Background
The brain endothelial cells (BECs) are essential for protecting the central nervous system (CNS) from xenobiotics and pathogens, including Neisseria meningitidis, while maintaining CNS homeostasis through tight junction (TJ) proteins and specialized transporters. Among these, multidrug resistance (MDR) transporters such as P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are pivotal in restricting the entry of neurotoxic substances. Although the impact of N. meningitidis infection on BBB TJ is well-documented, its effect on MDR transporters remains largely unexplored.
Methods
We employed induced pluripotent stem cell-derived brain-like endothelial cells (iBECs) as an in vitro BECs model due to their human-like morphology and expression of junctional proteins and MDR transporters. iBECs were exposed to various N. meningitidis strains, isogenic mutants, heat-inactivated bacteria, conditioned media, or purified capsule polysaccharide (CPS). P-gp and BCRP activities were assessed using intracellular accumulation assays with Rhodamine 123 and Chlorin e6, respectively, in the presence of P-gp inhibitors cyclosporin A and PSC833 and BCRP inhibitor Ko143. Gene expression and protein levels were determined by qPCR and western blotting, and sphingolipid quantification was performed via liquid chromatography tandem-mass spectrometry (LC-MS/MS).
Results
Infection of iBECs with N. meningitidis inhibited P-gp activity, whereas BCRP activity remained unaffected. P-gp inhibition occurred without changes in gene expression or protein abundance. Cells infected with N. meningitidis showed reduced efficacy of P-gp inhibitors, an effect not seen with the BCRP inhibitor Ko143. N. meningitidis CPS was identified as a key factor in modulating P-gp activity. Notably, the inhibitory effect of N. meningitidis on P-gp activity was blocked by a specific sphingosine 1-phosphate receptor 1 (S1PR1) antagonist as well as by sphingosine kinase inhibitors, revealing a mechanistic link between S1PR1 signaling and P-gp modulation during infection. Furthermore, S1PR1 was upregulated in infected iBECs. Although LC-MS/MS measurement showed no increase in S1P levels in infected cells compared to uninfected controls, these findings suggest a crucial role for S1PR1 signaling in mediating the observed effects.
Conclusions
These findings demonstrate that N. meningitidis infection impairs P-gp function through S1PR1-dependent pathways, suggesting that targeting this signaling cascade may offer a novel therapeutic strategy to preserve BBB integrity during bacterial infections.
