gw-3965 and Brain-Ischemia

Chronic cerebral hypoperfusion (CCH), a leading cause of various cerebrovascular diseases, leads to cognitive dysfunction due to neuron loss and impaired neurogenesis. Liver X receptors (LXRs), including LXRα and LXRβ isoforms, are crucial for cholesterol metabolism, synaptic plasticity as well as neurogenesis. However, it is not clear the potential roles of LXRs in the pathogenesis of cognitive impairment induced by CCH. In this study, we demonstrated that LXRβ expression decreased in hippocampus of CCH mice. GW3965, a synthetic dual agonist for both LXRα and LXRβ, ameliorated impairment of learning and memory in CCH mice by promoting neuronal survival and neural stem cells (NSCs) proliferation in dentate gyrus (DG) of CCH mice. The proliferative effects of GW3965 were further confirmed in cultured neural progenitor cells (NPCs) and showed in a concentration-dependent manner. Moreover, GW3965 phosphorylated protein kinase B (Akt) at Ser473 in a time- and concentration-dependent manner in NPCs. Furthermore, both LY294002, an inhibitor for phosphoinositide-3-kinase (PI3K), and short hairpin RNAs for LXRβ knockdown, abrogated GW3965-induced Akt phosphorylation, and therefore abolished GW3965-mediated proliferation-promoting of NPCs. All the data suggested that GW3965 ameliorated impaired cognitive functions in CCH by promoting NSC proliferation through PI3K/Akt pathway followed LXRβ activation. This study correlates a deficit of LXRβ in cognitive dysfunction in CCH with impaired neurogenesis in hippocampus, and LXRs may serve as a potential therapeutic target for chronic cerebral ischemia.

Topics: Animals; Benzoates; Benzylamines; Brain Ischemia; Cell Proliferation; Cognitive Dysfunction; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Neural Stem Cells; Neurogenesis

The blood-brain barrier (BBB) consists of dense contacts between endothelial cells, the tight junctions, which are complemented by membrane-bound transporters belonging to the ATP-binding cassette (ABC) transporter family. Liver X receptors (LXR) have previously been shown to stabilize the integrity of atherosclerotic noncerebral arteries. Their effects on ischemic cerebral vessels are still unknown. By delivering LXR agonists, T0901317 and GW3965, to mice submitted to 30 minutes intraluminal middle cerebral artery occlusion, we show that LXR activation reduces brain swelling and decreases BBB permeability by upregulating LXR's target calpastatin that deactivates calpain-1/2, stabilizing p120 catenin. p120 catenin specifically interacts with RhoA and Cdc42, inactivating the former and overactivating the latter, thus restoring the postischemic expression, phosphorylation and interaction of the tight junction proteins occludin and zona occludens-1. Moreover, LXR activation deactivates matrix metalloproteases-2/9 and inhibits microvascular apoptosis by deactivating JNK1/2 and caspase-3. In addition to the cholesterol transporters ABCA1 and ABCG1, which have previously been shown to be upregulated by LXR in noncerebral vessels, LXR activation increases the abundance of the drug transporters ABCB1 and ABCC1 on ischemic brain capillaries, as we further show. That LXR activation promotes endothelial integrity in different ways makes this receptor attractive as target for stroke therapies.

Topics: Animals; ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily B, Member 1; Benzoates; Benzylamines; Blood-Brain Barrier; Brain; Brain Edema; Brain Ischemia; Disease Models, Animal; Endothelial Cells; Hydrocarbons, Fluorinated; Liver X Receptors; Mice; Mice, Inbred C57BL; Middle Cerebral Artery; Multidrug Resistance-Associated Proteins; Orphan Nuclear Receptors; Sulfonamides; Tight Junctions; Up-Regulation

Recent studies have found that liver X receptors (LXRs) agonists decrease brain inflammation and exert neuroprotective effect. The aim of this study was to examine the mechanisms of action of liver X receptor agonist GW3965 against brain injury following global cerebral ischemia in the rat. The 48 male SD (Sprague-Dawley) rats were randomly partitioned into three groups: sham, global ischemia (4-vessel occlusion for 15 min; 4VO) treated with vehicle and global ischemia treated with GW3965 (20 mg/kg, via i.p. injection at 10 min after reperfusion). The functional outcome was determined by neurological evaluation at 24 h post ischemia and by testing rats in T maze at 3 and 7 days after reperfusion. The rats' daily body weight, incidence of seizures and 72 h mortality were also determined. After Nissl staining and TUNEL in coronal brain sections, the numbers of intact and damaged cells were counted in the CA1 sector of the hippocampus. The expression of phosphorylated inhibitor of kappaB (p-IkappaBalpha), nuclear factor-kappaB (NF-kappaB) subunit p65, and cyclo-oxygenase-2 (COX-2) were analyzed with Western blot at 12 h after reperfusion. GW3965 tended to reduce 72 h mortality and the incidence of post-ischemic seizures. GW3965-treated rats showed an improved neuronal survivability in CA1 and a significant increase in the percentage of spontaneous alternations detected in T-maze on day 7 after ischemia. GW3965-induced neuroprotection was associated with a significant reduction in nuclear translocation of NF-kB p65 subunit and a decrease in the hippocampal expression of NF-kB target gene, COX-2. LXR receptor agonist protects against neuronal damage following global cerebral ischemia. The mechanism of neuroprotection may include blockade of NF-kappaB activation and the subsequent suppression of COX-2 in the post ischemic brain.

Topics: Active Transport, Cell Nucleus; Animals; Benzoates; Benzylamines; Brain Ischemia; Cyclooxygenase 2; Down-Regulation; Encephalitis; Gene Expression Regulation; Hippocampus; Liver X Receptors; Male; Maze Learning; Nerve Degeneration; Neurons; Neuroprotective Agents; NF-kappa B; Orphan Nuclear Receptors; Rats; Rats, Sprague-Dawley; Transcription Factor RelA

Stroke is characterized by massive inflammation in areas surrounding the injury that magnifies damage to the brain. The liver X receptors (LXRs) are nuclear receptors that regulate cholesterol, lipid, and glucose metabolism. Synthetic LXR agonists have potent anti-inflammatory properties in a variety of settings, including neuroinflammation. However, the ability of LXR agonists to suppress stroke-associated inflammation has not been evaluated. Here, we have used time-lapse magnetic resonance imaging (MRI) to show that a single dose of an LXR ligand administered post-injury dramatically reduces brain damage in a model of acute brain ischemia. Neuroprotection was associated with suppression of neuroinflammation.

Topics: Animals; Benzoates; Benzylamines; Brain Ischemia; Cerebral Infarction; Disease Models, Animal; DNA-Binding Proteins; Ligands; Liver X Receptors; Magnetic Resonance Imaging; Male; Orphan Nuclear Receptors; Rats; Rats, Sprague-Dawley; Receptors, Cytoplasmic and Nuclear

The liver X receptors (LXRs) belong to the nuclear receptor superfamily and act as transcriptional regulators of cholesterol metabolism in several tissues. Recent work also has identified LXRs as potent antiinflammatory molecules in macrophages and other immune cells. Combined changes in lipid and inflammatory profiles are likely mediating the protective role of LXRs in models of chronic injury like atherosclerosis. These beneficial actions, however, have not been illustrated in other models of acute injury such as stroke in which inflammation is an important pathophysiological feature.. We have studied LXR expression and function in the course of experimental stroke caused by permanent middle cerebral artery occlusion in rats and mice. Here, we show that administration of the synthetic LXR agonists GW3965 or TO901317 after the ischemic occlusion improves stroke outcome as shown by decreased infarct volume area and better neurological scores in rats. Neuroprotection observed with LXR agonists correlated with decreased expression of proinflammatory genes in the brain and with reduced nuclear factor-kappaB transcriptional activity. Loss of function studies using LXRalpha,beta(-/-) mice demonstrated that the effect of LXR agonists is receptor specific. Interestingly, infarcted brain area and inflammatory signaling were significantly extended in LXRalpha,beta(-/-) mice compared with control animals, indicating that endogenous LXR signaling mediates neuroprotection in this setting.. This work highlights the transcriptional action of LXR as a protective pathway in brain injury and the potential use of LXR agonists as therapeutic agents in stroke.

Topics: Animals; Benzoates; Benzylamines; Brain; Brain Ischemia; DNA-Binding Proteins; Inflammation; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Neuroprotective Agents; Orphan Nuclear Receptors; Rats; Rats, Inbred F344; Receptors, Cytoplasmic and Nuclear; Stroke