Crosslinking of membrane CD13 in human neutrophils mediates phagocytosis and production of reactive oxygen species, neutrophil extracellular traps and proinflammatory cytokines

Developing Cell-Membrane-Associated Liposomes for Liver Diseases

Over the past decade, a marked escalation in the prevalence of hepatic pathologies has been observed, adversely impacting the quality of life for many. The predominant therapeutic strategy for liver diseases has been pharmacological intervention; however, its efficacy is often constrained. Currently, liposomes are tiny structures that can deliver drugs directly to targeted areas, enhancing their effectiveness. Specifically, cell membrane-associated liposomes have gained significant attention. Despite this, there is still much to learn about the binding mechanism of this type of liposome. Thus, this review comprehensively summarizes relevant information on cell membrane-associated liposomes, including their clinical applications and future development directions. First, we will briefly introduce the composition and types of cell membrane-associated liposomes. We will provide an overview of their structure and discuss the various types of liposomes associated with cell membranes. Second, we will thoroughly discuss various strategies of drug delivery using these liposomes. Lastly, we will discuss the application and clinical challenges associated with using cell membrane-associated liposomes in treating liver diseases. We will explore their potential benefits while also addressing the obstacles that need to be overcome. Furthermore, we will provide prospects for future development in this field. In summary, this review underscores the promise of cell membrane-associated liposomes in enhancing liver disease treatment and highlights the need for further research to optimize their utilization. In summary, this review underscores the promise of cell membrane-associated liposomes in enhancing liver disease treatment and highlights the need for further research to optimize their utilization.

Anaplasma phagocytophilum invasin AipA interacts with CD13 to elicit Src kinase signaling that promotes infection

Host-microbe interactions that facilitate entry into mammalian cells are essential for obligate intracellular bacterial survival and pathogenesis. Anaplasma phagocytophilum is an obligate intracellular bacterium that invades neutrophils to cause granulocytic anaplasmosis. The invasin-receptor pairs and signaling events that induce Anaplasma uptake are inadequately defined. A. phagocytophilum invasion protein A orchestrates entry via residues 9-21 (AipA9-21) engaging an unknown receptor. Yeast two-hybrid screening suggested that AipA binds within C-terminal amino acids 851-967 of CD13 (aminopeptidase N), a multifunctional protein that, when crosslinked, initiates Src kinase and Syk signaling that culminates in endocytosis. Co-immunoprecipitation validated the interaction and confirmed that it requires the AipA N-terminus. CD13 ectopic expression on non-phagocytic cells increased susceptibility to A. phagocytophilum infection. Antibody blocking and enzymatic inhibition experiments found that the microbe exploits CD13 but not its ectopeptidase activity to infect myeloid cells. A. phagocytophilum induces Src and Syk phosphorylation during invasion. Inhibitor treatment established that Src is key for A. phagocytophilum infection, while Syk is dispensable and oriented the pathogen-invoked signaling pathway by showing that Src is activated before Syk. Disrupting the AipA-CD13 interaction with AipA9-21 or CD13781-967 antibody inhibited Src and Syk phosphorylation and also infection. CD13 crosslinking antibody that induces Src and Syk signaling restored infectivity of anti-AipA9-21-treated A. phagocytophilum. The bacterium poorly infected CD13 knockout mice, providing the first demonstration that CD13 is important for microbial infection in vivo. Overall, A. phagocytophilum AipA9-21 binds CD13 to induce Src signaling that mediates uptake into host cells, and CD13 is critical for infection in vivo.

IMPORTANCE

Diverse microbes engage CD13 to infect host cells. Yet invasin-CD13 interactions, the signaling they invoke for pathogen entry, and the relevance of CD13 to infection in vivo are underexplored. Dissecting these concepts would advance fundamental understanding of a convergently evolved infection strategy and could have translational benefits. Anaplasma phagocytophilum infects neutrophils to cause granulocytic anaplasmosis, an emerging disease for which there is no vaccine and few therapeutic options. We found that A. phagocytophilum uses its surface protein and recently identified protective immunogen, AipA, to bind CD13 to elicit Src kinase signaling, which is critical for infection. We elucidated the AipA CD13 binding domain, which CD13 region AipA engages, and established that CD13 is key for A. phagocytophilum infection in vivo. Disrupting the AipA-CD13 interaction could be utilized to prevent granulocytic anaplasmosis and offers a model that could be applied to protect against multiple infectious diseases.

Detailed phenotyping reveals diverse and highly skewed neutrophil subsets in both the blood and airways during active tuberculosis infection

Introduction

Neutrophils play a complex and important role in the immunopathology of TB. Data suggest they are protective during early infection but become a main driver of immunopathology if infection progresses to active disease. Neutrophils are now recognized to exist in functionally diverse states, but little work has been done on how neutrophil states or subsets are skewed in TB disease.

Methods

To address this, we carried out comprehensive phenotyping by flow cytometry of neutrophils in the blood and airways of individuals with active pulmonary TB with and without HIV co-infection recruited in Durban, South Africa.

Results

Active TB was associated with a profound skewing of neutrophils in the blood toward phenotypes associated with activation and apoptosis, reduced phagocytosis, reverse transmigration, and immune regulation. This skewing was also apparently in airway neutrophils, particularly the regulatory subsets expressing PDL-1 and LOX-1. HIV co-infection did not impact neutrophil subsets in the blood but was associated with a phenotypic change in the airways and a reduction in key neutrophil functional proteins cathelicidin and arginase 1.

Discussion

Active TB is associated with profound skewing of blood and airway neutrophils and suggests multiple mechanisms by which neutrophils may exacerbate the immunopathology of TB. These data indicate potential avenues for reducing neutrophil-mediated lung pathology at the point of diagnosis.

CD13 facilitates immune cell migration and aggravates acute injury but promotes chronic post-stroke recovery

INTRODUCTION

Acute stroke leads to the activation of myeloid cells. These cells express adhesion molecules and transmigrate to the brain, thereby aggravating injury. Chronically after stroke, repair processes, including angiogenesis, are activated and enhance post-stroke recovery. Activated myeloid cells express CD13, which facilitates their migration into the site of injury. However, angiogenic blood vessels which play a role in recovery also express CD13. Overall, the specific contribution of CD13 to acute and chronic stroke outcomes is unknown.

METHODS

CD13 expression was estimated in both mice and humans after the ischemic stroke. Young (8-12 weeks) male wild-type and global CD13 knockout (KO) mice were used for this study. Mice underwent 60 min of middle cerebral artery occlusion (MCAO) followed by reperfusion. For acute studies, the mice were euthanized at either 24- or 72 h post-stroke. For chronic studies, the Y-maze, Barnes maze, and the open field were performed on day 7 and day 28 post-stroke. Mice were euthanized at day 30 post-stroke and the brains were collected for assessment of inflammation, white matter injury, tissue loss, and angiogenesis. Flow cytometry was performed on days 3 and 7 post-stroke to quantify infiltrated monocytes and neutrophils and CXCL12/CXCR4 signaling.

RESULTS

Brain CD13 expression and infiltrated CD13+ monocytes and neutrophils increased acutely after the stroke. The brain CD13+lectin+ blood vessels increased on day 15 after the stroke. Similarly, an increase in the percentage area CD13 was observed in human stroke patients at the subacute time after stroke. Deletion of CD13 resulted in reduced infarct volume and improved neurological recovery after acute stroke. However, CD13KO mice had significantly worse memory deficits, amplified gliosis, and white matter damage compared to wild-type animals at chronic time points. CD13-deficient mice had an increased percentage of CXCL12+cells but a reduced percentage of CXCR4+cells and decreased angiogenesis at day 30 post-stroke.

CONCLUSIONS

CD13 is involved in the trans-migration of monocytes and neutrophils after stroke, and acutely, led to decreased infarct size and improved behavioral outcomes. However, loss of CD13 led to reductions in post-stroke angiogenesis by reducing CXCL12/CXCR4 signaling.

Lipid Metabolism Reprogramming of Immune Cells in Acne: An Update

Acne vulgaris is one of the most widespread skin conditions and the main reason for visiting a dermatologist. Inflammatory response and abnormal infiltrations of immune cells are the main pathogenesis of acne. The increased lipid is the prerequisite for the acne, and the perturbation of lipid composition and content is consistent with the severity of acne. Furthermore, the increased lipid production not only contributes to the occurrence and development of acne, but also sensitizes the function of immune cells. The lipid metabolic dysfunction aggravates the severity of local tissue and provides pro-inflammatory-cytokine cues, which indicates the crucial roles of lipid metabolism on immune cells. Recent advances have demonstrated the lipid metabolism reprogramming of various immune cells in acne lesion. The abnormal lipid accumulation, lipolysis, and fatty acid oxidation lead to the activation and differentiation of immune cells, which promotes the pro-inflammatory cytokines production. Thus, this review discusses the emerging role of lipid metabolism reprogramming of immune cells in the progress of acne and aims to constitute food for others' projects involved in acne research.