Диссертация обосновывает концепцию о мультифакторном контроле регуляции гормонопоэза, взаимодействии между различными системами вторичных мессенджеров, которые опосредуют внутриклеточный перенос сигналов агонистов, обеспечивающих функциональную активность адренокортикальных клеток, а также их трансрегуляторные влияния.
Ключевые слова: кора надпочечников, мессенджерные процессы в адренокортикоцитах, кортикотропин, ионы калия, эстрогены, производные этаноламина, протеинкиназы, транскрипционные факторы.
SUMMARY
Kovzun O.I. Molecular mechanisms of signal transduction of adrenal cortex regulators. – Manuscript.
Thesis for a scientific degree of doctor of biological sciences by speciality 14.01.14 – Endocrinology. – Komisarenko Institute of Endocrinology and Metabolism of Academy of Medical Sciences of Ukraine, Kyiv, 2008
The thesis describes the research of the molecular mechanisms of regulation of adrenocortical function. The signal transduction of main regulator of adrenocortical function – ACTH, and estrogens, potassium ions, N-acylethanolamines – is considered.
Corticotropin and prolactin receptors in the adrenal cortex and their regulation has been characterized. The postreceptoral system of the agonists signal transduction have been studied. It was shown that either cAMP-dependent protein kinase A, or protein kinase C are involved to postreceptoral messenger mechanism, that mediates ACTH action in adrenocortical cells. Important steps in the ACTH signaling are mitogen-activated protein kinase (JNK) and nuclear transcriptional factor (c-jun).
The main messenger system participating in estrogens effects in adrenal cortex were estimated. The influence of estradiol on cAMP and cGMP levels, protein kinases A and C activities, mitogen-activated protein kinase, transcriptional factors levels and corticosteroids secretion was investigated. Estradiol raised the activities of protein kinases A and C in membrane fraction of adrenal cortex tissue. Significant increase of steroidogenesis was observed. It was declared that cAMP dependent signaling system, protein kinase C, mitogen-activated protein kinase (ERK1/2) and nuclear transcriptional factor (c-fos) are involved in activation of steroidogenesis in the adrenal cortex by estradiol.
The possibility of involvement of several messenger systems, such as cAMP-dependent messenger cascade and protein kinase C, in К+ signal transduction in human adrenocortical cells as well as hypothesis on crosstalk between messenger mechanisms for main physiological agonists controlling steroid biosynthesis in adrenals are discussed.
The messenger mechanisms mediating N-acylethanolamines (NAE) regulatory signals in adrenal cortex were studied. It was shown, that N-acylethanolamines treatment resulted in a decrease of cAMP level in adrenocortical cells. The rise of protein kinase C activity was obtained in membrane fraction after N-acylethanolamines in vitro treatment (3.3 μg/ml). Activity of cAMP-dependent protein kinase A significantly decreased in cytosol fraction of adrenocorticocytes. It was conclused, that steroidogenenis activation is mediated of protein kinase C activation, inhibition is mediated of cAMP-dependent messenger system.
The role of protein kinase C isoforms and receptor tyrosine kinases in tumorogenesis of adrenal cortex is described. Translocation of PKCα from cytosol to membrane fraction was detected in adenomas and carcinomas of adrenal cortex. In conclusion it may be argued that some isoforms of PKC might be involved in oncogenesis in human adrenal gland.
The effect of corticotropin and inhibitor of protein kinase C, chelerythrine chloride on the change of caspase-3 level and on the rate of DNA laddering in hyperplasia adrenal cortex tissue of patient with Cushing’s syndrome was studied. It was established that ACTH caused significant antiapoptotic effect in human adrenal cortex. The obtained data suggest an antiapoptotic effect of ACTH in adrenal cortex estimated according to the caspase-3 level and on the rate of DNA fragmentation depends on activation of protein kinase C. The reactivity of human adrenal tumors depends on influence of N-acyletanolamines mixture in different types of tumors. It was shown that DNA fragmentation, as a final event of apoptosis, is significantly increased in tumor aldosteroma tissue in comparison with adjacent normal tissue.
Some interactions and transregulation influences between different second messenger systems, which mediate intracellular signal transduction of agonists andprovide functional activity of adrenocortical cells are discussed.
Key words: adrenal cortex, messenger mechanisms of adrenocortical cells, corticotropin, potassium ions, estrogens, N-acylethanolamines, protein kinases, transcriptional factors.