Intracerebral haemorrhage: mechanisms of injury and therapeutic targets

DARPP-32 to quantify intracerebral hemorrhage-induced neuronal death in basal ganglia

Quantification of acute brain injury in basal ganglia is essential for mechanistic and therapeutic studies in experimental intracerebral hemorrhage (ICH). Using conventional counting of degenerating cells based on morphological or immunohistochemical criteria, it is hard to define the boundary of the whole lesion area. Dopamine- and cAMP-regulated phosphoprotein, Mr 32 kDa (DARPP-32) is a cytosolic protein highly enriched in medium-sized spiny neurons of the striatum. We developed new methods for quantifying lesion area by detecting the difference of the DARPP-32 negative area and the hematoma clot, and by measuring DARPP-32 protein level for semi-qualification in rat model of ICH. We found that DARPP-32 negative area around hematoma was present at day-1, peaked at day-3, and decreased at day-14 after ICH, a time course paralleled by DARPP-32 Western blots. The DARPP-32 negative area matched well with the necrotic area determined using propidium iodide. Treatment with an iron chelator, deferoxamine, attenuated the ICH-induced reduction in DARPP-32 protein levels. These results suggest that DARPP-32 is a simple and quantifiable indicator of ICH-induced neuronal death in basal ganglia.

Emerging roles of Nrf2 and phase II antioxidant enzymes in neuroprotection

Phase II metabolic enzymes are a battery of critical proteins that detoxify xenobiotics by increasing their hydrophilicity and enhancing their disposal. These enzymes have long been studied for their preventative and protective effects against mutagens and carcinogens and for their regulation via the Keap1 (Kelch-like ECH associated protein 1)/Nrf2 (Nuclear factor erythroid 2 related factor 2)/ARE (antioxidant response elements) pathway. Recently, a series of studies have reported the altered expression of phase II genes in postmortem tissue of patients with various neurological diseases. These observations hint at a role for phase II enzymes in the evolution of such conditions. Furthermore, promising findings reveal that overexpression of phase II genes, either by genetic or chemical approaches, confers neuroprotection in vitro and in vivo. Therefore, there is a need to summarize the current literature on phase II genes in the central nervous system (CNS). This should help guide future studies on phase II genes as therapeutic targets in neurological diseases. In this review, we first briefly introduce the concept of phase I, II and III enzymes, with a special focus on phase II enzymes. We then discuss their expression regulation, their inducers and executors. Following this background, we expand our discussion to the neuroprotective effects of phase II enzymes and the potential application of Nrf2 inducers to the treatment of neurological diseases.

Susceptibility to intracerebral hemorrhage-induced brain injury segregates with low aerobic capacity in rats

Although low exercise capacity is a risk factor for stroke, the exact mechanisms that underlie this connection are not known. As a model system for exploring the association between aerobic capacity and disease risks we applied two-way artificial selection over numerous generations in rats to produce low capacity runners (LCR) and high capacity runners (HCR). Here we compared intracerebral hemorrhage (ICH)-induced brain injury in both genders of these rat lines. HCR and LCR rats had 100μl blood injected into the right caudate and were killed at days 1, 3, 7 and 28 for brain water content determination, immunohistochemistry, histology, Western blot, and behavioral tests. Compared to male HCRs, male LCRs had more severe ICH-induced brain injury including worse brain edema, necroptosis, brain atrophy, and neurological deficits, but not increased numbers of Fluoro-Jade C positive cells or elevated cleaved caspase-3 levels. This was associated with greater microglial activation, and heme oxygenase-1 and protease activated receptor (PAR)-1 upregulation. In females, edema was also greater in LCRs than in HCRs, although it was less severe in females than in males for both LCRs and HCRs. Thus, ICH-induced brain injury was more severe in LCRs, a model of low exercise capacity, than in HCRs. Increased activation of microglia and PAR-1 may participate mechanistically in increased ICH-susceptibility. Females were protected against ICH-induced brain edema formation in both HCRs and LCRs.