Presence of calpain‐induced proteolysis in retinal degeneration and dysfunction in a rat model of acute ocular hypertension

Oka, Takayuki; Tamada, Yoshiyuki; Nakajima, Emi; Shearer, Thomas R.; Azuma, Mitsuyoshi

doi:10.1002/jnr.20827

Cited by 49 publications

(41 citation statements)

References 74 publications

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“…Accumulation of hyperphosphorylated protein causes neurofibrillary tangles and neuronal cell death. In retina, p35 was proteolyzed to p25 by several factors, such as hypoxia, ocular hypertension, photoreceptor cell death, and ganglion cell death (Tamada et al, 2005;Oka et al, 2006Oka et al, , 2007Shimazawa et al, 2010). In the present study, p35 was decreased 48 h after light exposure, and SNJ-1945 treatment (200 mg/kg p.o.…”

Section: Discussionsupporting

confidence: 52%

Calpain Inhibitor Protects Cells against Light-Induced Retinal Degeneration

Imai¹,

Shimazawa²,

Nakanishi³

et al. 2010

J Pharmacol Exp Ther

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Calpains are activated by excessive light exposure and related to retinal degeneration. We investigated the protective effects of ((1S)-1-((((1S)-1-benzyl-3-cyclopropylamino-2,3-di-oxopropyl)amino)carbonyl)-3-methylbutyl)carbamic acid 5-methoxy-3-oxapentyl ester (SNJ-1945), a calpain inhibitor, against lightinduced retinal degeneration in mice. SNJ-1945 was orally administrated at doses of 100 and 200 mg/kg at 30 min before and just after light exposure. Light-induced calpain activation was evaluated by using proteolysis of ␣-spectrin and p35 (a neuron-specific activator for cyclin-dependent kinase 5). The effects of SNJ-1945 against light-induced retinal damage were examined by the thickness of the outer nuclear layer (ONL). Photoreceptor apoptosis was assessed by counting terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells in ONL. Retinal functions were measured in terms of a-and b-wave amplitudes by using an electroretinogram. As the mechanism of SNJ-1945, caspase-3/7 measurement was carried out. SNJ-1945 inhibited the proteolysis of ␣-spectrin and p35 by light exposure and presented a decrease in the numbers of TUNEL-positive cells and ONL atrophy. Furthermore, SNJ-1945 presented a decrease in a-and b-wave amplitude and caspase-3/7 activation induced by light exposure. These findings suggest that the activation of calpain plays a pivotal role in photoreceptor degeneration by light exposure, and SNJ-1945 may be a candidate for effectively treating diseases related to photoreceptor degeneration.

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Section: Discussionsupporting

confidence: 52%

Calpain Inhibitor Protects Cells against Light-Induced Retinal Degeneration

Imai¹,

Shimazawa²,

Nakanishi³

et al. 2010

J Pharmacol Exp Ther

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“…It has recently been reported that elevated IOP could trigger calcineurin cleavage by calpains (64). In addition, it has been shown that calpains are activated after acute ocular hypertension in a rat model (65). These data raise the possibility that the calpain-dependent myocilin processing in ocular tissues, such as the CB and TM, could be enhanced by elevated IOP, pointing out a possible role of myocilin in the regulation and/or response to IOP variations.…”

Section: Discussionmentioning

confidence: 87%

Characterization of the Intracellular Proteolytic Cleavage of Myocilin and Identification of Calpain II as a Myocilin-processing Protease

Sánchez-Sánchez

Martínez-Redondo

Aroca-Aguilar

et al. 2007

Journal of Biological Chemistry

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MYOC, a gene involved in different types of glaucoma, encodes myocilin, a secreted glycoprotein of unknown function, consisting of an N-terminal leucine-zipper-like domain, a central linker region, and a C-terminal olfactomedin-like domain. Recently, we have shown that myocilin undergoes an intracellular endoproteolytic processing. We show herein that the proteolytic cleavage in the linker region splits the two terminal domains. The C-terminal domain is secreted to the culture medium, whereas the N-terminal domain mainly remains intracellularly retained. In transiently transfected 293T cells, the cleavage was prevented by calpain inhibitors, such as calpeptin, calpain inhibitor IV, and calpastatin. Since calpains are calciumactivated proteases, we analyzed how changes in either intra-or extracellular calcium affected the cleavage of myocilin. Intracellular ionomycin-induced calcium uptake enhanced myocilin cleavage, whereas chelation of extracellular calcium by EGTA inhibited the proteolytic processing. Calpains I and II cleaved myocilin in vitro. However, in cells in culture, only RNA interference knockdown of calpain II reduced myocilin processing. Subcellular fractionation and digestion of the obtained fractions with proteinase K showed that full-length myocilin resides in the lumen of the endoplasmic reticulum together with a subpopulation of calpain II. These data revealed that calpain II is responsible for the intracellular processing of myocilin in the lumen of the endoplasmic reticulum. We propose that this cleavage might regulate extracellular interactions of myocilin, contributing to the control of intraocular pressure.

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“…However, the cleaved p25 protein was not detected in retinal extracts obtained from 6 to 24 h after NMDA injection in this study. Previously, Oka et al (2006a) reported that transient ocular hypertension for 120 min and reperfusion induced a persistent decrease in p35 during 7 days and a transient increase in p25 at an early stage (4 h) after the ischemic insult, and its increase returned to a normal level by 12 h. Collectively, the immunofluorescence in retinal cross sections is considered to show p35, but not p25, at 6 and 24 h after NMDA injection. Furthermore, some condensed immunopositive cells in GCL at 24 h after NMDA are considered to result from morphological changes accompanied by cell death but not nuclear translocation of p25.…”

Section: Retinal Protection By Calpain Inhibitor 385mentioning

confidence: 98%

A Novel Calpain Inhibitor, ((1S)-1-((((1S)-1-Benzyl-3-cyclopropylamino-2,3-di-oxopropyl)amino)carbonyl)-3-methylbutyl)carbamic Acid 5-Methoxy-3-oxapentyl Ester (SNJ-1945), Reduces Murine Retinal Cell Death In Vitro and In Vivo

Shimazawa¹,

Suemori²,

Inokuchi³

et al. 2009

J Pharmacol Exp Ther

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We examined whether ((1S)-1-((((1S)-1-benzyl-3-cyclopropylamino-2,3-di-oxopropyl)amino)carbonyl)-3-methylbutyl)carbamic acid 5-methoxy-3-oxapentyl ester (SNJ-1945), a new orally available calpain inhibitor, might reduce retinal cell death in vivo and/or in vitro. Retinal cell damage was induced in vivo in mice by intravitreal injection of N-methyl-D-aspartate (NMDA), and SNJ-1945 was intraperitoneally or orally administered twice. NMDA-induced calpain activity (measured as the cleaved products of ␣-spectrin) and its substrate, p35 (a neuron-specific activator for cyclin-dependent kinase 5), in the retina were examined by immunoblotting. In RGC-5 (a rat retinal ganglion cell line) cell culture, cell damage was induced by a 4-h oxygenglucose deprivation (OGD) treatment followed by an 18-h reoxygenation period. In mouse retinas, SNJ-1945 (30 or 100 mg/kg i.p., 100 or 200 mg/kg p.o.) significantly inhibited the cell loss in the ganglion cell layer (GCL) and the thinning of the inner plexiform layer induced by NMDA. Furthermore, the number of positive cells for terminal deoxynucleotidyl transferase dUTP nick-end labeling was significantly reduced in the GCL and the inner nuclear layer of retinas treated with SNJ-1945 compared with vehicle-treated retinas 24 h after NMDA injection. Levels of cleaved ␣-spectrin products increased and p35 decreased 6 h after NMDA injection or later, and their effects were attenuated by SNJ-1945. In vitro, SNJ-1945 (10 and 100 M) inhibited the OGD stress-induced reduction in cell viability. In conclusion, SNJ-1945 may afford valuable neuroprotection against retinal diseases, because it was effective against retinal damage both in vitro and in vivo. Our results also indicate that calpain activation and subsequent p35 degradation may be involved in the mechanisms underlying retinal cell death.Retinal ganglion cell (RGC) death is a common feature of many ophthalmic disorders, including glaucoma, optic neuropathies, and various retinovascular diseases (diabetic retinopathy and retinal vein occlusions). Retinal ganglion cells are extremely sensitive to the effects of both glutamate and its analog N-methyl-D-aspartate (NMDA), both of which produce a dosedependent cell loss in vivo and in vitro. In addition, glutamate toxicity has been implicated in the pathophysiology of glaucoma (Dreyer, 1998). Activation of Ca 2ϩ -permeable NMDA receptors and the subsequent neuronal Ca 2ϩ overloading have been shown to mediate glutamate-induced neuron death (Choi, 1994). Induction of the Ca 2ϩ -activated neutral cysteine protease -calpain by micromolar concentrations of Ca 2ϩ occurs early in excitotoxic neuron death (Siman et al., 1989;Faddis et al., 1997). Similar to the caspases, -calpain cleaves a variety of cytoskeletal proteins, enzymes, and transcription factors and could also interfere with the proteolytic activity of the caspases (Croall and DeMartino, 1991).

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Presence of calpain‐induced proteolysis in retinal degeneration and dysfunction in a rat model of acute ocular hypertension

Cited by 49 publications

References 74 publications

Calpain Inhibitor Protects Cells against Light-Induced Retinal Degeneration

Calpain Inhibitor Protects Cells against Light-Induced Retinal Degeneration

Characterization of the Intracellular Proteolytic Cleavage of Myocilin and Identification of Calpain II as a Myocilin-processing Protease

A Novel Calpain Inhibitor, ((1S)-1-((((1S)-1-Benzyl-3-cyclopropylamino-2,3-di-oxopropyl)amino)carbonyl)-3-methylbutyl)carbamic Acid 5-Methoxy-3-oxapentyl Ester (SNJ-1945), Reduces Murine Retinal Cell Death In Vitro and In Vivo

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