Rationale: Within the lung, efficient gas exchange is determined by the alveolar-capillary membrane. When this membrane is compromised, fluid leaks into the alveolus and disrupts gas exchange. Bacterial pneumonia can promote alveolar-capillary membrane disruption and progress toward ARDS. Infiltration of immune cells into the lung tissue and airspaces is another key feature of ARDS; however, an exacerbated immune response can promote collateral tissue damage and increase lung injury. Soluble adenylyl cyclase isoform 10 (AC10/sAC) is expressed in capillary endothelial cells, and when activated, AC10 disrupts the pulmonary endothelial barrier and induces edema in the isolated lung. Although recently AC10 was implicated in immune cell recruitment in the systemic circulation, its role during lung infection is not fully resolved. Thus, we hypothesized that loss of AC10 would improve survival, attenuate lung edema and alter immune cell recruitment during acute P. aeruginosa-induced lung injury. Methods: Wild type (WT) and AC10 knockout mice were inoculated intratracheally with P. aeruginosa (1E6 to 2.5E6 colony forming units, CFUs) or vehicle control (PBS). Bronchoalveolar lavage fluid (BALF) was collected for protein quantification and cytokine/chemokine analysis. Survival was assessed over 96-hours, and lung injury evaluated histologically. To determine bacterial burden, organs (lungs, kidney, liver, spleen and brain) were harvested 6 and 24 hours after inoculation, homogenized and cultured overnight at 37 ºC on Pseudomonas isolation agar for quantification of CFUs. Finally, to distinguish the contribution of hematopoietic versus non- hematopoietic cells, bone marrow chimera mice were generated by reconstituting lethally irradiated AC10 knockout mice with bone marrow from WT congenic donors, or lethally irradiated WT mice with bone marrow from AC10 knockout donors. Following infection, BALF and lung tissue from WT, AC10 knockout mice, and bone marrow chimera mice, were analyzed by flow cytometry for total CD45+ leukocytes, Ly6G+ neutrophils, and neutrophil CD11b surface expression. Results: Compared to WT controls, AC10 knockout mice had decreased protein content in BALF and a distinct cytokine/chemokine profile, following infection. Genetic ablation of AC10 increased survival at 96-hours and histological analysis suggested attenuated lung injury without altering bacterial clearance at either 6 or 24 hours. The total number of CD45+ white blood cells and Ly6G+ neutrophils were similar between genotypes; however, AC10 knockout mice demonstrated reduced CD11b surface expression on Ly6G+ neutrophils. Importantly, reduced CD11b surface expression on neutrophils was recapitulated in AC10 knockout mice reconstituted with WT bone marrow, indicating that AC10 in non-hematopoietic compartments regulates neutrophil phenotype during infection. Conclusion: AC10 exacerbates lung injury and mortality during acute P. aeruginosa-induced lung injury by promoting alveolar-capillary disruption and enhancing neutrophil CD11b surface expression, rather than altering immune cell recruitment or bacterial clearance. These finding identify AC10 as an “edema factor” that modulates neutrophil phenotype and represents a potential therapeutic target in ARDS associated P. aeruginosa pneumonia. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Stone et al. (2026) studied this question.