Allograft inflammatory factor-1 in myeloid cells drives autoimmunity in type 1 diabetes

Characterizing the immune landscape of tumor-infiltrating lymphocytes in non-small cell lung cancer

Tumor-Infiltrating Lymphocytes (TILs) immunotherapy is a highly promising treatment for Non-small Cell Lung Cancer (NSCLC), which is responsible for 18% of all cancer-related deaths. The heterogeneity of TILs remains poorly understood. Here, we utilized combined single-cell RNA (scRNA)/T cell receptor sequencing (scTCR-seq) data from lung adenocarcinoma (LUAD) patients. Naïve CD4+ and effector memory CD8+ T cells were increased in tumor tissue compared with circulating blood samples. Activated signaling pathways were detected, and GZMA was identified as a potential novel diagnostic biomarker. During the transitional phase, macrophages (FTL) and dendritic (AIF1) cells transported the most CD3 TCR clones to T cells, while cytotoxicity CD8+ T (NKG7) cells transported to terminal exhausted CD8+ T cells. In both transition and expansion phases, T helper cells (CXCL13) are transported to regulatory T cells (Tregs). Additionally, we investigated the expression profiles of key cytokines, checkpoint receptors, and their ligands. Cytotoxicity CD8+ T cells (CCL5 and IFNG), T helper cells (FTL, TNFRSF4, and TIGIT), and regulatory T cells (CTLA4, TIGIT and FTL) exhibited functional roles in both primary and metastatic tumor stages. Taken together, our study provides a single-cell resolution of the TIL immune landscape and suggests potential treatment strategies to overcome drug resistance.

Targeting allograft inflammatory factor 1 reprograms kidney macrophages to enhance repair

The role of macrophages (MΦs) remains incompletely understood in kidney injury and repair. The plasticity of MΦs offers an opportunity to polarize them toward mediating injury resolution in both native and transplanted kidneys undergoing ischemia and/or rejection. Here, we show that infiltrating kidney MΦs augmented their own allograft inflammatory factor 1 (AIF-1) expression after injury. Aif1 genetic deletion led to MΦ polarization toward a reparative phenotype while halting the development of kidney fibrosis. The enhanced repair was mediated by higher levels of antiinflammatory and proregenerative markers, leading to a reduction in cell death and an increase in proliferation of kidney tubular epithelial cells after ischemia followed by reperfusion injury (I/RI). Adoptive transfer of Aif1-/- MΦs into Aif1+/+ mice conferred protection against I/RI. Conversely, depletion of MΦs reversed the tissue-reparative effects in Aif1-/- mice. We further demonstrated increased expression of AIF-1 in human kidney biopsies from native kidneys with acute kidney injury or chronic kidney disease, as well as in biopsies from kidney allografts undergoing acute or chronic rejection. We conclude that AIF-1 is a MΦ marker of renal inflammation, and its targeting uncouples MΦ reparative functions from profibrotic functions. Thus, therapies inhibiting AIF-1 when ischemic injury is inevitable have the potential to reduce the global burden of kidney disease.

Mechanical regulation of macrophage metabolism by allograft inflammatory factor 1 leads to adverse remodeling after cardiac injury

Myocardial infarction (MI) mobilizes macrophages, the central protagonists of tissue repair in the infarcted heart. Although necessary for repair, macrophages also contribute to adverse remodeling and progression to heart failure. In this context, specific targeting of inflammatory macrophage activation may attenuate maladaptive responses and enhance cardiac repair. Allograft inflammatory factor 1 (AIF1) is a macrophage-specific protein expressed in a variety of inflammatory settings, but its function after MI is unknown. Here we identify a maladaptive role for macrophage AIF1 after MI in mice. Mechanistic studies show that AIF1 increases actin remodeling in macrophages to promote reactive oxygen species-dependent activation of hypoxia-inducible factor (HIF)-1α. This directs a switch to glycolytic metabolism to fuel macrophage-mediated inflammation, adverse ventricular remodeling and progression to heart failure. Targeted knockdown of Aif1 using antisense oligonucleotides improved cardiac repair, supporting further exploration of macrophage AIF1 as a therapeutic target after MI.

Proteome-wide Mendelian randomization highlights AIF1 and HLA-DQA2 as targets for primary sclerosing cholangitis

BACKGROUND

Primary sclerosing cholangitis (PSC) is a kind of cholestatic liver disease without effective therapies and its pathogenesis is largely unknown.

METHODS

We performed the proteome-wide Mendelian randomization (MR) design to estimate the causal associations of protein levels with PSC risk. Therein, genetic associations with 4,907 plasma protein levels were extracted from a proteome-wide genome-wide association study (GWAS) with 35,559 individuals and those with PSC were obtained from the International PSC Study Group (2,871 cases and 12,019 controls) and the FinnGen study (1,491 cases and 301,383 controls). The colocalization analysis was performed to detect causal variants shared by proteins and PSC. The identified proteins were further enriched in pathways and diseases. A phenome-wide association screening was performed and potential drugs were assessed as well.

RESULTS

The results indicated that genetically predicted plasma levels of 14 proteins were positively associated with an increased risk of PSC and 8 proteins were inversely associated with PSC risk in both PSC GWAS data sets, and they all survived in sensitivity analyses. The colocalization indicated that AIF1 (allograft inflammatory factor 1) and HLA-DQA2 (major histocompatibility complex, class II, DQ alpha 2) were shared proteins with PSC, and they should be direct targets for PSC. The phenome-wide screening suggested that variants located at AIF1 or HLA-DQA2 region were closely associated with several autoimmune diseases, such as rheumatoid arthritis, implicating the shared pathogenesis among them.

CONCLUSIONS

Our study highly pinpointed two candidate targets (AIF1 and HLA-DQA2) for PSC.

AIF1: Function and Connection with Inflammatory Diseases

Macrophages are a type of immune cell distributed throughout all tissues of an organism. Allograft inflammatory factor 1 (AIF1) is a calcium-binding protein linked to the activation of macrophages. AIF1 is a key intracellular signaling molecule that participates in phagocytosis, membrane ruffling and F-actin polymerization. Moreover, it has several cell type-specific functions. AIF1 plays important roles in the development of several diseases: kidney disease, rheumatoid arthritis, cancer, cardiovascular diseases, metabolic diseases and neurological disorders, and in transplants. In this review, we present a comprehensive review of the known structure, functions and role of AIF1 in inflammatory diseases.

Increased adipose catecholamine levels and protection from obesity with loss of Allograft Inflammatory Factor-1

Recent studies implicate macrophages in regulation of thermogenic, sympathetic neuron-mediated norepinephrine (NE) signaling in adipose tissues, but understanding of such non-classical macrophage activities is incomplete. Here we show that male mice lacking the allograft inflammatory factor-1 (AIF1) protein resist high fat diet (HFD)-induced obesity and hyperglycemia. We link this phenotype to higher adipose NE levels that stem from decreased monoamine oxidase A (MAOA) expression and NE clearance by AIF1-deficient macrophages, and find through reciprocal bone marrow transplantation that donor Aif1-/- vs WT genotype confers the obesity phenotype in mice. Interestingly, human sequence variants near the AIF1 locus associate with obesity and diabetes; in adipose samples from participants with obesity, we observe direct correlation of AIF1 and MAOA transcript levels. These findings identify AIF1 as a regulator of MAOA expression in macrophages and catecholamine activity in adipose tissues - limiting energy expenditure and promoting energy storage - and suggest how it might contribute to human obesity.

Diabetes With Multiple Autoimmune and Inflammatory Conditions Linked to an Activating SKAP2 Mutation

OBJECTIVE

Multiple genome-wide association studies have identified a strong genetic linkage between the SKAP2 locus and type 1 diabetes (T1D), but how this leads to disease remains obscure. Here, we characterized the functional consequence of a novel SKAP2 coding mutation in a patient with T1D to gain further insight into how this impacts immune tolerance.

RESEARCH DESIGN AND METHODS

We identified a 24-year-old individual with T1D and other autoimmune and inflammatory conditions. The proband and first-degree relatives were recruited for whole-exome sequencing. Functional studies of the protein variant were performed using a cell line and primary myeloid immune cells collected from family members.

RESULTS

Sequencing identified a de novo SKAP2 variant (c.457G>A, p.Gly153Arg) in the proband. Assays using monocyte-derived macrophages from the individual revealed enhanced activity of integrin pathways and a migratory phenotype in the absence of chemokine stimulation, consistent with SKAP2 p.Gly153Arg being constitutively active. The p.Gly153Arg variant, located in the well-conserved lipid-binding loop, induced similar phenotypes when expressed in a human macrophage cell line. SKAP2 p.Gly153Arg is a gain-of-function, pathogenic mutation that disrupts myeloid immune cell function, likely resulting in a break in immune tolerance and T1D.

CONCLUSIONS

SKAP2 plays a key role in myeloid cell activation and migration. This particular mutation in a patient with T1D and multiple autoimmune conditions implicates a role for activating SKAP2 variants in autoimmune T1D.