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Hindlimb suspension and SPE-like radiation impairs clearance of bacterial infections.

ABSTRACT: A major risk of extended space travel is the combined effects of weightlessness and radiation exposure on the immune system. In this study, we used the hindlimb suspension model of microgravity that includes the other space stressors, situational and confinement stress and alterations in food intake, and solar particle event (SPE)-like radiation to measure the combined effects on the ability to control bacterial infections. A massive increase in morbidity and decrease in the ability to control bacterial growth was observed using 2 different types of bacteria delivered by systemic and pulmonary routes in 3 different strains of mice. These data suggest that an astronaut exposed to a strong SPE during extended space travel is at increased risk for the development of infections that could potentially be severe and interfere with mission success and astronaut health.

SUBMITTER: Li M

PROVIDER: S-EPMC3893249 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Hindlimb suspension and SPE-like radiation impairs clearance of bacterial infections.

Li Minghong M Holmes Veronica V Zhou Yu Y Ni Houping H Sanzari Jenine K JK Kennedy Ann R AR Weissman Drew D

PloS one 20140115 1

A major risk of extended space travel is the combined effects of weightlessness and radiation exposure on the immune system. In this study, we used the hindlimb suspension model of microgravity that includes the other space stressors, situational and confinement stress and alterations in food intake, and solar particle event (SPE)-like radiation to measure the combined effects on the ability to control bacterial infections. A massive increase in morbidity and decrease in the ability to control b ...[more]

PMID: 24454913

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Project description:Background & aimsAlthough transient bacteremia is common during dental and endoscopic procedures, infections developing during sterile diseases like acute pancreatitis (AP) can have grave consequences. We examined how impaired bacterial clearance may cause this transition.MethodsBlood samples from patients with AP, normal controls, and rodents with pancreatitis or those administered different nonesterified fatty acids (NEFAs) were analyzed for albumin-unbound NEFAs, microbiome, and inflammatory cell injury. Macrophage uptake of unbound NEFAs using a novel coumarin tracer were done and the downstream effects-NEFA-membrane phospholipid (phosphatidylcholine) interactions-were studied on isothermal titration calorimetry.ResultsPatients with infected AP had higher circulating unsaturated NEFAs; unbound NEFAs, including linoleic acid (LA) and oleic acid (OA); higher bacterial 16S DNA; mitochondrial DNA; altered β-diversity; enrichment in Pseudomonadales; and increased annexin V-positive myeloid (CD14) and CD3-positive T cells on admission. These, and increased circulating dead inflammatory cells, were also noted in rodents with unbound, unsaturated NEFAs. Isothermal titration calorimetry showed progressively stronger unbound LA interactions with aqueous media, phosphatidylcholine, cardiolipin, and albumin. Unbound NEFAs were taken into protein-free membranes, cells, and mitochondria, inducing voltage-dependent anion channel oligomerization, reducing ATP, and impairing phagocytosis. These were reversed by albumin. In vivo, unbound LA and OA increased bacterial loads and impaired phagocytosis, causing infection. LA and OA were more potent for these amphipathic interactions than the hydrophobic palmitic acid.ConclusionsRelease of stored LA and OA can increase their circulating unbound levels and cause amphipathic liponecrosis of immune cells via uptake by membrane phospholipids. This impairs bacterial clearance and causes infection during sterile inflammation.

Project description:BACKGROUND:The purpose of this study was to determine the efficacy of besifloxacin ophthalmic suspension 0.6% when used in the treatment of bacterial conjunctivitis infections due to Pseudomonas aeruginosa. METHODS:We undertook a post hoc analysis of clinical outcomes in patients with bacterial conjunctivitis due to P. aeruginosa across four prospective, multicenter, double-masked, randomized, controlled, clinical studies of besifloxacin ophthalmic suspension 0.6%. Efficacy outcomes included bacterial eradication and clinical resolution of the baseline infection at follow-up visits. Bacterial eradication was defined as the absence of ocular bacterial species present at or above threshold at baseline, while clinical resolution was defined as grade 0 ocular discharge and bulbar conjunctival injection. Safety outcomes included the incidence of adverse events, changes in visual acuity, and biomicroscopy and ophthalmoscopy findings. Patient outcomes were summarized and bacterial eradication and clinical resolution rates integrated. RESULTS:Of 1317 patients with culture-confirmed bacterial conjunctivitis across four clinical studies, nine (0.7%) were infected with P. aeruginosa at baseline, and of these, five were randomized to treatment with besifloxacin ophthalmic suspension 0.6%. Bacterial eradication of the baseline infection was observed at both follow-up visits in all five patients. Clinical resolution was achieved in two of five patients by the first follow-up visit and four of five patients by the second follow-up visit. There were no adverse events reported in these patients. There were no clinically meaningful biomicroscopy findings or changes in ophthalmoscopy or visual acuity. CONCLUSION:The incidence of bacterial conjunctivitis due to P. aeruginosa was low. Treatment of patients with P. aeruginosa infections with besifloxacin ophthalmic suspension 0.6% led to bacterial eradication of P. aeruginosa by the first follow-up visit and high rates of clinical resolution.

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Hindlimb suspension and SPE-like radiation impairs clearance of bacterial infections.

Publications

Hindlimb suspension and SPE-like radiation impairs clearance of bacterial infections.

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