TRPA1 Mediates Mechanical Currents in the Plasma Membrane of Mouse Sensory Neurons

Mechanosensitive channels serve as essential sensors for cells to interact with their environment. The identity of mechanosensitive channels that underlie somatosensory touch transduction is still a mystery. One promising mechanotransduction candidate is the Transient Receptor Potential Ankyrin 1 (TRPA1) ion channel. To determine the role of TRPA1 in the generation of mechanically-sensitive currents, we used dorsal root ganglion (DRG) neuron cultures from adult mice and applied rapid focal mechanical stimulation (indentation) to the soma membrane. Small neurons (diameter <27 µm) were studied because TRPA1 is functionally present in these neurons which largely give rise to C-fiber afferents in vivo. Small neurons were classified by isolectin B4 binding

Keratin 8 expression in colon cancer associates with low faecal butyrate levels

<p>Abstract</p> <p>Background</p> <p>Butyrate has been implicated in the mechanistic basis of the prevention of colorectal cancer by dietary fibre. Numerous in vitro studies have shown that butyrate regulates cell cycle and cell death. More recently we have shown that butyrate also regulates the integrity of the intermediate filament (IF) cytoskeleton <it>in vitro</it>. These and other data suggest a link between the role of diet and the implication of a central role for the keratin 8 (K8) as guardian of the colorectal epithelium.</p> <p>Methods</p> <p>In this cross-sectional study possible links between butyrate levels, field effects and keratin expression in cancer were addressed directly by analysing how levels of expression of the IF protein K8 in tumours, in adjacent fields and at a distant landmark site may be affected by the level of butyrate in the colon microenvironment. An immunohistochemical scoring protocol for K8 was developed and applied to samples, findings were further tested by immunoblotting.</p> <p>Results</p> <p>Levels of K8 in colorectal tumours are lower in subjects with higher levels of faecal butyrate. Immunoblotting supported this finding.Although there were no significant relationships with butyrate on the non-tumour tissues, there was a consistent trend in all measures of extent or intensity of staining towards a reduction in expression with elevated butyrate, consistent with the inverse association in tumours.</p> <p>Conclusions</p> <p>The data suggest that butyrate may associate with down-regulation of the expression of K8 in the cancerized colon. If further validated these findings may suggest the chemopreventive value of butyrate is limited to early stage carcinogenesis as low K8 expression is associated with a poor prognosis.</p

TRPA1 Contributes to the Acute Inflammatory Response and Mediates Carrageenan-Induced Paw Edema in the Mouse

Transient receptor potential ankyrin 1 (TRPA1) is an ion channel involved in thermosensation and nociception. TRPA1 is activated by exogenous irritants and also by oxidants formed in inflammatory reactions. However, our understanding of its role in inflammation is limited. Here, we tested the hypothesis that TRPA1 is involved in acute inflammatory edema. The TRPA1 agonist allyl isothiocyanate (AITC) induced inflammatory edema when injected intraplantarly to mice, mimicking the classical response to carrageenan. Interestingly, the TRPA1 antagonist HC-030031 and the cyclo-oxygenase (COX) inhibitor ibuprofen inhibited not only AITC but also carrageenan-induced edema. TRPA1-deficient mice displayed attenuated responses to carrageenan and AITC. Furthermore, AITC enhanced COX-2 expression in HEK293 cells transfected with human TRPA1, a response that was reversed by HC-030031. This study demonstrates a hitherto unknown role of TRPA1 in carrageenan-induced inflammatory edema. The results also strongly suggest that TRPA1 contributes, in a COX-dependent manner, to the development of acute inflammation

The human keratins: biology and pathology

The keratins are the typical intermediate filament proteins of epithelia, showing an outstanding degree of molecular diversity. Heteropolymeric filaments are formed by pairing of type I and type II molecules. In humans 54 functional keratin genes exist. They are expressed in highly specific patterns related to the epithelial type and stage of cellular differentiation. About half of all keratins—including numerous keratins characterized only recently—are restricted to the various compartments of hair follicles. As part of the epithelial cytoskeleton, keratins are important for the mechanical stability and integrity of epithelial cells and tissues. Moreover, some keratins also have regulatory functions and are involved in intracellular signaling pathways, e.g. protection from stress, wound healing, and apoptosis. Applying the new consensus nomenclature, this article summarizes, for all human keratins, their cell type and tissue distribution and their functional significance in relation to transgenic mouse models and human hereditary keratin diseases. Furthermore, since keratins also exhibit characteristic expression patterns in human tumors, several of them (notably K5, K7, K8/K18, K19, and K20) have great importance in immunohistochemical tumor diagnosis of carcinomas, in particular of unclear metastases and in precise classification and subtyping. Future research might open further fields of clinical application for this remarkable protein family

Relevance of TRPA1 and TRPM8 channels as vascular sensors of cold in the cutaneous microvasculature.

Cold exposure is directly related to skin conditions, such as frostbite. This is due to the cold exposure inducing a vasoconstriction to reduce cutaneous blood flow and protect against heat loss. However, a long-term constriction will cause ischaemia and potentially irreversible damage. We have developed techniques to elucidate the mechanisms of the vascular cold response. We focused on two ligand-gated transient receptor potential (TRP) channels, namely, the established "cold sensors" TRP ankyrin 1 (TRPA1) and TRP melastin (TRPM8). We used the anaesthetised mouse and measured cutaneous blood flow by laser speckle imaging. Two cold treatments were used. A generalised cold treatment was achieved through whole paw water immersion (10 °C for 5 min) and a localised cold treatment that will be potentially easier to translate to human studies was carried out on the mouse paw with a copper cold probe (0.85-cm diameter). The results show that TRPA1 and TRPM8 can each act as a vascular cold sensor to mediate the vasoconstrictor component of whole paw cooling as expected from our previous research. However, the local cooling-induced responses were only blocked when the TRPA1 and TRPM8 antagonists were given simultaneously. This suggests that this localised cold probe response requires both functional TRPA1 and TRPM8.We thank the Biotechnology and Biological Sciences Research Council (BBSRC), (DT) British Heart Foundation (BHF) (AA), Medical Research Council (MRC) (FA) and Science without Borders (Brazilian government; LB) for funding. Y Pan was a KCL MSc Pharmacology student