Connexin hemichannel inhibition reduces acetaminophen-induced liver injury in mice

Abstract

Historically, connexin hemichannels have been considered as structural precursors of gap junctions. However, accumulating evidence points to independent roles for connexin hemichannels in cellular signaling by connecting the intracellular compartment with the extracellular environment. Unlike gap junctions, connexin hemichannels seem to be mainly activated in pathological processes. The present study was set up to test the potential involvement of hemichannels composed of connexin32 and connexin43 in acute hepatotoxicity induced by acetaminophen. Prior to this, in vitro testing was performed to confirm the specificity and efficiency of TAT-Gap24 and TAT-Gap19 in blocking connexin32 and connexin43 hemichannels, respectively. Subsequently, mice were overdosed with acetaminophen followed by treatment with TAT-Gap24 or TAT-Gap19 or a combination of both after 1.5 hour. Sampling was performed 3, 6, 24 and 48 hours following acetaminophen administration. Evaluation of the effects of connexin hemichannel inhibition was based on a series of clinically relevant read-outs, measurement of inflammatory cytokines and oxidative stress. Subsequent treatment of acetaminophen-overdosed mice with TAT-Gap19 only marginally affected liver injury. In contrast, a significant reduction in serum alanine aminotransferase activity was found upon administration of TAT-Gap24 to intoxicated animals. Furthermore, co-treatment of acetaminophen-overdosed mice with both peptides revealed an additive effect as even lower serum alanine aminotransferase activity was observed. Blocking of connexin32 or connexin43 hemichannels individually was found to decrease serum quantities of pro-inflammatory cytokines, while no effects were observed on the occurrence of hepatic oxidative stress. This study shows for the first time a role for connexin hemichannels in acetaminophen-induced acute liver failure.

Contribution of Connexin Hemichannels to the Decreases in Cell Viability Induced by Linoleic Acid in the Human Lens Epithelial Cells (HLE-B3)

“…Indeed, to our knowledge connexin channels are the only channels inhibited by extracellular divalent cations, La 3+ and Gap27. Furthermore, we observed that extracellular ATP concentration increase in HLE-B3 cells in response to DCFS, an effect that was significantly reduced by CBX, which is consistent with ATP efflux through hemichannels (Kang et al, 2008;Maes et al, 2017). On the other hand, we found that exposure to LA increases HLE-B3 cells Etd + uptake rate, which also was prevented by La 3+ , CBX, and Gap 27.…”

Connexin and Pannexin (Hemi)Channels: Emerging Targets in the Treatment of Liver Disease

“…Furthermore, high Cx43 immunoreactivity is seen around inflamed and necrotic areas in acute‐on‐chronic liver failure in rat . Interestingly, specific Cx32 and/or Cx43 hemichannel inhibition reduces levels of proinflammatory cytokines and alanine aminotransaminase after acetaminophen overdosing (Table ) . Recently, it has been shown that levels of hepatic Panx1 increase in acetaminophen‐overdosed mice (Table ).…”

The Potential for Connexin Hemichannels to Drive Breast Cancer Progression through Regulation of the Inflammatory Response

“…Subsequent work showed that the peptide also selectively inhibited Cx43 hemichannels in astrocytes [ 121 ]. More recently, Gap19 was shown to reduce serum levels of pro-inflammatory cytokines in mouse models of acetaminophen-induced liver injury and non-alcoholic steatohepatitis [ 122 , 123 ]. Conversely, in a mouse model of sepsis, Gap19 was surprisingly found to increase macrophage hemichannel activity and decrease animal survival [ 118 ].…”