No abstract

TRPA1 is a Ca2+-permeable cation channel that is activated by painful low temperatures (˂17 °C), irritating chemicals, reactive metabolites and mediators of inflammation. In the bladder TRPA1 is predominantly expressed in sensory afferent nerve endings, where it mediates sensory transduction. The contractile effect of its activation on detrusor smooth muscle (DSM) is explained by the release from sensory afferents of inflammatory factors – tachykinins and prostaglandins, which cause smooth muscle cell contraction. Diabetes is a systemic disease, with common complications being diabetic cystopathies and urinary incontinence. However, data on how diabetes affects bladder contractility associated with TRPA1 activation are not available. In this study, by using a rat model with streptozotocin-induced type I diabetes, contractility measurements of DSM strips in response to TRPA1-activating and modulating pharmacological agents and assessment of TRPA1 mRNA expression in bladder-innervating dorsal root ganglia, we have shown that diabetes enhances the TRPA1-dependent mechanism involved in bladder DSM contractility. This is not due to changes in TRPA1 expression, but mainly due to the general inflammatory reaction caused by diabetes. The latter leads to an increase in cyclooxygenase-2-dependent prostaglandin synthesis through the mechanisms associated with substance P activity. This results in the enhanced functional coupling between the tachykinin and prostanoid systems, and the concomitant increase of their impact on DSM contractility in response to TRPA1 activation.

No abstract

Trpm8 is a nonselective Ca 2+ -permeable ion channel activated by temperatures below 28 °C and cooling chemical compounds such as menthol and icilin. Trpm8 is expressed in sensory neurons where it functions for temperature detection. However, Trpm8 is also expressed in various internal organs where temperature is stably higher than 36 °C, that is much higher than cool temperature needed for Trpm8 activation. This opens possible makes roles for Trpm8, such as nociception. Trpm8 mRNA is expressed in vas deferens (VD), a smooth muscle organ of male reproductive system. However, no Trpm8-mediated currents were previously registered in the myocytes. VD is located outside of testes, and it consists of smooth muscle tube covered by the epithelium. It actively contracts and transfers sperm from testes to ejaculatory ducts prior to ejaculation. Temperature in VD is stably high, thus, Trpm8 role there could be outside of cold detection. The objective of this study was to analyze Trpm8 mRNA and protein expression in rat VD, as well as splice variant analysis. Trpm8 mRNA expression in VD was confirmed with RT-PCR, and Trpm8 protein was detected by the Western-blot analysis. Additionally, we found that both mRNA and protein of shorter non-classical isoform, as well as canonical isoform of Trpm8 in VD. We isolated smooth muscle cells from VD and performed a multi-cell PCR. This technique makes possible non-myocytic mRNA detection that could be isolated from e.g. sensory neurons termini where Trpm8 is expressed at much higher levels. Interestingly, in the isolated smooth muscle cells, no canonical Trpm8 transcript was found, though the non-classical isoform was present. We propose the shorter isoform could be formed as a result of alternative splicing. This would account for a difference in Trpm8 function in VD, i.e. no Trpm8-mediated currents registered in the myocytes. A shorter isoform could have a truncated N-terminal domain, that is consistent with known human Trpm8 isoforms sM8-6 and sM8-18.