Insulin protects cardiomyocytes against reoxygenation-induced hypercontracture. This is due to acceleration of cytosolic [Ca2+] recovery by enhanced Ca2+ sequestration into the sarcoplasmic reticulum via SERCA activation. This protective mechanism is activated through the survival pathway consisting of PI 3-kinase, eNOS, and PKG.
Molecular mechanisms of cerebral vasospasm after subarachnoid hemorrhage (SAH) include specific modes of cell signaling like activation of nuclear factor (NF)-jB 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 Ca 2 + 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 Ca 2 + concentrations and cell contraction as an indicator of endothelial barrier function were examined by fura-2 microflurometry. Activation of NF-jB and VCAM-1 expression were measured by immunocytochemistry. Incubation of HCEC with SAH-CSF provoked cytosolic Ca 2 + oscillations (0.31±0.09 per min), cell contraction, NF-jB activation, and VCAM-1 expression, whereas exposure to native CSF had no significant effect. When endoplasmic reticulum (ER) Ca 2 + -ATPase and ER inositol trisphosphate (IP3)-sensitive Ca 2 + channels were blocked by thapsigargin or xestospongin, the frequency of the Ca 2 + oscillations was reduced significantly. In analogy to the reduction of Ca 2 + oscillation frequency, the blockers impaired HCEC contraction, NF-jB activation, and VCAM-1 expression. Cisternal SAH-CSF induces cytosolic Ca 2 + oscillations in HCEC that results in cellular constriction, NF-jB activation, and VCAM-1 expression. The Ca 2 + oscillations depend on the function of ER Ca 2 + -ATPase and IP3-sensitive Ca 2 + channels.
PARP represents a downstream effector of NADP(H) oxidase and acts as a necessary intermediate step for the hypoxic proliferative response of endothelial cells.
sGC/PKG activation during reperfusion reduces reperfusion-induced endothelial intercellular gap formation by attenuation of cytosolic calcium overload and reduction of contractile activation in endothelial cells. This mechanism protects the heart against reperfusion-induced oedema.
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