Effects of ultrasonic processing on caspase-3, calpain expression and myofibrillar structure of chicken during post-mortem ageing.

In this investigation, ultrasonic treatments at a frequency of 40 kHz and power of 1,500 W made caspase-3 and calpain activities significantly higher in chicken muscle after slaughter during 5d storage (p<0.01). Additionally Western blotting analysis of α-spectrin showed that ultrasonic treatments caused the production of α-spectrin degradation products of 120 and 150 kDa more dense than the control (p<0.01). Degradation of calpastatin during chicken meat ageing was induced by ultrasound treatments (p<0.01), which suggested the ability of caspase-3 to cleave calpastatin. SDS-PAGE showed that all treatments enhanced accumulation of the 30 kDa troponin-T degradation product (p<0.01), and transmission electron microscopy images of myofibrils displayed that damage of ultrasound treatment for 60 min was more extensive than at 30 min. The findings proved the low-frequency and high power ultrasonic treatments improved disruption of myofibrillar structures and increased proteolysis of chicken meat faster by triggering an apoptosis cascade.

Effects of inhibitors on the synergistic interaction between calpain and caspase-3 during post-mortem aging of chicken meat.

Calpain has been considered to be the most important protease involved in tenderization during the conversion of muscle into meat. However, recent evidence suggests the possible involvement of the key apoptosis protease, caspase, on post-mortem tenderization. This study used inhibitors of calpain and caspase-3 to treat chicken muscle immediately after slaughter and followed the changes in caspase-3 and calpain activities together with their expression during 5 days of aging. Addition of calpain inhibitors to the system resulted in significantly higher caspase-3 activities (p < 0.01) during storage. Western blot analysis of pro-caspase-3 and α-spectrin cleavage of the 120 kDa peptide (SBDP 120) showed that the addition of calpain inhibitors resulted in the formation of higher amounts of the active form of caspase-3 compared with the control (p < 0.01). Inclusion of inhibitors of caspase-3 led to lower calpain activities (p < 0.01) and dramatically reduced the expression of calpain-1 and calpain-2 (p < 0.01). Concomitantly, this inhibition resulted in greater calpastatin expression compared with the control (p < 0.01). The findings of this investigation show that calpain prevented the activation of caspase-3, whereas caspase-3 appeared to enhance the calpain activity during post-mortem aging through inhibition of calpastatin. It is therefore suggested that there is a relationship between caspase-3 and calpain which contributes to the tenderizing process during the conversion of muscle tissue into meat.

Effects of camptothecin, etoposide and Ca2+ on caspase-3 activity and myofibrillar disruption of chicken during postmortem ageing.

Recently, a novel consideration has focused on the potential relationship of apoptosis and the protease caspases and the underlying mechanism for meat postmortem tenderization. In this study, apoptosis inducers, camptothecin and etoposide as well as Ca(2+) were used to treat chicken muscle immediately after slaughter and follow the changes in caspase-3 activities and changes in the myofibrillar structures during 7 days of ageing. All three treatments resulted in significantly higher caspase-3 activities during storage (p<0.05), with the natural substrates, whereas Western blotting analysis of the α-spectrin cleavage product, 120 kDa peptide (SBDP 120), showed that Ca(2+) was more effective than either camptothecin or etopside, and all were most active up to day 3 (p<0.01). According to SDS-PAGE, each treatment enhanced the accumulation of the 30 kD Troponin-T degradation product, especially during the first 3 days (p<0.05), and this was supported by the degradation of myofibrils observed by electron microscopy (TEM). TEM images showed the treatments resulted in enlargement of the I-bands and shrinkage of A-bands; however Z-lines were only slightly affected, even at day 7. The findings revealed that the three apoptosis inducers could increase myofibrillar dissociation and proteolysis during the first 3 days of chicken meat ageing. Because of the high activity of caspase-3 during the early postmortem period, it is possible that caspase-3 contributes to the conversion of muscle into meat.