Search Results

You are looking at 1 - 3 of 3 items for

  • Author: Paula Grammas x
  • Refine by access: All content x
Clear All Modify Search
Akhilesh K Pandey Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Neuropsychiatry

Search for other papers by Akhilesh K Pandey in
Google Scholar
PubMed
Close
,
Wei Li Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Neuropsychiatry

Search for other papers by Wei Li in
Google Scholar
PubMed
Close
,
Xiangling Yin Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Neuropsychiatry

Search for other papers by Xiangling Yin in
Google Scholar
PubMed
Close
,
Douglas M Stocco Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Neuropsychiatry

Search for other papers by Douglas M Stocco in
Google Scholar
PubMed
Close
,
Paula Grammas Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Neuropsychiatry

Search for other papers by Paula Grammas in
Google Scholar
PubMed
Close
, and
XingJia Wang Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Neuropsychiatry

Search for other papers by XingJia Wang in
Google Scholar
PubMed
Close

Previous studies have reported the roles of Ca2+ in steroidogenesis. The present study has investigated an inhibitory effect of Ca2+ influx through L-type Ca2+ channels on gene expression of steroidogenic acute regulatory (STAR) protein that regulates the transfer of substrate cholesterol to the inner mitochondrial membrane for steroidogenesis. Blocking Ca2+ influx through L-type Ca2+ channels using the selective Ca2+ channel blocker, nifedipine, markedly enhanced cAMP-induced STAR protein expression and progesterone production in MA-10 mouse Leydig cells. This was confirmed by utilization of different L-type Ca2+ channel blockers. Reverse transcription-PCR analyses of Star mRNA and luciferase assays of Star promoter activity indicated that blocking Ca2+ influx through L-type Ca2+ channels acted at the level of Star gene transcription. Further studies showed that blocking the Ca2+ channel enhanced Star gene transcription by depressing the expression of DAX-1 (NR0B1 as listed in the MGI Database) protein, a transcriptional repressor of Star gene expression. It was also observed that there is a synergistic interaction between nifedipine and cAMP. Normally, sub-threshold levels of cAMP are unable to induce steroidogenesis, but in the presence of the L-type Ca2+ channel blocker, they increased STAR protein and steroid hormone to the maximal levels. However, in the absence of minimal levels of cAMP, none of the L-type Ca2+ channel blockers are able to induce Star gene expression. These observations indicate that Ca2+ influx through L-type Ca2+ channels is involved in an inhibitory effect on Star gene expression. Blocking L-type Ca2+ channel attenuated the inhibition and reduced the threshold of cAMP-induced Star gene expression in Leydig cells.

Free access
Kuladip Jana Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Nutrition Sciences, Department of Neuropsychiatry

Search for other papers by Kuladip Jana in
Google Scholar
PubMed
Close
,
Xiangling Yin Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Nutrition Sciences, Department of Neuropsychiatry

Search for other papers by Xiangling Yin in
Google Scholar
PubMed
Close
,
Randolph B Schiffer Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Nutrition Sciences, Department of Neuropsychiatry

Search for other papers by Randolph B Schiffer in
Google Scholar
PubMed
Close
,
Jau-Jiin Chen Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Nutrition Sciences, Department of Neuropsychiatry

Search for other papers by Jau-Jiin Chen in
Google Scholar
PubMed
Close
,
Akhilesh K Pandey Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Nutrition Sciences, Department of Neuropsychiatry

Search for other papers by Akhilesh K Pandey in
Google Scholar
PubMed
Close
,
Douglas M Stocco Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Nutrition Sciences, Department of Neuropsychiatry

Search for other papers by Douglas M Stocco in
Google Scholar
PubMed
Close
,
Paula Grammas Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Nutrition Sciences, Department of Neuropsychiatry

Search for other papers by Paula Grammas in
Google Scholar
PubMed
Close
, and
XingJia Wang Garrison Institute on Aging, Department of Cell Biology and Biochemistry, Department of Nutrition Sciences, Department of Neuropsychiatry

Search for other papers by XingJia Wang in
Google Scholar
PubMed
Close

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.

Free access
XingJia Wang Departments of Neuropsychiatry, Garrison Institute on Aging,
Cell Biology and Biochemistry,
Neuropsychiatry, and
Pathology, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA

Search for other papers by XingJia Wang in
Google Scholar
PubMed
Close
,
Chwan-Li Shen Departments of Neuropsychiatry, Garrison Institute on Aging,
Cell Biology and Biochemistry,
Neuropsychiatry, and
Pathology, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA

Search for other papers by Chwan-Li Shen in
Google Scholar
PubMed
Close
,
Matthew T Dyson Departments of Neuropsychiatry, Garrison Institute on Aging,
Cell Biology and Biochemistry,
Neuropsychiatry, and
Pathology, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA

Search for other papers by Matthew T Dyson in
Google Scholar
PubMed
Close
,
Xianling Yin Departments of Neuropsychiatry, Garrison Institute on Aging,
Cell Biology and Biochemistry,
Neuropsychiatry, and
Pathology, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA

Search for other papers by Xianling Yin in
Google Scholar
PubMed
Close
,
Randolph B Schiffer Departments of Neuropsychiatry, Garrison Institute on Aging,
Cell Biology and Biochemistry,
Neuropsychiatry, and
Pathology, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA

Search for other papers by Randolph B Schiffer in
Google Scholar
PubMed
Close
,
Paula Grammas Departments of Neuropsychiatry, Garrison Institute on Aging,
Cell Biology and Biochemistry,
Neuropsychiatry, and
Pathology, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA

Search for other papers by Paula Grammas in
Google Scholar
PubMed
Close
, and
Douglas M Stocco Departments of Neuropsychiatry, Garrison Institute on Aging,
Cell Biology and Biochemistry,
Neuropsychiatry, and
Pathology, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA

Search for other papers by Douglas M Stocco in
Google Scholar
PubMed
Close

The essential role of arachidonic acid (AA) in steroidogenesis has been previously demonstrated. The present study continues the investigation into how AA regulates steroidogenesis by examining the effects of epoxygenase-derived AA metabolites on cAMP-stimulated steroidogenic acute regulatory (StAR) gene expression and steroid hormone production in MA-10 mouse Leydig cells. The HPLC analysis of cell extracts from MA-10 cells treated with the cAMP analog dibutyryl cAMP (dbcAMP) demonstrated an increase in three epoxygenase-generated AA metabolites: 5,6-epoxyeicosatrienoic acid (EET), 8,9-EET, and 11,12-EET. Incubating MA-10 cells with each of the EETs induced a dose–dependent increase in StAR protein expression and steroid hormone production in the presence of dbcAMP. These metabolites also significantly enhanced StAR gene transcription as determined by luciferase assays of StAR promoter activity and reverse transcriptase-PCR analysis of StAR mRNA levels. While the EETs enhanced steroidogenesis, inhibiting the activity of protein kinase A (PKA) abolished the stimulatory effects of these AA metabolites on StAR expression and steroid hormone production. This study suggests that cAMP stimulation of MA-10 cells increases epoxygenase-generated AA metabolites and the co-action of these metabolites with PKA significantly increases StAR gene expression and steroid hormone production.

Free access