| Summary: | 碩士 === 高雄醫學大學 === 醫學研究所碩士班 === 93 === Sepsis is a clinical syndrome that results from the systemic response of the body to infection and is characterized and modulated by various pro-inflammatory and anti-inflammatory pathways. If homeostasis cannot be maintained, progressive and sequential dysfunction of various organ systems can occur. In the heart, enzyme/receptor systems have been reported to be damaged during sepsis, causing a decrease of contractility and leading to cardiac dysfunction and even death. Cardiomyocyte apoptosis contributes to the cardiogenic pathology of the septic shock. In the mitochondrial pathway, dephosphorylated Bad was found in the mitochondria and that has been implicated in apoptosis. However, the underlying molecular mechanisms for cardiac dysfunction have not yet been fully understood during sepsis.
Our previous results showed that cytosolic protein kinase C (cPKC) was activated in rat ventricles during the early hyperdynamic phase of sepsis, whereas membrane-associated protein kinase C (mPKC) activity was unchanged. During late sepsis, both cPKC and mPKC activities remained unchanged. Moreover, differential functions and responses are showed in various regions of heart under the state of physiology and pathology. For the moment, at least 12 protein kinase C (PKC) isoforms have been identified and may play different roles in cell signaling pathways leading to changes in cardiac contractility, the hypertrophic response, and tolerance to myocardial ischemia. Furthermore, the PKC isoforms have been shown to exert both inhibitory and stimulatory influences on apoptosis. Therefore, the present study was continuously investigated the roles of PKC isoforms in various regions of rat ventricles during sepsis.
Sepsis was induced by cecal ligation and puncture (CLP). Experiments were divided into three groups: control, early sepsis, and late sepsis. Early and late sepsis refers to those animals sacrificed at 9 and 18 hr after CLP, respectively. Ventricular septum, Left ventricle, and right ventricle were extracted, respectively. The protein contents of various PKC isoforms and Bad were quantified by Western blot and densitometric analysis. Myocardial apoptosis pattern was detected by terminal deoxynucleotidyl transferase-mediated dUTP in situ nick-end labeling (TUNEL). Ultrastructure of mitochondria was observed by electron microscopy. Our results showed: (1) PKC��, ��, ��, ��, ζ, ι, λ, and μ expressions were unevenly distributed in normal rat ventricles. Among them, the expression of membrane-associated PKC�� (mPKC��) was more than cytosolic PKC�� (cPKC��) in the septum, right and left ventricle under physiological condition; (2) While the PKC�� translocated from cytosol to membrane was decreased in left ventricle and septum during the progression of sepsis; (3) Myocardial apoptosis and Bad translocated from cytosol to mitochondria were increased in left ventricle and septum during the development of sepsis. (4) Mitochondria became swelling and its crista was disarrayed in left ventricle and septum during sepsis.
In conclusion, the PKCe translocation is decreased in septum and left ventricle that may decrease phosphorylation of the pro-apoptotic protein Bad. Then, the Bad translocated from cytosol to mitochondria and causing ultrastructure deformity of mitochondria. Finally, myocardial apoptosis is increased during the progression of sepsis. Therefore, we suggest that the area-specific inactivation of PKCe may contribute to the cardiac damage during sepsis.
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