Regulation of PHLDA1 Expression by JAK2-ERK1/2-STAT3 Signaling Pathway

HDAC Inhibition Restores Response to HER2-Targeted Therapy in Breast Cancer via PHLDA1 Induction

The downregulation of Pleckstrin Homology-Like Domain family A member 1 (PHLDA1) expression mediates resistance to targeted therapies in receptor tyrosine kinase-driven cancers. The restoration and maintenance of PHLDA1 levels in cancer cells thus constitutes a potential strategy to circumvent resistance to inhibitors of receptor tyrosine kinases. Through a pharmacological approach, we identify the inhibition of MAPK signalling as a crucial step in PHLDA1 downregulation. Further ChIP-qPCR analysis revealed that MEK1/2 inhibition produces significant epigenetic changes at the PHLDA1 locus, specifically a decrease in the activatory marks H3Kme3 and H3K27ac. In line with this, we show that treatment with the clinically relevant class I histone deacetylase (HDAC) inhibitor 4SC-202 restores PHLDA1 expression in lapatinib-resistant human epidermal growth factor receptor-2 (HER2)+ breast cancer cells. Critically, we show that when given in combination, 4SC-202 and lapatinib exert synergistic effects on 2D cell proliferation and colony formation capacity. We therefore propose that co-treatment with 4SC-202 may prolong the clinical efficacy of lapatinib in HER2+ breast cancer patients.

Quantifying stimulus-response specificity to probe the functional state of macrophages

Immune sentinel macrophages initiate responses to pathogens via hundreds of immune response genes. Each immune threat demands a tailored response, suggesting that the capacity for stimulus-specific gene expression is a key functional hallmark of healthy macrophages. To quantify this property, termed "stimulus-response specificity" (SRS), we developed a single-cell experimental workflow and analytical approaches based on information theory and machine learning. We found that the response specificity of macrophages is driven by combinations of specific immune genes that show low cell-to-cell heterogeneity and are targets of separate signaling pathways. The "response specificity profile," a systematic comparison of multiple stimulus-response distributions, was distinctly altered by polarizing cytokines, and it enabled an assessment of the functional state of macrophages. Indeed, the response specificity profile of peritoneal macrophages from old and obese mice showed characteristic differences, suggesting that SRS may be a basis for measuring the functional state of innate immune cells. A record of this paper's transparent peer review process is included in the supplemental information.

TDAG51 deficiency attenuates dextran sulfate sodium-induced colitis in mice

Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is a group of chronic inflammatory diseases of the gastrointestinal tract. Although the multifactorial etiology of IBD pathogenesis is relatively well documented, the regulatory factors that confer a risk of IBD pathogenesis remain less explored. In this study, we report that T-cell death-associated gene 51 (TDAG51/PHLDA1) is a novel regulator of the development of dextran sulfate sodium (DSS)-induced colitis in mice. TDAG51 expression was elevated in the colon tissues of DSS-induced experimental colitis mice. TDAG51 deficiency protected mice against acute DSS-induced lethality and body weight changes and disease severity. DSS-induced structural damage and mucus secretion in colon tissues were significantly reduced in TDAG51-deficient mice compared with wild-type mice. We observed similar results in a DSS-induced chronic colitis mouse model. Finally, we showed that the production of inflammatory mediators, including proinflammatory enzymes, molecules and cytokines, was decreased in DSS-treated TDAG51-deficient mice compared with DSS-treated wild-type mice. Thus, we demonstrated that TDAG51 deficiency plays a protective role against DSS-induced colitis by decreasing the production of inflammatory mediators in mice. These findings suggest that TDAG51 is a novel regulator of the development of DSS-induced colitis and is a potential therapeutic target for IBD.

JMJD3 Promotes Porphyromonas gingivalis Lipopolysaccharide-Induced Th17-Cell Differentiation by Modulating the STAT3-RORc Signaling Pathway

The immune response mediated by Th17 cells is essential in the pathogenesis of periodontitis. Emerging evidence has demonstrated that lipopolysaccharide from Porphyromonas gingivalis (Pg-LPS) could promote Th17-cell differentiation directly, while the downstream signaling remains elusive. This study was aimed to explore the role of JMJD3 (a JmjC family histone demethylase) and signal transducers and activators of transcription 3 (STAT3) in Th17-cell differentiation triggered by Pg-LPS and clarify the interaction between them. We found that the expression of JMJD3 and STAT3 was significantly increased under Th17-polarizing conditions. Pg-LPS could promote Th17-cell differentiation from CD4⁺ T cells, with an increased expression of JMJD3 and STAT3 compared to the culture without Pg-LPS. The coimmunoprecipitation results showed that the interactions of JMJD3 and STAT3, STAT3 and retinoid-related orphan nuclear receptor γt (RORγt) were enhanced following Pg-LPS stimulation during Th17-cell differentiation. Further blocking assays were performed and the results showed that inhibition of STAT3 or JMJD3 both suppressed the Th17-cell differentiation, JMJD3 inhibitor could reduce the expression of STAT3 and p-STAT3, while JMJD3 expression was not affected when STAT3 was inhibited. Taken together, this study found that JMJD3 could promote Pg-LPS induced Th17-cell differentiation by modulating the STAT3-RORc signaling pathway.

PHLDA1 Suppresses TLR4-Triggered Proinflammatory Cytokine Production by Interaction With Tollip

Pleckstrin homology-like domain, family A, member 1 (PHLDA1) has been reported to be expressed in many mammalian tissues and cells. However, the functions and exact mechanisms of PHLDA1 remain unclear. In this study, we found that PHLDA1 expression was significantly altered in macrophages after exposure to lipopolysaccharide (LPS) in vitro, suggesting that PHLDA1 may be involved in the regulation of TLR4 signaling pathway activated by LPS. PHLDA1 attenuated the production of LPS-stimulated proinflammatory cytokines (TNF-α, IL-6, and IL-1β). Further research showed that the phosphorylation levels of some important signal molecules in TLR4/MyD88-mediated MAPK and NF-κB signaling pathways were reduced by PHLDA1, which in turn impaired the transcription factors NF-κB and AP1 nuclear translocation and their responsive element activities. Furthermore, we found that PHLDA1 repressed LPS-induced proinflammatory cytokine production via binding to Tollip which restrained TLR4 signaling pathway. A mouse model of endotoxemia was established to confirm the above similar results. In brief, our findings demonstrate that PHLDA1 is a negative regulator of LPS-induced proinflammatory cytokine production by Tollip, suggesting that PHLDA1 plays an anti-inflammatory role through inhibiting the TLR4/MyD88 signaling pathway with the help of Tollip. PHLDA1 may be a novel therapeutic target in treating endotoxemia.

A nomogram for predicting metabolic steatohepatitis: The combination of NAMPT, RALGDS, GADD45B, FOSL2, RTP3, and RASD1

Objective

To identify differentially expressed and clinically significant mRNAs and construct a potential prediction model for metabolic steatohepatitis (MASH).

Method

We downloaded four microarray datasets, GSE89632, GSE24807, GSE63067, and GSE48452, from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) analysis and weighted gene co-expression network analysis were performed to screen significant genes. Finally, we constructed a nomogram of six hub genes in predicting MASH and assessed it through receiver operating characteristic (ROC) curve, calibration plot, and decision curve analysis (DCA). In addition, qRT-PCR was used for relative quantitative detection of RNA in QSG-7011 cells to further verify the expression of the selected mRNA in fatty liver cells.

Results

Based on common DEGs and brown and yellow modules, seven hub genes were identified, which were NAMPT, PHLDA1, RALGDS, GADD45B, FOSL2, RTP3, and RASD1. After logistic regression analysis, six hub genes were used to establish the nomogram, which were NAMPT, RALGDS, GADD45B, FOSL2, RTP3, and RASD1. The area under the ROC of the nomogram was 0.897. The DCA showed that when the threshold probability of MASH was 0–0.8, the prediction model was valuable to GSE48452. In QSG-7011 fatty liver model cells, the relative expression levels of NAMPT, GADD45B, FOSL2, RTP3, RASD1 and RALGDS were lower than the control group.

Conclusion

We identified seven hub genes NAMPT, PHLDA1, RALGDS, GADD45B, FOSL2, RTP3, and RASD1. The nomogram showed good performance in the prediction of MASH and it had clinical utility in distinguishing MASH from simple steatosis.

miR-194 ameliorates hepatic ischemia/reperfusion injury via targeting PHLDA1 in a TRAF6-dependent manner

Hepatic ischemia/reperfusion injury (IRI) is an inevitable pathological process in liver resection, shock and transplantation. However, the internal mechanism of hepatic IRI, including inflammatory transduction of multiple signaling pathways, is not fully understood. In the present study, we identified pleckstrin homology-like domain family member 1 (PHLDA1), suppressed by microRNA (miR)-194, as a critical intersection of dual inflammatory signals in hepatic IRI. PHLDA1 was upregulated in hepatic IRI with a concomitant downregulation of miR-194. Overexpression of miR-194 diminished PHLDA1 and inhibitors of the nuclear factor kappa-B kinase (IKK) pathway, thus leading to remission of hepatic pathological injury, apoptosis and release of cytokines. Further enrichment of PHLDA1 reversed the function of miR-194 both in vivo and in vitro. For an in-depth query, we verified PHLDA1 as a direct target of miR-194. Notably, inflammatory signal transduction of PHLDA1 was induced by activating TNF receptor-associated factor 6 (TRAF6), sequentially initiating IKK and mitogen-activated protein kinase (MAPK), both of which aggravate stress and inflammation in hepatic IRI. In conclusion, the miR-194/PHLDA1 axis was a key upstream regulator of IKK and MAPK in hepatic IRI. Targeting PHLDA1 might be a potential strategy for hepatic IRI therapy.

PHLDA1 promotes microglia-mediated neuroinflammation via regulating K63-linked ubiquitination of TRAF6

Microglia-mediated neuroinflammation plays an important role in the progression of neurodegenerative diseases including Parkinson's disease (PD). Pleckstrin homology-like domain family A member 1 (PHLDA1) plays an important role in immunological regulation, particularly in the Toll-like receptor-mediated immune response. Here, we explored the potential roles of PHLDA1 in microglia-mediated inflammation and neuronal protection. We found that PHLDA1 expression was rapidly increased in response to inflammatory stimuli in microglia cells in vivo or in vitro. Knockdown of PHLDA1 using adeno-associated virus serotype (AAV) ameliorated MPTP-induced motor deficits and inhibited neuroinflammation in mice. In support of this observation in vivo, we found that LPS-induced proinflammatory gene expression, including TNF-α, IL-1β, iNOS, and COX-2, was decreased in PHLDA1-deficient microglial cells. Mechanistic studies demonstrated that increased expression of PHLDA1, upon LPS stimulation in microglia, led to direct interaction with TRAF6 and enhanced its K63-linked ubiquitination-mediated NF-κB signaling activation. PHLDA1 deficiency interfered with TRAF6 K63-linked ubiquitination and inhibited microglial inflammatory responses. These findings reveal the first evidence that PHLDA1 is an important modulator of microglial function that is associated with microglia-mediated dopaminergic neurotoxicity. The data therefore provided the first evidence that PHLDA1 may be a potent modulator for neuroinflammation, and PHLDA1 may be a novel drug target for treatment of neuroinflammation-related diseases such as PD.

Hyaluronic acid-based extracellular matrix triggers spontaneous M2-like polarity of monocyte/macrophage

Hyaluronic acid (HA) is found in various tumor tissues, and is considered tumor-associated extracellular matrix (ECM). Within this tumor-associated ECM, stromal cells, especially immune cells, are involved in tumor progression. However, the effects of tumor-associated ECM on the characteristics of immune cells remain unexplored. Therefore, we studied the triggering effect of HA on spontaneous M2-like polarity of monocytes/macrophages using HA-mixed collagen (HA-COL) matrix. In the presence of HA, expression of the HA receptor (CD44) and M2 polarity-related genes was upregulated in human monocytes (THP-1 cells). We confirmed the CD44-mediated activation of STAT3 in THP-1 cells cultured in an HA-rich environment. Furthermore, when we induced the THP-1 cells to differentiate into cells with M1 or M2 polarity within an HA-rich environment, the HA-rich environment influenced the direction of induction. Our findings might improve understanding of the crosstalk between immune cells and tumor-associated ECM, and facilitate development of tumor immunotherapy strategies.

A novel role for C-C motif chemokine receptor 2 during infection with hypervirulent Mycobacterium tuberculosis

C-C motif chemokine receptor 2 (CCR2) is a major chemokine axis that recruits myeloid cells including monocytes and macrophages. Thus far, CCR2-/- mice have not been found to be susceptible to infection with Mycobacterium tuberculosis (Mtb). Here, using a prototype W-Beijing family lineage 2 Mtb strain, HN878, we show that CCR2-/- mice exhibit increased susceptibility to tuberculosis (TB). Following exposure to Mtb HN878, alveolar macrophages (AMs) are amongst the earliest cells infected. We show that AMs accumulate early in the airways following infection and express CCR2. During disease progression, CCR2-expressing AMs exit the airways and localize within the TB granulomas. RNA-sequencing of sorted airway and non-airway AMs from infected mice show distinct gene expression profiles, suggesting that upon exit from airways and localization within granulomas, AMs become classically activated. The absence of CCR2+ cells specifically at the time of AM egress from the airways resulted in enhanced susceptibility to Mtb infection. Furthermore, infection with an Mtb HN878 mutant lacking phenolic glycolipid (PGL) expression still resulted in increased susceptibility in CCR2-/- mice. Together, these data show a novel role for CCR2 in protective immunity against clinically relevant Mtb infections.

The promotion of nephropathy by Porphyromonas gingivalis lipopolysaccharide via toll-like receptors

BACKGROUND

Recently, we reported that toll-like receptor (TLR)2 and TLR4 localized on the glomerular endothelium in the glomeruli of streptozotocin (STZ)-induced type 1 diabetic mice and high fat diet feed-induced type 2 diabetic mice, and that periodontal pathogen Porphyromonas gingivalis LPS (Pg-LPS) administration lowered the survival rate of diabetic mice. The present study aims to examine the effect of TLR4 blocking on the suppression of Pg-LPS-induced diabetic nephropathy.

METHODS

The survival rate and morphological/biochemical features for streptozotocin-induced diabetic mice with Pg-LPS and TLR4 blocker eritoran administration were investigated by reporter gene assay, urine and blood analysis, immunohistochemistry, and real time-PCR.

RESULTS AND CONCLUSIONS

All of the diabetic mice administered Pg-LPS were euthanized within the survival period of almost all of the diabetic mice. The blood urea nitrogen and creatinine, expression of TLR2 and TGF-b, and type 1 collagen accumulation, in the diabetic mice increased significantly with the Pg-LPS administration. In spite of the limited TLR4 activation with Pg-LPS, the TLR4 blocker eritoran decreased blood urea nitrogen and creatinine, and raised the survival rate of the Pg-LPS-administered diabetic mice slightly. The high expression levels of TLR2, TGF-b, and type 1 collagen in Pg-LPS-administered diabetic mice decreased with eritoran. Nuclear STAT3 which enhances TLR2 expression was detected in the TLR2-expressing glomeruli of diabetic mice. The TLR2 and STAT3 gene expression increased by the Pg-LPS administration but decreased with eritoran. These may suggest that Pg-LPS-induced diabetic nephropathy is mainly dependent on TLR2 signaling on glomerular endothelial cells, and that TLR4 blocker eritoran may play a role to slow the progress of diabetic nephropathy.

A novel role of breast cancer-derived hyaluronan on inducement of M2-like tumor-associated macrophages formation

Microenvironmental signals determine the differentiation types and distinct functions of macrophages. Tumor-associated macrophages (TAM) constitute major infiltrates around solid tumor cells and accelerate tumor progression due to their immunosuppressive functions. However, the mechanisms through which tumor microenvironment modulates macrophages transition are not completely elucidated. Hyaluronan (HA), a prominent component in tumor microenvironment, is a notable immunoregulator and its high level is often related to poor prognosis. Herein, we found that the number of M2 macrophages was highly correlated with HA expression in tumor tissues from breast cancer patients. Experimental data showed that breast cancer-derived HA stimulated M2-like TAM formation in a mouse model and had multiple effects on macrophages transformation in vitro, including upregulating CD204, CD206, IL-10 and TGF-β, activating STAT3 signal, and suppressing killing capacity. These data indicate that HA derived from breast cancer activates macrophages in an alternative manner. Further mechanism study revealed that HA-CD44-ERK1/2-STAT3 pathway served as an important regulator in M2-like TAM formation. Therefore, targeting TAM by abrogating HA-CD44 interaction may be a potential strategy for breast cancer immunotherapy.