Comparison of matrix metalloproteinase-9 between Wistar rat and spontaneously hypertensive rat in pulmonary injury model

Abstract

To compare the expression of matrix metalloproteinase-9 (MMP9) and observe the change of cigarette smoke-induced pulmonary injury in Wistar and spontaneously hypertensive (SH) rats. A total of 10 male Wistar rats and 10 male SH rats were randomly divided into four groups of Wistar control, Wistar cigarette smoking, SH control and SH cigarette smoking (n=5 each). The control groups were fed routinely while the cigarette smoking groups were placed into a homemade organic glass box and exposed to cigarette smoking for twice daily 6 days a week. After 8-week treatment, general condition, lung function and pathological changes of lung tissues were detected. The expressions of nuclear factor (NF)-κB, IκB-α and MMP9 were determined by Western blot. And real-time polymerase chain reaction (RT-PCR) was employed to detect the mRNA levels of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6). Immunohistochemistry was used to detect the expression of MMP9 in lung tissue. Both cigarette smoking groups were marantic along with intermittent cough and polypnea. Resistance index (RI) in Wistar control, Wistar cigarette smoking, SH control and SH cigarette smoking groups was (0.23±0.04), (0.33±0.05), (0.33±0.02) and (0.46±0.08) cmH2O·s·ml(-1) respectively. RI increased in Wistar cigarette smoking group versus Wistar control group. And SH cigarette smoking group was significantly higher than SH control and Wistar cigarette smoking groups (P<0.05). Hematoxylin & eosin staining demonstrated that the lesion of chronic bronchitic inflammation and emphysema existed in two cigarette smoking groups while it was more severe in SH rats than Wistar rats. The mean alveolar number (MAN) was significantly reduced in two cigarette smoking groups compared with that in control groups (P<0.05, respectively). And mean lining interval (MLI), damage index (DI), bronchial smooth muscle index and collagen index significantly increased in Wistar cigarette smoking group compared with Wistar control group, SH cigarette smoking group significantly increased than that in SH control and Wistar cigarette smoking groups (P<0.05, respectively). On Western blot, the protein level of NF-κB in Wistar control, Wistar cigarette smoking, SH control and SH cigarette smoking groups was (0.322±0.014), (0.558±0.044), (0.373±0.029) and (1.156±0.197) respectively. The protein level of MMP9 in these groups was (0.255±0.070), (0.456±0.089), (0.594±0.184) and (0.847±0.138) respectively. The protein levels of NF-κB and MMP9 increased obviously in Wistar cigarette smoking group versus Wistar control group and those in SH cigarette smoking group were significantly higher than SH control and Wistar cigarette smoking groups (P<0.05). Additionally, IκB-α expression in SH cigarette smoking group was markedly decreased in comparison to that in SH control group and Wistar cigarette smoking group (P<0.05). The mRNA level of TNF-α increased obviously in two cigarette smoking groups in comparison to those in controls (P<0.05) and the mRNA level of IL-6 significantly increased in the SH cigarette smoking group compared with SH control group and Wistar cigarette smoking group (P<0.05). As for immunohistochemistry, the MMP9 positive cells were prominently distributed in the lungs of cigarette smoking groups versus the stained cells in the control group. And SH cigarette smoking group was significantly higher than Wistar cigarette smoking group (P<0.05). Both Wistar and SH rats induced by cigarette smoking may have an onset of lung injury symptom analogous to chronic obstructive pulmonary disease and SH rat are more severe.