Polarized Lung Inflammation and Tie2/Angiopoietin-Mediated Endothelial Dysfunction during SevereOrientia tsutsugamushiInfection

Abstract

27 of Texas Medical Branch, 301 University Blvd, Galveston, TX 77555-0435 28 #d Current Address: Department of Physiology, OUHSC, 940 Stanton Young Blvd., Oklahoma 29 City, OK 73104-5042 30 31 32 33 * Corresponding Authors: Jinjun Liu: jupet@163.com; Lynn Soong: lysoong@utmb.edu 34 35 36 Abstract 38Orientia tsutsugamushi infection can cause acute lung injury and high mortality in humans; 39 however, the underlying mechanisms are unclear. Here, we tested a hypothesis that dysregulated 40 pulmonary inflammation and Tie2-mediated endothelial malfunction contribute to lung damage. 41 Using a murine model of lethal O. tsutsugamushi infection, we demonstrated pathological 42 characteristics of vascular activation and tissue damage: 1) a significant increase of ICAM-1, 43 VEGFR2, and angiopoietin-2 (Ang2) proteins in inflamed tissues and lung-derived endothelial 44 cells (EC), 2) a progressive loss of endothelial quiescent and junction proteins (Ang1, VE-45 cadherin/CD144, occuludin), and 3) a profound impairment of Tie2 receptor at the 46 transcriptional and functional levels. In vitro infection of primary human EC cultures and serum 47 52 (CD206 + CD64 + CD11b + Ly6G -) cells. In vitro studies indicated extensive bacterial replication in 53 M2-type, but not M1-type, MΦs, implying the protective and pathogenic roles of M1-skewed 54 responses. This is the first detailed investigation of lung cellular immune responses during acute 55 O. tsutsugamushi infection. It uncovers specific biomarkers for vascular dysfunction and M1-56 skewed inflammatory responses, highlighting future therapeutic research for the control of this 57 neglected tropical disease.58 59 4 Author Summary 60Scrub typhus is a life-threatening disease, infecting an estimated one million people yearly. 61Acute lung injury is the most common clinical observation; however, its pathogenic biomarkers 62 and mechanisms of progression remain unknown. Here, we used a lethal infection mouse model 63 that parallels certain aspects of severe scrub typhus, primary human endothelial cell cultures, and 64 patient sera to define pathogenic biomarkers following Orientia tsutsugamushi infections. We 65 found a significant increase in the levels of endothelial activation/stress markers (angiopoietins 66 and ICAM-1) in infected mouse lungs and in patient sera, but a progressive loss of endothelium-67 specific Tie2 receptor and junction proteins (VE-cadherin), at severe stages of disease. These 68 signs of vasculature disruption positively correlated with the timing and magnitude of 69 recruitment/activation of proinflammatory MΦ subsets in infected lungs. Bacterial growth in 70 vitro was favored in M2-like, but not in M1-like, MΦs. This study, for the first time, reveals 71 endothelial malfunction and dysregulated inflammatory responses, suggesting potential 72 therapeutic targets to ameliorate tissue damage and pathogenesis. 73 74 Scrub typhus is a febrile and potentially lethal illness that infects an estimated one million 75 individuals per year [1]. The disease is ca...

COVID-19-associated vasculitis and vasculopathy

“…Dysregulated inflammation is particularly deleterious and often associated with endothelial cell dysfunction. Trent et al [ 31 ] reported dysregulated pulmonary inflammation and Tie-2-related endothelial dysfunction contributing to lung damage and mortality in a murine model of Orienta Tsutsugamushi infection. Tissue findings included a high level of Ang-2 proteins in pulmonary endothelial cells, a progressive loss of endothelial cell quiescent and junction proteins, and a substantial decrease in Tie-2 receptor at the transcriptional and functional levels.…”

Orientia Tsutsugamushi Infection Stimulates Syk-Dependent Responses and Innate Cytosolic Defenses in Macrophages

“…Bacteria were added at a multiplicity of infection (MOI) of 5 or 10 and centrifuged at 2,000 RPM for 5 min to synchronize infection. The Karp strain of O. tsutsugamushi was utilized for all infections using the same bacterial stocks prepared from Vero cells, as described previously [24,27]. Experiments were performed in triplicate or quadruplicate.…”

“…Monocytes and Ms are significant sources of type 1 cytokines, including IL-12 and TNF, during infectious processes [29,30]. Considering that animal models of scrub typhus display robust M recruitment and type 1 responses in multiple organs [14,25,27], we evaluated whether Sykdependent signaling may play a role in generating such responses in vitro. After infection with O. tsutsugamushi (5 MOI), we observed statistically significant increases in M Il12p40, Tnf, and Il27p28 transcript levels at 4 hpi, with peak expression for all cytokines occurring at 6 hpi (Figure 3).…”

CCR2 Deficiency Impairs Ly6Clo and Ly6Chi Monocyte Responses in Orientia tsutsugamushi Infection

“…O. tsutsugamushi has long been known to be a potent inducer of monocyte-related chemokines in humans and mice ( 2 – 4 ). Robust evidence supports a macrophage/monocyte tropism for this pathogen in blood and tissue ( 1 , 5 , 6 ) and strong macrophage responses in infected tissues ( 7 , 8 ). Moreover, O. tsutsugamushi infects and replicates in human blood-derived monocytes ex vivo , as it does in neutrophils ( 9 , 10 ).…”

“…Similarly, in the lung of human patients, the typical finding is an interstitial pneumonia, which seems to be associated with disease severity ( 34 – 36 ). While it was shown that Orientia drives M1 responses in the lungs ( 8 ), no mechanistic studies on chemokine-driven recruitment of myeloid cells have been provided yet. In the present study, we hypothesized that CCR2 is critical for the development of pulmonary monocyte/macrophage responses and associated bacterial clearance in Orientia infection.…”