Mycobacterial trehalose 6,6′-dimycolate induced vascular occlusion is accompanied by subendothelial inflammation

Abstract

Mycobacterium tuberculosis (MTB) is a pathogen that infects and kills millions yearly. The mycobacterium's cell wall glycolipid trehalose 6,6'-dimycolate (TDM) has been used historically to model MTB induced inflammation and granuloma formation. Alterations to the model can significantly influence the induced pathology. One such method incorporates intraperitoneal preexposure, after which the intravenous injection of TDM generates pathological damage effectively mimicking the hypercoagulation, thrombus formation, and tissue remodeling apparent in lungs of infected individuals. The purpose of these experiments is to examine the histological inflammation involved in the TDM mouse model that induces development of the hemorrhagic response. TDM induced lungs of C57BL/6 mice to undergo granulomatous inflammation. Further histological examination of the peak response demonstrated tissue remodeling consistent with hypercoagulation. The observed vascular occlusion indicates that obstruction likely occurs due to subendothelial localized activity leading to restriction of blood vessel lumens. Trichrome staining revealed that associated damage in the hypercoagulation model is consistent with intra endothelial cell accumulation of innate cells, bordered by collagen deposition in the underlying parenchyma. Overall, the hypercoagulation model represents a comparative pathological instrument for understanding mechanisms underlying development of hemorrhage and vascular occlusion seen during MTB infection.

Recombinant Human Lactoferrin Reduces Inflammation and Increases Fluoroquinolone Penetration to Primary Granulomas During Mycobacterial Infection of C57Bl/6 Mice

“…Concurrently, the lactoferrin-treated mice exhibited granulomatous responses with maintained vascular structures and open alveolar spaces. Acute inflammation and reactivity during Mtb infection occurs primarily peripheral to vascular regions, coinciding with destruction in continuity of endothelial lined blood vessels ( Hunter et al 2018 ; Hwang et al 2019 ). In the experiments presented in this report, lactoferrin treatment allowed greater regions of lung tissue, and alveolar spaces, to remain unobstructed, as evident using the PECAM-1 endothelial surface marker.…”

“…Fixed lung was embedded in paraffin, sectioned, and stained for immunohistochemical examination, similar to methods described ( Hwang et al 2019 ), diluted at 1:2000, was performed according to manufacturer’s instructions with a modification of 20 min at low pH for antigen retrival, and visualized using standard HRP techniques and DAB chromogen using Dako reagents (Dako, Agilent, Santa Clara, CA). In a similar manner, M1-like marker CD38 (Invitrogen, ThermoFisher, Cat# 14-0381-02), diluted at 1:1000, M2-like marker CD 206 (Bioss, Cat# bs-4727R), diluted at 1:1000, and endothelial cell marker CD31/PECAM-1 (Cell Signaling, Cat# 77699T) diluted at 1:200 were used for visualization on serial slide sections.…”

Mycobacterial Trehalose 6,6′-Dimycolate–Induced M1-Type Inflammation

“…Initially, Bloch and Noll 17 (1955) utilized cord factor to mimic pathologies seen in early primary human disease, including changes to fibrinolytic activity 12,13 and thrombosis. 14 Perez et al 18 successfully repeated these experiments using purified TDM; Donnachie et al 19 and Hwang et al 20 built on this using molecular tools to further examine early events in extravascular coagulation. Alternative models of the primary TB response were developed using administered TDM to initiate a synchronized transient granulomatous response 21e23 ; these models are extremely effective to assess monocyte-macrophage factors involved in primary granuloma pathogenesis.…”