Yan Zhao

BACKGROUND: Pulmonary interstitial macrophages can be divided into 2 distinct subsets with different origins: resident macrophages (resMФs) and recruited macrophages (recMФs). However, their specific roles in pulmonary arterial hypertension remain unclear. METHODS: Bone marrow transplantation, the DT (diphtheria toxin) receptor system, and genetically modified murine models were utilized to explore how key TFs (transcription factors) regulate phenotype alterations in pulmonary resMФs and recMФs in an SU5416/hypoxia murine model of pulmonary hypertension (PH). Therapeutic approaches included DNA aptamer–based proteolysis-targeting chimera and small interfering RNA–loaded lipid nanoparticle for treating SU5416/hypoxia–exposed rats. RESULTS: Depletion of either resMФs or recMФs using DT treatment significantly reduced SU5416/hypoxia–induced PH in mice. Pulmonary recMФs exhibited a proinflammatory phenotype during PH, driven by the TF Hic1 (hypermethylated in cancer 1). Bone marrow transplantation with Hic1 ^−/− recMФs ameliorated PH in mice. Hic1 enhanced proinflammatory gene transcription by inhibiting Sirt1 (sirtuin 1)-mediated H3K9ac (histone H3 lysine 9 acetylation) deacetylation in the promoter regions. In contrast, pulmonary resMФs demonstrated a profibrotic transcriptome characterized by upregulation of MMP genes that are, in turn, regulated by Prrx2 (paired-related homeobox 2). Prrx2 deletion in resMФs protected against PH in mice by reducing perivascular fibrosis. Simultaneously targeting Prrx2 and Hic1 in macrophages significantly alleviated SU5416/hypoxia–induced PH in rats. CONCLUSIONS: The differential roles of pulmonary resMФs and recMФs in pulmonary vascular remodeling highlight novel therapeutic targets for pulmonary arterial hypertension treatment, specifically through inhibition of Hic1 and Prrx2 in macrophages.

VISTA is a key immune checkpoint receptor under investigation as a target for cancer immunotherapy. However, a better understanding of the signaling mechanisms of VISTA is needed to optimize the therapeutic potential. Here, we identified a conserved four amino acid (NPGF) intracellular motif in VISTA that suppresses cell proliferation by constraining cell-intrinsic growth receptor signaling. A class of triple-negative breast cancers (TNBC) with high VISTA expression and low proliferative index was identified and characterized. The NPGF motif bound to the adapter protein NUMB and recruited Rab11 endosomal recycling machinery. The NPGF motif sequestered NUMB at endosomes, which interfered with EGFR trafficking and signaling to suppress tumor growth. These tumor suppressive effects did not require canonical VISTA ligands or a functioning immune system. Mutation of the VISTA NPGF domain reverted VISTA-induced growth suppression in multiple breast cancer mouse models. The NPGF motif was also required for response of VISTA+ TNBCs to VISTA-blocking antibodies. These results define a mechanism by which VISTA recruits adapter proteins to control malignant epithelial cell growth and signaling. They also define distinct intracellular residues that are critical for response to therapeutic antibodies that could be exploited to improve immunotherapy.

The pathological retinal angiogenesis often causes blindness. Current anti‐angiogenic therapy for proliferative retinopathy targets the vascular endothelial growth factor (VEGF), but many patients do not radically benefit from this therapy. Herein, we report that circulating prostaglandin (PG) F _2α metabolites were increased in type 2 diabetic patients with proliferative retinopathy, and the PGF _2α receptor ( Ptgfr ) was upregulated in retinal endothelial cells (ECs) from a mouse model of oxygen‐induced retinopathy (OIR). Further, disruption of the PTGFR receptor in ECs attenuated OIR in mice. PGF _2α promoted the proliferation and tube formation of human retinal microvascular endothelial cells (HRMECs) via the release of ELR ⁺ CXC chemokines, such as CXCL8 and CXCL2. Mechanistically, the PGF _2α /PTGFR axis potentiated ELR ⁺ CXC chemokine expression in HRMECs through the G _q /CAMK2G/p38/ELK‐1/FOS pathway. Upregulated FOS‐mediated ELR ⁺ CXC chemokine expression was observed in retinal ECs from PDR patients. Moreover, treatment with PTGFR inhibitor lessened the development of OIR in mice in a CXCR2‐dependent manner. Therefore, inhibition of PTGFR may represent a new avenue for the treatment of retinal neovascularization, particularly in PDR.