Einat H, Yuan P, Manji HK. Increased anxiety-like behaviors and mitochondrial dysfunction in mice with targeted mutation of the Bcl-2 gene: further support for the involvement of mitochondrial function in anxiety disorders. Behav Brain Res 165: 172-180

College of Pharmacy, Duluth, University of Minnesota, 376 Kirby Plaza, 1208 Kirby Drive, Duluth, MN 55812, USA.
Behavioural Brain Research (Impact Factor: 3.03). 01/2006; 165(2):172-80. DOI: 10.1016/j.bbr.2005.06.012
Source: PubMed


There is growing evidence that anxiety disorders are associated with impairments of cellular plasticity and resilience. Paralleling these advances in our understanding of the neurobiologic underpinnings of anxiety disorders is the growing appreciation of the diverse functions that mitochondria play in regulating integrated CNS function. The emerging data suggest that mitochondrial Ca2+ sequestration has a key role in modulating the tone of synaptic plasticity in a variety of neuroanatomical regions, including those implicated in the pathophysiology of anxiety disorders. Furthermore, activation of peripheral mitochondrial benzodiazepine receptors resulted in reduced anxiety in rats. One of the major modulators of mitochondrial function is Bcl-2 proteins imbedded in the inner mitochondrial membrane. Bcl-2 overexpression increases mitochondria Ca2+ uptake capacity and resistance to Ca2+-inhibition of respiration and upregulation of Bcl-2 increases maximal uptake capacity of mitochondria. We have, therefore, explored the significance of Bcl-2 in the association between mitochondrial function and affective disorders testing Bcl-2 heterozygote mice in models of affective and anxiety disorders. Mutant mice have reduced mitochondrial Bcl-2 levels, and although they have no gross behavioral abnormalities, they demonstrate a significant increase of anxiety-like behaviors. Bcl-2 heterozygote mice spent less time in the center of an open field, spent less time outside an enclosure in the "emergence test", were less likely to explore the transparent part of a black/white box or the open arms of an elevated plus maze compared with WT controls. Mutant mice did not differ from WT in measures of locomotion or in the forced swim test for depression-like behavior suggesting a specific effect on anxiety-like behaviors. Our study, therefore demonstrates that Bcl-2 may be a key factor in anxiety disorders and that its effects may possibly originate from its role in the mitochondria.

Download full-text


Available from: Haim Einat
  • Source
    • "In another point of view, Einat et al. (2005) have reported that Bcl2 gene deletion in mice resulted in increased anxiety-like behavior, specifically, with insignificant impact on the gross behavioral. Otherwise, they discussed an apoptotic-independent rout for Bcl2 anti-anxiety activity (Einat et al. 2005). Our data suggest consistent conclusion that Nrf2 silencing upregulated caspase-3 cleavage, an irreversible step in apoptosis induction, along with a significant elevation in Bax/Bcl2 ratio. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Anxiety-related disorders are complex illnesses that underlying molecular mechanisms of these complicated emotional disorders are poorly understood. Nuclear factor erythroid 2-related factor 2 (Nrf2) is the most important regulator of the antioxidant defense system. Its protective actions are not only limited to antioxidative transactivation, but also plays important roles in encountering various physiological and pathological stresses. In this study, we evaluated whether silencing of Nrf2 plays a role in development of anxiety-related behavior. In this regard, we exerted small interfering RNA (siRNA) targeting Nrf2 in dorsal third ventricle and subsequently examined the effect of this silencing on anxiety-related behavior along with supposed molecular mechanisms. Therefore, we evaluated apoptotic markers and mitochondrial electron transport chain (ETC) activity in three brain regions: hippocampus, amygdala, and prefrontal cortex. Based on our result, Nrf2-silenced rats exhibited greater anxiety-like behavior compared to control group. Furthermore, Nrf2 silencing increased activity of ETC complexes. Also, Bax/Bcl2 ratio of all mentioned areas of the brain and cleavage of caspase-3 in hippocampus increased in Nrf2 silenced group, however, with a distinct pattern.
    Full-text · Article · Jul 2014 · Journal of Molecular Neuroscience
  • Source
    • "An unexpected finding was that the suicides of persons with a primary diagnosis of anxiety disorder occurred at an average altitude greater than that of suicides in MDD or schizophrenia. The results of animal studies by Einat et al. [42] and others [43] [44] provide support for the involvement of mitochondrial function in anxiety disorders. Very recent proteomic and metabolomic findings implicate a previously unrecognized role for mitochondria in modulating anxiety-related behaviors [43]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Bipolar disorder (BD) is a severe brain disease that is associated with a significant risk for suicide. Recent studies indicate that altitude of residence significantly affects overall rate of completed suicide, and is associated with a higher incidence of depressive symptoms. Bipolar disorder has shown to be linked to mitochondrial dysfunction that may increase the severity of episodes. The present study used existing data sets to explore the hypothesis that altitude has a greater effect of suicide in BD, compared with other mental illnesses. The study utilized data extracted from the National Violent Death Reporting System (NVDRS), a surveillance system designed by the Centers for Disease Control and Prevention (CDC) National Center for Injury Prevention and Control (NCIPC). Data were available for 16 states for the years 2005-2008, representing a total of 35,725 completed suicides in 922 U.S. counties. Random coefficient and logistic regression models in the SAS PROC MIXED procedure were used to estimate the effect of altitude on decedent's mental health diagnosis. Altitude was a significant, independent predictor of the altitude at which suicides occurred (F=8.28, p=0.004 and Wald chi-square=21.67, p<0.0001). Least squares means of altitude, independent of other variables, indicated that individuals with BD committed suicide at the greatest mean altitude. Moreover, the mean altitude at which suicides occurred in BD was significantly higher than in decedents whose mental health diagnosis was major depressive disorder (MDD), schizophrenia, or anxiety disorder. Identifying diagnosis-specific risk factors such as altitude may aid suicide prevention efforts, and provide important information for improving the clinical management of BD.
    Full-text · Article · Jan 2014 · Medical Hypotheses
  • Source
    • "Third, mitochondria-targeted antioxidant SkQ1 has been associated with decreased expression of anxiety behaviors in rats (Stefanova et al. 2010). Finally, mutant mice with reduced function of Bcl-2, a key modulator of mitochondrial function, demonstrate increased anxiety behavior (Einat et al. 2005). Exposure to cigarettes can lead to mitochondrial dysfunction (Miro et al. 1999; Anbarasi et al. 2005b), as demonstrated by increased levels of cholesterol, lipid peroxides and increased cholesterol/phospholipid ratio, in conjunction with decreased mitochondrial enzymes in those exposed to cigarette smoke. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Multiple studies have demonstrated an association between cigarette smoking and increased anxiety symptoms or disorders, with early life exposures potentially predisposing to enhanced anxiety responses in later life. Explanatory models support a potential role for neurotransmitter systems, inflammation, oxidative and nitrosative stress, mitochondrial dysfunction, neurotrophins and neurogenesis, and epigenetic effects, in anxiety pathogenesis. All of these pathways are affected by exposure to cigarette smoke components, including nicotine and free radicals. This review critically examines and summarizes the literature exploring the role of these systems in increased anxiety and how exposure to cigarette smoke may contribute to this pathology at a biological level. Further, this review explores the effects of cigarette smoke on normal neurodevelopment and anxiety control, suggesting how exposure in early life (prenatal, infancy, and adolescence) may predispose to higher anxiety in later life. A large heterogenous literature was reviewed that detailed the association between cigarette smoking and anxiety symptoms and disorders with structural brain changes, inflammation, and cell-mediated immune markers, markers of oxidative and nitrosative stress, mitochondrial function, neurotransmitter systems, neurotrophins and neurogenesis. Some preliminary data were found for potential epigenetic effects. The literature provides some support for a potential interaction between cigarette smoking, anxiety symptoms and disorders, and the above pathways; however, limitations exist particularly in delineating causative effects. The literature also provides insight into potential effects of cigarette smoke, in particular nicotine, on neurodevelopment. The potential treatment implications of these findings are discussed in regards to future therapeutic targets for anxiety. The aforementioned pathways may help mediate increased anxiety seen in people who smoke. Further research into the specific actions of nicotine and other cigarette components on these pathways, and how these pathways interact, may provide insights that lead to new treatment for anxiety and a greater understanding of anxiety pathogenesis.
    Full-text · Article · May 2013 · Brain and Behavior
Show more