Elsevier

European Journal of Pharmacology

Volume 793, 15 December 2016, Pages 21-27
European Journal of Pharmacology

Behavioural pharmacology
Antidepressant effects of TBE-31 and MCE-1, the novel Nrf2 activators, in an inflammation model of depression

https://doi.org/10.1016/j.ejphar.2016.10.037Get rights and content

Abstract

The Nuclear factor (erythroid 2-derived)-like 2 (Nrf2) plays a key role in inflammation which is implicated in the pathophysiology of depression. The Nrf2 activators have antidepressant effects in animal models of depression. The present study was undertaken to examine whether TBE-31 [(±)-(4bS,8aR,10aS)-10a-ethynyl-4b,8,8-trimethyl-3,7-dioxo-3,4b,7,8,8a,9,10,10a-octahydrophenanthrene-2,6-dicarbonitrile] and MCE-1 [(±)-3-ethynyl-3-methyl-6-oxocyclohexa-1,4-dienecarbonitrile], the novel Nrf2 activators, could show antidepressant effects in inflammation model of depression. We found that TBE-31 and MCE-1 significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration dependent manner. The Nrf2 siRNA, but not negative control of siRNA, significantly blocked the potentiating effects of TBE-31 and MCE-1 on neurite outgrowth in PC12 cells. Furthermore, oral administration of TBE-31 or MCE-1 significantly attenuated an increase in serum levels of tumor necrosis factor-α (TNF-α) after administration of lipopolysaccharide (LPS: 0.5 mg/kg). In the tail-suspension test and forced swimming test, oral administration of TBE-31 or MCE-1 significantly attenuated an increase in the immobility time after LPS (0.5 mg/kg) administration. These findings suggest that the novel Nrf2 activators such as TBE-31 and MCE-1 might be potential therapeutic drugs for inflammation-related depression.

Introduction

Accumulating evidence suggests that inflammation plays a role in the pathophysiology of depression (Dantzer et al., 2008, Hashimoto, 2009, Hashimoto, 2015, Miller et al., 2009, Raison et al., 2010). Systemic administration of lipopolysaccharide (LPS) can induce depression-like behavior in rodents after the induction of inflammation (Dantzer et al., 2008, O'Connor et al., 2009, Zhang et al., 2016). The current antidepressants such as serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) can block alterations in serum pro-inflammatory cytokines and depression-like behaviors induced by LPS (de Paiva et al., 2010, Dong et al., 2016, Ma et al., 2014, Ohgi et al., 2013, Yao et al., 2015). Taken together, it is likely that inflammation plays a role in the depression-like phenotype in rodents, and anti-inflammatory drugs could show antidepressant effect in inflammation model of depression.

Nuclear factor (erythroid 2-derived)-like 2 (Nrf2) is a transcription factor that plays a central role in cellular defense against oxidative and electrophilic insults (Ma and He, 2012, Ma, 2013, Suzuki et al., 2013; Suzuki and Yamamoto, 2015). Nrf2 binds to antioxidant response elements (ARE) located in the promoter region of genes encoding many phase II detoxifying or antioxidant enzymes and related stress-responsive proteins (Ma and He, 2012, Ma, 2013, Suzuki et al., 2013; Suzuki and Yamamoto, 2015). Under normal conditions, Nrf2 is repressed by Keap1 (Kelch-like erythroid cell-derived protein with CNC homology [ECH]-associated protein 1), which is an adaptor protein for the degradation of Nrf2 (Suzuki et al., 2013; Suzuki and Yamamoto, 2015). During oxidative stress, Nrf2 is de-repressed and activates the transcription of cytoprotective genes (Suzuki et al., 2013; Suzuki and Yamamoto, 2015). Interestingly, it is recognized that Keap1-Nrf2 system plays a role in inflammation (Kobayashi et al., 2013, Innamorato et al., 2008, Suzuki et al., 2013; Suzuki and Yamamoto, 2015; O’Connell and Hayes, 2015; Wardyn et al., 2015). Recently, we reported that sulforaphane, a natural compound with Nrf2 activator, shows antidepressant effect in inflammation model of depression (Zhang et al., in press), and that pretreatment with sulforaphane confers resilience to social defeat stress in rodents (Yao et al., 2016). These results suggest that Nrf2 activators would be potential therapeutic drugs for depression.

TBE-31 [(±)-(4bS,8aR,10aS)-10a-ethynyl-4b,8,8-trimethyl-3,7-dioxo-3,4b,7,8,8a,9,10,10a-octahydrophenanthrene-2,6-dicarbonitrile] is a novel Nrf2 activator (Fig. 1) (Dinkova-Kostova et al., 2010, Honda et al., 2007, Honda et al., 2011, Kostov et al., 2015; Ma and He, 2012). It retains and even exceeds the potency of CDDO (2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid) analogs, which are the most potent compounds in pool of semi-synthetic triterpenoids in various in vitro and in vivo assays, including induction of cytoprotective enzymes. Furthermore, TBE-31 showed anti-inflammation effect in cells, and blocked the formation of aflatoxin-B1 (AFB1)-DNA adducts and AFB1-induced tumorigenesis in vivo (Liby et al., 2008). MCE-1 [(±)-3-ethynyl-3-methyl-6-oxocyclohexa-1,4-dienecarbonitrile] is also a novel Nrf2 activator (Fig. 1) (Dinkova-Kostova et al., 2010, Zheng et al., 2012). A recent study showed that MCE-1 is a highly reactive Michael acceptor leading to reversible adducts with nucleophiles, which displays equal or greater potency than CDDO in inflammation and carcinogenesis related assays (Zheng et al., 2012).

The present study was undertaken to examine whether TBE-31 and MCE-1 show antidepressant effects in inflammation model of depression. First, we examined the effects of these compounds on nerve-growth factor (NGF)-induced neurite outgrowth in PC12 cells. Second, we examined whether these compounds could attenuate alterations in serum pro-inflammatory cytokine, tumor necrosis factor-α (TNF-α), after LPS administration. Finally, we examined the effects of TBE-31 and MCE-1 in inflammation-induced model of depression.

Section snippets

Quantification of neurite outgrowth in PC12 cells

PC12 cells (RIKEN Cell Bank, Tsukuba, Japan) were cultured at 37 ℃, 5% CO2 in Dulbecco's modified Eagle's medium (DMEM), supplemented with 5% heat-inactivated fetal bovine serum (FBS), 10% heat-inactivated horse serum and 1% penicillin. Medium was changed two to three times a week. PC12 cells were plated onto 24-well tissue culture plates coated with poly-D-lysine/laminin. Cells were plated at relatively low density (0.25×104 cells cm-2) in DMEM medium containing 0.5% FBS, 1%

Effects of TRB-31 and MCE-1 on NGF-induced neurite outgrowth in PC12 cells

Since neurite outgrowth is involved in the antidepressant's mechanisms, we examined the effects of TBE-31 and MCE-1 on NGF-induced neurite outgrowth in PC12 cells. MAP-2 (microtubule associated protein-2) immunocytochemistry showed that TBE-31 or MCE-1 increased the number of cells with NGF-induced neurite outgrowth in PC12 cells (Fig. 2A, B and C). One-way ANOVA revealed that TBE-31 and MCE-1 significantly (TBE-31: F3,39 =27.49, P<0.001, MCE-1: F3,39 =28.58, P<0.001) increased NGF-induced

Discussion

This study highlighted TBE-31 and MCE-1 as potential therapeutic drugs for inflammation-induced depression. First, TBE-31 and MCE-1 can potentiate NGF-induced neurite outgrowth in PC12 cells, through Nrf2 activation, suggesting that Nrf2 activators such as TBE-31 and MCE-1 are capable of enhancing the neuronal plasticity associated with antidepressant effect. Second, TBE-31 and MCE-1 have anti-inflammatory effects on the serum levels of TNF-α after LPS injection. Third, TBE-31 and MCE-1 showed

Acknowledgments and disclosures

This study was supported by a Grant-in-Aid from the Minister of Education, Culture, Sports, Science, and Technology of Japan (to K.H.), a Grant-in-Aid for Scientific Research on Innovative Areas of the Ministry of Education, Culture, Sports, Science and Technology, Japan (to K.H.) and funds from Stony Brook Foundation and Reata Pharmaceuticals (to T.H.). Dr. Wei Yao was supported by Ishidsu Shun Memorial Scholarship (Tokyo, Japan). Dr. Kenji Hashimoto has received research support from Abbvie,

References (45)

  • T. Suzuki et al.

    Toward clinical application of the Keap1-Nrf2 pathway

    Trends Pharmacol. Sci.

    (2013)
  • W. Yao et al.

    Effects of amycenone on serum levels of tumor necrosis factor-α, interleukin-10, and depression-like behavior in mice after lipopolysaccharide administration

    Pharmacol. Biochem. Behav.

    (2015)
  • H. Chen et al.

    Protective effects of the antioxidant sulforaphane on behavioral changes and neurotoxicity in mice after the administration of methamphetamine

    Psychopharmacology

    (2012)
  • R. Dantzer et al.

    From inflammation to sickness and depression: when the immune system subjugates the brain

    Nat. Rev. Neurosci.

    (2008)
  • K. Hashimoto

    Inflammatory biomarkers as differential predictors of antidepressant response

    Int. J. Mol. Sci.

    (2015)
  • K. Hashimoto et al.

    A novel target of action of minocycline in NGF-induced neurite outgrowth in PC12 cells: translation initiation factor eIF4AI

    PLoS One

    (2010)
  • T. Honda et al.

    Novel tricyclic compounds having acetylene groups at C-8a and cyano enones in rings A and C: highly potent anti-inflammatory and cytoprotective agents

    J. Med. Chem.

    (2007)
  • T. Honda et al.

    Tricyclic compounds containing nonenolizable cyano enones: a novel class of highly potent anti-inflammatory and cytoprotective agents

    J. Med. Chem.

    (2011)
  • N.G. Innamorato et al.

    The transcription factor Nrf2 is a therapeutic target against brain inflammation

    J. Immunol.

    (2008)
  • T. Ishima et al.

    Neurite outgrowth mediated by the heat shock protein Hsp90α: a novel target for the antipsychotic drug aripiprazole

    Transl. Psychiatry

    (2012)
  • E. Kobayashi et al.

    Roles nrf2 plays in myeloid cells and related disorders

    Oxid. Med. Cell. Longev.

    (2013)
  • J.M. Lee et al.

    An important role of Nrf2-ARE pathway in the cellular defense mechanism

    J. Biochem. Mol. Biol.

    (2004)
  • Cited by (0)

    View full text