Nuclear receptor nur77 promotes cerebral cell apoptosis and induces early brain injury after experimental subarachnoid hemorrhage in rats.

Nur77 is a potent proapoptotic member of the nuclear receptor superfamily that is expressed predominantly in brain tissue. It has been demonstrated that Nur77 mediates apoptosis in multiple organs. Nur77-mediated early brain injury (EBI) involves a conformational change in BCL-2 and triggers cytochrome C (cytoC) release resulting in cellular apoptosis. This study investigates whether Nur77 can promote cerebral cell apoptosis after experimentally induced subarachnoid hemorrhage (SAH) in rats. Sprague Dawley rats were randomly assigned to three groups: 1) untreated group, 2) treatment control group, and 3) SAH group. The experimental SAH group was divided into four subgroups, corresponding to 12 hr, 24 hr, 48 hr, and 72 hr after experimentally induced SAH. It remains unclear whether Nur77 can play an important role during EBI after SAH as a proapoptotic protein in cerebral cells. Cytosporone B (Csn-B) was used to demonstrate that Nur77 could be enriched and used to aggravate EBI after SAH. Rats treated with Csn-B were given an intraperitoneal injection (13 mg/kg) 30 min after experimentally induced SAH. We found that Nur77 promotes cerebral cell apoptosis by mediating EBI and triggering a conformational change in BCL-2, resulting in cytoC release. Nur77 activity, along with cerebral cell apoptosis, peaked at 24 hr after SAH onset. After induction of SAH, an injection of Csn-B, an agonist for Nur77, enhanced the expression and function of Nur77. In summary, we have demonstrated the proapoptotic effect of Nur77 within cerebral cells, an effect that can be further exacerbated with Csn-B stimulation.