Ozone induced innate inflammatory responses in the lung invo
Ozone-induced innate inflammatory responses in the lung involve neutrophil extravasation through enhanced trans-endothelial migration (Krishna et al., 1997). Catecholamines and glucocorticoids, which are increased by ozone inhalation (Bass et al., 2013, Miller et al., 2015, Miller et al., 2016a, Miller et al., 2016b) play a central role in initiating a dynamic process of egress of innate immune Cy5 amine (non-sulfonated) australia from their site of depot to the circulation and then migration to the site of inflammation, in this case the lung. It has been shown that increased circulating epinephrine and corticosterone can induce the innate neutrophil immune response (Dhabhar et al., 2012). We have shown that increases in pulmonary neutrophil extravasation is associated with ozone-induced increases in stress hormones and that adrenal demedullation and/or total adrenalectomy diminishes this inflammatory effect of ozone (Miller et al., 2016b). Here we observed that inhibiting βAR with PROP and both βAR+GR with PROP+MIFE, mimicking systemic impacts of adrenal demedullation and total adrenalectomy, respectively, nearly inhibited ozone-induced neutrophil increases in the lung in its entirety. However, inhibition of only GR using MIFE was ineffective in reversing lung neutrophilic inflammation, suggesting that βAR activation might be central in neutrophil extravasation to the lung after ozone exposure. This is further supported by studies demonstrating that PROP pretreatment prevents cigarette smoke-induced lung damage (Zhou et al., 2014a), and improves survival in a sepsis model (Wilson et al., 2013). The effects of AR and GR manipulation on ozone-induced responses are immune cell specific. The lack of ozone-induced lymphopenia in MIFE- but not PROP-pretreated rats highlights the role of GR in modulating the migration, redistribution and proliferation of lymphoid cells in the circulation (Dhabhar et al., 2012). This effect of MIFE was not recapitulated in the number of BALF lymphocytes, suggesting that ozone-induced changes in circulating lymphocytes are likely influenced by GR-mediated egress from their storage site but not extravasation into the lung. The acute stress response fine-tunes immune function depending on the timing and magnitude of the stressor by enhancing innate and adaptive immune responses (Dhabhar, 2014). MIFE pretreatment has been shown to reestablish lymphocyte mediated immune responses in immunosuppressed mice (Rearte et al., 2010). Further, a MIFE-mediated reduction in glucocorticoid-induced lymphocyte apoptosis may also explain these results (Smith and Cidlowski, 2010) since glucocorticoids inhibit the release of lymphocytes into the circulation and induce apoptosis (Baschant and Tuckermann, 2010, Laakko and Fraker, 2002, Viegas et al., 2008). A marked inhibition of ozone-induced increase in BALF NAG activity by MIFE might indicate a role for GR in modulating the macrophage response. It is possible that the initiation of a stress response by epinephrine might modulate the lung innate immune response and subsequent systemic corticosterone immune effects (Johnson et al., 2005, Vida et al., 2011, Zhou et al., 2014b). This assumption is supported by the observation that PROP markedly diminished ozone-induced inflammatory cytokine increases and neutrophilic inflammation in the lung, supporting a major contribution of βAR in local pulmonary modulation of the immune responses. Although the activation of the sympathetic arm of the stress axis (epinephrine and norepinephrine) has been shown to inhibit innate immune responses in humans (Kox et al., 2014), it is known that β2AR, which are abundant in the lung, can modulate nuclear factor kappa-beta-mediated inflammatory processes. Previous studies have shown that PROP blocked the stress-induced elevation of circulating IL-6 levels (Van Gool et al., 1990) and reduced air pollution-induced increases in IL-6 in mice (Chiarella et al., 2014). Since in vivo pulmonary effects of ozone can be blocked by inhibiting βAR and GR receptors, and ozone can increase circulating epinephrine and corticosterone through the activation of SAM and HPA axes, it is likely that when encountered by the lung, ozone acts upstream to increase βAR and GR activity systemically, and can also have direct lung cellular effects downstream of βAR and GR receptor activation to interrupt cell signaling.