Nampt/PBEF/Visfatin Exerts Neuroprotective Effects Against Ischemia/Reperfusion Injury via Modulation of Bax/Bcl-2 Ratio and Prevention of Caspase-3 Activation

Abstract

Nicotinamide phosphoribosyl transferase/pre-B cell colony-enhancing factor/visfatin (Nampt/PBEF/visfatin) is an adipocytokine. By synthesizing nicotinamide adenine dinucleotide (NAD(+)), Nampt/PBEF/visfatin functions to maintain an energy supply that has critical roles in cell survival. Cerebral ischemia leads to energy depletion and eventually neuronal death by apoptosis in specific brain regions specially the hippocampus. However, the role of Nampt/PBEF/visfatin in brain and cerebral ischemia remains to be investigated. This study investigated the role of administration Nampt/PBEF/visfatin in hippocampal CA3 area using a transient global cerebral ischemia model. Both common carotid arteries were occluded for 20 min followed by reperfusion. Saline as a vehicle and Nampt/PBEF/visfatin at a dose of 100 ng were injected intracerebroventricularly (ICV) at the time of cerebral reperfusion. To investigate the underlying mechanisms of Nampt/PBEF/visfatin neuroprotection, levels of expression of apoptosis-related proteins (caspase-3 activation, Bax protein levels, and Bcl-2 protein levels) 96 h after ischemia were determined by immunohistochemical staining. The number of active caspase-3-positive neurons in CA3 was significantly increased in the ischemia group, compared with the sham group (P < 0.001), and treatment with Nampt/PBEF/visfatin significantly reduced the ischemia/reperfusion-induced caspase-3 activation, compared to the ischemia group (P < 0.05). Also, results indicated a significant increase in Bax/Bcl-2 ratio in the ischemia group, compared with the sham group (P < 0.01). However, treatment with Nampt/PBEF/visfatin significantly attenuated the ischemia/reperfusion-induced increase in Bax/Bcl-2 ratio, compared with the ischemia group (P < 0.05). This study has indicated that Nampt/PBEF/visfatin entails neuroprotective effects against ischemia injury when used at the time of cerebral reperfusion. These neuroprotective mechanisms of Nampt/PBEF/visfatin occur through decrease the expression ofproapoptotic proteins (cleaved caspase-3 and Bax) and, on the other hand, increase the expression ofantiapoptotic proteins (Bcl-2). Thus, our findings indicate that Nampt/PBEF/visfatin is a new therapeutic target for cerebral ischemia.

Pre-B-cell colony-enhancing factor protects against apoptotic neuronal death and mitochondrial damage in ischemia

“…In the present study, we also showed that AAV-mediated PBEF overexpression significantly reduced caspase-3 activation during OGD stimulation in primary neuronal cultures. This finding is consistent with results showing that inhibition of PBEF by its inhibitor FK866 increases the expression of cleaved caspase-3 in OGD model of cultured neurons and recombinant PBEF administration through intracerebroventricular injection decreases caspase-3 activity in the rat hippocampal CA3 region after transient global cerebral ischemia836. Thus our study has established that PBEF can protect against apoptotic neuronal death through both caspase-independent and caspase-dependent pathways.…”

“…For example, in the myocardial injury model, PBEF can delay or inhibit mitochondrial permeability transition pore (mPTP) opening both in situ murine heart and the isolated murine cardiomyocytes52. Meanwhile, PBEF was found to inhibit apoptosis and prevent metabolic dysfunction via regulating the expression of mitochondrial-dependent anti-apoptotic protein Bcl-2, as well as pro-apoptotic proteins, such as Bax and cytochrome C36. These regulations depend on the activation of pro-survival kinases, PI3K/AKT and MEK1/2, mediated-signaling pathways.…”

Mitochondrial function in hypoxic ischemic injury and influence of aging

“…Nampt levels are reduced with aging and stress (Hsu et al , 2009), resulting in decreased NAD + and decreased SIRT1 activity (Imai, 2011). Accordingly, overexpression of Nampt in the heart (Hsu et al , 2009) and brain (Erfani et al , 2015) has been shown to reduce infarct size and apoptosis in response to ischemia and reperfusion. In a negative feedback loop, Nampt is also regulated by SIRT1 mediated deacetylation and inactivation of its transcription factors (Ramsey et al , 2009).…”

Pre-ischemic exercise reduces apoptosis in hippocampal CA3 cells after cerebral ischemia by modulation of the Bax/Bcl-2 proteins ratio and prevention of caspase-3 activation

“…We are faced with technical limitations in separating the CA3 area from other parts of the hippocampus for RT-PCR and Western blot analysis; we used immunohistochemical staining to better detect protein expression. Immunohistochemical staining was performed on 7-lm tissue sections (three sections per animal) [28]. Briefly, tissue sections were incubated for 30 min at 60°C, rehydrated through a descending alcohol series and treated with 10 % hydrogen peroxide in methanol for 10 min to reduce endogenous peroxidase activity.…”