Biomedical Research-tokyo最新文献

Gut epithelial cells are characterized by rapid, constant cell renewal. The disposal of aging epithelial cells around the villus tips of the small intestine occurs so regularly that it has been regarded as a consequence of well-controlled cell death, designated as apoptosis. However, the notion of live cell extrusion in the intestine has been intensively built among researchers, and the disposal processes of effete epithelial cells display species and regional differences. Chemical mediators and mechanical forces rising from surrounding cells contribute to the regulated cell replacement. Cytotoxic intraepithelial lymphocytes and lamina propria macrophages play a leading role in the selection of disposal cells and their extrusion to maintain fully the epithelial homeostasis in tandem with the dynamic reconstruction of junctional devices. Lymphocyte-mediated cell killing is predominant in the mouse and rat, while the disposal of epithelial cells in the guinea pig, monkey, and human is characterized by active phagocytosis by subepithelially gathering macrophages. The fenestrated basement membrane formed by immune cells supports their involvement and explains species differences in the disposal of epithelial cells. Via these fenestrations, macrophages and dendritic cells can engulf apoptotic epithelial cells and debris and convey substantial information to regional lymph nodes. In this review, we attempt to focus on morphological aspects concerning the apoptosis and disposal process of effete epithelial cells; in vitro or ex vivo analyses using cultured monolayer has become predominant in recent studies concerning the exfoliation of apoptotic enterocytes. Furthermore, we give attention to their species differences, which is controversial but crucial to our understanding.

Natriuretic peptides (NPs) are a family of peptide hormones produced in cardiac muscle cells and consist mainly of three types: atrial NP (ANP), B-type (or brain) NP (BNP), and C-type NP. We herein report the effects of ANP and BNP on central respiratory activity in brainstem-spinal cord preparation isolated from newborn rats. Bath application of these peptides (100 nM) induced a weak transient depression of the respiratory rhythm followed by recovery. Respiratory-related neurons in the rostral ventrolateral medulla showed a tendency for transient hyperpolarization followed by recovery during the application of ANP or BNP. The application of a membrane-permeable cGMP, 8-Br-cGMP (10 or 20 μM), did not induce significant effects on respiratory rhythm, suggesting no involvement of guanylyl cyclase in effects of ANP or BNP. We also examined effects of BNP on respiratory depression induced by the sedative dexmedetomidine, which exerts an inhibitory influence on respiratory rhythm. When pretreated with 50 nM BNP, the inhibitory effect of 100 nM dexmedetomidine was significantly reduced. Our findings suggest that ANP and BNP act as mild excitatory agents with sustained effects on respiratory rhythm after an initial transient depression.

Arginine methylation is a common post-translational modification which functions as an epigenetic regulator of transcription and plays a key role in various cell signaling pathways. The methylation of arginine residues is catalyzed by protein arginine methyltransferase (PRMT). However, the expression pattern and underlying mechanism of PRMTs and protein methylation profile in lipopolysaccharide (LPS)-induced innate immune responses are poorly understood. Using a shotgun proteomic approach, we found that LPS stimulation increased arginine and proline metabolism and responses to inflammation and bacterial infections. In comparison, cysteine and methionine metabolism, the pentose phosphate pathway, purine metabolism, and protein methylation factors were also decreased in LPS stimulated murine macrophage cell lines. We revealed that LPS stimulation downregulated PRMT1, PRMT5, and protein arginine methylation profiles in RAW264.7 cells using western blot analysis. Additionally, this phenomenon occurred in parallel with nitric oxide accumulation in LPS-induced macrophages. Using inflammation models, we demonstrate for the first time that LPS stimulation decreases PRMTs, leading to the decreasing of arginine methylation in macrophages.

Interleukin-6 signaling activates signal transducer and activator of transcription 3 (STAT3), resulting in matrix metalloproteinase-3 (MMP-3) production. The hip joints with rapidly destructive coxopathy (RDC) show rapid chondrolysis, probably by increased MMP-3. This study aimed to elucidate STAT3 activation in the synovial tissues with joint destruction in the early stage of RDC. Synovial tissues within 7 months from the disease onset were obtained from four RDC patients with femoral head destruction and high serum levels of MMP-3. RDC synovial tissues demonstrated the synovial lining hyperplasia with an increase of CD68-positive macrophages and CD3-positive T lymphocytes. STAT3 activation was found in the synovial tissues by immunohistochemistry using anti-phospho-STAT3 antibody. The majority of phospho-STAT3-positive cells were the synovial lining cells and exhibited negative expression of the macrophage or T cell marker. Treatment with CP690,550, a Janus Kinase inhibitor, resulted in a decrease in phospho-STAT3-positive cells, especially with high intensity, indicating effective suppression of STAT3 activation in RDC synovial tissues. Inhibitory effect of CP690,550 could work through the Janus Kinase/STAT3 axis in the synovial tissues in the early stage of RDC. Thus, STAT3 may be a potential therapeutic target for prevention of joint structural damage in RDC.

Mammals express a set of chitinase family proteins, comprising chitinases, which can hydrolyze chitin, and chitinase-like proteins without the chitinase activity but possessing chitin-binding properties. They act as endogenous lectins, regulating various physiological/pathological events. Ym1, originally identified as an eosinophil chemotactic factor or a macrophage-derived protein in parasite-infected mice, is a rodent-specific chitinase-like protein. Ym1 is also purified from eosinophilic crystals formed in the lung and urinary system in various disease models. We previously reported that major cellular sources of murine Ym1 are alveolar macrophages in the lung and neutrophils/monocytes lineage cells of the spleen and bone marrow under normal conditions. We here analyzed the detailed cellular expression of Ym1 in Mesocestoides corti (M. corti)-infected mice. Ym1 was significantly increased in the liver containing the larvae, lung, and peritoneal exudate cells in M. corti-infected mice, where activated macrophages expressed Ym1. Characteristic needle-shaped eosinophilic crystals appeared in the larvae-free lung, and Ym1 was localized to endoplasmic reticulum of activated alveolar macrophages. Moreover, swollen mesothelial cells covering the liver, spleen, and heart expressed Ym1 abundantly. Although the role of Ym1 in parasitic infection remains unclear, our findings focusing on an endogenous lectin may help in better understanding defense mechanism against parasites.

Biomolecular condensates are membrane-less compartments that are formed through an assembly of proteins and nucleic acids in the cell. Dysregulation of biological condensates has been implicated in diseases such as neurodegeneration and cancer. Ribonucleic acid (RNA) is known to affect the assembly of proteins in vitro, if and how RNA is involved in regulating biomolecular condensates in cells is not well investigated. Here we examined two nuclear proteins, FUS and HP1α, in which RNA was found to have an opposite contribution for the assembly of these proteins. Reduction of nuclear RNA, by inhibiting the transcription, triggered assembly of FUS that had been distributed in the nucleoplasm, whereas it dispersed spontaneously formed HP1α assembly. Notably, the cell cycle-dependent phosphorylation-mimicking substitutions in HP1α promoted its assembly formation. These transcription inhibitor experiments are versatile to examine diverse roles of nuclear RNA in regulating biomolecular condensates, in both physiological and pathological conditions.