Abnormal Ca2+ spark/STOC coupling in cerebral artery smooth muscle cells of obese type 2 diabetic mice

PLoS One. 2013;8(1):e53321. doi: 10.1371/journal.pone.0053321. Epub 2013 Jan 3.

Abstract

Diabetes is a major risk factor for stroke. However, the molecular mechanisms involved in cerebral artery dysfunction found in the diabetic patients are not completely elucidated. In cerebral artery smooth muscle cells (CASMCs), spontaneous and local increases of intracellular Ca2+ due to the opening of ryanodine receptors (Ca2+ sparks) activate large conductance Ca2+-activated K+ (BK) channels that generate spontaneous transient outward currents (STOCs). STOCs have a key participation in the control of vascular myogenic tone and blood pressure. Our goal was to investigate whether alterations in Ca(2+) spark and STOC activities, measured by confocal microscopy and patch-clamp technique, respectively, occur in isolated CASMCs of an experimental model of type-2 diabetes (db/db mouse). We found that mean Ca(2+) spark amplitude, duration, size and rate-of-rise were significantly smaller in Fluo-3 loaded db/db compared to control CASMCs, with a subsequent decrease in the total amount of Ca(2+) released through Ca(2+) sparks in db/db CASMCs, though Ca(2+) spark frequency remained. Interestingly, the frequency of large-amplitude Ca(2+) sparks was also significantly reduced in db/db cells. In addition, the frequency and amplitude of STOCs were markedly reduced at all voltages tested (from -50 to 0 mV) in db/db CASMCs. The latter correlates with decreased BK channel β1/α subunit ratio found in db/db vascular tissues. Taken together, Ca(2+) spark alterations lead to inappropriate BK channels activation in CASMCs of db/db mice and this condition is aggravated by the decrease in the BK β1 subunit/α subunit ratio which underlies the significant reduction of Ca(2+) spark/STOC coupling in CASMCs of diabetic animals.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Pressure
  • Calcium / metabolism*
  • Calcium Signaling / physiology*
  • Cerebral Arteries / cytology*
  • Diabetes Mellitus, Experimental / metabolism*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Obese
  • Microscopy, Confocal
  • Myocytes, Smooth Muscle / metabolism*
  • Normal Distribution
  • Patch-Clamp Techniques
  • Ryanodine Receptor Calcium Release Channel / metabolism

Substances

  • Ryanodine Receptor Calcium Release Channel
  • Calcium

Grant support

This work was funded by Conacyt (No. 80960), ICyTDF No.331/2010), Agence National de la Recherche (Geno-09-HyperEpac and Geno-09-Carythm), Région Ile de France (CODDIM: COD100256), European Union (2005 N°018802, CONTICA) and FRM (Fondation pour la Recherche médicale). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.