La modulazione dei canali transient receptor potential v1 e a1 con prostaglandina-e2e bradichinina è associata adaumento della risposta tussigena alla capsaicina ed a variazionidella regolazioneautonomica del ritmo cardiaco in soggetti sani

BACKGROUND There is evidence in animal models, that particulate (PM) inhalation, activates TRPV-1 and TRPA-1 pulmonary receptors and may change the autonomic regulation of cardiac activity, through a modulation of afferent signals in the central nervous system. This hypothetical neurogenic pathway could explain the adverse cardiovascular effects observed in susceptible subjects after acute PM exposures. OBJECTIVES The aim of the study was to verify that the activity of TRPV-1 and TRPA-1 can be modulated in vivo by inhaled stimuli and that changes in TRP channels activity modify the autonomic regulation of heart rhythm. To do this we evaluated in a group of healthy volunteers: 1. Cough response to capsaicin (CPS) and cinnmaldeide (CMA), exogenous agonists of TRPV-1 and TRPA-1 channels, before and after inhalation of PGE2 and BK, endogenous mediators that activate TRP channels in vitro; 2. Heart rate variability (HRV) after modulation of TRP channels with PGE2 and BK. We also evaluated: 3. The molecular mechanism of TRPV-1 channel modulation in vitro, on HeLa cells transfected with the TRPV-1 wild-type; 4. Whether presence of functional polymorphisms (SNPs) of TRPV-1 explains the variability of cough response to CPS and whether it modifies cough response to the modulation of TRP channels with PGE2 and BK. METHODS 1. 20 healthy volunteers were recruited. 17 performed PGE2 and BK or diluent inhalation, in a randomized double-blind fashion. Immediately after inhalation of the modulators, the sensitivity of TRPV-1 to CPS and of TRPA-1 to CMA was assessed with cough challenge. 2. Heart rate variability (HRV) was tested in 12 of the enrolled healthy volunteers recording the electrocardiogram (ECG) after inhalation of diluent, PGE2 and BK. We analyzed the variables of spectral components in the frequency domain, that represent indexes of sympathetic, vagal and sympathetic-vagal balance. 3. Functional properties of TRPV-1 channel were evaluated measuring [Ca2 +] in HeLa cells after treatment with CPS and CMA. HeLa cells were transfected with the TRPV-1 human channel. [Ca2 +] in HeLa cells was measured after pre-treatment with increasing doses of PGE2, BK or diesel exhaust particulate matter (DEP) followed by CPS stimulation. 4. All volunteers were characterized according to cough response to the CPS. We analyzed the DNA of each subjects to assess the presence of six functional polymorphisms (SNPs) of TRPV-1. RESULTS 1. Inhalation of PGE2 and BK is associated with a significant increase of cough response induced by CPS, while inconsistent changes after stimulation of TRPA-1 with CMA were detected. 2. Inhalation of PGE2 and BK significantly modifies HRV, leading to an imbalance of the autonomic regulation of heart rhythm. In particular we detected an upregulation of the sympathetic system and a downregulation of the vagal system. 3. Pretreatment with PGE2 or BK of HeLa cells expressing TRPV-1 did not modify CPS-induced cellular responses, demonstrating that in our experimental model, these two mediators do not directly sensitize the TRPV-1 channel. Treatment with DEP significantly increased TRPV-1-mediated cellular responses, indicating that it is directly sensitized by particulate matter. 4. We demonstrated that the variability of cough response to CPS between healthy subjects is partially explained by multiple SNPs of the TRPV-1 channel. The major contribution to sensitivity in terms of cough response to CPS in vivo is due to the combination of four SNPs: I315M; I585V; T469I; P91S. However, the modulation of TRPV-1 was irrespective of the presence of SNPs. These data support the hypothesis that PM inhalation, interfering with the function of TRPs, induces acute cardiovascular effects in susceptible subjects.