PROJECT SUMMARY (ABSTRACT)
Ozone (O3) is a harmful air pollutant that exacerbates chronic lung diseases in part by activating inflammatory
responses, inducing lung injury, and inhibiting resolution mechanisms. Resolution mechanisms are mediated
largely by specialized pro-resolving mediators (SPMs). SPMs are potent bioactive molecules that inhibit immune
cell recruitment, downregulate pro-inflammatory cytokine and chemokine production, and upregulate
phagocytosis of apoptotic cells – a resolution process termed ‘efferocytosis’. We have previously reported that
O3 decreases SPM production and inhibits efferocytosis, potentially contributing to exacerbated and persistent
inflammation observed in patients with pulmonary diseases exposed to O3. SPMs are metabolized primarily from
¿-3 fatty acids, such as docosahexaenoic acid (DHA). DHA can be consumed through diet or, more commonly
in western cultures, synthesized from the essential fatty acid a-linolenic acid by elongation of very long-chain
fatty acids protein 2 (ELOVL2). Preliminary data in this proposal indicates that DHA concentrations and ELOVL2
expression increase in the lung tissue following O3 exposure. Furthermore, ELOVL2 is increased in alveolar
macrophages (AMs) after O3 exposure, suggesting an immunological need for endogenous DHA in AMs. When
exogenous DHA was supplemented through diet, the O3-induced pulmonary and AM driven inflammatory
responses were reduced, AM efferocytosis was augmented, and markers of lung injury resolved faster.
Additionally, similar findings were noted when mice were pretreated with DHA derived SPM intermediates that
correlated with an increase in the SPM maresin 1 (MaR1) in lung tissue. MaR1 is a unique SPM that is primarily
produced by monocytes and macrophages that binds to leucine rich repeat containing G protein-coupled
receptor 6 (LGR6) to facilitate resolution processes. To examine MaR1 signaling following O3 exposure, we
measured LGR6 expression on AMs and found it to be significantly reduced when pulmonary inflammation was
ongoing. Taken together, these data indicate that endogenous DHA in AMs leading to MaR1 signaling may be
a crucial pathway to resolving O3-induced lung injury and inflammation. Therefore, we hypothesize that
endogenous DHA synthesis in AMs is required for production of MaR1 which reduces the severity and
improves resolution of O3-induced lung inflammation . To test this hypothesis, we will: 1) Examine how
endogenous DHA synthesis via ELOVL2 in AMs reduces O3-induced pulmonary inflammation and promotes
resolution responses, and 2) Determine if DHA-derived MaR1 signaling induces a pro-resolving AM phenotype
through LGR6, mitigating pulmonary inflammation and promoting resolution following O3 exposure. Completion
of the proposed aims and training included in this proposal will prepare the applicant for a successful career as
an independent investigator and will equip him with cutting edge techniques, a strong network of mentors, and
didactic training required for a successful career in academia.