Biology subjects

Sekiguchi, K.

Publications and source records attributed to Sekiguchi, K..

4 recordsLinked to original sources

bioRxiv2021

Resistance to chemical carcinogenesis induction via a dampened inflammatory response in naked mole-rats

Naked mole-rats (NMRs) have a very low spontaneous carcinogenesis rate, which has prompted scientists to study their cancer resistance mechanisms in order to provide clues for human cancer prevention. Although cancer resistance in NMRs has been intensively investigated at the cellular level, it is still unknown how strongly resistant NMR individuals are to carcinogenesis and how NMR tissues respond to experimental carcinogenesis induction. Here, we show that NMRs exhibit extraordinary resistance against potent chemical carcinogenesis induction through a dampened inflammatory response. Although carcinogenic insults damaged skin cells of both NMRs and mice, NMR skin showed markedly lower immune cell infiltration and reduced induction of inflammatory genes. NMRs harbor loss-of-function mutations in receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) genes, which are essential for necroptosis, a type of necrotic cell death that activates strong inflammation. A necroptosis-inducing stimulus did not increase death of NMR cells. After carcinogenic insults, leakage of the HMGB1, a marker of necrotic cell death, was not increased in NMR skin. In mice, inhibition or knockout of RIPK3 reduced immune cell infiltration and delayed the onset of chemical carcinogenesis. Therefore, necroptosis deficiency may serve as a cancer resistance mechanism via attenuating the inflammatory response in NMRs. Our study sheds light on the importance of a dampened inflammatory response as a non-cell-autonomous cancer resistance mechanism in NMRs. Further in vivo study of the unusual tissue immune system and carcinogenesis resistance of NMRs may lead to the development of new strategies to prevent carcinogenesis in humans. Significance StatementIn contrast with intensive studies of cancer resistance mechanisms in naked mole-rats (NMRs) at the cellular level, little is known about how NMR individuals respond to carcinogenesis induction, despite the fact that cell-to-cell interactions in tissues regulate carcinogenesis in vivo. Here, we demonstrate that NMRs are remarkably resistant to chemical carcinogenesis induction and characteristically have attenuated tissue inflammatory responses to carcinogenic insults. NMRs have loss-of-function mutations in RIPK3 and MLKL genes and thus cannot activate necroptosis, a type of inflammation-inducing cell death. RIPK3 inhibition in mice reduced immune cell infiltration in response to carcinogenic insults and delayed the onset of chemical-induced carcinogenesis. Our results highlight the importance of studies on dampened tissue inflammatory responses to understand cancer resistance of NMRs.

cancer biology↗

bioRxiv2021

Multiscale computer model of the spinal dorsal horn reveals changes in network processing associated with chronic pain

Pain-related sensory input is processed in the spinal dorsal horn (SDH) before being relayed to the brain. That processing profoundly influences whether stimuli are correctly or incorrectly perceived as painful. Significant advances have been made in identifying the types of excitatory and inhibitory neurons that comprise the SDH, and there is some information about how neuron types are connected, but it remains unclear how the overall circuit processes sensory input or how that processing is disrupted under chronic pain conditions. To explore SDH function, we developed a computational model of the circuit that is tightly constrained by experimental data. Our model comprises conductance-based neuron models that reproduce the characteristic firing patterns of spinal neurons. Excitatory and inhibitory neuron populations, defined by their expression of genetic markers, spiking pattern, or morphology, were synaptically connected according to available qualitative data. Using a genetic algorithm, synaptic weights were tuned to reproduce projection neuron firing rates (model output) based on primary afferent firing rates (model input) across a range of mechanical stimulus intensities. Disparate synaptic weight combinations could produce equivalent circuit function, revealing degeneracy that may underlie heterogeneous responses of different circuits to perturbations or pathological insults. To validate our model, we verified that it responded to reduction of inhibition (i.e. disinhibition) and ablation of specific neuron types in a manner consistent with experiments. Thus validated, our model offers a valuable resource for interpreting experimental results and testing hypotheses in silico to plan experiments for examining normal and pathological SDH circuit function. Significance StatementWe developed a multiscale computer model of the posterior part of spinal cord gray matter (spinal dorsal horn), involved in perception of touch and pain. The model reproduces several experimental observations and makes predictions about how specific types of spinal neurons and synapses influence projection neurons that send information to the brain. Misfiring of these projection neurons can produce anomalous sensations associated with chronic pain. Our computer model will not only assist in planning future experiments, but will also be useful for developing new pharmacotherapy for chronic pain disorders, connecting the effect of drugs acting at the molecular scale with emergent properties of neurons and circuits that shape the pain experience.

neuroscience↗

bioRxiv2020

Adhesion to type I collagen fibrous gels induces E- to N- cadherin switching without other EMT-related phenotypes in lung carcinoma cell A549

In culture system, environmental factors, such as increasing exogenous growth factors and adhesion to type I collagen (Col-I) induce epithelial-to-mesenchymal transition (EMT) in cells. Col-I molecules maintain a non-fibril form under acidic conditions, and they reassemble into fibrils under physiological conditions. Col-I fibrils often assemble to form three-dimensional gels. The gels and non-gel-form of Col-I can be utilized as culture substrates and different gel-forming state often elicit different cell behaviors. However, gel-form dependent effects on cell behaviors, including EMT induction, remain unclear. EMT induction in lung cancer cell line A549 has been reported via adhesion to Col-I but the effects of gel form dependency are unelucidated. This study investigated the changes in EMT-related behaviors in A549 cells cultured on Col-I gels. We examined cell morphology, proliferation, single-cell migration and expression of EMT-related features in A549 cells cultured on gels or non-gel form of Col-I and non-treated dish with or without transforming growth factor (TGF)-{beta}1. On Col-I gels, some cells kept cell-cell contacts and formed clusters, others maintained single-cell form. In cell-cell contact regions, E-cadherin expression was downregulated, whereas that of N-cadherin was upregulated. Vimentin and integrins 2 and {beta}1 expression were not increased. In TGF-{beta}1-treated A549 cells, cadherin switched from E- to N-cadherin. Their morphology changed to a mesenchymal form and cells scattered with no cluster formation. Vimentin, integrins 2 and {beta}1 expression were upregulated. Thus, we concluded that culture on Col-I fibrous gels induced E- to N-cadherin switching without other EMT-related phenotypes in A549 cells.

cell biology↗

bioRxiv2020

Mapping the molecular and structural specialization of the skin basement membrane for inter-tissue interactions

Inter-tissue interaction is fundamental to multicellularity. Although the basement membrane (BM) is located at tissue interfaces, its mode of action in inter-tissue interactions remains poorly understood, mainly because the molecular and structural details of the BM at distinct inter-tissue interfaces remain unclear. By combining quantitative transcriptomics and immunohistochemistry, we systematically identify the cellular origin, molecular identity and tissue distribution of extracellular matrix molecules in mouse hair follicles, and reveal that BM composition and architecture are exquisitely specialized for distinct inter-tissue interactions, including epidermal-fibroblast, epidermal-muscle and epidermal-nerve interactions. The epidermal-fibroblast interface, namely, hair germ-dermal papilla interface, makes asymmetrically organized side-specific heterogeneity in BM, defined by the newly characterized interface, hook and mesh BMs. One component of these BMs, laminin 5, is required for the topological and functional integrity of hair germ-dermal papilla interactions. Our study highlights the significance of BM heterogeneity in distinct inter-tissue interactions.

developmental biology↗