RSC Advances View Article Online PAPER View Journal | View Issue Brain region-specific metabolite networks regulate antidepressant effects of venlafaxine Cite this: RSC Adv.,2017,7, 46358 Shunjie Bai,abcd Qingchuan Hu,bcd Zhi Chen,abcd Zihong Liang,bce Wei Wang,abc Peng Shen,bcf Ting Wang,abcd Haiyang Wangbc and Peng Xie *abcdf Venlafaxine (VLX) is one of the most commonly prescribed clinical antidepressants. Although the initial targets of venlafaxine are known to be neurotransmitter systems, the mechanisms underlying chronic therapeutic effects in different key brain regions have not been fully clarified. In this study, we used depression-related behavior to evaluate the effects of chronic VLX therapy in rats. Gas chromatography- mass spectrometry-based metabolomics was used to characterize metabolomic responses to VLX in the hippocampus and prefrontal cortex. The results demonstrated significant differences in despair behaviors between VLX-treated and control groups of rats, and the metabolic profiles of both the hippocampus and prefrontal cortex were significantly altered after VLX treatment. Furthermore, the altered metabolites Received 7th August 2017 had significant brain region specificities, and the altered metabolites in the hippocampus had significant Creative Commons Attribution 3.0 Unported Licence. Accepted 20th September 2017 correlations with the despair behaviors. The results obtained from such a metabolic profiling strategy DOI: 10.1039/c7ra08726h potentially provide a unique perspective on the molecular mechanisms of VLX, and these findings could rsc.li/rsc-advances have important implications for antidepressant drug discovery efforts. 1. Introduction the patients.11 Recently, people have begun to explore new antidepressants, such as the rapid antidepressant effects of Depression is a leading cause of ill health and disability to ketamine and its metabolite, hydroxynorketamine.12 Under- society, and more than 300 million people globally are now standing the underlying molecular and neurobiological mech- This article is licensed under a living with depression.1–4 Antidepressant medications are anisms of VLX will offer novel therapeutic insights for exploring considered to be the primary treatment for the majority of the optimizing antidepressant therapy. population according to many clinical guidelines. Venlafaxine One of the key issues in studying the mechanisms of anti- Open Access Article. Published on 29 September 2017. Downloaded 9/28/2021 1:55:26 AM. (VLX), a rst-line antidepressant of the serotonin–norepineph- depressant action is to select the appropriate brain regions in rine reuptake inhibitor (SNRI), has been widely used for which antidepressant exert its effects. Our previous studies have management of depression and anxiety.5–8 Although the initial shown that metabolic dysfunction occurs in prefrontal cortex – – target of VLX is known, the mechanisms underlying the effects (PFC)13 16 and hippocampus (HP)17 20 in a rat model of depres- of chronic administration in vivo remain largely unclear. sion. Previous studies have also shown that PFC and HP Meanwhile, previous studies by our group as well as investiga- respond differently to antidepressants.21 Thus, examining how tors at other research institutes have demonstrated that VLX regulates the molecular and neurobiological changes in patients given VLX have high levels of discontinuation due to these functional brain regions may offer important mechanistic adverse events,9,10 as well as a number of cardiovascular side insights into its therapeutic actions. effects,11 and that VLX takes 6 to 8 weeks to become effective in Previous studies on antidepressants have focused on changes in neurotransmitters and neurotrophic factors, but ignored some other aspects of the biological alterations. aDepartment of Neurology, Yongchuan Hospital, Chongqing Medical University, Metabolomics is the quantitative analysis of the complete set of Chongqing 402460, China. E-mail: [email protected]; Fax: +86-23-68485111; metabolic products in a given biosample,22 and metabolites are Tel: +86-23-68485490 a direct reection of the phenotype. Metabolomics has been b Chongqing Key Laboratory of Neurobiology, Chongqing, China widely used in the study of the pathogenesis of depression and cInstitute of Neuroscience and the Collaborative Innovation Center for Brain Science, antidepressant drugs.2,13,23–26 Thus, metabolomics is a very Chongqing Medical University, Chongqing, China dKey Laboratory of Laboratory Medical Diagnostics of Education, Department of powerful way to provide valuable insight into the molecular Laboratory Medicine, Chongqing Medical University, Chongqing, China mechanisms targeted by pharmacotherapies, thereby facili- eDepartment of Neurology, The Inner Mongolia Autonomous Region People's Hospital, tating the development of novel antidepressant treatments. Hohhot, Inner Mongolia, China Here, we used depression-related behavior to evaluate the fDepartment of Neurology, The First Affiliated Hospital of Chongqing Medical effects of chronic VLX therapy in rats. A gas chromatography- University, Chongqing, China 46358 | RSC Adv.,2017,7, 46358–46369 This journal is © The Royal Society of Chemistry 2017 View Article Online Paper RSC Advances mass spectrometry (GC-MS)-based metabolomics method, and analyzed by SMART. TST was conducted in a black box coupled with multivariate statistical analysis, was used to (30  30  53 cm). Rats were individually hung on a hook by characterize metabolomic responses to chronic VLX treatment their tails using a small piece of adhesive tape. Test sessions in PFC and HP. Our ndings demonstrate fundamental differ- lasted 6 min and for the last 5 min the immobility of rats was ences in the molecular and brain region targets of VLX, and the measured and analyzed by SMART. results have important implications for antidepressant drug The Y-maze apparatus consisted of three arms intersected at discovery efforts. 120 (45 cm long, 10 cm wide and 29 cm high). Rats were placed at the end of one arm and allowed to freely explore the three arms for 8 min. The sequence and total number of arms entered 2. Materials and methods was noted. Percentage of spontaneous alternation was dened 2.1. Animals and ethics statement as [(number of alternations)/(total number of arm entries À 2)]  2 Healthy male Sprague-Dawley (SD) rats (10 weeks-old) weighing 100%. approximately 400 g at the beginning of the study were purchased from the animal facility of Chongqing Medical 2.3. Sample collection and preparation for GC-MS analysis University (China). For the duration of the study, the rats were Aer the behavioral tests were nished, the rats were anes- housed under a light–dark cycle of 12 h at 55 Æ 5% relative thetized with 10% chloral hydrate, and sacriced by decapita- humidity and 21–22 C, and allowed ad libitum access to rodent tion. The entire brain was removed and the hippocampus and diet and tap water. All animal experiments were reviewed and the prefrontal cortex were resected, quickly frozen in liquid approved by the Ethics Committee of Chongqing Medical nitrogen, and stored at À80 C for further analyses. Prior to GC- University (permit number: 20120126). MS analysis, the sample was homogenized in 600 mLof a methanol-water solution (4/1, v/v) with an internal standard À1 2.2. Drug treatment and behavioral testing solution (2-chloro-L-phenylalanine, 75 ng mL ). Then the Creative Commons Attribution 3.0 Unported Licence. mixture was sonicated for 10 min and subsequently centrifuged Rats were randomly divided into control (CON) and venlafaxine at 14 000 rpm for 10 min at 4 C. Finally, 550 mL of supernatant (VLX) groups a er one week of adaptive feed. The CON group was transferred into a glass derivative vial and vacuum-dried at (n ¼ 14) was treated with 0.9% NaCl solution, and the VLX group m À room temperature. The dried extract was mixed with 80 L ¼ 1 À (n 14) was treated with venlafaxine (5 mg kg , diluted in methoxamine hydrochloride in pyridine (15 mg mL 1), vortexed 0.9% NaCl solution, Sigma-Aldrich, USA) as described in our for 2 min, and incubated at 37 C for 90 min with continuous 27 previous study. Rats received injections intraperitoneally shaking. Subsequently, 80 mL BSTFA with 1% TMCS was added, daily. vortexed for 2 min, and the solution was maintained at 70 C for A er four weeks of drug treatment, a series of behavioral 60 min. Following derivatization and cooling to room temper- This article is licensed under a tests were performed during day time (light-on periods) under ature for 30 min, the derivative was used for GC-MS analysis. conditions of dim light and low noise. Body weights were recorded at baseline, week 1, week 2 and at the end of the 2.4. GC-MS analysis treatment. Open Access Article. Published on 29 September 2017. Downloaded 9/28/2021 1:55:26 AM. The open eld test (OFT) was applied to assess the locomotor GC-MS analysis was performed according to the methods used 24 m activity and exploratory behavior of rats, and was performed as in previous studies. A total of 0.5 L from each sample was described previously with minor modications.13,15,28 The open injected into the Agilent 7890A/5975C GC/MSD System (Agilent eld box consisted of a 100 cm  100 cm square arena with 40 Technologies, Santa Clara, California, USA) using the splitless  cm-high side walls. For the test, rats were individually placed mode. An Agilent J&W HP-5ms capillary column (30 m  m into the center of the open eld and le free to explore the arena 0.25 mm 0.25 m) was used for metabolite separation. High- purity helium (purity 99.999%) was used as a carrier gas at for 5 min. Prior to each test, the open eld area was wiped with À a constant ow rate of 6 mL min 1. The column temperature 75% ethanol. An automated video-tracking system (SMART, Panlab, Barcelona, Spain) was used to record and analyze the was initially maintained at 70 C for 2 min, increased to 160 C À1 behavior of each rat.