Blocking of connexin-mediated communication promotes neuroprotection during acute degeneration induced by mechanical trauma

PLoS One. 2012;7(9):e45449. doi: 10.1371/journal.pone.0045449. Epub 2012 Sep 20.

Abstract

Accruing evidence indicates that connexin (Cx) channels in the gap junctions (GJ) are involved in neurodegeneration after injury. However, studies using KO animal models endowed apparently contradictory results in relation to the role of coupling in neuroprotection. We analyzed the role of Cx-mediated communication in a focal lesion induced by mechanical trauma of the retina, a model that allows spatial and temporal definition of the lesion with high reproducibility, permitting visualization of the focus, penumbra and adjacent areas. Cx36 and Cx43 exhibited distinct gene expression and protein levels throughout the neurodegeneration progress. Cx36 was observed close to TUNEL-positive nuclei, revealing the presence of this protein surrounding apoptotic cells. The functional role of cell coupling was assessed employing GJ blockers and openers combined with lactate dehydrogenase (LDH) assay, a direct method for evaluating cell death/viability. Carbenoxolone (CBX), a broad-spectrum GJ blocker, reduced LDH release after 4 hours, whereas quinine, a Cx36-channel specific blocker, decreased LDH release as early as 1 hour after lesion. Furthermore, analysis of dying cell distribution confirmed that the use of GJ blockers reduced apoptosis spread. Accordingly, blockade of GJ communication during neurodegeneration with quinine, but not CBX, caused downregulation of initial and effector caspases. To summarize, we observed specific changes in Cx gene expression and protein distribution during the progress of retinal degeneration, indicating the participation of these elements in acute neurodegeneration processes. More importantly, our results revealed that direct control of GJ channels permeability may take part in reliable neuroprotection strategies aimed to rapid, fast treatment of mechanical trauma in the retina.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Communication / genetics
  • Cell Communication / physiology*
  • Chickens
  • Connexins / metabolism*
  • Immunohistochemistry
  • In Situ Nick-End Labeling
  • Neurodegenerative Diseases / etiology*
  • Neurodegenerative Diseases / metabolism*
  • Neurodegenerative Diseases / therapy
  • Polymerase Chain Reaction
  • Retina / metabolism*
  • Retina / pathology*
  • Wounds and Injuries / complications*

Substances

  • Connexins

Grants and funding

This work was supported by grants from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Universidade Federal do ABC (UFABC) and Universidade de São Paulo (USP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.