Sphingosine kinase 1 regulates the expression of proinflammatory cytokines and nitric oxide in activated microglia

Microglial activation has been implicated as one of the causative factors for neuroinflammation in various neurodegenerative diseases. The sphingolipid metabolic pathway plays an important role in inflammation, cell proliferation, survival, chemotaxis, and immunity in peripheral macrophages. In this study, we demonstrate that sphingosine kinase1 (SphK1), a key enzyme of the sphingolipid metabolic pathway, and its receptors are expressed in the mouse BV2 microglial cells and SphK1 alters the expression and production of proinflammatory cytokines and nitric oxide in microglia treated with lipopolysaccharide (LPS). LPS treatment increased the SphK1 mRNA and protein expression in microglia as revealed by the RT–PCR, Western blot and immunofluorescence. Suppression of SphK1 by its inhibitor, N, N Dimethylsphingosine (DMS), or siRNA resulted in decreased mRNA expression of TNF-α, IL-1β, and iNOS and release of TNF-α and nitric oxide (NO) in LPS-activated microglia. Moreover, addition of sphingosine 1 phosphate (S1P), a breakdown product of sphingolipid metabolism, increased the expression levels of TNF-α, IL-1β and iNOS and production of TNF-α and NO in activated microglia. Hence to summarize, suppression of SphK1 in activated microglia inhibits the production of proinflammatory cytokines and NO and the addition of exogenous S1P to activated microglia enhances their inflammatory responses. Since the chronic proinflammatory cytokine production by microglia has been implicated in neuroinflammation, modulation of SphK1 and S1P in microglia could be looked upon as a future potential therapeutic method in the control of neuroinflammation in neurodegenerative diseases.     

IL-1通过PKC/MAPK通路上调泡沫细胞ACAT-1的表达及活性

 摘要 目的 研究白细胞介素1(Interleukin 1, IL-1)是否通过蛋白激酶C/丝裂原激活蛋白激酶（PKC/MAPK）信号通路上调泡沫细胞中脂酰CoA胆固醇酯酰转移酶-1（ACAT-1）的表达及活性。方法 复苏并培养人单核细胞株THP-1细胞,与200nM乙酸肉豆蔻佛波酯（PMA）共孵育48h,再与氧化低密度脂蛋白（Ox-LDL）共孵育24h,油红O染色观察细胞质内脂质沉积;检测泡沫细胞、泡沫细胞加IL-1及泡沫细胞加IL-1/IL-1单克隆抗体三组细胞中PKC和MAPK的活性;在三组细胞中分别加入PKC和MAPK抑制剂,分别以Western blot及液相闪烁计数法检测ACAT-1的蛋白表达及酶活性。结果 与PMA共孵育48h后,THP-1细胞逐渐伸出突起,由圆形、悬浮式生长转变为多角形、梭形,呈阿米巴样贴壁生长;经Ox-LDL诱导24h后,油红O染色胞质内可见大量吞噬的脂质小滴。与泡沫细胞组相比,泡沫细胞加IL-1组PKC活性（P<0.05）、MAPK活性（P<0.05）、ACAT-1蛋白表达及活性增加（P<0.05）;PKC抑制剂和MAPK抑制剂能显著抑制IL-1上调ACAT-1表达（P<0.05）及活性（P<0.05）的作用。结论 IL-1上调泡沫细胞ACAT-1表达及活性的作用是通过PKC/MAPK信号通路途径实现的。     

Inhibitory effect of ZPDC glycoprotein on the expression of inflammation-related cytokines through p38 MAP kinase and JNK in lipopolysaccharide-stimulated RAW 264.7 cells

Objective:  This study was carried out to investigate the anti-inflammatory potentials of 24 kDa glycoprotein isolated from Zanthoxylum piperitum DC fruit (ZPDC glycoprotein) in lipopolysaccharide (LPS)-stimulated murine macrophage cell line (RAW 264.7 cells). Material and Methods:  RAW 264.7 cells were treated with ZPDC glycoprotein (50–200 μg/ml) in presence of LPS (2 μg/ml). The changes of the levels of inflammation-related factors were determined by using Western blot, EMSA, and RT-PCR. Results:  ZPDC glycoprotein has inhibitory effects on the phosphorylation of p38 mitogen-activated protein (MAP) kinase and c-Jun N-terminal kinase (JNK), on the DNA binding activity of activator protein-1 (AP-1), and on the expression of c-Jun and c-Fos in LPS-stimulated RAW 264.7 cells. Interestingly, the DNA binding activity of AP-1 was attenuated by treatment with inhibitors of p38 MAP kinase and JNK. In addition, ZPDC glycoprotein (200 μg/ml) not only diminished the production of superoxide anion, hydrogen peroxide, and nitric oxide, but also suppressed the expression of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and proteins (iNOS, COX-2, and MMP-9) in LPS- stimulated RAW 264.7 cells. Conclusions:  The present study demonstrates that ZPDC glycoprotein is a natural anti-oxidant and one of the modulators of pro-inflammatory signal transduction pathways in RAW 264.7 cells. Received 2 June 2008; returned for revision 12 August 2008; received from final revision 15 August 2008; accepted by G. Wallace 18 September 2008     

Altered intracellular expression of the chemokines MIP-1alpha,MIP-1beta and IL-8 by peripheral blood CD4+ and CD8+ T cells in mild allergic asthma

BACKGROUND: The ability of chemokines to regulate Th1 and Th2 responses suggests a role in the pathogenesis of atopic disorders such as allergic asthma where Th2 response dominance has been observed. Although the impact of allergic asthma on local chemokine production in the lung has been the subject of investigation, little is know about the influence of disease progression on peripheral chemokine production. We now report use of whole blood culture and flow cytometry to assess the influence of mild allergic asthma on peripheral T-cell chemokine expression. METHODS: Study participants included patients with mild allergic asthma (n = 7) and nonasthmatic controls (n = 7). Following in vitro stimulation of peripheral venous blood with phorbol 12-myristate acetate (PMA) and ionomycin, flow cytometry was used to estimate the percentage of CD4+ and CD8+ T cells producing a number of chemokines, including macrophage inflammatory proteins MIP-1alpha and MIP-1beta, RANTES (regulated on activation, T-cell expressed and secreted), monocytic chemotactic protein-1 (MCP)-1, and interleukin (IL)-8, or the cytokines interferon (IFN)-gamma and IL-4. Serum levels of MIP-1alpha, MIP-1beta, RANTES, MCP-1, IL-8, IFN-gamma and IL-4 were also assessed by quantitative ELISA. RESULTS: Intracellular expression of MIP-1beta by CD4+ and CD8+ T cells from allergic asthmatics was significantly reduced in comparison to that observed for nonasthmatics (median = 2.29% (1.75-3.50) vs 4.57% (3.38-6.64), P = 0.05; 14.20% (13.18-17.88) vs 44.10% (30.38-48.70), P = 0.01). Similarly, intracellular expression of MIP-1alpha by CD8+ T cells from allergic asthmatics was also significantly lower (3.67% (1.17-5.42) vs 17.10% (4.97-20.43), P = 0.05). Conversely, IL-8 expression by both CD4+ and CD8+ T cells from allergic asthmatics demonstrated significant enhancement (9.93% (7.77-11.28) vs 4.14% (3.61-7.11), P = 0.05; 8.40% (6.97-10.04) vs 4.98% (3.37-6.08), P = 0.05). Examination of intracellular IFN-gamma and IL-4 revealed no significant difference in the expression of either cytokine by CD4+ T-cells from allergic asthmatics and nonasthmatics. In contrast, expression of IFN-gamma was significantly reduced in CD8+ T-cells from allergic asthmatics (24.60% (21.08-32.50) vs 48.40% (41.50-55.28), P = 0.01). CONCLUSIONS: The occurrence in mild allergic asthma of peripheral T-cell chemokine expression suggestive of a diminished Th1 response, coinciding with marginal change in cytokine profiles indicative of a Th2 response bias, confirms the importance of chemokine involvement in the etiology of allergic asthma. The ability to use whole blood culture to estimate chemokine expression in T cell subsets may ultimately provide a practical means to evaluate disease status and to monitor early intervention therapies which target chemokines.     

Complement C3a induces axonal hypomyelination in the periventricular white matter through activation of WNT/β‐catenin signal pathway in septic neonatal rats experimentally induced by lipopolysaccharide

Neuroinflammation is thought to play a pivotal role in the pathogenesis of periventricular white matter (PWM) damage (PWMD) induced by neonatal sepsis. Because the complement cascade is implicated in inflammatory response, this study was carried out to determine whether C3a is involved in PWMD, and, if so, whether it would induce axonal hypomyelination. Furthermore, we explored if C3a would act through its C3a receptor (C3aR) and thence inhibit maturation of oligodendrocyte precursor cells (OPCs) via the WNT/β‐catenin signal pathway. Sprague Dawley (SD) rats aged 1 day were intraperitoneally injected with lipopolysaccharide (LPS) (1 mg/kg). C3a was upregulated in activated microglia and astrocytes in the PWM up to 7 days after LPS injection. Concomitantly, enhanced C3aR expression was observed in NG2⁺ oligodendrocytes (OLs). Myelin proteins including CNPase, PLP, MBP and MAG were significantly reduced in the PWM of 28‐day septic rats. The number of PLP⁺ and MBP⁺ cells was markedly decreased. By electron microscopy, myelin sheath thickness was thinner and the average g‐ratios were higher. This was coupled with an increase in number of NG2⁺ cells and decreased number of CC1⁺ cells. Olig1, Olig2 and SOX10 protein expression was significantly reduced in the PWM after LPS injection. Very strikingly, C3aRa administration for the first 7 days could reverse the above‐mentioned pathological alterations in the PWM of septic rats. When incubated with C3a, expression of MBP, CNPase, PLP, MAG, Olig1, Olig2, SOX10 and CC1 in primary cultured OPCs was significantly downregulated as opposed to increased NG2. Moreover, WNT/β‐catenin signaling pathway was found to be implicated in inhibition of OPCs maturation and differentiation induced by C3a in vitro. As a corollary, it is speculated that C3a in the PWM of septic rats is closely associated with the disorder of OPCs differentiation and maturation through WNT/β‐catenin signaling pathway, which would contribute ultimately to axonal hypomyelination.