A Pharmacological Analysis of the Neuroprotective Efficacy of the Brain- and Cell-Permeable Calpain Inhibitor MDL-28170 in the Mouse Controlled Cortical Impact Traumatic Brain Injury Model

There are currently no effective therapeutic agents for traumatic brain injury (TBI), but drug treatments for TBI can be developed by validation of new drug targets and demonstration that compounds directed to such targets are efficacious in TBI animal models using a clinically relevant route of drug administration. The cysteine protease, cathepsin B, has been implicated in mediating TBI, but it has not been validated by gene knockout (KO) studies. Therefore, this investigation evaluated mice with deletion of the cathepsin B gene receiving controlled cortical impact TBI trauma. Results indicated that KO of the cathepsin B gene resulted in amelioration of TBI, shown by significant improvement in motor dysfunction, reduced brain lesion volume, greater neuronal density in brain, and lack of increased proapoptotic Bax levels. Notably, oral administration of the small-molecule cysteine protease inhibitor, E64d, immediately after TBI resulted in recovery of TBI-mediated motor dysfunction and reduced the increase in cathepsin B activity induced by TBI. E64d outcomes were as effective as cathepsin B gene deletion for improving TBI. E64d treatment was effective even when administered 8 h after injury, indicating a clinically plausible time period for acute therapeutic intervention. These data demonstrate that a cysteine protease inhibitor can be orally efficacious in a TBI animal model when administered at a clinically relevant time point post-trauma, and that E64d-mediated improvement of TBI is primarily the result of inhibition of cathepsin B activity. These results validate cathepsin B as a new TBI therapeutic target.

Section: Discussionmentioning

confidence: 99%

The Cysteine Protease Cathepsin B Is a Key Drug Target and Cysteine Protease Inhibitors Are Potential Therapeutics for Traumatic Brain Injury

Hook

Sipes

et al. 2014

“…Immediately after completion of the bolus, infusion of 15 mg/kg/h MDL-28170 or equivalent volume of vehicle was initiated and continued for 2.5 h. To achieve maximum calpain inhibition at time of injury, optic nerve stretch was performed 30 min after completion of the initial IV bolus (Markgraf et al, 1998;Thompson et al, 2010).…”

Section: Mdl-28170 Therapymentioning

confidence: 99%

“…Intravenous MDL-28170 has been demonstrated to penetrate into the parenchyma of uninjured brains as well as having neuroprotective properties after ischemic and traumatic brain injury (Markgraf et al, 1998;Thompson et al, 2010). The blood-optic nerve barrier is similar in structure to the blood-FIG.…”

Section: Calpain Inhibition In Tbimentioning

confidence: 99%

Short-Duration Treatment with the Calpain Inhibitor MDL-28170 Does Not Protect Axonal Transport in anin VivoModel of Traumatic Axonal Injury

Wang

et al. 2012

Traumatic axonal injury is characterized by early cytoskeletal proteolysis and disruption of axonal transport. Calpain inhibition has been shown to protect axons in rodent models of traumatic brain injury. However, in these models, both white and gray matter are injured, making it difficult to determine if calpain inhibitors are directly protecting injured axons. To address this issue, we used our rat optic nerve stretch model to test the hypothesis that early calpain inhibition directly protects central nervous system (CNS) axons following stretch injury. Rats were given an intravenous bolus of the calpain inhibitor MDL-28170 (30 mg/kg) 30 min prior to unilateral optic nerve stretch, followed by a 15 mg/kg/h intravenous infusion over the next 2.5 h. Immunohistochemical analysis of optic nerves 30 min after stretch injury revealed variable increases of calpaincleaved a-spectrin that appeared less evident in stretched nerves from drug-treated rats, although this difference was not statistically significant. Retrograde axonal transport measured by Fluorogold Ò labeling of retinal ganglion cells was significantly impaired after stretch injury. However, there was no difference in the number of Fluorogold-labeled cells in the vehicle vs. drug treatment groups. These results suggest that early short-duration calpain inhibitor therapy with MDL-28170 is not an effective strategy to prevent disruption of axonal transport following isolated axonal stretch injury in the CNS.

“…TBI causes pronounced atrophy and dysfunction of cortical and sub-cortical structures, including the hippocampus, thalamus, and striatum (Adams et al, 1985;Anderson et al, 1996Anderson et al, ,2005Baldwin et al, 1997;Bramlett et al, 1997;Colicos et al, 1996;Dietrich et al, 1994;Pierce et al, 1998;Shin et al, 2011;Soares et al, 1995;Thompson et al, 2010). Because the frontal cortex, hippocampus, and striatum additionally express moderate to high levels of dynorphins they were chosen for analysis.…”

Section: Resultsmentioning

confidence: 99%

“…This strain has previously been well characterized in terms of time course of TBI-induced neurodegeneration, and motor and cognitive impairment Hunt et al, 2009;Kelso et al, 2006;Scheff et al, 1997;Thompson et al, 2010). The mice were group-housed (4 per cage) with a 12-h light/dark cycle with food and water available ad libitum.…”

Section: Experimental Animals and Surgical Proceduresmentioning

confidence: 99%

Lateralized Response of Dynorphin A Peptide Levels after Traumatic Brain Injury

Hussain

Fitting

Watanabe

et al. 2012

Traumatic brain injury (TBI) induces a cascade of primary and secondary events resulting in impairment of neuronal networks that eventually determines clinical outcome. The dynorphins, endogenous opioid peptides, have been implicated in secondary injury and neurodegeneration in rodent and human brain. To gain insight into the role of dynorphins in the brain's response to trauma, we analyzed short-term (1-day) and long-term (7-day) changes in dynorphin A (Dyn A) levels in the frontal cortex, hippocampus, and striatum, induced by unilateral left-side or right-side cortical TBI in mice. The effects of TBI were significantly different from those of sham surgery (Sham), while the sham surgery also produced noticeable effects. Both sham and TBI induced short-term changes and long-term changes in all three regions. Two types of responses were generally observed. In the hippocampus, Dyn A levels were predominantly altered ipsilateral to the injury. In the striatum and frontal cortex, injury to the right (R) hemisphere affected Dyn A levels to a greater extent than that seen in the left (L) hemisphere. The R-TBI but not L-TBI produced Dyn A changes in the striatum and frontal cortex at 7 days after injury. Effects of the R-side injury were similar in the two hemispheres. In naive animals, Dyn A was symmetrically distributed between the two hemispheres. Thus, trauma may reveal a lateralization in the mechanism mediating the response of Dyn A-expressing neuronal networks in the brain. These networks may differentially mediate effects of left and right brain injury on lateralized brain functions.