Biology subjects

Jensen, P. O.

Publications and source records attributed to Jensen, P. O..

3 recordsLinked to original sources

bioRxiv2025

Regulatory effects of beta-2-microglobulin on reactive oxygen species generation in polymorphonuclear cells

Beta-2-microglobulin ({beta}2m) constitutes the invariant light chain of the major histocompatibility complex class I (MHC I) and is present on all nucleated cells, as well as in biological fluids, platelets and neutrophil granules. Immune cells can increase their production and secretion of {beta}2m in response to cytokines such as IFN-{gamma}, IFN-, and TNF-. Elevated {beta}2m levels can be detected in various inflammatory, autoimmune, infectious and malignant diseases, often correlating with poor prognosis and reduced survival. So far, no specific functions have been agreed on for soluble {beta}2m. In the present study, we investigated the effects of exogenous {beta}2m and two proteolytically processed forms, cK58{beta}2m and dK58{beta}2m, on ROS production in polymorphonuclear leukocytes (PMNs). {beta}2m was shown to enhance ROS generation triggered by latex beads, while cK58{beta}2m and dK58{beta}2m suppressed both baseline ROS levels and responses to latex beads, TNF-, and fMLF. Among these, dK58{beta}2m was generally the most potent inhibitor. The inhibitory effect of cK58{beta}2m and dK58{beta}2m was also confirmed in DMSO-differentiated HL-60 cells, a neutrophil-like cell line. Furthermore, treatment with dK58{beta}2m impaired the recruitment of p47phox and p67phox to the plasma membrane following fMLF stimulation, two key subunits of the NADPH oxidase complex responsible for superoxide anion production in neutrophils. This may explain the reduced ROS production observed in cells treated with dK58{beta}2m. Taken together, these results suggest that {beta}2m, cK58{beta}2m and dK58{beta}2m can regulate ROS generation in PMNs and highlight a potential role for {beta}2m in modulating the innate immune response through control of ROS production.

immunology↗

bioRxiv2019

The origin of extracellular DNA in bacterial biofilm infections in vivo

Extracellular DNA (eDNA) plays an important role in both the aggregation of bacteria and in the interaction of the resulting biofilms with polymorphonuclear leukocytes (PMNs) during an inflammatory response. Here, transmission electron and confocal scanning laser microscopy were used to examine the interaction between biofilms of Pseudomonas aeruginosa and PMNs in a murine implant model and in lung tissue from chronically infected cystic fibrosis patients. PNA FISH, DNA staining, labeling of PMN DNA with a thymidine analogue, and immunohistochemistry were applied to localize bacteria, eDNA, PMN-derived eDNA, PMN-derived histone H3 (H3), neutrophil elastase (NE), and citrullinated H3 (citH3). Host-derived eDNA was observed surrounding bacterial aggregates but not within the biofilms. H3 localized to the lining of biofilms while NE was found throughout biofilms. CitH3, a marker for neutrophil extracellular traps (NETs) was detected only sporadically indicating that most host-derived eDNA in vivo was not a result of NETosis. Together these observations show that, in these in vivo biofilm infections with P. aeruginosa, the majority of eDNA is found external to the biofilm and derives from the host.\n\nAuthor summaryThe role of extracellular DNA (eDNA) has been described in vitro to play a major role in biofilm formation and antibiotic tolerance, but never for biofilm infections in vivo.\n\nTwo important characteristics of human chronic bacterial infections are aggregated bacteria and white blood cells (WBC). Bacteria use eDNA to stabilize biofilms and WBC use eDNA to trap bacteria. Given the importance of eDNA for both bacteria and WBC we show here for the first time that bacterial biofilms do not co-localize with either bacterial or WBC-derived eDNA during chronic infections. Our in vivo findings show eDNA is located outside biofilms as opposed to incorporated within the biofilm as commonly observed in vitro.\n\nWe believe that understanding the interplay between biofilms and WBC during chronic infection is essential if we are to elucidate the mechanisms underlying persistent infection and ascertain why WBC fail to eradicate bacteria; this will enable us to develop new treatment strategies.

microbiology↗

bioRxiv2018

Oxygen restriction induces a viable but non-culturable population in bacteria

Induction of a non-culturable state has been demonstrated for many bacteria. In a clinical perspective, the lack of growth due to these non-culturable bacteria can have major consequences for the diagnosis and treatment of patients. Here we show how anoxic conditioning (restriction of molecular oxygen, O2) generates difficult-to-culture (DTC) bacteria during biofilm growth. A significant subpopulation of Pseudomonas aeruginosa entered a DTC state after anoxic conditioning, ranging from five to 90 % of the total culturable population, in both planktonic and biofilm models. Anoxic conditioning also generated DTC subpopulations of Staphylococcus aureus and Staphylococcus epidermidis. Growth of the DTC populations were achieved by substituting O2 with 10 mM NO3- as an alternative electron acceptor for anaerobic respiration or, in the case of P. aeruginosa, by adding sodium pyruvate or catalase as scavengers against reactive oxygen species (ROS) during aerobic respiration. An increase in normoxic plating due to addition of catalase suggests the molecule hydrogen peroxide as a possible mechanism for induction of DTC P. aeruginosa. Anoxic conditioning also generated a true viable but non-culturable (VBNC) population of P. aeruginosa that was not resurrected by substituting O2 with NO3- during anaerobic respiration. Moreover, bacterial detection in clinical samples was improved significantly by supplementing 10 mM NO3- to LB plates and incubating under anoxic conditions. These results demonstrate that habituation to an infectious anoxic micro-environment complicates diagnostic culturing of bacteria, especially in the case of chronic infections where oxygen is restricted due to the host immune response. ImportanceDiagnostics of bacteria from chronic infections by standard culture-based methods is challenging. Bacteria in a non-culturable state may contribute to the lack of culturing from these infections. Many stressors are known to induce a non-culturable state, among others the absence of molecular oxygen, which is evident in chronic infections due to high rates of oxygen consumption by the host response. In this study, we have shown that Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis can enter a difficult-to-culture state after oxygen restriction. Regrowth was not possible using conventional normoxic plating where oxygen served as electron acceptor. Instead, regrowth was enabled during anoxic conditions with added nitrate as alternative electron acceptor. Our findings show that bacteria can habituate to their environment and that it has to be taken into consideration especially when culturing clinical samples e.g. from chronic infections.

microbiology↗