Maxi-K+ channel beta1 expression in sleep apnea patients and its modulation by CPAP treatment.
BACKGROUND
Maxi-K(+) channels play a major vasodilator role in the regulation of arterial tone. Hypoxia downregulates the expression of the maxi-K(+) channel beta1-subunit in rat and human arterial myocytes, thus facilitating vasoconstriction. We have investigated the relationships among hypoxemia, arterial pressure, and the expression of the beta1-subunit in patients with severe obstructive sleep apnea-hypopnea syndrome (SAHS), a highly prevalent condition that predisposes to hypertension.


METHODS
We studied 20 male patients with strong clinical suspicion of SAHS. Overnight polysomnography and 24-h ambulatory blood pressure monitoring were performed in each patient. Evaluation of beta1-subunit mRNA expression was made by a simple blood test using peripheral blood leukocytes (PBLs). The last two determinations were repeated 3 months after initiation of continuous positive airway pressure (CPAP) treatment.


RESULTS
In untreated obstructive SAHS patients, beta1-subunit mRNA levels were correlated with the minimum level of overnight blood O(2) saturation (r(2) = 0.56, P < 0.05) and systolic arterial pressure (r(2) = 0.64, P < 0.01). Notably, the correction of nocturnal hypoxemia with CPAP resulted in upregulation of beta1-subunit mRNA and to a parallel significant decrease of systolic and diastolic arterial pressures of 6.5 and 5.3 mm Hg, respectively.


CONCLUSIONS
These observations, although preliminary, suggest that the maxi-K(+) beta1-subunit could contribute to vascular dysregulation in SAHS patients. Leukocyte beta1 expression may be an independent readout of hypoxemia that could be useful as molecular marker for impending hypertension.
Navarro-Antolín
Javier
J
Laboratorio de Investigaciones Biomédicas, Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Sevilla, Spain.
Carmona-Bernal
Carmen
C
Rivero-Valdenebro
Verónica
V
Villar
José
J
Capote
Francisco
F
López-Barneo
José
J
D000328:Adult; D045422:Continuous Positive Airway Pressure; D015536:Down-Regulation; D006801:Humans; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits / Q000096:biosynthesis*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D012333:RNA, Messenger / Q000378:metabolism; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology* / Q000628:therapy
D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D012333:RNA, Messenger; D010100:Oxygen