Inhibition of connexin hemichannels alleviates non-alcoholic steatohepatitis in mice

Abstract

While gap junctions mediate intercellular communication and support liver homeostasis, connexin hemichannels are preferentially opened by pathological stimuli, including inflammation and oxidative stress. The latter are essential features of non-alcoholic steatohepatitis. In this study, it was investigated whether connexin32 and connexin43 hemichannels play a role in non-alcoholic steatohepatitis. Mice were fed a choline-deficient high-fat diet or normal diet for 8 weeks. Thereafter, TAT-Gap24 or TAT-Gap19, specific inhibitors of hemichannels composed of connexin32 and connexin43, respectively, were administered for 2 weeks. Subsequently, histopathological examination was carried out and various indicators of inflammation, liver damage and oxidative stress were tested. In addition, whole transcriptome microarray analysis of liver tissue was performed. Channel specificity of TAT-Gap24 and TAT-Gap19 was examined in vitro by fluorescence recovery after photobleaching analysis and measurement of extracellular release of adenosine triphosphate. TAT-Gap24 and TAT-Gap19 were shown to be hemichannel-specific in cultured primary hepatocytes. Diet-fed animals treated with TAT-Gap24 or TAT-Gap19 displayed decreased amounts of liver lipids and inflammatory markers, and augmented levels of superoxide dismutase, which was supported by the microarray results. These findings show the involvement of connexin32 and connexin43 hemichannels in non-alcoholic steatohepatitis and, simultaneously, suggest a role as potential drug targets in non-alcoholic steatohepatitis.

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

“…In accordance with this finding, more liver damage, inflammation, and oxidative stress were observed in Cx32 ‐/‐ mice with nonalcoholic steatohepatitis, with no differences in insulin and glucose tolerance measurements or liver regeneration . Inhibition of hemichannels consisting of Cx32 or Cx43 in mice suffering from nonalcoholic steatohepatitis lowers levels of liver lipids and inflammatory markers (Table ) …”

Connexin43 Hemichannel Targeting With TAT-Gap19 Alleviates Radiation-Induced Endothelial Cell Damage

“…In addition, upregulated Cx43 expression often correlates with increased inflammatory responses, while reduced Cx43 expression inhibits inflammation (Mori et al, 2006;Retamal et al, 2007;Cronin et al, 2008;Danesh-Meyer et al, 2008;Tsuchida et al, 2013;Mugisho et al, 2018). TAT-Gap19 has been demonstrated to significantly decrease IL-1β and TNF-α in non-alcoholic fatty liver mouse model (Willebrords et al, 2017). Peptide5, another mimetic peptide-based hemichannel blocker, was reported to reduce TNF-α and IL-1β in rat model of spinal cord injury (O'Carroll et al, 2013).…”

“…Here, we aimed at investigating the involvement of Cx43 hemichannels in endothelial cell responses induced by IR exposure, by making use of the Cx43-targeting peptide TAT-Gap19 (Abudara et al, 2014). TAT-Gap19 was previously reported to specifically block Cx43 hemichannels in different in vitro experimental models, as observed by ATP release and dye uptake assays (Abudara et al, 2014;Willebrords et al, 2017;Maatouk et al, 2018;Saez et al, 2018;Walrave et al, 2018). These findings were supported by electrophysiological measurements of Cx43 hemichannel unitary currents demonstrating that Gap19 inhibits Cx43 hemichannels in HeLa cells overexpressing Cx43 (Wang et al, 2013b;Gadicherla et al, 2017), in acutely isolated pig ventricular cardiomyocytes (Wang et al, 2013b) and in primary astrocytes (Freitas-Andrade et al, 2019).…”

Dietary inclusion of Antarctic krill meal during the finishing feed period improves health and fillet quality of Atlantic salmon (Salmo salarL.)

“…Chd13 is associated with circulating level of the adipocyte-secreted protein adiponectin that has anti-inflammatory potential and plays an important role in metabolic regulation, associated with the fatty liver index in humans (57) . The up-regulation of tight junction proteins (connexin, 1•6-fold) indicates improved cell-cell communication of salmon fed krill-supplemented diets, and Willebrords et al (58) reported involvement of connexin hemichannels in non-alcoholic steatohepatitis. Among genes shown to have a role in immune surveillance of KM was up-regulation of ladderlectin (three genes, 1•5-1•8 fold) with broad pathogen recognition in rainbow trout (59)(60)(61) .…”