Leishmania parasites have evolved sophisticated mechanisms to subvert macrophage immune responses by altering the host cell signal transduction machinery, including inhibition of JAK/STAT signalling and other transcription factors such as AP-1, CREB and NF-κB. AP-1 regulates pro-inflammatory cytokines, chemokines and nitric oxide production. Herein we show that upon Leishmania infection, AP-1 activity within host cells is abolished and correlates with lower expression of 5 of the 7 AP-1 subunits. Of interest, c-Jun, the central component of AP-1, is cleaved by Leishmania. Furthermore, the cleavage of c-Jun is dependent on the expression and activity of the major Leishmania surface protease GP63. Immunoprecipitation of c-Jun from nuclear extracts showed that GP63 interacts, and cleaves c-Jun at the perinuclear area shortly after infection. Phagocytosis inhibition by cytochalasin D did not block c-Jun down-regulation, suggesting that internalization of the parasite might not be necessary to deliver GP63 molecules inside the host cell. This observation was corroborated by the maintenance of c-Jun cleavage upon incubation with L. mexicana culture supernatant, suggesting that secreted, soluble GP63 could use a phagocytosis-independent mechanism to enter the host cell. In support of this, disruption of macrophage lipid raft microdomains by Methyl β-Cyclodextrin (MβCD) partially inhibits the degradation of full length c-Jun. Together our results indicate a novel role of the surface protease GP63 in the Leishmania-mediated subversion of host AP-1 activity.

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The preferential accumulation of vascular smooth muscle cells (vSMCs) on arteries versus veins during early development is a well-described phenomenon, but the molecular pathways underlying this polarization are not well understood. In zebrafish, the cxcr4a receptor (mammalian CXCR4) and its ligand cxcl12b (mammalian CXCL12) are both preferentially expressed on arteries at time points consistent with the arrival and differentiation of the first vSMCs during vascular development. We show that autocrine cxcl12b/cxcr4 activity leads to increased production of the vSMC chemoattractant ligand pdgfb by endothelial cells in vitro and increased expression of pdgfb by arteries of zebrafish and mice in vivo. Additionally, we demonstrate that expression of the blood flow-regulated transcription factor klf2a in primitive veins negatively regulates cxcr4/cxcl12 and pdgfb expression, restricting vSMC recruitment to the arterial vasculature. Together, this signalling axis leads to the differential acquisition of vSMCs at sites where klf2a expression is low and both cxcr4a and pdgfb are co-expressed, i.e. arteries during early development.

684Cerebral venous thrombosis (CVT) is an uncommon form of cerebrovascular disease, with an incidence of three to four cases per million persons. Although acute-onset headache is the most consistent presentation, CVT may also manifest as seizures, intracranial hypertension, and focal sensorimotor deficits 1 . Here, we report the unusual development of subacute parkinsonism secondary to multiple cerebral sinus thromboses. CASE REPORTA 57-year-old right-handed woman with a three year history of diffuse, intermittent headaches presented to the Jewish General Hospital (Montreal) with worsening non-pulsatile headache and progressive hypophonia, micrographia, bradyphrenia and gait unsteadiness over a three week period. There were no complaints of hyposmia, sleep disturbances, constipation or other pre-motor symptoms of idiopathic Parkinson disease. Her past medical history was unremarkable and her medication list included vitamin D and calcium supplements only. Physical examination revealed normal vital signs with no evidence of postural hypotension, normal level of consciousness, orientation, attention, language, affect, judgment and insight. There was facial hypomimia but the rest of the cranial nerve exam, including bilateral olfactory nerve testing, was normal. There was marked hypophonia and micrographia and moderate bradykinesia and cogwheel rigidity. Muscle power was normal and tremor was absent. The gait was narrow-based, small-steppage and unsteady. There was severe retropulsion on pull-testing. Sensory, cerebellar and reflex testing was unremarkable save for prominent glabellar tap and palmomental signs.A computed tomogram (CT) scan of the head (Figure) showed small, scattered hyperdensities in bilateral frontal, temporal and parietal lobes and in the region of the interpeduncular cistern. The white matter appeared abnormally hypodense consistent with generalized edema (a1-a2). Magnetic resonance imaging axial FLAIR sequences showed heterogeneous hyperintense signal of the transverse sinuses (left, arrow) and congested peripheral veins (b1-b2). Axial FLAIR and T2 sequences showed diffuse, hyperintense signal of the periventricular and subcortical white matter and mild sulcal effacement (c1-c2). Magnetic resonance venography (MRV) demonstrated occlusion of the transverse sinuses and distal internal cerebral veins, minimal flow within the vein of Galen, and severely congested cortical and subcortical veins and straight sinus (d1-d2).Routine hematology, erythrocyte sedimentation rate and Despite intravenous heparin and a therapeutic partial thromboplastin time, there was abrupt clinical deterioration characterized by confusion, worsening gait and double incontinence. A repeat CT of the head was unchanged. A trial of intra-jugular tPA and mechanical venous sinus thrombectomy were unsuccessful due to "rock-hard" clot consolidation. The patient was started on warfarin and dexamethasone with gradual improvement of neurological status to near-admission levels. She was discharged to a rehabilitation hospital on warfa...

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Funding Acknowledgements Type of funding sources: None. Introduction Atrial fibrillation (AF) is the most common clinically-relevant arrhythmia. Its initiation and maintenance is linked to the presence cardiovascular risk factors such as hypertension and obesity. Higher cardiorespiratory fitness (CRF) has been associated with a better prognosis. However, specific electroanatomical features associated with baseline CRF have not been described.  Purpose Compare electroanatomical substrate across exercise capacity levels in patients with AF Methods Patients referred for de novo AF radiofrequency ablation at the Centre for Heart Rhythm Disorders from August 2017 until June 2020 were screened for inclusion and CRF was evaluated in metabolic equivalents (METs) by a symptom-limited maximal treadmill exercise test using the standard Bruce protocol prior to ablation. Predicted CRF was calculated based on established equations and patients were categorized according to the percentage of predicted CRF achieved; low (<85%), adequate (85-100%) and high (>100%). Total mean and regional peak-to-peak bipolar voltages, percent of low voltage areas (% LVA), conduction velocity (CV) and percent of complex fractionated electrograms (% CFE) in sinus rhythm were compared across groups.  Results There were no between-group differences in baseline characteristics, medication use or echocardiographic features. Total mean voltage was significantly lower in the low CRF group compared to both adequate and high CRF. Compared to the high CRF group, roof (3.25 ± 1.2 mV vs 1.9 ± 1.3 mV, p < 0.05), posterior (3.8 ± 1.8 mV vs 1.7 ± 0.9 mV, p < 0.001) and inferior mean voltages (3.4 ± 2 mV vs 1.6 ± 0.7 mV, p < 0.05) were significantly lower in the low CRF group (figure 1A). Furthermore, compared with the adequate CRF group, mean voltages were significantly lower in the posterior (3.7 ± 1.5 mV vs 1.7 ± 0.9 mV, p < 0.001), inferior (3.4 ± 1 mV vs 1.6 ± 0.7 mV, p < 0.001) and lateral (4.2 ± 2.2 mV vs 2.1 ± 1.4 mV, p < 0.05) walls of the low CRF group. Anterior and septal mean voltages were not significantly different across CRF groups (P for trend = 0.07, 0.3 and 0.15, respectively). Conduction velocities were not significantly different across groups. The inferior %LVA was significantly higher in the low CRF (5.6 ± 6%) compared to adequate CRF group (23 ± 18%) (p < 0.05) (figure 1B). Total and regional % CFE was higher in the low CRF compared to adequate and high CRF. Conclusion Participants in the lower baseline CRF category showed significant reductions in regional voltages along with higher fractionation with preserved conduction velocities. Research on the effect of physical activity and CRF on left atrial arrhythmogenic substrate is required. Abstract Figure. Global and regional mV and % LVA by CRF

The preferential accumulation of vascular smooth muscle cells on arteries versus veins during early development is a well-described phenomenon, but the molecular pathways underlying this polarization are not well understood. During zebrafish embryogenesis the cxcr4a receptor (mammalian CXCR4) and its ligand cxcl12b (mammalian CXCL12) are both preferentially expressed on arteries at time points consistent with the arrival and differentiation of the first vascular smooth muscle cells (vSMCs). We show that autocrine cxcl12b/cxcr4 activity leads to increased production of the vSMC chemoattractant ligand pdgfb by endothelial cells in vitro and increased expression of pdgfb by arteries in vivo. Additionally, we demonstrate that expression of the well-characterized blood flow-regulated transcription factor klf2a in primitive veins negatively regulates cxcr4/cxcl12 and pdgfb expression, restricting vSMC recruitment to the arterial vasculature. Together, this signaling axis leads to the differential acquisition of smooth muscle cells at sites where klf2a expression is low and both cxcr4a and pdgfb are co-expressed, i.e. arteries during early development.