Claire Gibrat

Modulation of brain-derived neurotrophic factor as a potential neuroprotective mechanism of action of omega-3 fatty acids in a parkinsonian animal model.

While we recently reported the beneficial effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) in a mouse model of Parkinsons disease (PD), the mechanisms of action remain largely unknown. Here, we specifically investigated the contribution of the brain-derived neurotrophic factor (BDNF) to the neuroprotective effect of n-3 PUFA observed in a mouse model of PD generated by a subacute exposure to MPTP using a total of 7 doses of 20mg/kg over 5 days. The ten-month high n-3 PUFA treatment which preceded the MPTP exposure induced an increase of BDNF mRNA expression in the striatum, but not in the motor cortex of animals fed the high n-3 PUFA diet. In contrast, n-3 PUFA treatment increased BDNF protein levels in the motor cortex of MPTP-treated mice, an effect not observed in vehicle-treated mice. The mRNA expression of the high-affinity BDNF receptor tropomyosin-related kinase B (TrkB) was increased in the striatum of MPTP-treated mice fed the high n-3 PUFA diet compared to vehicle and MPTP-treated mice on the control diet and to vehicle mice on the high n-3 PUFA diet. These data suggest that the modulation of BDNF expression contributes, in part, to n-3 PUFA-induced neuroprotection in an animal model of PD.

Differences between subacute and chronic MPTP mice models: investigation of dopaminergic neuronal degeneration and α‐synuclein inclusions

Animal models are invaluable tools to study neurodegenerative disorders but a general consensus on the most accurate rodent model of Parkinson’s disease has not been reached. Here, we examined how different methods of MPTP administration influence the degeneration of the dopaminergic (DA) system. Adult male C57BL/6 mice were treated with the same cumulative dose of MPTP following four distinct procedures: (i) subacute i.p. injections; (ii) 28‐day chronic s.c. infusion; (iii) 28‐day chronic i.p. infusion; and (iv) 14‐day chronic i.p. infusion. Subacute MPTP treatment significantly affected all aspects of the DA system within the nigral and striatal territories. In contrast, the 28‐day chronic s.c. infusion did not significantly alter any components of the DA system. The 28‐ and 14‐day chronic i.p. infusions induced loss of tyrosine hydroxylase (TH)‐positive cells correlated with a decrease in Nurr1 mRNA levels, but no significant decrease in the density of TH striatal fibers. Importantly, however, only the 14‐day chronic MPTP i.p. infusion protocol promoted the formation of neuronal inclusions as noted by the expression of α‐synuclein protein within the cytoplasm of TH nigral neurons. Overall, we found that the 14‐day chronic MPTP i.p. infusion reproduces more accurately the pathological characteristics of early stage Parkinson’s disease.

Cystamine metabolism and brain transport properties: clinical implications for neurodegenerative diseases.

J. Neurochem. (2010) 114, 1651–1658.

The role of the MYD88-dependent pathway in MPTP-induced brain dopaminergic degeneration

BackgroundMounting evidence supports a significant role of inflammation in Parkinsons disease (PD) pathophysiology, with several inflammatory pathways being suggested as playing a role in the dopaminergic degeneration seen in humans and animal models of the disease. These include tumor necrosis factor, prostaglandins and oxidative-related stress components. However, the role of innate immunity has not been established in PD.MethodsBased on the fact that the myeloid differentiation primary response gene (88) (MyD88) is the most common adaptor protein implicated in toll-like receptor (TLR) signaling, critical in the innate immune response, we undertook a study to investigate the potential contribution of this specific pathway to MPTP-induced brain dopaminergic degeneration using MyD88 knock out mice (MyD88-/-), following our observations that the MyD88-dependent pathway was critical for MPTP dopaminergic toxicity in the enteric nervous system. Post-mortem analyses assessing nigrostriatal dopaminergic degeneration and inflammation were performed using HPLC, western blots, autoradiography and immunofluorescence.ResultsOur results demonstrate that MyD88-/- mice are as vulnerable to MPTP-induced dopamine and DOPAC striatal depletion as wild type mice. Furthermore, MyD88-/- mice show similar striatal dopamine transporter and tyrosine hydroxylase loss, as well as dopaminergic cell loss in the substantia nigra pars compacta in response to MPTP. To evaluate the extent of the inflammatory response created by the MPTP regimen utilized, we further performed bioluminescence imaging using TLR2-luc/gfp transgenic mice and microglial density analysis, which revealed a modest brain microglial response following MPTP. This was accompanied by a significant astrocytic reaction in the striatum, which was of similar magnitude both in wild type and MyD88-/- mice.ConclusionsOur results suggest that subacute MPTP-induced dopaminergic degeneration observed in the central nervous system is MyD88-independent, in contrast to our recent observations that this pathway, in the same cohort of animals, is critical in the loss of dopaminergic neurons in the enteric nervous system.

Cystamine prevents MPTP-induced toxicity in young adult mice via the up-regulation of the brain-derived neurotrophic factor.

Preclinical data suggest that cystamine stands as a promising neuroprotective agent against Huntingtons and Parkinsons diseases. To decipher the mechanisms of action of cystamine, we investigated the effects of various doses of cystamine (10, 50, and 200mg/kg) on the regulation of the brain-derived neurotrophic factor (BDNF), its receptor tropomyosin-receptor-kinase B (TrkB) and on the heat shock protein 70 (Hsp70) brain mRNA expression in relation to the time after administration. We have determined that the lower cystamine dose is the most efficient to promote putative neuroprotective effects. Indeed, an acute administration of 10mg/kg of cystamine increased the expression of BDNF mRNA in the substantia nigra compacta (SNc), although it did not significantly influence TrkB or Hsp70 mRNA. Higher cystamine doses resulted in the absence of activation of any of these markers or led to non-specific effects. We have also substantiated the neuroprotective effect of a 21-day treatment of 10mg/kg/day of cystamine in young adult mice against MPTP-induced loss of tyrosine hydroxylase-striatal fiber density, nigral dopamine cells and nigral Nurr1 mRNA expression. The neuroprotective action of cystamine in the same animals was associated with an up-regulation of BDNF in the SNc. Taken together, these results strengthen the neuroprotective potential of cystamine in the treatment of Parkinsons disease and point towards the up-regulation of BDNF as an important mechanism of action.

Recanalization of Chronic Total Occlusions in Patients With Previous Coronary Bypass Surgery and Consideration of Retrograde Access via Saphenous Vein Grafts

Background—The prevalence of native coronary chronic total occlusions (CTOs) after coronary artery bypass grafts (CABGs) is higher than in non-CABG population. We examined outcomes of CTO percutaneous coronary intervention (PCI) post-CABG versus without CABG. Then, we looked at feasibility and outcomes of retrograde CTO PCI via patent or occluded saphenous vein graft. Methods and Results—We compared patient and procedural characteristics of 470 CTO cases treated from January 2010 to December 2015 depending on history of CABG. We assessed major adverse cardiac events, including cardiac death, myocardial infarction, ischemia-driven target-vessel revascularization, or reocclusion 1 year after successful CTO PCI in patients treated before February 2015. Post-CABG patients (175 cases) had a higher J-CTO score (2.5 versus 2.1; P=0.002). In-hospital complications were similar, although the incidence of contrast-induced nephropathy was higher in post-CABG patients (4.6% versus 1%; P=0.01). With multivariable analysis, post-CABG status was associated with higher incidence of 1-year major adverse cardiac event (hazards ratio=2.2; P=0.02). As a second level analysis, we looked at the feasibility and safety of CTO PCI via saphenous vein grafts (19% of post-CABG cases) versus collateral channels (36%) versus with an antegrade-only approach (45%), and assessed short-term outcomes and complications. High success was achieved in the saphenous vein graft group. In-hospital events were similar in the 3 groups. Conclusions—Post-CABG CTO PCI is associated with similar high success and low complications compared with CTO PCI in patients who never had CABG. However, it is associated with higher recurrent events at 1 year. To achieve high success rate, use of saphenous vein grafts as retrograde conduits seems to be safe and effective.

Safety and Effectiveness of the Surfing Technique to Cross Septal Collateral Channels during Retrograde Chronic Total Occlusion Percutaneous Coronary Intervention.

AIMS Septal surfing and distal tip injections are two techniques used for septal crossing in retrograde chronic total occlusion (CTO) percutaneous coronary interventions (PCI). The aim of this study was to examine for the first time the safety and feasibility of the septal surfing technique. METHODS AND RESULTS Among 470 consecutive CTO PCIs performed in the Quebec hybrid CTO PCI program between January 2010 and December 2015, 240 (51%) involved a retrograde attempt. In the septal crossing subgroup, we evaluated whether the Werner collateral channel (CC) classification, CTO location, tortuosity, and number of large septal CCs influenced retrograde crossing success, time, and perforation. Septal channels were used in the majority (n=152, 63%) of cases. Patients in the septal subgroup were younger, had less bypass surgery, were more likely to have RCA CTO and had previous failure. Septal channels were successfully crossed with the wire using the surfing technique in 81%, irrespective of the CC size. Septal crossing success and time were not influenced by Werner CC class but by septal CC tortuosity. One quarter of cases had septal perforations; all were minor and asymptomatic. CONCLUSIONS Septal surfing is a safe and highly successful technique for crossing septal CCs when a retrograde approach is mandated for CTO PCI. The Werner class does not affect retrograde CC crossing success or time.

Cystamine/cysteamine rescues the dopaminergic system and shows neurorestorative properties in an animal model of Parkinson's disease

The neuroprotective properties of cystamine identified in pre-clinical studies have fast-tracked this compound to clinical trials in Huntingtons disease, showing tolerability and benefits on motor symptoms. We tested whether cystamine could have such properties in a Parkinsons disease murine model and now provide evidence that it can not only prevent the neurodegenerative process but also can reverse motor impairments created by a 6-hydroxydopamine lesion 3 weeks post-surgery. Importantly, we report that cystamine has neurorestorative properties 5 weeks post-lesion as seen on the number of nigral dopaminergic neurons which is comparable with treatments of cysteamine, the reduced form of cystamine used in the clinic, as well as rasagiline, increasingly prescribed in early parkinsonism. All three compounds induced neurite arborization of the remaining dopaminergic cells which was further confirmed in ex vivo dopaminergic explants derived from Pitx3-GFP mice. The disease-modifying effects displayed by cystamine/cysteamine would encourage clinical testing.

Partial neurorescue effects of DHA following a 6-OHDA lesion of the mouse dopaminergic system

Pre-clinical data collected in mouse models of Parkinsons disease (PD) support the neuroprotective potential of omega-3 polyunsaturated fatty acids (n-3 PUFA)-enriched diet on the dopaminergic (DAergic) system. In this study, we investigated the effects of an n-3 PUFA-rich diet using a neurorescue/neurorestorative paradigm. C57BL/6 adult mice were submitted to a striatal stereotaxic injection of the neurotoxin 6-hydroxydopamine (6-OHDA) to induce striatal DAergic denervation and subsequent nigral DAergic cell loss. Three weeks post-lesion, mice received either a docosahexaenoic acid (DHA)-enriched or a control diet for a period of 6 weeks. HPLC analyses revealed a 111% post-lesion increase in striatal dopamine levels in the DHA-fed animals compared to controls (ctrl, P<0.05), although no improvement in the motor behavior was observed. DHA treatment led to a 89% rise in tyrosine-hydroxylase (TH)-immunoreactive terminals within the striatum (P<0.05) in lesioned animals. Despite the fact that DHA did not change the number of TH+ neurons in the substantia nigra pars compacta (SNpc), morphological analyses revealed an increased in perimeters (+7%) and areas (+21%) of DAergic cell bodies in treated animals. Collectively, our results suggest that DHA induces a partial neurorescue/neurorestoration of the DAergic system and support further studies to investigate the potential of a diet-based intervention, or at least the combination of such approach, to current treatments in PD.

Incidence, predictors and longer-term impact of troponin elevation following hybrid chronic total occlusion percutaneous coronary intervention

We examined the incidence of periprocedural cardiac enzyme rise (PCER) [troponin T (TnT) or high‐sensivity (hs)TnT >5× the upper limit of normal (ULN)] and periprocedural myocardial infarction (PMI), predictors of PCER and impact of PCER on the longer‐term major adverse cardiac events (MACE) following hybrid chronic total occlusion (CTO) percutaneous coronary intervention (PCI).