The Molecular Mechanisms of Neuroinflammation in Alzheimer's Disease, the Consequence of Neural Cell Death.

Alzheimer's disease (AD) is accompanied by neural cell loss and memory deficit. Neural cell death, occurring via apoptosis and autophagy, is widely observed in the AD brain in addition to neuroinflammation mediated by necroptosis and the NLRP3 inflammasome. Neurotoxicity induced by amyloid-beta (Aß) and tau aggregates leads to excessive neural cell death and neuroinflammation in the AD brain. During AD progression, uncontrolled neural cell death results in the dysregulation of cellular activity and synaptic function. Apoptosis mediated by pro-apoptotic caspases, autophagy regulated by autophagy-related proteins, and necroptosis controlled by the RIPK/MLKL axis are representative of neural cell death occurred during AD. Necroptosis causes the release of cellular components, contributing to the pro-inflammatory environment in the AD brain. Inordinately high levels of neural cell death and pro-inflammatory events lead to the production of pro-inflammatory cytokines and feed-forward hyper neuroinflammation. Thus, neural cell death and neuroinflammation cause synaptic dysfunction and memory deficits in the AD brain. In this review, we briefly introduce the mechanisms of neural cell death and neuroinflammation observed in the AD brain. Combined with a typical strategy for targeting Aß and tau, regulation of neural cell death and neuroinflammation may be effective for the amelioration of AD pathologies.

Natural Products Targeting Amyloid Beta in Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by severe brain damage and dementia. There are currently few therapeutics to treat this disease, and they can only temporarily alleviate some of the symptoms. The pathogenesis of AD is mainly preceded by accumulation of abnormal amyloid beta (Aß) aggregates, which are toxic to neurons. Therefore, modulation of the formation of these abnormal aggregates is strongly suggested as the most effective approach to treat AD. In particular, numerous studies on natural products associated with AD, aiming to downregulate Aß peptides and suppress the formation of abnormal Aß aggregates, thus reducing neural cell death, are being conducted. Generation of Aß peptides can be prevented by targeting the secretases involved in Aß-peptide formation (secretase-dependent). Additionally, blocking the intra- and intermolecular interactions of Aß peptides can induce conformational changes in abnormal Aß aggregates, whereby the toxicity can be ameliorated (structure-dependent). In this review, AD-associated natural products which can reduce the accumulation of Aß peptides via secretase- or structure-dependent pathways, and the current clinical trial states of these products are discussed.

5-Methylthiopentyl Isothiocyanate, a Sulforaphane Analogue, Inhibits Pro-inflammatory Cytokines by Regulating LPS/ATP-mediated NLRP3 Inflammasome Activation.

BACKGROUND: Pro-inflammatory cytokines secreted from activated macrophages and astrocytes are crucial mediators of inflammation for host defense. Among them, the secretion of IL-1ß, a major pro-inflammatory cytokine, is especially mediated by the activation of NLRP3 inflammasome. Pro-IL-1ß, which is produced in response to the invaded pathogens, such as LPS, is cleaved and matured in the NLRP3 inflammasome by the recognition of ATP. Excessively activated IL-1ß induces other immune cells, resulting in the up-regulation of inflammation. Therefore, regulation of NLRP3 inflammasome can be a good strategy for alleviating inflammation. OBJECTIVE: Our study aimed to examine whether 5-methylthiopentyl isothiocyanate, a sulforaphane analogue (berteroin), has an anti-inflammatory effect on the NLRP3 inflammasome activation induced by LPS and ATP. METHODS: Primary bone marrow-derived macrophages (BMDMs) and astrocytes were stimulated by LPS and ATP with the treatment of 5-methylthiopentyl isothiocyanate, a sulforaphane analogue. The secretion of pro-inflammatory cytokines was measured by ELISA, and the expression level of NLRP3 inflammasome-associated proteins was detected by western blot. The association of NLRP3 inflammasome was assessed by co-immunoprecipitation, and the formation of ASC specks was evaluated by fluorescent microscope. RESULTS: 5-Methylthiopentyl isothiocyanate, a sulforaphane analogue (berteroin), decreased the release of pro-inflammatory cytokines, IL-1ß, and IL-6 in the BMDMs. Berteroin notably prevented the formation of both NLRP3 inflammasome and ASC specks, which reduced the secretion of IL-1ß. Additionally, berteroin reduced the IL-1ß secretion and cleaved IL-1ß expression in the primary astrocytes. DISCUSSION AND CONCLUSION: These results indicated the anti-inflammatory effects of 5-methylthiopentyl isothiocyanate (berteroin) by regulating NLRP3 inflammasome activation, suggesting that berteroin could be the potential natural drug candidate for the regulation of inflammation.

The Derivatives of Cromolyn Ameliorate the Abnormal Misfolding of Amyloid Proteins and Neuroinflammation in the Neural Cells.

BACKGROUND: The representative symptom of Alzheimer's Disease (AD) has mainly been mentioned to be misfolding of amyloid proteins, such as amyloid-beta (Aß) and tau protein. In addition, the neurological pathology related to neuroinflammatory signaling has recently been raised as an important feature in AD. Currently, numerous drug candidates continue to be investigated to reduce symptoms of AD, including amyloid proteins misfolding and neuroinflammation. OBJECTIVE: Our research aimed to identify the anti-AD effects of two chemical derivatives modified from cromoglicic acid, CNU 010 and CNU 011. METHODS: CNU 010 and CNU 011 derived from cromoglicic acid were synthesized. The inhibitory effects of Aß and tau were identified by thioflavin T assay. Moreover, western blots were conducted with derivates CNU 010 and CNU 011 to confirm the effects on inflammation. RESULTS: CNU 010 and CNU 011 significantly inhibited the aggregation of Aß and tau proteins. Moreover, they reduced the expression levels of mitogen-activated protein (MAP) kinase and nuclear factor kappa-light-chain-enhancer of activated B cells (NF- κB) signaling proteins, which are representative early inflammatory signaling markers. Also, the inhibitory effects on the lipopolysaccharide (LPS)-induced cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) expression referring to late inflammation were confirmed. CONCLUSION: Our results showing multiple beneficial effects of cromolyn derivatives against abnormal aggregation of amyloid proteins and neuroinflammatory signaling provide evidence that CNU 010 and CNU 011 could be further developed as potential drug candidates for AD treatment.

Effect of Homogenization Pressure on Plasmin Activity and Mechanical Stress-Induced Fat Aggregation of Commercially Sterilized Ultra High Temperature Milk during Storage.

Commercially sterilized ultra high temperature (UHT) milk was manufactured at different homogenization pressures (20, 25, and 30 MPa), and changes in fat particle size, mechanical stress-induced fat aggregation, plasmin activity, and lipid oxidation were monitored during ambient storage of the UHT milk for up to 16 wk. The particle sizes of milk fat globules were significantly decreased as homogenization pressure increased from 20 to 30 MPa (p<0.05). The presence of mechanical stress-induced fat aggregates in milk produced at 20 MPa was significantly higher than for UHT milk produced at either 25 or 30 MPa. This difference was maintained all throughout the storage. There were no significant differences in plasmin activity, trichloroacetic acid (12%, w/v) soluble peptides, and the extent of lipid oxidation. Based on these results, an increase of homogenization pressure from 20 (the typical homogenization pressure employed in the Korea dairy industry) to 25-30 MPa significantly decreased mechanical stress-induced fat aggregation without affecting susceptibility to lipid oxidation during storage.