Possible involvement of calpain activation in pathogenesis of chronic heart failure after acute myocardial infarction

Changes in proteolytic activity of the myocardium during the development of heart failure after left coronary artery ligation (CAL) of rats were examined. Hemodynamics of the rats at the eighth week (8w-CAL rat), but not at the second week (2w-CAL rat), after CAL showed the symptoms of chronic heart failure. Contents of mu-calpin and m-calpain, but not an intrinsic calpain inhibitor calpastatin, in the viable left ventricular muscle (viable LV) and the right ventricular muscle (RV) of the 2w-CAL and 8w-CAL rats were increased, which was associated with an elevation of intrinsic activities of leupeptin-sensitive, Ca(2+)-activated proteolysis in the cytosolic fractions of the viable LV and RV. Oral administration of 3 mg/kg/d trandolapril or 1 mg/kg/d candesartan from the second to eighth week after CAL improved the hemodynamics of 8w-CAL rats. The drug treatment attenuated the increases in mu-calpain and m-calpain contents and the elevation of the proteolytic activity of the viable LV and RV in the 8w-CAL rat. The drug treatment increased calpastatin content of the RV in the 8w-CAL rat. These results suggest that sustained activation of calpain is involved in the development of chronic heart failure and that trandolapril and candesartan prevent the activation of calpains after CAL.

Low activity by the calpain system in primate lenses causes resistance to calcium-induced proteolysis

The human genome contains 14 genes for 80 kDa catalytic subunit of the calcium-activated protease calpain (EC 34.22.17), yet no calpain-like cleavage sites have been detected on human lens crystallins in vivo. The purpose of the present study was to provide a comprehensive study of calpain activation in human and macaque lenses developing experimental cataract due to lens culture in ionophore A23187. Zymography was used to measure calpain activity; SDS-PAGE and immunoblotting were used to detect hydrolysis of potential lens protein substrates. Quantitative PCR was used to measure transcripts for calpains and the endogenous inhibitor calpastatin. We found that the lack of appreciable calpain-induced proteolysis in primate lenses is most likely due to relatively low levels of endogenous calpain activity compared to the high levels of endogenous calpain inhibitor, calpastatin.

Proteomic analysis of ursolic acid-induced apoptosis in cervical carcinoma cells

Proteomic analyses can efficiently detect the variation of protein in high throughput screening. Using 2DE/MALDI-TOF-MS and SELDI-TOF-MS, we tried to search several cellular proteins that are responsive to ursolic acid (UA) in HeLa cervical carcinoma cells. Compared to control, UA-treated HeLa cells unfolded 25 proteins in significant changes by 2DE/MALDI-TOF-MS, most of which were involved in apoptosis. SELDI-TOF-MS with two types of protein chips profiled and analyzed proteomic features after administration of UA. Interestingly, eight polypeptide peaks can be detected. Further identification and characterization of these proteins may build the molecular basis of UA-induced apoptosis and provide insight into the anti-proliferative mechanism in cervical carcinoma cells.

Changes in oxidative stress parameters and neurodegeneration markers in the brain of the senescence-accelerated mice SAMP-8

The senescence-accelerated strains of mice (SAMP) are well-characterized animal models of senescence. Senescence may be related to enhanced production or defective control of reactive oxygen species, which lead to neuronal damage. Therefore, the activity of various oxidative-stress related enzymes was determined in the cortex of 5 months-old senescence-accelerated mice prone-8 (SAMP-8) of both sexes and compared with senescence-accelerated mice-resistant-1 (SAMR-1). Glutathione reductase and peroxidase activities in SAMP-8 male mice were lower than in male SAMR-1, and a decreased catalase activity was found in both male and female SAMP-8 mice, which correlates with the lower catalase expression found by Western blotting. Nissl staining showed marked loss of neuronal cells in the cerebral cortex of five month-old SAMP-8 mice. SAMP-8 mice also had marked astrogliosis and microgliosis. We also found an increase in caspase-3 and calpain activity in the cortex. In addition, we observed morphological changes in the immunostaining of tau protein in SAMP-8, indicative of a loss of their structural function. Altogether, these results show that, at as early as 5 months of age, SAMP-8 mice have cytological and molecular alterations indicative of neurodegeneration in the cerebral cortex and suggestive of altered control of the production of oxidative species and hyper-activation of calcium-dependent enzymes.

Involvement of calpain in melanogenesis of mouse B16 melanoma cells

In the current study, the involvement of calpain, a cysteine proteinase in the regulation of melanogenesis was examined using mouse B16 melanoma cells. In response to alpha-melanocyte-stimulating hormone (a-MSH), B16 melanoma cells underwent differentiation characterized by increased melanin biosynthesis. The total calapain activity was decreased within 2 h following alpha-MSH-treatment, and restored to the initial level in 6-12 h. To further investigate the involvement of calpain in the regulation of melanogenesis, the effect of calpain inhibitors on alpha-MSH-induced melanogenesis was examined. Inhibition of calpain by either N-acetyl-Leu-Leu-norleucinal (ALLN) or calpastatin (CS) peptide blocked alpha-MSH-induced melanogenesis. The magnitude of inhibition of melanin biosynthesis was well correlated with a decrease in the activity of tyrosinase, a key regulatory enzyme in melanogenesis. Treatment of B16 cells with ALLN caused marked decrease in both tyrosinase protein and mRNA levels. These results indicate that calpain would be involved in the melanogenic signaling by modulating the expression of tyrosinase in mouse B16 melanoma cells.

Caspase and calpain function in cell death: bridging the gap between apoptosis and necrosis

Calpain and caspase are families of cysteine proteases that have important roles in the initiation, regulation and execution of cell death. The function of both groups of proteases in the progression of apoptotic and necrotic pathways is presented here in the context of a concise overview of regulated cell death. Many of the morphological differences between apoptotic and necrotic processes are thought to be as a consequence of the action of cysteine proteases. Recent studies suggest that caspase and calpain cascades are tightly interrelated and an appreciation of how these proteases cross-talk should enable a greater understanding of how the boundaries between apoptotic and necrotic cell death have become blurred. Furthermore, an assessment of the contribution that caspase and calpain make to human physiology and pathology is provided, with a description of how these proteases can be detected and quantified. Lastly, an evaluation is made of how caspase and calpain activation might be exploited diagnostically.

Detection and localization of calpain 3-like protease in a neuronal cell line: Possible regulation of apoptotic cell death through degradation of nuclear IκBα

Calpains are a family of calcium-dependent cysteine proteases involved in major cellular processes including cell death. Their intracellular localization is essential to the understanding of their biological functions. In a previous confocal microscopy study, we observed the presence of a calpain 3-like protein in the mammalian brain. We thus first identified and confirmed the presence of a calpain 3-like protease in a neuronal cell model (NGF-differentiated PC12 cells). The goal of this study was to determine, for the first time in non-muscular cells, the relation between the subcellular localization, activation and function of this protease. We thus investigated its ability to regulate nuclear IkappaBalpha and therefore NF-kappaB activation after cell death stimulation. The IkappaBalpha/NF-kappaB signalling pathway indeed influences the neurodegenerative process by directly affecting gene expression in neurons. In the present study, we found that calpain 3 is present in the cytoplasm and nucleus of neuron-like PC12 cells and could be activated through autolysis in the nuclei of cells undergoing apoptosis after ionomycin treatment. Moreover, in these conditions, we demonstrated formation of the IkappaBalpha/calpain 3 complex and an increase in calpain-dependent IkappaBalpha cleavage products in cell nuclei. Stimulation of calpain-dependent cell death in neuron activated nuclear calpain 3-like protease and IkappaBalpha proteolysis resulted in the regulation of NF-kappaB activation. These data suggest a new mechanism by which calpain 3 activation is able to regulate the IkappaBalpha/NF-kappaB pathway and thus neurodegenerative processes.

Expression and immunolocalization of the calpain–calpastatin system during parthenogenetic activation and fertilization in the rat egg

Calpastatin is an intrinsic intracellular inhibitor of calpain, a Ca2+-dependent thiol protease. The calpain–calpastatin system constitutes one functional proteolytic unit whose presence and function has already been investigated in various cell types, but not in the egg. We have previously shown that calpain is expressed in rat eggs and is activated upon egg activation. The present study was designed to investigate the calpain–calpastatin interplay throughout the process.

Western blot analysis revealed two main calpastatin isoforms, the erythrocyte type (77 kDa) and the muscle tissue type (110 kDa). By immunohistochemistry and confocal laser scanning microscopy, we demonstrated that the 110 kDa calpastatin was localized at the membrane area and highly abundant at the meiotic spindle in eggs at the first and second meiotic divisions. The 77 kDa calpastatin isoform appeared to be localized as a cortical sphere of clusters. The 110kDa calpastatin and β-tubulin have both been localized to the spindle of metaphase II eggs, both being scattered all through the cytoplasm following spindle disruption by nocodazole treatment, implying a dynamic interaction between calpastatin and microtubule elements. Upon egg activation, membranous calpastatin translocated to the cortex whereas cortical millimolar (m)-calpain shifted towards the membrane. Spindle calpastatin and calpain remained static.

We suggest that calpastatin serves as a regulator of m-calpain. The counter translocation of m-calpain and calpastatin could serve as a means of calpain escape from calpastatin inhibition and may reflect a step in the process of calpain activation, throughout egg activation, that is required for calpain to exert its proteolytic activity.

Expression and possible involvement of calpain isoforms in mammalian egg activation

At fertilization in mammals, the spermatozoon triggers a unique signal transduction mechanism within the egg, leading to its activation. It is well accepted that the earliest event observed in all activated eggs is an abrupt rise in intracellular calcium concentrations. However, little is known regarding the downstream proteins that are activated by this rise in calcium. Calpains constitute a family of intracellular calcium-dependent cysteine proteases whose members are expressed widely in a variety of cells. We investigated the expression and possible role of the calpain isoforms mu and m throughout egg activation. Both calpains were expressed in the rat egg and localized at the egg cortex as well as in the meiotic spindle. m Calpain translocated to the membrane and to the spindle area during parthenogenetic egg activation and during in vivo fertilization, upon sperm binding to the egg. The cytoskeletal protein alpha-spectrin (fodrin) was proteolysed by calpain during the egg-activation process, as demonstrated by specific calpain-breakdown products. Following parthenogenetic activation by ionomycin or puromycin, the calpain-selective permeable inhibitor, calpeptin, inhibited the resumption of meiosis and cortical reaction in a dose-dependent manner. Calpeptin was also effective in inhibiting in vitro fertilization. These results may imply a correlation between calpain activation and mammalian egg activation at fertilization and a possible role for calpain in the cascade of cellular events leading to resumption of meiosis.

Protein studies in dysferlinopathy patients using llama-derived antibody fragments selected by phage display

Mutations in dysferlin, a member of the fer1-like protein family that plays a role in membrane integrity and repair, can give rise to a spectrum of neuromuscular disorders with phenotypic variability including limb-girdle muscular dystrophy 2B, Myoshi myopathy and distal anterior compartment myopathy. To improve the tools available for understanding the pathogenesis of the dysferlinopathies, we have established a large source of highly specific antibody reagents against dysferlin by selection of heavy-chain antibody fragments originating from a nonimmune llama-derived phage-display library. By utilizing different truncated forms of recombinant dysferlin for selection and diverse selection methodologies, antibody fragments with specificity for two different dysferlin domains could be identified. The selected llama antibody fragments are functional in Western blotting, immunofluorescence microscopy and immunoprecipitation applications. Using these antibody fragments, we found that calpain 3, which shows a secondary reduction in the dysferlinopathies, interacts with dysferlin.

Identification of a novel calpain inhibitor using phage display

Calpains are calcium- and thiol-dependent proteases that cleave a variety of intracellular substrates. Overactivation of the calpains has been implicated in a number of diseases and conditions such as ischemic stroke indicating a need for the development of calpain inhibitors. A major problem with current calpain inhibitors has been specific targeting to calpain. To identify highly specific calpain interacting peptides, we developed a peptide-phage library screening method based on the calcium-dependent conformation change associated with calpain activation. A phage-peptide library representing greater than 2 billion expressed 12-mers was incubated with calpain I in the presence of calcium. The calcium-dependent bound phage was then eluted by addition of EGTA. After four rounds of selection we found a conserved 5-mer sequence represented by LSEAL. Synthetic LSEAL inhibited tau-calpain interaction and in vitro proteolysis of tau- and alpha-synuclein by calpains. Deletion of the portion of the tau protein containing a homologous sequence to LSEAL resulted in decreased calpain-mediated tau degradation. These data suggest that these peptides may represent novel calpastatin mimetics.

Biochemical properties of lens-specific calpain Lp85

Lens-specific Lp82 and ubiquitous m-calpain are neutral, calcium-activated, cysteine proteases. Both calpains are activated during rodent lens maturation and cataract formation. Lp85 calpain (Lens protein with MW=85 kDa) is a slightly larger splice variant of Lp82. Lp85 contains a 28 amino acid insert peptide (IS3) in calcium binding domain IV. Theoretically, the insert could alter the properties of Lp85 and influence proteolytic activity. The purpose of the present experiment was to compare the biochemical properties of Lp85 to Lp82 and m-calpain. Recombinant Lp85 and Lp82 were separately expressed using the baculovirus system and partially purified using Co2+ affinity and DEAE chromatographies. Calcium activation, pH dependency, and susceptibility to calpain inhibitors were assessed in a protease assay using BODIPY fluorescence-labeled casein substrate. Hydrolysis of lens proteins was assessed by SDS-PAGE and immunoblotting. Cleavage site analysis was performed by mass spectroscopy and Edman sequencing. Computer-based homology modeling was used to predict the influence of the IS3 region on the 3-dimensional structure of Lp85. Compared to m-calpain, Lp85 showed a lower calcium-activation requirement (K(50%act)=20 microM), marked insensitivity to, and cleavage of, the endogenous tissue inhibitor of calpains-calpastatin, and different preferred cleavage sites on alphaA-crystallin (five amino acid C-terminal truncation) and on aquaporin 0 (G239 and N246). Although the IS3 insert was predicted to form a loop protruding from the calcium binding region of Lp85, the biochemical properties of Lp85 studied were nearly identical to those of Lp82. Lp85 and Lp82 did not catalyze hydrolysis of each other, but both hydrolyzed m-calpain. Lp85 seems to be the enzymatic equivalent of Lp82. Both calpains could become active at lower cellular calcium levels than m-calpain. Lp85/Lp82 may have different functions than m-calpain since they cleave substrates at different sites. Lp85/Lp82 may regulate m-calpain activity by catalyzing the hydrolysis of calpastatin. The function of the IS3 insert on Lp85 remains unknown but is speculated to control subcellular distribution.

Effect of processing on turkey meat quality and proteolysis

Modern processing techniques for turkey involve rapid chilling to slow microbial growth and early deboning of the economically important breast meat. This paper shows that these 2 processes lead to significantly tougher meat with higher cooking losses. The toughening appears to be due to less extensive proteolysis and shortening of the sarcomeres. Calpains I and II and their inhibitor, calpastatin, were quantified in turkey breast. Calpain II was the more common isoform but showed no evidence of activation during aging. In contrast, calpain I and calpastatin activities declined rapidly and were no longer detected 24 h postslaughter. There was no evidence of an association between calpain activity and processing conditions.

Calpain 3/p94 is not involved in postmortem proteolysis1,2

Studies on the correlation between expression and/or autolysis of calpain and postmortem proteolysis in muscle have provided conflicting evidence regarding the possible role of calpain 3 in postmortem tenderization of meat. Thus, the objective of this research was to test the effect of postmortem storage on proteolysis and structural changes in muscle from normal and calpain 3 knockout mice. Knockout mice (n = 6) were sacrificed along with control mice (n = 6). Hind limbs were removed and stored at 4 degrees C; muscles were dissected at 0, 1, and 3 d postmortem and subsequently analyzed individually for degradation of desmin. Pooled samples for each storage time and mouse type were analyzed for degradation of nebulin, dystrophin, vinculin, and troponin-T. In a separate experiment, hind-limb muscles from knockout (n = 4) and control mice (n = 4) were analyzed for structural changes at 0 and 7 d postmortem using light microscopy. As an index of structural changes, fiber detachment, cracked or broken fibers, and the appearance of space between sarcomeres were quantified. Cumulatively, the results of the first experiment indicated that postmortem proteolysis of muscle occurred similarly in control and in calpain 3 knockout mice. Desmin degradation did not differ (P > 0.99), and there were no indications that degradation of nebulin, dystrophin, vinculin, and troponin-T were affected by the absence of calpain 3 in postmortem muscle. Structural changes were affected by time postmortem (P < 0.05), but not by the absence of calpain 3 from the muscles. In conclusion, these results indicate that calpain 3 plays a minor role, if any, in postmortem proteolysis in muscle.

Spatial resolution of calpain-catalyzed proteolysis in focal cerebral ischemia

Transient forebrain ischemia induces calpain-mediated degradation of the neuronal cytoskeleton, alpha-fodrin, and this results in ischemic neuronal death. In this study, we investigated the spatial distribution and temporal changes of calpain-catalyzed alpha-fodrin proteolysis in focal cerebral ischemia and examined the effects of a calpain inhibitor. Ischemia was induced in gerbils by 3-h middle cerebral artery occlusion followed by reperfusion. Animals were divided into four groups: a sham-operated group, an ischemic group, a vehicle-treated group, and a calpain inhibitor-treated group. Intravenous injections of vehicle or calpain inhibitor I were administered 30 min before ischemia. Infarct volumes were measured 1 day after reperfusion and the spatial distribution of calpain-catalyzed alpha-fodrin proteolysis was investigated by immunohistochemistry 15 min, 1 h, 4 h, and 1 day after reperfusion. Infarct volume (mean +/- SD) in the ischemic group and the vehicle-treated group was 204.6 +/- 19.1 mm3 and 212.4 +/- 16.3 mm3, respectively, and the calpain inhibitor I reduced the infarct volume [149.4 +/- 25.2 mm3 (P < 0.05)]. Immunoblot analysis demonstrated that calpain inhibitor reduced proteolysis. Ischemia induced fodrin proteolysis in the ischemic core and the peri-infarct zone within 15 min after reperfusion, with proteolysis developing quickly in the ischemic core and more slowly in the peri-infarct zone. Proteolysis preceded neuronal death in the peri-infarct zone. Calpain inhibitor I ameliorated neuronal death in the peri-infarct zone but not in the ischemic core. Thus, calpain plays a pivotal role on focal ischemia as well as in global ischemia.

The expression of calpain 1 and calpain 2 in spermatogenic cells and spermatozoa of the mouse

There is some evidence suggesting that Ca2+is involved in processes that occur during the development and function of spermatozoa. Calcium-dependent proteins, such as calmodulin, are expressed during mammalian spermatogenesis further suggesting that Ca2+takes part in its regulation. However, the precise roles of Ca2+in spermatogenesis remain to be elucidated. Calpains are a family of Ca2+-dependent cysteine proteases whose members are expressed ubiquitously or in a tissue-specific manner. Calpain has been demonstrated to mediate specific Ca2+-dependent processes including cell fusion, mitosis and meiosis. We herein followed the expression pattern of calpain’s ubiquitous isoforms, 1 and 2, throughout spermatogenesis at the RNA and protein levels by RT-PCR and Western blotting analysis. Both RNA and protein studies revealed that these isoforms are expressed in all spermatogenic cells. The expression of calpain 1 levels is slightly higher in spermatocytes entering the meiotic phase. Both calpain isoforms are also expressed in mouse spermatozoa and are localized to the acrosomal cap. Inducing capacitated spermatozoa to undergo the acrosome reaction in the presence of a selective calpain inhibitor significantly reduced the acrosome reaction rate in a dose-dependent manner. Thus, calpain, a pluripotential protease with numerous substrates, may serve as an effector in more than one pathway in the complex process of spermatogenesis and in the events preceding fertilization, such as the acrosome reaction.

Effects of ACE inhibitor and AT blocker on dystrophin-related proteins and calpain in failing heart

OBJECTIVES

Genetic depletion of dystrophin-related protein (DRP) complex causes cardiomyopathy in animals and humans. We found in a previous study that some types of DRP were degraded and that calpain content was increased in rats with non-genetically induced heart failure. The present study was aimed at examining the effects of an angiotensin-I-converting enzyme inhibitor (ACEI) trandolapril (Tra) or an angiotensin II type 1 receptor blocker (ARB) candesartan (Can), both of which are known to improve the pathophysiology of chronic heart failure (CHF) on degradation of DRP in failing hearts.

METHODS

Coronary artery-ligated (CAL) and sham-operated rats (Sham rats) were treated orally with 3 mg/kg/day trandolapril (Tra) or 1 mg/kg/day candesartan (Can) from the 2nd to 8th week after surgery.

RESULTS

Hemodynamic parameters of CAL rats at the 8th week after CAL (8w-CAL) indicated heart failure. alpha-Sarcoglycan (SG) and dystrophin in the surviving left ventricle (surviving LV) of 8w-CAL rats decreased, whereas beta-, gamma-, and delta-SGs remained unchanged. Calcium-activated neutral proteases mu-calpain and m-calpain increased in the surviving LV at the 8th week of postmyocardial infarction. Proteolytic activity in the presence of 5 mM Ca2+ markedly increased at the 2nd and 8th weeks, whereas 50 microM Ca2+ slightly but significantly increased proteolysis of casein. Tra or Can treatment improved the hemodynamic parameters, attenuated changes in alpha-SG and dystrophin, and reversed both calpain contents and activities of the failing heart back to sham levels.

CONCLUSION

These results suggest that attenuation in calpain-induced degradation of DRP complex is a possible mechanism for the Tra- or Can-mediated improvement of the pathogenesis of CHF following myocardial infarction.

Doxorubicin treatment in vivo activates caspase-12 mediated cardiac apoptosis in both male and female rats

We investigated in vivo the chemotherapeutic anthracycline agents doxorubicin and its ability to activate mitochondrial-mediated, receptor-mediated and endoplasmic/sarcoplasmic reticulum-mediated apoptosis transduction pathways in cardiac tissue from male and female rats. We administered a single low dose of doxorubicin (10 mg/kg of body weight, i.p.) and then isolated mitochondrial and cytosolic proteins one and four days later from the heart. Caspase-3 protein content and caspase-3 activity were significantly increased after day four of doxorubicin treatment in both male and female rats. However, while males had DNA fragmentation at day one but not day four following doxorubicin administration, females showed no significant increase in DNA fragmentation at either time. Caspase-12, localized in the SR, is considered a central caspase, and its activation by cleavage via calpain indicates activation of the SR-mediated pathway of apoptosis. Cleaved caspase-12 content and calpain activity significantly increased after day four of doxorubicin treatment in both sexes. In the mitochondrial-mediated pathway, there were no significant treatment effects observed in cytosolic cytochrome c and cleaved (active) caspase-9 in either sex. In control rats (saline injection), glutathione peroxidase (GPX) activity and hydrogen peroxide (H2O2) production were lower in females compared to males. Doxorubicin treatment did not significantly affect H2O2, GPX activity or ATP production in isolated mitochondria in either sex. Female rats produced significantly lower levels of H2O2 production one day after doxorubicin treatment, whereas male rats produced significantly less mitochondrial H2O2 four days after doxorubicin treatment. The receptor-mediated pathway (caspase-8 and c-FLIP) showed no evidence of being significantly activated by doxorubicin treatment. Hence, doxorubicin-induced apoptosis in vivo is mediated by the SR to a greater extent than other apoptotic pathways and should therefore be considered for targeted therapeutic interventions. Moreover, no major sex differences exist in apoptosis signaling transduction cascade due to doxorubicin treatment.

Schistosoma japonicum: localization of calpain in the penetration glands and secretions of cercariae

A monoclonal antibody was generated against the large subunit of Schistosoma japonicum calpain to study the localization and possible function of the molecule in vivo. Mice were immunized with recombinant S. japonicum calpain and polyclonal antisera and a monoclonal antibody specific to schistosome calpain was obtained. In immunohistochemistry, a monoclonal antibody against S. japonicum calpain, KG-2E11, bound weakly to calpain expressed at the surface of adult worm tegument, however, it bound strongly to the cercarial secretions ("footprints") of S. japonicum, emitted from the penetration glands. The present study indicates that calpain is multifunctional as it is expressed at various locations in different developmental stages. Calpain-based vaccines could thus possibly induce protective immunity against cercariae and the following early developing stages.

Novel glycosaminoglycan mimetic (RGTA, RGD120) contributes to enhance skeletal muscle satellite cell fusion by increasing intracellular Ca2+ and calpain activity

Glycosaminoglycans (GAG) are classes of molecules that play an important role in cellular processes. The use of GAG mimetics called regenerating agent (RGTA) represents a tool to investigate the effect of GAG moiety on cellular behavior. A first member of the RGTA family (RG1192), a dextran polymers with defined amounts of sulfate, carboxymethyl, as well as hydrophobic groups (benzylamide), was shown to stimulate skeletal muscle repair after damage and myoblast differentiation. To obtain a comprehensive insight into the mechanism of action of GAG mimetics, we investigated the effect on myoblast differentiation of a novel RGTA, named RGD120, which was devoid of hydrophobic substitution and had ionic charge similar to heparin. Myoblasts isolated from adult rat skeletal muscles and grown in primary cultures were used in this study. We found that chronic treatment with RGD120 increased the growth of adult myoblasts and induced their precocious fusion into myotubes in vitro. It also partially overcame the inhibitory effect of the calpain inhibitor N-acetyl-leu-leu-norleucinal (ALLN) on these events. Western blot and zymography analyses revealed that milli calpain was slightly increased by RGD120 chronic treatment. In addition, using fluorescent probes (Indo-1 and Boc-leu-met-MAC), we demonstrated that RGD120 added to prefusing myoblast cultures accelerates myoblast fusion into myotubes, induced an increase of cytosolic free calcium concentration, and concomitantly an increase of intracellular calpain protease activity. Altogether, these results suggested that the efficiency of RGD120 in stimulating myogenesis might be in part explained through its effect on calcium mobilization as well as on the calpain amount and activity.

Disruption of muscle membrane and phenotype divergence in two novel mouse models of dysferlin deficiency

Limb girdle muscular dystrophy type 2B and Miyoshi myopathy are clinically distinct forms of muscular dystrophy that arise from defects in the dysferlin gene. Here, we report two novel lines of dysferlin-deficient mice obtained by (a) gene targeting and (b) identification of an inbred strain, A/J, bearing a retrotransposon insertion in the dysferlin gene. The mutations in these mice were located at the 3' and 5' ends of the dysferlin gene. Both lines of mice lacked dysferlin and developed a progressive muscular dystrophy with histopathological and ultrastructural features that closely resemble the human disease. Vital staining with Evans blue dye revealed loss of sarcolemmal integrity in both lines of mice, similar to that seen in mdx and caveolin-3 deficient mice. However, in contrast to the latter group of animals, the dysferlin-deficient mice have an intact dystrophin glycoprotein complex and normal levels of caveolin-3. Our findings indicate that muscle membrane disruption and myofiber degeneration in dysferlinopathy were directly mediated by the loss of dysferlin via a new pathogenic mechanism in muscular dystrophies. We also show that the mutation in the A/J mice arose between the late 1970s and the early 1980s, and had become fixed in the production breeding stocks. Therefore, all studies involving the A/J mice or mice derived from A/J, including recombinant inbred, recombinant congenic and chromosome substitution strains, should take into account the dysferlin defect in these strains. These new dysferlin-deficient mice should be useful for elucidating the pathogenic pathway in dysferlinopathy and for developing therapeutic strategies.

Different expression of calpains in the anterior vaginal wall of women with and without uterovaginal prolapse

OBJECTIVE

Tissue ischemia-hypoxia can activate the calpain proteolytic system. Mechanical trauma to the upper vaginal wall and pelvic floor could compromise vascular perfusion and could also result in calpain expression. The aims of this investigation were to assess the expression messenger RNA and proteins for m-calpain and micro-calpain in the vaginal walls of women with and without uterovaginal prolapse.

METHODS

The anterior vaginal walls of 22 women with and without uterovaginal prolpase were evaluated using a reverse transcription polymerase chain reaction and western blotting for detecting calpain expression.

RESULTS

The number of messenger RNA transcripts of m- and micro-calpain was significantly less in women with uterovaginal prolapse than in women without uterovaginal prolapse (two of 11 and zero of 11 versus eight of 11 and five of 11, P < .05). All women had m-calpain protein expression in the anterior vaginal wall. However, the concentration of m-calpain protein was less, but not significantly different, in women with uterovaginal prolapse than in the women without uterovaginal prolapse (0.386 +/- 0.018 versus 0.439 +/- 0.011 optical density/mm2, P > .05). None of the women with uterovaginal prolapse had expression of micro-calpain mRNA or protein (zero of 11). Expression of protein of calpains in the anterior vaginal wall is not consistent with mRNA transcripts.

CONCLUSION

Calpain expression may be compromised in the anterior vaginal wall of women with uterovaginal prolapse who have abnormal histologic changes in the vaginal connective tissues or have anterior vaginal laxity.

Autolytic activation and localization in Schneider cells (S2) of calpain B from Drosophila

Calpain B is one of the two calpain homologues in Drosophila melanogaster that are proteolytically active. We studied its activation by Ca2+ both in vitro and in vivo, in Schneider (S2) cells. Activation involves the autolytic cleavage, at two major sites, of the N-terminal segment, the length of which was earlier underestimated. Site-directed mutagenesis at the autolytic sites did not prevent autolysis, but only shifted its sites. Calpain B mRNA was detectable in all developmental stages of the fly. In situ hybridization and immunostaining showed expression in ovaries, embryo and larvae, with high abundance in larval salivary glands. In S2 cells, calpain B was mainly in the cytoplasm and upon a rise in Ca2+ the enzyme adhered to intracellular membranes.

Short Commuunication: Effect of Dietary Protein Depletion and Repletion on Skeletal Muscle Calpastatin During Early Lactation

Sixteen multiparous Jersey cows were assigned at calving to one of 4 dietary treatments. An 18% crude protein (CP) diet was fed as a total mixed ration through 30 d in milk (DIM), and beginning at 31 DIM a 9, 12, 15, or 18% CP diet was fed through 58 DIM (depletion). All cows were then fed the 18% CP diet until 84 DIM (repletion). Muscle biopsies were taken under local anesthesia at 49 and 84 DIM from the semitendinosus muscle. Milk production, DMI, and milk component contents were measured. Calpain and calpastatin contents of muscle taken at biopsy were evaluated using Western blotting techniques. Milk production and milk protein content were reduced during the depletion period by decreasing dietary protein. Diet had no effect on milk fat content or DMI. During repletion, DMI was affected by dietary treatment. Western blots of muscle extracts indicated no differences in calpain content at any stage of the experiment or in calpastatin content of muscle at 49 DIM. However, at 84 DIM, calpastatin (135 kDa) was lower or undetectable in cows fed either the 9 or 12% CP diets from 31 to 59 DIM. Bands for a 110-kDa degradation product of calpastatin were present in some cows fed the 9, 12, and 15% CP diets during the depletion period. Results indicate a change in skeletal muscle calpain/calpastatin proteolytic system during protein repletion following depletion with diets of less than 15% CP during early to peak lactation in dairy cows.

Novel 6-Hydroxy-3-morpholinones as cornea permeable calpain inhibitors

A novel series of 6-hydroxy-3-morpholinones, in which the functional aldehyde and the hydroxy group of P(2) site form a cyclic hemiacetal, was identified as calpain inhibitors. The placement of isobutyl group at the 2-position of the 3-morpholinone was the most effective modification for inhibiting micro- and m-calpains. Substitutions of benzyl at the 5-position in the S-configuration had virtually no effect on inhibitory activity. Several compounds showed appreciable selectivity for calpains over cathepsin B. NMR experiments demonstrated that the representative 6-hydroxy-3-morpholinone 10a (SNJ-1757) was more stable to nucleophilic attack than the corresponding aldehyde inhibitor 24. Furthermore, 6-hydroxy-3-morpholinone 10a proved to have better corneal permeability than aldehyde inhibitor 24 in an in vitro experiment.