Excessive localized leukotriene B4 levels dictate poor skin host defense in diabetic mice
Stephanie L. Brandt, Sue Wang, Naiara N. Dejani, Nathan Klopfenstein, Seth Winfree, Luciano Filgueiras, Brian P. McCarthy, Paul R. Territo, C. Henrique Serezani
Stephanie L. Brandt, Sue Wang, Naiara N. Dejani, Nathan Klopfenstein, Seth Winfree, Luciano Filgueiras, Brian P. McCarthy, Paul R. Territo, C. Henrique Serezani
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Research Article Dermatology Inflammation

Excessive localized leukotriene B4 levels dictate poor skin host defense in diabetic mice

Abstract

Poorly controlled diabetes leads to comorbidities and enhanced susceptibility to infections. While the immune components involved in wound healing in diabetes have been studied, the components involved in susceptibility to skin infections remain unclear. Here, we examined the effects of the inflammatory lipid mediator leukotriene B4 (LTB4) signaling through its receptor B leukotriene receptor 1 (BLT1) in the progression of methicillin-resistant Staphylococcus aureus (MRSA) skin infection in 2 models of diabetes. Diabetic mice produced higher levels of LTB4 in the skin, which correlated with larger nonhealing lesion areas and increased bacterial loads compared with nondiabetic mice. High LTB4 levels were also associated with dysregulated cytokine and chemokine production, excessive neutrophil migration but impaired abscess formation, and uncontrolled collagen deposition. Both genetic deletion and topical pharmacological BLT1 antagonism restored inflammatory response and abscess formation, followed by a reduction in the bacterial load and lesion area in the diabetic mice. Macrophage depletion in diabetic mice limited LTB4 production and improved abscess architecture and skin host defense. These data demonstrate that exaggerated LTB4/BLT1 responses mediate a derailed inflammatory milieu that underlies poor host defense in diabetes. Prevention of LTB4 production/actions could provide a new therapeutic strategy to restore host defense in diabetes.

Authors

Stephanie L. Brandt, Sue Wang, Naiara N. Dejani, Nathan Klopfenstein, Seth Winfree, Luciano Filgueiras, Brian P. McCarthy, Paul R. Territo, C. Henrique Serezani

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Figure 5

Skin-macrophages drive detrimental host defense actions in diabetic mice.

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Skin-macrophages drive detrimental host defense actions in diabetic mice...
(A) CT and STZ mice were infected and treated with the BLT1 antagonist once a day for 9 days, and skin biopsies from days 1 and 9 after infection were subjected to IHC staining for macrophages (F4/80) in brown with blue counterstain. Top panels show 40× magnification, and bottom panels show 400× magnification from 3–5 mice from 2–4 experiments. Arrows indicate macrophages. (B) Monocytes and macrophages were depleted in diabetic MMDTR mice as described in the Methods prior to MRSA skin infection. After 6 hours, skin biopsies were collected and sectioned for immunofluorescence staining for neutrophils (Ly6G) shown in red and DAPI counterstain shown in blue. Representative images of 20× magnification from 3–4 mice. White arrows indicate neutrophils. (C) Infection areas of CT, STZ, and DT-treated STZ-MMDTR mice on day 2 after infection with MRSA. (D) Bacterial CFU in the skin CT, STZ, and DT-treated STZ-MMDTR determined 2 days after infection. (E) Percentage of neutrophils (Ly6G+) in the skin of CT, STZ, and DT-treated STZ-MMDTR determined by flow cytometry at day 2 after infection. (F) LTB4 ELISA on tissue homogenates detected 2 days after infection from CT, STZ, and DT-treated STZ-MMDTR mice. Data are mean ± SEM of 3–7 mice from 1–2 experiments. *P < 0.05 vs. CT mice. #P < 0.05 vs. STZ-treated mice. (G–J) Multiplex assay on skin biopsy homogenates 2 days after infection of CT, STZ, and DT-treated STZ-MMDTR CXCL2 (G), MMP8 (H), CCL2 (I), and P-selectin (J). Data are mean ± SEM of 3–7 mice from 1–2 experiments. *P < 0.05 vs. naive mice. #P < 0.05 vs. CT mice. ^P < 0.05 vs. STZ-treated mice.