Pharmacological analysis of the cortical neuronal cytoskeletal protective efficacy of the calpain inhibitor SNJ‐1945 in a mouse traumatic brain injury model

Abstract

The efficacy of the amphipathic ketoamide calpain inhibitor SNJ-1945 in attenuating calpain-mediated degradation of the neuronal cytoskeletal protein a-spectrin was examined in the controlled cortical impact (CCI) traumatic brain injury (TBI) model in male CF-1 mice. Using a single early (15 min after CCI-TBI) i.p. bolus administration of SNJ-1945 (6.25, 12.5, 25, or 50-mg/kg), we identified the most effective dose on a-spectrin degradation in the cortical tissue of mice at its 24 h peak after severe CCI-TBI. We then investigated the effects of a pharmacokinetically optimized regimen by examining multiple treatment paradigms that varied in dose and duration of treatment. Finally, using the most effective treatment regimen, the therapeutic window of a-spectrin degradation attenuation was assessed by delaying treatment from 15 min to 1 or 3 h post-injury. The effect of SNJ-1945 on a-spectrin degradation exhibited a U-shaped doseresponse curve when treatment was initiated 15 min post-TBI. The most effective 12.5 mg/kg dose of SNJ-1945 significantly reduced a-spectrin degradation by~60% in cortical tissue. Repeated dosing of SNJ-1945 beginning with a 12.5 mg/kg dose did not achieve a more robust effect compared with a single bolus treatment, and the required treatment initiation was less than 1 h. Although calpain has been firmly established to play a major role in post-traumatic secondary neurodegeneration, these data suggest that even brain and cell-permeable calpain inhibitors, when administered alone, do not show sufficient cytoskeletal protective efficacy or a practical therapeutic window in a mouse model of severe TBI. Such conclusions need to be verified in the human clinical situation.

CAPN5 genetic inactivation phenotype supports therapeutic inhibition trials

“…The inhibition of CAPN5 to treat patients is promising, as CAPN5 closely resembles its Caenorhabditis elegans homolog, Tra‐3 , and the reduction of Tra‐3 in C. elegans has been shown to rescue inflammatory neuronal degeneration (Syntichaki, Xu, Driscoll, & Tavernarakis, ). Additionally, SNJ‐1945, a small molecule inhibitor of calpains, rescued neuronal cell death in a model of traumatic brain injury as well as rescuing experimental autoimmune encephalitis (Bains et al, ; Trager et al, ). Inhibitors have also shown rescue effects for a variety of other common blinding disorders, such as retinitis pigmentosa (Ozaki et al, ), optic neuritis (Das et al, ; Smith et al, ), light‐induced retinal toxicity (Imai, Shimazawa, Nakanishi, Tsuruma, & Hara, ; Kanan, Moiseyev, Agarwal, Ma, & Al‐Ubaidi, ), retinal hypoxia (Hoang, Smith, & Senger, ; Shimazawa et al, ), retinal angiogenesis (Ma, Tochigi, Shearer, & Azuma, ) and diabetic retinopathy (Shanab et al, ).…”

“…For all calpains, the calcium residues within the catalytic domain provide for a layer of calcium dependence. Furthermore, calpains in higher vertebrates have evolved a second regulatory layer by acquiring a calmodulin‐like C‐terminal domain (Bains et al, ). CAPN5, however, is more similar to Tra‐3 , and lacks this additional regulatory domain.…”

Calpain Genetic Disruption and HSP90 Inhibition Combine To Attenuate Mammary Tumorigenesis

“…In contrast, cells expressing protease-dead CAPN2 (LD 50 , 27.2 M) behaved similarly to control cells, with 22.95% Ϯ 5.02% cell death (P ϭ 0.59) at 5 M 17AAG. The calpain inhibitor SNJ1945 (28), which was shown to inhibit calpain-1 autoproteolytic activity (Fig. 2C), also enhanced 17AAG-induced cell death in MDA-MB-231 cells (Fig.…”

Chronic traumatic encephalopathy-integration of canonical traumatic brain injury secondary injury mechanisms with tau pathology

“…In fact, calpain-cleaved αII-spectrin breakdown products are frequently used to assess post-TBI axonal damage and neuroprotection following TBI (Bains et al, 2013; Deng-Bryant et al, 2008; Deng et al, 2007; Mbye et al, 2009; Miller et al, 2014; Mustafa et al, 2011; Saatman et al, 1996). Similarly, mitochondrial release of cytochrome c leads to activation of the protease caspase-3 and induction of apoptosis (Galluzzi et al, 2009; Sullivan et al, 2005; Wang, 2000).…”