Cell polarization in ischemic stroke: molecular mechanisms and advances

Ischemic stroke is a cerebrovascular disease associated with high mortality and disability rates. Since the inflammation and immune response play a central role in driving ischemic damage, it becomes essential to modulate excessive inflammatory reactions to promote cell survival and facilitate tissue repair around the injury site. Various cell types are involved in the inflammatory response, including microglia, astrocytes, and neutrophils, each exhibiting distinct phenotypic profiles upon stimulation. They display either proinflammatory or anti-inflammatory states, a phenomenon known as ‘cell polarization.’ There are two cell polarization therapy strategies. The first involves inducing cells into a neuroprotective phenotype in vitro, then reintroducing them autologously. The second approach utilizes small molecular substances to directly affect cells in vivo. In this review, we elucidate the polarization dynamics of the three reactive cell populations(microglia, astrocytes, and neutrophils) in the context of ischemic stroke, and provide a comprehensive summary of the molecular mechanisms involved in their phenotypic switching. By unraveling the complexity of cell polarization, we hope to offer insights for future research on neuroinflammation and novel therapeutic strategies for ischemic stroke.

Ultrasound-responsive spherical nucleic acid against c-Myc/PD-L1 to enhance anti-tumoral macrophages in triple-negative breast cancer progression

Triple-negative breast cancer(TNBC)is the most challenging breast cancer subtype because of its aggressive behavior and limited therapeutic targets.c-Myc is hyperactivated in the majority of TNBC tissues,however,it has been considered an“undruggable”target due to its disordered structure.Herein,we developed an ultrasound-responsive spherical nucleic acid(SNA)against c-Myc and PD-L1 in TNBC.It is a self-assembled and carrier-free system composed of a hydrophilic small-interfering RNA(si RNA)shell and a hydrophobic core made of a peptide nucleic acid(PNA)-based antisense oligonucleotide(ASO)and a sonosensitizer.We accomplished significant enrichment in the tumor by enhanced permeability and retention(EPR)effect,the controllable release of effective elements by ultrasound activation,and the combination of targeted therapy,immunotherapy and physiotherapy.Our study demonstrated significant anti-tumoral effects in vitro and in vivo.Mass cytometry showed an invigorated tumor microenvironment(TME)characterized by a significant alteration in the composition of tumor-associated macrophages(TAM)and decreased proportion of PD-1-positive(PD-1+)T effector cells after appropriate treatment of the ultrasound-responsive SNA(USNA).Further experiments verified that tumor-conditioned macrophages residing in the TME were transformed into the anti-tumoral population.Our finding offers a novel therapeutic strategy against the“undruggable”c-Myc,develops a new targeted therapy for c-Myc/PD-L1 and provides a treatment option for the TNBC.

Homocysteine impedes neurite outgrowth recovery after intracerebral haemorrhage by downregulating pCAMK2A

Hyperhomocysteinemia(HHcy)is independently associated with poorer long-term prognosis in patients with intracerebral haemorrhage(ICH);however,the effect and mechanisms of HHcy on ICH are still unclear.Here,we evaluated neurite outgrowth and neurological functional recovery using simulated models of ICH with HHcy in vitro and in vivo.We found that the neurite outgrowth velocity and motor functional recovery in the ICH plus HHcy group were significantly slower than that in the control group,indicating that homocysteine(Hcy)significantly impedes the neurite outgrowth recovery after ICH.Furthermore,phosphoproteomic data and signalome analysis of perihematomal brain tissues suggested that calmodulin-dependent protein kinases 2(CAMK2A)kinase substrate pairs were significantly downregulated in ICH with HHcy compared with autologous blood injection only,both western blot and immunofluorescence staining confirmed this finding.Additionally,upregulation of pCAMK2A significantly increased neurite outgrowth recovery in ICH with HHcy.Collectively,we clarify the mechanism of HHcy-hindered neurite outgrowth recovery,and pCAMK2A may serve as a therapeutic strategy for promoting neurological recovery after ICH.

Reprogramming rat astrocytes into neurons using small molecules for cell replacement following intracerebral hemorrhage

Astrocytes are promising source cells to replace neurons lost to disease owing to a shared lineage and capacities for dedifferentiation and proliferation under pathological conditions.Reprogramming of astrocytes to neurons has been achieved by transcription factor modulation,but reprogramming in vitro or in vivo using small-molecule drugs may have several advantages for clinical application.For instance,small molecules can be extensively characterized for efficacy,toxicity,and tumorigenicity in vitro;induce rapid initiation and subsequent reversal of transdifferentiation upon withdrawal,and obviate the need for exogenous gene transfection.Here we report a new astrocyte-neuron reprogramming strategy using a combination of small molecules(0.5 m M valproic acid,1μM Rep Sox,3μM CHIR99021,2μM I-BET151,10μM ISX-9,and 10μM forskolin).Treatment with this drug combination gradually reduced expression levels of astroglial marker proteins(glial fibrillary acidic protein and S100),transiently enhanced expression of the neuronal progenitor marker doublecortin,and subsequently elevated expression of the mature neuronal marker Neu N in primary astrocyte cultures.These changes were accompanied by transition to a neuron-like morphological phenotype and expression of multiple neuronal transcription factors.Further,this drug combination induced astrocyte-to-neuron transdifferentiation in a culture model of intracerebral hemorrhage(ICH)and upregulated many transdifferentiation-associated signaling molecules in ICH model rats.In culture,the drug combination also reduced ICH model-associated oxidative stress,apoptosis,and pro-inflammatory cytokine production.Neurons derived from small-molecule reprogramming of astrocytes in adult Sprague-Dawley rats demonstrated long-term survival and maintenance of neuronal phenotype.This small-molecule-induced astrocyte-to-neuron transdifferentiation method may be a promising strategy for neuronal replacement therapy.

Neuroprotective effects of adipose-derived stem cells on ferrous sulfate-induced neurotoxicity

Background:Ferrous ion,a degradation product of hematomas,induces inflammatory reactions and other secondary injuries after intracerebral hemorrhage(ICH).Our study aimed to investigate the specific neuroprotective mechanism of adipose-derived stem cells(ADSCs)on ferrous ion-induced neural injury in vitro.Methods:ADSCs were co-cultured with primary cortical neurons in a transwell system treated with ferrous sulfate to generate an in vitro ICH model.ADSCs and cortical neurons were cultured in the upper and lower chambers,respectively.Neuron apoptosis was determined by flow cytometry.The levels of insulin-like growth factor-1(IGF-1),malondialdehyde(MDA)and nitric oxide synthase(NOS)activity in neuron culture medium were detected with commercial kits.In neurons,protein expression in phosphatidylinositol-3-kinase(PI3 K)/protein kinase B(Akt)signaling pathway,nuclear factor erythroid 2-related factor 2(Nrf2)/heme oxygenase-1(HO-1)signaling pathway and apoptosis-related proteins were detected by western blot.Results:ADSCs attenuated neural apoptosis,reduced MDA levels and NOS activity induced by ferrous sulfate.In neurons,IGF-1 was increased,as were p-PI3 K,p-Akt,Nrf2,HO-1,and Bcl-2 while cleaved caspase 3 was down-regulated.Conclusions:ADSCs exert neuroprotective effects against ferrous iron-induced neuronal damage by secreting IGF-1 and increasing the levels of Akt-dependent Nrf2/ARE signaling pathway.

Strategies to improve the migration of mesenchymal stromal cells in cell therapy

Mesenchymal stromal/stem cells(MSCs) are multipotent cells under consideration as a potential new therapy for a variety of inflammatory diseases including certain neurological disorders. It is generally thought that the efficacy of cell therapy in attenuating damage after ischemia, inflammation, or injury depends on the quantity of transplanted cells recruited to the target tissue. However, only a small number of systematically infused MSCs can effectively migrate to target sites, which significantly decreases the efficacy of exogenous cell-based therapy. In this review, we discuss specific factors influencing MSC migration, and summarize current strategies that effectively promote the motility of MSCs. In addition, we describe several protocols to improve the migration of stromal cells into the nervous system and, therefore,enhance the efficiency of engraftment as means of treating neurological disorders.