Abstract
Mycoplasma pneumoniae is one of the most common pathogenic causes of community-acquired pneumonia. Hydrogen sulfide, alanine, and pyruvate producing enzyme (HapE) is a recently discovered M. pneumoniae virulence factor that can produce H2S to promote erythrocyte lysis. However, other cytotoxic effects of HapE have not been explored. The present study examined the effects of this enzyme on normal human bronchial epithelial (NHBE) cells, in an attempt to identify additional mechanisms of M. pneumoniae pathogenesis. Recombinant HapE was purified for use in downstream assays. MTT and colony formation assays were conducted to determine the effects of HapE on cell viability and growth, while flow cytometry was used to examine changes in cell proliferation and cell cycle function. ELISA was performed to examine changes in the cytokine profile of HapE-treated cells. HapE treatment arrested NHBE cells in S phase and inhibited cell proliferation in a concentration-dependent manner. The anti-inflammatory factors interleukin (IL)-4 and IL-6 were significantly enhanced following HapE treatment. Increased secretion of pro-inflammatory factors was not observed. The effects of HapE on the respiratory epithelium may have an impact on the efficiency of host immune surveillance and pathogen elimination, and contribute to the pathogenesis of M. pneumoniae.
Highlights
Mycoplasma pneumoniae is a prevalent pathogen in respiratory tract infections in children [1]
The protein was isolated from inclusion bodies by performing a denaturation–renaturation cycle followed by purification by nickel-nitrilotriacetic acid (Ni-NTA) affinity chromatography (Figure 1A)
To study the role of HapE in the virulence of M. pneumoniae, we studied the effects of this protein in vitro using normal human bronchial epithelial (NHBE) cells, which provide a useful model for the respiratory epithelium
Summary
Mycoplasma pneumoniae is a prevalent pathogen in respiratory tract infections in children [1]. It causes up to 40% of community-acquired pneumonia (CAP) cases in children and as much as 18% of cases requiring hospitalization [2]. Global outbreaks of M. pneumoniae occur every 3–7 years. The clinical symptoms of M. pneumoniae infection are diverse [3]. Individuals with a mild infection can be free of symptoms. In addition to respiratory symptoms and general malaise or fever, more severe infections can cause multiple systemic extrapulmonary complications involving multiple organs and tissues [4,5]
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