Menthol, the cooling natural product of peppermint, is widely used in medicinal preparations for the relief of acute and inflammatory pain in sports injuries, arthritis and other painful conditions. Menthol induces the sensation of cooling by activating TRPM8, an ion channel in cold-sensitive peripheral sensory neurons. Recent studies identified additional targets of menthol, including the irritant receptor, TRPA1, voltage-gated ion channels and neurotransmitter receptors. It remains unclear which of these targets contribute to menthol-induced analgesia, or to the irritating side effects associated with menthol therapy. Here, we use genetic and pharmacological approaches in mice to probe the role of TRPM8 in analgesia induced by L-menthol, the predominant analgesic menthol isomer in medicinal preparations. L-menthol effectively diminished pain behavior elicited by chemical stimuli (capsaicin, acrolein, acetic acid), noxious heat and inflammation (complete Freund's adjuvant). Genetic deletion of TRPM8 completely abolished analgesia by L-menthol in all these models, while other analgesics (acetaminophen) remained effective. Loss of L-menthol-induced analgesia was recapitulated in mice treated with a selective TRPM8 inhibitor, AMG2850. Selective activation of TRPM8 with WS-12, a menthol derivative we characterized as a specific TRPM8 agonist in cultured sensory neurons and in vivo, also induced TRPM8-dependent analgesia of acute and inflammatory pain. L-menthol and WS-12 induced analgesia was blocked by naloxone, suggesting activation of endogenous opioid-dependent analgesic pathways. Our data show that TRPM8 is the principal mediator of menthol-induced analgesia of acute and inflammatory pain. In contrast to menthol, selective TRPM8 agonists may produce analgesia more effectively with diminished side effects.

Jordt S. TRPV4 inhibition counteracts edema and inflammation and improves pulmonary function and oxygen saturation in chemically induced acute lung injury. Am J Physiol Lung Cell Mol Physiol 307: L158 -L172, 2014. First published May 16, 2014; doi:10.1152/ajplung.00065.2014.-The treatment of acute lung injury caused by exposure to reactive chemicals remains challenging because of the lack of mechanism-based therapeutic approaches. Recent studies have shown that transient receptor potential vanilloid 4 (TRPV4), an ion channel expressed in pulmonary tissues, is a crucial mediator of pressure-induced damage associated with ventilator-induced lung injury, heart failure, and infarction. Here, we examined the effects of two novel TRPV4 inhibitors in mice exposed to hydrochloric acid, mimicking acid exposure and acid aspiration injury, and to chlorine gas, a severe chemical threat with frequent exposures in domestic and occupational environments and in transportation accidents. Postexposure treatment with a TRPV4 inhibitor suppressed acid-induced pulmonary inflammation by diminishing neutrophils, macrophages, and associated chemokines and cytokines, while improving tissue pathology. These effects were recapitulated in TRPV4-deficient mice. TRPV4 inhibitors had similar anti-inflammatory effects in chlorine-exposed mice and inhibited vascular leakage, airway hyperreactivity, and increase in elastance, while improving blood oxygen saturation. In both models of lung injury we detected increased concentrations of N-acylamides, a class of endogenous TRP channel agonists. Taken together, we demonstrate that TRPV4 inhibitors are potent and efficacious countermeasures against severe chemical exposures, acting against exaggerated inflammatory responses, and protecting tissue barriers and cardiovascular function. acute lung injury; chlorine; TRPV4 ACUTE LUNG INJURY (ALI) and its extreme manifestation, acute respiratory distress syndrome (ARDS), are associated with high levels of morbidity and mortality (28, 37). Major triggers of ALI and ARDS are pneumonia, sepsis, trauma, acid aspiration, inhalation of toxic gases or smoke, hyperoxia, high pressure ventilation, heart failure, or pancreatitis. A major hallmark of ALI and ARDS is the acute increase in permeability of the pulmonary vascular and epithelial barriers, resulting in edema and severe hypoxia (9). ALI and ARDS are often associated with exaggerated inflammatory responses due to neutrophil infiltration and increased macrophage activity in the injured lung (14,22). These inflammatory cells may aggravate injury through protease production, through generation of oxidative reactive species and proinflammatory cytokines and chemokines, and through prevention of inflammation resolution.The ion channel transient receptor potential vanilloid 4 (TRPV4) was recently identified as a major mediator of pulmonary dysfunction in animal models of ventilator-and heart failure-induced ALI, conditions associated with dramatic increases in pulmonary and vascular pressure (17,33). Among other ...

Allergic contact dermatitis is a common skin disease associated with inflammation and persistent pruritus. Transient receptor potential (TRP) ion channels in skin‐innervating sensory neurons mediate acute inflammatory and pruritic responses following exogenous stimulation and may contribute to allergic responses. Genetic ablation or pharmacological inhibition of TRPA1, but not TRPV1, inhibited skin edema, keratinocyte hyperplasia, nerve growth, leukocyte infiltration, and antihistamine‐resistant scratching behavior in mice exposed to the haptens, oxazolone and urushiol, the contact allergen of poison ivy. Hapten‐challenged skin of TRPA1‐deficient mice contained diminished levels of inflammatory cytokines, nerve growth factor, and endogenous pruritogens, such as substance P (SP) and serotonin. TRPA1‐deficient sensory neurons were defective in SP signaling, and SP‐induced scratching behavior was abolished in Trpa1–/– mice. SP receptor antagonists, such as aprepitant inhibited both hapten‐induced cutaneous inflammation and scratching behavior. These findings support a central role for TRPA1 and SP in the integration of immune and neuronal mechanisms leading to chronic inflammatory responses and pruritus associated with contact dermatitis.—Liu, B., Escalera, J., Balakrishna, S., Fan, L., Caceres, A. I., Robinson, E., Sui, A., McKay, M. C., McAlexander, M. A., Herrick, C. A., Jordt, S. E., TRPA1 controls inflammation and pruritogen responses in allergic contact dermatitis. FASEB J. 27, 3549–3563 (2013). http://www.fasebj.org

We describe a mechanism of gene regulation involving formation of a complex between PSF protein and mouse VL30 (mVL30) retrotransposon RNA. PSF represses transcription of the insulin-like growth factor 1 (IGF1)-inducible gene P450scc by binding to an insulin-like growth factor response element (IGFRE) motif in the gene. The complex with mVL30 RNA releases PSF, allowing transcription to proceed. Retrovirally mediated transmission of mVL30 RNA to human tumor cells induced several genes, including oncogenes, which also are induced by IGF1, and promoted metastasis. In mice, steroid synthesis is activated in steroidogenic cells by pituitary hormones, which concomitantly induce transcription of mVL30 RNA in the cells. We showed that steroid synthesis could also be activated in mouse steroidogenic adrenal cells by transfection with cDNA encoding either mVL30 RNA tracts that form a complex with PSF or a small interfering RNA (siRNA) that degrades PSF transcripts. These results suggest that mVL30 RNA regulates steroidogenesis, and possibly other physiological processes of mice, by complex formation with PSF. Retrotransposons such as mVL30 apparently evolved not only as ''junk'' DNA but also as transcriptionally active noncoding DNA that acquired physiological and pathological functions. The complete genome of a mouse VL30 (mVL30) retrotransposon is structurally similar to a retroviral genome, with 5Ј and 3Ј LTRs flanking an internal region containing Ϸ3.7 kb (1). In contrast to the internal region of an infectious retroviral genome that encodes gag, pol, and env proteins, the corresponding region of the mVL30 genome has numerous stop codons in all reading frames that probably block formation of a functional protein. The mouse genome contains multiple copies of transcriptionally active mVL30 DNA, and virtually all mouse cells contain mVL30 RNA although the level varies among different tissues and at different developmental stages (1). Because retroviral vectors for gene transfer and gene therapy usually are produced in packaging cells derived from mouse cells, these cells also contain mVL30 RNA. A remarkable property of retroviral vectors is the capacity to transmit mVL30 RNA from a packaging cell to cells infected by the retrovirus, which synthesize, integrate, and transcribe mVL30 cDNA (1). In an earlier report (2), we showed that retroviral-mediated transfection of tissue factor (TF) cDNA into a nonmetastatic human melanoma cell line increased the metastatic potential of the cells to which mVL30-1 RNA also had been transmitted. The increase in metastatic potential depended on expression of TF protein on the cell surface and also on transcription of mVL30-1 cDNA. Dependence on mVL30-1 RNA was surprising because the RNA seems to lack significant coding potential. Here, we report that mVL30-1 RNA forms a complex with PSF, a multifunctional regulatory protein that binds to RNA in spliceosomes (3, 4) and to an IGFRE motif in the insulin-like growth factor 1 (IGF1)-inducible gene P450ssc that represses transcription of the g...

The airways are densely innervated by peripheral sensory neurons. Activation of chemosensory C‐fibers by chemical irritants triggers defensive reflexes such as cough and sneezing, and initiates airway constriction and glandular fluid secretion. Local neuronal release of pro‐inflammatory peptides promotes edema formation and vascular leakage. We recently identified TRPA1 as the chemosensory receptor for noxious oxidants and electrophiles in the airways. Chemosensory neurons are activated or sensitized during chronic inflammatory states and may be involved in the initiation and maintenance of airway conditions such as asthma and chronic obstructive pulmonary disease (COPD). Inflammatory mediators, including prostaglandins, bradykinin, histamine, reactive oxygen species and lipid peroxidation products activate or sensitize TRPA1 and other sensory ion channels such as TRPV1, the capsaicin receptor. We asked whether absence of TRPA1 or TRPV1 would affect the inflammatory process in the ovalbumin (OVA) mouse model of allergic airway inflammation. OVA‐challenged TRPA1‐deficient mice showed dramatically diminished eosinophil infiltration in the airways. Multiplex analysis of bronchoalveolar lavage fluid showed a reduction in levels of Th2‐derived cytokines and chemokines. We conclude that neuronal TRPA1 channels are essential for establishment of OVA‐dependent airway inflammation in mice.