The Neuroprotective Effects Of Dexrazoxane In MPTP-induced Mouse Model Of Parkinson’s Disease

Parkinson’s disease (PD), a common progressive neurodegenerative disorder, ischaracterized by selective degeneration of dopamine neurons in the substantia nigra(SN) resulting in debilitating motor signs including tremor, bradykinesia and rigidity.It has a lifetime risk of2%, making it the second most common neurodegenerativedisease after Alzheimer’s disease. Current PD medications treat symptoms, mainlyby L-DOPA administration; none halt or retard dopaminergic neuron degeneration.Although various hypotheses, including genetic factors, mitochondrial dysfunction,oxidative stress, excitotoxicity, neuroinglamation and apoptosis have been proposedto be involved in the pathogenesis of PD, the exact mechanisms governingdopaminergic loss remain unclear. The main obstacle to developingneuroprotective therapies is a limited understanding of the key molecular events thatprovoke neurodegeneration. Various factors such as genetic factors, excitotoxicity,mitochondrial dysfunction, oxidative stress and inflammation have been proposed tobe involved in the pathogenesis of PD, the exact mechanisms governingdopaminergic loss remain unclear. Mitochondrial oxidative stress has beenimplicated in a range of degenerative disease. Oxidative stress infers an imbalancebetween the formation of cellular oxidants and the anti-oxidative processes.Oxidative stress may account for the nigral defect of complex I activity, in that complex I is highy vulnerable to oxidative damage and inhibition of complex I leadsto increased ROS formation. Meanwhile mitochondria participate in the regulationof both energy metabolism and cell death. Excessive ROS production impairsmitochondria membrane system, loss of mitochondrial membrane potential (ΔΨm)and activation mitochondrial permeability transition pore (PTP), resulting in releaseof pro-apoptotic proteins which subquently initiated mitochondrial apoptoticpathway. Also, excessive ROS production spreads to ERS and inflammation.Dexrazoxane is clinically used as a doxorubicin-cardioprotective agent and may actby preventing iron-based oxygen free-radical damage through the iron-chelatingability of ADR-925. The metabolisms of dexrazoxane were meant to be chelatecompound with iron. The protective mechanism of dexrazoxane is related toreduce the production of ROS, ERS and inflammation. When BBB is intact, Dex iskept out of brain, but whether Dex is available when BBB is interrupted in MPTP/pPD model mice remains unknown. In this study, we investigated whether Dex playeda neuroprotective part in in vivo model of PD, and the underlying mechanisms werefocused on inhibiting ROS production, ERS and inflammation.AIM: To investigate the role and the mechanism of Dexrazoxane onMPTP-induced degeneration of dopaminergic neurons in MPTP/p PD model usingC57BL/6J mice.METHODS: C57BL/6J mice were treated with MPTP (20mg·kg-1s.c.) andprobenecid (250mg·kg-1i.p.) daily for5weeks. Dex (3/10/30mg·kg-1·day-1, i.p.) wasadministered to mice every day after the first injection with MPTP and last for5weeks totally. Mice were killed3.5days after the final injection of MPTP.Immunohistochemistry was performed to examine tyrosine hydroxylase (TH), glial fibrillary acidic protein (GFAP), macrophage-1antigen (Mac-1) and IgG expression.The total numbers of TH, GFAP and Mac-1positive cells and Fe-positive spots in theSNc were obtained stereologically using the optical fractionator method. HPLC withelectrochemical detectionwas used to measure striatal levels of differentneurotransmitters, including DA, DOPAC, and HVA. The levels of GRP78, CHOP,caspase12, inflammasome and NF-κB were determined by Western blotting.RESULTS:1. Dex is available in MPTP/p PD model mouse, suggesting that Dex in brainmay exert neuroprotective effects on neurodegeneration when BBB is interrupted,including MPTP induced the lost of TH neuron, activation of astrocytes and microglia,deposition of iron in SNc and the decreased capability of the metabolism ofneurotransmitters (p<0.05). Pretreatment with Dex (10mg/kg) decreased mortalityinduced by MPTP/p and attenuated loss of TH neuron, activation of astrocytes andmicroglia and decreased the deposition of iron in SNc (p<0.05). However, Dex hadno effect on decreased dopamine level in striatum of PD mouse (p>0.05).2. Pretreatment with Dex protected neurons against MPTP-induced cytotoxicityin midbrain. The mechanisms for the effect of Dex are involved in suppressing MPTPinduced upregulation of GRP78, CHOP, and caspase12expression. Dex alsoinhibited activation of NF-kB pathway by reducing p65transported into nucleus.3. Pretreatment with Dex inhibited the expression of inflammasome composed ofNLRP3, caspase1and pre-IL-1β.CONCLUSION:1. Dex is available in MPTP/p PD model mouse, suggesting that Dex in brainmay exert neuroprotective effects on neurodegeneration when BBB is interrupted. 2. Dex inhibits endoplasmic reticulum stress, inflammation and relateddownstream pathway, to exert neuroprotective effects.In summary, the major contributions of the present study lie in:1. Dex has neuroprotective effects in neurotoxin induced PD model inwhich BBB is interrupted. Dex alleviates the behavioral symptom and attenuatesthe loss of TH neuron, the activation of astrocytes and microglia and the depositionof iron in PD animal model. We demonstrate for the first time that Dex may serve asa neuroprotectant to treat and prevent neurotoxin-induced neurodegeneration andtherefore has potential therapeutic value for treatment of PD.2. The neuroprotective effect of Dex is carried out through the inhibition ofROS, ERS and inflammation. Pretreatment with Dex protected neurons againstMPTP-induced cytotoxicity in midbrain. The mechanisms for the effect of Dex areinvolved in suppressing MPTP induced upregulation of GRP78, CHOP, andcaspase12expression. Dex also inhibited activation of NF-κB pathway by reducingp65transported into nucleus. Pretreatment with Dex inhibited the expression ofinflammasome composed of NLRP3, caspase1and pre-IL-1β, suggesting that Dexmay serve as a neuroprotectant to treat and prevent neurotoxin-inducedneurodegeneration and therefore has potential therapeutic value for treatment of PD.