Model biological systems demonstrate the inducibility of pathways that strongly reduce cryoprotectant toxicity.

Cryoprotectant toxicity is a limiting factor for the cryopreservation of many living systems. We were moved to address this problem by the potential of organ vitrification to relieve the severe shortage of viable donor organs available for human transplantation. The M22 vitrification solution is presently the only solution that has enabled the vitrification and subsequent transplantation with survival of large mammalian organs, but its toxicity remains an obstacle to organ stockpiling for transplantation. We therefore undertook a series of exploratory studies to identify potential pretreatment interventions that might reduce the toxic effects of M22. Hormesis, in which a living system becomes more resistant to toxic stress after prior subtoxic exposure to a related stress, was investigated as a potential remedy for M22 toxicity in yeast, in the nematode worm C. elegans, and in mouse kidney slices. In yeast, heat shock pretreatment increased survival by 18-fold after exposure to formamide and by over 9-fold after exposure to M22 at 30 °C; at 0 °C and with two-step addition, treatment with 90% M22 resulted in 100% yeast survival. In nematodes, surveying a panel of pretreatment interventions revealed 3 that conferred nearly total protection from acute whole-worm M22-induced damage. One of these protective pretreatments (exposure to hydrogen peroxide) was applied to mouse kidney slices in vitro and was found to strongly protect nuclear and plasma membrane integrity in both cortical and medullary renal cells exposed to 75-100% M22 at room temperature for 40 min. These studies demonstrate for the first time that endogenous cellular defenses, conserved from yeast to mammals, can be marshalled to substantially ameliorate the toxic effects of one of the most toxic single cryoprotectants and the toxicity of the most concentrated vitrification solution so far described for whole organs.

Myocardial infarction elevates endoplasmic reticulum stress and protein aggregation in heart as well as brain.

Cardiovascular diseases, including myocardial infarction (MI), constitute the leading cause of morbidity and mortality worldwide. Protein-aggregate deposition is a hallmark of aging and neurodegeneration. Our previous study reported that aggregation is strikingly elevated in hearts of hypertensive and aged mice; however, no prior study has addressed MI effects on aggregation in heart or brain. Here, we present novel data on heart and brain aggregation in mice following experimental MI, induced by left coronary artery (LCA) ligation. Infarcted and peri-infarcted heart tissue, and whole cerebra, were isolated from mice at sacrifice, 7 days following LCA ligation. Sham-MI mice (identical surgery without ligation) served as controls. We purified detergent-insoluble aggregates from these tissues, and quantified key protein constituents by high-resolution mass spectrometry (LC-MS/MS). Infarct heart tissue had 2.5- to 10-fold more aggregates than non-infarct or sham-MI heart tissue (each P = 0.001). Protein constituents from MI cerebral aggregates overlapped substantially with those from human Alzheimer's disease brain. Prior injection of mice with mesenchymal stem cell (MSC) exosomes, shown to limit infarct size after LCA ligation, reduced cardiac aggregation ~ 60%, and attenuated markers of endoplasmic reticulum (ER) stress in heart and brain (GRP78, ATF6, P-PERK) by 50-75%. MI also elevated aggregate constituents enriched in Alzheimer's disease (AD) aggregates, such as proteasomal subunits, heat-shock proteins, complement C3, clusterin/ApoJ, and other apolipoproteins. These data provide novel evidence that aggregation is elevated in mouse hearts and brains after myocardial ischemia, leading to cognitive impairment resembling AD, but can be attenuated by exosomes or drug (CDN1163) interventions that oppose ER stress.

Physiological Consequences of Targeting 14-3-3 and Its Interacting Partners in Neurodegenerative Diseases.

The mammalian 14-3-3 family comprises seven intrinsically unstructured, evolutionarily conserved proteins that bind >200 protein targets, thereby modulating cell-signaling pathways. The presence of 14-3-3 proteins in cerebrospinal fluid provides a sensitive and specific biomarker of neuronal damage associated with Alzheimer's disease (AD), Creutzfeldt−Jakob disease (CJD), spongiform encephalitis, brain cancers, and stroke. We observed significant enrichment of 14-3-3 paralogs G, S, and Z in human brain aggregates diagnostic of AD. We used intra-aggregate crosslinking to identify 14-3-3 interaction partners, all of which were significantly enriched in AD brain aggregates relative to controls. We screened FDA-approved drugs in silico for structures that could target the 14-3-3G/hexokinase interface, an interaction specific to aggregates and AD. C. elegans possesses only two 14-3-3 orthologs, which bind diverse proteins including DAF-16 (a FOXO transcription factor) and SIR-2.1 (a sensor of nutrients and stress), influencing lifespan. Top drug candidates were tested in C. elegans models of neurodegeneration-associated aggregation and in a human neuroblastoma cell-culture model of AD-like amyloidosis. Several drugs opposed aggregation in all models assessed and rescued behavioral deficits in C. elegans AD-like neuropathy models, suggesting that 14-3-3 proteins are instrumental in aggregate accrual and supporting the advancement of drugs targeting 14-3-3 protein complexes with their partners.

Design and Synthesis of Novel Hybrid 8-Hydroxy Quinoline-Indole Derivatives as Inhibitors of Aß Self-Aggregation and Metal Chelation-Induced Aß Aggregation.

A series of novel hybrid 8-hydroxyquinoline-indole derivatives (7a-7e, 12a-12b and 18a-18h) were synthesized and screened for inhibitory activity against self-induced and metal-ion induced Aß1-42 aggregation as potential treatments for Alzheimer's disease (AD). In vitro studies identified the most inhibitory compounds against self-induced Aß1-42 aggregation as 18c, 18d and 18f (EC50 = 1.72, 1.48 and 1.08 µM, respectively) compared to the known anti-amyloid drug, clioquinol (1, EC50 = 9.95 µM). The fluorescence of thioflavin T-stained amyloid formed by Aß1-42 aggregation in the presence of Cu2+ or Zn2+ ions was also dramatically decreased by treatment with 18c, 18d and 18f. The most potent hybrid compound 18f afforded 82.3% and 88.3% inhibition, respectively, against Cu2+- induced and Zn2+- induced Aß1-42 aggregation. Compounds 18c, 18d and 18f were shown to be effective in reducing protein aggregation in HEK-tau and SY5Y-APPSw cells. Molecular docking studies with the most active compounds performed against Aß1-42 peptide indicated that the potent inhibitory activity of 18d and 18f were predicted to be due to hydrogen bonding interactions, π-π stacking interactions and π-cation interactions with Aß1-42, which may inhibit both self-aggregation as well as metal ion binding to Aß1-42 to favor the inhibition of Aß1-42 aggregation.

Leave-one-out-analysis (LOOA): web-based tool to predict influential proteins and interactions in aggregate-crosslinking proteomic data.

Many age-progressive diseases are accompanied by (and likely caused by) the presence of protein aggregation in affected tissues. Protein aggregates are conjoined by complex protein-protein interactions, which remain poorly understood. Knowledge of the proteins that comprise aggregates, and their adherent interfaces, can be useful to identify therapeutic targets to treat or prevent pathology, and to discover small molecules for disease interventions. We present web-based software to evaluate and rank influential proteins and protein-protein interactions based on graph modelling of the cross linked aggregate interactome. We have used two network-graph-based techniques: Leave-One-Vertex-Out (LOVO) and Leave-One-Edge-Out (LOEO), each followed by dimension reduction and calculation of influential vertices and edges using Principal Components Analysis (PCA) implemented as an R program. This method enables researchers to quickly and accurately determine influential proteins and protein-protein interactions present in their aggregate interactome data.

Alzheimer's-specific brain amyloid interactome: Neural-network analysis of intra-aggregate crosslinking identifies novel drug targets.

Alzheimer's disease (AD) is characterized by peri-neuronal amyloid plaque and intra-neuronal neurofibrillary tangles. These aggregates are identified by the immunodetection of "seed" proteins (Aß1-42 and hyperphosphorylated tau, respectively), but include many other proteins incorporated nonrandomly. Using click-chemistry intra-aggregate crosslinking, we previously modeled amyloid "contactomes" in SY5Y-APPSw neuroblastoma cells, revealing that aspirin impedes aggregate growth and complexity. By an analogous strategy, we now construct amyloid-specific aggregate interactomes of AD and age-matched-control hippocampi. Comparing these interactomes reveals AD-specific interactions, from which neural-network (NN) analyses predict proteins with the highest impact on pathogenic aggregate formation and/or stability. RNAi knockdowns of implicated proteins, in C. elegans and human-cell-culture models of AD, validated those predictions. Gene-Ontology meta-analysis of AD-enriched influential proteins highlighted the involvement of mitochondrial and cytoplasmic compartments in AD-specific aggregation. This approach derives dynamic consensus models of aggregate growth and architecture, implicating highly influential proteins as new targets to disrupt amyloid accrual in the AD brain.

Protein homeostasis in the aged and diseased heart.

Protein homeostasis, the balance between protein synthesis and degradation, requires the clearance of misfolded and aggregated proteins and is therefore considered to be an essential aspect of establishing a physiologically effective proteome. Aging alters this balance, termed "proteostasis", resulting in the progressive accumulation of misfolded and aggregated proteins. Defective proteostasis leads to the functional deterioration of diverse regulatory processes during aging and is implicated in the etiology of multiple pathological conditions underlying a variety of neurodegenerative diseases and in age-dependent cardiovascular disease. Detergent-insoluble protein aggregates have been reported by us in both aged and hypertensive hearts. The protein constituents were found to overlap with protein aggregates seen in neurodegenerative diseases such as Alzheimer's disease. Therefore, targeting these protein components of aggregates may be a promising therapeutic strategy for cardiovascular pathologies associated with aging, ischemia, and/or hypertension.

Thiadiazolidinone (TDZD) Analogs Inhibit Aggregation-Mediated Pathology in Diverse Neurodegeneration Models, and Extend C. elegans Life- and Healthspan.

Chronic, low-grade inflammation has been implicated in aging and age-dependent conditions, including Alzheimer's disease, cardiomyopathy, and cancer. One of the age-associated processes underlying chronic inflammation is protein aggregation, which is implicated in neuroinflammation and a broad spectrum of neurodegenerative diseases such as Alzheimer's, Huntington's, and Parkinson's diseases. We screened a panel of bioactive thiadiazolidinones (TDZDs) from our in-house library for rescue of protein aggregation in human-cell and C. elegans models of neurodegeneration. Among the tested TDZD analogs, PNR886 and PNR962 were most effective, significantly reducing both the number and intensity of Alzheimer-like tau and amyloid aggregates in human cell-culture models of pathogenic aggregation. A C. elegans strain expressing human Aß1-42 in muscle, leading to AD-like amyloidopathy, developed fewer and smaller aggregates after PNR886 or PNR962 treatment. Moreover, age-progressive paralysis was reduced 90% by PNR886 and 75% by PNR962, and "healthspan" (the median duration of spontaneous motility) was extended 29% and 62%, respectively. These TDZD analogs also extended wild-type C. elegans lifespan by 15-30% (p < 0.001), placing them among the most effective life-extension drugs. Because the lead drug in this family, TDZD-8, inhibits GSK3ß, we used molecular-dynamic tools to assess whether these analogs may also target GSK3ß. In silico modeling predicted that PNR886 or PNR962 would bind to the same allosteric pocket of inactive GSK3ß as TDZD-8, employing the same pharmacophore but attaching with greater avidity. PNR886 and PNR962 are thus compelling candidate drugs for treatment of tau- and amyloid-associated neurodegenerative diseases such as AD, potentially also reducing all-cause mortality.

Structural modeling of GSK3ß implicates the inactive (DFG-out) conformation as the target bound by TDZD analogs.

Glycogen synthase kinase-3ß (GSK3ß) controls many physiological pathways, and is implicated in many diseases including Alzheimer's and several cancers. GSK3ß-mediated phosphorylation of target residues in microtubule-associated protein tau (MAPTAU) contributes to MAPTAU hyperphosphorylation and subsequent formation of neurofibrillary tangles. Inhibitors of GSK3ß protect against Alzheimer's disease and are therapeutic for several cancers. A thiadiazolidinone drug, TDZD-8, is a non-ATP-competitive inhibitor targeting GSK3ß with demonstrated efficacy against multiple diseases. However, no experimental data or models define the binding mode of TDZD-8 with GSK3ß, which chiefly reflects our lack of an established inactive conformation for this protein. Here, we used metadynamic simulation to predict the three-dimensional structure of the inactive conformation of GSK3ß. Our model predicts that phosphorylation of GSK3ß Serine9 would hasten the DFG-flip to an inactive state. Molecular docking and simulation predict the TDZD-8 binding conformation of GSK3ß to be inactive, and are consistent with biochemical evidence for the TDZD-8-interacting residues of GSK3ß. We also identified the pharmacophore and assessed binding efficacy of second-generation TDZD analogs (TDZD-10 and Tideglusib) that bind GSK3ß as non-ATP-competitive inhibitors. Based on these results, the predicted inactive conformation of GSK3ß can facilitate the identification of novel GSK3ß inhibitors of high potency and specificity.