| Background and ObjectiveChronic obstructive pulmonary disease (COPD) is a common and frequently-occurring disease of the respiratory system,with the characteristics of high morbidity, high disability rate and high mortality, The survey shows that its mortality rate ranked fourth in the common diseases, and its popular trend and death rate are still continuing to rise.The currently accepted view regarding to COPD is that COPD is not just the disease of local inflammation and structure remodeling limited to the airway and lung tissue, but a disease of chronic inflammation invoved multi-systems of whole body,and multi-factors participating and Multi-links interacting on each other.As is known to all,skeletal muscle (including diaphragm) consumption/wasting, as one of the systemic adverse effects of COPD, it not only influences the patient’s daily life and increases economic burden of family and society, but also seriously affects the disease prognosis. Studies have shown that skeletal muscle consumption/wasting is mainly due to accelerated muscle protein degradation, and skeletal muscle cell apoptosis also plays an important role. There are four pathways involved in skeletal muscle consumption/wasting:ATP-dependent ubiquitin-proteasome pathway, caspases pathway, lysosomal pathway and calpain pathway. Of which, calpain pathway is a Ca2+-dependent, hignly adjustable proteolytic system, composed of three parts:calpains, calpastatin and calpain activator, participates in the physiological and pathological process of skeletal muscle growth and development, muscle fiber protein degradation, muscle cell apoptosis and necrosis and so on. μ-calpain and m-calpain are the most important and most deeply studied calpain isozymes in calpain system, both play an important role in skeletal muscle atrophy by degrading cytoskeletal proteins and myofibrillar proteins, and mediating skeletal muscle cell apoptosis and necrosis.Studies have shown that μ-calpain and m-calpain involve in skeletal muscle atrophy induced by weightlessness, denervation, glucocorticoid and others. At the same time, studies have shown that both the expression and activity of the two calpains are enhanced when skeletal muscle injury caused by excessive exercise, they participate in the occurrence and development of this process.However, the role of μ-calpain and m-calpain in skeletal muscle atrophy of COPD patients has not been reported.Whether calpains are also involved in skeletal consumption/wasting of COPD patients? Following this thought, we designed the experiment study.Recur to COPD rat model, we detect μ-calpain and m-calpain protein and mRNA expression in presentative skeletal muscle--extensor digitorum longus (EDL) and diaphragm, study the changes of μ-calpain and m-calpain in skeletal muscle of COPD model rats, and explore the significance of calpains in skeletal muscle consumption/wasting of COPD model rats.Materials and methods40helthy male Wistar rats were randomly divided into model group(20rats)and control group(20rats). The model group made modle by the following method: lipopolysaccharide (LPS)was poured into trachea on first day and fourteenth day, rats were exposed to5%Hongqiqu cigarettes smoking in a homemade airtight box on the second day to the thirteenth day and the fifteenth day to the twenty-eighth day,twice a day, continued0.5h each time. When model group was injected LPS into trachea, on the same day and in the same way, control group rats were injected into trachea with the same amount of sterile normal saline. Madding model successfully, all rats were sacrificed on29th days of the experiment, removed lung tissue, diaphragm, and bilateral EDLs to do following determination:1. HE staining of lung tissue and skeletal muscle tissue pathological sections. 2. Immunohistochemical determination of μ-calpain and m-calpain protein expression in skeletal muscle.3. Polymeraseehain Reaction(RT-PCR) determined μ-calpain and m-calpainmRNA expression in skeletal muscle. Result1. Lung tissue pathological slices by HE staining, was observed under optical microscope, modle group rat lung tissue presented chronic non-specific inflammatory changes and changes of emphysema,conforming to the characteristics of pathological changes of lung tissue in COPD,confirmed the success of mading model. Diaphragm and EDL sections were observed under optical microscope.2. Immunohistochemical results showed that, compared with control group, μ-calpain protein expression enhanced in both diaphragm and EDL of COPD rats (P<0.01), and m-calpain protein expressed more in diaphragm and EDL in COPD model rats than control group rats(P<0.01), there were statistically significant difference between the two groups.3. RT-PCR results showed that,there was no statistical difference of μ-calpain mRNA in diaphragm and EDL between model group rats and control group rats (P>0.05).m-calpain mRNA expression enhanced in both diaphragm and EDL of COPD rats(P<0.05), there was a statistically significant difference between model group and control group.ConclusionCOPD model rat skeletal muscle existed atrophy phenomenon, and μ-calpain and m-Calpain protein expression enhanced in skeletal muscle in COPD model rats, m-calpain mRNA expression enhanced in COPD model rats, all prompted that calpains expression upregulated in skeletal muscle of COPD model rats, may be involve in COPD skeletal muscle consumption/wasting. |
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