BCL-2 transduction, using a herpes simplex virus amplicon, protects hippocampal neurons from transient global ischemia

Transient global ischemia results in selective neuronal damage of hippocamp al CA1 neurons. Five minutes of bilateral common carotid artery occlusion, in the Mongolian gerbil, effectively restricts forebrain blood flow, result ing in a delayed neuronal death of CA1 pyramidal cells. While there is a de lay of approximately 72 h in the appearance of cell death, markers related to the mechanism of ischemic death become apparent well before neurons die. Ischemia-induced increases in the cell-death-promoting protein, bar, may d isrupt the bcl-2/bax ratio necessary for normal neuronal functioning and th us promote transient ischemic death. In order to locally maintain this crit ical bcl-2/bax ratio and thus protect CA1 neurons from delayed neuronal dea th, a herpes simplex viral (HSV) vector was used to selectively introduce h uman bcl-2, under the control of the herpes IF 4/5 promoter, into the CA1 r egion of the gerbil hippocampus. Twenty-four hours prior to ischemia surger y, 1 mu l of HSVbcl-2 was infused unilaterally into the CA1 region at a rat e of 2 nl/min. Seventy-two hours after ischemia the animals were sacrificed and processed using Nissl, silver degeneration, and immunohistochemical (a nti-human bcl-2) staining. Immunohistochemistry demonstrated both glial and neuronal bcl-2 expression around the HSVbcl-2 infusion site. The evaluatio n following silver degeneration staining indicated a further degeneration o f CA1 neurons in the immediate area of the viral vector infusion. This dama ge seems to be the result of cellular debris associated with the processing of the viral amplicons. Silver degeneration staining is not present in the areas that demonstrate bcl-2 staining. These neurons appear to have been r escued from ischemic damage. This result was confirmed using the Nissl stai ning. Therefore, by altering the local ratio of bcl-2/bax using the HSVbcl- 2 vector one may protect CA1 pyramidal cell from the delayed neuronal death of transient global ischemia. (C) 1999 Academic Press.