Protection of retinal cells from ischemia by a novel gap junction inhibitor

Abstract

Retinal cells which become ischemic will pass apoptotic signal to adjacent cells, resulting in the spread of damage. This occurs through open gap junctions. A class of novel drugs, based on primaquine (PQ), was tested for binding to connexin 43 using simulated docking studies. A novel drug has been synthesized and tested for inhibition of gap junction activity using R28 neuro-retinal cells in culture. Four drugs were initially compared to mefloquine, a known gap junction inhibitor. The drug with optimal inhibitory activity, PQ1, was tested for inhibition and was found to inhibit dye transfer by 70% at 10 μM. Retinal ischemia was produced in R28 cells using cobalt chloride as a chemical agent. This resulted in activation of caspase-3 which was prevented by the PQ1 gap junction inhibitor. Results demonstrate that novel gap junction inhibitors may provide a means to prevent retinal damage during ischemia.

Pannexins, distant relatives of the connexin family with specific cellular functions?

“…Morphological and ultrastructural studies in crayfish axons (122,123) and in rodent spinal cord, (124) both expressing Panxs, revealed small rosette-like GJ plaques that were completely different from the Cx GJ plaques, which have a bright punctate staining. Shestopalov and Panchin (4) hypothesized that these small rosette-like GJ plaques and the fine puncta observed in the Review article C. D'hondt et al Cx43: EC 50 ¼ 3 mM (90) 50 mM (104) IC 50 ¼ 2-4 mM (74) 10-100 mM (227) IC 50 ¼ 2-4 mM (74) 5-10% increase (229) Cx32: 100 mM Human/mouse Panx1: NE (229) Cx43: >10 mM (231) Flufenamic acid (FFA) 20-60 mM (235) Cx46 and 50: 3 mM (31, 236) 30 mM…”

“…(86,177) n/a n/a PQ4 Cx43: 10 mM (231) n/a n/a n/a n/a Meclofenamic acid (MFA) Cx50: EC 50 ¼ 21 mM (226) NE (45) n/a n/a n/a Cx50: 100 mM (235) Arachidonic acid Cx43: 20 mM (259) n/a n/a n/a 4-5 mM (292) Cx43: EC 50 % 32 mM (250) Oleic acid Cx43: 20 mM (259) n/a n/a n/a n/a Cx43: EC 50 % 35 mM (250) Oleyl alcohol Cx43: EC 50 % 35 mM (250) n/a n/a n/a n/a Palmitoleic acid Cx43: EC 50 % 60 mM (250) Cx45: 50 mM (265) n/a n/a NE (265) Cx43: 50 mM (276) Cx 37 and 40: 50 mM (251) Stearic acid Cx43: EC 50 % 102 mM (250) n/a n/a n/a n/a Caprylic acid Cx43: EC 50 % 185 mM (250) n/a n/a n/a n/a (Continues) (32) indicating that glycosylation hinders GJ formation. Secondly, the preference of Panxs for hemichannel formation may also be an intrinsic property of these proteins.…”

Gap junction protein connexin43 (GJA1) in the human glaucomatous optic nerve head and retina

“…[18][19][20][21][22][23][24][25][26] Gap junction modulation has been identified as a potential neuroprotective target and recently it has been shown that gap junction inhibitors protect retinal neurosensory cells from ischemia in a cell culture model. 27 Connexin43 is the most abundant gap junction protein in the CNS and is primarily expressed on astrocytes. Alterations in connexin43 expression have been described following acute injury to the CNS [28][29][30][31][32][33][34] and in a variety of degenerative 35,36 and inflammatory diseases, 37 suggesting a role in the pathogenesis of neuronal damage.…”

Targeting neuronal gap junctions in mouse retina offers neuroprotection in glaucoma

“…In this scheme, toxic molecules are transferred intercellularly from dying cells to neighbors through communicating GJs, thereby producing a wave of ancillary cell degeneration (12,13). As the CNS locus with arguably the highest expression of GJs, bystander-mediated neuronal cell death in retina has been implicated in a number of pathologies, including excitotoxicity, retinitis pigmentosa, and ischemic retinopathy (12,(14)(15)(16)(17).…”