Cytosolic Ca2+ oscillations in human cerebrovascular endothelial cells after subarachnoid hemorrhage
Molecular mechanisms of cerebral vasospasm after subarachnoid hemorrhage (SAH) include specific modes of cell signaling like activation of nuclear factor (NF)-kB and vascular cell adhesion molecules (VCAM)-1 expression. The study's hypothesis is that cisternal cerebral spinal fluid (CSF) from patients after SAH may cause Ca2+ oscillations which induce these modes of vascular inflammation in an in vitro model of human cerebral endothelial cells (HCECs). HCECs were incubated with cisternal CSF from 10 SAH patients with confirmed cerebral vasospasm. The CSF was collected on days 5 and 6 after hemorrhage. Cytosolic Ca2+ concentrations and cell contraction as an indicator of endothelial barrier function were examined by fura-2 microflurometry. Activation of NF-κB and VCAM-1 expression were measured by immunocytochemistry. Incubation of HCEC with SAH-CSF provoked cytosolic Ca2+ oscillations (0.31 ± 0.09 per min), cell contraction, NF-κB activation, and VCAM-1 expression, whereas exposure to native CSF had no significant effect. When endoplasmic reticulum (ER) Ca2+-ATPase and ER inositol trisphosphate (IP3)-sensitive Ca2+ channels were blocked by thapsigargin or xestospongin, the frequency of the Ca2+ oscillations was reduced significantly. In analogy to the reduction of Ca2+ oscillation frequency, the blockers impaired HCEC contraction, NF-κB activation, and VCAM-1 expression. Cisternal SAH-CSF induces cytosolic Ca2+ oscillations in HCEC that results in cellular constriction, NF-κB activation, and VCAM-1 expression. The Ca2+ oscillations depend on the function of ER Ca2+-ATPase and IP3-sensitive Ca2+ channels.