Spatiotemporal depletion of connexins using antisense oligonucleotides

Connexins, Pannexins and Gap Junctions in Perinatal Brain Injury

Perinatal brain injury secondary to hypoxia-ischemia and/or infection/inflammation remains a major cause of disability. Therapeutic hypothermia significantly improves outcomes, but in randomized controlled trials nearly half of infants still died or survived with disability, showing that additional interventions are needed. There is growing evidence that brain injury spreads over time from injured to previously uninjured regions of the brain. At least in part, this spread is related to opening of connexin hemichannels and pannexin channels, both of which are large conductance membrane channels found in many brain cells. Opening of these membrane channels releases adenosine triphosphate (ATP), and other neuroactive molecules, into the extracellular space. ATP has an important role in normal signaling, but pathologically can trigger the assembly of the multi-protein inflammasome complex. The inflammasome complex promotes activation of inflammatory caspases, and release of inflammatory cytokines. Overall, the connexin hemichannel appears to play a primary role in propagation of injury and chronic disease, and connexin hemichannel blockade has been shown to be neuroprotective in multiple animal models. Thus, there is potential for some blockers of connexin or pannexin channels to be developed into targeted interventions that could be used in conjunction with or separate to therapeutic hypothermia.

Gap Junction Channels of Innexins and Connexins: Relations and Computational Perspectives

Gap junction (GJ) channels in invertebrates have been used to understand cell-to-cell communication in vertebrates. GJs are a common form of intercellular communication channels which connect the cytoplasm of adjacent cells. Dysregulation and structural alteration of the gap junction-mediated communication have been proven to be associated with a myriad of symptoms and tissue-specific pathologies. Animal models relying on the invertebrate nervous system have exposed a relationship between GJs and the formation of electrical synapses during embryogenesis and adulthood. The modulation of GJs as a therapeutic and clinical tool may eventually provide an alternative for treating tissue formation-related diseases and cell propagation. This review concerns the similarities between Hirudo medicinalis innexins and human connexins from nucleotide and protein sequence level perspectives. It also sets forth evidence of computational techniques applied to the study of proteins, sequences, and molecular dynamics. Furthermore, we propose machine learning techniques as a method that could be used to study protein structure, gap junction inhibition, metabolism, and drug development.

Intracellular oligonucleotide delivery using the cell penetrating peptide Xentry

The current study investigated the use of two cationic peptides, Xentry-KALA (XK) and Xentry-Protamine (XP), for intracellular delivery of Connexin43 antisense oligonucleotides (Cx43AsODN). The charge and size of Cx43AsODN:XK and Cx43AsODN:XP complexes was determined by Zetasizer analysis. The earliest positive zeta potential reading was obtained at a 1:2 and 1:1.2 charge ratio of Cx43AsODN:XK and Cx43AsODN:XP respectively, with Cx43AsODN:XK resulting in overall larger complexes than Cx43AsODN:XP. Gel shift mobility assays revealed complete complex formation at a 1:2.5 and 1:2.2 charge ratio of Cx43AsODN:XK and Cx43AsODN:XP, respectively. Cellular uptake studies were carried out in ARPE-19 cells. While both complexes were able to enter the cells, Cx43AsODN:XK uptake appeared punctate and circular indicative of endosomal containment. Cx43AsODN:XP uptake, in contrast, resulted in diffuse appearance inside the cell suggesting endosomal escape of the cargo. Finally, western blot analysis confirmed that Cx43AsODN:XP was able to knockdown Cx43 expression in these cells under normal and hypoxic conditions.

Connexin43 modulation inhibits scarring in a rabbit eye glaucoma trabeculectomy model

We investigated whether one subconjunctival injection of connexin43 antisense oligodeoxynucleotides (Cx43 AsODN) modulates postoperative scarring in a rabbit model of glaucoma trabeculectomy surgery. In a randomised, controlled, masked-observer study, 39 rabbits underwent trabeculectomy surgery with insertion of a 22-gauge cannula in the right eyes and were randomly divided into three treatment groups. Each rabbit received an injection of Cx43 AsODN in Pluronic gel, balanced salt solution or Pluronic gel alone into the formed bled. The animals were euthanized at 8 and 24 h and at 5 and 21 days. Histology and immunohistochemistry results demonstrated that Cx43 AsODN decreased Cx43 upregulation at 8 and 24 h which led to less myofibroblast upregulation at days 5 and 21 and reduced scarring at day 21 compared to controls. We conclude that postoperative use of Cx43 AsODN inhibited subconjunctival scarring and fibrosis. Cx43 AsODN injection may be a safe and effective anti-scarring agent in glaucoma trabeculectomy surgery.

Regulation of connexin43 gap junction protein triggers vascular recovery and healing in human ocular persistent epithelial defect wounds

Transiently blocking the expression of the gap junction protein connexin43 using antisense oligodeoxynucleotides or blocking hemichannels with connexin mimetic peptides has been shown to significantly improve outcomes in a range of acute wound models. Less is known about their likely effects in nonhealing wounds. In the eye, prolonged inflammation and lack of epithelial recovery in nonhealing corneal epithelial wounds may lead to corneal opacity, blindness or enucleation. We report here the first human applications of antisense oligodeoxynucleotides that transiently block translation of connexin43 in a prospective study of five eyes with severe ocular surface burns (persistent epithelial defects), which were unresponsive to established therapy for 7 days to 8 weeks prior to treatment. Connexin43-specific antisense oligodeoxynucleotide was delivered in cold, thermoreversible Poloxamer407 gel under either an amniotic membrane graft or a bandage contact lens. The connexin43-specific antisense application reduced inflammation within 1-2 days, and in all five eyes complete and stable corneal reepithelialization was obtained. Recovery of the vascular bed and limbal reperfusion appeared to precede corneal epithelial recovery. We conclude that connexin modulation provides a number of benefits for nonhealing ocular burn wounds, one of which is to promote vascular recovery.