TRPA1 functions as an excitatory ionotropic receptor in sensory neurons. It was originally described as a noxious cold-activated channel, but its cold sensitivity has been disputed in later studies, and the contribution of TRPA1 to thermosensing is currently a matter of strong debate. Here, we provide several lines of evidence to establish that TRPA1 acts as a cold sensor in vitro and in vivo. First, we demonstrate that heterologously expressed TRPA1 is activated by cold in a Ca 2؉ -independent and Ca 2؉ store-independent manner; temperature-dependent gating of TRPA1 is mechanistically analogous to that of other temperature-sensitive TRP channels, and it is preserved after treatment with the TRPA1 agonist mustard oil. Second, we identify and characterize a specific subset of cold-sensitive trigeminal ganglion neurons that is absent in TRPA1-deficient mice. Finally, cold plate and tail-flick experiments reveal TRPA1-dependent, cold-induced nociceptive behavior in mice. We conclude that TRPA1 acts as a major sensor for noxious cold.cold sensing ͉ pain ͉ sensory neurons ͉ TRP channels S ensing the environmental temperature is essential for animals to maintain thermal homeostasis and to avoid prolonged contact with harmfully hot or cold objects (1). Our understanding of the molecular basis of thermosensation has made great strides with the discovery that several members of the transient receptor potential (TRP) cation channel family exhibit highly temperature-sensitive gating and are expressed in cells of the sensory system (1). Mice lacking specific temperature-sensitive TRP channels illustrate how these channels serve as molecular thermometers in the peripheral sensory system (2). At least 3 heat-activated members of the TRPV subfamily (TRPV1, TRPV3, and TRPV4) are critically involved in sensing hot temperatures. TRPM8, a channel activated by cold temperatures and cooling compounds, such as menthol, plays a major role in cold sensing (1). Importantly, although TRPM8-deficient mice exhibit significant deficits in cold sensing in the temperature range between 28°C and 15°C, they retain a normal response to noxious cold temperatures, demonstrating the existence of TRPM8-independent mechanisms to detect noxious cold (3-5). TRPA1 has been put forward as a potential candidate to mediate detection of noxious cold, based on its expression in nociceptive neurons, and on the finding that heterologously expressed TRPA1 in CHO cells is activated by cold temperatures with a lower temperature threshold for activation than TRPM8 (6-8).At this point, however, the role of TRPA1 in (noxious) cold sensing is highly controversial. First, there is no consensus as to whether TRPA1 is directly gated by cold temperatures. Two groups have reported that they failed to detect cold-induced activation of heterologously expressed TRPA1 (9, 10), and a third report suggested that cold-induced activation of TRPA1 in overexpression systems is an indirect effect, caused by cold-induced Ca 2ϩ release from intracellular stores and subsequent Ca 2ϩ -d...

Here we provide evidence for a critical role of the transient receptor potential cation channel, subfamily V, member 4 (TRPV4) in normal bladder function. Immunofluorescence demonstrated TRPV4 expression in mouse and rat urothelium and vascular endothelium, but not in other cell types of the bladder. Intracellular Ca 2+ measurements on urothelial cells isolated from mice revealed a TRPV4-dependent response to the selective TRPV4 agonist 4α-phorbol 12,13-didecanoate and to hypotonic cell swelling. Behavioral studies demonstrated that TRPV4 -/-mice manifest an incontinent phenotype but show normal exploratory activity and anxietyrelated behavior. Cystometric experiments revealed that TRPV4 -/-mice exhibit a lower frequency of voiding contractions as well as a higher frequency of nonvoiding contractions. Additionally, the amplitude of the spontaneous contractions in explanted bladder strips from TRPV4 -/-mice was significantly reduced. Finally, a decreased intravesical stretch-evoked ATP release was found in isolated whole bladders from TRPV4 -/-mice. These data demonstrate a previously unrecognized role for TRPV4 in voiding behavior, raising the possibility that TRPV4 plays a critical role in urothelium-mediated transduction of intravesical mechanical pressure.

Reduced functional bladder capacity and concomitant increased micturition frequency (pollakisuria) are common lower urinary tract symptoms associated with conditions such as cystitis, prostatic hyperplasia, neurological disease, and overactive bladder syndrome. These symptoms can profoundly affect the quality of life of afflicted individuals, but available pharmacological treatments are often unsatisfactory. Recent work has demonstrated that the cation channel TRPV4 is highly expressed in urothelial cells and plays a role in sensing the normal filling state of the bladder. In this article, we show that the development of cystitis-induced bladder dysfunction is strongly impaired in Trpv4 −/− mice. Moreover, we describe HC-067047, a previously uncharacterized, potent, and selective TRPV4 antagonist that increases functional bladder capacity and reduces micturition frequency in WT mice and rats with cystitis. HC-067047 did not affect bladder function in Trpv4 −/− mice, demonstrating that its in vivo effects are on target. These results indicate that TRPV4 antagonists may provide a promising means of treating bladder dysfunction. transient receptor potential channels | urothelium

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Highlights d We single-cell RNA-sequenced 56,771 endothelial cells (ECs) from human, mouse, and cultured lung tumor models d Tip ECs were resolved into migratory and basementmembrane remodeling phenotypes d Capillary and venous ECs expressed immunoregulatory gene signatures d Integrated analysis identified collagen modification as an angiogenic pathway