Probes for CCL2

The neuromuscular junction is a synapse critical for muscle strength and coordinated motor function. Unlike CNS injuries, motor neurons mount robust regenerative responses after peripheral nerve injuries. Conversely, motor neurons selectively degenerate in diseases such as amyotrophic lateral sclerosis (ALS). To assess how these insults affect motor neurons in vivo, we performed ribosomal profiling of mouse motor neurons. Motor neuron-specific transcripts were isolated from spinal cords following sciatic nerve crush, a model of acute injury and regeneration, and in the SOD1G93A ALS model. Of the 267 transcripts upregulated after nerve crush, 38% were also upregulated in SOD1G93A motor neurons. However, most upregulated genes in injured and ALS motor neurons were context specific. Some of the most significantly upregulated transcripts in both paradigms were chemokines such as Ccl2 and Ccl7, suggesting an important role for neuroimmune modulation. Collectively these data will aid in defining pro-regenerative and pro-degenerative mechanisms in motor neurons.

Pulmonary fibrosis results from dysregulated lung repair and involves multiple cell types. The role of endothelial cells (EC) in lung fibrosis is poorly understood. Using single cell RNA-sequencing we identified endothelial transcription factors involved in lung fibrogenesis, including FOXF1, SMAD6, ETV6 and LEF1. Focusing on FOXF1, we found that FOXF1 is decreased in EC within human idiopathic pulmonary fibrosis (IPF) and mouse bleomycin-injured lungs. Endothelial-specific Foxf1 inhibition in mice increased collagen depositions, promoted lung inflammation, and impaired R-Ras signaling. In vitro, FOXF1-deficient EC increased proliferation, invasion and activation of human lung fibroblasts, and stimulated macrophage migration by secreting IL-6, TNFα, CCL2 and CXCL1. FOXF1 inhibited TNFα and CCL2 through direct transcriptional activation of Rras gene promoter. Transgenic overexpression or endothelial-specific nanoparticle delivery of Foxf1 cDNA decreased pulmonary fibrosis in bleomycin-injured mice. Nanoparticle delivery of FOXF1 cDNA can be considered for future therapies in IPF.

Triple-negative breast cancer (TNBC) has a high propensity for organ-specific metastasis. However, the underlying mechanisms are not well understood. Here, we show that the primary TNBC tumor-derived C-X-C motif chemokines 1/2/8 (CXCL1/2/8) stimulate lung resident fibroblasts to produce C-C motif chemokines 2/7 (CCL2/7), which in turn activate cholesterol synthesis in lung-colonizing TNBC cells and induce angiogenesis at lung metastatic sites. Inhibiting cholesterol synthesis in lung-colonizing breast tumor cells by the pulmonary administration of simvastatin-carrying HER3-targeting nanoparticles reduces the angiogenesis and growth of lung metastases in a syngeneic TNBC mouse model. Our findings reveal a novel, chemokine-regulated mechanism for the cholesterol synthesis pathway and a critical role of metastatic site-specific cholesterol synthesis in the pulmonary tropism of TNBC metastasis. The study has implications for the unresolved epidemiological observation that the use of cholesterol-lowering drugs has no effect on breast cancer incidence but can unexpectedly reduce breast cancer mortality, suggesting interventions of cholesterol synthesis in lung metastases as an effective treatment to improve survival in TNBC patients.

Immune surveillance of the brain plays an important role in health and disease. Peripheral leukocytes patrol blood-brain barrier interfaces, and after injury, monocytes cross the cerebrovasculature and follow a pattern of pro- and anti-inflammatory activity leading to tissue repair. We have shown that chronic social defeat (CSD) causes scattered vasculature disruptions. Here, we assessed CCR2+ monocyte trafficking to the vascular injury sites in Ccr2wt/rfp reporter mice both during CSD and one week following CSD cessation. We found that CSD for 14 days induced microhemorrhages where plasma fibrinogen leaked into perivascular spaces, but it did not affect the distribution or density of CCR2rfp+ monocytes in the brain. However, after recovery from CSD, many vascularly adhered CCR2+ cells were detected, and gene expression of the CCR2 chemokine receptor ligands CCL7 and CCL12, but not CCL2, was elevated in endothelial cells. Adhered CCR2+ cells were mostly the non-classical, anti-inflammatory Ly6Clo type, and they phagocytosed fibrinogen in perivascular spaces. In CCR2-deficient Ccr2rfp/rfp mice, fibrinogen levels remained elevated in recovery. Fibrinogen infused intracerebroventricularly induced CCR2+ cells to adhere to the vasculature and phagocytose perivascular fibrinogen in Ccr2wt/rfp but not Ccr2rfp/rfp mice. Depletion of monocytes with clodronate liposomes during CSD recovery prevented fibrinogen clearance and blocked behavioral recovery. We hypothesize that peripheral CCR2+ monocytes are not elevated in the brain on day 14 at the end of CSD and do not contribute to its behavioral effects at that time, but in recovery following cessation of stress, they enter the brain and exert restorative functions mediating vascular repair and normalization of behavior.