Theophylline Potentiates Lipopolysaccharide-Induced NO Production in Cultured Astrocytes

Elucidation of the functions of astrocytes is important for understanding of the pathogenic mechanism of various neurodegenerative diseases. Theophylline is a common drug for bronchial asthma and occasionally develops side-effects, such as acute encephalopathy; although the pathogenic mechanism of the side-effects is unknown. The lipopolysaccharide (LPS)-induced nitric oxide (NO) production is generally used for an index of the activation of astrocyte in vitro. In this study, in order to elucidate the effect of theophylline on the astrocytic functions, we examined the LPS-induced NO production and the expression of iNOS in cultured rat cortex astrocytes. Theophylline alone could not induce the NO production; however, NO production induced by LPS was enhanced by theophylline in a dose-dependent manner; and by isobutylmethylxanthine, a phosphodiesterase inhibitor. The theophylline enhancement of LPS-induced NO production was further increased by dibutyryl cyclic AMP, a membrane-permeable cAMP analog; and by forskolin, an adenylate cyclase activator. When the cells were preincubated with Rp-8-Br-cAMP, an inhibitor of protein kinase A, the theophylline enhancement of LPS-induced NO production was decreased. The extent of iNOS protein expression induced by LPS was also enhanced by theophylline. It is likely that phosphodiesterase inhibition is a major action mechanism for the theophylline enhancement of LPS-induced NO production in astrocytes. Theophylline-induced acute encephalopathy might be due to the hyper-activation of astrocytes via cAMP signaling to produce excess amount of NO.     

Apoptosis in multiple myeloma: Therapeutic implications

Apoptosis is the primary means by which most radio- and chemotherapy modalities kill cancer cells, and abnormalities in the apoptotic pathways may contribute to disease pathogenesis of cancer. Multiple Myeloma (MM) is a hematological malignancy which will affect 14,000 new individuals in the United States in 2001 and remains irreversibly fatal despite all available therapies. The current review focuses on the studies of apoptotic and survival signaling pathways in MM cells, which have both identified novel apoptotic and anti-apoptotic proteins and provided targets for novel therapeutics.     

Reactive Astrocytes as Therapeutic Targets for Brain Degenerative Diseases: Roles Played by Metabotropic Glutamate Receptors

Astrocytes are well known to play critical roles in the development and maintenance of the central nervous system (CNS). Moreover, recent reports indicate that these cells are heterogeneous with respect to the molecules they express and the functions they exhibit in the quiescent or activated state. Because astrocytes also contribute to pathology, promising new results raise the possibility of manipulating specific astroglial populations for therapeutic roles. In this mini-review, we highlight the function of metabotropic glutamate receptors (mGluRs), in particular mGluR3 and mGluR5, in reactive astrocytes and relate these to three degenerative CNS diseases: multiple sclerosis, Alzheimer’s disease and Amyotrophic Lateral Sclerosis. Previous studies demonstrate that effects of these receptors may be beneficial, but this varies depending on the subtype of receptor, the state of the astrocytes, and the specific disease to which they are exposed. Elucidating the role of mGluRs on astrocytes at specific times during development and disease will provide novel insights in understanding how to best use these to serve as therapeutic targets.

     

Thymosin-β4 Attenuates Ethanol-induced Neurotoxicity in Cultured Cerebral Cortical Astrocytes by Inhibiting Apoptosis

Thymosin-β4 (Tβ4) is a major actin monomer-binding peptide in mammalian tissues and plays a crucial role in the nervous system in synaptogenesis, neuronal survival and migration, axonal growth, and plastic changes of dendritic spines. However, it is unknown whether Tβ4 is also involved in challenges with external stress such as ethanol-induced neurotoxicity. In the present study, we investigated the effects of Tβ4 on ethanol-induced neurotoxicity in cultured cerebral cortical astrocytes and the underlying mechanisms. Primarily cultured astrocytes were treated with 1 μg/ml Tβ4 2 h prior to administration of 100 mM ethanol for 0.5, 1, 3 and 6 days, respectively. The results showed that ethanol caused neurotoxicity in cultured astrocytes, as shown by declined cell viability, distinct astroglial apoptosis and increased intracellular peroxidation. Tβ4 markedly promoted cell viability, ameliorated the injury of intracellular glial fibrillary acidic protein-immunopositive cytoskeletal structures, reduced the percentage of apoptotic astrocyte and cellular DNA fragmentation, suppressed caspase-3 activity and upregulated Bcl-2 expression, inhibited the accumulation of reactive oxygen species and production of malondialdehyde in ethanol-treated astrocytes in a time-dependent manner. These data indicated that Tβ4 attenuates ethanol-induced neurotoxicity in cultured cortical astrocytes through inhibition of apoptosis signaling, and one of the mechanisms underlying the capacity of Tβ4 to suppress apoptosis may in part be due to its effect of anti-peroxidation.     

Lipopolysaccharide-Induced Microglial Neuroinflammation: Attenuation by FK866

Neurochemical Research - Alleviating microglia-mediated neuroinflammation bears great promise to reduce neurodegeneration. Nicotinamide phosphoribosyltransferase (NAMPT) may exert cytokine-like...     

米诺环素对糖尿病大鼠视网膜神经细胞凋亡的影响

目的:观察米诺环素对糖尿病大鼠视网膜神经细胞的凋亡的影响,研究米诺环素对糖尿病视网膜神经保护作用,对米诺环素在糖尿病视网膜疾病中抑制神经细胞凋亡提供理论支持。方法:选择健康成年雄性SD大鼠30只,随机分成正常对照组、糖尿病模型组和米诺环素治疗组,每组10只。腹腔内注射链脲佐菌素(STZ)诱发大鼠糖尿病。米诺环素治疗组给予米诺环素腹腔注射(45mg/kg),共注射10d,模型组和对照组腹腔注射等体积生理盐水,于给药后8周的3组动物处死,冰浴下取其视网膜组织,随后制备视网膜石蜡切片,采用末端脱氧核糖核酸介导生物素化脱氧尿嘧啶缺口末端标记(TUNEL)法进行凋亡细胞原位标记,行视网膜神经细胞凋亡计数,对所有数据进行统计学分析。实验结果拟用均数和标准差(x±s)表示,P<0.05为差异有统计学意义。结果:相同观察时相,与阴性对照组比较,模型对照组大鼠视网膜TUNEL阳性细胞显著增多(P<0.01),在米诺环素组,大鼠视网膜TUNEL阳性细胞数比模型对照组明显减少,差异有统计学意义(P<0.01)。结论:米诺环素能有效降低糖尿病大鼠视网膜神经细胞的凋亡,对糖尿病视网膜神经细胞有保护作用。     

米诺环素对糖尿病大鼠视网膜神经细胞凋亡的影响

目的：观察米诺环素对糖尿病大鼠视网膜神经细胞的凋亡的影响,研究米诺环素对糖尿病视网膜神经保护作用,对米诺环素在糖尿病视网膜疾病中抑制神经细胞凋亡提供理论支持。方法：选择健康成年雄性SD大鼠30只,随机分成正常对照组、糖尿病模型组和米诺环素治疗组,每组10只。腹腔内注射链脲佐菌素（STZ）诱发大鼠糖尿病。米诺环素治疗纽给予米诺环素腹腔注射（45mg／kg）,共注射10d,模型组和对照组腹腔注射等体积生理盐水,于给药后8周的3组动物处死,冰浴下取其视网膜组织,随后制备视网膜石蜡切片,采用末端脱氧核糖核酸介导生物素化脱氧尿嘧啶缺口末端标记L（TUNEL）法进行凋亡细胞原位标记,行视网膜神经细胞凋亡计数,对所有数据进行统计学分析。实验结果拟用均数和标准差（x±s）表示,P〈0．05为差异有统计学意义。结果 相同观察时相,与阴性对照组比较,模型对照组大鼠视网膜TUNEL阳性细胞显著增多（P〈0．01）,在米诺环素组,大鼠视网膜TUNEL阳性细胞数比模型对照组明显减少,差异有统计学意义（P〈0．01）。结论：米诺环素能有效降低糖尿病大鼠视网膜神经细胞的凋亡,对糖尿病视网膜神经细胞有保护作用。     

Prospects of Parathyroid Hormone in Therapeutic Intervention

International Journal of Peptide Research and Therapeutics - Biologically active peptides and proteins have wide applications as therapeutic agents as well as diagnostics. Parathyroid hormone...     

基质蛋白:治疗HIV-1感染的新靶点

HIV—1基质蛋（matrix protein,MA）在HIV-1生命周期中的侵入融合、核运输及组装等环节中起着十分重要的调节作用。其结构中的N末端的核定位信号N（nuclear localization signal,NLS）是介导整合前复合体（preintegration complex,PIC）的核运输所必需的。MA在HIV—1复制中所起的关键作用以及核定位信号区的高度保守性,使它成为寻找新的作用机制和不易产生耐药性的抗艾滋病药物的新靶点。目前已报道了多种靶向MA核定位信号区的抑制剂。该文介绍HIV-1MA的结构、主要功能及靶向该蛋白质的抑制剂研究。     

Astrocytes: powering memory

Creating long-term memory requires a cellular program in neurons involving gene expression, protein synthesis, and formation of new synaptic connections. Suzuki et al. (2011) show that astrocytes, glial cells of the brain, play a necessary role in this program by converting glycogen to lactate and transporting it to neurons.     

Glucose Transport in Astrocytes: Regulation by Thyroid Hormone

Primary cultures of astrocytes from newborn rat brain showed evidence of a substrate-saturable process for glucose transport. The system shows a relatively high affinity for the substrate, with an apparent Km of approximately 1 mM. Maintenance of the cells in medium containing thyroid-hormone-free serum for 3, 6, or 9 days resulted in significantly reduced rates of hexose transport. Addition of exogenous triiodothyronine to the transport incubation medium of these "hypothyroid" cells markedly increased the net rate of 2-deoxyglucose uptake within 60 s to values equal to or above those of control cultures (cells maintained in normal serum). These findings support a key role for thyroid hormone in the transport of glucose across plasma membranes of brain cells and demonstrate the presence of this regulatory system in astrocytes.     

Expression of Sam68 Associates with Neuronal Apoptosis and Reactive Astrocytes After Spinal Cord Injury

Src-associated in mitosis (Sam68; 68 kDa) is a novel RNA-binding protein that belongs to the signal transduction and activation of RNA family involved in various biological processes. However, the expression and roles of Sam68 in the central nervous system remain unknown. In the present study, we performed a spinal cord injury (SCI) model in adult rats and found a significant increase of Sam68 protein levels in this model, which reached a peak at day 3 and then gradually returned to normal levels at day 14 after SCI. We use immunohistochemistry analysis revealing a widespread distribution of Sam68 in the spinal cord. In addition, double-immunofluorescence staining showed that Sam68 immunoreactivity was found predominantly in neurons and astrocytes. Moreover, colocalization of Sam68/active caspase-3 has been respectively detected in neuronal nuclei, and colocalization of Sam68/PCNA has been detected in glial fibrillary acidic protein. In vitro, we found that depletion of Sam68 by short interfering RNA inhibits neuronal apoptosis and astrocyte proliferation and decreases cyclin D1 protein levels. In conclusion, this is the first study to find the Sam68 expression in SCI. Our results suggest that Sam68 might be illustrated in the apoptosis of neurons and proliferation of astrocytes after SCI. This research will provide new drug targets for clinical treatment of SCI.     

Thrombin Regulation of Cell Function through Protease-Activated Receptors: Implications for Therapeutic Intervention

The serine protease thrombin is well recognized as being pivotal to the maintenance of hemostasis under both normal and pathological conditions. Its cellular actions are mediated through a unique family of protease-activated receptors (PARs). These receptors represent a novel family of G protein-coupled receptors that undergo proteolytic cleavage of their amino terminus and subsequent autoactivation by a tethered peptide ligand. This paper reviews the consequences of PAR activation in thrombosis, vascular injury, inflammation, tissue injury, and within the tumor microenvironment.     

The Octadecaneuropeptide ODN Protects Astrocytes against Hydrogen Peroxide-Induced Apoptosis via a PKA/MAPK-Dependent Mechanism

Astrocytes synthesize and release endozepines, a family of regulatory peptides, including the octadecaneuropeptide (ODN) an endogenous ligand of both central-type benzodiazepine (CBR) and metabotropic receptors. We have recently shown that ODN exerts a protective effect against hydrogen peroxide (H(2)O(2))-induced oxidative stress in astrocytes. The purpose of the present study was to determine the type of receptor and the transduction pathways involved in the protective effect of ODN in cultured rat astrocytes. We have first observed a protective activity of ODN at very low concentrations that was abrogated by the metabotropic ODN receptor antagonist cyclo(1-8)[DLeu(5)]OP, but not by the CBR antagonist flumazenil. We have also found that the metabotropic ODN receptor is positively coupled to adenylyl cyclase in astrocytes and that the glioprotective action of ODN upon H(2)O(2)-induced astrocyte death is PKA- and MEK-dependent, but PLC/PKC-independent. Downstream of PKA, ODN induced ERK phosphorylation, which in turn activated the expression of the anti-apoptotic gene Bcl-2 and blocked the stimulation by H(2)O(2) of the pro-apoptotic gene Bax. The effect of ODN on the Bax/Bcl-2 balance contributed to abolish the deleterious action of H(2)O(2) on mitochondrial membrane integrity and caspase-3 activation. Finally, the inhibitory effect of ODN on caspase-3 activity was shown to be PKA and MEK-dependent. In conclusion, the present results demonstrate that the potent glioprotective action of ODN against oxidative stress involves the metabotropic ODN receptor coupled to the PKA/ERK-kinase pathway to inhibit caspase-3 activation.