Alzheimer's disease (AD) is a neurodegenerative disease with major clinical hallmarks of memory loss, dementia, and cognitive impairment. Neuroinflammation is involved in the onset of several neurodegenerative disorders. Astrocyte is the most abundant type of glial cells in the central nervous system (CNS) and appears to be involved in the induction of neuroinflammation. Under stress and injury, astrocytes become astrogliotic leading to an upregulation of the expression of proinflammatory cytokines and chemokines, which are associated with the pathogenesis of AD. Cytokines and related molecules play roles in both neuroprotection and neurodegeneration in the CNS. During early AD pathogenesis, amyloid beta (Aβ), S100B and IL-1β could bring about a vicious cycle of Aβ generation between astrocytes and neurons leading to chronic, sustained and progressive neuroinflammation. In advanced stages of AD, TRAIL secreted from astrocytes have been shown to bind to death receptor 5 (DR5) on neurons to trigger apoptosis in a caspase-8-dependent manner. Furthermore, astrocytes could be reactivated by TGFβ1 to generate more Aβ and to undergo the aggravating astrogliosis. TGFβ2 was also observed to cooperate with Aβ to cause neuronal demise by destroying the stability of lysosomes in neurons. Inflammatory molecules can be either potential biomarkers for diagnosis or target molecules for therapeutic intervention. Understanding their roles and their relationship with activated astrocytes is particularly important for attenuating neuroinflammation in the early stage of AD. The main purpose of this review is to provide a comprehensive insight into the role of astrocytes in the neuroinflammatory pathogenesis of AD.

BACKGROUND: The new heart allocation system in the United States prioritizes patients supported by temporary mechanical circulatory support (TMCS) devices over those with uncomplicated durable continuous-flow left ventricular assist devices (CF-LVADs), which may increase the number of patients bridged to transplant with TMCS. Limited data are available in guiding post-transplant outcomes with various TMCS devices. We sought to describe post-transplant outcome and identify clinical variables associated with post-transplant outcome in patients bridged to transplant with TMCS. METHODS: Using data from the International Society for Heart and Lung Transplantation Thoracic Transplant Registry, we included subjects who underwent transplantation between 2005 and 2016 with known use of mechanical circulatory support. Pre-transplant recipient, donor, and transplant-specific variables were abstracted. The primary outcome was patient survival at 1-year post-transplant. Outcomes of patients bridged to transplant with TMCS were compared with those of patients bridged with CF-LVADs. Cox regression analyses were performed to identify clinical variables associated with the outcomes. RESULTS: There were 6,528 patients bridged to transplant with the following types of mechanical circulatory support: durable CF-LVADs (n = 6,206), extracorporeal membrane oxygenation (ECMO, n = 134), percutaneous temporary CF-LVADs (n = 75), surgically implanted temporary CF-LVADs (n = 38) or surgically implanted temporary BiVAD (n = 75). Bridging with ECMO (hazard ratio 3.79, 95% confidence interval [CI] 2.69−5.34, p < 0.001) or percutaneous temporary CF-LVADs (hazard ratio 1.83, 95% CI 1.09−3.08, p = 0.02) was independently associated with higher risk of mortality. Additional risk factors included older donor age, female/male donor-recipient match, older recipient age, higher recipient body mass index, higher recipient creatinine, and prolonged ischemic time.

Background: Significant improvements in myocardial structure and function have been reported in some patients with advanced heart failure (termed responders [R]) following left ventricular assist device (LVAD)–induced mechanical unloading. This therapeutic strategy may alter myocardial energy metabolism in a manner that reverses the deleterious metabolic adaptations of the failing heart. Specifically, our previous work demonstrated a post-LVAD dissociation of glycolysis and oxidative-phosphorylation characterized by induction of glycolysis without subsequent increase in pyruvate oxidation through the tricarboxylic acid cycle. The underlying mechanisms responsible for this dissociation are not well understood. We hypothesized that the accumulated glycolytic intermediates are channeled into cardioprotective and repair pathways, such as the pentose-phosphate pathway and 1-carbon metabolism, which may mediate myocardial recovery in R. Methods: We prospectively obtained paired left ventricular apical myocardial tissue from nonfailing donor hearts as well as R and nonresponders at LVAD implantation (pre-LVAD) and transplantation (post-LVAD). We conducted protein expression and metabolite profiling and evaluated mitochondrial structure using electron microscopy. Results: Western blot analysis shows significant increase in rate-limiting enzymes of pentose-phosphate pathway and 1-carbon metabolism in post-LVAD R (post-R) as compared with post-LVAD nonresponders (post-NR). The metabolite levels of these enzyme substrates, such as sedoheptulose-6-phosphate (pentose phosphate pathway) and serine and glycine (1-carbon metabolism) were also decreased in Post-R. Furthermore, post-R had significantly higher reduced nicotinamide adenine dinucleotide phosphate levels, reduced reactive oxygen species levels, improved mitochondrial density, and enhanced glycosylation of the extracellular matrix protein, α-dystroglycan, all consistent with enhanced pentose-phosphate pathway and 1-carbon metabolism that correlated with the observed myocardial recovery. Conclusions: The recovering heart appears to direct glycolytic metabolites into pentose-phosphate pathway and 1-carbon metabolism, which could contribute to cardioprotection by generating reduced nicotinamide adenine dinucleotide phosphate to enhance biosynthesis and by reducing oxidative stress. These findings provide further insights into mechanisms responsible for the beneficial effect of glycolysis induction during the recovery of failing human hearts after mechanical unloading.