Chronic intraperitoneal injection of polyethylene glycol 200 in mice induces hippocampal neuroinflammation.

In vivo treatment of hydrophobic substances requires the use of organic solvents, which are often toxic. Consequently, polyethylene glycols (PEGs), which are considered as nontoxic, have been widely used for many years in chemistry and biology. We used PEG 200, which was administrated by intraperitoneal (i.p.) injection once a week to mice. After 4 months of injections, at the dose of 1.67 mL/kg, a surprising increase in expression of GFAP (glial fibrillary acidic protein) and IBA1 (ionized calcium binding adaptor molecule 1), glial markers of astrocytes and microglia respectively, was observed in the mice's hippocampus. These results were associated with a dramatic increase in pro-inflammatory cytokine interleukin-1ß (IL-1ß) expression, all together suggesting an inflammatory process. It is important to communicate these results to the scientific community to provide awareness of this potential effect when PEG 200 is used under similar conditions as a vehicle in mice.

Longitudinal follow-up of autophagy and inflammation in brain of APPswePS1dE9 transgenic mice.

BACKGROUND: In recent years, studies have sought to understand the mechanisms involved in the alteration of autophagic flux in Alzheimer's disease (AD). Alongside the recent description of the impairment of lysosomal acidification, we wanted to study the relationships between inflammation and autophagy, two physiological components deregulated in AD. Therefore, a longitudinal study was performed in APPswePS1dE9 transgenic mice at three, six and twelve months of age. METHODS: Autophagic markers (Beclin-1, p62 and LC3) and the activation of mammalian Target of Rapamycin (mTOR) signaling pathway were quantified by western blot. Cytokine levels (IL-1ß, TNF-α and IL-6) were measured by ELISA. Transmission electron microscopy was performed to detect autophagic vacuoles. Mann-Whitney tests were used to compare wild-type (WT) versus APPswePS1dE9 mice. Longitudinal changes in parameters were analyzed with a Kruskal-Wallis test followed by a post-hoc Dunn's test. Correlation between two parameters was assessed using a Spearman test. RESULTS: Compared to 12-month old WT mice, 12-month old APPswePS1dE9 mice had higher levels of IL-1ß and TNF-α, a greater inhibition of the mTOR signaling pathway and lower levels of Beclin-1 expression both in cortex and hippocampus. Regarding the relationship of the various parameters in 12-month old APPswePS1dE9 mice, Beclin-1 rates were positively correlated with IL-1ß and TNF-α levels. And, on the contrary, TNF-α levels were inversely correlated with the levels of mTOR activation. Altogether, these results suggest that inflammation could induce autophagy in APPswePS1dE9 mice. However, these transgenic mice displayed a large accumulation of autophagic vesicles within dystrophic neurons in cortex and hippocampus, indicating a terminal failure in the autophagic process. CONCLUSIONS: This first demonstration of relationships between inflammation and autophagy in in vivo models of AD should be taken into account in new therapeutic strategies to prevent inflammation and/or stimulate autophagy in advanced neurodegenerative process such as AD.

Trans ε viniferin decreases amyloid deposits and inflammation in a mouse transgenic Alzheimer model.

As Alzheimer's disease (AD) induces several cellular and molecular damages, it could be interesting to use multi-target molecules for therapeutics. We previously published that trans ε-viniferin induced the disaggregation of Aß42 peptide and inhibited the inflammatory response in primary cellular model of AD. Here, effects of this stilbenoid were evaluated in transgenic APPswePS1dE9 mice. We report that trans ε-viniferin could go through the blood brain barrier, reduces size and density of amyloid deposits and decreases reactivity of astrocytes and microglia, after a weekly intraperitoneal injection at 10 mg/kg from 3 to 6 months of age.

Peripheral Blood Mononuclear Cells of Alzheimer's Disease Patients Control CCL4 and CXCL10 Levels in a Human Blood Brain Barrier Model.

BACKGROUND: Alzheimer's disease (AD) is accompanied by a neuroinflammation triggering chemoattractant signals towards peripheral blood mononuclear cells (PBMCs), which in turn could reduce amyloid plaques after transmigration through the blood brain barrier (BBB). But the chemotactic environment remains unclear. OBJECTIVE: To analyze five chemokines known to be involved in AD in three different cellular models to better understand the cellular and molecular interactions in the BBB. METHOD: Chemokines (CCL-2, 4 and 5, CXCL10 and CX3CL1) were measured in isolated cells, a BBB model without PBMCs (H4 and hCMEC/D3 cells, a neuroglioma and human endothelial cells, respectively) and in a complete BBB model with PBMCs from AD patients at a moderate stage. In one set of experiments, H4 cells were treated with Aß42. RESULTS: CCL2 and CCL5 significantly increased in hCMEC/D3 and H4 cells in the complete BBB model. In turn, the rate of CCL2 increased in PBMCs whereas for CCL5, it decreased. CXCL10 increased in all cellular actors in the complete BBB model, compared to isolated cells. For CCL4, PBMCs induced a robust increase in H4 and hCMEC/D3. In turn, the level of CCL4 decreased in PBMCs. Furthermore, PBMCs triggered a significant increase in CX3CL1 in hCMEC/D3. Surprisingly, no effect of Aß42 was observed in the complete BBB model. CONCLUSION: These findings highlight the interest of a BBB model in order to explore chemokine production. For the first time, results showed that PBMCs from patients with AD can control the production of CCL4 and CXCL10 in a human BBB model.

Inflammatory Stress on Autophagy in Peripheral Blood Mononuclear Cells from Patients with Alzheimer's Disease during 24 Months of Follow-Up.

Recent findings indicate that microglia in Alzheimer's disease (AD) is senescent whereas peripheral blood mononuclear cells (PBMCs) could infiltrate the brain to phagocyte amyloid deposits. However, the molecular mechanisms involved in the amyloid peptide clearance remain unknown. Autophagy is a physiological degradation of proteins and organelles and can be controlled by pro-inflammatory cytokines. The purpose of this study was to evaluate the impact of inflammation on autophagy in PBMCs from AD patients at baseline, 12 and 24 months of follow-up. Furthermore, PBMCs from healthy patients were also included and treated with 20 µM amyloid peptide 1-42 to mimic AD environment. For each patient, PBMCs were stimulated with the mitogenic factor, phytohaemagglutin (PHA), and treated with either 1 µM C16 as an anti-inflammatory drug or its vehicle. Autophagic markers (Beclin-1, p62/sequestosome 1 and microtubule-associated protein-light chain 3: LC3) were quantified by western blot and cytokines (Interleukin (IL)-1ß, Tumor necrosis Factor (TNF)-α and IL-6) by Luminex X-MAP® technology. Beclin-1 and TNF-α levels were inversely correlated in AD PBMCs at 12 months post-inclusion. In addition, Beclin-1 and p62 increased in the low inflammatory environment induced by C16. Only LC3-I levels were inversely correlated with cognitive decline at baseline. For the first time, this study describes longitudinal changes in autophagic markers in PBMCs of AD patients under an inflammatory environment. Inflammation would induce autophagy in the PBMCs of AD patients while an anti-inflammatory environment could inhibit their autophagic response. However, this positive response could be altered in a highly aggressive environment.

Impairment of autophagy in the central nervous system during lipopolysaccharide-induced inflammatory stress in mice.

BACKGROUND: Current evidence suggests a central role for autophagy in many neurodegenerative diseases including Alzheimer's disease, Huntington's disease, Parkinson's disease and amyotrophic lateral sclerosis. Furthermore, it is well admitted that inflammation contributes to the progression of these diseases. Interestingly, crosstalks between autophagy and inflammation have been reported in vitro and at the peripheral level such as in Crohn's disease. However, the impact of systemic inflammation on autophagic components in the brain remains to be documented. Therefore, this study monitored autophagy markers after acute and chronic lipopolysaccharide (LPS)-induced inflammatory stress in mice. RESULTS: We showed that acute inflammation, 24 h post-intraperitoneal 10 mg/kg LPS, substantially increased cytokine production (Interleukin(IL)-1ß, Tumor necrosis factor (TNF)-α and IL-6), decreased the levels of autophagy markers (Beclin-1, p62 and LC3 II) and reduced p70S6K activation in cortex and hippocampus. In hippocampus, IL-1ß levels and LC3 II expression were positively and highly correlated and a negative correlation was noted between TNF-α levels and p70S6K activation. Chronic inflammation by injection of 0.5 mg/kg LPS every three days during three months led to a moderate IL-1ß production and decreased TNF-α levels. Interestingly, Beclin-1 and LC3 II levels decreased while those of p62 increased. Cortical IL-1ß levels positively correlated with Beclin-1 and LC3 II and on the contrary inversely correlated with p62. CONCLUSION: The present study is the first showing links between IL-1ß-mediated inflammation and autophagy in the brain. It could open to new therapeutic strategies in brain diseases where regulation impairment of inflammation and autophagy progress with the severity of diseases.