CD200 in dentate gyrus improves depressive-like behaviors of mice through enhancing hippocampal neurogenesis via alleviation of microglia hyperactivation.

BACKGROUND: Neuroinflammation and microglia play critical roles in the development of depression. Cluster of differentiation 200 (CD200) is an anti-inflammatory glycoprotein that is mainly expressed in neurons, and its receptor CD200R1 is primarily in microglia. Although the CD200-CD200R1 pathway is necessary for microglial activation, its role in the pathophysiology of depression remains unknown. METHODS: The chronic social defeat stress (CSDS) with behavioral tests were performed to investigate the effect of CD200 on the depressive-like behaviors. Viral vectors were used to overexpress or knockdown of CD200. The levels of CD200 and inflammatory cytokines were tested with molecular biological techniques. The status of microglia, the expression of BDNF and neurogenesis were detected with immunofluorescence imaging. RESULTS: We found that the expression of CD200 was decreased in the dentate gyrus (DG) region of mice experienced CSDS. Overexpression of CD200 alleviated the depressive-like behaviors of stressed mice and inhibition of CD200 facilitated the susceptibility to stress. When CD200R1 receptors on microglia were knocked down, CD200 was unable to exert its role in alleviating depressive-like behavior. Microglia in the DG brain region were morphologically activated after exposure to CSDS. In contrast, exogenous administration of CD200 inhibited microglia hyperactivation, alleviated neuroinflammatory response in hippocampus, and increased the expression of BDNF, which in turn ameliorated adult hippocampal neurogenesis impairment in the DG induced by CSDS. CONCLUSIONS: Taken together, these results suggest that CD200-mediated alleviation of microglia hyperactivation contributes to the antidepressant effect of neurogenesis in dentate gyrus in mice.

In silico designed RNA aptamer against epithelial cell adhesion molecule for cancer cell imaging.

Aptamers are short, single-stranded oligonucleotides that bind to their targets with high affinity and specificity. Usually, aptamers are selected experimentally using SELEX approach. Here, we describe a computational approach for selection of aptamers for proteins, which involves generation of a virtual library of sequences, modeling of their 3D-structures and selection of perspective aptamers through docking, molecular dynamics simulation, binding free energy calculations and finally estimating the experimental affinity. Using this method, a 15-mer RNA aptamer was designed for epithelial cell adhesion molecule. Flow cytometry and fluorescence microscopy results reviled that RNA1 aptamer interacts specifically with human cancer cells that express EpCAM, but not with the EpCAM negative cells. The binding affinity of the RNA1 aptamer to MCF-7 and MDA-MB-231 is approximately 21.8 and 96.9 nM respectively. This novel RNA aptamer will help in the future development of targeted therapeutics and molecular imaging.

The HMGB1-RAGE axis in nucleus accumbens facilitates cocaine-induced conditioned place preference via modulating microglial activation.

INTRODUCTION: Repeated exposure to cocaine induces microglial activation. Cocaine exposure also induces a release of high mobility group box-1 (HMGB1) from neurons into the extracellular space in the nucleus accumbens (NAc). HMGB1 is an important late inflammatory mediator of microglial activation. However, whether the secretion of HMGB1 acts on microglia or contributes to cocaine addiction is largely unknown. METHODS: Rats were trained by intraperitoneal cocaine administration and cocaine-induced conditioned place preference (CPP). Expression of HMGB1 was regulated by viral vectors. Activation of microglia was inhibited by minocycline. Interaction of HMGB1 and the receptor for advanced glycation end products (RAGE) was disrupted by peptide. RESULTS: Cocaine injection facilitated HMGB1 signaling, together with the delayed activation of microglia concurrently in the NAc. Furthermore, the inhibition of HMGB1 or microglia activation attenuated cocaine-induced CPP. Box A, a specific antagonist to interrupt the interaction of HMGB1 and RAGE, abolished the expression of cocaine reward memory. Meanwhile, the inhibition of HMGB1-RAGE interaction suppressed cocaine-induced microglial activation, as well as the consolidation of cocaine-induced memory. CONCLUSION: All above results suggest that the neural HMGB1 induces activation of microglia through RAGE, which contributes to the consolidation of cocaine reward memory. These findings offer HMGB1-RAGE axis as a new target for the treatment of drug addiction.

A frog-derived bionic peptide with discriminative inhibition of tumors based on integrin αvß3 identification.

Aureins, natural active peptides extracted from skin secretions of Australian bell frogs, have become a research focus due to the antitumor effects caused by lysing cell membranes. However, clinical translation of Aureins is still limited by non-selective toxicity between normal and cancer cells. Herein, by structure-activity relationship analysis and rational linker design, a dual-function fusion peptide RA3 is designed by tactically fusing Aurein peptide A1 with strong anticancer activity, with a tri-peptide with integrin αvß3-binding ability which was screened in our previous work. Rational design and selection of fusion linkers ensures α-helical conformation and active functions of this novel fusion peptide, inducing effective membrane rupture and selective apoptosis of cancer cells. The integrin binding and tumor recognition ability of the fusion peptide is further validated by fluorescence imaging in cell and mouse models, in comparison with the non-selective A1 peptide. Meanwhile, increased stability and superior therapeutic efficacy are achieved in vivo for the RA3 fusion peptide. Our study highlights that aided by computational simulation technologies, the biomimetic fusion RA3 peptide has been successfully designed, surmounting the poor tumor-selectivity of the natural defensive peptide, serving as a promising therapeutic agent for cancer treatment.

AT1R-Specific Ligand Angiotensin II as a Novel SPECT Agent for Hepatocellular Carcinoma Diagnosis.

Hepatocellular carcinoma (HCC) is characterized by a high mortality and early diagnosis and treatment are critically needed. Ang II type 1 receptor (AT1R) has recently emerged as a potential molecular target for cancer diagnosis and intervention. Here, we labeled angiotensin II (Ang II), an AT1R ligand that is overexpressed in various solid cancers, with the near-infrared fluorescent dye, MPA, and radionuclide technetium-99m, and evaluated its capacity for HCC detection. These analyses were done in vitro using HepG2 (AT1R-positive) and BxPC3 (AT1R-negative) cell lines, and in vivo using a subcutaneous and orthotopic xenograft mouse model by fluorescence and SPECT imaging. Both Ang II-PEG4-MPA- and [99mTc]Tc-HYNIC-PEG4-Ang II-bound AT1R exhibited a high affinity in vitro and [99mTc]Tc-HYNIC-PEG4-Ang II displayed an acceptable level of in vitro stability in rat plasma and whole blood. In vivo imaging revealed excellent specific tumor-targeting in HepG2 mouse xenografts models. In vitro and in vivo competition experiments revealed specific Ang II-PEG4-MPA and [99mTc]Tc-HYNIC-PEG4-Ang II uptake by HepG2 cells and tumors. Altogether, AT1R-positive tumors were successfully detected via fluorescence and SPECT imaging using Ang II-PEG4-MPA and [99mTc]Tc-HYNIC-PEG4-Ang II, respectively. Given their superior targeting capacity, Ang II-PEG4-MPA and [99mTc]Tc-HYNIC-PEG4-Ang II are promising tools for HCC detection and warrant clinical translation.

GRPR-targeted SPECT imaging using a novel bombesin-based peptide for colorectal cancer detection.

Colorectal cancer (CRC) is the third most common cancer worldwide, and the prognosis of CRC is better with an earlier diagnosis. The presence of the gastrin-releasing peptide receptor (GRPR) has been documented in very high numbers on colorectal cancer cells, which makes it an ideal biomarker for the diagnosis of CRC. Bombesin (BBN) peptide analogs have been extensively investigated for the imaging of human cancers with GRPR overexpression. Recently, we have reported a novel GRPR-targeted peptide named the GB-6 peptide. The GB-6 peptide based on BBN7-14 was designed to improve in vivo metabolic stability and decrease intestinal uptake. Meanwhile, GB-6 greatly retained the original GRPR-binding affinity of BBN7-14. In this study, the GB-6 peptide was labeled with radionuclide 99mTc or fluorescent dye for colorectal cancer imaging. In vitro receptor binding was studied in Caco-2 cells, and the GRPR targeting capacity and kinetics in vivo were evaluated using Caco-2 tumor xenografted mice models. In addition, cells and mice were also subjected to the corresponding BBN7-14 conjugations for comparison. The GB-6 peptide exhibited specific GRPR binding in vitro with a high affinity similar to that of BBN7-14. Furthermore, we observed that GB-6 showed higher tumor uptake and displayed lower intestinal activity than corresponding unmodified probe BBN7-14 in Caco-2 tumor-bearing mice. Overall, our studies demonstrated that GB-6 has the potential for early detection of CRC patients, and it may also serve as a valuable tool for non-invasive monitoring of colorectal tumor growth.

Near-infrared light-activatable siRNA delivery by microcapsules for combined tumour therapy.

A polyelectrolyte microcapsule-based layer-by-layer (LbL) technique has been widely used as a multifunctional vehicle for combined tumor therapy. Meanwhile, with the rapid development of combined tumour therapy, the challenge for designing multifunctional drug delivery system has attracted much more attention. Herein, we developed a new type of microcapsule (MC) system called MPA@siRNA@DOX@MC, which conjugated with siRNA and DOX as well as ICG-Der-02 (MPA) by electrostatic absorption. MPA as indocyanine green (ICG) fluorescence dye, exhibiting high fluorescence emission and photothermal conversion ability under NIR laser irradiation, was uploaded onto this drug system for realizing the controllable drug release and cancer theranostics. In addition, the results revealed that MPA@siRNA@DOX@MC possessed several ideal properties including high drug-loading capacity, excellent siRNA transfection efficiency, siRNA sequence protection and remarkably improved tumour-targeting capacity. Moreover, the combined therapy based on this drug system displayed improved therapeutic efficacy and negligible side effects both in vivo and in vitro experiment. Ultimately, MPA@siRNA@DOX@MC drug delivery system successfully combined the photothermal therapy and chemotherapy with controlled siRNA sequence silencing may have a promising potential in combined tumor therapy.