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 4

Excessive LTB4 production drives poor neutrophil organization and altered chemokine/cytokine production at the site of infection of diabetic mice.

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Excessive LTB4 production drives poor neutrophil organization and altere...
(A) Biopsies were collected from CT and diabetic naive mice and infected mice, and they were treated daily with the BLT1 antagonist on days 1 and 9 after MRSA skin infection and sectioned for histology. Representative images of IHC for neutrophils (Ly6G/C) are stained in brown with blue counterstain from 3–5 mice from 2–4 experiments. Top panels show 4× magnification. Bottom panels show 40× magnification. Black arrows indicate neutrophils. (B) Intravital imaging from the infection site of LysEGFP CT and diabetic mice with frames taken at 0, 10, 20, and 30 minutes. The 30-minute frames include track paths of individual cells. The lines show the cell path and the color refers to the median velocity of the cell (red is fast, blue is slow). (C) Left graph: Median velocity of GFP+ cells. Middle graph: Track displacement of GFP+ cells. Right graph: Ratio of displacement/track duration to determine the directionality of GFP+ cells. (D) Tissue homogenate from CT and diabetic mice that were infected or not and treated with the BLT1 antagonist once a day for 9 days were subjected to a multiplex assay, and the heatmap of analytes from 3–8 mice are shown. (E–G)Skin homogenates were processed and subjected to ELISA for RAGE, ICAM-1, and CXCL2 abundance. Data are mean ± SEM of 3–8 mice from 2–4 experiments. *P < 0.05 vs. naive mice. #P < 0.05 vs. CT mice. ^P < 0.05 vs. STZ mice treated with vehicle control ointment.