| Background:Functional dyspepsia(FD),a common functional gastrointestinal disease,is often accompanied by visceral hypersensitivity.The pathogenesis of gastric hypersensitivity remains largely unknown.Our previous study has demonstrated that prenatal maternal stress(PMS)induced gastric hypersensitivity in offspring rats through upregulation of acid-sensing ion channels 1(ASIC-1)protein and downregulation of DNA methyltransferases(DNMTs)in gastric dorsal root ganglion(DRGs).In the process of embryonic development,folic acid(FA)can improve embryonic internal environment and prevent nervous system diseases.Under ischemic injury condition,FA supplementation improved neuronal survival and regeneration,which provided evidence for treatment for neuropathic pain.Therefore,the aim of the present study was to investigate the roles and mechanisms of FA on gastric hypersensitivity in adult rats with PMS.Our study would provide a potential treatment strategy and theoretical basis for clinical treatment for chronic visceral pain.Methods:1.Establishment of gastric hypersensitivity model:Pregnant Sprague Dawley(SD)rats were divided into PMS and CON group.PMS rats were subjected to heterotypic intermittent stress(HIS)from gestational day seven to twenty-one or until delivery.Rats in CON group were not treated.Male offspring in both groups were kept for further experiments.2.Measurement of gastric hypersensitivity:Gastric distention(GD)and electromyographic(EMG)recording were used to evaluate gastric hypersensitivity in CON and PMS rats.3.Labelling of gastric-specific DRG neurons:Gastric-specific DRG neurons were labeled with DiI,which was injected into stomach wall,for electrophysiological and immunofluorescence experiments.4.Neuronal excitability recording:Whole-cell patch clamp techniques were employed to measure gastric-specific DRG neuronal excitability.5.Detection of molecular expression:RT-PCR and Western Blotting were performed to detect the expression of ASIC-1 and DNMT-1 in rat gastric DRGs.6.Immunofluorescence staining:Immunofluorescence was performed to detect the expression and localization of ASIC-1 and DNMT-1 in rat gastric-specific DRG neurons,which were labeled with Dil.7.Drug administration:Intrathecal injection of LV-DNMT-1 was used to detect PMS gastric-specific DRG neuron excitability and gastric hypersensitivity of rats;intraperitoneal injection of FA was applied to detect gastric-specific DRG neuronal excitability and gastric hypersensitivity of PMS rats.Intrathecal injection of DC-517,an inhibitor of DNMT-1,was used to detect gastric hypersensitivity and ASIC-1 protein expression in PMS rats,whose dam was treated with FA.Results:1.PMS induced gastric hypersensitivity of adult rat offspring in 7 weeks while DNMT-1 protein and mRNA levels were significantly downregulated in DRGs.2.Intrathecal injection of LV-DNMT-1 greatly reduced gastric-specific DRG neuron excitability,meanwhile markedly attenuated gastric hypersensitivity of PMS rats.3.Intraperitoneal injection of FA significantly reduced gastric-specific DRG neuron excitability and markedly attenuated gastric hypersensitivity of PMS rats.4.Intrathecal injection DC-517,an inhibitor of DNMT-1,greatly enhanced gastric hypersensitivity in PMS rats,whose dam was treated with FA.5.Immunofluorescence showed DNMT-1 and ASIC-1 were co-localized in rat gastric-specific DRG neurons.6.Intraperitoneal injection of LV-DNMT-1 or FA markedly downregulated the expression of ASIC-1 in gastric DRGs of PMS rats.7.Intrathecal injection DC-517 significantly upregulated ASIC-1 expression in gastric DRGs of PMS rats treated with FA during pregnancy.Conclusions:Our data suggest that PMS induced gastric hypersensitivity in offspring rats correlated with upregulation of ASIC-1 protein and downregulation of DNMT-1 protein and mRNA level in DRGs.Folic acid treatment significantly alleviated gastric hypersensitivity by enhancing DNMT-1 expression and reducing ASIC-1 expression in PMS rats. |
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