Search

Burkholderia cenocepacia (B. cenocepacia) is an opportunistic bacterium; causing severe life threatening systemic infections in immunocompromised individuals including cystic fibrosis patients. The lack of gasdermin D (GSDMD) protects mice against endotoxin lipopolysaccharide (LPS) shock. On the other hand, GSDMD promotes mice survival in response to certain bacterial infections. However, the role of GSDMD during B. cenocepacia infection is not yet determined. Our in vitro study shows that GSDMD restricts B. cenocepacia replication within macrophages independent of its role in cell death through promoting mitochondrial reactive oxygen species (mROS) production. mROS is known to stimulate autophagy, hence, the inhibition of mROS or the absence of GSDMD during B. cenocepacia infections reduces autophagy which plays a critical role in the restriction of the pathogen. GSDMD promotes inflammation in response to B. cenocepacia through mediating the release of inflammasome dependent cytokine (IL-1β) and an independent one (CXCL1) (KC). Additionally, different B. cenocepacia secretory systems (T3SS, T4SS, and T6SS) contribute to inflammasome activation together with bacterial survival within macrophages. In vivo study confirmed the in vitro findings and showed that GSDMD restricts B. cenocepacia infection and dissemination and stimulates autophagy in response to B. cenocepacia. Nevertheless, GSDMD promotes lung inflammation and necrosis in response to B. cenocepacia without altering mice survival. This study describes the double-edged functions of GSDMD in response to B. cenocepacia infection and shows the importance of GSDMD-mediated mROS in restriction of B. cenocepacia. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

Autophagy is a highly regulated, biological process that provides energy during periods of stress and starvation. This conserved process also acts as a defense mechanism and clears microbes from the host cell. Autophagy is impaired in Cystic Fibrosis (CF) patients and CF mice, as their cells exhibit low expression levels of essential autophagy molecules. The genetic disorder in CF is due to mutations in the cystic fibrosis transmembrane conductance regulator (cftr) gene that encodes for a chloride channel. CF patients are particularly prone to infection by pathogens that are otherwise cleared by autophagy in healthy immune cells including Burkholderia cenocepacia (B. cenocepacia). The objective of this study is to determine the mechanism underlying weak autophagic activity in CF macrophages and find therapeutic targets to correct it. Using reduced representation bisulfite sequencing (RRBS) to determine DNA methylation profile, we found that the promoter regions of Atg12 in CF macrophages are significantly more methylated than in the wild-type (WT) immune cells, accompanied by low protein expression. The natural product epigallocatechin-3-gallate (EGCG) significantly reduced the methylation of Atg12 promoter improving its expression. Accordingly, EGCG restricted B. cenocepacia replication within CF mice and their derived macrophages by improving autophagy and preventing dissemination. In addition, EGCG improved the function of CFTR protein. Altogether, utilizing RRBS for the first time in the CF field revealed a previously unrecognized mechanism for reduced autophagic activity in CF. Our data also offers a mechanism by which EGCG exerts its positive effects in CF. • The promoter of Atg12 in Cystic Fibrosis macrophages is significantly more methylated than in the wild-type immune cells • Epigallocatechin-3-gallate (EGCG) significantly reduced the methylation of Atg12 promoter improving its expression. • EGCG restricted B. cenocepacia replication within CF mice and their derived macrophages by improving autophagy. • EGCG improved the function of CFTR protein [ABSTRACT FROM AUTHOR]

Burkholderia cenocepacia, the causative agent of cepacia syndrome, primarily affects cystic fibrosis patients, often leading to death. In the lung, epithelial cells serve as the initial barrier to airway infections, yet their responses to B. cenocepacia have not been fully investigated. Here, we examined the molecular responses of human airway epithelial cells to B. cenocepacia infection. Infection led to early signaling events such as activation of Erk, Akt, and NF-κB. Further, TNFα, IL-6, IL-8, and IL-1β were all significantly induced upon infection, but no IL-1β was detected in the supernatants. Because caspase-1 is required for IL-1β processing and release, we examined its expression in airway epithelial cells. Interestingly, little to no caspase-1 was detectable in airway epithelial cells. Transfection of caspase-1 into airway epithelial cells restored their ability to secrete IL-1β following B. cenocepacia infection, suggesting that a deficiency in caspase-1 is responsible, at least in part, for the attenuated IL-1β secretion. [ABSTRACT FROM AUTHOR]