title: Pleural cavity inflammation
title: fibres &amp; FALCs, macrophages &amp; malignancy
titleType: Subtitle
Creators: name: Iqbal, Nadia
Publisher: name: Lancaster University
Year: 2024
Subjects: macrophage
cancer
CARBON NANOTUBES
mesothelioma
Pleural Cavity
inflammation
fat associated lymphoid clusters
pericardium
mediastinum
adipose tissue

description: Malignant pleural mesothelioma (MPM) is a devastating cancer of the
 mesothelial linings caused most commonly by inhalational exposure to
 asbestos fibres. In humans there is a delay of 25-40 years between fibre
 exposure &amp; mesothelioma development. The role of the local immune
 response in the development of mesothelioma in the months and years
 proceeding fibre exposure is unclear. In this work, we aimed to understand
 the sequence of inflammation precipitating events which occur following
 arrival of asbestos-like fibres within the pleural space, to do this we
 utilised NM-401 multi-walled carbon nanotubes (MWCNTs/CNTs).
 
 
 CNTs share a similar fibrous shape, chemical characteristics, and
 bio-persistent properties to asbestos fibres. CNTs are manufactured for
 use in industries such as automotive, textiles, industrial and
 engineering. Environmental &amp; occupational exposure to CNTs is
 increasing annually despite these structures having been shown to mimic
 asbestos exposure leading to mesothelioma-like tumours in murine models.
 In our study, CNTs were injected intra-pleurally (i.pl) into wild type
 mice, pleural cavity lavage and adipose tissues were isolated at various
 time points after injection. Immune cell composition, cytokine and
 chemokine expression and release were determined by flow-cytometry,
 confocal microscopy &amp; multi-plex array. Intrapleural CNT delivery
 resulted in increases in small cavity macrophages (SCMs), specifically the
 Ly6C+ inflammatory macrophage (Inf-Mθ) population within the pleural
 lavage. The population defined as Inf-Mθ were recruited to Fat-Associated
 Lymphoid Clusters (FALCs) of the pericardium, FALCs revealed a significant
 loss of antigen presentation capacity observed by a reduction in MHC-II.
 The secretome of pericardial FALCs in mice exposed to CNTs was compared
 with matched serum &amp; pleural fluid from patients with
 mesothelioma. A noticeably similar secretome to that of human pleural
 fluid but not serum was found, including elevations in CXCL10 and IL-6. We
 reasoned that FALCs in the pleural adipose tissues may contribute to the
 inflammatory response after fibre exposure and in so doing, FALCs of the
 pleural cavity may play a significant role in the early formation of the
 mesothelioma tumour microenvironment.
 
 
 Fluorescence activated cell sorting (FACS) and quantitative polymerase
 chain reaction (qPCR) revealed higher expression of Cxcl10, Il-6 and Ccl2
 expression within CD45- Podaplanin+ (P+) stromal cells of pleural adipose
 tissue compared to the CD45+PDPN- leukocytes following CNT exposure in
 vivo. Further flow cytometric investigations revealed the early release of
 CXCL10 into the pleural cavity from the platelet derived growth factor
 receptor α+ (PDGFRα+) stromal compartment in FALCs. Local delivery of
 anti-CXCL10 blocking antibody into the pleural cavity simultaneously
 during CNT exposure reduced inflammatory myeloid cell recruitment to
 pericardial FALCs. This revealed a mechanistic relationship between FALC
 stromal cell release of CXCL10 and myeloid cell recruitment. In vitro
 mechanistic studies addressed the role of CXCL10 in co-ordination of the
 myeloid cell response; the human monocyte cell line THP-1 was
 differentiated into macrophages and exposed to CNTs. Confocal imaging
 revealed the activation of the DNA damage sensing Stimulator of Interferon
 Genes (STING) pathway. Complementary in vitro studies unravelled
 combinatorial effects of mesothelioma-relevant chemokines (CXCL10, IL-6,
 IL-4) on myeloid cell activation and functionality to improve
 understanding of immunoregulation during fibre-driven inflammation. THP-1
 cells were polarised to an anti-inflammatory pro-tumorigenic phenotype
 when incubated with CXCL10, IL-4 and IL-6 overnight. Analysis of human MPM
 and other cancers that caused effusion within the pleural space, revealed
 a considerably higher level of CXCL10 in MPM pleural fluid. Flow
 cytometric analysis of cells isolated from patient pleural fluid uncovered
 that the cellular infiltrate in MPM and other cancers of the pleural fluid
 is composed of a high level of CD68+ CD14+ macrophages which we believe
 are phenotypically similar to SCMs found in mice.