Modulation of subsets of cardiac B lymphocytes improves cardiac function after acute injury
Luigi Adamo, … , Deepta Bhattacharya, Douglas L. Mann
Luigi Adamo, … , Deepta Bhattacharya, Douglas L. Mann
Published June 7, 2018
Citation Information: JCI Insight. 2018;3(11):e120137. https://doi.org/10.1172/jci.insight.120137.
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Research Article Cardiology

Modulation of subsets of cardiac B lymphocytes improves cardiac function after acute injury

Abstract

Despite the long-standing recognition that the immune response to acute myocardial injury contributes to adverse left ventricular (LV) remodeling, it has not been possible to effectively target this clinically. Using 2 different in vivo models of acute myocardial injury, we show that pirfenidone confers beneficial effects in the murine heart through an unexpected mechanism that depends on cardiac B lymphocytes. Naive hearts contained a large population of CD19+CD11b–CD23–CD21–IgD+IgMlo lymphocytes, and 2 smaller populations of CD19+CD11b+ B1a and B1b cells. In response to tissue injury, there was an increase in neutrophils, monocytes, macrophages, as well as an increase in CD19+ CD11b– B lymphocytes. Treatment with pirfenidone had no effect on the number of neutrophils, monocytes, or macrophages, but decreased CD19+CD11b– lymphocytes. B cell depletion abrogated the beneficial effects of pirfenidone. In vitro studies demonstrated that stimulation with lipopolysaccharide and extracts from necrotic cells activated CD19+ lymphocytes through a TIRAP-dependent pathway. Treatment with pirfenidone attenuated this activation of B cells. These findings reveal a previously unappreciated complexity of myocardial B lymphocytes within the inflammatory infiltrate triggered by cardiac injury and suggest that pirfenidone exerts beneficial effects in the heart through a unique mechanism that involves modulation of cardiac B lymphocytes.

Authors

Luigi Adamo, Lora J. Staloch, Cibele Rocha-Resende, Scot J. Matkovich, Wenlong Jiang, Geetika Bajpai, Carla J. Weinheimer, Attila Kovacs, Joel D. Schilling, Philip M. Barger, Deepta Bhattacharya, Douglas L. Mann

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Figure 7

Analysis of B cell activation in wild-type and TIRAP-deficient immune cells.

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Analysis of B cell activation in wild-type and TIRAP-deficient immune ce...
(A and B) Unfractionated peritoneum-derived inflammatory cells (PDICs) were collected on day 4 after intraperitoneal injection of thioglycollate and placed in culture. Cells were cultured in media alone (control), in the presence of necrotic cell extracts from H9c2 cells (NCEs), in the presence of NCEs and pirfenidone (NCE-PFD), in the presence of LPS (LPS), or in the presence of LPS and pirfenidone (LPS-PFD). After 24 hours of culture, cells were collected for flow cytometric analysis and the prevalence of CD19+CD86hi cells was quantified. Three biological replicates per experiment are reported. (A) Results from inflammatory cells collected from wild-type mice. (B) Results from inflammatory cells collected from TIRAP–/– animals. (C and D) B lymphocytes were purified from the spleen and cultured for 24 hours under the same conditions described for panels A and B. After 24 hours of culture, cells were collected for flow cytometric analysis and the prevalence of CD19+CD86hi cells was quantified. Three biological replicates per experiment are reported. Panel C shows results from splenic B cells purified from wild-type mice, and panel D shows results from B lymphocytes collected from TIRAP–/– animals. (E and F) Mice were subjected to acute myocardial injury either by exposure to diphtheria toxin (DT) (E) or through 90 minutes of closed-chest ischemia followed by reperfusion (I/R) (F). Mice were fed regular chow (control) or chow enriched with pirfenidone (PFD). On day 4 after injury, the myocardium was collected and analyzed via flow cytometry to assess the number of myocardial CD19+CD86hi cells. In E, n = 4 per/group; in F, n = 4 control, n = 5 PFD. *P < 0.05, ***P < 0.001. Bars represent the mean, and error bars represent standard deviation. P values were calculated with 1-way ANOVA followed by Tukey’s test for multiple comparisons in panels A–D and with Student’s t test in panels E and F.