Dysfunction Of Middle Cerebral Artery Contraction In Adult Male Offspring Exposed To Dexamethasone During Pregnancy

Objective:To investigate the effects and related mechanisms of antenatal long-acting glucocorticoids（GCs）drug（dexamethasone,DEX）exposure on the vasoconstrictive function of the middle cerebral artery（MCA）in adult male offspring.Methods:Sprague-Dawley（SD）rats were used as experimental animals,and pregnant rats were randomly divided into the dexamethasone exposure group（DEX）and the control group（vehicle normal saline,VEX）（20 rats for each group）.In the DEX group,pregnant rats were injected intraperitoneally with DEX sodium phosphate injection at a dose of 200μg/kg on alternate days during late pregnancy（gestational days 14,16,18,and20）.In the VEX group,pregnant rats were injected with an equal volume of physiological saline using the same method and at the same time.After natural delivery,the male offspring were raised until 120 days old,and the MCA was collected for experiments.Previous studies have shown that prenatal adverse factors have gender-dependent detrimental effects on offspring vascular function.Male offspring are more prone to developing vascular dysfunction compared to females.Therefore,this project primarily focuses on studying the vascular function of adult male offspring MCA.Since the cerebral blood flow circulation is regulated by key factors such as angiotensin II（Ang II）,a vascular tension detection system was used to measure the vasoconstrictive response of the MCA induced by Ang II in adult male offsprings from both groups.Acutely isolated MCA smooth muscle cells were used for electrophysiological experiments.Using protein kinase C（PKC）pathway inhibitor（GF109203X,GF）,PKC pathway agonist（Phorbol-12,13-dibutyrate,PDBu）,endoplasmic reticulum inositol-1,4,5-trisphosphate receptor inhibitor（2-aminoethyl diphenylborinate,2APB）,L-type Ca²⁺channel inhibitor（nifedipine,NIFE）,and agonist（Bayk8644）,we investigated the mechanisms underlying the changes in vasoconstrictive function of the MCA in adult offsprings exposed to antenatal DEX at the level of vascular tissue and cellular electrophysiology.Reverse transcription polymerase chain reaction（Real-Time PCR）and protein immunoblotting（Western blot）were used to detect the transcription and protein expression levels of relevant genes,respectively.DNA methylation sequencing and chromatin immunoprecipitation assays were used to explore the intrinsic relationship between epigenetic modifications and changes in gene expression.Results:The response to Ang II-mediated vasoconstriction in the offspring MCAs of the DEX group was significantly stronger than that of the VEX group.In both groups of offspring MCAs,GF and 2APB partially inhibited the Ang II-mediated vasoconstriction,but neither of them eliminated the difference in vasoconstriction between the two groups.NIFE significantly inhibited the Ang II-mediated vasoconstriction in both groups and eliminated the difference in vasoconstriction mediated by Ang II between the two groups.There was no significant difference in PDBu-mediated vasoconstriction between the two groups.Bayk8644-mediated constriction in the DEX group was significantly stronger than the VEX group,and the Ca²⁺channel current density of the isolated smooth muscle cells from DEX offspring MCA was significantly higher than that in the VEX offspring MCA.Molecular biological studies found that the m RNA and protein levels of Cav1.2(L-type Ca²⁺channelα1c subunit)in the MCA of the DEX group were higher than those of the VEX group,while the expression level of Cav3.2(T-type Ca²⁺channelα1h subunit)had no significant difference between the two groups.The increased Cav1.2 expression in the DEX group was associated with changes in histone modifications within its gene promoter region.Conclusions:Antenatal DEX exposure leads to the enhancement of Ang II-mediated vasoconstriction in adult male offspring MCA,which is related to the enhancement of L-type Ca²⁺channels;the increase of Cav1.2 in DEX offspring MCA was associated with histone modification-mediated transcriptional activation.