LL-37 causes cell death of human nasal epithelial cells, which is inhibited with a synthetic glycosaminoglycan.

Andrew J Thomas,Jeremiah A Alt,Brock M Davis,Abigail Pulsipher,Noam A Cohen

doi:10.1371/journal.pone.0183542

Andrew J Thomas, Jeremiah A Alt + Show 3 more

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https://doi.org/10.1371/journal.pone.0183542

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Abstract

LL-37 is an immune peptide that regulates innate and adaptive immune responses in the upper airways. Elevated levels of LL-37 have been linked to cell death and inflammatory diseases, such as chronic rhinosinusitis (CRS). Glycosaminoglycans (GAGs) are polysaccharides that are found on respiratory epithelial cells and serve important roles in mucosal surface repair. Recent findings suggest that a synthetic glycosaminoglycan (GM-0111) can protect against LL-37-induced sinonasal mucosal inflammation and cell death in a murine model of acute RS. Herein, we elucidated the mechanisms by which LL-37 causes sinonasal inflammation and how GM-0111 can prevent these mechanisms. When challenged with LL-37, human nasal epithelial cells (HNEpCs) and mouse macrophages (J774.2) demonstrated increased release of adenosine triphosphate (ATP) and interleukin (IL)-6 and -8, as well as cell death and lysis. These cellular responses were all blocked dose-dependently by pre-treatment with GM-0111. We identified that LL-37-induced cell death is associated with caspase-1 and -8 activation, but not activation of caspase-3/7. These responses were again blocked by GM-0111. Our data suggest that LL-37 causes cellular death of HNEpCs and macrophages through the pro-inflammatory necrotic and/or pyroptotic pathways rather than apoptosis, and that a GM-0111 is capable of inhibiting these pro-inflammatory cellular events.

Highlights

IntroductionChronic rhinosinusitis (CRS) is a debilitating condition of sinonasal mucosal inflammation that affects up to 49 million Americans.[1,2,3,4,5] Patients with CRS experience significant declines in quality of life more disabling than other chronic conditions such as coronary heart disease and Parkinson’s Disease.[6,7,8,9,10,11] Despite its large impact on society, the pathogenesis of this condition remains unclear, as CRS is complex with multiple etiologies (e.g., allergen, bacterial, viral, or fungal exposure).[12,13,14,15] Regardless of etiology, a seemingly unchecked state of persistent inflammation is common in most patients
For human nasal epithelial cells (HNEpCs), mean adenosine triphosphate (ATP) levels were increased from 9.8 nM ± 0.94 with no treatment to 112.6 nM ± 2.96 with 10 μM LL-37 (P < 0.0001), and levels were decreased to 12.44 ± 1.43 when pre-treated with 100 μg/mL GM-0111 in addition to the 10 μM LL-37 (P < 0.0001 for comparison to LL-37 alone)
For J774.2 cells, mean ATP levels were increased from 2.27 nM ± 0.28 with no treatment to 9.15 nM ± 3.13 with 10 μM LL-37 (P < 0.001), and levels were decreased to 2.79 ± 0.72 when pre-treated with 100 μg/mL GM0111 (P < 0.001 for comparison to LL-37 alone)

Summary

Introduction

Chronic rhinosinusitis (CRS) is a debilitating condition of sinonasal mucosal inflammation that affects up to 49 million Americans.[1,2,3,4,5] Patients with CRS experience significant declines in quality of life more disabling than other chronic conditions such as coronary heart disease and Parkinson’s Disease.[6,7,8,9,10,11] Despite its large impact on society, the pathogenesis of this condition remains unclear, as CRS is complex with multiple etiologies (e.g., allergen, bacterial, viral, or fungal exposure).[12,13,14,15] Regardless of etiology, a seemingly unchecked state of persistent inflammation is common in most patients.

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