The Mechanism Of Apoptosis Inducers On Caspase-3 Activation Pathway During Matutation Of Lamb

Tenderness is an important factor and the most important sensory feature that determines the quality of meat.Studying the factors affecting the tenderness and its tenderizing mechanism would help meat producers supply tender meat with good quality to meet the majority of consumers' demands.The tenderness of the meat is greatly improved during the post-mortem maturation.In the modern meat industry,the slaughtered animals lose a great deal of blood in a very short period of time,while important functions and oxygen intake stop.In this case,the muscle cells of the animal are inevitably in a hypoxic-ischemic state,causing the muscle cells to undergo "apoptosis." The important role of apoptosis and its key effector,Caspase-3,in the maturation of meat has been confirmed.During the maturation of post-mortem meat,the apoptotic effector enzyme Caspase-3 is activated and causes myofibril degradation.So it's a key protease involved in post-mortem tenderizing.However,the activation mechanism and regulatory factors of Caspase-3 in meat maturation are not clear.In view of this key issue in improving the tenderness of meat,the study used Guanzhong dairy goat meat of Shaanxi as the research object,and used the hypoxic-ischemic environment and apoptosis of muscle cells after being slaughtered as research background.After treatment of lamb with apoptosis inducers calcium chloride and Tea Polyphenols,Western Blot was used as the main research method,combined with relevant physical and chemical techniques to explore the effect of reagent treatment on the tenderness of dairy goats,the apoptosis of dairy goat skeletal muscle cells during the normal maturation of lamb,and further studied the molecular mechanism of Caspase-3 activation,the key effect of apoptosis.The specific research content and results are as follows:(1)Exploring the effect of apoptosis inducer treatment on the apoptosis of skeletal muscle cells:Calcium chloride and tea polyphenols were used to treat the longissimus dorsi muscle of slaughtered mutton,and incubated with normal saline as a control.The cytoplasmic protein was extracted from 0,1,3,and 5 days(4 ?)of meat samples.The expression of Caspase-3 and its substrate,Parp-1,were detected by Western Blot.The results showed that compared with the control group,the zymogen fragment of the Caspase-3 protease and the cleavage substrate Parp-1 of the treated group were significantly attenuated(P<0.05),ie,their activity were significantly increased.It shows that both of these agents can effectively induce apoptosis of skeletal muscle cells in dairy goats;(2)Exploring the effect of apoptosis inducer treatment on the tenderness of post-mortem mutton: Calcium chloride and tea polyphenols were used to treat the longissimus dorsi muscle of slaughtered mutton,and incubated with normal saline as a control.The protein was extracted from 0,1,3,and 5 days(4 ?)of meat samples,and spectrophotometric method was used to determine the change of myofibril fragmentation index(MFI).The myofibrillar protein was extracted from meat samples,and Western blot was used to detect the expression of Desmin.The results showed that the myofibril fragmentation index(MFI)values of the mutton in the treated group were significantly higher than those in the control group(P <0.05),and the degree of degradation of the skeletal muscle myosin(Desmin)was also significantly increased,indicating that the reagent treatment can accelerate the maturation process of lamb after slaughter and effectively improve its tenderness;(3)Exploring the effect of apoptosis inducer treatment on Caspase-3 activation pathway in dairy goat skeletal muscle cells: Calcium chloride and tea polyphenols were used to treat the longissimus dorsi muscle of slaughtered mutton,and incubated with normal saline as a control.The cytoplasmic protein was extracted from 0,1,3,and 5 days(4 ?)of meat samples.The changes of key regulatory factors expression such as Fas,Fas-L,Caspase-8 in death receptor activation pathway and Bax,Bcl-2,Caspase-9,cytochrome C in mitochondrial activation pathway of Caspase-3 were detected by Western Blot.The results showed that the expression of Fas,Fas-L,Bax/Bcl-2 and cytosolic cytochrome C in the treatment group was significantly higher than that in the control group(P <0.05),while The expression of Caspase-8 and Caspase-9 zymogen was significantly lower than that in the control group.This indicates that the activation of Caspase-3 during the post-mortem maturation of mutton is mediated by both the Caspase-8 mediated death receptor pathway and the cytochrome C,Caspase-9 mediated mitochondrial pathways.Therefore,the above-mentioned Caspase-3 activation key factors can be regulated to finally control the effect of Caspase-3 effector enzymes on meat tenderization and meat maturation.