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The nucleus tractus solitarii (NTS) is the primary central station that integrates visceral afferent information and regulates respiratory, gastrointestinal, cardiovascular, and other physiological functions. Leptin receptor b (LepRb)-expressing neurons of the NTS (NTSLepRb neurons) are implicated in central respiration regulation, respiratory facilitation, and respiratory drive enhancement. Furthermore, LepRb dysfunction is involved in obesity, insulin resistance, and sleep-disordered breathing. However, the monosynaptic inputs and outputs of NTSLepRb neurons in whole-brain mapping remain to be elucidated. Therefore, the exploration of its whole-brain connection system may provide strong support for comprehensively understanding the physiological and pathological functions of NTSLepRb neurons. In the present study, we used a cell type-specific, modified rabies virus and adeno-associated virus with the Cre-loxp system to map monosynaptic inputs and outputs of NTSLepRb neurons in LepRb-Cre mice. The results showed that NTSLepRb neurons received inputs from 48 nuclei in the whole brain from five brain regions, including especially the medulla. We found that NTSLepRb neurons received inputs from nuclei associated with respiration, such as the pre-Bötzinger complex, ambiguus nucleus, and parabrachial nucleus. Interestingly, some brain areas related to cardiovascular regulation—i.e., the ventrolateral periaqueductal gray and locus coeruleus—also sent a small number of inputs to NTSLepRb neurons. In addition, anterograde tracing results demonstrated that NTSLepRb neurons sent efferent projections to 15 nuclei, including the dorsomedial hypothalamic nucleus and arcuate hypothalamic nucleus, which are involved in regulation of energy metabolism and feeding behaviors. Quantitative statistical analysis revealed that the inputs of the whole brain to NTSLepRb neurons were significantly greater than the outputs. Our study comprehensively revealed neuronal connections of NTSLepRb neurons in the whole brain and provided a neuroanatomical basis for further research on physiological and pathological functions of NTSLepRb neurons.

Abstract Bone marrow‐derived mesenchymal stem cells (BM‐MSCs) are important precursors of tumor stromal cells. Previously, we have demonstrated that miR‐155‐5p inhibition directly induced transition of BM‐MSCs into gastric cancer‐associated MSCs. Whether miR‐155‐5p is involved in the education of BM‐MSCs by gastric cancer cells has not been established. Murine BM‐MSCs (mMSCs) were isolated and grown in conditioned medium derived from gastric cancer cell line MFC (MFC‐CM). The tumor‐promoting phenotype and function of mMSCs were detected by immunofluorescence staining, quantitative reverse transcription‐polymerase chain reaction (qRT‐PCR), cell colony formation assay, transwell migration, and invasion assays. Luciferase reporter assays and western blot analyses were conducted to reveal the relationship between nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) p65 and mmu‐miR‐155‐5p. miRNA mimics, inhibitor, and the NF‐κB inhibitor pyrrolidine dithiocarbamic acid (PDTC) were used to evaluate the role of miR‐155‐5p‐NF‐κB signaling in the education of mMSCs by MFC‐CM. We successfully established the education model of mMSCs by MFC‐CM and found that mmu‐miR‐155‐5p expression levels were reduced in mMSCs. Mimicking this deregulation by transfecting miRNA inhibitor into mMSCs produced a similar effect as that of MFC‐CM on mMSCs. NF‐κB p65 was validated as a target of mmu‐miR‐155‐5p, which also negatively regulated NF‐κB activation. Inhibition of NF‐κB activation by PDTC abolished the effect of the miRNA inhibitor on mMSCs. mmu‐miR‐155‐5p overexpression partially blocked the effect of MFC‐CM in educating mMSCs, while PDTC treatment completely eliminated MFC‐CM activity. These results indicate that miR‐155‐5p is not the sole miRNA mediating the education of BM‐MSCs by gastric cancer cells, but downstream NF‐κB signaling is indispensable for this process.

Chronic inflammation has a decisive role in tumorigenesis, particularly in gastric carcinogenesis. The CC chemokine ligand 2 (CCL2), an important inflammatory cytokine, is involved in the initiation, development and progression of various types of cancer. However, the role of CCL2 in gastric cancer remains to be elucidated. The present study demonstrated that recombinant CCL2 stimulation caused no effect on the morphology, proliferation and migration of human GES-1 gastric mucosa epithelial cells, in which the protein expression of CC-chemokine receptor 2 (CCR2) was markedly low. However, the expression of CCR2 was significantly upregulated in the GES-1 cells following pretreatment with the chemical carcinogen, N-methyl-N-nitro-N'-nitrosoguanidine (MNNG), for 12 h or transformed with MNNG (MC cells). The present study used CCL2 to stimulate MNNG pretreated GES-1 cells and MC cells, and demonstrated that CCL2 clearly promoted their migration and the epithelial-mesenchymal transition (EMT). However, no effect was observed on the proliferative ability of the cells. Taken together, these findings suggested that the CCL2/CCR2 chemokine signaling may regulate the EMT in gastric epithelial cells and resulted in gastric carcinogenesis in response to the intake of the carcinogen, MNNG. [ABSTRACT FROM AUTHOR]