The Rapid Antidepressant Effects Of Captopril And Its Mechanism

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The rapid antidepressant effects of CaptoprilObjective: Captopril is a classic,easily applicable and safe antihypertensive agent by inhibiting the renin-angiotensin system(RAS)system.Although captopril is a poor penetrator of the blood-brain barrier,a series of case reports from different groups indicated its rapid mood-elevating effect in certain depressive patients.Yet,despite noting these cases,no studies identify the effect of captopril on depression and explain the mechanism.Here,we investigated that the effects of captopril treatment at the clinic dose in previous case reports on the CUMS-induced depressive-like behavior in mice.Methods: Mice subjected to chronic unexpectable mild stress(CUMS)paradigm showed depressive-like behaviors.We assessed the depressive-like behaviors,anxiety behavior and locomotor activity through a series of behavioral tests,including sucrose preference test(SPT),tail suspension test(TST),forced swim test(FST),novelty suppressed feeding test(NSFT),open field test(OFT)and elevated plus maze test(EPM).To quantify the gene expression levels of Renin-Angiotensin system(RAS),we used quantitative real-time polymerase chain reaction(q PCR).Enzyme linked immunosorbent assay(ELISA)was utilized to measure the content of angiotensin II(Ang II)and bradykinin(BK)in brain tissue or blood sample.Bradykinin B1 receptor(B1R)and bradykinin B2 receptor(B2R)were detected by western blotting.Stereotaxic infusion of Ang II neutralizing antibody into m PFC inhibit the effect of Ang II.Results: Intrapeitoneal(i.p.)injection with captopril at the dose of 9.75 mg/kg,19.5 mg/kg and 39 mg/kg exhibited antidepressant-like effects in mice,namely reduction in immobility time in FST(Vehicle: 103.6 ± 9.9 s;9.75 mg/kg captopril: 69.3 ± 7.2 s;19.5 mg/kg captopril: 64.7 ±.2 s;39 mg/kg Captopril: 57.9 ± 5 s),lowered the immobility time in TST(Vehicle: 215 ± 9.5 s;9.75 mg/kg captopril: 158.6 ± 14.6 s;19.5 mg/kg captopril:151.1 ± 12.3 s;39 mg/kg captopril: 160.6 ± 9.7 s).(2)Captopril had no significant influence in the anxiety-like behaviors and locomotor activity in the NSFT,OFT and EPM.(3)Captopril treatment(19.5 mg/kg and 39 mg/kg,i.p.)rescued the CUMS-induced depressive behaviors,including improving the anhedonia measured by sucrose preference(CON: 78.29 ± 1.14%;CUMS: 38.26 ± 6.08%;19.5 mg/kg captopril: 75.57 ± 7.86%;39 mg/kg captopril: 72.45 ± 2.59%),depair assessed by immobility time in FST(CON: 105.8 ± 9.89 s;CUMS: 151 ± 10.97 s;19.5 mg/kg captopril: 112.8 ± 10.05 s;39 mg/kg captopril:125 ± 6.89 s),as well as TST(CON: 140.5 ± 11.66 s;CUMS: 222.4 ± 14.72 s;19.5 mg/kg captopril: 159.7 ± 14.27 s;39 mg/kg captopril: 173.7 ± 11.23 s).Single administration of captopril(19.5 mg/kg,i.p.)produced a longlasting antidepressant effects in SPT after 1 d(CON: 83.26 ± 0.98%;CUMS: 39.33 ± 7.63%;CUMS+Captopril: 76.32 ± 4.41%),3d(CON: 79.96 ± 0.93%;CUMS: 50.49 ± 4.67%;CUMS+Captopril: 72.76 ± 3.44%),and 7 d(CON: 83.09 ± 1.23%;CUMS: 55.08 ± 4.46%;CUMS+Captopril: 80.09 ± 1.95%).(4)There was no siginificant change in the RAS(ACE,Ang II,AT1 R,AT2R)expression in the medial prefrontal cortex(m PFC),hippocampus,nucleus accumbens(NAc)and habenula of mice under CUMS.(5)Utilizing the pharmacological inhibitors like Aliskiren and Valsartan,alonging with Ang II neutralizing antibody showed no effects on the depressive-like behaviors.(6)CUMS descreased the bradykinin level in m PFC(CUMS: 59.6 ± 3.4% of CON),reversed by Captopril treatment(94.9 ± 7.7% of CON),whereas bradykinin level in Hippocampus and NAc showed no significant change.Bradykinin in the plasma of CUMS mice was downregulated and upregulated by Captopril(CON: 1271 ± 185.2 pg/ml;CUMS: 734.3 ± 65.1 pg/ml;CUMS+Captopril 1717 ± 443.6 pg/ml).By detection with the clinical plasma sample,data showed that compared with healthy controls(9117 ± 1197 pg/ml),plasma bradykinin in depressive patients falled to 5473 ± 774 pg/ml.Measurement of bradykinin B1 recptor(B1R)and bradykinin B2 recptor(B2R)protein in m PFC of CUMS.Locally infused with bradykinin intra-m PFC markedly removed the CUMS-elicited depressive symptoms in mice,generating a rise in sucrose preference(CON: 81.1 ± 1.4%;CUM: 55.6 ± 5.1%;CUMS+Bradykinin: 72.1 ± 5%),decrease in immobility time of TST(CON: 98.9 ± 10.5 s;CUMS: 171 ± 16.5 s;CUMS+Bradykinin: 93.8 ± 16.2 s).Conclusion: Our study demonstrates that captopril produced a rapid antidepressant effects in 24 h in mice.The bradykinin signaling may play a key role in the processs of captopril's function.Part ? The mechanism of captopril-induced antidepressant effectsObjective: As an angiotensin converting enzyme inhibitor(ACEI),captopril can inhibit ACE resulting in increase in bradykinin level.The above results showed that its rapid antidepressant activity was not dependent on the inhibition of the RAS,but was critically dependent on the activation of bradykinin system.Bradykinin has various physiological functions mediated by bradykinin receptors.Furthermore,bradykinin is an agonist of CDC42(cell division control protein 42 homolog),a member of Rho GTPase family.Rho GTPase family acts as a molecular switch on many cellular responses during physiological process,including synaptic plasticity.Studies show that CDC42 can activate the m TORC1(the mammalian target of Rapamycin complex 1)pathway,m TORC1-BDNF(brain derived neurotrophic factor)signaling acts as the mechanism of many rapid-acting antidepressant agents,like ketamine.However,the role of CDC42-m TORC1-BDNF signaling in the process of depression remains unclear.Here,we further explored the role and mechanism of bradykinin/B2R/CDC42/m TOR pathway in the antidepressant effect exerted by captopril in mice.Methods: Behavioral experiments were applied to assess the depressive-like behaviors of mice.Pharmacological inhibit B1 R,B2R,m TOR or CDC42 with systematic administration or stereotaxic infusion of antagonists.Combining with stereotaxic infusion experiment,we genetically knockdown B2 R expression through lentivirous-mediated sh RNA expression.Western blotting was utilized to measure the phosphorylation and total expression of p70S6 K,as well as the expression of pro BDNF.Referring to the mechanism of activated/inactivated Rho family,we measured the GTP-bound CDC42,indicating the activated CDC42.Three-dimensional structured imaging of dendritic spines was captured by confocal microscopy and then measured with Imaris software.Results:(1)Continuously pharmacological blocking B2 R,rather than B1 R result in depressive-like subtype in mice,namely rising in immobility time in FST(Vehicle: 116.7 ± 14.3 s;HOE140:158.6 ± 10.7 s).Genetic knockdown of B2 R lead to depressive despair behaviors,including increased immobile time in FST(from 112 ± 37.77 s to 152.28 ± 6.5 s)and in TST(from 145.5 ± 9.18 s to 196.5 ± 7.55 s).(2)Locally block B2 R by HOE140 within m PFC ruined the antidepressant function of Captopril in CUMS mice,referring to decrease in sucrose preference(Captopril: 74.1 ± 2.6%,HOE140+Captopril: 54.4 ± 3.7%),gain in immobile time in FST(Captopril: 118.08 ± 6.64 s;HOE140+Captopril: 163.1 ± 6.79 s)and TST(Captopril 158.4 ± 7.17 s;HOE140+Captopril: 202.1 ± 10.13 s).Genetic knockdown of B2 R prevent the therapeutic effects of captopril on CUMS mice(SPT: CUMS+Captopril group 74.3 ± 2.4%;FST: 128.6 ± 5.8 s;TST: 177 ± 6.5s;CUMS+LV-B2 R sh RNA+Captopril group: SPT: 46.3 ± 4%;FST: 165.8 ± 9.4 s;TST: 208 ± 7.8 s).(3)Captopril obviously upregulated the activation of CDC42 in m PFC of CUMS mice(CUMS+Captopril: 72± 11.9% of CON).(4)Captopril obviously upregulated the activation of CDC42 in m PFC of CUMS mice(CUMS+Captopril: 72 ± 11.9% of CON).(5)Infusion of selective inhibitor of CDC42,ML141 abolished the antidepressant effects of captopril,and reversed the captopril triggered increase in spine density of m PFC in CUMS mice(CUMS+Captopril: 1.54 ± 0.11 per ?m;CUMS+ML141+Captopril: 0.82 ± 0.1 per ?m).(6)Captopril treatment activated the m TOR signal(CUMS: 56.51 ± 6% of CON+CUMS+Captopril: 103.3 ± 18% of CON)and BDNF signal(CUMS: 51.52 ± 2.62% of CON;CUMS+Captopril: 118.9 ± 25.82% of CON),which were then disrupt by B2 R knockdown,resulting that the m TOR signal(CUMS+Captopril:103.3 ± 18.02% of CON;CUMS+B2R sh RNA+Captopril: 40.92 ± 5.82% of CON)and BDNF signal(CUMS+Captopril: 118.9 ± 25.82% of CON;CUMS+B2R sh RNA+Captopril: 47.64 ± 2.87 of CON)were reversed.(7)Rapamycin administration with m PFC of CUMS mice hindered the antidepressant impact of captopril in SPT(CUMS+Captopril: 77.4 ± 2.44%;CUMS+Rapamycin+Captopril: 34.6 ± 4.4%),FST(CUMS+Captopril: 80.7 ± 12.1 s;CUMS+Rapamycin+Captopril: 143.3 ± 10.5 s)and TST(CUMS+Captopril: 143.3 ± 15.1 s;CUMS+Rapamycin+Captopril: 191.7 ± 15.4 s).Conclusion: The antidepressant effects of captopril mainly depend on the increase in the number of spine synapses in the m PFC of depressive mice through activating synaptogenesis via bradykinin/B2R/CDC42/m TOR pathway.