The role of inflammatory processes in Alzheimer's disease

Anti-neuroinflammatory agents for the treatment of Alzheimer’s disease

Alzheimer’s disease (AD) is complicated and difficult to fully understand, it might need multiple drug-discovery strategies to combat the disease. Regardless of the cause of AD, neuronal death in the brain plays a key role in AD progression and is directly linked to neuroinflammation. Thus, the regulation of neuroinflammatory processes might be a practical strategy for the treatment of AD. This review highlights the development of anti-neuroinflammatory agents that have shown promise in vitro or in vivo by attenuating microglial activation or cognitive decline. The agents are categorized based on the related signaling pathways, including the receptor for advanced glycation end products, p38 MAPKs, NF-κB and peroxisome proliferator-activated receptor γ; and inhibitors against microglial activation lacking clear mechanisms. These anti-neuroinflammatory agents support the concept and represent important chemical probes for the development of anti-neuroinflammatory drugs for the treatment of AD.

Effects of triptolide on degeneration of dendritic spines induced by Aβ1-40 injection in rat hippocampus

Although the exact cause of Alzheimer's disease (AD) remains elusive, mounting evidence continues to support the involvement of neuroinflammation in the development of AD. Triptolide isolated from the herb Tripterygium wilfordii Hook F has anti-inflammatory and immunosuppressive activities. In this study, we observed the effects of triptolide on dendritic spines of hippocampal neurons in model rats with AD. Thirty male SD rats were randomly divided into control group, AD model group and triptolide-treated group. The AD model group was made with bilateral microinjection of aggregated beta-amyloid protein (Aβ)1-40 into hippocampus in rats and the control group rats were injected with normal saline in the same way. The triptolide-treated group rats were administered triptolide intraperitoneally for 30 days after microinjection of aggregated Aβ1-40 into hippocampus. Dendritic morphology of hippocampal neurons in each group was analyzed using Golgi staining and ImageJ software. Our data showed that the total number of intersection points of dendrites and spine density in hippocampal neurons in the AD model group were decreased as compared with the control group. However, the total number of intersection points of dendrites and spine density in hippocampal neurons in the triptolide-treated group were increased as compared with the AD model group. Our results indicate that triptolide can alleviate the degeneration of dendritic spines in hippocampal neurons in model rats with AD.

Thrombin, a mediator of cerebrovascular inflammation in AD and hypoxia

Considerable evidence implicates hypoxia and vascular inflammation in Alzheimer's disease (AD). Thrombin, a multifunctional inflammatory mediator, is demonstrable in the brains of AD patients both in the vessel walls and senile plaques. Hypoxia-inducible factor 1α (HIF-1α), a key regulator of the cellular response to hypoxia, is also upregulated in the vasculature of human AD brains. The objective of this study is to investigate inflammatory protein expression in the cerebrovasculature of transgenic AD mice and to explore the role of thrombin as a mediator of cerebrovascular inflammation and oxidative stress in AD and in hypoxia-induced changes in brain endothelial cells. Immunofluorescent analysis of the cerebrovasculature in AD mice demonstrates significant (p < 0.01–0.001) increases in thrombin, HIF-1α, interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinases (MMPs), and reactive oxygen species (ROS) compared to controls. Administration of the thrombin inhibitor dabigatran (100 mg/kg) to AD mice for 34 weeks significantly decreases expression of inflammatory proteins and ROS. Exposure of cultured brain endothelial cells to hypoxia for 6 h causes an upregulation of thrombin, HIF-1α, MCP-1, IL-6, and MMP2 and ROS. Treatment of endothelial cells with the dabigatran (1 nM) reduces ROS generation and inflammatory protein expression (p < 0.01–0.001). The data demonstrate that inhibition of thrombin in culture blocks the increase in inflammatory protein expression and ROS generation evoked by hypoxia. Also, administration of dabigatran to transgenic AD mice diminishes ROS levels in brain and reduces cerebrovascular expression of inflammatory proteins. Taken together, these results suggest that inhibiting thrombin generation could have therapeutic value in AD and other disorders where hypoxia, inflammation, and oxidative stress are involved.

Up-regulation and activation of the P2Y(2) nucleotide receptor mediate neurite extension in IL-1β-treated mouse primary cortical neurons

The pro-inflammatory cytokine interleukin-1β (IL-1β), whose levels are elevated in the brain in Alzheimer's and other neurodegenerative diseases, has been shown to have both detrimental and beneficial effects on disease progression. In this article, we demonstrate that incubation of mouse primary cortical neurons (mPCNs) with IL-1β increases the expression of the P2Y2 nucleotide receptor (P2Y2R) and that activation of the up-regulated receptor with UTP, a relatively selective agonist of the P2Y2R, increases neurite outgrowth. Consistent with the accepted role of cofilin in the regulation of neurite extension, results indicate that incubation of IL-1β-treated mPCNs with UTP increases the phosphorylation of cofilin, a response absent in PCNs isolated from P2Y2R(-/-) mice. Other findings indicate that function-blocking anti-αv β3/5 integrin antibodies prevent UTP-induced cofilin activation in IL-1β-treated mPCNs, suggesting that established P2Y2R/αv β3/5 interactions that promote G12 -dependent Rho activation lead to cofilin phosphorylation involved in neurite extension. Cofilin phosphorylation induced by UTP in IL-1β-treated mPCNs is also decreased by inhibitors of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), suggesting a role for P2Y2R-mediated and Gq-dependent calcium mobilization in neurite outgrowth. Taken together, these studies indicate that up-regulation of P2Y2Rs in mPCNs under pro-inflammatory conditions can promote cofilin-dependent neurite outgrowth, a neuroprotective response that may be a novel pharmacological target in the treatment of neurodegenerative diseases.

The evaluation of neutrophil-lymphocyte ratio in Alzheimer's disease

BACKGROUND/AIM

There is growing consensus in the literature that inflammation plays a significant role in the pathophysiology of Alzheimer's disease (AD). The blood neutrophil-lymphocyte ratio (NLR) is a new, inexpensive and easily applicable marker of inflammation. The aim of this study was to investigate the association between NLR, as an inflammatory biomarker, and AD.

METHODS

241 AD patients and 175 patients with normal cognitive function were evaluated in this study.

RESULTS

The mean ± SD NLR of AD patients was significantly higher than that of patients with normal cognitive function (3.21 ± 1.35 vs. 2.07 ± 0.74, p < 0.001, respectively). Receiver operating characteristic curve analysis suggested that the optimum NLR cutoff point for AD was 2.48 with 69.29% sensitivity, 79.43% specificity, 82.30% positive predictive values and 65.30% negative predictive values. Logistic regression analysis showed that elevated NLR (OR: 4.774, 95% CI: 2.821-8.076, p < 0.001) was an independent variable for predicting AD.

CONCLUSION

Elderly people with AD have higher NLR than healthy controls. Elevated NLR levels are usually considered as an inflammatory marker. The results of this study suggested that inflammation plays a role in the pathogenesis of AD.

Is increased red cell distribution width (RDW) indicating the inflammation in Alzheimer's disease (AD)?

Increasing evidence indicates that inflammation has a substantial role in the pathogenesis and progression of AD. RDW, a measure of heterogeneity in the size of circulating erythrocytes, is associated with inflammatory markers in many numerous diseases. Present study was undertaken to assess the interrelationships between RDW and AD. A total of 197 patients with AD (male/female: 96/101, mean age 76.2 ± 6.9) and 133 patients as controls with normal cognitive function (male/female: 72/61, mean age 71.68 ± 5.3) were enrolled in this cross-sectional study. RDW values of all participants were measured. Mini-Mental State Examination (MMSE) and clock drawing tests were performed for cognitive assessment. DSM-IV and NINCDS-ADRDA criteria were used for diagnosis of AD. The mean RDW values were significantly higher in AD group (13.93 ± 1.1 vs. 13.24 ± 1.2; p<0.001) and also a negative moderate correlation between RDW and MMSE was identified (r: -0.453; p<0.001). After adjusting for confounders, RDW has the strongest association with AD (odd ratio (OR) 1.51, CI=1.10-2.07). In present study RDW levels were significantly increased in patients with AD. Whereas elevated RDW value is usually considered as a novel biomarker of inflammation, the results of our study may support the role of inflammation in pathophysiology of AD. Furthermore the correlation of RDW with poorer cognition status suggests that it may be used as a marker of AD severity.

Effect of Rhizoma Polygonati on 12-O-tetradecanoylphorbol-acetate-induced ear edema in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizoma Polygonati is originated from the dried rhizomes of Polygonatum sibircum Red. It has long been used in traditional Chinese medicine for the treatment of inflammatory disorders.

AIM OF THE STUDY

The present study aims to investigate the anti-inflammatory effect of aqueous extract of Rhizoma Polygonati (ERP) in a mouse model of inflammation induced by 12-O-tetradecanoylphorbol-acetate (TPA).

MATERIALS AND METHODS

The anti-inflammatory effect was evaluated by measuring the ear thickness and activity of myeloperoxidase (MPO). The anti-inflammatory mechanism was explored by determining the protein and mRNA levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6.

RESULTS

The results showed that ERP significantly decreased the ear thickness and MPO activity in mouse model of inflammation induced by TPA. In addition, ERP also remarkably inhibited the protein and mRNA levels of iNOS, COX-2, TNF-α, IL-1β, and IL-6.

CONCLUSIONS

These results indicate that ERP has potential anti-inflammatory effect on TPA-induced inflammatory in mice, and the anti-inflammatory effect may be mediated, at least in part, by inhibiting the mRNA expression of a panel of inflammatory mediators including iNOS, COX-2, TNF-α, IL-1β, and IL-6.