acetyl-aspartyl-glutamyl-valyl-aspartal and calpeptin

We examined the influence of sepsis on the expression and activity of the calpain and caspase systems in skeletal muscle. Sepsis was induced in rats by cecal ligation and puncture (CLP). Control rats were sham operated. Calpain activity was determined by measuring the calcium-dependent hydrolysis of casein and by casein zymography. The activity of the endogenous calpain inhibitor calpastatin was measured by determining the inhibitory effect on calpain activity in muscle extracts. Protein levels of mu- and m-calpain and calpastatin were determined by Western blotting, and calpastatin mRNA was measured by real-time PCR. Caspase-3 activity was determined by measuring the hydrolysis of the fluorogenic caspase-3 substrate Ac-DEVD-AMC and by determining protein and mRNA expression for caspase-3 by Western blotting and real-time PCR, respectively. In addition, the role of calpains and caspase-3 in sepsis-induced muscle protein breakdown was determined by measuring protein breakdown rates in the presence of specific inhibitors. Sepsis resulted in increased muscle calpain activity caused by reduced calpastatin activity. In contrast, caspase-3 activity, mRNA levels, and activated caspase-3 29-kDa fragment were not altered in muscle from septic rats. Sepsis-induced muscle proteolysis was blocked by the calpain inhibitor calpeptin but was not influenced by the caspase-3 inhibitor Ac-DEVD-CHO. The results suggest that sepsis-induced muscle wasting is associated with increased calpain activity, secondary to reduced calpastatin activity, and that caspase-3 activity is not involved in the catabolic response to sepsis.

Topics: Animals; Bacterial Infections; Calcium-Binding Proteins; Calpain; Caspase 3; Caspases; Cells, Cultured; Cysteine Proteinase Inhibitors; Dipeptides; Enzyme Activation; Male; Muscle Fibers, Skeletal; Muscle Proteins; Muscle, Skeletal; Oligopeptides; Rats; Rats, Sprague-Dawley; RNA, Messenger

We have previously demonstrated that calpain is responsible for the cleavage of Bax, a proapoptotic protein, during drug-induced apoptosis of HL-60 cells (Wood, D. E., Thomas, A., Devi, L. A., Berman, Y., Beavis, R. C., Reed, J. C., and Newcomb, E. W. (1998) Oncogene 17, 1069-1078). Here we show the sequential activation of caspases and calpain during drug-induced apoptosis of HL-60 cells. Time course experiments using the topoisomerase I inhibitor 9-amino-20(S)-camptothecin revealed that cleavage of caspase-3 substrates poly(ADP-ribose) polymerase (PARP) and the retinoblastoma protein as well as DNA fragmentation occurred several hours before calpain activation and Bax cleavage. Pretreatment with the calpain inhibitor calpeptin blocked calpain activation and Bax cleavage but did not inhibit PARP cleavage, DNA fragmentation, or 9-amino-20(S)-camptothecin-induced morphological changes and cell death. Pretreatment with the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk) inhibited PARP cleavage, DNA fragmentation, calpain activation, and Bax cleavage and increased cell survival by 40%. Interestingly, Z-VAD-fmk-treated cells died in a caspase- and calpain-independent manner that appeared morphologically distinct from apoptosis. Our results suggest that excessive or uncontrolled calpain activity may play a role downstream of and distinct from caspases in the degradation phase of apoptosis.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Calpain; Caspase 3; Caspases; Coumarins; Cysteine Proteinase Inhibitors; Dipeptides; DNA Fragmentation; Enzyme Activation; HL-60 Cells; Humans; Oligopeptides

Involvement of proteases has been postulated in several neurodegenerative processes. Accordingly, protease inhibition has been proposed as a potential therapeutic tool to limit damage in some neuropathological states. The timed turn-over of proteins is, however, an essential biochemical process and its prolonged block may be dangerous to the cell. We report here data on toxicity consequent to 24-h exposure of cerebellar granule neurons in culture to inhibitors of different classes of proteases. Inhibition of calpains (calcium-activated cysteine proteases) resulted in dose-dependent neuronal death which largely occurred through apoptotic process. Leupeptin, an inhibitor acting on a broad spectrum of cellular serine proteases, was less toxic but resulted in definite morphological alteration of the cells. On the contrary, inhibitors of caspases, proteases belonging to the ICE (interleukin 1-beta converting enzyme) family, did not apparently damage granule neurons upon exposure for 24 h to high concentrations (up to 200 microM) of two inhibitors specific for ICE (Ac-YAVD-CHO) and CPP-32 (Ac-DEVD-CHO), respectively. These results suggest that inhibition of proteases that are activated by stressful stimuli but are not essential for the normal functioning of healthy cells, as it is likely the case for caspases, may not be harmful to neurons. Instead, the potential risks and side effects of prolonged inhibition of proteases such as calpains, that regulate the disposal and the turn-over of key cellular proteins, should be carefully tested in the assessment of possible neuroprotective roles.

Topics: Animals; Apoptosis; Cells, Cultured; Cerebellum; Cysteine Proteinase Inhibitors; Dipeptides; In Situ Nick-End Labeling; L-Lactate Dehydrogenase; Leupeptins; Neurons; Oligopeptides; Protease Inhibitors; Rats; Rats, Wistar