The fragile X mental retardation protein (FMRP) is a regulator of local translation through its mRNA targets in the neurons. Previous studies have demonstrated that FMRP may function in distinct ways during the development of different visual subcircuits. However, the localization of the FMRP in different types of retinal cells is unclear. In this work, the FMRP expression in rat retina was detected by Western blot and immunofluorescence double labeling. Results showed that the FMRP expression could be detected in rat retina and that the FMRP had a strong immunoreaction (IR) in the ganglion cell (GC) layer, inner nucleus layer (INL), and outer plexiform layer (OPL) of rat retina. In the outer retina, the bipolar cells (BCs) labeled by homeobox protein ChX10 (ChX10) and the horizontal cells (HCs) labeled by calbindin (CB) were FMRP-positive. In the inner retina, GABAergic amacrine cells (ACs) labeled by glutamate decarbonylase colocalized with the FMRP. The dopaminergic ACs (tyrosine hydroxylase marker) and cholinergic ACs (choline acetyltransferase (ChAT) marker) were co-labeled with the FMRP. In most GCs (labeled by Brn3a) and melanopsin-positive intrinsically photosensitive retinal GCs (ipRGCs) were also FMRP-positive. The FMRP expression was observed in the cellular retinal binding protein-positive Müller cells. These results suggest that the FMRP could be involved in the visual pathway transmission.

ObjectivesThe overexpansion of CD3+B220+cells is the hallmark and main pathological mechanism of clinical manifestations of spontaneously developed MRL/lpr mice, which are primarily used as a mouse model of SLE. Our recent report demonstrated that blocking brain-derived neurotrophic factor precursor (proBDNF) suppressed the antibody-secreting cell differentiation and proliferation and inhibited the progression of SLE; however, the effect of proBDNF blockade on these CD3+B220+cells in MRL/lpr mice is unclear.MethodsTo explore the effect of proBDNF on CD3+B220+cells, MRL/lpr mice at 12 weeks old were intraperitoneally injected with monoclonal anti-proBDNF antibody (McAb-proB) or control IgG continuously for 8 weeks. The manifestations in mice were observed, and peripheral blood and splenocytes were collected and analysed via flow cytometry at 20 weeks old. In addition, splenic CD3+B220+cells were subjected to RNA sequencing (RNA-seq) analysis to identify transcriptomic alterations.ResultsCD3+B220+cells in peripheral blood (p=0.0101) and spleen (p<0.0001) were expanded in MRL/lpr mice. Meanwhile, inhibition of proBDNF signalling reduced the percentage of CD3+B220+cells in peripheral blood (p=0.0036) and spleen (p=0.0280), alleviated lymphadenopathy, reduced urine protein level (p<0.0001) and increased the body weight (p=0.0493). RNA-seq revealed 501 upregulated and 206 downregulated genes in splenic CD3+B220+cells in McAb-proB-treated MRL/lpr mice compared with IgG-treated mice. The differentially expressed genes were found to be involved in apoptosis, tumour necrosis factor signalling, and T cell differentiation and proliferation.ConclusionSystemic blockade of proBDNF inhibited the overexpansion of CD3+B220+cells and altered their signals related to cell cycle, cell apoptosis and the immune response, which may contribute to the attenuation of disease symptoms in murine lupus.

Background The imbalance of monocyte/macrophage polarization toward the preferential proinflammatory phenotype and a lack of normal inflammation resolution are present in acute myocardial infarction (AMI). Our previous study showed that upregulation of brain‐derived neurotrophic factor precursor (proBDNF) in M2‐like monocytes may contribute to the proinflammatory response in the Stanford type‐A acute aortic dissection. The present study aimed to investigate the role of proBDNF signaling in monocytes/macrophages in the progress of AMI. Methods and Results We observed the upregulation of proBDNF in the proinflammatory monocytes of patients with AMI. The upregulation of proBDNF was also observed in the circulating proinflammatory Ly6C high monocytes and cardiac F4/80 + CD86 + macrophages 3 days after AMI in a mice model. To neutralize proBDNF, the mice subjected to AMI were injected intraperitoneally with a monoclonal anti‐proBDNF antibody. Echocardiography, 2,3,5‐triphenyltetrazolium chloride staining, and positron emission tomography/computed tomography results demonstrate that monoclonal anti‐proBDNF antibody treatment further impaired cardiac functions, increased infarct size, and exacerbated the proinflammatory state. Moreover, the level of proinflammatory Ly6C high in the blood and F4/80 + CD86 + in the heart was further increased in monoclonal anti‐proBDNF antibody mice. RNA sequencing revealed that matrix metalloprotease‐9 protein level was dramatically increased, along with the activated proinflammatory‐related cytokines. Matrix metalloprotease‐9 inhibitor treatment attenuated the deteriorated effect of monoclonal anti‐proBDNF antibody on cardiac function and infarct areas. Conclusions Our study shows that endogenous proBDNF in monocytes/macrophages may exert protective roles in cardiac remodeling after AMI by regulating matrix metalloprotease‐9 activity.