Dose-dependent folic acid and memantine treatments promote synergistic or additive protection against Aß(25-35) peptide-induced apoptosis in SH-SY5Y cells mediated by mitochondria stress-associated death signals.

Increased dietary folic acid (FA) is associated with reduced risks of Alzheimer's disease (AD). The AD drug memantine (Mn) has had limited therapeutic effects for the treatment of patients with moderate to severe AD. This study investigated whether and the underlying mechanisms by which the combination of Mn and FA may have synergistic or additive effects in protecting against amyloid-ß(25-35) peptide (Aß)-induced neurocytotoxicity. Aß treatment of human neuroblastoma SH-SY5Y cells significantly induced a 6-fold increase of apoptotic cells compared with the Aß-untreated group. Preincubation of Aß-exposed cells with FA (500 µM) or Mn (20 µM) caused a 22% and 10% reduction of apoptotic cells, respectively, whereas the combo-treatments at such doses synergistically alleviated Aß-induced apoptosis by 60% (P<0.05). The apoptotic protection by the combo-treatments coincided with attenuating Aß-elicited mitochondrial (mt) membrane depolarization and abolishing Aß-induced mt cytochrome c release to the cytosol. Increased levels of FA at 1000 µM in combination with 20 µM Mn exerted an additive protection against Aß(25-35)-induced-apoptosis as compared to the isolate Mn group (P<0.05). The combo-treatments reversed Aß-elicited mt membrane depolarization, attenuated Aß-elicited mt cytochrome c release to the cytosol, and diminished Aß-promoted superoxide generation. The apoptotic-protection by such combo-treatments was partially abolished by carbonyl cyanide 3-chlorophenylhydrazone (mt membrane potential uncoupler) and sodium azide (mt cytochrome c oxidase inhibitor). Taken together, the data demonstrated that dose-dependent FA and Mn synergistically or additively protected SH-SY5Y cells against Aß-induced apoptosis, which was partially, if not completely, mediated by mt stress-associated death signals.

YC-1 potentiates cAMP-induced CREB activation and nitric oxide production in alveolar macrophages.

Alveolar macrophages play significant roles in the pathogenesis of several inflammatory lung diseases. Increases in exhaled nitric oxide (NO) are well documented to reflect disease severity in the airway. In this study, we investigated the effect of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), a known activator of soluble guanylyl cyclase, on prostaglandin (PG)E1 (a stable PGE2 analogue) and forskolin (a adenylate cyclase activator) induced NO production and inducible NO synthase (iNOS) expression in rat alveolar macrophages (NR8383). YC-1 did not directly cause NO production or iNOS expression, but drastically potentiated PGE1- or forskolin-induced NO production and iNOS expression in NR8383 alveolar macrophages. Combination treatment with YC-1 and PGE1 significantly increased phosphorylation of the cAMP response element-binding protein (CREB), but not nuclear factor (NF)-κB activation. The combined effect on NO production, iNOS expression, and CREB phosphorylation was reversed by a protein kinase (PK)A inhibitor (H89), suggesting that the potentiating functions were mediated through a cAMP/PKA signaling pathway. Consistent with this, cAMP analogues, but not the cGMP analogue, caused NO release, iNOS expression, and CREB activation. YC-1 treatment induced an increase in PGE1-induced cAMP formation, which occurred through the inhibition of cAMP-specific phosphodiesterase (PDE) activity. Furthermore, the combination of rolipram (an inhibitor of PDE4), but not milronone (an inhibitor of PDE3), and PGE1 also triggered NO production and iNOS expression. In summary, YC-1 potentiates PGE1-induced NO production and iNOS expression in alveolar macrophages through inhibition of cAMP PDE activity and activation of the cAMP/PKA/CREB signaling pathway.

Changes in dietary folate intake differentially affect oxidised lipid and mitochondrial DNA damage in various brain regions of rats in the absence/presence of intracerebroventricularly injected amyloid ß-peptide challenge.

Accumulating evidence suggests that changes in dietary folate intake may modulate the risks of Alzheimer's disease (AD) through as yet unknown mechanisms. The aims of the present study were to investigate how dietary folate affects the brain folate distribution, levels of oxidised lipid and DNA damage in the absence/presence of ß-amyloid(25-35) (Aß) peptide challenge, a pathogenic hallmark of AD. Male Wistar rats were assigned to diets with folic acid at 0 (folate deprivation; FD), 8 (moderate folate; MF) and 8 mg folic acid/kg diet+0·003 % in drinking-water (folate supplementation; FS) for 4 weeks. A single injection of Aß peptide (1 mg/ml) or the vehicle solution was intracerebroventricularly (icv) administrated to rats a week before killing. Brain folate, a marker of oxidative injury, and neuronal death were assayed. In the absence of an Aß injection, FD rats showed reduced folate levels, and increased 2-thiobarbituric acid-reactive substances and a mitochondrial (mt)DNA 4834 bp large deletion (mtDNA4834 deletion) in the hippocampus compared with the counterpart brains of control rats (P < 0·05). A single icv injection of Aß peptide potentiated lipid peroxidation in the medulla of FD rats, which was ameliorated by feeding FD rats with the MF and FS diets (P < 0·05). Feeding the FS diet to Aß-injected rats enriched brain folate levels and reduced mtDNA4834 deletion in the hippocampal and medullary regions compared with corresponding tissues of Aß+FD rats (P < 0·05). Aß+FS rats had reduced rates of neuronal death in the frontal cortex compared with Aß+FD rats (P < 0·05). Taken together, our data revealed that folate deprivation differentially depleted brain folate levels, and increased lipid peroxidation and mtDNA4834 deletions, particularly, in the hippocampus. Upon Aß challenge, the FS diet may protect various brain regions against lipid peroxidation, mitochondrial genotoxicity and neural death associated with folate deprivation.

The isolated and combined effects of folic acid and synthetic bioactive compounds against Abeta(25-35)-induced toxicity in human microglial cells.

Folic acid plays an important role in neuronal development. A series of newly synthesized bioactive compounds (NSCs) was reported to exhibit immunoactive and neuroprotective functions. The isolated and combined effects of folic acid and NSCs against beta-amyloid (Abeta)-induced cytotoxicity are poorly understood. These effects were tested using human microglia cells (C13NJ) subjected to Abeta(25-35) challenge. According to an MTT assay, treatment of C13NJ cells with Abeta(25-35) at 10-100 microM for 48 h induced 18%-43% cellular death in a dose-dependent manner (p < 0.05). Abeta(25-35) treatment at 25 microM induced nitrite oxide (NO) release, elevated superoxide production, and reduced the distribution of cells in the S phase. Preincubation of C13NJ with 100 microM folic acid protected against Abeta(25-35)-induced cell death, which coincided with a reduction in NO release by folic acid supplements. NSC47 at a level of 50 microM protected against Abeta(25-35)-induced cell death and reduced Abeta-promoted superoxide production (p < 0.05). Folic acid in combination with NSC47 at their cytoprotective doses did not synergistically ameliorate Abeta(25-35)-associated NO release, superoxide production, or cell cycle arrest. Taken together, folic acid or NSC treatment alone, but not the combined regimen, protected against Abeta(25-35)-induced cell death, which may partially, if not completely, be mediated by free radical-scavenging effects.

Folic Acid potentiates the effect of memantine on spatial learning and neuronal protection in an Alzheimer's disease transgenic model.

Folic acid deficiency and hyperhomocysteinemia potentiate amyloid-beta (Abeta) neuron toxicity. Memantine, an NMDA antagonist used in moderate to severe AD, is considered to be neuroprotective. We propose that folic acid might have a synergistic effect for memantine in protecting neurons from Abeta accumulation. We treated 8-month-old Tg2576 transgenic mice with memantine (30 mg/kg/day) with or without folic acid (8 mg/kg/day) for 4 months. Escape latencies in the Morris water maze were significantly shorter in the folic acid-memantine treatment group Tg(+)_M+F compared to both the non-treatment transgenic controls Tg(+) and the memantine-treatment group Tg(+)_M (both p < 0.05). Analysis of Abeta40 and Abeta42 showed lower brain loads in both treatment groups but this did not reach statistical significance. Histopathology analysis showed that Tg(+)_M+F had lower ratios of neuronal damage than Tg(+) (p < 0.001) and Tg(+)_M (p< 0.005). DNA analysis revealed that in the Tg(+)M_+F group, transcription was upregulated in 72 brain genes involved in neurogenesis, neural differentiation, memory, and neurotransmission compared to the Tg(+)_M group. In conclusion, we found that folic acid may potentiate the effect of memantine on spatial learning and neuronal protection. The benefit of combination therapy may be through co-action on the methylation-controlled Abeta production, and modification of brain gene expression.

Viscolin, a new chalcone from Viscum coloratum, inhibits human neutrophil superoxide anion and elastase release via a cAMP-dependent pathway.

The mistletoe Viscum coloratum is used in traditional Chinese medicine to treat inflammatory diseases. In this study, a cellular model in isolated human neutrophils, which are important in the pathogenesis of rheumatoid arthritis, chronic obstructive pulmonary disease, and other inflammatory diseases, was established to elucidate the anti-inflammatory functions of V. coloratum. The partially purified extract of V. coloratum (PPE-SVC) potently inhibited formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP)-induced superoxide anion generation and elastase release in a concentration-dependent manner with IC(50) values of 0.58+/-0.03 and 4.93+/-0.54 microg/ml, respectively. Furthermore, a new chalcone derivative, viscolin (4',4''-dihydroxy-2',3',6',3''-tetramethoxy-1,3-diphenylpropane), was isolated from PPE-SVC. Viscolin was demonstrated to inhibit superoxide anion generation and elastase release, as well as to accelerate resequestration of cytosolic calcium in FMLP-activated human neutrophils. Furthermore, the inhibitory effects of viscolin were reversed by protein kinase A (PKA) inhibitor, suggesting that PKA mediates the viscolin-caused inhibitions. Viscolin induced a substantial increase in cAMP levels, and that occurred through the inhibition of phosphodiesterase (PDE) activity but not an increase in adenylate cyclase function. Consistent with this, viscolin potentiated the PGE(1)-caused inhibition of superoxide anion release and calcium mobilization, as well as elevation of cAMP formation. These results demonstrate that inhibition of inflammatory responses in human neutrophils by viscolin is associated with an elevation of cellular cAMP through inhibition of PDE. Comparable results were also observed by PPE-SVC, indicating that the effect of PPE-SVC is at least partly mediated by viscolin. In summary, viscolin is a novel inhibitor of PDE and might be useful for treatment of neutrophilic inflammation.