TRP Channels Expression Profile in Human End-Stage Heart Failure.

Objectives: Many studies indicate the involvement of transient receptor potential (TRP) channels in the development of heart hypertrophy. However, the data is often conflicted and has originated in animal models. Here, we provide systematic analysis of TRP channels expression in human failing myocardium. Methods and results: Left-ventricular tissue samples were isolated from explanted hearts of NYHA III-IV patients undergoing heart transplants (n = 43). Quantitative real-time PCR was performed to assess the mRNA levels of TRPC, TRPM and TRPV channels. Analysis of functional, clinical and biochemical data was used to confirm an end-stage heart failure diagnosis. Compared to myocardium samples from healthy donor hearts (n = 5), we detected a distinct increase in the expression of TRPC1, TRPC5, TRPM4 and TRPM7, and decreased expression of TRPC4 and TRPV2. These changes were not dependent on gender, clinical or biochemical parameters, nor functional parameters of the heart. We detected, however, a significant correlation of TRPC1 and MEF2c expression. Conclusions: The end-stage heart failure displays distinct expressional changes of TRP channels. Our findings provide a systematic description of TRP channel expression in human heart failure. The results highlight the complex interplay between TRP channels and the need for deeper analysis of early stages of hypertrophy and heart failure development.

Transcriptomic analysis of the ion channelome of human platelets and megakaryocytic cell lines.

Ion channels have crucial roles in all cell types and represent important therapeutic targets. Approximately 20 ion channels have been reported in human platelets; however, no systematic study has been undertaken to define the platelet channelome. These membrane proteins need only be expressed at low copy number to influence function and may not be detected using proteomic or transcriptomic microarray approaches. In our recent work, quantitative real-time PCR (qPCR) provided key evidence that Kv1.3 is responsible for the voltage-dependent K+ conductance of platelets and megakaryocytes. The present study has expanded this approach to assess relative expression of 402 ion channels and channel regulatory genes in human platelets and three megakaryoblastic/erythroleukaemic cell lines. mRNA levels in platelets are low compared to other blood cells, therefore an improved method of isolating platelets was developed. This used a cocktail of inhibitors to prevent formation of leukocyte-platelet aggregates, and a combination of positive and negative immunomagnetic cell separation, followed by rapid extraction of mRNA. Expression of 34 channel-related transcripts was quantified in platelets, including 24 with unknown roles in platelet function, but that were detected at levels comparable to ion channels with established roles in haemostasis or thrombosis. Trace expression of a further 50 ion channel genes was also detected. More extensive channelomes were detected in MEG-01, CHRF-288-11 and HEL cells (195, 185 and 197 transcripts, respectively), but lacked several channels observed in the platelet. These "channelome" datasets provide an important resource for further studies of ion channel function in the platelet and megakaryocyte.

Correlation Between DNA Methylation of TRPA1 and Chronic Pain States in Human Whole Blood Cells.

OBJECTIVES: Neuro-immune interactions with functional changes in the peripheral blood cells including changes in the transient receptor potential ankyrin 1 (TRPA1) appear to play a pivotal role in the development of chronic pain in humans. The aim of this study was to examine the association between TRPA1 DNA methylation in whole blood cells and the pain states in chronic pain patients. METHODS: After collecting blood samples from 12 chronic pain patients, the authors measured DNA methylation levels in whole blood cells. Significant associations between the patient's demographic data and the chronic pain states were determined by a multiple linear regression analysis that used age, body mass index, pain duration, depression, anxiety, cognitive impairment, activities of daily living, neuropathic pain, and pain states as the dependent variables, and the TRPA1 DNA methylation levels as the independent variables. RESULTS: Multiple regression analysis revealed a significant correlation between increases of the methylation levels of the CpG island in the TRPA1 gene and increases in the number of neuropathic pain symptoms, which were evaluated using the Douleur Neuropathique 4 (DN4) questionnaire. Decreases in the TRPA1 mRNA expression were also significantly related to increases in the DN4 score. The presence of a burning sensation, which is one of pain symptoms in the DN4 questionnaire, was significantly correlated with the increase in DNA methylation level of TRPA1. CONCLUSIONS: TRPA1 DNA methylation levels in whole blood cells appear to be associated with pain symptoms in chronic pain patients.

TRP channels in platelet function.

Ca2+ entry forms an essential component of platelet activation; however, the mechanisms associated with this process are not understood. Ca2+ entry upon receptor activation occurs as a consequence of intracellular store depletion (referred to as store-operated Ca2+ entry or SOCE), a direct action of second messengers on cation entry channels or the direct occupancy of a ligand-gated P2(Xi) receptor. The molecular identity of the SOCE channel has yet to be established. Transient receptor potential (TRP) proteins are candidate cation entry channels and are classified into a number of closely related subfamilies including TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin) and TRPML (mucolipins). From the TRPC family, platelets have been shown to express TRPC6 and TRPC1, and are likely to express other TRPC and other TRP members. TRPC6 is suggested to be involved with receptor-activated, diacyl-glycerol-mediated cation entry. TRPC1 has been suggested to be involved with SOCE, though many of the suggested mechanisms remain controversial. As no single TRP channel has the properties described for SOCE in platelets, it is likely that it is composed of a heteromeric association of TRP and related subunits, some of which may be present in intracellular compartments in the resting cell.