In the last decade, the T cell immunoglobulin and mucin domain 1 (TIM-1) has emerged as a key regulator of innate and adaptive immune responses, representing a promising therapeutic target to be investigated. TIM-1 is widely distributed across immune cells, such as T, B and dendritic cells, where it exerts multiple functions. Despite being well investigated in cancer, transplantation, atopic and autoimmune diseases, several functional aspects of TIM-1 are still unclear. Recently, we have shown a novel function for TIM-1 as adhesion receptor for T helper (Th) 1 and Th17 cells, controlling their recruitment during inflammatory conditions. Neutrophils represent the first leukocyte population recruited to the injured site and several adhesion molecules are implicated in this process. Although neutrophils are classically associated with acute inflammatory processes, they are now emerging as crucial players also in chronic inflammatory diseases, including Alzheimer’s disease (AD). However, the potential involvement of TIM-1 in neutrophil biology has never been investigated. The main goal of this project was to investigate neutrophil TIM-1 expression and its role in neutrophil recruitment during inflammation. By using flow cytometry and immunofluorescence staining, we demonstrated for the first time, that TIM-1 was expressed in mouse and human neutrophils, mainly stored in the cytoplasm under resting conditions. However, neutrophil activation after exposure to different inflammatory stimuli, including chemokines, fMLP, C5a, PMA and toll-like receptor (TLR) ligands rapidly triggered TIM-1 translocation to the cell surface. In the light of previous studies describing TIM-1 as an adhesion molecule and our results showing rapid translocation on neutrophil plasma membrane in response to chemotactic signals, we next tested the involvement of TIM-1 in neutrophil adhesion during inflammatory responses. By using a model of sterile thioglycolate-induced peritonitis, we demonstrated that the systemic blockade of TIM-1 or injection of exogenous neutrophils lacking a TIM- 1 functional domain, strongly reduced neutrophil accumulation in the inflamed peritoneum, indicating that TIM-1 had a role in neutrophil recruitment during acute inflammation. 4 We also found that the oligomeric form of amyloid b 1-42 (Ab1-42) peptide, a potent inflammatory mediator and pivotal key player in the development and progression of AD, strongly upregulated TIM-1 expression on neutrophil surface, suggesting a potential TIM-1 contribution in neutrophil responses during neuroinflammation. By flow cytometry, we demonstrated that TIM-1 expression increases on circulating neutrophils of 3xTg-AD mice, an animal model of AD, compared to sex- and agematched WT controls. Moreover, in 3XTg-AD mice, TIM-1-positive neutrophils accumulated in the meninges and in the choroid plexus, which are main access sites of leukocytes to the inflamed brain. Since a soluble form of TIM-1 (sTIM-1) was detected in several pathological diseases, we also measured sTIM-1 levels in the serum of 3xTg-AD mice. Interestingly, sTIM-1 significantly accumulated in the serum during disease progression, while it remained stable in the controls during aging, indicating TIM-1 as a new potential biomarker for AD. We also investigated the impact of TIM-1 on memory decline and neuropathological changes in 3xTg- AD mice crossed with TIM-1Δmucin mice lacking functional TIM-1. By using different behavioral tests we observed a significant restoration of spatial and associative memory in 3xTg-AD/Tim-1Δmucin mice when compared to 3xTg-AD control animals. Moreover, TIM-1 deficiency led to a drastic reduction of neutrophil accumulation in the brain during early disease and reduced neuropathological features, such as amyloid deposition, microglial activation and tau hyperphosphorylation, suggesting a role for TIM-1 in the induction of brain inflammation and neuropathological changes in an animal model of AD. Collectively, our findings shed a new light on the role of TIM-1 as a novel trafficking receptor for neutrophils suggesting that TIM-1 blockade may have a beneficial effect on the development of acute and chronic inflammatory responses.
|Titolo:||TIM-1 glycoprotein mediates neutrophil peripheral recruitment during inflammation|
ARIOLI, JESSICA (Corresponding)
|Data di pubblicazione:||2020|
|Appare nelle tipologie:||07.13 Doctoral Thesis|