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The cellular correlate for cold sensing has been ascribed to either Trpm8-expressing or Na V 1.8-expressing neurons. Importantly, transcriptomic analysis shows that these neuronal populations are nonoverlapping. Using in vivo GCaMP imaging in live mice we show that the vast majority of acute cold-sensing neurons activated at ≥1 °C do not express Na V 1.8, and that the loss of Na V 1.8 does not affect acute cold-sensing behavior in mice. Instead, we show that cold-responding neurons are enriched with Trpm8 as well as numerous potassium channels, including Kcnk9. By contrast, Na V 1.8-positive neurons signal prolonged extreme cold. These observations highlight the complexity of cold sensing in DRG neurons, and the role of Na V 1.8-negative neurons in cold sensing down to 1 °C. The ability to detect environmental cold serves as an important survival tool. The sodium channels Na V 1.8 and Na V 1.9, as well as the TRP channel Trpm8, have been shown to contribute to cold sensation in mice. Surprisingly, transcriptional profiling shows that Na V 1.8/Na V 1.9 and Trpm8 are expressed in nonoverlapping neuronal populations. Here we have used in vivo GCaMP3 imaging to identify cold-sensing populations of sensory neurons in live mice. We find that ∼80% of neurons responsive to cold down to 1 °C do not express Na V 1.8, and that the genetic deletion of Na V 1.8 does not affect the relative number, distribution, or maximal response of cold-sensitive neurons. Furthermore, the deletion of Na V 1.8 had no observable effect on transient cold-induced (≥5 °C) behaviors in mice, as measured by the cold-plantar, cold-plate (5 and 10 °C), or acetone tests. In contrast, nocifensive-like behavior to extreme cold-plate stimulation (−5 °C) was completely absent in mice lacking Na V 1.8. Fluorescence-activated cell sorting (FACS) and subsequent microarray analysis of sensory neurons activated at 4 °C identified an enriched repertoire of ion channels, which include the Trp channel Trpm8 and potassium channel Kcnk9, that are potentially required for cold sensing above freezing temperatures in mouse DRG neurons. These data demonstrate the complexity of cold-sensing mechanisms in mouse sensory neurons, revealing a principal role for Na V 1.8-negative neurons in sensing both innocuous and acute noxious cooling down to 1 °C, while Na V 1.8-positive neurons are likely responsible for the transduction of prolonged extreme cold temperatures, where tissue damage causes pan-nociceptor activation.

The ability to detect environmental cold serves as an important survival tool. The sodium channels NaV1.8 and NaV1.9, as well as the TRP channel Trpm8, have been shown to contribute to cold sensation in mice. Surprisingly, transcriptional profiling shows that NaV1.8/NaV1.9 and Trpm8 are expressed in nonoverlapping neuronal populations. Here we have used in vivo GCaMP3 imaging to identify cold-sensing populations of sensory neurons in live mice. We find that ~80% of neurons responsive to cold down to 1 °C do not express NaV1.8, and that the genetic deletion of NaV1.8 does not affect the relative number, distribution, or maximal response of cold-sensitive neurons. Furthermore, the deletion of NaV1.8 had no observable effect on transient cold-induced (≥5 °C) behaviors in mice, as measured by the cold-plantar, cold-plate (5 and 10 °C), or acetone tests. In contrast, nocifensive-like behavior to extreme cold-plate stimulation (−5 °C) was completely absent in mice lacking NaV1.8. Fluorescence-activated cell sorting (FACS) and subsequent microarray analysis of sensory neurons activated at 4 °C identified an enriched repertoire of ion channels, which include the Trp channel Trpm8 and potassium channel Kcnk9, that are potentially required for cold sensing above freezing temperatures in mouse DRG neurons. These data demonstrate the complexity of cold-sensing mechanisms in mouse sensory neurons, revealing a principal role for NaV1.8-negative neurons in sensing both innocuous and acute noxious cooling down to 1 °C, while NaV1.8-positive neurons are likely responsible for the transduction of prolonged extreme cold temperatures, where tissue damage causes pannociceptor activation.

ObjectivesThe objective of this study was to evaluate efficacy, safety and tolerability of the first-in-class, anti-CCL17 monoclonal antibody, GSK3858279, in treating knee osteoarthritis (OA) pain.MethodsThis was a phase I, randomised, placebo-controlled, two-part, proof-of-mechanism and proof-of-concept study. In part A, healthy participants were randomised 3:1 to receive GSK3858279 as either single intravenous (0.1–10 mg/kg) doses, a subcutaneous (3 mg/kg up to 240 mg maximum) dose, or placebo, to evaluate safety and tolerability. In part B, participants with knee OA pain were randomised 1:1 to receive weekly subcutaneous 240 mg GSK3858279, or placebo, for 8 weeks, to assess safety and change from baseline (CFB) in average and worst knee pain intensity. Exploratory endpoints included CFB in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain, function and stiffness scores.ResultsGSK3858279 demonstrated greater median CFB (95% credible interval (CrI)) in average and worst knee pain intensity versus placebo (average, –1.18 (–2.15, –0.20); worst, –1.09 (–2.29, 0.12)) at week 8. Median CFB (95% CrI) for GSK3858279 versus placebo in WOMAC pain and function scores were –1.41 (–2.35, –0.46) and –1.29 (–2.28, –0.29), respectively, at week 8. Overall, 72% (26/36; part A) and 88% (21/24; part B) of participants receiving GSK3858279 experienced adverse events (AEs); with nasopharyngitis being the most common in part A and injection site reactions in part B. No serious AEs or deaths were observed.GSK3858279 improved pain intensity and WOMAC pain and function scores in adults with knee OA pain and demonstrated favourable safety and tolerability in both healthy participants and adults with knee OA pain.

A side effect of bortezomib (a drug used to treat multiple myeloma) is neuropathic pain, probably owing to increased sphingolipid synthesis. Fingolimod, a drug used to treat multiple sclerosis, down-regulates a sphingolipid receptor and is a candidate analgesic.

LOS ANGELES, Oct. 23.--(To the Editor of The Times:]. I have read in a recent issue of The Times President Paul Shoup's complaints regarding the jitney bus and its disastrous results to the electric roads.

In the Michigan Farmer of July 14, a correspondent makes some inquiries about chess, and the answer is given that chess will never grow from anything but chess seed.

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.