Plastic Surgery Research Council
Members Only  |  Contact  |  PSRC on Facebook
PSRC 60th Annual Meeting
Program and Abstracts

Back to 2015 Annual Meeting Program


Perilymphatic Inflammation and iNOS Production Play a Key Role in the Regulation of Lymphatic Dysfunction in Obesity
Jeremy S. Torrisi, BA, Daniel A. Cuzzone, MD, Geoffrey E. Hespe, BS, Matthew D. Nitti, BA, Jason C. Gardenier, MD, Ira L. Savetsky, MD, Gabriela Garcia Nores, MD, Raghu Kataru, Ph.D, Babak J. Mehrara, MD, FACS.
Memorial Sloan Kettering Cancer Center, New York, NY, USA.

PURPOSE: Obesity is an increasingly common and highly morbid condition, affecting 1 in 4 Americans with rising incidence in both adult and pediatric populations. Recently, our group and others have shown that obesity leads to profound dysfunction of the lymphatic system; however, the mechanism regulating this response remains unknown. Previous studies have shown that expression of inducible nitric oxide synthase (iNOS) by inflammatory cells is a potent regulator of lymphatic pumping function. Because we have previously shown that obesity increases perilymphatic inflammation, the purpose of this study was to determine how iNOS expression by inflammatory cells regulates lymphatic function in obesity.
METHODS: Male C57BL6/J mice were fed either a normal chow diet (10% fat) or high fat diet (60% fat) for 8-10 weeks. Mice were then treated with the specific iNOS inhibitor 1400W for 10 days intraperitoneally at a concentration of 10 mg/kg or with vehicle (PBS). Following treatment, we analyzed lymphatic function using Tc99 lymphoscintigraphy, indocyanine green (ICG) lymphangiography, and dendritic cell (DC) trafficking. In addition, a cross-section of the mouse’s hindlimb was harvested, fixed and decalcified for histological analysis. Staining for inflammatory cell infiltrate, iNOS expression and lymphatic vessels was performed using immunohistochemistry and immunofluorescence. Serum was harvested for analysis of metabolic data.
RESULTS: Obese animals treated with the iNOS inhibitor showed profound increases in Tc99 lymph node uptake, lymphatic pumping capacity (as assessed by ICG lymphangiography), and dendritic cell trafficking to peripheral lymph nodes (2-4 fold increase as compared with controls). Furthermore, transplanted DCs injected into the footpads of experimental animals 16 hours prior to harvesting were found to compromise 2.24 times more of the inguinal and popliteal lymph node cell populations in the iNOS inhibited obese animals. Histologic analysis showed that iNOS inhibited obese animals had markedly decreased iNOS expression and a profound decrease in perilymphatic iNOS+ cells. Interestingly, iNOS inhibition did not decrease general or perilymphatic inflammation, as tissue CD45+ cell counts and perilymphatic CD45+ cell counts were not significantly decreased in iNOS inhibited animals. In addition, short term iNOS inhibition did not change serum HDL, LDL, triglyceride, cholesterol and glucose levels.
CONCLUSION: We have shown that iNOS inhibition in the setting of obesity can significantly improve lymphatic function. We found that inhibition of iNOS did not decrease overall inflammation but decreased the number of perilymphatic iNOS+ inflammatory cells. This finding, together with the observation that iNOS inhibited animals had improved lymphatic pumping capacity supports the hypothesis that perilymphatic inflammation in obesity decreases lymphatic function, at least in part, by increasing iNOS expression and thereby disturbing gradients of NOS expression in lymphatic collectors. These studies are important and have clinical relevance because they may provide a novel means of treating obesity-associated diseases since the lymphatic vasculature has been recently shown to play a role in these responses.


Back to 2015 Annual Meeting Program