title: Chronic potentiation of cardiac L-type Ca(2+) channels by pirfenidone.
abstract: OBJECTIVE
  On the basis of its ability to inhibit fibrosis, pirfenidone has drawn the attention as an intriguing candidate for treating cardiac disease. However, its precise electrophysiological effects have yet to be elucidated. Here, we have investigated its potential to modulate ion channels.
  
  
  RESULTS
  Adult rat cardiac myocytes were investigated using whole-cell patch-clamp, western-blot and qRT-PCR techniques. Pirfenidone increased the density of L-type Ca(2+) current (I(CaL,) 50-100%), without significantly altering Na(+), K(+), or T-type Ca(2+) currents. The effect was dose-dependent, with an EC(50) of 2.8 µM. Its onset was slow, with a lag period larger than 1 h and time to maximum of 24-48 h. Concomitant changes were observed in the voltage-dependent activation of I(CaL) (-5 mV shift in both V(1/2) and k). In contrast, the following properties of I(CaL) remained normal: steady-state inactivation, Ca(V)1.2 levels (mRNA and protein), and intramembrane charge movement. Indeed, the conductance-to-charge ratio, or G(max)/Q(max), was increased by 80%. The effect on I(CaL) was mimicked by an inhibitor of nitric oxide (NO) synthase (NOS), and attenuated by both cyclic adenosine monophosphate (cAMP) and cAMP-dependent protein kinase (PKA) inhibitors. Conversely, cytokines, reactive oxygen species, and Ca(2+) were all ruled out as possible intermediaries. Additional experiments suggest that pirfenidone increases action potential duration by ∼50%.
  
  
  CONCLUSIONS
  Pirfenidone augments I(CaL), not through higher expression of L-type channels, but through promoting their Ca(2+)-conducting activity. A possible inhibition of NOS expression is likely involved, with subsequent reduced NO production and stimulated cAMP/PKA signalling. These findings may be relevant to the cardioprotective effect of pirfenidone.
authors: Department of Biochemistry,  Cinvestav-IPN, AP 14-740, México City DF 07000,  México.
authors: Roberto
authors: R
authors: Ramos-Mondragón
authors: Carlos A
authors: CA
authors: Galindo
authors: Maricela
authors: M
authors: García-Castañeda
authors: José L
authors: JL
authors: Sánchez-Vargas
authors: Ana V
authors: AV
authors: Vega
authors: Norma L
authors: NL
authors: Gómez-Viquez
authors: Guillermo
authors: G
authors: Avila
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D020747:Calcium Channels, T-Type / Q000187:drug effects*; D002478:Cells, Cultured; D004353:Drug Evaluation, Preclinical; D017774:Long-Term Potentiation / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects; D011728:Pyridones / Q000494:pharmacology*; D051381:Rats; D020239:Receptor Cross-Talk; D015290:Second Messenger Systems; D015222:Sodium Channels / Q000187:drug effects; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D015221:Potassium Channels; D011728:Pyridones; D015222:Sodium Channels; C508962:Tgfb1 protein, rat; D053773:Transforming Growth Factor beta1; C093844:pirfenidone; D019001:Nitric Oxide Synthase