In vitro evidence of the role of hemoglobin during vasospasm on the modifications of the expression of PKCalpha and zeta.

The cellular events leading to cerebral vasospasm after subarachnoid hemorrhage (SAH) are poorly understood, although the family of protein kinase C (PKC) is already known to play crucial roles in this pathology. Hemoglobin (Hb) is one of the major causes of the cerebral vasospasm that follows SAH. In the present study we investigated whether Hb can in vitro regulate PKC expression in endothelial as opposed to smooth-muscle cells. The levels of expression of PKCalpha and PKCzeta were quantitatively determined by means of computer-assisted fluorescence microscopy in the A7r5 smooth-muscle rat cells and human umbilical endothelial cells (HUVECs). Hb significantly modified both calcium-dependent PKCalpha and calcium-independent PKCzeta expression in HUVECs and A7r5 smooth-muscle rat cells. Our data showed that, in vitro, Hb promptly and markedly modified the levels of expression of both calcium-dependent PKCalpha and calcium-independent PKCzeta. We are currently investigating the effects of specific PKC antagonists associated or not with calcium channel blockers on the expression of PKC and the in vivo severity of SAH-induced vasospasm. Our results encourage the prophylactic use of specific PKC isoform antagonists associated with calcium channel blockers early after SAH to prevent cerebral vasospasm.