Dysfunctional TRPM8 signalling in the vascular response to environmental cold in ageing

Ageing is associated with increased vulnerability to environmental cold exposure. Previously, we identified the role of the cold-sensitive transient receptor potential (TRP) A1, M8 receptors as vascular cold sensors in mouse skin. We hypothesised that this dynamic cold-sensor system may become dysfunctional in ageing. We show that behavioural and vascular responses to skin local environmental cooling are impaired with even moderate ageing, with reduced TRPM8 gene/protein expression especially. Pharmacological blockade of the residual TRPA1/TRPM8 component substantially diminished the response in aged, compared with young mice. This implies the reliance of the already reduced cold-induced vascular response in ageing mice on remaining TRP receptor activity. Moreover, sympathetic-induced vasoconstriction was reduced with downregulation of the α2c adrenoceptor expression in ageing. The cold-induced vascular response is important for sensing cold and retaining body heat and health. These findings reveal that cold sensors, essential for this neurovascular pathway, decline as ageing onsets.

Dysfunctional TRPM8 signalling in the vascular response to environmental cold in ageing.

Ageing is associated with increased vulnerability to environmental cold exposure. Previously, we identified the role of the cold-sensitive transient receptor potential (TRP) A1, M8 receptors as vascular cold sensors in mouse skin. We hypothesised that this dynamic cold-sensor system may become dysfunctional in ageing. We show that behavioural and vascular responses to skin local environmental cooling are impaired with even moderate ageing, with reduced TRPM8 gene/protein expression especially. Pharmacological blockade of the residual TRPA1/TRPM8 component substantially diminished the response in aged, compared with young mice. This implies the reliance of the already reduced cold-induced vascular response in ageing mice on remaining TRP receptor activity. Moreover, sympathetic-induced vasoconstriction was reduced with downregulation of the α2c adrenoceptor receptor in ageing. The cold-induced vascular response is important for sensing cold and retaining body heat and health. These findings reveal that cold sensors, essential for this neurovascular pathway, decline as ageing onsets.

Reduced TRPM8 expression underpins reduced migraine risk and attenuated cold pain sensation in humans

Multiple genome-wide association studies have identified non-coding single-nucleotide variants (SNVs) near (e.g., rs10166942[C]) or within (rs17862920[T]) the TRPM8 gene that encodes a cold thermosensor is associated with reduced migraine risk. Furthermore, rs10166942[C]) and rs10166942[T]) are more prevalent in populations that reside in hotter and colder climates, respectively. Here we assessed whether these alleles affect TRPM8 expression in humans and human physiologic responses to cold challenge. Here we show that TRPM8 expression is decreased from the chromosome harboring the rs10166942[C] allele in the human dorsal root ganglia. Moreover, carriers of rs10166942[C] required significantly lower temperatures and longer duration of exposure to reach a cold pain threshold (CPTh), which correlated with decreased TRPM8 expression expected in the carriers. This study provides evidence for a genotype-dependent influence on cold pain sensation suggesting that carriers of the reduced migraine risk allele have reduced sensitivity to cold stimuli and that TRPM8 acts as a cold thermosensor and cold pain transducer in humans. Reduced TRPM8 expression and function underpins the migraine protection in carriers of rs10166942[C]; thus, the evaluation of TRPM8 antagonists as migraine therapeutics is warranted. Furthermore, these results provide mechanistic insights for evolutionary positive selection of rs10166942[T] allele in adaptation along latitudinal cline to colder climates.

ROLE OF TRPM8 GENE POLYMORPHISMS IN THE FORMATION OF ASTHMA PHENOTYPE WITH COLD AIRWAY HYPERRESPONSIVENESS

The aim of the study was to evaluate the effect of TRPM8 cold thermoreceptor gene polymorphisms on the development of asthma phenotype with cold airway hyperresponsiveness (CAH). 167 cases of mild-to-moderate persistent asthma were retrospectively analyzed. In each case, the examination included two repeated bronchoprovocation tests with 3-min isocapic cold air hyperventilation with 6-month interval, standard spirometry and genotyping of seven TRPM8 polymorphisms (rs11562975, rs17868387, rs28901637, rs138810119, rs2052030, rs17865682 and rs1003540). A double positive response to the bronchoprovocation test served as a criterion for the phenotype of asthma with CAH. Based on the results of the study, previously revealed relationship between rs11562975 polymorphism and CAH was confirmed, and also three new polymorphisms (rs17868387, rs17865682 and rs1003540) differentially associated with CAH asthma phenotype were identified. The obtained data indicate the contribution of the molecular genetic peculiarities of TRPM8 to the pathogenesis of CAH and substantiate the further search for additional molecular mechanisms of cold-induced respiratory reactions.

TRPM8 GENE POLYMORPHISM AND SMOKING AS THE FACTORS OF SEVERE BRONCHIAL OBSTRUCTION IN PATIENTS WITH ASTHMA

The aim of the study was to determine the role of rs11562975 polymorphism of TRPM8 gene and tobacco smoking in the formation of severe bronchial obstruction in asthma patients. According to this aim, 416 patients with varying severity of asthma were examined. The study design included standard spirometry, genotyping of rs11562975 TRPM8 gene polymorphism and evaluation of the status and duration of smoking. The study revealed the detrimental effect of smoking on the respiratory function in patients with a pack/year index ≥10. rs11562975 polymorphism had a modulating effect on the smoking in patients with asthma. The influence of smoking ≥10 packs-years on the formation of severe bronchial obstruction was more pronounced among carriers of GC genotype, compared to patients with GG genotype. In case of pack-year history ≥20, the GC genotype significantly increased the risk of severe bronchial obstruction in the examined patients

Expression of temperature-sensitive ion channel TRPM8 in sperm cells correlates with vertebrate evolution

Transient Receptor Potential cation channel, subfamily Melastatin, member 8 (TRPM8) is involved in detection of cold temperature, different noxious compounds and in execution of thermo- as well as chemo-sensitive responses at cellular levels. Here we explored the molecular evolution of TRPM8 by analyzing sequences from various species. We elucidate that several regions of TRPM8 had different levels of selection pressure but the 4th–5th transmembrane regions remain highly conserved. Analysis of synteny suggests that since vertebrate origin, TRPM8 gene is linked with SPP2, a bone morphogen. TRPM8, especially the N-terminal region of it, seems to be highly variable in human population. We found 16,656 TRPM8 variants in 1092 human genomes with top variations being SNPs, insertions and deletions. A total of 692 missense mutations are also mapped to human TRPM8 protein of which 509 seem to be delateroiours in nature as supported by Polyphen V2, SIFT and Grantham deviation score. Using a highly specific antibody, we demonstrate that TRPM8 is expressed endogenously in the testis of rat and sperm cells of different vertebrates ranging from fish to higher mammals. We hypothesize that TRPM8 had emerged during vertebrate evolution (ca 450 MYA). We propose that expression of TRPM8 in sperm cell and its role in regulating sperm function are important factors that have guided its molecular evolution, and that these understandings may have medical importance.