A human antibody against pathologic IAPP aggregates protects beta cells in type 2 diabetes models

In patients with type 2 diabetes, pancreatic beta cells progressively degenerate and gradually lose their ability to produce insulin and regulate blood glucose. Beta cell dysfunction and loss is associated with an accumulation of aggregated forms of islet amyloid polypeptide (IAPP) consisting of soluble prefibrillar IAPP oligomers as well as insoluble IAPP fibrils in pancreatic islets. Here, we describe a human monoclonal antibody selectively targeting IAPP oligomers and neutralizing IAPP aggregate toxicity by preventing membrane disruption and apoptosis in vitro. Antibody treatment in male rats and mice transgenic for human IAPP, and human islet-engrafted mouse models of type 2 diabetes triggers clearance of IAPP oligomers resulting in beta cell protection and improved glucose control. These results provide new evidence for the pathological role of IAPP oligomers and suggest that antibody-mediated removal of IAPP oligomers could be a pharmaceutical strategy to support beta cell function in type 2 diabetes

Selective Regulation of NR2B by Protein Phosphatase-1 for the Control of the NMDA Receptor in Neuroprotection

An imbalance between pro-survival and pro-death pathways in brain cells can lead to neuronal cell death and neurodegeneration. While such imbalance is known to be associated with alterations in glutamatergic and Ca2+ signaling, the underlying mechanisms remain undefined. We identified the protein Ser/Thr phosphatase protein phosphatase-1 (PP1), an enzyme associated with glutamate receptors, as a key trigger of survival pathways that can prevent neuronal death and neurodegeneration in the adult hippocampus. We show that PP1α overexpression in hippocampal neurons limits NMDA receptor overactivation and Ca2+ overload during an excitotoxic event, while PP1 inhibition favors Ca2+ overload and cell death. The protective effect of PP1 is associated with a selective dephosphorylation on a residue phosphorylated by CaMKIIα on the NMDA receptor subunit NR2B, which promotes pro-survival pathways and associated transcriptional programs. These results reveal a novel contributor to the mechanisms of neuroprotection and underscore the importance of PP1-dependent dephosphorylation in these mechanisms. They provide a new target for the development of potential therapeutic treatment of neurodegeneration

Protein phosphatase 1 regulates the histone code for long-term memory

Chromatin remodeling through histone posttranslational modifications (PTMs) and DNA methylation has recently been implicated in cognitive functions, but the mechanisms involved in such epigenetic regulation remain poorly understood. Here, we show that protein phosphatase 1 (PP1) is a critical regulator of chromatin remodeling in the mammalian brain that controls histone PTMs and gene transcription associated with long-term memory. Our data show that PP1 is present at the chromatin in brain cells and interacts with enzymes of the epigenetic machinery including HDAC1 (histone deacetylase 1) and histone demethylase JMJD2A (jumonji domain-containing protein 2A). The selective inhibition of the nuclear pool of PP1 in forebrain neurons in transgenic mice is shown to induce several histone PTMs that include not only phosphorylation but also acetylation and methylation. These PTMs are residue-specific and occur at the promoter of genes important for memory formation like CREB (cAMP response element-binding protein) and NF-kappaB (nuclear factor-kappaB). These histone PTMs further co-occur with selective binding of RNA polymerase II and altered gene transcription, and are associated with improved long-term memory for objects and space. Together, these findings reveal a novel mechanism for the epigenetic control of gene transcription and long-term memory in the adult brain that depends on PP1

The memory gene KIBRA is a bidirectional regulator of synaptic and structural plasticity in the adult brain

Memory formation is associated with activity-dependent changes in synaptic plasticity. The mechanisms underlying these processes are complex and involve multiple components. Recent work has implicated the protein KIBRA in human memory, but its molecular functions in memory processes remain not fully understood. Here, we show that a selective overexpression of KIBRA in neurons increases hippocampal long-term potentiation (LTP) but prevents the induction of long-term depression (LTD), and impairs spatial long-term memory in adult mice. KIBRA overexpression increases the constitutive recycling of AMPA receptors containing GluA1 (GluA1-AMPARs), and favors their activity-dependent surface expression. It also results in dramatic dendritic rearrangements in pyramidal neurons both in vitro and in vivo. KIBRA knockdown in contrast, abolishes LTP, decreases GluA1-AMPARs recycling and reduces dendritic arborization. These results establish KIBRA as a novel bidirectional regulator of synaptic and structural plasticity in hippocampal neurons, and of long-term memory, highly relevant to cognitive processes and their pathologies

Idebenone Protects against Retinal Damage and Loss of Vision in a Mouse Model of Leber’s Hereditary Optic Neuropathy

<div><p>Leber’s hereditary optic neuropathy (LHON) is an inherited disease caused by mutations in complex I of the mitochondrial respiratory chain. The disease is characterized by loss of central vision due to retinal ganglion cell (RGC) dysfunction and optic nerve atrophy. Despite progress towards a better understanding of the disease, no therapeutic treatment is currently approved for this devastating disease. Idebenone, a short-chain benzoquinone, has shown promising evidence of efficacy in protecting vision loss and in accelerating recovery of visual acuity in patients with LHON. It was therefore of interest to study suitable LHON models <i>in vitro</i> and <i>in vivo</i> to identify anatomical correlates for this protective activity. At nanomolar concentrations, idebenone protected the rodent RGC cell line RGC-5 against complex I dysfunction <i>in vitro.</i> Consistent with the reported dosing and observed effects in LHON patients, we describe that in mice, idebenone penetrated into the eye at concentrations equivalent to those which protected RGC-5 cells from complex I dysfunction <i>in vitro</i>. Consequently, we next investigated the protective effect of idebenone in a mouse model of LHON, whereby mitochondrial complex I dysfunction was caused by exposure to rotenone. In this model, idebenone protected against the loss of retinal ganglion cells, reduction in retinal thickness and gliosis. Furthermore, consistent with this protection of retinal integrity, idebenone restored the functional loss of vision in this disease model. These results support the pharmacological activity of idebenone and indicate that idebenone holds potential as an effective treatment for vision loss in LHON patients.</p></div

Pharmacokinetic analysis of idebenone in eye fluids.

<p>Concentrations of idebenone in aqueous humor (open circle) and vitreous humor (filled triangle) following once daily administration of idebenone in the diet for 21 days (A) and following single oral administration of idebenone at 60 mg/kg (B) were determined. Concentrations of idebenone in the eye fluids are expressed as ng/ml (left y axis) and nM (right y axis). For (A), sampling time was more than 8h after last dose of idebenone, the values therefore represent trough levels.</p

Idebenone prevents rotenone-induced RGC death. Analysis of RGCs in the mouse retina 7 days after intravitreal injection of rotenone or DMSO (Sham).

<p>Mice were treated with dietary idebenone (IDE 200, 400 and 2000 mg/kg body weight) or vehicle. (A) Images of retinal slices stained with anti-Brn3a primary antibody to visualize RGCs. Scale bar = 25 µm. (B) Quantification of RGCs (RGC number/mm) following idebenone treatment and rotenone injection (n = 6 to 10 per group). Data expressed as mean ± SEM.</p

Idebenone time-dependently restores rotenone-induced loss of vision.

<p>Visual acuity was evaluated by counting the number of head movements at a velocity of 3 rpm 7 days prior injection (day -7) and 1 to 70 days after injection (day 1, 7, 21, 35, 70) of rotenone (5 mM). Mice were treated with dietary idebenone 2000 mg/kg or vehicle for the time of the experiment. (A) Schematic representation of the experimental setup. After vehicle (DMSO) injection, head movements in both directions of drum rotation (clockwise: CW; counterclockwise CCW) remain intact. Injection of rotenone into the left eye however, affects only the CW responses (dashed arrow) whereas CCW responses remain unaffected. (B) Quantification of clockwise (CW) head movement (number of head movements/2 min) following vehicle treatment and rotenone injection (vehicle + rotenone, n = 10 animals), and idebenone 2000 mg/kg treatment and rotenone injection (IDE 2000+ rotenone, n = 11 animals). Data are expressed as mean ± SEM. Statistical significance relative to vehicle + rotenone group: p≤0.05 (*); (C) Percentage of mice showing clockwise (CW) head movements for each treatment group 70 days after injection. Responder: group of mice showing head movements; Non-responder: group of mice without head movements.</p

Idebenone protects against rotenone-induced gliosis.

<p>For analysis of gliosis 7 days after intravitreal injection of rotenone or DMSO (Sham), mice were treated with dietary idebenone (IDE 200, 400 and 2000 mg/kg body weight) or vehicle. (A) Images of retinal slices stained with anti-GFAP primary antibody to visualize Müller glial cell projections (white arrows). White arrowheads indicate outer plexiform layer and also illustrate rotenone induced reduction in retinal thickness (i.e. distance between white arrow heads and ganglion cell layer at the top of the images). Scale bar = 15 µm. (B) Quantification of gliosis (GFAP signal based on relative fluorescence units, RFU) following idebenone treatment and rotenone injection (n = 3 to 7 per group). Data are expressed as mean ± SEM.</p