Sensing hot and cold with TRP channels

Elevated TRPV2 expression in the facial nerve of rats by cold stimulation: Implications for Bell's palsy

OBJECTIVE

Bell's palsy, also referred to as clinical manifestations of unilateral facial nerve palsy, encompasses downward angling of the corners of the mouth, the absence of forehead creases, and unilateral incomplete eyelid closure. The incidence of Bell's palsy has increased progressively in recent years, but the underlying mechanism of its occurrence remains unknown; therefore, it is essential to investigate both the cause and treatment of Bell's palsy. Member 2 of the Subfamily V Transient Receptor Potential Cation Channel is a mechanically and thermally sensitive ion channel that plays a crucial role in neural growth and development. Using a novel modeling technique, we endeavored to develop an animal model of Bell's palsy and determine whether TRPV2 expression is altered throughout the course of a facial nerve injury.

MATERIALS AND METHODS

The rats were categorized into 3 groups, and their facial nerve function was assessed using RT-qPCR, WB, and pathologic testing, respectively, after undergoing unilateral cold air stimulation for 1, 3, and 7 days. TRPV2 expression was identified using these techniques.

RESULTS

In response to cold stimulation, rats exhibited facial nerve paralysis symptoms, demyelinating lesions in the facial nerve, and increased TRPV2 expression.

CONCLUSIONS

Extended cold stimulation of the facial nerve in rats may lead to an imbalance in facial nerve homeostasis and increased TRPV2 expression. These findings will contribute to the understanding of the potential mechanism by which cold stimulation affects the facial nerve. Moreover, this finding implies that TRPV2 could possibly function as an additional diagnostic marker or therapeutic target in the context of Bell's palsy.

Bronchoconstriction damages airway epithelia by crowding-induced excess cell extrusion

Asthma is deemed an inflammatory disease, yet the defining diagnostic feature is mechanical bronchoconstriction. We previously discovered a conserved process called cell extrusion that drives homeostatic epithelial cell death when cells become too crowded. In this work, we show that the pathological crowding of a bronchoconstrictive attack causes so much epithelial cell extrusion that it damages the airways, resulting in inflammation and mucus secretion in both mice and humans. Although relaxing the airways with the rescue treatment albuterol did not affect these responses, inhibiting live cell extrusion signaling during bronchoconstriction prevented all these features. Our findings show that bronchoconstriction causes epithelial damage and inflammation by excess crowding-induced cell extrusion and suggest that blocking epithelial extrusion, instead of the ensuing downstream inflammation, could prevent the feed-forward asthma inflammatory cycle.

A brainstem-hypothalamus neuronal circuit reduces feeding upon heat exposure

Empirical evidence suggests that heat exposure reduces food intake. However, the neurocircuit architecture and the signalling mechanisms that form an associative interface between sensory and metabolic modalities remain unknown, despite primary thermoceptive neurons in the pontine parabrachial nucleus becoming well characterized1. Tanycytes are a specialized cell type along the wall of the third ventricle2 that bidirectionally transport hormones and signalling molecules between the brain's parenchyma and ventricular system3-8. Here we show that tanycytes are activated upon acute thermal challenge and are necessary to reduce food intake afterwards. Virus-mediated gene manipulation and circuit mapping showed that thermosensing glutamatergic neurons of the parabrachial nucleus innervate tanycytes either directly or through second-order hypothalamic neurons. Heat-dependent Fos expression in tanycytes suggested their ability to produce signalling molecules, including vascular endothelial growth factor A (VEGFA). Instead of discharging VEGFA into the cerebrospinal fluid for a systemic effect, VEGFA was released along the parenchymal processes of tanycytes in the arcuate nucleus. VEGFA then increased the spike threshold of Flt1-expressing dopamine and agouti-related peptide (Agrp)-containing neurons, thus priming net anorexigenic output. Indeed, both acute heat and the chemogenetic activation of glutamatergic parabrachial neurons at thermoneutrality reduced food intake for hours, in a manner that is sensitive to both Vegfa loss-of-function and blockage of vesicle-associated membrane protein 2 (VAMP2)-dependent exocytosis from tanycytes. Overall, we define a multimodal neurocircuit in which tanycytes link parabrachial sensory relay to the long-term enforcement of a metabolic code.

Utilization of Infrared Thermography in Assessing Thermal Responses of Farm Animals under Heat Stress

Heat stress is a condition that can affect the health, performance, and welfare of farm animals. The perception of thermal stress leads to the activation of the autonomic nervous system to start a series of physiological and behavioral mechanisms to restore thermostability. One of these mechanisms is vasodilation of peripheral blood vessels to increase heat loss through the skin. Due to this aspect, infrared thermography has been suggested as a method to assess the thermal state of animals and predict rectal temperature values noninvasively. However, it is important to consider that predicting rectal temperature is challenging, and its association with IRT is not always a direct linear relationship. The present review aims to analyze the neurobiological response associated with heat stress and how thermal imaging in different thermal windows can be used to recognize heat stress in farmed ungulates.

Targeting TRP channels: recent advances in structure, ligand binding, and molecular mechanisms

Transient receptor potential (TRP) channels are a large and diverse family of transmembrane ion channels that are widely expressed, have important physiological roles, and are associated with many human diseases. These proteins are actively pursued as promising drug targets, benefitting greatly from advances in structural and mechanistic studies of TRP channels. At the same time, the complex, polymodal activation and regulation of TRP channels have presented formidable challenges. In this short review, we summarize recent progresses toward understanding the structural basis of TRP channel function, as well as potential ligand binding sites that could be targeted for therapeutics. A particular focus is on the current understanding of the molecular mechanisms of TRP channel activation and regulation, where many fundamental questions remain unanswered. We believe that a deeper understanding of the functional mechanisms of TRP channels will be critical and likely transformative toward developing successful therapeutic strategies targeting these exciting proteins. This endeavor will require concerted efforts from computation, structural biology, medicinal chemistry, electrophysiology, pharmacology, drug safety and clinical studies.

Epigenetic Connections of the TRPA1 Ion Channel in Pain Transmission and Neurogenic Inflammation - a Therapeutic Perspective in Migraine?

Persistent reprogramming of epigenetic pattern leads to changes in gene expression observed in many neurological disorders. Transient receptor potential cation channel subfamily A member 1 (TRPA1), a member of the TRP channels superfamily, is activated by many migraine triggers and expressed in trigeminal neurons and brain regions that are important in migraine pathogenesis. TRP channels change noxious stimuli into pain signals with the involvement of epigenetic regulation. The expression of the TRPA1 encoding gene, TRPA1, is modulated in pain-related syndromes by epigenetic alterations, including DNA methylation, histone modifications, and effects of non-coding RNAs: micro RNAs (miRNAs), long non-coding RNAs, and circular RNAs. TRPA1 may change epigenetic profile of many pain-related genes as it may modify enzymes responsible for epigenetic modifications and expression of non-coding RNAs. TRPA1 may induce the release of calcitonin gene related peptide (CGRP), from trigeminal neurons and dural tissue. Therefore, epigenetic regulation of TRPA1 may play a role in efficacy and safety of anti-migraine therapies targeting TRP channels and CGRP. TRPA1 is also involved in neurogenic inflammation, important in migraine pathogenesis. The fundamental role of TRPA1 in inflammatory pain transmission may be epigenetically regulated. In conclusion, epigenetic connections of TRPA1 may play a role in efficacy and safety of anti-migraine therapy targeting TRP channels or CGRP and they should be further explored for efficient and safe antimigraine treatment. This narrative/perspective review presents information on the structure and functions of TRPA1 as well as role of its epigenetic connections in pain transmission and potential in migraine therapy.

Bronchoconstriction damages airway epithelia by excess crowding-induced extrusion

Asthma is deemed an inflammatory disease, yet the defining diagnostic symptom is mechanical bronchoconstriction. We previously discovered a conserved process that drives homeostatic epithelial cell death in response to mechanical cell crowding called cell extrusion(1, 2). Here, we show that the pathological crowding of a bronchoconstrictive attack causes so much epithelial cell extrusion that it damages the airways, resulting in inflammation and mucus secretion. While relaxing airways with the rescue treatment albuterol did not impact these responses, inhibiting live cell extrusion signaling during bronchoconstriction prevented all these symptoms. Our findings propose a new etiology for asthma, dependent on the mechanical crowding of a bronchoconstrictive attack. Our studies suggest that blocking epithelial extrusion, instead of ensuing downstream inflammation, could prevent the feed-forward asthma inflammatory cycle.

Hydrogen peroxide production by epidermal dual oxidase 1 regulates nociceptive sensory signals

Keratinocytes of the mammalian skin provide not only mechanical protection for the tissues, but also transmit mechanical, chemical, and thermal stimuli from the external environment to the sensory nerve terminals. Sensory nerve fibers penetrate the epidermal basement membrane and function in the tight intercellular space among keratinocytes. Here we show that epidermal keratinocytes produce hydrogen peroxide upon the activation of the NADPH oxidase dual oxidase 1 (DUOX1). This enzyme can be activated by increasing cytosolic calcium levels. Using DUOX1 knockout animals as a model system we found an increased sensitivity towards certain noxious stimuli in DUOX1-deficient animals, which is not due to structural changes in the skin as evidenced by detailed immunohistochemical and electron-microscopic analysis of epidermal tissue. We show that DUOX1 is expressed in keratinocytes but not in the neural sensory pathway. The release of hydrogen peroxide by activated DUOX1 alters both the activity of neuronal TRPA1 and redox-sensitive potassium channels expressed in dorsal root ganglia primary sensory neurons. We describe hydrogen peroxide, produced by DUOX1 as a paracrine mediator of nociceptive signal transmission. Our results indicate that a novel, hitherto unknown redox mechanism modulates noxious sensory signals.

TRPV4 Promotes Metastasis in Melanoma by Regulating Cell Motility through Cytoskeletal Rearrangement

The abnormal expression of Transient Receptor Potential cation channel subfamily V member 4 (TRPV4) is closely related to the progression of multiple tumors. In addition, TRPV4 is increasingly being considered a potential target for cancer therapy, especially in tumor metastasis prevention. However, the biological correlation between TRPV4 and tumor metastasis, as well as the specific role of TRPV4 in malignant melanoma metastasis, is poorly understood. In this study, we aimed to examine the role of TRPV4 in melanoma metastasis through experiments and clinical data analysis, and the underlying anticancer mechanism of Baicalin, a natural compound, and its inhibitory effect on TRPV4 with in vivo and in vitro experiments. Our findings suggested that TRPV4 promotes metastasis in melanoma by regulating cell motility via rearranging the cytoskeletal, and Baicalin can inhibit cancer metastasis, whose mechanisms reverse the recruitment of activated cofilin to leading-edge protrusion and the increasing phosphorylation level of cortactin, which is provoked by TRPV4 activation.

Body temperature variation controls pre-mRNA processing and transcription of antiviral genes and SARS-CoV-2 replication

Antiviral innate immunity represents the first defense against invading viruses and is key to control viral infections, including SARS-CoV-2. Body temperature is an omnipresent variable but was neglected when addressing host defense mechanisms and susceptibility to SARS-CoV-2 infection. Here, we show that increasing temperature in a 1.5°C window, between 36.5 and 38°C, strongly increases the expression of genes in two branches of antiviral immunity, nitric oxide production and type I interferon response. We show that alternative splicing coupled to nonsense-mediated decay decreases STAT2 expression in colder conditions and suggest that increased STAT2 expression at elevated temperature induces the expression of diverse antiviral genes and SARS-CoV-2 restriction factors. This cascade is activated in a remarkably narrow temperature range below febrile temperature, which reflects individual, circadian and age-dependent variation. We suggest that decreased body temperature with aging contributes to reduced expression of antiviral genes in older individuals. Using cell culture and in vivo models, we show that higher body temperature correlates with reduced SARS-CoV-2 replication, which may affect the different vulnerability of children versus seniors toward severe SARS-CoV-2 infection. Altogether, our data connect body temperature and pre-mRNA processing to provide new mechanistic insight into the regulation of antiviral innate immunity.

A Review on the Role of TRP Channels and Their Potential as Drug Targets_An Insight Into the TRP Channel Drug Discovery Methodologies

Transient receptor potential (TRP) proteins are a large group of ion channels that control many physiological functions in our body. These channels are considered potential therapeutic drug targets for various diseases such as neurological disorders, cancers, cardiovascular disease, and many more. The Nobel Prize in Physiology/Medicine in the year 2021 was awarded to two scientists for the discovery of TRP and PIEZO ion channels. Improving our knowledge of technologies for their study is essential. In the present study, we reviewed the role of TRP channel types in the control of normal physiological functions as well as disease conditions. Also, we discussed the current and novel technologies that can be used to study these channels successfully. As such, Flux assays for detecting ionic flux through ion channels are among the core and widely used tools for screening drug compounds. Technologies based on these assays are available in fully automated high throughput set-ups and help detect changes in radiolabeled or non-radiolabeled ionic flux. Aurora’s Ion Channel Reader (ICR), which works based on label-free technology of flux assay, offers sensitive, accurate, and reproducible measurements to perform drug ranking matching with patch-clamp (gold standard) data. The non-radiolabeled trace-based flux assay coupled with the ICR detects changes in various ion types, including potassium, calcium, sodium, and chloride channels, by using appropriate tracer ions. This technology is now considered one of the very successful approaches for analyzing ion channel activity in modern drug discovery. It could be a successful approach for studying various ion channels and transporters, including the different members of the TRP family of ion channels.

Dietary Supplementation With Yucca Alleviates Heat Stress in Growing Broilers Exposed to High Ambient Temperature

Yucca contains high a content of saponin that has a glucocorticord-like effect in animals, e.g., anti-inflammation and anti-microbiota. The objective of the present study was to test the hypothesis that dietary supplementation of yucca powder may alleviate heat stress and improve growth performance of growing broilers subjected to cycling high ambient temperature. A total of 240 male broiler chicks (yellow feathered chicken) aged 28 days, with body weight (BW) of 792 ± 43.7 g, were randomly allocated to one of four treatments (6 replicates per treatment): control (normal temperature, 24 ± 2°C, 24 h), fed diets supplemented with 100 mg/kg yucca under normal temperature (Y), high ambient temperature exposure (HT, 34 ± 2°C, 11 h), fed diets supplemented with 100 mg/kg yucca (HT+Y) under high ambient temperature. After 7 days of adaption, the experiment was conducted for 4 weeks (aged 28–56 days). HT significantly reduced feed intake, BW, and average daily gain (ADG) of broiler, but yucca improved the feed intake under HT condition. Yucca supplementation reduced (P < 0.05) the HT-induced increase in temperature of rectum and leg skin. Supplementation of yucca increased the hypothalamic mRNA expression of TRPV2, TRPV4, and TRPM8 (P < 0.05). Yucca reduced (P < 0.05) the plasma lipid oxidation product malondialdehyde (MDA), but did not affect the activities of antioxidant enzyme superoxide oxidase (SOD) and glutathione peroxidase (Gpx). Yucca did not affect the plasma neuro peptide Y (NPY), which was reduced by HT, yucca reduced circulation cholecystokinin (CCK) and hypothalamic mRNA expression of CCK. Supplementation of yucca increased the mRNA expression of both heat and cool sensing receptors. The results of the present study indicate that yucca could improve antioxidant status and attenuate the heat stress response by regulating hypothalamic temperature-sensing genes in growing chickens. Besides, yucca supplementation improved feed intake probably through modulating CCK in growing broilers under high ambient temperature.

Transient Receptor Potential Vanilloid 1 Plays a Major Role in Low Temperature-Mediated Skin Barrier Dysfunction

BACKGROUND

Children born in the fall and winter are at increased risk for developing atopic dermatitis (AD) and food allergy (FA). Since these seasons are associated with low temperature, we hypothesized that low temperature exposure may compromise keratinocyte differentiation and contribute to skin barrier dysfunction.

OBJECTIVE

To examine whether low temperature causes skin barrier dysfunction.

METHODS

Primary human epidermal keratinocytes (HEKs) were differentiated in 1.3mM CaCl₂ media and cultured at different temperatures. The cells were transfected with transient receptor potential cation channel subfamily V member 1 (TRPV1) or signal transducer and activator of transcription (STAT) 3 small-interfering RNA (siRNA) to examine the effects of these gene targets in HEKs exposed to low temperature. Gene expression of TRPV1, epidermal barrier proteins, and keratinocyte-derived cytokines were evaluated. Organotypic skin equivalents were generated using HEKs transfected with control or TRPV1 siRNA and grown at 25^oC or 37^oC. Transepidermal water loss (TEWL) and levels of epidermal barrier proteins were evaluated.

RESULTS

Filaggrin (FLG) and loricrin (LOR) expression, but not keratin (KRT)-1 and KRT-10 expression, was downregulated in HEKs incubated at 25^oC while TRPV1 silencing increased intracellular Ca²⁺ influx (keratinocyte differentiation signal) and enhanced the expression of epidermal differentiation proteins. Interleukin (IL)-1β and thymic stromal lymphopoietin (TSLP) induced by low temperature inhibited FLG expression in keratinocytes through the TRPV1/STAT3 pathway. Moreover, low temperature-mediated inhibition of FLG and LOR was recovered, and TEWL was decreased in organotypic skin transfected with TRPV1 siRNA.

CONCLUSION

TRPV1 is critical in low temperature-mediated skin barrier dysfunction. Low temperature exposure induced TSLP, an alarmin implicated in epicutaneous allergen sensitization.

CLINICAL IMPLICATIONS

Low temperature causes skin barrier dysfunction through TRPV1 and TSLP, which may explain the pathways involved in promoting allergic sensitization through the skin.

Hypothermia Induced by Oxcarbazepine after Transient Forebrain Ischemia Exerts Therapeutic Neuroprotection through Transient Receptor Potential Vanilloid Type 1 and 4 in Gerbils

In the present study, we investigated the neuroprotective effect of post-ischemic treatment with oxcarbazepine (OXC; an anticonvulsant compound) against ischemic injury induced by transient forebrain ischemia and its mechanisms in gerbils. Transient ischemia was induced in the forebrain by occlusion of both common carotid arteries for 5 min under normothermic conditions (37 ± 0.2 °C). The ischemic gerbils were treated with vehicle, hypothermia (whole-body cooling; 33.0 ± 0.2 °C), or 200 mg/kg OXC. Post-ischemic treatments with vehicle and hypothermia failed to attenuate and improve, respectively, ischemia-induced hyperactivity and cognitive impairment (decline in spatial and short-term memory). However, post-ischemic treatment with OXC significantly attenuated the hyperactivity and the cognitive impairment, showing that OXC treatment significantly reduced body temperature (to about 33 °C). When the hippocampus was histopathologically examined, pyramidal cells (principal neurons) were dead (lost) in the subfield Cornu Ammonis 1 (CA1) of the gerbils treated with vehicle and hypothermia on Day 4 after ischemia, but these cells were saved in the gerbils treated with OXC. In the gerbils treated with OXC after ischemia, the expression of transient receptor potential vanilloid type 1 (TRPV1; one of the transient receptor potential cation channels) was significantly increased in the CA1 region compared with that in the gerbils treated with vehicle and hypothermia. In brief, our results showed that OXC-induced hypothermia after transient forebrain ischemia effectively protected against ischemia–reperfusion injury through an increase in TRPV1 expression in the gerbil hippocampal CA1 region, indicating that TRPV1 is involved in OXC-induced hypothermia.

Neurochemical characterization of mouse dorsal root ganglion neurons expressing organic cation transporter 2

Organic cation transporters (OCTs) are poly-specific carriers for endogenous and exogenous cationic compounds. These are widely distributed in the nervous system and mediate neuronal activities. As antineoplastic cationic drugs accumulate in the dorsal root ganglion (DRG), OCT function has been studied mainly in cultured DRG neurons. However, the histological distribution of OCTs in the DRG is unclear. This study investigated the localization of OCT2 (a member of OCTs) in mouse DRG neurons and determined their histochemical properties. OCT2 expression was found in about 20% of DRG neurons, which were small to medium size. OCT2-expressing neurons were labeled with markers for peptidergic nociceptive (substance P or calcitonin gene-related peptide) and tactile/proprioceptive (neurofilament 200 or tropomyosin receptor kinase B or C) neurons. OCT2 was also expressed in cholinergic DRG neurons identified by choline acetyltransferase promoter-derived Cre expression. In the spinal dorsal horn, OCT2 was distributed in superficial to deep laminae. OCT2 immunoreactivity was punctate in appearance and localized in the nerve terminals of sensory afferents with labeling of neurochemical markers. Our findings suggest that OCT2 as a low-affinity, high-capacity carrier may take up substrates including cationic neurotransmitters and drugs from the extracellular space around cell bodies in DRG neurons.

Perinatal Infection: A Major Contributor to Efficacy of Cooling in Newborns Following Birth Asphyxia

Neonatal encephalopathy (NE) is a global burden, as more than 90% of NE occurs in low- and middle-income countries (LMICs). Perinatal infection seems to limit the neuroprotective efficacy of therapeutic hypothermia. Efforts made to use therapeutic hypothermia in LMICs treating NE has led to increased neonatal mortality rates. The heat shock and cold shock protein responses are essential for survival against a wide range of stressors during which organisms raise their core body temperature and temporarily subject themselves to thermal and cold stress in the face of infection. The characteristic increase and decrease in core body temperature activates and utilizes elements of the heat shock and cold shock response pathways to modify cytokine and chemokine gene expression, cellular signaling, and immune cell mobilization to sites of inflammation, infection, and injury. Hypothermia stimulates microglia to secret cold-inducible RNA-binding protein (CIRP), which triggers NF-κB, controlling multiple inflammatory pathways, including nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasomes and cyclooxygenase-2 (COX-2) signaling. Brain responses through changes in heat shock protein and cold shock protein transcription and gene-expression following fever range and hyperthermia may be new promising potential therapeutic targets.

Cyclic Hypoxia: An Update on Its Characteristics, Methods to Measure It and Biological Implications in Cancer

Regions of hypoxia occur in most if not all solid cancers. Although the presence of tumor hypoxia is a common occurrence, the levels of hypoxia and proportion of the tumor that are hypoxic vary significantly. Importantly, even within tumors, oxygen levels fluctuate due to changes in red blood cell flux, vascular remodeling and thermoregulation. Together, this leads to cyclic or intermittent hypoxia. Tumor hypoxia predicts for poor patient outcome, in part due to increased resistance to all standard therapies. However, it is less clear how cyclic hypoxia impacts therapy response. Here, we discuss the causes of cyclic hypoxia and, importantly, which imaging modalities are best suited to detecting cyclic vs. chronic hypoxia. In addition, we provide a comparison of the biological response to chronic and cyclic hypoxia, including how the levels of reactive oxygen species and HIF-1 are likely impacted. Together, we highlight the importance of remembering that tumor hypoxia is not a static condition and that the fluctuations in oxygen levels have significant biological consequences.

Exploring the 'cold/hot' properties of traditional Chinese medicine by cell temperature measurement

Context: It is common sense that chewing a mint leaf can cause a cooling feeling, while chewing ginger root will produce a burning feeling. In Traditional Chinese Medicine (TCM), this phenomenon is referred to as 'cold/hot' properties of herbs. Herein, it is reported that TCM with different "cold/hot" properties have different effects on the variation of cells.Objective: To explore the intrinsic 'cold/hot' properties of TCM from the perspective of cellular and molecular biology.Materials and methods: A375 cells were selected using Cancer Cell Line Encyclopaedia (CCLE) analysis and western blots. Hypaconitine and baicalin were selected by structural similarity analysis from 56 and 140 compounds, respectively. A wireless thermometry system was used to measure cellular temperature change induced by different compounds. Alteration of intracellular calcium influx was investigated by means of calcium imaging.Results: The IC₅₀ values of GSK1016790A, HC067047, hypaconitine, and baicalin for A375 cells are 8.363 nM, 816.4 μM, 286.4 μM and 29.84 μM, respectively. And, 8 μM hypaconitine induced obvious calcium influx while 8 μM baicalin inhibited calcium influx induced by TRPV4 activation. Cellular temperature elevated significantly when treated with GSK1016790A or hypaconitine, while the results were reversed when cells were treated with HC067047 or baicalin.Discussion and conclusions: The changes in cellular temperature are speculated to be caused by the alteration of intracellular calcium influx mediated by TRPV4. In addition, the 'cold/hot' properties of compounds in TCM can be classified by using cellular temperature detection.

Ca2+ as a therapeutic target in cancer

Ca2+ is a ubiquitous and dynamic second messenger molecule that is induced by many factors including receptor activation, environmental factors, and voltage, leading to pleiotropic effects on cell function including changes in migration, metabolism and transcription. As such, it is not surprising that aberrant regulation of Ca2+ signals can lead to pathological phenotypes, including cancer progression. However, given the highly context-specific nature of Ca2+-dependent changes in cell function, delineation of its role in cancer has been a challenge. Herein, we discuss the distinct roles of Ca2+ signaling within and between each type of cancer, including consideration of the potential of therapeutic strategies targeting these signaling pathways.

A Conserved Kinase-Based Body-Temperature Sensor Globally Controls Alternative Splicing and Gene Expression

Homeothermic organisms maintain their core body temperature in a narrow, tightly controlled range. Whether and how subtle circadian oscillations or disease-associated changes in core body temperature are sensed and integrated in gene expression programs remain elusive. Furthermore, a thermo-sensor capable of sensing the small temperature differentials leading to temperature-dependent sex determination (TSD) in poikilothermic reptiles has not been identified. Here, we show that the activity of CDC-like kinases (CLKs) is highly responsive to physiological temperature changes, which is conferred by structural rearrangements within the kinase activation segment. Lower body temperature activates CLKs resulting in strongly increased phosphorylation of SR proteins in vitro and in vivo. This globally controls temperature-dependent alternative splicing and gene expression, with wide implications in circadian, tissue-specific, and disease-associated settings. This temperature sensor is conserved across evolution and adapted to growth temperatures of diverse poikilotherms. The dynamic temperature range of reptilian CLK homologs suggests a role in TSD.

Impact of Adaptive Thermogenesis in Mice on the Treatment of Obesity

Obesity and associated metabolic diseases have become a priority area of study due to the exponential increase in their prevalence and the corresponding health and economic impact. In the last decade, brown adipose tissue has become an attractive target to treat obesity. However, environmental variables such as temperature and the dynamics of energy expenditure could influence brown adipose tissue activity. Currently, most metabolic studies are carried out at a room temperature of 21 °C, which is considered a thermoneutral zone for adult humans. However, in mice this chronic cold temperature triggers an increase in their adaptive thermogenesis. In this review, we aim to cover important aspects related to the adaptation of animals to room temperature, the influence of housing and temperature on the development of metabolic phenotypes in experimental mice and their translation to human physiology. Mice studies performed in chronic cold or thermoneutral conditions allow us to better understand underlying physiological mechanisms for successful, reproducible translation into humans in the fight against obesity and metabolic diseases.

Searching for analgesic drug candidates alleviating oxaliplatin-induced cold hypersensitivity in mice

Oxaliplatin is a third-generation, platinum-based derivative used to treat advanced colorectal cancer. Within the patient population on oxaliplatin therapy, a lower incidence of hematological adverse effects and gastrointestinal toxicity is noted, but severe neuropathic pain episodes characterized by increased cold and tactile hypersensitivity are present in ~95% of patients. This drug is also used to induce a rodent model of chemotherapy-induced peripheral neuropathy (CIPN)-related neuropathic pain which is widely used in the search for novel therapies for CIPN prevention and treatment. This paper provides a step-by-step, detailed description of the prevention and intervention protocols used in our laboratory for the assessment of oxaliplatin-induced cold allodynia in mice. To establish cold sensitivity in mice, the cold plate test was used. Latencies to pain reaction in response to cold stimulus (2.5°C) for vehicle-treated non-neuropathic mice, vehicle-treated mice injected with oxaliplatin (neuropathic control), and oxaliplatin-treated mice treated additionally with duloxetine are compared. Duloxetine is a serotonin/noradrenaline reuptake inhibitor which was found to produce significant pain relief in patients with CIPN symptoms. In our present study, duloxetine administered intraperitoneally at the dose of 30 mg/kg served as a model antiallodynic drug which attenuated or partially prevented cold allodynia caused by oxaliplatin.

Loss of barrier integrity in alveolar epithelial cells downregulates ENaC expression and activity via Ca2+ and TRPV4 activation

The epithelial Na channel (ENaC) plays an essential role in lung physiology by modulating the amount of liquid lining the respiratory epithelium. Here, we tested the effect of breaking alveolar epithelial cell barrier integrity on ENaC expression and function. We found that either mechanical wounding by scratching the monolayer or disruption of tight junction with EDTA induced a ~ 50% decrease of α,β and γENaC mRNA expression and an 80% reduction of ENaC short-circuit current (I_sc) at 6 h. Scratching the cell monolayer generated a Ca²⁺ wave that spread from the margin of the scratch to distant cells. Pretreatment with BAPTA-AM, an intracellular Ca²⁺ chelator, abolished the effect of mechanical wounding and EDTA on αENaC mRNA expression, suggesting that [Ca²⁺]_i is important for this modulation. We tested the hypothesis that a mechanosensitive channel such as TRPV4, a cationic channel known to increase [Ca²⁺]_i, could mediate this effect. Activation of the channel with the TRPV4 specific agonist GSK-1016790A (GSK) decreased αENAC mRNA expression and almost completely abolished ENaC I_sc. Pretreatment of alveolar epithelial cells with HC-067047 (HC0), a specific TRPV4 antagonist, reduced the extent of αENAC mRNA downregulation by mechanical wounding and EDTA. Altogether, our results suggest that mechanical stress induced by wounding or TRPV4-mediated loss of tight junction increases [Ca²⁺]_i and elicits a Ca²⁺ wave that affects ENaC expression and function away from the site of injury. These data are important to better understand how Ca²⁺ signaling affects lung liquid clearance in injured lungs.

Altered heat nociception in cockroach Periplaneta americana L. exposed to capsaicin

Some natural alkaloids, e.g. capsaicin and camphor, are known to induce a desensitization state, causing insensitivity to pain or noxious temperatures in mammals by acting on TRP receptors. Our research, for the first time, demonstrated that a phenomenon of pharmacological blockade of heat sensitivity may operate in American cockroach, Periplaneta americana (L.). We studied the escape reaction time from 50°C for American cockroaches exposed to multiple doses of different drugs affecting thermo-TRP. Capsaicin, capsazepine, and camphor induced significant changes in time spent at noxious ambient temperatures. Moreover, we showed that behavioral thermoregulation in normal temperature ranges (10-40°C) is altered in treated cockroaches, which displayed a preference for warmer regions compared to non-treated insects. We also measured the levels of malondialdehyde (MDA) and catalase activity to exclude the secondary effects of the drugs on these processes. Our results demonstrated that increase in time spent at 50°C (five versus one trial at a heat plate) induced oxidative stress, but only in control and vehicle-treated groups. In capsaicin, capsazepine, menthol, camphor and AITC-treated cockroaches the number of exposures to heat had no effect on the levels of MDA. Additionally, none of the tested compounds affected catalase activity. Our results demonstrate suppression of the heat sensitivity by repeated capsazepine, camphor and capsaicin administration in the American cockroach.

Thermal Discrimination and Transgenerational Temperature Response in Bemisia tabaci Mediterranean (Hemiptera: Aleyrodidae): Putative Involvement of the Thermo-Sensitive Receptor BtTRPA

Anthropogenic climate change and global warming are expected to alter the geographic distribution and abundance of many ectothermic species, which will increase the invasion of new areas by exotic species. To survive in variable or fluctuating temperature conditions, insects require sensitive thermal sensory mechanisms to detect external thermal stimuli and induce the appropriate behavioral and physiological responses. TRPA, a thermal-activated transient receptor potential (TRP) family ion channel, is essential for thermotaxis in insects. Here, we investigated the potential role of BtTRPA in short-term and long-term thermal stress in Bemisia tabaci Mediterranean (Gennadius; Hemiptera: Aleyrodidae). We found that BtTRPA was mainly expressed in the head, where the antennae are located. Under short-term thermal stress, the BtTRPA gene was robustly expressed after exposure to acute low or high temperatures, BtTRPA expression reached the highest levels after exposure to 0°C for 3 h and 40°C for 5 h, but was relatively low after exposure to milder stimuli (12 and 35°C). These results demonstrated that BtTRPA could discriminate between innocuous and noxious temperature stimuli. Under long-term thermal stress, the highest expression level of BtTRPA occurred at G1 exposed to mild innocuous temperature of 21 and 31°C, along with BtTRPA sharply increased and peaked in adult females, implying that mild innocuous long-term thermal exposure could cause transgenerational expression effects to enhance the ability of offspring to cope with the same stress. This study demonstrates that the channel BtTRPA is important in temperature sensing and provides a molecular basis for thermosensation regulation in response to varied environmental temperature in B. tabaci Mediterranean.

Febrile temperature reprograms by redox-mediated signaling the mitochondrial metabolic phenotype in monocyte-derived dendritic cells

Fever-like hyperthermia is known to stimulate innate and adaptive immune responses. Hyperthermia-induced immune stimulation is also accompanied with, and likely conditioned by, changes in the cell metabolism and, in particular, mitochondrial metabolism is now recognized to play a pivotal role in this context, both as energy supplier and as signaling platform. In this study we asked if challenging human monocyte-derived dendritic cells with a relatively short-time thermal shock in the fever-range, typically observed in humans, caused alterations in the mitochondrial oxidative metabolism. We found that following hyperthermic stress (3h exposure at 39°C) TNF-α-releasing dendritic cells undergo rewiring of the oxidative metabolism hallmarked by decrease of the mitochondrial respiratory activity and of the oxidative phosphorylation and increase of lactate production. Moreover, enhanced production of reactive oxygen and nitrogen species and accumulation of mitochondrial Ca²⁺ was consistently observed in hyperthermia-conditioned dendritic cells and exhibited a reciprocal interplay. The hyperthermia-induced impairment of the mitochondrial respiratory activity was (i) irreversible following re-conditioning of cells to normothermia, (ii) mimicked by exposing normothermic cells to the conditioned medium of the hyperthermia-challenged cells, (iii) largely prevented by antioxidant and inhibitors of the nitric oxide synthase and of the mitochondrial calcium porter, which also inhibited release of TNF-α. These observations combined with gene expression analysis support a model based on a thermally induced autocrine signaling, which rewires and sets a metabolism checkpoint linked to immune activation of dendritic cells.

Activation of the TRPV1 Thermoreceptor Induced by Modulated or Unmodulated 1800 MHz Radiofrequency Field Exposure

The existence of effects of radiofrequency field exposure at environmental levels on living tissues and organisms remains controversial, in particular regarding potential "nonthermal" effects produced in the absence of temperature elevation. Therefore, we investigated whether TRPV1, one of the most studied thermosensitive channels, can be activated by the heat produced by radiofrequency fields and by some specific nonthermal interaction with the fields. We have recently shown that TRPV1 activation can be assessed in real-time on live cells using the bioluminescence resonance energy transfer technique. Taking advantage of this innovative assay, we monitored TRPV1 thermal and chemical modes of activation under radiofrequency exposure at 1800 MHz using different signals (CW, GSM, UMTS, LTE, Wi-Fi and WiMAX) at specific absorption rates between 8 and 32 W/kg. We showed that, as expected, TRPV1 channels were activated by the heat produced by radiofrequency field exposure of transiently-transfected HEK293T cells, but found no evidence of TRPV1 activation in the absence of temperature elevation under radiofrequency field exposure. There was no evidence either that, at fixed temperature, radiofrequency exposure altered the maximal efficacy of the agonist Capsaicin to activate TRPV1.

Molecular basis of dental sensitivity: The odontoblasts are multisensory cells and express multifunctional ion channels

Odontoblasts are the dental pulp cells responsible for the formation of dentin. In addition, accumulating data strongly suggest that they can also function as sensory cells that mediate the early steps of mechanical, thermic, and chemical dental sensitivity. This assumption is based on the expression of different families of ion channels involved in various modalities of sensitivity and the release of putative neurotransmitters in response to odontoblast stimulation which are able to act on pulp sensory nerve fibers. This review updates the current knowledge on the expression of transient-potential receptor ion channels and acid-sensing ion channels in odontoblasts, nerve fibers innervating them and trigeminal sensory neurons, as well as in pulp cells. Moreover, the innervation of the odontoblasts and the interrelationship been odontoblasts and nerve fibers mediated by neurotransmitters was also revisited. These data might provide the basis for novel therapeutic approaches for the treatment of dentin sensibility and/or dental pain.

TRPs in Pain Sensation

According to the International Association for the Study of Pain (IASP) pain is characterized as an "unpleasant sensory and emotional experience associated with actual or potential tissue damage". The TRP super-family, compressing up to 28 isoforms in mammals, mediates a myriad of physiological and pathophysiological processes, pain among them. TRP channel might be constituted by similar or different TRP subunits, which will result in the formation of homomeric or heteromeric channels with distinct properties and functions. In this review we will discuss about the function of TRPs in pain, focusing on TRP channles that participate in the transduction of noxious sensation, especially TRPV1 and TRPA1, their expression in nociceptors and their sensitivity to a large number of physical and chemical stimuli.

Effects of Taxol on Regeneration in a Rat Sciatic Nerve Transection Model

Recent studies describe taxol as a candidate treatment for promoting central nerve regeneration. However, taxol has serious side effects including peripheral neurotoxicity, and little information is known about the effect of taxol on peripheral nerve regeneration. We investigated the effects of taxol on regeneration in a rat sciatic nerve transection model. Rats were divided into four groups (n = 10): normal saline (i.p.) as the control, Cremophor EL vehicle, and 2 or 6 mg/kg of taxol in the Cremophor EL solution (four times in day-2, 4, 6, and 8), respectively. We evaluated neuronal electrophysiology, animal behaviour, neuronal connectivity, macrophage infiltration, location and expression levels of calcitonin gene-related peptide (CGRP), and expression levels of both nerve growth factors and immunoregulatory factors. In the high-dose taxol group (6 mg/kg), neuronal electrophysiological function was significantly impaired. Licking latencies were significantly changed while motor coordination was unaffected. Neuronal connectivity, macrophage density, and expression levels of CGRP was dramatically reduced. Expression levels of nerve growth factors and immunoregulatory factors was also reduced, while it was increased in the low-dose taxol group (2 mg/kg). These results indicate that taxol can modulate local inflammatory conditions, impair nerve regeneration, and impede recovery of a severe peripheral nerve injury.

ICEPO: the ion channel electrophysiology ontology

Ion channels are transmembrane proteins that selectively allow ions to flow across the plasma membrane and play key roles in diverse biological processes. A multitude of diseases, called channelopathies, such as epilepsies, muscle paralysis, pain syndromes, cardiac arrhythmias or hypoglycemia are due to ion channel mutations. A wide corpus of literature is available on ion channels, covering both their functions and their roles in disease. The research community needs to access this data in a user-friendly, yet systematic manner. However, extraction and integration of this increasing amount of data have been proven to be difficult because of the lack of a standardized vocabulary that describes the properties of ion channels at the molecular level. To address this, we have developed Ion Channel ElectroPhysiology Ontology (ICEPO), an ontology that allows one to annotate the electrophysiological parameters of the voltage-gated class of ion channels. This ontology is based on a three-state model of ion channel gating describing the three conformations/states that an ion channel can adopt: closed, open and inactivated. This ontology supports the capture of voltage-gated ion channel electrophysiological data from the literature in a structured manner and thus enables other applications such as querying and reasoning tools. Here, we present ICEPO (ICEPO ftp site: ftp://ftp.nextprot.org/pub/current_release/controlled_vocabularies/), as well as examples of its use.

Ultraviolet Radiation on the Skin: A Painful Experience?

Excessive exposure of skin to ultraviolet radiation (UVR) has dramatic clinical effects in humans, and it is a significant public health concern. Discomfort and sensory changes caused by skin sunburn are the main common features experienced by many of us, a phenomena triggered by the combination of long and short wavelengths radiation (UVA and UVB, respectively). Although the biological processes underlying UVR exposure are not fully understood, in the last few years many studies have made significant progress in characterizing sunburn at the cellular and molecular levels, making use of both humans and laboratory animal models. Here we review and reason that UVR can be used as an excellent model of sensitization and inflammation for pain research. UVR, particularly UVB, produces a controllable and sterile inflammation that causes a robust dose‐dependent hypersensitivity with minimal confounding effects. Importantly, we show that UVR animal models precisely recapitulate the sensory, cellular, and molecular changes observed in human skin, giving it great confidence as a translational model. Furthermore, in this article, we give an overview of the pharmacology underlying UVB inflammation, the latest advances in the field, and potential new targets for inflammatory pain.

A novel caffeoyl triterpene attenuates cerebral ischemic injury with potent anti-inflammatory and hypothermic effects

Despite the intense efforts in searching for stroke therapies, an urgent need still exists to explore novel neuroprotective agents for ischemic stroke that have high efficacy and wide therapeutic time-window. Here, we provide the first demonstration that 28-O-caffeoyl betulin (B-CA), a novel derivative of naturally occurring caffeoyl triterpene, could significantly alleviate brain infarction and neurological deficit when given as late as 6 h after transient middle cerebral artery occlusion in the rat. Moreover, post-ischemia B-CA administration exhibited long-term (14 days post stroke) protective effects on both brain infarction and functional (i.e., motor and sensory) deficits. Protective B-CA effects correlated with decreased inflammatory responses as indicated by inhibition of microglia and astrocyte activation [stained with ionized calcium-binding adapter molecule 1 (Iba-1) and glial fibrillary acidic protein (GFAP) antibody, respectively], as well as suppression of tumor necrosis factor-α, interleukin-1β, and cyclooxygenase-2 overproduction in the ipsilateral cortex of ischemic rat. B-CA administration caused significant hypothermia in the focal cerebral ischemic rat, which may contribute to its ameliorative effects on brain damage and inflammation. In view of its potency in wide therapeutic time-window, robust anti-inflammatory and hypothermic effects, this novel caffeoyl triterpene derivative may lead toward the development of effective therapeutic strategies for the treatment of ischemic stroke.

Thermosensory signaling by TRPM is processed by brain serotonergic neurons to produce planarian thermotaxis

For most organisms, sensitive recognition of even slight changes in environmental temperature is essential for adjusting their behavioral strategies to ensure homeostasis and survival. However, much remains to be understood about the molecular and cellular processes that regulate thermosensation and the corresponding behavioral responses. Planarians display clear thermotaxis, although they have a relatively simple brain. Here, we devised a quantitative thermotaxis assay and unraveled a neural pathway involved in planarian thermotaxis by combinatory behavioral assays and RNAi analysis. We found that thermosensory neurons that expressed a planarian Dugesia japonica homolog of the Transient Receptor Potential Melastatin family a (DjTRPMa) gene were required for the thermotaxis. Interestingly, although these thermosensory neurons are distributed throughout their body, planarians with a dysfunctional brain due to regeneration-dependent conditional gene knockdown (Readyknock) of the synaptotagmin gene completely lost their thermotactic behavior. These results suggest that brain function is required as a central processor for the thermosensory response. Therefore, we investigated the type(s) of brain neurons involved in processing the thermal signals by gene knockdown of limiting enzymes for neurotransmitter biosynthesis in the brain. We found that serotonergic neurons with dendrites that were elongated toward DjTRPMa-expressing thermosensory neurons might be required for the processing of signals from thermosensory neurons that results in thermotaxis. These results suggest that serotonergic neurons in the brain may interact with thermosensory neurons activated by TRPM ion channels to produce thermotaxis in planarians.

Influence of cooling rate on activity of ionotropic glutamate receptors in brain slices at hypothermia

Hypothermia is a known approach in the treatment of neurological pathologies. Mild hypothermia enhances the therapeutic window for application of medicines, while deep hypothermia is often accompanied by complications, including problems in the recovery of brain functions. The purpose of present study was to investigate the functioning of glutamate ionotropic receptors in brain slices cooled with different rates during mild, moderate and deep hypothermia. Using a system of gradual cooling combined with electrophysiological recordings in slices, we have shown that synaptic activity mediated by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-D-aspartate receptors in rat olfactory cortex was strongly dependent on the rate of lowering the temperature. High cooling rate caused a progressive decrease in glutamate receptor activity in brain slices during gradual cooling from mild to deep hypothermia. On the contrary, low cooling rate slightly changed the synaptic responses in deep hypothermia. The short-term potentiation may be induced in slices by electric tetanization at 16 °C in this case. Hence, low cooling rate promoted preservation of neuronal activity and plasticity in the brain tissue.

Functional expression and axonal transport of α7 nAChRs by peptidergic nociceptors of rat dorsal root ganglion

In recent pain studies on animal models, α7 nicotinic acetylcholine receptor (nAChR) agonists demonstrated analgesic, anti-hyperalgesic and anti-inflammatory effects, apparently acting through some peripheral receptors. Assuming possible involvement of α7 nAChRs on nociceptive sensory neurons, we investigated the morphological and neurochemical features of the α7 nAChR-expressing subpopulation of dorsal root ganglion (DRG) neurons and their ability to transport α7 nAChR axonally. In addition, α7 receptor activity and its putative role in pain signal neurotransmitter release were studied. Medium-sized α7 nAChR-expressing neurons prevailed, although the range covered all cell sizes. These cells accounted for one-fifth of total medium and large DRG neurons and <5% of small ones. 83.2% of α7 nAChR-expressing DRG neurons were peptidergic nociceptors (CGRP-immunopositive), one half of which had non-myelinated C-fibers and the other half had myelinated Aδ- and likely Aα/β-fibers, whereas 15.2% were non-peptidergic C-fiber nociceptors binding isolectin B4. All non-peptidergic and a third of peptidergic α7 nAChR-bearing nociceptors expressed TRPV1, a capsaicin-sensitive noxious stimulus transducer. Nerve crush experiments demonstrated that CGRPergic DRG nociceptors axonally transported α7 nAChRs both to the spinal cord and periphery. α7 nAChRs in DRG neurons were functional as their specific agonist PNU282987 evoked calcium rise enhanced by α7-selective positive allosteric modulator PNU120596. However, α7 nAChRs do not modulate neurotransmitter CGRP and glutamate release from DRG neurons since nicotinic ligands affected neither their basal nor provoked levels, showing the necessity of further studies to elucidate the true role of α7 nAChRs in those neurons.

Embryonic thermosensitive TRPA1 determines transgenerational diapause phenotype of the silkworm, Bombyx mori

In the bivoltine strain of the silkworm, Bombyx mori, embryonic diapause is induced transgenerationally as a maternal effect. Progeny diapause is determined by the environmental temperature during embryonic development of the mother; however, its molecular mechanisms are largely unknown. Here, we show that the Bombyx TRPA1 ortholog (BmTrpA1) acts as a thermosensitive transient receptor potential (TRP) channel that is activated at temperatures above ∼ 21 °C and affects the induction of diapause in progeny. In addition, we show that embryonic RNAi of BmTrpA1 affects diapause hormone release during pupal-adult development. This study identifying a thermosensitive TRP channel that acts as a molecular switch for a relatively long-term predictive adaptive response by inducing an alternative phenotype to seasonal polyphenism is unique.

What do we really know and what do we need to know: some controversies, perspectives, and surprises

TRP channels comprise one of the most rapid growing research topics in ion channel research, in fields related to ion channels including channelopathies and translational medicine. We provide here a critical survey on our current knowledge of TRP channels and highlight some of the still open or controversial questions. This comprises questions related to evolution of TRP channels; biophysics, i.e., permeation; pore properties and gating; modulation; the still-elusive 3D structure; and channel subunits but also their role as general sensory channels and in human diseases. We will conclude that our knowledge on TRP channels is still at the very beginning of an exciting research journey.

Pharmacologically induced hypothermia via TRPV1 channel agonism provides neuroprotection following ischemic stroke when initiated 90 min after reperfusion

Traditional methods of therapeutic hypothermia show promise for neuroprotection against cerebral ischemia-reperfusion (I/R), however, with limitations. We examined effectiveness and specificity of pharmacological hypothermia (PH) by transient receptor potential vanilloid 1 (TRPV1) channel agonism in the treatment of focal cerebral I/R. Core temperature (T(core)) was measured after subcutaneous infusion of TRPV1 agonist dihydrocapsaicin (DHC) in conscious C57BL/6 WT and TRPV1 knockout (KO) mice. Acute measurements of heart rate (HR), mean arterial pressure (MAP), and cerebral perfusion were measured before and after DHC treatment. Focal cerebral I/R (1 h ischemia + 24 h reperfusion) was induced by distal middle cerebral artery occlusion. Hypothermia (>8 h) was initiated 90 min after start of reperfusion by DHC infusion (osmotic pump). Neurofunction (behavioral testing) and infarct volume (TTC staining) were measured at 24 h. DHC (1.25 mg/kg) produced a stable drop in T(core) (33°C) in naive and I/R mouse models but not in TRPV1 KO mice. DHC (1.25 mg/kg) had no measurable effect on HR and cerebral perfusion but produced a slight transient drop in MAP (<6 mmHg). In stroke mice, DHC infusion produced hypothermia, decreased infarct volume by 87%, and improved neurofunctional score. The hypothermic and neuroprotective effects of DHC were absent in TRPV1 KO mice or mice maintained normothermic with heat support. PH via TRPV1 agonist appears to be a well-tolerated and effective method for promoting mild hypothermia in the conscious mouse. Furthermore, TRPV1 agonism produces effective hypothermia in I/R mice and significantly improves outcome when initiated 90 min after start of reperfusion.

Moist heat or dry heat for delayed onset muscle soreness

Background

Heat is commonly used in physical therapy following exercise induced delayed onset muscle soreness (DOMS). Most heat modalities used in a clinical setting for DOMS are only applied for 5 to 20 minutes. This minimal heat exposure causes little, if any, change in deep tissue temperature. For this reason, long duration dry chemical heat packs are used at home to slowly and safely warm tissue and reduce potential heat damage while reducing pain associated from DOMS. Clinically, it has been shown that moist heat penetrates deep tissue faster than dry heat. Therefore, in home use chemical moist heat may be more efficacious than dry heat to provide pain relief and reduce tissue damage following exercise DOMS. However, chemical moist heat only lasts for 2 hours compared to the 8 hours duration of chemical dry heat packs. The purpose of this study was to compare the beneficial effect of dry heat versus moist heat on 100 young subjects after exercise induce DOMS.

Methods

One hundred subjects exercised for 15 minutes accomplishing squats. Before and for 3 days after, strength, muscle soreness, tissue resistance, and the force to passively move the knee were recorded. Heat and moist heat were applied in different groups either immediately after exercise or 24 hours later.

Results

The research results of this study showed that immediate application of heat, either dry (8 hours application) or moist (2 hours application), had a similar preservation of quadriceps muscle strength and muscle activity. Results also revealed that the greatest pain reduction was shown after immediate application of moist heat. Never the less, immediate application of dry heat had a similar effect but to a lesser extent.

Conclusion

It should be noted that moist heat had not only similar benefits of dry heat but in some cases enhanced benefits, and with only 25% of the time of application of the dry heat.

CEM43°C thermal dose thresholds: a potential guide for magnetic resonance radiofrequency exposure levels?

OBJECTIVE

To define thresholds of safe local temperature increases for MR equipment that exposes patients to radiofrequency fields of high intensities for long duration. These MR systems induce heterogeneous energy absorption patterns inside the body and can create localised hotspots with a risk of overheating.

METHODS

The MRI + EUREKA research consortium organised a "Thermal Workshop on RF Hotspots". The available literature on thresholds for thermal damage and the validity of the thermal dose (TD) model were discussed.

RESULTS/CONCLUSIONS

The following global TD threshold guidelines for safe use of MR are proposed: 1. All persons: maximum local temperature of any tissue limited to 39 °C 2. Persons with compromised thermoregulation AND (a) Uncontrolled conditions: maximum local temperature limited to 39 °C (b) Controlled conditions: TD < 2 CEM43°C 3. Persons with uncompromised thermoregulation AND (a) Uncontrolled conditions: TD < 2 CEM43°C (b) Controlled conditions: TD < 9 CEM43°C The following definitions are applied: Controlled conditions A medical doctor or a dedicated trained person can respond instantly to heat-induced physiological stress Compromised thermoregulation All persons with impaired systemic or reduced local thermoregulation

KEY POINTS

• Standard MRI can cause local heating by radiofrequency absorption. • Monitoring thermal dose (in units of CEM43°C) can control risk during MRI. • 9 CEM43°C seems an acceptable thermal dose threshold for most patients. • For skin, muscle, fat and bone,16 CEM43°C is likely acceptable.

Modulation of thermoreceptor TRPM8 by cooling compounds

ThermoTRPs, a subset of the Transient Receptor Potential (TRP) family of cation channels, have been implicated in sensing temperature. TRPM8 and TRPA1 are both activated by cooling. TRPM8 is activated by innocuous cooling (<30 °C) and contributes to sensing unpleasant cold stimuli or mediating the effects of cold analgesia and is a receptor for menthol and icilin (mint-derived and synthetic cooling compounds, respectively). TRPA1 (Ankyrin family) is activated by noxious cold (<17 °C), icilin, and a variety of pungent compounds. Extensive amount of medicinal chemistry efforts have been published mainly in the form of patent literature on various classes of cooling compounds by various pharmaceutical companies; however, no prior comprehensive review has been published. When expressed in heterologous expression systems, such as Xenopus oocytes or mammalian cell lines, TRPM8 mediated currents are activated by a number of cooling compounds in addition to menthol and icilin. These include synthetic p-menthane carboxamides along with other class of compounds such as aliphatic/alicyclic alcohols/esters/amides, sulphones/sulphoxides/sulphonamides, heterocyclics, keto-enamines/lactams, and phosphine oxides. In the present review, the medicinal chemistry of various cooling compounds as activators of thermoTRPM8 channel will be discussed according to their chemical classes. The potential of these compounds to emerge as therapeutic agents is also discussed.

Myocardial protection with mild hypothermia

Mild hypothermia, 32-35° C, is very potent at reducing myocardial infarct size in rabbits, dogs, sheep, pigs, and rats. The benefit is directly related to reduction in normothermic ischaemic time, supporting the relevance of early and rapid cooling. The cardioprotective effect of mild hypothermia is not limited to its recognized reduction of infarct size, but also results in conservation of post-ischaemic contractile function, prevention of no-reflow or microvascular obstruction, and ultimately attenuation of left ventricular remodelling. The mechanism of the anti-infarct effect does not appear to be related to diminished energy utilization and metabolic preservation, but rather to survival signalling that involves either the extracellular signal-regulated kinases and/or the Akt/phosphoinositide 3-kinase/mammalian target of rapamycin pathways. Initial clinical trials of hypothermia in patients with ST-segment elevation myocardial infarction were disappointing, probably because cooling was too slow to shorten normothermic ischaemic time appreciably. New approaches to more rapid cooling have recently been described and may soon be available for clinical use. Alternatively, it may be possible to pharmacologically mimic the protection provided by cooling soon after the onset of ischaemia with an activator of mild hypothermia signalling, e.g. extracellular signal-regulated kinase activator, that could be given by emergency medical personnel. Finally, the protection afforded by cooling can be added to that of pre- and post-conditioning because their mechanisms differ. Thus, myocardial salvage might be greatly increased by rapidly cooling patients as soon as possible and then giving a pharmacological post-conditioning agent immediately prior to reperfusion.