Neurotrophic interactions between neurons and astrocytes following AAV1-Rheb(S16H) transduction in the hippocampus in vivo

Background and Purpose: We recently reported that AAV1-Rheb(S16H) transduction could protect hippocampal neurons through the induction of brain-derived neurotrophic factor (BDNF) in the rat hippocampus in vivo. It is still unclear how neuronal BDNF produced by AAV1-Rheb(S16H) transduction induces neuroprotective effects in the hippocampus and whether its up-regulation contributes to the enhance of a neuroprotective system in the adult brain. Experimental Approach: To determine the presence of a neuroprotective system in the hippocampus of patients with Alzheimer's disease (AD), we examined the levels of glial fibrillary acidic protein, BDNF and ciliary neurotrophic factor (CNTF) and their receptors, tropomyocin receptor kinase B (TrkB) and CNTF receptor α(CNTFRα), in the hippocampus of AD patients. We also determined whether AAV1-Rheb(S16H) transduction stimulates astroglial activation and whether reactive astrocytes contribute to neuroprotection in models of hippocampal neurotoxicity in vivo and in vitro. Key Results: AD patients may have a potential neuroprotective system, demonstrated by increased levels of full-length TrkB and CNTFRα in the hippocampus. Further AAV1-Rheb(S16H) transduction induced sustained increases in the levels of full-length TrkB and CNTFRα in reactive astrocytes and hippocampal neurons. Moreover, neuronal BDNF produced by Rheb(S16H) transduction of hippocampal neurons induced reactive astrocytes, resulting in CNTF production through the activation of astrocytic TrkB and the up-regulation of neuronal BDNF and astrocytic CNTF which had synergistic effects on the survival of hippocampal neurons in vivo. Conclusions and Implications: The results demonstrated that Rheb(S16H) transduction of hippocampal neurons could strengthen the neuroprotective system and this intensified system may have a therapeutic value against neurodegeneration in the adult brain. © 2019 The Authors. British Journal of Pharmacology published by John Wiley & Sons Ltd on behalf of British Pharmacological Society1

Aluminum modifies the properties of Alzheimer's disease PHF tau proteins in vivo and in vitro

Hyperphosphorylated adult human CNS tau (PHF tau or A68) forms paired helical filaments (PHFs) in neurofibrillary tangles (NFTs), neuropil threads, and dystrophic neurites associated with senile plaques (SPs) during the progression of Alzheimer's disease (AD). While amyloid fibrils in SPs are composed of beta-amyloid (A beta), NFTs and SPs contain similar associated components such as ubiquitin, alpha 1- antichymotrypsin (ACT), apolipoprotein E (ApoE), heparan sulfate proteoglycans (HSPGs), and aluminum salts. Thus, SPs and NFTs may result from specific interactions between PHF tau, A beta, and these other components. In fact, intracerebral injections of PHF tau induce co-deposits of A beta, ACT, and ubiquitin (Shin et al., 1993). To examine this issue further, we probed interactions between PHF tau, aluminum salts, and other plaque and tangle components. We investigated in vivo interactions of PHF tau and aluminum chloride (AlCl3) with other plaque and tangle components by injecting PHF tau with and without AlCl3 into the rodent brain. PHF tau co-injected with AlCl3 formed aggregates that persisted much longer in the rat brain, and induced longer-lived co-deposits of A beta, ubiquitin, ACT, and ApoE than PHF tau alone. Injections of PHF tau with AlCl3 also induced neurons near the injection site to acquire PHF tau-like properties as monitored with antibodies (AT8, T3P, PHF1) that recognize defined PHF tau epitopes containing phosphoserine residues (Ser202, Ser396, Ser404). Injections of AlCl3 alone as well as injections of normal adult and fetal CNS tau, several different synthetic peptides, neurofilament proteins, ACT, HSPGs, or ApoE with and without AlCl3 failed to induce co-deposits of A beta or alter the immunoreactivity of tau in rodent neurons. To determine if aluminum salts interact directly and specifically with PHF tau in situ, we pretreated sections of AD hippocampus with 10 mM AlCl3 and then probed these sections by immunohistochemistry with antibodies to PHF tau as well as to a number of other plaque and tangle components. Preincubation of these sections with AlCl3 diminished PHF tau immunoreactivity in NFTs and SPs using the PHF tau-specific antibodies AT8, T3P, and PHF1, while the immunoreactivity of other plaque and tangle proteins (A beta, ubiquitin, ACT, HSPGs, ApoE) was not abolished. We also examined the effects of AlCl3 on PHF tau and normal adult human CNS tau in vitro. AlCl3 had no effect on normal adult human CNS tau, while increasing concentrations of AlCl3 (from 0.1 to 1.0 mM) induced PHF tau to aggregate at the top of the stacking gel, and at high concentrations (0.3 and 1.0 mM) of AlCl3, PHF tau completely failed to enter the gel. These studies suggest that aluminum binds to PHF tau, induces these proteins to aggregate, and retards their proteolysis. Further, since intracerebral injections of PHF tau with and without AlCl3 in rats appear uniquely capable of inducing co-deposits of a number of proteins found in authentic AD SPs and NFTs (including A beta, ubiquitin, ACT, and ApoE), we speculate that the contributions of PHF tau to plaque and tangle formation in AD may be modulated by aluminum

Aluminum modifies the properties of Alzheimer\u27s disease PHF tau proteins in vivo and in vitro

Hyperphosphorylated adult human CNS tau (PHF tau or A68) forms paired helical filaments (PHFs) in neurofibrillary tangles (NFTs), neuropil threads, and dystrophic neurites associated with senile plaques (SPs) during the progression of Alzheimer\u27s disease (AD). While amyloid fibrils in SPs are composed of beta-amyloid (A beta), NFTs and SPs contain similar associated components such as ubiquitin, alpha 1- antichymotrypsin (ACT), apolipoprotein E (ApoE), heparan sulfate proteoglycans (HSPGs), and aluminum salts. Thus, SPs and NFTs may result from specific interactions between PHF tau, A beta, and these other components. In fact, intracerebral injections of PHF tau induce co-deposits of A beta, ACT, and ubiquitin (Shin et al., 1993). To examine this issue further, we probed interactions between PHF tau, aluminum salts, and other plaque and tangle components. We investigated in vivo interactions of PHF tau and aluminum chloride (AlCl3) with other plaque and tangle components by injecting PHF tau with and without AlCl3 into the rodent brain. PHF tau co-injected with AlCl3 formed aggregates that persisted much longer in the rat brain, and induced longer-lived co-deposits of A beta, ubiquitin, ACT, and ApoE than PHF tau alone. Injections of PHF tau with AlCl3 also induced neurons near the injection site to acquire PHF tau-like properties as monitored with antibodies (AT8, T3P, PHF1) that recognize defined PHF tau epitopes containing phosphoserine residues (Ser202, Ser396, Ser404). Injections of AlCl3 alone as well as injections of normal adult and fetal CNS tau, several different synthetic peptides, neurofilament proteins, ACT, HSPGs, or ApoE with and without AlCl3 failed to induce co-deposits of A beta or alter the immunoreactivity of tau in rodent neurons. To determine if aluminum salts interact directly and specifically with PHF tau in situ, we pretreated sections of AD hippocampus with 10 mM AlCl3 and then probed these sections by immunohistochemistry with antibodies to PHF tau as well as to a number of other plaque and tangle components. Preincubation of these sections with AlCl3 diminished PHF tau immunoreactivity in NFTs and SPs using the PHF tau-specific antibodies AT8, T3P, and PHF1, while the immunoreactivity of other plaque and tangle proteins (A beta, ubiquitin, ACT, HSPGs, ApoE) was not abolished. We also examined the effects of AlCl3 on PHF tau and normal adult human CNS tau in vitro. AlCl3 had no effect on normal adult human CNS tau, while increasing concentrations of AlCl3 (from 0.1 to 1.0 mM) induced PHF tau to aggregate at the top of the stacking gel, and at high concentrations (0.3 and 1.0 mM) of AlCl3, PHF tau completely failed to enter the gel. These studies suggest that aluminum binds to PHF tau, induces these proteins to aggregate, and retards their proteolysis. Further, since intracerebral injections of PHF tau with and without AlCl3 in rats appear uniquely capable of inducing co-deposits of a number of proteins found in authentic AD SPs and NFTs (including A beta, ubiquitin, ACT, and ApoE), we speculate that the contributions of PHF tau to plaque and tangle formation in AD may be modulated by aluminum

Skullcap (Scutellaria Baicalensis) Hexane Fraction Inhibits the Permeation of Ovalbumin and Regulates Th1/2 Immune Responses

Skullcap (Scutellaria baicalensis) is well known for its anti-inflammatory and anti-allergic effects. In our previous study, we found that skullcap could inhibit allergen permeation and regulate Th1/2 immune balance. To reveal the key fractions and components of skullcap, we fractionated skullcap extract into five fractions: hexane, chloroform, ethyl acetate, butanol, and water fraction. Among these fractions, the hexane fraction significantly suppressed the production of Th2-mediated cytokines (Interleukin (IL)-4, 5, 10 and 13) and increased Th1-mediated cytokines (Interferon (IFN)-γ and IL-12). Furthermore, the hexane fraction inhibited the permeation of ovalbumin (OVA), used as an allergen, across the intestinal epithelial cell monolayer. To confirm the active compounds in the hexane fraction, fatty acids were analyzed. Linoleic acid (LA, C18:2 (>59.7%)) was identified as the most important fatty acid in the skullcap hexane fraction. LA significantly suppressed IL-4 production and increased IFN-γ secretion, as well as inhibiting OVA permeation. Thus, LA significantly diminished the permeation of allergen by enhancing intestinal barrier function and regulated allergic responses to maintain Th1/Th2 immune balance

Effects of Silibinin Against Prothrombin Kringle-2-Induced Neurotoxicity in the Nigrostriatal Dopaminergic System In Vivo

Parkinson's disease (PD) and Alzheimer's disease exhibit common features of neurodegenerative diseases and can be caused by numerous factors. A common feature of these diseases is neurotoxic inflammation by activated microglia, indicating that regulation of microglial activation is a potential mechanism for preserving neurons in the adult brain. Recently, we reported that upregulation of prothrombin kringle-2 (pKr-2), one of the domains that make up prothrombin and which is cleaved and generated by active thrombin, induces nigral dopaminergic (DA) neuronal death through neurotoxic microglial activation in the adult brain. In this study, we show that silibinin, a flavonoid found in milk thistle, can suppress the production of inducible nitric oxide synthase and neurotoxic inflammatory cytokines, such as interleukin-1β and tumor necrosis factor-α, after pKr-2 treatment by downregulating the extracellular signal-regulated kinase signaling pathway in the mouse substantia nigra. Moreover, as demonstrated by immunohistochemical staining, measurements of the dopamine and metabolite levels, and open-field behavioral tests, silibinin treatment protected the nigrostriatal DA system resulting from the occurrence of pKr-2-triggered neurotoxic inflammation in vivo. Thus, we conclude that silibinin may be beneficial as a natural compound with anti-inflammatory effects against pKr-2-triggered neurotoxicity to protect the nigrostriatal DA pathway and its properties, and thus, may be applicable for PD therapy. © 2019, Mary Ann Liebert, Inc.1

TLR4-mediated autophagic impairment contributes to neuropathic pain in chronic constriction injury mice

Abstract Neuropathic pain is a complex, chronic pain state characterized by hyperalgesia, allodynia, and spontaneous pain. Accumulating evidence has indicated that the microglial Toll-like receptor 4 (TLR4) and autophagy are implicated in neurodegenerative diseases, but their relationship and role in neuropathic pain remain unclear. In this study, we examined TLR4 and its association with autophagic activity using a chronic constriction injury (CCI)-induced neuropathic pain model in wild-type (WT) and TLR4-knockout (KO) mice. The mice were assigned into four groups: WT-Contralateral (Contra), WT-Ipsilateral (Ipsi), TLR4 KO-Contra, and TLR4 KO-Ipsi. Behavioral and mechanical allodynia tests and biochemical analysis of spinal cord tissue were conducted following CCI to the sciatic nerve. Compared with the Contra group, mechanical allodynia in both the WT- and TLR4 KO-Ipsi groups was significantly increased, and a marked decrease of allodynia was observed in the TLR4 KO-Ipsi group. Although glial cells were upregulated in the WT-Ipsi group, no significant change was observed in the TLR4 KO groups. Moreover, protein expression and immunoreactive cell regulation of autophagy (Beclin 1, p62) were significantly increased in the neurons, but not microglia, of WT-Ipsi group compared with the WT-Contra group. The level of PINK1, a marker for mitophagy was increased in the neurons of WT, but not in TLR4 KO mice. Together, these results show that TLR4-mediated p62 autophagic impairment plays an important role in the occurrence and development of neuropathic pain. And what is more, microglial TLR4-mediated microglial activation might be indirectly coupled to neuronal autophage

CD200R/Foxp3-mediated signalling regulates microglial activation

The heterogeneity of microglial functions have either beneficial or detrimental roles in specific physiological or pathological environments. However, the details of what transcriptional mechanisms induce microglia to take beneficial phenotypes remain unknown. Here, we report that Foxp3 is essential for beneficial outcome of the microglial response and depends upon signalling by the immunoglobulin CD200 through its receptor (CD200R). Foxp3 expression was up-regulated in microglia activated by excitotoxicity-induced hippocampal neuroinflammation. Suppression of CD200R prevented anti-inflammatory phenotype of microglia, but over-expression of Foxp3 enhanced it. Phosphorylation of STAT6, a downstream effector of CD200R, modulated transcription of Foxp3. Finally, CD200R/Foxp3-mediated signalling enhanced hippocampal neuronal viability and conferred a degree of neuroprotection, presumably by counteracting inducible nitric oxide synthase. We conclude that enhancement of Foxp3 through CD200R could be neuroprotective by targeting the microglia.Y

A Novel Role for hGas7b in Microtubular Maintenance: POSSIBLE IMPLICATION IN TAU-ASSOCIATED PATHOLOGY IN ALZHEIMER DISEASE*

Here, we report a novel role for hGas7b (human growth arrest specific protein 7b) in the regulation of microtubules. Using a bioinformatic approach, we studied the actin-binding protein hGas7b with a structural similarity to the WW domain of a peptidyl prolyl cis/trans isomerase, Pin1, that facilitates microtubule assembly. Thus, we have demonstrated that hGas7b binds Tau at the WW motif and that the hGas7b/Tau protein complex interacts with the microtubules, promoting tubulin polymerization. Tau, in turn, contributes to protein stability of hGas7b. Furthermore, we observed decreased levels of hGas7b in the brains from patients with Alzheimer disease. These results suggest an important role for hGas7b in microtubular maintenance and possible implication in Alzheimer disease