A subpopulation of CD146+ macrophages enhances antitumor immunity by activating the NLRP3 inflammasome.

As one of the main tumor-infiltrating immune cell types, tumor-associated macrophages (TAMs) determine the efficacy of immunotherapy. However, limited knowledge about their phenotypically and functionally heterogeneous nature restricts their application in tumor immunotherapy. In this study, we identified a subpopulation of CD146+ TAMs that exerted antitumor activity in both human samples and animal models. CD146 expression in TAMs was negatively controlled by STAT3 signaling. Reducing this population of TAMs promoted tumor development by facilitating myeloid-derived suppressor cell recruitment via activation of JNK signaling. Interestingly, CD146 was involved in the NLRP3 inflammasome-mediated activation of macrophages in the tumor microenvironment, partially by inhibiting transmembrane protein 176B (TMEM176B), an immunoregulatory cation channel. Treatment with a TMEM176B inhibitor enhanced the antitumor activity of CD146+ TAMs. These data reveal a crucial antitumor role of CD146+ TAMs and highlight the promising immunotherapeutic approach of inhibiting CD146 and TMEM176B.

CD146 Associates with Gp130 to Control a Macrophage Pro-inflammatory Program That Regulates the Metabolic Response to Obesity.

The mechanism of obesity-related metabolic dysfunction involves the development of systemic inflammation, largely mediated by macrophages. Switching of M1-like adipose tissue macrophages (ATMs) to M2-like ATMs, a population of macrophages associated with weight loss and insulin sensitivity, is considered a viable therapeutic strategy for obesity-related metabolic syndrome. However, mechanisms for reestablishing the polarization of ATMs remain elusive. This study demonstrates that CD146+ ATMs accumulate in adipose tissue during diet-induced obesity and are associated with increased body weight, systemic inflammation, and obesity-induced insulin resistance. Inactivating the macrophage CD146 gene or antibody targeting of CD146 alleviates obesity-related chronic inflammation and metabolic dysfunction. Macrophage CD146 interacts with Glycoprotein 130 (Gp130), the common subunit of the receptor signaling complex for the interleukin-6 family of cytokines. CD146/Gp130 interaction promotes pro-inflammatory polarization of ATMs by activating JNK signaling and inhibiting the activation of STAT3, a transcription factor for M2-like polarization. Disruption of their interaction by anti-CD146 antibody or interleukin-6 steers ATMs toward anti-inflammatory polarization, thus attenuating obesity-induced chronic inflammation and metabolic dysfunction in mice. The results suggest that macrophage CD146 is an important determinant of pro-inflammatory polarization and plays a pivotal role in obesity-induced metabolic dysfunction. CD146 could constitute a novel therapeutic target for obesity complications.

CD146 bound to LCK promotes T cell receptor signaling and antitumor immune responses in mice.

Initiation of T cell receptor (TCR) signaling involves the activation of the tyrosine kinase LCK; however, it is currently unclear how LCK is recruited and activated. Here, we have identified the membrane protein CD146 as an essential member of the TCR network for LCK activation. CD146 deficiency in T cells substantially impaired thymocyte development and peripheral activation, both of which depend on TCR signaling. CD146 was found to directly interact with the SH3 domain of coreceptor-free LCK via its cytoplasmic domain. Interestingly, we found CD146 to be present in both monomeric and dimeric forms in T cells, with the dimerized form increasing after TCR ligation. Increased dimerized CD146 recruited LCK and promoted LCK autophosphorylation. In tumor models, CD146 deficiency dramatically impaired the antitumor response of T cells. Together, our data reveal an LCK activation mechanism for TCR initiation. We also underscore a rational intervention based on CD146 for tumor immunotherapy.

TiO2 supported single Ag atoms nanozyme for elimination of SARS-CoV2.

The outbreak of SARS-coronavirus 2 (SARS-CoV2) has become a global health emergency. Although enormous efforts have been made, there is still no effective treatment against the new virus. Herein, a TiO2 supported single-atom nanozyme containing atomically dispersed Ag atoms (Ag-TiO2 SAN) is designed to serve as a highly efficient antiviral nanomaterial. Compared with traditional nano-TiO2 and Ag, Ag-TiO2 SAN exhibits higher adsorption (99.65%) of SARS-CoV2 pseudovirus. This adsorption ability is due to the interaction between SAN and receptor binding domain (RBD) of spike 1 protein of SARS-CoV2. Theoretical calculation and experimental evidences indicate that the Ag atoms of SAN strongly bind to cysteine and asparagine, which are the most abundant amino acids on the surface of spike 1 RBD. After binding to the virus, the SAN/virus complex is typically phagocytosed by macrophages and colocalized with lysosomes. Interestingly, Ag-TiO2 SAN possesses high peroxidase-like activity responsible for reactive oxygen species production under acid conditions. The highly acidic microenvironment of lysosomes could favor oxygen reduction reaction process to eliminate the virus. With hACE2 transgenic mice, Ag-TiO2 SAN showed efficient anti-SARS-CoV2 pseudovirus activity. In conclusion, Ag-TiO2 SAN is a promising nanomaterial to achieve effective antiviral effects for SARS-CoV2.

Targeting the CD146/Galectin-9 axis protects the integrity of the blood-brain barrier in experimental cerebral malaria.

Cerebral malaria (CM) is a life-threatening diffuse encephalopathy caused by Plasmodium falciparum, in which the destruction of the blood-brain barrier (BBB) is the main cause of death. However, increasing evidence has shown that antimalarial drugs, the current treatment for CM, do little to protect against CM-induced BBB damage. Therefore, a means to alleviate BBB dysfunction would be a promising adjuvant therapy for CM. The adhesion molecule CD146 has been reported to be expressed in both endothelial cells and proinflammatory immune cells and mediates neuroinflammation. Here, we demonstrate that CD146 expressed on BBB endothelial cells but not immune cells is a novel therapeutic target in a mouse model of experimental cerebral malaria (eCM). Endothelial CD146 is upregulated during eCM development and facilitates the sequestration of infected red blood cells (RBCs) and/or proinflammatory lymphocytes in CNS blood vessels, thereby promoting the disruption of BBB integrity. Mechanistic studies showed that the interaction of CD146 and Galectin-9 contributes to the aggregation of infected RBCs and lymphocytes. Deletion of endothelial CD146 or treatment with the anti-CD146 antibody AA98 prevents severe signs of eCM, such as limb paralysis, brain vascular leakage, and death. In addition, AA98 combined with the antiparasitic drug artemether improved the cognition and memory of mice with eCM. Taken together, our findings suggest that endothelial CD146 is a novel and promising target in combination with antiparasitic drugs for future CM therapies.

Soluble CD146, a cerebrospinal fluid marker for neuroinflammation, promotes blood-brain barrier dysfunction.

The blood-brain barrier (BBB) dysfunction is an initial event of various neuroinflammatory diseases. However, the absence of reliable markers and mechanisms for BBB damage greatly limits the diagnosis and treatment of neuroinflammatory diseases. Soluble CD146 (sCD146) is mainly derived from vascular endothelial cells (ECs) and highly elevated in inflammatory settings. Based on a small cohort, our previous study showed that sCD146 is elevated in the cerebrospinal fluid (CSF) of multiple sclerosis (MS), which is accompanied with BBB damage. Nevertheless, whether sCD146 monitors and regulates the BBB dysfunction remains unknown. Methods: Coupled serum and CSF samples from patients with or without neuroinflammatory diseases were collected via multicenter collaborations. sCD146 was measured by sandwich ELISA using anti-CD146 antibodies AA1 and AA98, both of which were generated in our laboratory. The correlations between sCD146 and other clinical parameters or inflammatory factors were analyzed by Spearman's correlation coefficient analysis. The role of sCD146 on BBB function was examined in an in vitro BBB model. Results: Between July 20, 2011, and February 31, 2017, we collected coupled serum and CSF samples from 823 patients, of which 562 (68.3%) had neuroinflammatory diseases, 44 (5.3%) had remitting MS, and 217 (26.4%) had non-inflammatory neurological diseases (NIND). We found that sCD146 in CSF, but not in serum, is abnormally elevated in neuroinflammatory diseases (37.3 ± 13.3 ng/mL) compared with NIND (4.7 ± 2.9 ng/mL) and remitting MS (4.6 ± 3.5 ng/mL). Abnormally elevated CSF sCD146 is significantly correlated with the hyperpermeability-related clinical parameters of BBB and neuroinflammation-related factors. Moreover, CSF sCD146 shows higher sensitivity and specificity for evaluating BBB damage. Using an in vitro BBB model, we found that sCD146 impairs BBB function by promoting BBB permeability via an association with integrin αvß1. Blocking integrin αvß1 significantly attenuates sCD146-induced hyperpermeability of the BBB. Conclusion: Our study provides convincing evidence that CSF sCD146 is a sensitive marker of BBB damage and neuroinflammation. Furthermore, sCD146 is actively involved in BBB dysfunction.