Interruption of endolysosomal trafficking leads to stroke brain injury.

Abstract Background and purpose Dysfunction of the endolysosomal system can cause cell death. A key molecule for controlling the endolysosomal trafficking activities is the N-ethylmaleimide-sensitive factor (NSF) ATPase. This study investigates the cascades of NSF ATPase inactivation events, endolysosomal damage, cathepsin release, and neuronal death after focal brain ischemia. Methods A total of 62 rats were used in this study. They were subjected to sham surgery or 2 h of focal brain ischemia followed by 1, 4, and 24 h of reperfusion. Confocal microscopy and Western blot analysis were utilized to analyze the levels, redistribution, and co-localization of key proteins of the Golgi apparatus, late endosomes, endolysosomes, and lysosomes. Light and electron microscopy were used to examine the histopathology, protein aggregation, and endolysosomal ultrastructures. Results Two hours of focal brain ischemia in rats led to acute neuronal death at the striatal core in 4 h and a slower type of neuronal death in the neocortical area during 1–24 h reperfusion periods. Confocal microscopy showed that NSF immunoreactivity was irreversibly and selectively depleted from most, if not all, post-ischemic penumbral neurons. Western blot analysis further demonstrated that NSF depletion from brain sections was due to its deposition into dense inactive aggregates that could not be recognized by the NSF antibody. Commitantly, the Golgi apparatus was completely fragmented and cathepsin B (CTSB)-containing endolysosomal structures, as well as p62/SQSTM1- and EEA1-immunopositive structures were massively accumulated in the post-ischemic penumbral neurons. Ultimately, CTSB was released into the cytoplasm and extracellular space, causing stroke brain injury. Conclusion Stroke Inactivates NSF, resulting in disruption of the reforming of functional endolysosomal compartments, blockade of the endocytic and autophagic pathways, a large scale of CTSB release into the cytoplasm and extracellular space, and stroke brain injury in the rat model.