CITED2 Restrains Proinflammatory Macrophage Activation and Response. Mol Cell Biol. 2018;38. [PMID: 29203644 DOI: 10.1128/mcb.00452-17]

Akkermansia muciniphila alleviates abdominal aortic aneurysms via restoring CITED2 activated by EPAS1

Abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease that has been linked to gut microbiome dysbiosis. Therefore, this study aims to investigate the effects of Akkermansia muciniphila (Am) on AAA mice and the biomolecules involved. AAA mice were generated using angiotensin II (Ang II), and 16sRNA sequencing was used to identify an altered abundance of microbiota in the feces of AAA mice. Vascular smooth muscle cell (VSMC) markers and apoptosis, and macrophage infiltration in mouse aortic tissues were examined. The abundance of Am was reduced in AAA mouse feces, and endothelial PAS domain-containing protein 1 (EPAS1) was downregulated in AAA mice and VSMC induced with Ang II. Am delayed AAA progression in mice, which was blunted by knockdown of EPAS1. EPAS1 was bound to the Cbp/p300-interacting transactivator 2 (CITED2) promoter and promoted CITED2 transcription. CITED2 reduced VSMC apoptosis and delayed AAA progression. Moreover, EPAS1 inhibited macrophage inflammatory response by promoting CITED2 transcription. In conclusion, gut microbiome dysbiosis in AAA induces EPAS1-mediated dysregulation of CITED2 to promote macrophage inflammatory response and VSMC apoptosis.

CITED4 gene therapy protects against maladaptive cardiac remodeling after ischemia/reperfusion injury in mice

Cardiac signaling pathways functionally important in the heart's response to exercise often protect the heart against pathological stress, potentially providing novel therapeutic targets. However, it is important to determine which of these pathways can be feasibly targeted in vivo. Transgenic overexpression of exercise-induced CITED4 has been shown to protect against adverse remodeling after ischemia/reperfusion injury (IRI). Here we investigated whether somatic gene transfer of CITED4 in a clinically relevant time frame could promote recovery after IRI. Cardiac CITED4 gene delivery via intravenous AAV9 injections in wild type mice led to an approximately 3-fold increase in cardiac CITED4 expression. After 4 weeks, CITED4-treated animals developed physiological cardiac hypertrophy without adverse remodeling. In IRI, delivery of AAV9-CITED4 after reperfusion resulted in a 6-fold increase in CITED4 expression 1 week after surgery, as well as decreased apoptosis, fibrosis, and inflammatory markers, culminating in a smaller scar and improved cardiac function 8 weeks after IRI, compared with control mice receiving AAV9-GFP. Somatic gene transfer of CITED4 induced a phenotype suggestive of physiological cardiac growth and mitigated adverse remodeling after ischemic injury. These studies support the feasibility of CITED4 gene therapy delivered in a clinically relevant time frame to mitigate adverse ventricular remodeling after ischemic injury.

Missense mutations in the CITED2 gene may contribute to congenital heart disease

BACKGROUND

Congenital heart disease (CHD) is a lifelong abnormality present from birth. Multiple studies have shown that mutations in genes involved in heart development could cause congenital heart disease. The CITED2 gene works as a transcription factor in the hypoxic pathway for the development of the heart. Therefore, five CHD types, ventricular septal defect, atrial septal defect, atrioventricular septal defect, tetralogy of fallot, and patent ductus arteriosus, were evaluated by conducting a targeted single nucleotide polymorphism (SNP) analysis of the CITED2 gene variant rs375393125 (T > C). This study aimed to identify the association of CITED2 gene mutations in CHD patients.

METHODS

Three hundred fifty samples, 250 from patients and 100 from controls, were collected for this genetic analysis. Allele-specific PCR and gel electrophoresis were used to identify the target missense mutations. The genotypic results of the CHDs were further validated through Sanger sequencing.

RESULTS

The frequency of the homozygous mutant (CC) in CHD patients was 48.4%, and of the heterozygous mutant (TC) genotype was 11.4%; these percentages are higher than controls (1%). The control samples had only one heterozygous TC and no homozygous CC genotype. The chi-square value was obtained at 103.9 with a probability of 0.05, more significant than the significance value of 21.03. The odds ratio was 43.7, which is > 1. The calculated value of ANOVA was 11.6, which was more significant than the F critical value of 3.7. As a result of sequencing, the mutant sample of each selected CHD type was found heterozygous or homozygous, and the results were like those obtained through conventional PCR.

CONCLUSION

The samples of CHD patients showed mutations. Therefore, the CITED2 gene SNP might be associated with CHD.

Collagen XVIII regulates extracellular matrix integrity in the developing nephrons and impacts nephron progenitor cell behavior

Renal development is a complex process in which two major processes, tubular branching and nephron development, regulate each other reciprocally. Our previous findings have indicated that collagen XVIII (ColXVIII), an extracellular matrix protein, affects the renal branching morphogenesis. We investigate here the role of ColXVIII in nephron formation and the behavior of nephron progenitor cells (NPCs) using isoform-specific ColXVIII knockout mice. The results show that the short ColXVIII isoform predominates in the early epithelialized nephron structures whereas the two longer isoforms are expressed only in the later phases of glomerular formation. Meanwhile, electron microscopy showed that the ColXVIII mutant embryonic kidneys have ultrastructural defects at least from embryonic day 16.5 onwards. Similar structural defects had previously been observed in adult ColXVIII-deficient mice, indicating a congenital origin. The lack of ColXVIII led to a reduced NPC population in which changes in NPC proliferation and maintenance and in macrophage influx were perceived to play a role. The changes in NPC behavior in turn led to notably reduced overall nephron formation. In conclusion, the results show that ColXVIII has multiple roles in renal development, both in ureteric branching and in NPC behavior.

Oestrogen promotes the progression of adenomyosis by inhibiting CITED2 through miR-145

RESEARCH QUESTION

Is the microRNA miR-145 involved in adenomyosis, and by what mechanisms does it affect disease development and is itself regulated?

DESIGN

Fluorescence in-situ hybridization was used to observe the expression pattern of miR-145 in adenomyosis ectopic endometrium (n = 13), adenomyosis eutopic endometrium (n = 15) and non-adenomyosis eutopic endometrium (n = 14). RNA sequencing was used to screen target genes as well as downstream pathways of miR-145, which were validated by reporter gene assay, quantitative polymerase chain reaction and western blot, and further analysed using cell migration assay and chromatin immunoprecipitation assay.

RESULTS

The fluorescence in-situ hybridization assay revealed a noteworthy elevation in miR-145 expression in adenomyosis tissue compared with non-adenomyosis tissue. Furthermore, RNA sequencing analysis revealed that overexpression of miR-145 resulted in heightened expression of genes associated with the cytokine signalling pathway, nucleotide-binding and oligomerization domain-like pathway and adhesion pathway, including IL-1β and IL-6. Our study has identified CITED2 as a downstream direct target gene of miR-145, which is implicated in the inhibition of stromal cell migration induced by miR-145. Moreover, chromatin immunoprecipitation was used to validate the direct effect of oestradiol on the promoter region of miR-145, mediated by oestrogen receptor α, which facilitates the upregulation of miR-145 expression.

CONCLUSION

Our findings provide evidence supporting the role of oestradiol, acting through its receptor α, in modulating the discovered miR-145-CITED2 signalling axis, thereby promoting the progression of adenomyosis.

Exploring the role of CITED transcriptional regulators in the control of macrophage polarization

Macrophages are tissue resident innate phagocytic cells that take on contrasting phenotypes, or polarization states, in response to the changing combination of microbial and cytokine signals at sites of infection. During the opening stages of an infection, macrophages adopt the proinflammatory, highly antimicrobial M1 state, later shifting to an anti-inflammatory, pro-tissue repair M2 state as the infection resolves. The changes in gene expression underlying these transitions are primarily governed by nuclear factor kappaB (NF-κB), Janus kinase (JAK)/signal transducer and activation of transcription (STAT), and hypoxia-inducible factor 1 (HIF1) transcription factors, the activity of which must be carefully controlled to ensure an effective yet spatially and temporally restricted inflammatory response. While much of this control is provided by pathway-specific feedback loops, recent work has shown that the transcriptional co-regulators of the CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxy-terminal domain (CITED) family serve as common controllers for these pathways. In this review, we describe how CITED proteins regulate polarization-associated gene expression changes by controlling the ability of transcription factors to form chromatin complexes with the histone acetyltransferase, CBP/p300. We will also cover how differences in the interactions between CITED1 and 2 with CBP/p300 drive their contrasting effects on pro-inflammatory gene expression.

Engineering Tumor Stroma Morphogenesis Using Dynamic Cell-Matrix Spheroid Assembly

The tumor microenvironment consists of resident tumor cells organized within a compositionally diverse, three-dimensional (3D) extracellular matrix (ECM) network that cannot be replicated in vitro using bottom-up synthesis. We report a new self-assembly system to engineer ECM-rich 3D MatriSpheres wherein tumor cells actively organize and concentrate microgram quantities of decellularized ECM dispersions which modulate cell phenotype. 3D colorectal cancer (CRC) MatriSpheres were created using decellularized small intestine submucosa (SIS) as an orthotopic ECM source that had greater proteomic homology to CRC tumor ECM than traditional ECM formulations such as Matrigel. SIS ECM was rapidly concentrated from its environment and assembled into ECM-rich 3D stroma-like regions by mouse and human CRC cell lines within 4-5 days via a mechanism that was rheologically distinct from bulk hydrogel formation. Both ECM organization and transcriptional regulation by 3D ECM cues affected programs of malignancy, lipid metabolism, and immunoregulation that corresponded with an in vivo MC38 tumor cell subpopulation identified via single cell RNA sequencing. This 3D modeling approach stimulates tumor specific tissue morphogenesis that incorporates the complexities of both cancer cell and ECM compartments in a scalable, spontaneous assembly process that may further facilitate precision medicine.

Cited2 inhibited hypoxia-induced proliferation and migration of PASMCs via the TGF-β1/Cited2/PPARγ pathway

Objectives

Proliferation and migration of pulmonary artery smooth muscle cells (PASMCs) contribute to hypoxia-induced pulmonary hypertension (HPH). The transcription factor Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (Cited2) has been implicated in the control of tumor cells and mesenchymal stem cell (MSC) and cardiomyocyte growth or migration. Whether Cited2 is involved in the proliferation and migration of PASMCs and the underlying mechanisms deserve to be explored.

Materials and Methods

Cited2 expression was detected in rat PASMCs under hypoxia conditions and HPH rat models. The effect of Cited2 on the proliferation and migration of PASMC was detected by overexpression or knockdown of the Cited2 gene. After PAMSCs were treated with recombinant TGF-β1 and the lentivirus vector overexpressing Cited2, expression of peroxisome proliferator-activated receptor gamma (PPARγ) was examined by western blotting.

Results

We revealed that hypoxia down-regulated the expression of Cited2 in PASMCs and rat pulmonary arteries. Cited2 overexpression inhibited the proliferation and migration of PASMCs under hypoxia, while Cited2 knockdown induced the proliferation and migration of PASMCs. Cited2 inhibits the negative regulation of the TGF-β1 pathway on PPARγ to inhibit the proliferation and migration of PASMCs.

Conclusion

These findings suggest that increased Cited2 expression contributes to the inhibition of PASMCs proliferation and migration by regulating TGF-β1-mediated target gene expression in HPH and provides a new target for molecular therapy of HPH.

Myeloid-CITED2 Deficiency Exacerbates Diet-Induced Obesity and Pro-Inflammatory Macrophage Response

Macrophages are the principal component of the innate immune system that are found in all tissues and play an essential role in development, homeostasis, tissue repair, and immunity. Clinical and experimental studies have shown that transcriptionally dynamic pro-inflammatory macrophages are involved in the pathogenesis of diet-induced obesity and insulin resistance. However, cell-intrinsic mechanisms must exist that bridle uncontrolled pro-inflammatory macrophage activation in metabolic organs and disease pathogenesis. In this study, we show that CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxyl-terminal domain 2 (CITED2) is an essential negative regulator of pro-inflammatory macrophage activation and inflammatory disease pathogenesis. Our in vivo studies show that myeloid-CITED2 deficiency significantly elevates high-fat diet (HFD)-induced expansion of adipose tissue volume, obesity, glucose intolerance, and insulin resistance. Moreover, myeloid-CITED2 deficiency also substantially augments HFD-induced adipose tissue inflammation and adverse remodeling of adipocytes. Our integrated transcriptomics and gene set enrichment analyses show that CITED2 deficiency curtails BCL6 signaling and broadly elevates BCL6-repressive gene target expression in macrophages. Using complementary gain- and loss-of-function studies, we found that CITED2 deficiency attenuates, and CITED2 overexpression elevates, inducible BCL6 expression in macrophages. At the molecular level, our analyses show that CITED2 promotes BCL6 expression by restraining STAT5 activation in macrophages. Interestingly, siRNA-mediated knockdown of STAT5 fully reversed elevated pro-inflammatory gene target expression in CITED2-deficient macrophages. Overall, our findings highlight that CITED2 restrains inflammation by promoting BCL6 expression in macrophages, and limits diet-induced obesity and insulin resistance.

Uncovering the anti-inflammatory mechanisms of phenolic-enriched maple syrup extract in lipopolysaccharide-induced peritonitis in mice: insights from data-independent acquisition proteomics analysis

Our group has previously reported on the phytochemical composition and biological activities of a phenolic-enriched maple syrup extract (MSX), which showed promising anti-inflammatory effects in several disease models including diabetes and Alzheimer's disease. However, the efficacious doses of MSX and its molecular targets involved in the anti-inflammatory effects are not fully elucidated. Herein, the efficacy of MSX in a peritonitis mouse model was evaluated in a dose-finding study and the underlying mechanisms were explored using data-independent acquisition (DIA) proteomics assay. MSX (at 15, 30 and 60 mg kg-1) alleviated lipopolysaccharide-induced peritonitis by reducing the levels of pro-inflammatory cytokines including interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) in the serum and major organs of the mice. Furthermore, DIA proteomics analyses identified a panel of proteins that were significantly altered (both up- and down-regulated) in the peritonitis group, which were counteracted by the MSX treatments. MSX treatment also modulated several inflammatory upstream regulators including interferon gamma and TNF. Ingenuity pathway analysis suggested that MSX may modulate several signaling pathways in the processes of initiation of cytokine storm, activation of liver regeneration, and suppression of hepatocyte apoptosis. Together, these proteomic and in vivo findings indicate that MSX could regulate inflammation signaling pathways and modulate inflammatory markers and proteins, providing critical insight to its therapeutic potential.

MAPK/MAK/MRK overlapping kinase (MOK) controls microglial inflammatory/type-I IFN responses via Brd4 and is involved in ALS

Amyotrophic lateral sclerosis (ALS) is a fatal and incurable neurodegenerative disease affecting motor neurons and characterized by microglia-mediated neurotoxic inflammation whose underlying mechanisms remain incompletely understood. In this work, we reveal that MAPK/MAK/MRK overlapping kinase (MOK), with an unknown physiological substrate, displays an immune function by controlling inflammatory and type-I interferon (IFN) responses in microglia which are detrimental to primary motor neurons. Moreover, we uncover the epigenetic reader bromodomain-containing protein 4 (Brd4) as an effector protein regulated by MOK, by promoting Ser492-phospho-Brd4 levels. We further demonstrate that MOK regulates Brd4 functions by supporting its binding to cytokine gene promoters, therefore enabling innate immune responses. Remarkably, we show that MOK levels are increased in the ALS spinal cord, particularly in microglial cells, and that administration of a chemical MOK inhibitor to ALS model mice can modulate Ser492-phospho-Brd4 levels, suppress microglial activation, and modify the disease course, indicating a pathophysiological role of MOK kinase in ALS and neuroinflammation.

Regulation of macrophage IFNγ-stimulated gene expression by the transcriptional coregulator CITED1

Macrophages serve as a first line of defense against microbial pathogens. Exposure to interferon-γ (IFNγ) increases interferon-stimulated gene (ISG) expression in these cells, resulting in enhanced antimicrobial and proinflammatory activity. Although this response must be sufficiently vigorous to ensure the successful clearance of pathogens, it must also be carefully regulated to prevent tissue damage. This is controlled in part by CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxyl-terminal domain 2 (CITED2), a transcriptional coregulator that limits ISG expression by inhibiting STAT1 and IRF1. Here, we show that the closely related Cited1 is an ISG, which is expressed in a STAT1-dependent manner, and that IFNγ stimulates the nuclear accumulation of CITED1 protein. In contrast to CITED2, ectopic CITED1 enhanced the expression of a subset of ISGs, including Ccl2, Ifit3b, Isg15 and Oas2. This effect was reversed in a Cited1-null cell line produced by CRISPR-based genomic editing. Collectively, these data show that CITED1 maintains proinflammatory gene expression during periods of prolonged IFNγ exposure and suggest that there is an antagonistic relationship between CITED proteins in the regulation of macrophage inflammatory function. This article has an associated First Person interview with the first author of the paper.

VEGF to CITED2 ratio predicts the collateral circulation of acute ischemic stroke

Objective

The research objective was to evaluate the predicting role of the vascular endothelial growth factor to CBP/P300-interacting transactivator with Glu/Asp-rich C-terminal domain 2 Ratio (VEGF/CITED2) from peripheral blood mononuclear cells (PBMCs) in the collateral circulation of acute ischemic stroke (AIS).

Methods

In an observational study of patients with AIS, the western blot was applied to test the protein expression of VEGF and CITED2. Then, we calculated the VEGF/CITED2 and collected other clinical data. Binary logistic regression analysis between collateral circulation and clinical data was performed. Finally, receiver operating characteristic (ROC) curve analysis was used to explore the predictive value of VEGF/CITED2.

Results

A total of 67 patients with AIS were included in the study. Binary logistic regression analysis indicated the VEGF/CITED2 (OR 165.79, 95%CI 7.25–3,791.54, P = 0.001) was an independent protective factor. The ROC analyses showed an area under the ROC curve of the VEGF/CITED2 was 0.861 (95%CI 0.761–0.961). The optimal cutoff value of 1.013 for VEGF/CITED2 had a sensitivity of 89.1% and a specificity of 85.7%.

Conclusion

In patients with AIS, the VEGF/CITED2 was related to the establishment of collateral circulation. The VEGF/CITED2 is a potentially valuable biomarker for predicting collateral circulation.

Clinical trial registration

ClinicalTrials.gov, identifier: NCT05345366.

Dynamic transcriptome analysis of the muscles in high-fat diet-induced obese zebrafish (Danio rerio) under 5-HT treatment

Peripheral 5-hydroxytryptamine (5-HT, also called serotonin) is reportedly a potential therapeutic target in obesity-related metabolic diseases due to its regulatory role in energy homeostasis in mammals. However, information on the detailed effect of peripheral 5-HT on the energy metabolism in fishes, especially the lipid metabolism, and the underlying mechanism remains elusive. In this study, a diet-induced obesity model was developed in the zebrafish (Danio rerio), a prototypical animal model for metabolic disorders. The zebrafish were fed a high-fat diet for 8 weeks and were simultaneously injected with PBS, 0.1 mM and 10 mM 5-HT, intraperitoneally. The body weight was significantly lower in the zebrafish injected with 0.1 mM 5-HT (P < 0.05), however, there was no change in body length (P > 0.05) at the end of the 8-week treatment. The muscle tissues from the zebrafish treated with PBS and 5-HT were collected for transcriptomic analysis and the RNA-seq revealed 1134, 3713, and 2535 genes were screened out compared to the muscular DEGs among three groups. The enrichment analysis revealed DEGs to be significantly associated with multiple metabolic pathways, including ribosome, oxidative phosphorylation, proteasome, PPAR signaling pathway, and ferroptosis. Additionally, the qRT-PCR validated 12 DEGs out of which 10 genes exhibited consistent trends. Taken together, this data provided useful information on the transcriptional characteristics of the muscle tissue in the obese zebrafish exposed to 5-HT, offering important insights into the regulatory effect of peripheral 5-HT in teleosts, as well as novel approaches for preventing and treating obesity-related metabolic dysfunction.

CITED2 coordinates key hematopoietic regulatory pathways to maintain the HSC pool in both steady-state hematopoiesis and transplantation

Hematopoietic stem cells (HSCs) reside at the apex of the hematopoietic differentiation hierarchy and sustain multilineage hematopoiesis. Here, we show that the transcriptional regulator CITED2 is essential for life-long HSC maintenance. While hematopoietic-specific Cited2 deletion has a minor impact on steady-state hematopoiesis, Cited2-deficient HSCs are severely depleted in young mice and fail to expand upon aging. Moreover, although they home normally to the bone marrow, they fail to reconstitute hematopoiesis upon transplantation. Mechanistically, CITED2 is required for expression of key HSC regulators, including GATA2, MCL-1, and PTEN. Hematopoietic-specific expression of anti-apoptotic MCL-1 partially rescues the Cited2-deficient HSC pool and restores their reconstitution potential. To interrogate the Cited2→Pten pathway in HSCs, we generated Cited2;Pten compound heterozygous mice, which had a decreased number of HSCs that failed to reconstitute the HSC compartment. In addition, CITED2 represses multiple pathways whose elevated activity causes HSC exhaustion. Thus, CITED2 promotes pathways necessary for HSC maintenance and suppresses those detrimental to HSC integrity.

BHLHE40 promotes macrophage pro-inflammatory gene expression and functions

Macrophages are the principal innate immune cells that populate all major organs and provide the first line of cellular defense against infections and/or injuries. The immediate and early-responding macrophages must mount a robust pro-inflammatory response to protect the host by eliminating deleterious agents. The effective pro-inflammatory macrophage response requires the activation of complex transcriptional programs that modulate the dynamic regulation of inflammatory and metabolic gene expression. Therefore, transcription factors that govern pro-inflammatory and metabolic gene expression play an essential role in shaping the macrophage inflammatory response. Herein, we identify the basic helix-loop-helix family member e40 (BHLHE40), as a critical transcription factor that promotes broad pro-inflammatory and glycolytic gene expression by elevating HIF1α levels in macrophages. Our in vivo studies revealed that myeloid-BHLHE40 deficiency significantly attenuates macrophage and neutrophil recruitment to the site of inflammation. Our integrated transcriptomics and gene set enrichment analysis (GSEA) studies show that BHLHE40 deficiency broadly curtails inflammatory signaling pathways, hypoxia response, and glycolytic gene expression in macrophages. Utilizing complementary gain- and loss-of-function studies, our analyses uncovered that BHLHE40 promotes LPS-induced HIF1α mRNA and protein expression in macrophages. More importantly, forced overexpression of oxygen stable form of HIF1α completely reversed attenuated pro-inflammatory and glycolytic gene expression in BHLHE40-deficient macrophages. Collectively, these results demonstrate that BHLHE40 promotes macrophage pro-inflammatory gene expression and functions by elevating HIF1α expression in macrophages.

CITED2 inhibits STAT1-IRF1 signaling and atherogenesis

Macrophages are the principal component of the innate immune system. They play very crucial and multifaceted roles in the pathogenesis of inflammatory vascular diseases. There is an increasing recognition that transcriptionally dynamic macrophages are the key players in the pathogenesis of inflammatory vascular diseases. In this context, the accumulation and aberrant activation of macrophages in the subendothelial layers govern atherosclerotic plaque development. Macrophage-mediated inflammation is an explicitly robust biological response that involves broad alterations in inflammatory gene expression. Thus, cell-intrinsic negative regulatory mechanisms must exist which can restrain inflammatory response in a spatiotemporal manner. In this study, we identified CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxyl-terminal domain 2 (CITED2) as one such cell-intrinsic negative regulator of inflammation. Our in vivo studies show that myeloid-CITED2-deficient mice on the Apoe^-/- background have larger atherosclerotic lesions on both control and high-fat/high-cholesterol diets. Our integrated transcriptomics and gene set enrichment analyses studies show that CITED2 deficiency elevates STAT1 and interferon regulatory factor 1 (IRF1) regulated pro-inflammatory gene expression in macrophages. At the molecular level, our studies identify that CITED2 deficiency elevates IFNγ-induced STAT1 transcriptional activity and STAT1 enrichment on IRF1 promoter in macrophages. More importantly, siRNA-mediated knockdown of IRF1 completely reversed elevated pro-inflammatory target gene expression in CITED2-deficient macrophages. Collectively, our study findings demonstrate that CITED2 restrains the STAT1-IRF1 signaling axis in macrophages and limits the development of atherosclerotic plaques.

VDAC Genes Expression and Regulation in Mammals

VDACs are pore-forming proteins, coating the mitochondrial outer membrane, and playing the role of main regulators for metabolites exchange between cytosol and mitochondria. In mammals, three isoforms have evolutionary originated, VDAC1, VDAC2, and VDAC3. Despite similarity in sequence and structure, evidence suggests different biological roles in normal and pathological conditions for each isoform. We compared Homo sapiens and Mus musculus VDAC genes and their regulatory elements. RNA-seq transcriptome analysis shows that VDAC isoforms are expressed in human and mouse tissues at different levels with a predominance of VDAC1 and VDAC2 over VDAC3, with the exception of reproductive system. Numerous transcript variants for each isoform suggest specific context-dependent regulatory mechanisms. Analysis of VDAC core promoters has highlighted that, both in a human and a mouse, VDAC genes show features of TATA-less ones. The level of CG methylation of the human VDAC genes revealed that VDAC1 promoter is less methylated than other two isoforms. We found that expression of VDAC genes is mainly regulated by transcription factors involved in controlling cell growth, proliferation and differentiation, apoptosis, and bioenergetic metabolism. A non-canonical initiation site termed "the TCT/TOP motif," the target for translation regulation by the mTOR pathway, was identified in human VDAC2 and VDAC3 and in every murine VDACs promoter. In addition, specific TFBSs have been identified in each VDAC promoter, supporting the hypothesis that there is a partial functional divergence. These data corroborate our experimental results and reinforce the idea that gene regulation could be the key to understanding the evolutionary specialization of VDAC isoforms.

Tumor-promoting macrophages prevail in malignant ascites of advanced gastric cancer

Gastric cancer (GC) patients develop malignant ascites as the disease progresses owing to peritoneal metastasis. GC patients with malignant ascites have a rapidly deteriorating clinical course with short survival following the onset of malignant ascites. Better optimized treatment strategies for this subset of patients are needed. To define the cellular characteristics of malignant ascites of GC, we used single-cell RNA sequencing to characterize tumor cells and tumor-associated macrophages (TAMs) from four samples of malignant ascites and one sample of cerebrospinal fluid. Reference transcriptomes for M1 and M2 macrophages were generated by in vitro differentiation of healthy blood-derived monocytes and applied to assess the inflammatory properties of TAMs. We analyzed 180 cells, including tumor cells, macrophages, and mesothelial cells. Dynamic exchange of tumor-promoting signals, including the CCL3–CCR1 or IL1B–IL1R2 interactions, suggests macrophage recruitment and anti-inflammatory tuning by tumor cells. By comparing these data with reference transcriptomes for M1-type and M2-type macrophages, we found noninflammatory characteristics in macrophages recovered from the malignant ascites of GC. Using public datasets, we demonstrated that the single-cell transcriptome-driven M2-specific signature was associated with poor prognosis in GC. Our data indicate that the anti-inflammatory characteristics of TAMs are controlled by tumor cells and present implications for treatment strategies for GC patients in which combination treatment targeting cancer cells and macrophages may have a reciprocal synergistic effect.

New strategies for treating advanced gastric cancer could emerge from insights into the interactions between white blood cells called macrophages and tumor cells in fluid known as malignant ascites that accumulates in the abdomen. Researchers in Seoul, South Korea, led by Hae-Ock Lee at The Catholic University of Korea and Woong-Yang Park at the Samsung Medical Center compared macrophages from healthy subjects with those from gastric cancer ascites. They identified molecular signaling interactions between tumor cells and macrophages that recruited macrophages into the ascites and converted them into more anti-inflammatory forms. The macrophages were then able to promote the activities of the cancer cells. The results suggest that chemicals able to inhibit or deplete proteins now identified as involved in controlling these synergistic interactions could become a new class of therapeutic agents.

Intracellular Cryptococcus neoformans disrupts the transcriptome profile of M1- and M2-polarized host macrophages

Macrophages serve as a first line of defense against infection with the facultative intracellular pathogen, Cryptococcus neoformans (Cn). However, the ability of these innate phagocytic cells to destroy ingested Cn is strongly influenced by polarization state with classically (M1) activated macrophages better able to control cryptococcal infections than alternatively (M2) activated cells. While earlier studies have demonstrated that intracellular Cn minimally affects the expression of M1 and M2 markers, the impact on the broader transcriptome associated with these states remains unclear. To investigate this, an in vitro cell culture model of intracellular infection together with RNA sequencing-based transcriptome profiling was used to measure the impact of Cn infection on gene expression in both polarization states. The gene expression profile of both M1 and M2 cells was extensively altered to become more like naive (M0) macrophages. Gene ontology analysis suggested that this involved changes in the activity of the Janus kinase-signal transducers and activators of transcription (JAK-STAT), p53, and nuclear factor-κB (NF-κB) pathways. Analyses of the principle polarization markers at the protein-level also revealed discrepancies between the RNA- and protein-level responses. In contrast to earlier studies, intracellular Cn was found to increase protein levels of the M1 marker iNos. In addition, common gene expression changes were identified that occurred post-Cn infection, independent of polarization state. This included upregulation of the transcriptional co-regulator Cited1, which was also apparent at the protein level in M1-polarized macrophages. These changes constitute a transcriptional signature of macrophage Cn infection and provide new insights into how Cn impacts gene expression and the phenotype of host phagocytes.

Role of CITED2 in stem cells and cancer

Cbp/P300 interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2) is a transcription co-factor that interacts with several other transcription factors and co-factors, and serves critical roles in fundamental cell processes, including proliferation, apoptosis, differentiation, migration and autophagy. The interacting transcription factors or co-factors of CITED2 include LIM homeobox 2, transcription factor AP-2, SMAD2/3, peroxisome proliferator-activated receptor γ, oestrogen receptor, MYC, Nucleolin and p300/CBP, which regulate downstream gene expression, and serve important roles in the aforementioned fundamental cell processes. Emerging evidence has demonstrated that CITED2 serves an essential role in embryonic and adult tissue stem cells, including hematopoietic stem cells and tendon-derived stem/progenitor cells. Additionally, CITED2 has been reported to function in different types of cancer. Although the functions of CITED2 in different tissues vary depending on the interaction partner, altered CITED2 expression or altered interactions with transcription factors or co-factors result in alterations of fundamental cell processes, and may affect stem cell maintenance or cancer cell survival. The aim of this review is to summarize the molecular mechanisms of CITED2 function and how it serves a role in stem cells and different types of cancer based on the currently available literature.

CITED2 limits pathogenic inflammatory gene programs in myeloid cells

Monocyte‐derived macrophages are the major innate immune cells that provide the first line of cellular defense against infections or injuries. These recruited macrophages at the site of inflammation are exposed to a broad range of cytokines that categorically incite a robust pro‐inflammatory response. However, macrophage pro‐inflammatory activation must be under exquisite control to avert unbridled inflammation. Thus, endogenous mechanisms must exist that rigorously preserve macrophage quiescence and yet, allow nimble pro‐inflammatory macrophage response with precise spatiotemporal control. Herein, we identify the CBP/p300‐interacting transactivator with glutamic acid/aspartic acid‐rich carboxyl‐terminal domain 2 (CITED2) as a critical intrinsic negative regulator of inflammation, which broadly attenuates pro‐inflammatory gene programs in macrophages. Our in vivo studies revealed that myeloid‐CITED2 deficiency significantly heightened macrophages and neutrophils recruitment to the site of inflammation. Our integrated transcriptomics and gene set enrichment analysis (GSEA) studies uncovered that CITED2 deficiency broadly enhances NFκB targets, IFNγ/IFNα responses, and inflammatory response gene expression in macrophages. Using complementary gain‐ and loss‐of‐function studies, we observed that CITED2 overexpression attenuate and CITED2 deficiency elevate LPS‐induced NFκB transcriptional activity and NFκB‐p65 recruitment to target gene promoter in macrophages. More importantly, blockade of NFκB signaling completely reversed elevated pro‐inflammatory gene expression in macrophages. Collectively, our findings show that CITED2 restrains NFκB activation and curtails broad pro‐inflammatory gene programs in myeloid cells.

CITED2 and the modulation of the hypoxic response in cancer

CITED2 (CBP/p300-interacting transactivator with Glu/Asp-rich C-terminal domain, 2) is a ubiquitously expressed protein exhibiting a high affinity for the CH1 domain of the transcriptional co-activators CBP/p300, for which it competes with hypoxia-inducible factors (HIFs). CITED2 is particularly efficient in the inhibition of HIF-1α-dependent transcription in different contexts, ranging from organ development and metabolic homeostasis to tissue regeneration and immunity, being also potentially involved in various other physiological processes. In addition, CITED2 plays an important role in inhibiting HIF in some diseases, including kidney and heart diseases and type 2-diabetes. In the particular case of cancer, CITED2 either functions by promoting or suppressing cancer development depending on the context and type of tumors. For instance, CITED2 overexpression promotes breast and prostate cancers, as well as acute myeloid leukemia, while its expression is downregulated to sustain colorectal cancer and hepatocellular carcinoma. In addition, the role of CITED2 in the maintenance of cancer stem cells reveals its potential as a target in non-small cell lung carcinoma and acute myeloid leukemia, for example. But besides the wide body of evidence linking both CITED2 and HIF signaling to carcinogenesis, little data is available regarding CITED2 role as a negative regulator of HIF-1α specifically in cancer. Therefore, comprehensive studies exploring further the interactions of these two important mediators in cancer-specific models are sorely needed and this can potentially lead to the development of novel targeted therapies.

A mechanistic integrative computational model of macrophage polarization: Implications in human pathophysiology

Macrophages respond to signals in the microenvironment by changing their functional phenotypes, a process known as polarization. Depending on the context, they acquire different patterns of transcriptional activation, cytokine expression and cellular metabolism which collectively constitute a continuous spectrum of phenotypes, of which the two extremes are denoted as classical (M1) and alternative (M2) activation. To quantitatively decode the underlying principles governing macrophage phenotypic polarization and thereby harness its therapeutic potential in human diseases, a systems-level approach is needed given the multitude of signaling pathways and intracellular regulation involved. Here we develop the first mechanism-based, multi-pathway computational model that describes the integrated signal transduction and macrophage programming under M1 (IFN-γ), M2 (IL-4) and cell stress (hypoxia) stimulation. Our model was calibrated extensively against experimental data, and we mechanistically elucidated several signature feedbacks behind the M1-M2 antagonism and investigated the dynamical shaping of macrophage phenotypes within the M1-M2 spectrum. Model sensitivity analysis also revealed key molecular nodes and interactions as targets with potential therapeutic values for the pathophysiology of peripheral arterial disease and cancer. Through simulations that dynamically capture the signal integration and phenotypic marker expression in the differential macrophage polarization responses, our model provides an important computational basis toward a more quantitative and network-centric understanding of the complex physiology and versatile functions of macrophages in human diseases.

Kruppel-like factor 6 and miR-223 signaling axis regulates macrophage-mediated inflammation

Macrophage-mediated inflammation is an explicitly robust biologic response that plays a critical role in maintaining tissue homeostasis by eliminating deleterious agents. These tissue macrophages tailor appropriate responses to external cues by altering inflammatory gene expression. Therefore, transcription factors and regulators that modulate inflammatory gene expression play an essential role in shaping the macrophage inflammatory response. Here, we identify that Kruppel-like factor (KLF)6 promotes inflammation by restraining microRNA-223 (miR-223) expression in macrophages. We uncovered that pro- and anti-inflammatory agents oppositely regulate KLF6 and miR-223 expression in macrophages. Using complementary gain- and loss-of-function studies, we observed that overexpression of KLF6 attenuates and deficiency of KLF6 elevates miR-223 expression in macrophages. Furthermore, heightened miR-223 expression in KLF6-deficient macrophages significantly attenuates inducible proinflammatory gene expression. Concordantly, myeloid-Klf6 deficiency significantly curbs diet-induced adipose tissue inflammation, obesity, glucose intolerance, and insulin resistance. At the molecular level, KLF6 directly represses miR-223 expression by occupying its promoter region. More importantly, genetic inhibition of miR-223-3P in KLF6-deficient macrophages completely reversed attenuated proinflammatory gene expression in macrophages. Collectively, our studies reveal that KLF6 promotes proinflammatory gene expression and functions by repressing miR-223 expression in macrophages.-Kim, G.-D., Ng, H. P., Patel, N., Mahabeleshwar, G. H. Kruppel-like factor 6 and miR-223 signaling axis regulates macrophage-mediated inflammation.

CITED2 mediates the cross-talk between mechanical loading and IL-4 to promote chondroprotection

Osteoarthritis (OA) pathogenesis is mediated largely through the actions of proteolytic enzymes such as matrix metalloproteinase (MMP) 13. The transcriptional regulator CITED2, which suppresses the expression of MMP13 in chondrocytes, is induced by interleukin (IL)-4 in T cells and macrophages, and by moderate mechanical loading in chondrocytes. We tested the hypothesis that CITED2 mediates cross-talk between IL-4 signaling and mechanical loading-induced pathways that result in chondroprotection, at least in part, by downregulating MMP13. IL-4 induced CITED2 gene expression in human chondrocytes in a dose- and time-dependent manner through JAK/STAT signaling. Mechanical loading combined with IL-4 resulted in additive effects on inducing CITED2 expression and downregulating of MMP13 in human chondrocytes in vitro. In vivo, IL-4 gene knockout (KO) mice exhibited reduced basal levels of CITED2 expression in chondrocytes. While moderate treadmill running induced CITED2 expression and reduced MMP13 expression in wild-type mice, these effects were blunted (for CITED2) or abolished (for MMP13) in chondrocytes of IL-4 gene KO mice. Moreover, intra-articular injections of mouse recombinant IL-4 combined with regular cage activity mitigated post-traumatic OA to a greater degree compared to immobilized mice treated with IL-4 alone. These data suggest that using moderate loading to enhance IL-4 may be a potential therapeutic strategy for chondroprotection in OA.