Abstract
Purpose: :
Intercellular communication mediated by connexin (Cx) channels in the gap junctions (GJ) plays an important role in a variety of tissues allowing the exchange of small molecules up to 1kDa and ions. Accruing evidence indicates that gap junctions are involved in neurodegeneration after injury. The passage of calcium ions through the GJs plays an important role in neuronal survival/death, due to its cytoxicity in high concentrations. However, studies using GJ pharmacological blockers and KO animal models endowed apparently contradictory results in relation to the role of coupling in neuroprotection. In this work, we analyzed the expression of Cx in a focal retinal lesion induced by mechanical trauma (Fig.1). Remarkably, this model allowed spatial and temporal de[[Unsupported Character - fi]]nition of the lesion with high reproducibility, permitting visualization of the focus, penumbra and adjacent areas.
Methods: :
In the retina, Cx36 is abundantly expressed and plays essential roles in the visual signaling. Combining techniques such as real time PCR, western blot and IHC, we assessed the spatiotemporal expression of Cx in this experimental condition.
Results: :
We analyzed Cx36 and Cx43 expression pattern during retinal degeneration. Cx36 expression steady state levels mildly changed during the degenerative process, whereas Cx43 exhibited modifications in the phosphorylation status, protein levels and gene expression. The functional role of cell coupling was assessed by employing GJ blockers and openers, combined with methods for evaluating cellular death/viability (TUNEL, Fluoro-Jade and lactate dehydrogenase, LDH). Indeed, changes in cell coupling affected secondary cell loss. CBX, a broad-spectrum GJ blocker, reduced LDH release after 4 hours in a concentration-dependent manner. Quinine, a Cx36- and Cx50- specific blocker, reduced significantly the LDH released after 1, 2 and 4 hours in a concentration-dependent manner.
Conclusions: :
To summarize, Cx expression in chick retina was modulated during degenerative processes. In addition, control of GJ channel permeability may take part in reliable neuroprotection strategies.
Keywords: neuroprotection • retina • gap junctions/coupling