Antioxidant defence in adrenocortical cells

Oxidative stress (OS) is involved in many human disease states including neurodegenerative diseases, cancer, stroke, diabetes and heart disease. We study patients with a rare disease called Familial Glucocorticoid Deficiency (FGD) in which the body fails to produce a glucocorticoid called cortisol. Patients with this disease do not have a mechanism to cope with stress. If their body becomes stressed, for example by illness, their blood sugar levels drop, they become liable to infections and they may die if untreated. ACTH, acting through its receptor, is the hormone that is produced in response to stress and it causes the cells of the adrenal gland to produce cortisol. We have previously found defects in three genes in this pathway that cause FGD. More recently we have discovered that defects in four genes usually associated with a cells defence against oxidative stress, can also cause the disease. Exactly how OS prevents cortisol secretion is not fully understood and we believe that other genes may also be involved. This project aims to discover the mechanism by which OS affects the cells of the adrenal to prevent them making cortisol. We also hope to find other genes in this pathway by studying the genetic make-up of FGD patients. If we can discover how the OS causes its effect then this might give us clues to the mechanism in other diseases like those listed above and it may then be possible to design drugs to reduce it.

Decades of research support the idea that oxidative stress (OS) initiates and promotes cardiovascular, neurologic, and immune-related conditions. OS may arise from an imbalance between the production of reactive oxygen species (ROS) and the detoxification of these species by antioxidant defence systems such as the glutathione and thioredoxin systems. At present, relatively little is known about the contribution of individual enzymes to the redox metabolism in different cell types. We have discovered mutations in four antioxidant (AO) genes in patients with Familial Glucocorticoid Deficiency (FGD) a disease of adrenal resistance to ACTH and loss of cortisol secretion. This suggests that the adrenal cortex may be exquisitely sensitive to ROS and AO defence of primary importance to this cell type. Failure of AO defence leads to increased ROS, decreased glutathione ratios, steroidogenic acute regulatory protein reduction and hence reduced steroidogenesis.
Our aims are;
A Delineation of a larger spectrum of anti-oxidant genes involved in the pathogenesis of FGD by whole exome sequencing of 100 affected individuals to identify novel mono- or (possibly) oligogenic variants.
B Assessment of the effect of knockdown of antioxidant genes in human adrenocortical cell lines (H295R and HAC15) on;
i) ROS levels, glutathione ratio, STAR mRNA and protein levels
ii) steroidogenic profiles
iii) altered AO gene expression
C To attempt to rescue the phenotype in knockdown cell lines
i) by pharmacological intervention
ii) by overexpression of another antioxidant system
Understanding the mechanisms by which OS causes adrenal cell dysfunction could have a much wider indirect impact. Such knowledge may be instructive in the wide range of more prevalent human disorders associated with OS (listed above). Utilising knockdown adrenal cell lines as models for OS and AO treatment as proposed here could give us insights into more effective treatments for these conditions.

Decades of research support the idea that oxidative stress (OS) initiates and promotes cardiovascular, neurologic, and immune-related conditions. OS may arise from an imbalance between the production of reactive oxygen species (ROS) and the detoxification of these species by antioxidant defence systems such as the glutathione and thioredoxin systems. At present, relatively little is known about the contribution of individual enzymes to the redox metabolism in different cell types. We have identified mutations in four different antioxidant genes in patients with Familial Glucocorticoid Deficiency (OMIM 202200) causing isolated adrenal dysfunction. Our data suggest that, in humans, the glutathione and thioredoxin systems are crucial for ROS detoxification in adrenal cells. There are many publications on antioxidant defence by these systems in tissues and organs especially liver, heart and pancreas, but most of these studies have been performed in mice and rats. There has been no study of this system in the human adrenal. Characterising the antioxidant genes that cause FGD may lead to a better understanding of the mechanisms by which OS causes cell dysfunction in the adrenal and could have a much wider indirect impact. Such knowledge may be instructive in the wide range of more prevalent human disorders associated with oxidative stress including neurodegenerative diseases, cancer, stroke, diabetes and cardiac dysfunction. Utilising knockdown adrenal cell lines as models for OS and antioxidant treatment as proposed here could give us insights into more effective treatments for these conditions.