Karakterizacija i putevi sinhronizacije perifernog biološkog časovnika i steroidogeneze u Lajdigovim ćelijama pacova
Characterization and pathways of synhronization of peripheral biological clock and steroidogenesis in rat Leydig cells
Author
Baburski, Aleksandar Z.Mentor
Kostić, TatjanaCommittee members
Kostić, TatjanaMatić, Gordana
Matić, Gordana
Andrić, Silvana
Metadata
Show full item recordAbstract
Biološki časovnik organizuje metabolizam i fiziološke procese u cirkadijalne
ritmove. Na nivou ćelije, on se sastoji od grupe gena koji preko negativnih
povratnih sprega održavaju ritam sopstvene transkripcije, ali regulišu i ritmičnost
transkripcije mnogih drugih gena. Iako je poznato da su određeni geni časovnika
neophodni za sintezu testosterona i fertilnost mužjaka, još uvek nema preciznih
podataka o cirkadijalnoj fiziologiji testosteron produkujućih Lajdigovih ćelija. Ova
studija je dizajnirana da definiše (1) cirkadijalni obrazac endokrine funkcije
Lajdigovih ćelija uključujući i eksprimiranje gena perifernog časovnika i (2)
upletenost LH-cAMP signalizacije u sinhronizaciju ritma Lajdigovih ćelija
korišćenjem in vivo modela poremećene cAMP homeostaze (hipogonadotropni
hipogonadizam, starački hipogonadizam, pinealektomija) i in vitro stimulacije
Lajdigovih ćellija. Rezultati su pokazali cirkadijaln ritam funkcije Lajdigovih ćelija
koji se ogleda u vremenski koordinisan...oj oscilatornoj produkciji testosterona i
intracelularnog cAMP, cirkadijalnom eksprimiranju regulatora (Nur77 i Arr19),
steroidogenih elementa (Star/StAR, Cyp11a1 i Cyp17a1), kao i elementa časovnika
(Bmal1/BMAL1, Per1/2/3, Cry1/2, Rev-erba/b/REV-ERBA, Rorb, Dec1/2, Dbp i
E4bp4). Ritam transkripcije osnovnih gena časovnika kao i ključnog elementa
steroidogeneze (Star) se održava i u primarnoj kulturi ovih ćelija. Redukcija cAMP
detektovana u Lajdigovim ćelijama pacova sa hipogonadotropnim
hipogonadizmom stimuliše transkripciju većeg broja gena časovnika: Per2, Rorb,
Rev-erbb, Dec1/2, E4bp4, Ck1e/d, i inhibiše Npas2. Sa druge strane, in vitro
stimulacija cAMP-signalizacije povećava transkripciju Per1, Dec1/2, Rorb, Npas2 i
E4bp4, i smanjuje transkripciju Rev-erba. Starenje, dovodi do opadanja robusnosti
cirkadijalne funkcije Lajdigovih ćelija koja se ogleda u smanjenju oscilacija
intracelularnog cAMP, smanjenja amplitude eksprimiranja najvažnijih gena
časovnika (Bmal1/BMAL1, Per1/2, Rev-erba/REV-ERBA), gena uključenih u
metabolizam holesterola (Lipe, Soat2, Scarb1) i steroidogenih gena, (Star/StAR,
Cyp11a1, Cyp17a1, Hsd3b1/2/HSD3B, Hsd17b4)...
Biological clock organizes metabolic and physiological processes in circadian
rhythms. At cell level, it consists of group of genes that regulate its own
transcription by negative feedback loop, also regulating transcription rhythmicity
of other genes. Although, it is known that some clock genes are necessary for
testosterone synthesis and male fertility, there is no precise data about circadian
physiology of testosterone-producing Leydig cells. This thesis was design to define
(1) circadian pattern of endocrine function of Leydig cells, including expression of
clock genes, and (2) involvement of LH-cAMP signaling in synchronization of
Leydig cells rhythm using in vivo model of disturbed cAMP homeostasis
(hypogonadotropic hypogonadism, hypogonadism in aging, pinealectomy) and in
vitro Leydig cell stimulation. Results confirmed circadian rhythmicity of Leydig cell
function represented by temporal coordination of cyclic testosterone production
and intracellular cAMP, circadia...n expression of regulators (Nur77, Arr19),
steroidogenic (Star/StAR, Cyp11a1 i Cyp17a1) and clock elements (Bmal1/BMAL1,
Per1/2/3, Cry1/2, Rev-erba/b/REV-ERBA, Rorb, Dec1/2, Dbp, E4bp4). Rhythm in
transcription of core clock genes as well as key steroidogenic element (Star) was
preserved in primary Leydig cell culture. Reduction in cAMP, detected in Leydig
cells from hypogonadotropic hypogonadal rats, stimulated transcription of some
clock genes: Per2, Rorb, Rev-erbb, Dec1/2, E4bp4, Ck1e/d, but inhibited Npas2. On
the other hand, in vitro stimulation of cAMP signaling increased transcription of
Per1, Dec1/2, Rorb, Npas2 and E4bp4, and reduced transcription of Rev-erba. Aging
dulled robustness of circadian function of Leydig cells, represented by decline in
intracellular cAMP oscillations and amplitude of expression of core clock genes
(Bmal1/BMAL1, Per1/2, Rev-erba/REV-ERBA), genes involved in cholesterol
metabolism (Lipe, Soat2, Scarb1) and steroidogenic genes (Star/StAR, Cyp11a1,
Cyp17a1, Hsd3b1/2/HSD3B, Hsd17b4). Abolishment of melatonin, a main cue that
spread information of light regime via cAMP signaling, stimulated expression of
clock (Bmal1/BMAL1, Per1/2) and steroidogenic (Star/StAR, Hsd3b/HSD3B)
elements...