Rapamycin prevents bronchiolitis obliterans through increasing infiltration of regulatory B cells in a murine tracheal transplantation model.
OBJECTIVE
B lymphocytes are generally considered to be activators of the immune response; however, recent findings have shown that a subtype of B lymphocytes, regulatory B lymphocytes, play a role in attenuating the immune response. Bronchiolitis obliterans remains the major limitation to modern-day lung transplantation. The role of regulatory B lymphocytes in bronchiolitis obliterans has not been elucidated. We hypothesized that regulatory B lymphocytes play a role in the attenuation of bronchiolitis obliterans.


METHODS
We performed a standard heterotopic tracheal transplant model. Tracheas from Balb/c mice were transplanted into C57BL/6 recipients. Rapamycin treatment and dimethyl sulfoxide control groups were each treated for the first 14 days after the transplant. Tracheas were collected on days 7, 14, and 28 post-transplantation. Luminal obliteration was evaluated by hematoxylin-eosin staining and Picrosirius red staining. Immune cell infiltration and characteristics, and secretion of interleukin-10 and transforming growth factor-β1 were accessed by immunohistochemistry. Cytokines and transforming growth factor-β1 were measured using the Luminex assay (Bio-Rad, Hercules, Calif).


RESULTS
The results revealed that intraperitoneal injection of rapamycin for 14 days after tracheal transplantation significantly reduced luminal obliteration on day 28 when compared with the dimethyl sulfoxide control group (97.78% ± 3.63% vs 3.02% ± 2.14%, P < .001). Rapamycin treatment markedly induced regulatory B lymphocytes (B220(+)IgM(+)IgG(-)IL-10(+)TGF-β1(+)) cells when compared with dimethyl sulfoxide controls. Rapamycin treatment inhibited interleukin-1β, 6, 13, and 17 on days 7 and 14. Rapamycin also greatly increased interleukin-10 and transforming growth factor-β1 production in B cells and regulatory T lymphocytes infiltration on day 28.


CONCLUSIONS
Mammalian target of rapamycin inhibition decreases the development of bronchiolitis obliterans via inhibition of proinflammatory cytokines and increasing regulatory B lymphocytes cell infiltration, which subsequently produces anti-inflammatory cytokines and upregulates regulatory T lymphocyte cells.
Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va.
Yunge
Y
Zhao
Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va.
Jacob R
JR
Gillen
Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va.
Akshaya K
AK
Meher
Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va.
Jordan A
JA
Burns
Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va.
Irving L
IL
Kron
Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va. Electronic address: cll2y@virginia.edu.
Christine L
CL
Lau
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001402:B-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D001989:Bronchiolitis Obliterans / Q000209:etiology / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D018836:Inflammation Mediators / Q000378:metabolism; D008297:Male; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010641:Phenotype; D020123:Sirolimus / Q000494:pharmacology*; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology; D013997:Time Factors; D014132:Trachea / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000637:transplantation*
D000893:Anti-Inflammatory Agents; D016207:Cytokines; D018836:Inflammation Mediators; D020123:Sirolimus
FoxP3β regulatory T cells; bronchiolitis obliterans; mouse heterotopic tracheal transplant; rapamycin; regulatory B lymphocytes