Calpains are intracellular nonlysosomal Ca(2+-) regulated cysteine proteases, widely located in the tissues of most mammals. Skeletal muscle tissue mainly expresses m-calpain, µ-caplain, n-calpain, and their endogenous inhibitor calpastatin. They are closely related to the cell apoptosis, cytoskeleton formation, cell cycles, etc. Calpains are also considered to be participating in the protein degradation process. Severe burns are typically followed by hypermetabolic responses that are characterized by hyperdynamic circulatory responses with increased proteolysis and cell apoptosis. Recently, overloading of Ca(2+) in skeletal muscle cells, which activates the calpains is observed after a serious burn. This paper aims to review the current research of the relationship between calpains and post-burn skeletal muscle wasting from the perspectives of structure, function, and physiological activities.
Animals ; Burns ; metabolism ; pathology ; Calpain ; metabolism ; Muscle, Skeletal ; metabolism ; pathology

Animals ; Calpain ; metabolism ; Epithelial Cells ; metabolism ; Kidney ; cytology ; Kidney Tubules ; cytology ; metabolism ; Rats ; Reperfusion Injury ; metabolism

OBJECTIVETo investigate the effect of N,N-dimethylformamide (DMF) on calcium homeostasis and calpain I and II gene expression in human hepatocytes (HL-7702).

METHODSHL-7702 cells were exposed to different concentrations of DMF (10, 25, 50, 100, or 200 mmol/L); other HL-7702 cells, which were used as a control group, were exposed to the equal volume of DMEM; the intracellular Ca(2+) concentration was monitored using the calcium fluorescent probe (fluo-3/AM). After 24-h exposure to DMF (10, 25, 50, 100, 150, or 200 mmol/L), the morphology of hepatocytes was observed under an inverted phase contrast microscope, and the cell viability was measured by MTT assay. After 24-h exposure to DMF (10, 25, 50, 100, or 150 mmol/L), the mRNA expression levels of calpain I and II in hepatocytes were measured by real-time quantitative PCR.

RESULTSThere were significant differences in cell viability among different exposure groups (P < 0.01); the 50, 100, 150, and 200 mmol/L DMF exposure groups had a significantly lower cell viability than the control group (P < 0.05). Under the inverted phase contrast microscope, HL-7702 cells gradually lost the original shape, with swelling and shrinking, as the dose of DMF increased, and those treated with 150 mmol/L DMF even became round and floated. The fluorescence density of fluo-3 in hepatocytes increased as the dose of DMF rose, demonstrating a dose-response relationship, and there were significant differences among these exposure groups (P < 0.05). There were significant differences in mRNA expression levels of calpain I and II among these exposure groups (P < 0.01), and the expression increased as the dose of DMF rose; but DMF did not promote the mRNA expression of calpain I at a concentration of 150 mmol/L.

CONCLUSIONDMF can cause damage to hepatocytes, which is related to intracellular calcium increase and calpain mRNA increase.

Calcium ; metabolism ; Calpain ; metabolism ; Cell Line ; Dimethylformamide ; pharmacology ; Hepatocytes ; drug effects ; metabolism ; Humans

OBJECTIVETo investigate the time course of calpain activity changes in rat neurons following fluid percussion injury (FPI) under normothermia (37 degrees celsius;) and mild hypothermia (32-/+0.5) degrees celsius;.

METHODSIn vitro cultured rat neurons were subjected to FPI followed by application of mild hypothermia for intervention at different time points, and the changes in intraneuronal calpain activity following FPI and the interventional effect of mild hypothermia on calpain activity were evaluated by UV-spectrophotometry at different time points.

RESULTSRemarkable changes occurred in calpain activity in the neurons following FPI at 37 degrees celsius;, and mild hypothermia produced obvious interventional effect on calpain activity in close relation to the timing of intervention initiation.

CONCLUSIONIntraneuronal calpain activity changes following FPI are involved in the pathological process of cellular injury, and mild hypothermia might offer protection against traumatic brain injury to some extent by regulating calpain activity. The interventional effect of mild hypothermia is associated with the timing of the intervention initiation.

Animals ; Calpain ; metabolism ; Female ; Hypothermia, Induced ; Neurons ; metabolism ; pathology ; Percussion ; Pregnancy ; Rats ; Rats, Wistar ; Time Factors

The aim of the present study was to investigate the expressions of calpain and calpastatin in the myocardium of simulated weightlessness rats, and to elucidate the underlying mechanism of cardiac troponin I (cTnI) degradations. Tail-suspended (SUS) rats were used as a simulated weightlessness model on the ground. The myocardium of rats was homogenized, and the expressions of calpain-1, calpain-2, calpastatin and cTnI were analyzed by Western blotting technique. Calpastatin expression was significantly decreased in 2- and 4-week SUS groups compared with that in the synchronous controls (P<0.05). Calpain-2 expression was slightly decreased, whereas calpain-1 expression was unaltered in SUS groups. However, calpain-1/calpastatin and calpain-2/calpastatin ratios were increased after tail-suspension, being significantly higher in 2- and 4-week SUS groups than those in the synchronous controls (P<0.05, P<0.01). Cardiac TnI degradation was significantly increased after tail-suspension (P<0.01), but cTnI degradation in both SUS and control groups was significantly inhibited by a non-specific inhibitor of calpain, PD150606 (P<0.01). These results suggest that an increase in calpain activity may enhance cTnI degradation in the myocardium of tail-suspended rats.
Animals ; Calcium-Binding Proteins ; metabolism ; Calpain ; metabolism ; Hindlimb Suspension ; Myocardium ; metabolism ; Proteolysis ; Rats ; Troponin I ; metabolism ; Weightlessness Simulation

Calpain I (mu-calpain) and II (m-calpain) are well known calcium-activated neutral cysteine proteases. Many reports have shown that activation of calpain is related to cataract formation, neuronal degeneration, blood clotting, ischemic injuries, muscular dystrophy and cornified cell envelope (CE) formation. Here, we report that insoluble CE formation was reduced after treatment with calpain I inhibitor (N-acetyl-leucyl-leucyl-norleucinal) on normal human epidermal keratinocytes (NHEK), whereas serine and thiol protease inhibitors had no effect on the reduction of CE. When NHEK cells were confluent, keratinocytes were treated with various concentrations (0.5 microM-0.5 mM) of calpain I inhibitor or serine and thiol protease inhibitors under calcium induced differentiation. Insoluble CE formation was reduced about 90% in the 50 microM calpain inhibitor I treated group by day 9 of culture, whereas insoluble CE was reduced only 10% in the same condition. Interestingly TGase activity was blocked by 90% in the 0.5 mM calpain inhibitor treated group within 72 h, whereas TGase activity was retained by 80% in the 0.5 mM serine protease inhibitor treated group at 7 day treatment. Therefore it can be suggested that cysteine protease calpains might be responsible for the activation of the TGase 1 enzyme to complete insoluble CE formation during epidermal differentiation.
Calcium/pharmacology ; Calpain/metabolism* ; Calpain/antagonists & inhibitors* ; Cell Differentiation ; Dose-Response Relationship, Drug ; Epidermis/metabolism ; Human ; In Vitro ; Keratinocytes/metabolism ; Keratinocytes/enzymology ; Protease Inhibitors/pharmacology ; Protein-Glutamine gamma-Glutamyltransferase/metabolism* ; Protein-Glutamine gamma-Glutamyltransferase/antagonists & inhibitors* ; Tissue Culture

Calpains, calcium-activated cysteine proteases with a neutral pH optimum, lead to degration of cystoskeletion and structural protein, and delayed neuronal death. The activation of calpains contribute to apoptosis. Calpain inhibitors provide a novel and potential treatment for cerebral ischemia due to improvement of cerebral infarct and ischemia.
Animals ; Apoptosis ; drug effects ; Brain Ischemia ; drug therapy ; metabolism ; Calcium-Binding Proteins ; therapeutic use ; Calpain ; antagonists & inhibitors ; metabolism ; physiology ; Humans

To explore the changes and regulation mechanism of dystropin and desmin under muscle injury without mechanic stress, 40 male Sprague-Dawley rats were randomly divided into 5 groups, which included normoxia control and hypoxia groups for 1, 2, 4 and 7 d with 10% O2. Two rats from each group were examined for sarcolemma integrity using Evans blue dye (EBD) and EBD-positive fiber typing by metachromatic dye-ATPase method. The rest six rats from each group were analyzed for the changes of protein content and gene expression using Western blot, RT-PCR and fluorescence assays. The results showed that the EBD-positive muscle fibers, mainly type IIA and type IIB, appeared at 1 d after hypoxia exposure. Both the ratio of EBD-positive cell and the mean fluorescence density were significantly higher in hypoxia groups than those in control group (P<0.05). The contents of dystrophin and desmin fluctuated after hypoxia exposure, increased at 1 d, decreased at 2 d, increased dramatically again at 4 d, and returned to a normal level at 7 d. Consistently, the gene expression began to increase significantly after 2 d. The total activity of calpain was significantly higher in hypoxia groups at 1, 4 and 7 d. Significantly higher levels of HSP70 and HSP90 were also observed at 4 and 7 d, respectively (P<0.05). These results suggest that the mechanical stress is not the only cause of damage of sarcolemma membrane integrity. In contrast to eccentric contraction, hypoxia-induced muscle damage is not accompanied by the loss of dystrophin and desmin. The types of muscle fibers recruited by motor units and the activities of calpain may be important in hypoxia-induced damage of sarcolemma membrane integrity.
Animals ; Calpain ; metabolism ; Desmin ; metabolism ; Dystrophin ; metabolism ; Hypoxia ; metabolism ; physiopathology ; Male ; Muscle, Skeletal ; metabolism ; pathology ; Rats ; Rats, Sprague-Dawley ; Sarcolemma ; pathology

OBJECTIVETo investigate the effects of polybrominated diphenyl ether-153 (BDE-153) exposure during lactation period on the calcium ion (Ca(2+)) concentration and calcium-activated enzyme levels in cerebral cortical cells among adult rats and to provide a scientific basis for the study on the developmental neurotoxicity of BDE-153.

METHODSForty newborn male rats were randomly and equally divided into four groups according to their body weights and litters: 1, 5, and 10 mg/kg BDE-153 groups and olive oil solvent control group. On postnatal day 10 (PND 10), the BDE-153 groups were administrated BDE-153 (0.1 ml/10 g body weight) by intraperitoneal injection, while the olive oil solvent control group was given an equal volume of olive oil. Two months later, these rats were decapitated, and the cerebral cortex was separated quickly on an ice-cold dish. The Ca(2+) concentration in cerebral cortical cells was measured by flow cytometry. The activities of calcineurin (CaN) and Ca(2+)-Mg(2+)-ATP enzyme were determined by colorimetric method. The mRNA and protein expression of calpain-1 and calpain-2 was measured by real-time quantitative PCR and Western blot.

RESULTSThe mean fluorescence intensities of intracellular Ca(2+) in control group and 1, 5, and 10 mg/kg BDE-153 groups were 10.83, 1.48, 1.93, and 0.62, respectively; the 1, 5, and 10 mg/kg BDE-153 groups had significantly lower intercellular Ca(2+) concentrations than the control group (P < 0.05). The activities of CaN and Ca(2+)-Mg(2+)-ATP enzyme and mRNA and protein expression of calpain-1 showed no significant differences between the 1, 5, and 10 mg/kg BDE-153 groups and control group (P > 0.05). The protein expression of calpain-2 increased as the dose of BDE-153 rose. Compared with the control group (mRNA: 0.81±0.26; protein: 0.15±0.07), the 5 and 10 mg/kg BDE-153 groups had significantly higher mRNA expression of calpain-2 (5 mg/kg BDE-153 group: 1.16±0.52; 10 mg/kg BDE-153 group: 1.32±0.23) and significantly higher protein expression of calpain-2 (5 mg/kg BDE-153 group: 0.31±0.07; 10 mg/kg BDE-153 group: 0.37±0.06) (P < 0.05). The 10 mg/kg BDE-153 group had significantly higher protein expression of calpain-2 than the 1 mg/kg BDE-153 group (0.37±0.06 vs 0.22±0.07, P < 0.05).

CONCLUSIONCa(2+-) mediated calpain-2 activation may be one of the main mechanisms of BDE-153 neurotoxicity.

Animals ; Animals, Newborn ; Ca(2+) Mg(2+)-ATPase ; metabolism ; Calcineurin ; metabolism ; Calcium ; metabolism ; Calpain ; metabolism ; Cerebral Cortex ; metabolism ; Male ; Polybrominated Biphenyls ; toxicity ; Rats ; Rats, Sprague-Dawley

Primary neuronal culture is a powerful tool to study neuronal development, aging, and degeneration. However, cultured neurons show signs of cell death after 2 or 3 weeks. Although the mechanism underlying this phenomenon has not been elucidated, several preventive methods have been identified. Here we show that the neuronal loss in primary cortical culture involves calpain activation and subsequent neuronal cell death. Neuronal loss during cultivation showed destruction of neurites and synapses, and a decrease in neuron numbers. micro-Calpain and micro-calpain were initially activated and accumulated by increased RNA expression. This neuronal death exhibited neurodegenerative features, such as conversion of p35 to p25, which is important in the developmental process and in the pathogenesis of Alzheimer's disease. But, postnatal and aged rat cortex did not show calpain activation and prolonged processing of p35 to p25, in contrast to the long-term culture of cortical neurons. In addition, the inhibition of calpains by ALLM or ALLN blocked the conversion of p35 to p25, indicating that the calpain activity is essential for the neurodegenerative features of cell death. Taken together, this study shows that the neuronal loss in primary cortical cultures involves neurodegeneration-like cell death through the activation of calpains and the subsequent processing of p35 to p25, but not developmental apoptosis or aging. Our results suggest that the long term primary culture of cortical neurons represent a valuable model of neurodegeneration, such as Alzheimer's disease.
Transcription, Genetic/genetics ; Time Factors ; Rats ; Phosphotransferases/*metabolism ; Neurons/*cytology/*metabolism ; Cells, Cultured ; Cell Shape ; Caspases/antagonists & inhibitors/metabolism ; Calpain/antagonists & inhibitors/genetics/*metabolism ; *Apoptosis ; Animals