Proinflammatory cytokines increase glial fibrillary acidic protein expression in enteric glia

BACKGROUND: Enteric glia protect the integrity of the gut, as loss of enteric glial fibrillary acidic protein (GFAP) positive (+) glia leads to a haemorrhagic jejunoileitis. Crohn's disease (CD) and necrotising enterocolitis (NEC) show pathological changes in enteric glia. Therefore, factors controlling GFAP+ enteric glia are of great interest. The aim of the present study was to characterise enteric glia and determine the effect of interleukin 1beta (IL-1beta), interleukin 4 (IL-4), tumour necrosis factor alpha (TNF-alpha), and lipopolysaccharides (LPS) on cultured enteric glia. METHODS: Dissected rat colon and cultured enteric glia cells were double labelled with anti-GFAP and anti-S-100 antibodies. For regulatory studies, enteric glia cells were treated with cytokines and LPS. Proliferation was assayed using bromodeoxyuridine (BrdU) and mitosis of enteric glia was blocked by demecolcine. RESULTS: We were able to distinguish GFAP negative (-) from GFAP+ glia subtypes in situ and in primary cultures. Incubation of cells with IL-1beta, TNF-alpha, and LPS led to a significant increase in GFAP+ enteric glia while IL-4 had no effect on GFAP expression. After incubation with IL-1beta, total intracellular GFAP of enteric glia cells was increased. Upregulation of GFAP+ enteric glia could also be observed after stimulation with IL-1beta on blocking mitosis. BrdU uptake in stimulated enteric glia showed no increased proliferation rate. CONCLUSIONS: Two different types of enteric glia based on GFAP expression exist in the gut. Proinflammatory cytokines and LPS cause a dramatic increase in GFAP+ enteric glia. This suggests that cytokines play an important role in controlling GFAP+ enteric glia which might in turn be involved in modulating the integrity of the bowel during inflammation.     

Plasma glial fibrillary acidic protein levels in children with sickle cell disease

To determine if glial fibrillary acidic protein (GFAP) is associated with brain injury in children with sickle cell disease (SCD), we measured plasma GFAP among cross-sectional groups of unselected children with SCD, subsets of children with SCD and normal brain MRI or MRI evidence of cerebral infarct, healthy pediatric controls, and adults with brain injury. Children with SCD had higher plasma GFAP than healthy pediatric controls (mean concentrations 0.14 ± 0.37 vs. 0.07 ± 0.08 ng/mL; P 5 0.003); also, 16.0% (16/100) of children with SCD and cerebral infarct had GFAP elevations above the 95th percentile of healthy pediatric controls (P 5 0.04). Although not statistically significant, children with SCD and cerebral infarct had more elevated GFAP levels than with SCD and no infarct (16/100, 16.0% vs. 14/168, 8.3%; P 5 0.07). Children with SCD and acute brain ischemia had a higher proportion of elevated GFAP than SCD children with normal MRI (3/6, 50% vs.8.3%; P 5 0.01). GFAP was associated with elevated systolic blood pressure in the preceding year and correlated positively with white blood cell count and negatively with age and performance IQ. Plasma GFAP is elevated among children with SCD and may be associated with subclinical brain injury.     

Humanin及衍生物对阿尔茨海默病小鼠海马胶质纤维酸性蛋白表达的影响

目的探讨Humanin(HN)及衍生物[Gly14]-humanin(HNG)在体内是否存在对实验性阿尔茨海默病(AD)小鼠的神经保护作用及可能的机制。方法选择健康雄性小鼠84只,随机分为假手术组(9只)、β淀粉样蛋白(Aβ)模型组(15只)、HN治疗组(30只)和HNG治疗组(30只)。HN组又分为10 μmol/L HN组和100μmol/LHN组,HNG组又分为10 nmol/L HNG组和100 nmol/L HNG组,4组均于3、7、14天应用免疫组织化学方法观察海马胶质纤维酸性蛋白(GFAP)表达的变化。结果 HN治疗组和HNG治疗组3、7、14天GFAP阳性细胞的表达较假手术组和Aβ模型组均减少。3、14天100 μmol/L HN组GFAP阳性细胞数少于10 μmol/L HN组(P<0.05);3、7、14天100 nmol/L HNG组GFAP阳性细胞数少于10 nmol/L HNG组(P<0.05)。3天100 nmol/LHNG组GFAP阳性细胞数少于100μmol/L HN组(P<0.05)。结论在体内,HN和HNG可以减少因Aβ_(25-35),毒性引起的GFAP的表达,这种改变有时间及剂量依赖性,证实了它们具有神经保护作用。     

Spontaneous inflammatory demyelinating disease in transgenic mice showing central nervous system-specific expression of tumor necrosis factor alpha.

Cytokines are now recognized to play important roles in the physiology of the central nervous system (CNS) during health and disease. Tumor necrosis factor alpha (TNF-alpha) has been implicated in the pathogenesis of several human CNS disorders including multiple sclerosis, AIDS dementia, and cerebral malaria. We have generated transgenic mice that constitutively express a murine TNF-alpha transgene, under the control of its own promoter, specifically in their CNS and that spontaneously develop a chronic inflammatory demyelinating disease with 100% penetrance from around 3-8 weeks of age. High-level expression of the transgene was seen in neurons distributed throughout the brain. Disease is manifested by ataxia, seizures, and paresis and leads to early death. Histopathological analysis revealed infiltration of the meninges and CNS parenchyma by CD4+ and CD8+ T lymphocytes, widespread reactive astrocytosis and microgliosis, and focal demyelination. The direct action of TNF-alpha in the pathogenesis of this disease was confirmed by peripheral administration of a neutralizing anti-murine TNF-alpha antibody. This treatment completely prevented the development of neurological symptoms, T-cell infiltration into the CNS parenchyma, astrocytosis, and demyelination, and greatly reduced the severity of reactive microgliosis. These results demonstrate that overexpression of TNF-alpha in the CNS can cause abnormalities in nervous system structure and function. The disease induced in TNF-alpha transgenic mice shows clinical and histopathological features characteristic of inflammatory demyelinating CNS disorders in humans, and these mice represent a relevant in vivo model for their further study.     

Molecular cloning and primary structure of human glial fibrillary acidic protein.

Glial fibrillary acidic protein (GFAP) is an intermediate-filament (IF) protein that is highly specific for cells of astroglial lineage, although its tissue-specific role is speculative. Determination of the primary structure of this protein should be of importance for understanding the functional role it plays in astroglia. Therefore, we isolated a cDNA clone encoding this protein and determined its nucleotide sequence. The predicted amino acid sequence indicates that GFAP shares structural similarities--particularly in the central rod domain and to a lesser degree in the carboxyl-terminal domain--with other IF proteins found in nonepithelial cell types. Considerable sequence divergence in the amino-terminal region of GFAP suggests that the tissue-specific functions of this IF protein might be mediated through this region of the molecule. In contrast, conservation of structural characteristics and a moderate degree of sequence conservation in the carboxyl-terminal region suggest functional similarities. Blot hybridization analysis using the GFAP cDNA as a probe failed to detect GFAP mRNA in both normal and neoplastic human tissues in which IF proteins other than GFAP are known to be expressed.     

Serum and transforming growth factor beta regulate glial fibrillary acidic protein in serum-free-derived mouse embryo cells.

Serum-free mouse embryo (SFME) cells, derived in medium in which serum is replaced with growth factors and other supplements, display distinctive properties: (i) SFME cells do not lose proliferative potential or show gross chromosomal aberration upon extended culture, (ii) these cells depend on epidermal growth factor for survival; and (iii) SFME cell proliferation is reversibly inhibited by serum. Treatment of SFME cells with serum or transforming growth factor beta led to the appearance of glial fibrillary acidic protein, a specific marker for astrocytes. The appearance of glial fibrillary acidic protein in cultures was reversed upon removal of transforming growth factor beta or serum. Cells with properties similar to SFME cells were also isolated from adult mouse brain. These results suggest a role for transforming growth factor beta in astrocyte differentiation in developing organisms and in response to injury and identify the cell type that has the unusual properties of SFME cells.     

Potential antiinflammatory effects of interleukin 4: suppression of human monocyte tumor necrosis factor alpha, interleukin 1, and prostaglandin E2.

Stimulated human monocytes/macrophages are a source of mediators such as tumor necrosis factor alpha (TNF-alpha), interleukin 1 (IL-1), and prostaglandin E2 (PGE2), which can modulate inflammatory and immune reactions. Therefore, the ability to control the production of such mediators by monocytes/macrophages may have therapeutic benefits, and it has been proposed that glucocorticoids may act in this way. Purified human monocytes, when stimulated in vitro with lipopolysaccharide (LPS) or with LPS and gamma interferon (IFN-gamma), produce TNF-alpha, IL-1, and PGE2. Cotreatment of stimulated cells with the purified human lymphokine, interleukin 4 (IL-4 greater than or equal to 0.1-0.5 unit/ml; 12-60 pM) dramatically blocked the increased levels of these three mediators; for TNF-alpha and IL-1, the inhibition was manifest at the level of mRNA. Thus, IL-4 can suppress some parameters of monocyte activation and, as for B cells, have opposite effects to IFN-gamma. The effects of IL-4 on human monocytes are similar to those obtained with the glucocorticoid dexamethasone (0.1 microM).     

Plasma glial fibrillary acidic protein levels in a child with sickle cell disease and stroke

A 12-year-old boy with HbSS sickle cell disease (SCD) was admitted with an acute febrile illness and developed overt stroke 3 days later. Plasma glial fibrillary acidic protein levels were elevated, as compared to pediatric controls, 32 h prior to the clinical diagnosis of stroke, peaked immediately prior to the exchange transfusion, and remained elevated 1 year later despite chronic transfusion therapy. Stroke in SCD can occur in the setting of acute illness, and a biomarker that could predict the onset and triage ill children to therapeutic intervention more quickly would be useful.     

Elevated blood pressure in transgenic mice with brain-specific expression of human angiotensinogen driven by the glial fibrillary acidic protein promoter

In addition to the circulatory renin (REN)-angiotensin system (RAS), a tissue RAS having an important role in cardiovascular function also exists in the central nervous system. In the brain, angiotensinogen (AGT) is expressed in astrocytes and in some neurons important to cardiovascular control, but its functional role remains undefined. We generated a transgenic mouse encoding the human AGT (hAGT) gene under the control of the human glial fibrillary acidic protein (GFAP) promoter to experimentally dissect the role of brain versus systemically derived AGT. This promoter targets expression of transgene products to astrocytes, the most abundant cell type expressing AGT in brain. All transgenic lines exhibited hAGT mRNA expression in brain, with variable expression in other tissues. In one line examined in detail, transgene expression was high in brain and low in tissues outside the central nervous system, and the level of plasma hAGT was not elevated over baseline. In the brain, hAGT protein was mainly localized in astrocytes, but was present in neurons in the subfornical organ. Intracerebroventricular (ICV) injection of human REN (hREN) in conscious unrestrained mice elicited a pressor response, which was abolished by ICV preinjection of losartan. Double-transgenic mice expressing the hREN gene and the GFAP-hAGT transgene exhibited a 15-mm Hg increase in blood pressure and an increased preference for salt. Blood pressure in the hREN/GFAP-hAGT mice was lowered after ICV, but not intravenous losartan. These studies suggest that AGT synthesis in the brain has an important role in the regulation of blood pressure and electrolyte balance.     

Experimental infection in tumor necrosis factor alpha receptor, interferon gamma and interleukin 4 deficient mice by pathogenic Leptospira interrogans

Only recently, knockout mouse models were applied in studies on the pathogenesis of leptospirosis. Current data suggest an important role of innate immunity receptors and interferon gamma dependant cellular response on protection. It is not clear, however, whether T helper cell polarization influences on outcome of leptospiral infection. We report findings of experimental infection of C57BL/6 (interferon gamma or tumor necrosis factor alpha receptor deficient) and BALB/c (interleukin 4 deficient) mice infected by pathogenic Leptospira interrogans serovar Copenhageni. Specific cytokine gene deficiency had no impact on outcome since all animals survived. TNFR knockout mice, however, exhibited more severe residual renal inflammation during convalescence thus suggesting this cytokine is important in early control of infection, protecting kidneys from relevant pathology.     

缺血预处理对脑缺血再灌注大鼠脑组织胶质纤维酸性蛋白表达的影响

目的 观察脑缺血预处理对脑缺血再灌注大鼠脑组织胶质纤维酸性蛋白(glial fibrillary acidic protein,GFAP)表达的影响,探讨星形胶质细胞活化在脑缺血耐受中的意义.方法 36只健康雄性Sprague-Dawley大鼠随机分为缺血预处理再缺血组、缺血组和对照组,每组12只,前2组分别在2 h大脑中动脉闭塞(middle cerebral artery occlusion,MCAO)前3 d给予10 min的MCAO预处理或假手术,第2次MCAO后24 h处死,对照组仅给予2次间隔3 d的假手术.比较各组脑梗死体积、组织病理学变化和GFAP表达.结果 缺血预处理后再缺血组和缺血组梗死体积分别为(136.85±14.51)mm3和(281.37±29.93)mm3,前者较后者显著缩小53.15%(P=0.007);同时,缺血预处理再缺血组神经元变性坏死显著减轻,并伴有GFAP表达显著上调(2组免疫组化染色平均吸光度分别为102.66±8.39和86.28±6.19,P=0.009).结论 缺血预处理可诱导脑缺血耐受,促进GFAP表达,星形胶质细胞活化可能是脑缺血耐受产生的机制之一.     

缺血预处理对脑缺血再灌注大鼠脑组织胶质纤维酸性蛋白表达的影响

Objective To observe the effect of focal cerebral ischemic preconditioning on the expression of glial fibrillary acidic protein (GFAP) and to investigate the significance of astrocyte activation in cerebral ischemic tolerance.Methods Thirty-six healthy male SpragueDawley rats were randomly divided into reischenmic,ischemic and control groups (n = 12 in each group) after ischemic preconditioning.The former two groups received 10 minutes middle cerebral artery occlusion (MCAO) preconditioning or sham operation 3 days before the 2-hour MCAO.The rats were killed 24 hours after the second MCAO.The control group only receivedthe two sham operations with an interval of three days.The infarct volume,histopathological changes,and GFAP expression in each group were compared.Results The infarct volume after ischemic preconditioning in the reischenmic and ischemic groups was 136.85 ± 14.51 mm3and 281.37 ± 29.93 mm3 respectively.The former was significantly reduced 53.15%compared to the latter (P =0.007).At the same time,neuronal degeneration and necrosis was reduced significantly,and GFAP expression was upregulated significantly (the mean absorbance for immunohistochemical staining in both groups was 102.66 ± 8.39 and 86.28 ± 6.19respectively,P = 0.009) after ischemic preconditioning in the reischemic group.Conclusions Focal ischemic preconditioning may induce brain ischemic tolerance and promote GFAP expression.The activation of astrocytes may be one of the mechanisms of cerebral ischemic tolerance.     

Human immunodeficiency virus type 1 protease cleaves the intermediate filament proteins vimentin, desmin, and glial fibrillary acidic protein.

The intermediate filament proteins vimentin, desmin, and glial fibrillary acidic protein are cleaved in vitro by human immunodeficiency virus type 1 protease (HIV-1 PR). Microsequencing showed that HIV-1 PR cleaved both human and murine vimentin between leucine-422 and arginine-423 within the sequence between positions 418 and 427, Ser-Ser-Leu-Asn-Leu/Arg-Glu-Thr-Asn-Leu (SSLNL/RETNL). Minor cleavages at other sites were also observed. Heat-denatured vimentin was cleaved by HIV-1 PR less efficiently than native vimentin. A decapeptide containing the sequence SSLN-LRETNL was also cleaved in vitro by HIV-1 PR as predicted. The presence of a charged residue (arginine) at the primary cleavage site distinguishes this from other known naturally occurring cleavage sites. Microinjection of HIV-1 PR into cultured human fibroblasts resulted in a 9-fold increase in the percentage of cells with an altered and abnormal distribution of vimentin intermediate filaments. Most commonly, the intermediate filaments collapsed into a clump with a juxtanuclear localization. These results support the possibility that intermediate filament proteins may serve as substrates within HIV-1-infected cells.     

Coexpression of vimentin and glial fibrillary acidic protein in glial cells of the adult rat pineal gland

In the present work, coexpression of vimentin (VIM) and glial fibrillary acidic protein (GFAP) is demonstrated in the glial cells of the adult rat pineal gland. Serial consecutive Epon semithin sections (0.5 microns thick) were alternately immunostained for VIM and GFAP. GFAP positive cells and processes were found in the proximal region of the pineal gland, near the pineal stalk. Most of these cells were also immunostained for VIM in adjacent semithin sections. The significance of the coexpression VIM-GFAP and the restricted location of GFAP positive cells is discussed in relation with the maturation of pineal glial cells.     

Essential role of tumor necrosis factor alpha in alcohol-induced liver injury in mice.

BACKGROUND & AIMS: Tumor necrosis factor (TNF)-alpha is associated with increased mortality in alcoholics, but its role in early alcohol-induced liver injury is not fully understood. Recently, it was shown that injury induced by the enteral alcohol delivery model of Tsukamoto and French was reduced by antibodies to TNF-alpha. To obtain clear evidence for or against the hypothesis that TNF-alpha is involved, we studied TNF receptor 1 (TNF-R1, p55) or 2 (TNF-R2, p75) knockout mice. METHODS: Long-term enteral alcohol delivery was modified for male gene-targeted mice lacking TNF-R1 and TNF-R2. Animals were given a high-fat liquid diet continuously with either ethanol or isocaloric maltose-dextrin as a control for 4 weeks. RESULTS: Ethanol elevated serum levels of alanine aminotransferase nearly 3-fold in wild-type and TNF-R2 knockout mice but not in TNF-R1 knockout mice. Likewise, ethanol caused severe liver injury in wild-type mice (pathology score, 5.5 +/- 0.6) and TNF-R2 knockout mice (pathology score, 5.0 +/- 0.4), but not in TNF-R1 knockout mice (pathology score, 0.8 +/- 0.4; P < 0.001). CONCLUSIONS: Long-term ethanol feeding caused liver injury in wild-type and TNF-R2 knockout mice but not in TNF-R1 knockout mice, providing solid evidence in support of the hypothesis that TNF-alpha plays an important role in the development of early alcohol-induced liver injury via the TNF-R1 pathway. Moreover, the long-term enteral ethanol feeding technique we described for the first time for knockout mice provides a useful new tool for alcohol research.