Bacterial aggregate size determines phagocytosis efficiency of polymorphonuclear leukocytes.

The ability of bacteria to aggregate and form biofilms impairs phagocytosis by polymorphonuclear leukocytes (PMNs). The aim of this study was to examine if the size of aggregates is critical for successful phagocytosis and how bacterial biofilms evade phagocytosis. We investigated the live interaction between PMNs and Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Staphylococcus epidermidis using confocal scanning laser microscopy. Aggregate size significantly affected phagocytosis outcome and larger aggregates were less likely to be phagocytized. Aggregates of S. epidermidis were also less likely to be phagocytized than equally-sized aggregates of the other three species. We found that only aggregates of approx. 5 µm diameter or smaller were consistently phagocytosed. We demonstrate that planktonic and aggregated cells of all four species significantly reduced the viability of PMNs after 4 h of incubation. Our results indicate that larger bacterial aggregates are less likely to be phagocytosed by PMNs and we propose that, if the aggregates become too large, circulating PMNs may not be able to phagocytose them quickly enough, which may lead to chronic infection.

[6]-Gingerol Facilitates CXCL8 Secretion and ROS Production in Primary Human Neutrophils by Targeting the TRPV1 Channel.

SCOPE: Clarifying the function of sensory active TRP (transient receptor potential) channels in non-sensory tissue is of growing interest, especially with regard to food ingredients in nutritionally relevant concentrations. The study hypothesizes the TRPV1 agonist [6]-gingerol to facilitate cellular immune responses of primary human neutrophils, after treatment with 50 nM, a concentration that can be reached in the circulation after habitual dietary intake. METHODS AND RESULTS: qRT-PCR analyses reveal a high abundancy of TRP channel RNA expression in the types of primary leukocytes investigated, namely neutrophils, monocytes, NK cells, T cells, and B cells. Incubation of neutrophils with 50 nM of the known TRPV1 ligand [6]-gingerol led to increased surface expression of CD11b, CD66b, and the fMLF receptor FPR1, as shown by flow cytometry. Upon subsequent stimulation with fMLF, the neutrophils display an about 30% (p < 0.05) increase in CXCL8 secretion as well as in ROS production. Pharmacological inhibition of TRPV1 by trans-tert-butylcyclohexanol abolishes the [6]-gingerol induced effects. CONCLUSIONS: The TRPV1 channel is functionally expressed in human neutrophils. Activation of the channel with [6]-gingerol as a food-derived ligand in nutritionally relevant concentrations leads to an enhanced responsiveness in the cells towards activating stimuli, thereby facilitating a canonical cellular immune response in human neutrophils.

Oxidative Stress and Its Consequences in the Blood of Rats Irradiated with UV: Protective Effect of Cannabidiol.

UVA/UVB radiation disturbs the redox balance of skin cells, and metabolic consequences can be transferred into the blood and internal tissues, especially after chronic skin exposure to UV radiation. Therefore, the aim of this study was to evaluate the effect of cannabidiol (CBD), an antioxidant and anti-inflammatory phytocannabinoid, on oxidative stress and its consequences in the blood of nude rats whose skin was exposed to UVA/UVB radiation for 4 weeks. It was shown that CBD penetrated the blood and in UVB-irradiated rats was preferentially located in the membranes of polymorphonuclear leukocytes, which promoted reduction of ROS generation and up-regulation of antioxidant ability by increasing the activity of glutathione reductase and thioredoxin reductase, while the level of reduced glutathione decreased by UV radiation. Consequently, reduction in UV-induced lipid peroxidation, assessed as 4-hydroxynonenal (4-HNE) and 8-isoprostane (8-isoPGF2α) as well as protein modifications, estimated as 4-HNE-protein adducts and protein carbonyl groups, was observed. CBD, by countering the UV-induced down-regulation of 2-arachidonylglycerol, promoted its antioxidant/anti-inflammatory effects by reducing CB1 and increasing PPARγ receptor activation and consequently ROS and TNF-α down-regulation. The results suggest that CBD applied topically to the skin minimizes redox changes not only at the skin level, but also at the systemic level.

Supramolecular Toxin Complexes for Targeted Pharmacological Modulation of Polymorphonuclear Leukocyte Functions.

The targeted pharmacological modulation of polymorphonuclear leukocytes (PMNs) is of major medical interest. These innate immune cells play a central role in the defense against pathogenic microorganisms. However, their excessive chemotactic recruitment into tissues after traumatic injury is detrimental due to local and systemic inflammation. Rho-GTPases, being the master regulators of the actin cytoskeleton, regulate migration and chemotaxis of PMNs, are attractive pharmacological targets. Herein, supramolecular protein complexes are assembled in a "mix-and-match" approach containing the specific Rho-inhibiting clostridial C3 enzyme and three PMN-binding peptides using an avidin platform. Selective delivery of the C3 Rho-inhibitor with these complexes into the cytosol of human neutrophil-like NB-4 cells and primary human PMNs ex vivo is demonstrated, where they catalyze the adenosine diphosphate (ADP) ribosylation of Rho and induce a characteristic change in cell morphology. Notably, the complexes do not deliver C3 enzyme into human lung epithelial cells, A549 lung cancer cells, and immortalized human alveolar epithelial cells (hAELVi), demonstrating their cell type-selectivity. The supramolecular complexes represent attractive molecular tools to decipher the role of PMNs in infection and inflammation or for the development of novel therapeutic approaches for diseases that are associated with hyperactivity and reactivity of PMNs such as post-traumatic injury.

Aggregatibacter (Actinobacillus) actimycetemcomitans leukotoxin and human periodontitis - A historic review with emphasis on JP2.

Aggregatibacter (Actinobacillus) actimycetemcomitans (Aa) is a gram-negative bacterium that colonizes the human oral cavity and is causative agent for localized aggressive (juvenile) periodontitis (AgP). In the middle of 1990s, a specific JP2 clone of belonging to the cluster of serotype b strains of Aa with highly leukotoxicity (leukotoxin, LtxA) able to kill human immune cells was isolated. JP2 clone of Aa was strongly associated with in particularly in rapidly progressing forms of aggressive periodontitis. The JP2 clone of Aa is transmitted through close contacts. Therefore, AgP patients need intense monitoring of their periodontal status as the risk for developing severely progressing periodontitis lesions are relatively high. Furthermore, timely periodontal treatment, including periodontal surgery supplemented by the use of antibiotics, is warranted. More importantly, periodontal attachment loss should be prevented by early detection of the JP2 clone of Aa by microbial diagnosis testing and/or preventive means.

Intraoperative evaluation of polymorphonuclear leukocyte during second-stage revision surgery promote overdiagnosis of persistent periprosthetic joint infection.

OBJECTIVE: The aim of this study was to evaluate whether intraoperative histopathological examination could predict the risk of relapse of infection in periprosthetic joint infections (PJI). METHODS: The study included 25 patients (14 women and 11 men, with a mean age of 67.0 years (range, 37-83 years)), who had two-staged revision surgery for a PJI. Following prosthetic removal in the first stage, all patient underwent an intraoperative histopathological examination during the second stage. The patients were divided into PMNs-positive group (≥five PMNs per high-powered field) or -negative group (

Early adaption to the antarctic environment at dome C: consequences on stress-sensitive innate immune functions.

UNLABELLED: Abstract Feuerecker, Matthias, Brian Crucian, Alex P. Salam, Ales Rybka, Ines Kaufmann, Marjan Moreels, Roel Quintens, Gustav Schelling, Manfred Thiel, Sarah Baatout, Clarence Sams, and Alexander Choukèr. Early adaption in the Antarctic environment at Dome C: Consequences on stress-sensitive innate immune functions. High Alt Med Biol 15:341-348, 2014.-Purpose/Aims: Medical reports of Antarctic expeditions indicate that health is affected under these extreme conditions. The present study at CONCORDIA-Station (Dome C, 3233 m) seeks to investigate the early consequences of confinement and hypobaric hypoxia on the human organism. METHODS: Nine healthy male participants were included in this study. Data collection occurred before traveling to Antarctica (baseline), and at 1 week and 1 month upon arrival. Investigated parameters included basic physiological variables, psychological stress tests, cell blood count, stress hormones, and markers of innate immune functions in resting and stimulated immune cells. By testing for the hydrogen peroxide (H2O2) production of stimulated polymorphonuclear leukocytes (PMNs), the effects of the hypoxia-adenosine-sensitive immune modulatory pathways were examined. RESULTS: As compared to baseline data, reduced oxygen saturation, hemoconcentration, and an increase of secreted catecholamines was observed, whereas no psychological stress was seen. Upon stimulation, the activity of PMNs and L-selectin shedding was mitigated after 1 week. Endogenous adenosine concentration was elevated during the early phase. In summary, living conditions at high altitude influence the innate immune system's response. After 1 month, some of the early effects on the human organism were restored. CONCLUSION: As this early adaptation is not related to psychological stress, the changes observed are likely to be induced by environmental stressors, especially hypoxia. As hypoxia is triggering ATP-catabolism, leading to elevated endogenous adenosine concentrations, this and the increased catecholamine concentration might contribute to the early, but reversible downregulation of innate immune functions. This indicates the slope of innate immune adaptation to hypoxia.