Zong-yong Zhang

Strategy to Suppress Oxidative Damage-Induced Neurotoxicity in PC12 Cells by Curcumin: the Role of ROS-Mediated DNA Damage and the MAPK and AKT Pathways

Oxidative damage plays a key role in causation and progression of neurodegenerative diseases. Inhibition of oxidative stress represents one of the most effective ways in treating human neurologic diseases. Herein, we evaluated the protective effect of curcumin on PC12 cells against H2O2-induced neurotoxicity and investigated its underlying mechanism. The results indicated that curcumin pre-treatment significantly suppressed H2O2-induced cytotoxicity, inhibited the loss of mitochondrial membrane potential (Δψm) through regulation of Bcl-2 family expression, and ultimately reversed H2O2-induced apoptotic cell death in PC12 cells. Attenuation of caspase activation, poly(ADP-ribose) polymerase (PARP) cleavage, DNA damage, and accumulation of reactive oxygen species (ROS) all confirmed its protective effects. Moreover, curcumin markedly alleviated the dysregulation of the MAPK and AKT pathways induced by H2O2. Taken together, our findings suggest that the strategy of using curcumin could be a highly effective way in combating oxidative damage-mediated human neurodegenerative diseases.

Enhanced Therapeutic Potential of Nano-Curcumin Against Subarachnoid Hemorrhage-Induced Blood-Brain Barrier Disruption Through Inhibition of Inflammatory Response and Oxidative Stress

Curcumin and nano-curcumin both exhibit neuroprotective effects in early brain injury (EBI) after experimental subarachnoid hemorrhage (SAH). However, the mechanism that whether curcumin and its nanoparticles affect the blood–brain barrier (BBB) following SAH remains unclear. This study investigated the effect of curcumin and the poly(lactide-co-glycolide) (PLGA)-encapsulated curcumin nanoparticles (Cur-NPs) on BBB disruption and evaluated the possible mechanism underlying BBB dysfunction in EBI using the endovascular perforation rat SAH model. The results indicated that Cur-NPs showed enhanced therapeutic effects than that of curcumin in improving neurological function, reducing brain water content, and Evans blue dye extravasation after SAH. Mechanically, Cur-NPs attenuated BBB dysfunction after SAH by preventing the disruption of tight junction protein (ZO-1, occludin, and claudin-5). Cur-NPs also up-regulated glutamate transporter-1 and attenuated glutamate concentration of cerebrospinal fluid following SAH. Moreover, inhibition of inflammatory response and microglia activation both contributed to Cur-NPs’ protective effects. Additionally, Cur-NPs markedly suppressed SAH-mediated oxidative stress and eventually reversed SAH-induced cell apoptosis in rats. Our findings revealed that the strategy of using Cur-NPs could be a promising way in improving neurological function in EBI after experimental rat SAH.

Attenuation of Cisplatin-Induced Neurotoxicity by Cyanidin, a Natural Inhibitor of ROS-Mediated Apoptosis in PC12 Cells

Cisplatin-based chemotherapy in clinic is severely limited by its adverse effect, including neurotoxicity. Oxidative damage contributes to cisplatin-induced neurotoxicity, but the mechanism remains unclearly. Cyanidin, a natural flavonoid compound, exhibits powerful antioxidant activity. Hence, we investigated the protective effects of cyanidin on PC12 cells against cisplatin-induced neurotoxicity and explored the underlying mechanisms. The results showed that cisplatin-induced cytotoxicity was completely reversed by cyanidin through inhibition of PC12 cell apoptosis, as proved by the attenuation of Sub-G1 peak, PARP cleavage, and caspases-3 activation. Mechanistically, cyanidin significantly inhibited reactive oxygen species (ROS)-induced DNA damage in cisplatin-treated PC12 cells. Our findings revealed that cyanidin as an apoptotic inhibitor effectively blocked cisplatin-induced neurotoxicity through inhibition of ROS-mediated DNA damage and apoptosis, predicating its therapeutic potential in prevention of chemotherapy-induced neurotoxicity.Graphical AbstractCisplatin caused DNA damage, activated p53, and subsequently induced PC12 cells apoptosis by triggering ROS overproduction. However, cyanidin administration effectively inhibited DNA damage, attenuated p53 phosphorylation, and eventually reversed cisplatin-induced PC12 cell apoptosis through inhibition ROS accumulation.

Intranasal Delivery of Granulocyte Colony-Stimulating Factor Enhances Its Neuroprotective Effects Against Ischemic Brain Injury in Rats

Granulocyte colony-stimulating factor (G-CSF) is a hematopoietic growth factor with strong neuroprotective properties. However, it has limited capacity to cross the blood-brain barrier and thus potentially limiting its protective capacity. Recent studies demonstrated that intranasal drug administration is a promising way in delivering neuroprotective agents to the central nervous system. The current study therefore aimed at determining whether intranasal administration of G-CSF increases its delivery to the brain and its neuroprotective effect against ischemic brain injury. Transient focal cerebral ischemia in rat was induced with middle cerebral artery occlusion. Our resulted showed that intranasal administration is 8–12 times more effective than subcutaneous injection in delivering G-CSF to cerebrospinal fluid and brain parenchyma. Intranasal delivery enhanced the protective effects of G-CSF against ischemic injury in rats, indicated by decreased infarct volume and increased recovery of neurological function. The neuroprotective mechanisms of G-CSF involved enhanced upregulation of HO-1 and reduced calcium overload following ischemia. Intranasal G-CSF application also promoted angiogenesis and neurogenesis following brain ischemia. Taken together, G-CSF is a legitimate neuroprotective agent and intranasal administration of G-CSF is more effective in delivery and neuroprotection and could be a practical approach in clinic.

GABAB receptor promotes its own surface expression by recruiting a Rap1-dependent signaling cascade

ABSTRACT G-protein-coupled receptors (GPCRs) are key players in cell signaling, and their cell surface expression is tightly regulated. For many GPCRs such as β2-AR (β2-adrenergic receptor), receptor activation leads to downregulation of receptor surface expression, a phenomenon that has been extensively characterized. By contrast, some other GPCRs, such as GABAB receptor, remain relatively stable at the cell surface even after prolonged agonist treatment; however, the underlying mechanisms are unclear. Here, we identify the small GTPase Rap1 as a key regulator for promoting GABAB receptor surface expression. Agonist stimulation of GABAB receptor signals through Gαi/o to inhibit Rap1GAPII (also known as Rap1GAP1b, an isoform of Rap1GAP1), thereby activating Rap1 (which has two isoforms, Rap1a and Rap1b) in cultured cerebellar granule neurons (CGNs). The active form of Rap1 is then recruited to GABAB receptor through physical interactions in CGNs. This Rap1-dependent signaling cascade promotes GABAB receptor surface expression by stimulating receptor recycling. Our results uncover a new mechanism regulating GPCR surface expression and also provide a potential explanation for the slow, long-lasting inhibitory action of GABA neurotransmitter. Summary: GABAB receptor activation induces Rap1 activation to promote its own surface expression by stimulating receptor recycling, thereby providing a potential explanation for the long-lasting action of GABA.

Adoptive Regulatory T-cell Therapy Attenuates Perihematomal Inflammation in a Mouse Model of Experimental Intracerebral Hemorrhage

The CD4+CD25+ regulatory T cells (Tregs), an innate immunomodulator, suppress cerebral inflammation and maintain immune homeostasis in multiple central nervous system injury, but its role in intracerebral hemorrhage (ICH) has not been fully characterized. This study investigated the effect of Tregs on brain injury using the mouse ICH model, which is established by autologous blood infusion. The results showed that tail intravenous injection of Tregs significantly reduced brain water content and Evans blue dye extravasation of perihematoma at day (1, 3 and 7), and improved short- and long-term neurological deficits following ICH in mouse model. Tregs treatment reduced the content of pro-inflammatory cytokines interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and malondialdehyde, while increasing the superoxide dismutase (SOD) enzymatic activity at day (1, 3 and 7) following ICH. Furthermore, Tregs treatment obviously reduced the number of NF-κB+, IL-6+, TUNEL+ and active caspase-3+ cells at day 3 after ICH. These results indicate that adoptive transfer of Tregs may provide neuroprotection following ICH in mouse models.

Adoptive Regulatory T-cell Therapy Attenuates Subarachnoid Hemor-rhage-induced Cerebral Inflammation by Suppressing TLR4/NF-B Signaling Pathway

Inflammation is one major cause of poor outcomes of subarachnoid hemorrhage (SAH). The recent evidence suggested that adoptive regulatory T-cell (Treg) therapy conferred potential neuroprotection by suppressing cerebral inflammation against cerebral ischemia. Therefore, we proposed that Treg transfer might protect the brain against SAH by decreasing cerebral inflammation. In this study, we injected the autologous blood into cisterna magna twice to make the SAH model and administrated Tregs by vein to SAH rats. Intriguingly, adoptive transfer of Tregs significantly ameliorated SAH-induced brain edema and increased cerebral blood flow. Moreover, Treg-afforded cerebral protection was accompanied by suppressing SAH-induced cerebral inflammation. Concurrently, administration of Tregs attenuated the activation of the toll-like receptor 4 and nuclear factor-kappa B (TLR4/NF-κB) signaling pathway, which should be involved in the suppression of SAH-induced cerebral inflammation. Altogether, our study suggested that Treg adoptive transfer could attenuate SAH-induced cerebral inflammation by suppressing the activation of the TLR4/NF-κB signaling pathway, and thus provided new insights into the potent Treg cells-based therapy specifically targeting on post-SAH inflammatory dysregulation.

Allosteric control of an asymmetric transduction in a G protein-coupled receptor heterodimer

GPCRs play critical roles in cell communication. Although GPCRs can form heteromers, their role in signaling remains elusive. Here we used rat metabotropic glutamate (mGlu) receptors as prototypical dimers to study the functional interaction between each subunit. mGluRs can form both constitutive homo- and heterodimers. Whereas both mGlu2 and mGlu4 couple to G proteins, G protein activation is mediated by mGlu4 heptahelical domain (HD) exclusively in mGlu2-4 heterodimers. Such asymmetric transduction results from the action of both the dimeric extracellular domain, and an allosteric activation by the partially-activated non-functional mGlu2 HD. G proteins activation by mGlu2 HD occurs if either the mGlu2 HD is occupied by a positive allosteric modulator or if mGlu4 HD is inhibited by a negative modulator. These data revealed an oriented asymmetry in mGlu heterodimers that can be controlled with allosteric modulators. They provide new insight on the allosteric interaction between subunits in a GPCR dimer.

Selenocysteine induces apoptosis in human glioma cells: evidence for TrxR1-targeted inhibition and signaling crosstalk

Thioredoxin reductase (TrxR) as a selenium (Se)-containing antioxidase plays key role in regulating intracellular redox status. Selenocystine (SeC) a natural available Se-containing amino acid showed novel anticancer potential through triggering oxidative damage-mediated apoptosis. However, whether TrxR-mediated oxidative damage was involved in SeC-induced apoptosis in human glioma cells has not been elucidated yet. Herein, SeC-induced human glioma cell apoptosis was detected in vitro, accompanied by PARP cleavage, caspases activation and DNA fragmentation. Mechanically, SeC caused mitochondrial dysfunction and imbalance of Bcl-2 family expression. SeC treatment also triggered ROS-mediated DNA damage and disturbed the MAPKs and AKT pathways. However, inhibition of ROS overproduction effectively attenuated SeC-induced oxidative damage and apoptosis, and normalized the expression of MAPKs and AKT pathways, indicating the significance of ROS in SeC-induced apoptosis. Importantly, U251 human glioma xenograft growth in nude mice was significantly inhibited in vivo. Further investigation revealed that SeC-induced oxidative damage was achieved by TrxR1-targeted inhibition in vitro and in vivo. Our findings validated the potential of SeC to inhibit human glioma growth by oxidative damage-mediated apoptosis through triggering TrxR1-targeted inhibition.

The GluN1/GluN2B NMDA receptor and metabotropic glutamate receptor 1 negative allosteric modulator has enhanced neuroprotection in a rat subarachnoid hemorrhage model

ABSTRACT Excessive glutamate in cerebrospinal fluid after subarachnoid hemorrhage (SAH) causes excitotoxic damage through calcium overloading and a subsequent apoptotic cascade. GluN1/GluN2B containing N‐methyl‐Daspartate (NMDA) receptor and metabotropic glutamate receptor 1 (mGluR1) can play a leading role in glutamate‐mediated excitotoxicity. Here we report that Ifenprodil (100 &mgr;M), a negative allosteric modulator (NAM) of GluN1/GluN2B NMDA receptors, and JNJ16259685 (10 &mgr;M), a NAM of mGluR1, have an additive efficacy against glutamate (100 &mgr;M)‐induced Ca2+ release and cell apoptosis in primary cortical, hippocampal, and cerebellar granule neurons. Compared with intraperitoneal injection of Ifenprodil (10 mg/kg) and JNJ16259685 (1 mg/kg) separately, the combination therapy of Ifenprodil plus JNJ16259685 significantly improves the neurological deficit at 24 h and 72 h after experimental SAH. It reduces the number of TUNEL/DAPI‐positive and activated caspase‐3/NeuN‐positive cells in cortical and hippocampal CA1 regions at 72 h, decreases levels of glutamate in cerebrospinal fluid at 72 h, and reduces the mitochondrial Ca2+ concentration. Meanwhile, the combination therapy attenuates apoptosis as shown by an increased Bcl‐2 expression, decreased Bax expression and release of cytochrome c, and reduction of cleaved caspase‐9 and caspase‐3 at 24 h after SAH. These findings indicate that targeting both the intracellular Ca2+ overloading and neuronal apoptosis using the Ifenprodil and JNJ16259685 is a promising new therapy for SAH. Graphical abstract Excessive glutamate causes over‐stimulation of GluN1/GluN2B NMDA receptors and mGluR1, which in turn contributes to the calcium overload and cell death. Blockage of GluN1/GluN2B NMDA receptors and mGluR1 using combination therapy of Ifenprodil and JNJ16259685 has additive efficacy against SAH‐induced neurological deficit and neuronal apoptosis. Figure. No Caption available. HighlightsIfenprodil and JNJ16259685 have additive effect against glutamate‐mediated Ca2+ overloading and cell apoptosis.Ifenprodil and JNJ16259685 have enhanced neuroprotection against early brain injury after SAH.A dual‐target inhibition of Ca2+ overloading and apoptosis using the Ifenprodil and JNJ16259685