Effects of CXCR7-neutralizing antibody on neurogenesis in the hippocampal dentate gyrus and cognitive function in the chronic phase of cerebral ischemia

Atypical Roles of the Chemokine Receptor ACKR3/CXCR7 in Platelet Pathophysiology

The manifold actions of the pro-inflammatory and regenerative chemokine CXCL12/SDF-1α are executed through the canonical GProteinCoupledReceptor CXCR4, and the non-canonical ACKR3/CXCR7. Platelets express CXCR4, ACKR3/CXCR7, and are a vital source of CXCL12/SDF-1α themselves. In recent years, a regulatory impact of the CXCL12-CXCR4-CXCR7 axis on platelet biogenesis, i.e., megakaryopoiesis, thrombotic and thrombo-inflammatory actions have been revealed through experimental and clinical studies. Platelet surface expression of ACKR3/CXCR7 is significantly enhanced following myocardial infarction (MI) in acute coronary syndrome (ACS) patients, and is also associated with improved functional recovery and prognosis. The therapeutic implications of ACKR3/CXCR7 in myocardial regeneration and improved recovery following an ischemic episode, are well documented. Cardiomyocytes, cardiac-fibroblasts, endothelial lining of the blood vessels perfusing the heart, besides infiltrating platelets and monocytes, all express ACKR3/CXCR7. This review recapitulates ligand induced differential trafficking of platelet CXCR4-ACKR3/CXCR7 affecting their surface availability, and in regulating thrombo-inflammatory platelet functions and survival through CXCR4 or ACKR3/CXCR7. It emphasizes the pro-thrombotic influence of CXCL12/SDF-1α exerted through CXCR4, as opposed to the anti-thrombotic impact of ACKR3/CXCR7. Offering an innovative translational perspective, this review also discusses the advantages and challenges of utilizing ACKR3/CXCR7 as a potential anti-thrombotic strategy in platelet-associated cardiovascular disorders, particularly in coronary artery disease (CAD) patients post-MI.

Precise gene delivery systems with detachable albumin shell remodeling dysfunctional microglia by TREM2 for treatment of Alzheimer's disease

Intervention of the over-activated microglia-aggravated neuroinflammation represents a promising therapeutic strategy for Alzheimer's disease (AD). Upregulation of triggering receptor expressed on myeloid cells-2 (TREM2) attenuates the neuroinflammatory processes and normalizes the dysfunctional microglia. However, Trem2-gene therapy for AD by the effective non-invasive delivery systems is unexploited. Herein, we report the microglia-targeted gene delivery systems (PHSA@PF/pTREM2) composed of a core of fluorinated polyethylenimine condensing the TREM2-encoding plasmid (PF/pTREM2) and a shell of human serum albumin conjugated with both cis-aconitic anhydride and neural cell adhesion molecule-mimetic peptide P2 (PHSA). Thanks to the shedding effect of the albumin coated, PHSA@PF/pTREM2 exhibit prolonged blood circulation and low cytotoxicity. PHSA@PF/pTREM2 achieve brain accumulation as high as 2.17% injected dose per gram of brain and the microglial-targeting effect (targeting specificity of 41.9%) via the systemic administration. The nanocomplexes can be detached PHSA-shell in the acidic endo-lysosomes via the cleavage of cis-aconitic amide bond, resulting in PF/pTREM2 exposure for efficient endo-lysosomal escape and gene transfection. PHSA@PF/pTREM2 upregulate the TREM2 level and regulate microglial polarization toward M2-phenotype for remodeling the inflammatory microenvironment and enhanced Aβ clearance, leading to an improvement of cognitive performance in APP/PS1 mice. This work provides a promising gene delivery platform to reverse dysfunctional microglia for AD therapy.

Discovery of the Potent, Selective, Orally Available CXCR7 Antagonist ACT-1004-1239

The chemokine receptor CXCR7, also known as ACKR3, is a seven-transmembrane G-protein-coupled receptor (GPCR) involved in various pathologies such as neurological diseases, autoimmune diseases, and cancers. By binding and scavenging the chemokines CXCL11 and CXCL12, CXCR7 regulates their extracellular levels. From an original high-throughput screening campaign emerged hit 3 among others. The hit-to-lead optimization led to the discovery of a novel chemotype series exemplified by the trans racemic compound 11i. This series provided CXCR7 antagonists that block CXCL11- and CXCL12-induced ß-arrestin recruitment. Further structural modifications on the trisubstituted piperidine scaffold of 11i yielded compounds with high CXCR7 antagonistic activities and balanced ADMET properties. The effort described herein culminated in the discovery of ACT-1004-1239 (28f). Biological characterization of ACT-1004-1239 demonstrated that it is a potent, insurmountable antagonist. Oral administration of ACT-1004-1239 in mice up to 100 mg/kg led to a dose-dependent increase of plasma CXCL12 concentration.

Pleiotropic Effects of Exosomes as a Therapy for Stroke Recovery

Stroke is the leading cause of disability, and stroke survivors suffer from long-term sequelae even after receiving recombinant tissue plasminogen activator therapy and endovascular intracranial thrombectomy. Increasing evidence suggests that exosomes, nano-sized extracellular membrane vesicles, enhance neurogenesis, angiogenesis, and axonal outgrowth, all the while suppressing inflammatory reactions, thereby enhancing functional recovery after stroke. A systematic literature review to study the association of stroke recovery with exosome therapy was carried out, analyzing species, stroke model, source of exosomes, behavioral analyses, and outcome data, as well as molecular mechanisms. Thirteen studies were included in the present systematic review. In the majority of studies, exosomes derived from mesenchymal stromal cells or stem cells were administered intravenously within 24 h after transient middle cerebral artery occlusion, showing a significant improvement of neurological severity and motor functions. Specific microRNAs and molecules were identified by mechanistic investigations, and their amplification was shown to further enhance therapeutic effects, including neurogenesis, angiogenesis, axonal outgrowth, and synaptogenesis. Overall, this review addresses the current advances in exosome therapy for stroke recovery in preclinical studies, which can hopefully be preparatory steps for the future development of clinical trials involving stroke survivors to improve functional outcomes.

Advances in CXCR7 Modulators

CXC chemokine receptor 7 (CXCR7) is a G-protein-coupled receptor that signals through the β-arrestin pathway. Its ligands include interferon-inducible T cell α chemoattractant (CXCL11) and stromal cell-derived factor-1 (CXCL12). It interacts with CXCR4, and the two are associated with various cancers, as well as other disease states such as coronary artery disease, stroke, inflammation and human immunodeficiency virus (HIV). Antibodies and small interfering RNA (siRNA) have shown the utility of antagonists of CXCR7 in these disease states. Although some small molecules were initially reported as antagonists due to their displayed activity, many function as agonists while still producing the desired pharmacologic effects. A potential reason for this contradiction is that effects may be due to elevated extracellular CXCL12 levels.