Arachidonic Acid Metabolism Regulates Escherichia coli Penetration of the Blood-Brain Barrier

Abstract

Escherichia coli K1 meningitis occurs following penetration of the blood-brain barrier, but the underlying mechanisms involved in E. coli penetration of the blood-brain barrier remain incompletely understood. We have previously shown that host cytosolic phospholipase A 2 ␣ (cPLA 2 ␣) contributes to E. coli invasion of human brain microvascular endothelial cells (HBMEC), which constitute the blood-brain barrier, but the underlying mechanisms remain unclear. cPLA 2 ␣ selectively liberates arachidonic acid from membrane phospholipids. Here, we provide the first direct evidence that host 5-lipoxygenase and lipoxygenase products of arachidonic acid, cysteinyl leukotrienes (LTs), contribute to E. coli K1 invasion of HBMEC and penetration into the brain, and their contributions involve protein kinase C alpha (PKC␣). These findings demonstrate that arachidonic acid metabolism regulates E. coli penetration of the blood-brain barrier, and studies are needed to further elucidate the mechanisms involved with metabolic products of arachidonic acid for their contribution to E. coli invasion of the blood-brain barrier.The mortality and morbidity associated with neonatal Gramnegative bacillary meningitis have remained significant despite advances in antimicrobial chemotherapy and supportive care. Inadequate knowledge of the pathogenesis has contributed to this mortality and morbidity (18)(19)(20). Escherichia coli K1 is the most common Gram-negative organism that causes neonatal meningitis. Most cases of neonatal E. coli K1 meningitis develop as a result of hematogenous spread, but the underlying mechanisms involved in E. coli penetration of the blood-brain barrier remain incompletely understood (18)(19)(20).Several lines of evidence from experimental animal models as well as human cases of E. coli K1 meningitis indicate that E. coli penetrates into the brain initially in the cerebral vasculature (3, 21). We have developed the in vitro model of the blood-brain barrier by isolation and cultivation of human brain microvascular endothelial cells (HBMEC) (22,34,37). Upon cultivation on collagen-coated Transwell inserts, these HBMEC exhibit morphological and functional properties of tight junction formation and a polarized monolayer. These are shown by our demonstrations of tight junction proteins (such as ZO-1), adherens junction proteins (such as ␤-catenin), and their spatial separation, limited permeability to inulin (molecular mass, 4,000 Da), and development of high transendothelial electrical resistance (22, 34, 37). We have also developed the animal models of experimental hematogenous meningitis, which mimic the pathogenesis of E. coli meningitis in humans, e.g., hematogenous infection of the meninges (10,11,17,21,40,41).Using these in vitro and in vivo models, we have shown that E. coli invasion of HBMEC is a prerequisite for penetration into the brain and requires specific microbial determinants (10, 11, 17-20, 40, 41). This was shown in animal models of experimental hematogenous E. coli meningitis; mutants of E. coli K1 d...

Pathogens Penetrating the Central Nervous System: Infection Pathways and the Cellular and Molecular Mechanisms of Invasion

“…The activation of cytosolic phospholipase A 2 generated arachidonic acid metabolites, induced host actin cytoskeletal rearrangements, and was essential for E. coli K1 invasion of HBMECs (173,(175)(176)(177). OmpA and invasion of brain endothelial cell protein A (IbeA) also trigger the phosphorylation of STAT3, which results in the activation of Rac1, a Rho family GTPase that regulates host cytoskeletal rearrangements (178).…”

Host Cytosolic Phospholipase A 2 α Contributes to Group B Streptococcus Penetration of the Blood-Brain Barrier

“…cPLA 2 ␣ Ϫ/Ϫ and wild-type 10-to 13-week-old mice, either male or female, that had been backcrossed on the BALB/c strain for Ͼ10 generations were used (41). All procedures and handling techniques were approved by the Johns Hopkins University Animal Care and Use Committee.…”

“…HBMEC (ϳ70% confluence) were infected with dialyzed adenovirus constructs containing cPLA 2 ␣-S505A or green fluorescent protein (GFP) vector, or dominant-negative PKC␣ or a vector control, as previously described (35,36,41). Clinical isolates of type III GBS strains were used for HBMEC adherence and invasion assays.…”

“…The lysates of HBMEC incubated with GBS or S. gordonii were prepared for Western blotting and immunoprecipitation, as described previously (35,36,41).…”

Klebsiella pneumoniae Induces an Inflammatory Response in an In Vitro Model of Blood-Retinal Barrier

“…Bacterial invasion and adhesion assays. Invasion of BREC by K. pneumoniae in monoculture and in coculture with BRPC was performed as described by Zhu et al (36). Bacteria (10 7 CFU/well) were added to confluent cells in monoculture or in coculture, and incubations were performed at 37°C for 60 min to allow invasion to occur.…”