Chronic cerebral hypoperfusion, a mild ischemic condition, is associated with the cognitive deficits of Alzheimer's disease (AD). Luteolin, a polyphenolic compound found in foods of plant origin, belonging to the flavone subclass of flavonoids, has been shown to possess antioxidant, anti-inflammatory and antitumorigenic properties. In the present study, the effects of luteolin on chronic cerebral hypoperfusion-associated neurocognitive pathologies were investigated by using rats with permanent bilateral common carotid artery occlusion, a rat model of chronic cerebral hypoperfusion. As expected, we found that luteolin could attenuate cognitive dysfunction in chronic cerebral hypoperfused rats, as assessed using Morris water maze tests. Daily oral administration of luteolin (50, 100 and 200 mg/kg) significantly scavenged oxygen free radicals, enhanced antioxidant potential, decreased the lipid peroxide production and suppressed inflammatory reaction in the cerebral cortex and hippocampus induced by chronic cerebral hypoperfusion. Meanwhile, the results indicated that cerebral hypoperfusion activated nuclear factor-κB (NF-κB), increased the expression of β-site amyloid precursor protein cleaving enzyme (BACE1), as well as elevated amyloid beta (Aβ) levels in the cortex and hippocampus. However, long-term administration of luteolin significantly down-regulated the expression of NF-κB and BACE1, accompanied by diminishing the deposition of Aβ. Our results suggest a potential therapeutic use of luteolin for cerebral hypoperfusion associated cognitive dysfunction in AD.

A corollary of the neuroinflammation hypothesis is that selective suppression of neurotoxic products produced by excessive glial activation will result in neuroprotection. We report here that daily oral administration to mice of the brain-penetrant compound 4,6-diphenyl-3-(4-(pyrimidin-2-yl)piperazin-1-yl)pyridazine (MW01-5-188WH), a selective inhibitor of proinflammatory cytokine production by activated glia, suppressed the human amyloid-beta(A beta) 1-42-induced upregulation of interleukin-1 beta, tumor necrosis factor-alpha, and S100B in the hippocampus. Suppression of neuroinflammation was accompanied by restoration of hippocampal synaptic dysfunction markers synaptophysin and postsynaptic density-95 back toward control levels. Consistent with the neuropathophysiological improvements, MW01-5-188WH therapy attenuated deficits in Y maze behavior, a hippocampal-linked task. Oral MW01-5-188WH therapy begun 3 weeks after initiation of intracerebroventricular infusion of human A beta decreased the numbers of activated astrocytes and microglia and the cytokine levels in the hippocampus without modifying amyloid plaque burden or altering peripheral tissue cytokine upregulation in response to an in vivo inflammatory challenge. The results provide a novel integrative chemical biology proof in support of the neuroinflammation hypothesis of disease progression, demonstrate that neurodegeneration can be attenuated independently of plaque modulation by targeting innate brain proinflammatory cytokine responses, and indicate the feasibility of developing efficacious, safe, and selective therapies for neurodegenerative disorders by targeting key glial activation pathways.

Chronically activated glia associated with amyloid plaques might contribute to neuronal dysfunction in Alzheimer’s disease (AD) through generation of neuroinflammatory molecules. Apolipoprotein E (apoE), also found associated with amyloid plaques, has been hypothesized to serve an anti-inflammatory role in the CNS through its ability to modulate β-amyloid (Aβ)-induced glial activation. To further characterize the effect of apoE on inflammation, we examined the ability of exogenously added human apoE3 and apoE4 to modulate neuroinflammatory responses of cultured rat glia. Apolipoprotein E3 (apoE3) and apoE4 suppressed oligomeric Aβ-induced production of inducible nitric oxide synthase and cyclo-oxygenase-2, supporting an anti-inflammatory role for apoE. Exogenous apoE also inhibited Aβ-induced production of endogenous apoE. However, exogenous apoE in the absence of Aβ stimulated production of the pro-inflammatory cytokine interleukin-1β in an isoform-dependent manner, with apoE4 inducing a significantly greater response than apoE3. These data support the idea that Aβ stimulation of glial apoE limits neuroinflammation but that overproduction of apoE by activated glia might exacerbate inflammation. In addition, the observation that apoE4 has more robust pro-inflammatory activity than apoE3 provides a mechanistic link between the APOE4 allele and AD, and suggests potential apoE-based therapeutic strategies.

Excessive glial activation, with overproduction of cytokines and oxidative stress products, is detrimental and a hallmark of neurodegenerative disease pathology. Suppression of glial activation is a potential therapeutic approach, and protein kinases are targets of some antiinflammatory drugs. To address an unmet need for selective inhibitors of glial activation, we developed a novel 3-amino-6-phenylpyridazine derivative that selectively blocks increased IL-1beta, iNOS, and NO production by activated glia, without inhibition of potentially beneficial glial functions.

Activated glia (astrocytes and microglia) and their associated neuroinflammatory sequelae have been linked to the disease progression of several neurodegenerative disorders, including Alzheimer's disease. We found that the experimental anti-inflammatory drug K252a, an inhibitor of calmodulin regulated protein kinases (CaMKs), can block induction of both the oxidative stress related enzyme iNOS and the proinflammatory cytokine IL-1 beta in primary cortical glial cultures and the microglial BV-2 cell line. We also found that the profile of CaMKIV and CaMKII isoforms in primary cortical glial cultures and BV-2 cells is distinct from that found in neurons. Knowledge of cellular mechanisms and high throughput screens of a pharmacologically focused chemical library allowed the discovery of novel pyridazine-based compounds that are cell permeable ligand modulators of gene regulating protein kinases involved in the induction of iNOS and IL-1 beta in activated glia. Pyridazine-based compounds are attractive for the development of new therapeutics due to the retention of the remarkable pharmacological properties of K252a and related indolocarbazole alkaloids, and presence of enhanced functional selectivity in a comparatively simple structure amenable to diverse synthetic chemistries.