Biochemical and Cellular Characterization and Inhibitor Discovery of Pseudomonas aeruginosa 15-Lipoxygenase

Pseudomonas aeruginosa is an opportunistic pathogen that can cause nosocomial and chronic infections in immunocompromised patients. P. aeruginosa secretes a lipoxygenase, LoxA, but the biological role of this enzyme is currently unknown. LoxA is poorly similar in sequence to both soybean LOX-1 (s15-LOX-1) and human 15-LOX-1 (37 and 39%, respectively) yet has kinetics comparably fast versus those of s15-LOX-1 (at pH 6.5, Kcat = 181 ± 6 s(-1) and Kcat/KM = 16 ± 2 μM(-1) s(-1)). LoxA is capable of efficiently catalyzing the peroxidation of a broad range of free fatty acid (FA) substrates (e.g., AA and LA) with high positional specificity, indicating a 15-LOX. Its mechanism includes hydrogen atom abstraction [a kinetic isotope effect (KIE) of >30], yet LoxA is a poor catalyst against phosphoester FAs, suggesting that LoxA is not involved in membrane decomposition. LoxA also does not react with 5- or 15-HETEs, indicating poor involvement in lipoxin production. A LOX high-throughput screen of the LOPAC library yielded a variety of low-micromolar inhibitors; however, none selectively targeted LoxA over the human LOX isozymes. With respect to cellular activity, the level of LoxA expression is increased when P. aeruginosa undergoes the transition to a biofilm mode of growth, but LoxA is not required for biofilm growth on abiotic surfaces. However, LoxA does appear to be required for biofilm growth in association with the host airway epithelium, suggesting a role for LoxA in mediating bacterium-host interactions during colonization

Building a national framework for multicentre research and clinical trials: experience from the Nigeria Implementation Science Alliance

There is limited capacity and infrastructure in sub-Saharan Africa to conduct clinical trials for the identification of efficient and effective new prevention, diagnostic and treatment modalities to address the disproportionate burden of disease. This paper reports on the process to establish locally driven infrastructure for multicentre research and trials in Nigeria known as the Nigeria Implementation Science Alliance Model Innovation and Research Centres (NISA-MIRCs). We used a participatory approach to establish a research network of 21 high-volume health facilities selected from all 6 geopolitical zones in Nigeria capable of conducting clinical trials, implementation research using effectiveness-implementation hybrid designs and health system research. The NISA-MIRCs have a cumulative potential to recruit 60 000 women living with HIV and an age-matched cohort of HIV-uninfected women. We conducted a needs assessment, convened several stakeholder outreaches and engagement sessions, and established a governance structure. Additionally, we selected and trained a core research team, developed criteria for site selection, assessed site readiness for research and obtained ethical approval from a single national institutional review board. We used the Exploration, Preparation, Implementation, Sustainment framework to guide our reporting of the process in the development of this network. The NISA-MIRCs will provide a nationally representative infrastructure to initiate new studies, support collaborative research, inform policy decisions and thereby fill a significant research infrastructure gap in Africa's most populous country

Building a national framework for multicentre research and clinical trials: experience from the Nigeria Implementation Science Alliance

There is limited capacity and infrastructure in sub-Saharan Africa to conduct clinical trials for the identification of efficient and effective new prevention, diagnostic and treatment modalities to address the disproportionate burden of disease. This paper reports on the process to establish locally driven infrastructure for multicentre research and trials in Nigeria known as the Nigeria Implementation Science Alliance Model Innovation and Research Centres (NISA-MIRCs). We used a participatory approach to establish a research network of 21 high-volume health facilities selected from all 6 geopolitical zones in Nigeria capable of conducting clinical trials, implementation research using effectiveness-implementation hybrid designs and health system research. The NISA-MIRCs have a cumulative potential to recruit 60 000 women living with HIV and an age-matched cohort of HIV-uninfected women. We conducted a needs assessment, convened several stakeholder outreaches and engagement sessions, and established a governance structure. Additionally, we selected and trained a core research team, developed criteria for site selection, assessed site readiness for research and obtained ethical approval from a single national institutional review board. We used the Exploration, Preparation, Implementation, Sustainment framework to guide our reporting of the process in the development of this network. The NISA-MIRCs will provide a nationally representative infrastructure to initiate new studies, support collaborative research, inform policy decisions and thereby fill a significant research infrastructure gap in Africa\u27s most populous country

Pseudomonas aeruginosa utilizes host polyunsaturated phosphatidylethanolamines to trigger theft-ferroptosis in bronchial epithelium

Ferroptosis is a death program executed via selective oxidation of arachidonic acid-phosphatidylethanolamines (AA-PE) by 15-lipoxygenases. In mammalian cells and tissues, ferroptosis has been pathogenically associated with brain, kidney, and liver injury/diseases. We discovered that a prokaryotic bacterium, Pseudomonas aeruginosa, that does not contain AA-PE can express lipoxygenase (pLoxA), oxidize host AA-PE to 15-hydroperoxy-AA-PE (15-HOO-AA-PE), and trigger ferroptosis in human bronchial epithelial cells. Induction of ferroptosis by clinical P. aeruginosa isolates from patients with persistent lower respiratory tract infections was dependent on the level and enzymatic activity of pLoxA. Redox phospholipidomics revealed elevated levels of oxidized AA-PE in airway tissues from patients with cystic fibrosis (CF) but not with emphysema or CF without P. aeruginosa. We believe that the evolutionarily conserved mechanism of pLoxA-driven ferroptosis may represent a potential therapeutic target against P. aeruginosa-associated diseases such as CF and persistent lower respiratory tract infections