Microarray analysis reveals complex remodeling of cardiac ion channel expression with altered thyroid status: relation to cellular and integrated electrophysiology.
Although electrophysiological remodeling occurs in various myocardial diseases, the underlying molecular mechanisms are poorly understood. cDNA microarrays containing probes for a large population of mouse genes encoding ion channel subunits ("IonChips") were developed and exploited to investigate remodeling of ion channel transcripts associated with altered thyroid status in adult mouse ventricle. Functional consequences of hypo- and hyperthyroidism were evaluated with patch-clamp and ECG recordings. Hypothyroidism decreased heart rate and prolonged QTc duration. Opposite changes were observed in hyperthyroidism. Microarray analysis revealed that hypothyroidism induces significant reductions in KCNA5, KCNB1, KCND2, and KCNK2 transcripts, whereas KCNQ1 and KCNE1 expression is increased. In hyperthyroidism, in contrast, KCNA5 and KCNB1 expression is increased and KCNQ1 and KCNE1 expression is decreased. Real-time RT-PCR validated these results. Consistent with microarray analysis, Western blot experiments confirmed those modifications at the protein level. Patch-clamp recordings revealed significant reductions in I(to,f) and I(K,slow) densities, and increased I(Ks) density in hypothyroid myocytes. In addition to effects on K+ channel transcripts, transcripts for the pacemaker channel HCN2 were decreased and those encoding the alpha1C Ca2+ channel (CaCNA1C) were increased in hypothyroid animals. The expression of Na+, Cl-, and inwardly rectifying K+ channel subunits, in contrast, were unaffected by thyroid hormone status. Taken together, these data demonstrate that thyroid hormone levels selectively and differentially regulate transcript expression for at least nine ion channel alpha- and beta-subunits. Our results also document the potential of cDNA microarray analysis for the simultaneous examination of ion channel transcript expression levels in the diseased/remodeled myocardium.
Le Bouter
Sabrina
S
INSERM U533, Physiopathologie et Pharmacologie Cellulaires et Moléculaires, Faculté de Médecine, Nantes, France.
Demolombe
Sophie
S
Chambellan
Arnaud
A
Bellocq
Chloé
C
Aimond
Franck
F
Toumaniantz
Gilles
G
Lande
Gilles
G
Siavoshian
Sepideh
S
Baró
Isabelle
I
Pond
Amber L
AL
Nerbonne
Jeanne M
JM
Léger
Jean J
JJ
Escande
Denis
D
Charpentier
Flavien
F
D000818:Animals; D001835:Body Weight; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D020869:Gene Expression Profiling; D006339:Heart Rate / Q000502:physiology; D006352:Heart Ventricles / Q000473:pathology / Q000503:physiopathology*; D006980:Hyperthyroidism / Q000503:physiopathology*; D007037:Hypothyroidism / Q000503:physiopathology*; D007473:Ion Channels / Q000096:biosynthesis* / Q000235:genetics*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D009929:Organ Size; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction
D007473:Ion Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger