Receptor-Interacting Protein 140 Orchestrates the Dynamics of Macrophage M1/M2 Polarization

Biallelic variants in the calpain regulatory subunit CAPNS1 cause pulmonary arterial hypertension

Purpose

The aim of this study was to identify the monogenic cause of pulmonary arterial hypertension (PAH), a multifactorial and often fatal disease, in 2 unrelated consanguine families.

Methods

We performed exome sequencing and validated variant pathogenicity by whole-blood RNA and protein expression analysis in both families. Further RNA sequencing of preserved lung tissue was performed to investigate the consequences on selected genes that are involved in angiogenesis, proliferation, and apoptosis.

Results

We identified 2 rare biallelic variants in CAPNS1, encoding the regulatory subunit of calpain. The variants cosegregated with PAH in the families. Both variants lead to loss of function (LoF), which is demonstrated by aberrant splicing resulting in the complete absence of the CAPNS1 protein in affected patients. No other LoF CAPNS1 variant was identified in the genome data of more than 1000 patients with unresolved PAH.

Conclusion

The calpain holoenzyme was previously linked to pulmonary vascular development and progression of PAH in patients. We demonstrated that biallelic LoF variants in CAPNS1 can cause idiopathic PAH by the complete absence of CAPNS1 protein. Screening of this gene in patients who are affected by PAH, especially with suspected autosomal recessive inheritance, should be considered.

Biology of macrophage fate decision: Implication in inflammatory disorders

The activation of immune cells in response to stimuli present in their microenvironment is regulated by their metabolic profile. Unlike the signal transduction events, which overlap to a huge degree in diverse cellular processes, the metabolome of a cell reflects a more precise picture of cell physiology and function. Different factors governing the cellular metabolome include receptor signaling, macro and micronutrients, normoxic and hypoxic conditions, energy needs, and biomass demand. Macrophages have enormous plasticity and can perform diverse functions depending upon their phenotypic state. This review presents recent updates on the cellular metabolome and molecular patterns associated with M1 and M2 macrophages, also termed "classically activated macrophages" and "alternatively activated macrophages," respectively. M1 macrophages are proinflammatory in nature and predominantly Th1-specific immune responses induce their polarization. On the contrary, M2 macrophages are anti-inflammatory in nature and primarily participate in Th2-specific responses. Interestingly, the same macrophage cell can adapt to the M1 or M2 phenotype depending upon the clues from its microenvironment. We elaborate on the various tissue niche-specific factors, which govern macrophage metabolism and heterogeneity. Furthermore, the current review provides an in-depth account of deregulated macrophage metabolism associated with pathological disorders such as cancer, obesity, and atherosclerosis. We further highlight significant differences in various metabolic pathways governing the cellular bioenergetics and their impact on macrophage effector functions and associated disorders.

The Regulating Effect of CII-3 and Its Active Components from Periplaneta americana on M1/M2 Macrophage Polarization

CII-3 is the effective part of Periplaneta americana for application in oncotherapy. This study investigated its main chemical components for macrophage polarization regulation activity. Compounds were separated and purified, and their structures were elucidated based on NMR and HR-ESI-MS analyses. After inducing the M1 and M2 phenotype macrophages, CII-3 and testing components were added and co-incubated to evaluate their effects on the relevant markers of macrophages. Then, gradient concentrations of CII-3 and active monomers were further investigated for their effects on M2 macrophages. The effects were detected by RT-PCR, ELISA, flow cytometry, and immunofluorescence. Twelve compounds were identified from CII-3. CII-3 and pericanaside (5) had no obvious effect on M1 macrophages, while they significantly reduced the expression levels of M2 macrophage markers. Specifically, they significantly reduced the levels of TGF-β and IL-10 and the mRNA expression levels of ARG-1 and CD206 in the M2 phenotypes of RAW264.7 and Ana-1 macrophages. The conditioned medium of CII-3 and pericanaside (5) could inhibit the migration capacity of CT26.WT tumor cells. Macrophage M1/M2 polarization is a dynamic equilibrium, and the M2 phenotype, which can promote the growth of tumor cells, is relatively highly expressed in the tumor microenvironment. CII-3 and pericanaside could significantly reduce the phenotype of M2-type macrophages, indicating that the anti-tumor activity of CII-3 could be related to the inhibitory effect on M2 polarization, and pericanaside was one of the active components.

The Immune-Centric Revolution in the Diabetic Foot: Monocytes and Lymphocytes Role in Wound Healing and Tissue Regeneration-A Narrative Review

Monocytes and lymphocytes play a key role in physiologic wound healing and might be involved in the impaired mechanisms observed in diabetes. Skin wound macrophages are represented by tissue resident macrophages and infiltrating peripheral blood recruited monocytes which play a leading role during the inflammatory phase of wound repair. The impaired transition of diabetic wound macrophages from pro-inflammatory M1 phenotypes to anti-inflammatory pro-regenerative M2 phenotypes might represent a key issue for impaired diabetic wound healing. This review will focus on the role of immune system cells in normal skin and diabetic wound repair. Furthermore, it will give an insight into therapy able to immuno-modulate wound healing processes toward to a regenerative anti-inflammatory fashion. Different approaches, such as cell therapy, exosome, and dermal substitute able to promote the M1 to M2 switch and able to positively influence healing processes in chronic wounds will be discussed.

Whole-genome sequencing in diverse subjects identifies genetic correlates of leukocyte traits: The NHLBI TOPMed program

Many common and rare variants associated with hematologic traits have been discovered through imputation on large-scale reference panels. However, the majority of genome-wide association studies (GWASs) have been conducted in Europeans, and determining causal variants has proved challenging. We performed a GWAS of total leukocyte, neutrophil, lymphocyte, monocyte, eosinophil, and basophil counts generated from 109,563,748 variants in the autosomes and the X chromosome in the Trans-Omics for Precision Medicine (TOPMed) program, which included data from 61,802 individuals of diverse ancestry. We discovered and replicated 7 leukocyte trait associations, including (1) the association between a chromosome X, pseudo-autosomal region (PAR), noncoding variant located between cytokine receptor genes (CSF2RA and CLRF2) and lower eosinophil count; and (2) associations between single variants found predominantly among African Americans at the S1PR3 (9q22.1) and HBB (11p15.4) loci and monocyte and lymphocyte counts, respectively. We further provide evidence indicating that the newly discovered eosinophil-lowering chromosome X PAR variant might be associated with reduced susceptibility to common allergic diseases such as atopic dermatitis and asthma. Additionally, we found a burden of very rare FLT3 (13q12.2) variants associated with monocyte counts. Together, these results emphasize the utility of whole-genome sequencing in diverse samples in identifying associations missed by European-ancestry-driven GWASs.

New Insights on the Effects of Dietary Omega-3 Fatty Acids on Impaired Skin Healing in Diabetes and Chronic Venous Leg Ulcers

Long-chain Omega-3 polyunsaturated fatty acids (Omega-3 PUFAs) are widely recognized as powerful negative regulators of acute inflammation. However, the precise role exerted by these dietary compounds during the healing process is still largely unknown, and there is increasing interest in understanding their specific effects on the implicated cells/molecular factors. Particular attention is being focused also on their potential clinical application in chronic pathologies characterized by delayed and impaired healing, such as diabetes and vascular diseases in lower limbs. On these bases, we firstly summarized the current knowledge on wound healing (WH) in skin, both in normal conditions and in the setting of these two pathologies, with particular attention to the cellular and molecular mechanisms involved. Then, we critically reviewed the outcomes of recent research papers investigating the activity exerted by Omega-3 PUFAs and their bioactive metabolites in the regulation of WH in patients with diabetes or venous insufficiency and showing chronic recalcitrant ulcers. We especially focused on recent studies investigating the mechanisms through which these compounds may act. Considerations on the optimal dietary doses are also reported, and, finally, possible future perspectives in this area are suggested.

Modulation of mitochondrial and inflammatory homeostasis through RIP140 is neuroprotective in an adrenoleukodystrophy mouse model

AIMS

Mitochondrial dysfunction and inflammation are at the core of axonal degeneration in several multifactorial neurodegenerative diseases, including multiple sclerosis, Alzheimer's disease, and Parkinson's disease. The transcriptional coregulator RIP140/NRIP1 (receptor-interacting protein 140) modulates these functions in liver and adipose tissue, but its role in the nervous system remains unexplored. Here, we investigated the impact of RIP140 in the Abcd1^- mouse model of X-linked adrenoleukodystrophy (X-ALD), a genetic model of chronic axonopathy involving the convergence of redox imbalance, bioenergetic failure, and chronic inflammation.

METHODS AND RESULTS

We provide evidence that RIP140 is modulated through a redox-dependent mechanism driven by very long-chain fatty acids (VLCFAs), the levels of which are increased in X-ALD. Genetic inactivation of RIP140 prevented mitochondrial depletion and dysfunction, bioenergetic failure, inflammatory dysregulation, axonal degeneration and associated locomotor disabilities in vivo in X-ALD mouse models.

CONCLUSIONS

Together, these findings show that aberrant overactivation of RIP140 promotes neurodegeneration in X-ALD, underscoring its potential as a therapeutic target for X-ALD and other neurodegenerative disorders that present with metabolic and inflammatory dyshomeostasis.

Regulation of exosome secretion by cellular retinoic acid binding protein 1 contributes to systemic anti-inflammation

Background

Intercellular communications are important for maintaining normal physiological processes. An important intercellular communication is mediated by the exchange of membrane-enclosed extracellular vesicles. Among various vesicles, exosomes can be detected in a wide variety of biological systems, but the regulation and biological implication of exosome secretion/uptake remains largely unclear.

Methods

Cellular retinoic acid (RA) binding protein 1 (Crabp1) knockout (CKO) mice were used for in vivo studies. Extracellular exosomes were monitored in CKO mice and relevant cell cultures including embryonic stem cell (CJ7), macrophage (Raw 264.7) and hippocampal cell (HT22) using Western blot and flow cytometry. Receptor Interacting Protein 140 (RIP140) was depleted by Crispr/Cas9-mediated gene editing. Anti-inflammatory maker was analyzed using qRT-PCR. Clinical relevance was accessed by mining multiple clinical datasets.

Results

This study uncovers Crabp1 as a negative regulator of exosome secretion from neurons. Specifically, RIP140, a pro-inflammatory regulator, can be transferred from neurons, via Crabp1-regulated exosome secretion, into macrophages to promote their inflammatory polarization. Consistently, CKO mice, defected in the negative control of exosome secretion, have significantly elevated RIP140-containing exosomes in their blood and cerebrospinal fluid, and exhibit an increased vulnerability to systemic inflammation. Clinical relevance of this pathway is supported by patients’ data of multiple inflammatory diseases. Further, the action of Crabp1 in regulating exosome secretion involves its ligand and is mediated by its downstream target, the MAPK signaling pathway.

Conclusions

This study presents the first evidence for the regulation of exosome secretion, which mediates intercellular communication, by RA-Crabp1 signaling. This novel mechanism can contribute to the control of systemic inflammation by transferring an inflammatory regulator, RIP140, between cells. This represents a new mechanism of vitamin A action that can modulate the homeostasis of system-wide innate immunity without involving gene regulation.

Anti-Inflammatory Effects of an Extract from Pseudomonas aeruginosa and Its Purified Product 1-Hydroxyphenazine on RAW264.7 Cells

The purpose of this study was to discuss the effects of an extract from the culture medium of Pseudomonas aeruginosa (P. aeruginosa) 2016NX1 (chloroform extract of P. aeruginosa, CEPA) and its purified product 1-hydroxyphenazine on RAW264.7 cell inflammation. Cell viability was evaluated by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) method. TNF-α production was determined by an ELISA method. The effects of CEPA and its purified product 1-hydroxyphenazine on cell morphology were investigated using an inverted microscope. Quantitative real-time PCR was performed to determine mRNA expression levels. CEPA and 1-hydroxyphenazine had no obvious toxicity to cells when their concentrations were no more than 20 μg ml^-1 and 5 μg ml^-1, respectively. Both CEPA and 1-hydroxyphenazine suppressed the secretion of TNF-α and significantly reduced the mRNA expression levels of TNF-α, IL-1β, and IL-6. Both CEPA and 1-hydroxyphenazine inhibited M1 cell polarization after lipopolysaccharide (LPS) stimulation. The results in this article lay a good foundation for the biopharmaceutical applications of CEPA and 1-hydroxyphenazine in the future. CEPA and 1-hydroxyphenazine had certain anti-inflammatory activity, and inhibited LPS-induced RAW264.7 cell inflammation. Our findings suggest that CEPA and 1-hydroxyphenazine are potential chemicals with anti-inflammatory activity.

Effects of chronic stress on depressive-like behaviors and JMJD3 expression in the prefrontal cortex and hippocampus of C57BL/6 and ob/ob mice

BACKGROUND

Depression is a psychiatric disorder which is accompanied by neuroinflammatory responses. Obesity is considered as a low-grade inflammatory state. Studies have found that obese individuals are more likely to suffer from depression, but its possible mechanism has not been specifically illuminated. The Jumonji domain protein 3 (JMJD3) is a specific histone demethylase of trimethylation at lysine 27 of histone-H3 (H3K27me3). Over-expressions of JMJD3 induces the demethylation of H3K27me3 and results in the expression of pro-inflammatory genes, while its upregulation may be limited by adiponectin (APN). However, the role of JMJD3 in susceptibility to neuroinflammation and depression in obesity has not been clarified.

METHODS

Chronic unpredictable mild stress (CUMS) was selected to build depression model in C57BL/6 and ob/ob mice. Sucrose preference test, tail suspension test, open field test and Morris water maze test were used to detect depressive-like behaviors and memory impairment. Microglial activation, pro-inflammatory cytokines, APN, NF-ĸB, JMJD3 and H3K27me3 expressions in the serum, prefrontal cortex (PFC) and hippocampus (HIP) were examined in C57BL/6 and ob/ob mice. Meanwhile, GSK-J4 was used to inhibit JMJD3 expression.

RESULTS

CUMS led to depressive-like behaviors and memory impairment, microglial activation, increased expressions of pro-inflammatory cytokines, NF-κB and JMJD3, decreased expression of H3K27me3 in the PFC and HIP in C57BL/6 and ob/ob mice. Meanwhile, ob/ob mice showed worse behavioral injury and memory impairment, microglial excessively activation, over-expression of pro-inflammatory cytokines and NF-ĸB and decreased H3K27me3 levels than C57BL/6 mice. CUMS also decreased the APN levels in the serum and brain tissues in ob/ob mice compared to C57BL/6 mice. But GSK-J4 could relieve these alterations.

CONCLUSIONS

JMJD3 might be involved in the susceptibility to depressive-like behaviors and neuroinflammation of obese mice by the demethylation of H3K27me3, and decreased levels of APN could reduce Enhancer of zeste homolog 2 (EZH2) binding with H3K27me3. The role of JMJD3 in severer inflammatory state in the comorbidity of obesity and depression was considered.

Accelerated diabetic wound healing by topical application of combination oral antidiabetic agents-loaded nanofibrous scaffolds: An in vitro and in vivo evaluation study

The combination of oral antidiabetic drugs, pioglitazone, metformin, and glibenclamide, which also exhibit the strongest anti-inflammatory action among oral antidiabetic drugs, were loaded into chitosan/gelatin/polycaprolactone (PCL) by electrospinning and polyvinyl pyrrolidone (PVP)/PCL composite nanofibrous scaffolds by pressurized gyration to compare the diabetic wound healing effect. The combination therapies significantly accelerated diabetic wound healing in type-1 diabetic rats and organized densely packed collagen fibers in the dermis, it also showed better regeneration of the dermis and epidermis than single drug-loaded scaffolds with less inflammatory cell infiltration and edema. The formation of the hair follicles started in 14 days only in the combination therapy and lower proinflammatory cytokine levels were observed compared to single drug-loaded treatment groups. The combination therapy increased the wettability and hydrophilicity of scaffolds, demonstrated sustained drug release over 14 days, has high tensile strength and suitable cytocompatibility on L929 (mouse fibroblast) cell and created a suitable area for the proliferation of fibroblast cells. Consequently, the application of metformin and pioglitazone-loaded chitosan/gelatin/PCL nanofibrous scaffolds to a diabetic wound area offer high bioavailability, fewer systemic side effects, and reduced frequency of dosage and amount of drug.

Wound healing: cellular mechanisms and pathological outcomes

Wound healing is a complex, dynamic process supported by a myriad of cellular events that must be tightly coordinated to efficiently repair damaged tissue. Derangement in wound-linked cellular behaviours, as occurs with diabetes and ageing, can lead to healing impairment and the formation of chronic, non-healing wounds. These wounds are a significant socioeconomic burden due to their high prevalence and recurrence. Thus, there is an urgent requirement for the improved biological and clinical understanding of the mechanisms that underpin wound repair. Here, we review the cellular basis of tissue repair and discuss how current and emerging understanding of wound pathology could inform future development of efficacious wound therapies.

Mismatch between circulating cytokines and spontaneous cytokine production by leukocytes in hyperinflammatory COVID-19

The disease COVID‐19 has developed into a worldwide pandemic. Hyperinflammation and high levels of several cytokines, for example, IL‐6, are observed in severe COVID‐19 cases. However, little is known about the cellular origin of these cytokines. Here, we investigated whether circulating leukocytes from patients with COVID‐19 had spontaneous cytokine production. Patients with hyperinflammatory COVID‐19 (n = 6) and sepsis (n = 3) were included at Skåne University Hospital, Sweden. Healthy controls were also recruited (n = 5). Cytokines were measured in COVID‐19 and sepsis patients using an Immulite immunoassay system. PBMCs were cultured with brefeldin A to allow cytokine accumulation. In parallel, LPS was used as an activator. Cells were analyzed for cytokines and surface markers by flow cytometry. High levels of IL‐6 and measurable levels of IL‐8 and TNF, but not IL‐1β, were observed in COVID‐19 patients. Monocytes from COVID‐19 patients had spontaneous production of IL‐1β and IL‐8 (P = 0.0043), but not of TNF and IL‐6, compared to controls. No spontaneous cytokine production was seen in lymphocytes from either patients or controls. Activation with LPS resulted in massive cytokine production by monocytes from COVID‐19 patients and healthy controls, but not from sepsis patients. Finally, monocytes from COVID‐19 patients produced more IL‐1β than from healthy controls (P = 0.0087) when activated. In conclusion, monocytes contribute partly to the ongoing hyperinflammation by production of IL‐1β and IL‐8. Additionally, they are responsive to further activation. This data supports the notion of IL‐1β blockade in treatment of COVID‐19. However, the source of the high levels of IL‐6 remains to be determined.

CAPN1 promotes malignant behavior and erlotinib resistance mediated by phosphorylation of c-Met and PIK3R2 via degrading PTPN1 in lung adenocarcinoma

BACKGROUND

Calpain 1 (CAPN1) has been found to be a promoter of cancer progression. PTPN1 as a physiological target molecule of CAPN1 plays a dephosphorylated role on multiple receptor tyrosine kinases. This study aimed to reveal the effects of CAPN1/PTPN1 on malignant phenotype and EGFR-TKI resistance of lung adenocarcinoma (LUAD) cells.

METHODS

A total of 84 primary LUAD tissues and paired paracancerous normal tissues were collected. Quantitative real-time PCR (qRT-PCR) and immunohistochemical (IHC) methods were used to measure the expression of CAPN1 and PTPN1 in tissues. qRT-PCR and western blot were used to detect the expressions of CAPN1, PTPN1, c-Met and PIK3R2 in cell lines. Cell counting kit-8 (CCK-8), colony formation and transwell assay were carried out to evaluate cell erlotinib resistance, proliferation, migration and invasion. Co-IP assay was used to verify the interaction between proteins. Cycloheximide (CHX) was applied to block protein synthesis.

RESULTS

CAPN1, c-Met and PIK3R2 were significantly upregulated and the correlation was positive in LUAD, while PTPN1 was decreased. EGFR-sensitive mutation was related to CAPN1/PTPN1. in vitro studies showed that PTPN1 can mediate dephosphorylation of c-Met and PIK3R2 by binding with both, thereby weakening cell proliferation, metastasis and erlotinib resistance, while CAPN1 could enhance the degradation of PTPN1 protein as a cancer promoter.

CONCLUSIONS

CAPN1 enhances the malignant behavior and erlotinib resistance of LUAD cells via degrading PTPN1 and then activating c-Met/PIK3R2, which suggests CAPN1/PTPN1 may serve as tumor markers or potential targets for diagnosis and treatment of LUAD.

KEY POINTS

Significant findings of the study Superior CAPN1 and inferior PTPN1 were related to activation of c-Met/PIK3R2 in lung adenocarcinoma. Moreover, regulations of CAPN1 and PTPN1 induced the changes of malignant behavior and erlotinib resistance. What this study adds Our findings confirmed that CAPN1/PTPN1 play crucial roles on proliferation, metastasis and erlotinib resistance of LUAD cells as c-Met/PIK3R2 regulators, and validated the regulatory mechanism of CAPN1 on PTPN1 in tumor model for the first time.

Salmonella enterica serovar Typhimurium sseK3 induces apoptosis and enhances glycolysis in macrophages

Background

Salmonella enterica serovar Typhimurium (S. Typhimurium) is an important infectious disease pathogen that can survive and replicate in macrophages. Glycolysis is essential for immune responses against S. Typhimurium infection in macrophages, and is also associated with apoptosis. S. Typhimurium secreted effector K3 (SseK3) was recently identified as a novel translated and secreted protein. However, there is no study about the role of sseK3 in the relationship between apoptosis and glycolysis in cells infected with S. Typhimurium. It is unclear whether this protein exerts a significant role in the progress of apoptosis and glycolysis in S. Typhimurium-infected macrophages.

Results

Macrophages were infected with S. Typhimurium SL1344 wild-type (WT), ΔsseK3 mutant or sseK3-complemented strain, and the effects of sseK3 on apoptosis and glycolysis were determined. The adherence and invasion in the ΔsseK3 mutant group were similar to that in the WT and sseK3-complemented groups, indicating that SseK3 was not essential for the adherence and invasion of S. Typhimurium in macrophages. However, the percentage of apoptosis in the ΔsseK3 mutant group was much lower than that in the WT and sseK3-complemented groups. Caspase-3, caspase-8, and caspase-9 enzyme activity in the ΔsseK3 mutant group were significantly lower than in the WT group and sseK3-complemented groups, indicating that sseK3 could improve the caspase-3, caspase-8, and caspase-9 enzyme activity. We also found that there were no significant differences in pyruvic acid levels between the three groups, but the lactic acid level in the ΔsseK3 mutant group was much lower than that in the WT and sseK3-complemented groups. The ATP levels in the ΔsseK3 mutant group were remarkably higher than those in the WT and sseK3-complemented groups. These indicated that the sseK3 enhanced the level of glycolysis in macrophages infected by S. Typhimurium.

Conclusions

S. Typhimurium sseK3 is likely involved in promoting macrophage apoptosis and modulating glycolysis in macrophages. Our results could improve our understanding of the relationship between apoptosis and glycolysis in macrophages induced by S. Typhimurium sseK3.

Protein tyrosine phosphatase 1B inhibition as a potential therapeutic target for chronic wounds in diabetes

Non-healing diabetic foot ulcers (DFUs) are a serious complication in diabetic patients. Their incidence has increased in recent years. Although there are several treatments for DFUs, they are often not effective enough to avoid amputation. Protein tyrosine phosphatase 1B (PTP1B) is expressed in most tissues and is a negative regulator of important metabolic pathways. PTP1B is overexpressed in tissues under diabetic conditions. Recently, PTP1B inhibition has been found to enhance wound healing. PTP1B inhibition decreases inflammation and bacterial infection at the wound site and promotes angiogenesis and tissue regeneration, thereby facilitating diabetic wound healing. In summary, the pharmacological modulation of PTP1B activity may help treat DFUs, suggesting that PTP1B inhibition is an outstanding therapeutic target.

The extracellular sulfatase SULF2 promotes liver tumorigenesis by stimulating assembly of a promoter-looping GLI1-STAT3 transcriptional complex

The expression of the extracellular sulfatase SULF2 has been associated with increased hepatocellular carcinoma (HCC) growth and poor patient survival. However, the molecular mechanisms underlying SULF2-associated tumor growth remain unclear. To address this gap, here we developed a transgenic mouse overexpressing Sulf2 in hepatocytes under the control of the transthyretin promoter. In this model, Sulf2 overexpression potentiated diethylnitrosamine-induced HCC. Further analysis indicated that the transcription factor GLI family zinc finger 1 (GLI1) mediates Sulf2 expression during HCC development. A cross of the Sulf2-overexpressing with Gli1-knockout mice revealed that Gli1 inactivation impairs SULF2-induced HCC. Transcriptomic analysis revealed that Sulf2 overexpression is associated with signal transducer and activator of transcription 3 (STAT3)-specific gene signatures. Interestingly, the Gli1 knockout abrogated SULF2-mediated induction of several STAT3 target genes, including suppressor of cytokine signaling 2/3 (Socs2/3); Pim-1 proto-oncogene, Ser/Thr kinase (Pim1); and Fms-related tyrosine kinase 4 (Flt4). Human orthologs were similarly regulated by SULF2, dependent on intact GLI1 and STAT3 functions in HCC cells. SULF2 overexpression promoted a GLI1-STAT3 interaction and increased GLI1 and STAT3 enrichment at the promoters of their target genes. Interestingly, the SULF2 overexpression resulted in GLI1 enrichment at select STAT3 consensus sites, and vice versa. siRNA-mediated STAT3 or GLI1 knockdown reduced promoter binding of GLI1 and STAT3, respectively. Finally, chromatin-capture PCR confirmed long-range co-regulation of SOCS2 and FLT3 through changes in promoter conformation. These findings define a mechanism whereby SULF2 drives HCC by stimulating formation of a GLI1-STAT3 transcriptional complex.

Cellular retinoic acid binding protein 1 protects mice from high-fat diet-induced obesity by decreasing adipocyte hypertrophy

Objectives

Obesity, an emerging global health issue, involves numerous factors; understanding its underlying mechanisms for prevention and therapeutics is urgently needed. Cellular retinoic acid binding protein 1 (Crabp1) knockout (CKO) mice exhibit an obese phenotype under normal diet feedings, which prompted us to propose that Crabp1 could play a role in modulating adipose tissue development/homeostasis. Studies were designed to elucidate the underlying mechanism of Crabp1’s action in reducing obesity.

Subjects/methods

In animal studies, 6 weeks old male wild type and CKO mice were fed with normal diet (ND) or high fat diet (HFD) for 10 weeks. Body weight and food intake were regularly monitored. Glucose tolerance test and biological parameters of plasma (glucose and insulin levels) were measured after 10 weeks of ND vs. HFD feedings. Visceral adipose tissues were collected for histological and molecular analyses to determine affected signaling pathways. In cell culture studies, the 3T3L1 adipocyte differentiation model was used to examine and validate relevant signaling pathways.

Results

CKO mice, compared to WT mice, gained more body weight, exhibited more elevated fasting plasma glucose levels, and developed more severe impaired glucose tolerance under both ND and HFD. Histological examination revealed readily increased adipocyte hypertrophy and adipose tissue inflammation under HFD feedings. In 3T3L1 adipocytes, Crabp1 silencing enhanced extracellular signal-regulated kinase 1/2 (ERK1/2) activation, accompanied by elevated markers and signaling pathways of lipid accumulation and adipocyte hypertrophy.

Conclusions

This study identifies Crabp1’s physiological role against the development of obesity. The protective function of CRABP1 is likely attributed to its classically proposed (canonical) activity as a trap for RA, which will reduce RA availability, thereby dampening RA-stimulated ERK1/2 activation and adipocyte hypertrophy. The results suggest Crabp1 as a potentially new therapeutic target in managing obesity and metabolic diseases.

The effects of CD14 and IL-27 on induction of endotoxin tolerance in human monocytes and macrophages

Upon repeated exposure to endotoxin or lipopolysaccharide (LPS), myeloid cells enter a refractory state called endotoxin tolerance as a homeostatic mechanism. In innate immune cells, LPS is recognized by co-receptors Toll-like receptor 4 (TLR4) and CD-14 to initiate an inflammatory response for subsequent cytokine production. One such cytokine, interleukin (IL)-27, is produced by myeloid cells in response to bacterial infection. In monocytes, IL-27 has proinflammatory functions such as up-regulating TLR4 expression for enhanced LPS-mediated cytokine production; alternatively, IL-27 induces inhibitory functions in activated macrophages. This study investigated the effects of IL-27 on the induction of endotoxin tolerance in models of human monocytes compared with macrophages. Our data demonstrate that IL-27 inhibits endotoxin tolerance by up-regulating cell surface TLR4 expression and soluble CD14 production to mediate stability of the surface LPS-TLR4-CD14 complex in THP-1 cells. In contrast, elevated basal expression of membrane-bound CD14 in phorbol 12-myristate 13-acetate (PMA)-THP-1 cells, primary monocytes, and primary macrophages may promote CD14-mediated endocytosis and be responsible for the preservation of an endotoxin-tolerized state in the presence of IL-27. Overall, the efficacy of IL-27 in inhibiting endotoxin tolerance in human THP-1 monocytes and PMA-THP-1 macrophages is affected by membrane-bound and soluble CD14 expression.

Protein tyrosine phosphatase 1B inactivation limits aging-associated heart failure in mice

We have previously shown that protein tyrosine phosphatase 1B (PTP1B) inactivation in mice [PTP1B-deficient (PTP1B−/−) mice] improves left ventricular (LV) angiogenesis, perfusion, remodeling, and function and limits endothelial dysfunction after myocardial infarction. However, whether PTP1B inactivation slows aging-associated cardiovascular dysfunction remains unknown. Wild-type (WT) and PTP1B−/− mice were allowed to age until 18 mo. Compared with old WT mice, in which aging increased the LV mRNA expression of PTP1B, old PTP1B−/− mice had 1) reduced cardiac hypertrophy with decreased LV mRNA levels of hypertrophic markers and atrial and brain natriuretic peptides, 2) lower LV fibrosis (collagen: 16 ± 3% in WT mice and 5 ± 3% in PTP1B−/− mice, P < 0.001) with decreased mRNA levels of transforming growth-factor-β1 and matrix metalloproteinase-2, and 3) higher LV capillary density and lower LV mRNA level of hypoxic inducible factor-1α, which was associated over time with a higher rate of proangiogenic M2 type macrophages and a stable LV mRNA level of VEGF receptor-2. Echocardiography revealed an age-dependent LV increase in end-diastolic volume in WT mice together with alterations of fractional shortening and diastole (transmitral Doppler E-to-A wave ratio). Invasive hemodynamics showed better LV systolic contractility and better diastolic compliance in old PTP1B−/− mice (LV end-systolic pressure-volume relation: 13.9 ± 0.9 in WT mice and 18.4 ± 1.6 in PTP1B−/− mice; LV end-diastolic pressure-volume relation: 5.1 ± 0.8 mmHg/relative volume unit in WT mice and 1.2 ± 0.3 mmHg/relative volume unit in PTP1B−/− mice, P < 0.05). In addition, old PTP1B−/− mice displayed a reduced amount of LV reactive oxygen species. Finally, in isolated resistance mesenteric arteries, PTP1B inactivation reduced aging-associated endothelial dysfunction (flow-mediated dilatation: −0.4 ± 2.1% in WT mice and 8.2 ± 2.8% in PTP1B−/− mice, P < 0.05). We conclude that PTP1B inactivation slows aging-associated LV remodeling and dysfunction and reduces endothelial dysfunction in mesenteric arteries.

NEW & NOTEWORTHY The present study shows that protein tyrosine phosphatase 1B inactivation in aged mice improves left ventricular systolic and diastolic function associated with reduced adverse cardiac remodeling (hypertrophy, fibrosis, and capillary rarefaction) and limits vascular endothelial dysfunction. This suggests that protein tyrosine phosphatase 1B inhibition could be an interesting treatment approach in age-related cardiovascular dysfunction.

Long non-coding RNA cox-2 prevents immune evasion and metastasis of hepatocellular carcinoma by altering M1/M2 macrophage polarization

Macrophages have been shown to demonstrate a high level of plasticity, with the ability to undergo dynamic transition between M1 and M2 polarized phenotypes. We investigate long non-coding RNA (lncRNA) cox-2 in macrophage polarization and the regulatory mechanism functions in hepatocellular carcinoma (HCC). Lipopolysaccharide (LPS) was used to induce RAW264.7 macrophages into M1 type, and IL-4 was to induce RAW264.7 macrophages into M2 type. We selected mouse hepatic cell line Hepal-6 and hepatoma cell line HepG2 for co-incubation with M1 or M2 macrophages. Quantitative real-time PCR was used to detect the expressions of lncRNA cox-2 and mRNAs. ELISA was conducted for testing IL-12 and IL-10 expressions; Western blotting for epithelial mesenchymal transition related factors (E-cadherin and Vimentin). An MTT, colony formation assay, flow cytometry, transwell assay, and stretch test were conducted to test cell abilities. The M1 macrophages had higher lncRNA cox-2 expression than that in the non-polarized macrophages and M2 macrophages. The lncRNA cox-2 siRNA decreased the expression levels of IL-12, iNOS, and TNF-α in M1 macrophages, increased the expression levels of IL-10, Arg-1, and Fizz-1 in M2 macrophages (all P < 0.05). The lncRNA cox-2 siRNA reduces the ability of M1 macrophages to inhibit HCC cell proliferation, invasion, migration, EMT, angiogenesis and facilitate apoptosis while strengthening the ability of M2 macrophages to promote proliferation HCC cell growth and inhibit apoptosis. These findings indicate that lncRNA cox-2 inhibits HCC immune evasion and tumor growth by inhibiting the polarization of M2 macrophages.

The Emerging Role of Vitamin B6 in Inflammation and Carcinogenesis

Vitamin B6 serves as a coenzyme catalyzing more than 150 enzymes regulating metabolism and synthesis of proteins, carbohydrates, lipids, heme, and important bioactive metabolites. For several years vitamin B6 and its vitamers (B6) were recognized as antioxidant and antiinflammatory and in modulating immunity and gene expression. During the last 10 years, there were growing reports implicating B6 in inflammation and inflammation-related chronic illnesses including cancer. It is unclear if the deficiency of B6 or additional intake of B6, above the current requirement, should be the focus. Whether the current recommended daily intake for B6 is adequate should be revisited, since B6 is important to human health beyond its role as a coenzyme and its status is affected by many factors including but not limited to age, obesity, and inflammation associated with chronic illnesses. A link between inflammation B6 status and carcinogenesis is not yet completely understood. B6-mediated synthesis of H₂S, a gasotransmitter, and taurine in health and disease, especially in maintaining mitochondrial integrity and biogenesis and inflammation, remains an important area to be explored. Recent developments in the molecular role of B6 and its direct interaction with inflammasomes, and nuclear receptor corepressor and coactivator, receptor-interacting protein 140, provide a strong impetus to further explore the multifaceted role of B6 in carcinogenesis and human health.

Glyburide and retinoic acid synergize to promote wound healing by anti-inflammation and RIP140 degradation

Chronic inflammation underlies the development of metabolic diseases and individuals with metabolic disease often also suffer from delayed wound healing due to prolonged inflammation. Resolving inflammation provides a therapeutic strategy in treating metabolic diseases. We previously showed that during an anti-inflammatory response when macrophages were alternatively (M2) polarized, retinoic acid (RA) dramatically activated arginase 1 gene (Arg1), a gene crucial for wound healing. Here we report that a widely used sulfonylurea drug for type 2 diabetes mellitus (T2DM), glyburide, enhances the anti-inflammatory response and synergizes with RA to promote wound healing. Our data also delineate the mechanism underlying glyburide’s anti-inflammatory effect, which is to stimulate the degradation of a pro-inflammatory regulator, Receptor Interacting Protein 140 (RIP140), by activating Ca2+/calmodulin-dependent protein kinase II (CamKII) that triggers specific ubiquitination of RIP140 for degradation. By stimulating RIP140 degradation, glyburide enhances M2 polarization and anti-inflammation. Using a high-fat diet induced obesity mouse model to monitor wound healing effects, we provide a proof-of-concept for a therapeutic strategy that combining glyburide and RA can significantly improve wound healing. Mechanistically, this study uncovers a new mechanism of action of glyburide and a new pathway modulating RIP140 protein degradation that is mediated by CamKII signaling.

Punicalagin, a PTP1B inhibitor, induces M2c phenotype polarization via up-regulation of HO-1 in murine macrophages

Current data have shown that punicalagin (PUN), an ellagitannin isolated from pomegranate, possesses anti-inflammatory and anti-oxidant properties; however, its direct targets have not yet been reported. This is the first report that PTP1B serves as a direct target of PUN, with IC₅₀ value of 1.04μM. Results from NPOI further showed that the K_on and K_off of PUN-PTP1B complex were 3.38e2M^-1s^-1 and 4.13e-3s^-1, respectively. The active site Arg24 of PTP1B was identified as a key binding site of PUN by computation simulation and point mutation. Moreover, inhibition of PTP1B by PUN promoted an M2c-like macrophage polarization and enhanced anti-inflammatory cytokines expression, including IL-10 and M-CSF. Based on gene expression profile, we elucidated that PUN treatment significantly up-regulated 275 genes and down-regulated 1059 genes. M1-like macrophage marker genes, such as Tlr4, Irf1/2, Hmgb1, and Stat1 were down-regulated, while M2 marker genes, including Tmem171, Gpr35, Csf1, Il1rn, Cebpb, Fos, Vegfα, Slc11a1, and Bhlhe40 were up-regulated in PUN-treated macrophages. Hmox-1, a gene encoding HO-1 protein, was preferentially expressed with 16-fold change. Inhibition of HO-1 obviously restored PUN-induced M2 polarization and IL-10 secretion. In addition, phosphorylation of both Akt and STAT3 contributed to PUN-induced HO-1 expression. This study provided new insights into the mechanisms of PUN-mediated anti-inflammatory and anti-oxidant activities and provided new therapeutic strategies for inflammatory diseases.

Innate immunity orchestrates adipose tissue homeostasis

Obesity is strongly associated with multiple diseases including insulin resistance, type 2 diabetes, cardiovascular diseases, fatty liver disease, neurodegenerative diseases and cancers, etc. Adipose tissue (AT), mainly brown AT (BAT) and white AT (WAT), is an important metabolic and endocrine organ that maintains whole-body homeostasis. BAT contributes to non-shivering thermogenesis in a cold environment; WAT stores energy and produces adipokines that fine-tune metabolic and inflammatory responses. Obesity is often characterized by over-expansion and inflammation of WAT where inflammatory cells/mediators are abundant, especially pro-inflammatory (M1) macrophages, resulting in chronic low-grade inflammation and leading to insulin resistance and metabolic complications. Macrophages constitute the major component of innate immunity and can be activated as a M1 or M2 (anti-inflammatory) phenotype in response to environmental stimuli. Polarized M1 macrophage causes AT inflammation, whereas polarized M2 macrophage promotes WAT remodeling into the BAT phenotype, also known as WAT browning/beiging, which enhances insulin sensitivity and metabolic health. This review will discuss the regulation of AT homeostasis in relation to innate immunity.

RIP140 in monocytes/macrophages regulates osteoclast differentiation and bone homeostasis

Osteolytic bone diseases, such as osteoporosis, are characterized by diminished bone quality and increased fracture risk. The therapeutic challenge remains to maintain bone homeostasis with a balance between osteoclast-mediated resorption and osteoblast-mediated formation. Osteoclasts are formed by the fusion of monocyte/macrophage-derived precursors. Here we report, to our knowledge for the first time, that receptor-interacting protein 140 (RIP140) expression in osteoclast precursors and its protein regulation are crucial for osteoclast differentiation, activity, and coupled bone formation. In mice, monocyte/macrophage-specific knockdown of RIP140 (mϕRIP140KD) resulted in a cancellous osteopenic phenotype with significantly increased bone resorption and reduced bone formation. Osteoclast precursors isolated from mϕRIP140KD mice had significantly increased differentiation potential. Furthermore, conditioned media from mϕRIP140KD primary osteoclast cultures significantly suppressed osteoblast differentiation. This suppressive activity was effectively and rapidly terminated by specific Syk-stimulated RIP140 protein degradation. Mechanistic analysis revealed that RIP140 functions primarily by inhibiting osteoclast differentiation through forming a transcription-suppressor complex with testicular receptor 4 (TR4) to repress osteoclastogenic genes. These data reveal that monocyte/macrophage RIP140/TR4 complexes may serve as a critical transcription regulatory complex maintaining homeostasis of osteoclast differentiation, activity, and coupling with osteoblast formation. Accordingly, we propose a potentially novel therapeutic strategy, specifically targeting osteoclast precursor RIP140 protein in osteolytic bone diseases.

Gut microbiota from metabolic disease-resistant, macrophage-specific RIP140 knockdown mice improves metabolic phenotype and gastrointestinal integrity

While fecal microbiota transplantation (FMT) presents an attractive therapeutic strategy, it remains unclear how to choose the microbiota repertoire that most effectively transfers benefit to recipients. We identified a beneficial taxonomic repertoire in a transgenic mouse model (RIP140mϕKD) which resists the development of high fat diet (HFD)-induced metabolic diseases due to enhanced anti-inflammation engineered by lowering receptor interacting protein (RIP140) expression in macrophage. We confirmed using FMT from HFD-fed RIP140mϕKD to wild type (WT) mice that recipient mice acquired the microbiota repertoire of donor mice. Importantly, FMT from RIP140mϕKD to WT not only effectively transferred the beneficial taxonomic repertoire to WT recipients, but also enabled recipient animals acquiring the anti-inflammatory status of RIP140mϕKD donor animals and avoid HFD-induced insulin resistance, which is associated with significantly improved intestinal integrity. We conclude that FMT can transfer not only microbiota but also the donors' intestinal innate immune status and improved intestinal integrity.

Synergistic activation of Arg1 gene by retinoic acid and IL-4 involves chromatin remodeling for transcription initiation and elongation coupling

All-trans Retinoic acid (RA) and its derivatives are potent therapeutics for immunological functions including wound repair. However, the molecular mechanism of RA modulation in innate immunity is poorly understood, especially in macrophages. We found that topical application of RA significantly improves wound healing and that RA and IL-4 synergistically activate Arg1, a critical gene for tissue repair, in M2 polarized macrophages. This involves feed forward regulation of Raldh2, a rate-limiting enzyme for RA biosynthesis, and requires Med25 to coordinate RAR, STAT6 and chromatin remodeler, Brg1 to remodel the +1 nucleosome of Arg1 for transcription initiation. By recruiting elongation factor TFIIS, Med25 also facilitates transcriptional initiation-elongation coupling. This study uncovers synergistic activation of Arg1 by RA and IL-4 in M2 macrophages that involves feed forward regulation of RA synthesis and dual functions of Med25 in nucleosome remodeling and transcription initiation-elongation coupling that underlies robust modulatory activity of RA in innate immunity.