Extending the Calpain–Cathepsin Hypothesis to the Neurovasculature: Protection of Brain Endothelial Cells and Mice from Neurotrauma

Abstract

The calpain–cathepsin hypothesis posits a key role for elevated calpain-1 and cathepsin-B activity in the neurodegeneration underlying neurotrauma and multiple disorders including Alzheimer’s disease (AD). AD clinical trials were recently halted on alicapistat, a selective calpain-1 inhibitor, because of insufficient exposure of neurons to the drug. In contrast to neuroprotection, the ability of calpain-1 and cathepsin-B inhibitors to protect the blood–brain barrier (BBB), is understudied. Since cerebrovascular dysfunction underlies vascular dementia, is caused by ischemic stroke, and is emerging as an early feature in the progression of AD, we studied protection of brain endothelial cells (BECs) by selective and nonselective calpain-1 and cathepsin-B inhibitors. We show these inhibitors protect both neurons and murine BECs from ischemia–reperfusion injury. Cultures of primary BECs from ALDH2 –/– mice that manifest enhanced oxidative stress were sensitive to ischemia, leading to reduced cell viability and loss of tight junction proteins; this damage was rescued by calpain-1 and cathepsin-B inhibitors. In ALDH2 –/– mice 24 h after mild traumatic brain injury (mTBI), BBB damage was reflected by significantly increased fluorescein extravasation and perturbation of tight junction proteins, eNOS, MMP-9, and GFAP. Both calpain and cathepsin-B inhibitors alleviated BBB dysfunction caused by mTBI. No clear advantage was shown by selective versus nonselective calpain inhibitors in these studies. The lack of recognition of the ability of calpain inhibitors to protect the BBB may have led to the premature abandonment of this therapeutic approach in AD clinical trials and requires further mechanistic studies of cerebrovascular protection by calpain-1 inhibitors.

Exploratory factor analysis yields grouping of brain injury biomarkers significantly associated with outcomes in neonatal and pediatric ECMO

“…This factor’s association with lower levels of unfavorable neurologic outcomes in neonatal and pediatric ECMO is supported by the previously discussed neuroprotective properties of BDNF. Interestingly, this suggested neuroprotective property of MMP-9 stands in contrast to previously demonstrated pathogenic properties of other proteases, such as calpain, in many neuropathologies including neonatal encephalopathy 54 – 56 . Additionally, the agnostic grouping of these two biomarkers involved in the same signaling pathway supports that EFA did in fact group combinations that indicate a unique pathophysiologic process.…”

Targeting the Extracellular Matrix in Traumatic Brain Injury Increases Signal Generation from an Activity-Based Nanosensor

“… 70 In TBI, MMP-9 is a possible candidate for multiplexing as MMP-9 levels are elevated in patients post-TBI, and MMP-9 is implicated in BBB permeability. 71 Tethering substrates for multiple proteases onto a single nanomaterial scaffold and visualization in 3D would allow for the study of spatial activation of proteases in relation to each other; for example, calpain-1 has been shown to activate MMP-9 in TBI 72 and stroke. 73 In the future, the TBI-ABN platform could be redesigned for in vivo measurements with quenchable quantum dots 74 and tissue-penetrating near-infrared optical imaging through cranial windows, or with superparamagnetic iron oxide nanoparticles 75 and magnetic resonance imaging (MRI).…”

PIEZO1 Ion Channel Mediates Ionizing Radiation-Induced Pulmonary Endothelial Cell Ferroptosis via Ca2+/Calpain/VE-Cadherin Signaling

“…Oxidative stress is closely related with ferroptosis. Specific calpain-1 inhibitor rescues cell damage caused by oxidative stress in brain endothelial cells ( Knopp et al, 2021 ). Previous studies established that inhibition of calpain activity efficiently prevents high glucose-induced ROS production in human umbilical vein endothelial cells ( Chen et al, 2014 ).…”