Methicillin‐resistant Staphylococcus aureus causes sustained collecting lymphatic vessel dysfunction

Abstract

Methicillin‐resistant Staphylococcus aureus (MRSA) is a major cause of morbidity and mortality worldwide and is a frequent cause of skin and soft tissue infections (SSTIs). Lymphedema—fluid accumulation in tissue caused by impaired lymphatic vessel function—is a strong risk factor for SSTIs. SSTIs also frequently recur in patients and sometimes lead to acquired lymphedema. However, the mechanism of how SSTIs can be both the consequence and the cause of lymphatic vessel dysfunction is not known.Here, we used the endemic USA300 strain of community‐associated MRSA (CA‐MRSA), a common cause of serious bacterial infections in the United States, to establish a model of localized MRSA infection. We used intravital imaging to determine whether MRSA infections inhibit lymphatic vessel contractility and lymph flow. In vivo studies used C57BL/6, iNOS−/− C57BL/6, MyD88−/− C57BL/6, LysMgfp/gfp C57BL/6, and alpha SMAP‐DsRed/C57BL/6 mice to assess the effects of host‐derived molecules to lymphatic contractility after infection. Alpha SMA‐DsRed transgenic mice were visualized and immunofluorescence staining of alpha SMA+ lymphatic muscle cells (LMCs) of WT mice was performed to analyze LMC coverage of lymphatic vessels on multiple days after infection. To define the molecular mechanisms related to this response, we performed cell viability and cell lysis assays and measured killing of LMCs by MRSA‐conditioned supernatant from wild type and mutant MRSA strain(s). Similar experiments were performed using recombinant MRSA toxins.Intravital imaging in mice revealed an acute reduction in both lymphatic vessel contractility and lymph flow after localized MRSA infection. Moreover, chronic lymphatic impairment is observed long after MRSA is cleared and inflammation is resolved. Associated with decreased collecting lymphatic vessel function was the loss and disorganization of lymphatic muscle cells (LMCs), which are critical for lymphatic contraction. In vitro, incubation with MRSA‐conditioned supernatant led to LMC death. Proteomic analysis identified several accessory gene regulator (agr)–controlled MRSA exotoxins that contribute to LMC death. Infection with agr mutant MRSA resulted in sustained lymphatic function compared to animals infected with wild‐type MRSA.Our findings suggest that agr is a promising target to preserve lymphatic vessel function and promote immunity during SSTIs.Support or Funding InformationThis work was supported by the National Institutes of Health under award numbers R21AI097745, DP2OD008780, R01CA214913, and R01HL128168 to Timothy Padera. Dennis Jones was supported in part by the UNCF‐Merck Science Initiative Postdoctoral Fellowship, Burroughs Wellcome Fund Postdoctoral Enrichment Program Award, and NIH NCI F32CA183465.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.