Macrophage Polarization during Murine Lyme Borreliosis

Abstract

Infection of C3H mice with Borrelia burgdorferi, the causative agent of Lyme disease, reliably produces an infectious arthritis and carditis that peak around 3 weeks postinfection and then spontaneously resolve. Macrophage polarization has been suggested to drive inflammation, the clearance of bacteria, and tissue repair and resolution in a variety of infectious disease models. During Lyme disease it is clear that macrophages are capable of clearing Borrelia spirochetes and exhausted neutrophils; however, the role of macrophage phenotype in disease development or resolution has not been studied. Using classical (NOS2) and alternative (CD206) macrophage subset-specific markers, we determined the phenotype of F4/80 ؉ macrophages within the joints and heart throughout the infection time course. Within the joint, CD206؉ macrophages dominated throughout the course of infection, and NOS2؉ macrophage numbers became elevated only during the peak of inflammation. We also found dual NOS2 ؉ CD206 ؉ macrophages which increased during resolution. In contrast to findings for the ankle joints, numbers of NOS2 ؉ and CD206؉ macrophages in the heart were similar at the peak of inflammation. 5-Lipoxygenase-deficient (5-LOX ؊/؊ ) mice, which display a failure of Lyme arthritis resolution, recruited fewer F4/80 ؉ cells to the infected joints and heart, but macrophage subset populations were unchanged. These results highlight differences in the inflammatory infiltrates during Lyme arthritis and carditis and demonstrate the coexistence of multiple macrophage subsets within a single inflammatory site. Macrophages play a dynamic role in the immune system as both inflammatory and anti-inflammatory mediators. Their phenotype is highly flexible and dependent upon the cytokine stimulus of the microenvironment they infiltrate (1). They are routinely classified as proinflammatory and immunomodulatory (M1) or anti-inflammatory and remodeling (M2) macrophages, but their phenotype actually lies within a spectrum of inflammatory to anti-inflammatory polarization (2). The language within the field is currently being modified to ensure that the macrophages being studied have a clear phenotypic description, and we use the nomenclature recently suggested (3). Within the last 15 years, much work has been done to phenotypically characterize macrophage subsets. Identifying unique surface and intracellular markers, as well as understanding transcriptional regulation, has allowed the importance of specific macrophage phenotypes in infectious and autoimmune models to be uncovered.Classically activated M1 macrophages are proinflammatory cells capable of destroying pathogens, tumor cells, and various foreign compounds. Stimulation of undifferentiated macrophages with lipopolysaccharide (LPS) and gamma interferon (IFN-␥), or tumor necrosis factor alpha (TNF-␣), induces polarization to the M1 phenotype (4, 5). They can be recognized both in vitro and in vivo by the production of nitric oxide species (NOS), as well as other proinflammatory molecules, including ...

Metabolites of prostaglandin synthases as potential biomarkers of Lyme disease severity and symptom resolution

“…It lowered the upregulation of cPLA 2 , PGE 2 , PGJ 2 on days 7, 14, and 21, respectively, seen in WT miceBlaho et al [29]C3H, DBA, and COX-2 −/− mice B. burgdorferi strain N40 (final inoculum: 1 × 10 5 )0–35- Eicosanoid levels were generally elevated in C3H mice, while DBA mice followed similar but muted trends in eicosanoid fluctuation- Some eicosanoids, such as LTB 4 and PD 1 were significantly increased during B. burgdorferi infection in C3H, but not DBA mice- COX-2 −/− mice displayed a dramatic reduction in LTC 4 , LTE 4 , 5-HETE compared to WT following B. burgdorferi infectionBlaho et al [44]C3H/Hej and 5-LOX −/− mice B. burgdorferi strain N40 (final inoculum: 1 × 10 5 )0–35- 5-LOX, FLAP, and LTB 4 were upregulated in WT ankle joints on days 7–14 post- B. burgdorferi infection- 5-LOX −/− mice had greater ankle swelling and arthritis scores than WT on days 7–28 and showed a failure to resolve inflammation compared to WT animals- Spirochete clearance and IgM levels were equal in both groups, but 5-LOX −/− mice had lower IgG levels than WT on day 28 post-treatmentDumlao et al [46]C2H/HeJ mice B. burgdorferi strain N40 (final inoculum: 1 × 10 5 ); SO diet- high in n-6 FA’s vs. FO diet high in n-3 FA’s0–25- Diet did not have any effect on Lyme arthritis or carditis scores, number of spirochetes, or cellular makeup in day 25 post-treatment- Fish oil (FO) diet resulted in a global shift toward EPA- and DHA-metabolites during B. burgdorferi infection vs. SO (soybean oil) diet which resulted in an increase in AA- and LA-derived metabolitesLasky et al [45]C3H and 5-LOX −/− mice B. burgdorferi strain N40 (final inoculum: 1 × 10 5 )0–56- M2 and rM macrophages were decreased in the ankle joints of 5-LOX −/− mice on day 21, compared to wild-type. There were no differences in the number of M1 macrophages- In the heart tissue, 5-LOX −/− mice had fewer M2 macrophages, but not M1 or rM macrophages, compared to WT on day 21 post-treatment- By day 56, there were no difference in macrophage subset or number …”

Leukotriene B4 receptor BLT1 signaling is critical for neutrophil apoptosis and resolution of experimental Lyme arthritis

“…Inflammatory cells were isolated from ankle joints and processed for flow cytometry as described . Live cells were determined using trypan blue exclusion.…”

“…27 In addition, BLT1 is highly expressed on murine neutrophils and M2 macrophages 28 which make up the majority of the cellular infiltrate in the joints during experimental Lyme arthritis. 29 Since the role of BLT2 in arthritis models is largely unknown, we chose to focus on BLT1 in the current study. We show that LTB 4 signaling through BLT1 unexpectedly participates in the initiation of apoptosis through the induction of the death-inducing signaling complex (DISC).…”

“…Inflammatory cells were isolated from ankle joints and processed for flow cytometry as described. 29 Live cells were determined using trypan blue exclusion. About 1 × 10 6 cells were blocked in a 96-well U bottom plate (Greiner Bio-One, Kremsmunster, Austria) with Fc Block (anti-CD16/ CD32) (eBioscience, San Diego, CA, USA) for 15 minutes at 4°C.…”

“…This approach has the advantage of leaving other 5‐LO‐mediated pathways intact, especially those important for inflammation resolution, such as specialized pro‐resolving mediators (SPM) . In addition, BLT1 is highly expressed on murine neutrophils and M2 macrophages which make up the majority of the cellular infiltrate in the joints during experimental Lyme arthritis . Since the role of BLT2 in arthritis models is largely unknown, we chose to focus on BLT1 in the current study.…”