Targeting of mechanisms of elevated anxiety in female Wfs1-deficient mice
Date
2018-08-28
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Abstract
Wolframi sündroom on pärilik neurodegeneratiivne haigus, mille teket seostatakse mutatsioonidega WFS1 geenis. Sündroomi põhilisteks sümptomiteks on suhkrudiabeet, magediabeet, nägemisnärvi atroofia ja kurtus. Lisaks eelnimetatule, esineb nii Wolframi sündroomiga patsientidel kui ka mutantse WFS1 geeni kandjatel mitmesuguseid psühhiaatrilisi häireid, sealhulgas depressiooni ja ärevust. WFS1 geeni täpne funktsioon on seni siiski selgusetu ja selle uurimiseks loodi Tartu Ülikoolis Wfs1-puudulikkusega hiir. Peagi ilmnes asjaolu, et Wfs1-puudulikkusega hiirtel esineb lisaks muudele häiretele ka kõrgenenud ärevus uudses keskkonnas.
Antud töö keskendub kõrgenenud ärevust põhjustavate molekulaarsete mehhanismide uurimisele Wfs1-puudulikkusega emastel hiirtel. Uuringu sihtmärkideks said valitud GABAergiline süsteem, endoplasmaatilise retiikulumi (ER) stress ja Na-pump. Nimelt uurisime närvirakkudes erutuse tekke ja leviku eest vastutava Na-pumba aktiivsust ja selle alaühikute ekspressiooni hiirte erinevates ajuosades. Mõõtsime stressihormooni (kortikosteroon) taset hiirte veres pärast uudse keskkonnaga tutvumist ning uurisime, kuidas uudse keskkonna poolt põhjustatud stress mõjutab ajurakkude ER-is tekkivat stressi ja sellega toimetulekut Wfs1-puudulikkusega hiirtel võrrelduna nende metsiktüüpi pesakaaslastega. Võrdlesime GABAergilise süsteemi toimimist metsiktüüpi ja Wfs1-puudulikkusega hiirtel, kasutades modulaatorina etanooli.
Tuvastasime, et uudne keskkond põhjustab Wfs1-puudulikkusega hiirtel märkimisväärselt kõrgemat kortikosterooni taset veres võrreldes metsiktüüpi pesakaaslastega. Näitasime ER stressi markerite ekspressiooni ja Na-pumba aktiivsuse muutusi hiireliinile iseloomuliku käitumise eest vastutavates ajuosades. Samuti leidsime, et Wfs1-puudulikkusega hiired on tundlikumad etanooli rahustava ja hüpnootilise efekti suhtes, mis viitab muutustele GABAergilises süsteemis. Häiretele GABAergilise süsteemi talitluses Wfs1-puudulikkusega hiirtel viitas ka GABA retseptori alaühiku ekspressiooni tõus. Ilmselt on just GABAergilisel süsteemil keskne roll ärevuse tekkimisel Wfs1-puudulikkusega hiirtel.
Wolfram syndrome (WS) is a hereditary neurodegenerative disorder, that is associated with mutations in WFS1 gene. Main symptoms of WS are diabetes mellitus, diabetes insipidus, optic atrophy and deafness. In addition, patients with WS and heterozygous carriers of mutant WFS1 gene suffer from various psychiatric disorders, including depression and anxiety. The exact function of WFS1 gene remains unknown. To investigate function of WFS1 gene, Wfs1-deficient mice were created. It soon became evident, that in addition to other disorders, Wfs1-deficient mice have elevated anxiety in unfamiliar environment. The goal of the present study was to investigate molecular mechanisms behind the elevated anxiety in female Wfs1-deficient mice. We investigated functioning of GABAergic system, endoplasmic reticulum (ER) stress and Na+-K+ ATPase. Namely, we measured activity of Na+-K+ ATPase and the expression levels of its subunits in different brain regions. Blood levels of stress hormone (corticosterone) were measured in mice after exposure to unfamiliar environment, and the effect of this stressor on expression levels of ER stress markers was investigated. We also investigated functioning of GABAergic system by using ethanol as GABA receptor modulator and measuring expression levels of GABA receptors subunits in Wfs1-deficient mice compared to wild-type mice. We established, that Wfs1-deficient mice have significantly higher blood corticosterone levels after exposure to unfamiliar environment, compared to their wild-type littermates. We showed changes in expression levels of ER stress markers and activity of Na+-K+ ATPase in brain structures responsible for dominant behavioral traits of studied mouse lines. We also demonstrated that Wfs1-deficient mice are more sensitive to the anxiolytic and hypnotic effects of ethanol. This and the fact that Wfs1-deficient mice had higher expression level of one of the GABA receptor subunits after ethanol administration, shows disturbances in the functioning of GABAergic system. Most probably, GABAergic system plays a central role in the regulation of anxiety in Wfs1-deficient mice.
Wolfram syndrome (WS) is a hereditary neurodegenerative disorder, that is associated with mutations in WFS1 gene. Main symptoms of WS are diabetes mellitus, diabetes insipidus, optic atrophy and deafness. In addition, patients with WS and heterozygous carriers of mutant WFS1 gene suffer from various psychiatric disorders, including depression and anxiety. The exact function of WFS1 gene remains unknown. To investigate function of WFS1 gene, Wfs1-deficient mice were created. It soon became evident, that in addition to other disorders, Wfs1-deficient mice have elevated anxiety in unfamiliar environment. The goal of the present study was to investigate molecular mechanisms behind the elevated anxiety in female Wfs1-deficient mice. We investigated functioning of GABAergic system, endoplasmic reticulum (ER) stress and Na+-K+ ATPase. Namely, we measured activity of Na+-K+ ATPase and the expression levels of its subunits in different brain regions. Blood levels of stress hormone (corticosterone) were measured in mice after exposure to unfamiliar environment, and the effect of this stressor on expression levels of ER stress markers was investigated. We also investigated functioning of GABAergic system by using ethanol as GABA receptor modulator and measuring expression levels of GABA receptors subunits in Wfs1-deficient mice compared to wild-type mice. We established, that Wfs1-deficient mice have significantly higher blood corticosterone levels after exposure to unfamiliar environment, compared to their wild-type littermates. We showed changes in expression levels of ER stress markers and activity of Na+-K+ ATPase in brain structures responsible for dominant behavioral traits of studied mouse lines. We also demonstrated that Wfs1-deficient mice are more sensitive to the anxiolytic and hypnotic effects of ethanol. This and the fact that Wfs1-deficient mice had higher expression level of one of the GABA receptor subunits after ethanol administration, shows disturbances in the functioning of GABAergic system. Most probably, GABAergic system plays a central role in the regulation of anxiety in Wfs1-deficient mice.
Description
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Keywords
animal models, anxiety, molecular mechanisms, behavioural physiology, behaviour modifications, Wolfram syndrome, dopaminergic system