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Figure 5 | Molecular Medicine

Figure 5

From: Midkine Is Expressed and Differentially Processed during Chronic Obstructive Pulmonary Disease Exacerbations and Ventilator-Associated Pneumonia Associated with Staphylococcus aureus Infection

Figure 5

Detection and stability of MK in airway secretions from COPD and VAP, respectively. (A) Airway secretions from patients suffering from COPD exacerbations or VAP associated with S. aureus infection were analyzed for MK by ELISA. The results show significantly less MK in sputum from COPD patients compared with higher levels in VAP patients (p = 0.030, as determined by the Mann-Whitney U test). (B) To investigate the stability of MK in airway secretions, recombinant MK was incubated in sputa from three COPD patients or three VAP patients for 1 or 18 h and the integrity of the molecule was subsequently analyzed by Western blot. The kinetics of degradation was more rapid in COPD sputa, showing little or no MK remaining after 1 h in 2 of 3 patients. (C) To investigate and compare protease activity in airway secretions, sputa obtained from three COPD and three VAP patients were analyzed for protease activity by zymography. COPD sputa generated significantly larger clearing zones in the collagen matrix, indicating the presence of higher proteolytic activity (p < 0.01). The sizes of the clearing zones were measured, and the data represent mean ± SD. p value was calculated using the Student t test. n.d., Not detectable.

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