Potential Role of PUMA in Delayed Death of Hippocampal CA1 Neurons After Transient Global Cerebral Ischemia

Abstract

p53-upregulated modulator of apoptosis (PUMA), a BH3-only member of the Bcl-2 protein family, is required for p53-dependent and -independent forms of apoptosis. PUMA localizes to mitochondria and interacts with antiapoptotic Bcl-2 and Bcl-X(L) or proapoptotic Bax in response to death stimuli. Although studies have shown that PUMA is associated with pathomechanisms of cerebral ischemia, clearly defined roles for PUMA in ischemic neuronal death remain unclear. The purpose of this study was to determine potential roles for PUMA in cerebral ischemia. Five minutes of transient global cerebral ischemia (tGCI) were induced by bilateral common carotid artery occlusion combined with hypotension. PUMA was upregulated in vulnerable hippocampal CA1 neurons after tGCI as shown by immunohistochemistry. In Western blot and coimmunoprecipitation analyses, PUMA localized to mitochondria and was bound to Bcl-X(L) and Bax in the hippocampal CA1 subregion after tGCI. PUMA upregulation was inhibited by pifithrin-alpha, a specific inhibitor of p53, suggesting that PUMA is partly controlled by the p53 transcriptional pathway after tGCI. Furthermore, reduction in oxidative stress by overexpression of copper/zinc superoxide dismutase, which is known to be protective of vulnerable ischemic hippocampal neurons, inhibited PUMA upregulation and subsequent hippocampal CA1 neuronal death after tGCI. These results imply a potential role for PUMA in delayed CA1 neuronal death after tGCI and that it could be a molecular target for therapy.