Enhanced Macrophage Pannexin 1 Expression and Hemichannel Activation Exacerbates Lethal Experimental Sepsis

We have recently reported an important role of Connexin 43 (Cx43) hemichannels in the pathogenesis of lethal sepsis through facilitating ATP efflux to potentiate the double-stranded RNA-activated protein kinase R (PKR)-dependent macrophage activation. Here we further elucidated the possible role of Pannexin 1 (Panx1) hemichannel in lethal sepsis by assessing its expression along with the impact of a Panx1-specific mimetic inhibitory peptide, 10Panx, on macrophage hemichannel activity in vitro and animal sepsis lethality in vivo. Both crude bacterial lipopolysaccharide (LPS) and purified serum amyloid A (SAA) effectively induced the expression and extracellular release of Panx1 by macrophages or monocytes as judged by Western blotting and immunocytochemistry assays. In animal model of lethal sepsis, Panx1 expression levels were significantly elevated in the heart, but reduced in the kidney, lung, spleen, and blood. At relatively lower doses (10, 50, and 100 mg/kg), the Panx1 mimetic peptide, 10Panx, reproducibly exacerbated the sepsis-induced animal lethality, reducing survival rates from 60-70% to 0-10%. Consistently, 10Panx did not inhibit, but rather promoted, the LPS-induced elevation of Lucifer Yellow dye uptake, ATP release, and Nitric Oxide (NO) production. Collectively, these findings suggested that elevated macrophage Panx1 expression and hemichannel activation contribute to the pathogenesis of lethal sepsis.