Disrupted presynaptic nectin1-based neuronal adhesion in the entorhinal-hippocampal circuit contributes to early-life stress-induced memory deficits.

The cell adhesion molecule nectin3 and its presynaptic partner nectin1 have been linked to early-life stress-related cognitive disorders, but how the nectin1-nectin3 system contributes to stress-induced neuronal, circuit, and cognitive abnormalities remains to be studied. Here we show that in neonatally stressed male mice, temporal order and spatial working memories, which require the medial entorhinal cortex (MEC)-CA1 pathway, as well as the structural integrity of CA1 pyramidal neurons were markedly impaired in adulthood. These cognitive and structural abnormalities in stressed mice were associated with decreased nectin levels in entorhinal and hippocampal subregions, especially reduced nectin1 level in the MEC and nectin3 level in the CA1. Postnatal suppression of nectin1 but not nectin3 level in the MEC impaired spatial memory, whereas conditional inactivation of nectin1 from MEC excitatory neurons reproduced the adverse effects of early-life stress on MEC-dependent memories and neuronal plasticity in CA1. Our data suggest that early-life stress disrupts presynaptic nectin1-mediated interneuronal adhesion in the MEC-CA1 pathway, which may in turn contribute to stress-induced synaptic and cognitive deficits.

GPR17 mediates ischemia-like neuronal injury via microglial activation.

GPR17 is a G (i)-coupled dual receptor, linked to P2Y and CysLT receptors stimulated by uracil nucleotides and cysteinyl leukotrienes, respectively. Recent evidence has demonstrated that GPR17 inhibition ameliorates the progression of cerebral ischemic injury by regulating neuronal death and microglial activation. The present study aimed to assess the detailed regulatory roles of this receptor in oxygen­glucose deprivation/recovery (OGD/R)­induced ischemia­like injury in vitro and explore the underlying mechanism. The results demonstrated that OGD/R induced ischemic neuronal injury and microglial activation, including enhanced phagocytosis and increased inflammatory cytokine release in neuron­glial mixed cultures of cortical cells. GPR17 upregulation during OGD/R was spatially and temporally correlated with neuronal injury and microglial activation. In addition, GPR17 knockdown inhibited OGD/R­induced responses in neuron­glial mixed cultures. GPR17 knockdown also attenuated cell injury induced by the agonist leukotriene D4 (LTD4) or uridine 5'­diphosphate (UDP) in neuron­glial mixed cultures. However, GPR17 knockdown did not affect OGD/R­induced ischemic neuronal injury in primary cultures of neurons. In primary astrocyte cultures, neither GPR17 nor OGD/R induced injury. By contrast, GPR17 knockdown ameliorated OGD/R­induced microglial activation, boosting phagocytosis and inflammatory cytokine release in primary microglia cultures. Finally, the results demonstrated that the conditioned medium of microglia pretreated with OGD/R induced neuronal death, and the neuronal injury was significantly inhibited by GPR17 knockdown. These findings suggested that GPR17 may mediate ischemia­like neuronal injury and microglial activation in vitro; however, the protective effects on ischemic neuronal injury might depend upon microglial activation. Whether GPR17 regulates neuronal injury mediated by oligodendrocyte linkage remains to be investigated.

NAMPT inhibitor protects ischemic neuronal injury in rat brain via anti-neuroinflammation.

Nicotinamide phosphoribosyltransferase (NAMPT) is an important neuroprotective factor in cerebral ischemia, and it has been reported that NAMPT inhibitors can aggravate neuronal injury in the acute phase. However, because it is a cytokine, NAMPT participates in many inflammatory diseases in the peripheral system, and its inhibitors have therapeutic effects. Following cerebral ischemia, the peripheral and resident inflammatory and immune cells produce many pro-inflammatory mediators in the ischemic area, which induce neuroinflammation and impair the brain. However, the effects of NAMPT inhibitors in the neuroinflammation after ischemic brain injury remain unknown. Here, we found that FK866, a potent NAMPT inhibitor, decreased the level of TNF-α, NAMPT and IL-6 in the ischemic brain tissue one day after middle-cerebral-artery occlusion and reperfusion (MCAO/R), improved neurological dysfunction, decreased infarct volume and neuronal loss, and inhibited microgliosis and astrogliosis 14days after MCAO/R. The expression of NAMPT protein was induced in Iba1-positive microglia/macrophages in the ischemia core 14days after MCAO/R. In vitro studies show that oxygen-glucose deprivation and recovery (OGD/R) activate microglia. Activated microglia increased the activity of NF-κB, increased the mRNA synthesis of TNF-α, NAMPT and IL-6, and increased the secretion of TNF-α, NAMPT and IL-6. On the other hand, NAMPT can act synergistically with other cytokines and activate microglia. FK866 strongly inhibited these changes and alleviated OGD/R-induced activation of microglia. As such, NAMPT is a crucial determinant of cellular inflammation after cerebral ischemia. NAMPT inhibitors are novel compounds to protect neuronal injury from ischemia via anti-inflammatory effects.

Specific cell surface labeling of GPCRs using split GFP.

Specific cell surface labeling is essential for visualizing the internalization processes of G-protein coupled receptors (GPCRs) and for gaining mechanistic insight of GPCR functions. Here we present a rapid, specific, and versatile labeling scheme for GPCRs at living-cell membrane with the use of a split green fluorescent protein (GFP). Demonstrated with two GPCRs, GPR17 and CysLT2R, we show that two ß-stands (ß-stands 10 and 11) derived from a superfolder GFP (sfGFP) can be engineered to one of the three extracellular loop of a GPCR. The complementary fragment of sfGFP has nine ß-strands (ß-stands 1-9) that carries the mature fluorophore, and can be proteolytically derived from the full-length sfGFP. Separately the GFP fragments are non-fluorescent, but become fluorescent upon assembly, thus allowing specific labeling of the target proteins. The two GFP fragments rapidly assemble and the resulting complex is extremely tight under non-denaturing conditions, which allows real-time and quantitative assessment of the internalized GPCRs. We envision that this labeling scheme will be of great use for labeling other membrane proteins in various biological and pharmacological applications.

[Antioxidative effects of cysteinyl leukotriene receptor antagonists montelukast and HAMI 3379 on ischemic injury in rat cortical neurons in vitro].

OBJECTIVE: To investigate the antioxidative effects of two cysteinyl leukotriene receptors antagonists (CysLT1R and CysLT2R) montelukast and HAMI 3379 on ischemic injury of rat cortical neurons in vitro. METHODS: Cultured rat cortical neurons were pretreated with CysLT1R antagonist montelukast and CysLT2R antagonist HAMI 3379, and then exposed to oxygen-glucose deprivation/recovery (OGD/R）or H2O2. Reactive oxygen species (ROS) mitochondrial membrane potential (MMP) depolarization, neuronal viability and lactate dehydrogenase (LDH) release were determined. Meanwhile, RNA interference was used to inhibit the expression of CysLT1R and CysLT2R，and the effects were observed. RESULTS: ROS production in neurons was significantly increased after 1 h OGD, which reached the peak at 30 min and lasted for 1.5 h after recovery. Montelukast and HAMI 3379 at 0.01-1µmol/L moderately decreased OGD/R-induced ROS production (P<0.05). Montelukast mildly attenuated OGD/R-induced MMP depolarization (P<0.05)，but HAMI 3379 had no effect. H2O2 reduced neuronal viability and increased LDH release, namely inducing neuronal injury. Montelukast and HAMI 3379 at 0.1-1µmol/L moderately attenuated H2O2-induced neuronal injury (P<0.05). However, both CysLT1R siRNA and CysLT2R shRNA did not significantly affect the responses mentioned above. CONCLUSION: In ischemic neuronal injury, montelukast and HAMI 3379 exert a moderate antioxidative effect, and this effect may be receptor-independent.

[Effect of histone deacetylase inhibitor NL101 on rat neurons].

OBJECTIVE: To investigate the protective effect of histone deacetylase inhibitor NL101 on L-homocysteine (HCA)-induced toxicity in rat neurons, and the toxic effect on normal rat neurons. METHODS: In the presence of NL101 at various concentrations, HCA (5 mmol/L)-induced changes in cell density, necrosis, and viability were determined in the mixed cultures of rat cortical cells and the primary cultures of rat neurons. The direct effect of NL101 on primary neurons was also observed in the absence of HCA. Histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) was used as the control. After the treatments, cell viability, the density, and morphology of neurons and glial cells, and cell necrosis were determined. RESULTS: In the mixed cultures of cortical cells, NL101 had no effect on HCA (5 mmol/L)-induced cell number reduction at 0.001-10µmol/L; however, it significantly attenuated necrosis at 1-10 µmol/L, and increased neuronal number at 1 µmol/L. NL101 had no effect on the mixed cortical cells in the absence of HCA. In the primary neurons, NL101 reduced neuronal viability and mildly increased necrosis at 1-10 µmol/L in the absence of HCA, while it significantly attenuated HCA-induced neuronal viability reduction at 0.01-10 µmol/L and reduced neuronal necrosis at 1-10 µmol/L. The effects of NL101 were apparently similar to those of SAHA. CONCLUSION: NL101 has protective effect on HCA-induced neuronal injury but it is neurotoxic at high concentrations, which is similar to the typical histone deacetylase inhibitor SAHA.

[Effects of the water channel aquaporin 4 deficiency on bleomycin-induced lung fibrosis in mice].

OBJECTIVE: To evaluate the effect of water channel aquaporin 4 (AQP4) on bleomycin-induced lung fibrosis in mice. METHODS: In wild type and AQP4 gene knockout (AQP4-/-) mice, lung fibrosis was induced by injection of bleomycin (3 mg/kg) into the trachea and saline injection was used as a control. At d3, 7, 14, 28 after bleomycin-treatment, mice were randomly sacrificed in batch and the lung coefficient was determined. Serum levels of TGF-ß1 and TNF-α were measured by ELISA and hydroxyproline contents in lung tissue were determined by Alkaline hydrolysis method. H-E staining and Masson's staining were performed to examine the pathological changes of lung tissues after bleomycin-treatment. RESULTS: On d14 after bleomycin-treatment, the lung coefficients in wild type mice and AQP4-/- mice were 1.9-fold (12.69 ± 6.05 vs 6.80 ± 0.82, q=4.204, P<0.05) and 2.3-fold (14.05 ± 5.82 vs 6.05± 0.58, q=5.172, P<0.01) of that in control, respectively, but no significant difference was found between wild type and AQP4-/- mice in the lung coefficient value (P>0.05). The hydroxyproline contents in the lung increased after bleomycin-treatment; on d28, the lung hydroxyproline contents in wild type and in AQP4-/- mice were 1.55-fold (0.85 ± 0.22 g/mg vs 0.55 ± 0.14 µg/mg, q=4.313, P<0.05) and 1.4-fold (0.84 ± 0.13 µg/mg vs 0.60 ± 0.14µg/mg, q=4.595，P<0.05) of that in control, respectively, but no significant difference was noticed between wild type and AQP4-/- mice in lung hydroxyproline contents. There was a tendency that serum TGF-ß1 and TNF-α levels increased in bleomycin-treated mice, but no significant difference was found between wild type and AQP4-/- mice. AQP4-knockout showed no effects on pathological changes of lung tissues with H-E staining and Masson's staining in mice with bleomycin-induced lung fibrosis. CONCLUSION: AQP4 might not be involved in bleomycin-induced lung fibrosis in mice.

[Effects of leukotriene D4 on proliferation and migration of lung epithelial A549 cells in vitro].

OBJECTIVE: To investigate the effects of cysteinyl leukotriene (CysLT) receptor agonist leukotriene D4 (LTD4) on proliferation and migration in lung epithelial A549 cells. METHODS: The expression of CysLT1 receptor and CysLT2 receptor was determined by immunofluoresence staining in A549 cells. A549 cells were treated with LTD4 (0.01-100 nmol/L) for 24-72 h. Cell viability was detected by MTT reduction assay. Cell migration was determined by modified scratch and healing model. RESULTS: In A549 cells, CysLT1 receptor and CysLT2 receptor were mainly expressed in the cytoplasm, membrane and few in the nuclei. The treatment of LTD4 (0.01-100 nmol/L) for 24-72 h caused no effect on cell viability (Ps>0.05); when A549 cells were treated with 100 nmol/L LTD4 for 24, 48 and 72 h the cell viability was (103.00±4.46)%，(107.00±9.45)% and (105.00±9.02)% of control, respectively (Ps>0.05). The migration rate of A549 cells after scratching during the first 24 h was markedly greater than that during the second and third 24 h in the same concentration groups; however, no significant difference in migration rate was noticed when the cells were treated with different concentrations of LTD4 (0.01-100 nmol/L)(Ps>0.05). The migration of A549 cells was 1.15-fold, 1.21-fold and 1.06-fold of that of control when the cells were treated with 100 nmol/L LTD4 for 24, 48 and 72 h, respectively (Ps>0.05). CONCLUSION: The proliferation and migration of A549 cells are not changed when treated with 0.01-100 nmol LTD4 for up to 72h.

Cysteinyl leukotriene receptor 1 mediates LTD4-induced activation of mouse microglial cells in vitro.

AIM: To investigate the roles of cysteinyl leukotriene receptors CysLT1R and CysLT2R in leukotriene D4 (LTD4)-induced activation of microglial cells in vitro. METHODS: Mouse microglial cell line BV2 was transfected with pcDNA3.1(+)-hCysLT1R or pcDNA3.1(+)-hCysLT2R. The expression of relevant mRNAs and proteins in the cells was detected using RT-PCR and Western blotting, respectively. Phagocytosis was determined with flow cytometry analysis. The release of interleukin-1ß (IL-1ß) from the cells was measured using an ELISA assay. RESULTS: The expression of CysLT1R or CysLT2R was considerably increased in the transfected BV2 cells, and the receptors were mainly distributed in the plasma membrane and cytosol. Treatment of the cells expressing CysLT1R or CysLT2R with CysLT receptor agonist LTD4 (0.1-100 nmol/L) concentration-dependently enhanced the phagocytosis, and increased mRNA expression and release of IL-1ß. Moreover, the responses of hCysLT1R-BV2 cells to LTD4 were significantly larger than those of hCysLT2R-BV2 or WT-BV2 cells. Pretreatment of hCysLT1R-BV2 cells with the selective CysLT1R antagonist montelukast (1 µmol/L) significantly blocked LTD4-induced phagocytosis as well as the mRNA expression and release of IL-1ß, whereas the selective CysLT2R antagonist HAMI 3379 (1 µmol/L) had no such effects. CONCLUSION: CysLT1R mediates LTD4-induced activation of BV2 cells, suggesting that CysLT1R antagonists may exert anti-inflammatory activity in brain diseases.

HAMI 3379, a CysLT2 receptor antagonist, attenuates ischemia-like neuronal injury by inhibiting microglial activation.

The cysteinyl leukotrienes (CysLTs) are inflammatory mediators closely associated with neuronal injury after brain ischemia through the activation of their receptors, CysLT1R and CysLT2R. Here we investigated the involvement of both receptors in oxygen-glucose deprivation/recovery (OGD/R)-induced ischemic neuronal injury and the effect of the novel CysLT2R antagonist HAMI 3379 [3-({[(1S,3S)-3- carboxycyclohexyl]amino}carbonyl)-4-(3-{4-[4-(cyclo-hexyloxy)butoxy]phenyl}propoxy)benzoic acid] in comparison with the CysLT1R antagonist montelukast. In primary neurons, neither the nonselective agonist leukotriene D4 (LTD4) nor the CysLT2R agonist N-methyl-leukotriene C4 (NMLTC4) induced neuronal injury, and HAMI 3379 did not affect OGD/R-induced neuronal injury. However, in addition to OGD/R, LTD4 and NMLTC4 induced cell injury and neuronal loss in mixed cultures of cortical cells, and neuronal loss and necrosis in neuron-microglial cocultures. Moreover, they induced phagocytosis and cytokine release (interleukin-1ß and tumor necrosis factor-α) from primary microglia, and conditioned medium from the treated microglia induced neuronal necrosis. HAMI 3379 inhibited all of these responses, and its effects were the same as those of CysLT2R interference by CysLT2R short hairpin RNA, indicating CysLT2R dependence. In comparison, montelukast moderately inhibited OGD/R-induced primary neuronal injury and most OGD/R- and LTD4-induced (but not NMLTC4-induced) responses in mixed cultures, cocultures, and microglia. The effects of montelukast were both dependent and independent of CysLT1Rs because interference by CysLT1R small interfering RNA had limited effects on neuronal injury in neuron-microglial cocultures and on cytokine release from microglia. Our findings indicated that HAMI 3379 effectively blocked CysLT2R-mediated microglial activation, thereby indirectly attenuating ischemic neuronal injury. Therefore, CysLT2R antagonists may represent a new type of therapeutic agent in the treatment of ischemic stroke.

Aggravated inflammation and increased expression of cysteinyl leukotriene receptors in the brain after focal cerebral ischemia in AQP4-deficient mice.

OBJECTIVE: Aquaporin-4 (AQP4), the main water channel protein in the brain, plays a critical role in water homeostasis and brain edema. Here, we investigated its role in the inflammatory responses after focal cerebral ischemia. METHODS: In AQP4-knockout (KO) and wild-type mice, focal cerebral ischemia was induced by 30 min of middle cerebral arterial occlusion (MCAO). Ischemic neuronal injury and cellular inflammatory responses, as well as the expression and localization of cysteinyl leukotriene CysLT(2) and CysLT(1) receptors, were determined at 24 and 72 h after MCAO. RESULTS: AQP4-KO mice showed more neuronal loss, more severe microglial activation and neutrophil infiltration, but less astrocyte proliferation in the brain after MCAO than wild-type mice. In addition, the protein levels of both CysLT(1) and CysLT(2) receptors were up-regulated in the ischemic brain, and the up-regulation was more pronounced in AQP4-KO mice. The CysLT(1) and CysLT(2) receptors were primarily localized in neurons, microglia and neutrophils; those localized in microglia and neutrophils were enhanced in AQP4-KO mice. CONCLUSION: AQP4 may play an inhibitory role in postischemic inflammation.

Nuclear translocation of cysteinyl leukotriene receptor 1 is involved in oxygen-glucose deprivation-induced damage to endothelial cells.

AIM: Cysteinyl leukotriene receptor 1 (CysLT(1) receptor) is located in epithelial cells, and translocates from the plasma membrane to the nucleus in a ligand-dependent manner. Here, we investigated whether CysLT(1) receptors translocated to the nucleus in endothelial cells after ischemic insult in vitro and whether it was involved in ischemic injury to endothelial cells. METHODS: EA.hy926 cell line, derived from human umbilical vein endothelial cells, was subjected to oxygen-glucose deprivation (OGD). The expression and distribution of CysLT(1) receptors were detected by immunofluorescent staining, immunogold labeling and immunoblotting analyses. Cell viability was evaluated using MTT reduction assay. Necrosis and apoptosis were determined by double fluorescent staining with propidium iodide and Hoechst 33342. RESULTS: CysLT(1) receptors were primarily distributed in the cytoplasm and nucleus in EA.hy926 cells, and few was found in the cell membrane. OGD induced the translocation of CysLT(1) receptors from the cytoplasm to the nucleus in a time-depen dent manner, with a peak reached at 6 h. OGD-induced nuclear translocation of CysLT(1) receptors was inhibited by pretreatment with the CysLT(1) receptor antagonist pranlukast (10 µmol/L), or by preincubation with NLS-pep, a peptide corresponding to the nuclear localization sequence of CysLT(1) receptor (10 µg/mL). However, zileuton, an inhibitor of 5-lipoxygenase that was a key enzyme in cysteinyl leukotriene generation, did not inhibit the nuclear translocation of CysLT(1) receptors. Moreover, preincubation with NLS-pep (0.4 µg/mL) significantly ameliorated OGD-induced cell viability reduction and necrosis. CONCLUSION: CysLT(1) receptors in endothelial cells translocate to the nucleus in a ligand-independent manner after ischemic insult in vitro, and it is involved in the ischemic injury.

Intracerebroventricular injection of HAMI 3379, a selective cysteinyl leukotriene receptor 2 antagonist, protects against acute brain injury after focal cerebral ischemia in rats.

Cysteinyl leukotrienes (CysLTs) induce inflammatory responses by activating their receptors, CysLT(1)R and CysLT(2)R. We recently reported that CysLT(2)R is involved in neuronal injury, astrocytosis and microgliosis after focal cerebral ischemia in rats. Here, we determined whether HAMI 3379, a selective CysLT(2)R antagonist, protects against acute brain injury after focal cerebral ischemia in rats. We induced transient focal cerebral ischemia by 30 min of middle cerebral artery occlusion (MCAO), followed by 24h of reperfusion. HAMI 3379 (1, 10 or 100 ng) was injected intracerebroventricularly (i.c.v.) 30 min before MCAO, and the CysLT(1)R antagonist pranlukast (0.1mg/kg, i.p.) was used as a positive control. HAMI 3379 at 10 and 100 ng (but not at 1 ng) attenuated the neurological deficits, and reduced infarct volume, brain edema, IgG exudation, neuronal degeneration and neuronal loss. This protective effect was similar to that of pranlukast. Thus, HAMI 3339 at 10-100 ng i.c.v. is neuroprotective against acute brain injury after focal cerebral ischemia in rats. These findings suggest therapeutic potential for CysLT(2)R antagonists in the treatment of ischemic stroke.

Transforming growth factor ß1-induced astrocyte migration is mediated in part by activating 5-lipoxygenase and cysteinyl leukotriene receptor 1.

BACKGROUND: Transforming growth factor-ß 1 (TGF-ß 1) is an important regulator of cell migration and plays a role in the scarring response in injured brain. It is also reported that 5-lipoxygenase (5-LOX) and its products, cysteinyl leukotrienes (CysLTs, namely LTC4, LTD4 and LTE4), as well as cysteinyl leukotriene receptor 1 (CysLT1R) are closely associated with astrocyte proliferation and glial scar formation after brain injury. However, how these molecules act on astrocyte migration, an initial step of the scarring response, is unknown. To clarify this, we determined the roles of 5-LOX and CysLT1R in TGF-ß 1-induced astrocyte migration. METHODS: In primary cultures of rat astrocytes, the effects of TGF-ß 1 and CysLT receptor agonists on migration and proliferation were assayed, and the expression of 5-LOX, CysLT receptors and TGF-ß1 was detected. 5-LOX activation was analyzed by measuring its products (CysLTs) and applying its inhibitor. The role of CysLT1R was investigated by applying CysLT receptor antagonists and CysLT1R knockdown by small interfering RNA (siRNA). TGF-ß 1 release was assayed as well. RESULTS: TGF-ß 1-induced astrocyte migration was potentiated by LTD4, but attenuated by the 5-LOX inhibitor zileuton and the CysLT1R antagonist montelukast. The non-selective agonist LTD4 at 0.1 to 10 nM also induced a mild migration; however, the selective agonist N-methyl-LTC4 and the selective antagonist Bay cysLT2 for CysLT2R had no effects. Moreover, CysLT1R siRNA inhibited TGF-ß 1- and LTD4-induced astrocyte migration by down-regulating the expression of this receptor. However, TGF-ß 1 and LTD4 at various concentrations did not affect astrocyte proliferation 24 h after exposure. On the other hand, TGF-ß 1 increased 5-LOX expression and the production of CysLTs, and up-regulated CysLT1R (not CysLT2R), while LTD4 and N-methyl-LTC4 did not affect TGF-ß 1 expression and release. CONCLUSIONS: TGF-ß 1-induced astrocyte migration is, at least in part, mediated by enhanced endogenous CysLTs through activating CysLT1R. These findings indicate that the interaction between the cytokine TGF-ß 1 and the pro-inflammatory mediators CysLTs in the regulation of astrocyte function is relevant to glial scar formation.

[Effect of montelukast on morphological changes in neurons after ischemic injury].

OBJECTIVE: To determine the effect of montelukast, a cysteinyl leukotriene receptor 1 antagonist, on morphological changes in rat neurons after ischemic injury. METHODS: The in vivo ischemia injury was induced by oxygen-glucose deprivation (OGD) for 2 h and reperfusion (R) for 24 h (OGD/R) in rat neurons primary culture and mixed cortex culture. In the presence or absence of various concentrations of montelukast, neuron number, area of neuron, number of neuritis per neuron, branch number of primary neuritis and primary neurite length were determined for evaluating morphological changes in neurons. RESULTS: OGD/R significantly reduced neuron number, and altered neuron morphology. In cortical neuron cultures, montelukast (0.0001-1 µmol/L) attenuated OGD/R-induced reduction in neuron number, and inhibited OGD/R-induced increase in branch number of primary neuritis. In the mixed cultures, montelukast (0.0001-0.1 µmol/L) increased the primary neurite length, and reduced number of neuritis and branch number of primary neurite after OGD/R. CONCLUSION: Montelukast has a protective effect on ischemic injury in neurons.

Aggravated chronic brain injury after focal cerebral ischemia in aquaporin-4-deficient mice.

The water channel aquaporin-4 (AQP4) is important in brain water homeostasis, and is also involved in astrocyte growth and glial scar formation. It has been reported that AQP4 deficiency attenuates acute ischemic brain injury as a result of reducing cytotoxic edema. Here, we determined whether AQP4 deficiency influences chronic brain injury after focal cerebral ischemia induced by 30 min of middle cerebral artery occlusion (MCAO). AQP4(-/-) mice exhibited a lower survival rate and less body weight gain than wild-type mice, but their neurological deficits were similar to wild-type mice during 35 days after MCAO. At 35 days after MCAO, AQP4(-/-) mice showed more severe brain atrophy and cavity formation in the ischemic hemisphere as well as more neuronal loss in the hippocampus. Furthermore, astrocyte proliferation and glial scar formation were impaired in AQP4(-/-) mice. Therefore, AQP4 deficiency complicated by astrocyte dysfunction aggravates chronic brain injury after focal cerebral ischemia, suggesting that AQP4 may be important in the chronic phase of the post-ischemic recovery process.

Aquaporin-4 deficiency attenuates acute lesions but aggravates delayed lesions and microgliosis after cryoinjury to mouse brain.

OBJECTIVE: To determine whether aquaporin-4 (AQP4) regulates acute lesions, delayed lesions, and the associated microglial activation after cryoinjury to the brain. METHODS: Brain cryoinjury was applied to AQP4 knockout (KO) and wild-type mice. At 24 h and on days 7 and 14 after cryoinjury, lesion volume, neuronal loss, and densities of microglia and astrocytes were determined, and their changes were compared between AQP4 KO and wild-type mice. RESULTS: Lesion volume and neuronal loss in AQP4 KO mice were milder at 24 h following cryoinjury, but worsened on days 7 and 14, compared to those in wild-type mice. Besides, microglial density increased more, and astrocyte proliferation and glial scar formation were attenuated on days 7 and 14 in AQP4 KO mice. CONCLUSION: AQP4 deficiency ameliorates acute lesions, but worsens delayed lesions, perhaps due to the microgliosis in the late phase.

Anti-proliferation effect of APO866 on C6 glioblastoma cells by inhibiting nicotinamide phosphoribosyltransferase.

Nicotinamide phosphoribosyltransferase (NAMPT) is a key enzyme in the salvaging pathway for the synthesis of nicotinamide adenine dinucleotide (NAD) that is involved in cell metabolism and proliferation. NAMPT is normally absent in astrocyte but highly expressed in glioblastoma, suggesting that it may promote cell survival through synthesizing more NAD. In this report, we evaluated the effect of APO866, a potent inhibitor of NAMPT against C6 glioblastoma. We found that APO866 inhibited the growth of C6 glioblastoma cells with IC(50) in nano-molar range. APO866 depleted intracellular NAD, caused marked inhibition of ERK activation and induced G2/M cell-cycle arrest. The effects by APO866 were abrogated by nicotinamide mononucleotide (NMN), the direct product of NAMPT. Administration of U0126, an ERK1/2 inhibitor, inhibited cell growth but displayed no synergistic effect with APO866. Taken together, our results indicated that APO866 is a potent growth inhibitor against glioblastoma through targeting NAMPT.

[Construction of HEK293 cell lines expressing hCysLT2 receptor and its application in screening of antagonists].

OBJECTIVE: To construct HEK293 cell lines stably expressing hCysLT(2) receptor, and to evaluate its application in screening of synthetic compounds with antagonist activity. METHODS: The recombinant plasmid pcDNA3.1(+)-hCysLT(2) was transfected into HEK293 cells using Lipofectamin 2000. The transfected HEK293 cells were selected in 96 well plates by limiting dilution with 600 µg/ml C418 for 8 weeks. The expression of human CysLT(2) receptor was detected by RT-PCR and immunofluorescence staining. In HEK293 cells stably transfected with hCysLT(2), the agonist LTD(4)-induced elevation of intracellular calcium concentration ([Ca2(+)]i) was measured as the index for screening compounds with antagonist activity. RESULT: After selection in 96 well plates by limiting dilution, 12 monoclones were obtained and 11 of them highly expressed hCysLT(2) receptor. The positive control ATP at 50 µmol/L and LTD(4) at 100 nmol/L elevated [Ca2(+)]i in hCysLT(2)-HEK293 cells. AP-2100984 inhibited LTD(4)-induced [Ca2(+)]i elevation, but selective CysLT(1) receptor antagonists did not exert such an effect. The newly synthesized compounds DXW2, DXW3, DXW4, DXW5, DXW9, DXW25, DXW26, DXW29 and DXW35 at 1 µmol/L significantly inhibited LTD(4)-induced [Ca2(+)]i elevation. The IC(50) values of DXW4 and DXW5 were 0.25 µmol/L and 7.5 µmol/L. CONCLUSION: HEK293 cell lines stably expressing hCysLT(2) receptor have been successfully constructed, and can be used to screen compounds with CysLT(2) receptor antagonist activity.

[Effects of agonist and antagonist of cysteinyl leukotriene receptors on differentiation of rat glioma C6 cells].

OBJECTIVE: To investigate the role of cysteinyl leukotriene (CysLT) receptors in the differentiation of rat glioma C6 cells. METHODS: Rat glioma C6 cells were treated with the agonist LTD(4), the CysLT(1) receptor antagonist montelukast and the differentiation inducer forskolin. Cell morphology and GFAP protein expression were determined after treatments. RESULT: Forskolin (10 µmol/L) induced morphological changes and GFAP protein expression (cell differentiation) in C6 cells, but LTD(4) (0.1-100 nmol/L) did not induce these changes. Montelukast (1 µmol/L) alone did not affect C6 cell differentiation, while it induced the differentiation when combined with the LTD(4) (100 nmol/L). CONCLUSION: The CysLT(2) receptor may modulate the differentiation of rat glioma C6 cells.