β2-Adrenergic Receptor Antagonist Butoxamine Partly Abolishes the Protection of 100% Oxygen Treatment Against Zymosan-Induced Generalized Inflammation in Mice

Abstract

We have demonstrated that 100% oxygen inhalation is beneficial to zymosan-induced generalized inflammation, and reactive oxygen species may be involved in the protection of oxygen treatment. Other investigators suggest that reactive oxygen species may modulate the sympathetic nervous system activity and β2-adrenergic receptor (β2AR)-mediated pathway. Moreover, studies have demonstrated that β2AR agonists are beneficial to sepsis. Therefore, we assessed the effects of β2AR antagonist butoxamine on the protection of oxygen treatment against zymosan-induced generalized inflammation in mice. Mice were given oxygen treatment by exposure to 100% oxygen for 3 h starting at 4 and 12 h after zymosan injection, respectively. In the mortality study, survival was monitored for 7 days after zymosan injection in mice. At 24 h after zymosan injection, mice were killed, and blood sample and organs were harvested for analysis. We observed that 100% oxygen treatment prevented the abnormal changes in organ histopathology, lactate dehydrogenase and C-reactive protein in serum, inflammatory cytokines in serum and tissue, and arterial blood gas analysis and improved the survival rate in zymosan-challenged mice. We found that pretreatment with β2AR antagonist butoxamine partly abolished the protection of 100% oxygen inhalation. We also showed that zymosan induced the increase in serum 3'-5'-cyclic adenosine monophosphate (cAMP) and the decrease in tissue cAMP. However, oxygen treatment increased the cAMP levels in both serum and tissue, which were partly abolished by pretreatment with butoxamine. Thus, 100% oxygen inhalation may protect against zymosan-induced generalized inflammation in mice partly through activation of β2AR pathway and subsequently enhance cAMP levels in both serum and tissue.