Activation of microglia and induction of pro-inflammatory cytokines in the hippocampus of type 2 diabetic rats

Abstract

Objectives:

The majority of immune cells in the brain are comprised of microglia, which undergo morphological changes when activated to remove damaged neurons and infectious agents from the brain tissue. In this study, we investigated the effects of type 2 diabetes on microglial activation and the subsequent secretion of pro-inflammatory cytokines, such as interferon-gamma (IFN-gamma) and interleukin-1beta (IL-1beta), in the hippocampus using Zucker diabetic fatty (ZDF) rats and Zucker lean control (ZLC) rats at various diabetic stages.

Methods:

Zucker lean control and Zucker diabetic fatty rats were sacrificed at 12 (early diabetic stage), 20, or 30 weeks of age (chronic diabetic stage), and the hippocampus was obtained via transcardiac perfusion or dissection for immunohistochemistry and western blot analysis, respectively.

Results:

Zucker diabetic fatty rats demonstrated significantly higher glucose levels at 12 and 30 weeks of age compared to ZLC rats. Microglia immunoreactive to ionized calcium-binding adapter molecule 1 (Iba-1) had hypertrophied cytoplasm with retracted processes at 30 weeks of age. In contrast, Iba-1-immunoreactive microglia displayed similar morphology in ZDF and ZLC rats at 12 and 20 weeks of age. Similarly, IFN-gamma and IL-1beta protein levels were significantly increased in ZDF rats compared to ZLC rats at 30 weeks of age, but not at 12 and 20 weeks of age. Interleukin-1beta immunoreactivity in the ZDF rats predominantly increased in the dentate gyrus and CA1 region of the hippocampus compared to that of ZLC rats at 30 weeks of age. In addition, IL-1beta immunoreactive structures in ZDF rats at 30 weeks of age were detected near the astrocytes and microglia.

Conclusion:

These results suggest that chronic diabetes activates microglia and significantly increases pro-inflammatory cytokine levels in the hippocampus.     

The roles of Dok family adapters in immunoreceptor signaling

Summary:  The mammalian Dok protein family has seven members (Dok-1–Dok-7). The Dok proteins share structural similarities characterized by the NH₂-terminal pleckstrin homology and phosphotyrosine-binding domains followed by SH2 target motifs in the COOH-terminal moiety, indicating an adapter function. Indeed, Dok-1 was originally identified as a 62 kDa protein that binds with p120 rasGAP, a potent inhibitor of Ras, upon tyrosine phosphorylation by a variety of protein tyrosine kinases. Among the Dok family, only Dok-1, Dok-2, and Dok-3 are preferentially expressed in hematopoietic/immune cells. Dok-1 and its closest relative Dok-2 act as negative regulators of the Ras–Erk pathway downstream of many immunoreceptor-mediated signaling systems, and it is believed that recruitment of p120 rasGAP by Dok-1 and Dok-2 is critical to their negative regulation. By contrast, Dok-3 does not bind with p120 rasGAP. However, accumulating evidence has demonstrated that Dok-3 is a negative regulator of the activation of JNK and mobilization of Ca²⁺ in B-cell receptor-mediated signaling, where the interaction of Dok-3 with SHIP-1 and Grb2 appears to be important. Here, we review the physiological roles and underlying mechanisms of Dok family proteins.     

Novel compound FLZ alleviates rotenone-induced PD mouse model by suppressing TLR4/MyD88/NF-κB pathway through microbiota–gut–brain axis

Parkinson's disease (PD) is the second most common neurodegenerative disease, but none of the current treatments for PD can halt the progress of the disease due to the limited understanding of the pathogenesis. In PD development, the communication between the brain and the gastrointestinal system influenced by gut microbiota is known as microbiota–gut–brain axis. However, the explicit mechanisms of microbiota dysbiosis in PD development have not been well elucidated yet. FLZ, a novel squamosamide derivative, has been proved to be effective in many PD models and is undergoing the phase I clinical trial to treat PD in China. Moreover, our previous pharmacokinetic study revealed that gut microbiota could regulate the absorption of FLZ in vivo. The aims of our study were to assess the protective effects of FLZ treatment on PD and to further explore the underlying microbiota-related mechanisms of PD by using FLZ as a tool. In the current study, chronic oral administration of rotenone was utilized to induce a mouse model to mimic the pathological process of PD. Here we revealed that FLZ treatment alleviated gastrointestinal dysfunctions, motor symptoms, and dopaminergic neuron death in rotenone-challenged mice. 16S rRNA sequencing found that PD-related microbiota alterations induced by rotenone were reversed by FLZ treatment. Remarkably, FLZ administration attenuated intestinal inflammation and gut barrier destruction, which subsequently inhibited systemic inflammation. Eventually, FLZ treatment restored blood–brain barrier structure and suppressed neuroinflammation by inhibiting the activation of astrocytes and microglia in the substantia nigra (SN). Further mechanistic research demonstrated that FLZ treatment suppressed the TLR4/MyD88/NF-κB pathway both in the SN and colon. Collectively, FLZ treatment ameliorates microbiota dysbiosis to protect the PD model via inhibiting TLR4 pathway, which contributes to one of the underlying mechanisms beneath its neuroprotective effects. Our research also supports the importance of microbiota–gut–brain axis in PD pathogenesis, suggesting its potential role as a novel therapeutic target for PD treatment.     

用三通管行脑脊液置换术治疗蛛网膜下腔出血的临床观察

目的　探讨蛛网膜下腔出血的治疗方法 ,以提高疗效 ,改善预后。方法　腰椎穿刺 (颈椎侧方穿刺 ) ,用三通管置换脑脊液。结果　治疗组较对照组脑积水死亡率明显减少 ,头痛时间明显缩短 ,总有效率明显提高 ,差异有显著意义 (P <0 0 5 )。结论　脑脊液置换术是治疗蛛网膜下腔出血的有效方法     

静脉留置针置管改进技术对穿刺成功率的影响

目的 探讨静脉留置针的不同穿刺方法对静脉留置针穿刺成功率的影响.方法 将行静脉留置针穿刺的160例肺癌患者随机分为观察组80例和对照组80例.对照组按传统的静脉留置针的方法穿刺并固定,观察组采用改良的静脉留置针的方法穿刺并用贴膜固定,比较两组穿刺的成功率.结果 观察组的静脉留置针的一次性穿刺成功率为97.5%,对照组为77.5%,差异有统计学意义（P＜0.05）,且渗液渗血、发生静脉炎等并发症发生情况与对照组比较,差异无统计学意义（P＞0.05）.结论 采用改良的静脉留置针的穿刺方法可明显提高静脉留置针的穿刺成功率,节约护理操作时间,对穿刺局部并发症的发生无影响.     

Compartmentalization of ITAM and integrin signaling by adapter molecules

Summary:  Adapters are multidomain molecules that recruit effector proteins during signal transduction by immunoreceptors and integrins. The absence of these scaffolding molecules profoundly affects development and function of various hematopoietic lineages, underscoring their importance as regulators of signaling cascades. An emerging aspect of the mechanism by which engaged immunoreceptors and integrins transmit signals within the cell is by differential usage of various adapters that function to nucleate formation of distinct signaling complexes in a specific location within the cell. In this review, we discuss the mechanisms by which adapter proteins coordinate signal transduction with an emphasis on the role of subcellular compartmentalization in adapter function.     

The microglia/macrophage response in the neonatal rat facial nucleus following axotomy

Microglia represent a population of brain macrophage precursor cells which are intrinsic to the CNS parenchyma. Transection of the facial nerve in the newborn rat causes death of the affected motor neurons which is accompanied by massive activation of local microglia. Many of these cells develop into macrophages as can be shown by immunocytochemistry for OX-42 and ED1. Using the new polyclonal microglial marker ionized calcium binding adapter molecule 1, iba1, in combination with immunocytochemical double-labeling for the proliferating cell nuclear antigen (PCNA), or [³H]thymidine autoradiography, and confocal microscopy, qualitative as well as quantitative differences can be demonstrated between the newborn and the adult axotomized rat facial nucleus. While microglial cells are the only cell population which responds to axotomy by cell division in the adult facial nucleus, GFAP positive reactive astrocytes can be shown to undergo mitosis following axotomy in the newborn rat. Furthermore, ED1 immunoreactivity, early expression of MHC class II molecules and morphological transformation of microglia into macrophages can only be observed under conditions of neuronal degeneration, i.e., in the neonatal rat facial nucleus. Thus, the combination of cellular markers described here should be useful for studies employing the neonatal rat facial nucleus as an in vivo assay system to test the efficacy of neurotrophic factors.     

Regulation of T-cell receptor signalling by membrane microdomains

There is now considerable evidence suggesting that the plasma membrane of mammalian cells is compartmentalized by functional lipid raft microdomains. These structures are assemblies of specialized lipids and proteins and have been implicated in diverse biological functions. Analysis of their protein content using proteomics and other methods revealed enrichment of signalling proteins, suggesting a role for these domains in intracellular signalling. In T lymphocytes, structure/function experiments and complementary pharmacological studies have shown that raft microdomains control the localization and function of proteins which are components of signalling pathways regulated by the T-cell antigen receptor (TCR). Based on these studies, a model for TCR phosphorylation in lipid rafts is presented. However, despite substantial progress in the field, critical questions remain. For example, it is unclear if membrane rafts represent a homogeneous population and if their structure is modified upon TCR stimulation. In the future, proteomics and the parallel development of complementary analytical methods will undoubtedly contribute in further delineating the role of lipid rafts in signal transduction mechanisms.     

DAP12: an adapter protein with dual functionality

Summary:  Expressed predominantly on myeloid and natural killer (NK) cells, DAP12 is an adapter protein that can associate with a variety of receptors. To date, DAP12 has predominantly been characterized as an adapter protein that activates various myeloid and NK cell effector functions; however, recent findings have demonstrated that DAP12 can also inhibit myeloid functions. Here we review the dual functionality of DAP12 and present evidence that DAP12 can suppress as well as activate NK cells.