Background
The plasma fraction GRF6019 shows multiple benefits on age‐related changes in the mouse brain, including enhanced synaptic density and neurogenesis. In a trial of GRF6019 in ...mild‐to‐moderate Alzheimer’s disease (AD), cognition stabilized over a 24‐week period (Hannestad et al., 2020). Here we present the volumetric MRI data from that trial.
Method
Participants were 60‐90 years old with probable AD according to NIA‐AA criteria, and Mini Mental State Examination score 12‐24. They received 1 daily infusion of 100 mL or 250 mL of GRF6019 over 5 consecutive days at Week 1 and Week 13. MRIs were done at baseline at the end of the study using a MP‐RAGE or IR‐SPGR sequence. The 3D T1‐weighted scans were acquired sagittally over approximately 192 slices at a thickness of 1.0‐1.2. Images underwent the Freesurfer pipeline and hand editing to correct over‐ and under‐estimations of hippocampal volumes. Hippocampal and lateral ventricular volumes were extracted and normalized by the estimated total intracranial volume. Fold‐changes between baseline and 6 months were estimated and log2‐transformed to obtain a symmetrical distribution. MRI images from ADNI were analyzed in the same manner.
Result
Hippocampal volumes decreased from baseline by 2% (p<0.001, one‐sample Wilcoxon test) in ADNI AD participants (n=75), while hippocampal volumes did not significantly change in ADNI control participants (n=82; 0.03%, p>0.05) or in GRF6019‐treated AD trial participants (n=34; 0.3%, p>0.05). Lateral ventricle volumes increased from baseline by 5.2% in ADNI AD but showed smaller increases in ADNI controls (2.7%) and in GRF6019‐treated individuals (3.1%). The difference in change from baseline between GRF6019 AD and ADNI AD was significant in the right lateral ventricle (p<0.005, two‐samples Wilcoxon test) but not in the left lateral ventricle. There was no apparent difference in the change from baseline in MRI volumes between the 100 ml and 250 mL dose of GRF6019.
Conclusion
In mild‐to‐moderate AD, the plasma fraction GRF6019 slowed hippocampal atrophy and lateral ventricle enlargement compared to matched individuals with AD in ADNI. The MRI data are consistent with the lack of cognitive worsening observed in these trial participants and supports continued clinical development of GRF6019 in AD.
Background
Our pre‐clinical work provided evidence of the interest of plasma fraction treatment to reverse age‐related cognitive decline. One of the most potent plasma fractions, GRF6019 was tested ...on patients with Alzheimer’s disease (AD). GRF6019 was safe and well tolerated, and patients experienced no cognitive decline and minimal functional decline. However, understanding these responses requires large‐scale mapping of the underlying molecular mechanisms. Recent affinity‐based approaches can measure levels of thousands of proteins in plasma but the increased signal‐to‐noise ratio and the large‐scale analysis of the proteomics changes require sophisticated bioinformatic techniques. To this end, we applied network propagation methods and combined protein‐protein interaction (PPI) networks, known AD‐associated proteins and GRF6019 induced protein changes to shed the light on the molecular mechanisms underlying patients’ responses to GRF6019 treatment.
Method
Phase 2 clinical trials with repeated infusions of the plasma fraction GRF6019 were conducted in patients with AD (GRF6019‐201 n = 40 and GRF6019‐202 n = 26). Proteomic measurements from 136 plasma samples across three timepoints were performed by SomaLogic and Olink platforms. GRF6019‐induced proteomics changes were expressed by a Modulation Score (MS) for each protein. This MS captures the amplitude of the proteomics changes and the consistency of these changes within and between trials. Network propagation modeled the spread of MS on the PPI network. The network propagation algorithm we applied was the fusion of Hierarchical HotNet (permutation part) and NetCore (coreness normalization part). The algorithm highlighted the perturbed proteins which are close in the PPI network topology to proteins with high MS.
Result
Highly perturbed proteins were more strongly associated with AD and other age‐related diseases (e.g.: AMD, Ischemic stroke) than proteins with high MS. Several pathways involved in AD were found to be associated to the perturbed proteins, such as complement and monocyte activation, or regulation of neurogenesis. Furthermore, the high overlap between proteins perturbed by GRF6019 and known AD‐associated proteins indicates the importance of indirect links between the GRF6019 treatment and AD.
Conclusion
Network propagation procedure highlights the importance of interactome‐based analysis in understanding complex plasma proteomics signals. These results suggest that the treatment of AD patients with a complex plasma fraction modulates AD‐related biological pathways.
Striatal enriched protein tyrosine phosphatase (STEP) acts in the central nervous system to dephosphorylate a number of important proteins involved in synaptic function including ERK and NMDA ...receptor subunits. These proteins are also linked to stroke, in which cerebral ischemia triggers a complex cascade of events. Here we demonstrate that STEP is regulated at both the transcriptional and the post‐transcriptional levels in rat models of cerebral ischemia and that its regulation may play a role in the outcome of ischemic insults. After transient middle cerebral artery occlusion, there are profound decreases in the levels of STEP mRNA, whilst in global ischemia STEP mRNA is selectively down‐regulated in areas susceptible to ischemic damage. In a neuroprotective preconditioning paradigm, and in regions of the brain that are relatively resistant to ischemic damage, STEP mRNA levels are increased. Furthermore, there is a significant processing of STEP after ischemia to generate a novel species, STEP33, resulting in a redistribution of STEP from membrane‐bound to soluble compartments. Concomitant with the cleavage of mature forms of STEP, there are changes in the phosphorylation state of ERK. We show that the cleavage of STEP leads to a catalytically active form, but this cleaved form no longer binds to and dephosphorylates its substrate pERK. Therefore, in response to ischemic insults, there are profound reductions in both the amount and the activity of STEP, its localization, as well as the activity of one of its key substrates, pERK. These changes in STEP may reflect a critical role in the outcomes of ischemic brain injury.
α-Amino-3-hydroxy-5-methylisoxazolepropionate (AMPA) receptors mediate most fast excitatory synaptic transmission in the mammalian CNS. They play a central role in synapse stabilisation and ...plasticity and their prolonged activation is potently neurotoxic. Developmental and activity-dependent changes in the functional synaptic expression of these receptors are subject to tight cellular regulation. The molecular and cellular mechanisms which control the postsynaptic insertion and arrangement of individual AMPA receptor variants are therefore the subject of intense investigation and in the last two years there has been significant progress towards elucidating some of the processes involved. Much of the new information has come from the application of the yeast two-hybrid assay, which has led to the discovery of a hitherto unexpected complexity of proteins which selectively interact with individual AMPA receptor subunits. These proteins have been implicated in the regulation of AMPA receptor post-translational modification, targeting and trafficking, surface expression and anchoring. The aim of this article is to present an overview of the major interacting proteins described so far and to place these in the context of how they may participate in the well ordered series of events controlling the cell biology of AMPA receptors.
Background
Aging is the greatest non‐genetic risk factor for many diseases including Alzheimer’s Disease (AD) and its mechanisms are thus increasingly recognized as potential therapeutic targets.
...Since the molecular relationships between normal aging and AD are still largely unknown, we took advantage of recent methodological developments to measure more than 7k proteins in plasma to identify common but also different molecular mechanisms involved in aging and AD.
Method
Recently, we developed new data‐driven bioinformatics approaches that uncovered marked non‐linear alterations in the human plasma proteome with age (Lehallier et al. Nature Medicine 2019). We applied these machine learning approaches to 271 patients at different stages of AD (61 subjects with Subjective Cognitive Decline: SCD, 106 with Mild Cognitive Impairment: MCI and 104 with AD) and compared these changes to those observed in a healthy aging cohort (370 subjects, 18‐69 years).
Result
The analysis of proteomics trajectories confirmed marked non‐linear alterations in the human plasma proteome with aging and uncovered the complex molecular choreography of AD. By analyzing trajectories of groups of proteins, we identified multiple clusters of proteins that are differentially affected during aging and AD. These clusters were enriched for various biological processes relevant for AD progression such as the complement and coagulation cascades, axon guidance and angiogenesis (q<0.05)
Conclusion
Altogether, our results reveal the intricate connections between aging and AD at the molecular level. The integrated proteomics trajectories analysis performed in this study allows the identification of new targets possibly playing a key role in AD but also pinpoints when these proteins are deviating from their normal trajectories and thus when they should be targeted by new therapies.
Background
AMBAR trial (phase 2b/3 clinical trial) evaluates plasma exchange efficacy with albumin replacement (PE‐Alb) in mild‐to‐moderate Alzheimer’s Disease (AD) patients. It includes an intensive ...period (IP) comprising 6‐weeks of conventional therapeutic PE‐Alb (TPE; 1 TPE/week) followed by 12‐month maintenance period of low volume PE‐Alb (LVPE; 1 LVPE/month). Our previous study reporting deep plasma and CSF proteomics profiling identified multiple AD‐associated pathways modulated by PE‐Alb (Feng et al. CTAD2022). Here we dissected immune pathways changes over time and reported their crosstalk between plasma and CSF to further understand molecular mechanisms of PE‐Alb.
Method
7288 proteins were measured by SomaScan technology in 671 plasma samples (148 patients, 5 visits) and 422 CSF samples (144 patients, 3 visits). Acute effects (post‐TPE/LVPE versus pre‐TPE/LVPE samples) for plasma, and lasting effects (baseline to either end of IP or end of study (EOS)) for both matrices were calculated through a mixed model approach comparing PE‐Alb‐treated patients versus placebo. Network features of the top identified proteoforms were explored in STRING and OmniPath databases. Relationships between enriched pathways were analyzed by pathway crosstalk based on Jaccard coefficient and correlations between plasma and CSF proteomes at each visit were calculated by spearman correlation.
Result
Plasma samples showed that 90 proteoforms from acute TPE, 16 from acute LVPE, and 14 at the end of IP were significantly decreased and enriched in immune and inflammation‐related pathways. Three proteins involved in immunoglobulin‐mediated immune pathways were in the core of the interactome network and were consistently decreasing over time, one of them also significantly decreased in the CSF proteome. Finally, 113 proteins with spearman correlations >0.5 at least at one of the 3 visits were detected and were significantly enriched in immune system functions (adjusted‐pvalue<0.05).
Conclusion
This analysis demonstrates acute and lasting PE‐Alb effects on immune and inflammatory pathways. We identified 3 potential players and a crosstalk between plasma and CSF immune proteomes, suggesting the importance of the modulation of peripheral inflammation in AD treatment. This study further helps understand the molecular basis of AMBAR therapeutic approach that may contribute to slowing down AD progression.
Abstract only
Aging results in cognitive decline and molecular changes that contribute to the risk of developing aging‐associated disease. As the aging population is rapidly increasing, with those ...over 60‐years‐old set to double by 2050, there is urgent need for a better understanding of the aging process and development of therapeutics for diseases of aging. Recent publications have shown that some aging‐associated phenotypes can be driven by plasma and plasma‐derived factors. In these studies, we sought to identify and validate detrimental effects of aged plasma and plasma‐derived factors on cognitive, histological, and molecular readouts in order to discover novel therapeutic targets for age‐related diseases. Our data show that administration of aged human plasma into young immunodeficient NSG (NOD.Cg‐Prkdcscid Il2rgtm1Wjl/SzJ) mice results in a decrease in neurogenesis and mild impairment in cognition. These results indicate that factors in aged human plasma can drive detrimental effects in the brains of young NSG mice. Plasma proteomics have identified aging signatures and specific proteins that are potential drivers of these negative effects in aging, and beta‐2 microglobulin (B2M) has been shown to be a pro‐aging factor with deleterious effects on cognition and neurogenesis. To confirm B2M as a negative factor, we treated young mice (WT; C57BL/6J) with recombinant human B2M and assessed changes in behavioral performance and histological markers. We found that systemic administration of B2M resulted in cognitive impairment during contextual fear conditioning and decreased neurogenesis, suggesting that it is a driver of negative effects during aging. Our data elucidate molecular pathways that contribute to the aging process and provide promising targets for developing translational therapeutics.
Support or Funding Information
Studies were funded by Alkahest.
Background
Age‐related diseases, especially Alzheimer’s Disease (AD), have multifaceted nature because of the different factors and pathways contributing to these diseases. Multi‐modal plasma ...therapies have the potential to impact multiple pathways and modulate different mechanisms of diseases in a safe and versatile way. Here we discuss insights from deep plasma proteomics profiling in patients from the GRF6019 and AMBAR clinical trials in which multi‐modal plasma therapeutics were used and limited cognitive decline was observed.
Method
The GRF6019 phase 2 trials were based on the infusion of a complex plasma fraction while the AMBAR phase 2b/3 trial used plasma exchange and albumin replacement (PE‐Alb). Patients in these trials were mild‐to‐moderate AD and 1143 plasma samples were analyzed using the SomaScan platform. The trajectories of 7k proteins were analyzed using classic and new machine learning techniques.
Result
GRF6019 infusion resulted in an acute and broad impact on the plasma proteome but the detectable long‐term effects on molecular level were minimal. Pathways analysis of protein trajectories pointed out to the immune system, ECM remodeling but also brain specific biological processes linked to neurons and axon guidance, suggesting that various biological pathways were significantly modulated (q<0.05). PE‐Alb treatment also induced an acute effect on several hundreds of proteins (461 proteins with log2FC←1 & q<0.05) but some proteomics changes lasted for weeks after the end of the intensive period (25 proteins with q<0.05). A significant part of these changes (19% of acute and 56% of lasting response proteins) were related to immune and inflammatory‐related pathways. In addition, several individual proteins from the immune pathway were associated with improvement of CDR‐SB or ADCS‐CGIC at the end of the AMBAR trial suggesting that multiple parts of the immune system might need to be targeted to slow‐down AD progression.
Conclusion
AD has multifaceted nature and plasma therapeutics have proven safety, efficacy, and versatility. The proteomics results from these trials shed the light on the underlying mode of action of multi‐modal plasma‐derived therapies and demonstrate that they can modulate multiple pathways relevant to AD, with a strong effect on the immune and inflammatory responses which may contribute to slowing down AD progression.
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