No abstract

Increasing evidence demonstrates that β-amyloid (Aβ) elicits oxidative stress, which contributes to the pathogenesis and disease progression of Alzheimer's disease (AD). Thus, there is interest in developing antioxidant therapies for the prevention/treatment of cognitive decline during AD. We reported previously that puerarin has antioxidative properties in vitro. Therefore, the aim of the present study was to determine whether puerarin improves cognitive function and reduces oxidative stress in amyloid precursor protein/presenilin-1 (APP/PS1) mice, a well established AD mouse model, and explore its potential mechanism. Our results show that oral administration of puerarin significantly ameliorates cognitive impairment in APP/PS1 mice assessed by the Morris water maze (MWM) test. This was accompanied by a significant decrease in the levels of lipid peroxidation (LPO) through, at least in part, induction of nuclear factor erythroid 2-related factor 2 (Nrf2) target gene heme oxygenase 1 (HO-1) in the hippocampus of APP/PS1 transgenic mice at 9 months of age, but without altering brain Aβ burden. Furthermore, puerarin significantly activated Akt, reduced activation of glycogen synthase kinase 3β (GSK-3β), and induced nuclear translocation of Nrf2 in the hippocampus of APP/PS1 mice but did not alter ERK1/2 phosphorylation. Thus, puerarin may improve cognitive performance in APP/PS1 mice through activation of the Akt/GSK-3β signaling pathway. These findings suggest that puerarin might be an attractive agent for prevention and treatment of cognitive impairment and dementia.

Recently, the significantly higher incidence of Alzheimer's disease (AD) in women than in men has been attributed to the loss of neuroprotective estrogen after menopause. Does phytoestrogen have the ability to protect against amyloid-β (Aβ) toxicity? The aim of this study was to evaluate hypothesis that β-ecdysterone (β-Ecd) protects SH-SY5Y cells from Aβ-induced apoptosis by separate signaling pathways involving protein kinase B (Akt) and c-Jun N-terminal kinase (JNK). Here, we demonstrate that phytoestrogen β-Ecd inhibits Aβ-triggered mitochondrial apoptotic pathway, as indicated by Bcl-2/Bax ratio elevation, cytochrome c (cyt c) release reduction, and caspase-9 inactivation. Interestingly, β-Ecd upregulates Bcl-2 expression in SH-SY5Y cells under both basal and Aβ-challenged conditions, but downregulates Bax expression only in Aβ-challenged conditions. Subsequently, Akt-dependent NF-κB activation is required for Bcl-2 upregulation, but not Bax downregulation, in response to β-Ecd, which was validated by the use of LY294002 and Bay11-7082. Notably, β-Ecd attenuates the Aβ-evoked reactive oxygen species (ROS) production, apoptosis signal-regulating kinase 1 (ASK1) phosphorylation and JNK activation without altering the basal ASK1 phosphorylation and JNK activation. ROS-scavenging by diphenyleneiodonium (DPI) abrogated the ability of β-Ecd to alter the activation of ASK1. Simultaneously, inhibition of JNK by SP600125 abolished β-Ecd-induced Bax downregulation in Aβ-challenged SH-SY5Y cells, whereas LY294002 failed to do so. Consequently, β-Ecd possesses neuroprotection by different and complementary pathways, which together promote a Bcl-2/Bax ratio. These data support our hypothesis and suggest that β-Ecd is a promising candidate for the treatment of AD.

Endoplasmic reticulum stress (ERS) and mitochondrial dysfunctions are thought to be involved in the dopaminergic neuronal death in Parkinson's disease (PD). In this study, we found that isorhynchophylline (IRN) significantly attenuated 1-methyl-4-phenylpyridinium (MPP)-induced apoptotic cell death and oxidative stress in PC12 cells. IRN markedly reduced MPP-induced-ERS responses, indicative of inositol-requiring enzyme 1 (IRE1) phosphorylation and caspase-12 activation. Furthermore, IRN inhibits MPP-triggered apoptosis signal-regulating kinase 1 (ASK1)/c-Jun N-terminal Kinase (JNK) signaling-mediated mitochondria-dependent apoptosis pathway. IRN-mediated attenuation of endoplasmic reticulum modulator caspase-12 activation was abolished by diphenyleneiodonium (DPI) or IRE-1α shRNA, but not by SP600125 or pifithrin-α in MPP-treated PC12 cells. Inhibitions of MPP-induced both cytochrome c release and caspase-9 activation by IRN were blocked by pre-treatment with DPI or pifithrin-α, but not by IRE-1α shRNA. IRN blocks the generation of reactive oxygen species upstream of both ASK1/JNK pathway and IRE1/caspase-12 pathway. Altogether, our in vitro findings suggest that IRN possesses potent neuroprotective activity and may be a potential candidate for the treatment of PD.

The pathogenesis of Parkinson's disease (PD) is multifactorial event. Combination therapies might be more effective in controlling the disease. Thus, the studies reported were designed to test the hypothesis that gastrodin (GAS)-induced de novo synthesis of nuclear factor E2-related factor 2 (Nrf2) and isorhynchophylline (IRN) inhibition of Nrf2 nuclear export contribute to their additive or synergistic neuroprotective effect. Here, we have demonstrated that the combination of GAS and IRN (GAS/IRN) protects SH-SY5Y cells against 1-methyl-4-phenylpyridinium (MPP) toxicity in a synergistic manner. Concomitantly, GAS/IRN led to a statistically significant reduction of oxidative stress, as assessed by reactive oxygen species (ROS) and lipid hydroperoxides (LPO), and enhancement of both glutathione (GSH) and thioredoxin (Trx) systems compared with treatment with either agent alone in MPP-challenged SH-SY5Y cells. Interestingly, GAS but not IRN activated extracellular signal-regulated kinases 1 and 2 (ERK1/2), leading to a increase in de novo synthesis of Nrf2 and nuclear import of Nrf2. Simultaneously, IRN but not GAS suppressed both constitutive glycogen synthase kinase (GSK)-3β and Fyn activation, which inhibited nuclear export of Nrf2. Importantly, simultaneous inhibition of GSK-3β pathway by IRN and activation of ERK1/2 pathway by GAS synergistically induced accumulation of Nrf2 in the nucleus in SH-SY5Y cells challenged with MPP. Furthermore, the activation of the ERK1/2 pathway and inhibition of GSK-3β pathway by GAS/IRN are mediated by independent mechanisms. Collectively, these novel findings suggest an in vitro model of synergism between IRN and GAS in the induction of neuroprotection warrant further investigations in vivo.

The aim of this study was to evaluate the hypothesis that emodin inhibits extracellular matrix (ECM)-related gene expression in activated hepatic stellate cells (HSCs) by blocking canonical or/and noncanonical components of transforming growth factor β1 (TGFβ1) intracellular signaling. Here, we demonstrate that emodin suppressed the gene expression of HSCs activation markers type I collagen, fibronectin, and α-smooth muscle actin, as well as HSCs proliferation. Mechanistically, emodin suppresses TGFβ1, TGFβ receptor II, TGFβ receptor I, and Smad4 gene expression, as well as Smad luciferase activity. Simultaneously, emodin reduced p38 mitogen-activated protein kinase (p38 ) activity but not c-Jun N-terminal kinases and extracellular signal-regulated kinases 1 and 2 phosphorylation in HSC-T6 cells. Interestingly, deprivation of TGFβ using a neutralizing antibody abolished emodin-mediated inhibitions of the both Smad transcriptional activity and p38 phosphorylation. Furthermore, emodin-mediated inhibition of HSCs activation could be partially blocked by PD98059 inhibition of p38 or short hairpin RNA-imposed knockdown of Smad4. Conversely, simultaneous inhibition of Smad4 and p38 pathways completely reverses the effects of emodin, suggesting that Smad and p38 locate downstream of TGFβ1 and regulate collagen genes expression in HSCs. Collectively, these data suggest that emodin is a promising candidate for the treatment of hepatic fibrosis.