Hemichannels in cardiomyocytes open transiently during ischemia and contribute to reperfusion injury following brief ischemia

Am J Physiol Heart Circ Physiol. 2007 Sep;293(3):H1714-20. doi: 10.1152/ajpheart.00022.2007. Epub 2007 Jun 8.

Abstract

The aim of this study was to investigate changes in hemichannel activity during in vitro simulated ischemia [oxygen-glucose deprivation (OGD)] and the contribution of hemichannels to ischemia-reperfusion injury in rat neonatal cardiomyocytes. Dye uptake assays showed that hemichannels opened as OGD progressed, peaking after 1 h, and then closed, returning to the pre-OGD state after 2 h of OGD. The increase in dye uptake after 1 h of OGD was inhibited by hemichannel blockers (lanthanum chloride and a connexin 43 mimetic peptide, Gap26). During OGD, intracellular Ca(2+) concentration ([Ca(2+)](i)) began to increase after 1 h and reached several micromolar after 2 h. After 1 h of OGD, Gap26 inhibited the increases in hemichannel activity and [Ca(2+)](i). In contrast, dantrolene [an endo(sarco)plasmic reticulum Ca(2+) release inhibitor] suppressed the increase in [Ca(2+)](i), but not in hemichannel activity. After 2 h of OGD, the combined administration of 2',4'-dichlorobenzamil and dantrolene reduced [Ca(2+)](i) to <1 microM and increased hemichannel activity to the level attained after 1 h of OGD. Simulated ischemia-reperfusion, induced by 1 h of OGD followed by 2 h of recovery, reduced cell viability to 54% of the control level. The addition of Gap26 to OGD medium improved viability to 80% of the control level. In conclusion, this study demonstrated that 1) hemichannels open transiently during OGD, 2) closure of hemichannels, but not their opening, is regulated by an increase in [Ca(2+)](i) during OGD, and 3) open hemichannels contribute to cell injury during recovery from OGD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Cells, Cultured
  • Connexins / antagonists & inhibitors
  • Connexins / physiology*
  • Dantrolene / pharmacology
  • Ischemic Preconditioning, Myocardial*
  • Lanthanum / pharmacology
  • Muscle Relaxants, Central / pharmacology
  • Myocardial Reperfusion Injury / metabolism
  • Myocardial Reperfusion Injury / physiopathology*
  • Myocytes, Cardiac / drug effects
  • Myocytes, Cardiac / physiology*
  • Peptides / pharmacology
  • Rats
  • Rats, Sprague-Dawley

Substances

  • Connexins
  • Gap 26 peptide
  • Muscle Relaxants, Central
  • Peptides
  • lanthanum chloride
  • Lanthanum
  • Dantrolene
  • Calcium