The Leukotriene B4 and its Receptor BLT1 Act as Critical Drivers of Neutrophil Recruitment in Murine Bullous Pemphigoid-Like Epidermolysis Bullosa Acquisita

Abstract

Recruitment of neutrophils and eosinophils into the skin is a hallmark of pemphigoid diseases. The molecular cues regulating granulocyte recruitment into the skin and the individual contributions of neutrophils and eosinophils to pemphigoid diseases are, however, poorly understood. The lipid mediator leukotriene B (LTB) is a potent granulocyte chemoattractant and is abundant in the skin blister fluid of bullous pemphigoid (BP) patients, but its pathogenic significance is unknown. Using mouse models of BP-like epidermolysis bullosa acquisita and of BP, we show that LTB and its receptor BLT1 act as critical drivers of neutrophil entry into the skin upon antibody deposition at the dermal-epidermal junction. Mice deficient in 5-lipoxygenase, a key enzyme in LTB biosynthesis, or in BLT1 exhibited dramatic resistance to neutrophil recruitment and, consequently, skin inflammation. Accordingly, liquid chromatography-mass spectrometry, used to comprehensively profile lipid mediator generation in the first 48 hours after antibody deposition, showed a pronounced parallel increase in LTB and in neutrophils in the skin. Subsequent mechanistic studies in BP-like epidermolysis bullosa acquisita uncovered that neutrophils are necessary for skin inflammation, whereas eosinophils are dispensable, thus identifying neutrophils as major culprits of blister formation. Our results highlight LTB/BLT1 as absolutely critical drivers of murine pemphigoid disease-like skin inflammation.

Mechanisms of Autoantibody-Induced Pathology

“…Of these, C5a, GM-CSF, CXCL1/2, TNF, and leukotriene B4 promote inflammation (44, 380, 386–389), while IL-1ra and IL-6 have profound anti-inflammatory activities (390, 391). These insights have almost exclusively been obtained from EBA mouse models, where inhibition of C5a, GM-CSF, CXCL1/2, or TNF impaired disease induction and/or ameliorated or even improved already manifest EBA.…”

From bench to bedside: evolving therapeutic targets in autoimmune blistering disease

“…The importance of complement activation at the DEJ and its downstream effectors in BP is underscored by the contribution of C5a and leukotriene B 4 (LTB 4 ) in neutrophil recruitment . The C5a‐LTB 4 axis promotes neutrophil activation and extravasation in a sequential manner.…”

“…LTB 4 directs neutrophil extravasation from the vasculature and mediates additional granulocyte recruitment . Mouse models deficient in multiple components of this axis including C5, 5‐lipoxygenase and LTB 4 receptor 1 exhibited decreased skin inflammation . Still, the role of complement remains controversial.…”

“…The importance of complement activation at the DEJ and its downstream effectors in BP is underscored by the contribution of C5a and leukotriene B 4 (LTB 4 ) in neutrophil recruitment. [189][190][191][192] The C5a-LTB 4 axis promotes neutrophil activation and extravasation in a sequential manner. Production of C5a near the DEJ and engagement with its respective receptor on neutrophils boosts LTB 4 release.…”

“…192 Mouse models deficient in multiple components of this axis including C5, 5-lipoxygenase and LTB 4 receptor 1 exhibited decreased skin inflammation. 191,193 Still, the role of complement remains controversial. While the extent of complement activation correlates with disease severity in BP, tissue destruction can still occur independently of complement.…”