism by inhibiting aromatase activity (Dhawan et al, 2002;Kellis & Vickery, 1984). This testosterone-increasing activity of chrysin was confirmed in the recent studies with Leydig cells isolated from mouse and MA-10 mouse Leydig cell line, with the steroid hormone productions of the Leydig cells being significantly enhanced by chrysin (Jana et al, 2008). However, it failed to induce the significant increase in steroid hormone when MA-10 Leydig cells were co-incubated with 22(R)hydroxycholesterol, suggesting that this flavonoid increase steroidogenesis mainly by improving the cholesterol transfer to the mitochondrial inner membrane.…”

“…As shown in Fig. 2C, in the absence of cAMP, flavonoid alone is not able to induce significant increases in StAR protein expression and steroid hormone production (Jana et al, 2008;Li et al, 2011). In the studies without exogenous cAMP, the endogenous cAMP becomes important for the steroidogenic effect of flavonoids.…”

“…The transcription factors that act on StAR promoter were examined in the Leydig cells incubated with chrysin. It was found that this flavonoid significantly reduced the transcriptional repressor, DAX-1 protein (Jana et al, 2008). As DAX-1 protein and DAX-1 mRNA were reduced, StAR protein and steroid hormone production dramatically increased.…”

“…This possibility was examined by the experiments with MA-10 mouse Leydig cells cultured for 6 hours in the medium containing increasing concentrations of luteolin and a cAMP analog (dbcAMP). StAR and DAX-1 proteins, steroid production, StAR mRNA and StAR promoter activity were analyzed as described in the previous study (Jana et al, 2008). As shown in Fig.…”

Development of chrysin loaded poloxamer micelles and toxicity evaluation in fish embryos

“…The fruit of this plant is commonly used in Thailand and other East Asian countries as food and herbal medicine. Chrysin possesses several biological activities including, anti-cancer (3,4), anti-inflammation (5,6), and antioxidant properties (7,8) and is reported to cause an increase of testosterone production via suppression of aromatase, an enzyme that converts androgen to estrogen (9). However, biological actions are only facilitated given the stable structure and low molecular weights of the active compounds that can be soluble and pass through cell membranes (10).…”