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

Abstract

Group B Streptococcus (GBS) is the most common bacterium causing neonatal meningitis, and neonatal GBS meningitis continues to be an important cause of mortality and morbidity. Here we provide the first direct evidence that host cytosolic phospholipase A 2 ␣ (cPLA 2 ␣) contributes to type III GBS invasion of human brain microvascular endothelial cells (HBMEC), which constitute the blood-brain barrier and penetration into the brain, the key step required for the development of GBS meningitis. This was shown by our demonstration that pharmacological inhibition and gene deletion of cPLA 2 ␣ significantly decreased GBS invasion of the HBMEC monolayer and penetration into the brain. cPLA 2 ␣ releases arachidonic acid from membrane phospholipids, and we showed that the contribution of cPLA 2 ␣ to GBS invasion of HBMEC involved lipoxygenated metabolites of arachidonic acid, cysteinyl leukotrienes (LTs). In addition, type III GBS invasion of the HBMEC monolayer involves protein kinase C␣ (PKC␣), as shown by time-dependent PKC␣ activation in response to GBS as well as decreased GBS invasion in HBMEC expressing dominant-negative PKC␣. PKC␣ activation in response to GBS, however, was abolished by inhibition of cPLA 2 ␣ and cysteinyl LTs, suggesting that cPLA 2 ␣ and cysteinyl LTs contribute to type III GBS invasion of the HBMEC monolayer via PKC␣. These findings demonstrate that specific host factors involving cPLA 2 ␣ and cysteinyl LTs contribute to type III GBS penetration of the blood-brain barrier and their contribution involves PKC␣.Neonatal bacterial meningitis continues to be an important cause of mortality and morbidity. Group B Streptococcus (GBS) is the most common bacterium causing neonatal meningitis (3, 5, 6, 12, 13, 18-20, 22, 25, 26, 37), and inadequate knowledge of its pathogenesis has contributed to this mortality and morbidity (20,26). Experimental data indicate limited efficacy with antimicrobial chemotherapy alone (19).Several lines of evidence from human cases of GBS meningitis as well as animal models of experimental hematogenous GBS meningitis indicate that GBS penetrates into the brain initially in the cerebral vasculature (2,7,8).We have developed an in vitro model of the blood-brain barrier using human brain microvascular endothelial cells (HBMEC) (21,34,38). These HBMEC have been shown to exhibit morphological and functional properties of tight junction formation as well as a polarized monolayer (21,34,38). In addition, we and others have developed animal models of experimental hematogenous GBS meningitis (7,8,19). These animal models have important similarities to GBS meningitis in human neonates, such as hematogenous infection of the meninges. Using these in vitro and in vivo models, we have shown that type III GBS strains, which account for the majority of cerebrospinal fluid (CSF) isolates from neonates with GBS meningitis, invade the HBMEC monolayer and penetrate the brain (19,31,35,36,40). Type III GBS internalization into the HBMEC monolayer has also been documented by transmission electr...

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

“…It has also been demonstrated that group B streptococcus invasion occurs via cytoskeletal rearrangements that are induced following the activation of RhoA and Rac1 (205). Furthermore, group B streptococcus induces serine 505 phosphorylation of host cytosolic phospholipase A 2 , which leads to the release of arachidonic acid metabolites, including cysteinyl leukotrienes (206). In vitro pharmacological inhibition studies demonstrated that the activation of cytosolic phospholipase A 2 was required for efficient group B streptococcal invasion of HBMECs.…”

“…In addition, brain colonization by group B streptococcus was significantly reduced in mice deficient in cytosolic phospholipase A 2 compared to wild-type animals in a model of hematogenous meningitis. Following cytosolic phospholipase A 2 activation and the release of cysteinyl leukotrienes, downstream signaling activates protein kinase C␣, which is involved in the regulation of actin cytoskeletal rearrangements (206).…”

A novel approach for locating mice brain regions of Cryptococcus neoformans CNS invasion

“…Our previous work showed that host cytosolic phospholipase A2 (cPLA2) contributes to group B Streptococcus penetration of the blood-brain barrier (BBB) (Maruvada et al, 2011). However, the role of cPLA2 in C. neoformans CNS infection remains unclear.…”

Group B Streptococcus meningitis.

“…However, the magnitudes of bacteraemia were similar between cPLA 2  −/− and wild-type mice, suggesting that decreased penetration was not the result of decreased levels of blood-borne bacteria. Interestingly, cPLA 2  deletion did not aff ect GBS penetration into non-brain organs, such as the kidneys and spleen, as similar numbers of bacterial counts were recovered from cPLA 2  −/− and wild-type mice (Maruvada et al, 2011). The basis for this selective role of host cPLA 2  in GBS neurotropism is unknown.…”

“…Host factors involved in arachidonic acid metabolism also contribute to penetration of the BBB by GBS (Maruvada et al, 2011). Pharmacological inhibition and gene deletion demonstrated that host cytosolic phos pholipase A 2  (cPLA 2 ) contributes to type III GBS invasion of HBMEC monolayers and penetration into the brain in vivo.…”