Influences of Chronic Mild Stress Exposure on Motor, Non-Motor Impairments and Neurochemical Variables in Specific Brain Areas of MPTP/Probenecid Induced Neurotoxicity in Mice
Authors: Musthafa Mohamed Essa
Rajamani Barathidasan
Arokiasamy Justin Thenmozhi
Udaiyappan Janakiraman
Thamilarasan Manivasagam
Mohammed A S Khan
Chidambaram SaravanaBabu
Gilles J Guillemin
Journal: PLoS ONE (2016)
Discipline: Multidisciplinary
Keywords: Parkinson's disease; movement disorder; dopaminergic neurons; non-motor symptoms; depression
Affiliations: Department of Biochemistry and Biotechnology, Annamalai University, Annamalainagar, 608002, Tamilnadu, India., Department of Food Science and Nutrition, CAMS, Sultan Qaboos University, Muscat, Oman., Ageing and Dementia Research Group, Sultan Qaboos University, Muscat, Oman., Centre for Toxicology and Developmental Research, Sri Ramachandra University, Porur, Chennai-600 116, Tamilnadu, India., Neuropharmacology group, Faculty of Medicine and Health Sciences, Deb Bailey MND Research Laboratory, Macquarie University, NSW, 2109, Australia., Harvard Medical School, Massachusetts General Hospital, Shriners Hospital for Children, Boston, Massachusetts, 02114, United States of America.

Abstract:  Parkinson's disease (PD) is regarded as a movement disorder mainly affecting the elderly population and occurs due to progressive loss of dopaminergic (DAergic) neurons in nigrostriatal pathway. Patients suffer from non-motor symptoms (NMS) such as depression, anxiety, fatigue and sleep disorders, which are not well focussed in PD research. Depression in PD is a predominant /complex symptom and its pathology lies exterior to the nigrostriatal system. The main aim of this study is to explore the causative or progressive effect of chronic mild stress (CMS), a paradigm developed as an animal model of depression in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (25 mg/kg. body wt.) with probenecid (250 mg/kg, s.c.) (MPTP/p) induced mice model of PD. After ten i.p. injections (once in 3.5 days for 5 weeks) of MPTP/p or exposure to CMS for 4 weeks, the behavioural (motor and non-motor) impairments, levels and expressions of dopamine (DA), serotonin (5-HT), DAergic markers such as tyrosine hydroxylase (TH), dopamine transporter (DAT), vesicular monoamine transporters-2 (VMAT 2) and α-synuclein in nigrostriatal (striatum (ST) and substantia nigra (SN)) and extra-nigrostriatal (hippocampus, cortex and cerebellum) tissues were analysed. Significantly decreased DA and 5-HT levels, TH, DAT and VMAT 2 expressions and increased motor deficits, anhedonia-like behaviour and α-synuclein expression were found in MPTP/p treated mice. Pre and/or post exposure of CMS to MPTP/p mice further enhanced the MPTP/p induced DA and 5-HT depletion, behaviour abnormalities and protein expressions. Our results could strongly confirm that the exposure of stress after MPTP/p injections worsens the symptoms and neurochemicals status of PD. 

Retracted: Yes

PubPeer comments:
 In this paper, mice were divided into six groups, each of which received a different treatment. Figure 4A shows 6 panels with brain tissue. Each panel represents a different treatment group. However, panel  CMS+MPTP p appears to show some unexpected similarities to panel  CMS+MPTP p+CMS . In addition, each of these 2 panels as well as the  CMS panel appear to show repetitive elements within the same photo. Here is a highlighted version of this figure, with boxes of the same color representing parts of the photos that look similar. Could the authors please clarify if these images represent different mice? ![file] , 
 #1 I see a repetition within the background tissue along the top edge of the CMS panel (black rectangles), while tissue also is flipped vertically to become part of the lower edge (red rectangles). ![file] , 
 Dear Elisabeth and Hoya Thank you so much for reporting this issue. Immediately I have contacted Dr. Manivasagam (senior author), to clarify this with the research scholar (1st author) who performed this work, who is currently doing post doc in the US. As a collaborator, I do all the time offering support for the structure of the project and editing revising the manuscript, not the data or laboratory works. I assure that the senior author will address this important issue asap. Regards, Essa , 
 2020 retraction. https: journals.plos.org plosone article?id=10.1371 journal.pone.0236885 Following the publication of this article [1], concerns were raised regarding Figs 4, 6, 7, 8, 9, 10, and 12: Similar patterns were noted between select regions of the CMS+MPTP p and CMS+MPTP p+CMS panels of Fig 4A. While these panels are not identical, they appear to have several elements in common. Similarities were also noted between regions within panels of Fig 4A, in the CMS, CMS+MPTP p, and CMS+MPTP p+CMS panels. The u03b2-actin blots presented in Fig 6A appear similar to the u03b2-actin blots presented in Fig 10A. Furthermore, the u03b2-actin blots presented in Fig 5A appear similar to the u03b2-actin blots presented in Fig 7A and Fig 9A. The authors have clarified the same blots were used in the experiments shown in Figs 5, 7, and 9, and hence the same control blots applied. The Cortex u03b2-actin blot presented in Fig 8A appears similar to the Cortex u03b2-actin blot presented in Fig 12A. Furthermore, the Hippocampus u03b2-actin blot presented in Fig 8A appears similar to the Cerebellum u03b2-actin blot presented in Fig 12A, and the Cerebellum u03b2-actin blot presented in Fig 8A appears similar to the Hippocampus u03b2-actin blot presented in Fig 12A. The authors have clarified that the same blots were used in the Fig 8A and 12A experiments, and so the same control data applied. The authors also indicated that the u03b2-actin blots for the Hippocampus and the Cerebellum have been exchanged inadvertently. The blot data (A) and densitometry data (B) in Fig 7 and Fig 9 appear similar. The authors commented that this is the result of an accidental full figure duplication. The figure legends of Fig 6, Fig 8, and Fig 9 do not match the data presented in the figures: Fig 6 presents protein expression of tyrosine hydroxylase (TH) in the Cortex, Hippocampus, and Cerebellum, as is described in the Fig 8 legend. The Fig 6 legend states u201cImpact of stress on protein expression of DAT in striatum and SN of control and -MPTP p treated miceu201d. Fig 8 presents protein expression of dopamine transporter (DAT) in the Cortex, Hippocampus, and Cerebellum, as is described in the Fig 9 legend. The Fig 8 legend states u201cImpact of stress on protein expression of TH in cortex, hippocampus and cerebellum of control and -MPTP p treated mice.u201d Fig 9 presents protein expression of vesicular monoamine transportersu2013 2 (VMAT-2) in the stadium and the substantia nigra, as is described in the Fig 7 legend. The Fig 9 legend states u201cInfluence of stress on protein expression of DAT in cortex, hippocampus and cerebellum of control and MPTP p treated mice.u201d DAT results for the striatum and substantia nigra experiments described in the Fig 6 legend are not reported in the figures, according to the data labels within figures, and were not provided in post-publication discussions. The authors have provided underlying primary data for the western blots presented in the paper, but in some cases the blot image data provided did not match the results shown in the corresponding figure panel. The primary data for Fig 4A are unavailable. The authors indicate that Fig 4A experiments were outsourced to a private laboratory, which has not been declared previously. Replicate data were provided in support of Fig 4A but the concerns about the published figure have not been resolved. In light of the extent of data reporting issues, and the unresolved concerns that question the integrity of data reported in Fig 4A, the PLOS ONE Editors retract this article. MME, CSB, GJG, and MASK agreed with the retraction. TM and AJT did not confirm agreement or disagreement with the retraction decision. RB either did not respond directly or could not be reached. UJ did not agree with the retraction. Reference 1.Janakiraman U, Manivasagam T, Thenmozhi AJ, Essa MM, Barathidasan R, SaravanaBabu C, et al. (2016) Influences of Chronic Mild Stress Exposure on Motor, Non-Motor Impairments and Neurochemical Variables in Specific Brain Areas of MPTP Probenecid Induced Neurotoxicity in Mice. PLoS ONE 11(1): e0146671. https: doi.org 10.1371 journal.pone.0146671 ,