mTORC1 and mTORC2 selectively regulate macrophage differentiation. Rapid and robust inflammatory responses play a critical role in protecting the host against infections and environmental insults. Likewise, the early induction of negative feedback loops promotes healing and prevents autoimmunity and tissue destruction due to over exuberant responses. Chronic persistent unregulated inflammation often leads to tissue destruction by promoting the development of fibrosis. Although pulmonary fibrosis appears to be the end result of chronic unremitting immune activation, often neither the inciting agents nor the precise factors driving the fibrotic response are known. Macrophages play a crucial role in directing both host-innate and acquired immune responses. Classically activated macrophages (CAM) are induced by IFN-? or LPS and skew the immune response toward a Th1 environment. Alternatively activated macrophages (AAM) are induced by IL-4 or IL-13 and promote a Th2 environment. AAM macrophages have been implicated in both physiologic and pathologic processes such as homeostasis, inflammation, cancer and fibrosis. However, the precise role and even phenotypic definition of """"""""alternatively activated"""""""" macrophage subsets in modulating diseases remains unclear. While it is clear that the environment influences the development of macrophages along a CAM (IFN- ?) or AAM (IL-4) pathway, the precise signaling mechanisms regulating this differentiation remains largely unknown. Recently our collaborator (Jonathan Powell) has determined that the serine/threonine kinase mTOR plays a critical role in directing T helper cell differentiation. T cells lacking mTOR complex 1 (TORC1) selectively fail to develop into Th1 and Th17 cells while T cells lacking TORC2 activity fail to develop into Th2 cells but retain their ability to become Th1 and Th17 cells. We hypothesize that similar to T cell differentiation, macrophage differentiation is also controlled by mTOR. To test this hypothesis, our lab has generated a novel mouse model in which mTOR, mTORC1, or mTORC2 are selectively knocked out in murine macrophages. Indeed our preliminary data support this hypothesis and further delineate a critical role for mTOR in macrophages in regulating the inflammation leading to pulmonary fibrosis. To this end we will test the hypothesis that mTOR plays a critical role in the development of alternatively activated macrophages and pulmonary fibrosis by pursuing the following Specific Aims:
Aim 1 - mTOR regulates macrophage differentiation and Aim 2 - alternatively activated macrophages (M2) promote pulmonary fibrosis.

Public Health Relevance

Pulmonary fibrosis is a devastating disease associated with significant morbidity and mortality. Alternatively activated macrophages have been associated with pulmonary fibrosis, though their exact role in this disease is unknown. By studying the role of mTOR in the differentiation of macrophages, we hope to identify new therapeutic targets.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Exploratory/Developmental Grants (R21)
Project #
Application #
Study Section
Lung Injury, Repair, and Remodeling Study Section (LIRR)
Program Officer
Eu, Jerry Pc
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Johns Hopkins University
Schools of Medicine
United States
Zip Code
Oh, Min-Hee; Collins, Samuel L; Sun, Im-Hong et al. (2017) mTORC2 Signaling Selectively Regulates the Generation and Function of Tissue-Resident Peritoneal Macrophages. Cell Rep 20:2439-2454
Hallowell, R W; Collins, S L; Craig, J M et al. (2017) mTORC2 signalling regulates M2 macrophage differentiation in response to helminth infection and adaptive thermogenesis. Nat Commun 8:14208
Vigeland, Christine L; Collins, Samuel L; Chan-Li, Yee et al. (2016) Deletion of mTORC1 Activity in CD4+ T Cells Is Associated with Lung Fibrosis and Increased ?? T Cells. PLoS One 11:e0163288
Collins, Samuel L; Chan-Li, Yee; Oh, MinHee et al. (2016) Vaccinia vaccine-based immunotherapy arrests and reverses established pulmonary fibrosis. JCI Insight 1:e83116
Heikamp, Emily B; Patel, Chirag H; Collins, Sam et al. (2014) The AGC kinase SGK1 regulates TH1 and TH2 differentiation downstream of the mTORC2 complex. Nat Immunol 15:457-64
Limjunyawong, Nathachit; Mitzner, Wayne; Horton, Maureen R (2014) A mouse model of chronic idiopathic pulmonary fibrosis. Physiol Rep 2:e00249
Zhao, Hongyun; Chan-Li, Yee; Collins, Samuel L et al. (2014) Pulmonary delivery of docosahexaenoic acid mitigates bleomycin-induced pulmonary fibrosis. BMC Pulm Med 14:64
Black, Katharine E; Collins, Samuel L; Hagan, Robert S et al. (2013) Hyaluronan fragments induce IFN? via a novel TLR4-TRIF-TBK1-IRF3-dependent pathway. J Inflamm (Lond) 10:23
Collins, Samuel L; Chan-Li, Yee; Hallowell, Robert W et al. (2012) Pulmonary vaccination as a novel treatment for lung fibrosis. PLoS One 7:e31299
Powell, Jonathan D; Pollizzi, Kristen N; Heikamp, Emily B et al. (2012) Regulation of immune responses by mTOR. Annu Rev Immunol 30:39-68