Abstract 14704: Dietary Endotoxin Mediated Impairments in Mesenteric Lymphatic Vessel Contractility is Regulated by Neighboring Immune Cells in Mesentery
Introduction: We have previously shown that metabolic syndrome (MetSyn) impairs the intrinsic contractility of collecting lymphatics. Elevated levels of dietary endotoxins like lipopolysaccharide (LPS) have been closely associated with MetSyn. The mechanisms of LPS modulated changes or immune cells-lymphatics interaction in the regulation of lymphatic contractility is not well understood.
Hypothesis: During an inflammatory pathologic condition, dynamic modulation of specific immune cell populations on or near mesenteric lymphatics would result in changes in cytokines/chemokines, which would modulate lymphatic function.
Methods: Rats were intraperitoneally injected with LPS (10mg/kg), and immune cells [neutrophils, macrophages (MØ) and monocytes] were detected by confocal microscopy after 6hr, 24hrs and 3 days in whole mount mesenteric lymphatics using specific markers. Separately lymphatic vessels were isolated and subjected to varying transmural pressures to evaluate contractile responses.
Results: In LPS treated animals there was a significant reduction in the number of neutrophils at 3 days (48.2±6.5%, p<0.023) and an increase in monocytes and MØ present on or near the vicinity of the lymphatics. Mesenteric arcades were stained for M1 and M2 populations of MØ and a significant increase in the M2 polarized MØ was found. The LPS-treated rats showed a significant reduction in phasic contraction frequency at each pressure that resulted a decrease in lymphatic pump function. Analysis of effects of key cytokines released by neutrophils (IL4 and IL8) on a lymphatic muscle cell culture model showed maximum activation of phosphorylated myosin light chain 20 (pMLC20) at 30 mins (2.6±.0.04, p<0.012). The activation of pMLC20 was associated with corresponding activation of pAKT (1.89±.0.12, p<0.035) and ERK1/2 (2.39±.0.09, p<0.003). These cytokines also mitigated the direct LPS-induced decrease in pMLC20.
Conclusions: Our data demonstrate that LPS significantly impairs lymphatic function by modulating the immune cell population on/near lymphatics, thereby reducing the availability of key cytokines and their influence on lymphatic muscle contraction, providing novel targets for therapeutic development.
Author Disclosures: S. Chakraborty: None. S.D. Zawieja: None. W. Wang: None. D.C. Zawieja: None. M. Muthuchamy: None.
- © 2014 by American Heart Association, Inc.