Mitochondria-Endoplasmic Reticulum Contact Sites Dynamics and Calcium Homeostasis Are Differentially Disrupted in PINK1-PD or PRKN-PD Neurons.

BACKGROUND: It is generally believed that the pathogenesis of PINK1/parkin-related Parkinson's disease (PD) is due to a disturbance in mitochondrial quality control. However, recent studies have found that PINK1 and Parkin play a significant role in mitochondrial calcium homeostasis and are involved in the regulation of mitochondria-endoplasmic reticulum contact sites (MERCSs). OBJECTIVE: The aim of our study was to perform an in-depth analysis of the role of MERCSs and impaired calcium homeostasis in PINK1/Parkin-linked PD. METHODS: In our study, we used induced pluripotent stem cell-derived dopaminergic neurons from patients with PD with loss-of-function mutations in PINK1 or PRKN. We employed a split-GFP-based contact site sensor in combination with the calcium-sensitive dye Rhod-2 AM and applied Airyscan live-cell super-resolution microscopy to determine how MERCSs are involved in the regulation of mitochondrial calcium homeostasis. RESULTS: Our results showed that thapsigargin-induced calcium stress leads to an increase of the abundance of narrow MERCSs in wild-type neurons. Intriguingly, calcium levels at the MERCSs remained stable, whereas the increased net calcium influx resulted in elevated mitochondrial calcium levels. However, PINK1-PD or PRKN-PD neurons showed an increased abundance of MERCSs at baseline, accompanied by an inability to further increase MERCSs upon thapsigargin-induced calcium stress. Consequently, calcium distribution at MERCSs and within mitochondria was disrupted. CONCLUSIONS: Our results demonstrated how the endoplasmic reticulum and mitochondria work together to cope with calcium stress in wild-type neurons. In addition, our results suggests that PRKN deficiency affects the dynamics and composition of MERCSs differently from PINK1 deficiency, resulting in differentially affected calcium homeostasis. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Lesion patterns in successful and failed thrombolysis in middle cerebral artery stroke.

INTRODUCTION: Thrombolysis has been shown to improve neurological recovery in acute stroke. But the response to thrombolysis is variable across patients. We sought to investigate this variability by analyzing the lesion patterns following systemic thrombolysis with recombinant tissue plasminogen activator (rtPA) and tirofiban in middle cerebral artery (MCA) stroke. METHODS: One hundred three consecutive stroke patients (67 +/- 14 years) were grouped according to the site of MCA occlusion and successful or failed recanalization as assessed with magnetic resonance angiography. Infarct lesions were analyzed in T2-weighted magnetic resonance images after 10 days. RESULTS: Patients recovered markedly upon successful recanalization following thrombolysis (p < 0.05) but remained severely impaired when there was no recanalization within 24 h. Infarct lesions were smaller after successful than after failed recanalization (p < 0.005). They occurred throughout the cerebral cortex on the cerebral convexity in distal MCA occlusions with large individual heterogeneity. In contrast, there was a large lesion overlap in insular cortex, basal ganglia, internal capsule, and paraventricular white matter in proximal MCA occlusions. CONCLUSION: Systemic thrombolysis with rtPA and tirofiban of MCA occlusions resulted in early neurological recovery and preferentially peri-insular infarcts. In failed recanalization of the MCA stem there was a large lesion overlap in the hemispheric white matter and a lack of recovery.