VEGF receptor-1 involvement in pericyte loss induced by Escherichia coli in an in vitro model of blood brain barrier

The key aspect of neonatal meningitis is related tothe ability of pathogens to invade the blood–brainbarrier (BBB) and to penetrate the central nervoussystem. In the present study we show that, in an invitro model of BBB, on the basis of co-culturingprimary bovine brain endothelial cells (BBEC)and primary bovine retinal pericytes (BRPC),Escherichia coli infection determines changes oftransendothelial electrical resistance (TEER) andpermeability (Pe) to sodium fluorescein. In theco-culture model, within BBEC, bacteria are able tostimulate cytosolic and Ca2+-independent phospholipaseA2 (cPLA2 and iPLA2) enzyme activities.In supernatants of E. coli-stimulated co-cultures,an increase in prostaglandins (PGE2) and VEGFproduction in comparison with untreated cocultureswere found. Incubation with E. coli inpresence of AACOCF3 or BEL caused a decreaseof PGE2 and VEGF release. SEM and TEM imagesof BBEC and BRPC showed E. coli adhesion toBBEC and BRPC but only in BBEC the invasionoccurs. VEGFR-1 but not VEGFR-2 blockade bythe specific antibody reduced E. coli invasion inBBEC. In our model of BBB infection, a significantloss of BRPC was observed. Following VEGFR-1,but not VEGFR-2 blockade, or in presence ofAACOCF3 or BEL, elevated TEER values, reducedpermeability and BRPC loss were found. Thesedata suggest that VEGFR-1 negatively regulatesBRPC survival and its blockade protects thebarrier integrity. PGs and VEGF could exert a biologicaleffect on BBB, probably by BRPC coverageablation, thus increasing BBB permeability. Ourresults show the role played by the BBEC as wellas BRPC during a bacterial attack on BBB. A betterunderstanding of the mechanisms by which E. colienter the nervous system and how bacteria alterthe communication between endothelial cells andpericytes may provide exciting new insight forclinical intervention.