1. The Common Mechanism Of Monoamine Antidepressants In Preventing Water Confinement Stress And Indomethacin-induced Gastric Mucosal Injury. 2. The Role And Mechanism Of N-acetylaspartate In Acute And Chronic Stress

1.Common modulator in preventive effects of monoamine-based antidepressants on water immersion restraint stress-and indomethacin-induced gastric mucosal damageGastric ulcer is a common and recurrent disease of digestive tract.At present,the drug treatment includes gastric acid secretion inhibitors(such as omeprazole),antacids(such as aluminum hydroxide),mucosal protectors(such as bismuth glue)and anti-Helicobacter pylori(antibiotics).Nowadays,the target of treating gastric ulcer is more and more extensive,which is no longer limited to the traditional kinds of drug.Multiple kinds of monoamine-based antidepressants have been shown prophylactic effects in experimentally induced gastric ulcer.Previous studies have found that several monoamine antidepressants include selective serotonin norepinephrine reuptake inhibitor(SNRIs),tricyclic agent(TCAs),monoamine oxidase inhibitor(MAOs)and selective serotonin reuptake inhibitor(SSRIs)can reduce the gastric mucosa damage caused by many factors such as stress,non-steroidal anti-inflammatory drugs and so on.The imbalance of redox reaction plays an important role in the occurrence of gastrointestinal mucosal injury.NADPH oxidase is one of the most important sources of reactive oxygen species(ROS)in gastrointestinal tract.From the perspective of oxidative stress,we started with the NADPH oxidases modulation in the protective effects of pretreated SNRI duloxetine on gastric mucosa lesion induced by water immersion restraint stress(WIRS)and indomethacin,and extended to TCAs,MAOs and SSRIs to explore the potential generalized molecular mechanisms of prophylactic gastroprotective of monoamine-based antidepressants.We found that the prophylactic protective effect of duloxetine on gastric mucosa was related to the reduction of oxidative stress of lipid and protein,and did not affect the ability of antioxidation.Meanwhile,pretreated duloxetine prevented the increase of gastric mucosal NADPH oxidase activity and NADPH oxidase inhibitor apocynin dose-dependently protected gastric mucosa from damage by the two factors.Furthermore,dual oxidase 2(DUOX2)and NADPH oxidase4(NOX4)are involved in the protective effects of duloxetine in both models.We then examined NADPH oxidases expression modulated by the other monoamine-based antidepressants including selective serotonin reuptake inhibitor(SSRIs)fluoxetine,tricyclic agent(TCAs)amitriptyline and monoamine oxidase inhibitor(MAOs)moclobemide in the two models,and all the three antidepressants reduced the DUOX2 expression in the gastric mucosa.Therefore,DUOX2 was a common modulator in the preventive effects of all the monoamine-based antidepressants on WIRS-and indomethacin-induced gastric lesion.Our work provided a peripheral common molecular target for monoamine modulatory antidepressants,which may be helpful to reveal the mechanisms of this kind of drugs more than regulation of monoamine.2.The role of N-acetylaspartate in acute and chronic stressStress,such as physical factors(such as mechanical stimulation),chemical factors(such as reactive oxygen species),biological factors(such as pathogens,bacteria,viruses,parasites)and social environmental factors(such as life pressure,war,loss of relatives,etc.)can cause physiological and psychological abnormalities.N-acetylaspartate(NAA)is a highly abundant brain metabolite,and its concentration in the brain can reach 10 mM or more.NAA is generated by L-aspartate N-acetyltransferase(ASP-NAT)encoded by NAT8L gene and catalysed by asparacylase,under the action of N-acetylaspartylglutamate synthetase ?(NAAGSI),NAA and glutamate synthesize N-acetylaspartylglutamate(NAAG).The glutamic acid carboxypeptidase ?(GCP?)and GCP? on the membrane are hydrolyzed and metabolized NAAG to NAA and glutamate.Using 1H-MRS,we found antidepressant duloxetine hydrochloride decreased the NAA/creatine ratio in stress-related nucleus CeA while reduced the gastric ulcer damage caused by WIRS.And there is a linear negative correlation between the change of ulcer index and NAA/creatine.Therefore,it is possible to produce anti-stress effect by intervening enzyme in specific brain area to reduce the source of NAA or increase the metabolism of NAA.We explored the NAA/creatine modulation in the specific brain regions by the acute and chronic stress,probed key synthetic and metabolitic enzymes involved in reducing the content of NAA in acute and chronic stress,then investigated whether it can transform the state of stress activation and treatment resistance through its intervention.In the model of WIRS induced gastric ulcer of rats,we found exogenous injection of NAA into CeA aggravated the damage of gastric mucosa,while NAA did not reduce gastric ulcer through peripheral administration.And knock down of NAA synthetase Nat8l in CeA by adeno-associated virus alleviated the damage of gastric mucosa.We established chronic unpredictable mild stress(CUMS)model and social defeat(SD)model and distinguished stress susceptible and stress resistant animals according to the behavior tests.The susceptible rate to CUMS was 33%,and to SD was 61.9%.After fluoxetine,a selective 5-HT reuptake inhibitor,was given to the susceptible rats,there was a significant difference in the change of NAA between the CeA area of the treatment-responsive group and the treatment-resistant group,but there was no such change in the dorsolateral prefrontal cortex(dlPFC)area,indicating that changing the content of NAA in specific brain area can change the therapeutic response of animals to the antidepressant fluoxetine.Furthermore,we injected adeno-associated virus into CeA to knock down the NAA synthetase nat81,and found that it reversed the depression like behavior of stress-resistant animals,and showed stress susceptibility in behavioral measurement,suggesting that nat81 may change the stress state of animals by regulating the content of NAA.Combined with the results of acute stress,nat8l may be a molecular marker of stress susceptibility/resistance of animals.Western blotting showed that the GCP? content in dlPFC brain area of stress resistant animals was significantly lower than that in the control group,and the GCP? content in dlPFC of stress susceptible animals was significantly higher than that in stress resistant animals,suggesting that GCP? in dlPFC plays an important role in the process of regulating animals' chronic stress response.the GCP? content decreased,indicating that stress can lead to the decrease of the transformation ability of NAAG to NAA.In addition,the content of NAAGSI in stress resistant rats was significantly lower than that in control group,suggesting that in order to maintain the stability of their own behavior or maintain normal physiological state,organism would feedback regulate the content of related metabolic enzymes to maintain the balance of NAAG.The enzymes targeted at NAA may change the response state of the organism to stress,which is the target of antidepressant treatment.